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Sample records for samarium doped lanthanum

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

    NASA Technical Reports Server (NTRS)

    Byvik, C. E.

    1971-01-01

    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.

  2. Magnetic properties of nano-clusters lanthanum chromite powders doped with samarium and strontium ions synthesized via a novel combustion method

    SciTech Connect

    Rashad, M.M.; El-Sheikh, S.M.

    2011-03-15

    Graphical abstract: Nanocrystalline Sm{sup 3+} and Sr{sup 2+} doped LaCrO{sub 3} powders have been synthesized through a novel gel combustion synthesis using triethanol amine (TEA). The saturation magnetization of the LaCrO{sub 3} increased with an increase Sm{sup 3+} ion and it decreased with an increase in the Sr{sup 3+} ion to 0.3 at temperature 1000 {sup o}C for 2 h due to the formation of a monodispersed uniform octahedral structure as shown in the Fig. Research highlights: {yields} Single-phase orthorhombic lanthanum chromite LaCrO{sub 3} nanoclusters have been successfully synthesized through a novel gel combustion synthesis using triethanol amine (TEA). {yields} Sr{sup 2+} ions doped LaCrO{sub 3} increased the unit cell volume and the crystallite size whereas Sm{sup 3+} ions doped LaCrO{sub 3} decreased the unit cell volume and the crystallite size. {yields} The saturation magnetization of the LaCrO{sub 3} powders increased continuously with an increase in the Sm concentration and it decreased with an increase in the Sr ion up to 0.3 at annealing temperature of 1000 {sup o}C for 2 h. -- Abstract: A novel approach to synthesize a single-phase orthorhombic perovskite lanthanum chromite LaCrO{sub 3} clusters doped with Sm{sup 3+} and Sr{sup 2+} ions via gel combustion route was reported. The producing materials were synthesized using metal nitrates as oxidizers and triethanol amine (TEA), N-butyl amine (NBA) or ethylene diamine (EDA) as a fuel. The effect of the annealing temperature, type of organic fuel and the variation of the samarium and/or strontium substitution and its impact on crystal structure, crystallite size, microstructure and magnetic properties of the LaCrO{sub 3} powders formed was systematically studied. The results revealed that a well crystalline single phase of pure LaCrO{sub 3} can be achieved at annealing temperature from 800 to 1000 {sup o}C for 2 h. Moreover, each organic carrier materials exhibited a different degree of effectiveness in the synthesis of the mixed oxide powders. The crystal structure was influenced by doped Sm{sup 3+} and/or Sr{sup 2+} ions. The crystallite size of the produced powders was increased with the increase the annealing temperature, increasing the Sm{sup 3+} ion and the decrease of Sr{sup 2+} ion substitution. The microstructures of the produced powders were found to be nanoclusters octahedra-like shaped. The saturation magnetization of the LaCrO{sub 3} powders increased continuously with an increase in the Sm{sup 3+} ion concentration and it decreased with an increase in the Sr{sup 2+} ion up to 0.3 at annealing temperature of 1000 {sup o}C for 2 h. The maximum saturation magnetization (0.279 emu/g) was achieved at the Sm{sup 3+} ion molar ratio 0.3 and annealing temperature 1000 {sup o}C. Moreover, wide coercivities can be obtained at different synthesis conditions (49.25 to 522 Oe).

  3. Sintering and Property Characterization of Strontium-Doped Lanthanum Chromite

    SciTech Connect

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

    1999-12-01

    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.

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

    SciTech Connect

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

    2014-04-24

    Samarium doped Barium Zirconium Titanate ceramic with general formula Ba{sub 1?x}Sm{sub 2x/3}Zr{sub 0.05}Ti{sub 0.95}O{sub 3} [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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

    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.

  6. Magnetoelectric behavior of sodium doped lanthanum manganites

    NASA Astrophysics Data System (ADS)

    Kalyana Lakshmi, Y.; Venkataiah, G.; Reddy, P. Venugopal

    2009-07-01

    Nanocrystalline samples of sodium doped manganites with compositional formula La1-xNaxMnO3 (0.025⩽x⩽0.25) were prepared by polyvinyl alcohol assisted precursor method. After characterizing the samples by x-ray diffraction and transmission electron microscopy a systematic investigation of electrical, magnetic, and thermopower properties has been undertaken. The resistivity data were analyzed using effective medium approximation. From the analysis it has been found that the metallic fraction is increasing up to x=0.10 and remains constant with further doping. A close examination of the resistivity data clearly indicates that the sodium doped samples are slowly transformed from colossal magnetoresistance behavior to charge ordering behavior. Thermoelectric power data at low temperatures were analyzed by considering the magnon drag concept, while the high temperature data were explained by small polaron conduction mechanism.

  7. Thermal conductivity analysis of lanthanum doped manganites

    SciTech Connect

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

    2014-04-24

    The temperature-dependent thermal conductivity of the doped manganites La{sub 0.7}Ca{sub 0.3}MnO{sub 3} 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.

  8. X-ray absorption fine structure of samarium-doped borate glasses

    SciTech Connect

    Shimizugawa, Y.; Sawaguchi, N.; Kawamura, K.; Hirao, K.

    1997-05-01

    Samarium L{sub III} x-ray absorption fine structure spectra for both Sm{sup 2+} and Sm{sup 3+}-doped (100-X)B{sub 2}O{sub 3} XNa{sub 2}O (X=10,15,20) glasses and both Sm{sup 2+} and Sm{sup 3+}-doped 85B{sub 2}O{sub 3} (15-X)Al{sub 2}O{sub 3} XNa{sub 2}O (X=5,10) glasses were measured using synchrotron radiation. The oxygen coordination number of samarium in Sm{sup 2+}-doped glass is different from that of the Sm{sup 3+}-doped glass with the same composition while the nearest neighbor Sm{endash}O distances are closely the same. The change of coordination numbers with alkali or aluminum addition was related to the variation of the optical hole width of Sm{sup 2+}-doped glasses. {copyright} {ital 1997 American Institute of Physics.}

  9. Spectroscopy of vanadium (III) doped gallium lanthanum sulphide chalcogenide glass

    NASA Astrophysics Data System (ADS)

    Hughes, M.; Rutt, H.; Hewak, D.; Curry, R. J.

    2007-01-01

    Vanadium doped gallium lanthanum sulphide glass (V:GLS) displays three absorption bands at 580, 730, and 1155nm identified by photoluminescence excitation measurements. Broad photoluminescence, with a full width at half maximum of ˜500nm, is observed peaking at 1500nm when exciting at 514, 808, and 1064nm. The fluorescence lifetime and quantum efficiency at 300K were measured to be 33.4μs and 4%, respectively. From the available spectroscopic data, the authors propose the vanadium ions' valence to be 3+ and be in tetrahedral coordination. The results indicate a potential for the development of a laser or optical amplifier based on V:GLS.

  10. Thermodynamic properties of doped lanthanum manganites

    SciTech Connect

    Hildrum, R.; Brustad, M. . Dept. of Electrochemistry); Wang Changzhen . Div. of Physicochemistry of Metallurgy); Johannesen, O. )

    1994-08-01

    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.

  11. Photoluminescence of samarium-doped TiO{sub 2} nanotubes

    SciTech Connect

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

    2011-10-15

    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.

  12. Europium doped lanthanum zirconate nanoparticles with high concentration quenching

    SciTech Connect

    Alaparthi, Suresh B.; Lu, Long; Tian, Yue; Mao, Yuanbing

    2014-01-01

    Graphical abstract: - Highlights: • Eu:La{sub 2}Zr{sub 2}O{sub 7} nanoparticles were prepared facilely by a kinetically modified molten salt method. • High color purity and concentration quenching were achieved in these La{sub 2}Zr{sub 2}O{sub 7}:Eu nanoparticles. • Concentration quenching mechanism was discussed for Eu{sup 3+} in these Eu:La{sub 2}Zr{sub 2}O{sub 7} nanoparticles. - Abstract: A series of Eu{sup 3+} doped lanthanum zirconate (La{sub 2}Zr{sub 2}O{sub 7}) nanoparticles (NPs, 20 ± 5 nm in diameter) with cubic fluorite structure were facilely synthesized by a kinetically modified molten salt synthetic (MSS) process and characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and photoluminescence spectra (PL). Under the excitation of 405 nm, intense red emission with high color purity can be observed in the Eu{sup 3+} doped La{sub 2}Zr{sub 2}O{sub 7} NPs. Moreover, the as-prepared Eu:La{sub 2}Zr{sub 2}O{sub 7} NPs possess high concentration quenching, which is as high as ∼32.5 mol% of europium dopants in the La{sub 2}Zr{sub 2}O{sub 7} host. The corresponding concentration quenching mechanism was discussed as well. Our results confirm that the kinetically modified MSS process is a promising approach for preparing rare earth (RE) ions doped A{sub 2}B{sub 2}O{sub 7} nanoparticles with uniform RE doping and high concentration quenching.

  13. Photoinduced hydroxyl radical and photocatalytic activity of samarium-doped TiO(2) nanocrystalline.

    PubMed

    Xiao, Qi; Si, Zhichun; Zhang, Jiang; Xiao, Chong; Tan, Xiaoke

    2008-01-15

    Sm(3+)-doped TiO(2) nanocrystalline has been prepared by sol-gel auto-combustion technique and characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) method, and also UV-vis diffuse reflectance spectroscopy (DRS). These Sm(3+)-doped TiO(2) samples were tested for methylene blue (MB) decomposition and *OH radical formation. The analysis of *OH radical formation on the sample surface under UV irradiation was performed by fluorescence technique with using terephthalic acid, which readily reacted with *OH radical to produce highly fluorescent product, 2-hydroxyterephthalic acid. It was observed that the presence of Sm(3+) ion as a dopant significantly enhanced the photocatalytic activity for MB degradation under UV light irradiation because both the larger specific surface area and the greater the formation rate of *OH radical were simultaneously obtained for Sm(3+)-doped TiO(2) nanocrystalline. The adsorption experimental demonstrated that Sm(3+)-TiO(2) had a higher MB adsorption capacity than undoped TiO(2) and the adsorption capacity of MB increased with the increase of samarium ion content. The results also indicated that the greater the formation rate of *OH radical was, the higher photocatalytic activity was achieved. In this study, the optimum amount of Sm(3+) doping was 0.5 mol%, at which the recombination of photo-induced electrons and holes could be effectively inhibited, the highest formation rate of *OH radicals was, and thereby the highest photocatalytic activity was achieved. PMID:17540502

  14. Crystal structure of Eu-doped magnetoplumbite-type lanthanum aluminum oxynitride with emission site splitting

    SciTech Connect

    Masubuchi, Yuji; Hata, Tomoyuki; Motohashi, Teruki; Kikkawa, Shinichi

    2011-09-15

    Eu-doped lanthanum aluminum oxynitride (LaAl{sub 12}(O,N){sub 19}) with magnetoplumbite structure was prepared by nitridation of the oxide precursor obtained from aluminum glycine gel and subsequent post-annealing. Eu-doped lanthanum aluminum oxynitride exhibited blue light emission at 440 nm with a shoulder at 464 nm under excitation at 254 nm. Isostructural Eu-doped calcium aluminum oxide (CaAl{sub 12}O{sub 19}) exhibited a single emission peak at 415 nm. Structural refinement using neutron powder diffraction indicated that the lanthanum site occupied partially by Eu{sup 2+} splits into 2d and 6h sites in the aluminum oxynitride. The longer emission and the shoulder peak in the former aluminum oxynitride were observed in relation to the increasing covalency as well as crystal field splitting around doped Eu{sup 2+} induced by site splitting involved with the two kinds of anions. - Graphical Abstract: Magnetoplumbite type Eu-doped lanthanum aluminum oxynitride has lanthanum site splitting induced by two kinds of anions, causing two emission peaks. Highlights: > Magnetoplumbite type LaAl{sub 12}(O,N){sub 19} doped with Eu shows emission peak splitting. > ND analysis is performed on La{sub 0.97}Eu{sub 0.03}Al{sub 12}(O,N){sub 19} and Ca{sub 0.97}Eu{sub 0.03}Al{sub 12}O{sub 19}. > La{sub 0.97}Eu{sub 0.03}Al{sub 12}(O,N){sub 19} has lanthanum site splitting. > The lanthanum site splitting is induced by coexisting of two kinds of anions.

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

    SciTech Connect

    Damas, Pedro; Coelho, João; Hungerford, Graham; Hussain, N. Sooraj

    2012-11-15

    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.

  16. Optically erasable samarium-doped fluorophosphate glasses for high-dose measurements in microbeam radiation therapy

    NASA Astrophysics Data System (ADS)

    Morrell, B.; Okada, G.; Vahedi, S.; Koughia, C.; Edgar, A.; Varoy, C.; Belev, G.; Wysokinski, T.; Chapman, D.; Sammynaiken, R.; Kasap, S. O.

    2014-02-01

    Previous work has demonstrated that fluorophosphate (FP) glasses doped with trivalent samarium (Sm3+) can be used as a dosimetric detector in microbeam radiation therapy (MRT) to measure high radiation doses and large dose variations with a resolution in the micrometer range. The present work addresses the use of intense optical radiation at 405 nm to erase the recorded dose information in Sm3+-doped FP glass plates and examines the underlying physics. We have evaluated both the conversion and optical erasure of Sm3+-doped FP glasses using synchrotron-generated high-dose x-rays at the Canadian Light Source. The Sm-ion valency conversion is accompanied by the appearance of x-ray induced optical absorbance due to the trapping of holes and electrons into phosphorus-oxygen hole (POHC) and electron (POEC) capture centers. Nearly complete Sm2+ to Sm3+ reconversion (erasure) may be achieved by intense optical illumination. Combined analysis of absorbance and electron spin resonance measurements indicates that the optical illumination causes partial disappearance of the POHC and the appearance of new POEC. The suggested model for the observed phenomena is based on the release of electrons during the Sm2+ to Sm3+ reconversion process, the capture of these electrons by POHC (and hence their disappearance), or by PO groups, with the appearance of new and/or additional POEC. Optical erasure may be used as a practical means to erase the recorded data and permits the reuse of these Sm-doped FP glasses in monitoring dose in MRT.

  17. Optically erasable samarium-doped fluorophosphate glasses for high-dose measurements in microbeam radiation therapy

    SciTech Connect

    Morrell, B.; Okada, G.; Vahedi, S.; Koughia, C. Kasap, S. O.; Edgar, A.; Varoy, C.; Belev, G.; Wysokinski, T.; Chapman, D.; Sammynaiken, R.

    2014-02-14

    Previous work has demonstrated that fluorophosphate (FP) glasses doped with trivalent samarium (Sm{sup 3+}) can be used as a dosimetric detector in microbeam radiation therapy (MRT) to measure high radiation doses and large dose variations with a resolution in the micrometer range. The present work addresses the use of intense optical radiation at 405 nm to erase the recorded dose information in Sm{sup 3+}-doped FP glass plates and examines the underlying physics. We have evaluated both the conversion and optical erasure of Sm{sup 3+}-doped FP glasses using synchrotron-generated high-dose x-rays at the Canadian Light Source. The Sm-ion valency conversion is accompanied by the appearance of x-ray induced optical absorbance due to the trapping of holes and electrons into phosphorus-oxygen hole (POHC) and electron (POEC) capture centers. Nearly complete Sm{sup 2+} to Sm{sup 3+} reconversion (erasure) may be achieved by intense optical illumination. Combined analysis of absorbance and electron spin resonance measurements indicates that the optical illumination causes partial disappearance of the POHC and the appearance of new POEC. The suggested model for the observed phenomena is based on the release of electrons during the Sm{sup 2+} to Sm{sup 3+} reconversion process, the capture of these electrons by POHC (and hence their disappearance), or by PO groups, with the appearance of new and/or additional POEC. Optical erasure may be used as a practical means to erase the recorded data and permits the reuse of these Sm-doped FP glasses in monitoring dose in MRT.

  18. Effect of silver nanoparticles incorporated with samarium-doped magnesium tellurite glasses

    NASA Astrophysics Data System (ADS)

    Yusoff, N. M.; Sahar, M. R.

    2015-01-01

    Silver nanoparticles (Ag NPs) are incorporated in samarium doped tellurite glass of a composition (89-x)TeO2-10MgO-1Sm2O3-xAgCl, where 0.0≤x≤0.6 mol%, by a melt quenching technique. It is found that all the glasses are amorphous in nature, and the existence of Ag NPs with an average size of 16.94 nm is confirmed by Transmission Electron Microscopy. Meanwhile, their physical properties such as glass density, molar volume and ionic packing density are computed utilizing the normal method. The density and ionic packing density are observed to decrease with increasing Ag NPs, but increase when the Ag NPs are beyond 0.2 mol%. On the other hand, the molar volume behaves exactly opposite to the increase in Ag NPs content. It decreases when the Ag NPs content value is more than 0.2 mol%. The optical energy band gap and Urbach energy are evaluated from the absorption spectra in the range of 200-900 nm at room temperature. It is also observed that the direct and indirect optical energy band gaps reduce with Ag NPs content, but enhance when the Ag NPs are beyond 0.2 mol%. Meanwhile, the Urbach energy is found to increase as the Ag NPs content is increased but decreases when Ag NPs is 0.2 mol%. The refractive index is deduced from indirect optical energy band gap. Meanwhile, molar refraction and electronic polarizability have been calculated from the Lorentz-Lorentz relation. Refractive index and electronic polarizability are also observed to raise with Ag NPs content, but drop off when Ag NPs content is more than 0.2 mol%. In this paper, all properties are discussed with respect to the Ag NPs concentration.

  19. Indexing the structural parameters and investigating the magnetic properties of lanthanum doped strontium hexaferrites

    NASA Astrophysics Data System (ADS)

    Azim, M.; Atiq, S.; Riaz, S.; Naseem, S.

    2014-06-01

    Sr1-xLaxFe12O19 (x= 0, 0.1, 0.15, 0.2) nano-crystallites were synthesized using a sol-gel based combustion technique. Sintering of the samples at 800 °C helped to develop the stable hexagonal phase. Data received from the X-ray diffraction was used to confirm and determine the crystal structure of the samples by manipulating the lattice parameters, volume of the unit cell, crystallite size, X-ray density and porosity of the samples. Room temperature magnetic measurements were performed using a vibrating sample magnetometer with an applied field of ±10 kOe. The magnetic hysteresis loops reveal that lanthanum doping at Sr-sites has enhanced the coercivity of the samples in the series with some compromise on magnetization while remanence remains almost constant, enabling the lanthanum doped samples appropriate for hard magnetic applications.

  20. Cobalt doped lanthanum chromite material suitable for high temperature use

    DOEpatents

    Ruka, Roswell J.

    1986-01-01

    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.

  1. Cobalt doped lanthanum chromite material suitable for high temperature use

    DOEpatents

    Ruka, R.J.

    1986-12-23

    A high temperature, solid electrolyte electrochemical cell, subject to thermal cycling temperatures of between about 25 C and about 1,200 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. 2 figs.

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

    SciTech Connect

    Chayapiwut, Nakorn; Honma, Tsuyoshi; Benino, Yasuhiko; Fujiwara, Takumi; Komatsu, Takayuki . E-mail: komatsu@chem.nagaokaut.ac.jp

    2005-11-15

    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.

  3. Sintering mechanisms and thermal expansion behavior for stoichiometric doped lanthanum chromites under reducing environment

    SciTech Connect

    Mori, Masashi; Yamamoto, Tohru; Itoh, Hibiki; Abe, Toshio

    1995-12-31

    Sintering mechanisms and thermal expansion behavior of Mg, Ca or Sr doped LaCrO{sub 3} in a reducing environment have been investigated. In the case of Mg doped LaCrO{sub 3} under Ar-CO atmosphere, MgO particles are deposited in the grain-boundary during the sintering process, and then a solid state densification proceeds in the form of lanthanum chromite with a chromium deficit. For the Ca or Sr substitution, a liquid phase with a Ca or Sr-rich composition would percolate from the particles during the liquid phase sintering process. For all these materials, a difference of the thermal expansion coefficients between air and hydrogen was observed. Especially, after being measured in air, the thermal expansion slope showed a remarkable change during the first heating cycle under a hydrogen atmosphere. The temperatures were 465 C for the Ca-doped sample and 614 C for the Sr-doped one.

  4. Sintering and Property Characterization of Strontium-Doped Lanthanum Chromite

    SciTech Connect

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

    1999-08-01

    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.

  5. Doping of ceria surfaces with lanthanum: a DFT + U study

    NASA Astrophysics Data System (ADS)

    Yeriskin, Irene; Nolan, Michael

    2010-04-01

    In this paper we use density functional theory corrected for on-site Coulomb interactions (DFT + U) to study the defects formed in the ceria (111) and (110) surfaces doped with La. To describe consistently the defect formed with substitutional La3 + doping at a Ce4 + site we use DFT and DFT + U, with U = 5 eV for Ce 4f states and U = 7 eV for O 2p states. When La3 + substitutes on a Ce3 + site, an \\mathrm {La}_{\\mathrm {Ce}}^{\\prime }+\\mathrm {O}_{\\mathrm {O}}^{\\bdot } defect state, with an oxygen hole, is formed at both surfaces, but only with the DFT + U approach. The formation energy of an oxygen vacancy in a structure with two La dopants in their most stable distribution is reduced over the undoped surfaces but remains positive. Formation of an oxygen vacancy results in the appearance of a reduced Ce3 + cation and a compensated oxygen hole, instead of compensation of both oxygen holes, which is typical of metal oxides doped with lower valence cations. We tentatively suggest that the key role in the formation of this unusual defect is played by cerium and arises from the ease with which cerium can be reduced, as compared to other metal oxides. Experimental confirmation of these results is suggested.

  6. Lanthanum-doped Bi4Ti3O12 ceramics prepared by high-pressure technique

    NASA Astrophysics Data System (ADS)

    Lin, Xue; Guan, Qing-Feng; Liu, Yang; Li, Hai-Bo

    2010-10-01

    We present an effective way in this paper to increase the density of lanthanum doped bismuth titanate ceramics, Bi4—xLaxTi3O12 (BLT), thereby significantly improving the performance of the BLT ceramics. Dense BLT ceramicses, Bi4—xLaxTi3O12 (x = 0.25, 0.5, 0.75, 1.0), are prepared by using nanocrystalline powders fabricated by a —gel method and high-pressure technique. The microstructures of the BLT ceramicses prepared separately by conventional-pressure and high-pressure techniques are investigated by using x-ray diffraction and transmission electron microscope. The influence of La-doping on the densification of bismuth titanate ceramics is investigated. The experimental results indicate that the phase compositions of all samples with various lanthanum dopings sintered at 900 °C possess layer-structure of Bi4Ti3O12. The green compacts are pressed under 2.5 GPa, 3.0 GPa, 3.5 GPa and 4.0 GPa, separately. It is found that the density of BLT ceramics is significantly increased due to the decreasing of porosity in the green compacts by high-pressure process.

  7. Ultrasonic-assisted sol-gel synthesis of samarium, cerium co-doped TiO2 nanoparticles with enhanced sonocatalytic efficiency.

    PubMed

    Eskandarloo, Hamed; Badiei, Alireza; Behnajady, Mohammad A; Ziarani, Ghodsi Mohammadi

    2015-09-01

    In this work, pure TiO2 and samarium, cerium mono-doped and co-doped TiO2 catalysts were synthesized by an ultrasonic-assisted sol-gel method and their sonocatalytic efficiency studied toward removal of Methyl Orange as a model organic pollutant from the textile industry. The relationship of structure and sonocatalytic performance of catalysts was established by using various techniques, such as XRD, TEM, SEM, EDX, DRS, and PL. A comparison on the removal efficiency of sonolysis alone and sonocatalytic processes was performed. The results showed that the samarium, cerium co-doped TiO2 catalyst with narrower band gap energy and smaller particle size leads to a rapid removal of pollutant. It was believed that Sm(3+) and Ce(4+) ions can serve as superficial trapping for electrons at conduction band of TiO2 and prolonged the lifetime of electron-hole pairs. Finally, the effect of synthesis and operational variables on the sonocatalytic activity of co-doped TiO2 catalyst was studied and optimized using response surface methodology as a statistical technique. The results showed that the maximum removal efficiency (96.33%) was achieved at the optimum conditions: samarium content of 0.6 wt%, cerium content of 0.82 wt%, initial pollutant concentration of 4.31 mg L(-1), catalyst dosage of 0.84 mg L(-1), ultrasonic irradiation power of 700 W, and irradiation time of 50 min. PMID:25682738

  8. Electrochemical properties of dense Sr-doped lanthanum manganite electrodes prepared by a laser ablation method

    SciTech Connect

    Endo, Akira; Honma, Itaru; Ihara, Manabu; Komiyama, Hiroshi; Yamada, Koichi; Kajimura, Atsuko; Sasaki, Hirokazu; Mizusaki, Junichiro; Tagawa, Hiroaki

    1995-12-31

    In order to clarify the reaction mechanism on SOFC cathode, it is necessary to evaluate the contribution of oxygen bulk diffusion of electrode materials. In this work, the authors prepared dense Sr-doped lanthanum manganites (LSM) films on yttria stabilized zirconia (YSZ) substrates by a laser ablation method using KrF eximer laser. Scanning electron microscopy measurements indicated that dense LSM films (6--32{micro}m) were formed. Using these samples, electrochemical properties (oxide-ionic conductivity and ac impedance) were measured in Ar-O{sub 2} atmospheres.

  9. Energetics of magnesium, strontium, and barium doped lanthanum gallate perovskites

    NASA Astrophysics Data System (ADS)

    Cheng, Jihong; Navrotsky, Alexandra

    2004-01-01

    LaGaO 3 perovskites doped with Sr or Ba at the La site and Mg at the Ga site were prepared by solid-state reaction or sol-gel method and characterized. Enthalpies of formation from constituent oxides at 298 K were determined by high-temperature oxide melt solution calorimetry. Energetic trends are discussed in terms of defect chemistry. As oxygen deficiency increases, formation enthalpies define three trends, LaGa 1- yMg yO 3- δ (LGM), La 1- xSr xGa 1- yMg yO 3- δ (LSGM), and La 1- xBa xGa 1- yMg yO 3- δ (LBGM). They become less exothermic with increasing doping, suggesting a dominant destabilization effect from oxygen vacancies. The endothermic enthalpy of vacancy formation is 275±37, 166±18 and 138±12 kJ/mol of VO·· for LGM, LBGM and LSGM, respectively. Tolerance factor and ion size mismatch also affect enthalpies. In terms of energetics, Sr is the best dopant for the La site and Mg for the Ga site, supporting earlier studies, including oxygen ion conductivity and computer modeling.

  10. Samarium and manganese-doped lead titanate ceramic fiber/epoxy 1-3 composite for high-frequency transducer application.

    PubMed

    Li, Kun; Chan, Helen L W; Choy, Chung L

    2003-10-01

    Samarium- (Sm) and manganese- (Mn) doped lead titanate ceramic fibers with a diameter of 35 microm were prepared using a sol-gel method. The X-ray diffraction pattern shows that the fibers have a pure perovskite structure. The 1-3 composite disks with a thickness of 31-41 microm and with ceramic volume fraction of approximately 0.68 have been prepared using the samarium and manganese doped lead titanate (PSmT) fibers. The resonance characteristics of the poled composite disks were measured. A focused transducer was fabricated using a concave 1-3 composite disk with nonuniform thickness in order to enhance its bandwidth. The insertion loss (IL), pulse-echo response and frequency spectrum of the composite transducer were measured. The center frequency of the transducer was approximately 31 MHz with a -3 dB bandwidth of approximately 123% and a low IL of 29.3 dB. PMID:14609077

  11. Optical, luminescent and laser properties of highly transparent ytterbium doped yttrium lanthanum oxide ceramics

    NASA Astrophysics Data System (ADS)

    Ivanov, M.; Kopylov, Yu.; Kravchenko, V.; Li, Jiang; Pan, Yubai; Kynast, U.; Leznina, M.; Strek, W.; Marciniak, Lukasz; Palashov, O.; Snetkov, I.; Mukhin, I.; Spassky, D.

    2015-12-01

    This paper describes the fabrication and investigation of highly transparent Yb-doped yttrium lanthanum oxide ceramics. For sintering of the ceramics we used a technology, which consists of several consecutive steps: (a) synthesis of weakly agglomerated nanopowder by laser ablation, (b) compacting of the green body with cold isostatic pressing (CIP), and (c) sintering in vacuum. After calcinations of the synthesized nanopowder at 1200 °C, a pure single-phase solid solution Yb3+:(LaxY1-x)2O3 was formed. The lanthanum ions proved to be a good aid to sinter yttria ceramics doped with Yb3+ at comparatively moderate temperatures of about 1650 °C. The ceramics have a relative density higher than 99.99% and grain sizes around 40 μm. The absorption coefficient of 3.2 mm thick Yb0.12La0.27Y1.61O3 ceramics is 0.01 cm-1 at 1150 nm. Laser oscillation at a wavelength of 1033 nm is demonstrated.

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

    PubMed

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

    2013-06-01

    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

  13. Influence of lanthanum doping on the dielectric, ferroelectric and relaxor behaviour of barium bismuth titanate ceramics

    NASA Astrophysics Data System (ADS)

    Kumar, Sunil; Varma, K. B. R.

    2009-04-01

    Barium lanthanum bismuth titanate (Ba1-(3/2)xLaxBi4Ti4O15, x = 0-0.4) ceramics were fabricated using the powders synthesized via the solid-state reaction route. X-ray powder diffraction analysis confirmed the above compositions to be monophasic and belonged to the m = 4 member of the Aurivillius family of oxides. The effect of the partial presence of La3+ on Ba2+ sites on the microstructure, dielectric and relaxor behaviour of BaBi4Ti4O15 (BBT) ceramics was investigated. For the compositions pertaining to x <= 0.1, the dielectric constant at both room temperature and in the vicinity of the temperature of the dielectric maximum (Tm) of the parent phase (BBT) increased significantly with an increase in x while Tm remained almost constant. Tm shifted towards lower temperatures accompanied by a decrease in the magnitude of the dielectric maximum (ɛm) with an increase in the lanthanum content (0.1 < x <= 0.4). The dielectric relaxation was modelled using the Vogel-Fulcher relation and a decrease in the activation energy for frequency dispersion with increasing x was observed. The frequency dispersion of Tm was found to decrease with an increase in lanthanum doping, and for compositions corresponding to x >= 0.3, Tm was frequency independent. Well-developed P(polarization)-E(electric field) hysteresis loops were observed at 150 °C for all the samples and the remanent polarization (2Pr) was improved from 6.3 µC cm-2 for pure BBT to 13.4 µC cm-2 for Ba0.7La0.2Bi4Ti4O15 ceramics. Dc conductivities and associated activation energies were evaluated using impedance spectroscopy.

  14. Magnetic phase transition of nanocrystalline Fe-doped samarium oxide (Sm1.90Fe0.10O3)

    NASA Astrophysics Data System (ADS)

    Mandal, J.; Sarkar, B. J.; Deb, A. K.; Chakrabarti, P. K.

    2014-12-01

    Nanocrystalline Fe3+ doped samarium oxide (Sm1.90Fe0.10O3) has been prepared by the co-precipitation method. The as prepared sample has been annealed at 700 °C for 6 h in an argon atmosphere. The pure crystallographic phase as well as the substitution of Fe3+ ions in the lattice of Sm2O3 is confirmed by Rietveld analysis of the X-ray diffraction patterns. The variation of magnetic susceptibility (χ) with temperature (T) is recorded by a Faraday Magnetometer in the temperature range of 300-14 K. The variation of χ vs. T down to ~50 K was successfully fitted by the Curie-Weiss law and below this temperature, susceptibility increases very rapidly, which suggests the presence of ordering at low temperature. To explore this, magnetic measurements are also carried out at different temperatures down to 2 K by using a SQUID Magnetometer. No hysteretic behavior is observed down to 50 K, but a feeble ferromagnetic behavior is observed in the magnetization vs. field curve recorded at ~30 K. A clear hysteresis loop is observed at 2 K with a comparatively high value of maximum magnetization (~3.32 emu/gm). The observed magnetic phase transition is analyzed by using the dipole-dipole interaction among the magnetic nanoparticles at low temperature.

  15. A SnO2-samarium doped ceria additional anode layer in a direct carbon fuel cell

    NASA Astrophysics Data System (ADS)

    Yu, Baolong; Zhao, Yicheng; Li, Yongdan

    2016-02-01

    The role of a SnO2-samarium doped ceria (SDC) additional anode layer in a direct carbon fuel cell (DCFC) with SDC-(Li0.67Na0.33)2CO3 composite electrolyte and lithiated NiO-SDC-(Li0.67Na0.33)2CO3 composite cathode is investigated and compared with a NiO-SDC extra anode layer. Catalytic grown carbon fiber mixed with (Li0.67Na0.33)2CO3 is used as a fuel. At 750 °C, the maximum power outputs of 192 and 143 mW cm-2 are obtained by the cells with SnO2-SDC and NiO-SDC layers, respectively. In the SnO2-SDC layer, the reduction of SnO2 and the oxidation of Sn happen simultaneously during the cell operation, and the Sn/SnO2 redox cycle provides an additional route for fuel conversion. The formation of an insulating dense interlayer between the anode and electrolyte layers, which usually happens in DCFCs with metal anodes, is avoided in the cell with the SnO2-SDC layer, and the stability of the cell is improved consequently.

  16. Structures, Stabilities, and Electronic Properties for Rare-Earth Lanthanum Doped Gold Clusters

    NASA Astrophysics Data System (ADS)

    Zhao, Ya-Ru

    2015-02-01

    The structures, stabilities, and electronic properties of rare-earth lanthanum doped gold La2Aun (n = 1-9) and pure gold Aun (n ≤ 11) clusters have been investigated by using density functional theory. The optimized geometries show that the lowest energy structures of La2Aun clusters favour the 3D structure at n ≥ 3. The lanthanum atoms can strongly enhance the stabilities of gold clusters and tend to occupy the most highly coordinated position. By analysing the gap, vertical ionization potential, and chemical hardness, it is found that the La2Au6 isomer possesses higher stability for small-sized La2Aun clusters (n = 1-9). The charges in the La2Aun clusters transfer from La atoms to the Aun host. In addition, Wiberg bond indices analysis reveals that the intensity of different bonds of La2Aun clusters exhibits a sequence of La-La bond > La-Au bond > Au-Au bond.

  17. Patterns of glow peak movement in rare earth doped lanthanum fluoride

    NASA Astrophysics Data System (ADS)

    Yang, B.; Townsend, P. D.

    2000-12-01

    Low temperature thermoluminescence data from rare earth doped lanthanum fluoride is characterized by numerous glow peaks. These differ in temperature as a function of the substituted rare earth ion, dopant concentration and thermal annealing. Analysis of the component bands in terms of activation energy, frequency factor and kinetic order reveals simple patterns in which the movement of the glow peaks is related to the ionic radii of the rare earth ions. Models for the thermoluminescence signals resulting from close association of the dopant recombination sites and the charge traps are discussed. Further consideration of a preference for impurity clustering, in order to reduce lattice strain, is used to explain the concentration and annealing induced changes.

  18. Room temperature optical and dielectric properties of Sr and Ni doped lanthanum ferrite nanoparticles

    NASA Astrophysics Data System (ADS)

    Naseem, Swaleha; Khan, Wasi; Singh, B. R.; Naqvi, A. H.

    2015-06-01

    Strontium and nickel doped lanthanum ferrite (LaFeO3) nanoparticles (NPs) were prepared reverse micelle (RM) and calcinated at 700°C. 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 spectroscopy and band gap energy was estimated 3.89 eV. Room temperature dielectric constant (ɛ') decreases abruptly at lower frequencies owing to the charge transport relaxation time. The observed behavior of the dielectric properties can be attributed on the basis of Koop's theory based on Maxwell-Wagner's two layer model in studied nanoparticles.

  19. Optical response and magnetic characteristic of samarium doped zinc phosphate glasses containing nickel nanoparticles

    NASA Astrophysics Data System (ADS)

    Azmi, Siti Amlah M.; Sahar, M. R.

    2015-11-01

    A magnetic glass of composition 40ZnO-(58-x) P2O5-1Sm2O3-xNiO, with x=0.0, 1.0, 1.5 and 2.0 mol% is prepared by melt-quenching technique. The glass is characterized by X-ray diffraction, high-resolution transmission electron microscope (HRTEM), photoluminescence (PL) spectroscopy and vibrating sample magnetometer (VSM) analysis. The X-rays diffraction confirms the amorphous nature of the glass while the HRTEM analysis reveals the presence of nickel nanoparticles in the glass samples. High-resolution TEM reveals that the lattice spacing of nickel nanoparticles is 0.35 nm at (100) plane. Photoluminescence emission shows the existence of four peaks that correspond to the transition from the upper level of 4G5/2 to the lower level of 6H5/2, 6H7/2, 6H9/2, and 6H11/2. It is observed that all peaks experience significant quenching effect with the increasing concentration of nickel nanoparticles, suggesting a strong energy transfer from excited samarium ions to the nickel ions. The glass magnetization and susceptibility at 12 kOe at room temperature are found to be in the range of (3.87±0.17×10-2-7.19±0.39×10-2) emu/g and (3.24±0.16×10-6-5.99±0.29×10-6) emu/Oe g respectively. The obtained hysteresis curve indicates that the glass samples are paramagnetic materials. The studied glass can be further used towards the development of magneto-optical functional glass.

  20. Sonocatalytic degradation of Acid Blue 92 using sonochemically prepared samarium doped zinc oxide nanostructures.

    PubMed

    Khataee, Alireza; Saadi, Shabnam; Vahid, Behrouz; Joo, Sang Woo; Min, Bong-Ki

    2016-03-01

    Pure and Sm-doped ZnO nanoparticles were synthesized applying a simple sonochemical method. The nanocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) techniques which confirmed the successful synthesis of the doped sonocatalyst. The sonocatalytic degradation of Acid Blue 92 (AB92), a model azo dye, was more than that with sonolysis alone. The 6% Sm-doped ZnO nanoparticles had a band gap of 2.8 eV and demonstrated the highest activity. The degradation efficiency (DE%) of sonolysis and sonocatalysis with undoped ZnO and 6% Sm-doped ZnO was 45.73%, 63.9%, and 90.10%, after 150 min of treatment, respectively. Sonocatalytic degradation of AB92 is enhanced with increasing the dopant amount and catalyst dosage and with decreasing the initial AB29 concentration. DE% declines with the addition of radical scavengers such as chloride, carbonate, sulfate, and tert-butanol. However, the addition of enhancers including potassium periodates, peroxydisulfate, and hydrogen peroxide improves DE% by producing more free radicals. The results show adequate reusability of the doped sonocatalyst. Degradation intermediates were recognized by gas chromatography-mass spectrometry (GC-MS). Using nonlinear regression analysis, an empirical kinetic model was developed to estimate the pseudo-first-order constants (kapp) as a function of the main operational parameters, including the initial dye concentration, sonocatalyst dosage, and ultrasonic power. PMID:26584981

  1. Lanthanum and zirconium co-doped ZnO nanocomposites: synthesis, characterization and study of photocatalytic activity.

    PubMed

    Moafi, Hadi Fallah; Zanjanchi, Mohammad Ali; Shojaie, Abdollah Fallah

    2014-09-01

    Nanocomposits of zinc oxide co-doped with lanthanum and zirconium were prepared using the modified sol-gel method. The samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), diffuse reflectance spectroscopy (DRS), and BET surface area measurement. For comparison, the La and Zr mono doped ZnO have also been prepared under the same conditions. The XRD results revealed that all the materials showed a hexagonal wurtzite crystal structure. It was found that the particle size of La-Zr-doped ZnO is much smaller as compared to that of pure ZnO. The effect of operational parameters such as, doping concentration, catalyst loading, pH and initial concentration of methylene blue on the extent of degradation was investigated. The photocatalytic activity of the undoped ZnO, mono-doped and La-Zr-ZnO photocatalysts was evaluated by the photocatalytic degradation of methylene blue in aqueous solution. The presence of lanthanium and/or zirconium causes a red shift in the absorption band of ZnO. The results show that the photocatalytic activity of the La-Zr-ZnO photocatalyst is much higher than that of undoped and mono-doped ZnO, resulting from the La and Zr synergistic effect. The co-operation of the lanthanum and zirconium ion leads to the narrowing of the band gap and greatly improves the photocatalytic activity. The photocatalyst co-doped with lanthanum and zirconium 4 mol% shows the best photoactivity and photodecomposition efficiencies were improved by 92% under UV-Vis irradiation at the end of 30 min, compared with the pure and mono doped samples. PMID:25924382

  2. The incorporation of silver nanoparticles in samarium doped magnesium tellurite glass: Effect on the characteristic of bonding and local structure

    NASA Astrophysics Data System (ADS)

    Yusoff, N. M.; Sahar, M. R.

    2015-08-01

    Samarium doped magnesium tellurite glass with and without silver nanoparticles is prepared using melt quenching technique. All glasses are amorphous in nature. The existence of silver nanoparticles in a glass matrix with an average size of 16.94 nm has been confirmed by Transmission Electron Microscopy. The UV-vis spectra are complemented with Judd-Ofelt calculation to get the Judd-Ofelt intensity parameters. It has also been used to calculate nephelauxetic ratio, bonding parameter and Racah parameters. It is found that Judd-Ofelt intensity parameters Ω2 ,Ω4 and Ω6 increase with an increase of Ag NPs contents up to 0.2 mol% and decrease thereafter. Nephelauxetic ratio, β decreases with increasing the concentration of Ag NPs, while bonding parameter, δ increases as the concentration of Ag NPs increases. The value of Racah parameters decreases as the concentration of Ag NPs increases. Fourier Transform Infrared (FTIR) and Raman spectroscopy have been manipulated to observe the structural modification of [TeO4] trigonal bipyramidal structural unit. In the FTIR spectrum, it is found that the structural unit of [TeO4] trigonal bipyramidal, [TeO3+1] polyhedral and/or [TeO3] trigonal pyramidal groups are located at 651-663 cm-1 and 772 cm-1, respectively. It is observed that the [TeO4] tbp wavenumber shifts to a higher wavenumber as the concentration of Ag NPs increases up to 0.2 mol% and decreases thereafter. Meanwhile, for the Raman spectra, it is found that [TeO4] tbp, [TeO3+1] polyhedral and [TeO3] tp groups are located at 646-666 cm-1, 714-741 cm-1, and 745-772 cm-1, respectively.

  3. Synthesis, thermal and photoluminescent properties of ZnSe- based oxyfluoride glasses doped with samarium

    NASA Astrophysics Data System (ADS)

    Kostova, I.; Okada, G.; Pashova, T.; Tonchev, D.; Kasap, S.

    2014-12-01

    Rare earth (RE) doped glasses and glass ceramic materials have recently received considerable attention because of their potential or realized applications as X-ray intensifying screens, phosphors, detectors, waveguides, lasers etc. [1]. In this work, we present a new RE doped ZnO-ZnSe-SrF2-P2O5-B2O3-Sm2O3-SmF3 (ZSPB) glass system synthesized by melt quenching technique. The resulting glasses were visually fully transparent and stable with glass the transition temperatures around 530°C. The thermal properties of this glass system were characterized by Modulated Differential Scanning Calorimetry (MDSC) measurements before and after annealing at 650°C. We have characterized these glasses by Raman spectroscopy and photoluminescence (PL) measurements over the UV-VIS range using light emitting diodes (LED) and laser diodes (LD) excitation sources. We have also irradiated thermally treated and non-treated glass samples by X-rays and have studied the resulting PL. We discuss the results in terms of previously reported models for Sm-doped Zn-borophosphate oxide, oxyfluoride and oxyselenide glasses.

  4. Nickel and titanium doubly doped lanthanum strontium chromite for high temperature electrochemical devices

    NASA Astrophysics Data System (ADS)

    Gupta, Sapna; Singh, Prabhakar

    2016-02-01

    Lanthanum chromite based materials are promising candidate for use as electrochemical components in high temperature electrochemical devices. In this study, nickel and titanium doubly doped lanthanum strontium chromites are developed and the effects of nickel and titanium co-doping of the chromite perovskite La0.85Sr0.15Cr1-2yNiyTiyO3-δ (0.05 ≤ y ≤ 0.3) on the electrical conductivity, chemical stability, microstructure, density, thermal expansion and electrochemical performance are measured. Density and the electrical conductivity increases with nickel concentration whereas Sr-segregation on the surface of La0.85Sr0.15Cr1-2yNiyTiyO3-δ has been observed for y ≥ 0.2 and is associated with reduction in the electrical conductivity. For y = 0.1, La0.85Sr0.15Cr1-2yNiyTiyO3-δ shows the highest electrical conductivity in air and reducing atmosphere (PO2 ∼10-24 atm). The conductivity of La0.85Sr0.15Cr1-2yNiyTiyO3-δ (y = 0.1) in reducing atmosphere (3.58 S cm-1 at 950 °C) also remains higher than the most widely investigated compositions such as (La0.75Sr0.25)0.95Cr0.5Mn0.5O3-δ (2.81 S cm-1) and (La0.75Sr0.25)0.95Cr0.7Fe0.3O3-δ (1.41 S cm-1). Smaller deviation in the oxygen stoichiometry is similarly observed for La0.85Sr0.15Cr0.8Ni0.1Ti0.1O3-δ (δ = 0.011) when compared to La0.75Sr0.25CrO3-δ (δ = 0.091), La0.75Sr0.25Cr0.5Mn0.5O3-δ (δ = 0.175) and La0.75Sr0.25Cr0.5Fe0.5O3-δ (δ = 0.148) at 1000 °C and ∼10-24 atm. Highest electrochemical performance and structural/interfacial stability is obtained for new composition La0.85Sr0.15Cr0.8Ni0.1Ti0.1O3-δ (LSCNT0.1) when mixed with 8YSZ in both oxidizing and reducing atmosphere.

  5. Determination of the variation of the fluorescence line positions of ruby, strontium tetraborate, alexandrite, and samarium-doped yttrium aluminum garnet with pressure and temperature

    NASA Astrophysics Data System (ADS)

    Raju, Selva Vennila; Zaug, Joseph M.; Chen, Bin; Yan, Jinyuan; Knight, Jason W.; Jeanloz, Raymond; Clark, Simon M.

    2011-07-01

    The pressure and temperature dependent fluorescence line-shift of strontium tetraborate has been measured concurrently with x-ray diffraction from the pressure standards sodium chloride or gold. Temperature was found to have a small effect on the fluorescence line-shift under pressure. We found a maximum pressure uncertainty of ±1.8 GPa at 25 GPa (7.2%) and 857 K when making no temperature correction. The fluorescence line-shifts for ruby, Alexandrite, and samarium-doped yttrium aluminum garnet were also determined, using our strontium tetraborate calibration to determine pressure and a thermocouple to measure temperature. Fluorescence measurements were extended up to 800 K for ruby and Alexandrite. Temperature was found to have a small effect on the fluorescence line-shift of samarium-doped yittrium aluminum garnet. We found a maximum uncertainty of ±2.7 GPa at 25 GPa (11.1%) and 857 K when no temperature correction was applied. We determined equations relating to the fluorescence line position from these data, which include a cross derivative term to account for the combined effect of pressure and temperature. We present a method to independently determine pressure and/or temperature from combined fluorescence line-shift measurements of a pair of optical sensors.

  6. Spatially resolved measurement of high doses in microbeam radiation therapy using samarium doped fluorophosphate glasses

    NASA Astrophysics Data System (ADS)

    Okada, Go; Morrell, Brian; Koughia, Cyril; Edgar, Andy; Varoy, Chris; Belev, George; Wysokinski, Tomasz; Chapman, Dean; Kasap, Safa

    2011-09-01

    The measurement of spatially resolved high doses in microbeam radiation therapy has always been a challenging task, where a combination of high dose response and high spatial resolution (microns) is required for synchrotron radiation peaked around 50 keV. The x-ray induced Sm3+ → Sm2+ valence conversion in Sm3+ doped fluorophosphates glasses has been tested for use in x-ray dosimetry for microbeam radiation therapy. The conversion efficiency depends almost linearly on the dose of irradiation up to ˜5 Gy and saturates at doses exceeding ˜80 Gy. The conversion shows strong correlation with x-ray induced absorbance of the glass which is related to the formation of phosphorus-oxygen hole centers. When irradiated through a microslit collimator, a good spatial resolution and high "peak-to-valley" contrast have been observed by means of confocal photoluminescence microscopy.

  7. High-temperature superconductivity in space-charge regions of lanthanum cuprate induced by two-dimensional doping

    NASA Astrophysics Data System (ADS)

    Baiutti, F.; Logvenov, G.; Gregori, G.; Cristiani, G.; Wang, Y.; Sigle, W.; van Aken, P. A.; Maier, J.

    2015-10-01

    The exploitation of interface effects turned out to be a powerful tool for generating exciting material properties. Such properties include magnetism, electronic and ionic transport and even superconductivity. Here, instead of using conventional homogeneous doping to enhance the hole concentration in lanthanum cuprate and achieve superconductivity, we replace single LaO planes with SrO dopant planes using atomic-layer-by-layer molecular beam epitaxy (two-dimensional doping). Electron spectroscopy and microscopy, conductivity measurements and zinc tomography reveal such negatively charged interfaces to induce layer-dependent superconductivity (Tc up to 35 K) in the space-charge zone at the side of the planes facing the substrate, where the strontium (Sr) profile is abrupt. Owing to the growth conditions, the other side exhibits instead a Sr redistribution resulting in superconductivity due to conventional doping. The present study represents a successful example of two-dimensional doping of superconducting oxide systems and demonstrates its power in this field.

  8. Electrical performance of nanostructured strontium-doped lanthanum manganite impregnated onto yttria-stabilized zirconia backbone

    NASA Astrophysics Data System (ADS)

    Ju, Jiangwei; Lin, Jie; Wang, Yusu; Zhang, Yanxiang; Xia, Changrong

    2016-01-01

    Strontium-doped lanthanum manganite (LSM) nanoparticles are deposited onto porous yttria-stabilized zirconia frameworks via an ion impregnation/infiltration process. The apparent conductivity of the impregnated LSM nanostructure is investigated regarding the fabricating parameters including LSM loading, heat treatment temperature, heating rate, and annealing at 750 °C for 400 h. Besides, the conductivity, the intrinsic conductivity as well as Bruggeman factor of the impregnated LSM is estimated from the apparent conductivity using the analytical model for the three-dimensional impregnate network. The conductivity increases with LSM loading while the interfacial polarization resistance exhibits the lowest value at an optimal loading of about 5 vol.%, which corresponds to the largest three-phase boundary as predicted using the numerical infiltration methodology. At the optimal loading, the area specific ohmic resistance of the impregnated LSM is about 0.032 Ω cm2 at 700 °C for a typical impregnated cathode of 30 μm thick. It is only 5.5% of the cathode interfacial polarization resistance and 3.3% of the total resistance for a single cell consisting of a Ni-YSZ support, a 10 μm thick electrolyte and a 30 μm thick cathode, demonstrating that the ohmic resistance is negligible in the LSM impregnated cathode for SOFCs.

  9. Electrocatalytic Properties of Nanocrystalline Calcium-Doped Lanthanum Cobalt Oxide for Bifunctional Oxygen Electrodes

    SciTech Connect

    Malkhandi, S; Yang, B; Manohar, AK; Manivannan, A; Prakash, GKS; Narayanan, SR

    2012-04-19

    Calcium-doped lanthanum cobalt oxide is a promising electrocatalyst for oxygen evolution and oxygen reduction in rechargeable metal air batteries and water electrolyzers operating with alkaline electrolyte. Nanocrystalline perovskite of composition La0.6Ca0.4CoO3 with a unique cellular internal structure was prepared at 350 degrees C and then annealed in air at progressively higher temperatures in the range of 600-750 degrees C. The samples were characterized by electrochemical techniques and X-ray photoelectron spectroscopy. The area-specific electrocatalytic activity for oxygen evolution/oxygen reduction, the oxidation state of cobalt, and the crystallite size increased with annealing temperature, while the Tafel slope remained constant. These trends provide new insights into the role of the cobalt center in oxygen evolution and oxygen reduction, and how preparation conditions can be altered to tune the activity of the cobalt center for electrocatalysis. We expect these findings to guide the design of electrocatalysts for bifunctional oxygen electrodes, in general.

  10. Probing highly luminescent europium-doped lanthanum orthophosphate nanorods for strategic applications.

    PubMed

    Saraf, Mohit; Kumar, Pawan; Kedawat, Garima; Dwivedi, Jaya; Vithayathil, Sajna Antony; Jaiswal, Nagendra; Kaipparettu, Benny Abraham; Gupta, Bipin Kumar

    2015-03-16

    Herein we have established a strategy for the synthesis of highly luminescent and biocompatible europium-doped lanthanum orthophosphate (La0.85PO4Eu0.15(3+)) nanorods. The structure and morphogenesis of these nanorods have been probed by XRD, SEM, and TEM/HRTEM techniques. The XRD result confirms that the as-synthesized nanorods form in a monazite phase with a monoclinic crystal structure. Furthermore, the surface morphology shows that the synthesized nanorods have an average diameter of ?90 nm and length of ?2 ?m. The HRTEM images show clear lattice fringes that support the presence of better crystal quality and enhanced photoluminescence hypersensitive red emission at 610 nm ((5)D0-(7)F2) upon 394 nm wavelength excitation. Furthermore, time-resolved spectroscopy and an MTT assay of these luminescent nanorods demonstrate a photoluminescent decay time of milliseconds with nontoxic behavior. Hence, these obtained results suggest that the as-synthesized luminescent nanorods could be potentially used in invisible security ink and high-contrast bioimaging applications. PMID:25732726

  11. Doping controlled spin reorientation in dysprosium-samarium orthoferrite single crystals

    NASA Astrophysics Data System (ADS)

    Cao, Shixun; Zhao, Weiyao; Kang, Baojuan; Zhang, Jincang; Ren, Wei

    2015-03-01

    As one of the most important phase transitions, spin reorientation (SR) in rare earth transition metal oxides draws much attention of emerging materials technologies. The origin of SR is the competition between different spin configurations which possess different free energy. We report the control of spin reorientation (SR) transition in perovskite rare earth orthoferrite Dy1-xSmxFeO3, a whole family of single crystals grown by optical floating zone method from x =0 to 1. Temperature dependence of the magnetizations under zero-field-cooling (ZFC) and field-cooling (FC) processes are studied. We have found a remarkable linear change of SR transition temperature in Sm-rich samples for x>0.2, which covers an extremely wide temperature range including room temperature. The a-axis magnetization curves under FCC process bifurcate from and then jump down to that of warming process (ZFC and FCW curves) in single crystals when x =0.5-0.9, suggesting complicated 4f-3d electron interactions among Dy3+-Sm3+, Dy3+-Fe3+, and Sm3+-Fe3+ sublattices of diverse magnetic configurations for materials physics and design. The magnetic properties and the doping effect on SR transition temperature in these single crystals might be useful in the spintronics device application. This work is supported by the National Key Basic Research Program of China (Grant No. 2015CB921600), and the National Natural Science Foundation of China (NSFC, Nos. 51372149, 50932003, 11274222).

  12. Synthesis, structural, optical and Raman studies of pure and lanthanum doped ZnSe nanoparticles

    SciTech Connect

    Kumar, Pushpendra; Singh, Jai; Pandey, Mukesh Kumar; Jeyanthi, C.E.; Siddheswaran, R.; Paulraj, M.; Hui, K.N.; Hui, K.S.

    2014-01-01

    Graphical abstract: - Highlights: Template-free synthesis of ZnSe and ZnSe:La nanoparticles was developed at low temperature 100 C. Cubic ZnSe and ZnSe:La nanoparticles were obtained by chemical route. As-synthesized ZnSe:La nanoparticles showed higher emission intensity than ZnSe nanoparticles. Band gap (E{sub g}) of ZnSe nanoparticles was bigger than ZnSe nanoparticles due to nanosized effect. - Abstract: In this work, a simple, effective and reproducible chemical synthetic route for the production of high-quality, pure ZnSe nanoparticles (NPs), and lanthanum-doped ZnSe (ZnSe:La) NPs is presented. The wide bandgap, luminescent pure ZnSe and ZnSe:La NPs has been synthesized at a low temperature (100 C) in a single template-free step. The size and optical bandgap of the NPs was analyzed from powder X-ray diffraction (XRD), UVvisible (UVvis) spectroscopy, transmission electron microscopy (TEM), and high resolution transmission electron microscopy (HRTEM). A broad photoluminescence (PL) emission across the visible spectrum has been demonstrated by a systematic blue-shift in emission due to the formation of small nanoparticles. Here, contribution to emission intensity from surface states of NPs increases with La doping. TEM data revealed that the average size of ZnSe and ZnSe:La NPs is 14 and 8 nm, respectively. On the other hand, band gap energy E{sub g} of ZnSe and ZnSe:La NPs were found to be 3.59 eV and 3.65 eV, respectively. Results showed that hydrazine hydrate played multiple roles in the formation of ZnSe and ZnSe:La NPs. A possible reaction mechanism for the growth of NPs is also discussed.

  13. Enhanced ionic conductivity of apatite-type lanthanum silicate electrolyte for IT-SOFCs through copper doping

    NASA Astrophysics Data System (ADS)

    Ding, Xifeng; Hua, Guixiang; Ding, Dong; Zhu, Wenliang; Wang, Hongjin

    2016-02-01

    Apatite-type Lanthanum silicate (LSO) is among the most promising electrolyte for intermediate temperature solid oxide fuel cells (IT-SOFCs) owing to the high conductivity and low activation energy at lower temperature than traditional doped-zirconia electrolyte. The ionic conductivity as well as the sintering density of lanthanum silicate oxy-apatite, La10Si6-xCuxO27-δ (LSCO, 0 ≤ x ≤ 2), was effectively enhanced through a small amount of doped copper. The phase composition, relative density, ionic conductivity and thermal expansion behavior of La10Si6-xCuxO27-δ was systematically investigated by X-ray diffraction (XRD), Archimedes' drainage method, scanning electron microscope (SEM), electrochemical impedance spectra (EIS) and thermal dilatometer techniques. With increasing copper doping content, the ionic conductivity of La10Si6-xCuxO27-δincreased, reaching a maximum of 4.8 × 10-2 S cm-1 at 800 °C for x = 1.5. The improved ionic conductivity could be primarily associated with the enhanced grain conductivity. The power output performance of NiO-LSCO/LSCO/LSCF single cell was superior to that obtained on NiO-LSO/LSO/LSCF at different temperatures using hydrogen as fuel and oxygen as oxidant, which could be attributed to the enhanced oxygen ionic conductivity as well as the sintering density for the copped doped lanthanum silicate. In conclusion, the apatite La10Si4.5Cu1.5O25.5 is a promising candidate electrolyte for IT-SOFCs.

  14. Dielectric investigations of polycrystalline samarium bismuth ferrite ceramic

    SciTech Connect

    Palaimiene, E.; Macutkevic, J.; Banys, J.; Karpinsky, D. V.; Kholkin, A. L.

    2015-01-05

    Results of broadband dielectric investigations of samarium doped bismuth ferrite ceramics are presented in wide temperature range (20–800 K). At temperatures higher than 400 K, the dielectric properties of samarium bismuth ferrite ceramics are governed by Maxwell-Wagner relaxation and electrical conductivity. The DC conductivity increases and activation energy decreases with samarium concentration. In samarium doped bismuth ferrite, the ferroelectric phase transition temperature decreases with samarium concentration and finally no ferroelectric order is observed at x = 0.2. At lower temperatures, the dielectric properties of ferroelectric samarium doped bismuth ferrite are governed by ferroelectric domains dynamics. Ceramics with x = 0.2 exhibit the relaxor-like behaviour.

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

    SciTech Connect

    Bhatt, Himal; Bahadur, J.; Deo, M.N.; Ramanathan, S.; Pandey, K.K.; Sen, D.; Mazumder, S.; Sharma, Surinder M.

    2011-01-15

    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.

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

    PubMed

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

    2013-01-01

    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. PMID:23503148

  17. Spray pyrolytic synthesis of samarium doped ceria (Ce 0.8Sm 0.2O 1.9) films for solid oxide fuel cell applications

    NASA Astrophysics Data System (ADS)

    Patil, B. B.; Pawar, S. H.

    2007-03-01

    Uniform, adherent, single phase samarium doped ceria films have been successfully deposited by spray pyrolysis technique for their application in solid oxide fuel cell. These films have been deposited at different substrate temperatures on glass substrate and subsequently heat treated in tube furnace. Effect of substrate temperature and annealing temperature on phase formation was studied with thermo-gravimetric analysis and differential temperature analysis, X-ray diffraction, scanning electron microscope, and energy dispersive X-ray analysis techniques. These studies showed the formation of single phase Ce 0.8Sm 0.2O 1.9 films, at substrate temperature 400 C and annealing temperature 550 C. Electrical resistivity of the films, at room temperature was of the order of 10 7 ? cm while at 400 C it is found to be of the order of 10 1 ? cm. This reveals the use of these films for making low temperature solid oxide fuel cells.

  18. Effects of some rare earth and carbonate-based co-dopants on structural and electrical properties of samarium doped ceria (SDC) electrolytes for solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Anwar, Mustafa; Khan, Zuhair S.; Mustafa, Kamal; Rana, Akmal

    2015-09-01

    In the present study, samarium doped ceria (SDC) and SDC-based composite with the addition of K2CO3 were prepared by co-precipitation route and effects of pH of the solution and calcination temperature on microstructure of SDC and SDC-K2CO3, respectively, were investigated. Furthermore, experimentation was performed to investigate into the ionic conductivity of pure SDC by co-doping with yttrium i.e., YSDC, XRD and SEM studies show that the crystallite size and particle size of SDC increases with the increase in pH. The SEM images of all the samples of SDC synthesized at different pH values showed the irregular shaped and dispersed particles. SDC-K2CO3 was calcined at 600∘C, 700∘C and 800∘C for 4 h and XRD results showed that crystallite size increases while lattice strain, decreases with the increase in calcination temperature and no peaks were detected for K2CO3 as it is present in an amorphous form. The ionic conductivity of the electrolytes increases with the increase in temperature and SDC-K2CO3 shows the highest value of ionic conductivity as compared to SDC and YSDC. Chemical compatibility tests were performed between the co-doped electrolyte and lithiated NiO cathode at high temperature. It revealed that the couple could be used up to the temperature of 700∘C.

  19. Glass-Like Thermal Conductivity of (010)-Textured Lanthanum-Doped Strontium Niobate Synthesized with Wet Chemical Deposition

    DOE PAGESBeta

    Foley, Brian M.; Brown-Shaklee, Harlan J.; Campion, Michael J.; Medlin, Douglas L.; Clem, Paul G.; Ihlefeld, Jon F.; Hopkins, Patrick E.

    2014-11-08

    We have measured the cross-plane thermal conductivity (κ) of (010)-textured, undoped, and lanthanum-doped strontium niobate (Sr2-xLaxNb2O7-δ) thin films via time-domain thermoreflectance. Then the thin films were deposited on (001)-oriented SrTiO3 substrates via the highly-scalable technique of chemical solution deposition. We find that both film thickness and lanthanum doping have little effect on κ, suggesting that there is a more dominant phonon scattering mechanism present in the system; namely the weak interlayer-bonding along the b-axis in the Sr2Nb2O7 parent structure. We also compare our experimental results with two variations of the minimum-limit model for κ and discuss the nature of transportmore » in material systems with weakly-bonded layers. The low cross-plane κ of these scalably-fabricated films is comparable to that of similarly layered niobate structures grown epitaxially.« less

  20. Glass-Like Thermal Conductivity of (010)-Textured Lanthanum-Doped Strontium Niobate Synthesized with Wet Chemical Deposition

    SciTech Connect

    Foley, Brian M.; Brown-Shaklee, Harlan J.; Campion, Michael J.; Medlin, Douglas L.; Clem, Paul G.; Ihlefeld, Jon F.; Hopkins, Patrick E.

    2014-11-08

    We have measured the cross-plane thermal conductivity (κ) of (010)-textured, undoped, and lanthanum-doped strontium niobate (Sr2-xLaxNb2O7-δ) thin films via time-domain thermoreflectance. Then the thin films were deposited on (001)-oriented SrTiO3 substrates via the highly-scalable technique of chemical solution deposition. We find that both film thickness and lanthanum doping have little effect on κ, suggesting that there is a more dominant phonon scattering mechanism present in the system; namely the weak interlayer-bonding along the b-axis in the Sr2Nb2O7 parent structure. We also compare our experimental results with two variations of the minimum-limit model for κ and discuss the nature of transport in material systems with weakly-bonded layers. The low cross-plane κ of these scalably-fabricated films is comparable to that of similarly layered niobate structures grown epitaxially.

  1. Preparation of samarium monosulfide via samarium naphthalenide

    SciTech Connect

    Andreev, O.V.; Nekrasova, T.V.; Bochkarev, M.N.

    1994-02-01

    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.

  2. High-temperature superconductivity in space-charge regions of lanthanum cuprate induced by two-dimensional doping.

    PubMed

    Baiutti, F; Logvenov, G; Gregori, G; Cristiani, G; Wang, Y; Sigle, W; van Aken, P A; Maier, J

    2015-01-01

    The exploitation of interface effects turned out to be a powerful tool for generating exciting material properties. Such properties include magnetism, electronic and ionic transport and even superconductivity. Here, instead of using conventional homogeneous doping to enhance the hole concentration in lanthanum cuprate and achieve superconductivity, we replace single LaO planes with SrO dopant planes using atomic-layer-by-layer molecular beam epitaxy (two-dimensional doping). Electron spectroscopy and microscopy, conductivity measurements and zinc tomography reveal such negatively charged interfaces to induce layer-dependent superconductivity (Tc up to 35 K) in the space-charge zone at the side of the planes facing the substrate, where the strontium (Sr) profile is abrupt. Owing to the growth conditions, the other side exhibits instead a Sr redistribution resulting in superconductivity due to conventional doping. The present study represents a successful example of two-dimensional doping of superconducting oxide systems and demonstrates its power in this field. PMID:26481902

  3. High-temperature superconductivity in space-charge regions of lanthanum cuprate induced by two-dimensional doping

    PubMed Central

    Baiutti, F.; Logvenov, G.; Gregori, G.; Cristiani, G.; Wang, Y.; Sigle, W.; van Aken, P. A.; Maier, J.

    2015-01-01

    The exploitation of interface effects turned out to be a powerful tool for generating exciting material properties. Such properties include magnetism, electronic and ionic transport and even superconductivity. Here, instead of using conventional homogeneous doping to enhance the hole concentration in lanthanum cuprate and achieve superconductivity, we replace single LaO planes with SrO dopant planes using atomic-layer-by-layer molecular beam epitaxy (two-dimensional doping). Electron spectroscopy and microscopy, conductivity measurements and zinc tomography reveal such negatively charged interfaces to induce layer-dependent superconductivity (Tc up to 35 K) in the space-charge zone at the side of the planes facing the substrate, where the strontium (Sr) profile is abrupt. Owing to the growth conditions, the other side exhibits instead a Sr redistribution resulting in superconductivity due to conventional doping. The present study represents a successful example of two-dimensional doping of superconducting oxide systems and demonstrates its power in this field. PMID:26481902

  4. Site selective spectroscopy and crystal field analysis of Eu/sup 3 +/ doped lanthanum--calcium--zirconium--silicon borate

    SciTech Connect

    Capobianco, J.A.; Proulx, P.P.; Raspa, N.; Simkin, D.J.; Krashkevich, D.

    1989-03-15

    The fluorescence of Eu/sup 3 +/ doped lanthanum--calcium--zirconium--silicon borate ceramic was studied at 77 and 300 K using laser excited site selective spectroscopy. The fluorescence spectrum excited at 514.532 nm reveals the presence of three distinct sites for Eu/sup 3 +/. The sites were assigned to Eu/sup 3 +/ substituting for lanthanum in a ninefold coordination site in LaBO/sub 3/ and Eu/sup 3 +/ substituting for Ca/sup 2 +/ in six- and sevenfold coordination sites in Ca/sub 2/B/sub 2/O/sub 5/. To assign the spectra to the definite sites a phenomenological crystal field analysis was conducted, using C/sub 2//sub v/ symmetry. The crystal field for Eu/sup 3 +/ in Ca/sub 2/B/sub 2/O/sub 5/ was found to be dominated by electrostatic effects. The large /sup 7/F/sub 1/ level splitting and the value of the B/sub 20/ parameter support the concept of strong ionic bonding between europium and oxygen in Ca/sub 2/B/sub 2/O/sub 5/.

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

    NASA Astrophysics Data System (ADS)

    Chiang, Kophu

    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.

  6. Determination of the ionic conductivity of Sr-doped lanthanum manganite by modified Hebb-Wagner technique

    NASA Astrophysics Data System (ADS)

    Miruszewski, T.; Karczewski, J.; Bochentyn, B.; Jasinski, P.; Gazda, M.; Kusz, B.

    2016-04-01

    The Hebb-Wagner polarization method with the electron blocking electrode has been discussed in this paper in aim to determine a partial ionic conductivity of Sr-doped lanthanum manganite. The "limiting current" in the proposed system was measured using the two-point DC technique with additional Pt electrode between LSM and blocking electrode. The electrochemical model based on bulk diffusion processes and Boltzmann statistics has been also described. The ionic conductivity calculated with the use of proposed model for La0.7Sr0.3MnO3+δ was 5.3×10-4 S cm-1 at 800 °C and the activation energy of ionic conductivity was found to be (0.60±0.02) eV. This result is in agreement with previous literature reports and indicates the workability of the modified Hebb-Wagner system.

  7. On magnetic ordering in heavily sodium substituted hole doped lanthanum manganites

    NASA Astrophysics Data System (ADS)

    Sethulakshmi, N.; Unnimaya, A. N.; Al-Omari, I. A.; Al-Harthi, Salim; Sagar, S.; Thomas, Senoy; Srinivasan, G.; Anantharaman, M. R.

    2015-10-01

    Mixed valence manganite system with monovalent sodium substituted lanthanum manganites form the basis of the present work. Lanthanum manganites belonging to the series La1-xNaxMnO3 with x=0.5-0.9 were synthesized using modified citrate gel method. Variation of lattice parameters and unit cell volume with Na concentration were analyzed and the magnetization measurements indicated ferromagnetic ordering in all samples at room temperature. Low temperature magnetization behavior indicated that all samples exhibit antiferromagnetism along with ferromagnetism and it has also been observed that antiferromagnetic ordering dominates ferromagnetic ordering as concentration is increased. Evidence for such a magnetic inhomogeneity in these samples has been confirmed from the variation in Mn3+/Mn4+ ion ratio from X-ray Photoelectron Spectroscopy and from the absorption peak studies using Ferromagnetic Resonance Spectroscopy.

  8. Doped lanthanum ferrite cathode development for use in single-step co-fired solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Zink, Peter Andrew

    A major obstacle to the commercialization of solid oxide fuel cells (SOFCs) is the high operating temperature range (800 to 1000°C). Lowering the operating temperature to approximately 600°C allows for cost reduction through the use of inexpensive stack housing and sealing materials, but conventional SOFC cathode materials have high charge transfer resistance at those temperatures which results in poor performance. This research focused on developing an SOFC cathode material with low charge transfer resistance at low operating temperatures and a porous microstructure that would not impede mass transfer when synthesized using the single-step co-firing process. Towards this goal, mixed ionic and electronic conducting lanthanum ferrite perovskite cathode materials were synthesized using calcium and cerium as dopants. A specific stoichiometry of calcium doped lanthanum ferrite, La0.78Ca0.16FeO3+/-delta (LCF), proved to be a superior cathode compared to state-of-the-art conventional cathode materials across a range of measures. In order to understand the LCF cathode performance, the defect model structure was determined using thermogravimetric (TGA) measurements, oxygen-ion permeability and four-probe conductivity measurements as a function of temperature and oxygen partial pressure (pO2). The results were analyzed to determine defect concentrations and mobility. The electrochemical performance of LCF was characterized using electrochemical impedance spectroscopy measurements on symmetrical cells which compared favorably to conventional lanthanum manganite cathode materials. Reactivity of LCF with yttria-stabilized zirconia (YSZ) electrolyte was confirmed and prevented using a gadolinium doped ceria (GDC) barrier layer. Microstructural analysis showed evidence of a small amount (2--5 wt%) of secondary phase that precipitated from LCF as a liquid during sintering at approximately 1220°C. The secondary phase was a poor n-type oxide (Ca-Fe-O), present within both the LCF cathode and GDC barrier layer microstructures. In spite of the presence of the liquid phase, LCF symmetrical cells yielded adequate microstructures and satisfactory electrochemical performance. To understand the reasons for the superior electrochemical performance of LCF, the chemical oxygen ion diffusivity and surface exchange coefficient were determined using conductivity relaxation measurements. Both of these parameters in LCF were found to be an order of magnitude greater than conventional cathode materials.

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

    NASA Astrophysics Data System (ADS)

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

    2013-01-01

    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.

  10. Preparation and photocatalytic activity of magnetic samarium-doped mesoporous titanium dioxide at the decomposition of methylene blue under visible light

    NASA Astrophysics Data System (ADS)

    Shi, Zhongliang; Lai, Hong; Yao, Shuhua

    2012-08-01

    Preparation of samarium-doped mesoporous titanium dioxide (Sm/MTiO2) coated magnetite (Fe3O4) photocatalysts (Sm/MTiO2/Fe3O4) and their activities under visible light were reported. The catalysts with Sm/MTiO2 shell and a Fe3O4 core were prepared by coating photoactive Sm/MTiO2 onto a magnetic Fe3O4 core through the hydrolysis of tetrabutyltitanate (Ti(OBu)4, TBT) with precursors of Sm(NO3)3 and TBT in the presence of Fe3O4 nanoparticles. The morphological, structural and optical properties of the prepared samples were characterized by BET surface area, transmission electron microscopy (TEM), X-ray diffraction (XRD) and UV-vis absorption spectroscopy. The effect of Sm ion content on the photocatalytic activity was studied. The photocatalytic activities of obtained photocatalysts under visible light were estimated by measuring the decomposition rate of methylene blue (MB, 50 mg/L) in an aqueous solution. The results showed that the prepared photocatalyst was activated by visible light and used as effective catalyst in photooxidation reactions. In addition, the possibility of cyclic usage of the prepared photocatalyst was also confirmed. Moreover, Sm/MTiO2 was tightly bound to Fe3O4 and could be easily recovered from the medium by a simple magnetic process. It can therefore be potentially applied for the treatment of water contaminated by organic pollutants.

  11. The properties of samarium-doped zinc oxide/phthalocyanine structure for optoelectronics prepared by pulsed laser deposition and organic molecular evaporation

    NASA Astrophysics Data System (ADS)

    Novotný, M.; Marešová, E.; Fitl, P.; Vlček, J.; Bergmann, M.; Vondráček, M.; Yatskiv, R.; Bulíř, J.; Hubík, P.; Hruška, P.; Drahokoupil, J.; Abdellaoui, N.; Vrňata, M.; Lančok, J.

    2016-03-01

    Samarium-doped zinc oxide (ZnO:Sm)/zinc phthalocyanine (ZnPc) thin film multilayer structure was prepared by combination of pulsed laser deposition (PLD) and organic molecular evaporation (OME). ZnO:Sm thin film was grown by PLD (Nd:YAG, λ = 266 nm, τ = 6 ns) from Sm2O3:ZnO (1 % Sm) target in oxygen ambient at pressure of 10 and 20 Pa at room temperature on fused silica and Si(100) substrates. ZnPc thin film was deposited on ZnO:Sm layer by OME. ZnO:Sm films of c-axis-oriented hexagonal wurtzite structure and α-form ZnPc were obtained. Emission of intra-4f transition in Sm3+ ions and photoluminescence enhancement of near-band-edge emission of ZnO in ZnO:Sm/ZnPc were observed. Electrical properties were not affected by Sm3+ dopant as ZnO:Sm film exhibited high electrical resistivity ~5 × 104 Ω cm.

  12. Structural and spectroscopic properties of rare-earth (Nd3+, Er3+, and Yb3+) doped transparent lead lanthanum zirconate titanate ceramics

    NASA Astrophysics Data System (ADS)

    de Camargo, Andrea S. S.; de O. Nunes, Luiz Antonio; Santos, Ivair A.; Garcia, Ducinei; Eiras, José Antonio

    2004-02-01

    This work presents the structural and spectroscopic characterization of transparent lead lanthanum zirconate titanate ceramics doped with Nd3+, Er3+, or Yb3+ ions. High optical quality samples presenting the perovskite structure were prepared through a mixed oxides method followed by conventional sintering or uniaxial hot pressing. Absorption and luminescence spectra were measured, and radiative emission parameters were calculated for Nd3+- and Er3+-doped samples. The results indicate the potential of these polycrystalline host-ion combinations for the construction of diode-pumped lasers in the near-infrared region.

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

    SciTech Connect

    Setz, L.F.G.; Colomer, M.T.; Mello-Castanho, S.R.H.

    2011-07-15

    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.

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

    SciTech Connect

    Shi, Qingle; Lu, Lihua; Jin, Hongjian; Zhang, Hua; Zeng, Yanwei

    2012-03-15

    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.

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

    DOEpatents

    Singh, Prabhakar; Ruka, Roswell J.

    1995-01-01

    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.

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

    DOEpatents

    Singh, P.; Ruka, R.J.

    1995-02-14

    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.

  17. Strongly enhanced oxygen ion transport through samarium-doped CeO2 nanopillars in nanocomposite films

    SciTech Connect

    Yang, Sangmo; Lee, Shinbuhm; Jian, Jie; Zhang, Wenrui; Lu, Ping; Jia, Quanxi; Wang, Haiyan; Noh, Tae Won; Kalinin, Sergei V.; MacManus-Driscoll, Judith L.

    2015-10-08

    Enhancement of oxygen ion conductivity in oxides is important for low-temperature (<500 °C) operation of solid oxide fuel cells, sensors and other ionotronic devices. While huge ion conductivity has been demonstrated in planar heterostructure films, there has been considerable debate over the origin of the conductivity enhancement, in part because of the difficulties of probing buried ion transport channels. Here we create a practical geometry for device miniaturization, consisting of highly crystalline micrometre-thick vertical nanocolumns of Sm-doped CeO2 embedded in supporting matrices of SrTiO3. The ionic conductivity is higher by one order of magnitude than plain Sm-doped CeO2 films. By using scanning probe microscopy, we show that the fast ion-conducting channels are not exclusively restricted to the interface but also are localized at the Sm-doped CeO2 nanopillars. This work offers a pathway to realize spatially localized fast ion transport in oxides of micrometre thickness.

  18. Strongly enhanced oxygen ion transport through samarium-doped CeO2 nanopillars in nanocomposite films

    DOE PAGESBeta

    Yang, Sangmo; Lee, Shinbuhm; Jian, Jie; Zhang, Wenrui; Lu, Ping; Jia, Quanxi; Wang, Haiyan; Noh, Tae Won; Kalinin, Sergei V.; MacManus-Driscoll, Judith L.

    2015-10-08

    Enhancement of oxygen ion conductivity in oxides is important for low-temperature (<500 °C) operation of solid oxide fuel cells, sensors and other ionotronic devices. While huge ion conductivity has been demonstrated in planar heterostructure films, there has been considerable debate over the origin of the conductivity enhancement, in part because of the difficulties of probing buried ion transport channels. Here we create a practical geometry for device miniaturization, consisting of highly crystalline micrometre-thick vertical nanocolumns of Sm-doped CeO2 embedded in supporting matrices of SrTiO3. The ionic conductivity is higher by one order of magnitude than plain Sm-doped CeO2 films. Bymore » using scanning probe microscopy, we show that the fast ion-conducting channels are not exclusively restricted to the interface but also are localized at the Sm-doped CeO2 nanopillars. This work offers a pathway to realize spatially localized fast ion transport in oxides of micrometre thickness.« less

  19. Strongly enhanced oxygen ion transport through samarium-doped CeO2 nanopillars in nanocomposite films

    SciTech Connect

    Yang, Sang Mo; Lee, Shinbuhm; Jian, Jie; Zhang, Wenrui; Lu, Ping; Jia, Quanxi; Wang, Haiyan; Won Noh, Tae; Kalinin, Sergei V.; MacManus‐Driscoll, Judith L.

    2015-10-08

    Enhancement of oxygen ion conductivity in oxides is important for low-temperature (<500 °C) operation of solid oxide fuel cells, sensors and other ionotronic devices. While huge ion conductivity has been demonstrated in planar heterostructure films, there has been considerable debate over the origin of the conductivity enhancement, in part because of the difficulties of probing buried ion transport channels. Here we create a practical geometry for device miniaturization, consisting of highly crystalline micrometre-thick vertical nanocolumns of Sm-doped CeO2 embedded in supporting matrices of SrTiO3. The ionic conductivity is higher by one order of magnitude than plain Sm-doped CeO2films. Then by using scanning probe microscopy, we show that the fast ion-conducting channels are not exclusively restricted to the interface but also are localized at the Sm-doped CeO2 nanopillars. Furthermore, this work offers a pathway to realize spatially localized fast ion transport in oxides of micrometre thickness.

  20. Strongly enhanced oxygen ion transport through samarium-doped CeO2 nanopillars in nanocomposite films

    DOE PAGESBeta

    Yang, Sang Mo; Lee, Shinbuhm; Jian, Jie; Zhang, Wenrui; Lu, Ping; Jia, Quanxi; Wang, Haiyan; Won Noh, Tae; Kalinin, Sergei V.; MacManus‐Driscoll, Judith L.

    2015-10-08

    Enhancement of oxygen ion conductivity in oxides is important for low-temperature (<500 °C) operation of solid oxide fuel cells, sensors and other ionotronic devices. While huge ion conductivity has been demonstrated in planar heterostructure films, there has been considerable debate over the origin of the conductivity enhancement, in part because of the difficulties of probing buried ion transport channels. Here we create a practical geometry for device miniaturization, consisting of highly crystalline micrometre-thick vertical nanocolumns of Sm-doped CeO2 embedded in supporting matrices of SrTiO3. The ionic conductivity is higher by one order of magnitude than plain Sm-doped CeO2films. Then bymore » using scanning probe microscopy, we show that the fast ion-conducting channels are not exclusively restricted to the interface but also are localized at the Sm-doped CeO2 nanopillars. Furthermore, this work offers a pathway to realize spatially localized fast ion transport in oxides of micrometre thickness.« less

  1. Strongly enhanced oxygen ion transport through samarium-doped CeO2 nanopillars in nanocomposite films.

    PubMed

    Yang, Sang Mo; Lee, Shinbuhm; Jian, Jie; Zhang, Wenrui; Lu, Ping; Jia, Quanxi; Wang, Haiyan; Noh, Tae Won; Kalinin, Sergei V; MacManus-Driscoll, Judith L

    2015-01-01

    Enhancement of oxygen ion conductivity in oxides is important for low-temperature (<500 °C) operation of solid oxide fuel cells, sensors and other ionotronic devices. While huge ion conductivity has been demonstrated in planar heterostructure films, there has been considerable debate over the origin of the conductivity enhancement, in part because of the difficulties of probing buried ion transport channels. Here we create a practical geometry for device miniaturization, consisting of highly crystalline micrometre-thick vertical nanocolumns of Sm-doped CeO2 embedded in supporting matrices of SrTiO3. The ionic conductivity is higher by one order of magnitude than plain Sm-doped CeO2 films. By using scanning probe microscopy, we show that the fast ion-conducting channels are not exclusively restricted to the interface but also are localized at the Sm-doped CeO2 nanopillars. This work offers a pathway to realize spatially localized fast ion transport in oxides of micrometre thickness. PMID:26446866

  2. Strongly enhanced oxygen ion transport through samarium-doped CeO2 nanopillars in nanocomposite films

    NASA Astrophysics Data System (ADS)

    Yang, Sang Mo; Lee, Shinbuhm; Jian, Jie; Zhang, Wenrui; Lu, Ping; Jia, Quanxi; Wang, Haiyan; Won Noh, Tae; Kalinin, Sergei V.; MacManus-Driscoll, Judith L.

    2015-10-01

    Enhancement of oxygen ion conductivity in oxides is important for low-temperature (<500 °C) operation of solid oxide fuel cells, sensors and other ionotronic devices. While huge ion conductivity has been demonstrated in planar heterostructure films, there has been considerable debate over the origin of the conductivity enhancement, in part because of the difficulties of probing buried ion transport channels. Here we create a practical geometry for device miniaturization, consisting of highly crystalline micrometre-thick vertical nanocolumns of Sm-doped CeO2 embedded in supporting matrices of SrTiO3. The ionic conductivity is higher by one order of magnitude than plain Sm-doped CeO2 films. By using scanning probe microscopy, we show that the fast ion-conducting channels are not exclusively restricted to the interface but also are localized at the Sm-doped CeO2 nanopillars. This work offers a pathway to realize spatially localized fast ion transport in oxides of micrometre thickness.

  3. Strongly enhanced oxygen ion transport through samarium-doped CeO2 nanopillars in nanocomposite films

    PubMed Central

    Yang, Sang Mo; Lee, Shinbuhm; Jian, Jie; Zhang, Wenrui; Lu, Ping; Jia, Quanxi; Wang, Haiyan; Won Noh, Tae; Kalinin, Sergei V.; MacManus-Driscoll, Judith L.

    2015-01-01

    Enhancement of oxygen ion conductivity in oxides is important for low-temperature (<500 °C) operation of solid oxide fuel cells, sensors and other ionotronic devices. While huge ion conductivity has been demonstrated in planar heterostructure films, there has been considerable debate over the origin of the conductivity enhancement, in part because of the difficulties of probing buried ion transport channels. Here we create a practical geometry for device miniaturization, consisting of highly crystalline micrometre-thick vertical nanocolumns of Sm-doped CeO2 embedded in supporting matrices of SrTiO3. The ionic conductivity is higher by one order of magnitude than plain Sm-doped CeO2 films. By using scanning probe microscopy, we show that the fast ion-conducting channels are not exclusively restricted to the interface but also are localized at the Sm-doped CeO2 nanopillars. This work offers a pathway to realize spatially localized fast ion transport in oxides of micrometre thickness. PMID:26446866

  4. First-principles study of Ce3 +-doped lanthanum silicate nitride phosphors: Neutral excitation, Stokes shift, and luminescent center identification

    NASA Astrophysics Data System (ADS)

    Jia, Yongchao; Miglio, Anna; Poncé, Samuel; Gonze, Xavier; Mikami, Masayoshi

    2016-04-01

    We study from first principles two lanthanum silicate nitride compounds, LaSi3N5 and La3Si6N11 , pristine as well as doped with Ce3 + ion, in view of explaining their different emission color, and characterizing the luminescent center. The electronic structures of the two undoped hosts are similar, and do not give a hint to quantitatively describe such difference. The 4 f →5 d neutral excitation of the Ce3 + ions is simulated through a constrained density functional theory method coupled with a Δ SCF analysis of total energies, yielding absorption energies. Afterwards, atomic positions in the excited state are relaxed, yielding the emission energies and Stokes shifts. Based on these results, the luminescent centers in LaSi3N5 :Ce and La3Si6N11 :Ce are identified. The agreement with the experimental data for the computed quantities is quite reasonable and explains the different color of the emitted light. Also, the Stokes shifts are obtained within 20% difference relative to experimental data.

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

    X-ray diffraction (XRD), dielectric constant (ɛ'), dielectric loss factor (ɛ″), and ac conductivity (σac) 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 α-phase. The incorporation of La3+ ions within the PVDF polymer matrix forms complexes which reduce the order structure of PVDF. Three relaxation processes, namely; ρ, αa, and αc 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.

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

    SciTech Connect

    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

    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.

  7. Electronic structure of doped lanthanum cuprates studied with resonant inelastic x-ray scattering

    NASA Astrophysics Data System (ADS)

    Ellis, D. S.; Kim, Jungho; Zhang, Harry; Hill, J. P.; Gu, Genda; Komiya, Seiki; Ando, Yoichi; Casa, D.; Gog, T.; Kim, Young-June

    2011-02-01

    We report a comprehensive Cu K-edge resonant inelastic x-ray scattering (RIXS) investigation of La2-xSrxCuO4 (LSCO) for 0⩽x⩽0.35, stripe-ordered La1.875Ba0.125CuO4 (LBCO), and La2Cu0.96Ni0.04O4 (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=(π,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→upper Hubbard band, lower-lying band→upper Hubbard band, and lower-lying band→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 ~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.

  8. Samarium/Cobalt Magnets

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

    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.

  9. Doped Lanthanum Hafnates as Scintillating Materials for High-Energy Photon Detection

    NASA Astrophysics Data System (ADS)

    Wahid, Kareem; Pokhrel, Madhab; Mao, Yuanbing

    Recent years have seen the emergence of nanocrystalline complex oxide scintillators for use in X-ray and gamma-ray detection. In this study, we investigate the structural and optical properties of La2Hf2O7 nanoparticles doped with varying levels of Eu3+ or Ce3+ by use of X-ray diffraction, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, and optical photoluminescence. In addition, scintillation response under X-ray and gamma-ray exposure is reported. The authors thank the support from the Defense Threat Reduction Agency (DTRA) of the U.S. Department of Defense (Award #HDTRA1-10-1-0114).

  10. A first-principles study of co-doping in lanthanum bromide

    NASA Astrophysics Data System (ADS)

    Aberg, Daniel; Sadigh, Babak; Schleife, Andre; Erhart, Paul

    2015-03-01

    It was recently shown that the energy resolution of Ce-doped LaBr3 scintillator radiation detectors can be crucially improved by co-doping with Sr, Ca, or Ba. Here we outline a mechanism for this enhancement on the basis of electronic structure calculations. We show that Sr dopants create and bind to Br vacancies, resulting in stable neutral complexes. The association with Sr causes the deep vacancy level to move toward the conduction band edge. This is essential for reducing the effective carrier density available for Auger quenching during thermalization of hot carriers. Subsequent de-trapping of electrons from the complexes can activate Ce dopants that have previously captured a hole leading to luminescence. This mechanism implies an overall reduction of Auger quenching of free carriers, which is expected to improve the linearity of the photon light yield with respect to the energy of incident electron or photon. Optical properties of the Ce-Sr-vacancy triple complex are discussed and compared to experiment. Prepared by LLNL under Contract DE-AC52-07NA27344. Support from the National Nuclear Security Administration Office of Nonproliferation Research and Development (NA-22) is acknowledged.

  11. Synthesis and Luminescence Properties of Terbium-Doped Lanthanum Oxychloride Nanostructures.

    PubMed

    Kong, Qingling; Wang, Jinxian; Dong, Xiangting; Yu, Wensheng; Liu, Guixia

    2015-06-01

    LaOCl:Tb3+ nanofibers, nanotubes and nanobelts were prepared via electrospinning combined with a double-crucible chlorination technique using NH4Cl powders as chlorinating agent. Different morphologies of LaOCl:Tb3+ nanostructures were obtained through adjusting some of the electrospun parameters. The as-prepared LaOCl:Tb3+ nanostructures are tetragonal in structure with space group of P4/nmm. The diameters of LaOCl:Tb3+ nanofibers, nanotubes and the width of LaOCl:Tb3+ nanobelts are respectively 133.99 16.95 nm, 140.57 17.82 nm and 5.32 0.63 ?m under the 95% confidence level. Under the excitation of 230-nm ultraviolet light, the LaOCl:Tb3+ nanostructures emit the predominant emission peaks at 544 nm originated from the energy levels transition of 5D4 --> 7F5 of Tb3+ ions. The optimum molar percentage of Tb3+ in the LaOCl:Tb3+ nanofibers is 7%. LaOCl:Tb3+ nanobelts exhibit the strongest PL intensity of the three nanostructures under the same doping molar concentration. The possible formation mechanisms of LaOCl:Tb3+ nanostructures are also proposed. PMID:26369042

  12. 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

    Abdulvagidov, Sh. B. Gamzatov, A. G.; Mel'nikov, O. V.; Gorbenko, O. Yu.

    2009-12-15

    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.

  13. Metals fact sheet - samarium

    SciTech Connect

    1993-10-01

    The crustal abundance of samarium is 7 ppm, similar to that of praseodymium and gadolinium. About 50 percent of the total samarium oxide produced worldwide comes from the mining of monazite. Bastnasite accounts for approximately 40 percent of samarium oxide production, and the remaining 10 percent is derived from other rare earth minerals such as xenotime, apatite, loparite, and rare earth clays. Monazite is usually found in alluvial or beach deposits associated with other heavy minerals, typically rutile and zircon, and is recovered by suction dredging or bucket wheel excavation. The heavy minerals are subsequently separated by gravity, magnetic, and/or electrostatic means, and the resulting monazite concentrate undergoes a series of caustic and acid leaching steps to isolate the rare earths. Bastnasite, on the other hand, is a fluorocarbonate associated with igneous intrusions in quartzite or epithermal, fluorite-bearing veins, and is mined by open-pit methods. The ore is beneficiated by flotation, then acid-leached, filtered and calcined to produce a rare earth concentrate. Although a light rare earth, samarium oxide is isolated only after about three stages of solvent extraction, together with heavier oxides of gadolinium, terbium, and yttrium.

  14. Variation in band gap of lanthanum chromate by transition metals doping LaCr{sub 0.9}A{sub 0.1}O{sub 3} (A:Fe/Co/Ni)

    SciTech Connect

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

    2014-04-24

    Transition metal (Fe, Co, Ni) doped lanthanum chromate (LaCrO{sub 3}) nanoparticles (NPs) were prepared by gel combustion method and calcinated at 800°C. 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 LaCrO{sub 3} at about 315 nm. Influence of Fe, Co, Ni doping was studied and compared with pure lanthanum chromate nanoparticles.

  15. CW blue laser emission by second harmonic generation of 900-nm oscillation of Nd-doped strontium and lanthanum aluminate (ASL)

    NASA Astrophysics Data System (ADS)

    Varona, C.; Loiseau, P.; Aka, G.; Ferrand, B.; Lupei, V.

    2006-04-01

    Nd-doped strontium and lanthanum (ASL) crystals Sr 1-xLa x-yNd yMg xAl 12-xO 19 (0.05 <= x <= 0.5; y = 0.05) were grown by Czochralski pulling technique. Up to 1.67W of 900nm IR output laser power for an absorbed power of 2.53W was obtained under Ti:sapphire pumping at 792nm. Intracavity second harmonic generation experiments led to 320mW of blue laser power at 450nm with a 10mm-long BiB 3O 6 nonlinear crystal. Other nonlinear crystals were also evaluated such as LBO.

  16. Study of the Durability of Doped Lanthanum Manganite and Cobaltite Cathode Materials under ''Real World'' Air Exposure Atmospheres

    SciTech Connect

    Singh, Prabhakar; Mahapatra, Manoj; Ramprasad, Rampi; Minh, Nguyen; Misture, Scott

    2014-11-30

    The overall objective of the program is to develop and validate mechanisms responsible for the overall structural and chemical degradation of lanthanum manganite as well as lanthanum ferrite cobaltite based cathode when exposed to “real world” air atmosphere exposure conditions during SOFC systems operation. Of particular interest are the evaluation and analysis of degradation phenomena related to and responsible for (a) products formation and interactions with air contaminants, (b) dopant segregation and oxide exolution at free surfaces, (c) cation interdiffusion and reaction products formation at the buried interfaces, (d) interface morphology changes, lattice transformation and the development of interfacial porosity and (e) micro-cracking and delamination from the stack repeat units. Reaction processes have been studied using electrochemical and high temperature materials compatibility tests followed by structural and chemical characterization. Degradation hypothesis has been proposed and validated through further experimentation and computational simulation.

  17. Formation mechanism and characteristics of lanthanum-doped BaTiO{sub 3} powders and ceramics prepared by the sol–gel process

    SciTech Connect

    Ianculescu, Adelina Carmen; Vasilescu, Catalina Andreea; Crisan, Maria; Raileanu, Malina; Vasile, Bogdan Stefan; Calugaru, Mihai; Crisan, Dorel; Dragan, Nicolae; Curecheriu, Lavinia; Mitoseriu, Liliana

    2015-08-15

    Pure and lanthanum-doped barium titanate nanopowders described by two different formulae, as Ba{sub 1−x}La{sub x}TiO{sub 3}, for lower La concentrations (0 ≤ x ≤ 0.005) and Ba{sub 1−x}La{sub x}Ti{sub 1−x/4}O{sub 3} for higher La concentration (x = 0.025) were prepared by an alkoxide sol–gel method. Single phase compositions were obtained after annealing at 900 °C for 2 h, in air. The increase of the lanthanum content causes structural and morphological changes in the oxide powders, including the evolution of the unit cell from tetragonal toward a cubic symmetry, the particle size decrease and a higher aggregation tendency. SEM investigations of the ceramics sintered at 1300 °C for 4 h indicate significant changes of the microstructural features (strong decrease of the average grain size and increase of the intergranular porosity) with the raise of La amount. Lanthanum addition to barium titanate prepared by sol–gel induces a more significant shift of the Curie temperature toward lower values, than that one reported in literature for ceramics of similar compositions, but processed by the conventional solid state method. The compositions with smaller La amount (x ≤ 0.005) show semiconducting properties at room temperature and high relative dielectric permittivity values, while the undoped ceramics and those doped with higher La content (x = 0.025) are good dielectrics. The ceramic with x = 0.025 exhibits acceptable low losses, a very diffuse ferroelectric–paraelectric transition and Curie temperature closed to the room temperature, being thus susceptible for high tunability applications. - Highlights: • Ba{sub 1−x}La{sub x}TiO{sub 3} (x ≤ 0.005) and Ba{sub 1−x}La{sub x}Ti{sub 1−x/4}O{sub 3} (x = 0.025) were prepared by sol–gel. • Ceramics with x < 0.5 exhibit semiconductor and high dielectric properties. • Ceramic with x = 0.025 exhibits acceptable low losses and diffuse phase transition.

  18. Design and fabrication of lanthanum-doped tin-silver-copper lead-free solder for the next generation of microelectronics applications in severe environment

    NASA Astrophysics Data System (ADS)

    Sadiq, Muhammad

    Tin-Lead solder (Sn-Pb) has long been used in the Electronics industry. But, due to its toxic nature and environmental effects, certain restrictions are made on its use by the European Rehabilitation of Hazardous Substances (RoHS) directive, and therefore, many researchers are looking to replace it. The urgent need for removing lead from solder alloys led to the very fast introduction of lead-free solder alloys without a deep knowledge of their behavior. Therefore, an extensive knowledge and understanding of the mechanical behavior of the emerging generation of lead-free solders is required to satisfy the demands of structural reliability. Sn-Ag-Cu (SAC) solders are widely used as lead-free replacements but their coarse microstructure and formation of hard and brittle Inter-Metallic Compounds (IMCs) have limited their use in high temperature applications. Many additives are studied to refine the microstructure and improve the mechanical properties of SAC solders including iron (Fe), bismuth (Bi), antimony (Sb) and indium (In) etc. Whereas many researchers studied the impact of novel rare earth (RE) elements like lanthanum (La), cerium (Ce) and lutetium (Lu) on SAC solders. These RE elements are known as “vitamins of metals” because of their special surface active properties. They reduce the surface free energy, refine the grain size and improve the mechanical properties of many lead free solder alloys like Sn-Ag, Sn-Cu and SAC but still a systematic study is required to explore the special effects of “La” on the eutectic SAC alloys. The objective of this PhD thesis is to extend the current knowledge about lead free solders of SAC alloys towards lanthanum doping with varying environmental conditions implemented during service. This thesis is divided into six main parts.

  19. Stability of the Zhang-Rice Singlet with Doping in Lanthanum Strontium Copper Oxide Across the Superconducting Dome and Above

    NASA Astrophysics Data System (ADS)

    Brookes, N. B.; Ghiringhelli, G.; Charvet, A.-M.; Fujimori, A.; Kakeshita, T.; Eisaki, H.; Uchida, S.; Mizokawa, T.

    2015-07-01

    The spin character of the states at the top of the valence band in doped La2 -xSrxCuO4 (x =0.03 , 0.07, 0.15, 0.22, and 0.30) has been investigated using spin-polarized resonant photoemission. A clear Zhang-Rice singlet (ZRS) is observed at all doping levels. Its stability and polarization are preserved as a function of doping, suggesting that the concept of the ZRS can be used across a wide doping range and up to the metallic nonsuperconducting overdoped regime. The results are significant for theoretical models that use the ZRS approximation and for the understanding of the peculiar interplay between the ZRS and the remaining localized spins.

  20. Stability of the Zhang-Rice Singlet with Doping in Lanthanum Strontium Copper Oxide Across the Superconducting Dome and Above.

    PubMed

    Brookes, N B; Ghiringhelli, G; Charvet, A-M; Fujimori, A; Kakeshita, T; Eisaki, H; Uchida, S; Mizokawa, T

    2015-07-10

    The spin character of the states at the top of the valence band in doped La(2-x)Sr(x)CuO(4) (x=0.03, 0.07, 0.15, 0.22, and 0.30) has been investigated using spin-polarized resonant photoemission. A clear Zhang-Rice singlet (ZRS) is observed at all doping levels. Its stability and polarization are preserved as a function of doping, suggesting that the concept of the ZRS can be used across a wide doping range and up to the metallic nonsuperconducting overdoped regime. The results are significant for theoretical models that use the ZRS approximation and for the understanding of the peculiar interplay between the ZRS and the remaining localized spins. PMID:26207496

  1. Hydrothermal synthesis of doped lanthanum zirconate nanomaterials and the effect of V–Ge substitution on their structural, electrical and dielectric properties

    SciTech Connect

    Farid, Muhammad Asim; Asghar, Muhammad Adnan; Ashiq, Muhammad Naeem Ehsan, Muhammad Fahad; Athar, Muhammad

    2014-11-15

    Graphical abstract: Variation of dielectric constant with frequency for all the synthesized materials. - Highlights: • Hydrothermal method has been successfully employed to synthesize the zirconates. • XRD confirmed the formation of required phase. • Increased electrical resistivity makes these materials useful for microwave devices. • Dielectric parameters of zirconates decrease with increasing frequency. • Dielectric constant decreases with increasing substituents concentration. - Abstract: A hydrothermal method was successfully employed for the synthesis of a series of vanadium and germanium co-doped pyrochlore lanthanum zirconates with composition La{sub 2−x}V{sub x}Zr{sub 2−y}Ge{sub y}O{sub 7} (where x, y = 0.0, 0.25, 0.50, 0.75 and 1.0). The XRD and FTIR analyses confirmed the formation of single phase except vanadium and germanium substituted samples and the crystallite sizes are in the range of 7–31 nm for V{sup 3+}–Ge{sup 4+} substituted samples. The theoretical compositions are confirmed by the ED-XRF studies. The room temperature electrical resistivity increase with the substituents concentration which suggests that the synthesized materials can be used for microwave devices as such devices required highly resistive materials. Dielectric properties were measured in the frequency range of 6 kHz to 1 MHz. The dielectric parameters decrease with increase in frequency. The DC resistivity data is in good agreement with the dielectric data.

  2. Electrochemical ammonia synthesis from steam and nitrogen using proton conducting yttrium doped barium zirconate electrolyte with silver, platinum, and lanthanum strontium cobalt ferrite electrocatalyst

    NASA Astrophysics Data System (ADS)

    Yun, Dae Sik; Joo, Jong Hoon; Yu, Ji Haeng; Yoon, Hyung Chul; Kim, Jong-Nam; Yoo, Chung-Yul

    2015-06-01

    Electrochemical ammonia synthesis from steam and nitrogen has been systematically investigated using a proton-conducting electrolyte supported cell based on 20 mol% yttrium doped barium zirconate (BaZr0.8Y0.2O3-δ) in a temperature range of 475-600 °C at atmospheric pressure. Silver (Ag), platinum (Pt), and lanthanum strontium cobalt ferrite (La0.6Sr0.4Co0.2Fe0.8O3-δ) are used for both anode and cathode electrocatalysts. Maximum ammonia formation rates of 4.9 × 10-11 mol cm-2 s-1 and 8.5 × 10-11 mol cm-2 s-1 are observed for Ag and La0.6Sr0.4Co0.2Fe0.8O3-δ electrocatalysts, respectively, when a voltage of 0.8 V is applied. However, Pt electrocatalyst shows a negligible ammonia formation rate lower than 1 × 10-12 mol cm-2 s-1. This is ascribed to the high activity of Pt for the hydrogen evolution reaction rather than the ammonia formation reaction. The conversion efficiency of all electrocatalysts is below 1%, primarily due to the limited nitrogen disassociation activity of the electrocatalysts.

  3. Synthesis and Luminescence Properties of Novel Ce(3+)- and Eu(2+)-Doped Lanthanum Bromothiosilicate La3Br(SiS4)2 Phosphors for White LEDs.

    PubMed

    Lee, Szu-Ping; Liu, Shuang-De; Chan, Ting-Shan; Chen, Teng-Ming

    2016-04-13

    Novel Ce(3+)- and Eu(2+)-doped lanthanum bromothiosilicate La3Br(SiS4)2:Ce(3+)and La3Br(SiS4)2:Eu(2+) phosphors were prepared by solid-state reaction in an evacuated and sealed quartz glass ampule. The La3Br(SiS4)2:Ce(3+) phosphor generates a cyan emission upon excitation at 375 nm, whereas the La3Br(SiS4)2:Eu(2+) phosphor could be excited with extremely broad range from UV to blue region (300 to 600 nm) and generates a reddish-orange broadband emission centered at 640 nm. In addition, thermal luminescence properties of La3Br(SiS4)2:Ce(3+)and La3Br(SiS4)2:Eu(2+) phosphors from 20 to 200 °C were investigated. The combination of a 450 nm blue InGaN-based LED chip with the red-emitting La3Br(SiS4)2:Eu(2+) phosphor, and green-emitting BOSE:Eu(2+) commercial phosphor produced a warm-white light with the CRI value of ∼95 and the CCT of 5,120 K. Overall, these results show that the prepared phosphors may have potential applications in pc-WLED. PMID:26998783

  4. Photocatalytic degradation of Reactive Black 5 and Malachite Green with ZnO and lanthanum doped nanoparticles

    NASA Astrophysics Data System (ADS)

    Kaneva, N.; Bojinova, A.; Papazova, K.

    2016-02-01

    Here we report the preparation of ZnO particles with different concentrations of La3+ doping (0, 0.5 and 1 wt%) via sol-gel method. The nanoparticles are synthesized directly from Zn(CH3COO)2.2H2O in the presence of 1-propanol and triethylamine at 80°C. The conditions are optimized to obtain particles of uniform size, easy to isolate and purify. The nanoparticles are characterized by SEM, XRD and UV-Vis analysis. The photocatalytic properties of pure and La-doped ZnO are studied in the photobleaching of Malachite Green (MG) and Reactive Black 5 (RB5) dyes in aqueous solutions upon UV illumination. It is observed that the rate constant increases with the La loading up to 1 wt%. The doping helps to achieve complete mineralization of MG within a short irradiation time. 1 wt% La-doped ZnO nanoparticles show highest photocatalytic activity. The La3+ doped ZnO particles degrade faster RB5 than MG. The reason is weaker N=N bond in comparison with the C-C bond between the central carbon atom and N,N-dimethylaminobenzyl in MG. The as-prepared ZnO particles can find practical application in photocatalytic purification of textile wastewaters.

  5. Structural and magnetic properties of yttrium and lanthanum-doped Ni-Co and Ni-Co-Zn spinel ferrites

    SciTech Connect

    Stergiou, Charalampos; Litsardakis, George

    2014-11-05

    Rare earth doping of Co-rich spinel ferrites is investigated through the preparation of two groups of polycrystalline Ni-Co and Ni-Co-Zn ferrites, where Fe is partly substituted by Y and La. The characterization of the sintered ferrites by means of X-ray powder diffraction and Rietveld profile analysis, indicates the subtle expansion of the spinel unit cell and the cation redistribution in the doped ferrites in order to accommodate the incorporation of Y and La in the lattice. The impurity traces, detected only in the Ni-Co-Zn group, is ascribed to the Zn population in the tetrahedral A-sites impeding the cation transfer. Moreover, the examined microstructure of the doped Ni-Co samples comprises enlarged and more homogeneous grains, whereas grain growth is moderated in the doped Ni-Co-Zn ferrites. The discussed characteristics of the crystal and magnetic structure along with the morphological aspects define the impact of Y and La doping on the static magnetic properties of Ni-Co and Ni-Co-Zn ferrites, saturation magnetization MS and coercivity HC, which were extracted from the respective hysteresis loops.

  6. Structural and magnetic properties of yttrium and lanthanum-doped Ni-Co and Ni-Co-Zn spinel ferrites

    NASA Astrophysics Data System (ADS)

    Stergiou, Charalampos; Litsardakis, George

    2014-11-01

    Rare earth doping of Co-rich spinel ferrites is investigated through the preparation of two groups of polycrystalline Ni-Co and Ni-Co-Zn ferrites, where Fe is partly substituted by Y and La. The characterization of the sintered ferrites by means of X-ray powder diffraction and Rietveld profile analysis, indicates the subtle expansion of the spinel unit cell and the cation redistribution in the doped ferrites in order to accommodate the incorporation of Y and La in the lattice. The impurity traces, detected only in the Ni-Co-Zn group, is ascribed to the Zn population in the tetrahedral A-sites impeding the cation transfer. Moreover, the examined microstructure of the doped Ni-Co samples comprises enlarged and more homogeneous grains, whereas grain growth is moderated in the doped Ni-Co-Zn ferrites. The discussed characteristics of the crystal and magnetic structure along with the morphological aspects define the impact of Y and La doping on the static magnetic properties of Ni-Co and Ni-Co-Zn ferrites, saturation magnetization MS and coercivity HC, which were extracted from the respective hysteresis loops.

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

    DOEpatents

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

    1992-07-21

    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.

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

    DOEpatents

    Richards, Von L.; Singhal, Subhash C.; Pal, Uday B.

    1992-01-01

    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.

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

    PubMed

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

    2013-01-01

    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

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

    SciTech Connect

    Thongbai, Prasit; Putasaeng, Bundit; Yamwong, Teerapon; Maensiri, Santi

    2012-09-15

    Highlights: ► Grain size of CaCu{sub 3}Ti{sub 4}O{sub 12} ceramics was greatly decreased by doping with Sm{sup 3+}. ► ε′ and tan δ 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 ε′ ∼ 10,863 and low tan δ ∼ 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 (ε′) and loss tangent (tan δ) of CaCu{sub 3}Ti{sub 4}O{sub 12} ceramics. Interestingly, high dielectric permittivity (ε′ ∼ 10,863) and low loss tangent (tan δ ∼ 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.

  11. Growth and barium zirconium oxide doping study on superconducting M-barium copper oxide (M = yttrium, samarium) films using a fluorine-free metal organic decomposition process

    NASA Astrophysics Data System (ADS)

    Lu, Feng

    We present a fluorine-free metal organic deposition (F-free MOD) process - which is possibly a rapid and economic alternative to commercial trifluoroacetates metal organic deposition (TFA-MOD) and metal organic chemical vapor deposition (MOCVD) processes - for the fabrication of high quality epitaxial high temperature superconducting YBa2Cu3O7-x (YBCO) films on both Rolling-Assisted Biaxially Textured Substrates (RABiTS) and single crystal substrates. We first studied the growth of YBCO and SmBCO films, and their resulting microstructure and superconducting properties. We produced epitaxial c-axis YBCO films with high critical current density (Jc) in excess of 106 A/cm2 at 77K in self field at the thickness of ˜1 mum. Because industrial applications demand high quality YBCO films with very high Jc, we investigated introducing BaZrO3 (BZO) nano-pinning sites in HTS thin films by our F-free MOD technique to improve Jc and the global pinning force (Fp). BZO-doped YBCO films were fabricated by adding extra Ba and Zr in the precursor solutions, according to the molar formula 1 YBCO + x BZO. We found the BZO content affects the growth of YBCO films and determined the optimum BZO content which leads to the most effective pinning enhancement and the least YBCO degradation. We achieved the maximum pinning force of ˜ 10 GN/m3 for x = 0.10 BZO-doped, 200 nm thick YBCO film on SrTiO3 single crystal substrates by modifying the pyrolysis from a one-step to a two-plateau decomposition during the F-free MOD process. For growing optimum BZO-doped YBCO films on RABiTS substrates, the F-free MOD process was also optimized by adjusting the maximum growth temperature and growth time to achieve stronger pinning forces. Through-process quenching studies indicate that BZO form 10--25 nm nanoparticles at the early stage of the process and are stable during the following YBCO growth, demonstrating that chemically doping YBCO films with BZO using the F-free MOD process is a very effective way to enhance pinning for YBCO coated conductors.

  12. Built-in Electric Field Induced Mechanical Property Change at the Lanthanum Nickelate/Nb-doped Strontium Titanate Interfaces

    NASA Astrophysics Data System (ADS)

    Chien, Teyu; Liu, Jian; Yost, Andrew J.; Chakhalian, Jak; Freeland, John W.; Guisinger, Nathan P.

    2016-01-01

    The interactions between electric field and the mechanical properties of materials are important for the applications of microelectromechanical and nanoelectromechanical systems, but relatively unexplored for nanoscale materials. Here, we observe an apparent correlation between the change of the fractured topography of Nb-doped SrTiO3 (Nb:STO) within the presence of a built-in electric field resulting from the Schottky contact at the interface of a metallic LaNiO3 thin film utilizing cross-sectional scanning tunneling microscopy and spectroscopy. The change of the inter-atomic bond length mechanism is argued to be the most plausible origin. This picture is supported by the strong-electric-field-dependent permittivity in STO and the existence of the dielectric dead layer at the interfaces of STO with metallic films. These results provided direct evidence and a possible mechanism for the interplay between the electric field and the mechanical properties on the nanoscale for perovskite materials.

  13. Dielectric behavior of samarium-doped BaZr{sub 0.2}Ti{sub 0.8}O{sub 3} ceramics

    SciTech Connect

    Li, Yuanliang; Wang, Ranran; Ma, Xuegang; Li, Zhongqiu; Sang, Rongli; Qu, Yuanfang

    2014-01-01

    Graphical abstract: - Highlights: • We investigate dielectric properties and phase transition of Sm{sup 3+}-doped BaZr{sub 0.2}Ti{sub 0.8}O{sub 3} ceramics. • The additive amount of Sm{sub 2}O{sub 3} can greatly affect the dielectric properties. • The materials undergo a diffuse type ferroelectric phase transition. • There is an alternation of substitution preference of Sm{sup 3+} ion for the host cations in perovskite lattice. - Abstract: The dielectric properties and phase transition of Sm{sup 3+}-doped BaZr{sub 0.2}Ti{sub 0.8}O{sub 3} (BZT20) ceramics were investigated. Room temperature X-ray diffraction study suggested that the compositions had single-phase cubic symmetry. Microstructure studies showed that the grain size decreased and that the Sm{sub 2}O{sub 3} amount markedly affected the dielectric properties of BZT20. A dielectric constant of 5700 at 0.2 mol% Sm{sub 2}O{sub 3} and a dissipation factor of only 0.0011 at 2 mol% Sm{sub 2}O{sub 3} were observed, indicating that BZT20 had significant potential applications. Moreover, the dielectric constant, dissipation factor, phase-transition temperature, and maximum dielectric constant increased with increased Sm{sub 2}O{sub 3} amount at ≤0.2 mol% Sm{sub 2}O{sub 3} but decreased with increased Sm{sub 2}O{sub 3} amount at >0.2 mol% Sm{sub 2}O{sub 3}.

  14. Effect of sintering time on structural, microstructural and chemical composition of Ni-doped lanthanum gallate perovskites

    NASA Astrophysics Data System (ADS)

    Colomer, M. T.; Kilner, J. A.

    2015-08-01

    This work reports the effect of two different sintering times, 6 and 48 h on the structural, microstructural, and chemical features of Ni-doped La0.90Sr0.10GaO3.00-δ. Independently of the sintering time, La0.90Sr0.10Ga1-xNixO3.00-δ (where x=0.10, and 0.20 (mol)) presents a rhombohedral symmetry with a lattice volume that decreases when NiO dopant increases. Besides the perovskite, LaSrGa3.00O7.00 (nominal composition) is present as second phase in all cases. When the samples are doped with NiO, the peaks of this second phase are shifted with respect to the peaks of the pure phase. These shifts suggest that this second phase could admit some Ni ions in its structure. According to the XRD patterns, the amount of the latter phase is larger when sintering time is increased. Electron probe microanalysis (EPMA) indicated that the matrix of the samples sintered for 6 h is constituted by a perovskite with an experimental composition very close to the nominal one. However, when the samples are sintered for 48 h the matrix of each sample is constituted by two perovskites; both with compositional deviations with respect to their nominal one. In particular, a significant Sr depletion compensated by a La increment in the A site is observed. Those compositional deviations could be mainly due to the diffusion of the cations in the bulk and/or from the bulk to the surface of the samples. That diffusion can favour the formation, not only, of a second perovskite with a different composition in relation with the first one formed, but also, the formation of second phases. In addition, a very slight broadening of Bragg peaks of the perovskites sintered for 48 h is observed by XRD and can be related to the presence of two different perovskites in each sample according to EPMA results. By BSEM and EPMA analyses La4.00Ga2.00O9.00 (nominal composition) is also observed as second phase when samples are treated for 48 h.

  15. Field effect and magnetically induced capacitive tuning in hole doped lanthanum(1-x) strontium(x) manganese oxide

    NASA Astrophysics Data System (ADS)

    Marton, Zsolt

    Electrostatic modulation of interface conduction between semiconductors and insulating oxides is the foundation of semiconductor technology. This field effect concept can be applied on complex oxides, such as high temperature superconductors and colossal magnetoresistive manganites, in order to create new electronic and magnetic phases. Competition and coexistence of multiple nanoscale phases make them exciting to study around phase transitions. This study on hole doped La1-xSrxMnO3 systems has a two-fold purpose. One is the demonstration of the field effect on La1-xSr xMnO3 (x = 0.125, 0.2, 0.3, 0.5) thin films. It is an important step towards electrostatic control of material properties, however, a challenging task because of their charge carrier densities of 0.01-1 hole/unit cell, a few orders of magnitude larger than in doped semiconductors. Control by linear dielectrics needs huge, constantly applied bias. Energy efficient tuning with low voltages requires highly polar ferroelectric. Pb(Zr0.2Ti 0.8)O3 was chosen, whose remanence provides 0.5 charge carrier/unit cell on the manganite/ferroelectric interface. La1-xSrxMnO 3/Pb(Zr0.2Ti0.8)O3 heterostructures were synthesized by pulsed laser epitaxy and remarkable conduction modifications were observed in the La1-xSrxMnO3. This can be a strong foundation of a new tool to research electronic oxides. The second purpose of this work is to utilize the phase separation in manganites. There has been extensive research on multiferroic materials, in which dielectric and magnetic responses are controlled by magnetic and electric field, respectively. In order to demonstrate magnetically tuned capacitance, insulating La7/8Sr1/8MnO3 was studied. Drastic capacitance change in magnetic field was shown through a phase transitions and explained in the framework of electronic phase separation. It makes this material eligible for high frequency magnetoelectric applications. Modulating charge carriers, mobility and magnetism in magnetic oxides, superconductors and superlattices has a great impact on the emerging field of oxide electronics. These compounds overcome the scaling limitations of conventional semiconductors; using low operation voltage oxide ferroelectrics lowers energy consumption. This thesis shows that changing fundamental physical properties of complex oxides on the atomic scale is possible by ferroelectric field effect. This technique is proposed as a tool to study thin films, artificially stacked structures and to induce and optimize novel phases and phenomena.

  16. Built-in Electric Field Induced Mechanical Property Change at the Lanthanum Nickelate/Nb-doped Strontium Titanate Interfaces

    PubMed Central

    Chien, TeYu; Liu, Jian; Yost, Andrew J.; Chakhalian, Jak; Freeland, John W.; Guisinger, Nathan P.

    2016-01-01

    The interactions between electric field and the mechanical properties of materials are important for the applications of microelectromechanical and nanoelectromechanical systems, but relatively unexplored for nanoscale materials. Here, we observe an apparent correlation between the change of the fractured topography of Nb-doped SrTiO3 (Nb:STO) within the presence of a built-in electric field resulting from the Schottky contact at the interface of a metallic LaNiO3 thin film utilizing cross-sectional scanning tunneling microscopy and spectroscopy. The change of the inter-atomic bond length mechanism is argued to be the most plausible origin. This picture is supported by the strong-electric-field-dependent permittivity in STO and the existence of the dielectric dead layer at the interfaces of STO with metallic films. These results provided direct evidence and a possible mechanism for the interplay between the electric field and the mechanical properties on the nanoscale for perovskite materials. PMID:26743875

  17. Built-in Electric Field Induced Mechanical Property Change at the Lanthanum Nickelate/Nb-doped Strontium Titanate Interfaces.

    PubMed

    Chien, TeYu; Liu, Jian; Yost, Andrew J; Chakhalian, Jak; Freeland, John W; Guisinger, Nathan P

    2016-01-01

    The interactions between electric field and the mechanical properties of materials are important for the applications of microelectromechanical and nanoelectromechanical systems, but relatively unexplored for nanoscale materials. Here, we observe an apparent correlation between the change of the fractured topography of Nb-doped SrTiO3 (Nb:STO) within the presence of a built-in electric field resulting from the Schottky contact at the interface of a metallic LaNiO3 thin film utilizing cross-sectional scanning tunneling microscopy and spectroscopy. The change of the inter-atomic bond length mechanism is argued to be the most plausible origin. This picture is supported by the strong-electric-field-dependent permittivity in STO and the existence of the dielectric dead layer at the interfaces of STO with metallic films. These results provided direct evidence and a possible mechanism for the interplay between the electric field and the mechanical properties on the nanoscale for perovskite materials. PMID:26743875

  18. A novel high-k Y5V barium titanate ceramics co-doped with lanthanum and cerium

    NASA Astrophysics Data System (ADS)

    Lu, Da-Yong; Sun, Xiu-Yun; Toda, Masayuki

    2007-04-01

    Structural, dielectric, and ferroelectric properties of a novel high-k Y5V (Ba1-xLax)(Ti1-x/4-yCey)O3 ceramics (where x=0.03 and y=0.05, denoted by BL3TC5) with the highest Y5V dielectric response (??>10 000) among rare-earth-doped BaTiO3 ceramics to date are investigated in detail using SEM, TEM, XRD, DSC, EPR, Raman spectroscopy (RS), temperature and frequency, electric field dependences of dielectric permittivity (??), and temperature and electric field dependences of ferroelectric hysteresis loops. The BL3TC5 diffusion of ferroelectric phase transition occurs around dielectric peak temperatures (Tm) near a room temperature characteristic of dielectric thermal relaxation. Powder XRD data and defect complex model were given. Relaxor behavior associated with an order/disorder model and formation of a solid solution were discussed. The EPR results provided the evidence of Ti vacancies as compensating for lattice defects. High-k relaxor nature of BL3TC5 is characterized by an average cubic structure with long-range lattice disordering and local polar ordering; a slow change of the ?? (T) and Pr(T) curves around Tm; no phase transition observed by DSC; and a broad, red-shifted A1 (TO2) Raman phonon mode at 251 cm-1 accompanying the disappearance of the silent mode at 305 cm-1 and a clear anti-resonance effect at 126 cm-1 at room temperature.

  19. Evolution of orientation degree, lattice dynamics and electronic band structure properties in nanocrystalline lanthanum-doped bismuth titanate ferroelectric films by chemical solution deposition.

    PubMed

    Zhang, Jinzhong; Chen, Xiangui; Jiang, Kai; Shen, Yude; Li, Yawei; Hu, Zhigao; Chu, Junhao

    2011-08-21

    Ferroelectric lanthanum (La)-substituted bismuth titanate (Bi(4-x)La(x)Ti(3)O(12), BLT) nanocrystalline films with the composition range of 0 ≤x≤ 1 have been directly deposited on n-type Si (100) substrates by chemical solution deposition. The La substitution effects on the preferred orientation, surface morphology, phonon modes, emission bands and electronic band structures of the BLT films have been investigated by microscopy, Raman scattering, photoluminescence and spectroscopic ellipsometry at room temperature. X-Ray diffraction analysis shows that the films are polycrystalline and exhibit the pure perovskite phase structure. With increasing La composition, the (100)-orientation degree can be enhanced and the root-mean-square roughnesses slightly increase from 6.5 to 8.3 nm. It was found that the Raman-active mode A(1g)[Bi] at about 59 cm(-1) is unchanged while the B(1g) and A(1g)[Ti] phonon modes at about 648 and 853 cm(-1) are shifted towards higher frequency by about 36.6 and 8.4 cm(-1), respectively. Photoluminescence spectra show that the intensity of the peak located at about 2.3 eV increases with the La composition, except for the Bi(3)LaTi(3)O(12) film, due to the smallest grain size and oxygen vacancy defects. The optical constants of the BLT films have been uniquely extracted by fitting the measured ellipsometric spectra with a four-phase layered model (air/surface rough layer/BLT/Si) in the photon energy range of 0.73-4.77 eV. The Adachi dielectric function model has been successfully applied and reasonably describes the optical response behavior of the ferroelectric BLT films. Moreover, the film packing density decreases while the optical band gap linearly increases from 3.610 ± 0.066 to 3.758 ± 0.068 eV with increasing La composition. It is surmised that the phenomena are mainly ascribed to the variations of the electronic structure, especially for the conduction band, which is perturbed by the La doping. PMID:21743909

  20. Effects of rapid thermal annealing on structural, chemical, and electrical characteristics of atomic-layer deposited lanthanum doped zirconium dioxide thin film on 4H-SiC substrate

    NASA Astrophysics Data System (ADS)

    Lim, Way Foong; Quah, Hock Jin; Lu, Qifeng; Mu, Yifei; Ismail, Wan Azli Wan; Rahim, Bazura Abdul; Esa, Siti Rahmah; Kee, Yeh Yee; Zhao, Ce Zhou; Hassan, Zainuriah; Cheong, Kuan Yew

    2016-03-01

    Effects of rapid thermal annealing at different temperatures (700-900 °C) on structural, chemical, and electrical characteristics of lanthanum (La) doped zirconium oxide (ZrO2) atomic layer deposited on 4H-SiC substrates have been investigated. Chemical composition depth profiling analysis using X-ray photoelectron spectroscopy (XPS) and cross-sectional studies using high resolution transmission electron microscopy equipped with energy dispersive X-ray spectroscopy line scan analysis were insufficient to justify the presence of La in the investigated samples. The minute amount of La present in the bulk oxide was confirmed by chemical depth profiles of time-of-flight secondary ion mass spectrometry. The presence of La in the ZrO2 lattice led to the formation of oxygen vacancies, which was revealed through binding energy shift for XPS O 1s core level spectra of Zrsbnd O. The highest amount of oxygen vacancies in the sample annealed at 700 °C has yielded the acquisition of the highest electric breakdown field (∼ 6.3 MV/cm) and dielectric constant value (k = 23) as well as the highest current-time (I-t) sensor response towards oxygen gas. The attainment of both the insulating and catalytic properties in the La doped ZrO2 signified the potential of the doped ZrO2 as a metal reactive oxide on 4H-SiC substrate.

  1. Metals fact sheet - lanthanum

    SciTech Connect

    1995-04-01

    Mosander was the first to extract the elusive rare earth, lanthanum, from unrefined cerium nitrate in 1839. The name was derived from the Greek word lanthanein, meaning {open_quotes}to escape notice.{close_quotes} Lanthanum is the lightest rare earth and a very malleable metal-soft enough to be cut with a knife. Used primarily as an additive in steels and non-ferrous metals, lanthanum is the lightest rare earth element and one of four rare earths from which mischmetal is made. Additional applications include advanced batteries, optical fibers, and phosphors.

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

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

    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

  3. Lanthanum-Induced Gastrointestinal Histiocytosis

    PubMed Central

    Araya, Hiwot; Longacre, Teri A.; Pasricha, Pankaj J.

    2015-01-01

    A patient with end-stage renal disease (ESRD) on hemodialysis presented with fever, anorexia, and nausea shortly after starting oral lanthanum carbonate for phosphate control. Gastric and duodenal biopsies demonstrated diffuse histiocytosis with intracellular aggregates of basophilic foreign material. Transmission electron microscopy, an underutilized diagnostic test, revealed the nature of the aggregates as heavy metal particles, consistent with lanthanum. Symptoms and histiocytosis improved after discontinuation of lanthanum. Lanthanum may be an underdiagnosed cause of gastrointestinal histiocytosis. PMID:26157959

  4. Effects of lanthanum doping on the dielectric, piezoelectric properties and defect mechanism of PZN-PZT ceramics prepared by hot pressing

    NASA Astrophysics Data System (ADS)

    Zeng, X.; Ding, A. L.; Deng, G. C.; Liu, T.; Zheng, X. S.

    2005-07-01

    The structure and electrical properties of Pb(Zn1/3Nb2/3)0.3(Zr0.55Ti0.45)0.7O3-xLa ceramics system by hot pressing with the composition near to the morphotropic phase boundary (MPB) were investigated as a function of La doping content. PZN-PZT specimens shifted from rhombohedral phase towards tetragonal phase with increasing La doping. Dielectric spectroscopy showed that La doping decreased dielectric permittivity maximum remarkably, and increased the degree of diffuse phase transition (DPT) with lower ferroelectric phase transition temperature. The growth of 1:1 chemically ordered domains through La doping was considered the cause of the dielectric dispersion. The high piezoelectric coefficient, d33 (716 pC/N), and electromechanical coupling factor, kp (0.62) were obtained in spite of existence of the pyrochlore phase. Oxygen vacancy conduction was the dominant mechanism. La doping reduced the concentration of oxygen vacancies, thus increased the electrical resistivity.

  5. Removal of the samarium isobaric interference from promethium mass analysis

    SciTech Connect

    Shaw, R.W.; Young, J.P.; Smith, D.H.

    1988-02-01

    Resonance ionization mass spectroscopy (RIMS) is used to eliminate isobaric interference when determining the isotopic abundances of an element. In this application, RIMS is applied to the determination of promethium with the removal of samarium interference. In particular, promethium-147 is separated form samarium-147 and samarium-152.

  6. Synthesis of Samarium Cobalt Nanoblades

    SciTech Connect

    Darren M. Steele

    2010-08-25

    As new portable particle acceleration technologies become feasible the need for small high performance permanent magnets becomes critical. With particle accelerating cavities of a few microns, the photonic crystal fiber (PCF) candidate demands magnets of comparable size. To address this need, samarium cobalt (SmCo) nanoblades were attempted to be synthesized using the polyol process. Since it is preferable to have blades of 1-2 {micro}m in length, key parameters affecting size and morphology including method of stirring, reaction temperature, reaction time and addition of hydroxide were examined. Nanoparticles consisting of 70-200 nm spherical clusters with a 3-5 nm polyvinylpyrrolidone (PVP) coating were synthesized at 285 C and found to be ferromagnetic. Nanoblades of 25nm in length were observed at the surface of the nanoclusters and appeared to suggest agglomeration was occurring even with PVP employed. Morphology and size were characterized using a transmission electron microscope (TEM). Powder X-Ray Diffraction (XRD) analysis was conducted to determine composition but no supportive evidence for any particular SmCo phase has yet been observed.

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

    SciTech Connect

    Bol'shchikov, F A; Ryabochkina, P A; Zharikov, Evgeny V; Lis, Denis A; Subbotin, Kirill A; Zakharov, N G; Antipov, Oleg L

    2010-12-09

    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)

  8. Energy stabilization of the s-symmetry superatom molecular orbital by endohedral doping of C82 fullerene with a lanthanum atom

    NASA Astrophysics Data System (ADS)

    Feng, Min; Shi, Yongliang; Lin, Chungwei; Zhao, Jin; Liu, Fupin; Yang, Shangfeng; Petek, Hrvoje

    2013-08-01

    Energy stabilization of the superatom molecular orbitals (SAMOs) in fullerenes is investigated with the goal of involving their nearly free-electron bands in practical charge transport applications. Combining low-temperature scanning tunneling microscopy-based spectroscopic methods and density functional theory calculations on an endohedral metallofullerene La@C82, we confirm that the s-SAMO of C82 fullerene is stabilized by as much as 2 eV with respect to that of C60 by endohedral doping with the La atom. On the copper metal substrate, the s-SAMO energy is further lowered to just 1 eV above the Fermi level, making the applications of s-SAMO state in transport more plausible. We conclude that in an endohedral metallofullerene, the s-SAMO state is stabilized through the hybridization with the s-symmetry valence state of the metal atom and the stabilization energy correlates with the ionization potential of the free atom.

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

    SciTech Connect

    E. L. BROSHA; R. MUKUNDAN; ET AL

    2000-10-01

    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{sub 3} 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 open loop, steady-state mode around stoichiometry at 1500 RPM and 50 Nm. The sensor showed a stable EMF response (with no hysteresis) to varying concentrations of total exhaust gas HC content. The sensor response was measured at 620 and 670 C and shows temperature behavior characteristic of mixed potential-type sensors. The results of these engine-dynamometer tests are encouraging; however, the limitations associated with Au current collection present the biggest impediment to automotive use.

  10. Lanthanum Bromide Detectors for Safeguards Measurements

    SciTech Connect

    Wright, J.

    2011-05-25

    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.

  11. Lanthanum Telluride: Mechanochemical Synthesis of a Refractory Thermoelectric Material

    NASA Astrophysics Data System (ADS)

    May, Andrew; Snyder, Jeff; Fleurial, Jean-Pierre

    2008-01-01

    Recent experimental work on lanthanum telluride has confirmed its significant potential as an n-type material for high temperature thermoelectric (TE) power generation application. The phase of interest, La3-xTe4, has a Th3P4 defect structure where x is the lanthanum vacancy with values ranging between 0 and 1/3. Thermoelectric properties change rapidly with x since the carrier concentration, n, is proportional to the (1-3x) parameter. Controlling the Te to La stoichiometry in lanthanum telluride is thus vital to achieving the optimum self-doping level for the highest dimensionless figure of merit ZT value. We report on a significant improvement in reproducibly preparing this refractory compound over prior lengthy and unwieldy high temperature experimental techniques developed in the 1980's. Mechanochemical processes are utilized to synthesize precise stoichiometries of lanthanum telluride at room temperature, enabling improved characterization, analysis and modeling of its transport properties as a function of the number of La vacancies. We report TE properties for a large range of the allowed compositions, with ZT values greater than 1.0 obtained at 1275 K for several compositions. In addition to stoichiometric optimization within the pure compound, chemical substitutions can enhance performance by decreasing the lattice thermal conductivity and tuning the electrical properties for maximum ZT values at lower temperatures; preliminary studies indicate that the addition of ytterbium increases ZT. Some properties pertaining to device development are discussed. Specifically, lanthanum telluride has a low sublimation rate, and a coefficient of thermal expansion that closely matches a p-type rare earth compound analog (the Yb14MnSb11 Zintl compound).

  12. Chlorination of lanthanum oxide.

    PubMed

    Gaviría, Juan P; Navarro, Lucas G; Bohé, Ana E

    2012-03-01

    The reactive system La(2)O(3)(s)-Cl(2)(g) was studied in the temperature range 260-950 °C. The reaction course was followed by thermogravimetry, and the solids involved were characterized by X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy. The results showed that the reaction leads to the formation of solid LaOCl, and for temperatures above 850 °C, the lanthanum oxychloride is chlorinated, producing LaCl(3)(l). The formation of the oxychloride progresses through a nucleation and growth mechanism, and the kinetic analysis showed that at temperatures below 325 °C the system is under chemical control. The influence of diffusive processes on the kinetics of production of LaOCl was evaluated by studying the effect of the reactive gas flow rate, the mass of the sample, and the chlorine diffusion through the boundary layer surrounding the solid sample. The conversion curves were analyzed and fitted according to the Johnson-Mehl-Avrami description, and the reaction order with respect to the chlorine partial pressure was obtained by varying this partial pressure between 10 and 70 kPa. The rate equation was obtained, which includes the influence of the temperature, chlorine partial pressure, and reaction degree. PMID:22280490

  13. The magnetic anisotropy of samarium-alnico pseudobinary alloys

    NASA Astrophysics Data System (ADS)

    Chang, Y. H.; Weng, C. I.; Hsu, T. K.

    1984-01-01

    The anisotropy properties of samarium-Alnico V pseudobinary alloys have been investigated. With alloys containing less than 12.0 mol% samarium, the K1 values are negative at 77 K and increase with increasing temperature to approximately zero at room temperature. The K2 values remain positive at all temperatures. We do not find the easy cone that has long been thought to be existed in those alloys with K1 < 0 and K2 #62; 0. In alloys with samarium contents between 13.3 and 19.0 mol%, the K1 and K2 values are positive at all temperatures. The anisotropy fields are not changed monotonically in the whole range of 10.1 to 19.0 mol% of samarium. It is concluded that the alloys are characteristics in thermodynamically of first-order transition. We have found that the "hard cone" exists in each of those alloys with samarium content more than 16.0 mol% and at temperatures above 77 K. The alloys with samarium less that 13.4 mol% also have "hard cone" under 77 K. However, the observed "hard cone" is different from the well known one in the first-order magnetization process, and it will collapse to the easy axis when the measuring field and temperature increase while under room temperature.

  14. Preparation of porous lanthanum phosphate with templates

    SciTech Connect

    Onoda, Hiroaki; Ishima, Yuya; Takenaka, Atsushi; Tanaka, Isao

    2009-08-05

    Malonic acid, propionic acid, glycine, n-butylamine, and urea were added to the preparation of lanthanum phosphate from lanthanum nitrate and phosphoric acid solutions. All additives were taken into lanthanum phosphate particles. The additives that have a basic site were easy to contain in precipitates. The addition of templates improved the specific surface area of lanthanum phosphate. The amount of pore, with radius smaller than 4 nm, increased with the addition of templates. The remained additives had influence on the acidic properties of lanthanum phosphate.

  15. Ames Lab 101: Lanthanum Decanting

    ScienceCinema

    Riedemann, Trevor

    2012-08-29

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

    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.

  17. 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)

    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

    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.

  18. DISSOLUTION OF LANTHANUM FLUORIDE PRECIPITATES

    DOEpatents

    Fries, B.A.

    1959-11-10

    A plutonium separatory ore concentration procedure involving the use of a fluoride type of carrier is presented. An improvement is given in the derivation step in the process for plutonium recovery by carrier precipitation of plutonium values from solution with a lanthanum fluoride carrier precipitate and subsequent derivation from the resulting plutonium bearing carrier precipitate of an aqueous acidic plutonium-containing solution. The carrier precipitate is contacted with a concentrated aqueous solution of potassium carbonate to effect dissolution therein of at least a part of the precipitate, including the plutonium values. Any remaining precipitate is separated from the resulting solution and dissolves in an aqueous solution containing at least 20% by weight of potassium carbonate. The reacting solutions are combined, and an alkali metal hydroxide added to a concentration of at least 2N to precipitate lanthanum hydroxide concomitantly carrying plutonium values.

  19. Thermoelectric Properties of Lanthanum Sulfide

    NASA Technical Reports Server (NTRS)

    Wood, C.; Lockwood, R.; Parker, J. B.; Zoltan, A.; Zoltan, L. D.; Danielson, L.; Raag, V.

    1987-01-01

    Report describes measurement of Seebeck coefficient, electrical resistivity, thermal conductivity, and Hall effect in gamma-phase lanthanum sulfide with composition of La3-x S4. Results of study, part of search for high-temperature thermoelectric energy-conversion materials, indicate this sulfide behaves like extrinsic semiconductor over temperature range of 300 to 1,400 K, with degenerate carrier concentration controlled by stoichiometric ratio of La to S.

  20. The Basis for Developing Samarium AMS for Fuel Cycle Analysis

    SciTech Connect

    Buchholz, B A; Biegalski, S R; Whitney, S M; Tumey, S J; Weaver, C J

    2008-10-13

    Modeling of nuclear reactor fuel burnup indicates that the production of samarium isotopes can vary significantly with reactor type and fuel cycle. The isotopic concentrations of {sup 146}Sm, {sup 149}Sm, and {sup 151}Sm are potential signatures of fuel reprocessing, if analytical techniques can overcome the inherent challenges of lanthanide chemistry, isobaric interferences, and mass/charge interferences. We review the current limitations in measurement of the target samarium isotopes and describe potential approaches for developing Sm-AMS. AMS sample form and preparation chemistry will be discussed as well as possible spectrometer operating conditions.

  1. Samarium-145 and its use as a radiation source

    DOEpatents

    Fairchild, Ralph G.; Laster, Brenda H.; Packer, Samuel

    1989-01-01

    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.

  2. [Histochemical staining methods for lanthanum].

    PubMed

    Miyagawa, Makoto

    2011-09-01

    In recent years lanthanum compounds have been widely used in the optical and electronic industries. Although release of lanthanum (La) into the environment and exposure to humans are feared, acute or chronic biologic effects of La remain to be elucidated. The present study was undertaken to establish the experimental animal model for La toxicity and histological staining methods for La. After intraperitoneal injections of lanthanum chloride, white precipitates deposited on the surface of the liver. Existence of La in the precipitates was confirmed by a X-ray fluorescent microanalysis. Liver tissues from La treated rats were fixed in paraformaldehyde, embedded in paraffin and cut into thin sections which were used as a La containing standard section. Several reagents for histological stains and spectrophotometry for metals were applied in both test-tube experiments and stainings of tissue sections to test for La. Alizarin complexone (ALC) was found of capable of staining La in tissue. A simple new technique used was described for light microscopic detection of La. PMID:22111301

  3. [Histochemical staining methods for lanthanum].

    TOXLINE Toxicology Bibliographic Information

    Miyagawa M

    2011-09-01

    In recent years lanthanum compounds have been widely used in the optical and electronic industries. Although release of lanthanum (La) into the environment and exposure to humans are feared, acute or chronic biologic effects of La remain to be elucidated. The present study was undertaken to establish the experimental animal model for La toxicity and histological staining methods for La. After intraperitoneal injections of lanthanum chloride, white precipitates deposited on the surface of the liver. Existence of La in the precipitates was confirmed by a X-ray fluorescent microanalysis. Liver tissues from La treated rats were fixed in paraformaldehyde, embedded in paraffin and cut into thin sections which were used as a La containing standard section. Several reagents for histological stains and spectrophotometry for metals were applied in both test-tube experiments and stainings of tissue sections to test for La. Alizarin complexone (ALC) was found of capable of staining La in tissue. A simple new technique used was described for light microscopic detection of La.

  4. Multifunctionality of nanocrystalline lanthanum ferrite

    NASA Astrophysics Data System (ADS)

    Rai, Atma; Thakur, Awalendra K.

    2016-05-01

    Nanocrystalline lanthanum ferrite has been synthesized by adopting modified Pechini route. No evidence of impurity or secondary phase has been detected up to the detection of error limit of X-ray diffractometer (XRD). Rietveld refinement of X-ray diffraction pattern reveals orthorhombic crystal system with space group Pnma (62).Crystallite size and lattice strain was found to be ˜42.8nm and 0.306% respectively. Optical band gap was found to be 2.109 eV, by UV-Visible diffused reflectance spectrum (DRS). Brunauer-Emmet-Teller (BET) surface area was found to be ˜3.45 m2/g. Magnetization-hysteresis (M-H) loop was recorded at room temperature (300K) reveals weak ferromagnetism in Nanocrystalline lanthanum ferrite. The weak ferromagnetism in lanthanum ferrite is due to the uncompensated antiferromagnetic spin ordering. Ferroelectric loop hysteresis observed at room temperature at 100Hz depicts the presence of ferroelectric ordering in LaFeO3.Simultanious presence of magnetic and ferroelectric ordering at room temperature makes it suitable candidate of Multiferroic family.

  5. Effect of Lanthanum Doping on Ferroelectric and Strain Properties of 0.96Bi1/2(Na0.84K0.16)1/2TiO3-0.04SrTiO3 Lead-Free Ceramics

    NASA Astrophysics Data System (ADS)

    Tran, Vu Diem Ngoc; Ullah, Aman; Dinh, Thi Hinh; Lee, Jae-Shin

    2016-05-01

    Lead-free 0.96[Bi1/2(Na0.84K0.16)1/2](1- x)La x TiO3-0.04SrTiO3 (BNKTLa x-ST, with x = 0.00, 0.01, 0.02, 0.03, 0.04, and 0.05) ceramics have been synthesized using a conventional solid-state reaction method and their phase transition, dielectric, ferroelectric, and strain properties investigated. X-ray diffraction patterns revealed formation of pure perovskite phase. A phase transition from coexistence of rhombohedral and tetragonal to a pseudocubic phase was observed at x = 0.02. Polarization and bipolar strain hysteresis loops indicated that the ferroelectric order (FE) of BNKT-ST is significantly disrupted by lanthanum doping. The destabilization of the FE order results in degradation of the remanent polarization, coercive field, depolarization temperature ( T d), electromechanical coupling factor ( k p), and static d 33, accompanied by large electric-field-induced strain of 0.34% at 60 kV/cm with normalized strain of d 33 * = S max/ E max = 600 pm/V at a critical composition of around x = 0.02.

  6. Discovery of samarium, europium, gadolinium, and terbium isotopes

    SciTech Connect

    May, E.; Thoennessen, M.

    2013-01-15

    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.

  7. Co-Cu-Sm (Cobalt-Copper-Samarium)

    NASA Astrophysics Data System (ADS)

    Materials Science International Team MSIT

    This document is part of Subvolume C2 'Non-Ferrous Metal Systems. Part 2: Selected Copper Systems' of Volume 11 'Ternary Alloy Systems - Phase Diagrams, Crystallographic and Thermodynamic Data critically evaluated by MSIT®' of Landolt-Börnstein - Group IV 'Physical Chemistry'. It provides data of the ternary system Cobalt-Copper-Samarium.

  8. SOLITONS AND OPTICAL FIBERS: Self-Q-switched ytterbium-doped cladding-pumped fibre laser

    NASA Astrophysics Data System (ADS)

    Grukh, Dmitrii A.; Kurkov, Andrei S.; Razdobreev, I. M.; Fotiadi, A. A.

    2002-11-01

    A self-Q-switched ytterbium-doped double-clad fibre laser is described. A samarium-doped fibre is used as a filter for protecting a pump source. A fibre coupler is employed to obtain a nonlinear feedback. The mechanism of pulse formation in the laser is considered, and the dependence of its output pulse on the coupler parameters is studied.

  9. Equilibrium distribution of samarium and europium between fluoride salt melts and liquid bismuth

    NASA Astrophysics Data System (ADS)

    Zagnit'ko, A. V.; Ignat'ev, V. V.

    2016-01-01

    The extraction of samarium and europium from a melt of a molar composition 73LiF-27BeF2 into liquid bismuth with additions of lithium as a reducing agent at a temperature of 600-610°C was studied. The equilibrium distribution coefficients of samarium and europium were measured. In the metal fluoride salt melt under study, the valence of samarium and europium was shown to be equal to two.

  10. Field free, directly heated lanthanum boride cathode

    DOEpatents

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

    1987-02-02

    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.

  11. Field free, directly heated lanthanum boride cathode

    DOEpatents

    Leung, Ka-Ngo; Moussa, David; Wilde, Stephen B.

    1991-01-01

    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.

  12. Structure and magnetic properties of samarium-alnico pseudobinary alloys

    NASA Astrophysics Data System (ADS)

    Chang, Y. H.; Weng, C. I.; Chen, H. S.

    1983-10-01

    Ten alloys of the samarium-alnico system containing 10-19 at. % Sm were investigated. It has been found that the structure of the high temperature phases changes with varying samarium content. Seven phases including 1:5 and 2:17 and those designated R1, R2, K, U1, and U2 are identified by the x-ray Debye-Scherrer method. The 1:5 and 2:17 phases correspond to the CaCu5 and Th2Zn17 structures, respectively. The R1 and R2 phases are assumed to be the superlattices of the 2:17 phase and the K phase the superlattice of R2. The maximum saturation magnetic moment is 89.6 emu/g for the alloy containing 10.7 at. % samarium. Curie temperatures of the R1 and 2:17 phases are 697 and 694 °K, respectively. The unknown phase U1 which is analyzed containing little Sm has a magnetic order temperature up to 1146 °K. The intrinsic coercivity of these alloys never exceeds one thousand oersted. The easy magnetization directions of the 1:5 and R phases are found to persist along the c axis even though the atomic ratio of Fe to Co is as high as two. The behavior of reaching maxima in intrinsic coercivity and remanence versus temperature curves below room temperature is due to the corresponding variation of anisotropy field with temperature.

  13. Compact lanthanum hexaboride hollow cathode.

    PubMed

    Goebel, Dan M; Watkins, Ronald M

    2010-08-01

    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

  14. Lanthanum

    MedlinePlus

    ... medications called phosphate binders. It works by preventing absorption of phosphate from food in the stomach. ... it at room temperature and away from excess heat and moisture (not in the bathroom). Throw away ...

  15. Energy stabilization of the s -symmetry superatom molecular orbital by endohedral doping of C 82 fullerene with a lanthanum atom

    SciTech Connect

    Feng, Min; Shi, Yongliang; Lin, Chungwei; Zhao, Jin; Liu, Fupin; Yang, Shangfeng; Petek, Hrvoje

    2013-08-01

    Energy stabilization of the superatom molecular orbitals (SAMOs) in fullerenes is investigated with the goal of involving their nearly free-electron bands in practical charge transport applications. Combining low-temperature scanning tunneling microscopy-based spectroscopic methods and density functional theory calculations on an endohedral metallofullerene La@C82, we confirm that the s-SAMO of C82 fullerene is stabilized by as much as 2 eV with respect to that of C60 by endohedral doping with the La atom. On the copper metal substrate, the s-SAMO energy is further lowered to just 1 eV above the Fermi level, making the applications of s-SAMO state in transport more plausible. We conclude that in an endohedral metallofullerene, the s-SAMO state is stabilized through the hybridization with the s-symmetry valence state of the metal atom and the stabilization energy correlates with the ionization potential of the free atom.

  16. METHOD FOR DISSOLVING LANTHANUM FLUORIDE CARRIER FOR PLUTONIUM

    DOEpatents

    Koshland, D.E. Jr.; Willard, J.E.

    1961-08-01

    A method is described for dissolving lanthanum fluoride precipitates which is applicable to lanthanum fluoride carrier precipitation processes for recovery of plutonium values from aqueous solutions. The lanthanum fluoride precipitate is contacted with an aqueous acidic solution containing dissolved zirconium in the tetravalent oxidation state. The presence of the zirconium increases the lanthanum fluoride dissolved and makes any tetravalent plutonium present more readily oxidizable to the hexavalent state. (AEC)

  17. Thermodynamic properties of lanthanum molybdates

    NASA Astrophysics Data System (ADS)

    Suponitskiy, Yu. L.; Proshina, O. P.; Dyunin, A. G.; Liashenko, S. E.

    2016-02-01

    The enthalpy of solution of LaOHMoO4 and Cs2MoO4 in aqueous HCl at 298 K has been determined by solution calorimetry, and the standard enthalpy of formation of lanthanum hydroxomolybdate has been calculated. The enthalpies of solution of NaLa(MoO4)2 and Na5La(MoO4)4 in molybdate melt at 973 K have been determined by high-temperature melt solution microcalorimetry, and the high-temperature enthalpies of the double molybdates in the 298-1000 K range have been measured by the mixing method. The standard enthalpies of formation of the double molybdates have been calculated using data available from the literature. The low-temperature heat capacity of NaLa(MoO4)2 in the 60-300 K range has been measured on an adiabatic vacuum calorimeter. The basic thermodynamic properties of NaLa(MoO4)2, Na5La(MoO4)4, and LaOHMoO4 have been calculated.

  18. 40 CFR 721.10601 - Lanthanum lead titanium zirconium oxide.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Lanthanum lead titanium zirconium... Specific Chemical Substances § 721.10601 Lanthanum lead titanium zirconium oxide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as lanthanum...

  19. 40 CFR 721.10601 - Lanthanum lead titanium zirconium oxide.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Lanthanum lead titanium zirconium... Specific Chemical Substances § 721.10601 Lanthanum lead titanium zirconium oxide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as lanthanum...

  20. Ionization of Samarium by Chemical Releases in the Upper Atmosphere

    NASA Astrophysics Data System (ADS)

    Siefring, C. L.; Bernhardt, P. A.; Holmes, J. M.; Pedersen, T. R.; Caton, R.; Miller, D.; Groves, K. M.

    2014-12-01

    The release of Samarium vapor into the upper atmosphere was studied using during the Air Force Research Laboratory sponsored Metal Oxide Space Cloud (MOSC) rocket launches in May 2009. The Naval Research Laboratory supported these experiments with 3-D photochemical modeling of the artificial plasma cloud including (1) reactions with atomic oxygen, (2) photo excitation, (3) photoionization, (4) dissociative recombination, and (5) ion and neutral diffusion. NRL provided the experimental diagnostic instrument on the rocket which was a dual frequency radio beacon on the rocket to measure changes in total electron content. The AFRL provided ground based diagnostics of incoherent scatter radar and optical spectroscopy and imagery. The NRL Chemical Release Model (CRM) has over 600 excited states of atomic Samarium neutrals, atomic ions, along with Samarium Oxide Ions and electrons. Diffusive transport of neutrals in cylindrical geometry and ions along magnetic field lines is computed along with the reactive flow to predict the concentrations of Sm, Sm-Ion, Sm0, and SmO Ion. Comparison of the CRM with observations demonstrates that Sm release into the upper atmosphere initially produces enhanced electron densities and SmO-Ions. The diatomic ions recombine with electrons to yield neutral Sm and O. Only the photo ionization of Sm yields a stable atomic ion that does not substantially recombine. The MOSC releases in sunlight yielded long duration ion clouds that can be replicated with the CRM. The CRM predicts that Sm releases in darkness would not produce long duration plasma clouds because of the lack of photo excitation and photoionization.

  1. Samarium Diiodide-Mediated Reactions in Total Synthesis

    PubMed Central

    Nicolaou, K. C.; Ellery, Shelby P.; Chen, Jason S.

    2009-01-01

    Introduced by Henri Kagan more than three decades ago, samarium diiodide (SmI2) has found increasing applications in chemical synthesis. This single-electron reducing agent has been particularly useful in C–C bond formations, including those found in total synthesis endeavors. This Review highlights selected applications of SmI2 in total synthesis, with special emphasis on novel transformations and mechanistic considerations. The examples discussed are both illustrative of the power of this reagent in complex molecule construction and inspirational for the design of synthetic strategies toward such targets, both natural and designed. PMID:19714695

  2. Lanthanum as an electron microscopic stain.

    PubMed

    Shaklai, M; Tavassoli, M

    1982-12-01

    Applications of lanthanum as an electron microscopic tracer have been reviewed. This electron-dense trivalent cation, which binds avidly to calcium binding sites, can be used as tracer for delineating extracellular spaces and intercellular junctions. It has served as a basis for classification of junctional structures. It can also be used as a calcium probe, a tracer in studying the permeability of barriers, as an intracellular marker and as an electron microscopic stain for such membrane components as surface glycoprotein. Each of these applications may require a different methodology. Thus methodological considerations in the use of this tracer have also been reviewed. The recent recognition that lanthanum is more than a passive tracer and that by reacting with different cell components may serve as a true stain, will extend the use of lanthanum in electron microscope histochemistry. PMID:6185564

  3. Structural analysis, magnetic and electrical properties of samarium substituted lithium-nickel mixed ferrites

    NASA Astrophysics Data System (ADS)

    Al-Hilli, Muthafar F.; Li, Sean; Kassim, Kassim S.

    2012-03-01

    A series of Sm-doped Li-Ni ferrites with formula of (Li0.5Fe0.5)0.4Ni0.6SmyFe2-yO4, where 0.0≤y≤0.1 were prepared by double sintering ceramic technique. The structure was characterized by X-ray diffraction, which has confirmed the formation of single-phase spinel structure. The samarium concentration dependence of lattice parameters obeys Vegard's law. The octahedral site radii increased with Sm content while the tetrahedral site radii decreased. Deviation from the ideal crystal structure (Δ) is found to decrease with Sm substitution, and the hopping length on the octahedral site is found to increase with Sm content. Hall measurement confirmed p-type conductivity behavior for Sm-doped ferrite and the main charge transport mechanism is hopping of halls between Ni2+ and Ni3+. Sintering at 1300 °C resulted in low resistivity ferrite, which was found to increase with Sm content. Resistivity is governed by both charge carrier mobility and carrier concentration. It decreases with frequency, and this behavior with frequency is discussed according to Koop's theorem. The dielectric constant is found to decrease more rapidly at low frequencies than at higher frequencies while the dielectric constant increases with Sm content. The decrease in ε″ with frequency agrees with Deby's type relaxation process. Maximum in ε″ is observed when the hopping frequency is equal to the external electric field frequency. The variation in tan δ with frequency shows a similar nature to that of ε″ with frequency. The magnetization under applied magnetic field for the samples exhibits a clear hysteretic behavior. The scanning electron microscope (SEM) studies showed that the domain walls may tend to be trapped (pinned) by non-magnetic inclusions, precipitates and voids. The saturation magnetization (MS) increases with the sintering temperature, while the coercivity (HCi) is found to decrease.

  4. Contamination of YBCO bulk superconductors by samarium and ytterbium

    NASA Astrophysics Data System (ADS)

    Volochova, D.; Jurek, K.; Radusovska, M.; Piovarci, S.; Antal, V.; Kovac, J.; Jirsa, M.; Diko, P.

    2014-01-01

    Y-Ba-Cu-O (YBCO, Y-123) single-grain bulk superconductors with a nominal composition Y1.5Ba2Cu3Ox and 1 wt% CeO2 addition were prepared by the optimized Top-Seeded Melt-Growth process. Small single-crystalline pieces cut from the SmBa2Cu3Oy (Sm-123) bulk were used for seeding of epitaxial growth. Wavelength-dispersive spectrometry (WDS) confirmed that prepared samples contain besides samarium from the seed also ytterbium from the substrate. The influence of maximum melting temperature, Tmax and dwell time on the contamination of the bulk samples was studied. Y2BaCuO5 (Y-211) barriers against samarium diffusion from the seed to melted sample were tested. Using a NdBa2Cu3Oz (Nd-123) seed and a combination of Y2O3 and Yb2O3 substrate led to a high critical temperature (Tc(50%) = 91.54 K) of prepared sample.

  5. Influence of samarium doping on electronic and magneto-transport properties of La{sub 0.9−x}Sm{sub x}Sr{sub 0.1}MnO{sub 3} (0.1≤x≤0.5) nanoparticles

    SciTech Connect

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

    2014-04-24

    We report detailed field dependent electronic- (ρ-T) and magneto- transport (MR-H) studies of La{sub 1−x}Sm{sub x}Sr{sub 0.1}MnO{sub 3} (0.1≤x≤0.5) nanoparticles. Doping induced disorder at La site is observed in field dependent ρ-T measurements of the sample. At low doping side, nice metal to insulator transition (MIT) peak appears in ρ-T data whereas with increasing of Sm{sup +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.

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

    NASA Astrophysics Data System (ADS)

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

    2010-05-01

    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.

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

    NASA Technical Reports Server (NTRS)

    Kesseli, James; Pollak, Tom; Lacy, Dovie

    1988-01-01

    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.

  8. Investigation into nanostructured lanthanum halides and CeBr3 for nuclear radiation detection

    NASA Astrophysics Data System (ADS)

    Guss, Paul; Guise, Ronald; Mukhopadhyay, Sanjoy; Yuan, Ding

    2011-09-01

    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. 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. 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.

  9. Investigation into Nanostructured Lanthanum Halides and CeBr3 for Nuclear Radiation Detection

    SciTech Connect

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

    2011-07-06

    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.

  10. Effect of samarium nanoparticles on the electrical transport properties of polyaniline

    NASA Astrophysics Data System (ADS)

    Gupta, K.; Mukherjee, P. S.; Meikap, A. K.; Jana, P. C.

    2014-06-01

    A comprehensive study of the effect of samarium nanoparticles on electrical transport properties of polyaniline has been reported. Samples are prepared by chemical oxidative polymerization of aniline in the presence of samarium nanoparticles and characterized by XRD, FESEM, EDS, HRTEM and UV-Vis spectrometer. When the samarium content in polyaniline matrix increases, energy band gap decreases and conductivity increases by four orders of magnitude. A transformation of negative to positive magnetoconductivity has been observed by incorporating samarium nanoparticles in polyaniline matrix. Two types of activation behavior have been observed from the dielectric relaxation behavior. AC conductivity strongly depends on magnetic field. Although, at present, no theoretical model is found in literature to explain directly the behavior of ac conductivity in the presence of magnetic field, it may be due to the change of grain and interfacial boundary resistances by magnetic field.

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

    NASA Technical Reports Server (NTRS)

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

    1983-01-01

    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.

  12. Resonance ionization mass spectrometric study of the promethium/samarium isobaric pair

    SciTech Connect

    Shaw, R.W.; Young, J.P.; Smith, D.H.

    1988-01-01

    Samarium daughters are problematic in isotope ratio measurements of promethium because they are isobaric. Resonance ionization mass spectrometry was utilized to circumvent this problem. An ionization selectivity factor of at least 1000:1 has been measured for promethium over samarium at 584.6 nm. Resonance ionization spectra have been recorded for both elements over the 528-560 and 580-614 nm wavelength ranges.

  13. On-line ultrasonic characterisation of barium doped lanthanum perovskites

    NASA Astrophysics Data System (ADS)

    Thamilmaran, P.; Arunachalam, M.; Sankarrajan, S.; Sakthipandi, K.

    2015-06-01

    Perovskite manganite samples La1-xBaxMnO3 with the composition of x=0.30, 0.33 and 0.36 were prepared by employing solid state reaction technique. The X-ray diffraction (XRD) patterns confirmed the rhombhedral structure with R3c space group of the samples. The obtained energy dispersive analysis X-rays (EDX) spectra of the samples have confirmed the elemental composition of the samples. The scanning electron microscope (SEM) images of the samples were used to find out the size of the particles. In-situ ultrasonic measurements were carried out on the samples by through transmission method. The temperature dependence of the ultrasonic parameters revealed interesting features of the samples. The observed ultrasonic velocities and attenuation both in longitudinal and shear mode are related to the paramagnetic (PM) to ferromagnetic (FM) phase transition in the prepared samples. The results confirmed that an increase in the barium content in the sample leads to an increase in the phase transition temperature TC.

  14. Permeability of the Body Wall of Romanomermis culicivorax to Lanthanum.

    PubMed

    Platzer, A; Platzer, E G

    1985-07-01

    Ultrastructural study of the body wall of preparasitic, parasitic, and postparasitic stages of Romanomermis culicivorax showed that the cuticle of all three stages was permeable to lanthanum. The cuticle of the parasitic stage was the thinnest and showed the greatest permeability. Lanthanum accumulated on the apical surfaces of the hypodermal cells but was not found intracellularly. The negative staining characteristics of lanthanum enhanced the detection of numerous smooth septate junctions in the hypodermis of the parasitic stage. PMID:19294092

  15. [Pharmacodynamic and pharmacokinetic profile of lanthanum carbonate].

    PubMed

    Joki, Nobuhiko

    2009-02-01

    Lanthanum (La) is a rare-earth element in transition Group III b of the periodic table. It is a ductile and malleable, silvery-white metal, soft enough to be cut with a knife. Lanthanum carbonate (La2[CO3]3) is the most recent non-calcium, non-aluminum phosphate binder to be developed for the treatment of hyperphosphatemia. This drug has already been registered and available in the US and EU. Precilinical studies have shown that it is as effective as aluminium, without the associated toxicity, and is minimally absorbed. In clinical studies (La2[CO3]3) has a similar ability to calcium carbonate in controlling serum phosphate level without hypercalcemia. In this review I would like to summarize the pharmacodynamic and pharmacokinetic profile of this new phosphate binder (La2[CO3]3) which will be registered in our country in the near future. PMID:19182361

  16. Ambi-site substitution of Mn in lanthanum germanate apatites

    SciTech Connect

    Kendrick, E.; Knight, K.S.; Slater, P.R.

    2009-08-05

    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.

  17. Photoluminescence properties of cerium oxide nanoparticles as a function of lanthanum content

    SciTech Connect

    Deus, R.C.; Cortés, J.A.; Ramirez, M.A.; Ponce, M.A.; Andres, J.; Rocha, L.S.R.; and others

    2015-10-15

    Highlights: • CeO{sub 2} nanoparticles were obtained by microwave-hydrothermal method. • Rietveld refinement reveals a cubic structure. • KOH mineralizer agent exhibit weak agglomeration at low temperature and shorter time. - Abstract: The structural and photoluminescent properties at room temperature of CeO{sub 2} and La-doped CeO{sub 2} particles were undertaken. The obtained particles were synthesized by a microwave-assisted hydrothermal method (MAH) under different lanthanum contents. X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Fourier transform Raman (FT-Raman), Ultra-violet spectroscopy (UV–vis) and photoluminescence (PL) measurements were carried out. XRD revealed that the powders are free of secondary phases and crystallize in the cubic structure. Raman data show that increasing La doping content increase oxygen vacancies due to lattice expansion. The UV/vis absorption spectroscopy suggested the presence of intermediate energy levels in the band gap of structurally ordered powders. Lanthanum addition creates oxygen vacancies and shifts the photoluminescence in the low energy range leading to intense PL emission.

  18. Neutralized lanthanum solution: a largely noncolloidal ultrastructural tracer.

    PubMed

    Schatzki, P F; Newsome, A

    1975-05-01

    Lanthanum nitrate solution adjusted to pH 7.4 and pH 7.7 was subjected to column chromatography, ultrafiltration and conductivity measurements. Lanthanum concentration was measured by a colorimetric method employing eriochrome cyanine RC. Under these conditions, lanthanum was not excluded from the column by a packing with an exclusion limit of 1800 daltons. Ultrafiltration through a membrane with a filter limit of 500 daltons allowed approximately 75% of the lanthanum to pass. Conductivity measurements showed a decrease of charge of about 20% on adding sodium hydroxide to a solution of lanthanum nitrate up to a pH of 7.7. It is concluded that approximately 80% of the lanthanum exists as a charged particle of less than 500 daltons at pH 7.7; the other 20% consists of larger, possibly colloidal particles. Nonfiltered and ultrafiltered lanthanum have equally good staining and tracer properties in the electron microscope, suggesting that staining depends largely on the ultrafiltrable noncolloidal lanthanum ion. PMID:1145657

  19. A new nanosensor composed of laminated samarium borate and immobilized laccase for phenol determination

    NASA Astrophysics Data System (ADS)

    Hu, Ping; Zhou, Xinlin; Wu, Qingsheng

    2014-02-01

    A new nanosensor composed of laminated samarium borate and immobilized laccase was developed for phenol determination. The laminated samarium borate was synthesized by a mild solid-state-hydrothermal (S-S-H) method without any surfactant or Template. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) were used to characterize the samples. The morphology of the as-prepared materials was characterized by SEM, which shows that laminated samarium borate are uniform nanosheets with a layer-by-layer self-assembled single-crystal structure. These laminated samarium borate have typical diameters of 3 ~ 5 μm and the thickness of each layer is in the range of 10 ~ 80 nm. And then, these SmBO3 multilayers were used to immobilize the laccase. The proposed nanosensor composed of laminated samarium borate and immobilized laccase was successfully developed for phenol determination. Cyclic voltammetry were used to study the nanosensor. The proposed nanosensor displayed high sensitivity toward phenolic compounds. The linearity of the nanosensor for the detection of hydroquinone was obtained from 1 to 50 μM with a detection limit of 3 × 10-7 M (based on the S/N = 3).

  20. A new nanosensor composed of laminated samarium borate and immobilized laccase for phenol determination

    PubMed Central

    2014-01-01

    A new nanosensor composed of laminated samarium borate and immobilized laccase was developed for phenol determination. The laminated samarium borate was synthesized by a mild solid-state-hydrothermal (S-S-H) method without any surfactant or Template. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) were used to characterize the samples. The morphology of the as-prepared materials was characterized by SEM, which shows that laminated samarium borate are uniform nanosheets with a layer-by-layer self-assembled single-crystal structure. These laminated samarium borate have typical diameters of 3 ~ 5 μm and the thickness of each layer is in the range of 10 ~ 80 nm. And then, these SmBO3 multilayers were used to immobilize the laccase. The proposed nanosensor composed of laminated samarium borate and immobilized laccase was successfully developed for phenol determination. Cyclic voltammetry were used to study the nanosensor. The proposed nanosensor displayed high sensitivity toward phenolic compounds. The linearity of the nanosensor for the detection of hydroquinone was obtained from 1 to 50 μM with a detection limit of 3 × 10-7 M (based on the S/N = 3). PMID:24528570

  1. Self-activating and doped tantalate phosphors.

    SciTech Connect

    Nyman, May Devan; Rohwer, Lauren Elizabeth Shea

    2011-01-01

    An ideal red phosphor for blue LEDs is one of the biggest challenges for the solid-state lighting industry. The appropriate phosphor material should have good adsorption and emission properties, good thermal and chemical stability, minimal thermal quenching, high quantum yield, and is preferably inexpensive and easy to fabricate. Tantalates possess many of these criteria, and lithium lanthanum tantalate materials warrant thorough investigation. In this study, we investigated red luminescence of two lithium lanthanum tantalates via three mechanisms: (1) Eu-doping, (2) Mn-doping and (3) self-activation of the tantalum polyhedra. Of these three mechanisms, Mn-doping proved to be the most promising. These materials exhibit two very broad adsorption peaks; one in the UV and one in the blue region of the spectrum; both can be exploited in LED applications. Furthermore, Mn-doping can be accomplished in two ways; ion-exchange and direct solid-state synthesis. One of the two lithium lanthanum tantalate phases investigated proved to be a superior host for Mn-luminescence, suggesting the crystal chemistry of the host lattice is important.

  2. The features of structural transformations in lanthanum manganites La{sub 1−x}A{sub x}MnO{sub 3+δ} (A = Ca, Sr, Ba)

    SciTech Connect

    Sedykh, Vera D.

    2014-10-27

    In this work, the effect of the ionic radius and concentration of a doping element on the features of the structural transformations in polycrystalline lanthanum manganites, La{sub 1−x}A{sub x}MnO{sub 3+δ} (A = Ca, Sr, Ba), has been studied by Mössbauer spectroscopy and X-ray diffraction analysis. For Mössbauer investigations, a small amount of {sup 57}Fe (2 at%) Mössbauer isotope was introduced into the samples. It follows from the analysis of the obtained data that both common features of the structural transformations and differences between them exist in lanthanum manganites depending on ionic radius and concentration of a doping element.

  3. Lanthanum citrate induces anoikis of Hela cells.

    PubMed

    Su, Xiange; Zheng, Xiaona; Ni, Jiazuan

    2009-11-28

    Some reports show that lanthanum, a rare earth element, induces apoptosis in certain cancer cells. In the present paper, we report the first observation of anoikis induced by lanthanum citrate (LaCit) in Hela cells at a concentration of 0.001-0.1 mmol/L after 48h-treatment. Before cell treatment, Hela cells were subjected to anoikis-resistant selection to remove anoikis-sensitive cells and ensure specificity of LaCit-induced anoikis. Anoikis was determined by Annexin/PI, AO/EB staining, cleavage of PARP and soft-agar colony forming assay. Further, findings of decreased mitochondrial membrane potential, the cleavage of caspase-9 and a dose-dependent increase expression of Bax were detected, suggesting that the intrinsic caspase pathway was involved in the anoikis induced by LaCit. In addition, activation of caspase-8 occurred later than that of caspase-9. LaCit also caused reorganization of actin cytoskeleton, and was accompanied by an increase in co-localization of F-actin with mitochondria, implying that both actin cytoskeleton and mitochondria may play important roles in LaCit -induced anoikis. PMID:19679391

  4. Co-doped Barium Phosphate Glass

    NASA Astrophysics Data System (ADS)

    Jiménez, J. A.

    2014-09-01

    Co-doping of a P2O5:BaO glass matrix with divalent tin and trivalent samarium ions has been realized by the melt-quenching technique with the purpose of investigating the material's luminescent properties. Photoluminescence excitation spectra obtained by monitoring Sm3+ 4G5/2 emission showed a broad excitation band around 290 nm (absent in a Sm3+-doped reference), typical of donor/acceptor energy transfer. Under such excitation, the material exhibits a reddish-white emission. Time-resolved spectra recorded under the 290-nm excitation (non-resonant with Sm3+ excitation peaks) exposed a broad blue-white band characteristic of twofold-coordinated Sn centers and orange-red emission bands of Sm3+ ions, which appeared well separated in time in accord with their emission decay dynamics. Consequently, the data indicate that light absorption occurs at Sn centers (donors) followed by energy transfer to samarium ions (acceptors) which results in populating the 4G5/2 emitting state in Sm3+. Energy transfer pathways likely resulting in the sensitization of Sm3+ photoluminescence are discussed. Results are put into context in terms of the potential of SnO and rare-earth co-doped barium phosphate glasses for use in white light-emitting devices.

  5. The energetics of lanthanum tantalate materials

    SciTech Connect

    Forbes, Tori Z.; Nyman, May; Rodriguez, Mark A.; Navrotsky, Alexandra

    2010-11-15

    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

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

    SciTech Connect

    Jiang, Y.; Wang, S.; Zhang, Y.; Yan, J.; Li, W.

    1998-02-01

    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.

  7. Reversible C-C coupling in phenanthroline complexes of divalent samarium and thulium.

    PubMed

    Nocton, Grgory; Ricard, Louis

    2015-02-28

    The reaction of a series of organolanthanide fragments of samarium and thulium with phenanthroline is reported. All adducts couple in the 4-position of the phenanthroline ligand to yield the 4-4' dimers when they crystallize. The analysis of the solution structure revealed a thermally reversible C-C coupling in all cases. PMID:25634655

  8. Mechanisms of magma generation beneath hawaii and mid-ocean ridges: uranium/thorium and samarium/neodymium isotopic evidence.

    PubMed

    Sims, K W; Depaolo, D J; Murrell, M T; Baldridge, W S; Goldstein, S J; Clague, D A

    1995-01-27

    Measurements of uranium/thorium and samarium/neodymium isotopes and concentrations in a suite of Hawaiian basalts show that uranium/thorium fractionation varies systematically with samarium/neodymium fractionation and major-element composition; these correlations can be understood in terms of simple batch melting models with a garnet-bearing peridotite magma source and melt fractions of 0.25 to 6.5 percent. Midocean ridge basalts shows a systematic but much different relation between uranium/thorium fractionation and samarium/neodymium fractionation, which, although broadly consistent with melting of a garnet-bearing peridotite source, requires a more complex melting model. PMID:17788786

  9. Laser glazing of lanthanum magnesium hexaaluminate

    NASA Astrophysics Data System (ADS)

    Zhang, Yanfei; Wang, Yaomin; Jarligo, Maria Ophelia; Zhong, Xinghua; Li, Qin; Cao, Xueqiang

    2008-08-01

    Lanthanum magnesium hexaalumminate (LMA) is an important candidate for thermal barrier coatings due to its thermal stability and low thermal conductivity. On the other hand, laser glazing method can potentially make thermal barrier coatings impermeable, resistant to corrosion on the surface and porous at bulk. LMA powder was synthesized at 1600 °C by solid-state reaction, pressed into tablet and laser glazed with a 5-kW continuous wave CO2 laser. Dendritic structures were observed on the surface of the laser-glazed specimen. The thicker the tablet, the easier the sample cracks. Cracking during laser glazing is attributed to the low thermal expansion coefficient and large thickness of the sample.

  10. Sintering aid for lanthanum chromite refractories

    DOEpatents

    Flandermeyer, Brian K.; Poeppel, Roger B.; Dusek, Joseph T.; Anderson, Harlan U.

    1988-01-01

    An electronically conductive interconnect layer for use in a fuel cell or other electrolytic device is formed with sintering additives to permit densification in a monolithic structure with the electrode materials. Additions including an oxide of boron and a eutectic forming composition of Group 2A metal fluorides with Group 3B metal fluorides and Group 2A metal oxides with Group 6B metal oxides lower the required firing temperature of lanthanum chromite to permit densification to in excess of 94% of theoretical density without degradation of electrode material lamina. The monolithic structure is formed by tape casting thin layers of electrode, interconnect and electrolyte materials and sintering the green lamina together under common densification conditions.

  11. Diminiode thermionic energy conversion with lanthanum-hexaboride electrodes

    NASA Technical Reports Server (NTRS)

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

    1978-01-01

    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.

  12. Lanthanum Halide Nanoparticle Scintillators for Nuclear Radiation Detection

    SciTech Connect

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

    2013-02-01

    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.

  13. Diminiode thermionic energy conversion with lanthanum-hexaboride electrodes

    NASA Technical Reports Server (NTRS)

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

    1978-01-01

    This paper presents 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. 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.

  14. Ferromagnetism in Sm doped ZnO nanorods by a hydrothermal method

    NASA Astrophysics Data System (ADS)

    Piao, Jingyuan; Tseng, Li-Ting; Yi, Jiabao

    2016-04-01

    Sm doped ZnO nanorods with various concentrations have been successfully synthesized using a hydrothermal method. XRD analysis indicates that there are no impurities or secondary phases in all the samples. The continuous expansion of d-spacing from XRD and TEM analysis suggests the effective corporation of Sm ions in ZnO. It is found that pure ZnO is paramagnetic. Both 1% and 5% Sm doped ZnO nanorods are ferromagnetic at room temperature. 5% Sm doped ZnO has a large paramagnetic signal at low temperature, suggesting the formation of the precipitation or clusters of samarium oxide.

  15. Fabrication, characterization and electrical conductivity of Ru-doped LaCrO3 dense perovskites

    NASA Astrophysics Data System (ADS)

    Jiao, Handong; Wang, Junxiang; Ge, Jianbang; Zhang, Long; Zhu, Hongmin; Jiao, Shuqiang

    2016-04-01

    Ru-doped lanthanum chromates (LaRuxCr1-xO3) were prepared through a solid-state reaction method. The perovskite pellets with high bulk density over 98% were obtained using the as-prepared LaRuxCr1-xO3 powders as starting materials by spark plasma sintering (SPS) process. The pellets performed high electrical conductivity, which increased with increasing of temperature and ruthenium content (0≤x≤0.10). The activation energy of lanthanum chromate was found to be decreased due to the ruthenium doping.

  16. Lanthanum as an intracellular stain for electron microscopy.

    PubMed

    Leeson, T S; Higgs, G W

    1982-07-01

    Results obtained after the normal aldehyde fixation of duodenal enterocytes for electron microscopy have been compared with results obtained when 0.1% Malachite Green or 10 mM lanthanum chloride had been added during aldehyde fixation. Sections were examined without further staining, and after counterstaining with lead citrate and uranyl acetate. In unstained sections, lanthanum-treated material showed improved contrast when compared to results from the other two methods. Also, after counterstaining, areas showing excellent contrast were much more frequent and more readily detected in the lanthanum-treated material. In the microvilli of enterocytes fixed in the presence of lanthanum, the plasmalemma-glycocalyx was defined more clearly and the results were more pleasing subjectively. When Malachite Green was present in the fixative, good contrast was observed more frequently than in routinely fixed tissues, but less often than in those treated with lanthanum. It is suggested that the addition of lanthanum chloride or Malachite Green to the fixative may prove useful in many ultrastructural studies. PMID:6181017

  17. Competition of magnetization mechanisms in (NdDy)(FeCo)B alloys, doped with samarium

    NASA Astrophysics Data System (ADS)

    Kablov, E. N.; Ospennikova, O. G.; Piskorskii, V. P.; Korolev, D. V.; Kunitsina, E. I.; Dmitriev, A. I.; Morgunov, R. B.

    2016-01-01

    It is found that magnetic hysteresis in sintered magnets (Nd0.62Dy0.33Sm0.05)16.2(Fe0.77Co0.23)78.1B5.7 for the temperature range T = 150-350 K, is caused by a mechanism associated with the displacement of domain walls, which ceases at temperatures below 150 K. In addition, the formation of magnetic hysteresis in this temperature range is affected by the mechanism involving the nucleation of the reverse magnetization phase, which is observed at temperatures down to 36 K.

  18. Lutetium-doped EuO films grown by molecular-beam epitaxy

    SciTech Connect

    Melville, A.; Heeg, T.; Mairoser, T.; Schmehl, A.; Shai, D. E.; Monkman, E. J.; Harter, J. W.; Hollaender, B.; Schubert, J.; Shen, K. M.; Mannhart, J.; Schlom, D. G.

    2012-05-28

    The effect of lutetium doping on the structural, electronic, and magnetic properties of epitaxial EuO thin films grown by reactive molecular-beam epitaxy is experimentally investigated. The behavior of Lu-doped EuO is contrasted with doping by lanthanum and gadolinium. All three dopants are found to behave similarly despite differences in electronic configuration and ionic size. Andreev reflection measurements on Lu-doped EuO reveal a spin-polarization of 96% in the conduction band, despite non-magnetic carriers introduced by 5% lutetium doping.

  19. Tuning oxygen vacancy photoluminescence in monoclinic Y2WO6 by selectively occupying yttrium sites using lanthanum

    PubMed Central

    Ding, Bangfu; Han, Chao; Zheng, Lirong; Zhang, Junying; Wang, Rongming; Tang, Zilong

    2015-01-01

    The effect of isovalent lanthanum (La) doping on the monoclinic Y2WO6 photoluminescence was studied. Introducing the non-activated La3+ into Y2WO6 brings new excitation bands from violet to visible regions and strong near-infrared emission, while the bands position and intensity depend on the doping concentration. It is interesting to find that doping La3+ into Y2WO6 promotes the oxygen vacancy formation according to the first-principle calculation, Raman spectrum, and synchrotron radiation analysis. Through the Rietveld refinement and X-ray photoelectron spectroscopy results, La3+ is found to mainly occupy the Y2 (2f) site in low-concentration doped samples. With increasing doping concentration, the La3+ occupation number at the Y3 (4g) site increases faster than those at the Y1 (2e) and Y2 (2f) sites. When La3+ occupies different Y sites, the localized energy states caused by the oxygen vacancy pair change their position in the forbidden band, inducing the variation of the excitation and emission bands. This research proposes a feasible method to tune the oxygen vacancy emission, eliminating the challenge of precisely controlling the calcination atmosphere. PMID:25821078

  20. Large-area lanthanum hexaboride electron emitter

    SciTech Connect

    Goebel, D.M.; Hirooka, Y.; Sketchley, T.A.

    1985-09-01

    A large-area cathode assembly which is capable of continuous, high-current electron emission is described. The cathode utilizes an indirectly heated lanthanum hexaboride (LaB/sub 6/) disk as the thermionic electron emitter. The LaB/sub 6/ cathode emits over 600 A of electrons at an average of 20 A/cm/sup 2/ continuously with no observable lifetime limits to date after about 400 h of operation in a plasma discharge. Proper clasping of the LaB/sub 6/ disk is required to avoid impurity production from chemical reactions with the holder and to provide adequate support if the disk fractures during rapid thermal cycling. Modification of the LaB/sub 6/ surface composition due to preferential sputtering of boron by hydrogen and argon ions in the plasma discharge has been observed. The surface appearance is consistent with the formation of LaB/sub 4/ as a result of boron depletion. The electron emission capability of the cathode is not significantly altered by the surface change. This surface modification by preferential sputtering is not observed in hollow cathodes where the ion energy from the cathode sheath voltage is typically less than 50 V. The electron emission by the cathode has not been affected by exposure to both air and water during operation. Utilizing thick disks of this intermediate temperature cathode material results in reliable, high-current, long-lifetime electron emitter assemblies.

  1. Phosphate adsorption on lanthanum loaded biochar.

    PubMed

    Wang, Zhanghong; Shen, Dekui; Shen, Fei; Li, Tianyu

    2016-05-01

    To attain a low-cost and high-efficient phosphate adsorbent, lanthanum (La) loaded biochar (La-BC) prepared by a chemical precipitation method was developed. La-BC and its pristine biochar (CK-BC) were comparatively characterized using zeta potential, BET surface area, scanning electron microscopy/energy dispersive spectrometer (SEM-EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR). The adsorption ability and the mechanisms during adsorption process for the La-BC samples were also investigated. La loaded on the surface of biochar can be termed as La-composites (such as LaOOH, LaONO3 and La(OH)3), leading to the decrease of negative charge and surface area of biochar. La-BC exhibited the high adsorption capacity to phosphate compared to CK-BC. Adsorption isotherm and adsorption kinetic studies showed that the Langmuir isotherm and second order model could well describe the adsorption process of La-BC, indicating that the adsorption was dominated by a homogeneous and chemical process. The calculated maximum adsorption capacity was as high as 46.37 mg g(-1) (computed in P). Thermodynamic analysis revealed that the adsorption was spontaneous and endothermic. SEM, XRD, XPS and FT-IR analysis suggested that the multi-adsorption mechanisms including precipitation, ligand exchange and complexation interactions can be evidenced during the phosphate adsorption process by La-composites in La-BC. PMID:26871732

  2. Cytocompatibility of a free machining titanium alloy containing lanthanum.

    PubMed

    Feyerabend, Frank; Siemers, Carsten; Willumeit, Regine; Rsler, Joachim

    2009-09-01

    Titanium alloys like Ti6Al4V are widely used in medical engineering. However, the mechanical and chemical properties of titanium alloys lead to poor machinability, resulting in high production costs of medical products. To improve the machinability of Ti6Al4V, 0.9% of the rare earth element lanthanum (La) was added. The microstructure, the mechanical, and the corrosion properties were determined. Lanthanum containing alloys exhibited discrete particles of cubic lanthanum. The mechanical properties and corrosion resistance were slightly decreased but are still sufficient for many applications in the field of medical engineering. In vitro experiments with mouse macrophages (RAW 264.7) and human bone-derived cells (MG-63, HBDC) were performed and revealed that macrophages showed a dose response below and above a LaCl3 concentration of 200 microM, while MG-63 and HBDC tolerated three times higher concentrations without reduction of viability. The viability of cells cultured on disks of the materials showed no differences between the reference and the lanthanum containing alloy. We therefore propose that lanthanum containing alloy appears to be a good alternative for biomedical applications, where machining of parts is necessary. PMID:18646202

  3. 40 CFR 721.10370 - Phosphonic acid, p-octyl-, lanthanum (3+) salt (2:1).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Phosphonic acid, p-octyl-, lanthanum... New Uses for Specific Chemical Substances § 721.10370 Phosphonic acid, p-octyl-, lanthanum (3+) salt... substance identified as phosphinic acid, p-octyl-, lanthanum (3+) salt (2:1) (PMN P-10-99; CAS No....

  4. 40 CFR 721.10370 - Phosphonic acid, p-octyl-, lanthanum (3+) salt (2:1).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Phosphonic acid, p-octyl-, lanthanum... New Uses for Specific Chemical Substances § 721.10370 Phosphonic acid, p-octyl-, lanthanum (3+) salt... substance identified as phosphinic acid, p-octyl-, lanthanum (3+) salt (2:1) (PMN P-10-99; CAS No....

  5. 40 CFR 721.10370 - Phosphonic acid, p-octyl-, lanthanum (3+) salt (2:1).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Phosphonic acid, p-octyl-, lanthanum... New Uses for Specific Chemical Substances § 721.10370 Phosphonic acid, p-octyl-, lanthanum (3+) salt... substance identified as phosphinic acid, p-octyl-, lanthanum (3+) salt (2:1) (PMN P-10-99; CAS No....

  6. Spin reorientation transition in dysprosium-samarium orthoferrite single crystals

    NASA Astrophysics Data System (ADS)

    Zhao, Weiyao; Cao, Shixun; Huang, Ruoxiang; Cao, Yiming; Xu, Kai; Kang, Baojuan; Zhang, Jincang; Ren, Wei

    2015-03-01

    We report the control of spin reorientation (SR) transition in perovskite D y1 -xS mxFe O3 , a whole family of single crystals grown by an optical floating zone method from x =0 to 1 with an interval of 0.1. Powder x-ray diffractions and Rietveld refinements indicate that lattice parameters a and c increase linearly with Sm doping concentration, whereas b keeps a constant. Temperature dependence of the magnetizations under zero-field-cooling (ZFC) and field-cooling (FC) processes are studied in detail. We have found a remarkable linear change of SR transition temperature in Sm-rich samples for x >0.2 , which covers an extremely wide temperature range including room temperature. The a -axis magnetization curves under the FC during cooling (FCC) process bifurcate from and then jump back to that of the ZFC and FC warming process in single crystals when x =0.5 -0.9 , suggesting complicated 4 f -3 d electron interactions among D y3 + -S m3 +,D y3 + -F e3 + , and S m3 + -F e3 + sublattices of diverse magnetic configurations. The magnetic properties from the doping effect on SR transition temperature in these single crystals might be useful in the material physics and device design applications.

  7. Calcium and lanthanum solid base catalysts for transesterification

    SciTech Connect

    Ng, K. Y. Simon; Yan, Shuli; Salley, Steven O.

    2015-07-28

    In one aspect, a heterogeneous catalyst comprises calcium hydroxide and lanthanum hydroxide, wherein the catalyst has a specific surface area of more than about 10 m.sup.2/g. In another aspect, a heterogeneous catalyst comprises a calcium compound and a lanthanum compound, wherein the catalyst has a specific surface area of more than about 10 m.sup.2/g, and a total basicity of about 13.6 mmol/g. In further another aspect, a heterogeneous catalyst comprises calcium oxide and lanthanum oxide, wherein the catalyst has a specific surface area of more than about 10 m.sup.2/g. In still another aspect, a process for preparing a catalyst comprises introducing a base precipitant, a neutral precipitant, and an acid precipitant to a solution comprising a first metal ion and a second metal ion to form a precipitate. The process further comprises calcining the precipitate to provide the catalyst.

  8. Rare earth elements in the aragonitic shell of freshwater mussel Corbicula fluminea and the bioavailability of anthropogenic lanthanum, samarium and gadolinium in river water.

    PubMed

    Merschel, Gila; Bau, Michael

    2015-11-15

    High-technology metals - such as the rare earth elements (REE) - have become emerging contaminants in the hydrosphere, yet little is known about their bioavailability. The Rhine River and the Weser River in Germany are two prime examples of rivers that are subjected to anthropogenic REE input. While both rivers carry significant loads of anthropogenic Gd, originating from contrast agents used for magnetic resonance imaging, the Rhine River also carries large amounts of anthropogenic La and lately Sm which are discharged into the river from an industrial point source. Here, we assess the bioavailability of these anthropogenic microcontaminants in these rivers by analyzing the aragonitic shells of the freshwater bivalve Corbicula fluminea. Concentrations of purely geogenic REE in shells of comparable size cover a wide range of about one order of magnitude between different sampling sites. At a given sampling site, geogenic REE concentrations depend on shell size, i.e. mussel age. Although both rivers show large positive Gd anomalies in their dissolved loads, no anomalous enrichment of Gd relative to the geogenic REE can be observed in any of the analyzed shells. This indicates that the speciations of geogenic and anthropogenic Gd in the river water differ from each other and that the geogenic, but not the anthropogenic Gd is incorporated into the shells. In contrast, all shells sampled at sites downstream of the industrial point source of anthropogenic La and Sm in the Rhine River show positive La and Sm anomalies, revealing that these anthropogenic REE are bioavailable. Only little is known about the effects of long-term exposure to dissolved REE and their general ecotoxicity, but considering that anthropogenic Gd and even La have already been identified in German tap water and that anthropogenic La and Sm are bioavailable, this should be monitored and investigated further. PMID:26151653

  9. 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)

    Kulaksız, Serkan; Bau, Michael

    2013-01-01

    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 μm). 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.

  10. Lanthanum Carbonate for Hyperphosphatemia in Patients on Peritoneal Dialysis

    PubMed Central

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

    2013-01-01

    ♦ 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 Ca×P 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 Ca×P 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 Ca×P product in CAPD patients with hyperphosphatemia. Lanthanum carbonate was well tolerated in our population. PMID:23209037

  11. Nanostructured Lanthanum Halides and CeBr3 for Nuclear Radiation and Detection

    SciTech Connect

    Paul Guss, Sanjoy Mukhopadhyay, Ron Guise, Ding Yuan

    2010-06-09

    Scintillator materials are used to detect, and in some cases identify, gamma rays. Higher performance scintillators are expensive, hard to manufacture, fragile, and sometimes require liquid nitrogen or cooling engines. But whereas lower-quality scintillators are cheap, easy to manufacture, and more rugged, their performance is lower. At issue: can the desirable qualities of high-and low-performance scintillators be combined to achieve better performance at lower cost? Preliminary experiments show that a LaF{sub 3}:Ce oleic acid-based nanocomposite exhibits a photopeak when exposed to {sup 137}Cs source gamma-radiation. The chemical synthesis of the cerium-doped lanthanum halide nanoparticles are scalable and large quantities of material can be produced at a time, unlike typical crystal growth processes such as the Bridgeman process. Using a polymer composite (Figure 1), produced by LANL, initial measurements of the unloaded and 8% LaF{sub 3}:Ce-loaded sample have been made using {sup 137}Cs sources. Figure 2 shows an energy spectrum acquired for CeF{sub 3}. The lighter plot is the measured polymer-only spectrum and the black plot is the spectrum from the nanocomposite scintillator. As the development of this material continues, the energy resolution is expected to improve and the photopeak-to-Compton ratio will become greater at higher loadings. These measurements show the expected Compton edge in the polymer-only sample, and the Compton edge and photo-peak expected in the nanophosphor composites that LANL has produced. Using a porous VYCORR with CdSe/ZnS core shell quantum dots, Letant has demonstrated that he has obtained signatures of the 241Am photopeak with energy resolution as good at NaI (Figure 3). We begin with the fact that CeBr{sub 3} crystals do not have a self-activity component as strong as the lanthanum halides. The radioactive 0.090% {sup 138}La component of lanthanum leads to significant self-activity, which will be a problem for very large detector volumes. Yet a significant strength of the nanostructure detector concept is the ability to create extremely large detector volumes by mixing nanoparticles into a transparent matrix. This would argue for use of nanoparticles other than lanthanum halides. Nanocomposites are easy to prepare; it is much less costly to use nanocomposites than to grow large whole crystals of these materials. The material can be fabricated at an industrial scale, further reducing cost. This material potentially offers the performance of $300/cc material (e.g., lanthanum bromide) at a cost of $1/cc. Because the material acts as a plastic, it is rugged and flexible, and can be made in large sheets, increasing the sensitivity of a detector using it. It would operate at ambient temperatures. Very large volumes of detector may be produced at greatly reduced cost, enhancing the non-proliferation posture of the nation for the same dollar value.

  12. Effects of lanthanum in cellular systems. A review.

    PubMed

    Das, T; Sharma, A; Talukder, G

    1988-12-01

    Lanthanum belongs to the group of elements known as "lanthanons," which also includes cerium, europium, promethium, and thulium. It is the most electropositive element of the rare earth group, is uniformly trivalent, and is similar in its chemical properties to the alkaline earth elements. The effects of this element and its compounds on cellular systems are of considerable interest because of their increasing use in industry and as a substitute or antagonist for calcium in a variety of cellular reactions. Lanthanum is also being employed extensively in studying anatomical barriers, membrane structure, and subcellular transport systems, particularly the calcium pathway. PMID:2484565

  13. Enhancement of superconductivity of lanthanum and yttrium sesquicarbide

    DOEpatents

    Krupka, M.C.; Giorgi, A.L.; Krikorian, N.H.; Szklarz, E.G.

    1971-06-22

    A method of enhancing the superconductivity of body-centered cubic lanthanum and yttrium sesquicarbide through formation of the sesquicarbides from ternary alloys of novel composition (N/sub x/M/sub 1-x/)C/sub z/, where N is yttrium or lanthanum, M is thorium, any of the Group IV and VI transition metals, or gold, germanium or silicon, and z is approximately 1.2 to 1.6. These ternary sesquicarbides have superconducting transition temperatures as high as 17.0/sup 0/K.

  14. SEPARATION OF PLUTONIUM FROM LANTHANUM BY CHELATION-EXTRACTION

    DOEpatents

    James, R.A.; Thompson, S.G.

    1958-12-01

    Plutonium can be separated from a mixture of plutonlum and lanthanum in which the lanthanum to plutonium molal ratio ls at least five by adding the ammonium salt of N-nitrosoarylhydroxylamine to an aqueous solution having a pH between about 3 and 0.2 and containing the plutonium in a valence state of at least +3, to form a plutonium chelate compound of N-nitrosoarylhydroxylamine. The plutonium chelate compound may be recovered from the solution by extracting with an immiscible organic solvent such as chloroform.

  15. Near-threshold effects in lanthanum 4d emission

    SciTech Connect

    Shulakov, A.S.; Zimkina, T.M.; Braiko, A.P.; Stepanov, A.P.

    1985-04-01

    The characteristics of the ultrasoft x-ray emission spectrum of lanthanum in the vicinity of the N/sub 4,5/--O/sub 2,3/ transitions have been studied. The transitions were excited by electrons with an energy varied over the region of the excitation and ionization potentials of the 4d shell (98.4--203.9 eV). The emission is shown to result primarily from transitions from excited initial state of the ion core of lanthanum, even when high-energy electrons are used to excite the spectra.

  16. Enhancement of Superconductivity of Lanthanum and Yttrium Sesquicarbide

    DOEpatents

    Krupka, M. C.; Giorgi, A. L.; Krikorian, N. H.; Szklarz, E. G.

    1972-06-22

    A method of enhancing the superconductivity of body-centered cubic lanthanum and yttrium sesquicarbide through formation of the sesquicarbides from ternary alloys of novel composition (N/sub x/M/sub 1-x/)C/sub z/, where N is yttrium or lanthanum, M is thorium, any of the Group IV and VI transition metals, or gold, germanium or silicon, and z is approximately 1.2 to 1.6. These ternary sesquicarbides have superconducting transition temperatures as high as 17.0/sup 0/K.

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

    SciTech Connect

    Paravati, Anthony J.; Russo, Andrea L.; Aitken, Candice

    2011-10-01

    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.

  18. Giant negative thermal expansion in La-doped CaFe2As2

    NASA Astrophysics Data System (ADS)

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

    2012-09-01

    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.

  19. Phase dependent structural and electronic properties of Lanthanum Orthophosphate (LaPO4)

    NASA Astrophysics Data System (ADS)

    Neupane, Mahesh; Garrett, Gregory; Rudin, Sergey; Andzelm, Jan

    Lanthanum orthophosphate (LaPO4) belongs to the family of rare-earth (RE) orthophosphates. The La-ion lacks valence 4f-electron, so for it to exhibit f-electron dependent physics, it must be doped with additional RE elements. In the bulk form, LaPO4 exist in both a stable monoclinic and a metastable hexagonal phase, which both possess indirect energy transition characteristics. Though the overall optoelectronic properties of the RE-doped LaPO4 depend on the accuracy of the observed bulk energy gap, the reported experimental and theoretical energy gaps varies between ~81,2 and ~53 eV, respectively. Through this theoretical study, we attempt to establish a correlation between electronic properties of bulk LaPO4 and various levels of first principle theories. Compared to experimental data, the PBE0 functional over-predicts energy gaps and the energy differences between the indirect-to-direct transition energies by 25%. The HSE06 gives a good description of electronic properties and predicts the energy gaps to be 7.68 (monoclinic) and 7.29 eV (hexagonal). Analysis on the structural stability also reveals that the total energy difference between the two phases is 6meV, consistent with the experimentally observed instantaneous pressure and temperature dependent phase transition.

  20. Growth and characterization of rare earths doped triglycine sulfate crystals

    NASA Astrophysics Data System (ADS)

    Batra, A. K.; Guggilla, Padmaja; Cunningham, Dewanna; Aggarwal, M. D.; Lal, R. B.

    2006-01-01

    Ferroelectric triglycine sulfate (TGS) single crystals have been grown by a temperature-lowering technique from the aqueous solution by doping with samarium sulfate, ytterbium sulfate and terbium sulfate in the ferroelectric phase. The effects of these different dopants on the morphology, growth and various properties such as dielectric, pyroelectric and piezoelectric of doped TGS crystals have been investigated. The decrease in values of dielectric constant and pyroelectric coefficient is observed while the dielectric loss has increased. Using these parameters, figure-of-merits for their use in infrared sensors have also been reported and compared with pure TGS crystal. The Vickers's hardness of doped TGS crystals along (0 1 0) crystallographic face has increased.

  1. Ab initio energetics of lanthanum substitution in ferroelectric bismuth titanate

    NASA Astrophysics Data System (ADS)

    Shah, S. H.; Bristowe, P. D.

    2011-04-01

    Using first principles calculations and atomistic thermodynamics the bulk and defect properties of orthorhombic bismuth titanate (Bi4Ti3O12) and bismuth lanthanum titanate (Bi3.25La0.75Ti3O12) 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.

  2. Discovery of cesium, lanthanum, praseodymium and promethium isotopes

    SciTech Connect

    May, E.; Thoennessen, M.

    2012-09-15

    Currently, forty-one cesium, thirty-five lanthanum, thirty-two praseodymium, and thirty-one promethium 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.

  3. Cu-La-Ni (Copper-Lanthanum-Nickel)

    NASA Astrophysics Data System (ADS)

    Materials Science International Team MSIT

    This document is part of Subvolume C2 'Non-Ferrous Metal Systems. Part 2: Selected Copper Systems' of Volume 11 'Ternary Alloy Systems - Phase Diagrams, Crystallographic and Thermodynamic Data critically evaluated by MSIT®' of Landolt-Börnstein - Group IV 'Physical Chemistry'. It provides data of the ternary system Copper-Lanthanum-Nickel.

  4. Structural Characterization of Methanol Substituted Lanthanum Halides

    PubMed Central

    Boyle, Timothy J.; Ottley, Leigh Anna M.; Alam, Todd M.; Rodriguez, Mark A.; Yang, Pin; Mcintyre, Sarah K.

    2010-01-01

    The first study into the alcohol solvation of lanthanum halide [LaX3] derivatives as a means to lower the processing temperature for the production of the LaBr3 scintillators was undertaken using methanol (MeOH). Initially the de-hydration of {[La(µ-Br)(H2O)7](Br)2}2 (1) was investigated through the simple room temperature dissolution of 1 in MeOH. The mixed solvate monomeric [La(H2O)7(MeOH)2](Br)3 (2) compound was isolated where the La metal center retains its original 9-coordination through the binding of two additional MeOH solvents but necessitates the transfer of the innersphere Br to the outersphere. In an attempt to in situ dry the reaction mixture of 1 in MeOH over CaH2, crystals of [Ca(MeOH)6](Br)2 (3) were isolated. Compound 1 dissolved in MeOH at reflux temperatures led to the isolation of an unusual arrangement identified as the salt derivative {[LaBr2.75•5.25(MeOH)]+0.25 [LaBr3.25•4.75(MeOH)]−0.25} (4). The fully substituted species was ultimately isolated through the dissolution of dried LaBr3 in MeOH forming the 8-coordinated [LaBr3(MeOH)5] (5) complex. It was determined that the concentration of the crystallization solution directed the structure isolated (4 concentrated; 5 dilute) The other LaX3 derivatives were isolated as [(MeOH)4(Cl)2La(µ-Cl)]2 (6) and [La(MeOH)9](I)3•MeOH (7). Beryllium Dome XRD analysis indicated that the bulk material for 5 appear to have multiple solvated species, 6 is consistent with the single crystal, and 7 was too broad to elucidate structural aspects. Multinuclear NMR (139La) indicated that these compounds do not retain their structure in MeOD. TGA/DTA data revealed that the de-solvation temperatures of the MeOH derivatives 4 – 6 were slightly higher in comparison to their hydrated counterparts. PMID:20514349

  5. Responses in sediment phosphorus and lanthanum concentrations and composition across 10 lakes following applications of lanthanum modified bentonite.

    PubMed

    Dithmer, Line; Nielsen, Ulla Gro; Lürling, Miquel; Spears, Bryan M; Yasseri, Said; Lundberg, Daniel; Moore, Alanna; Jensen, Nicholai D; Reitzel, Kasper

    2016-06-15

    A combined field and laboratory scale study of 10 European lakes treated between 2006 and 2013 with a lanthanum (La) modified bentonite (LMB) to control sediment phosphorus (P) release was conducted. The study followed the responses in sediment characteristics including La and P fractions and binding forms, P adsorption capacity of discrete sediment layers, and pore water P concentrations. Lanthanum phosphate mineral phases were confirmed by solid state (31)P MAS NMR and LIII EXAFS spectroscopy. Rhabdophane (LaPO4 · nH2O) was the major phase although indications of monazite (LaPO4) formation were also reported, in the earliest treated lake. Molar ratios between La and P in the sediments were generally above 1, demonstrating excess La relative to P. Lanthanum was vertically mixed in the sediment down to a depth of 10 cm for eight of the ten lakes, and recovery of La in excess of 100% of the theoretical aerial load indicated translocation of the LMB towards the deepest areas of the lakes. Lanthanum was generally recovered from bed sediment samples following sequential chemical extraction from the HCl fraction. Soluble reactive P (SRP) release experiments on intact sediment cores indicated conditions of P retention (with the exception of two lakes) by sediments, indicating effective control of sediment P release, i.e. between two and nine years after treatment. PMID:26971297

  6. Phase behavior of lanthanum strontium manganites

    SciTech Connect

    Zheng, F.; Pederson, L.R.

    1999-08-01

    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}.

  7. A novel and efficient samarium iodide-mediated synthesis of neoflavonoids (4-arycloumarins)

    SciTech Connect

    Nagasawa, Kazuo; Ryohke, Hirosi; Ohnishi, Makoto; Ito, Keiichi

    1995-12-31

    Bioactive 4-arylcoumarins (4-aryl-2H-1-benzopyran-2-ones) have been recently isolated from the plants belonging to the families like Leguminosae, Guttiferae, and Compositae, some of which are still used as the traditional folk medicine. Despite many methods reported so far, there appears to be of limited success or of no success in some cases (II{sub b-g}) and, therefore, a simpler and more reliable one remains to be highly desired. Thus, a new and sterling protocol is now presented for the synthesis of neoflavonoids, which involves the intramolecular Reformatsky-type reaction via a one electron transfer process with samarium diiodide as a key step.

  8. Rare-earth-doped polymer optical waveguide amplifiers

    NASA Astrophysics Data System (ADS)

    Gao, Renyuan; Norwood, Robert A.; Teng, C. C.; Garito, Anthony F.

    2000-05-01

    The optical properties and characteristics of rare earth- doped polymers have been studied to evaluate their viability for use in optical amplifiers. Rare earth ions are encapsulated in organic, covalently bonded chromophores. The optical properties of various rare earth chromophores doped into polymers are measured and calculated and are then used in numerical simulations of amplifiers and lasers. The result provide an estimate of their potential device performance and establish the fundamental bases for applications in photonics. Owing to their distinct advantages, such as chromophore energy transfer effects, high rare earth ion concentrations, shielding of the ion form high energy vibrations of the host, enhanced optical transition moments and controllable decay rates and branching ratios, rare earth-doped polymers are found to be promising candidates for various device applications. Numerical simulations for samarium and europium doped polymers indicate that gains about 10 dB and greater are achievable in relatively short polymer optical fiber and waveguide amplifiers. Studies of the dependence of metastable state lifetime of rare earth doped polymer systems on doping concentrations reveal that rare earth chromophores dissociation occurs at low concentrations. These results are used to optimize the parameters of our rare earth doped polymer optical waveguide amplifiers.

  9. A simple spectrophotometric assay for micromolar amounts of lanthanum in the presence of calcium and phosphate.

    PubMed

    Fernandez-Gavarron, F; Brand, J G; Rabinowitz, J L

    1987-10-01

    A sensitive spectrophotometric assay for micromolar amounts of lanthanum in the presence of calcium and phosphate (as hydroxyapatite) was developed utilizing the change in absorption (at 652 nm) when the dye arsenazo III was complexed with lanthanum. Arsenazo III was used at a level of 25 microM and the solution pH was maintained at 3.1 with 0.2 M sodium acetate. Lanthanum concentrations down to 0.5 microM could be reliably assayed. Calcium ion did not complex well with arsenazo III at pH 3.1. With calcium present at 100 microM and lanthanum at 10 microM, the assay was 115 times more sensitive for lanthanum. The assay is simple, rapid, reproducible and, unlike the assay using radioactive lanthanum, can be performed at any time. PMID:3455624

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

    NASA Astrophysics Data System (ADS)

    Roca, R. Alvarez; Botero, E. R.; Guerrero, F.; Guerra, J. D. S.; Garcia, D.; Eiras, J. A.

    2009-01-01

    The influence of the microstructural characteristics on the dielectric and electrical properties has been investigated for Nd3+ 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 μm. The porosity and grain size dependences of the phase transition parameters, such as the maximum dielectric permittivity and its corresponding temperature (ɛm and Tm, 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.

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

    SciTech Connect

    Roca, R. Alvarez; Guerrero, F.; Botero, E. R.; Garcia, D.; Eiras, J. A.; Guerra, J. D. S.

    2009-01-01

    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.

  12. Investigation into Nanostructured Lanthanum Halides and CeBr{sub 3} for Nuclear Radiation Detection

    SciTech Connect

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

    2011-06-22

    This slide-show presents work on radiation detection with nanostructured lanthanum halides and CeBr{sub 3}. The goal is 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 the nano-structured lanthanum bromide, lanthanum fluoride, cerium bromide, or other nanocrystal material. Homogeneous and nano structure cases are compared.

  13. Biocompatibility of new, clinically used, and recycled orthodontic samarium-cobalt magnets.

    PubMed

    Bondemark, L; Kurol, J; Wennberg, A

    1994-06-01

    The aim of this study was to compare the cytotoxic effect of new, clinically used, and recycled samarium-cobalt magnets (SmCO5). Cytotoxicity was assessed by two in vitro methods, the millipore filter method and an extraction method. In the filter method, the test material and the target cells are separated by a thin, permeable membrane. The test assesses the cytotoxicity of both water soluble and nonwater soluble components of the test material. The extraction test, which has a higher sensitivity, assesses the cytotoxicity of water soluble components only. According to the filter method, one magnet (new) showed a mild cytotoxic effect; all other tested magnets showed no cytotoxicity. Judged by the extraction test, new as well as clinically used magnets demonstrated a weak cytotoxic effect, suggesting the presence of a small amount of leachable cytotoxic components. The level of exerted cytotoxicity of such components was significantly lower for clinically used than for new magnets. When recycled magnets were tested, the cytotoxicity had significantly decreased, (p < 0.001), and the cytotoxicity could be considered negligible. The results thus revealed that SmCO5 magnets can be recycled with maintained good biocompatibility. Because a small amount of water soluble cytotoxic agents seem to leach out from new partially stainless steel-coated samarium-cobalt magnets, it is recommended that they be stored in water for 24 hours before clinical use, thereby conceivably decreasing the oral exposure of water soluble cytotoxic agents. PMID:8198081

  14. Axial effects of xenon-samarium poisoning in the advanced test reactor

    SciTech Connect

    Auslander, D.J.; Smith, A.C.; McCracken, R.T. )

    1990-01-01

    The paper details an analytical study of the time-dependent behavior in the spatial distributions of xenon and samarium fission product poisons in the Advanced Test Reactor (ATR) during operation and after shutdown. The results of this study provide insight into the behavior and significance of the changing spatial distributions of fission product poisons with respect to the prediction of shim positions at critical for reactor restart after a xenon shutdown. The study was performed with the PDQ neutron diffusion theory code and ENDF/B-V cross sections using a one-dimensional radial model of an ATR lobe and a two-dimensional radial-axial (RZ) model of an ATR lobe. The PDQ results were supported by a review of the basic differential equations, which describe the buildup and decay of the xenon and samarium fission product poisons and precursors. The ATR is a 250-MW, uranium-aluminum-fueled reactor used to study the effects of irradiation on reactor materials. Forty highly enriched uranium fuel elements are arranged in a serpentine configuration within the compact core resulting in a very high power density of (1.0 MW/[ell] of core).

  15. Lanthanum-based cathodes for organic light-emitting devices

    NASA Astrophysics Data System (ADS)

    D'Iorio, Marie; Gorjanc, Tim; Roussy, M.; Lam, J.; Williams, B.

    1998-12-01

    The fabrication of organic light emitting diodes with vacuum sublimed molecules is emerging as a competitive flat panel display alternative because of brightness, efficiency and operating lifetimes of these devices. The requirement for a low work function metal as a cathode limits the choice of materials to reactive elements such as magnesium, calcium, lithium that can be alloyed or co-deposited with silver or aluminum for greater stability and lifetime of the device. From the scandium-subgroup of elements, we have investigated lanthanum as a potential cathode because preliminary studies indicated that the electroluminescence onset could occur as low as 4 volts. Current-voltage, Auger spectroscopy and spectro-photometric data will be presented on standard devices using indium tin oxide, triphenyl diamine derivative and aluminum quinolinate and lanthanum-based cathodes.

  16. Nanoscale assembly of lanthanum silica with dense and porous interfacial structures

    PubMed Central

    Ballinger, Benjamin; Motuzas, Julius; Miller, Christopher R.; Smart, Simon; Diniz da Costa, João C.

    2015-01-01

    This work reports on the nanoscale assembly of hybrid lanthanum oxide and silica structures, which form patterns of interfacial dense and porous networks. It was found that increasing the molar ratio of lanthanum nitrate to tetraethyl orthosilicate (TEOS) in an acid catalysed sol-gel process alters the expected microporous metal oxide silica structure to a predominantly mesoporous structure above a critical lanthanum concentration. This change manifests itself by the formation of a lanthanum silicate phase, which results from the reaction of lanthanum oxide nanoparticles with the silica matrix. This process converts the microporous silica into the denser silicate phase. Above a lanthanum to silica ratio of 0.15, the combination of growth and microporous silica consumption results in the formation of nanoscale hybrid lanthanum oxides, with the inter-nano-domain spacing forming mesoporous volume. As the size of these nano-domains increases with concentration, so does the mesoporous volume. The absence of lanthanum hydroxide (La(OH)3) suggests the formation of La2O3 surrounded by lanthanum silicate. PMID:25644988

  17. Nuclear Magnetic Resonance Study of the Metal - Transition in Lanthanum Hydrides.

    NASA Astrophysics Data System (ADS)

    Chang, Chii-Tzong

    Proton spin-lattice relaxation time (T _1) measurements have been used to investigate the metal-nonmetal (MNM) transition in the lanthanum hydride system, LaH_{rm x} (2 <=q x <=q 3), on samples prepared from highest purity Ames Laboratory lanthanum and also from the same lanthanum doped with controlled low levels of gadolinium. The dependence of hydrogen diffusion parameters on hydrogen concentration x was also determined. The temperature and composition dependence of the MNM transition in this system affects the proton T _1 through the electronic density -of-states at the Fermi level, N(E_{ rm F}). In the pure samples, T _1 depends directly on N(E_ {rm F}) at low temperatures through the Korringa relation, (T_{rm 1 e}T)^{-1/2} ~ N(E_ {rm F}), where T_ {rm 1 e} is the conduction electron contribution to T_1. These measurements over the temperature range 77 <=q T <=q 200 K show that N(E _{rm F}) follows free-electron behavior, N(E_{rm F}) ~ (3 - x)^{1/3}, up to x = 2.8. In the Gd-doped samples, the Gd^ {3+} ion moment contributes an additional relaxation rate, R_{rm 1 p} = T_{rm 1 p}^{-1}. At low temperatures (7 <=q T <=q 150 K), R_{rm 1 p} reflects the temperature dependence of the spectral density function of the Gd^{3+} ion spin fluctuations, characterized by the ion spin-lattice relaxation time tau_ {rm i}. For 2.50 <=q x <=q 2.87, the measurements show tau_{rm i} ~ T^{-1 }, indicating that Gd^{3+ } ion spin relaxation is due to interaction with the conduction electrons, consistent with metallic behavior. At high temperatures (T > 250 K) R_{rm 1 p} reflects fast atomic diffusion of proton magnetization to the Gd^{3+} ions, and R_{rm 1 p} ~ tau_ {rm i}. For x >=q 2.8, it was found that tau_ {rm i} ~ T^{-5}, showing that Gd ^{3+}^in relaxation is governed by the two-phonon process characteristic of insulating solids. In contrast, for x < 2.7 it was found that tau_{rm i} follows approximately Korringa-like behavior, i.e., tau_{rm i} ~ T^{-1 }, showing that LaH_{rm x} remains metallic at high temperatures for these x-values, in agreement with earlier measurements of the ^{139}La NMR Knight shift. These results are summarized as follows: (a) LaH _{rm x} is metallic at all temperatures at all x-values up to 2.8 < x < 2.9, (b) LaH_ {rm x} is at least weakly metallic at all x-values at low temperatures (T < 150 K), and (c) for x >=q 2.87 LaH _{rm x} is nonmetallic at high temperatures (T > 250 K). ftn*DOE Report IS-T 1378. This work was performed under contract No. W-7405-Eng-82 with the U.S. Department of Energy.

  18. Synthesis and luminescence properties of the lithium-containing lanthanum-oxycarbonate-like borates

    SciTech Connect

    Kang, Youjun; Liu, Chunmeng; Kuang, Xiaojun; Mi, Jinxiao; Liang, Hongbin; Su, Qiang

    2012-10-15

    The lithium-containing lanthanum-oxycarbonate-like borate, Li{sub 0.6}La{sub 2}O{sub 2.25}(BO{sub 3}){sub 0.7}, has been synthesized by solid-state reactions and was found to be isostructural with the type II lanthanum-oxycarbonate La{sub 2}O{sub 2}(CO{sub 3}). The new compound, lithium-containing lanthanum-oxycarbonate-like borate Li{sub 0.6}La{sub 2}O{sub 2.25}(BO{sub 3}){sub 0.7} has been synthesized and its structure characterized by the Rietveld method using powder X-ray diffraction data. It crystallizes in space group P6{sub 3}/mmc with lattice parameters of a=b=4.03396(3) A, c=16.5863(2) A, V=233.746(4) A{sup 3}. The mechanism of the lithium incorporation in the borate is that four Li{sup +} cations replace one (B{sub 2}O){sup 4+} group, i.e. Li{sub 0.6}La{sub 2}O{sub 2.25}(BO{sub 3}){sub 0.7} can be described as Li{sub 2x}La{sub 2}O{sub 1.5+2.5x}(BO{sub 3}){sub 1-x}, x=0.3 and the lithium incorporation stabilized the type II borate. The luminescent properties of Li{sub 0.6}La{sub 2}O{sub 2.25}(BO{sub 3}){sub 0.7} doped with Eu{sup 3+} were studied, indicating a potential application in white light emitting diodes (WLEDs). - Graphical abstract: The similar compounds of the new compound Li{sub 0.6}La{sub 2}O{sub 2.25}(BO{sub 3}){sub 0.7}. Projections along the b-axes of crystal structures for (a) La{sub 2}O{sub 2}CO{sub 3}-II, (b) A-type La{sub 2}O{sub 3}, (c) Li{sub 0.52}La{sub 2}O{sub 2.52}(CO{sub 3}){sub 0.74}. Highlights: Black-Right-Pointing-Pointer The new compound Li{sub 0.6}La{sub 2}O{sub 2.25}(BO{sub 3}){sub 0.7} has been synthesized. Black-Right-Pointing-Pointer Its structure is characterized by the Rietveld method using powder X-ray diffraction data. Black-Right-Pointing-Pointer This compound crystallizes in space group P6{sub 3}/mmc. Black-Right-Pointing-Pointer The mechanism of lithium incorporation in borate is that two Li{sup +} cations replace one (BO{sub 0.5}){sup 2+} group. Black-Right-Pointing-Pointer The Eu{sup 3+} doped samples have potential application in WLEDs.

  19. Lanthanum(III) catalysts for highly efficient and chemoselective transesterification.

    PubMed

    Hatano, Manabu; Ishihara, Kazuaki

    2013-03-11

    A facile, atom-economical, and chemoselective esterification is crucial in modern organic synthesis, particularly in the areas of pharmaceutical, polymer, and material science. However, a truly practical catalytic transesterification of carboxylic esters with various alcohols has not yet been well established, since, with many conventional catalysts, the substrates are limited to 1°- and cyclic 2°-alcohols. In sharp contrast, if we take advantage of the high catalytic activities of La(Oi-Pr)(3), La(OTf)(3), and La(NO(3))(3) as ligand-free catalysts, ligand-assisted or additive-enhanced lanthanum(III) catalysts can be highly effective acid-base combined catalysts in transesterification. A highly active dinuclear La(III) catalyst, which is prepared in situ from lanthanum(III) isopropoxide and 2-(2-methoxyethoxy)ethanol, is effective for the practical transesterification of methyl carboxylates, ethyl acetate, weakly reactive dimethyl carbonate, and much less-reactive methyl carbamates with 1°-, 2°-, and 3°-alcohols. As the second generation, nearly neutral "lanthanum(III) nitrate alkoxide", namely La(OR)(m)(NO(3))(3-m), has been developed. This catalyst is prepared in situ from inexpensive, stable, low-toxic lanthanum(III) nitrate hydrate and methyltrioctylphosphonium methyl carbonate, and is highly useful in the non-epimerized transesterification of α-substituted chiral carboxylic esters, even under azeotropic reflux conditions. In these practical La(III)-catalyzed transesterifications, colorless esters can be obtained in small- to large-scale synthesis without the need for inconvenient work-up or careful purification procedures. PMID:23325290

  20. Lanthanum halide nanoparticle scintillators for nuclear radiation detection

    SciTech Connect

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

    2013-02-14

    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.

  1. Effect of pressure on the magnetic properties of lanthanum manganite

    SciTech Connect

    Gonchar', L. E. Leskova, Yu. V.; Nikiforov, A. E.; Kozlenko, D. P.

    2010-08-15

    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.

  2. Unexpected Efficiency of a Luminescent Samarium(III) Complex for Combined Visible and Near-Infrared Biphotonic Microscopy.

    PubMed

    Bui, Anh Thy; Grichine, Alexei; Brasselet, Sophie; Duperray, Alain; Andraud, Chantal; Maury, Olivier

    2015-12-01

    An original samarium(III) complex based on a triazacyclononane platform functionalized with a charge-transfer antenna chromophore exhibited optimized brightness and was successfully used as an emissive species for two-photon microscopy experiments in both the visible and near-infrared spectral ranges. PMID:26489885

  3. Waveshifting fiber readout of lanthanum halide scintillators

    NASA Astrophysics Data System (ADS)

    Case, G. L.; Cherry, M. L.; Stacy, J. G.

    2006-07-01

    Newly developed high-light-yield inorganic scintillators coupled to waveshifting optical fibers provide the capability of efficient X-ray detection and millimeter scale position resolution suitable for high-energy cosmic ray instruments, hard X-ray/gamma ray astronomy telescopes and applications to national security. The CASTER design for NASA's proposed Black Hole Finder Probe mission, in particular, calls for a 6 8 m2 hard X-ray coded aperture imaging telescope operating in the 20 600 keV energy band, putting significant constraints on cost and readout complexity. The development of new inorganic scintillator materials (e.g., cerium-doped LaBr3 and LaCl3) provides improved energy resolution and timing performance that is well suited to the requirements for national security and astrophysics applications. LaBr3 or LaCl3 detector arrays coupled with waveshifting fiber optic readout represent a significant advance in the performance capabilities of scintillator-based gamma cameras and provide the potential for a feasible approach to affordable, large area, extremely sensitive detectors. We describe some of the applications and present laboratory test results demonstrating the expected scintillator performance.

  4. Enhanced field emission from lanthanum hexaboride coated multiwalled carbon nanotubes: Correlation with physical properties

    SciTech Connect

    Patra, Rajkumar; Ghosh, S.; Sheremet, E.; Rodriguez, R. D.; Lehmann, D.; Zahn, D. R. T.; Jha, Menaka; Ganguli, A. K.; Schmidt, H.; Schulze, S.; Hietschold, M.; Schmidt, O. G.

    2014-10-28

    Detailed results from field emission studies of lanthanum hexaboride (LaB{sub 6}) coated multiwalled carbon nanotube (MWCNT) films, pristine LaB{sub 6} films, and pristine MWCNT films are reported. The films have been synthesized by a combination of chemical and physical deposition processes. An impressive increase in field enhancement factor and temporal stability as well as a reduction in turn-on field and threshold field are observed in LaB{sub 6}-coated MWCNTs compared to pristine MWCNT and pristine LaB{sub 6} films. Surface morphology of the films has been examined by scanning electron microscopy. Introduction of LaB{sub 6} nanoparticles on the outer walls of CNTs LaB{sub 6}-coated MWCNTs films is confirmed by transmission electron microscopy. The presence of LaB{sub 6} was confirmed by X-ray photoelectron spectroscopy results and further validated by the Raman spectra. Raman spectroscopy also shows 67% increase in defect concentration in MWCNTs upon coating with LaB{sub 6} and an upshift in the 2D band that could be attributed to p-type doping. Ultraviolet photoelectron spectroscopy studies reveal a reduction in the work function of LaB{sub 6}-coated MWCNT with respect to its pristine counterpart. The enhanced field emission properties in LaB{sub 6}-coated MWCNT films are correlated with a change in microstructure and work function.

  5. Develop techniques for ion implantation of PLZT (lead-lanthanum-zirconate-titanate) for adaptive optics

    SciTech Connect

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

    1987-07-01

    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 ferroelectric and anti-ferroelectric PLZT with a variety of species or combinations of species. These included Ne, O, Ni, Ne/Cr, Ne/Al, Ne/Ni, Ne/O, and Ni/O, at a variety of energies and fluences. An indium-tin oxide (ITO) electrode coating was designed to give a balance of high conductivity and optical transmission at near uv to near ir wavelengths. Samples were characterized for photosensitivity; implanted layer thickness, index of refraction, and density; electrode (ITO) conductivity; and in some cases, residual stress curvature. Thin film anti-ferroelectric PLZT was deposited in a preliminary experiment. The structure was amorphous with x-ray diffraction showing the beginnings of a structure at substrate temperatures of approximately 550/sup 0/C. This report summarizes the research and provides a sampling of the data taken during the report period.

  6. Infrared luminescence of Tm{sup 3+}/Yb{sup 3+} codoped lanthanum aluminum germanate glasses

    SciTech Connect

    Zhang Qiang; Zhang Guang; Chen Guorong; Qiu Jianrong; Chen Danping

    2010-01-15

    Tm{sup 3+} doped and Tm{sup 3+}/Yb{sup 3+} codoped lanthanum aluminum germanate (LAG) glasses are prepared by melt-quenching method and characterized optically. Based on the measurement of absorption spectrum, Judd-Ofelt intensity parameters ({Omega}{sub 2},{Omega}{sub 4},{Omega}{sub 6}) are calculated. The radiation emission rates, branching ratios, and lifetimes of Tm{sup 3+} are calculated to evaluate the spectroscopic properties of Tm{sup 3+} in LAG glass. The infrared emission properties of the samples are investigated and the results show that the 1.8 {mu}m emission can be greatly enhanced by adding proper amount of Yb{sup 3+} under the excitation of 980 nm. The energy transfer processes of Yb{sup 3+}-Yb{sup 3+} and Yb{sup 3+}-Tm{sup 3+} are analyzed, and the results show that Yb{sup 3+} ions can transfer their energy to Tm{sup 3+} ions with high efficiency and large energy transfer coefficient.

  7. Growth of Lithium Lanthanum Titanate Nanosheets and Their Application in Lithium-Ion Batteries.

    PubMed

    Lin, Xi; Wang, Hongqiang; Du, Haiwei; Xiong, Xinrun; Qu, Bo; Guo, Zaiping; Chu, Dewei

    2016-01-20

    In this work, lithium-doped lanthanum titanate (LLTO) nanosheets have been prepared by a facile hydrothermal approach. It is found that with the incorporation of lithium ions, the morphology of the product transfers from rectangular nanosheets to irregular nanosheets along with a transition from La2Ti2O7 to Li0.5La0.5TiO3. The as-prepared LLTO nanosheets are used to enhance electrochemical performance of the LiCo1/3Ni1/3Mn1/3O2 (CNM) electrode by forming a higher lithium-ion conductive network. The LiCo1/3Ni1/3Mn1/3O2-Li0.5La0.5TiO3 (CNM-LLTO) electrode shows better a lithium diffusion coefficient of 1.5 × 10(-15) cm(2) s(-1), resulting from higher lithium-ion conductivity of LLTO and shorter lithium diffusion path, compared with the lithium diffusion coefficient of CNM electrode (5.44 × 10(-16) cm(2) s(-1)). Superior reversibility and stability are also found in the CNM-LLTO electrode, which retains a capacity at 198 mAh/g after 100 cycles at a rate of 0.1 C. Therefore, it can be confirmed that the existence of LLTO nanosheets can act as bridges to facilitate the lithium-ion diffusion between the active materials and electrolytes. PMID:26697735

  8. Neutron Capture and Transmission Measurements and Resonance Parameter Analysis of Samarium

    SciTech Connect

    Leinweber, G.; Burke, J.A.; Knox, H.D.; Drindak, N.J.; Mesh, D.W.; Haines, W.T.; Ballad, R.V.; Block, R.C.; Slovacek, R.E.; Werner, C.J.; Trbovich, M.J.; Barry, D.P.; Sato, T.

    2002-09-15

    The purpose of the present work is to measure the neutron cross sections of samarium accurately. The most significant isotope is {sup 149}Sm, which has a large neutron absorption cross section at thermal energies and is a {sup 235}U fission product with a 1% yield. Its cross sections are thus of concern to reactor neutronics.Neutron capture and transmission measurements were performed by the time-of-flight technique at the Rensselaer Polytechnic Institute (RPI) LINAC facility using metallic and liquid Sm samples. The capture measurements were made at the 25-m flight station with a multiplicity-type capture detector, and the transmission total cross-section measurements were performed at 15- and 25-m flight stations with {sup 6}Li glass scintillation detectors. Resonance parameters were determined by a combined analysis of six experiments (three capture and three transmission) using the multilevel R-matrix Bayesian code SAMMY version M2.The significant features of this work are as follows. Dilute samples of samarium nitrate in deuterated water (D{sub 2}O) were prepared to measure the strong resonances at 0.1 and 8 eV without saturation. Disk-shaped spectroscopic quartz cells were obtained with parallel inner surfaces to provide a uniform thickness of solution. The diluent feature of the SAMMY program was used to analyze these data. The SAMMY program also includes multiple-scattering corrections to capture yield data and resolution functions specific to the RPI facility.Resonance parameters for all stable isotopes of samarium were deduced for all resonances up to 30 eV. Thermal capture cross-section and capture resonance integral (RI) calculations were made using the resultant resonance parameters and were compared to results obtained using resonance parameters from ENDF/B-VI updated through release 3. Extending the definition of the capture RI to include the strong 0.1-eV resonance in {sup 149}Sm, present measurements agree within estimated uncertainties with ENDF/B-VI release 3. The thermal capture cross section was calculated from the present measurements of the resonance parameters and also agrees with ENDF within estimated uncertainties. The present measurements reduce the statistical uncertainties in resonance parameters compared to prior measurements.

  9. Neutron Capture and Transmission Measurements and Resonance Parameter Analysis of Samarium

    SciTech Connect

    G. Leinweber; J.A. Burke; H.D. Knox; N.J. Drindak; D.W. Mesh; W.T. Haines; R.V. Ballad; R.C. Block; R.E. Slovacek; C.J. Werner; M.J. Trbovich; D.P. Barry; T. Sato

    2001-07-16

    The purpose of the present work is to accurately measure the neutron cross sections of samarium. The most significant isotope is {sup 149}Sm, which has a large neutron absorption cross section at thermal energies and is a {sup 235}U fission product with a 1% yield. Its cross sections are thus of concern to reactor neutronics. Neutron capture and transmission measurements were performed by the time-of-flight technique at the Rensselaer Polytechnic institute (RPI) LINAC facility using metallic and liquid Sm samples. The capture measurements were made at the 25 meter flight station with a multiplicity-type capture detector, and the transmission total cross-section measurements were performed at 15- and 25-meter flight stations with {sup 6}Li glass scintillation detectors. Resonance parameters were determined by a combined analysis of six experiments (three capture and three transmission) using the multi-level R-matrix Bayesian code SAMMY version M2. The significant features of this work are as follows. Dilute samples of samarium nitrate in deuterated water (D{sub 2}O) were prepared to measure the strong resonances at 0.1 and 8 eV without saturation. Disk-shaped spectroscopic quartz cells were obtained with parallel inner surfaces to provide a uniform thickness of solution. The diluent feature of the SAMMY program was used to analyze these data. The SAMMY program also includes multiple scattering corrections to capture yield data and resolution functions specific to the RPI facility. Resonance parameters for all stable isotopes of samarium were deduced for all resonances up to 30 eV. Thermal capture cross-section and capture resonance integral calculations were made using the resultant resonance parameters and were compared to results obtained using resonance parameters from ENDF/B-VI updated through release 3. Extending the definition of the capture resonance integral to include the strong 0.1 eV resonance in {sup 149}Sm, present measurements agree within estimated uncertainties with EnDF/B-VI release 3. The thermal capture cross-section was calculated from the present measurements of the resonance parameters and also agrees with ENDF within estimated uncertainties. The present measurements reduce the statistical uncertainties in resonance parameters compared to prior measurements.

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

    NASA Astrophysics Data System (ADS)

    Niedra, Janis M.; Overton, Eric

    1991-11-01

    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.

  11. Radiation absorbed dose calculations for samarium-153-EDTMP localized in bone

    SciTech Connect

    Heggie, J.C. )

    1991-05-01

    Calculations have been undertaken to estimate the likely radiation dose received by patients undergoing treatment with samarium-153-EDTMP. Previously known bone structure parameters have been employed to partition correctly the energy absorbed in the bone matrix between red bone marrow, yellow marrow, and various types of mineral bone. Both uniform surface and volume distribution of the radioactivity are considered. The key findings of the calculations can be stated in terms of the MIRD 'S-factors' for red bone marrow and the endosteal layer of cells on bone surfaces. In particular, the S-factor for red bone marrow is either 0.0276 mGy/MBq.h or 0.0077 mGy/MBq.h for surface and volume distributed radioactivity, respectively. For the endosteal layer of thickness (10 microns) on bone surfaces, the corresponding values are 0.0723 mGy/MBq.h and 0.0213 mGy/MBq.h, respectively.

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

    NASA Technical Reports Server (NTRS)

    Niedra, Janis M.; Overton, Eric

    1991-01-01

    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.

  13. One-step chemical synthesis of samarium telluride thin films and their supercapacitive properties

    NASA Astrophysics Data System (ADS)

    Kumbhar, V. S.; Lokhande, A. C.; Gaikwad, N. S.; Lokhande, C. D.

    2016-02-01

    The letter reports synthesis of samarium telluride (Sm2Te3) thin films through a one-step chemical route. The formation of Sm2Te3 is confirmed by X-ray diffraction and X-ray photoelectron spectroscopy studies. The surface morphological study is carried out using field emission scanning electron microscopy and contact angle measurement techniques. The film shows barley-like microstructure with an average length of barley of about 5 μm and diameter of about 300 nm. The Sm2Te3 film surface exhibits lyophilic nature with contact angle of 21.3° for propylene carbonate electrolyte. Cyclic voltammetry results revealed specific capacitance of 207 F g-1 with power density of 14.18 kW kg-1 in LiClO4-propylene carbonate electrolyte.

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

    PubMed Central

    Zuo, Wenli

    2013-01-01

    A new ethylenediaminetetraacetic acid- (EDTA-) mediated hydrothermal route to prepare chrysanthemum-shaped samarium orthovanadate (SmVO4) nanocrystals with decavanadate (K6V10O28·9H2O) 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. PMID:24068882

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

    NASA Astrophysics Data System (ADS)

    Golmojdeh, Hosein; Zanjanchi, Mohamad Ali

    2014-02-01

    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.

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

    PubMed

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

    2014-07-01

    Hollow core/shell hematite microspheres with diameter of ca. 1-2 μm 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

  17. Phase I. Lanthanum-based Start Materials for Hydride Batteries

    SciTech Connect

    Gschneidner, K. A.; Schmidt, F. A.; Frerichs, A. E.; Ament, K. A.

    2013-08-20

    The purpose of Phase I of this work is to focus on developing a La-based start material for making nickel-metal (lanthanum)-hydride batteries based on our carbothermic-silicon process. The goal is to develop a protocol for the manufacture of (La1-xRx)(Ni1-yMy)(Siz), where R is a rare earth metal and M is a non-rare earth metal, to be utilized as the negative electrode in nickel-metal hydride (NiMH) rechargeable batteries.

  18. Simulations of a monolithic lanthanum bromide gamma-ray detector

    NASA Astrophysics Data System (ADS)

    Ertley, Camden; Bancroft, Christopher; Bloser, Peter; Connor, Taylor; Legere, Jason; McConnell, Mark; Ryan, James

    2010-08-01

    We have been working on the development of a detector design for a large area coded aperture imaging system operating in the 10-600 keV energy range. The detector design is based on an array of Lanthanum Bromide (LaBr3) scintillators, each directly coupled to a Hamamatsu 64-channel multi-anode photomultiplier tube (MAPMT). This paper focuses on the development of the GEANT4-based simulations as an aid in the optimization of the detector design. The simulations have been validated by comparisons with various laboratory data sets. We will summarize the current status and latest findings from this study.

  19. Cerium-activated lanthanum beryllate as a gamma detector material

    SciTech Connect

    Czirr, J.B.; Berrondo, M.

    1994-12-31

    The authors have tested a single crystal of Ce-activated lanthanum beryllate BEL(Ce) as a potential gamma detector material. The density (6.1 g.cm{sup {minus}3}) and decay time (50 ns) are competitive with other recently developed materials. The scintillation efficiency is 57 to 95% that of BGO. For an excitation wavelength of 340 nm, the emission spectra is a broad peak centered at 450 mn. The H{sub 2} annealed sample is transparent for wavelengths greater than 400 mn. They are continuing a program to improve the scintillation efficiency by varying the crystal growth conditions.

  20. METHOD OF SEPARATING PLUTONIUM FROM LANTHANUM FLUORIDE CARRIER

    DOEpatents

    Watt, G.W.; Goeckermann, R.H.

    1958-06-10

    An improvement in oxidation-reduction type methods of separating plutoniunn from elements associated with it in a neutron-irradiated uranium solution is described. The method relates to the separating of plutonium from lanthanum ions in an aqueous 0.5 to 2.5 N nitric acid solution by 'treating the solution, at room temperature, with ammonium sulfite in an amount sufficient to reduce the hexavalent plutonium present to a lower valence state, and then treating the solution with H/sub 2/O/sub 2/ thereby forming a tetravalent plutonium peroxide precipitate.

  1. 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

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

    2013-01-01

    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

  2. Studies on effective atomic numbers, electron densities from mass attenuation coefficients near the K edge in some samarium compounds.

    PubMed

    Akman, F; Durak, R; Turhan, M F; Kaçal, M R

    2015-07-01

    The effective atomic numbers and electron densities of some samarium compounds were determined using the experimental total mass attenuation coefficient values near the K edge in the X-ray energy range from 36.847 up to 57.142 keV. The measurements, in the region from 36.847 to 57.142 keV, were done in a transmission geometry utilizing the Kα2, Kα1, Kβ1 and Kβ2 X-rays from different secondary source targets excited by the 59.54 keV gamma-photons from an Am-241 annular source. This paper presents the first measurement of the effective atomic numbers and electron densities for some samarium compounds near the K edge. The results of the study showed that the measured values were in good agreement with the theoretically calculated ones. PMID:25880612

  3. Sparkle/AM1 Parameters for the Modeling of Samarium(III) and Promethium(III) Complexes.

    PubMed

    Freire, Ricardo O; da Costa, Nivan B; Rocha, Gerd B; Simas, Alfredo M

    2006-01-01

    The Sparkle/AM1 model is extended to samarium(III) and promethium(III) complexes. A set of 15 structures of high crystallographic quality (R factor < 0.05 Å), with ligands chosen to be representative of all samarium complexes in the Cambridge Crystallographic Database 2004, CSD, with nitrogen or oxygen directly bonded to the samarium ion, was used as a training set. In the validation procedure, we used a set of 42 other complexes, also of high crystallographic quality. The results show that this parametrization for the Sm(III) ion is similar in accuracy to the previous parametrizations for Eu(III), Gd(III), and Tb(III). On the other hand, promethium is an artificial radioactive element with no stable isotope. So far, there are no promethium complex crystallographic structures in CSD. To circumvent this, we confirmed our previous result that RHF/STO-3G/ECP, with the MWB effective core potential (ECP), appears to be the most efficient ab initio model chemistry in terms of coordination polyhedron crystallographic geometry predictions from isolated lanthanide complex ion calculations. We thus generated a set of 15 RHF/STO-3G/ECP promethium complex structures with ligands chosen to be representative of complexes available in the CSD for all other trivalent lanthanide cations, with nitrogen or oxygen directly bonded to the lanthanide ion. For the 42 samarium(III) complexes and 15 promethium(III) complexes considered, the Sparkle/AM1 unsigned mean error, for all interatomic distances between the Ln(III) ion and the ligand atoms of the first sphere of coordination, is 0.07 and 0.06 Å, respectively, a level of accuracy comparable to present day ab initio/ECP geometries, while being hundreds of times faster. PMID:26626380

  4. Computational removal of lanthanum-cerium bromide self-activity

    NASA Astrophysics Data System (ADS)

    Yuan, Ding; Guss, Paul; Mukhopadhyay, Sanjoy

    2011-07-01

    It has been reported that detectors made of lanthanum-cerium halides, such as LaBr3(Ce) and CeBr3 have superior energy resolution for gamma-radiation detection compared to that offered by conventional sodium iodide [NaI(T1)] detectors. However, it has also been observed that the lanthanum-cerium halides contain certain amount of self-activity caused by the radioactive isotope 138La. Additionally, LaBr3(Ce) and CeBr3 crystals have also been reported to be affected by ?-contamination in the low-energy and ?-contamination in the high-energy regions. This paper presents a computational approach to reduce self-activity and contamination for LaBr3(Ce) and CeBr3 detectors using a third reference NaI(T1) detector. This procedure can be implemented as an automatic self-calibration module for gamma-radiation detectors made of LaBr3(Ce) and/or CeBr3 crystals.

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

    SciTech Connect

    Menaka; Patra, Rajkumar; Ghosh, Santanu; Ganguli, Ashok K.

    2012-10-15

    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.

  6. Lanthanum-hexaboride carbon composition for use in corrosive hydrogen-fluorine environments

    DOEpatents

    Holcombe, C.E. Jr.; Kovach, L.; Taylor, A.J.

    1980-01-22

    The present invention relates to a structural composition useful in corrosive hydrogen-fluorine environments at temperatures in excess of 1400/sup 0/K. The composition is formed of a isostatically pressed and sintered or a hot-pressed mixture of lanthanum hexaboride particles and about 10 to 30 vol% carbon. The lanthanum-hexaboride reacts with the high-temperature fluorine-containing gases to form an adherent layer of corrosion-inhibiting lanthanum trifluoride on exposed surfaces of the composition. The carbon in the composite significantly strengthens the composite, enhances thermal shock resistance, and significantly facilitates the machining of the composition.

  7. Lanthanum-hexaboride carbon composition for use in corrosive hydrogen-fluorine environments

    DOEpatents

    Holcombe, Cressie E.; Kovach, Louis; Taylor, Albert J.

    1981-01-01

    The present invention relates to a structural composition useful in corrosive hydrogen-fluorine environments at temperatures in excess of 1400.degree. K. The composition is formed of a isostatically pressed and sintered or a hot-pressed mixture of lanthanum hexaboride particles and about 10-30 vol. % carbon. The lanthanum-hexaboride reacts with the high-temperature fluorine-containing bases to form an adherent layer of corrosion-inhibiting lanthanum trifluoride on exposed surfaces of the composition. The carbon in the composite significantly strengthens the composite, enhances thermal shock resistance, and significantly facilitates the machining of the composition.

  8. Strontium-doped samarium manganite as cathode materials for oxygen reduction reaction in solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Li, W.; Xiong, C. Y.; Jia, L. C.; Pu, J.; Chi, B.; Chen, X.; Schwank, J. W.; Li, J.

    2015-06-01

    SmxSr1-xMnO3 with x = 0.3, 0.5 and 0.8, denoted as SSM37, SSM55 and SSM82, respectively, have been prepared via a sol-gel route as materials for cathodes in solid oxide fuel cells. Their activities in the oxygen reduction reaction (ORR) have been evaluated in comparison with the state-of-the-art cathode material La0.8Sr0.2MnO3 (LSM82) by electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS) and thermogravimetry (TG). Among all the prepared cathodes, the SSM55 exhibits the lowest values, while the LSM82 exhibits the highest polarization resistance, at open circuit voltage (OCV) and temperatures from 650 to 800 °C. This result indicates that the prepared SmxSr1-xMnO3 is a promising replacement for LSM82 as cathode material for SOFCs, and the SSM55 represents the optimal concentration in SmxSr1-xMnO3 series. The remarkably high ORR activity of the SSM55 is ascribed to its high surface Mn4+/Mn3+ and Oad/Olattice ratios and fast surface oxygen exchange kinetics.

  9. Airplane dopes and doping

    NASA Technical Reports Server (NTRS)

    Smith, W H

    1919-01-01

    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.

  10. Cellulose-lanthanum hydroxide nanocomposite as a selective marker for detection of toxic copper

    NASA Astrophysics Data System (ADS)

    Marwani, Hadi M.; Lodhi, Mazhar Ullah; Khan, Sher Bahadar; Asiri, Abdullah M.

    2014-09-01

    In this current report, a simple, reliable, and rapid method based on modifying the cellulose surface by doping it with different percentages of lanthanum hydroxide (i.e., 1% La(OH)3-cellulose (LC), 5% La(OH)3-cellulose (LC2), and 10% La(OH)3-cellulose (LC3)) was proposed as a selective marker for detection of copper (Cu(II)) in aqueous medium. Surface properties of the newly modified cellulose phases were confirmed by Fourier transform infrared spectroscopy, field emission scanning electron microscope, energy dispersive X-ray spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopic analysis. The effect of pH on the adsorption of modified cellulose phases for Cu(II) was evaluated, and LC3 was found to be the most selective for Cu(II) at pH 6.0. Other parameters, influencing the maximum uptake of Cu(II) on LC3, were also investigated for a deeper mechanistic understanding of the adsorption phenomena. Results showed that the adsorption capacity for Cu(II) was improved by 211% on the LC3 phase as compared to diethylaminoethyl cellulose phase after only 2 h contact time. Adsorption isotherm data established that the adsorption process nature was monolayer with a homogeneous adsorbent surface. Results displayed that the adsorption of Cu(II) onto the LC3 phase obeyed a pseudo-second-order kinetic model. Selectivity studies toward eight metal ions, i.e., Cd(II), Co(II), Cr(III), Cr(VI), Cu(II), Fe(III), Ni(II), and Zn(II), were further performed at the optimized pH value. Based on the selectivity study, it was found that Cu(II) is highly selective toward the LC3 phase. Moreover, the efficiency of the proposed method was supported by implementing it to real environmental water samples with adequate results.

  11. Application of artificial neural network in 3D imaging with lanthanum bromide calorimeter

    NASA Astrophysics Data System (ADS)

    Gostojic, A.; Tatischeff, V.; Kiener, J.; Hamadache, C.; Karkour, N.; Linget, D.; Grave, X.; Gibelin, L.; Travers, B.; Blin, S.; Barrillon, P.

    2015-07-01

    Gamma-ray astronomy in the energy range from 0.1 up to 100 MeV holds many understudied questions connected with e.g. stellar nucleosynthesis, the active Sun, neutron stars and black holes. To access the physics behind, a significant improvement in detection sensitivity is needed compared to previous missions, e.g. CGRO and INTEGRAL. One of the promising concepts for a future gamma-ray mission is an Advanced Compton Telescope. Under the project of creating a prototype of such instrument, we study the perspectives of using a novel inorganic scintillator as a calorimeter part. Modern inorganic crystal or ceramics scintillators are constantly improving on qualities such as energy resolution and radiation hardness, and this makes them a smart choice for a new space-borne telescope. At CSNSM Orsay, we have assembled a detection module from a 5 × 5cm2 area and 1 cm thick, cerium-doped lanthanum (III) bromide (LaBr3:Ce) inorganic scintillator coupled to a 64 channel multi-anode photomultiplier. The readout of the PMT signals is carried out with the ASIC MAROC, used previously for the luminometer of the ATLAS detector (CERN). Characterization, thorough measurements with various radioactive sources, as well as, single photoelectron detection have been done. Furthermore, we made a comparison of measurements with a detailed GEANT4-based simulation which includes tracking of the optical photons. Finally, we have studied the 3D reconstruction of the first interaction point of incident gamma rays, utilizing a neural network algorithm. This spatial position resolution plays a crucial part in the future implementations and, together with the other measured properties, it makes our detector module very interesting for the next generation of space telescopes operating in the MeV range.

  12. Cellulose-lanthanum hydroxide nanocomposite as a selective marker for detection of toxic copper

    PubMed Central

    2014-01-01

    In this current report, a simple, reliable, and rapid method based on modifying the cellulose surface by doping it with different percentages of lanthanum hydroxide (i.e., 1% La(OH)3-cellulose (LC), 5% La(OH)3-cellulose (LC2), and 10% La(OH)3-cellulose (LC3)) was proposed as a selective marker for detection of copper (Cu(II)) in aqueous medium. Surface properties of the newly modified cellulose phases were confirmed by Fourier transform infrared spectroscopy, field emission scanning electron microscope, energy dispersive X-ray spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopic analysis. The effect of pH on the adsorption of modified cellulose phases for Cu(II) was evaluated, and LC3 was found to be the most selective for Cu(II) at pH 6.0. Other parameters, influencing the maximum uptake of Cu(II) on LC3, were also investigated for a deeper mechanistic understanding of the adsorption phenomena. Results showed that the adsorption capacity for Cu(II) was improved by 211% on the LC3 phase as compared to diethylaminoethyl cellulose phase after only 2 h contact time. Adsorption isotherm data established that the adsorption process nature was monolayer with a homogeneous adsorbent surface. Results displayed that the adsorption of Cu(II) onto the LC3 phase obeyed a pseudo-second-order kinetic model. Selectivity studies toward eight metal ions, i.e., Cd(II), Co(II), Cr(III), Cr(VI), Cu(II), Fe(III), Ni(II), and Zn(II), were further performed at the optimized pH value. Based on the selectivity study, it was found that Cu(II) is highly selective toward the LC3 phase. Moreover, the efficiency of the proposed method was supported by implementing it to real environmental water samples with adequate results. PMID:25258599

  13. Optical amplification in disordered electrooptic Tm{sup 3+} and Ho{sup 3+} codoped lanthanum-modified lead zirconate titanate ceramics and study of spectroscopy and communication between cations

    SciTech Connect

    Zhao, Hua; Zhang, Kun; Xu, Long; Sun, Fankui; Zhang, Jingwen; Chen, Xuesheng; Li, Kewen K.

    2014-02-21

    Rare earth doped electro-optic (EO) ceramics of lanthanum-modified lead zirconate titanate (PLZT) are promising in building multifunctional optical devices, by taking advantage of both EO effect and optical activity. In this work, the combination of the measured spectra of absorption and photoluminescence, the fluorescent decay, the calculated Judd-Ofelt parameters, and measured single pass gain in Tm{sup 3+}, Ho{sup 3+} codoped PLZT ceramics have marked them out as promising gain media in building electrically controllable lasers/optical amplifiers and other multifunctional devices. Optical energy storage was also observed in the optical amplification dynamics.

  14. Phase transformation, thermal expansion and electrical conductivity of lanthanum chromite

    SciTech Connect

    Gupta, Sapna; Mahapatra, Manoj K.; Singh, Prabhakar

    2013-09-01

    Graphical abstract: - Highlights: • Orthorhombic and rhombohedral phases co-exist at ≥260 °C and cubic above 1000 °C. • Polymorphic changes with temperature in air and Ar–3%H{sub 2} are observed. • Lattice volume change in Ar–3%H{sub 2} atmosphere corresponds to Cr{sup 4+} → Cr{sup 3+} transition. • Change in valence state of Cr{sup 4+} to Cr{sup 3+} results in lower electrical conductivity. • Experimental evidence is provided for poor densification of LaCrO{sub 3} in air. - Abstract: This paper addresses discrepancies pertaining to structural, thermal and electrical properties of lanthanum chromite. Experimental evidence is provided to support the hypothesis for poor densification in air as well as reduction in electrical conductivity in reducing atmosphere. Sintering condition for the synthesis of LaCrO{sub 3} was optimized to 1450 °C and 10 h. Thermo-analytical (differential scanning calorimetry – DSC) and high temperature X-ray diffraction (HT-XRD) studies show that orthorhombic lanthanum chromite transforms into rhombohedral structure at ∼260 °C and cubic structure above 1000 °C. Co-existence of the structural phases and the variation in each polymorph with temperature in both air and 3%H{sub 2}–Ar atmosphere is reported. Presence and absence of Cr-rich phase at inter-particle neck are observed in oxidizing and reducing atmospheres respectively. The linear thermal expansion co-efficient was calculated to be 10.8 ± 0.2 × 10{sup −6} °C{sup −1} in the temperature range of RT–1400 °C. Electrical conductivity of lanthanum chromite was found to be 0.11 S/cm in air. A decrease in electrical conductivity (0.02 S/cm at 800 °C) of LaCrO{sub 3}, as observed in reducing atmosphere (3%H{sub 2}–Ar), corresponds to lattice volume change as indicated by peak shift in HT-XRD results.

  15. Morphology-controlled nonaqueous synthesis of anisotropic lanthanum hydroxide nanoparticles

    SciTech Connect

    Djerdj, Igor; Garnweitner, Georg; Sheng Su, Dang; Niederberger, Markus

    2007-07-15

    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.

  16. 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

    Harihara Venkataraman, B.; Fujiwara, Takumi; Komatsu, Takayuki

    2009-06-15

    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.

  17. Effect of Adsorbed Nitrogen on the Thermionic Emission from Lanthanum Hexaboride

    NASA Technical Reports Server (NTRS)

    Carter, Arlen F.; Wood, George P.

    1959-01-01

    The emission properties of lanthanum hexaboride in an atmosphere of nitrogen were investigated. The emitter was not poisoned by adsorbed nitrogen. This result should have application to magnetohydrodynamic devices in which electron flow from channel walls is required.

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

    SciTech Connect

    Ding Yuan, Paul Guss, and Sanjoy Mukhopadhyay

    2009-04-01

    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 the gamma spectral measurement and affect the precision of the nuclide identification process. This paper demonstrates a self-correction procedure for self-activity and contamination reduction from spectra collected by lanthanum-cerium halide detectors. It can be implemented as an automatic self-correction module for the future gamma radiation detector made of lanthanum-cerium halide crystals.

  19. 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 ...

  20. Uranyl sensitization of samarium (III) luminescence in a two-dimensional coordination polymer

    SciTech Connect

    Knope, Karah E.; de Lill, Daniel T.; Rowland, Clare E.; Cantos, Paula M.; de Bettencourt-Dias, Ana; Cahill, Christopher L.

    2012-01-02

    Heterometallic carboxyphosphonates UO₂2+/Ln3+ have been prepared from the hydrothermal reaction of uranyl nitrate, lanthanide nitrate (Ln = Sm, Tb, Er, Yb), and phosphonoacetic acid (H₃PPA). Compound 1, (UO₂)₂(PPA)(HPPA)₂Sm(H₂O)·2H₂O (1) adopts a two-dimensional structure in which the UO₂2+ metal ions bind exclusively to the phosphonate moiety, whereas the Ln3+ ions are coordinated by both phosphonate and carboxylate functionalities. Luminescence studies of 1 show very bright visible and near-IR samarium(III)-centered emission upon direct excitation of the uranyl moiety. The Sm3+ emissive state exhibits a double-exponential decay with lifetimes of 67.2 ± 6.5 and 9.0 ± 1.3 μs as measured at 594 nm, after excitation at both 365 and 420 nm. No emission is observed in the region typical of the uranyl cation, indicating that all energy is either transferred to the Sm3+ center or lost to nonradiative processes. Herein we report the synthesis, crystal structure, and luminescent behavior of 1, as well as those of the isostructural terbium, erbium, and ytterbium analogues.

  1. Lunar prospector measurements of the distribution of incompatible elements gadolinium, samarium and thorium

    SciTech Connect

    Elphic, R.C.; Lawrence, D.J.; Feldman, W.C.; Barraclough, B.L.; Maurice, S.; Binder, A.B.; Lucey, P.G.

    1999-04-01

    Lunar Prospector neutron spectrometer (NS) and gamma ray spectrometer (GRS) observations have been used to map out the distribution of incompatible elements on the lunar surface. Specifically, the GRS data provide maps of the distribution of thorium and potassium while the NS data provide information on the distribution of iron and titanium, and the rare earth elements gadolinium and samarium. Using results of analysis of Celementine spectral reflectance (CSR) data, the Fe- and Ti-contributions to the NS data can be removed, leaving primarily rare earth element contributions from Gd and Sm. The Th and K maps correlate with the inferred Gd and Sm maps (r {approximately} 0.93), but there are regions of significant disagreement. One of these is in the KREEP-rich circum-Imbrium ring. No clear explanation has emerged for this disagreement, though Th, K, Gd and Sm have differing degrees of incompatibility. These results clearly are important to discussions of the geochemistry of the Procellarum-Imbrium Th-rich Terrane and the South-Pole-Aitken Terrane.

  2. M-H characteristics and demagnetization resistance of samarium-cobalt permanent magnets to 300 C

    NASA Technical Reports Server (NTRS)

    Niedra, J. M.

    1992-01-01

    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 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. These quasistatic demagnetization data were 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.

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

    SciTech Connect

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

    1995-02-01

    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.

  4. PENTAMETHYLCYCLOPENTADIENYL DERIVATIVES OF THE TRIVALENT LANTHANIDE ELEMENTS (NEODYMIUM, SAMARIUM, AND YTTERBIUM)

    SciTech Connect

    Tilley, T. Don; Andersen, R.A.

    1980-07-01

    The anionic complexes of the type (ML{sub x})(Me{sub 5}C{sub 5}){sub 2}M'Cl{sub 2}, where M is lithium or sodium, L is diethyl ether or N,N,-N{prime},N{prime}-tetramethylethylenediamine, and M{prime} is neodymium, samarium, or ytterbium, have been prepared from the metal trichlorides and the pentamethylcyclopentadienide anion. The neutral species (Me{sub 5}C{sub 5}){sub 2}NdCl(THF), (Me{sub 5}C{sub 5}){sub 2}NdN(SiMe{sub 3}){sub 2}, and (Me{sub 5}C{sub 5}){sub 2}YbCl(THF) have also been prepared. The mono-ring derivatives (Na(OEt{sub 2}){sub 2})((C{sub 5}Me{sub 5})NdCl{sub 3}) and (Me{sub 5}C{sub 5})Nd(N(SiMe{sub 3}){sub 2}){sub 2} are also described.

  5. Near-electrode processes in lanthanum-gallium tantalate crystals

    SciTech Connect

    Buzanov, O. A.; Zabelina, E. V. Kozlova, N. S. Sagalova, T. B.

    2008-09-15

    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.

  6. Nitrogen and deuterium nuclear quadrupole resonance in lanthanum nicotinate dihydrate

    NASA Astrophysics Data System (ADS)

    Davidson, M. M.; Edmonds, D. T.; Mailer, J. P. G.

    1981-01-01

    Using nuclear double quadrupole resonance techniques the nuclear quadrupole resonance (NQR) spectra of the three inequivalent 14N sites and the four water 2D sites have been obtained at 77 K for lanthanum nicotinate dihydrate. The quadrupole coupling constants e2qQ/h in kHz and the anisotropy constant η are for nitrogen 4418 and 0.362, 4222 and 0.335, and 4220 and 0.327. For the deuterons they are 233.73 and 0.080, 177.47 and 0.153 for one water molecule and 219.73 and 0.098, 189.07 and 0.148 for the other. An attempt is made to extract structural data from these NQR results.

  7. Recent advances of lanthanum-based perovskite oxides for catalysis

    DOE PAGESBeta

    Zhu, Huiyuan; Zhang, Pengfei; Dai, Sheng

    2015-09-21

    There is a need to reduce the use of noble metal elements especially in the field of catalysis, where noble metals are ubiquitously applied. To this end, perovskite oxides, an important class of mixed oxide, have been attracting increasing attention for decades as potential replacements. Benefiting from the extraordinary tunability of their compositions and structures, perovskite oxides can be rationally tailored and equipped with targeted physical and chemical properties e.g. redox behavior, oxygen mobility, and ion conductivity for enhanced catalysis. Recently, the development of highly efficient perovskite oxide catalysts has been extensively studied. This review article summarizes the recent developmentmore » of lanthanum-based perovskite oxides as advanced catalysts for both energy conversion applications and traditional heterogeneous reactions.« less

  8. Recent advances of lanthanum-based perovskite oxides for catalysis

    SciTech Connect

    Zhu, Huiyuan; Zhang, Pengfei; Dai, Sheng

    2015-09-21

    There is a need to reduce the use of noble metal elements especially in the field of catalysis, where noble metals are ubiquitously applied. To this end, perovskite oxides, an important class of mixed oxide, have been attracting increasing attention for decades as potential replacements. Benefiting from the extraordinary tunability of their compositions and structures, perovskite oxides can be rationally tailored and equipped with targeted physical and chemical properties e.g. redox behavior, oxygen mobility, and ion conductivity for enhanced catalysis. Recently, the development of highly efficient perovskite oxide catalysts has been extensively studied. This review article summarizes the recent development of lanthanum-based perovskite oxides as advanced catalysts for both energy conversion applications and traditional heterogeneous reactions.

  9. Synthesis and characterization of strontium-lanthanum apatites

    SciTech Connect

    Boughzala, K.; Salem, E. Ben; Chrifa, A. Ben; Gaudin, E.; Bouzouita, K. . E-mail: khaled.bouzouita@ipeim.rnu.tn

    2007-07-03

    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.

  10. Deposition and investigation of lanthanum cerium hexaboride thin films

    NASA Astrophysics Data System (ADS)

    Kuzanyan, A. S.; Harutyunyan, S. R.; Vardanyan, V. O.; Badalyan, G. R.; Petrosyan, V. A.; Kuzanyan, V. S.; Petrosyan, S. I.; Karapetyan, V. E.; Wood, K. S.; Wu, H.-D.; Gulian, A. M.

    2006-09-01

    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 °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 ρ( 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.

  11. Synthesis, structural and optical properties of Sm{sup 3+} and Nd{sup 3+} doped cadmium sulfide nanocrystals

    SciTech Connect

    L, Saravanan; R, Jayavel; A, Pandurangan; Jih-Hsin, Liu; Hsin-Yuan, Miao

    2014-04-01

    Graphical abstract: Samarium (Sm{sup 3+}) and neodymium (Nd{sup 3+}) doped cadmium sulfide nanocrystals have been prepared via precipitation method. The structural and the luminescent properties of the as-synthesised nanocrystals have been discussed. - Highlights: • Cubic phase lanthanide ion doped cadmium sulfide nanocrystals were prepared by co-precipitation method. • HRTEM displays randomly aggregated nanoparticles with well-defined lattice fringes. • Energy gap and optical properties were affected by the different doping ions. • Effect of Sm and Nd ion doping on photo-emission of CdS nanocrystals was clarified. - Abstract: Cubic phase samarium (Sm{sup 3+}) and neodymium (Nd{sup 3+}) doped cadmium sulfide nanocrystals were synthesized through the chemical co-precipitation method. The crystallite size computed with high intense (1 1 1) peak using Scherrer formula was ∼3 nm. Morphology was examined with scanning electron microscopy (SEM). The transmission electron microscopy (TEM) images further established the formation of nanoclusters and EDAX spectra confirms the presence of cadmium, sulphide and rare earth elements in the sample. SAED pattern shows the crystallinity of the synthesized sample. Blue shift in the bandgap energy in the reflectance UV spectra, illustrates size quantization effect and dopant ion incorporation into the host lattice. The effect of doping concentrations of Sm{sup 3+} and Nd{sup 3+} on the luminescence spectra of CdS was studied. The emission spectra revealed that the intensity increased considerably in the presence of dopant ions. The variation in the optical properties and the enhancement in the luminescence were discussed for different doping levels.

  12. [Identification of rat sinus node pacemaker cells by intracellular injection of lanthanum ions].

    PubMed

    Sutiagin, P V; Pylaev, A S

    1983-05-01

    Action potentials of pacemaker cells were recorded on an isolated preparation of rat right atrium. Lanthanum ions were injected via a recording microelectrode. The sinus node area was treated for electron microscopy. The electron-dense clusters of lanthanum ions were identified in pacemaker cell organelles, such as cytoplasmic and mitochondrial matrix, external membrane of mitochondria, and inner surface of cytolemma. Treatment with La3+ produced no significant alterations in cellular morphology. PMID:6189535

  13. Inhibition of cutaneous contact hypersensitivity by calcium transport inhibitors lanthanum and diltiazem.

    PubMed

    Diezel, W; Gruner, S; Diaz, L A; Anhalt, G J

    1989-09-01

    Epidermal Langerhans cells (ELC) are bone marrow-derived immune cells that are important in allergic contact dermatitis. We examined the influence of calcium transport inhibitors, lanthanum and diltiazem hydrochloride, on allergic contact dermatitis induced by 1-chloro-2,4-dinitrobenzene (DNCB) in BALB/c mice. Systemic lanthanum at a dose of 0.08 mg/kg and topical lanthanum (50 microliters of 10% solution) were given 5 d before DNCB sensitization. Systemic diltiazem (30 mg/kg per dy) was given for 3 d during sensitization with DNCB. In all animals, challenge with topical DNCB to the ear skin was performed 5 d after sensitization and ear swelling was measured. Twenty four hours post-DNCB challenge, animals receiving systemic lanthanum demonstrated a 56% decrease in contact hypersensitivity (ear swelling) compared with non-lanthanum-treated animals (0.08 +/- 0.03 mm vs 0.18 mm +/- 0.02 mm, p less than 0.01). Topical lanthanum produced a 58% decrease in contact hypersensitivity (0.20 +/- 0.02 mm vs 0.41 +/- 0.03 mm, p less than 0.01). The DNCB-induced ear swelling also resolved more quickly in animals treated with lanthanum. Systemic diltiazem produced a 67% decrease in ear swelling (0.05 +/- 0.01 mm vs 0.15 +/- 0.02 mm, p less than 0.001). A decrease in epidermal Langerhans cell density of 13 to 14% was produced by systemic lanthanum, detected by both ATPase staining and Ia staining, respectively (p less than 0.05). Approximately 20% of the Langerhans cells were morphologically abnormal, having become "rounded," and lacking normal dendritic processes. From these results, we infer that calcium transport across the cell membrane of ELC may be important in the regulation of their function. Lanthanides and other calcium-channel blockers may be useful pharmacologic agents to probe these phenomena. PMID:2527909

  14. Fabrication and spectral properties of Nd 3+-doped yttrium lanthanum oxide transparent ceramics

    NASA Astrophysics Data System (ADS)

    Hu, Xiaoman; Yang, Qiuhong; Dou, Chuanguo; Xu, Jun; Zhou, Hongxu

    2008-06-01

    Transparent 1 at% Nd3+:Y1.9La0.1O3 ceramics were fabricated with nanopowders prepared by carbonate coprecipitation method. The powder compacts were sintered in H2 atmosphere at 1550 °C for 30 h. The Nd3+:Y1.9La0.1O3 ceramics display uniform grains of about 50 μm and high transparency. The highest transmittance of the ceramics reaches 67%. The strongest absorption peak is in the wavelength of 820 nm with absorption cross section of 2.48 × 10-20 cm2. The absorption is still high at LD wavelength 806 nm with absorption cross section of 1.78 × 10-20 cm2 and broad full width at half maximum (FWHM) of about 6.3 nm. The strongest emission peak was centered at 1078 nm with large stimulated emission cross section of 9.63 × 10-20 cm2 and broad FWHM of about 7.8 nm. The broad absorption and emission bandwidth of Nd3+:Y1.9La0.1O3 transparent ceramics are favorable to achieve the miniaturized LD pumping apparatus and ultrashort modelocked pulse laser output, respectively.

  15. Preparation and laser performance of Nd-doped yttrium lanthanum oxide transparent ceramic

    NASA Astrophysics Data System (ADS)

    Yang, Qiuhong; Lu, Shenzhou; Zhang, Bin; Zhang, Haojia; Zhou, Jun; Yuan, Zhijun; Qi, Yunfeng; Lou, Qihong

    2011-03-01

    1.5 at.% Nd:Y 1.8La 0.2O 3 transparent ceramic was fabricated by a solid-state reaction method and sintered at 1650-1700 °C for 40-50 h under H 2 atmosphere. The spectroscopic properties were investigated at room temperature. The transparent ceramic has excellent spectroscopic properties, with the absorption cross section of 1.50 × 10 -20 cm 2 and broad full width at half maximum (FWHM) of about 8 nm at LD wavelength 806 nm, the emission cross section of 2.03 × 10 -20 cm 2 at 1079 nm, and the decay lifetime of 200 μs. Laser performance was carried out using an uncoated Nd:Y 1.8La 0.2O 3 ceramic plate under laser diode end-pumping without any water cooling device. The room temperature thermal conductivity of this ceramic is 6.20 W/mK. For Nd:Y 1.8La 0.2O 3 ceramic laser, a maximum output power of 62 mW was obtained at 1079 nm under a 808 nm diode pump.

  16. Structure and magnetic interactions in (Sr, Sb)-doped lanthanum manganites

    NASA Astrophysics Data System (ADS)

    Karpinsky, D. V.; Troyanchuk, I. O.; Silibin, M. V.; Gavrilov, S. A.; Bushinky, M. V.; Sikolenko, V.; Frontzek, M.

    2016-05-01

    Ceramic samples La1-2xSr2xMn1-xSbxO3 (x≤0.2) have been studied by X-ray and neutron powder diffraction, magnetization measurements and charge density calculations have also been performed. The compounds are characterized by the rhombohedral structure at room temperature; temperature decrease causes structural transition to the orthorhombic structure. La1-2xSr2xMn1-xSbxO3 ceramics are characterized by homovalent manganese ions and have long range ferromagnetic order which gradually diminishes with the chemical substitution. It is considered that magnetic properties of the compounds are determined by the dominance of ferromagnetic superexchange interactions stabilized in the orbital disordered orthorhombic phase. Significant covalent component of the Mn-O chemical bonds contributes to the long-range ferromagnetic order of the compounds, the covalency of the chemical bonds is assumed to be isotropically distributed over the orthorhombic phase.

  17. Fabrication and XAFS analysis of Yb3+ doped yttrium lanthanum oxide transparent ceramics

    NASA Astrophysics Data System (ADS)

    Jiang, Cen; Yang, Qiuhong; Lu, Qing; Zhang, Haojia

    2013-12-01

    (YbxY0.90-xLa0.10)2O3 (x = 0.01-0.10) transparent ceramics were fabricated and their structural properties were investigated. The XRD showed our samples exhibited single cubic Y2O3 phase. The lattice parameters were refined with the Rietveld method. The compact structure and an average grain size of 40-50 μm were revealed by the microstructure. The local fine structure around Yb ions was investigated by using the XAFS (X-ray absorption fine structure) technique. The results showed that: the local structure around Yb ions in the samples with different concentration of Yb ions was basically similar, and Yb ions replaced Y position to form the solid solution. The Yb ions were trivalent. With the concentration of Yb2O3 increased, the coordination number (N) and first shell Yb-O bond length (R) decreased, and the degree of disorder (σ) increased.

  18. Magnetic transitions and electrical transport in Bi-doped lanthanum strontium manganites

    NASA Astrophysics Data System (ADS)

    Ahmed, A. M.; Mohamed, H. F.; Šoka, Martin

    2014-05-01

    The temperature dependence of the electrical resistivity ρ, thermoelectric power S and the magnetic susceptibility χ of La0.7-xBixSr0.3MnO3 (x = 0.05, 0.10, and 0.15 at. %) manganites were investigated. La0.7-xBixSr0.3MnO3 crystallizes in a single phase rhombohedral structure with parasitic phase inclusions. With increasing Bi concentration, a systematic decrease in the ferromagnetic transition temperature (Tc), the metal-semiconducting transition temperature (Tms1) and also the values of activation energies Eρ and ES from ρ(T) and S(T) were observed. On the other hand, in the high-temperature (T > Tms) paramagnetic semiconductor regime, the adiabatic small polaron hopping model fit well, thereby indicating that polaron hopping might be responsible for the conduction mechanism. In addition, the thermoelectric power data at low temperatures were analyzed by considering both the magnon and the phonon drag concept, while the high-temperature data were confirmed a small polaron hopping conduction mechanism.

  19. Interplay Between Structural, Jahn-Teller, and Magnetic States of Slightly Doped Lanthanum Manganites

    NASA Astrophysics Data System (ADS)

    Golenishchev-Kutuzov, V. A.; Golenishchev-Kutuzov, A. V.; Kalimullin, R. I.; Semennikov, A. V.

    2016-03-01

    By combining the results of elastic moduli, electrical resistivity, and magnetization measurements for La_{1-x} Srx MnO3 (x = 0.125, x = 0.15, and x = 0.175), we have constructed a phase diagram that describes the structural, magnetic, transport properties and the relationships among them as a function of the composition and temperature (140-340 K). The local, intermediate, and cooperative Jahn-Teller distortions of the octahedral structural units MnO6 have been studied. It is common for these distortions to be observed using probes of intermediate structures (domains or super-cells), but they are absent in the averaged crystallographic structure. In the cooperative Jahn-Teller distorted phase, the macroscopic sample length is temperature dependent. We presume that the structural transitions from the cooperative Jahn-Teller phase to the charge ordering phase at low temperatures (150 and 180 K at x = 0.125 and x = 0.15) are due to the increase in the spontaneous magnetization with the conservation of the local deformations of separate octahedra. The agreement between the types of the orbital ordering and the local, intermediate, and Jahn-Teller cooperative distortions of octahedra was established.

  20. Luminescence study on Eu or Tb doped lanthanum-gadolinium pyrosilicate crystal

    NASA Astrophysics Data System (ADS)

    Kurosawa, Shunsuke; Shishido, Toetsu; Sugawara, Takamasa; Nomura, Akiko; Yubuta, Kunio; Pejchal, Jan; Murakami, Rikito; Yokota, Yuui; Shoji, Yasuhiro; Ohashi, Yuji; Kamada, Kei; Yoshikawa, Akira

    2015-03-01

    (Eu0.01, Gd0.90, La0.09)2Si2O7 (Eu:La-GPS) and (Tb0.01, Gd0.90, La0.09)2Si2O7 (Tb:La-GPS) crystals were grown by the floating zone method, and their optical and scintillation properties were investigated. Gd3+-to-Tb3+ or -Eu3+ energy transfer processes were found, and photo-luminescence and radio-luminescence emission spectra showed 5D0-7Fi (i = 1-4) Eu3+ transitions in Eu:La-GPS, and 5D3-7Fi (i = 3-6) and 5D4-7Fi (i = 3-6) transitions in Tb:La-GPS. Using these scintillators, alpha-ray imaging was possible with a CMOS camera. These materials can be used for X-ray detection as well.

  1. Ce doped lanthanum tri-bromide SPET scanner for molecular imaging

    NASA Astrophysics Data System (ADS)

    Pani, R.; Pellegrini, R.; Cinti, M. N.; Bennati, P.; Betti, M.; Vittorini, F.; Mattioli, M.; Trotta, G.; Orsolini Cencelli, V.; Scafè, R.; Navarria, F.; Bollini, D.; Baldazzi, G.; Moschini, G.; de Notaristefani, F.

    2007-02-01

    The availability of LaBr 3:Ce crystals from St. Gobain has started various investigations in the field of medical imaging, in particular in PET, SPECT and Compton camera systems. At present LaBr 3:Ce crystals are available in a continuous shape covering up to 10×10 cm 2 with a thickness of 1 cm, in contrast, serious concerns are arising in pixellated manufacturing. With the aim of verifying the potentials introduced by LaBr 3:Ce for SPET imaging, two small γ cameras based on Anger camera principle have been assembled and imaging performances were compared. Two crystals of LaBr 3:Ce and NaI(Tl) with the same detection area (5×5 cm 2) and thickness of 5 and 1.5 mm, respectively were been integrally assembled with a H8500 Hamamatsu flat panel PMT. Through the thicker crystal, the LaBr 3:Ce camera showed superior imaging and detection performances at 140 keV compared with the NaI(Tl) one, with 0.9 mm FWHM intrinsic spatial resolution, 8% FWHM energy resolution and 80% intrinsic detection efficiency.

  2. Lanthanum Molybdate Nanoparticles from the Bradley Reaction: Factors Influencing Their Composition, Structure, and Functional Characteristics as Potential Matrixes for Luminescent Phosphors

    PubMed Central

    2014-01-01

    Interaction of lanthanum isopropoxide with molybdenum(VI) alkoxides in La/Mo ratios varying from 3:1 to 1:1 in acetophenon or allyl alcohol as solvents offers nanosized poorly crystalline products of complex composition, where the precipitation of Mo-rich ones is followed by the formation of La-rich ones with conservation of the reaction stoichiometry in total. Thermal treatment of the precipitates at temperatures over 700 °C leads to the formation of stoichiometric phases of the α- and β-La2Mo2O9 compositions. Introduction of smaller Re3+ cations such as Sm3+ by doping favors stabilization of the La2–xRExMo2O9 phase with improved crystallinity even after lower-temperature thermal treatment. The doping is successful only when the Re3+ (Sm3+, Eu3+, and Tb3+) is introduced as an alkoxide: application of Re3+(acac)3 as Re3+ sources leads to materials free from Re3+. The produced samples were characterized by XPD, TGA, SEM, and TEM studies as well as the luminescent properties for the Sm3+-doped phases. PMID:24392745

  3. Toxicity of Two Different Sized Lanthanum Oxides in Cultured Cells and Sprague-Dawley Rats

    PubMed Central

    2015-01-01

    In recent years, the use of both nano- and micro-sized lanthanum has been increasing in the production of optical glasses, batteries, alloys, etc. However, a hazard assessment has not been performed to determine the degree of toxicity of lanthanum. Therefore, the purpose of this study was to identify the toxicity of both nano- and micro-sized lanthanum oxide in cultured cells and rats. After identifying the size and the morphology of lanthanum oxides, the toxicity of two different sized lanthanum oxides was compared in cultured RAW264.7 cells and A549 cells. The toxicity of the lanthanum oxides was also analyzed using rats. The half maximal inhibitory concentrations of micro-La2O3 in the RAW264.7 cells, with and without sonication, were 17.3 and 12.7 times higher than those of nano-La2O3, respectively. Similar to the RAW264.7 cells, the toxicity of nano-La2O3 was stronger than that of micro-La2O3 in the A549 cells. We found that nano-La2O3 was absorbed in the lungs more and was eliminated more slowly than micro-La2O3. At a dosage that did not affect the body weight, numbers of leukocytes, and concentrations of lactate dehydrogenase and albumin in the bronchoalveolar lavage (BAL) fluids, the weight of the lungs increased. Inflammatory effects on BAL decreased over time, but lung weight increased and the proteinosis of the lung became severe over time. The effects of particle size on the toxicity of lanthanum oxides in rats were less than in the cultured cells. In conclusion, smaller lanthanum oxides were more toxic in the cultured cells, and sonication decreased their size and increased their toxicity. The smaller-sized lanthanum was absorbed more into the lungs and caused more toxicity in the lungs. The histopathological symptoms caused by lanthanum oxide in the lungs did not go away and continued to worsen until 13 weeks after the initial exposure. PMID:26191385

  4. Samarium(II) induced asymmetric reductive cyclizations: The total synthesis of (-)-C{sub 10} desmethyl arteannuin B

    SciTech Connect

    Schwaebe, M.K.; Little, R.D.

    1995-12-31

    Arteannuin B is a member of the qinghaosu family, a novel class of sesquiterpenes that exhibit powerful antimalarial activity even against chloroquinine resistant strains. It is readily convertible to qinghaosu in several high yielding steps and has potential antitumor activity. Several approaches to the construction of the cis-decalin backbone have involved the use of electrochemical and metal promoted reductions as well as alkylations. We report a short convenient total synthesis of (-)-C{sub 10} desmethyl arteannuin B utilizing an asymmetric reductive cyclization with samarium (II) iodide which selectively forms the cis-decalin ring structure while setting the trans relationship between the subunits of the {gamma}-hydroxy ester.

  5. High specific activity (samarium-153) EDTA for imaging of experimental tumor models

    SciTech Connect

    Tse, J.W.; Wiebe, L.I.; Noujaim, A.A.

    1989-02-01

    Enriched samarium oxide (98.2% /sup 152/Sm/sub 2/O/sub 3/) was irradiated in low neutron flux and high neutron flux reactors to produce /sup 153/Sm with specific activities of 14.3 GBq and 22.1 TBq mmol-1 Sm, respectively, at the time of use. Formulation of /sup 153/Sm as (/sup 153/Sm)EDTA, with a 1:10 molar ratio of SM:EDTA, provided a stable radiotracer in vitro and in vivo. High specific activity (/sup 153/Sm)EDTA showed superior uptake in cell culture (20.8 +/- 0.9% vs. 5.5 +/- 0.1% for 6 and 600 pmol Sm per 10(6) cells, respectively) and better tumor index values (51 vs. 37 at 10.9 nmol and 1.09 mumol Sm kg-1, respectively) in the BDF1 mouse/Lewis lung tumor model. High specific activity (153Sm)EDTA scintigrams of Copenhagen x Fisher rats bearing transplanted Dunning R3327 tumors clearly delineated the tumors within 6 hr, with moderate liver and bone uptake and low soft-tissue background. The injected radiotracer underwent rapid central compartment clearance and whole-body elimination. The absence of observed adverse histopathological toxicity combines with high image quality within 6 hr, to support the clinical tumor-imaging potential of this agent. Comparative studies with (/sup 67/Ga)citrate at molar-equivalent doses indicated that high specific activity (/sup 153/Sm)EDTA was a superior radiotracer in these in vitro and in vivo models.

  6. M-H characteristics and demagnetization resistance of samarium-cobalt permanent magnets to 300 C

    NASA Astrophysics Data System (ADS)

    Niedra, Janis M.

    1992-08-01

    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.

  7. M-H characteristics and demagnetization resistance of samarium-cobalt permanent magnets to 300 C

    NASA Technical Reports Server (NTRS)

    Niedra, Janis M.

    1992-01-01

    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.

  8. Effects of low-dose capecitabine on Samarium-153-EDTMP therapy for painful bone metastases

    PubMed Central

    Barai, Sukanta; Gambhir, Sanjay; Rastogi, Neeraj; Mandani, Anil; Siddegowda, Murthy

    2015-01-01

    Introduction: Samarium-153 (Sm-153)-EDTMP is routinely used for pain palliation in skeletal metastasis, however most patients report partial response. Many strategies have been contemplated to make radiation therapy for pain more effective, one of them being the use of radiosensitizers. Capecitabine is a chemotherapeutic drug and is routinely combined with external beam radiation to make the target more radio-sensitive. Aim of the study was to evaluate whether combining capecitabine in radiosensitizing dose with Sm-153-EDTMP produces superior analgesia compared to Sm alone. Materials and Methods: Forty-four patients with skeletal metastases from various primaries were randomized into two groups: The study group received 1 mCi/kg Sm-153-EDTMP plus capecitabine (1,650 mg/m2) orally for 8 days (equivalent to four t½ of 153Sm-EDTMP) and the control arm received 1 mCi/kg Sm-153-EDTMP plus placebo for the 8 days. After treatment, the patients were followed up for 12 weeks to evaluate the degree and duration of pain palliation and hematologic toxicity. Results: All 44 patients reported different degrees of pain relief with none reporting complete pain relief for the entire duration of 12 weeks posttherapy observation period. However the level of pain relief obtained in study arm was significantly better than the control arm with mean posttherapy pain score being 1.29 ± 1.05 and 3.59 ± 2.77 respectively with P of 0.001. Transient and mild hematologic toxicity, as determined by World Health Organization criteria, was apparent in both arms without significant differences. Conclusion: The addition of a low-dose of capecitabine significantly enhances the analgesic effect of Sm-153 without any additional side effects. PMID:25829727

  9. Electric properties and phase transition behavior in lead lanthanum zirconate stannate titanate ceramics with low zirconate content

    NASA Astrophysics Data System (ADS)

    Zeng, Tao; Lou, Qi-Wei; Chen, Xue-Feng; Zhang, Hong-Ling; Dong, Xian-Lin; Wang, Gen-Shui

    2015-11-01

    The phase transitions, dielectric properties, and polarization versus electric field (P-E) hysteresis loops of Pb0.97La0.02(Zr0.42Sn0.58-xTix)O3 (0.13≤ x ≤0.18) (PLZST) bulk ceramics were systematically investigated. This study exhibited a sequence of phase transitions by analyzing the change of the P-E hysteresis loops with increasing temperature. The antiferroelectric (AFE) to ferroelectric (FE) phase boundary of PLZST with the Zr content of 0.42 was found to locate at the Ti content between 0.14 and 0.15. This work is aimed to improve the ternary phase diagram of lanthanum-doped PZST with the Zr content of 0.42 and will be a good reference for seeking high energy storage density in the PLZST system with low-Zr content. Project supported by the National Natural Science Foundation of China (Grant Nos. 51202273, 11204304, and 11304334) and the Science and Technology Commission of Shanghai Municipality, China (Grant No. 14DZ2261000).

  10. Transition-metal-doped chalcogenide glasses for broadband near-infrared sources

    NASA Astrophysics Data System (ADS)

    Hughes, Mark A.; Aronson, Jonathan E.; Brocklesby, William S.; Shepherd, David P.; Hewak, Daniel W.; Curry, Richard J.

    2004-12-01

    In this paper we report the spectroscopic data for samples of 0.031% iron, 0.017% nickel, 0.01% chromium and 0.017% cobalt (molar) doped gallium lanthanum sulphide (GLS) glass. Photoluminescence (PL) with a full width half maximum (FWHM) of around 500 nm and peaking between 1120 nm and 1460 nm is observed when excited using wavelengths of 850 nm and 1064 nm. The emission lifetime for nickel-doped GLS at 300 K was measured to be 40 μs. Photoluminescence excitation (PLE) peaks for chromium-doped GLS at 700 nm and 1020 nm have been observed. By comparisons of our spectroscopic data to that of transition metals doped into other hosts we determine the oxidation states of the transition metal ions and propose transitions for the observed spectroscopic peaks.

  11. Potentiometric measurement of polymer-membrane electrodes based on lanthanum

    SciTech Connect

    Saefurohman, Asep Buchari, Noviandri, Indra; Syoni

    2014-03-24

    Quantitative analysis of rare earth elements which are considered as the standard method that has a high accuracy, and detection limits achieved by the order of ppm is inductively coupled plasma atomic emission spectroscopy (ICPAES). But these tools are expensive and valuable analysis of the high cost of implementation. In this study be made and characterized selective electrode for the determination of rare earth ions is potentiometric. Membrane manufacturing techniques studied is based on immersion (liquid impregnated membrane) in PTFE 0.5 pore size. As ionophores to be used tri butyl phosphate (TBP) and bis(2-etylhexyl) hydrogen phosphate. There is no report previously that TBP used as ionophore in polymeric membrane based lanthanum. Some parameters that affect the performance of membrane electrode such as membrane composition, membrane thickness, and types of membrane materials studied in this research. Manufacturing of Ion Selective Electrodes (ISE) Lanthanum (La) by means of impregnation La membrane in TBP in kerosene solution has been done and showed performance for ISE-La. FTIR spectrum results for PTFE 0.5 pore size which impregnated in TBP and PTFE blank showed difference of spectra in the top 1257 cm{sup −1}, 1031 cm{sup −1} and 794.7 cm{sup −1} for P=O stretching and stretching POC from group −OP =O. The result showed shift wave number for P =O stretching of the cluster (−OP=O) in PTFE-TBP mixture that is at the peak of 1230 cm{sup −1} indicated that no interaction bond between hydroxyl group of molecules with molecular clusters fosforil of TBP or R{sub 3}P = O. The membrane had stable responses in pH range between 1 and 9. Good responses were obtained using 10{sup −3} M La(III) internal solution, which produced relatively high potential. ISE-La showed relatively good performances. The electrode had a response time of 29±4.5 second and could be use for 50 days. The linear range was between 10{sup −5} and 10{sup −1} M.

  12. Titania-lanthanum phosphate photoactive and hydrophobic new generation catalyst

    SciTech Connect

    Jyothi, Chembolli K.; Jaimy, Kanakkanmavudi B.; Ghosh, Swapankumar; Sankar, Sasidharan; Smitha, V.S.; Warrier, K.G.K.

    2011-07-15

    Titania-lanthanum phosphate nanocomposites with multifunctional properties have been synthesized by aqueous sol-gel method. The precursor sols with varying TiO{sub 2}:LaPO{sub 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{sub 2} in TiO{sub 2}-LaPO{sub 4} composite precursors was found to be stable even on annealing at 800 deg. C. The glass substrates, coated with TL1 (TiO{sub 2}-LaPO{sub 4} composition with 1 mol% LaPO{sub 4}) and TL50 (composite precursor containing TiO{sub 2} and LaPO{sub 4} with molar ratio 1:1) sols and annealed at 400 deg. C, produced contact angles of 74 deg. and 92 deg., respectively, though it is only 62 deg. for pure TiO{sub 2} coating. The glass substrates, coated with TL50 sol, produced surfaces with relatively high roughness and uneven morphology. The TL1 material, annealed at 800 deg. C, has shown the highest UV photoactivity with an apparent rate constant, k{sub app}=24x10{sup -3} min{sup -1}, which is over five times higher than that observed with standard Hombikat UV 100 (k{sub app}=4x10{sup -3} min{sup -1}). The photoactivity combined with a moderate contact angle (85.3 deg.) shows that this material has a promise as an efficient self-cleaning precursor. - Graphical abstract: Multifunctional TiO{sub 2}-LaPO{sub 4} composite stabilizes anatase phase with enhanced photocatalytic activity, and moderately higher hydrophobicity is a promising material for self-cleaning application. Highlights: > Titania-lanthanum phosphate nanocomposites were synthesized by aqueous sol-gel method. > Transparent, hydrophobic, photoactive coatings were developed on glass substrates. > The glass substrates, coated with TL1 annealed at 400 deg. C, produced a contact angle of 74 deg. > The TL1 material at 800 deg. C has shown the highest UV photoactivity (k{sub app}=24x10{sup -3} min{sup -1}). > Photoactivity and moderate contact angle show that this is an efficient self-cleaning precursor.

  13. UV light sensing properties of Sm doped vertically aligned ZnO nanorod arrays

    NASA Astrophysics Data System (ADS)

    Kumar, D. Ranjith; Ranjith, K. S.; Rajendrakumar, R. T.

    2015-06-01

    Samarium doped ZnO nanorods were grown on silicon substrate by using vapor phase transport method (VPT) with the growth temperature of 950°C. The synthesized nanorods were characterized by XRD, field emission scanning electron microscopy, Raman spectra, and photocurrent measurements. The XRD result revealed that Sm was successfully doped into lattice plane of hexagonal ZnO nanorods. The FESEM result confirms the pure ZnO has nanorod like morphology with an average diameter and length of 130nm and 10µm respectively. The above observation is supported by the Micro-Raman spectroscopy result. The photocurrent in the visible region has been significantly enhanced due to deposition of Sm on the surface of the ZnO nanorods. Sm acts as a visible sensitizer because of its lower band gap compared to ZnO.

  14. Preparation and photoluminescence properties of Sm3+-doped ZrO2 nanotube arrays

    NASA Astrophysics Data System (ADS)

    Fu, Ning; Wang, Xixin; Ma, Yuanhui; Wang, Mingli; Li, Jiaxin; Zhao, Jianling

    2016-04-01

    Zr-Sm (3 at.% Sm) alloy was prepared through a powder metallurgical method. Sm3+-doped ZrO2 nanotube arrays have been achieved directly by anodizing the Zr-Sm alloy. The effects of electrolyte and annealing temperature on the morphologies and structures of the nanotube arrays were studied. The photoluminescence properties of Sm3+-doped ZrO2 nanotube arrays prepared in aqueous solution and formamide  +  glycerol solution were studied in detail as well. Results show that tetragonal ZrO2 promoted the photoluminescence efficiency of this system. Under excitation at 407 nm, the sample prepared in aqueous solution annealed at 600 °C displayed the strongest emission peak at 571 nm, corresponding to the 4G5/2  →  6H5/2 samarium transition.

  15. Observation of the highly excited states of Lanthanum

    SciTech Connect

    Xue, P.; Xu, X. Y.; Huang, W.; Xu, C. B.; Zhao, R. C.; Xie, X. P.

    1997-01-15

    The highly excited states of Lanthanum are studied by means of laser resonance ionization time-of-flight spectrometer. Based on the two-step laser resonance excitation with intermediate state 5d{sup 2}({sup 3}F)6p {sup 2}D{sub 5/2}{sup 0}, three new Rydberg state (RS) series (5d{sup 2}(a{sup 3}F{sub 2})ns, 5d{sup 2}(a{sup 3}F{sub 3})nd and 5d{sup 2}(a{sup 1}D{sub 2})ns) and a number of autoionizing states (AIS) are obtained. Theoretical calculation leads the quantum defects of ns and nd series to the value {delta}s=4.35 and {delta}{sub d}=2.80 respectively, which are very close to the experimental results. The Rydberg state series 5d{sup 2}(a{sup 3}F{sub 2})ns gives the first ionization limit to be 44979.8{+-}0.3 cm{sup -1}, which is an order more accurate than ever.

  16. Removing Phosphorus from Aqueous Solutions Using Lanthanum Modified Pine Needles

    PubMed Central

    Wang, Xianze; Liu, Zhongmou; Liu, Jiancong; Huo, Mingxin; Huo, Hongliang; Yang, Wu

    2015-01-01

    The renewable pine needles was used as an adsorbent to remove phosphorus from aqueous solutions. Using batch experiments, pine needles pretreated with alkali-isopropanol (AI) failed to effectively remove phosphorus, while pine needles modified with lanthanum hydroxide (LH) showed relatively high removal efficiency. LH pine needles were effective at a wide pH ranges, with the highest removal efficiency reaching approximately 85% at a pH of 3. The removal efficiency was kept above 65% using 10 mg/L phosphorus solutions at desired pH values. There was no apparent significant competitive behavior between co-existing anions of sulfate, nitrate, and chloride (SO42-, NO3- and Cl-); however, CO32- exhibited increased interfering behavior as concentrations increased. An intraparticle diffusion model showed that the adsorption process occurred in three phases, suggesting that a boundary layer adsorption phenomena slightly affected the adsorption process, and that intraparticle diffusion was dominant. The adsorption process was thermodynamically unfavorable and non-spontaneous; temperature increases improved phosphorus removal. Total organic carbon (TOC) assays indicated that chemical modification reduced the release of soluble organic compounds from 135.6 mg/L to 7.76 mg/L. This new information about adsorption performances provides valuable information, and can inform future technological applications designed to remove phosphorus from aqueous solutions. PMID:26630014

  17. Performance of Lanthanum Strontium Manganite Electrodes at High Pressure

    SciTech Connect

    Thomsen, Edwin C.; Coffey, Greg W.; Pederson, Larry R.; Marina, Olga A.

    2009-06-15

    The high-pressure performance of lanthanum strontium manganite (LSM), LSM-zirconia, and LSM/ceria composite electrodes was studied by impedance spectroscopy and dc methods. Electrode resistances decreased in proportion to P(O2)1/2 for the LSM electrode in both cathodic and anodic directions to at least 100 atm, a decrease that was attributed to dissociative oxygen adsorption, surface diffusion, and related phenomena. For the LSM-20/zirconia composite electrode, resistances decreased in proportion to P(O2)1/4 across the entire pressure range considered. Two principal features appeared in the impedance spectra, one that showed a P(O2)1/4 dependence attributed to charge transfer reactions, and one that was nearly pressure-independent, possibly due to transport in the zirconia portion of the composite. For the LSM-20/ceria composite electrode, resistances decreased as P(O2)0.3-0.4 at high pressure, depending on temperature. Two features appeared in the impedance spectra: one at low to intermediate frequency having a P(O2)1/2 dependence and one at high frequency having a P(O2)1/4 dependence. These features are attributed to dissociative oxygen adsorption and to charge transfer reactions, respectively. Results suggest that cathodic losses can be substantially lowered by operation of solid oxide fuel cells at greater than ambient pressure.

  18. Electrostriction in lead lanthanum zirconate-titanate ceramics

    SciTech Connect

    Meng, Z.Y.; Cross, L.E.; Kumar, U.

    1985-08-01

    Electric polarizations and elastic strain were measured simultaneously for several lead lanthanum zirconate-titanate (PLZT) compositions cycled around their high-field electric hysteresis loops. Using the accepted symbolism for compositions, where the first number gives the mole percent of La/sub 2/O/sub 3/ and the second two numbers give the ratio of PbZrO/sub 3/ to PbTiO/sub 3/ in the composition, data were taken for (7, 7.5, 8, 8.8, 9.5)/65/35 and 8/70/30 compositions. The results show that for all compositions in which the base state is macroscopically nonpolar, the strains are dominantly electrostrictive in nature. Both of the polarization-related constants, Q/sub 11/ and Q/sub 12/ are almost independent of temperature and of the same order as in other perovskites but decrease slightly in magnitude with increasing La/sub 2/O/sub 3/ content.

  19. The Bayo Canyon/radioactive lanthanum (RaLa) program

    SciTech Connect

    Dummer, J.E.; Taschner, J.C.; Courtright, C.C.

    1996-04-01

    LANL conducted 254 radioactive lanthanum (RaLa) implosion experiments Sept. 1944-March 1962, in order to test implosion designs for nuclear weapons. High explosives surrounding common metals (surrogates for Pu) and a radioactive source containing up to several thousand curies of La, were involved in each experiment. The resulting cloud was deposited as fallout, often to distances of several miles. This report was prepared to summarize existing records as an aid in evaluating the off-site impact, if any, of this 18-year program. The report provides a historical setting for the program, which was conducted in Technical Area 10, Bayo Canyon about 3 miles east of Los Alamos. A description of the site is followed by a discussion of collateral experiments conducted in 1950 by US Air Force for developing an airborne detector for tracking atmospheric nuclear weapons tests. All known off-site data from the RaLa program are tabulated and discussed. Besides the radiolanthanum, other potential trace radioactive material that may have been present in the fallout is discussed and amounts estimated. Off-site safety considerations are discussed; a preliminary off-site dose assessment is made. Bibliographical data on 33 persons important to the program are presented as footnotes.

  20. Genetics of superionic conductivity in lithium lanthanum titanates.

    PubMed

    Jay, E E; Rushton, M J D; Chroneos, A; Grimes, R W; Kilner, J A

    2015-01-01

    The self-diffusion of ions is a fundamental mass transport process in solids and has a profound impact on the performance of electrochemical devices such as the solid oxide fuel cell, batteries and electrolysers. The perovskite system lithium lanthanum titanate, La2/3-xLi3xTiO3 (LLTO) has been the subject of much academic interest as it displays very high lattice conductivity for a solid state Li conductor; making it a material of great technological interest for deployment in safe durable mobile power applications. However, so far, a clear picture of the structural features that lead to efficient ion diffusion pathways in LLTO, has not been fully developed. In this work we show that a genetic algorithm in conjunction with molecular dynamics can be employed to elucidate diffusion mechanisms in systems such as LLTO. Based on our simulations we provide evidence that there is a three-dimensional percolated network of Li diffusion pathways. The present approach not only reproduces experimental ionic conductivity results but the method also promises straightforward investigation and optimisation of the properties relating to superionic conductivity in materials such as LLTO. Furthermore, this method could be used to provide insights into related materials with structural disorder. PMID:25372938

  1. Lanthanum Titanate Nanoparticles ER Fluids with High Performance

    NASA Astrophysics Data System (ADS)

    Wang, De; Shen, Rong; Wei, Shiqiang; Lu, Kunquan

    A new type of electrorheological (ER) fluid consisting of lanthanum titanate (LTO) nanoparticles is developed. The ER fluids were prepared by suspending LTO powder in silicone oil and the particles were fabricated by wet chemical method. This ER fluid shows excellent ER properties: The static yield stress reaches over 150 kPa under 5 kV/mm with linear dependence on the applied DC electric field, and the current density is below 10 μA/cm2. In order to investigate the affect factor on the ER behavior, the LTO powder were heated under different temperatures. The ER performances of two particles treated under different temperatures were compared and the composition changes for those particles were analyzed with TG-FTIR technique. It was found that the static yield stress of the suspensions fell from over 150 kPa to about 40 kPa and the current densities decreased prominently as the rise of the heating temperature. TG-FTIR analysis indicated that polar groups remained in the particles such as alkyl group, hydroxyl group and carbonyl group etc., contribute to the ER effect significantly. The experimental results are helpful to understand the mechanism of the high ER effect and to synthesize better ER materials.

  2. Deposition and investigation of lanthanum-cerium hexaboride thin films

    SciTech Connect

    Kuzanyan, A.S. . E-mail: akuzan@ipr.sci.am; Harutyunyan, S.R.; Vardanyan, V.O.; Badalyan, G.R.; Petrosyan, V.A.; Kuzanyan, V.S.; Petrosyan, S.I.; Karapetyan, V.E.; Wood, K.S.; Wu, H.-D.

    2006-09-15

    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}.

  3. Rare-earth-doped polymers for optical amplification and lasing

    NASA Astrophysics Data System (ADS)

    Gao, Renyuan; Koeppen, C.; Zheng, G.; Garito, Anthony F.

    1998-04-01

    The optical properties and characteristics of rare earth- doped polymers have been studied to evaluate their viability for use in amplifier and laser applications. Rare earth ions are encapsulated in organic, covalent bonded chromophores. The optical properties of various rare earth chromophores doped into polymers are measured and calculated and are then used in numerical simulations of amplifiers and lasers. The result provide an estimate of their potential device performance and establish the fundamental bases for these applications in photonics. Owing to their distinct and important advantages, such as chromophore energy transfer effects, high rare earth ion concentrations, shielding of the ion from high energy vibrations of the host, enhanced optical transition moments, and controllable decay rates and branching ratios, rare earth-doped polymers are found to be promising candidates for various device applications. Numerical simulations for samarium chromophore, for example, indicate that gains about 10 dB and greater are achievable in relatively short polymer optical fiber amplifiers operating at 650 nm.

  4. Processing Techniques Developed to Fabricate Lanthanum Titanate Piezoceramic Material for High-Temperature Smart Structures

    NASA Technical Reports Server (NTRS)

    Goldsby, Jon C.; Farmer, Serene C.; Sayir, Ali

    2004-01-01

    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.

  5. Differences in the pattern of lanthanum diffusion into predentine and dentine in mouse incisors and molars.

    PubMed

    Torres-Quintana, M A; Septier, D; Goldberg, M

    1999-04-01

    Lanthanum nitrate was either perfused intravascularly or segments of mouse tooth were immersed in a fixative solution containing the tracer. The tracer deposits were examined in young (8-day-old) and older (8-week-old) mouse incisors and molars, demineralized or undemineralized. Lanthanum passed the distal junctional complex of odontoblasts and appeared in the predentine of incisors as large electron-dense stellate aggregates, 40-70 nm in diameter, and in molars as round, 20-40 nm dots. In dentine, tracer deposits were detected at three locations. Near the predentine dentine junction, the tracer densely stained a band 0.5-2.5 microm in width, also termed metadentine; in the inner circumpulpal dentine, the staining was weaker or lacking in an area extending 5-7 microm from the predentine-dentine junction; in outer circumpulpal dentine, lateral diffusion had occurred in porosities of intertubular dentine. Lanthanum impregnated the walls of dentine tubules and a peritubular-like dentine. In contrast, the mantle dentine was never stained. These differences in the pattern of diffusion prove that lanthanum staining is age-dependent and varies between mouse incisors and molars, independently of tissue processing. Architectural properties and driving flux are involved in the transport and localization of lanthanum in predentine and dentine. PMID:10348362

  6. Lanthanum: new drug. Hyperphosphataemia in dialysis patients: more potential problems than benefits.

    PubMed

    2007-04-01

    (1) In dialysis patients with chronic renal failure, hyperphosphataemia can cause osteorenal dystrophy, leading to bone pain, fractures and excess cardiovascular mortality. In addition to a low-phosphorus diet and dialysis, phosphorus chelators are usually needed to control blood phosphorus levels. The first choice is calcium carbonate, and sevelamer is an alternative. (2) Lanthanum carbonate, a phosphorus chelator, is now also licensed for the treatment of hyperphosphataemia in dialysis patients with chronic renal failure. (3) In addition to three dose-finding placebo-controlled studies, clinical evaluation includes 2 comparative randomised unblinded trials: one 6-month trial versus calcium carbonate and a 2-year trial versus other phosphorus chelators. During these trials, lanthanum was no more effective than the comparators in terms of effects on the mortality rate, incidence of fractures, or blood phosphorus level. (4) During these trials, adverse events attributed to treatment were more frequent with lanthanum than with the other phosphorus chelators. The main problems were gastrointestinal disorders (nausea, vomiting, diarrhoea, constipation and abdominal pain), headaches, seizures, and encephalopathy. (5) The accumulation of lanthanum in the bones and brain is troubling. The known long-term adverse effects of aluminium, another trivalent cation with weak gastrointestinal absorption, suggest that caution is also required with lanthanum. (6) In practice, when a phosphorus chelator is needed to treat hyperphosphataemia in dialysis patients with chronic renal failure, calcium carbonate is the first choice and sevelamer remains the best alternative. PMID:17458039

  7. Lanthanum carbonate stimulates bone formation in a rat model of renal insufficiency with low bone turnover.

    PubMed

    Fumoto, Toshio; Ito, Masako; Ikeda, Kyoji

    2014-09-01

    Control of phosphate is important in the management of chronic kidney disease with mineral and bone disorder (CKD-MBD), for which lanthanum carbonate, a non-calcium phosphate-binding agent, has recently been introduced; however, it remains to be determined whether it has any beneficial or deleterious effect on bone remodeling. In the present study, the effects of lanthanum carbonate were examined in an animal model that mimics low turnover bone disease in CKD, i.e., thyroparathyroidectomized (TPTX) and 5/6 nephrectomized (NX) rats undergoing a constant infusion of parathyroid hormone (PTH) and thyroxine injections (TPTX-PTH-5/6NX). Bone histomorphometry at the second lumbar vertebra and tibial metaphysis revealed that both bone formation and resorption were markedly suppressed in the TPTX-PTH-5/6NX model compared with the sham-operated control group, and treatment with lanthanum carbonate was associated with the stimulation of bone formation but not an acceleration of bone resorption. Lanthanum treatment caused a robust stimulation of bone formation with an activation of osteoblasts on the endosteal surface of femoral diaphysis, leading to an increase in cortical bone volume. Thus, lanthanum carbonate has the potential to stimulate bone formation in cases of CKD-MBD with suppressed bone turnover. PMID:24126694

  8. The chemoreceptor surface of the taste disc in the frog, Rana esculenta. An ultrastructural study with lanthanum nitrate.

    PubMed

    Zancanaro, C; Sbarbati, A; Franceschini, F; Balercia, G; Osculati, F

    1990-09-01

    The distribution of lanthanum on the taste disc of the frog, Rana esculenta, after en bloc staining of the tongue with lanthanum nitrate was studied at the ultrastructural level by means of scanning electron microscopy (in the secondary electron mode or in the back scattered electron mode), energy-dispersive X-ray microanalysis, transmission electron microscopy and electron spectroscopic imaging. It was consistently found that lanthanum distribution on the surface of the taste disc is not homogeneous and that the surface of putative receptor cells is in contact with strongly lanthanum-positive material. Calcium co-localizes with lanthanum at that level. These results suggest that different microenvironments exist at the surface of the taste disc and that this could be relevant to the receptor function. PMID:2175737

  9. Eutrophication management in surface waters using lanthanum modified bentonite: A review.

    PubMed

    Copetti, Diego; Finsterle, Karin; Marziali, Laura; Stefani, Fabrizio; Tartari, Gianni; Douglas, Grant; Reitzel, Kasper; Spears, Bryan M; Winfield, Ian J; Crosa, Giuseppe; D'Haese, Patrick; Yasseri, Said; Lürling, Miquel

    2016-06-15

    This paper reviews the scientific knowledge on the use of a lanthanum modified bentonite (LMB) to manage eutrophication in surface water. The LMB has been applied in around 200 environments worldwide and it has undergone extensive testing at laboratory, mesocosm, and whole lake scales. The available data underline a high efficiency for phosphorus binding. This efficiency can be limited by the presence of humic substances and competing oxyanions. Lanthanum concentrations detected during a LMB application are generally below acute toxicological threshold of different organisms, except in low alkalinity waters. To date there are no indications for long-term negative effects on LMB treated ecosystems, but issues related to La accumulation, increase of suspended solids and drastic resources depletion still need to be explored, in particular for sediment dwelling organisms. Application of LMB in saline waters need a careful risk evaluation due to potential lanthanum release. PMID:26706125

  10. 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

    Boyle, Timothy J.; Ottley, Leigh Anna M.; Yang, Pin; Chen, Ching-Fong; Sanchez, Margaret R.; Bell, Nelson Simmons

    2008-10-01

    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.

  11. Near fifty percent sodium substituted lanthanum manganites—A potential magnetic refrigerant for room temperature applications

    NASA Astrophysics Data System (ADS)

    Sethulakshmi, N.; Al-Omari, I. A.; Suresh, K. G.; Anantharaman, M. R.

    2014-03-01

    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 J.kg-1.K-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.

  12. The use of lanthanum chloride as a marker for intercellular junctions in rat exocrine pancreas.

    PubMed

    Leeson, T S; Leeson, C R

    1982-07-01

    A simple technique of perfusion and immersion of tissue in fixative containing lanthanum chloride as an extracellular tracer is described. In addition to functioning as a tracer, the lanthanum chloride appears to enhance electron staining. In rat exocrine pancreas, intercellular spaces between exocrine and centroductular cells were outlined clearly be electron dense material and, at cellular interfaces, spot desmosomes, gap junctions, and tight junctions were demonstrated. The technique proved simple and effective and should prove useful in studies of epithelial and other tissues. PMID:6183797

  13. Equilibrium distribution of lanthanum, neodymium, and thorium between lithium chloride melt and liquid bismuth

    NASA Astrophysics Data System (ADS)

    Zagnit'ko, A. V.; Ignat'ev, V. V.

    2013-04-01

    The distribution of lanthanum, neodymium, and thorium between a lithium chloride melt and liquid bismuth with additions of lithium as a reducing agent are investigated at 650°C. Equilibrium values of their distribution constants are measured. It is shown that in contrast to neodymium and lanthanum, thorium cannot be extracted from bismuth into lithium chloride. This allows us to propose an efficient scheme for separating lanthanides and thorium in a system for the extraction of fuel salts in molten-salt nuclear reactors.

  14. Lanthanum carbonate is not associated with QT interval modification in hemodialysis patients

    PubMed Central

    Di Iorio, Biagio; Cucciniello, Emanuele

    2010-01-01

    Lanthanum carbonate is an efficacious noncalcium, nonresin phosphate-binder that is being increasingly used in chronic kidney disease stage 5 (CKD-5) dialysis patients. Available evidence has indicated that QT interval changes correlate with mortality in healthy subjects and in dialysis patients. Experimental studies have suggested the possibility that lanthanum carbonate may produce prolongation of the QT interval. This is not accepted by other authors. There is no data confirming this in prospective clinical studies. The goal of this study was to verify the effect of lanthanum carbonate on the QT interval of the electrocardiogram (EKG) tracing. Material and methods We studied 25 hemodialyzed patients. After a six-month run-in period, with aluminum-hydroxide, lanthanum carbonate was administered at increasing doses: 500 mg twice a day for week 1; 750 mg, twice daily during week 2; 1000 mg twice daily during week 3; and 1000 mg three times daily during week 4. EKGs were recorded on patients prior to and 3 hours following each dialysis treatment. Assessments were made of differences in body weight; systolic blood pressure; diastolic blood pressure; length of PR and QRS complex; heart rate; QT; QT-c; QT-d; and axis of wave P, QRS complex and T using lanthanum carbonate at increasing doses. Results QT-c is before dialysis session during run-in 431 ± 20 msec with variation by −9 to + 1 msec (P = not significant [NS]) during lanthanum use; and 437 ± 25 msec after dialysis session with variation by −6 to −1 msec (P = NS) during lanthanum use. Any difference was observed during study among before and after dialysis session in QT-c (difference by 0.09 to 3.2%) (P = NS); and QT-d (difference by 8.6 to 9.1%) (P = NS). Conclusion Our study shows that lanthanum carbonate administration, at increasing doses, did not modify the EKG parameters. This effect is observed both in predialysis and in postdialysis recordings. Further studies are necessary with more prolonged observations. PMID:22291491

  15. High-efficiency, low-temperature cesium diodes with lanthanum-hexaboride electrodes

    NASA Technical Reports Server (NTRS)

    Morris, J. F.

    1974-01-01

    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.

  16. Synthesis and spectroscopy studies of fullerenes and discovery of macroscopic quantities of doped fullerenes

    SciTech Connect

    Chai, Yan.

    1992-01-01

    Synthesis techniques of carbon arc and laser vaporization in the furnace for production of fullerenes have been developed. The optimum conditions for the high yields of fullerenes were tested and studied. A fullerene growth model was proposed to explain the formation of the fullerenes and the extraordinary high yield of C[sub 60]. The results of a test of this growth model was in agreement with the implications of the model. The electronic spectra of neutral C[sub 60] and C[sub 70] in the regions from 375 to 415 nm and 595 to 640 nm have been studied in a supersonically cooled molecular beam by resonant two-photon ionization spectroscopy method. Sharp spectal features were observed in both regions for C[sub 60] and in only the longer wavelength region for C[sub 70]. Neither molecule has the spectra that correspond to the diffuse interstellar bands. The first method to produce macroscopic quantities of internal metal-doped fullerenes was developed successfully and improved. Lanthanum-doped fullerenes were produced by laser vaporization of a lanthanum oxide/graphite composite rod in a flow of argon at 1200[degrees]C. Many properties of these endohedral complexes were investigated in detail. Similar results were obtained with yttrium-doped fullerenes, and double-doped endohedral fullerene complexes were first observed as a stable species in both sublimed film and toluene solution. Macroscopic quantities of other interesting metal-doped or B-doped fullerenes have been obtained and studied. Purification of these metal-doped fullerenes is in the process.

  17. Lanthanum lead oxide hydroxide nitrates with a nonlinear optical effect.

    PubMed

    Wang, Genxiang; Luo, Min; Lin, Chensheng; Ye, Ning; Zhou, Yuqiao; Cheng, Wendan

    2014-12-01

    Two new lanthanum lead oxide hydroxide nitrates with acentric structure, [LaPb8O(OH)10(H2O)](NO3)7 (1) and [LaPb8O(OH)10(H2O)](NO3)7·2H2O (2), have been prepared under subcritical hydrothermal conditions and crystallize in the space groups of Cc and P2(1)2(1)2(1), respectively. The crystal structure of compound 1 consists of the novel [LaPb8O(OH)10(H2O)](7+) clusters regularly arranged along the ab plane with nitrate ions as the counterions around the clusters by Pb-O bonds, developing into a three-dimensional net framework, while the structure of compound 2 is composed of [LaPb8O(OH)10(H2O)](7+) clusters and [NO3](-) groups as the bridging groups, forming a three-dimensional net framework with crystallized water molecules filling in the gaps. The experiments confirmed that compound 1 is the residue of compound 2 after efflorenscence. Besides, the [LaPb8O(OH)10(H2O)](7+) clusters present mirror symmetry in structures of the two compounds. The second-harmonic-generation (SHG) measurements for the two nitrates indicate that the SHG responses for compounds 1 and 2 are 1.3 and 1.1 times that of KH2PO4, respectively. Theoretical calculations confirmed that the SHG efficiency of compounds 1 and 2 mainly arises from the NO3(-) groups in the structure. PMID:25385570

  18. Titania-lanthanum phosphate photoactive and hydrophobic new generation catalyst

    NASA Astrophysics Data System (ADS)

    Jyothi, Chembolli K.; Jaimy, Kanakkanmavudi B.; Ghosh, Swapankumar; Sankar, Sasidharan; Smitha, V. S.; Warrier, K. G. K.

    2011-07-01

    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=24×10 -3 min -1, which is over five times higher than that observed with standard Hombikat UV 100 ( kapp=4×10 -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.

  19. Back bombardment for dispenser and lanthanum hexaboride cathodes

    NASA Astrophysics Data System (ADS)

    Bakr, Mahmoud; Kinjo, R.; Choi, Y. W.; Omer, M.; Yoshida, K.; Ueda, S.; Takasaki, M.; Ishida, K.; Kimura, N.; Sonobe, T.; Kii, T.; Masuda, K.; Ohgaki, H.; Zen, H.

    2011-06-01

    The back bombardment (BB) effect limits wide usage of thermionic rf guns. The BB effect induces not only ramping-up of a cathode’s temperature and beam current, but also degradation of cavity voltage and beam energy during a macropulse. This paper presents a comparison of the BB effect for the case of dispenser tungsten-base (DC) and lanthanum hexaboride (LaB6) thermionic rf gun cathodes. For each, particle simulation codes are used to simulate the BB effect and electron beam dynamics in a thermionic rf gun cathode. A semiempirical equation is also used to investigate the stopping range and deposited heat power of BB electrons in the cathode material. A numerical simulation method is used to calculate the change of the cathode temperature and current density during a single macropulse. This is done by solving two differential equations for the rf gun cavity equivalent circuit and one-dimensional thermal diffusion equation. High electron emission and small beam size are required for generation of a high-brightness electron beam, and so in this work the emission properties of the cathode are taken into account. Simulations of the BB effect show that, for a pulse of 6μs duration, the DC cathode experiences a large change in the temperature compared with LaB6, and a change in current density 6 times higher. Validation of the simulation results is performed using experimental data for beam current beyond the gun exit. The experimental data is well reproduced using the simulation method.

  20. A new large area lanthanum hexaboride plasma source.

    PubMed

    Cooper, C M; Gekelman, W; Pribyl, P; Lucky, Z

    2010-08-01

    A new 18x18 cm(2) active area lanthanum hexaboride (LaB(6)) plasma source for use in a dc discharge has been developed at UCLA. The cathode consists of four tiled LaB(6) pieces indirectly heated to electron emission (1750 degrees C) by a graphite heater. A molybdenum mesh anode 33 cm in front of the LaB(6) accelerates the electrons, ionizing a fill gas to create a 20x20 cm(2) nearly square plasma. The source is run in pulsed operation with the anode biased up to +400 V dc with respect to the cathode for up to 100 ms at a 1 Hz repetition rate. Both the cathode and anode "float" electrically with respect to the chamber walls. The source is placed in a toroidal chamber 2 m wide and 3 m tall with a major radius of 5 m. Toroidal and vertical magnetic fields confine the current-free plasma which follows the field in a helix. The plasma starts on the bottom of the machine and spirals around it up to four times (120 m) and can be configured to terminate either on the top wall or on the neutral gas itself. The source typically operates with a discharge current up to 250 A in helium making plasmas with T(e)<30 eV, T(i)<16 eV, and n(e)<3x10(13) cm(-3) in a background field of 100 G

  1. Torque magnetometry study of Fe and Ni doped SmB6

    NASA Astrophysics Data System (ADS)

    Tinsman, Colin; Li, Gang; Lawson, Benjamin; Yu, Fan; Asaba, Tomoya; Wang, Xiangfeng; Paglione, Johnpierre; Li, Lu

    2015-03-01

    There has been renewed interest in the past few years regarding Samarium Hexaboride, a promising candidate to be a topological Kondo insulator. Work on this material represents an extension of the categorization of materials by the topology of their electronic band structure into systems with strong correlation effects. It is known that by introducing magnetic impurities, such as Iron, Nickel, and Europium, the magnetic ground state of SmB6 could be greatly altered. In this study we will present our torque magnetometry data of Fe and Ni doped SmB6, down to 20 mK, and up to 45 Tesla. It is found that the overall symmetry of the angular dependence of torque with respect to magnetic field changed for both Fe-doped SmB6 and Ni-doped SmB6. For pure SmB6, the angular dependence is proportional to sin (2 θ) , as expected for a paramagnetic material. By contrast, for Fe-doped SmB6 and Ni-doped SmB6, the torque vs. tilt angle profile becomes sin (4 θ) . Furthermore, for FexSmB6 the field dependence of torque shows a sharp bend feature around 9 Tesla, which softens with elevating temperature, and could be related to magnetic moment re-alignment.

  2. Physical and optical properties of Li2O-MgO-B2O3 doped with Sm3+

    NASA Astrophysics Data System (ADS)

    Reduan, S. A.; Hashim, S.; Ibrahim, Z.; Alajerami, Y. S. M.; Mhareb, M. H. A.; Maqableh, M.; Dawaud, R. S. E. S.; Tamchek, N.

    2014-02-01

    Samarium oxide doped lithium magnesium borate glass has been prepared using conventional melting method. The density and molar volume have been calculated and analyzed while their optical properties were studied by measuring the optical absorption and luminescence spectra at room temperature. From the XRD results, since the patterns do not exhibit any diffraction line thus it confirms their amorphous nature. It was found that the density of the glass samples increased and the molar volume decreased with respect to Sm3+ ions content. Meanwhile, the absorption spectra of this study showed four absorption bands with most outstanding peak at 1230 nm (6H5/2-6F7/2). Three emitted spectra transition were observed in this study which are 4G5/2-6H5/2 (blue), 4G5/2-6H9/2 (green), and 4G5/2-6H11/2(yellowish green). A great enhancement in the PL peaks at green region are observed particularly with the 0.5 mol% concentration, which may attribute to the energy transfer from Mg2+ to the trivalent ions of samarium oxide. Beyond the optimum concentration an opposite effect was remarked. This dwindling is attributed to the concentration quenching phenomenon. The current results agreed with other systematic studies that Sm3+ doped with lithium magnesium borate glasses are attractive solid-state laser materials for generation of various visible lights.

  3. Coproportionation thermodynamics of homoligand solvates of samarium(III) and Yttrium(III) nitrates with neutral organophosphorus compounds

    SciTech Connect

    Pyartman, A.K.

    1995-07-01

    The heats of coproportionation of homoligand solvates of samarium(III) and yttrium(III) nitrates with neutral organophosphorus compounds (tri-n-butyl phosphate, diisooctyl methylphosphonate, and diisoamyl methylphosphonate) in hexane at 298.15 K have been determined calorimetrically. The enthalpies of coproportionation are virtually independent of the nature and concentration of solvates of rare earth metal(III) nitrates in hexane and of the nature of neutral organophosphorus compound and amount to -1.1{plus_minus}0.2 kJ mol{sup -1}. The Gibbs free energy of coproportionation is -5.43 kJ mol{sup -1}, and the entropy is 14.5{plus_minus}0.7 J mol{sup -1} K{sup -1}.

  4. A Theoretical Study on the Spin-Hamiltonian Parameters for Samarium(III) Ion in Potassium Yttrium Tungstate Crystal

    NASA Astrophysics Data System (ADS)

    Yang, Wei-Qing; Zheng, Wen-Chen; Su, Ping; Liu, Hong-Gang

    2011-04-01

    The nine spin-Hamiltonian (SH) parameters (g-factors gi and hyperfine structure constants 147Ai and 149Ai for 147Sm3+ and 149Sm3+ isotopes, where i = x, y, z) for the Samarium(III) ion in monoclinic potassium yttrium tungstate [KY(WO4)2] crystal are calculated within the rhombic symmetry approximation from a diagonalization of energy matrix method. Differing from the conventional diagonalization method used in the calculation of crystal-field levels, in the present method, we attach the Zeeman (or magnetic) and hyperfine interaction terms to the conventional Hamiltonian and construct the 66×66 energy matrix for 4f5 ions in rhombic crystal field and under an external magnetic field by considering all the ground-term multiplets 4HJ. The calculated results are in reasonable agreement with the experimental values

  5. Sparkle/PM3 Parameters for the Modeling of Neodymium(III), Promethium(III), and Samarium(III) Complexes.

    PubMed

    Freire, Ricardo O; da Costa, Nivan B; Rocha, Gerd B; Simas, Alfredo M

    2007-07-01

    The Sparkle/PM3 model is extended to neodymium(III), promethium(III), and samarium(III) complexes. The unsigned mean error, for all Sparkle/PM3 interatomic distances between the trivalent lanthanide ion and the ligand atoms of the first sphere of coordination, is 0.074 Å for Nd(III); 0.057 Å for Pm(III); and 0.075 Å for Sm(III). These figures are similar to the Sparkle/AM1 ones of 0.076 Å, 0.059 Å, and 0.075 Å, respectively, indicating they are all comparable models. Moreover, their accuracy is similar to what can be obtained by present-day ab initio effective potential calculations on such lanthanide complexes. Hence, the choice of which model to utilize will depend on the assessment of the effect of either AM1 or PM3 on the quantum chemical description of the organic ligands. Finally, we present a preliminary attempt to verify the geometry prediction consistency of Sparkle/PM3. Since lanthanide complexes are usually flexible, we randomly generated 200 different input geometries for the samarium complex QIPQOV which were then fully optimized by Sparkle/PM3. A trend appeared in that, on average, the lower the total energy of the local minima found, the lower the unsigned mean errors, and the higher the accuracy of the model. These preliminary results do indicate that attempting to find, with Sparkle/PM3, a global minimum for the geometry of a given complex, with the understanding that it will tend to be closer to the experimental geometry, appears to be warranted. Therefore, the sparkle model is seemingly a trustworthy semiempirical quantum chemical model for the prediction of lanthanide complexes geometries. PMID:26633229

  6. PROCESS USING POTASSIUM LANTHANUM SULFATE FOR FORMING A CARRIER PRECIPITATE FOR PLUTONIUM VALUES

    DOEpatents

    Angerman, A.A.

    1958-10-21

    A process is presented for recovering plutonium values in an oxidation state not greater than +4 from fluoride-soluble fission products. The process consists of adding to an aqueous acidic solution of such plutonium values a crystalline potassium lanthanum sulfate precipitate which carries the plutonium values from the solution.

  7. Structural characterization and properties of lanthanum film as chromate replacement for tinplate

    NASA Astrophysics Data System (ADS)

    Huang, Xingqiao; Li, Ning

    2007-12-01

    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.

  8. Spacecraft charging control by thermal, field emission with lanthanum-hexaboride emitters

    NASA Technical Reports Server (NTRS)

    Morris, J. F.

    1978-01-01

    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.

  9. Intracellular and intramitochondrial binding of lanthanum in dark degenerating midgut cells of a collembolan (insect).

    PubMed

    Humbert, W

    1978-12-29

    Lanthanum is known to be a marker of extracellular spaces. Intracellular organelles are always devoid of stain. But dark and damaged cells may be entered by the marker, as studied at the cellular level, using the electron probe X-ray microanalyser. The technique may be used to detect increased permeability at a stage when no fine structural abnormality is discernible. PMID:738909

  10. Lanthanum acetate inhibits vascular calcification induced by vitamin D3 plus nicotine in rats.

    PubMed

    Zhou, Ye-Bo; Jin, Shao-Ju; Cai, Yan; Teng, Xu; Chen, Li; Tang, Chao-Shu; Qi, Yong-Fen

    2009-08-01

    Lanthanum, a rare earth element, has been used to decrease serum phosphorus level in patients with chronic renal disease and hyperphosphatemia. We aimed to observe the effect and mechanism of two doses of lanthanum acetate (375 and 750 mg/kg/day) on vascular calcification induced by vitamin D3 plus nicotine treatment in rats for 4 weeks. As compared with control rats, rats with calcification showed widespread calcified nodules and irregular elastic fibers in calcified aorta on von Kossa calcium staining and increased aortic calcium and phosphorus contents, alkaline phosphatase (ALP) activity and bone-related protein expressions for osteopontin (OPN) and type III sodium dependent phosphate cotransporter Pit-1 (Pit-1). After treatment with either dose of lanthanum acetate, the calcified nodules and degree of irregular elastic fibers decreased in aortas. Lanthanum acetate at 750 mg/kg/day was more effective than 375 mg/kg/day in lessening vascular calcification by significantly reducing plasma phosphorus level, calcium x phosphorus product and ALP activity, by 30.3%, 28.6%, and 68.6%, respectively; reducing aortic phosphorus and calcium contents and ALP activity, by 48%, 53.1%, and 63.5% (all P < 0.01), respectively; reducing aortic mRNA level of OPN and Pit-1, by 55.8% (P < 0.01) and 38.8% (P < 0.05) and protein level of OPN and Pit-1, by 37.2% and 27.2% (both P < 0.01), respectively; and increasing carboxylated matrix Gla-protein (MGP) protein expression by 33.7% (P < 0.05), as compared with rats treated with vitamin D3 and nicotine alone. Lanthanum acetate could effectively inhibit the pathogenesis of vascular calcification. PMID:19546357

  11. Gastrointestinal symptoms after the substitution of sevelamer hydrochloride with lanthanum carbonate in Japanese patients undergoing hemodialysis.

    PubMed

    Suzuki, D; Ichie, T; Hayashi, H; Sugiura, Y; Sugiyama, T

    2015-08-01

    Lanthanum carbonate has the same phosphorus depressant effect as the other phosphorus adsorbents, and is expected to decrease digestive symptom onset such as constipation in Japanese patients undergoing hemodialysis compared to sevelamar hydrochloride. In this study, we investigated the short- and long-term changes in digestive symptoms in these patients after substituting sevelamar hydrochloride with lanthanum carbonate. We studied 16 patients (4 men, 12 women) and evaluated their gastrointestinal symptoms before administration, at the time of administration, and 2, 4, 8, and 12 weeks after administration, using the Gastrointestinal Symptom Rating Scale. In addition, we conducted repeat evaluations 52 weeks after administration for the patients in whom lanthanum carbonate was administered continuously for 52 weeks. Fourteen (87.5%) out of the 16 patients could tolerate continuous administration for 12 weeks. The constipation score was 3.21 1.74 before administration, 2.07 0.83 2 weeks after administration, 1.76 0.83 4 weeks after administration, 1.57 0.56 8 weeks after administration, and 11.41 0.48 12 weeks after administration. The scores improved significantly 4 weeks after administration (p < 0.05) and even 12 weeks after continuous administration. Among the 16 study patients, 9 patients (1 men, 8 women) were received lanthanum carbonate continuously for 52 weeks. The constipation score was 3.74 1.92 at the start of administration, 1.37 0.56 12 weeks after administration, and 1.85 0.63 52 weeks after administration, with significant improvement even 52 weeks after administration (p < 0.05). This study shows that substituting sevelamar hydrochloride with lanthanum carbonate improves constipation symptoms in hemodialysis patients from an early stage, which indicates its usefulness in improving constipation symptoms caused by sevelamar hydrochloride. PMID:26380521

  12. Corrosion resistance and blood compatibility of lanthanum ion implanted pure iron by MEVVA

    NASA Astrophysics Data System (ADS)

    Zhu, Shengfa; Huang, Nan; Shu, Hui; Wu, Yanping; Xu, Li

    2009-10-01

    Pure iron is a potential material applying for coronary artery stents based on its biocorrodible and nontoxic properties. However, the degradation characteristics of pure iron in vivo could reduce the mechanical stability of iron stents prematurely. The purpose of this work was to implant the lanthanum ion into pure iron specimens by metal vapor vacuum arc (MEVVA) source at an extracted voltage of 40 kV to improve its corrosion resistance and biocompatibility. The implanted fluence was up to 5 × 10 17 ions/cm 2. The X-ray photoelectron spectroscopy (XPS) was used to characterize the chemical state and depth profiles of La, Fe and O elements. The results showed lanthanum existed in the +3 oxidation state in the surface layer, most of the oxygen combined with lanthanum and form a layer of oxides. The lanthanum ion implantation layer could effectively hold back iron ions into the immersed solution and obviously improved the corrosion resistance of pure iron in simulated body fluids (SBF) solution by the electrochemical measurements and static immersion tests. The systematic evaluation of blood compatibility, including in vitro platelets adhesion, prothrombin time (PT), thrombin time (TT), indicated that the number of platelets adhesion, activation, aggregation and pseudopodium on the surface of the La-implanted samples were remarkably decreased compared with pure iron and 316L stainless steel, the PT and TT were almost the same as the original plasma. It was obviously showed that lanthanum ion implantation could effectively improve the corrosion resistance and blood compatibility of pure iron.

  13. Samarium-153-ethylene diamine tetramethylene phosphonate, a beta-emitting bone-targeted radiopharmaceutical, useful for patients with osteoblastic bone metastases

    PubMed Central

    Longo, John; Lutz, Stephen; Johnstone, Candice

    2013-01-01

    Bone metastases are prevalent among cancer patients and frequently cause significant morbidity. Oncology providers must mitigate complications associated with bone metastases while limiting therapy-related adverse effects and their impact on quality of life. Multiple treatment modalities, including chemotherapy, surgery, external beam radiation therapy, and radioisotopes, among others, have been recommended and utilized for palliative treatment of bone metastases. Radioisotopes such as samarium-153 are commonly used in the setting of multifocal bone metastases due to their systemic distribution, affinity for osteoblastic lesions, acceptable toxicity profile, and convenience of administration. This review focuses on samarium-153, first defining its radiobiologic and pharmacokinetic properties before describing many clinical trials that support its use as a safe and effective tool in the palliation of patients with bone metastases. PMID:23976864

  14. Performance Evaluation of an Oxygen Sensor as a Function of the Samaria Doped Ceria Film Thickness

    SciTech Connect

    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

    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

  15. Thickness Dependency of Thin Film Samaria Doped Ceria for Oxygen Sensing

    SciTech Connect

    Sanghavi, Rahul P.; Nandasiri, Manjula I.; Kuchibhatla, Satyanarayana V N T; Jiang, Weilin; Varga, Tamas; Nachimuthu, Ponnusamy; Engelhard, Mark H.; Shutthanandan, V.; Thevuthasan, Suntharampillai; Kayani, Asghar N.; Prasad, Shalini

    2011-01-01

    High temperature oxygen sensors are widely used for exhaust gas monitoring in automobiles. This particular study explores the use of thin film single crystalline samaria doped ceria as the oxygen sensing material. Desired signal to noise ratio can be achieved in a material system with high conductivity. From previous studies it is established that 6 atomic percent samarium doping is the optimum concentration for thin film samaria doped ceria to achieve high ionic conductivity. In this study, the conductivity of the 6 atomic percent samaria doped ceria thin film is measured as a function of the sensing film thickness. Hysteresis and dynamic response of this sensing platform is tested for a range of oxygen pressures from 0.001 Torr to 100 Torr for temperatures above 673 K. An attempt has been made to understand the physics behind the thickness dependent conductivity behavior of this sensing platform by developing a hypothetical operating model and through COMSOL simulations. This study can be used to identify the parameters required to construct a fast, reliable and compact high temperature oxygen sensor.

  16. Interaction of oxygen with samarium on Al{sub 2}O{sub 3} thin film grown on Ni{sub 3}Al(111)

    SciTech Connect

    Cheng, Dingling; Xu, Qian E-mail: jfzhu@ustc.edu.cn; Han, Yong; Ye, Yifan; Pan, Haibin; Zhu, Junfa E-mail: jfzhu@ustc.edu.cn

    2014-03-07

    The interaction between oxygen and samarium (Sm) on the well-ordered thin Al{sub 2}O{sub 3} film grown on Ni{sub 3}Al(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 (O{sub 2}{sup 2−}) states and regular samarium oxide (O{sup 2−}) states. By contrast, when exposing O{sub 2} to Sm film less than one monolayer on Al{sub 2}O{sub 3}, no O{sub 2}{sup 2−} can be observed. Upon heating to higher temperatures, these metastable O{sub 2}{sup 2−} states dissociate, supplying active O atoms which can diffuse through the Al{sub 2}O{sub 3} thin film to further oxidize the underlying Ni{sub 3}Al(111) substrate, leading to the significant increase of the Al{sub 2}O{sub 3} 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 Ni{sub 3}Al substrate by supplying the active oxygen species at elevated temperatures.

  17. Facile preparation of apatite-type lanthanum silicate by a new water-based sol–gel process

    SciTech Connect

    Yamagata, Chieko; Elias, Daniel R.; Paiva, Mayara R.S.; Misso, Agatha M.; Castanho, Sonia R.H. Mello

    2013-06-01

    Highlights: ► We use a Na{sub 2}SiO{sub 3} waste solution as source of Si. ► We present a simple, rapid and low temperature method of lanthanum silicate apatite preparation. ► TEOS, a high cost reagent, was successfully substituted by a cheap price Na{sub 2}SiO{sub 3}, to obtain pure La{sub 9.56}(SiO{sub 4})6O{sub 2.33} lanthanum silicate apatite. - Abstract: In recent years, apatite-type lanthanum silicates ([Ln{sub 10−x}(XO{sub 4})6O{sub 3–1.5x}] (X = Si or Ge)) have been studied for use in SOFC (solid oxide fuel cells), at low temperature (600–800 °C), due to its ionic conductivity which is higher than that of YSZ (Yttrium Stabilized Zirconia) electrolyte. For this reason they are very promising materials as solid electrolyte for SOFCs. Synthesis of functional nanoparticles is a challenge in the nanotechnology. In this work, apatite-type lanthanum silicate nanoparticles were synthesized by a water-based sol–gel process, i.e., sol–gel technique followed by chemical precipitation of lanthanum hydroxide on the gel of the silica. Na{sub 2}SiO{sub 3} waste solution was used as silica source. Spherical aerogel silica was prepared by acid catalyzed reaction, followed by precipitation of lanthanum hydroxide to obtain the precursor of apatite-type lanthanum silicate. Powders of apatite-type lanthanum silicate achieved from the precursor were characterized by thermal analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM) and specific surface area measurements (BET). The apatite phase was formed at 900 °C.

  18. Highly Photosensitive PCFs with Extremely Germanium Doped Core

    NASA Astrophysics Data System (ADS)

    Schuster, K.; Kobelke, J.; Wang, Y.; Schwuchow, A.; Kirchhof, J.; Bartelt, H.; Pissadakis, S.

    2010-11-01

    We report about preparation and application of index guiding germanium doped microstructured fibers, special designed for Bragg grating inscription. Due to their maximum germanium oxide concentration of 36 mol% they show a very high photosensitivity. The core diameters of the PCFs were variied between 1.6 and 6.6 μm by changing the fiber diameters. For small core PCF preparation we integrated an additional microstructured cane overcladding step. The cores are about at half total diameter doped with germanium. The holey silica claddings are arranged in a five ring hexagonal package with a hole-pitch ratio of about 0.9 and 0.3. So we can vary the inscription efficiency of Ge doped PCFs. In difference to other highly doped or non-silica PCFs with highly polarizable and probably photosensitive core components, e.g. PCFs with lanthanum glass core, germanium doped PCFs show beside their high photosensitivity a low spectral loss. Measured with an unstructured fiber the highly germanium doped silica core material exhibits a minimum loss of about 6.5 dB/km. Inserted in the PCF structure the attenuation is increased to about 40 dB/km at a wavelength of 1.2 μm for the large core PCF. The small core PCF show an increased loss level in the hundred dB/km range. This effect is caused, as well as the increase of hydroxide impurification during the partial "atmospheric" PCF preparation procedure, by structural imperfections of the designed PCFs. The high germanium concentration in the central core region allows a suitable Bragg grating inscription.

  19. Fluorescence properties and electron paramagnetic resonance studies of γ-irradiated Sm3+-doped oxyfluoroborate glasses

    NASA Astrophysics Data System (ADS)

    Babu, B. Hari; Ravi Kanth Kumar, V. V.

    2012-11-01

    The permanent photoinduced valence manipulation of samarium doped oxyfluoroborate glasses as a function of γ-ray irradiation has been investigated using a steady-state fluorescence and electron paramagnetic resonance techniques. An increase in SrF2 content in the glass led to the red shift of the peaks in as prepared glass, while in irradiated glasses this led to the decrease in defect formation as well as increase in photoreduction of Sm3+ to Sm2+ ion. The energy transfer mechanism of induced permanent photoreduction of Sm3+ to Sm2+ ions in oxyfluoroborate glasses has been discussed. The decay analysis shows exponential behavior before irradiation and non-exponential behavior after irradiation. The energy transfer in irradiated glasses increases with the increase in SrF2 content in the glass and also with the irradiation dose.

  20. Plasma Spray Deposition of Lanthanum Phosphate and Phase Structure of the Resultant Coatings

    NASA Astrophysics Data System (ADS)

    Pragatheeswaran, A.; Ananthapadmanabhan, P. V.; Chakravarthy, Y.; Chaturvedi, Vandana; Bhandari, Subhankar; Ramachandran, K.

    2015-12-01

    Plasma-sprayed lanthanum phosphate coatings were prepared on stainless steel substrates at different input powers from 16 to 24 kW. Coatings were characterized by x-ray diffraction, scanning electron microscopy, and Fourier transformed infrared spectroscopy. Results showed that the as-sprayed coatings consist of lanthanum ortho (LaPO4), poly(La2P4O13), and oxy(La3PO7) phosphates. Subsequent heat treatment of the coatings resulted in the recombination of the La-polyphosphate and La-oxyphosphate to form LaPO4. SEM images of microstructure of the coatings and coating-substrate interface showed micro-cracks, voids, and porosity that were found to decrease with deposition power.

  1. Ab initio structure determination of lanthanum cyclo-tetratungstate {alpha}-La

    SciTech Connect

    Laligant, Y.; Le Bail, A.; Goutenoire, F.

    2001-06-01

    Lanthanum tungstate {alpha}-La{sub 2}W{sub 2}O{sub 9} was successfully synthesized by the ceramic route. Its crystal structure was determined ab initio from neutron diffraction data (space group P{bar 1} No. 2; a = 7.2489(1) {angstrom}, b = 7.2878(1) {angstrom}, c = 7.0435(1) {angstrom}, {alpha} = 96.367(1){degree}, {beta} = 94.715(1){degree}, {gamma} = 70.286(1){degree}; Z = 2; reliability factors: R{sub p} = 6.0%, R{sub wp} = 6.9%, R{sub B} = 3.0%). The structure exhibits isolated [W{sub 4}O{sub 18}]{sup 12{minus}} groups in the form of rings involving [WO{sub 6}] octahedra alternating with [WO{sub 5}] trigonal bipyramids sharing corners. These rings are inserted in the 3D framework built by the 9- and 10-fold coordination polyhedra of the lanthanum atoms.

  2. Lanthanum(III) and praseodymium(III) derivatives with dithiocarbamates derived from α-amino acids

    NASA Astrophysics Data System (ADS)

    Rai, Anita; Sengupta, Soumitra K.; Pandey, Om P.

    2006-06-01

    Lanthanum(III) and praseodymium(III) complexes with dithiocarbamates have been synthesized by the reactions of lanthanum(III) and praseodymium(III) chloride with barium dithiocarbamate and complexes of type [LnCl(L)H 2O] n have been obtained (where Ln = La(III) or Pr(III); L = barium salt of dithiocarbamate derived from glycine, L-leucine, L-valine, DL-alanine). The complexes have been characterized by elemental analysis, molar conductance, electronic absorption and fluorescence, infrared, far infrared, 1H NMR spectral studies. The presence of coordinated water molecule is inferred from thermogravimetric analysis which indicates the loss of one water molecule at 150-170 °C. The oscillator strength, Judd-Ofelt intensity parameter, stimulated emission cross-section, etc. have been obtained for different transitions of Pr 3+.

  3. Lanthanum(III) and praseodymium(III) derivatives with dithiocarbamates derived from alpha-amino acids.

    PubMed

    Rai, Anita; Sengupta, Soumitra K; Pandey, Om P

    2006-06-01

    Lanthanum(III) and praseodymium(III) complexes with dithiocarbamates have been synthesized by the reactions of lanthanum(III) and praseodymium(III) chloride with barium dithiocarbamate and complexes of type [LnCl(L)H2O]n have been obtained (where Ln=La(III) or Pr(III); L=barium salt of dithiocarbamate derived from glycine, L-leucine, L-valine, DL-alanine). The complexes have been characterized by elemental analysis, molar conductance, electronic absorption and fluorescence, infrared, far infrared, 1H NMR spectral studies. The presence of coordinated water molecule is inferred from thermogravimetric analysis which indicates the loss of one water molecule at 150-170 degrees C. The oscillator strength, Judd-Ofelt intensity parameter, stimulated emission cross-section, etc. have been obtained for different transitions of Pr3+. PMID:16330242

  4. Measurement of lanthanum and technetium in uranium fuels by inductively coupled plasma atomic emission spectroscopy.

    SciTech Connect

    Carney, K.; Crane, P.; Cummings, D.; Krsul, J.; McKnight, R.

    1999-06-10

    An important parameter in characterizing an irradiated nuclear fuel is determining the amount of uranium fissioned. By determining the amount of uranium fissioned in the fuel a burnup performance parameter can be calculated, and the amount of fission products left in the fuel can be predicted. The quantity of uranium fissioned can be calculated from the amount of lanthanum and technetium present in the fuel. Lanthanum and technetium were measured in irradiated fuel samples using an Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) instrument and separation equipment located in a shielded glove-box. A discussion of the method, interferences, detection limits, quality control and a comparison to other work will be presented.

  5. Atomization of yttrium, lanthanum, and neodymium in acetylene-nitrous oxide flame

    SciTech Connect

    Osipova, V.A.; Gorlova, M.N.; Kuzyakov, Y.Y.; Semenenko, K.A.

    1985-10-01

    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.

  6. Chromium and copper substituted lanthanum nano-ferrites: Their synthesis, characterization and application studies

    NASA Astrophysics Data System (ADS)

    Jauhar, Sheenu; Singhal, Sonal

    2014-10-01

    Nano-crystalline lanthanum ferrites substituted by chromium and copper having formula LaMxFe1-xO3 (M = Cr, Cu; 0.0 ⩽ x ⩽ 0.5) were synthesized using sol-gel auto-combustion method. The formation of ferrite particles was confirmed using Fourier Transform Infra-Red (FT-IR) spectra and powder X-ray Diffraction (XRD) techniques. The entire ferrite compositions were found to be pure phased with same symmetry as LaFeO3. The average crystallite size was calculated to be ∼60 nm. The ferrite compositions were observed to behave as semi-conductors, as their resistivity decreased with increasing temperature. These ferrite compositions were employed as catalysts in the decomposition of hydrogen peroxide solution (0.17 M). Pure LaFeO3 was found to have a very low catalytic activity towards the decomposition of hydrogen peroxide solution, while presence of copper in the lanthanum ferrite lattice was found to significantly enhance its catalytic activity. The rate constant in case of reactions catalysed by LaCu0.5Fe0.5O3 was nearly 25 times larger than that obtained from reactions catalysed by pure LaFeO3. However, chromium substitution was not found to influence the catalytic activity of lanthanum ferrites as chromium substituted lanthanum ferrites exhibited very low catalytic activity. This was explained on the basis of relative stability of oxidation states of the substituent ions and the presence of defects in the crystal lattice.

  7. Effect of chloride incorporation on the crystallization of zirconium-barium-lanthanum-aluminum fluoride glass

    NASA Technical Reports Server (NTRS)

    Neilson, G. F.; Smith, G. L.; Weinberg, M. C.

    1985-01-01

    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.

  8. Room temperature synthesis of high temperature stable lanthanum phosphate–yttria nano composite

    SciTech Connect

    Sankar, Sasidharan; Raj, Athira N.; Jyothi, C.K.; Warrier, K.G.K.; Padmanabhan, P.V.A.

    2012-07-15

    Graphical abstract: A facile aqueous sol–gel route involving precipitation–peptization mechanism followed by electrostatic stabilization is used for synthesizing nanocrystalline composite containing lanthanum phosphate and yttria. Highlights: ► A novel lanthanum phosphate–Y{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 sol–gel route involving precipitation–peptization 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. TG–DTA 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.

  9. Lanthanum silicate coated magnetic microspheres as a promising affinity material for phosphopeptide enrichment and identification.

    PubMed

    Cheng, Gong; Liu, Yan-Lin; Zhang, Ji-Lin; Sun, De-Hui; Ni, Jia-Zuan

    2012-08-01

    Novel Fe(3)O(4)@La(x)Si(y)O(5) affinity microspheres consisting of a superparamagnetic Fe(3)O(4) core and an amorphous lanthanum silicate shell have been synthesized. The core-shell-structured Fe(3)O(4)@La(x)Si(y)O(5) microspheres, with a mean size of ca. 480 nm, had rough lanthanum silicate surfaces and displayed relatively strong magnetism (47.2 emu g(-1)). This novel affinity material can be used for selective capture, rapid magnetic separation, and part dephosphorylation (which plays an important role in identifying phosphopeptides in MS) of the phosphopeptides in a peptide mixture. Its ability to selectively trap and magnetically isolate as well as label the phosphopeptides was evaluated using a standard phosphorylated protein (β-casein) and a real sample (human serum). Phosphopeptides and their corresponding label ions were detected for concentrations of β-casein as low as 1 × 10(-9) M and in mixtures of β-casein and BSA with molar ratios as low as 1:50. In addition, this affinity material, with its labeling properties, is superior to commercial TiO(2) beads in terms of interference from non-phosphopeptide molecules. These results reveal that the lanthanum silicate coated magnetic microspheres represent a promising affinity material for the rapid purification and recognition of phosphopeptides. PMID:22722743

  10. Preparation and Characterization of Lanthanum-Incorporated Hydroxyapatite Coatings on Titanium Substrates.

    PubMed

    Lou, Weiwei; Dong, Yiwen; Zhang, Hualin; Jin, Yifan; Hu, Xiaohui; Ma, Jianfeng; Liu, Jinsong; Wu, Gang

    2015-01-01

    Titanium (Ti) has been widely used in clinical applications for its excellent biocompatibility and mechanical properties. However, the bioinertness of the surface of Ti has motivated researchers to improve the physicochemical and biological properties of the implants through various surface modifications, such as coatings. For this purpose, we prepared a novel bioactive material, a lanthanum-incorporated hydroxyapatite (La-HA) coating, using a dip-coating technique with a La-HA sol along with post-heat treatment. The XRD, FTIR and EDX results presented in this paper confirmed that lanthanum was successfully incorporated into the structure of HA. The La-HA coating was composed of rod-like particles which densely compacted together without microcracks. The results of the interfacial shear strength test indicated that the incorporation of lanthanum increased the bonding strength of the HA coating. The mass loss ratios under acidic conditions (pH=5.5) suggested that the La-HA coatings have better acid resistance. The cytocompatibility of the La-HA coating was also revealed by the relative activity of alkaline phosphatase, cellular morphology and cell proliferation assay in vitro. The present study suggested that La-HA coated on Ti has promising potential for applications in the development of a new type of bioactive coating for metal implants. PMID:26404255

  11. Preparation and Characterization of Lanthanum-Incorporated Hydroxyapatite Coatings on Titanium Substrates

    PubMed Central

    Lou, Weiwei; Dong, Yiwen; Zhang, Hualin; Jin, Yifan; Hu, Xiaohui; Ma, Jianfeng; Liu, Jinsong; Wu, Gang

    2015-01-01

    Titanium (Ti) has been widely used in clinical applications for its excellent biocompatibility and mechanical properties. However, the bioinertness of the surface of Ti has motivated researchers to improve the physicochemical and biological properties of the implants through various surface modifications, such as coatings. For this purpose, we prepared a novel bioactive material, a lanthanum-incorporated hydroxyapatite (La-HA) coating, using a dip-coating technique with a La-HA sol along with post-heat treatment. The XRD, FTIR and EDX results presented in this paper confirmed that lanthanum was successfully incorporated into the structure of HA. The La-HA coating was composed of rod-like particles which densely compacted together without microcracks. The results of the interfacial shear strength test indicated that the incorporation of lanthanum increased the bonding strength of the HA coating. The mass loss ratios under acidic conditions (pH = 5.5) suggested that the La-HA coatings have better acid resistance. The cytocompatibility of the La-HA coating was also revealed by the relative activity of alkaline phosphatase, cellular morphology and cell proliferation assay in vitro. The present study suggested that La-HA coated on Ti has promising potential for applications in the development of a new type of bioactive coating for metal implants. PMID:26404255

  12. Lanthanum halide scintillators for time-of-flight 3-D pet

    DOEpatents

    Karp, Joel S.; Surti, Suleman

    2008-06-03

    A Lanthanum Halide scintillator (for example LaCl.sub.3 and LaBr.sub.3) with fast decay time and good timing resolution, as well as high light output and good energy resolution, is used in the design of a PET scanner. The PET scanner includes a cavity for accepting a patient and a plurality of PET detector modules arranged in an approximately cylindrical configuration about the cavity. Each PET detector includes a Lanthanum Halide scintillator having a plurality of Lanthanum Halide crystals, a light guide, and a plurality of photomultiplier tubes arranged respectively peripherally around the cavity. The good timing resolution enables a time-of-flight (TOF) PET scanner to be developed that exhibits a reduction in noise propagation during image reconstruction and a gain in the signal-to-noise ratio. Such a PET scanner includes a time stamp circuit that records the time of receipt of gamma rays by respective PET detectors and provides timing data outputs that are provided to a processor that, in turn, calculates time-of-flight (TOF) of gamma rays through a patient in the cavity and uses the TOF of gamma rays in the reconstruction of images of the patient.

  13. Synthesis and luminescence properties of encapsulated sol-gel glass samarium complexes

    NASA Astrophysics Data System (ADS)

    Zaitoun, M. A.; Momani, K.; Jaradat, Q.; Qurashi, I. M.

    2013-11-01

    Luminescence efficiency of lanthanide complexes generally largely depend on the choice of the organic ligand and the host matrix in which these complexes are doped. Two Sm(III) complexes, namely: Sm(III) dithicarbamate - Sm(L1)3B [L1 = (R)2NCS2B, R = C2H5 and B = 1,10-phenanthroline] and Sm(III) complex with the polytonic ligand L2 = N‧, N‧2-bis[(1E)-1-(2-pyridyl)ethylidene]ethanedihydrazide {Sm2-L2-(CH3COO)2; L2 = C16H16N6O2} are synthesized, these complexes are then trapped in sol-gel glass. Room temperature luminescence of Sm(L1)3B and {Sm2-L2-(CH3COO)2} complexes encapsulated in sol-gel glass are studied using a spectrofluorometer. Up on excitation by a UV light, ligand L1B absorbs this light and transfers it into the Sm(III) ions and emission bands were observed in the visible region and were attributed to f-f transitions of Sm(III). The observed emission indicated an efficient L1B ligand as a sensitizer, while ligand L2 shows no ability to work as a sensitizer. The branching ratio I4G5/2→6H9/2/I4G5/2→6H7/2) of electric dipole transition to magnetic dipole transition was used as an effective spectroscopic probe to predict symmetry of the site in which Sm(III) is located. The encapsulation of the Samaium complexes was performed for three reasons: (i) before rare earth (RE)-doped sol-gel glasses can be used in applications such as laser materials, several fluorescence quenching mechanisms must be overcome, we show in this work that lanthanide fluorescence is greatly enhanced by chelation and selecting a suitable host matrix (sol-gel) to accommodate the lanthanide complex, (ii) to improve the stability of the phosphor with efficient and high color-purity characteristics under ultraviolet excitation and (iii) this work provides a framework for preparing transparent composite glasses that are robust hosts to study the fundamental interactions between nano-materials and light.

  14. Samarium-153 therapy for prostate cancer: the evaluation of urine activity, staff exposure and dose rate from patients.

    PubMed

    Parlak, Yasemin; Gumuser, Gul; Sayit, Elvan

    2015-03-01

    The aim of this study was to determine the excretion of Samarium-153-ethylenediaminetetramethylphosphonic acid ((153)Sm-EDTMP) in urine and to calculate the dose rate of its retention in the body as a function of time and the dose received by the skin of laboratory staff's finger. Urine samples were collected from 11 patients after intravenous injection of (153)Sm-EDTMP. The measurements of dose rate were performed. Thermoluminescent dosemeters were used for absorbed dose measurements. Effective half-lives that were calculated from urine sample measurements were found as 7.1±3 h within the first 24 h. Whole body dose rates before collecting urine of patients were 60.0 ± 15.7 µSv h(-1) for within 1 h following (153)Sm-EDTMP administration. The highest finger radiation dose is to the right-hand thumb (3.8 ± 2 mGy). The results of the study imply that patients who recieved (153)Sm-EDTMP therapy should be kept a minumum of 8 h in an isolated room at hospital and that one staff should give therapy at most two patients per week. PMID:25063786

  15. Anion sensing and interfering behaviors of electrolyte-insulator-semiconductor sensors with nitrogen plasma-treated samarium oxide

    NASA Astrophysics Data System (ADS)

    Ye, Yu-Ren; Wang, Jer-Chyi; Chan, Ya-Ting

    2015-04-01

    In this article, we demonstrate a samarium oxide (Sm2O3) electrolyte-insulator-semiconductor (EIS) sensor with nitrogen plasma immersion ion implantation (PIII) treatment for anion sensing and interfering characterization. Chloride (Cl-), nitrite (NO2-), and nitrate (NO3-) ions were detected, and the sensitivity was about 49.75 mV/pCl, 53.8 mV/pNO2, and 56.19 mV/pNO3, respectively. Ion sensitivity was enhanced with the increase in ionic radius of the target ion. Titration was performed to analyze the interference of anions. To assess interferences from these ions (Cl-, NO2-, and NO3-), selectivity coefficients obtained by fixed interference method (FIM) measurements were presented. In result, the coefficients indicate that the interference can be ignored. Furthermore, characteristics of drift demonstrates that the sample exhibits long-term stability for significantly lower drift of chloride, nitrite, and nitrate ions, respectively. The Sm2O3 EIS sensor with nitrogen PIII treatment exhibits superior anion sensitivity, selectivity, and stability; therefore, this sensor is suitable for future biosensing applications.

  16. Ca2+-Doped CeBr3 Scintillating Materials

    SciTech Connect

    Guss, Paul; Foster, Michael E.; Wong, Bryan M.; Doty, F. Patrick; Shah, Kanai; Squillante, Michael R.; Shirwadkar, Urmila; Hawrami, Rastgo; Tower, Josh; Yuan, Ding

    2014-01-21

    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.

  17. Investigation of band gap narrowing in nitrogen-doped La2Ti2O7 with transient absorption spectroscopy.

    PubMed

    Yost, Brandon T; Cushing, Scott K; Meng, Fanke; Bright, Joeseph; Bas, Derek A; Wu, Nianqiang; Bristow, Alan D

    2015-12-14

    Doping a semiconductor can extend the light absorption range, however, it usually introduces mid-gap states, reducing the charge carrier lifetime. This report shows that doping lanthanum dititinate (La2Ti2O7) with nitrogen extends the valence band edge by creating a continuum of dopant states, increasing the light absorption edge from 380 nm to 550 nm without adding mid-gap states. The dopant states are experimentally resolved in the excited state by correlating transient absorption spectroscopy with a supercontinuum probe and DFT prediction. The lack of mid-gap states is further confirmed by measuring the excited state lifetimes, which reveal the shifted band edge only increased carrier thermalization rates to the band edge and not interband charge recombination under both ultraviolet and visible excitation. Terahertz (time-domain) spectroscopy also reveals that the conduction mechanism remains unchanged after doping, suggesting the states are delocalized. PMID:26531849

  18. Glass formation and crystallization in the alumina-silica-lanthanum phosphate system for ceramics composites

    NASA Astrophysics Data System (ADS)

    Guo, Shuling

    The formation, structure, and dynamics of glasses in the alumina-silica-lanthanum phosphate system and their crystallization were investigated as a function of composition. These are of interest because of their potential as precursors for synthesizing ceramic-matrix-composites via co-crystallization of lanthanum monazite and either mullite or alumina into finely mixed microstructures. The glasses were characterized by X-Ray Diffraction (XRD), Raman spectroscopy, Differential Scanning Calorimetry (DSC), Nuclear Magnetic Resonance (NMR), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Electron Energy Loss Spectrometry (EELS). Glass formation from rapidly quenched liquids was easiest and most consistent for compositions containing silica, such as for mullitemonazite compositions, and more difficult for alumina-monazite compositions. For mullite-monazite glasses, the glass transition temperatures increased linearly from 845°C to 906°C with increasing mullite content. An analysis of the glass structure indicated a network consisting of corner-linked aluminate, silicate and phosphate tetrahedra where aluminum played a central role of separating silicon and phosphorous. It was hypothesized that the glass network consisted of domains of aluminum silicate network edged by phosphate tetrahedra. A maximum in the crystallization temperature was attributed to the complexity of the glass network. At relatively mullite-rich compositions, simultaneous and cooperative crystallization of lanthanum phosphate and mullite correlated with the highest crystallization temperatures, and the lowest activation energies of crystallization. This was preceded by amorphous phase segregation in the glass at lower temperatures. An intermediate phase of lanthanum phosphate was discovered with an orthorhombic unit cell. For compositions of high phosphate contents, lanthanum phosphate precipitated first at about 900°C leaving an essentially pure mullite glass. Mullite crystallized at about 1000°C, matching the conditions for crystallizing pure mullite glass. The phosphate phase transformed to monazite at even higher temperatures. No amorphous phase segregation was observed in these cases. Microstructures were correlated with nucleation and growth conditions such that the continuous and isolated phases could be manipulated. Optimum nucleation temperatures were close to the glass transition temperature. Conditions were identified for forming a continuous boundary phase of monazite that isolated mullite grains, which is desired for fabricating ceramic-matrix-composites.

  19. First-principles study of codoping in lanthanum bromide

    NASA Astrophysics Data System (ADS)

    Erhart, Paul; Sadigh, Babak; Schleife, André; Åberg, Daniel

    2015-04-01

    Codoping of Ce-doped LaBr3 with Ba, Ca, or Sr improves the energy resolution that can be achieved by radiation detectors based on these materials. Here, we present a mechanism that rationalizes this enhancement on the basis of first-principles electronic structure calculations and point defect thermodynamics. It is shown that incorporation of Sr creates neutral VBr-SrLa complexes that can temporarily trap electrons. As a result, Auger quenching of free carriers is reduced, allowing for a more linear, albeit slower, scintillation light yield response. Experimental Stokes shifts can be related to different CeLa-SrLa-VBr triple complex configurations. Codoping with other alkaline as well as alkaline-earth metals is considered as well. Alkaline elements are found to have extremely small solubilities on the order of 0.1 ppm and below at 1000 K. Among the alkaline-earth metals the lighter dopant atoms prefer interstitial-like positions and create strong scattering centers, which has a detrimental impact on carrier mobilities. Only the heavier alkaline-earth elements (Ca, Sr, Ba) combine matching ionic radii with sufficiently high solubilities. This provides a rationale for the experimental finding that improved scintillator performance is exclusively achieved using Sr, Ca, or Ba. The present mechanism demonstrates that codoping of wide-gap materials can provide an efficient means for managing charge carrier populations under out-of-equilibrium conditions. In the present case dopants are introduced that manipulate not only the concentrations but also the electronic properties of intrinsic defects without introducing additional gap levels. This leads to the availability of shallow electron traps that can temporarily localize charge carriers, effectively deactivating carrier-carrier recombination channels. The principles of this mechanism are therefore not specific to the material considered here but can be adapted for controlling charge carrier populations and recombination in other wide-gap materials.

  20. Effect of lanthanum carbonate and calcium acetate in the treatment of hyperphosphatemia in patients of chronic kidney disease

    PubMed Central

    Scaria, P. Thomas; Gangadhar, Reneega; Pisharody, Ramdas

    2009-01-01

    Objectives: The tolerability and efficacy of lanthanum carbonate has not been studied in the Indian population. This study was, therefore, undertaken to compare the efficacy and tolerability of lanthanum carbonate with calcium acetate in patients with stage 4 chronic kidney disease. Design: A randomized open label two group cross-over study. Materials and Methods: Following Institutional Ethics Committee approval and valid consent, patients with stage 4 chronic kidney disease were randomized to receive either lanthanum carbonate 500mg thrice daily or calcium acetate 667 mg thrice daily for 4 weeks. After a 4-week washout period, the patients were crossed over for another 4 weeks. Serum phosphorous, serum calcium, serum alkaline phosphatase, and serum creatinine were estimated at fixed intervals. Results: Twenty-six patients were enrolled in the study. The mean serum phosphorous concentrations showed a declining trend with lanthanum carbonate (from pre-drug levels of 7.88 1.52 mg/dL-7.14 1.51 mg/dL) and calcium acetate (from pre-drug levels of 7.54 1.39 mg/dL-6.51 1.38 mg/dL). A statistically significant difference was seen when comparing the change in serum calcium produced by these drugs (P < 0.05). Serum calcium levels increased with calcium acetate (from pre-drug levels of 7.01 1.07-7.46 0.74 mg dL), while it decreased with lanthanum carbonate (from pre-drug levels 7.43 0.77-7.14 0.72 mg/dL). The incidence of adverse effects was greater with lanthanum carbonate. Conclusion: Lanthanum carbonate and calcium acetate are equally effective phosphate binders with trends obvious in the first 4 weeks of therapy. The decrease in serum calcium levels with lanthanum carbonate when compared to the increase in serum calcium levels due to calcium acetate is statistically significant. The drawback of lanthanum carbonate is its high cost and relatively higher incidence of adverse events during treatment. PMID:20523871

  1. Optical studies of Sm³⁺ ions doped zinc alumino bismuth borate glasses.

    PubMed

    Swapna, K; Mahamuda, Sk; Srinivasa Rao, A; Shakya, S; Sasikala, T; Haranath, D; Vijaya Prakash, G

    2014-05-01

    Zinc Alumino Bismuth Borate (ZnAlBiB) glasses doped with different concentrations of samarium (Sm(3+)) 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 Sm(3+) 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 Sm(3+) 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 (4)G5/2 level of Sm(3+) ions. From the measured emission cross-sections, branching ratios, strong photoluminescence features and CIE chromaticity coordinates, it was found that 1 mol% of Sm(3+) ions doped ZnAlBiB glasses are most suitable for the development of visible orange-red lasers. PMID:24530709

  2. Lanthanum Nitrate As Electrolyte Additive To Stabilize the Surface Morphology of Lithium Anode for Lithium-Sulfur Battery.

    PubMed

    Liu, Sheng; Li, Guo-Ran; Gao, Xue-Ping

    2016-03-30

    Lithium-sulfur (Li-S) battery is regarded as one of the most promising candidates beyond conventional lithium ion batteries. However, the instability of the metallic lithium anode during lithium electrochemical dissolution/deposition is still a major barrier for the practical application of Li-S battery. In this work, lanthanum nitrate, as electrolyte additive, is introduced into Li-S battery to stabilize the surface of lithium anode. By introducing lanthanum nitrate into electrolyte, a composite passivation film of lanthanum/lithium sulfides can be formed on metallic lithium anode, which is beneficial to decrease the reducibility of metallic lithium and slow down the electrochemical dissolution/deposition reaction on lithium anode for stabilizing the surface morphology of metallic Li anode in lithium-sulfur battery. Meanwhile, the cycle stability of the fabricated Li-S cell is improved by introducing lanthanum nitrate into electrolyte. Apparently, lanthanum nitrate is an effective additive for the protection of lithium anode and the cycling stability of Li-S battery. PMID:26981849

  3. DETERMINATION OF LEAD AND CADMIUM IN FISH AND CLAM TISSUE BY ATOMIC ABSORPTION SPECTROMETRY WITH A MOLYBDENUM AND LANTHANUM TREATED PYROLYTIC GRAPHITE ATOMIZER

    EPA Science Inventory

    A molybdenum and lanthanum treated pyrolytically coated graphite tube is employed for the furnace atomic absorption spectrometric determination of lead and cadmium directly in nitric-perchloric acid tissue digests. Lanthanum tends to promote the formation of a smooth lead atomiza...

  4. The theoretical basis and clinical methodology for stereotactic interstitial brain tumor irradiation using iododeoxyuridine as a radiation sensitizer and samarium-145 as a brachytherapy source

    SciTech Connect

    Goodman, J.H.; Gahbauer, R.A.; Kanellitsas, C.; Clendenon, N.R. ); Laster, B.H.; Fairchild, R.G. )

    1989-01-01

    High grade astrocytomas have proven resistant to all conventional therapy. A technique to produce radiation enhancement during interstitial brain tumor irradiation by using a radiation sensitizer (IdUrd) and by stimulation of Auger electron cascades through absorption of low energy photons in iodine (Photon activation) is described. Clinical studies using IdUrd, {sup 192}Ir as a brachytherapy source, and external radiation have produced promising results. Substituting samarium-145 for {sup 192}Ir in this protocol is expected to produce enhanced results. 15 refs.

  5. On the possibility of reduction of Ac{sup 3+} to Ac{sup 2+} in Aqueous-ethanolic solutions of bivalent samarium

    SciTech Connect

    Mikheev, N.B.; Veleshko, I.E.; Kamenskaya, A.N.

    1995-07-01

    In view of contradictory data on the existence of Ac{sup 2+} in aqueous solutions, the possibility of actinium reduction was examined in aqueous-ethanolic solutions in which bivalent f-elements are more stable than in aqueous media. In the presence of bivalent samarium (E{sub Sm}{sup 0}3+/Sm 2+=-1.5 V) Ac(III) is not reduced to Ac(II). These results disagree with the previously published data on the radiopolarographic generation of Ac(II) in aqueous solutions.

  6. Diode pumped neodymium doped ASL (Sr1-xLax-yNdyMgxAl12-xO19) laser

    NASA Astrophysics Data System (ADS)

    Zheng, Lihe; Loiseau, Pascal; Aka, Gérard

    2013-07-01

    Blue laser based on Neodymium doped strontium lanthanum magnesium aluminoxide (Sr1-xLax-yNdyMgxAl12-xO19) single crystal were constructed by second harmonic generation. Output power of 1.72 W at 900nm was obtained under 792nm laser diode pump. Intra cavity second harmonic generation were performed with non linear crystal LBO leading to output power of 76.6 mW at 450nm with absorbed power of 13.7 W and average absorption efficiency of 61% in Nd:ASL crystal.

  7. Phase I Trial of Vertebral Intracavitary Cement and Samarium (VICS): Novel Technique for Treatment of Painful Vertebral Metastasis

    SciTech Connect

    Ashamalla, Hani; Cardoso, Erico; Macedon, Mark; Guirguis, Adel; Weng Lijun; Ali, Shamsah; Mokhtar, Bahaa; Ashamalla, Michael; Panigrahi, Nokul

    2009-11-01

    Purpose: Kyphoplasty is an effective procedure to alleviate pain in vertebral metastases. However, it has no proven anticancer activity. Samarium-153-ethylene diamine tetramethylene phosphonate ({sup 153}Sm-EDTMP) is used for palliative treatment of bone metastases. A standard dose of 1 mCi/kg is administrated intravenously. The present study was conducted to determine the feasibility of intravertebral administration of {sup 153}Sm with kyphoplasty. Methods and Materials: A total of 33 procedures were performed in 26 patients. Of these 26 patients, 7 underwent procedures performed at two vertebral levels. The mean age of the cohort was 64 years (range, 33-86). The kyphoplasty procedure was performed using a known protocol; 1-4 mCi of {sup 153}Sm was admixed with the bone cement and administered under tight radiation safety measures. Serial nuclear body scans were obtained. Pain assessment was evaluated using a visual analog pain score. Results: All patients tolerated the procedure well. No procedure-related morbidities were noted. No significant change had occurred in the blood counts at 1 month after the procedure. One case was not technically satisfactory. Nuclear scans revealed clear radiotracer uptake in the other 32 vertebrae injected. Except for the first patient, no radiation leakage was encountered. The mean pain score using the visual analog scale improved from 8.6 before to 2.8 after the procedure (p < .0001). Follow-up bone scans demonstrated a 43% decrease in the tracer uptake. Conclusion: The results of our study have shown that the combination of intravertebral administration of {sup 153}Sm and kyphoplasty is well tolerated with adequate pain control. No hematologic adverse effects were found. A reduction of the bone scan tracer uptake was observed in the injected vertebrae. Longer follow-up is needed to study the antineoplastic effect of the procedure.

  8. Neutron Activated Samarium-153 Microparticles for Transarterial Radioembolization of Liver Tumour with Post-Procedure Imaging Capabilities

    PubMed Central

    Hashikin, Nurul Ab. Aziz; Yeong, Chai-Hong; Abdullah, Basri Johan Jeet; Ng, Kwan-Hoong; Chung, Lip-Yong; Dahalan, Rehir; Perkins, Alan Christopher

    2015-01-01

    Introduction Samarium-153 (153Sm) styrene divinylbenzene microparticles were developed as a surrogate for Yttrium-90 (90Y) microspheres in liver radioembolization therapy. Unlike the pure beta emitter 90Y, 153Sm possess both therapeutic beta and diagnostic gamma radiations, making it possible for post-procedure imaging following therapy. Methods The microparticles were prepared using commercially available cation exchange resin, Amberlite IR-120 H+ (620–830 μm), which were reduced to 20–40 μm via ball mill grinding and sieve separation. The microparticles were labelled with 152Sm via ion exchange process with 152SmCl3, prior to neutron activation to produce radioactive 153Sm through 152Sm(n,γ)153Sm reaction. Therapeutic activity of 3 GBq was referred based on the recommended activity used in 90Y-microspheres therapy. The samples were irradiated in 1.494 x 1012 n.cm-2.s-1 neutron flux for 6 h to achieve the nominal activity of 3.1 GBq.g-1. Physicochemical characterisation of the microparticles, gamma spectrometry, and in vitro radiolabelling studies were carried out to study the performance and stability of the microparticles. Results Fourier Transform Infrared (FTIR) spectroscopy of the Amberlite IR-120 resins showed unaffected functional groups, following size reduction of the beads. However, as shown by the electron microscope, the microparticles were irregular in shape. The radioactivity achieved after 6 h neutron activation was 3.104 ± 0.029 GBq. The specific activity per microparticle was 53.855 ± 0.503 Bq. Gamma spectrometry and elemental analysis showed no radioactive impurities in the samples. Radiolabelling efficiencies of 153Sm-Amberlite in distilled water and blood plasma over 48 h were excellent and higher than 95%. Conclusion The laboratory work revealed that the 153Sm-Amberlite microparticles demonstrated superior characteristics for potential use in hepatic radioembolization. PMID:26382059

  9. Comparison of the local and the average crystal structure of proton conducting lanthanum tungstate and the influence of molybdenum substitution.

    PubMed

    Magrasó, Anna; Frontera, Carlos

    2016-02-18

    We report on the comparison of the local and average structure reported recently for proton conducting lanthanum tungstate, of general formula La28-xW4+xO54+δv2-δ, and the impact of molybdenum-substitution on the crystal structure of the material. Partial replacement of W with 10 and 30 mol% Mo is investigated here, i.e. La27(W1-xMox)5O55.5 for x = 0.1 and 0.3. This study addresses the interpretation and the description of a disordered cation and anion sublattice in this material, which enables the understanding of the fundamental properties related to hydration, transport properties and degradation in lanthanum tungstate. The report shows that Mo-substituted lanthanum tungstate is a promising material as a dense oxide membrane for hydrogen separation at intermediate temperatures. PMID:26818222

  10. Pseudo-exfoliation material. Electron microscopy after the application of lanthanum as tracer particles and ionic stain.

    PubMed

    Davanger, M

    1980-08-01

    Lenses with pseudo-exfoliation (PE) were suspended in a solution of lanthanum, which was present partly in ionic form, partly as electron-dense tracer particles in colloidal solution, dependent on pH and on the concentration of lanthanum. By electron microscopy the tracer particles were found in a narrow zone along the surface of the PE excrescences. Only a few of the smallest particles had penetrated into their most superficial layer. In the specimens treated with ionic lanthanum, the effect was an electron-dense staining of the PE material within a 1-2 micrometer thick superficial layer. The PE fibrils as well as parts of the interfibrillar spaces were stained. These results indicate the presence of proteoglycans, and confirm the concept of an interfibrillar matrix which excludes other macromolecules and particles from penetrating into the material. PMID:6163308

  11. Nonaqueous synthesis of metal oxide nanoparticles: Short review and doped titanium dioxide as case study for the preparation of transition metal-doped oxide nanoparticles

    SciTech Connect

    Djerdj, Igor Arcon, Denis; Jaglicic, Zvonko; Niederberger, Markus

    2008-07-15

    The liquid-phase synthesis of metal oxide nanoparticles in organic solvents under exclusion of water is nowadays a well-established alternative to aqueous sol-gel chemistry. In this article, we highlight some of the advantages of these routes based on selected examples. The first part reviews some recent developments in the synthesis of ternary metal oxide nanoparticles by surfactant-free nonaqueous sol-gel routes, followed by the discussion of the morphology-controlled synthesis of lanthanum hydroxide nanoparticles, and the presentation of structural peculiarities of manganese oxide nanoparticles with an ordered Mn vacancy superstructure. These examples show that nonaqueous systems, on the one hand, allow the preparation of compositionally complex oxides, and, on the other hand, make use of the organic components (initially present or formed in situ) in the reaction mixture to tailor the morphology. Furthermore, obviously even the crystal structure can differ from the corresponding bulk material like in the case of MnO nanoparticles. In the second part of the paper we present original results regarding the synthesis of dilute magnetic semiconductor TiO{sub 2} nanoparticles doped with cobalt and iron. The structural characterization as well as the magnetic properties with special attention to the doping efficiency is discussed. - Graphical abstract: In the first part of this article, nonaqueous sol-gel routes to ternary metal oxide nanoparticles are briefly reviewed, followed by the discussion of the morphology-controlled synthesis of lanthanum hydroxide nanoparticles, and the appearance of an unprecedented superstructure in MnO nanoparticles. In the second part, doping experiments of TiO{sub 2} with Fe and Co are presented, along with their characterization including magnetic measurements.

  12. Preliminary Investigation of Lanthanum-Cerium Bromide Self-Activity Removal

    SciTech Connect

    Yuan, D., Guss, P.

    2011-09-01

    It has been reported that detectors made of lanthanum-cerium halides (LaBr3:Ce and CeBr3) have superior energy resolution for gamma-radiation detection compared to what is offered by conventional sodium iodide (NaI:T1) detectors16. Although superior energy resolution may be observed, one major barrier that has hindered the rapid adaptation of lanthanum halides is their self-activity, due primarily to the presence of isotope 138La, and the ? contamination, due to the trace amount of actinides68. It has also been observed that the lanthanum-cerium halides contain a substantial amount of self-activity caused by the radioactive isotope 138La. Additionally, LaBr3:Ce spectra are also affected by ? contaminations in the low-energy region. To use either LaBr3:Ce or CeBr3 for high-sensitivity gamma detection, it may be necessary to have the self-activity as well as ? and ? contaminations removed or reduced. This paper describes a novel algorithmic approach for self-activity and contamination reduction for LaBr3:Ce and CeBr3 detectors using a third reference NaI:T1 detector. We present a computational procedure for separating self-activity from the gamma spectra obtained by LaBr3:Ce detectors. With the self-activity spectra precalculated, it is possible to perform real-time self-activity removal. This procedure can be implemented as an automatic self-activity subtraction module for gamma-radiation detectors made of LaBr3:Ce and/or CeBr3 crystals. With this approach, it is possible to develop a new generation of LaBr3:Ce detectors capable of producing spectra as clean as those obtained by conventional NaI:T1 detectors, but with much improved energy resolutions.

  13. Preliminary investigation of lanthanum-cerium bromide self-activity removal

    NASA Astrophysics Data System (ADS)

    Yuan, Ding; Guss, Paul

    2011-09-01

    It has been reported that detectors made of lanthanum-cerium halides (LaBr3:Ce and CeBr3) have superior energy resolution for gamma-radiation detection compared to what is offered by conventional sodium iodide (NaI:T1) detectors. Although superior energy resolution may be observed, one major barrier that has hindered the rapid adaptation of lanthanum halides is their self-activity, due primarily to the presence of isotope 138La, and the ? contamination, due to the trace amount of actinides. It has also been observed that the lanthanum-cerium halides contain a substantial amount of self-activity caused by the radioactive isotope 138La. Additionally, LaBr3:Ce spectra are also affected by ? contaminations in the low-energy region. To use either LaBr3:Ce or CeBr3 for high-sensitivity gamma detection, it may be necessary to have the self-activity as well as ? and ? contaminations removed or reduced. This paper describes a novel algorithmic approach for self-activity and contamination reduction for LaBr3:Ce and CeBr3 detectors using a third reference NaI:T1 detector. We present a computational procedure for separating self-activity from the gamma spectra obtained by LaBr3:Ce detectors. With the self-activity spectra precalculated, it is possible to perform real-time self-activity removal. This procedure can be implemented as an automatic self-activity subtraction module for gamma-radiation detectors made of LaBr3:Ce and/or CeBr3 crystals. With this approach, it is possible to develop a new generation of LaBr3:Ce detectors capable of producing spectra as clean as those obtained by conventional NaI:T1 detectors, but with much improved energy resolutions.

  14. Thermochemistry of perovskites in the lanthanum-strontium-manganese-iron oxide system

    NASA Astrophysics Data System (ADS)

    Marinescu, Cornelia; Vradman, Leonid; Tanasescu, Speranta; Navrotsky, Alexandra

    2015-10-01

    The enthalpies of formation from binary oxides of perovskites (ABO3) based on lanthanum strontium manganite La(Sr)MnO3 (LSM) and lanthanum strontium ferrite La(Sr)FeO3 (LSF) and mixed lanthanum strontium manganite ferrite La(Sr)Mn(Fe)O3 (LSMF) were measured by high temperature oxide melt solution calorimetry. Using iodometric titration, the oxygen content was derived. The perovskites with A-site cation deficiency have greater oxygen deficiency than the corresponding A-site stoichiometric series. Stability of LSMF decreases with increasing iron content. Increasing oxygen deficiency clearly destabilizes the perovskites. The results suggest an enthalpy of oxygen incorporation that is approximately independent of composition. 0.35La2O3 (xl, 25 °C)+Mn2O3 (xl, 25 °C)+0.3SrO (xl, 25 °C)+Fe2O3 (xl, 25 °C)+O2 (g, 25 °C)→La0.7Sr0.3Mn1-yFeyO3-δ (xl, 25 °C). (b) ∆ubscriptshift="90%"superscriptshift="90%">Hf, ox * (La0.7Sr0.3Mn1-yFeyO3-δ) .0.35 La2O3 (xl, 25 ººC) + (0.7-y+ 2δ)/2 Mn2O3 (xl, 25 ºC) + 0.3 SrO (xl, 25 ºC) + y/2Fe2O3 (xl, 25 ºC) + (0.3-2δ) MnO2 (xl, 25 ºC)→La0.7Sr0.3Mn1-yFeyO3-δ (xl, 25 ºC).

  15. The single cell of low temperature solid oxide fuel cell with sodium carbonate-SDC (samarium-doped ceria) as electrolyte and biodiesel as fuel

    NASA Astrophysics Data System (ADS)

    Rahmawati, F.; Nuryanto, A.; Nugrahaningtyas, K. D.

    2016-02-01

    In this research NSDC (composite of Na2CO3-SDC) was prepared by the sol-gel method to produce NSDC1 and also by the ceramic method to produce NSDC2. The prepared NSDC then were analyzed by XRD embedded with Le Bail refinement to study the change of characteristic peaks, their crystal structure, and their cell parameters. Meanwhile, the measurement of impedance was conducted to study the electrical conductivity of the prepared materials. A single cell was prepared by coating NSDC-L (a composite of NSDC with Li0.2Ni0.7Cu0.1O2) on both surfaces of NSDC. The NSDC-L was used as anode and cathode. The ionic conductivity of NSDC1 and NSDC2 at 400 oC are 4.1109 x 10-2 S.cm-1 and 1.6231 x 10-2 S.cm-1, respectively. Both electrolytes have ionic conductivity higher than 1 x 10-4 S.cm-1, therefore, can be categorized as good electrolyte [1]. However, the NSDC1 shows electrodeelectrolyte conduction. It indicates the existence of electronic migration from electrolyte- electrode or vice versa. Those may cause a short circuit during fuel cell operation and will reduce the fuel cell performance fastly. The single cell tests were conducted at 300, 400, 500 and 600 °C. The single fuel cell with NSDC1 and NSDC2 as electrolyte show maximum power density at 400 °C with the power density of 3.736 x 10-2 mW.cm-2 and 2.245 x 10-2 mW.cm-2, respectively.

  16. Photoluminescence of cerium fluoride and cerium-doped lanthanum fluoride nanoparticles and investigation of energy transfer to photosensitizer molecules.

    PubMed

    Cooper, Daniel R; Kudinov, Konstantin; Tyagi, Pooja; Hill, Colin K; Bradforth, Stephen E; Nadeau, Jay L

    2014-06-28

    CexLa1-xF3 nanoparticles have been proposed for use in nanoscintillator-photosensitizer systems, where excitation of nanoparticles by ionizing radiation would result in energy transfer to photosensitizer molecules, effectively combining the effects of radiotherapy and photodynamic therapy. Thus far, there have been few experimental investigations of such systems. This study reports novel synthesis methods for water-dispersible Ce0.1La0.9F3/LaF3 and CeF3/LaF3 core/shell nanoparticles and an investigation of energy transfer to photosensitizers. Unbound deuteroporphyrin IX 2,4-disulfonic acid was found to substantially quench the luminescence of large (>10 nm diameter) aminocaproic acid-stabilized nanoparticles at reasonable concentrations and loading amounts: up to 80% quenching at 6% w/w photosensitizer loading. Energy transfer was found to occur primarily through a cascade, with excitation of "regular" site Ce(3+) at 252 nm relayed to photosensitizer molecules at the nanoparticle surface through intermediate "perturbed" Ce(3+) sites. Smaller (<5 nm) citrate-stabilized nanoparticles were coated with the bisphosphonate alendronate, allowing covalent conjugation to chlorin e6 and resulting in static quenching of the nanoparticle luminescence: ∼50% at ∼0.44% w/w. These results provide insight into energy transfer mechanisms that may prove valuable for optimizing similar systems. PMID:24827162

  17. High-current lanthanum-hexaboride electron emitter for a quasi-stationary arc plasma generator

    NASA Astrophysics Data System (ADS)

    Davydenko, V. I.; Ivanov, A. A.; Shul'zhenko, G. I.

    2015-11-01

    A high-current electron emitter on the basis of lanthanum hexaboride is developed for quasi-stationary arc plasma generators of ion sources. The emitter consists of a set of LaB6 washers interleaved with washers made of thermally extended graphite. The emitter is heated by the current flowing through the graphite washers. The thermal regime of emitter operation during plasma generation is considered. The emitter has been successfully used in the ion sources of the diagnostic injectors of fast hydrogen atomic beams.

  18. Photofragmentation of the Gas-Phase Lanthanum Isopropylcyclopentadienyl Complex: Computational Modeling vs Experiment.

    PubMed

    Han, Yulun; Meng, Qingguo; Rasulev, Bakhtiyor; May, P Stanley; Berry, Mary T; Kilin, Dmitri S

    2015-11-01

    Photofragmentation of the lanthanum isopropylcyclopentadienyl complex, La(iCp), was explored through time-dependent excited-state molecular dynamics (TDESMD), excited-state molecular dynamics (ESMD), and thermal molecular dynamics (MD). Simulated mass spectra were extracted from ab initio molecular dynamics simulations through a new and simple method and compared to experimental photoionization time-of-flight (PI-TOF) mass spectra. The computational results indicate that the value of excitation energy and mechanism of excitation determine the dissociation process. PMID:26438124

  19. Temperature Dependent Electrical and Micromechanical Properties of Lanthanum Titanate with Additions of Yttria

    NASA Technical Reports Server (NTRS)

    Goldsby, Jon C.

    2003-01-01

    Lanthanum titanate (La2Ti2O7) a layered distorted perovskite (1) with space group Pna2(sub 1) has been shown to have potential as a high temperature piezoelectric (2). However this highly refractory oxide compound must be consolidated at relatively high temperatures approximately 1400 C. Commercial La2Ti207 powders were mechanically alloyed with additions of Y2O3 to lower the consolidation temperature by 300 C and to provide post processing mechanical stability. Temperature dependent electrical, elastic and anelastic behavior were selected as nondestructive means of evaluating the effects of yttria on the properties of this ferroceramic material.

  20. High-current density, high-brightness electron beams from large-area lanthanum hexaboride cathodes

    NASA Astrophysics Data System (ADS)

    Loschialpo, P.; Kapetanakos, C. A.

    1987-12-01

    Large (approx. 5 cm) diameter lanthanum hexaboride (LaB6) cathodes operated at 10 kV have produced 1 to 5 micro electron pulses with current density between 10 and 20 A/sq cm. Normalized beam brightness, has been consistently measured. To obtain this high current density, the LaB6 cathodes have been heated to temperatures between approximately 1600 to 1800 C. Very uniform temperature profiles are obtained by applying a carefully tailored electron bombardment heating power distribution. These measurements have been made between pressure .000001 to .00001 Torr, i.e., under much less demanding vacuum conditions than that required by conventional dispenser type cathodes.

  1. Fabrication of Lanthanum Telluride 14-1-11 Zintl High-Temperature Thermoelectric Couple

    NASA Technical Reports Server (NTRS)

    Ravi, Vilupanur A.; Li, Billy Chun-Yip; Fleurial, Pierre; Star, Kurt

    2010-01-01

    The development of more efficient thermoelectric couple technology capable of operating with high-grade heat sources up to 1,275 K is key to improving the performance of radioisotope thermoelectric generators. Lanthanum telluride La3-xTe4 and 14-1-11 Zintls (Yb14MnSb11) have been identified as very promising materials. The fabrication of advanced high-temperature thermoelectric couples requires the joining of several dissimilar materials, typically including a number of diffusion bonding and brazing steps, to achieve a device capable of operating at elevated temperatures across a large temperature differential (up to 900 K). A thermoelectric couple typically comprises a heat collector/ exchanger, metallic interconnects on both hot and cold sides, n-type and ptype conductivity thermoelectric elements, and cold-side hardware to connect to the cold-side heat rejection and provide electrical connections. Differences in the physical, mechanical, and chemical properties of the materials that make up the thermoelectric couple, especially differences in the coefficients of thermal expansion (CTE), result in undesirable interfacial stresses that can lead to mechanical failure of the device. The problem is further complicated by the fact that the thermoelectric materials under consideration have large CTE values, are brittle, and cracks can propagate through them with minimal resistance. The inherent challenge of bonding brittle, high-thermal-expansion thermoelectric materials to a hot shoe material that is thick enough to carry the requisite electrical current was overcome. A critical advantage over prior art is that this device was constructed using all diffusion bonds and a minimum number of assembly steps. The fabrication process and the materials used are described in the following steps: (1) Applying a thin refractory metal foil to both sides of lanthanum telluride. To fabricate the n-type leg of the advanced thermoelectric couple, the pre-synthesized lanthanum telluride coupon was diffusion bonded to the metal foil using a thin adhesion layer. (2) Repeating a similar process for the 14-1-11 Zintl p-type leg of the advanced thermoelectric couple. (3) Bonding thick CTE-matched metal plates on the metallized lanthanum telluride and Yb14MnSb11 to form the hot and cold sides of the thermoelectric couple. The calculated conversion efficiency of such an advanced couple would be about 10.5 percent, about 35 percent better than heritage radioisotope thermoelectric technology that relies on Si-Ge alloys. In addition, unlike Si-Ge alloys, these materials can be combined with many other thermoelectric materials optimized for operation at lower temperatures to achieve conversion efficiency in excess of 15 percent (a factor of 2 increase over heritage technology).

  2. High-current lanthanum-hexaboride electron emitter for a quasi-stationary arc plasma generator

    SciTech Connect

    Davydenko, V. I. Ivanov, A. A. Shul’zhenko, G. I.

    2015-11-15

    A high-current electron emitter on the basis of lanthanum hexaboride is developed for quasi-stationary arc plasma generators of ion sources. The emitter consists of a set of LaB{sub 6} washers interleaved with washers made of thermally extended graphite. The emitter is heated by the current flowing through the graphite washers. The thermal regime of emitter operation during plasma generation is considered. The emitter has been successfully used in the ion sources of the diagnostic injectors of fast hydrogen atomic beams.

  3. Determination of lanthanum by graphite furnace atomic absorption spectrometry with a tantalum platform

    NASA Astrophysics Data System (ADS)

    Skroce, A.; McCormick, M.; Meehan, B.; Dolic, V.; Peverill, K.

    1993-11-01

    A simple and sensitive method has been developed for the determination of lanthanum by graphite furnace atomic absorption spectroscopy (GFAAS). The element was determined under stabilized temperature platform furnace (STPF) conditions with atomization from a tantalum platform. Under optimized furnace conditions, the use of the tantalum surface provided better analytical sensitivity than atomization from graphite. The characteristic mass and detection limit of the methods were 220 pg and 40 μg/l, respectively. At higher concentrations, the precision was about 4% RSD. The tube life was greater than 250 firings. Nitric and sulphuric acids decreased tube life.

  4. Lanthanum, constipation, bafflying X-rays and a perforated colonic diverticulum

    PubMed Central

    Korzets, Asher; Tsitman, Inna; Lev, Netta; Zingerman, Boris; Herman, Michal; Ben Dor, Naomi; Gafter, Uzi; Ori, Yaacov

    2012-01-01

    Lanthanum carbonate (LC) is used as a phosphate binder in dialysed patients. Abdominal pain and constipation are known side effects of its use. Furthermore, in radiological studies, LC tablets are seen as intense radio-opaque deposits within the entire gastrointestinal tract—findings which can lead to diagnostic misinterpretations. An elderly patient on peritoneal dialysis and taking LC presented with peritonitis, secondary to a perforated colonic diverticulum. The possible association between the use of LC, worsening constipation and complications arising from colonic diverticular disease, are discussed. PMID:25874091

  5. Temperature-Dependent Electrical and Micromechanical Properties of Lanthanum Titanate with Additions of Yttria

    NASA Technical Reports Server (NTRS)

    Goldsby, Jon C.

    2010-01-01

    Temperature-dependent elastic properties were determined by establishing continuous flexural vibrations in the material at its lowest resonance frequency of 31tHz. The imaginary part of the complex impedance plotted as a function of frequency and temperature reveals a thermally activated peak, which decreases in magnitude as the temperature increases. Additions of yttria do not degrade the electromechanical in particularly the elastic and anelastic properties of lanthanum titanate. Y2O3/La2Ti2O7 exhibits extremely low internal friction and hence may be more mechanical fatigue-resistant at low strains.

  6. Deposition of Lanthanum Strontium Cobalt Ferrite (LSCF) Using Suspension Plasma Spraying for Oxygen Transport Membrane Applications

    NASA Astrophysics Data System (ADS)

    Fan, E. S. C.; Kesler, O.

    2015-08-01

    Suspension plasma spray deposition was utilized to fabricate dense lanthanum strontium cobalt ferrite oxygen separation membranes (OSMs) on porous metal substrates for mechanical support. The as-sprayed membranes had negligible and/or reversible material decomposition. At the longer stand-off distance (80 mm), smooth and dense membranes could be manufactured using a plasma with power below approximately 81 kW. Moreover, a membrane of 55 μm was observed to have very low gas leakage rates desirable for OSM applications. This thickness could potentially be decreased further to improve oxygen diffusion by using metal substrates with finer surface pores.

  7. Comparison between features and performance characteristics of fifteen hp samarium cobalt and ferrite based brushless dc motors operated by same power conditioner

    SciTech Connect

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

    1983-01-01

    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 Co/sub 5/) is used as permanent magnet material, while in the other the magnets were made of strontium ferrite number 8. The two machines were built to operate from the same power conditioner, which consisted of a transistor chopper in series with a three phase full wave inverter/converter bridge, which consists of six transistor-diode switches. Both of the two motors achieved a continuous 2 hour rating of more than 15 hp with a peak one minute rating of 35 hp. System efficiency (combined motor and conditioner) under rated conditions of 90% was achieved for both machines. Details of these and other performance characteristics and design parameters are presented and analyzed to assess the impact of the choice of magnet material on design and performance for this, as well as other applications.

  8. Simple Resolution of Enantiomeric NMR Signals of α-Amino Acids by Using Samarium(III) Nitrate With L-Tartarate.

    PubMed

    Aizawa, Sen-Ichi; Kidani, Takahiro; Takada, Sayuri; Ofusa, Yumika

    2015-05-01

    Readily available L-tartaric acid, which is a bidentate ligand with two chiral centers forming a seven-membered chelate ring, was applied to the chiral ligand for the chiral nuclear magnetic resonance (NMR) shift reagent of samarium(III) formed in situ. This simple method does not cause serious signal broadening in the high magnetic field. Enantiomeric (13)C and (1)H NMR signals and enantiotopic (1)H NMR signals of α-amino acids were successfully resolved at pH 8.0 and the 1:3 molar ratio of Sm(NO3)3:L-tartaric acid. It is elucidated that the enantiomeric signal resolution is attributed to the anisotropic magnetic environment for the enantiomers induced by the chiral L-tartarato samarium(III) complex rather than differences in stability of the diastereomeric substrate adducts. The present (13)C NMR signal resolution was also effective for the practical simultaneous analysis of plural kinds of DL-amino acids. PMID:25847749

  9. Doped Artificial Spin Ice

    NASA Astrophysics Data System (ADS)

    Olson Reichhardt, Cynthia; Libal, Andras; Reichhardt, Charles

    We examine square and kagome artificial spin ice for colloids confined in arrays of double-well traps. Unlike magnetic artificial spin ices, colloidal and vortex artificial spin ice realizations allow creation of doping sites through double occupation of individual traps. We find that doping square and kagome ice geometries produces opposite effects. For square ice, doping creates local excitations in the ground state configuration that produce a local melting effect as the temperature is raised. In contrast, the kagome ice ground state can absorb the doping charge without generating non-ground-state excitations, while at elevated temperatures the hopping of individual colloids is suppressed near the doping sites. These results indicate that in the square ice, doping adds degeneracy to the ordered ground state and creates local weak spots, while in the kagome ice, which has a highly degenerate ground state, doping locally decreases the degeneracy and creates local hard regions.

  10. Samarium(III)-catalyzed C(sp3)-H bond activation: synthesis of indolizines via C-C and C-N coupling between 2-alkylazaarenes and propargylic alcohols.

    PubMed

    Wang, Xu; Li, Shen-yan; Pan, Ying-ming; Wang, Heng-shan; Liang, Hong; Chen, Zhen-feng; Qin, Xiao-huan

    2014-01-17

    A new rare earth metal and samarium-catalyzed C(sp(3))-H bond activation is reported in which 2-alkylazaarenes and propargylic alcohols were converted to indolizines. This process operates under mild conditions and solvent-free conditions. A broad scope of coupling partners has been established, and a likely mechanism has also been suggested. PMID:24359214

  11. Lanthanum chloride impairs spatial memory through ERK/MSK1 signaling pathway of hippocampus in rats.

    PubMed

    Liu, Huiying; Yang, Jinghua; Liu, Qiufang; Jin, Cuihong; Wu, Shengwen; Lu, Xiaobo; Zheng, Linlin; Xi, Qi; Cai, Yuan

    2014-12-01

    Rare earth elements (REEs) are used in many fields for their diverse physical and chemical properties. Surveys have shown that REEs can impair learning and memory in children and cause neurobehavioral defects in animals. However, the mechanism underlying these impairments has not yet been completely elucidated. Lanthanum (La) is often selected to study the effects of REEs. The aim of this study was to investigate the spatial memory impairments induced by lanthanum chloride (LaCl3) and the probable underlying mechanism. Wistar rats were exposed to LaCl3 in drinking water at 0 % (control, 0 mM), 0.25 % (18 mM), 0.50 % (36 mM), and 1.00 % (72 mM) from birth to 2 months after weaning. LaCl3 considerably impaired the spatial learning and memory of rats in the Morris water maze test, damaged the synaptic ultrastructure and downregulated the expression of p-MEK1/2, p-ERK1/2, p-MSK1, p-CREB, c-FOS and BDNF in the hippocampus. These results indicate that LaCl3 exposure impairs the spatial learning and memory of rats, which may be attributed to disruption of the synaptic ultrastructure and inhibition of the ERK/MSK1 signaling pathway in the hippocampus. PMID:25316495

  12. Solution processed lanthanum aluminate gate dielectrics for use in metal oxide-based thin film transistors

    SciTech Connect

    Esro, M.; Adamopoulos, G.; Mazzocco, R.; Kolosov, O.; Krier, A.; Vourlias, G.; Milne, W. I.

    2015-05-18

    We report on ZnO-based thin-film transistors (TFTs) employing lanthanum aluminate gate dielectrics (La{sub x}Al{sub 1−x}O{sub y}) grown by spray pyrolysis in ambient atmosphere at 440 °C. The structural, electronic, optical, morphological, and electrical properties of the La{sub x}Al{sub 1−x}O{sub y} films and devices as a function of the lanthanum to aluminium atomic ratio were investigated using a wide range of characterization techniques such as UV-visible absorption spectroscopy, impedance spectroscopy, spectroscopic ellipsometry, atomic force microscopy, x-ray diffraction, and field-effect measurements. As-deposited LaAlO{sub y} dielectrics exhibit a wide band gap (∼6.18 eV), high dielectric constant (k ∼ 16), low roughness (∼1.9 nm), and very low leakage currents (<3 nA/cm{sup 2}). TFTs employing solution processed LaAlO{sub y} gate dielectrics and ZnO semiconducting channels exhibit excellent electron transport characteristics with hysteresis-free operation, low operation voltages (∼10 V), high on/off current modulation ratio of >10{sup 6}, subthreshold swing of ∼650 mV dec{sup −1}, and electron mobility of ∼12 cm{sup 2} V{sup −1} s{sup −1}.

  13. Aquatic ecotoxicity of lanthanum - A review and an attempt to derive water and sediment quality criteria.

    PubMed

    Herrmann, Henning; Nolde, Jürgen; Berger, Svend; Heise, Susanne

    2016-02-01

    Rare earth elements (REE) used to be taken as tracers of geological origin for fluvial transport. Nowadays their increased applications in innovative environmental-friendly technology (e.g. in catalysts, superconductors, lasers, batteries) and medical applications (e.g. MRI contrast agent) lead to man-made, elevated levels in the environment. So far, no regulatory thresholds for REE concentrations and emissions to the environment have been set because information on risks from REE is scarce. However, evidence gathers that REE have to be acknowledged as new, emerging contaminants with manifold ways of entry into the environment, e.g. through waste water from hospitals or through industrial effluents. This paper reviews existing information on bioaccumulation and ecotoxicity of lanthanum in the aquatic environment. Lanthanum is of specific interest as one of the major lanthanides in industrial effluents. This review focuses on the freshwater and the marine environment, and tackles the water column and sediments. From these data, methods to derive quality criteria for sediment and water are discussed and preliminary suggestions are made. PMID:26528910

  14. Biodiesel production by free fatty acid esterification using Lanthanum (La3+) and HZSM-5 based catalysts.

    PubMed

    Vieira, Sara S; Magriotis, Zuy M; Santos, Nadiene A V; Saczk, Adelir A; Hori, Carla E; Arroyo, Pedro A

    2013-04-01

    In this work the use of the heterogeneous catalysts pure (LO) and sulfated (SLO) lanthanum oxide, pure HZSM-5 and SLO/HZSM-5 (HZSM-5 impregnated with sulfated lanthanum oxide (SO4(2-)/La2O3)) was evaluated. The structural characterization of the materials (BET) showed that the sulfation process led to a reduction of the SLO and SLO/HZSM-5 surface area values. FTIR showed bands characteristic of the materials and, FTIR-pyridine indicated the presence of strong Brønsted sites on the sulfated material. In the catalytic tests the temperature was the parameter that most influenced the reactions. The best reaction conditions were: 10% catalyst, 100°C temperature and 1:5 m(OA)/m(meOH) for LO, SLO, SLO/HZSM-5 and 10% catalyst, 100°C temperature and 1:20 m(OA)/m(meOH) for HZSM-5. Under these conditions the conversions were: 67% and 96%, for LO and SLO, respectively and 80% and 100%, for HZSM-5 and SLO/HZSM-5, respectively. All catalysts deactivated after the first use, but the deactivation of SLO/HZSM-5 was smaller. PMID:23428822

  15. A polynuclear coordination glutarate of lanthanum(III) with an uncommon cage feature.

    PubMed

    Benmerad, Belkacem; Guehria-Laïdoudi, Acoura; Dahaoui, Slimane; Lecomte, Claude

    2004-03-01

    The title compound, triaquatris(glutarato)dilanthanum(III) dihydrate, [[La2(C5H6O4)3(H2O)3] x 2H2O]n, is the first reported glutarate coordination polymer of lanthanum(III) without a protonated ligand. The noteworthy features in the structure are, firstly, the unusual binuclear lanthanum cage formed by three bridging bonds through O atoms involved in different coordination modes and, secondly, the very rare 'malonate' mode exhibited by a dicarboxylate ligand with an alkyl chain of five C atoms. To our knowledge, this eta7 chelation for the glutarate ligand has not been reported and was thought to be forbidden for steric reasons. The gauche-gauche conformation of the corresponding ligand favours cage formation, but trans geometries created along the ligating O atoms prevent cluster packing. The two independent La atoms are nine- and tenfold coordinated, leading to distorted one-face-sharing LaO7(H2O)2 and LaO9(H2O) polyhedra, respectively. In the three-dimensional framework, these asymmetric subunits are linked in a zigzag manner via one-edge-sharing LaO9(H2O) polyhedra and are connected by the carbon backbone chains of the ligands. The structure is very compact and, unlike many other reported dicarboxylate lanthanides, connectivity between the two metal atoms and the three ligands yields a crystal packing with cavities accommodating two guest water molecules but without an open framework. PMID:15004362

  16. Chemically produced nanostructured ODS-lanthanum oxide-tungsten composites sintered by spark plasma

    NASA Astrophysics Data System (ADS)

    Yar, Mazher Ahmed; Wahlberg, Sverker; Bergqvist, Hans; Salem, Hanadi G.; Johnsson, Mats; Muhammed, Mamoun

    2011-01-01

    High purity W and W-0.9La 2O 3 (wt.%) nanopowders were produced by a wet chemical route. The precursor was prepared by the reaction of ammonium paratungstate (APT) with lanthanum salt in aqueous solutions. High resolution electron microscopy investigations revealed that the tungstate particles were coated with oxide precipitates. The precursor powder was reduced to tungsten metal with dispersed lanthanum oxide. Powders were consolidated by spark plasma sintering (SPS) at 1300 and 1400 °C to suppress grain growth during sintering. The final grain size relates to the SPS conditions, i.e. temperature and heating rate, regardless of the starting powder particle size. Scanning electron microscopy revealed that oxide phases were mainly accumulated at grain boundaries while the tungsten matrix constituted of nanosized sub-grains. The transmission electron microscopy revealed that the tungsten grains consist of micron-scale grains and finer sub-grains. EDX analysis confirmed the presence of W in dispersed oxide phases with varying chemical composition, which evidenced the presence of complex oxide phases (W-O-La) in the sintered metals.

  17. Preconcentration of some metal ions with lanthanum-8-hydroxyquinoline co-precipitation system.

    PubMed

    Feist, Barbara; Mikula, Barbara

    2014-03-15

    A method of separation and preconcentration of cadmium, copper, nickel, lead and zinc at trace level using 8-hydroxyquinoline as a chelating agent and lanthanum(III) as a carrier element is proposed. The heavy metals were determined after preconcentration by inductively coupled plasma optical emission spectrometry (ICP-OES). The results were compared with those obtained using flame atomic absorption spectrometry (F-AAS). The influence of several parameters such as pH, amount of lanthanum(III) as a carrier element, amount of 8-hydroxyquinoline, duration of co-precipitation was examined. Moreover, effects of inorganic matrix on recovery of the determined elements were studied. The detection limits (DL) for ICP-OES were 0.31, 2.9, 1.4, 3.2 and 1.2 μg L(-1) for Cd, Cu, Ni, Pb and Zn, respectively, whereas for F-AAS DL were 0.63, 1.1, 3.2, 2.7 and 0.74 μg L(-1). The recovery of the method for the determined elements was better than 94% with relative standard deviation between 0.63% and 2.9%. The preconcentration factor was 60. The proposed method was successfully applied for determination of Cd, Cu, Ni, Pb, and Zn in plant materials. Accuracy of the proposed method was verified using certified reference material (NCS ZC85006 Tomato). PMID:24206710

  18. Syntheses, Characterization, Thermal, and Antimicrobial Studies of Lanthanum(III) Tolyl/Benzyldithiocarbonates

    PubMed Central

    Andotra, Savit; Kalgotra, Nidhi; Pandey, Sushil K.

    2014-01-01

    Lanthanum(III) tris(O-tolyl/benzyldithiocarbonates), [La(ROCS2)] (R = o-, m-, p-CH3C6H4 and C6H5CH2), were isolated as yellow solid by the reaction of LaCl3·7H2O with sodium salt of tolyl/benzyldithiocarbonates, ROCS2Na (R = o-, m-, p-CH3C6H4 and C6H5CH2), in methanol under anhydrous conditions in 1 : 3 molar ratio. These complexes have formed adducts with nitrogen and phosphorus donor molecules by straightforward reaction of these complexes with donor ligands, which have the composition of the type [La(ROCS2)3·nL] (where n = 2, L = NC5H5 or P(C6H5)3 and n = 1, L = N2C12H8 or N2C10H8). Elemental analyses, mass, IR, TGA, and heteronuclear NMR (1H, 13C and 31P) spectroscopic studies indicated bidentate mode of bonding by dithiocarbonate ligands leading to hexacoordinated and octacoordinated geometry around the lanthanum atom. Antimicrobial (antifungal and antibacterial) activity of the free ligands and some of the complexes have also been investigated which exhibited significantly more activity for the complexes than the free ligands. PMID:24817836

  19. Solution processed lanthanum aluminate gate dielectrics for use in metal oxide-based thin film transistors

    NASA Astrophysics Data System (ADS)

    Esro, M.; Mazzocco, R.; Vourlias, G.; Kolosov, O.; Krier, A.; Milne, W. I.; Adamopoulos, G.

    2015-05-01

    We report on ZnO-based thin-film transistors (TFTs) employing lanthanum aluminate gate dielectrics (LaxAl1-xOy) grown by spray pyrolysis in ambient atmosphere at 440 °C. The structural, electronic, optical, morphological, and electrical properties of the LaxAl1-xOy films and devices as a function of the lanthanum to aluminium atomic ratio were investigated using a wide range of characterization techniques such as UV-visible absorption spectroscopy, impedance spectroscopy, spectroscopic ellipsometry, atomic force microscopy, x-ray diffraction, and field-effect measurements. As-deposited LaAlOy dielectrics exhibit a wide band gap (˜6.18 eV), high dielectric constant (k ˜ 16), low roughness (˜1.9 nm), and very low leakage currents (<3 nA/cm2). TFTs employing solution processed LaAlOy gate dielectrics and ZnO semiconducting channels exhibit excellent electron transport characteristics with hysteresis-free operation, low operation voltages (˜10 V), high on/off current modulation ratio of >106, subthreshold swing of ˜650 mV dec-1, and electron mobility of ˜12 cm2 V-1 s-1.

  20. Synthesis and physico-chemical studies on neodymium(III) and samarium(III) complexes with tetraaza macrocyclic ligands

    SciTech Connect

    Goel, S.; Pandey, U.K.; Pandey, O.P.; Sengupta, S.K.

    1988-05-01

    Reactions of neodymium trichloride and samarium trichloride with 6,7,13,14-R/sub 4/ - 3,10-X/sub 2/-(14)-5,7,12,14-tetraene-1,5,8,12-N/sub 4/-(2,4,9,11-N/sub 4/) (R = CH/sub 3/, X = 0 (L/sub 1//sup (1)/); R = C/sub 6/H/sub 5/, X = O (L/sub 1//sup (2)/); R = CH/sub 3/, X = S(L/sub 2//sup (1)/)) and R = C/sub 6/H/sub 5/, X = S(/sub 2//sup (2)/)) have been studied in ethanol and complexes of the type (M(L/sub 1//sup (1)/ or L/sub 1//sup (2)/))Cl/sub 3/ and (M(L/sub 2//sup (1)/ or L/sub 2//sup (2)/)(H/sub 2/O)/sub 2/)Cl/sub 3/ (M = Nd(III) and Sm(III)) have been isolated. In addition, macrocyclic complexes of Nd(III) and Sm(III) with another series of tetraaza ligands, viz, 5,6,11,12-R/sub 4/-3,8-X/sub 2/-(12)-4,6,10,12-tetraene-1,4,7,10-N/sub 4/-(2,9-N/sub 2/) (R = CH/sub 3/, X = O (L/sub 3//sup (1)/); R = C/sub 6/H/sub 5/, X = O(L/sub 3//sup (2)/); R = CH/sub 3/, X = S(L/sub 4//sup (1)/); R = C/sub 6/H/sub 5/, X = S(L/sub 4//sup (2)/)), formulated as (M(L/sub 3//sup (1)/, L/sub 3//sup (2)/, L/sub 4//sup (1)/ or L/sub 4//sup (2)/)(H/sub 2/O)/sub 2/)Cl/sub 3/ (M = Nd(III) and Sm(III)) have been prepared by template condensation of Nd(III) and Sm(III) complexes of diacetylbis(semicarbazonethiosemicarbazone) or benzilibis(semicarbazonethiosemicarbazone) with diacetyl or benzil. The complexes have been identified by elemental analysis, electrical conductance, spectral and thermal measurements.

  1. The Level of Europium-154 Contaminating Samarium-153-EDTMP Activates the Radiation Alarm System at the US Homeland Security Checkpoints.

    PubMed

    Najeeb Al Hallak, Mohammed; McCurdy, Matt; Zouain, Nicolas; Hayes, Justin

    2009-01-01

    (153)Sm-EDTMP is a radiopharmaceutical composed of EDTMP (ethylenediamine-tetramethylenephosphonate) and Samarium-153 [1]. (153)Sm-EDTMP has an affinity for skeletal tissue and concentrates in areas with increased bone turnover; thus, it is successfully used in relieving pain related to diffuse bone metastases [1]. The manufacturing process of (153)Sm-EDTMP leads to contamination with (154)Eu (Europium-154) [2]. A previous study only alluded to the retention of (154)Eu in the bones after receiving treatment with (153)Sm-EDTMP [2]. Activation of the alarm at security checkpoints after (153)Sm-EDTMP therapy has not been previously reported. Two out of 15 patients who received (153)Sm-EDTMP at Roger Maris Cancer Center (Fargo, N. Dak., USA) activated the radiation activity sensors while passing through checkpoints; one at a US airport and the other while crossing the American-Canadian border. We assume that the (154)Eu which remained in the patients' bones activated the sensors. METHODS: In order to investigate this hypothesis, we obtained the consent from 3 of our 15 patients who received (153)Sm-EDTMP within the previous 4 months to 2 years, including the patient who had activated the radiation alarm at the airport. The patients were scanned with a handheld detector and a gamma camera for energies from 511 keV to 1.3 MeV. RESULTS: All three patients exhibited identical spectral images, and further analysis showed that the observed spectra are the result of (154)Eu emissions. CONCLUSION: Depending on the detection thresholds and windows used by local and federal authorities, the remaining activity of (154)Eu retained in patients who received (153)Sm-EDTMP could be sufficient enough to increase the count rates above background levels and activate the sensors. At Roger Maris Cancer Center, patients are now informed of the potential consequences of (153)Sm-EDTMP therapy prior to initiating treatment. In addition, patients treated with (153)Sm-EDTMP at Roger Maris Cancer Center receive laminated cards stating the date and the dose of treatment, as well as a statement that the holder may activate the alarm at the security checkpoints. PMID:20740180

  2. [Interdisciplinary strategies versus doping].

    PubMed

    Vitzthum, Karin; Mache, Stefanie; Quarcoo, David; Groneberg, David A; Schöffel, Norman

    2010-06-01

    Doping is a phenomenon which in the past years through the various incidences in professional cycling has come more and more into the focus of the public interest. Whilst in the young past the problems were to define the term "doping" exactly, today's problem is to prevent adolescents and children of doping. This shall be achieved by carrying out controls and serious sanctions for doping violations. Scientific research proved that doping usage can be avoided by broad specific prevention measures. In general, the earlier the athletes dope the higher the risk to become addicted later on in life to other legal or illegal drugs. The aim of this review is to analyse the prevalence of doping regarding youth-, competitive-, high performance and recreational sports and to examine further aspects of doping abuse, risks of addiction, the legal situation, current strategies in the fight against doping and to enhance chances of further doping prevention opportunities. By means of this data an all-embracing view should be given over the current situation, problems and prospects in German-speaking countries. PMID:20552290

  3. Enhancement of thermal shock resistance of reaction sintered mullite–zirconia composites in the presence of lanthanum oxide

    SciTech Connect

    Kumar, P.; Nath, M.; Ghosh, A.; Tripathi, H.S.

    2015-03-15

    Mullite–zirconia composites containing 20 wt.% zirconia were prepared by reaction sintering of zircon flour, sillimanite beach sand and calcined alumina. 0 to 8 mol% of La{sub 2}O{sub 3} with respect to zirconia was used as sintering aid. The effect of additive on the various physical, microstructures, mechanical and thermo-mechanical properties was studied. Quantitative phase analysis shows the change in tetragonal zirconia content with incorporation of lanthanum oxide. La{sub 2}O{sub 3} addition has significantly improved the thermal shock resistance of the samples. Samples without additive retained only 20% of initial flexural strength after 5 cycles, whereas samples containing 5 mol% La{sub 2}O{sub 3} retained almost 78% of its initial flexural strength even after 15 thermal shock cycles. - Highlights: • Mullite–zirconia composites were prepared by reaction sintering route utilizing zircon and sillimanite beach sand. • Lanthanum oxide was used as sintering aid. • The presence of lanthanum oxide decreased the densification temperature. • Lanthanum oxide significantly improved the thermal shock resistance of the composites.

  4. Vascular permeability of spinal nerve roots. A study in the rat with Evans blue and lanthanum as tracers.

    PubMed

    Pettersson, C A; Sharma, H S; Olsson, Y

    1990-01-01

    The permeability of blood vessels in rat spinal nerve roots was investigated with Evans blue-albumin as an in vivo macromolecular tracer and lanthanum nitrate as an electron microscopic ionic marker added to a fixative. Rats injected intravenously with Evans blue, showed macroscopic distinct staining of dorsal root ganglia, whereas spinal nerve roots remained unstained. Fluorescence microscopy, however, revealed clear extravascular fluorescence both in ventral and dorsal roots 2 or 18 h after tracer administration. Two different types of blood vessels exists in spinal nerve roots; large extrinsic (radicular) in the root sheath and minute intrinsic vessels in the parenchyma. Lanthanum added to a fixative, perfused through the vessels was detected in the lumen of both types of vessels, usually adhering to the luminal plasma membrane and in many invaginations from that membrane. Lanthanum also entered the clefts between endothelial cells but was always stopped at the junctions which are, thus, of the tight type. Diffuse penetration of the compound into the cytoplasm was seen in one endothelial cell, but no fenestrations were detected. Junctions between the endothelial cells of vessels in rat spinal nerve roots are impermeable to lanthanum and most likely also to other large molecular substances like albumin. Thus, probable routes for serum albumin to enter the nerve roots, where it normally is present, must be either by centripetal extracellular diffusion from the ganglia and the peripheral nerve or by vascular leakage in the roots, caused by for instance pinocytosis across endothelial cells. PMID:2082654

  5. Lake responses following lanthanum-modified bentonite clay (Phoslock®) application: an analysis of water column lanthanum data from 16 case study lakes.

    PubMed

    Spears, Bryan M; Lürling, Miquel; Yasseri, Said; Castro-Castellon, Ana T; Gibbs, Max; Meis, Sebastian; McDonald, Claire; McIntosh, John; Sleep, Darren; Van Oosterhout, Frank

    2013-10-01

    Phoslock(®) is a lanthanum (La) modified bentonite clay that is being increasingly used as a geo-engineering tool for the control of legacy phosphorus (P) release from lake bed sediments to overlying waters. This study investigates the potential for negative ecological impacts from elevated La concentrations associated with the use of Phoslock(®) across 16 case study lakes. Impact-recovery trajectories associated with total lanthanum (TLa) and filterable La (FLa) concentrations in surface and bottom waters were quantified over a period of up to 60 months following Phoslock(®) application. Both surface and bottom water TLa and FLa concentrations were <0.001 mg L(-1) in all lakes prior to the application of Phoslock(®). The effects of Phoslock(®) application were evident in the post-application maximum TLa and FLa concentrations reported for surface waters between 0.026 mg L(-1)-2.30 mg L(-1) and 0.002 mg L(-1) to 0.14 mg L(-1), respectively. Results of generalised additive modelling indicated that recovery trajectories for TLa and FLa in surface and bottom waters in lakes were represented by 2nd order decay relationships, with time, and that recovery reached an end-point between 3 and 12 months post-application. Recovery in bottom water was slower (11-12 months) than surface waters (3-8 months), most probably as a result of variation in physicochemical conditions of the receiving waters and associated effects on product settling rates and processes relating to the disturbance of bed sediments. CHEAQS PRO modelling was also undertaken on 11 of the treated lakes in order to predict concentrations of La(3+) ions and the potential for negative ecological impacts. This modelling indicated that the concentrations of La(3+) ions will be very low (<0.0004 mg L(-1)) in lakes of moderately low to high alkalinity (>0.8 mEq L(-1)), but higher (up to 0.12 mg L(-1)) in lakes characterised by very low alkalinity. The effects of elevated La(3+) concentrations following Phoslock(®) applications in lakes of very low alkalinity requires further evaluation. The implications for the use of Phoslock(®) in eutrophication management are discussed. PMID:23911225

  6. Sol-gel-derived hybrid materials multi-doped with rare-earth metal ions

    NASA Astrophysics Data System (ADS)

    Zelazowska, E.; Rysiakiewicz-Pasek, E.; Borczuch-Laczka, M.; Cholewa-Kowalska, K.

    2012-06-01

    Four different hybrid organic-inorganic materials based on TiO2-SiO2 matrices with organic additives and doped with rare-earth metal ions (III) from the group of europium, cerium, terbium, neodymium, dysprosium and samarium, were synthesized by sol-gel method. Tetraethyl orthosilicate, titanium (IV) isopropoxide and organic compounds, such as butyl acrylate, butyl methacrylate, ethyl acetoacetate, ethylene glycol dimethacrylate, ethyl acetate, propylene carbonate, organic solvents and certain inorganic salts were used in the synthesis. The inorganic part of the sols, which were used in the synthesis of all the hybrid materials, was prepared separately and then the organic parts were added. The materials obtained were aged for three weeks at room temperature and then heated in an electric oven for three hours at temperatures of 80 °C-150 °C. Scanning electron microscopy equipped with energy dispersive X-ray spectroscopy (SEM/EDX); X-ray diffraction (XRD); Fourier transform infrared spectroscopy (KBr technique); 29Si magic-angle spinning nuclear magnetic resonance; and fluorescence spectroscopy were used for the examination of morphology, microstructure and luminescence properties, respectively. Photoluminescence properties with relatively intense narrow emission lines of Tb, Eu, Dy, Nd, Sm respectively to the RE-ions doping, were observed for all the hybrid materials.

  7. Visible light emission and energy transfer processes in Sm-doped nitride films

    SciTech Connect

    Zanatta, A. R.

    2012-06-15

    Even though the great interest in studying the near-infrared light emission due to Er{sup 3+} ions for telecommunication purposes, efficient visible radiation can be achieved from many different rare-earth (RE) ions. In fact, visible and/or near-infrared light emission takes place in RE-doped wide bandgap semiconductors following either photon or electron excitation, suggesting their technological potential in devices such as light-emitting diodes (LED's) and flat-panel displays, for example. Taking into consideration these aspects, the present contribution reports on the investigation of AlN, BeN, GeN, and SiN thin films doped with samarium. The samples were prepared by sputtering and as a result of the deposition method and conditions they present an amorphous structure and Sm concentrations in the low 0.5 at. %. After deposition, the samples were submitted to thermal annealing treatments and investigated by different spectroscopic techniques. A detailed examination of the experimental data allowed to identify optical transitions due to Sm{sup 3+} and Sm{sup 2+} ions as well as differences in their mechanisms of photon excitation and recombination. Moreover, it is shown that the Sm-related spectral features and emission intensity are susceptible, respectively, to the atomic environment the Sm{sup 3+}/Sm{sup 2+} ions experience and to the presence of non-radiative recombination centers.

  8. The Anti-Doping Movement.

    PubMed

    Willick, Stuart E; Miller, Geoffrey D; Eichner, Daniel

    2016-03-01

    Historical reports of doping in sports date as far back as the ancient Greek Olympic Games. The anti-doping community considers doping in sports to be cheating and a violation of the spirit of sport. During the past century, there has been an increasing awareness of the extent of doping in sports and the health risks of doping. In response, the anti-doping movement has endeavored to educate athletes and others about the health risks of doping and promote a level playing field. Doping control is now undertaken in most countries around the world and at most elite sports competitions. As athletes have found new ways to dope, however, the anti-doping community has endeavored to strengthen its educational and deterrence efforts. It is incumbent upon sports medicine professionals to understand the health risks of doping and all doping control processes. PMID:26972261

  9. Influence of La doping on structural and dielectric properties of SrBi{sub 2}Nb{sub 2}O{sub 9} ceramics

    SciTech Connect

    Verma, Maya; Sreenivas, K.; Gupta, Vinay

    2009-01-15

    Lanthanum doped SrBi{sub 2}Nb{sub 2}O{sub 9} ceramics with the chemical formula SrBi{sub 2-x}La{sub x}Nb{sub 2}O{sub 9} (SBLN) (x=0-0.5) have been prepared through conventional solid state route. X-ray diffraction reveals the shrinkage of unit cell of strontium bismuth niobate with incorporation of La{sup 3+} dopant, having no lone pair electrons. Shifting of Raman phonon modes indicates the reduced rattling space of NbO{sub 6} octahedra with increase in La doping concentration. Further, the softening of lowest frequency phonon mode with increasing x in SBLN shows the transition from ferroelectric to paraelectric at room temperature. The dielectric properties for all the compositions are studied as a function of temperature (25 to 500 deg. C) over the frequency range of 10 kHz-1 MHz. With increase in lanthanum doping concentration the phase transition becomes diffused and transition temperature gets shifted toward lower temperature. A phase transition from normal ferroelectric to paraelectric has been observed via relaxor-type ferroelectrics with increase in x. The frequency dependence of transition temperature was studied in terms of Vogel-Fulcher relation for SBLN (x=0.4)

  10. Effects of lanthanum carbonate on vascular calcification in elderly maintenance hemodialysis patients.

    PubMed

    Wang, Xiao-Hui; Zhang, Xin; Mu, Chang-Jun; He, Yong; Peng, Qing-Ping; Yang, Guo-Sheng; Li, Ming-Mei; Liu, Duan; Li, Jing; Ding, Guo-Hua

    2015-08-01

    The effect of lanthanum carbonate on abdominal aortic calcification (AAC) in the elderly maintenance hemodialysis (MHD) patients was investigated. Fifty-four cases subjected to routine MHD complicated with skin pruritus admitted to our hospital were selected and randomly divided into case group (n=28) and control group (n=26). The control group was given routine MHD alone. The case group was given lanthanum carbonate additionally on the basis of routine MHD. The changes of itching degrees at first and third month, and serum calcium, phosphorus, calcium-phosphorus products, intact parathyroid hormone (iPTH) levels and AAC scores at third month after treatments were compared between the two groups. The correlation between calcium-phosphorus products and AAC scores was also analyzed. There was no significant difference in the baseline of blood urea nitrogen (BUN), serum creatinine (Scr), uric acid, albumin, hemoglobin, C reactive protein (CRP), low density lipoprotein (LDL), high density lipoprotein (HDL), triglyceride, total cholesterol between case group and control group (P>0.05 for all). There was also no significant difference in the baseline itching scores between the case group and the control group (P>0.05). At 1st and 3rd month after treatment, the itching scores in the case group were 14.2 ± 3.2 and 10.5 ± 2.3, respectively, which were significantly lower than the baseline and those in the control group (P<0.05 for all). At 1st and 3rd month after treatment, the itching scores in the control group were 23.6 ± 5.9 and 24.8 ± 6.3, respectively, which were significantly higher than the baseline (P<0.05). There was no significant difference in the baseline of serum calcium, phosphorus, calcium-phosphorus products, iPTH levels between the case group and control group (P>0.05). At 3rd month after treatment, serum phosphorus, calcium-phosphorus products and iPTH levels in the case group were decreased significantly as compared with the baseline (P<0.05), and the serum calcium, phosphorus, calcium-phosphorus products, and iPTH levels were statistically decreased as compared with those in the control group (P<0.05). The AAC scores showed statistically significant difference between the case group and the control group (P<0.05). The serum phosphorus and AAC scores showed a positive correlation in both two groups. It was suggested that the administration of lanthanum carbonate in the elderly MHD patients can effectively relieve itching, and simultaneously reduce serum phosphorus and iPTH levels, resulting in the attenuation of vascular calcification. PMID:26223918

  11. Trap State Introduction versus Band Gap Narrowing in Nitrogen-Doped La2Ti2O7

    NASA Astrophysics Data System (ADS)

    Yost, Brandon; Cushing, Scott; Wu, Nianqiang; Bristow, Alan

    2015-03-01

    Nitrogen doping was reported to extend lanthanum dititanate's (LTO), La2Ti2O7, absorption from 380 nm to 500 nm by narrowing the band gap without introducing trap states. N-LTO holds promise for solar water splitting if, unlike in N-doped TiO2, spectral coverage can be increased without decreasing carrier lifetimes and decrementing the overall performance. Therefore, in this presentation, the effect of N-doping on LTO is confirmed using transient absorption spectroscopy with a supercontinuum and THz probe. The supercontinuum probe reveals carrier evolution in both band edge and mid-gap defect states. By exciting above and below the band edge, the influence of N-doping on the density of trap states is directly compared to the band edge position. Further, comparison of dynamics measured with the supercontinuum and THz probes reveals which changes in lifetime correspond to increased mobility or increased trapping, showing how the shifted band edge modifies carrier dynamics, and that N-doping in LTO is an efficient strategy for solar energy harvesting.

  12. First-principles calculation on oxygen ion migration in alkaline-earth doped La2GeO5.

    PubMed

    Linh, Tran Phan Thuy; Sakaue, Mamoru; Meñez Aspera, Susan; Alaydrus, Musa; Wungu, Triati Dewi Kencana; Linh, Nguyen Hoang; Kasai, Hideaki; Mohri, Takahiro; Ishihara, Tatsumi

    2014-06-25

    By using first-principles calculations based on the density functional theory, we investigated the doping effects of alkaline-earth metals (Ba, Sr and Ca) in monoclinic lanthanum germanate La2GeO5 on its oxygen ion conduction. Although the lattice parameters of the doped systems changed due to the ionic radii mismatch, the crystal structures remained monoclinic. The contribution of each atomic orbital to electronic densities of states was evaluated from the partial densities of states and partial charge densities. It was confirmed that the materials behaved as ionic crystals comprising of cations of La and dopants and anions of oxygen and covalently formed GeO4. The doping effect on the activation barrier for oxygen hopping to the most stable oxygen vacancy site was investigated by the climbing-image nudged elastic band method. By tracing the charge density change during the hopping, it was confirmed that the oxygen motion is governed by covalent interactions. The obtained activation barriers showed excellent quantitative agreements with an experiment for the Ca- and Sr-doped systems in low temperatures as well as the qualitative trend, including the Ba-doped system. PMID:24888249

  13. High pressure phase transition in samarium monochalcogenides SmX (X = S, Se, Te) and their alloy SmS1-xSex

    NASA Astrophysics Data System (ADS)

    Dubey, Ritu; Singh, Sadhna

    2013-11-01

    Phase transition pressures, relative volume changes, elastic and thermophysical properties of Samarium monochalcogenides SmX (X = S, Se, Te) have been studied. An improved interaction potential model has been developed which includes Coulomb, three-body interaction, polarizability effect and overlap repulsive interaction operative up to second neighbor ions. In addition, we have investigated the phase transition pressure and associated volume collapse in SmS1-xSex alloy (0 ⩽ x ⩽ 1) which shows transition from discontinuous to continuous as x is reduces. The present results are in general in good agreement with experimental data available for the end point members (x = 0 and x = 1). The results for the alloy counter parts are also in fair agreement with experimental data generated from the vegard's law.

  14. Ultimate intrinsic-coercivity samarium-cobalt magnet: An Earth-based feasibility study for space-shuttle missions. [containerless melts

    NASA Technical Reports Server (NTRS)

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

    1980-01-01

    Techniques for containerless melting and solidification of the samarium-cobalt alloy without excessive oxidation were developed. The rationale for extending these experiments in a weightless environment is also discussed. The effect of oxygen content from 0.15 to 0.63 weight percent and grain size in the range of 2 to 10 micrometers has been examined on arc-plasma-sprayed SmCo5 magnets. Contrary to expectations, the larger grain sizes tended to improve the coercivities. This was attributed to an increase in homogeneity resulting from higher temperature treatments used to produce larger grain size. No significant differences in coercivity were observed on the basis of oxygen content in the range examined. It is expected that more meaningful data on the relationship between oxygen content and coercivity will be seen when the oxygen content can be lowered to less than 0.1 weight percent.

  15. The use of 185 MBq and 740 MBq of 153-samarium hydroxyapatite for knee synovectomy in haemophilia

    PubMed Central

    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

    2014-01-01

    The penetration of beta energy of 153-samarium (153Sm) (0.8 MeV) 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 185 MBq and 740 MBq of 153-samarium hydroxyapatite (153Sm-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 185 MBq of 153Sm-HA, average age 23 years; B – 17 patients (19 knees) with 740 MBq of 153Sm-HA, average age 21.3 years. The evaluation before and after 1 year 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 740 MBq of 153Sm-HA; the less penetration of its beta radiation was compensated by the increased biological effect with the higher used activity. PMID:24330418

  16. Writing of nonlinear optical Sm{sub 2}(MoO{sub 4}){sub 3} crystal lines at the surface of glass by samarium atom heat processing

    SciTech Connect

    Abe, M.; Benino, Y.; Fujiwara, T.; Komatsu, T.; Sato, R.

    2005-06-15

    Some glasses such as 21.25Sm{sub 2}O{sub 3}.63.75MoO{sub 3}.15B{sub 2}O{sub 3} (mol %) giving the formation of nonlinear optical Sm{sub 2}(MoO{sub 4}){sub 3} crystals through conventional crystallization in an electric furnace and through continuous-wave Nd: yttrium aluminum garnet (YAG) laser (wavelength: 1064 nm) irradiation (samarium atom heat processing) have been developed. It is proposed from x-ray diffraction analyses, micro-Raman-scattering spectra, and second-harmonic generation measurements that the crystal structure of Sm{sub 2}(MoO{sub 4}){sub 3} formed by the crystallization is the {beta}{sup '}-phase structure with an orthorhombic (noncentrosymmetric) symmetry. The lines consisting of nonlinear optical {beta}{sup '}-Sm{sub 2}(MoO{sub 4}){sub 3} crystals are written at the surface of glasses by YAG laser irradiation (laser power: P=0.4 W, laser scanning speed: S=1-10 {mu}m/s), and, in particular, homogeneous crystal lines are formed at the laser scanning speed of 1 {mu}m/s. Refractive index changes (not crystallization) are also induced by YAG laser irradiation of P=0.4 W and a high laser scanning speed of S=25 {mu}m/s. The crystallization mechanism in the laser-irradiated region has been proposed. The present study demonstrates that the samarium atom heat processing is a technique for the writing of rare earth containing optical nonlinear/ferroelectric crystal lines in glass.

  17. Strong correlation in 1D oxygen-ion conduction of apatite-type lanthanum silicate.

    PubMed

    Imaizumi, Kouta; Toyoura, Kazuaki; Nakamura, Atsutomo; Matsunaga, Katsuyuki

    2015-09-16

    Oxygen-ion conduction in apatite-type lanthanum silicate, La9.33+0.67x (SiO4)6O2+x (x = 1), has theoretically been analyzed in a first-principles manner followed by the nudged elastic band method and the kinetic Monte Carlo method. Unlike the conventional cooperative interstitialcy mechanism along the single O4 columns, diffusing interstitial oxygen ions are frequently blocked by adjacent interstitial oxygen ions (Oint ions), leading to the strongly-correlated diffusivity and conductivity of oxygen ions in the case of chemical compositions with large x values. The getting-out mechanism from the O4 column is of importance in the long-range conduction, which temporarily transfers a part of Oint ions out of the columns to relax the blocking effect. The getting-out mechanism plays a key role also in the conduction perpendicular to the c axis (in the ab plane). PMID:26302221

  18. Toxicity of lanthanum oxide (La2O3) nanoparticles in aquatic environments.

    PubMed

    Balusamy, Brabu; Taştan, Burcu Ertit; Ergen, Seyda Fikirdesici; Uyar, Tamer; Tekinay, Turgay

    2015-07-01

    This study demonstrates the acute toxicity of lanthanum oxide nanoparticles (La2O3 NP) on two sentinel aquatic species, fresh-water microalgae Chlorella sp. and the crustacean Daphnia magna. The morphology, size and charge of the nanoparticles were systematically studied. The algal growth inhibition assay confirmed absence of toxic effects of La2O3 NP on Chlorella sp., even at higher concentration (1000 mg L(-1)) after 72 h exposure. Similarly, no significant toxic effects were observed on D. magna at concentrations of 250 mg L(-1) or less, and considerable toxic effects were noted in higher concentrations (effective concentration [EC50] 500 mg L(-1); lethal dose [LD50] 1000 mg L(-1)). In addition, attachment of La2O3 NP on aquatic species was demonstrated using microscopy analysis. This study proved to be beneficial in understanding acute toxicity in order to provide environmental protection as part of risk assessment strategies. PMID:26022751

  19. Velocity of sound and elastic properties of lanthanum gallo-germanate glasses

    NASA Astrophysics Data System (ADS)

    Hwa, Luu-Gen

    2005-03-01

    The velocity of sound of a group of lanthanum gallo-germanate glasses is obtained by the ultrasonic pulse-echo measurements, at room temperature. Both longitudinal and transverse velocities of these glasses are composition dependence. The experimental results are used to obtain the elastic constants. The correlation of elastic stiffness, the cross-link density, and the fractal bond connectivity of these glasses are discussed. The derived experimental values of Young's modulus, bulk modulus, shear modulus and Poisson's ratio for our glasses are compared with those theoretically calculated values in terms of the Makishima-Mackenzie model. A possible existence of both tetrahedral (four-fold coordination) and octahedral (six-fold coordination) of Ga and Ge in the structure of these glasses is discussed.

  20. High-current density, high-brightness electron beams from large-area lanthanum hexaboride cathodes

    NASA Astrophysics Data System (ADS)

    Loschialpo, P.; Kapetanakos, C. A.

    1988-04-01

    Large diameter lanthanum hexaboride (LaB6) cathodes operated at 10 kV have produced 1-5-microsec electron pulses with current density between 10 and 20 A/sq cm. Normalized beam brightness, approximately 300,000 A/sq cm sq rad has been consistently measured. To obtain this high-current density, the LaB6 cathodes have been heated to temperatures between about 1600 and 1800 C. Very uniform temperature profiles are obtained by applying a carefully tailored electron bombardment heating power distribution. These measurements have been made between pressure 10 to the -6th to -10 to the -5th Torr, i.e., under much less demanding vacuum conditions than that required by conventional dispenser-type cathodes.

  1. Effect of R(3+) ions on the structure and properties of lanthanum borate glasses

    NASA Technical Reports Server (NTRS)

    Chakraborty, I. N.; Day, D. E.

    1985-01-01

    The present investigation of glass formation in the (mole percent) systems 25La2O3 (x)R2O3 (75-x)B2O3, where R = Al, Ga, and (25-x)La2O3 (x)Ln2O3 75B2O3, where Ln = Gd, Er, Y, notes that up to 25 mol pct Al2O3 or Ga2O3 can be substituted for B2O3, while no more than about 5 mol pct Ln2O3, substituted for La2O3, caused macro-phase separation. The substitution of either R2O3 or Ln2O3 in the lanthanum borate system changes the separation distance between adjacent B3O6 chains. The effect of this structural change on the molar volume, transformation temperature, thermal expansion coefficient, and transformation-range viscosity is discussed.

  2. A Search for Bremsstrahlung From Preliminary Breakdown Using A Lanthanum Bromide Detector

    NASA Astrophysics Data System (ADS)

    Lundberg, J. L.; Millan, R. M.; Eack, K. B.

    2008-12-01

    The process of lightning initiation, called preliminary breakdown, is as of yet not properly understood. We present information on a detector system designed to provide more information on the process of preliminary breakdown by the observation of bremsstrahlung caused by lightning initiation. The detector system was deployed for a test campaign to South Baldy Peak in New Mexico on August 7, 2008. The detector system is composed of a 3x3 sodium iodide scintillator and a 1.5x1.5 lanthanum bromide scintillator. The output of these detectors was digitized to preserve maximum information about the observed x-rays, and GPS synched timing information was recorded. Preliminary results will be presented as well as plans for improvements on the system for a future run planned for the summer of 2009.

  3. Data for effects of lanthanum complex on the thermo-oxidative aging of natural rubber.

    PubMed

    Zheng, Wei; Liu, Li; Zhao, Xiuying; He, Jingwei; Wang, Ao; Chan, Tung W; Wu, Sizhu

    2015-12-01

    Novel mixed antioxidants composed of antioxidant IPPD and lanthanum (La) complex were added as a filler to form natural rubber (NR) composites. By mechanical testing, Fourier transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR) and thermogravimetric analysis (TGA), a string of data, including the mechanical properties, the variation of internal groups and the thermal and thermo-oxidative decompositions of NR, was presented in this data article. The data accompanying its research article [1] studied the thermo-oxidative aging properties of NR in detail. The density function theoretical (DFT) calculations were also used as an assistant to study the thermo-oxidative aging mechanism of NR. The data revealed that this new rare-earth antioxidant could indeed enhance the thermo-oxidative aging resistance of NR, which is associated with its different function mechanism from that of the pure antioxidant IPPD. PMID:26693513

  4. Data for effects of lanthanum complex on the thermo-oxidative aging of natural rubber

    PubMed Central

    Zheng, Wei; Liu, Li; Zhao, Xiuying; He, Jingwei; Wang, Ao; Chan, Tung W.; Wu, Sizhu

    2015-01-01

    Novel mixed antioxidants composed of antioxidant IPPD and lanthanum (La) complex were added as a filler to form natural rubber (NR) composites. By mechanical testing, Fourier transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR) and thermogravimetric analysis (TGA), a string of data, including the mechanical properties, the variation of internal groups and the thermal and thermo-oxidative decompositions of NR, was presented in this data article. The data accompanying its research article [1] studied the thermo-oxidative aging properties of NR in detail. The density function theoretical (DFT) calculations were also used as an assistant to study the thermo-oxidative aging mechanism of NR. The data revealed that this new rare-earth antioxidant could indeed enhance the thermo-oxidative aging resistance of NR, which is associated with its different function mechanism from that of the pure antioxidant IPPD. PMID:26693513

  5. Deposition of sol-gel derived lanthanum zirconate titanate thin films on copper substrates.

    SciTech Connect

    Narayanan, M.; Kwon, D. K.; Ma, B.; Balchandran, U.; Energy Systems

    2008-06-23

    Lead lanthanum zirconate titanate (PLZT) thin films were directly deposited on copper substrates by chemical solution deposition and crystallized at temperatures of {approx_equal} 650 C under low pO{sub 2} conditions. Although the crystallization conditions used are conducive for copper oxidation, a thin layer ({approx}115 nm) of PLZT was sufficient to protect the underlying copper from oxidation. Films exhibited well saturated hysteresis loops with remanent polarization {approx}24 {micro}C/cm{sup 2} and dielectric constants {approx}730. Indirect evidence suggests that the oxygen vacancies created during the high temperature processing are responsible for the degradation of the electrical properties of these thin films. Techniques for avoiding this problem are proposed.

  6. Ba11La4Br34: a new barium lanthanum bromide

    PubMed Central

    Eagleman, Yetta; Wu, Guang; Gundiah, Gautam; Bourret-Courchesne, Edith; Derenzo, Stephen

    2011-01-01

    The structure of the title compound, barium lanthanum bromide (11/4/34), can be derived from the fluorite structure. The asymmetric unit contains two Ba sites (one with site symmetry 4/m..), one La site (site symmetry 4..), one mixed-occupied Ba and La site (ratio 1:1, site symmetry m..) and six Br sites (one with site symmetry \\=4.., one with 2.., one with m.., the latter being disordered over two positions with a 0.86:0.14 ratio). The fundamental building units of the structure are edge-sharing polyhedral clusters made up of Ba and La bromide clusters inter­connected to BaBr8 square prisms and BaBr10 groups. PMID:22064368

  7. Recovery of zinc, cadmium, and lanthanum by biopolymer gel particles of alginic acid

    SciTech Connect

    Konishi, Yasuhiro; Asai, Satoru; Midoh, Yuji; Oku, Muneharu )

    1993-07-01

    Biopolymer gel particles of alginic acid were found to be a useful material for recovering zinc, cadmium, and lanthanum from aqueous solutions. The metals sorbed by the gel particles could be completely eluted by using dilute HCl solution of 0.1 kmol/m[sup 3]. The distribution ratios of the individual metals between the gel and liquid phases were measured by using a batch method. The equilibrium data were consistent with predictions made assuming that sorption takes place with the ion-exchange reaction between metal ions and alginic acid. The maximum sorption capacity of the gel particles and the distribution equilibrium constants for the metals were determined by comparing the experimental data with the theoretical predictions. The observed effect of temperature on the distribution equilibrium was insignificant in the range from 15 to 35[degrees]C. 17 refs., 6 figs., 1 tab.

  8. Photoemission spectroscopy study of the lanthanum lutetium oxide/silicon interface

    SciTech Connect

    Nichau, A.; Schnee, M.; Schubert, J.; Bernardy, P.; Hollaender, B.; Buca, D.; Mantl, S.; Besmehn, A.; Breuer, U.; Rubio-Zuazo, J.; Castro, G. R.; Muecklich, A.; Borany, J. von

    2013-04-21

    Rare earth oxides are promising candidates for future integration into nano-electronics. A key property of these oxides is their ability to form silicates in order to replace the interfacial layer in Si-based complementary metal-oxide field effect transistors. In this work a detailed study of lanthanum lutetium oxide based gate stacks is presented. Special attention is given to the silicate formation at temperatures typical for CMOS processing. The experimental analysis is based on hard x-ray photoemission spectroscopy complemented by standard laboratory experiments as Rutherford backscattering spectrometry and high-resolution transmission electron microscopy. Homogenously distributed La silicate and Lu silicate at the Si interface are proven to form already during gate oxide deposition. During the thermal treatment Si atoms diffuse through the oxide layer towards the TiN metal gate. This mechanism is identified to be promoted via Lu-O bonds, whereby the diffusion of La was found to be less important.

  9. Large area directly heated lanthanum hexaboride cathode structure having predetermined emission profile

    DOEpatents

    Leung, Ka-Ngo; Gordon, Keith C.; Kippenham, Dean O.; Purgalis, Peter; Moussa, David; Williams, Malcom D.; Wilde, Stephen B.; West, Mark W.

    1989-01-01

    A large area directly heated lanthanum hexaboride (LaB.sub.6) cathode system (10) is disclosed. The system comprises a LaB.sub.6 cathode element (11) generally circular in shape about a central axis. The cathode element (11) has a head (21) with an upper substantially planar emission surface (23), and a lower downwardly and an intermediate body portion (26) which diminishes in cross-section from the head (21) towards the base (22) of the cathode element (11). A central rod (14) is connected to the base (22) of the cathode element (11) and extends along the central axis. Plural upstanding spring fingers (37) are urged against an outer peripheral contact surface (24) of the head end (21) to provide a mechanical and electrical connection to the cathode element (11).

  10. Large area directly heated lanthanum hexaboride cathode structure having predetermined emission profile

    DOEpatents

    Leung, Ka-Ngo; Gordon, K.C.; Kippenhan, D.O.; Purgalis, P.; Moussa, D.; Williams, M.D.; Wilde, S.B.; West, M.W.

    1987-10-16

    A large area directly heated lanthanum hexaboride (LaB/sub 6/) cathode system is disclosed. The system comprises a LaB/sub 6/ cathode element generally circular in shape about a central axis. The cathode element has a head with an upper substantially planar emission surface, and a lower downwardly and an intermediate body portion which diminishes in cross-section from the head towards the base of the cathode element. A central rod is connected to the base of the cathode element and extends along the central axis. Plural upstanding spring fingers are urged against an outer peripheral contact surface of the head end to provide a mechanical and electrical connection to the cathode element. 7 figs

  11. Enhanced lithium ion conductivity in lithium lanthanum titanate solid electrolyte nanowires prepared by electrospinning

    NASA Astrophysics Data System (ADS)

    Yang, Ting; Li, Ying; Chan, Candace K.

    2015-08-01

    Solid electrolytes have great potential to address the safety issues of Li-ion batteries, but better synthesis methods are still required for ceramics such as lithium lanthanum titanate (LLTO) since current techniques require high-temperature calcination for long times. Here we report a new approach that utilizes electrospinning to prepare phase-pure polycrystalline LLTO nanowires with well-crystallized tetragonal structure after only 3 h calcination at 1000 °C. Pellets prepared from the electrospun LLTO nanowires had higher density, less void space, and higher Li+ conductivity compared to those comprised of LLTO prepared with conventional sol-gel methods. This work demonstrates the potential that electrospinning can provide towards improving the properties of sol-gel derived ceramics.

  12. Optimal Timing of Bisphosphonate Administration in Combination with Samarium-153 Oxabifore in the Treatment of Painful Metastatic Bone Disease

    PubMed Central

    Rasulova, Nigora; Lyubshin, Vladimir; Arybzhanov, Dauranbek; Sagdullaev, Sh.; Krylov, Valery; Khodjibekov, Marat

    2013-01-01

    While bisphosphonates are indicated for prevention of skeletal-related events, radionuclide therapy is widely used for treatment of painful bone metastases. Combined radionuclide therapy with bisphosphonates has demonstrated improved effectiveness in achieving bone pain palliation in comparison to mono therapy with radionuclides or bisphosphonates alone. However, there are conflicting reports as to whether bisphosphonates adversely influence skeletal uptake of the bone-seeking radiotracers used for therapy. Recent studies analyzing influence of Zoledronic acid on total bone uptake of Samarium-153 EDTMP (Sm-153 EDTMP) by measuring cumulative urinary activity of Sm-153 on baseline study, as well as in combination with bisphosphonates (administrated 48 hours prior to Sm-153) did not provide any statistically significant difference in urinary excretion of Sm-153 between the two groups. It may be noted that the exact temporal sequence of bisphosphonate administration vis a vis radionuclide therapy has not yet been studied. One of the side effects of bisphosphonates is transient flare effect on bone pain. Radionuclide therapy may also have similar side effect. Keeping in view the above the current study was designed with the main objective of determining the exact timing of bisphosphonate administration in patients receiving combined therapy so as to achieve optimal efficacy of bone pain palliation. Ninety-three patients suffering from metastatic bone pain who received combination therapy with Sm-153 oxabifore (an analog of Sm-153 EDTMP) and Zoledronic acid were divided into three groups according to the timing of Zoledronic acid administration: Group I: 39 patients who received Zoledronic acid 7 or more days prior to Sm-153 oxabifore treatment; Group II: 32 patients who received Zoledronic acid 48-72 hours prior to Sm-153 oxabifore treatment and Group III: 22 patients who received Zoledronic acid 7 days after Sm-153 oxabifore treatment. Sm-153 oxabifore was administered to all patients at the standard bone palliation dose of 37 MBq/kg body weight. All patients received Zoledronic acid before and after treatment in standard dosage of 4 mg every 28 days. WB bone scan, CT, and MRI were performed before treatment in all patients to exclude cord compression and vertebral fractures. Pain scores and quality of life (QOL) measurements were recorded meticulously in all patients. In groups I, II, and III, pain relief occurred in 10.4 ± 3.1 (Range = 5-15); 3.1 ± 1.1 (Range = 1-5) and 22 ± 5.1 (Range = 15-35) days, respectively, following radionuclide therapy. There was statistically significant difference between pain score in all groups before and after treatment as well as statistically significant difference in time to pain relief onset between Group II and other groups of patients (P < 0.0001). Based on our results we concluded that administration of Zoledronic acid 48-72 hours prior to Sm-153 oxabifore treatment helps in achieving better pain relief, as well as at the shortest time interval from the start of therapy. PMID:23961250

  13. Synthesis of La and Nb doped PZT powder by the gel-combustion method

    NASA Astrophysics Data System (ADS)

    Cernea, M.; Montanari, G.; Galassi, C.; Costa, A. L.

    2006-03-01

    Lanthanum and niobium doped PZT with composition (Pb0.93La0.07)[(Zr0.60Ti0.40)]0.9825Nb0.0175O3 (PZTLN) was prepared by the gel-combustion method. A precursor sol was obtained from lead nitrate, zirconyl nitrate, lanthanum oxide, peroxo-citrato-niobium and a peroxo-citrate complex of titanium isopropoxide as starting precursors. Various molar ratios of citrate/nitrate (CA/NO3- = 1.3, 0.36 and 0.09) were used to prepare very fine powders of PZTLN. The gels resulting from these sols were transformed into powders by an auto-combustion process at <=400 °C. The powders consisted of rhombohedral PZT (PbZr0.60Ti0.40O3), pyrochlore (Pb2Ti2O6) and lead carbonate (Pb2O·CO3) phases. The pure rhombohedral phase is found in PZTLN pellets sintered at 1100 °C for all citrate/nitrate ratios. Titanium and niobium precursors were modified with peroxo radicals. During the gel-combustion reaction, the temperature of the gel increases, leading to lead evaporation. The loss of lead as well as the particle size increases as the CA/NO3- ratio decreases. The smallest grained powder (about 50 nm) was obtained with the ratio CA/NO3- equal to 0.09.

  14. Thermionic emission and surface composition of the lanthanum-boron and yttrium-boron systems

    SciTech Connect

    Jaskie, J.E.

    1981-12-01

    At thermionic temperatures, a difference between bulk and surface composition will exist unless the interior happens to be at the congruently vaporizing composition (CVC). Vaporization rates from the surface compete with diffusion rates in the bulk to cause this difference. The surface composition will tend toward the congruently vaporizing composition which is YB/sub 4/ in the yttrium-Boron system and LaB/sub 6/ in the Lanthanum-Boron system. The CVC is also a function of temperature and may vary slightly for the same bulk composition at different temperature. Four Yttrium-Boron (Y-B) compounds, YB/sub 2/ /sub 5/, YB/sub 5/, YB/sub 6/ /sub 4/, YB/sub 14/ and three Lanthanum-Boron (La-B) compounds, LaB/sub 6/ /sub 01/, LaB/sub 8/ /sub 5/ and LaB/sub 5/ /sub 9/ were tested in a variable spacing vacuum emission system with a guard assembly. Emitted current measurements were made with interelctrode potentials between 250 and 1400 volts. Schottky plots were used to extrapolate the zero field currents. When a sample is taken from equilibrium to a new temperature, a definite time lag appears while vaporization rates change to bring about a new equilibrium surface composition. This manifests itself in the recorded emission currents. After thermal equilibrium is reached a distinct change is seen in emission currents. A higher density is measured, reflecting the emission of a surface that has been raised to a higher temperature. But with time, at this temperature, the surface reacts through vaporization and a new composition appears that is closer to the congruently vaporizing composition, and hence, has a work function nearer that of the CVC.

  15. Neurotoxicological evaluation of long-term lanthanum chloride exposure in rats.

    PubMed

    He, Xiao; Zhang, Zhiyong; Zhang, Haifeng; Zhao, Yuliang; Chai, Zhifang

    2008-06-01

    With their widespread application in industry, agriculture, medicine, and daily life, rare earth elements (REEs) are widely used in various fields and eventually accumulated in human body. Therefore, understanding the effects of REEs on health has become more and more important. In this work, the neurotoxicity of lanthanum (La) was evaluated. Wistar rats were exposed to lanthanum chloride through oral administration at 0, 0.1, 2, and 40 mg/kg doses from gestation day 0 through 6 months of age. Experiments were carried out to reveal the effects of La exposure on brain functions from four aspects including behavioral performance, [Ca2+](i) level and the activity of Ca2+-ATPase (adenosine triphosphatase) in hippocampal cells, oxidative stress, and Nissl staining. Adverse effects were observed in 2 and 40 mg/kg dose groups and increased with dose. Morris water maze test showed that La exposure at 2 and 40 mg/kg could significantly impair the behavioral performance. (The preference for the target quadrant decreased by 16.6% and 19.4% versus control, respectively.) The neurotoxicological consequences demonstrated that the alteration in homeostasis of [Ca2+](i)/Ca2+-ATPase (the ratio of [Ca2+](i) vs. Ca2+-ATPase activity increased by 44% in rats of 40 mg/kg group), the inhibition to activities of antioxidant enzymes, and the subsequent cell damage (18% and 23% cell loss in CA3 subregion of rats in 2 and 40 mg/kg group, respectively) might be involved in the neurological adverse effects of REEs exposure. PMID:18319242

  16. Synthesis of nanoparticles of barium lanthanum hafnium oxide by a modified combustion process.

    PubMed

    John, Asha M; Jose, R; Divakar, R; Koshy, J

    2002-02-01

    Barium lanthanum hafnium oxide, a complex perovskite ceramic, has been synthesized as nanoparticles by a modified combustion process for the first time. The Ba, La, and Hf ions required for the formation of Ba2LaHfO5.5 were obtained in solution by dissolving in boiling nitric acid a stoichiometric mixture of BaCO3, La2O3, and HfO2 that had been heated at 1200 degrees C for 4 h. By complexing the ions with citric acid and using ammonia as fuel, it was possible to get Ba2LaHfO5.5 as nanoparticles in a single-step combustion process. The powder obtained by the present combustion process was characterized by X-ray diffraction, BET surface area analysis, differential thermal analysis, thermogravimetric analysis, infrared spectroscopy, and scanning and high-resolution transmission electron microscopy. According to the results of X-ray and electron diffraction, the powder synthesized through the combustion process showed single-phase barium lanthanum hafnium oxide. The transmission electron microscopic investigations showed a grain size of 42 nm, with a standard deviation of 8 nm. The nanoparticles of Ba2LaHfO5.5 synthesized by the present combustion technique could be sintered to > 97% of the theoretical density at a relatively low temperature of 1425 degrees C. Scanning electron microscopic studies on the sintered Ba2LaHfO5.5 samples showed that the final grain size of the sintered specimen was < 500 nm. PMID:12908329

  17. Surface complexation modeling of uranium(VI) sorbed onto lanthanum monophosphate.

    PubMed

    Ordoñez-Regil, E; Drot, R; Simoni, E

    2003-07-15

    Sorption/desorption are basic processes in the field of contaminant transport. In order to develop mechanistically accurate thermodynamic sorption models, the simulation of retention data has to take into account molecular scale informations provided by structural investigations. In this way, the uranyl sorption constants onto lanthanum monophosphate (LaPO(4)) were determined on the basis of a previously published structural investigation. The surface complexation modeling of U(VI) retention onto LaPO(4) has been performed using the constant capacitance model included in the FITEQLv3.2 program. The electrical behavior of the solid surface was investigated using electrophoretic measurements and potentiometric titration experiments. The point of zero charge was found to be 3.5 and surface complexation modeling has made it possible to calculate the surface acidity constants. The fitting procedure was done with respect to the spectroscopic results, which have shown that LaPO(4) presents two kinds of reactive surface sites (lanthanum atoms and phosphate groups). The uranyl sorption edges were determined for two surface coverages: 40 and 20% of the surface sites that are occupied, assuming complete sorption. The modeling of these experimental data was realized by considering two uranyl species ("free" uranyl and uranyl nitrate complex) sorbed only onto phosphate surface groups according to the previously published structural investigation. The obtained sorption constants present similar values for both surface complexes and make it possible to fit both sorption edges: logK(U)=9.4 for z.tbnd;P(OH)(2)+UO(2)(2+)<-->z.tbnd;P(OH)(2)UO(2)(2+) and logK(UN)=9.7 for z.tbnd;P(OH)(2)+UO(2)NO(3)(+)<-->z.tbnd;P(OH)(2)UO(2)NO(3)(+). PMID:12909028

  18. Dielectric and Ferroelectric Properties of Lead Lanthanum Zirconate Titanate Thin Films for Capacitive Energy Storage

    NASA Astrophysics Data System (ADS)

    Tong, Sheng

    As the increasing requirement of alternative energy with less pollution influence and higher energy efficient, new energy source and related storage methods are hot topic nowadays. Capacitors that supply high instant power are one of the keys in this application for both economic and functional design aspects. To lower the cost and increases the volumetric efficiency and reliability, relaxor thin films are considered as one of the candidates of the next generation capacitors. The research mainly focuses on dielectric and ferroelectric properties of lead lanthanum zirconate titanate or Pb1-xLax(ZryTi1-y)O3 (PLZT, x/y/1-y) relaxor thin films deposited on silicon (Si) and nickel (Ni) substrates in a range of thickness with different bottom electrodes, e.g. Platinum (Pt) and LaNiO3 (LNO). The final fabricated PLZT film capacitors will show strong potential for the energy storage application. The method adopted is the acetic acid assisted sol-gel deposition for the PLZT thin films. The wet chemical process is cost-effective and easily to scale up for plant/industrial products. We investigated the different bottom electrode/substrate influence in structure, microstructure, phases/defects, and heat-treatment conditions to achieve the optimized PLZT thin films. Issues of basic physical size effects in the PLZT thin films were also investigated, including thickness effects in the dielectric and ferroelectric properties of the films in a wide range of temperatures, the phase transition of the thin-film relaxors, lanthanum content effect, electrode-dielectric junction, misfit strain effect, etc. Based on the results and analysis, optimum PLZT film capacitors can be determined of proper substrate/electrode/dielectric that achieves the desired dielectric properties required for different applications, especially a more cost-effective method to develop volumetrically efficient capacitors with high charge density, energy density, dielectric breakdown strength, energy storage efficiency, and low dielectric loss, leakage current density.

  19. Chemical solution deposition of ferroelectric lead lanthanum zirconate titanate films on base-metal foils.

    SciTech Connect

    Ma, B.; Kwon, D.-K.; Narayanan, M.; Balachandran, U.

    2009-01-01

    Development of electronic devices with better performance and smaller size requires the passive components to be embedded within a printed wire board (PWB). The 'film-on-foil' approach is the most viable method for embedding these components within a PWB. We have deposited high-permittivity ferroelectric lead lanthanum zirconate titanate (Pb{sub 0.92}La{sub 0.08}Zr{sub 0.52}Ti{sub 0.48}O{sub x}, PLZT 8/52/48) films on base metal foils by chemical solution deposition. These prefabricated capacitor sheets can be embedded into PWBs for power electronic applications. To eliminate the parasitic effect caused by the formation of a low-permittivity interfacial oxide, a conductive buffer layer of lanthanum nickel oxide (LNO) was applied by chemical solution deposition on nickel foil before the deposition of PLZT. With a {approx} 0.7-{micro}m-thick ferroelectric PLZT film grown on LNO-buffered nickel foil, we measured capacitance densities of 1.5 {micro}F/cm{sup 2}, breakdown field strength E{sub b} > 1.2 MV/cm, and leakage current density of 2 x 10{sup -8}A/cm{sup 2}. The dielectric relaxation current decay obeys the Curie-von Schweidler law, with exponent n = 0.85 and 0.94 for PLZT grown directly on Ni and that grown on LNO-buffered Ni foils, respectively. When compared with samples deposited directly on Ni substrate, PLZT grown on LNO buffered Ni substrates exhibit slimmer hysteresis loop and better energy storage capability. With these desirable characters, PLZT film-on-foil capacitors hold particular promise for use in high-voltage embedded passives.

  20. Catalytic behaviors of lanthanum and neodymium oxides for dehydrogenation/dehydration of ethanol

    SciTech Connect

    Koprowski, R.J.

    1985-01-01

    Ethanol dehydrogenation and dehydration reactions have been employed to investigate the nature and behavior of catalytically active sites on lanthanum and neodymium sesquioxides. In support of this objective, x-ray powder diffraction, surface area determinations, and thermogravimetric analyses have been performed to augment previously reported characterization results. Activated lanthanum and neodymium oxide catalysts have been prepared by thermal dehydration of the corresponding trihydroxides. The catalytic reaction data on these materials, when correlated with complemented with infrared spectroscopic measurements of adsorbed species reported in the literature, indicate that arrays of at least two dissimilar types of catalytically active sites are generated. One kind of site (designated Type I) is much less numerous than the other (Type II) but is more strongly basic and has a much higher initial activity for alcohol dehydration. The latter reaction probably occurs via an ethoxide intermediate at 300-400/sup 0/C. The parallel alcohol dehydrogenation pathway, on the other hand, occurs only on Type II sites which have only moderate dehydration activity. The resulting aldehyde product re-absorbs exclusively on the more strongly basic Type I sites, where it undergoes a series of secondary condensation/decarboxylation reactions and consequently leads to a decrease in the overall rate of alcohol dehydration. The contrasting behavioral features of the two kinds of sites may be due to differing surface environments with Type I sites being in structurally more defective and/or more energetic surface locations than are Type II sites. Increases in prior pretreatment temperature of the oxides cause thermally-induced transformations of Type I sites into Type II sites by a surface annealing or re-structuring process with corresponding modifications in the observed catalytic behaviors for the two alcohol decomposition pathways.

  1. Effect of macroamounts of aluminum, magnesium, nickel, and chromium on the degree of yttrium and lanthanum atomization in an acetylene-nitrous oxide flame

    SciTech Connect

    Semenenko, K.A.; Osipova, V.A.; Panov, V.A.; Kuzyakov, Yu.Ya.

    1987-09-20

    Using the method of measuring absolute intensities in emission spectra, they have calculated the degree of atomization of yttrium and lanthanum in an acetylene-nitrous oxide flame, and have provided a quantitative appraisal of the effect of Al, Mg, Ni, and Cr on the number of yttrium and lanthanum atoms, ions, and molecules. Hypotheses are expressed concerning the mechanism of the effect of the principal elements in the flame.

  2. Aero dopes and varnishes

    NASA Technical Reports Server (NTRS)

    Britton, H T S

    1927-01-01

    Before proceeding to discuss the preparation of dope solutions, it will be necessary to consider some of the essential properties which should be possessed of a dope film, deposited in and on the surface of an aero fabric. The first is that it should tighten the material and second it should withstand weathering.

  3. The combination of lanthanum chloride and the calcimimetic calindol delays the progression of vascular smooth muscle cells calcification

    SciTech Connect

    Ciceri, Paola; Volpi, Elisa; Brenna, Irene; Elli, Francesca; Borghi, Elisa; Brancaccio, Diego; Cozzolino, Mario

    2012-02-24

    Highlights: Black-Right-Pointing-Pointer Lanthanum reduces the progression of high phosphate-induced calcium deposition. Black-Right-Pointing-Pointer Calcium receptor agonists and the calcimimetic calindol reduce calcium deposition. Black-Right-Pointing-Pointer Lanthanum and calindol cooperate on reducing calcium deposition. Black-Right-Pointing-Pointer Lanthanum and calindol may interact with the same receptor. -- Abstract: Phosphate (Pi)-binders are commonly used in dialysis patients to control high Pi levels, that associated with vascular calcification (VC). The aim of this study was to investigate the effects of lanthanum chloride (LaCl{sub 3}) on the progression of high Pi-induced VC, in rat vascular smooth muscle cells (VSMCs). Pi-induced Ca deposition was inhibited by LaCl{sub 3}, with a maximal effect at 100 {mu}M (59.0 {+-} 2.5% inhibition). Furthermore, we studied the effects on VC of calcium sensing receptor (CaSR) agonists. Gadolinium chloride, neomycin, spermine, and the calcimimetic calindol significantly inhibited Pi-induced VC (55.9 {+-} 2.2%, 37.3 {+-} 4.7%, 30.2 {+-} 5.7%, and 63.8 {+-} 5.7%, respectively). To investigate the hypothesis that LaCl{sub 3} reduces the progression of VC by interacting with the CaSR, we performed a concentration-response curve of LaCl{sub 3} in presence of a sub-effective concentration of calindol (10 nM). Interestingly, this curve was shifted to the left (IC{sub 50} 9.6 {+-} 2.6 {mu}M), compared to the curve in the presence of LaCl{sub 3} alone (IC{sub 50} 19.0 {+-} 4.8 {mu}M). In conclusion, we demonstrated that lanthanum chloride effectively reduces the progression of high phosphate-induced vascular calcification. In addition, LaCl{sub 3} cooperates with the calcimimetic calindol in decreasing Ca deposition in this in vitro model. These results suggest the potential role of lanthanum in the treatment of VC induced by high Pi.

  4. Doped graphene supercapacitors.

    PubMed

    Kumar, Nanjundan Ashok; Baek, Jong-Beom

    2015-12-11

    Heteroatom-doped graphitic frameworks have received great attention in energy research, since doping endows graphitic structures with a wide spectrum of properties, especially critical for electrochemical supercapacitors, which tend to complement or compete with the current lithium-ion battery technology/devices. This article reviews the latest developments in the chemical modification/doping strategies of graphene and highlights the versatility of such heteroatom-doped graphitic structures. Their role as supercapacitor electrodes is discussed in detail. This review is specifically focused on the concept of material synthesis, techniques for electrode fabrication and metrics of performance, predominantly covering the last four years. Challenges and insights into the future research and perspectives on the development of novel electrode architectures for electrochemical supercapacitors based on doped graphene are also discussed. PMID:26574192

  5. Doped graphene supercapacitors

    NASA Astrophysics Data System (ADS)

    Ashok Kumar, Nanjundan; Baek, Jong-Beom

    2015-12-01

    Heteroatom-doped graphitic frameworks have received great attention in energy research, since doping endows graphitic structures with a wide spectrum of properties, especially critical for electrochemical supercapacitors, which tend to complement or compete with the current lithium-ion battery technology/devices. This article reviews the latest developments in the chemical modification/doping strategies of graphene and highlights the versatility of such heteroatom-doped graphitic structures. Their role as supercapacitor electrodes is discussed in detail. This review is specifically focused on the concept of material synthesis, techniques for electrode fabrication and metrics of performance, predominantly covering the last four years. Challenges and insights into the future research and perspectives on the development of novel electrode architectures for electrochemical supercapacitors based on doped graphene are also discussed.

  6. Performance of a Lanthanum Bromide Detector and a New Conception Collimator for Radiopharmaceuticals Molecular Imaging in Oncology

    SciTech Connect

    Pani, Roberto; Pellegrini, Rosanna; Bennati, Paolo; Cinti, Maria Nerina; Scafe, Raffaele; De Vincentis, Giuseppe; Navarria, Francesco; Moschini, Giuliano; Rossi, Paolo; Cencelli, Valentino Orsolini; De Notaristefani, Francesco

    2009-03-10

    We have realized and tested a new-design compact gamma camera for high resolution SPET (Single Photon Emission Tomography), and small animals' radio-pharmaceutical molecular imaging. The camera is based on a 'continuous' Lanthanum tri-Bromide crystal, and a new Low Energy (LE) collimator. The crystal is interfaced to a 2x2 array of Hamamatsu-H8500 position sensitive photo-multipliers. The lead collimator features parallel hexagonal 1.0 mm holes, 18 mm length, 0.2 mm septa and 10x10 cm{sup 2} detection area. It was newly designed to fully exploit the high spatial resolution a Lanthanum crystal may provide. To better evaluate its role, we have compared our camera to three other systems with similar crystals and photomultipliers, but employing traditional collimators, either pinhole or parallel. The new camera seems to be complementary to pinhole systems and shows a very attractive trade-off between spatial resolution and detection area.

  7. Performance of a Lanthanum Bromide Detector and a New Conception Collimator for Radiopharmaceuticals Molecular Imaging in Oncology

    NASA Astrophysics Data System (ADS)

    Pani, Roberto; Pellegrini, Rosanna; Bennati, Paolo; Cinti, Maria Nerina; Scafè, Raffaele; De Vincentis, Giuseppe; Navarria, Francesco; Moschini, Giuliano; Cencelli, Valentino Orsolini; De Notaristefani, Francesco; Rossi, Paolo

    2009-03-01

    We have realized and tested a new-design compact gamma camera for high resolution SPET (Single Photon Emission Tomography), and small animals' radio-pharmaceutical molecular imaging. The camera is based on a "continuous" Lanthanum tri-Bromide crystal, and a new Low Energy (LE) collimator. The crystal is interfaced to a 2×2 array of Hamamatsu-H8500 position sensitive photo-multipliers. The lead collimator features parallel hexagonal 1.0 mm holes, 18 mm length, 0.2 mm septa and 10×10 cm2 detection area. It was newly designed to fully exploit the high spatial resolution a Lanthanum crystal may provide. To better evaluate its role, we have compared our camera to three other systems with similar crystals and photomultipliers, but employing traditional collimators, either pinhole or parallel. The new camera seems to be complementary to pinhole systems and shows a very attractive trade-off between spatial resolution and detection area.

  8. Progress in rare-earth-doped mid-infrared fiber lasers.

    PubMed

    Seddon, Angela B; Tang, Zhuoqi; Furniss, David; Sujecki, Slawomir; Benson, Trevor M

    2010-12-01

    The progress, and current challenges, in fabricating rare-earth-doped chalcogenide-glass fibers for developing mid-infrared (IR) fiber lasers are reviewed. For the first time a coherent explanation is forwarded for the failure to date to develop a gallium-lanthanum-sulfide glass mid-IR fiber laser. For the more covalent chalcogenide glasses, the importance of optimizing the glass host and glass processing routes in order to minimize non-radiative decay and to avoid rare earth ion clustering and glass devitrification is discussed. For the first time a new idea is explored to explain an additional method of non-radiative depopulation of the excited state in the mid-IR that has not been properly recognized before: that of impurity multiphonon relaxation. Practical characterization of candidate selenide glasses is presented. Potential applications of mid-infrared fiber lasers are suggested. PMID:21165021

  9. Experimental investigation on the concentration and voltage effects on the characteristics of deposited magnesium-lanthanum powder

    NASA Astrophysics Data System (ADS)

    Sahli, M.; Chetehouna, K.; Faubert, F.; Bariki, C.; Gascoin, N.; Bellel, N.

    2015-06-01

    In this paper, magnesium-lanthanum powders were synthesized by an electrodeposition technique using an aqueous solution, based on magnesium chloride hexahydrate and lanthanum nitrate for different values of voltage and La weight percentage. A copper cathode plate and a tungsten thread anode were used for the preparation of the Mg-La layers. The as-deposited powders were characterized by energy dispersive spectroscopy (EDS) to determine the chemical composition, scanning electron microscope to describe the morphology, X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectra in order to define the chemical structure. EDS analyses indicate the presence of three elements (Mg, La and O) in the different deposited layers, and the major one is O (51-74.2 at.%). The two other elements, Mg and La, are, respectively, ranked 2 and 3 in the different powders. Morphological description reveals the formation of heterogeneous chemical structures on the surfaces of specimens. They are characterized by aggregates with different sizes. The dark aggregates are associated with magnesium, and the bright ones are attributed to lanthanum. X-ray results showed the existence of two distinct phases in the obtained deposits which are magnesium hydroxide (Mg(OH)2) and lanthanum hydroxide (La(OH)3). FTIR analyses confirm the presence of the two phases identified in XRD diffractograms, and they can be exhibited by clear peaks. In the studied ranges of voltage and La weight percentage, their peak transmittances have non-monotonic behaviors. A design of experiments was used to determine the influence of these two processing parameters and their interaction on the products formation. The parameter effects were ranked as follow: The first was the voltage then the interaction between the two parameters and finally the La content.

  10. Photoluminescence and Structural Studies of Calcium Sulfide and Strontium SULFIDE:EUROPIUM(2+), SAMARIUM(3+) Thin Films.

    NASA Astrophysics Data System (ADS)

    Hua, Zonglu

    Rare earth doped II-VI thin films exhibit interesting optical properties due to the introduction of new levels into the wide band gap. The transition between these levels gives rise to photoluminescence which reveals versatile applications in optical memory devices. In this investigation, the temperature dependence of photoluminescence spectra of SrS singly and doubly doped with Eu^ {2+} and Sm^{3+} thin films was obtained. From band broadening and shifting a strong electron-lattice interaction was observed for the Eu^{2+} ionic transition. The temperature dependence of the emission intensity for different excitation energies in the range 2.84 eV to 5 eV, leads to the identification of two energy and electron transfer mechanisms. Namely, phonon-assisted energy and electron transfer with or without energy band involvement was observed depending on the excitation energy. The microstructure and its effects on the photoluminescence properties of SrS:Eu^{2+},Sm ^{3+} thin films was also studied by transmission electron microscopy, x-ray diffraction and photoluminescence techniques. The SrS:Eu^ {2+},Sm^{3+} thin films were prepared by e-beam evaporation at different substrate temperatures and growth rates. Both of these growth conditions affect the crystallinity of the thin films. An optimum deposition was obtained for a maximum efficiency of optical output.

  11. Isoelectronic co-doping

    DOEpatents

    Mascarenhas, Angelo

    2004-11-09

    Isoelectronic co-doping of semiconductor compounds and alloys with deep acceptors and deep donors is used to decrease bandgap, to increase concentration of the dopant constituents in the resulting alloys, and to increase carrier mobilities lifetimes. Group III-V compounds and alloys, such as GaAs and GaP, are isoelectronically co-doped with, for example, N and Bi, to customize solar cells, thermal voltaic cells, light emitting diodes, photodetectors, and lasers on GaP, InP, GaAs, Ge, and Si substrates. Isoelectronically co-doped Group II-VI compounds and alloys are also included.

  12. An electron-microscopic study of the T-system in progressive muscular dystrophy (Duchenne) using lanthanum.

    PubMed

    Oguchi, K; Tsukagoshi, H

    1980-01-01

    Muscle biopsies in 4 cases of Duchenne muscular dystrophy and two normal controls were examined by electron microscopy using lanthanum as a tracer for assessment of the T-system. Lanthanum was localized in the extracellular spaces, the basement membranes, intercellular spaces between muscle fibers and satellite cells, subsarcolemmal vesicles (caveola), motor end-plate, and the T-system in the controls. The T-system was sometimes connected with the caveolae, and was located at right angles to the myofibrils in the controls. In Duchenne muscular dystrophy, the T-system showed irregularities of position, tangle formations and dilatation of the diameters when observed using lanthanum as a tracer, even in muscle fibers which under light- and electron-microscopic examinations did not show any changes. Structure of the triad was destroyed and lanthanun was localized in the sarcoplasmic reticulum (SR). The changes of the T-system and triad seemed to play an important role in the high level of creatine phosphokinase (CPK) in the serum of Duchenne muscular dystrophy patients who do not show any clinical symptoms. Because of the destruction of the triad, CPK will easily flow out to the exterior of muscle fibers via the T-system. PMID:6153402

  13. Multiple-magnetic field 139La NMR and density functional theory investigation of the solid lanthanum(III) halides.

    PubMed

    Ooms, Kristopher J; Feindel, Kirk W; Willans, Mathew J; Wasylishen, Roderick E; Hanna, John V; Pike, Kevin J; Smith, Mark E

    2005-09-01

    Results from a solid-state 139La NMR spectroscopic investigation of the anhydrous lanthanum(III) halides (LaX3; X=F, Cl, Br, I) at applied magnetic fields of 7.0, 9.4, 11.7, 14.1, and 17.6 T are presented and highlight the advantages of working at high applied magnetic field strengths. The 139La quadrupolar coupling constants are found to range from 15.55 to 24.0 MHz for LaCl3 and LaI3, respectively. The lanthanum isotropic chemical shifts exhibit an inverse halogen dependence with values ranging from -135 ppm for LaF3 to 700 ppm for LaI3, which represents nearly half of the total lanthanum chemical shift range. The spans of the magnetic shielding tensors also vary widely, from 35 to 650 ppm for the solid LaF3 through LaI3. DFT calculations of the 139La electric field gradient and magnetic shielding tensors have been performed and provide a qualitative interpretation of the trends observed experimentally. PMID:16125375

  14. Influence of environmental factors on the phosphorus adsorption of lanthanum-modified bentonite in eutrophic water and sediment.

    PubMed

    Liu, SheJiang; Li, Jie; Yang, YongKui; Wang, Juan; Ding, Hui

    2016-02-01

    Lanthanum-modified bentonite has potential for wide application in eutrophication control. We investigated P adsorption on a lanthanum-modified bentonite by analysis of adsorption kinetics, equilibrium, and the effect of environmental factors. P adsorption closely followed the pseudo-second-order kinetic model, and the isotherm was well described by the Langmuir model. This adsorbent could effectively immobilize P into the sediment, but the adsorption process was strongly dependent on pH, anions, and low molecular weight organic acids (LMWOAs). P adsorption increased with increasing pH from 0.52 mg P/g at pH 3.0 to 0.93 mg P/g at pH 7.0 with no adsorption at pH 11. P adsorption was strongly inhibited in the presence of anions and three LMWOAs, with P even re-released at high concentrations. These environmental factors should be given significant attention when considering the application of lanthanum-modified bentonite in eutrophication control. PMID:26423284

  15. Studies on Ca2+-Doped CeBr3 Scintillating Materials

    SciTech Connect

    Guss, P.; Foster, M. E.; Wong, B. M.; Doty, F. P.; Shah, K.; Squillante, M.; Glodo, J.; Yuan, D.

    2013-07-03

    Despite the outstanding scintillation performance characteristics of cerium tribromide (CeBr3) and cerium-activated lanthanum tribromide (LaBr3:Ce), their commercial availability and application is limited due to the difficulties of growing large, crack-free single crystals from these fragile materials. The objective of this investigation was to employ aliovalent doping to increase crystal strength while maintaining the optical properties of the crystal. One divalent dopant (Ca2+) was investigated 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 investigated using the density functional theory within 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.

  16. Results for aliovalent doping of CeBr3 with Ca2+

    NASA Astrophysics Data System (ADS)

    Guss, Paul; Foster, Michael E.; Wong, Bryan M.; Patrick Doty, F.; Shah, Kanai; Squillante, Michael R.; Shirwadkar, Urmila; Hawrami, Rastgo; Tower, Joshua; Yuan, Ding

    2014-01-01

    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, i.e., 1.9% of the CeBr3 molecules were replaced by CaBr2 molecules, to match our target replacement of 1 out of 54 cerium atoms be replaced by a calcium atom. Precisely the mixture was composed of 2.26 g of CaBr2 added to 222.14 g of CeBr3. 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. Calculated lattice parameters are in 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.

  17. Studies on Ca2+-Doped CeBr3 Scintillating Materials

    SciTech Connect

    Guss, P.; Foster, M. E.; Wong, B. M.; Doty, F. P.; Shah, K.; Squillante, M. R.; Shirwadkar, U.; Hawrami, R.; Tower, J.; Yuan, D.

    2013-09-01

    Despite the outstanding scintillation performance characteristics of cerium tribromide (CeBr3) and cerium-activated lanthanum tribromide (LaBr3:Ce), their commercial availability and application is limited due to the difficulties of growing large, crack-free single crystals from these fragile materials. The objective of this investigation was to employ aliovalent doping to increase crystal strength while maintaining the optical properties of the crystal. One divalent dopant (Ca2+) was investigated 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 investigated using the density functional theory within 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.

  18. Synthesis of lanthanum zirconium oxide nanomaterials through composite-hydroxide-mediated approach

    SciTech Connect

    Jin, Hongyun; Engineering Research Center of Nano-Geomaterials of Ministry of Education, China University of Geosciences, Wuhan 430074 ; Huang, Dan; Gao, Qiang; Engineering Research Center of Nano-Geomaterials of Ministry of Education, China University of Geosciences, Wuhan 430074 ; Li, Li; Wang, Ning; Wang, Yongqian; Engineering Research Center of Nano-Geomaterials of Ministry of Education, China University of Geosciences, Wuhan 430074 ; Hou, Shuen; Engineering Research Center of Nano-Geomaterials of Ministry of Education, China University of Geosciences, Wuhan 430074

    2012-01-15

    Graphical abstract: Lanthanum zirconium oxide (La{sub 2}Zr{sub 2}O{sub 7}) with cubic pyrochlore structure thermal barrier coatings (TBCs) materials have been synthesized through composite-hydroxide-mediated method at 200 Degree-Sign C. Compared with YSZ TBCs material, La{sub 2}Zr{sub 2}O{sub 7} showed more excellent thermal stability and lower thermal conductivity. Highlights: Black-Right-Pointing-Pointer La{sub 2}Zr{sub 2}O{sub 7} TBCs were synthesized through composite-hydroxide-mediated method. Black-Right-Pointing-Pointer The XRD patterns showed a single phase for La{sub 2}Zr{sub 2}O{sub 7} after treated at 1300 Degree-Sign C. Black-Right-Pointing-Pointer The thermal conductivity value of La{sub 2}Zr{sub 2}O{sub 7} was lower than that of YSZ. Black-Right-Pointing-Pointer La{sub 2}Zr{sub 2}O{sub 7} showed more excellent stability and lower thermal conductivity than YSZ. -- Abstract: A novel thermal barrier coating material, lanthanum zirconium oxide (La{sub 2}Zr{sub 2}O{sub 7}) has been synthesized through the composite-hydroxide-mediated method at low temperature. The phase structures, morphology, thermal stability and thermal conductivity of the as-synthesized La{sub 2}Zr{sub 2}O{sub 7} were investigated systematically. The X-ray diffraction (XRD) patterns revealed a single phase with cubic pyrochlore structure for La{sub 2}Zr{sub 2}O{sub 7} after treated at 1300 Degree-Sign C for 100 h. The transmission electron microscope (TEM) and scanning electron microscope (SEM) analyses showed that the sample was made up of sphere-like nanoparticles with the size between 50 and 100 nm. Furthermore, the thermal analysis result demonstrated the La{sub 2}Zr{sub 2}O{sub 7} sample had high thermal stability even at 1300 Degree-Sign C. As the temperature increased to 1200 Degree-Sign C, the thermal conductivity value could be as low as 1.75 W m{sup -1} K{sup -1}. Due to the high-temperature stability and lower thermal conductivity, the La{sub 2}Zr{sub 2}O{sub 7} material is expected to be a promising candidate for the use of thermal barrier coatings.

  19. Lanthanum carbonate prevents accelerated medial calcification in uremic rats: role of osteoclast-like activity

    PubMed Central

    2013-01-01

    Background Arterial medial calcification (AMC) is frequent prevalence in patients with end stage renal disease. Evidence about hyperphosphatemia induced anabolic crosstalk between osteoblast and osteoclast in AMC of uremia is rare. Lanthanum carbonate as an orally administered phosphate-binding agent to reduce phosphate load and ameliorate AMC, but direct evidence is missing. Methods Detailed time-course studies were conducted of Sprague–Dawley rats fed with adenine and high phosphate diet to imitate the onset and progression of AMC of uremia. Calcification in great arteries was evaluated by VonKossa’s and Masson's trichrome staining. Osteoblast (Runx2, Osteocalcin) and osteoclast (RANKL, Cathepsin K, TRAP) related genes were analyzed by Immunohistochemistry and qRT-PCR. Serum PTH, RANKL and OPG levels were detected by ELISA kit. Results Serum phosphate was markedly increased in CRF group (6.94 ± 0.97 mmol/L) and 2%La group (5.12 ± 0.84 mmol/L) at week 4, while the latter group diminished significantly (2.92 ± 0.73 mmol/L vs CRF Group 3.48 ± 0.69, p < 0.01) at week 10. The rats that did not receive 2%La treatment had extensive von kossa staining for medial calcification in CRF group. In contrast, the rats in 2%La group just exhibit mild medial calcification. Inhibitory effect on progression of AMC was reflected by down regulated osteogenic genes and altered osteoclast-like genes. RANKL/OPG ratio in local calcification area was declined in 2%La group (vs CRF group, p <0.01), whereas marginal difference in serum among the three groups. In contrast to the robust expression of cathepsinK in calcified area, TRAP expression was not found. Conclusions Abnormal phosphate homeostasis, induction of osteogenic conversion and osteoclast suppression were contributed to the current mechanisms of uremia associated arterial medial calcification based on our studies. Beneficial effects of Lanthanum carbonate could be mainly due to the decreased phosphate retention and cross-talk between osteoblast and osteoclast-like cell, both of which can be the therapeutic target for uremia associated with AMC. PMID:24330832

  20. Sevalamer Hydrochloride, Sevelamer Carbonate and Lanthanum Carbonate: In Vitro and In Vivo Effects on Gastric Environment.

    PubMed

    Coppolino, Giuseppe; Lucisano, Silvia; Rivoli, Laura; Fuiano, Giorgio; Villari, Antonino; Villari, Iole; Leonello, Grazia; Lacquaniti, Antonio; Santoro, Domenico; Buemi, Michele

    2015-10-01

    Hyperphosphatemia is common in patients with chronic renal failure. Phosphate binders are associated with gastric intolerance, representing the main reason of drug discontinuation. The aim of this study was to compare the effects in vitro and in vivo of sevelamer hydrochloride (SH), sevelamer carbonate (SC) and lanthanum carbonate (LC) on gastric microenvironment. We have also evaluated the efficacy and tolerability of these drugs in hemodialysis (HD) patients. In vitro analysis: Dissolution time, ability to uptake phosphorus, changes in pH starting from gastric milieu and the amount of carbon dioxide (CO(2)) produced were the variables analyzed. In vivo analysis: 24-h esophago-gastric pH measurement was evaluated in 24 HD patients treated with phosphate binders and proton pump inhibitor (PPI). In vitro: LC dissolved over a longer time compared with SC (58 ± 2.4 vs. 12 ± 0.6 min; P < 0.001) and SH (58 ± 2.4 vs. 10.3 ± 0.8 min; P < 0.001), determining the most alkaline pH. SC had the highest chelation power, binding 4.00 × 10(-9)  mol/L of phosphoric acid. CO2 volume released was increased in LC solution (53.2 ± 7.8) compared to SC (33.9 ± 6.2; P < 0.001) and SH (2.3 ± 1.8; P < 0.001). In vivo: gastric pH increased after administration of phosphate binder. The most alkaline pH was recorded in patients treated with SC. The alkalinization of the gastric environment was not prevented by PPI therapy. 424 episodes of esophageal reflux were registered, 74% of them were alkaline. The LC group was characterized by the highest number of episodes. Sevelamer carbonate had a greater capacity and rapidity to chelate phosphorus, with a mild tolerability, due to its low CO(2) production. Sevelamer HCl was the most tolerated chelator because it did not produce CO(2), while lanthanum carbonate was the least soluble. PMID:25866250

  1. Enhanced visible light activity of nano-titanium dioxide doped with multiple ions: Effect of crystal defects

    SciTech Connect

    Jaimy, Kanakkanmavudi B.; Ghosh, Swapankumar; Gopakumar Warrier, Krishna

    2012-12-15

    Titanium dioxide photocatalysts co-doped with iron(III) and lanthanum(III) have been prepared through a modified sol-gel method. Doping with Fe{sup 3+} resulted in a relatively lower anatase to rutile phase transformation temperature, while La{sup 3+} addition reduced the crystal growth and thus retarded the phase transformation of titania nanoparticles. The presence of Fe{sup 3+} ions shifted the absorption profile of titania to the longer wavelength side of the spectrum and enhanced the visible light activity. On the other hand, La{sup 3+} addition improved the optical absorption of titania nanoparticles. Both the dopants improved the life time of excitons by proper transferring and trapping of photoexcited charges. In the present work, considerable enhancement in photocatalytic activity under visible light was achieved through synergistic effect of optimum concentrations of the two dopants and associated crystal defects. - Graphical abstract: Photocatalytic activity studies indicate a synergistic effect of dopants and crystal defects leading to an enhanced photochemical activity. Highlights: Black-Right-Pointing-Pointer An aqueous sol-gel synthesis of Fe{sup 3+} and La{sup 3+} co-doped TiO{sub 2} is being reported. Black-Right-Pointing-Pointer Optical and microstructural properties of titania were modified by co-doping. Black-Right-Pointing-Pointer Enhanced activity of titania by the crystal defects is being reported.

  2. Samarium and yttrium codoped BaCeO? proton conductor with improved sinterability and higher electrical conductivity.

    PubMed

    Shi, Zhen; Sun, Wenping; Wang, Zhongtao; Qian, Jing; Liu, Wei

    2014-04-01

    Acceptor-doped barium cerate is considered as one of the state-of-the-art high temperature proton conductors (HTPCs), and the proton conductivity of such HTPCs is heavily dependent on the dopant. In this work, a codoping strategy is employed to improve the electrical conductivity and sinterability of BaCeO3-based HTPC. BaCe0.8Sm(x)Y(0.2-x)O(3-?) (0 ? x ? 0.2) powders are synthesized by a typical citrate-nitrate combustion method. The XRD and Raman spectra reveal all the compounds have an orthorhombic perovskite structure. The effects of Sm and/or Y doping on the sinterability and electrical conductivity under different atmospheres are carefully investigated. The SEM results of the sintered BaCe0.8Sm(x)Y(0.2-x)O(3-?) pellets indicate a significant sintering enhancement with increasing Sm concentration. BaCe0.8Sm0.1Y0.1O(3-?) exhibits the highest electrical conductivity in hydrogen among the BaCe0.8Sm(x)Y(0.2-x)O(3-?) pellets. Anode-supported BaCe0.8Sm0.1Y0.1O(3-?) electrolyte membranes are also fabricated via a drop-coating process, and the corresponding single cell exhibits desirable power performance and durability at low temperatures. The results demonstrate that BaCe0.8Sm0.1Y0.1O(3-?) is a promising proton conductor with high conductivity and sufficient sinterability for proton-conducting solid oxide fuel cells operating at reduced temperatures. PMID:24646030

  3. Photo-induced self-cleaning and sterilizing activity of Sm3+ doped ZnO nanomaterials.

    PubMed

    Saif, M; Hafez, H; Nabeel, A I

    2013-01-01

    Highly active samarium doped zinc oxide self-cleaning and biocidal surfaces (x mol% Sm(3+)/ZnO where x=0, 1, 2 and 4 mol%) with crystalline porous structures were synthesized by hydrothermal method. Sm(3+)/ZnO thin films were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM), energy dispersive spectroscopic (EDS), UV-visible diffuse reflectance and fluorescence (FL) spectroscopy. The combination between doping and hydrothermal treatments significantly altered the morphology of ZnO into rod and plate-like nanoshapes structure and enhanced its absorption and emission of ultraviolet radiation. The photo-activity in term of quantitative determination of the active oxidative species (()OH) produced on the thin film surfaces was evaluated using fluorescent probe method. The results showed that, the hydrothermally treated 2.0 mol% Sm(3+)/ZnO film (S2) is the highly active one. The optical, structural, morphology and photo-activity properties of the highly active thin film (S2) make it promising surface for self-cleaning and sterilizing applications. PMID:23123120

  4. Intermediate-Temperature Solid-Oxide Fuel Cells with a Gadolinium-Doped Ceria Anodic Functional Layer Deposited via Radio-Frequency Sputtering.

    PubMed

    Tanveer, Waqas Hassan; Ji, Sanghoon; Yu, Wonjong; Cho, Gu Young; Lee, Yoon Ho; Cha, Suk Won

    2015-11-01

    We investigated the effects of the insertion of a gadolinium-doped ceria (GDC) anodic functional layer (AFL) on the electrochemical performance of intermediate-temperature solid-oxide fuel cells (SOFCs). Fully stabilized yttria-stabilized zirconia (YSZ) was used as an oxygen-ion-conducting and support material. Nickel-Samaria-doped ceriathin film was used as an anode material, while screen-printed lanthanum strontium magnetite served as a cathode material. In order to enhance the interfacial reaction on the anode side, a GDC-AFL with a thickness of about 140 nm, deposited via radio-frequency sputtering, was inserted into the anode-electrolyte interface. SOFCs with and without a GDC-AFL were electrochemically characterized. In an intermediate temperature range of about 700 - 800 degrees C, the application of the GDC-AFL led to an increase in the peak power density of approximately 16%. PMID:26726620

  5. Room-temperature scintillation properties of cerium-doped REOX (RE=Y, La, Gd, and Lu; X=F, Cl, Br, and I)

    SciTech Connect

    Eagleman, Yetta; Bourret-Courchesne, Edith; Derenzo, Stephen

    2010-12-10

    The scintillation properties of cerium-doped oxyhalides following the general formula REOX (RE=Y, La, Gd, and Lu; X=F, Cl, Br, and I) are reported. These materials were synthesized under dry conditions as microcrystalline powders from conventional solid state reactions. The room temperature X-ray excited emission and scintillation decay curves were measured and analyzed for each material. Additionally, the hygroscopic nature of the oxychlorides and oxybromides was compared to that of their corresponding rare earth halides. The yttrium, lanthanum, and gadolinium oxychlorides, and all of the oxybromides and oxyiodides are found to be activated by Ce{sup 3+}. GdOBr doped with 0.5% Ce{sup 3+} has the highest light output with a relative luminosity of about one-half that of LaBr{sub 3}: Ce{sup 3+}. It displays a single exponential decay of 30 ns.

  6. UV-A light-induced photodegradation of Acid Blue 113 in the presence of Sm-doped ZnO nanostructures

    NASA Astrophysics Data System (ADS)

    Pandiyarajan, Thangaraj; Mangalaraja, Ramalinga Viswanathan; Karthikeyan, Balasubramanian; Sathishkumar, Panneerselvam; Mansilla, Héctor D.; Contreras, David; Ruiz, José

    2015-05-01

    In this report, optical and photocatalytic degradation of Acid Blue 113 (AB 113) has been investigated in an aqueous heterogeneous media containing pure and Sm-doped ZnO nanostructures which were prepared by a simple wet chemical route. X-ray diffraction measurement confirmed that the prepared nanostructures were in hexagonal wurtzite structure and the dopant Sm ion was incorporated into the Zn lattice. Interesting morphological changes involving a nanosheet-star-spherical transition were observed upon Sm doping and annealing, which were identified through transmission electron microscope. Optical absorption measurements showed an exciton absorption band and a band gap narrowing with respect to the Sm concentrations. The photodegradation of Acid Blue 113 under UV-A radiation by using pure and Sm-doped ZnO nanostructures showed that samarium played an important role in the significant improvement of the photodegradation efficiency and the optimum amount of Sm ion was found to be 1 mmol %. Further, the possible degradation mechanism was proposed herein.

  7. Comparing Electrostatic and Nonelectrostatic Surface Complexation Modeling of the Sorption of Lanthanum on Hematite.

    PubMed

    Marmier; Fromage

    1999-04-15

    The sorption of lanthanum on hematite is studied in experiments for three different surface loading ratios. The experiments consist of following the evolution of the amount of cation sorbed on surface with pH, and as well as measuring the number of protons released during sorption for the three different surface loading conditions. The sorption edge shifts to high pH, and the number of protons released during sorption increases, when the surface loading increases. Three different surface complexation models (SCMs), with three different electrostatic descriptions of the interface, are used to fit the experimental sorption curves. The stoichiometries proposed by the models are compared with the measurement of the protons released. Descriptions of the interface are given by the diffuse layer model (DLM), the constant capacitance model (CCM), and a nonelectrostatic model (NEM). If the fit quality is comparable for the three models, only the electrostatic models are able to account for the dependence of stoichiometry on surface loading. On the other hand, the NEM gives the same stoichiometry, with the same number of protons released, when surface loading conditions change. This is not in agreement with experiment observations. The stoichiometries, confirmed by an independent experiment, and the value of the surface constants obtained are the same, error aside, for DLM and CCM for the three different surface loading ratios. The NEM gives different values, even if the fit quality is comparable. Copyright 1999 Academic Press. PMID:10092353

  8. Boron ion beam generation utilizing lanthanum hexaboride cathodes: Comparison of vacuum arc and planar magnetron glow

    NASA Astrophysics Data System (ADS)

    Nikolaev, A. G.; Oks, E. M.; Vizir, A. V.; Yushkov, G. Yu.; Frolova, V. P.

    2016-02-01

    Boron ion beams are widely used for semiconductor ion implantation and for surface modification for improving the operating parameters and increasing the lifetime of machine parts and tools. For the latter application, the purity requirements of boron ion beams are not as stringent as for semiconductor technology, and a composite cathode of lanthanum hexaboride may be suitable for the production of boron ions. We have explored the use of two different approaches to boron plasma production: vacuum arc and planar high power impulse magnetron in self-sputtering mode. For the arc discharge, the boron plasma is generated at cathode spots, whereas for the magnetron discharge, the main process is sputtering of cathode material. We present here the results of comparative test experiments for both kinds of discharge, aimed at determining the optimal discharge parameters for maximum yield of boron ions. For both discharges, the extracted ion beam current reaches hundreds of milliamps and the fraction of boron ions in the total extracted ion beam is as high as 80%.

  9. Bioaccumulation and effects of lanthanum on growth and mitotic index in soybean plants.

    PubMed

    de Oliveira, Cynthia; Ramos, Sílvio J; Siqueira, José O; Faquin, Valdemar; de Castro, Evaristo M; Amaral, Douglas C; Techio, Vânia H; Coelho, Lívia C; e Silva, Pedro H P; Schnug, Ewald; Guilherme, Luiz R G

    2015-12-01

    Rare earth elements such as lanthanum (La) have been used as agricultural inputs in some countries in order to enhance yield and improve crop quality. However, little is known about the effect of La on the growth and structure of soybean, which is an important food and feed crop worldwide. In this study, bioaccumulation of La and its effects on the growth and mitotic index of soybean was evaluated. Soybean plants were exposed to increasing concentrations of La (0, 5, 10, 20, 40, 80, and 160 µM) in nutrient solution for 28 days. Plant response to La was evaluated in terms of plant growth, nutritional characteristics, photosynthetic rate, chlorophyll content, mitotic index, modifications in the ultrastructure of roots and leaves, and La mapping in root and shoot tissues. The results showed that the roots of soybean plants can accumulate sixty-fold more La than shoots. La deposition occurred mainly in cell walls and in crystals dispersed in the root cortex and in the mesophyll. When La was applied, it resulted in increased contents of some essential nutrients (i.e., Ca, P, K, and Mn), while Cu and Fe levels decreased. Moreover, low La concentrations stimulated the photosynthetic rate and total chlorophyll content and lead to a higher incidence of binucleate cells, resulting in a slight increase in roots and shoot biomass. At higher La levels, soybean growth was reduced. This was caused by ultrastructural modifications in the cell wall, thylakoids and chloroplasts, and the appearance of c-metaphases. PMID:26232040

  10. Lanthanum manganite-based air electrode for solid oxide fuel cells

    DOEpatents

    Ruka, R.J.; Kuo, L.; Li, B.

    1999-06-29

    An air electrode material for a solid oxide fuel cell is disclosed. The electrode material is based on lanthanum manganite having a perovskite-like crystal structure ABO[sub 3]. The A-site of the air electrode material preferably comprises La, Ca, Ce and at least one lanthanide selected from Sm, Gd, Dy, Er, Y and Nd. The B-site of the electrode material comprises Mn with substantially no dopants. The ratio of A:B is preferably slightly above 1. A preferred air electrode composition is of the formula La[sub w]Ca[sub x]Ln[sub y]Ce[sub z]MnO[sub 3], wherein Ln comprises at least one lanthanide selected from Sm, Gd, Dy, Er, Y and Nd, w is from about 0.55 to about 0.56, x is from about 0.255 to about 0.265, y is from about 0.175 to about 0.185, and z is from about 0.005 to about 0.02. The air electrode material possesses advantageous chemical and electrical properties as well as favorable thermal expansion and thermal cycle shrinkage characteristics. 10 figs.

  11. Lanthanum manganite-based air electrode for solid oxide fuel cells

    DOEpatents

    Ruka, Roswell J.; Kuo, Lewis; Li, Baozhen

    1999-01-01

    An air electrode material for a solid oxide fuel cell is disclosed. The electrode material is based on lanthanum manganite having a perovskite-like crystal structure ABO.sub.3. The A-site of the air electrode material preferably comprises La, Ca, Ce and at least one lanthanide selected from Sm, Gd, Dy, Er, Y and Nd. The B-site of the electrode material comprises Mn with substantially no dopants. The ratio of A:B is preferably slightly above 1. A preferred air electrode composition is of the formula La.sub.w Ca.sub.x Ln.sub.y Ce.sub.z MnO.sub.3, wherein Ln comprises at least one lanthanide selected from Sm, Gd, Dy, Er, Y and Nd, w is from about 0.55 to about 0.56, x is from about 0.255 to about 0.265, y is from about 0.175 to about 0.185, and z is from about 0.005 to about 0.02. The air electrode material possesses advantageous chemical and electrical properties as well as favorable thermal expansion and thermal cycle shrinkage characteristics.

  12. Application of graphene oxide/lanthanum-modified carbon paste electrode for the selective determination of dopamine

    NASA Astrophysics Data System (ADS)

    Ye, Fengying; Feng, Chenqi; Fu, Ning; Wu, Huihui; Jiang, Jibo; Han, Sheng

    2015-12-01

    A home-made carbon paste electrode (CPE) was reformed by graphene oxide (GO)/lanthanum (La) complexes, and a modified electrode, called GO-La/CPE, was fabricated for the selective determination of dopamine (DA) by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Several factors affecting the electrocatalytic performance of the modified sensor were investigated. Owning to the combination of GO and La ions, the GO-La/CPE sensor exhibited large surface area, well selectivity, good repeatability and stability in the oxidation reaction of DA. At optimal conditions, the response of the GO-La/CPE electrode for determining DA was linear in the region of 0.01-0.1 μM and 0.1-400.0 μM. The limit of detection was down to 0.32 nM (S/N = 3). In addition, this modified electrode was successfully applied to the detection of DA in real urine and serum samples by using standard adding method, showing its promising application in the electroanalysis of real samples.

  13. Oxidative effects, nutrients and metabolic changes in aquatic macrophyte, Elodea nuttallii, following exposure to lanthanum.

    PubMed

    Zhang, Jingjing; Zhang, Tingting; Lu, Qianqian; Cai, Sanjuan; Chu, Weiyue; Qiu, Han; Xu, Ting; Li, Feifei; Xu, Qinsong

    2015-05-01

    We investigated the phytoremediation potential of Elodea nuttallii to remove rare earth metals from contaminated water. The laboratory experiments were designed to assess the responses induced by lanthanum (5-20mgL(-1)) in E. nuttallii over a period of 7 days. The results showed that most La (approximately 85%) was associated with the cell wall. The addition of La to the culture medium reduced the concentration of K, Ca, Cu, Mg, and Mn. However, O2(·-) levels increased with a concomitant increase in the malondialdehyde (MDA) concentration as the La concentration increased, which indicated that the cells were under oxidative stress. Significant reductions in the levels of chlorophyll (Chl) a, b, and carotenoids (Car) were observed in a concentration-dependent manner. However, the levels of reduced glutathione (GSH), total non-protein thiols (TNP-SH) and phytochelatins (PCs) increased for all La concentrations. The results suggested that La was toxic to E. nuttallii because it induced oxidative stress and disturbed mineral uptake. However, E. nuttallii was able to combat La induced damage via an immobilization mechanism, which involved the cell wall and the activation of non-enzymatic antioxidant. PMID:25700094

  14. Fracto-emission in lanthanum-based metallic glass microwires under quasi-static tensile loading

    NASA Astrophysics Data System (ADS)

    Banerjee, Amit; Jiang, Chenchen; Lohiya, Lokesh; Yang, Yong; Lu, Yang

    2016-04-01

    Plastic deformation in metallic glasses is highly localized and often associated with shear banding, which may cause momentary release of heat upon fracture. Here, we report an explosive fracture phenomenon associated with momentary (˜10 ms) light emission (flash) in Lanthanum-based (LaAlNi) metallic glass microwires (dia. ˜50 μm) under quasi-static tensile loading. The load-displacement data as well as the visual information of the tensile deformation process were acquired through an in situ measurement set-up, which clearly showed nonlinear stress (σ)-strain ( ɛ) curves prior to yielding and also captured the occurrence of the flash at high fracture stresses (˜1 GPa). Through the postmortem fractographic analysis, it can be revealed that the fracto-emission upon quasi-static loading could be mainly attributed to the localized adiabatic work accumulated at a very large elastic strain confined within the microscale sample volume, followed by a localized high temperature rise up to ˜1000 K at the fracture surface through localized energy dissipation. Our findings suggest that the La-based metallic glass microwires could be useful for energetic microchips, micro-ignition devices, and other functional applications.

  15. Thermoelectric Power Generation from Lanthanum Strontium Titanium Oxide at Room Temperature through the Addition of Graphene.

    PubMed

    Lin, Yue; Norman, Colin; Srivastava, Deepanshu; Azough, Feridoon; Wang, Li; Robbins, Mark; Simpson, Kevin; Freer, Robert; Kinloch, Ian A

    2015-07-29

    The applications of strontium titanium oxide based thermoelectric materials are currently limited by their high operating temperatures of >700 °C. Herein, we show that the thermal operating window of lanthanum strontium titanium oxide (LSTO) can be reduced to room temperature by the addition of a small amount of graphene. This increase in operating performance will enable future applications such as generators in vehicles and other sectors. The LSTO composites incorporated one percent or less of graphene and were sintered under an argon/hydrogen atmosphere. The resultant materials were reduced and possessed a multiphase structure with nanosized grains. The thermal conductivity of the nanocomposites decreased upon the addition of graphene, whereas the electrical conductivity and power factor both increased significantly. These factors, together with a moderate Seebeck coefficient, meant that a high power factor of ∼2500 μWm(-1)K(-2) was reached at room temperature at a loading of 0.6 wt % graphene. The highest thermoelectric figure of merit (ZT) was achieved when 0.6 wt % graphene was added (ZT = 0.42 at room temperature and 0.36 at 750 °C), with >280% enhancement compared to that of pure LSTO. A preliminary 7-couple device was produced using bismuth strontium cobalt oxide/graphene-LSTO pucks. This device had a Seebeck coefficient of ∼1500 μV/K and an open voltage of 600 mV at a mean temperature of 219 °C. PMID:26095083

  16. Highly selective water adsorption in a lanthanum metal-organic framework.

    PubMed

    Plessius, Raoul; Kromhout, Rosa; Ramos, André Luis Dantas; Ferbinteanu, Marilena; Mittelmeijer-Hazeleger, Marjo C; Krishna, Rajamani; Rothenberg, Gadi; Tanase, Stefania

    2014-06-23

    We present a new metal-organic framework (MOF) built from lanthanum and pyrazine-2,5-dicarboxylate (pyzdc) ions. This MOF, [La(pyzdc)1.5(H2O)2]⋅2 H2O, is microporous, with 1D channels that easily accommodate water molecules. Its framework is highly robust to dehydration/hydration cycles. Unusually for a MOF, it also features a high hydrothermal stability. This makes it an ideal candidate for air drying as well as for separating water/alcohol mixtures. The ability of the activated MOF to adsorb water selectively was evaluated by means of thermogravimetric analysis, powder and single-crystal X-ray diffraction and adsorption studies, indicating a maximum uptake of 1.2 mmol g(-1) MOF. These results are in agreement with the microporous structure, which permits only water molecules to enter the channels (alcohols, including methanol, are simply too large). Transient breakthrough simulations using water/methanol mixtures confirm that such mixtures can be separated cleanly using this new MOF. PMID:24867871

  17. Boron ion beam generation utilizing lanthanum hexaboride cathodes: Comparison of vacuum arc and planar magnetron glow.

    PubMed

    Nikolaev, A G; Oks, E M; Vizir, A V; Yushkov, G Yu; Frolova, V P

    2016-02-01

    Boron ion beams are widely used for semiconductor ion implantation and for surface modification for improving the operating parameters and increasing the lifetime of machine parts and tools. For the latter application, the purity requirements of boron ion beams are not as stringent as for semiconductor technology, and a composite cathode of lanthanum hexaboride may be suitable for the production of boron ions. We have explored the use of two different approaches to boron plasma production: vacuum arc and planar high power impulse magnetron in self-sputtering mode. For the arc discharge, the boron plasma is generated at cathode spots, whereas for the magnetron discharge, the main process is sputtering of cathode material. We present here the results of comparative test experiments for both kinds of discharge, aimed at determining the optimal discharge parameters for maximum yield of boron ions. For both discharges, the extracted ion beam current reaches hundreds of milliamps and the fraction of boron ions in the total extracted ion beam is as high as 80%. PMID:26931963

  18. Study of lanthanum aluminum silicate glasses for passive and active optical fibers

    NASA Astrophysics Data System (ADS)

    Schuster, K.; Litzkendorf, D.; Grimm, S.; Kobelke, J.; Schwuchow, A.; Ludwig, A.; Leich, M.; Jetschke, S.; Dellith, J.; Auguste, J.-L.; Leparmentier, S.; Humbert, G.; Werner, G.

    2013-03-01

    We report on SiO2-Al2O3-La2O3 glasses - with and without Yb2O3 - suitable for nonlinear and fiber laser applications. We also present successful supercontinuum generation and fiber laser operation around 1060 nm in step-index fibers. We have optimized the glass compositions in terms of thermal and optical requirements for both a high La2O3 (24 mol%) and Yb2O3(6 mol%) concentration. The aluminum concentration was adjusted to about 21 mol% Al2O3 to increase the solubility of lanthanum and ytterbium in the glass beyond possible MCVD based techniques. The glasses have been characterized by dilatometrical methods to find transition temperatures from 860 to 880°C and thermal expansion coefficients between 4.1 and 7.0 × 10-6 K-1. Structured step index fibers with a SiO2-Al2O3-La2O3 core and silica cladding have been realized showing a fiber loss minimum of about 500 dB/km at 1200 nm wavelength. The chromatic dispersion could be adjusted to shift the zero dispersion wavelength (ZDW) close to the pump wavelength of 1550 nm in a supercontinuum generation setup. First fiber laser experiments show an efficiency of about 41 % with a remarkably reduced photodarkening compared to MCVD based fibers.

  19. Inhibitory Effects of Lanthanum Chloride on Wear Particle-Induced Osteolysis in a Mouse Calvarial Model.

    PubMed

    Shang, Jiang-Yin-Zi; Zhan, Ping; Jiang, Chuan; Zou, Yang; Liu, Hucheng; Zhang, Bin; Dai, Min

    2016-02-01

    Osteolysis is a bone disorder associated with progressive destruction of bone tissues. However, the effects of lanthanum chloride (LaCl3) on osteolysis remain unknown. Therefore, the aim of this study was to determine the effects of LaCl3 on osteolysis in vivo. In a mouse calvarial model, C57BL/6J mice were injected with wear particles with or without LaCl3. Microcomputed tomography, hematoxylin and eosin staining, and tartrate-resistant acid phosphatase staining were performed for the pathological characterization of calvariae, and eight calvariae per group were prepared for the assay of TNF-α, IL-1β, and RANKL secretion using quantitative enzyme-linked immunosorbent assay (ELISA). In mice treated with high-dose LaCl3, particle-induced osteolysis and inflammatory reaction were reduced compared with that in the vehicle-treated control. Moreover, treatment with high-dose LaCl3 suppressed the wear particle-induced decrease in bone mineral content, bone mineral density, and bone volume fraction. Bone destruction and resorption were higher in the LaCl3-treated group than in the saline-treated group but lower than those in the wear particle group. Finally, our results showed that treatment with a high dose of LaCl3 suppressed osteoclastogenesis. Thus, LaCl3 may represent a novel therapeutic agent for the treatment or prevention of wear particle-induced osteolysis and aseptic loosening. PMID:26105543

  20. Fluorescent complexes of nucleic acids/8-hydroxyquinoline/lanthanum(III) and the fluorometry of nucleic acids

    SciTech Connect

    Cheng Zhi Huang; Ke An Li; Shen Yang Tong

    1996-07-01

    The ternary fluorescent complexes of nucleic acids/8-hydroxyquinoline/lanthanum (III) were studied. Nucleic acids in the study involve natured and thermally denatured calf thymus DNA, fish sperm DNA and yeast RNA. In the range of PH 8.0-8.4 (controlled by NH{sub 3}-NH{sub 4}Cl buffer) ternary fluorescent complexes are formed which emit at 485.0 nm for calf thymus DNA and at 480.0 nm for fish sperm DNA when excited at 265.0 nm. Based on the fluorescence reactions sensitive fluorometric methods for nucleic acids were proposed. Using optimal conditions, the calibration curves were linear in the range of 0.4 --3.6 {mu}g{sup .}ml{sup -1} for calf thymus DNA, 0.4 -- 4.0 {mu}g{sup .}ml{sup -1} for fish sperm DNA and 0.4 --4.0{mu}g{sup .}ml{sup -1} for yeast RNA, respectively. Five synthetic samples were determined with satisfaction.