Sample records for nanocrystalline nd2o3 supported

  1. Silver film on nanocrystalline TiO{sub 2} support: Photocatalytic and antimicrobial ability

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

    Vukoje, Ivana D., E-mail: ivanav@vinca.rs; Tomašević-Ilić, Tijana D., E-mail: tommashev@gmail.com; Zarubica, Aleksandra R., E-mail: zarubica2000@yahoo.com

    Highlights: • Simple photocatalytic rout for deposition of Ag on nanocrystalline TiO{sub 2} films. • High antibactericidal efficiency of deposited Ag on TiO{sub 2} support. • Improved photocatalytic performance of TiO{sub 2} films in the presence of deposited Ag. - Abstract: Nanocrystalline TiO{sub 2} films were prepared on glass slides by the dip coating technique using colloidal solutions consisting of 4.5 nm particles as a precursor. Photoirradiation of nanocrystalline TiO{sub 2} film modified with alanine that covalently binds to the surface of TiO{sub 2} and at the same time chelate silver ions induced formation of metallic silver film. Optical andmore » morphological properties of thin silver films on nanocrystalline TiO{sub 2} support were studied by absorption spectroscopy and atomic force microscopy. Improvement of photocatalytic performance of nanocrystalline TiO{sub 2} films after deposition of silver was observed in degradation reaction of crystal violet. Antimicrobial ability of deposited silver films on nanocrystalline TiO{sub 2} support was tested in dark as a function of time against Escherichia coli, Staphylococcus aureus, and Candida albicans. The silver films ensured maximum cells reduction of both bacteria, while the fungi reduction reached satisfactory 98.45% after 24 h of contact.« less

  2. Nanocrystalline NiNd0.01Fe1.99O4 as a gas sensor

    NASA Astrophysics Data System (ADS)

    Shinde, Tukaram J.; Gadkari, Ashok B.; Jadhav, Sarjerao R.; Kumar, Surender; Dalawai, Sanjeev P.; Vasambekar, Pramod N.

    2015-06-01

    Nanocrystalline NiNd0.01Fe1.99O4 has been synthesized by oxalate co-precipitation method and was characterized by X-ray diffraction technique. X-ray diffraction analysis confirms the formation of single phase cubic spinel structure. Crystallite size of the ferrite lies in the nano-particle range. The gas sensing properties of nanocrystalline ferrite were studied for gases like Cl2, LPG and C2H5OH. It was observed that NiNd0.01Fe1.99O4 is more sensitive towards chlorine followed by LPG at an operating temperature 277 °C compared to ethanol.

  3. Room temperature ferromagnetism of nanocrystalline Nd1.90Ni0.10O3

    NASA Astrophysics Data System (ADS)

    Sarkar, B. J.; Mandal, J.; Dalal, M.; Bandyopadhyay, A.; Chakrabarti, P. K.

    2018-05-01

    Nanocrystalline sample of Ni2+ doped neodymium oxide (Nd1.90Ni0.10O3-δ, NNO) is synthesized by co-precipitation method. Analysis of X-ray diffraction (XRD) pattern by Rietveld refinement method confirms the desired phase of NNO and complete substitution of Ni2+ ions in the Nd2O3 lattice. Analyses of transmission electron microscopy (TEM) and Raman spectroscopy of NNO recorded at room temperature (RT) also substantiate this fact. Besides, no traces of impurities are found in the analyses of XRD, TEM and Raman data. Room temperature hysteresis loop of NNO suggests the presence of weak ferromagnetism (FM) in low field region ( 600 mT), but in high field region paramagnetism of the host is more prominent. Magnetization vs. temperature ( M- T) curve in the entire temperature range (300-5 K) is analyzed successfully by a combined equation generated from three-dimensional (3D) spin wave model and Curie-Weiss law, which suggests the presence of mixed paramagnetic phase together with ferromagnetic phase in the doped sample. The onset of magnetic ordering is analyzed by oxygen vacancy mediated F-center exchange (FCE) coupling mechanism.

  4. Nanocrystalline NiNd{sub 0.01}Fe{sub 1.99}O{sub 4} as a gas sensor

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

    Shinde, Tukaram J., E-mail: pshindetj@yahoo.co.in; Gadkari, Ashok B.; Jadhav, Sarjerao R.

    2015-06-24

    Nanocrystalline NiNd{sub 0.01}Fe{sub 1.99}O{sub 4} has been synthesized by oxalate co-precipitation method and was characterized by X-ray diffraction technique. X-ray diffraction analysis confirms the formation of single phase cubic spinel structure. Crystallite size of the ferrite lies in the nano-particle range. The gas sensing properties of nanocrystalline ferrite were studied for gases like Cl{sub 2}, LPG and C{sub 2}H{sub 5}OH. It was observed that NiNd{sub 0.01}Fe{sub 1.99}O{sub 4} is more sensitive towards chlorine followed by LPG at an operating temperature 277 °C compared to ethanol.

  5. Spectroscopic Properties of B2O3-PbO-Nd2O3 Glasses

    NASA Astrophysics Data System (ADS)

    Simon, V.; Ardelean, I.; Milea, I.; Peteanu, M.; Simon, S.

    Samples belonging to xNd2O3(100-x) [2B2O3·PbO] glass system, with 0≤ x≤ 40 mol%, are investigated by IR and UV-VIS spectroscopies in order to obtain evidence for the influence of Nd2O3 on the local order from 2B2O3·PbO glass matrix. Besides the IR absorption bands characteristic to lead and boron arrangements, typical absorption lines of Nd3+ ions around 4000 cm-1 and 6000 cm-1 are recorded. The 6000 cm-1 band appears only for the samples with x≥25 mol% Nd2O3. The split of some UV-VIS absorption bands arising from transitions of neodymium ions in doublet lines as well as the shift of the absorption bands as the Nd2O3 content increases denote the influence of the lead-borate matrix on the radiative transitions of the lanthanide ion.

  6. Lanthanite-(Nd), Nd2(CO3)3·8H2O

    PubMed Central

    Morrison, Shaunna M.; Andrade, Marcelo B.; Wenz, Michelle D.; Domanik, Kenneth J.; Downs, Robert T.

    2013-01-01

    Lanthanite-(Nd), ideally Nd2(CO3)3·8H2O [dineodymium(III) tricarbonate octa­hydrate], is a member of the lanthanite mineral group characterized by the general formula REE 2(CO3)3·8H2O, where REE is a 10-coordinated rare earth element. Based on single-crystal X-ray diffraction of a natural sample from Mitsukoshi, Hizen-cho, Karatsu City, Saga Prefecture, Japan, this study presents the first structure determination of lanthanite-(Nd). Its structure is very similar to that of other members of the lanthanite group. It is composed of infinite sheets made up of corner- and edge-sharing of two NdO10-polyhedra (both with site symmetry ..2) and two carbonate triangles (site symmetries ..2 and 1) parallel to the ab plane, and stacked perpendicular to c. These layers are linked to one another only through hydrogen bonding involving the water mol­ecules. PMID:23476479

  7. [Effect of temperature on the structure of CaO-MgO-Al2O3-SiO2 nanocrystalline glass-ceramics studied by Raman spectroscopy].

    PubMed

    Li, Bao-Wei; Ouyang, Shun-Li; Zhang, Xue-Feng; Jia, Xiao-Lin; Deng, Lei-Bo; Liu, Fang

    2014-07-01

    In the present paper, nanocrystalline glass-ceramic of CaO-MgO-Al2O3-SiO2 system was produced by melting method. The CaO-MgO-Al2O3-SiO2 nanocrystalline glass-ceramic was measured by Raman spectroscopy in the temperature range from -190 to 310 degrees C in order to study the effect of temperature on the structure of this system nanocrystalline glass-ceramics. The results showed that different non-bridge oxygen bond silicon-oxygen tetrahedron structural unit changes are not consistent with rising temperature. Further analyses indicated that: the SiO4 tetrahedron with 2 non-bridged oxygen (Q2), the SiO4 tetrahedron with 3 non-bridged oxygen (Q(1)), which are situated at the edge of the 3-D SiO4 tetrahedrons network, and the SiO4 tetrahedron with 4 non-bridged oxygen (Q(0)), which is situated outside the 3-D network all suffered a significant influence by the temperature change, which has been expressed as: shifts towards the high wave-number, increased bond force constants, and shortened bond lengths. This paper studied the influence of temperature on CMAS system nanocrystalline glass-ceramics using variable temperature Raman technology. It provides experiment basis to the research on external environment influence on CMAS system nanocrystalline glass-ceramics materials in terms of structure and performance. In addition, the research provides experimental basis for controlling the expansion coefficient of nanocrystalline glass-ceramic of CaO-MgO-Al2O3-SiO2 system.

  8. Nd2O3-SiO2 nanocomposites: A simple sonochemical preparation, characterization and photocatalytic activity.

    PubMed

    Zinatloo-Ajabshir, Sahar; Mortazavi-Derazkola, Sobhan; Salavati-Niasari, Masoud

    2018-04-01

    Nd 2 O 3 -SiO 2 nanocomposites with enhanced photocatalytic activity have been obtained through simple and rapid sonochemical route in presence of putrescine as a new basic agent, for the first time. The influence of the mole ratio of Si:Nd, basic agent and ultrasonic power have been optimized to obtain the best Nd 2 O 3 -SiO 2 nanocomposites on shape, size and photocatalytic activity. The produced Nd 2 O 3 -SiO 2 nanocomposites have been characterized utilizing XRD, EDX, TEM, FT-IR, DRS and FESEM. Application of the as-formed Nd 2 O 3 -SiO 2 nano and bulk structures as photocatalyst with photodegradation of methyl violet contaminant under ultraviolet illumination was compared. Results demonstrated that SiO 2 has remarkable effect on catalytic performance of Nd 2 O 3 photocatalyst for decomposition. By introducing of SiO 2 to Nd 2 O 3 , decomposition efficiency of Nd 2 O 3 toward methyl violet contaminant under ultraviolet illumination was increased. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. Impedance spectroscopy study of SiO2-Li2O:Nd2O3 glasses

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

    Pereia, R.; Gozzo, C B; Guedes, I.

    2014-01-01

    In the present study, neodymium-doped lithium silicate glasses have been prepared by the conventional melt-quenching technique. The dielectric properties, electric modulus and electrical conductivity of SiO2-Li2O (SiLi-0Nd) and SiO2-Li2O:Nd2O3 (SiLi-1.35Nd) have been studied from 1 Hz to 1 MHz in the 333 423 K temperature range. At a given temperature and frequency, we observe that the resistivity increases while the conductivity accordingly decreases when neodymium ions are added to the glass matrix. The activation energy of two distinct regions was evaluated from the ln( dc)=f(1/T) plot and was found to be E1(T<363K)=0.61(0.66)eV and E2(T>363K)=1.26(1.09)eV for SiLi-0Nd (SiLi-1,35Nd). The dielectric constantmore » ( Re) decreases while the dielectric loss (tan ( )) increases under Nd2O3 doping. We also observe that for both glasses, Re and tan ( ) tend to increase with increasing temperature and decrease with increasing frequency.« less

  10. Nd3+-doped TeO2-Bi2O3-ZnO transparent glass ceramics for laser application at 1.06 μm

    NASA Astrophysics Data System (ADS)

    Hu, Xiaolin; Luo, Zhiwei; Liu, Taoyong; Lu, Anxian

    2017-04-01

    The high crystallinity transparent glass ceramics based on Nd3+-doped 70TeO2-15Bi2O3-15ZnO (TBZ) compositions were successfully prepared by two-step heat treatment process. The effects of Nd2O3 content on the thermal, structural, mechanical, and optical properties of TBZ glass ceramics were studied. The incorporation of Nd2O3 enhanced the crystallization tendency in the matrix glass composition. The crystal phase and morphology of Bi2Te4O11 in the glass ceramics were confirmed by X-ray diffraction and field emission scanning electron microscopy. Due to precipitate more crystal phase, the hardness values increased from 3.21 to 3.66 GPa. Eight absorption peaks were observed from 400 to 900 nm and three emission bands appeared in the range of 850-1400 nm. With the increasing of Nd2O3 content from 0.5 to 2.5 wt%, the intensity of absorption peaks enhanced and the emission intensity increased up to 1.0 wt% and then fell down for further dopant concentration. The fluorescence decay lifetime decreased rapidly starting from 1.5 wt% Nd2O3 content due to the obvious energy migration among Nd3+. According to the extreme strong emission band around 1062 nm and the optimum Nd2O3 content (1.0 wt%), N10 glass ceramic was considered as a potential material for 1.06 μm laser applications.

  11. Preparation of Nanocrystalline Powders of ZrO2, Stabilized by Y2O3 Dobs for Ceramics

    NASA Astrophysics Data System (ADS)

    Petrunin, V. F.; Korovin, S. A.

    The purpose of this study was to develop a synthesis conditions and produce samples of nanocrystalline zirconia powder in a high-temperature phase state. To increase the stability of this state at room temperature, Y2O3 was used as a dop in the two-stages chemical method including coprecipitation mixture of the corresponding hydroxides and air drying. To reduce agglomeration of nanoparticles during heat treatment of precursors the microwave oven instead of a muffle was used. Different characterisation methods have been used to determine that the obtained powders are nano-scale corresponds to a high-temperature tetragonal phase of ZrO2. It is shown that such nanocrystalline powders may be used to produce highly-dense nanoceramics.

  12. The effects of Nd2O3 concentration in the laser emission of TeO2-ZnO glasses

    NASA Astrophysics Data System (ADS)

    Moreira, L. M.; Anjos, V.; Bell, M. J. V.; Ramos, C. A. R.; Kassab, L. R. P.; Doualan, D. J. L.; Camy, P.; Moncorgé, R.

    2016-08-01

    The present work reports the modification introduced by different Nd2O3 concentration on optical properties and the laser operation of Nd3+ doped (TeO2-ZnO) bulk tellurite glass. The spectroscopic data are analyzed within the Judd Ofelt formalism framework and the results are compared to the fluorescence lifetime and emission measurements to derive values for the quantum efficiency and the stimulated emission cross section of the considered 4F3/2 → 4I11/2 infrared laser transition around 1062.5 nm. Continuous-wave laser action is achieved with this bulk tellurite glass by pumping the sample inside a standard plan-concave mirror laser cavity with different output couplers. It is possible to observe coherent emission only for the lower concentration (0.5%(wt.) of Nd2 O3). Also laser action could only be observed for this sample with threshold pump power of 73 mW associated with a laser slope efficiency of 8% for an output coupler transmission of 4% indicating that TeO2-ZnO are potential materials for laser action. The results presented in this work together with those previously reported with higher concentration (1.0% (wt) of Nd2O3) determine the adequate Nd2O3 concentration for laser action and guide the correct experimental procedure for TeO2-ZnO glasses preparation.

  13. Ga2O3 and GaN nanocrystalline film: reverse micelle assisted solvothermal synthesis and characterization.

    PubMed

    Sinha, Godhuli; Ganguli, Dibyendu; Chaudhuri, Subhadra

    2008-03-01

    Gallium oxide (beta-Ga2O3) nanoparticles were successfully deposited on quartz glass substrates using sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/n-hexane/ethylene glycol monomethyl ether (EGME) reverse micelle-mediated solvothermal process with different omega values. The mean diameter of Ga2O3 particles was approximately 2-3 nm and found to be approximately independent of omega values of the reverse micelles. However, when the Ga2O3 nanocrystalline films were nitrided at 900 degrees C under flowing NH3 atmosphere for 1 h, the mean diameter of the resulted gallium nitride (wurtzite-GaN) nanoparticles varied from 3-9 nm. Both nanocrystalline films of Ga2O3 and GaN were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, UV-vis spectroscopy and photoluminescence in order to study their chemical and physical properties explicitly.

  14. A neodymium(III)-ammonium complex involving oxalate and carbonate ligands: (NH4)2[Nd2(C2O4)3(CO3)(H2O)].H2O.

    PubMed

    Trombe, Jean-Christian; Galy, Jean; Enjalbert, Renée

    2002-10-01

    The title compound, diammonium aqua-mu-carbonato-tri-mu-oxalato-dineodymium(III) hydrate, (NH(4))(2)[Nd(2)(CO(3))(C(2)O(4))(3)(H(2)O)].H(2)O, involving the two ligands oxalate and carbonate, has been prepared hydrothermally as single crystals. The Nd atoms form a tetranuclear unit across the inversion centre at (1/2, 1/2, 1/2). Starting from this tetranuclear unit, the oxalate ligands serve to develop a three-dimensional network. The carbonate group acts as a bis-chelating ligand to two Nd atoms, and is monodentate to a third Nd atom. The oxalate groups are all bis-chelating. The two independent Nd atoms are ninefold coordinated and the coordination polyhedron of these atoms is a distorted monocapped antiprism.

  15. Cation and Vacancy Disorder in U 1-yNd yO 2.00-X Alloys

    DOE PAGES

    Barabash, Rozaliya I.; Voit, Stewart L.; Aidhy, Dilpuneet S.; ...

    2015-09-14

    In this study, the intermixing and clustering of U/Nd, O, and vacancies were studied by both laboratory and synchrotron-based x-ray diffraction in U 1-yNd yO 2-X alloys. It was found that an increased holding time at the high experimental temperature during initial alloy preparation results in a lower disorder of the Nd distribution in the alloys. Adjustment of the oxygen concentration in the U 1-yNd yO 2-X alloys with different Nd concentrations was accompanied by the formation of vacancies on the oxygen sublattice and a nanocrystalline component. The lattice parameters in the U 1-yNd yO 2-X alloys were also foundmore » to deviate significantly from Vegard's law when the Nd concentration was high (53%) and decreased with increasing oxygen concentration. Such changes indicate the formation of large vacancy concentrations during oxygen adjustment at these high temperatures. Finally, the change in the vacancy concentration after the oxygen adjustment was estimated relative to Nd concentration and oxygen stoichiometry.« less

  16. [Raman studies of nanocrystalline BaTiO3 ceramics].

    PubMed

    Xiao, Chang-jiang; Jin, Chang-qing; Wang, Xiao-hui

    2008-12-01

    High pressure can significantly increase the densification. Further, during the high pressure assisted sintering, the nucleation rate is increased due to reduced energy barrier and the growth rate is suppressed due to the decreased diffusivity. Thus high pressure enables the specimen to be fabricated with relatively lower temperature and shorter sintering period that assures to obtain dense nanocrystalline ceramics. Dense nanocrystalline BaTiO3 ceramics with uniform grain sizes of 60 and 30 nm, respectively, were obtained by pressure assisted sintering. The crystal structure and phase transitions were investigated by Raman scattering at temperatures ranging from -190 to 200 degrees C. The Raman results indicated that the evolution of Raman spectrum with grain size is characterized by an intensity decrease, a broadening of the line width, a frequency shift, and the disappearance of the Raman mode. With increasing temperature, similar to 3 mm BaTiO3 normal ceramics, the successive phase transitions from rhombohedral to orthorhombic, orthorhombic to tetragonal, and tetragonal to cubic were also observed in nanocrystalline BaTiO3 ceramics. In addition, when particle size is reduced to the nanoscale, one will find some unusual physical properties in nanocrystalline ceramics, compared with those of coarse-grained BaTiO3 ceramics. The different coexistences of multiphase were found at different temperature. Especially, the ferroelectric tetragonal and orthorhombic phase can coexist at room temperature in nanocrystalline BaTiO3 ceramics. The phenomenon can be explained by the internal stress. The coexistences of different ferroelectric phases at room temperature indicate that the critical grain size for the disappearance of ferroelectricity in nanocrystalline BaTiO3 ceramics fabricated by pressure assisted sintering is below 30 nm.

  17. Effects of nano-YAG (Y 3Al 5O 12) crystallization on the structure and photoluminescence properties of Nd 3+-doped K 2O-SiO 2-Y 2O 3-Al 2O 3 glasses

    NASA Astrophysics Data System (ADS)

    Tarafder, Anal; Molla, Atiar Rahaman; Karmakar, Basudeb

    2010-10-01

    Nd 3+-doped precursor glass in the K 2O-SiO 2-Y 2O 3-Al 2O 3 (KSYA) system was prepared by the melt-quench technique. The transparent Y 3Al 5O 12 (YAG) glass-ceramics were derived from this glass by a controlled crystallization process at 750 °C for 5-100 h. The formation of YAG crystal phase, size and morphology with progress of heat-treatment was examined by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and Fourier transformed infrared reflectance spectroscopy (FT-IRRS). The crystallite sizes obtained from XRD are found to increase with heat-treatment time and vary in the range 25-40 nm. The measured photoluminescence spectra have exhibited emission transitions of 4F 3/2 → 4I J ( J = 9/2, 11/2 and 13/2) from Nd 3+ ions upon excitation at 829 nm. It is observed that the photoluminescence intensity and excited state lifetime of Nd 3+ ions decrease with increase in heat-treatment time. The present study indicates that the incorporation of Nd 3+ ions into YAG crystal lattice enhance the fluorescence performance of the glass-ceramic nanocomposites.

  18. Effect of RE (Nd3+, Sm3+) oxide on structural, optical properties of Na2O-Li2O-ZnO-B2O3 glass system

    NASA Astrophysics Data System (ADS)

    Hivrekar, Mahesh M.; Bhoyar, D. N.; Mande, V. K.; Dhole, V. V.; Solunke, M. B.; Jadhav, K. M.

    2018-05-01

    Zinc borate glass activated with rare earth oxide (Nd2O3, Sm2O3) of Na2O-Li2O-ZnO-B2O3 quaternary system has been prepared successfully by melt quenching method. The nucleation and growth of RE oxide were controlled temperature range 950-1000° C and rapid cooling at room temperature. The physical, structural and optical properties were characterized by using X-ray diffraction (XRD), SEM, Ultraviolet-visible spectroscopy (UV-Vis). XRD and SEM studies confirmed the amorphous nature, surface morphology of prepared zinc borate glass. The physical parameters like density, molar volume, molar mass of Nd3+, Sm3+ doped borate glass are summarized in the present article. The optical absorption spectra along with tauc's plot are presented. The optical energy band gap increases due to the addition of rare earth oxide confirming the role of network modifier.

  19. Near-infrared luminescence of Bi2ZnOB2O6:Nd3+/PMMA composite

    NASA Astrophysics Data System (ADS)

    Jaroszewski, K.; Głuchowski, P.; Chrunik, M.; Jastrząb, R.; Majchrowski, A.; Kasprowicz, D.

    2018-01-01

    Near-infrared luminescence of a novel polymer composite system: PMMA doped with Bi2ZnOB2O6:Nd3+ microparticles, is reported for the first time. Luminescence properties of Bi2ZnOB2O6:Nd3+/PMMA were analyzed on the basis on excitation and emission spectra as well as fluorescence decay profiles. Excitation spectra monitored at 1062 nm (4F3/2 → 4I11/2) indicate numerous bands related to the optical transition of Nd3+ ions: from the 4I9/2 ground state to the 4D3/2, 2P1/2, 2K15/2, 4G7/2 + 4G9/2, 2K13/2, 4G5/2 + 2G7/2, 2H11/2, 4F9/2, 4F7/2 + 4S3/2, 4F5/2 + 2H9/2, 4F3/2 excited states. Many of them may be utilized to excite near-infrared emission of Nd3+ ions. In particular, distinctive Nd3+ emissions of the 4F3/2 → 4I9/2 and 4F3/2 → 4I11/2 transitions were detected, under excitation at 514 nm. The fluorescence decay profiles monitored at 1062 nm, excited at 514 nm, show relatively long emission lifetime of the 4F3/2 → 4I11/2 transition equal to 85 μs. Raman spectroscopy was used to determine vibrational properties and homogeneity of Bi2ZnOB2O6:Nd3+/PMMA composites. The obtained results suggest that Bi2ZnOB2O6:Nd3+/PMMA composite may be applied as an effective source of near-infrared emission in a new integrated optoelectronic devices.

  20. A Nanocrystalline Fe2O3 Film Anode Prepared by Pulsed Laser Deposition for Lithium-Ion Batteries

    NASA Astrophysics Data System (ADS)

    Teng, Xiaoling; Qin, Youzhi; Wang, Xia; Li, Hongsen; Shang, Xiantao; Fan, Shuting; Li, Qiang; Xu, Jie; Cao, Derang; Li, Shandong

    2018-02-01

    Nanocrystalline Fe2O3 thin films are deposited directly on the conduct substrates by pulsed laser deposition as anode materials for lithium-ion batteries. We demonstrate the well-designed Fe2O3 film electrodes are capable of excellent high-rate performance (510 mAh g- 1 at high current density of 15,000 mA g- 1) and superior cycling stability (905 mAh g- 1 at 100 mA g- 1 after 200 cycles), which are among the best reported state-of-the-art Fe2O3 anode materials. The outstanding lithium storage performances of the as-synthesized nanocrystalline Fe2O3 film are attributed to the advanced nanostructured architecture, which not only provides fast kinetics by the shortened lithium-ion diffusion lengths but also prolongs cycling life by preventing nanosized Fe2O3 particle agglomeration. The electrochemical performance results suggest that this novel Fe2O3 thin film is a promising anode material for all-solid-state thin film batteries.

  1. Comparison of magnetic and thermoelectric properties of (Nd,Ca)BaCo2O5.5 and (Nd,Ca)CoO3

    NASA Astrophysics Data System (ADS)

    Kolesnik, S.; Dabrowski, B.; Chmaissem, O.; Wojciechowski, K.; Świerczek, K.

    2012-04-01

    Magnetic and thermoelectric properties of Nd1-xCaxBaCo2O5.5 and Nd1-xCaxCoO3 have been studied. Ca doping in Nd1-xCaxBaCo2O5.5 (x ≤ 0.2) preserves the metal to insulator transition (MIT) at 340-360 K. While the antiferromagnetic state disappears upon doping, the Curie temperature is increasing and becomes close to MIT for x > 0.12. The magnetic susceptibility of Nd1-xCaxCoO3 is paramagnetic for x up to 0.2, similar to the parent compound, with some indication of cluster-glass-like behavior at temperatures below 30 K. The increasing effective paramagnetic moments with doping suggest a low spin state of Co3+ and a high spin state of Co4+. Maximum observed ZT reaches a value close to 0.2 for x = 0.15 at 800 K, which is one of the highest values for perovskite cobaltites.

  2. The luminescence properties of nanocrystalline phosphors Mg2SiO4:Eu3+

    NASA Astrophysics Data System (ADS)

    Kolomytsev, A. Y.; Mamonova, D. V.; Manshina, A. A.; Kolesnikov, I. E.

    2017-11-01

    Nanocrystalline Eu3+-doped Mg2SiO4 powders were prepared with combined Pechini-solid phase synthesis. The structural properties were investigated with XRD, SEM and Raman spectroscopy. XRD pattern indicated that Mg2SiO4:Eu3+ were obtained with formation of other phase: MgO. Raman spectrum revealed good homogeneity and crystallinity of synthesized nanopowders. The luminescence properties were studied with measurement of excitation and emission spectra and decay curves. The effect of Eu3+ concentration on 5D0 level lifetime was studied. Most probably, the observed shortening of 5D0 level lifetime with Eu3+ concentration is caused by increase of nonradiative process probability.

  3. Salt-assistant combustion synthesis of nanocrystalline Nd{sub 2}(Zr{sub 1-x}Sn{sub x}){sub 2}O{sub 7} (0 {<=} x {<=} 1) solid solutions

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

    Tong Yuping, E-mail: huabeitong@yahoo.cn; Wang Yanping

    2009-11-15

    Nanocrystalline Nd{sub 2}(Zr{sub 1-x}Sn{sub x}){sub 2}O{sub 7} series solid solutions were prepared by a convenient salt-assisted combustion process using glycine as fuel. The samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, transmission electron microscopy and high-resolution transmission electron microscopy. The results showed the Zr ion can be partially replaced by Sn ion. The partial substituted products were still single-phase solid solutions and the crystal form remained unchanged. TEM images reveal that the products are composed of well-dispersed square-shaped nanocrystals. The method provides a convenient and low-cost route for the synthesis of nanostructures of oxide materials.

  4. SmNiO3/NdNiO3 thin film multilayers

    NASA Astrophysics Data System (ADS)

    Girardot, C.; Pignard, S.; Weiss, F.; Kreisel, J.

    2011-06-01

    Rare earth nickelates RENiO3 (RE =rare earth), which attract interest due to their sharp metal-insulator phase transition, are instable in bulk form due to the necessity of an important oxygen pressure to stabilize Ni in its 3+ state of oxidation. Here, we report the stabilization of RE nickelates in [(SmNiO3)t/(NdNiO3)t]n thin film multilayers, t being the thickness of layers alternated n times. Both bilayers and multilayers have been deposited by metal-organic chemical vapor deposition. The multilayer structure and the presence of the metastable phases SmNiO3 and NdNiO3 are evidenced from by x-ray and Raman scattering. Electric measurements of a bilayer structure further support the structural quality of the embedded RE nickelate layers.

  5. Oxidant effect of La(NO3)3·6H2O solution on the crystalline characteristics of nanocrystalline ZrO2 films grown by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Oh, Nam Khen; Kim, Jin-Tae; Kang, Goru; An, Jong-Ki; Nam, Minwoo; Kim, So Yeon; Park, In-Sung; Yun, Ju-Young

    2017-02-01

    Nanocrystalline ZrO2 films were synthesized by atomic layer deposition method using CpZr[N(CH3)2]3 (Cp = C5H5) as the metal precursor and La(NO3)3·6H2O solution as the oxygen source. La element in the deposited ZrO2 films could not be detected as its content was below the resolution limit of the X-ray photoelectron spectroscopy. The alternative introduction of La(NO3)3·6H2O solution to conventionally used H2O as the oxidant effectively altered the crystalline structure, grain size, and surface roughness of the grown ZrO2 films. Specifically, the crystalline structure of the ZrO2 film changed from a mixture of tetragonal and monoclinic phases to monoclinic phase. The average grain size also increased, and the resulting film surface became rougher. The average grain sizes of the ZrO2 films prepared from La(NO3)3·6H2O solution at concentrations of 10, 20, 30, and 40% were 280, 256, 208, and 200 nm, respectively, whereas that prepared using H2O oxidant was 142 nm. However, the concentration of La(NO3)3·6H2O solution minimally influenced the crystalline characteristics of the nanocrystalline ZrO2 films i.e., the crystalline structure, grain size, and surface roughness except for crystallite size.

  6. Thermodynamic Studies on NdFeO 3(s)

    NASA Astrophysics Data System (ADS)

    Parida, S. C.; Dash, Smruti; Singh, Ziley; Prasad, R.; Jacob, K. T.; Venugopal, V.

    2002-02-01

    The enthalpy increments and the standard molar Gibbs energy of formation of NdFeO3(s) have been measured using a high-temperature Calvet microcalorimeter and a solid oxide galvanic cell, respectively. A λ-type transition, related to magnetic order-disorder transformation (antiferromagnetic to paramagnetic), is apparent from the heat capacity data at ∼687 K. Enthalpy increments, except in the vicinity of transition, can be represented by a polynomial expression: {H°m(T)-H°m(298.15 K)}/J·mol-1 (±0.7%)=-53625.6+146.0(T/K) +1.150×10-4(T/K)2 +3.007×106(T/K)-1; (298.15≤T/K ≤1000). The heat capacity, the first differential of {H°m(T)-H°m(298.15 K)} with respect to temperature, is given by Cop, m/J·K-1·mol-1=146.0+2.30×10-4(T/K)-3.007×106(T/K)-2. The reversible emf's of the cell, (-) Pt/{NdFeO3(s) +Nd2O3(s)+Fe(s)}//YDT/CSZ//{Fe(s)'FeO'(s)}/Pt(+), were measured in the temperature range from 1004 to 1208 K. It can be represented within experimental error by a linear equation: E/V:(0.1418±0.0003)-(3.890±0.023)×10-5(T/K). The Gibbs energy of formation of solid NdFeO3 calculated by the least-squares regression analysis of the data obtained in the present study, and data for Fe0.95O and Nd2O3 from the literature, is given by ΔfG°m(NdFeO3, s)/kJ·mol-1(±2.0)=-1345.9+0.2542(T/K); (1000≤T/K ≤1650). The error in ΔfG°m(NdFeO3, s, T) includes the standard deviation in emf and the uncertainty in the data taken from the literature. Values of ΔfH°m(NdFeO3, s, 298.15 K) and S°m(NdFeO3, s, 298.15 K) calculated by the second law method are -1362.5 (±6) kJ·mol-1 and 123.9 (±2.5) J·K-1·mol-1, respectively. Based on the thermodynamic information, an oxygen potential diagram for the system Nd-Fe-O was developed at 1350 K.

  7. Bi12TiO20 crystallization in a Bi2O3-TiO2-SiO2-Nd2O3 system

    NASA Astrophysics Data System (ADS)

    Slavov, S.; Jiao, Z.

    2018-03-01

    Polycrystalline mono-phase bismuth titanate was produced by free cooling from melts heated to 1170 °C. The control over the initial amounts in the starting compositions in the system Bi2O3/TiO2/SiO2/Nd2O3 and over the thermal gradient of the heat process resulted in the formation of specific structures and microstructures of monophase sillenite ceramics. The main phase Bi12TiO20 belongs to the amorphous network groups based on oxides of silicon, bismuth and titanium. In this work, we demonstrated a way to control the crystalline and amorphous phase formation in bulk poly-crystalline materials in the selected system.

  8. Phase equilibria and crystal chemistry of the CaO-1/2 >Nd2O3-CoOz system at 885 °C in air

    NASA Astrophysics Data System (ADS)

    Wong-Ng, W.; Laws, W.; Talley, K. R.; Huang, Q.; Yan, Y.; Martin, J.; Kaduk, J. A.

    2014-07-01

    The phase diagram of the CaO-1/2 >Nd2O3-CoOz system at 885 °C in air has been determined. The system consists of two calcium cobaltate compounds that have promising thermoelectric properties, namely, the 2D thermoelectric oxide solid solution, (Ca3-xNdx)Co4O9-z (0≤x≤0.5), which has a misfit layered structure, and Ca3Co2O6 which consists of 1D chains of alternating CoO6 trigonal prisms and CoO6 octahedra. Ca3Co2O6 was found to be a point compound without the substitution of Nd on the Ca site. The reported Nd2CoO4 phase was not observed at 885 °C. A ternary (Ca1-xNd1+x)CoO4-z (x=0) phase, or (CaNdCo)O4-z, was found to be stable at this temperature. A solid solution region of distorted perovskite (Nd1-xCax)CoO3-z (0≤x≤0.25, space group Pnma) was established. In the peripheral binary systems, while a solid solution region was identified for (Nd1-xCax)2O3-z (0≤x≤0.2), Nd was not found to substitute in the Ca site of CaO. Six solid solution tie-line regions and six three-phase regions were determined in the CaO-Nd2O3-CoOz system in air.

  9. Processing and optical properties of Nd3+-doped SiO2-TiO2-Al2O3 planar waveguides

    NASA Astrophysics Data System (ADS)

    Xiang, Qing; Zhou, Yan; Ooi, Boon Siew; Lam, Yee Loy; Chan, Yuen Chuen; Kam, Chan Hin

    2000-05-01

    We report here the processing and optical characterization of Nd3+-doped SiO2-TiO2-Al2O3 planar waveguides deposited on SOS substrates by the sol-gel route combined with spin-coating and rapid thermal annealing. The recipes used for preparing the solutions by sol-gel route are in mole ratio of 93SiO2:20AlO1.5: x ErO1.5. In order to verify the residual OH content in the films, FTIR spectra were measured and the morphology of the material by the XRD analysis. Five 2-layer films annealed at a maximum temperature of 500 degrees C, 700 degrees C, 900 degrees, 1000 degrees C, 1100 degrees C respectively were fabricated on silicon. The FTIR and XRD curves show that annealing at 1050 degrees C for 15s effectively removes the OH in the materia and keeps the material amorphous. The propagation loss of the planar waveguides was measured by using the method based on scattering in measurements and the result was obtained to be 1.54dB/cm. The fluorescence spectra were measured with 514nm wavelength of Ar+ laser by directly shining the pump beam on the film instead of prism coupling. The results show that the 1 mole Nd3+ content recipe has the strongest emission efficiency among the four samples investigated.

  10. Electron-beam irradiation induced transformation of Cu2(OH)3NO3 nanoflakes into nanocrystalline CuO

    NASA Astrophysics Data System (ADS)

    Padhi, S. K.; Gottapu, S. N.; Krishna, M. Ghanashyam

    2016-05-01

    The transmission electron microscope electron-beam (TEM e-beam) as a material modification tool has been demonstrated. The material modification is realised in the high-resolution TEM mode (largest condenser aperture, 150 μm, and 200 nm spot size) at a 200 keV beam energy. The Cu2(OH)3NO3 (CHN) nanoflakes used in this study were microwave solution processed that were layered single crystals and radiation sensitive. The single domain CHN flakes disintegrate into a large number of individual CuO crystallites within a 90 s span of time. The sequential bright-field, dark-field, and selected area electron diffraction modes were employed to record the evolved morphology, microstructural changes, and structural transformation that validate CHN modification. High-resolution transmission electron microscopy imaging of e-beam irradiated regions unambiguously supports the growth of CuO nanoparticles (11.8(3.2) nm in diameter). This study demonstrates e-beam irradiation induced CHN depletion, subsequent nucleation and growth of nanocrystalline CuO regions well embedded in the parent burnt porous matrix which can be useful for miniaturized sensing applications. NaBH4 induced room temperature reduction of CHN to elemental Cu and its printability on paper was also demonstrated.The transmission electron microscope electron-beam (TEM e-beam) as a material modification tool has been demonstrated. The material modification is realised in the high-resolution TEM mode (largest condenser aperture, 150 μm, and 200 nm spot size) at a 200 keV beam energy. The Cu2(OH)3NO3 (CHN) nanoflakes used in this study were microwave solution processed that were layered single crystals and radiation sensitive. The single domain CHN flakes disintegrate into a large number of individual CuO crystallites within a 90 s span of time. The sequential bright-field, dark-field, and selected area electron diffraction modes were employed to record the evolved morphology, microstructural changes, and structural

  11. Temperature-dependent luminescence and temperature-stimulated NIR-to-VIS up-conversion in Nd3+-doped La2O3-Na2O-ZnO-TeO2 glasses

    NASA Astrophysics Data System (ADS)

    Sobczyk, Marcin

    2013-04-01

    Telluride glasses of the composition xNd2O3-(7-x)La2O3-3Na2O-25ZnO-65TeO2, where (0≤x≤7) were prepared by the melt quench technique. Some physical and optical properties of the glasses were evaluated. The thermal behavior i.e. glass transition and crystallization temperatures were studied by using TGA-DTA technique. Optical properties of Nd3+-doped telluride glasses were investigated between 298 and 700 K. Basing on the obtained values of J-O parameter values (×10-20 cm2: Ω2=4.49±0.84, Ω4=5.03±0.61, Ω6=4.31±0.73), the radiative transition probabilities (AT), radiative lifetimes (τR), fluorescence branching ratios (β) and emission cross-sections (σem) were calculated for the 4F3/2→4IJ/2 (where J=9, 11 and 13) transitions of Nd3+ ions. The τR value of the 4F3/2 level amount to 164 μs and is slightly higher than the measured decay time of 162 μs. With the increasing of Nd2O3 concentration from 0.5 to 7.0 mol% the experimental lifetime of the fluorescent level decreases from 162 to 5.6 μs. The estimated quantum efficiency amount to 100%, based on a comparison of τR and the experimental decay time of a slightly doped Nd3+ telluride glass. An analysis of the non-radiative decay was based on the cross-relaxation mechanisms. The 4F3/2→4I9/2 and 4F5/2→4I9/2 transitions were analyzed with respect to the fluorescence intensity ratio (FIR) and were found to be temperature dependent. Infrared-to-visible up-conversion emissions with a maximum at 603.0 and 635.3 nm were observed at high temperatures using the 804 nm excitation and are due to the 4G5/2→4I9/2 and 4G5/2→4I11/2 transitions of Nd3+ ions, respectively. The near quadratic dependence of fluorescence on excitation laser power confirms that two photons contribute to up-conversion of the orange emissions. The temperature-stimulated up-conversion excitation processes have been analyzed in detail. The optical results indicate that the investigated glasses are potentially applicable as a 1063 nm

  12. NIR-to-NIR Deep Penetrating Nanoplatforms Y2O3:Nd3+/Yb3+@SiO2@Cu2S toward Highly Efficient Photothermal Ablation.

    PubMed

    Zhang, Zhiyu; Suo, Hao; Zhao, Xiaoqi; Sun, Dan; Fan, Li; Guo, Chongfeng

    2018-05-02

    A difunctional nano-photothermal therapy (PTT) platform with near-infrared excitation to near-infrared emission (NIR-to-NIR) was constructed through core-shell structures Y 2 O 3 :Nd 3+ /Yb 3+ @SiO 2 @Cu 2 S (YRSC), in which the core Y 2 O 3 :Nd 3+ /Yb 3+ and shell Cu 2 S play the role of bioimaging and photothermal conversion function, respectively. The structure and composition of the present PTT agents (PTAs) were characterized by powder X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectra. The NIR emissions of samples in the biological window area were measured by photoluminescence spectra under the excitation of 808 nm laser; further, the penetration depth of NIR emission at different wavelengths in biological tissue was also demonstrated by comparing with visible (vis) emission from Y 2 O 3 :Yb 3+ /Er 3+ @SiO 2 @Cu 2 S and NIR emission from YRSC through different injection depths in pork muscle tissues. The photo-thermal conversion effects were achieved through the outer ultrasmall Cu 2 S nanoparticles simultaneously absorb NIR light emission from the core Y 2 O 3 :Nd 3+/ Yb 3+ and the 808 nm excitation source to generate heat. Further, the heating effect of YRSC nanoparticles was confirmed by thermal imaging and ablation of YRSC to Escherichia coli and human hepatoma (HepG-2) cells. Results indicate that the YRSC has potential applications in PTT and NIR imaging in biological tissue.

  13. One-pot synthesis and optical properties of Eu3+-doped nanocrystalline TiO2 and ZrO2

    NASA Astrophysics Data System (ADS)

    Julián, Beatriz; Corberán, Rosa; Cordoncillo, Eloisa; Escribano, Purificación; Viana, Bruno; Sanchez, Clément

    2005-11-01

    A simple and versatile one-pot sol-gel synthesis of Eu3+-doped nanocrystalline TiO2 and ZrO2 nanomaterials is reported in this paper. It consists of the controlled crystallization of Eu3+-doped TiO2 or ZrO2 nanoparticles from an initial solution containing the metal alkoxide, the lanthanide precursor, a complexing agent and a non-complexing acid. The main interest is that it could be extended to different lanthanide ions and inorganic metal oxides to prepare other multifunctional nanomaterials. The characterization by XRD, HRTEM and SAED techniques showed that the TiO2 and ZrO2 crystallization takes place at very low temperatures (60 °C) and that the crystallite size can be tailored by modifying the synthetic conditions. The optical properties of the resulting materials were studied by emission spectra and decay measurements. Both Eu3+:TiO2 and Eu3+:ZrO2 samples exhibited long lifetime values after removing organic components (τ = 0.7 and 1.3 ms, respectively), but the Eu3+:ZrO2 system is specially promising for photonic applications since its τ value is longer than some reported for other inorganic or hybrid matrices in which Eu3+ ions are complexed. This behaviour has been explained through an effective dispersion of the lanthanide ions within the ZrO2 nanocrystals.

  14. Magnetic structure of the mixed antiferromagnet NdMn0.8Fe0.2O3

    NASA Astrophysics Data System (ADS)

    Mihalik, Matúš; Mihalik, Marián; Hoser, Andreas; Pajerowski, Daniel M.; Kriegner, Dominik; Legut, Dominik; Lebecki, Kristof M.; Vavra, Martin; Fitta, Magdalena; Meisel, Mark W.

    2017-10-01

    The magnetic structure of the mixed antiferromagnet NdMn0.8Fe0.2O3 was resolved. Neutron powder diffraction data definitively resolve the Mn sublattice with a magnetic propagation vector k =(000 ) and with the magnetic structure (Ax,Fy,Gz ) for 1.6 K Nd sublattice has a (0 ,fy,0 ) contribution in the same temperature interval. The Mn sublattice undergoes a spin-reorientation transition at T1≈13 K while the Nd magnetic moment abruptly increases at this temperature. Powder x-ray diffraction shows a strong magnetoelastic effect at TN but no additional structural phase transitions from 3 to 300 K. Density functional theory calculations confirm the magnetic structure of the undoped NdMnO3 as part of our analysis. Taken together, these results show that the magnetic structure of the Mn sublattice in NdMn0.8Fe0.2O3 is a combination of the Mn and Fe parent compounds, but the magnetic ordering of the Nd sublattice spans a broader temperature interval than in the case of NdMnO3 and NdFeO3. This result is a consequence of the fact that the Nd ions do not order independently, but via polarization from the Mn/Fe sublattice.

  15. Fascinating functional properties of Mn:Gd2O3 nanocrystalline phosphor

    NASA Astrophysics Data System (ADS)

    Heiba, Zein K.; Imam, N. G.; Bakr Mohamed, Mohamed

    2015-10-01

    In the present work we through the light on some of the fascinating structural, magnetic and optical properties of Mn:Gd2O3 nanophosphor. Manganese substituted nanocrystalline Mn:Gd2O3 was prepared via a sol gel procedure. The prepared samples were characterized applying X-ray diffraction (XRD), infrared spectroscopy (IR), squid magnometer and photoluminance (PL). XRD and IR analysis revealed a single phase solid solution up to x = 0.2. The cation distribution of Mn and Gd between the crystallographically non-equivalent sites 8b and 24d of the space group Ia 3 bar is found to be preferentially for all samples. The lattice parameter decreases with composition x, accompanied with systematic variation in the r.m.s. microstrain < εL2 > 1 / 2 . The magnetic measurement showed negative values for curie paramagnetic temperatures, θ, which indicates an antiferromagnetic interaction between the magnetic ions in Mn:Gd2O3. PL spectra showed a series of emission lines in the room temperature fluorescence measurements under UV excitation (220 nm). The observed emission lines are stokes-shifted and the non-linearity optical phenomenon is confirmed. Further, the emission lines are slightly shifted with Mn concentration (x). The blue emission around (390-402) nm was appeared due to Mn doping. Because of its fascinating properties, Mn:Gd2O3 is recommended for fuel cells, photocatalytic, and biomedical applications.

  16. Syntheses of nanocrystalline BaTiO3 and their optical properties

    NASA Astrophysics Data System (ADS)

    Yu, J.; Chu, J.; Zhang, M.

    Stoichiometric and titanium-excess nanocrystalline barium titanates were synthesized using a hydrothermal process at various hydrothermal temperatures and with further heat treatment at 500 °C and 900 °C. Owing to the different process conditions, the excess titanium exists in different states and configurations within the nanocrystalline BaTiO3 matrix; this was demonstrated by X-ray diffraction, Raman scattering, and photoluminescence. In these nanocrystalline BaTiO3, the 590, 571, 543 and 694 nm light emission bands were observed; mechanisms leading to such emissions were also discussed.

  17. Magnetic structure of the mixed antiferromagnet NdMn 0.8 Fe 0.2 O 3

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

    Mihalik, Matus; Mihalik, Marian; Hoser, Andreas

    The magnetic structure of the mixed antiferromagnet NdMn 0.8Fe 0.2O 3 was resolved. Neutron powder diffraction data definitively resolve the Mn sublattice with a magnetic propagation vector k=(000) and with the magnetic structure (A x, F y, G z) for 1.6 K N(≈ 59 K). The Nd sublattice has a (0, f y, 0) contribution in the same temperature interval. The Mn sublattice undergoes a spin-reorientation transition at T 1 ≈ 13 K while the Nd magnetic moment abruptly increases at this temperature. Powder x-ray diffraction shows a strong magnetoelastic effect at T N but no additional structural phase transitionsmore » from 3 to 300 K. Density functional theory calculations confirm the magnetic structure of the undoped NdMnO 3 as part of our analysis. Taken together, these results show that the magnetic structure of the Mn sublattice in NdMn 0.8Fe 0.2O 3 is a combination of the Mn and Fe parent compounds, but the magnetic ordering of the Nd sublattice spans a broader temperature interval than in the case of NdMnO 3 and NdFeO 3. Lastly, this result is a consequence of the fact that the Nd ions do not order independently, but via polarization from the Mn/Fe sublattice.« less

  18. Magnetic structure of the mixed antiferromagnet NdMn 0.8 Fe 0.2 O 3

    DOE PAGES

    Mihalik, Matus; Mihalik, Marian; Hoser, Andreas; ...

    2017-10-27

    The magnetic structure of the mixed antiferromagnet NdMn 0.8Fe 0.2O 3 was resolved. Neutron powder diffraction data definitively resolve the Mn sublattice with a magnetic propagation vector k=(000) and with the magnetic structure (A x, F y, G z) for 1.6 K N(≈ 59 K). The Nd sublattice has a (0, f y, 0) contribution in the same temperature interval. The Mn sublattice undergoes a spin-reorientation transition at T 1 ≈ 13 K while the Nd magnetic moment abruptly increases at this temperature. Powder x-ray diffraction shows a strong magnetoelastic effect at T N but no additional structural phase transitionsmore » from 3 to 300 K. Density functional theory calculations confirm the magnetic structure of the undoped NdMnO 3 as part of our analysis. Taken together, these results show that the magnetic structure of the Mn sublattice in NdMn 0.8Fe 0.2O 3 is a combination of the Mn and Fe parent compounds, but the magnetic ordering of the Nd sublattice spans a broader temperature interval than in the case of NdMnO 3 and NdFeO 3. Lastly, this result is a consequence of the fact that the Nd ions do not order independently, but via polarization from the Mn/Fe sublattice.« less

  19. Ten Ghz YBa2Cu3O(7-Delta) Superconducting Ring Resonators on NdGaO3 Substrates

    NASA Technical Reports Server (NTRS)

    To, H. Y.; Valco, G. J.; Bhasin, K. B.

    1993-01-01

    YBa2Cu3O(7-delta) thin films were formed on NdGaO3 substrates by laser ablation. Critical temperatures greater than 89 K and critical current densities exceeding 2 x 10(exp 8) Acm(sub -2) at 77 K were obtained. The microwave performance of films patterned into microstrip ring resonators with gold ground planes was measured. An unloaded quality factor six times larger than that of a gold resonator of identical geometry was achieved. The unloaded quality factor decreased below 70 K for both the superconducting and gold resonators due to increasing dielectric losses in the substrate. The temperature dependence of the loss tangent of NdGaO3 was extracted from the measurements.

  20. Two mixed-ligand lanthanide–hydrazone complexes: [Pr(NCS)3(pbh)2]·H2O and [Nd(NCS)(NO3)(pbh)2(H2O)]NO3·2.33H2O [pbh is N′-(pyridin-2-ylmethylidene)benzo­hydrazide, C13H11N3O

    PubMed Central

    Paschalidis, Damianos G.; Harrison, William T. A.

    2016-01-01

    The gel-mediated syntheses and crystal structures of [N′-(pyridin-2-ylmethylidene-κN)benzohydrazide-κ2 N′,O]tris(thiocyanato-κN)praseodymium(III) mono­hydrate, [Pr(NCS)3(C13H11N3O)2]·H2O, (I), and aqua(nitrato-κ2 O,O′)[N′-(pyri­din-2-ylmethylidene-κN)benzohydrazide-κ2 N′,O](thiocyanato-κN)neo­dym­ium(III) nitrate 2.33-hydrate, [Nd(NCS)(NO3)(C13H11N3O)2(H2O)]NO3·2.33H2O, (II), are reported. The Pr3+ ion in (I) is coordinated by two N,N,O-tridentate N′-(pyridin-2-ylmethylidene)benzohydrazide (pbh) ligands and three N-bonded thio­cyanate ions to generate an irregular PrN7O2 coordination polyhedron. The Nd3+ ion in (II) is coordinated by two N,N,O-tridentate pbh ligands, an N-bonded thio­cyanate ion, a bidentate nitrate ion and a water mol­ecule to generate a distorted NdN5O5 bicapped square anti­prism. The crystal structures of (I) and (II) feature numerous hydrogen bonds, which lead to the formation of three-dimensional networks in each case. PMID:26958385

  1. YBa2Cu3O7 thin films on nanocrystalline diamond films for HTSC bolometer

    NASA Technical Reports Server (NTRS)

    Cui, G.; Beetz, C. P., Jr.; Boerstler, R.; Steinbeck, J.

    1993-01-01

    Superconducting YBa2Cu3O(7-x) films on nanocrystalline diamond thin films have been fabricated. A composite buffer layer system consisting of diamond/Si3N4/YSZ/YBCO was explored for this purpose. The as-deposited YBCO films were superconducting with Tc of about 84 K and a relatively narrow transition width of about 8 K. SEM cross sections of the films showed very sharp interfaces between diamond/Si3N4 and between Si3N4/YSZ. The deposited YBCO film had a surface roughness of about 1000 A, which is suitable for high-temperature superconductive (HTSC) bolometer fabrication. It was also found that preannealing of the nanocrystalline diamond thin films at high temperature was very important for obtaining high-quality YBCO films.

  2. Sintering characteristic and microwave dielectric properties of 0.45Ca0.6Nd0.267TiO3-0.55Li0.5Nd0.5TiO3 ceramics with La2O3-B2O3-ZnO additive

    NASA Astrophysics Data System (ADS)

    Chen, Yawei; Zhang, Shuren; Li, Enzhu; Niu, Na; Yang, Hongcheng

    2018-02-01

    The La2O3-B2O3-ZnO (LBZ) glass was proved to be an effective sintering aid of the 0.45Ca0.6Nd0.26TiO3-0.55Li0.5Nd0.5TiO3 (CNT-LNT) ceramics. The influence of LBZ glass on the phase composition, low temperature sintering process, microstructure, activation energy, and dielectric properties of CNT-LNT ceramics was investigated in detail. The LBZ glass induced an obvious decrease of the CNT-LNT ceramics sintering temperature from 1350 to 1000 °C due to the liquid phase formation, which reduced the activation energy ( E a) of the CNT-LNT ceramics. In addition, the near zero temperature coefficient of resonant frequency (τƒ) value was obtained by adding moderate quantity of LBZ glass. CNT-LNT + 5 wt% LBZ (CNT-LNT + 5L) ceramics sintered at 1000°C/4 h displayed good microwave dielectric properties of: ɛ r = 101.7, Q × f = 1560 GHz ( f = 3.25 GHz) and τ ƒ = 2.3 ppm °C-1.

  3. Electronic structure of layered titanate Nd 2Ti 2O 7

    NASA Astrophysics Data System (ADS)

    Atuchin, V. V.; Gavrilova, T. A.; Grivel, J.-C.; Kesler, V. G.

    2008-10-01

    The electronic structure of the binary titanate Nd 2Ti 2O 7 has been studied by X-ray photoelectron spectroscopy (XPS). Spectral features of the valence band and all constituent element core levels have been considered. The Auger parameters of titanium and oxygen in Nd 2Ti 2O 7 are determined as αTi = 873.5 and αO = 1042.2 eV. Chemical bonding effects have been discussed with the binding energies differences ΔTi = (BE O 1s - BE Ti 2p 3/2) = 71.5 eV and ΔNd = (BE Nd 3d 5/2 - BE O 1s) = 452.5 eV as key parameters in comparison with those in other titanium- and neodymium-bearing oxides.

  4. Hydrothermal synthesis of mesoporous rod-like nanocrystalline vanadium oxide hydrate V{sub 3}O{sub 7}·H{sub 2}O from hydroquinone and V{sub 2}O{sub 5}

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

    Mjejri, I.; Etteyeb, N.; Sediri, F., E-mail: faouzi.sediri@ipeit.rnu.tn

    2013-09-01

    Graphical abstract: - Highlights: • Rod-like nanocrystalline V{sub 3}O{sub 7}·H{sub 2}O has heen synthesized hydrothermally. • Molar ratio is key factor for structure and morphology. • Electrochemical properties were also studied. • CV has revealed reversible redox behavior with charge–discharge cycling. - Abstract: Rod-like nanocrystalline V{sub 3}O{sub 7}·H{sub 2}O has been synthesized hydrothermally via a simple and elegant route. Techniques X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, thermal analysis (TG-DTA), X-ray photoelectron spectroscopy (XPS), UV–vis spectroscopy and nitrogen adsorption/desorption isotherms have been used to characterize the structure, morphology and composition of the materials.more » The as-prepared V{sub 3}O{sub 7}·H{sub 2}O nanorods are up to several of micrometers in length, about 130 nm in width and about 70 nm in thickness in average, respectively. Cyclic voltammetric characterization of thin films of V{sub 3}O{sub 7}·H{sub 2}O nanorods has revealed reversible redox behavior with charge–discharge cycling corresponding to the reversible lithium intercalation/deintercalation.« less

  5. Host-Sensitized and Tunable Luminescence of GdNbO4:Ln3+ (Ln3+ = Eu3+/Tb3+/Tm3+) Nanocrystalline Phosphors with Abundant Color.

    PubMed

    Liu, Xiaoming; Chen, Chen; Li, Shuailong; Dai, Yuhua; Guo, Huiqin; Tang, Xinghua; Xie, Yu; Yan, Liushui

    2016-10-17

    Up to now, GdNbO 4 has always been regarded as an essentially inert material in the visible region with excitation of UV light and electron beams. Nevertheless, here we demonstrate a new recreating blue emission of GdNbO 4 nanocrystalline phosphors with a quantum efficiency of 41.6% and host sensitized luminescence in GdNbO 4 :Ln 3+ (Ln 3+ = Eu 3+ /Tb 3+ /Tm 3+ ) nanocrystalline phosphors with abundant color in response to UV light and electron beams. The GdNbO 4 and GdNbO 4 :Ln 3+ (Ln 3+ = Eu 3+ /Tb 3+ /Tm 3+ ) nanocrystalline phosphors were synthesized by a Pechini-type sol-gel process. With excitation of UV light and low-voltage electron beams, the obtained GdNbO 4 nanocrystalline phosphor presents a strong blue luminescence from 280 to 650 nm centered around 440 nm, and the GdNbO 4 :Ln 3+ nanocrystalline phosphors show both host emission and respective emission lines derived from the characterize f-f transitions of the doping Eu 3+ , Tb 3+ , and Tm 3+ ions. The luminescence color of GdNbO 4 :Ln 3+ nanocrystalline phosphors can be tuned from blue to green, red, blue-green, orange, pinkish, white, etc. by varying the doping species, concentration, and relative ratio of the codoping rare earth ions in GdNbO 4 host lattice. A single-phase white-light-emission has been realized in Eu 3+ /Tb 3+ /Tm 3+ triply doped GdNbO 4 nanocrystalline phosphors. The luminescence properties and mechanisms of GdNbO 4 and GdNbO 4 :Ln 3+ (Ln 3+ = Eu 3+ /Tb 3+ /Tm 3+ ) are updated.

  6. A study of low threshold and high gain Nd3+ ions doped SiO2-B2O3-Na2CO3-NaF-CaF2 glasses for NIR laser applications

    NASA Astrophysics Data System (ADS)

    Megala, Rajesh; Gowthami, T.; John Sushma, N.; Kamala, S.; Deva Prasad Raju, B.

    2018-05-01

    Fluoroborosilicate glasses of composition 35SiO2-25B2O3-10Na2CO3-15NaF-15CaF2-xNd2O3 (where x = 0.1, 0.5. 1.0, 2.0 mol%) were prepared by melt quenching technique and various physical properties have been calculated. From the absorption spectra J-O Intensity parameters Ωλ (λ = 2, 4, 6) and radiative properties are evaluated by using J-O theory. The high values of Ω2 = 4.213 × 10-20 cm2, Ω4 = 5.345 × 10-20 cm2, Ω6 = 5.526 × 10-20 cm2 suggest that among the prepared glasses 0.5 mol% Nd glass is more asymmetric, more covalent and rigid in nature. The emission spectra were recorded with 808 nm laser as excitation source. The strong NIR emissions were observed at 876 nm, 1056 nm, 1328 nm corresponding to the transitions 4F3/2 → 4I9/2, 4F3/2 → 4I11/2, 4F3/2 → 4I13/2 respectively. Stimulated emission cross -section (σemi) and Gain bandwidth (σemi × Δλeff) were calculated. For 0.5 mol% Nd these values are found to be 3.30 × 10-20 cm2, 11 × 10-26 cm2. From the decay curve analysis the lifetime values for 4F3/2 level have been determined and these values are decreased with increase in Nd3+ ions concentration. These results may suggest that the prepared SBNCNd05 (Nd = 0.5 mol%) glass could be useful for 1056 nm laser applications.

  7. Probing structural changes in Ca(1-x)Nd2x/3TiO3 ceramics by Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Lowndes, Robert; Deluca, Marco; Azough, Feridoon; Freer, Robert

    2013-01-01

    Ceramics in the system Ca(1-x)Nd2x/3TiO3, intended for mobile communication applications, exhibit grossly non-linear variations in microwave dielectric properties with composition. There is evidence of a structural transition and the formation of vacancies on the A-site of the perovskite structure. High density, single phase perovskite Ca(1-x)Nd2x/3TiO3 ceramics have been prepared by the mixed oxide route. Raman spectroscopy was used to investigate the structural variations, which impact on dielectric properties. The Raman spectra show that with increasing Nd content, there is a transition from an ordered structure, to a disordered arrangement of cations and vacancies, and back to an ordered arrangement in Ca0.1Nd0.6TiO3. A structural phase transition from orthorhombic Pbnm to monoclinic C2/m coincides with the order-disorder transition at Ca0.1Nd0.6TiO3. Polarized Raman spectroscopy facilitated the assignment of the Raman modes and investigation of the role of importance of domain structures. Large variation in the plane angles was attributed to differences in domain structures. Differences in the angular dependence of the Raman modes with Nd content reflect changes in the preferred orientation of the domains from lamellar twins, to wedge shaped and back to lamellar twins.

  8. Nd/TiO2 Anatase-Brookite Photocatalysts for Photocatalytic Decomposition of Methanol.

    PubMed

    Kočí, Kamila; Troppová, Ivana; Reli, Martin; Matějová, Lenka; Edelmannová, Miroslava; Drobná, Helena; Dubnová, Lada; Rokicińska, Anna; Kuśtrowski, Piotr; Čapek, Libor

    2018-01-01

    Neodymium enriched TiO 2 anatase-brookite powders were prepared by unconventional method via using pressurized hot fluids for TiO 2 crystallization and purification. The photocatalysts were tested in the CH 3 OH photocatalytic decomposition and they were characterized with respect to the textural (nitrogen adsorption), structural (XRD, XPS, and Raman spectroscopies), chemical (XRF), and optical (DR UV-Vis spectroscopy) and photoelectrochemical measurement. All prepared materials were nanocrystalline, had biphasic (anatase- brookite) structure and relatively large specific surface area (125 m 2 .g -1 ). The research work indicates that the doping of neodymium on TiO 2 photocatalysts significantly enhances the efficiency of photocatalytic reaction. The photocatalytic activity increased with increasing portion of hydroxyl oxygen to the total amount of oxygen species. It was ascertained that the optimal amount of 1 wt% Nd in TiO 2 accomplished the increasing of hydrogen production by 70% in comparison with pure TiO 2 . The neodymium doped on the titanium dioxide act as sites with accumulation of electrons. The higher efficiency of photocatalytic process was achieved due to improved electron-hole separation on the modified TiO 2 photocatalysts. This result was confirmed by electrochemical measurements, the most active photocatalysts proved the highest photocurrent responses.

  9. Nd/TiO2 Anatase-Brookite Photocatalysts for Photocatalytic Decomposition of Methanol

    PubMed Central

    Kočí, Kamila; Troppová, Ivana; Reli, Martin; Matějová, Lenka; Edelmannová, Miroslava; Drobná, Helena; Dubnová, Lada; Rokicińska, Anna; Kuśtrowski, Piotr; Čapek, Libor

    2018-01-01

    Neodymium enriched TiO2 anatase-brookite powders were prepared by unconventional method via using pressurized hot fluids for TiO2 crystallization and purification. The photocatalysts were tested in the CH3OH photocatalytic decomposition and they were characterized with respect to the textural (nitrogen adsorption), structural (XRD, XPS, and Raman spectroscopies), chemical (XRF), and optical (DR UV-Vis spectroscopy) and photoelectrochemical measurement. All prepared materials were nanocrystalline, had biphasic (anatase- brookite) structure and relatively large specific surface area (125 m2.g−1). The research work indicates that the doping of neodymium on TiO2 photocatalysts significantly enhances the efficiency of photocatalytic reaction. The photocatalytic activity increased with increasing portion of hydroxyl oxygen to the total amount of oxygen species. It was ascertained that the optimal amount of 1 wt% Nd in TiO2 accomplished the increasing of hydrogen production by 70% in comparison with pure TiO2. The neodymium doped on the titanium dioxide act as sites with accumulation of electrons. The higher efficiency of photocatalytic process was achieved due to improved electron-hole separation on the modified TiO2 photocatalysts. This result was confirmed by electrochemical measurements, the most active photocatalysts proved the highest photocurrent responses. PMID:29552558

  10. Nd-doped Bi2O3 nanocomposites: simple synthesis and improved photocatalytic activity for hydrogen production under visible light

    NASA Astrophysics Data System (ADS)

    Al-Namshah, Khadijah S.; Mohamed, Reda M.

    2018-04-01

    Bi2O3 has 2.4 eV band gap energy, which means it absorb in visible region. Though the photocatalytic activity of Bi2O3 is extremely little due to rapid rate of photogenerated electron-hole recombination. To face the economical and practical needs, the photocatalytic efficiency of Bi2O3 should be upgraded. In this paper, this was achieved by addition of neodymium to Bi2O3 nanosheets and Nd/Bi2O3 nanocomposites were prepared by a easy process at room temperature using a surfactant of Pluronic F127. The Bi2O3 nanosheets and Nd/Bi2O3 nanocomposites were investigated by many tools. The photocatalytic activity of Nd/Bi2O3 samples is better than Bi2O3 due to reduced band gap and reduced electron-hole recombination of Bi2O3 with addition of neodymium. In addition, Nd/Bi2O3 nanocomposites exhibit photocatalytic stability for hydrogen production which enables it to be reused on other occasions also.

  11. Measurement of host-to-activator transfer efficiency in nano-crystalline Y{sub 2}O{sub 3}:Eu{sup 3+} under VUV excitation

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

    Waite, Christopher; Mann, Rusty; Diaz, Anthony L., E-mail: DiazA@cwu.edu

    2013-02-15

    We have conducted a systematic study of the excitation and reflectance spectra of nano-crystalline Y{sub 2}O{sub 3}:Eu prepared by combustion synthesis. Excitation through the host lattice becomes relatively more efficient as the firing temperature of the precursor is increased, while reflectance properties remain essentially unchanged. Using these data, host-to-activator transfer efficiencies were calculated for excitation at the band edge of Y{sub 2}O{sub 3}, and evaluated using a competition kinetics model. From this analysis we conclude that the relatively low luminous efficiency of these materials is due more to poor bulk crystallinity than to surface loss effects. - Graphical abstract: Themore » low luminous efficiency of nano-crystalline Y{sub 2}O{sub 3}:Eu{sup 3+} prepared by combustion synthesis is due to poor bulk crystallinity rather than surface loss effects. Highlights: Black-Right-Pointing-Pointer We report on the optical properties of Y{sub 2}O{sub 3}:Eu{sup 3+} prepared by combustion synthesis. Black-Right-Pointing-Pointer Host-to-activator transfer efficiencies under VUV excitation were calculated. Black-Right-Pointing-Pointer The low luminous efficiency of these materials is due to poor bulk crystallinity.« less

  12. Phase equilibria, crystal structure and properties of complex oxides in the Nd{sub 2}O{sub 3}–SrO–CoO system

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

    Aksenova, T.V.; Efimova, T.G.; Lebedev, O.I.

    2017-04-15

    The phase equilibria in the ½Nd{sub 2}O{sub 3}–SrO–CoO system were systematically studied at 1373 K in air. The intermediate phases formed in the ½Nd{sub 2}O{sub 3}–SrO–CoO system at 1373 K in air are: Nd{sub 1-x}Sr{sub x}CoO{sub 3-δ} (0.0≤x≤0.5 with orthorhombic structure, sp. gr. Pbnm and 0.6≤x≤0.95 whose structure was detected as cubic according to XRD sp. gr. Pm3m, but shown to be tetragonal by TEM due to the oxygen vacancy ordering), Nd{sub 2-y}Sr{sub y}CoO{sub 4-δ} (0.6≤y≤1.1 with tetragonal K{sub 2}NiF{sub 4}-type structure, sp. gr. I4/mmm) and Nd{sub 2-z}Sr{sub z}O{sub 3} (0.0≤z≤0.15 with hexagonal structure, sp. gr. P-3m1). The unit cellmore » parameters for the single phase samples were refined by the Rietveld analysis. The changes of oxygen content in Nd{sub 1-x}Sr{sub x}CoO{sub 3-δ} (0.6≤x≤0.95) and Ruddlesden-Popper oxide Nd{sub 2-y}Sr{sub y}CoO{sub 4-δ} were examined by TGA. All were found to be oxygen deficient phases. High-temperature dilatometry allows calculating the thermal expansion coefficient and evaluating the chemical expansion coefficient at high temperature. The projection of isothermal-isobaric phase diagram for the Nd–Sr–Co–O system at 1373 K in air to the compositional triangle of metallic components has been constructed. The phase equilibria in the studied Nd–Sr–Co–O system were compared to La–Sr–Co–O and Nd–M–Co–O (M=Ca and Ba). - Graphical abstract: Crystal structure of vacancy ordered supercell for Nd{sub 0.2}Sr{sub 0.8}CoO{sub 3-δ} and projection of phase diagram for the Nd–Sr–Co–O system onto the triangle edge of metallic components at 1373 K in air. - Highlights: • The diagram for the Nd–Sr–Co–O system at 1373 K in air has been constructed. • The crystal structure of Nd{sub 1-x}Sr{sub x}CoO{sub 3-δ} and Nd{sub 2-y}Sr{sub y}CoO{sub 4±δ} was refined. • The formation of superstructure due to the oxygen vacancy ordering was proved. • The changes of

  13. Influence of temperature on AC conductivity of nanocrystalline CuAlO2

    NASA Astrophysics Data System (ADS)

    Prakash, T.

    2012-07-01

    Nanocrystalline CuAlO2 was synthesized by mechanical alloying of Cu2O and α-Al2O3 powders in the molar ratio of 1:1 for 20 h in toluene medium with tungsten carbide balls and vials using planetary ball mill. The ball milling was carried out at 300 rpm with a ball to powder weight ratio of 10:1 and then annealed at 1373 K in a platinum crucible for 20 h to get CuAlO2 phase with average crystallite size 45 nm. Complex impedance spectroscopic measurement in the frequency region 1 Hz to 10 MHz between the temperatures 333 to 473 K was carried out for nanocrystalline CuAlO2 sample. The obtained complex impedance data was analyzed for AC conductivities, DC and AC conductivities correlations and crossover frequencies ( f co ). The BNN (Barton, Nakajima and Namikawa) relation was applied to understand the correlation between DC and AC conductivities. The observed experimental results were discussed in the paper.

  14. Synthesis of nanocrystalline TiO 2 in toluene by a solvothermal route

    NASA Astrophysics Data System (ADS)

    Kim, Chung-Sik; Moon, Byung Kee; Park, Jong-Ho; Tae Chung, Su; Son, Se-Mo

    2003-07-01

    A solvothermal synthetic method to TiO 2 nanoparticles has been investigated in toluene solutions with titanium isopropoxide (TIP) as precursor. Weight ratios of precursor to solvent prepared in the mixture are 5/100, 10/100, 20/100, 30/100 and 40/100. At the weight ratio of 10/100, 20/100 and 30/100, TiO 2 nanocrystalline particles were obtained after synthesis at 250°C for 3 h in an autoclave. X-ray diffraction and tranmission electron microscopy shows that the product has uniform anatase structure with average particle size below 20 nm. As the composition of TIP in the solution increases, the particle size of TiO 2 powder tends to increase. At 5/100 and 40/100, however, pale yellow colloidal solution is obtained after synthesis and crystalline phase of TiO 2 is not produced. The specific surface area of the TiO 2 nanocrystalline powder was also investigated using BET surface area analyzer.

  15. Multiple magnetic scattering in small-angle neutron scattering of Nd-Fe-B nanocrystalline magnet.

    PubMed

    Ueno, Tetsuro; Saito, Kotaro; Yano, Masao; Ito, Masaaki; Shoji, Tetsuya; Sakuma, Noritsugu; Kato, Akira; Manabe, Akira; Hashimoto, Ai; Gilbert, Elliot P; Keiderling, Uwe; Ono, Kanta

    2016-06-20

    We have investigated the influence of multiple scattering on the magnetic small-angle neutron scattering (SANS) from a Nd-Fe-B nanocrystalline magnet. We performed sample-thickness- and neutron-wavelength-dependent SANS measurements, and observed the scattering vector dependence of the multiple magnetic scattering. It is revealed that significant multiple scattering exists in the magnetic scattering rather than the nuclear scattering of Nd-Fe-B nanocrystalline magnet. It is considered that the mean free path of the neutrons for magnetic scattering is rather short in Nd-Fe-B magnets. We analysed the SANS data by the phenomenological magnetic correlation model considering the magnetic microstructures and obtained the microstructural parameters.

  16. Site-selective laser spectroscopy of Nd3+ ions in 0.8CaSiO3-0.2Ca3(PO4)2 biocompatible eutectic glass-ceramics.

    PubMed

    Sola, D; Balda, R; Peña, J I; Fernández, J

    2012-05-07

    In this work we report the influence of the crystallization stage of the host matrix on the spectroscopic properties of Nd3+ ions in biocompatible glass-ceramic eutectic rods of composition 0.8CaSiO3-0.2Ca3(PO4)2 doped with 1 and 2 wt% of Nd2O3. The samples were obtained by the laser floating zone technique at different growth rates between 50 and 500 mm/h. The microstructural analysis shows that a growth rate increase or a rod diameter decrease leads the system to a structural arrangement from three (two crystalline and one amorphous) to two phases (one crystalline and one amorphous). Electron backscattering diffraction analysis shows the presence of Ca2SiO4 and apatite-like crystalline phases. Site-selective laser spectroscopy in the (4)I(9/2)→(4)F(3/2)/(4)F(5/2) transitions confirms that Nd(3+) ions are incorporated in crystalline and amorphous phases in these glass-ceramic samples. In particular, the presence of Ca(2)SiO(4) crystalline phase in the samples grown at low rates, which has an excellent in vitro bioactivity, can be unambiguously identified from the excitation spectra and lifetime measurements of the (4)F(3/2) state of Nd(3+) ions.

  17. Synthesis, characterization, and photocatalytic properties of core/shell mesoporous silica nanospheres supporting nanocrystalline titania

    NASA Astrophysics Data System (ADS)

    Cendrowski, K.; Chen, X.; Zielinska, B.; Kalenczuk, R. J.; Rümmeli, M. H.; Büchner, B.; Klingeler, R.; Borowiak-Palen, E.

    2011-11-01

    The facile bulk synthesis of silica nanospheres makes them an attractive support for the transport of chemical compounds such as nanocrystalline titanium dioxide. In this contribution we present a promising route for the synthesis of mesoporous silica nanospheres (m-SiO2) with diameter in range 200 nm, which are ideal supports for nanocrystalline titanium dioxide (TiO2). The detailed microscopic and spectroscopic characterizations of core/shell structure (m-SiO2/TiO2) were conducted. Moreover, the photocatalytic potential of the nanostructures was investigated via phenol decomposition and hydrogen generation. A clear enhancement of photoactivity in both reactions as compared to commercial TiO2-Degussa P25 catalyst is detected.

  18. The new insight into the structure-activity relation of Pd/CeO2-ZrO2-Nd2O3 catalysts by Raman, in situ DRIFTS and XRD Rietveld analysis.

    PubMed

    Yang, X; Yang, L; Lin, J; Zhou, R

    2016-01-28

    Pd/CeO2-ZrO2-Nd2O3 (CZN) catalysts with different CeO2/ZrO2 molar ratios were synthesized and have been characterized by multiple techniques, e.g. XRD in combination with Rietveld refinement, UV-Raman, XPS and in situ DRIFTS. The XRD pattern of CZN with CeO2/ZrO2 molar ratios ≥1/2 can be indexed satisfactorily to the fluorite structure with a space group Fm3̄m, while the XRD patterns of CZ12 only display diffraction peaks of the tetragonal phase (S.G. P42/nmc). Nd addition can effectively stabilize the cubic structure of the CZN support and increase the enrichment of defect sites on the surface, which may be related to the better catalytic activity of Pd/CZN12 catalysts compared with Pd/CZ12. The presence of moderate ZrO2 can increase the concentration of O* active species, leading to accelerate the formation of nitrate species and thus enhance the catalytic activity of NOx and HC elimination. The Pd-dispersion decreases with the increasing Zr content, leading to the decreased CO catalytic activity, especially for the aged catalysts. The change regularity of the OSC value is almost the same with the in situ dynamic operational window, demonstrating that the in situ dynamic operational window is basically affected by the OSC value.

  19. Ultraviolet emission enhancement in ZnO thin films modified by nanocrystalline TiO2

    NASA Astrophysics Data System (ADS)

    Zheng, Gaige; Lu, Xi; Qian, Liming; Xian, Fenglin

    2017-05-01

    In this study, nanocrystalline TiO2 modified ZnO thin films were prepared by electron beam evaporation. The structural, morphological and optical properties of the samples were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), UV-visible spectroscopy, fluorescence spectroscopy, respectively. The composition of the films was examined by energy dispersive X-ray spectroscopy (EDX). The photoluminescent spectrum shows that the pure ZnO thin film exhibits an ultraviolet (UV) emission peak and a strong green emission band. Surface analysis indicates that the ZnO thin film contains many oxygen vacancy defects on the surface. After the ZnO thin film is modified by the nanocrystalline TiO2 layer, the UV emission of ZnO is largely enhanced and the green emission is greatly suppressed, which suggests that the surface defects such as oxygen vacancies are passivated by the TiO2 capping layer. As for the UV emission enhancement of the ZnO thin film, the optimized thickness of the TiO2 capping layer is ∼16 nm. When the thickness is larger than 16 nm, the UV emission of the ZnO thin film will decrease because the TiO2 capping layer absorbs most of the excitation energy. The UV emission enhancement in the nanocrystalline TiO2 modified ZnO thin film can be attributed to surface passivation and flat band effect.

  20. Green synthesis of nanocrystalline α-Al2O3 powders by both wet-chemical and mechanochemical methods

    NASA Astrophysics Data System (ADS)

    Gao, Huiying; Li, Zhiyong; Zhao, Peng

    2018-03-01

    Nanosized α-Al2O3 powders were prepared with AlCl3ṡ6H2O and NH4HCO3 as raw materials by both wet-chemical and mechanochemical methods, through the synthesis of the ammonium aluminum carbonate hydroxide (AACH) precursor followed by calcination. The environmentally benign starch was used as an effective dispersant during the preparation of nanocrystalline α-Al2O3 powders. X-ray diffraction (XRD), thermogravimetric differential thermal analysis (TG-DTA), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were employed to characterize the precursor AACH and products. The results show that nanosized spherical α-Al2O3 powders without hard agglomeration and with particle size in the range of 20-40 nm can be obtained by the two methods. Comparing the two “green” processes, the mechanochemical method has better prospects for commercial production.

  1. Controlled synthesis, characterization and photoluminescence property of olive-like tetragonal α-Nd{sub 2}(MoO{sub 4}){sub 3}

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

    Zhang, Youjin, E-mail: zyj@ustc.edu.cn; Zheng, Ao; Yang, Xiaozhi

    2012-09-15

    Highlights: ► The olive-like tetragonal α-Nd{sub 2}(MoO{sub 4}){sub 3} was gained with EDTA assisted hydrothermal method. ► The product was characterized by XRD, XPS, FTIR, FESEM, and PL. ► The possible formation mechanism for olive-like α-Nd{sub 2}(MoO{sub 4}){sub 3} was proposed. ► The PL in visible region of the olive-like α-Nd{sub 2}(MoO{sub 4}){sub 3} was studied. -- Abstract: The olive-like tetragonal α-Nd{sub 2}(MoO{sub 4}){sub 3} was obtained by a convenient and facile complex agent assisted hydrothermal method. The product was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, field-emission scanning electron microscopy (FESEM) andmore » photoluminescence (PL). The possible formation mechanism of the olive-like α-Nd{sub 2}(MoO{sub 4}){sub 3} was proposed. The photoluminescence property in visible region of the olive-like tetragonal α-Nd{sub 2}(MoO{sub 4}){sub 3} was studied.« less

  2. Efficient laser operation of Nd3+:Lu2O3 at various wavelengths between 917 nm and 1463 nm

    NASA Astrophysics Data System (ADS)

    von Brunn, P.; Heuer, A. M.; Fornasiero, L.; Huber, G.; Kränkel, C.

    2016-08-01

    Even though the first Nd3+-doped sesquioxide lasers have been realized more than 50 years ago, up to now no reports on efficient laser operation of Nd3+:doped sesquioxides can be found. In this work, we review the favorable spectroscopic properties of the sesquioxide Nd3+:Lu2O3 in terms of ground state absorption, stimulated emission, and excited state absorption cross sections as well as the upper level lifetime. Making use of these properties, we achieved efficient laser performance on eight different laser transitions in the wavelength range between 917 nm and 1463 nm under Ti:sapphire laser pumping using state-of-the-art HEM-grown Nd3+:Lu2O3 crystals with good optical quality. At the strongest transition around 1076 nm we determined a slope efficiency of 69%, which represents the highest efficiency ever obtained for a Nd3+-doped sesquioxide. Furthermore, we could generate watt level output powers and high slope efficiencies for seven other transitions. Lasers at 917 nm, 1053 nm, 1108 nm and 1463 nm were realized for the first time and the latter represents one of the longest laser wavelengths obtained on the 4F3/2  →  4I13/2 transition in Nd3+-doped materials.

  3. Thermal analyses, spectral characterization and structural interpretation of Nd3+/Er3+ ions co-doped TeO2-ZnCl2 glasses system

    NASA Astrophysics Data System (ADS)

    Ahmed, Kasim F.; Ibrahim, Saeed O.; Sahar, Md. R.; Mawlud, Saman Q.; Khizir, Hersh A.

    2017-09-01

    The Nd3+/Er3+ ions co-doped in the system of zinc-tellurite with the composition of (70-2x)TeO2-30ZnCl2-xNd2O3-xEr2O3 concentration from 1.0 to 3.0 mol% (x=1, 2 and 3) glasses were prepared by using conventional melt-quenching technique. The amorphous nature of the glass been confirmed by using X-RAY Diffraction Spectroscopy. Thermal characteristic were determined using a DTA. The obtained results discussed in terms of the glass structure. The glass structure studied by means of FTIR. Seven significant vibrational peaks around 471, 687, 742, 768, 1632, 2833 and 3378 cm-1 which correspond to the structural bonding of the glass are observed in a range of 400-4000cm-1. The peaks observed are consistent with the stretching and bending vibrations of the Te-O, TeO4 trigonal bipyramids, TeO3 trigonal pyramids, Te-O-Te and OH linkages respectively.

  4. Structure Evolution and Multiferroic Properties in Cobalt Doped Bi4NdTi3Fe1-xCoxO15-Bi3NdTi2Fe1-xCoxO12-δ Intergrowth Aurivillius Compounds

    PubMed Central

    Zhang, D. L.; Huang, W. C.; Chen, Z. W.; Zhao, W. B.; Feng, L.; Li, M.; Yin, Y. W.; Dong, S. N.; Li, X. G.

    2017-01-01

    Here, we report the structure evolution, magnetic and ferroelectric properties in Co-doped 4- and 3-layered intergrowth Aurivillius compounds Bi4NdTi3Fe1-xCoxO15-Bi3NdTi2Fe1-xCoxO12-δ. The compounds suffer a structure evolution from the parent 4-layered phase (Bi4NdTi3FeO15) to 3-layered phase (Bi3NdTi2CoO12-δ) with increasing cobalt doping level from 0 to 1. Meanwhile the remanent magnetization and polarization show opposite variation tendencies against the doping level, and the sample with x = 0.3 has the largest remanent magnetization and the smallest polarization. It is believed that the Co concentration dependent magnetic properties are related to the population of the Fe3+ -O-Co3+ bonds, while the suppressed ferroelectric polarization is due to the enhanced leakage current caused by the increasing Co concentration. Furthermore, the samples (x = 0.1–0.7) with ferromagnetism show magnetoelectric coupling effects at room temperature. The results indicate that it is an effective method to create new multiferroic materials through modifying natural superlattices. PMID:28272495

  5. Tannic acid alleviates bulk and nanoparticle Nd2O3 toxicity in pumpkin: a physiological and molecular response.

    PubMed

    Chen, Guangcai; Ma, Chuanxin; Mukherjee, Arnab; Musante, Craig; Zhang, Jianfeng; White, Jason C; Dhankher, Om Parkash; Xing, Baoshan

    2016-11-01

    The effect of dissolved organic matter (DOM) on nanoparticle toxicity to plants is poorly understood. In this study, tannic acid (TA) was selected as a DOM surrogate to explore the mechanisms of neodymium oxide NPs (Nd2O3 NPs) phytotoxicity to pumpkin (Cucurbita maxima). The results from the tested concentrations showed that 100 mg L(-1) Nd2O3 NPs were significantly toxic to pumpkin in term of fresh biomass, and the similar results from the bulk particles and the ionic treatments were also evident. Exposure to 100 mg L(-1) of Nd2O3 NPs and BPs in 1/5 strength Hoagland's solution not only significantly inhibited pumpkin growth, but also decreased the S, Ca, K and Mg levels in plant tissues. However, 60 mg L(-1) TA significantly moderated the observed phytotoxicity, decreased Nd accumulation in the roots, and notably restored S, Ca, K and Mg levels in NPs and BPs treated pumpkin. TA at 60 mg L(-1) increased superoxide dismutase (SOD) activity in both roots (17.5%) and leaves (42.9%), and catalase (CAT) activity (243.1%) in the roots exposed to Nd2O3 NPs. This finding was confirmed by the observed up-regulation of transcript levels of SOD and CAT in Nd2O3 NPs treated pumpkin analyzed by quantitative reverse transcription polymerase chain reaction. These results suggest that TA alleviates Nd2O3 BPs/NPs toxicity through alteration of the particle surface charge, thus reducing the contact and uptake of NPs by pumpkin. In addition, TA promotes antioxidant enzymatic activity by elevating the transcript levels of genes involved in ROS scavenging. Our results shed light on the mechanisms underlying the influence of DOM on the bioavailability and toxicity of NPs to terrestrial plants.

  6. FIELD DEPENDENCE OF THE SPIN REORIENTATION TEMPERATURE IN MICRO AND NANOCRYSTALLINE FORMS OF Nd{sub 2}Fe{sub 14}B.

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

    LEWIS,L.H.; HARLAND,C.L.

    2002-08-18

    Insight into the anisotropy behavior of Nd{sub 2}Fe{sub 14}B may be obtained by measurements of the spin reorientation temperature T{sub S} where the overall magnetocrystalline anisotropy changes to allow the magnetic moment to relax from an easy axis to an easy cone configuration. DC magnetization measurements made at various applied fields on sintered and nanocrystalline forms of Nd{sub 2}Fe{sub 14}B indicate a T{sub S} that remains constant for the sintered sample but is strongly field-dependent for the nanocrystalline forms of the material. Specifically, T{sub S} decreases with decreasing applied fields of strengths 5 T, 1 T and 0.01 T. Amore » simple model that minimizes the total energy of the system leads to the conclusion that the spin reorientation temperature is insensitive to applied field. Therefore it is concluded that the apparent decrease in the system's spin reorientation temperatures with decrease in measuring field can be attributed to the nanoscale structure of the system and a difference in the anisotropy constants compared to their bulk values.« less

  7. Raman spectroscopy, thermal and optical properties of TeO2-ZnO-Nb2O5-Nd2O3 glasses

    NASA Astrophysics Data System (ADS)

    Kamalaker, V.; Upender, G.; Ramesh, Ch.; Chandra Mouli, V.

    2012-04-01

    The glasses with composition 75TeO2-10ZnO-(15-x)Nb2O5-xNd2O3 (0 ≤ x ≤ 9 mol%) were prepared using melt quenching method and their physical properties such as density (ρ), molar volume (VM), average crosslink density (n¯), oxygen packing density (OPD) and number of bonds per unit volume (nb) were determined. Raman spectroscopic studies showed that the glass network consists of TeO4, TeO3+1, TeO3 and NbO6 units as basic structural units. The glass transition temperature (Tg), crystallization onset (To) and thermal stability (ΔT) were determined from DSC thermograms. The Raman and DSC results were found to be correlated with the physical properties. In the optical absorption spectra six absorption bands were observed with different relative intensities at around 464, 522, 576, 742, 801 and 871 nm which are assigned to the transition of electrons from (ground state) 4I9/2 → G11/2; 4I9/22K3/2, 2G7/2; 4I9/2 → 4G5/2, 4G7/2; 4I9/2 → 4S3/2; 4F7/22H9/2, 4F5/2 and 4I9/22F3/2 respectively. From optical absorption data the energy band gap (Eopt) and Urbach energy (ΔE) were calculated.

  8. High output power of differently cut Nd:MgO:LiTaO3 CW lasers

    NASA Astrophysics Data System (ADS)

    Sun, D. H.; Liu, S. D.; Wang, D. Z.; Sang, Y. H.; Kang, X. L.; Liu, H.; Bi, Y.; Yan, B. X.; He, J. L.; Wang, J. Y.

    2013-04-01

    A high-quality Nd3+ and Mg2+ co-doped LiTaO3 (Nd:MgO:LT) crystal was grown by the Czochralski method. The polarized absorption spectra and fluorescence spectra were studied, and the absorption cross section was calculated by Judd-Ofelt (J-O) theory. The laser performance with different sample cuts of the crystal was investigated for the first time, and it was found that Nd:MgO:LT crystal with different cutting directions (a and c) exhibits different laser properties. By optimizing a partial reflectivity mirror in the laser experimental setting, a high continuous wave output power of 3.58 W was obtained at 1092 and 1076 nm with an optical-to-optical conversion efficiency of 22.78% and slope efficiency of 26.06%. The results indicate that Nd:MgO:LT crystal is a promising candidate for the manufacture of Nd3+ doped periodically poled MgO:LiTaO3 crystal (Nd:PPMgOLT), which should have considerable applications in self-frequency doubling and optical parametric oscillation laser devices.

  9. Nd3+-doped TeO2-PbF2-AlF3 glasses for laser applications

    NASA Astrophysics Data System (ADS)

    Lalla, E. A.; Rodríguez-Mendoza, U. R.; Lozano-Gorrín, A. D.; Sanz-Arranz, A.; Rull, F.; Lavín, V.

    2016-01-01

    A study of the optical properties of Nd3+ ion in TeO2-PbF2-AlF3 glasses has been carried out for different Nd3+ concentrations. Based on the Judd-Ofelt theory, intensity parameters and radiative properties were determined from the absorption spectra. Focusing on the suitability of this host for laser applications, the spectroscopic quality factor χ was obtained with a value of 1.07, a value of the order of other compositions proposed as laser hosts. For the most intense emission corresponding with the 4F3/2 → 4I11/2 transition (1.06 μm), the absorption and emission and have been calculated with values of 1.20 × 10-20 cm2, 2.08 × 10-20 cm2. A positive value for the gain cross-sections has been found for a population inversion factor γ of 0.4 in the spectral range from 1060 to 1110 nm. All these results suggest the potentially use of this system as a laser host.

  10. Magnetism from Fe2O3 nanoparticles embedded in amorphous SiO2 matrix

    NASA Astrophysics Data System (ADS)

    Sendil Kumar, A.; Bhatnagar, Anil K.

    2018-02-01

    Fe2O3 nanoparticles are embedded in amorphous SiO2 matrix by coprecipitation method with varying concentrations. Conditions are optimized to get almost monodispersed Fe2O3 nanoparticles with high chemical stability. Microstructure of synthesized nanoparticles is well characterized and found that Fe2O3 is in nanocrystalline form and embedded uniformly in amorphous SiO2 matrix. Enhanced surface reactivity is found for nanoparticles which influences physical properties of the SiO2 supported Fe2O3 system due to adsorption. In oxide nanoparticles, significant number of defect sites at the surface is expected but when supported medium such as SiO2 it reduces this defect concentration. Field- and temperature-dependent magnetisation studies on these samples show superparamagnetic behaviour. Superparamagnetic behaviour is seen in all the concentration systems but the coercivity observed in the lower concentration systems is found to be anomalous compared to that of higher concentrations. The observed magnetic behaviour comes from either unsaturated bond existing due to the absence of anions at the surface of nanoparticles or reconstruction of atomic orbitals taking place at interface of Fe2O3-SiO2 system.

  11. Induced emission cross section of a possible laser line in Nd:Y2O3 ceramics at 1.095 μm

    NASA Astrophysics Data System (ADS)

    Fukabori, Akihiro; Sekita, Masami; Ikegami, Takayasu; Iyi, Nobuo; Komatsu, Toshiki; Kawamura, Masayuki; Suzuki, Makoto

    2007-02-01

    In this study, we measured the change of the optical transmittance for calcination temperatures, in steps of 10°, at two different sintering temperatures. It was found that the optical transmittance is highly dependent on the calcination temperature. The highest optical transmittance obtained was 70% for the transparent Y2O3 (yttria) ceramics produced without the use of additives and high injection presure in this study, higher than the highest reported value of 65%. Optical absorption and emission spectra of Nd :Y2O3 obtained from a low temperature synthesis process were measured. The energy level structure of Nd3+ in the Y2O3 ceramics was determined for a 1mol% Nd concentration. The induced emission cross section was calculated to be in the range of 3.2×10-19-1.1×10-17cm2 for the 1mol% Nd-doped Y2O3 ceramics. Furthermore, a laser line possibly has been identified in this study, in the Nd :Y2O3 ceramic at 1.095μm.

  12. Raman spectroscopy, thermal and optical properties of TeO2-ZnO-Nb2O5-Nd2O3 glasses.

    PubMed

    Kamalaker, V; Upender, G; Ramesh, Ch; Mouli, V Chandra

    2012-04-01

    The glasses with composition 75TeO2-10ZnO-(15-x)Nb2O5-xNd2O3 (0≤x≤9 mol%) were prepared using melt quenching method and their physical properties such as density (ρ), molar volume (VM), average crosslink density (nc¯), oxygen packing density (OPD) and number of bonds per unit volume (nb) were determined. Raman spectroscopic studies showed that the glass network consists of TeO4, TeO3+1, TeO3 and NbO6 units as basic structural units. The glass transition temperature (Tg), crystallization onset (To) and thermal stability (ΔT) were determined from DSC thermograms. The Raman and DSC results were found to be correlated with the physical properties. In the optical absorption spectra six absorption bands were observed with different relative intensities at around 464, 522, 576, 742, 801 and 871 nm which are assigned to the transition of electrons from (ground state) 4I9/2→G11/2; 4I9/22K3/2, 2G7/2; 4I9/2→4G5/2, 4G7/2; 4I9/2→4S3/2; 4F7/22H9/2, 4F5/2 and 4I9/22F3/2 respectively. From optical absorption data the energy band gap (Eopt) and Urbach energy (ΔE) were calculated. Copyright © 2012 Elsevier B.V. All rights reserved.

  13. Structural morphology, upconversion luminescence and optical thermometric sensing behavior of Y2O3:Er(3+)/Yb(3+) nano-crystalline phosphor.

    PubMed

    Joshi, C; Dwivedi, A; Rai, S B

    2014-08-14

    Infrared-to-visible upconverting rare earths Er(3+)/Yb(3+) co-doped Y2O3 nano-crystalline phosphor samples have been prepared by solution combustion method followed by post-heat treatment at higher temperatures. A slight increase in average crystallite size has been found on calcinations verified by X-ray analysis. Transmission electron microscopy (TEM) confirms the nano-crystalline nature of the as-prepared and calcinated samples. Fourier transform infrared (FTIR) analysis shows the structural changes in as-prepared and calcinated samples. Upconversion and downconversion emission recorded using 976 and 532 nm laser sources clearly demonstrates a better luminescence properties in the calcinated samples as compared to as-prepared sample. Upconversion emission has been quantified in terms of standard chromaticity diagram (CIE) showing a shift in overall upconversion emission of as-prepared and calcinated samples. Temperature sensing behaviour of this material has also been investigated by measurement of fluorescence intensity ratio (FIR) of various signals in green emission in the temperature range of 315 to 555 K under 976 nm laser excitation. Copyright © 2014 Elsevier B.V. All rights reserved.

  14. ZrO2-modified mesoporous nanocrystalline TiO2-xNx as efficient visible light photocatalysts.

    PubMed

    Wang, Xinchen; Yu, Jimmy C; Chen, Yilin; Wu, Ling; Fu, Xianzhi

    2006-04-01

    Mesoporous nanocrystalline TiO2-xNx and TiO2-xNx/ZrO2 visible-light photocatalysts have been prepared by a sol-gel method. The photocatalysts were characterized by XRD, N2 adsorption-desorption, TEM, XPS, UV/Vis, and IR spectroscopy. The photocatalytic activity of the samples was evaluated by the decomposition of ethylene in air under visible light (lambda > 450 nm) illumination. Results revealed that nitrogen was doped into the lattice of TiO2 by the thermal treatment of NH3-adsorbed TiO2 hydrous gels, converting the TiO2 into a visible-light responsive catalyst. The introduction of ZrO2 into TiO2-xNx considerably inhibits the undesirable crystal growth during calcination. Consequently, the ZrO2-modified TiO2-xNx displays higher porosity, higher specific surface area, and an improved thermal stability over the corresponding unmodified TiO2-xNx samples.

  15. Studies on the sensing behaviour of nanocrystalline CuGa(2)O(4) towards hydrogen, liquefied petroleum gas and ammonia.

    PubMed

    Biswas, Soumya Kanti; Sarkar, Arpita; Pathak, Amita; Pramanik, Panchanan

    2010-06-15

    In the present article, the gas sensing behaviour of nanocrystalline CuGa(2)O(4) towards H(2), liquefied petroleum gas (LPG) and NH(3) has been reported for the first time. Nanocrystalline powders of CuGa(2)O(4) having average particle sizes in the range of 30-60nm have been prepared through thermal decomposition of an aqueous precursor solution comprising copper nitrate, gallium nitrate and triethanol amine (TEA), followed by calcination at 750 degrees C for 2h. The synthesized nanocrystalline CuGa(2)O(4) powders have been characterised through X-ray diffraction (XRD), transmission electron microscopy (TEM), field-emission scanning electron microscopy (FESEM) study, energy dispersive X-ray (EDX) analysis and BET (Brunauer-Emmett-Teller) surface area measurement. The synthesized CuGa(2)O(4) having spinel structure with specific surface area of 40m(2)/g exhibits maximum sensitivity towards H(2), LPG, and NH(3) at 350 degrees C.

  16. Monoclinic β-Li2TiO3 nanocrystalline particles employing novel urea assisted solid state route: Synthesis, characterization and sintering behavior

    NASA Astrophysics Data System (ADS)

    Tripathi, Biranchi M.; Mohanty, Trupti; Prakash, Deep; Tyagi, A. K.; Sinha, P. K.

    2017-07-01

    Pure phase monoclinic nano-crystalline Li2TiO3 powder was synthesized by a novel urea assisted solid state synthesis method using readily available and economical precursors. A single phase and well crystalline Li2TiO3 powder has been obtained at slightly lower temperature (600-700 °C) and shorter duration (2 h) as compared to the conventional solid state method. The proposed method has significant advantages in comparison to other viable methods mainly in terms of phase purity, powder properties and sinterability. Analysis of chemical composition using inductively coupled plasma atomic emission spectroscopy (ICP-AES) shows no loss of lithium from Li2TiO3 in the proposed method. The emergence of monoclinic Li2TiO3 phase was confirmed by X-ray diffraction (XRD) pattern of as-synthesized powder. The crystallite size of Li2TiO3 powder was calculated to be in the range of 15-80 nm, which varied as a function of urea composition and temperature. The morphology of as-prepared Li2TiO3 powders was examined by scanning electron microscope (SEM). The effect of urea composition on phase and morphology was investigated so as to delineate the role of urea. Upon sintering at < 1000 °C temperature, the Li2TiO3 powder compact attained about 98% of the theoretical density with fine grained (grain size: 2-3 μm) microstructure. It indicates excellent sinter-ability of Li2TiO3 powder synthesized by the proposed method. The fine grained structure is desirable for better tritium breeding performance of Li2TiO3. Electrochemical impedance spectroscopy at variable temperature showed good electrical properties of Li2TiO3. The proposed method is simple, anticipated to be cost effective and convenient to realise for large scale production of phase pure nanocrystalline and having significantly enhanced sinter-ability Li2TiO3 powder.

  17. Optical evaluation on Nd3+-doped phosphate glasses for O-band amplification.

    PubMed

    Lei, Weihong; Chen, Baojie; Zhang, Xiangling; Pun, Edwin Yun Bun; Lin, Hai

    2011-02-20

    We have fabricated and characterized optically Nd3+-doped phosphate [Li2O-CaO-BaO-Al2O3-La2O3-P2O5 (LCBALP)] glasses for drawing single-mode glass fiber. The 4F3/2→4I13/2 transition emission from the Nd3+ is at the 1.327 μm wavelength with a full width at half-maximum of 43 nm, and the spontaneous transition probability and quantum efficiency are calculated to be 1836 s-1 and 52%, respectively. The maximum stimulated emission cross sections for 4F3/2→4I11/2 and 4F3/2→4I13/2 transitions are derived to be 1.82×10(-20) cm2 and 6.97×10(-21) cm2, respectively, and the theoretical gain coefficient at the 1.327 μm wavelength is evaluated to be 0.182 dB/cm when the fractional factor of the excited neodymium ions equals 0.6, which indicates that Nd3+-doped LCBALP phosphate glasses are potential candidates in developing O-band optical fiber amplifiers.

  18. Effect of ultrasonic treatment and temperature on nanocrystalline TiO 2

    NASA Astrophysics Data System (ADS)

    Kim, D. H.; Ryu, H. W.; Moon, J. H.; Kim, J.

    Nanocrystalline TiO 2 particles were precipitated from the ethanol solution of titanium isopropoxide (Ti(O- iPr) 4) and H 2O 2 by refluxing at 80 °C for 48 h. The obtained particles were filtered and dried at 100 °C for 12 h. The dried powder itself, the sample with heating at 400 °C, and the sample with ultrasonically treating were prepared to investigate the effects of post treatments on materials characteristics and electrochemical properties of nanocrystalline TiO 2. The X-ray diffraction patterns of all of the samples were fitted well to the anatase phase. The field emission-TEM image of as-prepared sample shows a uniform spherical morphology with 5 nm particle size and the sample heated at 400 °C shows slightly increased particle size of about 10 nm while maintaining spherical shape. The sample treated with ultrasonic for 5 h or more at room temperature shows high aspect ratio particle shape with an average diameter of 5 nm and a length of 20 nm. According to the results of the electrochemical testing, as-prepared sample, the sample heated at 400 °C for 3 h, and the sample treated with ultrasonic show initial capacities of 270, 310 and 340 mAh g -1, respectively.

  19. Effect of Fe3O4 addition on dielectric properties of LaFeO3 nano-crystalline materials synthesized by sol-gel method

    NASA Astrophysics Data System (ADS)

    Laysandra, H.; Triyono, D.

    2017-04-01

    Dielectric properties of nano-crystalline material LaFeO3.xFe3O4 with x = 0, 0.1, 0.2, 0.3, and 0.4 at.% have been studied by impedance spectroscopy method. LaFeO3 was synthesized by sol-gel method resulting nano-particle. Then, it was mixed with Fe3O4 powder. The mixture powder was pressed to form pellet and then sintered at 1300°C for 1 h to form nano-crystalline of LaFeO3.xFe3O4. X-ray diffraction characterization at room temperature for all samples show two phases i.e. perovskite LaFeO3 (orthorhombic) as a main phase and Fe3O4 (cubic) as second phase. It is found that the crystallite size of main phase increases with addition of Fe3O4 until 0.3 at.%. The electrical properties as a function of temperature (300-500 K) and frequency (100 Hz - 1 MHz) are presented in Nyquist and Bode plots. It is observed that from equivalent circuit and their parameters, dielectrical properties are contributed by grain and grain boundary. The dielectric constant, ε‧ were calculated by parallel plate method and their values reach up to 107 exhibiting typical colossal dielectric constant (CDC) material like behavior.

  20. Low temperature biosynthesis of Li2O-MgO-P2O5-TiO2 nanocrystalline glass with mesoporous structure exhibiting fast lithium ion conduction.

    PubMed

    Du, Xiaoyong; He, Wen; Zhang, Xudong; Ma, Jinyun; Wang, Chonghai; Li, Chuanshan; Yue, Yuanzheng

    2013-04-01

    We demonstrate a biomimetic synthesis methodology that allows us to create Li2O-MgO-P2O5-TiO2 nanocrystalline glass with mesoporous structure at lower temperature. We design a 'nanocrystal-glass' configuration to build a nanoarchitecture by means of yeast cell templates self-assembly followed by the controlled in-situ biomineralization of materials on the cell wall. Electrochemically active nanocrystals are used as the lamellar building blocks of mesopores, and the semiconductive glass phase can act both as the 'glue' between nanocrystals and functionalized component. The Li2O-MgO-P2O5-TiO2 nanocrystalline glass exhibits outstanding thermal stability, high conductivity and wide potential window. This approach could be applied to many other multicomponent glass-ceramics to fabricate mesoporous conducting materials for solid-state lithium batteries. Copyright © 2012 Elsevier B.V. All rights reserved.

  1. Mechanochemical stabilization and sintering of nanocrystalline the (ZrO2)0.97 (Y2O3)0.03 solid solution from pure oxides

    NASA Astrophysics Data System (ADS)

    Rendtorff, N. M.; Suárez, G.; Sakka, Y.; Aglietti, E. F.

    2011-10-01

    The mechanochemical activation processing has proved to be an effective technique to enhance a solid-state reaction at relatively low temperatures. In such a process, the mechanical effects of milling, such as reduction of particle size and mixture homogenization, are accompanied by chemical effects, such as partial decomposition of salts or hydroxides resulting in very active reactants. The objective of the present work is to obtain (ZrO2)0.97(Y2O3)0.03 nanocrystalline tetragonal solid solution powders directly using a high energy milling on a mixture of the pure oxides. A second objective is to evaluate the efficiency of the processing proposed and to characterize both textural and structural evolution of the mixtures during the milling processes and throughout posterior low temperature treatments. The Textural and structural evolution were studied by XRD analysis, specific area measurements (BET) and SEM. Firstly a decrease of the crystallinity of the reactants was observed, followed by the disappearance of Y2O3 diffraction peaks and the partial appearance of the tetragonal phase at room temperature. The solid solution proportion was increased with the high energy milling time, obtaining complete stabilization of the tetragonal solid solution with long milling treatments (60 min).The obtained powders were uniaxially pressed and sintered at different temperatures (600-1400°C) the influence of the milling time was correlated with the sinterization degree and final crystalline composition of the materials. Finally, fully stabilized nanocrystalline zirconia materials were obtained satisfactorily by the proposed method.

  2. Impacts of neodymium on structural, spectral and dielectric properties of LiNi0.5Fe2O4 nanocrystalline ferrites fabricated via micro-emulsion technique

    NASA Astrophysics Data System (ADS)

    Gilani, Zaheer Abbas; Warsi, Muhammad Farooq; Khan, Muhammad Azhar; Shakir, Imran; Shahid, Muhammad; Anjum, Muhammad Naeem

    2015-09-01

    Soft ferrites are technologically advanced smart materials and their properties can be tailored by controlling the chemical composition and judicial choice of the metal elements. In this article we discussed the effect of rare earth neodymium (Nd3+) on various properties of LiNi0.5NdxFe2-xO4 spinel ferrites. These ferrites have been synthesized by facile micro-emulsion route and characterized by X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), a.c. electrical conductivity and thermal analysis. The influence of Nd3+ doping on structural and electrical parameters has been investigated. XRD analysis revealed the formation of single cubic spinel structure for x≤0.07. Few traces of secondary phase (NdFeO3) were found for x≥0.105. The secondary phase induced owing to the solubility limit of Nd3+ cations in these ferrites. The lattice parameter (a) and crystallite size (D) both exhibit non-linear relation. The values of "a" and "D" were found in the range 8.322-8.329 Å and 25-32 nm respectively. These variations were attributed to the larger ionic radius of Nd3+ cations as compared to the host cations and lattice strain produced in these ferrites. The dielectric parameters were studied in the range 1 MHz to 3 GHz and these parameters were damped by Nd3+ incorporation and also by increasing the frequency. The reduced dielectric parameters observed in wide frequency range proposed that these nanocrystalline ferrites are potential candidates for fabricating the devices which are required to operate at GHz frequencies.

  3. The Effect of Molar Ratio on Crystal Structure and Morphology of Nd1+XFeO3 (X=0.1, 0.2, and 0.3) Oxide Alloy Material Synthesized by Solid State Reaction Method

    NASA Astrophysics Data System (ADS)

    Zharvan, V.; Kamaruddin, Y. N. I.; Samnur, S.; Sujiono, E. H.

    2017-05-01

    Perovskite is an oxide alloy which has a structure of ABO3 (A = La, Nd, Sm, Gd; B = Fe, CO, Ni) and has an excellent catalytic activity and gas-sensitive properties. NdFeO3 and its derivatives are important candidates for gas sensors. In this study, the effect of molar ratio (x=0.1, 0.2 and 0.3) on crystal structure and morphology of Nd1+xFeO3 synthesized by solid state reaction method has been studied. Nd1+xFeO3 samples were prepared using Nd2O3 (99.99 %) and Fe2O3 (99.99 %) as precursors. All of the samples were characterized using XRD to identify the phase and using SEM to identify the morphology. The synthesized Nd1+xFeO3 samples showed that molar ratio strongly influences the intensity, FWHM, and crystalline size. The samples of Nd1+xFeO3 have homogenous morphology and have three major phases, i.e. NdFeO3, Nd(OH)3 and Nd2O3 with crystalline sizes of NdFeO3 of 137.0±0.1 nm, 152.2±0.1 nm and 137.0±0.1 nm for Nd1.1FeO3, Nd1.2FeO3, and Nd1.3FeO3, respectively. These results indicated that the sample of Nd1.2FeO3 was a good candidate for a gas sensor material.

  4. Energy transfer dynamics of Er3+/Nd3+ embedded SiO2-Al2O3-Na2CO3-SrF2-CaF2 glasses for optical communications

    NASA Astrophysics Data System (ADS)

    Gelija, Devarajulu; Kadathala, Linganna; Borelli, Deva Prasad Raju

    2018-04-01

    The fluorescence and upconversion studies of Er3+ doped and Er3+/Nd3+ co-doped silicate based oxyfluoride glasses have been systematically analyzed. The broad band NIR emissions (830-1700 nm), includes optical bands like O, E, S, C and L were observed in the Er3+-Nd3+ co-doped glasses. The NIR emission intensity peaks centered at 876, 1057, 1329 and 1534 nm were observed for the Er3+-Nd3+ co-doped glasses. In the co-doped samples the strongest emission intensity at 1534 nm increased up to 0.5 mol % and then decreased to 3.0 mol % of Nd3+ ions under the excitation of 980 nm. The upconversion studies of the co-doped samples were recorded under the excitation of 980 and 808 nm and found the upconversion emission peaks centered at 524, 530, 547, 590 and 656 nm. The energy transfer processes between the relevant excitation levels of Er3+ and Nd3+ ions and energy transfer efficiency were discussed. The obtained results indicate that Nd3+ can be an efficient sensitizer for Er3+ to enhance upconversion emission at green laser transition for sensors and NIR emission at 1534 nm for optical communication applications.

  5. Lattice crossover and phase transitions in NdAlO{sub 3}-GdAlO{sub 3} system

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

    Vasylechko, L., E-mail: crystal-lov@polynet.lviv.ua; Shmanko, H.; Ohon, N.

    2013-02-15

    Phase and structural behaviour in the (1-x)NdAlO{sub 3}-xGdAlO{sub 3} system in a whole concentration range has been studied by means of in situ high-resolution X-ray synchrotron powder diffraction technique and differential thermal analysis. Two kinds of solid solutions Nd{sub 1-x}Gd{sub x}AlO{sub 3} have been found at room temperature: one with rhombohedral (x<0.15) and one with orthorhombic (x{>=}0.20) symmetry. A morphotropic phase transition occurs at x Almost-Equal-To 0.15, where the co-existence of both phases was observed. Peculiarity of the orthorhombic solid solution is the lattice parameter crossover at the compositions with x=0.33, 0.49 and 0.62. First-order structural transition Pbnm{r_reversible}R3{sup Macron }cmore » has been detected both from in situ powder diffraction and thermal analysis data. Continuous phase transformation R3{sup Macron }c{r_reversible}Pm3{sup Macron }m above 2140 K has been predicted for Nd-rich sample Nd{sub 0.85}Gd{sub 0.15}AlO{sub 3} from the extrapolation of high-temperature behaviour of the lattice parameter ratio of the rhombohedral phase. Based on the experimental data, the phase diagram of the pseudo-binary system NdAlO{sub 3}-GdAlO{sub 3} has been constructed. - Graphical abstract: Concentration dependencies of normalized lattice parameters of Nd{sub 1-x}Gd{sub x}AlO{sub 3} perovskite solid solutions. Highlights: Black-Right-Pointing-Pointer Two kinds of solid solutions Nd{sub 1-x}Gd{sub x}AlO{sub 3} were found in the NdAlO{sub 3}-GdAlO{sub 3} system. Black-Right-Pointing-Pointer Morphotropic transition between both perovskite phases occurs at x Almost-Equal-To 0.15. Black-Right-Pointing-Pointer Lattice parameter crossover was found in orthorhombic solid solution. Black-Right-Pointing-Pointer Temperature driven first-order phase transition Pbnm{r_reversible}R3{sup Macron }c was found in Nd{sub 1-x}Gd{sub x}AlO{sub 3}. Black-Right-Pointing-Pointer Phase diagram of the pseudo-binary system NdAlO{sub 3}-GdAlO{sub 3

  6. EPR studies of Er 3+, Nd 3+ and Ce 3+ in YAlO 3 single crystals

    NASA Astrophysics Data System (ADS)

    Asatryan, H. R.; Rosa, J.; Mareš, J. A.

    1997-10-01

    EPR spectra of Er 3+, Nd 3+ and Ce 3+ ions in YAlO 3 lattice have been studied. These spectra can be described by spin Hamiltonian with an effective spin S = {1}/{2} and rhombohedric symmetry. The g factors as well as the constants of hyperfine interaction of Nd 3+ and Er 3+ were obtained. It was stated that all the resonances which are upon the interest of this article, belong to the RE 3+ ions replacing the Y 3+ cations in the YAlO 3 lattice.

  7. Solvothermal synthesis of nanocrystalline TiO 2 in toluene with surfactant

    NASA Astrophysics Data System (ADS)

    Kim, Chung-Sik; Moon, Byung Kee; Park, Jong-Ho; Choi, Byung-Chun; Seo, Hyo-Jin

    2003-10-01

    Synthesis of narrow-dispersed nanocrystalline TiO 2 was investigated by surfactant-aided solvothermal synthetic method in toluene solutions. Titanium isopropoxide (TIP) was used as precursor, which was decomposed at high temperature in the surfactant-dissolved solution. After the solution was thermally treated at 250°C for 20 h in an autoclave, low-dispersed TiO 2 nanocrystalline particles with average size of <6 nm were synthesized. When sufficient amount of TIP or surfactant was added in the solution, long dumbbell-shaped nanorods were formed, which may be due to the oriented growth of particles along [0 0 1] axis. Characterization of products was investigated by X-ray diffraction and transmission electron microscopy.

  8. Novel Electronic Behavior Driving NdNiO 3 Metal-Insulator Transition

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

    Upton, M. H.; Choi, Yongseong; Park, Hyowon

    2015-07-01

    We present evidence that the metal-insulator transition (MIT) in a tensile-strained NdNiO3 (NNO) film is facilitated by a redistribution of electronic density and that it neither requires Ni charge disproportionation nor a symmetry change [U. Staub et al., Phys. Rev. Lett. 88, 126402 (2002); R. Jaramillo et al., Nat. Phys. 10, 304 (2014)]. Given that epitaxial tensile strain in thin NNO films induces preferential occupancy of the e(g) d(x2-y2) orbital we propose that the larger transfer integral of this orbital state with the O 2p orbital state mediates a redistribution of electronic density from the Ni atom. A decrease inmore » the Ni d(x2-y2) orbital occupation is directly observed by resonant inelastic x-ray scattering below the MIT temperature. Furthermore, an increase in the Nd charge occupancy is measured by x-ray absorption at the Nd L-3 edge. Both spin-orbit coupling and crystal field effects combine to break the degeneracy of the Nd 5d states, shifting the energy of the Nd e(g) d(x2-y2) orbit towards the Fermi level, allowing the A site to become an active acceptor during the MIT. This work identifies the relocation of electrons from the Ni 3d to the Nd 5d orbitals across the MIT. We propose that the insulating gap opens between the Ni 3d and O 2p states, resulting from Ni 3d electron localization. The transition seems to be neither a purely Mott-Hubbard transition nor a simple charge transfer.« less

  9. Low temperature magnetic properties of Nd2Ru2O7

    NASA Astrophysics Data System (ADS)

    Ku, S. T.; Kumar, D.; Lees, M. R.; Lee, W.-T.; Aldus, R.; Studer, A.; Imperia, P.; Asai, S.; Masuda, T.; Chen, S. W.; Chen, J. M.; Chang, L. J.

    2018-04-01

    We present magnetic susceptibility, heat capacity, and neutron diffraction measurements of polycrystalline Nd2Ru2O7 down to 0.4 K. Three anomalies in the magnetic susceptibility measurements at 146, 21 and 1.8 K are associated with an antiferromagnetic ordering of the Ru4+ moments, a weak ferromagnetic signal attributed to a canting of the Ru4+ and Nd3+ moments, and a long-range-ordering of the Nd3+ moments, respectively. The long-range order of the Nd3+ moments was observed in all the measurements, indicating that the ground state of the compound is not a spin glass. The magnetic entropy of Rln2 accumulated up to 5 K, suggests the Nd3+ has a doublet ground state. Lattice distortions accompany the transitions, as revealed by neutron diffraction measurements, and in agreement with earlier synchrotron x-ray studies. The magnetic moment of the Nd3+ ion at 0.4 K is estimated to be 1.54(2)µ B and the magnetic structure is all-in all-out as determined by our neutron diffraction measurements.

  10. Weakly-agglomerated nanocrystalline (ZrO 2) 0.9(Yb 2O 3) 0.1 powders hydrothermally synthesized at low temperature

    NASA Astrophysics Data System (ADS)

    Dell'Agli, Gianfranco; Mascolo, Giuseppe; Mascolo, Maria Cristina; Pagliuca, Concetta

    2006-09-01

    Nanocrystalline ytterbia (10 mol%)-doped cubic zirconia powders were synthesized by hydrothermal treatment of either an amorphous co-precipitate of hydrated ytterbia-zirconia or of zirconia xerogel in mixture with crystalline Yb 2O 3. The treatments were performed at 110 °C in the presence of diluted (0.2 M) or concentrated (2.0 M) solution of (K 2CO 3 + KOH) mineralizer and for different reaction times. The reaction times for the full crystallization of cubic-YbSZ-based products were determined for both the employed precursors and for each mineralizer solution. The various fully crystallized products were characterized in their degree of agglomeration and sintered at 1500 °C for 2 h. The best performance on sintering was achieved with the less agglomerated powder synthesized from the mechanical mixture and in the presence of the diluted solution of the mineralizer. The resulting density was the highest achieved with materials having the same composition.

  11. Effect of Gd3+ substitution on structural, magnetic, dielectric and optical properties of nanocrystalline CoFe2O4

    NASA Astrophysics Data System (ADS)

    Joshi, Seema; Kumar, Manoj; Chhoker, Sandeep; Kumar, Arun; Singh, Mahavir

    2017-03-01

    Nanoparticles of CoGdxFe2-xO4 with x=0.0, 0.03, 0.05, 0.07, 0.10 and 0.15 were synthesized by co-precipitation method. Gd3+ substitution effect on different properties of nanocrystalline CoFe2O4 has been studied. X-ray diffraction and Raman spectroscopy confirmed the formation of single phase cubic mixed spinel structure. Cation distribution has been proposed from Rietveld refined data. Mössbauer spectra at room temperature showed two ferrimagnetic Zeeman sextets with one superparamagnetic doublet. Mössbauer parameters suggested that Gd3+ ions occupy the octahedral site in CoFe2O4. Room temperature magnetic measurements exhibited that the saturation magnetization decreased from 91 emu/gm to 54 emu/gm for x=0.0 to 0.15 samples. The coercivity decreased from 1120 Oe to 340 Oe for x=0.0 to 0.07 samples and increased from 400 Oe to 590 Oe for x=0.10 and 0.15 samples, respectively. Raman analysis showed that the degree of inversion with Gd3+ substitution supporting the variation of coercivity. Electron spin resonance spectra revealed the dominancy of superexchange interactions in these samples. Optical band gap measurement suggested that all samples are indirect band gap materials and band gap has been decreased with Gd3+ substitution. Both dielectric constant and dielectric loss is found to decrease because of the decrease in hopping rate with the Gd3+ substitution for Fe3+ at the octahedral sites. Low dielectric loss suggested the applicability of Gd3+ doped CoFe2O4 nanoparticles for high frequency microwave device applications.

  12. Study of lattice strain and optical properties of nanocrystalline SnO2

    NASA Astrophysics Data System (ADS)

    Ahmad, Naseem; Khan, Shakeel; Bhargava, Richa; Ansari, Mohd Mohsin Nizam

    2018-05-01

    Nanocrystalline SnO2 has been synthesized by co-precipitation method by using two solvents (water and ethylene glycol). The structure and surface morphology were investigated using XRD and scanning electron microscope (SEM). The optical properties were studied using diffused reflectance spectroscopy (DRS). From the XRD analysis, the prepared materials are found to be pure crystalline with tetragonal rutile structure. The lattice strain and crystallite size, were calculated using Williamson-Hall method, are found to be 0.00413 & 16.3 nm in water assisted SnO2 and 0.00495 & 35.6 nm for EG assisted SnO2. Study of surface morphology of the samples was carried out using SEM. It has been seen that the solvents which are used in synthesis can also alter the optical properties of the materials. The optical band gap of the water based SnO2 and EG based SnO2 are found to be 3.92eV and 3.86eV respectively.

  13. Physical properties of nanoparticles Nd added Bi1.7Pb0.3Sr2Ca2Cu3Oy superconductors

    NASA Astrophysics Data System (ADS)

    Abbas, Muna; Abdulridha, Ali; Jassim, Amal; Hashim, Fouad

    2018-05-01

    Bi1.7Pb0.3Sr2Ca2Cu3Oy bulks were synthesized, with the addition of Nd2O3 nanoparticles, by the solid state reaction method. The concentrations of Nd were varied from 0.1 to 0.6. The superconducting properties of the samples were investigated and studied to determine the influence of Nd2O3 addition on superconducting properties and microstructural development. The structural characteristics of the synthesized superconductor samples were carried out through X-ray diffractions. DC Four point probe method was used to study the electrical resistivity behavior and to evaluate the transition temperature (TC) for all samples. It was found that: 0.2 weight percentage of Nd2O3 yield the highest TC 123 K for highest volume fraction of 2223-phase, while excessive addition decreased both of them. The results point to compelling indications of correlations between charge carriers and superconductivity. Energy-dispersive X-ray spectroscopy (EDX) analysis for Bi1.7Pb0.3Nd0.2Sr2Ca2Cu3Oy superconductor shows that Nd may be substituted at Ca sites creating point defects, which act as flux pinning centers. Scanning electron microscopy (SEM) was employed to examine the microstructure of some samples. Their results showed precipitation of Nd nanoparticles on the surface as plate-like grains.

  14. The effect of micro-structure on upconversion luminescence of Nd3+/Yb3+ co-doped La2O3-TiO2-ZrO2 glass-ceramics

    NASA Astrophysics Data System (ADS)

    Zhang, Minghui; Wen, Haiqin; Pan, Xiuhong; Yu, Jianding; Jiang, Meng; Yu, Huimei; Tang, Meibo; Gai, Lijun; Ai, Fei

    2018-03-01

    Nd3+/Yb3+ co-doped La2O3-TiO2-ZrO2 glasses have been prepared by aerodynamic levitation method. The glasses show high refractive index of 2.28 and Abbe number of 18.3. Glass-ceramics heated at 880 °C for 50 min perform the strongest upconversion luminescence. X-ray diffraction patterns of glass-ceramics with different depths indicate that rare earth ions restrain crystallization. Body crystallization mechanism mixed with surface crystallization is confirmed in the heat treatment. Surface crystals achieve priority to grow, resulting in important effects on upconversion luminescence. The results of atomic force microscope and scanning electron microscope indicate that crystal particles with uniform size distribute densely and homogenously on the surface and large amount of glass matrix exists in the glass ceramics heated at 880 °C for 50 min. Crystals in the glass-ceramics present dense structure and strong boundaries, which can reduce the mutual nonradiative relaxation rate among rare earth ions and then improve upconversion luminescence effectively. Based on micro-structural study, the mechanism that upconversion luminescence can be improved by heat treatment has been revealed. The results of micro-structural analysis agree well with the spectra.

  15. Optical and structural properties of Nd:MgO:LiNbO3 crystal irradiated by 2.8-MeV He ions

    NASA Astrophysics Data System (ADS)

    Jia, Chuan-Lei; Li, Song; Song, Xiao-Xiao

    2017-07-01

    We report the optical and structural properties of helium-implanted optical waveguides in Nd:MgO:LiNbO3 laser crystals. The prism-coupling method is used to investigate the dark-mode properties at the wavelength of 632.8 nm. The spontaneous generation of ultraviolet, blue, red, and near-infrared fluorescence emissions is demonstrated under excitation with an 808-nm laser diode. The effects of ion irradiation on the structural properties are characterized using the high-resolution X-ray diffraction technique. The results show that the initial luminescence properties of Nd:MgO:LiNbO3 crystals are slightly modified by irradiation with 2.8 MeV He ions at fluences of 1.5 × 1016 ions/cm2 at room temperature.

  16. Momentum Dependence of Charge Excitations in YBa2Cu3O7-δ and Nd2-xCexCuO4

    NASA Astrophysics Data System (ADS)

    Ishii, Kenji

    2006-03-01

    Resonant inelastic x-ray scattering (RIXS) studies at Cu K-edge on high-Tc superconducting cuprates, YBa2Cu3O7-δ and Nd2-xCexCuO4 are presented. The superconductivity occurs in the vicinity of the Mott insulating state and it is important to clarify the nature of the Mott gap and its doping dependence. Because RIXS has an advantage that we can measure charge excitation in a wide energy-momentum space, it gives a unique opportunity to study the electronic structure of materials. We apply this technique to high-Tc superconducting cuprates. In particular the electronic structure of strongly correlated metals is in the focus of our RIXS study. The experiments were performed at BL11XU of SPring-8, Japan, where a specially designed spectrometer for inelastic x-ray scattering is installed. In optimally doped YBa2Cu3O7-δ, anisotropic spectra are observed in the ab plane of a twin-free crystal. The Mott gap excitation from the one-dimensional CuO chain is enhanced at 2 eV near the zone boundary of the chain direction, while the excitation from the CuO2 plane is broad at 1.5-4 eV and almost independent of momentum. Theoretical calculation based on the one-dimensional and two-dimensional Hubbard model reproduces the observed features in the RIXS spectra when smaller values of the on-site Coulomb energy of the chain than that of the plane are assumed. This means that the charge transfer gap of the chain is smaller than that of the plane. On the other hand, both interband excitation across the Mott gap and intraband excitation in the upper Hubbard band are observed in the electron-doped Nd2-xCexCuO4. The intensity of the interband excitation is concentrated at ˜ 2 eV near the zone boundary while a dispersion relation with a momentum-dependent width emerges in the intraband excitation. The author would like to acknowledge to his collaborators, K. Tsutsui, Y. Endoh, T. Tohyama, K. Kuzushita, T. Inami, K. Ohwada, M. Hoesch, M. Tsubota, Y. Murakami, J. Mizuki, S. Maekawa, T

  17. Epitaxial growth of iridate pyrochlore Nd 2Ir 2O 7 films

    DOE PAGES

    Gallagher, J. C.; Esser, B. D.; Morrow, R.; ...

    2016-02-29

    Epitaxial films of the pyrochlore Nd 2Ir 2O 7 have been grown on (111)-oriented yttria-stabilized zirconia (YSZ) substrates by off-axis sputtering followed by post-growth annealing. X-ray diffraction (XRD) results demonstrate phase-pure epitaxial growth of the pyrochlore films on YSZ. Scanning transmission electron microscopy (STEM) investigation of an Nd 2Ir 2O 7 film with a short post-annealing provides insight into the mechanism for crystallization of Nd 2Ir 2O 7 during the post-annealing process. STEM images reveal clear pyrochlore ordering of Nd and Ir in the films. As a result, the epitaxial relationship between the YSZ and Nd 2Ir 2O 7 ismore » observed clearly while some interfacial regions show a thin region with polycrystalline Ir nanocrystals.« less

  18. Temperature dependence of the radiation tolerance of nanocrystalline pyrochlores A 2Ti 2O 7 (A = Gd, Ho and Lu)

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

    Wen, J.; Sun, C.; Dholabhai, P. P.

    A potentially enhanced radiation resistance of nanocrystalline materials, as a consequence of the high density of interfaces and surfaces, has attracted much attention both to understand the fundamental role of these defect sinks and to develop them for high-radiation environments. Here, irradiation response of nanocrystalline A 2Ti 2O 7 (A = Gd, Ho and Lu) pyrochlore powders with grain sizes of 20–30 nm was investigated by 1-MeV Kr 2+ ion bombardment. In situ transmission electron microscopy (TEM) revealed that the critical amorphization fluence for each nanocrystalline compound at room temperature was greater than that for their coarse-grained counterparts, indicating anmore » enhanced amorphization resistance. The effect of temperature on the irradiation response of one of these compounds, nanocrystalline Lu 2Ti 2O 7, was further examined by performing ion irradiation at an elevated temperature range of 480–600 K. The critical amorphization temperature (T c) was found to be noticeably higher in nanocrystalline Lu 2Ti 2O 7 (610 K) than its coarse-grained counterpart (480 K), revealing that nanocrystalline Lu 2Ti 2O 7 is less resistant to amorphization compared to its coarse-grained phase under high temperatures. We interpret these results with the aid of atomistic simulations. Molecular statics calculations find that cation antisite defects are less energetically costly to form near surfaces than in the bulk, suggesting that the nanocrystalline form of these materials is generally less susceptible to amorphization than coarse-grained counterparts at low temperatures where defect kinetics are negligible. In contrast, at high temperatures, the annealing efficiency of antisite defects by cation interstitials is significantly reduced due to the sink properties of the surfaces in the nanocrystalline pyrochlore, which contributes to the observed higher amorphization temperature in the nano-grained phase than in coarse-grained counterpart. Altogether, these

  19. Temperature dependence of the radiation tolerance of nanocrystalline pyrochlores A 2Ti 2O 7 (A = Gd, Ho and Lu)

    DOE PAGES

    Wen, J.; Sun, C.; Dholabhai, P. P.; ...

    2016-03-21

    A potentially enhanced radiation resistance of nanocrystalline materials, as a consequence of the high density of interfaces and surfaces, has attracted much attention both to understand the fundamental role of these defect sinks and to develop them for high-radiation environments. Here, irradiation response of nanocrystalline A 2Ti 2O 7 (A = Gd, Ho and Lu) pyrochlore powders with grain sizes of 20–30 nm was investigated by 1-MeV Kr 2+ ion bombardment. In situ transmission electron microscopy (TEM) revealed that the critical amorphization fluence for each nanocrystalline compound at room temperature was greater than that for their coarse-grained counterparts, indicating anmore » enhanced amorphization resistance. The effect of temperature on the irradiation response of one of these compounds, nanocrystalline Lu 2Ti 2O 7, was further examined by performing ion irradiation at an elevated temperature range of 480–600 K. The critical amorphization temperature (T c) was found to be noticeably higher in nanocrystalline Lu 2Ti 2O 7 (610 K) than its coarse-grained counterpart (480 K), revealing that nanocrystalline Lu 2Ti 2O 7 is less resistant to amorphization compared to its coarse-grained phase under high temperatures. We interpret these results with the aid of atomistic simulations. Molecular statics calculations find that cation antisite defects are less energetically costly to form near surfaces than in the bulk, suggesting that the nanocrystalline form of these materials is generally less susceptible to amorphization than coarse-grained counterparts at low temperatures where defect kinetics are negligible. In contrast, at high temperatures, the annealing efficiency of antisite defects by cation interstitials is significantly reduced due to the sink properties of the surfaces in the nanocrystalline pyrochlore, which contributes to the observed higher amorphization temperature in the nano-grained phase than in coarse-grained counterpart. Altogether, these

  20. In-situ and self-distributed: A new understanding on catalyzed thermal decomposition process of ammonium perchlorate over Nd{sub 2}O{sub 3}

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

    Zou, Min, E-mail: zoumin3362765@163.com; Wang, Xin, E-mail: wangx@mail.njust.edu.cn; Jiang, Xiaohong, E-mail: jxh0668@sina.com

    2014-05-01

    Catalyzed thermal decomposition process of ammonium perchlorate (AP) over neodymium oxide (Nd{sub 2}O{sub 3}) was investigated. Catalytic performances of nanometer-sized Nd{sub 2}O{sub 3} and micrometer-sized Nd{sub 2}O{sub 3} were evaluated by differential scanning calorimetry (DSC). In contrast to universal concepts, catalysts in different sizes have nearly similar catalytic activities. Based on structural and morphological variation of the catalysts during the reaction, combined with mass spectrum analyses and studies of unmixed style, a new understanding of this catalytic process was proposed. We believed that the newly formed chloride neodymium oxide (NdOCl) was the real catalytic species in the overall thermal decompositionmore » of AP over Nd{sub 2}O{sub 3}. Meanwhile, it was the “self-distributed” procedure which occurred within the reaction that also worked for the improvement of overall catalytic activities. This work is of great value in understanding the roles of micrometer-sized catalysts used in heterogeneous reactions, especially the solid–solid reactions which could generate a large quantity of gaseous species. - Graphical abstract: In-situ and self-distributed reaction process in thermal decomposition of AP catalyzed by Nd{sub 2}O{sub 3}. - Highlights: • Micro- and nano-Nd{sub 2}O{sub 3} for catalytic thermal decomposition of AP. • No essential differences on their catalytic performances. • Structural and morphological variation of catalysts digs out catalytic mechanism. • This catalytic process is “in-situ and self-distributed” one.« less

  1. CO2 Sensors Based on Nanocrystalline SnO2 Doped with CuO

    NASA Technical Reports Server (NTRS)

    Xu, Jennifer C.; Hunter, Gary W.; Liu, Chung Chiun; Ward, Benjamin J.

    2008-01-01

    Nanocrystalline tin oxide (SnO2) doped with copper oxide (CuO) has been found to be useful as an electrical-resistance sensory material for measuring the concentration of carbon dioxide in air. SnO2 is an n-type semiconductor that has been widely used as a sensing material for detecting such reducing gases as carbon monoxide, some of the nitrogen oxides, and hydrocarbons. Without doping, SnO2 usually does not respond to carbon dioxide and other stable gases. The discovery that the electrical resistance of CuO-doped SnO2 varies significantly with the concentration of CO2 creates opportunities for the development of relatively inexpensive CO2 sensors for detecting fires and monitoring atmospheric conditions. This discovery could also lead to research that could alter fundamental knowledge of SnO2 as a sensing material, perhaps leading to the development of SnO2-based sensing materials for measuring concentrations of oxidizing gases. Prototype CO2 sensors based on CuO-doped SnO2 have been fabricated by means of semiconductor-microfabrication and sol-gel nanomaterial-synthesis batch processes that are amendable to inexpensive implementation in mass production.

  2. Effect of rapid thermal annealing on nanocrystalline TiO2 thin films synthesized by swift heavy ion irradiation

    NASA Astrophysics Data System (ADS)

    Thakurdesai, Madhavi; Kanjilal, D.; Bhattacharyya, Varsha

    2012-08-01

    Irradiation by swift heavy ions (SHI) is unique tool to synthesize nanocrystalline thin films. We have reported transformation of 100 nm thick amorphous films into nanocrystalline film due to irradiation by 100 MeV Ag ion beam. Oblate shaped nanoparticles having anatase phase of TiO2 were formed on the surface of the irradiated films. In the present investigation, these films are annealed at 350 °C for 2 min in oxygen atmosphere by Rapid Thermal Annealing (RTA) method. During RTA processing, the temperature rises abruptly and this thermal instability is expected to alter surface morphology, structural and optical properties of nanocrystalline TiO2 thin films. Thus in the present work, effect of RTA on SHI induced nanocrystalline thin films of TiO2 is studied. The effect of RTA processing on the shape and size of TiO2 nanoparticles is studied by Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). Glancing Angle X-ray Diffraction (GAXRD) studies are carried to investigate structural changes induced by RTA processing. Optical characterization is carried out by UV-vis spectroscopy and photoluminescence (PL) spectroscopy. The changes observed in structural and optical properties of nanocrystalline TiO2 thin films after RTA processing are attributed to the annihilation of SHI induced defects.

  3. Efficient reuse of the waste sintered NdFeB magnet with Dy2O3 addition

    NASA Astrophysics Data System (ADS)

    Li, Chencheng; Sun, Aizhi; Tian, Zhenya; Zhang, Xun; Ma, Bin

    2018-09-01

    In this paper, the efficient recycling method of sintered NdFeB waste was studied. The production process can be greatly simplified by crushing the recovered waste magnet into hundreds of micron-sized magnetic powder and preparing the magnet directly with orientating, molding and sintering. The magnetic properties of the magnet prepared by commercial N45 recovered waste can reach Br = 1.09 T, (BH)max = 196 kJ/m3 and Hcj = 601 kA/m. Adding a small amount of Dy2O3 can significantly improve the Br of the above magnet. The maximum Hcj can reach 1310 kA/m and (BH)max can reach 204 kJ/m3. The microstructure analysis shows that Dy2O3 diffused along the grain boundaries mainly and forms Dy-rich shell around the Nd2Fe14B grains which increase the difficulty of forming anti-magnetization.

  4. Four-wave-mixing and nonlinear cavity dumping of 280 picosecond 2nd Stokes pulse at 1.3 μm from Nd:SrMoO4 self-Raman laser

    NASA Astrophysics Data System (ADS)

    Smetanin, S. N.; Jelínek, M., Jr.; Kubeček, V.; Jelínková, H.; Ivleva, L. I.; Shurygin, A. S.

    2016-01-01

    The 280 picosecond 2nd Stokes Raman pulses at 1.3 μm were generated directly from the miniature diode-pumped Nd:SrMoO4 self-Raman laser. Using the 90° phase matching insensitive to the angular mismatch, the self-Raman laser allowed for the achievement of the four-wave-mixing generation of the 2nd Stokes Raman pulse directly in the active Nd:SrMoO4 crystal at stimulated Raman scattering (SRS) self-conversion of the laser radiation. The passive Cr:YAG Q-switching and nonlinear cavity dumping was used without any phase locking device.

  5. Structure and Dielectric Properties of (Sr0.2Ca0.488Nd0.208) TiO3-Li3NbO4 Ceramic Composites

    NASA Astrophysics Data System (ADS)

    Xia, C. C.; Chen, G. H.

    2017-12-01

    The new ceramic composites of (1-x) Li3NbO4-x (Sr0.2Ca0.488Nd0.208)TiO3 were prepared by the conventional solid state reaction method. The sintering behavior, phase composition, microstructure and microwave dielectric properties of the ceramics were investigated specially. The SEM and XRD results show that (1-x) Li3NbO4-x (Sr0.2Ca0.488Nd0.208) TiO3 (0.35≤x≤0.5) composites were composed of two phase, i.e. perovskite and Li3NbO4. With the increase of x, the ɛr increases from 27.1 to 38.7, Q×f decreases from 55000 GHz to 16770 GHz, and the τ f increases from -49 ppm/°C to 226.7 ppm/°C. The optimized dielectric properties with ɛr∼31.4, Q×f~16770GHz and τf~-8.1ppm/°C could be obtained as x=0.4 sintered at 1100°C for 4h. The as-prepared ceramic is expected to be used in resonators, filters, and other microwave devices.

  6. Crystallographic and magnetic properties of nanocrystalline perovskite structure SmFeO3 orthoferrite

    NASA Astrophysics Data System (ADS)

    Kumar, Ashwini; Shen, Jingdong; Zhao, Huihui; Zhengjian, Qi; Li, Qi

    2018-05-01

    In this article, we present the structural and magnetic studies of pristine SmFeO3 nanocrystalline ceramic samples as sintered at temperature 850 °C and 1000 °C. X-ray powder diffraction data confirm the existence of single-phase nature with orthorhombic (Pbnm) structure of the samples. The SEM image reveals spherical particles with a size range of 60-130 nm for SFO-850 and SFO-1000 samples. X-ray absorption spectroscopy studies on Fe L3,2 and O K-edges of SmFeO3 sample revealed the homo-valence state of Fe in these materials. From magnetization studies it has been observed the materials exhibit ferromagnetic and antiferromagnetic (canted spin structure) sub-lattices, which results strong magnetic anisotropy in the system.

  7. Basic molten salt process-A new route for synthesis of nanocrystalline Li 4Ti 5O 12-TiO 2 anode material for Li-ion batteries using eutectic mixture of LiNO 3-LiOH-Li 2O 2

    NASA Astrophysics Data System (ADS)

    Rahman, M. M.; Wang, Jia-Zhao; Hassan, Mohd Faiz; Chou, Shulei; Wexler, David; Liu, Hua-Kun

    A nanocrystalline Li 4Ti 5O 12-TiO 2 duplex phase has been synthesized by a simple basic molten salt process (BMSP) using an eutectic mixture of LiNO 3-LiOH-Li 2O 2 at 400-500 °C. The microstructure and morphology of the Li 4Ti 5O 12-TiO 2 product are characterized by means of X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM). The sample prepared by heat-treating at 300 °C for 3 h (S-1) reveals dense agglomerates of ultra-fine nanocrystalline Li 4Ti 5O 12; with heat treatment at 400 °C for 3 h (S-2), there is a duplex crystallite size (fine < 10 nm, and coarse > 20 nm) of Li 4Ti 5O 12-TiO 2; at 500 °C for 3 h (S-3), a much coarser and less-dense distribution of lithium titanate (crystallite size ∼15-30 nm) is observed. According to the results of electrochemical testing, the S-2 sample shows initial discharge capacities of 193 mAh g -1 at 0.2 C, 168 mAh g -1 at 0.5 C, 146 mAh g -1 at 1 C, 135 mAh g -1 at 2 C, and 117 mAh g -1 at 5 C. After 100 cycles, the discharge capacity is 138 mAh g -1 at 1 C with a capacity retention of 95%. The S-2 sample yields the best electrochemical performance in terms of charge-discharge capacity and rate capability compared with other samples. Its superior electrochemical performance can be mainly attributed to the duplex crystallite structure, composed of fine (<10 nm) and coarse (>20) nm nanoparticles, where lithium ions can be stored within the grain boundary interfaces between the spinel Li 4Ti 5O 12 and the anatase TiO 2.

  8. Orbital configuration in CaTiO 3 films on NdGaO 3

    DOE PAGES

    Cao, Yanwei; Park, Se Young; Liu, Xiaoran; ...

    2016-10-13

    Despite its use as a constituent layer for realization of a polar metal and interfacial conductivity, the microscopic study of electronic structure of CaTiO 3 is still very limited. Here, we epitaxially stabilized CaTiO 3 films on NdGaO 3 (110) substrates in a layer-by-layer way by pulsed laser deposition. The structural and electronic properties of the films were characterized by reflection-high-energy-electron-diffraction, X-ray diffraction, and element-specific resonant X-ray absorption spectroscopy. To reveal the orbital polarization and the crystal field splitting of the titanium 3d state, X-ray linear dichroism was carried out on CaTiO 3 films, demonstrating the orbital configuration of dmore » xz/d yz < d xy < d 3z2-r2 < d x2-y2. To further explore the origin of this configuration, we performed the first-principles density function theory calculations, which linked the orbital occupation to the on-site energy of Ti 3d orbitals. Finally, these findings can be important for understanding and designing exotic quantum states in heterostructures based on CaTiO 3.« less

  9. Photoemission study of absorption mechanisms in Bi2.0Sr1.8Ca0.8La0.3Cu2.1O8+δ, BaBiO3, and Nd1.85Ce0.15CuO4

    NASA Astrophysics Data System (ADS)

    Lindberg, P. A. P.; Shen, Z.-X.; Wells, B. O.; Dessau, D. S.; Ellis, W. P.; Borg, A.; Kang, J.-S.; Mitzi, D. B.; Lindau, I.; Spicer, W. E.; Kapitulnik, A.

    1989-11-01

    Photoemission measurements in the constant-final-state (absorption) mode were performed on three different classes of high-temperature superconductors Bi2.0Sr1.8Ca0.8La0.3Cu2.1O8+δ, BaBiO3, and Nd1.85Ce0.15CuO4 using synchrotron radiation from 20 to 200 eV. Absorption signals from all elements but Ce are identified. The results firmly show that the Bi 6s electrons are more delocalized in BaBiO3 than in Bi2.0Sr1.8Ca0.8La0.3Cu2.1O8+δ, in agreement with the results of band-structure calculations. Differences in the absorption signals due to O and Bi excitations between BaBiO3 and Bi2.0Sr1.8Ca0.8La0.3Cu2.1O8+δ are discussed. Delayed absorption onsets attributed to giant resonances (Ba 4d-->4f, La 4d-->4f, and Nd 4d-->4f transitions) are also reported.

  10. Optical and electrical properties of mechanochemically synthesized nanocrystalline delafossite CuAlO2.

    PubMed

    Prakash, T; Prasad, K Padma; Ramasamy, S; Murty, B S

    2008-08-01

    Nanocrystalline p-type semiconductor copper aluminum oxide (CuAlO2) has been synthesized by mechanical alloying using freshly prepared Cu2O and alpha-AlO2O3 nanocrystals in toluene medium. A study on structural property performed with different alloying and post annealing durations, by X-ray diffraction (XRD) reveals the formation of single phase with average crystallite size approximately 45 nm. Optical absorbance onset at 364.5 nm confirms its wide band gap nature (E(g) = 3.4 eV) and the fluorescence emission behaviour (390 nm) confirms its direct band type transition. The activation energy for electrical conduction has been calculated by Arrhenius plots using impedance measurement. Both grain and grain boundary conductivity takes place with almost equal activation energies of approximately 0.45 eV. The paper discusses synthesis, structural, optical and electrical properties of delafossite CuAlO2 in detail.

  11. A comparative study of CeO2-Al2O3 support prepared with different methods and its application on MoO3/CeO2-Al2O3 catalyst for sulfur-resistant methanation

    NASA Astrophysics Data System (ADS)

    Jiang, Minhong; Wang, Baowei; Yao, Yuqin; Li, Zhenhua; Ma, Xinbin; Qin, Shaodong; Sun, Qi

    2013-11-01

    The CeO2-Al2O3 supports prepared with impregnation (IM), deposition precipitation (DP), and solution combustion (SC) methods for MoO3/CeO2-Al2O3 catalyst were investigated in the sulfur-resistant methanation. The supports and catalysts were characterized by N2-physisorption, transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy (RS), and temperature-programmed reduction (TPR). The N2-physisorption results indicated that the DP method was favorable for obtaining better textural properties. The TEM and RS results suggested that there is a CeO2 layer on the surface of the support prepared with DP method. This CeO2 layer not only prevented the interaction between MoO3 and γ-Al2O3 to form Al2(MoO4)3 species, but also improved the dispersion of MoO3 in the catalyst. Accordingly, the catalysts whose supports were prepared with DP method exhibited the best catalytic activity. The catalysts whose supports were prepared with SC method had the worst catalytic activity. This was caused by the formation of Al2(MoO4)3 and crystalline MoO3. Additionally, the CeO2 layer resulted in the instability of catalysts in reaction process. The increasing of calcination temperature of supports reduced the catalytic activity of all catalysts. The decrease extent of the catalysts whose supports were prepared with DP method was the lowest as the CeO2 layer prevented the interaction between MoO3 and γ-Al2O3.

  12. Fluorescence properties of Nd3+-doped tellurite glasses.

    PubMed

    Kumar, K Upendra; Prathyusha, V A; Babu, P; Jayasankar, C K; Joshi, A S; Speghini, A; Bettinelli, M

    2007-07-01

    The compositional and concentration dependence of luminescence of the (4)F(3/2)-->(4)I(J) (J=13/2, 11/2 and 9/2) transitions in four Nd(3+)-doped tellurite based glasses has been studied. The free-ion energy levels obtained for 60TeO(2)+39ZnO(2)+1.0Nd(2)O(3) (TZN10) glass have been analysed using the free-ion Hamiltonian model and compared with similar results obtained for Nd(3+):glass systems. The absorption spectrum of TZN10 glass has been analysed using the Judd-Ofelt theory. Relatively longer decay rates have been obtained for Nd(3+)-doped phosphotellurite glasses. The emission characteristics of the (4)F(3/2)-->(4)I(11/2) transition, of the Nd(3+):TZN10 glass, are found to be comparable to those obtained for Nd(3+):phosphate laser glasses. The non-exponential shape of the emission decay curves for the (4)F(3/2)-->(4)I(11/2) transition is attributed to the presence of energy transfer processes between the Nd(3+) ions.

  13. Structural, optical and dielectric properties of Ce0.9Nd0.1O1.95 nanocrystalline oxygen ion conductors: Effect of sintering temperature

    NASA Astrophysics Data System (ADS)

    Anirban, Sk.; Dutta, A.

    2015-01-01

    Neodymium doped nanocrystalline ceria [Ce0.9Nd0.1O1.95] was prepared through citrate auto-ignition method. The prepared samples were sintered at five different temperatures starting from 400 °C up to 1200 °C. Rietveld's powder structure refinement analysis of XRD data confirmed the single phase cubic fluorite structure of the prepared samples with space group Fm 3 barm and the obtained particle size and lattice parameter values were found to vary with sintering temperature from 6.68 nm to 39.51 nm and from 5.39077 Å to 5.42317 Å respectively. The optical properties were studied using FT-IR and UV-vis absorption spectra. The FT-IR spectra confirm the presence of functional groups and chemical bonding in the material. The optical band gap was calculated from UV-vis spectra and its value was found to decrease from 3.70 eV to 2.46 eV with increase in sintering temperature. The dc conductivity was found to be thermally activated and decreased with increase in sintering temperature. The nature of impedance spectra reveals the presence of both grain and grain boundary effect. The tangent loss exhibited the presence of relaxation peaks due to the presence of defect pair in the synthesized samples.

  14. Textured Nd2Fe14B flakes with enhanced coercivity

    NASA Astrophysics Data System (ADS)

    Cui, B. Z.; Zheng, L. Y.; Marinescu, M.; Liu, J. F.; Hadjipanayis, G. C.

    2012-04-01

    Morphology, structure, and magnetic properties of the [001] textured Nd2Fe14B nanocrystalline flakes prepared by surfactant-assisted high energy ball milling (HEBM) and subsequent annealing were studied. These flakes have a thickness of 80-200 nm, a length of 0.5-10 μm, and an average grain size of 10-14 nm. The addition of some amount of Dy, Nd70Cu30 alloy, and an appropriate post annealing increased the coercivity iHc of the Nd2Fe14B flakes. iHc was 3.7, 4.3, and 5.7 kOe for the Nd15.5Fe78.5B6, Nd14Dy1.5Fe78.5B6 and 83.3 wt.% Nd14Dy1.5Fe78.5B6 + 16.7 wt.% Nd70Cu30 flakes prepared by HEBM for 5 h in heptane with 20 wt.% oleylamine, respectively. After annealing at 450 °C for 0.5 h, their iHc increased to 5.1, 6.2, and 7.0 kOe, respectively. Anisotropic magnetic behavior was found in all of the as-milled and annealed flakes. Both, the thickening of Nd-rich phase at grain boundaries via diffusion of Nd70Cu30 and the surface modification of the Nd2Fe14B flake could be the main reasons for the coercivity enhancement in the as-milled and annealed Nd70Cu30-added Nd2Fe14B flakes.

  15. Enhancement of photocatalytic activity of combustion-synthesized CeO2/C3N4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Li, Dong-Feng; Yang, Ke; Wang, Xiao-qin; Ma, Ya-Li; Huang, Gui-Fang; Huang, Wei-Qing

    2015-09-01

    Nanocrystalline CeO2/C3N4 was synthesized via a one-step solution combustion method using urea as fuel for the first time. The effects of the molar ratio of urea to cerium chloride on the photocatalytic activity of the synthesized samples were investigated. The synthesized nanocrystalline CeO2/C3N4 shows small size and large surface exposure area. Photocatalytic degradation of methylene blue demonstrates that the synthesized nanocrystalline CeO2/C3N4 possesses enhanced photocatalytic activity. It is proposed that the enhanced photocatalytic activity might be related to the favorable morphology and structure, and the effective charge separation between C3N4 and CeO2 in the photocatalytic process.

  16. Hydrazinium lanthanide oxalates: synthesis, structure and thermal reactivity of N2H5[Ln2(C2O4)4(N2H5)]·4H2O, Ln = Ce, Nd.

    PubMed

    De Almeida, Lucie; Grandjean, Stéphane; Rivenet, Murielle; Patisson, Fabrice; Abraham, Francis

    2014-03-28

    New hydrazinium lanthanide oxalates N2H5[Ln2(C2O4)4(N2H5)]·4H2O, Ln = Ce (Ce-HyOx) and Nd (Nd-HyOx), were synthesized by hydrothermal reaction at 150 °C between lanthanide nitrate, oxalic acid and hydrazine solutions. The structure of the Nd compound was determined from single-crystal X-ray diffraction data, space group P2₁/c with a = 16.315(4), b = 12.127(3), c = 11.430(2) Å, β = 116.638(4)°, V = 2021.4(7) Å(3), Z = 4, and R1 = 0.0313 for 4231 independent reflections. Two distinct neodymium polyhedra are formed, NdO9 and NdO8N, an oxygen of one monodentate oxalate in the former being replaced by a nitrogen atom of a coordinated hydrazinium ion in the latter. The infrared absorption band at 1005 cm(-1) confirms the coordination of N2H5(+) to the metal. These polyhedra are connected through μ2 and μ3 oxalate ions to form an anionic three-dimensional neodymium-oxalate arrangement. A non-coordinated charge-compensating hydrazinium ion occupies, with water molecules, the resulting tunnels. The N-N stretching frequencies of the infrared spectra demonstrate the existence of the two types of hydrazine ions. Thermal reactivity of these hydrazinium oxalates and of the mixed isotypic Ce/Nd (CeNd-HyOx) oxalate were studied by using thermogravimetric and differential thermal analyses coupled with gas analyzers, and high temperature X-ray diffraction. Under air, fine particles of CeO2 and Ce(0.5)Nd(0.5)O(1.75) are formed at low temperature from Ce-HyOx and CeNd-HyOx, respectively, thanks to a decomposition/oxidation process. Under argon flow, dioxymonocyanamides Ln2O2CN2 are formed.

  17. 2nd & 3rd Generation Vehicle Subsystems

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This paper contains viewgraph presentation on the "2nd & 3rd Generation Vehicle Subsystems" project. The objective behind this project is to design, develop and test advanced avionics, power systems, power control and distribution components and subsystems for insertion into a highly reliable and low-cost system for a Reusable Launch Vehicles (RLV). The project is divided into two sections: 3rd Generation Vehicle Subsystems and 2nd Generation Vehicle Subsystems. The following topics are discussed under the first section, 3rd Generation Vehicle Subsystems: supporting the NASA RLV program; high-performance guidance & control adaptation for future RLVs; Evolvable Hardware (EHW) for 3rd generation avionics description; Scaleable, Fault-tolerant Intelligent Network or X(trans)ducers (SFINIX); advance electric actuation devices and subsystem technology; hybrid power sources and regeneration technology for electric actuators; and intelligent internal thermal control. Topics discussed in the 2nd Generation Vehicle Subsystems program include: design, development and test of a robust, low-maintenance avionics with no active cooling requirements and autonomous rendezvous and docking systems; design and development of a low maintenance, high reliability, intelligent power systems (fuel cells and battery); and design of a low cost, low maintenance high horsepower actuation systems (actuators).

  18. The effect of TiO2 on nucleation and crystallization of a Li2O-Al2O3-SiO2 glass investigated by XANES and STEM.

    PubMed

    Kleebusch, Enrico; Patzig, Christian; Krause, Michael; Hu, Yongfeng; Höche, Thomas; Rüssel, Christian

    2018-02-13

    Glass ceramics based on Li 2 O/Al 2 O 3 /SiO 2 are of high economic importance, as they often show very low coefficients of thermal expansion. This enables a number of challenging applications, such as cooktop panels, furnace windows or telescope mirror blanks. Usually, the crystallization of the desired LAS crystal phases within the glasses must be tailored by a careful choice of crystallization schedule and type of nucleation agents to be used. The present work describes the formation of nanocrystalline TiO 2 within an LAS base composition that contains solely TiO 2 as nucleating agent. Using a combination of scanning transmission electron microscopy as well as X-ray absorption spectroscopy, it is found that a mixture of four- and six-fold coordinated Ti 4+ ions exists already within the glass. Heating of the glass to 740 °C immediately changes this ratio towards a high content of six-fold coordinated Ti, which accumulates in liquid-liquid phase-separation droplets. During the course of thermal treatment, these droplets eventually evolve into nanocrystalline TiO 2 precipitations, in which Ti 4+ is six-fold coordinated. Thus, it is shown that the nucleation of nanocrystalline TiO 2 is initiated by a gradual re-arrangement of the Ti ions in the amorphous, glassy matrix, from a four-fold towards a six-fold coordination.

  19. Slow spin relaxation induced by magnetic field in [NdCo(bpdo)(H2O)4(CN)6]⋅3H2O.

    PubMed

    Vrábel, P; Orendáč, M; Orendáčová, A; Čižmár, E; Tarasenko, R; Zvyagin, S; Wosnitza, J; Prokleška, J; Sechovský, V; Pavlík, V; Gao, S

    2013-05-08

    We report on a comprehensive investigation of the magnetic properties of [NdCo(bpdo)(H2O)4(CN)6]⋅3H2O (bpdo=4, 4'-bipyridine-N,N'-dioxide) by use of electron paramagnetic resonance, magnetization, specific heat and susceptibility measurements. The studied material was identified as a magnet with an effective spin S = 1/2 and a weak exchange interaction J/kB = 25 mK. The ac susceptibility studies conducted at audio frequencies and at temperatures from 1.8 to 9 K revealed that the application of a static magnetic field induces a slow spin relaxation. It is suggested that the relaxation in the magnetic field appears due to an Orbach-like process between the two lowest doublet energy states of the magnetic Nd(3+) ion. The appearance of the slow relaxation in a magnetic field cannot be associated with a resonant phonon trapping. The obtained results suggest that the relaxation is influenced by nuclear spin driven quantum tunnelling which is suppressed by external magnetic field.

  20. The enhancement of photovoltaic parameters in dye-sensitized solar cells of nano-crystalline SnO2 by incorporating with large SrTiO3 particles.

    PubMed

    Aponsu, G M L P; Wijayarathna, T R C K; Perera, I K; Perera, V P S; Siriwardhana, A C P K

    2013-05-15

    In this paper, the performance of nano-porous electrodes made of a composite material of SrTiO3 and SnO2 are compared with those made of bare SnO2. When these particular devices are analyzed in a comparative mode the results confirmed the enhancement of photovoltaic parameters in the former device. The performance of respective cells were examined by several methods including I-V characteristic measurements, photocurrent action spectra, dark I-V measurements, Mott-Schottky measurements and X-ray diffraction measurements. Even though such improvements in this particular cell could be explicated by the formation of a potential energy barrier of SrTiO3 particles of comparably large width at the SrTiO3/SnO2 interface, the passivation of voids in the SnO2 film by SrTiO3 particles to a certain extent could not be totally ruled out. Besides, high energetic electrons injected by dye molecules move more credibly through mini-bands formed in the chain of nano-crystalline SnO2 particles to the back contact. The blocking of the recombination path and the shifting up of the uppermost electron occupied level of SnO2 accompanying the conduction band edge in the SrTiO3/SnO2 composite film, may have lead to the observed enhancement of the fill factor and photovoltage, respectively. Copyright © 2013 Elsevier B.V. All rights reserved.

  1. Dielectric and AC conductivity studies of Nd substituted 0.8BaTiO{sub 3}-0.2(Bi{sub 0.5(1-x)}Nd{sub 0.5x}K{sub 0.5})TiO{sub 3} lead free ceramics

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

    Ramesh, M. N. V.; Ramesh, K. V., E-mail: kv-ramesh5@yahoo.co.in

    2016-05-23

    0.8BaTiO{sub 3} – 0.2(Bi{sub 0.5(1-x)}Nd{sub 0.5x}K{sub 0.5})TiO{sub 3} (0.01 ≤ x ≤ 0.06) lead free ceramic materials have been prepared by solid state reaction method and followed by high energy ball milling process. X-ray diffraction studies confirm the tetragonal structure of the materials at room temperature. Lattice parameters and density are decreasing with increase of Nd substitution. Microstructure studies were done by using Scanning electron microscope and it found that grain size is decreasing with increase of Nd substitution. Temperature and frequency dependent dielectric studies reveal relaxor behaviour of the materials. Dielectric constant, dielectric loss and Curie temperature are decreasingmore » with Nd substitution. Maximum Curie temperature of 195°C was observed at 1 MHz for x=0.01 Nd substituted sample. Degree of diffuseness was calculated from the modified Curie-Weiss law and it is increasing with Nd substitution. AC conductivity is increasing with increase of Nd substitution and observed maximum activation energy of 0.52 eV for x=0.02 Nd substituted sample.« less

  2. Nanocrystalline SnO2 formation by oxygen ion implantation in tin thin films

    NASA Astrophysics Data System (ADS)

    Kondkar, Vidya; Rukade, Deepti; Kanjilal, Dinakar; Bhattacharyya, Varsha

    2018-03-01

    Metallic tin thin films of thickness 100 nm are deposited on fused silica substrates by thermal evaporation technique. These films are implanted with 45 keV oxygen ions at fluences ranging from 5 × 1015 to 5 × 1016 ions cm-2. The energy of the oxygen ions is calculated using SRIM in order to form embedded phases at the film-substrate interface. Post-implantation, films are annealed using a tube furnace for nanocrystalline tin oxide formation. These films are characterized using x-ray diffraction, Raman spectroscopy, UV-vis spectroscopy and photoluminescence spectroscopy. XRD and Raman spectroscopy studies reveal the formation of single rutile phase of SnO2. The size of the nanocrystallites formed decreases with an increase in the ion fluence. The nanocrystalline SnO2 formation is also confirmed by UV-vis and photoluminescence spectroscopy.

  3. High pressure luminescence of Nd3+ in YAlO3 perovskite nanocrystals: A crystal-field analysis

    NASA Astrophysics Data System (ADS)

    Hernández-Rodríguez, Miguel A.; Muñoz-Santiuste, Juan E.; Lavín, Víctor; Lozano-Gorrín, Antonio D.; Rodríguez-Hernández, Plácida; Muñoz, Alfonso; Venkatramu, Vemula; Martín, Inocencio R.; Rodríguez-Mendoza, Ulises R.

    2018-01-01

    Pressure-induced energy blue- and red-shifts of the 4F3/2 → 4I9/2,11/2 near-infrared emission lines of Nd3+ ions in YAlO3 perovskite nano-particles have been measured from ambient conditions up to 29 GPa. Different positive and negative linear pressure coefficients have been calibrated for the emission lines and related to pressure-induced changes in the interactions between those Nd3+ ions and their twelve oxygen ligands at the yttrium site. Potentiality of the simple overlap model, combined with ab initio structural calculations, in the description of the effects of these interactions on the energy levels and luminescence properties of the optically active Nd3+ ion is emphasized. Simulations show how the energies of the 4f3 ground configuration and the barycenters of the multiplets increase with pressure, whereas the Coulomb interaction between f-electrons decreases and the crystal-field strength increases. All these effects combined explain the wavelength blue-shifts of some near-infrared emission lines of Nd3+ ions. Large pressure rates of various emission lines suggest that a YAlO3 perovskite nano-crystal can be a potential candidate for near-infrared optical pressure sensors.

  4. Micromagnetic finite element simulation of nanocrystalline α-Fe/Nd2Fe14B/Fe3B magnets

    NASA Astrophysics Data System (ADS)

    Saiden, N. M.; Schrefl, T.; Davies, H. A.; Hrkac, G.

    2014-09-01

    Nanocomposite Nd2Fe14B permanent magnets with Fe3B and α-Fe as the soft phase have been simulated using micromagnetic modelling. This paper reviews extensively the results from the simulation point of view. The magnetization configuration along the hysteresis loop is discussed in details. It was clear that the grain size and phase distribution play important roles in determining the magnetic properties. By changing the size of the grain and the volume fraction of the hard and soft phase, the magnetic properties change and the relationship between microstructure and properties is investigated. The remanence, Jr increases with decreasing of grain size, but oppositely for coercivity, Hc. The highest Jr, 1.46 T was obtained with a grain size 10 nm, and volume fraction of α-Fe, 40%. Whereas, the highest Hc with combination Nd2Fe14B 80% and 20% Fe3B, 947 kA/m. On the other hand, if Nd2Fe14B alone, the Hc able to reach up to 1000 kA/m. From this study, micromagnetic modelling contributes to a better understanding how microstructure and phase distribution influences the magnetic properties.

  5. Multiferroic properties in NdFeO3-PbTiO3 solid solutions

    NASA Astrophysics Data System (ADS)

    Kumar, Sunil; Pal, Jaswinder; Kaur, Shubhpreet; Agrawal, P.; Singh, Mandeep; Singh, Anupinder

    2018-05-01

    The x(NdFeO3) - 1-x(PbTiO3) where x = 0.2 solid solution was prepared using solid state reaction route. The X-ray diffraction (XRD) data reveals the single phase formation. The microstructure shows grain growth with lesser porosity. The energy dispersive analysis confirms the presence of elements in stochiometric proportion. The polarization vs. Electric field loop estabilished a ferroelectric type behavior but lossy in nature. This lossy nature may be due to the presence of large leakage current in solid solution. The Magnetization vs. Magnetic field plot exhibits a unsaturated hysteriss loop indicates that the sample is not purely ferromagnetic.

  6. Measurements of defect structures by positron annihilation lifetime spectroscopy of the tellurite glass TeO2-P2O5-ZnO-LiNbO3 doped with ions of rare earth elements: Er3+, Nd3+ and Gd3+

    NASA Astrophysics Data System (ADS)

    Golis, E.; Yousef, El. S.; Reben, M.; Kotynia, K.; Filipecki, J.

    2015-12-01

    The objective of the study was the structural analysis of the TeO2-P2O5-ZnO-LiNbO3 tellurite glasses doped with ions of the rare-earth elements: Er3+, Nd3+ and Gd3+ based on the PALS (Positron Annihilation Lifetime Spectroscopy) method of measuring positron lifetimes. Values of positron lifetimes and the corresponding intensities may be connected with the sizes and number of structural defects, such as vacancies, mono-vacancies, dislocations or pores, the sizes of which range from a few angstroms to a few dozen nanometres. Experimental positron lifetime spectrum revealed existence of two positron lifetime components τ1 and τ2. Their interpretation was based on two-state positron trapping model where the physical parameters are the annihilation velocity and positron trapping rate.

  7. Effect of zirconia morphology on sulfur-resistant methanation performance of MoO3/ZrO2 catalyst

    NASA Astrophysics Data System (ADS)

    Liu, Chen; Wang, Weihan; Xu, Yan; Li, Zhenhua; Wang, Baowei; Ma, Xinbin

    2018-05-01

    Two kinds of ZrO2 support with different morphologies were prepared by facile solvothermal method in different solvents. The obtained two supports showed monoclinic zirconia (m-ZrO2) and tetragonal zirconia (t-ZrO2) phase with similar crystalline size. Their supported Mo-based catalysts were prepared by impregnation method and the effect of zirconia morphology on the performance of sulfur-resistant methanation was examined. The results indicated that the MoO3/m-ZrO2 has higher CO conversion than the MoO3/t-ZrO2 catalyst. Characterizations by XRD, Raman, H2-TPR and IR confirmed that the m-ZrO2 is superior to t-ZrO2 for dispersing molybdenum species. In addition, the MoO3/m-ZrO2 catalyst has weaker interaction between support and active Mo speices than the MoO3/t-ZrO2 catalyst, which facilitates to forming active species of nanocrystalline MoS2 layers for sulfur-resistant methanation. The weaker interaction of molybdenum species with m-ZrO2 is related with the more covalent character of the Zrsbnd O bond and more oxygen defective structure of m-ZrO2. A larger number of Lewis acid centers appear on the surface of m-ZrO2, which verified the substantial vacancies on m-ZrO2 exposing coordinately unsaturated Zr3+ and Zr4+ cations. Meanwhile, the less Lewis acid of t-ZrO2 result in stronger interaction between support and molybdenum species and trigger crystalline phase MoO3 and Mosbnd Osbnd Zr linkages.

  8. Effect of cobalt doping on structural and optical properties of nanocrystalline La0.8Pb0.2CrO3 orthochromite

    NASA Astrophysics Data System (ADS)

    Zarrin, Naima; Shahidhusain

    2018-04-01

    We have synthesized nanocrystalline La0.8Pb0.2Cr1-xCoxO3 (0≤x≤0.3) through sol-gel process and studied their structural and optical properties. X-ray diffraction patterns reveal that the samples conform in the orthorhombic crystal symmetry with Pnma space group. Structural parameters are refined by Rietveld Refinement using Fullprof software. Lattice parameters and unit cell volume of doped samples are found to decrease with increase in Co doping. The optical energy band gapdecreases whereas Urbach energy increases with the increase in Co content.

  9. Photocatalytic Water Splitting for O2 Production under Visible Light Irradiation Using NdVO4-V2O5 Hybrid Powders

    PubMed Central

    Chiang, Tzu Hsuan; Chen, Tso-Ming

    2017-01-01

    The study investigated photocatalytic water splitting for O2 production under visible light irradiation using neodymium vanadium oxide (NdVO4) and vanadium oxide (V2O5) hybrid powders. The results in a sacrificial agent of 0.01 M AgNO3 solution were obtained, and the highest photocatalytic O2 evolution was 2.63 μmol/h, when the hybrid powders were prepared by mixing Nd and V at a volume ratio of 1:3 at a calcination temperature of 350 °C for 1 h. The hybrid powders were synthesized by neodymium nitrate and ammonium metavanadate using the glycothermal method in ethylene glycol at 120 °C for 1 h. The hybrid powders consisted of two shapes, NdVO4 nanoparticles and the cylindrical V2O5 particles, and they possessed the ability for photocatalytic oxygen (O2) evolution during irradiation with visible light. The band gaps and structures of the hybrid powders were analyzed using UV-visible spectroscopy and transmission electron microscopy. PMID:28772692

  10. Nanocrystalline CeO2-δ coated β-MnO2 nanorods with enhanced oxygen transfer property

    NASA Astrophysics Data System (ADS)

    Huang, Xiubing; Zhao, Guixia; Chang, Yueqi; Wang, Ge; Irvine, John T. S.

    2018-05-01

    In this research, β-MnO2 nanorods were synthesized by a hydrothermal method, followed by a facile precipitation method to obtain nanocrystalline CeO2-δ coated β-MnO2 nanorods. The as-prepared samples were characterized by XRD, HRTEM, FESEM, XPS and in-situ high-temperature XRD. The HRTEM results show that well dispersed CeO2-δ nanocrystals sized about 5 nm were coated on the surface of β-MnO2 nanorods. The oxygen storage and transfer property of as-synthesized materials were evaluated using TGA under various atmospheres (air, pure N2, and 5%H2/95%Ar). The TGA results indicate that CeO2-δ modification could favour the reduction of Mn4+ to Mn3+ and/or Mn2+ at lower temperature as compared with pure β-MnO2 nanorods and the physically mixed CeO2-δ-β-MnO2 under low oxygen partial pressure conditions (i.e., pure N2, 5%H2/95%Ar). Specifically, CeO2-δ@β-MnO2 sample can exhibit 7.5 wt% weight loss between 100 and 400 °C under flowing N2 and 11.4 wt% weight loss between 100 and 350 °C under flowing 5%H2/95%Ar. During the reduction process under pure N2 or 5%H2/95%Ar condition, the oxygen ions in β-MnO2 nanorods are expected to be released to the surroundings in the form of O2 or H2O with the coated CeO2-δ nanocrystals acting as mediator as inferred from the synergistic effect between the well-interacted CeO2-δ nanocrystals and β-MnO2 nanorods.

  11. Highly oriented NdFeCoB nanocrystalline magnets from partially disproportionated compacts by reactive deformation under low pressure

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

    Zheng, Qing; Li, Jun; Liu, Ying, E-mail: liuying5536@163.com

    2014-05-07

    In the present investigation, we take advantage of the ultrafine grain size of NdFeCoB partially hydrogen-disproportionated phases, and prepare anisotropic nanocrystalline magnets with full density and homogenous microstructure and texture by reactive deformation under low pressure. Our results suggest that the pressure could properly promote an occurrence of desorption-recombination reaction due to a shorter-range rearrangement of the atoms, and the newly recombined Nd{sub 2}Fe{sub 14}B grains with fine grain size could undergo deformation immediately after the phase transformation, and then an obvious anisotropy and uniform alignment would be obtained. The maximum magnetic properties, (BH){sub max} = 25.8 MGOe, Br = 11.8 kG, H{sub cj} = 5.5more » kOe, were obtained after being treated for 5 min at 820 °C in vacuum. The present study highlights the feasibility to prepare anisotropic nanocrystalline magnets with homogeneous microstructure and a strong (00l) texture of uniform grain size under low pressure.« less

  12. Amorphization of nanocrystalline monoclinic ZrO2 by swift heavy ion irradiation.

    PubMed

    Lu, Fengyuan; Wang, Jianwei; Lang, Maik; Toulemonde, Marcel; Namavar, Fereydoon; Trautmann, Christina; Zhang, Jiaming; Ewing, Rodney C; Lian, Jie

    2012-09-21

    Bulk ZrO(2) polymorphs generally have an extremely high amorphization tolerance upon low energy ion and swift heavy ion irradiation in which ballistic interaction and ionization radiation dominate the ion-solid interaction, respectively. However, under very high-energy irradiation by 1.33 GeV U-238, nanocrystalline (40-50 nm) monoclinic ZrO(2) can be amorphized. A computational simulation based on a thermal spike model reveals that the strong ionizing radiation from swift heavy ions with a very high electronic energy loss of 52.2 keV nm(-1) can induce transient zones with temperatures well above the ZrO(2) melting point. The extreme electronic energy loss, coupled with the high energy state of the nanostructured materials and a high thermal confinement due to the less effective heat transport within the transient hot zone, may eventually be responsible for the ionizing radiation-induced amorphization without transforming to the tetragonal polymorph. The amorphization of nanocrystalline zirconia was also confirmed by 1.69 GeV Au ion irradiation with the electronic energy loss of 40 keV nm(-1). These results suggest that highly radiation tolerant materials in bulk forms, such as ZrO(2), may be radiation sensitive with the reduced length scale down to the nano-metered regime upon irradiation above a threshold value of electronic energy loss.

  13. Metal-insulator transition in Nd(1-x)Eu(x)NiO(3) compounds.

    PubMed

    Escote, M T; Barbeta, V B; Jardim, R F; Campo, J

    2006-07-05

    Polycrystalline Nd(1-x)Eu(x)NiO(3) (0≤x≤0.5) compounds were synthesized in order to investigate the character of the metal-insulator (MI) phase transition in this series. Samples were prepared through the sol-gel route and subjected to heat treatments at ∼1000 °C under oxygen pressures as high as 80 bar. X-ray diffraction (XRD) and neutron powder diffraction (NPD), electrical resistivity ρ(T), and magnetization M(T) measurements were performed on these compounds. The NPD and XRD results indicated that the samples crystallize in an orthorhombic distorted perovskite structure, space group Pbnm. The analysis of the structural parameters revealed a sudden and small expansion of ∼0.2% of the unit cell volume when electronic localization occurs. This expansion was attributed to a small increase of ∼0.003 Å of the average Ni-O distance and a simultaneous decrease of ∼-0.5° of the Ni-O-Ni superexchange angle. The ρ(T) measurements revealed a MI transition occurring at temperatures ranging from T(MI)∼193 to 336 K for samples with x = 0 and 0.50, respectively. These measurements also show a large thermal hysteresis in NdNiO(3) during heating and cooling processes, suggesting a first-order character of the phase transition at T(MI). The width of this thermal hysteresis was found to decrease appreciably for the sample Nd(0.7)Eu(0.3)NiO(3). The results indicate that cation disorder associated with increasing substitution of Nd by Eu is responsible for changing the first-order character of the transition in NdNiO(3).

  14. Quantum origins of moment fragmentation in Nd2Zr2O7

    NASA Astrophysics Data System (ADS)

    Benton, Owen

    2016-09-01

    Spin-liquid states are often described as the antithesis of magnetic order. Recently, however, it has been proposed that in certain frustrated magnets the magnetic degrees of freedom may "fragment" in such a way as to give rise to a coexistence of spin liquid and ordered phases. Recent neutron-scattering results [S. Petit, E. Lhotel, B. Canals, M. Ciomaga Hatnean, J. Ollivier, H. Muttka, E. Ressouche, A. R. Wildes, M. R. Lees, and G. Balakrishnan, Nat. Phys. 12, 746 (2016), 10.1038/nphys3710] suggest that this scenario may be realized in the pyrochlore magnet Nd2Zr2O7 . These observations show the characteristic pinch-point features of a Coulombic spin liquid occurring alongside the Bragg peaks of an "all-in-all-out" ordered state. Here we explain the quantum origins of this apparent magnetic moment fragmentation, within the framework of a quantum model of nearest-neighbor exchange, appropriate to Nd2Zr2O7 . This model is able to capture both the ground-state order and the pinch points observed at finite energy. The observed fragmentation arises due to the combination of the unusual symmetry properties of the Nd3 + ionic wave functions and the structure of equations of motion of the magnetic degrees of freedom. The results of our analysis suggest that Nd2Zr2O7 is proximate to a U (1 ) spin-liquid phase and is a promising candidate for the observation of a Higgs transition in a magnetic system.

  15. Nanocrystalline SnO2:F thin films for liquid petroleum gas sensors.

    PubMed

    Chaisitsak, Sutichai

    2011-01-01

    This paper reports the improvement in the sensing performance of nanocrystalline SnO(2)-based liquid petroleum gas (LPG) sensors by doping with fluorine (F). Un-doped and F-doped tin oxide films were prepared on glass substrates by the dip-coating technique using a layer-by-layer deposition cycle (alternating between dip-coating a thin layer followed by a drying in air after each new layer). The results showed that this technique is superior to the conventional technique for both improving the film thickness uniformity and film transparency. The effect of F concentration on the structural, surface morphological and LPG sensing properties of the SnO(2) films was investigated. Atomic Force Microscopy (AFM) and X-ray diffraction pattern measurements showed that the obtained thin films are nanocrystalline SnO(2) with nanoscale-textured surfaces. Gas sensing characteristics (sensor response and response/recovery time) of the SnO(2):F sensors based on a planar interdigital structure were investigated at different operating temperatures and at different LPG concentrations. The addition of fluorine to SnO(2) was found to be advantageous for efficient detection of LPG gases, e.g., F-doped sensors are more stable at a low operating temperature (300 °C) with higher sensor response and faster response/recovery time, compared to un-doped sensor materials. The sensors based on SnO(2):F films could detect LPG even at a low level of 25% LEL, showing the possibility of using this transparent material for LPG leak detection.

  16. Nanocrystalline SnO2:F Thin Films for Liquid Petroleum Gas Sensors

    PubMed Central

    Chaisitsak, Sutichai

    2011-01-01

    This paper reports the improvement in the sensing performance of nanocrystalline SnO2-based liquid petroleum gas (LPG) sensors by doping with fluorine (F). Un-doped and F-doped tin oxide films were prepared on glass substrates by the dip-coating technique using a layer-by-layer deposition cycle (alternating between dip-coating a thin layer followed by a drying in air after each new layer). The results showed that this technique is superior to the conventional technique for both improving the film thickness uniformity and film transparency. The effect of F concentration on the structural, surface morphological and LPG sensing properties of the SnO2 films was investigated. Atomic Force Microscopy (AFM) and X-ray diffraction pattern measurements showed that the obtained thin films are nanocrystalline SnO2 with nanoscale-textured surfaces. Gas sensing characteristics (sensor response and response/recovery time) of the SnO2:F sensors based on a planar interdigital structure were investigated at different operating temperatures and at different LPG concentrations. The addition of fluorine to SnO2 was found to be advantageous for efficient detection of LPG gases, e.g., F-doped sensors are more stable at a low operating temperature (300 °C) with higher sensor response and faster response/recovery time, compared to un-doped sensor materials. The sensors based on SnO2:F films could detect LPG even at a low level of 25% LEL, showing the possibility of using this transparent material for LPG leak detection. PMID:22164007

  17. Textured Nd2Fe14B flakes with enhanced coercivity

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

    Cui, BZ; Zheng, LY; Marinescu, M

    2012-04-01

    Morphology, structure, and magnetic properties of the [001] textured Nd2Fe14B nanocrystalline flakes prepared by surfactant-assisted high energy ball milling (HEBM) and subsequent annealing were studied. These flakes have a thickness of 80-200 nm, a length of 0.5-10 mu m, and an average grain size of 10-14nm. The addition of some amount of Dy, Nd70Cu30 alloy, and an appropriate post annealing increased the coercivity H-i(c) of the Nd2Fe14B flakes. iHc was 3.7, 4.3, and 5.7 kOe for the Nd15.5Fe78.5B6, Nd14Dy1.5Fe78.5B6 and 83.3wt.% Nd14Dy1.5Fe78.5B6+16.7 wt.% Nd70Cu30 flakes prepared by HEBM for 5 h in heptane with 20 wt.% oleylamine, respectively. After annealingmore » at 450 degrees C for 0.5h, their iHc increased to 5.1, 6.2, and 7.0 kOe, respectively. Anisotropic magnetic behavior was found in all of the as-milled and annealed flakes. Both, the thickening of Nd-rich phase at grain boundaries via diffusion of Nd70Cu30 and the surface modification of the Nd2Fe14B flake could be the main reasons for the coercivity enhancement in the as-milled and annealed Nd70Cu30-added Nd2Fe14B flakes. (C) 2012 American Institute of Physics. [doi: 10.1063/1.3679425]« less

  18. Superparamagnetic nanocrystalline ZnFe2O4 with a very high Curie temperature.

    PubMed

    Deka, Sasanka; Joy, P A

    2008-08-01

    Studies on the magnetic properties of nanocrystalline ZnFe2O4 synthesized by an autocombustion method are reported. Superparamagnetic behavior is observed for the nanocrystalline materials with particle sizes of 8 nm and 17 nm, with superparamagnetic blocking temperatures of 65 K and 75 K, respectively. Magnetic hysteresis with very large coercivities of 533 Oe and 325 Oe, respectively, are observed at 12 K. Studies on the temperature variation of the magnetization above room temperature indicate that the Curie temperature is as high as approximately 800 K when compared to the paramagnetic nature of bulk zinc ferrite at room temperature.

  19. Al{sub 2}TiO{sub 5}-Al{sub 2}O{sub 3}-TiO{sub 2} nanocomposite: Structure, mechanical property and bioactivity studies

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

    Kalita, Samar Jyoti, E-mail: Samar.Kalita@und.nodak.edu; Somani, Vikas

    2010-12-15

    Novel biomaterials are of prime importance in tissue engineering. Here, we developed novel nanostructured Al{sub 2}TiO{sub 5}-Al{sub 2}O{sub 3}-TiO{sub 2} composite as a biomaterial for bone repair. Initially, nanocrystalline Al{sub 2}O{sub 3}-TiO{sub 2} composite powder was synthesized by a sol-gel process. The powder was cold compacted and sintered at 1300-1500 {sup o}C to develop nanostructured Al{sub 2}TiO{sub 5}-Al{sub 2}O{sub 3}-TiO{sub 2} composite. Nano features were retained in the sintered structures while the grains showed irregular morphology. The grain-growth and microcracking were prominent at higher sintering temperatures. X-ray diffraction peak intensity of {beta}-Al{sub 2}TiO{sub 5} increased with increasing temperature. {beta}-Al{sub 2}TiO{submore » 5} content increased from 91.67% at 1300 {sup o}C to 98.83% at 1500 {sup o}C, according to Rietveld refinement. The density of {beta}-Al{sub 2}TiO{sub 5} sintered at 1300 {sup o}C, 1400 {sup o}C and 1500 {sup o}C were computed to be 3.668 g cm{sup -3}, 3.685 g cm{sup -3} and 3.664 g cm{sup -3}, respectively. Nanocrystalline grains enhanced the flexural strength. The highest flexural strength of 43.2 MPa was achieved. Bioactivity and biomechanical properties were assessed in simulated body fluid. Electron microscopy confirmed the formation of apatite crystals on the surface of the nanocomposite. Spectroscopic analysis established the presence of Ca and P ions in the crystals. Results throw light on biocompatibility and bioactivity of {beta}-Al{sub 2}TiO{sub 5} phase, which has not been reported previously.« less

  20. Transport, electronic, and structural properties of nanocrystalline CuAlO2 delafossites

    NASA Astrophysics Data System (ADS)

    Durá, O. J.; Boada, R.; Rivera-Calzada, A.; León, C.; Bauer, E.; de la Torre, M. A. López; Chaboy, J.

    2011-01-01

    This work reports on the effect of grain size on the electrical, thermal, and structural properties of CuAlO2 samples obtained by solid-state reaction combined with ball milling. Electrical characterization made in microcrystalline and nanocrystalline samples shows that the electrical conductivity decreases several orders of magnitude for the nanocrystalline samples, and, in addition, there is a large discrepancy between the activation energies associated to thermoelectric power ES. The study of the Cu K-edge x-ray absorption spectra of the CuAlO2 samples shows that the local structure around Cu is preserved after the sintering process, indicating that the observed behavior of the electrical conductivity is of intrinsic origin. Complex conductivity measurements as a function of frequency allow us to discard grain-boundaries effects on the electrical transport. Thus, the changes in σ(T) and S(T) are interpreted in terms of charge localization in the framework of small polarons. This is in agreement with the analysis of the near-edge region of the absorption spectra, which indicates that sintering favors the Cu-O hybridization. As a consequence, oxygen atoms progressively lose their capability of trapping holes, and the electrical conductivity is also enhanced.

  1. Scintillation properties of YAlO3 doped with Lu and Nd perovskite single crystals

    NASA Astrophysics Data System (ADS)

    Akatsuka, Masaki; Usui, Yuki; Nakauchi, Daisuke; Kato, Takumi; Kawano, Naoki; Okada, Go; Kawaguchi, Noriaki; Yanagida, Takayuki

    2018-05-01

    YAlO3 (YAP) single crystals doped with Lu and Nd were grown by the Floating Zone (FZ) method to evaluate their scintillation properties particularly emissions in the near-infrared (NIR) range. The Nd concentration was fixed to 0 or 1 mol% while the Lu concentration was varied from 0 to 30%. When X-ray was irradiated, the scintillation of Nd-doped samples was observed predominantly at 1064 nm due to 4F3/2 → 4I11/2 transition of Nd3+. In contrast, a weak emission around 700 nm appeared in the samples doped with only Lu, and the emission origin was attributed to defect centers. In the Nd3+-doped samples, the decay time was 94-157 μs due to the 4f-4f transitions of Nd3+ whereas the Lu-doped samples showed signal with the decay time of 1.45-1.54 ms. The emission origin of the latter signal was attributed to the perovskite lattice defect.

  2. Wear-triggered self-healing behavior on the surface of nanocrystalline nickel aluminum bronze/Ti3SiC2 composites

    NASA Astrophysics Data System (ADS)

    Zhai, Wenzheng; Lu, Wenlong; Zhang, Po; Wang, Jian; Liu, Xiaojun; Zhou, Liping

    2018-04-01

    Self-healing can protect materials from diverse damages, but is intrinsically difficult in metals. This paper demonstrates a potential method through a simultaneous decomposition and oxidation of Ti3SiC2 to achieve healing of stress cracking on the surface of nickel aluminum bronze (NAB)/Ti3SiC2 nanocrystalline composites during fretting wear. At the finest nanocrystalline materials, a crack recovery would be attained at 76.5%. The repetitive fretting wear leads to a modest amount of 'flowability' of Ti3SiC2 toward the crack, facilitating crack recovery. Along with the wear-triggered self-healing, the NAB/Ti3SiC2 shows an improved tribological performance with the stable decreased friction torque due to the formation of lubrication TiO2 oxide.

  3. The formation and structure of mechano-synthesized nanocrystalline Sr{sub 3}Fe{sub 2}O{sub 6.4}: XRD Rietveld, Mössabuer and XPS analyses

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

    Al-Rawas, A.D., E-mail: arawas@squ.edu.om; Widatallah, H.M.; Al-Harthi, S.H.

    2015-05-15

    Highlights: • The formation of mechano-synthesized nanocrystalline Sr{sub 3}Fe{sub 2}O{sub 7−δ} is investigated. • Pre-milling the reactants substantially lowers the formation temperature. • The core and surface structures were studied. • XRD and {sup 57}Fe Mössbauer spectroscopic analyses indicate the δ-value to be 0.60. • XPS shows a complex surface structure for the mechanosynthesized Sr{sub 3}Fe{sub 2}O{sub 7−δ} nanoparticles. - Abstract: The influence of ball milling and subsequent sintering of a 3:1 molar mixture of SrCO{sub 3} and α-Fe{sub 2}O{sub 3} on the formation of Sr{sub 3}Fe{sub 2}O{sub 7−δ} double perovskite is investigated with different analytical techniques. Milling the mixturemore » for 110 h leads to the formation of SrCO{sub 3}-α-Fe{sub 2}O{sub 3} nanocomposites and the structural deformation of α-Fe{sub 2}O{sub 3} via the incorporation of Sr{sup 2+} ions. Subsequent sintering of the pre-milled reactants’ mixture has led to the partial formation of an SrFeO{sub 3} perovskite-related phase in the temperature range 400–600 °C. This was followed by the progressive development of an Sr{sub 3}Fe{sub 2}O{sub 7−δ} phase that continued to increase with increasing sintering temperature until a single-phased nanocrystalline Sr{sub 3}Fe{sub 2}O{sub 7−δ} phase was attained at 950 °C (12 h). This temperature is ∼350 °C lower than the temperature at which the material is prepared conventionally using the ceramic method. The evolution of different structural phases during the reaction process is discussed. Rietveld refinement of the X-ray diffraction data shows a value of 0.60 for the oxygen deficiency δ, in consistency with the Fe{sup 3+}/Fe{sup 4+} ratio derived from the {sup 57}Fe Mössbauer data recorded at both 300 K and 78 K. The Mössbauer data suggests that the Sr{sub 3}Fe{sub 2}O{sub 6.4} nanoparticles are superparamagnetic with blocking temperatures below 78 K. The surfaces of the Sr{sub 3}Fe{sub 2}O{sub 6

  4. Influence of Nb addition on vacancy defects and magnetic properties of the nanocrystalline Nd-Fe-B permanent magnets

    NASA Astrophysics Data System (ADS)

    Szwaja, Małgorzata; Gębara, Piotr; Filipecki, Jacek; Pawlik, Katarzyna; Przybył, Anna; Pawlik, Piotr; Wysłocki, Jerzy J.; Filipecka, Katarzyna

    2015-05-01

    In present work, influence of Nb addition on vacancy defects and magnetic properties of nanocrystalline Nd-Fe-B permanent magnets, was investigated. Samples with composition (Nd,Fe,B)100-xNbx (where x=6,7,8) were studied in as-cast state and after annealing. Samples were prepared by arc-melting with high purity of constituent elements under Ar atmosphere. Ribbons were obtained by melt-spinning technique under low pressure of Ar. Ribbon samples in as-cast state had amorphous structure and soft magnetic properties. Positron annihilation lifetime spectroscopy PALS has been applied to detection of positron - trapping voids (vacancy defects). With increase of Nb in alloy increasing of vacancy defects concentration was observed. Heat treatment of the samples was carried out at various temperatures (from 923 K to 1023 K) for 5 min, in order to obtain nanocrystalline structure. The aim of present work was to determine the influence of Nb addition and annealing conditions on the vacancy defects and magnetic properties of the Nd-Fe-B- type alloys in as-cast state and after heat treatment.

  5. Effect of film thickness on NO2 gas sensing properties of sprayed orthorhombic nanocrystalline V2O5 thin films

    NASA Astrophysics Data System (ADS)

    Mane, A. A.; Moholkar, A. V.

    2017-09-01

    The nanocrystalline V2O5 thin films with different thicknesses have been grown onto the glass substrates using chemical spray pyrolysis (CSP) deposition method. The XRD study shows that the films exhibit an orthorhombic crystal structure. The narrow scan X-ray photoelectron spectrum of V-2p core level doublet gives the binding energy difference of 7.3 eV, indicating that the V5+ oxidation state of vanadium. The FE-SEM micrographs show the formation of nanorods-like morphology. The AFM micrographs show the high surface area to volume ratio of nanocrystalline V2O5 thin films. The optical study gives the band gap energy values of 2.41 eV, 2.44 eV, 2.47 eV and 2.38 eV for V2O5 thin films deposited with the thicknesses of 423 nm, 559 nm, 694 nm and 730 nm, respectively. The V2O5 film of thickness 559 nm shows the NO2 gas response of 41% for 100 ppm concentration at operating temperature of 200 °C with response and recovery times of 20 s and 150 s, respectively. Further, it shows the rapid response and reproducibility towards 10 ppm NO2 gas concentration at 200 °C. Finally, NO2 gas sensing mechanism based on chemisorption process is discussed.

  6. Lattice Parameter Behavior with Different Nd and O Concentrations in (U 1-yNd y)O 2±x Solid Solution

    DOE PAGES

    Lee, Seung Min; Knight, Travis W.; Voit, Stwart L.; ...

    2016-02-02

    The solid solution of (U1-yFPy)O- 2±x, has the same fluorite structure as UO 2±x lambda, and the lattice parameter is affected by dissolved fission product and oxygen concentrations. We investigated the relation between the lattice parameter and the concentrations of neodymium and oxygen in the fluorite structure of (U 1-yNd y)O 2±x using X-ray diffraction. Moreover, the lattice parameter behavior in the (U 1-yNd y)O 2±x, solid solution shows a linear change as a function of the oxygen-to-metal ratio and solubility of neodymium. The lattice parameter depends on the radii of ions forming the fluorite structure and also can bemore » expressed by a particular rule (modified Vegard's law). Furthermore, the numerical analyses of the lattice parameters for the stoichiometric and nonstoichionietric solid solutions were conducted, and the lattice parameter model for the (U1-yNdy)O 2±x, solid solution was assessed. There is a very linear relationship between the lattice parameter and the Nd and O concentration for the stoichiometry and nonstoichiometry of the (U 1-yNd y)O 2±x solid solution was verified.« less

  7. Energy transfer efficiency from Cr(3+) to Nd(3+) in solar-pumped laser using transparent Nd/Cr:Y(3)Al(5)O(12) ceramics.

    PubMed

    Hasegawa, Kazuo; Ichikawa, Tadashi; Mizuno, Shintaro; Takeda, Yasuhiko; Ito, Hiroshi; Ikesue, Akio; Motohiro, Tomoyoshi; Yamaga, Mitsuo

    2015-06-01

    We report energy transfer efficiency from Cr3+ to Nd3+ in Nd (1.0 at.%)/Cr (0.4 at.%) co-doped Y3Al5O12 (YAG) transparent ceramics in the laser oscillation states. The laser oscillation has performed using two pumping lasers operating at 808 nm and 561 nm; the former pumps Nd3+ directly to create the 1064 nm laser oscillation, whereas the latter assists the performance via Cr3+ absorption and sequential energy transfer to Nd3+. From the laser output power properties and laser mode analysis, the energy transfer efficiency was determined to be around 65%, which is close to that obtained from the spontaneous Nd3+ emission.

  8. Impedance spectroscopic and dielectric properties of nanosized Y2/3Cu3Ti4O12 ceramic

    NASA Astrophysics Data System (ADS)

    Sharma, Sunita; Yadav, Shiv Sundar; Singh, M. M.; Mandal, K. D.

    2014-11-01

    Yttrium Copper Titanate (Y2/3Cu3Ti4O12) nanoceramic is structurally analogous to CaCu3Ti4O12 (CCTO). X-ray diffraction (XRD) of Y2/3Cu3Ti4O12 (YCTO) shows the presence of all normal peaks of CCTO. SEM micrograph exhibits the presence of bimodal grains of size ranging from 1-2 μm. Bright field TEM image clearly displays nanocrystalline particle which is supported by presence of a few clear rings in the corresponding selected area electron diffraction (SAED) pattern. It exhibits a high value of dielectric constant (ɛ‧ = 8434) at room temperature and 100 Hz frequency with characteristic relaxation peaks. Impedance and modulus studies revealed the presence of temperature-dependent Maxwell-Wagner type of relaxation in the ceramic.

  9. Bulk and nanocrystalline electron doped Gd0.15Ca0.85MnO3: Synthesis and magnetic characterization

    NASA Astrophysics Data System (ADS)

    Dhal, Lakshman; Chattarpal; Nirmala, R.; Santhosh, P. N.; Kumary, T. Geetha; Nigam, A. K.

    2014-09-01

    Polycrystalline Gd0.15Ca0.85MnO3 sample was prepared by solid state reaction method and nanocrystalline samples of different grain sizes of the same were prepared by sol-gel method. Phase purity and composition were verified by room temperature X-ray diffraction and SEM-EDAX analysis. Magnetization data of bulk Gd0.15Ca0.85MnO3 in 5 kOe field shows a peak at 119 K (TN) suggesting an antiferromagnetic transition. Nanocrystalline Gd0.15Ca0.85MnO3 sample ( 54 nm size) also shows a cusp at 107 K and a broad thermal hysteresis between field cooled cooling (FCC) and field cooled warming (FCW) data around this temperature. This thermal hysteresis suggests possible crystal structural transition. Field variation of magnetization of bulk Gd0.15Ca0.85MnO3 at 5 K shows a tendency to saturate, but yields a magnetic moment value of only 1.12 μB/f.u. in 70 kOe. The value of magnetization of nanocrystalline sample at 5 K in 70 kOe field is slightly larger and is 1.38 μB/f.u. which is probably due to the surface moments of the nanoparticle samples. Both the samples show Curie-Weiss-like behaviour in their paramagnetic state.

  10. Tungsten Bronze Barium Neodymium Titanate (Ba(6-3n)Nd(8+2n)Ti(18)O(54)): An Intrinsic Nanostructured Material and Its Defect Distribution.

    PubMed

    Azough, Feridoon; Cernik, Robert Joseph; Schaffer, Bernhard; Kepaptsoglou, Demie; Ramasse, Quentin Mathieu; Bigatti, Marco; Ali, Amir; MacLaren, Ian; Barthel, Juri; Molinari, Marco; Baran, Jakub Dominik; Parker, Stephen Charles; Freer, Robert

    2016-04-04

    We investigated the structure of the tungsten bronze barium neodymium titanates Ba(6-3n)Nd(8+2n)Ti(18)O(54), which are exploited as microwave dielectric ceramics. They form a complex nanostructure, which resembles a nanofilm with stacking layers of ∼12 Å thickness. The synthesized samples of Ba(6-3n)Nd(8+2n)Ti(18)O(54) (n = 0, 0.3, 0.4, 0.5) are characterized by pentagonal and tetragonal columns, where the A cations are distributed in three symmetrically inequivalent sites. Synchrotron X-ray diffraction and electron energy loss spectroscopy allowed for quantitative analysis of the site occupancy, which determines the defect distribution. This is corroborated by density functional theory calculations. Pentagonal columns are dominated by Ba, and tetragonal columns are dominated by Nd, although specific Nd sites exhibit significant concentrations of Ba. The data indicated significant elongation of the Ba columns in the pentagonal positions and of the Nd columns in tetragonal positions involving a zigzag arrangement of atoms along the b lattice direction. We found that the preferred Ba substitution occurs at Nd[3]/[4] followed by Nd[2] and Nd[1]/[5] sites, which is significantly different to that proposed in earlier studies. Our results on the Ba(6-3n)Nd(8+2n)Ti(18)O(54) "perovskite" superstructure and its defect distribution are particularly valuable in those applications where the optimization of material properties of oxides is imperative; these include not only microwave ceramics but also thermoelectric materials, where the nanostructure and the distribution of the dopants will reduce the thermal conductivity.

  11. Characterization of nanocrystalline ZnO:Al films by sol-gel spin coating method

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

    Gareso, P. L., E-mail: pgareso@gmail.com; Rauf, N., E-mail: pgareso@gmail.com; Juarlin, E., E-mail: pgareso@gmail.com

    2014-09-25

    Nanocrystalline ZnO films doped with aluminium by sol-gel spin coating method have been investigated using optical transmittance UV-Vis and X-ray diffraction (X-RD) measurements. ZnO films were prepared using zinc acetate dehydrate (Zn(CH{sub 3}COO){sub 2}@@‡2H{sub 2}O), ethanol, and diethanolamine (DEA) as a starting material, solvent, and stabilizer, respectively. For doped films, AlCl{sub 3} was added to the mixture. The ZnO:Al films were deposited on a transparent conductive oxide (TCO) substrate using spin coating technique at room temperature with a rate of 3000 rpm in 30 sec. The deposited films were annealed at various temperatures from 400°C to 600°C during 60 minutes.more » The transmittance UV-Vis measurement results showed that after annealing at 400°C, the energy band gap profile of nanocrystalline ZnO:Al film was a blue shift. This indicated that the band gap of ZnO:Al increased after annealing due to the increase of crystalline size. As the annealing temperature increased the bandgap energy was a constant. In addition to this, there was a small oscillation occurring after annealing compared to the as–grown samples. In the case of X-RD measurements, the crystalinity of the films were amorphous before annealing, and after annealing the crystalinity became enhance. Also, X-RD results showed that structure of nanocrystalline ZnO:Al films were hexagonal polycrystalline with lattice parameters are a = 3.290 Å and c = 5.2531 Å.« less

  12. Single-crystal and textured polycrystalline Nd2Fe14B flakes with a submicron or nanosize thickness

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

    Cui, BZ; Zheng, LY; Li, WF

    2012-02-01

    This paper reports on the fabrication, structure and magnetic property optimization of Nd2Fe14B single-crystal and [0 0 1] textured poly-nanocrystalline flakes prepared by surfactant-assisted high-energy ball milling (HEBM). Single-crystal Nd2Fe14B flakes first with micron and then with submicron thicknesses were formed via continuous basal cleavage along the (1 1 0) planes of the irregularly shaped single-crystal microparticles during the early stage of HEBM. With further milling, [0 0 1] textured polycrystalline submicron Nd2Fe14B flakes were formed. Finally, crystallographically anisotropic polycrystalline Nd2Fe14B nanoflakes were formed after milling for 5-6 h. Anisotropic magnetic behavior was found in all of the flake samples.more » Nd2Fe14B flakes prepared with either oleic acid (OA) or oleylamine (OY) as the surfactant exhibited similar morphology, structure and magnetic properties. Both the addition of some low-melting-point eutectic Nd70Cu30 alloy and an appropriate post-annealing can increase the coercivity of the Nd2Fe14B flakes. The coercivity of Nd2Fe14B nanoflakes with an addition of 16.7 wt.% Nd70Cu30 by milling for 5 h in heptane with 20 wt.% OY increased from 3.7 to 6.8 kOe after annealing at 450 degrees C for 0.5 h. The mechanism for formation and coercivity enhancement of Nd2Fe14B single-crystal and textured poly-nanocrystalline flakes with a submicron or nanosize thickness was discussed. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.« less

  13. Evidence of extended cation solubility in atomic layer deposited nanocrystalline BaTiO3 thin films and its strong impact on the electrical properties.

    PubMed

    Falmbigl, Matthias; Karateev, Igor A; Golovina, Iryna S; Plokhikh, Aleksandr V; Parker, Thomas C; Vasiliev, Alexander L; Spanier, Jonathan E

    2018-06-22

    Thin films of ≈50 nm thickness with Ba/Ti-ratios ranging from 0.8 to 1.06 were prepared by depositing alternating layers of Ba(OH)2 and TiO2. Annealing at 750 °C promoted the solid-solid transformation into polycrystalline BaTiO3 films containing a mixture of the perovskite and the hexagonal polymorphs with average crystallite sizes smaller than 14 nm and without impurity phases. This, together with an increase of the cubic lattice parameters for Ba-rich films, suggests an extended metastable solubility range for the perovskite-phase in these nanocrystalline thin films on both sides of the stoichiometric composition. Mapping of the cation distribution utilizing energy-filtered transmission electron microscopy corroborates defect accommodation within the BaTiO3 grains. While the cation off-stoichiometry in thermodynamic equilibrium is negligible for BaTiO3, the metastable extended solubility range in the thin films can be directly correlated to the low annealing temperature and nanocrystalline nature. The leakage current behavior can be explained by the formation of Schottky defects for nonstoichiometric films, and the cation ratio has a distinct impact on the dielectric properties: while excess-BaO has a marginal detrimental effect on the permittivity, the dielectric constant declines rapidly by more than 50% towards the Ti-rich side. The present findings highlight the importance of compositional control for the synthesis of nanocrystalline BaTiO3 thin films, in particular for low annealing and/or deposition temperatures. Our synthesis approach using alternating layers of Ba(OH)2 and TiO2 provides a route to precisely control the cation stoichiometry.

  14. Orientation dependence of ferroelectric and piezoelectric properties of Bi3.15Nd0.85Ti3O12 thin films on Pt(100)/TiO2/SiO2/Si substrates

    NASA Astrophysics Data System (ADS)

    Hu, G. D.

    2006-11-01

    Bi3.15Nd0.85Ti3O12 (BNT0.85) thin films with (100) [α(100)=87.8%], (117) [α(117)=77.1%], and (001) [α(001)=98.8%] preferred orientations were deposited on Pt(100)/TiO2/SiO2/Si substrates using a metal organic decomposition process. The remanent polarization of (100)-predominant BNT0.85 film is about 50% and three times larger than those of (117)-preferred and (001)-oriented films, respectively, suggesting that the major polarization vector of BNT0.85 is close to the a axis rather than the c axis. This result can be further demonstrated by the piezoelectric measurements using an atomic force microscope in the piezoresponse mode.

  15. Chemical strain-dependent two-dimensional transport at R AlO 3 / SrTiO 3 interfaces ( R = La , Nd , Sm , and Gd )

    DOE PAGES

    Li, Chen; Shen, Xuan; Yang, Yurong; ...

    2016-12-27

    Perovskite RAlO 3 (R = La, Nd, Sm, and Gd) films have been deposited epitaxially on (001) TiO 2-terminated SrTiO 3 substrates. In this paper, it is observed that the two-dimensional transport characteristics at the RAlO 3/SrTiO 3 interfaces are very sensitive to the species of rare-earth element, that is to chemical strain. Although electron energy loss spectroscopy measurements show that electron transfer occurs in all the four polar/nonpolar heterostructures, the amount of electrons transferred across SmAlO 3/SrTiO 3 and GdAlO 3/SrTiO 3 interfaces are much less than those across LaAlO 3/SrTiO 3 and NdAlO 3/SrTiO 3 interfaces. First-principles calculationsmore » reveal the competition between ionic polarization and electronic polarization in the polar layers in compensating the build-in polarization due to the polar discontinuity at the interface. Finally, in particular, a large ionic polarization is found in SmAlO 3/SrTiO 3 and GdAlO 3/SrTiO 3 systems (which experience the largest tensile epitaxial strain), hence reducing the amount of electrons transferred.« less

  16. New family of lanthanide-based inorganic-organic hybrid frameworks: Ln2(OH)4[O3S(CH2)nSO32H2O (Ln = La, Ce, Pr, Nd, Sm; n = 3, 4) and their derivatives.

    PubMed

    Liang, Jianbo; Ma, Renzhi; Ebina, Yasuo; Geng, Fengxia; Sasaki, Takayoshi

    2013-02-18

    We report the synthesis and structure characterization of a new family of lanthanide-based inorganic-organic hybrid frameworks, Ln(2)(OH)(4)[O(3)S(CH(2))(n)SO(3)]·2H(2)O (Ln = La, Ce, Pr, Nd, Sm; n = 3, 4), and their oxide derivatives. Highly crystallized samples were synthesized by homogeneous precipitation of Ln(3+) ions from a solution containing α,ω-organodisulfonate salts promoted by slow hydrolysis of hexamethylenetetramine. The crystal structure solved from powder X-ray diffraction data revealed that this material comprises two-dimensional cationic lanthanide hydroxide {[Ln(OH)(2)(H(2)O)](+)}(∞) layers, which are cross-linked by α,ω-organodisulfonate ligands into a three-dimensional pillared framework. This hybrid framework can be regarded as a derivative of UCl(3)-type Ln(OH)(3) involving penetration of organic chains into two {LnO(9)} polyhedra. Substitutional modification of the lanthanide coordination promotes a 2D arrangement of the {LnO(9)} polyhedra. A new hybrid oxide, Ln(2)O(2)[O(3)S(CH(2))(n)SO(3)], which is supposed to consist of alternating {[Ln(2)O(2)](2+)}(∞) layers and α,ω-organodisulfonate ligands, can be derived from the hydroxide form upon dehydration/dehydroxylation. These hybrid frameworks provide new opportunities to engineer the interlayer chemistry of layered structures and achieve advanced functionalities coupled with the advantages of lanthanide elements.

  17. γ-Fe 2 O 3 Nanocrystalline Microspheres with Hybrid Behavior of Battery-Supercapacitor for Superior Lithium Storage

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

    Tian, Lei-Lei; Zhang, Ming-Jian; Wu, Chao

    Maghemite (γ-Fe2O3) nanocrystalline microspheres (MNMs) self-assembled with 52 nm nanocrystals bridged with FeOOH around grain boundaries were formed by solvothermal reaction and thermal oxidation. The unique architecture endows the MNMs with the lithium storage behavior of a hybrid battery-supercapacitor electrode: initial charge capacity of 1060 mAh g–1 at the 100 mA g–1 rate, stable cyclic capacity of 1077.9 mAh g–1 at the same rate after 140 cycles, and rate capability of 538.8 mAh g–1 at 2400 mA g–1. This outstanding performance was attributed to the nanocrystal superiority, which shortens the Li+ diffusion paths. The mechanism of this hybrid anode materialmore » was investigated with experimental measurements and structural analysis. The results indicate that at the first discharge, the MNM nanocrystal microsphere, whose structure can buffer the volume change that occurs during lithiation/delithiation, goes through four stages: Li+ insertion in cation vacancies, spinel-to-rocksalt transformation, Li+ intercalation of Li1.75+xFe2O3 nanocrystals, and interfacial Li storage around nanocrystal boundaries. Only the latter two stages were reversible at and after the second charging/discharging cycle, exhibiting the hybrid behavior of a battery-supercapacitor with superior lithium storage.« less

  18. Thermal, spectroscopic properties and laser performance at 1.06 and 1.33 μm of Nd : Ca 4YO(BO 3) 3 and Nd : Ca 4GdO(BO 3) 3 crystals

    NASA Astrophysics Data System (ADS)

    Wang, Changqing; Zhang, Huaijin; Meng, Xianlin; Zhu, Li; Chow, Y. T.; Liu, Xuesong; Cheng, Ruiping; Yang, Zhaohe; Zhang, Shaojun; Sun, Lianke

    2000-11-01

    Nd : Ca 4YO(BO 3) 3 (Nd : YCOB) and Nd : Ca 4GdO(BO 3) 3 (Nd : GdCOB) crystals were grown by Czochralski method. Thermal expansion and specific heat of these two crystals were experimentally determined. Their fluorescence spectra were measured within the range from 1000 to 1500 nm. Laser output experiments at 1.06 and 1.33 μm of Nd : YCOB and Nd : GdCOB crystals were performed with a cw Ti : sapphire laser as the pump source.

  19. The crystal structures of BiTeO 3I, NdTeO 3X (X=Cl, Br) and Bi 5TeO 8.5I 2: some crystal chemistry peculiarities of layered Bi(Ln)Te oxyhalides

    NASA Astrophysics Data System (ADS)

    Berdonosov, Peter S.; Charkin, Dmitry O.; Kusainova, Ardak M.; Hervoches, Charles H.; Dolgikh, Valeriy A.; Lightfoot, Philip

    2000-09-01

    Four new layered oxyhalides related to the Sillen family have been prepared and characterized by Rietveld refinement of powder X-ray and neutron diffraction data. BiTeO 3I and NdTeO 3Br both adopt tetragonal symmetry, space group P4/ nmm (for BiTeO 3I, a=4.10811(8), c=27.988(1) Å; NdTeO 3Br, a=4.06603(7), c=26.922(1) Å, at 25°C). The structures are composed of triple and double fluorite-related mixed metal oxide layers separated by single and double halogen layers, in the sequence MTe 2O 5XXMTe 2O 5XM 2O 2X, which may be represented by the symbol X 13X 13X 22, where the subscript signifies the number of halogen layers and the superscript the number of metal sublayers within the fluorite block, by analogy with Sillen's notation. The double fluorite layers are occupied exclusively by Bi, whereas there is an ordered arrangement of Bi/Te within the triple fluorite layers, with Te exclusively occupying the outer sublayers of the block. NdTeO 3Cl adopts an orthorhombically distorted form of this structure type, space group Pmmn, a=4.08096(8), b=4.03441(8), c=25.7582(7) Å at 25°C. Bi 5TeO 8.5I 2 adopts a distorted, non-centrosymmetric version of the simpler X 13 structure type, space group Cmm2, a=5.6878(3), b=5.7230(3), c=9.7260(6) Å, consisting of single halogen layers sandwiched between triple fluorite layers, in which there is partial ordering of the Bi/Te cations.

  20. ZnO and MgZnO Nanocrystalline Flexible Films: Optical and Material Properties

    DOE PAGES

    Huso, Jesse; Morrison, John L.; Che, Hui; ...

    2011-01-01

    An emore » merging material for flexible UV applications is Mg x Zn 1 − x O which is capable of tunable bandgap and luminescence in the UV range of ~3.4 eV–7.4 eV depending on the composition x . Studies on the optical and material characteristics of ZnO and Mg 0.3 Zn 0.7 O nanocrystalline flexible films are presented. The analysis indicates that the ZnO and Mg 0.3 Zn 0.7 O have bandgaps of 3.34 eV and 4.02 eV, respectively. The photoluminescence (PL) of the ZnO film was found to exhibit a structural defect-related emission at ~3.316 eV inherent to the nanocrystalline morphology. The PL of the Mg 0.3 Zn 0.7 O film exhibits two broad peaks at 3.38 eV and at 3.95 eV that are discussed in terms of the solubility limit of the ZnO-MgO alloy system. Additionally, external deformation of the film did not have a significant impact on its properties as indicated by the Raman LO-mode behavior, making these films attractive for UV flexible applications.« less

  1. Electrical and optical properties of NdAlO{sub 3} synthesized by an optimized combustion process

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

    Harilal, Midhun; Faculty of Industrial Sciences and Technology, Universiti Malaysia Pahang, 26300 Kuantan, Pahang; Nair, V. Manikantan

    2014-04-01

    Nanocrystals of neodymium aluminate (NdAlO{sub 3}) are synthesized using an optimized single step auto-ignition citrate complex combustion process. The combustion product was characterized by X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy and Ultraviolet–visible reflection spectroscopy. The combustion product is single phase and composed of aggregates of nanocrystals of sizes in the range 20–40 nm. The NdAlO{sub 3} crystallized in rhombohedral perovskite structure with lattice parameters a = 5.3223 Å and c = 12.9292 Å. The absorption spectrum of the NdAlO{sub 3} nanocrystals shows characteristic absorption bands of the Nd atom. The polycrystalline fluffy combustion product ismore » sintered to high density (∼ 97%) at ∼ 1450 °C for 4 h and the microstructure was characterized by scanning electron microscopy. The electrical properties of the sintered product were studied using dielectric measurements. The sintered NdAlO{sub 3} has a dielectric constant (ε{sub r}) and a dielectric loss (tan δ) of 21.9 and ∼ 10{sup −3} at 5 MHz, respectively. - Highlights: • NdAlO{sub 3} nanocrystals were synthesized through a citrate combustion process. • The nanocrystals were sintered to ∼ 97% of theoretical density. • The materials were characterized using a number of analytical techniques. • Nanostructured NdAlO{sub 3} showed crystal field splitting of Nd ions. • Dielectric properties of the sintered NdAlO{sub 3} ceramics were studied.« less

  2. Tunability of morphological properties of Nd-doped TiO2 thin films

    NASA Astrophysics Data System (ADS)

    Rehan, Imran; Sultana, Sabiha; Khan, Nauman; Qamar, Zahid; Rehan, Kamran

    2016-11-01

    In this work, an endeavor is made toward structural assessment and morphological variation of titanium dioxide (TiO2) thin films when doped with neodymium (Nd). The electron beam deposition technique was employed to fabricate Nd-based TiO2 thin films on n-Type Si substrates. Nd concentration was varied from 0.0 to 2.0 atomic percent (at.%) under identical growth environments. The films were deposited in an oxygen-deficient environment to cause the growth of rutile phases. Energy dispersive x-ray spectroscopy confirmed the presence and variation of Nd dopant in TiO2. X-ray diffraction analysis showed the transformation of amorphous structures of the as-grown samples to anatase polycrystalline after annealing at 500 °C, while atomic force microscopy exposed linearity in grain density in as-grown samples with doping until 1 at.%. Raman spectrums of as-grown and annealed samples revealed the growth of the anatase phase in the annealed samples. Based on these results it can be proposed that Nd doping has pronounced effects on the structural characteristics of TiO2 thin films.

  3. Effects of Nd-, Pr-, Tb- and Y-doping on the structural, textural, electrical and N2O decomposition activity of mesoporous NiO nanoparticles

    NASA Astrophysics Data System (ADS)

    Abu-Zied, Bahaa M.; Bawaked, Salem M.; Kosa, Samia A.; Ali, Tarek T.; Schwieger, Wilhelm; Aqlan, Faisal M.

    2017-10-01

    Recently, nickel oxide, NiO, promoted with various dopants showed an interesting activity behavior in N2O direct decomposition. In this paper, the activity of a series of rare earth (Nd, Pr, Tb and Y) doped NiO catalysts was investigated for this reaction. These catalysts have been prepared by the calcination of their corresponding oxalate mixtures, which have been synthesized via the microwave-assisted precipitation route using oxalic acid as precipitant. Characterization of the obtained catalysts was carried out by using various physico-chemical techniques including TGA, FT-IR, XRD, FE-SEM, TEM, TPR, XPS and electrical conductivity. The results obtained revealed the nanocrystalline nature of the prepared catalysts. Moreover, the presence of the various dopants has led to a noticeable decrease of the NiO crystallites size, mesoporosity development and an increase of its surface area and pore volume. There is a substantial activity increase upon doping NiO with the various rare earth oxides. Such activity increase is associated with the structural modifications as well as the electrical conductivity increase of these catalysts.

  4. Dielectric relaxation of NdMnO{sub 3} nanoparticles

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

    Saha, Sujoy, E-mail: sahasujoy3@gmail.com; Chanda, Sadhan; Dutta, Alo

    2013-11-15

    Graphical abstract: (a) TEM image of particle distribution of NMO. (b) HRTEM image of a single NMO particle under 4,000,000× magnification. (c) SAED pattern of a single NMO nanoparticle. - Highlights: • NdMnO{sub 3} nanoparticles are synthesized by sol–gel process. • TEM micrograph shows a granular characteristic with an average particle size of ∼50 nm. • HRTEM is consistent with the spacing between the (2 0 0) planes of the orthorhombic NdMnO{sub 3}. • Band gap is found to be 4.4 eV. • Cole–Cole model has been used to explain the dielectric relaxation in the material. • The activation energymore » of the material is found to be ∼0.43 eV. - Abstract: The neodymium manganate (NdMnO{sub 3}) nanoparticles are synthesized by the sol–gel process. The phase formation and particle size of the sample are determined by X-ray diffraction analysis and transmission electron microscopy. The band gap of the material is obtained by UV–visible absorption spectroscopy using Tauc relation. Dielectric properties of the sample have been investigated in the frequency range from 42 Hz to 1 MHz and in the temperature range from 303 K to 573 K. The dielectric relaxation peaks are observed in the frequency dependent dielectric loss spectra. The Cole–Cole model is used to explain the dielectric relaxation mechanism of the material. The complex impedance plane plot confirms the existence of both the grain and grain-boundary contribution to the relaxation. The temperature dependence of both grain and grain-boundary resistances follow the Arrhenius law with the activation energy of 0.427 and 0.431 eV respectively. The frequency-dependent conductivity spectra follow the power law.« less

  5. Optical and structural investigation of Dy3+-Nd3+ co-doped in magnesium lead borosilicate glasses.

    PubMed

    Rao, T G V M; Rupesh Kumar, A; Neeraja, K; Veeraiah, N; Rami Reddy, M

    2014-01-24

    MgO-PbO-B2O3-SiO2-Nd2O3-Dy2O3 glasses are prepared by melt-quenching technique. The samples are characterized by X-ray diffraction (XRD), optical absorption, luminescence and Fourier transform infrared (FT-IR) spectral studied. XRD analysis evidently indicates that the prepared samples are fully amorphous nature. From the optical absorption spectra, the bonding environment surrounding the Dy(3+) and their energy level scheme in glass network is analyzed. Enhancement of Dy(3+) emission by non-radiative energy transfers from Nd(3+) has been observed here. The samples emits intensive bluish yellow color from the (4)F9/2→(6)H15/2, (6)H13/2 transition of Dy(3+) ions in these glasses which are nearer to white light and it is also supported by the chromaticity color coordinates. The FT-IR spectra reveal that network connectivity is increased with replacement of bonds B-O-B, Si-O-Si by more resistant B-O-Si bonds with gradually increasing the content of Dy(3+) ions in the glass network. Along with spectroscopic parameters some physical parameters like density, refractive index etc. are measured for the glasses. Copyright © 2013 Elsevier B.V. All rights reserved.

  6. Nd3+, Y3+-codoped SrF2 laser ceramics

    NASA Astrophysics Data System (ADS)

    Li, Weiwei; Mei, Bingchu; Song, Jinghong

    2015-09-01

    0.15 at.% Nd3+, 5 at.% Y3+-codoped SrF2 laser ceramic based on single crystal was prepared by extensive plastic deformation. Microstructure, optical and laser properties of the Nd3+, Y3+:SrF2 ceramic were investigated. The lasing of Nd3+, Y3+-codoped SrF2 ceramics with diode pumping have been observed and true CW laser operation around 1057 nm and 1050 nm was obtained with a slope efficiency of 31.9%. In particular, the fracture toughness of the ceramic is 0.98 MPa m1/2, which is approximately two times higher than that of single crystal.

  7. Fluctuations and All-In-All-Out Ordering in Dipole-Octupole Nd2Zr2O7

    NASA Astrophysics Data System (ADS)

    Lhotel, E.; Petit, S.; Guitteny, S.; Florea, O.; Ciomaga Hatnean, M.; Colin, C.; Ressouche, E.; Lees, M. R.; Balakrishnan, G.

    2015-11-01

    By means of neutron scattering and magnetization measurements down to 90 mK, we determine the magnetic ground state of the spin-ice candidate Nd2Zr2O7. We show that, despite ferromagnetic interactions, Nd2Zr2O7 undergoes a transition around 285 mK towards an all-in-all-out antiferromagnetic state, with a strongly reduced ordered magnetic moment. We establish the (H ,T ) phase diagram in the three directions of the applied field and reveal a metamagnetic transition around 0.1 T, associated with an unexpected shape of the magnetization curves. We propose that this behavior results from the peculiar nature of the Nd3 + doublet, a dipolar-octupolar doublet, different from the standard Kramers doublet studied to date, thus revealing the importance of multipolar correlations in the properties of pyrochlore oxides.

  8. Photomagnetic switching of heterometallic complexes [M(dmf)4(H2O)3(mu-CN)Fe(CN)5].H2O (M=Nd, La, Gd, Y) analyzed by single-crystal X-ray diffraction and ab initio theory.

    PubMed

    Svendsen, Helle; Overgaard, Jacob; Chevallier, Marie A; Collet, Eric; Chen, Yu-Sheng; Jensen, Frank; Iversen, Bo B

    2010-06-25

    Single-crystal X-ray diffraction measurements have been carried out on [Nd(dmf)(4)(H(2)O)(3)(mu-CN)Fe(CN)(5)].H(2)O (1; dmf=dimethylformamide), [Nd(dmf)(4)(H(2)O)(3)(mu-CN)Co(CN)(5)].H(2)O (2), [La(dmf)(4)(H(2)O)(3)(mu-CN)Fe(CN)(5)].H(2)O (3), [Gd(dmf)(4)(H(2)O)(3)(mu-CN)Fe(CN)(5)].H(2)O (4), and [Y(dmf)(4)(H(2)O)(3)(mu-CN)Fe(CN)(5)].H(2)O (5), at 15(2) K with and without UV illumination of the crystals. Significant changes in unit-cell parameters were observed for all the iron-containing complexes, whereas 2 showed no response to UV illumination. Photoexcited crystal structures have been determined for 1, 3, and 4 based on refinements of two-conformer models, and excited-state occupancies of 78.6(1), 84(6), and 86.6(7)% were reached, respectively. Significant bond-length changes were observed for the Fe-ligand bonds (up to 0.19 A), the cyano bonds (up to 0.09 A), and the lanthanide-ligand bonds (up to 0.10 A). Ab initio theoretical calculations were carried out for the experimental ground-state geometry of 1 to understand the electronic structure changes upon UV illumination. The calculations suggest that UV illumination gives a charge transfer from the cyano groups on the iron atom to the lanthanide ion moiety, {Nd(dmf)(4)(H(2)O)(3)}, with a distance of approximately 6 A from the iron atom. The charge transfer is accompanied by a reorganization of the spin state on the {Fe(CN)(6)} complex, and a change in geometry that produces a metastable charge-transfer state with an increased number of unpaired electrons, thus accounting for the observed photomagnetic effect.

  9. Nano-crystalline phase evolution and structural modification in Co/V substituted Li2O-Bi2O3-B2O3 glasses

    NASA Astrophysics Data System (ADS)

    Yadav, Arti; Dahiya, M. S.; Hooda, A.; Agarwal, A.; Khasa, S.

    2018-05-01

    Co/V substituted Li2O-Bi2O3-B2O3 glasses having composition 7CoO•23Li2O•20Bi2O3•50B2O3(CLBB) and xCoO•(30-x)Li2O•20Bi2O3•50B2O3(x = 0.0, 2.0, 5.0, 7.0 and 10.0 mol%, CVLBB1-5 respectively) developed via melt- quench route. The effect of annealing on structural properties of prepared samples was investigated by using XRD patterns and FTIR spectroscopy. Glasses annealed at 400˚C remained amorphous whereas glasses annealed at 500˚C changes from glasses to glass ceramics. The different crystalline phases i.e. Bi2(V0.9Co0.1)O5.25, LiCoVO4, V2O5 & Bi2(VO5) evolve on annealing at 500°C for 6 hours confirmed from the corresponding XRD patterns. The crystallite size of prepared samples were found to vary as 38-60nm This indicated that CoO and V2O5 introduced in matrix act as crystallizing agents and cause structural modification as studied by the FTIR spectra for all heat treated compositions.

  10. Microwave assisted combustion synthesis of nanocrystalline CoFe2O4 for LPG sensing

    NASA Astrophysics Data System (ADS)

    Chaudhari, Prashant; Acharya, S. A.; Darunkar, S. S.; Gaikwad, V. M.

    2015-08-01

    A microwave-assisted citrate precursor method has been utilized for synthesis of nanocrystalline powders of CoFe2O4. The process takes only a few minutes to obtain as-synthesized CoFe2O4. Structural properties of the synthesized material were investigated by X-ray diffraction; scanning electron microscopy, Thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy. The gas sensing properties of thick film of CoFe2O4 prepared by screen printing towards Liquid Petroleum Gas (LPG) revealed that CoFe2O4 thick films are sensitive and shows maximum sensitivity at 350°C for 2500 ppm of LPG.

  11. Two-photon momentum density in La2-xSrxCuO4 and Nd2-xCexCuO4

    NASA Astrophysics Data System (ADS)

    Blandin, P.; Massidda, S.; Barbiellini, B.; Jarlborg, T.; Lerch, P.; Manuel, A. A.; Hoffmann, L.; Gauthier, M.; Sadowski, W.; Walker, E.; Peter, M.; Yu, Jaejun; Freeman, A. J.

    1992-07-01

    We present calculations of the electron-positron momentum density for the high-Tc superconductors La2-xSrxCuO4 and Nd2-xCexCuO4, together with experimental two-dimensional angular correlation of annihilation radiation (2D-ACAR) for Nd2-xCexCuO4. The calculations are based on first-principles electronic structure obtained using the full-potential linearized augmented-plane-wave and the linear muffin-tin orbital methods. Our results indicate a non-negligible overlap of the positron wave function with the CuO2 plane electrons responsible for the Fermi surfaces in these compounds. Therefore, these compounds may be well suited for investigating Fermi-surface-related effects. After the folding of umklapp terms according to Lock, Crisp, and West, the predicted Fermi-surface breaks are mixed with strong effects induced by the positron wave function in La2-xSrxCuO4, while their resolution is better in Nd2-xCexCuO4. A comparison of our calculations with the most recent experimental results for La2-xSrxCuO4 shows good agreement. For Nd2-xCexCuO4 good agreement is observed between theoretical and experimental 2D-ACAR profiles.

  12. Enhanced photovoltaic performance of dye-sensitized solar cells based on NaYF4:Yb(3+), Er(3+)-incorporated nanocrystalline TiO2 electrodes.

    PubMed

    Zhu, Guang; Wang, Hongyan; Zhang, Quanxin; Zhang, Li

    2015-08-01

    Near infrared to visible up-conversion of light by rare earth ion-doped phosphors (NaYF4:Yb(3+), Er(3+)) that convert multiple photons of lower energy to higher energy photons offer new possibilities for improved performance of photovoltaic devices. Here, up-conversion phosphor NaYF4:Yb(3+), Er(3+) doped nanocrystalline TiO2 films are designed and used as a electrode for dye-sensitized solar cells, and the photovoltaic performance of DSSCs based on composite electrodes are investigated. The results show the cell with NaYF4:Yb(3+), Er(3+) achieves a power conversion efficiency of 7.65% under one sun illumination (AM 1.5G, 100mWcm(-2)), which is an increase of 14% compared to the cell without NaYF4:Yb(3+), Er(3+) (6.71%). The performance improvement is attributed to the dual effects of enhanced light harvesting from extended light absorption range and increased light scattering, and lower electron transfer resistance. Copyright © 2015 Elsevier Inc. All rights reserved.

  13. Crystal-field energy level analysis for Nd(3+) ions at the low symmetry C(1) site in [Nd(hfa)(4)(H(2)O)](N(C(2)H(5))(4)) single crystals.

    PubMed

    Mech, Agnieszka; Gajek, Zbigniew; Karbowiak, Mirosław; Rudowicz, Czesław

    2008-09-24

    Optical absorption measurements of Nd(3+) ions in single crystals of [Nd(hfa)(4)(H(2)O)](N(C(2)H(5))(4)) (hfa = hexafluoroacetyloacetonate), denoted Nd(hfa) for short, have been carried out at 4.2 and 298 K. This compound crystallizes in the monoclinic system (space group P 2(1)/n). Each Nd ion is coordinated to eight oxygen atoms that originate from the hexafluoroacetylacetonate ligands and one oxygen atom from the water molecule. A total of 85 experimental crystal-field (CF) energy levels arising from the Nd(3+) (4f(3)) electronic configuration were identified in the optical spectra and assigned. A three-step CF analysis was carried out in terms of a parametric Hamiltonian for the actual C(1) symmetry at the Nd(3+) ion sites. In the first step, a total of 27 CF parameters (CFPs) in the Wybourne notation B(kq), admissible by group theory, were determined in a preliminary fitting constrained by the angular overlap model predictions. The resulting CFP set was reduced to 24 specific independent CFPs using appropriate standardization transformations. Optimizations of the second-rank CFPs and extended scanning of the parameter space were employed in the second step to improve reliability of the CFP sets, which is rather a difficult task in the case of no site symmetry. Finally, seven free-ion parameters and 24 CFPs were freely varied, yielding an rms deviation between the calculated energy levels and the 85 observed ones of 11.1 cm(-1). Our approach also allows prediction of the energy levels of Nd(3+) ions that are hidden in the spectral range overlapping with strong ligand absorption, which is essential for understanding the inter-ionic energy transfer. The orientation of the axis system associated with the fitted CF parameters w.r.t. the crystallographic axes is established. The procedure adopted in our calculations may be considered as a general framework for analysis of CF levels of lanthanide ions at low (triclinic) symmetry sites.

  14. Hydrogen Storage Characteristics of Nanocrystalline and Amorphous Nd-Mg-Ni-Based NdMg12-Type Alloys Synthesized via Mechanical Milling

    NASA Astrophysics Data System (ADS)

    Zhang, Yanghuan; Shang, Hongwei; Hou, Zhonghui; Yuan, Zeming; Yang, Tai; Qi, Yan

    2016-12-01

    In this study, Mg was partially substituted by Ni with the intent of improving the hydrogen storage kinetics performance of NdMg12-type alloy. Mechanical milling technology was adopted to fabricate the nanocrystalline and amorphous NdMg11Ni + x wt pct Ni ( x = 100, 200) alloys. The effects of Ni content and milling duration on the microstructures and hydrogen storage kinetics of as-milled alloys have been systematically investigated. The structures were characterized by XRD and HRTEM. The electrochemical hydrogen storage properties were tested by an automatic galvanostatic system. Moreover, the gaseous hydrogen storage properties were investigated by Sievert apparatus and a differential scanning calorimeter connected with a H2 detector. Hydrogen desorption activation energy of alloy hydrides was estimated by using Arrhenius and Kissinger methods. The results reveal that the increase of Ni content dramatically ameliorates the gaseous and electrochemical hydrogen storage kinetics performance of the as-milled alloys. Furthermore, high rate discharge ability (HRD) reach the maximum value with the variation of milling time. The maximum HRDs of the NdMg11Ni + x wt pct Ni ( x = 100, 200) alloys are 80.24 and 85.17 pct. The improved gaseous hydrogen storage kinetics of alloys via increasing Ni content and milling time can be attributed to a decrease in the hydrogen desorption activation energy.

  15. Citrate gel-combustion synthesis and sintering of nanocrystalline ThO2 powders

    NASA Astrophysics Data System (ADS)

    Sanjay Kumar, D.; Ananthasivan, K.; Amirthapandian, S.; Dasgupta, Arup; Jogeswara Rao, G.

    2017-12-01

    A systematic study of the influence of citric acid to nitrate mole (R) ratio (R = 0 to 0.50) on the citrate gel-combustion synthesis of nanocrystalline (nc) ThO2 in bulk quantities (30 g) by using citrate gel-combustion was carried out. The nc-ThO2 powders were characterized for their bulk density, size distribution of particles, specific surface area, carbon residue and X-ray crystallite size. All these powders were compacted at pressures varying from 60 to 353 MPa and sintered by using the "two-step sintering" method. Powders prepared from a mixture with an "R" value of 0.125 compacted at 243 MPa yielded a maximum sintered density of 98.8 ± 0.3% T.D. For nc-ThO2, this is the highest sintered density reported so far. The microstructural investigations on nc-ThO2 powders were carried out by using both scanning electron microscopy (SEM) and transmission electron microscopy (TEM). SEM images of the sintered thoria monoliths revealed faceted grains with well defined grain boundaries. Shrinkage anisotropy factor (α) revealed that the compacts prepared from the powders obtained from starting mixtures with R values of 0.125-0.50 had undergone uniform sintering (near isotropic shrinkage).

  16. Effects of Molar Ratios and Sintering Times on Crystal Structures and Surface Morphology of Nd1+xFeO3 Oxide Alloy Prepared by using Solid Reaction Method

    NASA Astrophysics Data System (ADS)

    Sujiono, E. H.; Agus, J.; Samnur, S.; Triyana, K.

    2018-05-01

    The effects of molar ratios and sintering times on crystal structures and surface morphology on NdFeO3 oxide alloy have been studied. NdFeO3 oxide alloy formed by chemical preparation with solid reaction method using raw oxide Fe2O3 (99.9 %) and Nd2O3 (99.9 %) powders. In this article we reported the effects of molar ratios x = (–0.1, –0.2 and –0.3) and sintering times for 15 h and 20 h on crystal structures and surface morphology of Nd1+xFeO3 synthesized by solid-state reaction method. The results indicate that variation of molar ratio and sintering time has influenced the FWHM, crystalline size and grain size. The Nd1+xFeO3 have a major phase is NdFeO3, and other minor phases are Fe2O3, Nd2O3 and Nd(OH)3. The dominant intensity of hkl (121) with a value in FWHM, crystallite size, and grain size an indication the results will be applied as a gas sensor material as the focus of the further study.

  17. Nanocrystalline sp{sup 2} and sp{sup 3} carbons: CVD synthesis and applications

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

    Terranova, M. L.; Rossi, M.; Tamburri, E., E-mail: emanuela.tamburri@uniroma2.it

    The design and production of innovative materials based on nanocrystalline sp{sup 2}- and sp{sup 3}-coordinated carbons is presently a focus of the scientific community. We present a review of the nanostructures obtained in our labs using a series of synthetic routes, which make use of chemical vapor deposition (CVD) techniques for the selective production of non-planar graphitic nanostructures, nanocrystalline diamonds, and hybrid two-phase nanostructures.

  18. Electronic polarizability, optical basicity and interaction parameter for Nd2O3 doped lithium-zinc-phosphate glasses

    NASA Astrophysics Data System (ADS)

    Algradee, M. A.; Sultan, M.; Samir, O. M.; Alwany, A. Elwhab B.

    2017-08-01

    The Nd3+-doped lithium-zinc-phosphate glasses were prepared by means of conventional melt quenching method. X-ray diffraction results confirmed the glassy nature of the studied glasses. The physical parameters such as the density, molar volume, ion concentration, polaron radius, inter-ionic distance, field strength and oxygen packing density were calculated using different formulae. The transmittance and reflectance spectra of glasses were recorded in the wavelength range 190-1200 nm. The values of optical band gap and Urbach energy were determined based on Mott-Davis model. The refractive indices for the studied glasses were evaluated from optical band gap values using different methods. The average electronic polarizability of the oxide ions, optical basicity and an interaction parameter were investigated from the calculated values of the refractive index and the optical band gap for the studied glasses. The variations in the different physical and optical properties of glasses with Nd2O3 content were discussed in terms of different parameters such as non-bridging oxygen and different concentrations of Nd cation in glass system.

  19. The cause of ‘weak-link’ grain boundary behaviour in polycrystalline Bi2Sr2CaCu2O8 and Bi2Sr2Ca2Cu3O10 superconductors

    NASA Astrophysics Data System (ADS)

    Wang, Guanmei; Raine, Mark J.; Hampshire, Damian P.

    2018-02-01

    The detrimental effects of grain boundaries have long been considered responsible for the low critical current densities ({J}{{c}}) in high temperature superconductors. In this paper, we apply the quantitative approach used to identify the cause of the ‘weak-link’ grain boundary behaviour in YBa2Cu3O7 (Wang et al 2017 Supercond. Sci Technol. 30 104001), to the Bi2Sr2CaCu2O8 and Bi2Sr2Ca2Cu3O10 materials that we have fabricated. Magnetic and transport measurements are used to characterise the grain and grain boundary properties of micro- and nanocrystalline materials. Magnetisation measurements on all nanocrystalline materials show non-Bean-like behaviour and are consistent with surface pinning. Bi2Sr2CaCu2O8: our microcrystalline material has very low grain boundary resistivity ({ρ }{{GB}}), which is similar to that of the grains ({ρ }{{G}}) such that {ρ }{{GB}}≈ {ρ }{{G}}=2× {10}-5 {{Ω }}{{m}} (assuming a grain boundary thickness (d) of 1 nm) equivalent to an areal resistivity of {ρ }{{G}}=2× {10}-14 {{{Ω }}{{m}}}2. The transport {J}{{c}} values are consistent with well-connected grains and very weak grain boundary pinning. However, unlike low temperature superconductors (LTS) in which decreasing grain size increases the pinning along the grain boundary channels, any increase in pinning produced by making the grains in our Bi2Sr2CaCu2O8 materials nanocrystalline was completely offset by a decrease in the depairing current density of the grain boundaries caused by their high resistivity. We suggest a different approach to increasing {J}{{c}} from that used in LTS materials, namely incorporating additional strong grain and grain boundary pinning sites in microcrystalline materials to produce high {J}{{c}} values. Bi2Sr2Ca2Cu3O10: both our micro- and nanocrystalline samples have {ρ }{{GB}}/{ρ }{{G}} of at least 103. This causes strong suppression of {J}{{c}} across the grain boundaries, which explains the low transport {J}{{c}} values we find

  20. Optical properties of Nd3+ doped bismuth zinc borate glasses

    NASA Astrophysics Data System (ADS)

    Shanmugavelu, B.; Venkatramu, V.; Ravi Kanth Kumar, V. V.

    2014-03-01

    Glasses with compositions of (100-x) (Bi2ZnOB2O6) - x Nd2O3 (where x = 0.1, 0.3, 0.5, 1 and 2 mol%) were prepared by melt quenching method and characterized through optical absorption, emission and decay curve measurements. Optical absorption spectra have been analyzed using Judd-Ofelt theory. The emission spectra exhibit three peaks at 919, 1063 and 1337 nm corresponding to 4F3/2 to 4I9/2, 4I11/2 and 4I13/2 transitions in the near infrared region. The emission intensity of the 4F3/2 to 4I11/2 transition increases with increase of Nd3+ concentration up to 1 mol% and then concentration quenching is observed for 2 mol% of Nd3+ concentration. The lifetimes for the 4F3/2 level are found to decrease with increase in Nd2O3 concentration in the glasses. The decay curves of the glass up to 0.3 mol% of Nd3+ exhibit single exponential nature and thereafter the curves become nonexponential nature (0.5, 1 and 2 mol%). The nonexponential curve has been fitted to the Inokuti-Hirayama model to understand the nature of energy transfer process.

  1. Clean to dirty limit and T c suppression in NdFeAsO0.7F0.3 studied by H c2 analysis

    NASA Astrophysics Data System (ADS)

    Pallecchi, I.; Tarantini, C.; Shen, Y.; Singh, R. K.; Newman, N.; Cheng, P.; Jia, Y.; Wen, H.-H.; Putti, M.

    2018-07-01

    In this work, we investigate the temperature dependence of the upper critical field, dH c2/dT, in an increasingly disordered NdFeAsO0.7F0.3 (NdFeAs(O,F)) single crystal that has been progressively irradiated up to a 5.25 × 1016 cm- 2 total α-particle dose. For the H∣∣ab-plane, dH c2/dT does not vary remarkably with irradiation, while for the H∣∣c-axis it increases sharply after the first irradiation of 3.60 × 1015 cm-2 and then more gradually with further irradiation doses. Focusing on the H∣∣c-axis, we develop a phenomenological analysis of the H c2 slope which allows us to inspect the crossover from the clean to the dirty regime. From the H c2 slope normalized to the critical temperature and to its clean limit value, we extract the ratio of the coherence length ξ BCS to the mean free path {\\ell } and we find that when T c is reduced by a factor of four from its pristine value, ξ BCS/{\\ell } becomes as large as ˜7 and {\\ell } reaches values of ˜1.8 nm, indicating that NdFeAs(O,F) is well into the dirty regime. Our analysis of the H c2 slope also allows us to compare the pair-breaking effectiveness of scattering in different superconductors, showing similarity between unconventional NdFeAs(O,F) and moderate-T c phonon-mediated devices, such as MgB2 and A15 compounds, but much a stronger difference with YBa2Cu3O7-δ . This work thus shows that dH c2/dT is a reliable parameter, providing an alternative to residual resistivity, for investigating the pair-breaking mechanism induced by impurity scattering in superconductors.

  2. Crystal-field energy level analysis for Nd3+ ions at the low symmetry C1 site in [Nd(hfa)4(H2O)](N(C2H5)4) single crystals

    NASA Astrophysics Data System (ADS)

    Mech, Agnieszka; Gajek, Zbigniew; Karbowiak, Mirosław; Rudowicz, Czesław

    2008-09-01

    Optical absorption measurements of Nd3+ ions in single crystals of [Nd(hfa)4(H2O)](N(C2H5)4) (hfa = hexafluoroacetyloacetonate), denoted Nd(hfa) for short, have been carried out at 4.2 and 298 K. This compound crystallizes in the monoclinic system (space group P 21/n). Each Nd ion is coordinated to eight oxygen atoms that originate from the hexafluoroacetylacetonate ligands and one oxygen atom from the water molecule. A total of 85 experimental crystal-field (CF) energy levels arising from the Nd3+ (4f3) electronic configuration were identified in the optical spectra and assigned. A three-step CF analysis was carried out in terms of a parametric Hamiltonian for the actual C1 symmetry at the Nd3+ ion sites. In the first step, a total of 27 CF parameters (CFPs) in the Wybourne notation Bkq, admissible by group theory, were determined in a preliminary fitting constrained by the angular overlap model predictions. The resulting CFP set was reduced to 24 specific independent CFPs using appropriate standardization transformations. Optimizations of the second-rank CFPs and extended scanning of the parameter space were employed in the second step to improve reliability of the CFP sets, which is rather a difficult task in the case of no site symmetry. Finally, seven free-ion parameters and 24 CFPs were freely varied, yielding an rms deviation between the calculated energy levels and the 85 observed ones of 11.1 cm-1. Our approach also allows prediction of the energy levels of Nd3+ ions that are hidden in the spectral range overlapping with strong ligand absorption, which is essential for understanding the inter-ionic energy transfer. The orientation of the axis system associated with the fitted CF parameters w.r.t. the crystallographic axes is established. The procedure adopted in our calculations may be considered as a general framework for analysis of CF levels of lanthanide ions at low (triclinic) symmetry sites.

  3. Template-assisted formation of microsized nanocrystalline CeO2 tubes and their catalytic performance in the carboxylation of methanol

    PubMed Central

    Naumann, Meike; Schäfer, Christian; Brandner, Armin; Hofmann, Heiko J; Claus, Peter

    2011-01-01

    Summary Polymethylmethacrylate (PMMA)/ceria composite fibres were synthesized by using a sequential combination of polymer electrospinning, spray-coating with a sol, and a final calcination step to yield microstructured ceria tubes, which are composed of nanocrystalline ceria particles. The PMMA template is removed from the organic/inorganic hybrid material by radio frequency (rf) plasma etching followed by calcination of the ceramic green-body fibres. Microsized ceria (CeO2) tubes, with a diameter of ca. 0.75 µm, composed of nanocrystalline agglomerated ceria particles were thus obtained. The 1-D ceramic ceria material was characterized by X-ray diffraction, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), UV–vis and photoluminescence spectroscopy (PL), as well as thermogravimetric analysis (TGA). Its catalytic performance was studied in the direct carboxylation of methanol with carbon dioxide leading to dimethyl carbonate [(CH3O)2CO, DMC], which is widely employed as a phosgene and dimethyl sulfate substitute, and as well as a fuel additive. PMID:22259761

  4. In-situ XAFS study for calcination process of Cr catalyst supported on γ-Al2O3 and SiO2

    NASA Astrophysics Data System (ADS)

    Watanabe, T.; Ikeda, K.; Katayama, M.; Inada, Y.

    2016-05-01

    The catalytic performance is largely affected by the oxidation state of supported Cr species, and its control changes the activity of Cr catalysts and the selectivity of products. In this study, the calcination process of the supported Cr catalysts on γ-Al2O3 and SiO2 was investigated by in-situ XAFS spectroscopy. The hydrate species was first supported by the impregnation method and was converted to CrO3 via Cr2O3 during the calcination process on both supporting materials. It was found that the temperature to complete the oxidation from Cr2O3 to CrO3 on SiO2 was higher than that on γ-Al2O3. The similarity of the interatomic distance between the surface oxygen atoms of the intermediate Cr2O3 species to that of SiO2 contributes to the stabilization of Cr2O3 on SiO2 during the calcination process.

  5. Nanocrystalline (U0.5Ce0.5)O2±x solid solutions through citrate gel-combustion

    NASA Astrophysics Data System (ADS)

    Maji, D.; Ananthasivan, K.; Venkata Krishnan, R.; Balakrishnan, S.; Amirthapandian, S.; Joseph, Kitheri; Dasgupta, Arup

    2018-04-01

    Nanocrystalline powders of (U0.5Ce0.5)O2±x solid solutions were synthesized in bulk (100-200 g) through the citrate gel combustion. The fuel (citric acid) to oxidant (nitrate) mole ratio (R) was varied from 0.1 to 1.0. Two independent lots of the products obtained through the gel-combustion were calcined at 973 K in air and in a mixture of argon containing 8% H2 respectively. All these powders were characterized for their bulk density, X-ray crystallite size, specific surface area, size distribution of the particles, porosity as well as residual carbon. The morphology and microstructures of these powders were studied by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) respectively. Nanocrystalline single phase fluorite solid solutions having a typical crystallite size of about (7-15 nm) were obtained. These powders were highly porous comprising cuboidal flaky agglomerates. The combustion mixture with an 'R' value of 0.25 was found to undergo volume combustion and was found to yield a product that was distinctly different. The systematic investigation on synthesis and characterization of nanocrystalline UCeO2 is reported for the first time.

  6. Multiferroic properties of nanocrystalline BaTiO 3

    NASA Astrophysics Data System (ADS)

    Mangalam, R. V. K.; Ray, Nirat; Waghmare, Umesh V.; Sundaresan, A.; Rao, C. N. R.

    2009-01-01

    Some of the Multiferroics [H. Schmid, Ferroelectrics 162 (1994) 317] form a rare class of materials that exhibit magneto-electric coupling arising from the coexistence of ferromagnetism and ferroelectricity, with potential for many technological applications [J.F. Scott, Nat. Mater. 6 (2007) 256; N.A. Spaldin, M. Fiebig, Science 309 (2005) 391]. Over the last decade, an active research on multiferroics has resulted in the identification of a few routes that lead to multiferroicity in bulk materials [C. Ederer, N.A. Spaldin, Nat. Mater. 3 (2004) 849; D.V. Efremov, J. van den Brink, D.I. Khomskii, Nat. Mater. 3 (2004) 853; N. Hur, S. Park, P.A. Sharma, J.S. Ahn, S. Guha, S.W. Cheong, Nature 429 (2004) 392]. While ferroelectricity in a classic ferroelectric such as BaTiO 3 is expected to diminish with the reducing particle size, [C.H. Ahn, K.M. Rabe, J.M. Triscone, Science 303 (2004) 488; J. Junquera, P. Ghosez, Nature 422 (2003) 506] ferromagnetism cannot occur in its bulk form [N.A. Hill, J. Phys. Chem. B 104 (2000) 6694]. Here, we use a combination of experiment and first-principles simulations to demonstrate that multiferroic nature emerges in intermediate size nanocrystalline BaTiO 3, ferromagnetism arising from the oxygen vacancies at the surface and ferroelectricity from the core. A strong coupling between a surface polar phonon and spin is shown to result in a magnetocapacitance effect observed at room temperature, which can open up possibilities of new electro-magneto-mechanical devices at the nano-scale.

  7. Composition spread studies of Nd1-xLaxNiO3 combinatorial thin films

    NASA Astrophysics Data System (ADS)

    Suchoski, Richard; Jin, Kui; Yasui, Shintaro; Greene, Richard; Takeuchi, Ichiro

    2013-03-01

    Rare earth nickelates have attracted a great deal of attention in recent years due to a host of interesting features, one being a transition from paramagnetic metal to antiferromagnetic insulator through distortions from the ideal perovskite unit cell. This metal-to-insulator transition (MIT) can be manipulated by modifying variables such as temperature, rare earth ion size, oxygen content, or stress from lattice-mismatched epitaxial thin film growth. Research on this family has been extensive, though there still exists an absence of thin film studies focusing on intermediate compositions. We have fabricated epitaxial thin film composition spreads of Nd1-xLaxNiO3 grown via combinatorial PLD to investigate these transitional compositions. While our films exhibit a smooth composition progression, we observe a composition threshold where orthorhombic NdNiO3 transforms to rhombohedral LaNiO3, correlating with disappearance of the MIT, and displays a non-Vegard evolution of the film's in-plane lattice constant in HRXRD and Raman scattering data of the A1g rotational mode. This work was performed at the Center for Nanophysics and Advanced Materials (CNAM) at UMD, and supported by AFO SR MURI Grant #FA95500910603.

  8. Structure and performance of anisotropic nanocrystalline Nd-Fe-B magnets fabricated by high-velocity compaction followed by deformation

    NASA Astrophysics Data System (ADS)

    Zhao, L. Z.; Deng, X. X.; Yu, H. Y.; Guan, H. J.; Li, X. Q.; Xiao, Z. Y.; Liu, Z. W.; Greneche, J. M.

    2017-12-01

    High-velocity compaction (HVC) has been proposed as an effective approach for the fabrication of nanocrystalline Nd-Fe-B magnets. In this work, the effect of powder size on the density of HVCed magnets has been studied and the anisotropic nanocrystalline Nd-Fe-B magnets were prepared by HVC followed by hot deformation (HD). It is found that a proper particle size range is beneficial to high density. The investigations on the microstructure, magnetic domain structure, and hyperfine structure, indicate that the deformed grain structure and the magnetic domain structure with uniform paramagnetic grain boundary phase give good magnetic properties of HVC + HDed magnets. These magnets also have good mechanical and anti-corrosion properties. The results indicate that HVC is not only a near-net-shape, room temperature and binder-free process but is also able to maintain uniform nanostructure and to achieve good magnetic properties in both isotropic and anisotropic magnets. As a result, HVC can be employed as an ideal alternative process for bonding or hot pressing for the conventional MQI, MQII and MQIII magnets.

  9. Structural and magnetic investigations of single-crystalline neodymium zirconate pyrochlore Nd2Zr2O7

    NASA Astrophysics Data System (ADS)

    Hatnean, M. Ciomaga; Lees, M. R.; Petrenko, O. A.; Keeble, D. S.; Balakrishnan, G.; Gutmann, M. J.; Klekovkina, V. V.; Malkin, B. Z.

    2015-05-01

    We report structural and magnetic properties studies of large high-quality single crystals of the frustrated magnet Nd2Zr2O7 . Powder x-ray diffraction analysis confirms that Nd2Zr2O7 adopts the pyrochlore structure. Room-temperature x-ray diffraction and time-of-flight neutron-scattering experiments show that the crystals are stoichiometric in composition with no measurable site disorder. The temperature dependence of the magnetic susceptibility shows no magnetic ordering at temperatures down to 0.5 K. Fits to the magnetic susceptibility data using a Curie-Weiss law reveal a ferromagnetic coupling between the Nd moments. Magnetization versus field measurements show a local Ising anisotropy along the <111 > axes of the Nd3 + ions in the ground state. Specific heat versus temperature measurements in zero applied magnetic field indicate the presence of a thermal anomaly below T ˜7 K, but no evidence of magnetic ordering is observed down to 0.5 K. The experimental temperature dependence of the single-crystal bulk dc susceptibility and isothermal magnetization are analyzed using crystal field theory and the crystal field parameters and exchange coupling constants determined.

  10. Properties of blue emitting CaAl2O4:Eu2+, Nd3+ phosphor by optimizing the amount of flux and fuel

    NASA Astrophysics Data System (ADS)

    Wako, A. H.; Dejene, B. F.; Swart, H. C.

    2014-04-01

    Long afterglow CaAl2O4:0.03Eu2+, 0.03Nd3+ phosphor was prepared by solution-combustion synthesis. The active role of boric acid (H3BO3) as a flux in enhancing the Eu2+ photoluminescence and the effect of a varied amount of urea (CO (NH2)2) as a fuel on the morphological, structural and photoluminescent (PL) properties of the CaAl2O4:0.03Eu2+, 0.03Nd3+ systems were investigated. The results of X-ray diffraction, scanning electron microscopy, and PL spectra revealed the influence of the dosage of urea and hence the heated process on the crystallinity, morphology, and luminescence of the phosphor. The addition of H3BO3 favoured the formation of a monoclinic CaAl2O4 phase while the variation of the amount of CO (NH2)2 showed mixed phases although still predominantly monoclinic. Both H3BO3 and CO(NH2)2 to some extent influence the luminescence intensity of the obtained phosphor but unlike the case of CO(NH2)2, the presence of H3BO3 did not evidently shift the emission peak due to no obvious change in the energy level difference of the 4f-5d levels. The broad blue emissions consisting mainly of symmetrical bands having maxima between 440 and 445 nm originate from the energy transitions between the ground state (4f7) and the excited state (4f65d1) of the Eu2+ ions while the narrow emissions in the red region (600-630 nm) arise from the 5D0→7F2 transitions of the remnant unreduced Eu3+ions. Higher concentrations of H3BO3 (0.228 mol and 0.285 mol) reduce both intensity and lifetime of the phosphor. The optimized content of H3BO3 was 0.171 mol for the obtained phosphor with the best optical properties.

  11. Cationic surfactant assisted sonochemical synthesis of Nd3+ doped Zn2SiO4 nanostructures for solid state lighting applications

    NASA Astrophysics Data System (ADS)

    Basavaraj, R. B.; Malleshappa, J.; Darshan, G. P.; Prasad, B. Daruka; Nagabhushana, H.

    2018-04-01

    For the first time cationic surfactant assisted ultrasound synthesis route has been used for the preparation of pure and Nd3+ (0.5-9 mol %) doped Zn2SiO4 nanophosphors. The shape, size and morphology of the products were tuned by controlling the various experimental parameters. The final product was well characterized by sophisticated techniques viz. powder X-ray diffraction (PXRD), Ultraviolet visible spectroscopy (UV-Vis) and photoluminescence (PL). The powder X-ray diffraction patterns confirmed that the synthesized samples exhibit hexagonal phase without any impurity. The DRS spectra showed major peaks at 275, 360, 529, 586, 680, 742 and 806 nm due to the transitions of the 4f electrons of Nd3+ from the ground-state 4I9/2 to 2F5/2, 4D3/2 + 4D5/2 + 2I11/2, 2K13/2 + 4G7/2 + 4G9/2, 4G5/2 + 2G7/2, 4F7/2 + 4S3/2, 4F5/2 + 2H9/2 and 4F3/2 respectively. The band energy gap (Eg) of the samples were estimated and found to be in the range 5.32 - 5.52 eV. Under 421 nm excitation, PL spectra exhibit strong near ultraviolet emission peaks at˜444 nm, 459 nm and 520 nm were attributed to 2P3/2 → 4I13/2, 2P3/2 → 4I15/2, 1I6 → 3H4, 2P1/2 → 4I9/2 and 4G7/2 → 4I9/2 transitions respectively. The photometric studies indicate that the synthesized Zn2SiO4: Nd3+ nanophosphors can be tuned from blue to pale green by varying the dopant concentration. The current synthesis route is rapid, environmentally benign, cost-effective and useful for industrial applications such as solid state lighting and display devices.

  12. Oxidative coupling of methane over supported La{sub 2}O{sub 3} and La-promoted MgO catalysts: Influence of catalyst-support interactions

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

    Choudhary, V.R.; Mulla, S.A.R.; Uphade, B.S.

    1997-06-01

    Methane-to-C{sub 2}-hydrocarbon conversion activity and selectivity (or yield) of MgO and La-promoted MgO catalysts in the oxidative coupling of methane and strong basicity of the catalysts are decreased appreciably when these catalysts are deposited on commonly used commercial low surface area porous catalyst carriers containing Al{sub 2}O{sub 3}, SiO{sub 2}, SiC, or ZrO{sub 2} + HfO{sub 2} as the main components. The decrease in the strong basicity and catalytic activity/selectivity or yield is mostly due to strong chemical interactions between the active catalyst component (viz., MgO and La{sub 2}O{sub 3}) and the reactive components of the catalyst support (viz., Al{submore » 2}O{sub 3} and SiO{sub 2}), resulting in the formation of catalytically inactive binary metal oxides on the support surface. However, the influence of support on the activity/selectivity of La{sub 2}O{sub 3} is relatively very small, and also the chemical interactions of La{sub 2}O{sub 3} with the supports (except that containing a high concentration of SiO{sub 2}) are almost absent. The catalyst-support interactions are thus found to be strongly dependent upon the nature (chemical composition) of both catalyst and support. For developing better supported catalysts for the oxidative coupling of methane, supported La{sub 2}O{sub 3} with some promoters shows high promise.« less

  13. Impedance spectroscopy study on graphene wrapped nanocrystalline V{sub 2}O{sub 5}

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

    Bhaskaram, D. Surya, E-mail: dsurya.b@gmail.com; Govindaraj, G.; Cheruku, Rajesh

    2016-05-23

    Nanocrystalline V{sub 2}O{sub 5} was synthesized by solvothermal technique, which has potential application as electrode material in supercapacitors. The graphene oxide (GO) was prepared by modified Hummer’s method. The V{sub 2}O{sub 5}/ reduced graphene oxide (RGO) composite was synthesized using surfactant free hydrothermal technique to enhance the functionality in terms of conductivity and surface area of V{sub 2}O{sub 5}. The structural characterization was accomplished through X-ray diffraction and Raman spectroscopy. Morphology was identified by SEM and surface area of VRGO was enhanced by 8 times in comparison with V{sub 2}O{sub 5} nano particles, as confirmed through BET surface area analysis.more » Electrical characterization was done through impedance spectroscopy and the results showed decrease in sample resistance after wrapping V{sub 2}O{sub 5} with RGO.« less

  14. Disordered Nd:LuYSiO5 crystal lasers operating on the 4F3/2 → 4I11/2 and 4F3/2 → 4I13/2 transitions

    NASA Astrophysics Data System (ADS)

    Guan, Xiaofeng; Zhou, Zhiyong; Huang, Xiaoxu; Xu, Bin; Xu, Huiying; Cai, Zhiping; Xu, Xiaodong; Xu, Jun

    2017-11-01

    We report on diode-pumped disordered Nd:LuYSiO5 (Nd:LYSO) crystal lasers operating on the 4F3/2 → 4I11/2 and 4F3/2 → 4I 13/2 transitions. Simultaneous laser operation at 1074 and 1078 nm is achieved with maximum output power of 4.46 W and slope efficiency of 39.6%. Single wavelength laser at 1358 nm with maximum output power of 1.15 W and slope efficiency of 11.8% is also obtained. Moreover, four single-wavelength lasers at 1058, 1107, 1330 and 1386 nm with relatively low gains are achieved with maximum output powers of 2.72, 1.22, 0.52 and 0.42 W, respectively, for the first time to our knowledge. Lasing at non-traditional emission lines was obtained by using output couplers with dielectric coatings for specific wavelength ranges.

  15. Nanocrystalline Fe-Fe2O3 particle-deposited N-doped graphene as an activity-modulated Pt-free electrocatalyst for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Dhavale, Vishal M.; Singh, Santosh K.; Nadeema, Ayasha; Gaikwad, Sachin S.; Kurungot, Sreekumar

    2015-11-01

    The size-controlled growth of nanocrystalline Fe-Fe2O3 particles (2-3 nm) and their concomitant dispersion on N-doped graphene (Fe-Fe2O3/NGr) could be attained when the mutually assisted redox reaction between NGr and Fe3+ ions could be controlled within the aqueous droplets of a water-in-oil emulsion. The synergistic interaction existing between Fe-Fe2O3 and NGr helped the system to narrow down the overpotential for the oxygen reduction reaction (ORR) by bringing a significant positive shift to the reduction onset potential, which is just 15 mV higher than its Pt-counterpart. In addition, the half-wave potential (E1/2) of Fe-Fe2O3/NGr is found to be improved by a considerable amount of 135 mV in comparison to the system formed by dispersing Fe-Fe2O3 nanoparticles on reduced graphene oxide (Fe-Fe2O3/RGO), which indicates the presence of a higher number of active sites in Fe-Fe2O3/NGr. Despite this, the ORR kinetics of Fe-Fe2O3/NGr are found to be shifted significantly to the preferred 4-electron-transfer pathway compared to NGr and Fe-Fe2O3/RGO. Consequently, the H2O2% was found to be reduced by 78.3% for Fe-Fe2O3/NGr (13.0%) in comparison to Fe-Fe2O3/RGO (51.2%) and NGr (41.0%) at -0.30 V (vs. Hg/HgO). This difference in the yield of H2O2 formed between the systems along with the improvements observed in terms of the oxygen reduction onset and E1/2 in the case of Fe-Fe2O3/NGr reveals the activity modulation achieved for the latter is due to the coexistence of factors such as the presence of the mixed valancies of iron nanoparticles, small size and homogeneous distribution of Fe-Fe2O3 nanoparticles and the electronic modifications induced by the doped nitrogen in NGr. A controlled interplay of these factors looks like worked favorably in the case of Fe-Fe2O3/NGr. As a realistic system level validation, Fe-Fe2O3/NGr was employed as the cathode electrode of a single cell in a solid alkaline electrolyte membrane fuel cell (AEMFC). The system could display an open

  16. Optical properties of Nd3+ doped bismuth zinc borate glasses.

    PubMed

    Shanmugavelu, B; Venkatramu, V; Ravi Kanth Kumar, V V

    2014-03-25

    Glasses with compositions of (100-x) (Bi2ZnOB2O6) -x Nd2O3 (where x=0.1, 0.3, 0.5, 1 and 2 mol%) were prepared by melt quenching method and characterized through optical absorption, emission and decay curve measurements. Optical absorption spectra have been analyzed using Judd-Ofelt theory. The emission spectra exhibit three peaks at 919, 1063 and 1337 nm corresponding to (4)F3/2 to (4)I9/2, (4)I11/2 and (4)I13/2 transitions in the near infrared region. The emission intensity of the (4)F3/2 to (4)I11/2 transition increases with increase of Nd(3+) concentration up to 1 mol% and then concentration quenching is observed for 2 mol% of Nd(3+) concentration. The lifetimes for the (4)F3/2 level are found to decrease with increase in Nd2O3 concentration in the glasses. The decay curves of the glass up to 0.3 mol% of Nd(3+) exhibit single exponential nature and thereafter the curves become nonexponential nature (0.5, 1 and 2 mol%). The nonexponential curve has been fitted to the Inokuti-Hirayama model to understand the nature of energy transfer process. Copyright © 2013 Elsevier B.V. All rights reserved.

  17. Nd3+-doped heavy metal oxide based multicomponent borate glasses for 1.06 μm solid-state NIR laser and O-band optical amplification applications

    NASA Astrophysics Data System (ADS)

    Lakshminarayana, G.; Kaky, Kawa M.; Baki, S. O.; Lira, A.; Meza-Rocha, A. N.; Falcony, C.; Caldiño, U.; Kityk, I. V.; Méndez-Blas, A.; Abas, A. F.; Alresheedi, M. T.; Mahdi, M. A.

    2018-04-01

    Nd3+-doped glasses in the composition (50-x) B2O3-10 PbO-10 BaO-10 Al2O3-10 ZnO-10 Na2O-(x) Nd2O3 (x = 0.0, 0.1, 0.25, 0.5, 0.75, 1.0, 1.5, and 2.0 mol %) were fabricated using melt quenching method. Upon 592 nm visible and 808 nm LD excitations, the luminescence spectra show a strong 4F3/2 → 4I11/2 (1.06 μm) emission transition, and two less intense 4F3/2 → 4I9/2 (0.89 μm) and 4F3/2 → 4I13/2 (1.331 μm) emission transitions. The intensity of such emissions increases up to 0.5 mol % Nd3+, and above this doping level, quenching occurs. For 0.5 mol % Nd3+-doped glass, following Judd-Ofelt intensity parameters and emission spectrum, AR, τR, βR and βexp, including Δλeff,σem(λp), (σem × (Δλeff)) and (σem × (τrad)), are derived for Nd3+ ion 4F3/2 → 4I11/2 and 4F3/2 → 4I13/2 fluorescence transitions. The highest σem(λp) for the 1.06 and 1.331 μm fluorescence bands are found to be 6.216 × 10-20 and 2.295 × 10-20cm2, respectively. The 4F3/2 level lifetimes are found to decrease with an increase in Nd2O3 content and the decay curves of the glass up to 1.5 mol % Nd3+ exhibit single exponential nature. From 'τexp' of the Nd3+: 4F3/2 level, quantum efficiency (η), (σem × (τexp)), and saturation intensity (IS) are 48.87%, 51.09 × 10-25 cm2s and 3.67 × 108 W/m2, respectively, for the 0.5 mol % Nd3+-doped glass. Higher thermal stability, very low χ, high AR, large βexp., moderate τR, large gain bandwidth and high optical gain values indicate that 0.5 mol % Nd3+-doped glass could be a potential gain medium for solid-state NIR lasers at 1.06 μm. Moreover, for the 1.331 μm emission, large Δλeff and the theoretical gain coefficient value of 1.579 dB/cm, evaluated with an excited Nd3+ ion fractional factor of 0.6, indicate that this glass might be a promising candidate in developing O-band optical fiber amplifiers.

  18. High performance batch production of LREBa 2Cu 3O y using novel thin film Nd-123 seed

    NASA Astrophysics Data System (ADS)

    Muralidhar, M.; Suzuki, K.; Fukumoto, Y.; Ishihara, A.; Tomita, M.

    2011-11-01

    A batch production for fabrication of LREBa2Cu3Oy (LRE: Sm, Gd, NEG) "LRE-123" pellets are developed in air and Ar-1% O2 using a novel thin film Nd-123 seeds grown on MgO crystals. The SEM and XRD results conformed that the quality and orientation of the seed crystals are excellent. On the other hand, new seeds can withstand temperatures >1100 °C, as a result, the cold seeding process was applied even to grow Sm-123 material in Air. The trapped field observed in the best 45 mm single-grain puck of Gd-123 was in the range of 1.35 T and 0.35 T at 77.3 K and 87.3 K, respectively. The average trapped field at 77.3 K in the 24 mm diameter NEG-123 samples batch lies between 0.9 and 1 T. The maximum trapped field of 1.2 T was recorded at the sample surface. Further, the maximum trapped field of 0.23 T at 77 K was recorded in a sample with 16 mm diameter of Sm-123 with 3 mol% BaO2 addition. As a result we made more then 130 single grain pucks within a couple of months. Taking advantage of the single grain batch processed material, we constructed self-made chilled levitation disk, which was used on the open day of railway technical research Institute. More then 150 children stood on the levitation disk and revel the experience of levitation. The present results prove that a high-performance good-quality class of LREBa2Cu3Oy material can be made by using a novel thin film Nd-123 seeds.

  19. Nd-ordering-driven Mn spin reorientation and magnetization reversal in the magnetostructurally coupled compound NdMn O3

    NASA Astrophysics Data System (ADS)

    Kumar, A.; Yusuf, S. M.; Ritter, C.

    2017-07-01

    A detailed neutron diffraction study on NdMn O3 infers that the low temperature transition at 15 K is due to the ordering of Nd sublattice moment with a (0 ,-Fy,0 ) type spin arrangement. Interestingly, the ordering of the Nd sublattice drives a reorientation (by 180∘) of the net ferromagnetic moment of the Mn sublattice along the b axis. Such a Mn spin reorientation from (Ax,Fy,0 ) (with an antiferromagnetic ordering temperature of 73 K) to (Ax,-Fy,0 ) at 15 K, explains the magnetization reversal phenomenon present in this perovskite compound at 15 K. Moreover at 15 K, significant crystallographic structural distortions in terms of temperature variations of lattice parameters and bond angles are found. A sign change in the temperature variation of magnetic entropy is also found at 15 K. The present study signifies the role of rare-earth (Nd) moment ordering in tuning various physical properties, such as magnetocaloric and magnetoelastic of the larger size (>0.912 Å ) R ion based R Mn O3 compounds.

  20. Room Temperature Antiferromagnetic Ordering of Nanocrystalline Tb1.90Ni0.10O3

    NASA Astrophysics Data System (ADS)

    Mandal, J.; Dalal, M.; Sarkar, B. J.; Chakrabarti, P. K.

    2017-02-01

    Nanocrystalline Ni-doped terbium oxide (Tb1.90Ni0.10O3) has been synthesized by the co-precipitation method followed by annealing at 700°C for 6 h in vacuum. The crystallographic phase and the substitution of Ni2+ ions in the lattice of Tb2O3 are confirmed by Rietveld analysis of the x-ray diffraction pattern using the software MAUD. High-resolution transmission electron microscopy is also carried out to study the morphology of the sample. Magnetic measurements are carried out at different temperatures from 5 K to 300 K using a superconducting quantum interference device (SQUID) magnetometer. The dependence of the magnetization of Tb1.90Ni0.10O3 as a function of temperature ( M- T) and magnetic field ( M- H) suggests the presence of both paramagnetic and antiferromagnetic phase at room temperature, but antiferromagnetic phase dominates below ˜120 K. The lack of saturation in the M- H curve and good fitting of the M- T curve by the Johnston formula also indicate the presence of both paramagnetic and antiferromagnetic phase at room temperature. Interestingly, an antiferromagnetic to ferromagnetic phase transition is observed below ˜40 K. The result also shows a high value of magnetization at 5 K.

  1. Growth of Nd doped (Lu, Gd)3(Ga, Al)5O12 single crystal by the micro pulling down method and their scintillation properties

    NASA Astrophysics Data System (ADS)

    Kamada, Kei; Kurosawa, Shunsuke; Yamaji, Akihiro; Shoji, Yasuhiro; Pejchal, Jan; Ohashi, Yuji; Yokota, Yuui; Yoshikawa, Akira

    2015-03-01

    Nd 1 mol% doped (Lu, Gd)3(Ga, Al)5O12 (LGGAG) single crystals were grown by the micro-pulling down (μ-PD) method. Luminescence and scintillation properties such as absorption, excitation and emission spectra, light yield and decay time were evaluated. Nd1%:Lu3Al5O12 showed the highest light output of around 8200 photons/MeV among the grown crystals. Scintillation decay time of Nd:Y3Al5O12 was 1.32 μs (36%) 2.02 μs (64%). Nd:Lu3Ga3Al2O12 was relatively high dense scintillator of 7.38 g/cm3 with good light yield of 6800 photons/MeV and scintillation decay time of 0.20 μs (5%) 2.60 μs (95%).

  2. Catalytic Ethanol Dehydration to Ethylene over Nanocrystalline χ- and γ-Al2O3 Catalysts.

    PubMed

    Janlamool, Jakrapan; Jongsomjit, Bunjerd

    2017-01-01

    The study is aimed to investigate the combination of nanocrystalline γ- and χ- alumina that displays the attractive chemical and physical properties for the catalytic dehydration of ethanol. The correlation between the acid density and ethanol conversion was observed. The high acid density apparently results in high catalytic activity, especially for the equally mixed γ- and χ- phase alumina (G50C50). In order to obtain a better understanding on how different catalysts would affect the ethylene yield, one of the most powerful techniques such as X-ray photoelectron spectroscopy (XPS) was performed. Hence, the different O 1s surface atoms can be identified and divided into three types including lattice oxygen (O, 530.7 eV), surface hydroxyl (OH, 532.1 eV) and lattice water (H 2 O, 532.9 eV). It was remarkably found that the large amount of O 1s surface atoms in lattice water can result in increased ethylene yield. In summary, the appearance of metastable χ-alumina structure exhibited better catalytic activity and ethylene yield than γ- alumina. Thus, the introduction of metastable χ- alumina structure into γ- alumina enhanced catalytic activity and ethylene yield. As the result, it was found that the G50C50 catalyst exhibits the ethylene yield (80%) at the lowest reaction temperature ca. 250°C among other catalysts.

  3. Synthesis and energy transfer studies of LaMgAl{sub 11}O{sub 19}:Cr{sup 3+}, Nd{sup 3+} phosphors

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

    Zhu, Jicheng; Xia, Zhiguo; Liu, Quanlin, E-mail: qlliu@ustb.edu.cn

    2016-02-15

    Highlights: • Cr{sup 3+}/Nd{sup 3+} co-doped LaMgAl{sub 11}O{sub 19} phosphors were synthesized. • The energy transfer mechanism is ascribed to the dipole–quadrupole interaction. • The materials can convert the UV–vis light into near-infrared emission. - Abstract: Cr{sup 3+}/Nd{sup 3+} co-activated LaMgAl{sub 11}O{sub 19} phosphors have been synthesized by high temperature solid-state method. In the LaMgAl{sub 11}O{sub 19}:Cr{sup 3+}/Nd{sup 3+} system, Cr{sup 3+} can absorb the UV–vis photons (350–650 nm), and then energy transfer takes place between Cr{sup 3+} and Nd{sup 3+}, and finally the samples give near infrared emission originated from Nd{sup 3+}. Energy transfer from Cr{sup 3+} to Nd{supmore » 3+} is discussed via the variations of the lifetime values of Cr{sup 3+}, and the mechanism has been ascribed to the dipole–quadrupole interaction. The absorption of Cr{sup 3+} in the visible region and the following energy transfer from Cr{sup 3+} to Nd{sup 3+} indicated that the material can potentially serve as spectral convertors to improve the photovoltaic conversion efficiency of silicon-based solar cell.« less

  4. Enhanced ferromagnetic properties in Nd and Gd co-doped BiFeO3 ceramics

    NASA Astrophysics Data System (ADS)

    Jena, A. K.; Chelvane, J. Arout; Mohanty, J.

    2018-05-01

    Structural, optical and magnetic properties of Nd3+ and Gd3+ doped BiFeO3 were studied. X-ray diffraction studies confirmed that all the co-doped Bi1-x-yNdxGdyFeO3 samples are polycrystalline in nature crystallizing in rhombohedral type structure (Space group: R3c). In addition to this presence of residual phases like Bi2Fe4O9, Bi25FeO40 were also observed. Raman spectra confirms the structural distortion in co-doped ceramics. Band gap of samples decrease from 2.08eV to 1.95eV with increase in Gd concentration. Room temperature magnetization measurement indicated enhancement of magnetic properties with increase in Gd concentration.

  5. Synthesis of nanocrystalline α - Zn 2SiO 4 at ZnO-porous silicon interface: Phase transition study

    NASA Astrophysics Data System (ADS)

    Singh, R. G.; Singh, Fouran; Mehra, R. M.; Kanjilal, D.; Agarwal, V.

    2011-05-01

    Thermal annealing induced formation of nanocrystalline Zinc silicate (α-Zn 2SiO 4) at the interface of ZnO-porous silicon (PSi) nanocomposites is reported. The PSi templates were formed by electrochemical anodization of p-type (100) Si and ZnO crystallites were deposited on the PSi surface by a Sol-gel spin coating process. The formation of α-Zn 2SiO 4 is confirmed by glancing angle X-ray diffraction and Fourier transform infrared spectroscopy studies. The presence of intense yellow-green emission also confirms the formation of α-Zn 2SiO 4. The mechanism of silicate phase formation at the ZnO-PSi interface and the origin of various photoluminescence (PL) bands are discussed in view of its potential applications in advanced optoelectronic devices.

  6. Synthesis of nanocrystalline ZnO thin films by electron beam evaporation

    NASA Astrophysics Data System (ADS)

    Kondkar, V.; Rukade, D.; Bhattacharyya, V.

    2018-05-01

    Nanocrystalline ZnO thin films have potential for applications in variety of optoelectronic devices. In the present study, nanocrystalline thin films of ZnO are grown on fused silica substrate using electron beam (e-beam) evaporation technique. Phase identification is carried out using Glancing angle X-ray diffraction (GAXRD) and Raman spectroscopy. Ultraviolet-Visible (UV-Vis) spectroscopic analysis is carried out to calculate energy band gap of the ZnO film. Surface morphology of the film is investigated using atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM). Highly quality nanocrystalline thin films of hexagonal wurtzite ZnO are synthesized using e-beam evaporation technique.

  7. Crystal growth and scintillation properties of Nd-doped Lu 3Al 5O 12 single crystals with different Nd concentrations

    NASA Astrophysics Data System (ADS)

    Sugiyama, Makoto; Fujimoto, Yutaka; Yanagida, Takayuki; Yokota, Yuui; Pejchal, Jan; Furuya, Yuki; Tanaka, Hidehiko; Yoshikawa, Akira

    2011-04-01

    Nd 0.1%, 0.5%, 1% and 3% doped Lu 3Al 5O 12 (Nd:LuAG) single crystals were grown in the nitrogen atmosphere by the micro-pulling down (μ-PD) method. The grown crystals had a single-phase confirmed by powder XRD analysis. In absorption spectra, some weak absorption lines due to Nd 3+ 4f-4f transitions were observed and their intensity increased with the increase of Nd concentration. When excited by 241Am α-ray, a broad emission peak due to defects in the host lattice at 320 nm and some sharp lines due to Nd 3+ 4f-4f transitions at wavelength longer than 400 nm were observed. The decay time profiles of Nd:LuAG under γ-ray excitation were well approximated by two exponential function of 340-760 ns and 3-5 μs for each sample. By pulse height measurement using 137Cs, Nd 0.5%:LuAG showed the highest light yield of 7600 ± 760 photons/MeV.

  8. Magnetic properties and magnetocrystalline anisotropy of Nd 2Fe 17, Nd 2Fe 17X 3, and related compounds

    DOE PAGES

    Pandey, Tribhuwan; Parker, David S.

    2018-02-26

    The electronic and magnetic properties of Nd 2Fe 17 and Nd 2Fe 17X 3 (X = C or N) compounds have been calculated using the first-principles density functional calculations. Among these, the nitrogen and carbon interstitial compounds exhibit all of the required properties such as a saturation moment of 1.6 T, Curie temperature of 700–750 K, however easy magnetic axis lies in the planar direction making them less attractive for permanent magnet applications. The calculated magnetocrystalline anisotropy energy is found to be -2.7 MJ/m 3 for Nd 2Fe 17C 3 and -4.7 MJ/m 3 for Nd 2Fe 17N 3. Finally,more » we further explored the possibility of changing the easy axis direction through La/Ce alloying at Nd site. Although the MAE is found to be smaller in magnitude for all the La/Ce alloys it still maintains planar direction.« less

  9. CW and passively Q-switched laser performance of Nd:Lu2SiO5 crystal

    NASA Astrophysics Data System (ADS)

    Xu, Xiaodong; Di, Juqing; Zhang, Jian; Tang, Dingyuan; Xu, Jun

    2016-01-01

    We demonstrated an efficient and controllable dual-wavelength continuous-wave (CW) laser of Nd:Lu2SiO5 (Nd:LSO) crystal. The maximum output power was 3.02 W at wavelength of 1075 nm and 1079 nm, and with increasing of absorbed pump power, the ratio of 1079 nm laser rose. The slope efficiency of 65.6% and optical-to-optical conversion efficiency of 63.3% were obtained. The passively Q-switched laser properties of Nd:LSO were investigated for the first time. The shortest pulse, maximum pulse energy and peak power were 11.58 ns, 29.05 μJ and 2.34 kW, respectively.

  10. Dual-wavelength laser operation in a-cut Nd:MgO:LiNbO3

    NASA Astrophysics Data System (ADS)

    Fan, M. Q.; Li, T.; Zhao, S. Z.; Li, G. Q.; Li, D. C.; Yang, K. J.; Qiao, W. C.; Li, S. X.

    2016-03-01

    Diode-pumped dual-wavelength a-cut Nd:MgO:LiNbO3 lasers near 1085 and 1093 nm were experimentally and theoretically investigated. The simultaneous dual-wavelength emitting was mainly attributed to the Boltzmann distribution of the occupation in the Stark-split energy-levels in manifold 4I11/2. Under an absorbed pump power of 7.45 W, a maximum continuous wave (CW) output power of 1.23 W was obtained, giving a slope efficiency of 21.2%. Using Cr:YAG as saturable absorber, the shortest pulse duration of 28 ns was obtained with a repetition rate of 24 kHz, resulting in a peak power of 729 W.

  11. Improve oxidation resistance at high temperature by nanocrystalline surface layer

    NASA Astrophysics Data System (ADS)

    Xia, Z. X.; Zhang, C.; Huang, X. F.; Liu, W. B.; Yang, Z. G.

    2015-08-01

    An interesting change of scale sequence occurred during oxidation of nanocrystalline surface layer by means of a surface mechanical attrition treatment. The three-layer oxide structure from the surface towards the matrix is Fe3O4, spinel FeCr2O4 and corundum (Fe,Cr)2O3, which is different from the typical two-layer scale consisted of an Fe3O4 outer layer and an FeCr2O4 inner layer in conventional P91 steel. The diffusivity of Cr, Fe and O is enhanced concurrently in the nanocrystalline surface layer, which causes the fast oxidation in the initial oxidation stage. The formation of (Fe,Cr)2O3 inner layer would inhabit fast diffusion of alloy elements in the nanocrystalline surface layer of P91 steel in the later oxidation stage, and it causes a decrease in the parabolic oxidation rate compared with conventional specimens. This study provides a novel approach to improve the oxidation resistance of heat resistant steel without changing its Cr content.

  12. Synthesis and characterization of nanocrystalline LaMnO3 modified BaTiO3 ferroelectric ceramics prepared by chemical route

    NASA Astrophysics Data System (ADS)

    Dhak, Prasanta; Adak, Mrinal Kanti; Dhak, Debasis

    2016-02-01

    Nanocrystalline Ba1-3xTi1-3xLa2xMn4xO3, [x = 0.006, 0.008, 0.01 and 0.05] (abbreviated hereafter as BTLM) by chemical route. The phase formation and purity were checked by X-ray diffraction (XRD) study and transmission electron microscopy (TEM). The grain morphology after sintering was studied by scanning electron microscopy (SEM). The crystallite sizes range from 21 nm to 30 nm, while the particle size ranges between 27 nm and 38 nm. The grain size 212 nm and grain density 96.8% were found to be maximum for BTLM x = 0.05 and x = 0.01, respectively. The temperature dependence of dielectric constants was found to be more diffused and the peak value of the dielectric constant was decreased and more flat with the increase of the substituent concentration. The tangent loss was found to be decreased and reached to the minimum value of 0.032 for BTLM x = 0.05. The remnant polarization Pr, was 10 μC/cm2 for BTLM x = 0.01.

  13. Low-voltage organic thin film transistors (OTFTs) using crosslinked polyvinyl alcohol (PVA)/neodymium oxide (Nd2O3) bilayer gate dielectrics

    NASA Astrophysics Data System (ADS)

    Khound, Sagarika; Sarma, Ranjit

    2018-01-01

    We have reported here on the design, processing and dielectric properties of pentacene-based organic thin film transitors (OTFTs) with a bilayer gate dilectrics of crosslinked PVA/Nd2O3 which enables low-voltage organic thin film operations. The dielectric characteristics of PVA/Nd2O3 bilayer films are studied by capacitance-voltage ( C- V) and current-voltage ( I- V) curves in the metal-insulator-metal (MIM) structure. We have analysed the output electrical responses and transfer characteristics of the OTFT devices to determine their performance of OTFT parameters. The mobility of 0.94 cm2/Vs, the threshold voltage of - 2.8 V, the current on-off ratio of 6.2 × 105, the subthreshold slope of 0.61 V/decade are evaluated. Low leakage current of the device is observed from current density-electric field ( J- E) curve. The structure and the morphology of the device are studied using X-ray diffraction (XRD) and atomic force microscope (AFM), respectively. The study demonstrates an effective way to realize low-voltage, high-performance OTFTs at low cost.

  14. Optical and dielectric properties of isothermally crystallized nano-KNbO3 in Er3+-doped K2O-Nb2O5-SiO2 glasses.

    PubMed

    Chaliha, Reenamoni Saikia; Annapurna, K; Tarafder, Anal; Tiwari, V S; Gupta, P K; Karmakar, Basudeb

    2010-01-01

    Precursor glass of composition 25K(2)O-25Nb(2)O(5)-50SiO(2) (mol%) doped with Er(2)O(3) (0.5 wt% in excess) was isothermally crystallized at 800 degrees C for 0-100 h to obtain transparent KNbO(3) nanostructured glass-ceramics. XRD, FESEM, TEM, FTIRRS, dielectric constant, refractive index, absorption and fluorescence measurements were carried out to analyze the morphology, dielectric, structure and optical properties of the glass-ceramics. The crystallite size of KNbO(3) estimated from XRD and TEM is found to vary in the range 7-23 nm. A steep rise in the dielectric constant of glass-ceramics with heat-treatment time reveals the formation of ferroelectric nanocrystalline KNbO(3) phase. The measured visible photoluminescence spectra have exhibited green emission transitions of (2)H(11/2), (4)S(3/2)-->(4)I(15/2) upon excitation at 377 nm ((4)I(15/2)-->(4)G(11/2)) absorption band of Er(3+) ions. The near infrared (NIR) emission transition (4)I(13/2)-->(4)I(15/2) is detected around 1550 nm on excitation at 980 nm ((4)I(15/2)-->(4)I(11/2)) of absorption bands of Er(3+) ions. It is observed that photoluminescent intensity at 526 nm ((2)H(11/2)-->(4)I(15/2)), 550 nm ((4)S(3/2)-->(4)I(15/2)) and 1550 nm ((4)I(13/2)-->(4)I(15/2)) initially decrease and then gradually increase with increase in heat-treatment time. The measured lifetime (tau(f)) of the (4)I(13/2)-->(4)I(15/2) transition also possesses a similar trend. The measured absorption and fluorescence spectra reveal that the Er(3+) ions gradually enter into the KNbO(3) nanocrystals. Copyright 2009 Elsevier B.V. All rights reserved.

  15. Optical Properties of ZnO-Alloyed Nanocrystalline Films

    DOE PAGES

    Che, Hui; Huso, Jesse; Morrison, John L.; ...

    2012-01-01

    ZnO is emore » merging as one of the materials of choice for UV applications. It has a deep excitonic energy level and a direct bandgap of ~3.4 eV. Alloying ZnO with certain atomic constituents adds new optical and electronic functionalities to ZnO. This paper presents research on M g x Z n 1 − x O and Z n S 1 − x O x nanocrystalline flexible films, which enable tunable optical properties in the deep-UV and in the visible range. The ZnO and Mg 0 .3 Zn 0 .7 O films were found to have bandgaps at 3.35 and 4.02 eV, respectively. The photoluminescence of the Mg 0 .3 Zn 0 .7 O exhibited a bandedge emission at 3.95 eV, and at lower energy 3.38 eV due to the limited solubility inherent to these alloys. ZnS 0 .76 O 0 .24 and ZnS 0 .16 O 0 .84 were found to have bandgaps at 3.21 and 2.65 eV, respectively. The effect of nitrogen doping on ZnS 0 .16 O 0 .84 is discussed in terms of the highly lattice mismatched nature of these alloys and the resulting valence-band modification.« less

  16. Evaluation of Nd-Loaded SnO2:F Films Coated via Spray Pyrolysis

    NASA Astrophysics Data System (ADS)

    Turgut, G.

    2018-05-01

    Thin layers of single (F)- and double (F/Nd)-incorporated tin oxide have been coated on glass substrate via spray pyrolysis. The structural, morphological, electrical, and optical features of F-incorporated samples were evaluated depending on the Nd loading. X-ray diffraction analysis revealed that samples had tetragonal tin oxide structure with (211) and (200) preferential directions. The crystallite size and strain values varied from 37.98 nm and 1.21 × 10-3 to 52.12 nm and 1.88 × 10-3. Scanning electron microscopy analysis showed that the samples consisted of pyramidal, polyhedral, and needle-shaped granules. The lowest sheet resistance value of 1.22 Ω was found for 1.8 at.% Nd + 25 at.% F-coloaded SnO2. However, the widest optical bandgap of 4.01 eV was observed for the single 25 at.% F-loaded sample. The Urbach tail and figure of merit also changed in the ranges of 664 meV to 1296 meV and 6.4 × 10-2 Ω-1 to 2.3 × 10-3 Ω-1, respectively. The results presented herein indicate that the character of F-doped tin oxide films can be controlled by Nd loading and that these films could be useful for technological applications.

  17. Evaluation of Nd-Loaded SnO2:F Films Coated via Spray Pyrolysis

    NASA Astrophysics Data System (ADS)

    Turgut, G.

    2018-07-01

    Thin layers of single (F)- and double (F/Nd)-incorporated tin oxide have been coated on glass substrate via spray pyrolysis. The structural, morphological, electrical, and optical features of F-incorporated samples were evaluated depending on the Nd loading. X-ray diffraction analysis revealed that samples had tetragonal tin oxide structure with (211) and (200) preferential directions. The crystallite size and strain values varied from 37.98 nm and 1.21 × 10-3 to 52.12 nm and 1.88 × 10-3. Scanning electron microscopy analysis showed that the samples consisted of pyramidal, polyhedral, and needle-shaped granules. The lowest sheet resistance value of 1.22 Ω was found for 1.8 at.% Nd + 25 at.% F-coloaded SnO2. However, the widest optical bandgap of 4.01 eV was observed for the single 25 at.% F-loaded sample. The Urbach tail and figure of merit also changed in the ranges of 664 meV to 1296 meV and 6.4 × 10-2 Ω-1 to 2.3 × 10-3 Ω-1, respectively. The results presented herein indicate that the character of F-doped tin oxide films can be controlled by Nd loading and that these films could be useful for technological applications.

  18. Preparation of γ-Al2O3 films by laser chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Gao, Ming; Ito, Akihiko; Goto, Takashi

    2015-06-01

    γ- and α-Al2O3 films were prepared by chemical vapor deposition using CO2, Nd:YAG, and InGaAs lasers to investigate the effects of varying the laser wavelength and deposition conditions on the phase composition and microstructure. The CO2 laser was found to mostly produce α-Al2O3 films, whereas the Nd:YAG and InGaAs lasers produced γ-Al2O3 films when used at a high total pressure. γ-Al2O3 films had a cauliflower-like structure, while the α-Al2O3 films had a dense and columnar structure. Of the three lasers, it was the Nd:YAG laser that interacted most with intermediate gas species. This promoted γ-Al2O3 nucleation in the gas phase at high total pressure, which explains the cauliflower-like structure of nanoparticles observed.

  19. Structural and dielectric characteristics of Ba3Ln3Ti5Nb5O30 (Ln = La, Nd, Sm) filled tungsten bronze ceramics

    NASA Astrophysics Data System (ADS)

    Chen, Wang; Gao, Ting Ting; Zhu, Xiao Li; Chen, Xiang Ming

    2018-03-01

    In the present work, the structural, dielectric and relaxor ferroelectric properties were investigated for Ba3Ln3Ti5Nb5O30 (Ln = La, Nd, Sm) ceramics. The filled tungsten bronze phase with space group P4/mbm was confirmed for all compositions, while a small amount of secondary phase was detected in Ba3Nd3Ti5Nb5O30 and Ba3Sm3Ti5Nb5O30. The typical relaxor ferroelectric behaviors were observed: a broad peak of dielectric constant shifting to higher temperatures and decreasing its magnitude with increasing frequency and the frequency dispersion obeying the Vogel-Fulcher relationship. The P-E (polarization-electric field) hysteresis loops were obtained for Ba3Ln3Ti5Nb5O30 (Ln = La, Nd, Sm) ceramics at low temperatures. The nanoscale ferroelectric 180° domains with strip-like shape were observed in the paraelectric matrix at room temperature, where the commensurate structural modulations were determined in the domains and incommensurate ones were determined in the matrix. The significant differences were determined between the present ceramics and Ba4Ln2Ti4Nb6O30 and Ba5LnTi3Nb7O30 because of the different distribution patterns of A1 and A2 cations.

  20. Effect of PbO on the spectral and thermo-optical properties of Nd3+-doped phosphate laser glass

    NASA Astrophysics Data System (ADS)

    Yin, Qianwen; Kang, Shuai; Wang, Xue; Li, Shunguang; He, Dongbing; Hu, Lili

    2017-04-01

    Nd3+-doped P2O5-K2O-Al2O3-BaO-PbO phosphate glasses with various PbO/BaO ratios were synthesized using the melt quenching technique. Raman, absorption, and emission spectra were measured to investigate the effects of PbO/BaO ratios on the structures and spectroscopic properties of the glasses. The emission cross-sections of the Nd3+-doped phosphate glasses were calculated using the Judd-Ofelt theory, and were found to increase from 4.37 × 10-20 to 4.50 × 10-20 cm2 as the PbO/BaO ratio increased. In addition, thermo-optical properties were measured using an interferometric technique. The thermo-optical coefficients, which were -1.49 × 10-6, -1.65 × 10-6, and -1.64 × 10-6 K-1, respectively, were all largely negative values. The thermal expansion coefficients of the three glass samples varied within a small range. The results showed that increasing the PbO/BaO ratio of phosphate glasses can improve the laser properties while maintaining their good thermo-optical properties.

  1. Observation of magnetization and exchange bias reversals in NdFe0.5Cr0.5O3

    NASA Astrophysics Data System (ADS)

    Sharannia, M. P.; De, Santanu; Singh, Ripandeep; Das, A.; Nirmala, R.; Santhosh, P. N.

    2017-05-01

    Polycrystalline NdFe0.5Cr0.5O3 has orthorhombic structure with Pnma space group and is magnetically ordered at room temperature as confirmed by neutron diffraction. The magnetic structure involves CxGyFz type ordering of Fe3+/Cr3+ ions. NdFe0.5Cr0.5O3 shows magnetization reversal and sign reversal of exchange bias at 16 K. Nd3+ moments that get induced by the internal field of |Fe+Cr| sublattice couple antiferromagnetically with the ferromagnetic component of |Fe+Cr| sublattice. Nd3+ moments overcome the |Fe+Cr| moments at 16 K below which the material shows negative magnetization and positive exchange bias.

  2. Crystallite size strain analysis of nanocrystalline La0.7Sr0.3MnO3 perovskite by Williamson-Hall plot method

    NASA Astrophysics Data System (ADS)

    Kumar, Dinesh; Verma, Narendra Kumar; Singh, Chandra Bhal; Singh, Akhilesh Kumar

    2018-04-01

    The nanocrystalline Sr-doped LaMnO3 (La0.7Sr0.3MnO3 = LSMO) perovskite manganites having different crystallite size were synthesized using the nitrate-glycine auto-combustion method. The phase purity of the manganites was checked by X-ray diffraction (XRD) measurement. The XRD patterns of the sample reveal that La0.7S0.3MnO3 crystallizes into rhombohedral crystal structure with space group R-3c. The size-dependence of structural lattice parameters have been investigated with the help of Rietveld refinement. The structural parameters increase as a function of crystallite size. The crystallite-size and internal strain as a function of crystallite-size have been calculated using Williamson-Hall plot.

  3. Intrinsic ferromagnetism in nanocrystalline Mn-doped ZnO depending on Mn concentration.

    PubMed

    Subramanian, Munisamy; Tanemura, Masaki; Hihara, Takehiko; Soga, Tetsuo; Jimbo, Takashi

    2011-04-01

    The physical properties of Zn(1-x)Mn(x)O nanoparticles synthesized by thermal decomposition are extensively investigated by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Raman light scattering and Hysteresis measurements. XRD and XPS spectra reveal the absence of secondary phase in nanocrystalline ZnO doped with 5% or less Mn; and, later confirms that the valance state of Mn to be 2+ for all the samples. Raman spectra exhibit a peak at 660 cm(-1) which we attribute to the intrinsic lattice defects of ZnO with increasing Mn concentration. Overall, our results demonstrate that ferromagnetic properties can be realized while Mn-doped ZnO obtained in the nanocrystalline form.

  4. Spectroscopic investigations of Nd3+ doped flouro- and chloro-borate glasses.

    PubMed

    Mohan, Shaweta; Thind, Kulwant Singh; Sharma, Gopi; Gerward, Leif

    2008-10-01

    Spectroscopic and physical properties of Nd3+ doped sodium lead flouro- and chloro-borate glasses of the type 20NaX-30PbO-49.5B2O3-0.5Nd2O3 (X=F and Cl) have been investigated. Optical absorption spectra have been used to determine the Slater Condon (F2, F4, and F6), spin orbit xi4f and Racah parameters (E1, E2, and E3). The oscillator strengths and the intensity parameters Omega2, Omega4 and Omega6 have been determined by the Judd-Ofelt theory, which in turn provide the radiative transition probability (A), total transition probability (A(T)), radiative lifetime (tauR) and branching ratio (beta) for the fluorescent level 4F3/2. The lasing efficiency of the prepared glasses has been characterized by the spectroscopic quality factor (Omega4/Omega6), the value of which is in the range of 0.2-1.5, typical for Nd3+ in different laser hosts. Nephelauxetic effect results in a red shift in the energy levels of Nd3+ for chloroborate glass. The radiative transition probability of the potential lasing transition 4F3/2-->4I11/2 of Nd3+ ions is found to be higher for flouroborate as compared to chloroborate glass.

  5. Structure Characterization and Catalytic Properties of Cr2O3 Doped with MgO Supported on MgF2

    NASA Astrophysics Data System (ADS)

    Goslar, J.; Wojciechowska, M.; Zieliński, M.; Tomska-Foralewska, I.; Przystajko, W.

    2006-08-01

    A characterization of double oxide systems containing Cr2O3 doped with MgO and supported on MgF2 was carried out. The catalysts were prepared by impregnation and co-impregnation methods and characterized by the Brunauer-Emmett-Teller method, EPR, and temperature programmed reduction. The results proved the interactions between supported oxides and the presence of spinel-like phase after treatment at 400 ºC. Magnesium oxide clearly influences the catalytic activity as well as selectivity of chromium catalysts supported on MgF2. The MgO-Cr2O3/MgF2 systems were active and selective in the reaction of CO oxidation at the room temperature and in the dehydrogenation of cyclohexene.

  6. Neutron Diffraction Study of Parasitic Nd-Moment Order in the Checkerboard-Type Phase Nd 1.3Sr 0.7NiO 4

    DOE PAGES

    Kobayashi, Riki; Yoshizawa, Hideki; Matsuda, Masaaki; ...

    2015-05-25

    In this paper, the Nd-moment order in the layered nickelate Nd 2-xSr xNiO 4 (x = 0.7) has been investigated by performing a neutron diffraction experiment using a single crystal sample. First, the checkerboard (CB)-type charge order was confirmed by observing the temperature dependence of the nuclear superlattice peak at Q=(5,0,0) between 1.9 and 300 K, which indicates that the transition temperature of the CB-type charge order is above 300 K. Magnetic superlattice peaks with the propagation vector k=(1-ε,0,1) appear below 67 K, and the value of ε was determined to be 0.455 in good agreement with previous studies. Themore » intensity of the magnetic superlattice peaks appearing below 67 K shows a sharp increase below ≈20 K. This behavior indicates that the Nd moments freeze under the influence of the Ni ordering. The CB-type antiferromagnetic (AFM) Ni order in the NiO 2 layers is stacked antiferromagnetically in the c-axis direction, while the Nd moments in the Nd/SrO 2 layers are coupled antiferromagnetically with the Ni moments. Finally, the Nd moments are parallel to the c-axis, while the Ni moments are canted towards the c-axis direction from the basal ab-plane at low temperatures where the Nd moments are well ordered.« less

  7. Improvement of the magnetic moment of NiZn ferrites induced by substitution of Nd3+ ions for Fe3+ ions

    NASA Astrophysics Data System (ADS)

    Wu, Xuehang; Chen, Wen; Wu, Wenwei; Wu, Juan; Wang, Qing

    2018-05-01

    Four types of Ni-Zn based ferrites materials having the general formula Ni0.5Zn0.5NdxFe2-xO4 (0.0 ≤ x ≤ 0.12) have been successfully synthesized by calcining oxalates in air and the influence of Nd content on the structure and magnetic properties of Ni0.5Zn0.5NdxFe2-xO4 is studied. X-ray diffraction examination confirms that a high-crystallized Ni0.5Zn0.5NdxFe2-xO4 with cubic spinel structure is obtained when the precursor is calcined at 1000 °C in air for 2 h. The substitutions of Nd3+ ions for partial Fe3+ ions do not change the spinel crystalline structure of MFe2O4. The incorporation of Nd3+ ions in place of Fe3+ ions in Ni-Zn ferrites increases the average crystallite size. Specific saturation magnetization decreases with increase in Nd content. This is because Nd3+ ions with smaller magnetic moment preferentially fill the octahedral sites. In addition, antiferromagnetic FeNdO3 increases with increase in Nd content. In this study, Ni0.5Zn0.5Nd0.08Fe1.92O4, calcined at 1000 °C, exhibits the highest magnetic moment (4.2954 μB) and the lowest coercivity (28.82 Oe).

  8. Enhanced 1.32 μm fluorescence and broadband amplifying for O-band optical amplifier in Nd3+-doped tellurite glass

    NASA Astrophysics Data System (ADS)

    Zhou, Zi-zhong; Zhou, Ming-han; Su, Xiu-e.; Cheng, Pan; Zhou, Ya-xun

    2017-01-01

    WO3 oxides with relatively high phonon energy and different concentrations were introduced into the Nd3+-doped tellurite-based glasses of TeO2-ZnO-Na2O to improve the 1.32 μm band fluorescence emission. The absorption spectra, Raman spectra, 1.32 μm band fluorescence spectra and differential scanning calorimeter (DSC) curves were measured, together with the Judd-Ofelt intensity parameters, stimulated emission and gain parameters were calculated to evaluate the effects of WO3 amount on the glass structure and spectroscopic properties of 1.32 μm band fluorescence. It is shown that the introduction of an appropriate amount of WO3 oxide can effectively improve the 1.32 μm band fluorescence intensity through the enhanced multi-phonon relaxation (MPR) processes between the excited levels of Nd3+. The results indicate that the prepared Nd3+-doped tellurite glass with an appropriate amount of WO3 oxide is a potential gain medium applied for the O-band broad and high-gain fiber amplifier.

  9. Near-infrared photoluminescence in La0.98AlO3: 0.02Ln3+(Ln = Nd/Yb) for sensitization of c-Si solar cells

    NASA Astrophysics Data System (ADS)

    Sawala, N. S.; Koparkar, K. A.; Bajaj, N. S.; Omanwar, S. K.

    2016-05-01

    The host matrix LaAlO3 was synthesized by conventional solid state reaction method in which the Nd3+ ions and Yb3+ ions successfully doped at 2mol% concentrations. The phase purity was confirmed by X ray powder diffraction (XRD) method. The photoluminescence (PL) properties were studied by spectrophotometer in near infra red (NIR) and ultra violet visible (UV-VIS) region. The Nd3+ ion doped LaAlO3 converts a visible (VIS) green photon (587 nm) into near infrared (NIR) photon (1070 nm) while Yb3+ ion doped converts ultra violet (UV) photon (221 nm) into NIR photon (980 nm). The La0.98AlO3: 0.02Ln3+(Ln = Nd / Yb) can be potentiality used for betterment of photovoltaic (PV) technology. This result further indicates its potential application as a luminescence converter layer for enhancing solar cells performance.

  10. Preparation and Characterization of Zirconia-Coated Nanodiamonds as a Pt Catalyst Support for Methanol Electro-Oxidation

    PubMed Central

    Lu, Jing; Zang, Jianbing; Wang, Yanhui; Xu, Yongchao; Xu, Xipeng

    2016-01-01

    Zirconia-coated nanodiamond (ZrO2/ND) electrode material was successfully prepared by one-step isothermal hydrolyzing from ND-dispersed ZrOCl2·8H2O aqueous solution. High-resolution transmission electron microscopy reveals that a highly conformal and uniform ZrO2 shell was deposited on NDs by this simple method. The coating obtained at 90 °C without further calcination was mainly composed of monoclinic nanocrystalline ZrO2 rather than common amorphous Zr(OH)4 clusters. The ZrO2/NDs and pristine ND powder were decorated with platinum (Pt) nanoparticles by electrodeposition from 5 mM chloroplatinic acid solution. The electrochemical studies indicate that Pt/ZrO2/ND catalysts have higher electrocatalytic activity and better stability for methanol oxidation than Pt/ND catalysts in acid. PMID:28335361

  11. Dopant occupancy and exposure energy in Hf:Nd:LiNbO3 crystal as a function of [Li]/[Nb] ratios

    NASA Astrophysics Data System (ADS)

    Dai, Li; Liu, Chunrui; Han, Xianbo; Yan, Zhehua; Tan, Chao; Wang, Luping; Xu, Yuheng

    2017-09-01

    A series of Hf: Nd: LiNbO3 crystals with various [Li]/[Nb] ratios ([Li]/[Nb] = 0.94, 1.05, 1.20, 1.38) in the melt were grown by conventional Czochralski technique. The distribution coefficients of Hf4+ and Nd3+ ions were recorded by an inductively coupled plasma-atomic emission spectrometer (ICP-AES). The effective distribution coefficient of Hf4+ is reduced and that of Nd3+ is increased with the increase of [Li]/[Nb] ratio in the melts. In all cases, the effective distribution coefficients is less than 1. The IR transmission spectroscopy of the Hf: Nd: LiNbO3 crystals were measured, getting the results that Hf: Yb: Ho: LiNbO3 crystals with 1.05 [Li]/[Nb] ratios was the stoichiometric. The optical damage resistance ability of Hf:Nd:LiNbO3 crystals were studied by light-induced scattering exposure energy flux threshold method and it increases with the increasing of [Li]/[Nb] ratios. When the [Li]/[Nb] ratio is 1.38 in the melt (the sample 4#), the exposure energy achieves 687.35 J/cm2, approximately 441 folds than that of the sample 1# ([Li]/[Nb] = 0.94) in magnitude.

  12. Large magnetic response in (Bi4Nd)Ti3(Fe0.5Co0.5)O15 ceramic at room-temperature

    NASA Astrophysics Data System (ADS)

    Yang, F. J.; Su, P.; Wei, C.; Chen, X. Q.; Yang, C. P.; Cao, W. Q.

    2011-12-01

    Ceramics of Nd/Co co-substituted Bi5Ti3FeO15, i.e., (Bi4Nd)Ti3(Fe0.5Co0.5)O15 were prepared by the conventional solid-state reaction method. The X-ray diffraction pattern demonstrates that the sample of the layered perovskite phase was successfully obtained, even if little Bi-deficient pyrochlore Bi2Ti2O7 also existed. The ferroelectric and magnetic Curie temperatures were determined to be 1077 K and 497 K, respectively. The multiferroic property of the sample at room temperature was demonstrated by ferroelectric and magnetic measurements. Remarkably, by Nd/Co co-substituting, the sample exhibited large magnetic response with 2Mr = 330 memu/g and 2Hc = 562 Oe at applied magnetic field of 8 kOe at room temperature. The present work suggests the possibility of doped Bi5Ti3FeO15 as a potential multiferroic.

  13. Tunable femtosecond laser based on the Nd3+:BaLaGa 3O 7 disordered crystal

    NASA Astrophysics Data System (ADS)

    Agnesi, A.; Pirzio, F.; Tartara, L.; Ugolotti, E.; Zhang, H.; Wang, J.; Yu, H.; Petrov, V.

    2014-03-01

    We demonstrate clear inhomogeneous linewidth broadening for the disordered laser crystal Nd:BaLaGa3O7 (Nd:BLG), which is very promising for the replacement of Nd:glass for ultrafast sources in multiwatt power applications. A Nd:BLG laser oscillator passively mode-locked and pumped by a Ti:sapphire laser generated pulses of 316-fs duration at 1060 nm, whose spectrum completely fills the fluorescence peak at such wavelength. More interestingly, sub-picosecond pulses were smoothly tunable in a 20-nm range, from 1070 to 1090 nm. The shortest pulses achieved were 290 fs long, centered at 1075 nm.

  14. Band-gap engineering of La1-x Nd x AlO3 (x = 0, 0.25, 0.50, 0.75, 1) perovskite using density functional theory: A modified Becke Johnson potential study

    NASA Astrophysics Data System (ADS)

    Sandeep; D, P. Rai; A, Shankar; M, P. Ghimire; Anup Pradhan, Sakhya; T, P. Sinha; R, Khenata; S, Bin Omran; R, K. Thapa

    2016-06-01

    The structural, electronic, and magnetic properties of the Nd-doped Rare earth aluminate, La1-x Nd x AlO3 (x = 0% to 100%) alloys are studied using the full potential linearized augmented plane wave (FP-LAPW) method within the density functional theory. The effects of the Nd substitution in LaAlO3 are studied using the supercell calculations. The computed electronic structure with the modified Becke-Johnson (mBJ) potential based approximation indicates that the La1-x Nd x AlO3 alloys may possess half-metallic (HM) behaviors when doped with Nd of a finite density of states at the Fermi level (E F). The direct and indirect band gaps are studied each as a function of x which is the concentration of Nd-doped LaAlO3. The calculated magnetic moments in the La1-x Nd x AlO3 alloys are found to arise mainly from the Nd-4f state. A probable half-metallic nature is suggested for each of these systems with supportive integral magnetic moments and highly spin-polarized electronic structures in these doped systems at E F. The observed decrease of the band gap with the increase in the concentration of Nd doping in LaAlO3 is a suitable technique for harnessing useful spintronic and magnetic devices. Project supported by the DST-SERB, Dy (Grant No. SERB/3586/2013-14), the UGCBSR, FRPS (Grant No. F.30-52/2014), the UGC (New Delhi, India) Inspire Fellowship DST (India), and the Deanship of Scientific Research at King Saud University (Grant No. RPG-VPP-088). M P Ghimire thanks the Alexander von Humboldt Foundation, Germany for the financial support.

  15. Key role of lattice symmetry in the metal-insulator transition of NdNiO 3 films

    DOE PAGES

    Zhang, Jack Y.; Kim, Honggyu; Mikheev, Evgeny; ...

    2016-04-01

    Here, bulk NdNiO 3 exhibits a metal-to-insulator transition (MIT) as the temperature is lowered that is also seen in tensile strained films. In contrast, films that are under a large compressive strain typically remain metallic at all temperatures. To clarify the microscopic origins of this behavior, we use position averaged convergent beam electron diffraction in scanning transmission electron microscopy to characterize strained NdNiO 3 films both above and below the MIT temperature. We show that a symmetry lowering structural change takes place in case of the tensile strained film, which undergoes an MIT, but is absent in the compressively strainedmore » film. Using space group symmetry arguments, we show that these results support the bond length disproportionation model of the MIT in the rare-earth nickelates. Furthermore, the results provide insights into the non-Fermi liquid phase that is observed in films for which the MIT is absent.« less

  16. Nanocrystalline ZnCO3-A novel sorbent for low-temperature removal of H2S.

    PubMed

    Balichard, Kevin; Nyikeine, Camille; Bezverkhyy, Igor

    2014-01-15

    The reactivity of a nanocrystalline ZnCO3 toward H2S (0.2vol% in N2/H2 mixture) at 140-180°C was characterized by thermal gravimetric analysis and by breakthrough curves measurements. We have found that under used conditions transformation of ZnCO3 into ZnS is complete and the rate determining step of the sulfidation is the surface reaction. Such behavior is in strike contrast with that of ZnO whose sulfidation is severely limited by diffusion. The higher reactivity of ZnCO3 in comparison with ZnO is attributed to the different microstructure of ZnS layer formed in these materials after a partial sulfidation. As in ZnO-ZnS transformation the molar volume increases (from 14.5 to 23.8cm(3)/mol), a continuous protective ZnS layer is formed hampering the access of H2S to the non reacted ZnO core. By contrast, in ZnCO3-ZnS transformation the molar volume decreases (from 27.9 to 23.8cm(3)/mol), which produces a discontinuous non-protective ZnS layer enabling a complete transformation of ZnCO3 even at 140°C. The higher reactivity of ZnCO3 results in a considerable increase of the breakthrough sulfur capacity of the carbonate in comparison with oxide. The material has therefore a good potential for being used as a disposable sorbent for H2S capture at low temperature. Copyright © 2013 Elsevier B.V. All rights reserved.

  17. A diode-pumped Nd:YAlO3 dual-wavelength yellow light source

    NASA Astrophysics Data System (ADS)

    Zhang, Jing; Fu, Xihong; Zhai, Pei; Xia, Jing; Li, Shutao

    2013-11-01

    We present what is, to the best of our knowledge, the first diode-pumped Nd:YAlO3 (Nd:YAP) continuous-wave (cw) dual-wavelength yellow laser at 593 nm and 598 nm, based on sum-frequency generation between 1064 and 1339 nm in a-axis polarization using LBO crystal and between 1079 and 1341 nm in c-axis polarization using PPKTP crystal, respectively. At an incident pump power of 17.3 W, the maximum output power obtained at 593 nm and 598 nm is 0.18 W and 1.86 W, respectively. The laser experiment shows that Nd:YAP crystal can be used for an efficient diode-pumped dual-wavelength yellow laser system.

  18. Undulated oxo-centered layers in PbLn3O4(VO4) (Ln= La and Nd) and relationship with Nd4O4(GeO4)

    NASA Astrophysics Data System (ADS)

    Colmont, Marie; Mentré, Olivier; Henry, Natacha; Pautrat, Alain; Leclercq, Bastien; Capet, Frédéric; Djelal, Nora; Roussel, Pascal

    2018-04-01

    Single crystals of PbLa3O4(VO4) have been synthesized using the flux growth technique and characterized by X-ray diffraction. The crystal structure of the tittle phase was solved by charge flipping and refined to R1 = 0.024 (wR2 = 0.031) for 2777 reflections [I>3σ(I)]. The compound is orthorhombic and crystallized in the space group Cmcm: a = 5.8686(6)Å, b = 17.898(2)Å, c = 7.9190(7)Å, V = 831.8(1)Å3, Z = 4. The structure is built on [PbLa3O4]3+ layers with zig-zag cross-sections, surrounded by isolated (VO4)3- tetrahedra. Its crystal structure shows direct relationship with the isoformular Nd4O4(GeO4) compound which crystallized in the primitive non centrosymmetric Pb21m sub-group. Its stability in temperature and under air was checked as well as optical properties. In a second part, lanthanum was substituted by neodymium giving rise to a paramagnet and f→ f electronic excitations superposed to the broad absorption front below 3.05 eV related to the presence of VO4 groups.

  19. Eu 3+-doped wide band gap Zn 2SnO 4 semiconductor nanoparticles: Structure and luminescence

    DOE PAGES

    Dimitrievska, Mirjana; Ivetić, Tamara B.; Litvinchuk, Alexander P.; ...

    2016-08-03

    Nanocrystalline Zn 2SnO 4 powders doped with Eu 3+ ions were synthesized via a mechanochemical solid-state reaction method followed by postannealing in air at 1200 °C. X-ray diffraction (XRD), energy-dispersive X-ray (EDX), and Raman and photoluminescence (PL) spectroscopies provide convincing evidence for the incorporation of Eu 3+ ions into the host matrix on noncentrosymmetric sites of the cubic inverse spinel lattice. Microstructural analysis shows that the crystalline grain size decreases with the addition of Eu 3+. Formation of a nanocrystalline Eu 2Sn 2O 7 secondary phase is also observed. Luminescence spectra of Eu 3+-doped samples show several emissions, including narrow-bandmore » magnetic dipole emission at 595 nm and electric dipole emission at 615 nm of the Eu 3+ ions. Excitation spectra and lifetime measurements suggest that Eu 3+ ions are incorporated at only one symmetry site. According to the crystal field theory, it is assumed that Eu 3+ ions participate at octahedral sites of Zn 2+ or Sn 4+ under a weak crystal field, rather than at the tetrahedral sites of Zn2+, because of the high octahedral stabilization energy for Eu 3+. Activation of symmetry forbidden (IR-active and silent) modes is observed in the Raman scattering spectra of both pure and doped samples, indicating a disorder of the cation sublattice of Zn 2SnO 4 nanocrystallites. These results were further supported by the first principle lattice dynamics calculations. The spinel-type Zn 2SnO 4 shows effectiveness in hosting Eu 3+ ions, which could be used as a prospective green/red emitter. As a result, this work also illustrates how sustainable and simple preparation methods could be used for effective engineering of material properties.« less

  20. The crystal structure of the monohydrate R{sub 2}Mo{sub 6}O{sub 21}.H{sub 2}O (R=Pr, Nd, Sm, and Eu): a layer structure containing disordered [Mo{sub 2}O{sub 7}]{sup 2-} groups

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

    Naruke, Haruo; Yamase, Toshihiro

    2005-03-15

    Although R{sub 2}O{sub 3}:MoO{sub 3}=1:6 (R=rare earth) compounds are known in the R{sub 2}O{sub 3}-MoO{sub 3} phase diagrams since a long time, no structural characterization has been achieved because a conventional solid-state reaction yields powder samples. We obtained single crystals of R{sub 2}Mo{sub 6}O{sub 21}.H{sub 2}O (R=Pr, Nd, Sm, and Eu) by thermal decomposition of [R{sub 2}(H{sub 2}O){sub 12}Mo{sub 8}O{sub 27}].nH{sub 2}O at around 685-715{sup o}C for 2h, and determined their crystal structures. The simulated XRD patterns of R{sub 2}Mo{sub 6}O{sub 21}.H{sub 2}O were consistent with those of previously reported R{sub 2}O{sub 3}:MoO{sub 3}=1:6 compounds. All R{sub 2}Mo{sub 6}O{sub 21}.H{submore » 2}O compounds crystallize isostructurally in tetragonal, P4/ncc (No. 130), a=8.9962(5), 8.9689(6), 8.9207(4), and 8.875(2)A; c=26.521(2), 26.519(2), 26.304(2), and 26.15(1)A; Z=4; R{sub 1}=0.026, 0.024, 0.024, and 0.021, for R=Pr, Nd, Sm, and Eu, respectively. The crystal structure of R{sub 2}Mo{sub 6}O{sub 21}.H{sub 2}O consists of two [Mo{sub 2}O{sub 7}]{sup 2-}-containing layers (A and B layers) and two interstitial R(1){sup 3+} and R(2){sup 3+} cations. Each [Mo{sub 2}O{sub 7}]{sup 2-} group is composed of two corner-sharing [MoO{sub 4}] tetrahedra. The [Mo{sub 2}O{sub 7}]{sup 2-} in the B layer exhibits a disorder to form a pseudo-[Mo{sub 4}O{sub 9}] group, in which four Mo and four O sites are half occupied. R(1){sup 3+} achieves 8-fold coordination by O{sup 2-} to form a [R(1)O{sub 8}] square antiprism, while R(2){sup 3+} achieves 9-fold coordination by O{sup 2-} and H{sub 2}O to form a [R(2)(H{sub 2}O)O{sub 8}] monocapped square antiprism. The disorder of the [Mo{sub 2}O{sub 7}]{sup 2-} group in the B layer induces a large displacement of the O atoms in another [Mo{sub 2}O{sub 7}]{sup 2-} group (in the A layer) and in the [R(1)O{sub 8}] and [R(2)(H{sub 2}O)O{sub 8}] polyhedra. A remarkable broadening of the photoluminescence spectrum of Eu{sub 2}Mo

  1. Red shifts of the Eg(1) Raman mode of nanocrystalline TiO2:Er monoliths grown by sol-gel process

    NASA Astrophysics Data System (ADS)

    Palomino-Merino, R.; Trejo-Garcia, P.; Portillo-Moreno, O.; Jiménez-Sandoval, S.; Tomás, S. A.; Zelaya-Angel, O.; Lozada-Morales, R.; Castaño, V. M.

    2015-08-01

    Nanocrystalline monoliths of Er doped TiO2 were prepared by the sol-gel technique, by controlling the Er-doping levels into the TiO2 precursor solution. As-prepared and annealed in air samples showed the anatase TiO2 phase. The average diameter of the nanoparticles ranged from 19 to 2.6 nm as the nominal concentration of Er varies from 0% to 7%, as revealed by EDS analysis in an electron microscope. Photo Acoustic Spectroscopy (PAS) allowed calculate the forbidden band gap, evidencing an absorption edge at around 300 nm, attributed to TiO2 and evidence of electronic transitions or Er3+. The Raman spectra, corresponding to the anatase phase, show the main phonon mode Eg(1) band position at 144 cm-1 with a red shift for the annealing samples.

  2. Boosted surface acidity in TiO2 and Al2O3-TiO2 nanotubes as catalytic supports

    NASA Astrophysics Data System (ADS)

    Camposeco, R.; Castillo, S.; Mejía-Centeno, Isidro; Navarrete, J.; Nava, N.

    2015-11-01

    In this study, titanate nanotubes (NT) and titanate nanotubes with alumina (NT-Al) were studied as solid acid catalytic supports to show the relationship between the kind of acidity and catalytic activity. The supports were characterized by XRD, TEM, FTIR, XPS, and tested in the SCR-NO with NH3. It was found that the amount of Brönsted acid sites was maintained and the Lewis acid sites were significantly affected by the addition of alumina (1, 3, 5 and 10 wt.%); such acidity was higher than that of the titanate nanotubes (NT) by two-fold. To confirm the formation of titanate nanotubes and titanate nanotubes with alumina, transmission electron microscopy (TEM) was used. X-ray diffraction (XRD) revealed the formation of the H2Ti4O9·H2O phase. All NT and NT-Al supports presented catalytic activity to remove NO with NH3 under lean conditions, confirming the presence of an important amount of Brönsted and Lewis acid sites in both NT and NT-Al supports.

  3. Dispersion of nanocrystalline Fe 3O 4 within composite electrodes: Insights on battery-related electrochemistry

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

    David C. Bock; Takeuchi, Kenneth J.; Pelliccione, Christopher J.

    2016-04-20

    Aggregation of nanosized materials in composite lithium-ion-battery electrodes can be a significant factor influencing electrochemical behavior. In this study, aggregation was controlled in magnetite, Fe 3O 4, composite electrodes via oleic acid capping and subsequent dispersion in a carbon black matrix. A heat treatment process was effective in the removal of the oleic acid capping agent while preserving a high degree of Fe 3O 4 dispersion. Electrochemical testing showed that Fe 3O 4 dispersion is initially beneficial in delivering a higher functional capacity, in agreement with continuum model simulations. However, increased capacity fade upon extended cycling was observed for themore » dispersed Fe 3O 4 composites relative to the aggregated Fe 3O 4 composites. X-ray absorption spectroscopy measurements of electrodes post cycling indicated that the dispersed Fe 3O 4 electrodes are more oxidized in the discharged state, consistent with reduced reversibility compared with the aggregated sample. Higher charge-transfer resistance for the dispersed sample after cycling suggests increased surface-film formation on the dispersed, high-surface-area nanocrystalline Fe 3O 4 compared to the aggregated materials. Furthermore, this study provides insight into the specific effects of aggregation on electrochemistry through a multiscale view of mechanisms for magnetite composite electrodes.« less

  4. Dispersion of Nanocrystalline Fe 3 O 4 within Composite Electrodes: Insights on Battery-Related Electrochemistry

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

    Bock, David C.; Pelliccione, Christopher J.; Zhang, Wei

    2016-04-20

    Aggregation of nanosized materials in composite lithium-ion-battery electrodes can be a significant factor influencing electrochemical behavior. In this study, aggregation was controlled in magnetite, Fe 3O 4, composite electrodes via oleic acid capping and subsequent dispersion in a carbon black matrix. A heat treatment process was effective in the removal of the oleic acid capping agent while preserving a high degree of Fe 3O 4 dispersion. Electrochemical testing showed that Fe 3O 4 dispersion is initially beneficial in delivering a higher functional capacity, in agreement with continuum model simulations. However, increased capacity fade upon extended cycling was observed for themore » dispersed Fe 3O 4 composites relative to the aggregated Fe 3O 4 composites. X-ray absorption spectroscopy measurements of electrodes post cycling indicated that the dispersed Fe 3O 4 electrodes are more oxidized in the discharged state, consistent with reduced reversibility compared with the aggregated sample. Higher charge-transfer resistance for the dispersed sample after cycling suggests increased surface-film formation on the dispersed, high-surface-area nanocrystalline Fe 3O 4 compared to the aggregated materials. This study provides insight into the specific effects of aggregation on electrochemistry through a multiscale view of mechanisms for magnetite composite electrodes.« less

  5. Interfacial magnetic coupling in hetero-structure of Fe/double-perovskite NdBaMn2O6 single crystal

    NASA Astrophysics Data System (ADS)

    Lin, W. C.; Tsai, C. L.; Ogawa, K.; Yamada, S.; Gandhi, Ashish C.; Lin, J. G.

    2018-04-01

    The interfacial magnetic coupling between metallic Fe and the double-perovskite NdBaMn2O6 single crystal was investigated in the heterostructure of 4-nm Pd/10-nm Fe/NdBaMn2O6. A considerable magnetic coupling effect was observed in the temperature range coincident with the magnetic phase transition of NdBaMn2O6. When the temperature was elevated above 270 K, NdBaMn2O6 transformed from a state of antiferromagnetic fluctuating domains to a superparamagnetism-like (ferromagnetic fluctuation) state with high magnetic susceptibility. Concurrently, the interfacial magnetic coupling between the Fe layer and the NdBaMn2O6 crystal was observed, as indicated by the considerable squareness reduction and coercivity enhancement in the Fe layer. Moreover, the presence of the Fe layer changed the magnetic structure of NdBaMn2O6 from conventional 4-fold symmetry to 2-fold symmetry. These observations offer applicable insights into the mutual magnetic interaction in the heterostructures of metallic ferromagnetism/perovskite materials.

  6. Structural, optical and magnetic behaviour of nanocrystalline Volborthite

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

    Arvind, Hemant K., E-mail: hemantarvind@gmail.com; Kumar, Sudhish, E-mail: skmlsu@gmail.com; Kalal, Sangeeta

    2016-05-06

    Nanocrystalline sample of Volborthite (Copper Pyrovanadate: Cu{sub 3}V{sub 2} (OH){sub 2}O{sub 7}.2H{sub 2}O) has been synthesized using wet chemical route and characterized by XRD, SEM, FTIR, UV-Vis-NIR spectroscopic and magnetization measurements. Room temperature X-ray diffraction analysis confirms the single phase monoclinic structure and nanocrystalline nature of Volborthite. The UV-Visible optical absorption spectrum displays two broad absorption peaks in the range of 200-350 nm and 400-1000 nm. The direct band gap is found to be E{sub g}= ∼2.74 eV. Bulk Volborthite was reported to be a natural frustrated antiferromagnet, however our nanocrystalline Volborthite display week ferromagnetic hysteresis loop with very small coercivity andmore » retentivity at room temperature.« less

  7. Laser and thermal properties of Nd:YGd2Sc2Al2GaO12 garnet ceramic Laser and thermal properties of Nd:YSGG garnet ceramic

    NASA Astrophysics Data System (ADS)

    Brenier, A.; Alombert-Goget, G.; Guyot, Y.; Boulon, G.

    2012-10-01

    The absorption and fluorescence properties of the Nd-doped YGd2Sc2Al2GaO12 mixed garnet ceramics have been measured at different temperatures. Under laser diode pumping an efficient laser emission has been demonstrated with 45% slope efficiency. The emission is constituted by two lines at 1058.6 and 1061.3 nm, subjected to a red shift and a variable relative intensity versus pump power. The role of the temperature has been investigated playing with the cavity parameters. The thermal conductivity of the 1% Nd-doped material has been determined (3.2 W/m/K) measuring the radial temperature distribution of the exit face of the sample including the axial heat flow in the analysis. The M2 beam quality factor and the dioptric power of the thermal lens have been investigated versus the pump power. The thermo-optic coefficient χ was determined as 44.4×10-6 K-1.

  8. Effect of DC bias on dielectric properties of nanocrystalline CuAlO2

    NASA Astrophysics Data System (ADS)

    Prakash, T.; Ramasamy, S.; Murty, B. S.

    2013-03-01

    Grain boundary effect on the room temperature dielectric behavior in mechanically alloyed nanocrystalline CuAlO2 has been investigated using impedance spectroscopy under the applied DC bias voltages 0 V to 4.8 V in a periodic interval of 0.2 V. Analysis of impedance data confirms the existence of double Schottky potential barrier heights ( Φ b ) between two adjacent grains (left and right side) with grain boundary and its influences in dielectric relaxation time ( τ), dielectric constant ( ɛ') and dielectric loss (tan δ) factor. Also, clear evidence on the suppression of Φ b was demonstrated in the higher applied bias voltages with the parameter τ. At equilibrium state, τ is 0.63 ms and it was reduced to 0.13 ms after the 3.2 V applied DC bias. These observed DC bias voltage effects are obeying `brick layer model' and also elucidates Φ b is playing a crucial role in controlling dielectric properties of nanomaterials.

  9. Photocatalysis applications of some hybrid polymeric composites incorporating TiO2 nanoparticles and their combinations with SiO2/Fe2O3

    PubMed Central

    Buruiana, Tinca; Melinte, Violeta; Buruiana, Emil C

    2017-01-01

    Polymer nanocomposites containing titanium oxide nanoparticles (TiO2 NPs) combined with other inorganic components (Si–O–Si or/and γ-Fe2O3) were prepared by the dispersion of premade NPs (nanocrystalline TiO2, TiO2/SiO2, TiO2/Fe2O3, TiO2/SiO2/Fe2O3) within a photopolymerizable urethane dimethacrylate (polytetrahydrofuran-urethane dimethacrylate, PTHF-UDMA). The physicochemical characterization of nanoparticles and hybrid polymeric composites with 10 wt % NPs (S1–S4) was realized through XRD, TEM and FTIR analyses. The mean size (10–30 nm) and the crystallinity of the NPs varied as a function of the inorganic constituent. The catalytic activity of these hybrid films was tested for the photodegradation of phenol, hydroquinone and dopamine in aqueous solution under UV or visible-light irradiation. The best results were obtained for the films with TiO2/Fe2O3 or TiO2/SiO2/Fe2O3 NPs. The degradation of the mentioned model pollutants varied between 71% and 100% (after 250 min of irradiation) depending on the composition of the hybrid film tested and the light applied (UV–visible light). Also, it was established that such hybrid films can be reused at least for five cycles, without losing too much of the photocatalytic efficiency (ca. 7%). These findings could have implications in the development of new nanocatalysts. PMID:28243566

  10. Interaction of Ce{sub 1−x}Er{sub x}O{sub 2−y} nanoparticles with SiO{sub 2}-effect of temperature and atmosphere

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

    Kepinski, L., E-mail: L.Kepinski@int.pan.wroc.pl; Krajczyk, L.; Mista, W.

    2014-01-15

    Morphology, microstructure and phase evolution of homogeneous, nanocrystalline Ce{sub 1−x}Er{sub x}O{sub 2−x/2} mixed oxide (x=0.3 and 0.5), prepared by microemulsion method, supported on amorphous SiO{sub 2} was studied in oxidizing and reducing atmosphere by XRD, TEM, SEM-EDS and N{sub 2} adsorption. The system is structurally and chemically stable in the oxidizing atmosphere up to 1000 °C, exhibiting only a small increase of the mean crystallite size of the oxide to ∼4 nm. At 1100 °C formation of Er silicate with unusual structure isomorphic with y-Y{sub 2}Si{sub 2}O{sub 7} (yttrialite), stabilized by Ce{sup 4+} ions was observed. In the reducing atmospheremore » the Ce{sub 1−x}Er{sub x}O{sub 2−x/2} reacted with SiO{sub 2} already at 900 °C, due to high affinity of the reduced Ce{sup 3+} to form a silicate phase. At higher temperature the silicate crystallized into the tetragonal, low temperature A-(Ce{sub 1−x}Er{sub x}){sub 2}Si{sub 2}O{sub 7} polymorph. Such systems, containing nanocrystalline silicate particles with Er{sup 3+} ions placed in well defined sites embedded in silica matrix, may be interesting as highly efficient active components of optical waveguides amplifiers integrated with Si microelectronics. The nanocrystalline Ce–Er–O/SiO{sub 2} system prepared by the impregnation of the silica with the aqueous solution of nitrates appeared to be chemically inhomogeneous and less stable in both oxidising and reducing atmosphere. - Graphical abstract: Structure evolution of Ce{sub 0.5}Er{sub 0.5}O{sub 1.75} in air and in H{sub 2}. Display Omitted - Highlights: • Homogeneous 3 nm Ce{sub 1−x}Er{sub x}O{sub 2−y} particles were prepared and uniformly dispersed on SiO{sub 2}. • Er diffusion to SiO{sub 2} determines the stability of the mixed oxide in air to ∼1000 °C. • Spreading of Ce{sub 1−x}Er{sub x}O{sub 2−y} onto SiO{sub 2} occurs in hydrogen at 900 °C. • Nanocrystalline A-(Ce,Er){sub 2}Si{sub 2}O{sub 7} silicate

  11. Dual-wavelength Nd:CaLnAlO4 lasers at 1.365 and 1.390 μm

    NASA Astrophysics Data System (ADS)

    Loiko, Pavel; Maria Serres, Josep; Mateos, Xavier; Xu, Xiaodong; Xu, Jun; Griebner, Uwe; Petrov, Valentin; Aguiló, Magdalena; Díaz, Francesc; Major, Arkady

    2018-02-01

    Tetragonal calcium rare-earth aluminates, CaLnAlO4, are attractive laser host crystals. The emission of Nd3+ ions at 1.3- 1.4 μm due to the 4F3/2 -> 4I13/2 transition is of interest for medicine, fiber optics, and light conversion. We report on compact Nd:CaLnAlO4 lasers using a plane-plane cavity. With an a-cut 0.8 at.% Nd:CaYAlO4 crystal diode-pumped at 802 nm, a maximum continuous-wave output power of 365 mW was achieved at 1.365 & 1.390 μm corresponding to the σ-polarization. The 4F3/2 -> 4I13/2 laser performance of the Nd:CaLnAlO4 crystals was compared to that from a monoclinic Nd:KGd(WO4)2. At the 4F3/2-> 4I11/2 transition (1.08 μm), a Nd:CaYAlO4 micro-laser generated multi-watt output (>4 W) with a slope efficiency of 39%.

  12. Synthesis of Copper-Based Nanostructured Catalysts on SiO2-Al2O3, SiO2-TiO2, and SiO2-ZrO2 Supports for NO Reduction.

    PubMed

    Namkhang, Pornpan; Kongkachuichay, Paisan

    2015-07-01

    The selective catalytic reduction of NO over a series of Cu-based catalysts supported on modified silica including SiO2-Al2O3, SiO2-TiO2, and SiO2-ZrO2 prepared via a sol-gel process and a flame spray pyrolysis (FSP) was studied. The prepared catalysts were characterized by means of TEM, XRD, XRF, TPR, and nitrogen physisorption measurement techniques, to determine particle diameter, morphology, crystallinity, phase composition, copper reducibility, surface area, and pore size of catalysts. The particles obtained from sol-gel method were almost spherical while the particles obtained from the FSP were clearly spherical and non-porous nanosized particles. The effects of Si:Al, Si:Ti, and Si:Zr molar ratio of precursor were identified as the domain for different crystalline phase of materials. It was clearly seen that a high SiO2 content inhibited the crystallization of materials. The BET surface area of catalysts obtained from sol-gel method was higher than that from the FSP and it shows that surface area increased with increasing SiO2 molar ratio due to high surface area from SiO2. The catalyst performances were tested for the selective catalytic reduction of NO with H2. It was found that the catalyst prepared over 7 wt% Cu on Si02-Al2O3 support was the most active compared with the others which converted NO as more than 70%. Moreover, the excess copper decreased the performance of NO reduction, due to the formation of CuO agglomeration covered on the porous silica as well as the alumina surface, preventing the direct contact of CO2 and AL2O3.

  13. Effect of V-Nd co-doping on phase transformation and grain growth process of TiO2

    NASA Astrophysics Data System (ADS)

    Khatun, Nasima; Amin, Ruhul; Anita, Sen, Somaditya

    2018-05-01

    The pure and V-Nd co-doped TiO2 samples are prepared by the modified sol-gel process. The phase formation is confirmed by XRD spectrum. Phase transformation is delayed in V-Nd co-doped TiO2 (TVN) samples compared to pure TiO2. The particle size is comparatively small in TVN samples at both the temperature 450 °C and 900 °C. Hence the effect of Nd doping is dominated over V doping in both phase transformation and grain growth process of TiO2.

  14. Structure, ferroelectric ordering, and semiempirical quantum calculations of lanthanide based metal-organic framework: [Nd(C4H5O6)(C4H4O6)][3H2O

    NASA Astrophysics Data System (ADS)

    Ahmad, Bhat Zahoor; Want, Basharat

    2016-04-01

    We investigate the structure and ferroelectric behavior of a lanthanide based metal-organic framework (MOF), [Nd(C4H5O6)(C4H4O6)][3H2O]. X-ray crystal structure analyses reveal that it crystallizes in the P41212 space group with Nd centres, coordinated by nine oxygen atoms, forming a distorted capped square antiprismatic geometry. The molecules, bridged by tartrate ligands, form a 2D chiral structure. The 2D sheets are further linked into a 3D porous framework via strong hydrogen-bonding scheme (O-H…O2.113 Å). Dielectric studies reveal two anomalies at 295 K and 185 K. The former is a paraelectric-ferroelectric transition, and the later is attributed to the freezing down of the motion of the hydroxyl groups. The phase transition is of second order, and the spontaneous polarization in low temperature phase is attributed to the ordering of protons of hydroxyl groups. The dielectric nonlinearity parameters have been calculated using Landau- Devonshire phenomenological theory. In addition, the most recent semiempirical models, Sparkle/PM7, Sparkle/RM1, and Sparkle/AM1, are tested on the present system to assay the accuracy of semiempirical quantum approaches to predict the geometries of solid MOFs. Our results show that Sparkle/PM7 model is the most accurate to predict the unit cell structure and coordination polyhedron geometry. The semiempirical methods are also used to calculate different ground state molecular properties.

  15. Crystalline and magnetooptical characteristics of (Tb,Bi)3(Fe,Ga)5O12 deposited on (Y,Nd)3Al5O12

    NASA Astrophysics Data System (ADS)

    Morimoto, Ryohei; Goto, Taichi; Nakamura, Yuichi; Boey Lim, Pang; Uchida, Hironaga; Inoue, Mitsuteru

    2018-06-01

    We prepared Bi- and Ga-substituted Tb3Fe5O12 (BiGa:TIG) films on a Nd-substituted Y3Al5O12 (Nd:YAG) single crystal substrate by pulsed laser deposition, and investigated their magnetic, optical, and magnetooptical properties. A BiGa:TIG film deposited with a substrate temperature of 700 °C shows the easy axis of magnetization along the out-of-plane direction of the film and the Faraday rotation angle of 900°/cm at a wavelength of 1064 nm. The epitaxial growth of the film is confirmed by X-ray diffraction analysis.

  16. Fabrication of GaN doped ZnO nanocrystallines by laser ablation.

    PubMed

    Gopalakrishnan, N; Shin, B C; Bhuvana, K P; Elanchezhiyan, J; Balasubramanian, T

    2008-08-01

    Here, we present the fabrication of pure and GaN doped ZnO nanocrystallines on Si(111) substrates by KrF excimer laser. The targets for the ablation have been prepared by conventional ceramic method. The fabricated nanocrystallines have been investigated by X-ray diffraction, photoluminescence and atomic force microscopy. The X-ray diffraction analysis shows that the crystalline size of pure ZnO is 36 nm and it is 41 nm while doped with 0.8 mol% of GaN due to best stoichiometry between Zn and O. Photoluminescence studies reveal that intense deep level emissions have been observed for pure ZnO and it has been suppressed for the GaN doped ZnO structures. The images of atomic force microscope show that the rms surface roughness is 27 nm for pure ZnO and the morphology is improved with decrease in rms roughness, 18 nm with fine crystallines while doped with 1 mol% GaN. The improved structural, optical and morphological properties of ZnO nanocrystalline due to GaN dopant have been discussed in detail.

  17. Effect of microstructural features on the laser efficiency of Nd{sup 3+}:Y{sub 3}Al{sub 5}O{sub 12} ceramics

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

    Vorona, I O; Yavetskiy, R P; Tolmachev, A V

    2015-09-30

    The optical properties and microstructure of transparent Nd{sup 3+}:Y{sub 3}Al{sub 5}O{sub 12} ceramics synthesised by different reactive sintering routes are studied. It is found that the residual porosity of optical ceramics is directly related to the homogeneity of the microstructure of initial compacts, which can be estimated by the existence of particle agglomerates larger than 1 mm in initial nanopowders. A qualitative correlation is established between the residual porosity, the optical losses and the lasing slope efficiency of Nd{sup 3+}:Y{sub 3}Al{sub 5}O{sub 12} ceramics. The maximum laser efficiency (η = 49%) was observed in the samples with the lowest porositymore » (2.3 × 10{sup -3} vol %). (lasers)« less

  18. Enhancement of activity and sulfur resistance of CeO2 supported on TiO2-SiO2 for the selective catalytic reduction of NO by NH3.

    PubMed

    Liu, Caixia; Chen, Liang; Li, Junhua; Ma, Lei; Arandiyan, Hamidreza; Du, Yu; Xu, Jiayu; Hao, Jiming

    2012-06-05

    A series of novel metal-oxide-supported CeO(2) catalysts were prepared via the wet impregnation method, and their NH(3)-SCR activities were investigated. The Ce/TiO(2)-SiO(2) catalyst with a Ti/Si mass ratio of 3/1 exhibited superior NH(3)-SCR activity and high N(2) selectivity in the temperature range of 250-450 °C. The characterization results revealed that the activity enhancement was correlated with the properties of the support material. Cerium was highly dispersed on the TiO(2)-SiO(2) binary metal oxide support, and the interaction of Ti and Si resulted in greater conversion of Ce(4+) to Ce(3+) on the surface of the catalyst compared to that on the single metal oxide supports. As a result of in the increased number of acid sites on Ce/TiO(2)-SiO(2) that resulted from the addition of SiO(2), the NH(3) adsorption capacity was significantly improved. All of these factors played significant roles in the high SCR activity. More importantly, Ce/TiO(2)-SiO(2) exhibited strong resistance to SO(2) and H(2)O poisoning. After the addition of SiO(2), the number of Lewis-acid sites was not decreased, but the number of Brønsted-acid sites on the TiO(2)-SiO(2) carrier was increased. The introduction of SiO(2) further weakened the alkalinity over the surface of the Ce/TiO(2)-SiO(2) catalyst, which resulted in sulfate not easily accumulating on the surface of the Ce/TiO(2)-SiO(2) catalyst in comparison with Ce/TiO(2).

  19. Synthesis and characterization of molybdenum catalysts supported on {gamma}-Al{sub 2}O{sub 3}-CeO{sub 2} composite oxides

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

    Farooq, Muhammad; Ramli, Anita; Subbarao, Duvvuri

    2012-09-26

    The physical and chemical properties of a catalyst play a vital role in various industrial applications. Molybdenum catalysts supported on {gamma}-Al{sub 2}O{sub 3} and {gamma}-Al{sub 2}O{sub 3}-CeO{sub 2} mixed oxides with varying loading of CeO{sub 2} (5, 10, 15, 20 wt% with respect to {gamma}-Al{sub 2}O{sub 3}) were prepared by wet impregnation method. The physiochemical properties of these synthesized Mo catalysts were studied with various characterization techniques such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR), field emission scanning electron microscopy-energy dispersive analysis (FESEM-EDX) and X-ray fluorescence spectrometer (XRF). The results showed that the addition of CeO{submore » 2} into the support affected the binding energies of the elements and reducibility of the metal oxides formed after calcination of catalyst samples due to the change in metal-support interaction. Further, the characterization techniques showed that the active metal was well dispersed on the surface of support material.« less

  20. Home-made experiment of Dye-sensitized TiO2 Nanocrystalline Solar Cells and its education evaluation

    NASA Astrophysics Data System (ADS)

    Tai, M. F.; Shieh, M. C.; Chen, T. W.

    2010-03-01

    Dyes extracted from some natural fruits including anthocyanins absorb sunlight and effectively activate electrons of anthocyanins. Thus these activated electrons are conducted between TiO2 nanocrystals and form electric potential and current between two electrodes. The dyes can be gotten from the natural fruits, such as blackberries, raspberry, pomegranate seeds and bing cherries. This principle permits making a dye sensitized TiO2 nanocrystallines solar cell (DSSC). All required materials and tools for fabricating a home- made DSSC are easy to obtain around home. The procedures are perfect hands-on experiment as well as demonstration in K-12 schools or home settings. We have designed several protocols for fabricating DSSC and have successfully demonstrated in more than 100 activities with different level students. K-12 Students were able to build their own working DSSC's within 2-3 hours sessions and learned about alternative energy sources. These experiments can inspire students and general public about the modern technology in daily life. Low cost (low than US 3 in Taiwan)and safety are also ensured in our DSSC experiments.

  1. Enhanced luminescence in Eu-doped ZnO nanocrystalline films

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

    Suzuki, Keigo, E-mail: ksuzuki@murata.com; Murayama, Koji; Tanaka, Nobuhiko

    We found an enhancement of Eu{sup 3+} emissions in Eu-doped ZnO nanocrystalline films fabricated by microemulsion method. The Eu{sup 3+} emission intensities were increased by reducing annealing temperatures from 633 K to 533 K. One possible explanation for this phenomenon is that the size reduction enhances the energy transfer from ZnO nanoparticles to Eu{sup 3+} ions. Also, the shift of the charge-transfer band into the low-energy side of the absorption edge is found to be crucial, which seems to expedite the energy transfer from O atoms to Eu{sup 3+} ions. These findings will be useful for the material design of Eu-doped ZnOmore » phosphors.« less

  2. The chemical and catalytic properties of nanocrystalline metal oxides prepared through modified sol-gel synthesis

    NASA Astrophysics Data System (ADS)

    Carnes, Corrie Leigh

    The goal of this research was to synthesize, characterize and study the chemical properties of nanocrystalline metal oxides. Nanocrystalline (NC) ZnO, CuO, NiO, Al2O3, and the binary Al2O 3/MgO and ZnO/CuO were prepared through modified sol gel methods. These NC metal oxides were studied in comparison to the commercial (CM) metal oxides. The samples were characterized by XRD, TGA, FTIR, BET, and TEM. The NC samples were all accompanied by a significant increase in surface area and decrease in crystallite size. Several chemical reactions were studied to compare the NC samples to the CM samples. One of the reactions involved a high temperature reaction between carbon tetrachloride and the oxide to form carbon dioxide and the corresponding metal chloride. A similar high temperature reaction was conducted between the metal oxide and hydrogen sulfide to form water and the corresponding metal sulfide. A room temperature gas phase adsorption was studied where SO2 was adsorbed onto the oxide. A liquid phase adsorption conducted at room temperature was the destructive adsorption of paraoxon (a toxic insecticide). In all reactions the NC samples exhibited greater activity, destroying or adsorbing a larger amount of the toxins compared to the CM samples. To better study surface area effects catalytic reactions were also studied. The catalysis of methanol was studied over the nanocrystalline ZnO, CuO, NiO, and ZnO/CuO samples in comparison to their commercial counterparts. In most cases the NC samples proved to be more active catalysts, having higher percent conversions and turnover numbers. A second catalytic reaction was also studied, this reaction was investigated to look at the support effects. The catalysis of cyclopropane to propane was studied over Pt and Co catalysts. These catalysts were supported onto NC and CM alumina by impregnation. By observing differences in the catalytic behavior, support effects have become apparent.

  3. Influence of neodymium concentration on excitation and emission properties of Nd doped gallium oxide nanocrystalline films

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

    Podhorodecki, A.; Banski, M.; Misiewicz, J.

    Gallium oxide and more particularly {beta}-Ga{sub 2}O{sub 3} matrix is an excellent material for new generation of devices electrically or optically driven as it is known as the widest band gap transparent conductive oxide. In this paper, the optical properties of neodymium doped gallium oxide films grown by magnetron sputtering have been analyzed. The influence of the Nd ions concentration on the excitation/emission mechanisms of Nd ions and the role of gallium oxide matrix have been investigated. The grain size reduction into gallium oxide films have been observed when concentration of Nd increases. It has been found for all samplesmore » that the charge transfer is the main excitation mechanism for Nd ions where defect states play an important role as intermediate states. As a consequence Nd emission efficiency increases with temperature giving rise to most intensive emission at 1087 nm at room temperature.« less

  4. Ilyukhinite (H3O,Na)14Ca6Mn2Zr3Si26O72(OH)23H2O, a New Mineral of the Eudialyte Group

    NASA Astrophysics Data System (ADS)

    Chukanov, N. V.; Rastsvetaeva, R. K.; Rozenberg, K. A.; Aksenov, S. M.; Pekov, I. V.; Belakovsky, D. I.; Kristiansen, R.; Van, K. V.

    2017-12-01

    A new eudialyte-group mineral, ilyukhinite, ideally (H3O,Na)14Ca6Mn2Zr3Si26O72(OH)2 · 3H2O, has been found in peralkaline pegmatite at Mt. Kukisvumchorr, Khibiny alkaline pluton, Kola Peninsula, Russia. It occurs as brownish orange, with vitreous luster anhedral grains up to 1 mm across in hydrothermally altered peralkaline rock, in association with aegirine, murmanite, albite, microcline, rhabdophane-(Ce), fluorite, sphalerite and molybdenite. The Mohs hardness is 5; cleavage is not observed. D meas 2.67(2), D calc 2.703 g/cm3. Ilyukhinite is optically uniaxial (-): ω = 1.585(2), ɛ = 1.584(2). The IR spectrum is given. The average chemical composition of ilyukhinite (wt %; electron microprobe, ranges given in parentheses; H2O determined by gas chromatography) is as follows: 3.07 (3.63-4.43) Na2O, 0.32 (0.28-0.52) K2O, 10.63 (10.26-10.90) CaO, 3.06 (2.74-3.22) MnO, 1.15 (0.93-1.37) FeO, 0.79 (0.51-0.89) La2O3, 1.21 (0.97-1.44) Ce2O3, 0.41 (0.30-0.56) Nd2O3, 0.90 (0.77-1.12) TiO2, 10.94 (10.15-11.21) ZrO2, 1.40 (0.76-1.68) Nb2O5, 51.24 (49.98-52.28) SiO2, 1.14 (0.89-1.37) SO3, 0.27 (0.19—0.38) Cl, 10.9(5 )H2O,-0.06-O = C1, total is 98.27. The empirical formula is H36.04(Na3.82K0.20)(Ca5.65Ce0.22La0.14Nd0.07)(Mn1.285Fe0.48)(Zr2.645Ti0.34)Nb0.31Si25.41S0.42Cl0.23O86.82. The crystal structure has been solved ( R = 0.046). Ilyukhinite is trigonal, R3 m; a = 14.1695(6) Å, b = 31.026(1) Å, V = 5394.7(7) Å3, Z = 3. The strongest XRD reflections [ d, Å (I, %) ( hkl)] are 11.44 (82) (101), 7.09 (70) (110), 6.02 (44) (021), 4.371 (89) 205), 3.805 (47) (303, 033), 3.376 (41) (131), 2.985 (100) (315, 128), 2.852 (92) (404). Ilyukhinite was named in memory of Vladimir V. Ilyukhin (1934-1982), an outstanding Soviet crystallographer. The type specimen of ilyukhinite has been deposited in the collection of the Natural History Museum, University of Oslo, Norway.

  5. Structural, Optical and Impedance Spectroscopic Characterizations of Nanocrystalline A2Ti2Zr5O16 (A = Mg, Ca, Ba and Sr)

    NASA Astrophysics Data System (ADS)

    Sandeep, K.; Thomas, Jijimon K.; Solomon, Sam

    2018-04-01

    A nanocrystalline A2Ti2Zr5O16 (A = Mg, Ca, Ba and Sr) system has been synthesized by a modified combustion technique. The cation-deficient calzirtite (Ca2Ti2Zr5O16) is found to be a tetragonal structure with the space group I4(1)/acd. The average size of the particle from the transmission electron microscopy image is estimated to be 23.30 nm and 20.16 nm for Ca2Ti2Zr5O16 and Ba2Ti2Zr5O16, respectively. The optical bandgap calculated using a Tauc plot is between 3.01 eV and 3.46 eV. Raman and Fourier transform infrared spectroscopy (FTIR) studies were carried out to confirm the phase purity of the sample. The scanning electron microscopy (SEM) image of a Ca2Ti2Zr5O16 sample sintered at 1360°C for 3 h shows minimum porosity with 96% of the theoretical density. The frequency-dependent dielectric study shows that the dielectric constant is maximized at low frequencies and decreases as the frequency increases. The Cole-Cole plot reveals that the material exhibits conduction due to the contributions of grain, grain boundary and electrode effects. The photoluminescence spectra of the samples were recorded and the transitions causing emission have been identified.

  6. Gas response properties of citrate gel synthesized nanocrystalline MgFe{sub 2}O{sub 4}: Effect of sintering temperature

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

    Patil, J.Y.; Mulla, I.S.; Suryavanshi, S.S., E-mail: sssuryavanshi@rediffmail.com

    2013-02-15

    Graphical abstract: Display Omitted Highlights: ► Synthesis of nanocrystalline MgFe{sub 2}O{sub 4} by economical citrate gel combustion method. ► Structural, morphological, and gas response properties of MgFe{sub 2}O{sub 4}. ► Enhancement in selectivity of MgFe{sub 2}O{sub 4} towards LPG with sintering temperature. ► Use of MgFe{sub 2}O{sub 4} to detect different gases at different operating temperatures. -- Abstract: Spinel type MgFe{sub 2}O{sub 4} material was synthesized by citrate gel combustion method. The effect of sintering temperature on structural, morphological, and gas response properties was studied. The powder X-ray diffraction pattern and transmission electron microscope study confirms nanocrystalline spinel structure ofmore » the synthesized powder. The material was tested for response properties to various reducing gases like liquid petroleum gas (LPG), acetone, ethanol, and ammonia. The results demonstrated n-type semiconducting behavior of MgFe{sub 2}O{sub 4} material. It was revealed that MgFe{sub 2}O{sub 4} sintered at 973 K was most sensitive to LPG at 648 K and to acetone at 498 K. However MgFe{sub 2}O{sub 4} sintered at 1173 K exhibited higher response and selectivity to LPG with marginal increase in the operating temperature. Furthermore, the sensor exhibited a fast response and a good recovery. It was observed that the particles size, porosity, and surface activity of the sensor material is affected by the sintering temperature.« less

  7. New insight into singlet oxygen generation at surface modified nanocrystalline TiO2--the effect of near-infrared irradiation.

    PubMed

    Buchalska, Marta; Labuz, Przemysław; Bujak, Łukasz; Szewczyk, Grzegorz; Sarna, Tadeusz; Maćkowski, Sebastian; Macyk, Wojciech

    2013-07-14

    The generation of singlet oxygen in aqueous colloids of nanocrystalline TiO2 (anatase) modified by organic chelating ligands forming surface Ti(IV) complexes was studied. Detailed studies revealed a plausible and to date unappreciated influence of near-infrared irradiation on singlet oxygen generation at the surface of TiO2. To detect (1)O2, direct and indirect methods have been applied: a photon counting technique enabling time-resolved measurements of (1)O2 phosphorescence, and fluorescence measurements of a product of singlet oxygen interaction with Singlet Oxygen Sensor Green (SOSG). Both methods proved the generation of (1)O2. Nanocrystalline TiO2 modified with salicylic acid appeared to be the most efficient photosensitizer among the tested materials. The measured quantum yield reached the value of 0.012 upon irradiation at 355 nm, while unmodified TiO2 colloids appeared to be substantially less efficient generators of singlet oxygen with the corresponding quantum yield of ca. 0.003. A photocatalytic degradation of 4-chlorophenol, proceeding through oxidation by OH˙, was also monitored. The influence of irradiation conditions (UV, vis, NIR or any combination of these spectral ranges) on the generation of both singlet oxygen and hydroxyl radicals has been tested and discussed. Simultaneous irradiation with visible and NIR light did not accelerate OH˙ formation; however, for TiO2 modified with catechol it influenced (1)O2 generation. Singlet oxygen is presumably formed according to Nosaka's mechanism comprising O2˙(-) oxidation with a strong oxidant (hole, an oxidized ligand); however, the energy transfer from NIR-excited titanium(iii) centers (trapped electrons) plays also a plausible role.

  8. Magnetic texturing due to the partial ordering of Fe+3 and Cu+2 in NdBaCuFeO5

    NASA Astrophysics Data System (ADS)

    Pissas, M.

    2017-06-01

    The crystal and magnetic structure of the oxygen deficient double perovskite NdBaCuFeO5 was studied, using neutron powder diffraction data. The structure was refined from neutron powder diffraction data using the space groups P 4 / mmm and P 4 mm . For 2K ⩽ T ⩽TN2 = 260K three families of magnetic Bragg peaks exist. These peaks can be indexed with commensurate propagation vectors k1 =[1/2 1/2 1/2], k2 =[1/2 1/2 0] and the incommensurate k3 =[1/2 1/2 0.4]. Above TN2 only magnetic Bragg peaks originated from k1 and k2 propagation, were observed. The incommensurate magnetic structure can be attributed to a circular inclined spiral ordering as in YBaCuFeO5 compound.

  9. Phase separation, crystallization and polyamorphism in the Y2O3 Al2O3 system

    NASA Astrophysics Data System (ADS)

    Skinner, Lawrie B.; Barnes, Adrian C.; Salmon, Philip S.; Crichton, Wilson A.

    2008-05-01

    A detailed study of glass formation from aerodynamically levitated liquids in the (Y2O3)x(Al2O3)1-x system for the composition range 0.21<=x<=0.41 was undertaken by using pyrometric, optical imaging and x-ray diffraction methods. Homogeneous and clear single-phase glasses were produced over the composition range 0.27 \\lesssim x \\lesssim 0.33 . For Y2O3-rich compositions (0.33 \\lesssim x \\le 0.375 ), cloudy materials were produced which contain inclusions of crystalline yttrium aluminium garnet (YAG) of diameter up to 40 µm in a glassy matrix. For Y2O3-poor compositions around x = 0.24, cloudy materials were also produced, but it was not possible to deduce whether this resulted from (i) sub-micron inclusions of a nano-crystalline or glassy material in a glassy matrix or (ii) a glass formed by spinodal decomposition. For x = 0.21, however, the sample cloudiness results from crystallization into at least two phases comprising yttrium aluminium perovskite and alumina. The associated pyrometric cooling curve shows slow recalescence events with a continuous and slow evolution of excess heat which contrasts with the sharp recalescence events observed for the crystallization of YAG at compositions near x = 0.375. The materials that are the most likely candidates for demonstrating homogeneous nucleation of a second liquid phase occur around x = 0.25, which corresponds to the limit for formation of a continuous random network of corner-shared AlO4 tetrahedra.

  10. Thermopower and magnetocaloric properties in NdSrMnO/CrO3 composites

    NASA Astrophysics Data System (ADS)

    Ahmed, A. M.; Mohamed, H. F.; Paixão, J. A.; Mohamed, Sara A.

    2018-06-01

    The thermoelectric power (TEP) and magnetocaloric effect (MCE) for (Nd0.6Sr0.4MnO3)1-x/(CrO3)x composites have been measured. The TEP measurements show a negative sign value of the Seebeck coefficient (S), in microvolts. TEP data construe in the low range of temperature by the magnon and phonon drag model, whereas at high temperature by small polaron conduction mechanism. Magnetic measurements exhibit that all composites show a paramagnetic-ferromagnetic transition with decreasing temperature. The Arrott plots of composites reveal the occurrence of a second order phase transition. The maximum value of magnetic entropy change (ΔS) is 2.37 J kg-1 K-1, achieved fore the composite with x = 0.015. Moreover, the maximum value of relative cooling power (RCP) is 122.1 J kg-1, achieved for the composite with x = 0.020. These composites may be appropriate for magnetic application near room temperature.

  11. Understanding the magnetic behavior of heat treated CaO-P2O5-Na2O-Fe2O3-SiO2 bioactive glass using electron paramagnetic resonance studies

    NASA Astrophysics Data System (ADS)

    Shankhwar, Nisha; Kothiyal, G. P.; Srinivasan, A.

    2014-09-01

    Bioactive glass of composition 41CaO-44SiO2-4P2O5-8Fe2O3-3Na2O has been heat treated in the temperature (TA) range of 750-1150 °C for time periods (tA) ranging from 1 h to 3 h to yield magnetic bioactive glass ceramics (MBCs). X-ray diffraction studies indicate the presence of bone mineral (hydroxyapatite and wollastonite) and magnetic (magnetite and α-hematite) phases in nanocrystalline form in the MBCs. Electron paramagnetic resonance (EPR) study was carried out to understand the variation in saturation magnetization and coercivity of the MBCs with TA and tA. These studies reveal the nature and amount of iron ions present in the MBCs and their interaction in the glassy oxide matrix as a function of annealing parameters. The deterioration in the magnetic properties of the glass heat treated above 1050 °C is attributed to the crystallization of the non-magnetic α-hematite phase. These results are expected to be useful in the application of these MBCs as thermoseeds in hyperthermia treatment of cancer.

  12. Nanocrystalline SnO2 formation using energetic ion beam.

    PubMed

    Mohanty, T; Batra, Y; Tripathi, A; Kanjilal, D

    2007-06-01

    Nanocrystalline tin oxide (SnO2) thin films grown by RF magnetron sputtering technique were characterized by UV-Visible absorption spectroscopy and Photoluminescence spectroscopy. From atomic force microscopic (AFM) and Glancing angle X-ray diffraction (GAXRD) measurements, the radius of grains was found to be approximately 6+/-2 nm. The thin films were bombarded with 250 keV Xe2+ ion beam to observe the stability of nanophases against radiation. For ion bombarded films, optical absorption band edge is shifted towards red region. Atomic force microscopy studies show that the radius of the grains was increased to approximately 8 +/- 1 nm and the grains were nearly uniform in size. The size of the grains has been reduced after ion bombardment in the case of films grown on Si. During this process, defects such as vacancies, voids were generated in the films as well as in the substrates. Ion bombardment induces local temperature increase of thin films causing melting of films. Ion beam induced defects enhances the diffusion of atoms leading to uniformity in size of grains. The role of matrix on ion beam induced grain growth is discussed.

  13. Controlling the preferential orientation in sol-gel prepared CaCu3Ti4O12 thin films by LaAlO3 and NdGaO3 substrates

    NASA Astrophysics Data System (ADS)

    Pongpaiboonkul, Suriyong; Kasa, Yumairah; Phokharatkul, Ditsayut; Putasaeng, Bundit; Hodak, Jose H.; Wisitsoraat, Anurat; Hodak, Satreerat K.

    2016-11-01

    Researchers have paid considerable attention to CaCu3Ti4O12 (CCTO) due to the colossal dielectric constant over a wide range of frequency and temperature. Despite of the growing number of works dealing with CCTO, there have been few studies of the role played by the substrate in inducing structural and dielectric effects of this material. In this work, highly-oriented CCTO thin films have been deposited on LaAlO3(100), NdGaO3(100) and NdGaO3(110) substrates using a sol-gel method. These single crystal substrates were chosen in terms of small lattice mismatch between CCTO and the substrate. The X-ray diffraction patterns showed that the CCTO film layers grow with different orientations depending upon the substrate used. We show that the preferred orientation of CCTO thin films can be manipulated to a high degree by growing it on specific crystal planes of the substrates without the use of buffer layers. Colossal dielectric constants are observed in our films which appear to correlate with the film crystallinity and preferred orientation.

  14. Secondary ion mass spectrometric investigation on ruthenium oxide systems: a comparison between poly- and nanocrystalline deposits

    PubMed

    Barison; Barreca; Daolio; Fabrizio; Piccirillo

    2000-01-01

    The influence of different RuO(2) crystallite sizes was investigated by secondary ion mass spectrometry (SIMS) on the oxide deposited on various support materials (Ni, Ti, Al(2)O(3), oxidized Si(100)). In order to examine the effect of an oxidic environment on the film structure, RuO(2) 20%-TiO(2) 80% at. mixed oxide was deposited on Ti. The polycrystalline coatings were prepared by heating the Ru (and Ti)-containing solution dropped on the supports.1 RuO(2) nanocrystalline coatings were grown by chemical vapor deposition (CVD) from Ru(COD)(eta(3)-allyl)(2).2 The identification of mixed oxide clusters showed the higher reactivity of Ni and Al(2)O(3) over the other substrates. Diffusion and migration characteristics were observed to be influenced by the nature of the support. The results are complementary to those of a previous SIMS investigation.3 Copyright 2000 John Wiley & Sons, Ltd.

  15. Momentum density and Fermi surface of Nd2-xCexCuO4-δ

    NASA Astrophysics Data System (ADS)

    Shukla, A.; Barbiellini, B.; Hoffmann, L.; Manuel, A. A.; Sadowski, W.; Walker, E.; Peter, M.

    1996-02-01

    High-temperature positron two-dimensional angular correlation of annihilation radiation (2D-ACAR) measurements have recently been succesfully applied to map parts of the Fermi surface of YBa2Cu3O7-δ. Using the same principle, we have been able to observe with a bulk sensitive method, the Fermi surface of Nd2-xCexCuO4-δ. Although positron trapping by defects and correlation effects are strong, positron 2D-ACAR measurements provide a signal from the Fermi surface which agrees with band-structure calculations, confirming earlier surface sensitive photoemission experiments.

  16. Highly efficient passive mode locking of Nd:Lu2.9Gd0.1Al5O12 garnet crystal

    NASA Astrophysics Data System (ADS)

    Di, J. Q.; Xu, X. D.; Xia, C. T.; Tan, W. D.; Zhang, J.; Tang, D. Y.; Li, D. Z.; Zhou, D. H.; Wu, F.; Xu, J.

    2013-05-01

    Passive mode locking of Nd:Lu2.9Gd0.1Al5O12 (Nd:LuGdAG) crystal lasers was experimentally investigated. Stable mode-locked pulses with pulse widths as short as 9.7 ps were obtained for the Nd:LuGdAG crystal; the corresponding maximum output powers were 0.93 W while the mode-locked slope efficiencies were 43%, among the highest efficiencies ever reported for Nd3+ ps lasers. The results demonstrate that Nd:LuGdAG garnet crystal is a promising gain medium for efficient picosecond laser use.

  17. Structural and magnetically enhanced ferroelectric properties of Nd3+ and Fe3+ substituted Pb(Zr0.45Ti0.55)O3 ceramics

    NASA Astrophysics Data System (ADS)

    Kaur, Randeep; Singh, Anupinder

    2018-05-01

    The influence of Nd3+ and Fe3+ substitution on Pb(Zr0.45Ti0.55)O3 composition prepared via solid state reaction route have been studied. The structural evolution was investigated using an X-ray diffraction (XRD). Non perovskite Pb2Ti2O7, ZrO2 and PbO phases were observed along with the rhombohedral phase. The SEM micrograph shows the surface morphology of the samples. The density of the sample was calculated by using Archimedes principle and found to be 8.45g/cm3. The magnetic data depicts the presence of both the ferromagnetic as well as antiferromagnetic character in the solid solution. In ferroelectric studies, the values of remnant polarization (Pr) and coercive field (Ec) enhanced from 2.60 μC/cm2 - 3.44 µC/cm2 and 15.82kV/cm - 22.91kV/cm respectively.

  18. Tailoring the electronic transitions of NdNiO{sub 3} films through (111){sub pc} oriented interfaces

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

    Catalano, S., E-mail: sara.catalano@unige.ch; Gibert, M.; Zubko, P.

    2015-06-01

    Bulk NdNiO{sub 3} and thin films grown along the pseudocubic (001){sub pc} axis display a 1st order metal to insulator transition (MIT) together with a Néel transition at T = 200 K. Here, we show that for NdNiO{sub 3} films deposited on (111){sub pc} NdGaO{sub 3}, the MIT occurs at T = 335 K and the Néel transition at T = 230 K. By comparing transport and magnetic properties of layers grown on substrates with different symmetries and lattice parameters, we demonstrate a particularly large tuning when the epitaxy is realized on (111){sub pc} surfaces. We attribute this effect tomore » the specific lattice matching conditions imposed along this direction when using orthorhombic substrates.« less

  19. Structure and temperature effects on Nd3+ spectra in polycrystalline mixed scandium aluminum garnets Y3ScxAl5-xO12

    NASA Astrophysics Data System (ADS)

    Lupei, A.; Lupei, V.; Hau, S.; Gheorghe, C.; Voicu, F.

    2015-09-01

    New spectroscopic data obtained from high resolution low temperature absorption and emission spectra of Nd3+ in mixed scandium aluminum garnets Y3ScxAl5-xO12 - (x = 0-2) translucent ceramics revealed transition dependent composition effects: modification of the shapes (Lorentz at x = 0 and 2, quasi-Gauss at x = 1, x-dependent asymmetric for other x values, with obvious multicenter structure for low x), widths and shifts of the lines. Nd3+ electronic structure dependence on structural changes with composition is analyzed in terms of nephelauxetic effect and maximum splitting of manifolds: Sc3+ co-doping reduces the nephelauxetic effect, and the increase of 4F3/2 splitting from 85 cm-1 (x = 0) to 98 cm-1 (x = 2) denotes the lowering of local symmetry. The multicenter structure and inhomogeneous broadening of Nd3+ lines is attributed to crystal field distributions determined by the random occupancy of the octahedral sites by Sc3+ and Al3+. For low x (0.2) the resolved two satellites S1, S2 that accompany Nd:YAG lines are correlated to anisotropic crystal field perturbations produced by the n.n. Sc3+ by analogy to those determined by Y3+-antisites (excess of Y3+ ions that enter in octahedral sites of the melt-grown YAG crystals). The temperature evolution of the Nd3+ spectral characteristics (line intensity, shift, broadening) in the 10-300 K range is analyzed in terms of thermal population of the Stark levels, of the effect on electron-phonon interaction and on lattice expansion. The relevance of the spectroscopic properties on the laser emission characteristics in these systems is discussed.

  20. Lanthanide stannate pyrochlores (Ln2Sn2O7; Ln  =  Nd, Gd, Er) at high pressure

    NASA Astrophysics Data System (ADS)

    Turner, Katlyn M.; Tracy, Cameron L.; Mao, Wendy L.; Ewing, Rodney C.

    2017-12-01

    Lanthanide stannate pyrochlores (Ln2Sn2O7; Ln  =  Nd, Gd, and Er) were investigated in situ to 50 GPa in order to determine their structural response to compression and compare their response to that of lanthanide titanate, zirconate, and hafnate pyrochlores. The cation radius ratio of A3+/B4+ in pyrochlore oxides (A2B2O7) is thought to be the dominant feature that influences their response on compression. The ionic radius of Sn4+ is intermediate to that of Ti4+, Zr4+, and Hf4+, but the 〈Sn-O〉 bond in stannate pyrochlore is more covalent than the 〈B-O〉 bonds in titanates, zirconate, and hafnates. In stannates, based on in situ Raman spectroscopy, pyrochlore cation and anion sublattices begin to disorder with the onset of compression, first measured at 0.3 GPa. The extent of sublattice disorder versus pressure is greater in stannates with a smaller Ln3+ cation. Stannate pyrochlores (Fd-3m) begin a sluggish transformation to an orthorhombic, cotunnite-like structure at ~28 GPa similar transitions have been observed in titanate, zirconate, and hafnate pyrochlores at varying pressures (18-40 GPa) with cation radius ratio. The extent of the phase transition versus pressure varies directly with the size of the Ln3+ cation. Post-decompression from ~50 GPa, Er2Sn2O7 and Gd2Sn2O7 adopt a pyrochlore structure, rather than the multi-scale defect-fluorite  +  weberite-type structure adopted by Nd2Sn2O7 that is characteristic of titanate, zirconate, and hafnate pyrochlores under similar conditions. Like pyrochlore titanates, zirconates, and hafnates, the bulk modulus, B 0, of stannates varies linearly and inversely with cation radius ratio from 1 1 1 GPa (Nd2Sn2O7) to 251 GPa (Er2Sn2O7). The trends of bulk moduli in stannates in this study are in excellent agreement with previous experimental studies on stannates and suggest that the size of the Ln3+ cation is the primary determining factor of B 0. Additionally, when normalized to r A

  1. Microscopic treatment of upconversion in Nd3+-doped samples

    NASA Astrophysics Data System (ADS)

    Palatella, Luigi; Cornacchia, Francesco; Toncelli, Alessandra; Tonelli, Mauro

    2003-08-01

    We deal with the analysis of fluorescence decay of metastable manifolds of rare-earth ions in the presence of upconversion processes, with attention focused on Nd3+-doped crystals. In the literature this phenomenon is usually studied by means of rate equations or microscopic treatment. Here we show that only the second approach is correct in our experimental conditions, i.e., when the population dynamics is fast in comparison with the typical migration time τ0, and τ0 is considerably longer than the radiative lifetime. We studied the population dynamics after pulsed-laser excitation of some Nd3+-doped crystals, namely, BaY2F8:Nd3+ at 3.75%, LiYF4:Nd3+ at 1.05%, and KLa(MoO4)2:Nd3+ at 5.3%. We observed that the rate-equation formalism cannot reproduce the experimental data, therefore we used a microscopic treatment that gave much better results. From this analysis, after reaching the saturation regime, we were able to determine the donor-acceptor transfer constant Cda for the samples under investigation in an unconventional way.

  2. Bond-length fluctuations and the spin-state transition in LCoO3 (L=La, Pr, and Nd)

    NASA Astrophysics Data System (ADS)

    Yan, J.-Q.; Zhou, J.-S.; Goodenough, J. B.

    2004-04-01

    The temperature dependence of thermal conductivity, κ(T), and magnetic susceptibility, χ(T), have been measured on single crystals of LCoO3 (L=La, Pr, Nd) grown by the floating-zone method. The susceptibility measurement shows a progressive stabilization of the low-spin (LS) state of Co(III) with decreasing size of the L3+ ion, and the population of excited intermediate-spin (IS) or high-spin (HS) state Co(III) ions begins to increase at 200 K and 300 K for PrCoO3 and NdCoO3 compared with 35 K in LaCoO3. The low-temperature Curie-Weiss paramagnetic susceptibility of LCoO3 is an intrinsic property arising from surface cobalt and, possibly, a LS ground state bearing some IS character caused by the virtual excitation to the IS state. The transition from a LS to a IS/HS state introduces bond-length fluctuations that suppress the phonon contribution to κ(T) below 300 K. The suppressed κ(T) could be further reduced by dynamic Jahn-Teller distortions associated with the IS/HS species. A smooth transition in ρ(T) and α(T) and a nearly temperature independent α(T)≈20 μV/K above 600 K do not support a thermally induced, homogeneous Mott-Hubbard transition model for the high-temperature transition of LaCoO3 from an insulating to a conductive state. A two-phase process is proposed for the interval 300 K

  3. Modified structural characteristics and enhanced electrochemical properties of oxygen-deficient Li2MnO3-δ obtained from pristine Li2MnO3

    NASA Astrophysics Data System (ADS)

    Tan, Xiao; Liu, Rui; Xie, Congxin; Shen, Qiang

    2018-01-01

    Lithium-rich manganese(IV) oxide Li2MnO3 has hardly any activity as the cathode active substance of lithium-ion batteries (LIBs) but its reversible capacity can be greatly improved by introducing oxygen deficiencies. After the solid-state heat treatment of nanocrystalline Li2MnO3 by sodium borohydride (NaBH4), the resulting Li2MnO3-δ crystallites comparatively acquire distinguishable appearances in color and shape and slight differences in surface composition and lattice structure. As a LIB cathode within the potential range of 2.5-4.7 V, at 20 mA g-1 pristine Li2MnO3 gives the specific discharge capacities of 3.3, 5.0 and 7.4 mAh·g-1 in the 1st, 10th and 100th cycles, while the derivative Li2MnO3-δ delivers the relatively high values of 64.8, 103.8 and 140.2 mAh·g-1 in the 1st, 10th and 120th cycles, respectively. Aside from the similar phenomenon of gradual electrochemical activation, substituting Li2MnO3-δ for Li2MnO3 means the great enhancements of charge-transfer ability and electrochemical performances. Especially, the cationic-anionic redox mechanisms of Li2MnO3 and Li2MnO3-δ are similar to each other, suggesting a possible solution to prepare high-performance xLi2MnO3-δ·(1-x)LiMO2 solid solutions for application purposes.

  4. Influence of Weak External Magnetic Field on Amorphous and Nanocrystalline Fe-based Alloys

    NASA Astrophysics Data System (ADS)

    Degmová, J.; Sitek, J.

    2010-07-01

    Nanoperm, Hitperm and Finamet amorphous and nanocrystalline alloys were measured by Mössbauer spectrometry in a weak external magnetic field of 0.5 T. It was shown that the most sensitive parameters of Mössbauer spectra are the intensities of the 2nd and the 5th lines. Rather small changes were observed also in the case of internal magnetic field values. The spectrum of nanocrystalline Nanoperm showed the increase in A23 parameter (ratio of line intensities) from 2.4 to 3.7 and decrease of internal magnetic field from 20 to 19 T for amorphous subspectrum under the influence of magnetic field. Spectrum of nanocrystalline Finemet shown decrease in A23 parameter from 3.5 to 2.6 almost without a change in the internal magnetic field value. In the case of amorphous Nanoperm and Finemet samples, the changes are almost negligible. Hitperm alloy showed the highest sensitivity to the weak magnetic field, when the A23 parameter increased from 0.4 to 2.5 in the external magnetic fields. The A23 parameter of crystalline subspectrum increased from 2.7 to 3.8 and the value of internal magnetic field corresponding to amorphous subspectrum increased from 22 to 24 T. The behavior of nanocrystalline alloys under weak external magnetic field was analyzed within the three-level relaxation model of magnetic dynamics in an assembly of single-domain particles.

  5. Identification of Cr valence states in Cr and Nd co-doped Lu3Al5O12 laser ceramics

    NASA Astrophysics Data System (ADS)

    Zhang, Pande; Jiang, Benxue; Fan, Jintai; Mao, Xiaojian; Zhang, Long

    2017-09-01

    Cr and Nd co-doped laser ceramics, as the potential gain materials in inertial confinement fusion (ICF), have been widely investigated. And the study on valence states of chromium ions is important. The effects of sintering additives and annealing atmosphere on the valence state of chromium were studied in detail, and the results shown that the Cr valence states were demonstrated to be Cr2+ and Cr3+ ions in HIP-sintered Cr(0.2 at.%), Nd(0.8 at.%): LuAG laser ceramics. And the intensity of the near-infrared absorption band caused by Cr2+ ions was attenuated with the decreasing SiO2 concentration and increasing MgO amount. The near-infrared absorption could be eliminated by annealing in air. And the transformation of valence states of Cr ions in the Cr,Nd:LuAG ceramics were also confirmed by electron paramagnetic resonance and X-ray photoelectron spectroscopy.

  6. Oxidative coupling of methane over SrO deposited on different commercial supports precoated with La{sub 2}O{sub 3}

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

    Choudhary, V.R.; Mulla, S.A.R.; Uphade, B.S.

    1998-06-01

    The influence of catalyst carrier or support (with different chemical compositions and surface properties), catalyst deposition method (viz., impregnation and coating), precursor for strontium oxide (SrO; Sr-nitrate, acetate, hydroxide, and carbonate), and loading of SrO and lanthanum oxide (La{sub 2}O{sub 3}; 0--25 wt%) on the surface properties and performance of catalyst in oxidative coupling of methane (OCM; at 850 C, gas hourly space velocity = 1.02 {times} 10{sup 5} cm{sup 3}/g{center_dot}h and CH{sub 4}/O{sub 2} = 4 or 16) was thoroughly investigated. The basicity, acidity, and O{sub 2} chemisorption of the catalysts were studied by the temperature programmed desorption (TPD)more » of CO{sub 2}, NH{sub 3}, and O{sub 2}, respectively, from 50 to 950 C. The total and strong basic sites, acidity, and OCM activity of the supported catalyst were strongly influenced by the support used and also by the La{sub 2}O{sub 3} loading on the support. The catalyst with a sintered low surface area porous silica-Alumina support and high (20 wt%) La{sub 2}O{sub 3} and SrO loadings showed the best performance in the OCM process. The OCM activity was influenced by SrO loading, but to a smaller extent, and also by the method of SrO deposition. The OCM activity of the supported catalysts could be related to their strong basic sites (measured in terms of the CO{sub 2} desorbed between 500 and 950 C).« less

  7. Theoretical study of methanol synthesis from CO2 and CO hydrogenation on the surface of ZrO2 supported In2O3 catalyst

    NASA Astrophysics Data System (ADS)

    Dou, Maobin; Zhang, Minhua; Chen, Yifei; Yu, Yingzhe

    2018-06-01

    The interactions between ZrO2 support and In2O3 catalyst play pivotal role in the catalytic conversion of CO2 to methanol. Herein, a density functional theory study has been conducted to research the mechanism of methanol synthesis from CO2 and CO hydrogenation on the defective ZrO2 supported In2O3(110) surface (D surface). The calculations reveal that methanol is produced mainly via the HCOO reaction pathway from CO2 hydrogenation on D surface, and the hydrogenation of HCOO to form H2COO species with an activation barrier of 1.21 eV plays the rate determining step for the HCOO reaction pathway. The direct dissociation of CO2 to CO on D surface is kinetically and energetically prohibited. Methanol synthesis from CO hydrogenation on D surface is much facile comparing with the elementary steps involved in CO2 hydrogenation. The rate determining step of CO hydrogenation to methanol is the formation of H3CO species on the vacancy site with a barrier of 0.51 eV. ZrO2 support has significant effect on the suppressing of the dissociation of CO2 and stabilization of H2COO species on the surface of In2O3 catalyst.

  8. Thermo-optical characteristics and concentration quenching effects in Nd3+doped yttrium calcium borate glasses

    NASA Astrophysics Data System (ADS)

    Santos, D. R. S.; Santos, C. N.; de Camargo, A. S. S.; Silva, W. F.; Santos, W. Q.; Vermelho, M. V. D.; Astrath, N. G. C.; Malacarne, L. C.; Li, M. S.; Hernandes, A. C.; Ibanez, A.; Jacinto, C.

    2011-03-01

    In this work we present a comprehensive study of the spectroscopic and thermo-optical properties of a set of samples with composition xNd2O3-(5-x)Y2O3-40CaO-55B2O3 (0 ≤ x ≤ 1.0 mol%). Their fluorescence quantum efficiency (η) values were determined using the thermal lens technique and the dependence on the ionic concentration was analyzed in terms of energy transfer processes, based on the Förster-Dexter model of multipolar ion-ion interactions. A maximum η = 0.54 was found to be substantially higher than for yttrium aluminoborate crystals and glasses with comparable Nd3+ content. As for the thermo-optical properties of yttrium calcium borate, they are comparable to other well-known laser glasses. The obtained energy transfer microparameters and the weak dependence of η on the Nd3+ concentration with a high optimum Nd3+ concentration put this system as a strong candidate for photonics applications.

  9. Effects of oxygen deficiency on the transport and dielectric properties of NdSrNbO

    NASA Astrophysics Data System (ADS)

    Hzez, W.; Benali, A.; Rahmouni, H.; Dhahri, E.; Khirouni, K.; Costa, B. F. O.

    2018-06-01

    In the present study, Nd0.7Sr0.3NbO3-y (y = 0.1, 0.15, 0.2) compounds were prepared via a solid-solid reaction route. The prepared samples were characterized by electrochemical impedance spectroscopy in order to establish the effects of temperature, frequency, and oxygen vacancies on both the transport and dielectric properties of NdSrNbO. We found that both the electrical and dielectric properties were highly sensitive to the concentration of oxygen vacancies. The conduction mechanism data were explained well according to the Mott model and adiabatic small polaronic hopping model. Electrochemical impedance spectroscopy analysis showed that one relaxation process was present in the Nd0.7Sr0.3NbO2.9 system whereas two relaxation processes were observed in the Nd0.7Sr0.3NbO2.85 and Nd0.7Sr0.3NbO2.8 systems, where the latter behavior indicated the presence of many active regions (due to the contributions of different microstructures). The temperature and frequency dependences of the dielectric constant confirmed the contributions of different polarization mechanisms. In particular, the high dielectric constant values at low frequencies and high temperatures were mainly related to the presence of different Schottky barriers, whereas the low dielectric constant values at high frequencies were essentially related to the intrinsic effect. The constant dielectric values obtained for the samples are greater than those in the NdSrFeO system, which makes them interesting materials for use in applications that require high dielectric constants.

  10. Improvement of the field-trapping capabilities of bulk Nd Ba Cu O superconductors using Ba Cu O substrates

    NASA Astrophysics Data System (ADS)

    Matsui, Motohide; Nariki, Shinya; Sakai, Naomichi; Iwafuchi, Kengo; Murakami, Masato

    2006-07-01

    We used Ba-Cu-O substrates to fabricate bulk Nd-Ba-Cu-O superconductors using a top-seeded melt-growth method. There were several advantages for the use of Ba-Cu-O substrate compared to conventional substrate materials such as MgO, ZrO2, Al2O3, RE123 and RE211 (RE = rare earth). The Ba-Cu-O did not react with the precursor and minimized liquid loss. Accordingly, the introduction of large-sized cracks was suppressed. We also found that Tc values were high at the bottom regions, which was ascribed to the beneficial effect of Ba-Cu-O in suppressing Nd/Ba substitution. As a result, we obtained bulk Nd-Ba-Cu-O superconductors that exhibited fairly good field-trapping capabilities, even at the bottom surfaces.

  11. TL and OSL properties of beta irradiated Y2O3 nanocrystal

    NASA Astrophysics Data System (ADS)

    Shivaramu, N. J.; Lakshminarasappa, B. N.; Nagabhushana, K. R.; Tatumi, S. H.; Rocca, R. R.; Singh, Fouran

    2017-05-01

    Nanocrystalline yttrium oxide (Y2O3) is synthesized by low temperature sol-gel technique and synthesized material is annealed at 900°C. The annealed β-rayed Y2O3 two TL glows with prominent peak at 407 K and weak glow peak at 643 K were observed in all irradiated samples. It is found that TL glow peaks intensity linearly increases with increase in β-dose from 0.813 - 40.625 Gy. The TL kinetic parameters are calculated using glow curve deconvoluted (GCD) method. The TL glows exhibits general order kinetics. Intense optical stimulated luminescence (OSL) is observed in the Y2O3 sample. These material exhibits linearity and reproducibility and hence, it suggests that this material may be used as dosimetric applications.

  12. Raman spectra of Nd/Sn cosubstituted Ba6-3xSm8+2xTi18O54 microwave dielectric ceramics

    NASA Astrophysics Data System (ADS)

    Wu, S. Y.; Li, Y.; Chen, X. M.

    2004-11-01

    The Raman spectra and dielectric properties of Nd /Sn cosubstituted Ba6-3xSm8+2xTi18O54 (x =2/3) microwave dielectric ceramics were discussed as the functions of composition and sintering time. The peaks in 753cm-1 were caused by the second order scatter. The peaks in 425 and 403cm-1 became sharper with prolonging sintering time, and this reflected the increased lattice defects. The shoulder peak near 292cm-1 was caused by the octahedral tilt when A site is Nd3+. The Raman shifts in 590, 520, 280, and 232cm-1 indicated no obvious change in position, but all peaks became sharper with prolonging sintering time. This indicated the increased ordering degree of A-site cations. With prolonging sintering time, the Qf factor (Q is the inverse of dielectric loss, tan δ, and f is the resonant frequency) increased, and the temperature coefficient of resonant frequency significantly decreased or became more negative, while the dielectric constant indicated no significant variation.

  13. Ba6-3 x Nd8+2 x Ti18O54 Tungsten Bronze: A New High-Temperature n-Type Oxide Thermoelectric

    NASA Astrophysics Data System (ADS)

    Azough, Feridoon; Freer, Robert; Yeandel, Stephen R.; Baran, Jakub D.; Molinari, Marco; Parker, Stephen C.; Guilmeau, Emmanuel; Kepaptsoglou, Demie; Ramasse, Quentin; Knox, Andy; Gregory, Duncan; Paul, Douglas; Paul, Manosh; Montecucco, Andrea; Siviter, Jonathan; Mullen, Paul; Li, Wenguan; Han, Guang; Man, Elena A.; Baig, Hasan; Mallick, Tapas; Sellami, Nazmi; Min, Gao; Sweet, Tracy

    2016-03-01

    Semiconducting Ba6-3 x Nd8+2 x Ti18O54 ceramics (with x = 0.00 to 0.85) were synthesized by the mixed oxide route followed by annealing in a reducing atmosphere; their high-temperature thermoelectric properties have been investigated. In conjunction with the experimental observations, atomistic simulations have been performed to investigate the anisotropic behavior of the lattice thermal conductivity. The ceramics show promising n-type thermoelectric properties with relatively high Seebeck coefficient, moderate electrical conductivity, and temperature-stable, low thermal conductivity; For example, the composition with x = 0.27 (i.e., Ba5.19Nd8.54Ti18O54) exhibited a Seebeck coefficient of S 1000K = 210 µV/K, electrical conductivity of σ 1000K = 60 S/cm, and thermal conductivity of k 1000K = 1.45 W/(m K), leading to a ZT value of 0.16 at 1000 K.

  14. Microstructural and mechanical properties of Al2O3/ZrO2 nanomultilayer thin films prepared by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Balakrishnan, G.; Sastikumar, D.; Kuppusami, P.; Babu, R. Venkatesh; Song, Jung Il

    2018-02-01

    Single layer aluminium oxide (Al2O3), zirconium oxide (ZrO2) and Al2O3/ZrO2 nano multilayer films were deposited on Si (100) substrates at room temperature by pulsed laser deposition. The development of Al2O3/ZrO2 nanolayered structure is an important method used to stabilize the high temperature phase (tetragonal and cubic) of ZrO2 at room temperature. In the Al2O3/ZrO2 multilayer structure, the Al2O3 layer was kept constant at 5 nm, while the ZrO2 layer thickness varied from 5 to 20 nm (5/5, 5/10, 5/15 and 5/20 nm) with a total of 40 bilayers. The X-ray diffraction studies of single layer Al2O3 indicated the γ-Al2O3 of cubic structure, while the single layer ZrO2 indicated both monoclinic and tetragonal phases. The 5/5 and 5/10 nm multilayer films showed the nanocrystalline nature of ZrO2 with tetragonal phase. The high resolution transmission electron microscopy studies indicated the formation of well-defined Al2O3 and ZrO2 layers and that they are of uniform thickness. The atomic force microscopy studies revealed the uniform and dense distribution of nanocrystallites. The nanoindentation studies indicated the hardness of 20.8 ± 1.10 and 10 ± 0.60 GPa, for single layer Al2O3 and ZrO2, respectively, and the hardness of multilayer films varied with bilayer thickness.

  15. Judd-Ofelt analysis and energy transfer processes of Er3+ and Nd3+ doped fluoroaluminate glasses with low phosphate content

    NASA Astrophysics Data System (ADS)

    Huang, Feifei; Zhang, Yu; Hu, Lili; Chen, Danping

    2014-12-01

    Spectroscopic property and energy transfer processes of singly doped and codoped Er3+ and Nd3+ fluoroaluminate glasses with low phosphate content are systematically analyzed. The absorption spectra of these glasses are tested, and the Judd-Ofelt (J-O) and radiative parameters are discussed based on J-O theory and the parameters changes substantially because of the other codoping ions. As for Nd3+: the main emission bands at 0.9 and 1.05 μm decrease in the codoped sample under the excitation of an 800 nm laser diode from the emission spectra because the Er3+: 4I11/2 level reduces the Nd3+: 4F3/2 level effectively through the energy transfer process Nd3+: 4F3/2 → Er3+: 4I11/2. For Er3+, the emission at 1.5 μm is restrained by codoping with Nd3+ ions from the energy transfer process Er3+: 4I13/2Nd3+: 4I15/2. The emission at 2.7 μm is enhanced because the Nd3+ ions deplete the lower level and exert a positive effect on the upper laser level. The microparameters of the energy transfer between the Er3+ and Nd3+ ions are calculated and discussed using Forster-Dexter theory. The energy transfer efficiencies of the Nd3+: 4F3/2 to the Er3+: 4I11/2 and the Er3+: 4I13/2 to the Nd3+: 4I15/2 are 28.8% and 74.5%, respectively. These results indicate that Nd3+ can be an efficient sensitizer for Er3+ to obtain Mid-infrared (Mid-IR) emission and the codoped Er3+/Nd3+ fluoroaluminate glass with low phosphate content is suitable to be used as the fiber optical gain media for 2.7 μm laser generation.

  16. Nd:(Gd0.3Y0.7)2SiO5 crystal: A novel efficient dual-wavelength continuous-wave medium

    NASA Astrophysics Data System (ADS)

    Xu, Xiaodong; Di, Juqing; Zhang, Jian; Tang, Dingyuan; Xu, Jun

    2016-05-01

    Efficient dual-wavelength continuous-wave (CW) and passively Q-switched laser operation of Nd:(Gd0.3Y0.7)2SiO5 crystal were investigated for the first time to our knowledge. Maximum CW output power of 2.3 W was obtained under the absorbed pump power of 4.6 W, corresponding to the slope efficiency of 55%. Dual-wavelength CW laser with respective wavelengths around 1074 nm and 1078 nm were achieved. With Cr4+:YAG as the saturable absorber, passive Q-switched performance was obtained. The slope efficiency of passively Q-switched operation was 45%. The shortest pulse width, the corresponding pulse energy and peak power were calculated to be 13.1 ns, 50.2 μJ and 3.8 kW, respectively.

  17. Simultaneous dual-wavelength laser operation at 937 and 1062 nm in Nd3+:Gd3Ga5O12

    NASA Astrophysics Data System (ADS)

    Gao, F.; Sun, G. C.; Li, Y. D.; Dong, Y.; Li, S. T.

    2013-08-01

    Diode-end-pumped continuous-wave (cw) simultaneous dual-wavelength laser operation at 937 and 1062 nm in a single Nd3+:Gd3Ga5O12 (Nd:GGG) crystal was demonstrated. A total output power of 1.12 W at the two fundamental wavelengths was achieved at incident pump power of 17.6 W. The optical-to-optical conversion was up to 6.4% with respect to the incident pump power. To the best of our knowledge, this is first work on cw simultaneous dual-wavelength operation at 937 and 1062 nm in Nd:GGG crystal.

  18. Synthesis and Characterization of Nd(3+)-Doped CaF2 Nanoparticles.

    PubMed

    Yuan, Dan; Li, Weiwei; Mei, Bingchu; Song, Jinghong

    2015-12-01

    The Ca(1-x)F(2+x):Nd(x) nanoparticles were synthesized by chemical direct precipitation method. X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Image analyzer, absorption spectrum and transmittance were taken to characterization the phases, morphologies, sizes, size distribution and optical properties of the samples. The results indicate that the Ca(1-x)F(2+x):Nd(x) samples can be rationally modified in size and morphology by altering the Nd3+ ions doping concentration. With increasing concentration of Nd3+ ions, the particle size decreased from 24 to 14 nm, the intensity of the diffraction peaks decreased, the Ca(1-x)F(2+x):Nd(x) particles aggregated ion of the formed clusters which should have an effect on both speed and orientation of the particles growth. The transmittance of ceramics with a thickness of 2 mm showed that the transmittance can reach 90% when the doping concentration was 5%, which should be profitable for LD pumping.

  19. Synthesis and Thermodynamic Stability of Ba2B‧B″O6 and Ba3B*B″2O9 Perovskites Using the Molten Salt Method

    NASA Astrophysics Data System (ADS)

    Meng, Wei; Virkar, Anil V.

    1999-12-01

    A number of mixed perovskites of the types Ba2B‧B″O6 (BaB‧1/2B″1/2O3) and Ba3B*B″2O9 (BaB*1/3B″2/3O3) where B‧=Gd, La, Nd, Sm, or Y; B″=Nb and B*=Ca were synthesized by a conventional calcination process, as well as by the molten salt method. The former consists of calcining appropriate mixtures of oxide or carbonate precursors in air at elevated temperatures (∼1250°C). The latter method consists of adding appropriate mixtures of oxide or carbonate precursors to a molten salt bath at relatively low temperatures (on the order of 300 to 500°C) so that the requisite compound is formed by dissolution-reprecipitation. X-ray diffraction confirmed the formation of a single-phase perovskite in each case with calcination at 1250°C. In a molten salt bath, however, all except Ba2LaNbO6 and Ba2NdNbO6 formed the perovskite structure. On the contrary, powders of Ba2LaNbO6 and Ba2NdNbO6 formed by a high-temperature calcination process readily decomposed when introduced into the molten salt bath. The formation of the requisite perovskite at a temperature as low as 350°C in a molten salt suggests that: (a) The perovskite is stable at 350°C. (b) The molten salt exhibits sufficient precursor solubility for the dissolution-reprecipitation process to occur in a reasonable time. Similarly, the decomposition of Ba2LaNbO6 and Ba2NdNbO6 in a molten salt bath shows that these materials are thermodynamically unstable at the temperature of the molten salt bath.

  20. Optical, dielectric and morphological studies of sol-gel derived nanocrystalline TiO2 films.

    PubMed

    Vishwas, M; Sharma, Sudhir Kumar; Narasimha Rao, K; Mohan, S; Gowda, K V Arjuna; Chakradhar, R P S

    2009-10-15

    Nanocrystalline TiO(2) films have been synthesized on glass and silicon substrates by sol-gel technique. The films have been characterized with optical reflectance/transmittance in the wavelength range 300-1000 nm and the optical constants (n, k) were estimated by using envelope technique as well as spectroscopic ellipsometry. Morphological studies have been carried out using atomic force microscope (AFM). Metal-Oxide-Silicon (MOS) capacitor was fabricated using conducting coating on TiO(2) film deposited on silicon. The C-V measurements show that the film annealed at 300 degrees C has a dielectric constant of 19.80. The high percentage of transmittance, low surface roughness and high dielectric constant suggests that it can be used as an efficient anti-reflection coating on silicon and other optical coating applications and also as a MOS capacitor.

  1. Comparative study of different carbon-supported Fe2O3-Pt catalysts for oxygen reduction reaction.

    PubMed

    Tellez-Cruz, M M; Padilla-Islas, M A; Pérez-González, M; Solorza-Feria, O

    2017-11-01

    One of the challenges in electrocatalysis is the adequate dispersion of the catalyst on an appropriate porous support matrix, being up to now the most commonly used the carbon-based supports. To overcome this challenge, carbon supports must first be functionalized to guide the catalyst's nucleation, thereby, improving the dispersion and allowing the use of smaller amount of the catalyst material to achieve a higher electrochemically active surface area. This study present the effect of functionalized Vulcan carbon XC72 (FVC) and functionalized Black Pearl carbon (FBPC) as supports on the catalytic activity of decorated Fe 2 O 3 with Pt. Both carbons were functionalized with HNO 3 and subsequently treated with ethanolamine. Fe 2 O 3 nanoparticles were synthesized by chemical reduction and decorated with platinum by epitaxial growth. Pt and Fe 2 O 3 structural phases were identified by XRD and XPS; the Pt content was measured by XPS, and results showed to a high Pt content in Fe 2 O 3 -Pt/FBPC. TEM micrographs reveal nanoparticles with an average size of 2 nm in both supported catalysts. The Fe 2 O 3 -Pt/FVC catalyst presents the highest specific activity and mass activity, 0.21 mA cm -2 Pt and 140 mA mg Pt -1 , respectively, associated to the appropriate distribution of platinum on the Fe 2 O 3 nanoparticles.

  2. Near-infrared photoluminescence in La{sub 0.98}AlO{sub 3}: {sub 0.02}Ln{sup 3+}(Ln = Nd/Yb) for sensitization of c-Si solar cells

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

    Sawala, N. S., E-mail: nssawala@gmail.com; Koparkar, K. A.; Omanwar, S. K.

    2016-05-06

    The host matrix LaAlO{sub 3} was synthesized by conventional solid state reaction method in which the Nd{sup 3+} ions and Yb{sup 3+} ions successfully doped at 2mol% concentrations. The phase purity was confirmed by X ray powder diffraction (XRD) method. The photoluminescence (PL) properties were studied by spectrophotometer in near infra red (NIR) and ultra violet visible (UV-VIS) region. The Nd{sup 3+} ion doped LaAlO{sub 3} converts a visible (VIS) green photon (587 nm) into near infrared (NIR) photon (1070 nm) while Yb{sup 3+} ion doped converts ultra violet (UV) photon (221 nm) into NIR photon (980 nm). The La{sub 0.98}AlO{sub 3}: {sub 0.02}Ln{supmore » 3+}(Ln = Nd / Yb) can be potentiality used for betterment of photovoltaic (PV) technology. This result further indicates its potential application as a luminescence converter layer for enhancing solar cells performance.« less

  3. Correlation between impurity distribution and location of ferroelectric domain walls in Nd : Mg : LiNbO 3 single crystal

    NASA Astrophysics Data System (ADS)

    Naumova, I. I.; Evlanova, N. F.; Blokhin, S. A.; Lavrishchev, S. V.

    1998-04-01

    Using selective chemical etching, scanning electron microscope (SEM) and wave dispersive X-ray (WDX) microanalysis we showed that the ferroelectric domain walls coincide with the maxima and minima Nd-impurity modulation in a periodically poled Nd : Mg : LiNbO 3 crystal grown by the Czochralski method along the normal to the (0 1 1¯ 2) face. Asymmetric form of the Nd-modulation produces nonequal positive and negative domains for one period. Variations of instantaneous rate of growth were estimated for facet and nonfacet crystal region in the framework of Burton-Prim-Slichter theory.

  4. A Perspective on the Selective Catalytic Reduction (SCR) of NO with NH 3 by Supported V 2O 5 –WO 3/TiO 2 Catalysts

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

    Lai, Jun-Kun; Wachs, Israel E.

    We report the selective catalytic reduction (SCR) of NO x with NH 3 to harmless N 2 and H 2O plays a crucial role in reducing highly undesirable NO x acid gas emissions from large utility boilers, industrial boilers, municipal waste plants, and incinerators. The supported V 2O 5 –WO 3/TiO 2 catalysts have become the most widely used industrial catalysts for these SCR applications since introduction of this technology in the early 1970s. Lastly, this Perspective examines the current fundamental understanding and recent advances of the supported V 2O 5 –WO 3/TiO 2 catalyst system: (i) catalyst synthesis, (ii)more » molecular structures of titaniasupported vanadium and tungsten oxide species, (iii) surface acidity, (iv) catalytic active sites, (v) surface reaction intermediates, (vi) reaction mechanism, (vii) ratedetermining- step, and (viii) reaction kinetics.« less

  5. A Perspective on the Selective Catalytic Reduction (SCR) of NO with NH 3 by Supported V 2O 5 –WO 3/TiO 2 Catalysts

    DOE PAGES

    Lai, Jun-Kun; Wachs, Israel E.

    2018-06-04

    We report the selective catalytic reduction (SCR) of NO x with NH 3 to harmless N 2 and H 2O plays a crucial role in reducing highly undesirable NO x acid gas emissions from large utility boilers, industrial boilers, municipal waste plants, and incinerators. The supported V 2O 5 –WO 3/TiO 2 catalysts have become the most widely used industrial catalysts for these SCR applications since introduction of this technology in the early 1970s. Lastly, this Perspective examines the current fundamental understanding and recent advances of the supported V 2O 5 –WO 3/TiO 2 catalyst system: (i) catalyst synthesis, (ii)more » molecular structures of titaniasupported vanadium and tungsten oxide species, (iii) surface acidity, (iv) catalytic active sites, (v) surface reaction intermediates, (vi) reaction mechanism, (vii) ratedetermining- step, and (viii) reaction kinetics.« less

  6. A clear effect of charge compensation through Na+ co-doping on the luminescence spectra and decay kinetics of Nd3+-doped CaAl4O7

    NASA Astrophysics Data System (ADS)

    Puchalska, M.; Watras, A.

    2016-06-01

    We present a detailed analysis of luminescence behavior of singly Nd3+ doped and Nd3+, Na+ co-doped calcium aluminates powders: Ca1-xNdxAl4O7 and Ca1-2xNdxNaxAl4O7 (x=0.001-0.1). Relatively intense Nd3+ luminescence in IR region corresponding to typical 4F3/2→4IJ (J=9/2-13/2) transitions with maximum located at about 1079 nm was obtained in all samples on direct excitation into f-f levels. The effect of dopant concentration and charge compensation by co-doping with Na+ ions on morphology and optical properties were studied. The results show that both, the Nd3+ concentration and the alkali metal co-doping affected the optical properties but had no influence on the powders morphology. The studies of luminescence spectra (298 and 77 K) in a function of dopant concentration showed an increasing distortion of the local symmetry of Nd3+with raising activator content due to certain defects created in the crystal lattice. On the other hand Na+ addition led to significant narrowing of absorption and luminescence bands and also a reduction of the number of their components, showing smaller disturbance of Nd3+ ions local symmetries. Consequently, charge compensated by Na+ co-doping materials showed significantly enhanced Nd3+ luminescence. The decrease of emission intensity and luminescence lifetimes with increase of activator concentration was attributed mainly to phonon-assisted cross-relaxation processes between Nd3+ ions. Analysis with Inokuti-Hirayama model indicated dipole-dipole mechanism of ion-ion interaction. Na+ addition led to much smaller concentration quenching due to smaller clustering of dopant ions in CaAl4O7 lattice.

  7. Glass-ceramic nuclear waste forms obtained by crystallization of SiO 2-Al 2O 3-CaO-ZrO 2-TiO 2 glasses containing lanthanides (Ce, Nd, Eu, Gd, Yb) and actinides (Th): Study of the crystallization from the surface

    NASA Astrophysics Data System (ADS)

    Loiseau, P.; Caurant, D.

    2010-07-01

    Glass-ceramic materials containing zirconolite (nominally CaZrTi 2O 7) crystals in their bulk can be envisaged as potential waste forms for minor actinides (Np, Am, Cm) and Pu immobilization. In this study such matrices are synthesized by crystallization of SiO 2-Al 2O 3-CaO-ZrO 2-TiO 2 glasses containing lanthanides (Ce, Nd, Eu, Gd, Yb) and actinides (Th) as surrogates. A thin partially crystallized layer containing titanite and anorthite (nominally CaTiSiO 5 and CaAl 2Si 2O 8, respectively) growing from glass surface is also observed. The effect of the nature and concentration of surrogates on the structure, the microstructure and the composition of the crystals formed in the surface layer is presented in this paper. Titanite is the only crystalline phase able to significantly incorporate trivalent lanthanides whereas ThO 2 precipitates in the layer. The crystal growth thermal treatment duration (2-300 h) at high temperature (1050-1200 °C) is shown to strongly affect glass-ceramics microstructure. For the system studied in this paper, it appears that zirconolite is not thermodynamically stable in comparison with titanite growing form glass surface. Nevertheless, for kinetic reasons, such transformation (i.e. zirconolite disappearance to the benefit of titanite) is not expected to occur during interim storage and disposal of the glass-ceramic waste forms because their temperature will never exceed a few hundred degrees.

  8. Self-assembled chromophores within mesoporous nanocrystalline TiO2: towards biomimetic solar cells.

    PubMed

    Marek, Peter L; Sieger, Hermann; Scherer, Torsten; Hahn, Horst; Balaban, Teodor Silviu

    2009-06-01

    Artificial light-harvesting antennas consisting of self-assembled chromophores that mimic the natural pigments of photosynthetic bacteria have been inserted into voids induced in porous titania (TiO2, anatase) in order to investigate their suitability for hybrid solar cells. Mesoporous nanocrystalline TiO2 with additional uniform macropores was treated with precursor solutions of the pigment which was then induced to self-assemble within the voids. The chromophores were tailored to combine the self-assembly characteristics of the natural bacteriochlorophylls with the robustness of artificial Zn-porphyrins being stable for prolonged periods even upon heating to over 200 degrees C. They assemble on the TiO2 surface to form nano- to micro-crystalline structures with lengths from tens of nm up to several microm and show a photosensitization effect which is supposed to be dependent on the assembly size. The natural examples of these antennas are found in green sulfur bacteria which are able to use photosynthesis in deep water regions with minute light intensities. The implementation of biomimetic antennas for light harvesting and a better photon management may lead to a rise in efficiency of dye-sensitized solar cells also under low light illumination conditions.

  9. 100 MeV swift Si{sup 7+} ion induced thermoluminescence studies of nanocrystalline erbium doped ZrO{sub 2}

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

    Lokesha, H. S.; Nagabhushana, K. R., E-mail: bhushankr@gmail.com; Singh, Fouran

    2015-06-24

    Pure and erbium (1mol%) doped nanocrystalline ZrO{sub 2} is synthesized by combustion technique. Thermoluminescence (TL) properties ZrO{sub 2}pellets annealed at 873 K and irradiated by 100 MeV swift Si{sup 7+} ion for various fluence are recorded. The evolution crystalline structure and crystallite size are done using by XRD data. Two TL glow curves, a well resolved one peak at ∼420 K and an unresolved with peak at ∼598 K are observed. TL intensity increases up to 3×10{sup 12} ions cm{sup −2} beyond which the TL intensity decreases. The glow peak shape method is used to calculate the TL trap parameter and discussed in thismore » paper.« less

  10. High thermal stability of La 2O 3 and CeO 2-stabilized tetragonal ZrO 2

    DOE PAGES

    Wang, Shichao; Xie, Hong; Lin, Yuyuan; ...

    2016-02-15

    Catalyst support materials of tetragonal ZrO 2, stabilized by either La 2O 3 (La 2O 3-ZrO 2) or CeO 2 (CeO 2-ZrO 2), were synthesized under hydrothermal conditions at 200 °C with NH 4OH or tetramethylammonium hydroxide as the mineralizer. From In Situ synchrotron powder X-ray diffraction and small-angle X-ray scattering measurements, the calcined La 2O 3-ZrO 2 and CeO 2-ZrO 2 supports were nonporous nanocrystallites that exhibited rectangular shapes with thermal stability up to 1000 °C in air. These supports had an average size of ~10 nm and a surface area of 59-97 m 2/g. The catalysts Pt/La 2Omore » 3-ZrO 2 and Pt/CeO 2-ZrO 2 were prepared by using atomic layer deposition with varying Pt loadings from 6.3-12.4 wt %. Mono-dispersed Pt nanoparticles of ~3 nm were obtained for these catalysts. As a result, the incorporation of La 2O 3 and CeO 2 into the t-ZrO 2 structure did not affect the nature of the active sites for the Pt/ZrO 2 catalysts for the water-gas-shift (WGS) reaction.« less

  11. Nanocrystalline Ce 1- xY xO 2- x/2 (0≤ x≤0.35) Oxides via Carbonate Precipitation: Synthesis and Characterization

    NASA Astrophysics Data System (ADS)

    Li, Ji-Guang; Ikegami, Takayasu; Wang, Yarong; Mori, Toshiyuki

    2002-10-01

    A novel carbonate (co)precipitation method, employing nitrates as the starting salts and ammonium carbonate as the precipitant, has been used to synthesize nanocrystalline CeO 2 and Ce 1- xY xO 2- x/2 ( x≤0.35) solid-solutions. The resultant powders are characterized by elemental analysis, differential thermal analysis/thermogravimetry (DTA/TG), X-ray diffractometry (XRD), Brunauer-Emmett-Teller (BET) analysis, and high-resolution scanning electron microscopy (HRSEM). Due to the direct formation of carbonate solid-solutions during precipitation, Ce 1- xY xO 2- x/2 solid-solution oxides are formed directly during calcination at a very low temperature of ˜300°C for 2 h. The thus-produced oxide nanopowders are essentially non-agglomerated, as revealed by BET in conjunction with XRD analysis. The solubility of YO 1.5 in CeO 2 is determined via XRD to be somewhere in the range from 27 to 35 mol%, from which a Y 2O 3-related type-C phase appears in the final product. Y 3+-doping promotes the formation of spherical nanoparticles, retards thermal decomposition of the precursors, and suppresses significantly crystallite coarsening of the oxides during calcination. The activation energy for crystallite coarsening increases gradually from 68.7 kJ mol -1 for pure CeO 2 to 138.6 kJ mol -1 for CeO 2 doped with 35 mol% YO 1.5. The dopant effects on crystallite coarsening is elaborated from the view point of solid-state chemistry.

  12. Study of magnetic and electrical properties of nanocrystalline Mn doped NiO.

    PubMed

    Raja, S Philip; Venkateswaran, C

    2011-03-01

    Diluted Magnetic Semiconductors (DMS) are intensively explored in recent years for its applications in spintronics, which is expected to revolutionize the present day information technology. Nanocrystalline Mn doped NiO samples were prepared using chemical co-precipitation method with an aim to realize room temperature ferromagnetism. Phase formation of the samples was studied using X-ray diffraction-Rietveld analysis. Scanning electron microscopy and Energy dispersive X-ray analysis results reveal the nanocrystalline nature of the samples, agglomeration of the particles, considerable particle size distribution and the near stoichiometry. Thermomagnetic curves confirm the single-phase formation of the samples up to 1% doping of Mn. Vibrating Sample Magnetometer measurements indicate the absence of ferromagnetism at room temperature. This may be due to the low concentration of Mn2+ ions having weak indirect coupling with Ni2+ ions. The lack of free carriers is also expected to be the reason for the absence of ferromagnetism, which is in agreement with the results of resistivity measurements using impedance spectroscopy. Arrhenius plot shows the presence of two thermally activated regions and the activation energy for the nanocrystalline Mn doped sample was found to be greater than that of undoped NiO. This is attributed to the doping effect of Mn. However, the dielectric constant of the samples was found to be of the same order of magnitude very much comparable with that of undoped NiO.

  13. Critical behavior near the ferromagnetic phase transition in double perovskite Nd2NiMnO6

    NASA Astrophysics Data System (ADS)

    Ali, Anzar; Sharma, G.; Singh, Yogesh

    2018-05-01

    The knowledge of critical exponents plays a crucial role in trying to understand the interaction mechanism near a phase transition. In this report, we present a detailed study of the critical behaviour near the ferromagnetic (FM) transition (TC ˜ 193 K) in Nd2NiMnO6 using the temperature and magnetic field dependent isothermal magnetisation measurements. We used various analysis methods such as Arrott plot, modified Arrott plot, and Kouvel-Fisher plot to estimate the critical parameters. The magnetic critical parameters β = 0.49±0.02, γ = 1.05±0.04 and critical isothermal parameter δ = 3.05±0.02 are in excellent agreement with Widom scaling. The critical parameters analysis emphasizes that mean field interaction is the mechanism driving the FM transition in Nd2NiMnO6.

  14. Performance characteristics of nanocrystalline diamond vacuum field emission transistor array

    NASA Astrophysics Data System (ADS)

    Hsu, S. H.; Kang, W. P.; Davidson, J. L.; Huang, J. H.; Kerns, D. V.

    2012-06-01

    Nitrogen-incorporated nanocrystalline diamond (ND) vacuum field emission transistor (VFET) with self-aligned gate is fabricated by mold transfer microfabrication technique in conjunction with chemical vapor deposition (CVD) of nanocrystalline diamond on emitter cavity patterned on silicon-on-insulator (SOI) substrate. The fabricated ND-VFET demonstrates gate-controlled emission current with good signal amplification characteristics. The dc characteristics of the ND-VFET show well-defined cutoff, linear, and saturation regions with low gate turn-on voltage, high anode current, negligible gate intercepted current, and large dc voltage gain. The ac performance of the ND-VFET is measured, and the experimental data are analyzed using a modified small signal circuit model. The experimental results obtained for the ac voltage gain are found to agree with the theoretical model. A higher ac voltage gain is attainable by using a better test setup to eliminate the associated parasitic capacitances. The paper reveals the amplifier characteristics of the ND-VFET for potential applications in vacuum microelectronics.

  15. Performance characteristics of nanocrystalline diamond vacuum field emission transistor array

    NASA Astrophysics Data System (ADS)

    Hsu, S. H.; Kang, W. P.; Davidson, J. L.; Huang, J. H.; Kerns, D. V.

    2012-05-01

    Nitrogen-incorporated nanocrystalline diamond (ND) vacuum field emission transistor (VFET) with self-aligned gate is fabricated by mold transfer microfabrication technique in conjunction with chemical vapor deposition (CVD) of nanocrystalline diamond on emitter cavity patterned on silicon-on-insulator (SOI) substrate. The fabricated ND-VFET demonstrates gate-controlled emission current with good signal amplification characteristics. The dc characteristics of the ND-VFET show well-defined cutoff, linear, and saturation regions with low gate turn-on voltage, high anode current, negligible gate intercepted current, and large dc voltage gain. The ac performance of the ND-VFET is measured, and the experimental data are analyzed using a modified small signal circuit model. The experimental results obtained for the ac voltage gain are found to agree with the theoretical model. A higher ac voltage gain is attainable by using a better test setup to eliminate the associated parasitic capacitances. The paper reveals the amplifier characteristics of the ND-VFET for potential applications in vacuum microelectronics.

  16. Composite (La0.45Nd0.25)Sr0.3MnO3/5CuO materials for magnetic refrigeration applications

    NASA Astrophysics Data System (ADS)

    El Maalam, K.; Balli, M.; Habouti, S.; Dietze, M.; Hamedoun, M.; Hlil, E.-K.; Es-Souni, M.; El Kenz, A.; Benyoussef, A.; Mounkachi, O.

    2018-03-01

    In this work, the magnetocaloric properties of (La0.45Nd0.25)Sr0.3MnO3 (LNSMO)-based composites are studied. The structural, microstructural, magnetic and magnetocaloric properties of LNSMO and LNSMO/5CuO samples were investigated aiming to particularly clarify the secondary phase (CuO) role in driving the magnetocaloric behavior. The main phase LNSMO crystallizes in a rhombohedral R-3C (1 6 7) configuration. The XRD patterns of composite samples show both perovskite LNSMO and monoclinic Tenorite CuO structures. The microstructural analysis unveils that the CuO phase is mainly present in the grain boundaries and segregates region. On the other hand, it was found that the magnetocaloric effect could be significantly enhanced by adding a small amount of CuO (5% weight ratio). For a magnetic field changing from 0 to 1.5 T, the corresponding isothermal entropy change was found to be 2.55 J/kg K for the LNSMO/5CuO composite while it is only about 1.1 J/kg K for the mother material LNSMO. Our finding should inspire and open new ways for the enhancement of the magnetocaloric effect in manganites-based materials.

  17. Development of Nanocrystalline Zeolite Materials for the Decontamination of Chemical Warfare Agents

    DTIC Science & Technology

    2008-11-17

    phosphite (CH3O)2P(O)H or DMP. There is -40-20020406080100 In te ns ity ppm a) b) c) d) * ** ** ** * * 33 37 1225 9 Figure 6. 31P MAS NMR spectra...The main objective of this research is to use novel nanocrystalline zeolite materials synthesized in our laboratories for the decontamination of...nanocrystalline zeolite materials. In these studies, we have focused our attention on the decontamination of 2-CEES and DMMP, two simulants for mustard gas

  18. Nd: YAG laser irradiation effects on structural and magnetic properties of Ni1+xZrxFe2-2xO4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Saraf, Tukaram S.; Kounsalye, Jitendra S.; Birajdar, Shankar D.; Shamkuwar, N. R.

    2018-05-01

    The effect of 112 mJ Nd: YAG laser irradiation on structural, morphological, infrared and magnetic properties of Ni1+xZrxFe2-2xO4 spinel ferrite nanoparticles has been systematically investigated in the present work. The sol-gel auto combustion synthesis method was successfully executed for the synthesis of the present system. All the samples were characterized by X-ray diffraction technique (XRD), scanning electron microscopy (SEM) and infrared spectroscopy (IR) technique. The magnetic properties of the present samples were measured by pulse field hysteresis loop technique. All the properties were measured for laser irradiated samples as well, to understand the effect of irradiation on the properties. The single-phase cubic spinel structure was confirmed by X-ray diffraction patterns of all samples and the disordered structure was observed for irradiated samples. The two principle absorption bands in IR spectra also confirm the formation of the spinel structure. Spherical and agglomerated morphology was observed for Zr4+ substituted nickel ferrite, whereas scratched morphology was observed for the irradiated samples. The grain size confirms the nanocrystalline nature, the crystallite size also evident the same. The magnetic parameters decreased after Zr4+ ion doping and strongly influenced by the irradiation.

  19. 1.083 μm laser operation in Nd,Mg:LiTaO3 crystal

    NASA Astrophysics Data System (ADS)

    Hu, P. C.; Hang, Y.; Li, R.; Gong, J.; Yin, J. G.; Zhao, C. C.; He, X. M.; Yu, T.; Zhang, L. H.; Chen, W. B.; Zhu, Y. Y.

    2011-10-01

    Nd,Mg:LiTaO3 single crystal with high optical quality was grown by Czochralski technique. Absorption and fluorescence spectra were investigated. The peak absorption cross section at 806.5 nm and peak emission cross section at 1091 nm are 6.81×10-20 and 3.28×10-20 cm2, respectively. The fluorescence lifetime was measured to be 129 μs. With a laser-diode as the pump source, a maximum 375 mW continuous-wave laser output at 1083 nm has been obtained with a slope efficiency of 7.2% with respect to the pump power.

  20. Orientation-adjusted anomalous insulator-metal transition in NdNiO3/LaMnO3 bilayers

    NASA Astrophysics Data System (ADS)

    Pan, S. Y.; Shi, L.; Zhao, J. Y.; Zhou, S. M.; Xu, X. M.

    2018-04-01

    NdNiO3/LaMnO3 (NNO/LMO) bilayers were epitaxially grown on SrTiO3 (STO) substrates with different orientations by the polymer-assisted deposition technique. A well crystallization quality of the bilayers is confirmed by X-ray diffraction. Two consecutive transitions, an anomalous insulator-metal transition at ˜100 K followed by the typical metal-insulator transition at ˜171 K, are observed in the (001)-oriented NNO/LMO/STO bilayer. The anomalous insulator-metal transition temperature increases to 142 K for the (111)-oriented NNO/LMO/STO bilayer. Meanwhile, the magnetic properties of the NNO/LMO bilayers show an obvious difference with [100] and [111] orientations. Considering the different strain directions and the related oxygen octahedral distortion/rotation, it is suggested that the magnetic changes and the low-temperature anomalous insulator-metal transition in the NNO/LMO bilayers are attributed to the strong interlayer exchange coupling and charge transfer adjusted by the substrate orientation, which can be an effective technique to tune the properties of transition-metal oxide films.

  1. 926 nm laser operation in Nd:GdNbO4 crystal based on 4F3/2 → 4I9/2 transition

    NASA Astrophysics Data System (ADS)

    Yan, Renpeng; Li, Xudong; Yao, Wenming; Shen, Yingjie; Zhou, Zhongxiang; Peng, Fang; Zhang, Qingli; Dou, Renqing; Gao, Jing

    2018-05-01

    926 nm laser operation in a Nd:GdNbO4 crystal based on quasi-three-level 4F3/2 → 4I9/2 transition is reported, for the first time to our best knowledge. An average output power of 393 mW at 926 nm under 879 nm LD pumping is obtained with a slope efficiency of 33.3% and an optical-to-optical efficiency of 26.0%. The slope efficiency with respect to absorbed pump power is estimated to be 47.7%. Comparison between output characters of 926 nm laser under direct and indirect pumping is conducted. The average output power at 926 nm under 808 nm LD pumping reaches 305 mW with an optical-to-optical efficiency of 16.1%.

  2. Unconventional Superconductivity in the BiS_{2}-Based Layered Superconductor NdO_{0.71}F_{0.29}BiS_{2}.

    PubMed

    Ota, Yuichi; Okazaki, Kozo; Yamamoto, Haruyoshi Q; Yamamoto, Takashi; Watanabe, Shuntaro; Chen, Chuangtian; Nagao, Masanori; Watauchi, Satoshi; Tanaka, Isao; Takano, Yoshihiko; Shin, Shik

    2017-04-21

    We investigate the superconducting-gap anisotropy in one of the recently discovered BiS_{2}-based superconductors, NdO_{0.71}F_{0.29}BiS_{2} (T_{c}∼5  K), using laser-based angle-resolved photoemission spectroscopy. Whereas the previously discovered high-T_{c} superconductors such as copper oxides and iron-based superconductors, which are believed to have unconventional superconducting mechanisms, have 3d electrons in their conduction bands, the conduction band of BiS_{2}-based superconductors mainly consists of Bi 6p electrons, and, hence, the conventional superconducting mechanism might be expected. Contrary to this expectation, we observe a strongly anisotropic superconducting gap. This result strongly suggests that the pairing mechanism for NdO_{0.71}F_{0.29}BiS_{2} is an unconventional one and we attribute the observed anisotropy to competitive or cooperative multiple paring interactions.

  3. Spin-lattice coupling mediated multiferroicity in (ND 4) 2FeCl 5 • D 2O

    DOE PAGES

    Tian, Wei; Cao, Huibo; Wang, Jincheng; ...

    2016-12-07

    In this paper, we report a neutron diffraction study of the multiferroic mechanism in (ND 4) 2FeCl 5 • D 2O, a molecular compound that exhibits magnetically induced ferroelectricity. This material exhibits two successive magnetic transitions on cooling: a long-range order transition to an incommensurate (IC) collinear sinusoidal spin state at T N = 7.3 K, followed by a second transition to an IC cycloidal spin state at T FE = 6.8 K, the latter of which is accompanied by spontaneous ferroelectric polarization. The cycloid structure is strongly distorted by spin-lattice coupling, as evidenced by the observations of both oddmore » and even higher-order harmonics associated with the cycloid wave vector, and a weak commensurate phase that coexists with the IC phase. The second-order harmonic appears at T FE, thereby providing unambiguous evidence that the onset of the electric polarization is accompanied by a lattice modulation due to spin-lattice interaction. The neutron results, in conjunction with the negative thermal expansion and large magnetostriction observed, indicate that spin-lattice coupling plays a critical role in the ferroelectric mechanism of (ND 4) 2FeCl 5 • D 2O.« less

  4. Fischer-Tropsch Cobalt Catalyst Improvements with the Presence of TiO2, La2O3, and ZrO2 on an Alumina Support

    NASA Technical Reports Server (NTRS)

    Klettlinger, Jennifer Lindsey Suder

    2012-01-01

    The objective of this study was to evaluate the effect of titanium oxide, lanthanum oxide, and zirconium oxide on alumina supported cobalt catalysts. The hypothesis was that the presence of lanthanum oxide, titanium oxide, and zirconium oxide would reduce the interaction between cobalt and the alumina support. This was of interest because an optimized weakened interaction could lead to the most advantageous cobalt dispersion, particle size, and reducibility. The presence of these oxides on the support were investigated using a wide range of characterization techniques such as SEM, nitrogen adsorption, x-ray diffraction (XRD), temperature programmed reduction (TPR), temperature programmed reduction after reduction (TPR-AR), and hydrogen chemisorptions/pulse reoxidation. Results indicated that both La2O3 and TiO2 doped supports facilitated the reduction of cobalt oxide species in reference to pure alumina supported cobalt catalysts, however further investigation is needed to determine the effect of ZrO2 on the reduction profile. Results showed an increased corrected cluster size for all three doped supported catalysts in comparison to their reference catalysts. The increase in reduction and an increase in the cluster size led to the conclusion that the support-metal interaction weakened by the addition of TiO2 and La2O3. It is also likely that the interaction decreased upon presence of ZrO2 on the alumina, but further research is necessary. Preliminary results have indicated that the alumina-supported catalysts with titanium oxide and lanthanum oxide present are of interest because of the weakened cobalt support interaction. These catalysts showed an increased extent of reduction, therefore more metallic cobalt is present on the support. However, whether or not there is more cobalt available to participate in the Fischer-Tropsch synthesis reaction (cobalt surface atoms) depends also on the cluster size. On one hand, increasing cluster size alone tends to decrease the

  5. Structural and transport properties of NdCrO{sub 3} nanoceramics

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

    Saha, Sujoy; Sakhya, Anup Pradhan; Sinha, T. P.

    2013-02-05

    Reitveld refinement of the room temperature powder X-ray diffraction profile of NdCrO{sub 3} (NCO) nanoceramics synthesized by sol-gel processing shows orthorhombic Pnma (D{sub 2h}{sup 16}) space group symmetry. The refined lattice parameters are a = 5.482(3) A, b = 7.689(4) A and c = 5.416(3) A. Transmission electron microscopy (TEM) of NCO shows that the average particle size is around 70 nm. The electrical transport property of NCO is investigated by both conductivity and electric modulus formalism. The electrical data is taken by a LCR meter in a temperature range from 303 K to 573 K and in a frequencymore » range from 42 Hz to 1.1 MHz. The ac conductivity follows a power law. The Cole-Cole plot of impedance at 303 K shows grain effect.« less

  6. Structural and optical properties of nano-sized K3Nd(PO4)2:Yb3+ orthophosphate.

    PubMed

    Mizer, D; Macalik, L; Tomaszewski, P E; Lisiecki, R; Godlewska, P; Matraszek, A; Szczygieł, I; Zawadzki, M; Hanuza, J

    2009-09-01

    Nanocrystals of tripotassium neodymium bis-phosphate(V) doped with ytterbium ions, K3Nd(PO4)2: Yb3+, were synthesized by Pechini method. The obtained grains, having an average size of about 40 nm, were characterised by X-ray, electron microscopic, electron absorption, luminescence and IR studies. Moreover, fluorescence decay studies were carried out at room temperature. The energy transfer from the Nd3+ to Yb3+ was described and discussed. The results were compared to those of the K3Nd(PO4)2 bulk crystal.

  7. Performance characterization of CNTs and γ-Al2O3 supported cobalt catalysts in Fischer-Tropsch reaction

    NASA Astrophysics Data System (ADS)

    Ali, Sardar; Zabidi, Noor Asmawati Mohd; Subbarao, Duvvuri

    2014-10-01

    Catalysts were prepared via a wet impregnation method. Different physicochemical properties of the samples were revealed by transmission electron microscope (TEM), temperature programmed reduction (H2-TPR) and carbon dioxide desorption (CO2-desorption). Fischer-Tropsch reaction (FTS) was carried out in a fixed-bed microreactor at 220°C and 1 atm, with H2/ CO = 2v / v and space velocity, SV of 12L/g.h for 5 h. Various characterization techniques revealed that there was a stronger interaction between Co and Al2O3 support compared to that of CNTs support. CNTs support increased the reducibility and decreased Co particle size. A significant increase in % CO conversion and FTS reaction rate was observed over CNTs support compared to that of Co / Al2O3. Co/CNTs resulted in higher C5+ hydrocarbons selectivity compared to that of Co / Al2O3 catalyst. CNTs are a better support for Co compared to Al2O3.

  8. Structure, spectroscopic properties and laser performance of Nd:YNbO4 at 1066 nm

    NASA Astrophysics Data System (ADS)

    Ding, Shoujun; Peng, Fang; Zhang, Qingli; Luo, Jianqiao; Liu, Wenpeng; Sun, Dunlu; Dou, Renqin; Sun, Guihua

    2016-12-01

    We have demonstrated continuous wave (CW) laser operation of Nd:YNbO4 crystal at 1066 nm for the first time. A maximum output power of 1.12 W with the incident power of 5.0 W is successfully achieved corresponding to an optical-to-optical conversion efficiency of 22.4% and a slope efficiency of 24.0%. The large absorption cross section (8.7 × 10-20 cm2) and wide absorption band (6 nm) at around 808 nm indicates the good pumping efficiency by laser diodes (LD). The small emission cross section (29 × 10-20 cm2) and relative long lifetime of the 4F3/2 → 4I11/2 transition indicates good energy storage capacity of Nd:YNbO4. Moreover, the raw materials of Nd:YNbO4 are stable, thus, it can grow high-quality and large-size by Czochralski (CZ) method. Therefore the Nd:YNbO4 crystal is a potentially new laser material suitable for LD pumping.

  9. Anode-supported single-chamber solid oxide fuel cell based on cobalt-free composite cathode of Nd0.5Sr0.5Fe0.8Cu0.2O3-δ-Sm0.2Ce0.8O1.9 at intermediate temperatures

    NASA Astrophysics Data System (ADS)

    Yin, Jie-Wei; Zhang, Chunming; Yin, Yi-Mei; Shi, Huangang; Lin, Ye; Lu, Jun; Ma, Zi-Feng

    2015-07-01

    As a candidate of cathode material of single-chamber solid oxide fuel cell (SC-SOFC), cobalt-free mixed ionic electronic conductor (MIEC) Nd0.5Sr0.5Fe0.8Cu0.2O3-δ (NSFCu) is synthesized by sol-gel method with ethylene diamine tetraacetic acid and citric acid as co-complexing agents. The XRD shows NSFCu is stable after CO2 treatment and chemical compatible with SDC at high temperatures. CO2-TPD (CO2-temperature programmed desorption) demonstrates both CO2 adsorption and desorption phenomenon on NSFCu surface. However, the polarization resistances (Rp) of NSFCu and SDC (10:4 in weight) composite electrodes showed no decay in 5% CO2. Single cell using N2-O2-CH4 mixed gas (CH4 to O2 ratio = 1.5) as fuel shows maximum power density of 635 mW cm-2 at 700 °C. These results suggest that NSFCu-SDC is a promising composite cathode material for application in single-chamber solid oxide fuel cell.

  10. First Observation of Photoinduced Magnetization for the Cyano-Bridged 3d 4f Heterobimetallic Assembly Nd(DMF)4(H2O)3(μ-CN)Fe(CN)5ṡH2O (DMF=N,N-Dimethylformamide)

    NASA Astrophysics Data System (ADS)

    Li, Guangming; Akitsu, Takashiro; Sato, Osamu; Einaga, Yasuaki

    2004-12-01

    Photoinduced magnetization of the cyano-bridged 3d 4f hetero-bimetallic assembly Nd (DMF)4(H2O)3(μ-CN)Fe(CN)5ṡH2O (1) (DMF=N,N-dimethylformamide) is described in this paper. The χM T values are enhanced by about 45% after UV light illumination in the temperature range of 5 50 K. We propose that UV light illumination induces a structural distortion in 1. This small structural change is propagated by molecular interactions in the inorganic network. Furthermore, the cooperativity resulting from the molecular interaction functions to increase the activation energy of the relaxation processes, which makes observation of the photoexcited state possible. The flexible network structure through the hydrogen bonds in 1 plays an essential role for the photoinduced phenomenon. This finding may open up a new domain for developing molecule-based magnetic materials.

  11. Influences of lattice vibration and electron transition on thermal emissivity of Nd3+ doped LaMgAl11O19 hexaaluminates for metallic thermal protection system

    NASA Astrophysics Data System (ADS)

    Liu, Hong-Zhi; Liu, Zhan-Guo; Ouyang, Jia-Hu; Wang, Ya-Ming

    2012-10-01

    Normal spectral emissivity of La1-xNdxMgAl11O19 (x = 0.05, 0.10, 0.15, 0.25) ceramics has a maximum value at the Nd3+ content of x = 0.10 in the wavelength range of 3-6 μm. The difference in emissivity at short wavelengths of 3-6 μm is tightly linked to the absorption transitions from 4I9/2 to 4F3/2, 4I15/2, and 4I13/2 and the intensities of radiation transitions from 4F3/2 to 4I11/2 and 4I13/2 of Nd3+ in LaMgAl11O19 ceramics. However, in the wavelength range of 6-14 μm, the emissivity is quite similar for all the samples, which can be ascribed to the stretching vibration of Al-O tetrahedron and Al-O octahedron.

  12. Tailoring Nd3+ emission spectrum by a neodymium-doped tellurite all-solid photonic bandgap fiber

    NASA Astrophysics Data System (ADS)

    Tong, Hoang Tuan; Demichi, Daisuke; Suzuki, Takenobu; Ohishi, Yasutake

    2018-02-01

    A tellurite all-solid photonic bandgap fiber (ASPBF) whose cladding consists of 60 high-index rods arranged periodically around a central core was successfully fabricated. The diameter of high-index rod was about 5.0 μm and the distance between the center of two adjacent high-index rods was approximately 8.0 μm. The high-index rod was made of the TeO2-Li2O-WO3-MoO3-Nb2O5 (TLWMN) glass, the cladding was made of the TeO2-ZnO-Na2O-La2O3 (TZNL) glass as the background glass material and the central core was made of TZNL glass doped with 0.5 wt% of Nd2O3. A supercontinuum light from 0.6 to 2.4 μm was coupled into the core of fiber which is 2.2 cm long to measure its transmission spectrum. High transmission bands were obtained in the vicinity of 0.75 and 1.3 μm but the transmission was suppressed in the wavelength range from 1.0 to 1.06 μm. When a titanium∶Sapphire laser source at 0.75 μm was used, the emission spectrum was obtained with two peaks at 1.06 and 1.33 μm which are attributed to the 4F3/2->4I11/2 and 4F3/2->4I13/2 transitions of Nd3+ ion, respectively. The intensities of those emission peaks were compared with those obtained from a bulk glass having the same doping concentration of Nd3+. The results showed that by using tellurite ASPBF, the intensity of the 1.06-μm emission was suppressed by one-twelfth but the intensity of the 1.33-μm emission was maintained. This feature is very advantageous to filter out the 1.06-μm emission of Nd3+ ion in order to realize practical amplifier devices at 1.3 μm.

  13. A near ambient pressure XPS study of subnanometer silver clusters on Al 2O 3 and TiO 2 ultrathin film supports

    DOE PAGES

    Mao, Bao -Hua; Chang, Rui; Shi, Lei; ...

    2014-10-29

    Here, we have investigated model systems of silver clusters with different sizes (3 and 15 atoms) deposited on alumina and titania supports using ambient pressure X-ray photoelectron spectroscopy. The electronic structures of silver clusters and support materials are studied upon exposure to various atmospheres (ultrahigh vacuum, O 2 and CO) at different temperatures. Compared to bulk silver, the binding energies of silver clusters are about 0.55 eV higher on TiO 2 and 0.95 eV higher on Al 2O 3 due to the final state effect and the interaction with supports. No clear size effect of the silver XPS peak ismore » observed on different silver clusters among these samples. Silver clusters on titania show better stability against sintering. Al 2p and Ti 2p core level peak positions of the alumina and titania support surfaces change upon exposure to oxygen while the Ag 3d core level position remains unchanged. We discuss the origin of these core level shifts and their implications for catalytic properties of Ag clusters.« less

  14. Mechanism of γ-irradiation induced phase transformations in nanocrystalline Mn{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} ceramics

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

    Jagadeesha Angadi, V.; Anupama, A.V.; Choudhary, Harish K.

    The structural, infrared absorption and magnetic property transformations in nanocrystalline Mn{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} samples irradiated with different doses (0, 15, 25 and 50 kGy) of γ-irradiation were investigated in this work and a mechanism of phase transformation/decomposition is provided based on the metastable nature of the Mn-atoms in the spinel lattice. The nano-powder sample was prepared by solution combustion route and the pellets of the sample were exposed to γ-radiation. Up to a dose of 25 kGy of γ-radiation, the sample retained the single phase cubic spinel (Fd-3m) structure, but the disorder in the sample increased. On irradiatingmore » the sample with 50 kGy γ-radiation, the spinel phase decomposed into new stable phases such as α-Fe{sub 2}O{sub 3} and ZnFe{sub 2}O{sub 4} phases along with amorphous MnO phase, leading to a change in the surface morphology of the sample. Along with the structural transformations the magnetic properties deteriorated due to breakage of the ferrimagnetic order with higher doses of γ-irradiation. Our results are important for the understanding of the stability, durability and performance of the Mn-Zn ferrite based devices used in space applications. - Graphical abstract: The nanocrystalline Mn{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} ceramic sample transforms to crystalline α-Fe{sub 2}O{sub 3} and ZnFe{sub 2}O{sub 4} phases (and amorphous MnO phase) at a γ-irradiation dose of 50 kGy, as MnO goes out of the spinel lattice. The high energy γ-irradiation causes structural damage to the nanomaterials leading to change in morphology of the sample as seen in the SEM images. - Highlights: • Mn atoms are more unstable in the Mn-Zn ferrite spinel lattice than Zn-atoms. • Displacement of Mn atoms by γ-radiation from the lattice renders phase transformation. • In Mn{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4}, Mn-ferrite cell transforms to crystalline α-Fe{sub 2}O{sub 3} and amorphous MnO. • The stable Zn

  15. NIR emitting K2SrCl4:Eu2+, Nd3+ phosphor as a spectral converter for CIGS solar cell

    NASA Astrophysics Data System (ADS)

    Tawalare, P. K.; Bhatkar, V. B.; Omanwar, S. K.; Moharil, S. V.

    2018-05-01

    Intense near-infrared emitting phosphor K2SrCl4:Eu2+,Nd3+ with various concentrations of Nd3+ were synthesized. These are characterized with X-ray diffraction, reflectance, photoluminescence emission and photoluminescence excitation spectroscopy, PL lifetime measurements. The emission can be excited by a broad band in near ultra violet region as a consequence of Eu2+→Nd3+ energy transfer. The efficiency of Eu2+→Nd3+ energy transfer is as high as 95%. Fluorescence decay curves for Eu2+ doped samples are almost exponential and described by τ = 500 ns. Eu2+ lifetimes are shortened after Nd3+ doping. Near infrared Emission intensity is limited by Nd3+→Nd3+ energy transfer and the consequent concentration quenching. Nd3+ emission matches well with the spectral response of CIGS and CIS solar cells. Absorption of near ultra violet radiations followed by conversion to near infrared indicates the potential application in solar photovoltaics.

  16. Remarkable support effect on the reactivity of Pt/In2O3/MOx catalysts for methanol steam reforming

    NASA Astrophysics Data System (ADS)

    Liu, Xin; Men, Yong; Wang, Jinguo; He, Rong; Wang, Yuanqiang

    2017-10-01

    Effects of supports over Pt/In2O3/MOx catalysts with extremely low loading of Pt (1 wt%) and In2O3 loadings (3 wt%) are investigated for the hydrogen production of methanol steam reforming (MSR) in the temperature range of 250-400 °C. Under practical conditions without the pre-reduction, the 1Pt/3In2O3/CeO2 catalyst shows the highly efficient catalytic performance, achieving almost complete methanol conversion (98.7%) and very low CO selectivity of 2.6% at 325 °C. The supported Pt/In2O3 catalysts are characterized by means of Brunauer-Emmett-Teller (BET) surface area, X-ray diffraction (XRD), high-resolution transmission microscopy (HRTEM), temperature programmed reduction with hydrogen (H2-TPR), CO pulse chemisorption, temperature programmed desorption of methanol and water (CH3OH-TPD and H2O-TPD). These demonstrate that the nature of catalyst support of Pt/In2O3/MOx plays crucial roles in the Pt dispersion associated by the strong interaction among Pt, In2O3 and supporting materials and the surface redox properties at low temperature, and thus affects their capability to activate the reactants and determines the catalytic activity of methanol steam reforming. The superior 1Pt/3In2O3/CeO2 catalyst, exhibiting a remarkable reactivity and stability for 32 h on stream, demonstrates its potential for efficient hydrogen production of methanol steam reforming in mobile and de-centralized H2-fueled PEMFC systems.

  17. Structural, magnetic and magnetocaloric properties of Co-doped nanocrystalline La0.7Te0.3Mn0.7Co0.3O3

    NASA Astrophysics Data System (ADS)

    Meenakshi; Kumar, Amit; Mahato, Rabindra Nath

    2018-02-01

    Structural, magnetic and magnetocaloric properties of the nanocrystalline La0.7Te0.3Mn0.7Co0.3O3 perovskite manganite were investigated. X-ray diffraction pattern indicated that the nanocrystalline sample crystallized in orthorhombic crystal structure with Pbnm space group. The average particle size was calculated using scanning electron microscope and it was found to be ∼150 nm. Temperature dependence magnetization measurements revealed ferromagnetic-paramagnetic phase transition and the Curie temperature (TC) was found to be ∼201 K. Field dependence magnetization showed the hysteresis at low temperature with a coercive field of ∼0.34 T and linear dependence at high temperature corresponds to paramagnetic region. Based on the magnetic field dependence magnetization data, the maximum entropy change and relative cooling power (RCP) were estimated and the values were 1.002 J kg-1 K-1 and 90 J kg-1 for a field change of 5 T respectively. Temperature dependent resistivity ρ(T) data exhibited semiconducting-like behavior at high temperature and the electrical transport was well explained by Mott's variable-range hopping (VRH) conduction mechanism in the temperature range of 250 K-300 K. Using the VRH fit, the calculated hoping distance (Rh) at 300 K was 54.4 Å and density of states N(EF) at room temperature was 7.04 × 1018 eV-1 cm-3. These values were comparable to other semiconducting oxides.

  18. Nd2-xCexCuO4-y/Nd2-xCexOy boundary and resistive switchings in mesoscopic structures on base of epitaxial Nd1.86Ce0.14CuO4-у films

    NASA Astrophysics Data System (ADS)

    Tulina, N. A.; Rossolenko, A. N.; Ivanov, A. A.; Sirotkin, V. V.; Shmytko, I. M.; Borisenko, I. Yu.; Ionov, A. M.

    2016-08-01

    Reverse and stable bipolar resistive switching effect (BRSE) was observed in planar Nd2-xCex CuO4-y/Nd2-xCexOx/Ag heterostructure. It was shown that the СVС of the BRSE observed has a diode character. Simulations were used to consider the influence of the nonuniform distribution of an electric field at the interface of a heterojunction on the effect of bipolar resistive switching in investigated structures. The inhomogeneous distribution of the electric field near the contact edge creates regions of higher electric field strength which, in turn, stimulates motion and redistribution of defects, changes of the resistive properties of the whole structure and formation of a percolation channel.

  19. Enhanced magnetostrictive properties of nanocrystalline Dy3+ substituted Fe-rich Co0.8Fe2.2O4 for sensor applications

    NASA Astrophysics Data System (ADS)

    Kharat, Shahaji P.; Swadipta, Roy; Kambale, R. C.; Kolekar, Y. D.; Ramana, C. V.

    2017-10-01

    We report on the enhanced magnetostrictive properties of nanocrystalline Dysprosium (Dy3+) substituted iron-rich cobalt ferrites (Co0.8Fe(2.2-x)DyxO4, referred to as CFDO). The CFDO samples with a variable Dy concentration (x = 0.000-0.075) were synthesized by the sol-gel auto-combustion method. The phase purity and crystal structure were confirmed from X-ray diffraction analyses coupled with Rietveld refinement. Surface morphology analysis using scanning electron microscopy imaging indicates the agglomerated magnetic particles with a non-uniform particle size distribution, which is desirable to transfer the strain. The magnetostriction coefficient (λ11) measurements indicate that the CFDO with Dy concentration x = 0.025 exhibits the highest strain sensitivity, (dλ/dH) ˜1.432 nm/A (for H ≤ 1000 Oe). On the other hand, the magnetostriction coefficient (λ12) measurements indicate that the Dy concentration x = 0.075 exhibits the larger (dλ/dH) ˜ 0.615 nm/A (for H ≤ 1000 Oe). The maximum λ11value of 166 ppm (at H = 3300 Oe) was observed for a compound with Dy concentration x = 0.050. Magnetization measurements indicate that the saturation magnetization and coercivity of CFDO samples are dependent on the Dy3+content; the highest value of squareness ratio of 0.424 was observed for x = 0.050. The interplay between strain sensitivity (dλ/dH) and instantaneous susceptibility (dM/dH), as derived from magnetostriction and magnetization results, demonstrates that these CFDO materials may be useful for developing torque/stress sensors, as a constituent magnetostrictive phase for making the magnetoelectric composite materials and thus suitable for magnetoelectric sensor applications.

  20. Polarized spectral properties and potential application of large-size Nd3+:Ba3Gd2(BO3)4 crystal

    NASA Astrophysics Data System (ADS)

    Gao, S. F.; Lv, S. Z.; Zhu, Z. J.; Wang, Y.; You, Z. Y.; Li, J. F.; Xu, J. L.; Wang, H. Y.; Tu, C. Y.

    2014-06-01

    The Nd3+-doped Ba3Gd2(BO3)4 crystal with high optical quality and large size is reported in this paper. The growing processes and characteristics of Nd3+:Ba3Gd2(BO3)4 crystal are discussed. The absorption and luminescence spectra of Nd3+ in Ba3Gd2(BO3)4 crystal were measured at room temperature. The luminescence decay curve in correspondence with the 4F3/2 →4I11/2 transition centered at 1062 nm was also measured. The JO intensity parameters Ωt (t = 2,4,6) were calculated to be Ω2 = 1.263, Ω4 = 2.496, Ω6 = 3.606. The radiative lifetime τr and fluorescence lifetime τf are 317.771 and 115 μs respectively, and the fluorescence quantum efficiency is 37.1%.

  1. The effect of texture in (Bi3.5Nd0.5)(Ti2.97Nb0.03)O12 ceramics

    NASA Astrophysics Data System (ADS)

    Cao, Ziping; Ding, Aili; Zheng, Xinsen; Qiu, Pingsun; Cheng, Wenxiu

    2004-11-01

    (Bi3.5Nd0.5) (Ti2.97Nb0.03)O12 ferroelectric ceramics was successfully prepared by a hot-pressing method. XRD diffraction confirms that the samples hold different texture in the sliced planes parallel and perpendicular to the hot-pressing axis, respectively. The anisotropy of ferroelectric, dielectric and piezoelectric properties were all observed in the textured ceramics. Due to the great improvement of ferroelectric and piezoelectric properties, the sample which was sliced along the direction parallel to the hot-pressing axis can be considered as a good candidate of high temperature piezoelectric materials.

  2. Porous nanocrystalline silicon supported bimetallic Pd-Au catalysts: preparation, characterization and direct hydrogen peroxide synthesis

    NASA Astrophysics Data System (ADS)

    Potemkin, Dmitriy I.; Maslov, Dmitry K.; Loponov, Konstantin; Snytnikov, Pavel V.; Shubin, Yuri V.; Plyusnin, Pavel E.; Svintsitskiy, Dmitry A.; Sobyanin, Vladimir A.; Lapkin, Alexei A.

    2018-03-01

    Bimetallic Pd-Au catalysts were prepared on the porous nanocrystalline silicon (PSi) for the first time. The catalysts were tested in the reaction of direct hydrogen peroxide synthesis and characterised by standard structural and chemical techniques. It was shown that the Pd-Au/PSi catalyst prepared from conventional H2[PdCl4] and H[AuCl4] precursors contains monometallic Pd and a range of different Pd-Au alloy nanoparticles over the oxidized PSi surface. The PdAu2/PSi catalyst prepared from the [Pd(NH3)4][AuCl4]2 double complex salt single-source precursor predominantly contains bimetallic Pd-Au alloy nanoparticles. For both catalysts the surface of bimetallic nanoparticles is Pd-enriched and contains palladium in Pd0 and Pd2+ states. Among the catalysts studied, the PdAu2/PSi catalyst was the most active and selective in the direct H2O2 synthesis with H2O2 productivity of 0.5 at selectivity of 50 % and H2O2 concentration of 0.023 M in 0.03 M H2SO4-methanol solution after 5 h on stream at -10 °C and atmospheric pressure. This performance is due to high activity in the H2O2 synthesis reaction and low activities in the undesirable H2O2 decomposition and hydrogenation reactions. Good performance of the PdAu2/PSi catalyst was associated with the major part of Pd in the catalyst being in the form of the bimetallic Pd-Au nanoparticles. Porous silicon was concluded to be a promising catalytic support for direct hydrogen peroxide synthesis due to its inertness with respect to undesirable side reactions, high thermal stability and conductivity, possibility of safe operation at high temperatures and pressures and a well-established manufacturing process.

  3. Design of LaPO4:Nd3+ materials by using ionic liquids

    NASA Astrophysics Data System (ADS)

    Cybinska, J.; Guzik, M.; Lorbeer, C.; Zych, E.; Guyot, Y.; Boulon, G.; Mudring, A.-V.

    2017-01-01

    Monoclinic monazite-type Nd3+-doped lanthanum orthophosphate (LaPO4:Nd3+) nanoparticles were prepared by microwave treatment of simple lanthanide precursors such as Nd(OAc)3•xH2O, OAc = acetate) with task-specific dihydrogen phosphate ionic liquids (ILs) 1-butyl-1-methylpyrrolidinium dihydrogenphosphate- BmPyrH2PO4 (IL1) and 2-hydroxyethyl-N,N,N-trimethylammonium, [choline][H2PO4] (IL2) as the reaction medium, reactant and in-situ nanoparticle stabilizer. This synthesis route possesses many advantages as it is a fast and facile preparation method of the desired phosphate nanomaterials without the necessity for post-reaction heat treatment to obtain the anhydrous high temperature monazite phosphate phase. The nano-sized phosphors Nd3+:LaPO4 were carefully analyzed by the powder X-ray diffraction, electron microscopy and spectroscopic techniques taking advantage of the Nd3+ spectroscopic probe to analyze in detail the structural properties. Applied high resolution low temperature absorption and emission techniques allowed to complete the structural information unavailable from the XRD powder patterns. A clear influence of the used task-specific dihydrogen phosphate ILs on the structure, morphology, luminescence intensity and lifetimes of the obtained Nd3+:LaPO4 was found. It is worth noting that the Nd3+ luminescence in LaPO4 has never been reported up to now.

  4. Ridge waveguide laser in Nd:LiNbO3 by Zn-diffusion and femtosecond-laser structuring

    NASA Astrophysics Data System (ADS)

    Martínez de Mendívil, Jon; del Hoyo, Jesús; Solís, Javier; Lifante, Ginés

    2016-12-01

    Ridge waveguide lasers have been fabricated on Nd3+ doped LiNbO3 crystals. The fs-laser writing technique was used to define ridge structures on a gradient-index planar waveguide fabricated by Zn-diffusion. This planar waveguide was formed in a z-cut LiNbO3 substrate homogeneously doped with a 0.23% of Nd3+ ions. To obtain lateral light confinement, the surface was then micromachined using a multiplexed femtosecond laser writing beam, forming the ridge structures. By butting two mirrors at the channel waveguide end-facets, forming a waveguide laser cavity, TM-polarized laser action at 1085 nm was achieved by end-fire TM-pumping at 815 nm. The waveguide laser shows a threshold of 31 mW, with a 7% of slope efficiency.

  5. Pressure-induced structural transformations in lanthanide titanates: La{sub 2}TiO{sub 5} and Nd{sub 2}TiO{sub 5}

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

    Zhang, F.X., E-mail: zhangfx@umich.ed; Wang, J.W.; Lang, M.

    The structure of orthorhombic rare earth titanates of La{sub 2}TiO{sub 5} and Nd{sub 2}TiO{sub 5}, where Ti cations are in five-fold coordination with oxygen, has been studied at high pressures by X-ray diffraction (XRD), Raman scattering measurements, and quantum mechanical calculations. Both XRD and Raman results indicated two pressure-induced phase transitions during the process. An orthorhombic super cell (axbx2c) formed at a pressure between 6 and 10 GPa, and then transformed to a hexagonal high-pressure phase accompanied by partial decomposition. The hexagonal high-pressure phase is quenchable. Detailed structural analysis indicated that the five-coordinated TiO{sub 5} polyhedra remain during the formationmore » of super cell, but the orthorhombic-to-hexagonal phase transition at high pressures is a reconstructive process, and the five-fold Ti-O coordination increased to more than 6. This phase transition sequence was verified by quantum mechanical calculations. - Graphical abstract: At high pressures, La{sub 2}TiO{sub 5} and Nd{sub 2}TiO{sub 5} transform from the orthorhombic phase to an axbx2c superlattice of the orthorhombic structure and then to a hexagonal high-pressure phase. Display Omitted« less

  6. Significant reduction of saturation magnetization and microwave-reflection loss in barium-natural ferrite via Nd3+ substitution

    NASA Astrophysics Data System (ADS)

    Widanarto, W.; Ardenti, E.; Ghoshal, S. K.; Kurniawan, C.; Effendi, M.; Cahyanto, W. T.

    2018-06-01

    To minimize the signal degradation, many electronic devices require efficient microwave absorbers with very low reflection-losses within the X-band. We prepared a series of trivalent neodymium-ion (Nd3+) substituted barium-natural ferrite using a modified solid-state reaction method. The effect of the Nd3+-ion content on the structure, surface morphology, magnetic properties, and microwave reflection loss was studied. The composites were characterized using X-ray diffraction, a vibrating sample magnetometer, scanning electron microscopy, and a vector network analyzer. The XRD patterns of the sample without Nd3+ reveal the presence of BaFe12O19 (hexagonal) and BaFe2O4 (rhombohedral) phases. Furthermore, a new hexagonal crystal phase of Ba6Nd2Fe4O15 appeared after substituting Nd3+. The average size of the prepared barium-natural ferrite particles was estimated to be between 0.4 and 0.8 μm. Both saturation magnetization and microwave reflection losses of these barium-ferrites were significantly reduced by increasing the Nd3+ content.

  7. Evaluation of structural, morphological and magnetic properties of CuZnNi (CuxZn0.5-xNi0.5Fe2O4) nanocrystalline ferrites for core, switching and MLCI's applications

    NASA Astrophysics Data System (ADS)

    Akhtar, Majid Niaz; Khan, Muhammad Azhar; Ahmad, Mukhtar; Nazir, M. S.; Imran, M.; Ali, A.; Sattar, A.; Murtaza, G.

    2017-01-01

    The influence of Cu substitution on the structural and morphological characteristics of Ni-Zn nanocrystalline ferrites have been discussed in this work. The detailed and systematic magnetic characterizations were also done for Cu substituted Ni-Zn nanoferrites. The nanocrystalline ferrites of Cu substituted CuxZn0.5-xNi0.5Fe2O4 ferrites (x=0, 0.1, 0.2, 0.3, 0.4 and 0.5) were synthesized using sol gel self-combustion hybrid method. X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Transmission electron microscope (TEM) and Vibrating sample magnetometer (VSM) were used to investigate the properties of Cu substituted nanocrystalline ferrites. Single phase structure of Cu substituted in Ni-Zn nanocrystalline ferrites were investigated for all the samples. Crystallite size, lattice constant and volume of the cell were found to increase by increasing Cu contents in spinel structure. The better morphology with well-organized nanocrystals of Cu-Zn-Ni ferrites at x=0 and 0.5 were observed from both FESEM and TEM analysis. The average grain size was 35-46 nm for all prepared nanocrystalline samples. Magnetic properties such as coercivity, saturation, remanence, magnetic squareness, magneto crystalline anisotropy constant (K) and Bohr magneton were measured from the recorded M-H loops. The magnetic saturation and remanence were increased by the incorporation of Cu contents. However, coercivity follow the Stoner-Wolforth model except for x=0.3 which may be due to the site occupancy and replacement of Cu contents from octahedral site. The squareness ratio confirmed the super paramgnetic behaviour of the Cu substituted in Ni-Zn nanocrystalline ferrites. Furthermore, Cu substituted Ni-Zn nanocrystalline ferrites may be suitable for many industrial and domestic applications such as components of transformers, core, switching, and MLCI's due to variety of the soft magnetic characteristics.

  8. Tuning of magnetic ordering by Y substitution onto Tb site in the nanocrystalline TbMnO{sub 3}

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

    Chakraborty, Keka R., E-mail: kekarc@barc.gov.in, E-mail: smyusuf@barc.gov.in; Mukadam, M. D.; Yusuf, S. M., E-mail: kekarc@barc.gov.in, E-mail: smyusuf@barc.gov.in

    2015-10-28

    We report the magnetic properties, of nano-crystalline powders Tb{sub 1−x}Y{sub x}MnO{sub 3} (x = 0, 0.1, 0.2, 0.3 and 0.4), as perceived by neutron diffraction, and elucidate the effect of Tb site substitution on the magnetic structure of TbMnO{sub 3}. All samples crystallized in the orthorhombic structure conforming to space group Pnma, and exhibited an incommensurate collinear antiferromagnetic ordering of the Mn ions below ∼40 K. Furthermore, at T ≤ 20 K, all these samples showed a change in magnetic structure (of Mn moments) to a spiral ordering down to 2 K, the lowest measured temperature. For the samples with x = 0, 0.1, and 0.2, a short-ranged twomore » dimensional (2D) ordering of Tb moments was also observed at 2 K. However, for the other samples (x = 0.3 and 0.4), no magnetic ordering of Tb moments was found down to 2 K. So with Y substitution, a crossover from 2D ordering to a disordering of Tb moments was observed. The moments at the Mn site were found to be lower than the full Mn{sup 3+} (4μ{sub B}) moment for all the samples below 40 K. The magnetic properties of all the samples studied by us in nano form are more pronounced than those of the reported single crystals of same compositions [V. Yu. Ivanov et al., JETP Lett. 91, 392–397 (2010)].« less

  9. Specific heat of new perovskite-type cobaltates Pr{sub 1-x}Nd{sub x}CoO{sub 3}

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

    Thakur, Rasna, E-mail: rasnarishu@gmail.com; Thakur, Rajesh K.; Gaur, N. K.

    2016-05-23

    Specific heat and Bulk modulus (B) of new perovskite-type cobaltates Pr{sub 1-x}Nd{sub x}CoO{sub 3} has been studied by means of a Modified Rigid Ion Model (MRIM) and Atoms in Molecules (AIM) theory in a wide temperature range (1 K ≤ T ≤1000 K). The effect of Nd doping on the elastic, cohesive and thermal properties of PrCoO{sub 3} have been studied probably for the first time by an atomistic approach. The computed results are in good agreement with the available experimental data.

  10. Near infrared absorbing near infrared emitting highly-sensitive luminescent nanothermometer based on Nd(3+) to Yb(3+) energy transfer.

    PubMed

    Marciniak, Ł; Bednarkiewicz, A; Stefanski, M; Tomala, R; Hreniak, D; Strek, W

    2015-10-07

    A new type of near infrared absorbing near infrared emitting (NANE) luminescent nanothermometer is presented, with a physical background that relies on efficient Nd(3+) to Yb(3+) energy transfer under 808 nm photo-excitation. The emission spectra of LiLa0.9-xNd0.1YbxP4O12 (x = 0.05, 0.1, 0.2, 0.3, 0.5) nanocrystals were measured in a wide 100-700 °C temperature range. The ratio between the Nd(3+) ((4)F3/2→(4)I9/2) and Yb(3+) ((2)F5/2→(2)F7/2) luminescence bands, and the thermometer sensitivity were found to be strongly dependent on the Yb(3+) concentration. These phenomenological relations were discussed in terms of the competition between three phenomena, namely (a) Nd(3+)→ Yb(3+) phonon assisted energy transfer, (b) Yb(3+)→ Nd(3+) back energy transfer and (c) energy diffusion between Yb(3+) ions. The highest sensitivity of the temperature measurement was found for x = 0.5 (LiLa0.4Nd0.1Yb0.5P4O12), which was equal to 4 × 10(-3) K(-1) at 330 K. In stark contrast to conventional approaches, the proposed phosphate host matrix allows for a high level of doping, and thus, owing to the negligible concentration quenching, the presented luminophores exhibit a high absorption cross section and bright emission. Moreover, such optical remote thermometers, whose excitation and emission wavelengths are weakly scattered or absorbed and fall into the optical transmission window of the skin, may therefore become a practical solution for biomedical applications, such as remote control of thermotherapy.

  11. Rietveld analysis of the effect of annealing atmosphere on phase evolution of nanocrystalline TiO2 powders.

    PubMed

    Salari, M; Rezaee, M; Chidembo, A T; Konstantinov, K; Liu, H K

    2012-06-01

    The structural evolution of nanocrystalline TiO2 was studied by X-ray diffraction (XRD) and the Rietveld refinement method (RRM). TiO2 powders were prepared by the sol-gel technique. Post annealing of as-synthesized powders in the temperature range from 500 degrees C to 800 degrees C under air and argon atmospheres led to the formation of TiO2 nanoparticles with mean crystallite size in the range of 37-165 nm, based on the Rietveld refinement results. It was found that the phase structure, composition, and crystallite size of the resulting particles were dependent on not only the annealing temperature, but also the annealing atmosphere. Rietveld refinement of the XRD data showed that annealing the powders under argon atmosphere promoted the polymorphic phase transformation from anatase to rutile. Field emission scanning electron microscopy (FESEM) was employed to investigate the morphology and size of the annealed powders.

  12. Giant electrocaloric and energy storage performance of [(K0.5Na0.5)NbO3](1-x)-[LiSbO3] x nanocrystalline ceramics.

    PubMed

    Kumar, Raju; Singh, Satyendra

    2018-02-16

    Electrocaloric (EC) refrigeration, an EC effect based technology has been accepted as an auspicious way in the development of next generation refrigeration due to high efficiency and compact size. Here, we report the results of our experimental investigations on electrocaloric response and electrical energy storage properties in lead-free nanocrystalline (1 - x)K 0.5 Na 0.5 NbO 3 -xLiSbO 3 (KNN-xLS) ceramics in the range of 0.015 ≤ x ≤ 0.06 by the indirect EC measurements. Doping of LiSbO 3 has lowered both the transitions (T C and T O-T ) of KNN to the room temperature side effectively. A maximal value of EC temperature change, ΔT = 3.33 K was obtained for the composition with x = 0.03 at 345 K under an external electric field of 40 kV/cm. The higher value of EC responsivity, ζ = 8.32 × 10 -7  K.m/V is found with COP of 8.14 and recoverable energy storage of 0.128 J/cm 3 with 46% efficiency for the composition of x = 0.03. Our investigations show that this material is a very promising candidate for electrocaloric refrigeration and energy storage near room temperature.

  13. Properties of Resistive Hydrogen Sensors as a Function of Additives of 3 D-Metals Introduced in the Volume of Thin Nanocrystalline SnO2 Films

    NASA Astrophysics Data System (ADS)

    Sevast'yanov, E. Yu.; Maksimova, N. K.; Potekaev, A. I.; Sergeichenko, N. V.; Chernikov, E. V.; Almaev, A. V.; Kushnarev, B. O.

    2017-11-01

    Analysis of the results of studying electrical and gas sensitive characteristics of the molecular hydrogen sensors based on thin nanocrystalline SnO2 films coated with dispersed Au layers and containing Au+Ni and Au+Co impurities in the bulk showed that the characteristics of these sensors are more stable under the prolonged exposure to hydrogen in comparison with Au/SnO2:Sb, Au films modified only with gold. It has been found that introduction of the nickel and cobalt additives increases the band bending at the grain boundaries of tin dioxide already in freshly prepared samples, which indicates an increase in the density Ni of the chemisorbed oxygen. It is important that during testing, the band bending eφs at the grain boundaries of tin dioxide additionally slightly increases. It can be assumed that during crystallization of films under thermal annealing, the 3d-metal atoms in the SnO2 volume partially segregate on the surface of microcrystals and form bonds with lattice oxygen, the superstoichiometric tin atoms are formed, and the density Ni increases. If the bonds of oxygen with nickel and cobalt are stronger than those with tin, then, under the prolonged tests, atomic hydrogen will be oxidized not by lattice oxygen, but mainly by the chemisorbed one. In this case, stability of the sensors' characteristics increases.

  14. Magnetic Phase Transitions in NdCoAsO

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

    McGuire, Michael A; Gout, Delphine J; Garlea, Vasile O

    2010-01-01

    NdCoAsO undergoes three magnetic phase transitions below room temperature. Here we report the results of our experimental investigation of this compound, including determination of the crystal and magnetic structures using powder neutron diffraction, as well as measurements of electrical resistivity, thermal conductivity, Seebeck coefficient, magnetization, and heat capacity. These results show that upon cooling a ferromagnetic state emerges near 69 K with a small saturation moment of -0.2{micro}{sub B}, likely on Co atoms. At 14 K the material enters an antiferromagnetic state with propagation vector (0 0 1/2) and small ordered moments (-0.4{micro}{sub B}) on Co and Nd. Near 3.5more » K a third transition is observed, and corresponds to the antiferromagnetic ordering of larger moments on Nd, with the same propagation vector. The ordered moment on Nd reaches 1.39(5){micro}{sub B} at 300 mK. Anomalies in the magnetization, electrical resistivity, and heat capacity are observed at all three magnetic phase transitions.« less

  15. Mechanical properties and rapid low-temperature consolidation of nanocrystalline Cu-ZrO2 composites by pulsed current activated heating

    NASA Astrophysics Data System (ADS)

    Kang, Bo-Ram; Yoon, Jin-kook; Hong, Kyung-Tae; Shon, In-Jin

    2015-07-01

    Metal-ceramic compositr can be obtained with an optimum combination of low density, high oxidation resistance, and high hardness of the ceramic and toughness of the metal. Therefore, metal matrix composites are recognized as candidates for aerospace, automotive, biomaterials, and defense applications. Despite its many attractive properties, the low fracture toughness of ZrO2 limits its wide application. One of the most obvious tactics to improve the mechanical properties has been to fabricate a nanostructured material and composite material. Nano-powders of Cu and ZrO2 were synthesized from 2CuO and Zr powders by high-energy ball milling. Nanocrystalline 2Cu-ZrO2 composite was consolidated within 5 minutes from mechanically synthesized powders of ZrO2 and 2Cu at low temperature, by a pulsed current activated sintering method. The relative density of the composite was 98.5%. The fracture toughness of 2Cu-ZrO2 composite in this study is higher than that of monolithic ZrO2, without great decrease of hardness.

  16. Spectroelectrochemical studies of hole percolation on functionalised nanocrystalline TiO2 films: a comparison of two different ruthenium complexes.

    PubMed

    Li, Xiaoe; Nazeeruddin, Mohammad K; Thelakkat, Mukundan; Barnes, Piers R F; Vilar, Ramón; Durrant, James R

    2011-01-28

    We report the application of spectroelectrochemical techniques to compare the hole percolation dynamics of molecular networks of two ruthenium bipyridyl complexes adsorbed onto mesoporous, nanocrystalline TiO(2) films. The percolation dynamics of the ruthenium complex cis-di(thiocyanato)(2,2'-bipyridyl-4,4'-dicarboxylic acid)-(2,2'-bipyridyl-4,4'-tridecyl) ruthenium(II), N621, is compared with those observed for an analogous dye with an additional tri-phenyl amine (TPA) donor moiety, cis-di(thiocyanato)(2,2'-bipyridyl-4,4'-dicarboxylic acid)-(2,2'-bipyridyl-4,4'-bis(vinyltriphenylamine)) ruthenium(II), HW456. The in situ oxidation of these ruthenium complexes adsorbed to the TiO(2) films is monitored by cyclic voltammetry and voltabsorptometry, whilst the dynamics of hole (cation) percolation between adsorbed ruthenium complexes is monitored by potentiometric spectroelectrochemistry and chronoabsorptometry. The hole diffusion coefficient, D(eff), is shown to be dependent on the dye loading on the nanocrystalline TiO(2) film, with a threshold observed at ∼60% monolayer surface coverage for both dyes. The hole diffusion coefficient of HW456 is estimated to be 2.6 × 10(-8) cm(2)/s, 20-fold higher than that obtained for the control N621, attributed to stronger electronic coupling between the TPA moieties of HW456 accelerating the hole percolation dynamics. The presence of mercuric ions, previously shown to bind to the thiocyanates of analogous ruthenium complexes, resulted in a quenching of the hole percolation for N621/TiO(2) films and an enhancement for HW456/TiO(2) films. These results strongly suggest that the hole percolation pathway is along the overlapped neighbouring -NCS groups for the N621 molecules, whereas in HW456 molecules cation percolation proceeds between intermolecular TPA ligands. These results are discussed in the context of their relevance to the process of dye regeneration in dye sensitised solar cells, and to the molecular wiring of wide

  17. Evidence for a different electronic configuration as a primary effect during compression of orthorhombic perovskites: The case of Nd M3 +O3 (M =Cr ,Ga )

    NASA Astrophysics Data System (ADS)

    Ardit, M.; Dondi, M.; Merli, M.; Cruciani, G.

    2018-02-01

    (Mg ,Fe ) Si O3 perovskite is the most abundant mineral of the Earth's lower mantle, and compounds with the perovskite structure are perhaps the most widely employed ceramics. Hence, they attract both geophysicists and material scientists. Several investigations attempted to predict their structural evolution at high pressure, and recent advancements highlighted that perovskites having ions with the same formal valence at both polyhedral sites (i.e., 3 +:3 + ) define different compressional patterns when transition metal ions (TMI) are involved. In this study, in situ high-pressure synchrotron XRD measurements coupled with ab initio simulations of the electronic population of NdCr O3 perovskite are compared with the compressional feature of NdGa O3 . Almost identical from a steric point of view (C r3 + and G a3 + have almost the same ionic radius), the different electronic configuration of octahedrally coordinated ions - which leads to a redistribution of electrons at the 3 d orbitals for C r3 + - allows the crystal field stabilization energy (CFSE) to act as a vehicle of octahedral softening in NdCr O3 or it turns octahedra into rigid units when CFSE is null as in NdGa O3 . Besides to highlight that different electronic configurations can act as a primary effect during compression of perovskite compounds, our findings have a deep repercussion on the way the compressibility of perovskites have to be modeled.

  18. Mechanism of γ-irradiation induced phase transformations in nanocrystalline Mn0.5Zn0.5Fe2O4 ceramics

    NASA Astrophysics Data System (ADS)

    Jagadeesha Angadi, V.; Anupama, A. V.; Choudhary, Harish K.; Kumar, R.; Somashekarappa, H. M.; Mallappa, M.; Rudraswamy, B.; Sahoo, B.

    2017-02-01

    The structural, infrared absorption and magnetic property transformations in nanocrystalline Mn0.5Zn0.5Fe2O4 samples irradiated with different doses (0, 15, 25 and 50 kGy) of γ-irradiation were investigated in this work and a mechanism of phase transformation/decomposition is provided based on the metastable nature of the Mn-atoms in the spinel lattice. The nano-powder sample was prepared by solution combustion route and the pellets of the sample were exposed to γ-radiation. Up to a dose of 25 kGy of γ-radiation, the sample retained the single phase cubic spinel (Fd-3m) structure, but the disorder in the sample increased. On irradiating the sample with 50 kGy γ-radiation, the spinel phase decomposed into new stable phases such as α-Fe2O3 and ZnFe2O4 phases along with amorphous MnO phase, leading to a change in the surface morphology of the sample. Along with the structural transformations the magnetic properties deteriorated due to breakage of the ferrimagnetic order with higher doses of γ-irradiation. Our results are important for the understanding of the stability, durability and performance of the Mn-Zn ferrite based devices used in space applications.

  19. The effect of excitation intensity variation and silver nanoparticle codoping on nonlinear optical properties of mixed tellurite and zinc oxide glass doped with Nd2O3 studied through ultrafast z-scan spectroscopy

    NASA Astrophysics Data System (ADS)

    Moreira, L.; Falci, R. F.; Darabian, H.; Anjos, V.; Bell, M. J. V.; Kassab, L. R. P.; Bordon, C. D. S.; Doualan, J. L.; Camy, P.; Moncorgé, R.

    2018-05-01

    The research on Nd3+ doped new solid-state laser hosts with specific thermo-mechanical and optical properties is very active. Nd3+ doped tellurite glasses are suitable for these applications. They have high linear and nonlinear refraction index, wide transmittance range. The TeO2-ZnO (TZO) glass considered in the present work combines all those features and the nonlinear optical properties can be used for the development of Kerr-lens mode-locked sub picosecond lasers. Recently the laser performance of Nd3+ doped TZO glass and was reported and laser slope efficiency of 21% was observed. We investigate how the intensity variation and the silver nanoparticles codoping affects the nonlinear optical properties of Nd3+ doped TZO glasses. Intensity dependent nonlinear refraction indices coefficients at 750, 800 and 850 nm were observed. The nonlinear optical features were obtained through ultrafast single beam z-scan technique with excitations at 750, 800 and 850 nm and are up to two orders of magnitude higher than those reported in the literature.

  20. Tunable ultraviolet and blue light generation from Nd:YAB random laser bolstered by second-order nonlinear processes

    NASA Astrophysics Data System (ADS)

    Moura, André L.; Carreño, Sandra J. M.; Pincheira, Pablo I. R.; Fabris, Zanine V.; Maia, Lauro J. Q.; Gomes, Anderson S. L.; de Araújo, Cid B.

    2016-06-01

    Ultraviolet and blue light were obtained by nonlinear frequency conversion in a random laser (RL) based on Nd0.10Y0.90Al3(BO3)4 nanocrystalline powder. RL operation at 1062 nm, due to the 4F3/2 → 4I11/2 transition of neodymium ions (Nd3+), was achieved by exciting the Nd3+ with a tunable beam from 680 to 920 nm covering the ground state absorption transitions to the 4F9/2, (4F7/2,4S3/2), (4F5/2,2H9/2), and 4F3/2 states. Light from 340 to 460 nm was obtained via the second-harmonic generation of the excitation beam while tunable blue light, from 417 to 486 nm, was generated by self-sum-frequency mixing between the excitation beam and the RL emission.

  1. A Family of A-Site Cation-Deficient Double-Perovskite-Related Iridates: Ln9Sr2Ir4O24 (Ln = La, Pr, Nd, Sm).

    PubMed

    Ferreira, Timothy; Smith, Mark D; Zur Loye, Hans-Conrad

    2018-06-21

    The compositions of the general formula Ln 11- x Sr x Ir 4 O 24 (Ln = La, Pr, Nd, Sm; 1.37 ≥ x ≥ 2) belonging to a family of A-site cation-deficient double-perovskite-related oxide iridates were grown as highly faceted single crystals from a molten strontium chloride flux. Their structures were determined by single-crystal X-ray diffraction. On the basis of the single-crystal results, additional compositions, Ln 9 Sr 2 Ir 4 O 24 (Ln = La, Pr, Nd, Sm), were prepared as polycrystalline powders via solid-state reactions and structurally characterized by Rietveld refinement. The compositions Ln 9 Sr 2 Ir 4 O 24 (Ln = La, Pr, Nd, Sm) contain Ir(V) and Ir(IV) in a 1:3 ratio with an average iridium oxidation state of 4.25. The single-crystal compositions La 9.15 Sr 1.85 Ir 4 O 24 and Pr 9.63 Sr 1.37 Ir 4 O 24 contain relatively less Ir(V), with the average iridium oxidation states being 4.21 and 4.09, respectively. The magnetic properties of Ln 9 Sr 2 Ir 4 O 24 (Ln = La, Pr, Nd, Sm) were measured, and complex magnetic behavior was observed in all cases at temperatures below 30 K.

  2. Tuning the Curie temperature of epitaxial Nd0.6Sr0.4MnO3 thin films

    NASA Astrophysics Data System (ADS)

    Bhat, Shwetha G.; Kumar, P. S. Anil

    2018-02-01

    NdxSr1-xMnO3 (0.2 ≤ x ≤ 0.5) systems are widely studied in magnetism, popular for high colossal magnetoresistance and are ferromagnetic oxides with TC ranging from 200 K to 300 K. Recently, many of such compounds are re-visited for exploring the correlation of spin, charge and lattice degrees of freedom. Although, manganite thin films are the ideal candidates for studying the electron-correlation effects, the puzzle of obtaining a high quality epitaxial thin films of NdxSr1-xMnO3 are still unsolved contrary to its sister compound LaxSr1-xMnO3. Hence, in this study, we demonstrate the growth of best quality of Nd0.6Sr0.4MnO3 (NSMO) epitaxial thin films. This is evident from the TC and a sharp insulator-to-metal transition (IMT) coinciding at as high as ∼255 K against the bulk TC (∼270 K). It is the highest reported TC in Nd0.6Sr0.4MnO3 thin films to date. Moreover, as-deposited films with in situ oxygen annealing are not enough to relax the lattice of NSMO films due to the significant Jahn-Teller distortion in the film. With ex situ annealing processes alongside the various deposition and in situ annealing conditions, we have extensively studied the growth of epitaxial NSMO thin films on LaAlO3 (0 0 1) and SrTiO3 (0 0 1) to investigate the evolution of lattice and its one-to-one correspondence with the magnetism and the electrical properties of thin films. Accordingly, the enhanced magnetization, reduced resistivity and the higher TC and IMT of the NSMO films obtained from our extensive growth analysis looks promising for the future applications across the TC and IMT.

  3. Spectroscopy and enhanced frequency upconversion in Nd3+-Yb3+ codoped TPO glasses: energy transfer and NIR to visible upconverter.

    PubMed

    Azam, Mohd; Rai, Vineet Kumar; Mohanty, Deepak Kumar

    2017-09-22

    TeO 2 -Pb 3 O 4 (TPO) glasses codoped with Nd 3+ and Yb 3+ ions have been fabricated by conventional melting technique. The absorption, emission and excitation spectra of the samples have been recorded. The optical band gap in both the doped/codoped glasses is found to be ∼3.31 eV. Judd-Ofelt analysis has been carried out by using the absorption spectrum of 0.8 mol% Nd 3+ doped glass to determine the radiative properties viz radiative transition probabilities, branching ratios, radiative lifetimes, quality factor and emission cross sections of some emitting levels for Nd 3+ ions. The radiative transition probability for the 4 G 7/2  →  4 I 9/2 transition (∼1926 Hz) is found to be maximum compared to other 4 G 5/2  →  4 I 9/2 (∼1622 Hz) and 4 F 5/2  →  4 I 9/2 (∼865 Hz) transitions. Upconversion (UC) luminescence of the samples has been examined by the 980 nm CW diode laser excitation. Effect of addition of Yb 3+ ions in the Nd 3+ doped glasses on UC emission intensity has been discussed. The UC emission intensity corresponding to the green, red and NIR bands in the codoped glass has been enhanced by ∼17, ∼12 and ∼42 times as compared to that of the Nd 3+ singly doped glass. The quantum efficiency for the 4 G 7/2 level is found to be ∼32%. The nephelauxetic ratio, bonding parameter and covalency of Nd 3+ ions have been found positive which represents the covalent bonding between Nd 3+ ion and oxygen atom. The colour tunability from yellowish-green to dominant green region has been obtained in the optimized codoped TPO glass.

  4. Spectroscopy and enhanced frequency upconversion in Nd3+-Yb3+ codoped TPO glasses: energy transfer and NIR to visible upconverter

    NASA Astrophysics Data System (ADS)

    Azam, Mohd; Rai, Vineet Kumar; Mohanty, Deepak Kumar

    2017-09-01

    TeO2-Pb3O4 (TPO) glasses codoped with Nd3+ and Yb3+ ions have been fabricated by conventional melting technique. The absorption, emission and excitation spectra of the samples have been recorded. The optical band gap in both the doped/codoped glasses is found to be ˜3.31 eV. Judd-Ofelt analysis has been carried out by using the absorption spectrum of 0.8 mol% Nd3+ doped glass to determine the radiative properties viz radiative transition probabilities, branching ratios, radiative lifetimes, quality factor and emission cross sections of some emitting levels for Nd3+ ions. The radiative transition probability for the 4G7/2 → 4I9/2 transition (˜1926 Hz) is found to be maximum compared to other 4G5/2 → 4I9/2 (˜1622 Hz) and 4F5/2 → 4I9/2 (˜865 Hz) transitions. Upconversion (UC) luminescence of the samples has been examined by the 980 nm CW diode laser excitation. Effect of addition of Yb3+ ions in the Nd3+ doped glasses on UC emission intensity has been discussed. The UC emission intensity corresponding to the green, red and NIR bands in the codoped glass has been enhanced by ˜17, ˜12 and ˜42 times as compared to that of the Nd3+ singly doped glass. The quantum efficiency for the 4G7/2 level is found to be ˜32%. The nephelauxetic ratio, bonding parameter and covalency of Nd3+ ions have been found positive which represents the covalent bonding between Nd3+ ion and oxygen atom. The colour tunability from yellowish-green to dominant green region has been obtained in the optimized codoped TPO glass.

  5. Titanium mesh supported TiO2 nanowire arrays/upconversion luminescence Er3+-Yb3+ codoped TiO2 nanoparticles novel composites for flexible dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Liu, Wenwu; Zhang, Huanyu; Wang, Hui-gang; Zhang, Mei; Guo, Min

    2017-11-01

    Ti-mesh supported TiO2 nanowire arrays (NWAs)/upconversion luminescence Er3+-Yb3+ codoped TiO2 nanoparticles (UC-EY-TiO2 NPs) composite structured photoanodes for fully flexible dye sensitized solar cells (DSSCs) were firstly constructed via a hydrothermal and spin coating process. UV-vis-NIR absorption spectra of the TiO2 NWAs/UC-EY-TiO2 NPs composites exhibited strong absorption around near infrared (NIR) 980 nm. The composites excited by 980 nm NIR laser could emit upconversion fluorescence at 489, 526, 549 and 658 nm, which expanded the spectral response range and sunlight capturing capability of formed flexible DSSCs. Moreover, the TiO2 NWAs/UC-EY-TiO2 NPs was coated with an Nb2O5 thin layer to further suppress electron recombination losses. The complete flexible DSSCs based on Nb2O5 coated TiO2 NWAs/2.0 mol% Er3+-1.0 mol% Yb3+ codoped TiO2 NPs photoanode and Pt/ITO-PEN counter electrode exhibited an enhanced photon to current conversion efficiency of 8.10%, a 68% improvement compared to TiO2 NWAs/undoped TiO2 NPs based DSSCs (4.82%).

  6. Comparative study on cubic and tetragonal CexZr1-xO2 supported MoO3-catalysts for sulfur-resistant methanation

    NASA Astrophysics Data System (ADS)

    Liu, Zhaopeng; Xu, Yan; Cheng, Jiaming; Wang, Weihan; Wang, Baowei; Li, Zhenhua; Ma, Xinbin

    2018-03-01

    In this paper, two kinds of CexZr1-xO2 solid solution carriers with different Ce/Zr ratio were prepared by one-step co-precipitation method: the cubic Ce0.8Zr0.2O2 and the tetragonal Ce0.2Zr0.8O2 support. The MoO3/Ce0.8Zr0.2O2 and MoO3/Ce0.2Zr0.8O2 catalysts were prepared by incipient wetness impregnation method for comparative study on sulfur-resistant methanation reaction. The N2 adsorption/desorption, X-ray diffraction (XRD), Raman spectroscopy (RS), X-ray photoelectron (XPS), transmission electron microscopy (TEM), temperature-programmed reduction by hydrogen (H2-TPR) were undertaken to characterize the physico-chemical properties of the samples. The results indicated that the prepared MoO3/CexZr1-xO2 catalysts have a mesoporous structure with high surface area and uniform pore size distribution, achieving good MoO3 dispersion on CexZr1-xO2 supports. As for the catalytic performance of sulfur-resistant methanation, the cubic MoO3/Ce0.8Zr0.2O2 exhibited better than the tetragonal MoO3/Ce0.2Zr0.8O2 catalyst at reaction temperature 400 °C and 450 °C. CO conversion on the cubic MoO3/Ce0.8Zr0.2O2 catalyst was 50.1% at 400 °C and 75.5% at 450 °C, which is respectively 7% and 20% higher than that on the tetragonal MoO3/Ce0.2Zr0.8O2 catalyst. These were mainly attributed to higher content of active MoS2 on the surface of catalyst, the enhanced oxygen mobility, increased Mo-species dispersion as well as the excellent reducibility resulted from the increased amount of the reducible Ce3+ on the cubic MoO3/Ce0.8Zr0.2O2 catalyst.

  7. Effect of gate voltage polarity on the ionic liquid gating behavior of NdNiO 3/NdGaO 3 heterostructures

    DOE PAGES

    Dong, Yongqi; Xu, Haoran; Luo, Zhenlin; ...

    2017-05-16

    The effect of gate voltage polarity on the behavior of NdNiO 3 epitaxial thin films during ionic liquid gating is studied using in situ synchrotron X-ray techniques. We show that while negative biases have no discernible effect on the structure or composition of the films, large positive gate voltages result in the injection of a large concentration of oxygen vacancies (similar to 3%) and pronounced lattice expansion (0.17%) in addition to a 1000-fold increase in sheet resistance at room temperature. Despite the creation of large defect densities, the heterostructures exhibit a largely reversible switching behavior when sufficient time is providedmore » for the vacancies to migrate in and out of the thin film surface. The results confirm that electrostatic gating takes place at negative gate voltages for p-type complex oxides while positive voltages favor the electrochemical reduction of Ni 3+. Switching between positive and negative gate voltages therefore involves a combination of electronic and ionic doping processes that may be utilized in future electrochemical transistors.« less

  8. Growth of single crystals, thermal dependency of lattice parameters and Raman scattering in the Nd 2- xCe xCuO 4- δ system

    NASA Astrophysics Data System (ADS)

    Sadowski, W.; Hagemann, H.; François, M.; Bill, H.; Peter, M.; Walker, E.; Yvon, K.

    1990-09-01

    We report on the growth of Nd 2- xCe xCuO 4- δ single crystals (0< x<0.2) from Cu 2O flux. Free separated crystals with maximum size of 5x8x0.15 nm 3 have been obtained. Magnetic AC susceptibility measurements show a sharp superconducting transition at temperatures up to 23 K. The temperature dependence of the lattice parameters has been measured by means of X-ray powder diffraction between 10 K ( a=3.9413(3) Å, c=12.0290(18) Å) and 290 K ( a=3.9482(3) Å, c=12.0590(18) Å). Room temperature Raman spectra reveal a new band at 320 cm -1 which is not observed in Nd 2CuO 4. Raman spectra of crystals with Tc ranging from 7 to 22 K show a systematic intensity change of the broad band at 590 cm -1.

  9. A clear effect of charge compensation through Na{sup +} co-doping on the luminescence spectra and decay kinetics of Nd{sup 3+}-doped CaAl{sub 4}O{sub 7}

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

    Puchalska, M., E-mail: malgorzata.puchalska@chem.uni.wroc.pl; Watras, A.

    2016-06-15

    We present a detailed analysis of luminescence behavior of singly Nd{sup 3+} doped and Nd{sup 3+}, Na{sup +} co-doped calcium aluminates powders: Ca{sub 1−x}Nd{sub x}Al{sub 4}O{sub 7} and Ca{sub 1−2x}Nd{sub x}Na{sub x}Al{sub 4}O{sub 7} (x=0.001–0.1). Relatively intense Nd{sup 3+} luminescence in IR region corresponding to typical {sup 4}F{sub 3/2}→{sup 4}I{sub J} (J=9/2–13/2) transitions with maximum located at about 1079 nm was obtained in all samples on direct excitation into f–f levels. The effect of dopant concentration and charge compensation by co-doping with Na{sup +} ions on morphology and optical properties were studied. The results show that both, the Nd{sup 3+}more » concentration and the alkali metal co-doping affected the optical properties but had no influence on the powders morphology. The studies of luminescence spectra (298 and 77 K) in a function of dopant concentration showed an increasing distortion of the local symmetry of Nd{sup 3+}with raising activator content due to certain defects created in the crystal lattice. On the other hand Na{sup +} addition led to significant narrowing of absorption and luminescence bands and also a reduction of the number of their components, showing smaller disturbance of Nd{sup 3+} ions local symmetries. Consequently, charge compensated by Na{sup +} co-doping materials showed significantly enhanced Nd{sup 3+} luminescence. The decrease of emission intensity and luminescence lifetimes with increase of activator concentration was attributed mainly to phonon-assisted cross-relaxation processes between Nd{sup 3+} ions. Analysis with Inokuti–Hirayama model indicated dipole–dipole mechanism of ion-ion interaction. Na{sup +} addition led to much smaller concentration quenching due to smaller clustering of dopant ions in CaAl{sub 4}O{sub 7} lattice.« less

  10. [Enhanced electro-chemical oxidation of Acid Red 3R solution with phosphotungstic acid supported on gamma-Al2O3].

    PubMed

    Yue, Lin; Wang, Kai-Hong; Guo, Jian-Bo; Yang, Jing-Liang; Liu, Bao-You; Lian, Jing; Wang, Tao

    2013-03-01

    Supported phosphotungstic acid catalysts on gamma-Al2O3 (HPW/gamma-Al2O3) were prepared by solution impregnation and characterized by FTIR, XRD, TG-DTA and SEM. The heteropolyanion shows a Keggin structure. Electro-chemical oxidation of Acid Red 3R was investigated in the presence of HPW supported on gamma-Al2O3 as packing materials in the reactor. The results show that HPW/gamma-Al2O3 has a good catalytic activity for decolorization of Acid Red 3R. When HPW loading was 4.6%, pH value of Acid Red 3R was 3, the voltage was 25.0 V, air-flow was 0.04 m3 x h(-1), and electrode span was 3.0 cm, the decolorization efficiency of Acid Red 3R can reach 97.6%. The removal rate of color had still about 80% in this electro-chemical oxidation system, after HPW/gamma-Al2O3 was used for 10 times, but active component loss existed. The interim product was analyzed by means of Vis-UV absorption spectrum. It shows that the conjugated structure of dye is destroyed primarily.

  11. Low-threshold, CW, all-solid-state Ti:Al2O3 laser

    NASA Technical Reports Server (NTRS)

    Harrison, James; Finch, Andrew; Rines, David M.; Rines, Glen A.; Moulton, Peter F.

    1991-01-01

    A CW Ti:Al2O3 ring laser with a threshold power of 119 mW is demonstrated. It provides a tunable source of single-frequency, diffraction-limited radiation that is suitable for injection seeding. The Ti:Al2O3 laser is operated with a diode-laser-pumped, frequency-doubled, Nd:YAG laser as the sole pump source.

  12. The crystal structure of galgenbergite-(Ce), CaCe2(CO3)4•H2O

    NASA Astrophysics Data System (ADS)

    Walter, Franz; Bojar, Hans-Peter; Hollerer, Christine E.; Mereiter, Kurt

    2013-04-01

    Galgenbergite-(Ce) from the type locality, the railroad tunnel Galgenberg between Leoben and St. Michael, Styria, Austria, was investigated. There it occurs in small fissures of an albite-chlorite schist as very thin tabular crystals building rosette-shaped aggregates associated with siderite, ancylite-(Ce), pyrite and calcite. Electron microprobe analyses gave CaO 9.49, Ce2O3 28.95, La2O3 11.70, Nd2O3 11.86, Pr2O3 3.48, CO2 30.00, H2O 3.07, total 98.55 wt.%. CO2 and H2O calculated by stoichiometry. The empirical formula (based on Ca + REE ∑3.0) is C{{a}_{1.00 }}{{( {C{{e}_{1.04 }}L{{a}_{0.42 }}N{{d}_{0.42 }}P{{r}_{0.12 }}} )}_{2.00 }}{{( {C{{O}_3}} )}_4}\\cdot {{H}_2}O , and the simplified formula is CaC{{e}_2}{{( {C{{O}_3}} )}_4}\\cdot {{H}_2}O . According to X-ray single crystal diffraction galgenbergite-(Ce) is triclinic, space group Poverline{1},a=6.3916(5) , b = 6.4005(4), c = 12.3898(9) Å, α = 100.884(4), β = 96.525(4), γ = 100.492(4)°, V = 483.64(6) Å3, Z = 2. The eight strongest lines in the powder X-ray diffraction pattern are [ d calc in Å/( I)/ hkl]: 5.052/(100)/011; 3.011/(70)/0-22; 3.006/(66)/004; 5.899/(59)/-101; 3.900/(51)/1-12; 3.125/(46)/-201; 2.526/(42)/022; 4.694/(38)/-102. The infrared absorption spectrum reveals H2O (OH-stretching mode at 3,489 cm-1, HOH bending mode at 1,607 cm-1) and indicates the presence of distinctly non-equivalent CO3-groups by double and quadruple peaks of their ν1, ν2, ν3 and ν4 modes. The crystal structure of galgenbergite-(Ce) was refined with X-ray single crystal data to R1 = 0.019 for 2,448 unique reflections ( I > 2 σ( I)) and 193 parameters. The three cation sites of the structure Ca(1), Ce(2) and Ce(3) have a modest mixed site occupation by Ca and small amount of REE (Ce, La, Pr, Nd) and vice versa. The structure is based on double layers parallel to (001), which are composed of Ca(1)Ce(2)(CO3)2 single layers with an ordered chessboard like arrangement of Ca and Ce, and with a roof tile

  13. Physical properties and surface/interface analysis of nanocrystalline WO3 films grown under variable oxygen gas flow rates

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

    Vemuri, R. S.; Carbjal-Franco, G.; Ferrer, D. A.

    2012-10-15

    Nanocrystalline WO3 films were grown by reactive magnetron sputter-deposition in a wide range of oxygen gas flow rates while keeping the deposition temperature fixed at 400 oC. The physical characteristics of WO3 films were evaluated using grazing incidence X-ray diffraction (GIXRD), X-ray reflectivity (XRR) and transmission electron microscopy (TEM) measurements. Physical characterization indicates that the thickness, grain size, and density of WO3 films are sensitive to the oxygen gas flow rate during deposition. XRD data indicates the formation of tetragonal WO3 films. The grain size increases from 21 to 25 nm with increasing oxygen gas flow rate to 65%, atmore » which point the grain size exhibits a decreasing trend to attain the lowest value of 15 nm at 100% oxygen. TEM analysis provides a model consisting of isotropic WO3 film (nanocrystalline)-SiO2 interface (amorphous)-Si(100) substrate. XRR simulations, which are based on this model, provide excellent agreement to the experimental data indicating that the normalized thickness of WO3 films decreases with the increasing oxygen gas flow rate. The density of WO3 films increases with increasing oxygen gas flow rate.« less

  14. Activity and Stability of (Pr 1-xNd x) 2NiO 4 as Cathodes for Solid Oxide Fuel Cells: II. Electrochemical Performance and Performance Durability

    DOE PAGES

    Dogdibegovic, Emir; Guan, Wanbing; Yan, Jingbo; ...

    2016-09-21

    Single phase (Pr 1-xNd x) 2NiO 4 cathode powders (x = 0, 0.25, 0.50, 0.75, and 1.0) were synthesized via a glycine-nitrate combustion and high temperature calcination. Anode supported cells were used to investigate the cathode property. A reproducible performance, within 9% for each cathode composition, was observed providing a wealth of data for quantitative studies. Area specific resistance analysis and i-V measurements between 650 and 850°C showed a decrease in the cell performance with increasing Nd content. Impedance spectrum analysis suggests that the decline in performance results from an increase in electrode polarization. While Pr 2NiO 4 cells showedmore » significant performance degradation of 6.40%/1,000 hours, the degradation rate for (Pr 0.75Nd 0.25) 2NiO 4 cells was reduced by an order of magnitude (0.56%/1,000 hours) with a 7% lower power output. Furthermore, the cathodes with a higher Nd content showed further improvement in performance stability with a marginal degradation rate of 0.06%/1,000 hours.« less

  15. Structural, optical and photo-catalytic activity of nanocrystalline NiO thin films

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

    Al-Ghamdi, Attieh A.; Abdel-wahab, M. Sh., E-mail: mshabaan90@yahoo.com; Materials Science and Nanotechnology Department, Faculty of Postgraduate Studies for Advanced Sciences, Beni-Suef University, Beni-Suef

    2016-03-15

    Highlights: • Synthesis of nanocrystalline NiO thin films with different thicknesses using DC magnetron sputtering technique. • Effect of film thickness and particle size on photo-catalytic degradation of methyl green dye under UV light was studied. • The deposited NiO thin films are efficient, stable and possess high photo-catalytic activity upon reuse. - Abstract: Physical deposition of nanocrystalline nickel oxide (NiO) thin films with different thickness 30, 50 and 80 nm have been done on glass substrate by DC magnetron sputtering technique and varying the deposition time from 600, 900 to 1200 s. The results of surface morphology and opticalmore » characterization of these films obtained using different characterization techniques such as X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), photoluminescence (PL) and UV–vis spectrophotometry provide important information like formation of distinct nanostructures in different films and its effect on their optical band gap which has decreased from 3.74 to 3.37 eV as the film thickness increases. Most importantly these films have shown very high stability and a specialty to be recycled without much loss of their photo-catalytic activity, when tested as photo-catalysts for the degradation of methyl green dye (MG) from the wastewater under the exposure of 18 W energy of UV lamp.« less

  16. Continuous wave and passively Q-switched laser performance of Nd:LuxGd3-xGa5O12 crystal at 1062 nm

    NASA Astrophysics Data System (ADS)

    Fu, X. W.; Jia, Z. T.; Yang, H.; Li, Y. B.; Yuan, D. S.; Zhang, B. T.; Dong, C. M.; He, J. L.; Tao, X. T.

    2012-12-01

    Continuous wave (CW) and passively Q-switched (PQS) laser properties at 1062 nm of the Nd:LuxGd3-xGa5O12 (Nd:LGGG) disordered crystal have been demonstrated. The doping concentrations of Nd3+ and Lu3+ in the as obtained crystal were measured to be 0.96 and 0.66 at.%, respectively. In the CW regime, the output power of 9.73 W was obtained with an optical-to-optical efficiency as high as 60.7% and slope efficiency of 61.2%. During the passively Q-switched operation, the maximum output power of 1.24 W was achieved under the absorbed pump power of 6.86 W. The maximum peak power of 14.20 kW and single pulse energy of 148 μJ were obtained with the Toc = 10% under the absorbed pump power of 6.36 W. The results are much better than those obtained with Nd:LGGG crystal doped with 13.6 at.% Lu3+ and 0.53 at.% Nd3+ ions.

  17. WOx supported on γ-Al2O3 with different morphologies as model catalysts for alkanol dehydration

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

    Shi, Dachuan; Wang, Huamin; Kovarik, Libor

    2018-04-21

    The distinctive morphological and surface characteristics of platelet-like γ-Al2O3 were compared to a regular, commercial γ-Al2O3. γ-Al2O3 platelets display dominant (110) surface facets and higher densities of coordinative unsaturated penta-coordinate Al3+ (Al3+penta) sites than regular γ-Al2O3, as measured by solid-state magic-angle spinning nuclear magnetic resonance spectroscopy (MAS NMR). Such Al3+penta sites are also the preferred surface anchoring sites for tungsten oxide (WOx) species consistent with NMR analysis indicating that these sites are consumed upon WOx adsorption. The higher Al3+penta density on γ-Al2O3 platelets leads to greater WOx dispersion (or smaller WOx clusters), as demonstrated by scanning transmission electron microscopy andmore » ultraviolet–visible spectroscopy, and WOx species at intermediate WOx surface concentration are the most active for the probe reaction of 2-butanol dehydration. WOx on γ-Al2O3 platelets approaches the highest turnover rates at higher surface densities than WOx on regular γ-Al2O3, yet with similar highest rate values for both series of catalysts. This indicates that different Al2O3 supports mainly affect the dispersion of supported WOx rather than the intrinsic reactivity of individual WOx clusters with similar size.« less

  18. Decontamination of radionuclides using γ-Fe2O3 as a Nanosorbent

    NASA Astrophysics Data System (ADS)

    Bagla, Hemlata; Thakur, Jyotsna

    2017-04-01

    The release of radioactive waste into the environment and the disposal of conditioned waste is a major environmental concern which demands the improvement in the remediation processes [1]. Due to the advancements in Nanotechnology, novel and simple nanoparticles have been proved very efficient worldwide, in the radioactive waste treatment processes [2]. These nanoparticles prove to be an excellent nanosorbents owing to its very high surface area and other size dependent properties [3]. In the present study, nanocrystalline γ-Fe2O3 was synthesized by gel-combustion method. Gel combustion method [4, 5] is the most facile method of synthesis of nanocrystalline oxides. Fuel deficient composition of ferric nitrate (oxidant) and malonyl dihydrazide (fuel) were mixed well in de-ionised water and heated at temperature 300 °C. The smouldering combustion took place resulting in formation of γ-Fe2O3 which further calcined at 500 °C to remove undesirable impurities. The prepared powder further characterized by various techniques such as X-ray diffractometer, transmission electron microscopy, BET technique and zeta potential measurements. The crystallite size of γ-Fe2O3 was found to be 11 nm. TEM images showed that the grain size obtained was in agreement with the XRD report. Sorption study have been carried out using tracer technique for batch equilibration method at room temperature and atmospheric pressure. A known amount of sorbent (γ-Fe2O3) was mixed with 10 mL of solution containing radiotracer and 1mg/mL solution of carrier. Various parameters such as contact time, pH, amount of sorbent, concentration, temperature, agitation speed were optimized, determination of sorption capacity and interference study was also conducted. The activity is measured by using single channel NaI(Tl) well type gamma ray spectrometer. γ-Fe2O3 was found to be an efficient and cost effective sorbent for the decontamination of heavy radionuclides such as Cs-137, Sr-90, Cd-115m, Cr-51, Hg

  19. Magneto-crystalline anisotropy of NdFe0.9Mn0.1O3 single crystal

    NASA Astrophysics Data System (ADS)

    Mihalik, Marián; Mihalik, Matúš; Zentková, Mária; Uhlířová, Klára; Kratochvílová, Marie; Roupcová, Pavla

    2018-05-01

    Our present study on oriented single crystal revealed huge magneto-crystalline anisotropy with respect to principal crystallographic axes, even several magnetic transitions were observed below TN = 748 K (c-axis) at 700 K (a-axis) as well 657 K (b-axis). The spin reorientation of magnetic moment takes place in very narrow temperature range between 135 K and 125 K and is attributed to vanishing of ferromagnetic component aligned along b-axis. Measurements of magnetic isotherms trace the development of ferromagnetic component and revealed the intermediate temperature range between 120 K and 20 K which is characterised by zero ferromagnetic components in any principal crystal direction. The ferromagnetic component develops consecutive at low temperature below 20 K along a-axis. Our study indicates completely different magnetic structure of NdFe0.9Mn0.1O3 below 135 K in comparison with NdFeO3.

  20. Atomistic modeling of La3+ doping segregation effect on nanocrystalline yttria-stabilized zirconia.

    PubMed

    Zhang, Shenli; Sha, Haoyan; Castro, Ricardo H R; Faller, Roland

    2018-05-16

    The effect of La3+ doping on the structure and ionic conductivity change in nanocrystalline yttria-stabilized zirconia (YSZ) was studied using a combination of Monte Carlo and molecular dynamics simulations. The simulation revealed the segregation of La3+ at eight tilt grain boundary (GB) structures and predicted an average grain boundary (GB) energy decrease of 0.25 J m-2, which is close to the experimental values reported in the literature. Cation stabilization was found to be the main reason for the GB energy decrease, and energy fluctuations near the grain boundary are smoothed out with La3+ segregation. Both dynamic and energetic analysis on the Σ13(510)/[001] GB structure revealed La3+ doping hinders O2- diffusion in the GB region, where the diffusion coefficient monotonically decreases with increasing La3+ doping concentration. The effect was attributed to the increase in the site-dependent migration barriers for O2- hopping caused by segregated La3+, which also leads to anisotropic diffusion at the GB.

  1. Effect of Synthesis Temperature on Structure and Magnetic Properties of (La,Nd)0.7Sr0.3MnO3 Nanoparticles.

    PubMed

    Shlapa, Yulia; Solopan, Sergii; Bodnaruk, Andrii; Kulyk, Mykola; Kalita, Viktor; Tykhonenko-Polishchuk, Yulia; Tovstolytkin, Alexandr; Belous, Anatolii

    2017-12-01

    Two sets of Nd-doped La 0.7 Sr 0.3 MnO 3 nanoparticles were synthesized via sol-gel method with further heat treatment at 1073 and 1573 K, respectively. Crystallographic and magnetic properties of obtained nanoparticles were studied, and the effect of synthesis conditions on these properties was investigated. According to X-ray data, all particles crystallized in the distorted perovskite structure. Magnetic parameters, such as saturation magnetization, coercivity, Curie temperature, and specific loss power, which is released on the exposure of an ensemble of nanoparticles to AC magnetic field, were determined for both sets of samples. The correlation between the values of Curie temperature and maximal heating temperature under AC magnetic field was found. It was revealed that for the samples synthesized at 1573 K, the dependences of crystallographic and magnetic parameters on Nd content were monotonous, while for the samples synthesized at 1073 K, they were non-monotonous. It was concluded that Nd-doped La 0.7 Sr 0.3 MnO 3 nanoparticles are promising materials for self-controlled magnetic hyperthermia applications, but the researchers should be aware of the unusual behavior of the particles synthesized at relatively low temperatures.

  2. Water oxidation by size selected Co 27 clusters supported on Fe 2O 3

    DOE PAGES

    Pellin, Michael J.; Riha, Shannon C.; Tyo, Eric C.; ...

    2016-09-22

    The complexity of the water oxidation reaction makes understanding the role of individual catalytic sites critical to improving the process. Here, size-selected 27-atom cobalt clusters (Co 27) deposited on hematite (Fe 2O 3) anodes were tested for water oxidation activity. The uniformity of these anodes allows measurement of the activity of catalytic sites of well-defined nuclearity and known density. Grazing incidence X-ray absorption near-edge spectroscopy (GIXANES) characterization of the anodes before and after electrochemical cycling demonstrates that these Co 27 clusters are stable to dissolution even in the harsh water oxidation electrochemical environment. They are also stable under illumination atmore » the equivalent of 0.4suns irradiation. The clusters show turnover rates for water oxidation that are comparable or higher than those reported for Pd- and Co-based materials or for hematite. The support for the Co 27 clusters is Fe 2O 3 grown by atomic layer deposition on a Si chip. We have chosen to deposit a Fe2O3 layer that is only a few unit cells thick (2nm), to remove complications related to exciton diffusion. We find that the electrocatalytic and the photoelectrocatalytic activity of the Co 27/Fe 2O 3 material is significantly improved when the samples are annealed (with the clusters already deposited). Lastly, given that the support is thin and that the cluster deposition density is equivalent to approximately 5% of an atomic monolayer, we suggest that annealing may significantly improve the exciton diffusion from the support to the catalytic moiety.« less

  3. Nanocrystalline ZnO as a Visible Active Photocatalyst for the Degradation of Benzene-1,4-diol

    NASA Astrophysics Data System (ADS)

    Ramachandran, Saranya; Sivasamy, A.

    We have synthesized nanocrystalline ZnO by a simple precipitation method. The prepared ZnO was found to be highly phase pure and nanocrystalline hexagonal wurtzite structure. UV-Visible-DRS spectroscopy showed the material to have bandgap energy of 3.22eV. HR-SEM image revealed the material to be made up of distinct hexagonal particles with a highly porous surface. AFM analysis was employed to confirm the high surface roughness and porosity of the material. The photocatalytic activity of the prepared ZnO was evaluated by the degradation of benzene-1,4-diol (hydroquinone), under visible light irradiation. Preliminary experiments showed the catalyst to be effective at neutral pH with an optimum catalyst dosage of 4g/L. Kinetic studies showed the degradation reaction to follow pseudo-first-order kinetics. In the presence of commonly used industrial electrolytes, the catalyst exhibited a decrease in efficiency. Reusability studies showed the catalytic efficiency of ZnO to diminish marginally after the third cycle of reuse.

  4. Magnetic and thermodynamic properties of Nd3NiGe2

    NASA Astrophysics Data System (ADS)

    Matsumoto, Keisuke T.; Hiraoka, Koichi

    2018-05-01

    We here report the magnetization, M, and specific heat, C, of Nd3NiGe2 , which crystallizes in the orthorhombic Gd3NiSi2 -type structure. Nd ions occupy three nonequivalent sites in a unit cell. Upon cooling, magnetization divided by magnetic field, M / B , increased sharply at the Curie temperature, TC, of 87 K and below 40 K. The former result indicates that the increase in M / B observed at TC is due to the long-range ferromagnetic order. The increase below 40 K is derived from a short-range correlation because of the absence of clear anomaly in C (T) . At 10 K and 2 K, the values of M undergo metamagnetic transitions. The value of magnetic specific heat divided by temperature shows a shoulder-like anomaly at around 20 K, which is attributed to antiferromagnetic behavior. Furthermore, two peaks in C (T) were observed at 4.5 K and 3.8 K, and these peaks occurred at lower temperatures in the presence of a magnetic field. This behavior is typical of materials with antiferromagnetic order. These observations are attributed to the competition between ferromagnetic and antiferromagnetic interactions, which is a result of the three nonequivalent Nd sites.

  5. Diode-pumped continuous-wave Nd:Gd3Ga5O12 lasers at 1406, 1415 and 1423 nm

    NASA Astrophysics Data System (ADS)

    Lin, Haifeng; Zhu, Wenzhang; Xiong, Feibing; Ruan, Jianjian

    2018-05-01

    We report a diode-pumped continuous-wave Nd:Gd3Ga5O12 (GGG) laser operating at 1.4 μm spectral region. A dual-wavelength laser at 1423 and 1406 nm is achieved with output power of about 2.59 W at absorbed pump power of 13.4 W. Further increasing the pump power, simultaneous tri-wavelength laser at 1423, 1415 and 1406 nm is also obtained with a maximum output power of 3.96 W at absorbed pump power of 18.9 W. Single-wavelength lasing is also realized at the three emission lines using an intracavity etalon. The laser result is believed to be the highest output power achieved in Nd:GGG crystal, at present, to the best of our knowledge.

  6. Structural and mechanical properties of lanthanide doped La1/3Nb0.8Ta0.2O3 thin films prepared by sol-gel method

    NASA Astrophysics Data System (ADS)

    Brunckova, Helena; Medvecky, Lubomir; Kovalcikova, Alexandra; Fides, Martin; Mudra, Erika; Durisin, Juraj; Skvarla, Jiri; Kanuchova, Maria

    2017-04-01

    Transparent Eu and Nd doped lanthanum niobate tantalate La1/3Nb0.8Ta0.2O3 (LNT) thin films (˜150 nm) were prepared by sol-gel/spin-coating process on Pt/SiO2/Si substrates and annealing at 1100 °C. The x-ray diffraction analysis of films confirmed formation of the perovskite La1/3NbO3 and La1/3TaO3 phases with traces of pyrochlore LaNbO4. Eu and Nd doped LNT films were smoother with roughness 17.1 and 25.4 nm in comparison with LNT (43.3 nm). In all films was observed heterogeneous microstructure with the perovskite spherical and pyrochlore needle-like particles. The mechanical properties of films were characterized for the first time by conventional and continuous stiffness (CSM) nanoindentation. The Eu and Nd doped LNT film modulus (E) and hardness (H) were higher than LNT (˜99.8 and 4.4 GPa) determined by conventional nanoindentation. It was measured the significant effect of substrate on properties of Eu or Nd films (H ˜ 5.9 or 4.9 GPa and E ˜ 107.3 or 104.1 GPa) by CSM nanoindentation.

  7. Optical spectroscopy, 1.06 μm emission properties of Nd3 +-doped phosphate based glasses

    NASA Astrophysics Data System (ADS)

    Sk. Nayab, Rasool; Sasikala, T.; Mohan Babu, A.; Rama Moorthy, L.; C. K., Jayasankar

    2017-06-01

    Neodymium doped phosphate based glasses with composition of (P2O5 + K2O + Al2O3 + CaF2) were prepared. The samples were analysed through differential thermal analysis (DTA), Fourier transform infrared (FTIR), absorption, emission and decay measurements. Judd-Ofelt parameters (Ωλ) have been determined from the spectral intensities of absorption bands in order to calculate the radiative parameters like radiative transition probabilities (AR), radiative lifetime (τR) and branching ratios (βR) for the 4F3/2 → 4I11/2 laser transition of Nd3 + ion. The effective emission bandwidths (Δλeff), experimental branching ratios (βexp) and stimulated emission cross-sections (σe) have been determined from the emission spectrum. The decay curves of the 4F3/2 level exhibited almost single exponential nature for all the Nd3 + ion concentrations.

  8. Solid State Reduction of MoO3 with Carbon via Mechanical Alloying to Synthesize Nano-Crystaline MoO2

    NASA Astrophysics Data System (ADS)

    Saghafi, M.; Ataie, A.; Heshmati-Manesh, S.

    In this research, effect of milling time on solid state reduction of MoO3 with carbon has been investigated. It was found that mechanical activation of a mixture of MoO3 and carbon at ambient temperature by high energy ball milling was not able to reduce MoO3 to metallic molybdenum. MoO3 was converted to MoO2 at the first stage of reduction and peaks of the latter phase in X-ray diffraction patterns were detected when the milling time exceeded from 50 hours. The main effect of increased milling time at this stage was decreasing of MoO3 peak intensities and significant peak broadening due to decrease in size of crystallites. After prolonged milling, MoO3 was fully reduced to nano-crystalline MoO2 and its mean crystallite size was calculated using Williamson-Hall technique and found to be 17.5 nm. Thermodynamic investigations also confirm the possibility of reduction of MoO3 to MoO2 during the milling operation at room temperature. But, further reduction to metallic molybdenum requires thermal activation at higher temperature near 1100 K. XRD and SEM techniques were employed to evaluate the powder particles characteristics.

  9. Diode-pumped quasi-three-level Nd:GdV O4-Nd:YAG sum-frequency laser at 464 nm

    NASA Astrophysics Data System (ADS)

    Lu, Jie

    2014-04-01

    We report a laser architecture to obtain continuous-wave (cw) blue radiation at 464 nm. A 808 nm diode pumped a Nd:GdV O4 crystal emitting at 912 nm. A part of the pump power was then absorbed by the Nd:GdV O4 crystal. The remainder was used to pump a Nd:YAG crystal emitting at 946 nm. Intracavity sum-frequency mixing at 912 and 946 nm was then realized in a LiB3O5 (LBO) crystal to produce blue radiation. We obtained a cw output power of 1.52 W at 464 nm with a pump laser diode emitting 18.4 W at 808 nm.

  10. Microwave-assisted synthesis and humidity sensing of nanostructured {alpha}-Fe{sub 2}O{sub 3}

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

    Deshmukh, Rupali G.; Badadhe, Satish S.; Mulla, Imtiaz S.

    2009-05-06

    Nanocrystalline {alpha}-Fe{sub 2}O{sub 3} has been prepared on a large-scale by a facile microwave-assisted hydrothermal route from a solution of Fe(NO{sub 3}){sub 3}.9H{sub 2}O and pentaerythritol. A systematic study of the morphology, crystallinity and oxidation state of Fe using different characterization techniques, such as transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy was performed. It reveals that nanostructured {alpha}-Fe{sub 2}O{sub 3} comprises bundles of nanorods with a rhombohedral crystalline structure. The individual nanorod has 8-10 nm diameter and {approx}50 nm length. The as-prepared nanostructured {alpha}-Fe{sub 2}O{sub 3} (sensor) gives selective response towards humidity. The sensor shows high sensitivity, fastmore » linear response to change in the humidity with almost 100% reproducibility. The sensor works at room temperature and rejuvenates without heat treatment. The as-prepared nanostructured {alpha}-Fe{sub 2}O{sub 3} appears to be a promising humidity sensing material with the potential for commercialization.« less

  11. Synthesis of porous nanocrystalline NiO with hexagonal sheet-like morphology by homogeneous precipitation method

    NASA Astrophysics Data System (ADS)

    Sharma, Ravi Kant; Ghose, Ranjana

    2015-04-01

    Porous nanocrystalline NiO has been synthesized by a simple homogeneous precipitation method in short time at low calcination temperature without using any surfactant, chelating or gelating agents. The porous nanocrystalline NiO with a hexagonal sheet-like morphology were obtained by calcination of Ni(OH)2 nanoflakes at 500 °C. The calcination temperature strongly influences the morphology, crystallite size, specific surface area, pore volume and optical band gap of the samples. The samples were characterized using powder X-ray diffraction, thermal gravimetric analysis, FT-IR spectroscopy, UV-Visible diffuse reflectance spectroscopy, surface area measurements, field emission scanning electron microscopy coupled with energy dispersive X-ray analysis and transmission electron microscopy. The chemical activity of the samples was tested by catalytic reduction of 4-nitrophenol with NaBH4.

  12. Siudaite, Na8(Mn2+ 2Na)Ca6Fe3+ 3Zr3NbSi25O74(OH)2Cl·5H2O: a new eudialyte-group mineral from the Khibiny alkaline massif, Kola Peninsula

    NASA Astrophysics Data System (ADS)

    Chukanov, Nikita V.; Rastsvetaeva, Ramiza K.; Kruszewski, Łukasz; Aksenov, Sergey M.; Rusakov, Vyacheslav S.; Britvin, Sergey N.; Vozchikova, Svetlana A.

    2018-03-01

    The new eudialyte-group mineral siudaite, ideally Na8(Mn2+ 2Na)Ca6Fe3+ 3Zr3NbSi25O74(OH)2Cl·5H2O, was discovered in a peralkaline pegmatite situated at the Eveslogchorr Mt., Khibiny alkaline massif, Kola Peninsula, Russia. The associated minerals are aegirine, albite, microcline, nepheline, astrophyllite, and loparite-(Ce). Siudaite forms yellow to brownish-yellow equant anhedral grains up to 1.5 cm across. Its lustre is vitreous, and the streak is white. Cleavage is none observed. The Mohs' hardness is 4½. Density measured by hydrostatic weighing is 2.96(1) g/cm3. Density calculated using the empirical formula is equal to 2.973 g/cm3. Siudaite is nonpleochroic, optically uniaxial, negative, with ω = 1.635(1) and ɛ = 1.626(1) (λ = 589 nm). The IR spectrum is given. The chemical composition of siudaite is (wt%; electron microprobe, H2O determined by HCN analysis): Na2O 8.40, K2O 0.62, CaO 9.81, La2O3 1.03, Ce2O3 1.62, Pr2O3 0.21, Nd2O3 0.29, MnO 6.45, Fe2O3 4.51. TiO2 0.54, ZrO2 11.67, HfO2 0.29, Nb2O5 2.76, SiO2 47.20, Cl 0.54, H2O 3.5, -O = Cl - 0.12, total 99.32. According to Mössbauer spectroscopy data, all iron is trivalent. The empirical formula (based on 24.5 Si atoms pfu, in accordance with structural data) is [Na7.57(H2O)1.43]Σ9(Mn1.11Na0.88Ce0.31La0.20Nd0.05Pr0.04K0.41)Σ3(H2O)1.8(Ca5.46Mn0.54)Σ6(Fe3+ 1.76Mn2+ 1.19)Σ2.95Nb0.65(Ti0.20Si0.50)Σ0.71(Zr2.95Hf0.04Ti0.01)Σ3Si24.00Cl0.47O70(OH)2Cl0.47·1.82H2O. The crystal structure was determined using single-crystal X-ray diffraction data. The new mineral is trigonal, space group R3m, with a = 14.1885(26) Å, c = 29.831(7) Å, V = 5200.8(23) Å3 and Z = 3. Siudaite is chemically related to georgbarsanovite and is its analogue with Fe3+-dominant M2 site. The strongest lines of the powder X-ray diffraction pattern [d, Å (I, %) (hkl)] are: 6.38 (60) (-114), 4.29 (55) (-225), 3.389 (47) (131), 3.191 (63) (-228). 2.963 (100) (4-15), 2.843 (99) (-444), 2.577 (49) (3-39). Siudaite is named after the Polish

  13. Effect of mixing Ce{sup 3+} and Nd{sup 3+} ions in equimolar ratio on structural, optical and dielectric properties on pure cerium orthovanadate and neodymium orthovanadate

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

    Verma, Seema; Gupta, Rashmi; Bamzai, K.K., E-mail: kkbamz@yahoo.com

    2016-09-15

    Highlights: • CeV, NdV and mixed CeNdV nanoparticle prepared by chemical co precipitation method. • With mixing of Ce{sup 3+} and Nd{sup 3+} morphology is totally changed in mixed CeNdV. • Optical band energy of CeV, NdV and CeNdV shows good photocatalyst under UV light. • Conduction mechanism in CeV due to large polaron and small polaron in CeNdV. - Abstract: Cerium orthovanadate, neodymium orthovanadate and mixed cerium neodymium orthovanadate nanoparticles was prepared by co-precipitation method. Powder X-ray diffraction reveals tetragonal zircon structure. Slight increase in lattice parameter, volume and decrease in X-ray density inferred that Ce{sup 3+} and Nd{supmore » 3+} ion replaces each other. Transmission electron microscopy suggests change in morphology with the effect of mixing and validates formation of nanocrystalline material. The infrared transmittance spectrum confirmed the presence of various functional groups. Dielectric properties as function of frequency show dielectric constant and loss tangent decreases with increase in frequency which is due to Maxwell–Wagner type interfacial polarization. The variation of AC conductivity measurement with frequency suggests conduction mechanism due to large polaron hopping in CeV whereas small polaron in mixed CeNdV. The activation energy decreases with rising frequency indicates the conduction mechanism is based on polaron hopping between localized states in disordered manner.« less

  14. Nanocrystalline ferroelectric BaTiO3/Pt/fused silica for implants synthetized by pulsed laser deposition method

    NASA Astrophysics Data System (ADS)

    Jelínek, Miroslav; Drahokoupil, Jan; Jurek, Karel; Kocourek, Tomáš; Vaněk, Přemysl

    2017-09-01

    The thin-films of BaTiO3 (BTO)/Pt were prepared to test their potential as coatings for titanium-alloy implants. The nanocrystalline BTO/Pt bi-layers were successfully synthesized using fused silica as substrates. The bi-layers were prepared using KrF excimer laser ablation at substrate temperatures (Ts) ranging from 650 °C to 750 °C. The microstructure and composition of the deposits were investigated by scanning electron microscope, x-ray diffraction and wavelength dispersive x-ray spectroscopy methods. The electrical characterization of the Pt/BTO/Pt capacitors indicated ferroelectric-type response in BTO films containing (40-140) nm-sized grains. The technology, microstructure, and functional response of the layers are presented in detail.

  15. High surface area nanocrystalline hausmannite synthesized by a solvent-free route

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

    Herrera-Miranda, Daniel; Ponrouch, Alexandre; Pons, Josefina

    Highlights: ► High surface area Mn{sub 3}O{sub 4} nanoparticles obtained by a solvent-free low temperature route. ► 3,6,9-Trioxadecanoic acid allows to obtain nanocrystalline hausmannite. ► Tape casted electrodes show up to 300 mAh g{sup −1} capacity after more than 40 cycles at a C/3 rate. ► Upper cut off voltage strongly influences capacity retention upon cycling at high C rates. -- Abstract: Nanocrystalline high surface area Mn{sub 3}O{sub 4} powder was obtained at low temperature by a solvent-free route. The precursor was a mixture of manganese (II) acetate, 3,6,9-trioxadecanoic acid (TODA) and ammonium acetate that were intimately mixed by groundingmore » in an agate mortar. Nanocrystalline Mn{sub 3}O{sub 4} was obtained by thermal treatment at 120 °C. Powder X-ray diffraction, selected area electron diffraction, high resolution transmission electron microscopy, and Fourier transformed infrared characterization confirmed the formation of the hausmannite phase. The as-prepared mesoporous material has high specific surface area (120 m{sup 2} g{sup −1}). The performances of tape casted Mn{sub 3}O{sub 4} nanopowder electrodes were investigated as anode material for lithium ion batteries. High capacity values were achieved at diverse C rates. Capacity fading was found to be dependent on the upper cut off voltage, the presence of a plateau at 2.25 V vs. Li{sup +}/Li being detrimental for long term cyclability.« less

  16. Temperature and field dependent magnetization studies on nano-crystalline ZnFe2O4 thin films

    NASA Astrophysics Data System (ADS)

    Sahu, B. N.; Suresh, K. G.; Venkataramani, N.; Prasad, Shiva; Krishnan, R.

    2018-05-01

    Single phase nano-crystalline zinc ferrite (ZnFe2O4) thin films were deposited on fused quartz substrate using the pulsed laser deposition technique. The films were deposited at different substrate temperatures. The field dependence of magnetization at 10 K shows hysteresis loops for all the samples. Temperature dependence of the field cooled (FC) and zero field cooled (ZFC) magnetization indicated irreversible behavior between the FC and ZFC data, and the irreversibility depends on the measuring magnetic field. The thermo-magnetic irreversibility in the magnetization data is correlated with the magnitude of the applied field and the coercivity (HC) obtained from the M-H loops.

  17. Porous Nanocrystalline Silicon Supported Bimetallic Pd-Au Catalysts: Preparation, Characterization, and Direct Hydrogen Peroxide Synthesis

    PubMed Central

    Potemkin, Dmitriy I.; Maslov, Dmitry K.; Loponov, Konstantin; Snytnikov, Pavel V.; Shubin, Yuri V.; Plyusnin, Pavel E.; Svintsitskiy, Dmitry A.; Sobyanin, Vladimir A.; Lapkin, Alexei A.

    2018-01-01

    Bimetallic Pd-Au catalysts were prepared on the porous nanocrystalline silicon (PSi) for the first time. The catalysts were tested in the reaction of direct hydrogen peroxide synthesis and characterized by standard structural and chemical techniques. It was shown that the Pd-Au/PSi catalyst prepared from conventional H2[PdCl4] and H[AuCl4] precursors contains monometallic Pd and a range of different Pd-Au alloy nanoparticles over the oxidized PSi surface. The PdAu2/PSi catalyst prepared from the [Pd(NH3)4][AuCl4]2 double complex salt (DCS) single-source precursor predominantly contains bimetallic Pd-Au alloy nanoparticles. For both catalysts the surface of bimetallic nanoparticles is Pd-enriched and contains palladium in Pd0 and Pd2+ states. Among the catalysts studied, the PdAu2/PSi catalyst was the most active and selective in the direct H2O2 synthesis with H2O2 productivity of 0.5 mol gPd-1 h-1 at selectivity of 50% and H2O2 concentration of 0.023 M in 0.03 M H2SO4-methanol solution after 5 h on stream at −10°C and atmospheric pressure. This performance is due to high activity in the H2O2 synthesis reaction and low activities in the undesirable H2O2 decomposition and hydrogenation reactions. Good performance of the PdAu2/PSi catalyst was associated with the major part of Pd in the catalyst being in the form of the bimetallic Pd-Au nanoparticles. Porous silicon was concluded to be a promising catalytic support for direct hydrogen peroxide synthesis due to its inertness with respect to undesirable side reactions, high thermal stability, and conductivity, possibility of safe operation at high temperatures and pressures and a well-established manufacturing process. PMID:29637068

  18. Concentration-dependent studies of Nd3+ -doped zinc phosphate glasses for NIR photoluminescence at 1.05 μm.

    PubMed

    Reddy Prasad, V; Seshadri, M; Babu, S; Ratnakaram, Y C

    2017-05-01

    Nd 3 + -doped lead-free zinc phosphate glasses with the chemical compositions (60-x) NH 4 H 2 PO 4  + 20ZnO + 10BaF 2  + 10NaF + xNd 2 O 3 (where x = 0.5, 1.0, 1.5, 2.0 and 2.5 mol%) were prepared using a melt quenching technique. Vibrational bands were assigned and clearly elucidated by Raman spectral profiles for all the glass samples. Judd-Ofelt (J-O) intensity parameters (Ω λ : λ = 2, 4, 6) were obtained from the spectral intensities of different absorption bands of Nd 3 + ions. Radiative properties such as radiative transition probabilities (A R ), radiative lifetimes (τ R ) and branching ratios (β R ) for different excited states were calculated using J-O parameters. The near infrared (NIR) photoluminescence spectra exhibited three emission bands ( 4 F 3 /2 level to 4 I 13 /2 , 4 I 11 /2 and 4 I 9 /2 states) for all the concentrations of Nd 3 + ions. Various luminescence properties were studied by varying the Nd 3 + concentration for the three spectral profiles. Fluorescence decay curves of the 4 F 3 /2 level were recorded. The energy transfer mechanism that leads to quenching of the 4 F 3 /2 state lifetimes was discussed at higher concentration of Nd 3 + ions. These glasses are suggested as suitable hosts to produce efficient lasing action in NIR region at 1.05 μm. Copyright © 2016 John Wiley & Sons, Ltd.

  19. Growth and characterization of spindle-like Ga2O3 nanocrystals by electrochemical reaction in hydrofluoric solution

    NASA Astrophysics Data System (ADS)

    Feng, Lungang; Li, Yufeng; Su, Xilin; Wang, Shuai; Liu, Hao; Wang, Jiangteng; Gong, Zhina; Ding, Wen; Zhang, Ye; Yun, Feng

    2016-12-01

    We report a novel fabrication method of spindle-like gallium oxide (Ga2O3) nanocrystals via two steps processed by electrochemical reaction of the MOVPE-grown GaN epitaxial layer in HF/ethanol (1:6) electrolyte and subsequent heat treatment. Depending on the electrolyte concentration, reaction time and applied voltage, micrometer- to nanometer-size spindle-like gallium fluoride tri-hydrate (GaF3·3H2O) of different densities and geometrical dimensions were formed on the surface of GaN. EDS, XPS and XRD were used to characterize the properties of the material before and after heat treatment. It is found that due to heat treatment at above 600 °C, nanocrystalline Ga2O3 were transformed from the GaF3·3H2O via pyrohydrolysis reaction mechanism. The band gap of ∼5.1 eV of the spindle-like Ga2O3 was measured by the optical absorption spectroscopy.

  20. Comparisons of lanthanide/actinide +2 ions in a tris(aryloxide)arene coordination environment† †Electronic supplementary information (ESI) available: Additional computational details, spectroscopic information, crystallographic data collection, structure solution, and refinement (PDF), X-ray diffraction details of compounds 1-Ln (Ln = Nd, Gd, Dy, and Er), 2-Nd, 2-Ln/3-Ln (Ln = Gd, Dy, Er), 2-Dy/4-Dy, and 5-Dy/6-Dy. CCDC (CIF, 1538987–1538995 and 1566075 for 2-Dy/3-Dy), and DFT-optimized structural coordinates for 2-Nd and 2-Gd. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c7sc02337e Click here for additional data file. Click here for additional data file. Click here for additional data file.

    PubMed Central

    Fieser, Megan E.; Palumbo, Chad T.; La Pierre, Henry S.; Halter, Dominik P.; Voora, Vamsee K.; Ziller, Joseph W.

    2017-01-01

    A new series of Ln3+ and Ln2+ complexes has been synthesized using the tris(aryloxide)arene ligand system, ((Ad,MeArO)3mes)3–, recently used to isolate a complex of U2+. The triphenol precursor, (Ad,MeArOH)3mes, reacts with the Ln3+ amides, Ln(NR2)3 (R = SiMe3), to form a series of [((Ad,MeArO)3mes)Ln] complexes, 1-Ln. Crystallographic characterization was achieved for Ln = Nd, Gd, Dy, and Er. The complexes 1-Ln can be reduced with potassium graphite in the presence of 2.2.2-cryptand (crypt) to form highly absorbing solutions with properties consistent with Ln2+ complexes, [K(crypt)][((Ad,MeArO)3mes)Ln], 2-Ln. The synthesis of the Nd2+ complex [K(crypt)][((Ad,MeArO)3mes)Nd], 2-Nd, was unambiguously confirmed by X-ray crystallography. In the case of the other lanthanides, crystals were found to contain mixtures of 2-Ln co-crystallized with either a Ln3+ hydride complex, [K(crypt)][((Ad,MeArO)3mes)LnH], 3-Ln, for Ln = Gd, Dy, and Er, or a hydroxide complex, [K(crypt)][((Ad,MeArO)3mes)Ln(OH)], 4-Ln, for Ln = Dy. A Dy2+ complex with 18-crown-6 as the potassium chelator, [K(18-crown-6)(THF)2][((Ad,MeArO)3mes)Dy], 5-Dy, was isolated as a co-crystallized mixture with the Dy3+ hydride complex, [K(18-crown-6)(THF)2][((Ad,MeArO)3mes)DyH], 6-Dy. Structural comparisons of 1-Ln and 2-Ln are presented with respect to their uranium analogs and correlated with density functional theory calculations on their electronic structures. PMID:29163894

  1. Structural peculiarities and Raman spectra of TeO{sub 2}/WO{sub 3}-based glasses: A fresh look at the problem

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

    Mirgorodsky, Andreie; Colas, Maggy; Smirnov, Mikhael

    2012-06-15

    Ideas currently dominating the field of structural studies of TeO{sub 2}-based glasses are critically considered. A new physically and chemically consistent approach to the constitution of binary TeO{sub 2}-WO{sub 3} glasses is proposed, in which the reasoning coming from the Raman spectra reexamination are correlated with the basic principles of thermodynamics. Separation into two phases is suggested in such glasses. One phase is TeO{sub 2}, and another is Te(WO{sub 4}){sub 2} consisting of tetrahedral [WO{sub 4}]{sup 2-} anions and of Te{sup 4+} cations. Supplementary M{sub n}O{sub k} oxides added to the glasses are found incorporated in the former phase, thusmore » producing solid solutions (for M=Ti, Nb) or tellurite compounds (for M=Nd). - Graphical abstract: Raman scattering spectra of TeO{sub 2}-based glasses with the following compositions (mol%): (a) pure TeO{sub 2}, (b) 85TeO{sub 2}-15WO{sub 3}, (c) 80TeO{sub 2}-15WO{sub 3}-5TiO{sub 2} ,(d) 80TeO{sub 2}-10WO{sub 3}-5TiO{sub 2}-5Nb{sub 2}O{sub 5}, (e) 80TeO{sub 2}-12WO{sub 3}-5TiO{sub 2}-3 Nd{sub 2}O{sub 3}, (f) 80TeO{sub 2}-10WO{sub 3}-5TiO{sub 2}-5Nd{sub 2}O{sub 3}. Highlights: Black-Right-Pointing-Pointer Structural studies of TeO{sub 2}-WO{sub 3} glasses are critically considered. Black-Right-Pointing-Pointer The oxide glass formation is analyzed from Raman spectra and thermodynamic principles. Black-Right-Pointing-Pointer Separation into two phases, TeO{sub 2} and Te(WO{sub 4}){sub 2}, is intrinsic in such glasses. Black-Right-Pointing-Pointer TiO{sub 2} or Nb{sub 2}O{sub 5} addition to TeO{sub 2}-WO{sub 3} glasses leads to produce solid solutions. Black-Right-Pointing-Pointer Nd{sub 2}O{sub 3} addition to TeO{sub 2}-WO{sub 3} glasses leads to produce a tellurite compound.« less

  2. Pressure-induced Structural Transformations in LanthanideTitanates: La2TiO5 and Nd2TiO5

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

    F Zhang; J Wang; M Lang

    The structure of orthorhombic rare earth titanates of La{sub 2}TiO{sub 5} and Nd{sub 2}TiO{sub 5}, where Ti cations are in five-fold coordination with oxygen, has been studied at high pressures by X-ray diffraction (XRD), Raman scattering measurements, and quantum mechanical calculations. Both XRD and Raman results indicated two pressure-induced phase transitions during the process. An orthorhombic super cell (a x b x 2c) formed at a pressure between 6 and 10 GPa, and then transformed to a hexagonal high-pressure phase accompanied by partial decomposition. The hexagonal high-pressure phase is quenchable. Detailed structural analysis indicated that the five-coordinated TiO{sub 5} polyhedramore » remain during the formation of super cell, but the orthorhombic-to-hexagonal phase transition at high pressures is a reconstructive process, and the five-fold Ti-O coordination increased to more than 6. This phase transition sequence was verified by quantum mechanical calculations.« less

  3. General synthesis and structural evolution of a layered family of Ln8(OH)20Cl4 x nH2O (Ln = Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Y).

    PubMed

    Geng, Fengxia; Matsushita, Yoshitaka; Ma, Renzhi; Xin, Hao; Tanaka, Masahiko; Izumi, Fujio; Iyi, Nobuo; Sasaki, Takayoshi

    2008-12-03

    The synthesis process and crystal structure evolution for a family of stoichiometric layered rare-earth hydroxides with general formula Ln(8)(OH)(20)Cl(4) x nH(2)O (Ln = Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Y; n approximately 6-7) are described. Synthesis was accomplished through homogeneous precipitation of LnCl(3) x xH(2)O with hexamethylenetetramine to yield a single-phase product for Sm-Er and Y. Some minor coexisting phases were observed for Nd(3+) and Tm(3+), indicating a size limit for this layered series. Light lanthanides (Nd, Sm, Eu) crystallized into rectangular platelets, whereas platelets of heavy lanthanides from Gd tended to be of quasi-hexagonal morphology. Rietveld profile analysis revealed that all phases were isostructural in an orthorhombic layered structure featuring a positively charged layer, [Ln(8)(OH)(20)(H(2)O)(n)](4+), and interlayer charge-balancing Cl(-) ions. In-plane lattice parameters a and b decreased nearly linearly with a decrease in the rare-earth cation size. The interlamellar distance, c, was almost constant (approximately 8.70 A) for rare-earth elements Nd(3+), Sm(3+), and Eu(3+), but it suddenly decreased to approximately 8.45 A for Tb(3+), Dy(3+), Ho(3+), and Er(3+), which can be ascribed to two different degrees of hydration. Nd(3+) typically adopted a phase with high hydration, whereas a low-hydration phase was preferred for Tb(3+), Dy(3+), Ho(3+), Er(3+), and Tm(3+). Sm(3+), Eu(3+), and Gd(3+) samples were sensitive to humidity conditions because high- and low-hydration phases were interconvertible at a critical humidity of 10%, 20%, and 50%, respectively, as supported by both X-ray diffraction and gravimetry as a function of the relative humidity. In the phase conversion process, interlayer expansion or contraction of approximately 0.2 A also occurred as a possible consequence of absorption/desorption of H(2)O molecules. The hydration difference was also evidenced by refinement results. The number of coordinated water

  4. Synthesis of nanocrystalline rare earth oxides by glycothermal method

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

    Hosokawa, Saburo; Iwamoto, Shinji; Inoue, Masashi

    2008-11-03

    The reaction of yttrium acetate hydrate in 1,2-propanediol at 300 deg. C yielded a product containing acetate groups and glycol moieties. From this product, Y{sub 2}O{sub 3} was directly crystallized at 400 deg. C without the formation of a carbonate oxide phase. The thus-obtained Y{sub 2}O{sub 3} samples had a small crystallite size (2.2 nm) and significantly large surface area (280 m{sup 2}/g). Other nanocrystalline rare earth (Gd-Yb) oxides were also obtained by this method.

  5. Performance characterization of CNTs and γ-Al{sub 2}O{sub 3} supported cobalt catalysts in Fischer-Tropsch reaction

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

    Ali, Sardar, E-mail: alikhan-635@yahoo.com; Zabidi, Noor Asmawati Mohd, E-mail: noorasmawati-mzabidi@petronas.com.my; Subbarao, Duvvuri, E-mail: duvvuri-subbarao@petronas.com.my

    2014-10-24

    Catalysts were prepared via a wet impregnation method. Different physicochemical properties of the samples were revealed by transmission electron microscope (TEM), temperature programmed reduction (H{sub 2}-TPR) and carbon dioxide desorption (CO{sub 2}-desorption). Fischer-Tropsch reaction (FTS) was carried out in a fixed-bed microreactor at 220°C and 1 atm, with H{sub 2}/CO = 2v/v and space velocity, SV of 12L/g.h for 5 h. Various characterization techniques revealed that there was a stronger interaction between Co and Al{sub 2}O{sub 3} support compared to that of CNTs support. CNTs support increased the reducibility and decreased Co particle size. A significant increase in % CO conversion andmore » FTS reaction rate was observed over CNTs support compared to that of Co/Al{sub 2}O{sub 3}. Co/CNTs resulted in higher C{sub 5+} hydrocarbons selectivity compared to that of Co/Al{sub 2}O{sub 3} catalyst. CNTs are a better support for Co compared to Al{sub 2}O{sub 3}.« less

  6. Electrical impedance spectroscopy of neutron-irradiated nanocrystalline silicon carbide (3C-SiC)

    NASA Astrophysics Data System (ADS)

    Huseynov, Elchin M.

    2018-01-01

    It the present work, impedance spectra of nanocrystalline 3C-SiC particles have been comparatively analyzed before and after neutron irradiation. Resonance states and shifts were observed at the impedance spectra of nanocrystalline 3C-SiC particles after neutron irradiation. Relaxation time has been calculated from interdependence of real and imaginary parts of impedance of nanocrystalline 3C-SiC particles. Calculated relaxation times have been investigated as a function of neutron irradiation period. Neutron transmutation (31P isotopes production) effects on the impedance spectra and relaxation times have been studied. Moreover, influence of agglomeration and amorphous transformation to the impedance spectra and relaxation times of nanocrystalline 3C-SiC particles have been investigated.

  7. Mechanical properties of nanocrystalline cobalt

    NASA Astrophysics Data System (ADS)

    Karimpoor, Amir A.; Erb, Uwe

    2006-05-01

    Due to their excellent wear and corrosion properties, nanocrystalline cobalt and several cobalt alloys made by electrodeposition are currently being developed as environmentally benign replacement coatings for hard chromium electrodeposits. The focus of this study is on the mechanical properties of nanocrystalline cobalt, which are currently not well understood. A comparison is presented for hardness, tensile properties, Charpy impact properties and fracture surface analysis of both nanocrystalline (grain size: 12 nm) and conventional polycrystalline (grain size: 4.8 m) cobalt. It is shown that the hardness and tensile strength of nanocrystalline cobalt is 2-3 times higher than for polycrystalline cobalt. However, in contrast to other nanocrystalline materials tested previously, nanocrystalline cobalt retains considerable ductility with elongation to fracture values up to 7%.

  8. Preparation and Scintillating Properties of Sol-Gel Eu3+, Tb3+ Co-Doped Lu2O3 Nanopowders

    PubMed Central

    de Jesús Morales Ramírez, Ángel; Murillo, Antonieta García; de Jesús Carrillo Romo, Felipe; Hernández, Margarita García; Palmerin, Joel Moreno; Guerrero, Rosario Ruiz

    2011-01-01

    Nanocrystalline Eu3+, Tb3+ co-doped Lu2O3 powders with a maximum size of 25.5 nm were prepared by the sol-gel process, using lutetium, europium and terbium nitrates as precursors, and ethanol as a solvent. Differential thermal analysis (DTA) and infrared spectroscopy (IR) were used to study the chemical changes during the xerogel annealing. After the sol evaporation at 100 °C, the formed gel was annealed from 300 to 900 °C for 30 min under a rich O2 atmosphere, and the yielded product was analyzed by X-ray diffraction (XRD) to characterize the microstructural behavior and confirm the crystalline structure. The results showed that Lu2O3 nanopowders start to crystallize at 400 °C and that the crystallite size increases along with the annealing temperature. A transmission electron microscopy (TEM) study of samples annealed at 700 and 900 °C was carried out in order to analyze the microstructure, as well as the size, of crystallites. Finally, in regard to scintillating properties, Eu3+ dopant (5 mol%), Tb3+ codoped Lu2O3 exhibited a typical red emission at 611 nm (D°→7F2), furthermore, the effect of Tb3+ molar content (0.01, 0.015 and 0.02% mol) on the Eu3+ radioluminiscence was analyzed and it was found that the higher emission intensity corresponds to the lower Tb3+ content. PMID:22016655

  9. Swift-heavy ion irradiation response and annealing behavior of A2TiO5 (A = Nd, Gd, and Yb)

    NASA Astrophysics Data System (ADS)

    Park, Sulgiye; Tracy, Cameron L.; Zhang, Fuxiang; Palomares, Raul I.; Park, Changyong; Trautmann, Christina; Lang, Maik; Mao, Wendy L.; Ewing, Rodney C.

    2018-02-01

    The structural responses of A2BO5 (A = Nd, Gd, and Yb; B = Ti) compositions irradiated by high-energy Au ions (2.2 GeV) were investigated using transmission electron microscopy, synchrotron X-ray diffraction and Raman spectroscopy. The extent of irradiation-induced amorphization depends on the size of the A-site cation, with smaller lanthanides having less susceptibility to the accumulation of radiation damage. In the track-overlapping regime, complete amorphization is observed in all three compounds, despite the ability of Yb2TiO5 to incorporate a great deal of structural disorder into its initial defect-fluorite structure (Fm-3m). This is attributed to the high cation radius ratio (A:B = 2:1), which reduces the stability of the structure upon ion irradiation. The fully-amorphized samples were subsequently isochronally heated at temperature intervals from 100 °C to 850 °C. X-ray diffraction analysis indicated a similar damage recovery process in Nd2TiO5 and Gd2TiO5, where both compositions recover their original structures (Pnma) at 850 °C. In contrast, Yb2TiO5 exhibited recrystallization of a metastable, non-equilibrium orthorhombic phase at 550 °C, prior to a transformation to the stable defect-fluorite phase (Fm-3m) at 625 °C. These compositional variations in radiation tolerance and thermal recovery processes are described in terms of the energetics of disordering during the damage and recrystallization processes.

  10. Transport properties of Nd0.67Sr0.33Mn0.85Co0.15O3 manganite

    NASA Astrophysics Data System (ADS)

    Bhargav, Abhinav; Tank, Tejas M.; Sanyal, Sankar P.

    2018-05-01

    We have studied the structural and electrical transport properties of Nd0.67Sr0.33Mn0.85Co0.15O3 manganite prepared through conventional solid state reaction technique. The investigation of X-ray diffraction data and rietvield refinement show that the synthesized sample is single phase in nature and crystallizes in orthorhombic perovskite structure with Pbnm space group. The resistivity versus temperature measurement for sample Nd0.67Sr0.33Mn0.85Co0.15O3 was performed in the range 0-300K and at 0T field. The electrical transport mechanism of the sample is analyzed by different theoretical models, for temperatures below and above TP.

  11. Chemical synthesis of hexagonal indium nitride nanocrystallines at low temperature

    NASA Astrophysics Data System (ADS)

    Wang, Liangbiao; Shen, Qianli; Zhao, Dejian; Lu, Juanjuan; Liu, Weiqiao; Zhang, Junhao; Bao, Keyan; Zhou, Quanfa

    2017-08-01

    In this study, hexagonal indium nitride nanocystallines with high crystallinity have been prepared by the reaction of InCl3·4H2O, sulfur and NaNH2 in an autoclave at 160 °C. The crystal structures and morphologies of the obtained InN sample are characterized by X-ray diffraction and scanning electron microscope. As InCl3·4H2O is substituted by In(NO3)3·4.5H2O, InN nanocrystallines could also be obtained by using the similar method. The photoluminescence spectrum shows that the InN emits a broad peak positioned at 2.3 eV.

  12. WO x supported on γ-Al 2 O 3 with different morphologies as model catalysts for alkanol dehydration

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

    Shi, Dachuan; Wang, Huamin; Kovarik, Libor

    The distinctive morphological and surface characteristics of platelet-like γ-Al2O3 were compared to a regular, commercial γ-Al2O3. γ-Al2O3 platelets display dominant (110) surface facets and higher densities of coordinative unsaturated penta-coordinate Al3+ (Al3+penta) sites than regular γ-Al2O3, as measured by solid-state magic-angle spinning nuclear magnetic resonance spectroscopy (MAS NMR). Such Al3+penta sites are also the preferred surface anchoring sites for tungsten oxide (WOx) species consistent with NMR analysis indicating that these sites are consumed upon WOx adsorption. The higher Al3+penta density on γ-Al2O3 platelets leads to greater WOx dispersion (or smaller WOx clusters), as demonstrated by scanning transmission electron microscopy andmore » ultraviolet–visible spectroscopy, and WOx species at intermediate WOx surface concentration are the most active for the probe reaction of 2-butanol dehydration. WOx on γ-Al2O3 platelets approaches the highest turnover rates at higher surface densities than WOx on regular γ-Al2O3, yet with similar highest rate values for both series of catalysts. This indicates that different Al2O3 supports mainly affect the dispersion of supported WOx rather than the intrinsic reactivity of individual WOx clusters with similar size.« less

  13. X-ray absorption studies of gamma irradiated Nd doped phosphate glass

    NASA Astrophysics Data System (ADS)

    Rai, V. N.; Rajput, Parasmani; Jha, S. N.; Bhattacharyya, D.

    2015-06-01

    This paper presents the X-ray absorption near edge structure (XANES) studies of Nd doped phosphate glasses before and after gamma irradiation. The intensity and location of LIII edge white line peak of Nd changes depending on its concentration as well as on the ratio of O/Nd in the glass matrix. The decrease in the peak intensity of white line after gamma irradiation indicates towards reduction of Nd3+ to Nd2+ in the glass matrix, which increases with an increase in the doses of gamma irradiation. Similarity in the XANES spectra of Nd doped phosphate glasses and Nd2O3 suggests that coordination geometry around Nd3+ in glass samples may be identical to that of Nd2O3.

  14. FT-IR Spectroscopic Evidence Of Phase Transition For NaA-ROH-Kerosine-H2O Microemulsion System Containing Nd3+ Ions

    NASA Astrophysics Data System (ADS)

    Liao, Hua; Xu, Zhen-Hua; Shi, Nai; Wu, Jin-Guang; Xu, Guang-Xian

    1989-12-01

    In the previous investigation, the saponification of naphthenic acid extractant system has been proved to be a process of the formation of a microemulsion of 14/0 type, and its full extraction of rare earths is a process of destruction of the W/O microemulsion[1]. When NdCl3 is partially extracted with NaA (sodium naphthenate) secoctylalcohol-- kerosine-- water microemulsion system (ME), both the NdA3 and the NaA co-exist in the same organic phase. However,the formation mechanism of microemulsion containing neodymium has not been much studied. In this paper, 10 aliquots of fully saponificated extractants were equilibrated with various amounts of NdC13 solutions respectively, then ten organic phases with different extraction efficiencies of neodymium from 094 to 9094 were obtained. After extraction,the volume of neodymium containing organic phase increased by 5 to 4594, because of the transfer of water molecules. The appearance of these organic phase still remained clear and transparent. The average hydrodynamic radius of the drops were found to be 100-300 Angstrom by using light scattering techniques. The results give a direct evidence of the microemulsion formation in the organic phase. Their FT-IR spectra were measured with CaFa liquid cells utilizing a Nicolet 7199B FT-IR spectrometer. The presence of various amounts of water in the organic phases was clearly detected from the relative intensity changes of 1644 cm-I, which is assigned to the bending mode of 1110 molecules. Fig.1 shows the change of water contents to the percent extraction of neodymium. Comparsion with the FT-IR spectra, it is seen that the 1560 cm-1 peak of the full saponificated extractant is attributed to the asym. stretching vibration of COO''' group, it shifted to 1536 for 100% extration of Nd ions, indicating the formation of neodymium naphthenate (NdA ) from ionic sodium naphthenate. The sym. strethching vibration of COO''' located at 1406 cm-1, it shifted to 1408 cm in 45% Nd extration

  15. Nanocrystalline Anatase Titania Supported Vanadia Catalysts: Facet-dependent Structure of Vanadia

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

    Li, Wei-Zhen; Gao, Feng; Li, Yan

    2015-07-09

    Titania supported vanadia, a classic heterogeneous catalyst for redox reactions, typically has nonhomogeneous vanadia species on various titania facets, making it challenging not only to determine and quantify each species but also to decouple their catalytic contributions. We prepared truncated tetragonal bipyramidal (TiO2-TTB) and rod-like (TiO2-Rod) anatase titania with only {101} and {001} facets at ratios of about 80:20 and 93:7, respectively, and used them as supports of sub-monolayer vanadia. The structure and redox properties of supported vanadia were determined by XRD, TEM, XPS, EPR, Raman, FTIR and TPR, etc. It was found that vanadia preferentially occupy TiO2 {001} facetsmore » and form isolated O=V4+(O-Ti)2 species, and with further increase in vanadia surface coverage, isolated O=V5+(O-Ti)3 and oligomerized O=V5+(O-M)3 (M = Ti or V) species form on TiO2 {101} facets. The discovery on support facet-dependent structure of vanadia on anatase titania is expected to enable the elucidation of structure-function correlations on high surface area TiO2 supported vanadia catalysts. This work was supported by U. S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Biosciences and Geosciences. The research was performed in the Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the DOE Office of Biological and Environmental Research, and located at Pacific Northwest National Laboratory (PNNL). PNNL is operated for DOE by Battelle.« less

  16. Study of ND3-enhanced MAR processes in D2-N2 plasmas to induce plasma detachment

    NASA Astrophysics Data System (ADS)

    Abe, Shota; Chakraborty Thakur, Saikat; Doerner, Russ; Tynan, George

    2017-10-01

    The Molecular Assisted Recombination (MAR) process is thought to be a main channel of volumetric recombination to induce the plasma detachment operation. Authors have focused on a new plasma recombination process supported by ammonia molecules, which will be formed by impurity seeding of N2 for controlling divertor plasma temperature and heat loads in ITER. This ammonia-enhanced MAR process would occur throughout two steps. In this study, the first step of the new MAR process is investigated in low density plasmas (Ne 1016 m-3, Te 4 eV) fueled by D2 and N2. Ion and neutral densities are measured by a calibrated Electrostatic Quadrupole Plasma (EQP) analyzer, combination of an ion energy analyzer and mass spectrometer. The EQP shows formation of ND3 during discharges. Ion densities calculated by a rate equation model are compared with experimental results. We find that the model can reproduce the observed ion densities in the plasma. The model calculation shows that the dominant neutralization channel of Dx+(x =1-3) ions in the volume is the formation of NDy+(y =3 or 4) throughout charge/D+ exchange reactions with ND3. Furthermore, high density plasmas (Ne 1016 m-3) have been achieved to investigate electron-impact dissociative recombination processes of formed NDy+,which is the second step of this MAR process.

  17. Thin films sputtered from Ba{sub 2}NdFeNb{sub 4}O{sub 15} multiferroic targets on BaFe{sub 12}O{sub 19} coated substrates

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

    Bodeux, Romain; Univ. Bordeaux, ICMCB, UPR 9048, F-33600 Pessac; Michau, Dominique, E-mail: dominique.michau@icmcb.cnrs.fr

    2016-09-15

    Highlights: • Synthesis of Ba{sub 2}NdFeNb{sub 4}O{sub 15}/BaFe{sub 12}O{sub 19} (BaM) heterostructures by RF magnetron sputtering. • Growth of TTB layer were retained regardless of the underlayer (Pt bottom electrode or BaM). • Dielectric and magnetic properties were obtained from the Pt/TTB/BaM/Pt stacks. - Abstract: Ba{sub 2}NdFeNb{sub 4}O{sub 15} tetragonal tungsten bronze (TTB)/BaFe{sub 12}O{sub 19} (BaM) hexaferrite bilayers have been grown by RF magnetron sputtering on Pt/TiO{sub 2}/SiO{sub 2}/Si (PtS) substrates. The BaM layer is textured along (0 0 1) while the TTB layer is multioriented regardless of the PtS or BaM/PtS substrate. Dielectric properties of TTB films are similarmore » to those of bulk, i.e., ε ∼ 150 and a magnetic hysteresis loop is obtained from TTB/BaM bilayers, thanks to the BaM component. This demonstrates the possibility of transferring to 2 dimensional structures the composite multiferroic system TTB/BaM previously identified in 3 dimensional bulk ceramics.« less

  18. Identification of Nanocrystalline Inclusions in Bismuth-Doped Silica Fibers and Preforms.

    PubMed

    Iskhakova, Liudmila D; Milovich, Filipp O; Mashinsky, Valery M; Zlenko, Alexander S; Borisovsky, Sergey E; Dianov, Evgeny M

    2016-10-01

    The nature of nanocrystalline inclusions and dopant distribution in bismuth-doped silicate fibers and preforms are studied by scanning and transmission electron microscopy, and energy and wavelength-dispersive X-ray microanalysis. The core compositions are Bi:SiO2, Bi:Al2O3-SiO2, Bi:GeO2-SiO2, Bi:Al2O3-GeO2-SiO2, and Bi:P2O5-Al2O3-GeO2-SiO2. Nanocrystals of metallic Bi, Bi2O3, SiO2, GeO2, and Bi4(GeO4)3 are observed in these glasses. These inclusions can be the reason for the background optical loss in bismuth-doped optical fibers. The bismuth concentration of 0.0048±0.0006 at% is directly measured in aluminosilicate optical fibers with effective laser generation (slope efficiency of 27% at room temperature).

  19. Anomalous compression behavior of ˜12 nm nanocrystalline TiO2

    NASA Astrophysics Data System (ADS)

    Wang, Qiming; Li, Shourui; Peng, Fang; Lei, Li; Hu, Qiwei; Wang, Pei; Nan, Xiaolong; Liu, Jing; Zhu, Wenjun; He, Duanwei

    2017-06-01

    When the grain size decreases, there inevitably exists a critical size (dc) where the contribution of surface atoms to the physical properties is competitive with that of the interior atoms, giving rise to a wide variety of new phenomena. The behavior of granular materials near dc is particularly interesting because of the crossover, a continuous transition from one type of mechanism to another. In situ high-pressure x-ray diffraction experiments showed that the compression curve of nanocrystalline anatase TiO2 with grain size near dc reached a platform after about 5%-6% of deformation under hydrostatic compression. Eventually, the unit cell volume of anatase expanded at ˜14-16 GPa. We propose that the anomalous compression behavior is attributed to the formation and thickening of the stiff high density amorphous shell under high pressure, giving rise to a great arching effect at the grain boundary at the nanolevel. This process results in a remarkable difference in stress between inside and outside of the shell, generating the illusions of the hardening and the negative compressibility. This study offers a new insight into the mechanical properties of nanomaterials under extreme conditions.

  20. Monoclinic nanodomains in morphotropic phase boundary Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3}–PbTiO{sub 3}

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

    Sato, Y., E-mail: y-sato@sigma.t.u-tokyo.ac.jp; Hirayama, T.; Ikuhara, Y.

    2014-02-24

    Crystalline structure is a fundamental characteristic of many materials, and drastic changes in properties may accompany crystal phase transitions. A prominent example of this is the morphotropic phase boundary of (Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3}-PbTiO{sub 3}) single crystal, a region that exhibits a high piezoelectric effect. Although the highest piezoelectricity is often attributed to a monoclinic crystal phase, formation of ferroelectric nanodomains (NDs) complicates understanding of this crystal structure. In this Letter, we report dedicated transmission electron microscopy and electron diffraction analysis to understand the crystal structure at the ND level. Splitting of diffraction spots, caused by very small lattice distortionmore » in the NDs, is important to understanding crystal structure and has been unambiguously observed. The results can be explained by monoclinic phase NDs. Combining these results with our previous findings on ND dynamics [Sato et al. Phys. Rev. Lett. 107, 187601 (2011)], monoclinic NDs can potentially make a considerable contribution to the piezoelectricity in these materials.« less

  1. Photoluminescence, thermoluminescence glow curve and emission characteristics of Y2O3:Er3 + nanophosphor

    NASA Astrophysics Data System (ADS)

    N. J., Shivaramu; B. N., Lakshminarasappa; K. R., Nagabhushana; H. C., Swart; Fouran, Singh

    2018-01-01

    Nanocrystalline Er3 + doped Y2O3crystals were prepared by a sol gel technique. X-ray diffraction (XRD) patterns showed the cubic structure of Y2O3 and the crystallite size was found to be 25 nm. Optical absorption showed absorption peaks at 454, 495 and 521 nm. These peaks are attributed to the 4F3/2 + 4F5/2, 4F7/2 and 2H11/2 + 4S3/2 transitions of Er3 +. Under excitation at 378 nm, the appearance of strong green (520-565 nm) down conversion emission assigned to the (2H11/2,4S3/2) → 4I15/2 transition and the feeble red (650-665 nm) emission is assigned to the 4F9/2 → 4I15/2 transition. The color chromaticity coordinates showed emission in the green region. The strong green emission of Y2O3:Er3 + nanophosphor may be useful for applications in solid compact laser devices. Thermoluminescence (TL) studies of γ-irradiated Y2O3:Er3 + showed a prominent TL glow peak maximum at 383 K along with a less intense shoulder peak at 425 K and a weak glow at 598 K. TL emission peaks with maxima at 545, 490, 588 and 622 nm for the doped sample were observed at a temperature of 383 K and these emissions were due to defect related to the host material. TL kinetic parameters were calculated by a glow curve deconvolution (GCD) method and the obtained results are discussed in detail for their possible usage in high dose dosimetry.

  2. Photoluminescence properties of white light emitting La2O3:Dy3+ nanocrystals

    NASA Astrophysics Data System (ADS)

    Reenabati Devi, Konsam; Dorendrajit Singh, Shougaijam; David Singh, Th.

    2018-06-01

    White light emitting nanocrystalline La2O3:Dy3+ phosphors with different concentration (0.5-2 at.%) were synthesized by simple precipitation method. X-ray diffraction (XRD) pattern indicates all the samples crystallizes in the hexagonal phase. Average crystallite sizes of the samples calculated from XRD data were found to be in the range of 20-55 nm. Transmission electron microscopy, selected area electron diffraction, energy dispersive analysis of X-ray and photoluminescence (PL) of the samples are also reported. Strong PL excitation peak due to charge transfer band was observed at 230 nm. Photoluminescence emission peaks observed at 486 and 575 nm were probably attributed to 4F9/2-6H15/2 and 4F9/2-6H13/2 of Dy3+ ions respectively. Optimum luminescence intensity is found at 1 at.% Dy3+ doped La2O3 sample. Further, Commission Internationale de l'é clairage (CIE, 1931) co-ordinates and correlated color temperature (CCT) of the doped sample were calculated to investigate the phosphors' performance and technical applicability of the emitted light respectively. CCT of the 0.5 and 1 at.% samples is 5894 K (white light), within the range of vertical daylight, which makes the synthesised samples promising nanophosphor and may find application in simulating vertical daylight of the Sun.

  3. Photoluminescence properties of white light emitting La2O3:Dy3+ nanocrystals

    NASA Astrophysics Data System (ADS)

    Reenabati Devi, Konsam; Dorendrajit Singh, Shougaijam; David Singh, Th.

    2018-01-01

    White light emitting nanocrystalline La2O3:Dy3+ phosphors with different concentration (0.5-2 at.%) were synthesized by simple precipitation method. X-ray diffraction (XRD) pattern indicates all the samples crystallizes in the hexagonal phase. Average crystallite sizes of the samples calculated from XRD data were found to be in the range of 20-55 nm. Transmission electron microscopy, selected area electron diffraction, energy dispersive analysis of X-ray and photoluminescence (PL) of the samples are also reported. Strong PL excitation peak due to charge transfer band was observed at 230 nm. Photoluminescence emission peaks observed at 486 and 575 nm were probably attributed to 4F9/2-6H15/2 and 4F9/2-6H13/2 of Dy3+ ions respectively. Optimum luminescence intensity is found at 1 at.% Dy3+ doped La2O3 sample. Further, Commission Internationale de l'é clairage (CIE, 1931) co-ordinates and correlated color temperature (CCT) of the doped sample were calculated to investigate the phosphors' performance and technical applicability of the emitted light respectively. CCT of the 0.5 and 1 at.% samples is 5894 K (white light), within the range of vertical daylight, which makes the synthesised samples promising nanophosphor and may find application in simulating vertical daylight of the Sun.

  4. Thermodynamic Database for the NdO(1.5)-YO(1.5)-YbO(1.5)-ScO(1.5)-ZrO2 System

    NASA Technical Reports Server (NTRS)

    Jacobson, Nathan S.; Copland, Evan H.; Kaufman, Larry

    2001-01-01

    A database for YO(1.5)-NdO(1.5)-YbO(1.5)-ScO(1.5)-ZrO2 for ThermoCalc (ThermoCalc AB, Stockholm, Sweden) has been developed. The basis of this work is the YO(1.5)-ZrO2 assessment by Y. Du, Z. Jin, and P. Huang, 'Thermodynamic Assessment of the ZrO2-YO(1.5) System'. Experimentally only the YO(1.5)-ZrO2 system has been well-studied. All other systems are only approximately known. The major simplification in this work is the treatment of each single cation unit as a component. The pure liquid oxides are taken as reference states and two term lattice stability descriptions are used for each of the components. The limited experimental phase diagrams are reproduced.

  5. Multichannel Luminescence Properties of Mixed-Valent Eu2+/Eu3+ Coactivated SrAl3BO7 Nanocrystalline Phosphors for Near-UV LEDs.

    PubMed

    Liu, Xiaoming; Xie, Weijie; Lü, Ying; Feng, Jingchun; Tang, Xinghua; Lin, Jun; Dai, Yuhua; Xie, Yu; Yan, Liushui

    2017-11-20

    Up to now, orchestrating the coexistence of Eu 2+ and Eu 3+ activators in a single host lattice has been an extremely difficult task, especially for the appearance of the characteristic emission of Eu 2+ and Eu 3+ in order to generate white light. Nevertheless, here we demonstrate a new Eu 2+ /Eu 3+ coactivated SrAl 3 BO 7 nanocrystalline phosphor with abundant and excellent multichannel luminescence properties. A series of Eu 2+ /Eu 3+ coactivated SrAl 3 BO 7 nanocrystalline phosphors were prepared through a Pechini-type sol-gel method followed by a reduction process. With excitation of UV/NUV light, the prepared SrAl 3 BO 7 :Eu 2+ ,Eu 3+ phosphors show not only the characteristic f-f transitions of Eu 3+ ion ( 5 D J → 7 F J,J' , J, J' = 0-3), but also the 5d → 4f transitions of Eu 2+ ion with comparable intensity from 400 to 700 nm in the whole visible spectral region. The luminescence color of the SrAl 3 BO 7 :Eu 2+ ,Eu 3+ phosphor can be tuned from blue, blue-green, white, and orange to orange-red by changing the excitation wavelength, the overall doping concentration of europium ions (Eu 2+ , Eu 3+ ), and the relative ratio of Eu 2+ to Eu 3+ ions to some extent. A single-phase white-light emission has been realized in SrAl 3 BO 7 :Eu 2+ ,Eu 3+ phosphor. The obtained SrAl 3 BO 7 :Eu 2+ ,Eu 3+ phosphor has potential application in the area of NUV white-light-emitting diodes.

  6. Degradation of organic dyes using spray deposited nanocrystalline stratified WO3/TiO2 photoelectrodes under sunlight illumination

    NASA Astrophysics Data System (ADS)

    Hunge, Y. M.; Yadav, A. A.; Mahadik, M. A.; Bulakhe, R. N.; Shim, J. J.; Mathe, V. L.; Bhosale, C. H.

    2018-02-01

    The need to utilize TiO2 based metal oxide hetero nanostructures for the degradation of environmental pollutants like Rhodamine B and reactive red 152 from the wastewater using stratified WO3/TiO2 catalyst under sunlight illumination. WO3, TiO2 and stratified WO3/TiO2 catalysts were prepared by a spray pyrolysis method. It was found that the stratified WO3/TiO2 heterostructure has high crystallinity, no mixed phase formation occurs, strong optical absorption in the visible region of the solar spectrum, and large surface area. The photocatalytic activity was tested for degradation of Rhodamine B (Rh B) and reactive red 152 in an aqueous medium. TiO2 layer in stratified WO3/TiO2 catalyst helps to extend its absorption spectrum in the solar light region. Rh B and Reactive red 152is eliminated up to 98 and 94% within the 30 and 40 min respectively at optimum experimental condition by stratified WO3/TiO2. Moreover, stratified WO3/TiO2 photoelectrode has good stability and reusability than individual TiO2 and WO3 thin film in the degradation of Rh B and reactive red 152. The photoelectrocatalytic experimental results indicate that stratified WO3/TiO2 photoelectrode is a promising material for dye removal.

  7. Negative surface streamers propagating on TiO2 and γ-Al2O3-supported Ag catalysts: ICCD imaging and modeling study

    NASA Astrophysics Data System (ADS)

    Kim, Hyun-Ha; Teramoto, Yoshiyuki; Ogata, Atsushi; Kang, Woo Seok; Hur, Min; Song, Young-Hoon

    2018-06-01

    Surface streamers propagating on the surface of titanium dioxide (TiO2) and alumina (γ-Al2O3) were studied in negative polarity using intensified charge coupled device (ICCD) imaging and numerical simulation. Detailed time-resolved ICCD images of cathode-directed streamers (CDSs) emanating from a ground electrode are first presented in this report. Instead of primary streamers in positive polarity, only a glow-like discharge appeared in the early stage at the cathode under negative polarity. After this discharge disappeared, a counter-propagating CDS initiated from the ground electrode (anode). Numerical simulation indicated that strong electric fields at the pellet-anode and the formation of positive ion rich local spots were the main reason for the CDS formation near the ground electrode. The maximum velocity was 750 km s‑1 for Ag-supported γ-Al2O3 and 550 km s‑1 for Ag-supported TiO2, respectively. In contrast to the CDS in the gas-phase with a positive polarity, the CDS in a catalyst packed-bed under negative polarity showed more branching and a larger number of streamers in the presence of oxygen than in pure N2.

  8. Effect of Various Catalysts on the Stability of Characteristics of Acetone Sensors Based on Thin Nanocrystalline SnO2 Films

    NASA Astrophysics Data System (ADS)

    Sevastyanov, E. Yu.; Maksimova, N. K.; Potekaev, A. I.; Khludkova, L. S.; Chernikov, E. V.; Davydova, T. A.

    2018-02-01

    The results of studies of electrical and gas sensitive characteristics of acetone sensors based on thin nanocrystalline SnO2 films with various catalysts deposited on the surface (Pt/Pd, Au) and introduced into the volume (Au, Ni, Co) are presented. Films containing impurities of gold and 3d-metals were obtained by the method of magnetron sputtering of mosaic targets. Particular attention was paid to the influence of the longterm tests and humidity level on the properties of sensors. It is shown that the sensors with the deposited dispersed gold layers with Au+Ni and, especially, Au+Co additives introduced into the volume are characterized by the increased stability in the process of testing under prolonged exposure to acetone and also under conditions of varying humidity.

  9. Importance of uniaxial compression for the appearance of superconductivity in NdO1-xFxBiS2

    NASA Astrophysics Data System (ADS)

    A, Omachi; T, Hiroi; J, Kajitani; O, Miura; Y, Mizuguchi

    2014-05-01

    We have investigated the crystal structure and superconducting properties of the new layered superconductor NdO1-xFxBiS2. Bulk superconductivity with a Tc above 4.5 K was observed. It was found that the Tc depended on both F concentration and crystal structure. Uniaxial compression along the c axis upon F substitution seemed to be linked with the appearance of bulk superconductivity. Furthermore, we considered that a higher Tc can be achieved when the c/a parameter was optimized in the NdO1-xFxBiS2 system.

  10. Multifunctionality of nanocrystalline lanthanum ferrite

    NASA Astrophysics Data System (ADS)

    Rai, Atma; Thakur, Awalendra K.

    2016-05-01

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

  11. Multifunctionality of nanocrystalline lanthanum ferrite

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

    Rai, Atma, E-mail: atma@iitp.ac.in; Thakur, Awalendra K.; Centre for Energy and Environment, Indian Institute of Technology Patna 800013 India

    2016-05-06

    Nanocrystalline lanthanum ferrite has been synthesized by adopting modified Pechini route. No evidence of impurity or secondary phase has been detected up to the detection of error limit of X-ray diffractometer (XRD). Rietveld refinement of X-ray diffraction pattern reveals orthorhombic crystal system with space group Pnma (62).Crystallite size and lattice strain was found to be ∼42.8nm and 0.306% respectively. Optical band gap was found to be 2.109 eV, by UV-Visible diffused reflectance spectrum (DRS). Brunauer-Emmet-Teller (BET) surface area was found to be ∼3.45 m{sup 2}/g. Magnetization-hysteresis (M-H) loop was recorded at room temperature (300K) reveals weak ferromagnetism in Nanocrystalline lanthanummore » ferrite. The weak ferromagnetism in lanthanum ferrite is due to the uncompensated antiferromagnetic spin ordering. Ferroelectric loop hysteresis observed at room temperature at 100Hz depicts the presence of ferroelectric ordering in LaFeO{sub 3}.Simultanious presence of magnetic and ferroelectric ordering at room temperature makes it suitable candidate of Multiferroic family.« less

  12. Optical and scintillation properties of Nd-doped complex garnet

    NASA Astrophysics Data System (ADS)

    Yanagida, Takayuki; Sato, Hiroki

    2014-12-01

    Nd 1% doped complex garnet scintillators were prepared by Furukawa and their optical and scintillation properties were investigated on a comparison with previously reported Nd-doped YAG. Chemical compositions of newly developed complex garnets were Lu2Y1Al5O12, Lu2Y1Ga3Al2O12, Lu2Gd1Al5O12, Lu2Gd1Ga3Al2O12, Gd1Y2Al5O12, Gd1Y2Ga3Al2O12, and Gd3Ga3Al2O12. They all showed 50-80% transmittance from ultraviolet to near infrared wavelengths with several absorption bands due to Gd3+ or Nd3+ 4f-4f transition. In X-ray induced radioluminescence spectra, all samples exhibited intense lines at 310 nm due to Gd3+ or 400 nm due to Nd3+ depending on their chemical composition. Among them, the highest scintillation light yield was achieved by Lu2Y1Al5O12. Typical scintillation decay times of them resulted 1.5-3 μs. Thermally stimulated glow curve after 1 Gy exposure and X-ray induced afterglow were also investigated.

  13. Optical spectroscopy, 1.06μm emission properties of Nd3+-doped phosphate based glasses.

    PubMed

    Sk Nayab, Rasool; T, Sasikala; A, Mohan Babu; L, Rama Moorthy; C K, Jayasankar

    2017-06-05

    Neodymium doped phosphate based glasses with composition of (P 2 O 5 +K 2 O+Al 2 O 3 +CaF 2 ) were prepared. The samples were analysed through differential thermal analysis (DTA), Fourier transform infrared (FTIR), absorption, emission and decay measurements. Judd-Ofelt parameters (Ω λ ) have been determined from the spectral intensities of absorption bands in order to calculate the radiative parameters like radiative transition probabilities (A R ), radiative lifetime (τ R ) and branching ratios (β R ) for the 4 F 3/2 → 4 I 11/2 laser transition of Nd 3+ ion. The effective emission bandwidths (Δλ eff ), experimental branching ratios (β exp ) and stimulated emission cross-sections (σ e ) have been determined from the emission spectrum. The decay curves of the 4 F 3/2 level exhibited almost single exponential nature for all the Nd 3+ ion concentrations. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. Growth and optical properties of Co,Nd:LaMgAl11O19

    NASA Astrophysics Data System (ADS)

    Xu, Peng; Xia, Changtai; Di, Juqing; Xu, Xiaodong; Sai, Qinglin; Wang, Lulu

    2012-12-01

    Nd,Co:LaMgAl11O19 (abbreviated as Co,Nd:LMA) was grown using the Czochralski method. The structure, polarized absorption spectrum, fluorescence spectrum, and fluorescence decay time were analyzed. The as-grown crystal had very wide absorption bands at 794 nm, which can be pumped by GaAs laser diode without temperature stabilization. Two strong emission bands were present at 1056 nm and 1082 nm with full-width at half-maximum (FWHM) of 6 and 8 nm, respectively. The large FWHM is due to the inhomogeneity of the Nd ion sites. The lifetimes of the 4F3/2 manifold of Co,Nd:LMA at room temperature monitored at 905 nm, 1056 nm, and 1344 nm were 292, 288, and 350 μs, respectively, which was caused by the different contribution of the three different sites with D3h and C2v symmetry. The absorption band of Co is from 1.3 μm to 1.6 μm, and Co,Nd:LMA still has a strong emission around the 1.38 μm, indicating that the Co,Nd:LMA can be applied as a potential self-Q-switched material operating at 1.3 μm.

  15. Phase Evaluation in Al2O3 Fiber-Reinforced Ti2AlC During Sintering in the 1300 degrees C-1500 degrees C Temperature Range

    DTIC Science & Technology

    2011-01-01

    composition: 97% Al2O3 and 3% SiO2] fibers. In both cases, the fibers were chopped with a razor blade into 5 cm lengths. Mixing of the powder and...the presence of XRD amorphous Ti- aluminides (see below) or other phases cannot be ruled out at this juncture. When the XRD spectrum of the as-received...not shown). No peaks belonging to any Ti- aluminide were found suggesting them to be amorphous or at most nano-crystalline. A typical TEM micrograph of

  16. MnTiO3-driven low-temperature oxidative coupling of methane over TiO2-doped Mn2O3-Na2WO4/SiO2 catalyst

    PubMed Central

    Wang, Pengwei; Zhao, Guofeng; Wang, Yu; Lu, Yong

    2017-01-01

    Oxidative coupling of methane (OCM) is a promising method for the direct conversion of methane to ethene and ethane (C2 products). Among the catalysts reported previously, Mn2O3-Na2WO4/SiO2 showed the highest conversion and selectivity, but only at 800° to 900°C, which represents a substantial challenge for commercialization. We report a TiO2-doped Mn2O3-Na2WO4/SiO2 catalyst by using Ti-MWW zeolite as TiO2 dopant as well as SiO2 support, enabling OCM with 26% conversion and 76% C2-C3 selectivity at 720°C because of MnTiO3 formation. MnTiO3 triggers the low-temperature Mn2+↔Mn3+ cycle for O2 activation while working synergistically with Na2WO4 to selectively convert methane to C2-C3. We also prepared a practical Mn2O3-TiO2-Na2WO4/SiO2 catalyst in a ball mill. This catalyst can be transformed in situ into MnTiO3-Na2WO4/SiO2, yielding 22% conversion and 62% selectivity at 650°C. Our results will stimulate attempts to understand more fully the chemistry of MnTiO3-governed low-temperature activity, which might lead to commercial exploitation of a low-temperature OCM process. PMID:28630917

  17. Preparation of nanocrystalline TiN coated cubic boron nitride powders by a sol-gel process.

    PubMed

    Park, Hee S; Umer, M Adeel; Ryu, Ho J; Hong, Soon H

    2011-01-01

    Cubic boron nitride (cBN) particles coated with 20 wt% nanocrystalline TiN were prepared by coating the surface of cBN particles with TiO2, followed by nitridation with NH3 gas at 900 degrees C. Coating of TiO2 on cBN powders was accomplished by a sol-gel process from a solution of titanium (IV) isopropoxide and anhydrous ethanol. An amorphous TiO(x) layer of 50 nm thickness was homogenously formed on the surface of the cBN particles by the sol-gel process. The amorphous layer was then crystallized to an anatase TiO2 phase through calcination in air at 400 degrees C. The crystallized TiO2 layer was 50 nm in thickness, and the size of TiO2 particles comprising the layer was nearly 10 nm. The TiO2 on cBN surfaces was completely converted into nanocrystalline TiN of uniform particles 20 nm in size on cBN particles by nitridation under flowing NH3 gas.

  18. Synthesis and characterization of nanocrystalline Nd{sup 3+}-doped gadolinium scandium aluminum garnet powders by a gel-combustion method

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

    Su, Jing, E-mail: zlj007@126.com; Miao, Ju-hong; Xu, Lin-hua

    2012-07-15

    Graphical abstract: The graph shows the emission spectra (λ{sub ex} = 808 nm) of 1 at.% Nd:GSAG powders sintered at different temperatures for 3 h. Compared with the powder sintered at 900 °C, the PL intensity of the powder sintered at 1000 °C decreased significantly. The changes in the PL intensity should mainly due to the crystallinity and dispersion of the powders. Highlights: ► We synthesized Nd:GSAG nano-powders by gel-combustion method successfully. ► We analyzed the structure and the morphology of the heat-treated products. ► We studied the optical characteristics of Nd:GSAG nano-powders. -- Abstract: Nd{sup 3+}-doped gadolinium scandium aluminummore » garnet (Nd:GSAG) precursor was synthesized by a gel combustion method using metal nitrates and citric acid as raw materials. The structure and morphology of the precursor and the sintered powders were studied by means of X-ray diffraction (XRD), infrared spectroscopy (IR) and transmission electron microscopy (TEM). The results showed that the precursor transformed into pure GSAG polycrystalline phase at about 800 °C, and the powders sintered at 800–1000 °C were well-dispersed with average particle sizes in the range of 30–80 nm. Optical properties of Nd:GSAG nano-powders were characterized by using photoluminescence spectroscopy. The highest photoluminescence intensity was achieved for the powder sintered at 900 °C.« less

  19. Initial stage corrosion of nanocrystalline copper particles and thin films

    NASA Astrophysics Data System (ADS)

    Tao, Weimin

    1997-12-01

    density associated with mass transport of ions in the oxide layer. A hypothesis is developed that the high corrosion rate of the nanocrystalline copper is closely associated with the structure of the copper oxide layer. Therefore, a high "apparent" exchange current density for the nanocrystalline copper is associated with the high angle grain boundary structure in the initial oxide layer. Additional structure analysis was also carried out: (a) High resolution TEM imaging has provided a cross sectional view of the epitaxial interface between nanocrystalline copper and copper (I) oxide and explicitly discloses the presence of interface defects such as misfit dislocations. Based on this observation, a mechanism was proposed to explain the Cu/Cusb2O interface misfit accommodation. This appears to be the first time this interface has been directly examined. (b) A nanocrystalline analogue to a cross-section of Gwathmey's copper single crystal sphere was revealed by high resolution TEM imaging. A partially oxidized nanocrystalline copper particle is used to examine the variation of the Cu/Cusb2O orientation relationship with respect to changes in surface orientation. A new orientation relationship, Cu (011) //Cusb2O (11), ˜ Cu(011)//Cusb2O(111), was found for the oxidation of nanocrystalline copper.

  20. Structural and magnetic properties of nanocrystalline NiFe2O4 thin film prepared by spray pyrolysis technique

    NASA Astrophysics Data System (ADS)

    Chavan, Apparao R.; Chilwar, R. R.; Shisode, M. V.; Hivrekar, Mahesh M.; Mande, V. K.; Jadhav, K. M.

    2018-05-01

    The nanocrystalline NiFe2O4 thin film has been prepared using a spray pyrolysis technique on glass substrate. The prepared thin film was characterized by using X-ray diffraction (XRD), Fourier transform Infrared spectroscopy (FTIR), and Field Emission-Scanning Electron Microscopy (FE-SEM) characterization techniques for the structural and microstructural analysis. The magnetic property was measured using vibrating sample magnetometer (VSM) at room temperature. X-ray diffraction studies show the formation of single phase spinel structure of the thin film. The octahedral and tetrahedral vibration in the sample was studied by Fourier transform infrared (FT-IR) spectra. Magnetic hysteresis loop was recorded for thin film at room temperature. At 15 kOe, saturation magnetization (Ms) was found to increase while coercivity (Hc) decreases with thickness of the NiFe2O4 thin film.

  1. [Preparation and photoluminescence study of Er3+ : Y2O3 transparent ceramics].

    PubMed

    Luo, Jun-ming; Li, Yong-xiu; Deng, Li-ping

    2008-10-01

    Y2O3 acted as the matrix material, which was doped with different concentrations of Er3+, Er3+ : Y2O3 nanocrystalline powder was prepared by co-precipitation method, and Er3+ : Y2O3 transparent ceramics was fabricated by vacuum sintering at 1700 degrees C, 1 x 10(-3) Pa for 8 h. By using the X-ray diffraction (D/MAX-RB), transmission electron microscopy(Philips EM420), automatic logging spectrophotometer(DMR-22), fluorescence analyzer (F-4500) and 980 nm diode laser, the structural, morphological and luminescence properties of the sample were investigated. The results show that Er3+ dissolved completely in the Y2O3 cubic phase, the precursor was amorphous, weak diffraction peaks appeared after calcination at 400 degrees C, and if calcined at 700 degrees C, the precursor turned to pure cubic phase. With increasing the calcining temperature, the diffraction peaks became sharp quickly, and when the calcining temperature reached 1100 degrees C, the diffraction peaks became very sharp, indicating that the grains were very large. The particles of Er+ : Y2O3 is homogeneous and nearly spherical, the average diameter of the particles is in the range of 40-60 nm after being calcined at 1000 degrees C for 2 h. The relative density of Er3+ : Y2O3 transparent ceramics is 99.8%, the transmittance of the Er2+ : Y2O3 transparent ceramics is markedly lower than the single crystal at the short wavelength, but the transmittance is improved noticeably with increasing the wavelength, and the transmittance exceeds 60% at the wavelength of 1200 nm. Excited under the 980 nm diode laser, there are two main up-conversion emission bands, green emission centers at 562 nm and red emission centers at 660 nm, which correspond to (4)S(3/2) / (2)H(11/2) - (4)I(15/2) and (4)F(9/2) - (4)I(15/2) radiative transitions respectively. By changing the doping concentrations of Er3+, the color of up-conversion luminescence can be tuned from green to red gradually. The luminescence intensity is not reinforce

  2. Structural and magnetic properties of Ni0.8M0.2Fe2O4 (M = Cu, Co) nano-crystalline ferrites

    NASA Astrophysics Data System (ADS)

    Vijaya Babu, K.; Satyanarayana, G.; Sailaja, B.; Santosh Kumar, G. V.; Jalaiah, K.; Ravi, M.

    2018-06-01

    Nano-crystalline nickel ferrites are interesting materials due to their large physical and magnetic properties. In the present work, two kinds of spinel ferrites Ni0.8M0.2Fe2O4 (M = Cu, Co) are synthesized by using sol-gel auto-combustion method and the results are compared with NiFe2O4. The structural properties of synthesized ferrites are determined by using X-ray powder diffraction; scanning electron microscope and Fourier transform infrared spectroscopy. The cation distribution obtained from X-ray diffraction show that cobalt/copper occupies only tetrahedral site in spinel lattice. The lattice constant increases with the substitution of cobalt/copper. The structural parameters like bond lengths, tetrahedral and octahedral edges have been varied with the substitution. The microstructural study is carried out by using SEM technique and the average grain size is increased with nickel ferrite. The initial permeability (μi) is improving with the substitution. The observed g-value from ESR is approximately equal to standard value.

  3. Synthesis and characterisation of the n = 2 Ruddlesden–Popper phases Ln{sub 2}Sr(Ba)Fe{sub 2}O{sub 7} (Ln = La, Nd, Eu)

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

    Gurusinghe, Nicola N.M.; Figuera, Juand de la; Marco, José F.

    2013-09-01

    Graphical abstract: - Highlights: • Some Ruddlesden–Popper phases have been characterised. • Substitution on the A site influences cationic order. • The magnetic moment redirects with temperature - Abstract: A series of n = 2 Ruddlesden–Popper phases A{sub 2}B{sub 2}O{sub 7} of composition Ln{sub 2}Sr(Ba)Fe{sub 2}O{sub 7} (Ln = La, Nd, Eu) have been prepared. La{sub 2}SrFe{sub 2}O{sub 7} and La{sub 2}BaFe{sub 2}O{sub 7} crystallise in the tetragonal space group I4/mmm. The structures of Eu{sub 2}SrFe{sub 2}O{sub 7} and Nd{sub 2}SrFe{sub 2}O{sub 7} are best described in space group P4{sub 2}/mnm. Substitution on the A site with smaller lanthanide- andmore » larger alkaline metal- ions leads to enhanced cationic order in these phases and reflects increasing differences in cationic radii. All the compounds are antiferromagnetically ordered between 298 and 2 K. In La{sub 2}SrFe{sub 2}O{sub 7} the magnetic moment lies along [1 1 0] at all temperatures between 298 and 2 K whereas in La{sub 2}BaFe{sub 2}O{sub 7} the magnetic moment at 298 K lies along the crystallographic x-axis but redirects from the [1 0 0] to the [1 1 0] direction between 210 and 190 K and is retained in this direction until 2 K. In Nd{sub 2}SrFe{sub 2}O{sub 7} the magnetic moment at 298 K lies along [1 1 0] but rotates from [1 1 0] to [0 0 1] between 17 and 9 K. A series of {sup 57}Fe Mössbauer spectra recorded from La{sub 2}SrFe{sub 2}O{sub 7} between 290 and 600 K indicate a magnetic ordering temperature of T{sub N} ≥ 535 K.« less

  4. Catalytic ethanolysis and gasification of kraft lignin into aromatic alcohols and H2-rich gas over Rh supported on La2O3/CeO2-ZrO2.

    PubMed

    Yang, Jing; Zhao, Liang; Liu, Chunze; Wang, Yuanyuan; Dai, Liyi

    2016-10-01

    Efficient catalytic ethanolysis and gasification of kraft lignin were conducted over a versatile supported catalyst Rh/La2O3/CeO2-ZrO2 to give high-value aromatic alcohols and H2-rich gas. The removal of phenolic hydroxyl group was the most prevalent reaction, and importantly, almost no phenols, undesired char and saturating the aromatic ring were detected. Meanwhile, the feedstock and solvent both played key roles in H2 generation that contributed to the hydrodeoxygenation of liquid components and made the whole catalytic process out of H2 supply. Reusability tests of catalyst indicated that the crystalline phase transition and agglomeration of support, the loss of noble metal Rh and carbon deposition were the possible reasons for its deactivation in supercritical ethanol. Comparing with water, methanol and isopropanol system, ethanol was the only effective solvent for the depolymerization process. Copyright © 2016 Elsevier Ltd. All rights reserved.

  5. Cube-like α-Fe2O3 supported on ordered multimodal porous carbon as high performance electrode material for supercapacitors.

    PubMed

    Chaudhari, Nitin K; Chaudhari, Sudeshna; Yu, Jong-Sung

    2014-11-01

    Well-dispersed cube-like iron oxide (α-Fe2O3) nanoparticles (NPs) supported on ordered multimodal porous carbon (OMPC) are synthesized for the first time by a facile and efficient glycine-assisted hydrothermal route. The effect of OPMC support on growth and formation mechanism of the Fe2O3 NPs is discussed. OMPC as a supporting material plays a pivotal role of controlling the shape, size, and dispersion of the Fe2O3 NPs. As-synthesized α-Fe2O3/OMPC composites reveal significant improvement in the performance as electrode material for supercapacitors. Compared to the bare Fe2O3 and OMPC, the composite exhibits excellent cycling stability, rate capability, and enhanced specific capacitances of 294 F g(-1) at 1.5 A g(-1), which is twice that of OMPC (145 F g(-1)) and about four times higher than that of bare Fe2O3 (85 F g(-1)). The improved electrochemical performance of the composite can be attributed to the well-defined structure, high conductivity, and hierarchical porosity of OMPC as well as the unique α-Fe2O3 NPs with cube-like morphology well-anchored on the OMPC support, which makes the composite a promising candidate for supercapacitors. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Long-range stripe nanodomains in epitaxial (110) BiFeO 3 thin films on (100) NdGaO 3 substrate

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

    Sharma, Yogesh; Agarwal, Radhe; Phatak, Charudatta

    Here, we report the observation of ferroelectric and ferroelastic nanodomains in (110)-oriented BiFeO 3 (BFO) thin films epitaxially grown on low symmetric (100) NdGaO 3 (NGO) substrate. We observed long range ordering of ferroelectric 109° stripe nanodomains separated by periodic vertical domain walls in as-grown 130 nm thick BFO films. The effect of La 0.67Sr 0.33CoO 3 (LSCO) conducting interlayer on domain configurations in BFO/NGO film was also observed with relatively short range-ordering of stripe domains due to the modified electrostatic boundary conditions in BFO/LSCO/NGO film. Additional studies on B-site doping of Nb ions in BFO films showed change inmore » the domain structures due to doping induced change in lattice anisotropy while maintaining the stripe domain morphology with 109° domain wall. Finally, this long-range array of ferroelectric and ferroelastic domains can be useful for optoelectronic devices and ferroelastic templates for strain coupled artificial magnetoelectric heterostructures.« less

  7. Long-range stripe nanodomains in epitaxial (110) BiFeO 3 thin films on (100) NdGaO 3 substrate

    DOE PAGES

    Sharma, Yogesh; Agarwal, Radhe; Phatak, Charudatta; ...

    2017-07-07

    Here, we report the observation of ferroelectric and ferroelastic nanodomains in (110)-oriented BiFeO 3 (BFO) thin films epitaxially grown on low symmetric (100) NdGaO 3 (NGO) substrate. We observed long range ordering of ferroelectric 109° stripe nanodomains separated by periodic vertical domain walls in as-grown 130 nm thick BFO films. The effect of La 0.67Sr 0.33CoO 3 (LSCO) conducting interlayer on domain configurations in BFO/NGO film was also observed with relatively short range-ordering of stripe domains due to the modified electrostatic boundary conditions in BFO/LSCO/NGO film. Additional studies on B-site doping of Nb ions in BFO films showed change inmore » the domain structures due to doping induced change in lattice anisotropy while maintaining the stripe domain morphology with 109° domain wall. Finally, this long-range array of ferroelectric and ferroelastic domains can be useful for optoelectronic devices and ferroelastic templates for strain coupled artificial magnetoelectric heterostructures.« less

  8. Hydrodeoxygenation of p -Cresol over Pt/Al 2 O 3 Catalyst Promoted by ZrO 2 , CeO 2 , and CeO 2 –ZrO 2

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

    Wang, Weiyan; Wu, Kui; Liu, Pengli

    2016-07-20

    ZrO 2-Al 2O 3 and CeO 2-Al 2O 3 were prepared by a co-precipitation method and selected as supports for Pt catalysts. The effects of CeO 2 and ZrO 2 on the surface area and Brønsted acidity of Pt/Al 2O 3 were studied. In the hydrodeoxygenation (HDO) of p-cresol, the addition of ZrO 2 promoted the direct deoxygenation activity on Pt/ZrOO 2-Al 2O 3 via Caromatic-O bond scission without benzene ring saturation. Pt/CeOO 2-Al 2O 3 exhibited higher deoxygenation extent than Pt/Al 2O 3 due to the fact that Brønsted acid sites on the catalyst surface favored the adsorption ofmore » p-cresol. With the advantages of CeO 2 and ZrO 2 taken into consideration, CeO 2-ZrOO 2-Al 2O 3 was prepared, leading to the highest HDO activity of Pt/CeO 2-ZrOO 2-Al 2O 3. The deoxygenation extent for Pt/CeO 2-ZrOO 2-Al 2O 3 was 48.4% and 14.5% higher than that for Pt/ZrO2O 2-Al 2O 3 and Pt/CeOO 2-Al 2O 3, respectively.« less

  9. Swift-heavy ion irradiation response and annealing behavior of A 2TiO 5 (A = Nd, Gd, and Yb)

    DOE PAGES

    Park, Sulgiye; Tracy, Cameron L.; Zhang, Fuxiang; ...

    2017-09-28

    The structural responses of A 2BO 5 (A = Nd, Gd, and Yb; B = Ti) compositions irradiated by high-energy Au ions (2.2 GeV) were investigated using transmission electron microscopy, synchrotron X-ray diffraction and Raman spectroscopy. The extent of irradiation-induced amorphization depends on the size of the A-site cation, with smaller lanthanides having less susceptibility to the accumulation of radiation damage. In the track-overlapping regime, complete amorphization is observed in all three compounds, despite the ability of Yb 2TiO 5 to incorporate a great deal of structural disorder into its initial defect-fluorite structure (Fm-3m). This is attributed to the highmore » cation radius ratio (A:B = 2:1), which reduces the stability of the structure upon ion irradiation. The fully-amorphized samples were subsequently isochronally heated at temperature intervals from 100 °C to 850 °C. X-ray diffraction analysis indicated a similar damage recovery process in Nd 2TiO 5 and Gd 2TiO 5, where both compositions recover their original structures (Pnma) at 850 °C. In contrast, Yb2TiO5 exhibited recrystallization of a metastable, non-equilibrium orthorhombic phase at ~ 550 °C, prior to a transformation to the stable defect-fluorite phase (Fm-3m) at 625 °C. In conclusion, these compositional variations in radiation tolerance and thermal recovery processes are described in terms of the energetics of disordering during the damage and recrystallization processes.« less

  10. Swift-heavy ion irradiation response and annealing behavior of A 2TiO 5 (A = Nd, Gd, and Yb)

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

    Park, Sulgiye; Tracy, Cameron L.; Zhang, Fuxiang

    The structural responses of A 2BO 5 (A = Nd, Gd, and Yb; B = Ti) compositions irradiated by high-energy Au ions (2.2 GeV) were investigated using transmission electron microscopy, synchrotron X-ray diffraction and Raman spectroscopy. The extent of irradiation-induced amorphization depends on the size of the A-site cation, with smaller lanthanides having less susceptibility to the accumulation of radiation damage. In the track-overlapping regime, complete amorphization is observed in all three compounds, despite the ability of Yb 2TiO 5 to incorporate a great deal of structural disorder into its initial defect-fluorite structure (Fm-3m). This is attributed to the highmore » cation radius ratio (A:B = 2:1), which reduces the stability of the structure upon ion irradiation. The fully-amorphized samples were subsequently isochronally heated at temperature intervals from 100 °C to 850 °C. X-ray diffraction analysis indicated a similar damage recovery process in Nd 2TiO 5 and Gd 2TiO 5, where both compositions recover their original structures (Pnma) at 850 °C. In contrast, Yb2TiO5 exhibited recrystallization of a metastable, non-equilibrium orthorhombic phase at ~ 550 °C, prior to a transformation to the stable defect-fluorite phase (Fm-3m) at 625 °C. In conclusion, these compositional variations in radiation tolerance and thermal recovery processes are described in terms of the energetics of disordering during the damage and recrystallization processes.« less

  11. Investigation of electronic and local structural changes during lithium uptake and release of nano-crystalline NiFe2O4 by X-ray absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhou, Dong; Permien, Stefan; Rana, Jatinkumar; Krengel, Markus; Sun, Fu; Schumacher, Gerhard; Bensch, Wolfgang; Banhart, John

    2017-02-01

    Nano-crystalline NiFe2O4 particles were synthesized and used as active electrode material for a lithium ion battery that showed a high discharge capacity of 1534 mAh g-1 and charge capacity of 1170 mAh g-1 during the 1st cycle. X-ray absorption spectroscopy including XANES and EXAFS were used to investigate electronic and local structural changes of NiFe2O4 during the 1st lithiation and de-lithiation process. As lithium is inserted into the structure, tetrahedral site Fe3+ ions are reduced to Fe2+ and moved from tetrahedral sites to empty octahedral sites, while Ni2+ ions are unaffected. As a consequence, the matrix spinel structure collapses and transforms to an intermediate rock-salt monoxide phase. Meanwhile, the inserted Li is partially consumed by the formation of SEI and other side reactions during the conversion reaction. With further lithiation, the monoxide phase is reduced to highly disordered metallic Fe/Ni nanoparticles with a number of nearest neighbors of 6.0(8) and 8.1(4) for Fe and Ni, respectively. During subsequent de-lithiation, the metal particles are individually re-oxidized to Fe2O3 and NiO phases instead to the original NiFe2O4 spinel phase.

  12. A new ~1 μm laser crystal Nd:Gd2SrAl2O7: growth, thermal, spectral and lasing properties

    NASA Astrophysics Data System (ADS)

    Yuan, Feifei; Liao, Wenbin; Huang, Yisheng; Zhang, Lizhen; Sun, Shijia; Wang, Yeqing; Lin, Zhoubin; Wang, Guofu; Zhang, Ge

    2018-03-01

    Nd:Gd2SrAl2O7 crystals were grown by the Czochralski technique; thermal, spectral and laser properties were investigated in detail. The average thermal expansion coefficients along a- and c-axis are 12.6  ×  10-6 K-1 and 14.9  ×  10-6 K-1, respectively. At room temperature, the thermal conductivities are 4.98 and 5.24 W (m-1 * K-1) along the a- and c-axis, respectively. The absorption cross sections at ~808 nm are 13.7  ×  10-20 cm2 with a FWHM of 3.3 nm for π-polarization and 11.84  ×  10-20 cm2 with a FWHM of 3.4 nm for σ-polarization. The emission cross sections at ~1080 nm are 15  ×  10-20 cm2 and 12.7  ×  10-20 cm2 with a FWHM of about 5.1 nm and 12.5 nm for π- and σ-polarization, respectively. The fluorescence lifetime for the 4F3/2  →  4I11/2 transition was fitted to be 118 µs. Pumped by a fiber-coupled 808 nm laser diode, the maximum 1.55 W continuous-wave laser output at ~1.08 µm was achieved with a slope efficiency of 30.5%. All the results show that Nd:Gd2SrAl2O7 crystal is a promising laser material.

  13. Microscopic evidence for magnetic ordering in NdCu3Ru4O12 : 63,65Cu nuclear quadrupole resonance study

    NASA Astrophysics Data System (ADS)

    Yogi, M.; Niki, H.; Hedo, M.; Komesu, S.; Nakama, T.

    2018-05-01

    We have conducted 63,65Cu nuclear quadrupole resonance (NQR) measurements on A-site ordered perovskite compounds LaCu3Ru4O12 and NdCu3Ru4O12 to investigate their ground state and spin fluctuations. While there is only one Cu site in the crystal structure, multiple NQR resonance lines were observed. This is presumed to be due to the presence of slight distortion and lattice defects in the samples. The nuclear spin-lattice relaxation rate divided by temperature, 1 /T1 T , for LaCu3Ru4O12 showed almost constant value indicating the Fermi-liquid state. A remarkable increase in 1 /T1 T due to spin fluctuations was observed in NdCu3Ru4O12 . Furthermore, an evident magnetic phase transition at TM = 0.6 K was revealed from the distinct peak of 1 /T1 T and the broadening of the NQR spectrum.

  14. Synthesis of GO supported Fe2O3-TiO2 nanocomposites for enhanced visible-light photocatalytic applications.

    PubMed

    Jo, Wan-Kuen; Selvam, N Clament Sagaya

    2015-09-28

    This article reports novel ternary composites consisting of Fe2O3 nanorods, TiO2 nanoparticles, and graphene oxide (GO) flakes that provide enhanced photocatalytic performance and stability. Fe2O3 nanorods grow evenly and embed themselves on the agglomerated TiO2/GO surface, which facilitate the formation of heterojunctions for effective migration of charge carriers at the interface of Fe2O3/TiO2 in the ternary composites. The formation of heterostructured Fe2O3-TiO2/GO composites and the effect of GO addition on the photophysical properties of the composites were systematically investigated using various spectroscopic techniques. The photocatalytic performance of Fe2O3 was improved by coupling with TiO2 in the presence of GO, suggesting uncommon electron transfer from the conduction band of Fe2O3 to that of TiO2via GO under visible-light irradiation. An improved charge separation in the composite materials compared with that in bare Fe2O3 was confirmed by drastic fluorescence quenching and stronger absorption in the visible range. The optimum content of GO in the ternary composite was 1.0 wt%, which exhibited enhanced photocatalytic activity. The synergistic effect, heterostructured composite and role of GO, as an electron transporter, in the ternary composites account for the enhanced photocatalytic activity.

  15. Laser stimulated third harmonic generation studies in ZnO-Ta2O5-B2O3 glass ceramics entrenched with Zn3Ta2O8 crystal phases

    NASA Astrophysics Data System (ADS)

    Siva Sesha Reddy, A.; Jedryka, J.; Ozga, K.; Ravi Kumar, V.; Purnachand, N.; Kityk, I. V.; Veeraiah, N.

    2018-02-01

    In this study zinc borate glasses doped with different concentrations Ta2O5 were synthesized and were crystallized by heat treatment for prolonged times. The samples were characterized by XRD, SEM, IR and Raman spectroscopy techniques. The SEM images of the crystallized samples have indicated that the samples contain randomly distributed crystal grains with size ∼1 μm entrenched in the residual amorphous phase. XRD studies have exhibited diffraction peaks identified as being due to the reflections from (1 1 1) planes of monoclinic Zn3Ta2O8 crystal phase that contains intertwined tetrahedral zinc and octahedral tantalate structural units. The concentration of such crystal phases in the bulk samples is observed to increase with increase of Ta2O5 up to 3.0 mol%. The IR and Raman spectroscopy studies have confirmed the presence of ZnO4 and TaO6 structural units in the glass network in addition to the conventional borate structural units. For measuring third harmonic generation (THG) in the samples, the samples were irradiated with 532 nm laser beam and the intensity of THG of probing beam (Nd:YAG λ = 1064 nm 20 ns pulsed laser (ω)) is measured as a function of fundamental beam power varying up to 200 J/m2. The intensity of THG is found to be increasing with increase of fundamental beam power and found to be the maximal for the glass crystallized with 3.0 mol% of Ta2O5. The intensity of THG of the ceramicized samples is found to be nearly 5 times higher with respect to that of pre-crystallized samples. The generation of 3ω is attributed to the perturbation/interaction between Zn3Ta2O8 anisotropic crystal grains and the incident probing beam.

  16. Osteogenic cell differentiation on H-terminated and O-terminated nanocrystalline diamond films

    PubMed Central

    Liskova, Jana; Babchenko, Oleg; Varga, Marian; Kromka, Alexander; Hadraba, Daniel; Svindrych, Zdenek; Burdikova, Zuzana; Bacakova, Lucie

    2015-01-01

    Nanocrystalline diamond (NCD) films are promising materials for bone implant coatings because of their biocompatibility, chemical resistance, and mechanical hardness. Moreover, NCD wettability can be tailored by grafting specific atoms. The NCD films used in this study were grown on silicon substrates by microwave plasma-enhanced chemical vapor deposition and grafted by hydrogen atoms (H-termination) or oxygen atoms (O-termination). Human osteoblast-like Saos-2 cells were used for biological studies on H-terminated and O-terminated NCD films. The adhesion, growth, and subsequent differentiation of the osteoblasts on NCD films were examined, and the extracellular matrix production and composition were quantified. The osteoblasts that had been cultivated on the O-terminated NCD films exhibited a higher growth rate than those grown on the H-terminated NCD films. The mature collagen fibers were detected in Saos-2 cells on both the H-terminated and O-terminated NCD films; however, the quantity of total collagen in the extracellular matrix was higher on the O-terminated NCD films, as were the amounts of calcium deposition and alkaline phosphatase activity. Nevertheless, the expression of genes for osteogenic markers – type I collagen, alkaline phosphatase, and osteocalcin – was either comparable on the H-terminated and O-terminated films or even lower on the O-terminated films. In conclusion, the higher wettability of the O-terminated NCD films is promising for adhesion and growth of osteoblasts. In addition, the O-terminated surface also seems to support the deposition of extracellular matrix proteins and extracellular matrix mineralization, and this is promising for better osteoconductivity of potential bone implant coatings. PMID:25670900

  17. Tools for magnetostructural correlations for the 3d8(3A2 state) ions at orthorhombic sites: Comparative study with applications to Ni2+ ions in Y2BaNiO5 and Nd2BaNiO5

    NASA Astrophysics Data System (ADS)

    Gnutek, P.; Açıkgöz, M.; Rudowicz, C.

    2015-01-01

    Three approaches are employed to study magnetostructural correlations for the 3d8(3A2 state) ions at orthorhombic sites in crystals: (i) the higher-order perturbation theory (PT) of the microscopic spin Hamiltonian (MSH) parameters, (ii) the crystal field (CF) analysis (CFA) within all 3d8 states combined with the superposition model (SPM) calculations of CF parameters, and (iii) the second-order PT of MSH parameters. A comparative study is carried out to assess the merit of each modeling approach. These approaches enable predictions of the orthorhombic zero-field splitting parameters (ZFSPs) for the 3d8 ions at orthorhombic sites. Hence, correlation of the magnetic and spectroscopic properties with the structural ones may be considered. The approach (i) and (iii) take into account only the spin-orbit coupling (SOC) and a limited set of low lying states. Analysis of the expressions used in the approach (i) reveals discrepancies concerning: the sign of the SOC parameter, the cubic crystal field parameter Dq, the energy levels sequence, and numerical errors, which diminish its reliability. The distinction between the first- and second-kind orthorhombic symmetry is also elucidated. The approaches (i)-(iii) are applied for Ni2+ (S=1) ions in the Haldane gap systems Y2BaNiO5 and Nd2BaNiO5. The contributions to the ZFSPs due to the spin-spin and spin-other-orbit interactions considered using the approach (ii) are found nearly insignificant as compared with the dominant SOC ones. The results indicate that the approach (i)-corrected and (iii) may be employed only as an approximation. The approach (ii) together with the SPM/CFP modeling appear to be preferable and more reliable tools to study magnetostructural correlations and thus spectroscopic and magnetic properties of the 3d8(3A2 state) ions at orthorhombic sites in crystals.

  18. Photoluminescence, thermoluminescence glow curve and emission characteristics of Y2O3:Er3+ nanophosphor.

    PubMed

    N J, Shivaramu; B N, Lakshminarasappa; K R, Nagabhushana; H C, Swart; Fouran, Singh

    2018-01-15

    Nanocrystalline Er 3+ doped Y 2 O 3 crystals were prepared by a sol gel technique. X-ray diffraction (XRD) patterns showed the cubic structure of Y 2 O 3 and the crystallite size was found to be ~25nm. Optical absorption showed absorption peaks at 454, 495 and 521nm. These peaks are attributed to the 4 F 3/2 + 4 F 5/2 , 4 F 7/2 and 2 H 11/2 + 4 S 3/2 transitions of Er 3+ . Under excitation at 378nm, the appearance of strong green (520-565nm) down conversion emission assigned to the ( 2 H 11/2, 4 S 3/2 )→ 4 I 15/2 transition and the feeble red (650-665nm) emission is assigned to the 4 F 9/2 → 4 I 15/2 transition. The color chromaticity coordinates showed emission in the green region. The strong green emission of Y 2 O 3 :Er 3+ nanophosphor may be useful for applications in solid compact laser devices. Thermoluminescence (TL) studies of γ-irradiated Y 2 O 3 :Er 3+ showed a prominent TL glow peak maximum at 383K along with a less intense shoulder peak at ~425K and a weak glow at 598K. TL emission peaks with maxima at 545, 490, 588 and 622nm for the doped sample were observed at a temperature of 383K and these emissions were due to defect related to the host material. TL kinetic parameters were calculated by a glow curve deconvolution (GCD) method and the obtained results are discussed in detail for their possible usage in high dose dosimetry. Copyright © 2017 Elsevier B.V. All rights reserved.

  19. Synthesis and characterization of (3-Aminopropyl)trimethoxy-silane (APTMS) functionalized Gd2O3:Eu(3+) red phosphor with enhanced quantum yield.

    PubMed

    Jain, Akhil; Hirata, G A; Farías, M H; Castillón, F F

    2016-02-12

    We report the surface modification of nanocrystalline Gd2O3:Eu(3+) phosphor by (3-Aminopropyl)trimethoxysilane (APTMS). The nanoparticles were first coated with silica using the Stöber process, and then annealed at 650 °C for 2 h. Afterwards, APTMS was functionalized onto the silica layer to obtain Gd2O3:Eu(3+) nanoparticles bearing amine groups on the surface. The effect of silica coating, and the subsequent annealing process on the crystallization of the nanophosphor were analyzed by x-ray diffraction (XRD). High-resolution transmission electron microscopy (HR-TEM) confirmed the presence of a silica layer of ∼45 nm thickness. X-ray photoelectron (XPS) and Fourier transform infrared (FTIR) spectroscopy confirmed the presence of silica and the amine groups. Photoluminescence (PL) analysis demonstrated an increased emission after functionalization of nanoparticles. Absolute quantum yield (QY) measurements revealed an 18% enhancement in QY in functionalized nanoparticles compared with unmodified nanoparticles, which is of great importance for their biomedical applications.

  20. Synthesis and characterization of (3-Aminopropyl)trimethoxy-silane (APTMS) functionalized Gd2O3:Eu3+ red phosphor with enhanced quantum yield

    NASA Astrophysics Data System (ADS)

    Jain, Akhil; Hirata, G. A.; Farías, M. H.; Castillón, F. F.

    2016-02-01

    We report the surface modification of nanocrystalline Gd2O3:Eu3+ phosphor by (3-Aminopropyl)trimethoxysilane (APTMS). The nanoparticles were first coated with silica using the Stöber process, and then annealed at 650 °C for 2 h. Afterwards, APTMS was functionalized onto the silica layer to obtain Gd2O3:Eu3+ nanoparticles bearing amine groups on the surface. The effect of silica coating, and the subsequent annealing process on the crystallization of the nanophosphor were analyzed by x-ray diffraction (XRD). High-resolution transmission electron microscopy (HR-TEM) confirmed the presence of a silica layer of ∼45 nm thickness. X-ray photoelectron (XPS) and Fourier transform infrared (FTIR) spectroscopy confirmed the presence of silica and the amine groups. Photoluminescence (PL) analysis demonstrated an increased emission after functionalization of nanoparticles. Absolute quantum yield (QY) measurements revealed an 18% enhancement in QY in functionalized nanoparticles compared with unmodified nanoparticles, which is of great importance for their biomedical applications.

  1. Effect of rare-earth ion size on local electron structure in RBa 2Cu 3O 7- δ (R = Tm, Dy, Gd, Eu, Nd and Y) superconductors: A positron study

    NASA Astrophysics Data System (ADS)

    Chen, Zhenping; Zhang, Jincang; Su, Yuling; Xue, Yuncai; Cao, Shixun

    2006-02-01

    The effects of rare-earth ionic size on the local electron structure, lattice parameters and superconductivity have been investigated by positron annihilation technique (PAT) and related experiments for RBa 2Cu 3O 7- δ (R = Tm, Dy, Gd, Eu, Nd and Y) superconductors. The local electron density ne is evaluated as a function of the rare-earth radius. The results show that both the bulk-lifetime τB and the defect lifetime τ2 increase with increasing rare-earth ionic radius, while the local electron density ne decrease with increasing rare-earth ionic radius. These results prove that the changes of ne, the degree of orthorhombic distortion and the coupling between the Cu-O chains and the CuO 2 planes all have an effect on the superconductivity of RBa 2Cu 3O 7- δ systems.

  2. Spectroscopic investigations of Nd3+ doped Lithium Lead Alumino Borate glasses for 1.06 μm laser applications

    NASA Astrophysics Data System (ADS)

    Deopa, Nisha; Rao, A. S.; Gupta, Mohini; Vijaya Prakash, G.

    2018-01-01

    Neodymium doped lithium lead alumino borate glasses were synthesized with the molar composition 10Li2Osbnd 10PbOsbnd (10-x) Al2O3sbnd 70B2O3sbnd x Nd2O3 (where, x = 0.1, 0.5, 1.0, 1.5, 2.0 and 2.5 mol %) via conventional melt quenching technique to understand their lasing potentialities using the absorption, emission and photoluminescence decay spectral measurements. The oscillator strengths measured from the absorption spectra were used to estimate the Judd-Ofelt intensity parameters using least square fitting procedure. The emission spectra recorded for the as-prepared glasses under investigation exhibit two emission transitions 4F3/2 → 4I11/2 (1063 nm) and 4F3/2 → 4I9/2 (1350 nm) for which radiative parameters have been evaluated. The emission intensity increases with increase in Nd3+ ion concentration up to 1 mol % and beyond concentration quenching took place. The decay profile shows single exponential nature for lower Nd3+ ion concentration and non-exponential for higher concentration. To elucidate the nature of energy transfer process, the non-exponential decay curves were well fitted to Inokuti-Hirayama model. The relatively higher values of emission cross-sections, branching ratios and quantum efficiency values obtained for 1.0 mol% of Nd3+ ions in LiPbAlB glass suggests it's aptness in generating lasing action at 1063 nm in NIR region.

  3. Synchrotron X-ray Diffraction and High-Pressure Electrical Resistivity Studies for High-Tc Candidate Nd3.5Sm0.5Ni3O8

    NASA Astrophysics Data System (ADS)

    Uehara, Masatomo; Kobayashi, Kai; Yamamoto, Hiroki; Nakata, Akitoshi; Wakiya, Kazuhei; Umehara, Izuru; Gouchi, Jun; Uwatoko, Yoshiya

    2017-11-01

    Ln4Ni3O8 (Ln = La, Nd, Sm) has attracted much attention as a candidate for high-Tc superconductor due to its close structural and electrical similarities with high-Tc cuprates. However, Ln4Ni3O8 is not a superconductor and shows semiconducting behavior. Our recent work has revealed that Nd3.5Sm0.5Ni3O8 displays metallic behavior down to 20-40 K upon intercalation and subsequent deintercalation treatments with sulfur, followed by a weak semiconducting tendency at lower temperatures. A synchrotron X-ray diffraction experiment suggests that the structural change induced by sulfur treatment can be explained electrostatically by the removal of additional apical oxygen. High-pressure electrical resistivity measurements up to 8 GPa on a metallic sample show the enhancement of the semiconducting tendency at low temperatures, suggesting that the removal of additional apical oxygen is not totally completed under the present conditions of sulfur treatment.

  4. Photoinduced second-order optical susceptibilities of Er 2O 3 doped TeO 2-GeO 2-PbO glasses

    NASA Astrophysics Data System (ADS)

    Kassab, L. R. P.; Pinto, R. de A.; Kobayashi, R. A.; Piasecki, M.; Bragiel, P.; Kityk, I. V.

    2007-06-01

    Second-order optical susceptibilities were established in the optically poled erbium doped tellurite glasses near the melting temperature. The non-linear optical susceptibility was formed by bicolor coherent optical treatment performed by two coherent laser beams originated from 50 ps Nd-YAG laser ( λ = 1.32 μm) exciting the high pressure hydrogen laser cell emitting at 1907 nm. The non-centrosymmetric grating of the medium was created by coherent superposition of the fundamental laser illumination at 1907 nm and the doubled frequency one at 953.5 nm. The maximally all-optically poled SHG occurs for 2% doped Er 2O 3 (in weighting units) TeO 2-GeO 2-PbO glass. It was found that the photoinduced SHG demonstrates a saturation during the photo-treatment of 9-10 min using the two beams polarized at angle about 45° between them. During the coherent bicolor optical treatment it was achieved the value of second-order susceptibility up to 3.6 pm/V at 1907 nm. The optimal ratio between the fundamental beam with power density about 1.1 GW/cm 2 and writing doubled frequency seeding beam about 0.015 GW/cm 2 corresponds to the maximal of photoinduced SHG. For glasses with lower concentration of Er 2O 3, the relaxation of the second-order optical susceptibility is substantially longer and achieves SHG value that corresponds to 80% of the maximal ones. It is necessary to emphasize that efficient optically-poled grating exists only within the narrow temperature range near the glassing temperature. Possible physical mechanisms of the phenomenon observed are discussed. Generally the used glasses possess better parameters than early investigated germinate glasses.

  5. Selective Adsorption Resonances in the Scattering of n-H2 p-H2 n-D2 and o-D2 from Ag(111)

    NASA Astrophysics Data System (ADS)

    Yu, Chien-Fan; Whaley, K. Birgitta; Hogg, Charles S.; Sibener, Steven J.

    1983-12-01

    Diffractive and rotationally mediated selective adsorption scattering resonances are reported for n-H2 p-H2 n-D2 and o-D2 on Ag(111). Small resonance shifts and line-width differences are observed between n-H2 and p-H2 indicating a weak orientation dependence of the laterally averaged H2/Ag(111) potential. The p-H2 and o-D2 levels were used to determine the isotropic component of this potential, yielding a well depth of ~ 32 meV.

  6. Superhyperfine Structure of the EPR Spectra of Nd3+ Impurity Ions in Fluorite CaF2

    NASA Astrophysics Data System (ADS)

    Aminov, L. K.; Gafurov, M. R.; Kurkin, I. N.; Malkin, B. Z.; Rodionov, A. A.

    2018-05-01

    EPR spectra of a CaF2 single crystal that was grown from melt containing a small addition of NdF3 were studied. Signals corresponding to tetragonal centers of Nd3+ ions and cubic centers of Er3+ and Yb3+ ions were found. Superhyperfine structure (SHFS) in the spectra of the Nd3+ ions was observed for the first time in this crystal; parameters of the superhyperfine interaction of the Nd3+ ions with the nearest nine fluorine ions were determined. The dependence of the resolution of the Nd3+ EPR spectrum SHFS on the incident microwave power at the temperature of T ≈ 6 K was studied. Obtained results are discussed and compared with the literature data.

  7. Surfactant-assisted hydrothermal crystallization of nanostructured lithium metasilicate (Li{sub 2}SiO{sub 3}) hollow spheres: II-Textural analysis and CO{sub 2}-H{sub 2}O sorption evaluation

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

    Ortiz-Landeros, Jose; Gomez-Yanez, Carlos; Pfeiffer, Heriberto, E-mail: pfeiffer@iim.unam.mx

    In a previous work, the synthesis and structural-microstructural characterization of different nanocrystalline lithium metasilicate (Li{sub 2}SiO{sub 3}) samples were performed. Then, in this work, initially, a textural analysis was performed over the same samples. Li{sub 2}SiO{sub 3} samples prepared with a non-ionic surfactant (TRITON X-114) presented the best textural properties. Therefore, this sample was selected to evaluate its water vapor (H{sub 2}O) and carbon dioxide (CO{sub 2}) sorption properties. Sorption experiments were performed at low temperatures (30-80 deg. C) in presence of water vapor using N{sub 2} or CO{sub 2} as carrier gases. Results clearly evidenced that CO{sub 2} sorptionmore » on these materials is highly improved by H{sub 2}O vapor, and of course, textural properties enhanced the H{sub 2}O-CO{sub 2} sorption efficiency, in comparison with the solid-state reference sample. - Graphical abstract: Li{sub 2}SiO{sub 3} varied significantly its capacity of CO{sub 2} absorption as a function of the microstructural properties and by the water presence. Highlights: > We studied the CO{sub 2} absorption on different Li{sub 2}SiO{sub 3} samples in presence of H{sub 2}O vapor. > It was proved that CO{sub 2} absorption on Li{sub 2}SiO{sub 3} is controlled by different factors. > Li{sub 2}SiO{sub 3} with a porous microstructure produces a higher CO{sub 2} absorption. > H{sub 2}O vapor favors the CO{sub 2} absorption on Li{sub 2}SiO{sub 3} due to a surface hydroxylation.« less

  8. Presence of glassy state and large exchange bias in nanocrystalline BiFeO3

    NASA Astrophysics Data System (ADS)

    Srivastav, Simant Kumar; Johari, Anima; Patel, S. K. S.; Gajbhiye, N. S.

    2017-11-01

    We investigated the static and dynamic aspects of the magnetic properties for single phase nanocrystalline BiFeO3 with average crystallite size of 35 nm. The frequency dependence of the peak is observed in the real part of ac susceptibility χ‧ac vs T measurement and described well by the Vogel-Fulcher law as well as the power law. These analyses indicated the existence of cluster glass state with significant interaction among the spin clusters and results in cluster-glass like cooperative freezing at low temperature. The influence of temperature and magnetic field cooling on the exchange bias effect is investigated. A training effect is also observed. We have reported a significantly high ZFC & FC exchange bias of 200 Oe & 450 Oe at 300 K and 900 Oe & 2100 Oe at 5 K. The obtained results are interpreted in the framework of core-shell model, where the core of the BFO nanoparticles shows antiferromagnetic behavior and surrounded by CG-like ferromagnetic (FM) shell associated to uncompensated surface spins.

  9. Magnetization reversal properties of Pr{sub 1-x}(Gd/Nd){sub x}MnO{sub 3} (x=0.3, 0.5, 0.7)

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

    Biswas, Sanjay; Pal, Sudipta, E-mail: sudipta.pal@rediffmail.com; Bose, Esa

    2015-06-24

    We report measurements of the temperature dependent magnetic properties of single phase orthorhombic perovskites system associated with space group Pbnm compounds Pr{sub 1-x}(Gd/Nd){sub x}MnO{sub 3} (x=0.3, 0.5, 0.7). Magnetic properties radically changes with the doping of Gd or Nd. A magnetization reversal is observed below the Neel temperature (T{sub N}), in DC magnetization measurements (at 50 Oe) in the doped compounds. The reversal of magnetization may be due to the antiparallel coupling between the two magnetic sublattices (|Pr+ Gd/ Nd | and Mn). The hysteresis plot taken at 50K indicates a ferrimagnetic characteristic and existence of spin canting of ionsmore » in the magnetic sublattices.« less

  10. Fabrication of Nd3+ and Mn2+ ions Co-doped Spinal Strontium Nanoferrites for High Frequency Device Applications

    NASA Astrophysics Data System (ADS)

    Ahmad, Iqbal; Shah, Syed Mujtaba; Ashiq, Muhammad Naeem; Nawaz, Faisal; Shah, Afzal; Siddiq, Muhammad; Fahim, Iqra; Khan, Samiullah

    2016-10-01

    Microemulsion method has been used for the synthesis of high resistive spinal nanoferrites with nominal composition Sr1- x Nd x Fe2- y Mn y O4 (0.0 ≤ x ≤ 0.1, 0.0 ≤ y ≤ 1.0) for high frequency device applications. It has been confirmed by x-ray diffraction (XRD) results that these ferrites have a cubic spinal structure with a mean crystallite size ranging from 34 mm to 47 nm. The co-substitution of Nd3+ and Mn2+ ions was performed, and its effect on electrical, dielectric and impedance properties was analyzed employing direct current (DC) resistivity measurements, dielectric measurements and electrochemical impedance spectroscopy (EIS). The DC resistivity ( ρ) value was the highest for the composition Sr0.90Nd0.1FeMnO4, but for the same composition, dielectric parameters and alternating current (AC) conductivity showed their minimum values. In the lower frequency range, the magnitudes of dielectric parameters decrease with increasing frequency and show an almost independent frequency response at higher frequencies. Dielectric polarization has been employed to explain these results. It was inferred from the results of EIS that the conduction process in the studied ferrite materials is predominantly governed by grain boundary volume.

  11. Effects of trace elements on the crystal field parameters of Nd ions at the surface of Nd{sub 2}Fe{sub 14}B grains

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

    Toga, Yuta; Suzuki, Tsuneaki; Sakuma, Akimasa, E-mail: sakuma@solid.apph.tohoku.ac.jp

    2015-06-14

    Using first-principles calculations, we investigate the positional dependence of trace elements such as O and Cu on the crystal field parameter A{sub 2}{sup 0}, proportional to the magnetic anisotropy constant K{sub u} of Nd ions placed at the surface of Nd{sub 2}Fe{sub 14}B grains. The results suggest the possibility that the A{sub 2}{sup 0} parameter of Nd ions at the (001) surface of Nd{sub 2}Fe{sub 14}B grains exhibits a negative value when the O or Cu atom is located near the surface, closer than its equilibrium position. At the (110) surface, however, O atoms located at the equilibrium position providemore » a negative A{sub 2}{sup 0}, while for Cu additions A{sub 2}{sup 0} remains positive regardless of Cu's position. Thus, Cu atoms are expected to maintain a positive local K{sub u} of surface Nd ions more frequently than O atoms when they approach the grain surfaces in the Nd-Fe-B grains.« less

  12. Diode laser-based cavity ring-down instrument for NO3, N2O5, NO, NO2 and O3 from aircraft

    NASA Astrophysics Data System (ADS)

    Wagner, N. L.; Dubé, W. P.; Washenfelder, R. A.; Young, C. J.; Pollack, I. B.; Ryerson, T. B.; Brown, S. S.

    2011-03-01

    This article presents a diode laser based, cavity ring-down spectrometer for simultaneous in situ measurements of four nitrogen oxide species, NO3, N2O5, NO, NO2, as well as O3, designed for deployment on aircraft. The instrument measures NO3 and NO2 by optical extinction at 662 nm and 405 nm, respectively; N2O5 is measured by thermal conversion to NO3, while NO and O3 are measured by chemical conversion to NO2. The instrument has several advantages over previous instruments developed by our group for measurement of NO2, NO3 and N2O5 alone, based on a pulsed Nd:YAG and dye laser. First, the use of continuous wave diode lasers reduces the requirements for power and weight and eliminates hazardous materials. Second, detection of NO2 at 405 nm is more sensitive than our previously reported 532 nm instrument, and does not have a measurable interference from O3. Third, the instrument includes chemical conversion of NO and O3 to NO2 to provide measurements of total NOx (= NO + NO2) and Ox (= NO2 + O3) on two separate channels; mixing ratios of NO and O3 are determined by subtraction of NO2. Finally, all five species are calibrated against a single standard based on 254 nm O3 absorption to provide high accuracy. Disadvantages include an increased sensitivity to water vapor on the 662 nm NO3 and N2O5 channels and a modest reduction in sensitivity for these species compared to the pulsed laser instrument. The measurement precision for both NO3 and N2O5 is below 1 pptv (2σ, 1 s) and for NO, NO2 and O3 is 170, 46, and 56 pptv (2σ, 1 s) respectively. The NO and NO2 measurements are less precise than research-grade chemiluminescence instruments. However, the combination of these five species in a single instrument, calibrated to a single analytical standard, provides a complete and accurate picture of nighttime nitrogen oxide chemistry. The instrument performance is demonstrated using data acquired during a recent field campaign in California.

  13. Luminescence and energy transfer of Tb3+-doped BaO-Gd2O3-Al2O3-B2O3-SiO2 glasses.

    PubMed

    Zuo, Chenggang; Huang, Jinze; Liu, Shaoyou; Xiao, Anguo; Shen, Youming; Zhang, Xiangyang; Zhou, Zhihua; Zhu, Ligang

    2017-12-05

    Transparent Tb 3+ -doped BaO-Gd 2 O 3 -Al 2 O 3 -B 2 O 3 -SiO 2 glasses with the greater than 4g/cm 3 were prepared by high temperature melting method and its luminescent properties have been investigated by measured UV-vis transmission, excitation, emission and luminescence decay spectra. The transmission spectrum shows there are three weak absorption bands locate at about 312, 378 and 484nm in the glasses and it has good transmittance in the visible spectrum region. Intense green emission can be observed under UV excitation. The effective energy transfer from Gd 3+ ion to Tb 3+ ion could occur and sensitize the luminescence of Tb 3+ ion. The green emission intensity of Tb 3+ ion could change with the increasing SiO 2 /B 2 O 3 ratio in the borosilicate glass matrix. With the increasing concentration of Tb 3+ ion, 5 D 4 → 7 F J transitions could be enhanced through the cross relaxation between the two nearby Tb 3+ ions. Luminescence decay time of 2.12ms from 546nm emission is obtained. The results indicate that Tb 3+ -doped BaO-Gd 2 O 3 -Al 2 O 3 -B 2 O 3 -SiO 2 glasses would be potential scintillating material for applications in X-ray imaging. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. Temperature-dependent local structural properties of redox Pt nanoparticles on TiO 2 and ZrO 2 supports

    DOE PAGES

    Jeong, Eun -Suk; Park, Chang -In; Jin, Zhenlan; ...

    2015-01-21

    This paper examined the local structural properties of Pt nanoparticles on SiO 2, TiO 2–SiO 2, and ZrO 2–SiO 2 supports to better understand the impact of oxide-support type on the performance of Pt-based catalysts. In situ X-ray absorption fine structure (XAFS) measurements were taken for the Pt L3-edge in a temperature range from 300 to 700 K in He, H 2, and O 2 gas environments. The XAFS measurements demonstrated that Pt atoms were highly dispersed on TiO 2–SiO 2 and ZrO 2–SiO 2 forming pancake-shaped nanoparticles, whereas Pt atoms formed larger particles of hemispherical shapes on SiO 2more » supports. Contrary to the SiO 2 case, the coordination numbers for Pt, Ti, and Zr around Pt atoms on the TiO 2–SiO 2 and ZrO 2–SiO 2 supports were nearly constant from 300 to 700 K under the different gas environments. These results are consistent with the improvements in thermal stability of Pt nanoparticles achieved by incorporating TiO 2 or ZrO 2 on the surface of SiO 2 supports. XAFS analysis further indicated that the enhanced dispersion and stability of Pt were a consequence of the strong metal support interaction via Pt–Ti and Pt–Zr bonds.« less

  15. Laser-Marking Mechanism of Thermoplastic Polyurethane/Bi2O3 Composites.

    PubMed

    Zhong, Wei; Cao, Zheng; Qiu, Pengfei; Wu, Dun; Liu, Chunlin; Li, Huili; Zhu, He

    2015-11-04

    Using bismuth oxide (Bi2O3) as a laser-marking additive and thermoplastic polyurethane (TPU) as the matrix, TPU/Bi2O3 composite materials were prepared by melt blending in a torque rheometer. The sheet samples prepared from the TPU/Bi2O3 composites were treated in air by scanning with a neodymium-doped yttrium aluminum garnet (Nd: YAG) pulsed laser beam at a wavelength of 1064 nm. Compared with the pure TPU sample, the laser-marked composite samples exhibited differences in marking contrast as the Bi2O3 content increased from 0.1% to 1.0% based on stereomicroscope analysis. Scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, thermogravimetry analysis, and X-ray diffraction were used to characterize the laser-marked surface material of the composite samples. Furthermore, a mechanism for the laser-effected darkening of the TPU/Bi2O3 composites was proposed. The results herein indicated that the addition of the Bi2O3 laser-sensitive additive to TPU resulted in laser darkening of the TPU/Bi2O3 composites. The marking contrast and visual appearance of the surface of the TPU/Bi2O3 composites after laser irradiation was due to a synergistic effect consisting of carbonization via TPU pyrolysis and reduction of Bi2O3 to black bismuth metal.

  16. Hyperfine fields of Fe in Nd2Fe14BandSm2Fe17N3

    NASA Astrophysics Data System (ADS)

    Akai, Hisazumi; Ogura, Masako

    2015-03-01

    High saturation magnetization of rare-earth magnets originates from Fe and the strong magnetic anisotropy stems from f-states of rare-earth elements such as Nd and Sm. Therefore the hyperfine fields of both Fe and rare-earth provide us with important pieces of information: Fe NMR enable us to detect site dependence of the local magnetic moment and magnetic anisotropy (Fe sites also contribute to the magnetic anisotropy) while rare-earth NQR directly give the information of electric field gradients (EFG) that are related to the shape of the f-electron cloud as well as the EFG produced by ligands. In this study we focus on the hyperfine fields of materials used as permanent magnets, Nd2Fe14BandSm2Fe17N3 from theoretical points of view. The detailed electronic structure together with the hyperfine interactions are discussed on the basis of the first-principles calculation. In particular, the relations between the observed hyperfine fields and the magnetic properties are studies in detail. The effects of doping of those materials by other elements such as Dy and the effects of N adding in Sm2Fe17N3 will be discussed. This work was supported by Elements Strategy Initiative Center for Magnetic Materials Project, the Ministry of Education, Culture, Sports, Science and Technology, Japan.

  17. Nanocrystalline LaOx/NiO composite as high performance electrodes for supercapacitors.

    PubMed

    Du, Guo; Zeng, Zifan; Xiao, Bangqing; Wang, Dengzhi; Yuan, Yuan; Zhu, Xiaohong; Zhu, Jiliang

    2017-12-21

    Nanocrystalline LaO x /NiO composite electrodes were synthesized via two types of facile cathodic electrodeposition methods onto nickel foam followed by thermal annealing without any binders. Scanning electron microscopy and transmission electron microscopy investigation revealed that LaO x nanocrystalline particles with an average diameter of 50 nm are uniformly distributed in the NiO layer or alternately deposited with the NiO layer onto the substrate. It is speculated that LaO x particles can participate in the faradaic reaction directly and offer more redox sites. Besides this, the unique Ni/La layered structure facilitates the diffusion of ions and retards the electrode polarization, thus leading to a better rate capability and cycling stability of NiO. As a result, the obtained electrodes display very competitive electrochemical performance (a specific capacitance of 1238 F g -1 at a current density of 0.5 A g -1 , excellent rate capability of 86% of the original capacitance at 10 A g -1 and excellent cycling stability of 93% capacitance after 10 000 cycles). In addition, asymmetric coin devices were assembled using LaO x /NiO as the positive electrode and active carbon as the negative electrode. The assembled asymmetric devices demonstrate a high energy density of 13.12 W h kg -1 at a power density of 90.72 W kg -1 .

  18. Structural differences between superconducting and non-superconducting CaCuO2/SrTiO3 interfaces

    NASA Astrophysics Data System (ADS)

    Zarotti, Francesca; Di Castro, Daniele; Felici, Roberto; Balestrino, Giuseppe

    2018-06-01

    A study of the interface structure of superconducting and non-superconducting CaCuO2/SrTiO3 heterostructures grown on NdGaO3(110) substrates is reported. Using the combination of high resolution x-ray reflectivity and surface diffraction, the crystallographic structure of superconducting and non-superconducting samples has been investigated. The analysis has demonstrated the excellent sharpness of the CaCuO2/SrTiO3 interface (roughness smaller than one perovskite unit cell). Furthermore, we were able to discriminate between the superconducting and the non-superconducting phase. In the former case, we found an increase of the spacing between the topmost Ca plane of CaCuO2 block and the first TiO2 plane of the overlaying STO block, relative to the non-superconducting case. These results are in agreement with the model that foresees a strong oxygen incorporation in the interface Ca plane in the superconducting heterostructures.

  19. Structural and magnetic properties of two branches of the tripod-kagome-lattice family A2R3Sb3O14 (A = Mg, Zn; R = Pr, Nd, Gd, Tb, Dy, Ho, Er, Yb)

    NASA Astrophysics Data System (ADS)

    Dun, Z. L.; Trinh, J.; Lee, M.; Choi, E. S.; Li, K.; Hu, Y. F.; Wang, Y. X.; Blanc, N.; Ramirez, A. P.; Zhou, H. D.

    2017-03-01

    We present a systematic study of the structural and magnetic properties of two branches of the rare-earth tripod-kagome-lattice (TKL) family A2R3Sb3O14 (A = Mg, Zn; R = Pr, Nd, Gd, Tb, Dy, Ho, Er, Yb; here, we use abbreviation A-R, as in MgPr for Mg2Pr3Sb3O14 ), which complements our previously reported work on MgDy, MgGd, and MgEr [Z. L. Dun et al., Phys. Rev. Lett. 116, 157201 (2016), 10.1103/PhysRevLett.116.157201]. The present susceptibility (χdc, χac) and specific-heat measurements reveal various magnetic ground states, including the nonmagnetic singlet state for MgPr, ZnPr; long-range orderings (LROs) for MgGd, ZnGd, MgNd, ZnNd, and MgYb; a long-range magnetic charge ordered state for MgDy, ZnDy, and potentially for MgHo; possible spin-glass states for ZnEr, ZnHo; the absence of spin ordering down to 80 mK for MgEr, MgTb, ZnTb, and ZnYb compounds. The ground states observed here bear both similarities as well as striking differences from the states found in the parent pyrochlore systems. In particular, while the TKLs display a greater tendency towards LRO, the lack of LRO in MgHo, MgTb, and ZnTb can be viewed from the standpoint of a balance among spin-spin interactions, anisotropies, and non-Kramers nature of single-ion state. While substituting Zn for Mg changes the chemical pressure, and subtly modifies the interaction energies for compounds with larger R ions, this substitution introduces structural disorder and modifies the ground states for compounds with smaller R ions (Ho, Er, Yb).

  20. Elastic anomalies and acoustic dissipation associated with spin state transitions in LnCoO3 (Ln=La, Nd, Gd) and Co3O4: analogue behaviour for spin state transitions in minerals

    NASA Astrophysics Data System (ADS)

    Zhang, Z.; Carpenter, M. A.; Koppensteiner, J.; Schranz, W.

    2010-12-01

    Iron ions in lower mantle minerals magnesiowüstitue (Mg,Fe)O, perovskite (Mg,Fe)(Si,Al)O3 and post-perovskite phases undergo electronic spin state transitions from high spin (HS) to low spin (LS) or intermediate spin (IS) at high pressures and high temperatures. These spin state transitions give rise to changes in bulk and shear moduli which have significant implications for the physical and chemical properties of the lower mantle. However, the possibility of increased attenuation does not appear to have been considered yet. Co3+ is isoelectronic with Fe2+ and shows analogous HS/LS behaviour at ambient pressure in a temperature range which is easily accessible for in-situ investigations. We have studied spin state transitions in cobalt perovskites LaCoO3, NdCoO3, GdCoO3 and in Co3O4 using resonant ultrasound spectroscopy (RUS) at high frequencies 0.1-1.5 MHz, and dynamic mechanical analysis (DMA) at low frequencies 0.1-50 Hz, in the temperature range 10-1200 K. The specific objectives were to characterize anomalies in the shear moduli and in acoustic attenuation accompanying changes in the spin state of Co3+. Anomalies in shear moduli have been observed at ~110 K and ~590 K for LaCoO3, ~325 K and ~695 K for NdCoO3, ~720 K for GdCoO3, and ~30 K for Co3O4. For LaCoO3, a spin order parameter qspin is expected to couple with volume strain ea as λeaqspin and with shear strain es as λes2qspin. As a consequence of linear/quadratic coupling with es, the shear modulus is expected to vary linearly with qspin. This appears to be approximately the case for LaCoO3. Changes in spin state do not appear to give rise to acoustic attenuation at either DMA frequencies (~1 Hz) or RUS frequencies (~1 MHz), consistent with the expectation that spin/lattice relaxation is rapid in comparison with the time scale of applied stress in each case. On the other hand, for LaCoO3 there is a peak in dissipation near 590 K at low frequencies, which is attributed to freezing of ferroelastic twin

  1. Microwave irradiation-assisted deposition of Ga2O3 on III-nitrides for deep-UV opto-electronics

    NASA Astrophysics Data System (ADS)

    Jaiswal, Piyush; Ul Muazzam, Usman; Pratiyush, Anamika Singh; Mohan, Nagaboopathy; Raghavan, Srinivasan; Muralidharan, R.; Shivashankar, S. A.; Nath, Digbijoy N.

    2018-01-01

    We report on the deposition of Ga2O3 on III-nitride epi-layers using the microwave irradiation technique. We also report on the demonstration of a Ga2O3 device: a visible-blind, deep-UV detector, with a GaN-based heterostructure as the substrate. The film deposited in the solution medium, at <200 °C, using a metalorganic precursor, was nanocrystalline. XRD confirms that the as-deposited film, when annealed at high temperature, turns to polycrystalline β-Ga2O3. SEM shows the as-deposited film to be uniform, with a surface roughness of 4-5 nm, as revealed by AFM. Interdigitated metal-semiconductor-metal devices with Ni/Au contact exhibited a peak spectral response at 230 nm and a good visible rejection ratio. This demonstration of a deep-UV detector on the β-Ga2O3/III-nitride stack is expected to open up possibilities of functional and physical integration of β-Ga2O3 and GaN material families towards enabling next-generation high-performance devices by exciting band and heterostructure engineering.

  2. Crystallography, Spectroscopic Analysis, and Lasing Properties of Nd(3+) :Y3Sc2Al3O12

    DTIC Science & Technology

    1989-12-01

    aluminum garnet (GSAG), are formed from more stable constitu- ent oxides than gallium-containing materials, 2. Experimental Results and such as gadolinium ...the which an assessment can be made regarding aluminum -based systems, such as YAG, YSAG, Nd:YSAG as a laser material. or gadolinium scandium...Structure oxidation state variation or oxygen vacancies, and this problem is greatly reduced in alumi- Yttrium scandium aluminum garnet be- nate systems

  3. Crystal chemistry and the role of ionic radius in rare earth tetrasilicates: Ba2RE2Si4O12F2 (RE = Er3+-Lu3+) and Ba2RE2Si4O13 (RE = La3+-Ho3+).

    PubMed

    Fulle, Kyle; Sanjeewa, Liurukara D; McMillen, Colin D; Kolis, Joseph W

    2017-10-01

    Structural variations across a series of barium rare earth (RE) tetrasilicates are studied. Two different formulas are observed, namely those of a new cyclo-silicate fluoride, BaRE 2 Si 4 O 12 F 2 (RE = Er 3+ -Lu 3+ ) and new compounds in the Ba 2 RE 2 Si 4 O 13 (RE = La 3+ -Ho 3+ ) family, covering the whole range of ionic radii for the rare earth ions. The Ba 2 RE 2 Si 4 O 13 series is further subdivided into two polymorphs, also showing a dependence on rare earth ionic radius (space group P{\\overline 1} for La 3+ -Nd 3+ , and space group C2/c for Sm 3+ -Ho 3+ ). Two of the structure types identified are based on dinuclear rare earth units that differ in their crystal chemistries, particularly with respect to the role of fluorine as a structural director. The broad study of rare earth ions provides greater insight into understanding structural variations within silicate frameworks and the nature of f-block incorporation in oxyanion frameworks. The single crystals are grown from high-temperature (ca 953 K) hydrothermal fluids, demonstrating the versatility of the technique to access new phases containing recalcitrant rare earth oxides, enabling the study of structural trends.

  4. Optical absorption and photoluminescence study of nanocrystalline Zn0.92M0.08O (M: Li & Gd)

    NASA Astrophysics Data System (ADS)

    Punia, Khushboo; Lal, Ganesh; Kumar, Sudhish

    2018-05-01

    Nanocrystalline samples of Zn0.92Li0.08O and Zn0.92Gd0.08O have been synthesized using citrate sol-gel route without post synthesis annealing and characterized using powder X-ray diffraction (XRD), UV-Vis-NIR and Photoluminescence spectroscopic measurements. Analysis of XRD pattern and PL spectra revealed single phase formation of the nanocrystalline Zn0.92Li0.08O and Zn0.92Gd0.08O in the wurtzite type hexagonal structure with intrinsic crystal and surface defects. UV-Vis-NIR optical absorption measurements show that the maximum photo absorption occurs below 600nm in the UV& visible band. The estimated values of band gap energy were found to be 2.53eV and 2.73eV for Zn0.92Li0.08O and Zn0.92Gd0.08O respectively. The photoluminescence spectra excited at the wavelength 325nm displays two broad peaks in the UV and visible bands centered at ˜416 nm & ˜602 nm for Zn0.92Gd0.08O and ˜406nm & ˜598nm for Zn0.92Li0.08O. Both Gd and Li doping in ZnO leads to considerable decrease in the optical band gap energy and red shifting of the UV emission band towards the visible band.

  5. Controlled optical properties via chemical composition tuning in molybdenum-incorporated β-Ga2O3 nanocrystalline films

    NASA Astrophysics Data System (ADS)

    Battu, Anil K.; Manandhar, S.; Shutthanandan, V.; Ramana, C. V.

    2017-09-01

    An approach is presented to design refractory-metal incorporated Ga2O3-based materials with controlled structural and optical properties. The molybdenum (Mo)-content in Ga2O3 was varied from 0 to 11 at% in the sputter-deposited Ga-Mo-O films. Molybdenum was found to significantly affect the structure and optical properties. While low Mo-content (≤4 at%) results in the formation of single-phase (β-Ga2O3), higher Mo-content results in amorphization. Chemically-induced band gap variability (Eg ∼ 1 eV) coupled with structure-modification indicates the electronic-structure changes in Ga-Mo-O. The linear relationship between chemical-composition and optical properties suggests that tailoring the optical-quality and performance of Ga-Mo-O films is possible by tuning the Mo-content.

  6. Controlled optical properties via chemical composition tuning in molybdenum-incorporated β-Ga 2 O 3 nanocrystalline films

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

    Battu, Anil K.; Manandhar, S.; Shutthanandan, V.

    An approach is presented to design refractory-metal incorporated Ga2O3-based materials with controlled structural and optical properties. The molybdenum (Mo)-content in Ga2O3 was varied from 0 to 11 at% in the sputter-deposited Ga-Mo-O films. Molybdenum was found to significantly affect the structure and optical properties. While low Mo-content (≤4 at%) results in the formation of single-phase (β-Ga2O3), higher Mo-content results in amorphization. Chemically-induced band gap variability (Eg~1 eV) coupled with structure-modification indicates the electronic-structure changes in Ga-Mo-O. The linear relationship between chemical-composition and optical properties suggests that tailoring the optical-quality and performance of Ga-Mo-O films is possible by tuning the Mo-content.

  7. Photocatalytic activity of Ti3+ self-doped dark TiO2 ultrafine nanorods, grey SiO2 nanotwin crystalline, and their composite under visible light

    NASA Astrophysics Data System (ADS)

    Zhang, Renhui; Yang, Yingchang; Leng, Senlin; Wang, Qing

    2018-04-01

    Efficient electron-holes separation is of crucial importance for the improvement of photocatalytic activity for photocatalytic reaction. In this work, dark TiO2 (D-TiO2) nanorods, grey SiO2 (G-SiO2) and D-TiO2/G-SiO2 composite with surface defects are synthesized. We report that the efficiency of photo-generated electrons and holes separation is well enhanced by introducing G-SiO2 into D-TiO2 lattice. Using first-principles method, we find that surface defects (O or Si vacancy) can be conducive to improving the optical absorption under visible-light region. Combination of the experimental results, for D-TiO2/G-SiO2 composite, the surface defects of TiO2 nanocrystallines can significantly improve the photocatalytic efficiency.

  8. Highly efficient continuous-wave laser operation of LD-pumped Nd,Gd:CaF2 and Nd,Y:CaF2 crystals

    NASA Astrophysics Data System (ADS)

    Pang, Siyuan; Ma, Fengkai; Yu, Hao; Qian, Xiaobo; Jiang, Dapeng; Wu, Yongjing; Zhang, Feng; Liu, Jie; Xu, Jiayue; Su, Liangbi

    2018-05-01

    Spectroscopic properties of Nd:CaF2 crystals are investigated. The photoluminescence intensity in the near infrared region is drastically enhanced by co-doping Gd3+ ions and Y3+ in Nd:CaF2 crystals. Preliminary laser experiments are carried out with 0.3%Nd,5%Gd:CaF2 and 0.3%Nd,5%Y:CaF2 crystals under laser diode pumping; true continuous wave laser operation is achieved with slope efficiencies of 42% and 39%, respectively, and the maximum output power reaches 1.188 W.

  9. High Precision 142Nd/144Nd and 143Nd/144Nd Isotope Ratio Measurements in Rock Samples

    NASA Astrophysics Data System (ADS)

    Ali, A.; Srinivasan, G.

    2009-05-01

    The long-lived 147Sm-143Nd system with a half-life (T1/2) of 106 Gyr is generally used for geochronology. The short-lived 146Sm-142Nd system (T1/2= 103 Myr) is used as a geological tracer to track early (˜500 Ma) silicate differentiation [1] events in different planetary bodies. The isotope composition measurements by thermal ionization mass spectrometry (TIMS) require purification of Nd using chemical separation methods. This is important as an impure sample will give both a very poor ion yield and cause beam instability in the mass spectrometer, potentially resulting in a poor analysis [2]. The separation of Nd for 143Nd isotope measurement is, fairly straightforward because there is no isobaric interference of any other REE. While 142Nd isotope analysis needs chemically separated Nd fraction to be ˜100% Ce-free as latter is composed of a substantial amount of 142Ce isotope. A 4-steps technique, modified from Caro et al., [3], for the separation of Nd is established at the Cosmochemistry Laboratory of University of Toronto, Canada and applied to the measurement of Nd isotope ratios in geological reference sample BCR-2 (USGS, Columbia River basalt) using TIMS. Results of the isotopic ratios obtained for BCR-2 are in good agreement with published values [e.g., 4]. Analytical work on the samples discovered as the oldest rocks on Earth [5] from Nuvvuagittuq greenstone belt in Québec, Canada and various meteorites is in progress. An account of the procedures involved is briefly described here. All working solutions and acids were prepared using >18.2 MΩ.cm-1 H2O from a Milli-Q water system. Experiments were performed under Class 100 clean work bench with acid-cleaned apparatus and plastic-ware. The whole rock powders were weighed (20-30 mg) and dissolved in a mixture of HF and HNO3 using PFA vials and heated at 110°C. Further decomposition was done in Teflon bomb in the oven at 205°C. Later on contents of the Teflon bomb were transferred to vials and fluorides

  10. Electromagnetic modeling of waveguide amplifier based on Nd3+ Si-rich SiO2 layers by means of the ADE-FDTD method.

    PubMed

    Dufour, Christian; Cardin, Julien; Debieu, Olivier; Fafin, Alexandre; Gourbilleau, Fabrice

    2011-04-04

    By means of ADE-FDTD method, this paper investigates the electromagnetic modelling of a rib-loaded waveguide composed of a Nd3+ doped Silicon Rich Silicon Oxide active layer sandwiched between a SiO2 bottom cladding and a SiO2 rib. The Auxilliary Differential Equations are the rate equations which govern the levels populations. The Finite Difference Time Domain (FDTD) scheme is used to solve the space and time dependent Maxwell equations which describe the electromagnetic field in a copropagating scheme of both pumping (λpump = 488 nm) and signal (λsignal = 1064 nm) waves. Such systems are characterized by extremely different specific times such as the period of electromagnetic field ~ 10-15 s and the lifetimes of the electronic levels between ~ 10-10s and ~ 10-4 s. The time scaling method is used in addition to specific initial conditions in order to decrease the computational time. We show maps of the Poynting vector along the propagation direction as a function of the silicon nanograin (Si-ng) concentrations. A threshold value of 1024 Si-ng m-3 is extracted below which the pump wave can propagate so that a signal amplication is possible.

  11. Electromagnetic modeling of waveguide amplifier based on Nd3+ Si-rich SiO2 layers by means of the ADE-FDTD method

    PubMed Central

    2011-01-01

    By means of ADE-FDTD method, this paper investigates the electromagnetic modelling of a rib-loaded waveguide composed of a Nd3+ doped Silicon Rich Silicon Oxide active layer sandwiched between a SiO2 bottom cladding and a SiO2 rib. The Auxilliary Differential Equations are the rate equations which govern the levels populations. The Finite Difference Time Domain (FDTD) scheme is used to solve the space and time dependent Maxwell equations which describe the electromagnetic field in a copropagating scheme of both pumping (λpump = 488 nm) and signal (λsignal = 1064 nm) waves. Such systems are characterized by extremely different specific times such as the period of electromagnetic field ~ 10-15 s and the lifetimes of the electronic levels between ~ 10-10s and ~ 10-4 s. The time scaling method is used in addition to specific initial conditions in order to decrease the computational time. We show maps of the Poynting vector along the propagation direction as a function of the silicon nanograin (Si-ng) concentrations. A threshold value of 1024 Si-ng m-3 is extracted below which the pump wave can propagate so that a signal amplication is possible. PMID:21711829

  12. Texture design for microwave dielectric (Ca0.7Nd0.3)0.87TiO3 ceramics through reactive-templated grain growth.

    PubMed

    Tani, Toshihiko; Takeuchi, Tsuguto

    2015-06-01

    Plate-like Ca 3 Ti 2 O 7 (CT) and Nd 2 Ti 2 O 7 (NT) particles were synthesized in molten salts and used as reactive templates for the preparation of highly textured (Ca 0.7 Nd 0.3 ) 0.87 TiO 3 bulk ceramics (CNT) with preferred pseudocubic 〈100〉 and 〈110〉 orientations, respectively. During flux growth CT and NT particles developed facets parallel to the pseudocubic {100} and {110} planes, respectively, in a perovskite unit cell, since those planes correspond to the interlayers of the layered perovskite-type crystal structures. Complementary reactants for the CNT stoichiometry were wet-mixed with the reactive templates and the slurries were tape-cast. Then stacked tapes were heat-treated for dense single-phase CNT ceramics with a distorted and A-site deficient regular perovskite-type structure. The CNT ceramics prepared with CT and NT reactive templates exhibited strong pseudocubic 100- and 110-family x-ray diffraction peaks, respectively, with other peaks drastically suppressed when non-perovskite sources were used as complementary reactants. The textured ceramics possess unique microstructures; as either parallel or obliquely stacked block structures with a pseudocubic {100} plane faceted. The pseudocubic {100}-and {110}-textured CNT ceramics exhibited ∼10 and ∼20% higher products of the dielectric quality factor and frequency, Q · f , respectively, than conventional ceramic sintered at the same temperature. When Q · f is compared based on the same grain size, the {100}-textured CNT exhibited 27% higher values than non-textured while relative permittivity and temperature coefficient of resonant frequency were of similar values. Simple geometrical relationships between electric field and penetrated pseudocubic { hk 0}-type grain boundaries must lead to the reduced scattering and dielectric loss.

  13. Texture design for microwave dielectric (Ca0.7Nd0.3)0.87TiO3 ceramics through reactive-templated grain growth

    PubMed Central

    Tani, Toshihiko; Takeuchi, Tsuguto

    2015-01-01

    Plate-like Ca3Ti2O7 (CT) and Nd2Ti2O7 (NT) particles were synthesized in molten salts and used as reactive templates for the preparation of highly textured (Ca0.7Nd0.3)0.87TiO3 bulk ceramics (CNT) with preferred pseudocubic 〈100〉 and 〈110〉 orientations, respectively. During flux growth CT and NT particles developed facets parallel to the pseudocubic {100} and {110} planes, respectively, in a perovskite unit cell, since those planes correspond to the interlayers of the layered perovskite-type crystal structures. Complementary reactants for the CNT stoichiometry were wet-mixed with the reactive templates and the slurries were tape-cast. Then stacked tapes were heat-treated for dense single-phase CNT ceramics with a distorted and A-site deficient regular perovskite-type structure. The CNT ceramics prepared with CT and NT reactive templates exhibited strong pseudocubic 100- and 110-family x-ray diffraction peaks, respectively, with other peaks drastically suppressed when non-perovskite sources were used as complementary reactants. The textured ceramics possess unique microstructures; as either parallel or obliquely stacked block structures with a pseudocubic {100} plane faceted. The pseudocubic {100}-and {110}-textured CNT ceramics exhibited ∼10 and ∼20% higher products of the dielectric quality factor and frequency, Q · f, respectively, than conventional ceramic sintered at the same temperature. When Q · f is compared based on the same grain size, the {100}-textured CNT exhibited 27% higher values than non-textured while relative permittivity and temperature coefficient of resonant frequency were of similar values. Simple geometrical relationships between electric field and penetrated pseudocubic {hk0}-type grain boundaries must lead to the reduced scattering and dielectric loss. PMID:27877809

  14. Shielding properties of 80TeO2-5TiO2-(15-x) WO3-xAnOm glasses using WinXCom and MCNP5 code

    NASA Astrophysics Data System (ADS)

    Dong, M. G.; El-Mallawany, R.; Sayyed, M. I.; Tekin, H. O.

    2017-12-01

    Gamma ray shielding properties of 80TeO2-5TiO2-(15-x) WO3-xAnOm glasses, where AnOm is Nb2O5 = 0.01, 5, Nd2O3 = 3, 5 and Er2O3 = 5 mol% have been achieved. Shielding parameters; mass attenuation coefficients, half value layers, and macroscopic effective removal cross section for fast neutrons have been computed by using WinXCom program and MCNP5 Monte Carlo code. In addition, by using Geometric Progression method (G-P), exposure buildup factor values were also calculated. Variations of shielding parameters are discussed for the effect of REO addition into the glasses and photon energy.

  15. Structural properties and sensing performance of high-k Nd2TiO5 thin layer-based electrolyte-insulator-semiconductor for pH detection and urea biosensing.

    PubMed

    Pan, Tung-Ming; Lin, Jian-Chi; Wu, Min-Hsien; Lai, Chao-Sung

    2009-05-15

    For high sensitive pH sensing, an electrolyte-insulator-semiconductor (EIS) device with Nd(2)TiO(5) thin layers fabricated on Si substrates by means of reactive sputtering and the subsequent post-deposition annealing (PDA) treatment was proposed. In this work, the effect of thermal annealing (600, 700, 800, and 900 degrees C) on the structural characteristics of Nd(2)TiO(5) thin layer was investigated by X-ray diffraction, X-ray photoelectron spectroscopy, and atomic force microscopy. The observed structural properties were then correlated with the resulting pH sensing performances. For enzymatic field-effect-transistors-based urea biosensing, a hybrid configuration of the proposed Nd(2)TiO(5) thin layer with urease-immobilized alginate film attached was established. Within the experimental conditions investigated, the EIS device with the Nd(2)TiO(5) thin layer annealed at 800 degrees C exhibited a higher pH detection sensitivity of 57.2 mV/pH, a lower hysteresis voltage of 2.33 mV, and a lower drift rate of 1.80 mV/h compared to those at other annealing temperatures. These results are attributed to the formation of a thinner low-k interfacial layer at the oxide/Si interface and the higher surface roughness occurred at this annealing temperature. Furthermore, the presented urea biosensor was also proved to be able to detect urea with good linearity (R(2)=0.99) and reasonable sensitivity of 9.52 mV/mM in the urea concentration range of 3-40 mM. As a whole, the present work has provided some fundamental data for the use of Nd(2)TiO(5) thin layer for EIS-based pH detection and the extended application for biosensing.

  16. Characterization of Surface and Bulk Nitrates of γ-Al2O3-Supported Alkaline Earth Oxides using Density Functional Theory

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

    Mei, Donghai; Ge, Qingfeng; Kwak, Ja Hun

    2009-05-14

    “Surface" and "bulk" nitrates formed on a series of alkaline earth oxides (AEOs), AE(NO3)2, were investigated using first-principles density functional theory calculations. The formation of these surface and bulk nitrates was modeled by the adsorption of NO2+NO3 pairs on gamma-Al2O3-supported monomeric AEOs (MgO, CaO, SrO, and BaO) and on the extended AEO(001) surfaces, respectively. The calculated vibrational frequencies of the surface and bulk nitrates based on our proposed models are in good agreement with experimental measurements of AEO/gamma-Al2O3 materials after prolonged NO2 exposure. This indicates that experimentally observed "surface" nitrates are most likely formed with isolated two dimensional (including monomeric)more » AEO clusters on the gamma-Al2O3 substrate, while the "bulk" nitrates are formed on exposed (including (001)) surfaces (and likely in the bulk as well) of large three dimensional AEO particles supported on the gamma-Al2O3 substrate. Also in line with the experiments, our calculations show that the low and high frequency components of the vibrations for both surface and bulk nitrates are systematically red shifted with the increasing basicity and cationic size of the AEOs. The adsorption strengths of NO2+NO3 pairs are nearly the same for the series of alumina-supported monomeric AEOs, while the adsorption strengths of NO2+NO3 pairs on the AEO surfaces increase in the order of MgO < CaO < SrO ~ BaO. Compared to the NO2+NO3 pair that only interacts with monomeric AEOs, the stability of NO2+NO3 pairs that interact with both the monomeric AEO and the gamma-Al2O3 substrate is enhanced by about 0.5 eV. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.« less

  17. Optical absorption and photoluminescence properties of Nd3+ doped mixed alkali phosphate glasses-spectroscopic investigations.

    PubMed

    Ratnakaram, Y C; Srihari, N V; Kumar, A Vijaya; Naidu, D Thirupathi; Chakradhar, R P S

    2009-02-01

    Spectroscopic investigations were performed on 68NH(4)H(2)PO(4).xLi(2)CO(3)(30-x)K(2)CO(3) and 68NH(4)H(2)PO(4).xNa(2)CO(3)(30-x)K(2)CO(3) (where x=5, 10, 15, 20 and 25) glasses containing 2 mol% Nd(2)O(3). Various spectroscopic parameters (Racah (E(1), E(2), E(3)), spin-orbit (xi(4f)) and configuration interaction (alpha)) are reported. Judd-Ofelt intensity parameters (Omega(2), Omega(4), Omega(6)) are calculated for Nd(3+) doped two mixed alkali phosphate glass matrices. From the magnitude of Judd-Ofelt parameters, covalency is studied as a function of x in the glass matrix. Using Judd-Ofelt intensity parameters, total radiative transition probabilities (A(T)), radiative lifetimes (tau(R)), branching ratios (beta) and integrated absorption cross sections (Sigma) have been computed for certain excited states of Nd(3+) in these mixed alkali phosphate glasses. Emission cross sections (sigma(P)) are calculated for the two transitions, (4)G(7/2)-->(4)I(11/2) and (4)G(7/2)-->(4)I(13/2) of Nd(3+) in these mixed alkali phosphate glasses. Optical band gaps (E(opt)) for direct and indirect transitions are reported.

  18. Efficient Nd3+→Yb3+ energy transfer processes in high phonon energy phosphate glasses for 1.0 μm Yb3+ laser

    NASA Astrophysics Data System (ADS)

    Rivera-López, F.; Babu, P.; Basavapoornima, Ch.; Jayasankar, C. K.; Lavín, V.

    2011-06-01

    Efficient Nd3+→Yb3+ resonant and phonon-assisted energy transfer processes have been observed in phosphate glasses and have been studied using steady-state and time-resolved optical spectroscopies. Results indicate that the energy transfer occurs via nonradiative electric dipole-dipole processes and is enhanced with the concentration of Yb3+ acceptor ions, having an efficiency higher than 75% for the glass doped with 1 mol% of Nd2O3 and 4 mol% of Yb2O3. The luminescence decay curves show a nonexponential character and the energy transfer microscopic parameter calculated with the Inokuti-Hirayama model gives a value of 240 × 10-40 cm6 s-1, being one of the highest reported in the literature for Nd3+-Yb3+ co-doped matrices. From the steady-state experimental absorption and emission cross-sections, a general expression for estimating the microscopic energy transfer parameter is proposed based upon the theoretical methods developed by Miyakawa and Dexter and Tarelho et al. This expression takes into account all the resonant mechanisms involved in an energy transfer processes together with other phonon-assisted nonvanishing overlaps. The value of the Nd3+→Yb3+ energy transfer microscopic parameter has been calculated to be 200 × 10-40 cm6 s-1, which is in good agreement with that obtained from the Inokuti-Hirayama fitting. These results show the importance of the nonresonant phonon-assisted Nd3+→Yb3+ energy transfer processes and the great potential of these glasses as active matrices in the development of multiple-pump-channel Yb3+ lasers.

  19. Electronic structure of the indium tin oxide/nanocrystalline anatase (TiO2)/ruthenium-dye interfaces in dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Lyon, J. E.; Rayan, M. K.; Beerbom, M. M.; Schlaf, R.

    2008-10-01

    The electronic structure of two interfaces commonly found in dye-sensitized photovoltaic cells based on nanocrystalline anatase TiO2 ("Grätzel cells") was investigated using photoemission spectroscopy (PES). X-ray photoemission spectroscopy (XPS) and ultraviolet photoemission spectroscopy (UPS) measurements were carried out on the indium tin oxide (ITO)/TiO2 and the TiO2/cis-bis(isothiocyanato)bis(2,2'-bipyridyl-4,4'-dicarboxylato)-ruthenium(II)bis-tetrabutylammonium dye ("N719" or "Ruthenium 535-bisTBA") interfaces. Both contacts were investigated using a multistep deposition procedure where the entire structure was prepared in vacuum using electrospray deposition. In between deposition steps the surface was characterized with XPS and UPS resulting in a series of spectra, allowing the determination of the orbital and band lineup at the interfaces. The results of these efforts confirm previous PES measurements on TiO2/dye contacts prepared under ambient conditions, suggesting that ambient contamination might not have significant influence on the electronic structure at the dye/TiO2 interface. The results also demonstrate that there may be a significant barrier for electron injection at the sputtered ITO/TiO2 interface and that this interface should be viewed as a semiconductor heterojunction rather than as metal-semiconductor (Schottky) contact.

  20. Structural, thermal, optical, and photoacoustic study of nanocrystalline Bi{sub 2}Te{sub 3} produced by mechanical alloying

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

    Souza, S. M.; Triches, D. M.; Poffo, C. M.

    2011-01-01

    Nanocrystalline Bi{sub 2}Te{sub 3} was produced by mechanical alloying and its properties were investigated by differential scanning calorimetry (DSC) x-ray diffraction (XRD), Raman spectroscopy (RS), and photoacoustic spectroscopy (PAS). Combining the XRD and RS results, the volume fraction of the interfacial component in as-milled and annealed samples was estimated. The PAS results suggest that the contribution of the interfacial component to the thermal diffusivity of nanostructured Bi{sub 2}Te{sub 3} is very significant.