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1

Dynamic Nuclear Polarization in Samarium Doped Lanthanum Magnesium Nitrate. Ph.D. Thesis - Va. Polytechnic Inst.  

NASA Technical Reports Server (NTRS)

The dynamic nuclear polarization of hydrogen nuclei by the solid effect in single crystals of samarium doped lanthanum magnesium nitrate (Sm:LMN) was studied theoretically and experimentally. The equations of evolution governing the dynamic nuclear polarization by the solid effect were derived in detail using the spin temperature theory and the complete expression for the steady state enhancement of the nuclear polarization was calculated. Experimental enhancements of the proton polarization were obtained for eight crystals at 9.2 GHz and liquid helium temperatures. The samarium concentration ranged from 0.1 percent to 1.1 percent as determined by X-ray fluorescence. A peak enhancement of 181 was measured for a 1.1 percent Sm:LMN crystal at 3.0 K. The maximum enhancements extrapolated with the theory using the experimental data for peak enhancement versus microwave power and correcting for leakage, agree with the ideal enhancement (240 in this experiment) within experimental error for three of the crystals.

Byvik, C. E.

1971-01-01

2

Dimensional instability of doped lanthanum chromite  

Microsoft Academic Search

Lattice expansion phase stability, and dimensional stability of doped lanthanum chromites have been examined over a wide range of temperatures and oxygen partial pressures. Reduction of doped lanthanum chromite resulted in a linear expansion of the sample that was dependent on the acceptor (Sr, Ca) concentration, temperature, oxygen partial pressure, and oxygen content within the sample. Additional doping with aliovalent

Timothy R. Armstrong; J. W. Stevenson; L. R. Pederson; P. E. Raney

1996-01-01

3

Investigation of the thermal conductivity of selected compounds of lanthanum, samarium and europium  

Microsoft Academic Search

As part of the development of rare earth based ceramic materials for a variety of applications, the thermal conductivities of lanthanum aluminate, samarium zirconate and europium zirconate were investigated, employing the laser flash technique and covering a temperature range from 6501400 K. Based on the variation of the thermal resistivity as a function of temperature, the heat transport behaviour of

Girija Suresh; G Seenivasan; M. V Krishnaiah; P. Srirama Murti

1998-01-01

4

Dimensional instability of doped lanthanum chromite  

SciTech Connect

Lattice expansion phase stability, and dimensional stability of doped lanthanum chromites have been examined over a wide range of temperatures and oxygen partial pressures. Reduction of doped lanthanum chromite resulted in a linear expansion of the sample that was dependent on the acceptor (Sr, Ca) concentration, temperature, oxygen partial pressure, and oxygen content within the sample. Additional doping with aliovalent B-site additives significantly reduced lattice expansion in reducing environments. The lattice expansion in reducing environments was directly related to the loss of lattice oxygen and the simultaneous reduction of Cr{sup 4+} to Cr{sup 3+} to maintain electroneutrality.

Armstrong, T.R.; Stevenson, J.W.; Pederson, L.R.; Raney, P.E. [Pacific Northwest National Lab., Richland, WA (United States). Materials Sciences Dept.

1996-09-01

5

Photoluminescence of samarium-doped TiO 2 nanotubes  

NASA Astrophysics Data System (ADS)

Samarium (Sm)-modified TiO 2 nanotubes (TNTs) were synthesized by low-temperature soft chemical processing. X-ray powder diffraction analyses of the synthesized Sm-doped and non-doped TNTs show a broad peak near 2 ?=10, which is typical of TNTs. The binding energy of Sm 3d 5/2 for 10 mol% Sm-doped TNT (1088.3 eV) was chemically shifted from that of Sm 2O 3 (1087.5 eV), showing that Sm existed in the TiO 2 lattice. Sm-doped TNTs clearly exhibited red fluorescence, corresponding to the doped Sm 3+ ion in the TNT lattice. The Sm-doped TNT excitation spectrum exhibited a broad curve, which was similar to the UV-vis optical absorption spectrum. Thus, it was considered that the photoluminescence emission of Sm 3+-doped TNT with UV-light irradiation was caused by the energy transfer from the TNT matrix via the band-to-band excitation of TiO 2 to the Sm 3+ ion.

Park, Dong Jin; Sekino, Tohru; Tsukuda, Satoshi; Hayashi, Asuka; Kusunose, Takafumi; Tanaka, Shun-Ichiro

2011-10-01

6

Characterization of A-site deficient samarium doped barium titanate  

NASA Astrophysics Data System (ADS)

Ba1-xSm2x/3TiO3 (0.00?x?0.10, in a step of 0.02) ceramics have been prepared through solid state reaction route. Structural studies (XRD, FTIR, Raman) suggested a tetragonal symmetry of all the prepared ceramics and a decrease in tetragonality with increase in Sm content. Rietveld refinement technique has been employed to investigate the details of crystal structure and was found to be tetragonal at room temperature with space group P4mm. Photoluminescence study confirmed formation of shallow defects. The prepared materials are found to show photoemission in the violet, blue and green zone. Optical band gap values calculated from UV-visual diffuse reflectance spectra showed a decreasing trend in band gap values with increase in samarium concentration. Disk shaped pellets were prepared using PVA as binder. Scanning electron microscopy showed a drastic decrease in grain size on doping than undoped barium titanate. A regular increase in the grain size with increase in Sm content in the doped compositions is observed. Dielectric studies were performed over a wide temperature range from 15 K to 600 K at different frequencies. Normal ferroelectric character was obtained for all the compositions. A gradual decrease in the Curie temperature was noticed with increase in samarium content. P?E hysteresis loops showed a domain pinning effect which increased successively resulting in a decrease in the values of remnant polarization and coercive fields.

Ganguly, M.; Rout, S. K.; Woo, W. S.; Ahn, C. W.; Kim, I. W.

2013-02-01

7

Reaction mechanism between lanthanum manganite and yttria doped cubic zirconia  

Microsoft Academic Search

The reactivity between lanthanum deficient lanthanum manganite, La0.9MnO3, and yttria doped cubic zirconia (YSZ) has been examined at the temperature range between 1250C and 1400C. The reaction product of La2Zr2O7 was observed after some induced period, which depended on the reaction temperature and the yttrium content in YSZ. The induced period increased with increasing Y2O3 content in ZrO2. The reaction

M Mori; T Abe; H Itoh; O Yamamoto; G. Q Shen; Y Takeda; N Imanishi

1999-01-01

8

Coprecipitation synthesis of doped lanthanum chromite  

SciTech Connect

Two coprecipitation methods were used to synthesize powder precursors of doped lanthanum chromite (La,Ca)(Cr,Co)O[sub 3]. The effects of synthesis method and calcination temperature on the composition, sintered density, and microstructure of pressed compacts of (La,Ca)(Cr,Co)O[sub 3] were studied by differential thermal analysis/thermogravimetric analysis, x-ray diffraction, scanning electron microscopy, and density measurement. The cation ratios in the precipitated solids were, with few exceptions, within experimental error of the desired compositions for all four components. Powders obtained by both techniques could be sintered to densities exceeding 93% at 1400 [degree]C. The highest densities were obtained with calcining temperatures from 450 to 700 [degree]C. The sintered microstructures exhibited uniform grain sizes averaging 3--5 [mu]m. The Cr(VI) compounds, CaCrO[sub 4] and La[sub 2]CrO[sub 6], were observed in all of the calcined powders. The possible role of these phases on chromite densification is discussed.

De Guire, M.R. (Department of Materials Science and Engineering, Case Western Reserve University, Cleveland, Ohio 44106-7204 (United States)); Dorris, S.E.; Poeppel, R.B.; Morissette, S.; Balachandran, U. (Materials and Components Technology Division, Argonne National Laboratory, Argonne Illinois 60439 (United States))

1993-09-01

9

Optical properties of samarium doped zinc phosphate glasses  

NASA Astrophysics Data System (ADS)

Samarium doped zinc phosphate glasses having composition Sm2O3 (x)ZnO(60-x) P2O5 (40) (where x=0.1 0.5 mol%) were prepared by melt quenching method. The density of these glasses was measured by Archimedes method; the corresponding molar volumes have also been calculated. The values of density range from 3.34 to 3.87 gm/cm3 and those of molar volume range from 27.62 to 31.80 cm-3. The optical absorbance studies were carried out on these glasses to measure their energy band gaps. The absorption spectra of these glasses were recorded in UV-visible region. No sharp edges were found in the optical spectra, which verifies the amorphous nature of these glasses. The optical band gap energies for these glasses were found to be in the range of 2.89 4.20 eV. The refractive index and polarizability of oxide ion have been calculated by using Lorentz Lorentz relations. The values of refractive index range from 2.13 to 2.42 and those of polarizability of oxide ion range from 6.5110-24 to 7.8010-24 cm3.

Eraiah, B.; Bhat, Sudha G.

2007-04-01

10

Reaction between calcium-doped lanthanum chromite and silica  

SciTech Connect

Calcium-doped lanthanum chromite reacted with silica to form silicates and chromium oxide at 1,473--1,773K. A reaction mechanism was proposed at each temperature. At 1,473 K, a reaction zone was observed in two areas: one was the bulk reaction area where silicates and chromium oxide were formed near the reaction interface; the other was the grain boundary reaction where chromium oxide and calcium silicate spots were formed far from the reaction interface. Above 1,673 K, silicates in the La{sub 2}O-CaO-SiO{sub 2} system and chromium oxide were formed simultaneously in the reaction zone with no grain boundary reaction. No layered reaction products were observed in the reaction zone of the lanthanum chromite side. Formation of melt silicates above 1,723 K at the reaction interface resulted in strong bonding between calcium-doped lanthanum chromite and silica.

Horita, Teruhisa, Choi, J.S.; Lee, Y.K.; Sakai, Natsuko; Kawada, Tatsuya; Yokokawa, Harumi; Dokiya, Masayuki [National Institute of Materials and Chemical Research, Tsukuba, Ibaraki (Japan). Tsukuba Research Center

1995-07-01

11

Sintering and Property Characterization of Strontium-Doped Lanthanum Chromite  

SciTech Connect

Sr-doped lanthanum chromite (LSC-15 LA 0.85Sr 0.15 CrO3) is difficult to sinter to high densities in air. Typically <705 theoretical density at 1600 degrees C. This study considers three methods to enhance the densification of LSC-15.

Simner, Steven P.; Hardy, John S.; Stevenson, Jeffry W.; Armstrong, Timothy R.

1999-12-01

12

Passive gain-equalized wide-band erbium-doped fiber amplifier using samarium-doped fiber  

Microsoft Academic Search

A passive gain-equalization technique of erbium-doped fiber amplifier (EDFA) using a samarium-doped fiber to obtain wide-band flattened gain operation is reported. In the wavelength range from 1529-1559-nm, small inter-channel gain variations can be achieved. This simple technique is suitable for multiwavelength wide-band in-line-amplifier cascaded transmission applications.

Shien-Kuei Liaw; Yung-Kuang Chen

1996-01-01

13

Diode pumped white light emission from dysprosium and samarium doped glasses  

NASA Astrophysics Data System (ADS)

Glasses embedded with Dysprosium and Samarium were made by the melt quenching technique. Dy3+ -doped glasses exhibited bright white luminescence under 10 mW of 405 nm diode laser excitation. Color rending index of the glass was improved by adding Sm3+ as a co-dopant to the glass. Spectroscopic results of the glasses are discussed.

Reddy, B. Rami; Edwards, Vernessa M.; Surabhi, Raja

2014-03-01

14

Effect of samarium doping on the dielectric behavior of barium zircomium titanate ceramic  

NASA Astrophysics Data System (ADS)

Samarium doped Barium Zirconium Titanate ceramic with general formula Ba1-xSm2x/3Zr0.05Ti0.95O3 [x=0.0,0.01,0.02,0.03,0.04] has been prepared by high energy ball milling. The X-ray diffraction (XRD) patterns confirmed that these ceramics have a single phase with perovskite-type upto x?0.03 and a small secondary phase exist at x=0.04. The temperature dependent dielectric study shows a ferroelectric phase transition and transition temperature decreases with an increase in the Samarium content.

Badapanda, T.; Sarangi, S.; Behera, B.; Anwar, S.; Sinha, T. P.

2014-04-01

15

Some properties of strontium-doped lanthanum chromite  

Microsoft Academic Search

The properties of strontium-doped lanthanum chromite (La084Sr016CrO3) are discussed, with particular attention to its application as an electrode material for MHD power generation. The influence of firing temperature on the ceramic properties and the behaviour of strontium carbonate as a sintering agent are described. The thermal conductivity is 51 w m?1 degk?1 between 1100 and 2000k, and the thermal expansion

D B Meadowcroft

1969-01-01

16

Sinterability and electrical conductivity of calcium-doped lanthanum chromites  

Microsoft Academic Search

Calcium-doped lanthanum chromites, (La1-xCax) (Cr1-y Cay O3, have been synthesized to investigate effects of calcium doping on sinterability and electrical conductivity. X-ray diffractometric results have revealed that in addition to normal perovskites (La1-xCaxCrO3), chromium-deficient perovskites can exist as a single phase in the composition region 0.1 x < 0.3, although the deficit of chromium is small. These chromium-deficient perovskites show

N. Sakai; T. Kawada; H. Yokokawa; M. Dokiya; T. Iwata

1990-01-01

17

Low temperature processing of dense samarium-doped CeO 2 ceramics: sintering and grain growth behaviors  

Microsoft Academic Search

Samarium-doped CeO2 is a leading electrolyte for applications in solid oxide fuel cells (SOFCs), which requires a typical sintering temperature of 14001600 C. By synthesizing reactive powders via carbonate precipitation, fully dense CeO2 ceramics doped with 020 at.% of samarium have been fabricated in this work via pressureless sintering at a significantly lowered temperature of 1000 C. The resultant ceramics

Ji-Guang Li; Takayasu Ikegami; Toshiyuki Mori

2004-01-01

18

Thermal expansion of doped lanthanum gallates  

Microsoft Academic Search

Thermal expansion of several compositions of Sr and Mg-doped LaGaO3 including an A-site deficient composition (La0.9Sr0.1)0.98(Ga0.8Mg0.2)O2.821 were measured in the temperature range from 298 to 1273 K. The effect of doping on thermal expansion was studied by varying\\u000a the composition at one site of the perovskite structure (either A or B), while keeping the composition at the other site invariant.

K. T. Jacob; S. Jain; V. S. Saji; P. V. K. Srikanth

2010-01-01

19

Thermal conductivity analysis of lanthanum doped manganites  

NASA Astrophysics Data System (ADS)

The temperature-dependent thermal conductivity of the doped manganites La0.7Ca0.3MnO3 is theoretically analyzed within the framework of Kubo formulae. The Hamiltonian consists of phonon, electron and magnon thermal conductivity contribution term. In this process we took defects, carrier, grain boundary, scattering process term and then calculate phonon, electron and magnon thermal conductivity.

Mansuri, Irfan; Shaikh, M. W.; Khan, E.; Varshney, Dinesh

2014-04-01

20

Expansion on reduction of calcium doped lanthanum chromite  

SciTech Connect

Doped lanthanum chromites have been considered as interconnect materials for the solid oxide fuel cell (SOFC) because of their favorable chemical and electrical properties under both oxidizing and reducing environments. Several investigators have studied the materials properties of the doped lanthanum chromites to optimize their overall performance as an interconnect material. These properties include electrical conductivity, thermal expansion, sinterability, and chemical compatibility with other cell components. These properties are optimized by the amount of dopants substituted into chromite which are usually Ca or Sr. Figure 1 shows the range of values for these properties. Another important characteristic becoming more of a concern as investigators are building SOFC stacks is that doped lanthanum chromite expands when reduced in a low oxygen partial pressure (pO{sub 2}) (<10{sup -12} atm). Plates used to separate oxidizing and fuel gases can deform because of the pO{sub 2} gradient across the interconnect material. This presentation is a summary of work which will be presented at the Fourth International Symposium on Solid Oxide Fuel Cells. In this article, the possible causes of expansion on reduction of the interconnect will be discussed by using a two-dimensional crystal model. The biaxial strain of the stack is calculated under the assumption that the cell components are forced to remain planar. From this, the maximum stress buildup in the interconnect and electrolyte is estimated. In addition, the effects of thermal expansion mismatch and expansion on reduction of the interconnect are compared, and the optimum interconnect composition from a mechanical standpoint is reported.

Carter, J.D.; Hendriksen, P.V.; Mogensen, M. [Riso National Lab., Roskilde (Denmark). Materials Dept.

1995-07-01

21

Determinacao de elementos lantanidicos em oxidos purificados de lantanio, de samario e de gadolinio por espectrometria de emissao com plasma. (Inductively coupled plasma optical emission spectrometry analysis of lanthanum, samarium and gadolinium oxides for rare earths impurities).  

National Technical Information Service (NTIS)

An inductively coupled plasma optical emission spectrometry method is described for the determination of Sm, Eu, La, Gd, Dy, Pr, Ho, Nd, Tb and Y in purified oxides of lanthanum, samarium and gadolinium. The method enables a simple, precise and readily av...

L. C. P. Reino A. R. Lordello

1990-01-01

22

Thermodynamic properties of doped lanthanum manganites  

SciTech Connect

The thermodynamic properties of the perovskite compounds La[sub 0.8]Sr[sub 0.2]MnO[sub 3] (LSM), La[sub 0.9]Na[sub 0.1]MnO[sub 3] (LNM), and LaMnO[sub 3] (LM) were studied by use of the solid electrolyte galvanic cell method at 1,000 C, 1,050 C, and 1,100 C. Two samples of each compound were investigated as well as decomposed samples of LSM and LNM. The cell assembly was constructed by means of eight small stabilized zirconia tubes and a common Ni/NiO reference electrode. The equilibrium partial pressures of the samples were calculated form the measured EMF values. The results reveal that the equilibrium pO[sub 2] of LM appears to be one or two orders of magnitude lower than that of LSM and LNM, respectively, which means that LM is more stable than the doped perovskites. The variation in the standard free energy with temperature for the perovskite decomposition reaction was calculated from the pO[sub 2] equilibrium values, i.e. [Delta]G[degree]d (LSM) = 140.86 [minus] 0.05199T kJ/mole and [Delta]G[degree]d (LNM) = 106.06 [minus] 0.02572T kJ/mole. On the basis of the above equations, the reaction enthalpy and entropy changes were calculated. Perovskite oxides have received considerable attention in recent years for their use as cathodes in solid oxide fuel cells.

Hildrum, R.; Brustad, M. (Norwegian Inst. of Tech., Trondheim (Norway). Dept. of Electrochemistry); Wang Changzhen (Northeast Univ. of Technology, Shenyang (China). Div. of Physicochemistry of Metallurgy); Johannesen, O. (Kongsberg Coll. of Engineering (Norway))

1994-08-01

23

Nanoscale mapping of oxygen vacancy kinetics in nanocrystalline Samarium doped ceria thin films  

NASA Astrophysics Data System (ADS)

The position-dependent oxygen vacancy dynamics induced by a biased scanning probe microscopy tip in Samarium doped ceria thin films grown on MgO (100) substrates is investigated. The granularity of the samples gives rise to spatially dependent local electrochemical activity, as explored by electrochemical strain microscopy. The kinetics of the oxygen vacancy relaxation process is investigated separately for grain boundaries and grains. Higher oxygen vacancy concentration variation and slower diffusion are observed in the grain boundary regions as compared to the grains.

Doria, Sandra; Yang, Nan; Kumar, Amit; Jesse, Stephen; Tebano, Antonello; Aruta, Carmela; Di Bartolomeo, Elisabetta; Arruda, Thomas M.; Kalinin, Sergei V.; Licoccia, Silvia; Balestrino, Giuseppe

2013-10-01

24

Studies on combustion catalytic activity of some pure and doped lanthanum cobaltites  

Microsoft Academic Search

The aim of this work is to compare the catalytic activity of some pure and doped lanthanum cobaltites, prepared by solution combustion technique, with a Pt\\/Al2O3 commercial catalyst. As test reaction we used the combustion of lean methane mixtures. The experimental data evidenced a significantly better catalytic activity of a cerium-doped lanthanum cobaltite, prepared by using ?-alanine as fuel. The

Magdalena Bosomoiu; Grigore Bozga; Daniela Berger; Cristian Matei

2008-01-01

25

Altering the equilibrium condition in Sr-doped lanthanum manganite.  

SciTech Connect

The material of choice for a solid oxide fuel cell cathode based on a yttria-stabilized zirconia (YSZ) electrolyte is doped lanthanum manganite, (La, Sr)MnO{sub 3}. It excels at many of the attributes necessary for a system to work at the required operating temperature and is flexible enough to allow for materials optimization. Although strontium-doping increases the electronic conductivity of the material, the ionic conductivity of the material remains negligible under operating conditions. Studies have shown that the internal equilibrium of the material heavily favors oxidation of the manganese and rather than the loss of lattice oxygen as a charge compensation mechanism. This lack of oxygen vacancies in the structure retards the ability of the material to conduct oxygen ions; thus the optimized system requires a large number of engineered triple point boundary locations to work efficiently. We have successfully doped the host LSM lattice to alter the interred equilibrium of the material to increase its ionic conductivity and thus lower the cathodic overpotential of the system. Our presentation will discuss these new materials, the results of cell tests, and a number of characterization experiments performed.

Carter, J. D.; Krumpelt, M.; Vaughey, J.; Wang, X.

1999-05-28

26

YBCO bulk superconductors doped with gadolinium and samarium  

NASA Astrophysics Data System (ADS)

The YBa2Cu3O7-? (YBCO, Y123) bulk single-grain superconductors doped with GdBa2Cu3Oy (Gd123) or SmBa2Cu3Oz (Sm123) were prepared by the Top-seeded melt-growth process. The growth conditions of the samples were optimized for different dopant concentrations. Wavelength-dispersive spectrometry (WDS) confirmed that prepared samples contain besides dopants also Sm from the seed and Yb from the substrate. The critical temperature, Tc increases with increasing dopant concentration in the studied range. Peak effect in the field dependences of critical current density, Jc(B) at 77 K was observed.

Volochov, Daniela; Piovar?i, Samuel; Raduovsk, Monika; Antal, Vitaliy; Kov?, Jozef; Jurek, Karel; Jirsa, Milo; Diko, Pavel

2013-11-01

27

Temperature stability of samarium-doped ?-sialon ceramics  

Microsoft Academic Search

Dense Sm-doped ?-sialon ceramics along the tie line SmxSi12?4.5xAl4.5xO1.5xN16?1.5x between Si3N4 and Sm2O39AlN were prepared by hot-pressing at 1800 C. The materials were subsequently heattreated at different temperatures in the range 13001750 C for different times. The samples were either cooled by turning the furnace off, yielding a cooling rate (Tcol) ? 50 Cmin?1 or quenched (Tcol ? 400 Cmin?1)

Zhijian Shen; Thommy Ekstrm; Mats Nygren

1996-01-01

28

Photoluminescence of samarium-doped TiO{sub 2} nanotubes  

SciTech Connect

Samarium (Sm)-modified TiO{sub 2} nanotubes (TNTs) were synthesized by low-temperature soft chemical processing. X-ray powder diffraction analyses of the synthesized Sm-doped and non-doped TNTs show a broad peak near 2{theta}=10{sup o}, which is typical of TNTs. The binding energy of Sm {sup 3}d{sub 5/2} for 10 mol% Sm-doped TNT (1088.3 eV) was chemically shifted from that of Sm{sub 2}O{sub 3} (1087.5 eV), showing that Sm existed in the TiO{sub 2} lattice. Sm-doped TNTs clearly exhibited red fluorescence, corresponding to the doped Sm{sup 3+} ion in the TNT lattice. The Sm-doped TNT excitation spectrum exhibited a broad curve, which was similar to the UV-vis optical absorption spectrum. Thus, it was considered that the photoluminescence emission of Sm{sup 3+}-doped TNT with UV-light irradiation was caused by the energy transfer from the TNT matrix via the band-to-band excitation of TiO{sub 2} to the Sm{sup 3+} ion. - Graphical Abstract: Samarium-doped TiO{sub 2} nanotubes (TNTs) having a nanotubular structure were synthesized by soft chemical route. It was revealed that the energy associated by the band-to-band excitation of TNT matrix transferred to the doped Sm{sup 3+} ions in the lattice, resulting in emission of strong and visible red fluorescence. Highlights: > Sm-doped TiO{sub 2} nanotubes synthesized by low-temperature soft chemical processing. > Sm{sup 3+} substitutes Ti{sup 4+} ions in the nanotube lattice. > Clear fluorescent emission due to the f-f transition at the Sm{sup 3+} in a crystal field environment. > Band-to-band excitation of TiO{sub 2} and followed energy transfer to Sm{sup 3+} causes the luminescence.

Park, Dong Jin [Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577 (Japan); Sekino, Tohru, E-mail: sekino@tagen.tohoku.ac.jp [Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577 (Japan); Tsukuda, Satoshi [Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577 (Japan); Hayashi, Asuka [Institute of Scientific and Industrial Research (ISIR), Osaka University, 8-1, Mihogaoka, Ibaraki, Osaka 567-0047 (Japan); Kusunose, Takafumi [Faculty of Engineering, Kagawa University, Hayashi 2217-20, Takamatsu, Kagawa 761-0396 (Japan); Tanaka, Shun-Ichiro [Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577 (Japan)

2011-10-15

29

The evolution mechanism of the dislocation loops in irradiated lanthanum doped cerium oxide  

NASA Astrophysics Data System (ADS)

Cerium dioxide, a non-radioactive surrogate of uranium dioxide, is useful for simulating the radiation responses of uranium dioxide and mixed oxide fuel (MOX). Controlled additions of lanthanum can also be used to form various levels of lattice oxide or anion vacancies. In previous transmission electron microscopy (TEM) experimental studies, the growth rate of dislocation loops in irradiated lanthanum doped ceria was reported to vary with lanthanum concentration. This work reports findings of the evolution mechanisms of the dislocation loops in cerium oxide with and without lanthanum dopants based on a combination of molecular statics and molecular dynamics simulations. These dislocation loops are found to be b=1/3<111> interstitial type Frank loops. Calculations of the defect energy profiles of the dislocation loops with different structural configurations and radii reveal the basis for preference of nucleation as well as the driving force of growth. Frenkel pair evolution simulations and displacement cascade overlaps simulations were conducted for a variety of lanthanum doping conditions. The nucleation and growth processes of the Frank loop were found to be controlled by the mobility of cation interstitials, which is significantly influenced by the lanthanum doping concentration. Competition mechanisms coupled with the mobility of cation point defects were discovered, and can be used to explain the lanthanum effects observed in experiments.

Miao, Yinbin; Aidhy, Dilpuneet; Chen, Wei-Ying; Mo, Kun; Oaks, Aaron; Wolf, Dieter; Stubbins, James F.

2014-02-01

30

Lanthanum  

MedlinePLUS

... or any of the ingredients in lanthanum chewable tablets. Ask your pharmacist for a list of the ingredients.tell your doctor and pharmacist what prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take. ...

31

Structural and optical study of samarium doped lead zinc phosphate glasses  

NASA Astrophysics Data System (ADS)

Samarium doped lead-zinc-phosphate glasses with composition (60-x)P2O5-20PbO-20ZnO-xSm2O3 (x=0, 0.5, 1.0, 3.0 mol%) were prepared by melt quenching technique. Density, refractive index and polaron radius of Sm3+ ions were calculated. The IR spectra reveal significant structural changes only for high concentration of samarium ions. Differential thermal analysis confirms the large structural changes in the glass due to the decrease of thermal stablility in presence of 3 mol% Sm3+ ions. UV-vis-NIR absorption spectroscopy was carried out and Judd-Ofelt analysis was performed. Radiative rates, branching ratio and lifetime of 4G5/2 were calculated by taking into account both electric and magnetic dipole contributions. Absorption spectra consist of seven absorption peaks corresponding to the transitions from the 6H5/2 ground state to various excited energy levels. Photoluminescence spectra show four prominent emission bands centered at 560, 597, 642 and 700 nm corresponding to the 4G5/2-6HJ (J=5/2, 7/2, 9/2, and 11/2) transitions respectively and the intensities of all bands are enhanced by Sm3+ ions content. The calculated values are compared to other reports, available in literature.

Dousti, M. Reza; Ghoshal, S. K.; Amjad, Raja J.; Sahar, M. R.; Nawaz, Fakhra; Arifin, R.

2013-07-01

32

Liquid-phase-assisted sintering of calcium-doped lanthanum chromites  

Microsoft Academic Search

Investigations have been made on the low-temperature sinterability of calcium-doped lanthanum chromites which are to be used as interconnectors in solid oxide fuel cells (SOFCs). Nominally chromium deficient lanthanum calcium chromites (La[sub 0.7]Ca[sub 0.3]Cr[sub 1[minus]y]O[sub 3], y = 0.02) were found to be sinterable to 94% theoretical density at 1573 K in air, whereas no densification was observed for samples

Natsuko Sakai; Tatsuya Kawada; Harumi Yokokawa; Masayuki Dokiya; Isao Kojima

1993-01-01

33

Mechanical properties of magnesia-doped lanthanum chromite versus temperature  

SciTech Connect

Magnesia-doped lanthanum chromite is a potential material for use in solid oxide fuel cells as an interconnector due to its resistance to oxidation and reduction. The strength and toughness of La(Cr{sub 0.9}Mg{sub 0.1})O{sub 3} were measured from 25 to 1,000 C in the as-fired reduced state and after oxidation. The as-fired samples showed a peak in toughness of approximately 3.9 MPa{center_dot}m{sup 1/2} at 125 C which decreased to approximately 1.4 MPa{center_dot}m{sup 1/2} at 600 C and 2.8 MPa{center_dot}m{sup 1/2} at room temperature. This peak in toughness is hypothesized to be due to the rhombohedral-to-orthorhombic phase transition by a toughening mechanism that is currently being investigated. The strength was also affected by the phase transition for both the as-fired reduced and the oxidized samples.

Montross, C.S.; Yokokawa, Harumi; Dokiya, Masayuki [National Institute for Materials and Chemical Research, Tsukuba, Ibaraki (Japan); Bekessy, L. [Univ. of Queensland, Brisbane (Australia). Dept. of Mining and Metallurgy

1995-07-01

34

Enhancement of ferromagnetic and dielectric properties of lanthanum doped bismuth ferrite nanostructures  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer Rod shaped lanthanum doped bismuth ferrite was obtained. Black-Right-Pointing-Pointer The diameter of the particles were found to be decreasing on doping with lanthanum. Black-Right-Pointing-Pointer Both ferromagnetic and dielectric properties enhanced. Black-Right-Pointing-Pointer A transition due to spin canting is observed near 550 Degree-Sign C. Black-Right-Pointing-Pointer Electron spin resonance study shows the breakage of spin cycloid due to doping. -- Abstract: Cylindrical-shaped multiferroic Bi{sub 1-x}La{sub x}FeO{sub 3} (x = 0.0, 0.05, 0.1 and 0.15) were synthesized successfully by hydrothermal method. All samples were found to be rhombohedrally distorted perovskite structure. Diameter of the cylindrical particles reduces from {approx}450 nm for x = 0.0 to {approx}100 nm for x = 0.1 prepared under the same conditions. The Neel temperature as well as the dielectric constant was also found to increase with the increase in lanthanum content. Lanthanum doping also enhanced the magnetic properties. Magnetization measurements above room temperature show a significant increase in magnetization at around 400 Degree-Sign C. Enhanced magnetic properties due to lanthanum doping are caused by the breakage of spin cycloid as observed by electron spin resonance study.

Chaudhuri, A., E-mail: arka@bose.res.in [Magnetism Laboratory, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700 098 (India); Mandal, K. [Magnetism Laboratory, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700 098 (India)] [Magnetism Laboratory, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700 098 (India)

2012-04-15

35

Structural studies of lithium boro tellurite glasses doped with praseodymium and samarium oxides  

SciTech Connect

Graphical abstract: [TeO{sub 4}] trigonal bipyramid structural unit, which is formed by two unequivalent pair of oxygen atoms: two equatorial oxygens (O{sub eq}) and two axial oxygens (O{sub ax}). Highlights: ? Pr{sup 3+} and Sm{sup 3+} doped LBT glasses have been prepared and characterized. ? LBT glasses present normal surfaces without metallic clusters. ? Raman spectra revealed the network modifying behaviour of dopant ions. -- Abstract: This paper reports the preparation and structural studies of praseodymium and samarium (0.5, 2 and 4 mol%) oxide doped lithium boro tellurite glasses. These materials were prepared by the quenching technique in a ceramic crucible at 950 C. Structural characterization was performed by Raman spectroscopy, Scanning Electron Microscopy and Energy Dispersive X-ray spectroscopy techniques. Results from Raman analysis are in good agreement with those reported in the literature, revealing a normal glass structure for the host material. Understanding on how the glasses internal structure changed when the doping concentration increases was also assessed.

Damas, Pedro [Departamento de Fsica, Faculdade de Cincias, Universidade do Porto, Rua do Campo Alegre, 687, 4169-007 Porto (Portugal)] [Departamento de Fsica, Faculdade de Cincias, Universidade do Porto, Rua do Campo Alegre, 687, 4169-007 Porto (Portugal); Coelho, Joo [INESC Porto, Rua do Campo Alegre, 687, 4169-007 Porto (Portugal)] [INESC Porto, Rua do Campo Alegre, 687, 4169-007 Porto (Portugal); Hungerford, Graham [HORIBA Jobin Yvon IBH Ltd., Skypark 5, 45 Finnieston Street, Glasgow G3 8JU (United Kingdom)] [HORIBA Jobin Yvon IBH Ltd., Skypark 5, 45 Finnieston Street, Glasgow G3 8JU (United Kingdom); Hussain, N. Sooraj, E-mail: nandyala.sooraj@fc.up.pt [Departamento de Fsica, Faculdade de Cincias, Universidade do Porto, Rua do Campo Alegre, 687, 4169-007 Porto (Portugal); INESC Porto, Rua do Campo Alegre, 687, 4169-007 Porto (Portugal)

2012-11-15

36

Samarium doped calcium fluoride: A red scintillator and X-ray phosphor  

NASA Astrophysics Data System (ADS)

We report the photoluminescence, X-ray luminescence and scintillation properties of CaF2:Sm2+. Large single crystals of CaF2:Sm2+ were grown by simply slow cooling of the calcium fluorite melt doped with samarium metal. The photoluminescence at room temperature shows a broad red 5d?4f emission band peaked at 725 nm which is well matched to the response of silicon photodetectors, and only a very weak Sm3+ emission is observed. On cooling, the zero phonon lines of the Sm2+ emission can be observed. The lifetime of the broad emission is short at room temperature (46 ns), but temperature dependent, and slows on cooling, reaching a constant value of 1.25 ?s below 180 K. The X-ray luminescence comprises both red Sm2+ and Sm3+ emissions and a blue self-trapped exciton band for low Sm concentrations, but just the broad red emission Sm2+ for highly doped (~1%) samples. The scintillation decay at room temperature shows two components, of 58 ns and 870 ns, in an integrated intensity ratio of 0.7:1 for a 0.1% Sm sample. The light output is around 15,000 photons/MeV when cooled by dry ice, with a scintillation decay time of 1.4 ?s at that temperature. The performance of the material as an X-ray phosphor and scintillator is discussed.

Dixie, Laura Catherine; Edgar, Andrew; Bartle, Colin Murray

2014-07-01

37

Controlled size and morphology of EDTMP-doped hydroxyapatite nanoparticles as model for 153Samarium-EDTMP doping.  

PubMed

Hydroxyapatite (HA) nanoparticles have been studied as nano-sized carriers for the delivery of therapeutic agents. One important consideration for these carriers to be used effectively is their bio-distribution in vivo, of which particle size has a significant effect. In this work, HA nanoparticles doped with Ethylene-diamine-tetramethylene-phosphonate (EDTMP) were synthesized via co-precipitation as a model for HA doped with (153)Samarium ((153)Sm) EDTMP. EDTMP has high affinity for radioactive (153)Sm isotopes that can emit both gamma and beta radiation. The effects of synthesis temperature, amount of dopant and hydrothermal treatment on the size of HA-EDTMP nanoparticles were therefore studied. The results showed that the EDTMP ligand was successfully incorporated in the nanoparticles without changing the crystal structure as shown from X-ray diffractometer (XRD) analysis. From the Field Emission Scanning Electron Microscopy (FESEM) and Transmission Electron Microscopy (TEM) micrographs, it was observed that shorter rod-like nanoparticles, obtained at low synthesis temperatures, became elongated needle-like nanoparticles with increasing temperature. Increasing dopant amount by five fold increases particle size slightly, while a two fold increase in dopant amount has no significant effect. Hydrothermal treatment increases particle crystallinity and results in smooth elongated rod-like structures. The size of HA nanoparticles doped with EDTMP can therefore be manipulated by controlling synthesis temperature and through hydrothermal treatment. PMID:18360794

Han, Yuling Jamie; Loo, Say Chye Joachim; Phung, Ngoc Thao; Ong, Hooi Tin; Russell, Stephen J; Peng, Kah-Whye; Boey, Freddy; Ma, Jan

2008-09-01

38

Tape casting and sintering of strontium-doped lanthanum chromite for a planar solid oxide fuel cell bipolar plate  

Microsoft Academic Search

Nonagglomerated strontium-doped lanthanum chromite powders were prepared by a modified Pechini resinintermediate process and tape cast to form bipolar plates for a planar solid oxide fuel cell. An air-sintering technique for the strontium-doped lanthanum chromite was developed, which involved placing the green tape between CrO-fired plates. The sintering process was found to be diffusion controlled, with densification beginning at the

Lone-Wen Tai; Paul A. Lessing

1991-01-01

39

Mechanisms of enhanced sulfur tolerance on samarium (Sm)-doped cerium oxide (CeO2) from first principles.  

PubMed

The role of samarium (Sm) 4f states and Sm-perturbed O 2p states in determining the sulfur tolerance of Sm-doped CeO2 was elucidated by using the density functional theory (DFT) + U calculation. We find that the sulfur tolerance of Sm-doped CeO2 is closely related to the modification of O 2p states by the strong interaction between Sm 4f and O 2p states. In particular, the availability of unoccupied O 2p states near the Fermi level is responsible for enhancing the sulfur tolerance of Sm-doped CeO2 compared to the pure CeO2 by increasing the activity of the surface lattice oxygen toward sulfur adsorption, by weakening the interaction between Sm-O, and by increasing the migration tendency of the subsurface oxygen ion toward the surface. PMID:24756238

Lim, Dong-Hee; Kim, Hee Su; Yoon, Sung Pil; Han, Jonghee; Yoon, Chang Won; Choi, Sun Hee; Nam, Suk Woo; Ham, Hyung Chul

2014-05-14

40

A high-performance ceramic fuel cell with samarium doped ceriacarbonate composite electrolyte at low temperatures  

Microsoft Academic Search

An anode-supported ceramic fuel cell with samarium doped ceria (SDC)carbonate (Li2CO3Na2CO3) composite electrolyte was fabricated by a hot-press technique and tested at 450600C. NiO and lithiated NiO were used as the anode and cathode, respectively, with an effective electrode area of 3.14cm2. An open-circuit voltage (OCV) of 1.04V and a current density of 0.70A\\/cm2 at 0.6V was achieved with dry

Jianbing Huang; Lizhai Yang; Ruifeng Gao; Zongqiang Mao; Cheng Wang

2006-01-01

41

Thermoluminescent dosimetric characteristics of irradiated ternary alkali halides doped with lanthanum  

NASA Astrophysics Data System (ADS)

In the present study thermoluminesce properties of Lanthanum doped KCl0.2NaClxNaBr0.8-x ternary crystals with ? - irradiation has been carried out. The crystals were grown by slow evaporation and doped with rare earth Lanthanum ion. The grown crystals were irradiated with ? - radiation for dosages of 25 kGy, 50 kGy and 100 kGy. The results show that TL intensity as well as the peak position of the glow curves change with time of exposure. In few compositions, there is no change in intensity with time whereas; in few other compositions there is a small fading of intensity with time. Study reveals that these crystals have high capacity to store optical energy.

Maruthi, G.; Chandramani, R.

2013-02-01

42

Cr(3+)-Doped Lanthanum Gallogermanate Phosphors with Long Persistent IR Emission  

Microsoft Academic Search

Lanthanum gallogermanate co-doped with chromium (LaGaGeO:Cr{sup 3+}, M, where M = Li, Pb{sup 2+}, Zn{sup 2+}, Eu{sup 3+}, Tm{sup 3+}, and Dy{sup 3+}) samples have been prepared using a solid-state chemical reaction method. The phosphor with Dy{sup 3+} is observed to have a persistent IR emission for more than 8 h, which is recorded using a spectrometer. The wavelength of

George D Jia; Linda A Lewis; Xiao-jun Wang

2010-01-01

43

Phase Stability Analysis of Lanthanum-Doped Alumina During Synthesis and Sintering  

Microsoft Academic Search

The aim of this research was to study the phase stability during synthesis and consolidation of nanocrystalline lanthanum-doped gamma-Al2O 3 powders. We used solution combustion synthesis by dissolving precursor nitrate compounds and an organic fuel in a pre-heated muffle furnace at 500C. Several preliminary syntheses were carried out in order to obtain the correct fuel-to-oxidizer ratio necessary for the production

Lum-Ngwegia Ngwa Nforbi

2010-01-01

44

Electrical conductivity and chemical diffusion coefficient of Sr-doped lanthanum chromites  

Microsoft Academic Search

The electrical conductivity and chemical diffusion coefficient of Sr-doped lanthanum chromites were measured as a function of oxygen partial pressure (Po2) and temperature, and the results were discussed in light of defect chemistry. The electrical conductivity was independent of Po2 and in proportion to the Sr-content at high Po2, while at low Po2, the conductivity decreased exponentially with decrease of

I. Yasuda; M. Hishinuma

1995-01-01

45

Cr(3+)-Doped Lanthanum Gallogermanate Phosphors with Long Persistent IR Emission  

SciTech Connect

Lanthanum gallogermanate co-doped with chromium (La3Ga5GeO14:Cr3+,M, where M=Li, Pb2+, Zn2+, Eu3+, Tm3+, and Dy3+) samples have been prepared using a solid-state chemical reaction method. The phosphor with Dy3+ is observed to have a persistent IR emission for more than 8 h, which is recorded using a spectrometer. The wavelength of the major IR emission is in the range from 700 to 1100 nm. The intensity of the phosphorescence and persistent time can be modified by co-doping proper trapping centers.

Jia, George D [ORNL; Lewis, Linda A [ORNL; Wang, Xiao-jun [Georgia Southern University

2010-01-01

46

Cobalt doped lanthanum chromite material suitable for high temperature use  

DOEpatents

A high temperature, solid electrolyte electrochemical cell, subject to thermal cycling temperatures of between about 25.degree. C. and about 1200.degree. C., capable of electronic interconnection to at least one other electrochemical cell and capable of operating in an environment containing oxygen and a fuel, is made; where the cell has a first and second electrode with solid electrolyte between them, where an improved interconnect material is applied along a portion of a supporting electrode; where the interconnect is made of a chemically modified lanthanum chromite, containing cobalt as the important additive, which interconnect allows for adjustment of the thermal expansion of the interconnect material to more nearly match that of other cell components, such as zirconia electrolyte, and is stable in oxygen containing atmospheres such as air and in fuel environments.

Ruka, Roswell J. (Churchill, PA)

1986-01-01

47

Effect of a-site cation deficiency and YSZ additions on sintering and properties of doped lanthanum manganite  

SciTech Connect

The sintering behavior of Ca- and Sr-doped lanthanum manganite (the preferred SOFC cathode material) is highly dependent on the relative proportion of A and B site cations in the material. In general, A-site cation deficiency increases sintered density. The effect of additions of YSZ to lanthanum manganite (to expand the reactive region at the cathode/electrolyte interface and improve thermal expansion and sintering shrinkage matches) on sintering and other properties will also be reported.

Stevenson, J.W.; Armstrong, T.R.; Weber, W.J.

1995-06-01

48

Materials system for intermediate temperature solid oxide fuel cells based on doped lanthanum-gallate electrolyte  

NASA Astrophysics Data System (ADS)

The objective of this work was to identify a materials system for intermediate temperature solid oxide fuel cells (IT-SOFCs). Towards this goal, alternating current complex impedance spectroscopy was employed as a tool to study electrode polarization effects in symmetrical cells employing strontium and magnesium doped lanthanum gallate (LSGM) electrolyte. Several cathode materials were investigated including strontium doped lanthanum manganite (LSM), Strontium and iron doped lanthanum cobaltate (LSCF), LSM-LSGM, and LSCF-LSGM composites. Investigated Anode materials included nickel-gadolinium or lanthanum doped cerium oxide (Ni-GDC, or Ni-LDC) composites. The ohmic and the polarization resistances of the symmetrical cells were obtained as a function of temperature, time, thickness, and the composition of the electrodes. Based on these studies, the single phase LSM electrode had the highest polarization resistance among the cathode materials. The mixed-conducting LSCF electrode had polarization resistance orders of magnitude lower than that of the LSM-LSGM composite electrodes. Although incorporating LSGM in the LSCF electrode did not reduce the cell polarization resistance significantly, it could reduce the thermal expansion coefficient mismatch between the LSCF electrodes and LSGM electrolyte. Moreover, the polarization resistance of the LSCF electrode decreased asymptotically as the electrode thickness was increased thus suggesting that the electrode thickness needed not be thicker than this asymptotic limit. On the anode side of the IT-SOFC, Ni reacted with LSGM electrolyte, and lanthanum diffusion occurred from the LSGM electrolyte to the GDC barrier layer, which was between the LSGM electrolyte and the Ni-composite anode. However, LDC served as an effective barrier layer. Ni-LDC (70 v% Ni) anode had the largest polarization resistance, while all other anode materials, i.e. Ni-LDC (50 v% Ni), Ni-GDC (70 v% NO, and Ni-GDC (50 v% Ni), had similar polarization resistances. Ni-LDC (50 v% NO was selected to be the anode for the LSGM electrolyte with a thin LDC barrier layer. Finally, the performance of complete LSGM electrolyte-supported IT-SOFCs with the selected cathode (LSCF-LSGM) and anode (Ni-LDC) materials coupled with the LDC barrier layer was evaluated at 600--800C. The simulated cell performance of the anode-supported cell based on LSGM electrolyte was promising.

Gong, Wenquan

49

Crystal structure and physicochemical properties of doped lanthanum manganites  

NASA Astrophysics Data System (ADS)

Substituted lanthanum-strontium manganites La0.7Sr0.3Mn0.9Me0.1O3 ? (Me = Ti, Cr, Fe, and Cu) are obtained by standard ceramic and glycerin-nitrate techniques. High-temperature powder X-ray diffraction is employed to study the crystal structure of La0.7Sr0.3Mn0.9Me0.1O3 ? oxides. It is shown that in the range 298-1023 K in air, La0.7Sr0.3Mn0.9Me0.103 ? manganites crystallized in an orthorhombic cell (space group R-3c). The isobaric temperature dependences of unit cell parameters are determined. Thermal expansion coefficients are calculated for La0.7Sr0.3Mn0.9Me0.103 ? oxides. The conductivity of La0.7Sr0.3Mn0.9Me0.103 ? is studied as a function of temperature in the range 500 K ? T ? 1200 K in air. It is shown that substituting 3 d metal for manganese considerably lowers the conductivity of basic La0.7Sr0.3Mn0.9O3 ?. The chemical stability of iron-substituted manganite La0.7Sr0.3Mn0.9Fe0.1O3 ? is studied with respect to the electrolyte material.

Aksenova, T. V.; Gavrilova, L. Ya.; Cherepanov, V. A.

2012-12-01

50

Sintering and Property Characterization of Strontium-Doped Lanthanum Chromite  

SciTech Connect

The sintering of La0.85Sr0.15CrO3 (LSC-15) SOFC interconnect material can be significantly enhanced by doping with transition elements, such as Cu, Co, V and Ni, on the chromium B-site. Optimized compositions yielded densities greater than 93% theoretical after sintering at 1550?C for 2 hours, compared to <70% theoretical for un-doped stoichiometric LSC-15. Detailed XRD and DTA was used in an attempt to establish phenomena responsible for sintering, in particular the presence of low melting temperature second phases. High density materials were also evaluated for thermal expansion and electrical conductivity in air.

Simner, Steven P.; Hardy, John S.; Stevenson, Jeffry W.; Armstrong, Timothy R.

1999-08-01

51

Synthesis of Sm{sup 3+}-doped strontium barium niobate crystals in glass by samarium atom heat processing  

SciTech Connect

New glasses giving the crystallization of Sm{sup 3+}-doped Sr {sub x} Ba{sub 1-} {sub x} Nb{sub 2}O{sub 6} (SBN) ferroelectrics have been developed in the Sm{sub 2}O{sub 3}-SrO-BaO-Nb{sub 2}O{sub 5}-B{sub 2}O{sub 3} system, and the formation of SBN crystal dots and lines by continuous wave Nd:YAG laser (wavelength:1064 nm, power: 1 W) irradiations, i.e., samarium atom heat processing, has been examined. The formation of Sm{sup 3+}-doped SBN non-linear optical crystals is confirmed from X-ray diffraction analyses, micro-Raman scattering spectra, second harmonic generations, and photoluminescence spectra. Sm{sup 3+}-doped SBN crystal dots with the diameters of 20-70 {mu}m and lines with the widths of 20-40 {mu}m are written at the surface of some glasses such as 10Sm{sub 2}O{sub 3}.10SrO.10BaO.20Nb{sub 2}O{sub 5}.50B{sub 2}O{sub 3} (mol%) by Nd:YAG laser irradiations with the irradiation times of 20-70 s for the dots and with the scanning speeds of 1-5 {mu}m/s for the lines. The present study suggests that the samarium atom heat processing has a potential for the patterning of optical waveguides consisting of ferroelectric SBN crystals in glass substrates.

Chayapiwut, Nakorn [Department of Chemistry, Nagaoka University of Technology, 1603-1 Kamitomioka-cho, Nagaoka 940-2188 (Japan); Honma, Tsuyoshi [Department of Chemistry, Nagaoka University of Technology, 1603-1 Kamitomioka-cho, Nagaoka 940-2188 (Japan); Benino, Yasuhiko [Department of Chemistry, Nagaoka University of Technology, 1603-1 Kamitomioka-cho, Nagaoka 940-2188 (Japan); Fujiwara, Takumi [Department of Chemistry, Nagaoka University of Technology, 1603-1 Kamitomioka-cho, Nagaoka 940-2188 (Japan); Komatsu, Takayuki [Department of Chemistry, Nagaoka University of Technology, 1603-1 Kamitomioka-cho, Nagaoka 940-2188 (Japan)]. E-mail: komatsu@chem.nagaokaut.ac.jp

2005-11-15

52

Tape casting and sintering of strontium-doped lanthanum chromite for a planar solid oxide fuel cell bipolar plate  

SciTech Connect

Nonagglomerated strontium-doped lanthanum chromite powders were prepared by a modified Pechini resinintermediate process and tape cast to form bipolar plates for a planar solid oxide fuel cell. An air-sintering technique for the strontium-doped lanthanum chromite was developed, which involved placing the green tape between Cr{sub 2}O{sub 3}-fired plates. The sintering process was found to be diffusion controlled, with densification beginning at the surface and proceeding to the interior. A bipolar plate of 2-mm thickness was fired to more than 9.3.5% theoretical density when fired at 1670{degrees}C for 7 h.

Tai, L.W.; Lessing, P.A. (New Mexico Inst. of Mining and Technology, Socorro, NM (US))

1991-01-01

53

Effect of structure on the electronic density of states of doped lanthanum cuprate  

SciTech Connect

We present a series of detailed band calculations on the various structural phases of doped lanthanum cuprate: HTT, LTO, and LTT. The LTO distortion is shown to have little effect on the electronic density of states (DOS). A fit to the pressure dependence of the superconducting transition temperature indicates that only 2.5% of the DOS is affected by the HTT[r arrow]LTO transition. The LTT distortion also has little effect on the DOS for the experimental value of the octahedral tilt angle. Larger tilt angles, though, lead to a dramatic change in the DOS.

Norman, M.R. (Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States)); McMullan, G.J. (Cavendish Laboratory, Madingley Road, Cambridge CB3 OHE (United Kingdom)); Novikov, D.L.; Freeman, A.J. (Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208 (United States))

1993-10-01

54

Fine particles of lanthanum-and cobalt-doped strontium hexaferrite prepared through glass crystallization  

Microsoft Academic Search

Glass of nominal composition Sr0.6La0.4Fe11.6Co0.4O19 + 12SrB2O4 was prepared by rapidly quenching an oxide melt and was then heat-treated at temperatures from 550 to 900C to give glass-ceramics\\u000a containing fine lanthanum-and cobalt-doped strontium hexaferrite particles and microcrystalline SrB2O4. The materials were characterized by x-ray diffraction, scanning electron microscopy, electron probe x-ray microanalysis,\\u000a and magnetic measurements. The coercivity of the glass-ceramic

E. A. Gravchikova; D. D. Zaitsev; P. E. Kazin; M. V. Popov; Yu. D. Tretyakov; M. Jansen

2006-01-01

55

Anomaly diffuse and dielectric relaxation in strontium doped lanthanum molybdate  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer The anomaly diffuse and dielectric relaxation behaviors are fitted by the Cole-Cole approach. Black-Right-Pointing-Pointer The peak in the LSMO is corresponding to different oxygen ion diffusion process. Black-Right-Pointing-Pointer We first give better explanation about the strange conductivity change caused by doping. Black-Right-Pointing-Pointer The oxygen ion diffusion is due to a combination of the dipolar relaxation and the motion of ions. -- Abstract: The dielectric properties of the La{sub 2-x}Sr{sub x}Mo{sub 2}O{sub 9-{delta}} (x = 0-0.2) ceramics were investigated in the temperature range of 300-800 K. Dielectric measurement reveals that two dielectric anomalies, associated with the oxygen ion diffusion, exist in frequency spectrum with x = 0.5. The broad dielectric peaks in tan {delta}({omega}) can be well fitted by a modified Cole-Cole approach. When x = 0.1, only one dielectric relaxation peak is observed, corresponding to different oxygen ion diffusion processes, as distinct from the only relaxation peak in the pure La{sub 2}Mo{sub 2}O{sub 9}. The relaxation parameters {tau}{sub 0}, the dielectric relaxation strength {Delta}, and the activation energy E{sub a} were obtained. The result of this work shows that, the conductivity change caused by doping between the two phases is due to the combination of the dipolar effects and motion of ions.

Liu, Xiao [State Key Laboratory of Solidification Processing, School of Materials Science and Engineering, Northwestern Polytechnical University, Xi'an 710072 (China)] [State Key Laboratory of Solidification Processing, School of Materials Science and Engineering, Northwestern Polytechnical University, Xi'an 710072 (China); Fan, Huiqing, E-mail: hqfan3@163.com [State Key Laboratory of Solidification Processing, School of Materials Science and Engineering, Northwestern Polytechnical University, Xi'an 710072 (China)] [State Key Laboratory of Solidification Processing, School of Materials Science and Engineering, Northwestern Polytechnical University, Xi'an 710072 (China); Shi, Jing [State Key Laboratory of Solidification Processing, School of Materials Science and Engineering, Northwestern Polytechnical University, Xi'an 710072 (China)] [State Key Laboratory of Solidification Processing, School of Materials Science and Engineering, Northwestern Polytechnical University, Xi'an 710072 (China)

2011-12-15

56

Thermopower studies of rare earth doped lanthanum barium manganites  

NASA Astrophysics Data System (ADS)

Influence of rare earth doping on electrical, magnetic and thermopower studies of La0.34Re0.33Ba0.33MnO3 compound was investigated. Ferro to paramagnetic transition and metal to insulator transition temperatures decrease with decreasing ionic radius of the dopant ion. Electrical resistivity in the entire temperature range is explained by phase separation model. The magnitude of Seebeck coefficient increases with increasing dopant ionic radius. A cross over from negative to positive sign has also been observed in thermopower data with decreasing A site ionic radius (). The low temperature thermopower data has been explained using a qualitative model containing diffusion; magnon drag and phonon drag effects while the paramagnetic insulating part has been analyzed using small polaron hopping mechanism.

Reddy, G. Lalitha; Lakshmi, Y. Kalyana; kumar, N. Pavan; Rao, S. Manjunath; Reddy, P. Venugopal

2014-08-01

57

Intrinsic Mobility Limiting Mechanisms in Lanthanum-Doped Strontium Titanate  

NASA Astrophysics Data System (ADS)

The temperature dependent Hall mobility data from La-doped SrTiO3 thin films are analyzed and modeled considering various electron scattering mechanisms. We find that a 6 meV transverse optical phonon deformation potential scattering mechanism is necessary to explain the dependence of transport on temperature between 10-200 K. Also, we find that the low temperature electron mobility in intrinsic (nominally undoped) SrTiO3 is limited by acoustic phonon scattering. Adding the above two scattering mechanisms to longitudinal optical phonon and ionized impurity scattering mechanisms, excellent quantitative agreement between mobility measurement and model is achieved in the whole temperature range (2-300 K) and carrier concentrations ranging over a few orders of magnitude (81017 -21020 cm-3).

Verma, Amit; Kajdos, Adam P.; Cain, Tyler A.; Stemmer, Susanne; Jena, Debdeep

2014-05-01

58

Heterogeneous photocatalytic decomposition of benzene on lanthanum-doped TiO2 film at ambient temperature.  

PubMed

Lanthanum-doped anatase TiO2 thin films on glass prepared via a sol-gel process have been shown to have much higher photocatalytic activity for the degradation of gaseous benzene than pure anatase TiO2 thin film. The photodecomposition of benzene on both types of TiO2 films follows the first-order kinetics while the CO(2) and CO formation followed the zero-order kinetics. GC/MS identification of the intermediates produced during the photodegradation of benzene revealed that doping lanthanum into TiO2 thin film favors a cleavage of benzene ring. An optimal lanthanum amount with respect to photocatalytic activity was about 2.5 wt% (La2O3/TiO2). PMID:16814365

Zhang, Shicheng; Zheng, Zhijian; Wang, Jinhe; Chen, Jianmin

2006-12-01

59

Preparation, Characterization and Photocatalytic Activity of Lanthanum Doped Mesoporous Titanium Dioxide  

NASA Astrophysics Data System (ADS)

Lanthanum doped mesoporous titanium dioxide photocatalysts with different La content were synthesized by template method using tetrabutyltitanate (Ti(OC4H9)4) as precursor and Pluronic P123 as template. The catalysts were characterized by thermogravimetric differential thermal analysis, N2 adsorption-desorption measurements, X-ray diffraction, and UV-Vis adsorption spectroscopy. The effect of La3+ doping concentration from 0.1% to 1% on the photocatalytic activity of mesoporous TiO2 was investigated. The characterizations indicated that the photocatalysts possessed a homogeneous pore diameter of about 10 nm with high surface area of 165 m2/g. X-ray photoelectron spectroscopy measurements indicated the presence of C in the doped samples in addition to La. Compared with pure mesoporous TiO2, the La-doped samples extended the photoabsorption edge into the visible light region. The results of phenol photodecomposition showed that La-doped mesoporous TiO2 exhibited higher photocatalytic activities than pure mesoporous TiO2 under UV and visible light irradiation.

Shi, Zhong-liang; Lai, Hong; Yao, Shu-hua; Wang, Shao-feng

2012-02-01

60

Optical and magnetic properties of zinc oxide quantum dots doped with cobalt and lanthanum.  

PubMed

Cobalt and Lanthanum-doped ZnO QDs are synthesized by a modified sol-gel method under atmospheric conditions. The as-prepared quantum dots are characterized by X-ray powder diffraction (XRD), energy dispersive X-ray (EDX) analysis and high resolution transmission electron microscopy (HRTEM). The optical properties of the products are studied by fluorescent spectroscopy. With a proper Co and La doping, these nanoparticles possess exceptionally small size and enhanced fluorescence. Hysteresis loops of un-doped ZnO QDs and Co and La-doped ZnO QDs indicate that both the samples show ferromagnetic behavior at room temperature. Finally, these nanoparticles can label the BGC 803 cells successfully in short time and present no evidence of toxicity or adverse affect on cell growth even at the concentration up to 1 mM. We expect that the as-prepared Co and La-doped ZnO QDs can provide a better reliability of the collected data and find promising applications in biological, medical and other fields. PMID:23862449

Yu, Shiyong; Zhao, Jing; Su, Hai-Quan

2013-06-01

61

Synthesis and characterization of highly-active nickel and lanthanum co-doped SrTiO 3  

Microsoft Academic Search

A series of highly-active nickel and lanthanum co-doped SrTiO3 photocatalysts were synthesized via solgel process and their photocatalytic activities were evaluated by degradation of methylene blue (MB). The obtained samples were found by XRD, XPS and UVvis to have a perovskite structure in which Ni and La atoms were incorporated into SrTiO3. After Ni and La doped into SrTiO3, the

Aizhong Jia; Zhiqian Su; Lan-Lan Lou; Shuangxi Liu

2010-01-01

62

X-Ray Diffraction, FTIR, and NMR Characterization of SolGel Alumina Doped with Lanthanum and Cerium  

Microsoft Academic Search

Alumina doped with La and Ce was prepared by using the solgel technique. The doping concentrations were alternatively 2 and 5 wt% for each element. Samples were characterized as a function of temperature by using X-ray powder diffraction and FTIR spectroscopy. MAS-NMR studies showed that lanthanum and cerium interacted with alumina and produced a compound with aluminum ions in tetrahedral

A. Vazquez; T. Lpez; R. Gmez; Bokhimi; A. Morales; O. Novaro

1997-01-01

63

Sintering and thermal expansion characterization of Al-doped and Co-doped lanthanum strontium chromites synthesized by the Pechini method  

Microsoft Academic Search

The air-sintering and thermal expansion characteristics of Al-doped and Co-doped lanthanum strontium chromites synthesized by the Pechini method have been discussed as interconnect materials in high-temperature solid oxide fuel cells (SOFC). Fine perovskite powders with an average particle size of 0.24 ?m, and with a surface area of 3.5 m2\\/g, calcined at 800 C for 1 h, were obtained. After

Masashi Mori; Nigel M Sammes

2002-01-01

64

Synthesis of hexagonal lanthanum germanate apatites through site selective isovalent doping with yttrium  

SciTech Connect

Apatite-type lanthanum silicates/germanates have been attracting considerable interest as a new class of oxide ion conductors, whose conductivity is mediated by oxide ion interstitials. For the germanates, it has been shown that, depending on composition, the cell can be either hexagonal or triclinic, with evidence for reduced low-temperature conductivities for the latter, attributed to increased defect trapping in this lower symmetry cell. In this paper we show that site selective doping of Y into the triclinic apatite-type oxide ion conductors, La{sub 9.33+z}(GeO{sub 4}){sub 6}O{sub 2+3z/2} (0.33 {<=} z {<=} 0.67) results in a hexagonal lattice for the complete series with correspondingly enhanced low-temperature conductivity.

Kendrick, E. [Chemistry, University of Surrey, Guildford, Surrey GU2 7XH (United Kingdom); Slater, P.R. [Chemistry, University of Surrey, Guildford, Surrey GU2 7XH (United Kingdom)], E-mail: p.slater@surrey.ac.uk

2008-08-04

65

Bismuth doped lanthanum ferrite perovskites as novel cathodes for intermediate-temperature solid oxide fuel cells.  

PubMed

Bismuth is doped to lanthanum strontium ferrite to produce ferrite-based perovskites with a composition of La0.8-xBixSr0.2FeO3-? (0 ? x ? 0.8) as novel cathode material for intermediate-temperature solid oxide fuel cells. The perovskite properties including oxygen nonstoichiometry coefficient (?), average valence of Fe, sinterability, thermal expansion coefficient, electrical conductivity (?), oxygen chemical surface exchange coefficient (Kchem), and chemical diffusion coefficient (Dchem) are explored as a function of bismuth content. While ? decreases with x due to the reduced Fe(4+) content, Dchem and Kchem increase since the oxygen vacancy concentration is increased by Bi doping. Consequently, the electrochemical performance is substantially improved and the interfacial polarization resistance is reduced from 1.0 to 0.10 ? cm(2) at 700 C with Bi doping. The perovskite with x = 0.4 is suggested as the most promising composition as solid oxide fuel cell cathode material since it has demonstrated high electrical conductivity and low interfacial polarization resistance. PMID:24971668

Li, Mei; Wang, Yao; Wang, Yunlong; Chen, Fanglin; Xia, Changrong

2014-07-23

66

X-ray diffraction, FTIR, and NMR characterization of sol-gel alumina doped with lanthanum and cerium  

SciTech Connect

Alumina doped with La and Ce was prepared by using the sol-gel technique. The doping concentrations were alternatively 2 and 5 wt% for each element. Samples were characterized as a function of temperature by using X-ray powder diffraction and FTIR spectroscopy. MAS-NMR studies showed that lanthanum and cerium interacted with alumina and produced a compound with aluminum ions in tetrahedral symmetry. These interactions stabilized alumina structure and shifted its transformations to higher temperatures. When cerium-doped samples were heated at temperatures higher than 1000{degrees}C, CeO{sub 2} was segregated. For La doping such segregation was not observed. Bronsted acid sites were generated for the low doping concentrations of both elements. At the high doping concentration, however, only Lewis acid sites existed in a higher concentration than in undoped alumina.

Vazquez, A. [Universidad Autonoma Metropolitana-Iztapalapa (Mexico)] [Universidad Autonoma Metropolitana-Iztapalapa (Mexico); Lopez, T.; Gomez, R. [Universidad Autonoma Metropolitana-Iztapalapa (Mexico)] [Universidad Autonoma Metropolitana-Iztapalapa (Mexico); [Universidad de Guanajuato, Guanajuato (Mexico)] [and others

1997-02-01

67

Engineered hydrochar composites for phosphorus removal/recovery: Lanthanum doped hydrochar prepared by hydrothermal carbonization of lanthanum pretreated rice straw.  

PubMed

Engineered hydrochar composites (EHC) were synthesized by hydrothermal carbonization (HTC) of lanthanum pretreated rice straw. The as-prepared composite with about 30% lanthanum content showed greater P removal potential than La(OH)3, indicating the synergistic effect of hydrochar and lanthanum in P removal. The adsorption results showed that EHC showed great P adsorption capacities (>50mgPg(-1)) in the pH range of 2.5-10.5, and the presence of competing anions had little negative effects on P adsorption on EHC. The equilibrium time for P adsorption on EHC was considerably reduced under acid condition (12h) compared to alkaline condition (48h). The maximum adsorption capacity was 61.57mgPg(-1) according to Langmuir isotherms. These results suggested that EHC was highly effective in P adsorption in a wide range of pH and the presence of competing anions, thus EHC could be a promising adsorbent for phosphorus removal/recovery from wastewater. PMID:24727355

Dai, Lichun; Wu, Bo; Tan, Furong; He, Mingxiong; Wang, Wenguo; Qin, Han; Tang, Xiaoyu; Zhu, Qili; Pan, Ke; Hu, Qichun

2014-06-01

68

Thermally Induced Nanostructures in Samarium-Doped Glass Ceramics for X-Ray Sensor Applications  

NASA Astrophysics Data System (ADS)

There is much interest in various glass-ceramics doped with rare-earth (RE) metals for x-ray storage phosphor and/or x-ray scintillator applications for potential use in high resolution x-ray imaging. The phosphor and scintillator properties of these glass ceramics depend on the formation of RE embedded nanocrystals in their structure. The heat treatment and annealing of the starting RE-doped glasses is critically important to the formation and control of the glass ceramic nanocrystals. We have studied the thermal and photoluminescence properties of Sm-doped fluorochlorozirconate glass ceramics. We selected useful host compositions and appropriate heat treatment and annealing procedures needed to grow the required RE-doped nanocrystals in a glass matrix for sensor applications.

Tonchev, Dan; Belev, G.; Koughia, C.; Panigrahi, S.; Varoy, C.; Edgar, A.; Kasap, S. O.

69

Effect of oxide additives on the sintering behavior and electrical properties of strontium- and magnesium-doped lanthanum gallate  

Microsoft Academic Search

The effects of 14 different metal-oxide additives (metal=Mn, Fe, Co, Ni, Cu, B, Li, V, Zn, Si, Ca, Al, Bi, and Ba) on the sintering, phase purity, and electrical properties of strontium- and magnesium-doped lanthanum gallate (LSGM) are studied. The density, phase purity, and electrical conductivity depend closely on the sintering aids and sintering temperatures. The addition of V, Zn,

Sang Bu Ha; Yoon Ho Cho; Yun Chan Kang; Jong-Ho Lee; Jong-Heun Lee

2010-01-01

70

Temperature behavior of dielectric and piezoelectric properties of samarium-doped lead titanate ceramics  

Microsoft Academic Search

The dielectric and electromechanical coupling properties of Sm-doped and Mn-doped PbTiO3 ceramics were investigated from 4.2 to 300 K. The upper and lower limits of the ceramic dielectric and piezoelectric properties were calculated by averaging the single-domain constants that were determined from a phenomenological theory. Comparisons of the measured and calculated properties were then made. The measured dielectric permittivity ?T33

J. N. Kim; MICHAEL J. HAUN; SEI JOO JANG; L. E. Cross; X. R. Xue

1989-01-01

71

Top electrode-dependent resistance switching behaviors of lanthanum-doped ZnO film memory devices  

NASA Astrophysics Data System (ADS)

Lanthanum-doped ZnO (Zn0.99La0.01O) polycrystalline thin films were deposited on Pt/Ti/SiO2/Si substrates by a chemical solution deposition method. Metal/La-doped ZnO/Pt sandwich structures were constructed by depositing different top electrodes (Ag and Pt). Unipolar switching and bipolar switching characteristics were investigated in Pt/La-doped ZnO/Pt and Ag/La-doped ZnO/Pt structures, respectively. Compared with the undoped devices (Pt/ZnO/Pt and Ag/ZnO/Pt), the La-doped devices exhibits superior resistive switching performances, such as narrow distribution of the resistive switching properties ( R ON, R OFF, V Set, and V Reset), higher R OFF/ R ON ratio and sharp switching transition.

Xu, Dinglin; Xiong, Ying; Tang, Minghua; Zeng, Baiwen

2014-03-01

72

Effect of rare earth doping on thermo-physical properties of lanthanum zirconate ceramic for thermal barrier coatings  

Microsoft Academic Search

The effect of rare earth doping on thermo-physical properties of lanthanum zirconate was investigated. Oxide powders of various compositions La2Zr2O7 were synthesized by coprecipitation-calcination method. High-temperature dilatometer, DSC, and laser thermal diffusivity methods were used to analyze thermal expansion coefficient (TEC), specific heat, and thermal diffusivity. The results showed that CeO2 doped pyrochlores La2(Zr1.8Ce0.2)2O7 and La1.7(DyNd)0.15(Zr0.8Ce0.2)2O7 had higher TEC than

Hongming ZHOU; Danqing YI

2008-01-01

73

Thin film growth and characterization of the electron-doped superconductor samarium cerium copper oxide  

NASA Astrophysics Data System (ADS)

Sm2-xCexCuO 4-y belongs to a class of materials known as electron-doped superconductors (Ln2- xMxCuO4- y; Ln = Pr, Nd, Sm, Eu; M = Ce, Th) and has a moderately high superconducting critical temperature, Tc, of 20 K at optimal doping (x = 0.15). The trivalent rare earth site is doped with tetravalent Ce or Th; hence the name "electron-doped". Sm2- xCexCuO4- y also exhibits a unique magnetic structure at low temperatures (T < 6 K) due to the antiferro-magnetic ordering of the Sm3+ ions. In this study, thin films of the electron-doped superconductor Sm 2-xCexCuO 4-y (SCCO) have been grown by pulsed laser deposition (PLD) for a cerium concentration range of x = 0.13 to x = 0.19. The films have been characterized through x-ray diffraction, electrical transport, and thermal transport measurements. A temperature versus cerium content (T-x) phase diagram has been constructed from the electrical transport measurements and yields a superconducting region similar to that of two of the other electron-doped superconductors Nd2-xCe xCuO4-y and Pr 2-xCexCuO 4-y. Thermopower measurements were also performed on the samples and show a dramatic change from the under-doped region (x < 0.15) to the overdoped region (x > 0.15). Additionally, the standard Fisher-Fisher-Huse (FFH) vortex glass scaling model has been applied to the magnetoresistance data, as well as a modified scaling model (RRA), and the analysis yields values of the vortex glass melting temperature, T g, and critical exponent, nu(z-1). A magnetic field versus temperature (H-T) phase diagram has been constructed for the films with cerium content x ? 0.14, displaying the vortex glass melting lines. Magnetoresistance data taken as a function of angle, theta, is also discussed in the context of the vortex glass scaling model.

Scanderbeg, Daniel Joseph

74

Exchange bias and its tuning in magnetic compensated Nd doped ferromagnetic samarium metal  

NASA Astrophysics Data System (ADS)

Sm metal is a ferromagnet with a very small net magnetization as it comprises nearly compensated local moment (4f-orbital moment slightly greater than the 4f-spin moment) which is coupled to conduction electrons via RKKY exchange mechanism and results in antiferromagnetically coupled alignment between total local moment and the contribution from conduction electron polarization. Ferromagnetic Sm metal is considered to be in spin surplus state, as it yields magnetic compensation on doping with RE-ions (e.g., Nd) belonging to the first half of 4f-series. The results pertaining to identification and tuning of the exchange bias (EB) field in Nd doped Sm metal are presented.

Pandya, Swati; Ramakrishnan, S.; Grover, A. K.

2013-02-01

75

Reactions at the calcium doped lanthanum chromite-yttria stabilized zirconia interface  

SciTech Connect

Solid oxide fuel cell materials calcium doped lanthanum chromite (La,Ca)CrO{sub 3} and yttria stabilized zirconia (YSZ) are known to interact with each other. This interaction causes interruption of cosintering processes and the formation of secondary phases which degrade fuel cell performance. The present study shows by X-ray diffraction and microscopic analysis that Ca migrates via an exsolved Ca-Cr-O liquid phase emanating from (LaCa)CrO{sub 3} and reacts with YXZ to obtain an intermediate layer of CaZrO{sub 3}. The width of the CaZrO{sub 3} reaction region was found to increase with increasing Ca content in the exsolved Ca-Cr-O second phase. Calcium zirconate was observed to react with YSZ along the YSZ grain boundaries, eventually digesting YSZ grains into a CaZrO{sub 3} matrix. The results demonstrate the improbability of cosintering (La,Ca)CrO{sub 3} and YSZ in the presence of the Ca-Cr-O liquid phase and illustrate the importance of obtaining single phase (La,Ca)CrO{sub 3} to achieve compatibility with YSZ.

Carter, J.D.; Appel, C.C.; Mogensen, M. [Riso National Laboratory, Roskilde (Denmark)] [Riso National Laboratory, Roskilde (Denmark)

1996-03-01

76

Solid oxide fuel cells with doped lanthanum gallate electrolyte and LaSrCoO cathode, and Ni-samaria-doped ceria cermet anode  

Microsoft Academic Search

The electrode performance of a single solid-oxide fuel cell (SOFC) was evaluated using a 500 μm thick La{sub 0.9}Sr{sub 0.1}Ga{sub 0.8}O{sub 0.3} (LSGM) as the electrolyte membrane. A doped lanthanum cobaltite, La{sub 0.6}Sr{sub 0.4}CoO{sub 3-δ} was selected as the cathode material, and a samaria-doped ceria-NiO composite powder was used as the anode material. The spray-pyrolysis method was applied for synthesis

Radenka Maric; Satoshi Ohara; Takehisa Fukui; Hiroyuki Yoshida; Masayoshi Nishimura; Toru Inagaki; Kazuhiro Miura

1999-01-01

77

Effects of calcination on microscopic and mesoscopic structures in Ca- and Sr-doped nano-crystalline lanthanum chromites  

SciTech Connect

Calcination behavior of nano-crystalline lanthanum chromites doped with calcium and strontium has been probed by Fourier transform infrared spectroscopy, X-ray diffraction and small-angle neutron scattering as a function of temperature. Infrared spectroscopic results imply that over a range of temperatures, some intermediate phase of dopant chromates evolve and then dissolve back, which has also been confirmed by the XRD. Neutron scattering data reveal a fractal type correlation of building blocks in virgin powders. Increase in fractal dimension and reduction in upper cutoff vis-a-vis the densification of agglomerates were found with increasing calcination temperature. Calcination, beyond 900 {sup o}C, results in breaking down of the fractal morphology almost completely. Such shrinkage event also results in a modification of the microscopic structure. These changes have been attributed to the compaction of agglomerates of both Ca- and Sr-doped lanthanum chromites, assisted via liquid state sintering by the melting of the intermediate phases at intermediate calcination stages. -- Graphical Abstract: Dopant chromates evolve as intermediate phases during calcination of Ca- and Sr-doped nano-crystalline lanthanum chromites at intermediate temperatures, around 900 {sup o}C, evident from infrared spectroscopy. Such an event results in a modification of the microscopic and mesoscopic structures. Display Omitted Research highlights: {yields} Meso/microscopic structures of La{sub 0.7}Ca{sub 0.3}CrO{sub 3} and La{sub 0.8}Sr{sub 0.2}CrO{sub 3} modify during calcination. {yields} Transient phases CaCrO{sub 4} and SrCrO{sub 4} appear at intermediate temperatures. {yields} Bond length, unit cell volume, etc. modify as intermediate phases evolve and extinct. {yields} Compaction of the agglomerates takes place due to liquid state assisted sintering.

Bhatt, Himal, E-mail: himalphy@gmail.co [High Pressure and Synchrotron Radiation Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Bahadur, J. [Solid State Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Deo, M.N. [High Pressure and Synchrotron Radiation Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Ramanathan, S. [Materials Processing Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Pandey, K.K. [High Pressure and Synchrotron Radiation Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Sen, D.; Mazumder, S. [Solid State Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Sharma, Surinder M. [High Pressure and Synchrotron Radiation Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India)

2011-01-15

78

Emergence of superconductivity at 45 K by lanthanum and phosphorus co-doping of CaFe2As2  

PubMed Central

Co-doping of lanthanum and phosphorus in CaFe2As2 induces superconductivity at 45?K. This superconducting transition temperature is higher than the 38?K transition in Ba1?xKxFe2As2, which is the maximum found thus far among the 122?phases. Superconductivity with a substantial shielding volume fraction was observed at 0.12 ? x ? 0.18 and y = 0.06 in Ca1?xLaxFe2(As1?yPy)2. The superconducting phase of the present system seems to be not adjacent to an antiferromagnetic phase.

Kudo, Kazutaka; Iba, Keita; Takasuga, Masaya; Kitahama, Yutaka; Matsumura, Jun-ichi; Danura, Masataka; Nogami, Yoshio; Nohara, Minoru

2013-01-01

79

Persistent spectral hole burning in europium- and europium, samarium-doped calcium sulphide  

NASA Astrophysics Data System (ADS)

The presented work contains an account of photon-gated spectral hole burning and systematic spectroscopic study of the Eu, and Eu, Sm doped CaS powders. The dependence of the hole burning process and hole parameters on temperature, gating, laser power, exposure time, spectral position, etc. were studied and comprehensive spectroscopic investigation of the samples was accomplished. The high temperature (up to 25 K) and high speed (10 ns, similar to MgS:Eu) hole burning was demonstrated. The readout erasure was shown to be negligible for the powers below 4 ?W, and tuning the burning beam into the vibronic band was shown to efficiently erase holes. The spectral dependence of the erasure for CaS:Eu and CaS:Eu,Sm was shown to follow the absorption profile of the samples. The holes were shown to survive thermal cycling to 230 K. The temperature dependence of the hole width and depth were used to identify thermally induced localized oscillations and ion diffusion as likely mechanisms of the temperature-related hole broadening and erasure. Energies of Eu-localized oscillation modes of CaS:Eu in the temperature range of 3 to 250 K were established to be 2.7, 43, 91 and 153 cm-1. The experimentally determined Debye temperature of CaS:Eu (455 K) was shown to be in a good agreement with theoretical estimates. The dependence of hole burning in CaS:Eu on the Eu2+ concentration was studied and the best concentration of Eu in CaS for the hole burning purposes was found to be 0.01 mol %. The PMMA embedding of CaS:Eu was shown to increase the width of inhomogeneously broadened ZPL four times and to increase the width of a hole 30%. At the same time, PMMA embedding was shown to decrease the maximum thermal cycling temperature of a hole from 230 K to 180 K. Chlorination of CaS:Eu at the sample preparation stage was shown to change the ratio Eu2+/Eu3+ in the sample according to the redox process. The depth of the spectral holes in our samples was shown not to be limited by the concentration of Eu 3+.

Solonenko, Mikhail (Michael)

1999-10-01

80

Super broadband near-infrared emission and energy transfer in Bi-Er co-doped lanthanum aluminosilicate glasses  

NASA Astrophysics Data System (ADS)

The Bi-Er co-doped lanthanum aluminosilicate glasses, which exhibited a broadband near-infrared emission, were developed and observed in using the optical absorption and photoluminescence spectra. A super broadband near-infrared emission extending from 1.0 to 1.8 ?m with a full-width at half-maximum of 450 nm which covered the whole O, E, S, C and L bands, was observed in Bi-Er co-doped samples under 808 nm excitation, as a result of the overlap of the Bi-related emission band (1270 nm) and the emission from Er3+4I13/2 ? 4I15/2 transition (1545 nm). This report will discuss about a possible mechanism for energy transfer between Bi-related centers and Er3+ ion.

Minh Hau, Tran; Yu, Xue; Zhou, Dacheng; Song, Zhiguo; Yang, Zhengwen; Wang, Rongfei; Qiu, Jianbei

2013-01-01

81

Photoluminescence and visible diffuse-reflection spectroscopic evidence of samarium reduction in air-fired samples of mixed samarium: strontium tetraborate precipitates.  

PubMed

Photoluminescence and visible diffuse-reflection spectroscopies have provided evidence of the reduction of samarium to the divalent state in samarium-doped strontium borate and pure samarium borate samples. The samples were prepared by the air firing of homogeneous precipitates of divalent strontium and trivalent samarium ions from aqueous solutions with saturated sodium tetraborate. The use of this method in the preparation of divalent lanthanide ions has not been reported previously. Reduced samarium was observed in fired tetraborate precipitates prepared with solutions containing 1, 5, 10, 25, 50, 75, and 90 mole percent samarium versus strontium. Divalent samarium also was identified in fired precipitates of trivalent samarium solutions precipitated with tetraborate. Sm(2+) was identified as the primary emitting species in each of the eight compositions. However, diffuse-reflection spectroscopy indicated the presence of trivalent samarium in the studied samples, ranging from minimal for samples prepared with low samarium concentrations to nearly exclusive when pure samarium was studied. Quenching of the characteristic emission associated with the trivalent species is believed to result in the absence of the emission features arising from residual samarium(III) in the products. Although the absence of trivalent samarium emission enhanced the ability of emission spectroscopy to identify small amounts of divalent samarium, indicating that reduction had occurred, it limited the ability of this method to determine the extent of the reduction. Diffuse-reflection spectroscopy's ability to look at both species provided a much better analysis of the extent of samarium reduction. PMID:23452491

Brown, Telvin M; Jeffreys, Mareo C; Pehaire, Mario; Stump, Nathan A

2013-03-01

82

Dielectric properties and substitution mechanism of samarium-doped Ba{sub 0.68}Sr{sub 0.32}TiO{sub 3} ceramics  

SciTech Connect

Ba{sub 0.68}Sr{sub 0.32}TiO{sub 3} ceramics of perovskite structure are prepared by solid state reaction method with addition of x mol% Sm{sub 2}O{sub 3}, and their dielectric properties are investigated. It is found that, integrating with the lattice parameters and tolerance factor t, there is an alternation of substitution preference of Sm{sup 3+} for the host cations in perovskite lattice. Owing to the replacement of Sm{sup 3+} ions for Ba{sup 2+} ions in the A site, T{sub c} rises with the increase of Sm{sub 2}O{sub 3} doping when the doping content is below 0.1 mol%; meanwhile, when the content is more than 0.1 mol%, Sm{sup 3+} ions tend to occupy the B-site, causing a drop of T{sub c}. Owing to the modifications of Sm{sup 3+} doping, dielectric constant, dissipation factor and temperature stability of dissipation factor are influenced remarkably, making it a superior candidate for environment-friendly applications. Moreover, the creation of oxygen vacancies controls the dielectric constant when the addition is above 0.1 mol%, so the dielectric constant decreases with increasing of samarium.

Li Yuanliang [Key Laboratory for Advanced Ceramics and Machining Technology of Ministry of Education, Tianjin University, Tianjin 300072 (China)], E-mail: lylll2007@yahoo.cn; Qu Yuanfang [Key Laboratory for Advanced Ceramics and Machining Technology of Ministry of Education, Tianjin University, Tianjin 300072 (China)

2009-01-08

83

Phase Stability Analysis of Lanthanum-Doped Alumina During Synthesis and Sintering  

NASA Astrophysics Data System (ADS)

The aim of this research was to study the phase stability during synthesis and consolidation of nanocrystalline lanthanum-doped gamma-Al2O 3 powders. We used solution combustion synthesis by dissolving precursor nitrate compounds and an organic fuel in a pre-heated muffle furnace at 500C. Several preliminary syntheses were carried out in order to obtain the correct fuel-to-oxidizer ratio necessary for the production of the desired lanthanum-doped gamma-Al 2O3. The as-synthesized powders were then heat-treated at 1000C for 2 hours in order to remove impurities and improve the crystallinity of the powders. Sintered circular specimens were made by pressing the heat-treated powders and subsequently annealing them at 1800C for 4 hours. The use of this material in optical windows requires that the material have high strength and optical transparency. Elimination of all the pores during sintering is therefore crucial. In addition, preparing specimens of the gamma-Al2O3 phase is optimal, since the crystal structure is cubic and transparency is more readily achievable. Several different samples with varying weight percents of La were attempted to determine how much of the La could effectively prevent the gamma-Al2O 3 phase from transforming into the more stable alpha-Al2O 3 phase. The different phases of compounds produced with increasing amounts of La were also identified. The as-synthesized and heat-treated powders as well as the annealed circular discs were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The average particle sizes of the powders were determined by dynamic light scattering (DLS). XRD experiments showed that the gamma-alumina phase was stabilized when the powders were calcined at 1000C with 5 wt% La, 10 wt% La and 13 wt% La. Increasing the amount of La resulted in the formation of the La compounds LaAlO3 in the heat-treated powders containing 15 wt% La and above and LaAl11O18 in the sintered specimens. Crystallite sizes of the heat-treated powders were determined from the XRD line profile analysis of the peaks and were less than 50 nm for the heat-treated powders. Dynamic light scattering experiments were carried out to analyze the average particle sizes of the as-synthesized powders as well as the powders heat treated at 1000C for two hours. In all the DLS plots for the as-synthesized powders, particle sizes were less than 500 nm, while some of the heat-treated powders had sizes greater than 500 nm, and some even greater than 1 mum. The average particle sizes are considerably larger than the crystallite sizes because particles are generally formed from the agglomeration of crystallites and will therefore have larger sizes. SEM was done to analyze the morphology of the heat-treated powders as well as the sintered specimens. Only the specimens that contained 5 wt% La and 44.4 wt% La (the lowest and highest amounts, respectively) were analyzed, since the microstructures of the specimens with intermediate La amounts do not change much from each other. It was seen from the micrographs that the heat-treated powders were agglomerated. The SEM pictures of the 5 wt% La and 44.4 wt% La specimens showed that both specimens had grains which adopted a more or less hexagonal shape, and this was more defined in the Al2 O3:44.4 wt% La specimen since it contained a larger amount of the secondary phase LaAl11O18 which has a hexagonal structure. Both specimens contained pores at the triple points of the grains as well as internal porosity. The Al2O3:5 wt% La specimens had larger grain sizes ranging from ~2.0 mum to 17 mum compared to the ~2.0 mum to 3.0 mum grain sizes for the Al2O3:44.4 wt% La specimens. This observation could probably be due to the effect of particle pinning which occurs when a specimen has secondary particles in its microstructure that pins or hinders the growth of grains. Density measurements were done using the Archimedes' method. The percent densities of all sintered specimens were above 80% of the theoretical densities. Theoretical densities were calculated for ea

Ngwa Nforbi, Lum-Ngwegia

84

Variation in band gap of lanthanum chromate by transition metals doping LaCr0.9A0.1O3 (A:Fe/Co/Ni)  

NASA Astrophysics Data System (ADS)

Transition metal (Fe, Co, Ni) doped lanthanum chromate (LaCrO3) nanoparticles (NPs) were prepared by gel combustion method and calcinated at 800C. Microstructural studies were carried by XRD and SEM/EDS techniques. The results of structural characterization show the formation of all samples in single phase without any impurity. Optical properties were studied by UV- visible and photoluminescence techniques. The energy band gap was calculated and the variation was observed with the doping of transition metal ions. Photoluminescence spectra show the emission peak maxima for the pure LaCrO3 at about 315 nm. Influence of Fe, Co, Ni doping was studied and compared with pure lanthanum chromate nanoparticles.

Naseem, Swaleha; Khan, Wasi; Saad, A. A.; Shoeb, M.; Ahmed, Hilal; Husain, Shahid; Naqvi, A. H.

2014-04-01

85

Photon Echo Modulation in Praseodymium(iii) Doped Lanthanum-Trifluoride  

NASA Astrophysics Data System (ADS)

When measured as a function of laser pulse separation, photon echoes in solids often display a periodic variation in amplitude. Modulation phenomena of this kind occur whenever the two levels of the photon echo transition consist of several very closely spaced levels such that the energy splittings are small compared to the spectral linewidths of the pulsed lasers used, so that the excitation pulses are able to coherently excite the system into a superposition of several ground and excited states. The modulation frequencies of the photon echoes arising from such a coherently excited multi-level system are determined by the magnitude of the energy splittings within the multiplets, but the exact form of the modulation pattern depends on the interaction Hamiltonian used to describe the energy level structures of the ground and excited states. The photon echo modulation technique has been utilized to measure the hyperfine structure and relaxation characteristics of the terminal levels of the ('3)H(,4) - ('3)P(,0) (477.7 nm) transition in Praseodymium doped Lanthanum trifluoride (LaF(,3):P4('3+)). Using two home -made nitrogen laser pumped dye lasers modulated photon echoes have been observed over a 8 (mu)sec range of pulse separations. In this range, the echoes decay in a simple exponential manner by a factor of 10('5) and yield a homogeneous linewidth of 70 Khz (FWHM) for a 0.03% LaF(,3):Pr('3+) sample. Experiments performed with a less concentrated sample (0.01%) show that the homogeneous linewidth is even narrower, and is about 40 Khz (FWHM). By Fourier transforming the echo modulation data it was possible to determine the hyperfine energy level splittings and their associated linewidths in both the ground ('3)H(,4) and excited ('3)P(,0) states. The splittings for the ('3)H(,4) state have been determined to be 8.48 and 16.68 Mhz, which are in excellent agreement with the results of an optical-RF double resonance experiment performed by Erickson. The excited state hyperfine splittings are found to be 0.73 Mhz and 1.12 Mhz. Numerical calculations of the photon echo modulation pattern, using the theory proposed by Grischkowsky and Hartmann, are in excellent agreement with the experimentally observed modulation pattern. The calculated echo modulation curves were found to be very sensitive to the relative orientations of the principal axes associated with the ground and excited state interaction Hamiltonians. Comparison of theoretical patterns with the observed pattern have enabled us to estimate their relative orientations. Photon echo experiments performed on another transition in LaF(,3):Pr('3+) (the ('3)H(,4) - ('1)D(,2) transition at 592.2 nm) have, so far, been less amenable to theoretical analysis, partly because the sum of the energy splittings in the ('1)D(,2) state (as measured by Erickson) is almost equal to an energy splittings in the ground ('3)H(,4) state. Less than perfect agreement between experimental and calculated modulation curves for the ('3)H(,4) - ('1)D(,2) transition indicated the possibility of an error in the currently accepted values of the ('1)D(,2) energy splittings. But a photon echo nuclear double resonance (PENDOR) experiment has shown, however, that the energy splittings as determined by Erickson are correct.

Chiang, Kophu

86

Preparation of samarium monosulfide via samarium naphthalenide  

SciTech Connect

Samarium monosulfide in a state amorphous to X-rays was prepared by the successive interaction of lithium naphthalenide with samarium diiodide and a solution of sulfur in THF in inert atmosphere or under reduced pressure under standard (normal) conditions. Samarium monosulfide was transferred to the polycrystalline state (a = 5.95 {angstrom}, NaCl-like structure) by annealing in a vacuum (<0.1 Pa) or in an inert atmosphere at 500-600{degrees}C.

Andreev, O.V.; Nekrasova, T.V. [Tyumen State Univ. (Russian Federation); Bochkarev, M.N. [Inst. of Organometallic Chemistry, Novgorod (Russian Federation)] [and others

1994-02-01

87

Photocatalytic performance of novel samarium-doped spherical-like ZnO hierarchical nanostructures under visible light irradiation for 2,4-dichlorophenol degradation.  

PubMed

A novel samarium-doped spherical-like ZnO hierarchical nanostructure (Sm/ZnO) was synthesized via a facile and surfactant-free chemical solution route. The as-synthesized products were characterized by X-ray diffraction, Brunauer-Emmett-Teller surface area analysis, field emission scanning electron microscopy together with an energy dispersion X-ray spectrum analysis, transmission electron microscopy, UV-visible diffuse reflectance spectroscopy, and photoluminescence spectroscopy. The results revealed that Sm ion was successfully doped into ZnO. It was also observed that the Sm doping increased the visible light absorption ability of Sm/ZnO and a red shift for Sm/ZnO appeared when compared to pure ZnO. The photocatalytic studies revealed that the Sm/ZnO exhibited excellent photocatalytic degradation of 2,4-dichlorophenol (2,4-DCP) compared with the pure ZnO and commercial TiO2 under visible light irradiation. The photocatalytic enhancement of Sm/ZnO products was attributed to their high charge separation efficiency and OH generation ability as evidenced by the photoluminescence spectra. The photocatalytic investigation also showed that various parameters exerted their individual influence on the degradation rate of 2,4-DCP. By using a certain of radical scavengers, OH was determined to play a pivotal role for the 2,4-DCP degradation. Moreover, the Sm/ZnO could be easily separated and reused, indicating great potential for practical applications in environmental cleanup. PMID:23618322

Sin, Jin-Chung; Lam, Sze-Mun; Lee, Keat-Teong; Mohamed, Abdul Rahman

2013-07-01

88

Samarium-doped mesoporous TiO2 nanoparticles with improved photocatalytic performance for elimination of gaseous organic pollutants  

NASA Astrophysics Data System (ADS)

Mesoporous TiO2 doped with different amounts of Sm were prepared via a sol-gel route with Pluronic P123 as template. The materials were characterized by X-ray diffraction, transmission electron microscopy, and N2 sorption experiments, etc. The photocatalytic activity of the mesoporous TiO2 was tested in elimination of gaseous methanol and acetone. The Sm doped mesoporous TiO2 have higher activity than those of the commercial photocatalyst (Degussa, P25) and Sm doped TiO2 counterparts without mesopore structure under ultraviolet light irradiation. A possible mechanism was proposed to account for the high photocatalytic activity of the Sm doped mesoporous TiO2. The superior activity of the Sm doped mesoporous TiO2 may be attributed to the synergic effect of the high surface area, mesopore structure and doped Sm species.

Tang, Jianting; Chen, Xiaomiao; Liu, Yu; Gong, Wei; Peng, Zhenshan; Cai, Tiejun; Luo, Lianjing; Deng, Qian

2013-01-01

89

Modified resin--intermediate processing of perovskite powders:Part II. Processing for fine, nonagglomerated Sr-doped lanthanum chromite powders  

SciTech Connect

Nonagglomerated ceramic precursor for Sr-doped lanthanum chromite powder was prepared by a modified resin--intermediate process using equimolar citric acid, ethylene glycol, and metallic nitrates. Pure and well-crystallized submicron powders with a narrow particle-size distribution were calcined from an optimally pulverized resin at a temperature of 750 {degree}C for 2 h in flowing air. The material cost for organics used in the investigated process was considerably lower than the original Pechini process.

Tai, L. (Ceramic Engineering Department, University of Missouri-Rolla, Rolla, Missouri 65401 (United States)); Lessing, P.A. (Ceramics Section, EG G Idaho, Inc., Idaho National Engineering Laboratory, Idaho Falls, Idaho 83415 (United States))

1992-02-01

90

Modified resin-intermediate processing of perovskite powders:Part II. Processing for fine, nonagglomerated Sr-doped lanthanum chromite powders  

Microsoft Academic Search

Nonagglomerated ceramic precursor for Sr-doped lanthanum chromite powder was prepared by a modified resin--intermediate process using equimolar citric acid, ethylene glycol, and metallic nitrates. Pure and well-crystallized submicron powders with a narrow particle-size distribution were calcined from an optimally pulverized resin at a temperature of 750 °C for 2 h in flowing air. The material cost for organics used in

Lone-Wen Tai; Paul A. Lessing

1992-01-01

91

Doping of lanthanum cobaltite by Mn: thermal, magnetic, and catalytic effect  

Microsoft Academic Search

Great differences in crystallographic phases, magnetic properties, and catalytic activity were detected in lanthanum cobaltite\\u000a and cobaltite modified with the insertion of 10wt.% of Mn. Atomic absorption spectroscopy, BET area measurements, XRD analysis,\\u000a TPR, and FT-IR suggest that the total insertion of manganese in the LaCoO3 structure is successful. Thermal stability is reached for LaCo0.90Mn0.10O3 up to 973K without loss

Gina Pecchi; Claudia Campos; M. Graciela Jiliberto; Yanko Moreno; Octavio Pea

2008-01-01

92

Effects of magnetization on hole localization and MnO{sub 6} octahedra disorder in hole-doped lanthanum manganese perovskites  

SciTech Connect

The authors review the distortions of the MnO{sub 6} octahedra reduced by magnetization in hole-doped lanthanum manganese perovskites. The systems they consider include the colossal magnetoresistance (CMR) samples La{sub 1{minus}x}Ca{sub x}MnO{sub 3} (x = 0.21, 0.25, 0.30), La{sub 0.76}Ba{sub 0.33}MnO{sub 3}, and a poorer quality La{sub 0.76}Pb{sub 0.33}MnO{sub 3} sample. They also report preliminary work on three samples of oxygen-doped LaMnO{sub 3+{delta}} and a lanthanum-deficient La{sub 0.9}MnO{sub 3} sample. They find the same exponential relationship between the removal of the distortion and the sample magnetization in the Ba- and Pb-doped CMR samples as was found previously for the Ca doped samples. The MnO{sub 6} distortion in the oxygen-doped materials is found to slightly reduce below the magnetic transition, although much less so than in the CMR samples. Above T{sub C}, the antiferromagnetic LaMnO{sub 3.006} sample shows a softer temperature dependence of the Mn-O bond length distribution broadening. Surprisingly, even this sample shows deviations from thermal (Debye) behavior near T{sub N}, possibly due to FM coupling within MnO planes.

Booth, C.H.; Brosha, E.L.; Kwei, G.H. [Los Alamos National Lab., NM (United States); Bridges, F. [Univ. of California, Santa Cruz, CA (United States). Physics Dept.; Neumeier, J.J. [Florida Atlanta Univ., Boca Raton, FL (United States). Physics Dept.

1998-12-31

93

Electrical properties and thermal expansion of cobalt doped apatite-type lanthanum silicates based electrolytes for IT-SOFC  

SciTech Connect

Graphical abstract: The figure shows the dependence of conductivity on the Co content. It can be seen that La{sub 10}Si{sub 5.2}Co{sub 0.8}O{sub 26.6} exhibits the highest ionic conductivity of 3.33 Multiplication-Sign 10{sup -2} S/cm at 800 Degree-Sign C. When x {<=} 0.8, as doping Co weakens the binding energy and aids the migration of the interstitial oxide ions, the ionic conductivity improves. On the other hand, excess dopant of Co (0.8 < x {<=} 1.5) can decrease the number of interstitial oxide ions and reduce the ionic conductivity. Highlights: Black-Right-Pointing-Pointer The unit volumes of La{sub 10}Si{sub 6-x}Co{sub x}O{sub 27-x/2} increase with increasing cobalt content. Black-Right-Pointing-Pointer Doping Co can increase the thermal expansion because of the larger radius of Co{sup 3+} ion. Black-Right-Pointing-Pointer Conductivities of La{sub 10}Si{sub 6-x}Co{sub x}O{sub 27-x/2} first increase and then decrease with cobalt content. Black-Right-Pointing-Pointer Above 550 Degree-Sign C, La{sub 10}Si{sub 6-x}Co{sub x}O{sub 27-x/2} shows low activation energies of around 0.7 eV. -- Abstract: The thermal expansion and conductivities have been investigated for Co{sup 3+} doped lanthanum silicates. The apatite-type lanthanum silicates with formula La{sub 10}Si{sub 6-x}Co{sub x}O{sub 27-x/2} (x = 0.2, 0.4, 0.6, 0.8, 1.0, 1.5) were synthesized by sol-gel process. The thermal expansion coefficient (TEC) of La{sub 10}Si{sub 6-x}Co{sub x}O{sub 27-x/2} was improved with increasing cobalt content because of the lower valence and larger radius of Co{sup 3+} ion compared to Si{sup 4+}. Analysis of AC impedance spectroscopy showed that conductivity increased first and then decreased with increasing cobalt content. There is an optimum doping amount of cobalt and La{sub 10}Si{sub 5.2}Co{sub 0.8}O{sub 26.6} exhibits the highest conductivity of 3.33 Multiplication-Sign 10{sup -2} S/cm at 800 Degree-Sign C. When x {<=} 0.8, the local distortion caused by doping with Co{sup 3+} can significantly affect the oxygen channels and assist the migration of the interstitial oxide ions, resulting in the improvement of ionic conductivity. However, excess Co{sup 3+} dopant (0.8 < x {<=} 1.5) reduced the number of interstitial oxide ions and decreased the conductivity.

Shi, Qingle; Lu, Lihua; Jin, Hongjian [College of Materials Science and Engineering, Nanjing University of Technology, No.5 Xinmofan Road, Nanjing, Jiangsu (China)] [College of Materials Science and Engineering, Nanjing University of Technology, No.5 Xinmofan Road, Nanjing, Jiangsu (China); Zhang, Hua, E-mail: huazhang@njut.edu.cn [College of Materials Science and Engineering, Nanjing University of Technology, No.5 Xinmofan Road, Nanjing, Jiangsu (China)] [College of Materials Science and Engineering, Nanjing University of Technology, No.5 Xinmofan Road, Nanjing, Jiangsu (China); Zeng, Yanwei [College of Materials Science and Engineering, Nanjing University of Technology, No.5 Xinmofan Road, Nanjing, Jiangsu (China)] [College of Materials Science and Engineering, Nanjing University of Technology, No.5 Xinmofan Road, Nanjing, Jiangsu (China)

2012-03-15

94

Fabrication of Sr- and Co-doped lanthanum chromite interconnectors for SOFC  

SciTech Connect

Graphical abstract: FESEM micrographs of the fresh fracture surfaces for the La{sub 0.80}Sr{sub 0.20}Cr{sub 0.92}Co{sub 0.08}O{sub 3} sintered specimens cast from optimised suspensions with 13.5, 15 and 17.5 vol.% solids loading. Aqueous suspensions were prepared using ammonium polyacrylate (PAA) as dispersant and tetramethylammonium hydroxide (TMAH) to assure a basic pH and providing stabilization. Sintering of the green discs was performed in air at 1600 {sup o}C for 4 h. Highlights: {yields} Optimum casting slips were achieved with 3 wt.% of ammonium polyacrylate and 1 wt.% of tetramethylammonium hydroxide. -- Abstract: Many studies have been performed dealing with the processing conditions of electrodes and electrolytes in solid oxide fuel cells (SOFCs). However, the processing of the interconnector material has received less attention. Lanthanum chromite (LaCrO{sub 3}) is probably the most studied material as SOFCs interconnector. This paper deals with the rheology and casting behaviour of lanthanum chromite based materials to produce interconnectors for SOFCs. A powder with the composition La{sub 0.80}Sr{sub 0.20}Cr{sub 0.92}Co{sub 0.08}O{sub 3} was obtained by combustion synthesis. Aqueous suspensions were prepared to solids loading ranging from 8 to 17.5 vol.%, using ammonium polyacrylate (PAA) as dispersant and tetramethylammonium hydroxide (TMAH) to assure a basic pH and providing stabilization. The influence of the additives concentrations and suspension ball milling time were studied. Suspensions prepared with 24 h ball milling, with 3 wt.% and 1 wt.% of PAA and TMAH, respectively, yielded the best conditions for successful slip casting. Sintering of the green discs was performed in air at 1600 {sup o}C for 4 h leading to relatively dense materials.

Setz, L.F.G. [Departamento de Engenharia de Materiais, Universidade Federal de Sao Carlos - DEMa/UFSCar (Brazil) [Departamento de Engenharia de Materiais, Universidade Federal de Sao Carlos - DEMa/UFSCar (Brazil); Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN (Brazil); Santacruz, I. [Departamento de Quimica Inorganica, Cristalografia y Mineralogia, Universidad de Malaga, 29071 Malaga (Spain)] [Departamento de Quimica Inorganica, Cristalografia y Mineralogia, Universidad de Malaga, 29071 Malaga (Spain); Colomer, M.T., E-mail: tcolomer@icv.csic.es [Instituto de Ceramica y Vidrio, ICV (CSIC), 28049 Madrid (Spain); Mello-Castanho, S.R.H. [Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN (Brazil)] [Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN (Brazil); Moreno, R. [Instituto de Ceramica y Vidrio, ICV (CSIC), 28049 Madrid (Spain)] [Instituto de Ceramica y Vidrio, ICV (CSIC), 28049 Madrid (Spain)

2011-07-15

95

Solid oxide fuel cells with doped lanthanum gallate electrolyte and LaSrCoO{sub 3} cathode, and Ni-samaria-doped ceria cermet anode  

SciTech Connect

The electrode performance of a single solid-oxide fuel cell (SOFC) was evaluated using a 500 {micro}m thick La{sub 0.9}Sr{sub 0.1}Ga{sub 0.8}O{sub 0.3} (LSGM) as the electrolyte membrane. A doped lanthanum cobaltite, La{sub 0.6}Sr{sub 0.4}CoO{sub 3{minus}{delta}} was selected as the cathode material, and a samaria-doped ceria-NiO composite powder was used as the anode material. The spray-pyrolysis method was applied for synthesis of the starting powders of the cathode and anode. In this study, different microstructures of the cathode were obtained by varying the sintering temperature from 950 to 1200 C. High power density (the maximum power density of the cell was about 425 mW/cm{sup 2}, which is 95% of the theoretical value) of the solid oxide fuel cell at 800 C was achieved. The cell performance showed that, with a proper choice of electrode materials with optimized microstructure and LSGM as the electrolyte, a SOFC operating at temperatures T{sub op} {le} 800 is a realistic goal.

Maric, R.; Ohara, Satoshi; Fukui, Takehisa [Japan Fine Ceramics Center, Nagoya (Japan)] [Japan Fine Ceramics Center, Nagoya (Japan); Yoshida, Hiroyuki; Nishimura, Masayoshi; Inagaki, Toru [Kansai Electric Power Co., Inc., Hyogo (Japan)] [Kansai Electric Power Co., Inc., Hyogo (Japan); Miura, Kazuhiro [Kanden Kakou Co., Ltd., Hyogo (Japan)] [Kanden Kakou Co., Ltd., Hyogo (Japan)

1999-06-01

96

Method and closing pores in a thermally sprayed doped lanthanum chromite interconnection layer  

DOEpatents

A dense, substantially gas-tight electrically conductive interconnection layer is formed on an air electrode structure of an electrochemical cell by (A) providing an air electrode surface; (B) forming on a selected portion of the electrode surface, a layer of doped LaCrO.sub.3 particles doped with an element or elements selected from Ca, Sr, Ba, Mg, Co, Ni, Al and mixtures thereof by thermal spraying doped LaCrO.sub.3 particles, either by plasma arc spraying or flame spraying; (C) depositing a mixture of CaO and Cr.sub.2 O.sub.3 on the surface of the thermally sprayed layer; and (D) heating the doped LaCrO.sub.3 layer coated with CaO and Cr.sub.2 O.sub.3 surface deposit at from about 1000.degree. C. to 1200.degree. C. to substantially close the pores, at least at a surface, of the thermally sprayed doped LaCrO.sub.3 layer. The result is a dense, substantially gas-tight, highly doped, electrically conductive interconnection material bonded to the electrode surface. A solid electrolyte layer can be applied to the nonselected portion of the air electrode. A fuel electrode can be applied to the solid electrolyte, to form an electrochemical cell, for example for generation of electrical power.

Singh, Prabhakar (Export, PA); Ruka, Roswell J. (Pittsburgh, PA)

1995-01-01

97

Method and closing pores in a thermally sprayed doped lanthanum chromite interconnection layer  

DOEpatents

A dense, substantially gas-tight electrically conductive interconnection layer is formed on an air electrode structure of an electrochemical cell by (A) providing an air electrode surface; (B) forming on a selected portion of the electrode surface, a layer of doped LaCrO{sub 3} particles doped with an element or elements selected from Ca, Sr, Ba, Mg, Co, Ni, Al and mixtures thereof by thermal spraying doped LaCrO{sub 3} particles, either by plasma arc spraying or flame spraying; (C) depositing a mixture of CaO and Cr{sub 2}O{sub 3} on the surface of the thermally sprayed layer; and (D) heating the doped LaCrO{sub 3} layer coated with CaO and Cr{sub 2}O{sub 3} surface deposit at from about 1,000 C to 1,200 C to substantially close the pores, at least at a surface, of the thermally sprayed doped LaCrO{sub 3} layer. The result is a dense, substantially gas-tight, highly doped, electrically conductive interconnection material bonded to the electrode surface. A solid electrolyte layer can be applied to the nonselected portion of the air electrode. A fuel electrode can be applied to the solid electrolyte, to form an electrochemical cell, for example for generation of electrical power. 5 figs.

Singh, P.; Ruka, R.J.

1995-02-14

98

Some interesting observations on the magnetic and electric properties of Al doped lanthanum orthoferrite ( LaAlFeO)  

NASA Astrophysics Data System (ADS)

Aluminum doped lanthanum orthoferrite (La 0.5Al 0.5FeO 3) (LAFO) has been prepared by solid state reaction method. The crystallographic phase of the sample has been confirmed by X-ray diffraction. The static magnetic susceptibility (?m) of the sample at different magnetic fields has been measured in the temperature range 300-14 K. The magnetization of the sample measured at room temperature increases non-linearly with the increase of magnetic field, which suggests the presence of dipole-dipole/exchange interaction in the sample. Magnetization and ?m have been considerably enhanced compared to LaFeO 3. The dynamic hysteresis loops of the sample observed at room temperature also indicates the presence of hysteretic behavior of the sample. Though the LaFeO 3 is an antiferromagnetic insulator, the resistivity measured in the temperature range 300-470 K showed that LAFO is a semiconducting material with low resistivity. The variation of dielectric constant as a function of frequency and temperature predicts the presence of spontaneous polarization in the sample.

Acharya, S.; Chakrabarti, P. K.

2010-07-01

99

Oxygen nonstoichiometry and defect structure of undoped and doped lanthanum cobaltites  

Microsoft Academic Search

The results of oxygen nonstoichiometry are presented for the perovskite-type undoped cobaltite LaCoO3-?, doped with strontium La0.7Sr0.3CoO3-?, and doped with copper LaCo0.7Cu0.3O3-? as a function of oxygen partial pressure $${p_{\\\\rm {O_2}}}$$ and temperature. The modeling of the defect structure of these oxygen deficient perovskites is carried out. Two different\\u000a defect structure models are evolved. Within the framework of the first

A. Yu. Zuev; A. N. Petrov; A. I. Vylkov; D. S. Tsvetkov

2007-01-01

100

Dielectric relaxation and alternating current conductivity of polyvinylidene fluoride doped with lanthanum chloride  

NASA Astrophysics Data System (ADS)

X-ray diffraction (XRD), dielectric constant (?'), dielectric loss factor (\\eh''), and ac conductivity (?ac) of pure and LaCl3-doped polyvinylidene fluoride (PVDF) have been carried out. The dielectric properties have been studied in the temperature and frequency ranges; 140-450 K and 0.1-1000 kHz, respectively. XRD results reveal that pure and LaCl3-PVDF samples are in the ?-phase. The incorporation of La3+ ions within the PVDF polymer matrix forms complexes which reduce the order structure of PVDF. Three relaxation processes, namely; ?, ?a, and ?c were observed for pure PVDF. The first relaxation can be explained based on space charge formation or Maxwell-Wagner polarization. The second one occurs around the glass transition temperature, Tg, and is related to the micro-Brownian motion of the main polymer chain. It becomes broad and shifted to higher temperatures with the doping of LaCl3. The third process appears below the melting temperature of PVDF and can be attributed to molecular motions of the main polymer chain. The behavior of the ac conductivity shows that the conduction mechanism of pure, 5 wt. % and 10 wt. % of LaCl3-doped PVDF samples is follows the correlated barrier hopping (CBH) model, while 3 wt. % of LaCl3-doped PVDF exhibits a small polaron tunneling (SPT) conduction.

Hassen, A.; Hanafy, T.; El-Sayed, S.; Himanshu, A.

2011-12-01

101

Microwave-assisted synthesis of Eu3+ doped lanthanum orthoborates, their characterizations and luminescent properties  

NASA Astrophysics Data System (ADS)

LaBO3 with various particle sizes have been successfully prepared by microwave-assisted combustion and sol-gel synthesis methods. Urea, citric acid and glycine have been used as fuels during the synthesis process. Characterizations were done by X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) Spectroscopy, Photoluminescence Excitation and Emission Spectroscopies, Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy (TEM). The SEM micrographs show dissimilar morphologies of powders with different particle sizes. Luminescent properties of 2.5%, 5.0%, and 7.5% Eu doped LaBO3 synthesized with three different fuels were compared. The results showed that a 5% level is the critical doping amount for all, and the one synthesized with urea gives rise to the stronger emissions compared to others.

Badan, Cansin; Esenturk, Okan; Y?lmaz, Ay?en

2012-11-01

102

Electronic Structure of Doped Lanthanum Cuprates Studied with Resonant Inelastic X-Ray Scattering  

SciTech Connect

We report a comprehensive Cu K-edge resonant inelastic x-ray scattering (RIXS) investigation of La{sub 2-x}Sr{sub x}CuO{sub 4} (LSCO) for 0 {le} x {le} 0.35, stripe-ordered La{sub 1.875}Ba{sub 0.125}CuO{sub 4} (LBCO), and La{sub 2}Cu{sub 0.96}Ni{sub 0.04}O{sub 4} (LCNO) crystals. The RIXS spectra measured at three high-symmetry momentum-transfer (q) positions are compared as a function of doping and for the different dopants. The spectra in the energy range 1-6 eV can be described with three broad peaks, which evolve systematically with increased doping. The most systematic trend was observed for q = ({pi},0) corresponding to the zone boundary. As hole doping increased, the spectral weight transfer from high energies to low energies is nearly linear with x at this q. We interpret the peaks as interband transitions in the context of existing band models for this system, assigning them to Zhang-Rice band {yields} upper Hubbard band, lower-lying band {yields} upper Hubbard band, and lower-lying band {yields} Zhang-Rice band transitions. The spectrum of stripe-ordered LBCO was also measured, and found to be identical to the correspondingly doped LSCO, except for a relative enhancement of the near-infrared peak intensity at {approx}1.5-1.7 eV. The temperature dependence of this near-infrared peak in LBCO was more pronounced than for other parts of the spectrum, continuously decreasing in intensity as the temperature was raised from 25 to 300 K. Finally, we find that 4% Ni substitution in the Cu site has a similar effect on the spectra as does Sr substitution in the La site.

Hill, J.P.; Ellis, D.S.; Kim, J.; Zhang, H.; Gu, G.; Komiya, S.; Ando, Y.; Casa, D.; Gog, T.; Kim, Y.-J.

2011-02-24

103

Lanthanum oxide doping effect on dc electrical conductivity of ferroelectrics sodium vanadate and rubidium vanadate  

Microsoft Academic Search

The temperature dependence of dc electrical conductivity was measured by two-probe technique in the vicinity of phase transition\\u000a point for ferroelectrics sodium vanadate and rubidium vanadate doped with different concentrations of La2O3. These materials show a sharp change in conductivity at their phase transition temperatures. The results were found to obey\\u000a the conventional exponential law and the activation energies were

D V Pawar; T S Magdum; S H Chavan

1995-01-01

104

Doping and temperature dependence of the Raman spectra lanthanum strontium copper oxide  

NASA Astrophysics Data System (ADS)

Polarized Raman scattering experiments have been carried out on single crystals of La2-xSRxCuO 4 La214x as a function of doping 0?x?0.22 and temperature 15K?T?300K . The polarizations of the incident and scattered light are selected to probe excitations near the axes in k-space ( B1g electronic and magnetic excitations) and near the diagonal directions ( B2g electronic excitations). The low-energy w?800cm-1 B1g Raman response undergoes a strong spectral weight depletion (SWD) as the hole concentration (x) is decreased below the optimum doping level xopt?0.17 . The magnitude of the SWD in underdoped compounds increases slightly with decreasing temperature from 300K to 15K. Furthermore, the low-energy B1g spectral weight of underdoped compounds is transferred to higher frequency region occupied by two-magnon excitations. In contrast to the doping and temperature induced SWD of the B1g spectra, the normal state B2g spectra do not exhibit any obvious variations with temperature and doping. The results are consistent with the existence of a strong anisotropic interaction in underdoped samples that results in a normal state pseudogap on regions of the FS located near the zone axes. The strength of the interaction decreases rapidly with increasing x and the spectral evidence for the pseudogap vanishes for x?xopt . The results suggest that the pseudogap arises from short range antiferromagnetic correlations in the CuO2 planes. The B1g spectra of underdoped compounds is unaffected by the transition to the superconducting state. However, the B1g spectra of optimally and overdoped compounds exhibit a strong renormalization and clear pair-breaking peaks 2D when the samples are cooled below Tc. In contrast to this behavior, the B2g spectra exhibit a superconductivity induced redistribution and 2D peaks for all x studied. The low-energy B2g response functions vary linearly with frequency for all doping levels, suggesting an anisotropic superconducting gap with nodes near the (+/-1, +/-1) directions in k-space. Meanwhile, the low-energy B1g response function changes from w3 in the case of xopt?0.17 to w for the overdoped x = 0.22 crystals. This change in power law is associated with an enhanced residual scattering in the overdoped crystals. The results are in general agreement with many predictions of the nearly antiferromagnetic Fermi liquid model, in which a tendency to order antiferromagnetically competes with a spin-fluctuation mediated pairing. (Abstract shortened by UMI.)

Gharavi-Naeini, Jafar

105

Silica-clad neodymium-doped lanthanum phosphate fibers and fiber lasers  

Microsoft Academic Search

We have fabricated a neodymium-doped phosphate glass fiber with a silica cladding and used it to form a fiber laser. Phosphate and silicate glasses have considerably different glass transition temperatures and softening points making it hard to draw a fiber from these two glasses. A bulk phosphate glass of composition (Nd2O3)0.011(La2O3 )0.259(P2O5)0.725(Al 2O3)0.005 was prepared and the resultant material was

Richard A. Martin; Jonathan C. Knight

2006-01-01

106

Synthesis, luminescence and scintillation of rare earth doped lanthanum fluoride nanoparticles  

NASA Astrophysics Data System (ADS)

Scintillation from nanoparticles is a nascent field but offers valuable fundamental insights and practical utilities. In this work, the scintillation response of LaF 3:Eu nanoparticles is reported. Core/multi-shell nanoparticles were prepared using a modified solution precipitation method that takes advantage of the organic ligand ammonium di- n-octadecyldithiophosphate (ADDP) to simultaneously achieve shelling of doped core nanoparticles while avoiding agglomeration. Nanoparticles were characterized on their structure, morphology, luminescence, and scintillation behavior by means of X-ray diffraction, transmission electron microscopy, photoluminescence, and radioluminescence (RL) measurements, respectively. Analysis of the scintillation process revealed that the unique aspect of scintillation in nanoparticles when compared to bulk materials is related to the migration of carriers within the nanoparticle. Cladding of the Eu-doped core with an undoped shell was found to increase scintillation intensity by a factor of 3, and further shelling leads to a continuous decrease in RL intensity. Surface passivation, together with the decreasing probability of radiative recombination of carriers at the luminescent centers in the core with increasing number of shells grown around the core are suggested to describe the observed RL intensity behavior. Scintillation enhancement by means of shelling is a promising pathway to enhance the use of scintillator nanoparticles in detection devices.

Jacobsohn, L. G.; Sprinkle, K. B.; Kucera, C. J.; James, T. L.; Roberts, S. A.; Qian, H.; Yukihara, E. G.; DeVol, T. A.; Ballato, J.

2010-12-01

107

Dielectric relaxation and alternating current conductivity of lanthanum, gadolinium, and erbium-polyvinyl alcohol doped films.  

PubMed

Fourier transform infrared (FTIR) spectrum dielectric constant, ?', loss tangent, tan(?), electric modulus, M*, and ac conductivity, ?(ac), of pure polyvinyl alcohol (PVA) as well as La-, Gd-, and Er-PVA doped samples have been carried out. The dielectric properties have been studied in the temperature and frequency ranges; 300-450?K and 1?kHz-4?MHz, respectively. FTIR measurements reveal that La(3+), Gd(3+), and Er(3+) ions form complex configuration within PVA structure. Two relaxation processes, namely, ? and ? were observed in pure PVA sample. The first process is due to the interfacial or Maxwell-Wagner-Sillers polarization. The second one is related to the micro-Brownian motion of the main chains. For doped PVA samples, ?-relaxation process splits into ?(a) and ?(c). This splitting is due to the segmental motion in the amorphous (?(a)) and crystalline (?(c)) phases of PVA matrix. Electric modulus analysis was discussed to understand the mechanism of the electrical transport process. The behavior of ac conductivity for all PVA samples indicates that the conduction mechanism is correlated barrier hopping. PMID:22933826

Hanafy, Taha A

2012-08-01

108

High Temperature Electrical Properties and Defect Structures of Alkaline Earth-Doped Lanthanum Cuprate Superconductors.  

NASA Astrophysics Data System (ADS)

Existing oxygen nonstoichiometry data of rm La_{2-x}Ba_{x}CuO _{4-y} and rm La _{2-x}Sr_{x}CuO_ {4-y} have been fitted by defect structure models featuring isolated oxygen vacancies, neutral associates and singly charged associates, respectively. The associate models fit the data acceptably well up to x = 0.4 while the isolated vacancy model does not fit the data as satisfactorily. Therefore, the oxygen deficiency in both systems is attributed to dopant-vacancy associates rather than isolated oxygen vacancies. However, all three models are unable to reproduce the flattening of electrical properties at high doping levels. Jonker plots reveal that the flattening is caused by degeneracy. The oxygen partial pressure dependence of the electrical properties indicates that the associates are not neutral but singly charged. Thermoelectric power and electrical conductivity have been measured in situ for rm La_ {2-x}Ca_{x}CuO_{4 -y} with x = 0-0.16 in P(O_2 ) = 10^{-5} { -1} atm at T = 700-1000^circ C. The results are similar to those of rm La_{2-x}Ba_{x}CuO _{4-y} and rm La _{2-x}Sr_{x}CuO_ {4-y} yet significant magnitudes of oxygen deficiency reportedly occur in rm La_ {2-x}Ca_{x}CuO_{4 -y} at much lower doping levels. Defect structure models involving charged oxygen vacancies cannot simultaneously fit both properties. Neutral oxygen vacancies and their association with dopants were invoked to reconcile both electrical property and oxygen nonstoichiometry data. The proposed defect structure models have been rationalized based on the bond-length mismatch first observed by Goodenough and his coworkers. The Cu-O bonds in the CuO_2 layers are longer than the La-O bonds in the (LaO)_2 layers. Substitution of larger Ba or Sr for La relieves the mismatch by lengthening the La-O bonds. Holes created for charge compensation contribute to the relief by shortening the Cu-O bonds. Once the mismatch is completely relieved, charged oxygen vacancies are formed in the (LaO)_2 layers, to minimize further expansions. The electrostatic attraction leads to the association of oppositely charged dopants and vacancies. Substitution of smaller Ca for La aggravates the mismatch by further shortening the La-O bonds. Neutral oxygen vacancies, together with holes, form in the CuO _2 layers to shorten Cu-O bonds to compensate the shortening of the La-O bonds. The association of dopants and vacancies can be explained by the preference of Ca for eight-fold coordination.

Shen, Li.

1995-01-01

109

The hard X-ray response of Ce-doped lanthanum halide scintillators  

NASA Astrophysics Data System (ADS)

We summarize the results of a number of hard X-ray measurements on cerium-doped LaCl 3 and LaBr 3 scintillators. The experiment was carried out at the HASYLAB synchrotron radiation facility using highly monochromatic pencil beams across the energy range 10.5-100 keV. Additional full-area measurements were carried out using radioactive sources. All measurements were carried out at room temperature. The measured FWHM energy resolutions (? E/ E) under pencil beam illumination were 29% (LaBr 3) and 32.4% (LaCl 3) at 10.5 keV falling to 7.8% (LaBr 3) and 9.2% (LaCl 3) at 100 keV. At 662 keV, the energy resolutions were 3.9% and 3.0% FWHM. The proportionality of the energy responses shows marked deviations from linearity above and below the La edge at 39.8 keV. At the edge the energy response changes by 3%. Fine structure across the edge was also investigated using single photon count rate measurements taken in 1 eV steps across the edge. The data show considerable near-edge structure when compared to curves generated from standard atomic data tables. However, very little evidence was found for extended X-ray fine structure suggesting that the bulk of the structure arises from the local coordination environment.

Owens, Alan; Bos, A. J. J.; Brandenburg, S.; Dorenbos, P.; Drozdowski, W.; Ostendorf, R. W.; Quarati, F.; Webb, A.; Welter, E.

2007-04-01

110

Ti-doped A-site deficient lanthanum manganites: Local structure and properties  

NASA Astrophysics Data System (ADS)

A study of La 0.6Sr 0.4-xMnTi xO 3 ( x=0.0, 0.05, 0.1, 0.15, and 0.2) manganites with the Ti in B(=Mn)-position and vacancies in A(=La, Sr)-site is presented. The manganites belonged to the rhombohedral phase and small amount of Mn 3O 4 oxide was observed with increase of Ti content. X-ray adsorption fine structure (XAFS) analysis showed an appearance of Mn 2+ ions in perovskite cell and tremendous change of local structure. We suppose that the change of local structure was mainly caused by the appearance of Mn ions in the A-positions and partially by the formation of vacancies in the above position with the increase of x-value. Curie temperature, T, decreased drastically with x: T(x=0)=355 K and, T(x=0.05)=185 K. Further increase of Ti content changed the low-temperature magnetic state from the ferromagnetic to spin/cluster glass state. Effects of destruction of the e electron pathway and change of local structure on Curie temperature, caused by the Ti doping, is discussed.

Ulyanov, Alexander N.; Yang, Dong-Seok; Lee, Kyu-Won; Greneche, Jean-Marc; Chau, Nguyen; Yu, Seong-Cho

2006-05-01

111

Samarium/Cobalt Magnets  

NASA Technical Reports Server (NTRS)

Intrinsic magnetic coercivities of samarium cobalt magnets made to approach theoretical limit of 350 kA/m by carefully eliminating oxygen from finished magnet by hot isostatic pressing (HIP). HIP process viable alternative to currently used sintering process.

Das, D.; Kumar, K.; Frost, R.; Chang, C.

1985-01-01

112

Influence of the lanthanum deficit on electrical resistivity and heat capacity of silver-doped lanthanum manganites La{sub 1-x}Ag{sub y}MnO{sub 3}  

SciTech Connect

The electrical resistivity and heat capacity of the silver-doped lanthanum manganites La{sub 0.80}Ag{sub 0.15}MnO{sub 3} and La{sub 0.85}Ag{sub 0.15}MnO{sub 3} have been investigated. Despite the nonstoichiometry of the composition, the La{sub 0.80}Ag{sub 0.15}MnO{sub 3} manganite exhibits a bulk homogeneity and better physical properties from the applied point of view as compared to the La{sub 0.85}Ag{sub 0.15}MnO{sub 3} manganite, viz., the former compound has a higher spontaneous magnetoresistance and a larger jump of the heat capacity with a small width of the phase transition, and the anomalies of the heat capacity and electrical resistivity in the vicinity of the Curie point of this compound agree with the fluctuation nature of the second-order phase transition. The behavior of the properties of lanthanum-deficient manganites under investigation in the region of the phase transition is consistent with the classical theory of indirect exchange interaction. The behavior of the temperature dependence of the electrical resistivity has been analyzed in terms of two models. One of these models is based on the tunneling of charge carriers between ferrons or polarons, and the other model is based on the polaron hopping conduction. Both approaches lead to consistent results, and their combination has made it possible to estimate the tunneling distance of charge carriers. The origin of the influence of technological parameters characterizing the synthesis of La{sub 1-x}Ag{sub y}MnO{sub 3} ceramic materials on their physical properties has been elucidated.

Abdulvagidov, Sh. B., E-mail: abdulvagidov@iwt.ru; Gamzatov, A. G. [Russian Academy of Sciences, Amirkhanov Institute of Physics, Dagestan Scientific Center (Russian Federation); Mel'nikov, O. V.; Gorbenko, O. Yu. [Moscow State University (Russian Federation)

2009-12-15

113

2.8 and 1.55 ?m emission from diode-pumped Er3+-doped and Yb3+ co-doped lead lanthanum zirconate titanate transparent ferroelectric ceramic  

NASA Astrophysics Data System (ADS)

This work reports the observation of intense emissions at 2.8 and 1.55 ?m from optical quality diode-pumped Er3+-doped lead lanthanum zirconate titanate (PLZT) transparent ferroelectric ceramic. Radiative properties were calculated using the Judd Ofelt theory, and the respective values of ?=0.09 and ?=0.94 were obtained. The effect of ytterbium co-doping the PLZT: Er3+ samples was investigated in an attempt to increase intensities. It was found that Yb3+-->Er3+ energy transfer processes, that favor Er3+ upconversion, are detrimental to the efficiency of midinfrared emissions. Even so, the advantageous spectroscopic characteristics of PLZT: Er3+ associated with its excellent thermal and mechanical properties, indicate it is a potential cost-effective laser active media.

de Camargo, A. S. S.; Botero, . R.; Andreeta, . R. M.; Garcia, D.; Eiras, J. A.; Nunes, L. A. O.

2005-06-01

114

The samarium fullerene family  

NASA Astrophysics Data System (ADS)

Among the rare earth metals samarium is expected to form an ion of the two-valent redox state in endohedral fullerene structures. As compared to thulium and europium metallofullerenes a similar distribution of carbon cage structures is expected for samarium. The samarium fullerene structures produced by the Krtschmer-Huffman method were studied with respect to the influence of the Sm-carbon ratio on the type and yield of the metallofullerenes. The chromatographic separation carried out by a two step HPLC resulted in a larger family of Sm-fullerenes (C2n, 2n=74, 78, 82, 84, 86, 88, 90, 92) encapsulating one ion as detected by mass spectrometry. Only the Sm-C76 structure was missing. No dimetallofullerenes of Sm were found. The samarium structures of C74 and C82 were characterized by UV-Vis and IR spectroscopy. The results were compared with those of EuatC74 and TmatC82. The redox state of the metal ion in the metallofullerene was shown to be Sm2+ .

Georgi, Petra; Lieb, Silvio; de San Pio, Josu Navarro; Kuran, Pavel; Dunsch, Lothar

2000-11-01

115

Solid state NMR as a new approach for the structural characterization of rare-earth doped lead lanthanum zirconate titanate laser ceramics  

NASA Astrophysics Data System (ADS)

To facilitate the design of laser host materials with optimized emission properties, detailed structural information at the atomic level is essential, regarding the local bonding environment of the active ions (distribution over distinct lattice sites) and their extent of local clustering as well as their population distribution over separate micro- or nanophases. The present study explores the potential of solid state NMR spectroscopy to provide such understanding for rare-earth doped lead lanthanum zirconate titanate (PLZT) ceramics. As the NMR signals of the paramagnetic dopant species cannot be observed directly, two complementary approaches are utilized: (1) direct observation of diamagnetic mimics using 45Sc NMR and (2) study of the paramagnetic interaction of the constituent host lattice nuclei with the rare-earth dopant, using 207Pb NMR lineshape analysis. 45Sc MAS NMR spectra of scandium-doped PLZT samples unambiguously reveal scandium to be six-coordinated, suggesting that this rare-earth ion substitutes in the B site. Static 207Pb spin echo NMR spectra of a series of Tm-doped PLZT samples reveal a clear influence of paramagnetic rare-earth dopant concentration on the NMR lineshape. In the latter case high-fidelity spectra can be obtained by spin echo mapping under systematic incrementation of the excitation frequency, benefiting from the signal-to-noise enhancement afforded by spin echo train Fourier transforms. Consistent with XRD data, the 207Pb NMR lineshape analysis suggests that statistical incorporation into the PLZT lattice occurs at dopant levels of up to 1 wt.% Tm 3+, while at higher levels the solubility limit is reached.

Mohr, Daniel; de Camargo, Andrea S. S.; Schneider, Jos F.; Queiroz, Thiago B.; Eckert, Hellmut; Botero, riton R.; Garcia, Ducinei; Eiras, Jos A.

2008-10-01

116

Visible light responsive porous Lanthanum-doped Ag3PO4 photocatalyst with high photocatalytic water oxidation activity.  

PubMed

This paper report a facile route of synthesizing Ag3PO4 crystal with smooth surface, and La-doped Ag3PO4 crystal with porous surface by accurately controlling the kinetic parameters during chemical precipitation process. As a result of surface modification induced by La doping, the La-doped Ag3PO4 crystal shows a higher photocatalytic activity than Ag3PO4 crystal in O2 evolution from water splitting. The improved photocatalytic activity of La-doped Ag3PO4 is attributed to the synergistic effects of porous surface structure, abundant surface defects and increased surface area. The result also shows that La doping concentration has a remarkable effect on the photocatalytic activity of Ag3PO4. PMID:24998046

Xie, Ying Peng; Wang, Guo Sheng

2014-09-15

117

Cost Reduction of Lanthanum Chromite Materials  

Microsoft Academic Search

Acceptor doped lanthanum chromite (LaCrO3) has long been the interconnect material of choice for high temperature SOFCs, typically operating at 1000?C. However, lanthanum chromite is relatively expensive, and many developers are currently pursuing SOFCs operating at lower temperatures. As the operating temperature is lowered, metal interconnects (e.g., ferritic steels or chromium alloys) become increasingly viable, but they have their own

Steve P. Simner; Jeffry W. Stevenson; John S. Hardy; Lawrence A. Chick

2000-01-01

118

Cost Reduction of Lanthanum Chromite Materials  

Microsoft Academic Search

Acceptor doped lanthanum chromite (LaCrO3) has long been the interconnect material of choice for high temperature SOFCs, typically operating at 1000?C, and in fact it is also viable at 800?C, since its conductivity is still 90% of that at 1000?C. However, lanthanum chromite is relatively expensive to prepare and fabricate. As the SOFC operating temperature is lowered, metal interconnects (e.g.,

Steve P. Simner; Jeffry W. Stevenson; John S. Hardy; Lawrence A. Chick

2000-01-01

119

Crystal growth of Ce{sub 2}O(CO{sub 3}){sub 2}.H{sub 2}O in aqueous solutions: Film formation and samarium doping  

SciTech Connect

Crystalline cerium oxide carbonate hydrate (Ce{sub 2}O(CO{sub 3}){sub 2}.H{sub 2}O) was grown in aqueous solutions at a low temperature of 80 deg. C under ambient pressure. When cerium nitrate was used as a starting material, large Ce{sub 2}O(CO{sub 3}){sub 2}.H{sub 2}O particles were precipitated through homogeneous nucleation and subsequent fast crystal growth. In contrast, the usage of cerium chloride was found to promote the preferential precipitation of Ce{sub 2}O(CO{sub 3}){sub 2}.H{sub 2}O on foreign substrates through heterogeneous nucleation and slow crystal growth. This phenomenon was applied to a chemical bath deposition of Ce{sub 2}O(CO{sub 3}){sub 2}.H{sub 2}O films. Immersion of glass substrates in the solution at 80 deg. C for typically 24h resulted in formation of solid films with a unique morphology like a micrometer-scale brush. It was also found that samarium could be incorporated into Ce{sub 2}O(CO{sub 3}){sub 2}.H{sub 2}O during the crystal growth in the solutions, as evidenced by characteristic photoluminescence of Sm{sup 3+} in heating products of CeO{sub 2}. These results suggest that rare-earth oxide carbonate hydrates with a variety of compositions and morphologies can be synthesized from the aqueous solutions.

Oikawa, Masashi [Department of Applied Chemistry, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522 (Japan); Fujihara, Shinobu [Department of Applied Chemistry, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522 (Japan)]. E-mail: shinobu@applc.keio.ac.jp

2005-06-15

120

Tape method of forming a thin layer of doped lanthanum chromite particles and of bonding such on an electrode  

DOEpatents

A combustible polymer film, useful for application of an interconnection on an electrode is made by: (1) providing doped LaCro.sub.3 particles; (2) dispersing doped LaCrO.sub.3 particles in a solvent, to provide a dispersion; (3) screening the dispersion to provide particles in the range of from 30 micrometers to 80 micrometers; (4) admixing a fugitive polymer with the particles; (5) casting the dispersion to provide a film; (6) drying the film; and (7) stripping the film. The film can then be applied to a porous, preheated electrode top surface, and then electrochemical vapor depositing a dense skeletal LaCrO.sub.3 structure, between and around the doped LaCrO.sub.3 particles. Additional solid oxide electrolyte and fuel electrode layers can then be added to provide a fuel cell.

Richards, Von L. (Murrysville, PA); Singhal, Subhash C. (Murrysville, PA); Pal, Uday B. (Cambridge, MA)

1992-01-01

121

Tape method of forming a thin layer of doped lanthanum chromite particles and of bonding such on an electrode  

DOEpatents

A combustible polymer film, useful for application of an interconnection on an electrode is made by: (1) providing doped LaCro[sub 3] particles; (2) dispersing doped LaCrO[sub 3] particles in a solvent, to provide a dispersion; (3) screening the dispersion to provide particles in the range of from 30 micrometers to 80 micrometers; (4) admixing a fugitive polymer with the particles; (5) casting the dispersion to provide a film; (6) drying the film; and (7) stripping the film. The film can then be applied to a porous, preheated electrode top surface, and then a dense skeletal LaCrO[sub 3] structure is electrochemically vapor deposited between and around the doped LaCrO[sub 3] particles. Additional solid oxide electrolyte and fuel electrode layers can then be added to provide a fuel cell. 4 figs.

Richards, V.L.; Singhal, S.C.; Pal, U.B.

1992-07-21

122

Spin injection and detection in lanthanum- and niobium-doped SrTiO3 using the Hanle technique  

NASA Astrophysics Data System (ADS)

There has been much interest in the injection and detection of spin-polarized carriers in semiconductors for the purposes of developing novel spintronic devices. Here we report the electrical injection and detection of spin-polarized carriers into Nb-doped strontium titanate single crystals and La-doped strontium titanate epitaxial thin films using MgO tunnel barriers and the three-terminal Hanle technique. Spin lifetimes of up to ~100?ps are measured at room temperature and vary little as the temperature is decreased to low temperatures. However, the mobility of the strontium titanate has a strong temperature dependence. This behaviour and the carrier doping dependence of the spin lifetime suggest that the spin lifetime is limited by spin-dependent scattering at the MgO/strontium titanate interfaces, perhaps related to the formation of doping induced Ti3+. Our results reveal a severe limitation of the three-terminal Hanle technique for measuring spin lifetimes within the interior of the subject material.

Han, Wei; Jiang, Xin; Kajdos, Adam; Yang, See-Hun; Stemmer, Susanne; Parkin, Stuart S. P.

2013-07-01

123

Spin injection and detection in lanthanum- and niobium-doped SrTiO3 using the Hanle technique.  

PubMed

There has been much interest in the injection and detection of spin-polarized carriers in semiconductors for the purposes of developing novel spintronic devices. Here we report the electrical injection and detection of spin-polarized carriers into Nb-doped strontium titanate single crystals and La-doped strontium titanate epitaxial thin films using MgO tunnel barriers and the three-terminal Hanle technique. Spin lifetimes of up to ~100 ps are measured at room temperature and vary little as the temperature is decreased to low temperatures. However, the mobility of the strontium titanate has a strong temperature dependence. This behaviour and the carrier doping dependence of the spin lifetime suggest that the spin lifetime is limited by spin-dependent scattering at the MgO/strontium titanate interfaces, perhaps related to the formation of doping induced Ti(3+). Our results reveal a severe limitation of the three-terminal Hanle technique for measuring spin lifetimes within the interior of the subject material. PMID:23831939

Han, Wei; Jiang, Xin; Kajdos, Adam; Yang, See-Hun; Stemmer, Susanne; Parkin, Stuart S P

2013-01-01

124

Synthesis of lanthanum oxide doped photocatalytic nano titanium oxide through aqueous solgel method for titania multifunctional ultrafiltration membrane  

Microsoft Academic Search

An all aqueous sol gel route has been demonstrated for the synthesis of titania multifunctional ultrafiltration membrane on\\u000a porous alumina substrate. Doping with lanthana was used to increase the thermal stability of anatase phase. This resulted\\u000a in a nanoporous membrane with considerable percentage of anatase phase even after consolidation at 800C. The highly homogeneous\\u000a membranes with a thickness of ~45?m

K. A. Manjumol; V. S. Smitha; P. Shajesh; K. V. Baiju; K. G. K. Warrier

2010-01-01

125

Modified giant dielectric properties of samarium doped CaCu{sub 3}Ti{sub 4}O{sub 12} ceramics  

SciTech Connect

Highlights: ? Grain size of CaCu{sub 3}Ti{sub 4}O{sub 12} ceramics was greatly decreased by doping with Sm{sup 3+}. ? ?? and tan ? decreased with increasing the concentration of Sm{sup 3+} doping. ? Ca{sub 0.925}Sm{sub 0.05}Cu{sub 3}Ti{sub 4}O{sub 12} exhibited ?? ? 10,863 and low tan ? ? 0.043 at 20 C and 1 kHz. -- Abstract: Effects of Sm{sup 3+} substitution on the microstructure and dielectric properties of CaCu{sub 3}Ti{sub 4}O{sub 12} ceramics were investigated. The grain size of CaCu{sub 3}Ti{sub 4}O{sub 12} ceramics was greatly decreased by doping with Sm{sup 3+}, resulting from the ability of Sm{sup 3+} to inhibit the grain growth rate. This result can cause a decrease in the dielectric constant (??) and loss tangent (tan ?) of CaCu{sub 3}Ti{sub 4}O{sub 12} ceramics. Interestingly, high dielectric permittivity (?? ? 10,863) and low loss tangent (tan ? ? 0.043 at 20 C and 1 kHz) were observed in the Ca{sub 0.925}Sm{sub 0.05}Cu{sub 3}Ti{sub 4}O{sub 12} ceramic. Nonlinear electrical properties of CaCu{sub 3}Ti{sub 4}O{sub 12} ceramics were modified by doping with Sm{sup 3+}. The dielectric relaxation behavior of Sm-doped CaCu{sub 3}Ti{sub 4}O{sub 12} ceramics can be well ascribed based on the internal barrier layer capacitor model of Schottky barriers at the grain boundaries.

Thongbai, Prasit, E-mail: pthongbai@kku.ac.th [Integrated Nanotechnology Research Center (INRC), and Department of Physics, Faculty of Science, Khon Kaen University, Khon Kaen 40002 (Thailand)] [Integrated Nanotechnology Research Center (INRC), and Department of Physics, Faculty of Science, Khon Kaen University, Khon Kaen 40002 (Thailand); Putasaeng, Bundit; Yamwong, Teerapon [National Metal and Materials Technology Center (MTEC), Thailand Science Park, Pathumthani, 12120 (Thailand)] [National Metal and Materials Technology Center (MTEC), Thailand Science Park, Pathumthani, 12120 (Thailand); Maensiri, Santi [School of Physics, Institute of Science, Suranaree University, Nakhon Ratchasima 30000 (Thailand)] [School of Physics, Institute of Science, Suranaree University, Nakhon Ratchasima 30000 (Thailand)

2012-09-15

126

Magnetic phase transition and clustered state in Ca-doped lanthanum cobaltite and manganite with insulator ground states.  

PubMed

The transport and magnetic properties (ac linear and nonlinear (second and third orders) susceptibilities) are presented for La0.8Ca0.2MnO3 and La0.8Ca0.2CoO3 single crystals with insulator ground states. The ferromagnetic (FM) clusters with similar magnetic characteristics originate in the paramagnetic phases of both compounds below some temperature T(?). At high temperatures the FM clusters arise at the preferable sites that can be attributed to the chemical inhomogeneities, their density being weakly T-dependent. On cooling a homogeneous nucleation of the FM clusters develops below a definite temperature T(#) that is characterized by a fast growth of their density. These two stages are observed in both compounds. At the third stage a coalescence of the FM clusters starts in the doped cobaltite, whereas in the manganite the development of matrix FM ordering occurs which changes a cluster's behavior. The indicated features support the common nature of the cluster state in the doped cobaltite and manganite. The difference in their evolution is a consequence of the different magnetic properties of the matrices in the manganite and cobaltite. PMID:24476586

Ryzhov, V A; Lazuta, A V; Khavronin, V P; Molkanov, P L; Mukovskii, Ya M

2014-02-19

127

Near-infrared broadband luminescence and energy transfer in Bi-Tm-Er co-doped lanthanum aluminosilicate glasses  

NASA Astrophysics Data System (ADS)

The Bi-Tm-Er co-doped SiO2-Al2O3-La2O3 (SAL) glasses, which exhibited a broadband near-infrared (NIR) emission, were investigated by the optical absorption and photoluminescence spectra. A super broadband NIR emission extending from 0.95 to 1.6 ?m with a full-width at half-maximum (FWHM) of 430 nm which covered the whole O, E, S, C and L bands, was observed in Bi-Tm-Er co-doped samples under 808 nm excitation, as a result of the overlap of the Bi-related emission band (centered at 1270 nm) and the emission from Tm3+3H4?3F4 transition (1450 nm) as well as Er3+4I13/2?4I15/2 transition (1545 nm). In addition, a super broadband emission with amplitude relatively flat from 0.95 to 2.1 ?m has been observed. The possible energy transfer between Bi-related centers, Tm3+ ions and Er3+ ions was proposed.

Minh Hau, Tran; Wang, Rongfei; Yu, Xue; Zhou, Dacheng; Song, Zhiguo; Yang, Zhengwen; He, Xijia; Qiu, Jianbei

2012-09-01

128

Magnetic phase transition and clustered state in Ca-doped lanthanum cobaltite and manganite with insulator ground states  

NASA Astrophysics Data System (ADS)

The transport and magnetic properties (ac linear and nonlinear (second and third orders) susceptibilities) are presented for La0.8Ca0.2MnO3 and La0.8Ca0.2CoO3 single crystals with insulator ground states. The ferromagnetic (FM) clusters with similar magnetic characteristics originate in the paramagnetic phases of both compounds below some temperature T?. At high temperatures the FM clusters arise at the preferable sites that can be attributed to the chemical inhomogeneities, their density being weakly T-dependent. On cooling a homogeneous nucleation of the FM clusters develops below a definite temperature T# that is characterized by a fast growth of their density. These two stages are observed in both compounds. At the third stage a coalescence of the FM clusters starts in the doped cobaltite, whereas in the manganite the development of matrix FM ordering occurs which changes a clusters behavior. The indicated features support the common nature of the cluster state in the doped cobaltite and manganite. The difference in their evolution is a consequence of the different magnetic properties of the matrices in the manganite and cobaltite. In memory of Ya M Mukovskii who sadly passed away before this article was published.

Ryzhov, V. A.; Lazuta, A. V.; Khavronin, V. P.; Molkanov, P. L.; Mukovskii, Ya M.

2014-02-01

129

Novel Au/La-SrTiO3 microspheres: Superimposed Effect of Gold Nanoparticles and Lanthanum Doping in Photocatalysis.  

PubMed

Novel multielement Au/La-SrTiO3 microspheres were synthesized by a solvothermal method using monodisperse gold and La-SrTiO3 nanocrystals as building blocks. The porous Au/La-SrTiO3 microspheres had a large surface area of 94.6?m(2) ?g(-1) . The stable confined Au nanoparticles demonstrated strong surface plasmon resonance effect, leading to enhanced absorption in a broad UV/Vis/NIR range. Doping of rare-earth metal La also broadened the absorption band to the visible region. Both the conduction and valence bands of Au/La-SrTiO3 microspheres thus show favorable potential for proton reduction under visible light. The superimposed effect of Au nanoparticles and La doping in Au/La-SrTiO3 microspheres led to high photocurrent density in photoelectrochemical water splitting and good photocatalytic activity in photodegradation of rhodamine?B. The photocatalytic activities are in the order of the following: Au/La-SrTiO3 microspheres>Au/SrTiO3 microspheres>La-SrTiO3 microspheres>SrTiO3 microspheres. PMID:24817580

Wang, Guannan; Wang, Pei; Luo, He-Kuan; Hor, T S Andy

2014-07-01

130

Soft X-Ray Spectroscopic Study of Dense Strontium-Doped Lanthanum Manganite Cathodes for Solid Oxide Fuel Cell Applications  

SciTech Connect

The evolution of the Mn charge state, chemical composition, and electronic structure of La{sub 0.8}Sr{sub 0.2}MnO{sub 3} (LSMO) cathodes during the catalytic activation of solid oxide fuel cell (SOFC) has been studies using X-ray spectroscopy of as-processed, exposed, and activated dense thin LSMO films. Comparison of O K-edge and Mn L{sub 3,2}-edge X-ray absorption spectra from the different stages of LSMO cathodes revealed that the largest change after the activation occurred in the Mn charge state with little change in the oxygen environment. Core-level X-ray photoemission spectroscopy and Mn L{sub 3} resonant photoemission spectroscopy studies of exposed and as-processed LSMO determined that the SOFC environment (800 C ambient pressure of O{sub 2}) alone results in La deficiency (severest near the surface with Sr doping >0.55) and a stronger Mn{sup 4+} contribution, leading to the increased insulating character of the cathode prior to activation. Meanwhile, O K-edge X-ray absorption measurements support Sr/La enrichment nearer the surface, along with the formation of mixed Sr{sub x}Mn{sub y}O{sub z} and/or passive MnO{sub x} and SrO species.

L Piper; A Preston; S Cho; A DeMasi; J Laverock; K Smith; L Miara; J Davis; S Basu; et al.

2011-12-31

131

Soft X-Ray Spectroscopic Study of Dense Strontium-Doped Lanthanum Manganite Cathodes for Solid Oxide Fuel Cell Applications  

SciTech Connect

The modification of the Mn charge-state, chemical composition and electronic structure of La0.8Sr0.2MnO3 (LSMO) cathodes for solid oxide fuel cell (SOFC) applications remains an area of interest, due to the poorly understood enhanced catalytic activity (often referred to as the "burn-in" phenomenon) observed after many hours of operation. Using a combination of core-level X-ray photoemission spectroscopy (XPS), X-ray emission/absorption spectroscopy (XES/XAS), resonant inelastic X-ray scattering (RIXS) and resonant photoemission spectroscopy (RPES), we have monitored the evolution of these properties in LSMO at various stages of fabrication and operation. By rapidly quenching and sealing in vacuum, we were able to directly compare the pristine (as-fabricated) LSMO with both "heat-treated" (800C in air, and no bias) and "burnt-in" (800C in air, -1 V bias) LSMO cathodes i.e. before and after the activation observed in our electrochemical impendence spectroscopy measurements. Comparison between the O K-edge XAS/XES and Mn L3,2-edge XAS of pristine and burnt-in LSMO cathodes revealed a severe change in the oxygen environment along with a reduced Mn2+ presence near the surface following activation. The change in the oxygen environment is attributed to SrxMnyOz formation, along with possible passive SrO and Mn3O4 species. We present evidence from our heat-treated samples that SrxMnyOz regions form at elevated temperatures in air before the application of a cathodic bias. Our core-level XPS, Mn L3,2-edge RIXS and Mn L3 RPES studies of heat-treated and pristine LSMO determined that SOFC environments result in La-deficiency (severest near the surface) and stronger Mn4+ contribution, leading to the increased insulating character of the cathode prior to activation. The passive Mn2+ species near the surface and increased hole-doping (>0.6) of the LSMO upon exposure to the operating environment are considered responsible for the initially poor performance of the SOFC. Meanwhile, the improved oxygen reduction following the application of a cathodic bias is considered to be due to enhanced bulk oxygen-ion diffusion resulting from the migration of Mn2+ ions towards the LSMO/electrolyte interface and the SrxMnyOz regions facilitating enhanced bulk oxygen reduction reaction kinetics.

Piper, L.F.J.; Preston, Andrew R.H.; Cho, Sang Wan; DeMasi, Alexander; Chen, Bin; Laverock, J.; Smith, K. E.; Miara, Lincoln J.; Davis, Jacob N.; Basu, Soumendra; Pal, Uday B.; Gopalan, Srikanth; Saraf, Laxmikant V.; Kaspar, Tiffany C.; Matsuura, A. Y.; Glans, P.A.; Guo, Jianzhong

2010-12-02

132

Defect equilibria and chemical expansion in undoped and doped ceria and strontium doped lanthanum cobalt iron oxide oxygen conducting materials and their applications in solid-state electrochemical cells  

NASA Astrophysics Data System (ADS)

Ceramic oxygen conducting materials are used in many energy-related applications from fuel reforming to electricity generation. In a typical ceramic oxygen conductor, oxygen ions are transmitted through a dense membrane via defects in the material. Hence, defects control the performance of these materials. In low oxygen partial pressure, ceria based materials become non-stoichiometric and can form defect complexes that hinder ionic conductivity. In addition, oxygen non-stoichiometry induces strain (chemical expansion) that can result in stresses for composite or constrained applications. In this dissertation the non-stoichiometry and chemical expansion behavior is reported as a function of PO2 for undoped ceria, gadolinium doped ceria (GDC) and strontium doped lanthanum cobalt iron oxide (LSCF). Undoped ceria was measured at 800C and GDC and LSCF at 600--900C in a wide PO2 range. It was found that defect interactions could effectively be modeled in ceria based materials using defect complex formation in a mass action formalism and the results were used to model nonlinear chemical expansion behavior. In LSCF, non-stoichiometry and chemical expansion were modeled using using metallic and semi-conductor models. A semi-conductor model with B-site small polarons best represented the measured behavior. The resulting models and parameters can be used to predict mechanical and electrical behavior of SOFC components. Surface oxygen non-stoichiometry has also been measured by comparing low surface area to high surface area samples. It was found that surface defect concentration previously ignored in the literature can result in erroneous non-stoichiometry measurements. In the latter half of this dissertation these materials are applied in SOFC and ceramic oxygen generator (COG) technology. A strategy is presented here for advanced life support systems employs a catalytic layer combined with a COG cell so that CO2 is reduced all the way to solid carbon and oxygen without carbon buildup on the COG cell and subsequent deactivation. In addition, a highly porous GDC anode support is developed that is infiltrated with metal. SOFCs are fabricated that utilize the highly porous support and operate on hydrocarbon fuels that show initial performance > 250 mW/cm 2 at 600 C on vaporized dodecane.

Bishop, Sean R.

133

Crystal structure and ionic conductivity of Mg-doped apatite-type lanthanum silicates La10Si6?xMgxO27?x (x = 00.4)  

NASA Astrophysics Data System (ADS)

Lanthanum silicates La10Si6?xMgxO27?x (x = 00.4) were prepared by solid state synthesis to investigate the effect of Mg doping on crystal structure and ionic conductivity. Rietveld analysis of the powder XRD patterns reveals that Mg substitution on Si site results in significant enlargement of channel triangles, favoring oxide-ion conduction. Furthermore, an increase of Mg concentration significantly influences the linear density of interstitial oxygen, which plays an important role in ionic conductivity. The Arrhenius plots of La10Si6?xMgxO27?x (x = 00.4) suggest that Mg-doped samples present higher conductivity and lower activation energy than non-doped La10Si6O27, and La10Si5.8Mg0.2O26.8 exhibits the highest conductivity with a value of 3.010?2 S cm?1 at 700 C. Such conductive behavior agrees well with the refined results. The corresponding mechanism has been discussed in this paper.

Yin, Guang-Chao; Yin, Hong; Zhong, Lin-Hong; Sun, Mei-Ling; Zhang, Jun-Kai; Xie, Xiao-Jun; Cong, Ri-Dong; Wang, Xin; Gao, Wei; Cui, Qi-Liang

2014-04-01

134

Effect of samarium substitution on structural and magnetic properties of magnesium ferrite nanoparticles  

NASA Astrophysics Data System (ADS)

Samarium doped magnesium ferrite was prepared (MgSmxFe2-xO4) by sol-gel method. X-ray diffraction analysis reveals that the samples are single phasic with crystallite sizes in the 13-25 nm regime. Increase in lattice parameter with doping concentration suggests the expansion in unit cell with Sm3+ doping. Fourier Transform Infrared Spectrum shows substitution of Sm3+ ions in octahedral B site. Transmission Electron Micrograph shows the spherical shape of nano-particles. Magnetic measurement shows a decrease in magnetization with doping which is explained using dependence on particle size.

Thankachan, Smitha; Jacob, Binu P.; Xavier, Sheena; Mohammed, E. M.

2013-12-01

135

Toughening in lanthanum chromite due to metastable phase  

SciTech Connect

Alkali earth doped lanthanum chromite ceramics are preferred for use in solid oxide fuel cells because of their electronic conductivity and resistance to both oxidizing and reducing atmospheres. However, there is a phase transformation that can be disruptive which occurs at approximately 300 to 400 C at the orthorhombic to rhombohedral phase boundary in undoped and in magnesia or calcia doped lanthanum chromite. The purpose of this research was to investigate air sinterable, chromia deficient, calcia doped lanthanum chromite by 4 point bending for strength (MOR), and toughness (K{sub IC}) versus temperature to 1,000 C. The initial analysis was to verify the results of Mori et al. As-fired specimens sintered at 1,600 C were compared with specimens aged at 1,000 C for 48 hours after sintering at 1,600 C to investigate the effect of any residual transient phases on the properties.

Montross, C.S.; Yokokawa, Harumi; Dokiya, Masayuki [National Inst. for Materials and Chemical Research, Tsukuba, Ibaraki (Japan)] [National Inst. for Materials and Chemical Research, Tsukuba, Ibaraki (Japan)

1996-03-15

136

Sintering of lanthanum chromite using strontium vanadate  

Microsoft Academic Search

Small proportions (5 and 10 wt.%) of strontium vanadate (Sr3(VO4)2) were added to strontium-doped lanthanum chromite (La0.85Sr0.15CrO3) to produce high density fuel cell interconnect materials in air at 1550C without adversely affecting the desirable properties of the material. Compositions investigated were shown to have good electrical conductivity at SOFC operating temperatures in air and reducing environments, phase stability from room

S. P Simner; J. S Hardy; J. W Stevenson; T. R Armstrong

2000-01-01

137

Develop Techniques for Ion Implantation of PLZT (Lead-Lanthanum-Zirconate-Titanate) for Adaptive Optics.  

National Technical Information Service (NTIS)

Research was conducted at Pacific Northwest Laboratory to develop high photosensitivity adaptive optical elements utilizing ion implanted lanthanum-doped lead-zirconate-titanate (PLZT). One centimeter square samples were prepared by implanting ferroelectr...

C. R. Batishko J. L. Brimhall W. T. Pawlewicz K. A. Stahl L. H. Toburen

1987-01-01

138

Novel samarium/erbium and samarium/terbium codoped glass phosphor for application in warm white light-emitting-diode  

NASA Astrophysics Data System (ADS)

Tunable polychromatic light emission within the low color correlated temperature range was produced using terbiumand/ or erbium-samarium co-doped PbGeO3:PbF2:CdF2 glass phosphor. The phosphors were synthesized, and their luminescence characteristics were examined under UV-blue light-emitting-diode laser excitation. Luminescence emission around 490, 545, 600, and 645 nm in Tb3+/Sm3+ and 525, 545, 600, and 645 nm in Er3+/Sm3+ co-doped phosphor was obtained and analyzed as a function of the active ions concentration, and excitation wavelength. Color tunability in the red-orange-yellow-green region was achieved combining of Tb3+, Er3+, and Sm3+ ions contents. Results suggest that the color-tunable polychromatic light emitter phosphor herein reported is a promising novel candidate for application in cold white-light LED-based illumination technology

da Silva, Cosmo M.; Gouveia-Neto, Artur S.; Bueno, Luciano A.

2014-02-01

139

Thermovoltaic effect in polycrystalline samarium sulfide  

NASA Astrophysics Data System (ADS)

A thermovoltaic effect has been observed for the first time in a polycrystalline sample of samarium sulfide (SmS) with artificially created concentration gradient of excess (overstoichiometric) samarium ions, in which an electric voltage of 12-22.5 mV was generated in a temperature interval of 370-485 K. It is shown that the specific voltage generation in SmS due to the thermovoltaic effect can be observed in a temperature range of 100-1800 K.

Kaminski?, V. V.; Didik, V. A.; Kazanin, M. M.; Romanova, M. V.; Solov'ev, S. M.

2009-11-01

140

Cost Reduction of Lanthanum Chromite Materials  

SciTech Connect

Acceptor doped lanthanum chromite (LaCrO3) has long been the interconnect material of choice for high temperature SOFCs, typically operating at 1000?C. However, lanthanum chromite is relatively expensive, and many developers are currently pursuing SOFCs operating at lower temperatures. As the operating temperature is lowered, metal interconnects (e.g., ferritic steels or chromium alloys) become increasingly viable, but they have their own unique problems (including Cr-oxide formation and Cr volatilization), and it is therefore likely that uncoated metals cannot be used at temperatures greater than 700?C. For intermediate operating temperatures (700-800?C), the application of protective oxide coatings may allow the use of metal interconnects (if such coatings can be applied cost-effectively), but lanthanum chromite may offer better long-term performance. While the electrical conductivity of lanthanum chromite does decrease as temperature decreases, the conductivity at 800?C is only about 10% less than the conductivity at 1000?C. In this study, the authors have investigated the viability of replacing pure La in the acceptor doped LaCrO3 with a less expensive mixed lanthanide (Ln) precursor containing La3+ as the principle cation, but also Ce4+, Nd3+ and Pr3+ in significant proportions. Typical compositions investigated were of the formula Ln0.85Sr0.15Cr1-yMyO3, where 0.02?y?0.1 and M= Co, Cu, Ni, and V. Samples were studied with respect to sinterability in air, thermal expansion, conductivity in air and at low pO2, phase stability, and dilation under reducing atmospheres.

Simner, Steve P. (BATTELLE (PACIFIC NW LAB)); Stevenson, Jeffry W. (BATTELLE (PACIFIC NW LAB)); Hardy, John S. (BATTELLE (PACIFIC NW LAB)); Chick, Lawrence A. (BATTELLE (PACIFIC NW LAB))

2000-01-01

141

Tunable quasi-cw two-micron lasing in diode-pumped crystals of mixed Tm{sup 3+}-doped sodium - lanthanum - gadolinium molybdates and tungstates  

SciTech Connect

Two-micron lasing is obtained for the first time on the {sup 3}F{sub 4} {yields} {sup 3}H{sub 6} transition of Tm{sup 3+} ions in diode-pumped crystals of mixed sodium - lanthanum - gadolinium tungstate Tm:NaLa{sub 1/2}Gd{sub 1/2}(WO{sub 4}){sub 2} (C{sub Tm} = 3.6 at %) (3.6Tm : NLGW) and molybdate Tm:NaLa{sub 1/3}Gd{sub 2/3}(MoO{sub 4}){sub 2} (C{sub Tm} = 4.8 at %) (4.8Tm : NLGM). For the 3.6Tm : NLGW crystal, the quasi-cw laser output power exceeded 200 mW and the slope efficiency (with respect to absorbed pump power) for the {pi}- and {sigma}-polarisations at wavelengths of 1908 and 1918 nm was 34% and 30%, respectively. The laser wavelength of this crystal was continuously tuned within the spectral range of 1860 - 1935 nm. For the 4.8Tm : NLGM crystal, the slope efficiency for the {pi}- and {sigma}-polarisations at wavelengths of 1910 and 1918 nm was 27% and 23%, respectively, and the laser wavelength was tunable within the spectral range of 1870 - 1950 nm. (lasers)

Bol'shchikov, F A; Ryabochkina, P A [N.P. Ogarev Mordovian State University, Saransk (Russian Federation); Zharikov, Evgeny V; Lis, Denis A; Subbotin, Kirill A [A M Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Zakharov, N G; Antipov, Oleg L [Institute of Applied Physics, Russian Academy of Sciences, Nizhnii Novgorod (Russian Federation)

2010-12-09

142

Radiative lifetimes of neutral samarium  

NASA Astrophysics Data System (ADS)

Radiative lifetimes of 120 odd-parity levels of neutral samarium, ranging in energy from 17?190 to 33?507 cm-1, are measured using the technique of time-resolved laser-induced fluorescence on a slow atomic beam. This work is part of an ongoing study of radiative properties of rare earth neutral atoms, and is motivated by research needs in astrophysics and lighting technology. This set of Sm i lifetimes substantially increases the available published lifetime data, with 49 of the 120 level lifetimes measured for the first time. These data, most of which are accurate to 5%, will be combined with branching fractions determined from Fourier transform spectroscopy to produce a large set of measured Sm i transition probabilities.

Den Hartog, E. A.; Lawler, J. E.

2013-09-01

143

ZIRCONIA-BASED MIXED POTENTIAL CARBON MONOXIDE\\/HYDROCARBON SENSORS WITH LANTHANUM MAGNESIUM OXIDE, AND TERBIUM-DOPED YTTRIUM STABILIZED ZIRCONIA ELECTRODES  

Microsoft Academic Search

We have investigated the performance of dual metal oxide electrode mixed potential sensors in an engine-out, dynamometer environment. Sensors were fabricated by sputtering thin films of LaMnO and Tb-doped YSZ onto YSZ electrolyte. Au gauze held onto the metal oxide thin films with Au ink was used for current collection. The exhaust gas from a 4.8L, V8 engine operated in

E. L. BROSHA; R. MUKUNDAN

2000-01-01

144

Energy Transfer in Rare Earth Ion Clusters and Fluorescence from Rare Earth Doped LANTHANUM(1.85)STRONTIUM(0.15)COPPER -OXYGEN(4) Superconductors.  

NASA Astrophysics Data System (ADS)

Laser spectroscopy of rare earth ions in solids was used to study mechanisms of non-resonant energy transfer within rare earth clusters, and to detect insulating, impurity phases in rare earth doped La_{1.85 }Sr_{0.15}CuO _4 superconductors. The mechanisms of phonon-assisted, non-resonant energy transfer were studied in well-defined dimer sites in Er^{3+ }:SrF_2 and Pr ^{3+}:CaF_2. Application of a magnetic field to Er^{3+} :SrF_2 greatly increased the energy transfer rate. The magnetic field dependence in Er^{3+}:SrF _2 indicates that the mechanism of non-resonant energy transfer is a two-phonon, resonant process (Orbach process). Application of a magnetic field to Pr ^{3+}:CaF_2 had no effect on the energy transfer rate because no significant Zeeman splittings occurred. The temperature dependence of the energy transfer rate in Pr^{3+ }:CaF_2 showed the mechanism to be a one-phonon-assisted process at low temperatures and predominantly an Orbach process above 10 K. In the second part of this thesis, laser spectroscopy of a Eu ^{3+} probe ion is developed to detect impurity phases in La_{1.85 }Sr_{0.15}CuO _4 superconductors. Two impurity phases were found in polycrystalline La_ {1.85}Sr_{0.15} CuO_4: unreacted La _2O_3 starting material, and a La-silicate phase, which formed from contamination during sintering. The spectroscopic technique was found to be more than 100 times more sensitive than powder x -ray diffraction to detect minor impurity phases. In preparing the superconductors, several studies were made on the effect of Pr^{3+}, Eu ^{3+}, Bi^{3+ }, and fluorine dopants on the superconducting properties of La_{1.85}Sr _{0.15}CuO_4 and La_2Cuo_4 . Pr^{3+}, Eu ^{3+}, Bi^ {3+}, and F_2 doping all decreased the superconductivity in La_ {1.85}Sr^{0.15} CuO_4. Treating semi-conducting La_2CuO_4 in F_2 gas converted it to a superconductor with an onset T_{rm c} of 30-35 K.

Tissue, Brian Max

1988-12-01

145

Influence of samarium doping on electronic and magneto-transport properties of La0.9-xSmxSr0.1MnO3 (0.1?x?0.5) nanoparticles  

NASA Astrophysics Data System (ADS)

We report detailed field dependent electronic- (?-T) and magneto- transport (MR-H) studies of La1-xSmxSr0.1MnO3 (0.1?x?0.5) nanoparticles. Doping induced disorder at La site is observed in field dependent ?-T measurements of the sample. At low doping side, nice metal to insulator transition (MIT) peak appears in ?-T data whereas with increasing of Sm+3 contents, metallic behavior is suppressed under the insulating background although a weak signature of MIT is found. Anomalous resistive nature of the samples with increasing of x can be explained in such a way that doping at nonmagnetic La site with magnetic Sm+3 ion induces an extra magnetic coupling in the system which changes the long range ferromagnetic ordering to spin glass/cluster glass state in antiferromagnetic background. The field dependent magneto resistance (MR) mechanism at different temperatures is investigated using spin polarized tunneling model of conduction electrons between two adjacent grains at the grain boundaries. For the sample of x=0.5, maximum 83 % change in MR is found at 8 T near MIT which leads the colossal magneto resistance effect.

Das, Proloy T.; Gupta, Kajal; Jana, Paresh Chandra; Nath, Tapan Kumar

2014-04-01

146

Aerosol generation of lanthanum aluminate  

SciTech Connect

Spherical lanthanum aluminate powders approximately [mu]m in diameter were produced using spray pyrolysis techniques. These materials were characterized by Z-ray diffractometry and scanning electron microscopy. Two intermediate products were produced and identified as lanthanum oxide and aluminum oxide. These intermediates were present in varying amounts in all of the aerosol-furnace-prepared materials and reflect the short residence time of the aerosols in the furnace. Samples of each aerosol-furnace preparation were further annealed in air for 1 h at 1100 C, and all of them converted completely to lanthanum aluminate.

Lux, B.C.; Clark, R.D.; Salazar, A.; Sveum, L.K.; Krebs, M.A. (New Mexico Highlands Univ., Las Vegas, NM (United States). School of Science and Engineering, Dept. of Physical Sciences)

1993-10-01

147

Atomic transition probabilities of neutral samarium  

NASA Astrophysics Data System (ADS)

Absolute atomic transition probabilities from a combination of new emission branching fraction measurements using Fourier transform spectrometer data with radiative lifetimes from recent laser induced fluorescence measurements are reported for 299 lines of the first spectrum of samarium (Sm i). Improved values for the upper and lower energy levels of these lines are also reported. Comparisons to published transition probabilities from earlier experiments show satisfactory and good agreement with two of the four published data sets.

Lawler, J. E.; Fittante, A. J.; Den Hartog, E. A.

2013-11-01

148

Zur Isotopieverschiebung im Spektrum des Samariums  

Microsoft Academic Search

Zusammenfassung Es wurde die Hyperfeinstruktur einer Reihe von Samarium-Linien zwischen 4300 und 7200 mit einemFabry-Prot-Interferometer photographiert und vor allem im Hinblick auf die Isotopieverschiebung der geraden Isotope untersucht. Fr die ungeraden Isotope lie sich nur entnehmen, da der Kernspin des Sm 147 und Sm 149 ? 3\\/2 sein mu. Aus fnf photometrisch besonders genau analysierten Sm I-Linien wurden die

Peter Brix; Hans Kopfermann

1949-01-01

149

Metallic behavior of lanthanum disilicide  

NASA Technical Reports Server (NTRS)

Polycrystalline thin films of LaSi2 were prepared by reaction of sputter-deposited lanthanum layers with silicon wafers. Samples of the low-temperature tetragonal and the high-temperature orthorhombic phases were separately obtained. The room-temperature intrinsic resistivities were 24 and 57 microohm cm for the low- and high-temperature structures, respectively. Although lanthanum disilicide had been previously reported to be a semiconductor, classical metallic behavior was found for both phases.

Long, Robert G.; Bost, M. C.; Mahan, John E.

1988-01-01

150

Lanthanum Bromide Detectors for Safeguards Measurements  

SciTech Connect

Lanthanum bromide has advantages over other popular inorganic scintillator detectors. Lanthanum bromide offers superior resolution, and good efficiency when compared to sodium iodide and lanthanum chloride. It is a good alternative to high purity germanium detectors for some safeguards applications. This paper offers an initial look at lanthanum bromide detectors. Resolution of lanthanum bromide will be compared lanthanum chloride and sodium-iodide detectors through check source measurements. Relative efficiency and angular dependence will be looked at. Nuclear material spectra, to include plutonium and highly enriched uranium, will be compared between detector types.

Wright, J.

2011-05-25

151

[Lanthanum carbonate in clinical practice].  

PubMed

Lanthanum is an element belonging to the group called rare earths. Due to its low solubility, lanthanum carbonate has been widely studied as an intestinal phosphate binder. The results of different clinical trials show that it is an effective and well-tolerated phosphate binder used in monotherapy. Serum phosphate levels are controlled in approximately 70% of patients at 5 years without causing hypercalcemia. The only significant adverse effects observed are a low percentage of gastrointestinal disturbances (6%). Lanthanum carbonate does not alter serum values of liposoluble vitamins or affect the pharmacokinetics of digoxin, warfarin, furosemide, phenytoin, ACE inhibitors or beta-blockers. However, it does alter the pharmacokinetics of ciprofloxacin (quinolones in general), tetracyclines and doxycycline. Lanthanum carbonate (Fosrenol) is available in Spain as 500 mg, 750 mg, and 1,000 mg chewable tablets, which should not be swallowed without chewing to avoid loss of efficacy. The initial dose recommended by the WHO is 2,250 mg/day, which is equivalent to one 750 mg at each meal. Lanthanum carbonate or lanthanum phosphate can be clearly visualized on a plain x-ray of the abdomen in patients who have recently ingested it. In summary, lanthanum carbonate is a widely studied potent phosphate binder, which offers the possibility of improving control of serum phosphate in patients with chronic kidney disease, without significant side effects. The fact that it is available as chewable tablets and that the number of daily tablets required has been significantly reduced will probably facilitate better patient compliance. PMID:18847414

Torregrosa Prats, V

2008-01-01

152

Thermodynamic properties of higher lanthanum silicide  

Microsoft Academic Search

The thermodynamic properties of lanthanum disilicide were examined for the first time in the 960-1050°K range by measuring the electromotive force of a galvanic cell based on LaSn, the chlorides of potassium, sodium, and lanthanum, and lanthanum silicide and silicon. Reference electrodes were used to prevent lanthanum interaction with the electrolyte. The alloys were melted in an electric arc furnace

R. I. Polotskaya

1988-01-01

153

Lanthanum chromite-based materials for solid oxide fuel cell interconnects  

Microsoft Academic Search

One of the challenges for advancing solid oxide fuel cell (SOFC) technology is the development of interconnect materials with adequate conductivity and stability for efficient long-term use. One of the most promising interconnect materials is doped lanthanum chromite, which has good conductivity at high temperatures and is stable in oxidizing and reducing atmospheres. In this paper, the effects of strontium,

Jeffrey W. Fergus

2004-01-01

154

Cost Reduction of Lanthanum Chromite Materials  

SciTech Connect

Acceptor doped lanthanum chromite (LaCrO3) has long been the interconnect material of choice for high temperature SOFCs, typically operating at 1000?C, and in fact it is also viable at 800?C, since its conductivity is still 90% of that at 1000?C. However, lanthanum chromite is relatively expensive to prepare and fabricate. As the SOFC operating temperature is lowered, metal interconnects (e.g., ferritic steels or chromium alloys) become increasingly viable, but they have their own unique problems (including Cr-oxide formation and Cr volatilization), and it is therefore unlikely that bare metals can be used at temperatures greater than 700?C. For intermediate operating temperatures (700-800?C), development of cost-effective oxide coatings may allow use of metal interconnects, but the long-term performance of such coated metals remains in doubt. In the event that even coated metals prove unsatisfactory, lanthanum chromite may be the only viable choice, in which case it will be essential to continue to reduce chromite raw material and fabrication costs. In this study, the authors have investigated the practicality of replacing pure La in LaCrO3 with a less expensive mixed lanthanide (Ln) precursor, containing mainly La3+, but also significant proportions of Ce4+, Nd3+ and Pr3+. Typical compositions investigated were of the formula Ln0.85Sr0.15Cr1-yMyO3, where 0.02*y*0.1 and M= Co, Cu, Ni, and V. Samples were studied with respect to sinterability in air, thermal expansion, conductivity in air and at low pO2, phase stability, and dilation under reducing atmospheres. The most promising of the materials investigated was Ln0.85Sr0.15Cr0.95Cu0.05O3, which could be sintered to>90% theoretical density at 1250?C. This material exhibited conductivities>20 S/cm in air and>5 S/cm at pO2= 10-16 atm, and indicated no phase change from 25-1000?C. The TEC (25-1000?C) of the material, 9.4 x 10-6?C-1, was somewhat lower than that of the YSZ electrolyte (10.5x 10-6?C-1).

Simner, Steve P. (BATTELLE (PACIFIC NW LAB)); Stevenson, Jeffry W. (BATTELLE (PACIFIC NW LAB)); Hardy, John S. (BATTELLE (PACIFIC NW LAB)); Chick, Lawrence A. (BATTELLE (PACIFIC NW LAB))

2000-02-28

155

Samarium(III) catalyzed one-pot construction of coumarins  

Microsoft Academic Search

Samarium(III) nitrate hexahydrate as a catalyst is used as an alternative to conventional acid catalysts in the von Pechmann condensation of phenols with ethyl acetoacetate leading to the formation of coumarin derivatives.

Sushilkumar S. Bahekar; Devanand B. Shinde

2004-01-01

156

Terbium-activated lithiumlanthanumaluminosilicate oxyfluoride scintillating glass and glass-ceramic  

Microsoft Academic Search

Terbium-activated lithiumlanthanumaluminosilicate oxyfluoride scintillating glasses, 55SiO26Al2O328Li2O11LaF3 doped with different TbF3 concentrations, have been fabricated and investigated. By appropriate heat treatment of the as-prepared glasses above, transparent glass-ceramics were obtained. Differential scanning calorimetry, X-ray diffraction, optical absorption, and luminescence under both UV and beta-particle excitation have been investigated on as-prepared glasses and glass-ceramics. It has been found that these terbium-activated lithiumlanthanumaluminosilicate

Z. Pan; K. James; Y. Cui; A. Burger; N. Cherepy; S. A. Payne; R. Mu; S. H. Morgan

2008-01-01

157

Samarium-neodymium direct dating of fluorite mineralization  

Microsoft Academic Search

The direct dating of many styles of hydrothermal mineralization has proved difficult, limiting understanding of the geological processes that lead to crustal fluid flow and the formation of major ore deposits. The hydrothermal mineral fluorite (CaF) displays large variations in rare earth element (REE) abundance and samarium\\/neodymium ratios within a single vein. Samarium-neodymium dating of fluorite from the classic granite-hosted

J. T. Chesley; A. N. Halliday; R. C. Scrivener

1991-01-01

158

Ultrasonic Attenuation in Lanthanum Monochalcogenides  

Microsoft Academic Search

Ultrasonic attenuation due to phonon-phonon interaction and thermoelastic relaxation are studied in Lanthanum Monochalcogenides in direction at different higher temperatures. For evaluation of ultrasonic absorption coefficients the second and third order elastic constants (SOEC) and (TOEC) are also calculated. Shear wave attenuation shows maximum along propagation direction with polarized along and the attenuation increases at higher temperatures. Thermo-elastic loss is

Raja Ram Yadav; Devraj Singh

2001-01-01

159

Ames Lab 101: Lanthanum Decanting  

SciTech Connect

Ames Laboratory scientist Trevor Riedemann explains the process that allows Ames Laboratory to produce some of the purest lanthanum in the world. This and other high-purity rare-earth elements are used to create alloys used in various research projects and play a crucial role in the Planck satellite mission.

Riedemann, Trevor

2010-01-01

160

Ames Lab 101: Lanthanum Decanting  

ScienceCinema

Ames Laboratory scientist Trevor Riedemann explains the process that allows Ames Laboratory to produce some of the purest lanthanum in the world. This and other high-purity rare-earth elements are used to create alloys used in various research projects and play a crucial role in the Planck satellite mission.

Riedemann, Trevor

2012-08-29

161

Effect of lanthanum doping on the structural, ferroelectric, and strain properties of Bi1/2(Na0.82K0.18)1/2TiO3 lead-free ceramics  

NASA Astrophysics Data System (ADS)

To clarify the effect of A-site donor doping on the phase transition and the strain enhancement, we investigated the crystal structure, as well as the piezoelectric, ferroelectric and electric-field-induced strain (EFIS) properties of La-doped Bi1/2(Na0.82K0.18)1/2TiO3 (BNKT) ceramics. Similarly to our previous studies on BNKT doped with B-site donors such as Nb and Ta, La doping was found to induce a ferroelectric-to-nonpolar (FE-NP) phase transition, leading to a large enhancement in EFIS just after the transition. The result provides strong evidence that a close relationship exists between the Goldschumidt's tolerance factor and the FE-NP transition in BNKT, which has been observed in B-site-donor or isovalent impurity-doped BNKT.

Dinh, Thi Hinh; Lee, Hyun-Young; Yoon, Chang-Ho; Malik, Rizwan Ahmed; Kong, Young-Min; Lee, Jae-Shin; Tran, Vu Diem Ngoc

2013-04-01

162

Electrical properties of lanthanum chromite based ceramics in hydrogen and oxidizing atmospheres at high temperatures. Final report  

SciTech Connect

Several results regarding the effect of hydrogen on lanthanum chromite were determined. Thermally-activated diffusion of hydrogen through La(Mg)CrO/sub 3/ was found with a high activation energy. It was found that its electrical conductivity drops drastically, especially at low temperature, after exposure to hydrogen at high temperature. Also, the curvature of most of the conductivity plots, as well as the inability to observe the Hall effect, lends support to the proposal by Karim and Aldred that the small-polaron model which predicts thermally activated mobility is applicable to doped lanthanum chromite. From differential thermal analysis an apparent absorption of hydrogen near 300/sup 0/C was noticed. Upon cooling the lanthanum chromite in hydrogen and subsequently reheating it in air, desorption occurred near 170/sup 0/C. The immediate purpose of this study was to determine whether hydrogen has a deleterious effect on lanthanum chromite in solid oxide fuel cells.

Schmidt, V.H.

1981-06-01

163

Sintering aid for lanthanum chromite refractories  

SciTech Connect

A method of forming an electronically conductive, integral layer including lanthanum chromite is described comprising: depositing a layer including particulate lanthanum chromite containing a minor fraction of a sintering acid which includes a eutectic affording composition of at least two components providing a minor portion of a liquid phase in the layer during the sintering step, and eutectic affording composition having a melting point substantially below the melting point of the lanthanum chromite; sintering the layer at a sufficiently high temperature of not more than 1800/sup 0/K to form and densify an integral layer including lanthanum chromite.

Flandermeyer, B.K.; Poeppel, R.B.; Ellyn, G.; Dusek, J.T.; Anderson, H.U.

1988-06-07

164

Zn+La+ Co-Doped TiO2 Photocatalyst for the Purification of Air  

Microsoft Academic Search

The Zn2+-La3+Co-doped TiO2 photocatalysts prepared by doping lanthanum ion and zinc ion into TiO2 structure in a sol-gel process were shown to be efficient photocatalyst for the purification of Indoor air.The catalyst samples were then characterized by XRD and UV-vis analyses. The analytical results demonstrated that the lanthanum- zinc co-doping could inhibit the phase transformation of TiO2 and enhance the

Liu Baojiang; Cheng Xubang; He Jinxin

2009-01-01

165

Electromagnetic containerless reaction of samarium with cobalt for the formation of samarium-cobalt alloys  

NASA Technical Reports Server (NTRS)

The electromagnetic levitation technique has been used to obtain nearly stoichiometric SmCo5, with the reaction temperature controlled by a gas jet. The results of several experiments carried out at a 450 kHz, 25 kw RF power levitation facility using different reaction times and cooling rates are presented. It is shown that reaction rates achieved with the levitation technique are larger than the expected diffusion rate in the system liquid samarium-solid cobalt. It is also shown that substantial mixing occurs in the RF-levitated melt.

Chang, C. W.; Das, D. K.; Kumar, K.; Frost, R. T.

1982-01-01

166

Infrared absorption of lanthanum manganites  

NASA Astrophysics Data System (ADS)

Phonon energies in lanthanum manganites have been determined by dispersing powder in alkali halide matrices and measuring the absorption of far-infrared radiation. The method is illustrated with the classic colossal magneto-resistance material La 0.7Ca 0.3MnO 3. Relative to this, phonon energies associated with the Mn site are found to increase as Li is substituted for Mn. In the absence of Ca substituting for La, a new phonon mode is observed.

Gao, F.; Lewis, R. A.; Wang, X. L.; Dou, S. X.

167

Radiation Effects in Lanthanum Pyrozirconate  

SciTech Connect

The present paper reviews recent results on radiation resistance of lanthanum pyrozirconate obtained using empirical potentials molecular dynamic simulations. First, displacement cascades (DCs) with a 6 keV U4+ cation representing the ?- recoil nucleus have been performed in the lanthanum pyrozirconate La2Zr2O7. Only point defects are observed after each DC. They represent on average only 10% of the total number of displaced atoms during the cascade, with two times more cation anti-sites than Frenkel pairs. These calculations indicate that amorphization does not occur by a direct impact mechanism in pyrozirconate. Second, consequences of point defects accumulation have been simulated by introducing different types--either cation anti-sites or Frenkel pairs--and concentrations of point defects in pyrochlore. Results show that cation Frenkel pairs accumulation is the driving force for lanthanum zirconate amorphization. Under cation Frenkel pair accumulation, the crystal transits first from the pyrochlore to the disordered fluorite structure, with the oxygen atoms simply rearranging around cations. Amorphization occurs as a second step. These results consequently provide atomic-level interpretation to experimental irradiation observations of a two-step phase transition.

Chartier, Alan; Crocombette, J.-P.; Meis, Constantin; Weber, William J.; Corrales, Louis R.

2006-09-01

168

Samarium-145 and its use as a radiation source  

DOEpatents

The present invention covers a new radiation source, samarium-145, with radiation energies slightly above those of I-125 and a half-life of 340 days. The samarium-145 source is produced by neutron irradiation of SM-144. This new source is useful as the implanted radiation source in photon activation therapy of malignant tumors to activate the stable I-127 contained in the IdUrd accumulated in the tumor, causing radiation sensitization and Auger cascades that irreperably damage the tumor cells. This new source is also useful as a brachytherapy source.

Fairchild, Ralph G. (Setauket, NY); Laster, Brenda H. (Plainview, NY); Packer, Samuel (Great Neck, NY)

1989-01-01

169

Ultrasonic Attenuation in Lanthanum Monochalcogenides  

NASA Astrophysics Data System (ADS)

Ultrasonic attenuation due to phonon-phonon interaction and thermoelastic relaxation are studied in Lanthanum Monochalcogenides in <110> direction at different higher temperatures. For evaluation of ultrasonic absorption coefficients the second and third order elastic constants (SOEC) and (TOEC) are also calculated. Shear wave attenuation shows maximum along <110> propagation direction with polarized along <110> and the attenuation increases at higher temperatures. Thermo-elastic loss is very small compared to phonon-viscosity loss. Behavior of temperature dependence of the absorption is the same as in case of pure metals and dielectric crystals.

Yadav, Raja; Singh, Devraj

2001-06-01

170

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

171

Heating-induced endothermal effect in semiconducting samarium sulfide  

NASA Astrophysics Data System (ADS)

The effect of heat absorption is revealed in the temperature range where the thermovoltaic effect occurs in single-crystal samarium sulfide (SmS). It is shown that the heat absorption is caused by the collective injection of electrons from donor levels into the conduction band.

Egorov, V. M.; Kaminski?, V. V.

2009-08-01

172

Radiation effects of protons on samarium-cobalt permanent magnets  

Microsoft Academic Search

At TRIUMF the use of samarium-cobalt permanent magnet quadrupoles as the first element in a secondary channel has been studied as a means of increasing the solid angle acceptance of the channel. The high remanent induction B \\/SUB r\\/ and high coercive force H \\/SUB c\\/ of rareearth cobalt (REC) can be utilized to produce a highgradient quadrupole field in

E. W. Blackmore

1985-01-01

173

ber eine neue Erscheinung bei den Isotopen des Samariums  

Microsoft Academic Search

Zusammenfassung Hyperfeinstrukturuntersuchungen am Samarium zeigen einen Isotopenverschiebungseffekt, und zwar sind hier im Gegensatz zu den bisherigen Beobachtungen an anderen Elementen die Verschiebungen zwischen den einzelnen geraden Isotopen nicht mehr konstant, vielmehr sind die Isotope 150 und 152 etwa doppelt so weit getrennt wie 152 und 154. Die Beobachtungen lassen den Schlu zu, da beim Aufbau des Atomkerns zwischen Sm150 und

H. Schler; Th. Schmidt

1934-01-01

174

Discovery of samarium, europium, gadolinium, and terbium isotopes  

SciTech Connect

Currently, thirty-four samarium, thirty-four europium, thirty-one gadolinium, and thirty-one terbium isotopes have been observed and the discovery of these isotopes is described here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.

May, E.; Thoennessen, M., E-mail: thoennessen@nscl.msu.edu

2013-01-15

175

[Radiographic characteristics of lanthanum carbonate absorption].  

PubMed

Lanthanum carbonate is a new nonaluminium, noncalcium phosphate binder. The drug is well-tolerated its side-effects seem comparable to those of other phosphate binders. The most frequent side-effects are gastrointestinal complications. Cerny [New England Journal of Medecine 355(2006)1160.] and Kunzendorf have recently reported another effect of lanthanum carbonate based on its radiographic characteristics. We report another case of opacification of the intestine with lanthanum carbonate which underlines some difficulties in the use of this new phosphate binder. PMID:18243834

Vrigneaud, Laurence; Lefbvre, Delphine; Daem, Alexandre Olive; Lemaitre, Vincent

2008-04-01

176

Absolute bioavailability and disposition of lanthanum in healthy human subjects administered lanthanum carbonate.  

PubMed

Lanthanum carbonate [La2(CO3)3] is a noncalcium, non-aluminum phosphate binder indicated for hyperphosphatemia treatment in end-stage renal disease. A randomized, open-label, parallel-group, phase I study was conducted to determine absolute bioavailability and investigate excretory routes for systemic lanthanum in healthy subjects. Twenty-four male subjects were randomized to a single lanthanum chloride (LaCl3) intravenous infusion (120 microg elemental lanthanum over a 4-hour period), a single 1-g oral dose [chewable La2(CO3)3 tablets; 4 x 250 mg elemental lanthanum], or no treatment (control). Serial blood, urine, and fecal samples were collected for 7 days postdosing. The absolute bioavailability of lanthanum [administered as La2(CO3)3] was extremely low (0.00127% +/- 0.00080%), with individual values in the range of 0.00015% to 0.00224%. Renal clearance was negligible following oral administration (1.36 +/- 1.43 mL/min). Intravenous administration confirmed low renal clearance (0.95 +/- 0.60 mL/min), just 1.7% of total plasma clearance. Fecal lanthanum excretion was not quantifiable after intravenous administration owing to high and variable background fecal lanthanum and constraints on the size of the intravenous dose. These findings demonstrate that lanthanum absorption from the intestinal tract into the systemic circulation is extremely low and that absorbed drug is cleared predominantly by nonrenal mechanisms. PMID:16809799

Pennick, Michael; Dennis, Kerry; Damment, Stephen J P

2006-07-01

177

Anomalous Pressure Dependence of Dipolar Relaxation Times in Rare Earth Doped Lead Fluoride.  

National Technical Information Service (NTIS)

Electrical relaxation measurements at high pressures have been carried out on lead fluoride doped with lanthanum and cerium. A single, strong relaxation peak is observed and the relaxation time decreases with pressure. This is contrary to the behavior exh...

J. J. Fontanella M. C. Wintersgill D. R. Figueroa A. V. Chadwick C. G. Andeen

1984-01-01

178

Field free, directly heated lanthanum boride cathode  

DOEpatents

A directly heated cylindrical lanthanum boride cathode assembly is disclosed which minimizes generation of magnetic field which would interfere with electron emission from the cathode. The cathode assembly comprises a lanthanum boride cylinder in electrical contact at one end with a central support shaft which functions as one electrode to carry current to the lanthanum boride cylinder and in electrical contact, at its opposite end with a second electrode which is coaxially position around the central support shaft so that magnetic fields generated by heater current flowing in one direction through the central support shaft are cancelled by an opposite magnetic field generated by current flowing through the lanthanum boride cylinder and the coaxial electrode in a direction opposite to the current flow in the central shaft.

Leung, Ka-Ngo; Moussa, D.; Wilde, S.B.

1987-02-02

179

Stabilized lanthanum sulphur compounds. [thermoelectric materials  

NASA Technical Reports Server (NTRS)

Lanthanum sulfide is maintained in the stable cubic phase form over a temperature range of from 500 C to 1500 C by adding to it small amounts of calcium, barium, or strontium. This compound is an excellent thermoelectric material.

Reynolds, G. H.; Elsner, N. B.; Shearer, C. H. (inventors)

1983-01-01

180

Field free, directly heated lanthanum boride cathode  

DOEpatents

A directly heated cylindrical lanthanum boride cathode assembly is disclosed which minimizes generation of magnetic fields which would interfere with electron emission from the cathode. The cathode assembly comprises a lanthanum boride cylinder in electrical contact at one end with a central support shaft which functions as one electrode to carry current to the lanthanum boride cylinder and in electrical contact, at its opposite end with a second electrode which is coaxially position around the central support shaft so that magnetic fields generated by heater current flowing in one direction through the central support shaft are cancelled by an opposite magnetic field generated by current flowing through the lanthanum boride cylinder and the coaxial electrode in a direction opposite to the current flow in the central shaft.

Leung, Ka-Ngo (Hercules, CA); Moussa, David (San Francisco, CA); Wilde, Stephen B. (Pleasant Hill, CA)

1991-01-01

181

Lead Telluride Alloyed with Indium and Lanthanum.  

National Technical Information Service (NTIS)

Data are presented and discussed on the behavior of lead telluride alloyed with indium and with lanthanum. The data include Hall coefficient, conductance, thermal emf, Hall mobility, microhardness and bending strength. The possibility is demonstrated of d...

V. V. Gorbachev V. A. Linsky E. F. Makarov E. A. Zhemchuzhina A. I. Ivanov

1974-01-01

182

Thermodynamic representation of nonstoichiometric lanthanum manganite  

Microsoft Academic Search

The thermodynamic properties of the lanthanum manganites, La1 ? xMn1 ? y,O3 ? z, have been reevaluated within the ideal association model to simultaneously account for excess oxygen and lanthanum nonstoichiometry of LaMnO3 + ?, La0.95MnO3 + ? and La0.9MnO3 + ?. It has been found that a new set of parameters can reproduce the essential features of the thermogravimetric

Harumi Yokokawa; Teruhisa Horita; Natsuko Sakai; Masayuki Dokiya; Tatsuya Kawada

1996-01-01

183

Timing resolution measurements of a 3 in. lanthanum bromide detector  

NASA Astrophysics Data System (ADS)

Cerium-doped lanthanum bromide (LaBr3:Ce) is a scintillator that presents very good energy and timing resolutions and it is a perfect candidate for photon detector in future experiments to search for lepton flavor violation as in ??e? or ??e conversion. While energy resolution was thoroughly investigated, timing resolution at several MeV presents some experimental challenge. We measured the timing resolution of a 3 in.3 in. cylindrical LaBr3(Ce) crystal versus few reference detectors by means of a nuclear reaction from a Cockcroft-Walton accelerator that produces coincident ?-rays in the 4.4-11.6 MeV range. Preliminary results allow us to extrapolate the properties of a segmented ?-ray detector in the 50-100 MeV range.

Galli, L.; De Gerone, M.; Dussoni, S.; Nicol, D.; Papa, A.; Tenchini, F.; Signorelli, G.

2013-08-01

184

Compact lanthanum hexaboride hollow cathode  

NASA Astrophysics Data System (ADS)

A compact lanthanum hexaboride hollow cathode has been developed for space applications where size and mass are important and research and industrial applications where access for implementation might be limited. The cathode design features a refractory metal cathode tube that is easily manufactured, mechanically captured orifice and end plates to eliminate expensive e-beam welding, graphite sleeves to provide a diffusion boundary to protect the LaB6 insert from chemical reactions with the refractory metal tube, and several heater designs to provide long life. The compact LaB6 hollow cathode assembly including emitter, support tube, heater, and keeper electrode is less than 2 cm in diameter and has been fabricated in lengths of 6-15 cm for different applications. The cathode has been operated continuously at discharge currents of 5-60 A in xenon. Slightly larger diameter versions of this design have operated at up to 100 A of discharge current.

Goebel, Dan M.; Watkins, Ronald M.

2010-08-01

185

Compact lanthanum hexaboride hollow cathode.  

PubMed

A compact lanthanum hexaboride hollow cathode has been developed for space applications where size and mass are important and research and industrial applications where access for implementation might be limited. The cathode design features a refractory metal cathode tube that is easily manufactured, mechanically captured orifice and end plates to eliminate expensive e-beam welding, graphite sleeves to provide a diffusion boundary to protect the LaB6 insert from chemical reactions with the refractory metal tube, and several heater designs to provide long life. The compact LaB(6) hollow cathode assembly including emitter, support tube, heater, and keeper electrode is less than 2 cm in diameter and has been fabricated in lengths of 6-15 cm for different applications. The cathode has been operated continuously at discharge currents of 5-60 A in xenon. Slightly larger diameter versions of this design have operated at up to 100 A of discharge current. PMID:20815605

Goebel, Dan M; Watkins, Ronald M

2010-08-01

186

Lattice dynamics of the rare-earth element samarium  

NASA Astrophysics Data System (ADS)

The lattice dynamics of samarium is determined by in situ low-temperature nuclear inelastic scattering on a single crystalline (0001)Sm film, a polycrystalline Sm foil, and by first-principles theory. The ab initio calculated phonon dispersion relations and phonon density of states for the Sm-type structure and the double hexagonal-close-packed (dhcp) lattice, characteristic for light lanthanides, are compared. The dhcp unit cell, which is a factor of 2.24 smaller in height, exhibits more pronounced vibrational anisotropy in comparison to the Sm-type structure. The analysis reveals a minor influence of the spin-orbit coupling in the Sm atom on the lattice dynamics. A broadening of the longitudinal peak, not found in the calculations, suggests the influence of electron correlations on lattice dynamics in metallic samarium.

Bauder, Olga; Piekarz, Przemys?aw; Barla, Alessandro; Sergueev, Ilya; Rffer, Rudolf; ?a?ewski, Jan; Baumbach, Tilo; Parlinski, Krzysztof; Stankov, Svetoslav

2013-12-01

187

[Study on time-resolved fluorimetry of samarium].  

PubMed

In this paper, a simple and highly sensitive laser fluorimetric system is described, and the value of time discrimination for suppressing unwanted signals and decreasing the minimum detectable concentration is demonstrated. It is confirmed that time discrimination is very useful for ultratrale determination of fluorescent complex. This technique is successful with the combined use of a pulsed laser and a pulse-gate signal detection system for samarium complex. The linear range and the detectin limit of the method are 0. 01-10microg/ml and 3.3ng/ml, respectively. The RSD for Sm3+ (0. 5microg/ml) ( n =12) is 3.7%. The method was used to detemine samarium in rare earth mixtures. The recovery was in the range of 90.0-110.0%, and the mean recovery was 101.4% ( n = 6 ) PMID:15810428

Pan, L; Wang, S; Dong, X

1997-02-01

188

Recent developments in samarium diiodide promoted organic reactions.  

PubMed

In the early eighties, we introduced samarium diiodide for the transformation of various functional groups. Since then, this reducing agent has been extensively used for the reductive cleavage of single bonds, C-C bond formations, C-N bond formations, and ?-elimination reactions. In this Personal Account, we highlight our initial results, as well as some of the contributions from various research groups. Because of space limitations, we arbitrarily select some useful results that have recently been described in literature. PMID:23468168

Gopalaiah, Kovuru; Kagan, Henri B

2013-04-01

189

Colossal magnetoresistance properties of samarium based manganese perovskites  

Microsoft Academic Search

The study of the samarium manganites Sm1?x(Sr,Ca)xMnO3 has shown the magnetoresistance properties of this kind of compounds. It allowed us to evidence the effect of the two antagonist effects, interpolated cation size and Mn(IV) : Mn(III) ratio, on the transition temperature Tmax. By varying these two factors, we were able to get RR ratio of 105 at 75K under 5T

F. Damay; N Nguyen; A Maignan; M Hervieu; B Raveau

1996-01-01

190

Slow neutron capture gamma rays from samarium and gadolinium  

Microsoft Academic Search

Slow neutron capture gamma rays in the energy region below 1.5 MeV from samarium oxide and gadolinium oxide have been studied, employing a simple technique comprising a 2 curie polonium-beryllium neutron source and a single crystal scintillation spectrometer. The energies of the observed gamma components are estimated and compared with the values obtained by previous authors who have used reactors

D. L. Sastry; S. Jnanananda

1964-01-01

191

Synthesis of lanthanum chromite with additions of lithium oxide  

SciTech Connect

Chromites of the rare-earth elements (in particular, lanthanum chromite LaCrO/sub 3/) are used for the preparation of chemically stable refractory objects. The method of production of lanthanum chromite by the introduction of lithium oxide into a stoiciometric mixture of chromium and lanthanum oxides has been proposed by some of the authors of this work. The present work is devoted to a study of the influence of additions of lithium oxide on the synthesis of lanthanum chromite.

Spitsyn, V.I.; Pitov, V.A.; Kolesnikova, A.K.; Kuznetsov, D.G.; Suponitskii, Yu.L.; Spiridonov, F.M.

1981-01-01

192

Etude experimentale et theorique de l'evolution texturale et structurale de poudres de zircone pures et dopees. (Applied and theoretical study of textural and structural evolution of pure and doped zircon powders).  

National Technical Information Service (NTIS)

Using different preparation methods, undoped zircon constituted of quadratic and monoclinic phases, and quadratic phase zircon doped with lanthanum, magnesium or silicon were obtained and characterized. An applied kinetic study of the influence of the gas...

A. Methivier

1992-01-01

193

Thermodynamic characterization of lanthanum tellurate  

NASA Astrophysics Data System (ADS)

The standard Gibbs energy of formation of lanthanum tellurate, La 2TeO 6 was derived from its vapour pressure measurements in the temperature range 1420-1520 K employing TG based transpiration method. The temperature dependence of vapour pressure of TeO 2 vapour over the mixture La 2TeO 6 (s) + La 2O 3 (s) generated by the incongruent vapourisation reaction, LaTeO (s)?Lao (s)+TeO (g)+1/2O (g) could be represented as: log p (Pa) = [18.47-27127/ T (K)] 0.03 (1420-1520 K). Enthalpy increments on La 2TeO 6 were determined by using inverse drop calorimetry in the temperature range 583-1287 K and the thermodynamic functions, namely, heat capacity, entropy and Gibbs energy functions were derived. The mean value of -2381.3 2.0 kJ mol -1 was obtained for ? fH298? (La 2TeO 6) by combining the value of ? fG? (La 2TeO 6) derived from vapour pressure data and the free energy functions of La 2TeO 6 derived from the drop calorimetry data.

Pankajavalli, R.; Jain, Ashish; Babu, R.; Ananthasivan, K.; Anthonysamy, S.; Ganesan, V.

2010-02-01

194

Thermovoltaic effect in samarium sulfide-based Sm1 - x Eu x S heterostructures  

NASA Astrophysics Data System (ADS)

The thermovoltaic effect in samarium sulfide-based Sm1 - x Eu x S bulk heterostructures in the temperature interval 300-520 K is considered. It is shown that this effect is due to an artificially produced samarium ion concentration gradient, rather than to an external temperature gradient.

Kaminskii, V. V.; Kazanin, M. M.; Solov'ev, S. M.; Golubkov, A. V.

2012-06-01

195

An experimental analysis of a doped lithium fluoride direct absorption solar receiver  

NASA Technical Reports Server (NTRS)

An experimental analysis of two key elements of a direct absorption solar receiver for use with Brayton solar dynamic systems was conducted. Experimental data are presented on LiF crystals doped with dysprosium, samarium, and cobalt fluorides. In addition, a simulation of the cavity/window environment was performed and a posttest inspection was conducted to evaluate chemical reactivity, transmissivity, and condensation rate.

Kesseli, James; Pollak, Tom; Lacy, Dovie

1988-01-01

196

Spectral down-conversion in Sm-doped borate glasses for photovoltaic applications  

NASA Astrophysics Data System (ADS)

Borate glasses and borate glass ceramics are good candidates as a matrix material for fluorescent ions like samarium. The chosen network modifier influences the fluorescence efficiency of the incorporated rare earth ion. Sm3+-doped lithium, sodium, barium and lead borate glasses were examined with respect to their fluorescence properties and potential use as a down-converting top layer of a solar cell.

Dyrba, Marcel; Miclea, Paul T.; Schweizer, Stefan

2010-04-01

197

Thermovoltaic effect in samarium sulfide-based heterostructures  

NASA Astrophysics Data System (ADS)

The thermovoltaic effect in samarium sulfide-based bulk heterostructures with compositions Sm1 - x Eu x S and Sm1 - x Gd x S is considered in the temperature interval 300-460 K. It is shown that this effect can be observed when an external temperature gradient is absent, i.e., when the sample temperatures near the contacts from which a generated voltage is tapped off are the same. The temperature is measured with thermocouples and also by a contactless method using a thermal imager.

Kaminskii, V. V.; Kazanin, M. M.; Klishin, A. N.; Solov'ev, S. M.; Golubkov, A. V.

2011-06-01

198

Novel samarium(III) selective membrane sensor based on glipizid  

Microsoft Academic Search

We found that N-[2-[4-[[[(cyclohexyl amino)carbonyl]amino]sulfonyl]phenyl]ethyl]-5-methyl pyrazine carboxamide (glipizid) can be used as an excellent ionophore to make a novel samarium-selective membrane sensor. The electrode based on glipizid, containing sodium teraphenyl borate as lipophilic salt and benzyl acetate as a plasticiser, gave the best performance. The electrode exhibits a good Nernstian response towards Sm3+ions in the range of 1.010?1 to 1.010?6M

Mohammad Reza Ganjali; Mohammad Reza Pourjavid; Morteza Rezapour; Soheila Haghgoo

2003-01-01

199

Radiation effects on samarium-cobalt permanent magnets  

SciTech Connect

With the recent advances in rare-earth-cobalt (REC) permanent magnet technology, new applications are being implemented that were previously not feasible. One such application is the use of permanent magnetic lenses for accelerator and beam transport systems. In many of these areas the magnetic transport systems are subjected to high radiation levels. Consequently, there is considerable interest in the United States and abroad in the possible changes in the magnetic field when subjected to radiation. This is a description of our approach in performing the field measurements before and after irradiating samples of samarium-cobalt permanent magnets.

Brown, R.D.; Bush, E.D. Jr.; Hunter, W.T.

1982-07-01

200

Investigation into Nanostructured Lanthanum Halides and CeBr3 for Nuclear Radiation Detection  

SciTech Connect

Nanocomposites may enable the use of scintillator materials such as cerium-doped lanthanum fluoride (LaF3:Ce) and cerium bromide (CeBr3) without requiring the growth of large crystals [1]. Nanostructured detectors may allow us to engineer immensely sized detectors of flexible form factors that will have a broad energy range and an energy resolution sufficient to perform isotopic identification. Furthermore, nanocomposites are easy to prepare and very low in cost. It is much less costly to use nanocomposites rather than grow large whole crystals of scintillator materials; with nanocomposites fabricated on an industrial scale, costs are even less. Nanostructured radiation scintillator detectors may improve quantum efficiency and provide vastly improved detector form factors. Quantum efficiencies up to 60% have been seen in photoluminescence from silicon nanocrystals in a densely-packed ensemble [2]. We have fabricated nanoparticles with sizes <10 nm and characterized their nanocomposite radiation detector properties. This work investigates the properties of the nanostructured radiation scintillator in order to extend the gamma energy response on both low- and high-energy regimes by demonstrating the ability to detect low-energy x-rays and relatively high-energy activation prompt gamma rays simultaneously using nanostructured lanthanum bromide, lanthanum fluoride, or CeBr3. Preliminary results of this investigation are consistent with a significant response of these materials to nuclear radiation.

Guss, P. P., Guise, R., Mukhopadhyay, S., Yuan, D.

2011-07-06

201

Molecular structure, photophysical and thermal properties of samarium (III) complexes  

NASA Astrophysics Data System (ADS)

Some 8-coordinated samarium (III) complexes ( 1- 4) having bipy (2,2'-bipyridine), terpy (2,2':6',2?-terpyridine), phen (1,10-phenanthroline) and tp [hydrotris (pyrazol-1-yl) borate] as supporting ligands have been synthesized and structurally characterized by different techniques including X-ray crystallography. The X-ray studies demonstrated that the complexes 1, 2 and 4 crystallized in triclinic space group P1 with cell dimensions a = 8.5640(2) , b = 8.8696(2) , c = 15.8608(4) for 1; a = 7.2113(9) , b = 11.0737(14) , c = 13.6289(18) for 2; a = 12.440(3) , b = 12.874(3) , c = 17.822(4) for 4, whereas the complex 3 crystallized in the monoclinic space group P2 1/ c with cell dimensions a = 9.472(3) , b = 17.092(5) , c = 14.516(5) . The IR study suggested that the azide is coordinated in 1, 3-bridging mode in complex 4. The photophysical properties of above complexes have been studied with ultraviolet absorption and emission spectral studies. Thermogravimetric analyses suggested that all these complexes undergo the complete decomposition to form the thermally stable samarium oxide (Sm 2O 3).

Kumar, Rajeev; Singh, Udai P.

2008-03-01

202

Glasslike thermal conductivity in ytterbium-doped lanthanum zirconate pyrochlore  

Microsoft Academic Search

Glass-like thermal conductivity is observed in (La1?xYbx)2Zr2O7 (1\\/6?x?1\\/3), which exhibits great potential as a high-temperature thermal barrier coating material. In the pyrochlore-type La2Zr2O7, the large 16c-site La3+ is weakly bonded by its surrounding 48f-site oxygen ions, and substitution of La3+ with smaller and heavier Yb3+ gives rise to a large atomic displacement parameter (ADP) of Yb3+ which behaves as a

Chunlei Wan; Wei Zhang; Yifeng Wang; Zhixue Qu; Aibing Du; Ruifen Wu; Wei Pan

2010-01-01

203

Pure and doped lanthanum cobaltites obtained by combustion method  

Microsoft Academic Search

We report the synthesis of La1?xSrxCoO3 nanopowders by solution combustion method using metal nitrates and ?-alanine (alanine method) or urea (urea method) as fuel. The influence of metal nitrates\\/organicsubstance molar ratio and the type of fuel was investigated. The isolated complex precursors were characterized by atomic absorption spectroscopy (AAS), FT-IR spectra and DTATG analysis. The La1?xSrxCoO3 (x=00.3) powders were characterized

D. Berger; C. Matei; F. Papa; G. Voicu; V. Fruth

2007-01-01

204

Electron tunneling measurements on ferromagnetically doped lanthanum manganite films  

NASA Astrophysics Data System (ADS)

A series of tunneling and transport measurements on La0.67Ca 0.33MnO3 and La0.67Sr0.33MnO3 perovskite thin films is presented. Planar tunnel junctions were fabricated using the manganite thin film as one electrode. To ensure a high-quality tunnel junction, a well-characterized superconductor, Pb, is used as the other electrode. Below the Pb superconducting transition temperature, Tc, the associated superconducting gap and phonon structures are fully observed. Measurements of tunneling current and conductance as a function of bias voltage were obtained for temperatures ranging from 2 K to 300 K. For La0.67Ca0.33MnO3, our tunneling measurements show the density of electronic states at the Fermi level increasing slowly below 250 K, the ferromagnetic ordering temperature of the La 0.67Ca0.33MnO3 film. Carrier mobility plays a dominant role in electron transport as the material undergoes a ferromagnetic metal-insulator transition at 250 K. Our measurements are consistent with a Fermi level moving through a mobility edge as this material orders ferromagnetically. Below 40 K, we see a depletion in the density of states centered at the Fermi level and extending a few meV. The results are consistent with a depletion of one spin band. We also see evidence for inelastic excitations in the density of states over a broad energy range, We attribute these excitations to polaronically localized electrons coexisting with mobile carriers in the mixed valence state. Finally, it should be noted that preliminary results on La0.67Sr 0.33MnO3 samples are in agreement with those obtained for La0.67Ca0.33MnO3.

Hudspeth, Heather Diane

205

Inelastic Collisions of Slow Electrons with Lanthanum Trichloride Molecules  

Microsoft Academic Search

Inelastic collisions of electrons with lanthanum trichloride molecules were studied by the extended crossed-beam technique. About 90 excitation cross sections for spectral lines of the singly charged lanthanum ion were measured at an incident electron energy of 100 eV. Neither lanthanum atomic lines nor spectral bands due to LaCl molecule were detected. Plausible reactions of dissociative excitation of LaII are

Yu. M. Smirnov

2001-01-01

206

Samarium-146 in the early solar system - Evidence from neodymiun in the Allende meteorite  

NASA Technical Reports Server (NTRS)

A carbon-chromite fraction from the Allende C3V chondrite shows strikingly large isotopic enrichments of neodymium-142 (0.47 percent) and neodymium-143 (36 percent). Both apparently formed by alpha decay of samarium-146 and samarium-147 (half-lives 1.03 x 10 to the 8th and 1.06 x 10 to the 11th years), but the isotopic enrichment was greatly magnified by recoil of residual nuclei into a carbon film surounding the samarium-bearing grains. These data provide an improved estimate of the original abundance of extinct samarium-146 in the early solar system, Sm-146/Sm-144 = (4.5 + or - 0.5) x 10 to the -3rd, higher than predicted by some models of p-process nucleosynthesis. It may be possible to use this isotopic pair as a chronometer of the early solar system.

Lugmair, G. W.; Shimamura, T.; Lewis, R. S.; Anders, E.

1983-01-01

207

A note on the isotopic assignment of slow neutron resonances in Samarium, Iridium and Gadolinium  

Microsoft Academic Search

Some further isotopic assignments of slow neutron resonances have been ; made with the elements samarium, iridium, and gadoliniuma using tbe Harwell 15 ; Mev linear accelerator and capture gamma ray scintillation detectors.;

E. M. Bowey; J. R. Bird

1958-01-01

208

Ambi-site substitution of Mn in lanthanum germanate apatites  

SciTech Connect

A neutron diffraction study at 4 K of the Mn doped lanthanum germanate apatite-type oxide ion conductor of nominal starting composition 'La{sub 9.5}Mn{sub 0.5}(GeO{sub 4}){sub 6}O{sub 2.75}' is reported. The structure was refined in space group P6{sub 3}/m, although high thermal displacement parameters were observed for the oxide ion sites (particularly O3, and O4). Reduced thermal displacement parameters were obtained by splitting the O3 site, and allowing the O4 oxygen to move off site, which may indicate local regions of lower symmetry within the structure. In addition, the data suggested ambi-site substitution of Mn, with it being present on both the Ge site and the La site. Assuming no change in La:Mn:Ge ratio, a composition of La{sub 9.18}Mn{sub 0.28}(GeO{sub 4}){sub 5.8}(MnO{sub 4}){sub 0.2}O{sub 2} was determined. As such there are nominally no interstitial oxide ions, but rather cation vacancies on the La site. Therefore, the high conductivity for this sample is most likely related to the introduction of Frenkel-type defects at higher temperature, as previously proposed for other apatite-type systems containing vacancies on the La site.

Kendrick, E. [Chemical Sciences, University of Surrey, Guildford, Surrey GU2 7XH (United Kingdom); Knight, K.S. [ISIS Facility, Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot OX11 0QX (United Kingdom); Slater, P.R., E-mail: p.r.slater@bham.ac.uk [School of Chemistry, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom)

2009-08-05

209

Microstructures and Properties of Molybdenum Wires Doped with La.  

National Technical Information Service (NTIS)

The structures and properties of the La-doped molybdenum (La-Mo) powder, compact, rods and wires annealed at different temperatures were investigated. The experimental results show that the La exists in the powders in the forms of lanthanum nitrate, lanth...

M. L. Zhou J. Li T. Zuo

1995-01-01

210

Stability of lanthanum calcium chromite-lanthanum strontium manganite interfaces in solid oxide fuel cells  

SciTech Connect

An investigation has been made on the chemical stability of the cathode-interconnect interface in solid oxide fuel cells. Lanthanum calcium chromite and lanthanum strontium manganite (a dense 10% A-site deficient manganite, a porous 10% A-site deficient one or a dense 1% A-site deficient one) were placed between air and fuel (hydrogen/water) at a selected electrical current density. The electrical conductivity across the interfaces was slightly increased for 300 h. Changes in morphology, chemical composition, and phases were examined by scanning electron microscopy/energy dispersive X-ray and X-ray diffractometry analysis. The dense 10% A-site deficient cathode gave rise to the precipitation of manganese oxide at the air-side surface as well as at the interface. The porous cathode enhanced chemical reactions between lanthanum calcium chromite and lanthanum strontium manganite. The dense 1% A-site deficient cathode was most stable. These phenomena have been thermodynamically analyzed in terms of (1) irreversible mass transfer under an oxygen potential gradient, (2) changes of the stable composition region of the perovskite phases as a function of oxygen potential, and (3) an enhancing effect of the liquid formation on reactions of interfaces.

Nishiyama, H.; Aizawa, M. [TOTO, Ltd., Chigasaki, Kanagawa (Japan). Research and Development Div.; Yokokawa, H.; Horita, T.; Sakai, N.; Dokiya, M. [National Inst. of Materials and Chemical Research, Tsukuba, Ibaraki (Japan); Kawada, T. [Tohoku Univ., Sendai, Miyagi (Japan). Research Inst. for Scientific Measurements

1996-07-01

211

Intracellular localization of samarium in the lactating mammary gland cells: ultrastructural and microanalytical study.  

PubMed

The frequent use of some rare earths in the medical and industrial domains make us worry about their intracellular behavior into the body. Reason for which we have investigated the subcellular localization of one of these elements, the samarium, in the mammary gland of lactating female wistar rats using two very sensitive methods of observation and microanalysis, the transmission electron microscopy and the secondary ion mass spectrometry. The ultrastructural study showed the presence of electron dense deposits in the lactating mammary glandular epithelial cell lysosomes of the samarium-treated rats, but no loaded lysosomes were observed in those of control rats. The microanalytical study allowed both the identification of the chemical species present in those deposits as samarium isotopes ((152) Sm(+)) and the cartography of its distribution. Our results confirm the previous ones showing that lysosomes of the glandular epithelial cells are the site of the intracellular concentration of foreign elements such as gallium. The intralysosomal deposits observed in the mammary glandular cells of the samarium-treated rats are similar in their form and density to those observed with the same element in other varieties of cells, such as liver, bone marrow, and spleen cells. Our ultrastructural and microanalytical results and those obtained in previous studies allow deducing that the intralysosomal deposits are very probably composed of an insoluble samarium phosphate salt. PMID:22021164

Ahlem, Ayadi; Samira, Maghraoui; Jean-Nicolas, Audinot; Mohamed-Habib, Jaafoura; Henri-Nol, Migeon; Ali, El Hili; Leila, Tekaya

2012-04-01

212

Thermal stability of lanthanum scandate dielectrics on Si(100)  

SciTech Connect

The authors have examined the thermal stability of amorphous, molecular beam deposited lanthanum scandate dielectric thin films on top of Si (100) after a 1000 deg. C, 10 s rapid thermal anneal. After the anneal, crystallization of LaScO{sub 3} is observed. Excellent suppression of lanthanum and scandium diffusion into the substrate silicon is indicated by the back-side secondary ion mass spectrometry (SIMS) analyses. In contrast, front-side SIMS and high-resolution electron energy loss analyses of the amorphous Si/LaScO{sub 3}/Si (100) stack indicated the outdiffusion of lanthanum and scandium into the silicon capping layer during the anneal.

Sivasubramani, P.; Lee, T. H.; Kim, M. J.; Kim, J.; Gnade, B. E.; Wallace, R. M.; Edge, L. F.; Schlom, D. G.; Stevie, F. A.; Garcia, R.; Zhu, Z.; Griffis, D. P. [Department of Electrical Engineering, University of Texas at Dallas, Richardson, Texas 75080 and Department of Physics, University of Texas at Dallas, Richardson, Texas 75080 (United States); Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Analytical Instrumentation Facility, North Carolina State University, Raleigh, North Carolina 27695 (United States)

2006-12-11

213

Samarium (III) Selective Membrane Sensor Based on Tin (IV) Boratophosphate  

PubMed Central

A number of Sm (III) selective membranes of varying compositions using tin (IV) boratophosphate as electroactive material were prepared. Polyvinyl chloride, polystyrene and epoxy resin were used as binding materials. Membrane having composition of 40% exchanger and 60% epoxy resin exhibited best performance. This membrane worked well over a wide concentration range of 110-5M to 110-1 M of samarium ions with a Super-Nernstian slope of 40 mV/decade. It has a fast response time of less than 10 seconds and can be used for at least six months without any considerable divergence in potentials. The proposed sensor revealed good selectivities with respect to alkali, alkaline earth, some transition and rare earth metal ions and can be used in the pH range of 4.0-10.0. It was used as an indicator electrode in the potentiometric titration of Sm (III) ions against EDTA. Effect of internal solution was studied and the electrode was successfully used in non-aqueous media, too.

Mittal, Susheel K.; Sharma, Harish Kumar; Kumar, Ashok S. K.

2004-01-01

214

Electrical properties of complex perovskite samarium nickel titanate  

NASA Astrophysics Data System (ADS)

The complex perovskite oxide samarium nickel titanate, Sm(Ni1/2Ti1/2)O3 (SNT) is synthesized by solid-state reaction technique. The x-ray diffraction pattern of the sample at room temperature shows monoclinic phase. The microstructure analysis of the sample is performed using scanning electron microscope. Alternating current impedance spectroscopy is used to investigate the electrical properties of SNT in a temperature range from 313 K to 673 K and in a frequency range from 100 Hz to 1 MHz. A peak is observed in the frequency dependence of imaginary part of electric modulus ( M?( ?)) indicating a non-Debye type of relaxation. The relaxation peak of M?( ?) moves towards higher frequencies with the increase of temperature showing the thermally activated nature of the relaxation time. The relaxation times for M?( ?) at different temperatures are found to obey Arrhenius law with an activation energy of 0.57 eV. The scaling behaviour of M?( ?) shows that the relaxation describes the same mechanism at various temperatures. The complex impedance plane plots show that the relaxation mechanism in SNT is purely a bulk effect arising from the semiconductive grains of the sample. The frequency dependent conductivity is found to obey the power law.

Kumar, Nishant; Dutta, Alo; Prasad, S.; Sinha, T. P.

2013-09-01

215

Analytical and structural analysis of the lanthanum-deficient lanthanum hexaboride  

SciTech Connect

The blue lanthanum boride LaB/sub 6+delta/ previously reported as LaB/sub 9/, was investigated in arc-melted samples of LaB/sub 9/ bulk stoichiometry. The samples were structurally analyzed by high-resolution transmission electron microscopy including comparative computer imaging and analytically studied by using backscattered electron imaging, quantitative characteristic x-ray analysis, nuclear magnetic resonance, and other techniques. The blue boride observed has a composition of LaB/sub 6.13 +- 0.03/ due to random La vacancies in the LaB/sub 6/ structure and is interpreted as belonging to the nonstoichiometric LaB/sub 6/ phase region. The color change from purple to blue occurs for decreasing lanthanum content roughly at a composition LaB/sub 6/ /sub 07/. A modification of the La-B phase diagram is proposed.

McKelvy, M.J.; Eyring, L.; Storms, E.K.

1984-04-26

216

Kinetic study of the formation of oxygen vacancy on lanthanum manganite electrodes  

SciTech Connect

Strontium doped lanthanum manganite (LSM) has been considered one of the most promising cathode materials for solid oxide fuel cells (SOFC). The electrochemical reduction of oxygen on lanthanum manganite (LSM) electrodes has been investigated by cyclic voltammetry, alternating current (ac) impedance, and, in particular, potential step. An emphasis was given to the study of the kinetics of the formation of oxygen vacancy, which is shown to be the main cause for the reversed hysteresis in cyclic voltammograms and for the increase in the electrochemical activity of oxygen reduction on the cathodically polarized LSM electrode observed in both ac impedance and in potential step experiments. The potential step experiments show that the oxygen vacancy concentration increases exponentially with time when the LSM is under a cathodic polarization. In the present study, the rate controlling step for the formation of oxygen vacancies is the oxygen vacancy generation step. The cathodic current rising from the reaction on oxygen vacancies can make a significant contribution to the total reduction current.

Jiang, Y.; Wang, S.; Zhang, Y.; Yan, J.; Li, W. [Chinese Academy of Sciences, Dalian (China). Dalian Inst. of Chemical Physics

1998-02-01

217

Towards the core structure of Strychnos alkaloids using samarium diiodide-induced reactions of indole derivatives.  

PubMed

This report describes the development of a first and second generation approach towards the synthesis of the ABCEG pentacyclic core structure of Strychnos alkaloids. First, we discuss a sequential approach applying a series of functional group transformations to prepare suitable precursors for cyclization reactions. These include attempts of samarium diiodide-induced cyclizations or a Barbier-type reaction of a transient lithium organyl, which successfully led to a tetracyclic key building block earlier used for the synthesis of strychnine. Secondly, we account our first steps towards the development of an atom-economical samarium diiodide-induced cascade reaction using "dimeric" indolyl ketones as cyclization precursors. In this context, we discuss plausible mechanisms for the samarium diiodide-induced cascade reaction as well as transformations of the obtained tetracyclic dihydroindoline derivatives. PMID:24273006

Beemelmanns, Christine; Gross, Steffen; Reissig, Hans-Ulrich

2013-12-23

218

The energetics of lanthanum tantalate materials  

SciTech Connect

Lanthanum tantalates are important refractory materials with application in photocatalysis, solid oxide fuel cells, and phosphors. Soft-chemical synthesis utilizing the Lindqvist ion, [Ta{sub 6}O{sub 19}]{sup 8-}, has yielded a new phase, La{sub 2}Ta{sub 2}O{sub 7}(OH){sub 2}. Using the hydrated phase as a starting material, a new lanthanum orthotantalate polymorph was formed by heating to 850 {sup o}C, which converts to a previously reported LaTaO{sub 4} polymorph at 1200 {sup o}C. The stabilities of La{sub 2}Ta{sub 2}O{sub 7}(OH){sub 2} (LaTa-OH), the intermediate LaTaO{sub 4} polymorph (LaTa-850), and the high temperature phase (LaTa-1200) were investigated using high-temperature oxide melt solution calorimetry. The enthalpy of formation from the oxides were calculated from the enthalpies of drop solution to be -87.1{+-}9.6, -94.9{+-}8.8, and -93.1{+-}8.7 kJ/mol for LaTa-OH, LaTa-850, and LaTa-1200, respectively. These results indicate that the intermediate phase, LaTa-850, is the most stable. This pattern of energetics may be related to cation-cation repulsion of the tantalate cations. We also investigated possible LnTaO{sub 4} and Ln{sub 2}Ta{sub 2}O{sub 7}(OH){sub 2} analogues of Ln=Pr, Nd to examine the relationship between cation size and the resulting phases. - Graphical abstract: The energetics of three lanthanum tantalates were investigated by the high-temperature oxide melt solution calorimetry. The enthalpies of formation from the oxides were calculated from the enthalpies of drop solution to be -87.1{+-}9.6, -94.9{+-}8.8, and -93.1{+-}8.7 kJ/mol for La{sub 2}Ta{sub 2}O{sub 7}(OH){sub 2}, LaTaO{sub 4} (850 {sup o}C), and LaTaO{sub 4} (1200 {sup o}C), respectively. These results indicate that the intermediate phase, LaTaO{sub 4} (850 {sup o}C), is the most stable in energy. Display Omitted

Forbes, Tori Z., E-mail: tmforbes@ucdavis.ed [Peter A. Rock Thermochemistry Laboratory and NEAT ORU, University of California at Davis, Davis, CA 95616 (United States); Nyman, May, E-mail: mdnyman@sandia.go [Sandia National Laboratory, POB 5800, Albuquerque, NM 87185 (United States); Rodriguez, Mark A., E-mail: marodri@sandia.go [Sandia National Laboratory, POB 5800, Albuquerque, NM 87185 (United States); Navrotsky, Alexandra, E-mail: anavrotsky@ucdavis.ed [Peter A. Rock Thermochemistry Laboratory and NEAT ORU, University of California at Davis, Davis, CA 95616 (United States)

2010-11-15

219

Clinical pharmacokinetics of the phosphate binder lanthanum carbonate.  

PubMed

Lanthanum carbonate is considered to be the most potent of a new generation of noncalcium phosphate binders used to treat hyperphosphataemia in chronic kidney disease (CKD), a condition associated with progressive bone and cardiovascular pathology and a markedly elevated risk of death. Its phosphate-binding action involves ionic binding and precipitation of insoluble complexes within the lumen of the intestine, thereby preventing absorption of dietary phosphate. While pharmacokinetics have little relevance to the efficacy of lanthanum carbonate, they are of fundamental importance when it comes to evaluating safety. When administered as lanthanum carbonate, the oral bioavailability of lanthanum is low (approximately 0.001%). The small absorbed fraction is excreted predominantly in bile, with less than 2% being eliminated by the kidneys. Predictably, therefore, plasma exposure and pharmacokinetics have been shown to be similar in healthy human volunteers and CKD stage 5 patients. With almost complete plasma protein binding, free lanthanum concentrations in patients at steady state are <3 pg/mL. These properties greatly reduce systemic exposure, tissue deposition and the potential for adverse effects. While lanthanum has a variety of calcium-like actions in vitro, there is little or no evidence that these occur in vivo. This paradox is explained by the very low concentrations of circulating free lanthanum ions, which are many orders of magnitude lower than reported effect concentrations in vitro. Safety pharmacology and toxicology evaluations have failed to reveal any significant calcium-like actions in vivo, despite inclusion of high intravenous doses in some cases.Lanthanum carbonate has a low propensity to cause systemic drug interactions due to its poor absorption. However, the higher concentrations present in the gastrointestinal tract can form chelates with some drugs, such as fluoroquinolones, and reduce their absorption. The improved understanding of the pharmacokinetics of lanthanum that has emerged in recent years has helped to explain why the myriad of calcium-like effects described in vitro for lanthanum have little if any relevance in vivo. The pharmacokinetic investigations of lanthanum carbonate formed an important part of the stringent premarketing safety assessment process and have been influential in reassuring both regulators and physicians that the agent can be used safely and effectively in this vulnerable dialysis population. PMID:18698878

Damment, Stephen J P; Pennick, Michael

2008-01-01

220

High temperature thermal stabilization of alumina modified by lanthanum species  

Microsoft Academic Search

The effects of precursor pretreatment and addition methods of lanthanum species on stabilization of alumina (surface area loss, phase transformations and high temperature interaction with lanthanum species) have been investigated by BET specific surface area measurements (BET), X-ray powder diffraction (XRD), N2 adsorptiondesorption isotherms, thermal analysis and X-ray photoelectron spectroscopy (XPS) in the range of 6001150C. Although powder La2O3, which

Xiaoyin Chen; Yong Liu; Guoxing Niu; Zhuxian Yang; Maiying Bian; Adi He

2001-01-01

221

Preparation of calcium lanthanum sulfide powders via alkoxide sulfurization  

Microsoft Academic Search

This paper reports that calcium lanthanum sulfide powders are prepared by reacting methoxides of calcium and lanthanum with H[sub 2]S. Alkoxide mixtures of various La\\/Ca ratios dispersed in methanol were reacted with H[sub 2]S at 25[degrees] to 85[degrees] C and the amorphous gels obtained after the removal of methanol were heat-treated in H[sub 2]S for full sulfurization at various temperatures.

Yong Han; Mufit Akinc

1991-01-01

222

Lanthanum Halide Nanoparticle Scintillators for Nuclear Radiation Detection  

SciTech Connect

Nanoparticles with sizes <10 nm were fabricated and characterized for their nanocomposite radiation detector properties. This work investigated the properties of several nanostructured radiation scintillators, in order to determine the viability of using scintillators employing nanostructured lanthanum tribromide, lanthanum trifluoride, or cerium tribromide. Preliminary results of this investigation are consistent with the idea that these materials have an intrinsic response to nuclear radiation that may be correlated to the energy of the incident radiation.

Guss, P. P., Guise, R., Yuan, D., Mukhopadhyay, S., O'Brien, R., Lowe, D.

2013-02-01

223

High temperature investigations of lanthanum-nickel oxyphosphate  

Microsoft Academic Search

Thermal analysis X-ray powder diffraction, IR spectroscopy were carried out for the structural studies of lanthanum-nickel oxyphosphate La3(PO4)O3.Ni1?xO. The lanthanum-nickel phase crystallizes in the monoclinic system with the following lattice parametersa=11.57(2);b=12.22(3);c=6.73(2);?=111.36(4);V=886.87(1)3.

J. Kropiwnicka

1990-01-01

224

Diminiode thermionic energy conversion with lanthanum-hexaboride electrodes  

NASA Technical Reports Server (NTRS)

Thermionic conversion data obtained from a variable gap cesium diminiode with a hot pressed, sintered lanthanum hexaboride emitter and an arc melted lanthanum hexaboride collector are presented. Performance curves cover a range of temperatures: emitter 1500 to 1700 K, collector 750 to 1000 K, and cesium reservoir 370 to 510 K. Calculated values of emitter and collector work functions and barrier index are also given.

Kroeger, E. W.; Bair, V. L.; Morris, J. F.

1978-01-01

225

Lanthanum tetrazinc, LaZn4.  

PubMed

The structure of lanthanum tetrazinc, LaZn(4), has been determined from single-crystal X-ray diffraction data for the first time, approximately 70 years after its discovery. The compound exhibits a new structure type in the space group Cmcm, with one La atom and two Zn atoms occupying sites with m2m symmetry, and one Zn atom occupying a site with 2.. symmetry. The structure is closely related to the BaAl(4), La(3)Al(11), BaNi(2)Si(2) and CaCu(5) structure types, which can be presented as close-packed arrangements of 18-vertex clusters, in this case LaZn(18). The kindred structure types contain related 18-vertex clusters around atoms of the rare earth or alkaline earth metal. PMID:22669182

Oshchapovsky, Igor; Pavlyuk, Volodymyr; Dmytriv, Grygoriy; Griffin, Alexandra

2012-06-01

226

Fabrication of Sm 2+-doped macroporous aluminosilicate glasses with high alumina content  

Microsoft Academic Search

Macroporous Al2O3SiO2 glasses doped with Sm2+ have been prepared from a solgel system containing aluminum sec-butoxide, tetramethoxysilane, samarium chloride hexahydrate, poly(ethylene oxide), nitric acid, and water. Monolithic gels having interconnected macropores and skeletons are formed by inducing the phase separation parallel to the gelation. The use of aluminum sec-butoxide preheated at 80C as the starting material enables the incorporation of

Takayuki Hirao; Koji Fujita; Shunsuke Murai; Kazuki Nakanishi; Kazuyuki Hirao

2006-01-01

227

Direct umpolung of glycals and related 2,3-unsaturated N-acetylneuraminic Acid derivatives using samarium diiodide.  

PubMed

The umpolung of glycals with samarium diiodide offers a simple route to novel carbohydrate-derived nucleophilic reagents in a single step using a readily available reductant. The corresponding allyl samarium reagent that arises from the hexose series reacts with ketones at the C3?position with high stereoselectivity; carbon-carbon bond formation takes place only anti to the substituent at the C4?position of the dihydropyran ring. For the sialic acid series, the completely regio- and stereoselective coupling process of the samarium reagent occurs at the anomeric carbon atom and provides a new approach to the ?-C-glycosides of N-acetyl neuraminic acid. PMID:24764235

Le, Tien Xuan; Papin, Caroline; Doisneau, Gilles; Beau, Jean-Marie

2014-06-10

228

Thermovoltaic effect in thin-film samarium-sulfide-based structures  

NASA Astrophysics Data System (ADS)

We report the first observation of a thermovoltaic effect in thin films of samarium sulfide (SmS). According to this, a voltage of 1.1 V appeared in a thin-film SmS-based sandwich structure heated to temperatures in the 360 428 K interval.

Kaminski?, V. V.; Kazanin, M. M.

2008-04-01

229

ppt level detection of samarium(III) with a coated graphite sensor based on an antibiotic.  

PubMed

N-[2-[4-[[[(Cyclohexylamino)carbonyl]amino]sulfonyl]phenyl]ethyl]-5-methyl pyrazine carboxamide (glipizid) was explored as an electro-active material for preparing a polymeric membrane-based sensor selective to samarium ions. The membrane incorporated 30% poly(vinyl chloride) (PVC), 53% benzyl acetate (BA), 11% glipizid and 6% sodium tetraphenyl borate. When coated on the surface of a graphite electrode, it exhibits Nernstian responses in the concentration range of 1.0 x 10(-5) to 1.0 x 10(-10) M, with a detection limit of 8.0 x 10(-11)M samarium. The electrode shows high selectivity towards samarium over several cations (alkali, alkaline earth, transition and heavy metal ions), and specially lanthanide ions. The proposed sensor has a very short response time (< 15 s), and can be used in a wide pH range for at least ten weeks. It was used as an indicator electrode in potentiometric titration of Sm(III) ions with an EDTA solution, and for determination of samarium in binary and ternary mixtures. PMID:15293392

Ganjali, Mohammad Reza; Rezapour, Morteza; Pourjavid, Mohammad Reza; Haghgoo, Soheila

2004-07-01

230

The effects of samarium-cobalt magnets and pulsed electromagnetic fields on tooth movement  

Microsoft Academic Search

The purpose of this study was to determine whether the application of either samarium cobalt magnets or pulsed electromagnetic fields could increase the rate and amount of orthodontic tooth movement observed in guinea pigs. In addition, the objective was to evaluate the effect of a magnetic field on bony physiology and metabolism and to monitor for possible systemic side effects.

M. Ali Darendeliler; Peter M. Sinclair; Robert P. Kusy

1995-01-01

231

Solar Nebula Heterogeneity in p-Process Samarium and Neodymium Isotopes  

Microsoft Academic Search

Bulk carbonaceous chondrites display a deficit of ~100 parts per million (ppm) in 144Sm with respect to other meteorites and terrestrial standards, leading to a decrease in their 142Nd\\/144Nd ratios by ~11 ppm. The data require that samarium and neodymium isotopes produced by the p process associated with photodisintegration reactions in supernovae were heterogeneously distributed in the solar nebula. Other

Rasmus Andreasen; Mukul Sharma

2006-01-01

232

150 KVA Samarium Cobalt VSCF Starter Generator Electrical System. Phase I.  

National Technical Information Service (NTIS)

Development and construction of a solid rotor using rare earth samarium cobalt magnets for a 150 KVA Variable Speed Constant Frequency Starter/Generator electrical system is described. The system consists of the solid rotor 14-pole starter/generator which...

C. F. Triebel D. L. Lafuze L. J. Bailey L. W. Messenger

1976-01-01

233

The magnetocaloric effect and heat capacity of suspensions of high-dispersity samarium ferrite  

Microsoft Academic Search

The magnetocaloric effect and specific heat capacity of an aqueous suspension of samarium ferrite were determined calorimetrically over the temperature range 288 343 K in magnetic fields of 0 0.7 T. The data obtained were used to calculate changes in the magnetic component of the molar heat capacity and entropy of the magnetic phase and changes in the enthalpy of

V. V. Korolev; I. M. Aref'ev; A. G. Ramazanova

2008-01-01

234

Research on the Samarium-Type Intermediate Phases of Intra-Rare-Earth Binary Systems.  

National Technical Information Service (NTIS)

Four new binary intra-rare earth systems were investigated by metallography, hardness, and density measurements to confirm the presence of the intermediate samarium-type phase. The systems were: La-Lu, Nd-Lu, Sc-Gd, and Sc-La. The lutetium systems exhibit...

C. E. Lundin

1965-01-01

235

Microstructure Dependence of Oxygen-Ion Conductivity of Samarium-Doped Ceria Ceramics  

NASA Astrophysics Data System (ADS)

Superfine and uniform Ce0.8Sm0.2O1.9 powder was derived from a urea-combustion process with a U/Mn+ ratio of 2.0. The microstructure and oxygen-ion conductivity of the ceramics sintered at 1050-1400 C were investigated. The relative densities of the ceramics increased with sintering temperature through a maximum at 1200 C and then slightly declined. The relatively densities of the specimens attained 95.8-98.0% at the sintering temperatures of 1100-1200 C. The average grain size of the ceramics gradually enhanced from 110 to 500 nm with the elevation of sintering temperature from 1050 to 1350 C. The specimens sintered at 1100-1200 C achieved high oxygen-ion conductivities and low activation energies for the conduction. The results indicate an evident effect of the microstructure on the oxygen-ion conductivity. The superior oxygenion conducting properties of the specimens sintered at 1100-1200 C are attributed to their low sintering temperatures, high densification levels and fine-grained microstructures.

Huang, Duan-Ping; Xu, Qing; Liu, Han-Xing; Chen, Wen; Zhao, Kai; Kim, Bok-Hee

2013-07-01

236

Parameters estimation for passively all-fiber Q-switched erbium- and samarium-doped laser  

NASA Astrophysics Data System (ADS)

We present a heuristic method for fitting the parameter values of the theoretical model underlying the experimental passively all-fiber Q-switched laser behavior. We use genetic algorithms (GA) to obtain an agreement between the experimental data and the theoretical model throughout simulations of the laser response for several values of the continuous-wave pumping.

Elena Preda, Cristina; Mgret, Patrice

2013-05-01

237

Giant negative thermal expansion in La-doped CaFe2As2  

NASA Astrophysics Data System (ADS)

Lanthanum doping for calcium in CaFe2As2 results in negative thermal expansion that can be exceptionally large. The behavior is unusual among Fe-As materials, and is presumably associated with the close proximity of CaFe2As2 to a structural phase instability.

Rebello, A.; Neumeier, J. J.; Gao, Zhaoshun; Qi, Yanpeng; Ma, Yanwei

2012-09-01

238

Optimizing Lanthanum Chromite Interconnects for Solid Oxide Fuel Cells  

SciTech Connect

Optimizing the composition of strontium substituted lanthanum chromites to minimize expansion is not straightforward and must be done carefully to avoid compromising sinterability, electrical conductivity, and mechanical strength. In this study, a variety of lanthanum strontium chromites were modified with V, Cu, and Mg to allow densification in air at 1500?C, and their materials properties were evaluated. Both additives (?5 mole % V and 2 mole% Cu) resulted in full densification of Sr substituted (10 and 15 mole%) lanthanum chromite. Of the compositions evaluated, only La0.85Sr0.15Cr0.95V0.05O3 appeared to be a promising interconnect material, showing <0.1% expansion at 10-16 atm. While the coefficient of thermal expansion was less than that of stabilized zirconia, small additions of Co (1 mole%) increased the CTE to 10.1 ppm ?C-1. The results of this study indicated that Cu acted as an acceptor when added to lanthanum chromite, increasing both the electrical conductivity and expansion upon reduction. The effect of vanadium additions were two-fold. First, it acted as a donor in the chromite lattice effectively reducing the overall acceptor concentration. Secondly, during sintering, V reacted with Sr to form Sr3(VO4)2, an effective sintering aid for lanthanum chromite, and further reduced the acceptor level by removing Sr from the perovskite lattice.

Armstrong, Timothy R.; Simner, Steven P.; Hardy, John S.; Stevenson, Jeffry W.

1999-08-01

239

The samarium Grignard reaction. In situ formation and reactions of primary and secondary alkylsamarium(III) reagents  

SciTech Connect

This work shows that primary and secondary radicals are rapidly reduced in THF/HMPA to form primary- and secondary-alkylsamarium reagents. The primary- and secondary-radicals can be formed either by direct SmI{sup 2} reductions of primary- and secondary-halides or by a previous rapid radical cyclization. The samarium reagents have moderate stability in solution, and they react with a variety of typical electrophiles, including aldehydes and ketones. The work further shows that organosamarium intermediates can be involved in the traditional samarium Barbier reaction of aldehydes and ketones conducted in THF/HMPA. A new procedure called the {open_quotes}samarium Grignard{close_quotes} method is introduced, and it is suggested that this new procedure will have considerably more scope and generality than the samarium Barbier reaction. 37 refs., 4 tabs.

Curran, D.P.; Totleben, M.J. [Univ. of Pittsburgh, PA (United States)

1992-07-15

240

Crystallization of lanthanum and yttrium aluminosilicate glasses  

NASA Astrophysics Data System (ADS)

The crystallization behaviour of aluminosilicate glasses of lanthanum (LAS) and yttrium (YAS) containing 2-8 mol% of Ln 2O 3 (Ln = La or Y), 12-30 mol% of Al 2O 3, and 64-80 mol% of SiO 2 has been studied by DTA, XRD and SEM-EDX analysis. X-ray diffraction results indicate the presence of the mullite phase and La 2Si 2O 7 in the monoclinic high-temperature G form (group space P2 1/c) for the LAS glasses, and mullite y-Y 2Si 2O 7 in the monoclinic structure (group space C2/m) and a small amount of ?-Y 2Si 2O 7 in the orthorhombic structure (space group Pna2) for the YAS. For both cases, very little tridymite phase is observed. The results also show that the values of Tg for YAS are higher than those for LAS glasses. The crystallization of LAS glasses is more difficult than that of YAS. For all samples, we observed only one kind of mullite (Al/Si = 3.14).

Sadiki, Najim; Coutures, Jean Pierre; Fillet, Catherine; Dussossoy, Jean Luc

2006-01-01

241

Scintillators With Potential to Supersede Lanthanum Bromide  

Microsoft Academic Search

New scintillators for high-resolution gamma ray spectroscopy have been identified, grown and characterized. Our development efforts have focused on two classes of high-light-yield materials: europium-doped alkaline earth halides and cerium-doped garnets. Of the halide single crystals we have grown by the Bridgman method-SrI2, CaI2, SrBr2, BaI2 and BaBr2-SrI2 is the most promising. SrI2(Eu) emits into the Eu2+ band, centered at

Nerine J. Cherepy; Steve A. Payne; Stephen J. Asztalos; Giulia Hull; Joshua D. Kuntz; Thomas Niedermayr; Siddha Pimputkar; Jeffery J. Roberts; Robert D. Sanner; Thomas M. Tillotson; Edger van Loef; Cody M. Wilson; Kanai S. Shah; Utpal N. Roy; Rastgo Hawrami; Arnold Burger; Lynn A. Boatner; Woon-Seng Choong; William W. Moses

2009-01-01

242

Third Order Derivative Molecular Absorption Spectrophotometry Determination of Traces of Samarium With Methyl Thymol Blue - CTAB or CPB  

Microsoft Academic Search

A sensitive and selective method is described for the determination of traces of samarium by third order derivative molecular absorption spectrophotometry (TDMAS). The method is based on the formation of a stable, blue coloured water soluble ternary complex (Metal-Chromogenic reagent-surfactant) which is formed when cetyl trimethyl ammonium bromide or cetyl pyridinium bromide is added to binary samarium-methyl thymol blue system.

V. Bhagavathy; T. Prasada Rao; A. D. Damodaran

1988-01-01

243

Synthesis of air-sinterable lanthanum chromite powders  

SciTech Connect

Lanthanum chromites, used as current interconnections in solid oxide fuel cells (SOFCs), have high electrical conductivity and are chemically stable. However, they are difficult to fabricate under conditions compatible with other SOFC components. A novel powder synthesis technique, the glycine/nitrate process, has been developed that produces chromite powders that can be sintered to near-full density in air at 1823 K. This paper describes the glycine/nitrate process for the synthesis and fabrication of lanthanum chromites. The sintering behavior and properties of a series of glycine/nitrate-produced lanthanum chromites are discussed. Some of the materials produced by this method match the thermal expansion of the electrolyte and maintain high electrical conductivity. 16 refs., 10 figs.

Chick, L.A.; Bates, J.L.; Pederson, L.R.; Kissinger, H.E.

1989-10-01

244

Lanthanum Carbonate for Hyperphosphatemia in Patients on Peritoneal Dialysis  

PubMed Central

? Background: The efficacy of the phosphate binder lanthanum carbonate has been demonstrated for hemodialysis patients, but no studies have focused on patients undergoing continuous ambulatory peritoneal dialysis (CAPD). We evaluated whether lanthanum carbonate could control phosphate levels in patients on CAPD. ? Methods: In this 48-week open-label prospective study, 28 patients on CAPD with a phosphate level of 6 mg/dL or greater were given lanthanum carbonate titrated from 750 mg to 2250 mg daily to achieve a target serum phosphate level of less than 6 mg/dL. The primary efficacy endpoint was reduction of serum phosphate to less than 6 mg/dL. Serum levels of calcium and parathyroid hormone were also evaluated, as were the CaP product and adverse effects. ? Results: From week 4 to the end of the study at week 48, we observed a significant reduction of serum phosphate to 5.25 0.97 mg/dL from 6.88 1.06 mg/dL at study start (p < 0.01). At the end of the study, 78.6% of participants had achieved the target of less than 6 mg/dL. Because no change of serum calcium occurred, the CaP product declined significantly during the study. Intact parathyroid hormone declined gradually over the study period, but the change had not reached significance at the end of the study (p = 0.11). The mean final dose of lanthanum carbonate was 946 mg daily. The only adverse effect reported was mild nausea in 1 patient. ? Conclusions: Lanthanum carbonate is an effective phosphate binder that can control serum phosphate and CaP product in CAPD patients with hyperphosphatemia. Lanthanum carbonate was well tolerated in our population.

Ohno, Michiya; Ohashi, Hiroshige; Oda, Hiroshi; Yokoyama, Haruko; Okada, Miho; Nagaya, Mayu; Izumi, Kumiko; Ito, Hitomi; Katoh, Shuji

2013-01-01

245

Lanthanum carbonate incorporated chitosan microparticles for phosphate collection  

Microsoft Academic Search

Lanthanum carbonate incorporated chitosan microparticles (LCCM) is proposed for collection of phosphate from 0.9% saline and human plasma serum samples. Loading of ?4.1mg of La2(CO3)33H2O onto 0.1g of chitosan has been achieved. The optimal glutaraldehyde (cross-linker), acetic acid concentration and lanthanum carbonate to chitosan weight ratio for preparation of LCCM were found to be 84.685.7%, 0.30.4moll?1, and 1:1 respectively. Moreover,

P. K. Aneesh; K. P. Prathish; R. Kala; T. Prasada Rao

2009-01-01

246

Syntesis of lanthanum zirconate hydrosols by the ion exchange method  

NASA Astrophysics Data System (ADS)

Ion exchange of LaCl3 and ZrOCl2 aqueous solutions with anion-exchanger AV-17-8 was used to synthesize finely dispersed hydrosol of amorphous lanthanum zirconate La2Zr2O7. Heat treatment of dried La2Zr2O7 hydrosols at 700C and 1100C resulted in the formation of powders with fluorite and pyrochlore type structures, respectively. Epitaxial La2Zr2O7 films were obtained on SrTiO3 (001) single crystals. The substrate has an influence on the lanthanum zirconate crystal orientation, as well as strong inhibitory effect on sintering processes.

Bovina, E. A.; Tarasova, J. V.; Chibirova, F. Kh

2011-04-01

247

The thermally induced metal-semiconducting phase transition of samarium monosulfide (SmS) thin films.  

PubMed

High quality phase pure samarium monosulfide (SmS) thin films were prepared by electron beam evaporation using a samarium metal source in a H(2)S atmosphere. The optical properties (reflection, transmission, absorption) of the films in the semiconducting and metallic phase were analysed from the UV to the mid-IR and explained in terms of the electronic structure of SmS. In this paper it will be shown that metallic SmS thin films exhibit an apparently continuous thermally induced metallic to semiconducting phase transition when studied optically. Temperature dependent x-ray diffraction measurements, however, indicate that the metallic to semiconductor phase transition is in fact first order at a single grain level. The apparently continuous optical behaviour is therefore due to the polycrystalline nature of the films. PMID:21386220

Rogers, E; Smet, P F; Dorenbos, P; Poelman, D; van der Kolk, E

2010-01-13

248

Thermo-elastic and ductile properties of Samarium chalcogenides at high pressures  

NASA Astrophysics Data System (ADS)

Samarium chalcogenides crystallize in Fm3m space group at ambient condition and transform to Pm3m space group under high pressure. We have investigated the structural and elastic properties of Samarium chalcogenides using modified charge-transfer potential model. This model incorporates long-range Coulomb effects and charge-transfer (Coulomb screening due to f-electrons of Sm) effect modified by covalency and short-range repulsive interaction extended up to next-nearest neighbours. This model is capable of explaining the Cauchy-discrepancy. We have computed elastic constants, Poisson's ratio and its volume derivative, the ratio of volume thermal expansion coefficient to specific heat, Debye temperature and Grneisen parameter.

Baraiya, A. K.; Raypuria, G. S.; Gupta, D. C.

2013-02-01

249

Matrix effect in soft metal-bonded samarium-cobalt (SmCo 5 ) permanent magnets  

Microsoft Academic Search

This paper discusses the preparation of samarium-cobalt (SmCo5) alloy powders by reduction-diffusion process. These powders were blended with equal weight percentages of soft metal\\/alloy\\u000a powders, such as indium, tin and solder alloy (Pb-17Sn), to prepare bonded magnets. Important magnetic properties such as\\u000a remanence, coercivity and energy product of these magnets were measured. Effect of matrix metal\\/alloy on the magnetic properties

A Verma; P Verma; R K Sidhu

1996-01-01

250

Dielectric and Ferroelectric Studies on Gel Grown Samarium Tartrate (SmT) Crystals  

Microsoft Academic Search

Samarium tartrate (SmT) single crystals have been grown by gel encapsulation technique. The crystallinity of the grown crystals was confirmed by XRD technique. The dielectric constant, dielectric loss and ac conductivity was measured as a function of frequency in the range 5 kHz to 1 MHz and temperature range 20C to 275C. Dielectric studies show a transition peak at temperature

Sanjay Kumar; B. Kaur; P. N. Kotru; K. K. Bamzai

2007-01-01

251

Thermal behaviour of gel-grown pure and mixed rare earth tartrates of yttrium and samarium  

Microsoft Academic Search

Thermal behaviour of gel-grown pure and mixed rare earth tartrates of yttrium and samarium is investigated using thermogravimetric\\u000a analysis (TGA) and differential scanning calorimetry (DSC). The thermal behaviour suggests that the materials are unstable\\u000a at lower energies and pass through various stages of decomposition, decomposing to respective rare earth oxides which remain\\u000a stable on further heating. It is estimated that

Anima Jain; Sushma Bhat; Sanjay Pandita; M L Kaul; P N Kotru

1997-01-01

252

Evaluation of samarium-153 and holmium-166-EDTMP in the normal baboon model  

Microsoft Academic Search

Bone-seeking radiopharmaceuticals such as ethylenediaminetetramethylene phosphonate (EDTMP) complexes of samarium-153 and holmium-166 are receiving considerable attention for therapeutic treatment of bone metastases. In this study, using the baboon experimental model, multicompartmental analysis revealed that with regard to pharmacokinetics, biodistribution, and skeletal localisation, 166Ho-EDTMP was significantly inferior to 153Sm-EDTMP and 99mTc-MDP. A more suitable 166Ho-bone-seeking agent should thus be sought for

W. K. A. Louw; I. C. Dormehl; A. J. van Rensburg; N. Hugo; A. S. Alberts; O. E. Forsyth; G. Beverley; M. A. Sweetlove; J. Marais; M. G. Ltter; A. van Aswegen

1996-01-01

253

Chondrite Barium, Neodymium, and Samarium Isotopic Heterogeneity and Early Earth Differentiation  

Microsoft Academic Search

Isotopic variability in barium, neodymium, and samarium in carbonaceous chondrites reflects the distinct stellar nucleosynthetic contributions to the early solar system. We used 148Nd\\/144Nd to correct for the observed s-process deficiency, which produced a chondrite 146Sm-142Nd isochron consistent with previous estimates of the initial solar system abundance of 146Sm and a 142Nd\\/144Nd at average chondrite Sm\\/Nd ratio that is lower

Richard W. Carlson; Maud Boyet; Mary Horan

2007-01-01

254

YAG laser-induced crystalline dot patterning in samarium tellurite glasses  

Microsoft Academic Search

A CW YAG laser with a wavelength of 1064 nm and with a power of 1 W has been used to irradiate samarium tellurite glasses with the compositions of 10RO10Sm2O380TeO2 (R=Mg, Ba) at room temperature for 3060 s. It is found from polarized optical microscopy and from X-ray diffraction (XRD) analyses that crystalline dot patterns with sharp refractive index changes

Ryuji Sato; Yasuhiko Benino; Takumi Fujiwara; Takayuki Komatsu

2001-01-01

255

Radiation dose calculations in persons receiving injection of samarium-153 EDTMP  

Microsoft Academic Search

Samarium-153 EDTMP has been proposed as a radionuclide therapeutic agent to treat malignant bone tissue disorders. Data obtained from laboratory rats has been used to calculate the radiation dose for humans following the administration of (¹⁵³Sm)EDTMP. The data reveal that the highest doses are present in the skeleton and the urinary bladder wall (bladder dose varies with frequency of voiding).

K. W. Logan; W. A. Volkert; R. A. Holmes

1987-01-01

256

The magnetocaloric effect and heat capacity of suspensions of high-dispersity samarium ferrite  

Microsoft Academic Search

The magnetocaloric effect and specific heat capacity of an aqueous suspension of samarium ferrite were determined calorimetrically\\u000a over the temperature range 288343 K in magnetic fields of 00.7 T. The data obtained were used to calculate changes in the\\u000a magnetic component of the molar heat capacity and entropy of the magnetic phase and changes in the enthalpy of the process

V. V. Korolev; I. M. Arefev; A. G. Ramazanova

2008-01-01

257

Use of dispersive liquid-liquid microextraction for simultaneous preconcentration of samarium, europium, gadolinium and dysprosium  

Microsoft Academic Search

A new preconcetration method of dispersive liquid-liquid microextraction (DLLME) was developed for simultaneous preconcentration\\u000a of samarium, europium, gadolinium and dysprosium. DLLME technique was successfully used as a sample preparation method. In\\u000a this preconcentration method, an appropriate mixture of extraction solvent, disperser solvent was injected rapidly into an\\u000a aqueous solution containing Sm, Eu, Gd and Dy after complex formation using chelating

M. H. Mallah; F. Shemirani; M. Ghannadi Maragheh

2008-01-01

258

Scintillators with potential to supersede lanthanum bromide  

SciTech Connect

New scintillators for high-resolution gamma ray spectroscopy have been identified, grown and characterized. Our development efforts have focused on two classes of high light yield materials: Europium-doped alkaline earth halides and Cerium-doped garnets. Of the halide single crystals we have grown by the Bridgman method - SrI{sub 2}, CaI{sub 2}, SrBr{sub 2}, BaI{sub 2} and BaBr{sub 2} - SrI{sub 2} is the most promising. SrI{sub 2}(Eu) emits into the Eu{sup 2+} band, centered at 435 nm, with a decay time of 1.2 {micro}s and a light yield of up to 115,000 photons/MeV. It offers energy resolution better than 3% FWHM at 662 keV, and exhibits excellent light yield proportionality. Transparent ceramics fabrication allows production of Gadolinium- and Terbium-based garnets which are not growable by melt techniques due to phase instabilities. While scintillation light yields of Cerium-doped ceramic garnets are high, light yield non-proportionality and slow decay components appear to limit their prospects for high energy resolution. We are developing an understanding of the mechanisms underlying energy dependent scintillation light yield non-proportionality and how it affects energy resolution. We have also identified aspects of optical design that can be optimized to enhance energy resolution.

Cherepy, Nerine; Payne, Steven; Aszatlos, Steve; Hull, Giulia; Kuntz, J.; Niedermayr, Tom; Pimputkar, S.; Roberts, J.; Sanner, R.; Tillotson, T.; van Loef, Edger; Wilson, Cody; Shah, Kanai; Roy, U.; Hawrami, R.; Burger, Arnold; Boatner, Lynn; Choong, Woon-Seng; Moses, William

2009-06-01

259

A comparison of the catalytic performance of the layered oxychlorides of bismuth, lanthanum and samarium in the conversion of methane to ethylene  

Microsoft Academic Search

BiOCl is very efficient as a catalyst for the oxidative coupling of CH4 to yield C2 products, conversions of more than 20 percent and ratios of C2H4\\/C2H6 from 30 to 60, depending upon the precise conditions, being obtained at ca 700 C. Its longevity, however, is rather poor: under operating conditions the solid lacks structural stability. Although LaOCl and SmOCl,

John Williams; Richard H. Jones; John M. Thomas; John Kent

1989-01-01

260

Anthropogenic dissolved and colloid/nanoparticle-bound samarium, lanthanum and gadolinium in the Rhine River and the impending destruction of the natural rare earth element distribution in rivers  

NASA Astrophysics Data System (ADS)

The strong increase in the consumption of rare earth elements (REE) in high-tech products and processes is accompanied by increasing amounts of REE released into the environment. Following the first report of Gd contamination of the hydrosphere in 1996, anthropogenic Gd originating from contrast agents has now been reported worldwide from river and estuarine waters, coastal seawater, groundwater and tap water. Recently, microcontamination with La, that is derived from a point source where catalysts for petroleum refining are produced, has been detected in the Rhine River in Germany and the Netherlands. Here we report the occurrence of yet another REE microcontamination of river water: in addition to anthropogenic Gd and La, the Rhine River now also shows significant amounts of anthropogenic Sm. The anthropogenic Sm, which enters the Rhine River north of Worms, Germany, with the same industrial wastewater that carries the anthropogenic La, can be traced through the Middle and Lower Rhine to the Netherlands. At Leverkusen, Germany, some 250 km downstream from the point source at Worms, anthropogenic Sm still contributes up to 87% of the total dissolved Sm concentration of the Rhine River. Results from ultrafiltration suggest that while the anthropogenic Gd is not particle-reactive and hence exclusively present in the truly dissolved REE pool (<10 kDa), the anthropogenic La and Sm are also present in the colloidal/nanoparticulate REE pool (between 10 kDa and 0.2 ?m). Though difficult to quantify, our data suggest that the Rhine River may carry up to 5700 kg of anthropogenic La, up to 584 kg of anthropogenic Sm, and up to 730 kg of anthropogenic Gd per year toward the North Sea. There exist no regulatory limits for dissolved REE in natural waters, but total REE and Y (?REY) concentrations of up to 0.14 mg/kg in the plume downstream of and 52.2 mg/kg at the head of an effluent pipe at Rhine-km 447.3 at Worms get close to and well-above, respectively, the levels at which ecotoxicological effects have been documented. Because of the increasing use of REE and other formerly "exotic" trace elements in high-tech applications, these critical metals have now become emerging contaminants that should be monitored, and it appears that studies of their biogeochemical behavior in natural freshwaters might soon no longer be possible.

Kulaks?z, Serkan; Bau, Michael

2013-01-01

261

Topological surface state in the Kondo insulator samarium hexaboride.  

PubMed

Topological invariants of electron wavefunctions in condensed matter reveal many intriguing phenomena. A notable example is provided by topological insulators, which are characterized by an insulating bulk coexisting with a metallic boundary state. Although there has been intense interest in Bi-based topological insulators, their behaviour is complicated by the presence of a considerable residual bulk conductivity. Theories predict that the Kondo insulator system SmB6, which is known to undergo a transition from a Kondo lattice metal to a small-gap insulator state with decreasing temperature, could be a topological insulator. Although the insulating bulk and metallic surface separation has been demonstrated in recent transport measurements, these have not demonstrated the topologically protected nature of the metallic surface state. Here we report thickness-dependent transport measurements on doped SmB6, and show that magnetic and non-magnetic doping results in contrasting behaviour that supports the conclusion that SmB6 shows virtually no residual bulk conductivity. PMID:24658115

Kim, D J; Xia, J; Fisk, Z

2014-05-01

262

Topological surface state in the Kondo insulator samarium hexaboride  

NASA Astrophysics Data System (ADS)

Topological invariants of electron wavefunctions in condensed matter reveal many intriguing phenomena. A notable example is provided by topological insulators, which are characterized by an insulating bulk coexisting with a metallic boundary state. Although there has been intense interest in Bi-based topological insulators, their behaviour is complicated by the presence of a considerable residual bulk conductivity. Theories predict that the Kondo insulator system SmB6, which is known to undergo a transition from a Kondo lattice metal to a small-gap insulator state with decreasing temperature, could be a topological insulator. Although the insulating bulk and metallic surface separation has been demonstrated in recent transport measurements, these have not demonstrated the topologically protected nature of the metallic surface state. Here we report thickness-dependent transport measurements on doped SmB6, and show that magnetic and non-magnetic doping results in contrasting behaviour that supports the conclusion that SmB6 shows virtually no residual bulk conductivity.

Kim, D. J.; Xia, J.; Fisk, Z.

2014-05-01

263

Optical and physical properties of lanthanum gallogermanate glasses  

Microsoft Academic Search

Optical properties of lanthanum gallogermanate glasses were investigated by infrared (IR) transmission and IR reflectivity measurements. Several physical properties of these glasses, including density, index of refraction and ultrasonic velocities, were also measured. The experimental results are used to obtain elastic constants. These glasses are transparent over frequencies ranging from the near ultraviolet to the mid-IR (?8 ?m) and have

Luu-Gen Hwa; Yi-Rui Chang; Sung-Ping Szu

1998-01-01

264

Ab initio energetics of lanthanum substitution in ferroelectric bismuth titanate.  

PubMed

Using first principles calculations and atomistic thermodynamics the bulk and defect properties of orthorhombic bismuth titanate (Bi?Ti?O??) and bismuth lanthanum titanate (Bi?.??La?.??Ti?O??) have been investigated. Heats of formation, valid chemical conditions for synthesis, lanthanum substitution energies and oxygen and bismuth vacancy formation energies have been computed. The study improves our understanding of how native point defects and substitutional impurities influence the ferroelectric properties of these layered perovskite materials. It is found that lanthanum incorporation could occur on either of the two distinct bismuth sites in the structure and that the effect of substitution is to increase the formation energy of nearby native oxygen vacancies. The results provide direct atomistic evidence over a range of chemical conditions supporting the suggestion that lanthanum incorporation reduces the oxygen vacancy concentration. Oxygen vacancies contribute to ferroelectric fatigue by interacting strongly with domain walls, and therefore a decrease in their concentration is beneficial. The conditions that favor the greatest reduction in oxygen vacancy concentration are described. PMID:21460424

Shah, S H; Bristowe, P D

2011-04-20

265

Adverse Events in the Long-Term Follow-Up of Patients Treated With Samarium Sm 153 Lexidronam for Osseous Metastases  

SciTech Connect

Purpose: To investigate adverse events after samarium Sm 153 lexidronam and the effect of pre- and post-samarium Sm 153 lexidronam external beam radiation therapy (EBRT) and/or chemotherapy on myelosuppression in patients who received samarium Sm 153 lexidronam for osseous metastases. Methods and Materials: We performed a single-institution retrospective review of 139 patients treated with samarium Sm 153 lexidronam between November 1997 and February 2008. New-onset adverse events after samarium Sm 153 lexidronam were reported. The effect of samarium Sm 153 lexidronam on platelet and peripheral white blood cell counts and the duration of myelosuppression after samarium Sm 153 lexidronam plus EBRT and/or chemotherapy were calculated. Differences in the prevalence of adverse events among patients with varying treatment histories were evaluated with the Pearson chi-square test. Results: Hematologic follow-up was available for 103 patients. Chemotherapy and/or EBRT had no effect on the magnitude or duration of myelosuppression. The most common nonhematologic adverse events were acute lower extremity edema (n = 27) and acute and transient neuropathy (n = 29). Patients treated with chemotherapy after samarium Sm 153 lexidronam had a higher prevalence of lower extremity edema (9 of 18 [50%]) than those who were not treated with chemotherapy after samarium Sm 153 lexidronam (18 of 85 [21.2%]) (p = 0.01, chi-square test). No adverse events were correlated with EBRT. Conclusions: Our observation of new-onset, acute and transient edema and neuropathy after samarium Sm 153 lexidronam and of a relationship between edema and post-samarium Sm 153 lexidronam chemotherapy suggests the need for re-examination of patients in past series or for a prospective investigation with nonhematologic adverse events as a primary endpoint.

Paravati, Anthony J., E-mail: Anthony.J.Paravati@dartmouth.edu [Dartmouth Medical School, Hanover, NH (United States); Russo, Andrea L. [Dartmouth Medical School, Hanover, NH (United States); Aitken, Candice [Dartmouth Medical School, Hanover, NH (United States); Department of Medicine, Section of Radiation Oncology, Dartmouth-Hitchcock Medical Center, Lebanon, NH (Lebanon)

2011-10-01

266

Highly germanium and lanthanum modified silica based glasses in microstructured optical fibers for non-linear applications  

NASA Astrophysics Data System (ADS)

Modified core glass materials in silica-clad microstructured fibers (MOFs) promise efficient conversion of non-linear processes, e.g. for supercontinuum (SC) generation. We used extremely highly germanium-doped silica (max. 36 mol% GeO 2) and lanthanum aluminum silicate glasses with high lanthanum oxide concentration (max. 10 mol% La 2O 3) as core materials. The microstructured optical fibers (Ge-MOFs, La-MOFs) were prepared in five air ring architecture by a stack-and-draw technique using silica for the cladding region. The MOFs show loss minima of about 0.05 dB m -1 (Ge-MOF) and 1.3 dB m -1 (La-MOF) at a wavelength of 1.064 ?m. Such Ge-MOFs and La-MOFs are compatible with conventional silica fibers giving low loss splices with standard single mode fibers. The non-linearity of the La-MOF is approximately two times higher than that of the Ge-MOF, but shows a significantly higher spectral loss. Ge-MOF and La-MOF can both produce similar ultra-broad band supercontinuum spectra from VIS (540 nm and 500 nm) to IR range (2400 nm and 2220 nm) by being pumped with a passively Q-switched Nd:YAG microchip laser.

Kobelke, Jens; Schuster, Kay; Litzkendorf, Doris; Schwuchow, Anka; Kirchhof, Johannes; Tombelaine, Vincent; Bartelt, Hartmut; Leproux, Philippe; Couderc, Vincent; Labruyere, Alexis; Jamier, Raphael

2010-07-01

267

Sm3+ doped lithium aluminoborate glasses for orange coloured visible laser host material  

NASA Astrophysics Data System (ADS)

Samarium doped lithium aluminium borate glasses have been prepared by conventional melt quench technique and their detailed spectroscopic analysis has been done. The structural analysis has been done by using FTIR studies and density is measured by Archimedes method. The UV-vis-NIR absorption spectra show an increase in intensity of different transitions from the ground level 6H5/2 to various 2S+1LJ levels with an increase in samarium concentration at the expense of aluminium. The fluorescence spectra show several transitions from 4G5/2 to various 6HJ levels along with 4F3/2 to 6HJ and 4G7/2 to 6H5/2.

Kaur, Parvinder; Kaur, Simranpreet; Singh, Gurinder Pal; Singh, D. P.

2013-10-01

268

Comparison Between Features and Performance Characteristics of Fifteen HP Samarium Cobalt and Ferrite Based Brushless DC Motors Operated by Same Power Conditioner  

Microsoft Academic Search

The impact of samarium-cobalt and ferrite magnet materials on the design and performance characteristics of electronically commutated brushless dc motors of equal horsepower output is presented. This is accomplished through the design, construction and testing of two 15 hp, 120 volt brushless dc motors built for propulsion of electric vehicles, and similar applications. In one of these motors, samarium-cobalt (Sm

N. A. Demerdash; R. H. Miller; T. W. Nehl; B. P. Overton; C. J. Ford

1983-01-01

269

Phase behavior of lanthanum strontium manganites  

SciTech Connect

The phase stability of Sr-doped LaMnO{sub 3} (LSM) perovskite in the La-Sr-Mn-O system was investigated as a function of Sr content and A/B cation ratio. The perovskite structure changed with both Sr content and A/B cation ratio. As the Sr content was increased to 0.2 mol, the perovskite structure adopted an orthorhombic distortion. This changed to a monoclinic or hexagonal structure for 0.2 {le} Sr {le} 0.3 mol. When the Sr content increased to 0.3 mol, the structure reverted to orthorhombic symmetry. Data from X-ray powder diffractometry, scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray emission spectroscopy, showed that secondary phases in the La-Sr-Mn-O system were underdeveloped with respect to changes of the doped Sr content, A/B cation ratio, and thermal history. X-ray detectable minor phases present in the LSM material were Mn{sub 3}O{sub 4}, (La, Sr)Mn{sub 2}O{sub 4}, La{sub 2}O{sub 3}, La(OH){sub 3}, (La, Sr){sub 3}Mn{sub 2}O{sub 7}, and (La, Sr){sub 2}MnO{sub 4}.

Zheng, F.; Pederson, L.R.

1999-08-01

270

Grain growth kinetics and electrical properties of lanthanum modified lead zirconate titanate (9/65/35) based ferroelectric ceramics  

SciTech Connect

The influence of the microstructural characteristics on the dielectric and electrical properties has been investigated for Nd{sup 3+} doped lanthanum modified lead zirconate titanate ferroelectric ceramics, obtained by the conventional solid-state reaction method, by taking into account different sintering conditions. The grain growth mechanism has been investigated and a cubic-type grain growth law was observed for samples with grain size varying from 1.00 up to 2.35 {mu}m. The porosity and grain size dependences of the phase transition parameters, such as the maximum dielectric permittivity and its corresponding temperature ({epsilon}{sub m} and T{sub m}, respectively) were also investigated. The ac conductivity analyses followed the universal Jonscher law. The behavior of the frequency exponent (s) was analyzed through the correlated barrier hopping model. Both ac and dc conductivity results have been correlated with the observed microstructural features.

Roca, R. Alvarez; Guerrero, F. [Departamento de Fisica, Grupo de Ceramicas Ferroeletricas, UFSCar, Rod. Washington Luis, Km 235, CEP 13565-905 Sao Carlos, Sao Paulo (Brazil); Departamento de Fisica, Facultad de Ciencias Naturales, Universidad de Oriente, 90500 Santiago de Cuba (Cuba); Botero, E. R.; Garcia, D.; Eiras, J. A. [Departamento de Fisica, Grupo de Ceramicas Ferroeletricas, UFSCar, Rod. Washington Luis, Km 235, CEP 13565-905 Sao Carlos, Sao Paulo (Brazil); Guerra, J. D. S. [Grupo de Ferroeletricos e Materiais Multifuncionais, Instituto de Fisica, Universidade Federal de Uberlandia, 38400-902 Uberlandia, Minas Gerais (Brazil)

2009-01-01

271

Detection of divalent europium, ytterbium, and samarium ions in aqueous solution during anodic polarization of the corresponding amalgam  

SciTech Connect

Amalgams of europium, ytterbium, and samarium are oxidized both at constant current and at constant potential. It was found experimentally that the potential of the indicator electrode moved to negative values when the circuit was closed and anodic current (1.0 to 60.0 mA) or potential (of the starting wave, half wave, or limiting current) applied. The potential of the microelectrode was 0.05 V, and remained unchanged during the entire electrolysis time, when pure mercury was used as the anode. The data reported for europium, ytterbium, and samarium amalgam confirm the results otained previously. By measuring the redox potentials of couples Sm/sup 3 +/-Sm/sup 2/, Yb/sup 3 +/-Yb/sup 2 +/ and Eu/sup 3 +/-Eu/sup 2 +/ directly at the electrode surface the authors have established the formation of divalent samarium, ytterbium, and europium ions during anodic oxidation of the corresponding amalgams.

Sagadieva, K.Z.; Badavamova, G.L.; Zebreva, A.I.

1986-04-01

272

Catalytic asymmetric Michael reactions promoted by a lithium-free lanthanum-BINOL complex  

SciTech Connect

In this communication, we report about a new lithium-free BINOL-lanthanum complex, which is quite effective in catalytic asymmetric Michael reaction. We have succeeded in developing effective asymmetric base catalysts, in particular, asymmetric ester enolate catalysts for asymmetric Michael reactions. Two asymmetric lanthanum complexes are now available, namely, BINOL-lanthanum-lithium complex, which is quite effective in catalytic asymmetric nitrosaldol reactions, and a new lithium-free BINOL-lanthanum ester enolate complex, that is very effective in catalytic asymmetric Michael reactions. The two complexes complement each other in their ability to catalyze asymmetric nitroaldol and asymmetric Michael reactions. 14 refs., 1 fig., 2 tabs.

Sasai, Hiroaki; Arai, Takayoshi; Shibasaki, Masakatsu (Univ. of Tokyo (Japan))

1994-02-23

273

Genetic algorithm based approach to investigate doped metal oxide materials: Application to lanthanide-doped ceria  

NASA Astrophysics Data System (ADS)

A genetic algorithm (GA)-inspired method to effectively map out low-energy configurations of doped metal oxide materials is presented. Specialized mating and mutation operations that do not alter the identity of the parent metal oxide have been incorporated to efficiently sample the metal dopant and oxygen vacancy sites. The search algorithms have been tested on lanthanide-doped ceria (L=Sm,Gd,Lu) with various dopant concentrations. Using both classical and first-principles density-functional-theory (DFT) potentials, we have shown the methodology reproduces the results of recent systematic searches of doped ceria at low concentrations (3.2% L2O3 ) and identifies low-energy structures of concentrated samarium-doped ceria (3.8% and 6.6% L2O3 ) which relate to the experimental and theoretical findings published thus far. We introduce a tandem classical/DFT GA algorithm in which an inexpensive classical potential is first used to generate a fit gene pool of structures to enhance the overall efficiency of the computationally demanding DFT-based GA search.

Hooper, James; Ismail, Arif; Giorgi, Javier B.; Woo, Tom K.

2010-06-01

274

Nanostructured Lanthanum Zirconate Coating and Its Thermal Stability Properties  

Microsoft Academic Search

In this paper, nano-La2Zr2O7 thermal barrier coatings (MCrAlY+ La2Zr2O7) were prepared by atmospheric plasma sprayed (APS). The microstructures and thermal stability properties were systematically studied to compare with their conventional counterparts by Scanning Electric Microscopy (SEM) transmission electron microscope (TEM) and X-Ray diffraction(XRD). The results showed that the nanostructured lanthanum zirconate coatings were typical lamellar structure which was composed of

Xiao-dong ZHAO; Ke-li ZENG; Jian-gang XIE; Zhen-duo LI

2007-01-01

275

Ferroelectric domain structure of lanthanum-modified lead titanate ceramics  

Microsoft Academic Search

The ferroelectric domain configurations in lanthanum-modified lead titanate ceramics have been studied by transmission electron microscopy in conventional, analytical, and high-resolution modes. Results indicate a preponderance of {l brace}101{r brace}, twin-related 90° domains of equilibrium width 50 to 100 nm. These values are consistent with those derived from consideration of elastic strain energy. Below a critical grain size of approximately

Brain G. Demczyk; Raghaw S. Rai; Gareth Thomas

1990-01-01

276

Effect of pressure on the magnetic properties of lanthanum manganite  

SciTech Connect

The crystalline structure of pure lanthanum manganite under external hydrostatic pressure has been studied. The behavior of magnetic properties and nuclear magnetic resonance (NMR) spectra under these conditions is theoretically predicted. It is shown that an increase in the Neel temperature with pressure is not only caused by the general contraction of the crystal, but is also related to certain peculiarities in the baric behavior of the orbital structure.

Gonchar', L. E., E-mail: Lyudmila.Gonchar@usu.ru; Leskova, Yu. V.; Nikiforov, A. E. [Ural State University (Russian Federation); Kozlenko, D. P. [Joint Institute for Nuclear Research (Russian Federation)

2010-08-15

277

Lanthanum halide nanoparticle scintillators for nuclear radiation detection  

SciTech Connect

Nanoparticles with sizes <10 nm were fabricated and characterized for their nanocomposite radiation detector properties. This work investigated the properties of several nanostructured radiation scintillators, in order to determine the viability of using scintillators employing nanostructured lanthanum trifluoride. Preliminary results of this investigation are consistent with the idea that these materials have an intrinsic response to nuclear radiation that may be correlated to the energy of the incident radiation.

Guss, Paul; Guise, Ronald [Remote Sensing Laboratory, P.O. Box 98521, M/S RSL-48, Las Vegas, Nevada 89193 (United States); Yuan Ding [National Security Technologies, LLC, Los Alamos Operations, P.O. Box 809, M/S LAO/C320, Los Alamos, New Mexico 87544 (United States); Mukhopadhyay, Sanjoy [Remote Sensing Laboratory-Andrews, Building 1783, Arnold Avenue Andrews AFB, Maryland 20762 (United States); O'Brien, Robert; Lowe, Daniel [University of Nevada, Las Vegas, 4505 S. Maryland Parkway, Las Vegas, Nevada 89154 (United States); Kang Zhitao; Menkara, Hisham [Georgia Tech Research Institute, 925 Dalney St., Atlanta, Georgia 30332 (United States); Nagarkar, Vivek V. [RMD, Inc., 44 Hunt Street, Watertown, Massachusetts 02472 (United States)

2013-02-14

278

Magnetic properties of lanthanum orthoferrites containing lattice defects  

Microsoft Academic Search

Polycrystalline lanthanum orthoferrites were prepared by firing coprecipitated hydroxides of La3+ and Fe3+ at elevated temperatures. The materials fired at temperatures below 1100C were characterized by the coexistence of such lattice vacancies that the concentration ratio of VLa:VFe:Vo is always equal to that of the constituent atoms of LaFeO3. They exhibited a large magnetic susceptibility, a low Nel temperature, and

Hiroshi Yamamura; Shin-Ichi Shirasaki; Hirotoshi Oshima; Kazuyuki Kakegawa

1976-01-01

279

Lanthanum halide nanoparticle scintillators for nuclear radiation detection  

NASA Astrophysics Data System (ADS)

Nanoparticles with sizes <10 nm were fabricated and characterized for their nanocomposite radiation detector properties. This work investigated the properties of several nanostructured radiation scintillators, in order to determine the viability of using scintillators employing nanostructured lanthanum trifluoride. Preliminary results of this investigation are consistent with the idea that these materials have an intrinsic response to nuclear radiation that may be correlated to the energy of the incident radiation.

Guss, Paul; Guise, Ronald; Yuan, Ding; Mukhopadhyay, Sanjoy; O'Brien, Robert; Lowe, Daniel; Kang, Zhitao; Menkara, Hisham; Nagarkar, Vivek V.

2013-02-01

280

Mechanical properties of calcium- and strontium-substituted lanthanum chromite  

Microsoft Academic Search

Mechanical properties of acceptor (calcium and strontium)-substituted lanthanum chromites are reported as a function of composition, temperature and environment. The strength dependence on temperature for these perovskite conductors was found to depend on the acceptor type, with the calcium-substituted chromites showing a significant reduction in strength with increasing temperature, while the strength of strontium-substituted chromites was essentially invariant with temperature.

S. W. PAULIK; S. BASKARAN; T. R Armstrong

1998-01-01

281

Intramolecular, reductive cyclization of beta-ketoisothiocyanates promoted by using samarium diiodide.  

PubMed

A novel samarium diiodide (SmI2) promoted intramolecular cyclization of beta-ketoisothiocyanate, derived from alpha,beta-unsaturated esters and ammonium thiocyanate led to alpha-hydroxythiolactams and/or thiolactams in high yields. Treatment of beta-ketoisothiocyanate with two equivalents of SmI2 gave a mixture of alpha-hydroxythiolactam and thiolactam. Four equivalents of SmI2 afforded only thiolactam in high yields. The intramolecular cyclization took place with high to complete stereoselectivity. A mechanism to explain this transformation is proposed. PMID:15651025

Cho, Min Seok; Lee, In Sang; Kang, Sung Ho; Kim, Yong Hae

2005-02-18

282

Chelating Ligand-Mediated Hydrothermal Synthesis of Samarium Orthovanadate with Decavanadate as Vanadium Source  

PubMed Central

A new ethylenediaminetetraacetic acid- (EDTA-) mediated hydrothermal route to prepare chrysanthemum-shaped samarium orthovanadate (SmVO4) nanocrystals with decavanadate (K6V10O289H2O) as vanadium source has been developed. The present hydrothermal approach is simple and reproducible and employs a relatively mild reaction temperature. The EDTA, pH value, and temperature of the reaction systems play important roles in determining the morphologies and growth process of the SmVO4 products. The products have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), photoluminescence spectra (PL), and UV-Vis spectroscopy.

Zuo, Wenli

2013-01-01

283

NONLINEAR OPTICAL PHENOMENA: Resonances of coherent population trapping in samarium vapours  

Microsoft Academic Search

Resonances of coherent population trapping were detected in atomic vapours of the rare-earth element samarium. The coherent population trapping was produced by two external-cavity diode lasers (672 and 686 nm) in a Lambda-system formed by the three levels of 154Sm: the 4f66s2(7F0) ground state, the first fine-structure 4f66s2(7F1) sublevel of the ground state and the 4f6(7F)6s6p(3Po)9Fo1 upper level. The dependence

Nikolai N. Kolachevsky; A. V. Akimov; N. A. Kiselev; A. A. Papchenko; Vadim N. Sorokin; S. I. Kanorskii

2001-01-01

284

Thermally stimulated processes in samarium-modified lead titanate ferroelectric ceramics  

NASA Astrophysics Data System (ADS)

The thermally stimulated processes in a samarium-modified lead titanate ferroelectric system are analyzed from the thermally stimulated depolarization discharge current. The discharge due to the space charge injected during the poling process, the pyroelectric response and a conduction process related to oxygen vacancies are evaluated considering a theoretical decomposition by using a numerical method. The pyroelectric response is separated from other components to evaluate the polarization behavior and some pyroelectric parameters. High remanent polarization, pyroelectric coefficient and merit figure values are obtained at room temperature.

Peliz-Barranco, A.; Garca-Wong, A. C.; Gonzlez-Abreu, Y.; Gagou, Y.; Saint-Grgoire, P.

2013-08-01

285

Oxygen ion conductivity of the ceria-samarium oxide system with fluorite structure  

Microsoft Academic Search

Ionic conduction of oxygen in the ceria-samarium oxide system was investigated as a function of temperature, partial pressure of oxygen and the oxide composition, together with its crystal structure, density and defect structure. The ionic conductivity of (CeO2)1-x(SmO1.5)x was the highest in ZrO2-, ThO2- and CeO2-based oxide systems. The system CeO2-SmO1.5 consisted of the solid solution with a fluorite structure

Hidenori Yahiro; Yukari Eguchi; Koichi Eguchi; Hiromichi Arai

1988-01-01

286

Infiltrated lanthanum strontium chromite anodes for solid oxide fuel cells: Structural and catalytic aspects  

NASA Astrophysics Data System (ADS)

Infiltration is a widely used fabrication method for solid oxide fuel cell (SOFC) composite electrodes. Here we report a study of the structure and electrocatalytic properties of SOFC anodes composed of a layer of lanthanum, strontium chromite (La0.8Sr0.2CrO3, LSCr), both with and without added transition metal dopants, infiltrated into a porous yttria-stabilized zirconia (YSZ) matrix. The structural evolution of the electrode upon reduction and under typical SOFC operating conditions is compared to that reported previously for La0.8Sr0.2Cr0.5Mn0.5O3-YSZ composite anodes. For the transition metal doped materials, a portion of the metal dopants were found to be exsolved from the LSCr lattice upon reduction and to be effective in promoting electro-oxidation of hydrogen. Exsolved cobalt particles were also found to be relatively stable when exposed to hydrocarbon fuels with low activity for the formation of carbon deposits.

Oh, Tae-Sik; Yu, Anthony S.; Adijanto, Lawrence; Gorte, Raymond J.; Vohs, John M.

2014-09-01

287

Magnetoresistance of lanthanum manganites with activation-type conductivity  

SciTech Connect

The temperature dependence of the resistivity and magnetic moment of La{sub 0.85}Ba{sub 0.15}MnO{sub 3} and La{sub 0.85}Sr{sub 0.15}MnO{sub 3} manganite single crystals in magnetic fields up to 90 kOe is investigated. Analysis of the experimental results shows that the magnetoresistance of lanthanum manganites far from the Curie temperature T{sub C} can be described quantitatively by the s-d model normally used for ferromagnets and taking into account only the exchange interaction between the spins of charge carriers and magnetic moments. These data also show that the features of lanthanum manganites responsible for colossal magnetoresistance (CMR) are manifested in a narrow temperature interval {delta}T Almost-Equal-To 20 K near T{sub C}. Our results suggest a CMR mechanism analogous to the mechanism of giant magnetoresistance (GMR) observed in Fe/Cr-type multilayers with nanometer layer thickness. The nanostratification observed in lanthanum manganites and required for GMR can be described taking into account the spread in T{sub C} in the CMR range {delta}T.

Kurkin, M. I., E-mail: kurkin@imp.uran.ru; Neifeld, E. A.; Korolev, A. V.; Ugryumova, N. A.; Gudin, S. A.; Gapontseva, N. N. [Russian Academy of Sciences, Institute of Metal Physics, Ural Branch (Russian Federation)

2013-05-15

288

Electrochemical Deposition of Lanthanum Telluride Thin Films and Nanowires  

NASA Astrophysics Data System (ADS)

Tellurium alloys are characterized by their high performance thermoelectric properties and recent research has shown nanostructured tellurium alloys display even greater performance than bulk equivalents [1-2]. Increased thermoelectric efficiency of nanostructured materials have led to significant interests in developing thin film and nanowire structures. Here, we report on the first successful electrodeposition of lanthanum telluride thin films and nanowires. The electrodeposition of lanthanum telluride thin films is performed in ionic liquids at room temperature. The synthesis of nanowires involves electrodepositing lanthanum telluride arrays into anodic aluminum oxide (AAO) nanoporous membranes. These novel procedures can serve as an alternative means of simple, inexpensive and laboratory-environment friendly methods to synthesize nanostructured thermoelectric materials. The thermoelectric properties of thin films and nanowires will be presented to compare to current state-of-the-art thermoelectric materials. The morphologies and chemical compositions of the deposited films and nanowires are characterized using SEM and EDAX analysis. References: [1] D. M. Rowe, CRC Handbook of Thermoelectrics, CRC Press (1995). [2] A. May et al., Phys. Rev. B 78, 125205 (2008).

Chi, Su; Farias, Stephen; Cammarata, Robert

2013-03-01

289

Ethanol Gas Sensor Based on Pure and La-Doped Bismuth Vanadate  

NASA Astrophysics Data System (ADS)

Bismuth vanadate (BiVO4) and lanthanum-doped bismuth vanadate (La-doped BiVO4) were prepared via the precipitation method. Their films were produced by simple drop-coating of the initial solutions over gold electrodes, which were coated over a glass substrate. The structural properties of BiVO4 and La-doped BiVO4 samples were studied using x-ray diffractometer, diffuse reflectance spectroscopy, scanning electron microscopy, atomic force microscopy, and compositional analysis. A chamber was designed to install the sensing device and also controllable tools for gas flow rate and temperature. Changes in the resistance of the prepared layers were recorded during exposure to various amounts of ethanol vapor at different temperatures. Both BiVO4 and La-doped BiVO4 layers showed measurable responses in the form of resistance drop (increased conductivity). The higher temperatures up to 450 C led to stronger signals. The layer containing lanthanum showed signals with shorter recovery times. Introduction of lanthanum caused smaller crystallite sizes in addition to the formation of tetragonal phase of BiVO4. Presence of lanthanum increased the amounts of grain boundaries, magnitude of the response, and sensitivity. Sensitivity of La-doped BiVO4 was almost twice that of the BiVO4 at concentrations of 150-500 ppm of ethanol. Also, the correlation of the response as a function of concentration of ethanol in gas phase was exploited, and two different linear ranges were observed for the lower and higher concentrations.

Golmojdeh, Hosein; Zanjanchi, Mohamad Ali

2014-02-01

290

Application of a Boson Expansion Formalism Based on the Random Phase Approximation to Samarium Isotopes  

NASA Astrophysics Data System (ADS)

The Boson Expansion Theory of Kishimoto and Tamura has proved to be very successful in describing quadrupole collective motions in even-even nuclei. This theory, however, involves a complicated transformation from the Tamm-Dancoff phonons to the phonons of the Random Phase Approximation. In this thesis a Boson Expansion formalism, derived directly from the Random Phase Approximation and set forth by Pedracchi and Tamura, is used to derive the boson forms of the nuclear Hamiltonian and the electromagnetic transition operator. Detailed discussions of the formalism of Pedrocchi and Tamura and its extension needed to perform realistic calculations are presented. The technique used to deriving the boson forms and the formulae used in the calculations are also given a thorough treatment to demonstrate the simplicity of this approach. Finally, the theory is tested by applying it to calculate the energy levels and some electromagnetic properties of the Samarium isotopes. The results show that the present theory is capable of describing the range of behavior from a vibrational to a rotational character of the Samarium isotopes as good as the previous theory.

Jamaluddin, Muzhar Bin

291

Thermionic Topping of a Solar Power Plant Using Converters Containing Lanthanum Hexaboride Electrodes.  

National Technical Information Service (NTIS)

Properties of lanthanum boride for use as a thermionic emitter in a thermionic converter were studied, and results are presented and discussed. The vaporization rate of atoms from lanthanum borode, the work function, and the effect of cesium on these two ...

E. Storms

1978-01-01

292

Lanthanum hexaaluminate novel thermal barrier coatings for gas turbine applications materials and process development  

Microsoft Academic Search

Lanthanum hexaaluminate (LHA) with a magnetoplumbite structure is a promising competitor to yttria partially stabilized zirconia (Y-PSZ) as a thermal barrier coating (TBC), since most zirconia coatings age significantly, including undesired densification at temperatures exceeding 1100 C. The microstructure of calcined lanthanum hexaaluminate powders and thermally sprayed coatings show a platelet structure. The magnetoplumbite structure is characterized by the highly

R. Gadow; M. Lischka

2002-01-01

293

Magnetic properties of lanthanum manganite with monoclinic and cubic perovskite structure  

Microsoft Academic Search

The properties of lanthanum manganite with monoclinic perovskite structure, synthesized under various technological regimes, were investigated by magnetic and neutron-diffraction methods. It is shown that the magnetic properties of lanthanum manganite correlate with its crystal structure, and particularly with the degree of monoclinic distortions of the perovskite lattice.

N. N. Sirota; V. I. Pavlov; E. S. Lashkov; A. P. Karavai

1977-01-01

294

Samarium153-EDTMP:Pharmacokinetic, Toxicity and Pain Response Using an Escalating Dose Schedule in Treatment of Metastatic Bone Cancer  

Microsoft Academic Search

Samarium-153 emitsmedium-energy beta particlesand an imageable gammaphotonwith a physicalhalf-lifeof 46.3hr. Whenchelatedto ethylenediaminetetramethylenephosphonic acid(EDTMP), it is remarkably stablein vitro andin vivo.In this study, we administered escalating amounts of 1@Sm EDTMP, from 0.1 to 1.0 mCi\\/kg (3.7\\

Mehdi Farhanghi; Richard A. Holmes; Wynn A. Volkert; K. William Logan; Amolak Singh

295

Determination of the Nuclear Electric Charge Distribution of Samarium Isotopes 144, 148, 150, 152, 154 by the Muonic Atom Method.  

National Technical Information Service (NTIS)

The theory of the nucleus-negative muon system in the case of electrical interactions is discussed. The interactions of muons with the samarium isotopes 152, 154, 144, 148, 150 are investigated. After a description of the experimental device, from muon be...

P. Barreau

1977-01-01

296

Neutron and Charged-Particle Induced Cross Sections for Radiochemistry in the Region of Samarium, Europium, and Gadolinium  

SciTech Connect

We have developed a set of modeled nuclear reaction cross sections for use in radiochemical diagnostics. Systematics for the input parameters required by the Hauser-Feshbach statistical model were developed and used to calculate neutron and proton induced nuclear reaction cross sections in the mass region of samarium, europium and gadolinium (62 {le} Z {le} 64, 82 {le} N {le} 96).

Hoffman, R D; Kelley, K; Dietrich, F S; Bauer, R; Mustafa, M

2004-11-30

297

Trace Element Partitioning Determined by Beta Track Mapping: An Experimental Study Using Carbon and Samarium as Examples  

Microsoft Academic Search

A technique for experimental determination of concentrations and distribution of trace elements is described. The technique employs nuclear emulsions to register ; particles from spontaneous decay ot a radioactive isotope. At least 58 elements in the periodic system can be studied experimentally in this way. A detailed description of the technique using carbon 14 and samarium 151 as examples in

Bjrn O. Mysen; Martin G. Seitz

1975-01-01

298

Microstructure-properties relationships in samarium modified lead titanate piezoceramicsII. Dielectric, piezoelectric and mechanical properties  

Microsoft Academic Search

The influence of the microstructural parameters on the extrinsic contributions to the electromechanical behavior of samarium modified lead titanate piezoceramics is studied. A complete structural, compositional and microstructural characterization has been carried out to this purpose.The electromechanical coupling factors kp and k31 show strong dependence on the microstructure. There is not any important microstructural dependence of the electromechanical properties related

J. Ricote; C. Alemany; L. Pardo; C. E. Millar

1996-01-01

299

Chemical Vapor Deposition of Samarium Compounds for the Development of Thin Film Optical Switches Based on Phase Transition Materials.  

NASA Astrophysics Data System (ADS)

The physical properties of single crystals of samarium monosulfide exhibit a first order semiconductor -to-metal transition near 6.5 kbar. However, thin films of SmS show only a gradual change in their properties on applying pressure and this renders the technical utilization of the material difficult. Several mechanisms have been proposed as the cause of the smoothing of the transition. They include intrinsic stress, impurities, grain size, improper stoichiometry, and porosity, all of which can be traced to the physical vapor deposition techniques employed in preparing the films. In contrast, chemical vapor deposition was employed in this study because previous work had shown that it could minimize these detrimental modifications in thin films. A new CVD system was tested using a volatile organometallic as the samarium source and reacting it with H(,2)S. The deposited films contained considerable amounts of oxygen as evidenced by structure analysis, and the origin was traced to the samarium organometallic. The reaction of oxygen-free samarium tricyclopentadienyl with H(,2)S as well as chemical transport are suggested for deposition of stress-free SmS thin films in future work.

Hillman, Paul Dallas

300

Dielectric and tunability properties of La-doped BaTiO 3 ceramics  

Microsoft Academic Search

La-doped BaTiO3 (x=0.001; 0.0025; 0.005; 0.01; 0.025) ceramics were prepared via conventional solid state reaction and sintered at 1300C for 6h, resulting in dense single phase ceramics with homogeneous microstructures. The temperature dependence of dielectric permittivity of the ceramics has been investigated. The results show a decrease of TC with lanthanum addition. The degree of diffuseness of phase transition is

A. Ianculescu; Z. V. Mocanu; L. P. Curecheriu; L. Mitoseriu; L. Padurariu; R. Tru?c?

2011-01-01

301

Visible emission in Sm3+ and Tb3+ doped phosphate glass excited by UV radiation  

NASA Astrophysics Data System (ADS)

In the article analysis of UV absorption and visible fluorescence of Sm3+ and Tb3+ ions doped phosphate glass with molar composition: 65P2O5 + 8Al2O3 + 10BaO + 17(Na2O + MgO + ZnO) have been investigated. As a result of optical pumping fabricated glass with radiation from a deuterium lamp four luminescence bands were observed near to the wavelength of 600 nm for Sm3+ ions and 550 nm for Tb3+ ions. It was found that larger energy gap between laser and ground levels leads to the strongest emission in the visible range in terbium doped glasses than in glasses doped with samarium ions. Both fabricated glasses are characterized by the ability to selectively detect the radiation in the UV range.

Zmojda, Jacek; Dorosz, Dominik; Kochanowicz, Marcin; Miluski, Piotr; Czajkowski, Karol; Ragin, Tomasz

2013-10-01

302

Spectroscopic valence of cerium in cerium-lanthanum-iron compounds  

SciTech Connect

In Ce{sub 2}Fe{sub 14}B and Ce{sub 2}Fe{sub 17}, cerium is mixed valent and nonmagnetic. Any structural or compositional modification of these intermetallics which induces cerium to become trivalent and develop a local 4f moment should result in compounds with enhanced magnetostrictions, magnetocrystalline anisotropies, and net magnetic moments. Due to the dependence of cerium valence on steric volume, one approach for manipulating the valence is to increase the cell volume of these phases by forming pseudoternaries or pseudobinaries of these compounds with lanthanum. In this work, we report the spectroscopic valence of cerium obtained from the cerium L{sub 3} edge of La{sub 2{minus}x}Ce{sub x}Fe{sub 14}B, La{sub 2{minus}x}Ce{sub x}Fe{sub 17}, and selected hydrides and nitrides of these intermetallics. In La{sub 2{minus}x}Ce{sub x}Fe{sub 14}B the average cerium valence is found to decrease only slightly with increasing lanthanum content. Analysis of the extended x-ray absorption fine structure of the cerium and lanthanum L{sub 3} edges from the La{sub 2{minus}x}Ce{sub x}Fe{sub 14}B series is only consistent with cerium preferentially occupying the small 4f rare-earth site in the tetragonal Nd{sub 2}Fe{sub 14}B structure. In La{sub 2{minus}x}Ce{sub x}Fe{sub 17} the shift of cerium towards the trivalent state with decreasing x is more pronounced, but the shift is incomplete over the range of compositions investigated (x{ge}1). Although these results do not exclude the possibility of trivalent cerium in some of these compounds, none of the compounds provided unambiguous evidence of trivalent cerium. {copyright} {ital 1997} {ital The American Physical Society}

Capehart, T.W.; Mishra, R.K.; Fuerst, C.D.; Meisner, G.P.; Pinkerton, F.E.; Herbst, J.F. [Physics Department, General Motors Research Development Center, 30500 Mound Road, Warren, Michigan 48090-9055 (United States)] [Physics Department, General Motors Research Development Center, 30500 Mound Road, Warren, Michigan 48090-9055 (United States)

1997-05-01

303

Airplane dopes and doping  

NASA Technical Reports Server (NTRS)

Cellulose acetate and cellulose nitrate are the important constituents of airplane dopes in use at the present time, but planes were treated with other materials in the experimental stages of flying. The above compounds belong to the class of colloids and are of value because they produce a shrinking action on the fabric when drying out of solution, rendering it drum tight. Other colloids possessing the same property have been proposed and tried. In the first stages of the development of dope, however, shrinkage was not considered. The fabric was treated merely to render it waterproof. The first airplanes constructed were covered with cotton fabric stretched as tightly as possible over the winds, fuselage, etc., and flying was possible only in fine weather. The necessity of an airplane which would fly under all weather conditions at once became apparent. Then followed experiments with rubberized fabrics, fabrics treated with glue rendered insoluble by formaldehyde or bichromate, fabrics treated with drying and nondrying oils, shellac, casein, etc. It was found that fabrics treated as above lost their tension in damp weather, and the oil from the motor penetrated the proofing material and weakened the fabric. For the most part the film of material lacked durability. Cellulose nitrate lacquers, however were found to be more satisfactory under varying weather conditions, added less weight to the planes, and were easily applied. On the other hand, they were highly inflammable, and oil from the motor penetrated the film of cellulose nitrate, causing the tension of the fabric to be relaxed.

Smith, W H

1919-01-01

304

Syntesis of lanthanum zirconate hydrosols by the ion exchange method  

Microsoft Academic Search

Ion exchange of LaCl3 and ZrOCl2 aqueous solutions with anion-exchanger AV-17-8 was used to synthesize finely dispersed hydrosol of amorphous lanthanum zirconate La2Zr2O7. Heat treatment of dried La2Zr2O7 hydrosols at 700C and 1100C resulted in the formation of powders with fluorite and pyrochlore type structures, respectively. Epitaxial La2Zr2O7 films were obtained on SrTiO3 (001) single crystals. The substrate has an

E. A. Bovina; J. V. Tarasova; F. Kh Chibirova

2011-01-01

305

Lanthanum hexaboride hollow cathode for dense plasma production.  

PubMed

A hollow tube cathode using lanthanum hexaboride as the electron emitter has been designed and constructed. Tests in both argon and hydrogen indicate that this cathode is capable of producing over 800 A of electron current continuously, corresponding to over 25 A/cm(2) from the LaB(6). The cathode has been operated for over 300 h and exposed to air more than 100 times with no deterioration in emission. Projected lifetime is in excess of 3500 h for the sintered LaB(6) piece tested in this configuration. Construction details, performance characteristics, and discussions of space charge limits on emission are described. PMID:18699127

Goebel, D M; Crow, J T; Forrester, A T

1978-04-01

306

Study of Collective Quadrupole Excitation in Samarium 144, 148, 150, 152, and 154 Isotopes and Cerium 140 by Inelastic Electron Scattering.  

National Technical Information Service (NTIS)

The region of Samarium nuclei where spectacular variations of nuclear deformation appear was investigated. Transition charge densities of the first 2(+) states were determined by measuring the inelastic scattering cross sections of electrons on the six nu...

V. Meot

1987-01-01

307

Novel NiBa 1+ x Zr 0.3Ce 0.5Y 0.2O 3? ? hydrogen electrodes as effective reduction barriers for reversible solid oxide cells based on doped ceria electrolyte thin film  

Microsoft Academic Search

Samarium-doped ceria (SDC) is evaluated as electrolyte materials for intermediate temperature reversible solid oxide cells (RSOCs). The bulk resistances of cells with SDC thin-film electrolytes are 0.16 and 0.23?cm2 when operating in solid oxide electrolysis cell (SOEC) mode and in solid oxide fuel cell (SOFC) mode, respectively. This result suggests that the electrolyte is reduced to a greater extent in

Yuanyuan Rao; Zhiquan Wang; Wei Zhong; Ranran Peng; Yalin Lu

308

Separation\\/preconcentration of trace heavy metals in urine, sediment and dialysis concentrates by coprecipitation with samarium hydroxide for atomic absorption spectrometry  

Microsoft Academic Search

Multi-element determination of trace elements in urine and dialysis solutions by atomic absorption spectrometry has been investigated. Coprecipitation with samarium hydroxide was used for preconcentration of trace elements and elimination of matrix elements. To 10 ml of each sample was added 500 ?l of 2 mgml?1 samarium solutions; the pH was then adjusted to 12.2 in order to collect trace

Sibel Saracoglu; Mustafa Soylak; Latif Elci

2003-01-01

309

Novel borothermal route for the synthesis of lanthanum cerium hexaborides and their field emission properties  

SciTech Connect

The present study describes the development of a simple approach to stabilize polycrystalline lanthanum cerium hexaborides without using any flux and at ambient pressure. The nanostructured lanthanum-cerium borides were synthesized using hydroxide precursors. These precursors (La{sub 1-x}Ce{sub x}(OH){sub 3}, x=0.1, 0.2, 0.3 and 0.5) were synthesized via hydrothermal route in the presence of Tergitol (surfactant, nonylphenol ethoxylate) as a capping agent. The precursors on heating with boron at 1300 Degree-Sign C lead to the formation of nanostructures (cubes, rods and pyramids) of lanthanum cerium hexaboride. We have investigated the field emission behaviour of the hexaboride films fabricated by spin coating. It was observed that the pyramidal shaped nanostructures of La{sub 0.5}Ce{sub 0.5}B{sub 6} shows excellent field emission characteristics with high field enhancement factor of 4502. - Graphical abstract: Nanostructured lanthanum cerium hexaboride with efficient field emission have fabricated by low temperature hydroxide precursor mediated route. Highlights: Black-Right-Pointing-Pointer New methodology to prepare lanthanum cerium hexaboride at 1300 Degree-Sign C via borothermal route. Black-Right-Pointing-Pointer Nanostructured lanthanum cerium hexaboride film by spin coating process. Black-Right-Pointing-Pointer Nanopyramids based lanthanum cerium hexaboride shows excellent field emission.

Menaka [Department of Chemistry, Indian Institute of Technology, Hauz Khas, New Delhi-110016 (India)] [Department of Chemistry, Indian Institute of Technology, Hauz Khas, New Delhi-110016 (India); Patra, Rajkumar; Ghosh, Santanu [Department of Physics, Indian Institute of Technology, Hauz Khas, New Delhi-110016 (India)] [Department of Physics, Indian Institute of Technology, Hauz Khas, New Delhi-110016 (India); Ganguli, Ashok K., E-mail: ashok@chemistry.iitd.ac.in [Department of Chemistry, Indian Institute of Technology, Hauz Khas, New Delhi-110016 (India)

2012-10-15

310

The 23 to 300 C demagnetization resistance of samarium-cobalt permanent magnets  

NASA Technical Reports Server (NTRS)

The influence of temperature on knee point and squareness of the M-H demagnetization characteristic of permanent magnets is important information for the full utilization of the capabilities of samarium-cobalt magnets at high temperature in demagnetization resistent permanent magnet devices. Composite plots of the knee field and the demagnetizing field required to produce a given magnetic induction swing below remanence were obtained for several commercial Sm2Co17 type magnet samples in the temperature range of 23 to 300 C. Using the knee point to define the limits of operation safe against irreversible demagnetization, such plots are shown to provide an effective overview of the useable regions in the space of temperature-induction swing parameters. The observed second quadrant M-H characteristic squareness is shown, by two measures, to increase gradually with temperature, reaching a peak in the interval 200 to 300 C.

Niedra, Janis M.; Overton, Eric

1991-01-01

311

Preparation of hollow core/shell microspheres of hematite and its adsorption ability for samarium.  

PubMed

Hollow core/shell hematite microspheres with diameter of ca. 1-2 ?m have been successfully achieved by calcining the precursor composite microspheres of pyrite and polyvinylpyrrolidone (PVP) in air. The synthesized products were characterized by a wide range of techniques including powder X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), and Brunauer-Emmett-Teller (BET) gas sorptometry. Temperature- and time-dependent experiments unveil that the precursor pyrite-PVP composite microspheres finally transform into hollow core/shell hematite microspheres in air through a multistep process including the oxidation and sulfation of pyrite, combustion of PVP occluded in the precursor, desulfation, aggregation, and fusion of nanosized hematite as well as mass transportation from the interior to the exterior of the microspheres. The formation of the hollow core/shell microspheres dominantly depends on the calcination temperature under current experimental conditions, and the aggregation of hematite nanocrystals and the core shrinking during the oxidation of pyrite are responsible for the formation of the hollow structures. Moreover, the adsorption ability of the hematite for Sm(III) was also tested. The results exhibit that the hematite microspheres have good adsorption activity for trivalent samarium, and that its adsorption capacity strongly depends on the pH of the solution, and the maximum adsorption capacity for Sm(III) is 14.48 mg/g at neutral pH. As samarium is a typical member of the lanthanide series, our results suggest that the hollow hematite microspheres have potential application in removal of rare earth elements (REEs) entering the water environment. PMID:24892188

Yu, Sheng-Hui; Yao, Qi-Zhi; Zhou, Gen-Tao; Fu, Sheng-Quan

2014-07-01

312

Neutron diffraction study of the perovskite-type lanthanum cobaltite La 0.6Sr 0.4Co 0.8Fe 0.2O 3 ? ? at 1260C and 394C  

Microsoft Academic Search

Crystal structure of a perovskite-type strontium- and iron-co-doped lanthanum cobaltite, La0.6Sr0.4Co0.8Fe0.2O3?? (LSCF6482) has been studied by Rietveld analysis, maximum-entropy method (MEM) and MEM-based pattern fitting of in situ neutron powder diffraction data measured in air at 394C and 1260C. The LSCF6482 was trigonal R3c at 394C, and cubic Pm3m at 1260C. The refined occupancies of O atom were 1.0 and

Masatomo Yashima; Taisuke Kamioka

2008-01-01

313

Synthesis and characterization of rare-earth doped SrBi{sub 2}Nb{sub 2}O{sub 9} phase in lithium borate based nanocrystallized glasses  

SciTech Connect

Glass composites comprising of un-doped and samarium-doped SrBi{sub 2}Nb{sub 2}O{sub 9} nanocrystallites are fabricated in the glass system 16.66SrO-16.66[(1-x)Bi{sub 2}O{sub 3}-xSm{sub 2}O{sub 3}]-16.66Nb{sub 2}O{sub 5}-50Li{sub 2}B{sub 4}O{sub 7} (0<=x<=0.5, in mol%) via the melt quenching technique. The glassy nature of the as-quenched samples is established by differential thermal analyses. Transmission electron microscopic studies reveal the presence of about 15 nm sized spherical crystallites of the fluorite-like SrBi{sub 1.9}Sm{sub 0.1}Nb{sub 2}O{sub 9} phase in the samples heat treated at 530 deg. C. The formation of layered perovskite-type un-doped and samarium-doped SrBi{sub 2}Nb{sub 2}O{sub 9} nanocrystallites with an orthorhombic structure through the intermediate fluorite phase is confirmed by X-ray powder diffraction and micro-Raman spectroscopic studies. The influence of samarium doping on the lattice parameters, lattice distortions, and the Raman peak positions of SrBi{sub 2}Nb{sub 2}O{sub 9} perovskite phase is clarified. The dielectric constants of the perovskite SrBi{sub 2}Nb{sub 2}O{sub 9} and SrBi{sub 1.9}Sm{sub 0.1}Nb{sub 2}O{sub 9} nanocrystals are relatively larger than those of the corresponding fluorite-like phase and the precursor glass. - Graphical Abstract: This figure shows the XRD patterns at room temperature for the as-quenched and heat treated samples in Sm{sub 2}O{sub 3}-doped (x=0.1) glass. Based on these results, it is concluded that the formation of samarium-doped perovskite SBN phase takes place via an intermediate fluorite-like phase in the crystallization of this glass.

Harihara Venkataraman, B. [Department of Materials Science and Technology, Nagaoka University of Technology, 1603-1 Kamitomioka-cho, Nagaoka 940-2188 (Japan); Fujiwara, Takumi [Department of Applied Physics, Graduate School of Engineering, Tohoku University, Sendai 980-8579 (Japan); Komatsu, Takayuki, E-mail: komatsu@mst.nagaokaut.ac.j [Department of Materials Science and Technology, Nagaoka University of Technology, 1603-1 Kamitomioka-cho, Nagaoka 940-2188 (Japan)

2009-06-15

314

Preparation and use of samarium diiodide (SmI(2)) in organic synthesis: the mechanistic role of HMPA and Ni(II) salts in the samarium Barbier reaction.  

PubMed

Although initially considered an esoteric reagent, SmI(2) has become a common tool for synthetic organic chemists. SmI(2) is generated through the addition of molecular iodine to samarium metal in THF.(1,2-3) It is a mild and selective single electron reductant and its versatility is a result of its ability to initiate a wide range of reductions including C-C bond-forming and cascade or sequential reactions. SmI(2) can reduce a variety of functional groups including sulfoxides and sulfones, phosphine oxides, epoxides, alkyl and aryl halides, carbonyls, and conjugated double bonds.(2-12) One of the fascinating features of SmI-(2)-mediated reactions is the ability to manipulate the outcome of reactions through the selective use of cosolvents or additives. In most instances, additives are essential in controlling the rate of reduction and the chemo- or stereoselectivity of reactions.(13-14) Additives commonly utilized to fine tune the reactivity of SmI(2) can be classified into three major groups: (1) Lewis bases (HMPA, other electron-donor ligands, chelating ethers, etc.), (2) proton sources (alcohols, water etc.), and (3) inorganic additives (Ni(acac)(2), FeCl(3), etc).(3) Understanding the mechanism of SmI(2) reactions and the role of the additives enables utilization of the full potential of the reagent in organic synthesis. The Sm-Barbier reaction is chosen to illustrate the synthetic importance and mechanistic role of two common additives: HMPA and Ni(II) in this reaction. The Sm-Barbier reaction is similar to the traditional Grignard reaction with the only difference being that the alkyl halide, carbonyl, and Sm reductant are mixed simultaneously in one pot.(1,15) Examples of Sm-mediated Barbier reactions with a range of coupling partners have been reported,(1,3,7,10,12) and have been utilized in key steps of the synthesis of large natural products.(16,17) Previous studies on the effect of additives on SmI(2) reactions have shown that HMPA enhances the reduction potential of SmI(2) by coordinating to the samarium metal center, producing a more powerful,(13-14,18) sterically encumbered reductant(19-21) and in some cases playing an integral role in post electron-transfer steps facilitating subsequent bond-forming events.(22) In the Sm-Barbier reaction, HMPA has been shown to additionally activate the alkyl halide by forming a complex in a pre-equilibrium step.(23) Ni(II) salts are a catalytic additive used frequently in Sm-mediated transformations.(24-27) Though critical for success, the mechanistic role of Ni(II) was not known in these reactions. Recently it has been shown that SmI(2) reduces Ni(II) to Ni(0), and the reaction is then carried out through organometallic Ni(0) chemistry.(28) These mechanistic studies highlight that although the same Barbier product is obtained, the use of different additives in the SmI(2) reaction drastically alters the mechanistic pathway of the reaction. The protocol for running these SmI(2)-initiated reactions is described. PMID:23407417

Sadasivam, Dhandapani V; Choquette, Kimberly A; Flowers, Robert A

2013-01-01

315

Concentration dependence of the fluorescence decay profile in transition metal doped chalcogenide glass  

NASA Astrophysics Data System (ADS)

In this paper we present the fluorescence decay profiles of vanadium and titanium doped gallium lanthanum sulphide (GLS) glass at various doping concentrations between 0.01 and 1% (molar). We demonstrate that below a critical doping concentration the fluorescence decay profile can be fitted with the stretched exponential function: exp[-(t/?) ?], where ? is the fluorescence lifetime and ? is the stretch factor. At low concentrations the lifetime for vanadium and titanium doped GLS was 30 ?s and 67 ?s respectively. We validate the use of the stretched exponential model and discuss the possible microscopic phenomenon it arises from. We also demonstrate that above a critical doping concentration of around 0.1% (molar) the fluorescence decay profile can be fitted with the double exponential function: a*exp-(t/? I)+ b*exp-(t/? II), where ? I and ? II are characteristic fast and slow components of the fluorescence decay profile, for vanadium the fast and slow components are 5 ?s and 30 ?s respectively and for titanium they are 15 ?s and 67 ?s respectively. We also show that the fluorescence lifetime of vanadium and titanium at low concentrations in the oxide rich host gallium lanthanum oxy-sulphide (GLSO) is 43 ?s and 97 ?s respectively, which is longer than that in GLS. From this we deduce that vanadium and titanium fluorescing ions preferentially substitute into high efficiency oxide sites until at a critical concentration they become saturated and low efficiency sulphide sites start to be filled.

Hughes, M.; Hewak, D. W.; Curry, R. J.

2007-03-01

316

Dose response relationship and multiple dose efficacy and toxicity of samarium-153-EDTMP in metastatic cancer to bone  

Microsoft Academic Search

Introduction: The optimal dose of samarium-153-EDTMP (153Sm-EDTMP) for effective palliation of painful metastases to bone is under investigation. It is not known whether increased doses of 153Sm EDTMP will lead to better and longer pain and tumour control and survival. Multiple dose efficacy and toxicity is of importance as most Patients will require prolonged support for pain.Methods: Twenty-eight (28) patients

Albert S. Alberts; Ben J. Smit; Werner K. A. Louw; Ado Janse van Rensburg; Alet van Beek; Veronique Kritzinger; Johan S. Nel

1997-01-01

317

Morphology-controlled nonaqueous synthesis of anisotropic lanthanum hydroxide nanoparticles  

SciTech Connect

The preparation of lanthanum hydroxide and manganese oxide nanoparticles is presented, based on a nonaqueous sol-gel process involving the reaction of La(OiPr){sub 3} and KMnO{sub 4} with organic solvents such as benzyl alcohol, 2-butanone and a 1:1 vol. mixture thereof. The lanthanum manganese oxide system is highly complex and surprising results with respect to product composition and morphology were obtained. In dependence of the reaction parameters, the La(OH){sub 3} nanoparticles undergo a shape transformation from short nanorods with an average aspect ratio of 2.1 to micron-sized nanofibers (average aspect ratio is more than 59.5). Although not directly involved, KMnO{sub 4} plays a crucial role in determining the particle morphology of La(OH){sub 3}. The reason lies in the fact that KMnO{sub 4} is able to oxidize the benzyl alcohol to benzoic acid, which presumably induces the anisotropic particle growth in [0 0 1] direction upon preferential coordination to the {+-}(1 0 0), {+-}(0 1 0) and {+-}(-110) crystal facets. By adjusting the molar La(OiPr){sub 3}-to-KMnO{sub 4} ratio as well as by using the appropriate solvent mixture it is possible to tailor the morphology, phase purity and microstructure of the La(OH){sub 3} nanoparticles. Postsynthetic thermal treatment of the sample containing La(OH){sub 3} nanofibers and {beta}-MnOOH nanoparticles at the temperature of 800 deg. C for 8 h yielded polyhedral LaMnO{sub 3} and worm-like La{sub 2}O{sub 3} nanoparticles as final products. - Graphical abstract: Lanthanum hydroxide nanoparticles are synthesized based on a nonaqueous sol-gel process involving the reaction of La(OiPr){sub 3} and KMnO{sub 4} with organic solvents such as benzyl alcohol, 2-butanone and a 1:1 vol. mixture thereof. In dependence of the reaction parameters, the La(OH){sub 3} nanoparticles undergo a shape transformation from short nanorods to micron-sized nanofibers.

Djerdj, Igor [ETH Zuerich, Department of Materials, Wolfgang-Pauli-Strasse 10, 8093 Zurich (Switzerland); Department of Physics, Faculty of Science, University of Zagreb, Bijenicka 32, P.O. Box 331, 10002 Zagreb (Croatia); Garnweitner, Georg [Max Planck Institute of Colloids and Interfaces, Research Campus Golm, D-14424 Potsdam (Germany); Sheng Su, Dang [Department of Inorganic Chemistry, Fritz-Haber-Institute of the Max-Planck-Society, Faradayweg 4-6, D-14195 Berlin (Germany); Niederberger, Markus [ETH Zuerich, Department of Materials, Wolfgang-Pauli-Strasse 10, 8093 Zurich (Switzerland)], E-mail: markus.niederberger@mat.ethz.ch

2007-07-15

318

Modification of the Sulfur Dioxide-Iodine Thermochemical Hydrogen Cycle with Lanthanum Sulfites and Sulfates.  

National Technical Information Service (NTIS)

Variable composition, insoluble dilanthanum oxide-sulfite-sulfate-hydrates were prepared by reaction of lanthanum dioxymonosulfate with aqueous sulfur dioxide. These compositions reacted with iodine to yield sulfate in the solid phase, and hydrogen iodide...

E. I. Onstott M. G. Bowman M. F. Michnovicz C. M. Hollabaugh

1984-01-01

319

Sertoli-sertoli junctions and Sertoli-spermatid junctions after efferent ductule ligation and lanthanum treatment.  

PubMed

Seminiferous tubules, partially dilated by ligation of the efferent ductules, were examined after treatment with lanthanum. Lanthanum penetrated the intercellular spaces of the seminiferous epithelium, but only to the level of the Sertoli-Sertoli junctions. Further penetration from the interstitial surface of the tubule was restricted by membrane fusions (tight junctions) at the junctional complex. Lanthanum also penetrated the epithelium from the luminal surface permeating the adluminal intercellular spaces, including the site of the Sertoli-spermatid junction. The lanthanum occupying the Sertoli-spermatid junctional site appeared as a slightly narrower electron-opaque zone than that found in the non-specialized intercellular areas. The findings clearly reveal that only the Sertoli-Sertoli junctional site forms a restrictive barrier. In contrast to the specializations of plasma membrane which form the tight junction, the associated filaments and cisterna of endoplasmic reticulum may be components more directly related to maintaining and regulating cell adhesion. PMID:842475

Ross, M H

1977-01-01

320

METAL INTERACTIONS AT SULFIDE MINERAL SURFACES. PART 2. ADSORPTION AND DESORPTION OF LANTHANUM  

EPA Science Inventory

Batch-type adsorption experiments with four sulfide minerals (chalcocite, galena, pyrite, and sphalerite) were used to investigate the adsorption and desorption behavior of lanthanum (III) in the presence of ethylenediaminetetraacetic acid (EDTA), a model humic substance. Linear ...

321

New Samarium(III), Gadolinium(III), and Dysprosium(III) Complexes of Coumarin-3-Carboxylic Acid as Antiproliferative Agents  

PubMed Central

New complexes of samarium(III), gadolinium(III), and dysprosium(III) with coumarin-3-carboxylic acid (HCCA) were prepared by the reaction of the ligand with respective metal nitrates in ethanol. The structures of the final complexes were determined by means of physicochemical data, elemental analysis, IR and Raman spectra. The metal-ligand binding mode in the new Ln(III) complexes of coumarin-3-carboxylic acid was elucidated. The vibrational study gave evidence for bidentate coordination of CCA? to Ln(III) ions through the carbonylic oxygen and the carboxylic oxygen atoms. The complexes were tested for antiproliferative activitiy on the chronic myeloid leukemia-derived K-562, overexpressing the BCR-ABL fusion protein. Cytotoxicity towards tumor cells was determined for a broad concentration range. The samarium salt exerted a very weak antiproliferative effect on these cells. This is in contrast to the lanthanide complexes, especially samarium complex, which exhibited potent antiproliferative activity. The present study confirms our previous observations that the lanthanide complexes of coumarins exhibit antiproliferative activity towards K-562 cell line.

Kostova, Irena; Momekov, Georgi; Stancheva, Peya

2007-01-01

322

Interaction of oxygen with samarium on Al2O3 thin film grown on Ni3Al(111).  

PubMed

The interaction between oxygen and samarium (Sm) on the well-ordered thin Al2O3 film grown on Ni3Al(111) has been investigated by X-ray photoelectron spectroscopy and synchrotron radiation photoemission spectroscopy. At Sm coverage higher than one monolayer, exposure of oxygen to the Sm films at room temperature leads to the formation of both samarium peroxide (O2(2-)) states and regular samarium oxide (O(2-)) states. By contrast, when exposing O2 to Sm film less than one monolayer on Al2O3, no O2(2-) can be observed. Upon heating to higher temperatures, these metastable O2(2-) states dissociate, supplying active O atoms which can diffuse through the Al2O3 thin film to further oxidize the underlying Ni3Al(111) substrate, leading to the significant increase of the Al2O3 thin film thickness. Therefore, it can be concluded that Sm, presumably in its peroxide form, acts as a catalyst for the further oxidation of the Ni3Al substrate by supplying the active oxygen species at elevated temperatures. PMID:24606375

Cheng, Dingling; Xu, Qian; Han, Yong; Ye, Yifan; Pan, Haibin; Zhu, Junfa

2014-03-01

323

Self-Correction of Lanthanum-Cerium Halide Gamma Spectra (pre-print)  

Microsoft Academic Search

Lanthanum-cerium halide detectors generally exhibit superior energy resolutions for gamma radiation detection compared with conventional sodium iodide detectors. However, they are also subject to self-activities due to lanthanum-138 decay and contamination due to beta decay in the low-energy region and alpha decay in the high-energy region. The detectors self-activity and crystal contamination jointly contribute a significant amount of uncertainties to

Ding Yuan; Paul Guss; Sanjoy Mukhopadhyay

2009-01-01

324

B-site substituted lanthanum strontium ferrites as electrode materials for electrochemical applications  

Microsoft Academic Search

For electrochemical systems such as solid oxide fuel cells (SOFCs) or solid oxide electrolyzer cells (SOECs), perovskites are widely used as cathode material for the reduction of molecular oxygen. At present, strontium-substituted lanthanum manganite, La 1-x Sr x MnO 3-? (LSM), is used as standard SOFC cathode material for operation at high temperatures, whereas strontium-substituted lanthanum ferrite (LSF) is alternatively

Ulrich F. Vogt; Josef Sfeir; Joerg Richter; Christian Soltmann; Peter Holtappels

2008-01-01

325

Lanthanum-molybdenum multilayer mirrors for attosecond pulses between 80 and 130 eV  

Microsoft Academic Search

A novel multilayer material system consisting of lanthanum and molybdenum nano-layers for both broadband and highly reflecting multilayer mirrors in the energy range between 80 and 130 eV is presented. The simulation and design of these multilayers were based on an improved set of optical constants, which were recorded by extreme ultraviolet (XUV)\\/soft-x-ray absorption measurements on freestanding lanthanum nano-films between

M. Hofstetter; A. Aquila; M. Schultze; A. Guggenmos; S. Yang; E. Gullikson; M. Huth; B. Nickel; J. Gagnon; V. S. Yakovlev; E. Goulielmakis; F. Krausz; U. Kleineberg

2011-01-01

326

Effect of Heat Treatment Temperature on Performance of Plasma-Sprayed Apatite-Lanthanum Silicate Coatings as Electrolytes for IT-SOFC  

NASA Astrophysics Data System (ADS)

Magnesium-doped lanthanum silicate with apatite-type structure was prepared by solid state sintering, as a solid electrolyte for intermediate temperature solid oxide fuel cells. The electrolyte layers were fabricated by air plasma spraying, followed by post heat treatments, and their microstructures and phase composition were characterized by SEM and XRD. The gas permeation of electrolyte layers was measured by a specific instrument with pure H2 and O2 at room temperature. It is shown that amorphous and trace phases exist in as-sprayed electrolyte layer, and then disappear after a post heat treatment in air furnace at temperature up to 1000 C. The permeability can be decreased by the heat treatment, especially after 4 h at 1000 C.

Sun, Fu; Zhang, Nannan; Liao, Hanlin; Li, Jinglong

2012-12-01

327

High-Resolution Room Temperature Spectroscopy with Lanthanum Halides  

SciTech Connect

The most desirable features in a spectroscopic material are high sensitivity and high resolution. Cerium-activated crystals of lanthanum bromide (LaBr{sub 3}:Ce) have higher sensitivity and better spectroscopic resolution than sodium/cesium iodide (NaI/CsI) crystals because of higher density (5.29 g/cm{sup 3}), faster decay time (35 ns), minimal afterglow, and larger (63 000 photons/MeV) and more linear light output (6% nonlinearity over the energy range between 60 and 1332 keV). Of all the recent scintillator materials manufactured to date, LaBr{sub 3}, with cerium activators, is one of the most promising for high-resolution, fast timing techniques as applied to medical image reconstructions or associated particle imaging.

Mukhopadhyay, Sanjoy [Bechtel Nevada (United States)

2005-11-15

328

Field emission characteristics of lanthanum hexaboride coated silicon field emitters  

NASA Astrophysics Data System (ADS)

Lanthanum hexaboride(LaB6) films have been deposited on silicon tip field emitters by electron-beam evaporation. The field emission characteristics are studied in a diode test cell in a vacuum system. The experimental results show that the field emission stability of the LaB6-coated Si-tip FEA can be improved and the emission current is significantly enhanced to 75 A, in contrast to pure Si-tip FEA of 500 nA and Mo-coated Si-tip FEA of 300 nA with 1500 V applied to the anode. Furthermore, even at low vacuum (>1.5 10-5 Torr) it still exhibits good emission properties and strong ability to withstand ion bombardment. This LaB6-coated Si-tip FEA is an excellent electronic candidate, in particular a fit for travelling-wave tubes, klystrons and other large vacuum apparatus.

Wang, Xiaoju; Lin, Zulun; Qi, Kangcheng; Chen, Zexiang; Wang, Zhigang; Jiang, Yadong

2007-08-01

329

Synthesis and characterization of strontium-lanthanum apatites  

SciTech Connect

Two series of strontium-lanthanum apatites, Sr{sub 10-x}La {sub x}(PO{sub 4}){sub 6-x}(SiO{sub 4}) {sub x}F{sub 2} and Sr{sub 10-x}La {sub x}(PO{sub 4}){sub 6-x}(SiO{sub 4}) {sub x}O with 0 {<=} x {<=} 6, were synthesized by solid state reaction in the temperature range of 1200-1400 deg. C. The obtained materials were characterized by powder X-ray diffraction, infrared absorption spectroscopy and solid {sup 31}P Nuclear Magnetic Resonance. Pure solid solutions were obtained within a limited range of unsubstituted phosphate and silicate apatites. A variation of the lattice parameters was observed, with an increase of a and a decrease of c parameters, related to the radius of the corresponding substituted ions.

Boughzala, K. [U.R. Materiaux Inorganiques, Departement de Chimie, Faculte des Sciences, 5000 Monastir (Tunisia); Salem, E. Ben [U.R. Materiaux Inorganiques, Departement de Chimie, Faculte des Sciences, 5000 Monastir (Tunisia); Chrifa, A. Ben [Laboratoire de Thermodynamique Appliquee, Departement de Chimie, Faculte des Sciences de Tunis, Campus Universitaire, 1060 Tunis (Tunisia); Gaudin, E. [Institut de Chimie de la Matiere Condensee, Universite de Bordeaux, CNRS (UPR9048) 87 Avenue du Dr Schweitzer, 33608 Pessac Cedex (France); Bouzouita, K. [U.R. Materiaux Inorganiques, Departement de Chimie, Faculte des Sciences, 5000 Monastir (Tunisia)]. E-mail: khaled.bouzouita@ipeim.rnu.tn

2007-07-03

330

Magneto-transport properties of lanthanum and calcium deficient manganites  

NASA Astrophysics Data System (ADS)

We present a comparative study of the physical properties of the La0.5Ca0.5MnO3, La0.450.05Ca0.5MnO3 and La0.5Ca0.450.05MnO3 powder samples. Our synthesized samples have been elaborated using the conventional solid-state reaction technique they crystallize in the orthorhombic perovskite structure with Pnma space group. Resistivity measurements show that the defect effects in the A site on the electrical properties are substantially different for both lacunar samples. Electrical investigations show a metallic-semiconducting transition when temperature deceases for the calcium-deficient sample, however we observe a semiconducting behavior in the whole temperature range 20-300 K in the lanthanum-deficient one.

Walha, I.; Boujelben, W.; Koubaa, M.; Cheikh-Rouhou, A.; Haghiri-Gosnet, A. M.

2006-09-01

331

Near-electrode processes in lanthanum-gallium tantalate crystals  

SciTech Connect

The near-electrode processes on the surfaces of the polar cuts of lanthanum-gallium tantalate crystals grown in different atmospheres were investigated. The temperature dependences of short-circuit currents in the temperature range 20-700{sup o}C were measured and phase analysis of the sample surfaces after the temperature tests were performed. It is shown that short-circuit currents arise on the surfaces of polar cuts with identical conducting coatings without preliminary polarization. These currents are caused by the generation of intrinsic emf as a result of the electrochemical reactions on opposite polar cut surfaces coming in contact with a conducting coating. It is established that the crystal growth atmosphere and the conducting coating material significantly affect the temperature dependences of short-circuit currents.

Buzanov, O. A. [OAO Fomos Materials (Russian Federation); Zabelina, E. V., E-mail: e.zabelina@gmail.com; Kozlova, N. S., E-mail: kozlova_nina@mail.ru; Sagalova, T. B. [Moscow State Institute of Steel and Alloys (Russian Federation)

2008-09-15

332

Tribological behaviors of lanthanum-based phosphonate 3-aminopropyltriethoxysilane self-assembled films  

NASA Astrophysics Data System (ADS)

Lanthanum-based thin films deposited on the phosphonate 3-aminopropyltriethoxysilane (APTES) self-assembled monolayer (SAM) were prepared on the hydroxylated glass substrate by a self-assembling process from specially formulated solution. Chemical compositions of the films and chemical state of the elements were detected by X-ray photoelectron spectrometry (XPS). The thickness of the films was determined with an ellipsometer, while the morphologies of the original and worn surfaces of the samples were analyzed by means of atomic force microscopy (AFM) and scanning electron microscopy (SEM), respectively. The tribological properties of the films sliding against GCr15 steel ball were evaluated on a UMT-2MT reciprocating friction and wear tester. As the results, the target film was obtained and reaction may have taken place between the film and the glass substrate. The tribological results show that lanthanum-based thin films are superior in reducing friction and resisting wear compared with APTES-SAM and phosphorylated APTES-SAM. SEM observation of the morphologies of worn surfaces indicates that the wear of APTES-SAM and the phosphorylated APTES-SAM is characteristic of brittle fracture and severe abrasion. Differently, slight abrasion and micro-crack dominate the wear of lanthanum-based thin films. The superior friction reduction and wear resistance of lanthanum-based thin films are attributed to the enhanced load-carrying capacity of the inorganic lanthanum particles in the lanthanum-based thin films as well as good adhesion of the films to the substrate.

Gu, Qinlin; Cheng, Xianhua

2007-06-01

333

Studies on gel-grown pure and strontium-modified lanthanum tartrate crystals  

NASA Astrophysics Data System (ADS)

Crystals of pure and strontium-modified lanthanum tartrate bearing composition (La) 1-x(Sr) xC 4H 4O 6 nH 2O (where x=0, 0.04, 0.10, 0.15; n=5,5,6,8) were obtained using gel method. The materials were studied using CH analysis, X-ray powder diffraction, FTIR, EDAX and thermoanalytical techniques. X-ray powder diffraction results analyzed by using suitable software suggest that while unmodified lanthanum tartrate has a monoclinic structure with the space group P 21, the entry of strontium into its lattice changes the system to orthorhombic with the space group P 2121. The unit cell volume is observed to decrease with increase in the concentration of strontium in lanthanum tartrate. Thermal analysis suggests that pure lanthanum tartrate starts decomposing at 41.31 C whereas the strontium-modified lanthanum tartrate brings about better thermal stability which increases with an increase in strontium concentration. The percentage weight loss calculations from the thermogram supplemented by EDAX, CH analysis and FTIR spectroscopy suggest that both unmodified and strontium-modified lanthanum tartrate spherulitic crystals contain water of hydration; the amount of water of hydration being different for crystals with different content of strontium.

Firdous, A.; Quasim, I.; Ahmad, M. M.; Kotru, P. N.

2009-07-01

334

The management of hyperphosphatemia by lanthanum carbonate in chronic kidney disease patients  

PubMed Central

Hyperphosphatemia has been shown to be involved not only in the onset and progression of secondary hyperparathyroidism but also in vascular calcification. In addition, it influences the clinical course of patients with chronic kidney disease. Phosphate (Pi) binder is required in the management of hyperparaphosphatemia, because dietary Pi restriction and Pi removal by hemodialysis alone are insufficient. Lanthanum carbonate, a powerful Pi binder, has a similar effect to aluminum hydroxide in reducing serum Pi levels. As it is excreted via the liver, lanthanum carbonate has an advantage in patients with renal failure. The effect of lanthanum carbonate on serum Pi levels is almost two times higher than that of calcium (Ca) carbonate, which is commonly used. Lanthanum carbonate and Ca carbonate have an additive effect. Worldwide, there is 6 years worth of clinical treatment data on lanthanum carbonate; however, we have 3 years of clinical use in Japanese patients with hyperphosphatemia. No serious side effects have been reported. However, the most important concern is bone toxicity, which has been observed with use of aluminum hydroxide. For this study, clinical research involved analysis of bone biopsies. Although osteomalacia is the most noticeable side effect, this was not observed. Both the high- and the low-turnover bone disease concentrated into a normal bone turnover state. However, as the authors have less than 10 years clinical experience with lanthanum carbonate, patients should be monitored carefully. In addition, it is necessary to demonstrate whether potent treatment effects on hyperphosphatemia improve the long-term outcome.

Shigematsu, Takashi; Nakashima, Yuri; Ohya, Masaki; Tatsuta, Koichi; Koreeda, Daisuke; Yoshimoto, Wataru; Yamanaka, Shintaro; Sakaguchi, Toshifumi; Hanba, Yoshiyuki; Mima, Toru; Negi, Shigeo

2012-01-01

335

Development of mixed conducting dense nickel/Ca-doped lanthanum zirconate cermet for gas separation application  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer Phase pure La{sub 1.95}Ca{sub 0.05}Zr{sub 2}O{sub 7-{delta}} (LCZ) material is prepared by combustion synthesis. Black-Right-Pointing-Pointer LCZ and Ni-LCZ bulk samples are prepared with theoretical density close to 100%. Black-Right-Pointing-Pointer Bulk electrical conductivity {approx}400 S/cm is obtained for Ni-LCZ cermet at 750 Degree-Sign C. -- Abstract: La{sub 1.95}Ca{sub 0.05}Zr{sub 2}O{sub 7-{delta}} (LCZ) and Ni-LCZ cermet have been prepared by combustion synthesis and conventional solid state mixing methods respectively. Both the materials are sintered in air and controlled atmosphere (5% H{sub 2} in Ar). The density obtained for the material sintered at 1400 Degree-Sign C in controlled atmosphere is found to be more than 99.5%. This sintering temperature (1400 Degree-Sign C) is considered to be much lower compared to the conventional sintering temperature. The corresponding total conductivity for such Ni-LCZ cermet materials is {approx}400 S/cm measured at 750 Degree-Sign C having 40 vol% of Ni and 60 vol% LCZ.

Nag, S. [CSIR - Central Glass and Ceramic Research Institute, 196 Raja S. C. Mullick Road, Kolkata - 700 032 (India)] [CSIR - Central Glass and Ceramic Research Institute, 196 Raja S. C. Mullick Road, Kolkata - 700 032 (India); Mukhopadhyay, S. [Department of Chemical Technology, Calcutta University, 92 A. P. C. Road, Kolkata - 700 009 (India)] [Department of Chemical Technology, Calcutta University, 92 A. P. C. Road, Kolkata - 700 009 (India); Basu, R.N., E-mail: rajenbasu54@gmail.com [CSIR - Central Glass and Ceramic Research Institute, 196 Raja S. C. Mullick Road, Kolkata - 700 032 (India)

2012-03-15

336

Oxygen reaction on strontium-doped lanthanum cobaltite dense electrodes at intermediate temperatures  

Microsoft Academic Search

La0.7Sr0.3CoO3?? (LSC) powder was characterized by thermogravimetry. Thin, dense layers of LSC were deposited by RF magnetron sputtering on YSZ pellets. The electrochemical behavior was studied as functions of temperature (300530C) and oxygen partial pressure (0.21210?5 bar) by impedance spectroscopy. Impedance diagrams were decomposed into two elements, characteristic of the electrode polarization. The low frequency contribution can be described either

Armelle Ringued; J. Fouletier

2001-01-01

337

Crystal structures and magnetic properties of strontium and copper doped lanthanum ferrites  

NASA Astrophysics Data System (ADS)

The crystal and magnetic structures of La0.8Sr0.2Fe1-xCuxO3-w compounds, which exhibit coercive fields larger than any others reported for iron-based perovskites, have been analyzed at room temperature with the neutron powder diffraction technique and the Rietveld method of profile fitting. For x in the range 0.05-0.10 the material is monophasic with orthorhombic symmetry (space group Pnma), and crystallizes in the perovskite-like cell of LaFeO3, Fe/Cu cations occupy octahedral sites, La/Sr cations are twelve-fold coordinated. For x=0.20 the material is biphasic, with a main orthorhombic phase (space group Pnma) and a secondary rhombohedral phase with space group R-3c (hexagonal setting). The structural transition from the orthorhombic to the rhombohedral phase reduces the structural distortion of the (Fe/Cu)O6 octahedron. The average bond distance (Fe/Cu)-O and the pseudo-cubic unit cell volume decrease with increasing Cu content in accordance with the presence of higher valence states of the transition metals. The magnetic structure was modeled for the monophasic samples (x=0.05 and 0.10) assuming an antiferromagnetic interaction between Fe/Cu neighboring cations (G-type): the magnetic moments order antiferromagnetically along the b-axis, with the spin direction along a-axis. The magnetic moments of the Fe/Cu atoms are ?x=2.66(3)?B and 2.43(3)?B for the compositions x=0.05 and 0.10, respectively. By measuring the first magnetization curve and the hysteresis loops, coexisting antiferromagnetic and weak ferromagnetic interactions were observed for all samples.

Natali Sora, Isabella; Caronna, Tullio; Fontana, Francesca; de Julin Fernndez, Csar; Caneschi, Andrea; Green, Mark

2012-07-01

338

Fission gas transport and its interaction with irradiation induced defects in lanthanum doped ceria  

Microsoft Academic Search

Combined experimental and modeling efforts have been extremely productive in understanding irradiation-induced displacement damage in metal and metal alloy systems. In order to help understand the fundamental mechanisms of irradiation-induced defect formation and evolution in nuclear fuel, similar combined modeling and experimental efforts have been carried out. Ceria (CeO2) was selected as a surrogate material for Uranium Dioxide (UO2) due

Di Yun

2010-01-01

339

Superior oxygen ion conductivity of lanthanum gallate doped with strontium and magnesium  

Microsoft Academic Search

The solid solution range of the La(Sr)Ga(Mg)O perovskite was investigated and the oxygen ion conductivities of corresponding compositions were measured. The solubility of strontium could be extended by the addition of magnesium ions to establish a balance in the oxygen vacancies associated with A and B sites. In this way, the Sr limit in the solid solution was increased to

Peng-nian Huang; A. Petric

1996-01-01

340

Synthesis and physicochemical characterization of nanocrystalline cobalt doped lanthanum strontium ferrite  

NASA Astrophysics Data System (ADS)

Nanosized crystallites of La 0.6Sr 0.4Fe 0.8Co 0.2O 3- ? (LSCF), a promising cathode material for Intermediate Temperature-Solid Oxide Fuel Cells (IT-SOFCs) has been synthesized by alternative methods like ceramic route, polymerisable complex process and gel-combustion method and calcined at different temperatures. X-ray diffraction studies were used for the determination of phase purity, crystal structure and average crystallite size of the samples. Microstructure of LSCF samples was studied by SEM. Temperature-programmed reduction studies were done for evaluating the redox behavior of the samples prepared by alternative methods. The electrical conductivity measurements of sintered samples were carried out at elevated temperatures using four-probe method. The electrical conductivity of sample synthesized by gel-combustion method was more as compared to sample prepared by polymerisable complex process and ceramic route. The electrical conductivity decreased at high temperature due to loss of oxygen and the formation of oxygen vacancies. Thermo-dilatometry was used to study the linear thermal expansion behavior of the samples which shows that there is an observable increase in thermal expansion at high temperatures.

Nityanand, Chaubey; Nalin, Wani Bina; Rajkumar, Bharadwaj Shyamala; Chandra, Chattopadhyaya Mahesh

2011-05-01

341

Effect of aliovalent doping on the transport properties of lanthanum cuprates  

Microsoft Academic Search

Cuprates with perovskite-related structure and the general formula $${{La}}_{{1 - x}} {{A}}_{x} {{Cu}}_{{1 - y}} {{B}}_{y} {{O}}_{{2.5 \\\\pm d }} $$ (A=Ca, Ba, Sr; B=Li; x=0.1, 0.2, 0.3; y=0, 0.1) were prepared by the citrate route. Their structures were studied by X-ray powder diffraction and\\u000a their electrical conductivities (as a function of temperature) by four-point DC measurements on sintered bars.

A. Berenov; J. Wei; H. Wood; R. Rudkin; A. Atkinson

2007-01-01

342

On some transport properties of strontium-doped lanthanum chromite ceramics  

Microsoft Academic Search

D.C. Electrical conductivity, Hall mobility and magnetic susceptibility measurements on La1-xSrxCrO3 (0?x?0.25) perovskite ceramic system, and their temperature dependence, have been carried out to understand the nature of the transport mechanism in them. The electrical conductivity and Hall mobility displayed thermally activated temperature dependence with activation energies that varied from 0.13 to 0.23 ev. The variation of the d.c. conductivity

K. P. BANSALt; S. Kumari; B. K. Das; G. C. Jain

1983-01-01

343

Beam-hardening artifacts on computed tomography images caused by lanthanum carbonate hydrate in a patient on dialysis  

Microsoft Academic Search

Lanthanum carbonate hydrate is a nonaluminum, noncalcium phosphate binder containing lanthanum (La). It is effective in decreasing\\u000a the serum phosphate level in patients on dialysis. Because the atomic number of the La contained in lanthanum carbonate hydrate\\u000a is relatively high, at 57, this agent may cause strong artifacts on computed tomography (CT) images, which may be mistakenly\\u000a interpreted as foreign

Hiromitsu Hayashi; Minoru Machida; Tetsuro Sekine; Hidenori Yamaguchi; Tomonari Kiriyama; Shin-ichiro Kumita

2010-01-01

344

Effect of Temperature on Phase Separation in Liquid Binary System Constituted by Tetradecane and Samarium(III) Nitrate Solvate with Tri-n-Butyl Phosphate and Ternary System Constituted by Tetradecane, Tri-n-Butyl Phosphate, and Samarium(III) Nitrate Solvate with Tri-n-Butyl Phosphate  

Microsoft Academic Search

The phase diagrams of a binary liquid system constituted by tetradecane and samarium(III) nitrate solvate with tri-n-butyl phosphate and a ternary system constituted by tetradecane, tri-n-butyl phosphate, and samarium(III) nitrate solvate with tri-n-butyl phosphate were studied at 298.15-355.15 K. The distribution of components between the phases was considered. The points of critical compositions of the ternary system at various temperatures

A. K. Pyartman; A. V. Kudrova; V. A. Keskinov

2004-01-01

345

Early earth and solar system evolution - Insights from strontium, barium neodymium, and samarium isotopes  

NASA Astrophysics Data System (ADS)

Recent thermal ionization mass spectrometer advances have made it possible to determine the isotopic composition of both terrestrial and extra-terrestrial samples with unrivaled precision. The coupled long- and short-lived samarium- neodymium decay system ( 147 Sm[arrow right] 143 Nd, t ? =106 Ga, 146 Sm[arrow right] 142 Nd, t ? =103 Ma) have been used to confirm the presence of 142 Nd variations in early Archean samples, and to show that the depleted upper mantle is elevated in 142 Nd compared to chondrite meteorites. These results imply that major silicate differentiation of the Earth's mantle occurred within about 30 Ma after accretion. Furthermore, they require the presence of an enriched reservoir that has not interacted with the depleted mantle since initial differentiation. This study presents high-precision thermal ionization mass spectrometer data for strontium, barium, neodymium, and samarium isotopic compositions of meteorite and terrestrial samples in order to investigate: (i) whether the 142 Nd differences between meteorites and terrestrial samples are indeed caused by the decay of 146 Sm with variable Sm/Nd ratios, (ii) if their Nd isotopic compositions are fundamentally different due to variations in nucleosynthetic components or neutron fluences; and (iii) if traces of the early enriched reservoir can be found in deep mantle plume derived lavas carrying solar noble gas signatures. The Sm, Nd, and Ba isotopic compositions of carbonaceous chondrites are found to be different from that of ordinary chondrites, the eucrite parent body, and Earth, which are all identical. Non-radiogenic Sr isotopic compositions are identical for terrestrial samples and meteorites. Variations in nucleosynthetic components (s-, r-, and p-process) within the Solar System are evident from p- process deficits in Sm and Nd and r-process excesses in Ba for carbonaceous chondrites. The p-process deficit explains the bimodal 142 Nd distribution seen in chondrites but is insufficient to explain the difference between chondrites and the terrestrial upper mantle. No signs of the early enriched reservoir were found in deep mantle plume lavas from the Iceland hot spot and Deccan Flood basalts. However, this could be due to dilution with depleted upper mantle material. Combined, these results point to a homogenous inner Solar System with respect to heavy elements and confirm early terrestrial mantle differentiation.

Andreasen, Rasmus

2007-08-01

346

Development and evaluation of copper-67 and samarium-153 labeled conjugates for tumor radioimmunotherapy  

SciTech Connect

The potential of utilizing receptor-specific agents such as monoclonal antibodies (MAb), and MAb-derived smaller molecules, as carriers of radionuclides for the selective destruction of tumors has stimulated much research activity. The success of such applications depends on many factors, especially the tumor binding properties of the antibody reagent, the efficiency of labeling and in-vivo stability of the radioconjugate and, on the careful choice of the radionuclide best suited to treat the tumor under consideration. The radiolabeled antibody technique for radioimmunotherapy (RIT), however, has experienced many limitations, and its success has not matched the expectations that were raised more than a decade ago. The problems that have been identified include: (i) degradation of antibody immunoreactivity resulting from chemical manipulations required for labeling; (ii) lack of suitable radioisotopes and methods for stable attachment of the radiolabel; (iii) in-vivo instability of the radioimmunoconjugates; (iv) excessive accumulation of activity in non-target locations; and (v) lack of radioimmunoconjugate accessibility to cells internal to a tumor mass. A careful choice of the radionuclide(s) best suited to treat the tumor under consideration is one of the most important requirements for successful radioimmunotherapy. This study evaluates copper 67 and samarium 153 for tumor radioimmunotherapy.

Srivastava, S.C.; Mausner, L.F.; Mease, R.C.; Meinken, G.E.; Joshi, V.; Kolsky, K.; Sweet, M.; Steplewski, Z.

1995-02-01

347

The effect of electromotive-force generation on electrical properties of thin samarium sulfide films  

SciTech Connect

Electrical properties of thin SmS polycrystalline films with various values of the lattice constant at T = 300-580 K are studied. Specific features of the temperature dependences of electrical conductivity at T > 450 K are revealed. The effect of generation of the electromotive force with magnitude as large as 1.3 V at T = 440-470 K is observed when the films were subjected to the pressure of a spherical indenter. It is shown that it is possible to transform SmS films into a high-resistivity state (with the difference in the resistivity by three orders of magnitude) by applying an electric field with the strength higher than 100 V/cm. All the results obtained are accounted for using a model of the phenomenon of the electromotive-force generation in SmS under uniform heating of the sample and can also be attributed to the variable valence of samarium ions with respect to the lattice defects.

Kaminskii, V. V., E-mail: Vladimir.Kaminski@mail.ioffe.ru; Kazanin, M. M.; Solov'ev, S. M.; Sharenkova, N. V.; Volodin, N. M. [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation)

2006-06-15

348

High temperature phase transitions and critical exponents of Samarium orthoferrite determined by in situ optical ellipsometry  

NASA Astrophysics Data System (ADS)

Determining phase transitions has always been a great challenge in material science due to their important fundamental and technological aspects. Recently, iron-based perovskites (RFeO3), exhibiting phase transitions at high temperatures, have attracted much interest for their functional properties at room temperature, such as multiferroicity (BiFeO3) and ultrafast spin dynamics (TmFeO3). In this family of materials, Samarium orthoferrite (SmFeO3) is a weak ferromagnet, ordering at high temperatures and exhibiting an intrinsic spin reorientation transition above room temperature, which is ``hidden'' in macroscopic magnetization measurements in polycrystalline samples. In the present article, we show that the related magnetic high temperature phase transitions can be studied through their dielectric functions by spectroscopic ellipsometry in situ and without any need for an applied external magnetic field. The presence of this intrinsic spin reorientation transition is demonstrated for textured SmFeO3 films and we have determined a critical exponent of ? = 0.45 +/- 0.01 for the magnetic phase transition, coherently from optical, magneto-optical, and structural investigations.

Berini, B.; Fouchet, A.; Popova, E.; Scola, J.; Dumont, Y.; Franco, N.; da Silva, R. M. C.; Keller, N.

2012-03-01

349

In vitro bioequivalence approach for a locally acting gastrointestinal drug: lanthanum carbonate.  

PubMed

A conventional human pharmacokinetic (PK) in vivo study is often considered as the "gold standard" to determine bioequivalence (BE) of drug products. However, this BE approach is not always applicable to the products not intended to be delivered into the systemic circulation. For locally acting gastrointestinal (GI) products, well designed in vitro approaches might be more practical in that they are able not only to qualitatively predict the presence of the active substance at the site of action but also to specifically assess the performance of the active substance. For example, lanthanum carbonate chewable tablet, a locally acting GI phosphate binder when orally administrated, can release free lanthanum ions in the acid environment of the upper GI tract. The lanthanum ions directly reach the site of action to bind with dietary phosphate released from food to form highly insoluble lanthanum-phosphate complexes. This prevents the absorption of phosphate consequently reducing the serum phosphate. Thus, using a conventional PK approach to demonstrate BE is meaningless since plasma levels are not relevant for local efficacy in the GI tract. Additionally the bioavailability of lanthanum carbonate is less than 0.002%, and therefore, the PK approach is not feasible. Therefore, an alternative assessment method is required. This paper presents an in vitro approach that can be used in lieu of PK or clinical studies to determine the BE of lanthanum carbonate chewable tablets. It is hoped that this information can be used to finalize an in vitro guidance for BE studies of lanthanum carbonate chewable tablets as well as to assist with "in vivo" biowaiver decision making. The scientific information might be useful to the pharmaceutical industry for the purpose of planning and designing future BE studies. PMID:23249191

Yang, Yongsheng; Shah, Rakhi B; Yu, Lawrence X; Khan, Mansoor A

2013-02-01

350

Fabrication of photonic crystals in rare-earth doped chalcogenide glass films for enhanced upconversion  

NASA Astrophysics Data System (ADS)

Gallium lanthanum oxysulfide (GLSO) is a promising host material for observing strong upconversion emission from trivalent rare-earth ions such as erbium (Er3+). Its attractive properties include high rare-earth solubility due to the lanthanum content of the glass former, a high refractive index (n = 2.2 at 550nm) for high radiative efficiency, and a low maximum phonon energy of approximately 425cm -1. Photonic crystals meanwhile can provide controlled light extraction, and may be capable of suppressing unwanted IR emission from lower lying metastable states. Here, we describe the fabrication of photonic crystals in annealed films of Er3+-doped GLSO deposited by RF sputtering. The most intense visible upconversion emission is observed in films annealed at 550C, close to the bulk glass transition temperature. Hexagonal lattice photonic crystals are subsequently milled into the films using a focused ion beam (FIB). The milling parameters are optimized to produce the most vertical sidewall profile.

Pollard, M. E.; Knight, K. J.; Parker, G. J.; Hewak, D. W.; Charlton, M. D. B.

2012-02-01

351

Silica-lanthanum oxide: pioneer composite of rare-Earth metal oxide in selective phosphopeptides enrichment.  

PubMed

Relying on the successful journey of metal oxides in phosphoproteomics, lanthanum oxide is employed for the engineering of an affinity material for phosphopeptide enrichment. The lanthanum oxide is chemically modified on the surface of silica and characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and Fourier transform infrared spectroscopy (FTIR). The obtained silica-lanthanum oxide composite is applied for the selective enrichment of phosphopeptides from tryptic digest of standard protein (?-casein, ?-casein, and commercially available casein mixtures from bovine milk). The enriched entities are analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The mass spectroscopy (MS) results show that the silica-lanthanum oxide composite exhibits enhanced capability for phosphopeptide enrichment with sensitivity assessed to be 50 fmol. Sequence coverage of casein is interpreted showing successful recovery. As a real sample, a protein digest of nonfat milk is applied. Also, the ability of lanthanum in different formats is checked in the selective phosphopeptides enrichment. The composite holds promising future in economic ground as it also possesses the regenerative ability for repetitive use. PMID:23134445

Jabeen, Fahmida; Hussain, Dilshad; Fatima, Batool; Musharraf, S Ghulam; Huck, Christian W; Bonn, G?nther K; Najam-ul-Haq, Muhammad

2012-12-01

352

Processing Techniques Developed to Fabricate Lanthanum Titanate Piezoceramic Material for High-Temperature Smart Structures  

NASA Technical Reports Server (NTRS)

Piezoelectric ceramic materials are potential candidates for use as actuators and sensors in intelligent gas turbine engines. For piezoceramics to be applied in gas turbine engines, they will have to be able to function in temperatures ranging from 1000 to 2500 F. However, the maximum use temperature for state-of-the-art piezoceramic materials is on the order of 300 to 400 F. Research activities have been initiated to develop high-temperature piezoceramic materials for gas turbine engine applications. Lanthanum titanate has been shown to have high-temperature piezoelectric properties with Curie temperatures of T(sub c) = 1500 C and use temperatures greater than 1000 C. However, the fabrication of lanthanum titanate poses serious challenges because of the very high sintering temperatures required for densification. Two different techniques have been developed at the NASA Glenn Research Center to fabricate dense lanthanum titanate piezoceramic material. In one approach, lower sintering temperatures were achieved by adding yttrium oxide to commercially available lanthanum titanate powder. Addition of only 0.1 mol% yttrium oxide lowered the sintering temperature by as much as 300 C, to just 1100 C, and dense lanthanum titanate was produced by pressure-assisted sintering. The second approach utilized the same commercially available powders but used an innovative sintering approach called differential sintering, which did not require any additive.

Goldsby, Jon C.; Farmer, Serene C.; Sayir, Ali

2004-01-01

353

Rutherford backscattering spectrometry (RBS) characterization of oxide scale formed on (AISI304) steel after surface deposition of lanthanum  

Microsoft Academic Search

Oxidized AISI-304 steel samples coated with lanthanum have been investigated by Rutherford backscattering spectrometry (RBS) in order to determine the composition profile of the oxide scale. In this sense, RBS technique has been revealed as a very reliable and nondestructive method for depth profile analysis. Lanthanum deposition, specially over preoxidized specimens, has proven to improve their resistance to high temperature

F. J. Ager; M. A. Respaldiza; J. J. Benitez; J. C. Soares; M. F. da Silva; J. A. Odriozola

1996-01-01

354

The incorporation of plutonium in lanthanum zirconate pyrochlore  

NASA Astrophysics Data System (ADS)

The incorporation of plutonium (Pu) within lanthanum zirconate pyrochlore was investigated using air, argon, and N2-3.5%H2 sintering atmospheres together with Ca2+ and Sr2+ incorporation for charge compensation. The samples have been characterised in the first instance by X-ray diffraction (XRD), scanning electron microscopy (SEM) and diffuse reflectance spectroscopy (DRS). The results show Pu can be exchanged for La3+ on the A-site with and without charge compensation and for Zr4+ on the B-site. DRS measurements were made over the wavenumber range of 4000-19,000 cm-1 and the Pu in all air- and argon-sintered samples was found to be present as Pu4+ while that in samples sintered in N2-3.5%H2 was present as Pu3+. The Pu valence was confirmed for three of the samples using X-ray near-edge absorption spectroscopy (XANES). Pu valences >4+ were not observed in any of the samples.

Gregg, Daniel J.; Zhang, Yingjie; Middleburgh, Simon C.; Conradson, Steven D.; Triani, Gerry; Lumpkin, Gregory R.; Vance, Eric R.

2013-11-01

355

Lanthanum Molybdenum Oxide: Low Temperature Synthesis and Characterization  

SciTech Connect

A recently developed fast oxide ion conductor, namely lanthanum molybdenum oxide (La{sub 2}Mo{sub 2}O{sub 9}, LAMO), was synthesized instantaneously by a citrate-nitrate auto-ignition process at a fixed citrate to nitrate ratio of 0.3 and characterized by thermal analysis, x-ray diffraction, impedance spectroscopy, and thermal expansion measurements. Crystalline LAMO has formed instantaneously during the combustion process. The signature of the order-disorder transition of stoichiometric LAMO around 570 degrees C was evident from differential thermal analysis, differential scanning calorimetry electrical conductivity, and thermal expansion measurements. Though the in situ x-ray measurements did not indicate any clear evidence of a phase transition, a stepwise change in the lattice parameter near the vicinity of the transition temperature was apparent thereby confirming the phase transition to be of first order in nature. The thermal expansion coefficient of LAMO was calculated to be 13.92 x 10-6/ degrees K at 950 degrees C. The present method formed phase pure LAMO instantaneously and produced sintered samples with high conductivity, namely, 0.052 S/cm at 800 degrees C and 0.08 S/cm at 950 degrees C compared to LAMO prepared through various other solution routes.

Basu,S.; Devi, P.; Mati, A.; Lee, Y.; Hanson, J.

2006-01-01

356

Assessing Lanthanum-Bromide Detectors for Safeguards Applications  

SciTech Connect

Major detector technologies currently being used for gamma-ray spectroscopy in safeguards applications include systems based on sodium iodide (NaI), cadmium-zinc-telluride (CZT), cadmium-telluride (CdTe), and high-purity germanium (HPGe) crystals. Recently, a new scintillation detector based on a lanthanum bromide (LaBr3) crystal has become commercially available. The declared benefits of this new detector technology include higher resolution and improved efficiency compared with similarly configured NaI-based systems. Both detector systems offer the advantage of room-temperature operation. This paper describes the results of a study assessing the safeguards applicability and advantages for isotopic and quantitative analyses of uranium using the LaBr3-based detector, as well as an investigation into the general operating characteristics of the LaBr3-based detector. The results are compared with those from a widely used NaI-based detector system (Canberra's Inspector-1000 multichannel analyzer) operated under similar environmental conditions and hardware configuration, using commercially available software packages (NaIGEM and Genie-2000).

Gariazzo, Claudio Andres [ORNL; Saavedra, Steven F [ORNL; Smith, Steven E [ORNL; Solodov, Alexander A [ORNL

2008-01-01

357

Lanthanum reduces the excitation efficiency in fly photoreceptors  

PubMed Central

Lanthanum (La3+), a known inhibitor of Ca2+ binding proteins, was applied to the extracellular space of fly retina. Shot noise analysis indicated that a combination of intense light and La3+ caused a large (down to zero) reduction in the rate of occurrence of the quantal responses to single photons (quantum bumps) which sum to produce the photoreceptor potential. Light in the presence of La3+ also increased the effective bump duration. These effects are very similar to the effects of the mutations trp of Drosophila and nss of Lucilia flies on the quantum bump rate and duration. La3+ applied to the nss mutant caused only a small reduction in the bump rate, suggesting that La3+ may affect the nss gene product which is deficient in the mutant. The close similarity in the properties of the receptor potential of the La(3+)-treated photoreceptor of the wild type and of the nss mutant together with existing evidence for the highly reduced intracellular Ca2+ ([Ca2+]i) level in nss photoreceptors suggest that both La3+ and the mutation cause a severe reduction in [Ca2+]i. This effect may arise from an inhibition of a Ca2+ transporter protein located in the surface membrane that normally replenishes Ca2+ pools in the photoreceptors, a process essential for light excitation.

1991-01-01

358

First-principles thermodynamic modeling of lanthanum chromate perovskites  

NASA Astrophysics Data System (ADS)

Tendencies toward local atomic ordering in (A,A')(B,B')O3-? mixed composition perovskites are modeled to explore their influence on thermodynamic, transport, and electronic properties. In particular, dopants and defects within lanthanum chromate perovskites are studied under various simulated redox environments. (La1-x,Srx)(Cr1-y,Fey)O3-? (LSCF) and (La1-x,Srx)(Cr1-y,Ruy)O3-? (LSCR) are modeled using a cluster expansion statistical thermodynamics method built upon a density functional theory database of structural energies. The cluster expansions are utilized in lattice Monte Carlo simulations to compute the ordering of Sr and Fe(Ru) dopant and oxygen vacancies (Vac). Reduction processes are modeled via the introduction of oxygen vacancies, effectively forcing excess electronic charge onto remaining atoms. LSCR shows increasingly extended Ru-Vac associates and short-range Ru-Ru and Ru-Vac interactions upon reduction; LSCF shows long-range Fe-Fe and Fe-Vac interaction ordering, inhibiting mobility. First principles density functional calculations suggest that Ru-Vac associates significantly decrease the activation energy of Ru-Cr swaps in reduced LSCR. These results are discussed in view of experimentally observed extrusion of metallic Ru from LSCR nanoparticles under reducing conditions at elevated temperature.

Dalach, P.; Ellis, D. E.; van de Walle, A.

2012-01-01

359

Defect Energetics and Nonstoichiometry in Lanthanum Magnesium Hexaaluminate  

NASA Astrophysics Data System (ADS)

Computer-based atomistic simulation methods are applied to address quantitatively the defect energetics and crystal chemistry of lanthanum magnesium hexaaluminate (LMA). The tetrahedral site preference of Mg in the magnetoplumbite structure is determined by calculating lattice energies for different Mg ion distributions. It is revealed that the intrinsic and extrinsic disorders are much influenced by the distribution of Mg in the structure. Our calculations show that oxygen Frenkel disorder is the dominant defect mode to be expected, even though Schottky disorder may also exist. Several feasible defect processes in nonstoichiometric LMA are determined from the enthalpies of the quasi-chemical reactions for the processes with simple point defect energies. We have also modeled some defect complexes in the mirror plane regions. It is found that the Mg ions positioned in the tetrahedral sites suppress the formation of cation vacancies in the mirror plane, through hindering the relaxation of the 12 kAl ions by which the vacancies are stabilized. In Mg-deficient nonstoichiometric LMA, however, it is expected that the defect complex [V La+V Al+2(V Al+Al i)] will be formed in the interspinel layer. Our calculations also indicate that the O Ladefect is improbable in LMA not only as a simple point defect but also as a member of a defect complex.

Park, Jae-Gwan; Cormack, A. N.

1997-05-01

360

Work function measurement of lanthanum-boron compounds  

NASA Technical Reports Server (NTRS)

The relationship between emission properties and sample composition is studied for lanthanum-boron compounds. Specifically, the La-B system is considered between 1400 and 2100 K and between LaB(4.24) and LaB(29.2) to determine the phase relationship, chemical activity of the compounds, vapor composition, and vaporization rate. The results indicate that: (1) a blue-colored phase near LaB(9) exists between a purple-colored LaB(6) and elemental boron, (2) vaporization is sufficiently more rapid than diffusion so that great compositional differences exist between the surface and the interior, (3) an activation energy lowers the boron vaporization rate from LaB(6), and (4) a steady-state surface composition between LaB(6.04) and LaB(6.07) exists for freely vaporizing materials as a function of interior composition, purity, and temperature. It is noted that the ultimate life of a thermionic diode is governed by electrode vaporization rate whereas efficiency is governed by the electrode work function.

Jacobson, D. L.; Storms, E. K.

1978-01-01

361

A new homologous series of lanthanum copper oxides  

SciTech Connect

The authors report the synthesis and structural characterization of a new homologous series of lanthanum cuprates, with the formula La{sub 4+4n}Cu{sub 8+2n}O{sub 14+8n}. The n = 2 and n = 3 members, La{sub 2}Cu{sub 2}O{sub 5} and La{sub 8}Cu{sub 7}O{sub 19}, synthesized in the bulk, are stable in very narrow temperature ranges in air and oxygen. The n = 4 member was observed by electron microscopy. The crystal structure of La{sub 2}Cu{sub 2}O{sub 5} consists of thin ribbons of La{sub 2}CuO{sub 4} sandwiched between Cu-O planes of complex low dimensional geometry. The temperature-dependent magnetic susceptibilities of La{sub 2}Cu{sub 2}O{sub 5} and La{sub 8}Cu{sub 7}O{sub 19} are characteristic of low dimensional Heisenberg antiferromagnets with a low exchange coupling energy.

Cava, R.J.; Siegrist, T.; Hessen, B.; Krajewski, J.J.; Peck, W.F. Jr.; Batlogg, B.; Takagi, H.; Waszczak, J.V.; Schneemeyer, L.F. (AT and T Bell Labs., Murray Hill, NJ (United States)); Zandbergen, H.W. (Delft Univ. of Tech. (Netherlands))

1991-09-01

362

Deposition and investigation of lanthanum-cerium hexaboride thin films  

SciTech Connect

Thin films of lanthanum-cerium hexaboride, the promising thermoelectric material for low-temperature applications, are deposited on various substrates by the electron-beam evaporation, pulsed laser deposition and magnetron sputtering. The influence of the deposition conditions on the films X-ray characteristics, composition, microstructure and physical properties, such as the resistivity and Seebeck coefficient, is studied. The preferred (100) orientation of all films is obtained from XRD traces. In the range of 780-800 deg. C deposition temperature the highest intensity of diffractions peaks and the highest degree of the preferred orientation are observed. The temperature dependence of the resistivity and the Seebeck coefficient of films are investigated in the temperature range of 4-300 K. The features appropriate to Kondo effect in the dependences {rho}(T) and S(T) are detected at temperatures below 20 K. Interplay between the value of the Seebeck coefficient, metallic parameters and Kondo scattering of investigated films is discussed. - Graphical abstract: Kondo scattering in (La,Ce)B{sub 6} films: temperature dependence of the resistivity of (La,Ce)B{sub 6} films on various substrates and the ceramics La{sub 0.99}Ce{sub 0.01}B{sub 6}.

Kuzanyan, A.S. [Institute for Physical Research NAS, Ashtarak, 378410 (Armenia)]. E-mail: akuzan@ipr.sci.am; Harutyunyan, S.R. [Institute for Physical Research NAS, Ashtarak, 378410 (Armenia); Vardanyan, V.O. [Institute for Physical Research NAS, Ashtarak, 378410 (Armenia); Badalyan, G.R. [Institute for Physical Research NAS, Ashtarak, 378410 (Armenia); Petrosyan, V.A. [Institute for Physical Research NAS, Ashtarak, 378410 (Armenia); Kuzanyan, V.S. [Institute for Physical Research NAS, Ashtarak, 378410 (Armenia); Petrosyan, S.I. [Institute for Physical Research NAS, Ashtarak, 378410 (Armenia); Karapetyan, V.E. [Institute for Physical Research NAS, Ashtarak, 378410 (Armenia); Wood, K.S. [NRL, Washington, DC 20375 (United States); Wu, H.-D. [SFA/NRL, Washington, DC 20375 (United States); Gulian, A.M. [Physics Art Frontiers/NRL, Washington, DC 20375 (United States)

2006-09-15

363

Electrical and pyroelectric properties of lanthanum based niobate  

NASA Astrophysics Data System (ADS)

A lanthanum based new tungsten bronze (TB) ferroelectrics (K2Pb2La2W2Ti4Nb4O30) was synthesized by a mixed-oxide method at high temperature. Thermogravimetry analysis (TG) technique was used to decide the material preparation conditions. The formation of desired compound was confirmed by preliminary X-ray structural analysis. The SEM micrograph of the sintered sample exhibits uniform rod-like grain distribution without many voids. Detailed studies of the nature of variation of dielectric parameters with temperature and frequency shows dielectric anomaly at 310 C. The temperature dependence of electrical parameters (impedance, modulus, conductivity, etc) of the material exhibits a strong correlation between its micro-structure (i.e., bulk, grain boundary, etc) and electrical properties. The dc conductivity follows the Arrhenius equation, and thus its variation with rise in temperature reveals the negative temperature coefficient of resistance (NTCR) behavior of the material. The material obeys Jonscher's universal power law which is evident from the frequency dependence of ac conductivity. The variation of current with temperature shows that the material has high pyroelectric co-efficient and figure of merit. Hence the material is useful for pyroelectric sensors.

Padhee, R.; Das, Piyush R.; Parida, B. N.; Choudhary, R. N. P.

2013-02-01

364

Study of prolonged administration of lanthanum carbonate in dialysis patients.  

PubMed

Data of 36 months were accumulated regarding the effects of lanthanum carbonate (LA) on serum phosphate concentrations in dialysis patients. Fifty-three patients (average age and dialysis history 58.4 years and 9.1 years) were included in this study who have been receiving outpatient treatment since March 2009, and who have been unable to maintain serum phosphate concentrations of ?6.0?mg/dL via traditional therapeutic agents used for hyperphosphatemia. Patients were given dosage of LA in addition to, or instead of, co-hyperphosphatemia treatments already being received. Mean dosages of calcium carbonate (CC) and sevelamer hydrochloride (SH) before starting LA administration were 1301.9?mg and 2462.3?mg, respectively. Dosage of LA for all cases was 750?mg at initial dose; 1528.3?mg at 5 months; and 1416.7?mg at 30 months. Dosage of other phosphate binders were 905.7?mg of CC and 820.8?mg of SH at 5 months; and 687.5?mg of CC and 1031.3?mg of SH at 30 months. Serum phosphorus levels (P levels) were significantly decreased at 1 month of LA administration, and continued until 30 months of La treatment. These results suggest that LA successfully controlled serum P and Ca concentrations simultaneously within target ranges without affecting serum intact parathyroid hormone concentration, although further long-term prospective cohort study on LA would be required. PMID:23586507

Gotoh, Junichi; Kukita, Kazutaka; Tsuchihashi, Seiichiro; Hattori, Masahiro; Iida, Junichi; Horie, Takashi; Onodera, Kazuhiko; Furui, Hidenori; Tamaki, Toru; Meguro, Junichi; Yonekawa, Motoki; Kawamura, Akio

2013-04-01

365

Polymeric membrane and coated graphite samarium(III)-selective electrodes based on isopropyl 2-[(isopropoxycarbothioyl)disulfanyl]ethanethioate  

Microsoft Academic Search

New polymeric membrane (PME) and coated graphite (CGE) samarium(III)-selective electrodes were prepared based on isopropyl 2-[(isopropoxycarbothioyl) disulfanyl]ethanethioate as a suitable neutral ionophore. The electrodes exhibit Nernstian slopes for Sm3+ ions over wide concentration ranges (1.010?5 to 1.010?1M for PME and 1.010?6 to 1.010?1M for CGE). The PME and CGE have limits of detection of 3.110?6 and 5.010?7M, respectively, and response

Mojtaba Shamsipur; Morteza Hosseini; Kamal Alizadeh; Mohammad Mehdi Eskandari; Hashem Sharghi; Mir Fazlollah Mousavi; Mohammad Reza Ganjali

2003-01-01

366

Recent advances in the chemoselective reduction of functional groups mediated by samarium(II) iodide: a single electron transfer approach.  

PubMed

Recently, samarium(II) iodide reductants have emerged as powerful single electron donors for the highly chemoselective reduction of common functional groups. Complete control of the product formation can be achieved on the basis of a judicious choice of a Sm(II) complex/proton donor couple, even in the presence of extremely sensitive functionalities (iodides, aldehydes). In most cases, the reductions are governed by thermodynamic control of the first electron transfer, which opens up new prospects for unprecedented transformations via radical intermediates under mild regio-, chemo- and diastereoselective conditions that are fully orthogonal to hydrogenation or metal-hydride mediated processes. PMID:24013846

Szostak, Michal; Spain, Malcolm; Procter, David J

2013-12-01

367

Fabrication of large-volume, low-cost ceramic lanthanum halide scintillators for gamma ray detection : final report for DHS/DNDO/TRDD project TA-01-SL01.  

SciTech Connect

This project uses advanced ceramic processes to fabricate large, optical-quality, polycrystalline lanthanum halide scintillators to replace small single crystals produced by the conventional Bridgman growth method. The new approach not only removes the size constraint imposed by the growth method, but also offers the potential advantages of both reducing manufacturing cost and increasing production rate. The project goal is to fabricate dense lanthanum halide ceramics with a preferred crystal orientation by applying texture engineering and solid-state conversion to reduce the thermal mechanical stress in the ceramic and minimize scintillation light scattering at grain boundaries. Ultimately, this method could deliver the sought-after high sensitivity and <3% energy resolution at 662 keV of lanthanum halide scintillators and unleash their full potential for advanced gamma ray detection, enabling rapid identification of radioactive materials in a variety of practical applications. This report documents processing details from powder synthesis, seed particle growth, to final densification and texture development of cerium doped lanthanum bromide (LaBr{sub 3}:Ce{sup +3}) ceramics. This investigation demonstrated that: (1) A rapid, flexible, cost efficient synthesis method of anhydrous lanthanum halides and their solid solutions was developed. Several batches of ultrafine LaBr{sub 3}:Ce{sup +3} powder, free of oxyhalide, were produced by a rigorously controlled process. (2) Micron size ({approx} 5 {micro}m), platelet shape LaBr{sub 3} seed particles of high purity can be synthesized by a vapor phase transport process. (3) High aspect-ratio seed particles can be effectively aligned in the shear direction in the ceramic matrix, using a rotational shear-forming process. (4) Small size, highly translucent LaBr{sub 3} (0.25-inch diameter, 0.08-inch thick) samples were successfully fabricated by the equal channel angular consolidation process. (5) Large size, high density, translucent LaBr{sub 3} ceramics samples (3-inch diameter, > 1/8-inch thick) were fabricated by hot pressing, demonstrating the superior manufacturability of the ceramic approach over single crystal growth methods in terms of size capability and cost. (6) Despite all these advances, evidence has shown that LaBr{sub 3} is thermally unstable at temperatures required for the densification process. This is particularly true for material near the surface where lattice defects and color centers can be created as bromine becomes volatile at high temperatures. Consequently, after densification these samples made using chemically prepared ultrafine powders turned black. An additional thermal treatment in a flowing bromine condition proved able to reduce the darkness of the surface layer for these densified samples. These observations demonstrated that although finer ceramic powders are desirable for densification due to a stronger driving force from their large surface areas, the same desirable factor can lead to lattice defects and color centers when these powders are densified at higher temperatures where material near the surface becomes thermally unstable.

Boyle, Timothy J.; Ottley, Leigh Anna M.; Yang, Pin; Chen, Ching-Fong; Sanchez, Margaret R.; Bell, Nelson Simmons

2008-10-01

368

A phase I study of samarium-153 ethylenediaminetetramethylene phosphonate therapy for disseminated skeletal metastases  

SciTech Connect

Thirty-five patients with disseminated skeletal metastases from a variety of tumor types underwent clinical trial of samarium-153 ethylenediaminetetramethylene phosphonate (153Sm-EDTMP) on a day-patient basis. Individual beta radiation dosimetry was based on pharmacokinetic studies of a 20 mCi tracer dose of 153Sm-EDTMP. The retained skeletal activity varied unpredictably from 40% to 95% of the administered dose, but in all patients greater than 98% of the nonosseous activity was cleared in the urine within 6 hours. Prospective calculation of radiation dosimetry in each patient permitted an accurate dosage schedule based upon total red marrow exposure, starting at 100 cGy and escalating to 280 cGy to define the dose-limiting myelotoxicity. Pain was relieved in 22 of 34 evaluable patients (65%) for periods ranging from 4 to 35 weeks, following a single administration of 153Sm-EDTMP. Recurrence of pain responded to retreatment with 153Sm-EDTMP in five of nine patients. The dose-limiting toxicity was myelosuppression manifested particularly by delayed thrombocytopenia. Platelet counts less than 100 x 10(9)/L occurred in 42% of courses when bone marrow radiation absorbed dose exceeded 200 cGy. Myelosuppression was transient and platelet counts had recovered to pretreatment levels within 10 weeks of treatment. 153Sm-EDTMP is effective for the amelioration of pain due to disseminated skeletal metastases particularly with carcinoma of breast or prostate where 83% of patients experienced pain relief. In 15 of the 34 evaluable patients there was evidence of stabilization or regression of skeletal metastases on radiographs and follow-up technetium-99m methylene diphosphonate (99mTc-MDP) bone scans.

Turner, J.H.; Claringbold, P.G.; Hetherington, E.L.; Sorby, P.; Martindale, A.A. (Fremantle Hospital (Australia))

1989-12-01

369

Transport properties near the metal to insulator transition in samarium substituted (Bi,Pb)-2212 system  

SciTech Connect

The electrical transport properties of insulating and superconducting samples of Bi{sub 1.7}Pb{sub 0.4}Sr{sub 2-x}Sm{sub x}Ca{sub 1.1}Cu{sub 2.1}O{sub 8+d}elta system is studied across the metal to insulator transition (MIT) region by varying the x values from 0.5 to 1.0 in steps of 0.1. X-ray diffraction analysis, scanning electron microscopy, energy dispersive x-ray analysis (EDAX), and electrical resistivity measurements have been employed for the characterization of all samples. The x-ray and EDAX analyses indicate that samarium (Sm) atoms are incorporated into the crystalline structure of Bi{sub 1.7}Pb{sub 0.4}Sr{sub 2}Ca{sub 1}Cu{sub 2}O{sub 8+d}elta[(Bi,Pb)-2212]. Samples with x<=0.6 undergo superconducting transitions while those with 0.7<=x<=1.0 exhibit semiconducting behavior. The MIT is observed at 0.6

Shabna, R.; Sarun, P. M.; Vinu, S.; Syamaprasad, U. [National Institute for Interdisciplinary Science and Technology, CSIR, Trivandrum 695019 (India)

2009-06-01

370

M-H characteristics and demagnetization resistance of samarium-cobalt permanent magnets to 300 C  

NASA Technical Reports Server (NTRS)

The influence of temperature on the M-H demagnetization characteristics of permanent magnets is important information for the full utilization of the capabilities of samarium-cobalt magnets at high temperatures in demagnetization-resistant permanent magnet devices. In high temperature space power converters, such as free-piston Stirling engine driven linear alternators, magnet demagnetization can occur as a long-term consequence of thermal agitation of domains and of metallurgical change, and also as an immediate consequence of too large an applied field. Investigated here is the short-term demagnetization resistance to applied fields derived from basic M-H data. This quasistatic demagnetization data was obtained for commercial, high-intrinsic-coercivity, Sm2Co17-type magnets from 5 sources, in the temperature range 23 to 300 C. An electromagnet driven, electronic hysteresigraph was used to test the 1-cm cubic samples. The observed variation of the 2nd quadrant M-H characteristics was a typical rapid loss of M-coercivity and a relatively lesser loss of remanence with increasing temperature. The 2nd quadrant M-H curve knee point is used to define the limits of operation safe against irreversible demagnetization due to an excessive bucking field for a given flux density swing at temperature. Such safe operating area plots are shown to differentiate the high temperature capabilities of the samples from different sources. For most of the samples, their 2nd quadrant M-H loop squareness increased with temperature, reaching a peak or a plateau above 250 C.

Niedra, Janis M.

1992-01-01

371

Bifunctional lanthanum phosphate substrates as novel adsorbents and biocatalyst supports for perchlorate removal.  

PubMed

Porous lanthanum phosphate substrates, obtained by an environmentally benign colloidal forming process employing methyl cellulose, are reported here as excellent adsorbents of perchlorate with >98% efficiency and with 100% reusability. Additionally, the effectiveness of such substrates as biocatalyst supports that facilitate biofilm formation of perchlorate reducing microbes (Serratia marcescens NIIST 5) is also demonstrated for the first time. The adsorption of perchlorate ions is attributed to the pore structure of lanthanum phosphate substrate and the microbial attachment is primarily ascribed to its intrinsic hydrophobic property. Lanthanum phosphate thus emerges as a dual functional material that possesses an integrated adsorption/bioremediation property for the effective removal of ClO4(-) which is an increasingly important environmental contaminant. PMID:24872208

Sankar, Sasidharan; Prajeesh, Gangadharan Puthiya Veetil; Anupama, Vijaya Nadaraja; Krishnakumar, Bhaskaran; Hareesh, Padinhattayil; Nair, Balagopal N; Warrier, Krishna Gopakumar; Hareesh, Unnikrishnan Nair Saraswathy

2014-06-30

372

High-efficiency, low-temperature cesium diodes with lanthanum-hexaboride electrodes  

NASA Technical Reports Server (NTRS)

Lanthanum hexaboride electrodes in 1700 K cesium diodes may triple power outputs compared with those demonstrated for nuclear thermionic space applications. Still greater relative gains seem possible for emitters below 1700 K. Further improvements in cesium diode performance should result from the lower collector temperatures allowed for earth and low power space duties. Decreased temperatures will lessen thermal transport losses that attend thermionic conversion mechanisms. Such advantages will add to those from collector Carnot and electrode effects. If plasma ignition difficulties impede diode temperature reductions, recycling small fractions of the output power could provide ionization. So high efficiency, low temperature cesium diodes with lanthanum hexaboride electrodes appear feasible.

Morris, J. F.

1974-01-01

373

LaZnB5O10, the first lanthanum zinc borate  

PubMed Central

Lanthanum zinc pentaborate, LaZnB5O10, was synthesized by flux-supported solid-state reaction. It is a member of the LnMB5O10 (Ln = rare earth ion and M = divalent metal ion) structure type. The crystal shows a three-dimensional structure constructed from two-dimensional {[B5O10]5?}n layers with the lanthanum (coordination number nine) and zinc (coordination number six) ions filling in the interlayers.

Jiao, Zhi-Wei; Wang, Ru-Ji; Wang, Xiao-Qing; Shen, De-Zhong; Shen, Guang-Qiu

2010-01-01

374

Near fifty percent sodium substituted lanthanum manganites-A potential magnetic refrigerant for room temperature applications  

NASA Astrophysics Data System (ADS)

Nearly half of lanthanum sites in lanthanum manganites were substituted with monovalent ion-sodium and the compound possessed distorted orthorhombic structure. Ferromagnetic ordering at 300 K and the magnetic isotherms at different temperature ranges were analyzed for estimating magnetic entropy variation. Magnetic entropy change of 1.5 Jkg-1K-1 was observed near 300 K. An appreciable magnetocaloric effect was also observed for a wide range of temperatures near 300 K for small magnetic field variation. Heat capacity was measured for temperatures lower than 300 K and the adiabatic temperature change increases with increase in temperature with a maximum of 0.62 K at 280 K.

Sethulakshmi, N.; Al-Omari, I. A.; Suresh, K. G.; Anantharaman, M. R.

2014-03-01

375

Gamma spectrometry and chemical characterization of ceramic seeds with samarium-153 and holmium-166 for brachytherapy proposal.  

PubMed

Ceramic seeds were synthesized by the sol-gel technique with Si:Sm:Ca and Si:Ho:Ca. One set of seeds was irradiated in the TRIGA type nuclear reactor IPR-R1 and submitted to instrumental neutron activation analysis (INAA), K(0) method, to determine mass percentage concentration of natural samarium and holmium in the seed as well as to determine all existing radionuclides and their activities. Attention was paid to discrimination of Si-31, Ca-40, Ca-45, Ca-47, Ca-49, Sm-145, Sm-155, Sm-153 and Ho-166. A second sample was submitted to atomic emission spectrometry (ICP-AES) also to determine samarium and holmium concentrations in weight. A third sample was submitted to X-ray fluorescence spectrometry to qualitatively determine chemical composition. The measured activity was due to Sm-153 and Ho-166 with a well-characterized gamma spectrum. The X-ray fluorescence spectrum demonstrated that there is no discrepancy in seed composition. The maximum ranges in the water of beta particles from Sm-153 and Ho-166 decay were evaluated, as well as the dose rate and total dose delivered within the volume delimited by the range of the beta particles. The results are relevant for investigation of the viability of producing Sm-153 and Ho-166 radioactive seeds for use in brachytherapy. PMID:20685128

Valente, Eduardo S; Campos, Tarcsio P R

2010-12-01

376

Preparation and Quality Control of the [153Sm]-Samarium Maltolate Complex as a Lanthanide Mobilization Product in Rats  

PubMed Central

Development of lanthanide detoxification agents and protocols is of great importance in management of overdoses. Due to safety of maltol as a detoxifying agent in metal overloads, it can be used as a lanthanide detoxifying agent. In order to demonstrate the biodistribution of final complex, [153Sm]-samarium maltolate was prepared using Sm-153 chloride (radiochemical purity >99.9%; ITLC and specific activity). The stability of the labeled compound was determined in the final solution up to 24h as well as the partition coefficient. Biodistribution studies of Sm-153 chloride, [153Sm]-samarium maltolate were carried out in wild-type rats comparing the critical organ uptakes. Comparative study for Sm3+ cation and the labeled compound was conducted up to 48 h, demonstrating a more rapid wash out for the labeled compound. The effective and biological half lives of 2.3 h and 2.46h were calculated for the complex. The data suggest the detoxification property of maltol formulation for lanthanide overdoses.

Naseri, Zohreh; Hakimi, Amir; Jalilian, Amir R.; Nemati Kharat, Ali; Bahrami-Samani, Ali; Ghannadi-Maragheh, Mohammad

2011-01-01

377

Titania-lanthanum phosphate photoactive and hydrophobic new generation catalyst  

NASA Astrophysics Data System (ADS)

Titania-lanthanum phosphate nanocomposites with multifunctional properties have been synthesized by aqueous sol-gel method. The precursor sols with varying TiO 2:LaPO 4 ratios were applied as thin coating on glass substrates in order to be transparent, hydrophobic, photocatalytically active coatings. The phase compositions of the composite powders were identified by powder X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HR-TEM). The anatase phase of TiO 2 in TiO 2-LaPO 4 composite precursors was found to be stable even on annealing at 800 C. The glass substrates, coated with TL1 (TiO 2-LaPO 4 composition with 1 mol% LaPO 4) and TL50 (composite precursor containing TiO 2 and LaPO 4 with molar ratio 1:1) sols and annealed at 400 C, produced contact angles of 74 and 92, respectively, though it is only 62 for pure TiO 2 coating. The glass substrates, coated with TL50 sol, produced surfaces with relatively high roughness and uneven morphology. The TL1 material, annealed at 800 C, has shown the highest UV photoactivity with an apparent rate constant, kapp=2410 -3 min -1, which is over five times higher than that observed with standard Hombikat UV 100 ( kapp=410 -3 min -1). The photoactivity combined with a moderate contact angle (85.3) shows that this material has a promise as an efficient self-cleaning precursor.

Jyothi, Chembolli K.; Jaimy, Kanakkanmavudi B.; Ghosh, Swapankumar; Sankar, Sasidharan; Smitha, V. S.; Warrier, K. G. K.

2011-07-01

378

Enantioselective DNA condensation induced by heptameric lanthanum helical supramolecular enantiomers.  

PubMed

DNA condensation induced by a pair of heptameric La(III) helical enantiomers M-[La7(S-L)6(CO3)(NO3)6(OCH3)(CH3OH)7]2CH3OH5H2O and P-[La7(R-L)6(CO3)(NO3)6(OCH3)(CH3OH)5(H2O)2]2CH3OH4H2O (M-La and P-La, L=2-(2-hydroxybenzylamino)-3-carbamoylpropanoic acid) has been investigated by UV/vis spectroscopy, fluorescence spectroscopy, CD spectroscopy, EMSA, RALS, DLS, and SEM. The enantiomers M-La and P-La could induce CT-DNA condensation at a low concentration as observed in UV/vis spectroscopy. DNA condensates possessed globular nanoparticles with nearly homogeneous sizes in solid state determined by SEM (ca. 250nm for M-La and ca. 200nm for P-La). The enantiomers bound to DNA through electrostatic attraction and hydrogen bond interactions in a major groove, and rapidly condensed free DNA into its compact state. DNA decompaction has been acquired by using EDTA as disassembly agent, and analyzed by UV/vis spectroscopy, CD spectroscopy and EMSA. Moreover, the enantiomers M-La and P-La displayed discernible discrimination in DNA interaction and DNA condensation, as well as DNA decondensation. Our study suggested that lanthanum(III) enantiomers M-La and P-La were efficient DNA packaging agents with potential applications in gene delivery. PMID:24915440

Bao, Fei-Fei; Xu, Xin-Xin; Zhou, Wen; Pang, Chun-Yan; Li, Zaijun; Gu, Zhi-Guo

2014-09-01

379

Influence of samaria doping on the resistance of ceria thin films and its implications to the planar oxygen sensing devices  

SciTech Connect

In order to evaluate and analyze the effect of samarium (Sm) doping on the resistance of cerium oxide, we have grown highly oriented samaria doped ceria (SDC) thin films on sapphire, Al2O3 (0001) substrates by using oxygen plasma-assisted molecular beam epitaxy (OPA-MBE). The film growth was monitored using reflection high-energy electron diffraction (RHEED) which shows two-dimensional growth throughout the deposition. Following growth, the thin films were characterized by X-ray photoelectron spectroscopy (XPS), high-resolution X-ray diffraction (HRXRD), and Rutherford backscattering spectrometry (RBS). XPS depth-profile shows Sm atoms are uniformly distributed in ceria lattice throughout the bulk of the film. The valence states of Ce and Sm in doped thin films are found to be Ce4+ and Sm3+, respectively. HRXRD shows the samaria doped ceria films on Al2O3(0001) exhibit (111) preferred orientation. Ion-channeling in RBS measurements confirms high quality of the thin films. The resistance of the samaria doped ceria films, obtained by two probe measurement capability under various oxygen pressure (1mTorr-100Torr) and temperatures (623K to 973K), is significantly lower than that of pure ceria under same conditions. The 6Sm% doped ceria film is the optimum composition for highest conductivity. This is attributed to the increased oxygen vacant sites in fluorite crystal structure of the epitaxial thin films which facilitate faster oxygen diffusion through hopping process.

Gupta, Shilpi; Kuchibhatla, Satyanarayana V N T; Engelhard, Mark H.; Shutthanandan, V.; Nachimuthu, Ponnusamy; Jiang, Weilin; Saraf, Laxmikant V.; Thevuthasan, Suntharampillai; Prasad, Shalini

2009-05-27

380

Comparison of Effects of Overload on Parameters and Performance of Samarium-Cobalt and Strontium-Ferrite Radially Oriented Permanent Magnet Brushless DC Motors  

Microsoft Academic Search

Effects of high momentary overloads on the samarium-cobalt and strontium-ferrite permanent magnets and the magnetic field in electronically commutated brushless dc machines, as well as their impact on the associated machine parameters were studied. The effect of overload on the machine parameters, and subsequently on the machine system performance was also investigated. This was accomplished through the combined use of

N. A. Demerdash; T. A. Nyamusa

1985-01-01

381

Synthesis, characterization and the thermal decomposition of lithium tris(oxalato)lanthanum(III)nonahydrate and sodium tris(oxalato)lanthanum(III)octahydrate  

Microsoft Academic Search

Lithium tris(oxalato)lanthanum(III)nonahydrate (Li3[La(III)(C2O4)39H2O(LOL)), and sodium tris(oxalato)lanthanum(III)octahydrate (Na3[La(III)(C2O4)3]8H2O (SOL)), have been synthesized and characterized by elemental analysis, IR spectral, and X-ray powder diffraction studies. Thermal studies (TG, DTG and DTA) in air showed that LOL becomes anhydrous around 198C, followed by decomposition to Li2CO3, La2O3 and LiLaO2 at ca. 542C, via the formation of several intermediates. Finally, around 950C, the oxide

N. Deb; S. D. Baruah; N. N. Dass

1999-01-01

382

Characteristics of lanthanum strontium chromite prepared by glycine nitrate process  

Microsoft Academic Search

La1?xSrxCrO3 (x=0, 0.1, 0.15, 0.2, and 0.3) (LSC) powder materials were synthesized by the glycine-nitrate-process. XRD analysis indicated that the powder exhibits a single phase with perovskite structure. The mean primary particle size of the powder was around 30 nm based on the morphology observation by TEM. The sinterability of the powder was improved as Sr doping content x increases

Yong-Jie Yang; Ting-Lian Wen; Hengyong Tu; Da-Qian Wang; Jianhua Yang

2000-01-01

383

Comparison of effects of overload on parameters and performance of samarium-cobalt and strontium-ferrite radially oriented permanent magnet brushless DC motors  

SciTech Connect

Effects of high momentary overloads on the samarium-cobalt and strontium-ferrite permanent magnets and the magnetic field in electronically commutated brushless dc machines, as well as their impact on the associated machine parameters were studied. The effect of overload on the machine parameters, and subsequently on the machine system performance was also investigated. This was accomplished through the combined use of finite element analysis of the magnetic field in such machines, perturbation of the magnetic energies to determine machine inductances, and dynamic simulation of the performance of brushless dc machines, when energized from voltage source inverters. These effects were investigated through application of the above methods to two equivalent 15 hp brushless dc motors, one of which was built with samarium-cobalt magnets, while the other was built with strontium- ferrite magnets. For momentary overloads as high as 4.5 p.u. magnet flux reductions of 29% and 42% of the no load flux were obtained in the samarium-cobalt and strontiumferrite machines, respectively. Corresponding reductions in the line to line armature inductances of 52% and 46% of the no load values were reported for the samarium-cobalt and strontium-ferrite cases, respectively. The overload affected the profiles and magnitudes of armature induced back emfs. Subsequently, the effects of overload on machine parameters were found to have significant impact on the performance of the machine systems, where findings indicate that the samarium-cobalt unit is more suited for higher overload duties than the strontium-ferrite machine.

Demerdash, N.A.; Nehl, T.W.; Nyamusa, T.A.

1985-08-01

384

Effects of ultraviolet excitation on the spectroscopic properties of Sm3+ and Tb3+ doped aluminophosphate glasses  

NASA Astrophysics Data System (ADS)

Li2O-BaO-Al2O3-La2O3-P2O5 glasses optically activated with rare earth ions with the 4f5, and 4f8 electronic configuration (Sm3+ and Tb3+, respectively) were analyzed by Raman spectroscopy, absorption, excitation photoluminescence, decay curves and temperature dependent photoluminescence. The spectroscopic characteristics of the as-prepared and heat treated samples at temperatures below and above Tg were studied as well as their room temperature photometric properties under ultraviolet excitation. All the doped glasses exhibit typical signatures of the lanthanides in their trivalent charge state. For the samarium doped glass heat treated at 250 C (samarium doped glasses have much lower luminance intensity (around 0.3 Cd/m2) when compared with the 6-7 Cd/m2 observed for the terbium doped ones.

Nico, C.; Graa, M. P. F.; Elisa, M.; Sava, B. A.; Monteiro, R. C. C.; Rino, L.; Monteiro, T.

2013-10-01

385

Structural characterization and properties of lanthanum film as chromate replacement for tinplate  

NASA Astrophysics Data System (ADS)

Sulfide-stain resistance of La-passivated, unpassivated and Cr-passivated tinplate was measured using a cysteine tarnish test. Corrosion behavior of these tinplates was investigated using electrochemical impedance spectroscopy (EIS) measurement. The morphology, composition and thickness of lanthanum film were studied by atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and X-ray fluorescence spectrometry (XRF), respectively. La-passivation treatment remarkably enhances sulfide-stain resistance of tinplate, and sulfide-stain resistance of La-passivated tinplate is slightly higher than that of Cr-passivated tinplate. La-passivation treatment also significantly improves corrosion protection property of tinplate. In contact with 3.5% NaCl solution, corrosion resistance of La-passivated tinplate is close to that of Cr-passivated tinplate, and in contact with 0.1 M citric-citrate buffer solution, corrosion resistance of La-passivated tinplate is higher than that of Cr-passivated tinplate. Lanthanum film is composed of spherical particles about 50-1000 nm in diameter, while most part of tinplate's surface is covered with the small particles about 50-200 nm. The film mainly consists of lanthanum and oxygen, which mainly exist as La 2O 3 and its hydrates such as La(OH) 3 and LaOOH. The amount of lanthanum in the film is about 0.0409 g/m 2.

Huang, Xingqiao; Li, Ning

2007-12-01

386

Spacecraft Charging Control by Thermal, Field Emission with Lanthanum-Hexaboride Emitters.  

National Technical Information Service (NTIS)

Thermal, field emitters of lanthanum (or perhaps cerium) hexaboride (LaB6) with temperature variability up to about 1500K are suggested for spacecraft charging control. Such emitters operate at much lower voltages with considerably more control and add pl...

J. F. Morris

1978-01-01

387

Effect of Lanthanum on Nodule Count and Nodularity of Ductile Iron  

Microsoft Academic Search

The present study aims at finding out the effect of the addition of a single rare earth element, that is, lanthanum on the nodularity and nodule count of ductile iron under controlled conditions. For this purpose, four melts with different compositions were made, using a 28 kg inductotherm medium frequency induction furnace. The temperature was carefully maintained between 1400 and

M. Ashraf Sheikh; Javed Iqbal

2007-01-01

388

Fixation of lanthanum cation by natural bentonite in nitric media. Part I : Equilibrium study.  

National Technical Information Service (NTIS)

The present work deals with the study of lanthanum fixation from aqueous solution by a mineral ion exchanger. The main purpose of the work consists in investigating the opportunity of the use of natural clays and miscellaneous other materials in the rare ...

A. Azzouz S. Chegrouche S. Telmoune

1993-01-01

389

Surface Phonon Dispersion in Graphite and its Modification Under Interaction with Lanthanum  

Microsoft Academic Search

Using high resolution electron energy loss spectroscopy (HREELS) the surface phonon dispersion of graphite has been determined in the Gamma K direction over the whole energy range and the whole Brillouin zone. By depositing lanthanum and annealing we prepared a GIC-like phase which grows on top of an intermediate carbide. The phonon dispersion of this phase shows the same modes

Susanne Siebentritt; Roland Pues; Karl-Heinz Rieder; Alexander M. Shikin

1998-01-01

390

Modification of the sulfur dioxide-iodine thermochemical hydrogen cycle with lanthanum sulfites and sulfates  

Microsoft Academic Search

Variable composition, insoluble dilanthanum oxide-sulfite-sulfate-hydrates were prepared by reaction of lanthanum dioxymonosulfate with aqueous sulfur dioxide. These compositions reacted with iodine to yield sulfate in the solid phase, and hydrogen iodide and water in the gas phase. The highest yield of hydrogen iodide measured was 32% at 660 K for a few seconds reaction time of iodine with a reactant

E. I. Onstott; M. G. Bowman; M. F. Michnovicz; C. M. Hollabaugh

1984-01-01

391

Laser-induced electron emission from tungsten, tantalum and lanthanum hexaboride using ruby and argon lasers  

Microsoft Academic Search

A description is given of experiments carried out using pulsed ruby and argon lasers to investigate the possibility of producing pulses of high electron emission current densities from tantalum, tungsten and lanthanum hexaboride cathodes heated by a focused laser beam. Current densities as high as 104 A cm?2 were recorded using the ruby laser but subsequently it was shown, using

L G Pittaway; J Smith; E D Fletcher; B W Nicholls

1968-01-01

392

Separation of carrier free 151,152Tb produced in 16O irradiated lanthanum oxide matrix.  

PubMed

Charged particle activation of natural La2O3 with approximately 78.5 MeV 16O results in the formation of carrier free 151,152Tb isotopes in the matrix. The liquid cation exchanger, HDEHP, has effectively been utilised as an extractant in the quantitative separation of the activation products from the bulk target matrix of lanthanum oxide. PMID:10581678

Nayak, D; Lahiri, S; Ramaswami, A; Manohar, S B; Das, N R

1999-12-01

393

Lanthanum Inhibition of 45Ca Efflux from the Squid Giant Axon  

Microsoft Academic Search

LETTVIN et al.1 predicted that lanthanum ions, because of their relatively small size and high charge density, should have a much greater electrostatic attraction for any negative calcium binding site than calcium ions themselves. This was borne out for the membranes of the barnacle muscle fibres2 and the lobster axon3. If negatively charged sites located in the membrane also serve

C. van Breemen

1970-01-01

394

Determination of zirconium, barium, lanthanum, aluminium, sodium, hafnium and fluorine in fluorozirconate glasses  

Microsoft Academic Search

A procedure is described for the determination of the cationic and anionic components in fluorozirconate glasses. Zirconium, barium, aluminium, lanthanum, sodium and hafnium were determined by inductively coupled plasma atomic emission spectrometry (ICP\\/AES) after dissolution of the sample with an acid mixture in a microwave oven. The fluorine content was evaluated with two different techniques, namely potentiometry with a fluoride

O. Abollino; E. Mentasti; C. Sarzanini; E. Modone; M. Braglia

1992-01-01

395

Spacecraft charging control by thermal, field emission with lanthanum-hexaboride emitters  

NASA Technical Reports Server (NTRS)

Thermal, field emitters of lanthanum (or perhaps cerium) hexaboride (LaB6) with temperature variability up to about 1500K are suggested for spacecraft charging control. Such emitters operate at much lower voltages with considerably more control and add plasma-diagnostic versatility. These gains should outweigh the additional complexity of providing heat for the LaB6 thermal, field emitter.

Morris, J. F.

1978-01-01

396

Propagation of surface plasmon polariton in the single interface of gallium lanthanum sulfide and silver  

NASA Astrophysics Data System (ADS)

The propagation characteristics of the surface-plasmon-polariton (SPP) mode in the single interface of silver (Ag) and gallium lanthanum sulfide (GLS) have been studied both analytically and numerically. The obtained numerical results show an excellent agreement with the analytical ones. The locations of the spatial resonance point along the direction of propagation were determined for the dielectric and the metal.

Sagor, Rakibul Hasan; Saber, Md. Ghulam; Amin, Md. Ruhul

2014-03-01

397

Phosphate starvation as an antimicrobial strategy: the controllable toxicity of lanthanum oxide nanoparticles.  

PubMed

Lanthanum oxide nanoparticles were utilized to scavenge phosphate from microbial growth media for the use of targeted nutrient starvation as an antimicrobial strategy. Only in phosphate poor environments a toxic effect was observed. The effect was shown on Escherichia coli, Staphylococcus carnosus, Penicillium roqueforti, and Chlorella vulgaris. PMID:22410707

Gerber, Lukas C; Moser, Nadine; Luechinger, Norman A; Stark, Wendelin J; Grass, Robert N

2012-04-21

398

A new cold cathode using pulsed laser deposited lanthanum monosulfide thin films  

Microsoft Academic Search

Using MEMS technology, an array of cold cathodes was fabricated by pulsed laser deposition (PLD) of chemically and thermally stable lanthanum monosulfide (LaS) thin film anode and cathode contacts. The latter were defined via etching and processing of two different pieces of (100) Si wafers separated via a highly resistive sputter deposited aluminum nitride (AlN) layer whose thickness was used

M. Samiee; K. Garre; M. Cahay; P. B. Kosel; S. Fairchild; J. W. Fraser; D. J. Lockwood

2007-01-01

399

Tem Study of Phase and Domain Structures of Lanthanum Aluminate Arising from Phase Transitions.  

National Technical Information Service (NTIS)

The phase and domain structures of Lanthanum Aluminate arising from phase transitions have been studied carefully after the recent finding that the space group of a well annealed crystal, determined by convergent-beam electron diffraction, is Fm(3 bar)c, ...

Y. Yang Y. C. Chang C. Y. Yang Y. Q. Zhou K. K. Fung

1992-01-01

400

Performance Evaluation of an Oxygen Sensor as a Function of the Samaria Doped Ceria Film Thickness  

SciTech Connect

The current demand in the automobile industry is in the control of air-fuel mixture in the combustion engine of automobiles. Oxygen partial pressure can be used as an input parameter for regulating or controlling systems in order to optimize the combustion process. Our goal is to identify and optimize the material system that would potentially function as the active sensing material for such a device that monitors oxygen partial pressure in these systems. We have used thin film samaria doped ceria (SDC) as the sensing material for the sensor operation, exploiting the fact that at high temperatures, oxygen vacancies generated due to samarium doping act as conducting medium for oxygen ions which hop through the vacancies from one side to the other contributing to an electrical signal. We have recently established that 6 atom % Sm doping in ceria films has optimum conductivity. Based on this observation, we have studied the variation in the overall conductivity of 6 atom % samaria doped ceria thin films as a function of thickness in the range of 50 nm to 300 nm at a fixed bias voltage of 2 volts. A direct proportionality in the increase in the overall conductivity is observed with the increase in sensing film thickness. For a range of oxygen pressure values from 1 mTorr to 100 Torr, a tolerable hysteresis error, good dynamic response and a response time of less than 10 seconds was observed

Sanghavi, Rahul P.; Nandasiri, Manjula I.; Kuchibhatla, Satyanarayana V N T; Nachimuthu, Ponnusamy; Engelhard, Mark H.; Shutthanandan, V.; Jiang, Weilin; Thevuthasan, Suntharampillai; Kayani, Asghar N.; Prasad, Shalini

2010-12-01

401

REFOS study: efficacy and safety of lanthanum carbonate in clinical practice in Spain.  

PubMed

Lanthanum carbonate is a powerful phosphate binder that has shown efficacy and safety in clinical trials for hyperphosphataemia management, although there are few data in regular clinical practice. The study's objective was to evaluate, in regular clinical practice, its efficacy and safety in patients on dialysis. We retrospectively collected data from 15 months of monitoring, corresponding to 3 months prior to the start of treatment with lanthanum carbonate until 12 months after the start. Results included values of serum calcium, phosphorus, alkaline phosphatase, iPTH, hepatic enzymes and haemogram, as well as the daily-prescribed dose of lanthanum carbonate, the concomitant medication, treatment compliance and adverse events. 647 patients were included of which 522 completed the study. Abandonment, for the most part, was due to gastrointestinal disorders (26%) and hypophosphatemia (19%). Serum phosphorus decreased from 6.41.7 mg/dl (start) to 4.91.4 mg/dl (12 months) (P<.001). At the end of the monitoring period, 47% were within the desired phosphorus range (3.5-5mg/dl). There were no significant variations in the remaining parameters. Initial dose of lanthanum carbonate: 1900 mg/day; and end dose: 2300 mg/day. The variables independently associated with phosphataemia were baseline serum phosphorus and treatment compliance. In relation to safety, we observed 238 slight or moderate adverse effects in 117 patients, with 88% linked to gastrointestinal abnormalities. In conclusion, lanthanum carbonate reduces the serum phosphorus values in patients on dialysis with a good safety profile and acceptable adherence to that profile, with gastrointestinal disorders being the most frequent adverse effect. PMID:24849057

Torregrosa, Jos-Vicente; Gonzlez-Parra, Emilio; Gonzlez, M Teresa; Cannata-Anda, Jorge

2014-05-21

402

Self-magnetic compensation and shifted hysteresis loops in ferromagnetic samarium systems  

NASA Astrophysics Data System (ADS)

For Sm3+ ions in a vast majority of metallic systems, the following interesting scenario has been conjured up for long, namely, a magnetic lattice of tiny self- (spin-orbital) compensated 4f -moments exchange coupled (and phase reversed) to the polarization in the conduction band. We report here the identification of a self-compensation behavior in a variety of ferromagnetic Sm intermetallics via the fingerprint of a shift in the magnetic hysteresis (M-H) loop from the origin. Such an attribute, designated as exchange bias in the context of ferromagnetic/antiferromagnetic multilayers, accords these compounds a potential for niche applications in spintronics. We also present results on magnetic compensation behavior on small Gd doping (2.5at.%) in one of the Sm ferromagnets (viz., SmCu4Pd ). The doped system responds like a pseudoferrimagnet and it displays a characteristic left-shifted linear M-H plot for an antiferromagnet.

Kulkarni, P. D.; Dhar, S. K.; Provino, A.; Manfrinetti, P.; Grover, A. K.

2010-10-01

403

Beam-hardening artifacts on computed tomography images caused by lanthanum carbonate hydrate in a patient on dialysis.  

PubMed

Lanthanum carbonate hydrate is a nonaluminum, noncalcium phosphate binder containing lanthanum (La). It is effective in decreasing the serum phosphate level in patients on dialysis. Because the atomic number of the La contained in lanthanum carbonate hydrate is relatively high, at 57, this agent may cause strong artifacts on computed tomography (CT) images, which may be mistakenly interpreted as foreign bodies. We recently performed CT examination of a patient on Fosrenol chewable tablets (i.e., lanthanum carbonate hydrate). The CT images were difficult to evaluate because of strong beam hardening artifacts, and differentiation from foreign body aspiration was required. We report here our experience and a discussion of the characteristics of this artifact. PMID:20512553

Hayashi, Hiromitsu; Machida, Minoru; Sekine, Tetsuro; Yamaguchi, Hidenori; Kiriyama, Tomonari; Kumita, Shin-Ichiro

2010-05-01

404

Spin-flop transition in samarium metal investigated by capacitance dilatometry in a steady magnetic field of 45T  

NASA Astrophysics Data System (ADS)

The longitudinal and transversal forced magnetostrictions of a single crystal of samarium metal have been investigated in a static magnetic field up to 45T . The data show pronounced features of a spin-flop transition initiating at an applied field of about 30T . The measured forced magnetostriction is about 1 order of magnitude smaller than the spontaneous magnetostriction. Based on a model calculation of the magnetic phase diagram these features have been interpreted within the exchange striction model. The moments of the quasicubic Sm sites enter a spin-flop phase at about 30T and ferromagnetic saturation is predicted at 60T . Similarly the model predicts a spin-flop phase for the hexagonal Sm sites at 140T and ferromagnetic saturation at 390T .

Rotter, M.; Barcza, A.; Doerr, M.; Le, M. D.; Brooks, J.; Jobiliong, E.; Perenboom, J.

2007-10-01

405

Concentration dependence of the structure of aqueous solutions of samarium trichloride according to X-ray diffraction  

NASA Astrophysics Data System (ADS)

Aqueous solutions of samarium chloride in a wide range of concentration under ambient conditions are studied by X-ray diffraction analysis. The small-angle peaks in experimental scattering intensity curves are interpreted. It is shown that highly concentrated solutions are characterized by a unique structure that differs heavily from the structure of dilute systems. It is found that small-angle peaks also appear in the intensity curves of dilute solutions, indicating that the so-called long-range order is preserved in these solutions. It is revealed that the contributions to the total scattering pattern that govern the appearance of prepeaks are interionic interactions of different types (e.g., cation-cation, anion-cation, and anion-anion interactions) in concentrated systems and the distances between the cations in dilute solutions.

Smirnov, P. R.; Grechin, O. V.; Trostin, V. N.

2013-05-01

406

[Determination of non-rare earth impurities including Cu, Fe, Ca and Ni in samarium oxide by ICP-AES].  

PubMed

The direct determination of non-rare earth trace impurities including Cu, Fe, Ca and Ni in high purity Samarium oxide by means of ICP-AES is presented in this paper. By using orthogonality experimentation, we studied main factors of influential determination and selected compromise condition of simultaneous determination of Cu, Fe, Ca and Ni. Influence of matrix concentration was discussed. We used the method of matrix match and subtraction background. For the sample solution containing 5mg/mL of Sm2O3 the determination limits were 0. 0003% for Cu, 0.003% for Ni, 0.001% for Ca and Fe, respectively. The relative standard deviation was in the range of 2.6-9.2%. The recovery ratio of these elements was in the range of 90-110%. The method is simple and rapid. It was fit to productive control analysis and determination of production. PMID:15810337

Wang, J; Mo, L; Zhou, Z

1998-02-01

407

The use of 185MBq and 740MBq of 153-samarium hydroxyapatite for knee synovectomy in haemophilia.  

PubMed

The penetration of beta energy of 153-samarium ((153) Sm) (0.8MeV) is not only appropriate for synovectomy of median articulations but is possible to improve the radiobiological effect using increased activities. The aim of this study was to assess the effectiveness of 185MBq and 740MBq of 153-samarium hydroxyapatite ((153) Sm-HA) in knees of haemophilic patients. Thirty-one patients - 36 knees, 30 males, were divided into two groups without coinjection of corticosteroid: A - 14 patients (17 knees) treated with intra-articular dose of 185MBq of (153) Sm-HA, average age 23years; B - 17 patients (19 knees) with 740MBq of (153) Sm-HA, average age 21.3years. The evaluation before and after 1year of synovectomy used the following criteria: reduction in the number of haemarthroses and use of the coagulation factor and improvement in articular motility. Adverse-effects occurrence was considered too. Early and late scintigraphic studies were performed after synoviorthesis and no joint immobilization was recommended. The reduction in haemarthrosis and use of coagulation factor were: group 1 - 31.3% and 25%; group 2 - 81.5% and 79% with P<0.001 respectively; no significant improvement in knees motility was noted for both groups. Four cases of mild reactional synovitis were observed in each group. The scintigraphic control showed homogenous distribution of the radiopharmaceuticals with no articular escape; the material was considered safe by its permanence in the articulation. We have significant improvement in the synovectomy of haemophilic knees with 740MBq of (153) Sm-HA; the less penetration of its beta radiation was compensated by the increased biological effect with the higher used activity. PMID:24330418

Calegaro, J U M; Machado, J; Furtado, R G; de Almeida, J S C; de Vasconcelos, A V P; de Barboza, M F; de Paula, A P

2014-05-01

408

A multicenter study on the effects of lanthanum carbonate (Fosrenol) and calcium carbonate on renal bone disease in dialysis patients  

Microsoft Academic Search

A multicenter study on the affects of lanthanum carbonate (Fosrenol) and calcium carbonate on renal bone disease in dialysis patients.BackgroundLanthanum carbonate (LC) (Fosrenol) is a novel new treatment for hyperphosphatemia. In this phase III, open-label study, we compared the effects of LC and calcium carbonate (CC) on the evolution of renal osteodystrophy (ROD) in dialysis patients.MethodsNinety-eight patients were randomized to

Patrick C. D'Haese; Goce B. Spasovski; Aleksander Sikole; Alastair Hutchison; Tony J. Freemont; Sylvie Sulkova; Charles Swanepoel; Svetlana Pejanovic; Llubica Djukanovic; Alessandro Balducci; Giorgio Coen; Waldysaw Sulowicz; Anibal Ferreira; Armando Torres; Slobodan Curic; Milan Popovic; Nada Dimkovic; Marc E. De Broe

2003-01-01

409

Phase equilibrium and preparation, crystallization and viscous sintering of glass in the alumina-silica-lanthanum phosphate system  

Microsoft Academic Search

The phase equilibrium, viscosity of melt-quenched glasses, and processing of sol-gel glasses of the alumina-silica-lanthanum phosphate system were studied. These investigations were directed towards serving the objective of synthesizing nano-structured ceramic-matrix-composites via controlled crystallization of glass precursors. The thermal stability, phase equilibrium, and liquidus temperatures of the alumina- and mullite-lanthanum phosphate systems are determined. An iridium wire heater was constructed

Feng He

2009-01-01

410

The effect of lanthanum on the fabrication of ZrB 2ZrC composites by spark plasma sintering  

Microsoft Academic Search

The effect of the addition of the rare earth element, lanthanum, on the sintering characteristics of ZrB2ZrC composites has been analyzed during a spark plasma sintering (SPS) process. Microscopic observation confirmed that lanthanum accelerated mass transport by the formation of the liquid phase between the particles induced by the spark plasma in the initial stage of the SPS process, and

Kyoung Hun Kim; Kwang Bo Shim

2003-01-01

411

Cyan-white-red luminescence from europium doped Al2O3-La2O3-SiO2 glasses.  

PubMed

Aluminum-lanthanum-silicate glasses with different Eu doping concentration have been synthesized by conventional melt-quenching method at 1680 degrees C in reductive atmosphere. Under 395nm excitation, samples with low Eu doping concentration show mainly the cyan broad emission at 460nm due to 4f(6)5d(1)-4f(7) transition of Eu(2+); and the samples with higher Eu doping concentration show mainly some narrow emissions with maximum at 616nm due to (5)D(0)-(7)F(j) (J=0, 1, 2, 3, 4) transitions of Eu(3+). Cyan-white-red tunable luminescence under 395nm excitation has been obtained by changing the Eu doping concentration. PMID:18545375

Yang, Hucheng; Lakshminarayana, G; Zhou, Shifeng; Teng, Yu; Qiu, Jianrong

2008-04-28

412

Ca2+-Doped CeBr3 Scintillating Materials  

SciTech Connect

Despite the outstanding scintillation performance characteristics of cerium tribromide (CeBr3) and cerium-activated lanthanum tribromide, their commercial availability and application are limited due to the difficulties of growing large, crack-free single crystals from these fragile materials. This investigation employed aliovalent doping to increase crystal strength while maintaining the optical properties of the crystal. One divalent dopant (Ca2+) was used as a dopant to strengthen CeBr3 without negatively impacting scintillation performance. Ingots containing nominal concentrations of 1.9% of the Ca2+ dopant were grown. Preliminary scintillation measurements are presented for this aliovalently doped scintillator. Ca2+-doped CeBr3 exhibited little or no change in the peak fluorescence emission for 371 nm optical excitation for CeBr3. The structural, electronic, and optical properties of CeBr3 crystals were studied using the density functional theory within the generalized gradient approximation. The calculated lattice parameters are in good agreement with the experimental data. The energy band structures and density of states were obtained. The optical properties of CeBr3, including the dielectric function, were calculated.

Guss, Paul [NSTec; Foster, Michael E. [SNL; Wong, Bryan M. [SNL; Doty, F. Patrick [SNL; Shah, Kanai [RMD; Squillante, Michael R. [RMD; Shirwadkar, Urmila [RMD; Hawrami, Rastgo [RMD; Tower, Josh [RMD; Yuan, Ding [NSTec

2014-01-01

413

Cytotoxic activity of new lanthanum (III) complexes of bis-coumarins.  

PubMed

Complexes of lanthanum (III) with bis-coumarins: bis(4-hydroxy-2-oxo-2H-chromen-3-yl)-piridin-2-yl-methane; bis(4-hydroxy-2-oxo-2H-chromen-3-yl)-piridin-3-yl-methane and bis(4-hydroxy-2-oxo-2H-chromen-3-yl)-piridin-4-yl-methane were synthesized by reaction of lanthanum (III) salt and the ligands, in amounts equal to metal/ligand molar ratio of 1:2. The complexes were prepared by adding an aqueous solution of lanthanum (III) salt to an aqueous solution of the ligand subsequently raising the pH of the mixture gradually to ca. 5.0 by adding dilute solution of sodium hydroxide. The lanthanum (III) complexes with bis-coumarins were characterized by different physicochemical methods-elemental analysis, IR-, (1)H- and 13C-NMR spectroscopies and mass-spectral data. The spectral data of lanthanum (III) complexes were interpreted on the basis of comparison with the spectra of the free ligands. This analysis showed that in the La (III) complexes the ligands coordinated to the metal ion through both deprotonated hydroxyl groups. On the basis of the nu(C=O) red shift observed, participation of the carbonyl groups in the coordination to the metal ion was also suggested. Cytotoxic screening by MTT assay was carried out. In the present study, we performed comparative evaluation of the cytotoxic effects of the three newly synthesized lanthanum complexes against the acute myeloid leukemia derived HL-60 and the chronic myeloid leukemia (CML)-derived BV-173. In addition the cytotoxic effects of La (III) complex with bis(4-hydroxy-2-oxo-2H-chromen-3-yl)-piridin-2-yl-methane were evaluated on the SKW-3 cells. In order to elucidate some of the mechanistic aspects of the observed cytotoxic effects we evaluated the ability of this complex to trigger programmed cell death (apoptosis by means of agarose gel electrophoretic analysis of DNA), isolated from the cytosolic fraction of treated SKW-3 cells. In addition, microscopic morphological evaluation of the treated cells was carried out in order to establish morphological features indicative for programmed cell death. PMID:15922838

Kostova, Irena; Momekov, Georgi; Zaharieva, Maya; Karaivanova, Margarita

2005-06-01

414

Separation of lanthanum(III) and neodymium(III) by extraction with tributyl phosphate in the presence of a solid phase  

SciTech Connect

Lanthanum(III) and neodymium(III) extraction from nitric acid solutions with tributyl phosphate in the presence of a solid phase has been studied. The coefficient of neodymium nitrate distribution ..cap alpha.. in presence of solid phase has been found to increase with decrease of its concentration in the original solution and increase of lanthanum nitrate concentration. Separation is most pronounced in the neodymium nitrate microregion. A procedure has been proposed for quantitative neodymium extraction form lanthanum nitrate solutions with a neodymium and lanthanum separation coefficient higher than 25.

Korotkevich, I.B.; Kolesnikov, A.A.; Bomshtein, V.E.; Shikhaleeva, N.N.

1987-01-01

415

A Comparative Study of Samarium153-Ethylenediaminetetramethylene Phosphonic Acid with Pamidronate Disodium in the Treatment of Patients with Painful Metastatic Bone Cancer  

Microsoft Academic Search

Objective: To assess the therapeutic efficacy and toxicity of samarium-153-ethylenediaminetetramethylene phosphonic acid (153Sm-EDTMP) and pamidronate disodium in patients with painful metastatic bone cancer. Subjects and Methods: Eighteen patients with histopathologically confirmed malignancy and multifocal bone metastases were randomized into two equal groups of 9 patients each. Group A was treated with 153Sm-EDTMP, while group B was treated with pamidronate disodium.

Rong Fu Wang; Chun Li Zhang; Shou Li Zhu; Mei Zhu

2003-01-01

416

Structure of human uridine-cytidine kinase 2 determined by SIRAS using a rotating-anode X-ray generator and a single samarium derivative.  

PubMed

Uridine-cytidine nucleoside kinase 2 (UCK2) is the rate-limiting enzyme in the pyrimidine-nucleotide salvage pathway. UCK2 catalyzes the phosphorylation of the natural ribonucleosides cytidine and uridine to cytidine 5'-monophosphate (CMP) and uridine 5'-monophosphate (UMP), respectively, and activates several important frontline antimetabolite drugs. The present contribution reports the rapid crystal structure determination of human UCK2 complexed with a magnesium ion and the reaction products adenosine 5'-diphosphate (ADP) and CMP. Diffraction data were collected on a copper rotating-anode X-ray generator from one native UCK2 crystal and a single samarium-derivative crystal. Utilizing the relatively high anomalous signal from the samarium derivative at the Cu Kalpha wavelength, the structure was determined by single isomorphous replacement and single anomalous signal (SIRAS) phasing techniques. Two of the four major samarium sites are located in the active sites of the two UCK2 molecules that form the asymmetric unit and appear to displace the magnesium ions present in the native crystals. The crystal structures of UCK2 alone and in complex with various ligands have recently been determined using traditional multiple isomorphous replacement (MIR) phasing techniques and data from three heavy-atom derivatives. The reported structures validate our independently determined structure. Of more than 1000 kinase crystal structure entries in the Protein Data Bank, less than 1% of them have been determined by SIRAS. For the published kinase crystal structures determined by SIRAS, all data were reportedly collected at various synchrotron-radiation facilities. This study demonstrates that diffraction data collected from a single samarium derivative using Cu Kalpha radiation provides sufficient phasing power to determine a novel macromolecular crystal structure. PMID:15735337

Appleby, Todd C; Larson, Gary; Cheney, I Wayne; Walker, Heli; Wu, Jim Z; Zhong, Weidong; Hong, Zhi; Yao, Nanhua

2005-03-01

417

Multicentre trial on the efficacy and toxicity of single-dose samarium-153-ethylene diamine tetramethylene phosphonate as a palliative treatment for painful skeletal metastases in China  

Microsoft Academic Search

. A multicentre trial was organized in China as part of an international coordinated research project to study the efficacy\\u000a and toxicity of single-dose samarium-153 ethylene diamine tetramethylene phosphonate (EDTMP) as a palliative treatment for\\u000a painful skeletal metastases. One hundred and five patients with painful bone metastases from various primaries were treated\\u000a with 153Sm-EDTMP at a dose of 37MBq\\/kg(group I)

Jia-he Tian; Jin-ming Zhang; Qing-tian Hou; Qiao-hong Oyang; Jian-min Wang; Zhao-sheng Luan; Ling Chuan; Yi-jie He

1999-01-01

418

Lanthanum(III)-catalyzed degradation of cellulose at 250 degrees C.  

PubMed

Lanthanum(III) chloride was found to effectively catalyze the degradation of cellulose in water at 250 degrees C. The degradation conversion of cellulose in the presence of a catalytic amount of lanthanum chloride reached 80.3% after 180 s, which corresponded to the turnover number of 83, whereas the reaction did scarcely proceed in the absence of the catalyst. The degradation products were separately quantified as water-soluble (WS), methanol-soluble (MS), methanol-insoluble (MI), and gaseous (G) products. The HPLC and GC analyses revealed that the WS materials are mainly composed of 5-hydroxymethyl-2-furaldehyde (HMF), D-glucose, and levulinic acid. Cellobiose, the disaccharide component of cellulose, was scarcely detected during the reaction. PMID:11800491

Seri, Kei-ichi; Sakaki, Tsuyoshi; Shibata, Masao; Inoue, Yoshihisa; Ishida, Hitoshi

2002-02-01

419

High-efficiency, low-temperature cesium diodes with lanthanum-hexaboride electrodes  

NASA Technical Reports Server (NTRS)

Lanthanum-hexaboride electrodes in 1700 K cesium diodes may triple power outputs compared with those demonstrated for nuclear thermionic space applications. Still greater relative gains seem possible for emitters below 1700 K. Further improvements in cesium-diode performance should result from the lower collector temperatures allowed for earth and low-power-space duties. Decreased temperatures will lessen thermal-transport losses that attend thermionic-conversion mechanisms. Such advantages will add to those from collector-Carnot and electrode effects. If plasma ignition difficulties impede diode temperature reductions, recycling small fractions of the output power could provide ionization. So high-efficiency, low-temperature cesium diodes with lanthanum-hexaboride electrodes appear feasible.

Morris, J. F.

1974-01-01

420

Simultaneous determination of lanthanum and europium by higher order derivative molecular absorption spectrophotometry  

SciTech Connect

The identical properties of rare earth elements towards reaction with various chromogenic reagents in molecular absorption spectrophotometry (MAS) leads to a requirement for the development of procedures with greater selectivity. One way of solving this problem is by utilizing derivative spectroscopy, where the composite spectrum is transformed to the second or higher order derivative in wavelength domain. This paper reports the utilization of higher order derivative spectrophotometry for the simultaneous determination of lanthanum and europium. The developed procedure is simple, reliable and allows the determination of as low as 100 and 10 ppb of lanthanum and europium, respectively. Similar methodology can be adopted for the simultaneous determination of two or more of any closely related analytes by proper choice of derivative order in addition to selecting a suitable chromogenic reagent, pH and masking agents.

Rao, T.P.; Sukumar, R.

1986-01-01

421

History of Doping and Doping Control  

Microsoft Academic Search

\\u000a Although attempts to enhance athletic performance are probably much older, the word doping was first mentioned in 1889 in\\u000a an English dictionary. It described originally a mixed remedy containing opium, which was used to dope horses. Dope was\\u000a a spirit prepared from the residues of grapes, which Zulu warriors used as a stimulant at fights and religious procedures\\u000a and which

Rudhard Klaus Mller

422

Oxidation of toluene on lanthanum cobaltite perovskite (LaCoO 3 ) catalyst  

Microsoft Academic Search

Vapor phase oxidation of toluene to benzaldehyde has been studied on lanthanum cobaltite, LaCoO3, with a perovskite structure. Experimental data were obtained in the temperature range 350 to 600C and contact time 0.2 to 2 h. The overall kinetic analysis indicated the oxidation of toluene to benzaldehyde to be first order, with a frequency factor of 0.62 h?1 and an

K. L. Madhok

1986-01-01

423

Sol-Gel Route to Porous Lanthanum Cobaltite (LaCoO3) Thin Films  

Microsoft Academic Search

Sol- gel-derived LaCoO3 thin films were deposited on yttria- stabilized zirconia (YSZ) substrates from a lanthanum iso- propoxide- cobalt acetate (with 2-methoxyethanol) precursor solution. A chelating agent (2-ethylacetoacetate) and polyeth- ylene glycol (PEG) were used to modify the above-mentioned precursor solution. The La-Co precursor solution was suffi- ciently viscous, and transparent LaCoO3 gel films were pre- pared successfully using a

Hae Jin Hwang; Jooho Moon; Masanobu Awano; Kunihiko Maeda

2004-01-01

424

Synthesis of lanthanum cobaltite (LaCoO 3) by the polymerizable complex route  

Microsoft Academic Search

We report a simple technique for preparation of lanthanum cobaltite LaCoO3 powders by the polymerizable complex (PC) method based on the Pechini-type reaction route. A mixed solution of citric acid (CA) and ethylene glycol (EG) with La and Co ions was polymerized. The final materials obtained by the polyesterification between CA and EG were compared with those obtained by the

Monica Popa; Masato Kakihana

2002-01-01

425

Intermediate temperature solid oxide fuel cell based on lanthanum gallate electrolyte  

Microsoft Academic Search

The Kansai Electric Power Co. Inc. (KEPCO) and Mitsubishi Materials Corporation (MMC) have been developing intermediate temperature solid oxide fuel cells (IT-SOFCs) which are operable at a temperature range between 600 and 800C. There are some significant features in IT-SOFC of KEPCOMMC: (1) highly conductive lanthanum gallate-based oxide is adopted as an electrolyte to realize high-performance disk-type electrolyte-supported cells; (2)

Toru Inagaki; Futoshi Nishiwaki; Satoru Yamasaki; Taner Akbay; Kei Hosoi

2008-01-01

426

Single crystal growth and characterization of lanthanumneodymium oxalate octahydrate  

Microsoft Academic Search

Single crystals of mixed lanthanumneodymium oxalates are grown by gel diffusion method using agar gel as a medium of growth. The crystals grow in the agar gel with hexagonal morphology having (001), (110) and (010) as habit faces. Single crystal X-ray diffraction results show that the crystals belong to monoclinic system with cell parameters; a=10.344(2), b=9.643(6), c=11.721(2), ?=118.7 (2) ,

Basharat Want

2011-01-01

427

Room temperature synthesis of high temperature stable lanthanum phosphateyttria nano composite  

SciTech Connect

Graphical abstract: A facile aqueous solgel route involving precipitationpeptization mechanism followed by electrostatic stabilization is used for synthesizing nanocrystalline composite containing lanthanum phosphate and yttria. Highlights: ? A novel lanthanum phosphateY{sub 2}O{sub 3} nano composite is synthesized for the first time using a modified facile sol gel process. ? The composite becomes crystalline at 600 C and X-ray diffraction pattern is indexed for monoclinic LaPO{sub 4} and cubic yttria. ? The composite synthesized was tested up to 1300 C and no reaction between the phases of the constituents is observed with the morphologies of the phases being retained. -- Abstract: A facile aqueous solgel route involving precipitationpeptization mechanism followed by electrostatic stabilization is used for synthesizing nanocrystalline composite containing lanthanum phosphate and yttria. Lanthanum phosphate (80 wt%)yttria (20 wt%) nano composite (LaPO{sub 4}20%Y{sub 2}O{sub 3}), has an average particle size of ?70 nm after heat treatment of precursor at 600 C. TGDTA analysis reveals that stable phase of the composite is formed on heating the precursor at 600 C. The TEM images of the composite show rod shape morphology of LaPO{sub 4} in which yttria is acquiring near spherical shape. Phase identification of the composite as well as the phase stability up to 1300 C was carried out using X-ray diffraction technique. With the phases being stable at higher temperatures, the composite synthesized should be a potential material for high temperature applications like thermal barrier coatings and metal melting applications.

Sankar, Sasidharan; Raj, Athira N.; Jyothi, C.K. [Material Sciences and Technology Division, National Institute for Interdisciplinary Science and Technology, Council of Scientific and Industrial Research, Thiruvananthapuram 695019 (India)] [Material Sciences and Technology Division, National Institute for Interdisciplinary Science and Technology, Council of Scientific and Industrial Research, Thiruvananthapuram 695019 (India); Warrier, K.G.K., E-mail: wwarrierkgk@yahoo.co.in [Material Sciences and Technology Division, National Institute for Interdisciplinary Science and Technology, Council of Scientific and Industrial Research, Thiruvananthapuram 695019 (India)] [Material Sciences and Technology Division, National Institute for Interdisciplinary Science and Technology, Council of Scientific and Industrial Research, Thiruvananthapuram 695019 (India); Padmanabhan, P.V.A. [Bhabha Atomic Research Centre, Mumbai 400085 (India)] [Bhabha Atomic Research Centre, Mumbai 400085 (India)

2012-07-15

428

Lanthanum carbonate decreases PTH gene expression with no hepatotoxicity in uraemic rats  

Microsoft Academic Search

Background. Lanthanum (La) carbonate is an effective phosphate-binder, used to reverse hyperphosphatae- mia due to chronic kidney disease. Some recent studies in rodents have cast safety uncertainties. The aims of this study were to examine the effects of La on parathyroid hormone (PTH) gene expression and hepatic toxicity. Methods. Uraemia was induced in rats by a 0.3% adenine-containing diet for

Iddo Z. Ben-Dov; Orit Pappo; Miri Sklair-Levy; Hillel Galitzer; Yaron Ilan; Tally Naveh-Many; Justin Silver

2007-01-01

429

Atomization of yttrium, lanthanum, and neodymium in acetylene-nitrous oxide flame  

SciTech Connect

The degree of atomization of the element is the principal factor defining the sensitivity of the atomic-absorption determination. An attempt is made in this paper to establish its values for yttrium, lanthanum, and neodymium by the method of linear absorption, and also to estimate the effect of the degree of dissociation of the compounds, the degree of ionization, and the relative population of the ground energy level of the atoms on the efficiency of atomization of these elements.

Osipova, V.A.; Gorlova, M.N.; Kuzyakov, Y.Y.; Semenenko, K.A.

1985-10-01

430

Switching to lanthanum carbonate monotherapy provides effective phosphate control with a low tablet burden  

PubMed Central

Background. Despite recognized risks associated with hyperphosphataemia in patients with chronic kidney disease (CKD) Stage 5 on dialysis, the achievement of target levels of serum phosphate is poor. It is likely that this is partly due to poor adherence by patients to their phosphate-binder treatment regimens, which often comprise large daily tablet burdens. Methods. In this multicentre, open-label trial, patients on a stable dialysis regimen were screened while receiving phosphate-binder therapy, then entered into a washout phase. Patients with serum phosphate > 1.78 mmol/L after washout entered into the main 12-week treatment phase (N = 367), during which they were treated to target [Kidney Disease Outcomes Quality Initiative (K/DOQI)]: 1.131.78 mmol/L; 3.55.5 mg/dL) with lanthanum carbonate monotherapy. Efficacy variables included serum phosphate levels and the percentage of patients with serum phosphate control. Safety and tolerability assessments were also conducted. Results. Mean serum phosphate levels were significantly reduced following 12 weeks of lanthanum carbonate monotherapy versus previous phosphate-binder therapy. The mean number of phosphate-binder tablets being taken per day at screening was 7.6, but during treatment with lanthanum carbonate, most patients were taking doses of up to 3000 mg/day, achievable with 3 1000 mg tablets per day (maximum of 6). Conclusion. These findings suggest that lanthanum carbonate monotherapy offers effective control of serum phosphate and, due to a low tablet burden, may help to simplify the management of hyperphosphataemia in patients with CKD Stage 5.

Hutchison, Alastair J.; Laville, Maurice

2008-01-01

431

Magnetic properties of lanthanum orthoferrite fine powders prepared by different chemical routes  

Microsoft Academic Search

Fine powders of lanthanum iron oxide, LaFeO3, have been prepared by solid state reaction as well as sol-gel synthesis and nebulized spray pyrolysis. Structures, morphologies\\u000a and magnetic susceptibility measurements of these powders have been examined. The powders prepared by all the three low-temperature\\u000a routes contain nearly spherical particles with an average diameter of 40 nm. These samples show a lower

Benedict Ita; P. Murugavel; V. Ponnambalam; A. R. Raju

2003-01-01

432

Fabrication of polycrystalline lanthanum manganite (LaMnO 3) nanofibers by electrospinning  

Microsoft Academic Search

Lanthanum manganite (LaMnO3) nanofibers were successfully fabricated by electrospinning utilizing solgel precursors. Polycrystalline cubic-perovskite structure LaMnO3 fibers of 50100nm were obtained by calcination of the inorganic\\/organic hybrid fibers at 600C for 1h. The XRD results showed that the grain size of the fibers increased significantly with the increase of calcinations temperature. The average diameter of crystal grains was 17nm after

Xianfeng Zhou; Yong Zhao; Xinyu Cao; Yanfeng Xue; Dapeng Xu; Lei Jiang; Wenhui Su

2008-01-01

433

Effect of chloride incorporation on the crystallization of zirconium-barium-lanthanum-aluminum fluoride glass  

NASA Technical Reports Server (NTRS)

One aspect of the influence of preparation procedure on the crystallization behavior of a zirconium-barium-lanthanum-aluminum fluoride glass was studied. The crystallization pattern of this glass may be affected by the chlorine concentration within it. In particular, when such glasses are heated at low temperatures, the alpha-Ba-Zr-F6 crystalline phase forms only in those glasses which contain chloride.

Neilson, G. F.; Smith, G. L.; Weinberg, M. C.

1985-01-01

434

Ferroelectric properties of alkoxy-derived lanthanum-modified bismuth titanate thin films  

Microsoft Academic Search

Lanthanum-modified bismuth titanate (BLT) thin films were fabricated by sol-gel processing with alkoxide solutions, and their physical and electrical properties were investigated as a first step to develop FeRAM devices for use in automobiles. Alkoxide solutions with compositions of Bi:La:Ti = 3.25:0.75:3 and 3.5:0.5:3 were prepared, and applied to formation of a Pt\\/BLT\\/Pt\\/Ti capacitor structure on oxidized Si wafers by

Y. Kageyama; T. Yoshida; Y. Mitsushima; K. Suzuki; K. Kato

2001-01-01

435

Lithium lanthanum titanate as an electrolyte for novel lithium ion battery systems  

Microsoft Academic Search

Solid electrolytes with high lithium conductivity may serve as useful components for enabling novel lithium ion battery system design. This work demonstrates the integration of lithium lanthanum titanate (Li0.29La0.57TiO3) into a battery system separating electrodes based on liquid electrolyte. Specifically, binder free electrodes based on graphite and LiCoO2 were tested against lithium metal in liquid electrolyte with an intermediate solid

Li Sun; Ke Sun; Shen Dillon

2011-01-01

436

Design of a lanthanum bromide detector for time-of-flight PET  

Microsoft Academic Search

Recent improvements in the growth and packaging of lanthanum bromide (LaBr3), in addition to its superb intrinsic properties of high light output, excellent energy resolution, and fast decay time, make it a viable detection material for a positron emission tomography (PET) scanner based on time-of-flight (TOF). We have utilized theoretical simulations and experimental measurements to investigate the design and performance

A. Kuhn; S. Surti; J. S. Karp; P. S. Raby; K. S. Shah; A. E. Perkins; G. Muehllehner

2004-01-01

437

Lanthanum Chromite Based Catalysts for Oxidation of Methane Directly on SOFC Anodes  

Microsoft Academic Search

Catalytic properties of substituted lanthanum chromites were investigated for their use as anode materials for direct methane oxidation in solid oxide fuel cell (SOFC) anode materials. Different reaction mixtures were chosen to simulate the various SOFC operating conditions: partial oxidation, CO2 reforming by recycling, and H2O reforming. All experiments were performed in methane-rich atmospheres. Alkaline earth elements such as Ca,

Joseph Sfeir; Philippe A Buffat; Pedro Mckli; Nicolas Xanthopoulos; Ruben Vasquez; Hans Joerg Mathieu; Jan Van herle; K Ravindranathan Thampi

2001-01-01

438

Single crystal growth and characterization of lanthanum-neodymium oxalate octahydrate  

NASA Astrophysics Data System (ADS)

Single crystals of mixed lanthanum-neodymium oxalates are grown by gel diffusion method using agar gel as a medium of growth. The crystals grow in the agar gel with hexagonal morphology having (001), (110) and (010) as habit faces. Single crystal X-ray diffraction results show that the crystals belong to monoclinic system with cell parameters; a=10.344(2) , b=9.643(6) , c=11.721(2) , ?=118.7 (2) , bearing the space group P2/c. Fourier transform infrared spectrum of the crystals indicates the presence of water and other functional groups associated with the oxalate ions. Thermogravimetric and differential thermal analysis support the presence of 8H 2O molecules attached to the lanthanum-neodymium crystal lattice. The thermal decomposition in the nitrogen atmosphere leads to the formation of mixed lanthanum-neodymium oxide as the final product. Energy dispersive analysis of X-rays along with elemental analysis suggests the stoichiometry of the gel grown crystals to be La 1.5Nd 0.5(C 2O 4) 38H 2O.

Want, Basharat

2011-11-01

439

Facile and efficient one-pot synthesis of benzimidazoles using lanthanum chloride  

PubMed Central

Background We report the synthesis of benzimidazoles using lanthanum chloride as an efficient catalyst. One-pot synthesis of 2-substituted benzimidazole derivatives from o-phenylenediamine and a variety of aldehydes were developed under mild reaction conditions. Results We have examined the effect of different solvents using the same reaction conditions. The yield of the product varied with the nature of the solvents, and better conversion and easy isolation of products were found with acetonitrile. In a similar manner, the reaction with o-phenylenediamine and 3,4,5-trimethoxybenzaldehyde was carried out without any solvents. The observation shows that the reaction was not brought into completion, even after starting for a period of 9 h, and the reaction mixture showed a number of spots in thin-layer chromatography. Conclusions In conclusion, lanthanum chloride has been employed as a novel and efficient catalyst for the synthesis of benzimidazoles in good yields from o-phenylenediamine and a wide variety of aldehydes. All of the reactions were carried out in the presence of lanthanum chloride (10 mol%) in acetonitrile at room temperature.

2013-01-01

440

Lanthanum-molybdenum multilayer mirrors for attosecond pulses between 80 and 130 eV  

NASA Astrophysics Data System (ADS)

A novel multilayer material system consisting of lanthanum and molybdenum nano-layers for both broadband and highly reflecting multilayer mirrors in the energy range between 80 and 130 eV is presented. The simulation and design of these multilayers were based on an improved set of optical constants, which were recorded by extreme ultraviolet (XUV)/soft-x-ray absorption measurements on freestanding lanthanum nano-films between 30 eV and 1.3 keV. Lanthanum-molybdenum (La/Mo) multilayer mirrors were produced by ion-beam sputtering and characterized through both x-ray and XUV reflectivity measurements. We demonstrate the ability to precisely simulate and realize aperiodic stacks. Their stability against ambient air conditions is demonstrated. Finally, the La/Mo mirrors were used in the generation of single attosecond pulses from high-harmonic cut-off spectra above 100 eV. Isolated 200 attosecond-long pulses were measured by XUV-pump/IR-probe streaking experiments and characterized using frequency-resolved optical gating for complete reconstruction of attosecond bursts (FROG/CRAB) analyses.

Hofstetter, M.; Aquila, A.; Schultze, M.; Guggenmos, A.; Yang, S.; Gullikson, E.; Huth, M.; Nickel, B.; Gagnon, J.; Yakovlev, V. S.; Goulielmakis, E.; Krausz, F.; Kleineberg, U.

2011-06-01

441

The kinetics of uptake and recovery of lanthanum using freshwater algae as biosorbents: comparative analysis.  

PubMed

In this study, the adsorption and desorption kinetics of lanthanum (La) on micro algal cells was investigated. The internal transcribed spacer (ITS) and 18S ribosomal RNA gene (rRNA) were used for molecular identification of the species. The algal species were found to have 95-98% identities to Desmodesmus multivariabilis, Scenedesmus acuminutus, Chloroidium saccharophilum and Stichococcus bacillaris. The species were cultured and tested independently. D. multivariabilis was found to be the most efficient at adsorbing lanthanum with a maximum sorption capacity (qmax) of 100 mg/g and a high affinity (b) of 4.55 L/g. Desorption of La was also highest in D. multivariabilis with recovery up to 99.63% at initial concentration as high as 100 mg/L. Desorption data fitted best to the modified pseudo second-order with a better correlation coefficient (R(2)) of ?0.98 than first order model. The results showed feasibility of lanthanum recovery using algal sorbents, a cost effective method. PMID:24507581

Birungi, Z S; Chirwa, E M N

2014-05-01

442

Multicenter study of long-term (two-year) efficacy of lanthanum carbonate.  

PubMed

Long-term efficacy of lanthanum carbonate on hyperphosphatemia was examined in multicenter dialysis patients. Outcome and efficacy after 2 years was investigated in 101 patients who had undergone lanthanum carbonate administration. Thirty-three cases dropped out by the 2-year point; patients undergoing at least 2 years of administration totaled 68. Reasons for dropping out were as follows: improvement of hyperphosphatemia, nine cases; changing hospitals, seven cases; medical complications, five cases; digestive symptoms, four cases; poor compliance, four cases; parathyroidectomy, two cases; death, two cases. The mean dosage was increased from initial daily dosage of 744?mg to 1266?mg after 1 year, and to 1246?mg after 2 years. Serum phosphate concentration decreased significantly from the initial 6.15?mg to 5.57?mg/dL after 1 year, and to 5.45?mg/dL after 2 years. Although a lowering trend was observed in corrected calcium levels, the difference was not significant. Parathyroid hormone was unchanged. Achievement rate of Japanese Society for Dialysis Therapy (JSDT) management target values for both phosphorus and calcium improved from 32.7% to 50.0% after 1 year, and to 56.5% after 2 years. Lanthanum carbonate is useful as a therapeutic tool for hyperphosphatemia over long durations. PMID:23586506

Ando, Ryoichi; Kimura, Hitoshi; Sato, Hidehiko; Iwamoto, Shunsuke; Yoshizaki, Yuki; Chida, Yoshiko; Ishida, Yuji; Takayama, Masanobu; Yamada, Kouei; Tachibana, Ken; Ohtsuka, Masakazu; Kikuchi, Kan; Inoue, Atsushi

2013-04-01

443

Efficacy of continuous oral administration of lanthanum carbonate over 24 months.  

PubMed

To examine the efficacy of long-term administration of lanthanum carbonate, changes in serum Ca, phosphate, whole parathyroid hormone (wPTH), and ALP were examined in 40 patients who were able to tolerate dosage of lanthanum carbonate over a continuous period of 24 months. Concurrently, concomitant administration of other phosphate binders, cinacalcet, vitamin D, etc., was also examined. After 24 months, serum phosphorus levels (P levels) had decreased to within management target of guidelines, from 6.16??1.44?mg/dL to 5.58??1.15?mg/dL, and this effect was maintained for 2 years. There were no changes in Ca level. wPTH did not change significantly but tended to increase at 12 months. The dose of concomitantly administered calcium carbonate and sevelamer hydrochloride was reduced. The P-lowering function of lanthanum carbonate still held steady at 24 months following the start of dosage. Because of the rising trend seen in wPTH, dose of cinacalcet and/or vitamin D need to be modulated. Reducing the number of concomitantly administered phosphate binder tablets was desirable from the standpoint of patient adherence. PMID:23586509

Ishizu, Takashi; Hong, Zhang; Matsunaga, Tsuneaki; Kaneko, Yoko; Taru, Yoshinori

2013-04-01

444

Optical studies of Sm3+ ions doped Zinc Alumino Bismuth Borate glasses  

NASA Astrophysics Data System (ADS)

Zinc Alumino Bismuth Borate (ZnAlBiB) glasses doped with different concentrations of samarium (Sm3+) ions were prepared by using melt quenching technique and characterized for their lasing potentialities in visible region by using the techniques such as optical absorption, emission and emission decay measurements. Radiative properties for various fluorescent levels of Sm3+ ions were estimated from absorption spectral information using Judd-Ofelt (JO) analysis. The emission spectra and con-focal photoluminescence images obtained by 410 nm laser excitation demonstrates very distinct and intense orange-red emission for all the doped glasses. The suitable concentration of Sm3+ ions in these glasses to act as an efficient lasing material has been discussed by measuring the emission cross-section and branching ratios for the emission transitions. The quantum efficiencies were also been estimated from emission decay measurements recorded for the 4G5/2 level of Sm3+ ions. From the measured emission cross-sections, branching ratios, strong photoluminescence features and CIE chromaticity coordinates, it was found that 1 mol% of Sm3+ ions doped ZnAlBiB glasses are most suitable for the development of visible orange-red lasers.

Swapna, K.; Mahamuda, Sk.; Srinivasa Rao, A.; Shakya, S.; Sasikala, T.; Haranath, D.; Vijaya Prakash, G.