Sample records for earth doped high

  1. Rare Earth Doped High Temperature Ceramic Selective Emitters

    NASA Technical Reports Server (NTRS)

    Chubb, Donald L.; Pal, AnnaMarie; Patton, Martin O.; Jenkins, Phillip P.

    1999-01-01

    As a result of their electron structure, rare earth ions in crystals at high temperature emit radiation in several narrow bands rather than in a continuous blackbody manner. This study develops a spectral emittance model for films of rare earth containing materials. Although there are several possible rare earth doped high temperature materials, this study was confined to rare earth aluminum garnets. Good agreement between experimental and theoretical spectral emittances was found for erbium, thulium and erbium-holmium aluminum garnets. Spectral emittances of these films are sensitive to temperature differences across the film. Emitter efficiency is also a sensitive function of temperature. For thulium aluminum garnet the efficiency is 0.38 at 1700 K but only 0.19 at 1262 K.

  2. Effects of rare-earth co-doping on the local structure of rare-earth phosphate glasses using high and low energy X-ray diffraction.

    PubMed

    Cramer, Alisha J; Cole, Jacqueline M; FitzGerald, Vicky; Honkimaki, Veijo; Roberts, Mark A; Brennan, Tessa; Martin, Richard A; Saunders, George A; Newport, Robert J

    2013-06-14

    Rare-earth co-doping in inorganic materials has a long-held tradition of facilitating highly desirable optoelectronic properties for their application to the laser industry. This study concentrates specifically on rare-earth phosphate glasses, (R2O3)x(R'2O3)y(P2O5)(1-(x+y)), where (R, R') denotes (Ce, Er) or (La, Nd) co-doping and the total rare-earth composition corresponds to a range between metaphosphate, RP3O9, and ultraphosphate, RP5O14. Thereupon, the effects of rare-earth co-doping on the local structure are assessed at the atomic level. Pair-distribution function analysis of high-energy X-ray diffraction data (Q(max) = 28 Å(-1)) is employed to make this assessment. Results reveal a stark structural invariance to rare-earth co-doping which bears testament to the open-framework and rigid nature of these glasses. A range of desirable attributes of these glasses unfold from this finding; in particular, a structural simplicity that will enable facile molecular engineering of rare-earth phosphate glasses with 'dial-up' lasing properties. When considered together with other factors, this finding also demonstrates additional prospects for these co-doped rare-earth phosphate glasses in nuclear waste storage applications. This study also reveals, for the first time, the ability to distinguish between P-O and P[double bond, length as m-dash]O bonding in these rare-earth phosphate glasses from X-ray diffraction data in a fully quantitative manner. Complementary analysis of high-energy X-ray diffraction data on single rare-earth phosphate glasses of similar rare-earth composition to the co-doped materials is also presented in this context. In a technical sense, all high-energy X-ray diffraction data on these glasses are compared with analogous low-energy diffraction data; their salient differences reveal distinct advantages of high-energy X-ray diffraction data for the study of amorphous materials.

  3. Tunable, rare earth-doped solid state lasers

    DOEpatents

    Emmett, John L.; Jacobs, Ralph R.; Krupke, William F.; Weber, Marvin J.

    1980-01-01

    Laser apparatus comprising combinations of an excimer pump laser and a rare earth-doped solid matrix, utilizing the 5d-4f radiative transition in a rare earth ion to produce visible and ultra-violet laser radiation with high overall efficiency in selected cases and relatively long radiative lifetimes.

  4. Recent advances in rare earth doped alkali-alkaline earth borates for solid state lighting applications

    NASA Astrophysics Data System (ADS)

    Verma, Shefali; Verma, Kartikey; Kumar, Deepak; Chaudhary, Babulal; Som, Sudipta; Sharma, Vishal; Kumar, Vijay; Swart, Hendrik C.

    2018-04-01

    As a novel class of inorganic phosphor, the alkali-alkaline earth borate phosphors have gained huge attention due to their charming applications in solid-state lighting (SSL) and display devices. The current research drive shows that phosphors based on the alkali-alkaline earth borates have transformed the science and technology due to their high transparency over a broad spectral range, their flexibility in structure and durability for mechanical and high-laser applications. Recent advances in various aspects of rare-earth (RE) doped borate based phosphors and their utilizations in SSL and light emitting diodes are summarized in this review article. Moreover, the present status and upcoming scenario of RE-doped borate phosphors were reviewed in general along with the proper credential from the existing literature. It is believed that this review is a sole compilation of crucial information about the RE-doped borate phosphors in a single platform.

  5. 40 CFR 721.10423 - Complex strontium aluminate, rare earth doped (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... earth doped (generic). 721.10423 Section 721.10423 Protection of Environment ENVIRONMENTAL PROTECTION... New Uses for Specific Chemical Substances § 721.10423 Complex strontium aluminate, rare earth doped... substances identified generically as complex strontium aluminate, rare earth doped (PMNs P-12-22, P-12-23, P...

  6. Effects of rare earth doping on multi-core iron oxide nanoparticles properties

    NASA Astrophysics Data System (ADS)

    Petran, Anca; Radu, Teodora; Borodi, Gheorghe; Nan, Alexandrina; Suciu, Maria; Turcu, Rodica

    2018-01-01

    New multi-core iron oxide magnetic nanoparticles doped with rare earth metals (Gd, Eu) were obtained by a one step synthesis procedure using a solvothermal method for potential biomedical applications. The obtained clusters were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray microanalysis (EDX), X-ray photoelectron spectroscopy (XPS) and magnetization measurements. They possess high colloidal stability, a saturation magnetization of up to 52 emu/g, and nearly spherical shape. The presence of rare earth ions in the obtained samples was confirmed by EDX and XPS. XRD analysis proved the homogeneous distribution of the trivalent rare earth ions in the inverse-spinel structure of magnetite and the increase of crystal strain upon doping the samples. XPS study reveals the valence state and the cation distribution on the octahedral and tetrahedral sites of the analysed samples. The observed shift of the XPS valence band spectra maximum in the direction of higher binding energies after rare earth doping, as well as theoretical valence band calculations prove the presence of Gd and Eu ions in octahedral sites. The blood protein adsorption ability of the obtained samples surface, the most important factor of the interaction between biomaterials and body fluids, was assessed by interaction with bovine serum albumin (BSA). The rare earth doped clusters surface show higher afinity for binding BSA. In vitro cytotoxicity test results for the studied samples showed no cytotoxicity in low and medium doses, establishing a potential perspective for rare earth doped MNC to facilitate multiple therapies in a single formulation for cancer theranostics.

  7. Multicomponent, Rare-Earth-Doped Thermal-Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Miller, Robert A.; Zhu, Dongming

    2005-01-01

    Multicomponent, rare-earth-doped, perovskite-type thermal-barrier coating materials have been developed in an effort to obtain lower thermal conductivity, greater phase stability, and greater high-temperature capability, relative to those of the prior thermal-barrier coating material of choice, which is yttria-partially stabilized zirconia. As used here, "thermal-barrier coatings" (TBCs) denotes thin ceramic layers used to insulate air-cooled metallic components of heat engines (e.g., gas turbines) from hot gases. These layers are generally fabricated by plasma spraying or physical vapor deposition of the TBC materials onto the metal components. A TBC as deposited has some porosity, which is desirable in that it reduces the thermal conductivity below the intrinsic thermal conductivity of the fully dense form of the material. Undesirably, the thermal conductivity gradually increases because the porosity gradually decreases as a consequence of sintering during high-temperature service. Because of these and other considerations such as phase transformations, the maximum allowable service temperature for yttria-partially stabilized zirconia TBCs lies in the range of about 1,200 to 1,300 C. In contrast, the present multicomponent, rare-earth-doped, perovskite-type TBCs can withstand higher temperatures.

  8. Electronic Characteristics of Rare Earth Doped GaN Schottky Diodes

    DTIC Science & Technology

    2013-03-21

    REPORT TYPE Master’s Thesis 3. DATES COVERED (From – To) 04 Sep 2011 - Mar 2013 4. TITLE AND SUBTITLE ELECTRONIC CHARACTERISTICS OF RARE EARTH ...ELECTRONIC CHARACTERISTICS OF RARE EARTH DOPED GaN SCHOTTKY DIODES THESIS Aaron B. Blanning...United States. AFIT-ENP-13-M-03 Electronic Characteristics of Rare Earth Doped GaN Schottky Diodes THESIS Presented to the Faculty

  9. Review on dielectric properties of rare earth doped barium titanate

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ismail, Fatin Adila, E-mail: fatinadilaismail@gmail.com; Osman, Rozana Aina Maulat, E-mail: rozana@unimap.edu.my; Frontier Materials Research, Seriab, 01000 Kangar, Perlis

    2016-07-19

    Rare earth doped Barium Titanate (BaTiO{sub 3}) were studied due to high permittivity, excellent electrical properties and have wide usage in various applications. This paper reviewed on the electrical properties of RE doped BaTiO{sub 3} (RE: Lanthanum (La), Erbium (Er), Samarium (Sm), Neodymium (Nd), Cerium (Ce)), processing method, phase transition occurred and solid solution range for complete study. Most of the RE doped BaTiO{sub 3} downshifted the Curie temperature (T{sub C}). Transition temperature also known as Curie temperature, T{sub C} where the ceramics had a transition from ferroelectric to a paraelectric phase. In this review, the dielectric constant of La-dopedmore » BaTiO{sub 3}, Er-doped BaTiO{sub 3}, Sm-doped BaTiO{sub 3}, Nd-doped BaTiO{sub 3} and Ce-doped BaTiO{sub 3} had been proved to increase and the transition temperature or also known as T{sub C} also lowered down to room temperature as for all the RE doped BaTiO{sub 3} except for Er-doped BaTiO{sub 3}.« less

  10. Alkaline earth metal doped tin oxide as a novel oxygen storage material

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Dong, Qiang, E-mail: dong@tagen.tohoku.ac.jp; Yin, Shu; Yoshida, Mizuki

    2015-09-15

    Alkaline earth metal doped tin oxide (SnO{sub 2}) hollow nanospheres with a diameter of 50 nm have been synthesized successfully via a facial solvothermal route in a very simple system composed of only ethanol, acetic acid, SnCl{sub 4}·5H{sub 2}O and A(NO{sub 3}){sub 2}·xH{sub 2}O (A = Mg, Ca, Sr, Ba). The synthesized undoped SnO{sub 2} and A-doped SnO{sub 2} hollow nanospheres were characterized by the oxygen storage capacity (OSC), X-ray diffraction, transmission electron microscopy and the Brunauer–Emmet–Teller (BET) technique. The OSC values of all samples were measured using thermogravimetric-differential thermal analysis. The incorporation of alkaline earth metal ion into tinmore » oxide greatly enhanced the thermal stability and OSC. Especially, Ba-doped SnO{sub 2} hollow nanospheres calcined at 1000 °C for 20 h with a BET surface area of 61 m{sup 2} g{sup −1} exhibited the considerably high OSC of 457 μmol-O g{sup −1} and good thermal stability. Alkaline earth metal doped tin oxide has the potential to be a novel oxygen storage material.« less

  11. Synthesis and characterization of rare-earth-doped calcium tungstate nanocrystals

    NASA Astrophysics Data System (ADS)

    Suneeta, P.; Rajesh, Ch.; Ramana, M. V.

    2018-02-01

    In this paper, we report synthesis and characterization of rare-earth-ion-doped calcium tungstate (CaWO4) nanocrystals (NCs). Rare-earth ions, such as gadolinium (Gd), neodymium (Nd), praseodymium (Pr), samarium (Sm) and holmium (Ho), were successfully doped in the CaWO4 NCs by changing the synthesis conditions. The adopted synthesis route was found to be fast and eco-friendly. Structural characterizations, such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and compositional analysis, were performed using energy dispersive analysis of X-rays (EDAX) on as-synthesized NCs. The results indicate the size of the NCs ranging between 47 to 68nm and incorporation of rare-earth ions in CaWO4 NCs.

  12. Rare Earth Doped GaN Laser Structures Using Metal Modulated Epitaxy

    DTIC Science & Technology

    2015-03-30

    from Eu-doped GaN,” Appl. Phys. Lett., vol. 75, pp. 1189–1191, 1999. 24. D. S . Lee and A. J. Steckl, “Room-temperature-grown rare- earth -doped GaN...luminescent thin films,” Appl. Phys. Lett., vol. 79, pp. 1962–1964,2001. 25. D. S . Lee and A. J. Steckl, “Lateral color integration on rare- earth doped... s . 0.259nm/ s =1.14E13cm-2/ s =1 ML/ s .Our plasma source was optimized to work at 1.5 sccm and 230 W RF power and it provides a growth rate of 0.8 ML/ s

  13. Rare-earth doped polymer waveguides and light emitting diodes

    NASA Astrophysics Data System (ADS)

    Slooff, L. H.

    2000-11-01

    Polymer-based optical waveguide amplifiers offer a low-cost alternative for inorganic waveguide amplifiers. Due to the fact that their refractive index is almost similar to that of standard optical fibers, they can be easily coupled with existing fibers at low coupling losses. Doping the polymer with rare-earth ions that can yield optical gain is not straightforward, as the rare-earth salts are poorly soluble in the polymer matrix. This thesis studies two different approaches to dope a polymer waveguide with rare-earth ions. The first one is based on organic cage-like complexes that encapsulate the rare-earth ion and are designed to provide enough coordination sites to bind the rare-earth ion and to shield it from the surrounding matrix. Chapter 2 describes the optical properties of Er-doped organic polydentate cage complexes. The complexes show clear photoluminescence at 1.54 mm with a bandwidth of 70 nm, the highest reported for an erbium-doped material so far. The luminescence lifetime is very short (~1 ms) due to coupling to vibrational overtones of O-H and C-H bonds. Due to this short luminescence lifetime, high pump powers (~1 W) are needed for optical gain in a waveguide amplifier based on these complexes. The pump power can be reduced if the Er is excited via the aromatic part of the complex, which has a higher absorption cross section. In Chapter 3 a lissamine-functionalised neodymium complex is studied in which the highly absorbing lissamine acts as a sensitiser. The lissamine is first excited into the singlet state from which intersystem crossing to the triplet state can take place. From there it can transfer its energy to the Nd ion by a Dexter transfer mechanism. Room-temperature photoluminescence at 890, 1060, and 1340 nm from Nd is observed, together with luminescence from the lissamine sensitiser at 600 nm. Photodegradation of the lissamine sensitiser is observed, which is studied in more detail in Chapter 4. The observed change in time of the

  14. Fiber-optic thermometer application of thermal radiation from rare-earth end-doped SiO{sub 2} fiber

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Katsumata, Toru, E-mail: katsumat@toyo.jp; Morita, Kentaro; Komuro, Shuji

    2014-08-15

    Visible light thermal radiation from SiO{sub 2} glass doped with Y, La, Ce, Pr, Nd, Eu, Tb, Dy, Ho, Er, Tm, Yb, and Lu were studied for the fiber-optic thermometer application based on the temperature dependence of thermal radiation. Thermal radiations according to Planck's law of radiation are observed from the SiO{sub 2} fibers doped with Y, La, Ce, Pr, Eu, Tb, and Lu at the temperature above 1100 K. Thermal radiations due to f-f transitions of rare-earth ions are observed from the SiO{sub 2} fibers doped with Nd, Dy, Ho, Er, Tm, and Yb at the temperature above 900more » K. Peak intensities of thermal radiations from rare-earth doped SiO{sub 2} fibers increase sensitively with temperature. Thermal activation energies of thermal radiations by f-f transitions seen in Nd, Dy, Ho, Er, Tm, and Yb doped SiO{sub 2} fibers are smaller than those from SiO{sub 2} fibers doped with Y, La, Ce, Pr, Eu, Tb, and Lu. Thermal radiation due to highly efficient f-f transitions in Nd, Dy, Ho, Er, Tm, and Yb ions emits more easily than usual thermal radiation process. Thermal radiations from rare-earth doped SiO{sub 2} are potentially applicable for the fiber-optic thermometry above 900 K.« less

  15. All-optical control of long-lived nuclear spins in rare-earth doped nanoparticles.

    PubMed

    Serrano, D; Karlsson, J; Fossati, A; Ferrier, A; Goldner, P

    2018-05-29

    Nanoscale systems that coherently couple to light and possess spins offer key capabilities for quantum technologies. However, an outstanding challenge is to preserve properties, and especially optical and spin coherence lifetimes, at the nanoscale. Here, we report optically controlled nuclear spins with long coherence lifetimes (T 2 ) in rare-earth-doped nanoparticles. We detect spins echoes and measure a spin coherence lifetime of 2.9 ± 0.3 ms at 5 K under an external magnetic field of 9 mT, a T 2 value comparable to those obtained in bulk rare-earth crystals. Moreover, we achieve spin T 2 extension using all-optical spin dynamical decoupling and observe high fidelity between excitation and echo phases. Rare-earth-doped nanoparticles are thus the only nano-material in which optically controlled spins with millisecond coherence lifetimes have been reported. These results open the way to providing quantum light-atom-spin interfaces with long storage time within hybrid architectures.

  16. Rare Earth Doped Yttrium Aluminum Garnet (YAG) Selective Emitters

    NASA Technical Reports Server (NTRS)

    Chubb, Donald L.; Pal, AnnaMarie T.; Patton, Martin O.; Jenkins, Phillip P.

    1999-01-01

    As a result of their electron structure, rare earth ions in crystals at high temperature emit radiation in several narrow bands rather than in a continuous blackbody manner. This study presents a spectral emittance model for films and cylinders of rare earth doped yttrium aluminum garnets. Good agreement between experimental and theoretical film spectral emittances was found for erbium and holmium aluminum garnets. Spectral emittances of films are sensitive to temperature differences across the film. For operating conditions of interest, the film emitter experiences a linear temperature variation whereas the cylinder emitter has a more advantageous uniform temperature. Emitter efficiency is also a sensitive function of temperature. For holminum aluminum garnet film the efficiency is 0.35 at 1446K but only 0.27 at 1270 K.

  17. Rare earth doped M-type hexaferrites; ferromagnetic resonance and magnetization dynamics

    NASA Astrophysics Data System (ADS)

    Sharma, Vipul; Kumari, Shweta; Kuanr, Bijoy K.

    2018-05-01

    M-type hexagonal barium ferrites come in the category of magnetic material that plays a key role in electromagnetic wave propagation in various microwave devices. Due to their large magnetic anisotropy and large magnetization, their operating frequency exceeds above 50 GHz. Doping is a way to vary its magnetic properties to such an extent that its ferromagnetic resonance (FMR) response can be tuned over a broad frequency band. We have done a complete FMR study of rare earth elements neodymium (Nd) and samarium (Sm), with cobalt (Co) as base, doped hexaferrite nanoparticles (NPs). X-ray diffractometry, vibrating sample magnetometer (VSM), and ferromagnetic resonance (FMR) techniques were used to characterize the microstructure and magnetic properties of doped hexaferrite nanoparticles. Using proper theoretical electromagnetic models, various parameters are extracted from FMR data which play important role in designing and fabricating high-frequency microwave devices.

  18. Recent Advances of Rare-Earth Ion Doped Luminescent Nanomaterials in Perovskite Solar Cells.

    PubMed

    Qiao, Yu; Li, Shuhan; Liu, Wenhui; Ran, Meiqing; Lu, Haifei; Yang, Yingping

    2018-01-15

    Organic-inorganic lead halide based perovskite solar cells have received broad interest due to their merits of low fabrication cost, a low temperature solution process, and high energy conversion efficiencies. Rare-earth (RE) ion doped nanomaterials can be used in perovskite solar cells to expand the range of absorption spectra and improve the stability due to its upconversion and downconversion effect. This article reviews recent progress in using RE-ion-doped nanomaterials in mesoporous electrodes, perovskite active layers, and as an external function layer of perovskite solar cells. Finally, we discuss the challenges facing the effective use of RE-ion-doped nanomaterials in perovskite solar cells and present some prospects for future research.

  19. Recent Advances of Rare-Earth Ion Doped Luminescent Nanomaterials in Perovskite Solar Cells

    PubMed Central

    Qiao, Yu; Li, Shuhan; Liu, Wenhui; Ran, Meiqing; Lu, Haifei

    2018-01-01

    Organic-inorganic lead halide based perovskite solar cells have received broad interest due to their merits of low fabrication cost, a low temperature solution process, and high energy conversion efficiencies. Rare-earth (RE) ion doped nanomaterials can be used in perovskite solar cells to expand the range of absorption spectra and improve the stability due to its upconversion and downconversion effect. This article reviews recent progress in using RE-ion-doped nanomaterials in mesoporous electrodes, perovskite active layers, and as an external function layer of perovskite solar cells. Finally, we discuss the challenges facing the effective use of RE-ion-doped nanomaterials in perovskite solar cells and present some prospects for future research. PMID:29342950

  20. Modifying the size and uniformity of upconversion Yb/Er:NaGdF4 nanocrystals through alkaline-earth doping.

    PubMed

    Lei, Lei; Chen, Daqin; Huang, Ping; Xu, Ju; Zhang, Rui; Wang, Yuansheng

    2013-11-21

    NaGdF4 is regarded as an ideal upconversion (UC) host material for lanthanide (Ln(3+)) activators because of its unique crystal structure, high Ln(3+) solubility, low phonon energy and high photochemical stability, and Ln(3+)-doped NaGdF4 UC nanocrystals (NCs) have been widely investigated as bio-imaging and magnetic resonance imaging agents recently. To realize their practical applications, controlling the size and uniformity of the monodisperse Ln(3+)-doped NaGdF4 UC NCs is highly desired. Unlike the routine routes by finely adjusting the multiple experimental parameters, herein we provide a facile and straightforward strategy to modify the size and uniformity of NaGdF4 NCs via alkaline-earth doping for the first time. With the increase of alkaline-earth doping content, the size of NaGdF4 NCs increases gradually, while the size-uniformity is still retained. We attribute this "focusing" of size distribution to the diffusion controlled growth of NaGdF4 NCs induced by alkaline-earth doping. Importantly, adopting the Ca(2+)-doped Yb/Er:NaGdF4 NCs as cores, the complete Ca/Yb/Er:NaGdF4@NaYF4 core-shell particles with excellent size-uniformity can be easily achieved. However, when taking the Yb/Er:NaGdF4 NCs without Ca(2+) doping as cores, they could not be perfectly covered by NaYF4 shells, and the obtained products are non-uniform in size. As a result, the UC emission intensity of the complete core-shell NCs increases by about 30 times in comparison with that of the cores, owing to the effective surface passivation of the Ca(2+)-doped cores and therefore protection of Er(3+) in the cores from the non-radiative decay caused by surface defects, whereas the UC intensity of the incomplete core-shell NCs is enhanced by only 3 times.

  1. Porous silicon - rare earth doped xerogel and glass composites

    NASA Astrophysics Data System (ADS)

    Balakrishnan, S.; Gun'ko, Yurii K.; Perova, T. S.; Rafferty, A.; Astrova, E. V.; Moore, R. A.

    2005-06-01

    The development of components for photonics applications is growing exponentially. The sol-gel method is now recognised as a convenient and flexible way to deposit oxide or glass films on a variety of hosts, including porous silicon. In the present work we incorporated erbium and europium doped xerogel into porous silicon and developed new porous silicon - rare earth doped glass composites. Various characteris-ation techniques including FTIR, Raman Spectroscopy, Thermal Gravimetric Analysis and Scanning Electron Microscopy were employed in this work.

  2. Influence of rare earth doping on thermoelectric properties of SrTiO3 ceramics

    NASA Astrophysics Data System (ADS)

    Liu, J.; Wang, C. L.; Li, Y.; Su, W. B.; Zhu, Y. H.; Li, J. C.; Mei, L. M.

    2013-12-01

    Thermoelectric properties of SrTiO3 ceramics, doped with different rare earth elements, were investigated in this work. It's found that the ionic radius of doping elements plays an important role on thermoelectric properties: SrTiO3 ceramics doped with large rare earth ions (such as La, Nd, and Sm) exhibit large power factors, and those doped with small ions (such as Gd, Dy, Er, and Y) exhibit low thermal conductivities. Therefore, a simple approach for enhancing the thermoelectric performance of SrTiO3 ceramics is proposed: mainly doped with large ions to obtain a large power factor and, simultaneously, slightly co-doped with small ions to obtain a low thermal conductivity. Based on this rule, Sr0.8La0.18Yb0.02TiO3 ceramics were prepared, whose ZT value at 1 023 K reaches 0.31, increasing by a factor of 19% compared with the single-doped counterpart Sr0.8La0.2TiO3 (ZT = 0.26).

  3. Exploring high power, extreme wavelength operating potential of rare-earth-doped silica fiber

    NASA Astrophysics Data System (ADS)

    Zhou, Pu; Li, Ruixian; Xiao, Hu; Huang, Long; Zhang, Hanwei; Leng, Jinyong; Chen, Zilun; Xu, Jiangmin; Wu, Jian; Wang, Xiong

    2017-08-01

    Ytterbium-doped fiber laser (YDFL) and Thulium doped fiber laser (TDFL) have been two kinds of the most widely studied fiber laser in recent years. Although both silica-based Ytterbium-doped fiber and Thulium doped fiber have wide emission spectrum band (more than 200 nm and 400 nm, respectively), the operation spectrum region of previously demonstrated high power YDFL and TDFL fall into 1060-1100 nm and 1900-2050nm. Power scaling of YDFL and TDFL operates at short-wavelength or long-wavelength band, especially for extreme wavelength operation, although is highly required in a large variety of application fields, is quite challenging due to small net gain and strong amplified spontaneous emission (ASE). In this paper, we will present study on extreme wavelength operation of high power YDFL and TDFL in our group. Comprehensive mathematical models are built to investigate the feasibility of high power operation and propose effective technical methods to achieve high power operation. We have achieved (1) Diodepumped 1150nm long wavelength YDFL with 120-watt level output power (2) Diode-pumped 1178nm long wavelength YDFL operates at high temperature with 30-watt level output power (3) Random laser pumped 2153nm long wavelength TDFL with 20-watt level output power (4) Diode-pumped 1018nm short wavelength YDFL with a record 2 kilowatt output power is achieved by using home-made fiber combiner.

  4. Interfacing superconducting qubits and telecom photons via a rare-earth-doped crystal.

    PubMed

    O'Brien, Christopher; Lauk, Nikolai; Blum, Susanne; Morigi, Giovanna; Fleischhauer, Michael

    2014-08-08

    We propose a scheme to couple short single photon pulses to superconducting qubits. An optical photon is first absorbed into an inhomogeneously broadened rare-earth doped crystal using controlled reversible inhomogeneous broadening. The optical excitation is then mapped into a spin state using a series of π pulses and subsequently transferred to a superconducting qubit via a microwave cavity. To overcome the intrinsic and engineered inhomogeneous broadening of the optical and spin transitions in rare-earth doped crystals, we make use of a special transfer protocol using staggered π pulses. We predict total transfer efficiencies on the order of 90%.

  5. Structure and Magnetic Properties of Rare Earth Doped Transparent Alumina

    NASA Astrophysics Data System (ADS)

    Limmer, Krista; Neupane, Mahesh; Chantawansri, Tanya

    Recent experimental studies of rare earth (RE) doped alumina suggest that the RE induced novel phase-dependent structural and magnetic properties. Motivated by these efforts, the effects of RE doping of alpha and theta alumina on the local structure, magnetic properties, and phase stability have been examined in this first principles study. Although a direct correlation between the magnetic field dependent materials properties observed experimentally and calculated from first principles is not feasible because of the applied field and the scale, the internal magnetic properties and other properties of the doped materials are evaluated. The RE dopants are shown to increase the substitutional site volume as well as increasingly distort the site structure as a function of ionic radii. Doping both the alpha (stable) and theta (metastable) phases enhanced the relative stability of the theta phase. The energetic doping cost and internal magnetic moment were shown to be a function of the electronic configuration of the RE-dopant, with magnetic moment directly proportional to the number of unpaired electrons and doping cost being inversely related.

  6. Research of green emitting rare-earth doped materials as potential quantum-cutter

    NASA Astrophysics Data System (ADS)

    Moine, Bernard; Beauzamy, Lena; Gredin, Patrick; Wallez, Gilles; Labeguerie, Jessica

    2008-03-01

    Because the energy of vacuum ultraviolet (VUV) photons emitted by xenon plasma discharge is more than twice that of visible photons, quantum cutting appears to be a promising process in rare-earth doped materials in order to obtain efficient phosphors for mercury free lighting devices as well as for plasma display panels. With an aim of application, it is important to take into account the emitting color of the developed new phosphors. Most of the time, this leads to use systems with at least two kinds of rare earth ions: one of them playing the role of energy sensitizer, and the other one being in charge of emitting the light of the suitable color. We focus our attention on green rare-earth doped materials. In order to get very efficient phosphors, it is not only necessary to get the highest possible quantum yield, but also to have a material characterized by a strong absorption in the VUV range. Borate and fluoride matrices doped with Dy 3+/Tb 3+ couples of ions are selected according to the position of the 5d band of dysprosium as green emitters.

  7. Improving soft magnetic properties of Mn-Zn ferrite by rare earth ions doping

    NASA Astrophysics Data System (ADS)

    Zhong, X. C.; Guo, X. J.; Zou, S. Y.; Yu, H. Y.; Liu, Z. W.; Zhang, Y. F.; Wang, K. X.

    2018-04-01

    Mn-Zn ferrites doped with different Sm2O3, Gd2O3, Ce2O3 or Y2O3 were prepared by traditional ceramic technology using industrial pre-sintered powders. A small amount of Sm2O3, Gd2O3, Ce2O3 or Y2O3 can significantly improve the microstructure and magnetic properties. The single spinel phase structure can be maintained with the doping amount up to 0.07 wt.%. A refined grain structure and uniform grain size distribution can be obtained by doping. For all rare earth oxides, a small amount of doping can significantly increase the permeability and reduce the coercivity and magnetic core loss. The optimized doping amount for Sm2O3 or Gd2O3 is 0.01 wt.%, while for Ce2O3 or Y2O3 is 0.03 wt.%. A further increase of the doping content will lead to reduced soft magnetic properties. The ferrite sample with 0.01 wt.% Sm2O3 exhibits the good magnetic properties with permeability, loss, and coercivity of 2586, 316 W/kg, and 24A/m, respectively, at 200 mT and 100 kHz. The present results indicate that rare earth doping can be suggested to be one of the effective ways to improve the performance of soft ferrites.

  8. Evaluation Of Ion Exchange For Fabrication Of Rare-Earth Doped Waveguides

    NASA Astrophysics Data System (ADS)

    Howell, Brian P.; Beerling, Timothy

    1987-01-01

    Rare earth ions are frequently incorporated into lasers by doping common glasses with the ions in the glass melt. This paper describes the potential of using diffusion of the rare earth ion from molten salt baths to incorporate it in the glass. The paper discusses the molten salts, the rare earths as a group, the diffusion phenomena, the glasses, and finally the interaction of all these to produce the process. General predictions of the waveguide profile and potential problems are presented.

  9. Rare-earth metal oxide doped transparent mesoporous silica plates under non-aqueous condition as a potential UV sensor.

    PubMed

    Lee, Sang-Joon; Park, Sung Soo; Lee, Sang Hyun; Hong, Sang-Hyun; Ha, Chang-Sik

    2013-11-01

    Transparent mesoporous silica plates doped with rare-earth metal oxide were prepared using solvent-evaporation method based on the self-organization between structure-directing agent and silicate in a non-aqueous solvent. A triblock copolymer, Pluronic (F127 or P123), was used as the structure-directing agent, while tetraethyl orthosilicate (TEOS) was used as a silica source. The pore diameter and the surface area of the mesoporous silica plate prepared with the optimized conditions were ca 40 A and 600 m2 g(-1), respectively, for both structure-directing agent. Rare-earth metal oxides (Eu, Tb, Tm oxide) in mesochannel were formed via one-step synthetic route based on the preparation method of a silica plate. Optical properties of rare-earth metal oxide-doped mesoporous silica plates were investigated by UV irradiation and photoluminescence (PL) spectroscopy. Under the exitation wavelength of 254 nm, the doped mesoporous silica plates emitted red, green and blue for Eu, Tb and Tm oxides, respectively. Rare-earth metal oxide-doped mesoporous silica plates showed enhanced PL intensity compared to that of the bulk rare-earth metal oxide.

  10. Self-propagating high-temperature synthesis and luminescent properties of ytterbium doped rare earth (Y, Sc, Lu) oxides nanopowders

    NASA Astrophysics Data System (ADS)

    Permin, D. A.; Novikova, A. V.; Balabanov, S. S.; Gavrishchuk, E. M.; Kurashkin, S. V.; Savikin, A. P.

    2018-04-01

    This paper describes a comparative study of structural and luminescent properties of 5%Yb-doped yttrium, scandium, and lutetium oxides (Yb:RE2O3) powders and ceramics fabricated by self-propagating high-temperature synthesis. According to X-ray diffractometry and electron microscopy the chosen method ensures preparation of low-agglomerated cubic Ctype crystal structured powders at one step. No crucial differences in luminescence spectra were found the Yb:RE2O3 powders and ceramics. It was shown that the emission lifetimes of the Yb:RE2O3 powders are lowered by crystal structure defects, while its values for ceramics samples are compared to that of monocrystals and more influenced by rare earth impurities.

  11. Effect of rare-earth doping on the thermoelectric and electrical transport properties of the transition metal pentatelluride hafnium pentatelluride

    NASA Astrophysics Data System (ADS)

    Lowhorn, Nathan Dane

    The transition metal pentatellurides HfTe5 and ZrTe5 have been observed to possess interesting electrical transport properties. High thermopower and low resistivity values result in high thermoelectric power factors. In addition, they possess anomalous transport behavior. The temperature dependence of the resistivity is semimetallic except for a large resistive peak as a function of temperature at around 75 K for HfTe5 and 145 K for ZrTe5. At a temperature corresponding to this peak, the thermopower crosses zero as it moves from large positive values to large negative values. This behavior has been found to be extremely sensitive to changes in the energetics of the system through influences such as magnetic field, stress, pressure, microwave radiation, and substitutional doping. This behavior has yet to be fully explained. Previous doping studies have shown profound and varied effects on the anomalous transport behavior. In this study we investigate the effect on the electrical resistivity, thermopower, and magnetoresistance of doping HfTe5 with rare-earth elements. We have grown single crystals of nominal Hf0.75RE 0.25Te5 where RE = Ce, Pr, Nd, Sm, Gd, Tb, Dy, and Ho. Electrical resistivity and thermopower data from about 10 K to room temperature are presented and discussed in terms of the thermoelectric properties. Doping with rare-earth elements of increasing atomic number leads to a systematic suppression of the anomalous transport behavior. Rare-earth doping also leads to an enhancement of the thermoelectric power factor over that of previously studied pentatellurides and the commonly used thermoelectric material Bi2Te3. For nominal Hf0.75Nd0.25Te5 and Hf0.75 Sm0.25Te5, values more than a factor of 2 larger than that Bi2Te3 are observed. In addition, suppression of the anomalous transport behavior leads to a suppression of the large magnetoresistive effect observed in the parent compounds. Rare-earth doping of HfTe5 has a profound impact on the anomalous

  12. PAL spectroscopy of rare-earth doped Ga-Ge-Te/Se glasses

    NASA Astrophysics Data System (ADS)

    Shpotyuk, Ya.; Ingram, A.; Shpotyuk, O.

    2016-04-01

    Positron annihilation lifetime (PAL) spectroscopy was applied for the first time to study free-volume void evolution in chalcogenide glasses of Ga-Ge-Te/Se cut-section exemplified by glassy Ga10Ge15Te75 and Ga10Ge15Te72Se3 doped with 500 ppm of Tb3+ or Pr3+. The collected PAL spectra reconstructed within two-state trapping model reveal decaying tendency in positron trapping efficiency in these glasses under rare-earth doping. This effect results in unchanged or slightly increased defect-related lifetimes τ2 at the cost of more strong decrease in I2 intensities, as well as reduced positron trapping rate in defects and fraction of trapped positrons. Observed changes are ascribed to rare-earth activated elimination of intrinsic free volumes associated mainly with negatively-charged states of chalcogen atoms especially those neighboring with Ga-based polyhedrons.

  13. Multiscale optical imaging of rare-earth-doped nanocomposites in a small animal model

    NASA Astrophysics Data System (ADS)

    Higgins, Laura M.; Ganapathy, Vidya; Kantamneni, Harini; Zhao, Xinyu; Sheng, Yang; Tan, Mei-Chee; Roth, Charles M.; Riman, Richard E.; Moghe, Prabhas V.; Pierce, Mark C.

    2018-03-01

    Rare-earth-doped nanocomposites have appealing optical properties for use as biomedical contrast agents, but few systems exist for imaging these materials. We describe the design and characterization of (i) a preclinical system for whole animal in vivo imaging and (ii) an integrated optical coherence tomography/confocal microscopy system for high-resolution imaging of ex vivo tissues. We demonstrate these systems by administering erbium-doped nanocomposites to a murine model of metastatic breast cancer. Short-wave infrared emissions were detected in vivo and in whole organ imaging ex vivo. Visible upconversion emissions and tissue autofluorescence were imaged in biopsy specimens, alongside optical coherence tomography imaging of tissue microstructure. We anticipate that this work will provide guidance for researchers seeking to image these nanomaterials across a wide range of biological models.

  14. Sensing Using Rare-Earth-Doped Upconversion Nanoparticles

    PubMed Central

    Hao, Shuwei; Chen, Guanying; Yang, Chunhui

    2013-01-01

    Optical sensing plays an important role in theranostics due to its capability to detect hint biochemical entities or molecular targets as well as to precisely monitor specific fundamental psychological processes. Rare-earth (RE) doped upconversion nanoparticles (UCNPs) are promising for these endeavors due to their unique frequency converting capability; they emit efficient and sharp visible or ultraviolet (UV) luminescence via use of ladder-like energy levels of RE ions when excited at near infrared (NIR) light that are silent to tissues. These features allow not only a high penetration depth in biological tissues but also a high detection sensitivity. Indeed, the energy transfer between UCNPs and biomolecular or chemical indicators provide opportunities for high-sensitive bio- and chemical-sensing. A temperature-sensitive change of the intensity ratio between two close UC bands promises them for use in temperature mapping of a single living cell. In this work, we review recent investigations on using UCNPs for the detection of biomolecules (avidin, ATP, etc.), ions (cyanide, mecury, etc.), small gas molecules (oxygen, carbon dioxide, ammonia, etc.), as well as for in vitro temperature sensing. We also briefly summarize chemical methods in synthesizing UCNPs of high efficiency that are important for the detection limit. PMID:23650480

  15. Rare earth doped III-nitride semiconductors for spintronic and optoelectronic applications (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Palai, Ratnakar

    2016-10-01

    Since last four decades the information and communication technologies are relying on the semiconductor materials. Currently a great deal of attention is being focused on adding spin degree-of-freedom into semiconductor to create a new area of solid-state electronics, called spintronics. In spintronics not only the current but also its spin state is controlled. Such materials need to be good semiconductors for easy integration in typical integrated circuits with high sensitivity to the spin orientation, especially room temperature ferromagnetism being an important desirable property. GaN is considered to be the most important semiconductor after silicon. It is widely used for the production of green, blue, UV, and white LEDs in full color displays, traffic lights, automotive lightings, and general room lighting using white LEDs. GaN-based systems also show promise for microwave and high power electronics intended for radar, satellite, wireless base stations and spintronic applications. Rare earth (Yb, Eu, Er, and Tm) doped GaN shows many interesting optoelectronic and magnetoptic properties e. g. sharp emission from UV through visible to IR, radiation hardness, and ferromagnetism. The talk will be focused on fabrication, optoelectronic (photoluminescence, cathodeluminescence, magnetic, and x-ray photoelectron spectroscopy) properties of some rare earth doped GaN and InGaN semiconductor nanostructures grown by plasma assisted molecular beam epitaxy (MBE) and future applications.

  16. Rare-earth-doped optical-fiber core deposition using full vapor-phase SPCVD process

    NASA Astrophysics Data System (ADS)

    Barnini, A.; Robin, T.; Cadier, B.; Aka, G.; Caurant, D.; Gotter, T.; Guyon, C.; Pinsard, E.; Guitton, P.; Laurent, A.; Montron, R.

    2017-02-01

    One key parameter in the race toward ever-higher power fiber lasers remains the rare earth doped optical core quality. Modern Large Mode Area (LMA) fibers require a fine radial control of the core refractive index (RI) close to the silica level. These low RI are achieved with multi-component materials that cannot be readily obtained using conventional solution doping based Modified Chemical Vapor Deposition (MCVD) technology. This paper presents a study of such optical material obtained through a full-vapor phase Surface Plasma Chemical Vapor Deposition (SPCVD). The SPCVD process generates straight glassy films on the inner surface of a thermally regulated synthetic silica tube under vacuum. The first part of the presented results points out the feasibility of ytterbium-doped aluminosilicate fibers by this process. In the second part we describe the challenge controlling the refractive index throughout the core diameter when using volatile fluorine to create efficient LMA fiber profiles. It has been demonstrated that it is possible to counter-act the loss of fluorine at the center of the core by adjusting the core composition locally. Our materials yielded, when used in optical fibers with numerical apertures ranging from 0.07 to 0.09, power conversion efficiency up to 76% and low background losses below 20 dB/km at 1100nm. Photodarkening has been measured to be similar to equivalent MCVD based fibers. The use of cerium as a co-dopant allowed for a complete mitigation of this laser lifetime detrimental effect. The SPCVD process enables high capacity preforms and is particularly versatile when it comes to radial tailoring of both rare earth doping level and RI. Large core diameter preforms - up to 4mm - were successfully produced.

  17. Demonstration of ultra-low NA rare-earth doped step index fiber for applications in high power fiber lasers.

    PubMed

    Jain, Deepak; Jung, Yongmin; Barua, Pranabesh; Alam, Shaiful; Sahu, Jayanta K

    2015-03-23

    In this paper, we report the mode area scaling of a rare-earth doped step index fiber by using low numerical aperture. Numerical simulations show the possibility of achieving an effective area of ~700 um² (including bend induced effective area reduction) at a bend diameter of 32 cm from a 35 μm core fiber with a numerical aperture of 0.038. An effective single mode operation is ensured following the criterion of the fundamental mode loss to be lower than 0.1 dB/m while ensuring the higher order modes loss to be higher than 10 dB/m at a wavelength of 1060 nm. Our optimized modified chemical vapor deposition process in conjunction with solution doping process allows fabrication of an Yb-doped step index fiber having an ultra-low numerical aperture of ~0.038. Experimental results confirm a Gaussian output beam from a 35 μm core fiber validating our simulation results. Fiber shows an excellent laser efficiency of ~81%and aM² less than 1.1.

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

    NASA Astrophysics Data System (ADS)

    Zhang, Lei; Navrotsky, Alexandra

    2015-10-01

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

  19. Scintillation of rare earth doped fluoride nanoparticles

    NASA Astrophysics Data System (ADS)

    Jacobsohn, L. G.; McPherson, C. L.; Sprinkle, K. B.; Yukihara, E. G.; DeVol, T. A.; Ballato, J.

    2011-09-01

    The scintillation response of rare earth (RE) doped core/undoped (multi-)shell fluoride nanoparticles was investigated under x-ray and alpha particle irradiation. A significant enhancement of the scintillation response was observed with increasing shells due: (i) to the passivation of surface quenching defects together with the activation of the REs on the surface of the core nanoparticle after the growth of a shell, and (ii) to the increase of the volume of the nanoparticles. These results are expected to reflect a general aspect of the scintillation process in nanoparticles, and to impact radiation sensing technologies that make use of nanoparticles.

  20. Phase Transformation and Lattice Parameter Changes of Non-trivalent Rare Earth-Doped YSZ as a Function of Temperature

    NASA Astrophysics Data System (ADS)

    Jiang, Shengli; Huang, Xiao; He, Zhang; Buyers, Andrew

    2018-01-01

    To examine the effect of doping/co-doping on high-temperature phase compositions of YSZ, stand-alone YSZ and CeO2 and Nb2O5 co-doped YSZ samples were prepared using mechanical alloy and high-temperature sintering. XRD analysis was performed on these samples from room temperature to 1100 °C. The results show that the structure for the co-doped samples tends to be thermally stable when the test temperature is higher than a critical value. Monoclinic phase was dominant in Nb2O5 co-doped YSZ at temperatures lower than 600 °C, while for the YSZ and CeO2 co-doped YSZ, cubic/tetragonal phase was dominant in the whole test temperature range. The lattice parameters for all the samples increase with increasing test temperature generally. The lattice parameters for the two non-trivalent rare earth oxides co-doped YSZ show that the lattice parameter a for the cubic phase of the Ce4+ co-doped YSZ is consistently greater than that of 7YSZ which is related to the presence of larger radius of Ce4+ in the matrix. The lattice parameters a, b, c for the monoclinic phase of Ce4+ co-doped YSZ are much closer to each other than that of the Nb5+ co-doped YSZ, indicating the former has better tendency to form cubic/tetragonal phase, which is desired for vast engineering applications.

  1. Phase Transformation and Lattice Parameter Changes of Non-trivalent Rare Earth-Doped YSZ as a Function of Temperature

    NASA Astrophysics Data System (ADS)

    Jiang, Shengli; Huang, Xiao; He, Zhang; Buyers, Andrew

    2018-05-01

    To examine the effect of doping/co-doping on high-temperature phase compositions of YSZ, stand-alone YSZ and CeO2 and Nb2O5 co-doped YSZ samples were prepared using mechanical alloy and high-temperature sintering. XRD analysis was performed on these samples from room temperature to 1100 °C. The results show that the structure for the co-doped samples tends to be thermally stable when the test temperature is higher than a critical value. Monoclinic phase was dominant in Nb2O5 co-doped YSZ at temperatures lower than 600 °C, while for the YSZ and CeO2 co-doped YSZ, cubic/tetragonal phase was dominant in the whole test temperature range. The lattice parameters for all the samples increase with increasing test temperature generally. The lattice parameters for the two non-trivalent rare earth oxides co-doped YSZ show that the lattice parameter a for the cubic phase of the Ce4+ co-doped YSZ is consistently greater than that of 7YSZ which is related to the presence of larger radius of Ce4+ in the matrix. The lattice parameters a, b, c for the monoclinic phase of Ce4+ co-doped YSZ are much closer to each other than that of the Nb5+ co-doped YSZ, indicating the former has better tendency to form cubic/tetragonal phase, which is desired for vast engineering applications.

  2. Numerical simulations of the optical gain of crystalline fiber doped by rare earth and transition ion

    NASA Astrophysics Data System (ADS)

    Daoui, A. K.; Boubir, B.; Adouane, A.; Demagh, N.; Ghoumazi, M.

    2015-02-01

    A fiber laser is a laser whose gain medium is a doped fiber, although lasers whose cavity is made wholly of fibers have also been called fiber lasers. The gain media in a fiber laser is usually fiber doped with rare-earth ions, such as erbium (Er), neodymium (Nd), ytterbium (Yb), thulium (Tm), or praseodymium (Pr), which is doped into the core of the optical fiber, similar to those used to transmit telecommunications signals. Fiber lasers find many applications in materials processing, including cutting, welding, drilling, and marking metal. To maximize their market penetration, it is necessary to increase their output power. In this work, we present a detailed study based on the numerical simulation using MATLAB, of one of the principal characteristics of a fiber laser doped with rare earth ions and transition ion. The gain depends on several parameters such as the length of the doped fiber, the density, the pump power, noise, etc.). The used program resolves the state equations in this context together with those governing the light propagation phenomena. The developed code can also be used to study the dynamic operating modes of a doped fiber laser.

  3. The influence of different alkaline earth oxides on the structural and optical properties of undoped, Ce-doped, Sm-doped, and Sm/Ce co-doped lithium alumino-phosphate glasses

    NASA Astrophysics Data System (ADS)

    Othman, H. A.; Arzumanyan, G. M.; Möncke, D.

    2016-12-01

    Undoped, singly Sm doped, Ce doped, and Sm/Ce co-doped lithium alumino-phosphate glasses with different alkaline earth modifiers were prepared by melt quenching. The structure of the prepared glasses was investigated by FT-IR and Raman, as well as by optical spectroscopy. The effect of the optical basicity of the host glass matrix on the added active dopants was studied, as was the effect doping had on the phosphate structural units. The optical edge shifts toward higher wavelengths with an increase in the optical basicity due to the increased polarizability of the glass matrix, but also with increasing CeO2 concentration as a result of Ce3+/Ce4+ inter valence charge transfer (IV-CT) absorption. The optical band gap for direct and indirect allowed transitions was calculated for the undoped glasses. The glass sample containing Mg2+ modifier ions is found to have the highest value (4.16 eV) for the optical band gap while Ba2+ has the lowest value (3.61 eV). The change in the optical band gap arises from the structural changes and the overall polarizability (optical basicity). Refractive index, molar refractivity Rm and molar polarizability αm values increase with increasing optical basicity of the glasses. The characteristic absorption peaks of Sm3+ were also investigated. For Sm/Ce co-doped glasses, especially at high concentration of CeO2, the absorption of Ce3+ hinders the high energy absorption of Sm3+ and this effect becomes more obvious with increasing optical basicity.

  4. Multiscale optical imaging of rare-earth-doped nanocomposites in a small animal model.

    PubMed

    Higgins, Laura M; Ganapathy, Vidya; Kantamneni, Harini; Zhao, Xinyu; Sheng, Yang; Tan, Mei-Chee; Roth, Charles M; Riman, Richard E; Moghe, Prabhas V; Pierce, Mark C

    2018-03-01

    Rare-earth-doped nanocomposites have appealing optical properties for use as biomedical contrast agents, but few systems exist for imaging these materials. We describe the design and characterization of (i) a preclinical system for whole animal in vivo imaging and (ii) an integrated optical coherence tomography/confocal microscopy system for high-resolution imaging of ex vivo tissues. We demonstrate these systems by administering erbium-doped nanocomposites to a murine model of metastatic breast cancer. Short-wave infrared emissions were detected in vivo and in whole organ imaging ex vivo. Visible upconversion emissions and tissue autofluorescence were imaged in biopsy specimens, alongside optical coherence tomography imaging of tissue microstructure. We anticipate that this work will provide guidance for researchers seeking to image these nanomaterials across a wide range of biological models. (2018) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE).

  5. Rare-earth doped nanocomposites enable multiscale targeted short-wave infrared imaging of metastatic breast cancer

    NASA Astrophysics Data System (ADS)

    Pierce, Mark C.; Higgins, Laura M.; Ganapathy, Vidya; Kantamneni, Harini; Riman, Richard E.; Roth, Charles M.; Moghe, Prabhas V.

    2017-02-01

    We are investigating the ability of targeted rare earth (RE) doped nanocomposites to detect and track micrometastatic breast cancer lesions to distant sites in pre-clinical in vivo models. Functionalizing RE nanocomposites with AMD3100 promotes targeting to CXCR4, a recognized marker for highly metastatic disease. Mice were inoculated with SCP-28 (CXCR4 positive) and 4175 (CXCR4 negative) cell lines. Whole animal in vivo SWIR fluorescence imaging was performed after bioluminescence imaging confirmed tumor burden in the lungs. Line-scanning confocal fluorescence microscopy provided high-resolution imaging of RE nanocomposite uptake and native tissue autofluorescence in ex vivo lung specimens. Co-registered optical coherence tomography imaging allowed assessment of tissue microarchitecture. In conclusion, multiscale optical molecular imaging can be performed in pre-clinical models of metastatic breast cancer, using targeted RE-doped nanocomposites.

  6. Thermoluminescent properties of rare earth doped lithium strontium borate phosphors

    NASA Astrophysics Data System (ADS)

    Jakathamani, S.; Annalakshmi, O.; Jose, M. T.

    2018-04-01

    Thermoluminescence (TL) of borates is remarkable in the field of radiation dosimetry because they can detect both neutron and gamma radiations. Usually, the TL efficiency of pure borates is low and hence dopants have to be added to increase their TL output. Their sensitivity and thermal stability vary widely and depend strongly on the preparation method. In this study polycrystalline powders of different rare earth doped thermoluminescent phosphors of Lithium Strontium borate (LSB) were synthesized by solid state sintering technique. Among the different rare earth dopants, the phosphor doped with cerium was found to have a simple glow curve structure with a dosimetric peak at around 265°C for a heating rate of 5°C/s. In order to study the effect of dopant on the TL characteristics, LSB phosphor with different concentrations of Ce dopant was synthesized and the TL intensity was found to be maximum for a dopant concentration of 0.7 mol%. All other important dosimetric characteristics like dose response and fading were carried out for the LSB:Ce (0.7 mol%) phosphor. Kinetic parameters like trap depth and frequency factor were determined using Peak shape method from Chen's equation.

  7. Lanthanide Contraction Effect In Magnetic Thermoelectric Materials Of Rare Earth-doped Bi1.5Pb0.5Ca2Co2O8

    NASA Astrophysics Data System (ADS)

    Sutjahja, Inge Magdalena; Akbar, Taufik; Nugroho, Agung

    2010-12-01

    We report in this paper the result of synthesis and crystal structure characterization of magnetic thermoelectric materials of rare-earth-doped Bi1.5Pb0.5Ca2Co2O8, namely Bi1.5Pb0.5Ca1.9RE0.1Co2O8 (RE = La, Pr, Sm, Eu, Gd, Ho). Single phase samples have been prepared by solid state reaction process using precursors of Bi2O3, PbO, CaCO3, RE2O3, and Co3O4. The precursors were pulverized, calcinated, and sintered in air at various temperatures for several hours. Analysis of XRD data shows that Bi1.5Pb0.5Ca1.9RE0.1Co2O8 compound is a layered system consisting of an alternate stack of CoO2 layer and Bi2Sr2O4 block along the c-axis. The misfit structure along b-direction is revealed from the difference of the b-axis length belonging to two sublattices, namely hexagonal CdI2-type CoO2 layer and rock-salt (RS) NaCl-type Bi2Sr2O4 block, while they possess the common a- and c-axis lattice parameters and β angles. The overall crystal structure parameters (a, b, and c) increases with type of doping from La to Ho, namely by decreasing the ionic radii of rare-earth ion. We discuss this phenomenon in terms of the lanthanide contraction, an effect commonly found in the rare-earth compound, results from poor shielding of nuclear charge by 4f electrons. In addition, the values of b-lattice parameters in these rare-earth doped samples are almost the same with those belongs to undoped parent compound (Bi1.5Pb0.5Sr2Co2O8) and its related Y-doped (Bi1.5Pb0.5Ca1.9Y0.1Co2O8) samples, while the c-values reduced significantly in rare-earth doped samples, with opposite trend with those of variation of a-axis length. Morevover, the misfit degree in rare-earth doped compound is higher in compared to parent compound and Y-doped samples. We argue that these structural changes induced by rare-earth doping may provide information for the variation of electronic structure of Co-ions (Co3+ and Co4+), in particular their different spin states of low-spin, intermediate-spin, and high-spin. This, in

  8. Novel online security system based on rare-earth-doped glass microbeads

    NASA Astrophysics Data System (ADS)

    Officer, Simon; Prabhu, G. R.; Pollard, Pat; Hunter, Catherine; Ross, Gary A.

    2004-06-01

    A novel fluorescent security label has been produced that could replace numerous conventional fluorescent dyes in document security. This label utilizes rare earth ions doped in a borosilicate glass matrix to produce sharp spectral fluorescence peaks with characteristic long lifetimes due to the rare earth ions. These are subsequently detected by an online detection system based on fluorescence and the long lifetimes to avoid any interference from other fluorophores present in the background. Security is further enhanced by the interaction of the rare earth ions with each other and the effect of the host on the emission spectra and therefore the number of permutations that could be produced. This creates a very secure label with various applications for the security market.

  9. Imposing long-range ferromagnetic order in rare-earth-doped magnetic topological-insulator heterostructures

    NASA Astrophysics Data System (ADS)

    Duffy, L. B.; Frisk, A.; Burn, D. M.; Steinke, N.-J.; Herrero-Martin, J.; Ernst, A.; van der Laan, G.; Hesjedal, T.

    2018-05-01

    The combination of topological properties and magnetic order can lead to new quantum states and exotic physical phenomena, such as the quantum anomalous Hall (QAH) effect. The size of the magnetic gap in the topological surface states, key for the robust observation of the QAH state, scales with the magnetic moment of the doped three-dimensional topological insulator (TI). The pioneering transition-metal doped (Sb,Bi ) 2(Se,Te ) 3 thin films only allow for the observation of the QAH effect up to some 100 mK, despite the much higher magnetic ordering temperatures. On the other hand, high magnetic moment materials, such as rare-earth-doped (Sb,Bi ) 2(Se,Te ) 3 thin films, show large moments but no long-range magnetic order. Proximity coupling and interfacial effects, multiplied in artificial heterostructures, allow for the engineering of the electronic and magnetic properties. Here, we show the successful growth of high-quality Dy:Bi2Te3 /Cr:Sb2Te3 thin film heterostructures. Using x-ray magnetic spectroscopy we demonstrate that high transition temperature Cr:Sb2Te3 can introduce long-range magnetic order in high-moment Dy:Bi2Te3 —up to a temperature of 17 K—in excellent agreement with first-principles calculations, which reveal the origin of the long-range magnetic order in a strong antiferromagnetic coupling between Dy and Cr magnetic moments at the interface extending over several layers. Engineered magnetic TI heterostructures may be an ideal materials platform for observing the QAH effect at liquid He temperatures and above.

  10. Magnetic and magnetoelectric properties of NdCrTiO5 revealed by systematically rare-earth doping

    NASA Astrophysics Data System (ADS)

    Li, Qing; Feng, Zhenjie; Cheng, Cheng; Wang, Bojie; Chu, Hao; Huang, Ping; Wang, Difei; Qian, Xiaolong; Yu, Chuan; Wang, Guohua; Deng, Dongmei; Jing, Chao; Cao, Shixun; Zhang, Jincang

    2018-01-01

    We have systematically synthesized polycrystalline samples of Nd0.9A0.1CrTiO5 (A = Pr, Nd, Gd, Dy, Er, Tm, and Yb), and have investigated their crystal structure, polarization and magnetic susceptibility. The polarization values of doped samples are suppressed comparing to pure NdCrTiO5 sample, which indicates that the polarization is highly dependence with the magnetic moments of doping ions. The TN of Cr-Cr in Nd0.9A0.1CrTiO5 are dominated by both the suppression effect caused by doped magnetic moment increment and the enhancement effect caused by c axis contracting. We conclude that the magnetic moments in the rare-earth Nd sites play an important role in the magnetoelectric effect in NdCrTiO5 family. The substitution effect discussion here can help us well understand the intrinsic mechanism and provide a possible guidance in exploring new magnetoelectric coupling systems.

  11. Microstructural and electrical characteristics of rare earth oxides doped ZnO varistor films

    NASA Astrophysics Data System (ADS)

    Jiao, Lei; Mei, Yunzhu; Xu, Dong; Zhong, Sujuan; Ma, Jia; Zhang, Lei; Bao, Li

    2018-02-01

    ZnO-Bi2O3 varistor films doped with two kinds of rare earth element oxides (Lu2O3 and Yb2O3) were prepared by the sol-gel method. The effects of Lu2O3/Yb2O3 doping on the microstructure and electrical characteristics of ZnO-Bi2O3 varistor films were investigated. All samples show a homogenized morphology and an improved nonlinear relationship between the electric field (E) and current density (I). Both Yb2O3 and Lu2O3 doping can decrease the grain size of ZnO-Bi2O3 varistor films and improve the electrical properties, which have a positive effect on the development of ZnO varistor ceramics. Yb2O3 doping significantly increases the dielectric constant at low frequency. 0.2 mol. % Yb2O3 doped ZnO-Bi2O3 varistor films exhibit the highest nonlinear coefficient (2.5) and the lowest leakage current (328 μA) among Lu2O3/Yb2O3 doped ZnO-Bi2O3 varistor films. Similarly, 0.1 mol. % Lu2O3 doping increases the nonlinear coefficient to 1.9 and decrease the leakage current to 462 μA.

  12. Rare-earth doped transparent nano-glass-ceramics: a new generation of photonic integrated devices

    NASA Astrophysics Data System (ADS)

    Rodríguez-Armas, Vicente Daniel; Tikhomirov, Victor K.; Méndez-Ramos, Jorge; Yanes, Angel C.; Del-Castillo, Javier; Furniss, David; Seddon, Angela B.

    2007-05-01

    We report on optical properties and prospect applications on rare-earth doped oxyfluoride precursor glass and ensuing nano-glass-ceramics. We find out the spectral optical gain of the nano-glass-ceramics and show that its flatness and breadth are advantageous as compared to contemporary used erbium doped optical amplifiers. We present the possibility of flat gain cross-section erbium doped waveguide amplifiers as short 'chip', all-optical, devices capable of dense wavelength division multiplexing, including the potential for direct writing of these devices inside bulk glasses for three-dimensional photonic integration. We carried out a comparative study of the up-conversion luminescence in Er 3+-doped and Yb 3+-Er 3+-Tm 3+ co-doped samples, which indicates that these materials can be used as green/red tuneable up-conversion phosphors and white light simulation respectively. Observed changes in the spectra of the up-conversion luminescence provide a tool for tuning the colour opening the way for producing 3-dimensional optical recording.

  13. Europium-doped mesoporous titania thin films: rare-earth locations and emission fluctuations under illumination.

    PubMed

    Leroy, Celine Marie; Cardinal, Thierry; Jubera, Veronique; Treguer-Delapierre, Mona; Majimel, Jerome; Manaud, Jean Pierre; Backov, Renal; Boissière, Cedric; Grosso, David; Sanchez, Clement; Viana, Bruno; Pellé, Fabienne

    2008-10-06

    Herein, Eu(III)-doped 3D mesoscopically ordered arrays of mesoporous and nanocrystalline titania are prepared and studied. The rare-earth-doped titania thin films-synthesized via evaporation-induced self-assembly (EISA)-are characterized by using environmental ellipsoporosimetry, electronic microscopy (i.e. high-resolution scanning electron microscopy, HR-SEM, and transmission electron microscopy, HR-TEM), X-ray diffraction, and luminescence spectroscopy. Structural characterizations show that high europium-ion loadings can be incorporated into the titanium-dioxide walls without destroying the mesoporous arrangement. The luminescence properties of Eu(III) are investigated by using steady-state and time-resolved spectroscopy via excitation of the Eu(III) ions through the titania host. Using Eu(III) luminescence as a probe, the europium-ion sites can be addressed with at least two different environments within the mesoporous framework, namely, a nanocrystalline environment and a glasslike one. Emission fluctuations ((5)D(0)-->(7)F(2)) are observed upon continuous UV excitation in the host matrix. These fluctuations are attributed to charge trapping and appear to be strongly dependent on the amount of europium and the level of crystallinity.

  14. Growth of rare-earth doped single crystal yttrium aluminum garnet fibers

    NASA Astrophysics Data System (ADS)

    Bera, Subhabrata; Nie, Craig D.; Harrington, James A.; Cheng, Long; Rand, Stephen C.; Li, Yuan; Johnson, Eric G.

    2018-02-01

    Rare-earth doped single crystal (SC) yttrium aluminum garnet (YAG) fibers have great potential as high-power laser gain media. SC fibers combine the superior material properties of crystals with the advantages of a fiber geometry. Improving processing techniques, growth of low-loss YAG SC fibers have been reported. A low-cost technique that allows for the growth of optical quality Ho:YAG single crystal (SC) fibers with different dopant concentrations have been developed and discussed. This technique is a low-cost sol-gel based method which offers greater flexibility in terms of dopant concentration. Self-segregation of Nd ions in YAG SC fibers have been observed. Such a phenomenon can be utilized to fabricate monolithic SC fibers with graded index.

  15. Use of thulium-sensitized rare earth-doped low phonon energy crystalline hosts for IR sources.

    PubMed

    Ganem, Joseph; Bowman, Steven R

    2013-11-01

    Crystalline hosts with low phonon energies enable novel energy transfer processes when doped with rare earth ions. Two applications of energy transfer for rare earth ions in thulium-sensitized low phonon energy crystals that result in infrared luminescence are discussed. One application is an endothermic, phonon-assisted cross-relaxation process in thulium-doped yttrium chloride that converts lattice phonons to infrared emission, which raises the possibility of a fundamentally new method for achieving solid-state optical cooling. The other application is an optically pumped mid-IR phosphor using thulium-praseodymium-doped potassium lead chloride that converts 805-nm diode light to broadband emission from 4,000 to 5,500 nm. These two applications in chloride crystals are discussed in terms of critical radii calculated from Forster-Dexter energy transfer theory. It is found that the critical radii for electric dipole-dipole interactions in low phonon energy chloride crystals are comparable to those in conventional oxide and fluoride crystals. It is the reduction in multi-phonon relaxation rates in chloride crystals that enable these additional energy transfer processes and infrared luminescence.

  16. Use of thulium-sensitized rare earth-doped low phonon energy crystalline hosts for IR sources

    PubMed Central

    2013-01-01

    Crystalline hosts with low phonon energies enable novel energy transfer processes when doped with rare earth ions. Two applications of energy transfer for rare earth ions in thulium-sensitized low phonon energy crystals that result in infrared luminescence are discussed. One application is an endothermic, phonon-assisted cross-relaxation process in thulium-doped yttrium chloride that converts lattice phonons to infrared emission, which raises the possibility of a fundamentally new method for achieving solid-state optical cooling. The other application is an optically pumped mid-IR phosphor using thulium-praseodymium-doped potassium lead chloride that converts 805-nm diode light to broadband emission from 4,000 to 5,500 nm. These two applications in chloride crystals are discussed in terms of critical radii calculated from Forster-Dexter energy transfer theory. It is found that the critical radii for electric dipole-dipole interactions in low phonon energy chloride crystals are comparable to those in conventional oxide and fluoride crystals. It is the reduction in multi-phonon relaxation rates in chloride crystals that enable these additional energy transfer processes and infrared luminescence. PMID:24180684

  17. Use of thulium-sensitized rare earth-doped low phonon energy crystalline hosts for IR sources

    NASA Astrophysics Data System (ADS)

    Ganem, Joseph; Bowman, Steven R.

    2013-11-01

    Crystalline hosts with low phonon energies enable novel energy transfer processes when doped with rare earth ions. Two applications of energy transfer for rare earth ions in thulium-sensitized low phonon energy crystals that result in infrared luminescence are discussed. One application is an endothermic, phonon-assisted cross-relaxation process in thulium-doped yttrium chloride that converts lattice phonons to infrared emission, which raises the possibility of a fundamentally new method for achieving solid-state optical cooling. The other application is an optically pumped mid-IR phosphor using thulium-praseodymium-doped potassium lead chloride that converts 805-nm diode light to broadband emission from 4,000 to 5,500 nm. These two applications in chloride crystals are discussed in terms of critical radii calculated from Forster-Dexter energy transfer theory. It is found that the critical radii for electric dipole-dipole interactions in low phonon energy chloride crystals are comparable to those in conventional oxide and fluoride crystals. It is the reduction in multi-phonon relaxation rates in chloride crystals that enable these additional energy transfer processes and infrared luminescence.

  18. Enhanced near-infrared photoacoustic imaging of silica-coated rare-earth doped nanoparticles.

    PubMed

    Sheng, Yang; Liao, Lun-De; Bandla, Aishwarya; Liu, Yu-Hang; Yuan, Jun; Thakor, Nitish; Tan, Mei Chee

    2017-01-01

    Near-infrared photoacoustic (PA) imaging is an emerging diagnostic technology that utilizes the tissue transparent window to achieve improved contrast and spatial resolution for deep tissue imaging. In this study, we investigated the enhancement effect of the SiO 2 shell on the PA property of our core/shell rare-earth nanoparticles (REs) consisting of an active rare-earth doped core of NaYF 4 :Yb,Er (REDNPs) and an undoped NaYF 4 shell. We observed that the PA signal amplitude increased with SiO 2 shell thickness. Although the SiO 2 shell caused an observed decrease in the integrated fluorescence intensity due to the dilution effect, fluorescence quenching of the rare earth emitting ions within the REDNPs cores was successfully prevented by the undoped NaYF 4 shell. Therefore, our multilayer structure consisting of an active core with successive functional layers was demonstrated to be an effective design for dual-modal fluorescence and PA imaging probes with improved PA property. The result from this work addresses a critical need for the development of dual-modal contrast agent that advances deep tissue imaging with high resolution and signal-to-noise ratio. Copyright © 2016 Elsevier B.V. All rights reserved.

  19. Atomic-Level Structure Studies of Rare-Earth Doped Sodium Phosphate Glasses Using High Energy X-Ray Diffraction and Complementary Techniques

    NASA Astrophysics Data System (ADS)

    Amir, Faisal

    The atomic-scale structure of a series of (RE2 O3)x ( Na2O)y ( P2O5)1- x-y glasses (RE = Pr, Nd, Er) where has been characterized by high-energy X-ray diffraction technique (HEXRD). In addition, differential thermal analysis (DTA), Fourier transform infrared (FTIR) spectroscopy, and absorption and emission spectroscopy in visible and near IR ranges have been used as supplementary tools to validate structural features obtained from HEXRD techniques.Structural features such as inter-atomic distances and coordination numbers and their dependence on the concentration of RE 2 O3 have been obtained by analyzing pair distribution functions (PDF) extracted from diffraction data. Coordination numbers for P-O, Na-O, O-O, and P-P were found to be independent of the RE 2 O3 concentration. In contrast, the RE-O coordination number varies between ≈ 8 and 7.2 as the RE2 O3 concentration increases from 0.005 to 0.05. The variation of the bond distance between large rare-earth ions (Pr, Nd) and small rare-earth ion (Er) is approximately 0.2 A, which is attributed to lanthanide contraction. The Na-O coordination number in these glasses was observed to ≈ 5.0 as the RE2 O 3 content increases. The overlapping correlation of RE-O, Na-O, and O-O in the same vicinity makes it difficult to calculate these coordination numbers. DTA measurements were used for the investigation of thermal characteristics of glasses. From these measurements, it is evident that the glass transition temperature increases with increasing the RE2 O3 (RE=Pr, Er) content. FTIR was used to inspect the structural changes of the glasses. The doping of RE 2 O3 (RE=Pr, Er) induces depolymerization of the glasses at the Q3 tetrahedral sites. The forming of the ionic linkages between phosphate chains is attributed to the increase in non-bridging oxygen (NBO). The cross-linkages density (CLD) increases with the RE2 O3 (RE=Pr, Er) concentrations. Absorption spectra for x = 0.01 of Er 3+ and 0.005-0.05 for Nd3+ doped

  20. Rare Earth Ion-Doped Upconversion Nanocrystals: Synthesis and Surface Modification

    PubMed Central

    Chang, Hongjin; Xie, Juan; Zhao, Baozhou; Liu, Botong; Xu, Shuilin; Ren, Na; Xie, Xiaoji; Huang, Ling; Huang, Wei

    2014-01-01

    The unique luminescent properties exhibited by rare earth ion-doped upconversion nanocrystals (UCNPs), such as long lifetime, narrow emission line, high color purity, and high resistance to photobleaching, have made them widely used in many areas, including but not limited to high-resolution displays, new-generation information technology, optical communication, bioimaging, and therapy. However, the inherent upconversion luminescent properties of UCNPs are influenced by various parameters, including the size, shape, crystal structure, and chemical composition of the UCNPs, and even the chosen synthesis process and the surfactant molecules used. This review will provide a complete summary on the synthesis methods and the surface modification strategies of UCNPs reported so far. Firstly, we summarize the synthesis methodologies developed in the past decades, such as thermal decomposition, thermal coprecipitation, hydro/solvothermal, sol-gel, combustion, and microwave synthesis. In the second part, five main streams of surface modification strategies for converting hydrophobic UCNPs into hydrophilic ones are elaborated. Finally, we consider the likely directions of the future development and challenges of the synthesis and surface modification, such as the large-scale production and actual applications, stability, and so on, of the UCNPs. PMID:28346995

  1. Alkaline earth metal and samarium co-doped ceria as efficient electrolytes

    NASA Astrophysics Data System (ADS)

    Ali, Amjad; Raza, Rizwan; Kaleem Ullah, M.; Rafique, Asia; Wang, Baoyuan; Zhu, Bin

    2018-01-01

    Co-doped ceramic electrolytes M0.1Sm0.1Ce0.8O2-δ (M = Ba, Ca, Mg, and Sr) were synthesized via co-precipitation. The focus of this study was to highlight the effects of alkaline earth metals in doped ceria on the microstructure, densification, conductivity, and performance. The ionic conductivity comparisons of prepared electrolytes in the air atmosphere were studied. It has been observed that Ca0.1Sm0.1Ce0.8O2-δ shows the highest conductivity of 0.124 Scm-1 at 650 °C and a lower activation energy of 0.48 eV. The cell shows a maximum power density of 630 mW cm-2 at 650 °C using hydrogen fuel. The enhancement in conductivity and performance was due to increasing the oxygen vacancies in the ceria lattice with the increasing dopant concentration. The bandgap was calculated from UV-Vis data, which shows a red shift when compared with pure ceria. The average crystallite size is in the range of 37-49 nm. DFT was used to analyze the co-doping structure, and the calculated lattice parameter was compared with the experimental lattice parameter.

  2. Computer modelling of BaY2F8: defect structure, rare earth doping and optical behaviour

    NASA Astrophysics Data System (ADS)

    Amaral, J. B.; Couto Dos Santos, M. A.; Valerio, M. E. G.; Jackson, R. A.

    2005-10-01

    BaY2F8, when doped with rare earth elements, is a material of interest in the development of solid-state laser systems, especially for use in the infrared region. This paper presents the application of a computational technique, which combines atomistic modelling and crystal field calculations, in a study of rare earth doping of the material. Atomistic modelling is used to calculate the intrinsic defect structure and the symmetry and detailed geometry of the dopant ion-host lattice system, and this information is then used to calculate the crystal field parameters, which are an important indicator in assessing the optical behaviour of the dopant-crystal system. Energy levels are then calculated for the Dy3+-substituted material, and comparisons with the results of recent experimental work are made.

  3. Synthesis, characterization and processing of active rare earth-doped chalcohalide glasses

    NASA Astrophysics Data System (ADS)

    Debari, Roberto Mauro

    Applications for infrared-transmitting non-oxide glass fibers span a broad range of topics. They can be used in the military, the medical field, telecommunications, and even in agriculture. Rare earth ions are used as dopants in these glasses in order to stimulate emissions in the infrared spectral region. In order to extend the host glass transmission further into the infrared, selenium atoms were substituted for sulfur in the established Ge-S-I chalcohalide glass system and the fundamental properties of these latter glasses were explored. Over 30 different compositions in the Ge-Se-I glass system were investigated as to their thermal and optical properties. The resulting optimum host with a composition of Ge15Se80I5 has a broad transmission range from 0.7 mum to 17.0 mum and a high working range over 145°C. The host glass also exhibited a Tg of 125°C, making rotational casting of a cladding tube for rod-and-tube fiberization a possibility. The base glass was doped with 1000 to 4000 ppm/wt of erbium, dysprosium, or neodymium. When doped with Er3+-ions, absorptions at 1.54 mum and 3.42 mum were observed. Nd3+-doping resulted in an absorption peak near 4.24 mum and Dy3+ ions caused absorption at 1.30 mum. Fluorescence emissions were found for neodymium at 1.396 mum with a FWHM of 74 nm, and for dysprosium at 1.145 mum with a FWHM of 75 nm, at 1.360 mum with a FWHM of 98 rim and at 1.674 mum with a FWHM of 60 nm. High optical quality tubes of the host glass could be formed using rotational casting in silica ampoules. Glass tubes, 4 to 6 cm long with a 1 cm outer diameter and a tailored inner-hole diameter ranging from 0.4 to 0.6 cm could be synthesized by this process with excellent dimensional tolerances around the circumference as well as along the length. A preform of this size provided 25 continuous meters of unclad fiber with diameters ranging from 140 to 200 mum. A UV-curable acrylate cladding was applied via an external coating cup. An x-ray analysis of the

  4. Thermoelectric Properties of High-Doped Silicon from Room Temperature to 900 K

    NASA Astrophysics Data System (ADS)

    Stranz, A.; Kähler, J.; Waag, A.; Peiner, E.

    2013-07-01

    Silicon is investigated as a low-cost, Earth-abundant thermoelectric material for high-temperature applications up to 900 K. For the calculation of module design the Seebeck coefficient and the electrical as well as thermal properties of silicon in the high-temperature range are of great importance. In this study, we evaluate the thermoelectric properties of low-, medium-, and high-doped silicon from room temperature to 900 K. In so doing, the Seebeck coefficient, the electrical and thermal conductivities, as well as the resulting figure of merit ZT of silicon are determined.

  5. First-principles prediction of Si-doped Fe carbide as one of the possible constituents of Earth's inner core

    NASA Astrophysics Data System (ADS)

    Das, Tilak; Chatterjee, Swastika; Ghosh, Sujoy; Saha-Dasgupta, Tanusri

    2017-09-01

    We perform a computational study based on first-principles calculations to investigate the relative stability and elastic properties of the doped and undoped Fe carbide compounds at 200-364 GPa. We find that upon doping a few weight percent of Si impurities at the carbon sites in Fe7C3 carbide phases, the values of Poisson's ratio and density increase while VP, and VS decrease compared to their undoped counterparts. This leads to marked improvement in the agreement of seismic parameters such as P wave and S wave velocity, Poisson's ratio, and density with the Preliminary Reference Earth Model (PREM) data. The agreement with PREM data is found to be better for the orthorhombic phase of iron carbide (o-Fe7C3) compared to hexagonal phase (h-Fe7C3). Our theoretical analysis indicates that Fe carbide containing Si impurities can be a possible constituent of the Earth's inner core. Since the density of undoped Fe7C3 is low compared to that of inner core, as discussed in a recent theoretical study, our proposal of Si-doped Fe7C3 can provide an alternative solution as an important component of the Earth's inner core.

  6. GeS2–In2S3–CsI Chalcogenide Glasses Doped with Rare Earth Ions for Near- and Mid-IR Luminescence

    PubMed Central

    Li, Legang; Bian, Junyi; Jiao, Qing; Liu, Zijun; Dai, Shixun; Lin, Changgui

    2016-01-01

    Chalcogenide glass has been considered as a promising host for the potential laser gain and amplifier media operating in near- and mid-IR spectral region. In this work, the IR luminescence spectra of rare earth ions (Tm3+, Er3+, and Dy3+) doped 65GeS2–25In2S3–10CsI chalcogenide glasses were measured under the excitation of an 808 nm laser diode. To the best of our knowledge, it firstly provides the luminescence spectra of a full near- and mid-IR spectral range from 1 to 4 μm in rare earth ions doped chalcogenide glasses. The results of absorption spectra, luminescence spectra, and fluorescence decay curves were obtained in these samples with singly-, co- and triply-doping behaviors of Tm3+, Er3+, and Dy3+ ions. In order to search possible efficient IR emissions, the luminescence behavior was investigated specifically with the variation of doping behaviors and dopant ions, especially in the samples co- and triply-doped active ions. The results suggest that favorable near- and mid-IR luminescence of rare earth ions can be further modified in chalcogenide glasses through an elaborated design of doping behavior and optically active ions. PMID:27869231

  7. Optical spectroscopy of rare earth ion-doped TiO2 nanophosphors.

    PubMed

    Chen, Xueyuan; Luo, Wenqin

    2010-03-01

    Trivalent rare-earth (RE3+) ion-doped TiO2 nanophosphors belong to one kind of novel optical materials and have attracted increasing attention. The luminescence properties of different RE3+ ions in various TiO2 nanomaterials have been reviewed. Much attention is paid to our recent progresses on the luminescence properties of RE3+ (RE = Eu, Er, Sm, Nd) ions in anatase TiO2 nanoparticles prepared by a sol-gel-solvothermal method. Using Eu3+ as a sensitive optical probe, three significantly different luminescence centers of Eu3+ in TiO2 nanoparticles were detected by means of site-selective spectroscopy at 10 K. Based on the crystal-field (CF) splitting of Eu3+ at each site, C2v and D2 symmetries were proposed for Eu3+ incorporated at two lattice sites. A structural model for the formation of multiple sites was proposed based on the optical behaviors of Eu3+ at different sites. Similar multi-site luminescence was observed in Sm(3+)- or Nd(3+)-doped TiO2 nanoparticles. In Eu(3+)-doped TiO2 nanoparticles, only weak energy transfer from the TiO2 host to the Eu3+ ions was observed at 10 K due to the mismatch of energy between the TiO2 band-gap and the Eu3+ excited states. On the contrary, efficient host-sensitized luminescences were realized in Sm(3+)- or Nd(3+)-doped anatase TiO2 nanoparticles due to the match of energy between TiO2 band-gap and the Sm3+ and Nd3+ excited states. The excitation spectra of both Sm(3+)- and Nd(3+)-doped samples exhibit a dominant broad peak centered at approximately 340 nm, which is associated with the band-gap of TiO2, indicating that sensitized emission is much more efficient than direct excitation of the Sm3+ and Nd3+ ions. Single lattice site emission of Er3+ in TiO2 nanocrystals can be achieved by modifying the experimental conditions. Upon excitation by a Ti: sapphire laser at 978 nm, intense green upconverted luminescence was observed. The characteristic emission of Er3+ ions was obtained both in the ultraviolet-visible (UV-vis) and

  8. Scintillation properties of rare-earth doped NaPO3-Al(PO3)3 glasses

    NASA Astrophysics Data System (ADS)

    Kuro, Tomoaki; Okada, Go; Kawaguchi, Noriaki; Fujimoto, Yutaka; Masai, Hirokazu; Yanagida, Takayuki

    2016-12-01

    We systematically investigated photoluminescence (PL), scintillation and dosimeter properties of rare-earth (RE) doped NaPO3-Al(PO3)3 (NAP) glasses. The NAP glasses doped with a series of RE ions (La-Yb, except Pm) with a consistent concentration (0.3 wt%) were prepared by the conventional melt-quenching method. The PL and scintillation decay time profiles showed fast (ns) and slow (μs or ms) components: the fast components from 15 to 100 ns were due to the host or 5d-4f transition emission, and the slow components from 15 μs to 5 ms were due to the 4f-4f transitions of RE. The thermally stimulated luminescence (TSL) was evaluated as a dosimeter property, and glow peaks appeared around 400 °C in all the samples. The TSL dose response function was examined in the dose range from 10 mGy to 10 Gy. Among the samples tested, Nd and Tb doped glasses showed higher signal by at least one order of magnitude than those of non-doped and other RE-doped samples. Over the dose range tested, the TSL signals are linearly related with the incident X-ray dose, showing a potential for practical applications.

  9. THE STUDY OF HIGH DIELECTRIC CONSTANT MECHANISM OF La-DOPED Ba0.67Sr0.33TiO3 CERAMICS

    NASA Astrophysics Data System (ADS)

    Xu, Jing; He, Bo; Liu, Han Xing

    It is a common and effective method to enhance the dielectric properties of BST ceramics by adding rare-earth elements. In this paper, it is important to analyze the cause of the high dielectric constant behavior of La-doped BST ceramics. The results show that proper rare earth La dopant (0.2≤x≤0.7) may greatly increase the dielectric constant of BST ceramics, and also improve the temperature stability, evidently. According to the current-voltage (J-V) characteristics, the proper La-doped BST ceramics may reach the better semiconductivity, with the decrease and increase in La doping, the ceramics are insulators. By using the Schottky barrier model and electric microstructure model to find the surface or grain boundary potential barrier height, the width of the depletion layer and grain size do play an important role in impacting the dielectric constant.

  10. Recent developments in the growth, processing, and testing of rare earth doped YVO{sub 4} single crystals

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Mizell, G.; Fay, W.R.; Alekel, T. III

    1994-12-31

    The production of the laser host material YVO{sub 4} via high temperature solution growth (HTSG) is described as a facile alternative for producing optical quality crystals for research. The effects of dopant concentration on optical absorption properties in 0.7% and 3% Nd:YVO{sub 4} crystals are discussed. The rare earths ions Ho{sup 3+} and Er{sup 3+} have been doped into YVO{sub 4} with the HTSG method, and inaugural optical properties of Ho{sub 0.04}Y{sub 0.96}VO{sub 4} are presented.

  11. Spectral engineering of optical fiber through active nanoparticle doping

    NASA Astrophysics Data System (ADS)

    Lindstrom-James, Tiffany

    The spectral engineering of optical fiber is a method of intentional doping of the core region in order to absorb/emit specific wavelengths of light therby providing enhanced performance over current fibers. Efforts here focused on developing an understanding of optically active nanoparticles based on alkaline earth fluorides that could be easily and homogeneously incorporated into the core of a silica based optical fiber preform and result in efficient and tailorable spectral emissions. Doped and undoped calcium, strontium and barium fluoride nanoparticles were successfully synthesized and characterized for their physical, chemical, and optical behavior. Distinct spectroscopic differences as a result of different host materials, varying rare earth doping levels and processing conditions, indicated the ability to influence the spectral behavior of the doped nanoparticle. By using photoluminescence to predict diffusion behavior, the application of a simple one dimensional model for diffusion provided a method for predicting the diffusion coefficient of europium ions in alkaline earth fluorides with order of magnitude accuracy. Modified chemical vapor deposition derived silica preforms were individually solution doped with europium doped alkaline earth fluoride nanoparticles. By using the rare earth doped alkaline earth fluoride nanoparticles as the dopant materials in the core of optical fiber preforms, the resultant optical properties of the glass were significantly influenced by their presence in the core. The incorporation of these rare earth doped alkaline earth fluoride nanoparticles was found to significantly influence the local chemical and structural environment about the rare earth ion, demonstrated homogeneity and uniform distribution of the rare earth dopant and resulted in specifically unique spectral behavior when compared to conventional doping methods. A more detailed structural model of the doped core glass region has been developed based on the

  12. PULSION® HP: Tunable, High Productivity Plasma Doping

    NASA Astrophysics Data System (ADS)

    Felch, S. B.; Torregrosa, F.; Etienne, H.; Spiegel, Y.; Roux, L.; Turnbaugh, D.

    2011-01-01

    Plasma doping has been explored for many implant applications for over two decades and is now being used in semiconductor manufacturing for two applications: DRAM polysilicon counter-doping and contact doping. The PULSION HP is a new plasma doping tool developed by Ion Beam Services for high-volume production that enables customer control of the dominant mechanism—deposition, implant, or etch. The key features of this tool are a proprietary, remote RF plasma source that enables a high density plasma with low chamber pressure, resulting in a wide process space, and special chamber and wafer electrode designs that optimize doping uniformity.

  13. Mixedness determination of rare earth-doped ceramics

    NASA Astrophysics Data System (ADS)

    Czerepinski, Jennifer H.

    The lack of chemical uniformity in a powder mixture, such as clustering of a minor component, can lead to deterioration of materials properties. A method to determine powder mixture quality is to correlate the chemical homogeneity of a multi-component mixture with its particle size distribution and mixing method. This is applicable to rare earth-doped ceramics, which require at least 1-2 nm dopant ion spacing to optimize optical properties. Mixedness simulations were conducted for random heterogeneous mixtures of Nd-doped LaF3 mixtures using the Concentric Shell Model of Mixedness (CSMM). Results indicate that when the host to dopant particle size ratio is 100, multi-scale concentration variance is optimized. In order to verify results from the model, experimental methods that probe a mixture at the micro, meso, and macro scales are needed. To directly compare CSMM results experimentally, an image processing method was developed to calculate variance profiles from electron images. An in-lens (IL) secondary electron image is subtracted from the corresponding Everhart-Thornley (ET) secondary electron image in a Field-Emission Scanning Electron Microscope (FESEM) to produce two phases and pores that can be quantified with 50 nm spatial resolution. A macro was developed to quickly analyze multi-scale compositional variance from these images. Results for a 50:50 mixture of NdF3 and LaF3 agree with the computational model. The method has proven to be applicable only for mixtures with major components and specific particle morphologies, but the macro is useful for any type of imaging that produces excellent phase contrast, such as confocal microscopy. Fluorescence spectroscopy was used as an indirect method to confirm computational results for Nd-doped LaF3 mixtures. Fluorescence lifetime can be used as a quantitative method to indirectly measure chemical homogeneity when the limits of electron microscopy have been reached. Fluorescence lifetime represents the

  14. Rare earth ions doped ZnO: Synthesis, characterization and preliminary photoactivity assessment

    NASA Astrophysics Data System (ADS)

    Cerrato, Erik; Gionco, Chiara; Berruti, Ilaria; Sordello, Fabrizio; Calza, Paola; Paganini, Maria Cristina

    2018-08-01

    This work reports the effect of doping zinc oxide with lanthanide ions on structural, EPR and UV visible properties. Bare and doped samples were synthesized using the simple and green hydrothermal process. Different rare earth ions (RE = La, Ce, Pr, Er and Yb) with 1% molar ratio RE/Zn were used. The samples have been studied using X Ray Diffraction, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and UV visible diffuse reflectance spectroscopy. Finally, electron paramagnetic resonance (EPR) spectroscopy, was used to assess the materials photoactivity under UV irradiation, both in solid state, to see the charge carriers' generation and in solution, evaluating the OH• radical formation using the DMPO (5,5-Dimethyl-1-Pyrroline-N-Oxide) spin trapping technique. The results suggest that the synthesized materials could be interesting systems for the photocatalytic abatement of emerging organic persistent pollutants in wastewater treatment plants.

  15. Absorption and emission spectra of Ga1.7Ge25As8.3S65 glasses doped with rare-earth ions

    NASA Astrophysics Data System (ADS)

    Lupan, E. V.; Iaseniuc, O. V.; Ciornea, V. I.; Iovu, M. S.

    2016-12-01

    Excellent optical properties of chalcogenide glasses make them interesting for optoelectronic devices in the visible (VIS) and, especially, in the near- and mid-infrared (NIR and MIR) spectral regions. The rare-earth (RE3+) doped Ga17Ge25As8.3S65 glasses were prepared in evacuated ( 10-5 Pa) silica-glass ampoules which were heated up to 1000 °C at 2-4°C min-1, and then the melt was quenched. The absorption and photoluminescence spectra in the visible and near IR regions for GA1.7Ge25As8.3S65 doped with rare-earth RE+) ions (Sm3+, Nd3+, Pr3+, Dy3+ and co-doped with Ho3++Dy3+) are investigated. The energy transfer of the absorbed light in the broad band Urbach region of the host glass to the RE3+ ions is suggested for increasing the emission efficiency. The investigated Ga17Ge25As8.3S65 glasses doped with RE3+ ions are promising materials for optical amplifiers operating at 1300 and 1500 nm telecommunication windows.

  16. Health Sensing Functions in Thermal Barrier Coatings Incorporating Rare-Earth-Doped Luminescent Sublayers

    NASA Technical Reports Server (NTRS)

    Eldridge, J. I.; Singh, J.; Wolfe, D. E.

    2004-01-01

    Great effort has been directed towards developing techniques to monitor the health of thermal barrier coatings (TBCs) that would detect the approach of safety-threatening conditions. An unconventional approach is presented here where health sensing functionality is integrated into the TBC itself by the incorporation of rare-earth-doped luminescent sublayers to monitor erosion as well as whether the TBC is maintaining the underlying substrate at a sufficiently low temperature. Erosion indication is demonstrated in electron-beam physical vapor deposited (EB-PVD) TBCs consisting of 7wt% yttria-stabilized zirconia (7YSZ) with europium-doped and terbium-doped sublayers. Multiple ingot deposition produced sharp boundaries between the doped sublayers without interrupting the columnar growth of the TBC. The TBC-coated specimens were subjected to alumina particle jet erosion, and the erosion depth was then indicated under ultraviolet illumination that excited easily visible luminescence characteristic of sublayer that was exposed by erosion. In addition, temperature measurements from a bottom-lying europium-doped sublayer in a TBC produced by multiple ingot EB-PVD were accomplished by measuring the temperature-dependent decay time from the 606 nm wavelength emission excited in that sublayer with a 532 nm wavelength laser that was selected for its close match to one of the europium excitation wavelengths as well as being at a wavelength where the TBC is relatively transparent. It is proposed the low dopant levels and absence of interruption of the TBC columnar growth allow the addition of the erosion and temperature sensing functions with minimal effects on TBC performance.

  17. Magnetic properties of rare-earth-doped La0.7Sr0.3MnO3.

    PubMed

    Veverka, Pavel; Kaman, Ondřej; Knížek, Karel; Novák, Pavel; Maryško, Miroslav; Jirák, Zdeněk

    2017-01-25

    Rare-earth-doped ferromagnetic manganites La 0.63 RE 0.07 Sr 0.30 MnO 3 (RE  =  Gd, Tb, Dy, and Ho) are synthesized in the form of sintered ceramics and nanocrystalline phases with the mean size of crystallites  ≈30 nm. The electronic states of the dopants are investigated by SQUID magnetometry and theoretically interpreted based on the calculations of the crystal field splitting of rare-earth energy levels. The samples show the orthorhombic perovskite structure of Ibmm symmetry, with a complete FM order of Mn spins in bulk and reduced order in nanoparticles. Non-zero moments are also detected at the perovskite A sites, which can be attributed to magnetic polarization of the rare-earth dopants. The measurements in external field up to 70 kOe show a standard Curie-type contribution of the spin-only moments of Gd 3+ ions, whereas Kramers ions Dy 3+ and non-Kramers ions Ho 3+ contribute by Ising moments due to their doublet ground states. The behaviour of non-Kramers ions Tb 3+ is anomalous, pointing to singlet ground state with giant Van Vleck paramagnetism. The Tb 3+ doping leads also to a notably increased coercivity compared to other La 0.63 RE 0.07 Sr 0.30 MnO 3 systems.

  18. A primary exploration to quasi-two-dimensional rare-earth ferromagnetic particles: holmium-doped MoS2 sheet as room-temperature magnetic semiconductor

    NASA Astrophysics Data System (ADS)

    Chen, Xi; Lin, Zheng-Zhe

    2018-05-01

    Recently, two-dimensional materials and nanoparticles with robust ferromagnetism are even of great interest to explore basic physics in nanoscale spintronics. More importantly, room-temperature magnetic semiconducting materials with high Curie temperature is essential for developing next-generation spintronic and quantum computing devices. Here, we develop a theoretical model on the basis of density functional theory calculations and the Ruderman-Kittel-Kasuya-Yoshida theory to predict the thermal stability of two-dimensional magnetic materials. Compared with other rare-earth (dysprosium (Dy) and erbium (Er)) and 3 d (copper (Cu)) impurities, holmium-doped (Ho-doped) single-layer 1H-MoS2 is proposed as promising semiconductor with robust magnetism. The calculations at the level of hybrid HSE06 functional predict a Curie temperature much higher than room temperature. Ho-doped MoS2 sheet possesses fully spin-polarized valence and conduction bands, which is a prerequisite for flexible spintronic applications.

  19. Defect Clustering and Nano-Phase Structure Characterization of Multi-Component Rare Earth Oxide Doped Zirconia-Yttria Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Chen, Yuan L.; Miller, Robert A.

    2003-01-01

    Advanced oxide thermal barrier coatings have been developed by incorporating multi-component rare earth oxide dopants into zirconia-yttria to effectively promote the creation of the thermodynamically stable, immobile oxide defect clusters and/or nano-scale phases within the coating systems. The presence of these nano-sized defect clusters has found to significantly reduce the coating intrinsic thermal conductivity, improve sintering resistance, and maintain long-term high temperature stability. In this paper, the defect clusters and nano-structured phases, which were created by the addition of multi-component rare earth dopants to the plasma-sprayed and electron-beam physical vapor deposited thermal barrier coatings, were characterized by high-resolution transmission electron microscopy (TEM). The defect cluster size, distribution, crystallographic and compositional information were investigated using high-resolution TEM lattice imaging, selected area diffraction (SAD), electron energy-loss spectroscopy (EELS) and energy dispersive spectroscopy (EDS) analysis techniques. The results showed that substantial defect clusters were formed in the advanced multi-component rare earth oxide doped zirconia- yttria systems. The size of the oxide defect clusters and the cluster dopant segregation was typically ranging from 5 to 50 nm. These multi-component dopant induced defect clusters are an important factor for the coating long-term high temperature stability and excellent performance.

  20. Defect Clustering and Nano-Phase Structure Characterization of Multi-Component Rare Earth Oxide Doped Zirconia-Yttria Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Chen, Yuan L.; Miller, Robert A.

    1990-01-01

    Advanced oxide thermal barrier coatings have been developed by incorporating multi- component rare earth oxide dopants into zirconia-yttria to effectively promote the creation of the thermodynamically stable, immobile oxide defect clusters and/or nano-scale phases within the coating systems. The presence of these nano-sized defect clusters has found to significantly reduce the coating intrinsic thermal conductivity, improve sintering resistance, and maintain long-term high temperature stability. In this paper, the defect clusters and nano-structured phases, which were created by the addition of multi-component rare earth dopants to the plasma- sprayed and electron-beam physical vapor deposited thermal barrier coatings, were characterized by high-resolution transmission electron microscopy (TEM). The defect cluster size, distribution, crystallographic and compositional information were investigated using high-resolution TEM lattice imaging, selected area diffraction (SAD), and energy dispersive spectroscopy (EDS) analysis techniques. The results showed that substantial defect clusters were formed in the advanced multi-component rare earth oxide doped zirconia-yttria systems. The size of the oxide defect clusters and the cluster dopant segregation was typically ranging fiom 5 to 50 nm. These multi-component dopant induced defect clusters are an important factor for the coating long-term high temperature stability and excellent performance.

  1. Room temperature ferromagnetism with large magnetic moment at low field in rare-earth-doped BiFeO₃ thin films.

    PubMed

    Kim, Tae-Young; Hong, Nguyen Hoa; Sugawara, T; Raghavender, A T; Kurisu, M

    2013-05-22

    Thin films of rare earth (RE)-doped BiFeO3 (where RE=Sm, Ho, Pr and Nd) were grown on LaAlO3 substrates by using the pulsed laser deposition technique. All the films show a single phase of rhombohedral structure with space group R3c. The saturated magnetization in the Ho- and Sm-doped films is much larger than the values reported in the literature, and is observed at quite a low field of 0.2 T. For Ho and Sm doping, the magnetization increases as the film becomes thinner, suggesting that the observed magnetism is mostly due to a surface effect. In the case of Nd doping, even though the thin film has a large magnetic moment, the mechanism seems to be different.

  2. Upconversion-pumped luminescence efficiency of rare-earth-doped hosts sensitized with trivalent ytterbium

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Page, R.H.; Schaffers, K.I.; Waide, P.A.

    We discuss the upconversion luminescence efficiencies of phosphors that generate red, green, and blue light. The phosphors studied are single crystals and powders co-doped with Er{sup 3+} and Yb{sup 3+}, and with Tm{sup 3+} and Yb{sup 3+}. The Yb ions are pumped near 980 nm; transfers of two or three quanta to the co-doped rare earth ion generate visible luminescence. The main contribution embodied in this work is the quantitative measurement of this upconversion efficiency, based on the use of a calibrated integrating sphere, determination of the fraction of pump light absorbed, and careful control of the pump laser beammore » profile. The green phosphors are the most efficient, yielding efficiency values as high as 4 %, with the red and blue materials giving 1 - 2 %. Saturation was observed in all cases, suggesting that populations of upconversion steps of the ions are maximized at higher power. Quasi-CW modeling of the intensity- dependent upconversion efficiency was attempted; input data included level lifetimes, transition cross sections, and cross-relaxation rate coefficients. The saturation of the Yb,Er:fluoride media is explained as the pumping of Er{sup 3+} ions into a bottleneck (long-lived state)- the {sup 4}I{sub 13/2} metastable level, making them unavailable for further excitation transfer. 32 refs., 5 figs., 3 tabs.« less

  3. Rare-earth-doped materials with application to optical signal processing, quantum information science, and medical imaging technology

    NASA Astrophysics Data System (ADS)

    Cone, R. L.; Thiel, C. W.; Sun, Y.; Böttger, Thomas; Macfarlane, R. M.

    2012-02-01

    Unique spectroscopic properties of isolated rare earth ions in solids offer optical linewidths rivaling those of trapped single atoms and enable a variety of recent applications. We design rare-earth-doped crystals, ceramics, and fibers with persistent or transient "spectral hole" recording properties for applications including high-bandwidth optical signal processing where light and our solids replace the high-bandwidth portion of the electronics; quantum cryptography and information science including the goal of storage and recall of single photons; and medical imaging technology for the 700-900 nm therapeutic window. Ease of optically manipulating rare-earth ions in solids enables capturing complex spectral information in 105 to 108 frequency bins. Combining spatial holography and spectral hole burning provides a capability for processing high-bandwidth RF and optical signals with sub-MHz spectral resolution and bandwidths of tens to hundreds of GHz for applications including range-Doppler radar and high bandwidth RF spectral analysis. Simply stated, one can think of these crystals as holographic recording media capable of distinguishing up to 108 different colors. Ultra-narrow spectral holes also serve as a vibration-insensitive sub-kHz frequency reference for laser frequency stabilization to a part in 1013 over tens of milliseconds. The unusual properties and applications of spectral hole burning of rare earth ions in optical materials are reviewed. Experimental results on the promising Tm3+:LiNbO3 material system are presented and discussed for medical imaging applications. Finally, a new application of these materials as dynamic optical filters for laser noise suppression is discussed along with experimental demonstrations and theoretical modeling of the process.

  4. Monitoring the orientation of rare-earth-doped nanorods for flow shear tomography.

    PubMed

    Kim, Jongwook; Michelin, Sébastien; Hilbers, Michiel; Martinelli, Lucio; Chaudan, Elodie; Amselem, Gabriel; Fradet, Etienne; Boilot, Jean-Pierre; Brouwer, Albert M; Baroud, Charles N; Peretti, Jacques; Gacoin, Thierry

    2017-09-01

    Rare-earth phosphors exhibit unique luminescence polarization features originating from the anisotropic symmetry of the emitter ion's chemical environment. However, to take advantage of this peculiar property, it is necessary to control and measure the ensemble orientation of the host particles with a high degree of precision. Here, we show a methodology to obtain the photoluminescence polarization of Eu-doped LaPO 4 nanorods assembled in an electrically modulated liquid-crystalline phase. We measure Eu 3+ emission spectra for the three main optical configurations (σ, π and α, depending on the direction of observation and the polarization axes) and use them as a reference for the nanorod orientation analysis. Based on the fact that flowing nanorods tend to orient along the shear strain profile, we use this orientation analysis to measure the local shear rate in a flowing liquid. The potential of this approach is then demonstrated through tomographic imaging of the shear rate distribution in a microfluidic system.

  5. Synthesis of rare earth doped TiO2 nanorods as photocatalysts for lignin degradation.

    PubMed

    Song, Liang; Zhao, Xueyuan; Cao, Lixin; Moon, Ji-Won; Gu, Baohua; Wang, Wei

    2015-10-28

    A two-step process is developed to synthesize rare earth doped titania nanorods (RE-TiO2 NRs) as photocatalysts for efficient degradation of lignin under simulated sunlight irradiation. In this approach, protonated titanate nanotubes with layered structures were first prepared by a hydrothermal approach, and rare earth metal ions were subsequently bound to the negatively charged surface of the synthesized titanate via electrostatic incorporation. The as-synthesized RE-TiO2 NRs after calcination generally showed much higher photocatalytic efficiencies than those of undoped TiO2 NRs or the commercial P25 TiO2 photocatalyst. Using methyl orange (MO) as a probing molecule, we demonstrate that Eu-TiO2 NRs are among the best for degrading MO, with an observed rate constant of 4.2 × 10(-3) s(-1). The La(3+), Sm(3+), Eu(3+) and Er(3+) doped TiO2 NRs also showed higher photocatalytic efficiencies in degrading MO than the commercial P25 TiO2. We further demonstrate that lignin can be photodegraded effectively and rapidly at room temperature under simulated sunlight through two reaction routes, which could be important in controlling ways of lignin depolymerization or the formation of reaction products.

  6. Synthesis of rare earth doped TiO 2 nanorods as photocatalysts for lignin degradation

    DOE PAGES

    Song, Liang; Zhao, Xueyuan; Cao, Lixin; ...

    2015-09-10

    In this paper, a two-step process is developed to synthesize rare earth doped titania nanorods (RE–TiO 2 NRs) as photocatalysts for efficient degradation of lignin under simulated sunlight irradiation. In this approach, protonated titanate nanotubes with layered structures were first prepared by a hydrothermal approach, and rare earth metal ions were subsequently bound to the negatively charged surface of the synthesized titanate via electrostatic incorporation. The as-synthesized RE–TiO 2 NRs after calcination generally showed much higher photocatalytic efficiencies than those of undoped TiO 2 NRs or the commercial P25 TiO 2 photocatalyst. Using methyl orange (MO) as a probing molecule,more » we demonstrate that Eu–TiO 2 NRs are among the best for degrading MO, with an observed rate constant of 4.2 × 10 -3 s -1. The La 3+, Sm 3+, Eu 3+ and Er 3+ doped TiO 2 NRs also showed higher photocatalytic efficiencies in degrading MO than the commercial P25 TiO 2. Finally, we further demonstrate that lignin can be photodegraded effectively and rapidly at room temperature under simulated sunlight through two reaction routes, which could be important in controlling ways of lignin depolymerization or the formation of reaction products.« less

  7. Nanophotonic photon echo memory based on rare-earth-doped crystals

    NASA Astrophysics Data System (ADS)

    Zhong, Tian; Kindem, Jonathan; Miyazono, Evan; Faraon, Andrei; Caltech nano quantum optics Team

    2015-03-01

    Rare earth ions (REIs) are promising candidates for implementing solid-state quantum memories and quantum repeater devices. Their high spectral stability and long coherence times make REIs a good choice for integration in an on-chip quantum nano-photonic platform. We report the coupling of the 883 nm transition of Neodymium (Nd) to a Yttrium orthosilicate (YSO) photonic crystal nano-beam resonator, achieving Purcell enhanced spontaneous emission by 21 times and increased optical absorption. Photon echoes were observed in nano-beams of different doping concentrations, yielding optical coherence times T2 up to 80 μs that are comparable to unprocessed bulk samples. This indicates the remarkable coherence properties of Nd are preserved during nanofabrication, therefore opening the possibility of efficient on-chip optical quantum memories. The nano-resonator with mode volume of 1 . 6(λ / n) 3 was fabricated using focused ion beam, and a quality factor of 3200 was measured. Purcell enhanced absorption of 80% by an ensemble of ~ 1 × 106 ions in the resonator was measured, which fulfills the cavity impedance matching condition that is necessary to achieve quantum storage of photons with unity efficiency.

  8. Electron traps in Gd3Ga3Al2O12:Ce garnets doped with rare-earth ions

    NASA Astrophysics Data System (ADS)

    Khanin, V. M.; Rodnyi, P. A.; Wieczorek, H.; Ronda, C. R.

    2017-05-01

    The curves of thermally stimulated luminescence of Gd3Ga3Al2O12:Ce3+ ceramics (a nominally pure sample and samples doped with rare-earth ions) are measured in the temperature range of 80-550 K. The depth and the frequency factor of electron traps established by Eu and Yb impurities are determined. An energy-level diagram of rare-earth ions in the bandgap of Gd3Ga3Al2O12 is presented.

  9. Rare-Earth Oxide Ion (Tm3+, Ho3+, and U3+) Doped Glasses and Fibres for 1.8 to 4 Micrometer Coherent and Broadband Sources

    DTIC Science & Technology

    2006-07-24

    oxide ( TeO2 ) , fluorine- containing silicate (SiOF2) and germanate (GeOF2) glass hosts for each dopant by characterising the spectroscopic properties...Earth Oxide Ion (Tm3+, Ho3+, And U3+) Doped Glasses And Fibres For 1.8 To 4 Micrometer Coherent And Broadband Sources 5c. PROGRAM ELEMENT NUMBER 5d...Rare-earth oxide ion (Tm3+, Ho3+, and U3+) doped glasses and fibres for 1.8 to 4 micrometer coherent and broadband sources Report prepared

  10. In vivo demonstration of enhanced radiotherapy using rare earth doped titania nanoparticles†

    PubMed Central

    Townley, Helen E.; Kim, Jeewon; Dobson, Peter J.

    2017-01-01

    Radiation therapy is often limited by damage to healthy tissue and associated side-effects; restricting radiation to ineffective doses. Preferential incorporation of materials into tumour tissue can enhance the effect of radiation. Titania has precedent for use in photodynamic therapy (PDT), generating reactive oxygen species (ROS) upon photoexcitation, but is limited by the penetration depth of UV light. Optimization of a nanomaterial for interaction with X-rays could be used for deep tumour treatment. As such, titania nanoparticles were doped with gadolinium to optimize the localized energy absorption from a conventional medical X-ray, and further optimized by the addition of other rare earth (RE) elements. These elements were selected due to their large X-ray photon interaction cross-section, and potential for integration into the titania crystal structure. Specific activation of the nanoparticles by X-ray can result in generation of ROS leading to cell death in a tumour-localized manner. We show here that intratumoural injection of RE doped titania nanoparticles can enhance the efficacy of radiotherapy in vivo. PMID:22767269

  11. In vivo demonstration of enhanced radiotherapy using rare earth doped titania nanoparticles.

    PubMed

    Townley, Helen E; Kim, Jeewon; Dobson, Peter J

    2012-08-21

    Radiation therapy is often limited by damage to healthy tissue and associated side-effects; restricting radiation to ineffective doses. Preferential incorporation of materials into tumour tissue can enhance the effect of radiation. Titania has precedent for use in photodynamic therapy (PDT), generating reactive oxygen species (ROS) upon photoexcitation, but is limited by the penetration depth of UV light. Optimization of a nanomaterial for interaction with X-rays could be used for deep tumour treatment. As such, titania nanoparticles were doped with gadolinium to optimize the localized energy absorption from a conventional medical X-ray, and further optimized by the addition of other rare earth (RE) elements. These elements were selected due to their large X-ray photon interaction cross-section, and potential for integration into the titania crystal structure. Specific activation of the nanoparticles by X-ray can result in generation of ROS leading to cell death in a tumour-localized manner. We show here that intratumoural injection of RE doped titania nanoparticles can enhance the efficacy of radiotherapy in vivo.

  12. Yb-doped large-mode-area laser fiber fabricated by halide-gas-phase-doping technique

    NASA Astrophysics Data System (ADS)

    Peng, Kun; Wang, Yuying; Ni, Li; Wang, Zhen; Gao, Cong; Zhan, Huan; Wang, Jianjun; Jing, Feng; Lin, Aoxiang

    2015-06-01

    In this manuscript, we designed a rare-earth-halide gas-phase-doping setup to fabricate a large-mode-area fiber for high power laser applications. YbCl3 and AlCl3 halides are evaporated, carried respectively and finally mixed with usual host gas material SiCl4 at the hot zone of MCVD system. Owing to the all-gas-phasing reaction process and environment, the home-made Yb-doped fiber preform has a homogeneous large core and modulated refractive index profile to keep high beam quality. The drawn fiber core has a small numerical aperture of 0.07 and high Yb concentration of 9500 ppm. By using a master oscillator power amplifier system, nearly kW-level (951 W) laser output power was obtained with a slope efficiency of 83.3% at 1063.8 nm, indicating the competition and potential of the halide-gas-phase-doping technique for high power laser fiber fabrication.

  13. Reduced grain boundary energies in rare-earth doped MgAl 2O 4 spinel and consequent grain growth inhibition

    DOE PAGES

    Hasan, Md M.; Dholabhai, Pratik P.; Dey, Sanchita; ...

    2017-05-15

    In this paper, grain growth inhibition in MgAl 2O 4 spinel nanostructure was achieved by grain boundary (GB) segregation of rare-earth dopants. Microcalorimetric measurements showed that dense spinel compacts doped with 3 mol% of R 2O 3 (R = Y, Gd, and La) had decreased GB energies as compared to the undoped spinel, representing reduction in the driving force for grain growth. Segregation energies of the three dopants to the Σ3 (111) GB were calculated by atomistic simulation. The dopants with higher ionic radius tend to segregate more strongly to GBs. The GB energies were calculated from atomistic simulation and,more » consistent with experiments, a systematic reduction in GB energy with dopant ionic size was found. Finally, high temperature grain growth experiments revealed a significant reduction of grain growth in the doped nanostructures as compared to the undoped one, which was attributed to increased metastability or possibly also a GB dragging originated from the dopant segregation.« less

  14. Promoting effect of alkaline earth metal doping on catalytic activity of HC and NOx conversion over Pd-only three-way catalyst.

    PubMed

    Yang, Linyan; Lin, Siyu; Yang, Xue; Fang, Weimin; Zhou, Renxian

    2014-08-30

    The influence of alkaline earth metal (M=Mg, Ca, Sr and Ba) promoter on the structural/textural properties of Ce0.67Zr0.33O2 (designated as CZ) and the catalytic behavior of its supported Pd-only three-way catalyst (Pd/CZM) have been investigated. The results show that the modification with alkaline earth metal obviously improves the catalytic activity for hydrocarbon (HC) and nitrogen oxides (NOx) conversion, especially the introduction of Ba. Furthermore, the operation window of the promoted catalysts has also been widened. The doping of alkaline earth metal leads to the formation of more homogeneous Ce-Zr-M ternary solid solution with higher surface area and smaller crystallite size, and the corresponding Pd/CZM catalysts present improved reducibility of PdO species. The modification with Ca, Sr and Ba improves the thermal aging resistance, especially Ba. DRIFTS results reveal that the doping of alkaline earth metal enhances the oxygen and electron transfer ability and favors the dissociation of NO, which promotes the activation and storage capacity of the acidic atoms like NOx, and leads to enhanced catalytic activity performance. Copyright © 2014 Elsevier B.V. All rights reserved.

  15. Cladding pumped Yb-doped HOM power amplifier with high gain

    NASA Astrophysics Data System (ADS)

    Abedin, Kazi S.; Ahmad, Raja; DeSantolo, Anthony M.; Nicholson, Jeffrey W.; Westbrook, Paul S.; Headley, Clifford; DiGiovanni, David J.

    2018-02-01

    Higher-order mode (HOM) fibers have been engineered to allow propagation of linearly polarized symmetric modes LP0,N in a robust way. Compared with the fundamental mode LP(0,1), HOMs exhibits an effective area that can be larger by over two order magnitude, and thus propagating light in these modes could greatly suppress the effect of nonlinear effects. HOM fibers could also be doped with rare earth ions in order to amplify light propagating in these modes, which offers the enormous potential for generating high-intensity pulses. Excitation of HOM gain fiber using cladding pumping with multimode pump source is attractive for ytterbium based amplifiers, because of the availability of low-cost multimode pump diodes in the 975nm wavelength range. One problem associated with cladding pumping which leads to excitation of the large doped core (over 100 μm diameter) is that it could result in a large amount of amplifiedspontaneous- emission (ASE) noise, particularly when the input signal is weak. Optimization of amplifier design is critical in order to suppress ASE and achieve high gain and pump-to-signal conversion efficiency. We conducted numerical modeling of a cladding pumped HOM-amplifier, which revealed that this problem could be mitigated by using a relatively long gain-fiber that allowed reabsorption of the forward propagating ASE resulting in a further amplification of the signal. We demonstrate efficient amplification of a LP0,10 mode with an effective area 3140μm2 in an Yb-doped HOM amplifier cladding pumped at 975nm. We have successfully obtained a 20.2dB gain for 0.95 W 1064 nm input seed signal to more than 105W.

  16. Optical properties of highly n-doped germanium obtained by in situ doping and laser annealing

    NASA Astrophysics Data System (ADS)

    Frigerio, J.; Ballabio, A.; Gallacher, K.; Giliberti, V.; Baldassarre, L.; Millar, R.; Milazzo, R.; Maiolo, L.; Minotti, A.; Bottegoni, F.; Biagioni, P.; Paul, D.; Ortolani, M.; Pecora, A.; Napolitani, E.; Isella, G.

    2017-11-01

    High n-type doping in germanium is essential for many electronic and optoelectronic applications especially for high performance Ohmic contacts, lasing and mid-infrared plasmonics. We report on the combination of in situ doping and excimer laser annealing to improve the activation of phosphorous in germanium. An activated n-doping concentration of 8.8  ×  1019 cm-3 has been achieved starting from an incorporated phosphorous concentration of 1.1  ×  1020 cm-3. Infrared reflectivity data fitted with a multi-layer Drude model indicate good uniformity over a 350 nm thick layer. Photoluminescence demonstrates clear bandgap narrowing and an increased ratio of direct to indirect bandgap emission confirming the high doping densities achieved.

  17. Luminescence studies of rare earth doped yttrium gadolinium mixed oxide phosphor

    NASA Astrophysics Data System (ADS)

    Som, S.; Choubey, A.; Sharma, S. K.

    2012-09-01

    This paper reports the photoluminescence and thermoluminescence properties of gamma ray induced rare earth doped yttrium gadolinium mixed oxide phosphor. The europium (Eu3+) was used as rare earth dopant. The phosphor was prepared by chemical co-precipitation method according to the formula (Y2-x-yGdx) O3: Euy3+ (x=0.5; y=0.05). The photoluminescence emission spectrum of the prepared phosphor shows intense peaks in the red region at 615 nm for 5D0→7F2 transitions and the photoluminescence excitation spectra show a broad band located around 220-270 nm for the emission wavelength fixed at 615 nm. The thermoluminescence studies were carried out after irradiating the phosphor by gamma rays in the dose range from 100 Gy to 1 KGy. In the thermoluminescence glow curves, one single peak was observed at about 300 °C of which the intensity increases linearly in the studied dose range of gamma rays. The glow peak was deconvoluted by GlowFit program and the kinetic parameters associated with the deconvoluted peaks were calculated. The kinetic parameters were also calculated by various glow curve shape and heating rate methods.

  18. Physical and electrochemical properties of alkaline earth doped, rare earth vanadates

    NASA Astrophysics Data System (ADS)

    Adijanto, Lawrence; Balaji Padmanabhan, Venu; Holmes, Kevin J.; Gorte, Raymond J.; Vohs, John M.

    2012-06-01

    The effect of partial substitution of alkaline earth (AE) ions, Sr2+ and Ca2+, for the rare earth (RE) ions, La3+, Ce3+, Pr3+, and Sm3+, on the physical properties of REVO4 compounds were investigated. The use of the Pechini method to synthesize the vanadates allowed for high levels of AE substitution to be obtained. Coulometric titration was used to measure redox isotherms for these materials and showed that the addition of the AE ions increased both reducibility and electronic conductivity under typical solid oxide fuel cell (SOFC) anode conditions, through the formation of compounds with mixed vanadium valence. In spite of their high electronic conductivity, REVO4-yttira stabilized zirconia (YSZ) composite anodes exhibited only modest performance when used in SOFCs operating with H2 fuel at 973 K due to their low catalytic activity. High performance was obtained, however, after the addition of a small amount of catalytically active Pd to the anode.

  19. Multilayer Thermal Barrier Coating (TBC) Architectures Utilizing Rare Earth Doped YSZ and Rare Earth Pyrochlores

    NASA Technical Reports Server (NTRS)

    Schmitt, Michael P.; Rai, Amarendra K.; Bhattacharya, Rabi; Zhu, Dongming; Wolfe, Douglas E.

    2014-01-01

    To allow for increased gas turbine efficiencies, new insulating thermal barrier coatings (TBCs) must be developed to protect the underlying metallic components from higher operating temperatures. This work focused on using rare earth doped (Yb and Gd) yttria stabilized zirconia (t' Low-k) and Gd2Zr2O7 pyrochlores (GZO) combined with novel nanolayered and thick layered microstructures to enable operation beyond the 1200 C stability limit of current 7 wt% yttria stabilized zirconia (7YSZ) coatings. It was observed that the layered system can reduce the thermal conductivity by approximately 45 percent with respect to YSZ after 20 hr of testing at 1316 C. The erosion rate of GZO is shown to be an order to magnitude higher than YSZ and t' Low-k, but this can be reduced by almost 57 percent when utilizing a nanolayered structure. Lastly, the thermal instability of the layered system is investigated and thought is given to optimization of layer thickness.

  20. Doping Attitudes and Covariates of Potential Doping Behaviour in High-Level Team-Sport Athletes; Gender Specific Analysis.

    PubMed

    Sekulic, Damir; Tahiraj, Enver; Zvan, Milan; Zenic, Natasa; Uljevic, Ognjen; Lesnik, Blaz

    2016-12-01

    Team sports are rarely studied with regard to doping behaviour and doping-related factors regardless of their global popularity. This study aimed to investigate doping factors and covariates of potential doping behaviour in high-level team-sport athletes. The subjects were 457 high-performing, national- and international-level athletes (21.9 ± 3.4 years of age; 179 females) involved in volleyball (n = 77), soccer (n = 163), basketball (n = 114) and handball (n = 103). Previously validated self-administered questionnaires aimed at evidencing sport factors, doping-related factors, knowledge on sport nutrition and doping, and attitudes to performance enhancement were used. The results indicated a higher doping likelihood in male athletes, with a significant gender difference for basketball and handball. In males, a higher doping likelihood is found for athletes who had achieved better results at junior-age level, those who regularly consume dietary supplements, and who perceive their sport as being contaminated by doping. A higher sport achievement at senior-age level is protective against potential doping behaviour in males. In females, a higher likelihood of doping is evidenced in those athletes involved in binge drinking, while a lower tendency for doping is evidenced in female athletes who possess better knowledge on sport nutrition. Knowledge about doping is very low and thus education about doping is urgently needed. An improvement of knowledge on sport nutrition might be a potentially effective method for reducing the tendency for doping in females. Future studies should consider other approaches and theories, such as theory of planned behaviour and/or social-cognitive theory, in studying the problem of doping behaviour in team-sports.

  1. Studies on hydrothermal synthesis of photolumniscent rare earth (Eu3+ & Tb3+) doped NG@FeMoO4 for enhanced visible light photodegradation of methylene blue dye

    NASA Astrophysics Data System (ADS)

    Singh, R.; Kumar, M.; Khajuria, H.; Sharma, S.; Sheikh, H. Nawaz

    2018-02-01

    FeMoO4 nanorods and their rare earth (Eu3+ and Tb3+) doped composites with nitrogen doped graphene (NG) were synthesized by facile hydrothermal method in aqueous medium. X-ray diffraction (XRD) analysis of the as-synthesized samples was done to study the phase purity and crystalline nature. FTIR and Raman Spectroscopy have been studied for investigating the bonding in nanostructures. The surface morphology of the samples was investigated with field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The photolumniscent nature of the samples was investigated by the using the fluorescence spectrophotometer. The photocatalytic degradation efficiency of the prepared pure FeMoO4 and its rare earth doped composites with nitrogen doped graphene was evaluated as function of visible light irradiation versus concentration of methylene blue (MB dye). The prepared nanocomposites show enhanced photocatalytic efficiency as compared to the bare FeMoO4 nanorods.

  2. Synthesis and evaluation of rare-earth doped glasses and crystals for optical refrigeration

    NASA Astrophysics Data System (ADS)

    Patterson, Wendy

    This research focused on developing and characterizing rare-earth doped, solid-state materials for laser cooling. In particular, the work targeted the optimization of the lasercooling efficiency in Yb3+ and Tm3+ doped fluorides. The first instance of laser-induced cooling in a Tm3+-doped crystal, BaY2F8 was reported. Cooling by 3 degrees Kelvin below ambient temperature was obtained in a single-pass pump geometry at lambda = 1855 nm. Protocols were developed for materials synthesis and purification which can be applied to each component of ZBLANI:Yb 3+/Tm3+ (ZrF4 -- BaF2 -- LaF3 -- AlF3 -- NaF -- InF3: YbF3/TmF3) glass to enable a material with significantly reduced transition-metal impurities. A method for OH- impurity removal and ultra-drying of the metal fluorides was also improved upon. Several characterization tools were used to quantitatively and qualitatively verify purity, including inductively-coupled plasma mass spectrometry (ICP-MS). Here we found a more than 600-fold reduction in transition-metal impurities in a ZrCl2O solution. A non-contact spectroscopic technique for the measurement of laser-induced temperature changes in solids was developed. Two-band differential luminescence thermometry (TBDLT) achieved a sensitivity of ˜7 mK and enabled precise measurement of the zero-crossing temperature and net quantum efficiency. Several Yb3+-doped ZBLANI glasses fabricated from precursors of varying purity and by different processes were analyzed in detail by TBDLT. Laser-induced cooling was observed at room temperature for several of the materials. A net quantum efficiency of 97.39+/-0.01% at 238 K was found for the best ZBLANI:1%Yb 3+ laser-cooling sample produced from purified metal-fluoride precursors, and proved competitive with the best commercially procured material. The TBDLT technique enabled rapid and sensitive benchmarking of laser-cooling materials and provided critical feedback to the development and optimization of high-performance optical

  3. Doping Attitudes and Covariates of Potential Doping Behaviour in High-Level Team-Sport Athletes; Gender Specific Analysis

    PubMed Central

    Sekulic, Damir; Tahiraj, Enver; Zvan, Milan; Zenic, Natasa; Uljevic, Ognjen; Lesnik, Blaz

    2016-01-01

    Team sports are rarely studied with regard to doping behaviour and doping-related factors regardless of their global popularity. This study aimed to investigate doping factors and covariates of potential doping behaviour in high-level team-sport athletes. The subjects were 457 high-performing, national- and international-level athletes (21.9 ± 3.4 years of age; 179 females) involved in volleyball (n = 77), soccer (n = 163), basketball (n = 114) and handball (n = 103). Previously validated self-administered questionnaires aimed at evidencing sport factors, doping-related factors, knowledge on sport nutrition and doping, and attitudes to performance enhancement were used. The results indicated a higher doping likelihood in male athletes, with a significant gender difference for basketball and handball. In males, a higher doping likelihood is found for athletes who had achieved better results at junior-age level, those who regularly consume dietary supplements, and who perceive their sport as being contaminated by doping. A higher sport achievement at senior-age level is protective against potential doping behaviour in males. In females, a higher likelihood of doping is evidenced in those athletes involved in binge drinking, while a lower tendency for doping is evidenced in female athletes who possess better knowledge on sport nutrition. Knowledge about doping is very low and thus education about doping is urgently needed. An improvement of knowledge on sport nutrition might be a potentially effective method for reducing the tendency for doping in females. Future studies should consider other approaches and theories, such as theory of planned behaviour and/or social-cognitive theory, in studying the problem of doping behaviour in team-sports. Key points The doping knowledge among Kosovar team-sport athletes is very low and systematic anti-doping education is urgently needed. The highest risk of doping behaviour in males is found for those athletes who had been

  4. Rare-earth-doped nanophosphors for multicolor cathodoluminescence nanobioimaging using scanning transmission electron microscopy.

    PubMed

    Furukawa, Taichi; Fukushima, Shoichiro; Niioka, Hirohiko; Yamamoto, Naoki; Miyake, Jun; Araki, Tsutomu; Hashimoto, Mamoru

    2015-05-01

    We describe rare-earth-doped nanophosphors (RE-NPs) for biological imaging using cathodoluminescence(CL) microscopy based on scanning transmission electron microscopy (STEM). We report the first demonstration of multicolor CL nanobioimaging using STEM with nanophosphors. The CL spectra of the synthesized nanophosphors (Y2O3∶Eu, Y2O3∶Tb) were sufficiently narrow to be distinguished. From CL images of RE-NPs on an elastic carbon-coated copper grid, the spatial resolution was beyond the diffraction limit of light.Y2O3∶Tb and Y2O3∶Eu RE-NPs showed a remarkable resistance against electron beam exposure even at high acceleration voltage (80 kV) and retained a CL intensity of more than 97% compared with the initial intensity for 1 min. In biological CL imaging with STEM, heavy-metal-stained cell sections containing the RE-NPs were prepared,and both the CL images of RE-NPs and cellular structures, such as mitochondria, were clearly observed from STEM images with high contrast. The cellular CL imaging using RE-NPs also had high spatial resolution even though heavy-metal-stained cells are normally regarded as highly scattering media. Moreover, since theRE-NPs exhibit photoluminescence (PL) excited by UV light, they are useful for multimodal correlative imaging using CL and PL.

  5. Delta Doping High Purity CCDs and CMOS for LSST

    NASA Technical Reports Server (NTRS)

    Blacksberg, Jordana; Nikzad, Shouleh; Hoenk, Michael; Elliott, S. Tom; Bebek, Chris; Holland, Steve; Kolbe, Bill

    2006-01-01

    A viewgraph presentation describing delta doping high purity CCD's and CMOS for LSST is shown. The topics include: 1) Overview of JPL s versatile back-surface process for CCDs and CMOS; 2) Application to SNAP and ORION missions; 3) Delta doping as a back-surface electrode for fully depleted LBNL CCDs; 4) Delta doping high purity CCDs for SNAP and ORION; 5) JPL CMP thinning process development; and 6) Antireflection coating process development.

  6. High performance supercapacitors based on highly conductive nitrogen-doped graphene sheets.

    PubMed

    Qiu, Yongcai; Zhang, Xinfeng; Yang, Shihe

    2011-07-21

    Thermal nitridation of reduced graphene oxide sheets yields highly conductive (∼1000-3000 S m(-1)) N-doped graphene sheets, as a result of the restoration of the graphene network by the formation of C-N bonded groups and N-doping. Even without carbon additives, supercapacitors made of the N-doped graphene electrodes can deliver remarkable energy and power when operated at higher voltages, in the range of 0-4 V. This journal is © the Owner Societies 2011

  7. Sol-gel-derived hybrid materials multi-doped with rare-earth metal ions

    NASA Astrophysics Data System (ADS)

    Zelazowska, E.; Rysiakiewicz-Pasek, E.; Borczuch-Laczka, M.; Cholewa-Kowalska, K.

    2012-06-01

    Four different hybrid organic-inorganic materials based on TiO2-SiO2 matrices with organic additives and doped with rare-earth metal ions (III) from the group of europium, cerium, terbium, neodymium, dysprosium and samarium, were synthesized by sol-gel method. Tetraethyl orthosilicate, titanium (IV) isopropoxide and organic compounds, such as butyl acrylate, butyl methacrylate, ethyl acetoacetate, ethylene glycol dimethacrylate, ethyl acetate, propylene carbonate, organic solvents and certain inorganic salts were used in the synthesis. The inorganic part of the sols, which were used in the synthesis of all the hybrid materials, was prepared separately and then the organic parts were added. The materials obtained were aged for three weeks at room temperature and then heated in an electric oven for three hours at temperatures of 80 °C-150 °C. Scanning electron microscopy equipped with energy dispersive X-ray spectroscopy (SEM/EDX); X-ray diffraction (XRD); Fourier transform infrared spectroscopy (KBr technique); 29Si magic-angle spinning nuclear magnetic resonance; and fluorescence spectroscopy were used for the examination of morphology, microstructure and luminescence properties, respectively. Photoluminescence properties with relatively intense narrow emission lines of Tb, Eu, Dy, Nd, Sm respectively to the RE-ions doping, were observed for all the hybrid materials.

  8. Highly doped layer for tunnel junctions in solar cells

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Fetzer, Christopher M.

    A highly doped layer for interconnecting tunnel junctions in multijunction solar cells is presented. The highly doped layer is a delta doped layer in one or both layers of a tunnel diode junction used to connect two or more p-on-n or n-on-p solar cells in a multijunction solar cell. A delta doped layer is made by interrupting the epitaxial growth of one of the layers of the tunnel diode, depositing a delta dopant at a concentration substantially greater than the concentration used in growing the layer of the tunnel diode, and then continuing to epitaxially grow the remaining tunnel diode.

  9. Highly textured and transparent RF sputtered Eu2O3 doped ZnO films

    PubMed Central

    Sreedharan, Remadevi Sreeja; Ganesan, Vedachalaiyer; Sudarsanakumar, Chellappan Pillai; Bhavsar, Kaushalkumar; Prabhu, Radhakrishna; Mahadevan Pillai, Vellara Pappukutty Pillai

    2015-01-01

    Background Zinc oxide (ZnO) is a wide, direct band gap II-VI oxide semiconductor. ZnO has large exciton binding energy at room temperature, and it is a good host material for obtaining visible and infrared emission of various rare-earth ions. Methods Europium oxide (Eu2O3) doped ZnO films are prepared on quartz substrate using radio frequency (RF) magnetron sputtering with doping concentrations 0, 0.5, 1, 3 and 5 wt%. The films are annealed in air at a temperature of 773 K for 2 hours. The annealed films are characterized using X-ray diffraction (XRD), micro-Raman spectroscopy, atomic force microscopy, ultraviolet (UV)-visible spectroscopy and photoluminescence (PL) spectroscopy. Results XRD patterns show that the films are highly c-axis oriented exhibiting hexagonalwurtzite structure of ZnO. Particle size calculations using Debye-Scherrer formula show that average crystalline size is in the range 15–22 nm showing the nanostructured nature of the films. The observation of low- and high-frequency E2 modes in the Raman spectra supports the hexagonal wurtzite structure of ZnO in the films. The surface morphology of the Eu2O3 doped films presents dense distribution of grains. The films show good transparency in the visible region. The band gaps of the films are evaluated using Tauc plot model. Optical constants such as refractive index, dielectric constant, loss factor, and so on are calculated using the transmittance data. The PL spectra show both UV and visible emissions. Conclusion Highly textured, transparent, luminescent Eu2O3 doped ZnO films have been synthesized using RF magnetron sputtering. The good optical and structural properties and intense luminescence in the ultraviolet and visible regions from the films suggest their suitability for optoelectronic applications. PMID:25765728

  10. Silicon rich nitride ring resonators for rare - earth doped telecommunications-band amplifiers pumped at the O-band.

    PubMed

    Xing, P; Chen, G F R; Zhao, X; Ng, D K T; Tan, M C; Tan, D T H

    2017-08-22

    Ring resonators on silicon rich nitride for potential use as rare-earth doped amplifiers pumped at 1310 nm with amplification at telecommunications-band are designed and characterized. The ring resonators are fabricated on 300 nm and 400 nm silicon rich nitride films and characterized at both 1310 nm and 1550 nm. We demonstrate ring resonators exhibiting similar quality factors exceeding 10,000 simultaneously at 1310 nm and 1550 nm. A Dysprosium-Erbium material system exhibiting photoluminescence at 1510 nm when pumped at 1310 nm is experimentally demonstrated. When used together with Dy-Er co-doped particles, these resonators with similar quality factors at 1310 nm and 1550 nm may be used for O-band pumped amplifiers for the telecommunications-band.

  11. Towards atomic scale engineering of rare-earth-doped SiAlON ceramics through aberration-corrected scanning transmission electron microscopy

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Yurdakul, Hilmi; Idrobo Tapia, Juan C; Pennycook, Stephen J

    2011-01-01

    Direct visualization of rare earths in {alpha}- and {beta}-SiAlON unit-cells is performed through Z-contrast imaging technique in an aberration-corrected scanning transmission electron microscope. The preferential occupation of Yb and Ce atoms in different interstitial locations of {beta}-SiAlON lattice is demonstrated, yielding higher solubility for Yb than Ce. The triangular-like host sites in {alpha}-SiAlON unit cell accommodate more Ce atoms than hexagonal sites in {beta}-SiAlON. We think that our results will be applicable as guidelines for many kinds of rare-earth-doped materials.

  12. High-field transport properties of a P-doped BaFe2As2 film on technical substrate

    PubMed Central

    Iida, Kazumasa; Sato, Hikaru; Tarantini, Chiara; Hänisch, Jens; Jaroszynski, Jan; Hiramatsu, Hidenori; Holzapfel, Bernhard; Hosono, Hideo

    2017-01-01

    High temperature (high-Tc) superconductors like cuprates have superior critical current properties in magnetic fields over other superconductors. However, superconducting wires for high-field-magnet applications are still dominated by low-Tc Nb3Sn due probably to cost and processing issues. The recent discovery of a second class of high-Tc materials, Fe-based superconductors, may provide another option for high-field-magnet wires. In particular, AEFe2As2 (AE: Alkali earth elements, AE-122) is one of the best candidates for high-field-magnet applications because of its high upper critical field, Hc2, moderate Hc2 anisotropy, and intermediate Tc. Here we report on in-field transport properties of P-doped BaFe2As2 (Ba-122) thin films grown on technical substrates by pulsed laser deposition. The P-doped Ba-122 coated conductor exceeds a transport Jc of 105 A/cm2 at 15 T for main crystallographic directions of the applied field, which is favourable for practical applications. Our P-doped Ba-122 coated conductors show a superior in-field Jc over MgB2 and NbTi, and a comparable level to Nb3Sn above 20 T. By analysing the E − J curves for determining Jc, a non-Ohmic linear differential signature is observed at low field due to flux flow along the grain boundaries. However, grain boundaries work as flux pinning centres as demonstrated by the pinning force analysis. PMID:28079117

  13. High-field transport properties of a P-doped BaFe2As2 film on technical substrate

    NASA Astrophysics Data System (ADS)

    Iida, Kazumasa; Sato, Hikaru; Tarantini, Chiara; Hänisch, Jens; Jaroszynski, Jan; Hiramatsu, Hidenori; Holzapfel, Bernhard; Hosono, Hideo

    2017-01-01

    High temperature (high-Tc) superconductors like cuprates have superior critical current properties in magnetic fields over other superconductors. However, superconducting wires for high-field-magnet applications are still dominated by low-Tc Nb3Sn due probably to cost and processing issues. The recent discovery of a second class of high-Tc materials, Fe-based superconductors, may provide another option for high-field-magnet wires. In particular, AEFe2As2 (AE: Alkali earth elements, AE-122) is one of the best candidates for high-field-magnet applications because of its high upper critical field, Hc2, moderate Hc2 anisotropy, and intermediate Tc. Here we report on in-field transport properties of P-doped BaFe2As2 (Ba-122) thin films grown on technical substrates by pulsed laser deposition. The P-doped Ba-122 coated conductor exceeds a transport Jc of 105 A/cm2 at 15 T for main crystallographic directions of the applied field, which is favourable for practical applications. Our P-doped Ba-122 coated conductors show a superior in-field Jc over MgB2 and NbTi, and a comparable level to Nb3Sn above 20 T. By analysing the E - J curves for determining Jc, a non-Ohmic linear differential signature is observed at low field due to flux flow along the grain boundaries. However, grain boundaries work as flux pinning centres as demonstrated by the pinning force analysis.

  14. X-Ray Absorption Spectroscopy Studies of the Atomic Structure of Zirconium-Doped Lithium Silicate Glasses and Glass-Ceramics, Zirconium-Doped Lithium Borate Glasses, and Vitreous Rare-Earth Phosphates

    NASA Astrophysics Data System (ADS)

    Yoo, Changhyeon

    In the first part of this work, the atomic-scale structure around rare-earth (RE = Pr, Nd, Eu, Dy, and Er) cations (RE3+) in rare-earth sodium ultraphosphate (REUP) glasses were investigated using RE LIII -edge (RE = Nd, Er, Dy, and Eu) and K-edge (RE = Pr and Dy) Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy. (RE2O 3)x(Na2O)y(P2O5) 1-x-y glasses in the compositional range 0 ≤ x ≤ 0.14 and 0.3 ≤ x + y ≤ 0.4 were studied. For the nearest oxygen shell, the RE-oxygen (RE-O) coordination number decreases from 10.8 to 6.5 with increasing RE content for Pr-, Nd-, Dy-, and Er-doped sodium ultraphosphate glasses. For Eu-doped samples, the Eu-O coordination number was between 7.5 and 8.8. Also, the RE-O mean distance ranges were between 2.43-2.45 A, 2.40-2.43 A, 2.36-2.38 A, 2.30-2.35 A, and 2.28-2.30 A for Pr-, Nd-, Eu-, Dy-, and Er-doped samples, respectively. In the second part, a series of Zr-doped (3-10 mol%) lithium silicate (ZRLS) glass-ceramics and their parent glasses and a series of Zr-doped (2-6 mol% ZrO2) lithium borate (ZRLB) glasses were investigated using Zr K-edge EXAFS and X-ray Absorption Near Edge Structure (XANES) spectroscopy. Immediate coordination environments of all ZRLS glasses are remarkably similar for different compositions. For the nearest oxygen shell, the Zr-O coordination number ranges were between 6.1 and 6.3 for nucleated and crystallized samples, respectively. Also, the Zr-O mean distance remains similar around 2.10 A. For these glasses, the composition dependence of structural parameters was small. Small changes in the coordination environment were observed for ZRLS glass-ceramics after thermal treatments. In contrast, Zr coordination environment in ZRLB glasses appear to depend appreciably on the Zr concentration. For the nearest oxygen shell, the Zr-O coordination number increased from 6.1 to 6.8 and the Zr-O distance decreased from 2.18 A to 2.14 A with decreasing ZrO2 content.

  15. Rare Earth Doped IR Fiber Lasers For Medical Applications

    NASA Astrophysics Data System (ADS)

    Esterowitz, Leon; Allen, Roger

    1989-06-01

    Trivalent rare earth doped lasers in fluorozirconate glasses and fibers that lase between 2 and 3 μm are reviewed. There have been a large number of laser-fiber optic systems below 2pm developed for clinical microsurgery at a variety of sites. The required flexibility of the fiber optic waveguide varies with the clinical use, such as: intraocular (through a small diameter rigid tube), endoscopically accessible pulmonary and gastric mucosa (through a port of a fiber-optic endoscope of intermediate flexibility), and intra-arterial (as an integral part of a flexible catheter, which in the case of the coronaries must be very flexible so as to negotiate abrupt bends and bifurcations without damage to the vessels). Laser energy absorbed by tissue is capable of coagulation of tissue (denaturation of structural proteins), melting of fatty deposits or other structures (solid or gel to liquid phase transitions), as well as direct breakage of chemical bonds by high energy photons. It is of general interest to develop a pulsed laser system transmitted through flexible fiber optics that is capable of precise ablation of targeted tissue with minimal damage to the remaining tissue. Ideally, the device should be able to ablate any tissue because of the general absorptive properties of tissue, and not a specific chromophore such as melanin or hemoglobin, the concentration of which varies widely among tissues. Two obvious ubiquitous chromophores have been widely discussed: 1) proteins and nucleic acids whose high concentration and absorption coefficients lead to strong tissue absorption in the ultraviolet and 2) water whose strong infrared absorption bands have been widely utilized in CO2 laser surgery. Non-linear absorption occurring at very high power densities (~1 GW/cm2) has been shown to be very effective for non-invasive ocular (an optically transparent field) microsurgery at the image plane of a slit lamp, but this approach appears impractical in fiber optic systems because

  16. Dispersive heterodyne probing method for laser frequency stabilization based on spectral hole burning in rare-earth doped crystals.

    PubMed

    Gobron, O; Jung, K; Galland, N; Predehl, K; Le Targat, R; Ferrier, A; Goldner, P; Seidelin, S; Le Coq, Y

    2017-06-26

    Frequency-locking a laser to a spectral hole in rare-earth doped crystals at cryogenic temperature has been shown to be a promising alternative to the use of high finesse Fabry-Perot cavities when seeking a very high short term stability laser (M. J. Thorpe et al., Nature Photonics 5, 688 (2011)). We demonstrate here a novel technique for achieving such stabilization, based on generating a heterodyne beat-note between a master laser and a slave laser whose dephasing caused by propagation near a spectral hole generate the error signal of the frequency lock. The master laser is far detuned from the center of the inhomogeneous absorption profile, and therefore exhibits only limited interaction with the crystal despite a potentially high optical power. The demodulation and frequency corrections are generated digitally with a hardware and software implementation based on a field-programmable gate array and a Software Defined Radio platform, making it straightforward to address several frequency channels (spectral holes) in parallel.

  17. Production yield of rare-earth ions implanted into an optical crystal

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kornher, Thomas, E-mail: t.kornher@physik.uni-stuttgart.de; Xia, Kangwei; Kolesov, Roman

    2016-02-01

    Rare-earth (RE) ions doped into desired locations of optical crystals might enable a range of novel integrated photonic devices for quantum applications. With this aim, we have investigated the production yield of cerium and praseodymium by means of ion implantation. As a measure, the collected fluorescence intensity from both implanted samples and single centers was used. With a tailored annealing procedure for cerium, a yield up to 53% was estimated. Praseodymium yield amounts up to 91%. Such high implantation yield indicates a feasibility of creation of nanopatterned rare-earth doping and suggests strong potential of RE species for on-chip photonic devices.

  18. Environment spectrum and coherence behaviours in a rare-earth doped crystal for quantum memory.

    PubMed

    Gong, Bo; Tu, Tao; Zhou, Zhong-Quan; Zhu, Xing-Yu; Li, Chuan-Feng; Guo, Guang-Can

    2017-12-21

    We theoretically investigate the dynamics of environment and coherence behaviours of the central ion in a quantum memory based on a rare-earth doped crystal. The interactions between the central ion and the bath spins suppress the flip-flop rate of the neighbour bath spins and yield a specific environment spectral density S(ω). Under dynamical decoupling pulses, this spectrum provides a general scaling for the coherence envelope and coherence time, which significantly extend over a range on an hour-long time scale. The characterized environment spectrum with ultra-long coherence time can be used to implement various quantum communication and information processing protocols.

  19. An in situ vapour phase hydrothermal surface doping approach for fabrication of high performance Co3O4 electrocatalysts with an exceptionally high S-doped active surface.

    PubMed

    Tan, Zhijin; Liu, Porun; Zhang, Haimin; Wang, Yun; Al-Mamun, Mohammad; Yang, Hua Gui; Wang, Dan; Tang, Zhiyong; Zhao, Huijun

    2015-04-04

    A facile in situ vapour phase hydrothermal (VPH) surface doping approach has been developed for fabrication of high performance S-doped Co3O4 electrocatalysts with an unprecedentedly high surface S content (>47%). The demonstrated VPH doping approach could be useful for enrichment of surface active sites for other metal oxide electrocatalysts.

  20. N-Type delta Doping of High-Purity Silicon Imaging Arrays

    NASA Technical Reports Server (NTRS)

    Blacksberg, Jordana; Hoenk, Michael; Nikzad, Shouleh

    2005-01-01

    A process for n-type (electron-donor) delta doping has shown promise as a means of modifying back-illuminated image detectors made from n-doped high-purity silicon to enable them to detect high-energy photons (ultraviolet and x-rays) and low-energy charged particles (electrons and ions). This process is applicable to imaging detectors of several types, including charge-coupled devices, hybrid devices, and complementary metal oxide/semiconductor detector arrays. Delta doping is so named because its density-vs.-depth characteristic is reminiscent of the Dirac delta function (impulse function): the dopant is highly concentrated in a very thin layer. Preferably, the dopant is concentrated in one or at most two atomic layers in a crystal plane and, therefore, delta doping is also known as atomic-plane doping. The use of doping to enable detection of high-energy photons and low-energy particles was reported in several prior NASA Tech Briefs articles. As described in more detail in those articles, the main benefit afforded by delta doping of a back-illuminated silicon detector is to eliminate a "dead" layer at the back surface of the silicon wherein high-energy photons and low-energy particles are absorbed without detection. An additional benefit is that the delta-doped layer can serve as a back-side electrical contact. Delta doping of p-type silicon detectors is well established. The development of the present process addresses concerns specific to the delta doping of high-purity silicon detectors, which are typically n-type. The present process involves relatively low temperatures, is fully compatible with other processes used to fabricate the detectors, and does not entail interruption of those processes. Indeed, this process can be the last stage in the fabrication of an imaging detector that has, in all other respects, already been fully processed, including metallized. This process includes molecular-beam epitaxy (MBE) for deposition of three layers, including

  1. Laser doping of boron-doped Si paste for high-efficiency silicon solar cells

    NASA Astrophysics Data System (ADS)

    Tomizawa, Yuka; Imamura, Tetsuya; Soeda, Masaya; Ikeda, Yoshinori; Shiro, Takashi

    2015-08-01

    Boron laser doping (LD) is a promising technology for high-efficiency solar cells such as p-type passivated locally diffused solar cells and n-type Si-wafer-based solar cells. We produced a printable phosphorus- or boron-doped Si paste (NanoGram® Si paste/ink) for use as a diffuser in the LD process. We used the boron LD process to fabricate high-efficiency passivated emitter and rear locally diffused (PERL) solar cells. PERL solar cells on Czochralski Si (Cz-Si) wafers yielded a maximum efficiency of 19.7%, whereas the efficiency of a reference cell was 18.5%. Fill factors above 79% and open circuit voltages above 655 mV were measured. We found that the boron-doped area effectively performs as a local boron back surface field (BSF). The characteristics of the solar cell formed using NanoGram® Si paste/ink were better than those of the reference cell.

  2. High-field transport properties of a P-doped BaFe2As2 film on technical substrate.

    PubMed

    Iida, Kazumasa; Sato, Hikaru; Tarantini, Chiara; Hänisch, Jens; Jaroszynski, Jan; Hiramatsu, Hidenori; Holzapfel, Bernhard; Hosono, Hideo

    2017-01-12

    High temperature (high-T c ) superconductors like cuprates have superior critical current properties in magnetic fields over other superconductors. However, superconducting wires for high-field-magnet applications are still dominated by low-T c Nb 3 Sn due probably to cost and processing issues. The recent discovery of a second class of high-T c materials, Fe-based superconductors, may provide another option for high-field-magnet wires. In particular, AEFe 2 As 2 (AE: Alkali earth elements, AE-122) is one of the best candidates for high-field-magnet applications because of its high upper critical field, H c2 , moderate H c2 anisotropy, and intermediate T c . Here we report on in-field transport properties of P-doped BaFe 2 As 2 (Ba-122) thin films grown on technical substrates by pulsed laser deposition. The P-doped Ba-122 coated conductor exceeds a transport J c of 10 5  A/cm 2 at 15 T for main crystallographic directions of the applied field, which is favourable for practical applications. Our P-doped Ba-122 coated conductors show a superior in-field J c over MgB 2 and NbTi, and a comparable level to Nb 3 Sn above 20 T. By analysing the E - J curves for determining J c , a non-Ohmic linear differential signature is observed at low field due to flux flow along the grain boundaries. However, grain boundaries work as flux pinning centres as demonstrated by the pinning force analysis.

  3. In Situ Neutron Diffraction of Rare-Earth Phosphate Proton Conductors Sr/Ca-doped LaPO4 at Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Al-Wahish, Amal; Al-Binni, Usama; Bridges, C. A.; Huq, A.; Bi, Z.; Paranthaman, M. P.; Tang, S.; Kaiser, H.; Mandrus, D.

    Acceptor-doped lanthanum orthophosphates are potential candidate electrolytes for proton ceramic fuel cells. We combined neutron powder diffraction (NPD) at elevated temperatures up to 800° C , X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) to investigate the crystal structure, defect structure, thermal stability and surface topography. NPD shows an average bond length distortion in the hydrated samples. We employed Quasi-Elastic Neutron Scattering (QENS) and electrochemical impedance spectroscopy (EIS) to study the proton dynamics of the rare-earth phosphate proton conductors 4.2% Sr/Ca-doped LaPO4. We determined the bulk diffusion and the self-diffusion coefficients. Our results show that QENS and EIS are probing fundamentally different proton diffusion processes. Supported by the U.S. Department of Energy.

  4. Cobalt nanoparticles/nitrogen-doped graphene with high nitrogen doping efficiency as noble metal-free electrocatalysts for oxygen reduction reaction.

    PubMed

    Liang, Jingwen; Hassan, Mehboob; Zhu, Dongsheng; Guo, Liping; Bo, Xiangjie

    2017-03-15

    Nitrogen-doped graphene (N/GR) has been considered as active metal-free electrocatalysts for oxygen reduction reaction (ORR). However, the nitrogen (N) doping efficiency is very low and only few N atoms are doped into the framework of GR. To boost the N doping efficiency, in this work, a confined pyrolysis method with high N doping efficiency is used for the preparation of cobalt nanoparticles/nitrogen-doped GR (Co/N/GR). Under the protection of SiO 2 , the inorganic ligand NH 3 in cobalt amine complex ([Co(NH 3 ) 6 ] 3+ ) is trapped in the confined space and then can be effectively doped into the framework of GR without the introduction of any carbon residues. Meanwhile, due to the redox reaction between the cobalt ions and carbon atoms of GR, Co nanoparticles are supported into the framework of N/GR. Due to prevention of GR layer aggregation with SiO 2 , the Co/N/GR with high dispersion provides sufficient surface area and maximum opportunity for the exposure of Co nanoparticles and active sites of N dopant. By combination of enhanced N doping efficiency, Co nanoparticles and high dispersion of GR sheets, the Co/N/GR is remarkably active, cheap and selective noble-metal free catalysts for ORR. Copyright © 2016 Elsevier Inc. All rights reserved.

  5. Ultra High p-doping Material Research for GaN Based Light Emitters

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Vladimir Dmitriev

    2007-06-30

    The main goal of the Project is to investigate doping mechanisms in p-type GaN and AlGaN and controllably fabricate ultra high doped p-GaN materials and epitaxial structures. Highly doped p-type GaN-based materials with low electrical resistivity and abrupt doping profiles are of great importance for efficient light emitters for solid state lighting (SSL) applications. Cost-effective hydride vapor phase epitaxial (HVPE) technology was proposed to investigate and develop p-GaN materials for SSL. High p-type doping is required to improve (i) carrier injection efficiency in light emitting p-n junctions that will result in increasing of light emitting efficiency, (ii) current spreading inmore » light emitting structures that will improve external quantum efficiency, and (iii) parameters of Ohmic contacts to reduce operating voltage and tolerate higher forward currents needed for the high output power operation of light emitters. Highly doped p-type GaN layers and AlGaN/GaN heterostructures with low electrical resistivity will lead to novel device and contact metallization designs for high-power high efficiency GaN-based light emitters. Overall, highly doped p-GaN is a key element to develop light emitting devices for the DOE SSL program. The project was focused on material research for highly doped p-type GaN materials and device structures for applications in high performance light emitters for general illumination P-GaN and p-AlGaN layers and multi-layer structures were grown by HVPE and investigated in terms of surface morphology and structure, doping concentrations and profiles, optical, electrical, and structural properties. Tasks of the project were successfully accomplished. Highly doped GaN materials with p-type conductivity were fabricated. As-grown GaN layers had concentration N{sub a}-N{sub d} as high as 3 x 10{sup 19} cm{sup -3}. Mechanisms of doping were investigated and results of material studies were reported at several International conferences

  6. Atomic layer deposition of highly-doped Er:Al2O3 and Tm:Al2O3 for silicon-based waveguide amplifiers (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Roenn, John; Karvonen, Lasse; Pyymäki-Perros, Alexander; Peyghambarian, Nasser; Lipsanen, Harri; Säynätjoki, Antti; Sun, Zhipei

    2016-05-01

    Recently, rare-earth doped waveguide amplifiers (REDWAs) have drawn significant attention as a promising solution to on-chip amplification of light in silicon photonics and integrated optics by virtue of their high excited state lifetime (up to 10 ms) and broad emission spectrum (up to 200 nm) at infrared wavelengths. In the family of rare-earths, at least erbium, holmium, thulium, neodymium and ytterbium have been demonstrated to be good candidates for amplifier operation at moderate concentrations (< 0.1 %). However, efficient amplifier operation in REDWAs is a very challenging task because high concentration of ions (<0.1%) is required in order to produce reasonable amplification over short device length. Inevitably, high concentration of ions leads to energy-transfer between neighboring ions, which results as decreased gain and increased noise in the amplifier system. It has been shown that these energy-transfer mechanisms in highly-doped gain media are inversely proportional to the sixth power of the distance between the ions. Therefore, novel fabrication techniques with the ability to control the distribution of the rare-earth ions within the gain medium are urgently needed in order to fabricate REDWAs with high efficiency and low noise. Here, we show that atomic layer deposition (ALD) is an excellent technique to fabricate highly-doped (<1%) RE:Al2O3 gain materials by using its nanoscale engineering ability to delicately control the incorporation of RE ions during the deposition. In our experiment, we fabricated Er:Al2O3 and Tm:Al2O3 thin films with ALD by varying the concentration of RE ions from 1% to 7%. By measuring the photoluminescence response of the fabricated samples, we demonstrate that it is possible to incorporate up to 5% of either Er- or Tm-ions in Al2O3 host before severe quenching occurs. We believe that this technique can be extended to other RE ions as well. Therefore, our results show the exceptionality of ALD as a deposition technique for

  7. High-Current-Density Vertical-Tunneling Transistors from Graphene/Highly Doped Silicon Heterostructures.

    PubMed

    Liu, Yuan; Sheng, Jiming; Wu, Hao; He, Qiyuan; Cheng, Hung-Chieh; Shakir, Muhammad Imran; Huang, Yu; Duan, Xiangfeng

    2016-06-01

    Scalable fabrication of vertical-tunneling transistors is presented based on heterostructures formed between graphene, highly doped silicon, and its native oxide. Benefiting from the large density of states of highly doped silicon, the tunneling transistors can deliver a current density over 20 A cm(-2) . This study demonstrates that the interfacial native oxide plays a crucial role in governing the carrier transport in graphene-silicon heterostructures. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Advances in highly doped upconversion nanoparticles.

    PubMed

    Wen, Shihui; Zhou, Jiajia; Zheng, Kezhi; Bednarkiewicz, Artur; Liu, Xiaogang; Jin, Dayong

    2018-06-20

    Lanthanide-doped upconversion nanoparticles (UCNPs) are capable of converting near-infra-red excitation into visible and ultraviolet emission. Their unique optical properties have advanced a broad range of applications, such as fluorescent microscopy, deep-tissue bioimaging, nanomedicine, optogenetics, security labelling and volumetric display. However, the constraint of concentration quenching on upconversion luminescence has hampered the nanoscience community to develop bright UCNPs with a large number of dopants. This review surveys recent advances in developing highly doped UCNPs, highlights the strategies that bypass the concentration quenching effect, and discusses new optical properties as well as emerging applications enabled by these nanoparticles.

  9. Luminescence quenching versus enhancement in WO3-NaPO3 glasses doped with trivalent rare earth ions and containing silver nanoparticles

    NASA Astrophysics Data System (ADS)

    Dousti, M. Reza; Poirier, Gael Y.; Amjad, Raja J.; de Camargo, Andrea S. S.

    2016-10-01

    We report on the influence of silver nanoparticles (NPs) on the luminescence behavior of trivalent rare earth (RE) ion doped tungsten-phosphate glasses. In order to induce the growth of NPs, the as-prepared glass samples containing silver atoms, are exposed to heat-treatment above the glass transition temperature. The surface plasmon resonance band of the Ag NPs is observed in the visible range around 420 and 537 nm in the glasses with low and high tungsten content, respectively. Such difference in spectral shift of the plasmon band is attributed to the difference in the refractive index of the two studied glass compositions. Heat-treatment results in the general increase in number of NPs, while in the case of glasses with low tungsten content, it also imposes a shift to the Ag plasmon band. The NPs size distribution (4-10 nm) was determined in good agreement with the values obtained by using Mie theory and by transmission electron microscopy. The observed quenching in the visible luminescence of glasses doped with Eu3+, Tb3+ or Er3+is attributed to energy transfer from the RE ions to Ag species, while an enhanced near-infrared emission in Er3+ doped glasses is discussed in terms of the chemical contribution of silver, rather than the most commonly claimed enhancement of localized field or energy transfer from silver species to Er3+. The results are supported by the lifetime measurements. We believe that this study gives further insight and in-depth exploration of the somewhat controversial discussions on the influence of metallic NPs plasmonic effects in RE-doped glasses.

  10. Effect of Boron Doping on High-Resolution X-Ray Diffraction Metrology

    NASA Astrophysics Data System (ADS)

    Faheem, M.; Zhang, Y.; Dai, X.

    2018-03-01

    The effect of boron (B) doping on high-resolution X-ray diffraction (HXRD) metrology has been investigated. Twelve samples of Si1-xGex films were epitaxially grown on Si (100) substrates with different thicknesses, germanium (Ge) concentrations and with/without B dopants. Secondary ion mass spectroscopy (SIMS) and HXRD were employed for measurements of B doping, Ge concentration, strain, and thickness of the layers. The SIMS results show the absence of B in two samples while the rest of the samples have B doping in the range of 8.40 × 1018-8.7 × 1020 atoms/cm3 with Ge concentration of 13.3-55.2 at.%. The HXRD measurements indicate the layers thickness of 7.07-108.13 nm along with Ge concentration of 12.82-49.09 at.%. The difference in the Ge concentration measured by SIMS and HXRD was found to deend on B doping. For the undoped samples, the difference is 0.5 at.% and increases with B doping but with no linear proportionality. The difference in the Ge concentration was 7.11 at.% for the highly B-doped (8.7 × 1020 atoms/cm3) sample. The B doping influences the Si1-xGex structure, causing a change in the lattice parameter and producing tensile strains shifting Si1-xGex peaks towards Si (100) substrate peaks in the HXRD diffraction patterns. As a result, Vegard's law is no longer effective and makes a high impact on the HXRD measurement. The comparison between symmetric (004) and asymmetric (+113, +224) reciprocal space mappings (RSM) showed a slight difference in Ge concentration between the undoped and lower B-doped samples. However, there is a change of 0.21 at.% observed for the highly doped Si1-xGex samples. RSM's (+113) demonstrate the small SiGe peak broadening as B doping increases, which indicates a minor crystal distortion.

  11. High Resolution Fluorescence Imaging of Cancers Using Lanthanide Ion-Doped Upconverting Nanocrystals

    PubMed Central

    Naccache, Rafik; Rodríguez, Emma Martín; Bogdan, Nicoleta; Sanz-Rodríguez, Francisco; de la Cruz, Maria del Carmen Iglesias; de la Fuente, Ángeles Juarranz; Vetrone, Fiorenzo; Jaque, Daniel; Solé, José García; Capobianco, John A.

    2012-01-01

    During the last decade inorganic luminescent nanoparticles that emit visible light under near infrared (NIR) excitation (in the biological window) have played a relevant role for high resolution imaging of cancer. Indeed, semiconductor quantum dots (QDs) and metal nanoparticles, mostly gold nanorods (GNRs), are already commercially available for this purpose. In this work we review the role which is being played by a relatively new class of nanoparticles, based on lanthanide ion doped nanocrystals, to target and image cancer cells using upconversion fluorescence microscopy. These nanoparticles are insulating nanocrystals that are usually doped with small percentages of two different rare earth (lanthanide) ions: The excited donor ions (usually Yb3+ ion) that absorb the NIR excitation and the acceptor ions (usually Er3+, Ho3+ or Tm3+), that are responsible for the emitted visible (or also near infrared) radiation. The higher conversion efficiency of these nanoparticles in respect to those based on QDs and GNRs, as well as the almost independent excitation/emission properties from the particle size, make them particularly promising for fluorescence imaging. The different approaches of these novel nanoparticles devoted to “in vitro” and “in vivo” cancer imaging, selective targeting and treatment are examined in this review. PMID:24213500

  12. Rare-Earth Doping and Co-Doping of GaN for Magnetic and Luminescent Applications

    DTIC Science & Technology

    2010-08-16

    The main focus of this project is the study of Gadolinium doped Gallium Nitride. Calculations were carried out to elucidate the origin of the reported...Ga vacancies in the triple negative charge state, which is the most likely charge state in semi-insulating samples, 1. REPORT DATE (DD-MM-YYYY) 4...applications Report Title ABSTRACT The main focus of this project is the study of Gadolinium doped Gallium Nitride. Calculations were carried out to

  13. Effects of rare earth ionic doping on microstructures and electrical properties of CaCu{sub 3}Ti{sub 4}O{sub 12} ceramics

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Xue, Renzhong; Department of Technology and Physics, Zhengzhou University of Light Industry, Zhengzhou 450002; Chen, Zhenping, E-mail: xrzbotao@163.com

    2015-06-15

    Graphical abstract: The dielectric constant decreases monotonically with reduced RE doping ion radius and is more frequency independent compared with that of pure CCTO sample. - Highlights: • The mean grain sizes decrease monotonically with reduced RE doping ionic radius. • Doping gives rise to the monotonic decrease of ϵ{sub r} with reduced RE ionic radius. • The nonlinear coefficient and breakdown field increase with RE ionic doping. • α of all the samples is associated with the potential barrier width rather than Φ{sub b}. - Abstract: Ca{sub 1–x}R{sub x}Cu{sub 3}Ti{sub 4}O{sub 12}(R = La, Nd, Eu, Gd, Er; xmore » = 0 and 0.005) ceramics were prepared by the conventional solid-state method. The influences of rare earth (RE) ion doping on the microstructure, dielectric and electrical properties of CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO) ceramics were investigated systematically. Single-phase formation is confirmed by XRD analyses. The mean grain size decreases monotonically with reduced RE ion radius. The EDS results reveal that RE ionic doping reduces Cu-rich phase segregation at the grain boundaries (GBs). Doping gives rise to the monotonic decrease of dielectric constant with reduced RE ionic radius but significantly improves stability with frequency. The lower dielectric loss of doped samples is obtained due to the increase of GB resistance. In addition, the nonlinear coefficient and breakdown field increase with RE ionic doping. Both the fine grains and the enhancement of potential barrier at GBs are responsible for the improvement of the nonlinear current–voltage properties in doped CCTO samples.« less

  14. Highly concentrated, stable nitrogen-doped graphene for supercapacitors: Simultaneous doping and reduction

    NASA Astrophysics Data System (ADS)

    Jiang, Baojiang; Tian, Chungui; Wang, Lei; Sun, Li; Chen, Chen; Nong, Xiaozhen; Qiao, Yingjie; Fu, Honggang

    2012-02-01

    In this work, we developed a concentrated ammonia-assisted hydrothermal method to obtain N-doped graphene sheets by simultaneous N-doping and reduction of graphene oxide (GO) sheets. The effects of hydrothermal temperature on the surface chemistry and the structure of N-doped graphene sheets were also investigated. X-ray photoelectron spectroscopy (XPS) study of N-doped graphene reveals that the highest doping level of 7.2% N is achieved at 180 °C for 12 h. N binding configurations of sample consist of pyridine N, quaternary N, and pyridine-N oxides. N doping is accompanied by the reduction of GO with decreases in oxygen levels from 34.8% in GO down to 8.5% in that of N-doped graphene. Meanwhile, the sample exhibits excellent N-doped thermal stability. Electrical measurements demonstrate that products have higher capacitive performance than that of pure graphene, the maximum specific capacitance of 144.6 F/g can be obtained which ascribe the pseudocapacitive effect from the N-doping. The samples also show excellent long-term cycle stability of capacitive performance.

  15. High-Level Heteroatom Doped Two-Dimensional Carbon Architectures for Highly Efficient Lithium-Ion Storage.

    PubMed

    Wang, Zhijie; Wang, Yanyan; Wang, Wenhui; Yu, Xiaoliang; Lv, Wei; Xiang, Bin; He, Yan-Bing

    2018-01-01

    In this work, high-level heteroatom doped two-dimensional hierarchical carbon architectures (H-2D-HCA) are developed for highly efficient Li-ion storage applications. The achieved H-2D-HCA possesses a hierarchical 2D morphology consisting of tiny carbon nanosheets vertically grown on carbon nanoplates and containing a hierarchical porosity with multiscale pore size. More importantly, the H-2D-HCA shows abundant heteroatom functionality, with sulfur (S) doping of 0.9% and nitrogen (N) doping of as high as 15.5%, in which the electrochemically active N accounts for 84% of total N heteroatoms. In addition, the H-2D-HCA also has an expanded interlayer distance of 0.368 nm. When used as lithium-ion battery anodes, it shows excellent Li-ion storage performance. Even at a high current density of 5 A g -1 , it still delivers a high discharge capacity of 329 mA h g -1 after 1,000 cycles. First principle calculations verifies that such unique microstructure characteristics and high-level heteroatom doping nature can enhance Li adsorption stability, electronic conductivity and Li diffusion mobility of carbon nanomaterials. Therefore, the H-2D-HCA could be promising candidates for next-generation LIB anodes.

  16. High-Level Heteroatom Doped Two-Dimensional Carbon Architectures for Highly Efficient Lithium-Ion Storage

    PubMed Central

    Wang, Zhijie; Wang, Yanyan; Wang, Wenhui; Yu, Xiaoliang; Lv, Wei; Xiang, Bin; He, Yan-Bing

    2018-01-01

    In this work, high-level heteroatom doped two-dimensional hierarchical carbon architectures (H-2D-HCA) are developed for highly efficient Li-ion storage applications. The achieved H-2D-HCA possesses a hierarchical 2D morphology consisting of tiny carbon nanosheets vertically grown on carbon nanoplates and containing a hierarchical porosity with multiscale pore size. More importantly, the H-2D-HCA shows abundant heteroatom functionality, with sulfur (S) doping of 0.9% and nitrogen (N) doping of as high as 15.5%, in which the electrochemically active N accounts for 84% of total N heteroatoms. In addition, the H-2D-HCA also has an expanded interlayer distance of 0.368 nm. When used as lithium-ion battery anodes, it shows excellent Li-ion storage performance. Even at a high current density of 5 A g−1, it still delivers a high discharge capacity of 329 mA h g−1 after 1,000 cycles. First principle calculations verifies that such unique microstructure characteristics and high-level heteroatom doping nature can enhance Li adsorption stability, electronic conductivity and Li diffusion mobility of carbon nanomaterials. Therefore, the H-2D-HCA could be promising candidates for next-generation LIB anodes. PMID:29686985

  17. High-Level Heteroatom Doped Two-Dimensional Carbon Architectures for Highly Efficient Lithium-Ion Storage

    NASA Astrophysics Data System (ADS)

    Wang, Zhijie; Wang, Yanyan; Wang, Wenhui; Yu, Xiaoliang; Lv, Wei; Xiang, Bin; He, Yan-Bing

    2018-04-01

    In this work, high-level heteroatom doped two-dimensional hierarchical carbon architectures (H-2D-HCA) are developed for highly efficient Li-ion storage applications. The achieved H-2D-HCA possesses a hierarchical 2D morphology consisting of tiny carbon nanosheets vertically grown on carbon nanoplates and containing a hierarchical porosity with multiscale pore size. More importantly, the H-2D-HCA shows abundant heteroatom functionality, with sulfur (S) doping of 0.9 % and nitrogen (N) doping of as high as 15.5 %, in which the electrochemically active N accounts for 84 % of total N heteroatoms. In addition, the H-2D-HCA also has an expanded interlayer distance of 0.368 nm. When used as lithium-ion battery anodes, it shows excellent Li-ion storage performance. Even at a high current density of 5 A g-1, it still delivered a high discharge capacity of 329 mA h g-1 after 1000 cycles. First principle calculations verified that such unique microstructure characteristics and high-level heteroatom doping nature can enhance Li adsorption stability, electronic conductivity and Li diffusion mobility of carbon nanomaterials. Therefore, the H-2D-HCA could be promising candidates for next-generation LIB anodes.

  18. The manipulated left-handedness in a rare-earth-ion-doped optical fiber by the incoherent pumping field

    NASA Astrophysics Data System (ADS)

    Zhao, Shun-Cai; Guo, Hong-Wei; Wei, Xiao-Jing

    2017-10-01

    The left-handedness was demonstrated by the simulation with a three-level quantum system in an Er3+ -dopped ZrF4-BaF2-LaF3- AlF3-NaF (ZBLAFN) optical fiber. And the left-handedness can be regulated by the incoherent pumping field. Our scheme may provide a solid candidate other than the coherent atomic vapor for left-handedness, and may extend the application of the rare-earth-ion-doped optical fiber in metamaterials and of the incoherent pumping light field in quantum optics.

  19. Improvement of high-frequency characteristics of Z-type hexaferrite by dysprosium doping

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Mu Chunhong; Liu Yingli; Song Yuanqiang

    2011-06-15

    Z-type hexaferrite has great potential applications as anti-EMI material for magnetic devices in the GHz region. In this work, Dy-doped Z-type hexaferrites with nominal stoichiometry of Ba{sub 3}Co{sub 2}Dy{sub x}Fe{sub 24-x}O{sub 41} (x 0.0, 0.05, 0.5, 1.0) were prepared by an improved solid-state reaction method. The effects of rare earth oxide (Dy{sub 2}O{sub 3}) addition on the phase composition, microstructure and electromagnetic properties of the ceramics were investigated. Structure and micromorphology characterizations indicate that certain content of Dy doping will cause the emergence of the second phase Dy{sub 3}Fe{sub 5}O{sub 12} at the grain boundaries of the majority phase Z-typemore » hexaferrite, due to which the straightforward result is the grain refinement during the successive sintering process. Permeability spectra measurements show that the initial permeability reaches its maximum of 17 at 300 MHz with x = 0.5, while the cutoff frequency keeps above 800 MHz. The apparent specific anisotropy field H{sub K} of Dy-doped Z-type hexaferrites decreases with x increasing. The relationships among phase composition, grain size, permeability spectra, and anisotropy are theoretically investigated, and according to the analysis, Dy doping effects on its magnetic properties can be well explained and understood.« less

  20. Delta-doping optimization for high quality p-type GaN

    NASA Astrophysics Data System (ADS)

    Bayram, C.; Pau, J. L.; McClintock, R.; Razeghi, M.

    2008-10-01

    Delta (δ -) doping is studied in order to achieve high quality p-type GaN. Atomic force microscopy, x-ray diffraction, photoluminescence, and Hall measurements are performed on the samples to optimize the δ-doping characteristics. The effect of annealing on the electrical, optical, and structural quality is also investigated for different δ-doping parameters. Optimized pulsing conditions result in layers with hole concentrations near 1018 cm-3 and superior crystal quality compared to conventional p-GaN. This material improvement is achieved thanks to the reduction in the Mg activation energy and self-compensation effects in δ-doped p-GaN.

  1. High-pressure studies on Ba-doped cobalt perovskites by neutron diffraction

    NASA Astrophysics Data System (ADS)

    Cao, Huibo; Garlea, Vasile; Wang, Fangwei; Dos Santos, Antonio; Cheng, Zhaohua

    2012-02-01

    Cobalt perovskite possess rich structural, magnetic and electrical properties depending on the subtle balance of the interactions among the spin, charge, and orbital degrees of freedom. Divalent hole-doped cobalt perovskites LaA^2+CoO3 exhibit structural phase transitions, metal-insulator transitions, and multi-magnetic phase transitions. High-pressure measurement is believed to mimic the size effects of the doped ions. We performed neutron diffraction experiments on selected Ba-doped LaCoO3 under pressures up to 6.3 GPa at SNAP at Spallation Neutron Source of ORNL. This work focuses on the high-pressure effects of the selected Ba-doped samples and the change of the phase diagram with pressure.

  2. [Doping. High-tech cheating in sport].

    PubMed

    Striegel, H; Simon, P

    2007-07-01

    Today, doping is no longer limited to the classical drugs with well known effects and side effects. Older generation anabolic steroids are used mainly in fitness and recreational sports. In contrast, due to doping tests, substances used in competitive sports include peptide hormones, medications not yet approved, and even specially developed drugs, such as designer steroids. Of the peptide hormones, particularly growth hormones (human growth hormone), erythropoietin and generics, insulin, and presumably insulin-like growth factor 1 are used. Substance groups potentially relevant for doping are selective androgen receptor modulators and gene therapy drugs. For most of these, there is no knowledge about side effects in healthy individuals, and no adequate doping tests. Therefore, anti-doping measures cannot rely solely on the continual improvement of doping analyses, but should include increased measures for doping prevention. Not only sports organizations, but also governmental agencies should be involved in developing and implementing these measures.

  3. Rare-earth doped transparent ceramics for spectral filtering and quantum information processing

    NASA Astrophysics Data System (ADS)

    Kunkel, Nathalie; Ferrier, Alban; Thiel, Charles W.; Ramírez, Mariola O.; Bausá, Luisa E.; Cone, Rufus L.; Ikesue, Akio; Goldner, Philippe

    2015-09-01

    Homogeneous linewidths below 10 kHz are reported for the first time in high-quality Eu3+ doped Y 2O3 transparent ceramics. This result is obtained on the 7F0→5D0 transition in Eu3+ doped Y 2O3 ceramics and corresponds to an improvement of nearly one order of magnitude compared to previously reported values in transparent ceramics. Furthermore, we observed spectral hole lifetimes of ˜15 min that are long enough to enable efficient optical pumping of the nuclear hyperfine levels. Additionally, different Eu3+ concentrations (up to 1.0%) were studied, resulting in an increase of up to a factor of three in the peak absorption coefficient. These results suggest that transparent ceramics can be useful in applications where narrow and deep spectral holes can be burned into highly absorbing lines, such as quantum information processing and spectral filtering.

  4. Preparation of Ce- and La-Doped Li4Ti5O12 Nanosheets and Their Electrochemical Performance in Li Half Cell and Li4Ti5O12/LiFePO4 Full Cell Batteries

    PubMed Central

    Qin, Meng; Li, Yueming; Lv, Xiao-Jun

    2017-01-01

    This work reports on the synthesis of rare earth-doped Li4Ti5O12 nanosheets with high electrochemical performance as anode material both in Li half and Li4Ti5O12/LiFePO4 full cell batteries. Through the combination of decreasing the particle size and doping by rare earth atoms (Ce and La), Ce and La doped Li4Ti5O12 nanosheets show the excellent electrochemical performance in terms of high specific capacity, good cycling stability and excellent rate performance in half cells. Notably, the Ce-doped Li4Ti5O12 shows good electrochemical performance as anode in a full cell which LiFePO4 was used as cathode. The superior electrochemical performance can be attributed to doping as well as the nanosized particle, which facilitates transportation of the lithium ion and electron transportation. This research shows that the rare earth doped Li4Ti5O12 nanosheets can be suitable as a high rate performance anode material in lithium-ion batteries. PMID:28632167

  5. Temperature Sensing Above 1000 C Using Cr-Doped GdAlO3 Spin-Allowed Broadband Luminescence

    NASA Technical Reports Server (NTRS)

    Eldridge, Jeffrey I.; Chambers, Matthew D.

    2012-01-01

    Cr-doped GdAlO3 (Cr:GdAlO3) is shown to produce remarkably high-intensity spin-allowed broadband luminescence with sufficiently long decay times to make effective luminescence-decay-time based temperature measurements above 1000 C. This phosphor is therefore an attractive alternative to the much lower luminescence intensity rare-earth-doped thermographic phosphors that are typically utilized at these elevated temperatures. In particular, Cr:GdAlO3 will be preferred over rare-earth-doped phosphors, such as Dy:YAG, at temperatures up to 1200 C for intensity-starved situations when the much lower emission intensity from rare-earth-doped phosphors is insufficient for accurate temperature measurements in the presence of significant radiation background. While transition-metal-doped phosphors such as Cr:Al2O3 (ruby) are known to exhibit high luminescence intensity at low dopant concentrations, quenching due to nonradiative decay pathways competing with the (sup 2)E to (sup 4)A(sub 2) radiative transition (R line) has typically restricted their use for temperature sensing to below 600 C. Thermal quenching of the broadband (sup 4)T(sub 2) to (sup 4)A(sub 2) radiative transition from Cr:GdAlO3, however, is delayed until much higher temperatures (above 1000 C). This spin-allowed broadband emission persists to high temperatures because the lower-lying (sup 2)E energy level acts as a reservoir to thermally populate the higher shorter-lived (sup 4)T(sub 2) energy level and because the activation energy for nonradiative crossover relaxation from the (sup 4)T(sub 2) level to the (sup 4)A(sub 2) ground state is high. The strong crystal field associated with the tight bonding of the AlO6 octahedra in the GdAlO3 perovskite structure is responsible for this behavior.

  6. Compensation for effects of ambient temperature on rare-earth doped fiber optic thermometer

    NASA Technical Reports Server (NTRS)

    Adamovsky, G.; Sotomayor, J. L.; Krasowski, M. J.; Eustace, J. G.

    1989-01-01

    Variations in ambient temperature have a negative effect on the performance of any fiber optic sensing system. A change in ambient temperature may alter the design parameters of fiber optic cables, connectors, sources, detectors, and other fiber optic components and eventually the performance of the entire system. The thermal stability of components is especially important in a system which employs intensity modulated sensors. Several referencing schemes have been developed to account for the variable losses that occur within the system. However, none of these conventional compensating techniques can be used to stabilize the thermal drift of the light source in a system based on the spectral properties of the sensor material. The compensation for changes in ambient temperature becomes especially important in fiber optic thermometers doped with rare earths. Different approaches to solving this problem are searched and analyzed.

  7. Compensation for effects of ambient temperature on rare-earth doped fiber optic thermometer

    NASA Technical Reports Server (NTRS)

    Adamovsky, G.; Sotomayor, J. L.; Krasowski, M. J.; Eustace, J. G.

    1990-01-01

    Variations in ambient temperature have a negative effect on the performance of any fiber optic sensing system. A change in ambient temperature may alter the design parameters of fiber optic cables, connectors, sources, detectors, and other fiber optic components and eventually the performance of the entire system. The thermal stability of components is especially important in a system which employs intensity modulated sensors. Several referencing schemes have been developed to account for the variable losses that occur within the system. However, none of these conventional compensating techniques can be used to stabilize the thermal drift of the light source in a system based on the spectral properties of the sensor material. The compensation for changes in ambient temperature becomes especially important in fiber optic thermometers doped with rare earths. Different approaches to solving this problem are searched and analyzed.

  8. Luminescent rare earth vanadate nanoparticles doped with Eu3+ and Bi3 for sensing and imaging applications

    NASA Astrophysics Data System (ADS)

    Escudero, Alberto; Carrillo-Carrión, Carolina; Zyuzin, Mikhail; Hartmann, Raimo; Ashraf, Sumaira; Parak, Wolfgang J.

    2016-03-01

    Nanoparticles (NPs) are attracting interest in nanomedicine due to their potential medical applications, ranging from optical biolabels and contrast agents for magnetic resonance imaging to carriers for drug and gene delivery for disease therapy.[1] Rare earth (RE) based nanophosphors exhibit important advantages compared with other available luminescent materials, such as quantum dots and nanostructures functionalized with organic dyes, due to their lower toxicities, photostabilities, high thermal and chemical stabilities, high luminescence quantum yields, and sharp emission bands.[2] Yttrium orthovanadate NPs doped with Eu3+ and Bi3+, functionalized with poly acryl acid (PAA), and excitable by near-ultraviolet light have been synthesized by homogeneous precipitation at 120 °C from solutions of rare earth precursors (yttrium acetylacetonate and europium nitrate), bismuth nitrate, sodium orthovanadate, and PAA, in an ethylene glycol/water mixture. Quasispheres with sizes from 93 to 51 nm were obtained. The as synthesized NPs were already functionalized with PAA. The NPs showed the typical red luminescence of Eu3+, which can be excited with near-UV light through an energy transfer from the vanadate anion. The presence of Bi3+ shifts the maximum of the broad excitation band from 280 nm to 342 nm. This excitation path is much more efficient than the direct excitation of the Eu3+ electronic levels, and results in a much higher luminescence. The NPs can be uptaken by HeLa cells, and are eventually located in the lysosomes after being internalized. Finally, the functionalization with PAA provides -COOH anchors for adding functional ligands of biomedical interest that can be used for sensing applications.

  9. Heavy doping effects in high efficiency silicon solar cells

    NASA Technical Reports Server (NTRS)

    Lindholm, F. A.; Neugroschel, A.

    1986-01-01

    The temperature dependence of the emitter saturation current for bipolar devices was studied by varying the surface recombination velocity at the emitter surface. From this dependence, the value was derived for bandgap narrowing that is in better agreement with other determinations that were obtained from the temperature dependence measure on devices with ohmic contacts. Results of the first direct measurement of the minority-carrier transit time in a transparent heavily doped emitter layer were reported. The value was obtained by a high-frequency conductance method recently developed and used for doped Si. Experimental evidence is presented for significantly greater charge storage in highly excited silicon near room temperature than conventional theory would predict. These data are compared with various data for delta E sub G in heavily doped silicon.

  10. Development of lithium doped radiation resistent solar cells

    NASA Technical Reports Server (NTRS)

    Berman, P. A.

    1972-01-01

    Lithium-doped solar cells have been fabricated with initial lot efficiencies averaging 11.9 percent in an air mass zero (AMO) solar simulator and a maximum observed efficiency of 12.8 percent. The best lithium-doped solar cells are approximately 15 percent higher in maximum power than state-of-the-art n-p cells after moderate to high fluences of 1-MeV electrons and after 6-7 months exposure to low flux irradiation by a Sr-90 beta source, which approximates the electron spectrum and flux associated with near Earth space. Furthermore, lithium-doped cells were found to degrade at a rate only one tenth that of state-of-the-art n-p cells under 28-MeV electron irradiation. Excellent progress has been made in quantitative predictions of post-irradiation current-voltage characteristics as a function of cell design by means of capacitance-voltage measurements, and this information has been used to achieve further improvements in lithium-doped cell design.

  11. Selective Emitter Pumped Rare Earth Laser

    NASA Technical Reports Server (NTRS)

    Chubb, Donald L. (Inventor); Patton, Martin O. (Inventor)

    2001-01-01

    A selective emitter pumped rare earth laser provides an additional type of laser for use in many laser applications. Rare earth doped lasers exist which are pumped with flashtubes or laser diodes. The invention uses a rare earth emitter to transform thermal energy input to a spectral band matching the absorption band of a rare earth in the laser in order to produce lasing.

  12. Up-conversion in rare-earth doped micro-particles applied to new emissive two-dimensional displays

    NASA Astrophysics Data System (ADS)

    Milliez, Anne Janet

    Up-conversion (UC) in rare-earth co-doped fluorides to convert diode laser light in the near infrared to red, green and blue visible light is applied to make possible high performance emissive displays. The infrared-to-visible UC in the materials we study is a sequential form of non-linear two photon absorption in which a strong absorbing constituent absorbs two low energy photons and transfers this energy to another constituent which emits visible light. Some of the UC emitters' most appealing characteristics for displays are: a wide color gamut with very saturated colors, very high brightness operation without damage to the emitters, long lifetimes and efficiencies comparable to those of existing technologies. Other advantages include simplicity of fabrication, versatility of operating modes, and the potential for greatly reduced display weight and depth. Thanks to recent advances in material science and diode laser technology at the excitation wavelength, UC selected materials can be very efficient visible emitters. However, optimal UC efficiencies strongly depend on chosing proper operating conditions. In this thesis, we studied the conditions required for optimization. We demonstrated that high efficiency UC depends on high pump irradiance, low temperature and low scattering. With this understanding we can predict how to optimally use UC emitters in a wide range of applications. In particular, we showed how our very efficient UC emitters can be applied to make full color displays and very efficient white light sources.

  13. Dielectric and varistor properties of rare-earth-doped ZnO and CaCu3Ti4O12 composite ceramics

    NASA Astrophysics Data System (ADS)

    Lu, Huafei; Lin, Yuanhua; Yuan, Jiancong; Nan, Cewen; Chen, Kexin

    2013-02-01

    To investigate the multi-functional ceramics with both high permittivity and large nonlinear coefficient, we have prepared rare-earth Tb-and-Co doped ZnO and TiO2-rich CaCu3Ti4O12 (TCCTO) powders by chemical co-precipitation and sol-gel methods respectively, and then obtained the TCCTO/ZnO composite ceramics, sintered at 1100°C for 3 h in air. Analyzing the composite ceramics of the microstructure and phase composition indicated that the composite ceramics were composed of the main phases of ZnO and CaCu3Ti4O12 (CCTO). Our results revealed that the TCCTO/ZnO composite ceramics showed both high dielectric and good nonlinear electrical behaviors. The composite ceramic of TCCTO: ZnO = 0.3 exhibited a high dielectric constant of 210(1 kHz) with a nonlinear coefficient of 11. The dielectric behavior of TCCTO/ZnO composite could be explained by the mixture rule. With the high dielectric permittivity and tunable varistor behaviors, the composite ceramics has a potential application for the higher voltage transportation devices.

  14. Rare-earth doped transparent ceramics for spectral filtering and quantum information processing

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kunkel, Nathalie, E-mail: nathalie.kunkel@chimie-paristech.fr; Goldner, Philippe, E-mail: philippe.goldner@chimie-paristech.fr; Ferrier, Alban

    2015-09-01

    Homogeneous linewidths below 10 kHz are reported for the first time in high-quality Eu{sup 3+} doped Y {sub 2}O{sub 3} transparent ceramics. This result is obtained on the {sup 7}F{sub 0}→{sup 5}D{sub 0} transition in Eu{sup 3+} doped Y {sub 2}O{sub 3} ceramics and corresponds to an improvement of nearly one order of magnitude compared to previously reported values in transparent ceramics. Furthermore, we observed spectral hole lifetimes of ∼15 min that are long enough to enable efficient optical pumping of the nuclear hyperfine levels. Additionally, different Eu{sup 3+} concentrations (up to 1.0%) were studied, resulting in an increase ofmore » up to a factor of three in the peak absorption coefficient. These results suggest that transparent ceramics can be useful in applications where narrow and deep spectral holes can be burned into highly absorbing lines, such as quantum information processing and spectral filtering.« less

  15. High Performance, Low Temperature Solution-Processed Barium and Strontium Doped Oxide Thin Film Transistors.

    PubMed

    Banger, Kulbinder K; Peterson, Rebecca L; Mori, Kiyotaka; Yamashita, Yoshihisa; Leedham, Timothy; Sirringhaus, Henning

    2014-01-28

    Amorphous mixed metal oxides are emerging as high performance semiconductors for thin film transistor (TFT) applications, with indium gallium zinc oxide, InGaZnO (IGZO), being one of the most widely studied and best performing systems. Here, we investigate alkaline earth (barium or strontium) doped InBa(Sr)ZnO as alternative, semiconducting channel layers and compare their performance of the electrical stress stability with IGZO. In films fabricated by solution-processing from metal alkoxide precursors and annealed to 450 °C we achieve high field-effect electron mobility up to 26 cm 2 V -1 s -1 . We show that it is possible to solution-process these materials at low process temperature (225-200 °C yielding mobilities up to 4.4 cm 2 V -1 s -1 ) and demonstrate a facile "ink-on-demand" process for these materials which utilizes the alcoholysis reaction of alkyl metal precursors to negate the need for complex synthesis and purification protocols. Electrical bias stress measurements which can serve as a figure of merit for performance stability for a TFT device reveal Sr- and Ba-doped semiconductors to exhibit enhanced electrical stability and reduced threshold voltage shift compared to IGZO irrespective of the process temperature and preparation method. This enhancement in stability can be attributed to the higher Gibbs energy of oxidation of barium and strontium compared to gallium.

  16. High Performance, Low Temperature Solution-Processed Barium and Strontium Doped Oxide Thin Film Transistors

    PubMed Central

    2013-01-01

    Amorphous mixed metal oxides are emerging as high performance semiconductors for thin film transistor (TFT) applications, with indium gallium zinc oxide, InGaZnO (IGZO), being one of the most widely studied and best performing systems. Here, we investigate alkaline earth (barium or strontium) doped InBa(Sr)ZnO as alternative, semiconducting channel layers and compare their performance of the electrical stress stability with IGZO. In films fabricated by solution-processing from metal alkoxide precursors and annealed to 450 °C we achieve high field-effect electron mobility up to 26 cm2 V–1 s–1. We show that it is possible to solution-process these materials at low process temperature (225–200 °C yielding mobilities up to 4.4 cm2 V–1 s–1) and demonstrate a facile “ink-on-demand” process for these materials which utilizes the alcoholysis reaction of alkyl metal precursors to negate the need for complex synthesis and purification protocols. Electrical bias stress measurements which can serve as a figure of merit for performance stability for a TFT device reveal Sr- and Ba-doped semiconductors to exhibit enhanced electrical stability and reduced threshold voltage shift compared to IGZO irrespective of the process temperature and preparation method. This enhancement in stability can be attributed to the higher Gibbs energy of oxidation of barium and strontium compared to gallium. PMID:24511184

  17. Spectroscopic and neutron detection properties of rare earth and titanium doped LiAlO 2 single crystals

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Dickens, Peter T.; Marcial, José; McCloy, John

    In this study, LiAlO2 crystals doped with rare-earth elements and Ti were produced by the CZ method and spectroscopic and neutron detection properties were investigated. Photoluminescence revealed no clear luminescent activation of LiAlO2 by the rare-earth dopants though some interesting luminescence was observed from secondary phases within the crystal. Gamma-ray pulse height spectra collected using a 137Cs source exhibited only a Compton edge for the crystals. Neutron modeling using Monte Carlo N-Particle Transport Code revealed most neutrons used in the detection setup are thermalized, and while using natural lithium in the crystal growth, which contains 7.6 % 6Li, a 10more » mm Ø by 10 mm sample of LiAlO2 has a 70.7 % intrinsic thermal neutron capture efficiency. Furthermore, the pulse height spectra collected using a 241Am-Be neutron source demonstrated a distinct neutron peak.« less

  18. Spectroscopic and neutron detection properties of rare earth and titanium doped LiAlO 2 single crystals

    DOE PAGES

    Dickens, Peter T.; Marcial, Jose; McCloy, John; ...

    2017-05-17

    In this study, LiAlO 2 crystals doped with rare-earth elements and Ti were produced by the CZ method and spectroscopic and neutron detection properties were investigated. Photoluminescence revealed no clear luminescent activation of LiAlO 2 by the rare-earth dopants though some interesting luminescence was observed from secondary phases within the crystal. Gamma-ray pulse height spectra collected using a 137Cs source exhibited only a Compton edge for the crystals. Neutron modeling using Monte Carlo N-Particle Transport Code revealed most neutrons used in the detection setup are thermalized, and while using natural lithium in the crystal growth, which contains 7.6% 6Li, amore » 10 mm Ø by 10 mm sample of LiAlO 2 has a 70.7% intrinsic thermal neutron capture efficiency. Furthermore, the pulse height spectra collected using a 241Am-Be neutron source demonstrated a distinct neutron peak.« less

  19. Highly improved sensibility and selectivity ethanol sensor of mesoporous Fe-doped NiO nanowires

    NASA Astrophysics Data System (ADS)

    Li, X. Q.; Wei, J. Q.; Xu, J. C.; Jin, H. X.; Jin, D. F.; Peng, X. L.; Hong, B.; Li, J.; Yang, Y. T.; Ge, H. L.; Wang, Xinqing

    2017-12-01

    In this paper, nickel oxides (NiO) and iron (Fe)-doped NiO nanowires (NWs) with the various doping content (from 1 to 9 at%) were synthesized by using SBA-15 templates with the nanocasting method. All samples were synthesized in the same conditions and exhibited the same mesoporous-structures, uniform diameter, and defects. Mesoporous-structures with high surface area created more active sites for the adsorption of oxygen on the surface of all samples, resulting in the smaller surface resistance in air. The impurity energy levels from the donor Fe-doping provided electrons to neutralize the holes of p-type Fe-doped NiO NWs, which greatly enhanced the total resistance. The comparative gas-sensing study between NiO NWs and Fe-doped NiO NWs indicated that the high-valence donor Fe-doping obviously improved the ethanol sensitivity and selectivity for Fe-doped NiO NWs. And Ni0.94Fe0.06O1.03 NWs sensor presented the highest sensitivity of 14.30 toward ethanol gas at 320 °C for the high-valence metal-doping.

  20. Space-Confined Earth-Abundant Bifunctional Electrocatalyst for High-Efficiency Water Splitting.

    PubMed

    Tang, Yanqun; Fang, Xiaoyu; Zhang, Xin; Fernandes, Gina; Yan, Yong; Yan, Dongpeng; Xiang, Xu; He, Jing

    2017-10-25

    Hydrogen generation from water splitting could be an alternative way to meet increasing energy demands while also balancing the impact of energy being supplied by fossil-based fuels. The efficacy of water splitting strongly depends on the performance of electrocatalysts. Herein, we report a unique space-confined earth-abundant electrocatalyst having the bifunctionality of simultaneous hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), leading to high-efficiency water splitting. Outperforming Pt/C or RuO 2 catalysts, this mesoscopic, space-confined, bifunctional configuration is constructed from a monolithic zeolitic imidazolate framework@layered double hydroxide (ZIF@LDH) precursor on Ni foam. Such a confinement leads to a high dispersion of ultrafine Co 3 O 4 nanoparticles within the N-doped carbon matrix by temperature-dependent calcination of the ZIF@LDH. We demonstrate that the OER has an overpotential of 318 mV at a current density of 10 mA cm -2 , while that of HER is -106 mV @ -10 mA cm -2 . The voltage applied to a two-electrode cell for overall water splitting is 1.59 V to achieve a stable current density of 10 mA cm -2 while using the monolithic catalyst as both the anode and the cathode. It is anticipated that our space-confined method, which focuses on earth-abundant elements with structural integrity, may provide a novel and economically sound strategy for practical energy conversion applications.

  1. Computational discovery of lanthanide doped and Co-doped Y{sub 3}Al{sub 5}O{sub 12} for optoelectronic applications

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Choudhary, Kamal; Chernatynskiy, Aleksandr; Phillpot, Simon R.

    2015-09-14

    We systematically elucidate the optoelectronic properties of rare-earth doped and Ce co-doped yttrium aluminum garnet (YAG) using hybrid exchange-correlation functional based density functional theory. The predicted optical transitions agree with the experimental observations for single doped Ce:YAG, Pr:YAG, and co-doped Er,Ce:YAG. We find that co-doping of Ce-doped YAG with any lanthanide except Eu and Lu lowers the transition energies; we attribute this behavior to the lanthanide-induced change in bonding environment of the dopant atoms. Furthermore, we find infrared transitions only in case of the Er, Tb, and Tm co-doped Ce:YAG and suggest Tm,Ce:YAG and Tb,Ce:YAG as possible functional materials formore » efficient spectral up-conversion devices.« less

  2. Boron-doped diamond synthesized at high-pressure and high-temperature with metal catalyst

    NASA Astrophysics Data System (ADS)

    Shakhov, Fedor M.; Abyzov, Andrey M.; Kidalov, Sergey V.; Krasilin, Andrei A.; Lähderanta, Erkki; Lebedev, Vasiliy T.; Shamshur, Dmitriy V.; Takai, Kazuyuki

    2017-04-01

    The boron-doped diamond (BDD) powder consisting of 40-100 μm particles was synthesized at 5 GPa and 1500-1600 °C from a mixture of 50 wt% graphite and 50 wt% Ni-Mn catalyst with an addition of 1 wt% or 5 wt% boron powder. The size of crystal domains of doped and non-doped diamond was evaluated as a coherent scattering region by X-ray diffraction (XRD) and using small-angle neutron scattering (SANS), being ≥180 nm (XRD) and 100 nm (SANS). Magnetic impurities of NiMnx originating from the catalyst in the synthesis, which prevent superconductivity, were detected by magnetization measurements at 2-300 K. X-ray photoelectron spectroscopy, the temperature dependence of the resistivity, XRD, and Raman spectroscopy reveal that the concentration of electrically active boron is as high as (2±1)×1020 cm-3 (0.1 at%). To the best of our knowledge, this is the highest boron content for BDD synthesized in high-pressure high-temperature process with metal catalysts.

  3. Photoluminescence Studies of P-type Modulation Doped GaAs/AlGaAs Quantum Wells in the High Doping Regime

    NASA Astrophysics Data System (ADS)

    Wongmanerod, S.; Holtz, P. O.; Reginski, K.; Bugaiski, M.; Monemar, B.

    The influence of high Be-acceptor doping on the modulation-doped GaAs/Al0.3Ga0.7As quantum wells structures has been optically studied by using the low-temperature photoluminescence (PL) and photoluminescence excitation (PLE) techniques.The modulation doped samples were grown by the molecular-beam epitaxy technique with a varying Be acceptor concentration ranging from 1×1018 to 8×1018cm-3. Several novels physical effects were observed. The main effect is a significant shift of the main emission towards lower energies as the doping concentrations increase. There are two contradictory mechanisms, which determine the peak energy of the main emission; the shrinkage of the effective bandgap due to many body effects and the reduction of the exciton binding energy due to the carrier screening effect. We conclude that the first one is the dominating effect. At a sufficiently high doping concentration (roughly 2×1018cm-3), the lineshape of the main PL emission is modified, and a new feature, the so called Fermi-edge singularity (FES), appears on the high energy side of the PL emission and exhibits a blue-shift as a function of doping concentration. This feature has been found to be very sensitive to a temperature change, already in the range of 4.4-50K. In addition, PLE spectra with a suitable detection energy show that the absorption edge is blue-shifted with respect to the PL main emission. The resulting Stoke shift is due to phase-space-filling of the carriers, in agreement with the FES interpretation. Finally, we have found from the PLE spectra that the exciton quenching is initiated in the same doping regime. Compared to the exciton quenching in other p-type structures, the critical acceptor concentration required to quench the excitons is significantly lower than in the case of 2D structures with acceptor doping within the well, but larger than in the case of 3D bulk.

  4. Nitrogen-doped porous carbon derived from biomass waste for high-performance supercapacitor.

    PubMed

    Ma, Guofu; Yang, Qian; Sun, Kanjun; Peng, Hui; Ran, Feitian; Zhao, Xiaolong; Lei, Ziqiang

    2015-12-01

    High capacitance property and low cost are the pivotal requirements for practical application of supercapacitor. In this paper, a low cost and high capacitance property nitrogen-doped porous carbon with high specific capacitance is prepared. The as-prepared nitrogen-doped porous carbon employing potato waste residue (PWR) as the carbon source, zinc chloride (ZnCl2) as the activating agent and melamine as nitrogen doping agent. The morphology and structure of the carbon materials are studied by scanning electron microscopy (SEM), N2 adsorption/desorption, X-ray diffraction (XRD) and Raman spectra. The surface area of the nitrogen-doped carbon which prepared under 700°C is found to be 1052m(2)/g, and the specific capacitance as high as 255Fg(-1) in 2M KOH electrolyte is obtained utilize the carbon as electrode materials. The electrode materials also show excellent cyclability with 93.7% coulombic efficiency at 5Ag(-1) current density of for 5000cycles. Copyright © 2015 Elsevier Ltd. All rights reserved.

  5. A review of visible, near-IR, and mid-IR transitions in rare-earth doped glass waveguides for remote sensing and LIDAR

    NASA Astrophysics Data System (ADS)

    Jha, Animesh

    2006-12-01

    In the review article we explain the recent investigations on rare-earth doped glass and optical fibres for designing lasers which may be suitable for remote sensing and LIDAR applications. The paper explains the importance of engineering efficient lasing transitions in visible (480-650 nm) for generating UV lasers via one-stage harmonic generation. Besides visible transitions, we also demonstrate the transitions in near- and mid-IR via near-IR pumping scheme.

  6. Research and Development of High Energy 2 - Micron Lasers Based on TM: Doped Ceramic Laser Gain Media and TM: Doped Optical Fibers

    DTIC Science & Technology

    2016-07-20

    AFRL-AFOSR-VA-TR-2016-0257 RESEARCH AND DEVELOPMENT OF HIGH ENERGY 2 - MICRON LASERS BASED ON TM: DOPED CERAMIC LASER GAIN MEDIA AND TM: DOPED...2010 to 01/03/2016 4. TITLE AND SUBTITLE RESEARCH AND DEVELOPMENT OF HIGH ENERGY 2 - MICRON LASERS BASED ON TM: DOPED CERAMIC LASER GAIN MEDIA AND...NOTES 14. ABSTRACT Our research and development of 2-μm femtosecond lasers has included development of mode-locked Tm:fiber lasers , super-continuum

  7. Ho-nanoparticle-doping for improved high-energy laser fibers

    NASA Astrophysics Data System (ADS)

    Friebele, E. Joseph; Baker, Colin C.; Burdett, Ashley A.; Rhonehouse, Daniel L.; Bowman, Steven R.; Kim, Woohong; Sanghera, Jasbinder S.; Kucera, Courtney; Vargas, Amber; Ballato, John; Hemming, Alexander; Simakov, Nikita; Haub, John

    2017-02-01

    A significant issue for holmium-doped fiber lasers (HoDFLs) operating near 2 μm is multiphonon quenching due to the high phonon energy 1100 cm-1 of the silica host, which complicates power scaling due to reduced lifetimes and increased heating. Nanoparticle (NP) doping is a new technique where the structure surrounding the Ho ions is developed chemically prior to doping into the silica core. We have incorporated Ho3+ ions into various NPs, such as LaF3, Al2O3 and Lu2O3, to shield them from the silica glass matrix. Results indicate slightly longer lifetimes with Ho:LaF3 NPs and the possibility of further improvement with oxide NPs. We report the first of lasing in a Ho:Lu2O3 NP-doped fiber pumped at 1.95 μm and operating at 2.09 μm with a record slope efficiency of 85.2%.

  8. Highly resistive epitaxial Mg-doped GdN thin films

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lee, C.-M.; Warring, H.; Trodahl, H. J.

    2015-01-12

    We report the growth by molecular beam epitaxy of highly resistive GdN, using intentional doping with magnesium. Mg-doped GdN layers with resistivities of 10{sup 3} Ω cm and carrier concentrations of 10{sup 16 }cm{sup −3} are obtained for films with Mg concentrations up to 5 × 10{sup 19} atoms/cm{sup 3}. X-ray diffraction rocking curves indicate that Mg-doped GdN films have crystalline quality very similar to undoped GdN films, showing that the Mg doping did not affect the structural properties of the films. A decrease of the Curie temperature with decreasing the electron density is observed, supporting a recently suggested magnetic polaron scenario [F.more » Natali, B. J. Ruck, H. J. Trodahl, D. L. Binh, S. Vézian, B. Damilano, Y. Cordier, F. Semond, and C. Meyer, Phys. Rev. B 87, 035202 (2013)].« less

  9. Heteroatom-doped highly porous carbon from human urine.

    PubMed

    Chaudhari, Nitin Kaduba; Song, Min Young; Yu, Jong-Sung

    2014-06-09

    Human urine, otherwise potentially polluting waste, is an universal unused resource in organic form disposed by the human body. We present for the first time "proof of concept" of a convenient, perhaps economically beneficial, and innovative template-free route to synthesize highly porous carbon containing heteroatoms such as N, S, Si, and P from human urine waste as a single precursor for carbon and multiple heteroatoms. High porosity is created through removal of inherently-present salt particles in as-prepared "Urine Carbon" (URC), and multiple heteroatoms are naturally doped into the carbon, making it unnecessary to employ troublesome expensive pore-generating templates as well as extra costly heteroatom-containing organic precursors. Additionally, isolation of rock salts is an extra bonus of present work. The technique is simple, but successful, offering naturally doped conductive hierarchical porous URC, which leads to superior electrocatalytic ORR activity comparable to state of the art Pt/C catalyst along with much improved durability and methanol tolerance, demonstrating that the URC can be a promising alternative to costly Pt-based electrocatalyst for ORR. The ORR activity can be addressed in terms of heteroatom doping, surface properties and electrical conductivity of the carbon framework.

  10. Heteroatom-doped highly porous carbon from human urine

    NASA Astrophysics Data System (ADS)

    Chaudhari, Nitin Kaduba; Song, Min Young; Yu, Jong-Sung

    2014-06-01

    Human urine, otherwise potentially polluting waste, is an universal unused resource in organic form disposed by the human body. We present for the first time ``proof of concept'' of a convenient, perhaps economically beneficial, and innovative template-free route to synthesize highly porous carbon containing heteroatoms such as N, S, Si, and P from human urine waste as a single precursor for carbon and multiple heteroatoms. High porosity is created through removal of inherently-present salt particles in as-prepared ``Urine Carbon'' (URC), and multiple heteroatoms are naturally doped into the carbon, making it unnecessary to employ troublesome expensive pore-generating templates as well as extra costly heteroatom-containing organic precursors. Additionally, isolation of rock salts is an extra bonus of present work. The technique is simple, but successful, offering naturally doped conductive hierarchical porous URC, which leads to superior electrocatalytic ORR activity comparable to state of the art Pt/C catalyst along with much improved durability and methanol tolerance, demonstrating that the URC can be a promising alternative to costly Pt-based electrocatalyst for ORR. The ORR activity can be addressed in terms of heteroatom doping, surface properties and electrical conductivity of the carbon framework.

  11. Dietary supplementation and doping-related factors in high-level sailing

    PubMed Central

    2012-01-01

    Background Although dietary supplements (DSs) in sports are considered a natural need resulting from athletes’ increased physical demands, and although they are often consumed by athletes, data on DS usage in Olympic sailing are scarce. The aim of this study was to study the use of and attitudes towards DSs and doping problems in high-level competitive sailing. Methods The sample consisted of 44 high-level sailing athletes (5 of whom were female; total mean age 24.13 ± 6.67 years) and 34 coaches (1 of whom was female; total mean age 37.01 ± 11.70). An extensive, self-administered questionnaire of substance use was used, and the subjects were asked about sociodemographic data, sport-related factors, DS-related factors (i.e., usage of and knowledge about DSs, sources of information), and doping-related factors. The Kruskal-Wallis ANOVA was used to determine the differences in group characteristics, and Spearman’s rank order correlation and a logistic regression analysis were used to define the relationships between the studied variables. Results DS usage is relatively high. More than 77% of athletes consume DSs, and 38% do so on a regular basis (daily). The athletes place a high degree of trust in their coaches and/or physicians regarding DSs and doping. The most important reason for not consuming DSs is the opinion that DSs are useless and a lack of knowledge about DSs. The likelihood of doping is low, and one-third of the subjects believe that doping occurs in sailing (no significant differences between athletes and coaches). The logistic regression found crew number (i.e., single vs. double crew) to be the single significant predictor of DS usage, with a higher probability of DS consumption among single crews. Conclusion Because of the high consumption of DSs future investigations should focus on real nutritional needs in sailing sport. Also, since athletes reported that their coaches are the primary source of information about nutrition and DSs, further

  12. Luminescent properties of Mn2+ doped apatite nanophosphors

    NASA Astrophysics Data System (ADS)

    Ravindranadh, K.; Ravikumar, R. V. S. S. N.; Rao, M. C.

    2016-05-01

    Nanophosphors have been extensively investigated during the last decade due to their various high-performance application potential such as lamp industry, radiation dosimetry, X-ray imaging and colour display. The synthesis of inorganic nanophosphors using both ionizing radiation (IR) or UV light represents very promising technological field. Alkaline earth nanophosphors gathered a lot of attention in past decades because they are considered to be excellent host materials. Transition-metal oxides are well known luminescent emitters in the visible spectral region. Mn2+ doped calcium-lithium hydroxyapatite (CLHA) nanophosphors were prepared by mechanochemical synthesis. The prepared samples were characterized by photoluminescence studies. Photoluminescence spectra of Mn2+ doped CLHA nanophosphors exhibited green and strong orange emission bands at 534, 577 nm respectively under the excitation wavelength of 365 nm. The CIE chromaticity coordinates were also calculated from emission spectra for Mn2+ doped CLHA nanophosphors.

  13. Visualization of melanoma tumor with lectin-conjugated rare-earth doped fluoride nanocrystals

    PubMed Central

    Dumych, Tetiana; Lutsyk, Maxym; Banski, Mateusz; Yashchenko, Antonina; Sojka, Bartlomiej; Horbay, Rostyslav; Lutsyk, Alexander; Stoika, Rostyslav; Misiewicz, Jan; Podhorodecki, Artur; Bilyy, Rostyslav

    2014-01-01

    Aim To develop specific fluorescent markers for melanoma tumor visualization, which would provide high selectivity and reversible binding pattern, by the use of carbohydrate-recognizing proteins, lectins, combined with the physical ability for imaging deep in the living tissues by utilizing red and near infrared fluorescent properties of specific rare-earth doped nanocrystals (NC). Methods B10F16 melanoma cells were inoculated to C57BL/6 mice for inducing experimental melanoma tumor. Tumors were removed and analyzed by lectin-histochemistry using LABA, PFA, PNA, HPA, SNA, GNA, and NPL lectins and stained with hematoxylin and eosin. NPL lectin was conjugated to fluorescent NaGdF4:Eu3+-COOH nanoparticles (5 nm) via zero length cross-linking reaction, and the conjugates were purified from unbound substances and then used for further visualization of histological samples. Fluorescent microscopy was used to visualize NPL-NaGdF4:Eu3+ with the fluorescent emission at 600-720 nm range. Results NPL lectin selectively recognized regions of undifferentiated melanoblasts surrounding neoangiogenic foci inside melanoma tumor, PNA lectin recognized differentiated melanoblasts, and LCA and WGA were bound to tumor stroma regions. NPL-NaGdF4:Eu3+ conjugated NC were efficiently detecting newly formed regions of melanoma tumor, confirmed by fluorescent microscopy in visible and near infrared mode. These conjugates possessed high photostability and were compatible with convenient xylene-based mounting systems and preserved intensive fluorescent signal at samples storage for at least 6 months. Conclusion NPL lectin-NaGdF4:Eu3+ conjugated NC permitted distinct identification of contours of the melanoma tissue on histological sections using red excitation at 590-610 nm and near infrared emission of 700-720 nm. These data are of potential practical significance for development of glycans-conjugated nanoparticles to be used for in vivo visualization of melanoma tumor. PMID:24891277

  14. Structural and AC loss study for pure and doped MgB{sub 2} superconductor

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hansdah, J. S.; Sarun, P. M., E-mail: sarun.res@gmail.com

    2015-06-24

    Superconducting polycrystalline bulk MgB{sub 2} samples doped with n-C, n-Y{sub 2}O{sub 3} and n-Ho{sub 2}O{sub 3} were prepared by powder-in-sealed (PIST) method. XRD measurement shows the influence of dopants on phase and lattice parameters of samples. The ac susceptibility measurement reveals ac loss and activation energy of the samples. Nano-C doped sample shows less ac loss in all frequency (208 Hz – 999 Hz) among the doped samples; whereas n-Ho{sub 2}O{sub 3} doped sample shows highest ac loss. The activation energy is high for rare earth (n-Y{sub 2}O{sub 3} and n-Ho{sub 2}O{sub 3}) doped samples as compare to n-C doped samples whichmore » reveals the enhancement in flux-pinning properties of these materials.« less

  15. Synthesis, Characterization and Comparative Luminescence Studies of Rare-Earth-Doped Gd2O3 Nanoparticles

    NASA Astrophysics Data System (ADS)

    Pyngrope, D.; Singh, L. R.; Prasad, A. I.; Bora, A.

    2018-04-01

    A facile direct precipitation method was used for the synthesis of luminescence nanomaterial. Gd2O3 doped with rare earth element Eu3+ is synthesized by polyol route. The synthesized nanoparticles show their characteristic red emission. The nanoparticles are characterized by x-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and photoluminescence (PL) study. The synthesized nanoparticles are spherical particles with 30 nm size. The photoluminescence studies show the characteristic Eu3+ red emission. The PL study shows the intensity of the magnetic dipole transition ( 5 D0 \\to 7 F1 ) at 592 nm compared to that of the electronic dipole transition ( 5 D0 \\to 7 F2 ) at 615 nm. The nanomaterials can show significant application in various display devices and biomedical applications for tracking.

  16. Effect of temperature and rare-earth doping on charge-carrier mobility in indium-monoselenide crystals

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Abdinov, A. Sh., E-mail: abdinov-axmed@yandex.ru; Babayeva, R. F., E-mail: Babaeva-Rena@yandex.ru; Amirova, S. I.

    2013-08-15

    In the temperature range T = 77-600 K, the dependence of the charge-carrier mobility ({mu}) on the initial dark resistivity is experimentally investigated at 77 K ({rho}d{sub 0}), as well as on the temperature and the level (N) of rare-earth doping with such elements as gadolinium (Gd), holmium (Ho), and dysprosium (Dy) in n-type indium-monoselenide (InSe) crystals. It is established that the anomalous behavior of the dependences {mu}(T), {mu}({rho}d{sub 0}), and {mu}(N) found from the viewpoint of the theory of charge-carrier mobility in crystalline semiconductors is related, first of all, to partial disorder in indium-monoselenide crystals and can be attributedmore » to the presence of random drift barriers in the free energy bands.« less

  17. High-concentration boron doping of graphene nanoplatelets by simple thermal annealing and their supercapacitive properties.

    PubMed

    Yeom, Da-Young; Jeon, Woojin; Tu, Nguyen Dien Kha; Yeo, So Young; Lee, Sang-Soo; Sung, Bong June; Chang, Hyejung; Lim, Jung Ah; Kim, Heesuk

    2015-05-05

    For the utilization of graphene in various energy storage and conversion applications, it must be synthesized in bulk with reliable and controllable electrical properties. Although nitrogen-doped graphene shows a high doping efficiency, its electrical properties can be easily affected by oxygen and water impurities from the environment. We here report that boron-doped graphene nanoplatelets with desirable electrical properties can be prepared by the simultaneous reduction and boron-doping of graphene oxide (GO) at a high annealing temperature. B-doped graphene nanoplatelets prepared at 1000 °C show a maximum boron concentration of 6.04 ± 1.44 at %, which is the highest value among B-doped graphenes prepared using various methods. With well-mixed GO and g-B2O3 as the dopant, highly uniform doping is achieved for potentially gram-scale production. In addition, as a proof-of-concept, highly B-doped graphene nanoplatelets were used as an electrode of an electrochemical double-layer capacitor (EDLC) and showed an excellent specific capacitance value of 448 F/g in an aqueous electrolyte without additional conductive additives. We believe that B-doped graphene nanoplatelets can also be used in other applications such as electrocatalyst and nano-electronics because of their reliable and controllable electrical properties regardless of the outer environment.

  18. High-concentration boron doping of graphene nanoplatelets by simple thermal annealing and their supercapacitive properties

    NASA Astrophysics Data System (ADS)

    Yeom, Da-Young; Jeon, Woojin; Tu, Nguyen Dien Kha; Yeo, So Young; Lee, Sang-Soo; Sung, Bong June; Chang, Hyejung; Lim, Jung Ah; Kim, Heesuk

    2015-05-01

    For the utilization of graphene in various energy storage and conversion applications, it must be synthesized in bulk with reliable and controllable electrical properties. Although nitrogen-doped graphene shows a high doping efficiency, its electrical properties can be easily affected by oxygen and water impurities from the environment. We here report that boron-doped graphene nanoplatelets with desirable electrical properties can be prepared by the simultaneous reduction and boron-doping of graphene oxide (GO) at a high annealing temperature. B-doped graphene nanoplatelets prepared at 1000 °C show a maximum boron concentration of 6.04 ± 1.44 at %, which is the highest value among B-doped graphenes prepared using various methods. With well-mixed GO and g-B2O3 as the dopant, highly uniform doping is achieved for potentially gram-scale production. In addition, as a proof-of-concept, highly B-doped graphene nanoplatelets were used as an electrode of an electrochemical double-layer capacitor (EDLC) and showed an excellent specific capacitance value of 448 F/g in an aqueous electrolyte without additional conductive additives. We believe that B-doped graphene nanoplatelets can also be used in other applications such as electrocatalyst and nano-electronics because of their reliable and controllable electrical properties regardless of the outer environment.

  19. Optical properties of rare earth doped transparent oxyfluoride glass ceramics

    NASA Astrophysics Data System (ADS)

    Mendez-Ramos, J.; Lavin, V.; Martin, I. R.; Rodriguez-Mendoza, U. R.; Rodriguez, V. D.; Lozano-Gorrin, A. D.; Nunez, P.

    2003-01-01

    Optical properties of Eu3+ ions in oxyfluoride glasses and glass ceramics doped with low concentration (0.1 mol%) have been analysed and compared with previous results for high concentrated samples (2.5 mol%). The Eu3+ ions in the low dopant concentration glass ceramics are diluted into like crystalline environments with higher symmetry and lower coupled phonons energy than in the precursor glasses. Fluorescence line narrowing measurements indicate the presence of two main fluoride site distributions for the Eu3+ ions in these low concentrated glass ceramics.

  20. Contributed Review: A review of the investigation of rare-earth dopant profiles in optical fibers

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sidiroglou, F.; Baxter, G.; Roberts, A.

    Rare-earth doped optical fibers have captivated the interest of many researchers around the world across the past three decades. The growth of this research field has been stimulated primarily through their application in optical communications as fiber lasers and amplifiers, although rare-earth doped optical fiber based devices are now finding important uses in many other scientific and industrial areas (for example, medicine, sensing, the military, and material processing). Such wide commercial interest has provided a strong incentive for innovative fiber designs, alternative glass compositions, and novel fabrication processes. A prerequisite for the ongoing progress of this research field is developingmore » the capacity to provide high resolution information about the rare-earth dopant distribution profiles within the optical fibers. This paper constitutes a comprehensive review of the imaging techniques that have been utilized in the analysis of the distribution of the rare-earth ion erbium within the core of optical fibers.« less

  1. Contributed Review: A review of the investigation of rare-earth dopant profiles in optical fibers.

    PubMed

    Sidiroglou, F; Roberts, A; Baxter, G

    2016-04-01

    Rare-earth doped optical fibers have captivated the interest of many researchers around the world across the past three decades. The growth of this research field has been stimulated primarily through their application in optical communications as fiber lasers and amplifiers, although rare-earth doped optical fiber based devices are now finding important uses in many other scientific and industrial areas (for example, medicine, sensing, the military, and material processing). Such wide commercial interest has provided a strong incentive for innovative fiber designs, alternative glass compositions, and novel fabrication processes. A prerequisite for the ongoing progress of this research field is developing the capacity to provide high resolution information about the rare-earth dopant distribution profiles within the optical fibers. This paper constitutes a comprehensive review of the imaging techniques that have been utilized in the analysis of the distribution of the rare-earth ion erbium within the core of optical fibers.

  2. High-energy electron-induced damage production at room temperature in aluminum-doped silicon

    NASA Technical Reports Server (NTRS)

    Corbett, J. W.; Cheng, L. J.; Jaworowski, A.; Karins, J. P.; Lee, Y. H.; Lindstroem, L.; Mooney, P. M.; Oehrlen, G.; Wang, K. L.

    1979-01-01

    DLTS and EPR measurements are reported on aluminum-doped silicon that was irradiated at room temperature with high-energy electrons. Comparisons are made to comparable experiments on boron-doped silicon. Many of the same defects observed in boron-doped silicon are also observed in aluminum-doped silicon, but several others were not observed, including the aluminum interstitial and aluminum-associated defects. Damage production modeling, including the dependence on aluminum concentration, is presented.

  3. Doping of two-dimensional MoS2 by high energy ion implantation

    NASA Astrophysics Data System (ADS)

    Xu, Kang; Zhao, Yuda; Lin, Ziyuan; Long, Yan; Wang, Yi; Chan, Mansun; Chai, Yang

    2017-12-01

    Two-dimensional (2D) materials have been demonstrated to be promising candidates for next generation electronic circuits. Analogues to conventional Si-based semiconductors, p- and n-doping of 2D materials are essential for building complementary circuits. Controllable and effective doping strategies require large tunability of the doping level and negligible structural damage to ultrathin 2D materials. In this work, we demonstrate a doping method utilizing a conventional high-energy ion-implantation machine. Before the implantation, a Polymethylmethacrylate (PMMA) protective layer is used to decelerate the dopant ions and minimize the structural damage to MoS2, thus aggregating the dopants inside MoS2 flakes. By optimizing the implantation energy and fluence, phosphorus dopants are incorporated into MoS2 flakes. Our Raman and high-resolution transmission electron microscopy (HRTEM) results show that only negligibly structural damage is introduced to the MoS2 lattice during the implantation. P-doping effect by the incorporation of p+ is demonstrated by Photoluminescence (PL) and electrical characterizations. Thin PMMA protection layer leads to large kinetic damage but also a more significant doping effect. Also, MoS2 with large thickness shows less kinetic damage. This doping method makes use of existing infrastructures in the semiconductor industry and can be extended to other 2D materials and dopant species as well.

  4. Origins of conductivity improvement in fluoride-enhanced silicon doping of ZnO films.

    PubMed

    Rashidi, Nazanin; Vai, Alex T; Kuznetsov, Vladimir L; Dilworth, Jonathan R; Edwards, Peter P

    2015-06-07

    Fluoride in spray pyrolysis precursor solutions for silicon-doped zinc oxide (SiZO) transparent conductor thin films significantly improves their electrical conductivity by enhancing silicon doping efficiency and not, as previously assumed, by fluoride doping. Containing only earth-abundant elements, SiZO thus prepared rivals the best solution-processed indium-doped ZnO in performance.

  5. A doped activated carbon prepared from polyaniline for high performance supercapacitors

    NASA Astrophysics Data System (ADS)

    Li, Limin; Liu, Enhui; Li, Jian; Yang, Yanjing; Shen, Haijie; Huang, Zhengzheng; Xiang, Xiaoxia; Li, Wen

    A novel doped activated carbon has been prepared from H 2SO 4-doped polyaniline which is prepared by the oxypolymerization of aniline. The morphology, surface chemical composition and surface area of the carbon have been investigated by scanning electron microscope, X-ray photoelectron spectroscopy and Brunaner-Emmett-Teller measurement, respectively. Electrochemical properties of the doped activated carbon have been studied by cyclic voltammograms, galvanostatic charge/discharge, and electrochemical impedance spectroscopy measurements in 6 mol l -1 KOH. The specific capacitance of the carbon is as high as 235 F g -1, the specific capacitance hardly decreases at a high current density 11 A g -1 after 10,000 cycles, which indicates that the carbon possesses excellent cycle durability and may be a promising candidate for supercapacitors.

  6. Heteroatom-doped highly porous carbon from human urine

    PubMed Central

    Chaudhari, Nitin Kaduba; Song, Min Young; Yu, Jong-Sung

    2014-01-01

    Human urine, otherwise potentially polluting waste, is an universal unused resource in organic form disposed by the human body. We present for the first time “proof of concept” of a convenient, perhaps economically beneficial, and innovative template-free route to synthesize highly porous carbon containing heteroatoms such as N, S, Si, and P from human urine waste as a single precursor for carbon and multiple heteroatoms. High porosity is created through removal of inherently-present salt particles in as-prepared “Urine Carbon” (URC), and multiple heteroatoms are naturally doped into the carbon, making it unnecessary to employ troublesome expensive pore-generating templates as well as extra costly heteroatom-containing organic precursors. Additionally, isolation of rock salts is an extra bonus of present work. The technique is simple, but successful, offering naturally doped conductive hierarchical porous URC, which leads to superior electrocatalytic ORR activity comparable to state of the art Pt/C catalyst along with much improved durability and methanol tolerance, demonstrating that the URC can be a promising alternative to costly Pt-based electrocatalyst for ORR. The ORR activity can be addressed in terms of heteroatom doping, surface properties and electrical conductivity of the carbon framework. PMID:24909133

  7. Highly active lanthanum doped ZnO nanorods for photodegradation of metasystox.

    PubMed

    Korake, P V; Dhabbe, R S; Kadam, A N; Gaikwad, Y B; Garadkar, K M

    2014-01-05

    La-doped ZnO nanorods with different La contents were synthesized by microwave assisted method and characterized by various sophisticated techniques such as XRD, UV-Vis., EDS, XPS, SEM and TEM. The XRD patterns of the La-doped ZnO indicate hexagonal crystal structure with an average crystallite size of 30nm. It was found that the crystallite size of La-doped ZnO is much smaller as compared to pure ZnO and decreases with increasing La content. The photocatalytic activity of 0.5mol% La-doped ZnO in the degradation of metasystox was studied. It was observed that degradation efficiency of metasystox over La-doped ZnO increases up to 0.5mol% doping then decreases for higher doping levels. Among the catalyst studied, the 0.5mol% La-doped ZnO was the most active, showing high photocatalytic activity for the degradation of metasystox. The maximum reduction of concentration of metasystox was observed under static condition at pH 8. Reduction in the Chemical Oxygen Demand (COD) of metasystox was observed after 150min. The cytotoxicological studies of meristematic root tip cells of Allium cepa were studied. The results obtained indicate that photocatalytically degraded products of metasystox were less toxic as compared to metasystox. Copyright © 2013 Elsevier B.V. All rights reserved.

  8. Rare Earth Garnet Selective Emitter

    NASA Technical Reports Server (NTRS)

    Lowe, Roland A.; Chubb, Donald L.; Farmer, Serene C.; Good, Brian S.

    1994-01-01

    impurities, in the development of solid state laser crystals. Doping, dependent on the particular ion and crystal structure, may be as high as 100 at. % (complete substitution of yttrium ion with the rare earth ion). These materials have high melting points, 1940 C for YAG (Yttrium Aluminum Garnet), and low emissivity in the near infrared making them excellent candidates for a thin film selective emitter. As previously stated, the spectral emittance of a rare earth emitter is characterized by one or more well defined emission bands. Outside the emission band the emittance(absorptance) is much lower. Therefore, it is expected that emission outside the band for a thin film selective emitter will be dominated by the emitter substrate. For an efficient emitter (power in the emission band/total emitted power) the substrate must have low emittance, epsilon(sub S). This paper presents normal spectral emittance, epsilon(sub lambda), measurements of holmium(Ho) and erbium (Er) doped YAG thin film selective emitters at (1500 K), and compares those results with the theoretical spectral emittance.

  9. The Prevalence and Covariates of Potential Doping Behavior in Kickboxing; Analysis among High-Level Athletes

    PubMed Central

    Sekulic, Damir; Zenic, Natasa; Versic, Sime; Maric, Dora; Gabrilo, Goran; Jelicic, Mario

    2017-01-01

    Abstract The official reports on doping behavior in kickboxing are alarming, but there have been no empirical studies that examined this problem directly. The aim of this study was to investigate the prevalence, gender differences and covariates of potential-doping-behavior, in kickboxing athletes. A total of 130 high-level kickboxing athletes (92 males, 21.37 ± 4.83 years of age, 8.39 ± 5.73 years of training experience; 38 women, 20.31 ± 2.94 years of age; 9.84 ± 4.74 years of training experience) completed questionnaires to study covariates and potential-doping behavior. The covariates were: sport factors (i.e. experience, success), doping-related factors (i.e. opinion about penalties for doping users, number of doping testing, potential-doping-behavior, etc.), sociodemographic variables, task- and ego-motivation, knowledge on sports nutrition, and knowledge on doping. Gender-based differences were established by independent t-tests, and the Mann-Whitney test. Multinomial logistic regression analyses were performed to define the relationships between covariates and a tendency toward potential-doping behavior (positive tendency – neutral – negative tendency). The potential-doping behavior was higher in those athletes who perceived kickboxing as doping contaminated sport. The more experienced kickboxers were associated with positive intention toward potential-doping behavior. Positive intention toward potential-doping behavior was lower in those who had better knowledge on sports nutrition. The task- and ego-motivation were not associated to potential-doping behavior. Because of the high potential-doping-behavior (less than 50% of athletes showed a negative tendency toward doping), and similar prevalence of potential-doping behavior between genders, this study highlights the necessity of a systematic anti-doping campaign in kickboxing. Future studies should investigate motivational variables as being potentially related to doping behavior in younger

  10. Temperature and doping dependence of the high-energy kink in cuprates.

    PubMed

    Zemljic, M M; Prelovsek, P; Tohyama, T

    2008-01-25

    It is shown that spectral functions within the extended t-J model, evaluated using the finite-temperature diagonalization of small clusters, exhibit the high-energy kink in single-particle dispersion consistent with recent angle-resolved photoemission results on hole-doped cuprates. The kink and waterfall-like features persist up to large doping and to temperatures beyond J; hence, the origin can be generally attributed to strong correlations and incoherent hole propagation at large binding energies. In contrast, our analysis predicts that electron-doped cuprates do not exhibit these phenomena in photoemission.

  11. Furnace Cyclic Behavior of Plasma-Sprayed Zirconia-Yttria and Multi-Component Rare Earth Oxide Doped Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Nesbitt, James A.; McCue, Terry R.; Barrett, Charles A.; Miller, Robert A.

    2002-01-01

    Ceramic thermal barrier coatings will play an increasingly important role in advanced gas turbine engines because of their ability to enable further increases in engine temperatures. However, the coating performance and durability become a major concern under the increasingly harsh thermal cycling conditions. Advanced zirconia- and hafnia-based cluster oxide thermal barrier coatings with lower thermal conductivity and improved thermal stability are being developed using a high-heat-flux laser-rig based test approach. Although the new composition coatings were not yet optimized for cyclic durability, an initial durability screening of numerous candidate coating materials was carried out using conventional furnace cyclic tests. In this paper, furnace thermal cyclic behavior of the advanced plasma-sprayed zirconia-yttria-based thermal barrier coatings that were co-doped with multi-component rare earth oxides was investigated at 1163 C using 45 min hot cycles. The ceramic coating failure mechanisms were studied by using scanning electron microscopy combined with X-ray diffraction phase analysis after the furnace tests. The coating cyclic lifetime will be discussed in relation to coating phase structures, total dopant concentrations, and other properties.

  12. Unified electronic phase diagram for hole-doped high- Tc cuprates

    NASA Astrophysics Data System (ADS)

    Honma, T.; Hor, P. H.

    2008-05-01

    We have analyzed various characteristic temperatures and energies of hole-doped high- Tc cuprates as a function of a dimensionless hole-doping concentration (pu) . Entirely based on the experimental grounds, we construct a unified electronic phase diagram (UEPD), where three characteristic temperatures ( T∗ ’s) and their corresponding energies ( E∗ ’s) converge as pu increases in the underdoped regime. T∗ ’s and E∗ ’s merge together with the Tc curve and 3.5kBTc curve at pu˜1.1 in the overdoped regime, respectively. They finally go to zero at pu˜1.3 . The UEPD follows an asymmetric half-dome-shaped Tc curve, in which Tc appears at pu˜0.4 , reaches a maximum at pu˜1 , and rapidly goes to zero at pu˜1.3 . The asymmetric half-dome-shaped Tc curve is at odds with the well-known symmetric superconducting dome for La2-xSrxCuO4 (SrD-La214), in which two characteristic temperatures and energies converge as pu increases and merge together at pu˜1.6 , where Tc goes to zero. The UEPD clearly shows that pseudogap phase precedes and coexists with high temperature superconductivity in the underdoped and overdoped regimes, respectively. It is also clearly seen that the upper limit of high- Tc cuprate physics ends at a hole concentration that equals to 1.3 times the optimal doping concentration for almost all high- Tc cuprate materials and 1.6 times the optimal doping concentration for the SrD-La214. Our analysis strongly suggests that pseudogap is a precursor of high- Tc superconductivity, the observed quantum critical point inside the superconducting dome may be related to the end point of UEPD, and the normal state of the underdoped and overdoped high temperature superconductors cannot be regarded as a conventional Fermi liquid phase.

  13. Superconductivity by rare earth doping in the 1038-type compounds (Ca1-xREx) 10(FeAs)10(Pt3As8) with RE=Y, La-Nd, Sm-Lu

    NASA Astrophysics Data System (ADS)

    Stürzer, Tobias; Derondeau, Gerald; Bertschler, Eva-Maria; Johrendt, Dirk

    2015-01-01

    We report superconductivity in polycrystalline samples of the 1038-type compounds (Ca1-xREx) 10(FeAs)10(Pt3As8) up to Tc=35 K with RE=Y, La-Nd, Sm, Gd-Lu. The critical temperatures are nearly independent of the trivalent rare earth element used, yielding a common Tc(xRE) phase diagram for electron doping in all these systems. The absence of superconductivity in Eu2+ doped samples, as well as the close resemblance of (Ca1-xREx) 10(FeAs)10(Pt3As8) to the 1048 compound substantiate that the electron doping scenario in the RE-1038 and 1048 phases is analogous to other iron-based superconductors with simpler crystal structures.

  14. High p-type doping, mobility, and photocarrier lifetime in arsenic-doped CdTe single crystals

    NASA Astrophysics Data System (ADS)

    Nagaoka, Akira; Kuciauskas, Darius; McCoy, Jedidiah; Scarpulla, Michael A.

    2018-05-01

    Group-V element doping is promising for simultaneously maximizing the hole concentration and minority carrier lifetime in CdTe for thin film solar cells, but there are roadblocks concerning point defects including the possibility of self-compensation by AX metastability. Herein, we report on doping, lifetime, and mobility of CdTe single crystals doped with As between 1016 and 1020 cm-3 grown from the Cd solvent by the travelling heater method. Evidence consistent with AX instability as a major contributor to compensation in samples doped below 1017 cm-3 is presented, while for higher-doped samples, precipitation of a second phase on planar structural defects is also observed and may explain spatial variation in properties such as lifetime. Rapid cooling after crystal growth increases doping efficiency and mobility for times up to 20-30 days at room temperature with the highest efficiencies observed close to 45% and a hole mobility of 70 cm2/Vs at room temperature. A doping limit in the low 1017/cm3 range is observed for samples quenched at 200-300 °C/h. Bulk minority carrier lifetimes exceeding 20 ns are observed for samples doped near 1016 cm-3 relaxed in the dark and for unintentionally doped samples, while a lifetime of nearly 5 ns is observed for 1018 cm-3 As doping. These results help us to establish limits on properties expected for group-V doped CdTe polycrystalline thin films for use in photovoltaics.

  15. Thermoelectric Properties of Highly-Crystallized Ge-Te-Se Glasses Doped with Cu/Bi.

    PubMed

    Srinivasan, Bhuvanesh; Boussard-Pledel, Catherine; Dorcet, Vincent; Samanta, Manisha; Biswas, Kanishka; Lefèvre, Robin; Gascoin, Franck; Cheviré, François; Tricot, Sylvain; Reece, Michael; Bureau, Bruno

    2017-03-23

    Chalcogenide semiconducting systems are of growing interest for mid-temperature range (~500 K) thermoelectric applications. In this work, Ge 20 Te 77 Se₃ glasses were intentionally crystallized by doping with Cu and Bi. These effectively-crystallized materials of composition (Ge 20 Te 77 Se₃) 100- x M x (M = Cu or Bi; x = 5, 10, 15), obtained by vacuum-melting and quenching techniques, were found to have multiple crystalline phases and exhibit increased electrical conductivity due to excess hole concentration. These materials also have ultra-low thermal conductivity, especially the heavily-doped (Ge 20 Te 77 Se₃) 100- x Bi x ( x = 10, 15) samples, which possess lattice thermal conductivity of ~0.7 Wm -1 K -1 at 525 K due to the assumable formation of nano-precipitates rich in Bi, which are effective phonon scatterers. Owing to their high metallic behavior, Cu-doped samples did not manifest as low thermal conductivity as Bi-doped samples. The exceptionally low thermal conductivity of the Bi-doped materials did not, alone, significantly enhance the thermoelectric figure of merit, zT. The attempt to improve the thermoelectric properties by crystallizing the chalcogenide glass compositions by excess doping did not yield power factors comparable with the state of the art thermoelectric materials, as these highly electrically conductive crystallized materials could not retain the characteristic high Seebeck coefficient values of semiconducting telluride glasses.

  16. High temperature superconductivity in distinct phases of amorphous B-doped Q-carbon

    NASA Astrophysics Data System (ADS)

    Narayan, Jagdish; Bhaumik, Anagh; Sachan, Ritesh

    2018-04-01

    Distinct phases of B-doped Q-carbon are formed when B-doped and undoped diamond tetrahedra are packed randomly after nanosecond laser melting and quenching of carbon. By changing the ratio of doped to undoped tetrahedra, distinct phases of B-doped Q-carbon with concentration varying from 5.0% to 50.0% can be created. We have synthesized three distinct phases of amorphous B-doped Q-carbon, which exhibit high-temperature superconductivity following the Bardeen-Cooper-Schrieffer mechanism. The first phase (QB1) has a B-concentration ˜17 at. % (Tc = 37 K), the second phase (QB2) has a B-concentration ˜27 at. % (Tc = 55 K), and the third phase (QB3) has a B-concentration ˜45 at. % (Tc expected over 100 K). From geometrical modeling, we derive that QB1 consists of randomly packed tetrahedra, where one out of every three tetrahedra contains a B atom in the center which is sp3 bonded to four carbon atoms with a concentration of 16.6 at. %. QB2 consists of randomly packed tetrahedra, where one out of every two tetrahedra contains a B atom in the center which is sp3 bonded to four carbon atoms with a concentration of 25 at. %. QB3 consists of randomly packed tetrahedra, where every tetrahedron contains a B atom in the center which is sp3 bonded to four carbon atoms with a concentration of 50 at. %. We present detailed high-resolution TEM results on structural characterization, and EELS and Raman spectroscopy results on the bonding characteristics of B and C atoms. From these studies, we conclude that the high electronic density of states near the Fermi energy level coupled with moderate electron-phonon coupling result in high-temperature superconductivity in B-doped Q-carbon.

  17. High p-type doping, mobility, and photocarrier lifetime in arsenic-doped CdTe single crystals

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Nagaoka, Akira; Kuciauskas, Darius; McCoy, Jedidiah

    Here, Group-V element doping is promising for simultaneously maximizing the hole concentration and minority carrier lifetime in CdTe for thin film solar cells, but there are roadblocks concerning point defects including the possibility of self-compensation by AX metastability. Herein, we report on doping, lifetime, and mobility of CdTe single crystals doped with As between 10 16 and 10 20 cm –3 grown from the Cd solvent by the travelling heater method. Evidence consistent with AX instability as a major contributor to compensation in samples doped below 10 17 cm –3 is presented, while for higher-doped samples, precipitation of a secondmore » phase on planar structural defects is also observed and may explain spatial variation in properties such as lifetime. Rapid cooling after crystal growth increases doping efficiency and mobility for times up to 20–30 days at room temperature with the highest efficiencies observed close to 45% and a hole mobility of 70 cm 2/Vs at room temperature. A doping limit in the low 10 17/cm 3 range is observed for samples quenched at 200–300 °C/h. Bulk minority carrier lifetimes exceeding 20 ns are observed for samples doped near 10 16 cm –3 relaxed in the dark and for unintentionally doped samples, while a lifetime of nearly 5 ns is observed for 10 18 cm –3 As doping. These results help us to establish limits on properties expected for group-V doped CdTe polycrystalline thin films for use in photovoltaics.« less

  18. High p-type doping, mobility, and photocarrier lifetime in arsenic-doped CdTe single crystals

    DOE PAGES

    Nagaoka, Akira; Kuciauskas, Darius; McCoy, Jedidiah; ...

    2018-05-07

    Here, Group-V element doping is promising for simultaneously maximizing the hole concentration and minority carrier lifetime in CdTe for thin film solar cells, but there are roadblocks concerning point defects including the possibility of self-compensation by AX metastability. Herein, we report on doping, lifetime, and mobility of CdTe single crystals doped with As between 10 16 and 10 20 cm –3 grown from the Cd solvent by the travelling heater method. Evidence consistent with AX instability as a major contributor to compensation in samples doped below 10 17 cm –3 is presented, while for higher-doped samples, precipitation of a secondmore » phase on planar structural defects is also observed and may explain spatial variation in properties such as lifetime. Rapid cooling after crystal growth increases doping efficiency and mobility for times up to 20–30 days at room temperature with the highest efficiencies observed close to 45% and a hole mobility of 70 cm 2/Vs at room temperature. A doping limit in the low 10 17/cm 3 range is observed for samples quenched at 200–300 °C/h. Bulk minority carrier lifetimes exceeding 20 ns are observed for samples doped near 10 16 cm –3 relaxed in the dark and for unintentionally doped samples, while a lifetime of nearly 5 ns is observed for 10 18 cm –3 As doping. These results help us to establish limits on properties expected for group-V doped CdTe polycrystalline thin films for use in photovoltaics.« less

  19. Electrochemical capacitance voltage measurements in highly doped silicon and silicon-germanium alloys

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sermage, B.; Essa, Z.; Taleb, N.

    2016-04-21

    The electrochemical capacitance voltage technique has been used on highly boron doped SiGe and Si layers. Although the boron concentration is constant over the space charge depth, the 1/C{sup 2} versus voltage curves are not linear. They indeed present a negative curvature. This can be explained by the existence of deep acceptors which ionise under a high electric field (large inverse voltage) and not at a low inverse voltage. The measured doping concentration in the electrochemical capacitance voltage increases strongly as the inverse voltage increases. Thanks to a comparison with the boron concentration measured by secondary ions mass spectrometry, wemore » show that the relevant doping concentrations in device layers are obtained for small inverse voltage in agreement with the existence of deep acceptors. At the large inverse voltage, the measured doping can be more than twice larger than the boron concentration measured with a secondary ion mass spectroscopy.« less

  20. Yb-doped polarizing fiber

    NASA Astrophysics Data System (ADS)

    Gillooly, A.; Webb, A. S.; Favero, F. C.; Bouchan, T.; Cooper, L. J.; Read, D.; Hill, M.

    2017-02-01

    An ytterbium (Yb) doped polarizing fiber is demonstrated. The fiber offers the opportunity to build all-fiber lasers with single polarization output and without the need for free-space polarizing components. Traditional single polarization fiber lasers utilize polarization-maintaining (PM) gain fiber with a single polarization stimulation signal. Whilst this results in an approximation to a single polarization laser, the spontaneous emission from the unstimulated polarization state limits the polarization extinction ratio (PER). The PER is further limited as the stimulated signal is prone to crosstalk. Furthermore, controlling amplitude modulation of the stimulated signal is critical for maximizing the peak power of an optical pulse, particularly for high energy lasers. If light is allowed to leak in to the unstimulated axis it will travel at a different velocity to the stimulated axis and can cross-couple back into the signal axis, creating an interference effect which leads to amplitude modulation on the signal pulse. Single-polarization Yb-doped fiber ensures that light on the fast axis is constantly attenuated; ensuring that light on the unstimulated axis cannot propagate and thus cannot degrade the PER or create amplitude modulation. In this paper we report on, to the best of our knowledge, the first demonstration of a single polarization Yb-doped bowtie optical fiber manufactured using a combination of Modified Chemical Vapor Deposition (MCVD) and rare-earth solution doping technology. The fiber has a single-polarization window of 80nm at the operating wavelength of 1060nm and a PER of >18dB. The fabrication and characterization of the fiber is reported.

  1. Luminescence properties of pure and doped CaSO4 nanorods irradiated by 15 MeV e-beam

    NASA Astrophysics Data System (ADS)

    Salah, Numan; Alharbi, Najlaa D.; Enani, Mohammad A.

    2014-01-01

    Calcium sulfate (CaSO4) doped with proper activators is a highly sensitive phosphor used in different fields mainly for radiation dosimetry, lighting and display applications. In this work pure and doped nanorods of CaSO4 were produced by the co-precipitation technique. Samples from this material doped with Ag, Cu, Dy, Eu and Tb were exposed to different doses of 15 MeV e-beam and studied for their thermoluminesence (TL) and photoluminescence (PL) properties. Color center formation leading to PL emissions were investigated before and after e-beam irradiation. The samples doped with rare earths elements (i.e. Dy, Eu and Tb) were observed to have thinner nanorods than the other samples and have higher absorption in the UV region. The Ag and Tb doped samples have poor TL response to e-beam, while those activated by Cu, Dy and Eu have strong glow peaks at around 123 °C. Quite linear response curves in the whole studied exposures i.e. 0.1-100 Gy were also observed in Cu and Dy doped samples. The PL results show that pure CaSO4 nanorods have active color centers without irradiation, which could be enriched/modified by these impurities mainly rare earths and further enhanced by e-beam irradiation. Eu3+ → Eu2+ conversion is clearly observed in Eu doped sample after e-beam irradiation. These results show that these nanorods might be useful in lighting and display devices development.

  2. Spectroscopic identification of rare earth elements in phosphate glass

    NASA Astrophysics Data System (ADS)

    Devangad, Praveen; Tamboli, Maktum; Muhammed Shameem, K. M.; Nayak, Rajesh; Patil, Ajeetkumar; Unnikrishnan, V. K.; Santhosh, C.; Kumar, G. A.

    2018-01-01

    In this work, rare earth-doped phosphate glasses were synthesized and characterized using three different spectroscopic techniques. The absorption spectra of the prepared praseodymium (Pr) and samarium (Sm) doped glasses, recorded by a UV-VIS-NIR spectrophotometer, show the characteristic absorption bands of these elements. To confirm this inference, laser-induced fluorescence spectra of Pr and Sm were obtained at a laser excitation of 442 nm. Their emission bands are reported here. The elemental analysis of these samples was carried out using a laser-induced breakdown spectroscopy (LIBS) system. Characteristic emission lines of Pr and Sm have been identified and reported by the recorded LIBS spectra of glass samples. Results prove that using these three complimentary spectroscopic techniques (absorption, fluorescence and LIBS), we can meaningfully characterize rare earth-doped glass samples.

  3. Optical Diagnostics for High-Temperature Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Eldridge, Jeffrey I.

    2009-01-01

    Thermal barrier coatings (TBCs) are typically composed of translucent ceramic oxides that provide thermal protection for metallic components exposed to high-temperature environments, such as in jet turbine engines. Taking advantage of the translucent nature of TBCs, optical diagnostics have been developed that can provide an informed assessment of TBC health that will allow mitigating action to be taken before TBC degradation threatens performance or safety. In particular, rare-earth-doped luminescent sublayers have been integrated into the TBC structure to produce luminescence that monitors TBC erosion, delamination, and temperature gradients. Erosion monitoring of TBC-coated specimens is demonstrated by utilizing visible luminescence that is excited from a sublayer that is exposed by erosion. TBC delamination monitoring is achieved in TBCs with a base rare-earth-doped luminescent sublayer by the reflectance-enhanced increase in luminescence produced in regions containing buried delamination cracks. TBC temperature monitoring is demonstrated using the temperature-dependent decay time for luminescence originating from the specific coating depth associated with a rare-earth-doped luminescent sublayer. The design and implementation of these TBCs with integrated luminescent sublayers is discussed, including co-doping strategies to produce more penetrating near-infrared luminescence. It is demonstrated that integration of the rare-earth-doped sublayers is achieved with no reduction in TBC life. In addition, results for multilayer TBCs designed to also perform as radiation barriers are also presented.

  4. Temperature and Pressure Sensors Based on Spin-Allowed Broadband Luminescence of Doped Orthorhombic Perovskite Structures

    NASA Technical Reports Server (NTRS)

    Eldridge, Jeffrey I. (Inventor); Chambers, Matthew D. (Inventor)

    2014-01-01

    Systems and methods that are capable of measuring pressure or temperature based on luminescence are discussed herein. These systems and methods are based on spin-allowed broadband luminescence of sensors with orthorhombic perovskite structures of rare earth aluminates doped with chromium or similar transition metals, such as chromium-doped gadolinium aluminate. Luminescence from these sensors can be measured to determine at least one of temperature or pressure, based on either the intense luminescence of these sensors, even at high temperatures, or low temperature techniques discussed herein.

  5. Thermoelectric Properties of Highly-Crystallized Ge-Te-Se Glasses Doped with Cu/Bi

    PubMed Central

    Srinivasan, Bhuvanesh; Boussard-Pledel, Catherine; Dorcet, Vincent; Samanta, Manisha; Biswas, Kanishka; Lefèvre, Robin; Gascoin, Franck; Cheviré, François; Tricot, Sylvain; Reece, Michael; Bureau, Bruno

    2017-01-01

    Chalcogenide semiconducting systems are of growing interest for mid-temperature range (~500 K) thermoelectric applications. In this work, Ge20Te77Se3 glasses were intentionally crystallized by doping with Cu and Bi. These effectively-crystallized materials of composition (Ge20Te77Se3)100−xMx (M = Cu or Bi; x = 5, 10, 15), obtained by vacuum-melting and quenching techniques, were found to have multiple crystalline phases and exhibit increased electrical conductivity due to excess hole concentration. These materials also have ultra-low thermal conductivity, especially the heavily-doped (Ge20Te77Se3)100−xBix (x = 10, 15) samples, which possess lattice thermal conductivity of ~0.7 Wm−1 K−1 at 525 K due to the assumable formation of nano-precipitates rich in Bi, which are effective phonon scatterers. Owing to their high metallic behavior, Cu-doped samples did not manifest as low thermal conductivity as Bi-doped samples. The exceptionally low thermal conductivity of the Bi-doped materials did not, alone, significantly enhance the thermoelectric figure of merit, zT. The attempt to improve the thermoelectric properties by crystallizing the chalcogenide glass compositions by excess doping did not yield power factors comparable with the state of the art thermoelectric materials, as these highly electrically conductive crystallized materials could not retain the characteristic high Seebeck coefficient values of semiconducting telluride glasses. PMID:28772687

  6. High-density Two-Dimensional Small Polaron Gas in a Delta-Doped Mott Insulator

    PubMed Central

    Ouellette, Daniel G.; Moetakef, Pouya; Cain, Tyler A.; Zhang, Jack Y.; Stemmer, Susanne; Emin, David; Allen, S. James

    2013-01-01

    Heterointerfaces in complex oxide systems open new arenas in which to test models of strongly correlated material, explore the role of dimensionality in metal-insulator-transitions (MITs) and small polaron formation. Close to the quantum critical point Mott MITs depend on band filling controlled by random disordered substitutional doping. Delta-doped Mott insulators are potentially free of random disorder and introduce a new arena in which to explore the effect of electron correlations and dimensionality. Epitaxial films of the prototypical Mott insulator GdTiO3 are delta-doped by substituting a single (GdO)+1 plane with a monolayer of charge neutral SrO to produce a two-dimensional system with high planar doping density. Unlike metallic SrTiO3 quantum wells in GdTiO3 the single SrO delta-doped layer exhibits thermally activated DC and optical conductivity that agree in a quantitative manner with predictions of small polaron transport but with an extremely high two-dimensional density of polarons, ~7 × 1014 cm−2. PMID:24257578

  7. Yb-doped aluminophosphosilicate ternary fiber with high efficiency and excellent laser stability

    NASA Astrophysics Data System (ADS)

    Li, Yuwei; Peng, Kun; Zhan, Huan; Liu, Shuang; Ni, Li; Wang, Yuying; Yu, Juan; Wang, Xiaolong; Wang, Jianjun; Jing, Feng; Lin, Aoxiang

    2018-03-01

    By using chelate precursor doping technique and traditional modified chemical vapor deposition system, we fabricated Yb-doped aluminophosphosilicate (Al2O3-P2O5-SiO2, ternary Yb-APS) large-mode-area fiber and reported on its laser performance. The fiber preform was doped with Al, P and Yb with concentration of ∼8000 ppm, ∼1700 ppm and ∼400 ppm in molar percent, respectively. Tested with master oscillator power amplifier system, the home-made Yb-APS fiber was found to present 1.02 kW at 1061.1 nm with a high slope efficiency of 81.2% and excellent laser stability with power fluctuation less than ±1.1% for over 10 h. Compared with Yb-doped aluminosilicate (Al2O3-SiO2, binary Yb-AS) fiber, the introduction of P2O5 effectively suppressed photodarkening effect even the P/Al ratio is much less than 1, indicating that Yb-APS fiber is a better candidate for high power fiber lasers.

  8. The effect of strontium and barium doping on perovskite-structured energy materials for photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Wu, Ming-Chung; Chen, Wei-Cheng; Chan, Shun-Hsiang; Su, Wei-Fang

    2018-01-01

    Perovskite solar cell is a novel photovoltaic technology with the superior progress in efficiency and the simple solution processes. Develop lead-free or lead-reduced perovskite materials is a significant concern for high-performance perovskite solar cell. Among the alkaline earth metals, the Sr2+ and Ba2+ are suitable for Pb2+ replacement in perovskite film due to fitting Goldschmidt's tolerance factor. In this study, we adopted Ba-doped and Sr-doped perovskite structured materials with different doping levels, including 1.0, 5.0, and 10.0 mol%, to prepare perovskite solar cells. Both Ba-doped and Sr-doped perovskite structured materials have a related tendency in absorption behavior and surface morphology. At 10.0 mol% doping level, the power conversion efficiency (PCE) of Sr-doped perovskite solar cells is only ∼0.5%, but the PCE of Ba-doped perovskite solar cells can be achieved to ∼9.7%. Ba-doped perovskite solar cells showed the acceptable photovoltaic characteristics than Sr-doped perovskite solar cells. Ba dopant can partially replace the amount of lead in the perovskite solar cells, and it could be a potential candidate in the field of lead-free or lead-reduced perovskite energy materials.

  9. Heavily Doped PBSE with High Thermoelectric Performance

    NASA Technical Reports Server (NTRS)

    Snyder, G. Jeffrey (Inventor); Wang, Heng (Inventor); Pei, Yanzhong (Inventor)

    2015-01-01

    The present invention discloses heavily doped PbSe with high thermoelectric performance. Thermoelectric property measurements disclosed herein indicated that PbSe is high zT material for mid-to-high temperature thermoelectric applications. At 850 K a peak zT (is) greater than 1.3 was observed when n(sub H) approximately 1.0 X 10(exp 20) cm(exp -3). The present invention also discloses that a number of strategies used to improve zT of PbTe, such as alloying with other elements, nanostructuring and band modification may also be used to further improve zT in PbSe.

  10. Highly Al-doped TiO{sub 2} nanoparticles produced by Ball Mill Method: structural and electronic characterization

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Santos, Desireé M. de los, E-mail: desire.delossantos@uca.es; Navas, Javier, E-mail: javier.navas@uca.es; Sánchez-Coronilla, Antonio

    2015-10-15

    Highlights: • Highly Al-doped TiO{sub 2} nanoparticles were synthesized using a Ball Mill Method. • Al doping delayed anatase to rutile phase transformation. • Al doping allow controlling the structural and electronic properties of nanoparticles. - Abstract: This study presents an easy method for synthesizing highly doped TiO{sub 2} nanoparticles. The Ball Mill method was used to synthesize pure and Al-doped titanium dioxide, with an atomic percentage up to 15.7 at.% Al/(Al + Ti). The samples were annealed at 773 K, 973 K and 1173 K, and characterized using ICP-AES, XRD, Raman spectroscopy, FT-IR, TG, STEM, XPS, and UV–vis spectroscopy.more » The effect of doping and the calcination temperature on the structure and properties of the nanoparticles were studied. The results show high levels of internal doping due to the substitution of Ti{sup 4+} ions by Al{sup 3+} in the TiO{sub 2} lattice. Furthermore, anatase to rutile transformation occurs at higher temperatures when the percentage of doping increases. Therefore, Al doping allows us to control the structural and electronic properties of the nanoparticle synthesized. So, it is possible to obtain nanoparticles with anatase as predominant phase in a higher range of temperature.« less

  11. In Situ One-Step Synthesis of Hierarchical Nitrogen-Doped Porous Carbon for High Performance Supercapacitors

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Jeon, Ju Won; Sharma, Ronish; Meduri, Praveen

    2014-04-30

    Electrochemical performance of the existing state-of-the art capacitors is not very high, key scientific barrier is that its charge storage mechanism wholly depends on adsorption of electrolyte on electrode. We present a novel method for the synthesis of nitrogen -doped porous carbons and address the drawback by precisely controlling composition and surface area. Nitrogen-doped porous carbon was synthesized using a self-sacrificial template technique without any additional nitrogen and carbon sources. They exhibited exceptionally high capacitance (239 Fg-1) due to additional pseudocapacitance originating from doped nitrogen. Cycling tests showed no obvious capacitance decay even after 10,000 cycles, which meets the requirementmore » of commercial supercapacitors. Our method is simple and highly efficient for the production of large quantities of nitrogen-doped porous carbons.« less

  12. Hydrothermal method of synthesis of rare-earth tantalates and niobates

    DOEpatents

    Nyman, May D; Rohwer, Lauren E.S.; Martin, James E

    2012-10-16

    A hydrothermal method of synthesis of a family of rare-earth Group 5 oxides, where the Group 5 oxide is a niobate or tantalate. The rare-earth Group 5 oxides can be doped with suitable emitter ions to form nanophosphors.

  13. Alkali earth co-doping effects on luminescence and scintillation properties of Ce doped Gd3Al2Ga3O12 scintillator

    NASA Astrophysics Data System (ADS)

    Kamada, Kei; Nikl, Martin; Kurosawa, Shunsuke; Beitlerova, Alena; Nagura, Aya; Shoji, Yasuhiro; Pejchal, Jan; Ohashi, Yuji; Yokota, Yuui; Yoshikawa, Akira

    2015-03-01

    The Mg and Ca co-doped Ce:Gd3Al2Ga3O12 single crystals were prepared by micro pulling down method with a wide concentration range 0-1000 ppm of the codopants. Absorption and luminescence spectra were measured together with several other scintillation characteristics, namely the scintillation decay and light yield to reveal the effect of Mg and Ca co-doping. The scintillation decays were accelerated by both Mg and Ca codopants. Comparing to Ca co-doping, the Mg co-doped samples showed much faster decay and comparatively smaller light output decrease with increasing Mg dopant concentration.

  14. Gamma rays shielding and sensing application of some rare earth doped lead-alumino-phosphate glasses

    NASA Astrophysics Data System (ADS)

    Kaur, Preet; Singh, Devinder; Singh, Tejbir

    2018-03-01

    Seven rare earth (Sm3+, Eu3+ and Nd3+) doped lead alumino phosphate glasses were prepared. The protective and sensing measures from gamma rays were analysed in terms of parameters viz. density (ρ), refractive index, energy band gap (Eg), mean free path (mfp), effective atomic number (Zeff) and buildup factors (energy absorption EABF as well as exposure buildup factor EBF). The energy dependent parameters (mfp, Zeff, EABF and EBF) were investigated in the energy region from 15 keV to 15 MeV. EABF and EBF values were observed to be maximum in the intermediate energy region. Besides, the EABF and EBF values for the prepared samples are shown to have strong dependence on chemical composition of the glass at lower energy, whereas, it is almost independent of chemical composition in higher energy region. The prepared glass samples are found to have potential applications in radiation shielding as well as radiation sensing, which further find numerous applications in the field of medicine and industry.

  15. Doping of alkali, alkaline-earth, and transition metals in covalent-organic frameworks for enhancing CO2 capture by first-principles calculations and molecular simulations.

    PubMed

    Lan, Jianhui; Cao, Dapeng; Wang, Wenchuan; Smit, Berend

    2010-07-27

    We use the multiscale simulation approach, which combines the first-principles calculations and grand canonical Monte Carlo simulations, to comprehensively study the doping of a series of alkali (Li, Na, and K), alkaline-earth (Be, Mg, and Ca), and transition (Sc and Ti) metals in nanoporous covalent organic frameworks (COFs), and the effects of the doped metals on CO2 capture. The results indicate that, among all the metals studied, Li, Sc, and Ti can bind with COFs stably, while Be, Mg, and Ca cannot, because the binding of Be, Mg, and Ca with COFs is very weak. Furthermore, Li, Sc, and Ti can improve the uptakes of CO2 in COFs significantly. However, the binding energy of a CO2 molecule with Sc and Ti exceeds the lower limit of chemisorptions and, thus, suffers from the difficulty of desorption. By the comparative studies above, it is found that Li is the best surface modifier of COFs for CO2 capture among all the metals studied. Therefore, we further investigate the uptakes of CO2 in the Li-doped COFs. Our simulation results show that at 298 K and 1 bar, the excess CO2 uptakes of the Li-doped COF-102 and COF-105 reach 409 and 344 mg/g, which are about eight and four times those in the nondoped ones, respectively. As the pressure increases to 40 bar, the CO2 uptakes of the Li-doped COF-102 and COF-105 reach 1349 and 2266 mg/g at 298 K, respectively, which are among the reported highest scores to date. In summary, doping of metals in porous COFs provides an efficient approach for enhancing CO2 capture.

  16. Wide-band-gap, alkaline-earth-oxide semiconductor and devices utilizing same

    DOEpatents

    Abraham, Marvin M.; Chen, Yok; Kernohan, Robert H.

    1981-01-01

    This invention relates to novel and comparatively inexpensive semiconductor devices utilizing semiconducting alkaline-earth-oxide crystals doped with alkali metal. The semiconducting crystals are produced by a simple and relatively inexpensive process. As a specific example, a high-purity lithium-doped MgO crystal is grown by conventional techniques. The crystal then is heated in an oxygen-containing atmosphere to form many [Li].degree. defects therein, and the resulting defect-rich hot crystal is promptly quenched to render the defects stable at room temperature and temperatures well above the same. Quenching can be effected conveniently by contacting the hot crystal with room-temperature air.

  17. Study of optical properties of cerium ion doped barium aluminate phosphor

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lohe, P. P., E-mail: prachiti.lohe2012@gmail.com; Omanwar, S. K.; Bajaj, N. S.

    2016-05-06

    In the recent years due to their various optical and technological applications aluminate materials have attracted attention of several researchers. When these materials are doped with rare earth ions they show properties favorable for many optical applications such as high quantum efficiencies. These materials are used in various applications such as lamp phosphors, optically and thermoluminescence dosimeter etc Barium aluminate BaAl{sub 2}O{sub 4} doped with Ce is well known long lasting phosphor. This paper reports synthesis of BaAl{sub 2}O{sub 4}: Ce phosphor prepared by a simple combustion synthesis. The samples were characterized for the phase purity, chemical bonds and luminescentmore » properties.« less

  18. Highly tunable magnetism in silicene doped with Cr and Fe atoms under isotropic and uniaxial tensile strain

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zheng, Rui; Ni, Jun, E-mail: junni@mail.tsinghua.edu.cn; Collaborative Innovative Center of Quantum Matter, Beijing 100084

    2015-12-28

    We have investigated the magnetic properties of silicene doped with Cr and Fe atoms under isotropic and uniaxial tensile strain by the first-principles calculations. We find that Cr and Fe doped silicenes show strain-tunable magnetism. (1) The magnetism of Cr and Fe doped silicenes exhibits sharp transitions from low spin states to high spin states by a small isotropic tensile strain. Specially for Fe doped silicene, a nearly nonmagnetic state changes to a high magnetic state by a small isotropic tensile strain. (2) The magnetic moments of Fe doped silicene also show a sharp jump to ∼2 μ{sub B} at amore » small threshold of the uniaxial strain, and the magnetic moments of Cr doped silicene increase gradually to ∼4 μ{sub B} with the increase of uniaxial strain. (3) The electronic and magnetic properties of Cr and Fe doped silicenes are sensitive to the magnitude and direction of the external strain. The highly tunable magnetism may be applied in the spintronic devices.« less

  19. Ytterbium- and neodymium-doped vanadate laser hose crystals having the apatite crystal structure

    DOEpatents

    Payne, Stephen A.; Kway, Wayne L.; DeLoach, Laura D.; Krupke, William F.; Chai, Bruce H. T.

    1994-01-01

    Yb.sup.3+ and Nd.sup.3+ doped Sr.sub.5 (VO.sub.4).sub.3 F crystals serve as useful infrared laser media that exhibit low thresholds of oscillation and high slope efficiencies, and can be grown with high optical quality. These laser media possess unusually high absorption and emission cross sections, which provide the crystals with the ability to generate greater gain for a given amount of pump power. Many related crystals such as Sr.sub.5 (VO.sub.4).sub.3 F crystals doped with other rare earths, transition metals, or actinides, as well as the many structural analogs of Sr.sub.5 (VO.sub.4).sub.3 F, where the Sr.sup.2+ and F.sup.- ions are replaced by related chemical species, have similar properties.

  20. Highly Nitrogen-Doped Three-Dimensional Carbon Fibers Network with Superior Sodium Storage Capacity.

    PubMed

    Lei, Wen; Xiao, Weiping; Li, Jingde; Li, Gaoran; Wu, Zexing; Xuan, Cuijuan; Luo, Dan; Deng, Ya-Ping; Wang, Deli; Chen, Zhongwei

    2017-08-30

    Inspired by the excellent absorption capability of spongelike bacterial cellulose (BC), three-dimensional hierarchical porous carbon fibers doped with an ultrahigh content of N (21.2 atom %) (i.e., nitrogen-doped carbon fibers, NDCFs) were synthesized by an adsorption-swelling strategy using BC as the carbonaceous material. When used as anode materials for sodium-ion batteries, the NDCFs deliver a high reversible capacity of 86.2 mAh g -1 even after 2000 cycles at a high current density of 10.0 A g -1 . It is proposed that the excellent Na + storage performance is mainly due to the defective surface of the NDCFs created by the high content of N dopant. Density functional theory (DFT) calculations show that the defect sites created by N doping can strongly "host" Na + and therefore contribute to the enhanced storage capacity.

  1. Defect mediated magnetic interaction and high Tc ferromagnetism in Co doped ZnO nanoparticles.

    PubMed

    Pal, Bappaditya; Giri, P K

    2011-10-01

    Structural, optical and magnetic studies have been carried out for the Co-doped ZnO nanoparticles (NPs). ZnO NPs are doped with 3% and 5% Co using ball milling and ferromagnetism (FM) is studied at room temperature and above. A high Curie temperature (Tc) has been observed from the Co doped ZnO NPs. X-ray diffraction and high resolution transmission electron microscopy analysis confirm the absence of metallic Co clusters or any other phase different from würtzite-type ZnO. UV-visible absorption and photoluminescence studies on the doped samples show change in band structure and oxygen vacancy defects, respectively. Micro-Raman studies of doped samples shows defect related additional strong bands at 547 and 574 cm(-1) confirming the presence of oxygen vacancy defects in ZnO lattice. The field dependence of magnetization (M-H curve) measured at room temperature exhibits the clear M-H loop with saturation magnetization and coercive field of the order of 4-6 emu/g and 260 G, respectively. Temperature dependence of magnetization measurement shows sharp ferromagnetic to paramagnetic transition with a high Tc = 791 K for 3% Co doped ZnO NPs. Ferromagnetic ordering is interpreted in terms of overlapping of polarons mediated through oxygen vacancy defects based on the bound magnetic polaron (BMP) model. We show that the observed FM data fits well with the BMP model involving localised carriers and magnetic cations.

  2. High-resolution structural characterization and magnetic properties of epitaxial Ce-doped yttrium iron garnet thin films

    NASA Astrophysics Data System (ADS)

    Li, Zhong; Vikram Singh, Amit; Rastogi, Ankur; Gazquez, Jaume; Borisevich, Albina Y.; Mishra, Rohan; Gupta, Arunava

    2017-07-01

    Thin films of magnetic garnet materials, e.g. yttrium iron garnet (Y3Fe5O12, YIG), are useful for a variety of applications including microwave integrated circuits and spintronics. Substitution of rare earth ions, such as cerium, is known to enhance the magneto-optic Kerr effect (MOKE) as compared to pure YIG. Thin films of Ce0.75Y2.25Fe5O12 (Ce:YIG) have been grown using the pulsed laser deposition (PLD) technique and their crystal structure examined using high resolution scanning transmission electron microscopy. Homogeneous substitution of Ce in YIG, without oxidation to form a separate CeO2 phase, can be realized in a narrow process window with resulting enhancement of the MOKE signal. The thermally generated signal due to spin Seebeck effect for the optimally doped Ce:YIG films has also been investigated.

  3. Microstructure and high-temperature tribological properties of Si-doped hydrogenated diamond-like carbon films

    NASA Astrophysics Data System (ADS)

    Zhang, Teng Fei; Wan, Zhi Xin; Ding, Ji Cheng; Zhang, Shihong; Wang, Qi Min; Kim, Kwang Ho

    2018-03-01

    Si-doped DLC films have attracted great attention for use in tribological applications. However, their high-temperature tribological properties remain less investigated, especially in harsh oxidative working conditions. In this study, Si-doped hydrogenated DLC films with various Si content were synthesized and the effects of the addition of Si on the microstructural, mechanical and high-temperature tribological properties of the films were investigated. The results indicate that Si doping leads to an obvious increase in the sp3/sp2 ratio of DLC films, likely due to the silicon atoms preferentially substitute the sp2-hybridized carbon atoms and augment the number of sp3 sites. With Si doping, the mechanical properties, including hardness and adhesion strength, were improved, while the residual stress of the DLC films was reduced. The addition of Si leads to higher thermal and mechanical stability of DLC films because the Si atoms inhibit the graphitization of the films at an elevated temperature. Better high-temperature tribological properties of the Si-DLC films under oxidative conditions were observed, which can be attributed to the enhanced thermal stability and formation of a Si-containing lubricant layer on the surfaces of the wear tracks. The nano-wear resistance of the DLC films was also improved by Si doping.

  4. Effect of vanadium doping on the properties of high Curie point ferroelectric strontium niobate ceramic

    NASA Astrophysics Data System (ADS)

    Ning, Huanpo

    2017-10-01

    Different levels of isovalent dopant vanadium were doped on the B site of Sr2Nb2O7 to explore the doping effect on its dielectric and ferroelectric properties. A second phase could be detected with above 1 mol% V2O5 doping. The grains after doping remained anisotropic and plate-like. The samples are not dense, as there are pores present at the grain boundaries. The corrected dielectric constant for 0.1 mol%, 0.2 mol%, and 0.3 mol% V doped SNO at 1 MHz is around 46, 48 and 49, respectively, which indicates the effect of V doping on the increase of dielectric constant of SNO (ɛr is about 40 at 1 MHz). The Curie point Tc increased with the increase in the V doping level. The relatively high d33 (2.3 pC/N) measured from the non-dense and untextured samples indicates the potential effect of V2O5 doping on the improvement of piezoelectricity of SNO.

  5. Doping Polymer Semiconductors by Organic Salts: Toward High-Performance Solution-Processed Organic Field-Effect Transistors.

    PubMed

    Hu, Yuanyuan; Rengert, Zachary D; McDowell, Caitlin; Ford, Michael J; Wang, Ming; Karki, Akchheta; Lill, Alexander T; Bazan, Guillermo C; Nguyen, Thuc-Quyen

    2018-04-24

    Solution-processed organic field-effect transistors (OFETs) were fabricated with the addition of an organic salt, trityl tetrakis(pentafluorophenyl)borate (TrTPFB), into thin films of donor-acceptor copolymer semiconductors. The performance of OFETs is significantly enhanced after the organic salt is incorporated. TrTPFB is confirmed to p-dope the organic semiconductors used in this study, and the doping efficiency as well as doping physics was investigated. In addition, systematic electrical and structural characterizations reveal how the doping enhances the performance of OFETs. Furthermore, it is shown that this organic salt doping method is feasible for both p- and n-doping by using different organic salts and, thus, can be utilized to achieve high-performance OFETs and organic complementary circuits.

  6. Intralayer doping effects on the high-energy magnetic correlations in NaFeAs

    DOE PAGES

    Pelliciari, Jonathan; Huang, Yaobo; Das, Tanmoy; ...

    2016-04-26

    We used resonant inelastic x-ray scattering (RIXS) and dynamical susceptibility calculations to study the magnetic excitations in NaFe 1$-$xCo xAs ( x=0 , 0.03, and 0.08). Despite a relatively low ordered magnetic moment, collective magnetic modes are observed in parent compounds (x=0) and persist in optimally (x= 0.03) and overdoped (x = 0.08) samples. Their magnetic bandwidths are unaffected by doping within the range investigated. High-energy magnetic excitations in iron pnictides are robust against doping and present irrespectively of the ordered magnetic moment. Nonetheless, Co doping slightly reduces the overall magnetic spectral weight, differently from previous studies on hole-doped BaFemore » 2As 2 , where it was observed constant. Finally, we demonstrate that the doping evolution of magnetic modes is different for the dopants being inside or outside the Fe-As layer.« less

  7. Highly Tm3+ doped germanate glass and its single mode fiber for 2.0 μm laser

    PubMed Central

    Wen, Xin; Tang, Guowu; Yang, Qi; Chen, Xiaodong; Qian, Qi; Zhang, Qinyuan; Yang, Zhongmin

    2016-01-01

    Highly Tm3+ doped optical fibers are urgently desirable for 2.0 μm compact single-frequency fiber laser and high-repetition-rate mode-locked fiber laser. Here, we systematically investigated the optical parameters, energy transfer processes and thermal properties of Tm3+ doped barium gallo-germanate (BGG) glasses. Highly Tm3+ doped BGG glass single mode (SM) fibers were fabricated by the rod-in-tube technique. The Tm3+ doping concentration reaches 7.6 × 1020 ions/cm3, being the reported highest level in Tm3+ doped BGG SM fibers. Using ultra short (1.6 cm) as-drawn highly Tm3+ doped BGG SM fiber, a single-frequency fiber laser at 1.95 μm has been demonstrated with a maximum output power of 35 mW when in-band pumped by a home-made 1568 nm fiber laser. Additionally, a multilongitudinal-mode fiber laser at 1.95 μm has also been achieved in a 10 cm long as-drawn active fiber, yielding a maximum laser output power of 165 mW and a slope efficiency of 17%. The results confirm that the as-drawn highly Tm3+ doped BGG SM fibers are promising in applications that require high gain and high power from a short piece of active optical fiber. PMID:26828920

  8. Biomineralization-Inspired Synthesis of Cerium-Doped Carbonaceous Nanoparticles for Highly Hydroxyl Radical Scavenging Activity

    NASA Astrophysics Data System (ADS)

    Zou, Shenqiang; Zhu, Xiaofang; Zhang, Lirong; Guo, Fan; Zhang, Miaomiao; Tan, Youwen; Gong, Aihua; Fang, Zhengzou; Ju, Huixiang; Wu, Chaoyang; Du, Fengyi

    2018-03-01

    Cerium oxide nanoparticles recently have received extensive attention in biomedical applications due to their excellent anti-oxidation performance. In this study, a simple, mild, and green approach was developed to synthesize cerium-doped carbonaceous nanoparticles (Ce-doped CNPs) using bio-mineralization of bull serum albumin (BSA) as precursor. The resultant Ce-doped CNPs exhibited uniform and ultrasmall morphology with an average size of 14.7 nm. XPS and FTIR results revealed the presence of hydrophilic group on the surface of Ce-doped CNPs, which resulted in excellent dispersity in water. The CCK-8 assay demonstrated that Ce-doped CNPs possessed favorable biocompatibility and negligible cytotoxicity. Using H2O2-induced reactive oxygen species (ROS) as model, Ce-doped CNPs showed highly hydroxyl radical scavenging capability. Furthermore, flow cytometry and live-dead staining results indicated that Ce-doped CNPs protected cells from H2O2-induced damage in a dose-dependent effect, which provided a direct evidence for anti-oxidative performance. These findings suggest that Ce-doped CNPs as novel ROS scavengers may provide a potential therapeutic prospect in treating diseases associated with oxidative stress.

  9. Low- and high-index sol-gel films for planar and channel-doped waveguides

    NASA Astrophysics Data System (ADS)

    Canva, Michael; Chaput, Frederic; Lahlil, Khalid; Rachet, Vincent; Goudket, Helene; Boilot, Jean-Pierre; Levy, Yves

    2001-11-01

    In view of realizing integrated optic components based on effects such as electro-optic, chi(2):chi(2) cascading, stimulated emission,... one has to first synthesize materials with the proper functionality; this may be achieved by doping solid state matrices by the appropriate organic chromophores. Second, and as important, these materials have to be properly structured into the final optical guiding structures. We shall report on issues related to the realization of chromophore-doped planar waveguides as well as channel waveguides. These structures were realized by either photo-transformation such as photo- chromism and photo-bleaching or reactive ion etching technique, starting with chromophore doped sol-gel materials at high loading contents for which optical index may be controlled via the local dopant concentration. With these materials and techniques, waveguides and components characterized by propagation losses of the order of a cm-1, measured off the edge of the absorption band of the doping species, were fabricated. In order to be also able to study and use waveguide functionalized with low concentration of chromophore species, we developed new sol-gel materials of high optical index, yet low temperature processed. These new films are under study to evaluate their potential as host for organic doped waveguides devices.

  10. Effect of doping rare earths on magnetostriction characteristics of CoFe2O4 prepared from spent Li-ion batteries

    NASA Astrophysics Data System (ADS)

    Xi, Guoxi; Zhao, Tingting; Wang, Lu; Dun, Changwei; Zhang, Ye

    2018-04-01

    Recovering spent Li-ion batteries is beneficial to the economy and environment. Therefore, this study synthesized nanoparticles of cobalt ferrite doped with different rare earth ions (Nd, Ce, and Pr) by a sol-gel auto-combustion method using spent Li-ion batteries. The effect of the different doping elements on grain sizes, structure, magnetic and magnetostrictive properties, and strain derivative were confirmed by X-ray diffraction, scanning election microscopy, vibrating sample magnetometer, and a magnetostrictive coefficient measuring system. Substitution of a small amount of Fe3+ with RE3+ in CoRExFe2-xO4 (x = 0.025, 0.05, and 0.1) had a large effect on magnetostrictive properties and strain derivative, which was improved compared with pure cobalt ferrite at low magnetic field. The maximum strain derivative (dλ/dH = -1.49 × 10-9 A-1 m at 18 kA m-1) was obtained for Nd, x = 0.05. Changes in the magnetostriction coefficients and strain derivatives were correlated with changes in cation distribution, microstructure, and magnetic anisotropy, which depended strongly on RE3+ substitution and distribution in the spinel structure.

  11. Observation of high magnetocrystalline anisotropy on Co doping in rare earth free Fe2P magnetic material

    NASA Astrophysics Data System (ADS)

    Thakur, Jyoti; Singh, Om Pal; Tomar, Monika; Gupta, Vinay; Kashyap, Manish K.

    2018-04-01

    ab-initio investigation of magnetocrystalline anisotropy energy (MAE) for Fe2P and CoFeP using density functional theory based full-potential linear augmented plane wave (FPLAPW) is reported. CoFeP alloy exhibits large magnetic moment 13.28 µB and enhanced anisotropy energy reaching as high as 1326 µeV/f.u. This energy is nearly doubled as compared to its parent Fe2P alloy, making this system a promising candidate for a rare earth free permanent magnet. Substituitng Co at Fe-3f site in Fe2P helps in stabilizing the new structure and further improves the magnetic properties.

  12. H.sub.2O doped WO.sub.3, ultra-fast, high-sensitivity hydrogen sensors

    DOEpatents

    Liu, Ping [Denver, CO; Tracy, C Edwin [Golden, CO; Pitts, J Roland [Lakewood, CO; Lee, Se-Hee [Lakewood, CO

    2011-03-22

    An ultra-fast response, high sensitivity structure for optical detection of low concentrations of hydrogen gas, comprising: a substrate; a water-doped WO.sub.3 layer coated on the substrate; and a palladium layer coated on the water-doped WO.sub.3 layer.

  13. Study of absorption and IR-emission of Er3+, Dy3+, Tm3+ doped high-purity tellurite glasses

    NASA Astrophysics Data System (ADS)

    Motorin, S. E.; Dorofeev, V. V.; Galagan, B. I.; Sverchkov, S. E.; Koltashev, V. V.; Denker, B. I.

    2018-04-01

    A study of high-purity TeO2-ZnO based tellurite glasses doped with Er3+, Dy3+ or Tm3+ that could be used as laser media in the 2-3 μm spectral range is presented. The glasses are prepared by melting the oxides mixture inside a silica glass reactor in an atmosphere of purified oxygen. The low level of hydroxyl groups absorption allowed to measure correctly the luminescence decay characteristics of the dopants. The rare-earth ions absorption bands, the luminescence spectra and kinetic characteristics of emission from the levels 4I11/2, 4I13/2 of Er3+, 6H13/2 of Dy3+ and 3H4, 3H5, 3F4 of Tm3+ ions are investigated. The results confirm the high potential of tellurite glasses as an active media for bulk, planar waveguide and fiber lasers.

  14. High-Performance Organic Light-Emitting Diode with Substitutionally Boron-Doped Graphene Anode.

    PubMed

    Wu, Tien-Lin; Yeh, Chao-Hui; Hsiao, Wen-Ting; Huang, Pei-Yun; Huang, Min-Jie; Chiang, Yen-Hsin; Cheng, Chien-Hong; Liu, Rai-Shung; Chiu, Po-Wen

    2017-05-03

    The hole-injection barrier between the anode and the hole-injection layer (HIL) is of critical importance to determine the device performance of organic light-emitting diodes (OLEDs). Here, we report on a record-high external quantum efficiency (EQE) (24.6% in green phosphorescence) of OLEDs fabricated on both rigid and flexible substrates, with the performance enhanced by the use of nearly defect-free and high-mobility boron-doped graphene as an effective anode and hexaazatriphenylene hexacarbonitrile as a new type of HIL. This new structure outperforms the existing graphene-based OLEDs, in which MoO 3 , AuCl 3 , or bis(trifluoromethanesulfonyl)amide are typically used as a doping source for the p-type graphene. The improvement of the OLED performance is attributed mainly to the appreciable increase of the hole conductivity in the nearly defect-free boron-doped monolayer graphene, along with the high work function achieved by the use of a newly developed hydrocarbon precursor containing boron in the graphene growth by chemical vapor deposition.

  15. Quasiparticle mass enhancement approaching optimal doping in a high-T c superconductor

    DOE PAGES

    Ramshaw, B. J.; Sebastian, S. E.; McDonald, R. D.; ...

    2015-03-26

    In the quest for superconductors with higher transition temperatures (T c), one emerging motif is that electronic interactions favorable for superconductivity can be enhanced by fluctuations of a broken-symmetry phase. In recent experiments it is suggested that the existence of the requisite broken-symmetry phase in the high-T c cuprates, but the impact of such a phase on the ground-state electronic interactions has remained unclear. Here, we used magnetic fields exceeding 90 tesla to access the underlying metallic state of the cuprate YBa 2Cu 3O 6+δ over a wide range of doping, and observed magnetic quantum oscillations that reveal a strongmore » enhancement of the quasiparticle effective mass toward optimal doping. Finally, this mass enhancement results from increasing electronic interactions approaching optimal doping, and suggests a quantum critical point at a hole doping of p crit ≈ 0.18.« less

  16. Quasiparticle mass enhancement approaching optimal doping in a high-T c superconductor

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ramshaw, B. J.; Sebastian, S. E.; McDonald, R. D.

    In the quest for superconductors with higher transition temperatures (T c), one emerging motif is that electronic interactions favorable for superconductivity can be enhanced by fluctuations of a broken-symmetry phase. In recent experiments it is suggested that the existence of the requisite broken-symmetry phase in the high-T c cuprates, but the impact of such a phase on the ground-state electronic interactions has remained unclear. Here, we used magnetic fields exceeding 90 tesla to access the underlying metallic state of the cuprate YBa 2Cu 3O 6+δ over a wide range of doping, and observed magnetic quantum oscillations that reveal a strongmore » enhancement of the quasiparticle effective mass toward optimal doping. Finally, this mass enhancement results from increasing electronic interactions approaching optimal doping, and suggests a quantum critical point at a hole doping of p crit ≈ 0.18.« less

  17. N/S Co-doped Carbon Derived From Cotton as High Performance Anode Materials for Lithium Ion Batteries.

    PubMed

    Xiong, Jiawen; Pan, Qichang; Zheng, Fenghua; Xiong, Xunhui; Yang, Chenghao; Hu, Dongli; Huang, Chunlai

    2018-01-01

    Highly porous carbon with large surface areas is prepared using cotton as carbon sources which derived from discard cotton balls. Subsequently, the sulfur-nitrogen co-doped carbon was obtained by heat treatment the carbon in presence of thiourea and evaluated as Lithium-ion batteries anode. Benefiting from the S, N co-doping, the obtained S, N co-doped carbon exhibits excellent electrochemical performance. As a result, the as-prepared S, N co-doped carbon can deliver a high reversible capacity of 1,101.1 mA h g -1 after 150 cycles at 0.2 A g -1 , and a high capacity of 531.2 mA h g -1 can be observed even after 5,000 cycles at 10.0 A g -1 . Moreover, excellently rate capability also can be observed, a high capacity of 689 mA h g -1 can be obtained at 5.0 A g -1 . This superior lithium storage performance of S, N co-doped carbon make it as a promising low-cost and sustainable anode for high performance lithium ion batteries.

  18. N/S co-doped carbon derived from Cotton as high performance anode materials for lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Xiong, Jiawen; Pan, Qichang; Zheng, Fenghua; Xiong, Xunhui; Yang, Chenghao; Hu, Dongli; Huang, Chunlai

    2018-04-01

    Highly porous carbon with large surface areas is prepared using cotton as carbon sources which derived from discard cotton balls. Subsequently, the sulfur-nitrogen co-doped carbon was obtained by heat treatment the carbon in presence of thiourea and evaluated as Lithium-ion batteries anode. Benefiting from the S, N co-doping, the obtained S, N co-doped carbon exhibits excellent electrochemical performance. As a result, the as-prepared S, N co-doped carbon can deliver a high reversible capacity of 1101.1 mA h g-1 after 150 cycles at 0.2 A g-1, and a high capacity of 531.2 mA h g-1 can be observed even after 5000 cycles at 10.0 A g-1. Moreover, excellently rate capability also can be observed, a high capacity of 689 mA h g-1 can be obtained at 5.0 A g-1. This superior lithium storage performance of S, N co-doped carbon make it as a promising low-cost and sustainable anode for high performance lithium ion batteries.

  19. N/S Co-doped Carbon Derived From Cotton as High Performance Anode Materials for Lithium Ion Batteries

    PubMed Central

    Xiong, Jiawen; Pan, Qichang; Zheng, Fenghua; Xiong, Xunhui; Yang, Chenghao; Hu, Dongli; Huang, Chunlai

    2018-01-01

    Highly porous carbon with large surface areas is prepared using cotton as carbon sources which derived from discard cotton balls. Subsequently, the sulfur-nitrogen co-doped carbon was obtained by heat treatment the carbon in presence of thiourea and evaluated as Lithium-ion batteries anode. Benefiting from the S, N co-doping, the obtained S, N co-doped carbon exhibits excellent electrochemical performance. As a result, the as-prepared S, N co-doped carbon can deliver a high reversible capacity of 1,101.1 mA h g−1 after 150 cycles at 0.2 A g−1, and a high capacity of 531.2 mA h g−1 can be observed even after 5,000 cycles at 10.0 A g−1. Moreover, excellently rate capability also can be observed, a high capacity of 689 mA h g−1 can be obtained at 5.0 A g−1. This superior lithium storage performance of S, N co-doped carbon make it as a promising low-cost and sustainable anode for high performance lithium ion batteries. PMID:29755966

  20. High-contrast germanium-doped silica-on-silicon waveguides

    NASA Astrophysics Data System (ADS)

    Dumais, Patrick; Callender, Claire; Blanchetière, Chantal; Ledderhof, Chris

    2012-10-01

    Silica-on-silicon planar lightwave circuits have a number of advantages including stability and low insertion loss to optical fiber networks. Standard GeO2 doping levels in the waveguide cores lead to a refractive index contrast, n/n, of 0.75%-2%. This range of index contrast requires relatively large bend radii in order to minimize bend losses. This limits the density scaling of these circuits. By using high dopant levels for a Δn/n of 4%, the bend radius can be decreased to less than 1 mm, from which significant gains in optical circuit density can be obtained. In addition, low-loss ring resonators with free spectral ranges of a few tens of gigahertz can be realized, enabling some additional optical signal processing and filtering on that scale. Optical devices with such high dopant levels have been reported by Bellman et al. in 2004 [1] but to the authors' knowledge, no other experimental work on high-delta GeO2-doped waveguides has been reported since. In this paper, we present experimental measurements on high-delta devices including directional couplers, MMI couplers, Mach-Zehnder interferometers, and ring resonators. Device performance, including propagation loss, bend loss, interferometer contrast ratio and birefringence will be presented. We demonstrate that ring resonators with 40 GHz free spectral range can be fabricated for optical signal processing.

  1. Multicolor and near-infrared electroluminescence from the light-emitting devices with rare-earth doped TiO{sub 2} films

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhu, Chen; Gao, Zhifei; Wang, Canxing

    2015-09-28

    We report on multicolor and near-infrared electroluminescence (EL) from the devices using rare-earth doped TiO{sub 2} (TiO{sub 2}:RE) films as light-emitting layers, which are ascribed to the impact excitation of RE{sup 3+} ions, with the EL onset voltages below 10 V. The devices are in the structure of ITO/TiO{sub 2}:RE/SiO{sub 2}/Si, in which the SiO{sub 2} layer is ∼10 nm thick and RE includes Eu, Er, Tm, Nd, and so on. With sufficiently high positive voltage applied on the ITO electrode, the conduction electrons in Si can tunnel into the conduction band of SiO{sub 2} layer via the trap-assisted tunneling mechanism, gainingmore » the potential energy ∼4 eV higher than the conduction band edge of TiO{sub 2}. Therefore, as the electrons in the SiO{sub 2} layer drift into the TiO{sub 2}:RE layer, they become hot electrons. Such hot electrons impact-excite the RE{sup 3+} ions incorporated into the TiO{sub 2} host, leading to the characteristic emissions.« less

  2. Pyramidal defects in highly Mg-doped GaN: atomic structure and influence on optoelectronic properties

    NASA Astrophysics Data System (ADS)

    Leroux, M.; Vennéguès, P.; Dalmasso, S.; de Mierry, P.; Lorenzini, P.; Damilano, B.; Beaumont, B.; Gibart, P.; Massies, J.

    2004-07-01

    A detailed transmission electron microscopy study is performed on the pyramidal inversion domains that appear in highly Mg-doped GaN grown by metalorganics vapor phase epitaxy or by the high-pressure, high-temperature method. From a comparison between high resolution images of the inversion domain boundaries and simulations using different atomic models, we conclude that both basal and inclined domain boundaries are likely formed of a monomolecular layer of the definite compound Mg{3}N{2}. We show that, due to their high concentration, the formation of these defects may account for auto-compensation in Mg-doped GaN. We also show that the local band bending induced by the polarity inversion due to these defects can be at the origin of the blue luminescence of highly Mg-doped GaN, always observed when nanometric pyramidal inversion domains are also present.

  3. L-lactic acid and sodium p-toluenesulfonate co-doped polypyrrole for high performance cathode in sodium ion battery

    NASA Astrophysics Data System (ADS)

    Liao, Qishu; Hou, Hongying; Liu, Xianxi; Yao, Yuan; Dai, Zhipeng; Yu, Chengyi; Li, Dongdong

    2018-04-01

    In this work, polypyrrole (PPy) was co-doped with L-lactic acid (LA) and sodium p-toluenesulfonate (TsONa) for high performance cathode in sodium ion battery (SIB) via facile one-step electropolymerization on Fe foil. The as-synthesized LA/TsONa co-doped PPy cathode was investigated in terms of scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), galvanostatic charge/discharge and cyclic voltammetry (CV). The results suggested that some oval-bud-like LA/TsONa co-doped PPy particles did form and tightly combine with the surface of Fe foil; furthermore, LA/TsONa co-doped PPy cathode also delivered higher electrochemical performances than TsONa mono-doped PPy cathode. For example, the initial specific discharge capacity was as high as about 124 mAh/g, and the reversible specific capacity still maintained at about 110 mAh/g even after 50 cycles, higher than those of TsONa mono-doped PPy cathode. The synergy effect of multi components of LA/TsONa co-doped PPy cathode should be responsible for high electrochemical performances.

  4. Physical and optical absorption studies of Fe{sup 3+} - ions doped lithium borate glasses containing certain alkaline earths

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Bhogi, Ashok; Kumar, R. Vijaya; Kistaiah, P., E-mail: pkistaiah@yahoo.com

    Iron ion doped lithium borate glasses with the composition 15RO-25Li{sub 2}O-59B{sub 2}O{sub 3}-1Fe{sub 2}O{sub 3} (where R= Ca, Sr and Ba) have been prepared by the conventional melt quenching technique and characterized to investigate the physical and optical properties using XRD, density, molar volume and UV-Visible spectroscopy. The optical absorption spectra exhibit a band at around 460 nm which is assigned to {sup 6}A{sub 1g}(S) → 4E{sub g} (G) of Fe{sup 3+} ions with distorted octahedral symmetry. From ultraviolet absorption edges, the optical band gap and Urbach energies have been evaluated. The effect of alkaline earths on these properties ismore » discussed.« less

  5. Development of MoSi2 coating with Al doping by using high energy milling method

    NASA Astrophysics Data System (ADS)

    Simanjuntak, C. M. S.; Hastuty, S.; Izzuddin, H.; Sundawa, R.; Sudiro, T.; Sukarto, A.; Thosin, K. A. Z.

    2018-03-01

    MoSi2 is well known as a material for high temperature application because it has high oxidation and corrosion resistance. The aim of this research is to develop MoSi2 coating with Al doping on Stainless Steel 316 (SS316) substrate using High-Energy Milling method. Aluminium is added to the coating as a dopant to increase formation of MoSi2 coating layer on the substrate. The variations used here based on the concentrations of doping Al (at.%) and duration of milling. Results show that the MoSi2 coatings with variations of 30 and 50 at.% of Al doping and 3 and 6 hours of milling times were successfully coated on the surface of SS 316 using the high-energy milling method. The most optimum coating result after oxidation test at 1100 °C for 100 hours is shown by MoSi2-30%Al with 3 hours of milling times. From the oxidation results, the Al doping into MoSi2 coating was able to increase the oxidation resistance of the SS 316 substrate.

  6. Rare-Earth Activated Nitride Phosphors: Synthesis, Luminescence and Applications

    PubMed Central

    Xie, Rong-Jun; Hirosaki, Naoto; Li, Yuanqiang; Takeda, Takashi

    2010-01-01

    Nitridosilicates are structurally built up on three-dimensional SiN4 tetrahedral networks, forming a very interesting class of materials with high thermomechanical properties, hardness, and wide band gap. Traditionally, nitridosilicates are often used as structural materials such as abrasive particles, cutting tools, turbine blade, etc. Recently, the luminescence of rare earth doped nitridosilicates has been extensively studied, and a novel family of luminescent materials has been developed. This paper reviews the synthesis, luminescence and applications of nitridosilicate phosphors, with emphasis on rare earth nitrides in the system of M-Si-Al-O-N (M = Li, Ca, Sr, Ba, La) and their applications in white LEDs. These phosphors exhibit interesting luminescent properties, such as red-shifted excitation and emission, small Stokes shift, small thermal quenching, and high conversion efficiency, enabling them to use as down-conversion luminescent materials in white LEDs with tunable color temperature and high color rendering index.

  7. A synthetic high fidelity, high cadence spectral Earth database

    NASA Astrophysics Data System (ADS)

    Schwieterman, Edward; Meadows, Victoria; Robinson, Tyler D.; Lustig-Yaeger, Jacob; Sparks, William B.; Cracraft, Misty

    2016-10-01

    Earth is currently our only, and will always be our best, example of a living planet. While Earth data model comparisons have been effectively used in recent years to validate spectral models, observations by interplanetary spacecraft are limited to "snapshots" in terms of viewing geometry and Earth's dynamic surface and atmosphere state. We use the well-validated Virtual Planetary Laboratory 3D spectral Earth model to generate both simulated disk-averaged spectra and high resolution, spatially resolved spectral data cubes of Earth at a viewing geometry consistent with Lunar viewing angles at wavelengths from the far UV (0.1 μm) the to the far IR (200 μm). The database includes disk-averaged spectra from dates 03/19/2008 to 04/23/2008 at one-hour cadence and fully spectral data cubes for a subset of those times. These spectral products have a wide range of applications including calibration of spacecraft instrumentation (Robinson et al. 2014), modeling the radiation environment of permanently shadowed Lunar craters due to Earthshine (Glenar et al., in prep), and testing the detectability of atmospheric and surface features of an Earth-like planet orbiting a distant star with a large space-based telescope mission concepts such as LUVOIR. These data include the phase and time-dependent changes in spectral biosignatures (O2, O3, CH4, VRE) and habitability markers (N2, H2O, CO2, ocean glint). The advantages of the VPL Earth model data products over 1D spectra traditionally used for testing instrument architectures include accurate modeling of Earth's surface inhomogeneity (continental distribution and ice caps), cloud cover and variability, pole to equator temperature gradients, obliquity, phase-dependent scattering effects, and rotation. We present a subset of this spectral data including anticipated signal-to-noise calculations of an exoEarth twin at different phases using a coronagraph instrument model (Robinson et al. 2015). We also calculate time

  8. Single crystal fibers for high power lasers

    NASA Astrophysics Data System (ADS)

    Kim, W.; Florea, C.; Baker, C.; Gibson, D.; Shaw, L. B.; Bowman, S.; O'Connor, S.; Villalobos, G.; Bayya, S.; Aggarwal, I. D.; Sanghera, J. S.

    2012-11-01

    In this paper, we present our recent results in developing cladded-single crystal fibers for high power single frequency fiber lasers significantly exceeding the capabilities of existing silica fiber based lasers. This fiber laser would not only exploit the advantages of crystals, namely their high temperature stability, high thermal conductivity, superior environmental ruggedness, high propensity for rare earth ion doping and low nonlinearity, but will also provide the benefits from an optical fiber geometry to enable better thermal management thereby enabling the potential for high laser power output in short lengths. Single crystal fiber cores with diameters as small as 35μm have been drawn using high purity rare earth doped ceramic or single crystal feed rods by Laser Heated Pedestal Growth (LHPG) process. The mechanical, optical and morphological properties of these fibers have been characterized. The fibers are very flexible and show good overall uniformity. We also measured the optical loss as well as the non-radiative loss of the doped crystal fibers and the results show that the fibers have excellent optical and morphological quality. The gain coefficient of the crystal fiber matches the low quantum defect laser model and it is a good indication of the high quality of the fibers.

  9. Modification of Co/Cu nanoferrites properties via Gd3+/Er3+doping

    NASA Astrophysics Data System (ADS)

    Ateia, Ebtesam E.; Soliman, Fatma S.

    2017-05-01

    Pure nanoparticles of the rare earth-substituted cobalt and copper ferrites with general formula Me Gd0.025 Er0.05 Fe1.925 O4 (Me = Co, Cu) were prepared by the chemical citrate method. X-ray diffraction, field emission scanning electron microscopy, BET analysis are utilized to study the effect of rare earth substitution and its impact on the physical properties of the investigated samples. Rare earth-doped cobalt shows type IV isotherm suggesting mesopore structure with its hysteresis loop. The estimated crystallite sizes are found in the range of 21.49 and 36.11 nm for the doped Co and Cu samples, respectively. The magnetic properties of rare earth-substituted cobalt and copper ferrites showed a definite hysteresis loop at room temperature. An increase in coercivity and a decrease in saturation magnetization were detected. This can be explained in view of weaker nature of the Re3+-Fe3+ interaction compared to Fe3+-Fe3+ interaction. Greater than 1.13-fold increase in coercivity (Hc = 2184 Oe) was observed in doped cobalt nanoferrite samples compared to copper (Hc = 1936 Oe). It was found that the decreasing in temperature leads to great improvement in the magnetic properties of the investigated samples. As the magnetic recording performance of the magnetic samples is improved for well-crystallized samples with nano-structural, the effect of rare earth substitution seems to be particularly valuable in this regard.

  10. A review of earth abundant ZnO-based materials for thermoelectric and photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Wang, Yang; Zhou, Chuanle; Elquist, Aline M.; Ghods, Amirhossein; Saravade, Vishal G.; Lu, Na; Ferguson, Ian

    2018-02-01

    Zinc oxide (ZnO) is an earth abundant wide bandgap semiconductor of great interest in the recent years. ZnO has many unique properties, such as non-toxic, large direct bandgap, high exciton binding energy, high transparency in visible and infrared spectrum, large Seebeck coefficient, high thermal stability, high electron diffusivity, high electron mobility, and availability of various nanostructures, making it a promising material for many applications. The growth techniques of ZnO is reviewed in this work, including sputtering, PLD, MOCVD and MBE techniques, focusing on the crystalline quality, electrical and optical properties. The problem with p-type doping ZnO is also discussed, and the method to improve p-type doping efficiency is reviewed. This paper also summarizes the current state of art of ZnO in thermoelectric and photovoltaic applications, including the key parameters, different device structures, and future development.

  11. Dielectric and nonlinear current-voltage characteristics of rare-earth doped CaCu3Ti4O12 ceramics

    NASA Astrophysics Data System (ADS)

    Liu, Laijun; Fang, Liang; Huang, Yanmin; Li, Yunhua; Shi, Danping; Zheng, Shaoying; Wu, Shuangshuang; Hu, Changzheng

    2011-11-01

    CaCu3Ti4O12 (CCTO) ceramics doped with rare earth (RE) oxides, including Y2O3, La2O3, Eu2O3, and Gd2O3, were prepared by the traditional solid-state reaction method in order to investigate the effect of RE oxide dopants on the electrical properties as a varistor. The phase identification and morphology of the ceramics were investigated by x-ray diffraction (XRD) and scanning electron microscope (SEM), respectively. A high voltage measuring unit and precision impedance analyzer were used to determine the nonohmic (J-E) behaviors and measure the dielectric properties and impedance spectroscopy of the ceramics, respectively. The results showed that RE oxides enhanced greatly the breakdown electric flied but reduced the nonlinear coefficient and the mean grain size of CCTO ceramics. There was a good linear relationship between ln J and E1/2, which demonstrated that the Schottky barrier should exist at the grain boundary. A double Schottky barrier model composed of a depletion layer and a negative charge sheet was proposed, analogous to the barrier model for ZnO varistors. The depletion layer width determined by diffusion distance of RE ions and the effective surface states played important roles on the electrical properties of the ceramics.

  12. Structure-property-composition relationships in doped zinc oxides: enhanced photocatalytic activity with rare earth dopants.

    PubMed

    Goodall, Josephine B M; Illsley, Derek; Lines, Robert; Makwana, Neel M; Darr, Jawwad A

    2015-02-09

    In this paper, we demonstrate the use of continuous hydrothermal flow synthesis (CHFS) technology to rapidly produce a library of 56 crystalline (doped) zinc oxide nanopowders and two undoped samples, each with different particle properties. Each sample was produced in series from the mixing of an aqueous stream of basic zinc nitrate (and dopant ion or modifier) solution with a flow of superheated water (at 450 °C and 24.1 MPa), whereupon a crystalline nanoparticle slurry was rapidly formed. Each composition was collected in series, cleaned, freeze-dried, and then characterized using analytical methods, including powder X-ray diffraction, transmission electron microscopy, Brunauer-Emmett-Teller surface area measurement, X-ray photoelectron spectroscopy, and UV-vis spectrophotometry. Photocatalytic activity of the samples toward the decolorization of methylene blue dye was assessed, and the results revealed that transition metal dopants tended to reduce the photoactivity while rare earth ions, in general, increased the photocatalytic activity. In general, low dopant concentrations were more beneficial to having greater photodecolorization in all cases.

  13. Effects of fabrication methods on spin relaxation and crystallite quality in Tm-doped ? powders studied using spectral hole burning

    NASA Astrophysics Data System (ADS)

    Lutz, Thomas; Veissier, Lucile; Thiel, Charles W.; Woodburn, Philip J. T.; Cone, Rufus L.; Barclay, Paul E.; Tittel, Wolfgang

    2016-01-01

    High-quality rare-earth-ion (REI) doped materials are a prerequisite for many applications such as quantum memories, ultra-high-resolution optical spectrum analyzers and information processing. Compared to bulk materials, REI doped powders offer low-cost fabrication and a greater range of accessible material systems. Here we show that crystal properties, such as nuclear spin lifetime, are strongly affected by mechanical treatment, and that spectral hole burning can serve as a sensitive method to characterize the quality of REI doped powders. We focus on the specific case of thulium doped ? (Tm:YAG). Different methods for obtaining the powders are compared and the influence of annealing on the spectroscopic quality of powders is investigated on a few examples. We conclude that annealing can reverse some detrimental effects of powder fabrication and, in certain cases, the properties of the bulk material can be reached. Our results may be applicable to other impurities and other crystals, including color centers in nano-structured diamond.

  14. Optimization of rare-earth-doped fluorides for infrared lasers

    NASA Astrophysics Data System (ADS)

    Peterson, Rita Dedomenico

    2000-11-01

    The rare-earth-doped fluoride crystals Tm,Dy:BaY2F8 (Tm,Dy:BYF), Yb,Pr:NaYF4 (Yb,Pr:NYF), and Nd:NYF show considerable promise as infrared laser materials, operating at 3 μm, 1.3 μm, and 1.06 μm respectively. Lasing has been reported previously on all three ionic transitions, but not in these crystals. Optimization of these materials for laser applications requires a more complete spectroscopic characterization than is currently available, particularly with regard to the key parameters of fluorescence lifetime and stimulated emission cross section. To further the optimization process, polarized absorption and emission have been measured for Tm,Dy:BYF, Yb,Pr:NYF, and Nd:NYF, and relevant fluorescence lifetimes have been measured or estimated. For Tm,Dy:BYF and Yb,Pr:NYF which rely upon sensitization, energy transfer parameters were calculated. Results were used in a mathematical model to determine the conditions in which lasing may be obtained. The long upper laser level lifetime in Tm,Dy:BYF translates into low threshold pump intensity, but the ability to reach threshold depends strongly on active ion concentration. The short lifetime in Yb,Pr:NYF leads to much higher threshold pump intensities, but lasing is still attainable if resonator loss is minimized. In Nd:NYF lasing was demonstrated, with a maximum of 60 mW output from an absorbed pump power of 345 mW, and a slope efficiency of 21%. Thresholds were high owing to resonator losses near 9%. Two chief issues involving the optimization of these laser materials were identified and explored. First, identification of the orientation for which emission cross section is highest is complicated in Tm,Dy:BYF by the presence of strong magnetic dipole radiation on the 3 μm transition. This effect makes it necessary to account for the polarization of both the electric and magnetic fields of the emitted radiation when determining an optimal crystal orientation, an accounting further complicated by the low symmetry of

  15. Tunable optical properties of some rare earth elements-doped mayenite Ca12Al14O33 nanopowders elaborated by oxalate precursor route

    NASA Astrophysics Data System (ADS)

    Rashad, Mohamed M.; Mostafa, Ahmed G.; Mwakikunga, Bonex W.; Rayan, Diaa A.

    2017-01-01

    Rare earth (RE) ions-doped mayenite Ca12Al14- x RE x O33 nanopowders (where RE = La and Gd and x = 0-1.0) were synthesized using the oxalate precursor technique. The as-prepared precursors were calcined at 800 °C for 2 h. Obviously, all RE-doped Ca12Al14- x RE x O33 possessed a well-crystalline cubic mayenite phase till RE content of 0.8. The crystallo-chemical aspects including crystallite size, lattice parameters, theoretical X-ray density and bulk density were robustly on RE nature and ratio. The microstructure and the average grain size were significantly influenced by the RE kind and content. The high transparency of Ca12Al14- x RE x O33 over 80% was found to be evinced in the visible wavelength range of 400-800 nm. Besides, the incorporation of RE cation minimized the direct band gap energy from 4.42 eV for pure mayenite to 3.85 and 3.59 eV with x value 1.0 of La3+ and Gd3+ ions. The photoluminescence spectra of pure mayenite nanoparticles showed that the band edge emission ( λ exc = 248 nm) with an intense visible emission band at 360 nm was detected. Otherwise, the band edge emission showed a slight shift toward short wavelength due to the substitution Al3+ by RE3+ ions. Such results open a new avenue for application of mayenite as a good candidate for transparent low-temperature electron conductor for optoelectronics applications.

  16. Boosting the down-shifting luminescence of rare-earth nanocrystals for biological imaging beyond 1500 nm.

    PubMed

    Zhong, Yeteng; Ma, Zhuoran; Zhu, Shoujun; Yue, Jingying; Zhang, Mingxi; Antaris, Alexander L; Yuan, Jie; Cui, Ran; Wan, Hao; Zhou, Ying; Wang, Weizhi; Huang, Ngan F; Luo, Jian; Hu, Zhiyuan; Dai, Hongjie

    2017-09-29

    In vivo fluorescence imaging in the near-infrared region between 1500-1700 nm (NIR-IIb window) affords high spatial resolution, deep-tissue penetration, and diminished auto-fluorescence due to the suppressed scattering of long-wavelength photons and large fluorophore Stokes shifts. However, very few NIR-IIb fluorescent probes exist currently. Here, we report the synthesis of a down-conversion luminescent rare-earth nanocrystal with cerium doping (Er/Ce co-doped NaYbF 4 nanocrystal core with an inert NaYF 4 shell). Ce doping is found to suppress the up-conversion pathway while boosting down-conversion by ~9-fold to produce bright 1550 nm luminescence under 980 nm excitation. Optimization of the inert shell coating surrounding the core and hydrophilic surface functionalization minimize the luminescence quenching effect by water. The resulting biocompatible, bright 1550 nm emitting nanoparticles enable fast in vivo imaging of blood vasculature in the mouse brain and hindlimb in the NIR-IIb window with short exposure time of 20 ms for rare-earth based probes.Fluorescence imaging in the near-infrared window between 1500-1700 nm (NIR-IIb window) offers superior spatial resolution and tissue penetration depth, but few NIR-IIb probes exist. Here, the authors synthesize rare earth down-converting nanocrystals as promising fluorescent probes for in vivo imaging in this spectral region.

  17. High capacity nickel battery material doped with alkali metal cations

    DOEpatents

    Jackovitz, John F.; Pantier, Earl A.

    1982-05-18

    A high capacity battery material is made, consisting essentially of hydrated Ni(II) hydroxide, and about 5 wt. % to about 40 wt. % of Ni(IV) hydrated oxide interlayer doped with alkali metal cations selected from potassium, sodium and lithium cations.

  18. A high-performance supercapacitor electrode based on N-doped porous graphene

    NASA Astrophysics Data System (ADS)

    Dai, Shuge; Liu, Zhen; Zhao, Bote; Zeng, Jianhuang; Hu, Hao; Zhang, Qiaobao; Chen, Dongchang; Qu, Chong; Dang, Dai; Liu, Meilin

    2018-05-01

    The development of high-performance supercapacitors (SCs) often faces some contradictory and competing requirements such as excellent rate capability, long cycling life, and high energy density. One effective strategy is to explore electrode materials of high capacitance, electrode architectures of fast charge and mass transfer, and electrolytes of wide voltage window. Here we report a facile and readily scalable strategy to produce high-performance N-doped graphene with a high specific capacitance (∼390 F g-1). A symmetric SC device with a wide voltage window of 3.5 V is also successfully fabricated based on the N-doped graphene electrode. More importantly, the as-assembled symmetric SC delivers a high energy density of 55 Wh kg-1 at a power density of 1800 W kg-1 while maintaining superior cycling life (retaining 96.6% of the initial capacitance after 20,000 cycles). Even at a power density as high as 8800 W kg-1, it still retains an energy density of 29 Wh kg-1, higher than those of previously reported graphene-based symmetric SCs.

  19. Bismuth doping strategies in GeTe nanowires to promote high-temperature phase transition from rhombohedral to face-centered cubic structure

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhang, Jie; Huang, Rong; Wei, Fenfen

    2014-11-17

    The phase transition of Bi-doped (∼3 at. %) GeTe nanowires from a rhombohedral (R) to a face-centered cubic (C) structure was observed in in situ high-temperature X-ray diffraction. The promotion of high-temperature R-C phase transition by a doping approach was revealed. Ab initio energy calculations of doped GeTe at various Bi doping concentrations were performed to interpret the promoted temperature-induced phase transitions. Those results indicated that the total energy differences between R and C structures of doped GeTe decreased as Bi doping concentrations increased, which facilitated R-C phase transitions.

  20. Rapid solid-phase microwave synthesis of highly photoluminescent nitrogen-doped carbon dots for Fe3+ detection and cellular bioimaging

    NASA Astrophysics Data System (ADS)

    He, Guili; Xu, Minghan; Shu, Mengjun; Li, Xiaolin; Yang, Zhi; Zhang, Liling; Su, Yanjie; Hu, Nantao; Zhang, Yafei

    2016-09-01

    Recently, carbon dots (CDs) have been playing an increasingly important role in industrial production and biomedical field because of their excellent properties. As such, finding an efficient method to quickly synthesize a large scale of relatively high purity CDs is of great interest. Herein, a facile and novel microwave method has been applied to prepare nitrogen doped CDs (N-doped CDs) within 8 min using L-glutamic acid as the sole reaction precursor in the solid phase condition. The as-prepared N-doped CDs with an average size of 1.64 nm are well dispersed in aqueous solution. The photoluminescence of N-doped CDs is pH-sensitive and excitation-dependent. The N-doped CDs show a strong blue fluorescence with relatively high fluorescent quantum yield of 41.2%, which remains stable even under high ionic strength. Since the surface is rich in oxygen-containing functional groups, N-doped CDs can be applied to selectively detect Fe3+ with the limit of detection of 10-5 M. In addition, they are also used for cellular bioimaging because of their high fluorescent intensity and nearly zero cytotoxicity. The solid-phase microwave method seems to be an effective strategy to rapidly obtain high quality N-doped CDs and expands their applications in ion detection and cellular bioimaging.

  1. A Unique 3D Nitrogen-Doped Carbon Composite as High-Performance Oxygen Reduction Catalyst

    PubMed Central

    Karunagaran, Ramesh; Tung, Tran Thanh; Tran, Diana; Coghlan, Campbell; Doonan, Christian

    2017-01-01

    The synthesis and properties of an oxygen reduction catalyst based on a unique 3-dimensional (3D) nitrogen doped (N-doped) carbon composite are described. The composite material is synthesised via a two-step hydrothermal and pyrolysis method using bio-source low-cost materials of galactose and melamine. Firstly, the use of iron salts and galactose to hydrothermally produceiron oxide (Fe2O3) magnetic nanoparticle clusters embedded carbon spheres. Secondly, magnetic nanoparticles diffused out of the carbon sphere when pyrolysed in the presence of melamine as nitrogen precursor. Interestingly, many of these nanoparticles, as catalyst-grown carbon nanotubes (CNTs), resulted in the formation of N-doped CNTs and N-doped carbon spheres under the decomposition of carbon and a nitrogen environment. The composite material consists of integrated N-doped carbon microspheres and CNTs show high ORR activity through a predominantly four-electron pathway. PMID:28792432

  2. Connecting Earth observation to high-throughput biodiversity data.

    PubMed

    Bush, Alex; Sollmann, Rahel; Wilting, Andreas; Bohmann, Kristine; Cole, Beth; Balzter, Heiko; Martius, Christopher; Zlinszky, András; Calvignac-Spencer, Sébastien; Cobbold, Christina A; Dawson, Terence P; Emerson, Brent C; Ferrier, Simon; Gilbert, M Thomas P; Herold, Martin; Jones, Laurence; Leendertz, Fabian H; Matthews, Louise; Millington, James D A; Olson, John R; Ovaskainen, Otso; Raffaelli, Dave; Reeve, Richard; Rödel, Mark-Oliver; Rodgers, Torrey W; Snape, Stewart; Visseren-Hamakers, Ingrid; Vogler, Alfried P; White, Piran C L; Wooster, Martin J; Yu, Douglas W

    2017-06-22

    Understandably, given the fast pace of biodiversity loss, there is much interest in using Earth observation technology to track biodiversity, ecosystem functions and ecosystem services. However, because most biodiversity is invisible to Earth observation, indicators based on Earth observation could be misleading and reduce the effectiveness of nature conservation and even unintentionally decrease conservation effort. We describe an approach that combines automated recording devices, high-throughput DNA sequencing and modern ecological modelling to extract much more of the information available in Earth observation data. This approach is achievable now, offering efficient and near-real-time monitoring of management impacts on biodiversity and its functions and services.

  3. Luminescence properties of Sm3+-doped alkaline earth ortho-stannates

    NASA Astrophysics Data System (ADS)

    Stanulis, Andrius; Katelnikovas, Artūras; Enseling, David; Dutczak, Danuta; Šakirzanovas, Simas; Bael, Marlies Van; Hardy, An; Kareiva, Aivaras; Jüstel, Thomas

    2014-05-01

    A series of Sm3+ doped M2SnO4 (M = Ca, Sr and Ba) samples were prepared by a conventional high temperature solid-state reaction route. All samples were characterized by powder X-ray diffraction (XRD) analysis, photoluminescence (PL), photoluminescence thermal quenching (TQ) and fluorescence lifetime (FL) measurements. The morphology of synthesized phosphor powders was examined by scanning electron microscopy (SEM). Moreover, luminous efficacies (LE) and color points of the CIE 1931 color space diagram were calculated and discussed. Synthesized powders showed bright orange-red emission under UV excitation. Based on the results obtained we demonstrate that Sm3+ ions occupy Ca and Sr sites in the Ca2SnO4 and Sr2SnO4 ortho-stannate structures, respectively. In contrast, Sm3+ substitutes Sn in the barium ortho-stannate Ba2SnO4 structure.

  4. High resolution three-dimensional doping profiler

    DOEpatents

    Thundat, Thomas G.; Warmack, Robert J.

    1999-01-01

    A semiconductor doping profiler provides a Schottky contact at one surface and an ohmic contact at the other. While the two contacts are coupled to a power source, thereby establishing an electrical bias in the semiconductor, a localized light source illuminates the semiconductor to induce a photocurrent. The photocurrent changes in accordance with the doping characteristics of the semiconductor in the illuminated region. By changing the voltage of the power source the depth of the depletion layer can be varied to provide a three dimensional view of the local properties of the semiconductor.

  5. High Thermoelectric Power Factor of a Diketopyrrolopyrrole-Based Low Bandgap Polymer via Finely Tuned Doping Engineering

    PubMed Central

    Jung, In Hwan; Hong, Cheon Taek; Lee, Un-Hak; Kang, Young Hun; Jang, Kwang-Suk; Cho, Song Yun

    2017-01-01

    We studied the thermoelectric properties of a diketopyrrolopyrrole-based semiconductor (PDPP3T) via a precisely tuned doping process using Iron (III) chloride. In particular, the doping states of PDPP3T film were linearly controlled depending on the dopant concentration. The outstanding Seebeck coefficient of PDPP3T assisted the excellent power factors (PFs) over 200 μW m−1K−2 at the broad range of doping concentration (3–8 mM) and the maximum PF reached up to 276 μW m−1K−2, which is much higher than that of poly(3-hexylthiophene), 56 μW m−1K−2. The high-mobility of PDPP3T was beneficial to enhance the electrical conductivity and the low level of total dopant volume was important to maintain high Seebeck coefficients. In addition, the low bandgap PDPP3T polymer effiectively shifted its absorption into near infra-red area and became more colorless after doping, which is great advantage to realize transparent electronic devices. Our results give importance guidance to develop thermoelectric semiconducting polymers and we suggest that the use of low bandgap and high-mobility polymers, and the accurate control of the doping levels are key factors for obtaining the high thermoelectric PF. PMID:28317929

  6. Observation of Phase-Filling Singularities in the Optical Dielectric Function of Highly Doped n-Type Ge.

    PubMed

    Xu, Chi; Fernando, Nalin S; Zollner, Stefan; Kouvetakis, John; Menéndez, José

    2017-06-30

    Phase-filling singularities in the optical response function of highly doped (>10^{19}  cm^{-3}) germanium are theoretically predicted and experimentally confirmed using spectroscopic ellipsometry. Contrary to direct-gap semiconductors, which display the well-known Burstein-Moss phenomenology upon doping, the critical point in the joint density of electronic states associated with the partially filled conduction band in n-Ge corresponds to the so-called E_{1} and E_{1}+Δ_{1} transitions, which are two-dimensional in character. As a result of this reduced dimensionality, there is no edge shift induced by Pauli blocking. Instead, one observes the "original" critical point (shifted only by band gap renormalization) and an additional feature associated with the level occupation discontinuity at the Fermi level. The experimental observation of this feature is made possible by the recent development of low-temperature, in situ doping techniques that allow the fabrication of highly doped films with exceptionally flat doping profiles.

  7. Highly Microporous Nitrogen-doped Carbon Synthesized from Azine-linked Covalent Organic Framework and its Supercapacitor Function.

    PubMed

    Kim, Gayoung; Yang, Jun; Nakashima, Naotoshi; Shiraki, Tomohiro

    2017-12-11

    Porous carbons with nitrogen-doped (N-doped) structures are promising materials for advanced energy conversion and storage applications, including supercapacitors and fuel cell catalysts. In this study, microporous N-doped carbon was successfully fabricated through carbonization of covalent organic frameworks (COFs) with an azine-linked two-dimensional molecular network (ACOF1). In the carbonized ACOF1, micropores with diameters smaller than 1 nm are selectively formed, and a high specific surface area (1596 cm 2  g -1 ) is achieved. In addition, the highly porous structure with N-doped sites results in enhancement of the electrochemical capacitance. Detailed investigation for the micropore-forming process reveals that the formation of nitrogen gas during the thermal degradation of the azine bond contributes to the microporous structure formation. Therefore, the present direct carbonization approach using COFs allows the fabrication of microporous heteroatom-doped carbons, based on molecularly designed COFs, toward future electrochemical and energy applications. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Highly Sensitive and Selective Ethanol Sensor Fabricated with In-Doped 3DOM ZnO.

    PubMed

    Wang, Zhihua; Tian, Ziwei; Han, Dongmei; Gu, Fubo

    2016-03-02

    ZnO is an important n-type semiconductor sensing material. Currently, much attention has been attracted to finding an effective method to prepare ZnO nanomaterials with high sensing sensitivity and excellent selectivity. A three-dimensionally ordered macroporous (3DOM) ZnO nanostructure with a large surface area is beneficial to gas and electron transfer, which can enhance the gas sensitivity of ZnO. Indium (In) doping is an effective way to improve the sensing properties of ZnO. In this paper, In-doped 3DOM ZnO with enhanced sensitivity and selectivity has been synthesized by using a colloidal crystal templating method. The 3DOM ZnO with 5 at. % of In-doping exhibits the highest sensitivity (∼88) to 100 ppm ethanol at 250 °C, which is approximately 3 times higher than that of pure 3DOM ZnO. The huge improvement to the sensitivity to ethanol was attributed to the increase in the surface area and the electron carrier concentration. The doping by In introduces more electrons into the matrix, which is helpful for increasing the amount of adsorbed oxygen, leading to high sensitivity. The In-doped 3DOM ZnO is a promising material for a new type of ethanol sensor.

  9. Methanesulfonic acid-assisted synthesis of N/S co-doped hierarchically porous carbon for high performance supercapacitors

    NASA Astrophysics Data System (ADS)

    Huo, Silu; Liu, Mingquan; Wu, Linlin; Liu, Mingjie; Xu, Min; Ni, Wei; Yan, Yi-Ming

    2018-05-01

    Nitrogen and sulfur co-doped carbons are considered as electrode materials for high performance supercapacitors, while their further development is still limited by complicated synthesis procedure, unsatisfied structure and low energy density. Developing a simple synthetic strategy to obtain rationally structured carbon materials and high supercapacitor performance is remaining a grand challenge. Herein, we describe the synthesis of nitrogen and sulfur co-doped hierarchical porous carbons as high performance supercapacitors electrode by a methanesulfonic acid-assisted one-step carbonization and activation of the freeze-dried precursors mixture. The as-prepared carbon material not only exhibits ideally hierarchical pores, but also realizes uniform nitrogen and sulfur co-doping. In 6.0 M KOH electrolyte, the material can achieve a high specific capacitance of 272 F g-1 at 1.0 A g-1 and a promising rate performance retaining 172 F g-1 even at 100 A g-1. Moreover, a fabricated symmetric supercapacitor based on as-prepared nitrogen and sulfur co-doped hierarchical porous carbon delivers high energy densities of 12.4 W h kg-1 and 8.0 W h kg-1 in 6.0 M KOH liquid and KOH/PVA solid-state electrolytes, respectively. This work presents a simple and effective methanesulfonic acid-assisted approach for mass production of heteroatomic doping hierarchical porous carbons for future energy storage applications.

  10. P/M Processing of Rare Earth Modified High Strength Steels.

    DTIC Science & Technology

    1980-12-01

    AA094 165 TRW INC CLEVELAND OH MATERIALS TECHNOLOGY F 6 P/N PROCESSING OF RARE EARTH MODIFIED HIGH STRENGTH STEELS DEC So A A SHEXM(ER NOOŕT76-C...LEVEL’ (7 PIM PROCESSING OF RARE EARTH MODIFIED HIGH STRENGTH STEELS By A. A. SHEINKER 00 TECHNICAL REPORT Prepared for Office of Naval Research...Processing of Rare Earth Modified High 1 Technical -’ 3t eC"Strength Steels * 1dc4,093Se~ 9PEFRIGOGNZTONAEADADDRESS 10. PROGRAM ELEMENT. PROJECT. TASK

  11. Time Evolution of Radiation-Induced Luminescence in Terbium-Doped Silicate Glass

    NASA Technical Reports Server (NTRS)

    West, Michael S.; Winfree, William P.

    1996-01-01

    A study was made on two commercially available terbium-doped silicate glasses. There is an increased interest in silicate glasses doped with rare-earth ions for use in high-energy particle detection and radiographic applications. These glasses are of interest due to the fact that they can be formed into small fiber sensors; a property that can be used to increase the spatial resolution of a detection system. Following absorption of radiation, the terbium ions become excited and then emit photons via 4f-4f electronic transitions as they relax back to the ground state. The lifetime of these transitions is on the order of milliseconds. A longer decay component lasting on the order of minutes has also been observed. While radiative transitions in the 4f shell of rare-earth ions are generally well understood by the Judd-Olfelt theory, the pr'esence of a longer luminescence decay component is not. Experimental evidence that the long decay component is due, in part, to the thermal release of trapped charge carriers will be presented. In addition, a theoretical model describing the time evolution of the radiation-induced luminescence will be presented.

  12. Photoluminescence of rare-earth ion (Eu3+, Tm3+, and Er3+)-doped and co-doped ZnNb2O6 for solar cells

    NASA Astrophysics Data System (ADS)

    Gao, Sen-Pei; Qian, Yan-Nan; Wang, Biao

    2015-08-01

    Visible converted emissions produced at an excitation of 286 nm in ZnNb2O6 ceramics doped with rare-earth ions (RE = Eu3+, Tm3+, Er3+ or a combination of these ions) were investigated with the aim of increasing the photovoltaic efficiency of solar cells. The structure of RE:ZnNb2O6 ceramics was confirmed by x-ray diffraction patterns. The undoped ZnNb2O6 could emit a blue emission under 286-nm excitation, which is attributed to the self-trapped excitons’ recombination of the efficient luminescence centers of edge-shared NbO6 groups. Upon 286-nm excitation, Eu:ZnNb2O6, Tm:ZnNb2O6, and Er:ZnNb2O6 ceramics showed blue, green, and red emissions, which correspond to the transitions of 5D0 → 7FJ (J = 1-4) (Eu3+), 1G4 → 3H6 (Tm3+), and 2H11/2/4S3/2 → 4I15/2 (Er3+), respectively. The calculated CIE chromaticity coordinates of Eu:ZnNb2O6, Tm:ZnNb2O6, and Er:ZnNb2O6 are (0.50, 0.31), (0.14, 0.19), and (0.29, 0.56), respectively. RE ion-co-doped ZnNb2O6 showed a combination of characteristic emissions. The chromaticity coordinates of Eu/Tm:ZnNb2O6, Eu/Er:ZnNb2O6, and Tm/Er:ZnNb2O6 were calculated to be (0.29, 0.24), (0.45, 0.37), and (0.17, 0.25). Project supported by the National Natural Science Foundation of China (Grant Nos. 10572155 and 10732100) and the Research Fund for the Doctoral Program of Ministry of Education, China (Grant No. 20130171130003).

  13. Thermally stable and high reflectivity Al-doped silver thin films deposited by magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Loka, Chadrasekhar; Lee, Kwang; Joo, Sin Yong; Lee, Kee-Sun

    2018-03-01

    Thermally stable, high reflectance thin film coatings are indispensable in optoelectronic devices, especially as a potential back reflector for LEDs and solar cells. The silver has the drawback of agglomerating easily and poor thermal stability, which is limiting its application as a highly reflective coating in various optoelectronic applications. In this study, improved thermal stability by modification of the Ag film into an Ag/Al-doped Ag structure has been confirmed. In this paper, the surface morphology, optical reflectance, and thermal stability of the Ag/Al-doped Ag are investigated. The Ag/Al-doped Ag/sapphire films showed excellent thermal stability after annealing the films at 523 K with the highest reflectance about ∼86% as compared to the pure Ag films. The grain growth analysis results revealed that the Al-doping is effective to restrain the severe grain growth of silver films. The Auger electron spectroscopy results revealed that the outer diffusion of aluminum and the formation of Al-O bond at the outermost silver layer which is beneficial to retard the Ag grain growth.

  14. Superconductivity. Quasiparticle mass enhancement approaching optimal doping in a high-T(c) superconductor.

    PubMed

    Ramshaw, B J; Sebastian, S E; McDonald, R D; Day, James; Tan, B S; Zhu, Z; Betts, J B; Liang, Ruixing; Bonn, D A; Hardy, W N; Harrison, N

    2015-04-17

    In the quest for superconductors with higher transition temperatures (T(c)), one emerging motif is that electronic interactions favorable for superconductivity can be enhanced by fluctuations of a broken-symmetry phase. Recent experiments have suggested the existence of the requisite broken-symmetry phase in the high-T(c) cuprates, but the impact of such a phase on the ground-state electronic interactions has remained unclear. We used magnetic fields exceeding 90 tesla to access the underlying metallic state of the cuprate YBa2Cu3O(6+δ) over a wide range of doping, and observed magnetic quantum oscillations that reveal a strong enhancement of the quasiparticle effective mass toward optimal doping. This mass enhancement results from increasing electronic interactions approaching optimal doping, and suggests a quantum critical point at a hole doping of p(crit) ≈ 0.18. Copyright © 2015, American Association for the Advancement of Science.

  15. Direct quantification of rare earth doped titania nanoparticles in individual human cells

    NASA Astrophysics Data System (ADS)

    Jeynes, J. C. G.; Jeynes, C.; Palitsin, V.; Townley, H. E.

    2016-07-01

    There are many possible biomedical applications for titania nanoparticles (NPs) doped with rare earth elements (REEs), from dose enhancement and diagnostic imaging in radiotherapy, to biosensing. However, there are concerns that the NPs could disintegrate in the body thus releasing toxic REE ions to undesired locations. As a first step, we investigate how accurately the Ti/REE ratio from the NPs can be measured inside human cells. A quantitative analysis of whole, unsectioned, individual human cells was performed using proton microprobe elemental microscopy. This method is unique in being able to quantitatively analyse all the elements in an unsectioned individual cell with micron resolution, while also scanning large fields of view. We compared the Ti/REE signal inside cells to NPs that were outside the cells, non-specifically absorbed onto the polypropylene substrate. We show that the REE signal in individual cells co-localises with the titanium signal, indicating that the NPs have remained intact. Within the uncertainty of the measurement, there is no difference between the Ti/REE ratio inside and outside the cells. Interestingly, we also show that there is considerable variation in the uptake of the NPs from cell-to-cell, by a factor of more than 10. We conclude that the NPs enter the cells and remain intact. The large heterogeneity in NP concentrations from cell-to-cell should be considered if they are to be used therapeutically.

  16. Emission properties of Ce-doped alkaline earth borate glasses for scintillator applications

    NASA Astrophysics Data System (ADS)

    Torimoto, Aya; Masai, Hirokazu; Okada, Go; Kawaguchi, Noriaki; Yanagida, Takayuki

    2017-11-01

    We investigate the photoluminescence (PL) and X-ray-induced luminescence properties of 0.1 mol% Ce-doped MO-B2O3 (M = Ca, Sr, and Ba) glasses. We also determine the Ce3+/(Ce3++Ce4+) ratio by X-ray absorption near-edge structure analyses. The emission intensities of PL, X-ray scintillation, and thermally stimulated luminescence (TSL) depend on the host glass composition. The order of the PL intensity from highest to lowest is as follows: Ca-substituted glass, Ba-substituted glass, and Sr-substituted glass. Our results suggest that the optical absorption edge and quantum yield (QY) are influenced by the local coordination state of Ce3+, which, in turn, is likely to be affected by the optical basicity. The order of the X-ray scintillation intensity from highest to lowest is reverse of that of the PL intensity. This is probably because the interaction probability of X-rays with matter depends on the effective atomic number of the material and the effective atomic number has a stronger influence on the scintillation intensity than does the QY. Though the TSL glow curves reveal that the density and energy depth of the trap sites depend on the substituted alkaline earth oxides, we are unable to correlate the electron spin resonance (ESR) spectra with the TSL results. Therefore, it is considered that the ESR active sites are not responsible for the TSL in these systems.

  17. White emission materials from glass doped with rare Earth ions: A review

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Yasaka, P.; Kaewkhao, J., E-mail: mink110@hotmail.com; Physics Program, Faculty of Science and Technology, Nakhon Pathom Rajabhat University, 73000

    2016-03-11

    Solid State Lighting (SSL) based devices are predicted to play a crucial role in the coming years. Development of W-LED, which have an edge over traditional lighting sources due to their compact size, higher reliability, shock resistance, interesting design possibilities, higher transparency and an extremely long lifetime. Over the fifteen trivalent lanthanide ions, Dy{sup 3+} ions doped glasses are most appropriate for white light generation because of the fact that it exhibits two intense emission bands corresponds to the {sup 4}F{sub 9/2}→{sup 6}H{sub 15/2} (magnetic dipole) and {sup 4}F{sub 9/2}→{sup 6}H{sub 13/2} (electric dipole) transitions at around 480-500 nm and 580-600 nmmore » pertaining to blue and yellow regions respectively. In this work, the developments of Dy3+ doped in several glass structures for white emitting materials application have reviewed. Properties of Dy{sup 3+} doped in glasses were discussed for use as a solid state lighting materials application.« less

  18. Rare earth garnet selective emitter

    NASA Technical Reports Server (NTRS)

    Lowe, Roland A.; Chubb, Donald L.; Farmer, Serene C.; Good, Brian S.

    1994-01-01

    Thin film Ho-YAG and Er-YAG emitters with a platinum substrate exhibit high spectral emittance in the emission band (epsilon(sub lambda) approximately equal to 0.74, ((4)l(sub 15/2)) - ( (4)l(sub13/2)), for Er-YAG and epsilon(sub lambda) approximately equal to 0.65, ((5)l(sub 7))-((5)l(sub 8)) for Ho-YAG) at excellent candidates for high efficiency selective emitters in the thermophotovoltaics (TPV) systems operating at moderate temperatures (1200-1500K). Spectral emittance measurements of the thin films were made (1.2 less than lambda less than 3.0 microns) and compared to the theoretical emittances calculated using measured values of the spectral extinction coefficient. In this paper we present the results for a new class of rare earth ion selective emitters. These emitters are thin sections (less than 1 mm) of yttrium aluminum garnet (YAG) single crystal with a rare earth substitutional impurity. This paper presents normal spectral emittance, epsilon(sub lambda), measurements of holmium (Ho), and erbium (Er) doped YAG thin film selective emitters at 1500 K, and compares those results with the theoretical spectral emittance.

  19. Nanocrystalline semiconductor doped rare earth oxide for the photocatalytic degradation studies on Acid Blue 113: A di-azo compound under UV slurry photoreactor.

    PubMed

    Suganya Josephine, G A; Mary Nisha, U; Meenakshi, G; Sivasamy, A

    2015-11-01

    Preventive measures for the control of environmental pollution and its remediation has received much interest in recent years due to the world-wide increase in the contamination of water bodies. Contributions of these harmful effluents are caused by the leather processing, pharmaceutical, cosmetic, textile, agricultural and other chemical industries. Nowadays, advanced oxidation processes considered to be better option for the complete destruction of organic contaminants in water and wastewater. Acid Blue 113 is a most widely used di-azo compound in leather, textile, dying and food industry as a color rending compound. In the present study, we have reported the photo catalytic degradation of Acid Blue 113 using a nanocrystalline semiconductor doped rare earth oxide as a photo catalyst under UV light irradiation. The photocatalyst was prepared by a simple precipitation technique and were characterized by XRD, FT-IR, UV-DRS and FE-SEM analysis. The experimental results proved that the prepared photo catalyst was nanocrystalline and highly active in the UV region. The UV-DRS results showed the band gap energy was 3.15eV for the prepared photo catalyst. The photodegradation efficiency was analyzed by various experimental parameters such as pH, catalyst dosage, variation of substrate concentration and effect of electrolyte addition. The photo degradation process followed a pseudo first order kinetics and was continuously monitored by UV-visible spectrophotometer. The experimental results proved the efficacy of the nanocrystalline zinc oxide doped dysprosium oxide which are highly active under UV light irradiations. It is also suggested that the prepared material would find wider applications in environmental remediation technologies to remove the carcinogenic and toxic moieties present in the industrial effluents. Copyright © 2015 Elsevier Inc. All rights reserved.

  20. Enhancing GIS Capabilities for High Resolution Earth Science Grids

    NASA Astrophysics Data System (ADS)

    Koziol, B. W.; Oehmke, R.; Li, P.; O'Kuinghttons, R.; Theurich, G.; DeLuca, C.

    2017-12-01

    Applications for high performance GIS will continue to increase as Earth system models pursue more realistic representations of Earth system processes. Finer spatial resolution model input and output, unstructured or irregular modeling grids, data assimilation, and regional coordinate systems present novel challenges for GIS frameworks operating in the Earth system modeling domain. This presentation provides an overview of two GIS-driven applications that combine high performance software with big geospatial datasets to produce value-added tools for the modeling and geoscientific community. First, a large-scale interpolation experiment using National Hydrography Dataset (NHD) catchments, a high resolution rectilinear CONUS grid, and the Earth System Modeling Framework's (ESMF) conservative interpolation capability will be described. ESMF is a parallel, high-performance software toolkit that provides capabilities (e.g. interpolation) for building and coupling Earth science applications. ESMF is developed primarily by the NOAA Environmental Software Infrastructure and Interoperability (NESII) group. The purpose of this experiment was to test and demonstrate the utility of high performance scientific software in traditional GIS domains. Special attention will be paid to the nuanced requirements for dealing with high resolution, unstructured grids in scientific data formats. Second, a chunked interpolation application using ESMF and OpenClimateGIS (OCGIS) will demonstrate how spatial subsetting can virtually remove computing resource ceilings for very high spatial resolution interpolation operations. OCGIS is a NESII-developed Python software package designed for the geospatial manipulation of high-dimensional scientific datasets. An overview of the data processing workflow, why a chunked approach is required, and how the application could be adapted to meet operational requirements will be discussed here. In addition, we'll provide a general overview of OCGIS

  1. The Electronic Structure and Optical Properties of Anatase TiO₂ with Rare Earth Metal Dopants from First-Principles Calculations.

    PubMed

    Xie, Kefeng; Jia, Qiangqiang; Wang, Yizhe; Zhang, Wenxue; Xu, Jingcheng

    2018-01-24

    The electronic and optical properties of the rare earth metal atom-doped anatase TiO₂ have been investigated systematically via density functional theory calculations. The results show that TiO₂ doped by Ce or Pr is the optimal choice because of its small band gap and strong optical absorption. Rare earth metal atom doping induces several impurity states that tune the location of valence and conduction bands and an obvious lattice distortion that should reduce the probability of electron-hole recombination. This effect of band change originates from the 4 f electrons of the rare earth metal atoms, which leads to an improved visible light absorption. This finding indicates that the electronic structure of anatase TiO₂ is tuned by the introduction of impurity atoms.

  2. High Temperature Si-doped BN Interphases for Woven SiC/SiC Composites

    NASA Technical Reports Server (NTRS)

    Morscher, Gregory N.; Hurwitz, Frances; Yun, Hee Mann; Gray, Hugh R. (Technical Monitor)

    2002-01-01

    The hydrolytic stability of high-temperature deposited Si-doped BN has been shown in the past to be superior in comparison to "pure" BN processed at similar or even higher temperatures. This type of material would be very desirable as a SiC/SiC composite interphase that is formed by chemical infiltration into multi-ply woven preform. However, due to rapid deposition on the preform outer surface at the high processing temperature, this has proven very difficult. To overcome this issue, single plies of woven fabric were infiltrated with Si-doped BN. Three composite panels of different SiC fiber types were fabricated with Si-doped BN interphases including Sylramic, Hi-Nicalon Type S and Sylramic-iBN fiber-types. The latter fiber-type possesses a thin in-situ grown BN layer on the fiber surface. High Si contents (approx. 7 to 10 a/o) and low oxygen contents (less than 1 a/o) were achieved. All three composite systems demonstrated reasonable debonding and sliding properties. The coated Sylramic fabric and composites were weak due to fiber degradation apparently caused during interphase processing by the formation of TiN crystals on the fiber surface. The Hi-Nicalon Type S composites with Si-doped BN interphase were only slightly weaker than Hi-Nicalon Type S composites with conventional BN when the strength on the load-bearing fibers at failure was compared. On the other hand, the Sylramic-iBN fabric and composites with Si-doped BN showed excellent composite and intermediate temperature stress-rupture properties. Most impressive was the lack of any significant interphase oxidation on the fracture surface of stress-ruptured specimens tested well above matrix cracking at 815C.

  3. High-power thulium-doped fiber laser in an all-fiber configuration

    NASA Astrophysics Data System (ADS)

    Baravets, Yauhen; Todorov, Filip; Honzatko, Pavel

    2016-12-01

    High-power Tm-doped fiber lasers are greatly suitable for various applications, such as material processing, medicine, environmental monitoring and topography. In this work we present an all-fiber narrowband CW laser in near fundamental mode operation based on a Tm-doped double-clad active fiber pumped by 793 nm laser diodes with a central wavelength stabilized at 2039 nm by a fiber Bragg grating. The achieved output power is 60 W with a slope efficiency of 46%. The measured beam quality factor is less than 1.4. Further increasing of the output power is possible using various power scaling techniques, for example, coherent combination of several Tm-doped fiber lasers. The developed fiber laser could be employed for welding, cutting and marking of thermoplastics in industry, minimally invasive surgery in medicine or sensors in lidar systems. Future improvements of thulium fiber lasers are possible due to the extremely wide gain-bandwidth of the active medium and the rapid growth of 2-μm fiber components production.

  4. Doping Lanthanide into Perovskite Nanocrystals: Highly Improved and Expanded Optical Properties.

    PubMed

    Pan, Gencai; Bai, Xue; Yang, Dongwen; Chen, Xu; Jing, Pengtao; Qu, Songnan; Zhang, Lijun; Zhou, Donglei; Zhu, Jinyang; Xu, Wen; Dong, Biao; Song, Hongwei

    2017-12-13

    Cesium lead halide (CsPbX 3 ) perovskite nanocrystals (NCs) have demonstrated extremely excellent optical properties and great application potentials in various optoelectronic devices. However, because of the anion exchange, it is difficult to achieve white-light and multicolor emission for practical applications. Herein, we present the successful doping of various lanthanide ions (Ce 3+ , Sm 3+ , Eu 3+ , Tb 3+ , Dy 3+ , Er 3+ , and Yb 3+ ) into the lattices of CsPbCl 3 perovskite NCs through a modified hot-injection method. For the lanthanide ions doped perovskite NCs, high photoluminescence quantum yield (QY) and stable and widely tunable multicolor emissions spanning from visible to near-infrared (NIR) regions are successfully obtained. This work indicates that the doped perovskite NCs will inherit most of the unique optical properties of lanthanide ions and deliver them to the perovskite NC host, thus endowing the family of perovskite materials with excellent optical, electric, or magnetic properties.

  5. Universal optimal hole-doping concentration in single-layer high-temperature cuprate superconductors

    NASA Astrophysics Data System (ADS)

    Honma, T.; Hor, P. H.

    2006-09-01

    We argue that in cuprate physics there are two types, hole content per CuO2 plane (Ppl) and the corresponding hole content per unit volume (P3D), of hole-doping concentrations for addressing physical properties that are two dimensional (2D) and three dimensional (3D) in nature, respectively. We find that the superconducting transition temperature (Tc) varies systematically with P3D as a superconducting 'dome' with a universal optimal hole-doping concentration of P3Dopt = 1.6 × 1021 cm-3 for single-layer high-temperature superconductors. We suggest that P3Dopt determines the upper bound of the electronic energy of underdoped single-layer high-Tc cuprates.

  6. Highly Stable and Tunable Chemical Doping of Multilayer WS2 Field Effect Transistor: Reduction in Contact Resistance.

    PubMed

    Khalil, Hafiz M W; Khan, Muhammad Farooq; Eom, Jonghwa; Noh, Hwayong

    2015-10-28

    The development of low resistance contacts to 2D transition-metal dichalcogenides (TMDs) is still a big challenge for the future generation field effect transistors (FETs) and optoelectronic devices. Here, we report a chemical doping technique to achieve low contact resistance by keeping the intrinsic properties of few layers WS2. The transfer length method has been used to investigate the effect of chemical doping on contact resistance. After doping, the contact resistance (Rc) of multilayer (ML) WS2 has been reduced to 0.9 kΩ·μm. The significant reduction of the Rc is mainly due to the high electron doping density, thus a reduction in Schottky barrier height, which limits the device performance. The threshold voltage of ML-WS2 FETs confirms a negative shift upon the chemical doping, as further confirmed from the positions of E(1)2g and A1g peaks in Raman spectra. The n-doped samples possess a high drain current of 65 μA/μm, with an on/off ratio of 1.05 × 10(6) and a field effect mobility of 34.7 cm(2)/(V·s) at room temperature. Furthermore, the photoelectric properties of doped WS2 flakes were also measured under deep ultraviolet light. The potential of using LiF doping in contact engineering of TMDs opens new ways to improve the device performance.

  7. Highly crystalline lithium titanium oxide sheets coated with nitrogen-doped carbon enable high-rate lithium-ion batteries.

    PubMed

    Han, Cuiping; He, Yan-Bing; Li, Baohua; Li, Hongfei; Ma, Jun; Du, Hongda; Qin, Xianying; Yang, Quan-Hong; Kang, Feiyu

    2014-09-01

    Sheets of Li4Ti5O12 with high crystallinity are coated with nitrogen-doped carbon (NC-LTO) using a controlled process, comprising hydrothermal reaction followed by chemical vapor deposition (CVD). Acetonitrile (CH3 CN) vapor is used as carbon and nitrogen source to obtain a thin coating layer of nitrogen-doped carbon. The layer enables the NC-LTO material to maintain its sheet structure during the high-temperature CVD process and to achieve high crystallinity. Doping with nitrogen introduces defects into the carbon coating layer, and this increased degree of disorder allows fast transportation of lithium ions in the layer. An electrode of NC-LTO synthesized at 700 °C exhibits greatly improved rate and cycling performance due to a markedly decreased total cell resistance and enhanced Li-ion diffusion coefficient (D(Li)). Specific capacities of 159.2 and 145.8 mA h g(-1) are obtained using the NC-LTO sheets, at charge/discharge rates of 1 and 10 C, respectively. These values are much higher than values for LTO particles did not undergo the acetonitrile CVD treatment. A capacity retention value as high as 94.7% is achieved for the NC-LTO sheets after 400 cycles in a half-cell at 5 C discharge rate. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Magnetocaloric effect in heavy rare-earth elements doped Fe-based bulk metallic glasses with tunable Curie temperature

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Li, Jiawei; Huo, Juntao; Chang, Chuntao, E-mail: ctchang@nimte.ac.cn, E-mail: dujun@nimte.ac.cn

    2014-08-14

    The effects of heavy rare earth (RE) additions on the Curie temperature (T{sub C}) and magnetocaloric effect of the Fe-RE-B-Nb (RE = Gd, Dy and Ho) bulk metallic glasses were studied. The type of dopping RE element and its concentration can easily tune T{sub C} in a large temperature range of 120 K without significantly decreasing the magnetic entropy change (ΔS{sub M}) and refrigerant capacity (RC) of the alloys. The observed values of ΔS{sub M} and RC of these alloys compare favorably with those of recently reported Fe-based metallic glasses with enhanced RC compared to Gd{sub 5}Ge{sub 1.9}Si{sub 2}Fe{sub 0.1}. The tunable T{submore » C} and large glass-forming ability of these RE doped Fe-based bulk metallic glasses can be used in a wide temperature range with the final required shapes.« less

  9. Demonstrating the potential of yttrium-doped barium zirconate electrolyte for high-performance fuel cells.

    PubMed

    Bae, Kiho; Jang, Dong Young; Choi, Hyung Jong; Kim, Donghwan; Hong, Jongsup; Kim, Byung-Kook; Lee, Jong-Ho; Son, Ji-Won; Shim, Joon Hyung

    2017-02-23

    In reducing the high operating temperatures (≥800 °C) of solid-oxide fuel cells, use of protonic ceramics as an alternative electrolyte material is attractive due to their high conductivity and low activation energy in a low-temperature regime (≤600 °C). Among many protonic ceramics, yttrium-doped barium zirconate has attracted attention due to its excellent chemical stability, which is the main issue in protonic-ceramic fuel cells. However, poor sinterability of yttrium-doped barium zirconate discourages its fabrication as a thin-film electrolyte and integration on porous anode supports, both of which are essential to achieve high performance. Here we fabricate a protonic-ceramic fuel cell using a thin-film-deposited yttrium-doped barium zirconate electrolyte with no impeding grain boundaries owing to the columnar structure tightly integrated with nanogranular cathode and nanoporous anode supports, which to the best of our knowledge exhibits a record high-power output of up to an order of magnitude higher than those of other reported barium zirconate-based fuel cells.

  10. Highly doped InP as a low loss plasmonic material for mid-IR region.

    PubMed

    Panah, M E Aryaee; Takayama, O; Morozov, S V; Kudryavtsev, K E; Semenova, E S; Lavrinenko, A V

    2016-12-12

    We study plasmonic properties of highly doped InP in the mid-infrared (IR) range. InP was grown by metal-organic vapor phase epitaxy (MOVPE) with the growth conditions optimized to achieve high free electron concentrations by doping with silicon. The permittivity of the grown material was found by fitting the calculated infrared reflectance spectra to the measured ones. The retrieved permittivity was then used to simulate surface plasmon polaritons (SPPs) propagation on flat and structured surfaces, and the simulation results were verified in direct experiments. SPPs at the top and bottom interfaces of the grown epilayer were excited by the prism coupling. A high-index Ge hemispherical prism provides efficient coupling conditions of SPPs on flat surfaces and facilitates acquiring their dispersion diagrams. We observed diffraction into symmetry-prohibited diffraction orders stimulated by the excitation of surface plasmon-polaritons in a periodically structured epilayer. Characterization shows good agreement between the theory and experimental results and confirms that highly doped InP is an effective plasmonic material aiming it for applications in the mid-IR wavelength range.

  11. Surface Morphology of Undoped and Doped ZnSe Films

    NASA Technical Reports Server (NTRS)

    George, T.; Hayes, M.; Chen, H.; Chattopadhyay, K.; Thomas E.; Morgan, S.; Burger, A.

    1998-01-01

    Rare-earth doped ions in polar II-VI semiconductors have recently played an important role in the optical properties of materials and devices. In this study, undoped ZnSe and erbium doped ZnSe films were grown by radio frequency (RF) magnetron sputtering method. Atomic Force Microscopy (AFM) was used together with optical microscopy and UV-Vis spectroscopy to characterize the films. Doped samples were found to have higher surface roughness and quite different surface morphology compared to that of undoped samples. The grown films generally show a relatively smooth and uniform surface indicating that they are of overall good quality. The impact of plasma etching on ZnSe:Er film examined under AFM is also discussed.

  12. High power resonant pumping of Tm-doped fiber amplifiers in core- and cladding-pumped configurations.

    PubMed

    Creeden, Daniel; Johnson, Benjamin R; Rines, Glen A; Setzler, Scott D

    2014-11-17

    We have demonstrated ultra-high efficiency amplification in Tm-doped fiber with both core- and cladding-pumped configurations using a resonant tandem-pumping approach. These Tm-doped fiber amplifiers are pumped in-band with a 1908 nm Tm-doped fiber laser and operate at 1993 nm with >90% slope efficiency. In a core-pumped configuration, we have achieved 92.1% slope efficiency and 88.4% optical efficiency at 41 W output power. In a cladding-pumped configuration, we have achieved 123.1 W of output power with 90.4% optical efficiency and a 91.6% slope efficiency. We believe these are the highest optical efficiencies achieved in a Tm-doped fiber amplifier operating in the 2-micron spectral region.

  13. High-quality ZnO growth, doping, and polarization effect

    NASA Astrophysics Data System (ADS)

    Kun, Tang; Shulin, Gu; Jiandong, Ye; Shunming, Zhu; Rong, Zhang; Youdou, Zheng

    2016-03-01

    The authors have reported their recent progress in the research field of ZnO materials as well as the corresponding global advance. Recent results regarding (1) the development of high-quality epitaxy techniques, (2) the defect physics and the Te/N co-doping mechanism for p-type conduction, and (3) the design, realization, and properties of the ZnMgO/ZnO hetero-structures have been shown and discussed. A complete technology of the growth of high-quality ZnO epi-films and nano-crystals has been developed. The co-doping of N plus an iso-valent element to oxygen has been found to be the most hopeful path to overcome the notorious p-type hurdle. High mobility electrons have been observed in low-dimensional structures utilizing the polarization of ZnMgO and ZnO. Very different properties as well as new physics of the electrons in 2DEG and 3DES have been found as compared to the electrons in the bulk. Project supported by the National Natural Science Foundation of China (Nos. 61025020, 61274058, 61322403, 61504057, 61574075), the Natural Science Foundation of Jiangsu Province (Nos. BK2011437, BK20130013, BK20150585), the Priority Academic Program Development of Jiangsu Higher Education Institutions, and the Fundamental Research Funds for the Central Universities.

  14. High-sensitivity sucrose erbium-doped fiber ring laser sensor

    NASA Astrophysics Data System (ADS)

    Khaleel, Wurood Abdulkhaleq; Al-Janabi, Abdul Hadi M.

    2017-02-01

    We investigate a high-sensitivity sucrose sensor based on a standard erbium-doped fiber ring laser incorporating a coreless fiber (CF). A single-mode-coreless-single mode (SCS) structure with a very low insertion loss has been constructed. The SCS fiber structure performed dual function as an intracavity fiber filter and/or a sensing element. The gain medium (erbium-doped fiber) is pumped by a 975-nm wavelength fiber coupled diode laser. Laser emission around 1537 nm with -2 dBm peak output power is obtained when a CF in SCS structure has a diameter of 125 μm. The 3-dB line-width of the laser is <0.14 nm, which is beneficial to high precision sensing. The sucrose concentration varied from 0% to 60%, and the relationship between the lasing wavelength and the sucrose concentration exhibited linear behavior (R2=0.996), with sensitivity of 0.16 nm/% was obtained. To improve the measurement sensitivity, the CF is etched by hydrofluoric acid. The splice joint of etched CF with SMF is a taper, which improves its sensitivity to sucrose changes. An average sensitivity of 0.57 nm/% and a high signal-to-noise ratio of 50 dB make the proposed sensor suitable for potential applications.

  15. Thermoelectric properties of rare earth chalcogenides

    NASA Technical Reports Server (NTRS)

    Danielson, L. R.; Raag, V.; Wood, C.

    1985-01-01

    The rare earth chalcogenides are important thermoelectric materials due to their high melting points, self-doping capabilities, and low thermal conductivities. Lanthanum sulfides and lanthanum tellurides have been synthesized in quartz ampules, hot-pressed into samples, and measured. The n-type Seebeck coefficients, electrical resistivities, and power factors generally all increased as the temperature increased from 200 to 1000 C. The figure-of-merit for nonstoichiometric lanthanum telluride was 0.001/deg C at 1000 C, considerably higher than for silicon-germanium. Thermoelectric measurements were made for LaTe(2) and YbS(1.4), and p-type behavior was observed for these compounds from 300 to 1100 C.

  16. Effects of Doping on Thermal Conductivity of Pyrochlore Oxides for Advanced Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.; Zhu, Dongming; Eslamloo-Grami, Maryam

    2006-01-01

    Pyrochlore oxides of general composition, A2B2O7, where A is a 3(+) cation (La to Lu) and B is a 4(+) cation (Zr, Hf, Ti, etc.) have high melting point, relatively high coefficient of thermal expansion, and low thermal conductivity which make them suitable for applications as high-temperature thermal barrier coatings. The effect of doping at the A site on the thermal conductivity of a pyrochlore oxide La2Zr2O7, has been investigated. Oxide powders of various compositions La2Zr2O7, La(1.7)Gd(0.3)Zr2O7, La(1.7)Yb(0.3)Zr2O7 and La(1.7)Gd(0.15)Yb(0.15)Zr2O7 were synthesized by the citric acid sol-gel method. These powders were hot pressed into discs and used for thermal conductivity measurements using a steady-state laser heat flux test technique. The rare earth oxide doped pyrochlores La(1.7)Gd(0.3)Zr2O7, La(1.7)Yb(0.3)Zr2O7 and La(1.7)Gd(0.15)Yb(0.15)Zr2O7 had lower thermal conductivity than the un-doped La2Zr2O7. The Gd2O3 and Yb2O3 co-doped composition showed the lowest thermal conductivity.

  17. Optical Properties of Nd Doped Rare Earth Vanadates (Preprint)

    DTIC Science & Technology

    2010-07-01

    Rare earth orthovanadates are being used as substitute for traditional solid state laser hosts such as yttrium aluminium garnet (YAG). While the most...common of these is yttrium orthovanadate, other rare earth vanadates such as lutetium vanadate and gadolinium vanadate are being used for their... gadolinium vanadate are being used for their special properties in certain applications. We report new measurements of the refractive indices and thermo

  18. Enhanced B doping in CVD-grown GeSn:B using B δ-doping layers

    NASA Astrophysics Data System (ADS)

    Kohen, David; Vohra, Anurag; Loo, Roger; Vandervorst, Wilfried; Bhargava, Nupur; Margetis, Joe; Tolle, John

    2018-02-01

    Highly doped GeSn material is interesting for both electronic and optical applications. GeSn:B is a candidate for source-drain material in future Ge pMOS device because Sn adds compressive strain with respect to pure Ge, and therefore can boost the Ge channel performances. A high B concentration is required to obtain low contact resistivity between the source-drain material and the metal contact. To achieve high performance, it is therefore highly desirable to maximize both the Sn content and the B concentration. However, it has been shown than CVD-grown GeSn:B shows a trade-off between the Sn incorporation and the B concentration (increasing B doping reduces Sn incorporation). Furthermore, the highest B concentration of CVD-grown GeSn:B process reported in the literature has been limited to below 1 × 1020 cm-3. Here, we demonstrate a CVD process where B δ-doping layers are inserted in the GeSn layer. We studied the influence of the thickness between each δ-doping layers and the δ-doping layers process conditions on the crystalline quality and the doping density of the GeSn:B layers. For the same Sn content, the δ-doping process results in a 4-times higher B doping than the co-flow process. In addition, a B doping concentration of 2 × 1021 cm-3 with an active concentration of 5 × 1020 cm-3 is achieved.

  19. Morphology and Doping Engineering of Sn-Doped Hematite Nanowire Photoanodes.

    PubMed

    Li, Mingyang; Yang, Yi; Ling, Yichuan; Qiu, Weitao; Wang, Fuxin; Liu, Tianyu; Song, Yu; Liu, Xiaoxia; Fang, Pingping; Tong, Yexiang; Li, Yat

    2017-04-12

    High-temperature activation has been commonly used to boost the photoelectrochemical (PEC) performance of hematite nanowires for water oxidation, by inducing Sn diffusion from fluorine-doped tin oxide (FTO) substrate into hematite. Yet, hematite nanowires thermally annealed at high temperature suffer from two major drawbacks that negatively affect their performance. First, the structural deformation reduces light absorption capability of nanowire. Second, this "passive" doping method leads to nonuniform distribution of Sn dopant in nanowire and limits the Sn doping concentration. Both factors impair the electrochemical properties of hematite nanowire. Here we demonstrate a silica encapsulation method that is able to simultaneously retain the hematite nanowire morphology even after high-temperature calcination at 800 °C and improve the concentration and uniformity of dopant distribution along the nanowire growth axis. The capability of retaining nanowire morphology allows tuning the nanowire length for optimal light absorption. Uniform distribution of Sn doping enhances the donor density and charge transport of hematite nanowire. The morphology and doping engineered hematite nanowire photoanode decorated with a cobalt oxide-based oxygen evolution reaction (OER) catalyst achieves an outstanding photocurrent density of 2.2 mA cm -2 at 0.23 V vs Ag/AgCl. This work provides important insights on how the morphology and doping uniformity of hematite photoanodes affect their PEC performance.

  20. Improving of the electrical and magnetic properties of BiFeO{sub 3} by doping with yttrium

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ilić, Nikola I., E-mail: niksentije@gmail.com; Bobić, Jelena D.; Stojadinović, Bojan S.

    2016-05-15

    Bismuth ferrite is one of the most promising multiferroic materials, and the main barriers for exploiting all of its specific properties are difficulties in obtaining pure, high resistive material with nanosized grains. Doping of BiFeO{sub 3} with different transition metals and rare earth elements is often used way for overcoming these obstacles. Yttrium doped bismuth ferrite, Bi{sub 1−x}Y{sub x}FeO{sub 3} (x = 0; 0.01; 0.03; 0.05; 0.1), was prepared by auto-combustion method. X-ray diffraction patterns and Raman results showed that partial phase transition from rhombohedral to orthorhombic structure took place at around 10 mol% of Y. Effect of Y dopingmore » on microstructure was studied from SEM micrographies, showing the reduction of grain size in doped samples. Electrical measurements showed continuous improvement of resistivity with Y doping, whereas the values of saturation and remnant polarizations exhibit maximums at around 5 mol% of Y. Yttrium doping also enhanced magnetic properties, leading to weak ferromagnetism.« less

  1. Progress Towards Left-Handed Electromagnetic Waves in Rare-Earth Doped Crystals

    NASA Astrophysics Data System (ADS)

    Brewer, Nicholas Riley

    In 1968 Victor Veselago determined that a material with both a negative permittivity and negative permeability would have some extraordinary properties. The index of refraction of this material would be negative and light propagating inside would be 'left-handed'. This research went relatively unnoticed until the year 2000 when John Pendry discovered that a lens with an index of refraction of n = -1 could, in principle, have infinite resolution. Since 2000, research into negative index materials has exploded. The challenging part of this research is to get a material to respond to magnetic fields at optical frequencies. Artificially created metamaterials are able to achieve this and have been the focus of most negative index research. The long term goal of our project is to produce left-handed light in an atomic system. In order to do this, an atomic transition needs to be utilized that is magnetic dipole in character. Pure magnetic dipole transitions in the optical regime are more rare and fundamentally much weaker than the electric dipole transitions typically used in atomic physics experiments. They can be found, however, in the complex atomic structure of rare-earth elements. The 7F0 → 5D 1 transition in europium doped yttrium orthosilicate (Eu3+:Y 2SiO5) has a wavelength of 527.5 nm and is a pure magnetic dipole transition. We measured its dipole moment to be (0.063 +/- 0.005)mu B via Rabi oscillations, inferring a magnetization on the order of 10 -2 A/m. Demonstrating this large magnetic response at an optical frequency is a major first step in realizing left-handed light in atomic systems.

  2. Highly Doped Polycrystalline Silicon Microelectrodes Reduce Noise in Neuronal Recordings In Vivo

    PubMed Central

    Saha, Rajarshi; Jackson, Nathan; Patel, Chetan; Muthuswamy, Jit

    2013-01-01

    The aims of this study are to 1) experimentally validate for the first time the nonlinear current-potential characteristics of bulk doped polycrystalline silicon in the small amplitude voltage regimes (0–200 μV) and 2) test if noise amplitudes (0–15 μV) from single neuronal electrical recordings get selectively attenuated in doped polycrystalline silicon microelectrodes due to the above property. In highly doped polycrystalline silicon, bulk resistances of several hundred kilo-ohms were experimentally measured for voltages typical of noise amplitudes and 9–10 kΩ for voltages typical of neural signal amplitudes (>150–200 μV). Acute multiunit measurements and noise measurements were made in n = 6 and n = 8 anesthetized adult rats, respectively, using polycrystalline silicon and tungsten microelectrodes. There was no significant difference in the peak-to-peak amplitudes of action potentials recorded from either microelectrode (p > 0.10). However, noise power in the recordings from tungsten microelectrodes (26.36 ± 10.13 pW) was significantly higher (p < 0.001) than the corresponding value in polycrystalline silicon microelectrodes (7.49 ± 2.66 pW). We conclude that polycrystalline silicon microelectrodes result in selective attenuation of noise power in electrical recordings compared to tungsten microelectrodes. This reduction in noise compared to tungsten microelectrodes is likely due to the exponentially higher bulk resistances offered by highly doped bulk polycrystalline silicon in the range of voltages corresponding to noise in multiunit measurements. PMID:20667815

  3. Cobalt-Doped Nickel Phosphite for High Performance of Electrochemical Energy Storage.

    PubMed

    Li, Bing; Shi, Yuxin; Huang, Kesheng; Zhao, Mingming; Qiu, Jiaqing; Xue, Huaiguo; Pang, Huan

    2018-03-01

    Compared to single metallic Ni or Co phosphides, bimetallic Ni-Co phosphides own ameliorative properties, such as high electrical conductivity, remarkable rate capability, upper specific capacity, and excellent cycle performance. Here, a simple one-step solvothermal process is proposed for the synthesis of bouquet-like cobalt-doped nickel phosphite (Ni 11 (HPO 3 ) 8 (OH) 6 ), and the effect of the structure on the pseudocapacitive performance is investigated via a series of electrochemical measurements. It is found that when the cobalt content is low, the glycol/deionized water ratio is 1, and the reaction is under 200 °C for 20 h, the morphology of the sample is uniform and has the highest specific surface area. The cobalt-doped Ni 11 (HPO 3 ) 8 (OH) 6 electrode presents a maximum specific capacitance of 714.8 F g -1 . More significantly, aqueous and solid-state flexible electrochemical energy storage devices are successfully assembled. The aqueous device shows a high energy density of 15.48 mWh cm -2 at the power density of 0.6 KW cm -2 . The solid-state device shows a high energy density of 14.72 mWh cm -2 at the power density of 0.6 KW cm -2 . These excellent performances confirm that the cobalt-doped Ni 11 (HPO 3 ) 8 (OH) 6 are promising materials for applications in electrochemical energy storage devices. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. High power operation of cladding pumped holmium-doped silica fibre lasers.

    PubMed

    Hemming, Alexander; Bennetts, Shayne; Simakov, Nikita; Davidson, Alan; Haub, John; Carter, Adrian

    2013-02-25

    We report the highest power operation of a resonantly cladding-pumped, holmium-doped silica fibre laser. The cladding pumped all-glass fibre utilises a fluorine doped glass layer to provide low loss cladding guidance of the 1.95 µm pump radiation. The operation of both single mode and large-mode area fibre lasers was demonstrated, with up to 140 W of output power achieved. A slope efficiency of 59% versus launched pump power was demonstrated. The free running emission was measured to be 2.12-2.15 µm demonstrating the potential of this architecture to address the long wavelength operation of silica based fibre lasers with high efficiency.

  5. On the origin of high ionic conductivity in Na-doped SrSiO 3

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chien, Po-Hsiu; Jee, Youngseok; Huang, Chen

    Understanding the local structure and ion dynamics is at the heart of ion conductor research. This paper reports on high-resolution solid-state 29Si, 23Na, and 17O NMR investigation of the structure, chemical composition, and ion dynamics of a newly discovered fast ion conductor, Na-doped SrSiO 3, which exhibited a much higher ionic conductivity than most of current oxide ion conductors. Quantitative analyses reveal that with a small dose (<10 mol%) of Na, the doped Na integrates into the SrSiO 3 structure to form Na xSr 1-xSiO 3-0.5x, and with >10 mol% Na doping, phase separation occurs, leading to the formation ofmore » an amorphous phase β-Na 2Si 2O 5 and a crystalline Sr-rich phase. Variable-temperature 23Na and 17O magic-angle-spinning NMR up to 618 °C have shown significant changes in Na ion dynamics at high temperatures but little oxide ion motion, suggesting that Na ions are responsible for the observed high ionic conductivity. In addition, β-Na 2Si 2O 5 starts to crystallize at temperatures higher than 480 °C with prolonged heating, resulting in reduction in Na+ motion, and thus degradation of ionic conductivity. This study has contributed critical evidence to the understanding of ionic conduction in Na-doped SrSiO 3 and demonstrated that multinuclear high-resolution and high-temperature solid-state NMR is a uniquely useful tool for investigating ion conductors at their operating conditions.« less

  6. On the origin of high ionic conductivity in Na-doped SrSiO 3

    DOE PAGES

    Chien, Po-Hsiu; Jee, Youngseok; Huang, Chen; ...

    2016-02-17

    Understanding the local structure and ion dynamics is at the heart of ion conductor research. This paper reports on high-resolution solid-state 29Si, 23Na, and 17O NMR investigation of the structure, chemical composition, and ion dynamics of a newly discovered fast ion conductor, Na-doped SrSiO 3, which exhibited a much higher ionic conductivity than most of current oxide ion conductors. Quantitative analyses reveal that with a small dose (<10 mol%) of Na, the doped Na integrates into the SrSiO 3 structure to form Na xSr 1-xSiO 3-0.5x, and with >10 mol% Na doping, phase separation occurs, leading to the formation ofmore » an amorphous phase β-Na 2Si 2O 5 and a crystalline Sr-rich phase. Variable-temperature 23Na and 17O magic-angle-spinning NMR up to 618 °C have shown significant changes in Na ion dynamics at high temperatures but little oxide ion motion, suggesting that Na ions are responsible for the observed high ionic conductivity. In addition, β-Na 2Si 2O 5 starts to crystallize at temperatures higher than 480 °C with prolonged heating, resulting in reduction in Na+ motion, and thus degradation of ionic conductivity. This study has contributed critical evidence to the understanding of ionic conduction in Na-doped SrSiO 3 and demonstrated that multinuclear high-resolution and high-temperature solid-state NMR is a uniquely useful tool for investigating ion conductors at their operating conditions.« less

  7. Carbon doped GaN buffer layer using propane for high electron mobility transistor applications: Growth and device results

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Li, X.; Nilsson, D.; Danielsson, Ö.

    2015-12-28

    The creation of a semi insulating (SI) buffer layer in AlGaN/GaN High Electron Mobility Transistor (HEMT) devices is crucial for preventing a current path beneath the two-dimensional electron gas (2DEG). In this investigation, we evaluate the use of a gaseous carbon gas precursor, propane, for creating a SI GaN buffer layer in a HEMT structure. The carbon doped profile, using propane gas, is a two stepped profile with a high carbon doping (1.5 × 10{sup 18 }cm{sup −3}) epitaxial layer closest to the substrate and a lower doped layer (3 × 10{sup 16 }cm{sup −3}) closest to the 2DEG channel. Secondary Ion Mass Spectrometry measurement showsmore » a uniform incorporation versus depth, and no memory effect from carbon doping can be seen. The high carbon doping (1.5 × 10{sup 18 }cm{sup −3}) does not influence the surface morphology, and a roughness root-mean-square value of 0.43 nm is obtained from Atomic Force Microscopy. High resolution X-ray diffraction measurements show very sharp peaks and no structural degradation can be seen related to the heavy carbon doped layer. HEMTs are fabricated and show an extremely low drain induced barrier lowering value of 0.1 mV/V, demonstrating an excellent buffer isolation. The carbon doped GaN buffer layer using propane gas is compared to samples using carbon from the trimethylgallium molecule, showing equally low leakage currents, demonstrating the capability of growing highly resistive buffer layers using a gaseous carbon source.« less

  8. Electrochemically assisted photocatalysis: Highly efficient treatment using thermal titanium oxides doped and non-doped electrodes for water disinfection.

    PubMed

    Dos Santos, Andreia Betina Kreuser; Claro, Elis Marina Turini; Montagnolli, Renato Nallin; Cruz, Jaqueline Matos; Lopes, Paulo Renato Matos; Bidoia, Ederio Dino

    2017-12-15

    Electrochemically assisted photocatalysis (by electronic drainage) is a highly promising method for disinfection of water. In this research, the efficiency of photolytic oxidation using UV-A radiation and electrochemically assisted photocatalysis (with electric potential of 1.5 V) was studied by using electrodes prepared by thermal treatment and doped with silver, for inactivation of Escherichia coli and Staphylococcus aureus. The Chick-Watson microorganism inactivation model was applied and the electrical energy consumption of the process was calculated. It was observed no significant inactivation of microorganisms when UV-A light or electric potential were applied separately. However, the electrochemically assisted photocatalytic process, with Ag-doped electrode completely inactivated the microbial population after 10 (E. coli) and 60 min (S. aureus). The best performing non-doped electrodes achieved 52.74% (E. coli) and 44.09% (S. aureus) inactivation rates after 60 min. Thus, electrochemically assisted photocatalytic activity was not only effective for the inactivation of microorganisms, but also notably low on electrical energy consumption during the treatment due to small current and low electric potential applied. Copyright © 2017 Elsevier Ltd. All rights reserved.

  9. Metal-Organic Coordination Polymer to Prepare Density Controllable and High Nitrogen-Doped Content Carbon/Graphene for High Performance Supercapacitors.

    PubMed

    Luo, Jinwei; Zhong, Wenbin; Zou, Yubo; Xiong, Changlun; Yang, Wantai

    2017-01-11

    Design and preparation of carbon-based electrode material with high nitrogen-doping ratio and appropriate density attract much interest for supercapacitors in practical application. Herein, three porous carbon/graphene (NCG Cu , NCG Fe , and NCG Zn ) with high doping ratio of nitrogen have been prepared via directly pyrolysis of graphene oxide (GO)/metal-organic coordination polymer (MOCP) composites, which were formed by reacting 4,4'-bipyridine (BPD) with CuCl 2 , FeCl 3 , and ZnCl 2 , respectively. As-prepared NCG Cu , NCG Fe and NCG Zn showed high nitrogen doping ratio of 10.68, 12.99, and 11.21 at. %; and high density of 1.52, 0.84, and 1.15 g cm -3 , respectively. When as-prepared samples were used as supercapacitor electrodes, NCG Cu , NCG Fe and NCG Zn exhibited high gravimetric specific capacitances of 369, 298.5, 309.5 F g -1 , corresponding to high volumetric specific capacitances of 560.9, 250.7, 355.9 F cm -3 at a current density of 0.5 A g -1 , as well as good cycling stability, nearly 100% of the capacitance retained after 1000 cycles even at a large current density of 10 A g -1 . It is expected that the provided novel strategy can be used to develop electrode materials in high performance energy conversion/storage devices.

  10. Cellular Response to Doping of High Porosity Foamed Alumina with Ca, P, Mg, and Si.

    PubMed

    Soh, Edwin; Kolos, Elizabeth; Ruys, Andrew J

    2015-03-13

    Foamed alumina was previously synthesised by direct foaming of sulphate salt blends varying ammonium mole fraction (AMF), foaming heating rate and sintering temperature. The optimal product was produced with 0.33AMF, foaming at 100 °C/h and sintering at 1600 °C. This product attained high porosity of 94.39%, large average pore size of 300 µm and the highest compressive strength of 384 kPa. To improve bioactivity, doping of porous alumina by soaking in dilute or saturated solutions of Ca, P, Mg, CaP or CaP + Mg was done. Saturated solutions of Ca, P, Mg, CaP and CaP + Mg were made with excess salt in distilled water and decanted. Dilute solutions were made by diluting the 100% solution to 10% concentration. Doping with Si was done using the sol gel method at 100% concentration only. Cell culture was carried out with MG63 osteosarcoma cells. Cellular response to the Si and P doped samples was positive with high cell populations and cell layer formation. The impact of doping with phosphate produced a result not previously reported. The cellular response showed that both Si and P doping improved the biocompatibility of the foamed alumina.

  11. Effects of rare-earth doping on femtosecond laser waveguide writing in zinc polyphosphate glass

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Fletcher, Luke B.; Witcher, Jon J.; Troy, Neil

    We have investigated waveguide writing in Er-Yb doped zinc polyphosphate glass using a femtosecond laser with a repetition rate of 1 KHz. We find that fabrication of good waveguides requires a glass composition with an O/P ratio of 3.25. The dependence on laser writing parameters including laser fluence, focusing conditions, and scan speed is reported. Waveguide properties together with absorption and emission data indicate that these glasses can be used for the fabrication of compact, high gain amplifying devices.

  12. What to do when the Universities reject High School Earth Science

    NASA Astrophysics Data System (ADS)

    Van Norden, W.

    2011-12-01

    It is hard to imagine a state of the union more affected by Earth processes than the state of California. However, the University of California actively discourages High School students from taking Earth Science courses. For admission into the University of California students are required to take at least 2 years of courses that offer a fundamental knowledge in at least two of these three foundational subjects: biology, chemistry, and physics. Earth Science courses simply don't qualify as laboratory science courses. The UC Admissions will sometimes make an exception for an Earth Science course only if it is shown to contain a large component of biology, chemistry and physics topics. Since students don't get credit for admission for taking Earth Science, High Schools are quick to drop Earth Science courses for their college-bound students. A group of teachers and University professors have been working to reverse this policy by creating a rigorous capstone Earth Science course that clearly merits laboratory status. Getting this course accepted by the University of California is well on its way, but getting the course into the High Schools will take a lot of work and probably some extra funding.

  13. Spontaneous doping on high quality talc-graphene-hBN van der Waals heterostructures

    NASA Astrophysics Data System (ADS)

    Mania, E.; Alencar, A. B.; Cadore, A. R.; Carvalho, B. R.; Watanabe, K.; Taniguchi, T.; Neves, B. R. A.; Chacham, H.; Campos, L. C.

    2017-09-01

    Steady doping, added to its remarkable electronic properties, would make graphene a valuable commodity in the solar cell market, as energy power conversion could be substantially increased. Here we report a graphene van der Waals heterostructure which is able to spontaneously dope graphene (p-type) up to n ~ 2.2  ×  1013 cm-2 while providing excellent charge mobility (μ ~ 25 000 cm2 V-1 s-1). Such properties are achieved via deposition of graphene on atomically flat layered talc, a natural and abundant dielectric crystal. Raman investigation shows a preferential charge accumulation on graphene-talc van der Waals heterostructures, which are investigated through the electronic properties of talc/graphene/hBN heterostructure devices. These heterostructures preserve graphene’s good electronic quality, verified by the observation of quantum Hall effect at low magnetic fields (B  =  0.4 T) at T  =  4.2 K. In order to investigate the physical mechanisms behind graphene-on-talc p-type doping, we performed first-principles calculations of their interface structural and electronic properties. In addition to potentially improving solar cell efficiency, graphene doping via van der Waals stacking is also a promising route towards controlling the band gap opening in bilayer graphene, promoting a steady n or p type doping in graphene and, eventually, providing a new path to access superconducting states in graphene, predicted to exist only at very high doping.

  14. Autonomous Navigation Improvements for High-Earth Orbiters Using GPS

    NASA Technical Reports Server (NTRS)

    Long, Anne; Kelbel, David; Lee, Taesul; Garrison, James; Carpenter, J. Russell; Bauer, F. (Technical Monitor)

    2000-01-01

    The Goddard Space Flight Center is currently developing autonomous navigation systems for satellites in high-Earth orbits where acquisition of the GPS signals is severely limited This paper discusses autonomous navigation improvements for high-Earth orbiters and assesses projected navigation performance for these satellites using Global Positioning System (GPS) Standard Positioning Service (SPS) measurements. Navigation performance is evaluated as a function of signal acquisition threshold, measurement errors, and dynamic modeling errors using realistic GPS signal strength and user antenna models. These analyses indicate that an autonomous navigation position accuracy of better than 30 meters root-mean-square (RMS) can be achieved for high-Earth orbiting satellites using a GPS receiver with a very stable oscillator. This accuracy improves to better than 15 meters RMS if the GPS receiver's signal acquisition threshold can be reduced by 5 dB-Hertz to track weaker signals.

  15. Advanced Sulfur Cathode Enabled by Highly Crumpled Nitrogen-Doped Graphene Sheets for High-Energy-Density Lithium-Sulfur Batteries.

    PubMed

    Song, Jiangxuan; Yu, Zhaoxin; Gordin, Mikhail L; Wang, Donghai

    2016-02-10

    Herein, we report a synthesis of highly crumpled nitrogen-doped graphene sheets with ultrahigh pore volume (5.4 cm(3)/g) via a simple thermally induced expansion strategy in absence of any templates. The wrinkled graphene sheets are interwoven rather than stacked, enabling rich nitrogen-containing active sites. Benefiting from the unique pore structure and nitrogen-doping induced strong polysulfide adsorption ability, lithium-sulfur battery cells using these wrinkled graphene sheets as both sulfur host and interlayer achieved a high capacity of ∼1000 mAh/g and exceptional cycling stability even at high sulfur content (≥80 wt %) and sulfur loading (5 mg sulfur/cm(2)). The high specific capacity together with the high sulfur loading push the areal capacity of sulfur cathodes to ∼5 mAh/cm(2), which is outstanding compared to other recently developed sulfur cathodes and ideal for practical applications.

  16. 3D Polyaniline Architecture by Concurrent Inorganic and Organic Acid Doping for Superior and Robust High Rate Supercapacitor Performance

    NASA Astrophysics Data System (ADS)

    Gawli, Yogesh; Banerjee, Abhik; Dhakras, Dipti; Deo, Meenal; Bulani, Dinesh; Wadgaonkar, Prakash; Shelke, Manjusha; Ogale, Satishchandra

    2016-02-01

    A good high rate supercapacitor performance requires a fine control of morphological (surface area and pore size distribution) and electrical properties of the electrode materials. Polyaniline (PANI) is an interesting material in supercapacitor context because it stores energy Faradaically. However in conventional inorganic (e.g. HCl) acid doping, the conductivity is high but the morphological features are undesirable. On the other hand, in weak organic acid (e.g. phytic acid) doping, interesting and desirable 3D connected morphological features are attained but the conductivity is poorer. Here the synergy of the positive quality factors of these two acid doping approaches is realized by concurrent and optimized strong-inorganic (HCl) and weak-organic (phytic) acid doping, resulting in a molecular composite material that renders impressive and robust supercapacitor performance. Thus, a nearly constant high specific capacitance of 350 F g-1 is realized for the optimised case of binary doping over the entire range of 1 A g-1 to 40 A g-1 with stability of 500 cycles at 40 A g-1. Frequency dependant conductivity measurements show that the optimized co-doped case is more metallic than separately doped materials. This transport property emanates from the unique 3D single molecular character of such system.

  17. 3D Polyaniline Architecture by Concurrent Inorganic and Organic Acid Doping for Superior and Robust High Rate Supercapacitor Performance

    PubMed Central

    Gawli, Yogesh; Banerjee, Abhik; Dhakras, Dipti; Deo, Meenal; Bulani, Dinesh; Wadgaonkar, Prakash; Shelke, Manjusha; Ogale, Satishchandra

    2016-01-01

    A good high rate supercapacitor performance requires a fine control of morphological (surface area and pore size distribution) and electrical properties of the electrode materials. Polyaniline (PANI) is an interesting material in supercapacitor context because it stores energy Faradaically. However in conventional inorganic (e.g. HCl) acid doping, the conductivity is high but the morphological features are undesirable. On the other hand, in weak organic acid (e.g. phytic acid) doping, interesting and desirable 3D connected morphological features are attained but the conductivity is poorer. Here the synergy of the positive quality factors of these two acid doping approaches is realized by concurrent and optimized strong-inorganic (HCl) and weak-organic (phytic) acid doping, resulting in a molecular composite material that renders impressive and robust supercapacitor performance. Thus, a nearly constant high specific capacitance of 350 F g−1 is realized for the optimised case of binary doping over the entire range of 1 A g−1 to 40 A g−1 with stability of 500 cycles at 40 A g−1. Frequency dependant conductivity measurements show that the optimized co-doped case is more metallic than separately doped materials. This transport property emanates from the unique 3D single molecular character of such system. PMID:26867570

  18. 3D Polyaniline Architecture by Concurrent Inorganic and Organic Acid Doping for Superior and Robust High Rate Supercapacitor Performance.

    PubMed

    Gawli, Yogesh; Banerjee, Abhik; Dhakras, Dipti; Deo, Meenal; Bulani, Dinesh; Wadgaonkar, Prakash; Shelke, Manjusha; Ogale, Satishchandra

    2016-02-12

    A good high rate supercapacitor performance requires a fine control of morphological (surface area and pore size distribution) and electrical properties of the electrode materials. Polyaniline (PANI) is an interesting material in supercapacitor context because it stores energy Faradaically. However in conventional inorganic (e.g. HCl) acid doping, the conductivity is high but the morphological features are undesirable. On the other hand, in weak organic acid (e.g. phytic acid) doping, interesting and desirable 3D connected morphological features are attained but the conductivity is poorer. Here the synergy of the positive quality factors of these two acid doping approaches is realized by concurrent and optimized strong-inorganic (HCl) and weak-organic (phytic) acid doping, resulting in a molecular composite material that renders impressive and robust supercapacitor performance. Thus, a nearly constant high specific capacitance of 350 F g(-1) is realized for the optimised case of binary doping over the entire range of 1 A g(-1) to 40 A g(-1) with stability of 500 cycles at 40 A g(-1). Frequency dependant conductivity measurements show that the optimized co-doped case is more metallic than separately doped materials. This transport property emanates from the unique 3D single molecular character of such system.

  19. Novel and easy access to highly luminescent Eu and Tb doped ultra-small CaF2, SrF2 and BaF2 nanoparticles - structure and luminescence.

    PubMed

    Ritter, Benjamin; Haida, Philipp; Fink, Friedrich; Krahl, Thoralf; Gawlitza, Kornelia; Rurack, Knut; Scholz, Gudrun; Kemnitz, Erhard

    2017-02-28

    A universal fast and easy access at room temperature to transparent sols of nanoscopic Eu 3+ and Tb 3+ doped CaF 2 , SrF 2 and BaF 2 particles via the fluorolytic sol-gel synthesis route is presented. Monodisperse quasi-spherical nanoparticles with sizes of 3-20 nm are obtained with up to 40% rare earth doping showing red or green luminescence. In the beginning luminescence quenching effects are only observed for the highest content, which demonstrates the unique and outstanding properties of these materials. From CaF 2 :Eu10 via SrF 2 :Eu10 to BaF 2 :Eu10 a steady increase of the luminescence intensity and lifetime occurs by a factor of ≈2; the photoluminescence quantum yield increases by 29 to 35% due to the lower phonon energy of the matrix. The fast formation process of the particles within fractions of seconds is clearly visualized by exploiting appropriate luminescence processes during the synthesis. Multiply doped particles are also available by this method. Fine tuning of the luminescence properties is achieved by variation of the Ca-to-Sr ratio. Co-doping with Ce 3+ and Tb 3+ results in a huge increase (>50 times) of the green luminescence intensity due to energy transfer Ce 3+ → Tb 3+ . In this case, the luminescence intensity is higher for CaF 2 than for SrF 2 , due to a lower spatial distance of the rare earth ions.

  20. Senior High School Earth Sciences and Marine Sciences.

    ERIC Educational Resources Information Center

    Hackenberg, Mary; And Others

    This guide was developed for earth sciences and marine sciences instruction in the senior high schools of Duval County, Jacksonville, Florida. The subjects covered are: (1) Earth Science for 10th, 11th, and 12th graders; (2) Marine Biology I for 10th, 11th, and 12th graders; (3) Marine Biology II, Advanced, for 11th and 12th graders; (4) Marine…

  1. Monodisperse Ultrasmall Manganese-Doped Multimetallic Oxysulfide Nanoparticles as Highly Efficient Oxygen Reduction Electrocatalyst.

    PubMed

    Zhang, Yingying; Wang, Xiang; Hu, Dandan; Xue, Chaozhuang; Wang, Wei; Yang, Huajun; Li, Dongsheng; Wu, Tao

    2018-04-25

    The highly efficient and cheap non-Pt-based electrocatalysts such as transition-based catalysts prepared via facile methods for oxygen reduction reaction (ORR) are desirable for large-scale practical industry applications in energy conversion and storage systems. Herein, we report a straightforward top-down synthesis of monodisperse ultrasmall manganese-doped multimetallic (ZnGe) oxysulfide nanoparticles (NPs) as an efficient ORR electrocatalyst by simple ultrasonic treatment of the Mn-doped Zn-Ge-S chalcogenidometalate crystal precursors in H 2 O/EtOH for only 1 h at room temperature. Thus obtained ultrasmall monodisperse Mn-doped oxysulfide NPs with ultralow Mn loading level (3.92 wt %) not only exhibit comparable onset and half-wave potential (0.92 and 0.86 V vs reversible hydrogen electrode, respectively) to the commercial 20 wt % Pt/C but also exceptionally high metal mass activity (189 mA/mg at 0.8 V) and good methanol tolerance. A combination of transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, and electrochemical analysis demonstrated that the homogenous distribution of a large amount of Mn(III) on the surface of NPs mainly accounts for the high ORR activity. We believe that this simple synthesis of Mn-doped multimetallic (ZnGe) oxysulfide NPs derived from chalcogenidometalates will open a new route to explore the utilization of discrete-cluster-based chalcogenidometalates as novel non-Pt electrocatalysts for energy applications and provide a facile way to realize the effective reduction of the amount of catalyst while keeping desired catalytic performances.

  2. Convenient synthesis of Mn-doped Zn (O,S) nanoparticle photocatalyst for 4-nitrophenol reduction

    NASA Astrophysics Data System (ADS)

    Susanto Gultom, Noto; Abdullah, Hairus; Kuo, Dong-Hau

    2018-04-01

    The conversion of 4-nitrophenol as a toxic and waste pollutant to 4-aminophenol as a non-toxic and useful compound by photocatalytic reduction is highly important. In this work, the solid-solution concept by doping was involved to synthesis earth-abundant and green material of Mn-doped Zn(O,S). Zn(O,S) with different Mn doping contents was easily synthesized at low temperature 90°C for 4-NP reduction without using the reducing agent of NaBH4. The Mn-doped Zn(O,S) catalyst exhibited the enhancements in optical and electrochemical properties compared to un-doped Zn(O,S).It was found that 10% Mn-doped Zn(O,S) had the best properties and it could totally reduce 4-NP after 2h photoreactions under low UV illumination. The hydrogen ion was proposed to involve the 4-NP reduction to 4-AP, which is hydrogen ion and electron replaced the oxygen in amino (NO2) group of 4-NP to form the nitro (NH2) group. We alsoproposed the incorporation of Mn in Zn site in the Zn(O,S) host lattice could make the oxygen surface bonding weak for easily forming the oxygen vacancy. The more oxygen vacancy for more hydrogen ion would be generated to consume for 4-NP reduction.

  3. Sol-gel syntheses of pentaborate β-LaB5O9 and the photoluminescence by doping with Eu3+, Tb3+, Ce3+, Sm3+, and Dy3+

    NASA Astrophysics Data System (ADS)

    Yang, Ruirui; Sun, Xiaorui; Jiang, Pengfei; Gao, Wenliang; Cong, Rihong; Yang, Tao

    2018-02-01

    Rare earth (RE) borates have been extensively studied as good photoluminescent materials, however, the target hosts were limited to "RE3BO6", REBO3, and REB3O6 in the RE2O3-B2O3 phase diagram until the recent discovery of rare earth pentaborate. For the first time, the sol-gel method was employed to synthesize β-LaB5O9 doped with Eu3+, Tb3+, Ce3+, Sm3+, Dy3+. In comparison to the previous synthetic methods, the sol-gel method possesses superiorities including easily-controllable doping concentration, high yield and emission efficiency. Solid solutions of phosphors were prepared and carefully analyzed by powder X-ray diffraction. Concentration quenching or saturation was observed in Eu3+, Tb3+ and Ce3+ doped phosphors at round 10 at%. Eu3+, Tb3+, Sm3+, and Dy3+ emit red, green, orange, and close-to-white light, respectively. The absolute emission efficiency of Ce3+ is high and in the UV range, suggesting the function of being sensitizer once combined with other activators.

  4. Microfluidic active mixers employing ultra-high aspect-ratio rare-earth magnetic nano-composite polymer artificial cilia

    NASA Astrophysics Data System (ADS)

    Rahbar, Mona; Shannon, Lesley; Gray, Bonnie L.

    2014-02-01

    We present a new micromixer based on highly magnetic, flexible, high aspect-ratio, artificial cilia that are fabricated as individual micromixer elements or in arrays for improved mixing performance. These new cilia enable high efficiency, fast mixing in a microchamber, and are controlled by small electromagnetic fields. The artificial cilia are fabricated using a new micromolding process for nano-composite polymers. Cilia fibers with aspect-ratios as high as 8:0.13 demonstrate the fabrication technique's capability in creating ultra-high aspect-ratio microstructures. Cilia, which are realized in polydimethylsiloxane doped with rare-earth magnetic powder, are magnetized to produce permanent magnetic structures with bidirectional deflection capabilities, making them highly suitable as mixers controlled by electromagnetic fields. Due to the high magnetization level of the polarized nano-composite polymer, we are able to use miniature electromagnets providing relatively small magnetic fields of 1.1 to 7 mT to actuate the cilia microstructures over a very wide motion range. Mixing performances of a single cilium, as well as different arrays of multiple cilia ranging from 2 to 8 per reaction chamber, are characterized and compared with passive diffusion mixing performance. The mixer cilia are actuated at different amplitudes and frequencies to optimize mixing performance. We demonstrate that more than 85% of the total volume of the reaction chamber is fully mixed after 3.5 min using a single cilium mixer at 7 mT compared with only 20% of the total volume mixed with passive diffusion. The time to achieve over 85% mixing is further reduced to 70 s using an array of eight cilia microstructures. The novel microfabrication technique and use of rare-earth permanently-magnetizable nano-composite polymers in mixer applications has not been reported elsewhere by other researchers. We further demonstrate improved mixing over other cilia micromixers as enabled by the high aspect

  5. High gain photoconductive semiconductor switch having tailored doping profile zones

    DOEpatents

    Baca, Albert G.; Loubriel, Guillermo M.; Mar, Alan; Zutavern, Fred J; Hjalmarson, Harold P.; Allerman, Andrew A.; Zipperian, Thomas E.; O'Malley, Martin W.; Helgeson, Wesley D.; Denison, Gary J.; Brown, Darwin J.; Sullivan, Charles T.; Hou, Hong Q.

    2001-01-01

    A photoconductive semiconductor switch with tailored doping profile zones beneath and extending laterally from the electrical contacts to the device. The zones are of sufficient depth and lateral extent to isolate the contacts from damage caused by the high current filaments that are created in the device when it is turned on. The zones may be formed by etching depressions into the substrate, then conducting epitaxial regrowth in the depressions with material of the desired doping profile. They may be formed by surface epitaxy. They may also be formed by deep diffusion processes. The zones act to reduce the energy density at the contacts by suppressing collective impact ionization and formation of filaments near the contact and by reducing current intensity at the contact through enhanced current spreading within the zones.

  6. Ce Core-Level Spectroscopy, and Magnetic and Electrical Transport Properties of Lightly Ce-Doped YCoO3

    NASA Astrophysics Data System (ADS)

    Kobayashi, Yoshihiko; Koike, Tsuyoshi; Okawa, Mario; Takayanagi, Ryohei; Takei, Shohei; Minohara, Makoto; Kobayashi, Masaki; Horiba, Koji; Kumigashira, Hiroshi; Yasui, Akira; Ikenaga, Eiji; Saitoh, Tomohiko; Asai, Kichizo

    2016-11-01

    We have investigated the Ce and Co core level spectroscopy, and the magnetic and electrical transport properties of lightly Ce-doped YCoO3. We have successfully synthesized single-phase Y1-xCexCoO3 for 0.0 ≤ x ≤ 0.1 by the sol-gel method. Hard X-ray photoelectron and X-ray absorption spectroscopy experiments reveal that the introduced Ce ions are tetravalent, which is considered to be the first case of electron doping into bulk trivalent Co oxides with perovskite RECoO3 (RE: rare-earth element or Y) caused by RE site substitution. The magnitude of the effective magnetic moment peff obtained from the temperature dependence of magnetic susceptibility χ(T) at higher temperatures is close to that for high-spin Co2+ introduced by the Ce doping, implying that the electrons doped into the Co site induce Co2+ with a high-spin state. For x = 0.1, ferromagnetic ordering is observed below about 7 K. Electrical transport properties such as resistivity and thermoelectric power show that negative electron-like carriers are introduced by Ce substitution.

  7. Highly improved ethanol gas-sensing performance of mesoporous nickel oxides nanowires with the stannum donor doping.

    PubMed

    Wei, Junqi; Li, Xiaoqing; Han, Yanbing; Xu, Jingcai; Jin, Hongxiao; Jin, Dingfeng; Peng, Xiaoling; Hong, Bo; Li, Jing; Yang, Yanting; Ge, Hongliang; Wang, Xinqing

    2018-06-15

    Mesoporous nickel oxides (NiO) and stannum(Sn)-doped NiO nanowires (NWs) were synthesized by using SBA-15 templates with the nanocasting method. X-ray diffraction, transmission electron microscope, energy dispersive spectrometry, nitrogen adsorption/desorption isotherm and UV-vis spectrum were used to characterize the phase structure, components and microstructure of the as-prepared samples. The gas-sensing analysis indicated that the Sn-doping could greatly improve the ethanol sensitivity for mesoporous NiO NWs. With the increasing Sn content, the ethanol sensitivity increased from 2.16 for NiO NWs up to the maximum of 15.60 for Ni 0.962 Sn 0.038 O 1.038 , and then decreased to 12.24 for Ni 0.946 Sn 0.054 O 1.054 to 100 ppm ethanol gas at 340 °C. The high surface area from the Sn-doping improved the adsorption of oxygen on the surface of NiO NWs, resulting in the smaller surface resistance in air. Furthermore, owing to the recombination of the holes in hole-accumulation lay with the electrons from the donor impurity level and the increasing the body defects for Sn-doping, the total resistance in ethanol gas enhanced greatly. It was concluded that the sensitivity of Sn-doped NiO NWs based sensor could be greatly improved by the higher surface area and high-valence donor substitution from Sn-doping.

  8. Highly improved ethanol gas-sensing performance of mesoporous nickel oxides nanowires with the stannum donor doping

    NASA Astrophysics Data System (ADS)

    Wei, Junqi; Li, Xiaoqing; Han, Yanbing; Xu, Jingcai; Jin, Hongxiao; Jin, Dingfeng; Peng, Xiaoling; Hong, Bo; Li, Jing; Yang, Yanting; Ge, Hongliang; Wang, Xinqing

    2018-06-01

    Mesoporous nickel oxides (NiO) and stannum(Sn)-doped NiO nanowires (NWs) were synthesized by using SBA-15 templates with the nanocasting method. X-ray diffraction, transmission electron microscope, energy dispersive spectrometry, nitrogen adsorption/desorption isotherm and UV–vis spectrum were used to characterize the phase structure, components and microstructure of the as-prepared samples. The gas-sensing analysis indicated that the Sn-doping could greatly improve the ethanol sensitivity for mesoporous NiO NWs. With the increasing Sn content, the ethanol sensitivity increased from 2.16 for NiO NWs up to the maximum of 15.60 for Ni0.962Sn0.038O1.038, and then decreased to 12.24 for Ni0.946Sn0.054O1.054 to 100 ppm ethanol gas at 340 °C. The high surface area from the Sn-doping improved the adsorption of oxygen on the surface of NiO NWs, resulting in the smaller surface resistance in air. Furthermore, owing to the recombination of the holes in hole-accumulation lay with the electrons from the donor impurity level and the increasing the body defects for Sn-doping, the total resistance in ethanol gas enhanced greatly. It was concluded that the sensitivity of Sn-doped NiO NWs based sensor could be greatly improved by the higher surface area and high-valence donor substitution from Sn-doping.

  9. High spin state driven magnetism and thermoelectricity in Mn doped topological insulator Bi2Se3

    NASA Astrophysics Data System (ADS)

    Maurya, V. K.; Dong, C. L.; Chen, C. L.; Asokan, K.; Patnaik, S.

    2018-06-01

    We report on the synthesis, and structural - magnetic characterizations of Mn doped Bi2Se3 towards achieving a magnetically doped topological insulator. High quality single crystals of MnxBi2-xSe3 (x = 0, 0.03, 0.05, 0.1) are grown and analysed by X-ray diffraction (XRD), Low Energy Electron Diffraction (LEED), Scanning electron microscopy (SEM), and X-ray absorption near-edge structure spectroscopy (XANES). Magnetic properties of these samples under ZFC-FC protocol and isothermal magnetization confirm ferromagnetic correlation above x = 0.03 value. XANES measurements confirm that the dopant Mn is in Mn2+ state. This is further reconfirmed to be in high spin state by fitting magnetic data with Brillouin function for J = 5/2. Both Hall and Seebeck measurements indicate a sign change of charge carriers above x = 0.03 value of Mn doping. We propose Mn doped Bi2Se3 to be a potential candidate for electromagnetic and thermoelectric device applications involving topological surface states.

  10. High-power single-stage thulium-doped superfluorescent fiber source

    NASA Astrophysics Data System (ADS)

    Hu, Z. Y.; Yan, P.; Liu, Q.; Ji, E. C.; Xiao, Q. R.; Gong, M. L.

    2015-01-01

    In this paper, we report a high-power thulium (Tm)-doped superfluorescent fiber source (SFS) in the 2-μm spectral region. The SFS is based on double angle-cleaved facet operation and uses a simple single-stage geometry. The copropagating amplified spontaneous emission (ASE) yields a maximum output of 20.7 W at a center wavelength of 1,960.7 nm, with a full width at half maximum (FWHM) of ~45 nm. The counterpropagating ASE yields a maximum output of 25.2 W at a center wavelength of 1,948.2 nm, with a FWHM of ~50 nm. The maximum combined output of the SFS is as much as 45.9 W, which corresponds to a slope efficiency of 38.9 %. In addition, a model of the ~2 μm SFS in Tm-doped silica fibers pumped at ~790 nm is developed, and the influence of fiber length and end-facet reflectivity on the ASE output performance and the parasitic lasing threshold are studied numerically.

  11. Divalent europium doped CaF 2 and BaF 2 nanocrystals from ionic liquids

    DOE PAGES

    Anghel, Sergiu; Golbert, Sebastian; Meijerink, Andries; ...

    2016-10-11

    A new, facile and quick synthesis method for Eu 2+ doped the alkaline earth fluorides was developed using ionic liquids as solvent, precursor and capping agent. Reductive atmosphere and very high temperatures were avoided, while still attaining the desired structure, small particle sizes and divalent oxidation state of the lanthanide. Here, this opens the door for the development of new Ln 2+ doped nanomaterials. Here, the successful Eu 2+ incorporation was proven by optical spectroscopic measurements which showed the spin and parity allowed f-d transitions of Eu 2+ in CaF 2:Eu 2+/BaF 2:Eu 2+. 4f 7-4f 7 transitions could bemore » observed at low temperatures (7 K).« less

  12. The Electronic Structure and Optical Properties of Anatase TiO2 with Rare Earth Metal Dopants from First-Principles Calculations

    PubMed Central

    Xie, Kefeng; Jia, Qiangqiang; Wang, Yizhe; Zhang, Wenxue; Xu, Jingcheng

    2018-01-01

    The electronic and optical properties of the rare earth metal atom-doped anatase TiO2 have been investigated systematically via density functional theory calculations. The results show that TiO2 doped by Ce or Pr is the optimal choice because of its small band gap and strong optical absorption. Rare earth metal atom doping induces several impurity states that tune the location of valence and conduction bands and an obvious lattice distortion that should reduce the probability of electron–hole recombination. This effect of band change originates from the 4f electrons of the rare earth metal atoms, which leads to an improved visible light absorption. This finding indicates that the electronic structure of anatase TiO2 is tuned by the introduction of impurity atoms. PMID:29364161

  13. A F-doped tree-like nanofiber structural poly-m-phenyleneisophthalamide separator for high-performance lithium-sulfur batteries

    NASA Astrophysics Data System (ADS)

    Deng, Nanping; Wang, Yan; Yan, Jing; Ju, Jingge; Li, Zongjie; Fan, Lanlan; Zhao, Huijuan; Kang, Weimin; Cheng, Bowen

    2017-09-01

    In this study, F-doped tree-like nanofiber structural poly-m-phenyleneisophthalamide (PMIA) membranes are prepared via one-step electrospinning approach and their application performance as separators for lithium-sulfur batteries are discussed. The F-doped PMIA membrane can be regarded as matrix to form gel polymer electrolyte. The F doping endows the PMIA membranes with extraordinary high electrolyte uptake, excellent ability of preserving the liquid electrolyte and forceful chemisorption to polysulfides. And the tree-like structure effectively blocks polysulfides by the physical confinement. The lithium-sulfur cell with the F-doped PMIA separator exhibits high first-cycle discharge capacity of 1222.5 mAh g-1 and excellent cycling stability with good capacity retention of 745.7 mAh g-1 and coulombic efficiency of 97.97% after 800 cycles. The remarkable performance can be ascribed to the suppressed shuttle effects through both the physical trapping of polysulfides by the gel polymer electrolyte based on matrix with F-doped PMIA membrane and the tree-like structure in a working cell.

  14. Design and characterization of Yb and Nd doped transparent ceramics for high power laser applications: recent advancements

    NASA Astrophysics Data System (ADS)

    Lapucci, A.; Vannini, M.; Ciofini, M.; Pirri, A.; Nikl, M.; Li, J.; Esposito, L.; Biasini, V.; Hostasa, J.; Goto, T.; Boulon, G.; Maksimov, R.; Gizzi, L.; Labate, L.; Toci, G.

    2017-01-01

    We report a review on our recent developments in Yttebium and Neodymium doped laser ceramics, along two main research lines. The first is the design and development of Yb:YAG ceramics with non uniform doping distribution, for the management of thermo-mechanical stresses and for the mitigation of ASE: layered structures have been produced by solid state reactive sintering, using different forming processes (spray drying and cold press of the homogenized powders, tape cast of the slurry); samples have been characterized and compared to FEM analysis. The second is the investigation of Lutetium based ceramics (such as mixed garnets LuYAG and Lu2O3); this interest is mainly motivated by the favorable thermal properties of these hosts under high doping. We recently obtained for the first time high efficiency laser emission from Yb doped LuYAG ceramics. The investigation on sesquioxides has been focused on Nddoped Lu2O3 ceramics, fabricated with the Spark Plasma Sintering method (SPS). We recently achieved the first laser emission above 1 W from Nd doped Lu2O3 ceramics fabricated by SPS.

  15. Hole-doped cuprate high temperature superconductors

    NASA Astrophysics Data System (ADS)

    Chu, C. W.; Deng, L. Z.; Lv, B.

    2015-07-01

    Hole-doped cuprate high temperature superconductors have ushered in the modern era of high temperature superconductivity (HTS) and have continued to be at center stage in the field. Extensive studies have been made, many compounds discovered, voluminous data compiled, numerous models proposed, many review articles written, and various prototype devices made and tested with better performance than their nonsuperconducting counterparts. The field is indeed vast. We have therefore decided to focus on the major cuprate materials systems that have laid the foundation of HTS science and technology and present several simple scaling laws that show the systematic and universal simplicity amid the complexity of these material systems, while referring readers interested in the HTS physics and devices to the review articles. Developments in the field are mostly presented in chronological order, sometimes with anecdotes, in an attempt to share some of the moments of excitement and despair in the history of HTS with readers, especially the younger ones.

  16. Visible light responsive sulfated rare earth doped TiO(2)@fumed SiO(2) composites with mesoporosity: enhanced photocatalytic activity for methyl orange degradation.

    PubMed

    Zhan, Changchao; Chen, Feng; Yang, Jintao; Dai, Daoxing; Cao, Xiaohua; Zhong, Mingqiang

    2014-02-28

    Visible light (VL) responsive mesoporous sulfated rare earth ions (Nd(3+), La(3+), Y(3+)) incorporated TiO2@fumed SiO2 photocatalysts were prepared by sol-gel method with P123 (EO20PO70EO20) as a template. The resultant samples were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), N2 adsorption-desorption measurements (BET), UV-vis diffuse reflectance spectroscopy, photoluminescence (PL) spectra, Fourier transform infrared spectroscopy (FTIR) and thermal analyses (TG-DTA). In comparison with nondoped sample, RE-doped samples showed not only an increase in the surface areas and pore volumes, but also an inhibition of titania phase transition from anatase to rutile. Photo-degradation results revealed that RE-doped samples could greatly improve the photocatalytic activity, and the experimental degradation rates of methyl orange (MO) were higher than that catalyzed by undoped samples and Degussa P-25, obeyed the order of Nd(3+)>La(3+)>Y(3+). Nd-doped sample expressed the highest photoactivity and the optimal dosage was 0.25mol%, which resulted in MO degradation rates of 99.8% and 90.05% irradiation under UV for 60min and VL (λ>400nm) for 40h, respectively. The enhanced photocatalytic activity could be attributed to the higher specific area, good crystallinity, strong VL absorption and effective separation of photogenerated electron-hole pairs in the catalyst. Copyright © 2014 Elsevier B.V. All rights reserved.

  17. Tidal evolution of the Moon from a high-obliquity, high-angular-momentum Earth.

    PubMed

    Ćuk, Matija; Hamilton, Douglas P; Lock, Simon J; Stewart, Sarah T

    2016-11-17

    In the giant-impact hypothesis for lunar origin, the Moon accreted from an equatorial circum-terrestrial disk; however, the current lunar orbital inclination of five degrees requires a subsequent dynamical process that is still unclear. In addition, the giant-impact theory has been challenged by the Moon's unexpectedly Earth-like isotopic composition. Here we show that tidal dissipation due to lunar obliquity was an important effect during the Moon's tidal evolution, and the lunar inclination in the past must have been very large, defying theoretical explanations. We present a tidal evolution model starting with the Moon in an equatorial orbit around an initially fast-spinning, high-obliquity Earth, which is a probable outcome of giant impacts. Using numerical modelling, we show that the solar perturbations on the Moon's orbit naturally induce a large lunar inclination and remove angular momentum from the Earth-Moon system. Our tidal evolution model supports recent high-angular-momentum, giant-impact scenarios to explain the Moon's isotopic composition and provides a new pathway to reach Earth's climatically favourable low obliquity.

  18. Progress in efficient doping of high aluminum-containing group III-nitrides

    NASA Astrophysics Data System (ADS)

    Liang, Y.-H.; Towe, E.

    2018-03-01

    The group III-nitride (InN, GaN, and AlN) class of semiconductors has become one of two that are critical to a number of technologies in modern life—the other being silicon. Light-emitting diodes made from (In,Ga)N, for example, dominate recent innovations in general illumination and signaling. Even though the (In,Ga)N materials system is fairly well established and widely used in advanced devices, challenges continue to impede development of devices that include aluminum-containing nitride films such as (Al,Ga)N. The main difficulty is efficient doping of films with aluminum-rich compositions; the problem is particularly severe for p-type doping, which is essential for Ohmic contacts to bipolar device structures. This review briefly summarizes the fundamental issues related to p-type doping, and then discusses a number of approaches that are being pursued to resolve the doping problem or for circumventing the need for p-type doping. Finally, we discuss an approach to doping under liquid-metal-enabled growth by molecular beam epitaxy. Recent results from a number of groups appear to indicate that p-type doping of nitride films under liquid-metal-enabled growth conditions might offer a solution to the doping problem—at least for materials grown by molecular beam epitaxy.

  19. [Interdisciplinary strategies versus doping].

    PubMed

    Vitzthum, Karin; Mache, Stefanie; Quarcoo, David; Groneberg, David A; Schöffel, Norman

    2010-06-01

    Doping is a phenomenon which in the past years through the various incidences in professional cycling has come more and more into the focus of the public interest. Whilst in the young past the problems were to define the term "doping" exactly, today's problem is to prevent adolescents and children of doping. This shall be achieved by carrying out controls and serious sanctions for doping violations. Scientific research proved that doping usage can be avoided by broad specific prevention measures. In general, the earlier the athletes dope the higher the risk to become addicted later on in life to other legal or illegal drugs. The aim of this review is to analyse the prevalence of doping regarding youth-, competitive-, high performance and recreational sports and to examine further aspects of doping abuse, risks of addiction, the legal situation, current strategies in the fight against doping and to enhance chances of further doping prevention opportunities. By means of this data an all-embracing view should be given over the current situation, problems and prospects in German-speaking countries.

  20. High carrier concentration ZnO nanowire arrays for binder-free conductive support of supercapacitors electrodes by Al doping.

    PubMed

    Zheng, Xin; Sun, Yihui; Yan, Xiaoqin; Sun, Xu; Zhang, Guangjie; Zhang, Qian; Jiang, Yaru; Gao, Wenchao; Zhang, Yue

    2016-12-15

    Doping semiconductor nanowires (NWs) for altering their electrical and optical properties is a critical strategy for tailoring the performance of nanodevices. Here, we prepared in situ Al-doped ZnO nanowire arrays by using continuous flow injection (CFI) hydrothermal method to promote the conductivity. This reasonable method offers highly stable precursor concentration for doping that effectively avoid the appearance of the low conductivity ZnO nanosheets. Benefit from this, three orders of magnitude rise of the carrier concentration from 10 16 cm -3 to 10 19 cm -3 can be achieved compared with the common hydrothermal (CH) mothed in Mott-Schottky measurement. Possible effect of Al-doping was discussed by first-principle theory. On this basis, Al-doped ZnO nanowire arrays was developed as a binder-free conductive support for supercapacitor electrodes and high capacitance was triggered. It is owing to the dramatically decreased transfer resistance induced by the growing free-moving electrons and holes. Our results have a profound significance not merely in the controlled synthesis of other doping nanomaterials by co-precipitation method but also in the application of binder-free energy materials or other materials. Copyright © 2016 Elsevier Inc. All rights reserved.

  1. Coilable single crystal fibers of doped-YAG for high power laser applications

    NASA Astrophysics Data System (ADS)

    Maxwell, Gisele; Soleimani, Nazila; Ponting, Bennett; Gebremichael, Eminet

    2013-05-01

    Single crystal fibers are an intermediate between laser crystals and doped glass fibers. They can combine the advantages of both by guiding laser light and matching the efficiencies found in bulk crystals, making them ideal candidates for high-power laser and fiber laser applications. In particular, a very interesting feature of single crystal fiber is that they can generate high power in the eye-safe range (Er:YAG) with a high efficiency, opening new possibilities for portable directed energy weapons. This work focuses on the growth of a flexible fiber with a core of dopant (Er, Nd, Yb, etc…) that will exhibit good waveguiding properties. Direct growth or a combination of growth and cladding experiments are described. We have, to date, demonstrated the growth of a flexible foot long 45 microns doped YAG fiber. Scattering loss measurements at visible wavelengths along with dopant profile characterization are also presented. Laser characterization for these fibers is in progress.

  2. A lyophilized and thermal two step synthesis of CoFe alloy nanoparticles embedded in N-doped carbon nanosheets/carbon nanotubes for highly-efficient oxygen evolution reaction.

    PubMed

    Liu, Yang; Li, Feng; Yang, Haidong; Li, Jing; Ma, Ping; Zhu, Yan; Ma, Jiantai

    2018-05-22

    There is a vital need to explore highly-efficient and stable nonprecious-metal catalysts for oxygen evolution reaction (OER) to reduce the overpotential and further improve the energy conversion efficiency. Herein, we report a unique and cost-effective lyophilized and thermal two step procedure to synthesize high-performance CoFe alloy nanoparticles embedded in N-doped carbon nanosheets interspersed with carbon nanotubes (CoFe-N-CN/CNTs) hybrid. The lyophilization step during catalysts preparation is beneficial to uniform the dispersion of carbon-like precursors and avoid the agglomeration of metal particles. Meanwhile, the inserted CNTs and doped N in this hybrid provide better electrical conductivity, more chemically active sites, improved mass transport capability and effective gas adsorption/release channels. And all these lead to a high specific surface area of 240.67 m2 g-1, favorable stability and remarkable OER activities with an overpotential of only 285 mV at the current density of 10 mA cm-2 and a Tafel slope of 51.09 mV dec-1 in 1.0 M KOH electrolyte, which is even superior to commercial IrO2 catalysts. The CoFe-N-CN/CNTs hybrid thus exhibits great potential as a highly efficient and earth-abundant anode OER electrocatalyst. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Probing the Electronic Structure of - and Electron-Doped High-Temperature Superconductors with Photoemission and X-Ray Absorption Spectroscopies

    NASA Astrophysics Data System (ADS)

    Lederman, Eli R.

    1990-01-01

    The electronic structures of hole- and electron -doped high temperature superconductors have been probed using x-ray absorption near-edge spectroscopy (XANES) and photoelectron emission spectroscopy (PES). These measurements have been performed on RBa_2Cu _3O_{rm 7-y} , La_{rm 2-x}Sr _{rm x}CuO _4 and Ln_{rm 2 -x}Ce_{rm x} CuO_{rm 4} for R = Y, Eu and Ln = Nd, Pr and Sm. The parameters x and y have been varied to include a range of hole and electron carrier densities and the undoped parent compounds. Previous XANES and PES results have indicated that unoccupied states of O 2p character can be associated with the carriers in the materials RBa_2 Cu_3O_{ rm 7-y} and La_{ rm 2-x}Sr_{rm x}CuO_4 and that the density of holes increases with O and Sr content, respectively. Conduction was hole-based in all known high-T_{ rm c} cuprates until the recent discovery of superconductivity in Ln_{rm 2-x}Ce_{rm x} CuO_4. Hall coefficient measurements have suggested that the carriers in this system are electrons added with Ce doping. It has been anticipated that these electron-doped materials will provide an important test for models of high temperature superconductivity. PES measurements are presented that show significant Cu 3d character in the valence band of these electron-based materials, but that the Cu^{2+} /Cu^{1+} ratio is unchanged by the level of Ce doping, indicating that doped electrons are itinerant rather than highly correlated. Resonant photoemission from the valence band indicates the presence of unoccupied O 2p states, but these holes are less abundant than in the hole-doped materials. Measurements of XANES at the O 1s edge suggest that unoccupied states of O 2p character in the electron -doped materials are not related to conduction in a simple way. The density of these holes is shown to decrease upon Ce doping and the process of reduction, despite the fact that both are necessary of superconductivity. Furthermore, whereas the O 2p holes are at E_{rm F} in the

  4. Structure and thermoelectric property of Te doped paracostibite CoSb1-xTexS compounds

    NASA Astrophysics Data System (ADS)

    You, Yonghui; Su, Xianli; Liu, Wei; Yan, Yonggao; Fu, Jiefei; Cheng, Xin; Zhang, Cheng; Tang, Xinfeng

    2018-06-01

    Paracostibite (CoSbS), a newly developed thermoelectric material, has aroused lots of interest due to its highly earth abundant and inexpensive constituent elements and potential application for thermoelectric power generation in the intermediate temperature range. Herein, a series of CoSb1-xTexS (x = 0-0.09) compounds were prepared by vacuum melting and annealing followed by SPS processing, and the effects of Te doping on the structure and thermoelectric properties were systematically investigated. Doping Te on the Sb site increases the carrier concentration up to 7.24 × 1020 cm-3 for CoSb0.93Te0.07S compound which is several orders of magnitude higher than that of un-doped CoSbS, and enhances the power factor. The maximum power factor of 14.07 μW cm-1 K-2 is attained at 900 K. Concomitantly, doping with Te on the Sb site leads to effective scattering of heat carrying phonon, accompanying with a strong suppression of the thermal conductivity with the increase of Te content, resulting in an increase of the ZT. A maximum ZT of 0.43 at 900 K is attained for CoSb0.93Te0.07S compound, which is 139% higher than that of un-doped CoSbS compound.

  5. Gender- and Sport-Specific Associations Between Religiousness and Doping Behavior in High-Level Team Sports.

    PubMed

    Zvan, Milan; Zenic, Natasa; Sekulic, Damir; Cubela, Mladen; Lesnik, Blaz

    2017-08-01

    Religiousness is known to be specifically associated with substance abuse, but there is an evident lack of studies investigating the association between religiousness and doping behavior as a specific type of substance abuse in athletes. This study aimed to provide evidence for possible gender- and sport-specific associations between religiousness and doping behavior among team-sport athletes of both genders. The participants were 886 athletes (21.9 ± 3.8 years of age; 352 females) involved in four sports: volleyball (n = 154; 78 females), handball (n = 206; 68 females), soccer (n = 316; 110 females) and basketball (n = 230; 96 females) from Croatia and Slovenia (all traditionally Roman Catholics). The data were collected using a previously validated structured questionnaire that examined sociodemographic, sport- and doping-related factors. In addition, religiousness was captured by the Santa Clara Strength of Religious Faith questionnaire (SCSRF). Gender-stratified simple logistic regressions were applied to determine associations between covariates and doping behavior (criterion). There was no significant difference in potential doping behavior between males and females (OR 1.06, 95 % CI 0.76-1.46), while females reported higher religiousness (SCSRF: 23.11 ± 3.23 and 25.46 ± 7.2 for males and females, respectively; t test = 1.82, p < 0.05). Younger female athletes and those with higher SCSRF score are found to be less prone to doping behavior. When models were adjusted for personal opinion about doping presence in sport and age, the SCSRF remained a significant predictor of potential doping behavior (OR 0.95, 95 % CI 0.91-0.99). For males, the belief that doping was present in sport was strongly associated with a higher likelihood of doping. Our results suggest that highly religious females involved in three of the studies sports (i.e., volleyball, handball and basketball) show a weaker tendency toward doping. Meanwhile, there is no

  6. Rare earth doped zinc oxide varistors

    DOEpatents

    McMillan, A.D.; Modine, F.A.; Lauf, R.J.; Alim, M.A.; Mahan, G.D.; Bartkowiak, M.

    1998-12-29

    A varistor includes a Bi-free, essentially homogeneous sintered body of a ceramic composition including, expressed as nominal weight %, 0.2--4.0% oxide of at least one rare earth element, 0.5--4.0% Co{sub 3}O{sub 4}, 0.05--0.4% K{sub 2}O, 0.05--0.2% Cr{sub 2}O{sub 3}, 0--0.2% CaO, 0.00005--0.01% Al{sub 2}O{sub 3}, 0--2% MnO, 0--0.05% MgO, 0--0.5% TiO{sub 3}, 0--0.2% SnO{sub 2}, 0--0.02% B{sub 2}O{sub 3}, balance ZnO. 4 figs.

  7. Rare earth doped zinc oxide varistors

    DOEpatents

    McMillan, April D.; Modine, Frank A.; Lauf, Robert J.; Alim, Mohammad A.; Mahan, Gerald D.; Bartkowiak, Miroslaw

    1998-01-01

    A varistor includes a Bi-free, essentially homogeneous sintered body of a ceramic composition including, expressed as nominal weight %, 0.2-4.0% oxide of at least one rare earth element, 0.5-4.0% Co.sub.3 O.sub.4, 0.05-0.4% K.sub.2 O, 0.05-0.2% Cr.sub.2 O.sub.3, 0-0.2% CaO, 0.00005-0.01% Al.sub.2 O.sub.3, 0-2% MnO, 0-0.05% MgO, 0-0.5% TiO.sub.3, 0-0.2% SnO.sub.2, 0-0.02% B.sub.2 O.sub.3, balance ZnO.

  8. Phonon-mediated high-T c superconductivity in hole-doped diamond-like crystalline hydrocarbon

    DOE PAGES

    Lian, Chao-Sheng; Wang, Jian-Tao; Duan, Wenhui; ...

    2017-05-03

    We here predict by ab initio calculations phonon-mediated high-T c superconductivity in hole-doped diamond-like cubic crystalline hydrocarbon K 4-CH (space group I2 1/3). This material possesses three key properties: (i) an all-sp 3 covalent carbon framework that produces high-frequency phonon modes, (ii) a steep-rising electronic density of states near the top of the valence band, and (iii) a Fermi level that lies in the σ-band, allowing for a strong coupling with the C-C bond-stretching modes. The simultaneous presence of these properties generates remarkably high superconducting transition temperatures above 80 K at an experimentally accessible hole doping level of only amore » few percent. These results identify a new extraordinary electron-phonon superconductor and pave the way for further exploration of this novel superconducting covalent metal.« less

  9. Properties and mechanisms of surface doped barium titanate sintered in reducing atmospheres

    NASA Astrophysics Data System (ADS)

    Spang, David Irwin

    2001-07-01

    Barium titanate-based dielectric compositions for Multilayer Ceramic Capacitor (MLCC) applications that are properly formulated can maintain acceptable dielectric properties after firing in a reducing atmosphere. The data to be presented relates to the application of an experimental scheme to probe the fundamental nature of doped BaTiO3-based dielectrics exposed to low pO2 sintering atmospheres. Specifically, the effect of Y and Rare Earth dopants Nd, Dy, Ho, and Er and donor dopants Nb, and V have been studied for compositions in the system BaTi(Mn)O3 + SiO2. All dopants were applied to high purity barium titanate as chemical surface coatings. Each coated formulation was evaluated after firing under three different atmospheric conditions. These conditions were comprised of firing in air at 1250°C for 2 hours, firing at 10-10 atm pO2 at 1250°C for 2 hours, and firing at 10-10 atm pO2 at 1250°C for 2 hours with an anneal at 10 -9 atm pO2 at 1000°C for 1 hour. This testing method was useful in gaining insight into the mechanism of the dopant interaction and/or the compensation of the oxygen vacancy concentration. As a donor addition, vanadium was observed to produce the highest dissipation factor when sintered under oxidizing conditions and the lowest dissipation factor when sintered under reducing conditions. The V-doped formulations exhibited satisfactory basic MLCC electrical properties when sintered under reducing conditions. Niobium was observed to impart strong donor character to the dielectric formulations sintered under reducing conditions suggesting that it was unlikely that compensatory A-site cation vacancies were induced. For Y and Rare Earth doped formulations there was an observed shifting and suppression of the Curie Peak that seemed to be attributable to electrostrain effects, related to the ionic radius of the dopants. The observed difference in the TCC behavior of the Nd-doped formulations illustrated two possible effects of Nd doping. One is

  10. Surveillance of medium and high Earth orbits using large baseline stereovision

    NASA Astrophysics Data System (ADS)

    Danescu, Radu; Ciurte, Anca; Oniga, Florin; Cristea, Octavian; Dolea, Paul; Dascal, Vlad; Turcu, Vlad; Mircea, Liviu; Moldovan, Dan

    2014-11-01

    The Earth is surrounded by a swarm of satellites and associated debris known as Resident Space Objects (RSOs). All RSOs will orbit the Earth until they reentry into Earth's atmosphere. There are three main RSO categories: Low Earth Orbit (LEO), when the satellite orbits at an altitude below 1 500 km; a Medium Earth Orbit (MEO) for Global Navigation Satellite Systems (GNSS) at an altitude of around 20 000 km, and a Geostationary Earth Orbit (GEO) (also sometimes called the Clarke orbit), for geostationary satellites, at an altitude of 36 000 km. The Geostationary Earth Orbits and the orbits of higher altitude are also known as High Earth Orbits (HEO). Crucial for keeping an eye on RSOs, the Surveillance of Space (SofS) comprises detection, tracking, propagation of orbital parameters, cataloguing and analysis of these objects. This paper presents a large baseline stereovision based approach for detection and ranging of RSO orbiting at medium to high altitudes. Two identical observation systems, consisting of camera, telescope, control computer and GPS receiver are located 37 km apart, and set to observe the same region of the sky. The telescopes are placed on equatorial mounts able to compensate for the Earth's rotation, so that the stars appear stationary in the acquired images, and the satellites will appear as linear streaks. The two cameras are triggered simultaneously. The satellite streaks are detected in each image of the stereo pair using its streak-like appearance against point-like stars, the motion of the streaks between successive frames, and the stereo disparity. The detected satellite pixels are then put into correspondence using the epipolar geometry, and the 3D position of the satellite in the Earth Center, Earth Fixed (ECEF) reference frame is computed using stereo triangulation. Preliminary tests have been performed, for both MEO and HEO orbits. The preliminary results indicate a very high detection rate for MEO orbits, and good detection rate for

  11. Rare earth-doped materials with enhanced thermoelectric figure of merit

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Venkatasubramanian, Rama; Cook, Bruce Allen; Levin, Evgenii M.

    A thermoelectric material and a thermoelectric converter using this material. The thermoelectric material has a first component including a semiconductor material and a second component including a rare earth material included in the first component to thereby increase a figure of merit of a composite of the semiconductor material and the rare earth material relative to a figure of merit of the semiconductor material. The thermoelectric converter has a p-type thermoelectric material and a n-type thermoelectric material. At least one of the p-type thermoelectric material and the n-type thermoelectric material includes a rare earth material in at least one ofmore » the p-type thermoelectric material or the n-type thermoelectric material.« less

  12. Bringing Earth Magnetism Research into the High School Physics Classroom

    NASA Astrophysics Data System (ADS)

    Smirnov, A. V.; Bluth, G.; Engel, E.; Kurpier, K.; Foucher, M. S.; Anderson, K. L.

    2015-12-01

    We present our work in progress from an NSF CAREER project that aims to integrate paleomagnetic research and secondary school physics education. The research project is aimed at quantifying the strength and geometry of the Precambrian geomagnetic field. Investigation of the geomagnetic field behavior is crucial for understanding the mechanisms of field generation, and the development of the Earth's atmosphere and biosphere, and can serve as a focus for connecting high-level Earth science research with a standard physics curriculum. High school science teachers have participated in each summer field and research component of the project, gaining field and laboratory research experience, sets of rock and mineral samples, and classroom-tested laboratory magnetism activities for secondary school physics and earth science courses. We report on three field seasons of teacher field experiences and two years of classroom testing of paleomagnetic research materials merged into physics instruction on magnetism. Students were surveyed before and after dedicated instruction for both perceptions and attitude towards earth science in general, then more specifically on earth history and earth magnetism. Students were also surveyed before and after instruction on major earth system and magnetic concepts and processes, particularly as they relate to paleomagnetic research. Most students surveyed had a strongly positive viewpoint towards the study of Earth history and the importance of studying Earth Sciences in general, but were significantly less drawn towards more specific topics such as mineralogy and magnetism. Students demonstrated understanding of Earth model and the basics of magnetism, as well as the general timing of life, atmospheric development, and magnetic field development. However, detailed knowledge such as the magnetic dynamo, how the magnetic field has changed over time, and connections between earth magnetism and the development of an atmosphere remained largely

  13. Green synthesis of boron doped graphene and its application as high performance anode material in Li ion battery

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sahoo, Madhumita; Sreena, K.P.; Vinayan, B.P.

    2015-01-15

    Graphical abstract: Boron doped graphene (B-G), synthesized by simple hydrogen induced reduction technique using boric acid as boron precursor, have more uneven surface as a result of smaller bonding distance of boron compared to carbon, showed high capacity and high rate capability compared to pristine graphene as an anode material for Li ion battery application. - Abstract: The present work demonstrates a facile route for the large-scale, catalyst free, and green synthesis approach of boron doped graphene (B-G) and its use as high performance anode material for Li ion battery (LIB) application. Boron atoms were doped into graphene framework withmore » an atomic percentage of 5.93% via hydrogen induced thermal reduction technique using graphite oxide and boric acid as precursors. Various characterization techniques were used to confirm the boron doping in graphene sheets. B-G as anode material shows a discharge capacity of 548 mAh g{sup −1} at 100 mA g{sup −1} after 30th cycles. At high current density value of 1 A g{sup −1}, B-G as anode material enhances the specific capacity by about 1.7 times compared to pristine graphene. The present study shows a simplistic way of boron doping in graphene leading to an enhanced Li ion adsorption due to the change in electronic states.« less

  14. 3D nitrogen-doped graphene foam with encapsulated germanium/nitrogen-doped graphene yolk-shell nanoarchitecture for high-performance flexible Li-ion battery

    PubMed Central

    Mo, Runwei; Rooney, David; Sun, Kening; Yang, Hui Ying

    2017-01-01

    Flexible electrochemical energy storage devices have attracted extensive attention as promising power sources for the ever-growing field of flexible and wearable electronic products. However, the rational design of a novel electrode structure with a good flexibility, high capacity, fast charge–discharge rate and long cycling lifetimes remains a long-standing challenge for developing next-generation flexible energy-storage materials. Herein, we develop a facile and general approach to three-dimensional (3D) interconnected porous nitrogen-doped graphene foam with encapsulated Ge quantum dot/nitrogen-doped graphene yolk-shell nano architecture for high specific reversible capacity (1,220 mAh g−1), long cycling capability (over 96% reversible capacity retention from the second to 1,000 cycles) and ultra-high rate performance (over 800 mAh g−1 at 40 C). This work paves a way to develop the 3D interconnected graphene-based high-capacity electrode material systems, particularly those that suffer from huge volume expansion, for the future development of high-performance flexible energy storage systems. PMID:28051065

  15. A general quantitative pH sensor developed with dicyandiamide N-doped high quantum yield graphene quantum dots.

    PubMed

    Wu, Zhu Lian; Gao, Ming Xuan; Wang, Ting Ting; Wan, Xiao Yan; Zheng, Lin Ling; Huang, Cheng Zhi

    2014-04-07

    A general quantitative pH sensor for environmental and intracellular applications was developed by the facile hydrothermal preparation of dicyandiamide (DCD) N-doped high quantum yield (QY) graphene quantum dots (GQDs) using citric acid (CA) as the carbon source. The obtained N-doped GQDs have excellent photoluminesence (PL) properties with a relatively high QY of 36.5%, suggesting that N-doped chemistry could promote the QY of carbon nanomaterials. The possible mechanism for the formation of the GQDs involves the CA self-assembling into a nanosheet structure through intermolecular H-bonding at the initial stage of the reaction, and then the pure graphene core with many function groups formed through the dehydration between the carboxyl and hydroxyl of the intermolecules under hydrothermal conditions. These N-doped GQDs have low toxicity, and are photostable and pH-sensitive between 1.81 to 8.96, giving a general pH sensor with a wide range of applications from real water to intracellular contents.

  16. Manganese oxide nanowires wrapped with nitrogen doped carbon layers for high performance supercapacitors.

    PubMed

    Li, Ying; Mei, Yuan; Zhang, Lin-Qun; Wang, Jian-Hai; Liu, An-Ran; Zhang, Yuan-Jian; Liu, Song-Qin

    2015-10-01

    In this study, manganese oxide nanowires wrapped by nitrogen-doped carbon layers (MnO(x)@NCs) were prepared by carbonization of poly(o-phenylenediamine) layer coated onto MnO2 nanowires for high performance supercapacitors. The component and structure of the MnO(x)@NCs were controlled through carbonization procedure under different temperatures. Results demonstrated that this composite combined the high conductivity and high specific surface area of nitrogen-doped carbon layers with the high pseudo-capacitance of manganese oxide nanowires. The as-prepared MnO(x)@NCs exhibited superior capacitive properties in 1 M Na2SO4 aqueous solution, such as high conductivity (4.167×10(-3) S cm(-1)), high specific capacitance (269 F g(-1) at 10 mV s(-1)) and long cycle life (134 F g(-1) after 1200 cycles at a scan rate of 50 mV s(-1)). It is reckoned that the present novel hybrid nanowires can serve as a promising electrode material for supercapacitors and other electrochemical devices. Copyright © 2015 Elsevier Inc. All rights reserved.

  17. Microscopic effects of Dy doping in the topological insulator Bi2Te3

    NASA Astrophysics Data System (ADS)

    Duffy, L. B.; Steinke, N.-J.; Krieger, J. A.; Figueroa, A. I.; Kummer, K.; Lancaster, T.; Giblin, S. R.; Pratt, F. L.; Blundell, S. J.; Prokscha, T.; Suter, A.; Langridge, S.; Strocov, V. N.; Salman, Z.; van der Laan, G.; Hesjedal, T.

    2018-05-01

    Magnetic doping with transition metal ions is the most widely used approach to break time-reversal symmetry in a topological insulator (TI)—a prerequisite for unlocking the TI's exotic potential. Recently, we reported the doping of Bi2Te3 thin films with rare-earth ions, which, owing to their large magnetic moments, promise commensurately large magnetic gap openings in the topological surface states. However, only when doping with Dy has a sizable gap been observed in angle-resolved photoemission spectroscopy, which persists up to room temperature. Although disorder alone could be ruled out as a cause of the topological phase transition, a fundamental understanding of the magnetic and electronic properties of Dy-doped Bi2Te3 remained elusive. Here, we present an x-ray magnetic circular dichroism, polarized neutron reflectometry, muon-spin rotation, and resonant photoemission study of the microscopic magnetic and electronic properties. We find that the films are not simply paramagnetic but that instead the observed behavior can be well explained by the assumption of slowly fluctuating, inhomogeneous, magnetic patches with increasing volume fraction as the temperature decreases. At liquid helium temperatures, a large effective magnetization can be easily introduced by the application of moderate magnetic fields, implying that this material is very suitable for proximity coupling to an underlying ferromagnetic insulator or in a heterostructure with transition-metal-doped layers. However, the introduction of some charge carriers by the Dy dopants cannot be excluded at least in these highly doped samples. Nevertheless, we find that the magnetic order is not mediated via the conduction channel in these samples and therefore magnetic order and carrier concentration are expected to be independently controllable. This is not generally the case for transition-metal-doped topological insulators, and Dy doping should thus allow for improved TI quantum devices.

  18. Carbon-doped SnS2 nanostructure as a high-efficiency solar fuel catalyst under visible light.

    PubMed

    Shown, Indrajit; Samireddi, Satyanarayana; Chang, Yu-Chung; Putikam, Raghunath; Chang, Po-Han; Sabbah, Amr; Fu, Fang-Yu; Chen, Wei-Fu; Wu, Chih-I; Yu, Tsyr-Yan; Chung, Po-Wen; Lin, M C; Chen, Li-Chyong; Chen, Kuei-Hsien

    2018-01-12

    Photocatalytic formation of hydrocarbons using solar energy via artificial photosynthesis is a highly desirable renewable-energy source for replacing conventional fossil fuels. Using an L-cysteine-based hydrothermal process, here we synthesize a carbon-doped SnS 2 (SnS 2 -C) metal dichalcogenide nanostructure, which exhibits a highly active and selective photocatalytic conversion of CO 2 to hydrocarbons under visible-light. The interstitial carbon doping induced microstrain in the SnS 2 lattice, resulting in different photophysical properties as compared with undoped SnS 2 . This SnS 2 -C photocatalyst significantly enhances the CO 2 reduction activity under visible light, attaining a photochemical quantum efficiency of above 0.7%. The SnS 2 -C photocatalyst represents an important contribution towards high quantum efficiency artificial photosynthesis based on gas phase photocatalytic CO 2 reduction under visible light, where the in situ carbon-doped SnS 2 nanostructure improves the stability and the light harvesting and charge separation efficiency, and significantly enhances the photocatalytic activity.

  19. High performance capacitive deionization using modified ZIF-8-derived, N-doped porous carbon with improved conductivity.

    PubMed

    Li, Yang; Kim, Jeonghun; Wang, Jie; Liu, Nei-Ling; Bando, Yoshio; Alshehri, Abdulmohsen Ali; Yamauchi, Yusuke; Hou, Chia-Hung; Wu, Kevin C-W

    2018-06-05

    Zeolitic imidazolate framework (ZIF) composite-derived carbon exhibiting large surface area and high micropore volume is demonstrated to be a promising electrode material for the capacitive deionization (CDI) application. However, some inherent serious issues (e.g., low electrical conductivity, narrow pore size, relatively low pore volume, etc.) are still observed for nitrogen-doped porous carbon particles, which restrict their CDI performance. To solve the above-mentioned problems, herein, we prepared gold-nanoparticle-embedded ZIF-8-derived nitrogen-doped carbon calcined at 800 °C (Au@NC800) and PEDOT doped-NC-800 (NC800-PEDOT). The newly generated NC800-PEDOT and Au@NC800 electrodes exhibited notably increased conductivity, and they also achieved high electrosorption capacities of 16.18 mg g-1 and 14.31 mg g-1, respectively, which were much higher than that of NC800 (8.36 mg g-1). Au@NC800 and NC800-PEDOT can be promisingly applicable as highly efficient CDI electrode materials.

  20. Highly Flexible and Conductive Glycerol-Doped PEDOT:PSS Films Prepared Under an Electric Field

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Hiroyuki; Aizawa, Kengo; Chonan, Yasunori; Komiyama, Takao; Aoyama, Takashi; Sakai, Eiichi; Qiu, Jianhui; Sato, Naoki

    2018-06-01

    Poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) films doped with several sugar alcohols, viz. xylitol (XL), glycerol (GL), and polyglycerol (PG), at various levels have been synthesized and their thermoelectric properties studied. Among these specimens, 2.5 vol.% GL-doped films showed the best performance with electrical conductivity σ, Seebeck coefficient S, and power factor S 2 σ at room temperature reaching 1040 S/cm, 19 μV/K, and 37 μW/m-K2, respectively. Next, we synthesized films under an electric field E pr for the purpose of crystal growth. GL-doped films showed σ enhancement with increase of E pr. The highest σ value of 1300 S/cm was attained at E pr = 4 kV/cm. S and thermal conductivity κ values were almost independent of E pr. The ZT value was calculated to be between 0.017 and 0.101 at room temperature. We also examined film flexibility. High flexibility was achieved on GL doping, and it was not deteriorated when synthesized under an electric field.

  1. Highly Flexible and Conductive Glycerol-Doped PEDOT:PSS Films Prepared Under an Electric Field

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Hiroyuki; Aizawa, Kengo; Chonan, Yasunori; Komiyama, Takao; Aoyama, Takashi; Sakai, Eiichi; Qiu, Jianhui; Sato, Naoki

    2018-04-01

    Poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) films doped with several sugar alcohols, viz. xylitol (XL), glycerol (GL), and polyglycerol (PG), at various levels have been synthesized and their thermoelectric properties studied. Among these specimens, 2.5 vol.% GL-doped films showed the best performance with electrical conductivity σ, Seebeck coefficient S, and power factor S 2 σ at room temperature reaching 1040 S/cm, 19 μV/K, and 37 μW/m-K2, respectively. Next, we synthesized films under an electric field E pr for the purpose of crystal growth. GL-doped films showed σ enhancement with increase of E pr. The highest σ value of 1300 S/cm was attained at E pr = 4 kV/cm. S and thermal conductivity κ values were almost independent of E pr. The ZT value was calculated to be between 0.017 and 0.101 at room temperature. We also examined film flexibility. High flexibility was achieved on GL doping, and it was not deteriorated when synthesized under an electric field.

  2. Nano silver diffusion behaviour on conductive polymer during doping process for high voltage application

    NASA Astrophysics Data System (ADS)

    Mohammad, A.; Mahmood, A.; Chin, K. T.; Danquah, M. K.; van Stratan, S.

    2017-06-01

    Conductive polymer had opened a new era of engineering for microelectronics and semiconductor applications. However, it is still a challenge for high voltage applications due to lower electrical conductivity compare to metals. This results tremendous energy losses during transmission and restricts its usage. In order to address such problem a novel method was investigated using nano silver particle doped iodothiophene since silver is the highest electrical conductive material. The experiments were carried out to study the organometallic diffusion behaviour of nanosilver doped iodothiophene with different concentration of iodothiophene. Five different mixing ratio between nanosilver and the solution of iodothiophene dissolved in diethyl ether were used which are 1:1.25, 1:1.5, 1:2.5, 1:3 and l:5. It was revealed that there is an effective threshold concentration of which the nano silver evenly distributed and there was no coagulation observed. These parameters laid the foundation of better doping process between the nano silver and the polymer significantly which would contribute developing conductive polymer towards high voltage application for industries that are vulnerable to corrosive environment.

  3. Microscopic signature of insulator-to-metal transition in highly doped semicrystalline conducting polymers in ionic-liquid-gated transistors

    NASA Astrophysics Data System (ADS)

    Tanaka, Hisaaki; Nishio, Satoshi; Ito, Hiroshi; Kuroda, Shin-ichi

    2015-12-01

    Electronic state of charge carriers, in particular, in highly doped regions, in thin-film transistors of a semicrystalline conducting polymer poly(2,5-bis(3-alkylthiophene-2-yl)thieno[3,2-b]thiophene), has been studied by using field-induced electron spin resonance (ESR) spectroscopy. By adopting an ionic-liquid gate insulator, a gate-controlled reversible electrochemical hole-doping of the polymer backbone is achieved, as confirmed from the change of the optical absorption spectra. The edge-on molecular orientation in the pristine film is maintained even after the electrochemical doping, which is clarified from the angular dependence of the g value. As the doping level increases, spin 1/2 polarons transform into spinless bipolarons, which is demonstrated from the spin-charge relation showing a spin concentration peak around 1%, contrasting to the monotonic increase in the charge concentration. At high doping levels, a drastic change in the linewidth anisotropy due to the generation of conduction electrons is observed, indicating the onset of metallic state, which is also supported by the temperature dependence of the spin susceptibility and the ESR linewidth. Our results suggest that semicrystalline conducting polymers become metallic with retaining their molecular orientational order, when appropriate doping methods are chosen.

  4. Enabling Earth-Abundant Pyrite (FeS2) Semiconductor Nanostructures for High Performance Photovoltaic Devices

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Jin, Song

    2014-11-18

    This project seeks to develop nanostructures of iron pyrite, an earth-abundant semiconductor, to enable their applications in high-performance photovoltaic (PV) devices. Growth of high purity iron pyrite nanostructures (nanowires, nanorods, and nanoplates), as well as iron pyrite thin films and single crystals, has been developed and their structures characterized. These structures have been fundamentally investigated to understand the origin of the low solar energy conversion efficiency of iron pyrite and various passivation strategies and doping approaches have been explored in order to improve it. By taking advantage of the high surface-to-bulk ratio in nanostructures and effective electrolyte gating, we fullymore » characterized both the surface inversion and bulk electrical transport properties for the first time through electrolyte-gated Hall measurements of pyrite nanoplate devices and show that pyrite is n-type in the bulk and p-type near the surface due to strong inversion, which has important consequences to using nanocrystalline pyrite for efficient solar energy conversion. Furthermore, through a comprehensive investigation on n-type iron pyrite single crystals, we found the ionization of high-density bulk deep donor states, likely resulting from bulk sulfur vacancies, creates a non-constant charge distribution and a very narrow surface space charge region that limits the total barrier height, thus satisfactorily explains the limited photovoltage and poor photoconversion efficiency of iron pyrite single crystals. These findings suggest new ideas on how to improve single crystal pyrite and nanocrystalline or polycrystalline pyrite films to enable them for high performance solar applications.« less

  5. Unusually high critical current of clean P-doped BaFe2As2 single crystalline thin film

    NASA Astrophysics Data System (ADS)

    Kurth, F.; Tarantini, C.; Grinenko, V.; Hänisch, J.; Jaroszynski, J.; Reich, E.; Mori, Y.; Sakagami, A.; Kawaguchi, T.; Engelmann, J.; Schultz, L.; Holzapfel, B.; Ikuta, H.; Hühne, R.; Iida, K.

    2015-02-01

    Microstructurally clean, isovalently P-doped BaFe2As2 (Ba-122) single crystalline thin films have been prepared on MgO (001) substrates by molecular beam epitaxy. These films show a superconducting transition temperature (Tc) of over 30 K although P content is around 0.22, which is lower than the optimal one for single crystals (i.e., 0.33). The enhanced Tc at this doping level is attributed to the in-plane tensile strain. The strained film shows high transport self-field critical current densities (Jc) of over 6 MA/cm2 at 4.2 K, which are among the highest for Fe based superconductors (FeSCs). In-field Jc exceeds 0.1 MA/cm2 at μ 0 H = 35 T for H ‖ a b and μ 0 H = 18 T for H ‖ c at 4.2 K, respectively, in spite of moderate upper critical fields compared to other FeSCs with similar Tc. Structural investigations reveal no defects or misoriented grains pointing to strong pinning centers. We relate this unexpected high Jc to a strong enhancement of the vortex core energy at optimal Tc, driven by in-plane strain and doping. These unusually high Jc make P-doped Ba-122 very favorable for high-field magnet applications.

  6. Luminescence properties of erbium doped sodium barium borate glass with silver nanoparticles

    NASA Astrophysics Data System (ADS)

    Rajeshree Patwari, D.; Eraiah, B.

    2018-02-01

    Alteration in the absorption features of rare earth (RE) doped glasses with silver nanoparticles is ever-challenging in photonics. Erbium (Er3+) doped glasses with composition (60-x-y)B2O3-30Na2CO3-10BaO-xEr2O3-yAgCl where (x=0.5, 1.0 and y=1.0 mol %) are synthesized using melt-quenching method. The density is determined by Archimedes principle and molar volumes are calculated. Glass samples were characterized by XRD and UV-Visible spectroscopy. UV-Visible spectra shows eleven prominent absorption peaks centred around 366, 378, 408, 442, 452, 489, 521, 547, 652, 800 and 977 nm equivalent to the rare earth (Er3+) ion transitions. The sample without rare earth shows no peaks which specifies that rare earth ion plays a spirited role in the glass matrix. The glass samples with silver and without rare earth ion shows plasmon peak on heat treatment. The energy band gap values calculated for direct and indirect transitions are in the range of 3.126-3.440eV and 2.58-3.177eV respectively. The refractive indices and Urbach energies are also determined. Photoluminescence spectra are recorded and studied for excitation of the most intense peaks of wavelengths 378 and 521nm. The luminescence of erbium ion is enhanced by the presence of silver when the concentration of rare earth ion is less than that of silver.

  7. Preparation of ordered mesoporous alumina-doped titania films with high thermal stability and their application to high-speed passive-matrix electrochromic displays.

    PubMed

    Jiang, Xiangfen; Bastakoti, Bishnu Prasad; Weng, Wu; Higuchi, Tetsuya; Oveisi, Hamid; Suzuki, Norihiro; Chen, Wei-Jung; Huang, Yu-Tzu; Yamauchi, Yusuke

    2013-08-12

    Ordered mesoporous alumina-doped titania thin films with anatase crystalline structure were prepared by using triblock copolymer Pluronic P123 as structure-directing agent. Uniform Al doping was realized by using aluminum isopropoxide as a dopant source which can be hydrolyzed together with titanium tetraisopropoxide. Aluminum doping into the titania framework can prevent rapid crystallization to the anatase phase, thereby drastically increasing thermal stability. With increasing Al content, the crystallization temperatures tend to increase gradually. Even when the Al content doped into the framework was increased to 15 mol %, a well-ordered mesoporous structure was obtained, and the mesostructural ordering was still maintained after calcination at 550 °C. During the calcination process, large uniaxial shrinkage occurred along the direction perpendicular to the substrate with retention of the horizontal mesoscale periodicity, whereby vertically oriented nanopillars were formed in the film. The resulting vertical porosity was successfully exploited to fabricate a high-speed and high-quality passive-matrix electrochromic display by using a leuco dye. The vertical nanospace in the films can effectively prevent drifting of the leuco dye. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Energetics of Intermediate Temperature Solid Oxide Fuel Cell Electrolytes: Singly and Doubly doped Ceria Systems

    NASA Astrophysics Data System (ADS)

    Buyukkilic, Salih

    Solid oxide fuel cells (SOFCs) have potential to convert chemical energy directly to electrical energy with high efficiency, with only water vapor as a by-product. However, the requirement of extremely high operating temperatures (~1000 °C) limits the use of SOFCs to only in large scale stationary applications. In order to make SOFCs a viable energy solution, enormous effort has been focused on lowering the operating temperatures below 700 °C. A low temperature operation would reduce manufacturing costs by slowing component degradation, lessening thermal mismatch problems, and sharply reducing costs of operation. In order to optimize SOFC applications, it is critical to understand the thermodynamic stabilities of electrolytes since they directly influence device stability, sustainability and performance. Rare-earth doped ceria electrolytes have emerged as promising materials for SOFC applications due to their high ionic conductivity at the intermediate temperatures (500--700 °C). However there is a fundamental lack of understanding regarding their structure, thermodynamic stability and properties. Therefore, the enthalpies of formation from constituent oxides and ionic conductivities were determined to investigate a relationship between the stability, composition, structural defects and ionic conductivity in rare earth doped ceria systems. For singly doped ceria electrolytes, we investigated the solid solution phase of bulk Ce1-xLnxO2-0.5x where Ln = Sm and Nd (0 ≤ x ≤ 0.30) and analyzed their enthalpies of formation, mixing and association, and bulk ionic conductivities while considering cation size mismatch and defect associations. It was shown that for ambient temperatures in the dilute dopant region, the positive heat of formation reaches a maximum as the system becomes increasingly less stable due to size mismatch. In concentrated region, stabilization to a certain solubility limit was observed probably due to the defect association of trivalent cations

  9. Tuning Chemical Potential Difference across Alternately Doped Graphene p-n Junctions for High-Efficiency Photodetection.

    PubMed

    Lin, Li; Xu, Xiang; Yin, Jianbo; Sun, Jingyu; Tan, Zhenjun; Koh, Ai Leen; Wang, Huan; Peng, Hailin; Chen, Yulin; Liu, Zhongfan

    2016-07-13

    Being atomically thin, graphene-based p-n junctions hold great promise for applications in ultrasmall high-efficiency photodetectors. It is well-known that the efficiency of such photodetectors can be improved by optimizing the chemical potential difference of the graphene p-n junction. However, to date, such tuning has been limited to a few hundred millielectronvolts. To improve this critical parameter, here we report that using a temperature-controlled chemical vapor deposition process, we successfully achieved modulation-doped growth of an alternately nitrogen- and boron-doped graphene p-n junction with a tunable chemical potential difference up to 1 eV. Furthermore, such p-n junction structure can be prepared on a large scale with stable, uniform, and substitutional doping and exhibits a single-crystalline nature. This work provides a feasible method for synthesizing low-cost, large-scale, high efficiency graphene p-n junctions, thus facilitating their applications in optoelectronic and energy conversion devices.

  10. Microwave-assisted one-pot synthesis of water-soluble rare-earth doped fluoride luminescent nanoparticles with tunable colors

    PubMed Central

    Mi, Cong-Cong; Tian, Zhen-huang; Han, Bao-fu; Mao, Chuan-bin; Xu, Shu-kun

    2012-01-01

    Polyethyleneimine (PEI) functionalized multicolor luminescent LaF3 nanoparticles were synthesized via a novel microwave-assisted method, which can achieve fast and uniform heating under eco-friendly and energy efficient conditions. The as-prepared nanoparticles possess a pure hexagonal structure with an average size of about 12 nm. When doped with different ions (Tb3+ and Eu3+), the morphology and structure of the nanoparticles were not changed, whereas the optical properties varied with doped ions and their molar ratio, and as a result emission of four different colors (green, yellow, orange and red) were achieved by simply switching the types of doping ions (Eu3+ versus Tb3 +) and the molar ratio of the two doping ions. PMID:22879690

  11. Laser-induced local activation of Mg-doped GaN with a high lateral resolution for high power vertical devices

    NASA Astrophysics Data System (ADS)

    Kurose, Noriko; Matsumoto, Kota; Yamada, Fumihiko; Roffi, Teuku Muhammad; Kamiya, Itaru; Iwata, Naotaka; Aoyagi, Yoshinobu

    2018-01-01

    A method for laser-induced local p-type activation of an as-grown Mg-doped GaN sample with a high lateral resolution is developed for realizing high power vertical devices for the first time. As-grown Mg-doped GaN is converted to p-type GaN in a confined local area. The transition from an insulating to a p-type area is realized to take place within about 1-2 μm fine resolution. The results show that the technique can be applied in fabricating the devices such as vertical field effect transistors, vertical bipolar transistors and vertical Schottkey diode so on with a current confinement region using a p-type carrier-blocking layer formed by this technique.

  12. Radiation hardening of rare-earth doped fiber amplifiers

    NASA Astrophysics Data System (ADS)

    Vivona, Marilena; Girard, Sylvain; Marcandella, Claude; Pinsard, Emmanuel; Laurent, Arnaud; Robin, Thierry; Cadier, Benoît; Cannas, Marco; Boukenter, Aziz; Ouerdane, Y.

    2017-11-01

    We investigated the radiation hardening of optical fiber amplifiers operating in space environments. Through a real-time analysis in active configuration, we evaluated the role of Ce in the improvement of the amplifier performance against ionizing radiations. Ce-codoping is an efficient hardening solution, acting both in the limitation of defects in the host glass matrix of RE-doped optical fibers and in the stabilization of lasing properties of the Er3+-ions. On the one hand, in the near-infrared region, radiation induced attenuation measurements show the absence of radiation induced P-related defect species in host glass matrix of the Ce-codoped active fibers; on the other hand, in the Ce-free fiber, the higher lifetime variation shows stronger local modifications around the Er3+-ions with the absence of Ce.

  13. Role of light satellites in the high-resolution Earth observation domain

    NASA Astrophysics Data System (ADS)

    Fishman, Moshe

    1999-12-01

    Current 'classic' applications using and exploring space based earth imagery are exclusive, narrow niche tailored, expensive and hardly accessible. On the other side new, inexpensive and widely used 'consumable' applications will be only developed concurrently to the availability of appropriate imagery allowing that process. A part of these applications can be imagined today, like WWW based 'virtual tourism' or news media, but the history of technological, cultural and entertainment evolution teaches us that most of future applications are unpredictable -- they emerge together with the platforms enabling their appearance. The only thing, which can be ultimately stated, is that the definitive condition for such applications is the availability of the proper imagery platform providing low cost, high resolution, large area, quick response, simple accessibility and quick dissemination of the raw picture. This platform is a constellation of Earth Observation satellites. Up to 1995 the Space Based High Resolution Earth Observation Domain was dominated by heavy, super-expensive and very inflexible birds. The launch of Israeli OFEQ-3 Satellite by MBT Division of Israel Aircraft Industries (IAI) marked the entrance to new era of light, smart and cheap Low Earth Orbited Imaging satellites. The Earth Resource Observation System (EROS) initiated by West Indian Space, is based on OFEQ class Satellites design and it is capable to gather visual data of Earth Surface both at high resolution and large image capacity. The main attributes, derived from its compact design, low weight and sophisticated logic and which convert the EROS Satellite to valuable and productive system, are discussed. The major advantages of Light Satellites in High Resolution Earth Observation Domain are presented and WIS guidelines featuring the next generation of LEO Imaging Systems are included.

  14. Thermoluminesence of gamma rays irradiated CaSO4 nanorods doped with different elements

    NASA Astrophysics Data System (ADS)

    Salah, Numan

    2015-01-01

    Nanorods of calcium sulfate (CaSO4) activated by Ag, Cu, Dy, Eu and Tb were synthesized by the co-precipitation technique. They were irradiated by γ-rays in a wide range of exposures and studied for their thermoluminesence (TL) properties. The as-synthesized samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and photoluminescence (PL) emission spectra. SEM images show that the samples doped with rare earths elements (i.e. Dy, Eu and Tb) have thinner nanorods than the other samples, while XRD pattern shows a complete crystalline structures in a monoclinic phase. The TL glow curves of these samples show two components. The first one include low temperature glow peaks at around 125 °C, while the second component shows high temperature peaks in the range 230-270 °C. These glow peaks diver from sample to sample by their TL intensity. The TL results are promising, particularly that of Tb and Eu. Tb doped sample is found to be a highly TL sensitive with a prominent glow peak at around 270 °C, while Eu has created very active, high dense electron traps. The later shows quite linear response in the whole studied exposures i.e. 10 Gy-10 kGy. These results show that Eu or Tb doped CaSO4 nanorods might be proper candidates as dosimeters for high doses of ionizing radiations used in irradiation of foods and seeds.

  15. Origin of high Li⁺ conduction in doped Li₇La₃Zr₂O₁₂ garnets

    DOE PAGES

    Chen, Yan; Rangasamy, Ezhiylmurugan; Liang, Chengdu; ...

    2015-08-06

    Substitution of a native ion in the crystals with a foreign ion that differs in valence ( aliovalent doping) has been widely attempted to upgrade solid-state ionic conductors for various charge carriers including O²⁻, H⁺, Li⁺, Na⁺, etc. The doping helps promote the high-conductive framework and dredge the tunnel for fast ion transport. The garnet-type Li₇La₃Zr₂O₁₂ (LLZO) is a fast Li⁺ solid conductor, which received much attention as an electrolyte candidate for all-solid-state lithium ion batteries, showing great potential to offer high energy density and minimize battery safety concerns to meet extensive applications in large energy storage systems such asmore » those for electric vehicles and aerospace. In the Li-stuffed garnet framework of LLZO, the 3D pathway formed by the incompletely occupied tetrahedral sites bridged by a single octahedron enables the superior Li⁺ conductivity. For optimal performance, many aliovalent-doping efforts have been made throughout metal elements (Al³⁺, Ta⁵⁺) and metalloid elements (Ga³⁺, Te⁶⁺) in the periodic table with various valences to stabilize the high-conductive phase and increase the Li vacancy concentration.« less

  16. Record power, ultra-broadband supercontinuum source based on highly GeO2 doped silica fiber.

    PubMed

    Jain, D; Sidharthan, R; Moselund, P M; Yoo, S; Ho, D; Bang, O

    2016-11-14

    We demonstrate highly germania doped fibers for mid-infrared supercontinuum generation. Experiments ensure a highest output power of 1.44 W for a broadest spectrum from 700 nm to 3200 nm and 6.4 W for 800 nm to 2700 nm from these fibers, while being pumped by a broadband Erbium-Ytterbium doped fiber based master oscillator power amplifier. The effect of repetition frequency of pump source and length of germania-doped fiber has also been investigated. Further, germania doped fiber has been pumped by conventional supercontinuum source based on silica photonic crystal fiber supercontinuum source. At low power, a considerable broadening of 200-300 nm was observed. Further broadening of spectrum was limited due to limited power of pump source. Our investigations reveal the unexploited potential of germania doped fiber for mid-infrared supercontinuum generation. These measurements ensure the potential of germania based photonic crystal fiber or a step-index fiber supercontinuum source for high power ultra-broad band emission being by pumped a 1060 nm or a 1550 nm laser source. To the best of our knowledge, this is the record power, ultra-broadband, and all-fiberized supercontinuum light source based on silica and germania fiber ever demonstrated to the date.

  17. Properties of Transition Metal Doped Alumina

    NASA Astrophysics Data System (ADS)

    Nykwest, Erik; Limmer, Krista; Brennan, Ray; Blair, Victoria; Ramprasad, Rampi

    Crystallographic texture can have profound effects on the properties of a material. One method of texturing is through the application of an external magnetic field during processing. While this method works with highly magnetic systems, doping is required to couple non-magnetic systems with the external field. Experiments have shown that low concentrations of rare earth (RE) dopants in alumina powders have enabled this kind of texturing. The magnetic properties of RE elements are directly related to their f orbital, which can have as many as 7 unpaired electrons. Since d-block elements can have as many as 5 unpaired electrons the effects of substitutional doping of 3d transition metals (TM) for Al in alpha (stable) and theta (metastable) alumina on the local structure and magnetic properties, in addition to the energetic cost, have been calculated by performing first-principles calculations based on density functional theory. This study has led to the development of general guidelines for the magnetic moment distribution at and around the dopant atom, and the dependence of this distribution on the dopant atom type and its coordination environment. It is anticipated that these findings can aid in the selection of suitable dopants help to guide parallel experimental efforts. This project was supported in part by an internship at the Army Research Laboratory, administered by the Oak Ridge Institute for Science and Education, along with a grant of computer time from the DoD High Performance Computing Modernization Program.

  18. Folate receptor targeted, rare-earth oxide nanocrystals for bi-modal fluorescence and magnetic imaging of cancer cells.

    PubMed

    Setua, Sonali; Menon, Deepthy; Asok, Adersh; Nair, Shantikumar; Koyakutty, Manzoor

    2010-02-01

    Targeted cancer imaging using rare-earth oxide nanocrystals, free from heavy metals (Cd, Se, Te, Hg and Pb), showing bright red-fluorescence and magnetic resonance imaging (MRI) is presented. Y(2)O(3) nanocrystals (YO NC) doped in situ with fluorescent (Eu(3+)) and paramagnetic (Gd(3+)) impurities and conjugated with a potential cancer targeting ligand, folic acid (FA), were prepared using an all-aqueous wet-chemical process. Structural, optical and magnetic properties of these multifunctional nanocrystals were investigated by X-ray diffraction, electron microscopy, photoluminescence and magnetization studies. Highly monodisperse nanocrystals of size approximately 20 nm with cubic bixbyite crystal structure showed bright red-fluorescence when doped with Eu(3+). Co-doping with Gd(3+) and mild air drying resulted significantly enhanced fluorescence quantum efficiency of approximately 60% together with paramagnetic functionality, enabling T(1)-weighted MR contrast with approximately 5 times higher spin-lattice relaxivity compared to the clinically used Gd(3+) contrast agent. Cytotoxicity and reactive oxygen stress studies show no toxicity by YO NC in both normal and cancer cells up to higher doses of 500 microm and longer incubation time, 48h. Cancer targeting capability of FA conjugated NCs was demonstrated on folate receptor positive (FR+) human nasopharyngeal carcinoma cells (KB) with FR depressed KB (FRd) and FR negative (FR-) lung cancer cells A549 as controls. Fluorescence microscopy and flow-cytometry data show highly specific binding and cellular uptake of large concentration of FA conjugated NCs on FR+ve cells compared to the controls. Thus, the present study reveals, unique bi-modal contrast imaging capability, non-toxicity and cancer targeting capability of multiple impurities doped rare-earth oxide nanocrystals that can find promising application in molecular imaging.

  19. Angle-Dependent Microresonator ESR Characterization of Locally Doped Gd3 + :Al2O3

    NASA Astrophysics Data System (ADS)

    Wisby, I. S.; de Graaf, S. E.; Gwilliam, R.; Adamyan, A.; Kubatkin, S. E.; Meeson, P. J.; Tzalenchuk, A. Ya.; Lindström, T.

    2016-08-01

    Interfacing rare-earth-doped crystals with superconducting circuit architectures provides an attractive platform for quantum memory and transducer devices. Here, we present the detailed characterization of such a hybrid system: a locally implanted rare-earth Gd3 + in Al2O3 spin system coupled to a superconducting microresonator. We investigate the properties of the implanted spin system through angular-dependent microresonator electron spin resonance (micro-ESR) spectroscopy. We find, despite the high-energy near-surface implantation, the resulting micro-ESR spectra to be in excellent agreement with the modeled Hamiltonian, supporting the integration of dopant ions into their relevant lattice sites while maintaining crystalline symmetries. Furthermore, we observe clear contributions from individual microwave field components of our microresonator, emphasizing the need for controllable local implantation.

  20. Towards the development of new phosphors with reduced content of rare earth elements: Structural and optical characterization of Ce:Tb: Al{sub 2}SiO{sub 5}

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chiriu, D.; Stagi, L.; Carbonaro, C.M.

    2016-05-15

    Highlights: • A new promising inert matrix as host of luminescent ions is proposed. • Al2SiO5 matrix is free from Rare earths (critical raw materials). • Doping the matrix with Ce and Tb we obtain an efficient green emitter. • Cerium acts as sensitizer for Terbium emission. - Abstract: A new promising inert matrix as host of luminescent ions is proposed. Al2SiO5 samples, doped with rare earths (Ce, Tb single doped and co-doped) are proposed as good prospect for the development of new UV–vis converter with reduced content of rare earths elements. Structural characterization by Raman, XRD spectroscopy and TEMmore » imaging reveals the sillimanite phase and nano sized dimension of the investigated powders. Optical characterization by steady time and time resolved emission spectroscopy for the single doped and co-doped samples allows to identify an efficient energy transfer from Ce to Tb ions under near UV excitation wavelength. The intense green emission observed in the Ce:Tb co-doped Al2SiO5 system suggests its potential application as efficient blue pumped green emitter phosphor to be exploited for white LED: to this purpose we tested the compound in combination with a red emitting doping ion recording for Ce:Tb:Cr:ASO system a correlated color temperature of 6720 K.« less

  1. High-resolution photoluminescence spectroscopy of Sn-doped ZnO single crystals

    DOE PAGES

    Kumar, E. Senthil; Mohammadbeigi, F.; Boatner, Lynn A.; ...

    2016-01-01

    Here, Group IV donors in ZnO are poorly understood, despite evidence that they are effective n-dopants. We present high-resolution photoluminescence spectroscopy studies of unintentionally doped and Sn doped ZnO single crystals grown by the chemical vapor transport method. Doped samples showed greatly increased emission from the I10 bound exciton transition which was recently proven to be related to the incorporation of Sn impurities based on radio-isotope studies. PL linewidths are exceptionally sharp for these samples, enabling clear identification of several donor species. Temperature dependent PL measurements of the I10 line emission energy and intensity dependence reveal a behavior similar tomore » other shallow donors in ZnO. Ionized donor bound exciton and two electron satellite transitions of the I10 transition are unambiguously identified and yield a donor binding energy of 71 meV. In contrast to recent reports of Ge-related donors in ZnO, the spectroscopic binding energy for the Sn-related donor bound exciton follows a linear relationship with donor binding energy (Haynes rule), confirming the shallow nature of this defect center, which we attribute to a SnZn double donor compensated by an unknown single acceptor.« less

  2. High-Definition Television (HDTV) Images for Earth Observations and Earth Science Applications

    NASA Technical Reports Server (NTRS)

    Robinson, Julie A.; Holland, S. Douglas; Runco, Susan K.; Pitts, David E.; Whitehead, Victor S.; Andrefouet, Serge M.

    2000-01-01

    As part of Detailed Test Objective 700-17A, astronauts acquired Earth observation images from orbit using a high-definition television (HDTV) camcorder, Here we provide a summary of qualitative findings following completion of tests during missions STS (Space Transport System)-93 and STS-99. We compared HDTV imagery stills to images taken using payload bay video cameras, Hasselblad film camera, and electronic still camera. We also evaluated the potential for motion video observations of changes in sunlight and the use of multi-aspect viewing to image aerosols. Spatial resolution and color quality are far superior in HDTV images compared to National Television Systems Committee (NTSC) video images. Thus, HDTV provides the first viable option for video-based remote sensing observations of Earth from orbit. Although under ideal conditions, HDTV images have less spatial resolution than medium-format film cameras, such as the Hasselblad, under some conditions on orbit, the HDTV image acquired compared favorably with the Hasselblad. Of particular note was the quality of color reproduction in the HDTV images HDTV and electronic still camera (ESC) were not compared with matched fields of view, and so spatial resolution could not be compared for the two image types. However, the color reproduction of the HDTV stills was truer than colors in the ESC images. As HDTV becomes the operational video standard for Space Shuttle and Space Station, HDTV has great potential as a source of Earth-observation data. Planning for the conversion from NTSC to HDTV video standards should include planning for Earth data archiving and distribution.

  3. Incorporating Earth Science into Other High School Science Classes

    NASA Astrophysics Data System (ADS)

    Manning, C. L. B.; Holzer, M.; Colson, M.; Courtier, A. M. B.; Jacobs, B. E.

    2016-12-01

    As states begin to review their standards, some adopt or adapt the NGSS and others write their own, many basing these on the Framework for K-12 Science Education. Both the NGSS and the Frameworks have an increased emphasis on Earth Science but many high school teachers are being asked to teach these standards in traditional Biology, Chemistry and Physics courses. At the Earth Educators Rendezvous, teachers, scientists, and science education researchers worked together to find the interconnections between the sciences using the NGSS and identified ways to reference the role of Earth Sciences in the other sciences during lectures, activities and laboratory assignments. Weaving Earth and Space sciences into the other curricular areas, the teams developed relevant problems for students to solve by focusing on using current issues, media stories, and community issues. These and other lessons and units of study will be presented along with other resources used by teachers to ensure students are gaining exposure and a deeper understanding of Earth and Space Science concepts.

  4. Doping Optimization for High Efficiency in Semiconductor Diode Lasers and Amplifiers

    DTIC Science & Technology

    2016-03-01

    resistance 20 mΩ Ith Threshold current 350 mA Using this partial Taylor expansion in (32), the solution for the doping magnitude is C ≈ √ (2/L) I qAV0...2014. [3] M. Kanskar, T. Earles , T. Goodnough, E. Stiers, D. Botez, and L. J. Mawst, “High power conversion efficiency Al-free diode lasers for pumping

  5. Strain-Induced Extrinsic High-Temperature Ferromagnetism in the Fe-Doped Hexagonal Barium Titanate

    PubMed Central

    Zorko, A.; Pregelj, M.; Gomilšek, M.; Jagličić, Z.; Pajić, D.; Telling, M.; Arčon, I.; Mikulska, I.; Valant, M.

    2015-01-01

    Diluted magnetic semiconductors possessing intrinsic static magnetism at high temperatures represent a promising class of multifunctional materials with high application potential in spintronics and magneto-optics. In the hexagonal Fe-doped diluted magnetic oxide, 6H-BaTiO3-δ, room-temperature ferromagnetism has been previously reported. Ferromagnetism is broadly accepted as an intrinsic property of this material, despite its unusual dependence on doping concentration and processing conditions. However, the here reported combination of bulk magnetization and complementary in-depth local-probe electron spin resonance and muon spin relaxation measurements, challenges this conjecture. While a ferromagnetic transition occurs around 700 K, it does so only in additionally annealed samples and is accompanied by an extremely small average value of the ordered magnetic moment. Furthermore, several additional magnetic instabilities are detected at lower temperatures. These coincide with electronic instabilities of the Fe-doped 3C-BaTiO3-δ pseudocubic polymorph. Moreover, the distribution of iron dopants with frozen magnetic moments is found to be non-uniform. Our results demonstrate that the intricate static magnetism of the hexagonal phase is not intrinsic, but rather stems from sparse strain-induced pseudocubic regions. We point out the vital role of internal strain in establishing defect ferromagnetism in systems with competing structural phases. PMID:25572803

  6. Indium oxide co-doped with tin and zinc: A simple route to highly conducting high density targets for TCO thin-film fabrication

    NASA Astrophysics Data System (ADS)

    Saadeddin, I.; Hilal, H. S.; Decourt, R.; Campet, G.; Pecquenard, B.

    2012-07-01

    Indium oxide co-doped with tin and zinc (ITZO) ceramics have been successfully prepared by direct sintering of the powders mixture at 1300 °C. This allowed us to easily fabricate large highly dense target suitable for sputtering transparent conducting oxide (TCO) films, without using any cold or hot pressing techniques. Hence, the optimized ITZO ceramic reaches a high relative bulk density (˜ 92% of In2O3 theoretical density) and higher than the well-known indium oxide doped with tin (ITO) prepared under similar conditions. All X-ray diagrams obtained for ITZO ceramics confirms a bixbyte structure typical for In2O3 only. This indicates a higher solubility limit of Sn and Zn when they are co-doped into In2O3 forming a solid-solution. A very low value of electrical resistivity is obtained for [In2O3:Sn0.10]:Zn0.10 (1.7 × 10-3 Ω cm, lower than ITO counterpart) which could be fabricated to high dense ceramic target suing pressure-less sintering.

  7. A 23-dB bismuth-doped optical fiber amplifier for a 1700-nm band

    PubMed Central

    Firstov, Sergei V.; Alyshev, Sergey V.; Riumkin, Konstantin E.; Khopin, Vladimir F.; Guryanov, Alexey N.; Melkumov, Mikhail A.; Dianov, Evgeny M.

    2016-01-01

    It is now almost twenty-five years since the first Erbium-Doped Fiber Amplifier (EDFA) was demonstrated. Currently, the EDFA is one of the most important elements widely used in different kinds of fiber-optic communication systems. However, driven by a constantly increasing demand, the network traffic, growing exponentially over decades, will lead to the overload of these systems (“capacity crunch”) because the operation of the EDFA is limited to a spectral region of 1530–1610 nm. It will require a search for new technologies and, in this respect, the development of optical amplifiers for new spectral regions can be a promising approach. Most of fiber-optic amplifiers are created using rare-earth-doped materials. As a result, wide bands in shorter (1150–1530 nm) and longer wavelength (1600–1750 nm) regions with respect to the gain band of Er-doped fibers are still uncovered. Here we report on the development of a novel fiber amplifier operating in a spectral region of 1640–1770 nm pumped by commercially available laser diodes at 1550 nm. This amplifier was realized using bismuth-doped high-germania silicate fibers fabricated by MCVD technique. PMID:27357592

  8. High-power and highly efficient diode-cladding-pumped Ho3+-doped silica fiber lasers.

    PubMed

    Jackson, Stuart D; Bugge, Frank; Erbert, Götz

    2007-11-15

    We demonstrate high-power operation from a singly Ho3+-doped silica fiber laser that is cladding pumped directly with diode lasers operating at 1150 nm. Internal slope efficiencies approaching the Stokes limit were produced, and the maximum output power was 2.2W. This result was achieved using a low Ho3+-ion concentration and La3+-ion codoping, which together limit the transfer of energy between excited Ho3+ ions.

  9. High-power ultralong-wavelength Tm-doped silica fiber laser cladding-pumped with a random distributed feedback fiber laser

    PubMed Central

    Jin, Xiaoxi; Du, Xueyuan; Wang, Xiong; Zhou, Pu; Zhang, Hanwei; Wang, Xiaolin; Liu, Zejin

    2016-01-01

    We demonstrated a high-power ultralong-wavelength Tm-doped silica fiber laser operating at 2153 nm with the output power exceeding 18 W and the slope efficiency of 25.5%. A random distributed feedback fiber laser with the center wavelength of 1173 nm was employed as pump source of Tm-doped fiber laser for the first time. No amplified spontaneous emissions or parasitic oscillations were observed when the maximum output power reached, which indicates that employing 1173 nm random distributed feedback fiber laser as pump laser is a feasible and promising scheme to achieve high-power emission of long-wavelength Tm-doped fiber laser. The output power of this Tm-doped fiber laser could be further improved by optimizing the length of active fiber, reflectivity of FBGs, increasing optical efficiency of pump laser and using better temperature management. We also compared the operation of 2153 nm Tm-doped fiber lasers pumped with 793 nm laser diodes, and the maximum output powers were limited to ~2 W by strong amplified spontaneous emission and parasitic oscillation in the range of 1900–2000 nm. PMID:27416893

  10. High-power ultralong-wavelength Tm-doped silica fiber laser cladding-pumped with a random distributed feedback fiber laser.

    PubMed

    Jin, Xiaoxi; Du, Xueyuan; Wang, Xiong; Zhou, Pu; Zhang, Hanwei; Wang, Xiaolin; Liu, Zejin

    2016-07-15

    We demonstrated a high-power ultralong-wavelength Tm-doped silica fiber laser operating at 2153 nm with the output power exceeding 18 W and the slope efficiency of 25.5%. A random distributed feedback fiber laser with the center wavelength of 1173 nm was employed as pump source of Tm-doped fiber laser for the first time. No amplified spontaneous emissions or parasitic oscillations were observed when the maximum output power reached, which indicates that employing 1173 nm random distributed feedback fiber laser as pump laser is a feasible and promising scheme to achieve high-power emission of long-wavelength Tm-doped fiber laser. The output power of this Tm-doped fiber laser could be further improved by optimizing the length of active fiber, reflectivity of FBGs, increasing optical efficiency of pump laser and using better temperature management. We also compared the operation of 2153 nm Tm-doped fiber lasers pumped with 793 nm laser diodes, and the maximum output powers were limited to ~2 W by strong amplified spontaneous emission and parasitic oscillation in the range of 1900-2000 nm.

  11. Low-temperature charged impurity scattering-limited conductivity in relatively high doped bilayer graphene

    NASA Astrophysics Data System (ADS)

    Hu, Bo

    2015-08-01

    Based on semiclassical Boltzamnn transport theory in random phase approximation, we develop a theoretical model to investigate low-temperature carrier transport properties in relatively high doped bilayer graphene. In the presence of both electron-hole puddles and band gap induced by charged impurities, we calculate low-temperature charged impurity scattering-limited conductivity in relatively high doped bilayer graphene. Our calculated conductivity results are in excellent agreement with published experimental data in all compensated gate voltage regime of study by using potential fluctuation parameter as only one free fitting parameter, indicating that both electron-hole puddles and band gap induced by charged impurities play an important role in carrier transport. More importantly, we also find that the conductivity not only depends strongly on the total charged impurity density, but also on the top layer charged impurity density, which is different from that obtained by neglecting the opening of band gap, especially for bilayer graphene with high top layer charged impurity density.

  12. Heavily Sn-doped GaAs with abrupt doping profiles grown by migration-enhanced epitaxy at low temperatures

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chavanapranee, Tosaporn; Horikoshi, Yoshiji

    The characteristics of heavily Sn-doped GaAs samples grown at 300 deg. C by a migration-enhanced epitaxy (MEE) technique are investigated in comparison with those of the samples grown by a conventional molecular-beam epitaxy (MBE) at 580 deg. C. While no discernible difference is observed in the low doping regime, the difference in doping characteristics between the MBE- and MEE-grown samples becomes apparent when the doping concentration exceeds 1x10{sup 19} cm{sup -3}. Sn atoms as high as 4x10{sup 21} cm{sup -3} can be incorporated into MEE-grown GaAs films, unlike the MBE-grown samples that have a maximum doping level limited around 1x10{supmore » 19} cm{sup -3}. Due to an effective suppression of Sn segregation in the MEE growth case, high quality GaAs films with abrupt high-concentration Sn-doping profiles are achieved with the doping concentrations of up to 2x10{sup 21} cm{sup -3}. It has been shown that even though a high concentration of Sn atoms is incorporated into the GaAs film, the electron concentration saturates at 6x10{sup 19} cm{sup -3} and then gradually decreases with Sn concentration. The uniform doping limitation, as well as the electron concentration saturation, is discussed by means of Hall-effect measurement, x-ray diffraction, and Raman scattering spectroscopy.« less

  13. Fabrication of lanthanum-doped thorium dioxide by high-energy ball milling and spark plasma sintering

    NASA Astrophysics Data System (ADS)

    Scott, Spencer M.; Yao, Tiankai; Lu, Fengyuan; Xin, Guoqing; Zhu, Weiguang; Lian, Jie

    2017-03-01

    High-energy ball milling was used to synthesize Th1-xLaxO2-0.5x (x = 0.09, 0.23) solid solutions, as well as improve the sinterability of ThO2 powders. Dense La-doped ThO2 pellets with theoretical density above 94% were consolidated by spark plasma sintering at temperatures above 1400 °C for 20 min, and the densification behavior and the non-equilibrium effects on phase and structure were investigated. A lattice contraction of the SPS-densified pellets occurred with increasing ball milling duration, and a secondary phase with increased La-content was observed in La-doped pellets. A dependence on the La-content and sintering duration for the onset of localized phase segregation has been proposed. The effects of high-energy ball milling, La-content, and phase formation on the thermal diffusivity were also studied for La-doped ThO2 pellets by laser flash measurement. Increasing La-content and high energy ball milling time decreases thermal diffusivity; while the sintering peak temperature and holding time beyond 1600 °C dramatically altered the temperature dependence of the thermal diffusivity beyond 600 °C.

  14. Structural and optical properties of rare earth-doped (Ba{sub 0.77}Ca{sub 0.23}){sub 1-x}(Sm, Nd, Pr, Yb){sub x}TiO{sub 3}

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Moraes, A. P. A.; Universidade Federal do Mato Grosso, 78060-900, Araguaia-MT; Filho, A. G. Souza

    2011-06-15

    The structural, dielectric, and vibrational properties of pure and rare earth (RE)-doped Ba{sub 0.77}Ca{sub 0.23}TiO{sub 3} (BCT23; RE = Nd, Sm, Pr, Yb) ceramics obtained via solid-state reaction were investigated. The pure and RE-doped BCT23 ceramics sintered at 1450 deg. C in air for 4 h showed a dense microstructure in all ceramics. The use of RE ions as dopants introduced lattice-parameter changes that manifested in the reduction of the volume of the unit cell. RE-doped BCT23 samples exhibit a more homogenous microstructure due to the absence of a Ti-rich phase in the grain boundaries as demonstrated by scanning electronmore » microscopy imaging. The incorporation of REs led to perturbations of the local symmetry of TiO{sub 6} octahedra and the creation of a new Raman mode. The results of Raman scattering measurements indicated that the Curie temperature of the ferroelectric phase transition depends on the RE ion and ion content, with the Curie temperature shifting toward lower values as the RE content increases, with the exception of Yb{sup 3+} doping, which did not affect the ferroelectric phase transition temperature. The phase transition behavior is explained using the standard soft mode model. Electronic paramagnetic resonance measurements showed the existence of Ti vacancies in the structure of RE-doped BCT23. Defects are created via charge compensation mechanisms due to the incorporation of elements with a different valence state relative to the ions of the pure BCT23 host. It is concluded that the Ti vacancies are responsible for the activation of the Raman mode at 840 cm{sup -1}, which is in agreement with lattice dynamics calculations.« less

  15. Fabrication of water-dispersible and highly conductive PSS-doped PANI/graphene nanocomposites using a high-molecular weight PSS dopant and their application in H2S detection

    NASA Astrophysics Data System (ADS)

    Cho, Sunghun; Lee, Jun Seop; Jun, Jaemoon; Kim, Sung Gun; Jang, Jyongsik

    2014-11-01

    This work describes the fabrication of poly(4-styrenesulfonic acid)-doped polyaniline/graphene (PSS-doped PANI/graphene) nanocomposites and their use as sensing elements for hydrogen sulfide (H2S) detection. PSS with a weight-average molecular weight (Mw) of 1.96 × 106 was synthesized using low-temperature free-radical polymerization. The PSS was used as both a doping agent and a binding agent for the polymerization of aniline monomers in a biphasic system (water-chloroform) at -50 °C. The high Mw of PSS resulted in relatively large particle sizes and smooth surfaces of the PSS-doped PANI. These physical characteristics, in turn, resulted in low interparticle resistance and high conductivity. In addition, the PSS allowed homogeneous dispersion of reduced graphene sheets through electrostatic repulsion. The prepared PSS-doped PANI/graphene solutions showed good compatibility with flexible poly(ethylene terephthalate) (PET) substrates, making them suitable for flexible sensor electrodes. Changes in the charge-transport properties, such as protonation level, conjugation length, crystalline structure, and charge-transfer resistance, of the electrode materials were the main factors influencing the electrical and sensor performance of the PSS-doped PANI-based electrodes. PSS-doped PANI/graphene composites containing 30 wt% graphene showed the highest conductivity (168.4 S cm-1) and the lowest minimum detection level (MDL) for H2S gas (1 ppm). This result is consistent with the observed improvements in charge transport in the electrode materials via strong π-π stacking interactions between the PANI and the graphene sheets.This work describes the fabrication of poly(4-styrenesulfonic acid)-doped polyaniline/graphene (PSS-doped PANI/graphene) nanocomposites and their use as sensing elements for hydrogen sulfide (H2S) detection. PSS with a weight-average molecular weight (Mw) of 1.96 × 106 was synthesized using low-temperature free-radical polymerization. The PSS was

  16. NAVIGATION PERFORMANCE IN HIGH EARTH ORBITS USING NAVIGATOR GPS RECEIVER

    NASA Technical Reports Server (NTRS)

    Bamford, William; Naasz, Bo; Moreau, Michael C.

    2006-01-01

    NASA GSFC has developed a GPS receiver that can acquire and track GPS signals with sensitivity significantly lower than conventional GPS receivers. This opens up the possibility of using GPS based navigation for missions in high altitude orbit, such as Geostationary Operational Environmental Satellites (GOES) in a geostationary orbit, and the Magnetospheric MultiScale (MMS) Mission, in highly eccentric orbits extending to 12 Earth radii and higher. Indeed much research has been performed to study the feasibility of using GPS navigation in high Earth orbits and the performance achievable. Recently, GSFC has conducted a series of hardware in-the-loop tests to assess the performance of this new GPS receiver in various high Earth orbits of interest. Tracking GPS signals to down to approximately 22-25 dB-Hz, including signals from the GPS transmitter side-lobes, steady-state navigation performance in a geostationary orbit is on the order of 10 meters. This paper presents the results of these tests, as well as sensitivity analysis to such factors as ionosphere masks, use of GPS side-lobe signals, and GPS receiver sensitivity.

  17. Highly conducting and crystalline doubly doped tin oxide films fabricated using a low-cost and simplified spray technique

    NASA Astrophysics Data System (ADS)

    Ravichandran, K.; Muruganantham, G.; Sakthivel, B.

    2009-11-01

    Doubly doped (simultaneous doping of antimony and fluorine) tin oxide films (SnO 2:Sb:F) have been fabricated by employing an inexpensive and simplified spray technique using perfume atomizer from aqueous solution of SnCl 2 precursor. The structural studies revealed that the films are highly crystalline in nature with preferential orientation along the (2 0 0) plane. It is found that the size of the crystallites of the doubly doped tin oxide films is larger (69 nm) than that (27 nm) of their undoped counterparts. The dislocation density of the doubly doped film is lesser (2.08×10 14 lines/m 2) when compared with that of the undoped film (13.2×10 14 lines/m 2), indicating the higher degree of crystallinity of the doubly doped films. The SEM images depict that the films are homogeneous and uniform. The optical transmittance in the visible range and the optical band gap of the doubly doped films are 71% and 3.56 eV respectively. The sheet resistance (4.13 Ω/□) attained for the doubly doped film in this study is lower than the values reported for spray deposited fluorine or antimony doped tin oxide films prepared from aqueous solution of SnCl 2 precursor (without using methanol or ethanol).

  18. NH3 assisted photoreduction and N-doping of graphene oxide for high performance electrode materials in supercapacitors

    NASA Astrophysics Data System (ADS)

    Huang, Haifu; Luo, Guangsheng; Xu, Lianqiang; Lei, Chenglong; Tang, Yanmei; Tang, Shaolong; Du, Youwei

    2015-01-01

    Nitrogen-doped graphene was synthesized by simple photoreduction of graphene oxide (GO) deposited on nickel foam under NH3 atmosphere. The combination of photoreduction and NH3 not only reduces the GO in a shorter time but also induces nitrogen doping easily. The nitrogen doped content of N-rGO@NF reaches a high of 5.99 at% with 15 min of irradiation. The nitrogen-doped graphene deposited on Ni foam (N-rGO@NF) can be directly used as an electrode for supercapacitors, without any conductive agents and polymer binders. In the electrochemical measurement, N-rGO@NF displays remarkable electrochemical performance. In particular, the N-rGO@NF irradiated for 45 min at a high current density of 92.3 A g-1 retained about 77% (190.4 F g-1) of its initial specific capacitance (247.1 F g-1 at 0.31 A g-1). Furthermore, the stable voltage window could be extended to 2.0 and 1.5 V by using Li2SO4 and a mixed Li2SO4/KOH electrolyte, and the maximum energy density was high up to 32.6 and 21.2 Wh kg-1, respectively. The results show that compared to Li2SO4, a mixed electrolyte (Li2SO4/KOH) more efficiently balances the relationship between the high energy densities and high power densities.Nitrogen-doped graphene was synthesized by simple photoreduction of graphene oxide (GO) deposited on nickel foam under NH3 atmosphere. The combination of photoreduction and NH3 not only reduces the GO in a shorter time but also induces nitrogen doping easily. The nitrogen doped content of N-rGO@NF reaches a high of 5.99 at% with 15 min of irradiation. The nitrogen-doped graphene deposited on Ni foam (N-rGO@NF) can be directly used as an electrode for supercapacitors, without any conductive agents and polymer binders. In the electrochemical measurement, N-rGO@NF displays remarkable electrochemical performance. In particular, the N-rGO@NF irradiated for 45 min at a high current density of 92.3 A g-1 retained about 77% (190.4 F g-1) of its initial specific capacitance (247.1 F g-1 at 0.31 A g-1

  19. Replacing critical rare earth materials in high energy density magnets

    NASA Astrophysics Data System (ADS)

    McCallum, R. William

    2012-02-01

    High energy density permanent magnets are crucial to the design of internal permanent magnet motors (IPM) for hybride and electric vehicles and direct drive wind generators. Current motor designs use rare earth permanent magnets which easily meet the performance goals, however, the rising concerns over cost and foreign control of the current supply of rare earth resources has motivated a search for non-rare earth based permanent magnets alloys with performance metrics which allow the design of permanent magnet motors and generators without rare earth magnets. This talk will discuss the state of non-rare-earth permanent magnets and efforts to both improve the current materials and find new materials. These efforts combine first principles calculations and meso-scale magnetic modeling with advance characterization and synthesis techniques in order to advance the state of the art in non rare earth permanent magnets. The use of genetic algorithms in first principle structural calculations, combinatorial synthesis in the experimental search for materials, atom probe microscopy to characterize grain boundaries on the atomic level, and other state of the art techniques will be discussed. In addition the possibility of replacing critical rare earth elements with the most abundant rare earth Ce will be discussed.

  20. Advances in the growth of alkaline-earth halide single crystals for scintillator detectors

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Boatner, Lynn A; Ramey, Joanne Oxendine; Kolopus, James A

    2014-01-01

    Alkaline-earth scintillators such as strontium iodide and other alkaline-earth halides activated with divalent europium represent some of the most efficient and highest energy resolution scintillators for use as gamma-ray detectors in a wide range of applications. These applications include the areas of nuclear nonproliferation, homeland security, the detection of undeclared nuclear material, nuclear physics and materials science, medical diagnostics, space physics, high energy physics, and radiation monitoring systems for first responders, police, and fire/rescue personnel. Recent advances in the growth of large single crystals of these scintillator materials hold the promise of higher crystal yields and significantly lower detector productionmore » costs. In the present work, we describe new processing protocols that, when combined with our molten salt filtration methods, have led to advances in achieving a significant reduction of cracking effects during the growth of single crystals of SrI2:Eu2+. In particular, we have found that extended pumping on the molten crystal-growth charge under vacuum for time periods extending up to 48 hours is generally beneficial in compensating for variations in the alkaline-earth halide purity and stoichiometry of the materials as initially supplied by commercial sources. These melt-pumping and processing techniques are now being applied to the purification of CaI2:Eu2+ and some mixed-anion europium-doped alkaline-earth halides prior to single-crystal growth by means of the vertical Bridgman technique. The results of initial studies of the effects of aliovalent doping of SrI2:Eu2+ on the scintillation characteristics of this material are also described.« less

  1. Effects of Concentration of Nanoscale Tin-Doped Indium Oxide on Electrical Breakdown of High-Resistance Liquid Crystal

    NASA Astrophysics Data System (ADS)

    Liang, Bau-Jy; Liu, Don-Gey; Chang, Chih-Yuan; Shie, Wun-Yi

    2011-05-01

    According to our previous study, a high concentration of nanoscale tin-doped indium oxide (ITO) may be beneficial for protecting liquid crystal (LC) against attacks by electrostatic discharge (ESD). In this study, the influence of high-voltage stresses in an ESD test was investigated for cells doped with different concentrations of ITO. It was found that nano-ITO with a concentration of 0.4% in weight ratio deteriorated the physical properties of LC of transparency transition and charge retention. However, our experiment showed that the capability of ESD protection for the doped LC was still improved at the ITO concentration of 0.4 wt %. This finding supports the proposed model in our previous report. The role of ITO in the LC is not always beneficial, as discussed in this paper.

  2. Influence of high Mg doping on the microstructural and opto-electrical properties of AlGaN alloys

    NASA Astrophysics Data System (ADS)

    Xu, Qingjun; Zhang, Shiying; Liu, Bin; Tao, Tao; Xie, Zili; Xiu, Xiangqian; Chen, Dunjun; Chen, Peng; Han, Ping; Zheng, Youdou; Zhang, Rong

    2018-07-01

    Mg-doped AlxGa1-xN (x = 0.23 and 0.35) alloys have been grown on GaN templates with high temperature AlN (HT-AlN) interlayer by metalorganic chemical vapor deposition (MOCVD). A combination of secondary ion mass spectrometry (SIMS) and transmission electron microscopy (TEM) indicates the formation of more inversion domains in the high Al mole fraction Mg-doped AlGaN alloys at Mg concentration ∼1020 cm-3. For Mg-doped Al0.23Ga0.77N epilayer, the analysis of cathodoluminescence (CL) spectra supports the existence of self-compensation effects due to the presence of intrinsic defects and Mg-related centers. The energy level of Mg is estimated to be around 193 meV from the temperature dependence of the resistivity measured by Hall effect experiments. And hole concentration and mobility are measured to be 1.2 × 1018 cm-3 and 0.56 cm2/V at room temperature, respectively. The reduction of acceptor activation energy and low hole mobility are attributed to inversion domains and self-compensation. Moreover, impurity band conduction is dominant in carrier transport up to a relatively higher temperature in high Al content Mg-doped AlGaN alloys.

  3. Elasticity of Deep-Earth Materials at High P and T: Implication for Earths Lower Mantle

    NASA Astrophysics Data System (ADS)

    Bass, Jay; Sinogeikin, S. V.; Mattern, Estelle; Jackson, J. M.; Matas, J.; Wang, J.; Ricard, Y.

    2005-03-01

    Brillouin spectroscopy allows measurements of sound velocities and elasticity on phases of geophysical interest at high Pressures and Temperatures. This technique was used to measure the properties of numerous important phases of Earths deep interior. Emphasis is now on measurements at elevated P-T conditions, and measurements on dense polycrystals. Measurements to 60 GPa were made using diamond anvil cells. High temperature is achieved by electrical resistance and laser heating. Excellent results are obtained for polycrystalline samples of dense oxides such as silicate spinels, and (Mg,Al)(Si,Al)O3 --perovskites. A wide range of materials can now be characterized. These and other results were used to infer Earths average lower mantle composition and thermal structure by comparing mineral properties at lower mantle P-T conditions to global Earth models. A formal inversion procedure was used. Inversions of density and bulk sound velocity do not provide robust compositional and thermal models. Including shear properties in the inversions is important to obtain unique solutions. We discuss the range of models consistent with present lab results, and data needed to further refine lower mantle models.

  4. A model for the high-temperature transport properties of heavily doped n-type silicon-germanium alloys

    NASA Technical Reports Server (NTRS)

    Vining, Cronin B.

    1991-01-01

    A model is presented for the high-temperature transport properties of large-grain-size, heavily doped n-type silicon-germanium alloys. Electron and phonon transport coefficients are calculated using standard Boltzmann equation expressions in the relaxation time approximation. Good agreement with experiment is found by considering acoustic phonon and ionized impurity scattering for electrons, and phonon-phonon, point defect, and electron-phonon scattering for phonons. The parameters describing electron transport in heavily doped and lightly doped materials are significantly different and suggest that most carriers in heavily doped materials are in a band formed largely from impurity states. The maximum dimensionless thermoelectric figure of merit for single-crystal, n-type Si(0.8)Ge(0.2) at 1300 K is estimated at ZT about 1.13 with an optimum carrier concentration of n about 2.9 x 10 to the 20th/cu cm.

  5. Doping management for high-power fiber lasers: 100 W, few-picosecond pulse generation from an all-fiber-integrated amplifier.

    PubMed

    Elahi, P; Yılmaz, S; Akçaalan, O; Kalaycıoğlu, H; Oktem, B; Senel, C; Ilday, F Ö; Eken, K

    2012-08-01

    Thermal effects, which limit the average power, can be minimized by using low-doped, longer gain fibers, whereas the presence of nonlinear effects requires use of high-doped, shorter fibers to maximize the peak power. We propose the use of varying doping levels along the gain fiber to circumvent these opposing requirements. By analogy to dispersion management and nonlinearity management, we refer to this scheme as doping management. As a practical first implementation, we report on the development of a fiber laser-amplifier system, the last stage of which has a hybrid gain fiber composed of high-doped and low-doped Yb fibers. The amplifier generates 100 W at 100 MHz with pulse energy of 1 μJ. The seed source is a passively mode-locked fiber oscillator operating in the all-normal-dispersion regime. The amplifier comprises three stages, which are all-fiber-integrated, delivering 13 ps pulses at full power. By optionally placing a grating compressor after the first stage amplifier, chirp of the seed pulses can be controlled, which allows an extra degree of freedom in the interplay between dispersion and self-phase modulation. This way, the laser delivers 4.5 ps pulses with ~200 kW peak power directly from fiber, without using external pulse compression.

  6. Combinatorial search of rare-earth free permanent magnets

    NASA Astrophysics Data System (ADS)

    Gao, Tieren; Takeuchi, Ichiro; Fackler, Sean; Fang, Lei; Zhang, Ying; Krammer, Matthew; Anderson, Iver; McCallum, Bill; University of Maryland Collaboration; Ames Laboratory Collaboration

    2013-03-01

    Permanent magnets play important roles in modern technologies such as in generators, motors, speakers, and relays. Today's high performance permanent magnets contain at least one rare earth element such as Nd, Sm, Pr and Dy. However, rare earth elements are increasingly rare and expensive, and alternative permanent magnet materials which do not contain them are needed by the industry. We are using the thin film composition spread technique to explore novel compositions of permanent magnets without rare-earth. Ternary co-sputtering is used to generate composition spreads. We have thus far looked at Mo doped Fe-Co as one of the initial systems to search for possible compounds with enhanced coercive fields. The films were deposited on Si (100) substrates and annealed at different temperatures. The structural properties of films are mapped by synchrotron diffraction. We find that there is a structural transition from a crystalline to an amorphous state at about 20% atomic Mo. With increasing annealing temperature, the Mo onset concentration of the structural transition increases from 25% for 600°C to 35% for 700°C. We find that some of compounds display enhanced coercive field. With increasing Mo concentration, the magnetization of Fe-Co-Mo begins to switch from in-plane to out-of-plane direction. This work is funded by the BREM (Beyond Rare-earth Magnet) project (DOE EERE).

  7. Problem-Based Learning and Earth System Science - The ESSEA High School Earth System Science Online Course

    NASA Astrophysics Data System (ADS)

    Myers, R.; Botti, J.

    2002-12-01

    The high school Earth system science course is web based and designed to meet the professional development needs of science teachers in grades 9-12. Three themes predominate this course: Earth system science (ESS) content, collaborative investigations, and problem-based learning (PBL) methodology. PBL uses real-world contexts for in-depth investigations of a subject matter. Participants predict the potential impacts of the selected event on Earth's spheres and the subsequent feedback and potential interactions that might result. PBL activities start with an ill-structured problem that serves as a springboard to team engagement. These PBL scenarios contain real-world situations. Teams of learners conduct an Earth system science analysis of the event and make recommendations or offer solutions regarding the problem. The course design provides an electronic forum for conversations, debate, development, and application of ideas. Samples of threaded discussions built around ESS thinking in science and PBL pedagogy will be presented.

  8. Problem-Based Learning and Earth System Science - The ESSEA High School Earth System Science Online Course

    NASA Astrophysics Data System (ADS)

    Myers, R. J.; Botti, J. A.

    2001-12-01

    The high school Earth system science course is web based and designed to meet the professional development needs of science teachers in grades 9-12. Three themes predominate this course: Earth system science (ESS) content, collaborative investigations, and problem-based learning (PBL) methodology. PBL uses real-world contexts for in-depth investigations of a subject matter. Participants predict the potential impacts of the selected event on Earth's spheres and the subsequent feedback and potential interactions that might result. PBL activities start with an ill-structured problem that serves as a springboard to team engagement. These PBL scenarios contain real-world situations. Teams of learners conduct an Earth system science analysis of the event and make recommendations or offer solutions regarding the problem. The course design provides an electronic forum for conversations, debate, development, and application of ideas. Samples of threaded discussions built around ESS thinking in science and PBL pedagogy will be presented.

  9. Site preference for luminescent activator ions in doped fluoroperovskite RbZnF3.

    PubMed

    Saroj, Sanjay Kumar; Nagarajan, Rajamani

    2018-08-05

    With the dual objective of investigating the site preferences of larger sized activator ions and to append luminescence property to the perovskite structured RbZnF 3 , doping of manganese(II), cerium(III), europium(III) and terbium(III) ions (5 mol%) was carried out. Although cubic symmetry of RbZnF 3 was preserved for all the doped samples, site preference of rare-earth ions for the A-site Rb + leading to an inverse perovskite arrangement has been noticed from careful analysis of lattice parameters from refinement of powder X-ray diffraction data. Undoped RbZnF 3 exhibited rod-like morphology in the transmission electron microscopic image. In addition to an intense band around 230 nm assignable to the charge transfer from ZnF 3 - to Rb + , typical transitions of respective dopant ions were observed in their UV-visible spectra. The doped samples showed luminescence in blue, green and red regions and time decay experiments suggested uniform dispersion of them without any clustering effect. The lower phonon energy of RbZnF 3 matrix by virtue of the presence of heavier rubidium at the A-site together with its doping with rare-earth ions resulting in an inverse perovskite like arrangement could favour their utility in various practical applications. Copyright © 2018 Elsevier B.V. All rights reserved.

  10. Alkaline Earth Core Level Photoemission Spectroscopy of High-Temperature Superconductors

    NASA Technical Reports Server (NTRS)

    Vasquez, R.

    1993-01-01

    This paper examines photoemission measurements of the alkaline Earth core levels of high-temperature superconductors and related materials, models that seek to explain the large negative shifts observed relative to the corresponding alkaline Earth metals, and the effect of lattice site disorder on the core level spectra and the presence or absence of intrinsic surface peaks.

  11. Recent Progress in the Development of Neodymium Doped Ceramic Yttria

    NASA Technical Reports Server (NTRS)

    Prasad, Narasimha S.; Edwards, Chris; Trivedi, Sudhir B.; Kutcher, Susan; Wang, Chen-Chia; Kim, Joo-Soo; Hommerich, Uwe; Shukla, Vijay; Sadangi, Rajendra; Kear, Bernard

    2007-01-01

    Solid-state lasers play a significant role in providing the technology necessary for active remote sensing of the atmosphere. Neodymium doped yttria (Nd:Y2O3) is considered to be an attractive material due to its possible lasing wavelengths of aprrox.914 nm and approx.946 nm for ozone profiling. These wavelengths when frequency tripled can generate UV light at approx.305 nm and approx.315 nm, which is particularly useful for ozone sensing using differential absorption lidar technique. For practical realization of space based UV transmitter technology, ceramic Nd:Y2O3 material is considered to possess great potential. A plasma melting and quenching method has been developed to produce Nd3+ doped powders for consolidation into Nd:Y2O3 ceramic laser materials. This far-from-equilibrium processing methodology allows higher levels of rare earth doping than can be achieved by equilibrium methods. The method comprises of two main steps: (a) plasma melting and quenching to generate dense, and homogeneous doped metastable powders, (b) pressure assisted consolidation of these powders by hot isostatic pressing to make dense nanocomposite ceramics. Using this process, several 1" x 1" ceramic cylinders have been produced. The infrared transmission of undoped Y2O3 ceramics was as high as approx.75% without anti-reflection coating. In the case of Nd:Y2O3 ceramics infrared transmission values of approx.50% were achieved. Furthermore, Nd:Y2O3 samples with dopant concentrations of up to approx.2 at. % were prepared without significant emission quenching.

  12. P-Doped NiCo2S4 nanotubes as battery-type electrodes for high-performance asymmetric supercapacitors.

    PubMed

    Lin, Jinghuang; Wang, Yiheng; Zheng, Xiaohang; Liang, Haoyan; Jia, Henan; Qi, Junlei; Cao, Jian; Tu, Jinchun; Fei, Weidong; Feng, Jicai

    2018-06-19

    NiCo2S4 is a promising electrode material for supercapacitors, due to its rich redox reactions and intrinsically high conductivity. Unfortunately, in most cases, NiCo2S4-based electrodes often suffer from low specific capacitance, low rate capability and fast capacitance fading. Herein, we have rationally designed P-doped NiCo2S4 nanotube arrays to improve the electrochemical performance through a phosphidation reaction. Characterization results demonstrate that the P element is successfully doped into NiCo2S4 nanotube arrays. Electrochemical results demonstrate that P-doped NiCo2S4 nanotube arrays exhibit better electrochemical performance than pristine NiCo2S4, e.g. higher specific capacitance (8.03 F cm-2 at 2 mA cm-2), good cycling stability (87.5% capacitance retention after 5000 cycles), and lower charge transfer resistance. More importantly, we also assemble an asymmetric supercapacitor using P-doped NiCo2S4 nanotube arrays and activated carbon on carbon cloth, which delivers a maximum energy density of 42.1 W h kg-1 at a power density of 750 W kg-1. These results demonstrate that the as-fabricated P-doped NiCo2S4 nanotube arrays on carbon cloth show great potential as a battery-type electrode for high-performance supercapacitors.

  13. High Capacity of Hard Carbon Anode in Na-Ion Batteries Unlocked by PO x Doping

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Li, Zhifei; Ma, Lu; Surta, Todd Wesley

    2016-08-12

    The capacity of hard carbon anodes in Na-ion batteries 2.5 rarely reaches values beyond 300 mAh/g. We report that doping POx into local structures of hard carbon increases its reversible capacity from 283 to 359 mAh/g. We confirm that the doped POx is redox inactive by X-ray adsorption near edge structure measurements, thus not contributing to the higher capacity. We observe two significant changes of hard carbon's local structures caused by doping. First, the (002) d-spacing inside the turbostratic nanodomains is increased, revealed by both laboratory and synchrotron X-ray diffraction. Second, doping turns turbostratic nanodomains more defective along ab planes,more » indicated by neutron total scattering and the associated pair distribution function studies. The local structural changes of hard carbon are correlated to the higher capacity, where both the plateau and slope regions in the potential profiles are enhanced. Our study demonstrates that Na-ion storage in hard carbon heavily depends on carbon local structures, where such structures, despite being disordered, can be tuned toward unusually high capacities.« less

  14. High quality nitrogen-doped zinc oxide thin films grown on ITO by sol-gel method

    NASA Astrophysics Data System (ADS)

    Pathak, Trilok Kumar; Kumar, Vinod; Purohit, L. P.

    2015-11-01

    Highly transparent N-doped ZnO thin films were deposited on ITO coated corning glass substrate by sol-gel method. Ammonium nitrate was used as a dopant source of N with varying the doping concentration 0, 0.5, 1.0, 2.0 and 3.0 at%. The DSC analysis of prepared NZO sols is observed a phase transition at 150 °C. X-ray diffraction pattern showed the preferred (002) peak of ZnO, which was deteriorated with increased N concentrations. The transmittance of NZO thin films was observed to be ~88%. The bandgap of NZO thin films increased from 3.28 to 3.70 eV with increased N concentration from 0 to 3 at%. The maximum carrier concentration 8.36×1017 cm-3 and minimum resistivity 1.64 Ω cm was observed for 3 at% N doped ZnO thin films deposited on glass substrate. These highly transparent ZnO thin films can be used as a window layer in solar cells and optoelectronic devices.

  15. Compositionally modulated multilayer diamond-like carbon coatings with AlTiSi multi-doping by reactive high power impulse magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Dai, Wei; Gao, Xiang; Liu, Jingmao; Kwon, Se-Hun; Wang, Qimin

    2017-12-01

    Diamond-like carbon (DLC) coatings with AlTiSi multi-doping were prepared by a reactive high power impulse magnetron sputtering with using a gas mixture of Ar and C2H2 as precursor. The composition, microstructure, compressive stress, and mechanical property of the as-deposited DLC coatings were studied systemically by using SEM, XPS, TEM, Raman spectrum, stress-tester, and nanoindentation as a function of the Ar fraction. The results show that the doping concentrations of the Al, Ti and Si atoms increased as the Ar fraction increased. The doped Ti and Si preferred to bond with C while the doped Al mainly existed in oxidation state without bonding with C. As the doping concentrations increased, TiC carbide nanocrystals were formed in the DLC matrix. The microstructure of coatings changed from an amorphous feature dominant AlTiSi-DLC to a carbide nanocomposite AlTiSi-DLC with TiC nanoparticles embedding. In addition, the coatings exhibited the compositionally modulated multilayer consisting of alternate Al-rich layer and Al-poor layer due to the rotation of the substrate holder and the diffusion behavior of the doped Al which tended to separate from C and diffuse towards the DLC matrix surface owing to its weak interactions with C. The periodic Al-rich layer can effectively release the compressive stress of the coatings. On the other hand, the hard TiC nanoparticles were conducive to the hardness of the coatings. Consequently, the DLC coatings with relatively low residual stress and high hardness could be acquired successfully through AlTiSi multi-doping. It is believed that the AlCrSi multi-doping may be a good way for improving the comprehensive properties of the DLC coatings. In addition, we believe that the DLC coatings with Al-rich multilayered structure have a high oxidation resistance, which allows the DLC coatings application in high temperature environment.

  16. Structural, electrical and mechanical properties of selenium doped thallium based high-temperature superconductors

    NASA Astrophysics Data System (ADS)

    Cavdar, S.; Kol, N.; Koralay, H.; Ozturk, O.; Asikuzun, E.; Tasci, A. T.

    2016-01-01

    In this study, highly-refined chemical powders were synthesized by having them ready in appropriate stoichiometric proportions with conventional solid state reaction method so that they would produce the superconductor TlPb0.3Sr2Ca1-xSexCu2Oy (x = 0; 0.4; 0.6; 1.0). This study aims to understand effect of the selenium doping on the superconducting, structural and mechanical properties of the aforementioned superconducting material. The effect of the doping rates on the structural and electrical properties of the sample has been identified. Electrical characteristics of the TlPb0.3Sr2Ca1-xSexCu2Oy material were measured using standard four point probe method. Structural characteristics were examined with the powder X-ray diffractometer (XRD) and scanning electron microscope (SEM). Mechanical properties were analyzed with Vickers microhardness measurements on the sample surface. According to the results, it was observed that the reflection comes from the (00l) and parallel planes increased with Se doping. Particle size increases with increasing doping ratio. According to results of the mechanical measurements, all samples exhibit indentation size effect (ISE) behavior. Comparing the obtained results with theoretical studies, it was understood that Hays Kendall approach is the best method in determination of mechanical properties and analyzing microhardness of the materials.

  17. High-Performance Doping-Free Hybrid White OLEDs Based on Blue Aggregation-Induced Emission Luminogens.

    PubMed

    Liu, Baiquan; Nie, Han; Lin, Gengwei; Hu, Shiben; Gao, Dongyu; Zou, Jianhua; Xu, Miao; Wang, Lei; Zhao, Zujin; Ning, Honglong; Peng, Junbiao; Cao, Yong; Tang, Ben Zhong

    2017-10-04

    Doping-free white organic light-emitting diodes (DF-WOLEDs) have aroused research interest because of their simple properties. However, to achieve doping-free hybrid WOLEDs (DFH-WOLEDs), avoiding aggregation-caused quenching is challenging. Herein, blue luminogens with aggregation-induced emission (AIE) characteristics, for the first time, have been demonstrated to develop DFH-WOLEDs. Unlike previous DFH-WOLEDs, both thin (<1 nm) and thick (>10 nm) AIE luminogen (AIEgen) can be used for devices, enhancing the flexibility. Two-color devices show (i) pure-white emission, (ii) high CRI (85), and (iii) high efficiency. Particularly, 19.0 lm W 1- is the highest for pure-white DF-WOLEDs, while 35.0 lm W 1- is the best for two-color hybrid WOLEDs with CRI ≥ 80. A three-color DFH-WOLED shows broad color-correlated temperature span (2301-11628 K), (i) the first sunlight-like OLED (2500-8000 K) operating at low voltages, (ii) the broadest span among sunlight-like OLED, and (iii) possesses comparable efficiency with the best doping counterpart. Another three-color DFH-WOLED exhibits CRI > 90 at ≥3000 cd m -2 , (i) the first DF-WOLED with CRI ≥ 90 at high luminances, and (ii) the CRI (92.8) is not only the highest among AIE-based WOLEDs but also the highest among DF-WOLEDs. Such findings may unlock an alternative concept to develop DFH-WOLEDs.

  18. Highly sensitive H2 gas sensor of Co doped ZnO nanostructures

    NASA Astrophysics Data System (ADS)

    Bhati, Vijendra Singh; Ranwa, Sapana; Kumar, Mahesh

    2018-04-01

    In this report, the hydrogen gas sensing properties based on Co doped ZnO nanostructures are explored. The undoped and Co doped nanostructures were grown by RF magnetron sputtering system, and its structural, morphological, and hydrogen sensing behavior are investigated. The maximum relative response was occurred by the 2.5% Co doped ZnO nanostructures among undoped and other doped sensors. The enhancement of relative response might be due to large chemisorbed sites formation on the ZnO surface for the reaction to hydrogen gas.

  19. Luminescence properties of Ce{sup 3+} and Tb{sup 3+} co-doped SiO{sub x}N{sub y} thin films: Prospects for color tunability in silicon-based hosts

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ramírez, J. M., E-mail: joan-manel.ramirez@u-psud.fr; Ruiz-Caridad, A.; Estradé, S.

    2016-03-21

    In this work, the role of the nitrogen content, the annealing temperature, and the sample morphology on the luminescence properties of Ce{sup 3+} and Tb{sup 3+} co-doped SiO{sub x}N{sub y} thin films has been investigated. An increasing nitrogen atomic percentage has been incorporated in the host matrix by gradually replacing oxygen with nitrogen during fabrication while maintaining the Si content unaltered, obtaining a sequential variation in the film composition from nearly stoichiometric SiO{sub 2} to SiO{sub x}N{sub y}. The study of rare earth doped single layers has allowed us to identify the parameters that yield an optimum optical performance frommore » Ce{sup 3+} and Tb{sup 3+} ions. Ce{sup 3+} ions proved to be highly sensitive to the annealing temperature and the nitrogen content, showing strong PL emission for relatively low nitrogen contents (from 0 to 20%) and moderate annealing temperatures (800–1000 °C) or under high temperature annealing (1180 °C). Tb{sup 3+} ions, on the other hand, displayed a mild dependence on those film parameters. Rare earth co-doping has also been investigated by comparing the luminescence properties of three different approaches: (i) a Ce{sup 3+} and Tb{sup 3+} co-doped SiO{sub x}N{sub y} single layer, (ii) a bilayer composed of two SiO{sub x}N{sub y} single layers doped with either Ce{sup 3+} or Tb{sup 3+} ions, and (iii) a multilayer composed of a series of either Tb{sup 3+} or Ce{sup 3+}-doped SiO{sub x}N{sub y} thin films with interleaved SiO{sub 2} spacers. Bright green emission and efficient energy transfer from either Ce{sup 3+} ions or Ce silicates to Tb{sup 3+} ions has been observed in the co-doped single layer as a consequence of the strong ion-ion interaction. On the other hand, independent luminescence from Ce{sup 3+} and Tb{sup 3+} ions has been observed in the Ce{sup 3+} and Tb{sup 3+} co-doped bilayer and multilayer, providing a good scenario to develop light emitting devices with wide color

  20. Mo-doped SnO2 mesoporous hollow structured spheres as anode materials for high-performance lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Wang, Xuekun; Li, Zhaoqiang; Zhang, Zhiwei; Li, Qun; Guo, Enyan; Wang, Chengxiang; Yin, Longwei

    2015-02-01

    We designed a facile infiltration route to synthesize mesoporous hollow structured Mo doped SnO2 using silica spheres as templates. It is observed that Mo is uniformly incorporated into SnO2 lattice in the form of Mo6+. The as-prepared mesoporous Mo-doped SnO2 LIBs anodes exhibit a significantly improved electrochemical performance with good cycling stability, high specific capacity and high rate capability. The mesoporous hollow Mo-doped SnO2 sample with 14 at% Mo doping content displays a specific capacity of 801 mA h g-1 after 60 cycles at a current density of 100 mA g-1, about 1.66 times higher than that of the pure SnO2 hollow sample. In addition, even if the current density is as high as 1600 mA g-1 after 60 cycles, it could still retain a stable specific capacity of 530 mA h g-1, exhibiting an extraordinary rate capability. The greatly improved electrochemical performance of the Mo-doped mesoporous hollow SnO2 sample could be attributed to the following factors. The large surface area and hollow structure can significantly enhance structural integrity by acting as mechanical buffer, effectively alleviating the volume changes generated during the lithiation/delithiation process. The incorporation of Mo into the lattice of SnO2 improves charge transfer kinetics and results in a faster Li+ diffusion rate during the charge-discharge process.

  1. Rare Earth Element Partition Coefficients from Enstatite/Melt Synthesis Experiments

    NASA Technical Reports Server (NTRS)

    Schwandt, Craig S.; McKay, Gordon A.

    1997-01-01

    Enstatite (En(80)Fs(19)Wo(01)) was synthesized from a hypersthene normative basaltic melt doped at the same time with La, Ce, Nd, Sm, Eu, Dy, Er, Yb and Lu. The rare earth element concentrations were measured in both the basaltic glass and the enstatite. Rare earth element concentrations in the glass were determined by electron microprobe analysis with uncertainties less than two percent relative. Rare earth element concentrations in enstatite were determined by secondary ion mass spectrometry with uncertainties less than five percent relative. The resulting rare earth element partition signature for enstatite is similar to previous calculated and composite low-Ca pigeonite signatures, but is better defined and differs in several details. The partition coefficients are consistent with crystal structural constraints.

  2. Recent advancements in transparent ceramics and crystal fibers for high power lasers

    NASA Astrophysics Data System (ADS)

    Kim, W.; Baker, C.; Villalobos, G.; Florea, C.; Gibson, D.; Shaw, L. B.; Bowman, S.; Bayya, S.; Sadowski, B.; Hunt, M.; Askins, C.; Peele, J.; Aggarwal, I. D.; Sanghera, J. S.

    2013-05-01

    In this paper, we present our recent progress in the development of rare-earth (Yb3+ or Ho3+) doped Lu2O3 and Y2O3 sesquioxides for high power solid state lasers. We have fabricated high quality transparent ceramics using nano-powders synthesized by a co-precipitation method. This was accomplished by developments in high purity powder synthesis and low temperature scalable sintering technology developed at NRL. The optical, spectral and morphological properties as well as the lasing performance from our highly transparent ceramics are presented. In the second part of the paper, we discuss our recent research effort in developing cladded-single crystal fibers for high power single frequency fiber lasers has the potential to significantly exceed the capabilities of existing silica fiber based lasers. Single crystal fiber cores with diameters as small as 35μm have been drawn using high purity rare earth doped ceramic or single crystal feed rods by the Laser Heated Pedestal Growth (LHPG) process. Our recent results on the development of suitable claddings on the crystal fiber core are discussed.

  3. Three-dimensional N-doped graphene/polyaniline composite foam for high performance supercapacitors

    NASA Astrophysics Data System (ADS)

    Zhu, Jun; Kong, Lirong; Shen, Xiaoping; Chen, Quanrun; Ji, Zhenyuan; Wang, Jiheng; Xu, Keqiang; Zhu, Guoxing

    2018-01-01

    Three-dimensional (3D) graphene aerogel and its composite with interconnected pores have aroused continuous interests in energy storage field owning to its large surface area and hierarchical pore structure. Herein, we reported the preparation of 3D nitrogen-doped graphene/polyaniline (N-GE/PANI) composite foam for supercapacitive material with greatly improved electrochemical performance. The 3D porous structure can allow the penetration and diffusion of electrolyte, the incorporation of nitrogen doping can enhance the wettability of the active material and the number of active sites with electrolyte, and both the N-GE and PANI can ensure the high electrical conductivity of total electrode. Moreover, the synergistic effect between N-GE and PANI materials also play an important role on the electrochemical performance of electrode. Therefore, the as-prepared composite foam could deliver a high specific capacitance of 528 F g-1 at 0.1 A g-1 and a high cyclic stability with 95.9% capacitance retention after 5000 charge-discharge cycles. This study provides a new idea on improving the energy storage capacity of supercapacitors by using 3D graphene-based psedocapacitive electrode materials.

  4. Tungsten doped titanium dioxide nanowires for high efficiency dye-sensitized solar cells.

    PubMed

    Archana, P S; Gupta, Arunava; Yusoff, Mashitah M; Jose, Rajan

    2014-04-28

    Metal oxide semiconductors offering simultaneously high specific surface area and high electron mobility are actively sought for fabricating high performance nanoelectronic devices. The present study deals with synthesis of tungsten doped TiO2 (W:TiO2) nanowires (diameter ∼50 nm) by electrospinning and evaluation of their performance in dye-sensitized solar cells (DSCs). Similarity in the ionic radii between W(6+) and Ti(4+) and availability of two free electrons per dopant are the rationale for the present study. Materials were characterized by X-ray diffraction, scanning and transmission electron microscopy, X-ray fluorescence measurements, and absorption spectroscopy. Nanowires containing 2 at% W:TiO2 gave 90% higher short circuit current density (JSC) (∼15.39 mA cm(-2)) in DSCs with a nominal increase in the open circuit voltage compared with that of the undoped analogue (JSC ∼8.1 mA cm(-2)). The results are validated by multiple techniques employing absorption spectroscopy, electrochemical impedance spectroscopy and open circuit voltage decay. The above studies show that the observed increments resulted from increased dye-loading, electron density, and electron lifetime in tungsten doped samples.

  5. KH+Ti co-doped NaAlH4 for high-capacity hydrogen storage

    NASA Astrophysics Data System (ADS)

    Wang, Ping; Kang, Xiang-Dong; Cheng, Hui-Ming

    2005-10-01

    A method for preparation of Ti-doped NaAlH4 with high hydrogen capacity was developed, in which the NaH/Al mixture was mechanically milled with a catalytic amount of KH together with metallic Ti. The addition of KH was found to result in a pronounced improvement in the dehydriding performance of the Na3AlH6/NaH+Al step. As a result, the practical cycling hydrogen capacity has been markedly enhanced from 3.3 wt % for the Ti-doped hydride to 4.7 wt % for KH+Ti co-doped material. Moreover, the pronounced enhancement on hydrogen capacity arising upon adding KH was observed to persist in the following dehydrogenation/hydrogenation cycles. Structural investigation shows that the addition of KH has led to a lattice expansion. Moreover, it was found that the enthalpy change of the Na3AlH6/NaH+Al decomposition step underwent a considerable decrease upon adding KH. Therefore, the observed property improvement may be ascribed to a favorable thermodynamic adjustment arising upon the addition of KH.

  6. Emission efficiency optimization of RE 2O 3 doped molybdenum thermionic cathode by application of pattern recognition method

    NASA Astrophysics Data System (ADS)

    Wang, Jinshu; Liu, Wei; Liu, Yanqin; Zhou, Meiling

    2005-09-01

    As an alternative for thoriated tungsten thermionic cathodes, molybdenum doped with either a single rare earth oxide such as La 2O 3, Y 2O 3 and Sc 2O 3 or a mixture thereof has been produced by powder metallurgy. It is shown that carbonization can greatly improve the emission properties (i.e. emission capability and stability) of RE 2O 3 doped molybdenum due to the formation of a (metallic) rare earth atomic layer on the surface of the cathode by the reduction reaction of molybdenum carbide and rare earth oxide. Among all the carbonized samples, La 2O 3 and Y 2O 3 co-doped molybdenum cathode showed the best performance in emission. In addition, computer pattern recognition technique has been used to optimize the composition of the material and of the cathode preparation technique. We derive the equation of the emission efficiency as a function of cathode composition and carbonization degree. Based on the projecting coordinates obtained from the equation, the optimum projection region was identified, which can serve as guide for the composition and carbonization degree design.

  7. Photoelectrochemical properties of highly mobilized Li-doped ZnO thin films.

    PubMed

    Shinde, S S; Bhosale, C H; Rajpure, K Y

    2013-03-05

    Li-doped ZnO thin films with preferred (002) orientation have been prepared by spray pyrolysis technique in aqueous medium on to the corning glass substrates. The effect of Li-doping on to the photoelectrochemical, structural, morphological, optical, luminescence, electrical and thermal properties has been investigated. XRD and Raman study indicates that the films have hexagonal crystal structure. The transmittance, reflectance, refractive index, extinction coefficient and bandgap have been analyzed by optical study. PL spectra consist of a near band edge and visible emission due to the electronic defects, which are related to deep level emissions, such as oxide antisite (OZn), interstitial zinc (Zni), interstitial oxygen (Oi) and zinc vacancy (VZn). The Li-doped ZnO films prepared for 1at% doping possesses the highest electron mobility of 102cm(2)/Vs and carrier concentration of 3.62×10(19)cm(-3). Finally, degradation of 2,4,6-Trinitrotoluene using Li-doped ZnO thin films has been reported. Copyright © 2013 Elsevier B.V. All rights reserved.

  8. High-performance colossal permittivity materials of (Nb + Er) co-doped TiO2 for large capacitors and high-energy-density storage devices.

    PubMed

    Tse, Mei-Yan; Wei, Xianhua; Hao, Jianhua

    2016-09-21

    The search for colossal permittivity (CP) materials is imperative because of their potential for promising applications in the areas of device miniaturization and energy storage. High-performance CP materials require high dielectric permittivity, low dielectric loss and relatively weak dependence of frequency- and temperature. In this work, we first investigate the CP behavior of rutile TiO2 ceramics co-doped with niobium and erbium, i.e., (Er0.5Nb0.5)xTi1-xO2. Excellent dielectric properties were observed in the materials, including a CP of up to 10(4)-10(5) and a low dielectric loss (tan δ) down to 0.03, which are lower than that of the previously reported co-doped TiO2 CP materials when measured at 1 kHz. Stabilities of frequency and temperature were also accomplished via doping Er and Nb. Valence states of the elements in the material were analyzed using X-ray photoelectron spectroscopy. The Er induced secondary phases were observed using elemental mapping and energy-dispersive spectrometry. Consequently, this work may provide comprehensive guidance to develop high-performance CP materials for fully solid-state capacitor and energy storage applications.

  9. [Determination of doping in human urine by gas chromatography-high resolution mass spectrometry].

    PubMed

    Xing, Yan-Yi; Liu, Xin; Zhang, Yu-Mei; Wang, Xiao-Bing; Xu, You-Xuan

    2012-12-01

    A method was evaluated for determination of twenty-one doping (including nandrolone, boldenone and methandienone) in human urine by gas chromatography-high resolution mass spectrometry. Samples were prepared by liquid-liquid extraction, concentrated, TMS derivatization and limit of detection at ng x mL(-1) by MID/GC/HRMS. According to the code of the World Anti-Doping Agency (WADA), precision and recoveries of the procedure were evaluated by replicate analysis (n = 6), the recoveries in the range of 66%-103%, with the RSD below 10.0%. The precision within the day of the method with three different concentrations was also determined RSD were less than 9.5%, 10.0% and 9.7%.

  10. Synthesis of Er-doped Lu2O3 nanoparticles and transparent ceramics

    NASA Astrophysics Data System (ADS)

    Serivalsatit, K.; Wasanapiarnpong, T.; Kucera, C.; Ballato, J.

    2013-05-01

    Transparent rare earth-doped Lu2O3 ceramics have received much attention for use in solid-state scintillator and laser applications. The fabrication of these ceramics, however, requires ultrafine and uniform powders as precursors. Presented here is the synthesis of Er-doped Lu2O3 nanopowders by a solution precipitation method using Er-doped lutetium sulfate solution and hexamethylenetetramine as a precipitant and the fabrication of Er-doped Lu2O3 transparent ceramics from these nanopowders. The precipitated precursors were calcined at 1100 °C for 4 h in order to convert the precursors into Lu2O3 nanoparticles with an average particle size of 60 nm. Thermal decomposition and phase evolution of the precursors were studied by simultaneous thermal analysis (STA), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Er-doped Lu2O3 transparent ceramics were fabricated from these nanopowders using vacuum sintering followed by hot isostatic pressing at 1700 °C for 8 h. The transparent ceramics exhibit an optical transmittance of 78% at a wavelength of 1.55 μm.

  11. The Role of Defect Complexes in the Magneto-Optical Properties of Rare Earth Doped Gallium Nitride

    NASA Astrophysics Data System (ADS)

    Mitchell, Brandon

    Wide band gap semiconductors doped with rare earth ions (RE) have shown great potential for applications in optoelectronics, photonics, and spintronics. The 1.54mum Erbium (Er) emission has been extensively utilized in optical fiber communications, and Europium (Eu) is commonly used as a red color component for LEDs and fluorescence lamps. For the realization of spintronic-type devices, a dilutely doped semiconductor that exhibits room temperature ferromagnetic behavior would be desirable. Such behavior has been observed in GaN:Er. Furthermore, it was demonstrated that strain may play an important role in the control of this ferromagnetism; however, this requires further investigation. One motivation of this work is the realization of an all solid state white light source monolithically integrated into III/V nitride semiconductor materials, ideally GaN. For this, the current AlGaAs-based LEDs need to be replaced. One approach for achieving efficient red emission from GaN is dilute doping with fluorescent ions. In this regard, Eu has consistently been the most promising candidate as a dopant in the active layer for a red, GaN based, LED due to the sharp 5D0 to 7F2 transitions that result in red emission around 620nm. The success of GaN:Eu as the active layer for a red LED is based on the ability for the Eu ions to be efficiently excited by electron hole pairs. Thus, the processes by which energy is transferred from the host to the Eu ions has been studied. Complications arise, however, from the fact that Eu ions incorporate into multiple center environments, the structures of which are found to have a profound influence on the excitation pathways and efficiencies of the Eu ion. Therefore the nature of Eu incorporation and the resulting luminescence efficiency in GaN has been extensively investigated. By performing a comparative study on GaN:Eu samples grown under a variety of controlled conditions and using a variety of experimental techniques, the majority site has

  12. High-performance metal mesh/graphene hybrid films using prime-location and metal-doped graphene.

    PubMed

    Min, Jung-Hong; Jeong, Woo-Lim; Kwak, Hoe-Min; Lee, Dong-Seon

    2017-08-31

    We introduce high-performance metal mesh/graphene hybrid transparent conductive layers (TCLs) using prime-location and metal-doped graphene in near-ultraviolet light-emitting diodes (NUV LEDs). Despite the transparency and sheet resistance values being similar for hybrid TCLs, there were huge differences in the NUV LEDs' electrical and optical properties depending on the location of the graphene layer. We achieved better physical stability and current spreading when the graphene layer was located beneath the metal mesh, in direct contact with the p-GaN layer. We further improved the contact properties by adding a very thin Au mesh between the thick Ag mesh and the graphene layer to produce a dual-layered metal mesh. The Au mesh effectively doped the graphene layer to create a p-type electrode. Using Raman spectra, work function variations, and the transfer length method (TLM), we verified the effect of doping the graphene layer after depositing a very thin metal layer on the graphene layers. From our results, we suggest that the nature of the contact is an important criterion for improving the electrical and optical performance of hybrid TCLs, and the method of doping graphene layers provides new opportunities for solving contact issues in other semiconductor devices.

  13. Rare earth chalcogenide Ce3Te4 as high efficiency high temperature thermoelectric material

    NASA Astrophysics Data System (ADS)

    Wang, Xiaochun; Yang, Ronggui; Zhang, Yong; Zhang, Peihong; Xue, Yu

    2011-05-01

    The electronic band structures of Ce3Te4 have been studied using the first-principles density-functional theory calculations. It is found that the density of states of Ce3Te4 has a very high delta-shaped peak appearing 0.21 eV above the Fermi level, which mainly comes from the f orbital electrons of the rare-earth element Ce. Using the simple theory proposed by Mahan and Sofo, [Proc. Natl. Acad. Sci. U.S.A. 93, 7436 (1996)], we obtain an ideal value of zT=13.5 for Ce3Te4 at T=1200 K, suggesting that the rare-earth chalcogenide Ce3Te4 could be a promising high efficiency high temperature thermoelectric material.

  14. Delta-Doping at Wafer Level for High Throughput, High Yield Fabrication of Silicon Imaging Arrays

    NASA Technical Reports Server (NTRS)

    Hoenk, Michael E. (Inventor); Nikzad, Shoulch (Inventor); Jones, Todd J. (Inventor); Greer, Frank (Inventor); Carver, Alexander G. (Inventor)

    2014-01-01

    Systems and methods for producing high quantum efficiency silicon devices. A silicon MBE has a preparation chamber that provides for cleaning silicon surfaces using an oxygen plasma to remove impurities and a gaseous (dry) NH3 + NF3 room temperature oxide removal process that leaves the silicon surface hydrogen terminated. Silicon wafers up to 8 inches in diameter have devices that can be fabricated using the cleaning procedures and MBE processing, including delta doping.

  15. One-step electrochemical synthesis of nitrogen and sulfur co-doped, high-quality graphene oxide.

    PubMed

    Parvez, Khaled; Rincón, Rosalba A; Weber, Nils-Eike; Cha, Kitty C; Venkataraman, Shyam S

    2016-04-28

    High-quality graphene oxide (GO) with high crystallinity and electrical conductivity as well as in situ doped with nitrogen and sulfur is obtained via the electrochemical exfoliation of graphite. Furthermore, iron incorporated GO sheets show promising catalytic activity and stable methanol tolerance durability when used as electrocatalysts for the oxygen reduction reaction.

  16. Nitrogen-doped graphene prepared by a transfer doping approach for the oxygen reduction reaction application

    NASA Astrophysics Data System (ADS)

    Mo, Zaiyong; Zheng, Ruiping; Peng, Hongliang; Liang, Huagen; Liao, Shijun

    2014-01-01

    Well defined nitrogen-doped graphene (NG) is prepared by a transfer doping approach, in which the graphene oxide (GO) is deoxidized and nitrogen doped by the vaporized polyaniline, and the GO is prepared by a thermal expansion method from graphite oxide. The content of doped nitrogen in the doped graphene is high up to 6.25 at% by the results of elements analysis, and oxygen content is lowered to 5.17 at%. As a non-precious metal cathode electrocatalyst, the NG catalyst exhibits excellent activity toward the oxygen reduction reaction, as well as excellent tolerance toward methanol. In 0.1 M KOH solution, its onset potential, half-wave potential and limiting current density for the oxygen reduction reaction reach 0.98 V (vs. RHE), 0.87 V (vs. RHE) and 5.38 mA cm-2, respectively, which are comparable to those of commercial 20 wt% Pt/C catalyst. The well defined graphene structure of the catalyst is revealed clearly by HRTEM and Raman spectra. It is suggested that the nitrogen-doping and large surface area of the NG sheets give the main contribution to the high ORR catalytic activity.

  17. Analysis of Photoluminescence Thermal Quenching: Guidance for the Design of Highly Effective p-type Doping of Nitrides

    PubMed Central

    Liu, Zhiqiang; Huang, Yang; Yi, Xiaoyan; Fu, Binglei; Yuan, Guodong; Wang, Junxi; Li, Jinmin; Zhang, Yong

    2016-01-01

    A contact-free diagnostic technique for examining position of the impurity energy level of p-type dopants in nitride semiconductors was proposed based on photoluminescence thermal quenching. The Mg ionization energy was extracted by the phenomenological rate-equation model we developed. The diagnostic technique and analysis model reported here are priorities for the design of highly effective p-doping of nitrides and could also be used to explain the abnormal and seldom analyzed low characteristic temperature T0 (about 100 K) of thermal quenching in p-type nitrides systems. An In-Mg co-doped GaN system is given as an example to prove the validity of our methods. Furthermore, a hole concentration as high as 1.94 × 1018 cm−3 was achieved through In-Mg co-doping, which is nearly one order of magnitude higher than typically obtained in our lab. PMID:27550805

  18. Analysis of Photoluminescence Thermal Quenching: Guidance for the Design of Highly Effective p-type Doping of Nitrides.

    PubMed

    Liu, Zhiqiang; Huang, Yang; Yi, Xiaoyan; Fu, Binglei; Yuan, Guodong; Wang, Junxi; Li, Jinmin; Zhang, Yong

    2016-08-23

    A contact-free diagnostic technique for examining position of the impurity energy level of p-type dopants in nitride semiconductors was proposed based on photoluminescence thermal quenching. The Mg ionization energy was extracted by the phenomenological rate-equation model we developed. The diagnostic technique and analysis model reported here are priorities for the design of highly effective p-doping of nitrides and could also be used to explain the abnormal and seldom analyzed low characteristic temperature T0 (about 100 K) of thermal quenching in p-type nitrides systems. An In-Mg co-doped GaN system is given as an example to prove the validity of our methods. Furthermore, a hole concentration as high as 1.94 × 10(18) cm(-3) was achieved through In-Mg co-doping, which is nearly one order of magnitude higher than typically obtained in our lab.

  19. Analysis of Photoluminescence Thermal Quenching: Guidance for the Design of Highly Effective p-type Doping of Nitrides

    NASA Astrophysics Data System (ADS)

    Liu, Zhiqiang; Huang, Yang; Yi, Xiaoyan; Fu, Binglei; Yuan, Guodong; Wang, Junxi; Li, Jinmin; Zhang, Yong

    2016-08-01

    A contact-free diagnostic technique for examining position of the impurity energy level of p-type dopants in nitride semiconductors was proposed based on photoluminescence thermal quenching. The Mg ionization energy was extracted by the phenomenological rate-equation model we developed. The diagnostic technique and analysis model reported here are priorities for the design of highly effective p-doping of nitrides and could also be used to explain the abnormal and seldom analyzed low characteristic temperature T0 (about 100 K) of thermal quenching in p-type nitrides systems. An In-Mg co-doped GaN system is given as an example to prove the validity of our methods. Furthermore, a hole concentration as high as 1.94 × 1018 cm-3 was achieved through In-Mg co-doping, which is nearly one order of magnitude higher than typically obtained in our lab.

  20. A confined "microreactor" synthesis strategy to three dimensional nitrogen-doped graphene for high-performance sodium ion battery anodes

    NASA Astrophysics Data System (ADS)

    Li, Jiajie; Zhang, Yumin; Gao, Tangling; Han, Jiecai; Wang, Xianjie; Hultman, Benjamin; Xu, Ping; Zhang, Zhihua; Wu, Gang; Song, Bo

    2018-02-01

    In virtue of abundant sodium resources, sodium ion batteries (SIBs) have been regarded as one of the most promising alternatives for large-scale energy storage applications. However, the absence of a suitable anode material makes it difficult to realize these applications. Here, we demonstrate an effective synthesis strategy of using a "microreactor" consisting of melamine fiber (inside) and graphene oxide (GO, outside) to fabricate three dimensional (3D) nitrogen doped (N-doped) graphene as high-performance anode materials for sodium ion batteries. Through a controlled pyrolysis, the inside melamine fiber and the outside GO layer has been converted into N-doped graphene and reduced graphene oxide (r-GO) respectively, and thus the "microreactor" is transformed into interconnected 3D N-doped graphene structures. Such highly desired 3D graphene structures show reversible sodium storage capacities up to ∼305 mA h g-1 after 500 cycles at a current density of 0.2 A g-1 and promising long cycling stability with a stable capacity of ∼198 mA h g-1 at 5 A g-1 after 5000 cycles. The high capacity and superior durability in combination with the facile synthesis procedure of the 3D graphene structure make it a promising anode material for SIBs and other energy storage applications.

  1. Doped colloidal artificial spin ice

    DOE PAGES

    Libál, A.; Reichhardt, C. J. Olson; Reichhardt, C.

    2015-10-07

    We examine square and kagome artificial spin ice for colloids confined in arrays of double-well traps. Conversely, magnetic artificial spin ices, unlike colloidal and vortex artificial spin ice realizations, allow creation of doping sites through double occupation of individual traps. We find that doping square and kagome ice geometries produces opposite effects. For square ice, doping creates local excitations in the ground state configuration that produce a local melting effect as the temperature is raised. In contrast, the kagome ice ground state can absorb the doping charge without generating non-ground-state excitations, while at elevated temperatures the hopping of individual colloidsmore » is suppressed near the doping sites. Our results indicate that in the square ice, doping adds degeneracy to the ordered ground state and creates local weak spots, while in the kagome ice, which has a highly degenerate ground state, doping locally decreases the degeneracy and creates local hard regions.« less

  2. Doped colloidal artificial spin ice

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Libál, A.; Reichhardt, C. J. Olson; Reichhardt, C.

    We examine square and kagome artificial spin ice for colloids confined in arrays of double-well traps. Conversely, magnetic artificial spin ices, unlike colloidal and vortex artificial spin ice realizations, allow creation of doping sites through double occupation of individual traps. We find that doping square and kagome ice geometries produces opposite effects. For square ice, doping creates local excitations in the ground state configuration that produce a local melting effect as the temperature is raised. In contrast, the kagome ice ground state can absorb the doping charge without generating non-ground-state excitations, while at elevated temperatures the hopping of individual colloidsmore » is suppressed near the doping sites. Our results indicate that in the square ice, doping adds degeneracy to the ordered ground state and creates local weak spots, while in the kagome ice, which has a highly degenerate ground state, doping locally decreases the degeneracy and creates local hard regions.« less

  3. Experimental evidences for reducing Mg activation energy in high Al-content AlGaN alloy by MgGa δ doping in (AlN)m/(GaN)n superlattice

    PubMed Central

    Wang, Xiao; Wang, Wei; Wang, Jingli; Wu, Hao; Liu, Chang

    2017-01-01

    P-type doping in high Al-content AlGaN alloys is a main challenge for realizing AlGaN-based deep ultraviolet optoelectronics devices. According to the first-principles calculations, Mg activation energy may be reduced so that a high hole concentration can be obtained by introducing nanoscale (AlN)5/(GaN)1 superlattice (SL) in Al0.83Ga0.17N disorder alloy. In this work, experimental evidences were achieved by analyzing Mg doped high Al-content AlGaN alloys and Mg doped AlGaN SLs as well as MgGa δ doped AlGaN SLs. Mg acceptor activation energy was significantly reduced from 0.378 to 0.331 eV by using MgGa δ doping in SLs instead of traditional doping in alloys. This new process was confirmed to be able to realize high p-type doping in high Al-content AlGaN. PMID:28290480

  4. Experimental evidences for reducing Mg activation energy in high Al-content AlGaN alloy by MgGa δ doping in (AlN)m/(GaN)n superlattice

    NASA Astrophysics Data System (ADS)

    Wang, Xiao; Wang, Wei; Wang, Jingli; Wu, Hao; Liu, Chang

    2017-03-01

    P-type doping in high Al-content AlGaN alloys is a main challenge for realizing AlGaN-based deep ultraviolet optoelectronics devices. According to the first-principles calculations, Mg activation energy may be reduced so that a high hole concentration can be obtained by introducing nanoscale (AlN)5/(GaN)1 superlattice (SL) in Al0.83Ga0.17N disorder alloy. In this work, experimental evidences were achieved by analyzing Mg doped high Al-content AlGaN alloys and Mg doped AlGaN SLs as well as MgGa δ doped AlGaN SLs. Mg acceptor activation energy was significantly reduced from 0.378 to 0.331 eV by using MgGa δ doping in SLs instead of traditional doping in alloys. This new process was confirmed to be able to realize high p-type doping in high Al-content AlGaN.

  5. Experimental evidences for reducing Mg activation energy in high Al-content AlGaN alloy by MgGa δ doping in (AlN)m/(GaN)n superlattice.

    PubMed

    Wang, Xiao; Wang, Wei; Wang, Jingli; Wu, Hao; Liu, Chang

    2017-03-14

    P-type doping in high Al-content AlGaN alloys is a main challenge for realizing AlGaN-based deep ultraviolet optoelectronics devices. According to the first-principles calculations, Mg activation energy may be reduced so that a high hole concentration can be obtained by introducing nanoscale (AlN) 5 /(GaN) 1 superlattice (SL) in Al 0.83 Ga 0.17 N disorder alloy. In this work, experimental evidences were achieved by analyzing Mg doped high Al-content AlGaN alloys and Mg doped AlGaN SLs as well as Mg Ga δ doped AlGaN SLs. Mg acceptor activation energy was significantly reduced from 0.378 to 0.331 eV by using Mg Ga δ doping in SLs instead of traditional doping in alloys. This new process was confirmed to be able to realize high p-type doping in high Al-content AlGaN.

  6. Low temperature coefficient of resistance and high gage factor in beryllium-doped silicon

    NASA Technical Reports Server (NTRS)

    Robertson, J. B.; Littlejohn, M. A.

    1974-01-01

    The gage factor and resistivity of p-type silicon doped with beryllium was studied as a function of temperature, crystal orientation, and beryllium doping concentration. It was shown that the temperature coefficient of resistance can be varied and reduced to zero near room temperature by varying the beryllium doping level. Similarly, the magnitude of the piezoresistance gage factor for beryllium-doped silicon is slightly larger than for silicon doped with a shallow acceptor impurity such as boron, whereas the temperature coefficient of piezoresistance is about the same for material containing these two dopants. These results are discussed in terms of a model for the piezoresistance of compensated p-type silicon.

  7. Oxygen and nitrogen co-doped porous carbon nanosheets derived from Perilla frutescens for high volumetric performance supercapacitors

    NASA Astrophysics Data System (ADS)

    Liu, Bei; Liu, Yijiang; Chen, Hongbiao; Yang, Mei; Li, Huaming

    2017-02-01

    Biomass-derived O/N-co-doped porous carbons have become the most competitive electrode materials for supercapacitors because of their renewability and sustainability. We herein present a simple approach to fabricate O/N-co-doped porous carbon nanosheets by the direct pyrolysis of Perilla frutescens (PF) leaves. Under optimum pyrolysis temperature (700 °C), the PF leaf-derived carbon nanosheets (PFC-700) having O, N contents of 18.76 at.% and 1.70 at.%, respectively, exhibit a hierarchical pore structure with a moderate BET surface area (655 m2 g-1) and a relatively low pore volume (0.44 cm3 g-1). Such O/N-co-doped porous carbon nanosheets display both high gravimetric capacitance (270 F g-1 at 0.5 A g-1) and high volumetric capacitance (287 F cm-3 at 0.5 A g-1). In addition, the PFC-700-based symmetric supercapacitor offers a high volumetric energy density (14.8 Wh L-1 at 490 W L-1) as well as a high stability (about 96.1% of capacitance retention after 10000 cycles at 2 A g-1).

  8. Continuously tunable photonic fractional Hilbert transformer using a high-contrast germanium-doped silica-on-silicon microring resonator.

    PubMed

    Shahoei, Hiva; Dumais, Patrick; Yao, Jianping

    2014-05-01

    We propose and experimentally demonstrate a continuously tunable fractional Hilbert transformer (FHT) based on a high-contrast germanium-doped silica-on-silicon (SOS) microring resonator (MRR). The propagation loss of a high-contrast germanium-doped SOS waveguide can be very small (0.02 dB/cm) while the lossless bend radius can be less than 1 mm. These characteristics lead to the fabrication of an MRR with a high Q-factor and a large free-spectral range (FSR), which is needed to implement a Hilbert transformer (HT). The SOS MRR is strongly polarization dependent. By changing the polarization direction of the input signal, the phase shift introduced at the center of the resonance spectrum is changed. The tunable phase shift at the resonance wavelength can be used to implement a tunable FHT. A germanium-doped SOS MRR with a high-index contrast of 3.8% is fabricated. The use of the fabricated MRR for the implementation of a tunable FHT with tunable orders at 1, 0.85, 0.95, 1.05, and 1.13 for a Gaussian pulse with the temporal full width at half-maximum of 80 ps is experimentally demonstrated.

  9. Highly efficient synthesis of ordered nitrogen-doped mesoporous carbons with tunable properties and its application in high performance supercapacitors

    NASA Astrophysics Data System (ADS)

    Liu, Dan; Zeng, Chao; Qu, Deyu; Tang, Haolin; Li, Yu; Su, Bao-Lian; Qu, Deyang

    2016-07-01

    Nitrogen-doped ordered mesoporous carbons (OMCs) have been synthesized via aqueous cooperative assembly route in the presence of basic amino acids as either polymerization catalysts or nitrogen dopants. This method allows the large-scale production of nitrogen-doped OMCs with tunable composition, structure and morphology while maintaining highly ordered mesostructures. For instances, the nitrogen content can be varied from ∼1 wt% to ∼6.3 wt% and the mesophase can be either 3-D body-centered cubic or 2-D hexagonal. The specific surface area for typical OMCs is around 600 m2 g-1, and further KOH activation can significantly enhance the surface area to 1866 m2 g-1 without destroying the ordered mesostructures. Benefiting from hierarchically ordered porous structure, nitrogen-doping effect and large-scale production availability, the synthesized OMCs show a great potential towards supercapacitor application. When measured in a symmetrical two-electrode configuration with an areal mass loading of ∼3 mg cm-2, the activated OMC exhibits high capacitance (186 F g-1 at 0.25 A g-1) and good rate capability (75% capacity retention at 20 A g-1) in ionic liquid electrolyte. Even as the mass loading is up to ∼12 mg cm-2, the OMC electrode still yields a specific capacitance of 126 F g-1 at 20 A g-1.

  10. Computer modelling of the optical behaviour of rare earth dopants in BaY2F8

    NASA Astrophysics Data System (ADS)

    Jackson, R. A.; Valerio, M. E. G.; Couto Dos Santos, M. A.; Amaral, J. B.

    2005-01-01

    BaY2F8, when doped with rare earth elements is a material of interest in the development of solid-state laser systems, especially for use in the infrared region. This paper presents the application of a new computational technique, which combines atomistic modelling and crystal field calculations in a study of rare earth doping of the material. Atomistic modelling is used to calculate the symmetry and detailed geometry of the dopant ion-host lattice system, and this information is then used to calculate the crystal field parameters, which are an important indicator in assessing the optical behaviour of the dopant-crystal system. Comparisons with the results of recent experimental work on this material are made.

  11. High temperature ferromagnetism in Ni doped ZnO nanoparticles: Milling time dependence

    NASA Astrophysics Data System (ADS)

    Pal, Bappaditya; Giri, P. K.; Sarkar, D.

    2014-04-01

    We report on the room temperature ferromagnetism (RT FM) in the Zn1-xNixO (x = 0, 0.03, and 0.05) nanoparticles (NPs) synthesized by a ball milling technique. X-ray diffraction analysis confirms the single crystalline ZnO wurtzite structure with presence of small intensity secondary phase related peak which disappear with increasing milling time for Ni doped samples. HRTEM lattice images show that the doped NPs are single crystalline with a dspacing of 2.44 Å. Energy-dispersive X-ray spectroscopy analysis confirms the presence of Ni ions in the ZnO matrix. Magnetic measurement (RT) exhibits the hysteresis loop with saturation magnetization (Ms) of 1.6-2.56 (emu/g) and coercive field (Hc) of 296-322 Oe. M-T measurement shows a Curie temperature of the order of 325°C for 3% Ni doped sample. Micro -Raman studies show doping/disorder induced additional modes at ˜510, 547, 572 cm-1 in addition to 437 cm-1 peak of pure ZnO. UV-Vis absorption spectra illustrate band gap shift due to doping. Alteration of Ms value with the variation of doping concentration and milling time has been studied and discussed.

  12. Assessment of effect of Yb3+ ion pairs on a highly Yb-doped double-clad fibre laser

    NASA Astrophysics Data System (ADS)

    Vallés, J. A.; Martín, J. C.; Berdejo, V.; Cases, R.; Álvarez, J. M.; Rebolledo, M. Á.

    2018-03-01

    Using a previously validated characterization method based on the careful measurement of the characteristic parameters and fluorescence emission spectra of a highly Yb-doped double-clad fibre, we evaluate the contribution of ion pair induced processes to the output power of a double-clad Yb-doped fibre ring laser. This contribution is proved to be insignificant, contrary to analysis by other authors, who overestimate the role of ion pairs.

  13. In situ one-step synthesis of hierarchical nitrogen-doped porous carbon for high-performance supercapacitors.

    PubMed

    Jeon, Ju-Won; Sharma, Ronish; Meduri, Praveen; Arey, Bruce W; Schaef, Herbert T; Lutkenhaus, Jodie L; Lemmon, John P; Thallapally, Praveen K; Nandasiri, Manjula I; McGrail, Benard Peter; Nune, Satish K

    2014-05-28

    A hierarchically structured nitrogen-doped porous carbon is prepared from a nitrogen-containing isoreticular metal-organic framework (IRMOF-3) using a self-sacrificial templating method. IRMOF-3 itself provides the carbon and nitrogen content as well as the porous structure. For high carbonization temperatures (950 °C), the carbonized MOF required no further purification steps, thus eliminating the need for solvents or acid. Nitrogen content and surface area are easily controlled by the carbonization temperature. The nitrogen content decreases from 7 to 3.3 at % as carbonization temperature increases from 600 to 950 °C. There is a distinct trade-off between nitrogen content, porosity, and defects in the carbon structure. Carbonized IRMOFs are evaluated as supercapacitor electrodes. For a carbonization temperature of 950 °C, the nitrogen-doped porous carbon has an exceptionally high capacitance of 239 F g(-1). In comparison, an analogous nitrogen-free carbon bears a low capacitance of 24 F g(-1), demonstrating the importance of nitrogen dopants in the charge storage process. The route is scalable in that multi-gram quantities of nitrogen-doped porous carbons are easily produced.

  14. Heavy doping effects in high efficiency silicon solar cells

    NASA Technical Reports Server (NTRS)

    Lindholm, F. A.; Neugroschel, A.

    1985-01-01

    The use of a (silicon)/(heavily doped polysilicon)/(metal) structure to replace the conventional high-low junction (or back-surface-field, BSF) structure of silicon solar cells was examined. The results of an experimental study designed to explore both qualitatively and quantitatively the mechanism of the improved current gain in bipolar transistors with polysilicon emitter contact are presented. A reciprocity theorem is presented that relates the short circuit current of a device, induced by a carrier generation source, to the minority carrier Fermi level in the dark. A method for accurate measurement of minority-carrier diffusion coefficients in silicon is described.

  15. Highly improved hydration level sensing properties of copper oxide films with sodium and potassium doping

    NASA Astrophysics Data System (ADS)

    Sahin, Bünyamin; Kaya, Tolga

    2016-01-01

    In this study, un-doped, Na-doped, and K-doped nanostructured CuO films were successfully synthesized by the successive ionic layer adsorption and reaction (SILAR) technique and then characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and current-voltage (I-V) measurements. Structural properties of the CuO films were affected from doping. The XRD pattern indicates the formation of polycrystalline CuO films with no secondary phases. Furthermore, doping affected the crystal structure of the samples. The optimum conductivity values for both Na and K were obtained at 4 M% doping concentrations. The comparative hydration level sensing properties of the un-doped, Na-doped, and K-doped CuO nanoparticles were also investigated. A significant enhancement in hydration level sensing properties was observed for both 4 M% Na and K-doped CuO films for all concentration levels. Detailed discussions were reported in the study regarding atomic radii, crystalline structure, and conductivity.

  16. Evidence of dilute ferromagnetism in rare-earth doped yttrium aluminium garnet

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Farr, Warrick G.; Goryachev, Maxim; Le Floch, Jean-Michel

    This work demonstrates strong coupling regime between an erbium ion spin ensemble and microwave hybrid cavity-whispering gallery modes in a yttrium aluminium garnet dielectric crystal. Coupling strengths of 220 MHz and mode quality factors in excess of 10{sup 6} are demonstrated. Moreover, the magnetic response of high-Q modes demonstrates behaviour which is unusual for paramagnetic systems. This behaviour includes hysteresis and memory effects. Such qualitative change of the system's magnetic field response is interpreted as a phase transition of rare earth ion impurities. This phenomenon is similar to the phenomenon of dilute ferromagnetism in semiconductors. The clear temperature dependence of themore » phenomenon is demonstrated.« less

  17. Advancing radiation balanced lasers (RBLs) in rare-earth (RE)-doped solids

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hehlen, Markus Peter

    2016-11-21

    These slides cover the following topics: Mid-IR lasers in crystals using two-tone RBL (Single-dopant two-tone RBLs: Tm 3+, Er 3+, and Co-doped two-tone RBLs: (Yb 3+, Nd 3+) and (Ho 3+, Tm 3+); Advanced approaches to RBL crystals (Precursor purification, Micro-pulling-down crystal growth, and Bridgman crystal growth); Advanced approaches to RBL fibers (Materials for RBL glass fibers, Micro-structured fibers for RBL, and Fiber preform synthesis); and finally objectives.

  18. Delta-Doped Back-Illuminated CMOS Imaging Arrays: Progress and Prospects

    NASA Technical Reports Server (NTRS)

    Hoenk, Michael E.; Jones, Todd J.; Dickie, Matthew R.; Greer, Frank; Cunningham, Thomas J.; Blazejewski, Edward; Nikzad, Shouleh

    2009-01-01

    In this paper, we report the latest results on our development of delta-doped, thinned, back-illuminated CMOS imaging arrays. As with charge-coupled devices, thinning and back-illumination are essential to the development of high performance CMOS imaging arrays. Problems with back surface passivation have emerged as critical to the prospects for incorporating CMOS imaging arrays into high performance scientific instruments, just as they did for CCDs over twenty years ago. In the early 1990's, JPL developed delta-doped CCDs, in which low temperature molecular beam epitaxy was used to form an ideal passivation layer on the silicon back surface. Comprising only a few nanometers of highly-doped epitaxial silicon, delta-doping achieves the stability and uniformity that are essential for high performance imaging and spectroscopy. Delta-doped CCDs were shown to have high, stable, and uniform quantum efficiency across the entire spectral range from the extreme ultraviolet through the near infrared. JPL has recently bump-bonded thinned, delta-doped CMOS imaging arrays to a CMOS readout, and demonstrated imaging. Delta-doped CMOS devices exhibit the high quantum efficiency that has become the standard for scientific-grade CCDs. Together with new circuit designs for low-noise readout currently under development, delta-doping expands the potential scientific applications of CMOS imaging arrays, and brings within reach important new capabilities, such as fast, high-sensitivity imaging with parallel readout and real-time signal processing. It remains to demonstrate manufacturability of delta-doped CMOS imaging arrays. To that end, JPL has acquired a new silicon MBE and ancillary equipment for delta-doping wafers up to 200mm in diameter, and is now developing processes for high-throughput, high yield delta-doping of fully-processed wafers with CCD and CMOS imaging devices.

  19. Modeling pair distribution functions of rare-earth phosphate glasses using principal component analysis

    DOE PAGES

    Cole, Jacqueline M.; Cheng, Xie; Payne, Michael C.

    2016-10-18

    The use of principal component analysis (PCA) to statistically infer features of local structure from experimental pair distribution function (PDF) data is assessed on a case study of rare-earth phosphate glasses (REPGs). Such glasses, co-doped with two rare-earth ions (R and R’) of different sizes and optical properties, are of interest to the laser industry. The determination of structure-property relationships in these materials is an important aspect of their technological development. Yet, realizing the local structure of co-doped REPGs presents significant challenges relative to their singly-doped counterparts; specifically, R and R’ are difficult to distinguish in terms of establishing relativemore » material compositions, identifying atomic pairwise correlation profiles in a PDF that are associated with each ion, and resolving peak overlap of such profiles in PDFs. This study demonstrates that PCA can be employed to help overcome these structural complications, by statistically inferring trends in PDFs that exist for a restricted set of experimental data on REPGs, and using these as training data to predict material compositions and PDF profiles in unknown co-doped REPGs. The application of these PCA methods to resolve individual atomic pairwise correlations in t(r) signatures is also presented. The training methods developed for these structural predictions are pre-validated by testing their ability to reproduce known physical phenomena, such as the lanthanide contraction, on PDF signatures of the structurally simpler singly-doped REPGs. The intrinsic limitations of applying PCA to analyze PDFs relative to the quality control of source data, data processing, and sample definition, are also considered. Furthermore, while this case study is limited to lanthanide-doped REPGs, this type of statistical inference may easily be extended to other inorganic solid-state materials, and be exploited in large-scale data-mining efforts that probe many t

  20. Gram-scale production of B, N co-doped graphene-like carbon for high performance supercapacitor electrodes

    NASA Astrophysics Data System (ADS)

    Chen, Zhuo; Hou, Liqiang; Cao, Yan; Tang, Yushu; Li, Yongfeng

    2018-03-01

    Boron and nitrogen co-doped graphene-like carbon (BNC) with a gram scale was synthesized via a two-step method including a ball-milling process and a calcination process and used as electrode materials for supercapacitors. High surface area and abundant active sites of graphene-like carbon were created by the ball-milling process. Interestingly, the nitrogen atoms are doped in carbon matrix without any other N sources except for air. The textual and chemical properties can be easily tuned by changing the calcination temperature, and at 900 oC the BNC with a high surface area (802.35 m2/g), a high boron content (2.19 at%), a hierarchical pore size distribution and a relatively high graphitic degree was obtained. It shows an excellent performance of high specific capacitance retention about 78.2% at high current density (199 F/g at 100 A/g) of the initial capacitance (254 F/g at 0.25 A/g) and good cycling stability (90% capacitance retention over 1000 cycles at 100 A/g) measured in a three-electrode system. Furthermore, in a two-electrode system, a specific capacitance of 225 F/g at 0.25 A/g and a good cycling stability (93% capacitance retention over 20,000 cycles at 25 A/g) were achieved by using BNC as electrodes. The strategy of synthesis is facile and effective to fabricate multi-doped graphene-like carbon for promising candidates as electrode materials in supercapacitors.

  1. Biomass derived nitrogen-doped hierarchical porous carbon sheets for supercapacitors with high performance.

    PubMed

    Wang, Cunjing; Wu, Dapeng; Wang, Hongju; Gao, Zhiyong; Xu, Fang; Jiang, Kai

    2018-08-01

    A facile potassium chloride salt-locking technique combined with hydrothermal treatment on precursors was explored to prepare nitrogen-doped hierarchical porous carbon sheets in air from biomass. Benefiting from the effective synthesis strategy, the as-obtained carbon possesses a unique nitrogen-doped thin carbon sheet structure with abundant hierarchical pores and large specific surface areas of 1459 m 2  g -1 . The doped nitrogen in carbon framework has a positive effect on the electrochemical properties of the electrode material, the thin carbon sheet structure benefits for fast ion transfer, the abundant meso-pores provide convenient channels for rapid charge transportation, large specific surface area and lots of micro-pores guarantee sufficient ion-storage sites. Therefore, applied for supercapacitors, the carbon electrode material exhibits an outstanding specific capacitance of 451 F g -1 at 0.5 A g -1 in a three-electrode system. Moreover, the assembled symmetric supercapacitor based on two identical carbon electrodes also displays high specific capacitance of 309 F g -1 at 0.5 A g -1 , excellent rate capacity and remarkable cycling stability with 99.3% of the initial capacitance retention after 10,000 cycles at 5 A -1 . The synthesis strategy avoids expensive inert gas protection and the use of corrosive KOH and toxic ZnCl 2 activated reagents, representing a promising green route to design advanced carbon electrode materials from biomass for high-capacity supercapacitors. Copyright © 2018. Published by Elsevier Inc.

  2. Large-Area Carbon Nanosheets Doped with Phosphorus: A High-Performance Anode Material for Sodium-Ion Batteries.

    PubMed

    Hou, Hongshuai; Shao, Lidong; Zhang, Yan; Zou, Guoqiang; Chen, Jun; Ji, Xiaobo

    2017-01-01

    Large-area phosphorus-doped carbon nanosheets (P-CNSs) are first obtained from carbon dots (CDs) through self-assembly driving from thermal treatment with Na catalysis. This is the first time to realize the conversion from 0D CDs to 2D nanosheets doped with phosphorus. The sodium storage behavior of phosphorus-doped carbon material is also investigated for the first time. As anode material for sodium-ion batteries (SIBs), P-CNSs exhibit superb performances for electrochemical storage of sodium. When cycled at 0.1 A g -1 , the P-CNSs electrode delivers a high reversible capacity of 328 mAh g -1 , even at a high current density of 20 A g -1 , a considerable capacity of 108 mAh g -1 can still be maintained. Besides, this material also shows excellent cycling stability, at a current density of 5 A g -1 , the reversible capacity can still reach 149 mAh g -1 after 5000 cycles. This work will provide significant value for the development of both carbon materials and SIBs anode materials.

  3. Ferromagnetism in doped or undoped spintronics nanomaterials

    NASA Astrophysics Data System (ADS)

    Qiang, You

    2010-10-01

    Much interest has been sparked by the discovery of ferromagnetism in a range of oxide doped and undoped semiconductors. The development of ferromagnetic oxide semiconductor materials with giant magnetoresistance (GMR) offers many advantages in spintronics devices for future miniaturization of computers. Among them, TM-doped ZnO is an extensively studied n-type wide-band-gap (3.36 eV) semiconductor with a tremendous interest as future mini-computer, blue light emitting, and solar cells. In this talk, Co-doped ZnO and Co-doped Cu2O semiconductor nanoclusters are successfully synthesized by a third generation sputtering-gas-aggregation cluster technique. The Co-doped nanoclusters are ferromagnetic with Curie temperature above room temperature. Both of Co-doped nanoclusters show positive magnetoresistance (PMR) at low temperature, but the amplitude of the PMRs shows an anomalous difference. For similar Co doping concentration at 5 K, PMR is greater than 800% for Co-doped ZnO but only 5% for Co-doped Cu2O nanoclusters. Giant PMR in Co-doped ZnO which is attributed to large Zeeman splitting effect has a linear dependence on applied magnetic field with very high sensitivity, which makes it convenient for the future spintronics applications. The small PMR in Co-doped Cu2O is related to its vanishing density of states at Fermi level. Undoped Zn/ZnO core-shell nanoparticle gives high ferromagnetic properties above room temperature due to the defect induced magnetization at the interface.

  4. Highly reproducible alkali metal doping system for organic crystals through enhanced diffusion of alkali metal by secondary thermal activation.

    PubMed

    Lee, Jinho; Park, Chibeom; Song, Intek; Koo, Jin Young; Yoon, Taekyung; Kim, Jun Sung; Choi, Hee Cheul

    2018-05-16

    In this paper, we report an efficient alkali metal doping system for organic single crystals. Our system employs an enhanced diffusion method for the introduction of alkali metal into organic single crystals by controlling the sample temperature to induce secondary thermal activation. Using this system, we achieved intercalation of potassium into picene single crystals with closed packed crystal structures. Using optical microscopy and Raman spectroscopy, we confirmed that the resulting samples were uniformly doped and became K 2 picene single crystal, while only parts of the crystal are doped and transformed into K 2 picene without secondary thermal activation. Moreover, using a customized electrical measurement system, the insulator-to-semiconductor transition of picene single crystals upon doping was confirmed by in situ electrical conductivity and ex situ temperature-dependent resistivity measurements. X-ray diffraction studies showed that potassium atoms were intercalated between molecular layers of picene, and doped samples did not show any KH- nor KOH-related peaks, indicating that picene molecules are retained without structural decomposition. During recent decades, tremendous efforts have been exerted to develop high-performance organic semiconductors and superconductors, whereas as little attention has been devoted to doped organic crystals. Our method will enable efficient alkali metal doping of organic crystals and will be a resource for future systematic studies on the electrical property changes of these organic crystals upon doping.

  5. Microstructural parameters and high third order nonlinear absorption characteristics of Mn-doped PbS/PVA nanocomposite films

    NASA Astrophysics Data System (ADS)

    Ramezanpour, B.; Mahmoudi Chenari, Hossein; Sadigh, M. Khadem

    2017-11-01

    In this work, undoped and Mn-doped PbS/PVA nanocomposite films have been successfully fabricated using the simple solution-casting method. Their crystalline structure was examined by X-ray powder diffraction (XRD). XRD pattern show the formation of cubic structure of PbS for Mn-doped PbS in PVA matrix. Microstructure parameters of Mn-doped PbS/PVA nanocomposite films were obtained through the size-strain plot (SSP) method. The thermal stability of the nanocomposite film was determined using Thermogravimetric analysis (TGA). Furthermore, Z-scan technique was used to investigate the optical nonlinearity of nanocomposite films by a continuous-wave laser irradiation at the wavelength of 655 nm. This experimental results show that undoped PbS/PVA nanocomposite films indicate high nonlinear absorption characteristics. Moreover, the nanocomposite films with easy preparation characteristics, high thermal stability and nonlinear absorption properties can be used as an active element in optics and photonic devices.

  6. Enhanced performance of an S-band fiber laser using a thulium-doped photonic crystal fiber

    NASA Astrophysics Data System (ADS)

    Muhammad, A. R.; Emami, S. D.; Hmood, J. K.; Sayar, K.; Penny, R.; Abdul-Rashid, H. A.; Ahmad, H.; Harun, S. W.

    2014-11-01

    This work proposes a new method to enhance the performance of an S-band fiber laser by using a thulium-doped photonic crystal fiber (PCF). The proposed method is based on amplified spontaneous emission (ASE) suppression provided by the thulium-doped PCF unique geometric structure. The enhanced performance of this filter based PCF is dependent on the short and long cut-off wavelength characteristics that define the fiber transmission window. Realizing the short wavelength cut-off location requires the PCF cladding to be doped with a high index material, which provides a refractive index difference between the core and cladding region. Achieving the long cut-off wavelength necessitates enlarging the size of the air holes surrounding the rare-earth doped core region. The PCF structure is optimized so as to achieve the desired ASE suppression regions of below 0.8 μm and above 1.8 μm. The laser performance is simulated for different host media, namely pure silica, alumino-silicate, and fluoride-based fiber ZBLAN based on this thulium-doped PCF design. The host media spectroscopic details, including lifetime variations and quantum efficiency effect on the lasing emission are also discussed. Information on the filter based PCF design is gathered via a full-vectorial finite element method analysis and specifically a numerical modelling solution for the energy level rate equation using the Runge-Kutta method. Results are analyzed for gain improvement, lasing cavity, laser efficiency and effect of core size diameter variation. Results are compared with conventional thulium-doped fiber and thulium-doped PCF for every single host media. We observe that the ZBLAN host media is the most promising candidate due to its greater quantum efficiency.

  7. High-efficiency UV/optical/NIR detectors for large aperture telescopes and UV explorer missions: development of and field observations with delta-doped arrays

    NASA Astrophysics Data System (ADS)

    Nikzad, Shouleh; Jewell, April D.; Hoenk, Michael E.; Jones, Todd J.; Hennessy, John; Goodsall, Tim; Carver, Alexander G.; Shapiro, Charles; Cheng, Samuel R.; Hamden, Erika T.; Kyne, Gillian; Martin, D. Christopher; Schiminovich, David; Scowen, Paul; France, Kevin; McCandliss, Stephan; Lupu, Roxana E.

    2017-07-01

    Exciting concepts are under development for flagship, probe class, explorer class, and suborbital class NASA missions in the ultraviolet/optical spectral range. These missions will depend on high-performance silicon detector arrays being delivered affordably and in high numbers. To that end, we have advanced delta-doping technology to high-throughput and high-yield wafer-scale processing, encompassing a multitude of state-of-the-art silicon-based detector formats and designs. We have embarked on a number of field observations, instrument integrations, and independent evaluations of delta-doped arrays. We present recent data and innovations from JPL's Advanced Detectors and Systems Program, including two-dimensional doping technology, JPL's end-to-end postfabrication processing of high-performance UV/optical/NIR arrays and advanced coatings for detectors. While this paper is primarily intended to provide an overview of past work, developments are identified and discussed throughout. Additionally, we present examples of past, in-progress, and planned observations and deployments of delta-doped arrays.

  8. Highly scalable, resonantly cladding-pumped, Er-doped fiber laser with record efficiency.

    PubMed

    Dubinskii, M; Zhang, J; Ter-Mikirtychev, V

    2009-05-15

    We report the performance of a resonantly cladding-pumped, Yb-free, Er-doped fiber laser. We believe this is the first reported resonantly cladding-pumped fiber-Bragg-grating-based, Er-doped, large-mode-area (LMA) fiber laser. The laser, pumped by fiber-coupled InGaAsP/InP laser diode modules at 1,532.5 nm, delivers approximately 48 W of cw output at 1,590 nm. It is believed to be the highest power ever reported from a Yb-free Er-doped LMA fiber. This fully integrated laser also has the optical-to-optical efficiency of approximately 57%, to the best of our knowledge, the highest efficiency reported for cladding-pumped unidirectionally emitting Er-doped laser.

  9. Formation mechanism and optimization of highly luminescent N-doped graphene quantum dots

    PubMed Central

    Qu, Dan; Zheng, Min; Zhang, Ligong; Zhao, Haifeng; Xie, Zhigang; Jing, Xiabin; Haddad, Raid E.; Fan, Hongyou; Sun, Zaicheng

    2014-01-01

    Photoluminescent graphene quantum dots (GQDs) have received enormous attention because of their unique chemical, electronic and optical properties. Here a series of GQDs were synthesized under hydrothermal processes in order to investigate the formation process and optical properties of N-doped GQDs. Citric acid (CA) was used as a carbon precursor and self-assembled into sheet structure in a basic condition and formed N-free GQD graphite framework through intermolecular dehydrolysis reaction. N-doped GQDs were prepared using a series of N-containing bases such as urea. Detailed structural and property studies demonstrated the formation mechanism of N-doped GQDs for tunable optical emissions. Hydrothermal conditions promote formation of amide between –NH2 and –COOH with the presence of amine in the reaction. The intramoleculur dehydrolysis between neighbour amide and COOH groups led to formation of pyrrolic N in the graphene framework. Further, the pyrrolic N transformed to graphite N under hydrothermal conditions. N-doping results in a great improvement of PL quantum yield (QY) of GQDs. By optimized reaction conditions, the highest PL QY (94%) of N-doped GQDs was obtained using CA as a carbon source and ethylene diamine as a N source. The obtained N-doped GQDs exhibit an excitation-independent blue emission with single exponential lifetime decay. PMID:24938871

  10. Doping-dependent charge order correlations in electron-doped cuprates

    PubMed Central

    da Silva Neto, Eduardo H.; Yu, Biqiong; Minola, Matteo; Sutarto, Ronny; Schierle, Enrico; Boschini, Fabio; Zonno, Marta; Bluschke, Martin; Higgins, Joshua; Li, Yangmu; Yu, Guichuan; Weschke, Eugen; He, Feizhou; Le Tacon, Mathieu; Greene, Richard L.; Greven, Martin; Sawatzky, George A.; Keimer, Bernhard; Damascelli, Andrea

    2016-01-01

    Understanding the interplay between charge order (CO) and other phenomena (for example, pseudogap, antiferromagnetism, and superconductivity) is one of the central questions in the cuprate high-temperature superconductors. The discovery that similar forms of CO exist in both hole- and electron-doped cuprates opened a path to determine what subset of the CO phenomenology is universal to all the cuprates. We use resonant x-ray scattering to measure the CO correlations in electron-doped cuprates (La2−xCexCuO4 and Nd2−xCexCuO4) and their relationship to antiferromagnetism, pseudogap, and superconductivity. Detailed measurements of Nd2−xCexCuO4 show that CO is present in the x = 0.059 to 0.166 range and that its doping-dependent wave vector is consistent with the separation between straight segments of the Fermi surface. The CO onset temperature is highest between x = 0.106 and 0.166 but decreases at lower doping levels, indicating that it is not tied to the appearance of antiferromagnetic correlations or the pseudogap. Near optimal doping, where the CO wave vector is also consistent with a previously observed phonon anomaly, measurements of the CO below and above the superconducting transition temperature, or in a magnetic field, show that the CO is insensitive to superconductivity. Overall, these findings indicate that, although verified in the electron-doped cuprates, material-dependent details determine whether the CO correlations acquire sufficient strength to compete for the ground state of the cuprates. PMID:27536726

  11. Doping-dependent charge order correlations in electron-doped cuprates.

    PubMed

    da Silva Neto, Eduardo H; Yu, Biqiong; Minola, Matteo; Sutarto, Ronny; Schierle, Enrico; Boschini, Fabio; Zonno, Marta; Bluschke, Martin; Higgins, Joshua; Li, Yangmu; Yu, Guichuan; Weschke, Eugen; He, Feizhou; Le Tacon, Mathieu; Greene, Richard L; Greven, Martin; Sawatzky, George A; Keimer, Bernhard; Damascelli, Andrea

    2016-08-01

    Understanding the interplay between charge order (CO) and other phenomena (for example, pseudogap, antiferromagnetism, and superconductivity) is one of the central questions in the cuprate high-temperature superconductors. The discovery that similar forms of CO exist in both hole- and electron-doped cuprates opened a path to determine what subset of the CO phenomenology is universal to all the cuprates. We use resonant x-ray scattering to measure the CO correlations in electron-doped cuprates (La2-x Ce x CuO4 and Nd2-x Ce x CuO4) and their relationship to antiferromagnetism, pseudogap, and superconductivity. Detailed measurements of Nd2-x Ce x CuO4 show that CO is present in the x = 0.059 to 0.166 range and that its doping-dependent wave vector is consistent with the separation between straight segments of the Fermi surface. The CO onset temperature is highest between x = 0.106 and 0.166 but decreases at lower doping levels, indicating that it is not tied to the appearance of antiferromagnetic correlations or the pseudogap. Near optimal doping, where the CO wave vector is also consistent with a previously observed phonon anomaly, measurements of the CO below and above the superconducting transition temperature, or in a magnetic field, show that the CO is insensitive to superconductivity. Overall, these findings indicate that, although verified in the electron-doped cuprates, material-dependent details determine whether the CO correlations acquire sufficient strength to compete for the ground state of the cuprates.

  12. Human response to high-background radiation environments on Earth and in space

    NASA Astrophysics Data System (ADS)

    Durante, M.; Manti, L.

    The main long-term goal of the space exploration program is the colonization of the planets of the Solar System The high cosmic radiation equivalent dose rate represents a major problem for a stable and safe colonization of the planets The dose rate on Mars ranges between 60 and 150 mSv year depending on the Solar cycle and altitude and can reach values as high as 360 mSv year on the Moon The average dose rate on the Earth is about 3 mSv year reduced to about 1 mSv year excluding the internal exposure to Rn daughters However some areas of the Earth have anomalously high levels of background radiation Values 200-400 times higher than the world average are found in regions where monazite sand deposits are abundant Population in Tibet experience a high cosmic radiation background Epidemiological studies did not detect any adverse health effects in the populations living in those high-background radiation areas on Earth Chromosomal aberrations in the peripheral blood lymphocytes from the population living in the high-background radiation areas have been measured in several studies because the chromosomal damage represents an early biomarker of cancer risk Similar cytogenetic studies have been recently performed in cohort of astronauts involved in single or repeated space flights over many years A comparison of the cytogenetic findings in populations exposed at high dose rate on Earth or in space will be described

  13. Thermoelectric Properties of Barium Plumbate Doped by Alkaline Earth Oxides

    NASA Astrophysics Data System (ADS)

    Eufrasio, Andreza; Bhatta, Rudra; Pegg, Ian; Dutta, Biprodas

    Ceramic oxides are now being considered as a new class of thermoelectric materials because of their high stability at elevated temperatures. Such materials are especially suitable for use as prospective thermoelectric power generators because high temperatures are encountered in such operations. The present investigation uses barium plumbate (BaPbO3) as the starting material, the thermoelectric properties of which have been altered by judicious cation substitutions. BaPbO3 is known to exhibit metallic properties which may turn semiconducting as a result of compositional changes without precipitating a separate phase and/or altering the basic perovskite crystal structure. Perovskite structures are noted for their large interstitial spaces which can accommodate a large variety of ``impurity'' ions. As BaPbO3 has high electrical conductivity, σ = 2.43x105Ω-1 m-1 at room temperature, its thermopower, S, is relatively low, 23 μV/K, as expected. With a thermal conductivity, k, of 4.83Wm-1K-1, the figure of merit (ZT =S2 σ Tk-1) of BaPbO3 is only 0.01 at T = 300K. The objective of this investigation is to study the variation of thermoelectric properties of BaPbO3 as Ba and Pb ions are systematically substituted by alkaline earth ions.

  14. High-sensitivity stress sensor based on Bragg grating in BDK-doped photosensitive polymer optical fiber

    NASA Astrophysics Data System (ADS)

    Wang, Tongxin; Luo, Yanhua; Peng, Gang-Ding; Zhang, Qijin

    2012-02-01

    Bragg grating in a single-mode photosensitive polymer optical fiber (POF) with benzil dimethyl ketal (BDK)-doped in core has been inscribed through the Sagnac ring interference method. The Bragg wavelength of grating is about 1570nm. The stress and strain response of fiber Bragg grating (FBG) has been studied respectively. By fitting the experimental result, the strain sensitivity of FBG in POF has been found to be almost same to that of conventional silica fiber Bragg gratings. However, the stress sensitivity of FBG in POF is measured to be 421pm/MPa, which is 28 times higher than FBG in silica fiber. And such high stress sensitivity makes Bragg grating in a single-mode BDK-doped POF appear to be very attractive for constructing stress sensor with high resolution.

  15. Direct measurement of the effective infrared dielectric response of a highly doped semiconductor metamaterial.

    PubMed

    Al Mohtar, Abeer; Kazan, Michel; Taliercio, Thierry; Cerutti, Laurent; Blaize, Sylvain; Bruyant, Aurélien

    2017-03-24

    We have investigated the effective dielectric response of a subwavelength grating made of highly doped semiconductors (HDS) excited in reflection, using numerical simulations and spectroscopic measurement. The studied system can exhibit strong localized surface resonances and has, therefore, a great potential for surface-enhanced infrared absorption (SEIRA) spectroscopy application. It consists of a highly doped InAsSb grating deposited on lattice-matched GaSb. The numerical analysis demonstrated that the resonance frequencies can be inferred from the dielectric function of an equivalent homogeneous slab by accounting for the complex reflectivity of the composite layer. Fourier transform infrared reflectivity (FTIR) measurements, analyzed with the Kramers-Kronig conversion technique, were used to deduce the effective response in reflection of the investigated system. From the knowledge of this phenomenological dielectric function, transversal and longitudinal energy-loss functions were extracted and attributed to transverse and longitudinal resonance modes frequencies.

  16. High-Grading Lunar Samples for Return to Earth

    NASA Technical Reports Server (NTRS)

    Allen, Carlton; Sellar, Glenn; Nunez, Jorge; Winterhalter, Daniel; Farmer, Jack

    2009-01-01

    Astronauts on long-duration lunar missions will need the capability to "high-grade" their samples to select the highest value samples for transport to Earth and to leave others on the Moon. We are supporting studies to defile the "necessary and sufficient" measurements and techniques for highgrading samples at a lunar outpost. A glovebox, dedicated to testing instruments and techniques for high-grading samples, is in operation at the JSC Lunar Experiment Laboratory.

  17. Nitrogen-doped mesoporous carbons for high performance supercapacitors

    NASA Astrophysics Data System (ADS)

    Wu, Kai; Liu, Qiming

    2016-08-01

    The mesoporous carbons have been synthesized by using α-D(+)-Glucose, D-Glucosamine hydrochloride or their mixture as carbon precursors and mesoporous silicas (SBA-15 or MCF) as hard templates. The as-prepared products show a large pore volume (0.59-0.97 cm3 g-1), high surface areas (352.72-1152.67 m2 g-1) and rational nitrogen content (ca. 2.5-3.9 wt.%). The results of electrochemical tests demonstrate that both heteroatom doping and suitable pore structure play a decisive role in the performance of supercapacitors. The representative sample of SBA-15 replica obtained using D-Glucosamine hydrochloride only exhibits high specific capacitance (212.8 F g-1 at 0.5 A g-1) and good cycle durability (86.1% of the initial capacitance after 2000 cycles) in 6 M KOH aqueous electrolyte, which is attributed to the contribution of double layer capacitance and pseudo-capacitance. The excellent electrochemical performance makes it a promising electrode material for supercapacitors.

  18. Highly fluorescent Zn-doped carbon dots as Fenton reaction-based bio-sensors: an integrative experimental-theoretical consideration.

    PubMed

    Xu, Quan; Liu, Yao; Su, Rigu; Cai, Lulu; Li, Bofan; Zhang, Yingyuan; Zhang, Linzhou; Wang, Yajun; Wang, Yan; Li, Neng; Gong, Xiao; Gu, Zhipeng; Chen, Yusheng; Tan, Yanglan; Dong, Chenbo; Sreeprasad, Theruvakkattil Sreenivasan

    2016-10-20

    Heteroatom doped carbon dots (CDs), with high photoluminescence quantum yield (PLQY), are of keen interest in various applications such as chemical sensors, bio-imaging, electronics, and photovoltaics. Zinc, an important element assisting the electron-transfer process and an essential trace element for cells, is a promising metal dopant for CDs, which could potentially lead to multifunctional CDs. In this contribution, we report a single-step, high efficiency, hydrothermal method to synthesize Zn-doped carbon dots (Zn-CDs) with a superior PLQY. The PLQY and luminescence characteristic of Zn-CDs can be tuned by controlling the precursor ratio, and the surface oxidation in the CDs. Though a few studies have reported metal doped CDs with good PLQY, the as prepared Zn-Cds in the present method exhibited a PLQY up to 32.3%. To the best of our knowledge, there is no report regarding the facile preparation of single metal-doped CDs with a QY more than 30%. Another unique attribute of the Zn-CDs is the high monodispersity and the resultant highly robust excitation-independent luminescence that is stable over a broad range of pH values. Spectroscopic investigations indicated that the superior PLQY and luminescence of Zn-CDs are due to the heteroatom directed, oxidized carbon-based surface passivation. Furthermore, we developed a novel and sensitive biosensor for the detection of hydrogen peroxide and glucose leveraging the robust fluorescence properties of Zn-CDs. Under optimal conditions, Zn-CDs demonstrated high sensitivity and response to hydrogen peroxide and glucose over a wide range of concentrations, with a linear range of 10-80 μM and 5-100 μM, respectively, indicating their great potential as a fluorescent probe for chemical sensing.

  19. High-aspect ratio magnetic nanocomposite polymer cilium

    NASA Astrophysics Data System (ADS)

    Rahbar, M.; Tseng, H. Y.; Gray, B. L.

    2014-03-01

    This paper presents a new fabrication technique to achieve ultra high-aspect ratio artificial cilia micro-patterned from flexible highly magnetic rare earth nanoparticle-doped polymers. We have developed a simple, inexpensive and scalable fabrication method to create cilia structures that can be actuated by miniature electromagnets, that are suitable to be used for lab-on-a chip (LOC) and micro-total-analysis-system (μ-TAS) applications such as mixers and flow-control elements. The magnetic cilia are fabricated and magnetically polarized directly in microfluidic channels or reaction chambers, allowing for easy integration with complex microfluidic systems. These cilia structures can be combined on a single chip with other microfluidic components employing the same permanently magnetic nano-composite polymer (MNCP), such as valves or pumps. Rare earth permanent magnetic powder, (Nd0.7Ce0.3)10.5Fe83.9B5.6, is used to dope polydimethylsiloxane (PDMS), resulting in a highly flexible M-NCP of much higher magnetization and remanence [1] than ferromagnetic polymers typically employed in magnetic microfluidics. Sacrificial poly(ethylene-glycol) (PEG) is used to mold the highly magnetic polymer into ultra high-aspect ratio artificial cilia. Cilia structures with aspect ratio exceeding 8:0.13 can be easily fabricated using this technique and are actuated using miniature electromagnets to achieve a high range of motion/vibration.

  20. Chemically doped three-dimensional porous graphene monoliths for high-performance flexible field emitters.

    PubMed

    Kim, Ho Young; Jeong, Sooyeon; Jeong, Seung Yol; Baeg, Kang-Jun; Han, Joong Tark; Jeong, Mun Seok; Lee, Geon-Woong; Jeong, Hee Jin

    2015-03-12

    Despite the recent progress in the fabrication of field emitters based on graphene nanosheets, their morphological and electrical properties, which affect their degree of field enhancement as well as the electron tunnelling barrier height, should be controlled to allow for better field-emission properties. Here we report a method that allows the synthesis of graphene-based emitters with a high field-enhancement factor and a low work function. The method involves forming monolithic three-dimensional (3D) graphene structures by freeze-drying of a highly concentrated graphene paste and subsequent work-function engineering by chemical doping. Graphene structures with vertically aligned edges were successfully fabricated by the freeze-drying process. Furthermore, their number density could be controlled by varying the composition of the graphene paste. Al- and Au-doped 3D graphene emitters were fabricated by introducing the corresponding dopant solutions into the graphene sheets. The resulting field-emission characteristics of the resulting emitters are discussed. The synthesized 3D graphene emitters were highly flexible, maintaining their field-emission properties even when bent at large angles. This is attributed to the high crystallinity and emitter density and good chemical stability of the 3D graphene emitters, as well as to the strong interactions between the 3D graphene emitters and the substrate.

  1. A high-performance mesoporous carbon supported nitrogen-doped carbon electrocatalyst for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Xu, Jingjing; Lu, Shiyao; Chen, Xu; Wang, Jianan; Zhang, Bo; Zhang, Xinyu; Xiao, Chunhui; Ding, Shujiang

    2017-12-01

    Investigating low-cost and highly active electrocatalysts for oxygen reduction reactions (ORR) is of crucial importance for energy conversion and storage devices. Herein, we design and prepare mesoporous carbon supported nitrogen-doped carbon by pyrolysis of polyaniline coated on CMK-3. This electrocatalyst exhibits excellent performance towards ORR in alkaline media. The optimized nitrogen-doped mesoporous electrocatalyst show an onset potential (E onset) of 0.95 V (versus reversible hydrogen electrode (RHE)) and half-wave potential (E 1/2) of 0.83 V (versus RHE) in 0.1 M KOH. Furthermore, the as-prepared catalyst presents superior durability and methanol tolerance compared to commercial Pt/C indicating its potential applications in fuel cells and metal-air batteries.

  2. Evidence for a high temperature differentiation in a molten earth: A preliminary appraisal

    NASA Technical Reports Server (NTRS)

    Murthy, V. Rama

    1992-01-01

    If the earth were molten during its later stages of accretion as indicated by the present understanding of planetary accretion process, the differentiation that led to the formation of the core and mantle must have occurred at high temperatures in the range of 3000-5000 K because of the effect of pressure on the temperature of melting in the interior of the earth. This calls into question the use of low-temperature laboratory measurements of partition coefficients of trace elements to make inferences about earth accretion and differentiation. The low temperature partition coefficients cannot be directly applied to high temperature fractionations because partition coefficients refer to an equilibrium specific to a temperature for a given reaction, and must change in some proportion to exp 1/RT. There are no laboratory data on partition coefficients at the high temperatures relevant to differentiation in the interior of the earth, and an attempt to estimate high temperature distribution coefficients of siderophile elements was made by considering the chemical potential of a given element at equilibrium and how this potential changes with temperature, under some specific assumptions.

  3. Enhanced thermoelectric property of oxygen deficient nickel doped SnO2 for high temperature application

    NASA Astrophysics Data System (ADS)

    Paulson, Anju; Sabeer, N. A. Muhammad; Pradyumnan, P. P.

    2018-04-01

    Motivated by the detailed investigation on the thermoelectric performance of oxide materials our work concentrated on the influence of acceptor dopants and defect density in the lattice plane for the enhancement of thermoelectric power. The series of Sn1‑x Nix O2 (0.01 ≤ x ≤ 0.05) compositions were prepared by solid state reaction mechanism and found that 3 atomic percentage Ni doped SnO2 can be considered as a good candidate due to its promising electrical and transport properties. Defect lattices were introduced in the sample and the deviation from oxygen stochiometry was ensured using photoluminescence measurement. High power factor was obtained for the 3 atomic percentage nickel doped SnO2 due to the effective number of charge carrier concentration and the depletion of oxygen rich layers. Defect centered and acceptor doped SnO2 lattice opens a new door for energy harvesting at higher temperatures.

  4. The Electronic Structures and Optical Properties of Alkaline-Earth Metals Doped Anatase TiO2: A Comparative Study of Screened Hybrid Functional and Generalized Gradient Approximation.

    PubMed

    Ma, Jin-Gang; Zhang, Cai-Rong; Gong, Ji-Jun; Wu, You-Zhi; Kou, Sheng-Zhong; Yang, Hua; Chen, Yu-Hong; Liu, Zi-Jiang; Chen, Hong-Shan

    2015-08-24

    Alkaline-earth metallic dopant can improve the performance of anatase TiO2 in photocatalysis and solar cells. Aiming to understand doping mechanisms, the dopant formation energies, electronic structures, and optical properties for Be, Mg, Ca, Sr, and Ba doped anatase TiO2 are investigated by using density functional theory calculations with the HSE06 and PBE functionals. By combining our results with those of previous studies, the HSE06 functional provides a better description of electronic structures. The calculated formation energies indicate that the substitution of a lattice Ti with an AEM atom is energetically favorable under O-rich growth conditions. The electronic structures suggest that, AEM dopants shift the valence bands (VBs) to higher energy, and the dopant-state energies for the cases of Ca, Sr, and Ba are quite higher than Fermi levels, while the Be and Mg dopants result into the spin polarized gap states near the top of VBs. The components of VBs and dopant-states support that the AEM dopants are active in inter-band transitions with lower energy excitations. As to optical properties, Ca/Sr/Ba are more effective than Be/Mg to enhance absorbance in visible region, but the Be/Mg are superior to Ca/Sr/Ba for the absorbance improvement in near-IR region.

  5. Shape-Controlled Synthesis of Isotopic Yttrium-90-Labeled Rare Earth Fluoride Nanocrystals for Multimodal Imaging.

    PubMed

    Paik, Taejong; Chacko, Ann-Marie; Mikitsh, John L; Friedberg, Joseph S; Pryma, Daniel A; Murray, Christopher B

    2015-09-22

    Isotopically labeled nanomaterials have recently attracted much attention in biomedical research, environmental health studies, and clinical medicine because radioactive probes allow the elucidation of in vitro and in vivo cellular transport mechanisms, as well as the unambiguous distribution and localization of nanomaterials in vivo. In addition, nanocrystal-based inorganic materials have a unique capability of customizing size, shape, and composition; with the potential to be designed as multimodal imaging probes. Size and shape of nanocrystals can directly influence interactions with biological systems, hence it is important to develop synthetic methods to design radiolabeled nanocrystals with precise control of size and shape. Here, we report size- and shape-controlled synthesis of rare earth fluoride nanocrystals doped with the β-emitting radioisotope yttrium-90 ((90)Y). Size and shape of nanocrystals are tailored via tight control of reaction parameters and the type of rare earth hosts (e.g., Gd or Y) employed. Radiolabeled nanocrystals are synthesized in high radiochemical yield and purity as well as excellent radiolabel stability in the face of surface modification with different polymeric ligands. We demonstrate the Cerenkov radioluminescence imaging and magnetic resonance imaging capabilities of (90)Y-doped GdF3 nanoplates, which offer unique opportunities as a promising platform for multimodal imaging and targeted therapy.

  6. Synthesis of the missing oxide of xenon, XeO2, and its implications for Earth's missing xenon.

    PubMed

    Brock, David S; Schrobilgen, Gary J

    2011-04-27

    The missing Xe(IV) oxide, XeO(2), has been synthesized at 0 °C by hydrolysis of XeF(4) in water and 2.00 M H(2)SO(4(aq)). Raman spectroscopy and (16/18)O isotopic enrichment studies indicate that XeO(2) possesses an extended structure in which Xe(IV) is oxygen bridged to four neighboring oxygen atoms to give a local square-planar XeO(4) geometry based on an AX(4)E(2) valence shell electron pair repulsion (VSEPR) arrangement. The vibrational spectra of Xe(16)O(2) and Xe(18)O(2) amend prior vibrational assignments of xenon doped SiO(2) and are in accordance with prior speculation that xenon depletion from the Earth's atmosphere may occur by xenon insertion at high temperatures and high pressures into SiO(2) in the Earth's crust.

  7. Multiple doping of silicon-germanium alloys for thermoelectric applications

    NASA Technical Reports Server (NTRS)

    Fleurial, Jean-Pierre; Vining, Cronin B.; Borshchevsky, Alex

    1989-01-01

    It is shown that heavy doping of n-type Si/Ge alloys with phosphorus and arsenic (V-V doping interaction) by diffusion leads to a significant enhancement of their carrier concentration and possible improvement of the thermoelectric figure of merit. High carrier concentrations were achieved by arsenic doping alone, but for a same doping level higher carrier mobilities and lower resistivities are obtained through phosphorus doping. By combining the two dopants with the proper diffusion treatments, it was possible to optimize the different properties, obtaining high carrier concentration, good carrier mobility and low electrical resistivity. Similar experiments, using the III-V doping interaction, were conducted on boron-doped p-type samples and showed the possibility of overcompensating the samples by diffusing arsenic, in order to get n-type behavior.

  8. Long-Period Gratings in Highly Germanium-Doped, Single-Mode Optical Fibers for Sensing Applications

    PubMed Central

    Schlangen, Sebastian; Bremer, Kort; Zheng, Yulong; Böhm, Sebastian; Steinke, Michael; Wellmann, Felix; Neumann, Jörg; Overmeyer, Ludger

    2018-01-01

    Long-period fiber gratings (LPGs) are well known for their sensitivity to external influences, which make them interesting for a large number of sensing applications. For these applications, fibers with a high numerical aperture (i.e., fibers with highly germanium (Ge)-doped fused silica fiber cores) are more attractive since they are intrinsically photosensitive, as well as less sensitive to bend- and microbend-induced light attenuations. In this work, we introduce a novel method to inscribe LPGs into highly Ge-doped, single-mode fibers. By tapering the optical fiber, and thus, tailoring the effective indices of the core and cladding modes, for the first time, an LPG was inscribed into such fibers using the amplitude mask technique and a KrF excimer laser. Based on this novel method, sensitive LPG-based fiber optic sensors only a few millimeters in length can be incorporated in bend-insensitive fibers for use in various monitoring applications. Moreover, by applying the described inscription method, the LPG spectrum can be influenced and tailored according to the specific demands of a particular application. PMID:29702600

  9. Highly photostable NV centre ensembles in CVD diamond produced by using N2O as the doping gas

    NASA Astrophysics Data System (ADS)

    Tallaire, A.; Mayer, L.; Brinza, O.; Pinault-Thaury, M. A.; Debuisschert, T.; Achard, J.

    2017-10-01

    High density Nitrogen-Vacancy (NV) centre ensembles incorporated in plasma assisted chemical vapour deposition (CVD) diamond are crucial to the development of more efficient sensing devices that use the properties of luminescent defects. Achieving high NV doping with N2 as the dopant gas source during diamond growth is, however, plagued by the formation of macroscopic and point defects that quench luminescence. Moreover, such NVs are found to exhibit poor photostability under high laser powers. Although this effect can be harnessed to locally and durably switch off NV luminescence for data storage, it is usually undesirable for most applications. In this work, the use of N2O as an alternative doping source is proposed. Much higher amounts of the doping gas can be added without significantly generating defects, which allows the incorporation of perfectly photostable and higher density NV ensembles. This effect is believed to be related to the lower dissociation energy of the N2O molecule together with the beneficial effect of the presence of a low and controlled amount of oxygen near the growing surface.

  10. Rare-Earth-compound nanowires, nanotubes, and fullerene-like nanoparticles: synthesis, characterization, and properties.

    PubMed

    Wang, Xun; Li, Yadong

    2003-11-21

    Various low-dimensional nanostructures, such as nanowires, nanotubes, nanosheets, and fullerene-like nanoparticles have been selectively synthesized from rare-earth compounds (hydroxides, fluorides) based on a facile hydrothermal method. The subsequent dehydration, sulfidation, and fluoridation processes lead to the formation of rare-earth oxide, oxysulfide, and oxyhalide nanostructures, which can be functionalized further by doping with other rare-earth ions or by coating with metal nanoparticles. Owing to the interesting combination of novel nanostructures and functional compounds, these nanostructures can be expected to bring new opportunities in the vast research areas of and application in biology, catalysts, and optoelectronic devices.

  11. The electronic structures and work functions of (100) surface of typical binary and doped REB6 single crystals

    NASA Astrophysics Data System (ADS)

    Liu, Hongliang; Zhang, Xin; Xiao, Yixin; Zhang, Jiuxing

    2018-03-01

    The density function theory been used to calculate the electronic structures of binary and doped rare earth hexaborides (REB6), which exhibits the large density of states (DOS) near Fermi level. The d orbital elections of RE element contribute the electronic states of election emission near the Fermi level, which imply that the REB6 (RE = La, Ce, Gd) with wide distribution of high density d orbital electrons could provide a lower work function and excellent emission properties. Doping RE elements into binary REB6 can adjust DOS and the position of the Fermi energy level. The calculated work functions of considered REB6 (100) surface show that the REB6 (RE = La, Ce, Gd) have lower work function and doping RE elements with active d orbital electrons can significantly reduce work function of binary REB6. The thermionic emission test results are basically accordant with the calculated value, proving the first principles calculation could provide a good theoretical guidance for the study of electron emission properties of REB6.

  12. Plasmon-Assisted Efficiency Enhancement of Eu3+-Doped Tellurite Glass-Covered Solar Cells

    NASA Astrophysics Data System (ADS)

    Lima, Bismarck C.; Gómez-Malagón, L. A.; Gomes, A. S. L.; Garcia, J. A. M.; Kassab, L. R. P.

    2017-12-01

    Rare-earth-doped tellurite glass containing metallic nanoparticles can be exploited to manage the solar spectrum in order to increase solar cell efficiency. It is therefore possible to modify the incident solar spectrum profile to the spectrum that optimizes the solar cell recombination process by covering the solar cell with plasmonic luminescent downshifting layers. With this approach, the losses due to thermalization are minimized and the efficiency is increased. Due to the down-conversion process that couples the plasmon resonance of the metallic nanoparticles and the rare-earth electronic energy levels, it is possible to convert photons from the ultraviolet region to the visible and near-band-gap region of the semiconductor. It is demonstrated here that plasmon-assisted efficiency enhancements of 14.0% and 34.5% can be obtained for commercial Si and GaP solar cells, respectively, covered with Eu3+-doped TeO2-ZnO glass containing silver nanoparticles.

  13. Doping and musculoskeletal system: short-term and long-lasting effects of doping agents.

    PubMed

    Nikolopoulos, Dimitrios D; Spiliopoulou, Chara; Theocharis, Stamatios E

    2011-10-01

    Doping is a problem that has plagued the world of competition and sports for ages. Even before the dawn of Olympic history in ancient Greece, competitors have looked for artificial means to improve athletic performance. Since ancient times, athletes have attempted to gain an unfair competitive advantage through the use of doping substances. A Prohibited List of doping substances and methods banned in sports is published yearly by the World Anti-Doping Agency. Among the substances included are steroidal and peptide hormones and their modulators, stimulants, glucocorticosteroids, β₂-agonists, diuretics and masking agents, narcotics, and cannabinoids. Blood doping, tampering, infusions, and gene doping are examples of prohibited methods indicated on the List. Apart from the unethical aspect of doping, as it abrogates fair-play's principle, it is extremely important to consider the hazards it presents to the health and well-being of athletes. The referred negative effects for the athlete's health have to do, on the one hand, by the high doses of the performance-enhancing agents and on the other hand, by the relentless, superhuman strict training that the elite or amateur athletes put their muscles, bones, and joints. The purpose of this article is to highlight the early and the long-lasting consequences of the doping abuse on bone and muscle metabolism. © 2010 The Authors Fundamental and Clinical Pharmacology © 2010 Société Française de Pharmacologie et de Thérapeutique.

  14. Structural and optical properties of Nd- and Tb-doped BaY 2F 8

    NASA Astrophysics Data System (ADS)

    Valerio, Mário E. G.; Ribeiro, Viviane G.; de Mello, Ana C. S.; dos Santos, Marcos A. C.; Baldochi, Sonia L.; Mazzocchi, Vera L.; Parente, Carlos B. R.; Jackson, Robert A.; Amaral, Jomar B.

    2007-09-01

    In the present work, we report the optical properties of rare-earth doped BaY2F8 and its potential use as a scintillator in radiation detection. The samples were synthesized and grown by the zone melting method under a HF flow. X-ray powder diffraction was performed and quantitative phase analysis was done using the Rietveld method. Emission and excitation spectra of the doped samples were measured at room temperature. The identification of the transitions was done comparing the excitation and emission peaks with the results obtained from computer modelling. The scintillator properties of the pure and doped samples were checked by measuring the radioluminescence of the sample when excited with different types of radiation, revealing that these materials are promising radiation detectors.

  15. Examining the Features of Earth Science Logical Reasoning and Authentic Scientific Inquiry Demonstrated in a High School Earth Science Curriculum: A Case Study

    ERIC Educational Resources Information Center

    Park, Do-Yong; Park, Mira

    2013-01-01

    The purpose of this study was to investigate the inquiry features demonstrated in the inquiry tasks of a high school Earth Science curriculum. One of the most widely used curricula, Holt Earth Science, was chosen for this case study to examine how Earth Science logical reasoning and authentic scientific inquiry were related to one another and how…

  16. The High Definition Earth Viewing (HDEV) Payload

    NASA Technical Reports Server (NTRS)

    Muri, Paul; Runco, Susan; Fontanot, Carlos; Getteau, Chris

    2017-01-01

    The High Definition Earth Viewing (HDEV) payload enables long-term experimentation of four, commercial-of-the-shelf (COTS) high definition video, cameras mounted on the exterior of the International Space Station. The payload enables testing of cameras in the space environment. The HDEV cameras transmit imagery continuously to an encoder that then sends the video signal via Ethernet through the space station for downlink. The encoder, cameras, and other electronics are enclosed in a box pressurized to approximately one atmosphere, containing dry nitrogen, to provide a level of protection to the electronics from the space environment. The encoded video format supports streaming live video of Earth for viewing online. Camera sensor types include charge-coupled device and complementary metal-oxide semiconductor. Received imagery data is analyzed on the ground to evaluate camera sensor performance. Since payload deployment, minimal degradation to imagery quality has been observed. The HDEV payload continues to operate by live streaming and analyzing imagery. Results from the experiment reduce risk in the selection of cameras that could be considered for future use on the International Space Station and other spacecraft. This paper discusses the payload development, end-to- end architecture, experiment operation, resulting image analysis, and future work.

  17. Amphoteric doping of praseodymium Pr 3+ in SrTiO 3 grain boundaries

    DOE PAGES

    Yang, H.; Lee, H. S.; Kotula, P. G.; ...

    2015-03-26

    Charge Compensation in rare-earth Praseodymium (Pr 3+) doped SrTiO 3 plays an important role in determining the overall photoluminescence properties of the system. Here, the Pr 3+ doping behavior in SrTiO 3 grain boundaries (GBs) is analyzed using aberration corrected scanning transmission electron microscopy (STEM). The presence of Pr 3+ induces structure variations and changes the statistical prevalence of GB structures. In contrast to the assumption that Pr 3+ substitutes for A site as expected in the bulk, Pr 3+ is found to substitute both Sr and Ti sites inside GBs with the highest concentration in the Ti sites. Asmore » a result, this amphoteric doping behavior in the boundary plane is further confirmed by first principles theoretical calculations.« less

  18. Amphoteric Doping of Praseodymium Pr3+ in SrTiO3 Grain Boundaries

    DOE PAGES

    Yang, Hao; Lee, H. S.; Kotula, Paul G.; ...

    2015-03-23

    Charge Compensation in rare-earth Praseodymium (Pr 3+) doped SrTiO 3 plays an important role in determining the overall photoluminescence properties of the system. Here, the Pr 3+ doping behavior in SrTiO 3 grain boundaries (GBs) is analyzed using aberration corrected scanning transmission electron microscopy (STEM). The presence of Pr 3+ induces structure variations and changes the statistical prevalence of GB structures. In contrast to the assumption that Pr 3+ substitutes for A site as expected in the bulk, Pr 3+ is found to substitute both Sr and Ti sites inside GBs with the highest concentration in the Ti sites. Asmore » a result, this amphoteric doping behavior in the boundary plane is further confirmed by first principles theoretical calculations.« less

  19. Surface-Directed Synthesis of Erbium-Doped Yttrium Oxide Nanoparticles within Organosilane Zeptoliter Containers

    PubMed Central

    2015-01-01

    We introduce an approach to synthesize rare earth oxide nanoparticles using high temperature without aggregation of the nanoparticles. The dispersity of the nanoparticles is controlled at the nanoscale by using small organosilane molds as reaction containers. Zeptoliter reaction vessels prepared from organosilane self-assembled monolayers (SAMs) were used for the surface-directed synthesis of rare earth oxide (REO) nanoparticles. Nanopores of octadecyltrichlorosilane were prepared on Si(111) using particle lithography with immersion steps. The nanopores were filled with a precursor solution of erbium and yttrium salts to confine the crystallization step to occur within individual zeptoliter-sized organosilane reaction vessels. Areas between the nanopores were separated by a matrix film of octadecyltrichlorosilane. With heating, the organosilane template was removed by calcination to generate a surface array of erbium-doped yttria nanoparticles. Nanoparticles synthesized by the surface-directed approach retain the periodic arrangement of the nanopores formed from mesoparticle masks. While bulk rare earth oxides can be readily prepared by solid state methods at high temperature (>900 °C), approaches for preparing REO nanoparticles are limited. Conventional wet chemistry methods are limited to low temperatures according to the boiling points of the solvents used for synthesis. To achieve crystallinity of REO nanoparticles requires steps for high-temperature processing of samples, which can cause self-aggregation and dispersity in sample diameters. The facile steps for particle lithography address the problems of aggregation and the requirement for high-temperature synthesis. PMID:25163977

  20. Doping dependence of ordered phases and emergent quasiparticles in the doped Hubbard-Holstein model

    DOE PAGES

    Mendl, C. B.; Nowadnick, E. A.; Huang, E. W.; ...

    2017-11-15

    Here, we present determinant quantum Monte Carlo simulations of the hole-doped single-band Hubbard-Holstein model on a square lattice, to investigate how quasiparticles emerge when doping a Mott insulator (MI) or a Peierls insulator (PI). The MI regime at large Hubbard interaction U and small relative e-ph coupling strength λ is quickly suppressed upon doping, by drawing spectral weight from the upper Hubbard band and shifting the lower Hubbard band towards the Fermi level, leading to a metallic state with emergent quasiparticles at the Fermi level. On the other hand, the PI regime at large λ and small U persists outmore » to relatively high doping levels. We study the evolution of the d-wave superconducting susceptibility with doping, and find that it increases with lowering temperature in a regime of intermediate values of U and λ.« less