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1

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

NASA Technical Reports Server (NTRS)

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

Byvik, C. E.

1971-01-01

2

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

Microsoft Academic Search

As part of the development of rare earth based ceramic materials for a variety of applications, the thermal conductivities of lanthanum aluminate, samarium zirconate and europium zirconate were investigated, employing the laser flash technique and covering a temperature range from 650–1400 K. Based on the variation of the thermal resistivity as a function of temperature, the heat transport behaviour of

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

1998-01-01

3

Europium and samarium doped calcium sulfide thin films grown by PLD S. Christoulakis a,c  

E-print Network

Europium and samarium doped calcium sulfide thin films grown by PLD S. Christoulakis a,c , M Suchea Abstract Europium and samarium doped calcium sulfide thin films (CaS:Eu,Sm) with different thickness were and crystallinity. In this work we present preliminary results related to the deposition of europium and samarium

4

EXTENT OF PARTICULATE MARKER (SAMARIUM, LANTHANUM AND CERIUM) MOVEMENT FROM ONE DIGESTA PARTICLE TO ANOTHER 1'2  

Microsoft Academic Search

SUMMARY An in vitro and in vivo experiment was performed to determine the extent of move- ment of samarium (Sm), cerium (Ce), and lanthanum (La) from the original feedstuff upon which they were adsorbed to other feed particles. The rare-earth elements were demon- strated to be tenaciously bound to the parti- culate phase, with essentially none of the element occuring

Gary F. Hartnell; Larry D. Satter

5

Electrical properties of lanthanum doped barium titanate ceramics  

SciTech Connect

Pure and lanthanum doped barium titanate (BT) ceramics were prepared by sintering pellets at 1300 deg. C for 8 h, obtained from nanopowders synthesized by the polymeric precursor method. XRD results showed formation of a tetragonal structure. The presence of dopants changed the tetragonal structure to pseudo-cubic. The polygonal grain size was reduced up to 300 nm with addition of lanthanum as a donor dopant. Determined dielectric properties revealed that lanthanum modified BT ceramics possessed a diffused ferroelectric character in comparison with pure BT that is a classical ferroelectric material. In doped BT phase transition temperatures were shifted to lower temperatures and dielectric constant values were much higher than in pure BT. A modified Currie Weiss law was used to explore the connection between the doping level and degree of diffuseness of phase transitions. Impedance spectroscopy measurements were carried out at different temperatures in order to investigate electrical resistivity of materials and appearance of a PTCR effect. - Highlights: {yields} Pure and lanthanum doped BaTiO{sub 3} were prepared by polymeric precursors method. {yields} Change of structure from tetragonal to pseudo-cubic. {yields} Lanthanum as a donor dopant influenced on change of ferro-para phase transition. {yields} The diffuseness factor indicated the formation of diffuse ferroelectric material. {yields} Lanthanum affected on PTCR effect appearance in BT ceramics.

Vijatovic Petrovic, M.M., E-mail: miravijat@yahoo.com [Institute for Multidisciplinary Research, Belgrade University, Kneza Viseslava 1, Belgrade (Serbia); Bobic, J.D. [Institute for Multidisciplinary Research, Belgrade University, Kneza Viseslava 1, Belgrade (Serbia); Ramoska, T.; Banys, J. [Faculty of Physics, Vilnius University, Sauletekio al. 9, Vilnius (Lithuania); Stojanovic, B.D. [Institute for Multidisciplinary Research, Belgrade University, Kneza Viseslava 1, Belgrade (Serbia)

2011-10-15

6

Reaction mechanism between lanthanum manganite and yttria doped cubic zirconia  

Microsoft Academic Search

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

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

1999-01-01

7

High resolution investigation of Nd3+-doped strontium lanthanum aluminate  

Microsoft Academic Search

Strontium lanthanum aluminates crystals (ASL) doped with Nd3+ with formula Sr1-xNdyLax-yMgxAl12-xO19 are interesting crystals for lasers operating in i.r. (~900 nm range) or blue spectral ranges. This paper uses high-resolution spectroscopy, at low temperatures, for investigation of the influence of composition and Nd3+ doping of ASL crystals on emission properties. Preliminary spectral characteristics of two non-equivalent centers were determined. From

Daniel Vivien; Gerard Aka; Aurelia Lupei; Voicu Lupei; Cristian Gheorghe

2004-01-01

8

Luminescence of the samarium ions doped in the complex oxides with heterovalence substitution  

Microsoft Academic Search

Spectral investigation of luminescence both of cadmium tungstate (CdWO4) and calcium vanadate apatite (Ca5(VO4)3OH) crystals doped with samarium (Sm3+) ions are reported in the paper. Luminescence and excitation spectra of the investigated samples consist of both wide nonstructural spectral bands caused by matrix emission and narrow lines caused by electron transitions in the inner 4fn shell of the Sm3+ ions.

O. Chukova; S. Nedilko; Z. Moroz; M. Pashkovskyi

2003-01-01

9

The scintillation properties of cerium-doped lanthanum fluoride  

Microsoft Academic Search

We report on the scintillation properties of cerium-doped lanthanum fluoride (LaF3), a newly discovered dense (5.9 g\\/cm3) heavy-atom scintillator. We have investigated four dopant concentrations (0.01%, 1%, 10% and 50% mole fraction of CeF3) and measured the emission spectrum, light output and decay time distribution. The light output increases with increasing cerium concentration until a maximum is reached at 2200

W. W. Moses; S. E. Derenzo

1990-01-01

10

Single-Longitudinal-Mode Lanthanum-Codoped Bismuth-Based Erbium Doped Fiber Ring Laser  

E-print Network

Single-Longitudinal-Mode Lanthanum-Codoped Bismuth-Based Erbium Doped Fiber Ring Laser K. K and demonstrate a stable single-longitudinal-mode lanthanum-codoped bismuth oxide- based erbium doped fiber ring of the experimental setup to demonstrate the proposed SLM La-codoped bismuth based EDF ring laser. The fiber laser

Wai, Ping-kong Alexander

11

Thermal conductivity analysis of lanthanum doped manganites  

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

12

Lanthanum  

MedlinePLUS

Lanthanum is used to reduce blood levels of phosphate in patients with kidney disease. High levels of phosphate in the blood can cause bone problems. Lanthanum is in a class of medications called phosphate ...

13

Thermal conductivity analysis of lanthanum doped manganites  

SciTech Connect

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.

Mansuri, Irfan, E-mail: dr.irfan.mansuri@gmail.com [Indore Institute of Science and Technology, Pithampur Road Rau, Indore-453331 India and School of Physics, Devi Ahilya University, Khandwa Road Campus, Indore-452001 (India); Shaikh, M. W. [School of Physics, Devi Ahilya University, Khandwa Road Campus, Indore-452001, India and Acropolis Technical Campus, Village Tillore, Indore-453331 (India); Khan, E.; Varshney, Dinesh [School of Physics, Devi Ahilya University, Khandwa Road Campus, Indore-452001 (India)

2014-04-24

14

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

E-print Network

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

Hughes, M; Rutt, H; Hewak, D

2014-01-01

15

Synthesis of calcium doped lanthanum manganite by mechanosynthesis  

Microsoft Academic Search

Lanthanum manganite doped with calcium, Ca1\\/3La2\\/3MnO3??, was prepared by a high-energy ball milling. The precursors used were Mn2O3, La2O3 and CaO, mixed in the stoichiometric ratio to obtain this manganite. The mechano-chemical process was performed at room temperature in a SPEX 8000D mixer\\/mill, using hardened steel balls and stainless steel vials, in air atmosphere. X-ray diffraction was used to elucidate

A. M. Bolarín; F. Sánchez; S. Palomares; J. A. Aguilar; G. Torres-Villaseñor

2007-01-01

16

Magnetocaloric properties of doped lanthanum manganite films  

NASA Astrophysics Data System (ADS)

LaMnO3 films doped with Ca, Ba, or Sr have been fabricated using the metalorganic decomposition technique. These films exhibit paramagnetic-to-ferromagnetic phase transitions at 250, 300, and 350 K, respectively. By measuring the film magnetization as a function of field and temperature we have determined the entropy change associated with these transitions. The large magnetization of these materials results in a total entropy change a factor of five less than that of gadolinium, the prototypical high-temperature magnetocaloric material. Improvements in film morphology and composition may provide a further increase in the magnetization and total entropy change in these materials.

Morelli, Donald T.; Mance, Andrew M.; Mantese, Joseph V.; Micheli, Adolph L.

1996-01-01

17

Intrinsic properties of doped lanthanum manganite  

SciTech Connect

An investigation designed to display the intrinsic properties of perovskite manganites was accomplished by comparing the behavior of bulk samples with that of thin films; the results show the colossal magneto resistance at very low temperatures is not an intrinsic property of the thermodynamically stable 1/3 doped material. Epitaxial 1,500 {angstrom} films of perovskite La{sub 0.67}Ca{sub 0.33}MnO{sub 3} and La{sub 0.67}Sr{sub 0.33}MnO{sub 3} were grown by solid source chemical vapor deposition on LaAlO{sub 3} and post annealed in oxygen at 950 C. Below Tc/2 the intrinsic magnetization decreases as T{sup 2} (as can be expected for itinerant electron ferromagnets) while the intrinsic resistivity increases proportional to T{sup 2}. The constant and T{sup 2} coefficients of the resistivity are largely independent of magnetic field and alkaline earth element (Ca, Sr or Ba). The authors identify three distinct types of negative magnetoresistance. The largest effect is observed near the Curie temperature and is likely to be due to magnetic critical scattering. There is also magnetoresistance associated with the net magnetization of polycrystalline samples. The high temperature (above {Tc}) resistivity at La{sub 0.67}Ca{sub 0.33}MnO{sub 3} is consistent with small polaron hopping conductivity with a transition at 750K, while La{sub 0.67}Sr{sub 0.33}MnO{sub 3} does not exhibit activated conductivity until about 500K, well above {Tc}. The limiting low and high temperature resistivities may place a limit on the maximum possible magnetoresistance of these materials.

Snyder, G.J.; Beasley, M.R.; Geballe, T.H. [Stanford Univ., CA (United States). Dept. of Applied Physics; Hiskes, R.; DiCarolis, S. [Hewlett-Packard, Palo Alto, CA (United States)

1996-11-01

18

Dielectric Anisotropy of Flux Grown 1% Samarium Doped Gadolinium Vanadate (Sm:GdVO4) Single Crystal  

Microsoft Academic Search

Dielectric studies have been carried out on flux grown 1% samarium doped gadolinium vanadate single crystals. The variation of the dielectric constant (??), the dielectric loss (tan ?), imaginary dielectric constant (?) and electrical conductivity (?ac) at different temperatures and the frequencies of the applied field were studied. In order to observe the dielectric anisotropy, the observations were made along

K. K. Bamzai; Nidhi; Vishal Singh; P. N. Kotru; B. M. Wanklyn

2009-01-01

19

Improved tensile creep properties of yttrium-and lanthanum-doped alumina: a solid solution effect  

E-print Network

Improved tensile creep properties of yttrium- and lanthanum-doped alumina: a solid solution effect, Pennsylvania 18015 (Received 16 March 2000; accepted 30 October 2000) The tensile creep behavior of yttrium ppm yttrium, 100 ppm lanthanum) exhibited a uniform microstructure consisting of fine, equiaxed grains

Cho, Junghyun

20

Thermal decomposition of the rare earth sulfates of cerium(III), cerium(IV), lanthanum(III) and samarium(III)  

NASA Astrophysics Data System (ADS)

Surface and bulk chemical and elemental composition of the rare earth sulfates of cerium(III), cerium(IV), lanthanum(III) and samarium(III) were characterized during various stages of thermal decomposition. Decomposition was conducted under both vacuum and atmospheric conditions. In situ analysis was conducted on samples decomposed in vacuum. As identified by X-ray diffraction, the bulk decomposition of all the rare earth sulfate samples to their corresponding oxide, in atmosphere, proceeded via the formation of an oxysulfate. For the exception of cerium(III) sulfate, similar results were obtained in thermogravimetric analysis. The thermal decomposition profile, as determined by X-ray microanalysis was similar to that observed in thermogravimetric analysis and X-ray diffraction. Elemental maps revealed no observable concentration gradients of sulfur. Surface composition was not necessarily representative of the bulk composition. Thermal decomposition of sulfates to an oxide initiated at a lower temperature in vacuum than that observed at atmospheric pressure.

Poston, James A.; Siriwardane, Ranjani V.; Fisher, Edward P.; Miltz, Angela L.

2003-05-01

21

Altering the equilibrium condition in Sr-doped lanthanum manganite.  

SciTech Connect

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

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

1999-05-28

22

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

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

23

Improved chemical stability and conductivity of barium cerate nanopowders by Lanthanum doping.  

PubMed

Despite of the highest proton conductivity, barium cerate electrolytes are well known for the deficiency of chemical stability at elevated temperature under CO2 atmosphere. This work is focused on improving chemical stability of lanthanum doped barium cerate (BCL) powder for electrolyte. Although lanthanum doping causes distortion of perovskite structure lattice, immoderate doping could stabilize structure due to increasing symmetry of structure lattices. The thermogravimetric analysis and AC impedance measurements revealed that the lanthanum doping suppresses the reaction between barium and carbonate and this effect results in sufficient improvement in ionic conductivity in operating temperatures range. It was confirmed that BaCe0.7La0.3O3-delta (BCL30) was the most stable composition and the conductivity of BCL30 is high as 3.8 S x cm(-1) x K at 700 degrees C. PMID:24205607

Lee, Hunhyeong; Park, Inyu; Shin, Dongwook

2013-09-01

24

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

SciTech Connect

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

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

2012-04-15

25

Transport properties of silver-calcium doped lanthanum manganite  

NASA Astrophysics Data System (ADS)

Electrical properties of silver-calcium doped lanthanum manganite (La0.5Ca0.5-xAgxMnO3 with 0.0

Cherif, B.; Rahmouni, H.; Smari, M.; Dhahri, E.; Moutia, N.; Khirouni, K.

2015-01-01

26

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

SciTech Connect

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.

Morrell, B.; Okada, G.; Vahedi, S.; Koughia, C., E-mail: cyril.koughia@usask.ca; Kasap, S. O. [Department of Electrical and Computer Engineering, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5C9 (Canada); Edgar, A.; Varoy, C. [School of Chemical and Physical Sciences and MacDiarmid Institute, Victoria University of Wellington, Wellington 6140 (New Zealand); Belev, G.; Wysokinski, T.; Chapman, D. [Canadian Light Source, Inc., University of Saskatchewan, Saskatoon, Saskatchewan S7N 5C9 (Canada); Sammynaiken, R. [Saskatchewan Structural Sciences Centre, University of Saskatchewan, 110 Science Place, Saskatoon, Saskatchewan S7N 5C9 (Canada)

2014-02-14

27

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

NASA Astrophysics Data System (ADS)

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.

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

28

Influence of annealing temperature on the grain growth of samarium-doped ceria  

NASA Astrophysics Data System (ADS)

Samarium-doped ceria (SDC) can be used as electrolyte of solid oxide fuel cells (SOFCs). In this study, SDC films have been deposited by E-beam evaporation at room temperature (RT) and 200 °C, and then annealed at 500, 600, 700, and 800 °C. The structure and morphology of samples were analyzed by X-ray diffraction (XRD) and scanning electronic microscopy (SEM). Initial temperature for deposition of SDC films at RT and 200 °C, respectively, is shown to be critical with respect to crystallinity, texture coefficient, grain size, smoothness and morphology. The SDC film as deposited at RT is amorphous and extremely smooth. Whereas, the SDC film as deposited at 200 °C is crystalline, has a faceted surface, average grain size of 14 nm, arrow-head morphology, and no porosity. Generally, after annealing from 500 to 800 °C for both types of films, the grain size is shown to increase with increasing temperature and the development of pores is noted.

Huang, Hong-Hsin; Chang, Hung-Peng; Chien, Yu-Tsang; Huang, Ming-Chih; Wang, Jenn-Shing

2006-01-01

29

Combustion synthesis, sintering and magnetical properties of nanocristalline Ni-Zn ferrites doped with samarium  

Microsoft Academic Search

An investigation was made of combustion synthesis to uniformly incorporate small amounts of samarium additive into nanocrystalline Ni0.5Zn0.5Fe2 - xSmxO4 (0.0 = x = 0.1) nanopowders (˜26–20 nm particle size). The effect of the addition of the rare-earth ion samarium on the microstructure, relative density and magnetic properties of the Ni-Zn ferrite obtained by combustion reaction was studied. The samples

Ana Cristina F. M. Costa; Márcio R. Morelli; Ruth H. G. A. Kiminami

2004-01-01

30

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

NASA Astrophysics Data System (ADS)

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.

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

2015-01-01

31

Relaxor properties of lanthanum-doped bismuth layer-structured ferroelectrics  

Microsoft Academic Search

Several polycrystalline samples of bismuth layer-structured ferroelectrics (BLSF) family doped by lanthanum, Bi4-xLaxTi3O12, SrBi4-xLaxTi4O15, Sr2Bi4-xLaxTi5O18, and (Bi,La)4Ti3O12-Sr(Bi,La)4Ti4O15, were prepared by the traditional solid-state reaction method. Their ferroelectric and dielectric properties were investigated. The dielectric measurement data showed that the content of lanthanum determined the ferroelectric characteristics of the compounds. In each series samples, they behaved as normal ferroelectrics for small

Xiao-Bing Chen; Rong Hui; Jun Zhu; Wang-Ping Lu; Xiang-Yu Mao

2004-01-01

32

Effect of doping on surface reactivity and conduction mechanism in samarium-doped ceria thin films.  

PubMed

A systematic study by reversible and hysteretic electrochemical strain microscopy (ESM) in samples of cerium oxide with different Sm content and in several working conditions allows disclosing the microscopic mechanism underlying the difference in electrical conduction mechanism and related surface activity, such as water adsorption and dissociation with subsequent proton liberation. We have measured the behavior of the reversible hysteresis loops by changing temperature and humidity, both in standard ESM configuration and using the first-order reversal curve method. The measurements have been performed in much smaller temperature ranges with respect to alternative measuring techniques. Complementing our study with hard X-ray photoemission spectroscopy and irreversible scanning probe measurements, we find that water incorporation is favored until the doping with Sm is too high to allow the presence of Ce3+. The influence of doping on the surface reactivity clearly emerges from all of our experimental results. We find that at lower Sm concentration, proton conduction is prevalent, featured by lower activation energy and higher electrical conductivity. Defect concentrations determine the type of the prevalent charge carrier in a doping dependent manner. PMID:25415828

Yang, Nan; Belianinov, Alex; Strelcov, Evgheni; Tebano, Antonello; Foglietti, Vittorio; Di Castro, Daniele; Schlueter, Christoph; Lee, Tien-Lin; Baddorf, Arthur P; Balke, Nina; Jesse, Stephen; Kalinin, Sergei V; Balestrino, Giuseppe; Aruta, Carmela

2014-12-23

33

Dielectric investigations of polycrystalline samarium bismuth ferrite ceramic  

NASA Astrophysics Data System (ADS)

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.

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

2015-01-01

34

Cobalt doped lanthanum chromite material suitable for high temperature use  

DOEpatents

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

Ruka, Roswell J. (Churchill, PA)

1986-01-01

35

Cobalt doped lanthanum chromite material suitable for high temperature use  

DOEpatents

A high temperature, solid electrolyte electrochemical cell, subject to thermal cycling temperatures of between about 25 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.

Ruka, R.J.

1986-12-23

36

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

SciTech Connect

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

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

1995-06-01

37

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

NASA Astrophysics Data System (ADS)

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

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

1995-06-01

38

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

NASA Astrophysics Data System (ADS)

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

Gong, Wenquan

2005-07-01

39

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

NASA Astrophysics Data System (ADS)

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.

Zhao, Ya-Ru

2015-02-01

40

Sintering behavior of doped lanthanum and yttrium manganite  

SciTech Connect

The sintering behavior of doped manganite powders was found to be highly dependent on changes in calcination conditions and A/B cation ratio. Coarsening of combustion, synthesized powders by calcination allowed for higher green densities in dry-pressed compacts, which resulted in higher sintered densities for powders calcined in the temperature range 800--1,200 C. Sintered densities decreased for calcination temperatures greater than 1,200 C. Preparation of manganites with a deficiency of A-site cations improved the densification behavior substantially. This effect was attributed to an increased concentration of A-site vacancies which enhanced the diffusion of A-site cations during sintering. Modification of doped manganites by alteration of composition and calcination condition s allowed their sintering shrinkage to be ``tailored`` to more closely match the shrinkage of yttria-stabilized zirconia.

Stevenson, J.W.; Hallman, P.F.; Armstrong, T.R.; Chick, L.A. [Pacific Northwest Lab., Richland, WA (United States)

1995-03-01

41

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

PubMed

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 La(3+) doping at a Ce(4+) site we use DFT and DFT + U, with U = 5 eV for Ce 4f states and U = 7 eV for O 2p states. When La(3+) substitutes on a Ce(3+) site, an La'(Ce) + O.(o)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 Ce(3+) 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. PMID:21389507

Yeriskin, Irene; Nolan, Michael

2010-04-01

42

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

NASA Astrophysics Data System (ADS)

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.

Yeriskin, Irene; Nolan, Michael

2010-04-01

43

Spectral properties of Ce3+ doped yttrium lanthanum oxide transparent ceramics  

NASA Astrophysics Data System (ADS)

Ce3+-doped yttrium lanthanum oxide (Y0.9La0.1)2O3 transparent ceramics is fabricated with nanopowders and sintered in H2 atmosphere. The spectral properties of Ce:(Y0.9La0.1)2O3 transparent ceramics are investigated. There appear two characteristic absorption peaks of Ce3+ ions at 230 nm and 400 nm, separately. It is found that Ce3+ ions can efficiently produce emission at 384 nm from (Y0.9La0.1)2O3 transparent ceramic host, while the emission is completely quenched in Re2O3 (Re = Y, Lu, La) host materials.

Yang, Qiu-Hong; Zhou, Hong-Xu; Lu, Shen-Zhou

2010-02-01

44

Rate-controlling species for creep of the solid state electrolyte: doped lanthanum gallate  

Microsoft Academic Search

The rate-controlling species for creep of fine-grained doped lanthanum gallate, La0.8Sr0.2Ga0.85Mg0.15O2.825 (LSGM), was determined by comparing: (i) the activation energy for creep with activation energies determined by ionic conductivity, oxygen tracer diffusion and theoretical predictions; (ii) the magnitude of the diffusion coefficient determined from creep data with the self-diffusion coefficients; and (iii) the dependence of the stress on oxygen partial

J. Wolfenstine

1999-01-01

45

Czochralski growth and characterization of neodymium-doped strontium lanthanum aluminate (ASL:Nd) single crystals  

Microsoft Academic Search

Nd-doped strontium lanthanum aluminate crystals, Nd:ASL (Sr1?xNdyLax?yMgxAl12?xO19), with an extended composition parameter x (0.05 and 0.5) have been grown by the Czochralski pulling technique. Structural and compositional properties of the as-grown crystals have been studied using X-ray diffraction, chemical microanalysis and optical spectroscopy. The results show that high crystalline perfection and large size crystals of both compositions can be grown.

L. Gheorghe; V. Lupei; A. Lupei; C. Gheorghe; C. Varona; P. Loiseau; G. Aka; D. Vivien; B. Ferrand

2005-01-01

46

Modification of dielectric relaxations in sodium bismuth titanate with samarium doping  

NASA Astrophysics Data System (ADS)

Na0.5Bi(0.5-x) SmxTiO3 (NBST) ceramics with x=0.05, 0.1, and 0.15 are prepared through chemical route. The X-ray diffraction studies confirmed the formation of single phase. Dielectric measurements in the temperature region ranging from room temperature (˜30 °C) to 600 °C at different frequencies (10 kHz 1 MHz) showed anomalies at 130, 306, and 474 °C (at 10 kHz frequency) for x=0.05 sample. Other samples showed only two peaks. To establish the electrical nature of these relaxations, impedance measurements are done at different temperatures and frequencies. The relaxation time, obtained from both impedance and modulus data, is found to decrease with increase in temperature. The relaxations observed are of non-Debye type. Increase in samarium content increases the activation energy for relaxation.

Raghavender, M.; Kumar, G. S.; Prasad, G.

2006-08-01

47

Thermopower studies of rare earth doped lanthanum barium manganites  

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

48

Lasing action and optical amplification in Nd3+ doped electrooptic lanthanum lead zirconate titanate ceramics.  

PubMed

Both single-pass gain and lasing action at 1064.4 nm were observed in ceramic gain media of neodymium doped lanthanum-modified lead zirconate titanate, which exhibits good electrooptic (EO) effect from visible through mid-wave IR band (400 nm to 5.5 µm). These works have removed roadblocks off the way leading to development of long envisioned multifunctional optical devices. The impact of the Nd3+ doping concentration on the EO effect in the Nd3+:PLZT ceramics was studied. The finding of the slowly trailing-off was satisfactorily explained with the rich vacancy-based carrier traps, which are responsible for the long persistent optoenergy storage. PMID:21369120

Zhao, Hua; Sun, Xiudong; Zhang, Jingwen W; Zou, Yingyin K; Li, Kewen K; Wang, Yanyun; Jiang, Hua; Huang, Pi-Ling; Chen, Xuesheng

2011-02-14

49

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

PubMed

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

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

2006-12-01

50

Preparation and property-performance relationships in samarium-doped ceria nanopowders for solid oxide fuel cell electrolytes  

NASA Astrophysics Data System (ADS)

In a systematic study, Samarium doped ceria (SDC) nanopowders, SmxCe1-xO2-x/2 (x = 0.1, 0.2 or 0.3), were prepared by a low temperature citrate complexation route. The synthesis and crystallisation of the SDC powders were followed by thermochemical techniques (TGA/DTA), X-ray diffraction, elemental analysis, specific surface area determination (BET) and electron microscopy (SEM and TEM). Mean crystallite sizes were found to be around 10 nm for all compositions calcined at 500 °C. Dense electrolyte bodies were prepared at 1300 °C, 1400 °C and 1450 °C using two sintering times, 4 h or 6 h. Densities of 91-97% of theoretical were obtained, with a marked improvement in density on going from 1300 °C to higher sintering temperatures. Grain size analysis was conducted using SEM. Grain size distributions were related to %Sm and sintering conditions. Impedance spectroscopy was used to determine the total, bulk and grain boundary conductivities, the related activation energies and enthalpies of defect association and ion migration. Sintering at 1400 °C/6 h or 1450 °C/4 h gave superior grain structure and conductivity, with oversintering occurring after more severe treatments. At 600 °C the highest total ionic conductivity was 1.81 × 10-2 S cm-1 for Sm0.2Ce0.8O1.9. The relationships between chemical composition, sintering parameters, grain structure and electrochemical performance are discussed.

Kosinski, Marcin R.; Baker, Richard T.

2011-03-01

51

Intense Red Catho- and Photoluminescence from 200 nm Thick Samarium Doped Amorphous AlN Thin Films  

PubMed Central

Samarium (Sm) doped aluminum nitride (AlN) thin films are deposited on silicon (100) substrates at 77 K by rf magnetron sputtering method. Thick films of 200 nm are grown at 100–200 watts RF power and 5–8 m Torr nitrogen, using a metal target of Al with Sm. X-ray diffraction results show that films are amorphous. Cathodoluminescence (CL) studies are performed and four peaks are observed in Sm at 564, 600, 648, and 707 nm as a result of4G5/2 ? 6H5/2,4G5/2 ? 6H7/2,4G5/2 ? 6H9/2, and4G5/2 ? 6H11/2transitions. Photoluminescence (PL) provides dominant peaks at 600 and 707 nm while CL gives the intense peaks at 600 nm and 648 nm, respectively. Films are thermally activated at 1,200 K for half an hour in a nitrogen atmosphere. Thermal activation enhances the intensity of luminescence. PMID:20596367

2009-01-01

52

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

NASA Astrophysics Data System (ADS)

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 (?) with temperature (T) is recorded by a Faraday Magnetometer in the temperature range of 300-14 K. The variation of ? 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.

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

2014-12-01

53

Relaxor properties of lanthanum-doped bismuth layer-structured ferroelectrics  

NASA Astrophysics Data System (ADS)

Several polycrystalline samples of bismuth layer-structured ferroelectrics (BLSF) family doped by lanthanum, Bi4-xLaxTi3O12, SrBi4-xLaxTi4O15, Sr2Bi4-xLaxTi5O18, and (Bi,La)4Ti3O12-Sr(Bi,La)4Ti4O15, were prepared by the traditional solid-state reaction method. Their ferroelectric and dielectric properties were investigated. The dielectric measurement data showed that the content of lanthanum determined the ferroelectric characteristics of the compounds. In each series samples, they behaved as normal ferroelectrics for small x, but all of them tended to become relaxors when x was increased. The critical value of the La content causing relaxor characteristics is different for the different BLSFs due to the difference of the number of strontium atoms in their crystal structures. The appearance of the relaxor behavior was attributed to a ferroelectric microdomain state induced by random fields.

Chen, Xiao-Bing; Hui, Rong; Zhu, Jun; Lu, Wang-Ping; Mao, Xiang-Yu

2004-11-01

54

Relaxor properties of lanthanum-doped bismuth layer-structured ferroelectrics  

SciTech Connect

Several polycrystalline samples of bismuth layer-structured ferroelectrics (BLSF) family doped by lanthanum, Bi{sub 4-x}La{sub x}Ti{sub 3}O{sub 12}, SrBi{sub 4-x}La{sub x}Ti{sub 4}O{sub 15}, Sr{sub 2}Bi{sub 4-x}La{sub x}Ti{sub 5}O{sub 18}, and (Bi,La){sub 4}Ti{sub 3}O{sub 12}-Sr(Bi,La){sub 4}Ti{sub 4}O{sub 15}, were prepared by the traditional solid-state reaction method. Their ferroelectric and dielectric properties were investigated. The dielectric measurement data showed that the content of lanthanum determined the ferroelectric characteristics of the compounds. In each series samples, they behaved as normal ferroelectrics for small x, but all of them tended to become relaxors when x was increased. The critical value of the La content causing relaxor characteristics is different for the different BLSFs due to the difference of the number of strontium atoms in their crystal structures. The appearance of the relaxor behavior was attributed to a ferroelectric microdomain state induced by random fields.

Chen Xiaobing; Hui Rong; Zhu Jun; Lu Wangping; Mao Xiangyu [College of Physics Science and Technology, Yangzhou University, Yangzhou 225002 (China); National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210008 (China)

2004-11-15

55

Wavelength translation based on photoinduced broadband absorption in Nd3+ -doped lanthanum lead zirconate titanate ceramics.  

PubMed

A correlation between a photoinduced broadband absorption (BBA) and a strong long persistent optoenergy storage (LPOES), both evident in ceramic plates of neodymium-doped lanthanum-modified lead zirconate titanate (Nd:PLZT), has been proposed and verified experimentally. As a direct evidence of the suggested correlation, a 3.0 dB gain was obtained with a preilluminated Nd:PLZT plate by simply heating up the plate to 60 degrees C. Thermal history related gain profiles taken in an Nd:PLZT plate unveiled that the intrinsically rich carrier traps in the ceramics are highly responsible for the remarkable BBA and underlying LPOES, and hence thermal to near-IR wavelength translation. PMID:19448824

Zhang, Jingwen W; Li, Kewen K; Zhao, Hua; Zou, Yingyin K; Bartolo, Baldassare Di; Chen, Xuesheng

2009-05-15

56

Enhanced ionic conductivity in pyrochlore and fluorite mixed phase yttrium-doped lanthanum zirconate  

NASA Astrophysics Data System (ADS)

A series of yttrium-doped lanthanum zirconate (La1-xYx)2Zr2O7 (0 ? x ? 1) bulk samples were prepared and their ionic conductivities were studied by impedance spectroscopy. It is found that intermixing of Y and La ions increases the conductivity of the end members pyrochlore-type La2Zr2O7 and fluorite-type Y2Zr2O7. Highest conductivity which is 2-3 orders of magnitude higher than that of La2Zr2O7 and Y2Zr2O7 is achieved in a two-phase sample which consists of both pyrochlore and fluorite phases. The enhanced conductivity in the two-phase sample is attributed to the presence of the pyrochlore-fluorite phase boundary, which has higher conductivity than the pyrochlore and the fluorite phase grains. The effect of the conductive phase boundary has been confirmed by a 2-dimensional finite element modelling.

Yang, Fan; Wang, Yanfei; Zhao, Xiaofeng; Xiao, Ping

2015-01-01

57

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

PubMed

Bismuth is doped to lanthanum strontium ferrite to produce ferrite-based perovskites with a composition of La(0.8-x)Bi(x)Sr0.2FeO(3-?) (0 ? x ? 0.8) as novel cathode material for intermediate-temperature solid oxide fuel cells. The perovskite properties including oxygen nonstoichiometry coefficient (?), average valence of Fe, sinterability, thermal expansion coefficient, electrical conductivity (?), oxygen chemical surface exchange coefficient (K(chem)), and chemical diffusion coefficient (D(chem)) are explored as a function of bismuth content. While ? decreases with x due to the reduced Fe(4+) content, D(chem) and K(chem) increase since the oxygen vacancy concentration is increased by Bi doping. Consequently, the electrochemical performance is substantially improved and the interfacial polarization resistance is reduced from 1.0 to 0.10 ? cm(2) at 700 °C with Bi doping. The perovskite with x = 0.4 is suggested as the most promising composition as solid oxide fuel cell cathode material since it has demonstrated high electrical conductivity and low interfacial polarization resistance. PMID:24971668

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

2014-07-23

58

Kr and Xe irradiations in lanthanum (La) doped ceria: Study at the high dose regime  

NASA Astrophysics Data System (ADS)

In order to understand cavity and bubble formation and growth in oxide nuclear fuel materials, ion beam irradiation experiments were conducted with two common fission gas species: Kr and Xe. Ceria (CeO 2) was selected as a surrogate material for uranium dioxide (UO 2) due to its many similar properties to UO 2. Ion beam energies were chosen such that both cavities and gas bubbles structures were induced by ion irradiations. The ion irradiation experiments were carried out at 600 °C, at which temperature, cavity/gas bubble structures are believed to be immobile in this material. Lanthanum (La) was chosen as a dopant in CeO 2 to investigate the effect of impurities. The presence of La in the CeO 2 lattice also introduces a predictable initial concentration of oxygen vacancies, similar to the introduction of oxygen vacancies by the existence of Pu 3+ in MOX fuel [1]. The influence of two La concentrations, 5% and 25%, were examined. The study focused on the high dose regime where cavity/gas bubble structures were clearly identifiable with their sizes and number densities readily measurable. Cavity/gas bubble coarsening by coalescence was identified with TEM (Transmission Electron Microscopy) characterizations of as-irradiated La doped CeO 2 specimens. The results revealed that lanthanum trapping has significant influence on the cavity/bubble growth in the material lattice by comparing the cavity/gas bubble size distributions between 5% La doped ceria and 25% La doped ceria. Lattice and kinetic Monte Carlo calculations described in a previous work have provided insights to the interpretations of the experimental results [2]. Solid state Xe precipitates were observed in low energy Xe implantation in 5% La doped ceria to a very high fluence of 1 × 10 17 ions/cm 2 at 600 °C. The solid state Xe precipitate structures are represented by faceted morphology. Very similar observations of solid state/near solid state Xe bubbles were made by Nogita et al. in the outer region of UO 2 pellet irradiated to a pellet average burnup of 49 GWd/t [3].

Yun, Di; Oaks, Aaron J.; Chen, Wei-ying; Kirk, Marquis A.; Rest, Jeffrey; Insopov, Zinetula Z.; Yacout, Abdellatif M.; Stubbins, James F.

2011-11-01

59

Effect of samarium doping on the properties of solid-state synthesized multiferroic bismuth ferrite  

Microsoft Academic Search

Problems in the synthesis of phase-pure BiFeO3, a multiferroic material, are well known and presence of other phases often leads to inferior properties. Work reported here was carried out to obtain pure phase BiFeO3 via a solid-state-reaction method in both pure and Sm-doped form. X-ray diffraction (XRD) of the calcined undoped samples showed that maximum amount of pure BiFeO3 phase

K. S. Nalwa; A. Garg; A. Upadhyaya

2008-01-01

60

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

NASA Astrophysics Data System (ADS)

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.

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

2014-12-01

61

Electrical properties of lanthanum doped Bi 4Ti 3O 12 thin films annealed in different atmospheres  

Microsoft Academic Search

Pure and lanthanum doped Bi4Ti3O12 thin films were deposited on Pt\\/Ti\\/SiO2\\/Si substrate using a polymeric precursor solution. Annealing in static air and oxygen atmosphere was performed at 700°C for 2h. The obtained films were characterized by X-ray diffraction and atomic force microscopy. The dielectric constant and dissipation factor were measured in the frequency region from 1kHz to 1MHz. Electrical characterization

A. Z. Simões; A. Ries; B. D. Stojanovic; G. Biasotto; E. Longo; J. A. Varela

2007-01-01

62

Laser performance and spectroscopic analysis of optically written channel waveguides in neodymium-doped gallium lanthanum sulphide glass  

Microsoft Academic Search

We present a spectroscopic analysis and laser characterization of optically written waveguides in neodymium-doped gallium lanthanum sulphide (Nd3+-Ga:La:S) chalcogenide glass. Uniform channel waveguides were fabricated in Nd3+-Ga:La:S by exposure to radiation from a focused UV-laser beam (?=244 nm), producing a refractive index change ▵n?+10-3. The observed laser performance and fluorescence decay were in good agreement with values calculated from a

Arshad K. Mairaj; Alain M. Chardon; David P. Shepherd; Daniel W. Hewak

2002-01-01

63

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)

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.

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

2011-07-01

64

Anomalous Hall effect in calcium-doped lanthanum cobaltite and gadolinium  

NASA Astrophysics Data System (ADS)

The physical origin of the anomalous (proportional to magnetization) Hall effect is not very well understood. While many theories account for a Hall effect proportional to the magnetization of a material, these theories often predict effects significantly smaller than those found in ferromagnetic materials. An even more significant deficiency of the conventional theories is that they predict an anomalous Hall resistivity that is proportional to a power of the resistivity, and in the absence of a metal insulator transition cannot account for the anomalous Hall effect that peaks near TC. Recent models based on a geometric, or Berry, phase have had a great deal of success describing the anomalous Hall effect in double-exchange systems (e.g., lanthanum manganite and chromium dioxide). In gadolinium, as in double-exchange magnets, the exchange interaction is mediated by the conduction electrons and the anomalous Hall effect may therefore resemble that of CrO2 and other metallic double-exchange ferromagnets. Lanthanum cobaltite is similar to manganite in many ways, but a strong double-exchange interaction is not present. Calcium-doped lanthanum cobaltite films were found to have the largest anomalous Hall effect of any ferromagnetic metal. The primary purpose of this study is to gain insight into the origin of the anomalous Hall effect with the hope that these theories can be extended to account for the effect in other materials. The Hall resistivity, magnetoresistance, and magnetization of a Gadolinium single crystal were measured in fields up to 30 T. Cobaltite films were grown via laser ablation and characterized by a variety of techniques. Hall resistivity, magnetoresistance, magnetization, and magnetothermopower of L 1-xCaxCoO3 samples with 0.15 < x < 0.4 were measured in fields up to 7 T. The Gd results suggest that Berry's phase contributes partially to the Hall effect near TC. Berry's phase theories hold promise for explaining the large anomalous Hall effect in La1-xCaxCoO3 near T C, but the material presents many additional complexities, including a unique low temperature magnetoresistance. At low temperature, the Hall effect may be best explained by spin-polarized carriers scattering off of orbital disorder in spin-ordered clusters.

Baily, Scott Alan

65

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

NASA Astrophysics Data System (ADS)

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.

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

2011-09-01

66

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

SciTech Connect

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 Sm{sup 3+}{yields} Sm{sup 2+} valence conversion in Sm{sup 3+} 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 {approx}5 Gy and saturates at doses exceeding {approx}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.

Okada, Go; Morrell, Brian; Koughia, Cyril; Kasap, Safa [Department of Electrical and Computer Engineering, University of Saskatchewan, Saskatoon, SK S7N 5A9 (Canada); Edgar, Andy; Varoy, Chris [School of Chemical and Physical Sciences and MacDiarmid Institute, Victoria University of Wellington, Kelburn Parade (New Zealand); Belev, George; Wysokinski, Tomasz [Canadian Light Source Inc., University of Saskatchewan, Saskatoon, SK S7N 0X4 (Canada); Chapman, Dean [Department of Anatomy and Cell Biology, University of Saskatchewan, Saskatoon, SK S7N 5E5 (Canada)

2011-09-19

67

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

Microsoft Academic Search

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

Hongming ZHOU; Danqing YI

2008-01-01

68

Magnetocaloric effect in potassium doped lanthanum manganite perovskites prepared by a pyrophoric method.  

PubMed

The magnetocaloric effect (MCE) in fine grained perovskite manganites of the type La(1-x)K(x)MnO(3) (0lanthanum manganite enhances the Curie temperature (T(C)) of the system from 260.4 K (x = 0.05) to 309.7 K (x = 0.15). A large magnetic entropy change associated with the ferromagnetic-paramagnetic transition has been observed. The maximum entropy change |?S(M)(Max)| in an applied field of 1 T shows an enhancement by ?10% with increase in K content up to x = 0.15. La(0.85)K(0.15)MnO(3) exhibits the largest |?S(M)(Max)| value of 3.00 J kg(-1) K(-1) at 310 K amongst the compounds investigated. Moreover, the maximum magnetic entropy change exhibits a linear dependence with applied magnetic field. The estimated adiabatic temperature change at T(C) and at 1 T field also increases with K doping, being a maximum of 2.1 K for the La(0.85)K(0.15)MnO(3) compound. The relative cooling power (RCP) of La(1-x)K(x)MnO(3) compounds is estimated to be about one-third of that of the prototype magnetic refrigerant material (pure Gd). However, La(1-x)K(x)MnO(3) compounds possess an MCE around room temperature, which is comparable to that of Gd. Further, tailoring of their T(C), higher chemical stability, lower eddy current heating and lower cost of synthesis are some of the attractive features of K doped lanthanum manganites that are advantageous for a magnetic refrigerant. The temperature dependence of the magnetic entropy change (?S(M)) measured under various magnetic fields is explained fairly well using the Landau theory of phase transitions. Contributions of magnetoelastic and electron interaction are found to have a strong influence in the magnetocaloric effect of manganites. PMID:21690875

Das, Soma; Dey, T K

2006-08-16

69

Thermal-expansion behaviors and mechanisms for Ca- or Sr-doped lanthanum manganite perovskites under oxidizing atmospheres  

SciTech Connect

The thermal expansion behavior and mechanism of A-site-deficient lanthanum manganite perovskites, La{sub 1{minus}x}MnO{sub 3} (0 < x {le} 0.1), and alkaline earth metal (AE)-doped lanthanum manganite perovskites, La{sub 1{minus}x}AE{sub x}MnO{sub 3} (AE = Ca and Sr, 0 {le} x {le} 0.4), under oxidizing atmospheres have been investigated. The average linear thermal expansion coefficients of the AE-doped lanthanum manganites decreased with increasing Ca content up to 20 mol % and with increasing Sr content up to 10 mol %, and then increased. During the thermal cycle measurement, the La{sub 1{minus}x}MnO{sub 3} (0 {le} x {le} 0.1) perovskite samples and the La{sub 1{minus}x}AE{sub x}MnO{sub 3} perovskites (0 {le} x {le} 0.3) shrank, while no anomalous shrinkage behavior was observed for the La{sub 0.6}AE{sub 0.4}MnO{sub 3} samples. From the results of high-temperature X-ray diffraction analysis, no dependency of cell volume of the perovskites on aging time at selected temperatures and on thermal cycles was observed.

Mori, Masashi; Hiei, Yoshiko; Sammes, N.M.; Tompsett, G.A.

2000-04-01

70

Stability of strontium-doped lanthanum manganite cathode in humidified air  

NASA Astrophysics Data System (ADS)

The stability of strontium-doped lanthanum manganite (LSM) cathode has been studied using symmetric cells (humidified air, LSM/yttria-stabilized zirconia (YSZ)/LSM, humidified air) under a range of humidification levels (0-50%), temperatures (750-850 °C), and cathodic biases (0-0.5 V). Electrochemical impedance spectroscopy revealed an increase in non-ohmic resistance with increasing H2O/O2 ratio, temperature, and cathodic bias. Post-test surface and interface studies showed the segregation of SrO particles on the LSM surface and formation of Mn2O3 and La2Zr2O7 compounds at the cathodic LSM/YSZ interface. The increase in non-ohmic resistance is attributed to surface segregation of SrO and interfacial compound formation, whereas formation and growth of SrO at the LSM surface is attributed to water adsorption. La2Zr2O7 formation is attributed to interfacial reactions.

Hu, Boxun; Keane, Michael; Mahapatra, Manoj K.; Singh, Prabhakar

2014-02-01

71

Lanthanum-stabilized europium-doped cubic barium chloride: An efficient x-ray phosphor  

NASA Astrophysics Data System (ADS)

We report the photoluminescence and x-ray luminescence of lanthanum-stabilized cubic barium chloride with europium (Eu2+) doping, of general composition Ba1-x-yEuyLaxCl2+x. X-ray diffraction patterns confirm that the material adopts a cubic fluorite structure for x=0.125 and 0

Edgar, A.; Zimmermann, J.; von Seggern, H.; Varoy, C. R.

2010-04-01

72

Suppression of cavitation in melted tungsten by doping with lanthanum oxide  

NASA Astrophysics Data System (ADS)

Melting and boiling behaviour of pure tungsten and 1 wt% lanthanum-oxide-doped tungsten (WL10) are investigated, focusing on the material selection with respect to material loss induced by cavitation. Melting experiments under high heat loads are carried out in the high heat flux facility GLADIS. Pulsed hydrogen neutral beams with heat flux of 10 and 23 MW m-2 are applied onto the adiabatically loaded samples for intense surface melting. Melt layer of the two tungsten grades exhibit different microstructure characteristics. Substantive voids owning to cavitation in the liquid phase are observed in pure W and lead to porous resolidified material. However, little cavitation bubbles can be found in the dense resolidified layer of WL10. In order to find out the gaseous sources, vapour collection is performed and the components are subsequently detected. Based on the observations and analyses, the microstructure evolutions corresponding to melting and vapourization behaviour of the two tungsten grades are tentatively described, and furthermore, the underlying mechanisms of cavitation in pure W and its suppression in WL10 are discussed.

Yuan, Y.; Xu, B.; Fu, B. Q.; Greuner, H.; Böswirth, B.; Xu, H. Y.; Li, C.; Jia, Y. Z.; Qu, S. L.; Luo, G.-N.; Lu, G. H.; Liu, W.

2014-08-01

73

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

PubMed

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

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

2015-03-16

74

Surface and interface behaviors of Sr-doped lanthanum manganite air electrode in different moisture atmospheres  

NASA Astrophysics Data System (ADS)

Surface and interface reactions of the air electrode with the contacting components of solid oxide cells are essential for the long term operation stability and performance. In this work, an yttria-stabilized zirconia electrolyte (YSZ)/strontium-doped lanthanum manganite electrode (LSM)/AISI 441 alloy interconnect tri-layer structure has been fabricated in order to simulate the working environment of a real cell with Cr-containing interconnect. The samples are thermally treated in moist air atmospheres (0 vol%, 10 vol%, and 25 vol% moisture) at 800 °C for up to 500 h. The interactions among different cell components are characterized. The LSM air electrode shows slight grain growth but the growth is less in moist atmospheres. High moisture level affects the bonding between the LSM and the YSZ and leads to the formation of small particles on the YSZ surface. The amount of Cr deposition on the LSM surface is slightly more for the samples thermally treated in the moist atmospheres and shows no significant difference between the 10 vol% and 25 vol% moisture air. At the YSZ/LSM interface, La enrichment is significant and facilitates the Cr deposition while Mn depletion occurs. The YSZ surface composition is not strongly affected by the atmosphere.

Jin, Tongan; Lu, Kathy

2012-01-01

75

Magnetoresistance measurements in Ferro -- Antiferromagnetic bilayers based on the Ca-doped lanthanum manganite system  

NASA Astrophysics Data System (ADS)

We studied the isothermal magnetic field dependence of the resistance behavior in ferromagnetic--antiferromagnetic interface based on the Ca-doped lanthanum manganite system at temperatures below Neel temperature of the antiferromagnetic layer. We studied the influence of the thickness of the AF-layer, tAF, and F-layer, tF, on the ZFC and FC magnetoresistance (MR) in La2/3Ca1/3MnO3(tF)/ La1/3Ca2(3MnO3(tAF) bilayers. HFC was 400 Oe and the applied magnetic field, H. We systematically varied the tF and tAF thickness, maintaining constant the total bilayer thickness (d = tF+ tAF). We found that MR has hysteretic behavior as observed in [La2/3Ca1/3MnO3(tF)/La1/3Ca2(3MnO3(tAF)]N superlattices, but; MR increases with the increasing field from H=0 to a maximum and then decreases continuously. This behavior also appears for negative fields in both ZFC and FC loops. The position and magnitude of the maximum is not symmetric with respect to the axis H=0.

Gomez, M. E.; Marin, L.; Ramirez, G.; Prieto, P.

2011-03-01

76

Blocking effect of crystal–glass interface in lanthanum doped barium strontium titanate glass–ceramics  

SciTech Connect

Graphical abstract: The blocking effect of the crystal–glass interface on the carrier transport behavior in the lanthanum doped barium strontium titanate glass–ceramics: preparation and characterization. - Highlights: • La{sub 2}O{sub 3} addition promotes the crystallization of the major crystalline phase. • The Z? and M? peaks exist a significant mismatch for 0.5 mol% La{sub 2}O{sub 3} addition. • The Z? and M? peaks separate obviously for 1.0 mol% La{sub 2}O{sub 3} addition. • Crystallite impedance decreases while crystal–glass interface impedance increases. • La{sub 2}O{sub 3} addition increases blocking factor of the crystal–glass interface. - Abstract: The microstructures and dielectric properties in La{sub 2}O{sub 3}-doped barium strontium titanate glass–ceramics have been investigated by scanning electron microscopy (SEM) and impedance spectroscopy. SEM analysis indicated that La{sub 2}O{sub 3} additive decreases the average crystallite size. Impedance spectroscopy revealed that the positions of Z? and M? peaks are close for undoped samples. When La{sub 2}O{sub 3} concentration is 0.5 mol%, the Z? and M? peaks show a significant mismatch. Furthermore, these peaks separate obviously for 1.0 mol% La{sub 2}O{sub 3} addition. With increasing La{sub 2}O{sub 3} concentration, the contribution of the crystallite impedance becomes smaller, while the contribution of the crystal–glass interface impedance becomes larger. More interestingly, it was found that La{sub 2}O{sub 3} additive increases blocking factor of the crystal–glass interface in the temperature range of 250–450 °C. This may be attributed to a decrease of activation energy of the crystallite and an increase of the crystal–glass interface area.

Wang, Xiangrong [Beijing Fine Ceramics Laboratory, State Key Laboratory of New Ceramics and Fine Processing, Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084 (China); Zhang, Yong, E-mail: yzhang@tsinghua.edu.cn [Beijing Fine Ceramics Laboratory, State Key Laboratory of New Ceramics and Fine Processing, Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084 (China); Baturin, Ivan [Ferroelectric Laboratory, Institute of Natural Science, Ural Federal University, Ekaterinburg 620000 (Russian Federation); Liang, Tongxiang [Beijing Fine Ceramics Laboratory, State Key Laboratory of New Ceramics and Fine Processing, Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084 (China)

2013-10-15

77

Index matching between passive and active tellurite glasses for use in microstructured fiber lasers: erbium doped lanthanum-tellurite glass.  

PubMed

Active and passive variants of La-containing tellurite glasses have been developed with matched refractive indices. The consequences of adding lanthanum to the glass was studied through measurements of the crystallization stability, glass viscosity and the loss of unstructured fibers. Doping the glass with erbium allowed for any spectroscopic changes to be observed through measurements of the absorption and energy level lifetimes. The fluorescence emission spectra were measured at 1.5 microm and, to the best of our knowledge, for the first time in tellurite glass at 2.7 microm. PMID:19724556

Oermann, Michael R; Ebendorff-Heidepriem, Heike; Li, Yahua; Foo, Tze-Cheung; Monro, Tanya M

2009-08-31

78

Synthesis and characterization of Sr and Mg-doped Lanthanum gallate electrolyte materials prepared via the Pechini method  

Microsoft Academic Search

The powders of Sr- and Mg-doped lanthanum gallate (La0.85Sr0.15Ga0.80Mg0.2O2.825; LSGM) were synthesized by the Pechini method. The XRD pattern indicates that the main phase (LaGaO3) exists in the uncalcined powders. The LSGM materials are composed of the main phase without secondary phases when calcined at 1400°C. The LSGM materials contain fewer amounts of secondary phases than those prepared by the

Min Shi; Yudong Xu; Anping Liu; Ning Liu; Can Wang; P. Majewski; F. Aldinger

2009-01-01

79

Site-selective 900 nm quasi-three-level laser emission in Nd-doped strontium lanthanum aluminate  

Microsoft Academic Search

Neodymium-doped strontium lanthanum aluminate crystals Sr1-xLax-yNdyMgxAl12-xO19 contain two structural Nd centers with slightly different spectroscopic properties, whose proportion is determined by the composition parameter x. By choosing a composition with x=0.4, which grants the dominance of one of these centers (the center C1), whose properties are suitable for quasi-three-level Nd laser scheme, efficient 901 nm continuous-wave laser emission (slope efficiency

G. Aka; D. Vivien; V. Lupei

2004-01-01

80

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

NASA Astrophysics Data System (ADS)

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.

Zink, Peter Andrew

81

Spectroscopic and structural properties of Nd3+ doped strontium lanthanum aluminate laser crystals  

Microsoft Academic Search

Nd3+-activated strontium lanthanum aluminate Sr1-xNdyLax-yMgxAl12-xO19 (ASL:Nd) crystals give efficient 4F3\\/2-->4I9\\/2 laser emission at 900 nm, whose properties depend on the x and y composition parameters. Based on high-resolution spectroscopy and emission decay, this paper demonstrates that the composition dependence of the laser emission is caused by the presence of two structural centers, C1 and C2, whose relative proportion in crystals

A. Lupei; V. Lupei; C. Gheorghe; D. Vivien; G. Aka; P. Aschehoug

2004-01-01

82

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

SciTech Connect

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

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

1998-12-31

83

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

SciTech Connect

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

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

2011-07-15

84

Inherent inhomogeneity in the crystals of low-doped lanthanum manganites  

NASA Astrophysics Data System (ADS)

The X-band electron paramagnetic resonance (EPR) technique and the model analysis of the EPR susceptibility versus temperature were employed to characterize the dopant distribution in a number of La-manganite crystals, low doped with Ca, Sr, and Ba in a La site. Such distribution appears to be inhomogeneous as a result of technological-driven effect. It is emphasized that the above chemical disorder influences strongly both magnetic state and transport of the low-doped manganite crystals.

Rozenberg, E.; Auslender, M.; Shames, A. I.; Gorodetsky, G.; Mukovskii, Ya. M.

2008-06-01

85

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

DOEpatents

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

Singh, P.; Ruka, R.J.

1995-02-14

86

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

DOEpatents

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

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

1995-01-01

87

State of atoms and interatomic interactions in perovskite-like oxides: XXII. Effect of the Ca-Sr ratio on exchange interactions in lanthanum manganites doped with calcium and strontium  

Microsoft Academic Search

Magnetic properties of lanthanum manganites of the perovskite structure, doped with calcium and strontium in various ratios,\\u000a were studied. Magnetic dilution experiments and analysis of the temperature and concentration dependences of the magnetic\\u000a characteristics showed that the properties of the manganites under consideration nonmonotonically depend on the Ca-Sr ratio\\u000a in the lanthanum sublattice.

N. V. Chezhina; A. V. Fedorova; Ya. A. Rutskaya

2008-01-01

88

Study of specific absorption rate of strontium doped lanthanum manganite nanoparticles for self-controlled hyperthermia applications  

NASA Astrophysics Data System (ADS)

Magnetic and magnetothermal properties of strontium doped lanthanum manganite La1-xSrxMnO3 nanoparticles have been studied with the strontium concentration x varying between 0.15 and 0.45. La1-xSrxMnO3 nanoparticles were prepared by the citrate gel route. XRD results show that all samples exhibit the characteristic perovskite structure with average particle sizes between 33 and 44 nm. Adiabatic magnetothermia measurements were carried out in an RF magnetic field of 800 A/m and 214 kHz. Both magnetic and thermomagnetic behaviors are governed by the strontium content of the samples. The saturation magnetization, Curie temperature and specific absorption rate (SAR) vary non-monotonically with x. The SAR of the nanoparticles has been calculated using the linear response theory and good agreement with the experimental data has been observed. The intrinsic loss power (ILP) has been obtained from the SAR values. ILP values of our samples are comparable to those of magnetite.

Rashid, Amin ur; Ahmed, Ashfaq; Ahmad, S. N.; Shaheen, S. A.; Manzoor, Sadia

2013-12-01

89

Influence of small DC bias field on the electrical behaviour of Sr- and Mg-doped lanthanum gallate  

NASA Astrophysics Data System (ADS)

One of the promising electrolyte materials for solid oxide fuel cells application, Sr- and Mg-doped lanthanum gallate La0.9Sr0.1Ga0.8Mg0.2O3-? (LSGM), is synthesized by conventional solid state ceramic route. X-ray Rietveld analysis confirms the formation of main orthorhombic phase at room temperature along with a few minor secondary phases. SEM micrograph reveals the grain and grainboundary morphology of the system. Electrical conductivity of the LSGM sample is measured in the temperature range 573-873 K and in the frequency range 20 Hz-1 MHz at a few small DC bias fields (at 0.0, 0.5, 1.0, 1.5 and 2.0 V). The conductivity spectra show power-law behaviour. Electrical conductivity of the sample is found to be weakly dependent on DC bias field. This is attributed to field-dependent bulk and grainboundary conduction processes. In the present system, under investigated bias field range, the possibility of formation of Schottky barrier is ruled out. The concept of grainboundary channel (pathway) modulation on the application of bias field is proposed.

Raghvendra; Singh, Rajesh Kumar; Singh, Prabhakar

2014-09-01

90

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

NASA Astrophysics Data System (ADS)

Combined experimental and modeling efforts have been extremely productive in understanding irradiation-induced displacement damage in metal and metal alloy systems. In order to help understand the fundamental mechanisms of irradiation-induced defect formation and evolution in nuclear fuel, similar combined modeling and experimental efforts have been carried out. Ceria (CeO2) was selected as a surrogate material for Uranium Dioxide (UO2) due to its many similar properties. Lanthanum (La) was chosen as a dopant in CeO 2 to investigate the effect of impurities in a controlled manner. The presence of La in the CeO2 lattice introduces a predictable initial concentration of oxygen vacancies, making it possible to characterize hypo-stoichiometric effects in CeO2. The influence of two La concentrations, 5% and 25%, were examined. Radiation damage was induced using low energy ion implantations and high energy ion irradiation experiments, where the ion beam energy was selected for high displacement damage levels and/or high levels of implanted Xe or Kr. A combination of in situ TEM (Transmission Electron Microscopy) and ex situ TEM experiments were used to study the evolution of defect clusters and the influence of two common fission products, Xe and Kr. The irradiations were performed on thin film, single crystal materials so that the material composition and crystallinity could be directly controlled. The irradiation damage caused the formation of complex microstructures with dislocation loops, voids or bubbles, and dislocation networks at higher doses. The Burgers vectors of the dislocation loops were determined and the loops were found to be mainly [111] type Burgers vector pure edge loops. They have been tentatively identified as interstitial type. La, as an impurity, has revealed a strong defect trapping effect. Various sets of quantitative experimental results were obtained to characterize the dose and temperature effects of irradiation. These results also help to benchmark simulation codes being developed with a kinetic Monte Carlo model. These experimental results include size and size distributions of dislocation loops, voids and gas bubble structures created by irradiation. More importantly, this systematic experimental work has provided key insights into the understanding of the mechanisms of defect evolution in the materials investigated. A model including both defect production and annihilation mechanisms has been proposed to explain the observed defect kinetics in the lower dose regime. A coalescence driven model has been proposed for void/bubble growth in the higher dose regime. Experimental results also revealed that lanthanum trapping has significant influence on the void/bubble growth in the CeO2 lattice. Lattice and kinetic Monte Carlo calculations have provided key insights to the interpretations of experimental results.

Yun, Di

91

Paramagnetic spin dynamics in the nonhomogeneous crystals of low-doped lanthanum manganites  

NASA Astrophysics Data System (ADS)

The X-band electron paramagnetic resonance (EPR) technique and the model analysis of the EPR linewidth versus temperature were employed to characterize the dopant distribution in a number of La-manganite crystals, low doped with Ca, Sr, and Ba. Such distribution appears to be inhomogeneous in accordance with the results of previous study of EPR susceptibility. The technological originated competition between the quenching and annealing effects during the cooling of the crystals from the high temperatures seems to be the reason of their inherent inhomogeneity. It depends strongly on the dopant nature and, in the crystal doped with 15% of Ba, the inhomogeneity is small as compared to those in the Ca- and Sr-doped samples. It is emphasized that such chemical disorder influences strongly the crystal structure, magnetic state, and transport of these objects.

Auslender, M.; Shames, A. I.; Rozenberg, E.; Gorodetsky, G.; Mukovskii, Ya. M.

2009-04-01

92

Spectroscopic and structural properties of Nd3+ doped strontium lanthanum aluminate laser crystals  

NASA Astrophysics Data System (ADS)

Nd3+-activated strontium lanthanum aluminate Sr1-xNdyLax-yMgxAl12-xO19 (ASL:Nd) crystals give efficient 4F3/2?4I9/2 laser emission at 900 nm, whose properties depend on the x and y composition parameters. Based on high-resolution spectroscopy and emission decay, this paper demonstrates that the composition dependence of the laser emission is caused by the presence of two structural centers, C1 and C2, whose relative proportion in crystals is determined by composition parameter x. From the spectral data and crystal structure it is inferred that C2 center that prevails at low x, corresponds to a Nd3+ in a Sr2+ (2d) site of D3h local symmetry with no nearby Ln3+ (La3+ or Nd3+) ions. The C1 center lines, prevailing at large x parameter, which are broader and shift with composition, are composite lines of various structural centers of Nd3+ in a Sr2+ site with different occupancy of nearest-neighbor sites by Ln3+. The influence of the spectral and emission dynamics features of these centers on the laser properties is discussed and criteria for the selection of optimal composition is inferred.

Lupei, A.; Lupei, V.; Gheorghe, C.; Vivien, D.; Aka, G.; Aschehoug, P.

2004-09-01

93

Samarium/Cobalt Magnets  

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

94

Spin Freezing and Recovery of Sublattice Magnetization in Lightly Doped Lanthanum Cuprate  

SciTech Connect

{sup 139}La NQR studies in lightly doped La{sub 2}Cu{sub 1-x}Li{sub x}O{sub 4} and La{sub 1.8-x}Eu{sub 0.2}Sr{sub x}CuO{sub 4} are reviewed. A strong enhancement of the {sup 139}La relaxation rate with a peak accompanied by a sudden increase of the local field at low T has been observed similarly to La{sub 2-x}Sr{sub x}CuO{sub 4}. The anomalous magnetic properties are discussed in the light of the microscopic segregation of doped holes into hole-rich domain walls separating undoped AF domains.

Suh, B.J.; Hammel, P.C.; Sarrao, J.L.; Thompson, J.D.; Fisk, Z.; Hucker, M.; Buchner, B.

1998-10-24

95

p-n diode with hole- and electron-doped lanthanum manganites  

NASA Astrophysics Data System (ADS)

The hole-doped (p-) manganite La0.7Ca0.3MnO3 and the electron-doped (n-) manganite La0.7Ce0.3MnO3 undergo an insulator-to-metal transition at around 250 K, above which both behave as a polaronic semiconductor. We have fabricated an epitaxial trilayer (La0.7Ca0.3MnO3/SrTiO3/La0.7Ce0.3MnO3), where SrTiO3 is an insulator. At room temperature, i.e., in the semiconducting regime, it exhibits asymmetric current-voltage (I-V) characteristics akin to a p-n diode. The observed asymmetry in the I-V characteristics disappears at low temperatures where both the manganite layers are metallic. These results indicate that using the polaronic semiconducting regime of doped manganites, a p-n diode can be constructed.

Mitra, C.; Raychaudhuri, P.; Köbernik, G.; Dörr, K.; Müller, K.-H.; Schultz, L.; Pinto, R.

2001-10-01

96

Elastic behaviour of strontium-doped lanthanum calcium manganites in the vicinity of T C  

Microsoft Academic Search

Colossal magnetoresistance (CMR) manganites with compositional formula, La0.67Ca0.33?xSrxMnO3 (where x=0, 0.09, 0.11, 0.13, 0.33) were prepared by citrate gel route mainly to understand the elastic behaviour in the vicinity of their magnetic transition temperature TC. The structural characterizations of all the materials clearly indicate that samples upto x=0.13 doping, are having orthorhombic structure with Pbnm space group and sample with

G. Lalitha; P. Venugopal Reddy

2009-01-01

97

Volume of metallic phase in lightly doped lanthanum manganite single crystals  

NASA Astrophysics Data System (ADS)

The absorption spectra, temperature dependence of light transmission, and dc resistivity of La0.92Ca0.08MnO3 single crystal are investigated. The volume of the metallic phase in insulating matrix is evaluated by analyzing the temperature dependence of the light absorption and dc conductivity. Using the data published, we also calculate the metallic phase volume in La1-xSrxMnO3 , x=0.07 and 0.10. It is shown that in the lightly doped manganites, the metallic droplets lie in the ferromagnetically ordered regions, but only a small part of the ferromagnetic phase has metallic conductivity.

Mostovshchikova, E. V.; Bebenin, N. G.; Loshkareva, N. N.

2004-07-01

98

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

PubMed Central

Fourier transform infrared (FTIR) spectrum dielectric constant, ??, loss tangent, tan(?), electric modulus, M*, and ac conductivity, ?ac, of pure polyvinyl alcohol (PVA) as well as La-, Gd-, and Er-PVA doped samples have been carried out. The dielectric properties have been studied in the temperature and frequency ranges; 300–450?K and 1?kHz–4?MHz, respectively. FTIR measurements reveal that La3+, Gd3+, and Er3+ ions form complex configuration within PVA structure. Two relaxation processes, namely, ? and ? were observed in pure PVA sample. The first process is due to the interfacial or Maxwell-Wagner-Sillers polarization. The second one is related to the micro-Brownian motion of the main chains. For doped PVA samples, ?-relaxation process splits into ?a and ?c. This splitting is due to the segmental motion in the amorphous (?a) and crystalline (?c) phases of PVA matrix. Electric modulus analysis was discussed to understand the mechanism of the electrical transport process. The behavior of ac conductivity for all PVA samples indicates that the conduction mechanism is correlated barrier hopping. PMID:22933826

Hanafy, Taha A.

2012-01-01

99

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

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.

Naseem, Swaleha, E-mail: wasiamu@gmail.com; Khan, Wasi, E-mail: wasiamu@gmail.com; Saad, A. A., E-mail: wasiamu@gmail.com; Shoeb, M., E-mail: wasiamu@gmail.com; Ahmed, Hilal, E-mail: wasiamu@gmail.com; Naqvi, A. H. [Centre of Excellence in Materials Science (Nanomaterials), Department of Applied Physics, Z.H. College of Engg. and Technology, Aligarh Muslim University, Aligarh-202002 (India); Husain, Shahid [Department of Physics, Aligarh Muslim University, Aligarh-202002 (India)

2014-04-24

100

Impact of Thermal Aging on the Microstructure Evolution and Mechanical Properties of Lanthanum-Doped Tin-Silver-Copper Lead-Free Solders  

NASA Astrophysics Data System (ADS)

An extensive study is made to analyze the impact of pure lanthanum on the microstructure and mechanical properties of Sn-Ag-Cu (SAC) alloys at high temperatures. Different compositions are tested; the temperature applied for the isothermal aging is 150°C, and aging times of 10 h, 25 h, 50 h, 100 h, and 200 h are studied. Optical microscopy with cross-polarized light is used to follow the grain size, which is refined from 8 mm to 1 mm for as-cast samples and is maintained during thermal aging. Intermetallic compounds (IMCs) present inside the bulk Sn matrix affect the mechanical properties of the SAC alloys. Due to high-temperature exposure, these IMCs grow and hence their impact on mechanical properties becomes more significant. This growth is followed by scanning electron microscopy, and energy-dispersive spectroscopy is used for elemental mapping of each phase. A significant refinement in the average size of IMCs of up to 40% is identified for the as-cast samples, and the coarsening rate of these IMCs is slowed by up to 70% with no change in the interparticle spacing. Yield stress and tensile strength are determined through tensile testing at 20°C for as-cast samples and after thermal aging at 150°C for 100 h and 200 h. Both yield stress and tensile strength are increased by up to 20% by minute lanthanum doping.

Sadiq, Muhammad; Pesci, Raphaël; Cherkaoui, Mohammed

2013-03-01

101

Grain boundary effects on transport in metalorganic chemical vapor deposition-grown, Ca-doped lanthanum manganites  

NASA Astrophysics Data System (ADS)

The transport properties of metalorganic chemical vapor deposited films of lanthanum manganite grown on various substrates are investigated. The more disordered films show a magnetoresistance that is both large and relatively temperature independent over a wide temperature range. At low magnetic fields, a linear field dependence is observed and is attributed to spin-polarized intergrain tunneling. In addition, at low fields a hysteretic dependence of resistivity on the magnetic field has been observed. This effect has been attributed to the scattering of spin-polarized carriers at the grain boundary.

Heremans, J. J.; Watts, S.; Wirth, S.; Yu, X.; Gillman, E. S.; Dahmen, K. H.; von Molnár, S.

1998-06-01

102

Effects of lanthanum doping on the microstructure and electrical properties of sol-gel derived Pb 1-3 x/2 La x(Zr 0.5Ti 0.5)O 3 thin films  

NASA Astrophysics Data System (ADS)

Effects of lanthanum doping on the microstructure and electric properties of Pb(Zr 0.5Ti 0.5)O 3 films have been investigated. The films with x=0, 0.01, 0.02, and 0.03 were prepared by a 2-methoxyethanol-based sol-gel method on Pt(1 1 1)/Ti/SiO 2/Si(1 0 0) substrate. X-ray diffraction (XRD) patterns show that the all the films crystallize in perovskite phase and are (1 0 0)-oriented. Results of fine (2 0 0) scan XRD suggest that lanthanum doping plays a role in stabilizing film tetragonal phase, which is in agreement with the results observed in bulk materials. The ferroelectric and dielectric properties indicate that dielectric loss and remnant polarization ( Pr) of the films are improved by the addition of lanthanum doping. Loss tangents of the film undoped and the film with x=0.03 at 10 kHz are 0.025 and 0.015, respectively. The corresponding Pr values at 380 kV/cm are 14 and 18 ?C/cm 2, respectively. Possible explanations for the variations of electric properties have also been discussed.

Zhang, S. Q.; Li, W. L.; Li, N.; Fei, W. D.

2010-06-01

103

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

PubMed

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

Xie, Ying Peng; Wang, Guo Sheng

2014-09-15

104

X-ray radiometric determination of lanthanides (praseodymium, neodymium, and samarium) in soils  

NASA Astrophysics Data System (ADS)

A procedure of the modified energy-dispersive X-ray fluorescence method (X-ray radiometric analysis using a 241Am radionuclide source) was developed for the identification of praseodymium, neodymium, and samarium. The procedure is based on the exclusion of the disturbing effect of barium and lanthanum on the lines of praseodymium and neodymium, as well as the effect of lanthanum and cerium on the lines of samarium. On the basis of the new method, data were obtained on the geochemistry of three lanthanides in soils of the northern taiga. Praseodymium and neodymium were detected by the X-ray radiometric method even in podzols depleted of heavy metals. The method can detect samarium at the levels of the soil clarke and higher. Positive samarium (or, wider, rare-earth) anomalies can be expected in the soils located not far from the deposits of apatite-nephelines, loparites, and phosphorites and in the soils developed on alkaline granites and carbonate weathering crusts.

Savichev, A. T.; Vodyanitskii, Yu. N.

2011-04-01

105

Self-biased dielectric bolometer from epitaxially grown Pb(Zr,Ti)O3 and lanthanum-doped Pb(Zr,Ti)O3 multilayered thin films  

NASA Astrophysics Data System (ADS)

A self-biased dielectric bolometer has been realized by epitaxially grown lead zirconate titanate Pb1.1(Zr0.3Ti0.7)O3 (PZT 30/70) and lanthanum-doped lead zirconate titanate Pb0.83La0.17(Zr0.3Ti0.7)0.9575O3 (PLZT 17/30/70) multilayered thin films using the sol-gel technique. The high-resolution transmission electron microscopy images and electron diffraction pattern showed that the multilayered film had its preferred (111) orientation and the epitaxial growth between the PZT 30/70 and PLZT 17/30/70 layers. The self-biased phenomenon and a large pyroelectric current were observed in the prepoled sample without any external bias at the PLZT 17/30/70 phase transition temperature of 120 °C. Pyroelectric coefficient as high as 990 ?C/m2K is obtained in the multilayer thin films around 120 °C. It is obvious that there exists an induced polarization in the PLZT 17/30/70 layer. We attribute this self-biased effect to the strong remnant polarization in the immediately contacted tetragonal PZT 30/70 layers.

Liu, Weiguo; Jiang, Bin; Zhu, Weiguang

2000-08-01

106

Structure and properties of antimony-doped lanthanum molybdate La{sub 2}Mo{sub 2}O{sub 9}  

SciTech Connect

Polycrystalline samples of the composition La{sub 2}Mo{sub 2-x}Sb{sub x}O{sub 9-y}, where 0 {<=} x {<=} 0.05, were prepared by solid-phase synthesis. Single crystals of La{sub 2}Mo{sub 1.96}Sb{sub 0.04}O{sub 8.17} were obtained by spontaneous crystallization from flux. The structure of the metastable {beta}{sub ms} phase of this compound was determined at room temperature by X-ray diffraction. It was found that the La, Mo, and O1 atoms are displaced from the threefold axis on which they are located in the high-temperature {beta} phase. It was shown that molybdenum atoms in the crystal structure are partially replaced by antimony atoms, which are located on the threefold axis. In antimony-doped crystals, lanthanum atoms partially return to the site on the threefold axis and the coordination environment of molybdenum cations becomes more ordered, thus facilitating the stabilization of the cubic phase at room temperature. Calorimetric measurements (DSC) showed that the introduction of Sb as the dopant into the La{sub 2}Mo{sub 2}O{sub 9} structure leads to a decrease in the temperature of the {alpha} {yields} {beta} phase transition from 570 to 520 Degree-Sign C and to the partial suppression of this transition. The temperature behavior of the conductivity confirms the DSC data. Thus, doping with Sb contributes to the stabilization of the cubic phase at room temperature.

Alekseeva, O. A., E-mail: olalex@ns.crys.ras.ru; Verin, I. A.; Sorokina, N. I. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation); Kharitonova, E. P.; Voronkova, V. I. [Moscow State University (Russian Federation)

2011-05-15

107

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

NASA Astrophysics Data System (ADS)

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.

Stergiou, Charalampos; Litsardakis, George

2014-11-01

108

Thermoelectric response of Lanthanum-doped SrTiO3 thin-films grown under various oxygen partial pressures  

NASA Astrophysics Data System (ADS)

Doped strontium titanate is a strong candidate for the next-generation high-Z bulk thermoelectric material due to both its wide tunability in transport properties and very large carrier effective mass. Thermoelectric thin-films of Sr1-xLaxTiO3-? with various La content were grown via pulsed-laser deposition (PLD) on (001)-oriented LSAT substrates under various oxygen partial pressures. We find that electron transport is dominated by carriers from oxygen vacancies in samples grown at low pO2 < 10-6 Torr, and that thermopower as high as 1000 ?V/K can be achieved even in heavily La-doped samples. Doping combinations that yield resistivities as low as 5 m?-cm yield power factors @ 300K as high as 0.7 W/m-K, implying ZT > 0.1.

Scullin, Matthew L.; Ravichandran, Jayakanth; Huijben, Mark; Yu, Choongho; Mukerjee, Subroto; Moore, Joel; Majumdar, Arun; Ramesh, R.

2008-03-01

109

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

DOEpatents

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

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

1992-01-01

110

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

DOEpatents

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

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

1992-07-21

111

Scanning tunneling microscopy studies of an electron-doped high-Tc superconductor, praseodymium lanthanum cerium copper oxide  

NASA Astrophysics Data System (ADS)

It has been more than two decades since the first high temperature superconductor was discovered. In this time there has been tremendous progress in understanding these materials both theoretically and experimentally. Some important questions however remain to be answered; one of them is the temperature dependence of the superconducting gap which is in turn tied to question of the origin of the pseudogap and its connection with superconductivity. In this thesis, we present detailed Scanning Tunneling Microscopy (STM) spectroscopic studies of an electron doped superconductor, Pr0.88LaCe 0.12CuO4-delta (PLCCO). The electron doped compounds form an interesting venue for STM studies for many reasons. In the hole-doped materials, especially in the underdoped side of the phase diagram, there is mounting evidence of a second gap that survives to high temperatures (high temperature pseudogap) that may have a different origin from superconductivity. This complicates studies of the temperature dependence of the superconducting gap in these materials. In PLCCO however, there is little evidence for a high temperature pseudogap potentially allowing us to address the question of the temperature evolution of the superconducting gap without the complication of a second gap. Secondly, the low Tc of the optimally doped materials makes it easily accessible to temperature dependent STM studies. Finally, while hole-doped materials have been extensively studied by scanning tunneling microscopy (STM), there have been no detailed STM spectroscopic studies on the electron doped compounds. In the first part of the thesis, we investigate the effect of temperature on the superconducting gap of optimally doped PLCCO with Tc = 24K. STM spectroscopy data is analyzed to obtain the gap as a function of temperature from 5K to 35K. The gap is parameterized with a d-wave form and the STM spectra are fit at each temperature to extract the gap value. A plot of this gap value as a function of temperature shows clear deviations from what is expected from BCS theory. We find that similar to the hole-doped superconductors a fraction of the surface still shows a gap above Tc. The implications of our finding to the pseudogap phase are discussed. In the second part of the thesis, STM spectra are analyzed to determine the effect of impurities or vacancies on the local density of states. Electron doped superconductors require a post-annealing process to induce superconductivity. It is claimed that Cu vacancies in the CuO2 planes which suppress superconductivity are healed by this process. This implies that for the same doping, a sample with higher Tc should have fewer impurities compared to a sample with lower Tc. We studied two PLCCO samples with 12% Ce doping; one with higher Tc (24K) and the other with lower T c (21K). Through quasiparticle scattering study we find that there are more impurities in 21K samples than 24K sample, consistent with the picture of Cu vacancies in as grown samples. Finally, we present a discussion of the bosonic modes observed in the STM spectra and their connection to the spin excitations measured by neutron scattering.

Kunwar, Shankar

112

PHYSICOCHEMICAL PROPERTIES OF LANTHANUM, CERIUM, AND SAMARIUM HEXANITRONICKELATES WITH POTASSIUM  

Microsoft Academic Search

Description is given of the apparatus and the temperature determination ; by means of an optical pyrometer. A summary of the thermodynamic theory ; necessary for the understanding of the experiments is included. The relation ; between measured quantities and theory is compared. The method of effusion from ; a Knudsen cell in which chemical equilibrium was established and the

G. P. Alexandrov; Z. I. Iorysh; Zh. M. Shlaen

1963-01-01

113

SUBSTITUTION SITE OF LANTHANUM IONS IN LA-DOPED SrBi4Ti4O15 and Bi4Ti3O12-SrBi4Ti4O15  

Microsoft Academic Search

Ferroelectric ceramics of lanthanum-modified SrBi4Ti4O15 and Bi4Ti3O12-SrBi4Ti4O15 have been synthesized, and Raman spectrum measurements have been carried out at room temperature. The investigation on the Raman spectra suggest that La ions prefer to occupy the A site in the case of x ? 0.10, and at higher content they tend to be incorporated into Bi2O2 layers in the La-doped SrBi4Ti4O15.

JUN ZHU; JUN-HUI HE; XIAO-BING CHEN

2006-01-01

114

The low-frequency Raman spectra and nanostructure of As-Se-S and As-Se-Te chalcogenide semiconductors doped by samarium  

NASA Astrophysics Data System (ADS)

It has been established that the Raman scattering (RS) of chalcogenide glass-like semiconductors (CGS) materials As-Se-S and As-Se-Te at frequencies below 100 cm-1 consists of two parts: first - which the intensity with increasing frequency up to 30 ÷ 40 cm-1 decreases (quasi-elastic scattering); second - which have been observed a broad band with a maximum at frequencies of ~ 63 ÷ 67 cm-1 (boson peak - BP). Such a case is absent in the respective crystals. The observed features are associated with relaxation and excess density of states of acoustic vibrations in irregularities is localized with nanometer-size of material. It is shown that the contribution of the different types of scattering in a low-frequency range depends on the degree of disorder in the material, which varies with the change of chemical composition and by doping.

Isayeva, G. A.; Alekberov, R. I.; Mekhtiyeva, S. I.; Isayev, A. I.

2014-09-01

115

On the magnetic properties of F/AF Ca-doped lanthanum manganite bilayers: Approach to interface effects  

NASA Astrophysics Data System (ADS)

Magnetic measurements were performed on Ferromagnetic/Antiferromagnetic (F/AF) Ca-doped manganite bilayers in order to elucidate the interface contribution to the total magnetic moment. A 10-nm-thick La2/3Ca1/3MnO3 (F) film was used as a ferromagnetic layer and a 60-nm-thick La1/3Ca2/3MnO3 (AF) film as an Antiferromagnetic. The low thickness ratio (1/6) allowed us to enhance the magnetic moment effects due to the AF layer. The temperature dependence of the saturation magnetic moment (MS) was studied. MS was extracted from isothermal magnetic hysteresis loops from room temperature down to 10 K. By using the Heisenberg model frame for the saturation magnetization change, a ?5/2 term was found to better describe the experimental data, meaning long-wavelength spin waves dominate the temperature behaviour. By applying a field cooling field (FC), a significant exchange bias field (Hex) was found (around 20 Oe at 10 K). The Hex temperature dependence follows an exponential decay similar to that observed in the F/AF superlattice case.

Marín, L.; Ramírez, J.-G.; Gómez M., E.

2010-01-01

116

Microstructure, magnetoresistance, and magnetic properties of pulsed-laser-deposited external, internal, and mixed-doped lanthanum manganite films  

SciTech Connect

In this article we report our studies on the microstructure, magnetoresistance (MR) behavior, and magnetic properties of the La[sub 1[minus]x[minus]y]Ca[sub x]MnO[sub 3] system in thin-film form. By varying the values of [ital x] and [ital y] in La[sub 1[minus]x[minus]y]Ca[sub x]MnO[sub 3], we have synthesized an external- (x=0.3, y=0), an internal- (x=0, y=0.3), and a mixed-doped (x=0.2, y=0.1) system with the same Mn[sup 3+]/Mn[sup 4+] ratio. Thin films of these materials have been grown [ital in situ] on (100) LaAlO[sub 3] substrates using a pulsed-laser-deposition technique. Atomic force microscopy, x-ray diffraction and high-resolution transmission electron microscopy measurements carried out on these films have shown that the films are smooth, highly crystalline, and epitaxial on the (100) LaAlO[sub 3] substrates. Electrical resistance and magnetoresistance have been measured in the 10[endash]300 K range in magnetic fields up to 5 T using a superconducting quantum interference device magnetometer. The MR ratios (calculated using the expression, [R[sub 0][minus]R[sub H

Pietambaram, S.V.; Kumar, D.; Singh, R.K. (Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611-6400 (United States)); Lee, C.B. (Department of Electrical Engineering, North Carolina AT State University, Greensboro, North Carolina 27411 (United States)); Kaushik, V.S. (MRST Device Engineering Division, Motorola Inc., Austin, Texas (United States))

1999-09-01

117

Microstructure, magnetoresistance, and magnetic properties of pulsed-laser-deposited external, internal, and mixed-doped lanthanum manganite films  

NASA Astrophysics Data System (ADS)

In this article we report our studies on the microstructure, magnetoresistance (MR) behavior, and magnetic properties of the La1-x-yCaxMnO3 system in thin-film form. By varying the values of x and y in La1-x-yCaxMnO3, we have synthesized an external- (x=0.3, y=0), an internal- (x=0, y=0.3), and a mixed-doped (x=0.2, y=0.1) system with the same Mn3+/Mn4+ ratio. Thin films of these materials have been grown in situ on (100) LaAlO3 substrates using a pulsed-laser-deposition technique. Atomic force microscopy, x-ray diffraction and high-resolution transmission electron microscopy measurements carried out on these films have shown that the films are smooth, highly crystalline, and epitaxial on the (100) LaAlO3 substrates. Electrical resistance and magnetoresistance have been measured in the 10-300 K range in magnetic fields up to 5 T using a superconducting quantum interference device magnetometer. The MR ratios (calculated using the expression, [R0-RH]/RH, where R0 and RH are resistances in zero and applied fields) of the La0.7Ca0.3MnO3 (x=0.3, y=0), La0.7MnO3 (x=0, y=0.3), and La0.7Ca0.2MnO3 (x=0.2, y=0.1) films are found to be 825%, 700%, and 750% at 200, 240, and 220 K, respectively. The MR ratios of these films, calculated using the expression, [R0-RH]/RH, are 91%, 87%, and 88%, respectively, at the same temperatures. The variation in the insulator-to-metal transition and the MR ratio is attributed to internal chemical pressure and vacancy localization effects. Below Tc/2 (Tc is paramagnetic-to-ferromagnetic transition temperature), resistance increases as T2 for La0.7Ca0.3MnO3 and La0.7Ca0.2MnO3 while it increases as T5/2 for La0.7MnO3. The T2 and T5/2 dependence of resistance suggests that the transport is predominantly governed by an electron-electron scattering and a combination of electron-electron, electron-phonon, and electron-magnon scattering, respectively. High-temperature resistance has been observed to be consistent with small polaron hopping conductivity for all three systems. Magnetization measurements carried out on the films show that the films have reasonably square hysteresis loops with sharp Tc's. Below Tc/2, the magnetization decreases as T2 for La0.7Ca0.2MnO3 and La0.7MnO3, suggesting single-particle excitations in them, while it decreases as T3/2 for La0.7Ca0.3MnO3, representing collective oscillations in this system.

Pietambaram, Srinivas V.; Kumar, D.; Singh, Rajiv K.; Lee, C. B.; Kaushik, Vidya S.

1999-09-01

118

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

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

119

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

SciTech Connect

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

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

2010-12-09

120

Cost Reduction of Lanthanum Chromite Materials  

SciTech Connect

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

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

2000-01-01

121

Effect of trace lanthanum ion on dissolution and crystal growth of calcium carbonate  

NASA Astrophysics Data System (ADS)

Impurity effects of trace lanthanum ion (La 3+) on the dissolution and growth of calcium carbonate were studied with in situ observation techniques. Dissolution kinetics of two polymorphs of calcium carbonate, calcite and vaterite, were investigated by monitoring the pH in the solution with laser-induced fluorescence spectroscopy using a pH-sensitive reagent, seminaphthorhodafluors. No effect on dissolution of vaterite was observed with the spectroscopic observations, whereas calcite dissolution was significantly inhibited by lanthanum ion with concentrations higher than 1 ?M. Crystal growth and dissolution processes of calcite under the lanthanum-doped condition were observed by means of atomic force microscopy. Step propagations during crystal growth and dissolution of calcite were inhibited by trace lanthanum ion (5 ?M). An insoluble thin layer of lanthanum carbonate deposited on the step site of the calcite surface could be a possible cause of the inhibitions observed both for dissolution and growth.

Kamiya, Natsumi; Kagi, Hiroyuki; Tsunomori, Fumiaki; Tsuno, Hiroshi; Notsu, Kenji

2004-07-01

122

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

SciTech Connect

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.

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

2000-10-01

123

Oxidation of a thin samarium film on iridium  

NASA Astrophysics Data System (ADS)

Thermal desorption spectroscopy has been used to study the interaction of oxygen with a thin (<1 nm) samarium film deposited onto a textured iridium ribbon. Desorption of Sm atoms from Ir surface takes place from various states (chemisorbed, condensed, from compound with iridium, and oxide). The formation of samarium oxide is observed already at room temperature. As the temperature increases to T = 1100 K, a compound of samarium with iridium is formed at the first stage and then oxygen interacts with Sm atoms from this compound and "slow" (compared to the first process) growth of samarium oxide takes place.

Afanas'eva, E. Yu.

2014-06-01

124

Spectroscopy of erbium in La3+-doped tellurite glass & fibres  

Microsoft Academic Search

We study the spectroscopic properties of erbium doped tellurite glass and the effect of co-doping with lanthanum. This is a route towards the development of versatile fibre lasers for the mid-infrared.

M. R. Oermann; H. Ebendorff-Heidepriem; Yahua Li; T. M. Monro

2008-01-01

125

Synthesis and Magnetic Properties of Novel Lanthanide SERIES(2-X) Metal(x) Copper OXYGEN(4+Y) Compositions (lanthanide Series = Lanthanum, Praseodymium, Neodymium, Samarium, Europium, Gadolinium; Metal = Calcium, Strontium, Barium; 0 <= X <= 0.2; -0.5 <= Y <= 0.5)  

NASA Astrophysics Data System (ADS)

Ln_2CuO_4 (Ln = La, Pr, Nd, Sm, Eu, Gd) undergo structural transitions to oxygen-reduced structures Ln_2CuO_{4-d} with Ln = La, d = 1/3 and Ln = Pr, Nd, Sm, Eu, Gd, d = 1/2. The Nd_2CuO_4-type (T^'-phase) La _2CuO_{4+d} is observed after reoxygenation of oxygen-reduced La_2CuO _{3.67} structure below 500 ^circC. The magnetic properties of T/O (K_2NiF_4-type structure) -phase La_2CuO_4 systems show quite different behaviors compared with those of conventional solid state reacted La_2CuO_4 systems. The implications of these nonsuperconducting behaviors within the superconducting carrier concentrations are discussed from the structural point of view. La_{2-x}M_{x }CuO_{4+d} (M = Ca, Sr; x = 0.05, 0.15), synthesized by the low temperature route, also contain excess oxygen and show different physical properties. ^{139 }La NQR measurements of nonsuperconducting La_{1.85}Sr_{0.15 }CuO_{4.04} show metallic properties. The tolerance factor, which is based on ionic radii, is quite successful to describe structural properties of K_2NiF_4 related cuprate compounds. With anisotropic thermal motions of apical oxygens in La_2CuO_4, we discuss the crucial role of out-of-plane oxygens for stabilization of cuprate structures. The magnetic phase diagram and phase separation of La_{2-x}Sr_{x}CuO _{4+delta} system (0.000 <= x<= 0.030, 0.0<=delta) are reported. From the decrease of T_ {c} by doping level, we infer the localization and pair-breaking mechanism induced by doped holes. Phase separation is realized within the appearance of three-dimensional antiferromagnetic order. We also observe scaling properties of susceptibilities versus renormalized temperatures and infer the finite size effects by doped holes from the scaling. ^{139}La NQR spin-lattice relaxation rates vs temperature are presented for La_{2-x}Sr_{x }CuO_4 with x = 0.02 to 0.08. The spin -lattice relaxation rate below ~2 T_{N}(x) shows a power -law critical behavior while above ~2 T_{N}(x) it follows an exponential law with a small x-dependent spin-stiffness constant, where T_{N} is the magnetic ordering temperature. It is argued that the spin-lattice relaxation rate arises from fluctuations of the staggered magnetization in locally ordered mesoscopic domains. We infer that the magnetically ordered state is not a conventional spin glass.

Cho, Jin Hyung

1992-01-01

126

Magnetic structures in a dhcp samarium film  

NASA Astrophysics Data System (ADS)

Thick samarium films with a four plane dhcp structure instead of the nine-layer stacking characteristic of the element in bulk form, have been prepared by molecular-beam epitaxy. The magnetic structure of this dhcp phase has been elucidated using both neutron-scattering and resonant x-ray magnetic scattering experiments. The magnetic moments align along the c direction. In a given basal plane, for the hexagonal (h) sites as well as for the cubic (c) sites, the magnetic ordering is the same as in bulk samarium. However, the three-dimensional magnetic ordering is modified compared to the bulk one, since both types of planes (h and c) couple antiferromagnetically along the c axis. Moreover, both sets of sites order nearly simultaneously at about 25 K. Compared to bulk, the magnetic ordering temperature is thus lower for the hexagonal sites and higher for the cubic ones.

Dufour, C.; Dumesnil, K.; Soriano, S.; Mangin, Ph.; Brown, P. J.; Stunault, A.; Bernhoeft, N.

2002-09-01

127

Tripyrrolidinophosphoric acid triamide as an activator in samarium diiodide reductions.  

PubMed

The electrochemical and spectrophotometric characterization of the complex formed from samarium diiodide and 4 equiv of tripyrrolidinophosphoric acid triamide (TPPA) is presented. Kinetic studies indicate that the SmI(2)/TPPA complex possesses reactivity greater than the complex formed between samarium diiodide and 4 equiv of HMPA. Examples of the use of SmI(2)/TPPA in synthesis are presented. PMID:20979412

McDonald, Chriss E; Ramsey, Jeremy D; Sampsell, David G; Butler, Julie A; Cecchini, Michael R

2010-11-19

128

Samarium diiodide-catalyzed diastereoselective pinacol couplings.  

PubMed

A complex of samarium diiodide (SmI(2)) with tetraglyme catalyzes the intermolecular pinacol coupling of aromatic or aliphatic aldehydes at loadings of 10 mol % in the presence of Me(2)SiCl(2) and Mg. Diastereoselectivity of up to 95/5 (+/-/meso) has been achieved for aliphatic aldehydes and up to 19/81 (+/-/meso) for aromatic aldehydes. De values of up to 99% have been achieved in intramolecular pinacol coupling reactions using the SmI(2)/tetraglyme/Mg/Me(2)SiCl(2) catalytic system. PMID:15876019

Aspinall, Helen C; Greeves, Nicholas; Valla, Carine

2005-05-12

129

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

NASA Astrophysics Data System (ADS)

Several results regarding the effect of hydrogen on lanthanum chromite were determined. Thermally-activated diffusion of hydrogen through La(Mg)CrO3 was found with a high activation energy. It was found that its electrical conductivity drops drastically, especially at low temperature, after exposure to hydrogen at high temperature. Also, the curvature of most of the conductivity plots, as well as the inability to observe the Hall effect, lends support to the proposal by Karim and Aldred that the small-polaron model which predicts thermally activated mobility is applicable to doped lanthanum chromite. From differential thermal analysis, an apparent absorption of hydrogen near 3000 C was noticed. Upon cooling the lanthanum chromite in hydrogen and subsequently reheating it in air, desorption occurred near 1700 C. The immediate purpose of this study was to determine whether hydrogen has a deleterious effect on lanthanum chromite in solid oxide fuel cells.

Schmidt, V. H.

1981-06-01

130

Modified doping at cuprate / lanthanum manganite interfaces  

NASA Astrophysics Data System (ADS)

Oxide heterostructures allow combining materials with similar structure but with very different ground states, which may compete at the interface to yield novel behaviors and functionalities. We explore the YBa2Cu3O7 (YBCO) / La1-xCaxMnO3 (LCMO) interface in thin film heterostructures. For x=0.3 the manganite is ferromagnetic which causes a strong depression of the superconductivity at the YBCO side. There is also a depression of the ferromagnetic moment at the interface suggesting electron transfer from the manganite into the YBCO. This is confirmed from superlattices alternating YBCO and LaMnO3 (LMO), an A- type AF insulator. While for thin LMO layers (< 6 unit cells) there is little effect on YBCO superconductivity, thicker LMO layers result in reduced Tc values and induced ferromagnetism at the interface, thus providing a firm indication of charge transfer. The occurrence of charge transfer over length scales much longer than the Thomas Fermi screening length (1 nm) is a novel behavior which, we hope, will stimulate future theoretical studies. Work supported by CICYT MAT2005 06024 C02-02.

Santamaria, Jacobo; Garcia Barriocanal, J.; Rivera, A.; Leon, C.; Varela, M.; Pennycook, S. J.; Sefrioui, Z.

2007-03-01

131

Initial stages of the interaction with oxygen of samarium thin films grown on the iridium surface  

NASA Astrophysics Data System (ADS)

The interaction of thin (<1 nm) samarium films deposited on a textured iridium ribbon has been investigated by thermal desorption spectrometry. Samarium atoms deposited at T = 300 K desorb in three phases associated with the formation of a submonolayer samarium coverage on iridium, a compound of samarium with iridium, and a multilayer samarium film. The interaction with oxygen leads to the appearance of a new desorption phase, which is associated with the formation of samarium oxide. Oxidation of samarium is observed during exposure in oxygen already at room temperature. An increase in temperature of the iridium ribbon, at which exposure in oxygen occurs, to T = 1100 K leads to the formation of the compound of samarium with iridium. Further, the film of the compound decomposes in the course of interaction with oxygen, and samarium oxide grows on the Ir surface.

Afanas'eva, E. Yu.

2014-08-01

132

Metallic behavior of lanthanum disilicide  

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

133

Samarium-neodymium direct dating of fluorite mineralization  

Microsoft Academic Search

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

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

1991-01-01

134

Chlorination of lanthanum oxide.  

PubMed

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

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

2012-03-01

135

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

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

136

Cost Reduction of Lanthanum Chromite Materials  

SciTech Connect

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

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

2000-02-28

137

Samarium Ion Exchanged Montmorillonite for High Temperature Cumene Cracking Reaction  

NASA Astrophysics Data System (ADS)

Montmorillonite clay is cation exchanged with samarium and its catalytic influence in cumene cracking reaction is investigated. Effect of exchange with sodium ions on further exchange with samarium ions is also noted. Acidity measurements are done using Temperature Programmed Desorption (TPD) of ammonia. The retention of basic structure is proved from FTIR spectra and XRD patterns. Elemental analysis result shows that samarium exchange has occurred, which is responsible for the higher catalytic activity. Surface area and pore volume remains more or less unaffected upon exchange. Thermogravimetric analysis indicates the enhanced thermal stability on exchanging. Cumene cracking reaction is carried out at atmospheric pressure in a fixed bed glass reactor at 673 K. The predominance of Brønsted acidity is confirmed from high selectivity to benzene.

Binitha, N. N.; Silija, P. P.; Suraj, V.; Yaakob, Z.; Sugunan, S.

2011-02-01

138

Phenomenological model for giant magnetoresistance in lanthanum manganite  

NASA Astrophysics Data System (ADS)

The electrical conductivity of doped lanthanum manganite exhibits activated semiconducting behavior at high temperatures, and a transition to metallic behavior at low temperatures in the ferromagnetic state. These two regimes are combined in a new phenomenological equation for the conductivity that uses a mean-field magnetization and physically reasonable fitting parameters. This allows us to account quantitatively for reports of giant negative magnetoresistance in single crystals and thin films. We present new data on sputtered epitaxial thin films of La1-xCaxMnO3, and analyze other recent reports in the literature. The physical basis for such an expression is discussed.

Núñez-Regueiro, J. E.; Kadin, A. M.

1996-05-01

139

Ames Lab 101: Lanthanum Decanting  

ScienceCinema

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

Riedemann, Trevor

2012-08-29

140

The Basis for Developing Samarium AMS for Fuel Cycle Analysis  

SciTech Connect

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.

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

2008-10-13

141

Samarium-145 and its use as a radiation source  

DOEpatents

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

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

1989-01-01

142

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

NASA Astrophysics Data System (ADS)

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.

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

2002-11-01

143

CASTER - A Scintillator-Based Black Hole Finder Probe Based on Lanthanum Halide Scintillator  

NASA Astrophysics Data System (ADS)

The Black Hole Finder Probe is designed to survey the local Universe for black holes as part of NASA's Beyond Einstein program. CASTER (Coded Aperture Survey Telescope for Energetic Radiation) is a concept for a hard X-ray coded aperture imaging instrument operating in the 10-600 keV energy band with wide field of view and approximately 10 minute of arc angular resolution. With a detector area of approximately 6 m2, CASTER will obtain a 5? narrow line sensitivity at 511 keV approaching 10-7 photons cm-2sec-1. In order to fit a 6 m2 detector array into the constraints of a medium-sized ($400-600M) Beyond Einstein probe mission, CASTER uses newly developed lanthanum halide scintillator planes. We describe the CASTER design, demonstrate the sensitivity and resolution measured with cerium-doped lanthanum bromide and lanthanum chloride scintillators, and discuss the results expected from a CASTER mission.

Cherry, Michael; Bloser, P. F.; Budden, B. S.; Case, G. L.; Cravens, J. P.; Guzik, T. G.; Hurley, K. C.; Kippen, R. M.; Macri, J. R.; McConnell, M. L.; Miller, R. S.; Paciesas, W. S.; Ryan, J. M.; Schaefer, B. E.; Stacy, J. G.; Vestrand, W. T.; Wefel, J. P.

2006-09-01

144

MAGNETISM AND ELECTRON TRANSPORT IN MAGNETORESISTIVE LANTHANUM CALCIUM  

E-print Network

MAGNETISM AND ELECTRON TRANSPORT IN MAGNETORESISTIVE LANTHANUM CALCIUM MANGANITE A DISSERTATION with the large negative magnetoresistance found in lanthanum calcium manganite. Such large magnetoresistances 4, the intrinsic magnetic and electron transport properties of lanthanum calcium manganite

145

Discovery of Samarium, Europium, Gadolinium, and Terbium Isotopes  

E-print Network

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 discussed here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.

May, E

2012-01-01

146

Discovery of Samarium, Europium, Gadolinium, and Terbium Isotopes  

E-print Network

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 discussed here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.

E. May; M. Thoennessen

2012-01-19

147

Discovery of samarium, europium, gadolinium, and terbium isotopes  

SciTech Connect

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

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

2013-01-15

148

Sintering aid for lanthanum chromite refractories  

SciTech Connect

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

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

1988-06-07

149

Rapid Synthesis of Nonstoichiometric Lanthanum Sulfide  

NASA Technical Reports Server (NTRS)

New process relatively fast and simple. Improved method of synthesizing nonstoichiometric lanthanum sulfide faster and simpler. Product purer because some of prior sources of contamination eliminated.

Matsuda, S.; Shapiro, E.; Danielson, L.; Hardister, H.

1987-01-01

150

Thermoelectric Properties of Lanthanum Sulfide  

NASA Technical Reports Server (NTRS)

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.

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

1987-01-01

151

Radiation Effects in Lanthanum Pyrozirconate  

SciTech Connect

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

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

2006-09-01

152

PREPARATION AND PROPERTIES OF LANTHANUM URANYL CARBONATE  

Microsoft Academic Search

Lanthanum uranyl carbonate was prepared by mixing sodium uranyl ; carbonate solutions with lanthanum nitrate solutions. The reaction was studied ; by measuring the electric conductivity and the pH. The thermal decomposition of ; the product obtained was also studied. (tr-auth);

M. Bachelet; H. Gueniffey

1959-01-01

153

Electrical and Magnetic Properties of Strontium Substituted Lanthanum Manganate Perovskite Crystals Prepared Using Fused Salt Electrolysis  

Microsoft Academic Search

Crystals of Sr-doped perovskite lanthanum manganates, containing 7–34 mole percent Sr have been grown by fused salt electrolysis using Cs2MoO4–MoO3 solvents in stabilized zirconia crucibles. The rhombohedral crystals grow with cubic-like habits typically with facial areas 0.25–4 mm2 on edge with the average facial area decreasing with increasing Sr content. All measured crystals with Sr contents between 11.7 and 33.6

W. H. McCarroll; K. V. Ramanujachary; Ian D. Fawcett; M. Greenblatt

1999-01-01

154

Electrical and Magnetic Properties of Strontium Substituted Lanthanum Manganate Perovskite Crystals Prepared Using Fused Salt Electrolysis  

Microsoft Academic Search

Crystals of Sr-doped perovskite lanthanum manganates, containing 7-34 mole percent Sr have been grown by fused salt electrolysis using Cs2MoO4-MoO3 solvents in stabilized zirconia crucibles. The rhombohedral crystals grow with cubic-like habits typically with facial areas 0.25-4 mm2 on edge with the average facial area decreasing with increasing Sr content. All measured crystals with Sr contents between 11.7 and 33.6

W. H. McCarroll; K. V. Ramanujachary; Ian D. Fawcett; M. Greenblatt

1999-01-01

155

Investigation into nanostructured lanthanum halides and CeBr3 for nuclear radiation detection  

Microsoft Academic Search

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

Paul Guss; Ronald Guise; Sanjoy Mukhopadhyay; Ding Yuan

2011-01-01

156

Charge ordering in Lanthanum Calcium Manganite from ab-initio calculations  

Microsoft Academic Search

It is well known that Lanthanum Calcium Manganite compounds display an interesting charge-orderered state where electronic charge segregates preferentially between different atoms resulting in stripes across the material. By means of an ab-initio Hartree-Fock calculation, we have studied the nature of these charge-ordered stripes. In the half doped case, we have found that the periodicity of stripes is compatible with

Valeria Ferrari; Peter Littlewood

2003-01-01

157

Lattice dynamics of the rare-earth element samarium  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

158

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

SciTech Connect

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+?} (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.

Sedykh, Vera D., E-mail: sedykh@issp.ac.ru [Institute of Solid State Physics, Russian Academy of Sciences, Chernogolovka (Russian Federation)

2014-10-27

159

Timing resolution measurements of a 3 in. lanthanum bromide detector  

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

160

Field free, directly heated lanthanum boride cathode  

DOEpatents

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

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

1987-02-02

161

Field free, directly heated lanthanum boride cathode  

DOEpatents

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

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

1991-01-01

162

Stabilized lanthanum sulphur compounds. [thermoelectric materials  

NASA Technical Reports Server (NTRS)

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

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

1983-01-01

163

Thermodynamic representation of nonstoichiometric lanthanum manganite  

Microsoft Academic Search

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

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

1996-01-01

164

Samarium Diiodide-Mediated Reactions in Total Synthesis  

PubMed Central

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

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

2009-01-01

165

Thermovoltaic effect in samarium sulfide-based heterostructures  

NASA Astrophysics Data System (ADS)

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

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

2011-06-01

166

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

NASA Astrophysics Data System (ADS)

A series of Sm-doped Li-Ni ferrites with formula of (Li 0.5Fe 0.5) 0.4Ni 0.6Sm yFe 2- yO 4, 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 ( ?) 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 Ni 2+ and Ni 3+. 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 ?? with frequency agrees with Deby's type relaxation process. Maximum in ?? is observed when the hopping frequency is equal to the external electric field frequency. The variation in tan ? with frequency shows a similar nature to that of ?? 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.

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

2012-03-01

167

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

We report detailed field dependent electronic- (?-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 ?-T measurements of the sample. At low doping side, nice metal to insulator transition (MIT) peak appears in ?-T data whereas with increasing of Sm{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.

Das, Proloy T., E-mail: dasproloy@phy.iitkgp.ernet.in; Nath, Tapan Kumar [Department of Physics and Meteorology, IIT Kharagpur, Kharagpur-721302, W.B. (India); Gupta, Kajal; Jana, Paresh Chandra [Department of Physics and Techno Physics, Vidyasagar University, Midnapore-721102, W.B. (India)

2014-04-24

168

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

NASA Technical Reports Server (NTRS)

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

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

1983-01-01

169

EUROPIUM, SAMARIUM, AND NEODYMIUM ISOTOPIC FRACTIONS IN METAL-POOR STARS Ian U. Roederer,1  

E-print Network

EUROPIUM, SAMARIUM, AND NEODYMIUM ISOTOPIC FRACTIONS IN METAL-POOR STARS Ian U. Roederer,1 James E Received 2007 August 15; accepted 2007 November 12 ABSTRACT We have derived isotopic fractions of europium

Cowan, John

170

Thermoelectric properties of doubly doped Strontium Titanate thin films  

NASA Astrophysics Data System (ADS)

Lanthanum doped Strontium Titanate (SrTiO3) is amongst the most promising n-type thermoelectric materials for power generation. We report a double doping method for thin films of SrTiO3, grown on (001) oriented LSAT substrates by Pulsed Laser Deposition (PLD), where doping of SrTiO3 in the A-site by Lanthanum is accompanied by doping with oxygen vacancies. Based on careful transport measurements, we show that it is possible to obtain enhanced thermoelectric power factor in the limit of high effective mass and large carrier concentration in these thin films. The presence of oxygen vacancies also serves to decrease the thermal conductivity due to effective phonon scattering. The optimized doping concentration leads to a thermoelectric figure of merit, zT > 0.2 at room temperature.

Ravichandran, Jayakanth; Scullin, Matthew L.; Mukerjee, Subroto; Moore, Joel; Ramesh, R.; Majumdar, Arun

2009-03-01

171

Model of barrier conduction in samarium sulfide polycrystals  

NASA Astrophysics Data System (ADS)

A model of barrier conduction has been proposed based on the study of the dependence of the electrical conduction activation energy in semiconducting samples of samarium sulfide polycrystals on the annealing temperature. It has been shown that the height of potential energy barriers that conduction electrons overcome during electron transfer lies in the range of 0-0.08 eV. The existence of potential barriers is due to the joining of adjacent crystallites in the polycrystal during its annealing. At temperatures of 300-400 K, the conduction activation energy can be in the range from 0.04 to 0.12 eV, independently of the method used for synthesizing the material, and is determined only by the annealing temperature of the sample.

Kaminskii, V. V.; Kazakov, S. A.; Romanova, M. V.; Sharenkova, N. V.; Grevtsev, M. A.

2015-02-01

172

Structure, Stoichiometry, and Phase Purity of Calcium Substituted Lanthanum Manganite Powders  

Microsoft Academic Search

Calcium-doped lanthanum manganite La1?xCaxMnO3, synthesized by the glycine\\/nitrate method, was characterized by high resolution synchrotron X-ray powder diffraction, electron diffraction, and infrared spectroscopy. A strong correlation was observed between the cooling rate from the calcination temperature and the powder quality, indicating the importance of a homogeneous oxygen stoichiometry. The structure refinement reveals that La1?xCaxMnO3withx=0.2, 0.3, 0.4, and 0.6 has orthorhombic

S. Faaland; K. D. Knudsen; M.-A. Einarsrud; L. Rørmark; R. Høier; T. Grande

1998-01-01

173

Charge ordering in Lanthanum Calcium Manganite from ab-initio calculations  

NASA Astrophysics Data System (ADS)

It is well known that Lanthanum Calcium Manganite compounds display an interesting charge-orderered state where electronic charge segregates preferentially between different atoms resulting in stripes across the material. By means of an ab-initio Hartree-Fock calculation, we have studied the nature of these charge-ordered stripes. In the half doped case, we have found that the periodicity of stripes is compatible with experimental diffraction patterns, but require a novel interpretation of the electronic states of the manganese and oxygen atoms.

Ferrari, Valeria; Littlewood, Peter

2003-03-01

174

Investigation into nanostructured lanthanum halides and CeBr3 for nuclear radiation detection  

NASA Astrophysics Data System (ADS)

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.

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

2011-09-01

175

Investigation into Nanostructured Lanthanum Halides and CeBr3 for Nuclear Radiation Detection  

SciTech Connect

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

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

2011-07-06

176

Glasslike thermal conductivity in ytterbium-doped lanthanum zirconate pyrochlore  

Microsoft Academic Search

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

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

2010-01-01

177

Self-activating and doped tantalate phosphors.  

SciTech Connect

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.

Nyman, May Devan; Rohwer, Lauren Elizabeth Shea

2011-01-01

178

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

PubMed Central

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 ?m 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 ?M with a detection limit of 3?×?10-7 M (based on the S/N?=?3). PMID:24528570

2014-01-01

179

Ambi-site substitution of Mn in lanthanum germanate apatites  

SciTech Connect

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

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

2009-08-05

180

Growth and spectroscopic properties of samarium oxalate single crystals  

NASA Astrophysics Data System (ADS)

Single crystals of samarium oxalate decahydrate were synthesized using single diffusion gel technique and the conditions influencing the size, shape and quality were optimized. Highly transparent crystals of size 3×2×1 mm3 with a well defined hexagonal morphology were grown during a time period of two weeks. X ray powder diffraction analysis revealed that the grown crystals crystallize in the monoclinic system with space group P21/c and the proposed chemical formula and linkage of water molecules were confirmed using thermogravimetric analysis. The various functional groups of the oxalate ligand and the water of crystallization were identified by Fourier transform infrared spectroscopy. Spectroscopic investigations such as electric dipole transition probability, magnetic dipole transition probability and branching ratios of all possible transitions from 4G5/2 level of Sm3+ ions were estimated from the absorption spectra using JO theory. The spectroscopic analysis suggested that the crystal has a strong and efficient orange red emission. This is confirmed from the photoluminescence spectrum with a wavelength peak at 595 nm and hence this promising emission can be effectively used for optical amplification.

Vimal, G.; Mani, Kamal P.; Jose, Gijo; Biju, P. R.; Joseph, Cyriac; Unnikrishnan, N. V.; Ittyachen, M. A.

2014-10-01

181

Beyond Palliation: Therapeutic Applications of 153Samarium-EDTMP  

PubMed Central

Primary and metastatic malignant bone lesions result in significant pain and disability in oncology patients. Targeted bone-seeking radioisotopes including 153Samarium ethylene-diamine-tetramethylene-phosphonic acid (153Sm-EDTMP) have been shown to effectively palliate bone pain, often when external beam radiotherapy (EBRT) is not feasible. However, recent evidence also suggests 153Sm-EDTMP has cytotoxic activity either alone or in combination with chemotherapy or EBRT. 153Sm-EDTMP may be useful as anti-neoplastic therapy apart from pain palliation in a variety of malignancies. For prostate cancer patients, several phase I and II clinical trials have shown that combined 153Sm-EDTMP and docetaxel-based chemotherapy can result in >50% decrease in prostate-specific antigen with manageable myelosuppression. In hematologic malignancies, 153Sm-EDTMP produced clinical responses when combined with bortezomib in multiple myeloma. 153Sm-EDTMP also can be used with myeloablative chemotherapy for marrow conditioning prior to stem cell transplant. In osteosarcoma, 153Sm-EDTMP infusion delivers radiation to multiple unresectable lesions simultaneously and provides local cytotoxicity without soft tissue damage that can be combined with chemotherapy or radiation. Prior to routine incorporation of 153Sm-EDTMP into therapeutic regimens, we must learn how to ensure optimal delivery to tumors, determine which patients are likely to benefit, improve our ability to assess clinical response in bone lesions and further evaluate the efficacy 153Sm-EDTMP in combination with chemotherapy, radiation and novel targeted agents. PMID:25664221

Wilky, Breelyn A.; Loeb, David M.

2015-01-01

182

Selective iodine imaging using lanthanum K fluorescence.  

PubMed

Time-dependent subtraction techniques have tremendously improved the visualization of iodinated vessels. These techniques suffer from motion artifacts, however, since the mask image is acquired several seconds prior to the contrast image. A K-edge subtraction technique for selectively imaging iodine using the characteristic x rays from a lanthanum secondary target is presented. The K alpha lines of lanthanum closely straddle the K edge of iodine. A prepatient iodine filter will alter the ratio of K alpha 1 to K alpha 2 intensities; by subtracting two images made with different K alpha 1/K alpha 2 ratios, iodinated structures can be isolated. Since the method requires no mask image, motion artifacts are reduced. Preliminary images acquired with an image intensifier/photodiode array detector system are shown. Theoretical performance of this method is compared to other iodine-selective imaging techniques on the basis of exposure and dose. The feasibility of using lanthanum K fluorescence for rapid clinical iodine-selective imaging is discussed. PMID:6361506

Rutt, B K; Cunningham, I A; Fenster, A

1983-01-01

183

Atomic layer deposition of lanthanum aluminum oxide nano-laminates for electrical applications  

E-print Network

Atomic layer deposition of lanthanum aluminum oxide nano-laminates for electrical applications 12 March 2004; published online 3 May 2004 Lanthanum aluminum oxide thin films were grown by atomic is that the film reacts with water vapor to form lanthanum hydroxide.6 Lanthanum hydroxide then desorbs water

184

Lutetium-doped EuO films grown by molecular-beam epitaxy  

SciTech Connect

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.

Melville, A.; Heeg, T. [Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853 (United States); Mairoser, T.; Schmehl, A. [Zentrum fuer elektronische Korrelationen und Magnetismus, Universitaet Augsburg, Universitaetsstrasse 1, D-86159 Augsburg (Germany); Shai, D. E.; Monkman, E. J.; Harter, J. W. [Laboratory of Atomic and Solid State Physics, Department of Physics, Cornell University, Ithaca, New York 14853 (United States); Hollaender, B.; Schubert, J. [Peter Gruenberg Institute, PGI 9-IT, JARA-FIT, Research Centre Juelich, D-52425 Juelich (Germany); Shen, K. M. [Laboratory of Atomic and Solid State Physics, Department of Physics, Cornell University, Ithaca, New York 14853 (United States); Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853 (United States); Mannhart, J. [Max Planck Institute for Solid State Research, D-70569 Stuttgart (Germany); Schlom, D. G. [Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853 (United States); Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853 (United States)

2012-05-28

185

Measurement of lifetimes and tensor polarizabilities of odd parity states of atomic samarium  

E-print Network

dipole moment (EDM) measurement. For the most favorable candidate state (7 G1), the electron EDM dipole moment (EDM) of the electron by measuring the EDM of a metastable state of samarium. Some on the electron EDM is obtained from an experiment in atomic thallium [11]. It may be possible to improve

Pines, Alexander

186

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

PubMed

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

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

1995-01-27

187

IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 17, NO. 2, FEBRUARY 2005 297 La-Codoped Bismuth-Based Erbium-Doped Fiber  

E-print Network

IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 17, NO. 2, FEBRUARY 2005 297 La-Codoped Bismuth lasers using 84.6-cm-long lanthanum-codoped bismuth-based erbium doped fiber and a narrow-band tunable)-codoped bismuth-based erbium-doped fiber (Bi-EDF), laser tuning, microelectromechanical system (MEMS) filter. I

Wai, Ping-kong Alexander

188

The energetics of lanthanum tantalate materials  

SciTech Connect

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

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

2010-11-15

189

Diminiode thermionic energy conversion with lanthanum-hexaboride electrodes  

NASA Technical Reports Server (NTRS)

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

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

1978-01-01

190

Diminiode thermionic energy conversion with lanthanum-hexaboride electrodes  

NASA Technical Reports Server (NTRS)

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.

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

1978-01-01

191

Electrical and magnetic properties of strontium substituted lanthanum manganate perovskite crystals prepared using fused salt electrolysis  

SciTech Connect

Crystals of Sr-doped perovskite lanthanum manganates, containing 7--34 mole percent Sr have been grown by fused salt electrolysis using Cs{sub 2}-MoO{sub 4}-MoO{sub 3} solvents in stabilized zirconia crucibles. The rhombohedral crystals grow with cubic-like habits typically with facial areas 0.25--4 mm{sup 2} on edge with the average facial area decreasing with increasing Sr content. All measured crystals with Sr contents between 11.7 and 33.6 mole percent SR underwent transitions from a paramagnetic-insulator to a ferromagnetic-metallic state with values of {Tc} and T{sub IM} between 325 and > 400 K (for T{sub IM}), the values increasing with Sr content. A magnetoresistance of approximately 45% at 375 K was observed for a crystal of composition Sr{sub 0.336}La{sub 0.661}Mn{sub 0.997}O{sub 3}. The anomalously high {Tc} = 325 K for Sr{sub 0.117}La{sub 0.844}Mn{sub 0.990}O{sub 3} for a sample of such low Sr content is interpreted in terms of a high vacancy level on the A cation site which stabilizes the rhombohedral perovskite structure, which otherwise might have been expected to be orthorhombic type-1. The formation of Sr-doped lanthanum manganate perovskite at the cathode with the orthorhombic type-2 structure is interpreted in terms of an electrostatically assisted air oxidation mechanism. 42 refs., 4 figs., 2 tabs.

McCarroll, W.H. [Rider Univ., Lawrenceville, NJ (United States). Chemistry Dept.] [Rider Univ., Lawrenceville, NJ (United States). Chemistry Dept.; Ramanujachary, K.V. [Rowan Univ., Glassboro, NJ (United States). Dept. of Chemistry and Physics] [Rowan Univ., Glassboro, NJ (United States). Dept. of Chemistry and Physics; [Rutgers-the State Univ., Piscataway, NJ (United States). Dept. of Chemistry; Fawcett, I.D.; Greenblatt, M. [Rutgers-the State Univ., Piscataway, NJ (United States). Dept. of Chemistry] [Rutgers-the State Univ., Piscataway, NJ (United States). Dept. of Chemistry

1999-06-01

192

Electronic structure and properties of lanthanum  

NASA Astrophysics Data System (ADS)

The total energy and electronic structure of lanthanum have been calculated in the bcc, fcc, hcp and dhcp structures for pressures up to 50 GPa. The full potential linearized-augmented-planewave method was used with both the local-density and general-gradient approximations. The correct phase ordering has been found, with lattice parameters and bulk moduli in good agreement with experimental data. The GGA method shows excellent agreement overall while the LDA results show larger discrepancies. The calculated strain energies for the fcc and bcc structures demonstrate the respective stable and unstable configurations at ambient conditions. The calculated superconductivity properties under pressure for the fcc structure are also found to agree well with measurements. Both LDA and GGA, with minor differences, reproduce well the experimental results for Tc.

Nixon, Lane; Papaconstantopoulos, Dimitrios

2008-03-01

193

Lanthanum sulfides as high temperature thermoelectric materials  

NASA Technical Reports Server (NTRS)

Thermoelectric property measurements have been made for the nonstoichiometric lanthanum sulfides, LaS(R) with R in the range 1.33-1.50. The Seebeck coefficients and electrical resistivities increase with temperature from 200 to 1100 C. Power factors (defined as Seebeck coefficient squared divided by electrical resistivity) generally increase both as the temperature is increased and as the compound composition is varied from LaS(1.48) to LaS(1.35). The power factor values combined with estimates of thermal conductivities for LaS(1.38) and LaS(1.4) yield figures of merit greater than 0.0005 at 1000 C.

Danielson, L. R.; Matsuda, S.; Raag, V.

1984-01-01

194

Sintering aid for lanthanum chromite refractories  

DOEpatents

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.

Flandermeyer, Brian K. (Bolingbrook, IL); Poeppel, Roger B. (Glen Ellyn, IL); Dusek, Joseph T. (Downers Grove, IL); Anderson, Harlan U. (Rolla, MO)

1988-01-01

195

The Energetics of Lanthanum Tantalate Materials  

SciTech Connect

Lanthanum tantalates are important refractory materials with application in photocatalysis, solid oxide fuel cells, and phosphors. Soft-chemical synthesis utilizing the Lindqvist ion, [Ta{sub 6}O{sub 19}]{sup 8?}, has yielded a new phase, La{sub 2}Ta{sub 2}O{sub 7}(OH){sub 2}. Using the hydrated phase as a starting material, a new lanthanum orthotantalate polymorph was formed by heating to 850 °C, which converts to a previously reported LaTaO{sub 4} polymorph at 1200 °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.

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

2010-01-01

196

Overview of Samarium Sm 153 Lexidronam in the Treatment of Painful Metastatic Bone Disease  

PubMed Central

Bone pain associated with advanced prostate and other cancers is a frequent and significant complication, and the effective management of metastatic bone disease and accompanying symptoms continues to be one of the major problems facing patients and their physicians. Treatment is in part dependent on prior treatments; usually a combination of systemic and local modalities is used because no single treatment regimen is effective for an extended period of time. The 3 radionuclides currently approved for treatment of bone pain (phosphorus-32, strontium-89, and samarium-153) are discussed in this review as viable treatment options, with emphasis on the third-generation agent in this category, samarium Sm 153 lexidronam. Clinical trial data are described that support the use of this agent in patients with hormone-refractory prostate cancer with painful metastatic bone disease, and the efficacy of and role for combination therapies are also discussed. PMID:16985930

Sartor, Oliver

2004-01-01

197

Giant negative thermal expansion in La-doped CaFe2As2  

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

198

La doping effect on TZM alloy oxidation behavior , Kuai-She Wang a,  

E-print Network

, military, industrial and chemical appli- cations, where these alloys are subjected to high temperatures to obtain lanthanum-doped Mo. By the processes of mixing, ball-milling (using planetary ball milling machine, revolving speed 240 r/min, milling 2 h), vacuum drying (using vacuum drying oven, 70 °C, 4 h), compaction

Volinsky, Alex A.

199

Atomic emission determination of samarium, europium, ytterbium, and lutetium in silicate rocks  

SciTech Connect

A procedure is discussed that has been developed for the atomic emission determination of samarium, europium, ytterbium and lutetium in silicate rocks, using a cooled hollow cathode as the source of spectrum excitation. By using an isotope dilution procedure, the relative standard deviation can be reduced to 0.007 for a range of determined contents of the elements from n ha 10/sup -4/ to n ha 10/sup -3/% by weight.

Drobyshev, A.I.; Turkin, Yu.I.; Yakimova, N.M.

1986-06-01

200

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

Microsoft Academic Search

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

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

2007-01-01

201

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

Microsoft Academic Search

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

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

1997-01-01

202

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

PubMed

The effect of isovalent lanthanum (La) doping on the monoclinic Y2WO6 photoluminescence was studied. Introducing the non-activated La(3+) 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 La(3+) 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, La(3+) is found to mainly occupy the Y2 (2f) site in low-concentration doped samples. With increasing doping concentration, the La(3+) occupation number at the Y3 (4g) site increases faster than those at the Y1 (2e) and Y2 (2f) sites. When La(3+) 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

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

2015-01-01

203

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

PubMed Central

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

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

2015-01-01

204

Improvement in electrical characteristics of graded manganese doped barium strontium titanate thin films  

Microsoft Academic Search

Highly (100) textured graded manganese (Mn) doped Ba0.5Sr0.5TiO3 [BST (50\\/50)] thin films were deposited on lanthanum aluminate substrates using sol-gel technique. We have demonstrated that the graded acceptor doping is a promising technique to reduce the temperature coefficient of capacitance (TCC), loss tangent, and leakage current of BST thin films. In the temperature range between 175 and 260 K the

M. Jain; S. B. Majumder; R. S. Katiyar; F. A. Miranda; F. W. Van Keuls

2003-01-01

205

Epitaxial growth of dhcp samarium: single crystal films and Sm/Nd superlattices  

NASA Astrophysics Data System (ADS)

High quality single crystal (0 0 1) Sm films and (0 0 1) Sm/Nd superlattices have been prepared by molecular beam epitaxy. The epitaxial growth is controlled by in situ RHEED measurement and the crystallographic structure is determined ex situ from large angle X-ray scattering. We show how the crystal structure of several-thousands-angströms-thick samarium films can be tailored by the elaboration conditions (i.e. the deposition of a thin Nd template layer): either a nine hexagonal close-packed plane stacking sequence ("Sm-structure"), as bulk samarium, or a four hexagonal close-packed plane (dhcp) structure are obtained. Moreover, this unusual dhcp structure for pure samarium has also been stabilized in nanoscale (0 0 1) Sm/Nd superlattices that thus present a coherent dhcp stacking over several bilayers. Both dhcp Sm films and coherent dhcp Sm/Nd superlattices are of broad interest for investigations of the link between structure and magnetism in rare earth epitaxied systems.

Dufour, C.; Dumesnil, K.; Soriano, S.; Pierre, D.; Senet, Ch.; Mangin, Ph.

2002-01-01

206

Al NMR study of the structure of lanthanum and yttrium based aluminosilicate glasses and melts  

E-print Network

A 27 Al NMR study of the structure of lanthanum and yttrium based aluminosilicate glasses and melts actinides (Pu as well as minor actinides). Yttrium and lanthanum has been chosen to simulate actinides

Paris-Sud XI, Université de

207

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

SciTech Connect

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

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

2011-10-01

208

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

Code of Federal Regulations, 2014 CFR

...Phosphonic acid, p-octyl-, lanthanum (3+) salt (2:1). 721.10370 Section 721...Phosphonic acid, p-octyl-, lanthanum (3+) salt (2:1). (a) Chemical substance...phosphinic acid, p-octyl-, lanthanum (3+) salt (2:1) (PMN P-10-99; CAS...

2014-07-01

209

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

Code of Federal Regulations, 2013 CFR

...Phosphonic acid, p-octyl-, lanthanum (3+) salt (2:1). 721.10370 Section 721...Phosphonic acid, p-octyl-, lanthanum (3+) salt (2:1). (a) Chemical substance...phosphinic acid, p-octyl-, lanthanum (3+) salt (2:1) (PMN P-10-99; CAS...

2013-07-01

210

Cytogenetic and developmental toxicity of cerium and lanthanum to sea urchin embryos  

E-print Network

Cytogenetic and developmental toxicity of cerium and lanthanum to sea urchin embryos Rahime Oral1 was to evaluate the toxicity of two rare earth elements (REE), cerium and lanthanum on sea urchin embryos further studies of a more extended REE series. Key words: rare earth elements; cerium; lanthanum; sea

Paris-Sud XI, Université de

211

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

Microsoft Academic Search

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

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

1983-01-01

212

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

NASA Astrophysics Data System (ADS)

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

Kulaks?z, Serkan; Bau, Michael

2013-01-01

213

Blue-white tunable luminescence for white light-emitting diodes and wideband near-infrared luminescence from Sm3+-doped borophosphate glass  

NASA Astrophysics Data System (ADS)

Highly transparent samarium (Sm3+) doped borophosphate glasses were prepared using the melt-quenching technique. The tunable light emission and wideband near-infrared luminescence properties of Sm3+-doped glasses were investigated systemically. Tuning the Sm3+ concentration and excitation wavelength can generate hues that vary from blue to white. Two wide luminescence bands in the 850 nm to 1070 nm range and in the 1100 nm to 1250 nm range, respectively, were also achieved. The results suggest that Sm3+-doped borophosphate glasses can be used as conversion materials for blue light-emitting diode chips to generate white light-emitting diodes and for optical amplification.

Sheng, Qiuchun; Shen, Yinglong; Liu, Shuang; Li, Wentao; Chen, Danping

2012-08-01

214

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

215

XPS investigation of Mn valence in lanthanum manganite thin films under variation of oxygen content  

NASA Astrophysics Data System (ADS)

The question whether LaMnO3 accepts doping with tetravalent cations such as cerium and thus allows the preparation of electron-doped mixed-valent lanthanum manganites has been discussed controversially so far. Against the background of this problem, we present a comparative x-ray photoemission (XPS) study of epitaxial La0.7Ce0.3MnO3 (LCeMO) and La0.7Ca0.3MnO3 (LCMO) thin films. We focus on the exchange splitting of the Mn 3s core level peak, which is a direct indicator of the Mn valence and allows us to quantify the Mn valence in the outermost 3nm of the films. We demonstrate that, depending on the oxygen content, the Mn valence can be tuned between a mixed Mn3+/4+ state and a mixed Mn2+/3+ state in both the LCeMO and the LCMO film. The oxygen content was varied by heating in ultrahigh vacuum for deoxygenation and in an oxygen atmosphere for reoxidation. In the LCeMO film, the deoxygenation not only changes the Mn valence, but also the Ce valence is driven from the 4+ towards the 3+ state.

Beyreuther, Elke; Grafström, Stefan; Eng, Lukas M.; Thiele, Christian; Dörr, Kathrin

2006-04-01

216

Thermoelectric properties of non-stoichiometric lanthanum sulfides  

NASA Technical Reports Server (NTRS)

The lanthanum sulfides are promising candidate materials for high-efficiency thermoelectric applications at temperatures up to 1300 C. The non-stoichiometric lanthanum sulfides (LaS(x), where x is in the range 1.33-1.50) appear to possess the most favorable thermoelectric properties. The Seebeck coefficient and resistivity vary significantly with composition, so that an optimum value of alpha sq/rho (where alpha is the Seebeck coefficient and rho is the resistivity) can be chosen. The thermal conductivity remains approximately constant with stoichiometry, so a material with an optimum value of alpha sq/rho should possess the optimum figure-of-merit. Data for the Seebeck coefficient and electrical resistivity of non-stoichiometric lanthanum sulfides will be pressed, together with structural properties of these materials.

Shapiro, E.; Danielson, L. R.

1983-01-01

217

Syntesis of lanthanum zirconate hydrosols by the ion exchange method  

NASA Astrophysics Data System (ADS)

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

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

2011-04-01

218

Effect of seeding on the formation of lanthanum hexaaluminates synthesized through advanced sol gel process  

NASA Astrophysics Data System (ADS)

Advanced sol gel processing was used to synthesize high purity lanthanum hexaaluminate powders. The effect of seeding on the formation of lanthanum hexaaluminate was also studied by seeding the gel. Dry gel was calcined at various temperatures starting from 1100 °C to 1600 °C for 2 h to study the phase evolution. The combine effects of advanced sol gel processing and the presence of seeds promoted the formation of lanthanum hexaaluminate phase at lower temperature than the conventional routes. Lanthanum hexaaluminate phase was detected at 1201 °C and 1300 °C in seeded and un-seeded gels, respectively. The presence of seed decreases the temperature of formation of lanthanum hexaaluminate by 99 °C. Single phase lanthanum hexaaluminate was formed at 1600 °C in seeded gel whereas trace of lanthanum monoaluminate phase still present in un-seeded gel even at 1600 °C.

Jana, P.; Jayan, P. S.; Mandal, S.; Biswas, K.

2014-12-01

219

Open ended nitrogen-doped carbon nanotubes for the electrochemical storage of energy in a supercapacitor electrode  

NASA Astrophysics Data System (ADS)

Open ended nitrogen-doped carbon nanotubes (N-doped CNTs) are synthesized by pyrolysis of acetylene/ammonia (C2H2/NH3) mixture over lanthanum nickel (LaNi5) alloy catalyst and subsequent 3M, HNO3:H2SO4 acid mixture treatment. Transmission electron microscopy and X-ray photoelectron spectroscopy evaluations of the acid treated N-doped CNTs reveal that the nanotubes possess an open ended morphology and oxidation of pyridinic-N groups, respectively. The resultant open ended N-doped CNTs tested as a supercapacitor electrode material by cyclic voltammetry and exhibits high specific capacitance of 146 F g-1.

John, Anthuvan Rajesh; Arumugam, Pandurangan

2015-03-01

220

Scintillators with potential to supersede lanthanum bromide  

SciTech Connect

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

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

2009-06-01

221

Synthesis and characterization of boron-doped Bi 2 O 3 - La 2 O 3 fiber derived nanocomposite precursor  

Microsoft Academic Search

Boron doped poly(vinyl) alcohol\\/ bismuth - lanthanum acetate (PVA\\/Bi-La) nanofibers were prepared by electrospinning using\\u000a PVA as a precursor. The effect of boron doping was investigated in terms of solution properties, morphological changes and\\u000a thermal characteristics. The fibers were characterized by FT-IR, XRD, SEM and BET. The addition of boron did not only increase\\u000a the thermal stability of the fibers,

?enol Durmu?o?lu; ?brahim Uslu; Tuncay Tunç; Selda Keskin; Arda Aytimur; Ahmet Akdemir

222

Limiting parameters of ultrashort pulses from a lanthanum beryllate laser  

SciTech Connect

An investigation was made of passive mode locking using lanthanum beryllate as the active medium. Various passive switches were used to study the influence of their nonlinear parameters on the characteristics of ultrashort pulses. A minimal ultrashort pulse duration of approx.4 psec was obtained.

Demchuk, M.I.; Mikhailov, V.P.; Gilev, A.K.; Shkadarevich, A.P.; Stavrov, A.A.; Kovalev, D.V.

1985-06-01

223

Nano- and microsized Eu(3+) and Tb(3+)-doped lanthanide hydroxycarbonates and oxycarbonates. The influence of glucose and fructose as stabilizing ligands.  

PubMed

Europium and terbium-doped lanthanum hydroxycarbonate and lanthanum oxycarbonate nanoparticles were fabricated under two different reaction conditions using lanthanide acetate and urea as the starting materials. The photoluminescence properties of these hydroxycarbonate and oxycarbonate particles, and of their colloidal suspensions in water, were studied. The Eu(3+) (5)D(0)?(7)F(J) and Tb(3+) (5)D(4)?(7)F(J) emission spectra and the luminescence lifetimes in the two carbonate matrices were measured. Terbium-doped cerium oxycarbonate particles were synthesized, and the energy transfer process from Ce(3+) to Tb(3+) was investigated. The synthesis of lanthanum and cerium oxycarbonates was also carried out in the presence of stabilizing ligands: glucose and fructose. The influence of these ligands on the structure and luminescence was explored. PMID:23361038

Kaczmarek, Anna M; Miermans, Linde; Van Deun, Rik

2013-04-01

224

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

NASA Astrophysics Data System (ADS)

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

Golmojdeh, Hosein; Zanjanchi, Mohamad Ali

2014-02-01

225

Radiotracer study of the preparation of high-purity lanthanum fluoride  

SciTech Connect

This paper reports that the behavior of the impurities iron, cobalt, yttrium, and cerium is determined via radiotracer techniques for the preparation of high-purity lanthanum fluoride. The behavior of nickel and copper during the coprecipitation of a lanthanum nitrate solution is determined by graphite furnace atomic absorption spectrometric (GFAAS) analysis. There is no commercially available radiotracer for neodymium, a key impurity associated with absorption losses in fluoride glasses. However, the chemical behavior of neodymium and that of yttrium are very similar and, therefore, it is reasonable to assume that the behavior of yttrium throughout the processing is indicative of the behavior of neodymium. The concentrations of impurities in lanthanum nitrate, carbonate, and fluoride are estimated using the radiotracer and GFAAS data for each processing step. Results indicate that while high-purity lanthanum carbonate can be prepared, any impurities present in the lanthanum carbonate will be carried quantitatively into lanthanum fluoride upon hydrofluorination.

Ewing, K.J.; Jaganathan, J.; Peitersen, L.; Aggarwal, I.D. (Naval Research Lab., Code 6505, Washington, DC (US)); Sommers, J.A.; Fahey, J.V. (Teledyna Wah Chang Albany, Albany, OR (US))

1992-06-01

226

Extensive lanthanum deposition in the gastric mucosa: the first histopathological report.  

PubMed

Lanthanum carbonate is one of the new phosphate binders used for the treatment of hyperphosphatemia in patients with chronic kidney disease. It is poorly absorbed from the gastrointestinal tract, forms insoluble complexes within the lumen, and prevents the absorption of dietary phosphate. A 63-year-old female with a 7-year history of peritoneal dialysis, who was treated with lanthanum carbonate for four years, underwent endoscopic submucosal dissection for intramucosal gastric cancer. Resected specimens showed massive accumulation of macrophages containing fine, granular, brown material in the lamina propria. This was confirmed as lanthanum deposition by scanning electron microscopy with energy dispersive x-ray spectroscopy. Although lanthanum may be poorly absorbed, increased tissue accumulation of lanthanum, particularly in the liver and bone, has been reported in animals with chronic kidney disease. This report indicates enhanced gastrointestinal absorption of lanthanum in some patients or conditions, although its clinical significance awaits further studies. PMID:25413959

Makino, Mutsuki; Kawaguchi, Kenji; Shimojo, Hisashi; Nakamura, Hironori; Nagasawa, Masaki; Kodama, Ryo

2015-01-01

227

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

SciTech Connect

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.

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

2011-06-22

228

Neutron Capture and Transmission Measurements and Resonance Parameter Analysis of Samarium  

SciTech Connect

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.

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

229

Nanoscale assembly of lanthanum silica with dense and porous interfacial structures  

PubMed Central

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

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

2015-01-01

230

Nanoscale assembly of lanthanum silica with dense and porous interfacial structures  

NASA Astrophysics Data System (ADS)

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.

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

2015-02-01

231

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

PubMed

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

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

2015-01-01

232

Phase segregation in cerium-lanthanum solid solutions.  

PubMed

Electron energy-loss spectroscopy (EELS) in combination with scanning transmission electron microscopy (STEM) reveals that the La enrichment at the surface of cerium-lanthanum solid solutions is an averaged effect and that segregation occurs in a mixed oxide phase. This separation occurs within a crystalline particle, where the dopant-rich phase is located at the surface of the dopant-deficient phase. The limiting structure appears to be a solid solution with a La fraction of x = 0.6 in the bulk and x = 0.75 at the surface. Up to a La fraction of 0.6, this phase will coexist with a lanthanum-type structure in different proportions depending on the dopant amount. STEM-EELS appears to be a powerful technique to clarify the existence of a multiphase system, and it shows that XRF, XPS, and XRD measure averaged results and do not show the phase complexity of the solids. PMID:16706456

Bellière, V; Joorst, G; Stephan, O; de Groot, F M F; Weckhuysen, B M

2006-05-25

233

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

SciTech Connect

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.

Patra, Rajkumar; Ghosh, S., E-mail: santanu1@physics.iitd.ac.in [Nanostech Laboratory, Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016 (India); Sheremet, E.; Rodriguez, R. D.; Lehmann, D.; Zahn, D. R. T. [Semiconductor Physics, Technische Universität Chemnitz, 09107 Chemnitz (Germany); Jha, Menaka; Ganguli, A. K. [Department of Chemistry, Indian Institute of Technology Delhi, New Delhi 110016 (India); Schmidt, H. [Department of Materials for Nanoelectronics, Technische Universität Chemnitz, 09107 Chemnitz (Germany); Schulze, S.; Hietschold, M. [Solid Surfaces Analysis, Technische Universität Chemnitz, 09107 Chemnitz (Germany); Schmidt, O. G. [Department of Materials for Nanoelectronics, Technische Universität Chemnitz, 09107 Chemnitz (Germany); Leibniz Institute for Solid State Materials Research, IFW Dresden, Helmholtz Straße 20, 01069 Dresden (Germany)

2014-10-28

234

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

NASA Astrophysics Data System (ADS)

Detailed results from field emission studies of lanthanum hexaboride (LaB6) coated multiwalled carbon nanotube (MWCNT) films, pristine LaB6 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 LaB6-coated MWCNTs compared to pristine MWCNT and pristine LaB6 films. Surface morphology of the films has been examined by scanning electron microscopy. Introduction of LaB6 nanoparticles on the outer walls of CNTs LaB6-coated MWCNTs films is confirmed by transmission electron microscopy. The presence of LaB6 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 LaB6 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 LaB6-coated MWCNT with respect to its pristine counterpart. The enhanced field emission properties in LaB6-coated MWCNT films are correlated with a change in microstructure and work function.

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

2014-10-01

235

Influence of lanthanum on the optomagnetic properties of zinc ferrite prepared by combustion method  

NASA Astrophysics Data System (ADS)

Pure and lanthanum doped zinc ferrite nanoparticles were synthesized by a combustion method using glycine as fuel. The mechanism of formation of these nanoferrites is discussed briefly. The prepared nanoparticles characterized using powder X-ray diffraction analysis (XRD) revealed the formation of cubic spinel phase with high crystallinity. Average crystallite size, X-ray density and bulk density were found to decrease with an increase in La3+ concentration. The chemical elements and states on the surface of these ferrites were determined using X-ray photoelectron spectroscopy (XPS). The detailed core level spectra of the photoelectron peaks of Zn 2p, Fe 2p, La 3d and O 1s were analyzed. The magnetic behavior of these nanoparticles was studied using a vibrating sample magnetometer (VSM) and corresponding changes in the saturation magnetization (Ms), coercivity (Hc) and remanent magnetization (Mr) were analyzed. The optical behavior of these ferrite nanoparticles was characterized by UV-Diffuse reflectance studies (UV-DRS). From the UV-DRS studies, the optical band gap was found to be in the range of 1.87-1.97 eV. The combustion method significantly produces large amount of products within a short time. Therefore, this method is potentially suitable for manufacturing industries for preparing the magnetic nanoparticles.

Tholkappiyan, R.; Vishista, K.

2014-09-01

236

Spray pyrolytic deposition and characterization of lanthanum selenide (La 2Se 3) thin films  

NASA Astrophysics Data System (ADS)

The versatile spray pyrolysis technique was employed to prepare thin films of lanthanum selenide (La 2Se 3) on glass and fluorine doped tin oxide (FTO) coated glass substrates under optimized conditions. The deposition temperature was 250 °C. The X-ray studies reveal that the films are polycrystalline with single La 2Se 3 phase. The estimated optical band gap was found to be 2.6 eV. The dielectric properties such as dielectric constant and dielectric loss of the films deposited on FTO coated glass substrates were measured with FTO-La 2Se 3-Ag structure as a function of frequency and the results are reported. At room temperature dielectric constant and dielectric loss for 1 kHz frequency were found to be 6.2 and 0.048, respectively. The room temperature electrical resistivity was of the order of 10 5 ? cm. The La 2Se 3 films are found to be n-type semiconductor.

Bagde, G. D.; Sartale, S. D.; Lokhande, C. D.

2003-05-01

237

Structure, Stoichiometry, and Phase Purity of Calcium Substituted Lanthanum Manganite Powders  

NASA Astrophysics Data System (ADS)

Calcium-doped lanthanum manganite La 1- xCa xMnO 3, synthesized by the glycine/nitrate method, was characterized by high resolution synchrotron X-ray powder diffraction, electron diffraction, and infrared spectroscopy. A strong correlation was observed between the cooling rate from the calcination temperature and the powder quality, indicating the importance of a homogeneous oxygen stoichiometry. The structure refinement reveals that La 1- xCa xMnO 3with x=0.2, 0.3, 0.4, and 0.6 has orthorhombic symmetry with space group Pnma. The MnO 6octahedra are fairly symmetrical, but the octahedra are tilted about 20° relative to the ideal perovskite structure. Infrared spectroscopy revealed that only the O-Mn-O bending mode is significantly influenced by the substitution of La with Ca. In La 0.8Ca 0.2MnO 3we found diffraction evidence of a superstructure in domains in some of the grains. We propose that the superstructure in La 0.8Ca 0.2MnO 3is due to ordering of Ca 2+ions on A(La 3+) sites in the perovskite ABO 3structure.

Faaland, S.; Knudsen, K. D.; Einarsrud, M.-A.; Rørmark, L.; Høier, R.; Grande, T.

1998-11-01

238

Structure, stoichiometry, and phase purity of calcium substituted lanthanum manganite powders  

SciTech Connect

Calcium-doped lanthanum manganite La{sub 1{minus}x}Ca{sub x}MnO{sub 3}, synthesized by the glycine/nitrate method, was characterized by high resolution synchrotron X-ray powder diffraction, electron diffraction, and infrared spectroscopy. A strong correlation was observed between the cooling rate from the calcination temperature and the powder quality, indicating the importance of a homogeneous oxygen stoichiometry. The structure refinement reveals that La{sub 1{minus}x}Ca{sub x}MnO{sub 3} with x = 0.2, 0.3, 0.4, and 0.6 has orthorhombic symmetry with space group Pnma. The MnO{sub 6} octahedra are fairly symmetrical, but the octahedra are tilted about 20{degree} relative to the ideal perovskite structure. Infrared spectroscopy revealed that only the O-Mn-O bending mode is significantly influenced by the substitution of La with Ca. In La{sub 0.8}Ca{sub 0.2}MnO{sub 3} the authors found diffraction evidence of a superstructure in domains in some of the grains. They propose that the superstructure in La{sub 0.8}Ca{sub 0.2}MnO{sub 3} is due to ordering of Ca{sup 2+} ions on A (La{sup 3+}) sites in the perovskite ABO{sub 3} structure.

Faaland, S.; Einarsrud, M.A.; Roermark, L.; Hoeier, R.; Grande, T. [Norwegian Univ. of Science and Technology, Trondheim (Norway)] [Norwegian Univ. of Science and Technology, Trondheim (Norway); Knudsen, K.D. [ESRF, Grenoble (France)] [ESRF, Grenoble (France)

1998-11-01

239

Theoretical radiative lifetimes of levels in singly ionized lanthanum  

NASA Astrophysics Data System (ADS)

Theoretical radiative lifetimes of 29 levels in singly ionized lanthanum are determined using Cowan's 'Hartree-Fock and relativistic corrections' (HFR) method modified by us to include core-valence electron correlations in the core-polarization picture. The configuration mixing coefficients have been determined semiempirically through a least-squares fitting procedure treating Slater and spin-orbit integrals as free parameters. The results obtained compared with available experimental and other theoretical data confirm the importance of valence-core correlation effects.

Ku?aga-Egger, D.; Migda?ek, J.

2009-09-01

240

Nanostructured Lanthanum Zirconate Coating and Its Thermal Stability Properties  

Microsoft Academic Search

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

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

2007-01-01

241

Synthesis and Properties of Lanthanum Sodium Manganate Perovskites Crystals  

Microsoft Academic Search

Crystals up to 4 mm on the edge of sodium-substituted lanthanum manganates with the rhombohedral perovskite structure have been grown for the first time using fused salt electrolysis at 980–1000°C. Cs2MoO4–MoO3 mixtures have been employed as solvents. Substitution of Na for La appears to be limited to about 12 at.%. All the phases prepared have an average Mn valence of

W. H. McCarroll; Ian D. Fawcett; M. Greenblatt; K. V. Ramanujachary

1999-01-01

242

Synthesis and Properties of Lanthanum Sodium Manganate Perovskites Crystals  

Microsoft Academic Search

Crystals up to 4 mm on the edge of sodium-substituted lanthanum manganates with the rhombohedral perovskite structure have been grown for the first time using fused salt electrolysis at 980-1000 degC. Cs2MoO4-MoO3 mixtures have been employed as solvents. Substitution of Na for La appears to be limited to about 12 at.%. All the phases prepared have an average Mn valence

W. H. McCarroll; Ian D. Fawcett; M. Greenblatt; K. V. Ramanujachary

1999-01-01

243

Electrochemical behaviour of lanthanum fluoride in molten fluorides  

Microsoft Academic Search

The electrochemical behaviour of lanthanum fluoride dissolved in molten lithium fluoride and in eutectic mixture LiF-CaF2 was investigated by cyclic voltammetry and laboratory electrolysis. The cyclic voltammetry experiments were carried out at\\u000a 900°C and 800°C, respectively, in a graphite crucible (counter electrode). Several types of working electrodes (Mo, W, Ni\\u000a and Cu) were used. Ni\\/Ni(II) was used as a reference

Marta Ambrová; Jana Jurišová; Vladimír Danielik

2008-01-01

244

Lanthanum halide nanoparticle scintillators for nuclear radiation detection  

SciTech Connect

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

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

2013-02-14

245

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

PubMed

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 ?-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

Hatano, Manabu; Ishihara, Kazuaki

2013-03-11

246

Synthesis and Structure of (Ca,Sr)-Substituted Lanthanum Manganite  

Microsoft Academic Search

The phase composition and structure of equilibrium LaMnO3-CaMnO3-SrMnO3 samples prepared at 1500°C in air are investigated. The results demonstrate that the system contains a broad region of La1 ? x(Ca1 ? ySry)xMnO3 perovskite-like solid solutions in which calcium and strontium cations substitute for lanthanum. The solid solutions have an orthorhombic (Pnma), rhombohedral \\u000a

B. V. Slobodin; E. V. Vladimirova; S. L. Petukhov; L. L. Surat; I. A. Leonidov

2005-01-01

247

Effect of pressure on the magnetic properties of lanthanum manganite  

SciTech Connect

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

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

2010-08-15

248

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

PubMed Central

A new ethylenediaminetetraacetic acid- (EDTA-) mediated hydrothermal route to prepare chrysanthemum-shaped samarium orthovanadate (SmVO4) nanocrystals with decavanadate (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

Zuo, Wenli

2013-01-01

249

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

NASA Technical Reports Server (NTRS)

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

Niedra, Janis M.; Overton, Eric

1991-01-01

250

23 to 300{degrees}C demagnetization resistance of samarium-cobalt permanent magnets  

SciTech Connect

The influence of temperature on the 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 temperatures in demagnetization-resistant 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 Sm{sub 2}Co{sub 17}-type magnet samples in the temperature range of 23 to 300{degrees}C. The knee point was used to define the limits of operation safe against irreversible demagnetization, and the resulting plots are interpreted to show the temperature-induction swing limits of safe magnet operation. The observed second quadrant M-H characteristic squareness is shown, by two measures, to increase gradually with temperature and to peak in the interval 200 to 300{degrees}C.

Niedra, J.M.; Overton, E.

1991-10-01

251

Magnetoresistance of lanthanum manganites with activation-type conductivity  

SciTech Connect

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

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

2013-05-15

252

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

PubMed

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

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

2014-07-01

253

Airplane dopes and doping  

NASA Technical Reports Server (NTRS)

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

Smith, W H

1919-01-01

254

Waveshifting fiber readout of lanthanum halide scintillators  

NASA Astrophysics Data System (ADS)

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.

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

2006-07-01

255

Synthesis of Doped Rare Earth Manganate Perovskite Crystals Using Fused Salt Electrolysis  

Microsoft Academic Search

A facile method for the synthesis of doped lanthanum manganate crystals, suitable for the measurement of electrical and magnetic properties, is presented. Mixtures of sodium molybdate and molybdenum(VI) oxide are used as a solvent to which La2O3, MnCO3, and SrMoCO4are added as solutes which are then electrolyzed at 800–1040°C for varying lengths of time with Pt electrodes. Well-formed cubic crystals,

W. H. McCarroll; K. V. Ramanujachary; M. Greenblatt

1997-01-01

256

Controlled synthesis of Eu-doped La2O2S nanophosphors by refluxing method  

Microsoft Academic Search

A novel refluxing method is presented to synthesise Eu-doped La2O2S nanocrystalline phosphors by employing lanthanum formate, europium formate and sulphur powder as reactants and triethylene tetramine with n-dodecanethiol as solvents. The sizes and morphologies of La2O2S?:?Eu phosphors could be controlled from nanoflakes (10?±?2?nm in thickness), micrometre vesicles (1?µm in diameter), to spherical nanocrystals (average 100?nm in diameter) by simply adjusting

Dekun Ma; Sensen Liu; Yanqing Zhang; Changwei Zhang; Shaoming Huang

2012-01-01

257

Domain switching energies: Mechanical versus electrical loading in La-doped bismuth ferrite-lead titanate  

Microsoft Academic Search

The mechanical stress-induced domain switching and energy dissipation in morphotropic phase boundary (1-x)(Bi1 - yLay)FeO3-xPbTiO3 during uniaxial compressive loading have been investigated at three different temperatures. The strain obtained was found to decrease with increasing lanthanum content, although a sharp increase in strain was observed for compositions doped with 7.5 and 10 at. % La. Increased domain switching was found

T. Leist; K. G. Webber; W. Jo; T. Granzow; E. Aulbach; J. Suffner; J. Rödel

2011-01-01

258

High-temperature studies of the magnetic susceptibility of samarium and the Al{sub 2}Sm compound  

SciTech Connect

The magnetic susceptibility of metallic samarium and the Al{sub 2}Sm intermetallic compound has been experimentally studied by the Faraday method in the temperature range of 300-1800 K. It has been shown that the temperature dependences of the magnetic susceptibility of Sm and Al{sub 2}Sm in a crystalline state can be described in the framework of Van Vleck paramagnetism theory taking into account variable valence and the contribution from the conduction electrons. Using this theoretical interpretation of the data, the effective valence of samarium in the metallic state and in the Al{sub 2}Sm intermetallic compound has been estimated as a function of the temperature.

Uporova, N. S., E-mail: fominans@rambler.ru [Ural State Pedagogical University (Russian Federation); Uporov, S. A. [Russian Academy of Sciences, Institute of Metallurgy, Ural Branch (Russian Federation); Sidorov, V. E. [Ural State Pedagogical University (Russian Federation)

2012-02-15

259

Water Research 39 (2005) 22292236 Effect of counterions on lanthanum biosorption  

E-print Network

: Biosorption; Anions; Lanthanum; Sargassum; Speciation 1. Introduction Biosorption is a process where metal. Biosorption studies involving the removal of heavy metal ions have most often made use of nitrate saltsWater Research 39 (2005) 2229­2236 Effect of counterions on lanthanum biosorption by Sargassum

Volesky, Bohumil

2005-01-01

260

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

Microsoft Academic Search

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

R. Gadow; M. Lischka

2002-01-01

261

Factors Affecting Lanthanum and Cerium Biosorption on Pinus brutia Leaf Powder  

Microsoft Academic Search

The biosorption behavior of lanthanum and cerium ions from aqueous solution by leaf powder of Pinus brutia was separately studied in a batch system as a function of initial pH, contact time, initial metal ion concentration, temperature, and adsorbent amount. The uptake of lanthanum and cerium was increased when the initial pH of the solution was increased. Thermodynamic parameters such

Ceren Kütahyali; ?enol Sert; Berkan Çetinkaya; Süleyman Inan; Meral Eral

2010-01-01

262

Pharmacokinetics and biodistribution of samarium-153-labelled OC125 antibody coupled to CITCDTPA in a xenograft model of ovarian cancer  

Microsoft Academic Search

The use of samarium-153 in the context of radioimmunotherapy of cancers has been limited by the instability of antibody labelling, which produces high uptake concentrations in liver and bone. This study compares the pharmacokinetics and biodistribution of153Sm-labelled OC125 monoclonal antibody, in whole or F(ab')2 fragment form and with diethylene triamine penta-acetic acid (DTPA) or 6-p-isothiocyanatobenzyl diethylene triamine penta-acetic acid (CITCDTPA)

Françoise Kraeber-Bodéré; Anil Mishra; Philippe Thédrez; Alain Faivre-Chauvet; Manuel Bardiès; S. Imai; Jean Le Boterff; Jean-François Chatal

1996-01-01

263

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

PubMed Central

New complexes of samarium(III), gadolinium(III), and dysprosium(III) with coumarin-3-carboxylic acid (HCCA) were prepared by the reaction of the ligand with respective metal nitrates in ethanol. The structures of the final complexes were determined by means of physicochemical data, elemental analysis, IR and Raman spectra. The metal-ligand binding mode in the new Ln(III) complexes of coumarin-3-carboxylic acid was elucidated. The vibrational study gave evidence for bidentate coordination of CCA? to Ln(III) ions through the carbonylic oxygen and the carboxylic oxygen atoms. The complexes were tested for antiproliferative activitiy on the chronic myeloid leukemia-derived K-562, overexpressing the BCR-ABL fusion protein. Cytotoxicity towards tumor cells was determined for a broad concentration range. The samarium salt exerted a very weak antiproliferative effect on these cells. This is in contrast to the lanthanide complexes, especially samarium complex, which exhibited potent antiproliferative activity. The present study confirms our previous observations that the lanthanide complexes of coumarins exhibit antiproliferative activity towards K-562 cell line. PMID:18274603

Kostova, Irena; Momekov, Georgi; Stancheva, Peya

2007-01-01

264

Oxygen-conducting compounds with La2Mo2O9 structure in the ternary system La2Mo2O9-Sm2W2O9-Sm2Mo2O{9/+}: Synthesis and properties  

NASA Astrophysics Data System (ADS)

Polycrystalline samples in the ternary system La2Mo2O9-Sm2W2O9-Sm2Mo2O{9/+} were synthesized in air. The region of the existence of compounds with the lanthanum molybdate (La2Mo2O9) structure in this system was determined. The polymorphism of the synthesized compounds was studied. Doping with samarium or with samarium and tungsten was shown to lead to the suppression of the transition between the monoclinic and cubic phases ? ? ? and the appearance of the transition ? ms ? ? between two cubic phases. In samples with a high samarium content, the phase transition ? ms ? ? manifests itself as significant anomalies in the temperature dependences of the dielectric permeability and electric conductivity. An increase in the concentration of samarium in the samples leads to a substantial decrease in the conductivity compared with the nondoped compound La2Mo2O9.

Voronkova, V. I.; Kharitonova, E. P.

2014-07-01

265

Optical Properties of Pb0-ZnO-P2O5 Glasses Doped With Samarium and Neodymium  

NASA Astrophysics Data System (ADS)

(PbO)30(ZnO)20(P2O5)50-x(Nd2O3)x and (PbO)30(ZnO)20(P2O5)50-x(Sm2O3)x glasses (where x = 0.5, 1, 2%) have been prepared by conventional melt quenching method. Measurements of X-ray diffractrogram reveal samples prepared are amorphous in nature, DSC studies have been made and the glass transition temperature (Tg), crystallization temperature (Tc) and glass stability factor have been evaluated. These glasses exhibit high transition temperature (Tg) and high stability factor (S) indicating glasses are stable. IR spectra of these glasses show absorption peaks at 1215 cm-1, 1072 cm-1 and 728 cm-1 corresponding to P = O, P-O-P and P-O- vibrations. Optical absorption studies show absorption peaks in the range of 462.5-584 nm for various transition in the Nd3+ ion and 287.5-562.5 nm in case Sm3+.

Lakshmikantha, R.; Rajaramakrishna, R.; Anavekar, R. V.; Ayachit, N. H.

2011-07-01

266

Syntesis of lanthanum zirconate hydrosols by the ion exchange method  

Microsoft Academic Search

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

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

2011-01-01

267

Fabrication of lanthanum copper oxide nanofibers by electrospinning  

NASA Astrophysics Data System (ADS)

For about 75 years electrospinning has been explored as a simple and versatile method to produce nanofibers. Since electrospinning was introduced in the 1930s, most researchers have focused on fabrication and theoretical work for polymer nanofibers. Recently, more than 40 ceramic nanofibers were produced by electrospinning. However, few theoretical works have been performed on ceramic electrospinning. The objectives of this dissertation were to study the relationships among variables and responses using response surface methodology and to applying this to ceramic electrospinning theory. The theory was applied in the fabrication of ceramic nanofibers. Lanthanum nitrate/copper nitrate/polyacrylamide composite nanofibers were prepared by combining a sol-gel process and electrospinning. Porous lanthanum copper oxide nanofibers with diameters ranging from 75 nm to 175 nm were obtained by calcination of composite fibers. Responses dependent on experimental conditions were studied in polymer electrospinning and ceramic electrospinning, independently. In both types of electrospinning, solution parameters were found to be more important than process parameters in determining responses (fiber diameters, bead density). With varying ceramic precursor concentrations, fiber diameters decrease first, then increase though the conductivities increase continuously. Bead density shows the opposite trend. Regression analysis shows that bead density is inversely proportional to (fiber diameter)3 (sigmaBead ? 1h3 where sigmaBead is the bead density and h is the fiber diameter) Polymer (polyacrylamide) electrospinning and ceramic (lanthanum copper oxide) electrospinning was compared using the same parameters (pH, voltage). Ceramic electrospinning showed similar trends compared to polymer electrospinning although the electrospinning solution contained ceramic precursors. A higher conductivity of ceramic electrospinning solution produced thinner fibers. Additionally, it was verified experimentally that the proposed model in the polymer system could be applied to a ceramic system. Using the lanthanum copper oxide nanoparticles, three planar sensors were fabricated over tape-cast yttria-stabilized zirconia substrate with screen-printed electrodes. Sensing characteristics such as sensitivity, stability, signal to noise ratio, and response time were studied with varying NO gas concentration and temperature. At 450°C, sensitivity was 6.44 mV/log (ppm) and response time was 29.2 seconds. Electrospinning was found to be an effective route for the preparation of dispersible nanoparticles.

Park, Hyun

268

Work function measurement of lanthanum-boron compounds  

Microsoft Academic Search

The relationship between emission properties and sample composition is studied for lanthanum-boron compounds. Specifically, the La-B system is considered between 1400 and 2100 K and between LaB(4.24) and LaB(29.2) to determine the phase relationship, chemical activity of the compounds, vapor composition, and vaporization rate. The results indicate that: (1) a blue-colored phase near LaB(9) exists between a purple-colored LaB(6) and

D. L. Jacobson; E. K. Storms

1978-01-01

269

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

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.

Zhao, Hua; Zhang, Kun; Xu, Long; Sun, Fankui; Zhang, Jingwen, E-mail: jingwenz@gmail.com [Department of Physics, Harbin Institute of Technology, Harbin 150001 (China); Chen, Xuesheng [Department of Physics and Astronomy, Wheaton College, Norton Massachusetts 02766 (United States); Li, Kewen K. [Boston Applied Technologies, Inc., Woburn, Massachusetts 01801 (United States)

2014-02-21

270

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

SciTech Connect

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

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

2012-10-15

271

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

SciTech Connect

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

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

1995-02-01

272

Polarization-based isotope-selective two-color photoionization of atomic samarium using broadband lasers  

NASA Astrophysics Data System (ADS)

An isotope separation method based on polarization selection rules is applied to atomic samarium by using two-color resonance ionization spectroscopy with broadband lasers. In this method, odd isotopes with nonzero nuclear spin are selectively excited, while even isotopes with zero nuclear spin are prohibited from excitation using two parallel linearly polarized lasers. We have identified a two-color excitation scheme 0 cm-1 ( J = 0) ? 15650.5 cm-1 ( J = 1) ? 33116.8 cm-1 ( J = 1) ? Sm+ for selective excitation of the odd isotopes of Sm I. Using this scheme, selective excitation of odd isotopes of Sm I (147Sm and 149Sm) with an isotopic selectivity better than 40 has been demonstrated. In addition, the effect of different polarization states of the excitation lasers and relative polarization angle between them on the selectivity of odd isotopes has also been studied. The dependence of the even mass isotope signal on the relative polarization angle followed sin2 ?, which is in excellent agreement with theoretical predictions.

Seema, A. U.; Rath, Asawari D.; Mandal, P. K.; Dev, Vas

2015-03-01

273

Detection of long-lived europium-152 in samarium-153-lexidronam.  

PubMed

Samarium-153-lexidronam is a radiopharmaceutical used for pain palliation therapy in patients suffering from multilocular bone metastases. The postinjection residual of four pharmaceutical vials of (153)Sm-lexidronam and one patient were investigated for contamination with other isotopes using high-resolution gamma spectroscopy. In the spectra besides the already known contaminants europium-154, (155)Eu and (156)Eu, europium-152 was discovered in vitro and also in vivo. (152)Eu disintegrates with a half-life of 13.5years emitting a multitude of high energy photons. Due to these properties, it does not only affect radioactive waste management regarding e.g. the disposal of the postinjection residual, but also poses an additional dose burden to the patient and to third persons. In the postinjection residual a mean activity concentration of 10.4±1.1kBq europium-152 per GBq (153)Sm was detected. 62days after isotope application, 15.8±4.0kBq of (152)Eu were found within the patient. The lifetime effective dose to the patient from the europium impurities was determined using a multicompartment model. For (152)Eu the effective dose was 2.1mSv/GBq (153)Sm-lexidronam and the total effective dose from all impurities was 6.1mSv/GBq (153)Sm-lexidronam. The total absorbed dose to third persons caused by the europium impurities was estimated as 0.6mGy/GBq (153)Sm-lexidronam. PMID:25090002

Loebe, Tammo; Hettwig, Bernd; Fischer, Helmut W

2014-12-01

274

Europium, Samarium, and Neodymium Isotopic Fractions in Metal-Poor Stars  

E-print Network

We have derived isotopic fractions of europium, samarium, and neodymium in two metal-poor giants with differing neutron-capture nucleosynthetic histories. These isotopic fractions were measured from new high resolution (R ~ 120,000), high signal-to-noise (S/N ~ 160-1000) spectra obtained with the 2dCoude spectrograph of McDonald Observatory's 2.7m Smith telescope. Synthetic spectra were generated using recent high-precision laboratory measurements of hyperfine and isotopic subcomponents of several transitions of these elements and matched quantitatively to the observed spectra. We interpret our isotopic fractions by the nucleosynthesis predictions of the stellar model, which reproduces s-process nucleosynthesis from the physical conditions expected in low-mass, thermally-pulsing stars on the AGB, and the classical method, which approximates s-process nucleosynthesis by a steady neutron flux impinging upon Fe-peak seed nuclei. Our Eu isotopic fraction in HD 175305 is consistent with an r-process origin by the ...

Roederer, Ian U; Sneden, Christopher; Cowan, John J; Sobeck, Jennifer S; Pilachowski, Catherine A

2007-01-01

275

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

NASA Technical Reports Server (NTRS)

The influence of temperature on the M-H demagnetization characteristics of permanent magnets is important information for the full utilization of the capabilities of samarium-cobalt magnets at high temperatures in demagnetization-resistant permanent magnet devices. In high temperature space power converters, such as free-piston Stirling engine driven linear alternators, magnet demagnetization can occur as 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.

Niedra, J. M.

1992-01-01

276

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

PubMed

Heterometallic carboxyphosphonates UO(2)(2+)/Ln(3+) have been prepared from the hydrothermal reaction of uranyl nitrate, lanthanide nitrate (Ln = Sm, Tb, Er, Yb), and phosphonoacetic acid (H(3)PPA). Compound 1, (UO(2))(2)(PPA)(HPPA)(2)Sm(H(2)O)·2H(2)O (1) adopts a two-dimensional structure in which the UO(2)(2+) metal ions bind exclusively to the phosphonate moiety, whereas the Ln(3+) 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 Sm(3+) emissive state exhibits a double-exponential decay with lifetimes of 67.2 ± 6.5 and 9.0 ± 1.3 ?s 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 Sm(3+) 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. PMID:22171660

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

2012-01-01

277

Study of samarium modified lead zirconate titanate and nickel zinc ferrite composite system  

NASA Astrophysics Data System (ADS)

In the present work, composites of samarium substituted lead zirconate titanate and nickel zinc ferrite with compositional formula 0.95Pb1-3x/2 SmxZr0.65Ti0.35O3-0.05Ni0.8Zn0.2Fe2O4 (x=0, 0.01, 0.02 and 0.03) were prepared by the conventional solid state route. X-ray diffraction analysis was carried out to confirm the coexistence of individual phases. Microstructural study was done by using scanning electron microscope. Dielectric constant and loss were studied as a function of temperature and frequency. To study ferroelectric and magnetic properties of the composite samples, corresponding P-E and M-H hysteresis loops were recorded. Change in magnetic properties of electrically poled composite sample (x=0.02) was studied to confirm the magnetoelectric (ME) coupling. ME coefficient (dE/dH) of the samples (x=0 and 0.02) was measured as a function of DC magnetic field.

Rani, Rekha; Juneja, J. K.; Singh, Sangeeta; Raina, K. K.; Prakash, Chandra

2015-03-01

278

MOCVD of very thin films of lead lanthanum titanate  

SciTech Connect

Films of lead lanthanum titanate were deposited using metal-organic chemical vapor deposition (MOCVD) at temperatures between 500 and 550{degrees}C in a hot-wall reactor. The precursors used were Pb(THD){sub 2}, La(THD){sub 3}, and Ti(THD){sub 2}(I-OPr){sub 2} where THD = 2,2,6,6-tetramethyl-3,5-heptanedionate, O{sub 2}C{sub 11}H{sub 19}, and I-OPr = isopropoxide, OC{sub 3}H{sub 7}. The three precursors were delivered to the reactor using a single solution containing all three precursors dissolved in tetraglyme and the precursor solution was volatilized at 225{degrees}C. Films were deposited on Si and Si/Ti/Pt substrates, and characterized using Rutherford Backscattering Spectroscopy (RPS) and X-ray diffraction(XRD). Films deposited at 550{degrees}C had a composition which was close to that of the precursor solution while films deposited at 500{degrees}C were deficient in lanthanum. Even at 500{degrees}C, the desired perovskite phase showed an increase in the intensity of the X-ray lines, but did not change the width of these lines, implying the grain sizes had remained unchanged.

Beach, D.B.; Vallet, C.E.

1995-12-31

279

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

NASA Astrophysics Data System (ADS)

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.

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

2014-09-01

280

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

PubMed

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

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

2014-01-01

281

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

PubMed Central

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

2014-01-01

282

Passively Q-switched Yb- and Sm-doped fiber laser at 1064 nm  

NASA Astrophysics Data System (ADS)

The article describes a simple method of developing a Q-switched fiber laser utilizing the passive Q-switching technique. An ytterbium-doped double-clad fiber was used as the gain medium and a small length of samarium-doped fiber as a saturable absorber to obtain passive Q-switching operation. The laser was capable of operating at continuous wave (CW), Q-switched mode locked, and Q-switched regimes under suitable conditions. Further, the article presented, for the first time, properties of the laser with the orientation of the polarization controller plates inside the cavity. The all fiber laser produces very stable pulses with different energy and repetition rates.

Das, Gautam; Chaboyer, Zachary J.; Navratil, Joseph E.; Drainville, Robert A.

2015-01-01

283

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

DOEpatents

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.

Holcombe, Cressie E. (Knoxville, TN); Kovach, Louis (Oak Ridge, TN); Taylor, Albert J. (Ten Mile, TN)

1981-01-01

284

Atomic layer deposition of lanthanum aluminum oxide nano-laminates for electrical applications  

Microsoft Academic Search

Lanthanum aluminum oxide thin films were grown by atomic layer deposition from a lanthanum precursor, tris(N,N'-diisopropylacetamidinato)lanthanum (La(iPrAMD)3), trimethylaluminum and water. Smooth, amorphous films having compositions La0.5Al1.5O3 and La0.9Al1.1O3 were deposited on HF-last silicon and characterized without postdeposition annealing. The films contained less than 1 at. % of carbon according to Rutherford backstattering spectrometry and secondary ion mass spectrometry. A thin

Booyong S. Lim; Antti Rahtu; Philippe de Rouffignac; Roy G. Gordon

2004-01-01

285

Atomic layer deposition of lanthanum aluminum oxide nano-laminates for electrical applications  

Microsoft Academic Search

Lanthanum aluminum oxide thin films were grown by atomic layer deposition from a lanthanum precursor, tris(N,N?-diisopropylacetamidinato)lanthanum (La(iPrAMD)3), trimethylaluminum and water. Smooth, amorphous films having compositions La0.5Al1.5O3 and La0.9Al1.1O3 were deposited on HF-last silicon and characterized without postdeposition annealing. The films contained less than 1 at. % of carbon according to Rutherford backstattering spectrometry and secondary ion mass spectrometry. A thin

Booyong S. Lim; Antti Rahtu; Philippe de Rouffignac; Roy G. Gordon

2004-01-01

286

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

DOEpatents

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.

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

1980-01-22

287

Radio-opaque fecal impaction and pseudo-occlusion in a dialyzed patient taking lanthanum carbonate.  

PubMed

Lanthanum therapy is an efficient therapy of hyperphosphoremia by chelating phosphore in the digestive tract. Lanthanum is a silvery white metallic element that belongs to group 3 of the periodic table. This drug is lightly absorbed and has low water solubility. It should be borne in mind that abdominal X-rays of patients taking lanthanum carbonate may have a radio-opaque appearance typical of imaging agents. This characteristic is suggested to confirm adherence of the patient by doing an abdominal X-ray. We describe in our case a particular good compliant patient with slow digestive transit, which ends by pseudo-occlusion. PMID:22118504

Muller, Clotilde; Muller, Sandrine; Sissoko, Aicha; Klein, Alexandre; Faller, Bernadette; Chantrel, Francois

2012-10-01

288

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

289

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 ...

290

Effect of Adsorbed Nitrogen on the Thermionic Emission from Lanthanum Hexaboride  

NASA Technical Reports Server (NTRS)

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.

Carter, Arlen F.; Wood, George P.

1959-01-01

291

Synthesis, Magnetic Properties and Microstructure of Ni-Zn-Cr Ferrites Doped with Lanthanum  

Microsoft Academic Search

The precursors consisted of Ni2+, Zn2+, Cr3+, Fe3+ and La3+ ionic citrate were prepared by sol-gel process. Nanocrystalline powders of Zn0.4Ni0.6Cr0.5Fe1.5O4 and Zn0.4Ni0.6Cr0.5La0.02Fe1.48O4 were obtained at low sintering temperatures. The process that amorphous precursors translated to crystalline ferrites was researched by means of DSC-TG. The structure, morphology and magnetic properties of the obtained products were characterized by X-ray diffractometer (XRD),

Xu Feng; Zhou Xiangchun; Li Liangchao; Liu Hui; Jiang Jing

2007-01-01

292

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

NASA Astrophysics Data System (ADS)

(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 ?m 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 (?) increased.

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

2013-12-01

293

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

Microsoft Academic Search

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

Peng-nian Huang; A. Petric

1996-01-01

294

Polarization Characteristics of High Valence Ion Doped Bismuth Lanthanum Titanate Ceramics  

Microsoft Academic Search

Bi3.25La0.75Ti3?3xNb3xO12 (BLTN) and Bi3.25La0.75Ti3?3xV3xO12 (BLTV) ceramics (x = 0, 0.01, 0.03, 0.05, 0.07 and 0.1) were prepared by a solid state reaction method. For all BLTN and BLTV compositions, bismuth-layered perovskite structures were confirmed using X-ray diffraction. The remanent polarization increases and reaches to the maximum value at x = 0.05 for BLTN and at x = 0.01–0.03 for BLTV

JIN SOO KIM; HAI JOON LEE; SUN HEE KANG; SUN YOUNG LEE; ILL WON KIM

2004-01-01

295

Preparation of Zinc Doped Lanthanum Strontium Gallate Solid Electrolyte Using a Reaction-Sintering Process  

Microsoft Academic Search

La0.8Sr0.2Ga0.8Zn0.2O2.8 ceramics prepared using a reaction-sintering process was investigated in this study. Without any calcination involved, the mixture of raw materials was pressed and sintered directly. SrLaGa3O7 is the major phase in 1150°C sintered pellets and decreased at higher sintering temperature 1250°C. La0.8Sr0.2Ga0.8Zn0.2O2.8 became the major phase in pellets sintered at 1250 o C\\/2 h. Density of La0.8Sr0.2Ga0.8Zn0.2O2.8 ceramics increases

Y. C. LIOU; C. C. LAN; S. L. YANG

2008-01-01

296

Single–Step Synthesis of Nanocrystalline Doped-Lanthanum Hydroxide Materials from Heterometallic Alkoxides  

Microsoft Academic Search

The reactions between La3(OBut)9(HOBut)2 and various trimethylsilylamide species M[N(SiMe3)2] x(THF)y (M = K, Ba, Pb) have been investigated as a means to acceed to heterometallic La-M species. The La-K derivative was used as synthon in metathesis reaction toward CuCl2 in order to get an heterometallic La-Cu derivative. All compounds were characterized by elemental analysis, FT-IR, EPR and multinuclear NMR spectroscopies.

Stephane Daniele; Liliane G. Hubert-Pfalzgraf

2005-01-01

297

Chemical Preparation of Pure and Strontium-and/or Magnesium-Doped Lanthanum Gallate Powders  

E-print Network

-ion-conducting properties,1,2 in comparison, for instance, to yttria-stabilized zirconia electrolytes. Several researchers of thin films of the same.16 In contrast, a coprecipitation route (with NH4OH addition) from an aqueous

Tas, A. Cuneyt

298

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

NASA Astrophysics Data System (ADS)

Transparent 1 at% Nd 3+:Y 1.9La 0.1O 3 ceramics were fabricated with nanopowders prepared by carbonate coprecipitation method. The powder compacts were sintered in H 2 atmosphere at 1550 °C for 30 h. The Nd 3+:Y 1.9La 0.1O 3 ceramics display uniform grains of about 50 ?m 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 cm 2. The absorption is still high at LD wavelength 806 nm with absorption cross section of 1.78 × 10 -20 cm 2 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 cm 2 and broad FWHM of about 7.8 nm. The broad absorption and emission bandwidth of Nd 3+:Y 1.9La 0.1O 3 transparent ceramics are favorable to achieve the miniaturized LD pumping apparatus and ultrashort modelocked pulse laser output, respectively.

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

2008-06-01

299

Anomalous Hall effect in calcium-doped lanthanum cobaltite and gadolinium  

Microsoft Academic Search

The physical origin of the anomalous (proportional to magnetization) Hall effect is not very well understood. While many theories account for a Hall effect proportional to the magnetization of a material, these theories often predict effects significantly smaller than those found in ferromagnetic materials. An even more significant deficiency of the conventional theories is that they predict an anomalous Hall

Scott Alan Baily

2003-01-01

300

The grain size dependence of the resistance behaviors in doped lanthanum manganite polycrystalline films  

NASA Astrophysics Data System (ADS)

Using the sol-gel spin-coating method, La0.67Sr0.33MnO3 and La0.7Ca0.3MnO3 polycrystalline films have been prepared. The polycrystalline films show much lower resistivity peak temperature Tp than that of the corresponding epitaxial film, and Tp shifts to higher temperature when the annealing temperature increases. The magnetization measurement reveals that all of the polycrystalline films have the same magnetic transition temperature as the corresponding epitaxial films. These results are different from the previous works. We ascribe the difference to the grain size of our polycrystalline samples being much smaller, so the conduction through the grain boundaries predominates over the intragrain conduction. In this case, spin disorder and magnetocrystalline anisotropy should be taken into account in explaining the magnetotransport behavior.

Liu, Xiangdong; Jiao, Zhengkuan; Nakamura, Keikichi; Hatano, Takeshi; Zeng, Yuewu

2000-03-01

301

Magnetoresistance in polymer-assisted deposited Sr- and Ca-doped lanthanum manganite films  

NASA Astrophysics Data System (ADS)

We have grown epitaxial films of La0.67Sr0.33MnO3 (LSMO) and La0.67Ca0.33MnO3 (LCMO) on single crystalline LaAlO3 substrates by a cost effective polymer-assisted deposition technique. Film crystallinity, microstructure, resistivity, magnetization, and magnetoresistance (MR) were highly dependent on the annealing temperature in the film processing. High negative MR values of -50% (at 305K) and -88% (at 250K) were observed at magnetic field of 5T, for high temperature annealed LSMO and LCMO films, respectively. These results are comparable to those for films grown by pulsed laser deposition and rf sputtering techniques.

Jain, M.; Li, Y.; Hundley, M. F.; Hawley, M.; Maiorov, B.; Campbell, I. H.; Civale, L.; Jia, Q. X.; Shukla, P.; Burrell, A. K.; McCleskey, T. M.

2006-06-01

302

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

SciTech Connect

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

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

2012-03-15

303

Complexes between lanthanide picrates and N,N-dimethylacetamide (DMA). Synthesis, characterization and structure of the samarium compound  

Microsoft Academic Search

Complexes with the composition Ln(pic)3.3DMA (Ln?La?Lu, Y; pic, picrate; DMA, N,N-dimethylacetamide) were synthesized and characterized. They behave as non-electrolytes in nitromethane and acetonitrile. According to X-ray powder patterns, three different types of diffractograms were obtained: (a) La?Pr; (b) Nd?Yb, Y; (c) Lu. Single-crystal X-ray analysis of the samarium compound indicates that Sm3+ is coordinated by six oxygen donors from three

C. V. P. de Melo; G. Vicentini; E. E. Castellano; J. Zukerman-Schpector

1995-01-01

304

The extraction of thulium, dysprosium and samarium by di(n-octyl)arsinc acid (HDOAA) in chloroform  

E-print Network

into the organic phase. The maximum E values of 33 for thulium, 15 for dysprosium and a -3 41 for samarium were observed for the 1 x 10 M chloride/1M perchlor- ate, 1 x 10 M chloride/1M nitrate, and 1 x 10 M chloride/1M sulfate systems respectively. The data... behavior of Thulium( III) in the acetate/1 x 10-3M chloride/1N nitrate system. . Extraction behavior of Thulium(III) in the 1 x 10-3N chloride/4N nitrate system. Extraction behayior of Thulium( III) in the acetate/1 x 10 ~N chloride/1M sulfate system...

El Seoud, Monica Irma

1974-01-01

305

Polymeric membrane and coated graphite samarium(III)-selective electrodes based on isopropyl 2-[(isopropoxycarbothioyl)disulfanyl]ethanethioate  

Microsoft Academic Search

New polymeric membrane (PME) and coated graphite (CGE) samarium(III)-selective electrodes were prepared based on isopropyl 2-[(isopropoxycarbothioyl) disulfanyl]ethanethioate as a suitable neutral ionophore. The electrodes exhibit Nernstian slopes for Sm3+ ions over wide concentration ranges (1.0×10?5 to 1.0×10?1M for PME and 1.0×10?6 to 1.0×10?1M for CGE). The PME and CGE have limits of detection of 3.1×10?6 and 5.0×10?7M, respectively, and response

Mojtaba Shamsipur; Morteza Hosseini; Kamal Alizadeh; Mohammad Mehdi Eskandari; Hashem Sharghi; Mir Fazlollah Mousavi; Mohammad Reza Ganjali

2003-01-01

306

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

PubMed Central

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 ?- and ?-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

2014-01-01

307

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

NASA Astrophysics Data System (ADS)

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.

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

2013-04-01

308

Cerium and lanthanum promote floral initiation and reproductive growth of Arabidopsis thaliana  

Microsoft Academic Search

The effects of cerium and lanthanum on the vegetative growth, floral initiation and reproductive growth of Arabidopsis thaliana were studied. Addition of cerium nitrate (0.5–10 ?M) or lanthanum nitrate (0.5–50 ?M) to the culture medium significantly increased the lengths of primary roots, but had no significant effects on the number of rosette leaves produced per plant, plant heights and dry

Ya-Wen He; Chiang-Shiong Loh

2000-01-01

309

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

PubMed Central

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.

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

2015-01-01

310

Europium, Samarium, and Neodymium Isotopic Fractions in Metal-Poor Stars  

E-print Network

We have derived isotopic fractions of europium, samarium, and neodymium in two metal-poor giants with differing neutron-capture nucleosynthetic histories. These isotopic fractions were measured from new high resolution (R ~ 120,000), high signal-to-noise (S/N ~ 160-1000) spectra obtained with the 2dCoude spectrograph of McDonald Observatory's 2.7m Smith telescope. Synthetic spectra were generated using recent high-precision laboratory measurements of hyperfine and isotopic subcomponents of several transitions of these elements and matched quantitatively to the observed spectra. We interpret our isotopic fractions by the nucleosynthesis predictions of the stellar model, which reproduces s-process nucleosynthesis from the physical conditions expected in low-mass, thermally-pulsing stars on the AGB, and the classical method, which approximates s-process nucleosynthesis by a steady neutron flux impinging upon Fe-peak seed nuclei. Our Eu isotopic fraction in HD 175305 is consistent with an r-process origin by the classical method and is consistent with either an r- or an s-process origin by the stellar model. Our Sm isotopic fraction in HD 175305 suggests a predominantly r-process origin, and our Sm isotopic fraction in HD 196944 is consistent with an s-process origin. The Nd isotopic fractions, while consistent with either r-process or s-process origins, have very little ability to distinguish between any physical values for the isotopic fraction in either star. This study for the first time extends the n-capture origin of multiple rare earths in metal-poor stars from elemental abundances to the isotopic level, strengthening the r-process interpretation for HD 175305 and the s-process interpretation for HD196944.

Ian U. Roederer; James E. Lawler; Christopher Sneden; John J. Cowan; Jennifer S. Sobeck; Catherine A. Pilachowski

2007-12-16

311

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

NASA Technical Reports Server (NTRS)

The influence of temperature on the M-H demagnetization characteristics of permanent magnets is important information for the full utilization of the capabilities of samarium-cobalt magnets at high temperatures in demagnetization-resistant permanent magnet devices. In high temperature space power converters, such as free-piston Stirling engine driven linear alternators, magnet demagnetization can occur as a long-term consequence of thermal agitation of domains and of metallurgical change, and also as an immediate consequence of too large an applied field. Investigated here is the short-term demagnetization resistance to applied fields derived from basic M-H data. This quasistatic demagnetization data was obtained for commercial, high-intrinsic-coercivity, Sm2Co17-type magnets from 5 sources, in the temperature range 23 to 300 C. An electromagnet driven, electronic hysteresigraph was used to test the 1-cm cubic samples. The observed variation of the 2nd quadrant M-H characteristics was a typical rapid loss of M-coercivity and a relatively lesser loss of remanence with increasing temperature. The 2nd quadrant M-H curve knee point is used to define the limits of operation safe against irreversible demagnetization due to an excessive bucking field for a given flux density swing at temperature. Such safe operating area plots are shown to differentiate the high temperature capabilities of the samples from different sources. For most of the samples, their 2nd quadrant M-H loop squareness increased with temperature, reaching a peak or a plateau above 250 C.

Niedra, Janis M.

1992-01-01

312

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

NASA Astrophysics Data System (ADS)

The influence of temperature on the M-H demagnetization characteristics of permanent magnets is important information for the full utilization of the capabilities of samarium-cobalt magnets at high temperatures in demagnetization-resistant permanent magnet devices. In high temperature space power converters, such as free-piston Stirling engine driven linear alternators, magnet demagnetization can occur as a long-term consequence of thermal agitation of domains and of metallurgical change, and also as an immediate consequence of too large an applied field. Investigated here is the short-term demagnetization resistance to applied fields derived from basic M-H data. This quasistatic demagnetization data was obtained for commercial, high-intrinsic-coercivity, Sm2Co17-type magnets from 5 sources, in the temperature range 23 to 300 C. An electromagnet driven, electronic hysteresigraph was used to test the 1-cm cubic samples. The observed variation of the 2nd quadrant M-H characteristics was a typical rapid loss of M-coercivity and a relatively lesser loss of remanence with increasing temperature. The 2nd quadrant M-H curve knee point is used to define the limits of operation safe against irreversible demagnetization due to an excessive bucking field for a given flux density swing at temperature. Such safe operating area plots are shown to differentiate the high temperature capabilities of the samples from different sources. For most of the samples, their 2nd quadrant M-H loop squareness increased with temperature, reaching a peak or a plateau above 250 C.

Niedra, Janis M.

1992-08-01

313

Gas permeability of lanthanum oxycarbide targets for the SPES project  

NASA Astrophysics Data System (ADS)

The creation of a porous matrix made of interconnected and permeable paths is a key step for the processing of optimized metal carbide targets in the SPES (Selective Production of Exotic Species) project. Unlike close or non-connected open pores, permeable pores link more efficiently the interior and the surface of target disks, and therefore facilitate the effusion and convection transport mechanisms for a faster extraction of exotic nuclei with short decay times. This work describes the analysis of the interconnected porosity of lanthanum oxycarbide targets through the evaluation of permeability coefficients obtained in argon flow experiments at room and high temperature. Samples were produced by the sacrificial template method using phenolic resin (PR) as source of carbon for the carbothermal reaction of lanthanum oxide, and different amounts of polymethilmetacrylate (PMMA) microbeads as template for the production of porosity. Results showed that conventional targets prepared without sacrificial templates displayed relatively high total porosity (45.6%), but very low permeability coefficients (k1 = 4.21 × 10-17 m2 and k2 = 1.90 × 10-15 m), comparable to other dense ceramic materials. The linear increase in total porosity from 64.8% to 88.9% achieved by the gradual increase of PMMA from 30% to 80 wt.% resulted in a remarkable increase of five orders of magnitude for k1 (2.36 × 10-12 m2) and eight orders for k2 (7.48 × 10-7 m2). The addition of sacrificial fillers was found to be much more efficient to create interconnected and permeable paths in the structure than the carbothermal reduction itself. Preliminary tests with argon flow up to 450 °C revealed that the porous matrix also became more permeable with the increase in the gas temperature due to thermal expansion effects, but the extent of this gain depended on the initial porosity level of the sample.

Biasetto, L.; Innocentini, M. D. M.; Chacon, W. S.; Corradetti, S.; Carturan, S.; Colombo, P.; Andrighetto, A.

2013-09-01

314

Phonons and superconductivity in fcc and dhcp lanthanum  

NASA Astrophysics Data System (ADS)

We have investigated the structural and electronic properties of lanthanum in the face-centered-cubic (fcc) and double hexagonal-close-packed (dhcp) phases using a generalized gradient approximation of the density functional theory and the ab initio pseudopotential method. It is found that double hexagonal-close-packed is the more stable phase for lanthanum. Differences in the density of states at the Fermi level between these two phases are pointed out and discussed in detail. Using the calculated lattice constant and electronic band structure for both phases, a linear response approach based on the density functional theory has been applied to study phonon modes, polarization characteristics of phonon modes, and electron-phonon interaction. Our phonon results show a softening behavior of the transverse acoustic branch along the ?-L direction and the ?-M direction for face-centered-cubic and double hexagonal-close-packed phases, respectively. Thus, the transverse-phonon linewidth shows a maximum at the zone boundary M(L) for the double hexagonal-close-packed phase (face-centered-cubic phase), where the transverse-phonon branch exhibits a dip. The electron-phonon coupling parameter ? is found to be 0.97 (1.06) for the double hexagonal-close-packed phase (face-centered-cubic phase), and the superconducting critical temperature is estimated to be 4.87 (dhcp) and 5.88 K (fcc), in good agreement with experimental values of around 5.0 (dhcp) and 6.0 K (fcc). A few superconducting parameters for the double hexagonal-close-packed phase have been calculated and compared with available theoretical and experimental results. Furthermore, the calculated superconducting parameters for both phases are compared between each other in detail.

Ba?c?, S.; Tütüncü, H. M.; Duman, S.; Srivastava, G. P.

2010-04-01

315

Simple Resolution of Enantiomeric NMR Signals of ?-Amino Acids by Using Samarium(III) Nitrate With L-Tartarate.  

PubMed

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 ?-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. Chirality 27:353-357, 2015.© 2015 Wiley Periodicals, Inc. PMID:25847749

Aizawa, Sen-Ichi; Kidani, Takahiro; Takada, Sayuri; Ofusa, Yumika

2015-05-01

316

Preparation and Quality Control of the [153Sm]-Samarium Maltolate Complex as a Lanthanide Mobilization Product in Rats  

PubMed Central

Development of lanthanide detoxification agents and protocols is of great importance in management of overdoses. Due to safety of maltol as a detoxifying agent in metal overloads, it can be used as a lanthanide detoxifying agent. In order to demonstrate the biodistribution of final complex, [153Sm]-samarium maltolate was prepared using Sm-153 chloride (radiochemical purity >99.9%; ITLC and specific activity). The stability of the labeled compound was determined in the final solution up to 24h as well as the partition coefficient. Biodistribution studies of Sm-153 chloride, [153Sm]-samarium maltolate were carried out in wild-type rats comparing the critical organ uptakes. Comparative study for Sm3+ cation and the labeled compound was conducted up to 48 h, demonstrating a more rapid wash out for the labeled compound. The effective and biological half lives of 2.3 h and 2.46h were calculated for the complex. The data suggest the detoxification property of maltol formulation for lanthanide overdoses. PMID:21773065

Naseri, Zohreh; Hakimi, Amir; Jalilian, Amir R.; Nemati Kharat, Ali; Bahrami-Samani, Ali; Ghannadi-Maragheh, Mohammad

2011-01-01

317

Comparison of Effects of Overload on Parameters and Performance of Samarium-Cobalt and Strontium-Ferrite Radially Oriented Permanent Magnet Brushless DC Motors  

Microsoft Academic Search

Effects of high momentary overloads on the samarium-cobalt and strontium-ferrite permanent magnets and the magnetic field in electronically commutated brushless dc machines, as well as their impact on the associated machine parameters were studied. The effect of overload on the machine parameters, and subsequently on the machine system performance was also investigated. This was accomplished through the combined use of

N. A. Demerdash; T. A. Nyamusa

1985-01-01

318

Valence transition of samarium in hexaboride solid solutions Sm1-xMxB6 (M = Yb2+ , Sr2+ , La3+ , Y3+ , Th4+)  

E-print Network

deduced from the analysis of the cubic lattice parameter variation and from the magnetic susceptibility of samarium substitution by non magnetic divalent atoms (Yb2 +, Sr") which play a dilution role and reduce by non magnetic trivalent or tetravalent cations (La 3 +, Y", Th") which have a dilution role

Boyer, Edmond

319

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

NASA Astrophysics Data System (ADS)

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.

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

320

In vitro bioequivalence approach for a locally acting gastrointestinal drug: lanthanum carbonate.  

PubMed

A conventional human pharmacokinetic (PK) in vivo study is often considered as the "gold standard" to determine bioequivalence (BE) of drug products. However, this BE approach is not always applicable to the products not intended to be delivered into the systemic circulation. For locally acting gastrointestinal (GI) products, well designed in vitro approaches might be more practical in that they are able not only to qualitatively predict the presence of the active substance at the site of action but also to specifically assess the performance of the active substance. For example, lanthanum carbonate chewable tablet, a locally acting GI phosphate binder when orally administrated, can release free lanthanum ions in the acid environment of the upper GI tract. The lanthanum ions directly reach the site of action to bind with dietary phosphate released from food to form highly insoluble lanthanum-phosphate complexes. This prevents the absorption of phosphate consequently reducing the serum phosphate. Thus, using a conventional PK approach to demonstrate BE is meaningless since plasma levels are not relevant for local efficacy in the GI tract. Additionally the bioavailability of lanthanum carbonate is less than 0.002%, and therefore, the PK approach is not feasible. Therefore, an alternative assessment method is required. This paper presents an in vitro approach that can be used in lieu of PK or clinical studies to determine the BE of lanthanum carbonate chewable tablets. It is hoped that this information can be used to finalize an in vitro guidance for BE studies of lanthanum carbonate chewable tablets as well as to assist with "in vivo" biowaiver decision making. The scientific information might be useful to the pharmaceutical industry for the purpose of planning and designing future BE studies. PMID:23249191

Yang, Yongsheng; Shah, Rakhi B; Yu, Lawrence X; Khan, Mansoor A

2013-02-01

321

Comparison of effects of overload on parameters and performance of samarium-cobalt and strontium-ferrite radially oriented permanent magnet brushless DC motors  

SciTech Connect

Effects of high momentary overloads on the samarium-cobalt and strontium-ferrite permanent magnets and the magnetic field in electronically commutated brushless dc machines, as well as their impact on the associated machine parameters were studied. The effect of overload on the machine parameters, and subsequently on the machine system performance was also investigated. This was accomplished through the combined use of finite element analysis of the magnetic field in such machines, perturbation of the magnetic energies to determine machine inductances, and dynamic simulation of the performance of brushless dc machines, when energized from voltage source inverters. These effects were investigated through application of the above methods to two equivalent 15 hp brushless dc motors, one of which was built with samarium-cobalt magnets, while the other was built with strontium- ferrite magnets. For momentary overloads as high as 4.5 p.u. magnet flux reductions of 29% and 42% of the no load flux were obtained in the samarium-cobalt and strontiumferrite machines, respectively. Corresponding reductions in the line to line armature inductances of 52% and 46% of the no load values were reported for the samarium-cobalt and strontium-ferrite cases, respectively. The overload affected the profiles and magnitudes of armature induced back emfs. Subsequently, the effects of overload on machine parameters were found to have significant impact on the performance of the machine systems, where findings indicate that the samarium-cobalt unit is more suited for higher overload duties than the strontium-ferrite machine.

Demerdash, N.A.; Nehl, T.W.; Nyamusa, T.A.

1985-08-01

322

Spectral investigations of Sm3+ doped lead bismuth magnesium borophosphate glasses  

NASA Astrophysics Data System (ADS)

The multicomponent lead bismuth magnesium borophosphate glass systems (LBMBPS) doped with Samarium ions with the molar compositions of (50-x)PbO?xBi2O3?25MgHPO4?24B2O3?1Sm2O3 (where x=10, 20, 30, and 40) were fabricated using conventional melt quenching technique. The amorphous nature of these glass samples was confirmed with XRD studies. The spectral data from the optical absorption studies were employed to compute various spectroscopic parameters such as Judd-Ofelt intensity parameters. The Judd-Ofelt parameterization employed reflects the covalency and vibration frequencies of the ligands with Samarium ions. The radiative parameters such as radiative transition probabilities (A), the total radiative transitional probabilities (AT), radiative life times (?R), branching ratios (?) and absorption cross sections (?) were computed for certain lasing levels. The glass systems thus developed indicate their potential lasing candidature. The emission cross sections (?E) for the significant lasing transitions 4G5/2?6H5/2, 4G5/2?6H7/2, and 4G5/2?6H9/2 evaluated from the photoluminescence spectra were reported. The radiative properties obtained in our investigations suggest their lasing candidature.

Ravi Babu, Y. N. Ch.; Sree Ram Naik, P.; Vijaya Kumar, K.; Rajesh Kumar, N.; Suresh Kumar, A.

2012-09-01

323

Potentiometric measurement of polymer-membrane electrodes based on lanthanum  

NASA Astrophysics Data System (ADS)

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-1, 1031 cm-1 and 794.7 cm-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-1 indicated that no interaction bond between hydroxyl group of molecules with molecular clusters fosforil of TBP or R3P = O. The membrane had stable responses in pH range between 1 and 9. Good responses were obtained using 10-3 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 10-5 and 10-1 M.

Saefurohman, Asep; Buchari, Noviandri, Indra; Syoni

2014-03-01

324

Titania-lanthanum phosphate photoactive and hydrophobic new generation catalyst  

SciTech Connect

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.

Jyothi, Chembolli K.; Jaimy, Kanakkanmavudi B. [National Institute for Interdisciplinary Science and Technology (NIIST), CSIR, Trivandrum 695019 (India); Ghosh, Swapankumar, E-mail: swapankumar.ghosh2@mail.dcu.ie [National Institute for Interdisciplinary Science and Technology (NIIST), CSIR, Trivandrum 695019 (India); Sankar, Sasidharan; Smitha, V.S. [National Institute for Interdisciplinary Science and Technology (NIIST), CSIR, Trivandrum 695019 (India); Warrier, K.G.K., E-mail: wwarrierkgk@yahoo.co.in [National Institute for Interdisciplinary Science and Technology (NIIST), CSIR, Trivandrum 695019 (India)

2011-07-15

325

Investigation on scandium-doped manganate La 0.8Sr 0.2Mn 1? x Sc x O 3? ? cathode for intermediate temperaturesolid oxide fuel cells  

Microsoft Academic Search

Scandium-doped lanthanum strontium manganate La0.8Sr0.2Mn1?xScxO3?? (LSMS) combined with YSZ as composite cathode for anode-supported solid oxide fuel cell is investigated. The LSMS powders are prepared using the modified Pechini method. The XRD and H2-TPR results reveal that non-stoichiometric defects are introduced into the perovskite lattice of LSMS samples as a result of Sc substitution, which leads to increased oxygen ion

Xiangling Yue; Aiyu Yan; Min Zhang; Lin Liu; Yonglai Dong; Mojie Cheng

2008-01-01

326

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

NASA Technical Reports Server (NTRS)

Piezoelectric ceramic materials are potential candidates for use as actuators and sensors in intelligent gas turbine engines. For piezoceramics to be applied in gas turbine engines, they will have to be able to function in temperatures ranging from 1000 to 2500 F. However, the maximum use temperature for state-of-the-art piezoceramic materials is on the order of 300 to 400 F. Research activities have been initiated to develop high-temperature piezoceramic materials for gas turbine engine applications. Lanthanum titanate has been shown to have high-temperature piezoelectric properties with Curie temperatures of T(sub c) = 1500 C and use temperatures greater than 1000 C. However, the fabrication of lanthanum titanate poses serious challenges because of the very high sintering temperatures required for densification. Two different techniques have been developed at the NASA Glenn Research Center to fabricate dense lanthanum titanate piezoceramic material. In one approach, lower sintering temperatures were achieved by adding yttrium oxide to commercially available lanthanum titanate powder. Addition of only 0.1 mol% yttrium oxide lowered the sintering temperature by as much as 300 C, to just 1100 C, and dense lanthanum titanate was produced by pressure-assisted sintering. The second approach utilized the same commercially available powders but used an innovative sintering approach called differential sintering, which did not require any additive.

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

2004-01-01

327

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

PubMed

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

Fumoto, Toshio; Ito, Masako; Ikeda, Kyoji

2014-09-01

328

Influence of lanthanum oxide as quality promoter on cathodes for MCFC  

NASA Astrophysics Data System (ADS)

A novel material based on lithium nickel mixed oxides modified by lanthanum impregnation was investigated as an alternative cathode for molten carbonate fuel cells (MCFCs). The electrochemical behaviour of the new cathode material was evaluated in an eutectic mixture of lithium and potassium (Li:K, 62:38) at 650 °C by electrochemical impedance spectroscopy (EIS) as a function of lanthanum content, immersion time and gas composition. The impedance spectra inform on electrode structural changes during the first 100 h. The loss of lithium and the low dissolution of nickel and lanthanum are responsible of these changes. Later on, the structure reaches a stable state. The lanthanum-impregnated cathodes show higher catalytic activity for oxygen reduction and lower dissolution of nickel oxide than the lanthanum-free sample. The cathode material having 0.3 wt.% of La 2O 3 shows the best behaviour. The loss of lithium was confirmed by X-ray diffraction (XRD) and inductive coupled plasma-atomic emission spectroscopy (ICP-AES).

Escudero, M. J.; Nóvoa, X. R.; Rodrigo, T.; Daza, L.

329

Assessing Lanthanum-Bromide Detectors for Safeguards Applications  

SciTech Connect

Major detector technologies currently being used for gamma-ray spectroscopy in safeguards applications include systems based on sodium iodide (NaI), cadmium-zinc-telluride (CZT), cadmium-telluride (CdTe), and high-purity germanium (HPGe) crystals. Recently, a new scintillation detector based on a lanthanum bromide (LaBr3) crystal has become commercially available. The declared benefits of this new detector technology include higher resolution and improved efficiency compared with similarly configured NaI-based systems. Both detector systems offer the advantage of room-temperature operation. This paper describes the results of a study assessing the safeguards applicability and advantages for isotopic and quantitative analyses of uranium using the LaBr3-based detector, as well as an investigation into the general operating characteristics of the LaBr3-based detector. The results are compared with those from a widely used NaI-based detector system (Canberra's Inspector-1000 multichannel analyzer) operated under similar environmental conditions and hardware configuration, using commercially available software packages (NaIGEM and Genie-2000).

Gariazzo, Claudio Andres [ORNL; Saavedra, Steven F [ORNL; Smith, Steven E [ORNL; Solodov, Alexander A [ORNL

2008-01-01

330

Work function measurement of lanthanum-boron compounds  

NASA Technical Reports Server (NTRS)

The relationship between emission properties and sample composition is studied for lanthanum-boron compounds. Specifically, the La-B system is considered between 1400 and 2100 K and between LaB(4.24) and LaB(29.2) to determine the phase relationship, chemical activity of the compounds, vapor composition, and vaporization rate. The results indicate that: (1) a blue-colored phase near LaB(9) exists between a purple-colored LaB(6) and elemental boron, (2) vaporization is sufficiently more rapid than diffusion so that great compositional differences exist between the surface and the interior, (3) an activation energy lowers the boron vaporization rate from LaB(6), and (4) a steady-state surface composition between LaB(6.04) and LaB(6.07) exists for freely vaporizing materials as a function of interior composition, purity, and temperature. It is noted that the ultimate life of a thermionic diode is governed by electrode vaporization rate whereas efficiency is governed by the electrode work function.

Jacobson, D. L.; Storms, E. K.

1978-01-01

331

Study of prolonged administration of lanthanum carbonate in dialysis patients.  

PubMed

Data of 36 months were accumulated regarding the effects of lanthanum carbonate (LA) on serum phosphate concentrations in dialysis patients. Fifty-three patients (average age and dialysis history 58.4 years and 9.1 years) were included in this study who have been receiving outpatient treatment since March 2009, and who have been unable to maintain serum phosphate concentrations of ?6.0?mg/dL via traditional therapeutic agents used for hyperphosphatemia. Patients were given dosage of LA in addition to, or instead of, co-hyperphosphatemia treatments already being received. Mean dosages of calcium carbonate (CC) and sevelamer hydrochloride (SH) before starting LA administration were 1301.9?mg and 2462.3?mg, respectively. Dosage of LA for all cases was 750?mg at initial dose; 1528.3?mg at 5 months; and 1416.7?mg at 30 months. Dosage of other phosphate binders were 905.7?mg of CC and 820.8?mg of SH at 5 months; and 687.5?mg of CC and 1031.3?mg of SH at 30 months. Serum phosphorus levels (P levels) were significantly decreased at 1 month of LA administration, and continued until 30 months of La treatment. These results suggest that LA successfully controlled serum P and Ca concentrations simultaneously within target ranges without affecting serum intact parathyroid hormone concentration, although further long-term prospective cohort study on LA would be required. PMID:23586507

Gotoh, Junichi; Kukita, Kazutaka; Tsuchihashi, Seiichiro; Hattori, Masahiro; Iida, Junichi; Horie, Takashi; Onodera, Kazuhiko; Furui, Hidenori; Tamaki, Toru; Meguro, Junichi; Yonekawa, Motoki; Kawamura, Akio

2013-04-01

332

Genetics of superionic conductivity in lithium lanthanum titanates.  

PubMed

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

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

2015-01-01

333

Scintillation properties of SrI_2(Eu^2+) (Strontium iodide doped with europium) for high energy astrophysical detectors: Nonproportionality as a function of temperature and at high gamma-ray energies  

E-print Network

Strontium iodide doped with europium is a new scintillator material being developed as an alternative to lanthanum bromide doped with cerium for use in high energy astrophysical detectors. As with all scintillators, the issue of nonproportionality is important because it affects the energy resolution of the detector. In this study, we investigate how the nonproportionality of strontium iodide doped with europium changes as a function of temperature 16 deg. C to 60 deg. C by heating the strontium iodide doped with europium scintillator separate from the photomultiplier tube. In a separate experiment, we also investigate the nonproportionality at high energies (up to 6 MeV) of strontium iodide doped with europium at a testing facility located at NASA Goddard Space Flight Center. We find that the nonproportionality increases nearly monotonically as the temperature of the strontium iodide doped with europium scintillator is increased, although there is evidence of non-monotonic behavior near 40 deg. C, perhaps du...

Perea, R S; Groza, M; Caudel, D; Nowicki, S; Burger, A; Stassun, K G; Peterson, T E

2014-01-01

334

Fabrication of large-volume, low-cost ceramic lanthanum halide scintillators for gamma ray detection : final report for DHS/DNDO/TRDD project TA-01-SL01.  

SciTech Connect

This project uses advanced ceramic processes to fabricate large, optical-quality, polycrystalline lanthanum halide scintillators to replace small single crystals produced by the conventional Bridgman growth method. The new approach not only removes the size constraint imposed by the growth method, but also offers the potential advantages of both reducing manufacturing cost and increasing production rate. The project goal is to fabricate dense lanthanum halide ceramics with a preferred crystal orientation by applying texture engineering and solid-state conversion to reduce the thermal mechanical stress in the ceramic and minimize scintillation light scattering at grain boundaries. Ultimately, this method could deliver the sought-after high sensitivity and <3% energy resolution at 662 keV of lanthanum halide scintillators and unleash their full potential for advanced gamma ray detection, enabling rapid identification of radioactive materials in a variety of practical applications. This report documents processing details from powder synthesis, seed particle growth, to final densification and texture development of cerium doped lanthanum bromide (LaBr{sub 3}:Ce{sup +3}) ceramics. This investigation demonstrated that: (1) A rapid, flexible, cost efficient synthesis method of anhydrous lanthanum halides and their solid solutions was developed. Several batches of ultrafine LaBr{sub 3}:Ce{sup +3} powder, free of oxyhalide, were produced by a rigorously controlled process. (2) Micron size ({approx} 5 {micro}m), platelet shape LaBr{sub 3} seed particles of high purity can be synthesized by a vapor phase transport process. (3) High aspect-ratio seed particles can be effectively aligned in the shear direction in the ceramic matrix, using a rotational shear-forming process. (4) Small size, highly translucent LaBr{sub 3} (0.25-inch diameter, 0.08-inch thick) samples were successfully fabricated by the equal channel angular consolidation process. (5) Large size, high density, translucent LaBr{sub 3} ceramics samples (3-inch diameter, > 1/8-inch thick) were fabricated by hot pressing, demonstrating the superior manufacturability of the ceramic approach over single crystal growth methods in terms of size capability and cost. (6) Despite all these advances, evidence has shown that LaBr{sub 3} is thermally unstable at temperatures required for the densification process. This is particularly true for material near the surface where lattice defects and color centers can be created as bromine becomes volatile at high temperatures. Consequently, after densification these samples made using chemically prepared ultrafine powders turned black. An additional thermal treatment in a flowing bromine condition proved able to reduce the darkness of the surface layer for these densified samples. These observations demonstrated that although finer ceramic powders are desirable for densification due to a stronger driving force from their large surface areas, the same desirable factor can lead to lattice defects and color centers when these powders are densified at higher temperatures where material near the surface becomes thermally unstable.

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

2008-10-01

335

Performance Evaluation of an Oxygen Sensor as a Function of the Samaria Doped Ceria Film Thickness  

SciTech Connect

The current demand in the automobile industry is in the control of air-fuel mixture in the combustion engine of automobiles. Oxygen partial pressure can be used as an input parameter for regulating or controlling systems in order to optimize the combustion process. Our goal is to identify and optimize the material system that would potentially function as the active sensing material for such a device that monitors oxygen partial pressure in these systems. We have used thin film samaria doped ceria (SDC) as the sensing material for the sensor operation, exploiting the fact that at high temperatures, oxygen vacancies generated due to samarium doping act as conducting medium for oxygen ions which hop through the vacancies from one side to the other contributing to an electrical signal. We have recently established that 6 atom % Sm doping in ceria films has optimum conductivity. Based on this observation, we have studied the variation in the overall conductivity of 6 atom % samaria doped ceria thin films as a function of thickness in the range of 50 nm to 300 nm at a fixed bias voltage of 2 volts. A direct proportionality in the increase in the overall conductivity is observed with the increase in sensing film thickness. For a range of oxygen pressure values from 1 mTorr to 100 Torr, a tolerable hysteresis error, good dynamic response and a response time of less than 10 seconds was observed

Sanghavi, Rahul P.; Nandasiri, Manjula I.; Kuchibhatla, Satyanarayana V N T; Nachimuthu, Ponnusamy; Engelhard, Mark H.; Shutthanandan, V.; Jiang, Weilin; Thevuthasan, Suntharampillai; Kayani, Asghar N.; Prasad, Shalini

2010-12-01

336

Thickness Dependency of Thin Film Samaria Doped Ceria for Oxygen Sensing  

SciTech Connect

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.

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

337

Formation and characterization of porous silicon-samarium/gadolinium nanocomposites: effect of substrate oxidation and biosynthesis process  

NASA Astrophysics Data System (ADS)

Samarium and gadolinium nanoparticles synthesized by bioreduction process have been incorporated into nanostructured porous silicon template to form a nanocomposite. The structural and optical properties of PS-Gd and PS-Sm nanocomposites have been studied through TEM, SEM and UV-Vis spectroscopy. Extent of infiltration has been verified through reflectance interference Fourier transform spectroscopy as a function of substrate oxidation conditions. The substrates oxidized at 600 °C showed the maximum infiltration and the corresponding change of optical thickness due to nanoparticles. Such biodegradable nanocomposites in the form of particles can have potential applications in localized drug delivery and enhancement of the image contrast and optoelectronic devices. The results here reported open an energy-cheap procedure to take advantages of small rare earth nanoparticles and produced nanocomposites with their immersion in SiO2 substrates, with the perspective to be replied in other similar substrates under controlled conditions.

Perdigon-Lagunes, P.; Ascencio, J. A.; Agarwal, V.

2014-12-01

338

Photoneutron cross sections for samarium isotopes: Toward a unified understanding of (? ,n ) and (n ,? ) reactions in the rare earth region  

NASA Astrophysics Data System (ADS)

Photoneutron cross sections were measured for the seven stable samarium isotopes 144 ,147 ,148 ,149 ,150 ,152 ,154Sm near the neutron threshold with quasi-monochromatic laser-Compton scattering ? rays . Our photoneutron cross sections are found to be low by 20%-37% relative to existing data. The photoneutron data are analyzed with the talys reaction code by considering the Skyrme Hartree-Fock-Bogoliubov (HFB) plus quasiparticle random phase approximation (QRPA) model and the axially symmetric deformed Gogny HFB plus QRPA model of the E 1 ? -ray strength. Using the ? -ray strength function constrained by the present photoneutron data, we made a thorough analysis of the reverse (n ,? ) cross sections including the radioactive nucleus 151Sm with a half-life of 90 yr. The radiative neutron capture cross section for 153Sm with the half-life of 1.928 d is deduced with the ? -ray strength function method.

Filipescu, D. M.; Gheorghe, I.; Utsunomiya, H.; Goriely, S.; Renstrøm, T.; Nyhus, H.-T.; Tesileanu, O.; Glodariu, T.; Shima, T.; Takahisa, K.; Miyamoto, S.; Lui, Y.-W.; Hilaire, S.; Péru, S.; Martini, M.; Koning, A. J.

2014-12-01

339

Hartree-Fock-Bogoliubov Calculations in Coordinate Space: Neutron-Rich Sulfur, Zirconium, Cerium, and Samarium Isotopes  

E-print Network

Using the Hartree-Fock-Bogoliubov (HFB) mean field theory in coordinate space, we investigate ground state properties of the sulfur isotopes from the line of stability up to the two-neutron dripline ($^{34-52}S$). In particular, we calculate two-neutron separation energies, quadrupole moments, and rms-radii for protons and neutrons. Evidence for shape coexistence is found in the very neutron-rich sulfur isotopes. We compare our calculations with results from relativistic mean field theory and with available experimental data. We also study the properties of neutron-rich zirconium ($^{102,104}Zr$), cerium ($^{152}Ce$), and samarium ($^{158,160}Sm$) isotopes which exhibit very large prolate quadrupole deformations.

V. E. Oberacker; A. S. Umar; E. Teran; A. Blazkiewicz

2003-09-29

340

Nanocomposite Lanthanum Zirconate Thermal Barrier Coating Deposited by Suspension Plasma Spray Process  

NASA Astrophysics Data System (ADS)

This work seeks to develop an innovative nanocomposite thermal barrier coating (TBC) exhibiting low thermal conductivity and high durability compared with that of current TBCs. To achieve this objective, nanosized lanthanum zirconate particles were selected for the topcoat of the TBC system, and a new process—suspension plasma spray—was employed to produce desirable microstructural features: the nanocomposite lanthanum zirconate TBC contains ultrafine splats and high volume porosity, for lower thermal conductivity, and better durability. The parameters of plasma spray experiment included two main variables: (i) spray distance varying from 40 to 80 mm and (ii) the concentration of suspension 20, 25, and 30 wt.%, respectively. The microstructure of obtained coatings was characterized with scanning electron microscope and x-ray diffraction. The porosity of coatings is in the range of 6-10%, and the single phase in the as-sprayed coatings was pyrochlore lanthanum zirconate.

Wang, Chaohui; Wang, You; Wang, Liang; Hao, Guangzhao; Sun, Xiaoguang; Shan, Fan; Zou, Zhiwei

2014-10-01

341

Bifunctional lanthanum phosphate substrates as novel adsorbents and biocatalyst supports for perchlorate removal.  

PubMed

Porous lanthanum phosphate substrates, obtained by an environmentally benign colloidal forming process employing methyl cellulose, are reported here as excellent adsorbents of perchlorate with >98% efficiency and with 100% reusability. Additionally, the effectiveness of such substrates as biocatalyst supports that facilitate biofilm formation of perchlorate reducing microbes (Serratia marcescens NIIST 5) is also demonstrated for the first time. The adsorption of perchlorate ions is attributed to the pore structure of lanthanum phosphate substrate and the microbial attachment is primarily ascribed to its intrinsic hydrophobic property. Lanthanum phosphate thus emerges as a dual functional material that possesses an integrated adsorption/bioremediation property for the effective removal of ClO4(-) which is an increasingly important environmental contaminant. PMID:24872208

Sankar, Sasidharan; Prajeesh, Gangadharan Puthiya Veetil; Anupama, Vijaya Nadaraja; Krishnakumar, Bhaskaran; Hareesh, Padinhattayil; Nair, Balagopal N; Warrier, Krishna Gopakumar; Hareesh, Unnikrishnan Nair Saraswathy

2014-06-30

342

Vertically aligned nanorods of lanthanum hexaboride with efficient field emission properties  

NASA Astrophysics Data System (ADS)

The present study describes a borothermal reduction process to obtain nanostructured lanthanum hexaboride (LaB6) particles and their films. The morphology (nanorods and nanoparticles) of the boride nanostructures could be controlled by using a lanthanum hydroxide precursor (with controlled shape and size) obtained by a microemulsion mediated process. The LaB6 films fabricated by spin coating of nanorods of LaB6 led to an assembly of vertically oriented nanorods with excellent field emission properties (field enhancement factor of 4522). This methodology does not require any template for obtaining these vertically aligned nanorods. The field emission properties can be tuned by controlling the shape and size of the lanthanum hexaboride nanostructures.

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

2013-01-01

343

Eucalyptus tolerance mechanisms to lanthanum and cerium: subcellular distribution, antioxidant system and thiol pools.  

PubMed

Guanglin 9 (Eucalyptus grandis × Eucalyptus urophlla) and Eucalyptus grandis 5 are two eucalyptus species which have been found to grow normally in soils contaminated with lanthanum and cerium, but the tolerance mechanisms are not clear yet. In this study, a pot experiment was conducted to investigate the tolerance mechanisms of the eucalyptus to lanthanum and cerium. Cell walls stored 45.40-63.44% of the metals under lanthanum or cerium stress. Peroxidase and catalase activities enhanced with increasing soil La or Ce concentrations up to 200 mg kg(-1), while there were no obvious changes in glutathione and ascorbate concentrations. Non-protein thiols concentrations increased with increasing treatment levels up to 200 mg kg(-1), and then decreased. Phytochelatins concentrations continued to increase under La or Ce stress. Therefore, the two eucalyptus species are La and Ce tolerant plants, and the tolerance mechanisms include cell wall deposition, antioxidant system response, and thiol compound synthesis. PMID:25303462

Shen, Yichang; Zhang, Shirong; Li, Sen; Xu, Xiaoxun; Jia, Yongxia; Gong, Guoshu

2014-12-01

344

The use of 185 MBq and 740 MBq of 153-samarium hydroxyapatite for knee synovectomy in haemophilia  

PubMed Central

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

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

345

Antioxidant protection mechanism of chick hepatic mitochondria exposed to lanthanum chloride & neodymium chloride treatment.  

PubMed

Acute lanthanum chloride (250 mg/kg body wt) and neodymium chloride (200 mg/kg body wt) administrations resulted in significant enhancement of glutathione level in chick hepatic mitochondria. However, glutathione-s-transferase activity was depressed. There was no alteration in the activity of glutathione reductase. Activity of glucose-6-phosphate dehydrogenase was not altered under lanthanum and neodymium treatment. There was a significant enhancement of intramitochondrial glutathione peroxidase and superoxide dismutase. Lipid peroxidation remains the same as control group of animals. PMID:1916948

Ghosh, N; Chattopadhyay, D; Chatterjee, G C

1991-05-01

346

Synthesis, Characterization, and Cytotoxic Activity of New Lanthanum(III) Complexes of Bis-Coumarins  

PubMed Central

Complexes of lanthanum(III) with bis-coumarins: 3,3?-benzylidene-bis(4-hydroxy-2H-1-benzopyran-2-one) (H2L1) and bis(4-hydroxy-2-oxo-2H-chromen-3-yl)-(1H-pyrazol-3-yl)-methane (H2L2) were synthesized by reaction of lanthanum(III) salt and the ligands, in amounts equal to metal : ligand molar ratio of 1 : 2. The complexes were prepared by adding an aqueous solution of lanthanum(III) salt to an aqueous solution of the ligand subsequently raising the pH of the mixture gradually to circa 5.0 by adding dilute solution of sodium hydroxide. The lanthanum(III) complexes with bis-coumarins were characterized by different physicochemical methods—elemental analysis, IR-, 1H-, and 13C-NMR-spectroscopies, and mass spectral data. The spectral data of lanthanum(III) complexes were interpreted on the basis of comparison with the spectra of the free ligands. This analysis showed that in the La(III) complexes, the ligands coordinated to the metal ion through both deprotonated hydroxyl groups. On the basis of the ?(C=O) red shift observed, participation of the carbonyl groups in the coordination with the metal ion was also suggested. In the present study, we performed a cytotoxic-effects screening of the lanthanum complexes with H2L1 and H2L2 in a panel of human tumor cell lines, using the standard MTT-dye reduction assay for cell viability. The panel consisted of the acute myeloid leukemia-derived HL-60 and the chronic myeloid leukemia-derived BV-173. Following a 24- hour treatment of BV-173 cells with lanthanum complex of H2L1 at 100 or 200 ?M led to a DNA-laddering. The findings suggest that the observed cytotoxicity of the lanthanum complex of H2L1 on BV-173 is at least partly mediated through induction of programmed cell death. PMID:17497005

Kostova, Irena; Momekov, Georgi; Tzanova, Tzvetomira; Karaivanova, Margarita

2006-01-01

347

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

NASA Technical Reports Server (NTRS)

Lanthanum hexaboride electrodes in 1700 K cesium diodes may triple power outputs compared with those demonstrated for nuclear thermionic space applications. Still greater relative gains seem possible for emitters below 1700 K. Further improvements in cesium diode performance should result from the lower collector temperatures allowed for earth and low power space duties. Decreased temperatures will lessen thermal transport losses that attend thermionic conversion mechanisms. Such advantages will add to those from collector Carnot and electrode effects. If plasma ignition difficulties impede diode temperature reductions, recycling small fractions of the output power could provide ionization. So high efficiency, low temperature cesium diodes with lanthanum hexaboride electrodes appear feasible.

Morris, J. F.

1974-01-01

348

Self-assembly as a route to one-dimensional lanthanum(III) salicylaldimine coordination polymer  

Microsoft Academic Search

The self-assembled formation of a one-dimensional lanthanum salicylaldimine coordination polymer was proved by the X-ray diffraction analysis of new lanthanum(III) nitrate complex containing N,N'-bis(salicylidene)-1,5-pentanediamine ligand (H2L). It was obtained in situ in a one-step, metal-templated condensation of salicylaldehyde with 1,5-pentanediamine (cadaverine, biogenic polyamine) and characterized by microanalysis and spectroscopic (IR, ESI-MS, UV-Vis, and 1H NMR) data. The [La(NO3)3(?-H2L)2]? complex displayed

Wanda Radecka-Paryzek; Izabela Pospieszna-Markiewicz; Maciej Kubicki

2010-01-01

349

Enantioselective DNA condensation induced by heptameric lanthanum helical supramolecular enantiomers.  

PubMed

DNA condensation induced by a pair of heptameric La(III) helical enantiomers M-[La7(S-L)6(CO3)(NO3)6(OCH3)(CH3OH)7]·2CH3OH·5H2O and P-[La7(R-L)6(CO3)(NO3)6(OCH3)(CH3OH)5(H2O)2]·2CH3OH·4H2O (M-La and P-La, L=2-(2-hydroxybenzylamino)-3-carbamoylpropanoic acid) has been investigated by UV/vis spectroscopy, fluorescence spectroscopy, CD spectroscopy, EMSA, RALS, DLS, and SEM. The enantiomers M-La and P-La could induce CT-DNA condensation at a low concentration as observed in UV/vis spectroscopy. DNA condensates possessed globular nanoparticles with nearly homogeneous sizes in solid state determined by SEM (ca. 250 nm for M-La and ca. 200 nm for P-La). The enantiomers bound to DNA through electrostatic attraction and hydrogen bond interactions in a major groove, and rapidly condensed free DNA into its compact state. DNA decompaction has been acquired by using EDTA as disassembly agent, and analyzed by UV/vis spectroscopy, CD spectroscopy and EMSA. Moreover, the enantiomers M-La and P-La displayed discernible discrimination in DNA interaction and DNA condensation, as well as DNA decondensation. Our study suggested that lanthanum(III) enantiomers M-La and P-La were efficient DNA packaging agents with potential applications in gene delivery. PMID:24915440

Bao, Fei-Fei; Xu, Xin-Xin; Zhou, Wen; Pang, Chun-Yan; Li, Zaijun; Gu, Zhi-Guo

2014-09-01

350

Lanthanum lead oxide hydroxide nitrates with a nonlinear optical effect.  

PubMed

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

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

2014-12-01

351

A new large area lanthanum hexaboride plasma source.  

PubMed

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

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

2010-08-01

352

A new large area lanthanum hexaboride plasma source  

SciTech Connect

A new 18x18 cm{sup 2} active area lanthanum hexaboride (LaB{sub 6}) plasma source for use in a dc discharge has been developed at UCLA. The cathode consists of four tiled LaB{sub 6} pieces indirectly heated to electron emission (1750 deg. C) by a graphite heater. A molybdenum mesh anode 33 cm in front of the LaB{sub 6} accelerates the electrons, ionizing a fill gas to create a 20x20 cm{sup 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{sub e}<30 eV, T{sub i}<16 eV, and n{sub e}<3x10{sup 13} cm{sup -3} in a background field of 100 G

Cooper, C. M.; Gekelman, W.; Pribyl, P.; Lucky, Z. [University of California, Los Angeles, California 90095 (United States)

2010-08-15

353

Magnetic heat capacity in lanthanum manganite single crystals  

NASA Astrophysics Data System (ADS)

The heat capacity of single crystal La0.7D0.3MnO3, where D=Ca, Sr, has been measured through the Curie point in fields up to 70 kOe. The magnetic contribution of the Ca sample exhibits a sharp heat capacity peak at TC?218 K in zero field. The peak broadens and decreases in height with increasing field but, unlike an ordinary ferromagnet, the peak shifts substantially in temperature. As a consequence, the heat capacity data cannot be collapsed into a single scaling function. These features indicate that the transition is not an ordinary second-order ferromagnetic transition. Preliminary heat capacity data from the Sr-doped single crystal, with TC?360 K, do not exhibit the same shift in peak position with applied field. We attribute the difference in behavior between Ca- and Sr-doped samples to a change in the nature of the phase transition as TC lowers.

Lin, P.; Chun, S. H.; Salamon, M. B.; Tomioka, Y.; Tokura, Y.

2000-05-01

354

Interaction of oxygen with samarium on Al{sub 2}O{sub 3} thin film grown on Ni{sub 3}Al(111)  

SciTech Connect

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.

Cheng, Dingling; Xu, Qian, E-mail: qianxu@ustc.edu.cn, E-mail: jfzhu@ustc.edu.cn; Han, Yong; Ye, Yifan; Pan, Haibin; Zhu, Junfa, E-mail: qianxu@ustc.edu.cn, E-mail: jfzhu@ustc.edu.cn [National Synchrotron Radiation Laboratory and Collaborative Innovation Center of Suzhou Nano Science and Technology, University of Science and Technology of China, Hefei 230029 (China)] [National Synchrotron Radiation Laboratory and Collaborative Innovation Center of Suzhou Nano Science and Technology, University of Science and Technology of China, Hefei 230029 (China)

2014-03-07

355

Lanthanum chloride bidirectionally influences calcification in bovine vascular smooth muscle cells.  

PubMed

Vascular calcification (VC) is frequent prevalence in patients with chronic kidney disease (CKD) and atherosclerosis. Lanthanum carbonate is used as an orally administered phosphate-binding agent to reduce the gastrointestinal absorption of phosphate and ameliorate VC in advanced CKD. In this study, we used bovine vascular smooth muscle cells as a model VC in vitro and studied the effects of lanthanum chloride on calcium deposition. Exposure of cells to LaCl(3) at the concentration of 0.1 µM suppressed the ?-glycerophosphate-induced alkaline phosphatase activity and calcium deposition. Furthermore, LaCl(3) upregulated the ?-glycerophosphate-suppressed expression of calcium-sensing receptor. In contrast to the inhibitory effect of LaCl(3) on calcium deposition, higher level lanthanum (50 µM) was found to promote immediately precipitation of calcium phosphate in cell culture medium. At this concentration, LaCl(3) was found to induce cell apoptosis which involves caspases-9 and -3. These data indicate that the promotory effect of LaCl(3) on calcium deposition is likely mediated by induction of apoptosis. Our in vitro findings do suggest that, in the context of raised lanthanum, greater attention should be paid to potential toxic effects associated to the use of lanthanide-based drugs. PMID:22213182

Zhao, Wen-Hua; Gou, Bao-Di; Zhang, Tian-Lan; Wang, Kui

2012-05-01

356

Lanthanum induced primary neuronal apoptosis through mitochondrial dysfunction modulated by Ca²? and Bcl-2 family.  

PubMed

As a representative element of lanthanide, lanthanum has been widely used in various fields and eventually entered environment and accumulated in human body. Epidemiological and experimental evidences indicated that lanthanum has neurotoxicity; however, the detailed mechanism is still elusive. Here, we chose primary cerebral cortical neurons as model in vitro to investigate the mechanism underlying the toxic effects of lanthanum chloride (LaCl3). This study revealed the following findings: (1) LaCl3 treatment (0.01, 0.1, and 1.0 mM for 24 h) reduced the viability of cortical neurons and elevated apoptotic rate significantly in a dose-dependent manner. (2) LaCl3 triggered mitochondrial apoptotic pathway in cortical neurons, characterized with collapsed mitochondrial membrane potential, release of cytochrome c into cytosol, and increasing expression of activated caspase-3. (3) LaCl3 elevated intracellular Ca(2+) concentration, promoted reactive oxygen species generation, and upregulated pro-apoptotic Bax, whereas it downregulated anti-apoptotic Bcl-2 expression and consequently altered Bax/Bcl-2 ratio, which ultimately lead to neuronal mitochondrial apoptosis. Our results demonstrated that toxicity of lanthanum in cortical neurons perhaps partly attributed to enhanced mitochondrial apoptosis due to mitochondrial dysfunction modulated by Ca(2+) and Bcl-2 family. PMID:23338853

Wu, Jie; Yang, Jinghua; Liu, Qiufang; Wu, Shengwen; Ma, Honglin; Cai, Yuan

2013-04-01

357

Thermal and Mechanical Properties of Polyethylene Terephthalate\\/Polycarbonate Nanocomposites Modified by Lanthanum Acetyl Acetonate Hydrate  

Microsoft Academic Search

In attempts to improve the thermal and mechanical properties of polyethylene terephthalate\\/polycarbonate (PET\\/PC) blends nanofil 9 was used. Blending was carried out in a Brabender plasticorder, the chopped composites were then extruded using a single screw extruder to prepare samples for the thermal and mechanical testing. Lanthanum acetyl acetonate hydrate was used as a catalyst for potential transesterification reactions that

Yousef Ahmad Mubarak

2011-01-01

358

In situ Raman spectroscopy of lanthanum-strontium-cobaltite thin films  

E-print Network

Raman spectroscopy is used to probe the structural change of Lanthanum Strontium Cobaltite (La1.xSrxCoO 3 -8) thin films across change in composition (0%-60% strontium) and temperature (30*C-520°C). Raman shift peaks were ...

Breucop, Justin Daniel

2012-01-01

359

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

NASA Technical Reports Server (NTRS)

Thermal, field emitters of lanthanum (or perhaps cerium) hexaboride (LaB6) with temperature variability up to about 1500K are suggested for spacecraft charging control. Such emitters operate at much lower voltages with considerably more control and add plasma-diagnostic versatility. These gains should outweigh the additional complexity of providing heat for the LaB6 thermal, field emitter.

Morris, J. F.

1978-01-01

360

Extraction of thorium(IV), yttrium(III), and lanthanum(III) by mesityl oxide  

Microsoft Academic Search

Extraction of thorium(IV), yttrium(III), and lanthanum(III) by mesityl ; oxide was investigated. The aqueous phases were nitrate solutions with a nitric ; acid concentration varying from 3 to 12N. In all cases, the extraction increased ; with the HNOâ and mesityl oxide concentrations but decreased slightly as ; the initial metal concentration was increased. The largest separation factors ; obtained

E. C. Chen; Herbert Y. Lee

1973-01-01

361

Nonisothermal Thermal Decomposition Reaction Kinetics of Double-base Propellant Catalyzed with Lanthanum Citrate  

Microsoft Academic Search

The decomposition reaction kinetics of the double-base (DB) rocket propellant composed of the mixed ester of triethyleneglycol dinitrate (TEGDN) and nitroglycerin (NG), and nitrocellulose (NC) with lanthanum citrate as a combustion catalyst was investigated by thermogravimetry and differential thermogravimetry (TG-DTG), and differential scanning calorimetry (DSC) under atmospheric pressure and flowing nitrogen gas conditions. The results showed that the thermal decomposition

Jianhua Yi; Fengqi Zhao; Siyu Xu; Hongxu Gao; Rongzu Hu; Haixia Hao; Qing Pei; Yin Gao

2007-01-01

362

Prediction of yttrium, lanthanum, cerium, and neodymium leaching recovery from apatite concentrate using artificial neural networks  

Microsoft Academic Search

The assay and recovery of rare earth elements (REEs) in the leaching process is being determined using expensive analytical methods: inductively coupled plasma atomic emission spectroscopy (ICP-AES) and inductively coupled plasma mass spectroscopy (ICP-MS). A neural network model to predict the effects of operational variables on the lanthanum, cerium, yttrium, and neodymium recovery in the leaching of apatite concentrate is

E. Jorjani; A. H. Bagherieh; Sh. Mesroghli; S. Chehreh Chelgani

2008-01-01

363

Comparative evaluation of the in vitro efficacy of lanthanum carbonate chewable tablets.  

PubMed

The aims of this study were to systematically evaluate the effects of pH levels, phosphate concentrations, and tablet integrity on the phosphate binding profiles of lanthanum carbonate chewable tablets, and to compare the in vitro phosphate binding efficacy of one reference and two test products of lanthanum carbonate chewable tablets. Langmuir equation was utilized to calculate the binding constants k1 and k2 . The phosphate binding to the tablets of lanthanum carbonate product was pH dependent, with a faster binding rate at low pH. The crushed tablets bind phosphate more rapid. Compared with the whole tablets, the kinetic binding profiles from the crushed tablets were less variable under all conditions for both test and reference products. The phosphate level has a significant impact on the phosphate binding for both whole and crushed tablets under all pH conditions, with more binding at higher phosphate concentration. The phosphate binding profiles displayed significant difference among the products. For a crushed tablet, the phosphate binding to lanthanum reached equilibrium within 8 h under all conditions. The 90% confidence interval for the k2 ratio (test/reference) was well within the 80%-125% under all pH conditions. However, the k1 ratio varies from 54% to 144%. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 102:1370-1381, 2013. PMID:23334989

Yang, Yongsheng; Bykadi, Srikant; Carlin, Alan S; Shah, Rakhi B; Yu, Lawrence X; Khan, Mansoor A

2013-04-01

364

REFOS study: efficacy and safety of lanthanum carbonate in clinical practice in Spain.  

PubMed

Lanthanum carbonate is a powerful phosphate binder that has shown efficacy and safety in clinical trials for hyperphosphataemia management, although there are few data in regular clinical practice. The study's objective was to evaluate, in regular clinical practice, its efficacy and safety in patients on dialysis. We retrospectively collected data from 15 months of monitoring, corresponding to 3 months prior to the start of treatment with lanthanum carbonate until 12 months after the start. Results included values of serum calcium, phosphorus, alkaline phosphatase, iPTH, hepatic enzymes and haemogram, as well as the daily-prescribed dose of lanthanum carbonate, the concomitant medication, treatment compliance and adverse events. 647 patients were included of which 522 completed the study. Abandonment, for the most part, was due to gastrointestinal disorders (26%) and hypophosphatemia (19%). Serum phosphorus decreased from 6.4±1.7 mg/dl (start) to 4.9±1.4 mg/dl (12 months) (P<.001). At the end of the monitoring period, 47% were within the desired phosphorus range (3.5-5mg/dl). There were no significant variations in the remaining parameters. Initial dose of lanthanum carbonate: 1900 mg/day; and end dose: 2300 mg/day. The variables independently associated with phosphataemia were baseline serum phosphorus and treatment compliance. In relation to safety, we observed 238 slight or moderate adverse effects in 117 patients, with 88% linked to gastrointestinal abnormalities. In conclusion, lanthanum carbonate reduces the serum phosphorus values in patients on dialysis with a good safety profile and acceptable adherence to that profile, with gastrointestinal disorders being the most frequent adverse effect. PMID:24849057

Torregrosa, José-Vicente; González-Parra, Emilio; González, M Teresa; Cannata-Andía, Jorge

2014-05-21

365

Structural phase transitions and superconductivity in lanthanum copper oxides  

SciTech Connect

Despite the enormous effort expended over the past ten years to determine the mechanism underlying high temperature superconductivity in cuprates there is still no consensus on the physical origin of this fascinating phenomenon. This is a consequence of a number of factors, among which are the intrinsic difficulties in understanding the strong electron correlations in the copper oxides, determining the roles played by antiferromagnetic interactions and low dimensionality, analyzing the complex phonon dispersion relationships, and characterizing the phase diagrams which are functions of the physical parameters of temperature and pressure, as well as the chemical parameters of stoichiometry and hole concentration. In addition to all of these intrinsic difficulties, extrinsic materials issues such as sample quality and homogeneity present additional complications. Within the field of high temperature superconductivity there exists a subfield centered around the material originally reported to exhibit high temperature superconductivity by Bednorz and Mueller, Ba doped La{sub 2}CuO{sub 4}. This is structurally the simplest cuprate superconductor. The authors report on studies of phase differences observed between such base superconductors doped with Ba or Sr. What these studies have revealed is a fascinating interplay of structural, magnetic and superconducting properties which is unique in the field of high temperature superconductivity and is summarized in this paper.

Crawford, M.K.; Harlow, R.L.; McCarron, E.M. [DuPont, Wilmington, DE (United States)] [and others

1996-12-31

366

Magnetic heat capacity in lanthanum manganite single crystals  

SciTech Connect

The heat capacity of single crystal La{sub 0.7}D{sub 0.3}MnO{sub 3}, where D=Ca, Sr, has been measured through the Curie point in fields up to 70 kOe. The magnetic contribution of the Ca sample exhibits a sharp heat capacity peak at T{sub C}(approx =)218 K in zero field. The peak broadens and decreases in height with increasing field but, unlike an ordinary ferromagnet, the peak shifts substantially in temperature. As a consequence, the heat capacity data cannot be collapsed into a single scaling function. These features indicate that the transition is not an ordinary second-order ferromagnetic transition. Preliminary heat capacity data from the Sr-doped single crystal, with T{sub C}{approx_equal}360 K, do not exhibit the same shift in peak position with applied field. We attribute the difference in behavior between Ca- and Sr-doped samples to a change in the nature of the phase transition as T{sub C} lowers. (c) 2000 American Institute of Physics.

Lin, P. [Department of Physics and Materials Research Laboratory, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, Illinois 61801 (United States)] [Department of Physics and Materials Research Laboratory, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, Illinois 61801 (United States); Chun, S. H. [Department of Physics and Materials Research Laboratory, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, Illinois 61801 (United States)] [Department of Physics and Materials Research Laboratory, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, Illinois 61801 (United States); Salamon, M. B. [Department of Physics and Materials Research Laboratory, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, Illinois 61801 (United States)] [Department of Physics and Materials Research Laboratory, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, Illinois 61801 (United States); Tomioka, Y. [Joint Research Center for Atom Technology, 1-1-4 Higashi, Tsukuba 305-0046, (Japan)] [Joint Research Center for Atom Technology, 1-1-4 Higashi, Tsukuba 305-0046, (Japan); Tokura, Y. [Joint Research Center for Atom Technology, 1-1-4 Higashi, Tsukuba 305-0046, (Japan)] [Joint Research Center for Atom Technology, 1-1-4 Higashi, Tsukuba 305-0046, (Japan)

2000-05-01

367

Synthesis of doped rare earth manganate perovskite crystals using fused salt electrolysis  

SciTech Connect

A facile method for the synthesis of doped lanthanum manganate crystals, suitable for the measurement of electrical and magnetic properties, is presented. Mixtures of sodium molybdate and molybdenum(VI) oxide are used as a solvent to which La{sub 2}O{sub 3}, MnCO{sub 3}, and SrMoCO{sub 4} are added as solutes which are then electrolyzed at 800-1040{degrees}C for varying lengths of time with Pt electrodes. Well-formed cubic crystals, with edge dimensions up to 1.5 mm, form at the anode. Magnetization measurements show a transition to the ferromagnetic state in the temperature range {approximately}250-320 K, depending on the amount of aliovalent doping at the La sites. An insulator-to-metal transition is also observed in the vicinity of the ferromagnetic ordering temperature.

McCarroll, W.H. [Rider Univ., Lawrenceville, NJ (United States)] [Rider Univ., Lawrenceville, NJ (United States); Ramanujachary, K.V. [Rugers, State Univ. of New Jersey, Piscataway, NJ (United States)] [Rugers, State Univ. of New Jersey, Piscataway, NJ (United States); [Rowan College, Glassboro, NJ (United States); Greenblatt, M. [Rutgers, State Univ. of New Jersey, Piscataway, NJ (United States)] [Rutgers, State Univ. of New Jersey, Piscataway, NJ (United States)

1997-05-01

368

Improvement in electrical characteristics of graded manganese doped barium strontium titanate thin films  

NASA Astrophysics Data System (ADS)

Highly (100) textured graded manganese (Mn) doped Ba0.5Sr0.5TiO3 [BST (50/50)] thin films were deposited on lanthanum aluminate substrates using sol-gel technique. We have demonstrated that the graded acceptor doping is a promising technique to reduce the temperature coefficient of capacitance (TCC), loss tangent, and leakage current of BST thin films. In the temperature range between 175 and 260 K the reported TCC of Mn graded BST (50/50) films is less than 5.55×10-4/K, which is comparable to the best capacitors known so far. The lower temperature coefficient of the capacitance of the Mn graded films has been argued to be due to the induced compositional heterogeneity resulting into a distribution of the Curie temperature.

Jain, M.; Majumder, S. B.; Katiyar, R. S.; Miranda, F. A.; Van Keuls, F. W.

2003-03-01

369

A multicenter study on the effects of lanthanum carbonate (Fosrenol™) and calcium carbonate on renal bone disease in dialysis patients  

Microsoft Academic Search

A multicenter study on the affects of lanthanum carbonate (Fosrenol™) and calcium carbonate on renal bone disease in dialysis patients.BackgroundLanthanum carbonate (LC) (Fosrenol™) is a novel new treatment for hyperphosphatemia. In this phase III, open-label study, we compared the effects of LC and calcium carbonate (CC) on the evolution of renal osteodystrophy (ROD) in dialysis patients.MethodsNinety-eight patients were randomized to

Patrick C. D'Haese; Goce B. Spasovski; Aleksander Sikole; Alastair Hutchison; Tony J. Freemont; Sylvie Sulkova; Charles Swanepoel; Svetlana Pejanovic; Llubica Djukanovic; Alessandro Balducci; Giorgio Coen; Waldysaw Sulowicz; Anibal Ferreira; Armando Torres; Slobodan Curic; Milan Popovic; Nada Dimkovic; Marc E. De Broe

2003-01-01

370

Synthesis and luminescence properties of encapsulated sol-gel glass samarium complexes  

NASA Astrophysics Data System (ADS)

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.

Zaitoun, M. A.; Momani, K.; Jaradat, Q.; Qurashi, I. M.

2013-11-01

371

Anion sensing and interfering behaviors of electrolyte–insulator–semiconductor sensors with nitrogen plasma-treated samarium oxide  

NASA Astrophysics Data System (ADS)

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.

Ye, Yu-Ren; Wang, Jer-Chyi; Chan, Ya-Ting

2015-04-01

372

Magnetic and Transport Properties of Lanthanum Based CMR Systems  

NASA Astrophysics Data System (ADS)

The magnetic and transport properties of bulk polycrystalline samples of Ca doped manganite perovskites have been studied. The material properties were characterized using SEM, EDX and XRD. Magnetization measurements were performed using a SQUID magnetometer in order to determine Curie temperature and moment per Mn ion. The temperature and field (H) dependence of the electrical resistance, R(T,H) and Hall effect were measured by standard ac four and six probe techniques in magnetic fields up to 17 T*. Typical zero field I-M transition peaks near 275 K in R(T) and negative dR/dH at high fields were observed. However, for H < 0.2 T, positive MR is seen. The results of these measurements, including low field positive magnetoresistance, will be reported. *Performed at the National High Magnetic Field Lab (NHMFL) FSU, Tallahassee, FL

Estrada, Javier; Bleiweiss, Michael; Saygi, Salih; Datta, Timir; Yin, Ming; Palm, Eric; Brandt, Bruce; Iqbal, Zafar

2001-03-01

373

Sorption of tartrate ions to lanthanum (III)-modified calcium fluor- and hydroxyapatite.  

PubMed

The present article details the formation of lanthanum-modified apatites and the binding process of tartrate ions with these obtained apatites. Chemical analyses, FT-IR and (31)P NMR spectroscopies, XRD powder, TGA, and TEM analyses were employed for studying the reaction between Ca(10)(PO(4))(6)(OH)(2) (HAp) or Ca(10)(PO(4))(6)(F)(2) (FAp) and LaCl(3). The reaction was found to take place mainly through partial dissolution of the apatite followed by precipitation of a new phase containing lanthanum phosphate. When La(3+) was introduced in the presence of L(+)-tartaric acid (TAH(2)), no fundamental changes were observed in the HAp or FAp structures. However, there did occur a formation of a new phase of Ca or/and La tartrate salt. PMID:18996541

Aissa, Abdallah; Debbabi, Mongi; Gruselle, Michel; Thouvenot, René; Flambard, Alexandrine; Gredin, Patrick; Beaunier, Patricia; Tõnsuaadu, Kaia

2009-02-01

374

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

SciTech Connect

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{sup ?1}·K{sup ?1} was observed near 300?K. An appreciable magnetocaloric effect was also observed for a wide range of temperatures near 300?K for small magnetic field variation. Heat capacity was measured for temperatures lower than 300?K and the adiabatic temperature change increases with increase in temperature with a maximum of 0.62?K at 280?K.

Sethulakshmi, N.; Anantharaman, M. R., E-mail: mraiyer@yahoo.com [Department of Physics, Cochin University of Science and Technology, Cochin 682022, Kerala (India); Al-Omari, I. A. [Department of Physics, Sultan Qaboos University, PC 123 Muscat, Sultanate of Oman (Oman); Suresh, K. G. [Department of Physics, Indian Institute of Technology Bombay, Powai, Mumbai 400076 (India)

2014-03-03

375

Sensitive and reliable ascorbic acid sensing by lanthanum oxide/reduced graphene oxide nanocomposite.  

PubMed

A simple strategy for the detection and estimation of ascorbic acid (AA), using lanthanum oxide-reduced graphene oxide nanocomposite (LO/RGO) on indium tin oxide (ITO) substrate, is reported. LO/RGO displays high catalytic activity toward the oxidation of AA, and the synergism between lanthanum oxide and reduced graphene oxide was attributed to the successful and efficient detection. Detection mechanism and sensing efficacy of LO/RGO nanocomposite are investigated by electrochemical techniques. Chronoamperometric results under optimal conditions show a linear response range from 14 to 100 ?M for AA detection. Commercially available vitamin C tablets were also analyzed using the proposed LO/RGO sensor, and the remarkable recovery percentage (97.64-99.7) shows the potential application in AA detection. PMID:24879601

Mogha, Navin Kumar; Sahu, Vikrant; Sharma, Meenakshi; Sharma, Raj Kishore; Masram, Dhanraj T

2014-10-01

376

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

NASA Technical Reports Server (NTRS)

Lanthanum-hexaboride electrodes in 1700 K cesium diodes may triple power outputs compared with those demonstrated for nuclear thermionic space applications. Still greater relative gains seem possible for emitters below 1700 K. Further improvements in cesium-diode performance should result from the lower collector temperatures allowed for earth and low-power-space duties. Decreased temperatures will lessen thermal-transport losses that attend thermionic-conversion mechanisms. Such advantages will add to those from collector-Carnot and electrode effects. If plasma ignition difficulties impede diode temperature reductions, recycling small fractions of the output power could provide ionization. So high-efficiency, low-temperature cesium diodes with lanthanum-hexaboride electrodes appear feasible.

Morris, J. F.

1974-01-01

377

Energies, Landé g-factors, and lifetimes for some excited levels of doubly ionized lanthanum  

NASA Astrophysics Data System (ADS)

Using the relativistic Hartree-Fock (HFR) method developed by Cowan, we calculated the energy levels, Landé g-factors, and lifetimes for nd (n = 5-25), ns (n = 6-24), ng (n = 5-25), nf (n = 4-22), and np (n = 6-25) excited levels of doubly ionized lanthanum (La III, Z = 57). We compared the results with previously reported calculations and experiments.

Karaçoban, Betül; Özdemir, Leyla

2012-02-01

378

Energies, Landé g-factors, and lifetimes for some excited levels of doubly ionized lanthanum  

NASA Astrophysics Data System (ADS)

Using the relativistic Hartree-Fock (HFR) method developed by Cowan, we calculated the energy levels, Landé g-factors, and lifetimes for nd ( n = 5-25), ns ( n = 6-24), ng ( n = 5-25), nf ( n = 4-22), and np ( n = 6-25) excited levels of doubly ionized lanthanum (La III, Z = 57). We compared the results with previously reported calculations and experiments.

Karaçoban, Betül; Özdemir, Leyla

2012-02-01

379

Synthesis and Characterization of Worm-shaped Tubular Lanthanum Aluminum Composite Mesoporous Materials  

Microsoft Academic Search

The lanthanum aluminum mesoporous materials were synthesized using sodium dodecyl sulfate as a template agent by ultrasonic hydrothermal method. The resulting samples were characterized by low angle X-ray diffraction (XRD), N2 adsorption-desorption studies, transmission electron microscopy (TEM) and surface morphology analysis (SEM), surface acid (NH3-TPD), reducibility properties (TPR), X-ray energy dispersive spectrometer (EDS) and thermogravimetric analysis (TG\\/DTG).Al\\/La composite mesoporous material

Weiming SONG; Chunling ZUO; Qigang DENG

2011-01-01

380

Design of a lanthanum bromide detector for time-of-flight PET  

Microsoft Academic Search

Recent improvements in the growth and packaging of lanthanum bromide (LaBr3), in addition to its superb intrinsic properties of high light output, excellent energy resolution, and fast decay time, make it a viable detection material for a positron emission tomography (PET) scanner based on time-of-flight (TOF). We have utilized theoretical simulations and experimental measurements to investigate the design and performance

A. Kuhn; S. Surti; J. S. Karp; P. S. Raby; K. S. Shah; A. E. Perkins; G. Muehllehner

2004-01-01

381

Minimum loss predictions and measurements in gallium lanthanum sulphide based glasses and fibre  

Microsoft Academic Search

Measurements of the fundamental optical absorptions of gallium and lanthanum sulphide based chalcogenide glasses (Ga:La:S, and Ga:La:S:O) in glass and glass fibre forms are presented. Theoretical predictions of the minimum material losses in these glasses are given by calculating the loss from Rayleigh scattering and fitted data from the fundamental glass absorptions. The theoretical minimum loss for Ga:La:S is 0.5

D. J. Brady; T. Schweizer; J. Wang; D. W. Hewak

1998-01-01

382

Atomic Layer Deposition of Lanthanum-Based Ternary Oxides Hongtao Wang,a  

E-print Network

that interfacial layers could be avoided when ternary rare earth oxide GdScO3 films were deposited on Si by ALDAtomic Layer Deposition of Lanthanum-Based Ternary Oxides Hongtao Wang,a Jun-Jieh Wang,b Roy Gordon-based ternary oxide LaxM2-xO3 M = Sc, Lu, or Y films were deposited on HF-last Si substrates by atomic layer

383

Synergism between molybdenum and lanthanum in the disproportionation of hydrogen peroxide into singlet oxygen.  

PubMed

The catalytic disproportionation of hydrogen peroxide into singlet molecular oxygen was studied using the combined action of lanthanum(III) and molybdenum(VI). A synergistic effect was observed between both metals, resulting in a strong acceleration of the H2O2 disproportionation. An optimum in the catalytic activity was found at La/Mo and La/NaOH molar ratios of 4/1 and 1/3, respectively. PMID:16332047

Wahlen, Joos; De Vos, Dirk E; Groothaert, Marijke H; Nardello, Véronique; Aubry, Jean-Marie; Alsters, Paul L; Jacobs, Pierre A

2005-12-14

384

New Type of Freezing-Point Apparatus. Freezing Points of Dilute Lanthanum Chloride Solutions  

Microsoft Academic Search

A new type of freezing-point apparatus is described that reduces the errors of previous types. The freezing-point depressions of aqueous lanthanum chloride solutions up to 0.04 m are adequately expressed by the Debye-Hu¨ckel approximation for ions with a=6.15 A plus a very small linear term. The ``higher terms'' are computed by combining the equations of Mayer and Kirkwood, using the

G. Scatchard; B. Vonnegut; D. W. Beaumont

1960-01-01

385

Chromium and copper substituted lanthanum nano-ferrites: Their synthesis, characterization and application studies  

NASA Astrophysics Data System (ADS)

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.

Jauhar, Sheenu; Singhal, Sonal

2014-10-01

386

Lithium lanthanum titanium oxide solid-state electrolyte by spark plasma sintering  

Microsoft Academic Search

Inorganic lithium solid-state electrolytes with advantage of safety are considered as the candidates to substitute the organic liquid electrolytes in lithium ion batteries. Sintering of these solid electrolytes always requires high-temperature and long time. In this paper, spark plasma sintering was employed to prepare lithium lanthanum titanium oxide solid-state electrolyte. X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and electrochemical

Ao Mei; Qing-Hui Jiang; Yuan-Hua Lin; Ce-Wen Nan

2009-01-01

387

Enhanced ionic transport in lithium lanthanum titanium oxide solid state electrolyte by introducing silica  

Microsoft Academic Search

Inorganic lithium solid state electrolytes have been considered as candidates to substitute the organic liquid electrolytes in lithium batteries. However, their low conductivity is the bottleneck of their practical applications. In this paper, composite ceramic electrolytes based on lithium lanthanum titanium oxides were synthesized by adding SiO2. X-ray diffraction, Raman spectroscopy, scanning electron microscopy, energy dispersive spectroscopy and electrochemical impedance

Ao Mei; Xiao-Liang Wang; Yu-Chuan Feng; Shu-Jin Zhao; Guo-Jing Li; Hong-Xia Geng; Yuan-Hua Lin; Ce-Wen Nan

2008-01-01

388

Single crystal growth and characterization of lanthanum–neodymium oxalate octahydrate  

Microsoft Academic Search

Single crystals of mixed lanthanum–neodymium oxalates are grown by gel diffusion method using agar gel as a medium of growth. The crystals grow in the agar gel with hexagonal morphology having (001), (110) and (010) as habit faces. Single crystal X-ray diffraction results show that the crystals belong to monoclinic system with cell parameters; a=10.344(2)Å, b=9.643(6)Å, c=11.721(2)Å, ?=118.7 (2)° ,

Basharat Want

2011-01-01

389

Effect of chloride incorporation on the crystallization of zirconium-barium-lanthanum-aluminum fluoride glass  

NASA Technical Reports Server (NTRS)

One aspect of the influence of preparation procedure on the crystallization behavior of a zirconium-barium-lanthanum-aluminum fluoride glass was studied. The crystallization pattern of this glass may be affected by the chlorine concentration within it. In particular, when such glasses are heated at low temperatures, the alpha-Ba-Zr-F6 crystalline phase forms only in those glasses which contain chloride.

Neilson, G. F.; Smith, G. L.; Weinberg, M. C.

1985-01-01

390

Composition dependence of Pr 3+ spectral characteristics in strontium lanthanum aluminate crystals  

Microsoft Academic Search

An analysis of the high resolution spectra of the Pr3+ in strontium lanthanum aluminates, charge compensated with magnesium Sr1?xPryLax?yMgxAl12?xO19, (on a large composition range) is presented. The spectra are mainly dependent on the composition parameter x, and show more Pr3+ centers, two of them stable. Based on composition dependence and polarization data, structural models for the main two centers are

V. Lupei; A. Lupei; C. Gheorghe; L. Gheorghe; G. Aka; D. Vivien

2007-01-01

391

Lanthanum Carbonate Reduces Urine Phosphorus Excretion: Evidence of High-Capacity Phosphate Binding  

PubMed Central

The effectiveness of phosphate binders can be assessed by evaluating urinary phosphorus excretion in healthy volunteers, which indicates the ability of the phosphate binder to reduce gastrointestinal phosphate absorption. Healthy volunteers were enrolled into one of five separate randomized trials; four were open label and one double blind. Following a screening period of <28 days, participants received differing tablets containing lanthanum carbonate [LC, 3000 mg/day of elemental lanthanum (in one study other doses were also used)]. Participants received a standardized phosphate diet and remained in the relevant study center throughout the duration of each treatment period. The end point in all studies was the reduction in urinary phosphorus excretion. Reductions in mean 24-h urinary phosphorus excretion in volunteers receiving a lanthanum dose of 3000 mg/day were between 236 and 468 mg/day over the five separate studies. These data in healthy volunteers can be used to estimate the amount of reduction of dietary phosphate absorption by LC. The reduction in 24-h urinary phosphorus excretion per tablet was compared with published data on other phosphate binders. Although there are limitations, evidence suggests that LC is a very effective phosphate binder in terms of binding per tablet. PMID:22250993

Pennick, Michael; Poole, Lynne; Dennis, Kerry; Smyth, Michael

2012-01-01

392

Lanthanum halide scintillators for time-of-flight 3-D pet  

DOEpatents

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.

Karp, Joel S. (Glenside, PA); Surti, Suleman (Philadelphia, PA)

2008-06-03

393

The kinetics of uptake and recovery of lanthanum using freshwater algae as biosorbents: comparative analysis.  

PubMed

In this study, the adsorption and desorption kinetics of lanthanum (La) on micro algal cells was investigated. The internal transcribed spacer (ITS) and 18S ribosomal RNA gene (rRNA) were used for molecular identification of the species. The algal species were found to have 95-98% identities to Desmodesmus multivariabilis, Scenedesmus acuminutus, Chloroidium saccharophilum and Stichococcus bacillaris. The species were cultured and tested independently. D. multivariabilis was found to be the most efficient at adsorbing lanthanum with a maximum sorption capacity (qmax) of 100 mg/g and a high affinity (b) of 4.55 L/g. Desorption of La was also highest in D. multivariabilis with recovery up to 99.63% at initial concentration as high as 100 mg/L. Desorption data fitted best to the modified pseudo second-order with a better correlation coefficient (R(2)) of ?0.98 than first order model. The results showed feasibility of lanthanum recovery using algal sorbents, a cost effective method. PMID:24507581

Birungi, Z S; Chirwa, E M N

2014-05-01

394

Efficacy of continuous oral administration of lanthanum carbonate over 24 months.  

PubMed

To examine the efficacy of long-term administration of lanthanum carbonate, changes in serum Ca, phosphate, whole parathyroid hormone (wPTH), and ALP were examined in 40 patients who were able to tolerate dosage of lanthanum carbonate over a continuous period of 24 months. Concurrently, concomitant administration of other phosphate binders, cinacalcet, vitamin D, etc., was also examined. After 24 months, serum phosphorus levels (P levels) had decreased to within management target of guidelines, from 6.16?±?1.44?mg/dL to 5.58?±?1.15?mg/dL, and this effect was maintained for 2 years. There were no changes in Ca level. wPTH did not change significantly but tended to increase at 12 months. The dose of concomitantly administered calcium carbonate and sevelamer hydrochloride was reduced. The P-lowering function of lanthanum carbonate still held steady at 24 months following the start of dosage. Because of the rising trend seen in wPTH, dose of cinacalcet and/or vitamin D need to be modulated. Reducing the number of concomitantly administered phosphate binder tablets was desirable from the standpoint of patient adherence. PMID:23586509

Ishizu, Takashi; Hong, Zhang; Matsunaga, Tsuneaki; Kaneko, Yoko; Taru, Yoshinori

2013-04-01

395

Impact of lanthanum carbonate on cortical bone in dialysis patients with adynamic bone disease.  

PubMed

Among the most serious problems in patients with chronic kidney disease (CKD) is fragility of cortical bone caused by cortical thinning and increased cortical porosity; the cortical fragility is sometimes irreversible, with fractures generally initiating from cortical bone. Therefore, development of treatments for problems of cortical bone is urgently desired. Cortical bone has the three surfaces, including the periosteal surface, intracortical spaces and endocortical surface. Bone turnover at the endocortical surface and intracortical resorption spaces are increased as compared with that at cancellous surface. Bone growth sometimes depends on apposition at the periosteal surface. We treated hyperphosphatemia in two hemodialysis patients with adynamic bone disease with 750-1500?mg/day of lanthanum carbonate, which is a non-calcium containing phosphate binder; the treatment resulted in a decrease of the serum phosphorus levels (P levels), without significant change of the serum intact parathyroid hormone levels. We now report that treatment of these patients with lanthanum carbonate increased mineralization of the periosteal surface, increased bone mass within the intracortical resorption spaces and increased mineralization of the minimodeling surface at the endocortical surface. In addition, woven bone volume in cortical bone was decreased and mineralization of bone units, namely, osteons, was increased. Although these findings were not observed across all surfaces of the cortical bone in the patients, it is expected that lanthanum carbonate would increase the cortical stability in CKD patients, with consequent reduction in the fracture rate in these patients. PMID:23586512

Yajima, Aiji; Inaba, Masaaki; Tominaga, Yoshihiro; Tanaka, Motoko; Otsubo, Shigeru; Nitta, Kosaku; Ito, Akemi; Satoh, Shigeru

2013-04-01

396

Multicenter study of long-term (two-year) efficacy of lanthanum carbonate.  

PubMed

Long-term efficacy of lanthanum carbonate on hyperphosphatemia was examined in multicenter dialysis patients. Outcome and efficacy after 2 years was investigated in 101 patients who had undergone lanthanum carbonate administration. Thirty-three cases dropped out by the 2-year point; patients undergoing at least 2 years of administration totaled 68. Reasons for dropping out were as follows: improvement of hyperphosphatemia, nine cases; changing hospitals, seven cases; medical complications, five cases; digestive symptoms, four cases; poor compliance, four cases; parathyroidectomy, two cases; death, two cases. The mean dosage was increased from initial daily dosage of 744?mg to 1266?mg after 1 year, and to 1246?mg after 2 years. Serum phosphate concentration decreased significantly from the initial 6.15?mg to 5.57?mg/dL after 1 year, and to 5.45?mg/dL after 2 years. Although a lowering trend was observed in corrected calcium levels, the difference was not significant. Parathyroid hormone was unchanged. Achievement rate of Japanese Society for Dialysis Therapy (JSDT) management target values for both phosphorus and calcium improved from 32.7% to 50.0% after 1 year, and to 56.5% after 2 years. Lanthanum carbonate is useful as a therapeutic tool for hyperphosphatemia over long durations. PMID:23586506

Ando, Ryoichi; Kimura, Hitoshi; Sato, Hidehiko; Iwamoto, Shunsuke; Yoshizaki, Yuki; Chida, Yoshiko; Ishida, Yuji; Takayama, Masanobu; Yamada, Kouei; Tachibana, Ken; Ohtsuka, Masakazu; Kikuchi, Kan; Inoue, Atsushi

2013-04-01

397

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

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.

Goodman, J.H.; Gahbauer, R.A.; Kanellitsas, C.; Clendenon, N.R. (Ohio State Univ., Columbus, OH (USA)); Laster, B.H.; Fairchild, R.G. (Brookhaven National Lab., Upton, NY (USA))

1989-01-01

398

Long-term treatment with lanthanum carbonate reduces mineral and bone abnormalities in rats with chronic renal failure  

PubMed Central

Background. Lanthanum carbonate (FOSRENOL®, Shire Pharmaceuticals) is an effective non-calcium, non-resin phosphate binder for the treatment of hyperphosphataemia in patients with chronic kidney disease (CKD). In this study, we used a rat model of chronic renal failure (CRF) to examine the long-term effects of controlling serum phosphorus with lanthanum carbonate treatment on the biochemical and bone abnormalities associated with CKD–mineral and bone disorder (CKD–MBD). Methods. Rats were fed a normal diet (normal renal function, NRF), or a diet containing 0.75% adenine for 3 weeks to induce CRF. NRF rats continued to receive normal diet plus vehicle or normal diet supplemented with 2% (w/w) lanthanum carbonate for 22 weeks. CRF rats received a diet containing 0.1% adenine, with or without 2% (w/w) lanthanum carbonate. Blood and urine biochemistry were assessed, and bone histomorphometry was performed at study completion. Results. Treatment with 0.75% adenine induced severe CRF, as demonstrated by elevated serum creatinine. Hyperphosphataemia, hypocalcaemia, elevated calcium × phosphorus product and secondary hyperparathyroidism were evident in CRF + vehicle animals. Treatment with lanthanum carbonate reduced hyperphosphataemia and secondary hyperparathyroidism in CRF animals (P < 0.05), and had little effect in NRF animals. Bone histomorphometry revealed a severe form of bone disease with fibrosis in CRF + vehicle animals; lanthanum carbonate treatment reduced the severity of the bone abnormalities observed, particularly woven bone formation and fibrosis. Conclusions. Long-term treatment with lanthanum carbonate reduced the biochemical and bone abnormalities of CKD–MBD in a rat model of CRF. PMID:21098011

Damment, Stephen; Secker, Roger; Shen, Victor; Lorenzo, Victor; Rodriguez, Mariano

2011-01-01

399

Magnetic and Transport Properties of Lanthanum Based CMR Systems  

NASA Astrophysics Data System (ADS)

The magnetic and transport properties of bulk polycrystalline samples of Ca doped manganite perovskites have been studied. The material properties were characterized using SEM, EDX and XRD. Curie temperature (277 +/- 3 K) and moment per Mn ion (approximately 4.3 ?_B) were determined via magnetization measurements. The temperature and field (H) dependence of the electrical resistivity, ?(T,H) and Hall effect were measured by standard ac four and six probe techniques in magnetic fields up to 17 T*. Typical zero field I-M transition peaks near 275 K in ?(T) and negative d?/dH at high fields were observed. However, for H < 0.2 T, positive MR is seen. There is evidence of small polaron transport at both above and below T_C, as well as ordinary and anomalous Hall effects. *Performed at the National High Magnetic Field Lab (NHMFL) FSU, Tallahassee, FL. This work was partially supported by grants from NASA_EPSCOR and the USC nanocenter.

Estrada, Javier; Brower, Jerry; Bleiweiss, Michael; Datta, Timir; Palm, Eric; Brandt, Bruce; Tsu, Ray

2002-03-01

400

Phase I Trial of Vertebral Intracavitary Cement and Samarium (VICS): Novel Technique for Treatment of Painful Vertebral Metastasis  

SciTech Connect

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.

Ashamalla, Hani, E-mail: haa9002@nyp.or [Department of Radiation Oncology, New York Methodist Hospital, Weill Medical College, Cornell University, Brooklyn, NY (United States); Cardoso, Erico [Department of Surgery, New York Methodist Hospital, Weill Medical College, Cornell University, Brooklyn, NY (United States); Macedon, Mark; Guirguis, Adel [Department of Radiation Oncology, New York Methodist Hospital, Weill Medical College, Cornell University, Brooklyn, NY (United States); Weng Lijun [Department of Nuclear Medicine, New York Methodist Hospital, Weill Medical College, Cornell University, Brooklyn, NY (United States); Ali, Shamsah [Department of Surgery, New York Methodist Hospital, Weill Medical College, Cornell University, Brooklyn, NY (United States); Mokhtar, Bahaa; Ashamalla, Michael; Panigrahi, Nokul [Department of Radiation Oncology, New York Methodist Hospital, Weill Medical College, Cornell University, Brooklyn, NY (United States)

2009-11-01

401

The distribution of the lanthanum anomaly in the Dutch branches of the Rhine River  

NASA Astrophysics Data System (ADS)

The elements lanthanum to lutetium, usually referred as the REE, are increasingly used in numerous high technology products and processes. Such products are Gadolinium chelates, used as contrasting agents in medical imaging, and produce positive anthropogenic Gd-anomalies in rare earth shale normalized (Reenasc) patterns in rivers, surface and ground waters and shallow seas. Because of the increased use of the REE, the monitoring program of the Rhine-Meuse branches and surface water influenced by them in the Netherlands was extended from 2008 with the REE. In this monitoring program both the total and dissolved (< 0.45 ?m) fraction are analyzed. At the monitoring station Lobith, where the River Rhine enters the Netherlands, the REEnasc-patterns show beside the well-known Gd-anomaly a distinct La-anomaly. This positive La-anomaly in the Rhine River is recently also reported by Kulaksiz and Bau (2011, sampling was done in 2009) and first occur in the Rhine River north of the city of Worms, 400km upstream of the Dutch-German border. Kulaksiz and Bau could show that this anomaly is of anthropogenic origin and can be traced back to the effluent from a production plant for fluid catalytic cracking catalysts at Rhine river-km 447.4. The amount of anthropogenic lanthanum in the total fraction in Lobith station is an order of magnitude larger than in the dissolved fraction indicating that the suspended matter in the Rhine River is the major carrier of the anthropogenic lanthanum. All REEnasc- patterns of the branches of the Rhine River show in addition to the Gd-anomaly a positive La-anomaly, while in the Meuse River only a Gd-anomaly is observed. In the influenced surface waters of the Rhine and Meuse Rivers always a Gd-anomaly occurs but in those influenced by the Rhine tributaries also the La-anomaly occurs. In the poster the load of lanthanum over the years 2008, 2009 and 2010 in the dissolved and total fraction at Lobith and the distribution of the La anomaly over the branches of the Rhine River in the Netherlands (4 monitoring stations) and influenced surface water (5 monitoring stations) will be shown. The Meuse monitoring stations will be given for comparison. Kulaksiz, S., Bau, M., 2011. Rare earth elements in the Rhine River, Germany: First case of anthropogenic lanthanum as a dissolved microcontaminant in the hydrosphere. Environment International, 37: 973-879.

Verheul, M.; Klaver, G.; Bakker, I.; Petelet-Giraud, E.

2011-12-01

402

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...

403

Comparison between features and performance characteristics of fifteen hp samarium cobalt and ferrite based brushless dc motors operated by same power conditioner  

SciTech Connect

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.

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

1983-01-01

404

Nitrogen-doped perovskite-type La2Ti2O7 decorated on graphene composites exhibiting efficient photocatalytic activity toward bisphenol A in water.  

PubMed

Nitrogen-doped lanthanum titanate decorated on graphene sheets (GR/N-doped La2Ti2O7) used as photocatalyst was prepared by a two-step process. To synthesize GR/N-doped La2Ti2O7, La2Ti2O7 was initially developed under heat treatment in NH3 and subsequently decorated on GR by hydrothermal processing. The resulting GR/N-doped La2Ti2O7 was characterized by scanning electron microscopy, transmission electron microscopy, atomic force microscopy, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy. Characterization results indicated that N-doped La2Ti2O7 was approximately 6-8nm thick with single-crystalline perovskite structure and chemically attached onto GR nanosheets by the formation of TiN bond, TiC bond, and oxynitrides. The application of GR/N-doped La2Ti2O7 composites to bisphenol A decomposition exhibits high photocatalytic efficiency under irradiation compared with pure La2Ti2O7 materials. This finding was due to the synergistic effect of great adsorption, enhanced light absorption, efficient charge separation and transfer processes in the presence of GR, and reduced band gap energy because of N doping. This study provides new insights into the fabrication and practical application of high-performance photocatalysts in wastewater treatment. PMID:25801131

Hua, Zulin; Zhang, Xiaoyuan; Bai, Xue; Lv, Lingling; Ye, Zhengfang; Huang, Xin

2015-07-15

405

Sol-gel-derived hybrid materials multi-doped with rare-earth metal ions  

NASA Astrophysics Data System (ADS)

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.

Zelazowska, E.; Rysiakiewicz-Pasek, E.; Borczuch-Laczka, M.; Cholewa-Kowalska, K.

2012-06-01

406

Visible light emission and energy transfer processes in Sm-doped nitride films  

SciTech Connect

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.

Zanatta, A. R. [Instituto de Fisica de Sao Carlos - USP, Sao Carlos 13560-250 - SP (Brazil)

2012-06-15

407

Melt layer erosion of pure and lanthanum doped tungsten under VDE-like high heat flux loads  

NASA Astrophysics Data System (ADS)

Heat loads expected for VDEs in ITER were applied in the neutral beam facility GLADIS at IPP Garching. Several ˜3 mm thick rolled pure W and W-1 wt% La2O3 plates were exposed to pulsed hydrogen beams with a central heat flux of 23 MW/m2 for 1.5-1.8 s. The melting thresholds are determined, and melt layer motion as well as material structure evolutions are shown. The melting thresholds of the two W grades are very close in this experimental setup. Lots of big bubbles with diameters from several ?m to several 10 ?m in the re-solidified layer of W were observed and they spread deeper with increasing heat flux. However, for W-1 wt% La2O3, no big bubbles were found in the corrugated melt layer. The underlying mechanisms referred to the melt layer motion and bubble issues are tentatively discussed based on comparison of the erosion characteristics between the two W grades.

Yuan, Y.; Greuner, H.; Böswirth, B.; Luo, G.-N.; Fu, B. Q.; Xu, H. Y.; Liu, W.

2013-07-01

408

Phase formation mechanism and kinetics in solid-state synthesis of undoped and calcium-doped lanthanum manganite  

SciTech Connect

LaMnO{sub 3+{delta}} and La{sub 0.7}Ca{sub 0.3}MnO{sub 3} were synthesized from La{sub 2}O{sub 3}(La(OH){sub 3}), CaCO{sub 3} and MnO{sub 2} powder mixture with solid-state reaction technique. X-ray diffraction and thermal analysis were employed in the present study on the process of synthesizing of the two compound powders. The kinetic study on solid-state reaction between La{sub 2}O{sub 3} and MnO{sub 2} in the powder mixture was isothermally carried out for LaMnO{sub 3+{delta}} formation. The result showed that the reaction process was controlled by three-dimensional solid-ionic diffusion. Both Jander and Ginstling-Brounstein model can be used to describe the reaction kinetics satisfactorily. The relevant apparent activation energy values obtained were as great as 205 {+-} 11 and 189 {+-} 8 kJ/mol. The reaction process of La{sub 0.7}Ca{sub 0.3}MnO{sub 3} preparation from La{sub 2}O{sub 3}, SrCO{sub 3} and MnO{sub 2} powder mixture was also studied using X-ray diffraction and thermal analysis. The result indicated that the following steps composed the overall reaction: the decomposition of the reactant; the formation of La{sub 1-x}Ca{sub x}MnO{sub 3+{delta}}; La{sub 2}O{sub 3} and Mn{sub 3}O{sub 4} reacted with La{sub 1-x}Ca{sub x}MnO{sub 3} to form final La{sub 0.7}Ca{sub 0.3}MnO{sub 3} phase. The latest step was the most time-consuming one among others in the overall reaction.

Shu Qifeng [Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083 (China)], E-mail: shuqifeng@gmail.com; Zhang Jiayun; Yan Baijun; Liu Jianhua [Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083 (China)

2009-03-05

409

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

Microsoft Academic Search

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.

Peter Andrew Zink

2010-01-01

410

Phase formation mechanism and kinetics in solid-state synthesis of undoped and calcium-doped lanthanum manganite  

Microsoft Academic Search

LaMnO3+? and La0.7Ca0.3MnO3 were synthesized from La2O3(La(OH)3), CaCO3 and MnO2 powder mixture with solid-state reaction technique. X-ray diffraction and thermal analysis were employed in the present study on the process of synthesizing of the two compound powders. The kinetic study on solid-state reaction between La2O3 and MnO2 in the powder mixture was isothermally carried out for LaMnO3+? formation. The result

Qifeng Shu; Jiayun Zhang; Baijun Yan; Jianhua Liu

2009-01-01

411

Magnetic and Magneto-Optical Properties of Doped Oxides  

NASA Astrophysics Data System (ADS)

This thesis describes the growth, structural characterisation, magnetic and magneto-optics properties of lanthanum strontium manganite (LSMO), GdMnO3 and transition metal (TM)-doped In2O3 thin films grown under different conditions. The SrTiO3 has been chosen as a substrate because its structure is suitable to grow epitaxial LSMO and GdMnO3 films. However, the absorption of SrTiO3 above its band gap at about 3.26 eV is actually a limitation in this study. The LSMO films with 30% Sr, grown on both SrTiO3 and sapphire substrates, exhibit a high Curie temperature (Tc) of 340 K. The magnetic circular dichroism (MCD) intensity follows the magnetisation for LSMO on sapphire; however, the measurements on SrTiO3 were dominated by the birefringence and magneto-optical properties of the substrate. In the GdMnO3 thin films, there are two well-known features in the optical spectrum; the charge transfer transition between Mn d states at 2 eV and the band edge transition from the oxygen p band to d states at about 3 eV; these are observed in the MCD. This has been measured at remanence as well as in a magnetic field. The optical absorption at 3 eV is much stronger than at 2 eV, however, the MCD is considerably stronger at 2 eV. The MCD at 2 eV correlates well with the Mn spin ordering and it is very notable that the same structure appears in this spectrum, as is seen in LaMnO3. The results of the investigations of Co and Fe-doped In2O3 thin films show that TM ions in the films are TM2+ and substituted for In3+. The room temperature ferromagnetism observed in TM-doped In2O3 is due to the polarised electrons in localised donor states associated with oxygen vacancies. The formation of Fe3O4 nanoparticles in some Fe-doped films is due the fact that TM-doped In2O3 thin films are extremely sensitive to the growth method and processing condition. However, the origin of the magnetisation in these films is due to both the Fe-doped host matrix and also to the nanoparticles of Fe3O4.

Alqahtani, Mohammed

412

Study on Ferroelectric and Dielectric Properties of La-Doped CaBi 4Ti 4O 15Based Ceramics  

Microsoft Academic Search

Lanthanum doped bismuth layer structured ferroelectrics (BLSFs) Ca1-xLaxBi4(Ti0.9W0.1)4O15(x = 0, 0.2. 0.3, 0.4, 0.6) ceramics were prepared by solid-state reaction method. X-ray diffraction (XRD) patterns showed that single phase was formed when x = 0 ? 0.6. The effects of La3+ doping on dielectric, piezoelectric and ferroelectric properties of Ca1-xLaxBi4(Ti0.9W0.1)4O15 ceramics were studied. Ca0.7La0.3Bi4(Ti0.9W0.1)4O15 ceramic had optimal properties, its dielectric

Xialian Zheng; Xinyou Huang; Chunhua Gao

2007-01-01

413

Adsorption and enhanced photocatalytic activity of the {0 0 0 1} faceted Sm-doped ZnIn2S4 microspheres.  

PubMed

In this study, the doping effect of samarium on the structure, morphology, adsorption and photocatalytic performance of hexagonal ZnIn2S4 microspheres was studied. The photocatalytic activity of Sm-doped ZnIn2S4 microspheres was evaluated for the photodegradation of Rhodamine B (RhB) and methyl orange (MO) under visible light irradiation. The samples were characterized by XRD, SEM, XPS, UV-vis, TEM, and N2 adsorption-desorption analysis. The results show that the hexagonal ZnIn2S4 microspheres are composed of nanoplates growing along c-axis with the predominant negative-charged S plane. Compared with the photodegadation of MO dye, the negative-charged {0 0 0 1} facets not only are beneficial for the adsorption of RhB by -N(Et)2 groups but also can accumulate the separation of photogenerated electrons and holes, enhancing photodegradation efficiency by direct-hole photocatalysis. Moreover, Sm is partially substituted for In in the crystal lattice for forming the doping energy level which promotes the separation of photoinduced electron-hole pairs and enhances absorption of visible light. Hexagonal 2% Sm-doped ZnIn2S4 microspheres with exposed {0 0 0 1} facets resulted in higher photodegradation efficiency of RhB under visible light irradiation. PMID:25016456

Tan, Congwei; Zhu, Gangqiang; Hojamberdiev, Mirabbos; Lokesh, Koodlur Sannegowda; Luo, Xiancong; Jin, Lei; Zhou, Jianping; Liu, Peng

2014-08-15

414

Influence of La doping on structural and dielectric properties of SrBi{sub 2}Nb{sub 2}O{sub 9} ceramics  

SciTech Connect

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)

Verma, Maya; Sreenivas, K.; Gupta, Vinay [Department of Physics and Astrophysics, University of Delhi, Delhi 110007 (India)

2009-01-15

415

Aero dopes and varnishes  

NASA Technical Reports Server (NTRS)

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.

Britton, H T S

1927-01-01

416

Lanthanum salts improve bone formation in a small animal model of post-menopausal osteoporosis.  

PubMed

Two different lanthanum salts, lanthanum carbonate (LaCO(3)) and Lancer(®), a lanthanide citrate mixture, were tested for their effects on bone metabolism in a small animal model for post-menopausal osteoporosis. Forty female outbred Wistar Han rats, sham-operated (SHAM, positive control, n = 10) or ovariectomized (OVX, n = 30) at 4 months of age, were allotted into following groups (n = 10/group): (i) SHAM, (ii) OVX control (negative control), (iii) OVX + LaCO(3) (1.74 g/kg feed) and (iv) OVX + Lancer(®) (8 g/kg feed). Effects on bone were investigated by bone markers [osteocalcin (Oc) in serum and excretion of pyridinoline (PYD) in urine] and by physical parameters of bone structure and bone composition (bone mass, calcium, phosphorus and magnesium content in bone crude ash). Bone micro-architecture and bone mineral density were evaluated by peripheral quantitative computed tomography and micro-computed tomography (?CT). The animal model could be validated by differences between OVX control and SHAM. Body mass and feed intake were the same among the four groups. Oc was clearly increased in the two experimental groups (p < 0.001) vs. SHAM and OVX control. Bone mass and calcium content in bone ash were significantly higher than in OVX control. The Ca/P ratio in bone ash of the two lanthanide groups did not differ from SHAM. Bone-protecting effects of lanthanides were clearly demonstrated by an increased trabecular density which is the region of interest for osteoporotic bone loss. A 3D imaging of bone micro-architecture by ?CT visualized descriptively the positive effects of lanthanides on bone formation. The results of this study demonstrate an improvement of bone formation and bone-protecting effects of lanthanides in the OVX rat. Thus, lanthanum salts suggest a prevention of post-menopausal bone loss and may be of benefit in experimental osteopenia following ovariectomy. PMID:22845174

von Rosenberg, S J; Wehr, U A

2012-10-01

417

Preliminary Investigation of Lanthanum-Cerium Bromide Self-Activity Removal  

SciTech Connect

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) detectors1–6. 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 actinides6–8. 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.

Yuan, D., Guss, P.

2011-09-01

418

Formation of plate-like lanthanum-?-Aluminate crystal in Ce-TZP matrix  

Microsoft Academic Search

The reaction route and morphology of lanthanum-ß-aluminate (LBA) crystals formed in Ce-TZP matrix were studied by examining the crystal phase changes and the microstructures in relation to the heat-treatment time, heat-treatment temperatures and the particle size of raw Al2O3 powders. In the Ce-TZP matrix, the LBA crystal was formed by the reaction between La2O3 and Al2O3 through the LaAlO3 phase

M. Miura; H. Hongoh; T. Yogo; S. Hirano; T. Fujll

1994-01-01

419

Synthesis of lanthanum zirconium oxide nanomaterials through composite-hydroxide-mediated approach  

Microsoft Academic Search

A novel thermal barrier coating material, lanthanum zirconium oxide (La2Zr2O7) 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 La2Zr2O7 were investigated systematically. The X-ray diffraction (XRD) patterns revealed a single phase with cubic pyrochlore structure for La2Zr2O7 after treated at 1300°C for 100h. The transmission electron

Hongyun Jin; Dan Huang; Qiang Gao; Li Li; Ning Wang; Yongqian Wang; Shuen Hou

420

Chicken erythrocyte membrane: lipid profile and enzymatic activity under lanthanum chloride and neodymium chloride administration.  

PubMed

Acute single dose (ip) administration of two rare earth elements like lanthanum chloride (250 mg/kg body wt) and neodymium chloride (200 mg/kg body wt) to chicks have been found to reduce the activity of certain erythrocyte membrane bound enzymes, viz. acetylcholinesterase, NADH dehydrogenase, Mg(2+)-ATPase, p-nitrophenyl phosphatase. Erythrocyte membrane bound glycosidases e.g. beta-D-glucosidase, beta-D-galactosidase and beta-D-glucuronidase were also reduced. Other components such as cholesterol and phospholipid residues were reduced but their ratio (cholesterol/phospholipid) remaining unchanged. Membrane sulfhydryl groups were also significantly inhibited by these rare earth elements. PMID:1874535

Ghosh, N; Chattopadhyay, D; Chatterjee, G C

1991-03-01

421

Lanthanum, constipation, bafflying X-rays and a perforated colonic diverticulum  

PubMed Central

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.

Korzets, Asher; Tsitman, Inna; Lev, Netta; Zingerman, Boris; Herman, Michal; Ben Dor, Naomi; Gafter, Uzi; Ori, Yaacov

2012-01-01

422

Temperature Dependent Electrical and Micromechanical Properties of Lanthanum Titanate with Additions of Yttria  

NASA Technical Reports Server (NTRS)

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.

Goldsby, Jon C.

2003-01-01

423

Fabrication of Lanthanum Telluride 14-1-11 Zintl High-Temperature Thermoelectric Couple  

NASA Technical Reports Server (NTRS)

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).

Ravi, Vilupanur A.; Li, Billy Chun-Yip; Fleurial, Pierre; Star, Kurt

2010-01-01

424

Temperature-Dependent Electrical and Micromechanical Properties of Lanthanum Titanate with Additions of Yttria  

NASA Technical Reports Server (NTRS)

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.

Goldsby, Jon C.

2010-01-01

425

Preparation and thermophysical properties of CeO 2 doped La 2Zr 2O 7 ceramic for thermal barrier coatings  

Microsoft Academic Search

Lanthanum zirconate (La2Zr2O7, LZ) and CeO2 doped La2Zr2O7 (LCZ) ceramic were synthesized by the coprecipitation–calcination method. The chemical compositions, phase compositions, thermophysical properties of these materials were investigated. Inductively coupled plasma-atomic emission spectrometry (ICP-AES) and XRD results revealed that the compositions of all prepared ceramic materials were in the range of the synthesis of single La2Zr2O7 with pyrochlore structure. After

Hongming Zhou; Danqing Yi; Zhiming Yu; Lairong Xiao

2007-01-01

426

Synthesis of La and Nb doped PZT powder by the gel-combustion method  

NASA Astrophysics Data System (ADS)

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.

Cernea, M.; Montanari, G.; Galassi, C.; Costa, A. L.

2006-03-01

427

Gene doping in sports.  

PubMed

Gene or cell doping is defined by the World Anti-Doping Agency (WADA) as "the non-therapeutic use of genes, genetic elements and/or cells that have the capacity to enhance athletic performance". New research in genetics and genomics will be used not only to diagnose and treat disease, but also to attempt to enhance human performance. In recent years, gene therapy has shown progress and positive results that have highlighted the potential misuse of this technology and the debate of 'gene doping'. Gene therapies developed for the treatment of diseases such as anaemia (the gene for erythropoietin), muscular dystrophy (the gene for insulin-like growth factor-1) and peripheral vascular diseases (the gene for vascular endothelial growth factor) are potential doping methods. With progress in gene technology, many other genes with this potential will be discovered. For this reason, it is important to develop timely legal regulations and to research the field of gene doping in order to develop methods of detection. To protect the health of athletes and to ensure equal competitive conditions, the International Olympic Committee, WADA and International Sports Federations have accepted performance-enhancing substances and methods as being doping, and have forbidden them. Nevertheless, the desire to win causes athletes to misuse these drugs and methods. This paper reviews the current status of gene doping and candidate performance enhancement genes, and also the use of gene therapy in sports medicine and ethics of genetic enhancement. PMID:15157120

Unal, Mehmet; Ozer Unal, Durisehvar

2004-01-01

428

Isoelectronic co-doping  

DOEpatents

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.

Mascarenhas, Angelo

2004-11-09

429

Preconcentration of some metal ions with lanthanum-8-hydroxyquinoline co-precipitation system.  

PubMed

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 ?g 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 ?g 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

Feist, Barbara; Mikula, Barbara

2014-03-15

430

Three-year follow-up of lanthanum carbonate therapy in hemodialysis patients.  

PubMed

For 3 years following the start of lanthanum carbonate therapy, effects on other pharmaceutical treatment with sevelamer hydrochloride (SH), calcium carbonate (CC), and vitamin D, and those on clinical condition were examined. Dialysis patients with hyperphosphatemia (89 cases; average age 55.2 years; dialysis history of 10 years; 50 male and 39 female), who agreed to start lanthanum carbonate (LC) administration, were observed for a mean period of 32.6?±?6.2 months. Mean daily dosages of CC and SH before starting LC were 2.68?g and 0.73?g; mean daily dosage amounts of LC, CC, and SH at the time of final evaluation were 0.87?g, 2.30?g, and 0.99?g, respectively. After the application of LC, serum phosphate as well as serum calcium controls were significantly improved, and the amounts of active vitamin D agents applied was significantly increased. In conclusion, LC is useful in managing serum phosphorus levels (P levels), and little incidence of hypercalcemia suggests favorable concomitant use with active vitamin D agents in LC therapy. PMID:23586508

Takeuchi, Kazuhisa; Matsuda, Etsuko; Sekino, Makoto; Hasegawa, Yukiko; Kamo, Yoshie; Kikuchi, Natsue; Sekino, Hiroshi

2013-04-01

431

Structural, microstructural and vibrational characterization of apatite-type lanthanum silicates prepared by mechanical milling  

SciTech Connect

Apatite-type lanthanum silicates have been successfully prepared at room temperature by dry milling hexagonal A-La{sub 2}O{sub 3} and either amorphous or low cristobalite SiO{sub 2}. Milling a stochiometric mixture of these chemicals in a planetary ball mill with a moderate rotating disc speed (350 rpm), allows the formation of the target phase after only 3 h although longer milling times are needed to eliminate all SiO{sub 2} and La{sub 2}O{sub 3} traces. Thus, the mechanically activated chemical reaction proceeds faster when using amorphous silica instead of low cristobalite as silicon source and pure phases are obtained after only 9 and 18 h, respectively. As obtained powder phases are not amorphous and show an XRD pattern as well as IR and Raman bands characteristic of the lanthanum silicate. The domain size of the as-prepared phases varies gradually with the temperature of post-milling thermal treatment with activation energies of about 26(8) and 52(10) kJ mol{sup -1} K{sup -1} for the apatites obtained from amorphous silica and low-cristobalite, respectively. These values suggest crystallite growth to be favored when using amorphous silica as reactant.

Rodriguez-Reyna, E. [Cinvestav-Saltillo, Apartado Postal 663, 25000-Saltillo, Coahuila (Mexico); Fuentes, A.F. [Cinvestav-Saltillo, Apartado Postal 663, 25000-Saltillo, Coahuila (Mexico)]. E-mail: antonio.fernandez@cinvestav.edu.mx; Maczka, M. [Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P.O. Box 1410, 50-950 Wroclaw 2 (Poland); Hanuza, J. [Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P.O. Box 1410, 50-950 Wroclaw 2 (Poland); Department of Bioorganic Chemistry, Faculty of Engineering and Economics, University of Economics, Wroclaw (Poland); Boulahya, K. [Departamento de Quimica Inorganica, Facultad de Ciencias Quimicas, Universidad Complutense, 28040-Madrid (Spain); Amador, U. [Departamento de Ciencias Quimicas, Facultad de Farmacia, Universidad San Pablo CEU, 28668-Boadilla del Monte, Madrid (Spain)

2006-02-15

432

Syntheses, Characterization, Thermal, and Antimicrobial Studies of Lanthanum(III) Tolyl/Benzyldithiocarbonates  

PubMed Central

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

Andotra, Savit; Kalgotra, Nidhi; Pandey, Sushil K.

2014-01-01

433

Lanthanum chloride impairs spatial memory through ERK/MSK1 signaling pathway of hippocampus in rats.  

PubMed

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

Liu, Huiying; Yang, Jinghua; Liu, Qiufang; Jin, Cuihong; Wu, Shengwen; Lu, Xiaobo; Zheng, Linlin; Xi, Qi; Cai, Yuan

2014-12-01

434

Ultrasonic mediated synthesis of monodispersed lanthanum hydroxide nanorods for possible bioimplant application.  

PubMed

Monodispersed lanthanum hydroxide nano-rods (LaNRs) were synthesized for prospective biomedical application using a microwave heating and ultrasonic agitation methodology which does not require any toxic stabilizing agent. The average length and diameter of the LaNRs thus obtained were 183.4 ± 3.6 and 9.9 ± 0.2 nm respectively, as analyzed by HRTEM. FTIR spectrum confirmed the presence of OH groups. The thermal transformation of lanthanum hydroxide (La(OH)3) was studied by thermogravimetric analysis. The synthesized LaNRs were found to be stable for a period of 1 month at room temperature. They were biocompatible as evaluated by haemocompatibility assay and viability assay using human peripheral blood mononuclear cells. The pro-angiogenic property of LaNRs was demonstrated by in vivo chick chorioallantoic membrane assay. The LaNRs induced osteoblast differentiation of human adipose derived stem cells with significant calcium (Ca(2+)) deposition indicating potential applications in bone tissue engineering. PMID:25601669

Harini, Dhandapani; Rajaram, Anantanarayanan; Rajaram, Rama

2015-01-01

435

Ultimate intrinsic-coercivity samarium-cobalt magnet: An Earth-based feasibility study for space-shuttle missions. [containerless melts  

NASA Technical Reports Server (NTRS)

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.

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

1980-01-01

436

Efficacy, Tolerability, and Safety of Lanthanum Carbonate in Hyperphosphatemia: A 6Month, Randomized, Comparative Trial versus Calcium Carbonate  

Microsoft Academic Search

Background\\/Aims: Hyperphosphatemia is an important clinical consequence of renal failure, and its multiple adverse systemic effects are associated with significantly increased risks of morbidity and mortality in dialysis patients. Existing oral phosphate binders have not permitted control of serum phosphate within currently accepted guidelines. This study compares lanthanum carbonate with calcium carbonate for control of serum phosphate in hemodialysis patients.

A. J. Hutchison; B. Maes; J. Vanwalleghem; G. Asmus; E. Mohamed; R. Schmieder; W. Backs; R. Jamar; A. Vosskühler

2005-01-01

437

Ionic liquid-mediated synthesis of meso-scale porous lanthanum-transition-metal perovskites with high CO oxidation performance.  

PubMed

Lanthanum-transition-metal perovskites with robust meso-scale porous frameworks (meso-LaMO3) are synthesized through the use of ionic liquids. The resultant samples demonstrate a rather high activity for CO oxidation, by taking advantage of unique nanostructure-derived benefits. This synthesis strategy opens up a new opportunity for preparing functional mesoporous complex oxides of various compositions. PMID:25727232

Lu, Hanfeng; Zhang, Pengfei; Qiao, Zhen-An; Zhang, Jinshui; Zhu, Huiyuan; Chen, Jihua; Chen, Yinfei; Dai, Sheng

2015-04-01

438

Highly efficient site-selective laser emission in the 900 nm range in Nd:strontium lanthanum aluminate  

Microsoft Academic Search

Efficient quasi-three-level-laser emission in 900 nm range is obtained for Nd\\/sup 3+\\/ in strontium lanthanum aluminate. The dependence of laser emission on crystal composition and pump wavelength is correlated with the spectroscopic and structural properties.

G. Aka; D. Vivien; V. Lupei

2004-01-01

439

Rare earth elements and plant growth: I. Effects of lanthanum and cerium on root elongation of corn and mungbean  

Microsoft Academic Search

Root elongation of corn (Zea mays cv. Hycorn 82) and mungbean (Vigna radiata cv. Berken) seedlings was measured in dilute complete nutrient solutions to which varying amounts of lanthanum (La) or cerium (Ce) had been added. The nutrient solutions were aged for 9 d prior to conducting the root elongation experiments and solution samples ultra?filtered to 0.025 ?m before chemical

E. Diatloff; F. W. Smith; C. J. Asher

1995-01-01

440

Progress in rare-earth-doped mid-infrared fiber lasers.  

PubMed

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

Seddon, Angela B; Tang, Zhuoqi; Furniss, David; Sujecki, Slawomir; Benson, Trevor M

2010-12-01

441

Structural and optical properties of La-doped BaSnO3 thin films grown by PLD  

NASA Astrophysics Data System (ADS)

In this study the structural and optical properties of lanthanum-doped BaSnO3 powder samples and thin films deposited on fused silica were investigaed using laser ablation. Under an oxygen pressure of 5×10-4 mbar, phase pure BaSnO3 films with a lattice constant of 0.417 nm and grain size of 21 nm were prepared at 630 °C. The band gap of BaSnO3 powder sample and thin films was calculated to be 3.36 eV and 3.67 eV, respectively. There was a progressive increase in conductivity for thin films of BaSnO3 doped with 0~7 at% of La. The highest conductivity, 9 Scm-1, was obtained for 7 at% La-doped BaSnO3. Carrier concentration, obtained from Burstein-Moss (B-M) shift, nearly matches the measured values except for 3 at% and 10 at% La-doped BaSnO3 thin films.

James, K. K.; Krishnaprasad, P. S.; Hasna, K.; Jayaraj, M. K.

2015-01-01

442

Room-temperature scintillation properties of cerium-doped REOX (RE=Y, La, Gd, and Lu; X=F, Cl, Br, and I)  

SciTech Connect

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.

Eagleman, Yetta; Bourret-Courchesne, Edith; Derenzo, Stephen

2010-12-10

443

Large area directly heated lanthanum hexaboride cathode structure having predetermined emission profile  

DOEpatents

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

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

444

Twin step synthesis of lanthanum zirconate through transferred arc plasma processing  

NASA Astrophysics Data System (ADS)

Low power transferred arc plasma (TAP) processing is a simple and cost-effective method for large amount of ceramic processing in a very short period of time duration. In the present work, lanthanum zirconate (La2Zr2O7) was synthesized by transferred arc plasma (TAP) melting technique followed by mechanical milling. The mixture of La2O3 and ZrO2 powders with 1:2 mole ratio were ball milled for four hours and melted for three minutes in transferred arc plasma torch at 10 kW input power with 10 lpm of argon flow rate. The phase and microstructure formation of the processed samples were analyzed by X-ray diffraction (XRD) and Scanning Electron Microscope (SEM) images.

Yugeswaran, S.; Selvarajan, V.; Ananthapadmanabhan, P. V.; Lusvarghi, L.

2010-02-01

445

Sintering aid for lanthanum chromite refractories. [As interconnect layer between electrodes in fuel cells  

SciTech Connect

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.

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

1986-10-23

446

Superconductivity of lanthanum revisited: enhanced critical temperature in the clean limit  

NASA Astrophysics Data System (ADS)

The thickness dependence of the superconducting energy gap ?La of double hexagonally close packed (dhcp) lanthanum islands grown on W(110) is studied by scanning tunneling spectroscopy, from the bulk to the thin-film limit. Superconductivity is suppressed by the boundary conditions for the superconducting wavefunction on the surface and W/La interface, leading to a linear decrease of the critical temperature Tc as a function of the inverse film thickness. For the thick, bulk-like films, ?La and Tc are 40% larger compared to the literature values of dhcp La as measured by other techniques. This finding is reconciled by examining the effects of surface contamination as probed by modifications of the surface state, suggesting that the large Tc originates in the superior purity of the samples investigated here.

Löptien, P.; Zhou, L.; Khajetoorians, A. A.; Wiebe, J.; Wiesendanger, R.

2014-10-01

447

Complex formation of quercetin with lanthanum enhances binding to plant viral satellite double stranded RNA.  

PubMed

Due to the broad spectrum of biological activities of flavonoids, their target molecules in the cell are intensively studied. We examined the interactions of the flavonoid quercetin (Q) and its lanthanum complex (QLa(3+)) with very recently isolated plant viral satellite (sat) dsRNA. Comparison of the cumulative binding affinity and the estimated intercalative binding constant pointed towards an additional binding mode of quercetin to exclusively viral dsRNA, which is not recorded for synthetic dsRNAs. The QLa(3+) showed significantly higher affinity toward viral dsRNA than Q and La(3+) alone, most likely as the consequence of quercetin intercalation accompanied by additional electrostatic interaction of La(3+) with the negatively charged viral RNA backbone. PMID:19766320

Rusak, Gordana; Piantanida, Ivo; Bretschneider, Sabine; Ludwig-Müller, Jutta

2009-12-01

448

Ba11La4Br34: a new barium lanthanum bromide  

PubMed Central

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

Eagleman, Yetta; Wu, Guang; Gundiah, Gautam; Bourret-Courchesne, Edith; Derenzo, Stephen

2011-01-01

449

Metal-oxide-semiconductor characteristics of lanthanum cerium oxide film on Si  

NASA Astrophysics Data System (ADS)

Metal-organic decomposed lanthanum cerium oxide (La x Ce y O z ) film had been spin-coated on n-type Si substrate. Effects of post-deposition annealing temperature and time on the metal-oxide-semiconductor (MOS) properties of the film were studied. As temperature increased from 400 to 1000°C for 15 minutes dwell time, La x Ce y O z demonstrated a decrease in interface trap density ( D it) and total interface trap density ( D total), which were related to the formation of SiO x /silicates interfacial layer (IL). The lowest leakage current density and highest dielectric breakdown voltage ( V B) was obtained in 1000°C-annealed sample. When longer annealing times (30-120 minutes) were studied on the 1000°C-annealed sample, the sample annealed at 1000°C for 120 min showed the best MOS characteristics with V B of 30 V. Reasons contributing to such observation were discussed.

Lim, Way Foong; Lockman, Zainovia; Cheong, Kuan Yew