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Sample records for doped ceo2 ceramics

  1. Bioactivity of Y2O3 and CeO2 doped SiO2-SrO-Na2O glass-ceramics.

    PubMed

    Placek, L M; Keenan, T J; Wren, A W

    2016-08-01

    The bioactivity of yttrium and cerium are investigated when substituted for Sodium (Na) in a 0.52SiO2-0.24SrO-0.24-xNa2O-xMO glass-ceramics (where x = 0.08 and MO = Y2O3 or CeO2). Bioactivity is monitored through pH and inductively coupled plasma-optical emission spectrometry where pH of simulated body fluid ranged from 7.5 to 7.6 and increased between 8.2 and 10.0 after 14-day incubation with the glass-ceramic disks. Calcium (Ca) and phosphorus (P) levels in simulated body fluid after incubation with yttrium and cerium containing disks show a continual decline over the 14-day period. In contrast, Con disks (not containing yttrium or cerium) caused the elimination of Ca in solution after 1 day and throughout the incubation period, and initially showed a decline in P levels followed by an increase at 14 days. Scanning electron microscopy and energy dispersive spectroscopy confirmed the presence of Ca and P on the surface of the simulated body fluid-incubated disks and showed precipitates on Con and HCe (8 mol% cerium) samples. Cell viability of MC3T3 osteoblasts was not significantly affected at a 9% extract concentration. Optical microscopy after 24 h cell incubation with disks showed that Con samples do not support osteoblast or Schwann cell growth, while all yttrium and cerium containing disks have direct contact with osteoblasts spread across the wells. Schwann cells attached in all wells, but only showed spreading with the HY-S (8 mol% yttrium, heated to sintering temperature) and YCe (4 mol% yttrium and cerium) disks. Scanning electron microscopy of the compatible disks shows osteoblast and sNF96.2 Schwann cells attachment and spreading directly on the disk surfaces. PMID:27231265

  2. Origin of enhanced photocatalytic activity of F-doped CeO2 nanocubes

    NASA Astrophysics Data System (ADS)

    Miao, Hui; Huang, Gui-Fang; Liu, Jin-Hua; Zhou, Bing-Xin; Pan, Anlian; Huang, Wei-Qing; Huang, Guo-Fang

    2016-05-01

    CeO2 nanoparticles are synthesized using a low-temperature solution combustion method and subsequent heat treatment in air. It is found that F-doping leads to smaller particle size and the formation of CeO2 nanocubes with higher percentage of reactive facets exposed. The band gap is estimated to be 3.16 eV and 2.88 eV, for pure CeO2 and fluorine doped CeO2 (F-doped CeO2) nanocubes, respectively. The synthesized F-doped CeO2 nanocubes exhibit much higher photocatalytic activities than commercial TiO2 and spherical CeO2 for the degradation of MB dye under UV and visible light irradiation. The apparent reaction rate constant k of MB decomposition over the optimized F-doped CeO2 nanocubes is 9.5 times higher than that of pure CeO2 and 2.2 times higher than that of commercial TiO2. The enhanced photocatalytic activity of F-doped CeO2 nanocubes originates from the fact that F-doping induces the small size, the highly reactive facets exposed, the intense absorption in the UV-vis range and the narrowing of the band gap. This research provides some new insights for the synthesis of the doping of the foreign atoms into photocatalyst with controlled morphology and enhanced photocatalytic activity.

  3. Role of vacancies, light elements and rare-earth metals doping in CeO2.

    PubMed

    Shi, H; Hussain, T; Ahuja, R; Kang, T W; Luo, W

    2016-01-01

    The magnetic properties and electronic structures of pure, doped and defective cerium oxide (CeO2) have been studied theoretically by means of ab initio calculations based on the density function theory (DFT) with the hybrid HF/DFT technique named PBE0. Carbon (C), nitrogen (N), phosphorus (P), sulphur (S), lanthanum (La) and praseodymium (Pr) doped in CeO2 and CeO2 containing oxygen vacancies (Ov) were considered. Our spin-polarized calculations show that C, N, Pr dopants and Ov defects magnetize the non-magnetic CeO2 in different degree. The optical band gap related to photocatalysis for pure CeO2, corresponding to the ultraviolet region, is reduced obviously by C, N, S, Pr impurities and oxygen vacancies, shifting to the visible region and even further to the infrared range. Especially, N-, S- and Pr-doped CeO2 could be used to photocatalytic water splitting for hydrogen production. As the concentration of Ov increasing up to 5%, the CeO2 exhibits a half-metallic properties. PMID:27554285

  4. Role of vacancies, light elements and rare-earth metals doping in CeO2

    PubMed Central

    Shi, H.; Hussain, T.; Ahuja, R.; Kang, T. W.; Luo, W.

    2016-01-01

    The magnetic properties and electronic structures of pure, doped and defective cerium oxide (CeO2) have been studied theoretically by means of ab initio calculations based on the density function theory (DFT) with the hybrid HF/DFT technique named PBE0. Carbon (C), nitrogen (N), phosphorus (P), sulphur (S), lanthanum (La) and praseodymium (Pr) doped in CeO2 and CeO2 containing oxygen vacancies (Ov) were considered. Our spin-polarized calculations show that C, N, Pr dopants and Ov defects magnetize the non-magnetic CeO2 in different degree. The optical band gap related to photocatalysis for pure CeO2, corresponding to the ultraviolet region, is reduced obviously by C, N, S, Pr impurities and oxygen vacancies, shifting to the visible region and even further to the infrared range. Especially, N-, S- and Pr-doped CeO2 could be used to photocatalytic water splitting for hydrogen production. As the concentration of Ov increasing up to 5%, the CeO2 exhibits a half-metallic properties. PMID:27554285

  5. Structural and dielectric properties of Cu doped CeO2

    NASA Astrophysics Data System (ADS)

    Kumar, Pawan; Chand, F.; Kumar, Parmod; Meena, R. C.; Kumar, Ashish; Asokan, K.

    2016-05-01

    In the present work, we report the structural and dielectric properties of Cu doped CeO2 compounds synthesized by solid state reaction method. X-ray diffraction study confirms the formation of cubic phase with Fm-3m space group corresponding to fluorite CeO2 structure. The crystallite size was found to decrease with Cu concentration. Furthermore, the dielectric measurements were carried out by varying frequency in the temperature range of 120 to 380 K. It has been found that the increase in Cu concentration in the host lattice leads to an enhancement in dielectric constant.

  6. A dipole polarizable potential for reduced and doped CeO(2) obtained from first principles.

    PubMed

    Burbano, Mario; Marrocchelli, Dario; Yildiz, Bilge; Tuller, Harry L; Norberg, Stefan T; Hull, Stephen; Madden, Paul A; Watson, Graeme W

    2011-06-29

    In this paper we present the parameterization of a new interionic potential for stoichiometric, reduced and doped CeO(2). We use a dipole polarizable potential (DIPPIM: the dipole polarizable ion model) and optimize its parameters by fitting them to a series of density functional theory calculations. The resulting potential was tested by calculating a series of fundamental properties for CeO(2) and by comparing them against experimental values. The values for all the calculated properties (thermal and chemical expansion coefficients, lattice parameters, oxygen migration energies, local crystalline structure and elastic constants) are within 10-15% of the experimental ones, an accuracy comparable to that of ab initio calculations. This result suggests the use of this new potential for reliably predicting atomic scale properties of CeO(2) in problems where ab initio calculations are not feasible due to their size limitations. PMID:21654047

  7. Facile synthesis of ferromagnetic Ni doped CeO2 nanoparticles with enhanced anticancer activity

    NASA Astrophysics Data System (ADS)

    Abbas, Fazal; Jan, Tariq; Iqbal, Javed; Ahmad, Ishaq; Naqvi, M. Sajjad H.; Malik, Maaza

    2015-12-01

    NixCe1-xO2 (where x = 0, 0.01, 0.03, 0.05 and 0.07) nanoparticles were synthesized by soft chemical method and were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman, UV-vis absorption spectroscopy and vibrating sample magnetometer (VSM). XRD and Raman results indicated the formation of single phase cubic fluorite structure for the synthesized nanoparticles. Ni dopant induced excessive structural changes such as decrease in crystallite size as well as lattice constants and enhancement in oxygen vacancies in CeO2 crystal structure. These structural variations significantly influenced the optical and magnetic properties of CeO2 nanoparticles. The synthesized NixCe1-xO2 nanoparticles exhibited room temperature ferromagnetic behavior. Ni doping induced effects on the cytotoxicity of CeO2 nanoparticles were examined against HEK-293 healthy cell line and SH-SY5Y neuroblastoma cancer cell line. The prepared NixCe1-xO2 nanoparticles demonstrated differential cytotoxicity. Furthermore, anticancer activity of CeO2 nanoparticles observed to be significantly enhanced with Ni doping which was found to be strongly correlated with the level of reactive oxygen species (ROS) production. The prepared ferromagnetic NixCe1-xO2 nanoparticles with differential cytotoxic nature may be potential for future targeted cancer therapy.

  8. Effect of poling process on piezoelectric properties of BCZT - 0.08 wt.% CeO2 lead-free ceramics

    NASA Astrophysics Data System (ADS)

    Chandrakala, E.; Praveen, J. Paul; Das, Dibakar

    2016-05-01

    The properties of lead free piezoelectric materials can be tuned by suitable doping in the A and B sites of the perovskite structure. In the present study, cerium has been identified as a dopant to investigate the piezoelectric properties of lead-free BCZT system. BCZT - 0.08 wt.%CeO2 lead-free ceramics have been synthesized using sol-gel technique and the effects of CeO2 dopant on their phase structure and piezoelectric properties were investigated systematically. Poling conditions, such as temperature, electric field, and poling time have been optimized to get enhanced piezoelectric response. The optimized poling conditions (50°C, 3Ec and 30min) resulted in high piezoelectric charge coefficient d33 ~ 670pC/N, high electromechanical coupling coefficient kp ~ 60% and piezoelectric voltage coefficient g33 ~ 14 mV.m/N for BCZT - 0.08wt.% CeO2 ceramics.

  9. A facile synthesis of high quality nanostructured CeO2 and Gd2O3-doped CeO2 solid electrolytes for improved electrochemical performance.

    PubMed

    Kuo, Yu-Lin; Su, Yu-Ming; Chou, Hung-Lung

    2015-06-01

    This study describes the use of a composite nitrate salt solution as a precursor to synthesize CeO2 and Gd2O3-doped CeO2 (GDC) nanoparticles (NPs) using an atmospheric pressure plasma jet (APPJ). The microstructures of CeO2 and GDC NPs were found to be cubical and spherical shaped nanocrystallites with average particle sizes of 10.5 and 6.7 nm, respectively. Reactive oxygen species, detected by optical emission spectroscopy (OES), are believed to be the major oxidative agents for the formation of oxide materials in the APPJ process. Based on the material characterization and OES observations, the study effectively demonstrated the feasibility of preparing well-crystallized GDC NPs by the APPJ system as well as the gas-to-particle mechanism. Notably, the Bader charge of CeO2 and Ce0.9Gd0.1O2 characterized by density function theory (DFT) simulation and AC impedance measurements shows that Gd helps in increasing the charge on Ce0.9Gd0.1O2 NPs, thus improving their conductivity and making them candidate materials for electrolytes in solid oxide fuel cells. PMID:25959436

  10. Photoluminescent properties of Eu3+ doped electrospun CeO2 nanofibers

    NASA Astrophysics Data System (ADS)

    Fang, Dong; Zhang, Min; Luo, Zhiping; Cao, Tingting; Wang, Qing; Zhou, Zhi; Jiang, Ming; Xiong, Chuanxi

    2014-12-01

    In this study, CeO2 nanofibers and that doped with Eu3+ were prepared via a facile electrospinning route and annealed at different temperatures ranging from 500 to 900 °C. Their structures were investigated using X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Photoluminescence properties of the nanofibers were studied in detail. It was found that the nanofibers with Eu% concentration of 0.67 mol.% and annealed at 700 °C exhibited the highest intensities of the luminescence peaks between 550 and 650 nm.

  11. Loss of magnetization induced by doping in CeO2 films

    NASA Astrophysics Data System (ADS)

    Fernandes, V.; Schio, P.; de Oliveira, A. J. A.; Schreiner, W. H.; Varalda, J.; Mosca, D. H.

    2011-12-01

    This work reports the effect of Mn, Fe, Co, and Cu low doping (˜3 at. %) on the ferromagnetic behavior of oxygen-defective CeO2-δ films electrodeposited on SiO2/Si(001). Our results indicate that the incorporation of a small number of 3d dopants with unoccupied outermost atomic orbitals, presumably magnetically active, strongly perturb the ferromagnetic ground-state associated with the network of electron clouds surrounding oxygen vacancies. As a consequence, a strong loss of magnetization occurs and saturation magnetization becomes uncorrelated with number of oxygen vacancies.

  12. Catalytic propane reforming mechanism over Mn-Doped CeO2 (111)

    NASA Astrophysics Data System (ADS)

    Krcha, Matthew D.; Janik, Michael J.

    2015-10-01

    MnOx/CeOx mixed oxide systems exhibit encouraging hydrocarbon oxidation activity, without the inclusion of a noble metal. Using density functional theory (DFT) methods, we examined the oxidative reforming path of propane over the Mn-doped CeO2 (1 1 1) surface. A plausible set of elementary reaction steps are identified for conversion of propane to CO/CO2 and H2/H2O over the oxide surface. The rate-limiting reaction process may vary with redox conditions, with C-H dissociation limiting under more oxidizing conditions and more complex reaction sequences, including surface re-oxidation, limiting under highly reducing conditions. The possibility of intermediate desorption from the surface during the reforming process is low, with desorption energies of the intermediates being much less favorable than further surface reactions until CO/CO2 products are formed. The reforming paths over Mn-doped ceria are similar to those previously identified over Zr-doped ceria. The extent of surface reduction and the electronic structure of the surface intermediates are examined.

  13. Infrared and visible emissions of rare-earth-doped CeO2 phosphor.

    PubMed

    Chandrakar, D; Kaur, J; Dubey, V; Suryanarayana, N S; Parganiha, Y

    2015-12-01

    This paper reports the synthesis and characterization of Er(3+)-doped CeO2 phosphor with variable concentrations of erbium. The sample was synthesized using a solid-state reaction method, which is useful for the large-scale production of phosphors and is also eco-friendly. The prepared sample was characterized using an X-ray diffraction (XRD) technique. The XRD pattern confirmed that sample has the pure cubic fluorite crystal structure of CeO2. The crystallite size of the prepared phosphor was determined by Scherer's formula and the crystallite size giving an intense XRD peak is 40.06 nm. The surface morphology of the phosphor was determined by field emission gun scanning electron microscopy (FEGSEM). From the FEGSEM image, good surface morphology with some agglomerates was found. The functional group in the prepared sample was analysed by Fourier transform infrared (FTIR) spectroscopy. All samples prepared with variable concentrations of Er(3+) (0.1-2 mol%) were studied by photoluminescence analysis and it was found that the excitation spectra of the prepared phosphor shows broad excitation centred at 251 nm. Emission spectra at different concentrations of Er(3+) show strong peaks at 413 and 470 nm and a weaker peak at 594 nm. The dominant peaks at 413 and 470 nm are caused by the allowed electronic transition (4)S3/2 → (4)I15/2 and the weaker transition at 594 nm is due to the transition (4)F9/2 → (4)I15/2. Spectrophotometric determinations of peaks were evaluated using the Commission Internationale de I'Eclairage (CIE) technique. The emission spectra were also observed using an infrared (IR) laser 980 nm source, and three distinct peaks were found in the IR region at 848, 870 and 980 nm. The prepared phosphor has utility for application in display devices. PMID:25810371

  14. Electroluminescence from metal-oxide-semiconductor devices with erbium-doped CeO2 films on silicon

    NASA Astrophysics Data System (ADS)

    Lv, Chunyan; Zhu, Chen; Wang, Canxing; Gao, Yuhan; Ma, Xiangyang; Yang, Deren

    2015-04-01

    We report on erbium (Er)-related electroluminescence (EL) in the visible and near-infrared (NIR) from metal-oxide-semiconductor (MOS) devices with Er-doped CeO2 (CeO2:Er) films on silicon. The onset voltage of such EL under either forward or reverse bias is smaller than 10 V. Moreover, the EL quenching can be avoidable for the CeO2:Er-based MOS devices. Analysis on the current-voltage characteristic of the device indicates that the electron transportation at the EL-enabling voltages under either forward or reverse bias is dominated by trap-assisted tunneling mechanism. Namely, electrons in n+-Si/ITO can tunnel into the conduction band of CeO2 host via defect states at sufficiently high forward/reverse bias voltages. Then, a fraction of such electrons are accelerated by electric field to become hot electrons, which impact-excite the Er3+ ions, thus leading to characteristic emissions. It is believed that this work has laid the foundation for developing viable silicon-based emitters using CeO2:Er films.

  15. Mg Doping Induced Effects on Structural, Optical, and Electrical Properties as Well as Cytotoxicity of CeO2 Nanostructures

    NASA Astrophysics Data System (ADS)

    Iqbal, Javed; Jan, Tariq; Awan, M. S.; Naqvi, Sajjad Haider; Badshah, Noor; ullah, Asmat; Abbas, Fazzal

    2016-04-01

    Here, Mg x Ce1- x O2 (where x = 0, 0.01, 0.02, 0.03, 0.04, and 0.05) nanostructures have been successfully synthesized by using a simple, easy, and cost-effective soft chemical method. X-ray diffraction (XRD) patterns substantiate the single-phase formation of a CeO2 cubic fluorite structure for all samples. Infrared spectroscopy results depict the presence of peaks only related to Ce-O bonding, which confirms the XRD results. It has been observed via ultraviolet (UV)-visible spectroscopy that Mg doping has tuned the optical band gap of CeO2 significantly. The electrical conductivity of CeO2 nanostructures has been found to increase with Mg doping, which is attributed to enhancement in carrier concentration due to the different valance states of dopant and host ions. Selective cytotoxic behavior of Mg x Ce1- x O2 nanostructures has been determined for neuroblastoma (SH-SY5Y) cancerous and HEK-293 healthy cells. Both doped and undoped CeO2 nanostructures have been found to be toxic for cancer cells and safe toward healthy cells. This selective toxic behavior of the synthesized nanostructures has been assigned to the different levels of reactive oxygen species (ROS) generation in different types of cells. This makes the synthesized nanostructures a potential option for cancer therapy in the near future.

  16. Effect of Doping on Surface Reactivity and Conduction Mechanism in Sm-doped CeO2 Thin Films

    DOE PAGESBeta

    Yang, Nan; Belianinov, Alex; Strelcov, Evgheni; Tebano, Antonello; Daniele, Di Castro; Schlueter, Christoph; Lee, Tien-Lin; Baddorf, Arthur P.; Wisinger, Nina; Jesse, Stephen; et al

    2014-11-21

    Scanning probe microscopy measurements show irreversible surface electrochemistry in Sm-doped CeO2 thin films, which depends on humidity, temperature and doping concentration. A systematic study by electrochemical strain microscopy (ESM) in samples with two different Sm content and in several working conditions allows disclosing the microscopic mechanism underlying the difference in water adsorption and splitting with subsequent proton liberation. We measure the behavior of the hysteresis loops by changing temperature and humidity, both in standard ESM configuration and using the first order reversal curve (FORC) method. Complementing our study with spectroscopic measurements by hard x-ray photoemission spectroscopy we find that watermore » incorporation is favored until the doping with Sm is too high to allow the presence of Ce3+. The influence of doping on the surface reactivity and conduction mechanism clearly emerges from all of our experimental results. We find that at lower Sm concentration proton conduction is prevalent, featured by lower activation energy and higher mobility. Defect concentrations determine the type of the prevalent charge carrier in a doping dependent manner.« less

  17. Effect of Doping on Surface Reactivity and Conduction Mechanism in Sm-doped CeO2 Thin Films

    SciTech Connect

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

    2014-11-21

    Scanning probe microscopy measurements show irreversible surface electrochemistry in Sm-doped CeO2 thin films, which depends on humidity, temperature and doping concentration. A systematic study by electrochemical strain microscopy (ESM) in samples with two different Sm content and in several working conditions allows disclosing the microscopic mechanism underlying the difference in water adsorption and splitting with subsequent proton liberation. We measure the behavior of the hysteresis loops by changing temperature and humidity, both in standard ESM configuration and using the first order reversal curve (FORC) method. Complementing our study with spectroscopic measurements by hard x-ray photoemission spectroscopy we find that water incorporation is favored until the doping with Sm is too high to allow the presence of Ce3+. The influence of doping on the surface reactivity and conduction mechanism clearly emerges from all of our experimental results. We find that at lower Sm concentration proton conduction is prevalent, featured by lower activation energy and higher mobility. Defect concentrations determine the type of the prevalent charge carrier in a doping dependent manner.

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

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

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

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

    PubMed

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

    2015-01-01

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

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

    DOE PAGESBeta

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

    2015-10-08

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

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

    PubMed Central

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

    2015-01-01

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

  2. Structure and growth morphology of Gd 2O 3-doped CeO 2 thin films

    NASA Astrophysics Data System (ADS)

    Jiang, Xuening; Hao, Binkui

    2010-05-01

    Gd 2O 3-doped CeO 2 (Gd 0.1Ce 0.9O 1.95, GDC) thin films were synthesized on (1 0 0) Si single crystal substrates by a reactive radio frequency magnetron sputtering technique. Structures and surface morphologies were characterized by X-ray diffraction (XRD), Atomic Force Microscopy (AFM) and one-dimensional power spectral density (1DPSD) analysis. The XRD patterns indicated that, in the temperature range of 200-700 °C, f.c.c. structured GDC thin films were formed with growth orientations varying with temperature—random growth at 200 °C, (2 2 0) textures at 300-600 °C and (1 1 1) texture at 700 °C. GDC film synthesized at 200 °C had the smoothest surface with roughness of Rrms=0.973 nm. Its 1DPSD plot was characterized with a constant part at the low frequencies and a part at the high frequencies that could be fitted by the f-2.4 power law decay. Such surface feature and scaling behavior were probably caused by the high deposition rate and random growth in the GDC film at this temperature. At higher temperatures (300-700 °C), however, an intermediate frequency slope (- γ2≈-2) appeared in the 1DPSD plots between the low frequency constant part and the high frequency part fitted by f-4 power law decay, which indicated a roughing mechanism dominated by crystallographic orientation growth that caused much rougher surfaces in GDC films ( Rrms>4 nm).

  3. NO reduction by CO over CuO supported on CeO2-doped TiO2: the effect of the amount of a few CeO2.

    PubMed

    Deng, Changshun; Li, Bin; Dong, Lihui; Zhang, Feiyue; Fan, Minguang; Jin, Guangzhou; Gao, Junbin; Gao, Liwen; Zhang, Fei; Zhou, Xinpeng

    2015-06-28

    This work is mainly focused on the investigation of the influence of the amount of a few CeO2 on the physicochemical and catalytic properties of CeO2-doped TiO2 catalysts for NO reduction by a CO model reaction. The obtained samples were characterized by means of XRD, N2-physisorption (BET), LRS, UV-vis DRS, XPS, (O2, CO, and NO)-TPD, H2-TPR, in situ FT-IR, and a NO + CO model reaction. These results indicate that a small quantity of CeO2 doping into the TiO2 support will cause an obvious change in the properties of the catalyst and the TC-60 : 1 (the TiO2/CeO2 molar ratio is 60 : 1) support exhibits the most extent of lattice expansion, which indicates that the band lengths of Ce-O-Ti are longer than other TC (the solid solution of TiO2 and CeO2) samples, probably contributing to larger structural distortion and disorder, more defects and oxygen vacancies. Copper oxide species supported on TC supports are much easier to be reduced than those supported on the pure TiO2 and CeO2 surface-modified TiO2 supports. Furthermore, the Cu/TC-60 : 1 catalyst shows the highest activity and selectivity due to more oxygen vacancies, higher mobility of surface and lattice oxygen at lower temperature (which contributes to the regeneration of oxygen vacancies, and the best reducing ability), the most content of Cu(+), and the strongest synergistic effect between Ti(3+), Ce(3+) and Cu(+). On the other hand, the CeO2 doping into TiO2 promotes the formation of a Cu(+)/Cu(0) redox cycle at high temperatures, which has a crucial effect on N2O reduction. Finally, in order to further understand the nature of the catalytic performances of these samples, taking the Cu/TC-60 : 1 catalyst as an example, a possible reaction mechanism is tentatively proposed. PMID:26030478

  4. The peak effect in bulk Y-Ba-Cu-O superconductor with CeO2 doping by the infiltration growth method

    NASA Astrophysics Data System (ADS)

    Chen, Po-Wei; Chen, In-Gann; Chen, Shih-Yun; Wu, Maw-Kuen

    2011-08-01

    In this study, large single grain Y-Ba-Cu-O (YBCO) superconductors with CeO2 addition were fabricated by the infiltration and growth (IG) technique. It is noticeable that the CeO2 doped IG-YBCO sample showed a superior critical current density Jc(H, T) with a peak effect. The Jc (3 T, 65 K) of the IG-YBCO sample with CeO2 addition reached 105 A cm - 2, which was two times higher than that of the CeO2 doped top-seeded melt texture (TSMT)-YBCO sample. Microstructure analysis indicated that the concentration of Sm in the CeO2 doped IG-YBCO sample was 0.2 mol%. The Sm which dissolved from the SmBCO seed diffused into the bulk to form compositional fluctuations of (Y, Sm)BCO and was correlated to the effective pinning in high field regions (or peak effect) to improve the Jc(H, T) in high fields. In addition, the maximum trapped field value of 0.23 T and trapped field profile of the CeO2 doped sample grown by IG are larger than that of 0.13 T grown by TSMT using the same diameter of precursor pellets.

  5. Ethanol Sensor of CdO/Al2O3/CeO2 Obtained from Ce-DOPED Layered Double Hydroxides with High Response and Selectivity

    NASA Astrophysics Data System (ADS)

    Xu, Dongmei; Guan, Meiyu; Xu, Qinghong; Guo, Ying; Wang, Yao

    2013-06-01

    In this paper, Ce-doped CdAl layered double hydroxide (LDH) was first synthesized and the derivative CdO/Al2O3/CeO2 composite oxide was prepared by calcining Ce-doped CdAl LDH. The structure, morphology and chemical state of the Ce doped CdAl LDH and CdO/Al2O3/CeO2 were also investigated by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), solid state nuclear magnetic resonance (SSNMR), scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). The gas sensing properties of CdO/Al2O3/CeO2 to ethanol were further studied and compared with CdO/Al2O3 prepared from CdAl LDH, CeO2 powder as well as the calcined Ce salt. It turns out that CdO/Al2O3/CeO2 sensor shows best performance in ethanol response. Besides, CdO/Al2O3/CeO2 possesses short response/recovery time (12/72 s) as well as remarkable selectivity in ethanol sensing, which means composite oxides prepared from LDH are very promising in gas sensing application.

  6. Edge dislocation slows down oxide ion diffusion in doped CeO2 by segregation of charged defects

    NASA Astrophysics Data System (ADS)

    Sun, Lixin; Marrocchelli, Dario; Yildiz, Bilge

    2015-02-01

    Strained oxide thin films are of interest for accelerating oxide ion conduction in electrochemical devices. Although the effect of elastic strain has been uncovered theoretically, the effect of dislocations on the diffusion kinetics in such strained oxides is yet unclear. Here we investigate a 1/2<110>{100} edge dislocation by performing atomistic simulations in 4-12% doped CeO2 as a model fast ion conductor. At equilibrium, depending on the size of the dopant, trivalent cations and oxygen vacancies are found to simultaneously enrich or deplete either in the compressive or in the tensile strain fields around the dislocation. The associative interactions among the point defects in the enrichment zone and the lack of oxygen vacancies in the depletion zone slow down oxide ion transport. This finding is contrary to the fast diffusion of atoms along the dislocations in metals and should be considered when assessing the effects of strain on oxide ion conductivity.

  7. Enhancement of photocatalytic properties of TiO2 nanoparticles doped with CeO2 and supported on SiO2 for phenol degradation

    NASA Astrophysics Data System (ADS)

    Hao, Chunjing; Li, Jing; Zhang, Zailei; Ji, Yongjun; Zhan, Hanhui; Xiao, Fangxing; Wang, Dan; Liu, Bin; Su, Fabing

    2015-03-01

    A series of CeO2-TiO2 and CeO2-TiO2/SiO2 composites were prepared with TiCl4 and Ce (NO3)3·6H2O as precursors via a facile co-precipitation method. The obtained samples were characterized by various techniques such as X-ray diffraction (XRD), nitrogen adsorption (N2-BET), Fourier transformation infrared spectrum (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV-Vis spectroscopy measurements. The results indicated that TiO2 doped with CeO2 and supported on SiO2 could reduce the crystallite size, inhibit the phase transformation, enhance the thermal stability, and effectively extend the spectral response from UV to visible range. When applied to the phenol photodegradation on a homemade batch reactor with an external cooling jacket, the CeO2-TiO2/SiO2 catalysts exhibited significantly enhanced photodegradation efficiency in comparison with commercial Degussa P25 and CeO2-TiO2. The unique catalytic properties of CeO2-TiO2/SiO2 were ascribed to improved electron-hole pairs separation efficiency and formation of more reactive oxygen species owing to the presence of Ce3+/Ce4+, as well as high dispersion of active component of CeO2-TiO2 as a result of the introduction of SiO2 support. Furthermore, the catalysts can be easily recovered from the reaction solution by centrifugation and reused for four cycles without significant loss of activity.

  8. Identification of the arsenic resistance on MoO3 doped CeO2/TiO2 catalyst for selective catalytic reduction of NOx with ammonia.

    PubMed

    Li, Xiang; Li, Xiansheng; Li, Junhua; Hao, Jiming

    2016-11-15

    Arsenic resistance on MoO3 doped CeO2/TiO2 catalysts for selective catalytic reduction of NOx with NH3 (NH3-SCR) is investigated. It is found that the activity loss of CeO2-MoO3/TiO2 caused by As oxide is obvious less than that of CeO2/TiO2 catalysts. The fresh and poisoned catalysts are compared and analyzed using XRD, Raman, XPS, H2-TPR and in situ DRIFTS. The results manifest that the introduction of arsenic oxide to CeO2/TiO2 catalyst not only weakens BET surface area, surface acid sites and adsorbed NOx species, but also destroy the redox circle of Ce(4+) to Ce(3+) because of interaction between Ce and As. When MoO3 is added into CeO2/TiO2 system, the main SCR reaction path are found to be changed from the reaction between coordinated NH3 and ad-NOx species to that between an amide and gaseous NO. Additionally, for CeO2-MoO3/TiO2 catalyst, As toxic effect on active sites CeO2 can be released because of stronger As-Mo interaction. Moreover, not only are the reactable Brønsted and Lewis acid sites partly restored, but the cycle of Ce(4+) to Ce(3+) can also be free to some extent. PMID:27474851

  9. A DFT+U study on the contribution of 4f electrons to oxygen vacancy formation and migration in Ln-doped CeO2.

    PubMed

    Alaydrus, M; Sakaue, M; Kasai, H

    2016-05-14

    A rare earth doped form of ceria (CeO2) is of interest as a potential candidate for solid oxide fuel cells (SOFCs) because of its relatively high oxygen ion conductivity at temperatures below 600 °C. At the present time, computational chemistry has reached a certain maturity which allows the prediction of materials properties that are difficult to observe experimentally. However, understanding of the roles of dopants in the oxygen ion conduction in CeO2 is still incomplete for quantitatively reliable analysis due to the strong electron correlation of 4f electrons. In this study, density functional theory calculations with Hubbard U corrections are used to discuss ionic/covalent interactions in rare-earth-doped CeO2 and their consequences to oxygen ion conduction. This study suggests that the variable occupancy of empty 4f orbitals is important typically for early Ln elements to produce the covalent interactions that essentially affect the formation and migration of oxygen vacancies. This finding is important in understanding the factors responsible for oxygen ion diffusion in doped CeO2. PMID:27108893

  10. Photon management properties of rare-earth (Nd,Yb,Sm)-doped CeO2 films prepared by pulsed laser deposition.

    PubMed

    Balestrieri, Matteo; Colis, Silviu; Gallart, Mathieu; Schmerber, Guy; Bazylewski, Paul; Chang, Gap Soo; Ziegler, Marc; Gilliot, Pierre; Slaoui, Abdelilah; Dinia, Aziz

    2016-01-28

    CeO2 is a promising material for applications in optoelectronics and photovoltaics due to its large band gap and values of the refractive index and lattice parameters, which are suitable for silicon-based devices. In this study, we show that trivalent Sm, Nd and Yb ions can be successfully inserted and optically activated in CeO2 films grown at a relatively low deposition temperature (400 °C), which is compatible with inorganic photovoltaics. CeO2 thin films can therefore be efficiently functionalized with photon-management properties by doping with trivalent rare earth (RE) ions. Structural and optical analyses provide details of the electronic level structure of the films and of their energy transfer mechanisms. In particular, we give evidence of the existence of an absorption band centered at 350 nm from which energy transfer to rare earth ions occurs. The transfer mechanisms can be completely explained only by considering the spontaneous migration of Ce(3+) ions in CeO2 at a short distance from the RE(3+) ions. The strong absorption cross section of the f-d transitions in Ce(3+) ions efficiently intercepts the UV photons of the solar spectrum and therefore strongly increases the potential of these layers as downshifters and downconverters. PMID:26699802

  11. Surface morphology, optical and electrochemical properties of undoped and Ni-doped CeO2 thin films prepared by polymeric precursor method

    NASA Astrophysics Data System (ADS)

    Khosousi Sani, Zara; Esmaeli Ghodsi, Farhad; Mazloom, Jamal

    2016-04-01

    In this study, undoped and Ni-doped CeO2 thin films were deposited onto glass and ITO substrates by polymeric precursor (Pechini) method. Grazing incidence X-ray diffraction analysis revealed that the ceria thin film has a cerianite structure with the average crystallite size of 14 nm while the doped samples are amorphous. X-ray photoelectron spectroscopy (XPS) confirmed the presence of predominant Ce4+ oxidation state of ceria and Ni2+ in the films. Scanning electron microscopy (SEM) micrographs showed that the surface texture is crack free and the CeO2 grains regularly distributed on the surface. Optical constant (refractive index and extinction coefficient) and thickness of films were calculated using pointwise unconstraint minimization approach. The optical transmittance increases and the absorption edge has a blue shift by Ni incorporation. The highest band gap value (i.e., 3.43 eV) was obtained for 2.5 mol.% Ni doping sample. The refractive index and extinction coefficient of ceria films were decreased by Ni doping. The evaluated thicknesses are in the range of 150-170 nm. The strength of interband transition was appraised as a function of nickel content by using dielectric function. Luminescent emission intensity of the ceria film was enhanced by Ni doping. Cyclic voltammetry (CV) measurement revealed that the total charge density and ion storage capacitance of ceria thin film were increased by Ni doping.

  12. Hydrocracking of cumene over Ni/Al 2O 3 as influenced by CeO 2 doping and γ-irradiation

    NASA Astrophysics Data System (ADS)

    El-Shobaky, G. A.; Doheim, M. M.; Ghozza, A. M.

    2004-01-01

    Cumene hydrocracking was carried out over pure and doped Ni/Al 2O 3 solids and also, on these solids after exposure to different doses of γ-rays between 0.4 and 1.6 MGy. The dopant concentration was varied between 1 and 4 mol% CeO 2. Pure and doped samples were subjected to heat treatment at 400°C and cumene hydrocracking reaction was carried out using various solids at temperatures between 250°C and 400°C by means of micropulse technique. The results showed that both CeO 2 doping and γ-irradiation of the investigated system brought about an increase in its specific surface area. γ-irradiation of pure samples increased their catalytic activities effectively. However, the doping caused a decrease in the catalytic activity. γ-irradiation of the doped samples brought about a net decrease in the catalytic activity. The catalytic reaction products over different investigated solids were ethylbenzene as a major product together with different amounts of toluene, benzene and C 1-C 3 gaseous hydrocarbons. The selectivity towards the formation of various reaction products varies with the reaction temperature, doping and γ-irradiation.

  13. Near-infrared emissions from Yb3+-doped CeO2 and Ce2Si2O7 films based on silicon substrates subjected to thermal treatment

    NASA Astrophysics Data System (ADS)

    Mu, Guangyao; Wang, Shenwei; Li, Ling; Yin, Xue; Huang, Miaoling; Yi, Lixin

    2016-05-01

    Photoluminescence properties of Yb3+-doped CeO2 films annealed in different atmospheres were investigated. CeO2:Yb3+ films were deposited by electron-beam evaporation technique. Near-infrared emission around 970 nm was observed after annealing the films both in air and in Ar-H2 atmosphere, which is attributed to the Yb3+:2F5/2 → 2F7/2 transition. Optimization of the Yb3+ concentration for the 970 nm luminescence yield was also investigated. Characterized by different methods, Ce2Si2O7 was formed in the films annealed in reducing atmosphere, which was expected to be more applicable for the silicon-based optoelectronic applications.

  14. High power density cell using nanostructured Sr-doped SmCoO3 and Sm-doped CeO2 composite powder synthesized by spray pyrolysis

    NASA Astrophysics Data System (ADS)

    Shimada, Hiroyuki; Yamaguchi, Toshiaki; Suzuki, Toshio; Sumi, Hirofumi; Hamamoto, Koichi; Fujishiro, Yoshinobu

    2016-01-01

    High power density solid oxide electrochemical cells were developed using nanostructure-controlled composite powder consisting of Sr-doped SmCoO3 (SSC) and Sm-doped CeO2 (SDC) for electrode material. The SSC-SDC nano-composite powder, which was synthesized by spray pyrolysis, had a narrow particle size distribution (D10, D50, and D90 of 0.59, 0.71, and 0.94 μm, respectively), and individual particles were spherical, composing of nano-size SSC and SDC fragments (approximately 10-15 nm). The application of the powder to a cathode for an anode-supported solid oxide fuel cell (SOFC) realized extremely fine cathode microstructure and excellent cell performance. The anode-supported SOFC with the SSC-SDC cathode achieved maximum power density of 3.65, 2.44, 1.43, and 0.76 W cm-2 at 800, 750, 700, and 650 °C, respectively, using humidified H2 as fuel and air as oxidant. This result could be explained by the extended electrochemically active region in the cathode induced by controlling the structure of the starting powder at the nano-order level.

  15. Spectroscopic study of ZnO doped CeO 2-PbO-B 2O 3 glasses

    NASA Astrophysics Data System (ADS)

    Pal Singh, Gurinder; Singh, D. P.

    2011-09-01

    Glass samples of compositions xZnO- xCeO 2-(30- x)PbO-(70- x)B 2O 3 with x varying from 2% to 10% mole fraction are prepared by the melt quench technique. The structural and optical analysis of glasses is carried out by XRD, FTIR, density and UV-visible spectroscopic measurement techniques. The FTIR spectral analysis indicates that with the addition of ZnO contents in glass network, structural units of BO 3 are transformed into BO 4. It has been observed in our previous work that band gap decreases from 2.89 to 2.30 eV for CeO 2-PbO-B 2O 3 glasses with cerium content varying from 0% to 10% [Gurinder Pal Singh, Davinder Paul Singh, Physica B 406(3) (2011) 640-644]. With the incorporation of zinc in CeO 2-PbO-B 2O 3 glasses, the optical band gap energy decreases further from 2.38 to 2.03 eV. This causes more compaction of the borate network, which results in an increase of density (3.39-4.02 g/cm 3). Transmittance shows that ZnO in glass samples acts as a reducing agent thathelps to convert Ce 4+→Ce 3+ ions.

  16. Molecular dynamics simulation of fast particle irradiation to the Gd2O3-doped CeO2

    NASA Astrophysics Data System (ADS)

    Sasajima, Y.; Ajima, N.; Osada, T.; Ishikawa, N.; Iwase, A.

    2013-12-01

    The structural relaxation caused by the high-energy-ion irradiation of CeO2 with Gd2O3 addition was simulated by the molecular dynamics method. The amount of Gd2O3 was changed from 0 to 25 mol% by 5 mol%. As the initial condition, high thermal energy was supplied to the individual atoms within a cylindrical region of nanometer-order radius located in the center of the specimen. The potential proposed by Inaba et al. was utilized to calculate interaction between atoms [H. Inaba, R. Sagawa, H. Hayashi, K. Kawamura, Solid State Ionics 122 (1999) 95-103]. The supplied thermal energy was first spent to change the crystal structure into an amorphous one within a short period of about 0.3 ps, then it dissipated in the specimen. By increasing the concentration of Gd2O3, more structural disorder was observed in the sample, which is consistent to the actual experiment.

  17. CeO2 doped anatase TiO2 with exposed (001) high energy facets and its performance in selective catalytic reduction of NO by NH3

    NASA Astrophysics Data System (ADS)

    Wang, Haiqiang; Cao, Shuang; Fang, Zheng; Yu, Feixiang; Liu, Yue; Weng, Xiaole; Wu, Zhongbiao

    2015-03-01

    Ceria doped on anatase TiO2 with high energy (001) facets was synthesized in this paper, which was subsequently utilized for selective catalytic reduction (SCR) of NO by NH3. After subjected to a range of analytical techniques, such as XRD, BET, TEM, XPS ESR, H2-TPR and NH3-TPD, it was found that compared with Ce/P25 catalyst, the presence of (001) facets over the TiO2 support had yielded a remarkably high activity at 390-490 °C for NO removal. The unique feature of active-energy (001) facets had enhanced the thermal stability of CeO2 whilst the presence of Ti3+ over the TiO2 surface had effectively facilitated the SCR process, both of which resulted in the remarkable catalytic performance for the catalyst.

  18. Dielectric and piezoelectric properties of CeO2-added nonstoichiometric (Na0.5K0.5)0.97(Nb0.96Sb0.04)O3 ceramics for piezoelectric energy harvesting device applications.

    PubMed

    Oh, Youngkwang; Noh, Jungrae; Yoo, Juhyun; Kang, Jinhee; Hwang, Larkhoon; Hong, Jaeil

    2011-09-01

    In this study, nonstoichiometric (Na(0.5)K(0.5))(0.97)(Nb(0.96)Sb(0.04))O(3) ceramics were fabricated and their dielectric and piezoelectric properties were investigated according to the CeO(2) addition. In this ceramic composition, CeO(2) addition improved sinterability, electromechanical coupling factor k(p), mechanical quality factor Q(m), piezoelectric constant d(33), and g(33). At the sintering temperature of 1100°C, for the 0.2wt% CeO(2) added specimen, the optimum values of density = 4.359 g/cm(3), k(p) = 0.443, Q(m) = 588, ε(r) = 444, d(33) = 159 pC/N, and g(33) = 35 × 10(-3) V·m/N, were obtained. A piezoelectric energy harvesting device using 0.2 wt% CeO(2)- added lead-free (K(0.5)Na(0.5))(0.97)(Nb(0.96)Sb(0.04))O(3) ceramics and a rectifying circuit for energy harvesting were fabricated and their electrical characteristics were investigated. Under an external vibration acceleration of 0.7 g, when the mass, the frequency of vibration generator, and matching load resistance were 2.4 g, 70 Hz, and 721 Ω, respectively, output voltage and power of piezoelectric harvesting device indicated the optimum values of 24.6 mV(rms) and 0.839 μW, respectively-suitable for application as the electric power source of a ubiquitous sensor network (USN) sensor node. PMID:21937318

  19. Chemical reaction mechanisms between Y2O3 stabilized ZrO2 and Gd doped CeO2 with PH3 in coal syngas

    NASA Astrophysics Data System (ADS)

    Chen, Gang; Kishimoto, Haruo; Yamaji, Katsuhiko; Kuramoto, Koji; Gong, Mingyang; Liu, Xingbo; Hackett, Gregory; Gerdes, Kirk; Horita, Teruhisa

    2014-12-01

    To clarify the chemical stability of the key materials exposed to coal syngas (CSG) containing PH3 contaminant atmosphere, exposure tests of Y2O3 8 mol.% stabilized ZrO2 (YSZ) and Gd doped CeO2 (GDC) are carried out in simulated CSG with different concentrations of PH3. Significant reaction between YSZ and 10 ppm PH3 in CSG atmosphere is confirmed, and no obvious reaction is detected on the surface of YSZ after exposed in CSG with 1 ppm PH3. YPO4, Zr2.25(PO4)3 and monoclinic Y partial stabilized ZrO2 (m-PSZ) are identified on the YSZ pellet surface after exposed in CSG with 10 ppm PH3. GDC reacted with PH3 even at 1 ppm concentration. A (Ce0.9Gd0.1)PO4 layer is formed on the surface of GDC pellet after exposure in CSG with 10 ppm PH3. Possible reaction mechanisms between YSZ and GDC with PH3 in CSG are clarified. Compared with GDC, YSZ exhibits sufficient phosphorus resistance for devices directly exposed to a coal syngas atmosphere containing low concentration of PH3.

  20. Chemical reaction mechanisms between Y2O3 stabilized ZrO2 and Gd doped CeO2 with PH3 in coal syngas

    NASA Astrophysics Data System (ADS)

    Chen, Gang; Kishimoto, Haruo; Yamaji, Katsuhiko; Kuramoto, Koji; Gong, Mingyang; Liu, Xingbo; Hackett, Gregory; Gerdes, Kirk; Horita, Teruhisa

    2014-12-01

    To clarify the chemical stability of the key materials exposed to coal syngas (CSG) containing PH3 contaminant atmosphere, exposure tests of Y2O3 8 mol.% stabilized ZrO2 (YSZ) and Gd doped CeO2 (GDC) are carried out in simulated CSG with different concentrations of PH3. Significant reaction between YSZ and 10 ppm PH3 in CSG atmosphere is confirmed, and no obvious reaction is detected on the surface of YSZ after exposed in CSG with 1 ppm PH3. YPO4, Zr2.25(PO4)3 and monoclinic Y partial stabilized ZrO2 (m-PSZ) are identified on the YSZ pellet surface after exposed in CSG with 10 ppm PH3. GDC reacted with PH3 even at 1 ppm concentration. A (Ce0.9Gd0.1)PO4 layer is formed on the surface of GDC pellet after exposure in CSG with 10 ppm PH3. Possible reaction mechanisms between YSZ and GDC with PH3 in CSG are clarified. Compared with GDC, YSZ exhibits sufficient phosphorus resistance for devices directly exposed to a coal syngas atmosphere containing low concentration of PH3.

  1. An ultrasensitive electrochemical sensor for simultaneous determination of xanthine, hypoxanthine and uric acid based on Co doped CeO2 nanoparticles.

    PubMed

    Lavanya, N; Sekar, C; Murugan, R; Ravi, G

    2016-08-01

    A novel electrochemical sensor has been fabricated using Co doped CeO2 nanoparticles for selective and simultaneous determination of xanthine (XA), hypoxanthine (HXA) and uric acid (UA) in a phosphate buffer solution (PBS, pH5.0) for the first time. The Co-CeO2 NPs have been prepared by microwave irradiation method and characterized by Powder XRD, Raman spectroscopy, HRTEM and VSM measurements. The electrochemical behaviours of XA, HXA and UA at the Co-CeO2 NPs modified glassy carbon electrode (GCE) were studied by cyclic voltammetry and square wave voltammetry methods. The modified electrode exhibited remarkably well-separated anodic peaks corresponding to the oxidation of XA, HXA and UA over the concentration range of 0.1-1000, 1-600 and 1-2200μM with detection limits of 0.096, 0.36, and 0.12μM (S/N=3), respectively. For simultaneous detection by synchronous change of the concentrations of XA, HXA and UA, the linear responses were in the range of 1-400μM each with the detection limits of 0.47, 0.26, and 0.43μM (S/N=3), respectively. The fabricated sensor was further applied to the detection of XA, HXA and UA in human urine samples with good selectivity and high reproducibility. PMID:27157753

  2. A novel spectrofluorometric method for the determination of arsenic in human hair using Dy2O3-doped CeO2 nanoparticles.

    PubMed

    Hosseini, Mohammad Saeid; Belador, Foroogh

    2014-10-01

    This paper describes a simple and inexpensive method for the determination of arsenic in human hair samples based on spectrofluorometric detection. The applied Dy2O3-doped CeO2 (DDC) nanoparticles were synthesized using microwave-induced combustion technique and subjected to analytical samples containing As(V) species. At optimum conditions (pH 6, DDC concentration 3 mg L(-1) and excitation/emission wavelengths 250 nm/352 nm), the fluorescence emission of DDC nanoparticles was diminished by increasing the As(V) concentration present in the medium. The co-existent ions present in hair were not interfered. A method for the speciation of As(III) and As(V) is also described. The method was validated using a well-known separation/spectrofluorometric method. There was no significant difference at the 95% confidence level between the results of the two methods. The proposed method is characterized by a wide analytical concentration range (5.0 × 10(-8)-1.0 × 10(-5) M), a detection limit for As(V) of 1 × 10(-8) mol L(-1) and relative standard deviation of 1.4%. The recoveries for the spiked amounts of As(V) was found to be 93.3-104.0%. PMID:25096195

  3. Physico-Chemical Property and Catalytic Activity of a CeO2-Doped MnO(x)-TiO2 Catalyst with SO2 Resistance for Low-Temperature NH3-SCR of NO(x).

    PubMed

    Shin, Byeongkil; Chun, Ho Hwan; Cha, Jin-Sun; Shin, Min-Chul; Lee, Heesoo

    2016-05-01

    The effects of CeO2 addition on the catalytic activity and the SO2 resistance of CeO2-doped MnO(x)-TiO2 catalysts were investigated for the low-temperature selective catalytic reduction (SCR) with NH3 of NO(x) emissions in marine applications. The most active catalyst was obtained from 30 wt% CeO2-MnO(x)-TiO2 catalyst in the whole temperature range of 100-300 degrees C at a low gas hourly space velocity (GHSV) of 10,000 h(-)1, and its de-NO(x) efficiency was higher than 90% over 250 degrees C. The enhanced catalytic activity may contribute to the dispersion state and catalytic acidity on the catalyst surface, and the highly dispersed Mn and Ce on the nano-scaled TiO2 catalyst affects the increase of Lewis and Brønsted acid sites. A CeO2-rich additive on MnO(x)-TiO2 could provide stronger catalytic acid sites, associated with NH3 adsorption and the SCR performance. As the results of sulfur resistance in flue gas that contains SO2, the de-NO(x) efficiency of MnO(x)-TiO2 decreased by 15% over 200 degrees C, whereas that of 30 wt% ceria-doped catalyst increased by 14-21% over 150 degrees C. The high SO2 resistance of CeO2-MnO(x)-TiO2 catalysts that resulted from the addition of ceria suppressed the formation of Mn sulfate species, which led to deactivation on the surface of nano-catalyst. PMID:27483759

  4. Ionic conductivity in Gd-doped CeO2: Ab initio color-diffusion nonequilibrium molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Nilsson, Johan O.; Vekilova, Olga Yu.; Hellman, Olle; Klarbring, Johan; Simak, Sergei I.; Skorodumova, Natalia V.

    2016-01-01

    A first-principles nonequilibrium molecular dynamics (NEMD) study employing the color-diffusion algorithm has been conducted to obtain the bulk ionic conductivity and the diffusion constant of gadolinium-doped cerium oxide (GDC) in the 850-1150 K temperature range. Being a slow process, ionic diffusion in solids usually requires simulation times that are prohibitively long for ab initio equilibrium molecular dynamics. The use of the color-diffusion algorithm allowed us to substantially speed up the oxygen-ion diffusion. The key parameters of the method, such as field direction and strength as well as color-charge distribution, have been investigated and their optimized values for the considered system have been determined. The calculated ionic conductivity and diffusion constants are in good agreement with available experimental data.

  5. CO2 reforming of CH4 over CeO2-doped Ni/Al2O3 nanocatalyst treated by non-thermal plasma.

    PubMed

    Rahemi, Nader; Haghighi, Mohammad; Babaluo, Ali Akbar; Jafari, Mahdi Fallah; Estifaee, Pooya

    2013-07-01

    Ni/Al2O3 and Ni/Al2O3-CeO2 nanocatalysts have been prepared with impregnation method, treated with non-thermal plasma, characterized and tested for dry reforming of methane. For catalyst characterization, the following techniques have been used: XRD, FESEM, TEM, EDX dot mapping, BET, FTIR, TG-DTG, and XPS techniques. According to XRD and XPS, Ni in all catalysts exists as NiO and NiAl2O4 that existence of NiAl2O4 reveals strong interaction between active phase and support. Catalyst particles had smaller average particle size in plasma treated Ni/Al2O3-CeO2 nanocatalyst with less agglomeration. Homogenous dispersion of active phase, narrower particle size distribution, and uniform morphology has been observed in ceria containing plasma treated catalyst. The plasma treated Ni/Al2O3-CeO2 nanocatalyst showed bigger NiAl2O4/NiO ratio in XPS analysis that is indicative of stronger interaction between Ni and Al2O3 in the presence of CeO2. The dry reforming of methane was carried out at 550-850 degrees C using a mixture of CH4:CO2 (0.5:2). Improved morphology of the plasma treated Ni/Al2O3-CeO2 nanocatalyst, resulted from both CeO2 and plasma treatment, caused higher ability of catalyst in H2 and CO production. Product yield decreased at higher GHSVs, due to the fact that mass transport limitations will be more severe at low residence time, but this reduction would be less noticeable in the plasma treated Ni/Al2O3-CeO2 nanocatalyst. In addition, the plasma treated Ni/Al2O3-CeO2 nanocatalyst can keep the reactivity without deactivation for either CH4 or CO2 conversion better than other investigated catalysts. PMID:23901509

  6. Solid-state reaction synthesis and aqueous durability of Ce-doped zirconolite-rich ceramics

    NASA Astrophysics Data System (ADS)

    Wen, Guanjun; Zhang, Kuibao; Yin, Dan; Zhang, Haibin

    2015-11-01

    In this study, Ce-doped zirconolite-rich ceramics were prepared by solid-state reaction process using cerium as the surrogate of tetravalence actinide nuclide. The occupancy of Ce in the waste forms was investigated. The aqueous durability of Ce-doped zirconolite-rich ceramic was examined as well. The results show that zirconolite and pseudobrookite coexisted after being sintered at 1200 °C for 6 h. Meanwhile, perovskite is inevitable generated during the process. CeO2 can be successfully incorporated into the lattice structure of the zirconolite-rich ceramics. The maximum containing capacity of CeO2 is up to 14.95 wt% or y = 0.4. The normalized elemental leaching rates of Ce and Ca are fairly constant in low values of 1.2 × 10-6 and 2.3 × 10-2 g m-2 d-1 after 28 days. The normalized leaching rate of Fe is also in a low value of 2.9 × 10-4 g m-2 d-1 after 7 days.

  7. Effect of Ce doping of TiO2 support on NH3-SCR activity over V2O5-WO3/CeO2-TiO2 catalyst.

    PubMed

    Cheng, Kai; Liu, Jian; Zhang, Tao; Li, Jianmei; Zhao, Zhen; Wei, Yuechang; Jiang, Guiyuan; Duan, Aijun

    2014-10-01

    CeO2-TiO2 composite supports with different Ce/Ti molar ratios were prepared by a homogeneous precipitation method, and V2O5-WO3/CeO2-TiO2 catalysts for the selective catalytic reduction (SCR) of NOx with NH3 were prepared by an incipient-wetness impregnation method. These catalysts were characterized by means of BET, XRD, UV-Vis, Raman and XPS techniques. The results showed that the catalytic activity of V2O5-WO3/TiO2 was greatly enhanced by Ce doping (molar ratio of Ce/Ti=1/10) in the TiO2 support. The catalysts that were predominantly anatase TiO2 showed better catalytic performance than the catalysts that were predominantly fluorite CeO2. The Ce additive could enhance the surface adsorbed oxygen and accelerate the SCR reaction. The effects of O2 concentration, ratio of NH3/NO, space velocity and SO2 on the catalytic activity were also investigated. The presence of oxygen played an important role in NO reduction. The optimal ratio of NH3/NO was 1/1 and the catalyst had good resistance to SO2 poisoning. PMID:25288555

  8. Effects of Ce3+ doping concentrations on microstructure and luminescent properties of Ce3+:Lu3Al5O12 (Ce:LuAG) transparent ceramics

    NASA Astrophysics Data System (ADS)

    Xu, Jian; Fan, Lingcong; Shi, Ying; Li, Junlang; Xie, Jianjun; Lei, Fang

    2014-10-01

    Ce3+ doping behaviour in range from 1.0 to 10.0 mol% on Ce:LuAG polycrystalline powders and ceramics was investigated in this paper. It was found that CeO2 would segregate as secondary phase from Ce:LuAG powders when the Ce3+ doping concentration reached to 5.0 mol% under the calcination of 1100 °C for 10 h in air. However, this “over-doped” phenomenon disappeared after the powders being densified into transparent ceramics by vacuum sintering. When the Ce3+ doping concentration was further increased into 10.0 mol%, the CeO2 segregation regions were observed in the corresponding Ce:LuAG ceramic with an elongated rod morphology. The drastic dropping of in-line optical transmittance of the 10.0 mol% Ce:LuAG ceramic demonstrated that the CeO2 secondary phase would form defects and/or electron traps at grain boundaries which embarrassed the energy transfer from host lattice to Ce3+ luminescent centers leading to its poor scintillation property.

  9. Upconversion studies on Yb3+/Er3+ doped CeO2 and CeF3 phosphors: Enhanced near infrared emission

    NASA Astrophysics Data System (ADS)

    Singh, A. K.; Kumar, K.; Rai, S. B.; Kumar, D.

    2013-09-01

    Upconversion emission in CeF3: Er3+/Yb3+ and CeO2: Er3+/Yb3+ phosphors is studied using 976 nm diode laser excitation and the emission results are compared. The Ce3+ ion is found to interact with Er3+ ion that enhances the energy transfer rate among the levels of Er3+ ion. The increased energy transfer rate enables increase in the infrared emission (˜1530 nm) at the expense of visible upconversion emission. An intense emission at ˜1530 nm due to the 4I13/2→4I15/2 transition of Er3+ ion, with least emission in the UV/visible region, is observed in the CeF3: Er3+/Yb3+ phosphor. The emission intensity of 4I13/2→4I15/2 transition is also compared for LaF3, CeF3 and LaF3 hosts and it is found that the emission intensity is maximum for CeF3 host. The CeF3: Er3+/Yb3+ phosphor is found suitable for optical amplifiers, laser materials and infrared imaging probes around 1530 nm.

  10. Electrodeposited Biaxially Textured CeO2 and CeO2:Sm Buffer Layer for YBCO Superconductor Oxide Films

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Raghu; Phok, Sovannary; Spagnol, Priscila; Chaudhuri, Tapas

    2006-03-01

    Nonvacuum electrodeposition was used to prepare biaxially textured CeO2 and Sm-doped CeO2 coatings on Ni-W substrates. The samples were characterized by X-ray diffraction (including θ/2θ, pole figures, omega scans, and phi scans), atomic force microscopy (AFM), Auger electron spectroscopy (AES), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Full-width at half-maximum values of the ω scan and φ scan of the electrodeposited layers were better than those of the Ni-W base substrates, indicating improved biaxial texturing of the electrodeposited layers.

  11. Spectroscopic characterization of Co3O4 catalyst doped with CeO2 and PdO for methane catalytic combustion

    NASA Astrophysics Data System (ADS)

    Jodłowski, P. J.; Jędrzejczyk, R. J.; Rogulska, A.; Wach, A.; Kuśtrowski, P.; Sitarz, M.; Łojewski, T.; Kołodziej, A.; Łojewska, J.

    2014-10-01

    The study deals with the XPS, Raman and EDX characterization of a series of structured catalysts composed of cobalt oxides promoted by palladium and cerium oxides. The aim of the work was to relate the information gathered from spectroscopic analyses with the ones from kinetic tests of methane combustion to establish the basic structure-activity relationships for the catalysts studied. The most active catalyst was the cobalt oxide doped with little amount of palladium and wins a confrontation with pure palladium oxide catalyst which is commercially used in converters for methane. The analyses Raman and XPS analyses showed that this catalyst is composed of a cobalt spinel and palladium oxide. The quantitative approach to the composition of the catalysts by XPS and EDX methods revealed that the surface of palladium doped cobalt catalyst is enriched with palladium oxide which provides a great number of active centres for methane combustion indicated by kinetic parameters.

  12. Effect of CeO2 and Y2O3 on microstructure, bioactivity and degradability of laser cladding CaO-SiO2 coating on titanium alloy.

    PubMed

    Li, H C; Wang, D G; Chen, C Z; Weng, F

    2015-03-01

    To solve the lack of strength of bulk biomaterials for load-bearing applications and improve the bioactivity of titanium alloy (Ti-6Al-4V), CaO-SiO2 coatings on titanium alloy were fabricated by laser cladding technique. The effect of CeO2 and Y2O3 on microstructure and properties of laser cladding coating was analyzed. The cross-section microstructure of ceramic layer from top to bottom gradually changes from cellular-dendrite structure to compact cellular crystal. The addition of CeO2 or Y2O3 refines the microstructure of the ceramic layer in the upper and middle regions. The refining effect on the grain is related to the kinds of additives and their content. The coating is mainly composed of CaTiO3, CaO, α-Ca2(SiO4), SiO2 and TiO2. Y2O3 inhibits the formation of CaO. After soaking in simulated body fluid (SBF), the calcium phosphate layer is formed on the coating surface, indicating the coating has bioactivity. After soaking in Tris-HCl solution, the samples doped with CeO2 or Y2O3 present a lower weight loss, indicating the addition of CeO2 or Y2O3 improves the degradability of laser cladding sample. PMID:25637793

  13. Collective magnetic response of CeO2 nanoparticles

    NASA Astrophysics Data System (ADS)

    Coey, Michael; Ackland, Karl; Venkatesan, Munuswamy; Sen, Siddhartha

    2016-07-01

    The magnetism of nanoparticles and thin films of wide-bandgap oxides that include no magnetic cations is an unsolved puzzle. Progress has been hampered by both the irreproducibility of much of the experimental data, and the lack of any generally accepted theoretical explanation. The characteristic signature is a virtually anhysteretic, temperature-independent magnetization curve that saturates in an applied field that is several orders of magnitude greater than the magnetization. It would seem as if a tiny volume fraction, <~0.1%, of the samples is magnetic and that the energy scale is unusually high for spin magnetism. Here we investigate the effect of dispersing 4 nm CeO2 nanoparticles with powders of γAl2O3, sugar or latex microspheres. The saturation magnetization, Ms ≍ 60 A m-1 for compact samples, is maximized by 1 wt% lanthanum doping. Dispersing the CeO2 nanopowder reduces its magnetic moment by up to an order of magnitude, and there is a characteristic length scale of order 100 nm for the magnetism to appear in CeO2 nanoparticle clusters. The phenomenon is explained in terms of a giant orbital paramagnetism that appears in coherent mesoscopic domains due to resonant interaction with zero-point fluctuations of the vacuum electromagnetic field. The theory explains the observed temperature-independent magnetization curve and its doping and dispersion dependence, based on a length scale of 300 nm that corresponds to the wavelength of a maximum in the ultraviolet absorption spectrum of the magnetic CeO2 nanoparticles. The coherent domains occupy roughly 10% of the sample volume.

  14. Synthesis of supported CeO2 nanofibers via electrospinning

    NASA Astrophysics Data System (ADS)

    Starbova, K.; Nihtianova, D.; Petrov, D.; Starbov, N.; Lovchinov, V.

    2012-12-01

    Fibrous CeO2 non-woven mats are synthesized via electrospinning. Homogeneous and stable aqueous polymer/cerium acetate blend spinning solutions are used. It is shown how the parameters of the solution, electrospinning, thermal post-processing can be successfully combined thus providing the synthesis of fibrous webs with mean diameters in the nanosized range. The morphologies of the samples are recorded under SEM and HRTEM while SAED is applied for studying their phase composition. The results obtained pave the way for the development of functional immobilized and self-supporting electrospun ceria ceramic materials.

  15. Facet-Controlled CeO2 Nanocrystals for Oxidative Coupling of Methane.

    PubMed

    Sun, Yongnan; Shen, Yue; Song, Jianjun; Ba, Rongbin; Huang, Shuangshuang; Zhao, Yonghui; Zhang, Jun; Sun, Yuhan; Zhu, Yan

    2016-05-01

    Whether the catalysts of the high temperature reaction such methane oxidation coupling has a structure-sensitive catalytic behavior or not, it is discussed and confirmed the shape-specific impact on methane activity by designing the catalysts with different crystal facets exposed. CeO2 nanowires enclosed by {110} and {100} planes show the higher CH4 conversion and higher C2 hydrocarbons (C2H4 and C2H6) selectivity, compared with particle CeO2 rounded by {111} and {100} planes, suggesting that CeO2 (110) surface favors the activation of CH4. Encouraged by the result, to control facet-controlled synthesis of catalysts for tailoring the catalytic properties at high temperature, the CeO2 (110) surface is chosen as doped sites to form the doped catalyst such as Ca doped CeO2 nanowires for OCM reaction, enhancing C2 hydrocarbons selectivity dramatically and suppressing the deep oxidation product (CO and CO2) selectivity. PMID:27483809

  16. Nonlinear optical responses of erbium-doped YAG ceramics

    NASA Astrophysics Data System (ADS)

    Sun, Wangliang; Yi, Jun; Miao, Lili; Li, Jiang; Xie, Tengfei; Zhao, Chujun; Pan, Yubai; Wen, Shuangchun

    2016-07-01

    By performing the Z-scan measurements with ultrafast femtosecond laser centered at 800 nm wavelength, we can unambiguously distinguish the real and imaginary part of the third-order optical nonlinearity of the erbium-doped YAG ceramics. The reverse saturable absorption of the erbium-doped YAG ceramics has been observed experimentally, and the nonlinear refractive index of the ceramics is estimated to be about 10-21 m2/W. The experimental results may provide design guidelines for the high power laser design and its applications.

  17. Optical Ceramics Based on Yttrium Oxide Doped with Tetravalent Ions

    NASA Astrophysics Data System (ADS)

    Osipov, V. V.; Solomonov, V. I.; Shitov, V. A.; Maksimov, R. N.; Orlov, A. N.; Murzakaev, A. M.

    2015-05-01

    Optical ceramics activated by neodymium or ytterbium and based on Y2O3 with inclusions of CeO2 , ZrO2 , and HfO2 containing optical inhomogeneities in the form of an orange peel are investigated. It is indicated that in the ceramics with such inclusions not only the crystallite size and porosity, but also the transmission near the edge of the fundamental absorption band decrease, and the theoretically predicted transparency is not achieved (even in the infrared range). It is reported that in the ceramics containing Hf 4+ and Zr4+ , Hf 3+ and Zr3+ , additionally depopulating the 4 F 3/2 upper laser level of the Nd3+ ion activator, are also present. The dependences of the Nd:Y2O3 crystal lattice parameter on the Hf 4+ or Nd3+ content in it, constructed based on the results of x-ray diffraction analysis, are linear, that is, no peculiarities are observed for solid solutions of these compounds. Energy dispersion analysis with a resolution of about 1 μm also indicates the uniformity of the distribution of the chemical elements throughout the sample. At the same time, estimates based on the Rayleigh light scattering in the ceramics indicate that one of the additional phases must have sizes smaller than λ/20 = 20 nm. By the method of high-resolution transmission electron microscopy, particles with composition modulated on the nanolevel are detected in the 90(Nd0.01Y0.99)2O3 + 10HfO2 nanopowder from which the ceramics are synthesized given that the lattice period remains unchanged.

  18. Synthesis of Pu-Doped Ceramic

    SciTech Connect

    Anderson, E. B

    1998-09-02

    Plutonium-doped zircon containing about 10 wt% Pu was synthesized in this cooperative project between Russia and the United States conducted at the V. G. Khlopin Radium Institute. The sol-gel method was used for starting precursor preparation to provide complete mixing of initial components and to avoid dust formation inside the glove-box. The sol-gel process also gives interim Pu stabilization in the form of amorphous zirconium hydrosilicate (AZHS), which is a result of gel solidification. AZHS is a solid and relatively durable material that can be easy converted into crystalline zircon by pressureless sintering, thus avoiding significant radioactive contamination of laboratory equipment. A methanol-aqueous solution of tetraethoxysilane Si(OC2H5)4, Pu-nitrate, and zirconil oxynitrate was prepared in final stoichiometry of zircon (Zr,Pu)SiO4 80 wt% + zirconia (Zr,Pu)O2 20 wt%. Gelation occurred after 90 hours at room temperature. AZHS with excess of zirconia 20 wt% was obtained as an interim calcine product and then it was converted into zircon/zirconia ceramic by sintering at 1490 to 1500°C in air for different time periods. The samples obtained were studied by SRD and ESEM methods. It was found that both zircon yield and zircon cell parameters that are correlated with Pu incorporation depend on sintering time.

  19. Thermal analysis on grad-doped active-mirror Yb:YAG ceramic lasers

    NASA Astrophysics Data System (ADS)

    Cheng, Xiaojin; Wang, Jianlei; Jiang, Benxue

    2015-11-01

    Heat conduction, temperature distribution, thermal stress, and thermally induced refractive index of a diode-pumped active-mirror grad-doped Yb:YAG ceramic laser are analyzed and compared to a uniform-doped Yb:YAG ceramic laser. It is found that a rationally designed grad-doped Yb:YAG ceramic has a smaller temperature gradient than a uniform-doped Yb:YAG ceramic with the same absorption pump power, which results in higher output energy in the grad-doped Yb:YAG ceramic laser.

  20. Hydrogenated CeO2-xSx mesoporous hollow spheres for enhanced solar driven water oxidation.

    PubMed

    Xiao, Yuting; Chen, Yajie; Xie, Ying; Tian, Guohui; Guo, Shien; Han, Taoran; Fu, Honggang

    2016-02-11

    A facile route for the fabrication of hydrogenated sulfur-doped CeO2 (H-CeO2-xSx) mesoporous hollow spheres is reported. The spheres exhibited excellent photocatalytic activity due to the synergistic effect of the higher sulfur doping level and hydrogen post-treatment. PMID:26741276

  1. Electrical properties of niobium doped barium bismuth-titanate ceramics

    SciTech Connect

    Bobić, J.D.; Vijatović Petrović, M.M.; Banys, J.; Stojanović, B.D.

    2012-08-15

    Highlights: ► Pure and doped BaBi{sub 4}Ti{sub 4}O{sub 15} were prepared via the solid-state reaction method. ► The grain size was suppressed in Nb-doped samples. ► The diffuseness of the dielectric peak increased with dopant concentration. ► Niobium affected on relaxor behavior of barium bismuth titanate ceramics. ► The conductivity change was noticed in doped samples. -- Abstract: BaBi{sub 4}Ti{sub 4–5/4x}Nb{sub x}O{sub 15} (BBNTx, x = 0, 0.05, 0.15, 0.30) ceramics have been prepared by solid state method. XRD data indicate the formation of single-phase-layered perovskites for all compositions. SEM micrographs suggest that the grain size decreases with Nb doping. The effect of niobium doping on the dielectric and relaxor behavior of BaBi{sub 4}Ti{sub 4}O{sub 15} ceramics was investigated in a wide range of temperatures (20–777 °C) and frequencies (1.21 kHz to 1 MHz). Nb doping influences T{sub c} decrease as well as the decrease of dielectric permittivity at Curie temperature. At room temperature, undoped BaBi{sub 4}Ti{sub 4}O{sub 15} exhibits dielectric constant of ∼204 at 100 kHz, that slightly increases with Nb doping. The conductivity of BBNT5 ceramics is found to be lower than that of other investigated compositions. The value of activation energy of σ{sub DC} was found to be 0.89 eV, 1.01 eV, 0.93 eV and 0.71 eV for BBT, BBNT5, BBNT15 and BBNT30, respectively.

  2. Recent Progress in the Development of Neodymium Doped Ceramic Yttria

    NASA Technical Reports Server (NTRS)

    Prasad, Narasimha S.; Edwards, Chris; Trivedi, Sudhir B.; Kutcher, Susan; Wang, Chen-Chia; Kim, Joo-Soo; Hommerich, Uwe; Shukla, Vijay; Sadangi, Rajendra; Kear, Bernard

    2007-01-01

    Solid-state lasers play a significant role in providing the technology necessary for active remote sensing of the atmosphere. Neodymium doped yttria (Nd:Y2O3) is considered to be an attractive material due to its possible lasing wavelengths of aprrox.914 nm and approx.946 nm for ozone profiling. These wavelengths when frequency tripled can generate UV light at approx.305 nm and approx.315 nm, which is particularly useful for ozone sensing using differential absorption lidar technique. For practical realization of space based UV transmitter technology, ceramic Nd:Y2O3 material is considered to possess great potential. A plasma melting and quenching method has been developed to produce Nd3+ doped powders for consolidation into Nd:Y2O3 ceramic laser materials. This far-from-equilibrium processing methodology allows higher levels of rare earth doping than can be achieved by equilibrium methods. The method comprises of two main steps: (a) plasma melting and quenching to generate dense, and homogeneous doped metastable powders, (b) pressure assisted consolidation of these powders by hot isostatic pressing to make dense nanocomposite ceramics. Using this process, several 1" x 1" ceramic cylinders have been produced. The infrared transmission of undoped Y2O3 ceramics was as high as approx.75% without anti-reflection coating. In the case of Nd:Y2O3 ceramics infrared transmission values of approx.50% were achieved. Furthermore, Nd:Y2O3 samples with dopant concentrations of up to approx.2 at. % were prepared without significant emission quenching.

  3. Electrical properties of lanthanum doped barium titanate ceramics

    SciTech Connect

    Vijatovic Petrovic, M.M.; Bobic, J.D.; Ramoska, T.; Banys, J.; Stojanovic, B.D.

    2011-10-15

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

  4. Promotion effects of SiO2 or/and Al2O3 doped CeO2/TiO2 catalysts for selective catalytic reduction of NO by NH3.

    PubMed

    Zhao, Wenru; Tang, Yu; Wan, Yaping; Li, Liang; Yao, Si; Li, Xiaowei; Gu, Jinlou; Li, Yongsheng; Shi, Jianlin

    2014-08-15

    A series of the CeO2-based catalysts loaded on TiO2, TiO2-SiO2, TiO2-Al2O3, and TiO2-SiO2-Al2O3 supports were prepared by incipient impregnation method for the selective catalytic reduction (SCR) of NO by NH3 in the presence of oxygen. The SCR activities of the catalysts with different supports increases in the order of Ce/TiO2 < Ce/TiO2-20SiO2 ≈ Ce/TiO2-3.5Al2O3 < Ce/TiO2-20SiO2-3.5Al2O3. The Ce/TiO2-20SiO2-3.5Al2O3 catalyst showed 100% NO conversion in the temperature range of 250-425°C and 100% N2 selectivity in the whole temperature range. The catalytic activity of Ce/TiO2-20SiO2-3.5Al2O3 exhibited good stability and strong resistance to SO2 and H2O poisoning. The co-introduction of SiO2 and Al2O3 into TiO2 could increase the amount of chemisorbed oxygen and Lewis acid sites on the surface of catalyst, which should be responsible for the excellent SCR activity. PMID:24996153

  5. Thermo-optic quality assessment of doped optical ceramics

    NASA Astrophysics Data System (ADS)

    Willis, Christina C. C.; Bradford, Joshua D.; Maddox, Emily; Shah, Lawrence; Richardson, Martin

    2013-03-01

    The use of optical quality ceramics for laser applications is expanding, and with this expansion there is an increasing need for diagnostics to assess the quality of these materials. Ceramic material with flaws and contaminants yields significantly less efficient performance as laser gain media and can generate excessive amounts of waste heat. This is a concern that is especially relevant in high power laser applications where thermally induced damage can be catastrophic. In order to assess a set of ceramic and crystalline samples we induce and measure thermal lensing in order to produce a relative ranking based on the extent of the induced thermal lens. In these experiments thermal lensing is induced in a set of nine 10% Yb:YAG ceramic and single-crystal samples using a high power 940 nm diode, and their thermal response is measured using a Shack-Hartmann wavefront sensor. The materials are also ranked by their transmission in the visible region. Discrepancies between the two ranking methods reveal that transmission in the visible region alone is not adequate for an assessment of the overall quality of ceramic samples. The thermal lensing diagnostic technique proves to be a reliable and quick over-all assessment method of doped ceramic materials without requiring any a priori knowledge of material properties.

  6. Spectroscopic characteristics of chromium doped mullite glass-ceramics

    SciTech Connect

    Wojtowicz, A.J.; Meng, W.; Lempicki, A.; Beall, G.H.; Hall, D.W.; Chin, T.C.

    1988-06-01

    Characteristics of chromium doped mullite ceramics are discussed with reference to possible laser applications. Dominant features are attributed to large and inherent spectroscopic inhomogeneity of mullite. The spectroscopic data are analyzed using a generalized McCumber theory. The peak stimulated emission cross section is 0.54 x 10/sup -20/ cm/sup 2/. This, together with preliminary single-pass measurements, indicate that gain for mullite is about 2.6 times smaller than gain for alexandrite.

  7. Sintering and mechanical properties of gadolinium-doped ceria ceramics

    NASA Astrophysics Data System (ADS)

    Yasuda, K.; Uemura, K.; Shiota, T.

    2012-01-01

    Gadolinium-doped ceria (GDC) ceramics were made by sintering at various temperatures from 1000°C to 1400°C in air. The true density and apparent density were measured to calculate the relative density of GDC ceramics. The change in relative density revealed that densification of GDC ceramics increased up to 1200°C, and thereafter turned downward. It was suggested that pores were formed at 1300°C and 1400°C due to non-stoichiometry of ceria. JIS-type specimens were cut from the sintered body and tested by 4-point bending. Young's modulus and bending strength decreased with increasing the sintering temperature from 1200°C to 1400°C, corresponding to the change in the relative density.

  8. Fabrication and characterization of spark plasma sintered Ce:LuAG ceramic for scintillation application

    NASA Astrophysics Data System (ADS)

    Kumar, S. Arun; Senthilselvan, J.

    2016-05-01

    Rare earth Cerium doped Lutetium Aluminum Garnet (Ce:LuAG) ceramics are widely used as phosphor material in medical imaging and high-energy physics. Due to its technological importance, an attempt has been made to fabricate Ce:LuAG ceramics by using spark plasma sintering (SPS) technique. XRD patterns of SPS sintered Ce:LuAG ceramics reveals a mixed LuAG and CeO2 (antisite defect) phases. The microstructures of SPS sintered Ce:LuAG ceramics shows limited densification, inappropriate compaction of particles and existence of residual pores, voids between the grain boundaries affects the transparency of Ce:LuAG ceramics. Relative density and hardness of post sintered Ce:LuAG ceramic is also determined. The effect of Ce3+ doping concentration and sintering temperature on optical luminescence behavior of Ce:LuAG ceramic is presented.

  9. Ytterbium-doped glass-ceramics for optical refrigeration.

    PubMed

    Filho, Elton Soares de Lima; Krishnaiah, Kummara Venkata; Ledemi, Yannick; Yu, Ye-Jin; Messaddeq, Younes; Nemova, Galina; Kashyap, Raman

    2015-02-23

    We report for the first time the characterization of glass-ceramics for optical refrigeration. Ytterbium-doped nanocrystallites were grown in an oxyfluoride glass matrix of composition 2YbF(3):30SiO(2)-15Al(2)O(3)-25CdF(2)-22PbF(2)-4YF(3), forming bulk glass-ceramics at three different crystalisation levels. The samples are compared with a corresponding uncrystalised (glass) sample, as well as a Yb:YAG sample which has presented optical cooling. The measured X-ray diffraction spectra, and thermal capacities of the samples are reported. We also report for the first time the use of Yb:YAG as a reference for absolute photometric quantum efficiency measurement, and use the same setup to characterize the glass and glass-ceramic samples. The cooling figure-of-merit was measured by optical calorimetry using a fiber Bragg grating and found to depend on the level of crystallization of the sample, and that samples with nanocrystallites result in higher quantum efficiency and lower background absorption than the pure-glass sample. In addition to laser-induced cooling, the glass-ceramics have the potential to serve as a reference for quantum efficiency measurements. PMID:25836500

  10. Structural and electrical characteristics of dysprosium-doped barium stannate titanate ceramics

    SciTech Connect

    Wang, Shijie; Tan, Tai Aik; Lai, Man On; Lu, Li

    2010-03-15

    Effects of dysprosium (Dy) amphoteric doping on the structural, dielectric and electric properties of barium stannate titanate (BTS) ceramics have been studied. X-ray diffraction analyses reveal that all Dy-doped BTS ceramics exhibit cubic perovskite structure until to 1 mol%. Dy doping at the A site shows lower solubility than that at the B site. SEM surface morphologies display that the Dy B site doping is beneficial for the compact and homogeneous grain distribution. The dielectric constant and loss tangent are reduced with increase of the doping levels. Impedance spectroscopy investigation demonstrates that all samples are insulating at room temperature. Doping alters the full resistive regions of pure BTS ceramics to Doped BTS with insulating grain boundaries and semiconducting bulk regions, but the doping contents has little effect on changing the electric structures.

  11. Ferromagnetism induced by oxygen and cerium vacancies above the percolation limit in CeO2

    NASA Astrophysics Data System (ADS)

    Fernandes, V.; Schio, P.; de Oliveira, A. J. A.; Ortiz, W. A.; Fichtner, P.; Amaral, L.; Graff, I. L.; Varalda, J.; Mattoso, N.; Schreiner, W. H.; Mosca, D. H.

    2010-06-01

    We studied the structural, chemical and magnetic properties of non-doped ceria (CeO2) thin films electrodeposited on silicon substrates. Experimental results confirm that the observed room temperature ferromagnetism is driven by both cerium and oxygen vacancies. We investigated ceria films presenting vacancy concentrations well above the percolation limit. Irradiation experiments with neon ions were employed to generate highly oxygen defective CeO2 - δ structures. X-ray photoelectron spectroscopy and x-ray absorption near-edge structure spectroscopy were used to estimate the concentration of Ce3 + sites in the films, which can reach up to 50% of Ce3 + replacing Ce4 + , compared to a stoichiometric CeO2 structure. Despite the increment of structural disorder, we observe that the saturation magnetization continuously increases with Ce3 + concentration. Our experiments demonstrate that the ferromagnetism observed in ceria thin films, highly disordered and oxygen-deficient, preserving the fluorite-type structure only in a nanometer scale, remains intrinsically stable at room temperature.

  12. Thermo-optical properties of terbium-aluminum garnet ceramics doped with silicon and titanium.

    PubMed

    Starobor, Aleksey; Palashov, Oleg; Zhou, Shengming

    2016-04-01

    The Verdet constant and thermo-optical characteristics of a Si-doped and Ti-doped terbium aluminum garnet ceramics have been investigated. It is shown that the Verdet constant of the samples is ∼40% higher than that of TGG ceramics at 1064 nm. The best samples of Si:TAG have magneto-optical figures of merit more than 1.5 times greater than those of TGG ceramics. Si:TAG is better than TGG ceramics as a medium for high-power Faraday isolators. PMID:27192274

  13. Preparation and characterization of Yb-doped YAG ceramics

    NASA Astrophysics Data System (ADS)

    Hostaša, Jan; Esposito, Laura; Alderighi, Daniele; Pirri, Angela

    2013-02-01

    This work presents the results of the preparation of polycrystalline Yb:YAG ceramics for laser sources with dopant concentration from 0 up to 20 at.% via solid state reactive sintering. Samples were prepared via cold isostatic pressing of spray dried mixture of pure oxide powders with TEOS as a sintering aid. Sintering was conducted under high vacuum and clean atmosphere. Various sintering cycles were tested, so that optimum conditions could be selected in dependence on Yb concentration. Samples with optical transmittance higher than 80% were prepared and their laser performance was examined. Slope efficiency as high as 73% and a maximum output power of 6 W were obtained for the sample doped with 10% Yb. Final microstructure of prepared samples was analyzed via optical microscopy, scanning and transmission electron microscopy, and EDS.

  14. Spectroscopic characteristics of chromium-doped mullite glass-ceramics

    SciTech Connect

    Wojtowicz, A.J.; Meng, W.; Lempicki, A.; Beall, G.H.; Hall, D.W.

    1988-06-01

    The chromium (3+) ion has been widely used as an optical activator in solid-state, tunable laser materials. High octahedral field-stabilization energy and resistance against both oxidation and reduction minimize the dependence of chromium (3+) on the solid-state host matrix. However, the high sensitivity of electronic structure on crystal field strength makes the appropriate choice of host the condition for success. Characteristics of chromium-doped mullite ceramics are discussed with reference to possible laser applications. Dominant features are attributed to large and inherent spectroscopic inhomogeneity of mullite. The spectroscopic data are analyzed using a generalized McCumber theory. The peak-stimulated emission cross section is 0.54 x 10 to the -20 sq cm. This together with preliminary single-pass measurements, indicate that gain for mullite is about 2.6 times smaller than gain for alexandrite.

  15. Electrical and reliability characteristics of Mn-doped nano BaTiO3-based ceramics for ultrathin multilayer ceramic capacitor application

    NASA Astrophysics Data System (ADS)

    Gong, Huiling; Wang, Xiaohui; Zhang, Shaopeng; Tian, Zhibin; Li, Longtu

    2012-12-01

    Nano BaTiO3-based dielectric ceramics were prepared by chemical coating approach, which are promising for ultrathin multilayer ceramic capacitor (MLCC) applications. The doping effects of Mn element on the microstructures and dielectric properties of the ceramics were investigated. The degradation test and impedance spectroscopy were employed to study the resistance degradation and the conduction mechanism of Mn-doped nano-BaTiO3 ceramic samples. It has been found that the reliability characteristics greatly depended on the Mn-doped content. Moreover, the BaTiO3 ceramic with grain size in nanoscale is more sensitive to the Mn-doped content than that in sub-micron scale. The addition of 0.3 mol. % Mn is beneficial for improving the reliability of the nano BaTiO3-based ceramics, which is an important parameter for MLCC applications. However, further increasing the addition amount will deteriorate the performance of the ceramic samples.

  16. Local environment of Fe dopants in nanoscale Fe : CeO2-x oxygen storage material

    NASA Astrophysics Data System (ADS)

    Meledina, M.; Turner, S.; Galvita, V. V.; Poelman, H.; Marin, G. B.; van Tendeloo, G.

    2015-02-01

    Nanoscale Fe : CeO2-x oxygen storage material for the process of chemical looping has been investigated by advanced transmission electron microscopy and electron energy-loss spectroscopy before and after a model looping procedure, consisting of redox cycles at heightened temperature. Separately, the activity of the nanomaterial has been tested in a toluene total oxidation reaction. The results show that the material consists of ceria nanoparticles, doped with single Fe atoms and small FeOx clusters. The iron ion is partially present as Fe3+ in a solid solution within the ceria lattice. Furthermore, enrichment of reduced Fe2+ species is observed in nanovoids present in the ceria nanoparticles, as well as at the ceria surface. After chemical looping, agglomeration occurs and reduced nanoclusters appear at ceria grain boundaries formed by sintering. These clusters originate from surface Fe2+ aggregation, and from bulk Fe3+, which ``leaks out'' in reduced state after cycling to a slightly more agglomerated form. The activity of Fe : CeO2 during the toluene total oxidation part of the chemical looping cycle is ensured by the dopant Fe in the Fe1-xCexO2 solid solution, and by surface Fe species. These measurements on a model Fe : CeO2-x oxygen storage material give a unique insight into the behavior of dopants within a nanosized ceria host, and allow to interpret a plethora of (doped) cerium oxide-based reactions.Nanoscale Fe : CeO2-x oxygen storage material for the process of chemical looping has been investigated by advanced transmission electron microscopy and electron energy-loss spectroscopy before and after a model looping procedure, consisting of redox cycles at heightened temperature. Separately, the activity of the nanomaterial has been tested in a toluene total oxidation reaction. The results show that the material consists of ceria nanoparticles, doped with single Fe atoms and small FeOx clusters. The iron ion is partially present as Fe3+ in a solid solution

  17. CeO2 nanorods and gold nanocrystals supported on CeO2 nanorods as catalyst.

    PubMed

    Huang, P X; Wu, F; Zhu, B L; Gao, X P; Zhu, H Y; Yan, T Y; Huang, W P; Wu, S H; Song, D Y

    2005-10-20

    The formation mechanism of uniform CeO2 structure at the nanometer scale via a wet-chemical reaction is of great interest in fundamental study as well as a variety of applications. In this work, large-scale well-crystallized CeO2 nanorods with uniform diameters in the range of 20-30 nm and lengths up to tens of micrometers are first synthesized through a hydrothermal synthetic route in 5 M KOH solution at 180 degrees C for 45 h without any templates and surfactants. The nanorod formation involves dehydration of CeO2 nanoparticles and orientation growth along the 110 direction in KOH solution. Subsequently, gold nanoparticles with crystallite sizes between 10 and 20 nm are loaded on the surface of CeO2 nanorods using HAuCl4 solution as the gold source and NaBH4 solution as a reducing agent. The synthesized Au/CeO2 nanorods demonstrate a higher catalytic activity in CO oxidation than the pure CeO2 nanorods. PMID:16853472

  18. Effect of annealing temperature on the structural and optical properties of CeO2:Ni thin films

    NASA Astrophysics Data System (ADS)

    Murugan, R.; Vijayaprasath, G.; Sakthivel, P.; Mahalingam, T.; Ravi, G.

    2016-05-01

    High quality Ni-doped CeO2 (CeO2:Ni) thin films were deposited on glass substrates at room temperature by using radio frequency magnetron sputtering. The effect of annealing temperature on structural and optical properties of the CeO2:Ni films was investigated. The structural, optical and vibrational properties of the films were determined using X-ray diffraction (XRD), photoluminescence spectrometer (PL) and Raman spectrometer. It was found that the as-deposited film has a fluorite cubic structure. By increasing annealing temperature from 100°C to 300°C, the crystalline quality of the thin films could be improved. The UV and visible band emissions were observed in the photoluminescence spectra, due to exciton, defect related emissions respectively. The micro-Raman results show the characteristic peak of CeO2 F2g at 465 cm-1 and 2L0 at 1142 cm-1. Defect peaks like D and 0 bands were observed at 641 cm-1 and 548 cm-1 respectively. It is found from the spectra that the peak intensity of the films increased with increase of annealing temperature.

  19. Water Adsorption and Dissociation on CeO2 (111)

    NASA Astrophysics Data System (ADS)

    Gao, Yi; Han, Zhong-Kang; Shao, Nan; Mei, Wai-Ning

    The complexity and flexibility of ceria surface hinders the fully understanding of its reactivity and real applications. Here, we use H2O/CeO2(111) as the model system to investigate the water effect on the electron localization and vacancy diffusion on CeO2(111) surface by the first-principle calculations. Our results indicate the water adsorption would high affect the electronic structures of CeO2(111) surface, which further induce the dissociation of H2O molecule. This molecular mechanism might provide more guidance to the future applications including the watergas shift reactions.

  20. Ce-doped single crystal and ceramic garnets for γ ray detection

    SciTech Connect

    Hull, G; Roberts, J; Kuntz, J; Fisher, S; Sanner, R; Tillotson, T; Drobshoff, A; Payne, S; Cherepy, N

    2007-07-30

    Ceramic and single crystal Lutetium Aluminum Garnet scintillators exhibit energy resolution with bialkali photomultiplier tube detection as good as 8.6% at 662 keV. Ceramic fabrication allows production of garnets that cannot easily be grown as single crystals, such as Gadolinium Aluminum Garnet and Terbium Aluminum Garnet. Measured scintillation light yields of Cerium-doped ceramic garnets indicate prospects for high energy resolution.

  1. Ultrafine Nanocrystalline CeO2@C-Containing NaAlH4 with Fast Kinetics and Good Reversibility for Hydrogen Storage.

    PubMed

    Zhang, Xin; Liu, Yongfeng; Wang, Ke; Li, You; Gao, Mingxia; Pan, Hongge

    2015-12-21

    A nanocrystalline CeO2@C-containing NaAlH4 composite is successfully synthesized in situ by hydrogenating a NaH-Al mixture doped with CeO2@C. Compared with NaAlH4 , the as-prepared CeO2@C-containing NaAlH4 composite, with a minor amount of excess Al, exhibits significantly improved hydrogen storage properties. The dehydrogenation onset temperature of the hydrogenated [NaH-Al-7 wt % CeO2@C]-0.04Al sample is 77 °C lower than that of the pristine sample because of a reduced kinetic barrier. More importantly, the dehydrogenated sample absorbs ∼4.7 wt % hydrogen within 35 min at 100°C and 10 MPa of hydrogen. Compositional and structural analyses reveal that CeO2 is converted to CeH2 during ball milling and that the newly formed CeH2 works with the excess of Al to synergistically improve the hydrogen storage properties of NaAlH4. Our findings will aid in the rational design of novel catalyst-doped complex hydride systems with low operating temperatures, fast kinetics, and long-term cyclability. PMID:26632764

  2. Lead-barium fluoroborate glass ceramics doped with Nd3+ or Er3+

    NASA Astrophysics Data System (ADS)

    Petrova, O. B.; Sevostjanova, T. S.; Anurova, M. O.; Khomyakov, A. V.

    2016-02-01

    Lead-barium fluoroborate glasses in the PbF2-BaF2-B2O3, PbF2-BaO-B2O3, and PbO- BaF2-B2O3 systems doped with rare-earth ions (Nd3+ or Er3+) are synthesized and studied. It is shown that, based on these glasses, it is possible to produce transparent glass ceramics with fluoride crystalline phases, including ceramics with one crystalline phase of the fluorite structure. The spectral and luminescent properties of the doped glasses, glass ceramics, and polycrystalline complex fluorides containing Pb, Ba, and rare ions are studied.

  3. Differential scanning calorimetry investigations on Eu-doped fluorozirconate-based glass ceramics

    PubMed Central

    Paßlick, C.; Ahrens, B.; Henke, B.; Johnson, J. A.; Schweizer, S.

    2010-01-01

    The properties of Eu-doped fluorochlorozirconate (FCZ) glass ceramics upon thermal processing and the influence of Eu-doping on the formation of BaCl2 nanocrystals therein have been investigated. Differential scanning calorimetry indicates that higher Eu-doping shifts the crystallization peak of the nanocrystals in the glass to lower temperatures, while the glass transition temperature remains constant. The activation energy and the thermal stability parameters for the BaCl2 crystallization are determined. PMID:21286235

  4. Influence of rare earth doping on thermoelectric properties of SrTiO{sub 3} ceramics

    SciTech Connect

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

    2013-12-14

    Thermoelectric properties of SrTiO{sub 3} ceramics, doped with different rare earth elements, were investigated in this work. It's found that the ionic radius of doping elements plays an important role on thermoelectric properties: SrTiO{sub 3} ceramics doped with large rare earth ions (such as La, Nd, and Sm) exhibit large power factors, and those doped with small ions (such as Gd, Dy, Er, and Y) exhibit low thermal conductivities. Therefore, a simple approach for enhancing the thermoelectric performance of SrTiO{sub 3} ceramics is proposed: mainly doped with large ions to obtain a large power factor and, simultaneously, slightly co-doped with small ions to obtain a low thermal conductivity. Based on this rule, Sr{sub 0.8}La{sub 0.18}Yb{sub 0.02}TiO{sub 3} ceramics were prepared, whose ZT value at 1 023 K reaches 0.31, increasing by a factor of 19% compared with the single-doped counterpart Sr{sub 0.8}La{sub 0.2}TiO{sub 3} (ZT = 0.26)

  5. Electrical properties of palladium-doped CaCu3Ti4O12 ceramics

    NASA Astrophysics Data System (ADS)

    Singh, Arashdeep; Md Mursalin, Sk.; Rana, P.; Sen, Shrabanee

    2015-09-01

    The effect of doping palladium (Pd) at the Cu site of CaCu3Ti4O12 powders (CCPTO) synthesized by sol-gel technique on electrical properties was studied. XRD analysis revealed the formation of CCTO and CCPTO ceramics with some minor quantities of impurities. SEM micrographs revealed that the grain size decreased with Pd doping. TEM micrographs of CCPTO powder showed the formation of irregular-shaped particles of ~40 nm. The dielectric constant and dielectric loss showed a significant enhancement with Pd doping. A significant decrease in grain-boundary resistance with Pd doping was ascertained by impedance spectroscopy study.

  6. Ceramics

    NASA Astrophysics Data System (ADS)

    Yao, Lichun; Yang, Jian; Qiu, Tai

    2014-09-01

    The effects of CuO addition on phase composition, microstructure, sintering behavior, and microwave dielectric properties of 0.80Sm(Mg0.5Ti0.5)O3-0.20 Ca0.8Sr0.2TiO3(8SMT-2CST) ceramics prepared by a conventional solid-state ceramic route have been studied. CuO addition shows no obvious influence on the phase of the 8SMT-2CST ceramics and all the samples exhibit pure perovskite structure. Appropriate CuO addition can effectively promote sintering and grain growth, and consequently improve the dielectric properties of the ceramics. The sintering temperature of the ceramics decreases by 50°C by adding 1.00 wt.%CuO. Superior microwave dielectric properties with a ɛ r of 29.8, Q × f of 85,500 GHz, and τ f of 2.4 ppm/°C are obtained for 1.00 wt.%CuO doped 8SMT-2CST ceramics sintered at 1500°C, which shows dense and uniform microstructure as well as well-developed grain growth.

  7. Unusual Compression Behavior of Nanocrystalline CeO2

    PubMed Central

    Wang, Qiming; He, Duanwei; Peng, Fang; Lei, Li; Liu, Pingping; Yin, Shuai; Wang, Pei; Xu, Chao; Liu, Jing

    2014-01-01

    The x-ray diffraction study of 12 nm CeO2 was carried out up to ~40 GPa using an angle dispersive synchrotron-radiation in a diamond-anvil cell with different pressure transmitting medium (PTM) (4:1 methanol: ethanol mixture, silicone oil and none) at room temperature. While the cubic fluorite-type structure CeO2 was retained to the highest pressure, there is progressive broadening and intensity reduction of the reflections with increasing pressure. At pressures above 12 GPa, an unusual change in the compression curve was detected in all experiments. Significantly, apparent negative volume compressibility was observed at P = 18–27 GPa with silicone oil as PTM, however it was not detected in other circumstances. The expansion of the unit cell volume of cubic CeO2 was about 1% at pressures of 15–27 GPa. To explain this abnormal phenomenon, a dual structure model (hard amorphous shell and relatively soft crystalline core) has been proposed. PMID:24658049

  8. Defect Complex Effect in Nb Doped TiO2 Ceramics with Colossal Permittivity

    NASA Astrophysics Data System (ADS)

    Li, Fuchao; Shang, Baoqiang; Liang, Pengfei; Wei, Lingling; Yang, Zupei

    2016-07-01

    Donor-doped Nb x Ti1-x O2 (x = 1%, 2%, 4%, 6%, and 8%) ceramics with giant permittivity (>104) and a very low dielectric loss (˜0.05) were sintered under flowing N2 at 1400°C for 10 h. By increasing Nb doping concentration, two different dielectric responses were evidenced in the frequency dependence of dielectric properties of Nb doped TiO2 ceramics, which corresponded to the space charge polarization and the electron-pinned defect-dipoles effect, respectively. Especially, combined with the x-ray photoelectron spectroscopy results, the electron-pinned defect-dipoles induced by the 2({Nb}^{5 + } )_{{Ti}}^{ bullet } to 4({Ti}^{3 + } )^'_{{Ti}} leftarrow {V}_{{o}}^{ bullet bullet } defect complex were further confirmed to give rise to both their high ɛr and low tan δ in the high frequency range for the Nb x Ti1-x O2 ceramics with x > 4%.

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

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

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

  10. Resistance Measurements and Activation Energies Calculations of Pure and Platinum Doped Stannic Oxide Ceramics in Air

    SciTech Connect

    Ibrahim, Zuhairi; Othman, Zulkafli; Karim, Mohd Mustamam Abd; Holland, Diane

    2007-05-09

    Pure SnO2 and Pt-SnO2 ceramics were fabricated by the dry pressing method using a pressure of 40 Mpa and sintered at 1000 deg. C. Electrical resistance measurements were made using an impedance analyzer, in air and temperatures between 25 deg. C and 450 deg. C. The change in resistance in both pure and platinum-doped stannic oxide ceramics was discussed.

  11. Enhanced Multiferroic Properties of BiFeO3 Ceramics by mo Doping

    NASA Astrophysics Data System (ADS)

    Zhang, X.; Zhang, G. Q.; Miao, J.; Xu, X. G.; Jiang, Y.

    We have investigated the magnetic and electrical properties of multiferroic BiFe1-xMoxO3 ceramics (BFMO, x = 0.0%, 0.2%, 0.5% and 0.8%) prepared by the sol-gel method. The phase structure of BFMO samples were confirmed by X-ray diffraction. It was found that the substitution of Mo is responsible for the increasing of the magnetization in BFMO ceramics. Moreover, both dielectric and polarization-electric field properties suggest that the Mo doping could improve the dielectric and ferroelectric properties in BFMO ceramic.

  12. Optical properties of Dy3+ doped bismuth zinc borate glass and glass ceramics

    NASA Astrophysics Data System (ADS)

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

    2012-06-01

    Dy3+ doped bismuth zinc borate transparent glasses were prepared by melt quenching technique and these glasses were used precursor to obtain transparent glass ceramics by heat treatment method. XRD pattern of the glass ceramic shows the formation of the β-BiB3O6 and Bi2ZnOB2O6 phases. The visible emission intensity of the glass ceramics is stronger than the glass. This can be due to the formation of nano nonlinear optical crystallites in glass matrix.

  13. Microstructure and dielectric properties of (Nb + In) co-doped rutile TiO2 ceramics

    NASA Astrophysics Data System (ADS)

    Li, Jinglei; Li, Fei; Zhuang, Yongyong; Jin, Li; Wang, Linghang; Wei, Xiaoyong; Xu, Zhuo; Zhang, Shujun

    2014-08-01

    The (Nb + In) co-doped TiO2 ceramics recently attracted considerable attention due to their colossal dielectric permittivity (CP) (˜100,000) and low dielectric loss (˜0.05). In this research, the 0.5 mol. % In-only, 0.5 mol. % Nb-only, and 0.5-7 mol. % (Nb + In) co-doped TiO2 ceramics were synthesized by standard conventional solid-state reaction method. Microstructure studies showed that all samples were in pure rutile phase. The Nb and In ions were homogeneously distributed in the grain and grain boundary. Impedance spectroscopy and I-V behavior analysis demonstrated that the ceramics may compose of semiconducting grains and insulating grain boundaries. The high conductivity of grain was associated with the reduction of Ti4+ ions to Ti3+ ions, while the migration of oxygen vacancy may account for the conductivity of grain boundary. The effects of annealing treatment and bias filed on electrical properties were investigated for co-doped TiO2 ceramics, where the electric behaviors of samples were found to be susceptible to the annealing treatment and bias field. The internal-barrier-layer-capacitance mechanism was used to explain the CP phenomenon, the effect of annealing treatment and nonlinear I-V behavior for co-doped rutile TiO2 ceramics. Compared with CaCu3Ti4O12 ceramics, the high activation energy of co-doped rutile TiO2 (3.05 eV for grain boundary) was thought to be responsible for the low dielectric loss.

  14. Dose-Dependent Effects of CeO2 on Microstructure and Antibacterial Property of Plasma-Sprayed TiO2 Coatings for Orthopedic Application

    NASA Astrophysics Data System (ADS)

    Zhao, Xiaobing; Liu, Gaopeng; Zheng, Hai; Cao, Huiliang; Liu, Xuanyong

    2015-02-01

    Titanium and its alloys have been used extensively for orthopedic and dental implants. Although these devices have achieved high rates of success, two major complications may be encountered: the lack of osseointegration and the biomaterial-related infection. Accordingly, cerium oxide (CeO2)-doped titanium oxide (TiO2) materials were coated on titanium by an atmospheric plasma spraying (APS) technique. The phase structures, morphologies, and surface chemical states of the obtained coatings were characterized by x-ray diffraction, scanning electron microscopy, and x-ray photoelectron spectroscopy techniques. The in vitro antibacterial and cytocompatibility of the materials were studied with Staphylococcus aureus ( S. aureus, ATCC25923) and osteoblast precursor cell line MC3T3-E1. The results indicated that the addition of CeO2 shifts slightly the diffraction peaks of TiO2 matrix to low angles but does not change its rutile phase structure. In addition, the CeO2/TiO2 composite coatings possess dose-dependent corrosion resistance and antimicrobial properties. And doping of 10 wt.% CeO2 exhibits the highest activity against S. aureus, improved corrosion resistance, and competitive cytocompatibility, which argues a promising option for balancing the osteogenetic and antibacterial properties of titanium implants.

  15. Defect properties of cobalt-doped hexagonal barium titanate ceramics

    NASA Astrophysics Data System (ADS)

    Langhammer, H. T.; Böttcher, R.; Müller, T.; Walther, T.; Ebbinghaus, S. G.

    2015-07-01

    X-ray diffraction (XRD) patterns, electron paramagnetic resonance (EPR) powder spectra (9 and 34 GHz) and the magnetic susceptibility of BaTiO3 + 0.04 BaO + x/2 Co2O3 (0.001 ⩽ x ⩽ 0.02) ceramics were studied to investigate the incorporation of Co ions in the BaTiO3 lattice and their valence states as well as the development of the hexagonal phase (6H modification) in dependence on doping level x and sintering temperature Ts. At Ts = 1400 °C the 6H modification begins to occur at a nominal Co concentration x of about 0.001 and for x > 0.005 the samples are completely hexagonal at room temperature. Two different EPR spectra were observed in the 6H modification of BaTiO3, which were both assigned to paramagnetic Co2+ ions located at the two crystallographically non-equivalent Ti sites in 6H-BaTiO3. The EPR g tensor values as well as the molar paramagnetic susceptibility, measured in the temperature range 5 K-300 K at a magnetic field of 9 T, were analyzed in the framework of the ligand field theory using the program CONCORD. The combination of EPR and magnetic measurements reveals that in air-sintered 6H BaTiO3, the incorporated Co occurs as a mixture of paramagnetic Co2+ and diamagnetic Co3+ ions, whereas in samples annealed in reducing atmosphere the majority of Co is in the divalent state. The occurrence of Co4+ can be excluded for all investigated samples. The sample color caused by Co2+ and Co3+ ions is beige/light yellow and dark grey/black, respectively. The majority of the Co2+ ions substitutes Ti in the exclusively corner-sharing oxygen octahedra possessing nearly cubic symmetry. The corresponding ligand field parameter B04(3) amounts to about -28 000 cm-1 (Wybourne notation, 10Dq ≈ 20 000 cm-1). In the reduced samples nearly 5% of the detected Co2+ ions occupy the Ti site in the face-sharing oxygen octahedra, which are significantly trigonally distorted. The negative sign of the obtained ligand field parameter B02 ≈ -7300 cm-1

  16. Ho(3+)-doped nanophase glass ceramics for efficiency enhancement in silicon solar cells.

    PubMed

    Lahoz, Fernando

    2008-12-15

    Currently Er(3+)-doped fluorides are being used as upconversion phosphors to enhance the efficiency of Si solar cells, to our knowledge. However, this enhancement is strongly limited owing to the small solar spectral range around 1540 nm that is used. We demonstrate that Ho(3+)-doped oxyfluoride glass ceramics are adequate to enlarge the Si sub-bandgap region around 1170 nm that can be transformed into higher-energy photons, showing an upconversion efficiency 2 orders of magnitude higher than the precursor glass. As these materials are transparent at 1540 nm, they can be used complementarily with Er(3+)-doped phosphors for the same purpose. PMID:19079513

  17. EPR on Y-ceramics and Bi-vitroceramics doped with S state paramagnetic ions

    NASA Astrophysics Data System (ADS)

    Simon, Simion; Ilonca, Gheorghe; Barbur, Ioan; Ardelean, Ioan; Redac, Radu

    1989-12-01

    The effect of Gd doping and of thermal history on the EPR spectra from Y 1-xGd xBa 2Cu 3O 7-δ ceramics and, for the first time, from Bi 2-xGd xSr 2Ca 2O z vitroceramics was investigated. The results were correlated with the superconducting properties of the studied samples.

  18. Laser ceramic materials for subpicosecond solid-state lasers using Nd3+-doped mixed scandium garnets.

    PubMed

    Okada, Hajime; Tanaka, Momoko; Kiriyama, Hiromitsu; Nakai, Yoshiki; Ochi, Yoshihiro; Sugiyama, Akira; Daido, Hiroyuki; Kimura, Toyoaki; Yanagitani, Takagimi; Yagi, Hideki; Meichin, Noriyuki

    2010-09-15

    We have successfully developed and demonstrated broadband emission Nd-doped mixed scandium garnets based on laser ceramic technology. The inhomogeneous broadening of Nd(3+) fluorescence lines results in a bandwidth above 5 nm that is significantly broader than that for Nd:YAG and enables subpicosecond mode-locked pulse durations. We have also found the emission cross section of 7.8 × 10(-20) cm(2) to be adequate for efficient energy extraction and thermal conductivity of 4.7 W/mK from these new Nd-doped laser ceramics. The new laser ceramics are good candidates for laser host material in a diode-pumped subpicosecond laser system with high efficiency and high repetition rate. PMID:20847774

  19. Structure and distortion of lead fluoride nanocrystals in rare earth doped oxyfluoride glass ceramics.

    PubMed

    Ge, Jin; Zhao, Lijuan; Guo, Hui; Lan, Zijian; Chang, Lifen; Li, Yiming; Yu, Hua

    2013-10-28

    A series of rare earth (RE) doped oxyfluoride glasses with the composition of (45-x) SiO2-5Al2O3-40PbF2-10CdF2-xRe2O3 (x = 1, 5, 10, 15) (mol%) were prepared by a traditional melt-quenching method. Glass ceramics (GCs) were obtained after thermal treatment and characterized by X-ray diffraction (XRD) to investigate the nanocrystal structure and distortion. Both the dopant type and the doping level play an important role in the distortion of the PbF2-RE lattice. It is found that a cubic Pb3REF9 phase forms in low doping GCs, a tetragonal PbREF5 phase forms in middle doping GCs and cubic PbRE3F11 forms in high doping GCs. Accordingly, the site symmetry of RE(3+) dopants in β-PbF2 nanocrystal undergoes a transition of Oh···D4h···Oh with the increase of doping level. The change in the ligands coordinating the RE(3+) ions was further illustrated by the optical changes in Yb-doped GCs. This paper provides insights on the nanocrystal structure of RE at the atomic level and tries to make a complete description of the nanocrystal structure and distortion in these glass-ceramic materials, which will benefit the optimization of optical properties. PMID:24019159

  20. Cubic to tetragonal phase transition of Tm3+ doped nanocrystals in oxyfluoride glass ceramics

    NASA Astrophysics Data System (ADS)

    Li, Yiming; Zhao, Lijuan; Fu, Yuting; Shi, Yahui; Zhang, Xiaoyu; Yu, Hua

    2016-02-01

    Tm3+ ions doped β-PbF2 nanocrystals in oxyfluoride glass ceramics with different doping concentrations and thermal temperatures are prepared by a traditional melt-quenching and thermal treatment method to investigate the structure and the phase transition of Tm3+ doped nanocrystals. The structures are characterized by X-ray diffraction Rietveld analysis and confirmed with numerical simulation. The phase transitions are proved further by the emission spectra. Both of the doping concentration and thermal temperature can induce an Oh to D4h site symmetry distortion and a cubic to tetragonal phase transition. The luminescence of Tm3+ doped nanocrystals at 800 nm was modulated by the phase transition of the surrounding crystal field.

  1. Oxygen Diffusion in Nanocrystalline CeO2

    SciTech Connect

    Saraf, Laxmikant V.; Shutthanandan, V; Wang, Chong M.; Zhang, Yanwen; Marina, Olga A.; Thevuthasan, Suntharampillai

    2003-08-14

    A unique ability of CeO2 to gain or lose oxygen ion has valued importance in the area of solid oxide fuel cells and catalysts. The macroscopic nature of oxygen storage, release and thereby vacancy generation, transport is explained with the help of quantum mechanical phenomena of electron localization. In this study, 18O diffusion and related transport on 1-2 mm thick nanocrystalline ceria films prepared by sol-gel process with an average grain-size in the range of 3-6 nm are studied. Initial 18O diffusion results indicate increased diffusion in 6 nm average grain-size nano-ceria films compared to {approx} 38 nm average grain-size poly-ceria films. Conductivity values in the case of {approx} 3nm average grain size CeO2 films grown at 300 0C observed to be marginally increased compared to {approx} 6 nm average grain size ceria films grown at 450 0C. A detailed nano-grain analysis by high-resolution transmission electron microscopy (HRTEM) was carried out to understand the effect of nanocrystallinity on the blocking phenomena.

  2. Preparation and photocatalytic property of CeO 2 lamellar

    NASA Astrophysics Data System (ADS)

    Chen, Fengjuan; Cao, Yali; Jia, Dianzeng

    2011-08-01

    A novel room temperature solid-state chemical synthesis was introduced to successfully fabricate CeO 2 samples, coupled by a polyethylene glycol 400 (PEG 400)/cetyl trimethylammonium bromide (CTAB)/sodium dodecyl sulfate (SDS). The as-prepared products were characterized by XRD, TEM, SEM, BET and UV. A study of photocatalytic degradation of the methylene blue MB under UV illumination has been carried out. It is indicated that the samples exhibit excellent photocatalytic activity. Besides, the samples assisted with surfactants possess higher photocatalytic activity than the sample without any surfactants, wherein the sample with SDS as an additive shows the highest photocatalytic activity, which is able to reach 89.6% MB degradation ratio within 60 min illumination. Moreover, the effects of important operational parameters such as initial MB concentration, catalyst loading and pH were also investigated. The above sample under the optimum conditions obtained the maximum MB degradation ratio up to 96.5%, which is higher than that of the commercial TiO 2 P25 under the same conditions. It can be concluded that CeO 2 will be a potential photocatalyst in the application of organic pollutant.

  3. Fabrication and characterization of Eu3+-doped Lu2O3 scintillation ceramics

    NASA Astrophysics Data System (ADS)

    Kopylov, Yu. L.; Kravchenko, V. B.; Dulina, N. A.; Lopin, А. V.; Parkhomenko, S. V.; Tolmachev, A. V.; Yavetskiy, R. P.; Zelenskaya, O. V.

    2013-02-01

    Density, morphology, optical transmittance and luminescence of undoped and europium-doped Lu2O3 ceramics have been studied. It has been revealed that europium ions in concentration of 5 at.% act as a solid-state sintering aids in Lu2O3 ceramics promoting its densification. Lu2O3:Eu3+ optical ceramics with relative density of 98 ± 2%, with an average grain size of 50 μm and in-line transmittance of 41% in the visible wavelength range has been produced by vacuum sintering at Т = 1850 °С. The scintillation characteristics of Lu2O3:Eu3+ ceramics under excitation with α-particles (238Рu source, E = 5.46 МeV) have been determined for the first time (S = 500 ± 50 photons/МeV, R = 26.5%).

  4. Processing and scintillation properties of Eu 3+ doped Lu 2O 3 transparent ceramics

    NASA Astrophysics Data System (ADS)

    Shi, Y.; Chen, Q. W.; Shi, J. L.

    2009-03-01

    A novel processing was developed to fabricate transparent europium (Eu 3+) ion doped lutetia (Lu 2O 3) scintillation ceramics. The microstructural evolution of Eu 3+:Lu 2O 3 phosphor powder under different calcining temperatures was investigated by FTIR and TEM. Highly transparent polycrystalline Lu 2O 3 ceramics were densified from as-prepared powder by pressureless sintering under 1850 °C for 6 h in flowing H 2 atmosphere. Optical linear transmittances in the visible wavelength region for Lu 2O 3 ceramic could reach as high as above 80%. Integration of the X-ray excited emission spectra showed that Lu 2O 3:5at%Eu 3+ ceramic scintillator provided about 10 times overall emission intensity with respect to BGO single crystal at room temperature.

  5. Visible light induced degradation of methylene blue using CeO2/V2O5 and CeO2/CuO catalysts.

    PubMed

    Saravanan, R; Joicy, S; Gupta, V K; Narayanan, V; Stephen, A

    2013-12-01

    In the present study, the nanocatalysts CeO2, V2O5, CuO, CeO2/V2O5 and CeO2/CuO were synthesized by thermal decomposition method. This method is simple, fast and cost effective compared with other preparation methods. The synthesized catalysts were characterized by different techniques. The XRD and XPS results confirmed the structure and the oxidization states of the nanocomposite materials. DRS results suggested that the prepared CeO2/V2O5 and CeO2/CuO nanocomposites can generate more electrons and holes under visible light irradiation. The photocatalytic activities of prepared catalysts were evaluated using the degradation of aqueous methylene blue solution as a model compound under visible light irradiation. In addition, the nanocomposite (CeO2/V2O5 and CeO2/CuO) materials were employed to degrade the textile effluent under visible light condition. PMID:24094180

  6. Radioluminescence properties of Sm-doped fluorochlorozirconate glasses and glass-ceramics

    NASA Astrophysics Data System (ADS)

    Okada, Go; Edgar, Andy; Kasap, Safa; Yanagida, Takayuki

    2016-02-01

    We have investigated X-ray induced radioluminescence (XL) properties of Sm-doped fluorochlorozirconate (FCZ) glasses and glass-ceramics. The FCZ glass is a modified ZBLAN glass which shows a very high optical transmission over a wide spectral range. The glass matrix includes Sm3+-doped nanocrystals of BaCl2 after heat-treatment at temperatures above 250 °C. The glass-ceramic emits red light under UV and X-ray exposure. Since conventional Si-based photodetectors, e.g., CCDs, have the highest quantum efficiency to red light in general, the Sm-doped FCZ glass-ceramic plate can be a good candidate as a scintillator material for indirect radiation detection. Moreover, a very broad emission is present in the glass-ceramic around 300-500 nm, which is attributed to a self-trapped exciton (STE) emissions. The temperature dependence of X-ray induced luminescence and photoluminescence are very similar. The XL light yield is linearly proportional to the X-ray exposure rate for rates higher than 20 mR/s. For low exposure rates, emissions by Sm2+ are more sensitive than others, leading to a nonlinear response.

  7. Investigation of the additive induced doping effects in gelcast soft lead zirconate titanate ceramics

    SciTech Connect

    Guo Dong; Cai Kai; Li Longtu; Gui Zhilun

    2009-09-01

    Due to the high sensitivity of the electrical properties of electronic ceramics to various factors, knowledge about the possible influence of the processing procedure on their electrical performance is critical for applying a new technique to the fabrication of the materials. In this study, various electrical parameters, complex impedance spectra, ferroelectric hysteresis loops, and microstructures of soft lead zirconate titanate (PZT) ceramics formed by the gelcasting technique from suspensions with various dispersants were investigated in comparison with those of the conventional dry pressed ones. We found that the sodium ion, which is the main cation in many commercial surfactants, exhibited obvious hard doping effects; thus causing deteriorated performance of the gelcast PZT ceramics. While a certain impurity ion introduced by a dispersant was also found to induce soft doping characteristics and improve the electrical performance of the materials. The results suggest that the doping effects of the metal ions or impurities introduced by the dispersants, or other additives, should be generally considered for applying a wet processing technique to forming multicomponent electronic ceramics.

  8. Phase Formation in PZT Phosphorus-Doped Ceramics

    SciTech Connect

    Celi, L. A.; Caballero, A. C.; Villegas, M.; Moure, C.; Fernandez, J. F.; Eiras, J. A.

    2009-04-19

    The surface modification of lead zirconate titanate (PZT) ceramics with phosphate ester leaves a phosphorus residue absorbed onto the particle surface. During the sintering processes, this surface layer reacts with the PZT to form lead-rich compounds, such as Pb{sub 3}(PO{sub 4}){sub 2} and Pb{sub 4}(P{sub 2}O{sub 9}). The formation of such a compounds may be the responsible for the grain growth inhibition observed in PZT-modified ceramics, as well as the lead loss reduction.

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  10. Ceramics

    NASA Astrophysics Data System (ADS)

    Bin, Tang; Feng, Si; Ying-xiang, Li; He-tuo, Chen; Xiao, Zhang; Shu-ren, Zhang

    2014-11-01

    The effects of Ta2O5/Y2O3 codoping on the microstructure and microwave dielectric properties of Ba(Co0.56Zn0.40)1/3Nb2/3O3- xA- xB (A = 0.045 wt.% Ta2O5; B = 0.113 wt.% Y2O3) ceramics ( x = 0, 1, 2, 4, 8, 16, 32) prepared according to the conventional solid-state reaction technique were investigated. The x-ray diffraction (XRD) results showed that the main crystal phase in the sintered ceramics was BaZn0.33Nb0.67O3-Ba3CoNb2O9. The additional surface phase of Ba8CoNb6O24 and trace amounts of Ba5Nb4O15 second phase were present when Ta2O5/Y2O3 was added to the ceramics. The 1:2 B-site cation ordering was affected by the substitution of Ta5+ and Y3+ in the crystal lattice, especially for x = 4. Scanning electron microscopy (SEM) images of the optimally doped ceramics sintered at 1340°C for 20 h showed a compact microstructure with crystal grains in dense contact. Though the dielectric constant increased with the x value, appropriate addition would result in a tremendous modification of the Q × f and τ f values. Excellent microwave dielectric properties ( ɛ r = 35.4, Q × f = 62,993 GHz, and τ f = 2.6 ppm/°C) were obtained for the ceramic with x = 0.4 sintered in air at 1340°C for 20 h.

  11. Basic study of Eu2+-doped garnet ceramic scintillator produced by spark plasma sintering

    NASA Astrophysics Data System (ADS)

    Sugiyama, Makoto; Yanagida, Takayuki; Fujimoto, Yutaka; Yokota, Yuui; Ito, Akihiko; Nikl, Martin; Goto, Takashi; Yoshikawa, Akira

    2012-12-01

    We report a new discovery of Eu2+-doped bulk garnet ceramic scintillators based on reduction of Eu3+ ions without additives. Eu2+-doped Y3Al5O12 and Lu3Al5O12 ceramics were prepared by spark plasma sintering (SPS) method. Using SPS, the green and blue luminescence was observed under UV lamp excitation for Eu2+-doped Y3Al5O12 and Lu3Al5O12 ceramics, respectively. Under excitation by 241Am alpha-ray the Eu2+ 5d-4f emission was observed in radioluminescence spectra both samples. For the first time, scintillation response due to Eu2+ 5d-4f luminescence was observed in the bulk garnet oxide materials. In addition, Eu-doped Al2O3 prepared by SPS showed Eu2+ 5d-4f emission in the radioluminescence spectrum. It is confirmed that Al is a key element to reduce Eu3+ as well as highly reductive condition in SPS.

  12. Optical absorption and luminescence study of cobalt-doped magnesium aluminosilicate glass ceramics

    NASA Astrophysics Data System (ADS)

    Malyarevich, A. M.; Denisov, I. A.; Yumashev, K. V.; Dymshits, O. S.; Zhilin, A. A.

    2002-08-01

    Linear and nonlinear optical properties of cobalt-doped magnesium aluminosilicate transparent glass ceramics that were prepared under different conditions have been studied. It has been shown that absorption and luminescence spectra and absorption bleaching of these glass ceramics are defined mainly by tetrahedrally coordinated Co 2+ ions located in magnesium aluminum spinel nanocrystals. The lifetimes of the 4 T 1 ( 4 F) and 4 T 2 ( 4 F) excited states of the tetrahedral Co 2+ ions were found to be in the ranges 2540 and 120450 ns, respectively, depending on the Co concentration. 2002 Optical Society of America

  13. Lead fluorosilicate glass ceramics doped with Nd3+, Er3+, and Yb3+

    NASA Astrophysics Data System (ADS)

    Petrova, O. B.; Khomyakov, A. V.

    2013-06-01

    Glasses in the PbF2-PbO-SiO2 system doped with 1 mol % of rare-earth elements (Nd3+, Er3+, or Yb3+) are synthesized and studied. The glasses were heat-treated in order to obtain glass ceramics with a fluoride crystalline phase. The changes in the structure and spectral optical properties of glass ceramics with respect to initial glasses were determined by using X-ray diffraction analysis and by studying the luminescent characteristics of dopant ions.

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

    SciTech Connect

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

    2014-04-24

    Samarium doped Barium Zirconium Titanate ceramic with general formula Ba{sub 1−x}Sm{sub 2x/3}Zr{sub 0.05}Ti{sub 0.95}O{sub 3} [x=0.0,0.01,0.02,0.03,0.04] has been prepared by high energy ball milling. The X-ray diffraction (XRD) patterns confirmed that these ceramics have a single phase with perovskite-type upto x≤0.03 and a small secondary phase exist at x=0.04. The temperature dependent dielectric study shows a ferroelectric phase transition and transition temperature decreases with an increase in the Samarium content.

  15. Enhanced broadband near-infrared luminescence from Ni in Bi/Ni-doped transparent glass ceramics

    NASA Astrophysics Data System (ADS)

    Wu, Botao; Ruan, Jian; Qiu, Jianrong; Zeng, Heping

    2009-07-01

    Spectral properties of Bi/Ni-doped transparent MgO-Al2O3-Ga2O3-SiO2-TiO2 glass ceramics (GCs) containing spinel solution nanocrystals were investigated. The emission intensity of Ni in Bi/Ni-doped GCs was about 4 times stronger than that of Ni-doped GCs due to energy transfer from Bi to Ni. The Bi/Ni-doped GCs with 0.75 mol% Bi2O3 concentration exhibited a near-infrared emission with full width at half maximum of about 270 nm and a fluorescent lifetime of about 350 µs, making them very promising for applications in broadband optical amplifiers and tunable lasers.

  16. Structural properties of fluorozirconate-based glass ceramics doped with multivalent europium

    PubMed Central

    Paßlick, C.; Müller, O.; Lützenkirchen-Hecht, D.; Frahm, R.; Johnson, J. A.; Schweizer, S.

    2011-01-01

    The structure/property relationships of fluorochlorozirconate glass ceramics as a function of divalent and trivalent europium (Eu) co-doping and thermal processing have been investigated; the influence of doping ratio on the formation of barium chloride (BaCl2) nanocrystals therein was elucidated. X-ray absorption near-edge structure spectroscopy shows that the post-thermal annealing changes the Eu valence of the as-poured glass slightly, but during the melting process Eu3+ is more strongly reduced to Eu2+, in particular, when doped as a chloride instead of fluoride compound. The Eu2+-to-Eu3+ doping ratio also plays a significant role in chemical equilibrium in the melt. X-ray diffraction measurements indicate that a higher Eu2+ fraction leads to a BaCl2 phase transition from hexagonal to orthorhombic structure at a lower temperature. PMID:22275772

  17. Structural properties of fluorozirconate-based glass ceramics doped with multivalent europium

    SciTech Connect

    Passlick, C.; Mueller, O.; Luetzenkirchen-Hecht, D.; Frahm, R.; Johnson, J. A.; Schweizer, S.

    2011-12-01

    The structure/property relationships of fluorochlorozirconate glass ceramics as a function of divalent and trivalent europium (Eu) co-doping and thermal processing have been investigated; the influence of doping ratio on the formation of barium chloride (BaCl{sub 2}) nanocrystals therein was elucidated. X-ray absorption near-edge structure spectroscopy shows that the post-thermal annealing changes the Eu valence of the as-poured glass slightly, but during the melting process Eu{sup 3+} is more strongly reduced to Eu{sup 2+}, in particular, when doped as a chloride instead of fluoride compound. The Eu{sup 2+}-to-Eu{sup 3+} doping ratio also plays a significant role in chemical equilibrium in the melt. X-ray diffraction measurements indicate that a higher Eu{sup 2+} fraction leads to a BaCl{sub 2} phase transition from hexagonal to orthorhombic structure at a lower temperature.

  18. Dielectric, ferroelectric and piezoelectric properties of Nb{sup 5+} doped BCZT ceramics

    SciTech Connect

    Parjansri, Piewpan; Intatha, Uraiwan; Eitssayeam, Sukum

    2015-05-15

    Highlights: • Average grain size of BCZT ceramic decreased with the increasing Nb{sup 5+} doping. • Dielectric constant value is enhanced with Nb{sup 5+} doping. • Dielectric loss of BCZT − x Nb{sup 5+} ceramics was less than 0.03 at room temperature (1 kHz). • Piezoelectric coefficient decreased with the increasing Nb{sup 5+} doping. • The relaxation behavior is enhanced with the doping of Nb{sup 5+}. - Abstract: This work investigated the electrical properties of Nb{sup 5+} (0.0–1.0 mol%) doped with Ba{sub 0.90}Ca{sub 0.10}Zr{sub 0.10}Ti{sub 0.90}O{sub 3} while adding 1 mol% of Ba{sub 0.90}Ca{sub 0.10}Zr{sub 0.10}Ti{sub 0.90}O{sub 3} seeds. The mixed powder was ball milled for 24 h, calcined and sintered at 1200 °C for 2 h and 1450 °C for 4 h, respectively. The XRD patterns of the ceramic samples were investigated by X-ray diffraction. The electrical properties of ceramics were measured and the results indicated that all samples show a pure perovskite phase with no secondary phase. Density and average grain size values were in the range of 5.60–5.71 g/cm{sup 3} and 12.62–1.86 μm, respectively. The highest dielectric constant, ϵ{sub r} at room temperature (1 kHz) was 4636 found at 1.0 mol% Nb. The dielectric loss, tan δ was less than 0.03 for all samples at room temperature (1 kHz). Other electrical properties, P{sub r}, d{sub 33} and k{sub p} values were decreased with Nb doped relates to the decreasing grain size in BCZT ceramics. Moreover, the degrees of phase transition diffuseness and relaxation behavior were observed in the higher Nb doping.

  19. Dielectric Properties of Rare-Earth-Oxide-Doped BaTiO3 Ceramics Fired in Reducing Atmosphere

    NASA Astrophysics Data System (ADS)

    Okino, Yoshikazu; Shizuno, Hisamitsu; Kusumi, Shinya; Kishi, Hiroshi

    1994-09-01

    In order to gain an understanding of highly reliable electrical characteristics for the Ho-doped multilayer ceramic capacitors with Ni electrodes, dielectric properties of various rare-earth-oxide-doped BaTiO3 ceramics were studied. The smaller ionic radius rare-earth-oxide (Dy, Ho, Er)-doped samples showed lower resistivity in reducing atmosphere, but higher resistivity in oxidizing atmosphere at the cooling stage, compared with the larger-ion (La, Sm, Gd)-doped samples. Multilayer ceramic capacitors with Ni electrodes using the smaller-ion-doped materials showed smaller aging rate and longer lifetime. We developed Ni-electrode MLCs with X7R specification as 1 µ F in the 2125 type.

  20. Enhanced Dielectric Properties and High-Temperature Microwave Absorption Performance of Zn-Doped Al2O3 Ceramic

    NASA Astrophysics Data System (ADS)

    Wang, Yuan; Luo, Fa; Wei, Ping; Zhou, Wancheng; Zhu, Dongmei

    2015-07-01

    To improve the dielectric and microwave absorption properties of Al2O3 ceramic, Zn-doped Al2O3 ceramic was prepared by conventional ceramic processing. X-ray diffraction analysis confirmed that Zn atoms successfully entered the Al2O3 ceramic lattice and occupied Al sites. The complex permittivity increased with increasing Zn concentration, which is mainly attributed to the increase in charged vacancy defects and densification of the Al2O3 ceramic. In addition, the temperature-dependent complex permittivity of 3% Zn-doped Al2O3 ceramic was determined in the temperature range from 298 K to 873 K. Both the real and imaginary parts of the complex permittivity increased monotonically with increasing temperature, which can be ascribed to the shortened relaxation time and increasing electrical conductivity. The increased complex permittivity leads to a great improvement in microwave absorption. In particular, when the temperature is up to 873 K, the 3% Zn-doped Al2O3 ceramic exhibited the best absorption performance with a maximum peak (-12.1 dB) and broad effective absorption bandwidth (reflection loss less than -10 dB from 9.3 GHz to 12.3 GHz). These results reveal that Zn-doped Al2O3 ceramic is a promising candidate for use as a kind of high-temperature microwave absorption material.

  1. Microstructure, toughness and flexural strength of self-reinforced silicon nitride ceramics doped with yttrium oxide and ytterbium oxide.

    PubMed

    Zheng, Y. S.; Knowles, K. M.; Vieira, J. M.; Lopes, A. B.; Oliveira, F. J.

    2001-02-01

    Self-reinforced silicon nitride ceramics with additions of either yttrium oxide or ytterbium oxide have been investigated at room temperature after various processing heat treatments. Devitrification of the intergranular phase in these materials is very sensitive to the heat treatment used during processing and does not necessarily improve their strength and toughness. Hot-pressed ceramics without a subsequent devitrification heat treatment were the strongest. The ytterbium oxide-doped silicon nitride ceramics were consistently tougher, but less strong, than the yttrium oxide-doped silicon nitride ceramics. In all the ceramics examined, the fracture toughness showed evidence for R-curve behaviour. This was most significant in pressureless sintered ytterbium oxide-doped silicon nitride ceramics. A number of toughening mechanisms, including crack deflection, bridging, and fibre-like grain pull-out, were observed during microstructural analysis of the ceramics. In common with other silicon nitride-based ceramics, thin amorphous films were found at the grain boundaries in each of the ceramics examined. Arrays of dislocations left in the elongated silicon nitride grains after processing were found to belong to the {101;0}<0001> primary slip system. PMID:11207926

  2. Optical, scintillation and dosimeter properties of MgO translucent ceramic doped with Cr3+

    NASA Astrophysics Data System (ADS)

    Kato, Takumi; Okada, Go; Yanagida, Takayuki

    2016-04-01

    We have investigated the photoluminescence (PL), scintillation and thermally-stimulated luminescence (TSL) dosimeter properties of MgO translucent ceramic doped with Cr3+ ion (0.001, 0.01 and 0.1%). The ceramic samples were synthesized by a Spark Plasma Sintering (SPS) technique. The broad and sharp emission peaks appeared around 600-850 nm in all the samples. The PL decay time constants of all the samples were a few ms which were on the typical order of Cr3+ doped phosphors. As with the PL, the peak resulted from Cr3+ ion was detected in the scintillation spectra. The TSL glow curves showed the main peak around 140 °C. The TSL response was confirmed to be linear to the irradiation dose over the dose range from 0.1 to 1000 mGy.

  3. Preparation and photocatalytic activity of CeO 2/TiO 2 interface composite film

    NASA Astrophysics Data System (ADS)

    Jiang, Bangtong; Zhang, Shengyi; Guo, Xiaozhu; Jin, Baokang; Tian, Yupeng

    2009-03-01

    The CeO 2/TiO 2 and TiO 2/CeO 2 interface composite films were prepared on glass substrates by the sol-gel process via dip-coating and calcining technique. The scanning electron microscopy (SEM) revealed that the TiO 2 layer has a compact and uniformity glasslike surface with 200 nm in thickness, and the CeO 2 layer has a coarse surface with 240 nm in thickness. The X-ray diffractometer (XRD) analysis showed that the TiO 2 layer is made up of anatase phase, and the CeO 2 layer is structured by cubic fluorite phase. Through a series of photo-degradation experiments, the relationship of the photocatalytic activity with the constituents of the films was studied. In virtue of the efficient interfacial charge separation via the process of electron transfer from TiO 2 to CeO 2, the photocatalytic activity of the CeO 2/TiO 2 composite film is high. Contrarily, the photocatalytic activity of the TiO 2/CeO 2 composite film is low, due to its inert surface made up of CeO 2 with broad bandwidth. Apart from the effect of the film structure, the effect of film thickness on photocatalytic activity was also discussed.

  4. Spectral investigations on Dy{sup 3+}-doped transparent oxyfluoride glasses and nanocrystalline glass ceramics

    SciTech Connect

    Babu, P.; Jang, Kyoung Hyuk; Kim, Eun Sik; Shi, Liang; Seo, Hyo Jin; Rivera-Lopez, F.; Rodriguez-Mendoza, U. R.; Lavin, V.; Vijaya, R.; Jayasankar, C. K.; Rama Moorthy, L.

    2009-01-01

    Dysprosium-doped oxyfluoride glasses and nanocrystalline glass ceramics have been synthesized and studied by x-ray diffraction, absorption, and visible and near-infrared emission spectra. The samples emit intense white light when populating the {sup 4}F{sub 9/2} level with a 451 nm laser light and, from the visible emission spectra, yellow to blue intensity ratios and chromaticity color coordinates have been calculated and their relative variation have been discussed based on the concentration of Dy{sup 3+} ions and the heat treatment conditions used to prepare the glass ceramics. Infrared emission has also been observed in glasses and glass ceramics after laser excitation at 800 nm, showing bands at 1.33 and 1.67 {mu}m, useful for optical amplification in fiber amplifiers.

  5. Fabrication and Characterization of Dual Phase Magnesia-Zirconia Ceramics Doped with Plutonia

    SciTech Connect

    P. G. Medvedev; J. F. Jue; S. M. Frank; M.K. Meyer

    2005-05-01

    Dual phase magnesia-zirconia ceramics doped with plutonia are being studied as an inert matrix fuel (IMF) for light water reactors. The motivation of this work is to develop an IMF with a thermal conductivity superior to that of the fuels based on yttria stabilized zirconia. The concept uses the MgO phase as an efficient heat conductor to increase thermal conductivity of the composite. In this paper ceramic fabrication and characterization by scanning electron microscopy, energy and wavelength dispersive xray spectroscopy is discussed. Characterization shows that the ceramics consist of the two-phase matrix and PuO2-rich inclusions. The matrix is comprised of pure MgO phase and MgO-ZrO2-PuO2 solid solution. The PuO2-rich inclusion contained dissolved MgO and ZrO2.

  6. Fabrication and characterization of dual phase magnesia zirconia ceramics doped with plutonia

    NASA Astrophysics Data System (ADS)

    Medvedev, P. G.; Jue, J. F.; Frank, S. M.; Meyer, M. K.

    2006-06-01

    Dual phase magnesia-zirconia ceramics doped with plutonia are being studied as an inert matrix fuel (IMF) for light water reactors. The motivation of this work is to develop an IMF with a thermal conductivity superior to that of the fuels based on yttria stabilized zirconia. The concept uses the MgO phase as an efficient heat conductor to increase thermal conductivity of the composite. In this paper ceramic fabrication and characterization by scanning electron microscopy, energy and wavelength dispersive X-ray spectroscopy is discussed. Characterization shows that the ceramics consist of the two-phase matrix and PuO2-rich inclusions. The matrix is comprised of pure MgO phase and MgO-ZrO2-PuO2 solid solution. The PuO2-rich inclusion contained dissolved MgO and ZrO2.

  7. Preparation of a novel fluorescent nanocomposite: CeO2 / ANS by a simple method

    NASA Astrophysics Data System (ADS)

    Liu, X.; Lian, X.; Li, Y.; Zhang, N.

    2012-03-01

    For the first time, a novel fluorescent material, composed of CeO2/ANS nanocomposites was successfully synthesized by a simple ultrasonic method, using CeO2 nanoparticles and 8-anilino-1-naphthalenesulfonic acid (ANS) as the raw materials. The samples were characterized by scanning electron microscope (SEM), photoluminescence spectroscopy and Fourier transformation infrared spectroscopy (FTIR). The results showed that the PL intensity of the CeO2/ANS nanocomposites was higher than that of both CeO2 nanoparticles and ANS powders, and the peak wavelength was also different from the peak wavelength typical of each of the used materials, which suggests that the chemical reaction occurs between CeO2 nanoparticles and ANS molecules. In addition, the effect of the ANS concentrations on the photoluminescence of the nanocomposites was also investigated.

  8. Huge low-frequency dielectric response of (Nb,In)-doped TiO2 ceramics

    NASA Astrophysics Data System (ADS)

    Wu, Y. Q.; Zhao, X.; Zhang, J. L.; Su, W. B.; Liu, J.

    2015-12-01

    The (Nb,In)-doped TiO2 ceramics have drawn considerable attention as a type of promising giant-permittivity dielectric materials in recent years. However, a significant controversy concerning the giant dielectric mechanism currently exists, and clarifying it is vitally important from both scientific and technological viewpoints. This letter reports the results of a systematical comparison study, where two kinds of (Nb,In)-doped TiO2 ceramics with a substantial difference in dielectric loss are used. Dielectric properties and complex impedance are investigated over a broad frequency band of 3 mHz-110 MHz. A huge low-frequency dielectric response in addition to the giant dielectric relaxation appearing above 1 MHz is observed for both kinds of (Nb,In)-doped TiO2 ceramics in dielectric dispersion. The huge dielectric response observed in the low frequency range can be ascribed to a non-ohmic electrode-contact, and the dielectric relaxation appearing above 1 MHz can be attributed to an internal barrier layer capacitance effect. An electrical equivalent circuit model suggested can well describe the observed dielectric properties and electrical behaviors.

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

    SciTech Connect

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

    2015-09-01

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

  10. Microstructure evolution and electrical characterization of Lanthanum doped Barium Titanate (BaTiO3) ceramics

    NASA Astrophysics Data System (ADS)

    Billah, Masum; Ahmed, A.; Rahman, Md. Miftaur; Mahbub, Rubbayat; Gafur, M. A.; Bashar, M. Shahriar

    2016-07-01

    In the current work, we investigated the structural and dielectric properties of Lanthanum oxide (La2O3) doped Barium Titanate (BaTiO3) ceramics and established a correlation between them. Solid state sintering method was used to dope BaTiO3 with 0.3, 0.5 and 0.7 mole% La2O3 under different sintering parameters. The raw materials used were La2O3 nano powder of ~80nm grain size and 99.995% purity and BaTiO3 nano powder of 100nm grain size and 99.99% purity. Grain size distribution and morphology of fracture surface of sintered pellets were examined by Field Emission Scanning Electron Microscope and X-Ray Diffraction analysis was conducted to confirm the formation of desired crystal structure. The research result reveal that grain size and electrical properties of BaTiO3 ceramic significantly enhanced for small amount of doping (up to 0.5 mole% La2O3) and then decreased with increasing doping concentration. Desired grain growth (0.80-1.3 µm) and high densification (<90% theoretical density) were found by proper combination of temperature, sintering parameters and doping concentration. We found the resultant stable value of dielectric constant was 10000-12000 at 100-300 Hz in the temperature range of 30°-50° C for 0.5 mole% La2O3 with corresponding shift of curie temperature around 30° C. So overall this research showed that proper La3+ concentration can control the grain size, increase density, lower curie temperature and hence significantly improve the electrical properties of BaTiO3 ceramics.

  11. TEM investigation of irradiation damage in single crystal CeO 2

    NASA Astrophysics Data System (ADS)

    Ye, Bei; Kirk, Mark A.; Chen, Weiying; Oaks, Aaron; Rest, Jeffery; Yacout, Abdellatif; Stubbins, James F.

    2011-07-01

    In order to understand the evolution of radiation damage in oxide nuclear fuel, 150-1000 keV Kr ions were implanted into single crystal CeO 2, as a simulation of fluorite ceramic UO 2, while in situ transmission electron microscopy (TEM) observations were carried out. Two characteristic defect structures were investigated: dislocation/dislocation loops and nano-size gas bubbles. The growth behavior of defect clusters induced by 1 MeV Kr ions up to doses of 5 × 10 15 ions/cm 2 were followed at 600 °C and 800 °C. TEM micrographs clearly show the development of defect structures: nucleation of dislocation loops, transformation to extended dislocation lines, and the formation of tangled dislocation networks. The difference in dislocation growth rates at 600 °C and 800 °C revealed the important role which Ce-vacancies play in the loop formation process. Bubble formation, studied through 150 keV Kr implantations at room temperature and 600 °C, might be influenced by either the mobility of metal-vacancies correlated with at threshold temperature or the limitation of gas solubility as a function of temperature.

  12. Study of dielectric properties of Ca doped barium titanate ceramics

    NASA Astrophysics Data System (ADS)

    Pradhan, S. K.; Kumar, Amit; Sinha, A. N.; Kour, P.

    2016-05-01

    Ba1-xCax Zr0.52Ti0.48 O3 ceramics was prepared by sol gel method. The crystallite size was in nano scale range. The dielectric constant was increased with increase in Ca2+ concentration in the sample. The dielectric loss was decreased with increase in ca concentration in the sample. The ac conductivity of the sample was increased with increase in Ca2+ concentration in the sample. The ac conductivity of the sample follows Johnscher power law. AC conductivity analysis shows that the interactions between neighbouring dipoles were decreased with the increase in Ca2+ concentration in the sample.

  13. Enhanced electrical properties in multiferroic BiFeO3 ceramics co-doped by La3+ and V5+

    NASA Astrophysics Data System (ADS)

    Yu, Benfang; Li, Meiya; Wang, Jing; Pei, Ling; Guo, Dongyun; Zhao, Xingzhong

    2008-09-01

    La3+ and V5+ co-doped Bi0.85La0.15Fe1-xVxO3 (BLFVx, x = 0-0.1) ceramics were prepared by a rapid liquid sintering technique. The effects of the V5+-doping content on the structure and electrical properties of BLFVx ceramics were investigated. In the range of the V5+ content x from 0 to 0.03, BLFVx ceramics had a polycrystalline perovskite structure with tiny residual Bi2O3, while an impurity phase appeared for x > 0.03. As the x increased from 0 to 0.1, both the leakage current density and the dielectric loss (tan δ) for BLFVx ceramics decreased gradually, while the dielectric constant (ɛr) first increased and then decreased gradually in this process, reaching a maximum value of 273 for x = 0.03. Among the BLFVx ceramics, the BLFVx=0.01 ceramic showed a well-saturated hysteresis loop with large remanent polarization (Pr) of 39.4 µC cm-2 and a low coercive electric field (Ec) of ±43.1 kV cm-1 under an applied electric field of ±75 kV cm-1. In addition, these ceramics exhibited good anti-fatigue characteristics after 2 × 1010 read/write polarization cycles. These suggested that La3+ and V5+ co-doping was beneficial for enhancing the dielectric, ferroelectric and anti-fatigue properties of the BLFVx ceramics.

  14. Ultrahigh temperature Bi3Ti0.96Sc0.02Ta0.02NbO9-based piezoelectric ceramics

    NASA Astrophysics Data System (ADS)

    Gai, Zhi-Gang; Wang, Jin-Feng; Sun, Wen-bin; Wang, Chun-Ming; Zhao, Ming-Lei; Sun, Shang-Qian; Ming, Bao-Quan; Qi, Peng; Zheng, Li-mei; Du, Juan; Zhang, Shujun; Shrout, Thomas R.

    2008-07-01

    The effect of (Sc,Ta,Ce) doping on the properties of Bi3TiNbO9 (BTNO)-based ceramics was investigated. The cerium modification greatly improves the piezoelectric activity of Bi3(Ti0.96Sc0.02Ta0.02)NbO9-based ceramics and significantly decreases the dielectric dissipation. The d33 of Bi3Ti0.96Sc0.02Ta0.02NbO9+x wt %CeO2 (x =0.35) was found to be 18 pC/N, the highest value among the BTNO-based ceramics and almost three times as much as the reported d33 values of the pure BTNO ceramics (˜6 pC/N). The modification increased the resistivity ρ of the samples extremely, resolving the low resistivity problem for high temperature applications. The dielectric spectroscopy shows that the TC for all the ceramics is higher than 900 °C. The mechanical quality factor Q and planar coupling factors kp and kt of Bi3Ti0.96Sc0.02Ta0.02NbO9+0.35 wt %CeO2 ceramic were found to be 2835, 9%, and 23%, respectively, and it has high TC and stable piezoelectric properties, demonstrating that the (Sc,Ta,Ce) modified BTNO-based material is a wonderful candidate for high temperature applications.

  15. Photocatalytic and antibacterial properties of phytosynthesized CeO2 NPs using Moringa oleifera peel extract.

    PubMed

    Surendra, T V; Roopan, Selvaraj Mohana

    2016-08-01

    Biosynthetic methods are alternative approaches which are much safer than the normal techniques (physical and chemical) used for the methods for synthesis of metal nanoparticles. The benefits are sample as it is economic and environment friendly. Herein present investigation, we have reported a microwave mediated eco-friendly synthetic approach for preparing cerium oxide (CeO2) nanoparticles. Here, we used Moringa oleifera peel as the stabilizing and reducing agent towards synthesize of Ce2O NPs via microwave irradiation. The NPs were further characterized using UV-Vis, FT-IR, XRD and HR-TEM techniques. The FTIR analysis confirmed the phytochemical involvement in NPs stabilization. The crystallinity of CeO2 nanoparticles are well demonstrated through X-ray Diffraction and HR-TEM. The TEM images reveal the spherical shape of the CeO2 NPs having an average size of 45nm. Additionally, these CeO2 NPs were used successfully as a catalyst in the degradation of the dye, crystal violet. Also the antibacterial activity of the synthesized CeO2 NPs was evaluated using Staphylococcus aureus (Gram positive bacteria) and Escherichia coli (Gram negative bacteria). CeO2 NPs showed better activity on E. coli than S. aureus. We have demonstrated an eco-friendly preparation of CeO2 nanoparticles, a good photocatalyst and having better antibacterial properties. PMID:27236047

  16. Surface passivation of CeO2 catalyst and its ultraviolet screening effect.

    PubMed

    Kang, Joo-Hee; Kim, Yun-Hee; Paek, Seung-Min; Choy, Jin-Ho

    2011-07-01

    A new strategy was attempted to fabricate CeO2 nanoparticles using the surface fluorination technique to control the particle size and suppress the catalytic activity. The fluorinated CeO2 nanoparticles are fully characterized with XRD, XANES, UV-vis spectroscopy, HR-TEM, XPS along with the evaluation of photo and thermal catalytic activities. XRD patterns were not affected by surface fluorination. That is to say, the crystalline structure of CeO2 was not deteriorated upon fluorination. The TEM analysis showed that the fluorinated CeO2 nanoparticles with the primary particle size of 7 nm could be prepared. According to the X-ray absorption near edge structure (XANES) analysis, overall XANES spectrum was not changed upon fluorination, suggesting that the local structure of fluorinated CeO2 resembled that of the starting CeO2 nanoparticles. It was also revealed that both photo and thermal catalytic activities could be almost totally suppressed at the fluorination level of ca. 6.0 wt%. It is suggested that the selective surface fluorination with fluoride could lead to fluorinated CeO2 nanoparticles, which could be applied to new fields such as the cosmetics industries. PMID:22121733

  17. CeO2 nanorods-supported transition metal catalysts for CO oxidation.

    PubMed

    Mock, Samantha A; Sharp, Shannon E; Stoner, Thomas R; Radetic, Michael J; Zell, Elizabeth T; Wang, Ruigang

    2016-03-15

    A catalytically active oxide support in combination with metal catalysts is required in order to achieve better low temperature activity and selectivity. Here, we report that CeO2 nanorods with a superior surface oxygen release/storage capability were used as an active support of transition metal (TM) catalysts (Mn, Fe, Co, Ni, Cu) for CO oxidation reaction. The as-prepared CeO2 nanorods supported 10 wt% TM catalysts were highly active for CO oxidation at low temperature, except for the Fe sample. It is found that the 10%Cu-CeO2 catalyst performed best, and it provided a lower light-off temperature with T50 (50% conversion) at 75 °C and T100 (100% conversion) of CO to CO2 at 194 °C. The atomic level surface structure of CeO2 nanorods was investigated in order to understand the improved low temperature catalytic activity. The richness of surface roughness and various defects (voids, lattice distortion, bending, steps, twinning) on CeO2 nanorods could facilitate oxygen release and storage. According to XRD and Raman analysis, copper species migrate into the bulk CeO2 nanorods to a greater degree. Since CO adsorbed over the surface of the catalyst/support is detrimental to its catalytic activity, the surface defects on the CeO2 nanorods and CeO2-TM interactions were critical to the enhanced activity. PMID:26745742

  18. Electrochromic performance of sol-gel-deposited CeO2 films

    NASA Astrophysics Data System (ADS)

    Ozer, Nilgun; Cronin, John P.; Akyuz, Sevim

    1999-10-01

    Ceria (CeO2) films were prepared by a sol-gel technique onto fluorine doped tin oxide coated glass substrates. The coating solution was derived from cerium ammonium nitrate dissolved in ethanol with diethanolamine used as a complexing agent. Lithium intercalating properties of the films were investigated using cyclic voltammetry (CV) and UV-visible spectroscopy. The electrochemical examinations were performed in a 0.5 M LiClO4 propylene carbonate electrolyte. The additional film characterizations were performed in X-ray diffractometry (XRD), x-ray photoelectron spectroscopy, scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy. XRD of the films showed that they had an cerianite structure for heat treatment temperatures at or above 450 degree(s)C. The SEM examinations showed that the surface texture was uniform and homogeneous. CV examinations showed a reversible electrochemical insertion or extraction of Li+/e- ions maintaining a high optical transmissivity. Spectroelectrochemistry showed that these films can be used as optically passive counter-electrode in transmissive electrochromic devices.

  19. Synthesis of Non-uniformly Pr-doped SrTiO3 Ceramics and Their Thermoelectric Properties.

    PubMed

    Mehdizadeh Dehkordi, Arash; Bhattacharya, Sriparna; Darroudi, Taghi; Zeng, Xiaoyu; Alshareef, Husam N; Tritt, Terry M

    2015-01-01

    We demonstrate a novel synthesis strategy for the preparation of Pr-doped SrTiO3 ceramics via a combination of solid state reaction and spark plasma sintering techniques. Polycrystalline ceramics possessing a unique morphology can be achieved by optimizing the process parameters, particularly spark plasma sintering heating rate. The phase and morphology of the synthesized ceramics were investigated in detail using X-ray diffraction, scanning electron microcopy and energy-dispersive X-ray spectroscopy. It was observed that the grains of these bulk Pr-doped SrTiO3 ceramics were enhanced with Pr-rich grain boundaries. Electronic and thermal transport properties were also investigated as a function of temperature and doping concentration. Such a microstructure was found to give rise to improved thermoelectric properties. Specifically, it resulted in a significant improvement in carrier mobility and the thermoelectric power factor. Simultaneously, it also led to a marked reduction in the thermal conductivity. As a result, a significant improvement (> 30%) in the thermoelectric figure of merit was achieved for the whole temperature range over all previously reported maximum values for SrTiO3-based ceramics. This synthesis demonstrates the steps for the preparation of bulk polycrystalline ceramics of non-uniformly Pr-doped SrTiO3. PMID:26327483

  20. Optical thermometry based on luminescence behavior of Dy3+-doped transparent LaF3 glass ceramics

    NASA Astrophysics Data System (ADS)

    Bu, Y. Y.; Cheng, S. J.; Wang, X. F.; Yan, X. H.

    2015-11-01

    Dy3+-doped transparent LaF3 glass ceramics were fabricated, and its structures of resulting glass ceramics are studied by the X-ray diffraction and transmission electron microscopy. Optical temperature sensing of the resulting glass ceramics in the temperature range from 298 to 523 K is studied based on the down-conversion luminescence of Dy3+ ion. By using fluorescence intensity ratio method, the 4I15/2 and 4F9/2 of Dy3+ ions are verified as thermally coupled levels. A minimum S R = 1.16 × 10-4 K-1 is obtained at T = 294 K. By doping Eu3+ ion, the overall emission color of Eu3+-Dy3+ co-doped transparent glass ceramics can be tuned from white to yellow with the temperature increase through energy transfer between Eu3+ and Dy3+. Additionally, the thermal stability of the Dy3+ single-doped transparent glass ceramics becomes higher after doping Eu3+ ion.

  1. Spectroscopic properties of transparent Er-doped oxyfluoride glass-ceramics with GdF₃.

    PubMed

    Środa, Marcin; Szlósarczyk, Krzysztof; Różański, Marek; Sitarz, Maciej; Jeleń, Piotr

    2015-01-01

    Optically active glass-ceramics (GC) with the low-phonon phases of fluorides, doped with Er(3+) was studied. Glass based on SiO₂-Al₂O₃-Na₂F₂-Na₂O-GdF₃-BaO system was obtained. Dopant were introduced to the glass in an amount of 0.01 mol Er₂O₃ per 1 mol of glass. DTA/DSC study shows multi-stage crystallization. XRD identification of obtained phases did not confirm the presence of pure GdF₃ phase. Instead of that ceramization process led to formation of NaGdF₄ and BaGdF₅. The structural changes were studied using FT-IR spectroscopic method. The study of luminescence of the samples confirmed that optical properties of the obtained GC depend on crystallizing phases during ceramization. Time resolved spectroscopy of Er-doped glass showed the 3 and 8 times increase of lifetime of emission from (4)S₃/₂ and (4)F₉/₂ states, respectively. It confirms the erbium ions have ability to locate in the low phonon gadolinium-based crystallites. The results give possibility to obtain a new material for optoelectronic application. PMID:25049170

  2. Doping of BiScO3-PbTiO3 Ceramics for Enhanced Properties

    NASA Technical Reports Server (NTRS)

    Sehirlioglu, Alp; Sayir, Ali; Dynys, Fred

    2008-01-01

    High-temperature piezoelectrics are a key technology for aeronautics and aerospace applications such as fuel modulation to increase the engine efficiency and decrease emissions. The principal challenge for the insertion of piezoelectric materials is the limitation on upper use temperature which is due to low Curie-Temperature (T(sub c) and increasing electrical conductivity. BiScO3 -PbTiO3 (BS-PT) system is a promising candidate for improving the operating temperature for piezoelectric actuators due to its high TC (>400 C). Effects of Zr and Mn doping of the BS-PT ceramics have been studied and all electrical and electromechanical properties for Sc-deficient and Ti-deficient BS- PT ceramics are reported as a function of electrical field and temperature. Donor doping with Zr and Mn (in Sc deficient compositions) increased the DC-resistivity and decreased tan at all temperatures. Resulting ceramics exhibited saturated hysteresis loops with low losses and showed no dependence on the applied field (above twice the coercive field) and measurement frequency.

  3. Diffuse phase transition of Fe doped lead ytterbium tantalate ceramics

    NASA Astrophysics Data System (ADS)

    Rout, Dibyaranjan; Subramanian, V.; Hariharan, K.; Sivasubramanian, V.

    2006-02-01

    The effect of different concentration of Fe on the phase transition behavior of Lead ytterbium tantalate is investigated by dielectric and differential scanning calrimetry measurements. The samples are prepared through solid state reaction method and it has been found that the sintering temperature significantly lowered when the proportion of Pb(Fe 1/2Ta 1/2)O 3 increased. It has been observed that the doping in small amounts (0≤ x≤0.2) of Fe could meliorate the dielectric and ferroelectric properties. The diffuseness in the mode of phase transition increases and the phase transition temperature decreases as a function of Fe content. It is revealed that the dielectric data and heat capacity data follow a similar trend in the variation of the mode of phase transition and phase transition temperatures. The phase transition temperature values obtained from the heat capacity measurement well agreed with the values obtained from dielectric measurement.

  4. Rare Earth Doped High Temperature Ceramic Selective Emitters

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

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

  5. Eu doping in multiferroic BiFeO3 ceramics studied by Mossbauer and EXAFS spectroscopy.

    PubMed

    Kothari, Deepti; Raghavendra Reddy, V; Gupta, Ajay; Meneghini, Carlo; Aquilanti, Giuliana

    2010-09-01

    Bismuth ferrite ceramics (BiFeO(3)) are multifunctional materials classified as multiferroics for their special magnetic and electric properties that can be modified by substitutional doping at the Bi and/or Fe sites. Understanding the relation between magnetoelectric response and structural/electronic modification upon doping is a relevant issue. In this work, the structure of Eu-doped multiferroic systems (Bi(1-x)Eu(x)FeO(3), x = 0, 0.5, 0.1, 0.15) as well as the valence state of Fe and Eu ions have been investigated combining Mossbauer and x-ray absorption fine structure (XAFS) spectroscopy techniques. The Eu(3+) doping at the Bi site results in better magnetic properties. High temperature (57)Fe Mossbauer data and Fe K-edge XAFS results show that FeO(6) octahedron distortions reduce with Eu(3+) doping. It is conclusively shown that the observed magnetic properties in BiFeO(3) with chemical substitution (Eu) are mainly due to the structural distortions and not due to Fe multiple valence. (151)Eu Mossbauer measurements show that the Eu(3+)(Bi(3+)) site is magnetically inactive in BiFeO(3). PMID:21403301

  6. Eu doping in multiferroic BiFeO3 ceramics studied by Mossbauer and EXAFS spectroscopy

    NASA Astrophysics Data System (ADS)

    Kothari, Deepti; Raghavendra Reddy, V.; Gupta, Ajay; Meneghini, Carlo; Aquilanti, Giuliana

    2010-09-01

    Bismuth ferrite ceramics (BiFeO3) are multifunctional materials classified as multiferroics for their special magnetic and electric properties that can be modified by substitutional doping at the Bi and/or Fe sites. Understanding the relation between magnetoelectric response and structural/electronic modification upon doping is a relevant issue. In this work, the structure of Eu-doped multiferroic systems (Bi1 - xEuxFeO3, x = 0, 0.5, 0.1, 0.15) as well as the valence state of Fe and Eu ions have been investigated combining Mossbauer and x-ray absorption fine structure (XAFS) spectroscopy techniques. The Eu3 + doping at the Bi site results in better magnetic properties. High temperature 57Fe Mossbauer data and Fe K-edge XAFS results show that FeO6 octahedron distortions reduce with Eu3 + doping. It is conclusively shown that the observed magnetic properties in BiFeO3 with chemical substitution (Eu) are mainly due to the structural distortions and not due to Fe multiple valence. 151Eu Mossbauer measurements show that the Eu3 + (Bi3 + ) site is magnetically inactive in BiFeO3.

  7. Influence of high magnetic field on the luminescence of Eu{sup 3+}-doped glass ceramics

    SciTech Connect

    Jiang, Wei; Chen, Weibo; Chen, Ping; Xu, Beibei; Zheng, Shuhong; Guo, Qiangbing; Liu, Xiaofeng E-mail: qjr@zju.edu.cn; Zhang, Junpei; Han, Junbo; Qiu, Jianrong E-mail: qjr@zju.edu.cn

    2014-09-28

    Rare earth (RE) doped materials have been widely exploited as the intriguing electronic configuration of RE ions offers diverse functionalities from optics to magnetism. However, the coupling of magnetism with photoluminescence (PL) in such materials has been rarely reported in spite of its fundamental significance. In the present paper, the effect of high pulsed magnetic field on the photoluminescence intensity of Eu{sup 3+}-doped nano-glass-ceramics has been investigated. In our experiment, Eu-doped oxyfluoride glass and glass ceramic were prepared by the conventional melt-quenching process and controlled heat treatment. The results demonstrate that the integrated PL intensity of Eu{sup 3+} decreases with the enhancement of magnetic field, which can be interpreted in terms of cooperation effect of Zeeman splitting and magnetic field induced change in site symmetry. Furthermore, as a result of Zeeman splitting, both blue and red shift in the emission peaks of Eu{sup 3+} can be observed, and this effect becomes more prominent with the increase of magnetic field. Possible mechanisms associated with the observed magneto-optical behaviors are suggested. The results of the present paper may open a new gate for modulation of luminescence by magnetic field and remote optical detection of magnetic field.

  8. Effect of Fe doping on structural and impedance properties of PZTFN ceramics

    NASA Astrophysics Data System (ADS)

    Kumar, Arvind; Pal, Vijayeta; Mishra, S. K.

    2016-05-01

    An attempts have been made to synthesis the ceramics Pb1-3x/2 Fex(Zr0.52Ti0.48)1-5y/4 NbyO3 abbreviated as (PFZTN) for x = 1-6 mol% and y = 5.5 mol% by a semi-wet route. In the present paper, we have investigated the effect of Fe doping on structural and electrical properties of the PFZTN ceramics. X-ray diffraction (XRD) patterns reveal that PFZTN ceramics are single phase in nature. However, for x = 0.05 and 0.06, a secondary phase appears as discernible from the XRD profiles. Rietveld analysis of the powder diffraction data shows the presence of coexistence of tetragonal (P4mm space group) and rhombohedral phases (R3c space group) occurs near the morphotropic phase boundary (MPB) at x ≥ = 0.05. The log-log plots show that the conductivity increases with increase of temperature. The ac conductivity becomes sensitive at high frequency region and shifted towards higher frequency side with increasing temperature. It is observed that the activation energy (Ea) decreases with increasing frequency. This complex perovskite structure can be used as a multilayer ceramic capacitors and electromechanical transducers.

  9. Luminescence study of mixed valence Eu-doped nanocrystalline glass-ceramics

    NASA Astrophysics Data System (ADS)

    Bagga, Ruchika; Achanta, Venu Gopal; Goel, Ashutosh; Ferreira, José M. F.; Singh, Narinder Pal; Singh, Davinder Paul; Contini, Vittoria; Falconieri, Mauro; Sharma, Gopi

    2013-12-01

    Eu-doped nanocrystalline NaAlSiO4/NaY9Si6O26 glass-ceramics have been prepared by controlled crystallization of melt quenched bulk glasses. XRD, SEM and FTIR spectroscopy techniques were employed to characterize the crystallization process and the structural properties of the precursor glass and corresponding glass-ceramics. The formation of divalent europium (Eu2+) from Eu3+ ions during high temperature synthesis under ambient atmosphere was analyzed by photoluminescence spectroscopy and is discussed using the optical basicity model. The observed luminescence properties of Eu: NaY9Si6O26 are compared with that of Eu: β-PbF2 nanocrystals and their marked differences are discussed.

  10. Ultraviolet and white photon avalanche upconversion in Ho{sup 3+}-doped nanophase glass ceramics

    SciTech Connect

    Lahoz, F.; Martin, I.R.; Calvilla-Quintero, J.M.

    2005-01-31

    Ho{sup 3+}-doped fluoride nanophase glass ceramics have been synthesized from silica-based oxyfluoride glass. An intense white emission light is observed by the naked eye under near infrared excitation at 750 nm. This visible upconversion is due to three strong emission bands in the primary color components, red, green, and blue. Besides, ultraviolet signals are also recorded upon the same excitation wavelength. The excitation mechanism of both the ultraviolet and the visible emissions is a photon avalanche process with a relatively low pump power threshold at about 20 mW. The total upconverted emission intensity has been estimated to increase by about a factor of 20 in the glass ceramic compared to the precursor glass, in which an avalanche type mechanism is not generated.

  11. Enhanced multiferroic characteristics in Fe-doped BiTiO ceramics

    NASA Astrophysics Data System (ADS)

    Chen, X. Q.; Yang, F. J.; Cao, W. Q.; Wang, H.; Yang, C. P.; Wang, D. Y.; Chen, K.

    2010-07-01

    Modification of Bi 4Ti 3O 12 multiferroic ceramics prepared by a conventional solid state reaction method were investigated by substituting Ti partly with Fe. The introduction of Fe does not change the layered perovskite structure of Bi 4Ti 3O 12. Upon increasing Fe content, the remnant polarization of the samples is enhanced. The magnetism of the ceramics at room temperature develops from diamagnetism to weak ferromagnetism with increasing Fe doping. The largest variations of 15% and 6% in remnant polarization and magnetization, achieved in a Bi 4Ti 1Fe 2O 12-δ sample after poling it in a magnetic field at 1 T and a DC electric field at 30 kV/cm for 10 min, are evidence of magnetoelectric coupling between the electric dipoles and magnetic dipoles at room temperature. The present results suggest a new candidate for a room temperature multiferroic material with enhanced properties.

  12. Fruit juice extract mediated synthesis of CeO2 nanoparticles for antibacterial and photocatalytic activities

    NASA Astrophysics Data System (ADS)

    Reddy Yadav, L. S.; Manjunath, K.; Archana, B.; Madhu, C.; Raja Naika, H.; Nagabhushana, H.; Kavitha, C.; Nagaraju, G.

    2016-05-01

    Ceria ( CeO2 is a technologically important rare-earth material because of its unique properties and various engineering/biological applications. In the present work, cerium oxide nanoparticles have been prepared by a simple solution combustion method using watermelon juice as a novel combustible fuel. The structure and morphology of the synthesized CeO2 nanoparticles were analyzed using various analytical tools such as PXRD, FTIR, Raman, UV-Visible and SEM. PXRD pattern confirms that the prepared material is composed of cubic-phase cerium oxide nanoparticles. Photocatalytic degradation of Methylene blue dye using CeO2 nanoparticles shows 98% of degradation in UV irradiations. Furthermore the antibacterial properties of CeO2 nanoparticles were investigated by their bacterial activity against two bacterial strains using the agar well diffusion method.

  13. The microstructure of erbium-ytterbium co-doped oxyfluoride glass-ceramic optical fibers

    NASA Astrophysics Data System (ADS)

    Augustyn, Elżbieta; Żelechower, Michał; Stróż, Danuta; Chrapoński, Jacek

    2012-04-01

    Oxyfluoride transparent glass-ceramics combine some features of glasses (easier shaping or lower than single crystals cost of fabrication) and some advantages of rare-earth doped single crystals (narrow absorption/emission lines and longer lifetimes of luminescent levels). Since the material seems to be promising candidate for efficient fiber amplifiers, the manufacturing as well as structural and optical examination of the oxyfluoride glass-ceramic fibers doped with rare-earth ions seems to be a serious challenge. In the first stage oxyfluoride glasses of the following compositions 48SiO2-11Al2O3-7Na2CO3-10CaO-10PbO-11PbF2-3ErF3 and 48SiO2-11Al2O3-7Na2CO3-10CaO-10PbO-10PbF2-3YbF3-1ErF3 (in molar%) were fabricated from high purity commercial chemicals (Sigma-Aldrich). The fabricated glass preforms were drawn into glass fibers using the mini-tower. Finally, the transparent Er3+ doped and Er3+/Yb3+ co-doped oxyfluoride glass-ceramic fibers were obtained by controlled heat treatment of glass fibers. The preceding differential thermal analysis (DTA) studies allowed estimating both the fiber drawing temperature and the controlled crystallization temperature of glass fibers. X-ray diffraction examination (XRD) at each stage of the glass-ceramic fibers fabrication confirmed the undesirable crystallization of preforms and glass fibers has been avoided. The fibers shown their mixed amorphous-crystalline microstructure with nano-crystals of size even below 10 nm distributed in the glassy host. The crystal structure of the grown nano-crystals has been determined by XRD and confirmed by electron diffraction (SAED). Results obtained by both techniques seem to be compatible: Er3FO10Si3 (monoclinic; ICSD 92512), Pb5Al3F19 (triclinic; ICSD 91325) and Er4F2O11Si3 (triclinic; ICSD 51510) against to initially expected PbF2 crystals.

  14. Structural, topographical and electrical properties of cerium doped strontium barium niobate (Ce:SBN60) ceramics

    NASA Astrophysics Data System (ADS)

    Raj, S. Gokul; Mathivanan, V.; Kumar, G. Ramesh; Yathavan, S.; Mohan, R.

    2016-05-01

    Tungsten bronze type cerium doped strontium barium niobate (Ce:SBN - Sr0.6B0.4Nb2O6) ceramics were synthesized by solid state process. Cerium was used as dopant to improve its electrical properties. Influence of Ce+ ions on the photoluminescence properties was investigated in detail. The grain size topographical behavior of SBN powders and their associated abnormal grain growth (AGG) were completely analyzed through SEM studies. Finally dielectric, measurement discusses about the broad phase transition observed due to cerium dopant The results were discussed in detail.

  15. High temperature dielectric relaxation anomaly of Y3+ and Mn2+ doped barium strontium titanate ceramics

    NASA Astrophysics Data System (ADS)

    Yan, Shiguang; Mao, Chaoliang; Wang, Genshui; Yao, Chunhua; Cao, Fei; Dong, Xianlin

    2014-10-01

    Relaxation like dielectric anomaly is observed in Y3+ and Mn2+ doped barium strontium titanate ceramics when the temperature is over 450 K. Apart from the conventional dielectric relaxation analysis method with Debye or modified Debye equations, which is hard to give exact temperature dependence of the relaxation process, dielectric response in the form of complex impedance, assisted with Cole-Cole impedance model corrected equivalent circuits, is adopted to solve this problem and chase the polarization mechanism in this paper. Through this method, an excellent description to temperature dependence of the dielectric relaxation anomaly and its dominated factors are achieved. Further analysis reveals that the exponential decay of the Cole distribution parameter n with temperature is confirmed to be induced by the microscopic lattice distortion due to ions doping and the interaction between the defects. At last, a clear sight to polarization mechanism containing both the intrinsic dipolar polarization and extrinsic distributed oxygen vacancies hopping response under different temperature is obtained.

  16. Luminescence of Er/Yb and Tm/Yb doped FAp nanoparticles and ceramics

    NASA Astrophysics Data System (ADS)

    Grigorjeva, L.; Smits, K.; Millers, D.; Jankoviča, Dz

    2015-03-01

    The nanoparticles of hydroxiapatite and fluorapatite doped with Er/Yb and Tm/Yb were synthesized and characterized by FTIR, XRD, SEM and TEM methods. The results of up-conversion luminescence studies were presented for the samples as prepared, annealed at 500°C and at 900-1000 °C. At annealing above 800°C the ceramic state was formed. It is shown that fluorapatite host is more appropriate than hydroxiapatite host for rare ions luminescence and up-conversion processes. The post preparing annealing of nanarticles significantly enhanced the luminescence intensity. The Tm/Yb doped fluorapatite shows intense up-conversion luminescence in 790-800 nm spectral region and is potentially useful for biomedical applications.

  17. Structural and optical properties of Pr doped BiFeO3 multiferroic ceramics

    NASA Astrophysics Data System (ADS)

    Singh, Vikash; Subhash, Dwivedi, R. K.; Kumar, Manoj

    2013-02-01

    Pure and Pr substituted BiFeO3 (BFO) ceramics were synthesized by solid state reaction method. X-ray analysis shows the formation of BFO rhombohedral phase with R3c space group. Photoluminescent spectra of pure BFO showed blue emission corresponding to band gap at 2.67 eV. In Pr doped samples in addition to blue emission (2.67eV), a broad weak yellow emission has also been observed due to electronic transitions of dopant Pr3+ states. FTIR spectra showed two broad absorption peaks due to overlapping of Fe-O and Bi-O groups in the region 700 - 400 cm-1. These interesting optical properties of Pr doped BFO samples in visible region may find potential applications in optoelectronic devices.

  18. Toxicity of CeO2 nanoparticles - the effect of nanoparticle properties.

    PubMed

    Leung, Yu Hang; Yung, Mana M N; Ng, Alan M C; Ma, Angel P Y; Wong, Stella W Y; Chan, Charis M N; Ng, Yip Hang; Djurišić, Aleksandra B; Guo, Muyao; Wong, Mabel Ting; Leung, Frederick C C; Chan, Wai Kin; Leung, Kenneth M Y; Lee, Hung Kay

    2015-04-01

    Conflicting reports on the toxicity of CeO2 nanomaterials have been published in recent years, with some studies finding CeO2 nanoparticles to be toxic, while others found it to have protective effects against oxidative stress. To investigate the possible reasons for this, we have performed a comprehensive study on the physical and chemical properties of nanosized CeO2 from three different suppliers as well as CeO2 synthesized by us, and tested their toxicity. For toxicity tests, we have studied the effects of CeO2 nanoparticles on a Gram-negative bacterium Escherichia coli in the dark, under ambient and UV illuminations. We have also performed toxicity tests on the marine diatom Skeletonema costatum under ambient and UV illuminations. We found that the CeO2 nanoparticle samples exhibited significantly different toxicity, which could likely be attributed to the differences in interactions with cells, and possibly to differences in nanoparticle compositions. Our results also suggest that toxicity tests on bacteria may not be suitable for predicting the ecotoxicity of nanomaterials. The relationship between the toxicity and physicochemical properties of the nanoparticles is explicitly discussed in the light of the current results. PMID:25768267

  19. Er/Yb co-doped oxy-fluoride glass-ceramics core/polymer cladding optical fibers

    NASA Astrophysics Data System (ADS)

    Czerska, E.; Świderska, M.

    2014-11-01

    Erbium/ytterbium co-doped glasses can be applied as NIR laser sources (1.55 μm) or optical amplifiers in this range. About hundred meters of Er/Yb co-doped oxy-fluoride glass-ceramics fibers have been drawn from a glass preform followed by controlled annealing. Processing temperatures (drawing and annealing) were selected upon thermal analysis results (DTA/DSC plots). Glass-ceramic structure was confirmed by the XRD measurements. Obtained fibers show good optical properties. As a cladding material polymer material (acrylic resin) is considered due to its low deposition temperature and suitable value of refractive index.

  20. Strong red emission in Pr doped (Bi0.5Na0.5)TiO3 ferroelectric ceramics

    NASA Astrophysics Data System (ADS)

    Sun, Haiqin; Peng, Dengfeng; Wang, Xusheng; Tang, Mianmian; Zhang, Qiwei; Yao, Xi

    2011-07-01

    The photoluminescence of Pr doped (Bi0.5Na0.5)TiO3 ferroelectric ceramics prepared by conventional solid-state reaction were investigated. A bright red emission is observed at room temperature, which ascribed to 1D2→3H4 transition. The excitation bands are mainly located at 440 ˜ 505 nm, which is adaptable to the emission band of commercial blue light-emitting diodes (LEDs) chips. The optimal emission intensity was also obtained when Pr doping level was 0.003 mol. Meanwhile, the enhanced ferroelectric properties were obtained by Pr doping. The results show that Pr doped (Bi0.5Na0.5)TiO3 ceramics as a multifunctional material may be useful for white LEDs, sensor, and optical-electro integration.

  1. Influence of Zr4+ doping on structural and electrical properties of SrBi4Ti4O15 ceramic

    NASA Astrophysics Data System (ADS)

    Nayak, P.; Badapanda, T.; Panigrahi, S.

    2015-06-01

    This article reports a systematic study of doping effects on the structural and electrical properties of layer structured strontium bismuth titanate ceramic. In this study monophasic SrBi4Ti4-xZrxO15 with x=0.00, 0.05, 0.10, 0.15, 0.20, 0.25 ceramics were synthesized from the solid-state reaction route. X-ray diffraction analysis shows that the Zr-modified SBT ceramics have a pure four-layer Aurivillius phase structure. Dielectric properties revealed that the diffuseness of phase transition increases where as corresponding permittivity value decrease with increasing Zr content. Piezoelectric properties of SBTZ ceramics were improved by the modification of Zirconium ion. Moreover, the reason behind for improvement of piezoelectric properties of modified SBTZ ceramics was also discussed.

  2. Influence of CeO2 nanoparticles on growth and physiology of sorghum

    NASA Astrophysics Data System (ADS)

    Mu, Linlin; Liang, Wei-zhen; Kinsey, Erin; Rauh, Bradley; Kresovich, Stephen; Darnault, Christophe

    2016-04-01

    Cerium oxide nanoparticles (CeO2 NPs) are commonly used as polishing agents for industry and fuel additives to decrease the particulate matter emissions. CeO2 NPs may be encountered in the soil and water environment through their life cycle or accidental releases, and have potential phytotoxicity effects. Therefore, it is critical to assess the potential effects of CeO2 NPs in soil on plant growth and physiology. The objective of this research is to determine the physiological responses of three sorghums (Grassl, BtX623 and Rio) to the effect of CeO2 nanoparticles in potting soil environment. Sorghums were germinated and grown in potting soil in the greenhouse for three weeks cultivation with treatments of 0, 100, 500, 1000 mg CeO2 NPs per kg soil. Plant parameters, such as length, weight, and biomass of root and leaves were measured in each treatment with 12 replications. After three weeks germination, the sorghum plants were dig out and the roots were examined and scanned by the Silverfast SE Plus scanner to compare and analyze their dimensions and shapes. To further study the growth and physiological changes in plants due to the presence of CeO2 NPs in soil, one selected type of sorghum (Grassl) was grown under the four different CeO2 NPs concentration treatments for six months until plant maturity, and was also cut and harvested three times to study CeO2 NPs effect on plant re-growth. At the end of each growing period, above ground vegetative tissues were air-dried, grounded to 2mm particle size and compositional traits were estimated by using near-infrared spectroscopy. The influence of nanoparticles was observed on some of the plant traits. Preliminary results showed the influence of CeO2 NPs on the roots growth, as Grassl and Btx623 in 100 mgkg‑1 treatment grew significantly faster than other concentrations; however no significant difference between control and 100 mgkg‑1 treatment in Rio. CeO2 NPs concentration of 100 mgkg‑1 had no impact on sorghum growth, compared to the control treatment. Results of the six months growth and repetitive cutting experiments indicated that the different treatments, including the presence and/or concentrations of the nanoparticles, impacted some of the compositional traits of sorghum.

  3. Broadband mid-infrared wavelength conversion laser based on Cr2+ doped ceramic materials

    NASA Astrophysics Data System (ADS)

    Shang, Yaping; Yin, Ke; Li, Xiao; Wang, Peng; Xu, Xiaojun

    2015-10-01

    Broadband mid-infrared lasers are desirable for pretty important applications in fields of environmental protection, medical treatment, military applications, scientific, and other domains. Recently, super-continuum laser sources have achieved striking development. However, limited by the substrate materials, the output power scaling of the broadband mid-infrared fiber laser sources could not be increased drastically, especially for the long wavelength region. In this paper, we reported an experimental study about the broadband mid-infrared lasers based on Cr2+ doped II-VI ceramic materials, by using of a super-continuum laser source developed by our groups operating at 1550~2130nm with 200mW output power. The result suggested that the near-infrared spectral component of the super-continuum source was deeply absorbed by transition metal doped zinc chalcogenides ceramic materials, meanwhile the mid-infrared part, however, had been enhanced significantly by this new "power amplifier." Actually single-pass amplification efficiency was very limited. The best way to solve this problem was multi-pass amplification systems. We had shown an initial proof of this assumption by a double-pass experiments, the result was consistent with expected effect. Above all, the spectrum shaping from short wavelength to long wavelength was obtained. The innovative discovery had laid a solid foundation for high power, high efficiency, broadly tunable mid-infrared solid state lasers.

  4. Differentiation of human mesenchymal stem cells on niobium-doped fluorapatite glass-ceramics

    PubMed Central

    Kushwaha, Meenakshi; Pan, Xueliang; Holloway, Julie A.; Denry, Isabelle L.

    2011-01-01

    Objectives Our goal was to characterize the response of human mesenchymal stem cells (hMSCs) to a niobium-doped fluorapatite-based glass-ceramic (FAp). Methods The glass was prepared by twice melting at 1525°C for 3h, and cast into cylindrical ingots later sectioned into discs and heat-treated to promote crystallization of fluorapatite submicrometer crystals. Tissue culture polystyrene (TCP) was used as control. The surface of the FAp discs was either left as-heat treated, ground or etched. Initial cell attachment was assessed at 3h. Proliferation and alkaline phosphatase (ALP) expression data was collected at days 1, 4, and 8. Cell morphology was examined using SEM, at days 2 and 4. Mineralization was evaluated by Alizarin Red staining and SEM. Results Initial cell attachment on as heat-treated, etched, or ground surfaces was similar to that of the positive control group (p>0.05). The percentage of area covered by living cells increased significantly on as heat-treated, etched, or ground surfaces between days 1 and 8 (p<0.05). There was no significant difference amongst groups in cell coverage at day 8, compared to TCP control. SEM revealed well spread polygonal cells with numerous filopodia, either attached to the ceramic surface or connected to neighboring cells. ALP expression at day 8 was significantly higher in osteogenic media compared to growth media on both FAp and control. FAp discs stained positively with alizarin red and calcium-rich mineralized granules associated with fibrils were observed by SEM at day 35. Significance hMSCs displayed excellent attachment, proliferation, and differentiation on niobium-doped FAp glass-ceramic. PMID:22078764

  5. Single-step process to prepare CeO2 nanotubes with improved catalytic activity.

    PubMed

    González-Rovira, Leandro; Sánchez-Amaya, José M; López-Haro, Miguel; del Rio, Eloy; Hungría, Ana B; Midgley, Paul; Calvino, José J; Bernal, Serafín; Botana, F Javier

    2009-04-01

    CeO(2) nanotubes have been grown electrochemically using a porous alumina membrane as a template. The resulting material has been characterized by means of scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy, high-angle annular dark-field scanning transmission electron microscopy tomography, high-resolution electron microscopy (HREM), and electron energy loss spectroscopy. According to SEM, the outer diameter of the nanotubes corresponds to the pore size (200 nm) of the alumina membrane, and their length ranges between 30 and 40 microm. HREM images have revealed that the width of the nanotube walls is about 6 nm. The catalytic activity of these novel materials for the CO oxidation reaction is compared to that of a polycrystalline powder CeO(2) sample prepared by a conventional route. The activity of the CeO(2) nanotubes is shown to be in the order of 400 times higher per gram of oxide at 200 degrees C (77.2 x 10(-2) cm(3) CO(2) (STP)/(gxs) for the nanotube-shaped CeO(2) and 0.16 x 10(-2) cm(3) CO(2) (STP)/(gxs) for the powder CeO(2)). PMID:19245236

  6. CeO2-covered nanofiber for highly efficient removal of phosphorus from aqueous solution.

    PubMed

    Ko, Young Gun; Do, Taegu; Chun, Youngsang; Kim, Choong Hyun; Choi, Ung Su; Kim, Jae-Yong

    2016-04-15

    The lowering phosphorus concentration of lakes or rivers using adsorbents has been considered to be the most effective way to prevent water eutrophication. However, the development of an adsorbent is still challenging because conventional adsorbents have not shown a sufficient phosphorus adsorption capacity (0.3-2.0mmol/g) to treat industrial, agricultural or domestic wastewater at a large scale. Herein, a novel and effective strategy to remove phosphorus efficiently with a CeO2-covered nanofiber is shown. The CeO2-covered nanofiber was synthesized through (1) amine group immobilization onto an electrospun polyacrylonitrile nanofiber and (2) adsorption of Ce(3+) on it. The CeO2-covered nanofiber played a role in catching phosphate ions in an aqueous solution by the oxidation, reduction, and ion-exchange of adsorbed Ce(3+) on the nanofiber from CeO2 to CePO4, and enabled remarkable phosphate adsorption capacity of the nanofiber (ca. 17.0mmol/g) at the range of ca. pH 2-6. Our strategy might be the most feasible method to efficiently lower the phosphorus concentration in lakes or rivers owing to the easy and inexpensive preparation of CeO2-covered nanofiber at an industrial scale, with a high phosphate adsorption capacity. PMID:26795705

  7. Enzymatic glucose biosensor based on CeO2 nanorods synthesized by non-isothermal precipitation.

    PubMed

    Patil, Dewyani; Dung, Nguyen Quoc; Jung, Hyuck; Ahn, Se Yong; Jang, Dong Mi; Kim, Dojin

    2012-01-15

    Cerium oxide nanorods (CeO(2) NRs) were synthesized without templates through a low cost and simple non-isothermal precipitation method. The structure and morphology of CeO(2) NRs were characterized by X-ray diffraction and transmission electron microscopy. The CeO(2) NRs films, deposited on indium tin oxide (ITO)-coated glass substrates through electrophoretic deposition, were used for the immobilization of glucose oxidase (GOx). Field emission scanning electron microscopy, Fourier transform infrared spectroscopy, cyclic voltammetry, and electrochemical impedance spectroscopy were used to characterize the CeO(2) NRs/ITO and GOx/CeO(2) NRs/ITO electrodes. The GOx/CeO(2) NRs/ITO electrode exhibits a linear range for the detection of glucose from 2 to 26 mM (correlation coefficient: 0.99) at 1-2s response time. Biosensor sensitivity is 0.165 μA mM(-1) cm(-2) with 100 μM detection limit. The anti-interference ability of the biosensor was also examined. The mediator-less application of CeO(2) NRs for glucose sensing was demonstrated. PMID:22035972

  8. Dielectrical Properties of CeO2 Nanoparticles at Different Temperatures

    PubMed Central

    Zamiri, Reza; Abbastabar Ahangar, Hossein; Kaushal, Ajay; Zakaria, Azmi; Zamiri, Golnoosh; Tobaldi, David; Ferreira, J. M. F.

    2015-01-01

    A template-free precipitation method was used as a simple and low cost method for preparation of CeO2 nanoparticles. The structure and morphology of the prepared nanoparticle samples were studied in detail using X-ray diffraction, Raman spectroscopy and Scanning Electron Microscopy (SEM) measurements. The whole powder pattern modelling (WPPM) method was applied on XRD data to accurately measure the crystalline domain size and their size distribution. The average crystalline domain diameter was found to be 5.2 nm, with a very narrow size distribution. UV-visible absorbance spectrum was used to calculate the optical energy band gap of the prepared CeO2 nanoparticles. The FT-IR spectrum of prepared CeO2 nanoparticles showed absorption bands at 400 cm-1 to 450 cm-1 regime, which correspond to CeO2 stretching vibration. The dielectric constant (εr) and dielectric loss (tan δ) values of sintered CeO2 compact consolidated from prepared nanoparticles were measured at different temperatures in the range from 298 K (room temperature) to 623 K, and at different frequencies from 1 kHz to 1 MHz. PMID:25910071

  9. Raman and impedance spectroscopic studies of the specific features of the transport properties of electrolytes based on CeO2

    NASA Astrophysics Data System (ADS)

    Sal'nikov, V. V.; Pikalova, E. Yu.

    2015-10-01

    The solid solutions CeO2-(Sm,Nd)2O3 have been prepared by the solid-phase synthesis. The microstructure, density, and electrical conductivity of ceramic samples obtained by rolling with an organic binder, followed by sintering in air at a temperature of 1600°C have been investigated. The contributions to the total conductivity from the grain volume and grain boundaries in the temperature range of 250-700°C have been separated using impedance spectroscopy. The impedance spectroscopy data have revealed a significant effect of grain boundaries on the transport properties of the solid electrolyte with a Sm dopant as compared to the electrolyte with Nd. The optical properties of the polycrystalline electrolytes Ce1- x Nd x O2-δ and Ce0.8Sm0.2O2-δ have been studied using Raman spectroscopy. In the spectrum of the ceramic samples, there are two modes: a mode of CeO2 at a frequency of 465 cm-1 and an additional mode at a frequency of ~550 cm-1 due to vibrations associated with oxygen vacancies, the intensity of which depends on the dopant concentration and the energy of the dopant cation-oxygen vacancy bond. The binding energy of oxygen vacancies in the fluorite structure correlates with the behavior of bulk conductivity, and the solid solutions with samarium exhibit the highest bulk conductivity.

  10. Improved Thermoelectric Performances of SrTiO3 Ceramic Doped with Nb by Surface Modification of Nanosized Titania.

    PubMed

    Li, Enzhu; Wang, Ning; He, Hongcai; Chen, Haijun

    2016-12-01

    Nb-doped SrTiO3 ceramics doped with the surface modification of nanosized titania was prepared via liquid phase deposition approach and subsequent sintered in an Ar atmosphere. The surface modification of nanosized titania significantly improved the ratio of the electrical conductivity to thermal conductivity of SrTiO3 ceramic doped with Nb, and has little impact on the Seebeck coefficient, thus obviously improving the dimensionless thermoelectric figure of merit (ZT value). The surface modification of nanosized titania is a much better method to lower the thermal conductivity and to enhance the electrical conductivity than the mechanical mixing process of nanosized titania. The highest ZT value of 0.33 at 900 K was obtained. The reason for the improved thermoelectric performances by the surface modification of nano-sized titania was preliminary investigated. PMID:27067736

  11. Improved Thermoelectric Performances of SrTiO3 Ceramic Doped with Nb by Surface Modification of Nanosized Titania

    NASA Astrophysics Data System (ADS)

    Li, Enzhu; Wang, Ning; He, Hongcai; Chen, Haijun

    2016-04-01

    Nb-doped SrTiO3 ceramics doped with the surface modification of nanosized titania was prepared via liquid phase deposition approach and subsequent sintered in an Ar atmosphere. The surface modification of nanosized titania significantly improved the ratio of the electrical conductivity to thermal conductivity of SrTiO3 ceramic doped with Nb, and has little impact on the Seebeck coefficient, thus obviously improving the dimensionless thermoelectric figure of merit ( ZT value). The surface modification of nanosized titania is a much better method to lower the thermal conductivity and to enhance the electrical conductivity than the mechanical mixing process of nanosized titania. The highest ZT value of 0.33 at 900 K was obtained. The reason for the improved thermoelectric performances by the surface modification of nano-sized titania was preliminary investigated.

  12. Visible photoluminescence in polycrystalline terbium doped aluminum nitride (Tb:AlN) ceramics with high thermal conductivity

    SciTech Connect

    Wieg, A. T.; Kodera, Y.; Wang, Z.; Garay, J. E.; Imai, T.; Dames, C.

    2012-09-10

    Thermal management continues to be one of the major challenges in the development of high powered light sources such as solid state lasers. In particular, the relatively low thermal conductivity of standard photoluminescent (PL) materials limits the overall power output and/or duty cycle. We present a method based on current activated pressure assisted densification for the fabrication of high thermal conductivity PL materials: rare earth doped polycrystalline bulk aluminum nitride. Specifically, the ceramics are translucent and are doped with Tb{sup 3+}, allowing for emission in the visible. Remarkably, the ceramics have a room temperature thermal conductivity of 94 W/(m K) which is almost seven times higher than that of the state of the art host material, Nd-doped yttrium aluminum garnet. These light emitting properties coupled with very high thermal conductivity should enable the development of a wide variety of more powerful light sources.

  13. Effect of fabrication routes on the properties of Mn-doped BaTi2O5 ceramics

    NASA Astrophysics Data System (ADS)

    Liu, Wenfeng; Tsukada, Shinya; Akishige, Yukikuni

    2014-01-01

    In the present study, 0, 0.2, and 0.4 wt % MnO2 doped BaTi2O5 ceramics were fabricated by three different routes, i.e., sol-gel deriving powders and spark plasma sintering (SPS) sintering, solid state calcining and SPS sintering, sol-gel deriving powders and two times sintering. Only through the sol-gel technique and conventional sintering route, Mn could substitute for Ti as the acceptor doping and consequently caused the sharp drop of the Curie temperature as well as the enhanced dielectric constant and restricted ferroelectricity. Besides, the 0.2 wt % MnO2 doped BaTi2O5 ceramics fabricated by sol-gel deriving powders and SPS sintering exhibited the most superior dielectric and ferroelectric properties.

  14. Pressureless sintering of plasma-reacted nanosemicrystalline silicon nitride ceramics with doped sintering additives

    NASA Astrophysics Data System (ADS)

    Ryu, Kevin Hojun

    For the past few years, synthesis and consolidation of ceramics using nanoparticles have been a focus of much research. The obvious advantage is their low process temperatures (<200°C). In addition, the process results in super-plastic deformation, and drastically enhances the mechanical properties of the ceramics. Recently, a plasma-assisted chemical reaction was adopted to produce nanosize Si3N4 powders that have the characteristics of sintering additive elements on individual particles. Homogeneous size distribution of the additives can eliminate inhomogeneous shrinkage of the sintered body during the mixing process. In this work, the behavior of plasma-reacted nano-size Si3N 4 powders intrinsically doped with sintering additives was explored. These particles were doped with Y2O3 and Al2O 3, and processed under a low process temperature in the absence of pressurizing equipment. Several experiments were performed to address the effects of the powders on the phase transformation rate from a to b phase, and on the mechanical properties due to the microstructure evolution under different sintering conditions. The existence of sintering additive elements in each individual powder was verified by electron microscope and energy dispersive spectroscopy. The doped powders were 60% crystalline and had a specific surface area of ˜24 m2/g. The powders showed excellent sinterability at low temperature, compared to the other powders used in commercial processes. In spite of the low process temperature, the a→ b phase transformation occurred rapidly. The homogeneous distribution of Si3N4 powders was speculated as the reason for fast phase transformation. In addition, evolution of the microstructures in different sintering conditions produced materials with vastly different mechanical properties. Thus, one may obtain ceramics with desired mechanical properties by carefully controlling the sintering additives. Finally, a mathematical model, based on the previous work done by

  15. Surface structure and catalytic properties of MoO3/CeO2 and CuO/MoO3/CeO2.

    PubMed

    Yu, Wujiang; Zhu, Jie; Qi, Lei; Sun, Chuanzhi; Gao, Fei; Dong, Lin; Chen, Yi

    2011-12-15

    XRD, LRS, TPR and in situ NH(3) adsorption FT-IR were used to investigate the dispersion state of the copper oxide and molybdena species of MoO(3)/CeO(2) and CuO/MoO(3)/CeO(2) catalysts as well as their surface acidity. The results showed that the molybdena monolayer modification promoted the dispersion of CuO due to the formation of new tetrahedral vacancies. Meanwhile, CuO changed the structure of molybdenum species and then influenced the surface acidity of the samples. A detail discussion about the possible model of the surface structure of the catalyst was presented. In addition, combining with the in situ NH(3) adsorption FT-IR, the relationships between the activities for ''NO + NH(3) + O(2)'' reaction and surface acid properties (Brønsted and Lewis acid sites) of the catalysts were discussed. PMID:21930282

  16. Fabrication of rod-like CeO 2: Characterization, optical and electrochemical properties

    NASA Astrophysics Data System (ADS)

    Zhang, Dong-En; Ni, Xiao-Min; Zheng, Hua-Gui; Zhang, Xiao-Jun; Song, Ji-Mei

    2006-11-01

    One-dimensional CeO 2 nanoparticles were obtained via the thermal treatment of cerium oxalate nanorods, which were synthesized through a convenient precipitation route. The morphology of the precursor was maintained during the heating process, while the size of the subunits was tailored by adjusting the calcining temperature. The optical absorption spectrum indicates that the direct band gaps of CeO 2 decreases from 3.95 to 3.86 eV as the calcination temperature increases from 500 to 800 °C. Thus-prepared nanostructured CeO 2 with subunits of about 15 nm exhibited a first discharge specific capacity of 574 mAh g -1 vs. Li metal, much higher than that of the sample with bigger building blocks (30 nm, 519 mAh g -1).

  17. Upconversion emission properties of CeO2: Tm3+, Yb3+ inverse opal photonic crystals

    NASA Astrophysics Data System (ADS)

    Cheng, Gong; Wu, Hangjun; Yang, Zhengwen; Liao, Jiayan; Lai, Shenfeng; Qiu, Jianbei; Song, Zhiguo

    2014-10-01

    The ordered and disordered templates were assembled by vertical deposition of polystyrene microspheres. The CeO2: Tm3+, Yb3+ precursor solution was used to infiltrate into the voids of the ordered and disordered templates, respectively. Then the ordered and disordered templates were calcined at 950°C in an air furnace, and the CeO2: Tm3+, Yb3+ inverse opals were obtained. The upconversion emissions from CeO2: Tm3+, Yb3+ inverse opals were suppressed due to the photon trapping caused by Bragg reflection of lattice planes when the upconversion emission band was in the range of the photonic band gaps in the inverse opals.

  18. Structural, morphological, Raman, optical, magnetic, and antibacterial characteristics of CeO2 nanostructures

    NASA Astrophysics Data System (ADS)

    Abbas, Fazal; Iqbal, Javed; Jan, Tariq; Badshah, Noor; Mansoor, Qaisar; Ismail, Muhammad

    2016-01-01

    In this study, CeO2 nanostructures were synthesized by a soft chemical method. A hydrothermal treatment was observed to lead to an interesting morphological transformation of the nanoparticles into homogeneous microspheres composed of nanosheets with an average thickness of 40 nm. Structural analysis revealed the formation of a single-phase cubic fluorite structure of CeO2 for both samples. A Raman spectroscopic study confirmed the XRD results and furthermore indicated the presence of a large number of oxygen vacancies in the nanosheets. These oxygen vacancies led to room-temperature ferromagnetism (RTFM) of the CeO2 nanosheets with enhanced magnetic characteristics. Amazingly, the nanosheets exhibited substantially greater antibacterial activity than the nanoparticles. This greater antibacterial activity was attributed to greater exposure of high-surface-energy polar surfaces and to the presence of oxygen vacancies.

  19. First-principles characterization of formate and carboxyl adsorption on the stoichiometric CeO2(111) and CeO2(110) surfaces

    SciTech Connect

    Mei, Donghai

    2013-05-20

    Molecular adsorption of formate and carboxyl on the stoichiometric CeO2(111) and CeO2(110) surfaces was studied using periodic density functional theory (DFT+U) calculations. Two distinguishable adsorption modes (strong and weak) of formate are identified. The bidentate configuration is more stable than the monodentate adsorption configuration. Both formate and carboxyl bind at the more open CeO2(110) surface are stronger. The calculated vibrational frequencies of two adsorbed species are consistent with experimental measurements. Finally, the effects of U parameters on the adsorption of formate and carboxyl over both CeO2 surfaces were investigated. We found that the geometrical configurations of two adsorbed species are not affected by using different U parameters (U=0, 5, and 7). However, the calculated adsorption energy of carboxyl pronouncedly increases with the U value while the adsorption energy of formate only slightly changes (<0.2 eV). The Bader charge analysis shows the opposite charge transfer occurs for formate and carboxyl adsorption where the adsorbed formate is negatively charge whiled the adsorbed carboxyl is positively charged. Interestingly, with the increasing U parameter, the amount of charge is also increased. This work was supported by the Laboratory Directed Research and Development (LDRD) project of the Pacific Northwest National Laboratory (PNNL) and by a Cooperative Research and Development Agreement (CRADA) with General Motors. The computations were performed using the Molecular Science Computing Facility in the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL), which is a U.S. Department of Energy national scientific user facility located at PNNL in Richland, Washington. Part of the computing time was also granted by the National Energy Research Scientific Computing Center (NERSC)

  20. Oxygen vacancy formation in CeO2 and Ce(1-x)Zr(x)O2 solid solutions: electron localization, electrostatic potential and structural relaxation.

    PubMed

    Wang, Hai-Feng; Li, Hui-Ying; Gong, Xue-Qing; Guo, Yang-Long; Lu, Guan-Zhong; Hu, P

    2012-12-28

    Ceria (CeO(2)) and ceria-based composite materials, especially Ce(1-x)Zr(x)O(2) solid solutions, possess a wide range of applications in many important catalytic processes, such as three-way catalysts, owing to their excellent oxygen storage capacity (OSC) through the oxygen vacancy formation and refilling. Much of this activity has focused on the understanding of the electronic and structural properties of defective CeO(2) with and without doping, and comprehending the determining factor for oxygen vacancy formation and the rule to tune the formation energy by doping has constituted a central issue in material chemistry related to ceria. However, the calculation on electronic structures and the corresponding relaxation patterns in defective CeO(2-x) oxides remains at present a challenge in the DFT framework. A pragmatic approach based on density functional theory with the inclusion of on-site Coulomb correction, i.e. the so-called DFT + U technique, has been extensively applied in the majority of recent theoretical investigations. Firstly, we review briefly the latest electronic structure calculations of defective CeO(2)(111), focusing on the phenomenon of multiple configurations of the localized 4f electrons, as well as the discussions of its formation mechanism and the catalytic role in activating the O(2) molecule. Secondly, aiming at shedding light on the doping effect on tuning the oxygen vacancy formation in ceria-based solid solutions, we summarize the recent theoretical results of Ce(1-x)Zr(x)O(2) solid solutions in terms of the effect of dopant concentrations and crystal phases. A general model on O vacancy formation is also discussed; it consists of electrostatic and structural relaxation terms, and the vital role of the later is emphasized. Particularly, we discuss the crucial role of the localized structural relaxation patterns in determining the superb oxygen storage capacity in kappa-phase Ce(1-x)Zr(1-x)O(2). Thirdly, we briefly discuss some

  1. Simultaneous removal of elemental mercury and NO from flue gas by V2O5-CeO2/TiO2 catalysts

    NASA Astrophysics Data System (ADS)

    Zhang, Xunan; Li, Caiting; Zhao, Lingkui; Zhang, Jie; Zeng, Guangming; Xie, Yin'e.; Yu, Ming'e.

    2015-08-01

    A series of Ce-doped V2O5/TiO2 catalysts synthesized by an ultrasound assisted impregnation method were employed to investigate simultaneous removal of elemental mercury (Hg0) and NO in lab-scale experiments. Scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), X-ray diffractogram (XRD), and X-ray photoelectron spectroscopy (XPS) analyses were used to characterize the samples. Compared to TiO2 support, the catalytic performance of CeO2 doped on both TiO2 and V2O5/TiO2 catalysts have been improved. Remarkably, 1%V2O5-10% CeO2/TiO2 (V1Ce10Ti) exhibited the highest Hg0 oxidation efficiency of 81.55% at 250 °C with a desired NO removal efficiency under the same condition. Both the NO conversion and Hg0 oxidation efficiency were enhanced in the presence of O2. The activity was inhibited by the injection of NH3 with the increase of NH3/NO. When in the presence of 400 ppm SO2, Hg0 oxidation was slightly affected. Furthermore, Hg0 removal behavior under both oxidation and selective catalytic reduction (SCR) condition over V1Ce10Ti were well investigated to further probe into the feasibility of one single unit for multi-pollutants control in industry application. The existence of the redox cycle of V4+ + Ce4+ ↔ V5+ + Ce3+ in V2O5-CeO2/TiO2 catalyst could not only greatly improve the NO conversion, but also promote the oxidation of Hg0.

  2. Structural and dielectric properties of CuO-doped SrTiO{sub 3} ceramics

    SciTech Connect

    Naidu, K. Chandra Babu Sarmash, T. Sofi; Maddaiah, M.; Reddy, V. Narasimha; Subbarao, T.

    2015-06-24

    Copper-doped SrTiO{sub 3} (ST) ceramic powders were processed by solid-state route diffusion (SRD) bulk preparation technique. We reported the effect of Cu{sup +2} ions on the dielectric response of ST and it established the substantial increase in dielectric constant (ε{sub r}) than undoped ST from 303K-673K and low loss (tanδ) for good dielectric applications. In respect of the electrical properties ac- activation energies were computed of range 0.089-0.319eV using lnσ Vs 1/T plots. The microstructure was examined with grain sizes 6-9µm of uniform distribution by field emission scanning electron microscope (FESEM). Some additional phases SrCu{sub 3}Ti{sub 4}O{sub 12} and TiO{sub 2} rutiles were detected by X-ray diffraction technique.

  3. Transmission Electron Microscopy Investigation of Krypton Bubbles in Polycrystalline CeO2

    SciTech Connect

    Lingfeng He; Clarissa Yablinsky; Mahima Gupta; Jian Gan; Marquis A. Kirk; Todd R. Allen

    2013-05-01

    To gain an understanding of gas bubble transport in oxide nuclear fuel, this paper uses polycrystalline CeO2, composed of both nanograins and micrograins, as a surrogate material for UO2. The CeO2 was implanted with 150-keV Kr ions up to a dose of 1 x 1016 ions/cm2 at 600 degrees C. Transmission electron microscopy characterizations of small Kr bubbles in nanograin and micrograin regions were compared. The grain boundary acted as an efficient defect sink, as evidenced by smaller bubbles and a lower bubble density in the nanograin region as compared to the micrograin region.

  4. [The research on preparing CeO2 nanocrystalline by homogeneous precipitation method].

    PubMed

    Garidi; Li, Xia; Li, Li; Zhaorigetu

    2006-09-01

    CeO2 nanocrystallines were prepared by homogeneous complexed-precipitation method, using cerous nitrate and ammonium tartrate as raw materials. The effects of cerous tartrate complex compound and the way of producing precipitation on the particle size of samples were investigated. The samples were characterized by XRD, TEM and SEM. The SEM micrograph shows that the foam exhibits a perforated porousness stereostructure in shape, and the HRTEM picture of the particles reveals the clear crystal lattice. All the results indicate that the samples were CeO2 nanocrystalline. PMID:17112061

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

    SciTech Connect

    Wang, Xiangrong; Zhang, Yong; Baturin, Ivan; Liang, Tongxiang

    2013-10-15

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

  6. Fabrication of Dual Phase Magnesia-Zirconia Ceramics Doped with Plutonia and Erbia

    SciTech Connect

    Paul A. Lessing; Timothy A. Hyde

    2006-06-01

    Dual phase magnesia-zirconia ceramics doped with plutonia and erbia are being evaluated as an inert matrix fuel (IMF) for light water reactors (LWR). The motivation for this work is to develop an IMF with a thermal conductivity superior to that of the fuels based on single-phase yttria stabilized zirconia. The innovative fuel developed at INL is comprised of two major phases: pure MgO and quaternary solid solution consisting of MgO, ZrO{sub 2}, Er{sub 2}O{sub 3} and PuO{sub 2}. Pure MgO phase acts as an efficient heat conductor. It has been shown [1] that dual phase MgO-ZrO{sub 2} ceramics have the thermal conductivity superior to that of UO{sub 2} and have notable chemical resistance to water at the temperature of 573 K and pressure 8.6 MPa, which makes them attractive for use as an IMF matrix in LWRs.

  7. Fabrication of dual phase magnesia-zirconia ceramics doped with plutonia and erbia

    SciTech Connect

    P. G. Medvedev; J. F. Jue; S. M. Frank

    2006-06-01

    Dual phase magnesia-zirconia ceramics doped with plutonia and erbia are being evaluated as an inert matrix fuel (IMF) for light water reactors (LWR). The motivation for this work is to develop an IMF with a thermal conductivity superior to that of the fuels based on single-phase yttria stabilized zirconia. The innovative fuel developed at INL is comprised of two major phases: pure MgO and quaternary solid solution consisting of MgO, ZrO{sub 2}, Er{sub 2}O{sub 3} and PuO{sub 2}. Pure MgO phase acts as an efficient heat conductor. It has been shown [1] that dual phase MgO-ZrO{sub 2} ceramics have the thermal conductivity superior to that of UO{sub 2} and have notable chemical resistance to water at the temperature of 573 K and pressure 8.6 MPa, which makes them attractive for use as an IMF matrix in LWRs.

  8. Near room temperature magnetodielectric consequence in (Li, Ti) doped NiO ceramic

    NASA Astrophysics Data System (ADS)

    Mukherjee, S.; Chatterjee, S.; Rayaprol, S.; Kaushik, S. D.; Bhattacharya, S.; Jana, P. K.

    2016-04-01

    In the quest for high-k dielectrics with decent magnetodielectric (MD) response, ball-milled processed (Li, Ti) doped NiO ceramics have been evaluated by various experimental techniques. Magnetic properties in these ceramics manifest with a pronounced anomaly appearing at ˜260 K, suggesting ferrimagnetic phase (related to cluster magnetism) and co-existence with a glassy-like antiferromagnetic phase at ˜7 K. Room temperature neutron diffraction pattern shows the existence of short-range magnetic correlations. In the magnetically ordered state below 250 K, the magnetic structure is found to be phase coexistence of G-type antiferromagnet and ferrimagnet. Impedance spectroscopy measurements over a wide temperature range can be perfectly described with appropriate microstructural model (internal barrier layer capacitor), based on domain and domain boundary relaxations, justifying the enhancement of the dielectric response. The low-temperature (T < 100 K) dielectric relaxation is polaronic in nature, associated with the charge ordering of a mixed valence states of Ti ions (co-existence of Ti3+ and Ti4+). Finally, our investigations in external magnetic fields up to 15 T reveal the occurrence of negative MD effect near room temperature. This intriguing intrinsic feature has been understood by the mechanism of charge-hopping-mediated MD effects.

  9. Spectroscopic and dielectric investigations of tungsten ions doped zinc bismuth phosphate glass-ceramics

    NASA Astrophysics Data System (ADS)

    Srinivasa Rao, P.; Bala Murali Krishna, S.; Yusub, S.; Ramesh Babu, P.; Tirupataiah, Ch.; Krishna Rao, D.

    2013-03-01

    Pure and tungsten oxide doped ZnF2sbnd Bi2O3sbnd P2O5 glass-ceramics are prepared by the melt quenching and heat treatment techniques. These samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), electron dispersive spectroscopy (EDS) and differential thermal analysis (DTA) techniques. The X-ray diffraction and the scanning electron microscopic studies have revealed the presence of BiPO4, α-Zn3(PO4)2, α-Zn(PO3)2, Zn3(PO4)2, WOF4, WOPO4, γ-Bi2WO6, Bi2W2O9, microcrystalline phases in these samples. FTIR and Raman studies exhibit bands due WO4 and WO6 units along with conventional phosphate groups. The optical absorption and electron spin resonance (ESR) spectra of present glass-ceramics indicate the co-existence of both W5+ and W6+ ions. The analysis of dielectric properties (dielectric constant, loss tan δ, a.c. conductivity) over a range of frequency and temperature suggests a gradual increase in semi conducting character with increase in the concentration of WO3. The studies on dielectric breakdown strength indicated the lowest insulating strength for 5.0 mol% of WO3 in the present samples.

  10. Formation of nanostructures in Eu3+ doped glass-ceramics: an XAS study

    NASA Astrophysics Data System (ADS)

    Pellicer-Porres, J.; Segura, A.; Martínez-Criado, G.; Rodríguez-Mendoza, U. R.; Lavín, V.

    2013-01-01

    We describe the results of x-ray absorption experiments carried out to deduce structural and chemical information in Eu3+ doped, transparent, oxyfluoride glass and nanostructured glass-ceramic samples. The spectra were measured at the Pb and Eu-LIII edges. The Eu environment in the glass samples is observed to be similar to that of EuF3. Complementary x-ray diffraction experiments show that thermal annealing creates β-PbF2 type nanocrystals. X-ray absorption indicates that Eu ions act as seeds in the nanocrystal formation. There is evidence of interstitial fluorine atoms around Eu ions as well as Eu dimers. X-ray absorption at the Pb-LIII edge shows that after the thermal treatment most lead atoms form a PbO amorphous phase and that only 10% of the lead atoms remain available to form β-PbF2 type nanocrystals. Both x-ray diffraction and absorption point to a high Eu content in the nanocrystals. Our study suggests new approaches to the oxyfluoride glass-ceramic synthesis in order to further improve their properties.

  11. Effect of crystallization heat treatment on the microstructure of niobium-doped fluorapatite glass-ceramics

    PubMed Central

    Denry, I.; Holloway, J.A.; Gupta, P.K.

    2012-01-01

    Our goal was to study the effect of heat treatment temperature and heating rate on the microstructure and crystalline phases and assess the domain of existence of sub-micrometer fluorapatite crystals in niobium-doped fluorapatite glass-ceramics for biomedical applications. Glass-ceramic specimens were prepared by casting and heat treatment between 700 and 1200°C using a fast or a slow heating rate. The microstructure was characterized by atomic force microscopy and scanning electron microscopy. Crystalline phases were analyzed by x-ray diffraction. AFM of the as-cast glass revealed that amorphous phase separation occurred in this system. XRD confirmed the presence of fluorapatite in all specimens, together with forsterite and enstatite at higher temperatures. Both heating rate and heat treatment temperature strongly influenced microstructure and crystallinity. A dual microstructure with sub-micrometer fluorapatite crystals and polygonal forsterite crystals was obtained when slow heating rates and crystallization temperatures between 950 and 1100°C were used. Needle-shaped fluorapatite crystals appeared after heat treatment above 1100°C. Fast heating rates led to an increase in crystal size. Heat treatment temperatures should remain below 1100°C, together with slow heating rates, to prevent crystal dissolution, and preserve a dual microstructure of finely dispersed sub-micrometer crystals without growth of needle-shaped crystals. PMID:22454333

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

    NASA Astrophysics Data System (ADS)

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

    2009-04-01

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

  13. Polarity driven morphology of CeO2(1 0 0) islands on Cu(1 1 1)

    NASA Astrophysics Data System (ADS)

    Stetsovych, O.; Beran, J.; Dvořák, F.; Mašek, K.; Mysliveček, J.; Matolín, V.

    2013-11-01

    Thin ceria films supported by metal substrates represent important model systems for reactivity studies in heterogeneous catalysis. Here we report the growth study of the polar CeO2(1 0 0) phase as part of a mixed CeO2(1 1 1)-CeO2(1 0 0) thin film supported by Cu(1 1 1). The two ceria phases grow on different areas of the substrate, what allows a reliable growth characterization of the CeO2(1 0 0) islands on Cu(1 1 1). Scanning tunneling microscopy measurements reveal CeO2(1 0 0) to grow in the form of highly dispersed three dimensional (3D) islands on a CeO2(1 0 0) interfacial layer. The CeO2(1 0 0) islands exhibit a 2 × 2 surface reconstruction. The presence of the surface reconstruction together with the highly dispersed growth of CeO2(1 0 0) islands corresponds to the requirement for compensation of the surface dipole moment on the CeO2(1 0 0). CeO2(1 0 0) islands are further characterized by reflection high energy electron diffraction yielding their epitaxial relations with respect to the Cu(1 1 1) substrate. The growth of well characterized CeO2(1 0 0) islands supported by Cu(1 1 1) represents a starting point for developing a novel template for structure-related reactivity studies of ceria based model catalysts.

  14. Doping and defect structure of mixed-conducting ceramics for gas separation

    NASA Astrophysics Data System (ADS)

    Zuo, Chendong

    A worldwide energy crisis and increasing environmental concerns are strong incentives for using hydrogen as a sustainable and clean energy source. "Hydrogen economy" has been around since 1970s, but it started to look practicable only in recent years. The trend in the future is to switch from using hydrogen as the basic raw material in the chemical industry to the energy carrier in the transportation and distributed energy industries. To meet the expected rising demand, hydrogen has to be generated in a more cost-effective manner. As one of the most important operation units in the hydrogen production, a high performance hydrogen separation membrane system is essential to the coming hydrogen economy. The project of hydrogen separation membrane based on Mixed ionic and electronic conductor (MIEC) composite was initiated by DoE years ago, and the MIEC membrane has been developed in Argonne National Laboratory (ANL) for several years. The goal at ANL is to develop a dense, ceramic-based MIEC membrane that is highly selective, chemical stable in practical environments at operative temperatures up to ≈900°C, and can separate hydrogen from mixed gases at commercially significant fluxes under industrially relevant operating conditions, without the need for electrodes or electrical circuitry. The effort at ANL initially focused on BCY20 (BaCe0.8Y 0.2O3). BCY20 forms the matrix of ANL-1a and -2a ceramic-metal composite membranes (40-50 vol.% of a metal is dispersed in a ceramic matrix) and its bulk transport properties, including ionic transfer number, ionic and electronic conductivity, and chemical and mechanical stability have been systematically studied. However, exposure to CO2 and H2O-containing atmospheres, as would be present in a practical environment, will degrade the material as it reacts to form insulating barium carbonate (BaCO3 ) and cerium oxide (CeO2). This decomposition greatly limits its applicability in hydrogen separation, despite the promising

  15. Thermal, structural and spectroscopic properties of heavy metal oxide glass and glass-ceramics doped with Er3+ ions

    NASA Astrophysics Data System (ADS)

    Ragin, Tomasz; Zmojda, Jacek; Kochanowicz, Marcin; Miluski, Piotr; Jelen, Piotr; Sitarz, Maciej; Dorosz, Dominik

    2015-09-01

    In this paper, bismuth-germanate oxide glass doped with erbium ions has been synthesized. Composition of the glass has been chosen in terms of the low phonon energy and good transparency in the infrared region. Transparent glass-ceramics sample has been prepared by controlled crystallization process. Fourier transform infrared spectroscopy (FTIR) has been used to determinate structural properties of samples. The absorption coefficient, the luminescence intensity in visible and infrared region and the differential scanning calorimetry have been examined. Difference in the emission intensity and shape of the luminescence bands indicates the presence of crystalline phases in obtained glass-ceramics sample.

  16. Boron-Doped Strontium-Stabilized Bismuth Cobalt Oxide Thermoelectric Nanocrystalline Ceramic Powders Synthesized via Electrospinning

    NASA Astrophysics Data System (ADS)

    Koçyiğit, Serhat; Aytimur, Arda; Çınar, Emre; Uslu, İbrahim; Akdemir, Ahmet

    2014-01-01

    Boron-doped strontium-stabilized bismuth cobalt oxide thermoelectric nanocrystalline ceramic powders were produced by using a polymeric precursor technique. The powders were characterized by using x-ray diffraction (XRD), scanning electron microscopy (SEM), and physical properties measurement system (PPMS) techniques. The XRD results showed that these patterns have a two-phase mixture. The phases are face-centered cubic (fcc) and body-centered cubic (bcc). Values of the crystallite size, dislocation density, and microstrain were calculated by using the Scherrer equation. The lattice parameters were calculated for fcc and bcc phases. The SEM results showed that needle-like grains are formed in boron-undoped composite materials, but the needle-like grains changed to the plate-like grains with the addition of boron. The distribution of the nanofiber diameters was calculated and the average diameter of the boron-doped sample is smaller than the boron-undoped one. PPMS values showed that the electrical resistivity values decreased, but the thermal conductivity values, the Seebeck coefficients, and figure of merit ( ZT) increased with increasing temperature for the two samples.

  17. Fabrication, spectral and laser performance of 5 at.% Yb3+ doped (La0.10Y0.90)2O3 transparent ceramic

    NASA Astrophysics Data System (ADS)

    Zhang, Haojia; Yang, Qiuhong; Lu, Shenzhou; Huang, Dongdong; Wang, Yonggang; Wei, Zhiyi; Wang, Qing; Zhang, Yongdong

    2013-02-01

    A 5 at.% Yb3+ doped (La0.10Y0.90)2O3 transparent ceramic was fabricated with nano-powders and sintered in H2 atmosphere. Spectroscopic properties and laser performance of Yb:(La0.10Y0.90)2O3 ceramic were studied. The ceramic exhibits excellent spectroscopic properties, with broad absorption and emission bands, and its refractive index (n) is close to 2. The gain cross-section (σg) was calculated at different population inversion ratio (β) values. In addition, among Yb3+ doped YAG crystal, Y2O3 and (YLa)2O3 ceramic, (YLa)2O3 ceramic has the least pump intensity (Imin) of 1.25 KW cm-2. Furthermore, a diode-pumped C-W ceramic laser output has been demonstrated at 1075 nm with a slope-efficiency of 60.2%.

  18. Zr doped anatase supported reticulated ceramic foams for photocatalytic water purification

    SciTech Connect

    Plesch, G.; Vargová, M.; Vogt, U.F.; Gorbár, M.; Jesenák, K.

    2012-07-15

    Highlights: ► Thick photocatalytic anatase films on macroporous reticulated ceramic foams. ► Alumina and alumina–mullite macroporous reticulated foams as photocatalyst support. ► Zr doping significantly improves the TiO{sub 2} film activity in phenol photomineralization. ► Comparison of photocatalytic activity of thick films and powder suspensions. -- Abstract: Titanium dioxide films were deposited on macroporous reticulated Al{sub 2}O{sub 3} and alumina–mullite foams with pore sizes of 15 ppi (pores per inch). Coatings were prepared from suspensions of precursor powders of Aeroxide{sup ®} P25 nanopowder and precipitated TiO{sub 2} by using a dip coating process. The TiO{sub 2} forms films with a thickness of ∼2–20 μm. The photocatalytic activity was characterized as the mineralization rate of an aqueous phenol solution under UVA irradiation by the TOC technique. Precipitated TiO{sub 2} films have nearly the same photocatalytic activity as a titania suspension, in which powder aggregates have a size comparable with the thickness of the films. Samples made of Aeroxide{sup ®} P25 nanopowder, in which the size of aggregates is ∼0.1 μm show higher efficiency of photodecomposition in suspensions with films. The doping of precipitated anatase with Zr(IV) in the atomic ratio Zr/Ti = 0.008 significantly improves the photocatalytic activity of the foam supported titania. Zr doped anatase films show better performance as the films prepared only from Aeroxide{sup ®} P25 nanopowder.

  19. Low temperature environmental degradation of zirconia ceramics

    NASA Astrophysics Data System (ADS)

    Zhao, Zhenbo

    2005-11-01

    The low temperature environmental degradation (LTED) of yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) has been prevented, or at least retarded, by using both bulk doping and surface doping methods with either cation, or anion, stabilizers. The introduction of both mullite and alumina into 3Y-TZP by a bulk-doping method was found to be effective in suppressing the tetragonal-->monoclinic transformation induced by water during hydrothermal treatment thus giving rise to better mechanical properties. The beneficial effects of alumina on the phase stability of the 3Y-TZP ceramic are considered to be due to the increase in the elastic modulus of the constraining matrix, as well as to the segregation of A12O3 at grain boundaries. The LTED transformation kinetics as determined by x-ray diffraction (XRD) and White Light Interferometer (WLI) analysis showed that the isothermal tetragonal-to-monoclinic transformation starts from the surface and has an incubation-nucleation-growth mechanism which can be described by the Johnson-Mehl-Avrami equation. The degradation of Y-TZP ceramic after hydrothermal treatment can be effectively overcome by surface doping by a solid diffusion method with tetravalent dopants: CeO2 and GeO2; with trivalent dopants: La2O 3 and Fe2O3; and with divalent dopants: CuO and MgO. For surface CeO2-, GeO2- and Fe2O 3-doping, this degradation inhibition behaviour is attributed to a localized increase in cation stabilizer content which satisfies the requirements for stabilization of the tetragonal phase. However, in each case, the stability mechanisms are different. For surface La2O3doping, surface doping overcomes the formation of La2O3 and La 2Zr2O7 since the extra La2O3 can further diffuse to the center of the 3Y-TZP ceramic. For CuO-doping, small amounts of CuO form a liquid that can act as a conduit for the re-distribution of yttria. In the case of surface MgO modification, the stabilization results from the isolated nature of the

  20. Formation of CeO 2 buffer layer using multi-plume PLD

    NASA Astrophysics Data System (ADS)

    Sutoh, Y.; Nakaoka, K.; Miura, M.; Matsuda, J.; Nakanishi, T.; Nakai, A.; Yoshizumi, M.; Izumi, T.; Miyata, S.; Iijima, Y.; Yamada, Y.; Shiohara, Y.; Saitoh, T.

    2008-09-01

    The CeO 2 buffer layer was fabricated using the multi-plume pulsed laser deposition (PLD) method with different deposition rates controlled by the excimer laser energy and frequency on the Gd 2Zr 2O 7 template tape formed by the ion-beam assisted deposition (IBAD) with 14° of Δ φ (full width at half maximum (FWHM) value of X-ray diffraction φ-scan for Gd 2Zr 2O 7 (2 2 2) pole). The laser conditions with high pulse energy and low frequency resulted in a highly textured in-plane grain alignment (Δ φ). The surface roughness and Δ φ values were improved by increasing the thickness of the CeO 2 buffer layer. YBCO films with the thickness of 1 μm and 1.6 μm were further deposited by the advanced trifluoroacetates-metal organic deposition (TFA-MOD) on the CeO 2 buffered substrates with the deposition rate of 0.15 and 0.5 μm/min. The Jc values of 2.5 MA/cm 2 and 2 MA/cm 2 were obtained, respectively. High Jc films could be deposited on the CeO 2 buffer layer even at high deposition rate by the multi-plume deposition.

  1. Ionic liquid-assisted sonochemical preparation of CeO2 nanoparticles for CO oxidation

    DOE PAGESBeta

    Alammar, Tarek; Noei, Heshmat; Wang, Yuemin; Grünert, Wolfgang; Mudring, Anja -Verena

    2014-10-10

    CeO2 nanoparticles were synthesized via a one-step ultrasound synthesis in different kinds of ionic liquids based on bis(trifluoromethanesulfonylamide, [Tf2N]–, in combination with various cations including 1-butyl-3-methylimidazolium ([C4mim]+), 1-ethyl-2,3-dimethylimidazolium ([Edimim]+), butyl-pyridinium([Py4]+), 1-butyl-1-methyl-pyrrolidinium ([Pyrr14]+), and 2-hydroxyethyl-trimethylammonium ([N1112OH]+). Depending on synthetic parameters, such as ionic liquid, Ce(IV) precursor, heating method, and precipitator, formed ceria exhibits different morphologies, varying from nanospheres, nanorods, nanoribbons, and nanoflowers. The morphology, crystallinity, and chemical composition of the obtained materials were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), Raman spectroscopy, and N2 adsorption. The structural and electronic propertiesmore » of the as-prepared CeO2 samples were probed by CO adsorption using IR spectroscopy under ultrahigh vacuum conditions. The catalytic activities of CeO2 nanoparticles were investigated in the oxidation of CO. CeO2 nanospheres obtained sonochemically in [C4mim][Tf2N] exhibit the best performance for low-temperature CO oxidation. As a result, the superior catalytic performance of this material can be related to its mesoporous structure, small particle size, large surface area, and high number of surface oxygen vacancy sites.« less

  2. Fundamentals and Catalytic Applications of CeO2-Based Materials.

    PubMed

    Montini, Tiziano; Melchionna, Michele; Monai, Matteo; Fornasiero, Paolo

    2016-05-25

    Cerium dioxide (CeO2, ceria) is becoming an ubiquitous constituent in catalytic systems for a variety of applications. 2016 sees the 40(th) anniversary since ceria was first employed by Ford Motor Company as an oxygen storage component in car converters, to become in the years since its inception an irreplaceable component in three-way catalysts (TWCs). Apart from this well-established use, ceria is looming as a catalyst component for a wide range of catalytic applications. For some of these, such as fuel cells, CeO2-based materials have almost reached the market stage, while for some other catalytic reactions, such as reforming processes, photocatalysis, water-gas shift reaction, thermochemical water splitting, and organic reactions, ceria is emerging as a unique material, holding great promise for future market breakthroughs. While much knowledge about the fundamental characteristics of CeO2-based materials has already been acquired, new characterization techniques and powerful theoretical methods are deepening our understanding of these materials, helping us to predict their behavior and application potential. This review has a wide view on all those aspects related to ceria which promise to produce an important impact on our life, encompassing fundamental knowledge of CeO2 and its properties, characterization toolbox, emerging features, theoretical studies, and all the catalytic applications, organized by their degree of establishment on the market. PMID:27120134

  3. Coadsorption of gold with chlorine on CeO2 (111) surfaces: A first principles study

    NASA Astrophysics Data System (ADS)

    Lu, Zhan-Sheng; He, Bing-Ling; Ma, Dong-Wei; Yang, Zong-Xian

    2015-02-01

    To investigate the effects of chlorine on the Au/ceria catalysts, the adsorption of gold or chlorine and their coadsorpiton on the stoichiometric and partially reduced CeO2 (111) surfaces are studied from the first principles. It is found that the adsorption of Au is significantly enhanced by the chlorine preadsorption on the stoichiometric CeO2 (111) surface; while on the partially reduced CeO2 (111) surface, the preadsorbed chlorine inhabits the oxygen vacancy (which is the preferred adsorption site for gold), leading to a CeOCl phase and the dramatical weakening of the Au adsorption. Therefore, chlorine on the CeO2 (111) surface can affect the Au adsorption thus the activity of the Au/CeO2 catalyst. Project supported by the National Natural Science Foundation of China (Grant Nos. 11174070, 51401078, and 11147006), the China Postdoctoral Science Foundation (Grant No. 2012M521399), the Postdoctoral Research Sponsorship in Henan Province, China (Grant No. 2011038), and the Foundation for the Key Young Teachers of Henan Normal University and Start-up Foundation for Doctors of Henan Normal University, China.

  4. Study of the growth of CeO2 nanoparticles onto titanate nanotubes

    NASA Astrophysics Data System (ADS)

    Marques, Thalles M. F.; Ferreira, Odair P.; da Costa, Jose A. P.; Fujisawa, Kazunori; Terrones, Mauricio; Viana, Bartolomeu C.

    2015-12-01

    We report the study of the growth of CeO2 nanoparticles on the external walls and Ce4+ intercalation within the titanate nanotubes. The materials were fully characterized by multiple techniques, such as: Raman spectroscopy, infrared spectroscopy (FTIR), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The ion exchange processes in the titanate nanotubes were carried out using different concentrations of Ce4+ in aqueous solution. Our results indicate that the growth of CeO2 nanoparticles grown mediated by the hydrolysis in the colloidal species of Ce and the attachment onto the titanate nanotubes happened and get it strongly anchored to the titanate nanotube surface by a simple electrostatic interaction between the nanoparticles and titanate nanotubes, which can explain the small size and even distribution of nanoparticles on titanate supports. It was demonstrated that it is possible to control the amount and size of CeO2 nanoparticles onto the nanotube surface, the species of the Ce ions intercalated between the layers of titanate nanotubes, and the materials could be tuned for using in specific catalysis in according with the amount of CeO2 nanoparticles, their oxygen vacancies/defects and the types of Ce species (Ce4+ or Ce3+) present into the nanotubes.

  5. An Evaluation of the Potential Phototoxicity of CeO2 Nanoparticles in Retinal Pigment Epithelial Cells in-vitro

    EPA Science Inventory

    Cerium dioxide (CeO2) engineered nanoparticles (NP) are used as fuel-borne catalysts in off-road diesel engines, which can lead to exhaust emissions of respirable CeO2 NP. Other metal oxides may act as photo-catalysts which induce the generation of free radicals upon exposure to ...

  6. Sensor properties of the nanostructured In2O3-CeO2 system in detection of reducing gases

    NASA Astrophysics Data System (ADS)

    Gerasimov, G. N.; Gromov, V. F.; Trakhtenberg, L. I.; Belysheva, T. V.; Spiridonova, E. Yu.; Rozenbaum, V. M.

    2014-03-01

    The sensor properties of nanostructured In2O3-CeO2 composite films with different compositions in hydrogen and carbon monoxide detection in air in the temperature range 280-500°C were studied. The temperature curves of the sensor effect S have a shape typical for metal oxide sensors with maxima S max at definite temperatures Tmax. The maxima characterize the sensor properties of the films and increased considerably when small amounts of CeO2 were added to In2O3. The highest sensitivity was found in composite films with 3-10 wt % CeO2. When the composite was further enriched with ceric oxide, the sensitivity decreased; at 40 wt % CeO2 it was considerably lower than that of pure In2O3. The introduction of CeO2 in In2O3 also caused a shift of Tmax toward lower temperatures. The mechanism of the sensitivity of the In2O3-CeO2 composite was considered; it includes the promotion of sensor reactions by small CeO2 nanoclusters lying on the surface of In2O3 crystals and an electron transfer from In2O3 to CeO2.

  7. On the mechanism of nanoparticulate CeO2 toxicity to freshwater algae.

    PubMed

    Angel, Brad M; Vallotton, Pascal; Apte, Simon C

    2015-11-01

    The factors affecting the chronic (72-h) toxicity of three nanoparticulate (10-34nm) and one micron-sized form of CeO2 to the green alga, Pseudokirchneriella subcapitata were investigated. To characterise transformations in solution, hydrodynamic diameters (HDD) were measured by dynamic light scatter, zeta potential values by electrophoretic mobility, and dissolution by equilibrium dialysis. The protective effects of humic and fulvic dissolved organic carbon (DOC) on toxicity were also assessed. To investigate the mechanisms of algal toxicity, the CytoViva hyperspectral imaging system was used to visualise algal-CeO2 interactions in the presence and absence of DOC, and the role of reactive oxygen species (ROS) was investigated by 'switching off' ROS production using UV-filtered lighting conditions. The nanoparticulate CeO2 immediately aggregated in solution to HDDs measured in the range 113-193nm, whereas the HDD and zeta potential values were significantly lower in the presence of DOC. Negligible CeO2 dissolution over the time course of the bioassay ruled out potential toxicity from dissolved cerium. The nanoparticulate CeO2 concentration that caused 50% inhibition of algal growth rate (IC50) was in the range 7.6-28mg/L compared with 59mg/L for micron-sized ceria, indicating that smaller particles were more toxic. The presence of DOC mitigated toxicity, with IC50s increasing to greater than 100mg/L. Significant ROS were generated in the nanoparticulate CeO2 bioassays under normal light conditions. However, 'switching off' ROS under UV-filtered light conditions resulted in a similar IC50, indicating that ROS generation was not the toxic mechanism. The CytoViva imaging showed negligible sorption of nanoparticulate CeO2 to algal cells in the presence of DOC, and strong sorption in its absence, suggesting that this was the toxic mechanism. The results suggest that DOC in natural waters will coat CeO2 particles and mitigate toxicity to algal cells. PMID:26461912

  8. Growth-Rate Induced Epitaxial Orientation of CeO2 on Al2O3(0001)

    SciTech Connect

    Kuchibhatla, Satyanarayana V N T; Nachimuthu, Ponnusamy; Gao, Fei; Jiang, Weilin; Shutthanandan, V.; Engelhard, Mark H.; Seal, Sudipta; Thevuthasan, Suntharampillai

    2009-05-19

    High-quality ceria (CeO2) films were grown on sapphire (Al2O3) (0001) substrates using oxygen plasma-assisted molecular beam epitaxy. The epitaxial orientation of the ceria films has been found to be (100) and (111) at low (< 8 Å/min) and higher growth rates (up to ~30 Å/min), respectively. Evidence shows that CeO2 (100) film grows as three-dimensional islands, while CeO2 (111) proceeds with layered growth. Three in-plane domains at 30° to each other are observed in the CeO2 (100), which is attributed to the close match of the oxygen sub-lattices in the film and substrate that has a three-fold symmetry. Molecular dynamic simulations have further confirmed that the CeO2 film retains (100) orientation on the Al2O3 (0001) substrate.

  9. Highly Efficient Tm-Doped Yttrium Aluminum Garnet Ceramic Laser Based on the Novel Fiber-Bulk Hybrid Configuration

    NASA Astrophysics Data System (ADS)

    Liu, Jun; Shen, Deyuan; Huang, Haitao; Zhang, Xiaoqi; Tang, Dingyuan; Fan, Dianyuan

    2013-09-01

    A polycrystalline ceramic Tm3+-doped yttrium aluminum garnet (Tm:Y3Al5O12, Tm:YAG) laser based on the novel fiber-bulk hybrid configuration is demonstrated using a high-power and tunable Er,Yb co-doped fiber laser as the pump source. Lasing characteristics of a 4.0 at. % Tm:YAG ceramic are investigated at different pump wavelengths from 1617 to 1625 nm. With an output coupler of 10% transmission, a maximum output power of 3.9 W is obtained at 2013.2 nm under an 8.8 W incident pump power at the Tm:YAG absorption peak of 1620.4 nm, corresponding to a slope efficiency of 50.1% with respect to the incident pump power.

  10. Random lasing in Eu3+ doped borate glass-ceramic embedded with Ag nanoparticles under direct three-photon excitation

    NASA Astrophysics Data System (ADS)

    Xu, Xuhui; Zhang, Wenfei; Jin, Limin; Qiu, Jianbei; Yu, Siu Fung

    2015-10-01

    We report the observation of random lasing from Eu3+ doped borate glass ceramic films embedded with Ag nanoparticles through three-photon absorption at room temperature. Under 1179 nm ultrashort femtosecond pulse excitation, discrete sharp peaks with linewidth ~0.4 nm emerge randomly from a broad emission band with peak wavelength at ~612 nm. In addition, the number of sharp peaks increases with the increase of excitation power. We also show that the emission spectrum varies with different observation angles and the corresponding lasing threshold is dependent on the excitation area. Hence, we verify unambiguously that the Eu3+ doped borate glass ceramic film supports random lasing action via three-photon absorption excitation. In addition, Ag nanoparticles, which act as light scatterers, allow the formation of random microcavities inside the bulk film.

  11. Fundamental Understanding of the Interaction of Acid Gases with CeO2 : From Surface Science to Practical Catalysis

    DOE PAGESBeta

    Tumuluri, Uma; Rother, Gernot; Wu, Zili

    2016-03-21

    Acid gases including CO2, SO2, and NOx are ubiquitous in large-scale energy applications including heterogeneous catalysis. The adverse environmental and health effects of these acid gases have resulted in high interest in the research and development of technologies to remove or convert these acid gases. The main challenge for the development of these technologies is to develop catalysts that are highly efficient, stable, and cost-effective, and many catalysts have been reported in this regard. CeO2 and CeO2-based catalysts have gained prominence in the removal and conversion of CO2, SO2, and NOx because of their structural robustness and redox and acid–basemore » properties. In this article, we provide a brief overview of the application of CeO2 and CeO2-based catalysts for the removal of CO2, SO2, and NOx gases with an emphasis on the fundamental understanding of the interactions of these acid gases with CeO2. The studies summarized in this review range from surface science using single crystals and thin films with precise crystallographic planes to practical catalysis applications of nanocrystalline and polycrystalline CeO2 materials with defects and dopants. After an introduction to the properties of CeO2 surfaces, their catalytic properties for conversions of different acid gases are reviewed and discussed. Lastly, we find that the surface atomic structure, oxygen vacancies, and surface acid–base properties of CeO2 play vital roles in the surface chemistry and structure evolution during the interactions of acid gases with CeO2 and CeO2-based catalysts.« less

  12. Up-conversion luminescence from Er3+, Yb3+ co-doped GeO II-PbF II-Nb IIO 5 glass ceramic

    NASA Astrophysics Data System (ADS)

    Lv, Jinwen; Sang, Lanfen; Zhang, Jing; Fu, Xingguo

    2006-01-01

    The paper reports a new up-conversion luminescence material based on Yb 3+, Er 3+ co-doped germanate glass ceramic, the matrix system is GeO II-PbF II-Nb IIO 5. The luminescence characteristics of the Yb3+ , Er3+ co-doped glass ceramic have been studied. The structural properties of the germinate glass ceramic have been analysed by X-ray diffraction. Under the condition of 980nm semiconductor laser pumping, the green fluorescence intensity shows that the existence of niobate components plays an important role for up-conversion luminescence.

  13. Current-voltage characteristics and grain growth of Li{sub 2}CO{sub 3}-doped tungsten trioxide ceramics

    SciTech Connect

    Wang, Y.; Yang, X.S.; Li, Z.Q.; Yao, K.L.; Liu, Z.L

    2004-08-03

    Ceramics samples of tungsten trioxide doped with lithium carbonate from 0.5 to 5 mol% were prepared by conventional electroceramic technique. The current-voltage characteristics of these ceramics were measured under various ambient temperatures. All of the I-V curves showed non-ohmic electrical properties with obvious negative-resistance characteristic at room temperature. It is found that there exists a direct correlation between the negative-resistance phenomenon in the I-V curves and the electrical history of these samples. The suitability of some models regarding the negative-resistance characteristics is discussed. X-ray diffraction (XRD) revealed coexistence of two phases of tungsten trioxide, which depends on the amount of lithium. Scanning electron microscope (SEM) showed great differences for both grain shape and size between the Li-doped and undoped WO{sub 3} ceramics, and this indicates that Li{sub 2}CO{sub 3} doped into WO{sub 3} influences strongly the growing of WO{sub 3} during sintering process.

  14. Tunable Magnetic Properties in CuCr2- x Fe x O4 Ceramics by Doping of Fe

    NASA Astrophysics Data System (ADS)

    Zhu, C. M.; Wang, L. G.; Bao, D. L. G. C.; Luo, H.; Tian, Z. M.; Yuan, S. L.

    2016-08-01

    CuCr2- x Fe x O4 ceramics have been successfully synthesized using the sol-gel method for the first time. With pure formation, material structure has been characterized by x-ray diffraction. The samples have been identified as having the spinel structure with formulae CuCr2- x Fe x O4. Micrographs obtained by scanning electron microscopy show the dense microstructure of the samples. The stoichiometric ratio of the ceramics has been measured through energy dispersive spectra. Magnetic properties of CuCr2- x Fe x O4 ceramics have been discussed. Temperature dependence of magnetization presents the gradually increasing irreversible temperature as the content of Fe element increases from x = 0 to 1. Coercive field ( H C), remanent magnetization ( M r), and saturation magnetization ( M S) respectively display the monotonous variation phenomena with increasing content of Fe. The increasing M r, M S and the decreasing H C can be attributed to the change of magnetic exchange interaction because of the doped Fe. It also proves that the magnetic properties of CuCr2- x Fe x O4 ceramics can be effectively tuned by the doping content of Fe.

  15. Progress in rare-earth-doped nanocrystalline glass-ceramics for laser cooling

    NASA Astrophysics Data System (ADS)

    Venkata Krishnaiah, Kummara; Ledemi, Yannick; Soares de Lima Filho, Elton; Loranger, Sebastien; Nemova, Galina; Messaddeq, Younes; Kashyap, Raman

    2016-03-01

    Laser cooling with anti-Stokes fluorescencewas predicted by Pringsheim in 1929, but for solids was only demonstrated in 1995. There are many difficulties which have hindered laser assisted cooling, principally the chemical purity of a sample and the availability of suitable hosts. Recent progress has seen the cooled temperature plummet to 93K in Yb:YLF. One of the challenges for laser cooling to become ubiquitous, is incorporating the rare-earthcooling ion in a more easily engineered material, rather than a pure crystalline host. Rare-earth-doped nanocrystalline glass-ceramics were first developed by Wang and Ohwaki for enhanced luminescence and mechanical properties compared to their parent glasses. Our work has focused on creating a nanocrystalline environment for the cooling ion, in an easy to engineer glass. The glasses with composition 30SiO2-15Al2O3-27CdF2-22PbF2-4YF3-2YbF3 (mol%), have been prepared by the conventional melt-quenching technique. By a simple post fabrication thermal treatment, the rare-earth ions are embedded in the crystalline phase within the glass matrix. Nanocrystals with various sizes and rare-earth concentrations have been fabricated and their photoluminescence properties assessed in detail. These materials show close to unity photoluminescence quantum yield (PLQY) when pumped above the band. However, they exhibit strong up-conversion into the blue, characteristic of Tm trace impurity whose presence was confirmed. The purification of the starting materials is underway to reduce the background loss to demonstrate laser cooling. Progress in the development of these nano-glass-ceramics and their experimental characterization will be discussed.

  16. Wavelength tunability of laser based on Yb-doped YGAG ceramics

    NASA Astrophysics Data System (ADS)

    Šulc, Jan; Jelínková, Helena; Jambunathan, Venkatesan; Miura, Taisuke; Endo, Akira; Lucianetti, Antonio; Mocek, TomáÅ.¡

    2015-02-01

    The wavelength tunability of diode pumped laser based on Yb-doped mixed garnet Y3Ga2Al3O12 (Yb:YGAG) ceramics was investigated. The tested Yb:YGAG sample (10% Yb/Y) was in the form of 2mm thick plane-parallel face-polished plate (without AR coatings). A fiber (core diameter 100 μm, NA= 0.22) coupled laser diode (LIMO, LIMO35-F100-DL980-FG-E) with emission at wavelength 969 nm, was used for longitudinal Yb:YGAG pumping. The laser diode was operating in the pulsed regime (2 ms pulse length, 10 Hz repetition rate). The duty-cycle 2% ensured a low thermal load even under the maximum diode pumping power amplitude 20W (ceramics sample was only air-cooled). The 145mm long semi-hemispherical laser resonator consisted of a flat pumping mirror (HR @ 1.01 - 1.09 μm, HT @ 0.97 μm) and curved (r = 150mm) output coupler with a reflectivity of ˜ 97% @ 1.01 - 1.09 μm. Wavelength tuning of the ytterbium laser was accomplished by using a birefringent filter (single 1.5mm thick quartz plate) placed inside the optical resonator at the Brewster angle between the output coupler and the laser active medium. The laser was continuously tunable over ˜ 58nm (from 1022nm to 1080 nm) and the tuning band was mostly limited by the free spectral range of used birefringent filter. The maximum output power amplitude 3W was obtained at wavelength 1046nm for absorbed pump power amplitude 10.6W. The laser slope efficiency was 34%.

  17. Room-Temperature Magnetocapacitance in Fe-Doped K0.5Na0.5Nb0.95Ta0.05O3 Ceramics

    NASA Astrophysics Data System (ADS)

    Li, Huan; Yang, Wenlong; Li, Yu; Meng, Qingxin; Zhou, Zhongxiang

    2012-10-01

    Ferroelectric and magnetic properties of Fe-doped potassium-sodium tantalate niobate (K0.5Na0.5(Nb0.95Ta0.05)1-xFexO3-x; x = 0 and 0.01) ceramics prepared by the conventional sintering method were investigated. In comparison with pure ceramics, the 0.01 Fe-doped ceramics show magnetic and ferroelectric properties simultaneously at room temperature. The relative dielectric constant significantly decreases after applying a magnetic field for the Fe-doped ceramics, indicating the coupling between ferroelectric and ferromagnetic orders. Magnetocapacitance of -0.77% was observed at room temperature and 50 kHz by the application of a magnetic field of 5000 Oe.

  18. Effects of the excitation density on the laser output of two differently doped Yb:YAG ceramics.

    PubMed

    Pirri, Angela; Toci, Guido; Alderighi, Daniele; Vannini, Matteo

    2010-08-01

    We report the behavior of two Yb(3+) doped ceramics (i.e. 10% at. and 20% at.) under quasi-continuous wave laser pumping. Two different behaviors are found depending on the density of Yb(3+) in the excited level. Experimental results show that at low population inversion density, the maximum output power and the efficiency are almost independent on the doping concentration. In particular, an output power as high as 8.9 W with a corresponding slope efficiency of 52% with respect to the injected pump power was reached with the 20% at. sample. Conversely, at high population inversion densities, the 20% doped sample shows a sudden decrease of the laser output for increasing pump power, due to the onset of a nonlinear loss mechanism. Finally, we report a comparison of the experimental results with numerical simulations for the evaluation of the inversion density and of the temperature distribution. PMID:20721114

  19. Structural and Luminescence Properties of Sm(3+) Doped TTB -Type BaTa2O6 Ceramic Phosphors.

    PubMed

    Ekmekçi, Mete Kaan; İlhan, Mustafa; Başak, Ali Sadi; Deniz, Sabahattin

    2015-11-01

    Pure and 0.5 to 10 mole% Sm(3+) doped TTB (tetragonal tungsten bronze)-type BaTa2O6 ceramic phosphor was produced by the solid state reaction method which performed at 1425 °C for 20 h. XRD and SEM analysis indicated single TTB phase for undoped and 0.5 to 10 mole% Sm(3+) doped BaTa2O6 structures. SEM also showed that the BaTa2O6 grain size decreased with the increasing content of Sm(3+). Optical analysis indicated significant emissions in the visible spectral region as green (λ = 562.7 nm) and orange-reddish (λ = 597.1 nm). The emission intensity increased with the increasing doping concentration up to 2.5 mole%, and then decreased due to the concentration quenching effect. PMID:26410773

  20. Relaxor in KF-doped BaTi{sub 2}O{sub 5} ceramics by spark plasma sintering

    SciTech Connect

    Xu Jun; Akishige, Yukikuni

    2008-02-04

    Dense BaTi{sub 2}O{sub 5} ceramics with KF doping up to 5 at. % were synthesized by spark plasma sintering (SPS). The SPS method enabled us to overcome the densifying difficulty in conventional sintering which is caused by the limit of the decomposing temperature of this metastable phase. We observed drastic KF-doping effect on the ferroelectric (FE) properties of BaTi{sub 2}O{sub 5}. Although there is only very small change in lattice parameters upon KF doping, the peak temperature in dielectric constant strongly decreases in an exponential way. The diffuseness of phase transition increases and FE relaxor state sets in for KF content as low as 1 at. %. Possible structural reasons for the effect and the implication for the nature of FE phase transition in BaTi{sub 2}O{sub 5} are discussed.

  1. Synthesis of novel CeO2-BiVO4/FAC composites with enhanced visible-light photocatalytic properties.

    PubMed

    Zhang, Jin; Wang, Bing; Li, Chuang; Cui, Hao; Zhai, Jianping; Li, Qin

    2014-09-01

    To utilize visible light more effectively in photocatalytic reactions, a fly ash cenosphere (FAC)-supported CeO2-BiVO4 (CeO2-BiVO4/FAC) composite photocatalyst was prepared by modified metalorganic decomposition and impregnation methods. The physical and photophysical properties of the composite have been characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), and UV-Visible diffuse reflectance spectra. The XRD patterns exhibited characteristic diffraction peaks of both BiVO4 and CeO2 crystalline phases. The XPS results showed that Ce was present as both Ce(4+) and Ce(3+) oxidation states in CeO2 and dispersed on the surface of BiVO4 to constitute a p-n heterojunction composite. The absorption threshold of the CeO2-BiVO4/FAC composite shifted to a longer wavelength in the UV-Vis absorption spectrum compared to the pure CeO2 and pure BiVO4. The composites exhibited enhanced photocatalytic activity for Methylene Blue (MB) degradation under visible light irradiation. It was found that the 7.5wt.% CeO2-BiVO4/FAC composite showed the highest photocatalytic activity for MB dye wastewater treatment. PMID:25193845

  2. Effects of CeO2 nanoparticles on system performance and bacterial community dynamics in a sequencing batch reactor.

    PubMed

    Qiu, Guanglei; Neo, Sin-Yi; Ting, Yen-Peng

    2016-01-01

    The effects of CeO2 nanoparticles (NPs) on the system performance and the bacterial community dynamics in a sequencing batch reactor (SBR) were investigated, along with the fate and removal of CeO2 NPs within the SBR. Significant impact was observed on nitrification; NH4+-N removal efficiency decreased from almost 100% to around 70% after 6 days of continuous exposure to 1.0 mg/L of CeO2 NPs, followed by a gradual recovery until a stable value of around 90% after 20 days. Additionally, CeO2 NPs also led to a significant increase in the protein content in the soluble microbial products, showing the disruptive effects of CeO2 NPs on the extracellular polymeric substance matrix and related activated sludge structure. Denaturing gradient gel electrophoresis analysis showed remarkable changes in the bacterial community structure in the activated sludge after exposure to CeO2 NPs. CeO2 NPs were effectively removed in the SBR mainly via sorption onto the sludge. However, the removal efficiency decreased from 95 to 80% over 30 days. Mass balance evaluation showed that up to 50% of the NPs were accumulated within the activated sludge and were removed with the waste sludge. PMID:26744939

  3. Mechanical, lattice dynamical and electronic properties of CeO2 at high pressure: First-principles studies

    NASA Astrophysics Data System (ADS)

    Li, Mei; Jia, Huiling; Li, Xueyan; Liu, Xuejie

    2016-01-01

    The elastic constants (Cij), bulk modulus (B), shear modulus (G) and elastic modulus (E) of cubic fluorite CeO2 under high pressure have been studied using the plane-wave pseudopotential method based on density functional theory. The calculated results show that the mechanical properties (Cij, B, G and E) of CeO2 increase with increasing pressure, and the phase transition of CeO2 occurs beyond the pressure of 130 GPa. From the calculated phonon spectrum using Parlinsk-Li-Kawasoe method, we found that CeO2 appears imaginary frequency at 140 GPa, which indicates phase transition. The energy band, density of states and charge density of CeO2 under high pressure are calculated using GGA+U method. It is found that the high pressure makes the electron delocalization and Ce-O covalent bonding enhanced. As pressure increases, the band gap between O2p and Ce4f states near the Fermi level increases, and CeO2 nonmetallic nature promotes. The present research results in a better understanding of how CeO2 responds to compression.

  4. Facile synthesis of Sm3+/Eu3+ codoped CeO2 ultrafine nanocrystals and oxygen vacancy site dependent photoluminescence

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    Ultrafine nanocrystals of Sm3+/Eu3+ codoped CeO2 have been prepared successfully by a simple and facile oxalate decomposition method. The structure, phase and size of the nanocrystals were characterized by X-ray diffraction and transmission electron microscope which confirmed that monodispersed nanocrystals of size below 5 nm are formed by this novel technique. Spectroscopic investigations of the synthesized phosphors are carried out with the help of photoluminescence excitation, emission and decay analysis. The studies revealed that oxygen vacancies introduced in the crystal lattice for charge compensation strongly influences the luminescence properties of the phosphor material. By investigating the luminescence characteristics of the material with different doping concentrations of Sm3+ and Eu3+, the position of the oxygen vacancies with respect to the dopant ion is determined. Also it can be revealed that symmetry of Eu3+ ions are perturbed by the oxygen vacancies at nearest neighbor site which produce strong electric dipole transition emissions in the luminescence spectra. In the case of Sm3+ ions oxygen vacancies are repelled to the next nearest neighbor site and hence the cubic symmetry of the ions is preserved. In addition, occurrence of non radiative energy transfer from Sm3+ to Eu3+ in the phosphor material is confirmed by the close examination of the luminescence spectra. Chromaticity coordinates evidenced that color purity of the synthesized nanophosphors is marginally increased by the proper addition of Sm3+.

  5. Designed synthesis of multi-functional PEGylated Yb2O3:Gd@SiO2@CeO2 islands core@shell nanostructure.

    PubMed

    Li, Junqi; Yao, Shuang; Song, Shuyan; Wang, Xiao; Wang, Yinghui; Ding, Xing; Wang, Fan; Zhang, Hongjie

    2016-07-28

    Nanomaterials that can restrain or reduce the production of excessive reactive oxygen species such as H2O2 to defend and treat against Alzheimer's disease (AD) have attracted much attention. In this paper, we adopt the strategy of layer-by-layer deposition; namely, first synthesizing available gadolinium-doped ytterbia nanoparticles (Yb2O3:Gd NPs) as cores, and then coating them with silica via the classical Stöber method to prevent leakage and act as a carrier for subsequent ceria deposition and PEGylation, and finally obtain the expected core@shell-structured nanocomposite of PEGylated Yb2O3:Gd@SiO2@CeO2 islands. The nanomaterial has proved not only to be a high-performance dual-modal contrast agent for use in MRI and CT, but also to exhibit excellent catalase mimetic activity, which may help the prognosis, diagnosis and treatment of AD in the future. In addition, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR) spectroscopy characterization have revealed the successful design and synthesis of the cores with remarkable size uniformity, with well-distributed CeO2 islands decorated on the surface of SiO2 shells, and tightly immobilized PEG. PMID:27351951

  6. Dielectric and Ferroelectric Behavior of Bismuth-Doped Barium Titanate Ceramic Prepared by Microwave Sintering

    NASA Astrophysics Data System (ADS)

    Mahapatra, A.; Parida, S.; Sarangi, S.; Badapanda, T.

    2015-08-01

    Bismuth-doped barium titanate ceramics with the general formula Ba1- x Bi2 x/3TiO3 ( x = 0.0, 0.01, 0.025, 0.05) have been prepared by the solid state reaction technique. The phase formation and structural property of all compositions have been studied by x-ray diffraction (XRD) pattern and Rietveld refinement. XRD pattern reports the single phase tetragonal crystal system with space group of P4mm. All compositions have been sintered at 1100°C in a microwave furnace for 30 min. The variation of dielectric constant with respect to temperature and frequency was studied and it was found that the dielectric constant decreases whereas transition temperature increased with the increase in Bi content. The diffusivity parameter was calculated by the modified Curie-Weiss law and the diffusivity increased with the increase in Bi content. The ferroelectric property was studied by the P-E hysteresis loop and it was observed that the saturation polarization decreased, but the coercive field increased with Bi content. The optical band gap was calculated from UV-Visible spectroscopy and found to decrease with Bi content.

  7. Influence of cation distribution on the magnetic and dielectric properties of Zn doped CFO ceramics

    NASA Astrophysics Data System (ADS)

    Monaji, Vinitha Reddy; Paul Praveen, J.; Raja, Manivel; Das, Dibakar

    2016-05-01

    Cations site registry of Co1-xZnxFe2O4 (0 ≤ x ≤ 0.3) ceramics, synthesized by combustion method, has been estimated using Mossbauer spectroscopic study and Rietveld analysis and its influence on the magnetic and dielectric properties have been studied. Decreased B-site hyperfine field with progressive Zn doping due to the occupancy of non-magnetic Zn ions in the tetrahedral site of CFO lattice has been observed in Mössbauer data. Magnetic moment of Co1-xZnxFe2O4 (0 ≤ x ≤ 0.3) calculated from the cation distribution estimated from the Mössbauer data has been compared with the experimentally observed magnetic moment. Decreased dielectric constants (ɛ') with increasing Zn concentrations, in the frequency range 20Hz - 1MHz (at ~300K), indicates increased Fe+3 concentrations in the octahedral sites. The temperature dependent dielectric data showed a progressive reduction in the magnetic transition temperature (TC) from 528˚C for x = 0 to 422˚C for x = 0.3 of the Co1-xZnxFe2O4 (0 ≤ x ≤ 0.3) samples. Increasing relaxor behavior (γ = 1.85 for x = 0 to γ = 2.2 for x = 0.3) has been observed with increasing Zn content in the CFO lattice.

  8. Leaching effect in gadolinia-doped ceria aqueous suspensions for ceramic processes

    NASA Astrophysics Data System (ADS)

    Caldarelli, A.; Mercadelli, E.; Presto, S.; Viviani, M.; Sanson, A.

    2016-09-01

    Gadolinium doped ceria (CGO) is a commonly used electrolytic material for Solid Oxide Fuel Cells (SOFCs) and for this reason different shaping methods for its deposition are reported in literature. Most of these processes are based on the use of organic-based CGO suspensions, but water-based processes are acquiring increasingly interest for their economical and environmental friendly properties. In this paper we reported how the components of water-based suspension and some unexpected process parameters can deeply affect the functional properties of the final powder. In particular, we observed that CGO powders are strongly affected by ionic leaching induced by furoic acid used as dispersant: the extent of this leaching was related to the dispersant concentration and suspension's ball-milling-time; the phenomenon was confirmed by ICP-AES analyses on suspensions surnatant. Most importantly, ionic leaching affected the electrical properties of CGO: leached powder showed a higher ionic conductivity as a consequence of a partial removal of Gd ions at the grain boundaries. This work is therefore pointing out that when considering water-based suspensions, it is extremely important to carefully consider all the process parameters, including the organic components of the ceramic suspension, as these could lead to unexpected effects on the properties of the powder, affecting the performance of the final shaped material.

  9. Anomalous dielectric and thermal properties of Ba-doped PbZrO3 ceramics

    NASA Astrophysics Data System (ADS)

    Pirc, R.; Rožič, B.; Koruza, J.; Cordoyiannis, G.; Malič, B.; Kutnjak, Z.

    2015-11-01

    The dielectric and thermal properties of an antiferroelectric (AFE) material characterised by an intermediate ferroelectric (FE) phase between the AFE and paraelectric phase in zero field are studied by means of a generalised Landau-Kittel model of AFEs. A temperature-dependent coupling of the two sublattices is introduced in accordance with the Rae-Dove (RD) model of re-entrant phase transitions. The sublattice polarisation components are calculated as functions of temperature and the applied electric field by minimising numerically the free energy. The calculated dielectric susceptibility shows anomalies at the boundaries of the intermediate FE phase, characteristic for first-order phase transitions. It is shown that this behaviour is in qualitative agreement with the measured dielectric constant in Ba-doped PbZrO3 ceramics. The model also predicts a negative adiabatic electrocaloric temperature change Δ T in a broad temperature range in the AFE phase, in qualitative agreement with experiments. The dipolar heat capacity is also predicted to be negative in the intermediate phase in zero field, in analogy with the results of the RD model.

  10. Effect of composition and temperature on electric fatigue of La-doped lead zirconate titanate ceramics

    NASA Astrophysics Data System (ADS)

    Jiang, Q. Y.; Subbarao, E. C.; Cross, L. E.

    1994-06-01

    Composition and temperature of ferroelectric La-doped lead zirconate titanate ceramics influence its electric fatigue behavior, defined as the degradation of the electrical properties under the action of an ac field applied for a long time. Compositions of rhombohedral symmetry exhibit little or no fatigue compared with those of tetragonal and orthorhombic symmetry. At temperatures higher than the dielectric maximum, no fatigue effect was detected. Compositions close to phase boundaries (FE-AFE, FE-FE, or FE-PE) display significant fatigue behavior. Electric fatigue arises from the pinning of domains by space charges or injected carriers or from microcracking. The former (which are charge related) is accompanied by smaller strains and is recoverable by thermal and electrical treatment, while the latter (arising from microcracking) arises from large incompatible stresses between grains and is a permanent damage. The understanding of the mechanism of electric fatigue gained in the present study provides guidelines for enhancing the long-term reliability of devices based on ferroic materials.

  11. Enhanced ferromagnetic properties in Ho and Ni co-doped BiFeO3 ceramics

    NASA Astrophysics Data System (ADS)

    Park, J. S.; Yoo, Y. J.; Hwang, J. S.; Kang, J.-H.; Lee, B. W.; Lee, Y. P.

    2014-01-01

    The magnetic properties of polycrystalline Bi1-xHoxFe1-yNiyO3 (x = 0, 0.1; y = 0, 0.03), which were prepared by the solid-state method, have been investigated. The powder X-ray diffraction reveals that all the samples are polycrystalline and show rhombohedral perovskite structure. The micro-Raman scattering studies confirm that Bi0.9Ho0.1Fe0.97Ni0.03O3 has a compressive lattice distortion induced by the simultaneous substitution of Ho and Ni ions at A and B-sites, respectively. From the magnetization dependences at room temperature, Bi0.9Ho0.1Fe0.97Ni0.03O3 has enhanced magnetization (0.2280 emu/g) and low coercive field (280 Oe). It was revealed that the Ni dopant plays an important role for the improved ferromagnetic properties and the Ho dopant favors the magnetic exchange interactions in the co-doped ceramic.

  12. Preliminary evaluation of therapeutic ion release from Sr-doped zinc-silicate glass ceramics.

    PubMed

    Looney, Mark; O'Shea, Helen; Boyd, Daniel

    2013-01-01

    Bioactive and degradable porous bioceramics play an important role in many clinical situations. Porosity is essential to the performance of a material that is proposed to be used as an implantable osseous scaffold. Scaffolds provide a three dimensional support and template to osseous integration and vascularization. Combining the porosity of a scaffold with the ability of the scaffold material to deliver therapeutic ions to the site of implantation goes some way towards developing an ideal bone graft. A series of strontium-doped zinc silicate (Ca-Sr-Na-Zn-Si) glass ceramics scaffoldswere developed, whose porosity was measured to be between 93% and 96%, which is advantageous in terms of osseous integration and vascularization. The levels of Zn(2+) and Sr(2+) detected as a result of degradation of the crystalline phases were found to be 1.4-600 parts per million (ppm) and 0-583 ppm, respectively. The levels detected correlate well with the levels of Sr(2+) and Zn(2+)ions typically associated with clinical benefits, including antibacterial efficacy, osteoblastic differentiation and impaired osteoclastic resorption. PMID:21926151

  13. AC conductivity and structural properties of Mg-doped ZnO ceramic

    NASA Astrophysics Data System (ADS)

    Othman, Zayani Jaafar; Hafef, Olfa; Matoussi, Adel; Rossi, Francesca; Salviati, Giancarlo

    2015-11-01

    Undoped ZnO and Zn1- x Mg x O ceramic pellets were synthesized by the standard sintering method at the temperature of 1200 °C. The influence of Mg doping on the morphological, structural and electrical properties was studied. The scanning electron microscopy images revealed rough surface textured by grain boundaries and compacted grains having different shapes and sizes. Indeed, the X-ray diffraction reveals the alloying of hexagonal ZnMgO phase and the segregation of cubic MgO phase. The crystallite size, strain and stress were studied using Williamson-Hall (W-H) method. The results of mean particle size of Zn1- x Mg x O composites showed an inter-correlation with W-H analysis and Sherrer method. The electrical conductivity of the films was measured from 173 to 373 K in the frequency range of 0.1 Hz-1 MHz to identify the dominant conductivity mechanism. The DC conductivity is thermally activated by electron traps having activation energy of about 0.09 to 0.8 eV. The mechanisms of AC conductivity are controlled by the correlated barrier hopping model for the ZnO sample and the small polaron tunneling (SPT) model for Zn0.64Mg0.36O and Zn0.60Mg0.40O composites.

  14. Sponge phase producing porous CeO2 for catalytic oxidation of CO.

    PubMed

    Song, Shasha; Wang, Haiqiao; Song, Aixin; Dong, Shuli; Hao, Jingcheng

    2014-07-14

    The aggregation behavior of mixtures of the alkaline amino acid L-Arginine (L-Arg) and bis(2-ethylhexyl)phosphoric acid (DEHPA) in water was studied in detail. At a fixed L-Arg concentration, a phase sequence of micellar phase (L1 phase), vesicle phase (Lαv phase), planar lamellar phase (Lαl phase), and sponge phase (L3 phase) was obtained with increasing DEHPA concentration due to changes in the packing parameter. The phase transition of the lamellar structures was determined by freeze-fracture TEM and (2)H NMR spectroscopy. Rheological measurements reflected the phase transition through significant variations of both the elastic modulus and the viscous modulus. Porous CeO2 materials were produced by utilizing the L3 phase as template, and the porous CeO2 exhibited excellent catalytic oxidation activity toward CO due to its high surface area, which provides more active sites for CO conversion. PMID:24895013

  15. Erosion-Corrosion Property of CeO2-Modified HVOF WC-Co Coating

    NASA Astrophysics Data System (ADS)

    Liu, Yan; Hang, Zongqiu; Chen, Hui; Ceng, Shengbo; Gou, Guoqing; Wang, Xiaomin; Tu, Mingjing; Wu, Xiangyang

    2016-04-01

    Rare-earth elements have been widely used in materials manufacturing to improve hardness and toughness. In this work, conventional, nanostructured, and CeO2-modified WC-12Co powders were sprayed using high-velocity oxygen flame spraying. The erosion-corrosion behavior and interaction of erosion and corrosion of the coatings in 3.5 wt.% NaCl solution were investigated. In situ observation was employed to analyze the failure mechanism. The results showed that the CeO2-modified WC-12Co coating possessed the best erosion-corrosion resistance, while the lowest corrosion resistance was exhibited by the conventional WC-12Co coating. The results also suggested that the erosion-corrosion mechanism in the three coatings was dominated by corrosion-accelerated erosion. However, the extent of acceleration of erosion by corrosion differed.

  16. Molecular dynamics simulation of fast particle irradiation on the single crystal CeO2

    NASA Astrophysics Data System (ADS)

    Sasajima, Y.; Ajima, N.; Osada, T.; Ishikawa, N.; Iwase, A.

    2013-11-01

    We used a molecular dynamics method to simulate structural relaxation caused by the high-energy-ion irradiation of single crystal CeO2. As the initial condition, we assumed high thermal energy was supplied to the individual atoms within a cylindrical region of nanometer-order diameter located in the center of the single crystal. The potential proposed by Inaba et al. was utilized to calculate interactions between atoms [H. Inaba, R. Sagawa, H. Hayashi, K. Kawamura, Solid State Ionics 122 (1999) 95-103]. The supplied thermal energy was first spent to change the crystal structure into an amorphous one within a short period of about 0.3 ps, then it was dissipated in the crystal. We compared the obtained results with those of computer simulations for UO2 and found that CeO2 was more stable than UO2 when supplied with high thermal energy.

  17. Reactivity and reaction intermediates for acetic acid adsorbed on CeO2(111)

    DOE PAGESBeta

    Calaza, Florencia C.; Chen, Tsung -Liang; Mullins, David R.; Xu, Ye; Steven H. Overbury

    2015-05-02

    Adsorption and reaction of acetic acid on a CeO2(1 1 1) surface was studied by a combination of ultra-highvacuum based methods including temperature desorption spectroscopy (TPD), soft X-ray photoelectronspectroscopy (sXPS), near edge X-ray absorption spectroscopy (NEXAFS) and reflection absorption IRspectroscopy (RAIRS), together with density functional theory (DFT) calculations. TPD shows that thedesorption products are strongly dependent upon the initial oxidation state of the CeO2 surface, includingselectivity between acetone and acetaldehyde products. The combination of sXPS and NEXAFS demon-strate that acetate forms upon adsorption at low temperature and is stable to above 500 K, above whichpoint ketene, acetone and acetic acidmore » desorb. Furthermore, DFT and RAIRS show that below 500 K, bridge bondedacetate coexists with a moiety formed by adsorption of an acetate at an oxygen vacancy, formed bywater desorption.« less

  18. Mn3O4-CeO2 nano-catalysts: Synthesis, characterization and application

    NASA Astrophysics Data System (ADS)

    Anushree, Sharma, C.; Kumar, S.

    2016-05-01

    Nano-sized Mn3O4-CeO2 catalysts were synthesized by a cost effective co-precipitation method, and were studied as a heterogeneous catalyst for wet air oxidation of paper industry wastewater at mild operating conditions of 90 °C and 1 atm. The structural, micro-structural and textural properties of synthesized catalysts were studied through various characterization techniques, i.e. XRD, TEM, N2-sorption and EDS. The catalytic activity of Mn3O4-CeO2 was interestingly found to be higher than the corresponding single-metal oxides, and the Ce50Mn50 nano-catalyst with small crystallite size (4.5 nm), high specific surface area (75 m2g-1) and high porosity (0.24 ccg-1) was found to be most efficient with 69% color, 60% COD, 59% TOC, 48% AOX removal.

  19. Cell uptake, intracellular distribution, fate and reactive oxygen species generation of polymer brush engineered CeO2-x NPs

    NASA Astrophysics Data System (ADS)

    Qiu, Yuan; Rojas, Elena; Murray, Richard A.; Irigoyen, Joseba; Gregurec, Danijela; Castro-Hartmann, Pablo; Fledderman, Jana; Estrela-Lopis, Irina; Donath, Edwin; Moya, Sergio E.

    2015-04-01

    Cerium Oxide nanoparticles (CeO2-x NPs) are modified with polymer brushes of negatively charged poly (3-sulfopropylmethacrylate) (PSPM) and positively charged poly (2-(methacryloyloxy)ethyl-trimethylammonium chloride) (PMETAC) by Atom Transfer Radical Polymerisation (ATRP). CeO2-x NPs are fluorescently labelled by covalently attaching Alexa Fluor® 488/Fluorescein isothiocyanate to the NP surface prior to polymerisation. Cell uptake, intracellular distribution and the impact on the generation of intracellular Reactive Oxygen Species (ROS) with respect to CeO2-x NPs are studied by means of Raman Confocal Microscopy (CRM), Transmission Electron Microscopy (TEM) and Inductively Coupled Plasma Mass Spectroscopy (ICP-MS). PSPM and PMETAC coated CeO2-x NPs show slower and less uptake compared to uncoated Brush modified NPs display a higher degree of co-localisation with cell endosomes and lysosomes after 24 h of incubation. They also show higher co-localisation with lipid bodies when compared to unmodified CeO2-x NPs. The brush coating does not prevent CeO2-x NPs from displaying antioxidant properties.Cerium Oxide nanoparticles (CeO2-x NPs) are modified with polymer brushes of negatively charged poly (3-sulfopropylmethacrylate) (PSPM) and positively charged poly (2-(methacryloyloxy)ethyl-trimethylammonium chloride) (PMETAC) by Atom Transfer Radical Polymerisation (ATRP). CeO2-x NPs are fluorescently labelled by covalently attaching Alexa Fluor® 488/Fluorescein isothiocyanate to the NP surface prior to polymerisation. Cell uptake, intracellular distribution and the impact on the generation of intracellular Reactive Oxygen Species (ROS) with respect to CeO2-x NPs are studied by means of Raman Confocal Microscopy (CRM), Transmission Electron Microscopy (TEM) and Inductively Coupled Plasma Mass Spectroscopy (ICP-MS). PSPM and PMETAC coated CeO2-x NPs show slower and less uptake compared to uncoated Brush modified NPs display a higher degree of co-localisation with cell endosomes and lysosomes after 24 h of incubation. They also show higher co-localisation with lipid bodies when compared to unmodified CeO2-x NPs. The brush coating does not prevent CeO2-x NPs from displaying antioxidant properties. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr00884k

  20. Controlling polymorphic structures and investigating electric properties of Ca-doped zirconia using solid state ceramic method

    SciTech Connect

    Emam, W.I.; Mabied, Ahmed F.; Hashem, H.M.; Selim, M.M.; El-Shabiny, A.M.; Ahmed Farag, I.S.

    2015-08-15

    Structural study of Zr{sub 1−x}Ca{sub x}O{sub 2−x} samples with x=0.01–0.15 were prepared using solid state ceramic method. X-ray diffraction analysis revealed a mixture of the high temperature phase and the monoclinic one for the samples with x≤0.05. On the other hand, the formation of a single high temperature cubic phase was observed within a concentration range of x=0.06–0.10. At concentrations higher than 0.10 the calcium zirconate phase was observed besides the dominant high temperature one. Rietveld refinement of the single phase data clearly revealed, that substitution of zirconium by calcium increases both the lattice parameters as well as the tetrahedral bond length. Ionic to electronic conductivity ratio enhanced considerably as Ca-doping level ascends. The dielectric constant shows strong temperature dependence at lower frequencies. The dielectric loss factor increases rapidly with the increase in temperature at lower frequencies, while decreases with the increase in frequency at higher temperatures. The ionic conduction is considered as the dominant process at higher temperatures. - Graphical abstract: Forming a high temperature cubic zirconia phase at 1200 °C using ceramic solid state method and aliovalent cation. - Highlights: • Formation the high temperature cubic polymorph of zirconia using Ca-doping. • Solid state ceramic method was used for preparing the cubic Ca-doped zirconia. • Substitution of zirconium by calcium increases the lattice parameters and the bond length. • Ionic to electronic conductivity ratio enhanced considerably as Ca-doping level increases.

  1. Ceramics

    NASA Astrophysics Data System (ADS)

    Chen, Song; Zhu, De-Gui; Cai, Xu-Sheng

    2014-08-01

    The dense monoclinic-SrAl2Si2O8 ceramics have been prepared by a two-step sintering process at a sintering temperature of 1173 K (900 °C). Firstly, the pre-sintered monoclinic-SrAl2Si2O8 powders containing small SiO2·Al2O3 crystal phases were obtained by continuously sintering a powder mixture of SrCO3 and kaolin at 1223 K (950 °C) for 6 hours and 1673 K (1400 °C) for 4 hours, respectively. Subsequently, by the combination of the pre-sintered ceramic powders with the composite flux agents, which are composed of a SrO·3B2O3 flux agent and α-Al2O3, the low-temperature densification sintering of the monoclinic-SrAl2Si2O8 ceramics was accomplished at 1173 K (900 °C). The low-temperature sintering behavior and microstructure evolvement of the monoclinic-SrAl2Si2O8 ceramics have been investigated in terms of Al2O3 in addition to the composite flux agents. It shows that due to the low-meting characteristics, the SrO·3B2O3 flux agent can urge the dense microstructure formation of the monoclinic-SrAl2Si2O8 ceramics and the re-crystallization of the grains via a liquid-phase sintering. The introduction of α-Al2O3 to the SrO·3B2O3 flux agent can apparently lead to more dense microstructures for the monoclinic-SrAl2Si2O8 ceramics but also cause the re-precipitation of SiO2·Al2O3 compounds because of an excessive Al2O3 content in the SrO·3B2O3 flux agent.

  2. Investigation of oxygen vacancies in CeO2/Pt system with synchrotron light techniques

    NASA Astrophysics Data System (ADS)

    Braglia, L.; Bugaev, A. L.; Lomachenko, K. A.; Soldatov, A. V.; Lamberti, C.; Guda, A. A.

    2016-05-01

    A peculiar property of ceria is the ease to form oxygen vacancies, producing reactive sites or facilitating ionic diffusion. For these reasons ceria promotes catalytic activities for a number of important reactions when it is used as a support for transition metals. In our work we study the temporal evolution of oxygen vacancies formation by time-resolved XANES at Ce K- edge and XRD measurements on CeO2/Pt nanoparticles, successfully monitoring the reaction of CO oxidation.

  3. Role of molting on the biodistribution of CeO2 nanoparticles within Daphnia pulex.

    PubMed

    Auffan, Mélanie; Bertin, Delphine; Chaurand, Perrine; Pailles, Christine; Dominici, Christian; Rose, Jérôme; Bottero, Jean-Yves; Thiery, Alain

    2013-08-01

    As all arthropods, microcrustaceans shed their chitinous exoskeleton (cuticule, peritrophic membrane) to develop and grow. While the molting is the most crucial stage in their life cycle, it remains poorly investigated in term of pollutant biodistribution within the organisms. In this paper, we used optical, electronic, and X ray-based microscopies to study the uptake and release of CeO2 nanoparticles by/from Daphnia pulex over a molting stage. We measured that D. pulex molts every 59 ± 21 h (confidence interval) with growth rates about 1.1 or 1.8 μm per stage as a function of the pieces measured. Ingestion via food chain was the main route of CeO2 nanoparticles uptake by D. pulex. The presence of algae during the exposure to nanoparticles (sub-lethal doses) enhanced by a factor of 3 the dry weight concentration of Ce on the whole D. pulex. Nanoparticles were localized in the gut content, in direct contact with the peritrophic membrane, and on the cuticle. Interestingly, the depuration (24 h with Chlorella pseudomonas) was not efficient to remove the nanoparticles from the organisms. From 40% to 100% (depending on the feeding regime during exposure) of the CeO2 taken up by D. pulex is not release after the depuration process. However, we demonstrated for the first time that the shedding of the chitinous exoskeleton was the crucial mechanism governing the released of CeO2 nanoparticles regardless of the feeding regime during exposure. PMID:23664411

  4. CO Oxidation mechanism on CeO2-supported Au nanoclusters

    SciTech Connect

    Kim H. Y.; Henkelman, G.

    2013-09-08

    To reveal the richer chemistry of CO oxidation by CeO2 supported Au Nanoclusters(NCs)/Nanoparticles, we design Au13 and Au12 supported on a flat and a stepped-CeO2 model (Au/CeO2) and study various kinds of CO oxidation mechanisms at the Au-CeO2 interface and the Au NC as well.

  5. Oxygen vacancy-assisted coupling and enolization of acetaldehyde on CeO2(111).

    PubMed

    Calaza, Florencia C; Xu, Ye; Mullins, David R; Overbury, Steven H

    2012-10-31

    The temperature-dependent adsorption and reaction of acetaldehyde (CH(3)CHO) on a fully oxidized and a highly reduced thin-film CeO(2)(111) surface have been investigated using a combination of reflection-absorption infrared spectroscopy (RAIRS) and periodic density functional theory (DFT+U) calculations. On the fully oxidized surface, acetaldehyde adsorbs weakly through its carbonyl O interacting with a lattice Ce(4+) cation in the η(1)-O configuration. This state desorbs at 210 K without reaction. On the highly reduced surface, new vibrational signatures appear below 220 K. They are identified by RAIRS and DFT as a dimer state formed from the coupling of the carbonyl O and the acyl C of two acetaldehyde molecules. This dimer state remains up to 400 K before decomposing to produce another distinct set of vibrational signatures, which are identified as the enolate form of acetaldehyde (CH(2)CHO¯). Furthermore, the calculated activation barriers for the coupling of acetaldehyde, the decomposition of the dimer state, and the recombinative desorption of enolate and H as acetaldehyde are in good agreement with previously reported TPD results for acetaldehyde adsorbed on reduced CeO(2)(111) [Chen et al. J. Phys. Chem. C 2011, 115, 3385]. The present findings demonstrate that surface oxygen vacancies alter the reactivity of the CeO(2)(111) surface and play a crucial role in stabilizing and activating acetaldehyde for coupling reactions. PMID:23020248

  6. MnO2/CeO2 for catalytic ultrasonic degradation of methyl orange.

    PubMed

    Zhao, He; Zhang, Guangming; Zhang, Quanling

    2014-05-01

    Catalytic ultrasonic degradation of aqueous methyl orange was studied in this paper. Heterogeneous catalyst MnO2/CeO2 was prepared by impregnation of manganese oxide on cerium oxide. Morphology and specific surface area of MnO2/CeO2 catalyst were characterized and its composition was determined. Results showed big differences between fresh and used catalyst. The removal efficiency of methyl orange by MnO2/CeO2 catalytic ultrasonic process was investigated. Results showed that ultrasonic process could remove 3.5% of methyl orange while catalytic ultrasonic process could remove 85% of methyl orange in 10 min. The effects of free radical scavengers were studied to determine the role of hydroxyl free radical in catalytic ultrasonic process. Results showed that methyl orange degradation efficiency declined after adding free radical scavengers, illustrating that hydroxyl free radical played an important role in degrading methyl orange. Theoretic analysis showed that the resonance size of cavitation bubbles was comparable with the size of catalyst particles. Thus, catalyst particles might act as cavitation nucleus and enhance ultrasonic cavitation effects. Measurement of H2O2 concentration in catalytic ultrasonic process confirmed this hypothesis. Effects of pre-adsorption on catalytic ultrasonic process were examined. Pre-adsorption significantly improved methyl orange removal. The potential explanation was that methyl orange molecules adsorbed on catalysts could enter cavitation bubbles and undergo stronger cavitation. PMID:24369902

  7. STM and XPS study of CeO2(111) reduction by atomic hydrogen

    NASA Astrophysics Data System (ADS)

    Shahed, Syed Mohammad Fakruddin; Hasegawa, Tomo; Sainoo, Yasuyuki; Watanabe, Yoshihide; Isomura, Noritake; Beniya, Atsushi; Hirata, Hirohito; Komeda, Tadahiro

    2014-10-01

    Reduction of CeO2(111)/Ru(0001) surface by atomic hydrogen was investigated using scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). We observed the formation of oxygen vacancy trimers and hydroxyl trimers on the stoichiometric CeO2(111) surface when it was exposed to atomic hydrogen at room temperature. The reaction of an impinging hydrogen atom with a surface oxygen atom yields a hydroxyl species, which diffuse on the surface until stabilized by the formation of OH trimers. The hydrogen atoms were located at atop sites of the oxygen atoms in the topmost surface layer. A reaction between the hopping hydrogen atom and the hydroxyl species yields a water molecule, which is desorbed from the surface leaving an oxygen defect. The oxygen vacancies were also observed as a trimer of vacancies. XPS measurements showed an increase of a reduced Ce and hydroxyl species with an amount of exposed hydrogen atoms. The former was estimated by measuring the ratio of Ce3 +/Ce4 + in the Ce 3d components. Our study shows the formation of hydroxyl trimer species in atomic scale upon atomic hydrogen exposure to CeO2(111) surface which could offer new catalytic activity.

  8. Effect of B-site isovalent doping on electrical and ferroelectric properties of lead free bismuth titanate ceramics

    NASA Astrophysics Data System (ADS)

    Subohi, Oroosa; Kumar, G. S.; Malik, M. M.; Kurchania, Rajnish

    2016-06-01

    In the present work, zirconium modified bismuth titanate ceramics have been studied as potential lead-free ferroelectric materials over a broad temperature range (RT - 800 °C). Polycrystalline samples of Bi4Ti3-xZrxO12 (x=0.2, 0.4, 0.6) (BZrT) with high electrical resistivity were prepared using the solution combustion technique. The effect of Zr doping on the crystalline structure, ferroelectric properties and electrical conduction characteristics of BZrT ceramics were explored. Addition of zirconium to bismuth titanate enhances its dielectric constant and reduces the loss factor as it introduces orthorhombic distortion in bismuth titanate lattice which is exhibited by the growth along (00_10) lattice plane. Activation energy due to relaxation is found to be greater than that due to conduction thus confirming that electrical conduction in these ceramics is not due to relaxation of dipoles. Remanent polarization of the doped samples increases as the Zirconium content increases.

  9. Multi-susceptibile Single-Phased Ceramics with Both Considerable Magnetic and Dielectric Properties by Selectively Doping

    PubMed Central

    Liu, Chuyang; Zhang, Yujing; Jia, Jingguo; Sui, Qiang; Ma, Ning; Du, Piyi

    2015-01-01

    Multiferroic ceramics with extraordinary susceptibilities coexisting are vitally important for the multi-functionality and integration of electronic devices. However, multiferroic composites, as the most potential candidates, will introduce inevitable interface deficiencies and thus dielectric loss from dissimilar phases. In this study, single-phased ferrite ceramics with considerable magnetic and dielectric performances appearing simultaneously were fabricated by doping target ions in higher valence than that of Fe3+, such as Ti4+, Nb5+ and Zr4+, into BaFe12O19. In terms of charge balance, Fe3+/Fe2+ pair dipoles are produced through the substitution of Fe3+ by high-valenced ions. The electron hopping between Fe3+ and Fe2+ ions results in colossal permittivity. Whilst the single-phased ceramics doped by target ions exhibit low dielectric loss naturally due to the diminishment of interfacial polarization and still maintain typical magnetic properties. This study provides a convenient method to attain practicable materials with both outstanding magnetic and dielectric properties, which may be of interest to integration and multi-functionality of electronic devices. PMID:25835175

  10. Luminescent properties of Eu{sup 2+}-doped BaGdF{sub 5} glass ceramics a potential blue phosphor for ultra-violet light-emitting diode

    SciTech Connect

    Zhang, Weihuan; Zhang, Yuepin Ouyang, Shaoye; Zhang, Zhixiong; Wang, Qian; Xia, Haiping

    2015-01-14

    Eu{sup 2+} doped transparent oxyfluoride glass ceramics containing BaGdF{sub 5} nanocrystals were successfully fabricated by melt-quenching technique under a reductive atmosphere. The structure of the glass and glass ceramics were investigated by differential scanning calorimetry, X-ray diffraction (XRD), and transmission electron microscopy (TEM). The luminescent properties were investigated by transmission, excitation, and emission spectra. The decay time of the Gd{sup 3+} ions at 312 nm excited with 275 nm were also investigated. The results of XRD and TEM indicated the existence of BaGdF5 nanocrystals in the transparent glass ceramics. The excitation spectra of Eu{sup 2+} doped glass ceramics showed an excellent overlap with the main emission region of an ultraviolet light-emitting diode (UV-LED). Compared with the as-made glass, the emission of glass ceramics is much stronger by a factor of increasing energy transfer efficiency from Gd{sup 3+} to Eu{sup 2+} ions, the energy transfer efficiency from Gd{sup 3+} to Eu{sup 2+} ions was discussed. In addition, the chromaticity coordinates of glass and glass ceramics specimens were also discussed, which indicated that the Eu{sup 2+} doped BaGdF{sub 5} glass ceramics may be used as a potential blue-emitting phosphor for UV-LED.