WorldWideScience

Sample records for underpredicting o3 levels

  1. Increased phytotoxic O3 dose accelerates autumn senescence in an O3-sensitive beech forest even under the present-level O3.

    Science.gov (United States)

    Kitao, Mitsutoshi; Yasuda, Yukio; Kominami, Yuji; Yamanoi, Katsumi; Komatsu, Masabumi; Miyama, Takafumi; Mizoguchi, Yasuko; Kitaoka, Satoshi; Yazaki, Kenichi; Tobita, Hiroyuki; Yoshimura, Kenichi; Koike, Takayoshi; Izuta, Takeshi

    2016-09-07

    Ground-level ozone (O3) concentrations are expected to increase over the 21(st) century, especially in East Asia. However, the impact of O3 has not been directly assessed at the forest level in this region. We performed O3 flux-based risk assessments of carbon sequestration capacity in an old cool temperate deciduous forest, consisting of O3-sensitive Japanese beech (Fagus crenata), and in a warm temperate deciduous and evergreen forest dominated by O3-tolerant Konara oak (Quercus serrata) based on long-term CO2 flux observations. On the basis of a practical approach for a continuous estimation of canopy-level stomatal conductance (Gs), higher phytotoxic ozone dose above a threshold of 0 uptake (POD0) with higher Gs was observed in the beech forest than that in the oak forest. Light-saturated gross primary production, as a measure of carbon sequestration capacity of forest ecosystem, declined earlier in the late growth season with increasing POD0, suggesting an earlier autumn senescence, especially in the O3-sensitive beech forest, but not in the O3-tolerant oak forest.

  2. Conducting interface states at LaInO3/BaSnO3 polar interface controlled by Fermi level

    Science.gov (United States)

    Kim, Useong; Park, Chulkwon; Kim, Young Mo; Shin, Juyeon; Char, Kookrin

    2016-07-01

    We report on a new polar interface state between two band insulators: LaInO3 and BaSnO3, where the sheet conductance enhancement in the interface reaches more than the factor of 104 depending on the La doping concentration in BaSnO3 layer, by monitoring the conductance change before and after the polar interface formation as a function of La doping in BaSnO3. By eliminating the possibilities of oxygen vacancy involvement and cation diffusion, we show that the conductance enhancement is due to electronic reconstruction in the interface. Furthermore, we have found that the interfaces between BaSnO3 and the larger bandgap non-polar perovskites BaHfO3 and SrZrO3 did not show such a conductance enhancement. We discuss a model for the interface state where the Fermi level plays a critical role and the conductance enhancement is due to the existence of polarization in the polar perovskite, LaInO3.

  3. Crystal Field Levels of Pr3+ in PrFeO3 and PrGaO3 Determined by Inelastic Neutron Scattering

    DEFF Research Database (Denmark)

    Feldmann, K.; Henning, K.; Kaun, L.

    1975-01-01

    The crystal field splitting of the 3H4 ground state of the Pr ion in PrFeO3 and PrGaO3 has been investigated by inelastic scattering of thermal neutrons. At several temperatures the transitions have been measured by TAS and TOF methods for polycrystalline PrFeO3 and by the TOF method...... for polycrystalline PrGaO3. Energy level schemes which are different for these materials are given....

  4. Ground-level O3 pollution and its impacts on food crops in China: a review.

    Science.gov (United States)

    Feng, Zhaozhong; Hu, Enzhu; Wang, Xiaoke; Jiang, Lijun; Liu, Xuejun

    2015-04-01

    Ground-level ozone (O3) pollution has become one of the top environmental issues in China, especially in those economically vibrant and densely populated regions. In this paper, we reviewed studies on the O3 concentration observation and O3 effects on food crops throughout China. Data from 118 O3 monitoring sites reported in the literature show that the variability of O3 concentration is a function of geographic location. The impacts of O3 on food crops (wheat and rice) were studied at five sites, equipped with Open Top Chamber or O3-FACE (free-air O3 concentration enrichment) system. Based on exposure concentration and stomatal O3 flux-response relationships obtained from the O3-FACE experimental results in China, we found that throughout China current and future O3 levels induce wheat yield loss by 6.4-14.9% and 14.8-23.0% respectively. Some policies to reduce ozone pollution and impacts are suggested. Copyright © 2015 Elsevier Ltd. All rights reserved.

  5. Model study of the influence of cross-tropopause O3 transports on tropospheric O3 levels

    NARCIS (Netherlands)

    Roelofs, G.J.; Lelieveld, J.

    1997-01-01

    Cross-tropopause transport of O3 is a significant factor in the tropospheric budget and distribution of O3. Nevertheless, the distribution in the troposphere of O3 that originates from the stratosphere is uncertain. We study this with a chemistry - general circulation model with relatively high

  6. HIRDLS/Aura Level 3 Ozone (O3) Zonal Fourier Coefficients V007

    Data.gov (United States)

    National Aeronautics and Space Administration — The "HIRDLS/Aura Level 3 Ozone (O3) Zonal Fourier Coefficients" version 7 data product (H3ZFCO3) contains the entire mission (~3 years) of HIRDLS data expressed as...

  7. Elevated ground-level O3 negatively influences paddy methanogenic archaeal community

    Science.gov (United States)

    Feng, Youzhi; Lin, Xiangui; Yu, Yongchang; Zhang, Huayong; Chu, Haiyan; Zhu, Jianguo

    2013-01-01

    The current knowledge regarding the effect of global climate change on rice-paddy methane (CH4) emissions is incomplete, partly because information is limited concerning the mechanism of the microbial response to elevated ground-level ozone (O3). A field experiment was conducted in the China Ozone Free-Air Concentration Enrichment facility in a rice–wheat rotation system to investigate the responses of methanogenic archaeal communities to elevated ground-level O3 by culture-independent and -reliant approaches. We found that elevated ground-level O3 inhibited methanogenic activity and influenced the composition of paddy methanogenic communities, reducing the abundance and diversity of paddy methanogens by adversely affecting dominant groups, such as aceticlastic Methanosaeta, especially at the rice tillering stage. Our results indicated that continuously elevated ground-level O3 would negatively influence paddy methanogenic archaeal communities and its critical ecological function. These findings will contribute to a comprehensive understanding of the responses and feedbacks of paddy ecosystems to global climate change. PMID:24217205

  8. Warming Experiments Underpredict Plant Phenological Responses to Climate Change

    Science.gov (United States)

    Wolkovich, E. M.; Cook, B. I.; Allen, J. M.; Crimmins, T. M.; Betancourt, J. L.; Travers, S. E.; Pau, S.; Regetz, J.; Davies, T. J.; Kraft, N. J. B.; hide

    2012-01-01

    Warming experiments are increasingly relied on to estimate plant responses to global climate change. For experiments to provide meaningful predictions of future responses, they should reflect the empirical record of responses to temperature variability and recent warming, including advances in the timing of flowering and leafing. We compared phenology (the timing of recurring life history events) in observational studies and warming experiments spanning four continents and 1,634 plant species using a common measure of temperature sensitivity (change in days per degree Celsius). We show that warming experiments underpredict advances in the timing of flowering and leafing by 8.5-fold and 4.0-fold, respectively, compared with long-term observations. For species that were common to both study types, the experimental results did not match the observational data in sign or magnitude. The observational data also showed that species that flower earliest in the spring have the highest temperature sensitivities, but this trend was not reflected in the experimental data. These significant mismatches seem to be unrelated to the study length or to the degree of manipulated warming in experiments. The discrepancy between experiments and observations, however, could arise from complex interactions among multiple drivers in the observational data, or it could arise from remediable artefacts in the experiments that result in lower irradiance and drier soils, thus dampening the phenological responses to manipulated warming. Our results introduce uncertainty into ecosystem models that are informed solely by experiments and suggest that responses to climate change that are predicted using such models should be re-evaluated.

  9. Divergent responses of methanogenic archaeal communities in two rice cultivars to elevated ground-level O3.

    Science.gov (United States)

    Zhang, Jianwei; Tang, Haoye; Zhu, Jianguo; Lin, Xiangui; Feng, Youzhi

    2016-06-01

    Inhibitive effect of elevated ground-level ozone (O3) on paddy methane (CH4) emission varies with rice cultivars. However, little information is available on its microbial mechanism. For this purpose, the responses of methane-metabolizing microorganisms, methanogenic archaea and methanotrophic bacteria to O3 pollution were investigated in the O3-tolerant (YD6) and the O3-sensitive (IIY084) cultivars at two rice growth stages in Free Air Concentration Elevation of O3 (O3-FACE) system of China. It was found that O3 pollution didn't change the abundances of Type I and Type II methanotrophic bacteria at two rice stages. For methanogenic archaea, their abundances in both cultivars were decreased by O3 pollution at the tillering stage. Furthermore, a greater negative influence on methanogenic archaeal community was observed on IIY084 than on YD6: at tillering stage, the alpha diversity indices of methanogenic archaeal community in IIY084 was decreased to a greater extent than in YD6; IIY084 shifted methanogenic archaeal community composition and decreased the abundances and the diversities of Methanosarcinaceae and Methanosaetaceae as well as the abundance of Methanomicrobiales, while the diversity of Methanocellaceae were increased in YD6. These findings indicate that the variations in the responses of paddy CH4 emission to O3 pollution between cultivars could result from the divergent responses of their methanogenic archaea. Copyright © 2016 Elsevier Ltd. All rights reserved.

  10. Spatial distribution of ground-level urban background O3 concentrations in the Metropolitan Area of Buenos Aires, Argentina

    International Nuclear Information System (INIS)

    Pineda Rojas, Andrea L.; Venegas, Laura E.

    2013-01-01

    In this work, a recently developed urban-scale atmospheric dispersion model (DAUMOD-GRS) is applied to evaluate the ground-level ozone (O 3 ) concentrations resulting from anthropogenic area sources of NO x and VOC in the Metropolitan Area of Buenos Aires (MABA). The statistical comparison of model results with observations (including new available data from seventeen sites) shows a good model performance. Estimated summer highest diurnal O 3 1-h concentrations in the MABA vary between 15 ppb in the most urbanised area and 53 ppb in the suburbs. All values are below the air quality standard. Several runs are performed to evaluate the impact of possible future emission reductions on O 3 concentrations. Under all hypothetical scenarios, the maximum diurnal O 3 1-h concentration obtained for the area is slightly reduced (up to 4%). However, maximum diurnal O 3 concentrations could increase at some less urbanised areas of MABA depending on the relative reductions of the emissions of NO x and VOC. -- Highlights: ► A recently developed air quality model reproduces well observed O 3 levels in MABA. ► Modelled summer maximum diurnal O 3 concentrations vary in the area between 15 and 53 ppb. ► All hourly values are below the air quality standard (120 ppb). ► Possible future emission reductions would have small impact on the highest level. -- The distribution of summer maximum diurnal ground-level O 3 concentrations in the Metropolitan Area of Buenos Aires is evaluated applying a recently developed simple urban air quality model

  11. Investigating the response of tropical maize (Zea mays L.) cultivars against elevated levels of O3 at two developmental stages.

    Science.gov (United States)

    Singh, Aditya Abha; Agrawal, S B; Shahi, J P; Agrawal, Madhoolika

    2014-10-01

    Tropospheric ozone (O3) concentrations are rising in Indo-Gangetic plains of India, causing potential threat to agricultural productivity. Maize (Zea mays L.) is the third most important staple crop at global level after rice and wheat. Two high yielding cultivars of Indian maize (HQPM1-quality protein maize and DHM117-normal/non quality protein maize) were exposed to two levels of elevated O3 above the ambient level (NFC) viz. NFC + 15 ppb O3 (NFC + 15) and NFC + 30 ppb O3 (NFC + 30) using open top chambers under field conditions. The study was conducted to evaluate the biochemical responses of two cultivars at different developmental stages leading to change in yield responses. Initially at lower O3 dose, photosynthetic pigments showed an increase but reduction at later stage, while higher dose caused a decline at both the stages of sampling. Levels of superoxide radical (O2 (-)) and hydrogen peroxide (H2O2) significantly increased and contributed to lipid peroxidation at elevated O3. Histochemical localization assay of O2 (-) and H2O2 showed that guard cells of stomata and cells around trichomes took deeper stain at elevated O3 reflecting more formation of reactive oxygen species. Secondary metabolites like total phenol, flavonoids and anthocyanin pigments also increased in plants under O3 stress. Enzymatic antioxidants were triggered in both the cultivars due to elevated O3, while induction of non-enzymatic antioxidants was more in HQPM1. Native PAGE analysis also showed that SOD, POX, CAT, APX and GPX were stimulated at elevated O3 concentrations compared to NFC. SDS-PAGE showed reductions of major photosynthetic proteins with higher decrease in DHM117. Principal Component Analysis showed that both the cultivars showed differential response against O3 at two developmental stages. HQPM1 maintained the analogous defense strategy at both the sampling stages while DHM117 showed variable response. Overall metabolic induction of antioxidants related to defense was

  12. MLS/Aura Level 2 Ozone (O3) Mixing Ratio V004

    Data.gov (United States)

    National Aeronautics and Space Administration — ML2O3 is the EOS Aura Microwave Limb Sounder (MLS) standard product for ozone derived from radiances measured by the 240 GHz radiometer. The current version is 4.2....

  13. Ferroelectric and electrical characterization of multiferroic BiFeO3 at the single nanoparticle level

    Science.gov (United States)

    Vasudevan, R. K.; Bogle, K. A.; Kumar, A.; Jesse, S.; Magaraggia, R.; Stamps, R.; Ogale, S. B.; Potdar, H. S.; Nagarajan, V.

    2011-12-01

    Ferroelectric BiFeO3 (BFO) nanoparticles deposited on epitaxial substrates of SrRuO3 (SRO) and La1-xSrxMnO3 (LSMO) were studied using band excitation piezoresponse spectroscopy (BEPS), piezoresponse force microscopy (PFM), and ferromagnetic resonance (FMR). BEPS confirms that the nanoparticles are ferroelectric in nature. Switching behavior of nanoparticle clusters were studied and showed evidence for inhomogeneous switching. The dimensionality of domains within nanoparticles was found to be fractal in nature, with a dimensionality constant of ˜1.4, on par with ferroelectric BFO thin-films under 100 nm in thickness. Ferromagnetic resonance studies indicate BFO nanoparticles only weakly affect the magnetic response of LSMO.

  14. Ferroelectric and electrical characterization of multiferroic BiFeO3 at the single nanoparticle level

    Energy Technology Data Exchange (ETDEWEB)

    Vasudevan, Rama K [ORNL; Bogle, K A [University of New South Wales, Sydney, Australia; Kumar, Amit [ORNL; Jesse, Stephen [ORNL; Magaraggia, R [University of Glasgow; Stamps, R [University of Glasgow; Ogale, S [National Chemical Laboratory, India; Potdar, H S [National Chemical Laboratory, India

    2011-01-01

    Ferroelectric BiFeO3 (BFO) nanoparticles deposited on epitaxial substrates of SrRuO3 (SRO) and La1xSrxMnO3 (LSMO) were studied using band excitation piezoresponse spectroscopy (BEPS), piezoresponse force microscopy (PFM), and ferromagnetic resonance (FMR). BEPS confirms that the nanoparticles are ferroelectric in nature. Switching behavior of nanoparticle clusters were studied and showed evidence for inhomogeneous switching. The dimensionality of domains within nanoparticles was found to be fractal in nature, with a dimensionality constant of 1.4, on par with ferroelectric BFO thin-films under 100 nm in thickness. Ferromagnetic resonance studies indicate BFO nanoparticles only weakly affect the magnetic response of LSMO.

  15. O(3P) + C2H4 Potential Energy Surface: Study at the Multireference Level

    Czech Academy of Sciences Publication Activity Database

    West, A. C.; Kretchmer, J. S.; Sellner, B.; Park, K.; Hase, W. L.; Lischka, Hans; Windus, T. L.

    2009-01-01

    Roč. 113, č. 45 (2009), s. 12663-12674 ISSN 1089-5639 Institutional research plan: CEZ:AV0Z40550506 Keywords : hydrogen combustion * multireference methods * O(3P)+C2H4 reaction Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.899, year: 2009

  16. Why variation of ground-level O3 differed during air quality control for APEC and Parade

    Science.gov (United States)

    Xu, R.; Shao, M.; Li, X.

    2017-12-01

    Ozone (O3) is an important photochemical product, which represents the atmospheric oxidants capacity. The increasing ground-level O3 in Beijing attracts people's attention and became an urgent thing to manage in recent years. In the autumn of 2014 and summer of 2015, Asia-Pacific Economic Cooperation (APEC) China 2014 and the 2015 China Victory Day parade (Parade) were held in Beijing. Thus, spell of emission restrictions was conducted for improving the air quality for the two great events, respectively. Previous studies indicated that significant reduction in the emissions of primary anthropogenic pollutants had been achieved, and the monthly averaged concentration of CO, SO2, NOx (NO + NO2) and NMHCs were decreased by 30%-60% for both events. In contrast to the obvious reduction in primary pollutants, O3 increased by 42% in APEC but decreased by 33% in Parade, which was surprising as the control measures are almost the same during the two events. The regional transport from the surrounding areas contributed lot in APEC, and the non-linearity relationship of O3 and its precursors may be another reason. A zero-dimensional box model based on the compact Regional Atmospheric Chemical Mechanism version 2 (RACM 2) was applied to chase down the internal factor to determine the O3 variation. The EKMA plot showed that / was the important role to effect photochemical regime as well as ozone production efficiency. Except that, the influence of NO-O3 titration effect and low photolysis frequencies in autumn also contributed to that. As high / does help O3 control and NOx continues to fall down due to the government policy, reactivity-based regulations for VOC controls are more cost-effective. With source profile and annual PMF analysis of source apportionment by related studies, we suggest solvent use should be focus on involving VOC control.

  17. Spatial distribution of ground-level urban background O3 concentrations in the Metropolitan Area of Buenos Aires, Argentina.

    Science.gov (United States)

    Pineda Rojas, Andrea L; Venegas, Laura E

    2013-12-01

    In this work, a recently developed urban-scale atmospheric dispersion model (DAUMOD-GRS) is applied to evaluate the ground-level ozone (O3) concentrations resulting from anthropogenic area sources of NOx and VOC in the Metropolitan Area of Buenos Aires (MABA). The statistical comparison of model results with observations (including new available data from seventeen sites) shows a good model performance. Estimated summer highest diurnal O3 1-h concentrations in the MABA vary between 15 ppb in the most urbanised area and 53 ppb in the suburbs. All values are below the air quality standard. Several runs are performed to evaluate the impact of possible future emission reductions on O3 concentrations. Under all hypothetical scenarios, the maximum diurnal O3 1-h concentration obtained for the area is slightly reduced (up to 4%). However, maximum diurnal O3 concentrations could increase at some less urbanised areas of MABA depending on the relative reductions of the emissions of NOx and VOC. Copyright © 2012 Elsevier Ltd. All rights reserved.

  18. Temporal multiscaling characteristics of particulate matter PM 10 and ground-level ozone O3 concentrations in Caribbean region

    Science.gov (United States)

    Plocoste, Thomas; Calif, Rudy; Jacoby-Koaly, Sandra

    2017-11-01

    A good knowledge of the intermittency of atmospheric pollutants is crucial for air pollution management. We consider here particulate matter PM 10 and ground-level ozone O3 time series in Guadeloupe archipelago which experiments a tropical and humid climate in the Caribbean zone. The aim of this paper is to study their scaling statistics in the framework of fully developed turbulence and Kolmogorov's theory. Firstly, we estimate their Fourier power spectra and consider their scaling properties in the physical space. The power spectra computed follows a power law behavior for both considered pollutants. Thereafter we study the scaling behavior of PM 10 and O3 time series. Contrary to numerous studies where the multifractal detrended fluctuation analysis is frequently applied, here, the classical structure function analysis is used to extract the scaling exponent or multifractal spectrum ζ(q) ; this function provides a full characterization of a process at all intensities and all scales. The obtained results show that PM 10 and O3 possess intermittent and multifractal properties. The singularity spectrum MS(α) also confirms both pollutants multifractal features. The originality of this work comes from a statistical modeling performed on ζ(q) and MS(α) by a lognormal model to compute the intermittency parameter μ. By contrast with PM 10 which mainly depends on puffs of Saharan dust (synoptic-scale), O3 is more intermittent due to variability of its local precursors. The results presented in this paper can help to better understand the mechanisms governing the dynamics of PM 10 and O3 in Caribbean islands context.

  19. Role of atomic-level defects and electronic energy loss on amorphization in LiNbO3 single crystals

    Science.gov (United States)

    Sellami, N.; Crespillo, M. L.; Xue, H.; Zhang, Y.; Weber, W. J.

    2017-08-01

    Understanding complex non-equilibrium defect processes, where multiple irradiation mechanisms may take place simultaneously, is a long standing subject in material science. The separate and combined effects of elastic and inelastic energy loss are a very complicated and challenging topic. In this work, LiNbO3 has been irradiated with 0.9 MeV Si+ and 8 MeV O3+, which are representative of regimes where nuclear (S n) and electronic (S e) energy loss are dominant, respectively. The evolution of damage has been investigated by Rutherford backscattering spectrometry (RBS) in channeling configuration. Pristine samples were irradiated with 0.9 MeV Si+ ions to create different pre-existing damage states. Below the threshold (S e,th  =  5-6 keV nm-1) for amorphous track formation in this material, irradiation of the pristine samples with a highly ionizing beam of 8 MeV O3+ ions, with nearly constant S e of about 3 keV nm-1, induces a crystalline to amorphous phase transition at high ion fluences. In the pre-damaged samples, the electronic energy loss from the 8 MeV O3+ ions interacts synergistically with the pre-existing damage, resulting in a rapid, non-linear increase in damage production. There is a significant reduction in the incubation fluence for rapid amorphization with the increasing amount of pre-existing damage. These results highlight the important role of atomic-level defects on increasing the sensitivity of some oxides to amorphization induced by electronic energy loss. Controlling the nature and amount of pre-damage may provide a new approach to tuning optical properties for photonic device applications.

  20. Electronic Charges and Electric Potential at LaAlO3/SrTiO3 Interfaces Studied by Core-Level Photoemission Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, Harold

    2011-08-19

    We studied LaAlO{sub 3}/SrTiO{sub 3} interfaces for varying LaAlO{sub 3} thickness by core-level photoemission spectroscopy. In Ti 2p spectra for conducting 'n-type' interfaces, Ti{sup 3+} signals appeared, which were absent for insulating 'p-type' interfaces. The Ti{sup 3+} signals increased with LaAlO{sub 3} thickness, but started well below the critical thickness of 4 unit cells for metallic transport. Core-level shifts with LaAlO{sub 3} thickness were much smaller than predicted by the polar catastrophe model. We attribute these observations to surface defects/adsorbates providing charges to the interface even below the critical thickness.

  1. HIRDLS/Aura Level 3 Ozone (O3) 1deg Lat Zonal Fourier Coefficients V007 (H3ZFCO3) at GES DISC

    Data.gov (United States)

    National Aeronautics and Space Administration — The "HIRDLS/Aura Level 3 Ozone (O3) Zonal Fourier Coefficients" version 7 data product (H3ZFCO3) contains the entire mission (~3 years) of HIRDLS data expressed as...

  2. Lidar observations revealing transport of O3 in the presence of a nocturnal low-level jet: Regional implications for ;next-day; pollution

    Science.gov (United States)

    Sullivan, John T.; Rabenhorst, Scott D.; Dreessen, Joel; McGee, Thomas J.; Delgado, Ruben; Twigg, Laurence; Sumnicht, Grant

    2017-06-01

    Remotely sensed profiles of ozone (O3) and wind are presented continuously for the first time during a nocturnal low-level jet (NLLJ) event occurring after a severe O3 episode in the Baltimore-Washington D.C. (BW) urban corridor throughout 11-12 June 2015. High-resolution O3 lidar observations indicate a well-mixed and polluted daytime O3 reservoir, which decayed into a contaminated nocturnal residual layer (RL) with concentrations between 70 and 100 ppbv near 1 km above the surface. Observations indicate the onset of the NLLJ was responsible for transporting polluted O3 away from the region, while simultaneously affecting the height and location of the nocturnal residual layer. High-resolution modeling analyses and next-day (12 June) lidar, surface, and balloon-borne observations indicate the trajectory of the NLLJ and polluted residual layer corresponds with "next-day" high O3 at sites throughout the southern New England region (New York, Connecticut, Massachusetts). The novel O3 lidar observations are evidence of both nocturnal advection (via high NLLJ wind fields) and entrainment of the polluted residual layer in the presence of the "next-day" convectively growing boundary layer. In the greater context, the novel observational suite described in this work has shown that the chemical budget in areas downwind of major urban centers can be altered significantly overnight during transport events such as the NLLJ.

  3. A Cause and A Solution for the Underprediction of Extreme Wave Events in the Northeast Pacific

    Science.gov (United States)

    Ellenson, A. N.; Ozkan-Haller, H. T.; Thomson, J.; Brown, A. C.; Haller, M. C.

    2016-12-01

    Along the coastlines of Washington and Oregon, at least one 10 m wave height event occurs every year, and the strongest storms produce wave heights of 14-15 m. Extremely high wave heights can cause severe damage to coastal infrastructure and pose hazards to stakeholders along the coast. A system which can accurately predict such sea states is important for quantifying risk and aiding in preparation for extreme wave events. This study explores how to optimize forecast model performance for extreme wave events by utilizing different physics packages or wind input in four model configurations. The different wind input products consist of a reanalyzed Global Forecasting System (GFS) wind input and a Climate Forecast System Reanalysis (CFSR) from the National Center of Environmental Prediction (NCEP). The physics packages are the Tolman-Chalikov (1996) ST2 physics package and the Ardhuin et al (2009) ST4 physics package associated with version 4.18 of WaveWatch III. A hindcast was previously performed to assess the wave character along the Pacific Northwest Coastline for wave energy applications. Inspection of hindcast model results showed that the operational model, which consisted of ST2 physics and GFS wind, underpredicted events where wave height exceeded six meters.The under-prediction is most severe for cases with the combined conditions of a distant cyclone and a strong coastal jet. Three such cases were re-analyzed with the four model configurations. Model output is compared with observations at NDBC buoy 46050, offshore of Newport, OR. The model configuration consisting of ST4 physics package and CFSR wind input performs best as compared with the original model, reducing significant wave height underprediction from 1.25 m to approximately 0.67 m and mean wave direction error from 30 degrees to 17 degrees for wave heights greater than 6 m. Spectral analysis shows that the ST4-CFSR model configuration best resolves southerly wave energy, and all model

  4. Composite Sr- and V-doped LaCrO3/YSZ sensor electrode operating at low oxygen levels

    DEFF Research Database (Denmark)

    Lund, Anders; Jacobsen, Torben; Hansen, Karin Vels

    2012-01-01

    A porous composite electrode of La0.8Sr0.2Cr0.97V0.03O3 -delta (LSCV) and yttria-stabilised zirconia (YSZ) was evaluated as a possible candidate for high-temperature potentiometric oxygen sensor measuring electrodes. The oxygen processes at the electrode were characterised by performing electroch....... The relatively low response time at 700º C at an oxygen partial pressure of around 5x10-6 bar and an inlet gas flow rate of 8 L h-1 makes the LSCV/YSZ electrode suitable for use as an potentiometric oxygen sensor electrodes.......A porous composite electrode of La0.8Sr0.2Cr0.97V0.03O3 -delta (LSCV) and yttria-stabilised zirconia (YSZ) was evaluated as a possible candidate for high-temperature potentiometric oxygen sensor measuring electrodes. The oxygen processes at the electrode were characterised by performing...... and 400 nm. At oxygen partial pressures around 0.2 bar at 700º C, the oxygen reaction is dominated by solid-state diffusion of oxide ions and surface reaction kinetics. At oxygen partial pressures around 10-5 bar above 800º C, gas phase mass transport processes dominate the impedance spectra...

  5. Warfarin Dosing Algorithms Underpredict Dose Requirements in Patients Requiring ≥7 mg Daily: A Systematic Review and Meta-analysis.

    Science.gov (United States)

    Saffian, S M; Duffull, S B; Wright, Dfb

    2017-08-01

    There is preliminary evidence to suggest that some published warfarin dosing algorithms produce biased maintenance dose predictions in patients who require higher than average doses. We conducted a meta-analysis of warfarin dosing algorithms to determine if there exists a systematic under- or overprediction of dose requirements for patients requiring ≥7 mg/day across published algorithms. Medline and Embase databases were searched up to September 2015. We quantified the proportion of over- and underpredicted doses in patients whose observed maintenance dose was ≥7 mg/day. The meta-analysis included 47 evaluations of 22 different warfarin dosing algorithms from 16 studies. The meta-analysis included data from 1,492 patients who required warfarin doses of ≥7 mg/day. All 22 algorithms were found to underpredict warfarin dosing requirements in patients who required ≥7 mg/day by an average of 2.3 mg/day with a pooled estimate of underpredicted doses of 92.3% (95% confidence interval 90.3-94.1, I 2 = 24%). © 2017 American Society for Clinical Pharmacology and Therapeutics.

  6. Effects of Fuel to Synthesis of CaTiO3 by Solution Combustion Synthesis for High-Level Nuclear Waste Ceramics.

    Science.gov (United States)

    Jung, Choong-Hwan; Kim, Yeon-Ku; Han, Young-Min; Lee, Sang-Jin

    2016-02-01

    A solution combustion process for the synthesis of perovskite (CaTiO3) powders is described. Perovskite is one of the crystalline host matrics for the disposal of high-level radioactive wastes (HLW) because it immobilizes Sr and Lns elements by forming solid solutions. Solution combustion synthesis, which is a self-sustaining oxi-reduction reaction between nitrate and organic fuel, the exothermic reaction, and the heat evolved convert the precursors into their corresponding oxide products above 1100 degrees C in air. To investigate the effects of amino acid on the combustion reaction, various types of fuels were used; a glycine, amine and carboxylic ligand mixture. Sr, La and Gd-nitrate with equivalent amounts of up to 20% of CaTiO3 were mixed with Ca and Ti nitrate and amino acid. X-ray diffraction analysis, SEM and TEM were conducted to confirm the formed phases and morphologies. While powders with an uncontrolled shape are obtained through a general oxide-route process, Ca(Sr, Lns)TiO3 powders with micro-sized soft agglomerates consisting of nano-sized primary particles can be prepared using this method.

  7. Electronic structure origin of conductivity and oxygen reduction activity changes in low-level Cr-substituted (La,Sr)MnO3

    Science.gov (United States)

    Tsekouras, George; Boudoire, Florent; Pal, Banabir; Vondráček, Martin; Prince, Kevin C.; Sarma, D. D.; Braun, Artur

    2015-09-01

    The electronic structure of the (La0.8Sr0.2)0.98Mn1-xCrxO3 model series (x = 0, 0.05, or 0.1) was measured using soft X-ray synchrotron radiation at room and elevated temperature. O K-edge near-edge X-ray absorption fine structure (NEXAFS) spectra showed that low-level chromium substitution of (La,Sr)MnO3 resulted in lowered hybridisation between O 2p orbitals and M 3d and M 4sp valance orbitals. Mn L3-edge resonant photoemission spectroscopy measurements indicated lowered Mn 3d-O 2p hybridisation with chromium substitution. Deconvolution of O K-edge NEXAFS spectra took into account the effects of exchange and crystal field splitting and included a novel approach whereby the pre-peak region was described using the nominally filled t2g↑ state. 10% chromium substitution resulted in a 0.17 eV lowering in the energy of the t2g↑ state, which appears to provide an explanation for the 0.15 eV rise in activation energy for the oxygen reduction reaction, while decreased overlap between hybrid O 2p-Mn 3d states was in qualitative agreement with lowered electronic conductivity. An orbital-level understanding of the thermodynamically predicted solid oxide fuel cell cathode poisoning mechanism involving low-level chromium substitution on the B-site of (La,Sr)MnO3 is presented.

  8. O3 Nanoparticles

    KAUST Repository

    Wang, Juan

    2016-11-16

    Ti2O3 nanoparticles with high performance of photothermal conversion are demonstrated for the first time. Benefiting from the nanosize and narrow-bandgap features, the Ti2O3 nanoparticles possess strong light absorption and nearly 100% internal solar–thermal conversion efficiency. Furthermore, Ti2O3 nanoparticle-based thin film shows potential use in seawater desalination and purification.

  9. Impact of external industrial sources on the regional and local SO2 and O3 levels of the Mexico megacity

    Science.gov (United States)

    Almanza, V. H.; Molina, L. T.; Li, G.; Fast, J.; Sosa, G.

    2014-08-01

    The air quality of megacities can be influenced by external emission sources on both global and regional scales. At the same time their outflow emissions can exert an impact to the surrounding environment. The present study evaluates an SO2 peak observed on 24 March 2006 at the suburban supersite T1 and at ambient air quality monitoring stations located in the northern region of the Mexico City Metropolitan Area (MCMA) during the Megacity Initiative: Local and Global Research Observations (MILAGRO) field campaign. We found that this peak could be related to an important episodic emission event coming from Tizayuca region, northeast of the MCMA. Back-trajectory analyses suggest that the emission event started in the early morning at 04:00 LST and lasted for about 9 h. The estimated emission rate is about 2 kg s-1. To the best of our knowledge, sulfur dioxide emissions from the Tizayuca region have not been considered in previous studies. This finding suggests the possibility of "overlooked" emission sources in this region that could influence the air quality of the MCMA. This further motivated us to study the cement plants, including those in the state of Hidalgo and in the State of Mexico. It was found that they can contribute to the SO2 levels in the northeast (NE) region of the basin (about 42%), at the suburban supersite T1 (41%) and that at some monitoring stations their contribution can be even higher than the contribution from the Tula Industrial Complex (TIC). The contribution of the Tula Industrial Complex to regional ozone levels is estimated. The model suggests low contribution to the MCMA (1 to 4 ppb) and slightly higher contribution at the suburban T1 (6 ppb) and rural T2 (5 ppb) supersites. However, the contribution could be as high as 10 ppb in the upper northwest region of the basin and in the southwest and south-southeast regions of the state of Hidalgo. In addition, the results indicated that the ozone plume could also be transported to northwest

  10. Study on the Multi-level Resistance-Switching Memory and Memory-State-Dependent Photovoltage in Pt/Nd:SrTiO3 Junctions

    Science.gov (United States)

    Wang, Shengkai; Sun, Xianwen; Li, Guanghui; Jia, Caihong; Li, Guoqiang; Zhang, Weifeng

    2018-01-01

    Pt/Nd:SrTiO3 (STO)/In devices were fabricated by depositing Schottky-contact Pt and Ohmic-contact In electrodes on a single crystal STO with Nd doping. The Pt/Nd:STO/In devices show multi-level resistance-switching (RS) memory and memory-state-dependent photovoltage (PV) effects, which can be controlled by the applied pulse width or magnitude. Both the RS and PV are related to the bias-induced modulation of the interface barrier, both in height and width, at the Pt/Nd:STO interface. The results establish a strong connection between the RS/PV effects and the modulation of the Nd:STO interface triggered by applied electric field and provide a new route by using an open-circuit voltage for non-destructively sensing multiple non-volatile memory states.

  11. Observed trends in ground-level O3 in Monterrey, Mexico, during 1993-2014: comparison with Mexico City and Guadalajara

    Science.gov (United States)

    Hernández Paniagua, Iván Y.; Clemitshaw, Kevin C.; Mendoza, Alberto

    2017-07-01

    Here, we present an assessment of long-term trends in O3 and odd oxygen (O3 + NO2) at the industrial Monterrey metropolitan area (MMA) in NE Mexico. Diurnal amplitudes in Ox (AVd) are used as a proxy for net O3 production, which is influenced by the NO2 photolysis rate. No significant differences in the AVd are observed between weekends and weekdays, although the largest AVd values are observed at sites downwind of industrial areas. The highest O3 mixing ratios are observed in spring, with minimum values in winter. The largest annual variations in O3 are typically observed downwind of the MMA, with the lowest variations generally recorded in highly populated areas and close to industrial areas. A wind sector analysis of mixing ratios of O3 precursors revealed that the dominant sources of emissions are located in the industrial regions within the MMA and surrounding area. Significant increasing trends in O3 in spring, summer, and autumn are observed depending on site location, with trends in annual averages ranging between 0.19 and 0.33 ppb yr-1. Overall, from 1993 to 2014, within the MMA, O3 has increased at an average rate of 0.22 ppb yr-1 (p Mexico City metropolitan area (MCMA) for the same period. No clear trend is observed from 1996 to 2014 within the Guadalajara metropolitan area (GMA).

  12. O3 stars

    International Nuclear Information System (INIS)

    Walborn, N.R.

    1982-01-01

    A brief review of the 10 known objects in this earliest spectral class is presented. Two new members are included: HD 64568 in NGC 2467 (Puppis OB2), which provides the first example of an O3 V((f*)) spectrum; and Sk -67 0 22 in the Large Magellanic Cloud, which is intermediate between types O3 If* and WN6-A. In addition, the spectrum of HDE 269810 in the LMC is reclassified as the first of type O3 III (f*). The absolute visual magnitudes of these stars are rediscussed

  13. Topological crystalline insulator PbxSn1-xTe thin films on SrTiO3 (001 with tunable Fermi levels

    Directory of Open Access Journals (Sweden)

    Hua Guo

    2014-05-01

    Full Text Available In this letter, we report a systematic study of topological crystalline insulator PbxSn1-xTe (0 < x < 1 thin films grown by molecular beam epitaxy on SrTiO3(001. Two domains of PbxSn1-xTe thin films with intersecting angle of α ≈ 45° were confirmed by reflection high energy diffraction, scanning tunneling microscopy, and angle-resolved photoemission spectroscopy (ARPES. ARPES study of PbxSn1-xTe thin films demonstrated that the Fermi level of PbTe could be tuned by altering the temperature of substrate whereas SnTe cannot. An M-shaped valance band structure was observed only in SnTe but PbTe is in a topological trivial state with a large gap. In addition, co-evaporation of SnTe and PbTe results in an equivalent variation of Pb concentration as well as the Fermi level of PbxSn1-xTe thin films.

  14. Observed trends in ground-level O3 in Monterrey, Mexico, during 1993–2014: comparison with Mexico City and Guadalajara

    Directory of Open Access Journals (Sweden)

    I. Y. Hernández Paniagua

    2017-07-01

    Full Text Available Here, we present an assessment of long-term trends in O3 and odd oxygen (O3 + NO2 at the industrial Monterrey metropolitan area (MMA in NE Mexico. Diurnal amplitudes in Ox (AVd are used as a proxy for net O3 production, which is influenced by the NO2 photolysis rate. No significant differences in the AVd are observed between weekends and weekdays, although the largest AVd values are observed at sites downwind of industrial areas. The highest O3 mixing ratios are observed in spring, with minimum values in winter. The largest annual variations in O3 are typically observed downwind of the MMA, with the lowest variations generally recorded in highly populated areas and close to industrial areas. A wind sector analysis of mixing ratios of O3 precursors revealed that the dominant sources of emissions are located in the industrial regions within the MMA and surrounding area. Significant increasing trends in O3 in spring, summer, and autumn are observed depending on site location, with trends in annual averages ranging between 0.19 and 0.33 ppb yr−1. Overall, from 1993 to 2014, within the MMA, O3 has increased at an average rate of 0.22 ppb yr−1 (p < 0. 01, which is in marked contrast with the decline of 1.15 ppb yr−1 (p < 0. 001 observed in the Mexico City metropolitan area (MCMA for the same period. No clear trend is observed from 1996 to 2014 within the Guadalajara metropolitan area (GMA.

  15. Different defect levels configurations between double layers of nanorods and film in ZnO grown on c-Al2O3 by MOCVD

    International Nuclear Information System (INIS)

    Wu, Bin; Zhang, Yuantao; Shi, Zhifeng; Li, Xiang; Cui, Xijun; Zhuang, Shiwei; Zhang, Baolin; Du, Guotong

    2014-01-01

    Epitaxial ZnO structures with inherent two layers of nanorods layer on film layer were fabricated on c-Al 2 O 3 by metal-organic chemical vapor deposition (MOCVD) and studied by photoluminescence. Specially, photoluminescence spectra for the film layer were obtained by rendering the excitation from the substrate side. Different defect levels configurations between nanorods and film were revealed. Zinc vacancies tend to form in top nanorods layer, whereas abundant zinc–oxygen divacancies accumulate in bottom film layer. An acceptor state with activation energy of ∼200 meV is exclusive to the film layer. The stacking fault related acceptor and Al introduced donor are present in both layers. Besides, two other defect related donors contained in the nanorods layer perhaps also exist within the film layer. - Highlights: • Inherent double layer ZnO of nanorods on film layer were studied by PL. • V Zn tend to form in the nanorods layer, and V ZnO accumulate in the film layer. • An acceptor with activation energy of ∼200 meV is exclusive to the film layer. • Pure NBE emission without DLE in RT PL spectrum does not mean good crystallinity

  16. Low-level detection of a bacillus anthracis simulant using Love-wave biosensors on 36 degrees YX LiTaO3.

    Science.gov (United States)

    Branch, Darren W; Brozik, Susan M

    2004-03-15

    We present an acoustic Love-wave biosensor for detection of the Bacillus anthracis simulant, Bacillus thuringiensis at or below inhalational infectious levels. The present work is an experimental study of 36 degrees YX cut LiTaO3 based Love-wave devices for detection of pathogenic spores in aqueous conditions. Given that the detection limit (D1) of Love-wave-based sensors is a strong function of the overlying waveguide, two waveguide materials have been investigated, which are polyimide and polystyrene. To determine the mass sensitivity of Love-wave sensor, bovine serum albumin (BSA) protein was injected into the Love-wave test cell while recording the magnitude and phase shift across each sensor. Polyimide had the lowest mass detection limit with an estimated value of 1.0-2.0 ng/cm2, as compared to polystyrene where D1 = 2.0 ng/cm2. Suitable chemistries were used to orient antibodies on the Love-wave sensor using protein G. The thickness of each biofilm was measured using ellipsometry from which the surface concentrations were calculated. The monoclonal antibody BD8 with a high degree of selectivity for anthrax spores was used to capture the non-pathogenic simulant B. thuringiensis B8 spores. Bacillus subtilis spores were used as a negative control to determine whether significant non-specific binding would occur. Spore aliquots were prepared using an optical counting method, which permitted removal of background particles for consistent sample preparation. This work demonstrates that Love-wave biosensors are promising for low-level detection for whole-cell biological pathogens.

  17. O3 perovskite ceramic

    Indian Academy of Sciences (India)

    In addition, the oscillator energy, disper- sion energy and zero-frequency refractive index values were found from the analysis of the experimental data using. Wemple–DiDomenico single-effective-oscillator model. Keywords. Perovskite; BaTiO3; X-ray diffraction; spectroscopic ellipsometry; refractive index. 1. Introduction.

  18. O3 perovskite ceramic

    Indian Academy of Sciences (India)

    ray diffraction, scanning electron microscopy and ... The structure refinement of BaTi0.5(Fe0.33W0.17)O3 sample was performed in the cubic double and hexagonal setting of the Fm¯3m .... peak Ihex by the following quantitative equations [17]:.

  19. Raman and Fluorescence Spectroscopy of CeO2, Er2O3, Nd2O3, Tm2O3, Yb2O3, La2O3, and Tb4O7

    Directory of Open Access Journals (Sweden)

    Jianlan Cui

    2015-01-01

    Full Text Available To better understand and ascertain the mechanisms of flotation reagent interaction with rare earth (RE minerals, it is necessary to determine the physical and chemical properties of the constituent components. Seven rare earth oxides (CeO2, Er2O3, Nd2O3, Tm2O3, Yb2O3, La2O3, and Tb4O7 that cover the rare earth elements (REEs from light to heavy REEs have been investigated using Raman spectroscopy. Multiple laser sources (wavelengths of 325 nm, 442 nm, 514 nm, and 632.8 nm for the Raman shift ranges from 100 cm−1 to 5000 cm−1 of these excitations were used for each individual rare earth oxide. Raman shifts and fluorescence emission have been identified. Theoretical energy levels for Er, Nd, and Yb were used for the interpretation of fluorescence emission. The experimental results showed good agreement with the theoretical calculation for Er2O3 and Nd2O3. Additional fluorescence emission was observed with Yb2O3 that did not fit the reported energy level diagram. Tb4O7 was observed undergoing laser induced changes during examination.

  20. O3 Source Contribution During a Heavy O3 Pollution Episode in Shanghai China

    Science.gov (United States)

    Source culpability assessments are useful for developing effective emission control strategies. The Integrated Source Apportionment Method (ISAM) has been implemented in CMAQ to track contributions from source groups and regions to ambient levels and deposited amounts of O3. CMAQ...

  1. LIMS/Nimbus-7 Level 2 Vertical Profiles of O3, NO2, H2O, HNO3, Geopotential Height, and Temperature V006

    Data.gov (United States)

    National Aeronautics and Space Administration — The Limb Infrared Monitor of the Stratosphere (LIMS) version 6 Level-2 data product consists of daily, geolocated, vertical profiles of temperature, geopotential...

  2. Er^3+ ^4I_15/2 and ^4I_13/2 levels and magnetic g-tensors for C2 and C_3i sites in Y_2O3 by 1.5 mm diode laser spectroscopy

    Science.gov (United States)

    Reinemer, G.; Harris, T. L.; Sun, Y.; Cone, R. L.; Equall, R. W.

    2001-03-01

    Single mode 1.5 μm diode lasers provide an unusual ability to study and exploit Er^3+ ^4I_15/2 and ^4I_13/2 transitions in the technologically significant communications band. Allowed magnetic-dipole transitions and high-resolution spectroscopic techniques have been used to characterize the C_3i sites, for which all electric dipole transitions are forbidden by inversion symmetry. Levels were identified for both C2 and C_3i sites using fluorescence excitation and orientation-dependent Zeeman absorption for 0.005% Er^3+:Y_2O_3. The complete magnetic g-tensors for each site were measured for the lowest levels in both multiplets and have been used to determine the optimum direction for applying a magnetic field to suppress dephasing in coherent transient signal processing device applications. The techniques demonstrated here provide a new tool for accessing and characterizing sites where inversion symmetry has frustrated earlier efforts. The Y_2O3 host, with its excellent thermal conductivity and high IR transmission out to 8 μm, is an important material for laser development. It is a strong candidate for Er^3+-based coherent transient devices.

  3. Origin of the current discretization in deep reset states of an Al2O3/Cu-based conductive-bridging memory, and impact on state level and variability

    Science.gov (United States)

    Belmonte, A.; Degraeve, R.; Fantini, A.; Kim, W.; Houssa, M.; Jurczak, M.; Goux, L.

    2014-06-01

    In this paper, we develop a Quantum-Point-Contact (QPC) model describing the state conduction in a W/Al2O3/TiW/Cu Conductive-Bridging Memory cell (CBRAM). The model allows describing both the voltage- and the temperature-dependence of the conduction. For deep current levels, a resistance component is added in series to the point-contact constriction to account for electron scattering in the residual filament. The fitting of single-particle perturbation also allowed to estimate the number and effective size of the conduction-controlling particles in the QPC constriction. The results clearly point to smaller particles for CBRAM (Cu particles) as compared to oxide-based resistive RAM involving oxygen-vacancy defects, which is discussed as a possible origin of deeper reset level obtained in CBRAM. We also evidence a beneficial impact of this smaller particle size on lower Random-Telegraph-Noise amplitude measured on CBRAM devices.

  4. Improvements of uniformity and stoichiometry for zone-leveling Czochralski growth of MgO-doped LiNbO3 crystals

    International Nuclear Information System (INIS)

    Tsai, C.B.; Hsu, W.T.; Shih, M.D.; Tai, C.Y.; Hsieh, C.K.; Hsu, W.C.; Hsu, R.T.; Lan, C.W.

    2006-01-01

    The zone-leveling Czochralski (ZLCz) technique is a continuous feeding process and can be used for the growth of near-stoichiometric lithium niobate (SLN) single crystals. However, the finite crucible length can cause the variation of the zone length and thus the composition and stoichiometry, especially in the growth of a large diameter crystal. To solve the problems, several approaches were proposed for the growth of 4 cm-diameter 1 mol% MgO-doped SLN. The modification of the hot zone to minimize the zone variation was found useful for the uniformity, but the stoichiometry was inadequate even with the zone composition up to 60 mol% Li 2 O. A Li-excess feed was further used and a good Li/Nb ratio was obtained. Adding K 2 O (16 mol%) into the solution zone was useful as well, but it was inferior to using the Li-excess feed. In addition, a much lower growth rate was needed for getting an inclusion-free crystal

  5. Photoconductivity of transparent perovskite semiconductor BaSnO3 and SrTiO3 epitaxial thin films

    Science.gov (United States)

    Park, Jisung; Kim, Useong; Char, Kookrin

    2016-02-01

    We measured the photoconductivity of transparent semiconductor BaSnO3 and compared it with that of SrTiO3. Epitaxial BaSnO3 and SrTiO3 films were grown on MgO substrates to exclude any contribution to photoconductivity from the substrate due to its large bandgap. In spite of the same perovskite structure and similar bandgap sizes (3.1-3.2 eV), the photoconductive behaviors of the two materials are quite different in terms of their magnitude and time dependence. The photoconductivity of BaSnO3 persists for many hours after removal from light exposure, whereas the photoconductivity of SrTiO3 shows little persistent conductivity. In addition, the photoconductivity of BaSnO3 increases to a value over 25 times higher than that of SrTiO3, after 3 h of illuminations. The spectral photoconductive responses of both BaSnO3 and SrTiO3 show their highest peaks below 400 nm, suggesting that the electron-hole pair generation is the main mechanism of the photoconductivity for the both materials. The large persistent photoconductivity of BaSnO3 seems related with deep level defects with relatively large barriers for charge trapping and detrapping.

  6. TiO3 ceramics

    Indian Academy of Sciences (India)

    Administrator

    High purity Bi2O3, Na2CO3, TiO2, MgCO3 and Nb2O5. (purity over 99⋅5%) powders were used as starting mate- rials. Our preliminary experiments found that (Bi1/2Na1/2). Ti1–x(Mg1/3Nb2/3)xO3 ceramics were not well synthesized by mixing and calcinating all these above powders as used in the conventional oxide ...

  7. Acclimation to Chronic O3 in Field-grown Soybean is Characterized by Increased Levels of TCA Cycle Transcripts and ROS Scavenging Compounds in Addition to Decreased Photosynthetic Capacity

    Science.gov (United States)

    Tropospheric ozone (O3) is a pollutant that is generated by volatile organic compounds, nitrogen oxides and sunlight. When plants take in O3 through stomata, harmful reactive oxygen species (ROS) are produced that induce the production of ROS scavenging antioxidants. Climate change predictions indic...

  8. Negative magnetostrictive magnetoelectric coupling of BiFeO3

    NARCIS (Netherlands)

    Lee, Sanghyun; Fernandez-Diaz, M. T.; Kimura, H.; Noda, Y.; Adroja, D. T.; Lee, Seongsu; Park, Junghwan; Kiryukhin, V.; Cheong, S. -W.; Mostovoy, M.; Park, Je-Geun

    2013-01-01

    How magnetoelectric coupling actually occurs on a microscopic level in multiferroic BiFeO3 is not well known. By using high-resolution single crystal neutron diffraction techniques, we have determined the electric polarization of each individual element of BiFeO3, and concluded that magnetostrictive

  9. Total column density variations of ozone (O3 O3 O3) in presence of ...

    Indian Academy of Sciences (India)

    solar zenith angles (SZAs). The slant column densities (SCDs) as well as total column densities (TCDs) of NO2, O3, H2O and O4 are derived with different SZAs in clear and cloudy sky conditions. The large enhancements and reductions in TCDs of the above gases are observed in thick cumulonimbus (Cb) clouds and thin ...

  10. Fundamental absorption of Y2O3 and YAlO3

    International Nuclear Information System (INIS)

    Abramov, V.N.; Kuznetsov, A.I.

    1978-01-01

    Reflection spectra in the range of 4-14 eV were measured for Y 2 O 3 and YAlO 3 crystals. The spectra of the following optical characteristics were calculated with the aid of the Kramers-Kroning relation: absorption, refraction, dielectric constant, and effective number of electrons. Excitons with an energy of 6.0 eV and an oscillator strength of f approximately 0.1 were found in Y 2 O 3 , and the width of the forbidden zone was determined (approximately 6.1 eV). The scheme of genealogy and arrangement of the plane zones of Y 2 O 3 , in which a substantial role is attributed to interaction of 5s and 4d states of yttrium cations, is proposed and discussed at the qualitative level. The range of the beginning of fundamental absorption (hν > or approximately 7.5 eV) was determined for YAlO 3 . The composition dependence of the width of the forbidden zone of aluminated Ysub(x)Alsub(y)Osub(z) is plotted

  11. Multi-year application of WRF-CAM5 over East Asia-Part I: Comprehensive evaluation and formation regimes of O 3 and PM 2.5

    Energy Technology Data Exchange (ETDEWEB)

    He, Jian; Zhang, Yang; Wang, Kai; Chen, Ying; Leung, L. Ruby; Fan, Jiwen; Li, Meng; Zheng, Bo; Zhang, Qiang; Duan, Fengkui; He, Kebin

    2017-09-01

    Accurate simulations of air quality and climate require robust model parameterizations on regional and global scales. The Weather Research and Forecasting model with Chemistry version 3.4.1 has been coupled with physics packages from the Community Atmosphere Model version 5 (CAM5) (WRF-CAM5) to assess the robustness of the CAM5 physics package for regional modeling at higher grid resolutions than typical grid resolutions used in global modeling. In this two-part study, Part I describes the application and evaluation of WRF-CAM5 over East Asia at a horizontal resolution of 36-km for six years: 2001, 2005, 2006, 2008, 2010, and 2011. The simulations are evaluated comprehensively with a variety of datasets from surface networks, satellites, and aircraft. The results show that meteorology is relatively well simulated by WRF-CAM5. However, cloud variables are largely or moderately underpredicted, indicating uncertainties in the model treatments of dynamics, thermodynamics, and microphysics of clouds/ices as well as aerosol-cloud interactions. For chemical predictions, the tropospheric column abundances of CO, NO2, and O3 are well simulated, but those of SO2 and HCHO are moderately overpredicted, and the column HCHO/NO2 indicator is underpredicted. Large biases exist in the surface concentrations of CO, NO2, and PM10 due to uncertainties in the emissions as well as vertical mixing. The underpredictions of NO lead to insufficient O3 titration, thus O3 overpredictions. The model can generally reproduce the observed O3 and PM indicators. These indicators suggest to control NOx emissions throughout the year, and VOCs emissions in summer in big cities and in winter over North China Plain, North/South Korea, and Japan to reduce surface O3, and to control SO2, NH3, and NOx throughout the year to reduce inorganic surface PM.

  12. Multi-year application of WRF-CAM5 over East Asia-Part I: Comprehensive evaluation and formation regimes of O3 and PM2.5

    Science.gov (United States)

    He, Jian; Zhang, Yang; Wang, Kai; Chen, Ying; Leung, L. Ruby; Fan, Jiwen; Li, Meng; Zheng, Bo; Zhang, Qiang; Duan, Fengkui; He, Kebin

    2017-09-01

    Accurate simulations of air quality and climate require robust model parameterizations on regional and global scales. The Weather Research and Forecasting model with Chemistry version 3.4.1 has been coupled with physics packages from the Community Atmosphere Model version 5 (CAM5) (WRF-CAM5) to assess the robustness of the CAM5 physics package for regional modeling at higher grid resolutions than typical grid resolutions used in global modeling. In this two-part study, Part I describes the application and evaluation of WRF-CAM5 over East Asia at a horizontal resolution of 36-km for six years: 2001, 2005, 2006, 2008, 2010, and 2011. The simulations are evaluated comprehensively with a variety of datasets from surface networks, satellites, and aircraft. The results show that meteorology is relatively well simulated by WRF-CAM5. However, cloud variables are largely or moderately underpredicted, indicating uncertainties in the model treatments of dynamics, thermodynamics, and microphysics of clouds/ices as well as aerosol-cloud interactions. For chemical predictions, the tropospheric column abundances of CO, NO2, and O3 are well simulated, but those of SO2 and HCHO are moderately overpredicted, and the column HCHO/NO2 indicator is underpredicted. Large biases exist in the surface concentrations of CO, NOx, and PM10 due to uncertainties in the emissions as well as vertical mixing. The underpredictions of NO lead to insufficient O3 titration, thus O3 overpredictions. The model can generally reproduce the observed O3 and PM indicators. These indicators suggest to control NOx emissions throughout the year, and VOCs emissions in summer in big cities and in winter over North China Plain, North/South Korea, and Japan to reduce surface O3, and to control SO2, NH3, and NOx throughout the year to reduce inorganic surface PM.

  13. TES/Aura L2 O3 Limb V006

    Data.gov (United States)

    National Aeronautics and Space Administration — The TES Aura L2 O3 data consist of information for one molecular species for an entire Global Survey or Special Observation. TES Level 2 data contain retrieved...

  14. HNbO3 and HTaO3: new cubic perovskites prepared from LiNbO3 and LiTaO3 via ion exchange

    International Nuclear Information System (INIS)

    Rice, C.E.; Jackel, J.L.

    1982-01-01

    The synthesis of HNbO 3 and HTaO 3 from LiNbO 3 via ion exchange in hot aqueous acid solutions is reported. This reaction is accompanied by a topotactic structural transformation from the rhombohedral LiNbO 3 structure to the cubic perovskite structure; cell constants are a = 3.822(1) angstrom for HNbO 3 and 3.810(2) angstrom for HTaO 3 . These new compounds have been characterized by powder X-ray diffraction, thermogravimetric analysis, and solid-state NMR. They are electronic insulators and have low ionic conductivity. Evidence of partially proton-exchange phases Li/sub 1-x/H/sub x/MO 3 was also seen. The possible significance of this ion exchange reaction for devices using LiNbO 3 or LiTaO 3 is discussed

  15. Impact of the Manaus urban plume on trace gas mixing ratios near the surface in the Amazon Basin: Implications for the NO-NO2-O-3 photostationary state and peroxy radical levels

    NARCIS (Netherlands)

    Trebs, I.; Mayol-Bracero, O.L.; Pauliquevis, T.; Kuhn, U.; Sander, R.; Ganzeveld, L.N.; Meixner, F.X.; Kesselmeier, J.; Artaxo, P.; Andreae, M.O.

    2012-01-01

    We measured the mixing ratios of NO, NO2, O-3, and volatile organic carbon as well as the aerosol light-scattering coefficient on a boat platform cruising on rivers downwind of the city of Manaus (Amazonas State, Brazil) in July 2001 (Large-Scale Biosphere-Atmosphere Experiment in

  16. Acute ozone (O3) -induced impairment of glucose regulation: Age-related and temporal changes

    Science.gov (United States)

    O3 is associated with adverse cardiopulmonary health effects in humans and is thought to produce metabolic effects, such as insulin resistance. Recently, we showed that episodic O3 exposure increased insulin levels in aged rats. We hypothesized that O3 exposure could impair gluc...

  17. modified BiFeO3–BaTiO3

    Indian Academy of Sciences (India)

    based perovskite structures lead- free BiFeO3–BaTiO3 solid solutions are popularly studied due to the high Curie temperature (TC). It was reported that the BiFeO3–BaTiO3 system possessed high piezoelectric. ∗. Author for correspondence ...

  18. Synthesis and structural characterization of (Bi2O3)(Y2O3) x and ...

    Indian Academy of Sciences (India)

    Lattice parameters of fcc phase of Y2O3 doped samples were calculated from the X-ray diffraction data. The lattice constant `' gradually decreases with increasing content of dopant concentration () for the Y2O3 doped system and obeys Vegard's rule. The unit cell parameters for the (Bi2O3)1– (Gd2O3) doped ...

  19. Fe2O3nanoparticles anchored on 2D kaolinite with enhanced antibacterial activity.

    Science.gov (United States)

    Long, Mei; Zhang, Yi; Shu, Zhan; Tang, Aidong; Ouyang, Jing; Yang, Huaming

    2017-06-06

    An enhanced antibacterial activity of Fe 2 O 3 nanoparticles was achieved by controlling the distribution density of Fe 2 O 3 nanoparticles on modified kaolinite nanosheets (Fe 2 O 3 -Kln KAc ) by adjusting the pH value of the reaction system. A proper distribution density of Fe 2 O 3 nanoparticles generating higher levels of hydroxyl radicals led to a higher antibacterial activity.

  20. Modulation doping at BaSnO3LaInO3

    Science.gov (United States)

    Char, Kookrin; Shin, Juyeon; Kim, Young Mo; Kim, Youjung

    We recently reported on the conductance enhancement at the interface between two band insulators: LaInO3 (LIO) and BaSnO3 (BSO). These two-dimensional electron gas-like (2DEG) states at the LIO/Ba1-xLaxSnO3 (BLSO) polar interface display the stability, the controllability of the local carrier concentration, and the high electron mobility of BLSO. Search for the origin of enhanced conductance at the interface has been carried out, and one of the findings is that the doping level of BSO is a critical parameter for the polar charge contribution . We have also investigated a new modulated heterostructure by inserting an undoped BSO spacer layer at the LIO/BLSO interface. As increasing the thickness of the spacer layer, the carrier concentration and the mobility continually decreased. We attribute the results to the modified band bending as the thickness of the spacer layer varies and to the dislocation-limited transport. However, when we controlled the band bending by field effect, improved mobility was observed in these modulated heterostructures. This new modulated heterostructures of the LIO/BSO polar interface look promising not only for higher electron mobility devices but also for elucidating the mechanism of the 2DEG-like behavior. Samsung science and technology foundation.

  1. Photocatalytic properties of KBiO3 and LiBiO3 with tunnel structures

    Indian Academy of Sciences (India)

    LiBiO3 (ICDD PDF Card No. 01–086–1187). Lattice parameters obtained are close to the reported values for these oxides. KBiO3 crystallizes in cubic KSbO3 type structure (space group Im 3) with lattice parame- ter a = 10.0198(3) Å. LiBiO3 has orthorhombic struc- ture (space group Pccn) similar to LiSbO3 and the.

  2. The performance of Y2O3 as interface layer between La2O3 and p-type silicon substrate

    Directory of Open Access Journals (Sweden)

    Shulong Wang

    2016-11-01

    Full Text Available In this study, the performance of Y2O3 as interface layer between La2O3 and p-type silicon substrate is studied with the help of atomic layer deposition (ALD and magnetron sputtering technology. The surface morphology of the bilayer films with different structures are observed after rapid thermal annealing (RTA by atomic force microscopy (AFM. The results show that Y2O3/Al2O3/Si structure has a larger number of small spikes on the surface and its surface roughness is worse than Al2O3/Y2O3/Si structure. The reason is that the density of Si substrate surface is much higher than that of ALD growth Al2O3. With the help of high-frequency capacitance-voltage(C-V measurement and conductivity method, the density of interface traps can be calculated. After a high temperature annealing, the metal silicate will generate at the substrate interface and result in silicon dangling bond and interface trap charge, which has been improved by X-ray photoelectron spectroscopy (XPS and interface trap charge density calculation. The interface trapped charge density of La2O3/Al2O3/Si stacked gate structure is lower than that of La2O3/Y2O3/Si gate structure. If Y2O3 is used to replace Al2O3 as the interfacial layer, the accumulation capacitance will increase obviously, which means lower equivalent oxide thickness (EOT. Our results show that interface layer Y2O3 grown by magnetron sputtering can effectively ensure the interface traps near the substrate at relative small level while maintain a relative higher dielectric constant than Al2O3.

  3. Phase relations in the SiC-Al2O3-Pr2O3 system

    International Nuclear Information System (INIS)

    Pan, W.; Wu, L.; Jiang, Y.; Huang, Z.

    2016-01-01

    Phase relations in the Si-Al-Pr-O-C system, including the SiC-Al 2 O 3 -Pr 2 O 3 , the Al 2 O 3 -Pr 2 O 3 -SiO 2 and the SiC-Al 2 O 3 -Pr 2 O 3 -SiO 2 subsystems, were determined by means of XRD phase analysis of solid-state-reacted samples fabricated by using SiC, Al 2 O 3 , Pr 2 O 3 and SiO 2 powders as the starting materials. Subsolidus phase diagrams of the systems were presented. Two Pr-aluminates, namely PrAlO 3 (PrAP) and PrAl 11 O 18 (β(Pr) β-Al 2 O 3 type) were formed in the SiC-Al 2 O 3 -Pr 2 O 3 system. SiC was compatible with both of them. Pr-silicates of Pr 2 SiO 5 , Pr 2 Si 2 O 7 and Pr 9.33 Si 6 O 26 (H(Pr) apatite type) were formed owing to presence of SiO 2 impurity in the SiC powder. The presence of the SiO 2 extended the ternary system of SiC-Al 2 O 3 -Pr 2 O 3 into a quaternary system of SiC-Al 2 O 3 -SiO 2 -Pr 2 O 3 (Si-Al-Pr-O-C). SiC was compatible with Al 2 O 3 , Pr 2 O 3 and the Pr-silicates. The effect of SiO 2 on the phase relations and liquid phase sintering of SiC ceramics was discussed.

  4. Impact of the Manaus urban plume on trace gas mixing ratios near the surface in the Amazon Basin: Implications for the NO-NO2-O3 photostationary state and peroxy radical levels

    Science.gov (United States)

    Trebs, Ivonne; Mayol-Bracero, Olga L.; Pauliquevis, Theotonio; Kuhn, Uwe; Sander, Rolf; Ganzeveld, Laurens; Meixner, Franz X.; Kesselmeier, Jürgen; Artaxo, Paulo; Andreae, Meinrat O.

    2012-03-01

    We measured the mixing ratios of NO, NO2, O3, and volatile organic carbon as well as the aerosol light-scattering coefficient on a boat platform cruising on rivers downwind of the city of Manaus (Amazonas State, Brazil) in July 2001 (Large-Scale Biosphere-Atmosphere Experiment in Amazonia-Cooperative LBA Airborne Regional Experiment-2001). The dispersion and impact of the Manaus plume was investigated by a combined analysis of ground-based (boat platform) and airborne trace gas and aerosol measurements as well as by meteorological measurements complemented by dispersion calculations (Hybrid Single-Particle Lagrangian Integrated Trajectory model). For the cases with the least anthropogenic influence (including a location in a so far unexplored region ˜150 km west of Manaus on the Rio Manacapuru), the aerosol scattering coefficient, σs, was below 11 Mm-1, NOx mixing ratios remained below 0.6 ppb, daytime O3 mixing ratios were mostly below 20 ppb and maximal isoprene mixing ratios were about 3 ppb in the afternoon. The photostationary state (PSS) was not established for these cases, as indicated by values of the Leighton ratio, Φ, well above unity. Due to the influence of river breeze systems and other thermally driven mesoscale circulations, a change of the synoptic wind direction from east-northeast to south-southeast in the afternoon often caused a substantial increase of σs and trace gas mixing ratios (about threefold for σs, fivefold for NOx, and twofold for O3), which was associated with the arrival of the Manaus pollution plume at the boat location. The ratio Φ reached unity within its uncertainty range at NOx mixing ratios of about 3 ppb, indicating "steady-state" conditions in cases when radiation variations, dry deposition, emissions, and reactions mostly involving peroxy radicals (XO2) played a minor role. The median midday/afternoon XO2 mixing ratios estimated using the PSS method range from 90 to 120 parts per trillion (ppt) for the remote cases (

  5. Increasing the Aromatic Selectivity of Quinoline Hydrogenolysis Using Pd/MOx–Al2O3

    Energy Technology Data Exchange (ETDEWEB)

    Bachrach, Mark; Morlanes-Sanchez, Natalia; Canlas, Christian P.; Miller, Jeffrey T.; Marks, Tobin J.; Notestein, Justin M.

    2014-09-11

    Catalysts consisting of Pd nanoparticles supported on highly dispersed TiOx–Al2O3, TaOx–Al2O3, and MoOx–Al2O3 are studied for catalytic quinoline hydrogenation and selective C–N bond cleavage at 275 °C and 20 bar H2. The Pd/MOx–Al2O3 materials exhibit significantly greater aromatic product selectivity and thus 10–15 % less required H2 for a given level of denitrogenation relative to an unmodified Pd/Al2O3 catalyst.

  6. Resistance switching at the interface of LaAlO3/SrTiO3

    DEFF Research Database (Denmark)

    Chen, Yunzhong; Zhao, J.L.; Sun, J.R.

    2010-01-01

    behavior is suggested to be an intrinsic feature of the SrTiO3 single crystal substrates, which mainly originates from the modulation of oxygen ion transfer in SrTiO3 surface by external electric field in the vicinity of interface, whereas the LaAlO3 film acts as a barrier layer. © 2010 American Institute...

  7. Transport and excitations in a negative-U quantum dot at the LaAlO3/SrTiO3 interface

    DEFF Research Database (Denmark)

    Prawiroatmodjo, Guenevere E. D. K.; Leijnse, Martin Christian; Trier, Felix

    2017-01-01

    In a solid-state host, attractive electron–electron interactions can lead to the formation of local electron pairs which play an important role in the understanding of prominent phenomena such as high Tc superconductivity and the pseudogap phase. Recently, evidence of a paired ground state without...... superconductivity was demonstrated at the level of single electrons in quantum dots at the interface of LaAlO3 and SrTiO3. Here, we present a detailed study of the excitation spectrum and transport processes of a gate-defined LaAlO3/SrTiO3 quantum dot exhibiting pairing at low temperatures. For weak tunneling...

  8. Electronic structure and thermodynamics of V2O3 polymorphs.

    Science.gov (United States)

    Wessel, C; Reimann, C; Müller, A; Weber, D; Lerch, M; Ressler, T; Bredow, T; Dronskowski, R

    2012-10-05

    A metastable bixbyite-type polymorph of vanadium sesquioxide, V(2)O(3), has recently been synthesized, and it transforms to the corundum-type phase at temperatures around 550 °C. The possibility of a paramagnetic to canted antiferromagnetic or even spin-glass-like transition has been discussed. Quantum-chemical calculations on the density-functional theory level including explicit electronic correlation confirm the metastability as well as the semiconducting behavior of the material and predict that the bixbyite-type structure is about 0.1 eV less stable than the well-known corundum-type phase. Nonetheless, quasiharmonic phonon calculations manifest that bixbyite-type vanadium sesquioxide is a dynamically stable compound. Other possible V(2)O(3) polymorphs are shown to be even less suitable candidates for the composition V(2)O(3). Copyright © 2012 Wiley Periodicals, Inc.

  9. Characteristics of surface O3 over Qinghai Lake area in Northeast Tibetan Plateau, China

    International Nuclear Information System (INIS)

    Shen, Zhenxing; Cao, Junji; Zhang, Leiming; Zhao, Zhuzi; Dong, Jungang; Wang, Linqing; Wang, Qiyuan; Li, Guohui; Liu, Suixin; Zhang, Qian

    2014-01-01

    Surface O 3 was monitored continuously during Aug. 12, 2010 to Jul. 21, 2011 at a high elevation site (3200 m above sea level) in Qinghai Lake area (36°58′37″N, 99°53′56″E) in Northeast Tibetan Plateau, China. Daily average O 3 ranged from 21.8 ppbv to 65.3 ppbv with an annual average of 41.0 ppbv. Seasonal average of O 3 followed a decreasing order of summer > autumn > spring > winter. Diurnal variations of O 3 showed low concentrations during daytime and high concentrations during late night and early morning. An intensive campaign was also conducted during Aug. 13–31, 2010 to investigate correlations between meteorological or chemical conditions and O 3 . It was found that O 3 was poorly correlated with solar radiation due to the insufficient NO x in the ambient air, thus limiting O 3 formation under strong solar radiation. In contrast, high O 3 levels always coincided with strong winds, suggesting that stratospheric O 3 and long range transport might be the main sources of O 3 in this rural area. Back-trajectory analysis supported this hypothesis and further indicated the transport of air masses from northwest, northeast and southeast directions. - Highlights: • Surface O 3 was measured in Qinghai Lake area in Northeast Tibetan Plateau, China. • The O 3 chemical formation was under a strong NOx-limited in Qinghai Lake areas. • Stratospheric O 3 and transport might be the main sources of O 3 in this area

  10. Arbuscular mycorrhiza formation and its function under elevated atmospheric O3: A meta-analysis.

    Science.gov (United States)

    Wang, Shuguang; Augé, Robert M; Toler, Heather D

    2017-07-01

    We quantitatively evaluated the effects of elevated O 3 on arbuscular mycorrhiza (AM) formation and on AM role in promoting plant growth in regard to several moderating variables (O 3 levels, O 3 exposure duration, plant types, AM fungi family, and additional stress) by means of meta-analysis of published data. The analysis consisted of 117 trials representing 20 peer-reviewed articles and 16 unpublished trials. Relative to non-mycorrhizal controls, AM inoculation did not significantly alter plant growth (shoot biomass, root biomass, total biomass and plant height) when O 3 concentration was less than 80 ppb, but at concentrations above 80 ppb symbiosis was associated with increases of 68% in shoot biomass and 131% in root biomass. AM effects on plant growth were affected by the duration of O 3 exposure but did not differ much with AM fungi taxa or plant type. AM symbiosis has also led to higher yields under O 3 stress, relative to the non-mycorrhizal plants, and the AM effects have been more pronounced as O 3 concentration increases. As with biomass, AM effects on yield have been affected by the duration of O 3 exposure, with the greatest increase (100%) occurring at 61-90 d. AM-induced promotion of yield differed with fungal species but not with plant type or other abiotic stress. Colonization of roots by AM fungi has been negatively affected by elevated O 3 compared to ambient O 3 ; total mycorrhizal colonization rate (MCR), arbuscular MCR, vesicular MCR and hyphal coil MCR declined as O 3 levels rose. AM colonization rates were affected by duration of O 3 exposure, plant type, AM fungal taxa and other concurrent stresses in most cases. The analysis showed that AM inoculation has the potential to ameliorate detrimental effects of elevated O 3 on plant growth and productivity, despite colonization rates being negatively affected by elevated O 3 . Copyright © 2017. Published by Elsevier Ltd.

  11. Mnx/2Nbx/2O3 ceramics

    Indian Academy of Sciences (India)

    Unknown

    Abstract. The paper reports investigations of relative permittivity, εr, electrical conductivity, σ, saturation polarization, Ps, infrared absorption and structural properties of compensating valency substituted BaTiO3. The compositions investigated are BaTi(1–x)Mnx/2Nbx/2O3 for x = 0⋅00; 0⋅025; 0⋅05; 0⋅1; 0⋅2; 0⋅4.

  12. O3 flux-related responsiveness of photosynthesis, respiration, and stomatal conductance of adult Fagus sylvatica to experimentally enhanced free-air O3 exposure.

    Science.gov (United States)

    Löw, M; Häberle, K-H; Warren, C R; Matyssek, R

    2007-03-01

    Knowledge of responses of photosynthesis, respiration, and stomatal conductance to cumulative ozone uptake (COU) is still scarce, and this is particularly the case for adult trees. The effect of ozone (O(3)) exposure on trees was examined with 60-year-old beech trees (FAGUS SYLVATICA) at a forest site of southern Germany. Trees were exposed to the ambient O(3) regime (1 x O(3)) or an experimentally elevated twice-ambient O(3) regime (2 x O(3)). The elevated 2 x O (3) regime was provided by means of a free-air O(3) canopy exposure system. The hypotheses were tested that (1) gas exchange is negatively affected by O(3) and (2) the effects of O(3) are dose-dependent and thus the sizes of differences between treatments are positively related to COU. Gas exchange (light-saturated CO(2) uptake rate A(max), stomatal conductance g (s), maximum rate of carboxylation Vc (max), ribulose-1,5-bisphosphate turnover limited rate of photosynthesis J (max), CO(2) compensation point CP, apparent quantum yield of net CO(2) uptake AQ, carboxylation efficiency CE, day- and nighttime respiration) and chlorophyll fluorescence (electron transfer rate, ETR) were measured IN SITU on attached sun and shade leaves. Measurements were made periodically throughout the growing seasons of 2003 (an exceptionally dry year) and 2004 (a year with average rainfall). In 2004 Vc(max), J(max), and CE were lower in trees receiving 2 x O(3) compared with the ambient O(3) regime (1 x O(3)). Treatment differences in Vc (max), J (max), CE were rather small in 2004 (i.e., parameter levels were lower by 10 - 30 % in 2 x O(3) than 1 x O(3)) and not significant in 2003. In 2004 COU was positively correlated with the difference between treatments in A (max), g (s), and ETR (i.e., consistent with the dose-dependence of O(3)'s deleterious effects). However, in 2003, differences in A(max), g (s), and ETR between the two O(3) regimes were smaller at the end of the dry summer 2003 (i.e., when COU was greatest). The

  13. DNA damage in Populus tremuloides clones exposed to elevated O3

    International Nuclear Information System (INIS)

    Tai, Helen H.; Percy, Kevin E.; Karnosky, David F.

    2010-01-01

    The effects of elevated concentrations of atmospheric tropospheric ozone (O 3 ) on DNA damage in five trembling aspen (Populus tremuloides Michx.) clones growing in a free-air enrichment experiment in the presence and absence of elevated concentrations of carbon dioxide (CO 2 ) were examined. Growing season mean hourly O 3 concentrations were 36.3 and 47.3 ppb for ambient and elevated O 3 plots, respectively. The 4th highest daily maximum 8-h ambient and elevated O 3 concentrations were 79 and 89 ppb, respectively. Elevated CO 2 averaged 524 ppm (+150 ppm) over the growing season. Exposure to O 3 and CO 2 in combination with O 3 increased DNA damage levels above background as measured by the comet assay. Ozone-tolerant clones 271 and 8L showed the highest levels of DNA damage under elevated O 3 compared with ambient air; whereas less tolerant clone 216 and sensitive clones 42E and 259 had comparably lower levels of DNA damage with no significant differences between elevated O 3 and ambient air. Clone 8L was demonstrated to have the highest level of excision DNA repair. In addition, clone 271 had the highest level of oxidative damage as measured by lipid peroxidation. The results suggest that variation in cellular responses to DNA damage between aspen clones may contribute to O 3 tolerance or sensitivity. - Ozone tolerant clones and sensitive Populus tremuloides clones show differences in DNA damage and repair.

  14. Contributions of Kansas rangeland burning to ambient O3: Analysis of data from 2001 to 2016.

    Science.gov (United States)

    Liu, Zifei; Liu, Yang; Murphy, James P; Maghirang, Ronaldo

    2018-03-15

    Prescribed range/pasture burning is a common practice in Kansas to enhance the nutritional value of native grasses and control invading weeds, trees, and brush. A major concern associated with the burning is the contribution of smoke to elevated ground level ambient ozone (O 3 ). The objective of this study is to estimate contributions of Kansas rangeland burning to ambient O 3 mixing ratios through regression analysis (1) between observed O 3 data and available satellite burn activity data from 2001 to 2016; and (2) between observed O 3 data and the smoke contributions to PM 2.5 which were resolved from receptor modeling. Positive correlations were observed between ambient O 3 levels and the acres burned each year estimated from satellite imagery. When burned acres in April were larger than or equal to 1.9 million, O 3 >70ppb occurred at least at one of the ten monitoring sites in Kansas. Statistical regression models of daily maximum 8-hour O 3 mixing ratios were developed at each of the ten monitoring sites using meteorological predictors. The O 3 model residuals that were not explained by the meteorological effect models were affected by PM 2.5 contributors including sulfate/industrial sources and emissions that generated secondary organic particles, such as rangeland burning, which were derived from receptor modeling. The average O 3 model residual on the high O 3 days in April was 21±9ppb, which was likely associated with smoke emissions from burning. Research will continue to obtain daily satellite burn activity data and to correlate burn data with daily O 3 data, so that modeling of O 3 levels can be improved under influences of daily burn activities. Less frequency of high O 3 days was observed in April since 2011, which may be partly due to implementation of the Flint Hills Smoke Management Plan which promoted better timing of burns. Copyright © 2017 Elsevier B.V. All rights reserved.

  15. HfO2/Pr2O3 gate dielectric stacks

    Science.gov (United States)

    Sidorov, F.; Molchanova, A.; Rogozhin, A.

    2016-12-01

    Electrical properties of MOS structures based on molecular beam epitaxy formed HfO2/Pr2O3 gate dielectric stacks have been studied by CV, GV and IV characteristics. Electrical properties of the structures with HfO2/Pr2O3 and PEALD HfO2 dielectric layers were compared. Higher gate leakage current and lower interface trap level density in the structure with HfO2/Pr2O3 dielectric layer was observed.

  16. Raman spectroscopic study of structure and crystallisation behaviour of MoO3-La2O3-B2O3 and MoO3-ZnO-B2O3 glasses

    Science.gov (United States)

    Aleksandrov, L.; Komatsu, T.; Nagamine, K.; Oishi, K.

    2011-03-01

    In this study, we focus on the structure and crystallization behavior of MoO3-La2O3-B2O3 and MoO3-ZnO-B2O3 glasses. Glasses of both systems were prepared by a melt-quenching method. The thermal stability of the glasses was examined using differential thermal anaysis (DTA) measurements, and the crystalline phases formed by heat treatments were identified by X-ray diffraction (XRD) analysis. Raman scattering spectra at room temperature for the glasses and crystallized samples were measured with a laser microscope operated with an Ar+ (wavelength: 488 nm) laser. DTA measurements indicated that the thermal stability against crystallization of the glasses decreases drastically with increasing MoO3 content. XRD analysis confirmed that crystallization at 600°C for 3 h of glass with the nominal composition of 50MoO3-25La2O3-25B2O3 resulted in the formation of monoclinic LaMoBO6. Crystallization of 50ZnO-xMoO3-(50-x)B2O3 glasses formed triclinic α-ZnMoO4 as an initial crystalline phase. Moreover, for 30 mol% MoO3 glass, transmission electron microscopy observations showed the formation of α-ZnMoO4 nanocrystals with a diameter of ~ 5 nm. Raman bands at 860, 930 and 950 cm-1 suggested that the coordination state of Mo6+ ions in the glasses were mainly (MoO4)2- tetrahedral units. Therefore, MoO3-containing glasses have good potential for optical applications.

  17. Comparison of sludge treatment by O3 and O3/H2O2.

    Science.gov (United States)

    Yuxin, Zhao; Liang, Wang; Helong, Yu; Baojun, Jiang; Jinming, Jiang

    2014-01-01

    This work focuses on the comparison of sludge decomposition caused by ozone (O3) alone and by ozone/hydrogen peroxide (O3/H2O2). The content of carbonaceous organic materials, nitrogenous compounds and phosphoric substances in sludge supernatant were measured. The release of soluble chemical oxygen demand, total nitrogen (TN) and total phosphorus (TP) caused by O3/H2O2 treatment were more than by O3 alone. As a result, it can be concluded that the efficiency of sludge breakup in O3/H2O2 was better than that in O3 alone. However, a peak appeared in both systems for the biodegradable substances such as carbohydrate. Carbohydrate could be used as the carbon source for denitrification, and the releasing of TN and TP may become an additional burden for a subsequent biological system. So, it was of benefit for the enhancement of cryptic growth and cost reduction by raising and maintaining the content of biodegradable substance and reducing the concentrations of the nitrogenous and phosphoric substances as far as possible. Therefore, sludge treated by O3/H2O2 with lower O3 dose would be more suitable than O3 alone.

  18. Vacancy induced metallicity at the CaHfO3/SrTiO3 interface

    KAUST Repository

    Nazir, Safdar

    2011-03-31

    Density functional theory is used to study the electronic properties of the oxide heterointerfaceCaHfO3/SrTiO3. Structural relaxation is carried out with and without O vacancies. As compared to related interfaces, strongly reduced octahedral distortions are found. Stoichiometric interfaces between the wide band gap insulatorsCaHfO3 and SrTiO3 turn out to exhibit an insulating state. However, interface metallicity is introduced by O vacancies, in agreement with experiment. The reduced octahedral distortions and necessity of O deficiency indicate a less complicated mechanism for the creation of the interfacial electron gas.

  19. Dielectric response of BaZrO3/BaTiO3 superlattice

    Directory of Open Access Journals (Sweden)

    D. Wang

    2016-06-01

    Full Text Available We use the first-principles-based molecular dynamic approach to simulate dipolar dynamics of BaZrO3/BaTiO3 superlattice, and obtain its dielectric response. The dielectric response is decomposed into its compositional, as well as the in-plane and out-of-plane parts, which are then discussed in the context of chemical ordering of Zr/Ti ions. We reveal that, while the in-plane dielectric response of BaZrO3/BaTiO3 superlattice also shows dispersion over probing frequency, it shall not be categorized as relaxor.

  20. Metastable honeycomb SrTiO3/SrIrO3 heterostructures

    International Nuclear Information System (INIS)

    Anderson, T. J.; Ryu, S.; Podkaminer, J. P.; Ma, Y.; Eom, C. B.; Zhou, H.; Xie, L.; Irwin, J.; Rzchowski, M. S.; Pan, X. Q.

    2016-01-01

    Recent theory predictions of exotic band topologies in (111) honeycomb perovskite SrIrO 3 layers sandwiched between SrTiO 3 have garnered much attention in the condensed matter physics and materials communities. However, perovskite SrIrO 3 film growth in the (111) direction remains unreported, as efforts to synthesize pure SrIrO 3 on (111) perovskite substrates have yielded films with monoclinic symmetry rather than the perovskite structure required by theory predictions. In this study, we report the synthesis of ultra-thin metastable perovskite SrIrO 3 films capped with SrTiO 3 grown on (111) SrTiO 3 substrates by pulsed laser deposition. The atomic structure of the ultra-thin films was examined with scanning transmission electron microscopy (STEM), which suggests a perovskite layering distinct from the bulk SrIrO 3 monoclinic phase. In-plane 3-fold symmetry for the entire heterostructure was confirmed using synchrotron surface X-ray diffraction to measure symmetry equivalent crystal truncation rods. Our findings demonstrate the ability to stabilize (111) honeycomb perovskite SrIrO 3 , which provides an experimental avenue to probe the phenomena predicted for this material system.

  1. Effects of oxygen vacancy on the photoconductivity in BaSnO3

    Science.gov (United States)

    Park, Jisung; Char, Kookrin; Institute of Applied Physics, Department of Physics; Astronomy, Seoul National University Team

    We have found the photoconductive behavior of BaSnO3, especially their magnitude and time dependence, is very sensitive to the oxygen vacancy concentration. We made epitaxial BaSnO3 film with BaHfO3 buffer layer by pulsed laser deposition. As we had reported before, MgO substrate with its large band gap size about 7.8 eV was used to exclude any photoconductance from the substrate. BaHfO3 layer was used to reduce the threading dislocation density in BaSnO3 film. To control the oxygen vacancy concentration in the BaSnO3 film, we annealed the sample in Ar or O2 atmosphere with varying annealing conditions. After each annealing process, photoconductivity of BaSnO3 was measured during illumination of UV light. The result showed that the magnitude of photoconductivity of BaSnO3 increased after annealing at higher temperature in Ar atmosphere, while the changes in the dark current remains minimal. The result can be explained by a hole trap mechanism. Higher Fermi level due to the increased oxygen vacancy concentration can cause occupation of deep acceptor levels in dislocations of the BaSnO3 film. These occupied deep acceptor levels in turn trap photo-generated holes so that the recombination of electron-hole pair is deterred. Samsung Science and Technology Foundation.

  2. Frustration of Negative Capacitance in Al2O3/BaTiO3 Bilayer Structure.

    Science.gov (United States)

    Kim, Yu Jin; Park, Min Hyuk; Lee, Young Hwan; Kim, Han Joon; Jeon, Woojin; Moon, Taehwan; Kim, Keum Do; Jeong, Doo Seok; Yamada, Hiroyuki; Hwang, Cheol Seong

    2016-01-08

    Enhancement of capacitance by negative capacitance (NC) effect in a dielectric/ferroelectric (DE/FE) stacked film is gaining a greater interest. While the previous theory on NC effect was based on the Landau-Ginzburg-Devonshire theory, this work adopted a modified formalism to incorporate the depolarization effect to describe the energy of the general DE/FE system. The model predicted that the SrTiO3/BaTiO3 system will show a capacitance boost effect. It was also predicted that the 5 nm-thick Al2O3/150 nm-thick BaTiO3 system shows the capacitance boost effect with no FE-like hysteresis behavior, which was inconsistent with the experimental results; the amorphous-Al2O3/epitaxial-BaTiO3 system showed a typical FE-like hysteresis loop in the polarization - voltage test. This was due to the involvement of the trapped charges at the DE/FE interface, originating from the very high field across the thin Al2O3 layer when the BaTiO3 layer played a role as the NC layer. Therefore, the NC effect in the Al2O3/BaTiO3 system was frustrated by the involvement of reversible interface charge; the highly stored charge by the NC effect of the BaTiO3 during the charging period could not be retrieved during the discharging process because integral part of the polarization charge was retained within the system as a remanent polarization.

  3. LIMS/Nimbus-7 Level 3 Daily Vertical Profiles of O3, NO2, H2O, HNO3, Geopotential Height, and Temperature as 2deg Latitude Spaced Fourier Coefficients V006

    Data.gov (United States)

    National Aeronautics and Space Administration — The Limb Infrared Monitor of the Stratosphere (LIMS) version 6 Level-3 data product consists of daily, 2 degree zonal Fourier coefficients, of vertical profiles of...

  4. LIMS/Nimbus-7 Level 2 Vertical Profiles of O3, NO2, H2O, HNO3, Geopotential Height, and Temperature V006 (LIMSN7L2) at GES DISC

    Data.gov (United States)

    National Aeronautics and Space Administration — The Limb Infrared Monitor of the Stratosphere (LIMS) version 6 Level-2 data product consists of daily, geolocated, vertical profiles of temperature, geopotential...

  5. Surface modified Al2O3 in fluorinated polyimide/Al2O3 ...

    Indian Academy of Sciences (India)

    the mechanical and thermal properties of polymers (Li et al. 2010). Herein, we wish to report the synthesis and characte- rization of fluorinated PI–Al2O3 nanocomposite films via in situ polymerization using different contents of surface modified Al2O3 nanoparticles as filler and fluorinated PI as the matrix. PI which was used ...

  6. Photocatalytic properties of KBiO3 and LiBiO3 with tunnel structures

    Indian Academy of Sciences (India)

    In the present study, KBiO3 is synthesized by a standard oxidation technique while LiBiO3 is prepared by hydrothermal method. The synthesized catalysts are characterized by X-ray diffraction (XRD), Scanning ElectronMicroscopy (SEM), BET surface area analysis and Diffuse Reflectance Spectroscopy (DRS). The XRD ...

  7. Physical and electrical properties of SrTiO3 and SrZrO3

    Directory of Open Access Journals (Sweden)

    Muhamad Norhizatol Fashren

    2017-01-01

    Full Text Available Perovskite type oxide strontium titanate (SrTiO3 and strontium zirconate (SrZrO3 ceramic powder has been synthesized using conventional solid state reaction method. The powders were mixed and ground undergone calcinations at 1400°C for 12 h and sintered at 1550°C for 5h. X-ray Diffraction exposes physical properties SrTiO3 which exhibit cubic phase (space group: pm-3m at room temperature meanwhile SrZrO3 has Orthorhombic phase (space group: pnma. The electrical properties such as dielectric constant (εr, dielectric loss (tan δ, and conductivity (σ were studied in variation temperature and frequency. High dielectric constant of SrTiO3 and SrZrO3 were observed at 10 kHz for both samples about 240 and 21 respectively at room temperature. The dielectric loss of SrTiO3 and SrZrO3 is very low loss value approximately 0.00076 and 0.67512 indicates very good dielectric.

  8. modified BiFeO3–BaTiO3

    Indian Academy of Sciences (India)

    Zr0.05Ti0.95)O3 (BF–BZT) + 0.6 wt% MnO2 (used as a donor to reduce oxygen vacancies formed during calcination and sintering) ceramics were pre- pared by the conventional solid-state reaction method. Dried oxides of high-purity Bi2O3, ...

  9. Characteristics of ambient ozone (O3) pollution and health risks in Zhejiang Province.

    Science.gov (United States)

    Chen, Yuanchen; Zang, Lu; Chen, Jinyuan; Xu, Da; Yao, Defei; Zhao, Meirong

    2017-12-01

    Troposphere ozone, which is from secondary formation processes, has been increasing dramatically during the last decades in China, inducing high health risks. In this study, temporal and spatial distribution of O 3 was studied among 13 sites of three cities during 2014-2016. The objectives were to clarify the characteristics of the ambient pollution of O 3 under the influence from other pollutants and meteorological parameters and the health outcomes from exposure to O 3 . The concentrations of O 3 during summer were much higher than those during winter, and the concentrations in downtown areas were higher than in rural or mountain areas. PM 2.5 , NO 2 , SO 2 , and wind speed (WS) were negatively correlated with O 3 , and CO, temperature (T), and relative humidity (RH) were positively correlated with O 3 . In multivariable analysis, two separate factors-solar radiation and atmospheric diffusion status, affected the O 3 levels. The concentrations of O 3 reached the highest level at 15:00 and the lowest value at about 6:00-8:00, with the similar trend to T and WS, and opposite to RH. According to the dose-response model, relative risks (RRs) and population attributable fractions (PAFs) with confidence intervals (CIs) for chronic obstructive pulmonary disease (COPD) from exposure to O 3 were 1.0612 (CI 1.0607-1.0616) and 5.32% (CI 5.29-5.36%), respectively, attributable to 2000 deaths in Zhejiang Province in 2014.

  10. Thermoluminescence of LaAlO3

    International Nuclear Information System (INIS)

    Morales H, A.; Zarate M, J.; Rivera M, T.; Azorin N, J.

    2015-10-01

    In this paper the thermoluminescent properties of doped lanthanum aluminate (LaAlO 3 ) with dysprosium ion (Dy) were studied. The thermoluminescence characteristics in the samples were obtained using an ultraviolet radiation of 220 nm. The LaAlO 3 :Dy samples were prepared by the modified Pechini method (Spray Dryer). The structural and morphological characterization was obtained by X-ray diffraction (XRD) and scanning electron microscopy (Sem) techniques respectively. The size particle composing the agglomerate was determined by Sem, agglomerated particles composed size of 2μm were observed. The thermoluminescence response of LaAlO 3 :Dy was compared with that obtained with the undoped sample. Thermoluminescence brightness curves of LaAlO 3 :Dy showed a peak centered at 185 grades C. Sensitivity of doped sample was greater, about 100 times compared with the undoped sample. Thermoluminescence response in function of the wavelength showed a maximum at 220 nm. Also the fading in thermoluminescence response was studied. (Author)

  11. Spectroscopic properties of LaAlO3 single-crystal doped with Tb3+ ions

    Science.gov (United States)

    Sztolberg, D.; Brzostowski, B.; Dereń, P. J.

    2018-04-01

    LaAlO3 monocrystal doped with 0.5 wt% Tb3+ ions was grown by the Czochralski method. Absorption, emission and emission decay time were measured 300 K in the IR, visible and near UV range. The Tb3+ energy levels in LaAlO3 were assigned both from the absorption and emission spectra.

  12. Altered performance of forest pests under atmospheres enriched by C02 and O3

    Science.gov (United States)

    Kevin E. Percy; Caroline S. Awmack; Richard L. Lindroth; Mark E. Kubiske; Brian J. Kopper; J. G. Isebrands; Kurt S. Pregitzer; George R. Hendrey; Richard E. Dickson; Donald R. Zak; Elina Oksanen; Jaak Sober; Richard Harrington; David F. Karnosky

    2002-01-01

    Human activity causes increasing background concentrations of the greenhouse gases C02 and O3. Increased levels of C02 can be found in all terrestrial ecosystems. Damaging O3 concentrations currently occur over 29% of the world's temperate and subpolar forests but are...

  13. Hydrothermal syntheses and characterization of two layered molybdenum selenites, Rb2(MoO3)3SeO3 and Tl2(MoO3)3SeO3

    International Nuclear Information System (INIS)

    Dussack, L.L.; Harrison, W.T.A.; Jacobson, A.J.

    1996-01-01

    The hydrothermal syntheses of Rb 2 (MoO 3 ) 3 SeO 3 , and Tl 2 (MoO 3 ) 3 SeO 3 are described. These compounds have structures built up from hexagonal-WO 3 -type sheets and are isostructural with the previously reported Cs 2 (MoO 3 ) 3 SeO 3 and (NH 4 ) 2 (MoO 3 ) 3 SeO 3 . Powder X-ray, thermogravimetric, and spectroscopic data are presented and discussed

  14. Raman spectra of MgSiO3 . 10% Al2O3-perovskite at various pressures and temperatures

    International Nuclear Information System (INIS)

    Liu Lingun; Irifune, T.

    1995-01-01

    Variations of Raman spectra of MgSiO 3 . 10% Al 2 O 3 -perovskite were investigated up to about 270 kbar at room temperature and in the range 108-425 K at atmospheric pressure. Like MgSiO 3 -perovskite, the Raman frequencies of MgSiO 3 . 10% Al 2 O 3 -perovskite increase nonlinearly with increasing pressure and decrease linearly with increasing temperature within the experimental uncertainties and the range investigated. A comparison of these data with those of MgSiO 3 -perovskite suggests that MgSiO 3 . 10% Al 2 O 3 -perovskite is slightly more compressible than MgSiO 3 -perovskite, and that the volume thermal expansion for MgSiO 3 . 10% Al 2 O 3 -perovskite is also slightly greater than that for MgSiO 3 -perovskite. (orig.)

  15. Ho2O3 additive effects on BaTiO3 ceramics microstructure and dielectric properties

    Directory of Open Access Journals (Sweden)

    Paunović Vesna

    2012-01-01

    Full Text Available Doped BaTiO3-ceramics is very interesting for their application as PTCR resistors, multilayer ceramic capacitors, thermal sensors etc. Ho doped BaTiO3 ceramics, with different Ho2O3 content, ranging from 0.01 to 1.0 wt% Ho, were investigated regarding their microstructural and dielectric characteristics. The samples were prepared by the conventional solid state reaction and sintered at 1320° and 1380°C in an air atmosphere for 4 hours. The grain size and microstructure characteristics for various samples and their phase composition was carried out using a scanning electron microscope (SEM equipped with EDS system. SEM analysis of Ho/BaTiO3 doped ceramics showed that in samples doped with a rare-earth ions low level, the grain size ranged from 20-30μm, while with the higher dopant concentration the abnormal grain growth is inhibited and the grain size ranged between 2- 10μm. Dielectric measurements were carried out as a function of temperature up to 180°C. The low doped samples sintered at 1380°C, display the high value of dielectric permittivity at room temperature, 2400 for 0.01Ho/BaTiO3. A nearly flat permittivity-response was obtained in specimens with higher additive content. Using a Curie-Weiss low and modified Curie-Weiss low the Curie constant (C, Curie temperature (Tc and a critical exponent of nonlinearity (γ were calculated. The obtained value of γ pointed out that the specimens have almost sharp phase transition. [Projekat Ministarstva nauke Republike Srbije, br. 172057: Directed synthesis, structure and properties of multifunctional materials

  16. Neutron irradiation damage in Al2O3 and Y2O3

    International Nuclear Information System (INIS)

    Clinard, F.W. Jr.; Bunch, J.M.; Ranken, W.A.

    1975-01-01

    Two ceramics under consideration for use in fusion reactors, Al 2 O 3 and Y 2 O 3 , were irradiated in the EBR-II fission reactor at 650, 875, and 1025 0 K to fluences between 2 and 6 x 10 21 n/cm 2 (E greater than 0.1 MeV). Samples evaluated include sapphire, Lucalox, alumina, Y 2 O 3 , and Y 2 O 3 -10 percent ZrO 2 (Yttralox). All Al 2 O 3 specimens swelled significantly (1 to 3 percent), with most of the growth observed in sapphire along the c-axis at the higher temperatures. Al 2 O 3 samples irradiated at 875 to 1025 0 K contained a high density of small aligned ''pores''. Irradiated Y 2 O 3 -based ceramics exhibited dimensional stability and a defect content consisting primarily of unresolved damage and/or dislocation loops. The behavior of these ceramics under irradiation is discussed, and the relevance of fission neutron damage studies to fusion reactor applications is considered. (auth)

  17. Chemistry of the Fe2O3/BiFeO3 Interface in BiFeO3 Thin Film Heterostructures

    Directory of Open Access Journals (Sweden)

    Valanoor Nagarajan

    2010-12-01

    Full Text Available We investigate the interfacial chemistry of secondary Fe2O3 phases formed in a BiFeO3 (BFO layer in BFO/ La0.67Sr0.33MnO3 (LSMO/SrTiO3 (STO heterostructures. A combination of high-resolution spherical aberration corrected scanning TEM and spectroscopy results, reveals that specific chemical and crystallographic similarities between Fe2O3 and BFO, enable the BFO layer to form a facile host for Fe2O3.

  18. Pre-Treatment of Antibiotic Formulation Wastewater by O3, O3/H2O2, and O3/UV Processes

    OpenAIRE

    O, Pre-Treatment of Antibiotic Formulation

    2004-01-01

    The treatment of synthetically prepared antibiotic formulation wastewater with O3, O3/H2O2, and O3/UV processes was examined. The efficiencies of the treatment processes were compared by means of COD, absorbance removals, and biodegradability enhancement. The efficiencies of O3/pH = 7, O3/ pH = 12, and O3/H2O2 (50 mM) processes were almost identical in terms of COD and UV254 removals. The BOD5/COD ratio of formulation wastewater increased from 0.02 to 0.38 and 0.5 at the end of 1 hr...

  19. Exposure Assessment of Sb2O3 in PET Food Contact Materials.

    Science.gov (United States)

    Zhu, Lei; Wang, Zhu Tian; Xu, Hai Bin; Sun, Ru Bao; Zhang, Hong; Zhang, Jian Bo

    2016-04-01

    This study was conducted to do exposure assessment of the possible migration of antimony trioxide (Sb2O3) from Polyethylene terephthalate (PET) food contact materials (FCM). Consumption Factor (CF) and Food-type Distribution Factor (fT) were calculated from survey data with reference to the US FDA method. The most conservative migration conditions were obtained by testing Sb migration from PET FCM based on the Chinese national standard of GB/T 5009.101-2003[1]. Migration levels of Sb from PET FCM were tested and migration levels of Sb2O3 were obtained through molecular weight conversion between Sb and Sb2O3. Exposure assessment of Sb2O3 was undertaken. The Chinese Estimated Daily Intake (EDI) of Sb2O3 resulted from PET FCM was 90.7 ng p-1d-1. Copyright © 2016 The Editorial Board of Biomedical and Environmental Sciences. Published by China CDC. All rights reserved.

  20. O(3)-invariant tunneling in general relativity

    International Nuclear Information System (INIS)

    Berezin, V.A.; Tkachev, I.I.; Kuzmin, V.A.; AN SSSR, Moscow. Inst. Yadernykh Issledovanij)

    1987-12-01

    We derived a general formula for the action for any O(3)-invariant tunneling processes in false vacuum decay in general relativity. The general classification of the bubble Euclidean trajectories is elaborated and explicit expressions for bounces for some processes like the vacuum creation of a double bubble, in particular in the vicinity of a black hole; the subbarrier creation of the Einstein-Rosen bridge, creation from nothing of two Minkowski worlds connected by a shell etc., are given. (orig.)

  1. Adsorption heats of olefins on supported MoO3/Al2O3 catalists

    International Nuclear Information System (INIS)

    Grinev, V.E.; Madden, M.; Khalit, V.A.; Aptekar', E.L.; Aldag, A.; Krylov, O.V.

    1983-01-01

    Adsorption heats of C 2 H 4 , C 3 H 6 and C 4 H 8 on supported MoO 3 /Al 2 O 3 catalysts containing 6, 10 and 15 wt. % of MoO 3 at 25, 77 and 195 deg are determimed. Adsorption heat of an olefin increases with a growing length of its carbonic chain. The number of adsorbed olefin molecules grows with an increase in the MoO 3 concentration, while initial adsorption heats decrease. The number of adsorbed olefins is proportional to mean rate of molybdenum reduction in catalysts. Adsorption heats of oxygen on the surface of the catalysts with preliminarily adsorbed olefins are determined. It is shown that adsorption of oxygen and olefins proceeeds both on the same and on different centres of the surface. Mechanisms of surface interactions are discussed

  2. High-temperature phases of NaNbO3 and NaTaO3.

    Science.gov (United States)

    Darlington; Knight

    1999-02-01

    The high-temperature phases of the perovskites sodium niobate, NaNbO(3), and sodium tantalate, NaTaO(3), have been re-examined using the high-resolution powder diffractometer HRPD at the ISIS neutron spallation source; the two materials show the same sequence of phases with tilted octahedra. Diffraction patterns were measured every 5 K allowing structural changes with temperature within a single phase to be determined for the first time. Previous structure determinations within one phase had been performed at a single temperature only. The octahedra are tilted about pseudocubic directions and are also deformed; the magnitude of the deformation is shown to be proportional to the square of the angle of tilt as expected from a phenomenological theory applied to such transitions. The structures of NaNbO(3) between 753 and 793 K and of NaTaO(3) below 758 K are not as reported in the literature.

  3. Luminescence of Mn4+ ions in CaTiO3 and MgTiO3 perovskites: Relationship of experimental spectroscopic data and crystal field calculations

    Science.gov (United States)

    Đorđević, Vesna; Brik, Mikhail G.; Srivastava, Alok M.; Medić, Mina; Vulić, Predrag; Glais, Estelle; Viana, Bruno; Dramićanin, Miroslav D.

    2017-12-01

    Herein, the synthesis, structural and crystal field analysis and optical spectroscopy of Mn4+ doped metal titanates ATiO3 (A = Ca, Mg) are presented. Materials of desired phase were prepared by molten salt assisted sol-gel method in the powder form. Crystallographic data of samples were obtained by refinement of X-ray diffraction measurements. From experimental excitation and emission spectra and structural data, crystal field parameters and energy levels of Mn4+ in CaTiO3 and MgTiO3 were calculated by the exchange charge model of crystal-field theory. It is found that crystalline field strength is lower (Dq = 1831 cm-1) in the rhombohedral Ilmenite MgTiO3 structure due to the relatively longer average Mn4+sbnd O2- bond distance (2.059 Å), and higher (Dq = 2017 cm-1) in orthorhombic CaTiO3 which possess shorter average Mn4+sbnd O2- bond distance (1.956 Å). Spectral positions of the Mn4+2Eg → 4A2g transition maxima is 709 nm in MgTiO3 and 717 nm in CaTiO3 respectively in good agreement with calculated values.

  4. DO3SE model applicability and O3 flux performance compared to AOT40 for an O3-sensitive tropical tree species (Psidium guajava L. 'Paluma').

    Science.gov (United States)

    Assis, Pedro I L S; Alonso, Rocío; Meirelles, Sérgio T; Moraes, Regina M

    2015-07-01

    Phytotoxic ozone (O3) levels have been recorded in the Metropolitan Region of São Paulo (MRSP). Flux-based critical levels for O3 through stomata have been adopted for some northern hemisphere species, showing better accuracy than with accumulated ozone exposure above a threshold of 40 ppb (AOT40). In Brazil, critical levels for vegetation protection against O3 adverse effects do not exist. The study aimed to investigate the applicability of O3 deposition model (Deposition of Ozone for Stomatal Exchange (DO3SE)) to an O3-sensitive tropical tree species (Psidium guajava L. 'Paluma') under the MRSP environmental conditions, which are very unstable, and to assess the performance of O3 flux and AOT40 in relation to O3-induced leaf injuries. Stomatal conductance (g s) parameterization for 'Paluma' was carried out and used to calculate different rate thresholds (from 0 to 5 nmol O3 m(-2) projected leaf area (PLA) s(-1)) for the phytotoxic ozone dose (POD). The model performance was assessed through the relationship between the measured and modeled g sto. Leaf injuries were analyzed and associated with POD and AOT40. The model performance was satisfactory and significant (R (2) = 0.56; P < 0.0001; root-mean-square error (RMSE) = 116). As already expected, high AOT40 values did not result in high POD values. Although high POD values do not always account for more injuries, POD0 showed better performance than did AOT40 and other different rate thresholds for POD. Further investigation is necessary to improve our model and also to check if there is a critical level of ozone in which leaf injuries arise. The conclusion is that the DO3SE model for 'Paluma' is applicable in the MRSP as well as in temperate regions and may contribute to future directives.

  5. [Advanced Treatment of Incineration Leachate with O3-BAC and Double O3-BAC].

    Science.gov (United States)

    Du, An-jing; Fan, Ju-hong; Liu, Rui; Qiu, Song-kai; Wen, Xiao-gang; Chen, Lü-jun

    2015-11-01

    Ozone-biological activated carbon (O3-BAC) process and double O3-BAC process were respectively used for advanced treatment of the biologically treated effluent of incineration leachate, and their pollutant removal performances were compared. The results showed that the double O3-BAC removed 75.9% ± 2.1% of chemical oxygen demand (COD), 78.8% ± 2.9% of UV254 and 96.8% ± 0.9% of color at ozone dosage of 200 mg x L(-1). The treated effluent was with COD of below 100 mg x L(-1) and color of below 40 times, meeting the emission requirements of GB 16889-2008. At the same ozone dosage, however, the O3-BAC removed 68.2% ± 1.3% of COD, 69.7% ± 0.5% of UV254 and 92.5% ± 1.1% of color. The treated effluent was with COD of around 150 mg x L(-1) and color of about 60 times, failing to meet the emission requirements. Namely, ozone of 290 mg x L(-1) was required by O3-BAC in order to achieve similar pollutant removals as those in double O3-BAC at O3 dosage of 200 mg x L(-1). In double O3-BAC at ozone dosage of 200 mg x L(-1), total phosphorus was removed by 63.5% ± 4.4%, and the phosphorus concentration in the effluent was remained 1 mg x L(-1) or less, directly meeting the emission requirement of GB 16889-2008.

  6. Dielectric enhancement of BaTiO3/SrTiO3 superlattices with embedded Ni nanocrystals

    International Nuclear Information System (INIS)

    Xiong Zhengwei; Sun Weiguo; Wang Xuemin; Jiang Fan; Wu Weidong

    2012-01-01

    Highlights: ► The BaTiO 3 /SrTiO 3 superlattices with embedded Ni NCs were successfully fabricated by L-MBE. ► The influence with the various concentrations of Ni nanocrystals embedded in BaTiO 3 /SrTiO 3 superlattices was also discussed. ► The BaTiO 3 /SrTiO 3 superlattices with lower concentration of embedded Ni NCs had higher permittivity and dielectric loss compared with the pure BaTiO 3 /SrTiO 3 superlattices. ► The dielectric enhancement of BaTiO 3 /SrTiO 3 superlattices with embedded Ni NCs was proposed to explained by Drude quasi-free-electron theory. - Abstract: The self-organized Ni nanocrystals (NCs) were embedded in BaTiO 3 /SrTiO 3 superlattices using laser molecular beam epitaxy (L-MBE). The stress of the composite films was increased with the increasing concentration of embedded Ni NCs, as investigation in stress calculation. The influence with the various concentrations of Ni NCs embedded in BaTiO 3 /SrTiO 3 superlattices was also discussed. The internal stress of the films was too strong to epitaxial growth of BaTiO 3 /SrTiO 3 superlattices. Compared with the pure BaTiO 3 /SrTiO 3 superlattices, the BaTiO 3 /SrTiO 3 superlattices with lower concentration of embedded Ni NCs had higher permittivity and dielectric loss. Furthermore, the dielectric enhancement of BaTiO 3 /SrTiO 3 superlattices with embedded Ni NCs was proposed to explained by Drude quasi-free-electron theory.

  7. Nature of Weak Magnetism in SrTiO3/LaAlO3 Multilayers

    Science.gov (United States)

    Salman, Z.; Ofer, O.; Radovic, M.; Hao, H.; Ben Shalom, M.; Chow, K. H.; Dagan, Y.; Hossain, M. D.; Levy, C. D. P.; MacFarlane, W. A.; Morris, G. M.; Patthey, L.; Pearson, M. R.; Saadaoui, H.; Schmitt, T.; Wang, D.; Kiefl, R. F.

    2012-12-01

    We report the observation of weak magnetism in superlattices of LaAlO3/SrTiO3 using β-detected nuclear magnetic resonance. The spin lattice relaxation rate of Li8 in superlattices with a spacer layers of 8 and 6 unit cells of LaAlO3 exhibits a strong peak near ˜35K, whereas no such peak is observed in a superlattice with spacer layer thickness of 3 unit cells. We attribute the observed temperature dependence to slowing down of weakly coupled electronic moments at the LaAlO3/SrTiO3 interface. These results show that the magnetism at the interface depends strongly on the thickness of the spacer layer, and that a minimal thickness of ˜4-6 unit cells is required for the appearance of magnetism. A simple model is used to determine that the observed relaxation is due to small fluctuating moments (˜0.002μB) in the two samples with a larger LaAlO3 spacer thickness.

  8. Conductivity of A- and B-site doped LaAlO3, LaGaO3, LaScO3 and LaInO3 perovskites

    DEFF Research Database (Denmark)

    Lybye, D.; Poulsen, F.W.; Mogensen, Mogens Bjerg

    2000-01-01

    The conductivity of the materials LaAlO3, LaGaO3, LaScO3 and LaInO3 all doped with 10% strontium on the A-site and 10% magnesium at the B-site has been measured at different temperatures and oxygen partial pressures. The doped LaGaO3 is found to be an almost pure ionic conductor with a conductivi...

  9. Formation of a 25 mol% Fe2O3-Al2O3 solid solution prepared by ball milling

    DEFF Research Database (Denmark)

    Jiang, Jianzhong; Mørup, Steen; Linderoth, Søren

    1996-01-01

    The phase transformation process of a 25 mol% Fe2O3-Al2O3 powder mixture during high-energy ball milling has been studied by x-ray diffraction and Mossbauer spectroscopy. A metastable solid solution of 25 mol % Fe2O3 in Al2O3 with corundum structure has successfully been prepared after a milling...

  10. TES/Aura L2 O3 Limb Special Observation V006

    Data.gov (United States)

    National Aeronautics and Space Administration — The TES Aura L2 O3 data consist of information for one molecular species for an entire Global Survey or Special Observation. TES Level 2 data contain retrieved...

  11. Multiferroic RMnO3 thin films

    Science.gov (United States)

    Fontcuberta, Josep

    2015-03-01

    Multiferroic materials have received an astonishing attention in the last decades due to expectations that potential coupling between distinct ferroic orders could inspire new applications and new device concepts. As a result, a new knowledge on coupling mechanisms and materials science has dramatically emerged. Multiferroic RMnO3 perovskites are central to this progress, providing a suitable platform to tailor spin-spin and spin-lattice interactions. With views towards applications, the development of thin films of multiferroic materials have also progressed enormously and nowadays thin-film manganites are available, with properties mimicking those of bulk compounds. Here we review achievements on the growth of hexagonal and orthorhombic RMnO3 epitaxial thin films and the characterization of their magnetic and ferroelectric properties, we discuss some challenging issues, and we suggest some guidelines for future research and developments. En ce qui concerne les applications, le développement de films minces de matériaux multiferroïques a aussi énormément progressé, et de nos jours des films minces de manganites avec des propriétés similaires à celles des matériaux massifs existent. Nous passons en revue ici les résultats obtenus dans le domaine de la croissance de couches minces épitaxiés de RMnO3 hexagonal et orthorhombique et de la caractérisation de leurs propriétés magnétiques et ferroélectriques. Nous discutons certains enjeux et proposons quelques idées pour des recherches et développements futurs.

  12. Direct approach for flexoelectricity from first-principles calculations: cases for SrTiO3 and BaTiO3

    International Nuclear Information System (INIS)

    Xu, Tao; Wang, Jie; Shimada, Takahiro; Kitamura, Takayuki

    2013-01-01

    Understanding the nature of flexoelectricity, which is the linear response of electric polarization to a strain gradient, has recently become crucial for nanostructured dielectrics and ferroelectrics because of their complicated strain distribution. This paper presents a direct and full approach at the atomic level to predict flexoelectricity for dielectrics based on first-principles calculations. The flexoelectric coefficients of BaTiO 3 and SrTiO 3 are directly calculated as the representatives of ferroelectric and paraelectric materials, respectively. For SrTiO 3 , the flexoelectric coefficients predicted from our approach are in good agreement with the experimental measurements. For BaTiO 3 , our predictions have a large discrepancy from the experimental measurements. In a practical situation, defect and surface effects are inevitable, and have a significant influence on the flexoelectricity. Direct methods have the advantage of including the extrinsic contributions from surface and defect effects. (paper)

  13. Direct approach for flexoelectricity from first-principles calculations: cases for SrTiO3 and BaTiO3.

    Science.gov (United States)

    Xu, Tao; Wang, Jie; Shimada, Takahiro; Kitamura, Takayuki

    2013-10-16

    Understanding the nature of flexoelectricity, which is the linear response of electric polarization to a strain gradient, has recently become crucial for nanostructured dielectrics and ferroelectrics because of their complicated strain distribution. This paper presents a direct and full approach at the atomic level to predict flexoelectricity for dielectrics based on first-principles calculations. The flexoelectric coefficients of BaTiO3 and SrTiO3 are directly calculated as the representatives of ferroelectric and paraelectric materials, respectively. For SrTiO3, the flexoelectric coefficients predicted from our approach are in good agreement with the experimental measurements. For BaTiO3, our predictions have a large discrepancy from the experimental measurements. In a practical situation, defect and surface effects are inevitable, and have a significant influence on the flexoelectricity. Direct methods have the advantage of including the extrinsic contributions from surface and defect effects.

  14. Direct approach for flexoelectricity from first-principles calculations: cases for SrTiO3 and BaTiO3

    Science.gov (United States)

    Xu, Tao; Wang, Jie; Shimada, Takahiro; Kitamura, Takayuki

    2013-10-01

    Understanding the nature of flexoelectricity, which is the linear response of electric polarization to a strain gradient, has recently become crucial for nanostructured dielectrics and ferroelectrics because of their complicated strain distribution. This paper presents a direct and full approach at the atomic level to predict flexoelectricity for dielectrics based on first-principles calculations. The flexoelectric coefficients of BaTiO3 and SrTiO3 are directly calculated as the representatives of ferroelectric and paraelectric materials, respectively. For SrTiO3, the flexoelectric coefficients predicted from our approach are in good agreement with the experimental measurements. For BaTiO3, our predictions have a large discrepancy from the experimental measurements. In a practical situation, defect and surface effects are inevitable, and have a significant influence on the flexoelectricity. Direct methods have the advantage of including the extrinsic contributions from surface and defect effects.

  15. Atomic structures of Ruddlesden-Popper faults in LaCoO3/SrRuO3 multilayer thin films induced by epitaxial strain

    Science.gov (United States)

    Wang, Wei; Zhang, Hui; Shen, Xi; Guan, Xiangxiang; Yao, Yuan; Wang, Yanguo; Sun, Jirong; Yu, Richeng

    2018-05-01

    In this paper, scanning transmission electron microscopy is used to study the microstructures of the defects in LaCoO3/SrRuO3 multilayer films grown on the SrTiO3 substrates, and these films have different thickness of SrRuO3 (SRO) layers. Several types of Ruddlesden-Popper (R.P.) faults at an atomic level are found, and these chemical composition fluctuations in the growth process are induced by strain fields originating from the film-film and film-substrate lattice mismatches. Furthermore, we propose four types of structural models based on the atomic arrangements of the R.P. planar faults, which severely affect the functional properties of the films.

  16. Assessment of Ga2O3 technology

    Science.gov (United States)

    2016-09-15

    electronics application is the only driver for the technology at present. This type of electronics have a large commercial market , but there are...vol. 43, p. 7133, 2004. [119] A. J. Freeman, K. R. Poeppelmeier, T. O. Mason, R. P. H. Chang, and T. J. Marks, "Chemical and Thin-Film Strategies for...doped β-Ga2O3 single crystals," Applied Physics Letters, vol. 92, p. 201914, 2008. [138] R. A. Laudise, J. B. Mullin , B. Mutaftschiev, and K. Nassau

  17. Switchable Induced Polarization in LaAlO3/SrTiO3 Heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Bark, C [University of Wisconsin, Madison; Sharma, P. [University of Nebraska; Wang, Y. [University of Nebraska; Baek, Seung Hyub [University of Wisconsin, Madison; Lee, S. [University of Wisconsin, Madison; Ryu, S. [University of Wisconsin, Madison; Folkman, C H [University of Wisconsin; Paudel, Tula R [ORNL; Kumar, Amit [ORNL; Kalinin, Sergei V [ORNL; Sokolov, A. [University of Nebraska; Tsymbal, E Y [University of Nebraska, Lincoln; Rzchowski, M [University of Wisconsin; Gruverman, Alexei [ORNL; Eom, Professor Chang-Beom [University of Wisconsin, Madison

    2012-01-01

    Demonstration of a tunable conductivity of the LaAlO3/SrTiO3 interfaces drew significant attention to the development of oxide electronic structures where electronic confinement can be reduced to the nanometer range. While the mechanisms for the conductivity modulation are quite different and include metal insulator phase transition and surface charge writing, generally it is implied that this effect is a result of electrical modification of the LaAlO3 surface (either due to electrochemical dissociation of surface adsorbates or free charge deposition) leading to the change in the twodimensional electron gas (2DEG) density at the LaAlO3/SrTiO3 (LAO/STO) interface. In this paper, using piezoresponse force microscopy we demonstrate a switchable electromechanical response of the LAO overlayer, which we attribute to the motion of oxygen vacancies through the LAO layer thickness. These electrically induced reversible changes in bulk stoichiometry of the LAO layer are a signature of a possible additional mechanism for nanoscale oxide 2DEG control on LAO/STO interfaces.

  18. Facile Fabrication and Properties of Gd2O3:Eu3+, Y2O3:Eu3+ Nanophosphors and Gd2O3:Eu3+/Silica, Y2O3:Eu3+/Silica Nanocomposites

    Science.gov (United States)

    Anh, Tran Kim; Chau, Pham Thi Minh; Hai, Nguyen Thi Quy; Ha, Vu Thi Thai; Van Tuyen, Ho; Bounyavong, Sengthong; Thanh, Nguyen Trong; Minh, Le Quoc

    2018-01-01

    Gd2O3:Eu3+ and Y2O3:Eu3+ nanophosphors have been successfully fabricated by a combustion method at low temperature (350°C) in a short time (5 min) using natriethylenediaminetetraacetic acid (EDTA-Na2) as fuel. The structure, morphology and size of Gd2O3:Eu3+ and Y2O3:Eu3+ nanophosphors have been determined by x-ray diffraction and field emission scanning electron microscopy. Photoluminescence spectra indicated that the optimum Eu3+ ion concentrations with the strongest luminescence emission intensities are 5 mol.% for Y2O3:Eu3+ and 7 mol.% for Gd2O3:Eu3+. The nanocomposites of Gd2O3:Eu3+/silica and Y2O3:Eu3+/silica were fabricated by a sol-gel process with tetraethoxysilane (TEOS) as matrix material, and the nanocomposite compositions were analyzed by energy dispersion spectra. The strongest luminescence peaks from the 5D0-7F2 transition of the Eu3+ ion in Gd2O3:Eu3+ and Y2O3:Eu3+ nanophosphors are between 613 nm and 615 nm. The Gd2O3:Eu3+ and Y2O3:Eu3+ nanophosphors and their silica nanocomposites were studied to elucidate the influences of the Eu3+ concentration, host materials, annealing temperature, and weight ratio of TEOS and Gd2O3:Eu3+ or Y2O3:Eu3+.

  19. Preparation and photocatalytic properties of BaZrO3 and SrZrO3 modified with Cu2O/Bi2O3 quantum dots

    Science.gov (United States)

    Miodyńska, Magdalena; Bajorowicz, Beata; Mazierski, Paweł; Lisowski, Wojciech; Klimczuk, Tomasz; Winiarski, Michał Jerzy; Zaleska-Medynska, Adriana; Nadolna, Joanna

    2017-12-01

    In this study, we report a novel method of BaZrO3 and SrZrO3 surface modification by two different types of quantum dots (QDs, Cu2O and Bi2O3), which improved the photocatalytic performance of the obtained materials under UV-Vis light irradiation. Pristine BaZrO3 and SrZrO3 were prepared by the hydrothermal method. The deposition of Cu2O- and Bi2O3-QDs was carried out by chemical reduction. The morphology of the nanoparticles was estimated based on microscopic analysis (SEM, TEM). The perovskite structure and phase composition of polycrystals were confirmed by X-ray powder diffraction analysis (XRD). The elemental surface composition and the chemical character of detected elements were identified by X-ray photoelectron spectroscopy (XPS). The absorption ability and luminescence properties of nanocomposites were investigated by UV-Vis diffuse-reflectance spectroscopy (DRS UV-Vis) and luminescence spectroscopy. The influence of Cu2O/Bi2O3-QDs modification on the photocatalytic activity of BaZrO3 and SrZrO3 was evaluated by the phenol photodegradation process in the liquid phase under UV-Vis and toluene degradation in the gas phase under Vis irradiation. The highest photoactivity under UV-Vis light was observed for BaZrO3/1% Cu2O/33% Bi2O3 and SrZrO3/1% Cu2O/33% Bi2O3 samples. Research also demonstrated that single-type QD deposition (Cu2O or Bi2O3) on the zirconate surface decreases the photoactivity in comparison with pristine zirconates. The mechanism of photocatalytic activity of the obtained nanocomposites was investigated by the formation of hydroxyl radicals under UV-Vis irradiation in the presence of terephthalic acid.

  20. Octahedral rotations in strained LaAlO3/SrTiO3 (001 heterostructures

    Directory of Open Access Journals (Sweden)

    T. T. Fister

    2014-02-01

    Full Text Available Many complex oxides display an array of structural instabilities often tied to altered electronic behavior. For oxide heterostructures, several different interfacial effects can dramatically change the nature of these instabilities. Here, we investigate LaAlO3/SrTiO3 (001 heterostructures using synchrotron x-ray scattering. We find that when cooling from high temperature, LaAlO3 transforms from the Pm3¯m to the Imma phase due to strain. Furthermore, the first 4 unit cells of the film adjacent to the substrate exhibit a gradient in rotation angle that can couple with polar displacements in films thinner than that necessary for 2D electron gas formation.

  1. Magnetism Control by Doping in LaAlO3/SrTiO3 Heterointerfaces.

    Science.gov (United States)

    Yan, Hong; Zhang, Zhaoting; Wang, Shuanhu; Wei, Xiangyang; Chen, Changle; Jin, Kexin

    2018-04-25

    Magnetic two-dimensional electron gases at the oxide interfaces are always one of the key issues in spintronics, giving rise to intriguing magnetotransport properties. However, reports about magnetic two-dimensional electron gases remain elusive. Here, we obtain the magnetic order of LaAlO 3 /SrTiO 3 systems by introducing magnetic dopants at the La site. The transport properties with a characteristic of metallic behavior at the interfaces are investigated. More significantly, magnetic-doped samples exhibit obvious magnetic hysteresis loops and the mobility is enhanced. Meanwhile, the photoresponsive experiments are realized by irradiating all samples with a 360 nm light. Compared to magnetism, the effects of dopants on photoresponsive and relaxation properties are negligible because the behavior originates from SrTiO 3 substrates. This work paves a way for revealing and better controlling the magnetic properties of oxide heterointerfaces.

  2. Effect of Ga2O3 on the spectroscopic properties of erbium-doped boro-bismuth glasses.

    Science.gov (United States)

    Ling, Zhou; Ya-Xun, Zhou; Shi-Xun, Dai; Tie-Feng, Xu; Qiu-Hua, Nie; Xiang, Shen

    2007-11-01

    The spectroscopic properties and thermal stability of Er3+-doped Bi2O3-B2O3-Ga2O3 glasses are investigated experimentally. The effect of Ga2O3 content on absorption spectra, the Judd-Ofelt parameters Omega t (t=2, 4, 6), fluorescence spectra and the lifetimes of Er3+:4I 13/2 level are also investigated, and the stimulated emission cross-section is calculated from McCumber theory. With the increasing of Ga2O3 content in the glass composition, the Omega t (t=2, 4, 6) parameters, fluorescence full width at half maximum (FWHM) and the 4I 13/2 lifetimes of Er3+ first increase, reach its maximum at Ga2O3=8 mol.%, and then decrease. The results show that Er3+-doped 50Bi2O3-42B2O3-8Ga2O3 glass has the broadest FWHM (81nm) and large stimulated emission cross-section (1.03 x1 0(-20)cm2) in these glass samples. Compared with other glass hosts, the gain bandwidth properties of Er+3-doped Bi2O3-B2O3-Ga2O3 glass is better than tellurite, silicate, phosphate and germante glasses. In addition, the lifetime of 4I 13/2 level of Er(3+) in bismuth-based glass, compared with those in other glasses, is relative low due to the high-phonon energy of the B-O bond, the large refractive index of the host and the existence of OH* in the glass. At the same time, the glass thermal stability is improved in which the substitution of Ga2O3 for B2O3 strengthens the network structure. The suitability of bismuth-based glass as a host for a Er3+-doped broadband amplifier and its advantages over other glass hosts are also discussed.

  3. LOCAL PIEZOELECTRICITY IN SrTiO3-BiTiO3 CERAMICS

    OpenAIRE

    Grigalaitis, R.; Bagdzevicius, S.; Banys, J.; Tornau, E. E.; Bormanis, K.; Sternberg, A.; Bdikin, I.; Kholkin, A.

    2014-01-01

    Local piezoelectric properties of Bi-doped SrTiO3 ceramics have been investigated by piezoresponse force microscopy. The appearance of both out-of-plane and in-plane polarization components confirmed the piezoelectric nature of the obtained signal. The absence of labyrinth-like structures in observed piezoelectric contrast is not consistent with the expected existence of a relaxor ferroelectric state in this material. The close similarity of local piezoelectric properties in Bi-doped SrTiO3 w...

  4. 2DEGs at perovskite interfaces between KTaO3 or KNbO3 and stannates.

    Science.gov (United States)

    Fan, Xiaofeng; Zheng, Weitao; Chen, Xin; Singh, David J

    2014-01-01

    We report density functional studies of electron rich interfaces between KTaO3 or KNbO3 and CaSnO3 or ZnSnO3 and in particular the nature of the interfacial electron gasses that can be formed. We find that depending on the details these may occur on either the transition metal or stannate sides of the interface and in the later case can be shifted away from the interface by ferroelectricity. We also present calculations for bulk KNbO3, KTaO3, CaSnO3, BaSnO3 and ZnSnO3, showing the different transport and optical properties that may be expected on the two sides of such interfaces. The results suggest that these interfaces may display a wide range of behaviors depending on conditions, and in particular the interplay with ferroelectricity suggests that electrical control of these properties may be possible.

  5. Photolysis of Pure Solid O3 and O2 Films at 193nm

    Science.gov (United States)

    Raut, U.; Loeffler, M. J.; Fama, M.; Baragiola, R. A.

    2011-01-01

    We studied quantitatively the photochemistry of solid O3 and O2 films at 193 nm and 22 K with infrared spectroscopy and microgravimetry. Photolysis of pure ozone destroyed O3, but a small amount of ozone remained in the film at high fluence. Photolysis of pure O2 produced O3 in an amount that increased with photon fluence to a stationary level. For both O2 and O3 films, the O3:O2 ratio at large fluences is ?0.07, about two orders of magnitude larger than those obtained in gas phase photolysis. This enhancement is attributed to the increased photodissociation of O2 due to photoabsorption by O2 dimers, a process significant at solid-state densities. We obtain initial quantum yield for ozone synthesis from solid oxygen, phi (O3) = 0.24 0.06, and quantum yields for destruction of O3 and O2 in their parent solids, phi(-O3) = 1.0 0.2 and phi(-O2) = 0.36 0.1. Combined with known photoabsorption cross sections, we estimate probabilities for geminate recombination of 0.5 0.1 for O3 fragments and 0.88 0.03 for oxygen atoms from O2 dissociation. Using a single parameter kinetic model, we deduce the ratio of reaction cross sections for an O atom with O2 vs. O3 to be 0.1 0.2. The general good agreement of the model with the data suggests the validity of the central assumption of efficient energy and spin relaxation of photofragments in the solid prior to their reactions with other species.

  6. Long-term O3-precursor relationships in Hong Kong: field observation and model simulation

    Science.gov (United States)

    Wang, Yu; Wang, Hao; Guo, Hai; Lyu, Xiaopu; Cheng, Hairong; Ling, Zhenhao; Louie, Peter K. K.; Simpson, Isobel J.; Meinardi, Simone; Blake, Donald R.

    2017-09-01

    Over the past 10 years (2005-2014), ground-level O3 in Hong Kong has consistently increased in all seasons except winter, despite the yearly reduction of its precursors, i.e. nitrogen oxides (NOx = NO + NO2), total volatile organic compounds (TVOCs), and carbon monoxide (CO). To explain the contradictory phenomena, an observation-based box model (OBM) coupled with CB05 mechanism was applied in order to understand the influence of both locally produced O3 and regional transport. The simulation of locally produced O3 showed an increasing trend in spring, a decreasing trend in autumn, and no changes in summer and winter. The O3 increase in spring was caused by the net effect of more rapid decrease in NO titration and unchanged TVOC reactivity despite decreased TVOC mixing ratios, while the decreased local O3 formation in autumn was mainly due to the reduction of aromatic VOC mixing ratios and the TVOC reactivity and much slower decrease in NO titration. However, the decreased in situ O3 formation in autumn was overridden by the regional contribution, resulting in elevated O3 observations. Furthermore, the OBM-derived relative incremental reactivity indicated that the O3 formation was VOC-limited in all seasons, and that the long-term O3 formation was more sensitive to VOCs and less to NOx and CO in the past 10 years. In addition, the OBM results found that the contributions of aromatics to O3 formation decreased in all seasons of these years, particularly in autumn, probably due to the effective control of solvent-related sources. In contrast, the contributions of alkenes increased, suggesting a continuing need to reduce traffic emissions. The findings provide updated information on photochemical pollution and its impact in Hong Kong.

  7. Enhanced electron mobility in epitaxial (Ba,La)SnO3 films on BaSnO3(001) substrates

    Science.gov (United States)

    Lee, Woong-Jhae; Kim, Hyung Joon; Sohn, Egon; Kim, Tai Hoon; Park, Ju-Young; Park, Woanseo; Jeong, Hyunhak; Lee, Takhee; Kim, Jin Hyeok; Choi, Ki-Young; Kim, Kee Hoon

    2016-02-01

    We report the growth of Ba1-xLaxSnO3 (x = 0.00, 0.005, 0.01, 0.02, and 0.04) thin films on the insulating BaSnO3(001) substrate by pulsed laser deposition. The insulating BaSnO3 substrates were grown by the Cu2O-CuO flux, in which the molar fraction of KClO4 was systematically increased to reduce electron carriers and thus induce a doping induced metal-insulator transition, exhibiting a resistivity increase from ˜10-3 to ˜1012 Ω cm at room temperature. We find that all the Ba1-xLaxSnO3 films are epitaxial, showing good in-plane lattice matching with the substrate as confirmed by X-ray reciprocal space mappings and transmission electron microscopy studies. The Ba1-xLaxSnO3 (x = 0.005-0.04) films showed degenerate semiconducting behavior, and the electron mobility at room temperature reached 100 and 85 cm2 V-1 s-1 at doping levels 1.3 × 1020 and 6.8 × 1019 cm-3, respectively. This work demonstrates that thin perovskite stannate films of high quality can be grown on the BaSnO3(001) substrates for potential applications in transparent electronic devices.

  8. Cooper Pair Writing at the LaAlO3/ SrTiO 3 Interface

    Science.gov (United States)

    Cen, Cheng; Bogorin, Daniela F.; Bark, Chung Wung; Folkman, Chad M.; Eom, Chang-Beom; Levy, Jeremy

    2011-03-01

    Superconducting semiconductors offer unique ways to exert electrostatic control over macroscopic quantum phases. The recently demonstrated nanoscale control over conductivity at the LaAl O3 / SrTi O3 interface raises the question of whether nanoscale control over superconducting phases can be realized. Here we report low-temperature magnetotransport experiments on structures defined with nanoscale precision at the LaAl O3 / SrTi O3 interface. A quantum phase transition is observed that is associated with the formation of Cooper pairs, but a finite resistance is observed at the lowest temperatures. Higher mobility interfaces exhibit larger Ginsburg-Landau coherence lengths, a stronger suppression of pairing by magnetic field as well as Shubnikov-de Haas oscillations. Cooper pair localization, spin-orbit coupling, and finite-size effects may factor into an explanation for some of the unusual properties observed. The work is supported by Department of Energy and State of Florida, NSF (DMR-0906443 and DMR-0704022), DOE (DE-FG02-06ER46327) and the Fine Foundation.

  9. Surface modified Al2O3 in fluorinated polyimide/Al2O3 ...

    Indian Academy of Sciences (India)

    agglomeration. One approach to decrease the aggregation of inorganic Al2O3 is surface modification of these nanoparti- cles with coupling agent which usually has a long alkyl tail and shows a good compatibility with polymer .... ture and spatial distribution of the various components, through direct visualization. Figure 5 ...

  10. High-temperature phases of NaNbO3 and NaTaO3

    International Nuclear Information System (INIS)

    Darlington, C.N.W.

    1999-01-01

    The high-temperature phases of the perovskites sodium niobate, NaNbO 3 , and sodium tantalate, NaTaO 3 , have been re-examined using the high-resolution powder diffractometer HRPD at the ISIS neutron spallation source; the two materials show the same sequence of phases with tilted octahedra. Diffraction patterns were measured every 5 K allowing structural changes with temperature within a single phase to be determined for the first time. Previous structure determinations within one phase had been performed at a single temperature only. The octahedra are tilted about pseudocubic left angle 100 right angle directions and are also deformed; the magnitude of the deformation is shown to be proportional to the square of the angle of tilt as expected from a phenomenological theory applied to such transitions. The structures of NaNbO 3 between 753 and 793 K and of NaTaO 3 below 758 K are not as reported in the literature. (orig.)

  11. Carrier-Controlled Ferromagnetism in SrTiO_{3}

    Directory of Open Access Journals (Sweden)

    Pouya Moetakef

    2012-06-01

    Full Text Available Magnetotransport and superconducting properties are investigated for uniformly La-doped SrTiO_{3} films and GdTiO_{3}/SrTiO_{3} heterostructures, respectively. GdTiO_{3}/SrTiO_{3} interfaces exhibit a high-density 2D electron gas on the SrTiO_{3} side of the interface, while, for the SrTiO_{3} films, carriers are provided by the dopant atoms. Both types of samples exhibit ferromagnetism at low temperatures, as evidenced by a hysteresis in the magnetoresistance. For the uniformly doped SrTiO_{3} films, the Curie temperature is found to increase with doping and to coexist with superconductivity for carrier concentrations on the high-density side of the superconducting dome. The Curie temperature of the GdTiO_{3}/SrTiO_{3} heterostructures scales with the thickness of the SrTiO_{3} quantum well. The results are used to construct a stability diagram for the ferromagnetic and superconducting phases of SrTiO_{3}.

  12. Band alignment at epitaxial BaSnO3/SrTiO3(001) and BaSnO3/LaAlO3(001) heterojunctions

    Science.gov (United States)

    Chambers, Scott A.; Kaspar, Tiffany C.; Prakash, Abhinav; Haugstad, Greg; Jalan, Bharat

    2016-04-01

    We have spectroscopically determined the optical bandgaps and band offsets at epitaxial interfaces of BaSnO3 with SrTiO3(001) and LaAlO3(001). 28 u.c. BaSnO3 epitaxial films exhibit direct and indirect bandgaps of 3.56 ± 0.05 eV and 2.93 ± 0.05 eV, respectively. The lack of a significant Burstein-Moss shift corroborates the highly insulating, defect-free nature of the BaSnO3 films. The conduction band minimum is lower in electron energy in 5 u.c. films of BaSnO3 than in SrTiO3 and LaAlO3 by 0.4 ± 0.2 eV and 3.7 ± 0.2 eV, respectively. This result bodes well for the realization of oxide-based, high-mobility, two-dimensional electron systems that can operate at ambient temperature, since electrons generated in the SrTiO3 by modulation doping, or at the BaSnO3/LaAlO3 interface by polarization doping, can be transferred to and at least partially confined in the BaSnO3 film.

  13. Dielectric and electromechanical properties of LiNbO3-modified (BiNa)TiO3-(BaCa)TiO3 lead-free piezoceramics

    Science.gov (United States)

    Zaman, Arif; Hussain, Ali; Malik, Rizwan Ahmed; Maqbool, Adnan; Nahm, Sahn; Kim, Myong-Ho

    2016-05-01

    The dielectric and electromechanical properties of LiNbO3-modified (1-x) [0.91Na0.5Bi0.5TiO3-0.09Ba0.70Ca0.30TiO3]-xLiNbO3 (abbreviated as (BiNa)TiO3-(BaCa)TiO3-LN) lead-free piezoceramics were investigated. The electrical properties revealed that the addition of LiNbO3 (LN) induces a phase transition from a non-ergodic relaxor to an ergodic relaxor in the (BiNa)TiO3-(BaCa)TiO3-LN system. A large electrostrain of ~0.418% with a normalized strain of ~690 pm V-1 at 6 kV mm-1 was observed at the coexistence of the non-ergodic relaxor and ergodic relaxor phases for LN 0.020, where a field-assisted reversible phase transition between metastable ferroelectric and stable ergodic relaxor phases occurs. Subsequently, a gradual enhancement in the temperature stability of the dielectric constant was observed. At 3 mol.% LN, a nearly constant temperature and a frequency-invariant permittivity of ɛ r ~ 3300 over a broad temperature range of 147 °C-306 °C was observed along with small losses from room temperature up to 400 °C.

  14. Sorption of U(VI) in surfaces of SrTiO3

    International Nuclear Information System (INIS)

    Ortiz O, H.B.; Ordonez R, E.; Fernandez V, S.M.

    2004-01-01

    In this work is presented the physico chemical characterization and evaluation of those surface properties and of sorption of U on the SrTiO 3 like possible candidate for contention barrier in the deep geological confinement. The made studies showed that the SrTiO 3 presents maximum levels of sorption of positive nature species (mainly UO 2 2+ and UO 2 NO 3 + ). (Author)

  15. On the origin of metallic conductivity at the interface of LaAlO3/SrTiO3

    DEFF Research Database (Denmark)

    Chen, Yunzhong; Christensen, Dennis; Trier, Felix

    2012-01-01

    To determine the origin of the quasi-two-dimensional electron gas formed at the interface between the two complex oxides of LaAlO3 (LAO) and SrTiO3 (STO), various amorphous films of LAO, La2O3, Al2O3, and La7/8Sr1/8MnO3 (LSMO), were deposited on TiO2-terminated (0 0 1) STO substrates by pulsed...... laser deposition at room temperature. Metallic interfaces are observed when the over-layers are amorphous LAO, La2O3, or Al2O3, while insulating interfaces are observed when the over-layer is LSMO. The interfacial conductivity of these SrTiO3-based hetero-structures shows strong dependence on both film...

  16. Growth mechanism of NaClO 3 and NaBrO 3 crystals from aqueous ...

    Indian Academy of Sciences (India)

    A study of growth rates of NaClO3 and NaBrO3 has been carried out using a small growth cell by in situ observation. Normal growth rates of {100} faces of NaClO3 and {111} faces of NaBrO3 along ⟨ 110 ⟩ direction are measured under relatively high supersaturation ranging from 3–8%. In the initial stages of growth, {100}, ...

  17. Growth mechanism of NaClO3 and NaBrO3 crystals from aqueous ...

    Indian Academy of Sciences (India)

    A study of growth rates of NaClO3 and NaBrO3 has been carried out using a small growth cell by in situ observation. Normal growth rates of {100} faces of NaClO3 and {111} faces of NaBrO3 along ⟨ 110 ⟩ direction are measured under relatively high supersaturation ranging from 3–8%. In the initial stages of growth, {100}, ...

  18. Effect of Ga2O3 addition on the properties of Y2O3-doped AlN ceramics

    Directory of Open Access Journals (Sweden)

    Shin H.

    2015-01-01

    Full Text Available Effect Ga2O3 addition on the densification and properties of Y2O3-doped AlN ceramics was investigated under the constraint of total sintering additives (Y2O3 and Ga2O3 of 4.5 wt%. Ga was detected in the AlN grain as well as the grain boundary phases. YAlO3 and Y4Al2O9 were observed as the secondary crystalline phases in all of the investigated compositions. As the substitution of Ga2O3 for Y2O3 increased, the quantity of the Y4Al2O9 phase decreased while that of YAlO3 was more or less similar. Neither additional secondary phases was identified, nor was the sinterability inhibited by the Ga2O3 addition; the linear shrinkage and apparent density were above 20 percent and 3.34-3.37 g/cm3, respectively. However, the optical reflectance and the elastic modulus generally decreased whereas the Poisson ratio increased significantly. The dielectric constant and the loss tangent of 4.0Y2O3-0.5Ga2O3-95.5Y2O3 at the resonant frequency of 8.22 GHz were 8.63 and 0.003, respectively.

  19. Thermally excited multiband conduction in LaAlO3/SrTiO3 heterostructures exhibiting scattering

    NARCIS (Netherlands)

    Guduru, V.K.; McCollam, A.; Jost, A.; Wenderich, Sander; Hilgenkamp, H.; Maan, J.C.; Brinkman, Alexander; Zeitler, U.

    2013-01-01

    Magnetotransport measurements of charge carriers at the interface of a LaAlO 3 /SrTiO 3 heterostructure with 26 unit cells of LaAlO 3 show Hall resistance and magnetoresistance which at low and high temperatures is described by a single channel of electronlike charge carriers. At intermediate

  20. High oxygen ion conduction in sintered oxides of the $Bi_2O_3-Er_2O_3$ system

    NARCIS (Netherlands)

    Verkerk, M.J.; Keizer, Klaas; Burggraaf, A.J.

    1980-01-01

    The phase diagram of the Bi2O3-Er2O3 system was investigated. A monophasic f c c structure was stabilized for samples containing 17.5–45.5 mol% Er2O3. Above and below this concentration range polyphasic regions appear. The f c c phase showed high oxygen ion conduction. The ionic transference number

  1. Valence and conduction band offsets of β-Ga2O3/AlN heterojunction

    KAUST Repository

    Sun, Haiding

    2017-10-16

    Both β-Ga2O3 and wurtzite AlN have wide bandgaps of 4.5–4.9 and 6.1 eV, respectively. We calculated the in-plane lattice mismatch between the (−201) plane of β-Ga2O3 and the (0002) plane of AlN, which was found to be 2.4%. This is the smallest mismatch between β-Ga2O3 and binary III-nitrides which is beneficial for the formation of a high quality β-Ga2O3/AlN heterojunction. However, the valence and conduction band offsets (VBO and CBO) at the β-Ga2O3/AlN heterojunction have not yet been identified. In this study, a very thin (less than 2 nm) β-Ga2O3 layer was deposited on an AlN/sapphire template to form the heterojunction by pulsed laser deposition. High-resolution X-ray photoelectron spectroscopy revealed the core-level (CL) binding energies of Ga 3d and Al 2p with respect to the valence band maximum in individual β-Ga2O3 and AlN layers, respectively. The separation between Ga 3d and Al 2p CLs at the β-Ga2O3/AlN interface was also measured. Eventually, the VBO was found to be −0.55 ± 0.05 eV. Consequently, a staggered-gap (type II) heterojunction with a CBO of −1.75 ± 0.05 eV was determined. The identification of the band alignment of the β-Ga2O3/AlN heterojunction could facilitate the design of optical and electronic devices based on these and related alloys.

  2. Stomatal regulation, structural acclimation and metabolic shift towards defensive compounds reduce O3 load in birch under chronic O3 stress

    Science.gov (United States)

    Oksanen, E.; Riikonen, J.; Kontunen-Soppela, S.; Maenpaa, M.; Rousi, M.

    2009-12-01

    Northern forests are encountering new threats due to continuously increasing load of oxidative stress, e.g. due to rising tropospheric O3 levels, and simultaneous climate warming, which is more intense in northern latitudes as compared to global means. The proportion of silver birch (Betula pendula) in Finnish forests is expected to increase with climate warming. Unfortunately, we have growing evidence that the vitality and the carbon sink strength of birch trees are weakened under chronic O3 stress. In this study we investigated the effects of slightly elevated O3 concentration (1.3 x the ambient), temperature (T) and their combination on the antioxidant defense, gas exchange and leaf growth of Betula pendula saplings (clone 12) growing in open-field conditions over two growing seasons. The plants were measured for SLA (specific leaf area), total leaf area, net photosynthesis (Pn), stomatal conductance (gs), maximum rate of carboxylation (Vc,max), maximum rate of electron transport (Jmax), relative stomatal limitation to photosynthesis (ls), dark respiration (Rd), apoplastic concentrations of AA (ascorbic acid), DHA (dehydroascobate) and total ascorbate, the redox state of apoplastic ascorbate, and total antioxidant capacity. Elevated O3 enhanced the total antioxidant capacity in the apoplast in the first year of the experiment at the ambient T. However, during the second year of the experiment, the saplings responded to elevated O3 level by closing the stomata and by developing leaves with a lower leaf area per mass, rather than by accumulating ascorbate in the apoplast. O3 did not affect the total leaf area, whereas Pn was slightly and gs significantly reduced in the second year. Elevated T enhanced the total leaf area, Pn and Vc,max, redox state of ascorbate and total antioxidant capacity in the apoplast. The effects of T and O3 on total leaf area and net photosynthesis were counteractive. We were not able to detect significant differences in Rd between the

  3. Negative Capacitance in BaTiO3/BiFeO3 Bilayer Capacitors.

    Science.gov (United States)

    Hou, Ya-Fei; Li, Wei-Li; Zhang, Tian-Dong; Yu, Yang; Han, Ren-Lu; Fei, Wei-Dong

    2016-08-31

    Negative capacitances provide an approach to reduce heat generations in field-effect transistors during the switch processes, which contributes to further miniaturization of the conventional integrated circuits. Although there are many studies about negative capacitances using ferroelectric materials, the direct observation of stable ferroelectric negative capacitances has rarely been reported. Here, we put forward a dc bias assistant model in bilayer capacitors, where one ferroelectric layer with large dielectric constant and the other ferroelectric layer with small dielectric constant are needed. Negative capacitances can be obtained when external dc bias electric fields are larger than a critical value. Based on the model, BaTiO3/BiFeO3 bilayer capacitors are chosen as study objects, and negative capacitances are observed directly. Additionally, the upward self-polarization effect in the ferroelectric layer reduces the critical electric field, which may provide a method for realizing zero and/or small dc bias assistant negative capacitances.

  4. Growing LaAlO3/SrTiO3 interfaces by sputter deposition

    Directory of Open Access Journals (Sweden)

    I. M. Dildar

    2015-06-01

    Full Text Available Sputter deposition of oxide materials in a high-pressure oxygen atmosphere is a well-known technique to produce thin films of perovskite oxides in particular. Also interfaces can be fabricated, which we demonstrated recently by growing LaAlO3 on SrTiO3 substrates and showing that the interface showed the same high degree of epitaxy and atomic order as is made by pulsed laser deposition. However, the high pressure sputtering of oxides is not trivial and number of parameters are needed to be optimized for epitaxial growth. Here we elaborate on the earlier work to show that only a relatively small parameter window exists with respect to oxygen pressure, growth temperature, radiofrequency power supply and target to substrate distance. In particular the sensitivity to oxygen pressure makes it more difficult to vary the oxygen stoichiometry at the interface, yielding it insulating rather than conducting.

  5. Theory of Valence Transition in BiNiO_{3}.

    Science.gov (United States)

    Naka, Makoto; Seo, Hitoshi; Motome, Yukitoshi

    2016-02-05

    Motivated by the colossal negative thermal expansion recently found in BiNiO_{3}, the valence transition accompanied by the charge transfer between the Bi and Ni sites is theoretically studied. We introduce an effective model for Bi-6s and Ni-3d orbitals taking into account the valence skipping of Bi cations, and investigate the ground-state and finite-temperature phase diagrams within the mean-field approximation. We find that the valence transition is caused by commensurate locking of the electron filling in each orbital associated with charge and magnetic orderings, and the critical temperature and the nature of the transitions are strongly affected by the relative energy between the Bi and Ni levels and the effective electron-electron interaction in the Bi sites. The obtained phase diagram well explains the temperature- and pressure-driven valence transitions in BiNiO_{3} and the systematic variation of valence states for a series of Bi and Pb perovskite oxides.

  6. Theory of Valence Transition in BiNiO3

    Science.gov (United States)

    Naka, Makoto; Seo, Hitoshi; Motome, Yukitoshi

    2016-02-01

    Motivated by the colossal negative thermal expansion recently found in BiNiO3 , the valence transition accompanied by the charge transfer between the Bi and Ni sites is theoretically studied. We introduce an effective model for Bi -6 s and Ni -3 d orbitals taking into account the valence skipping of Bi cations, and investigate the ground-state and finite-temperature phase diagrams within the mean-field approximation. We find that the valence transition is caused by commensurate locking of the electron filling in each orbital associated with charge and magnetic orderings, and the critical temperature and the nature of the transitions are strongly affected by the relative energy between the Bi and Ni levels and the effective electron-electron interaction in the Bi sites. The obtained phase diagram well explains the temperature- and pressure-driven valence transitions in BiNiO3 and the systematic variation of valence states for a series of Bi and Pb perovskite oxides.

  7. Wide bandgap engineering of (AlGa)2O3 films

    International Nuclear Information System (INIS)

    Zhang, Fabi; Saito, Katsuhiko; Tanaka, Tooru; Nishio, Mitsuhiro; Guo, Qixin; Arita, Makoto

    2014-01-01

    Bandgap tunable (AlGa) 2 O 3 films were deposited on sapphire substrates by pulsed laser deposition (PLD). The deposited films are of high transmittance as measured by spectrophotometer. The Al content in films is almost the same as that in targets. The measurement of bandgap energies by examining the onset of inelastic energy loss in core-level atomic spectra using X-ray photoelectron spectroscopy is proved to be valid for determining the bandgap of (AlGa) 2 O 3 films as it is in good agreement with the bandgap values from transmittance spectra. The measured bandgap of (AlGa) 2 O 3 films increases continuously with the Al content covering the whole Al content range from about 5 to 7 eV, indicating PLD is a promising growth technology for growing bandgap tunable (AlGa) 2 O 3 films.

  8. Sintering behavior of Y2O3 doped Bi2O3 ceramics

    Directory of Open Access Journals (Sweden)

    Alizadeh M.

    2007-01-01

    Full Text Available Influence of sintering temperature and soaking time on densification of Bi2O3 samples doped with 25%mol Y2O3 was investigated by shrinkage and relative density measurements. Samples were sintered in air at different temperatures in the range of 800 to 1000°C for 24 hr. The results showed that samples sintered at 950°C have the maximum relative density. Several samples were sintered at 950°C for duration of 0 to 36 hr in order to evaluate the effect of soaking time on densification of samples. It was found that the samples were sintered at 950°C for 36hr had higher relative density than others did for smaller time duration X-ray diffraction (XRD analyses detected δ -Bi2O3 as the sole stable phase in all samples. Scanning Electron Microscopy (SEM investigation of fractured surface of the samples showed that porosities decrease by increasing of sintering temperature and grow by further increasing of temperature.

  9. Tunnel magnetoresistance in Ni 80Fe 20/Al 2O 3/Co/Al 2O 3/Co junctions

    Science.gov (United States)

    Kubota, H.; Watabe, T.; Miyazaki, T.

    1999-06-01

    Tunnel magnetoresistance (TMR) effect has been investigated in Ni 80Fe 20/Al 2O 3/Co/Al 2O 3/Co double tunnel junctions. The Al 2O 3 layer was formed by a direct sputtering method with an Al 2O 3 target. The dependence of the tunnel resistance and the MR ratio on the thickness of Al 2O 3 and that of the central Co layer were investigated. The relation between the structure of the interface and TMR effect was discussed.

  10. Trends in (LaMnO3)n/(SrTiO3)m superlattices with varying layer thicknesses

    KAUST Repository

    Jilili, J.

    2015-09-01

    We investigate the thickness dependence of the structural, electronic, and magnetic properties of (LaMnO3)n/(SrTiO3)m (n, m = 2, 4, 6, 8) superlattices using density functional theory. The electronic structure turns out to be highly sensitive to the onsite Coulomb interaction. In contrast to bulk SrTiO3, strongly distorted O octahedra are observed in the SrTiO3 layers with a systematic off centering of the Ti atoms. The systems favour ferromagnetic spin ordering rather than the antiferromagnetic spin ordering of bulk LaMnO3 and all show half-metallicity, while a systematic reduction of the minority spin band gaps as a function of the LaMnO3 and SrTiO3 layer thicknesses originates from modifications of the Ti dxy states.

  11. Microstructure and electrical properties of Sm2O3 doped Bi2O3-based ZnO varistor ceramics

    International Nuclear Information System (INIS)

    Ashraf, M.A.; Bhuiyan, A.H.; Hakim, M.A.; Hossain, M.T.

    2011-01-01

    Highlights: The EDX and XRD analyses of the samples show the presence of ZnO phases, Bi-rich phases, spinel phases and Sm 2 O 3 -based phases. For varistor ceramic containing 0.30 mol% Sm 2 O 3 the value of α is 44, maximum E b value is 3000 V cm -1 and minimum value of I L is 1.10 μA. It can be inferred from the above results that the 0.30 mol% Sm 2 O 3 doped ZnO varistor ceramics is the optimum composition for best performance of these Sm 2 O 3 doped Bi 2 O 3 -based ZnO varistor ceramics. - Abstract: The dependence of the bulk density, microstructure and dc electrical properties of bismuth oxide (Bi 2 O 3 )-based zinc oxide (ZnO) varistor ceramics for various samarium oxide (Sm 2 O 3 ) contents was investigated. The value of bulk density was found to 5.43-5.50 g cm -3 with Sm 2 O 3 (mol%) content. The maximum value of bulk density is observed to be 5.50 for 0.30 mol% Sm 2 O 3 containing varistor ceramics. The grain sizes for all the samples calculated from the scanning electron micrographs were found to decrease as Sm 2 O 3 increases. The presence of ZnO phases, Bi-rich phases, spinel phases and Sm 2 O 3 phases were observed in the samples by the energy dispersive X-ray analysis and X-ray diffraction analysis. As the Sm 2 O 3 amount increased in the Bi 2 O 3 -based ZnO varistor ceramics, the nonlinear coefficient, α increased up to 0.10 mol%, reaching a maximum value of 58 and then decreased. The breakdown electric field, E b , increased with the increase of Sm 2 O 3 content with a maximum value of 3220 V cm -1 for the 0.75 mol% Sm 2 O 3 doped ZnO varistor ceramics. The leakage current, I L , showed a minimum value of 1.10 μA for the composition of 0.30 mol% Sm 2 O 3 doped Bi 2 O 3 -based ZnO varistor ceramics. The 0.30 mol% Sm 2 O 3 -doped Bi 2 O 3 -based ZnO varistor ceramics sintered at 1200 deg. C exhibited a good stability for dc accelerated aging stress of 0.90 V 1mA /90 deg. C/12 h.

  12. Processing of Piezoelectric (Li,Na,K)NbO3 Porous Ceramics and (Li,Na,K)NbO3/KNbO3 Composites

    Science.gov (United States)

    Kakimoto, Ken-ichi; Imura, Tomoya; Fukui, Yasuchika; Kuno, Masami; Yamagiwa, Katsuya; Mitsuoka, Takeshi; Ohbayashi, Kazushige

    2007-10-01

    Porous Li0.06(Na0.5K0.5)0.94NbO3 (LNKN-6) ceramics with different pore volumes have been prepared using preceramic powder and phenol resin fiber (KynolTM) as a pore former. It was confirmed that the porous ceramics synthesized by the “two-stage firing method” suppressed the loss of alkali elements from the porous body during heat treatment. The porous LNKN-6 ceramics were then converted to LNKN-6/KNbO3 composites through soaking and heat treatment using a sol-gel precursor source composed of KNbO3 to form 3-3-type composites. The microstructure, dielectric, and piezoelectric properties of the porous LNKN-6 ceramics and LNKN-6/KNbO3 composites were characterized and compared. The LNKN-6/KNbO3 composites had a hollow structure whose pores in the region near the surface were filled and coated with KNbO3 precipitates; however, a large amount of residual air was trapped in the pores inside the composites. As a result, the LNKN-6/KNbO3 composites fabricated using 30 vol % KynolTM showed an enhanced piezoelectric voltage output coefficient (g33) of 63.0× 10-3 V\\cdotm/N, compared with monolithic LNKN-6 ceramics having a g33 of 30.2× 10-3 V\\cdotm/N.

  13. Enhanced electrical and magnetic properties in La0.7Sr0.3MnO3 thin films deposited on CaTiO3-buffered silicon substrates

    Directory of Open Access Journals (Sweden)

    C. Adamo

    2015-06-01

    Full Text Available We investigate the suitability of an epitaxial CaTiO3 buffer layer deposited onto (100 Si by reactive molecular-beam epitaxy (MBE for the epitaxial integration of the colossal magnetoresistive material La0.7Sr0.3MnO3 with silicon. The magnetic and electrical properties of La0.7Sr0.3MnO3 films deposited by MBE on CaTiO3-buffered silicon (CaTiO3/Si are compared with those deposited on SrTiO3-buffered silicon (SrTiO3/Si. In addition to possessing a higher Curie temperature and a higher metal-to-insulator transition temperature, the electrical resistivity and 1/f noise level at 300 K are reduced by a factor of two in the heterostructure with the CaTiO3 buffer layer. These results are relevant to device applications of La0.7Sr0.3MnO3 thin films on silicon substrates.

  14. Luminescent properties of Al2O3: Tb powders

    International Nuclear Information System (INIS)

    Esparza G, A.E.; Garcia, M.; Falcony, C.; Azorin N, J.

    2000-01-01

    In this work the photo luminescent and cathode luminescent characteristics of aluminium oxide (Al 2 O 3 ) powders impurified with terbium (Tb) were studied for their use in dosimetry. The optical, structural, morphological characteristics of the powders as function of variation in the impurity concentration and the annealing temperature will be presented. As regards the optical properties of powders (photoluminescence and cathode luminescence) it was observed a characteristic emission associated with radiative transitions between electron energy levels of terbium, the spectra associated with this emission consists of several peaks associated with such transitions. In the structural and morphological characterization (X-ray diffraction and scanning electron microscopy) it was appreciated that in accordance the annealing temperature of powders is augmented it is evident the apparition of certain crystalline phases. The results show that this is a promissory material for radiation dosimetry. (Author)

  15. Mass spectrometric study of thermodynamic properties in the Gd2O3-Y2O3system at high temperatures.

    Science.gov (United States)

    Kablov, Eugene N; Stolyarova, Valentina L; Lopatin, Sergey I; Vorozhtcov, Viktor A; Karachevtsev, Fedor N; Folomeikin, Yuriy I

    2017-03-30

    The Gd 2 O 3 -Y 2 O 3 system possesses a number of practical applications, one of the most important of them being production of casting molds for gas turbine engine blades. The components of this system are often added to zirconia or hafnia to obtain high-temperature ceramics which are used for the development of thermal barrier coatings. However, Gd 2 O 3 and Y 2 O 3 are more volatile than zirconia or hafnia and may vaporize selectively during synthesis or usage of high-temperature materials which may lead to changes in their physicochemical properties. Therefore, information on the vaporization processes and thermodynamic properties of the Gd 2 O 3 -Y 2 O 3 system is of great importance. High-temperature Knudsen effusion mass spectrometry was used to study the vaporization processes and to determine the thermodynamic properties of the Gd 2 O 3 -Y 2 O 3 system. Measurements were performed with a MS-1301 mass spectrometer. Vaporization was carried out using a tungsten twin effusion cell containing the sample under study and pure Gd 2 O 3 as a reference substance. Electron ionization at an energy of 25 eV was employed. At the temperature of 2630 K, GdO, YO and O vapor species were identified over the samples in the Gd 2 O 3 -Y 2 O 3 system. The Gd 2 O 3 and Y 2 O 3 activities and the vaporization rates of samples as functions of composition in the Gd 2 O 3 -Y 2 O 3 system were derived from the partial pressures of the vapor species mentioned. Using these data the Gibbs energy of mixing and excess Gibbs energy of the hexagonal solid solution in this system were calculated at 2630 K. The thermodynamic properties of the Gd 2 O 3 -Y 2 O 3 system, such as the activities of components and the excess Gibbs energy, obtained in the present study using Knudsen mass spectrometry at 2630 K, demonstrated significant negative deviations from ideal behavior. The vaporization rates of the samples were found to decrease as the Y 2 O 3 content increased. Copyright © 2016 John

  16. Zn2(TeO3Br2

    Directory of Open Access Journals (Sweden)

    Mats Johnsson

    2008-05-01

    Full Text Available Single crystals of dizinc tellurium dibromide trioxide, Zn2(TeO3Br2, were synthesized via a transport reaction in sealed evacuated silica tubes. The compound has a layered crystal structure in which the building units are [ZnO4Br] distorted square pyramids, [ZnO2Br2] distorted tetrahedra, and [TeO3E] tetrahedra (E being the 5s2 lone pair of Te4+ joined through sharing of edges and corners to form layers of no net charge. Bromine atoms and tellurium lone pairs protrude from the surfaces of each layer towards adjacent layers. This new compound Zn2(TeO3Br2 is isostructural with the synthetic compounds Zn2(TeO3Cl2, CuZn(TeO32, Co2(TeO3Br2 and the mineral sophiite, Zn2(SeO3Cl2.

  17. Shear-induced mechanical failure of β -G a2O3 from quantum mechanics simulations

    Science.gov (United States)

    An, Qi; Li, Guodong

    2017-10-01

    Monoclinic gallium oxide (β -G a2O3 ) has important applications in power devices and deep UV optoelectronic devices because of such novel properties as a wide band gap, high breakdown electric field, and a wide range of n -type doping conductivity. However, the intrinsic failure mechanisms of β -G a2O3 remain unknown, which limits the fabrication and packaging of β -G a2O3 -based electronic devices. Here we used density-functional theory at the Perdew-Burke-Ernzerhof level to examine the shear-induced failure mechanisms of β -G a2O3 along various plausible slip systems. We found that the (001 )/〈010 〉 slip system has the lowest ideal shear strength of 3.8 GPa among five plausible slip systems, suggesting that (001 )/〈010 〉 is the most plausible activated slip system. This slip leads to an intrinsic failure mechanism arising from breaking the longest Ga-O bond between octahedral Ga and fourfold-coordinated O. Then we identified the same failure mechanism of β -G a2O3 under biaxial shear deformation that mimics indentation stress conditions. Finally, the general stacking fault energy (SFE) surface is calculated for the (001) surface from which we concluded that there is no intrinsic stacking fault structure for β -G a2O3 . The deformation modes and SFE calculations are essential to understand the intrinsic mechanical processes of this semiconductor material, which provides insightful guidance for designing high-performance semiconductor devices.

  18. High-pressure structural behavior of GdAlO3 and GdFeO3 perovskites

    International Nuclear Information System (INIS)

    Ross, N.L.; Zhao, J.; Angel, R.J.

    2004-01-01

    The orthorhombic perovskites, GdAlO 3 and GdFeO 3 , have been studied using single-crystal X-ray diffraction up to 8.52 and 8.13GPa, respectively, in a diamond anvil cell at 298K. The evolution of the structures of GdAlO 3 and GdFeO 3 involves compression of both the GdO 12 and the octahedral (AlO 6 and FeO 6 ) sites. The compression of the GdO 12 site is anisotropic in both perovskites, with the four longest Gd-O distances compressing more than the eight shorter Gd-O bond lengths, resulting in a decrease in the distortion of GdO 12 with pressure. In GdAlO 3 , the GdO 12 site is less compressible than the AlO 6 site, resulting in an increase of both the interoctahedral Al-O1-Al and Al-O2-Al angles with increasing pressure. Thus GdAlO 3 perovskite becomes less distorted with increasing pressure. In GdFeO 3 , the GdO 12 site displays a similar compressibility as the FeO 6 site, with little change in the Fe-O2-Fe angle with pressure but an increase of the Fe-O1-Fe tilting angle. Thus GdFeO 3 perovskite becomes less distorted with increasing pressure, but the change is not as pronounced as GdAlO 3 . The high-pressure behavior of GdAlO 3 and GdFeO 3 is similar to orthorhombic YAlO 3 perovskite but contrasts with orthorhombic CaSnO 3 , which becomes more distorted with increasing pressure

  19. Synthesis of ferrite grade γ-Fe2O3

    Indian Academy of Sciences (India)

    Unknown

    carboxylates in air yield α-Fe2O3, but the controlled atmosphere of moisture requires for the oxalates to stabi- lize the metastable γ-Fe2O3. ... a starting material in ferrites synthesis enhances the solid state reaction and a better quality material could ... In air the ferrous oxalate decomposes to α-. Fe2O3, while in a controlled ...

  20. Photodegradation of phenol on Y2O3 surface

    International Nuclear Information System (INIS)

    Karunakaran, C.; Dhanalakshmi, R.; Anilkumar, P.

    2009-01-01

    Under UV light, phenol degrades on the surface of Y 2 O 3 , an insulator, and the degradation follows first-order kinetics, depends linearly on the light intensity and slows down with pH. The efficiency of degradation is higher with UV-C light than with UV-A light. While particulate anatase TiO 2 , ZnO, ZnS, Fe 2 O 3 , CuO, CdO, and Nb 2 O 5 individually photodegrade phenol, each semiconductor shows synergism when present along with Y 2 O 3 , indicating electron-transfer from phenol adsorbed on Y 2 O 3 to the illuminated semiconductors.

  1. Effect of Sb2O3 Modified by Various Surface Active Agents on Flame Retardant Properties of PVC Composite

    Directory of Open Access Journals (Sweden)

    XU Jian-lin

    2016-08-01

    Full Text Available Sb2O3 powders were prepared by high energy ball milling using polyethyleneglycol-6000,sodium dodecyl sulfate and OP-10 to modify the surface properties of the powder. The influence of Sb2O3 powders modified by various surface active agents on flame retardant properties of PVC composite materials was studied. The phase composition, morphology and the average particle size of the powders were characterized by XRD and TEM. The particle distribution and flame retardant properties of Sb2O3/PVC composite materials were studied by EDS, limiting oxygen index instrument and vertical burning test. The results show that nanometer Sb2O3 has good dispersion in the PVC matrix because of the higher space steric effect of organic film on the surface of nanometer Sb2O3 when polyethyleneglycol-6000 was used as the surface active agent. While the content of nanometer Sb2O3 is 1.26% in the PVC composite material, the oxygen index of the composite material is 27.1% and the composite material reaches fire retardant grade. Using sodium dodecyl sulfate and OP-10 as surface dispersants, the surface of Sb2O3 powders can not be coated completely. The particle size of Sb2O3 powders are 100nm and 150nm, respectively, The Sb2O3 powders have poor dispersion in the PVC matrix, and even some agglomerating phenomena took place. The oxygen index of Sb2O3/PVC composite materials are 24.7% and 25.3%, respectively, containing 1.26% Sb2O3 powders in Sb2O3/PVC composite material. The materials don't achieve flame retardant level.

  2. Elevated O3 and TYLCV Infection Reduce the Suitability of Tomato as a Host for the Whitefly Bemisia tabaci

    Science.gov (United States)

    Cui, Hongying; Sun, Yucheng; Chen, Fajun; Zhang, Youjun; Ge, Feng

    2016-01-01

    The effects of elevated atmospheric ozone (O3) levels on herbivorous insects have been well studied, but little is known about the combined effects of elevated O3 and virus infection on herbivorous insect performance. Using open-top chambers in the field, we determined the effects of elevated O3 and Tomato yellow leaf curl virus (TYLCV) infection on wild-type (Wt) tomato and 35S tomato (jasmonic acid (JA) defense-enhanced genotype) in association with whitefly, Bemisia tabaci Gennadius biotype B. Elevated O3 and TYLCV infection, alone and in combination, significantly reduced the contents of soluble sugars and free amino acids, increased the contents of total phenolics and condensed tannins, and increased salicylic acid (SA) content and the expression of SA-related genes in leaves. The JA signaling pathway was upregulated by elevated O3, but downregulated by TYLCV infection and O3 + TYLCV infection. Regardless of plant genotype, elevated O3, TYLCV infection, or O3 + TYLCV infection significantly decreased B. tabaci fecundity and abundance. These results suggest that elevated O3 and TYLCV infection, alone and in combination, reduce the nutrients available for B. tabaci, increase SA content and SA-related gene expression, and increase secondary metabolites, resulting in decreases in fecundity and abundance of B. tabaci in both tomato genotypes. PMID:27916792

  3. Elevated O3 and TYLCV Infection Reduce the Suitability of Tomato as a Host for the Whitefly Bemisia tabaci

    Directory of Open Access Journals (Sweden)

    Hongying Cui

    2016-11-01

    Full Text Available The effects of elevated atmospheric ozone (O3 levels on herbivorous insects have been well studied, but little is known about the combined effects of elevated O3 and virus infection on herbivorous insect performance. Using open-top chambers in the field, we determined the effects of elevated O3 and Tomato yellow leaf curl virus (TYLCV infection on wild-type (Wt tomato and 35S tomato (jasmonic acid (JA defense-enhanced genotype in association with whitefly, Bemisia tabaci Gennadius biotype B. Elevated O3 and TYLCV infection, alone and in combination, significantly reduced the contents of soluble sugars and free amino acids, increased the contents of total phenolics and condensed tannins, and increased salicylic acid (SA content and the expression of SA-related genes in leaves. The JA signaling pathway was upregulated by elevated O3, but downregulated by TYLCV infection and O3 + TYLCV infection. Regardless of plant genotype, elevated O3, TYLCV infection, or O3 + TYLCV infection significantly decreased B. tabaci fecundity and abundance. These results suggest that elevated O3 and TYLCV infection, alone and in combination, reduce the nutrients available for B. tabaci, increase SA content and SA-related gene expression, and increase secondary metabolites, resulting in decreases in fecundity and abundance of B. tabaci in both tomato genotypes.

  4. Effect of Nano-Al2O3 on the Toxicity and Oxidative Stress of Copper towards Scenedesmus obliquus

    Science.gov (United States)

    Li, Xiaomin; Zhou, Suyang; Fan, Wenhong

    2016-01-01

    Nano-Al2O3 has been widely used in various industries; unfortunately, it can be released into the aquatic environment. Although nano-Al2O3 is believed to be of low toxicity, it can interact with other pollutants in water, such as heavy metals. However, the interactions between nano-Al2O3 and heavy metals as well as the effect of nano-Al2O3 on the toxicity of the metals have been rarely investigated. The current study investigated copper toxicity in the presence of nano-Al2O3 towards Scenedesmus obliquus. Superoxide dismutase activity and concentration of glutathione and malondialdehyde in cells were determined in order to quantify oxidative stress in this study. Results showed that the presence of nano-Al2O3 reduced the toxicity of Cu towards S. obliquus. The existence of nano-Al2O3 decreased the growth inhibition of S. obliquus. The accumulation of copper and the level of oxidative stress in algae were reduced in the presence of nano-Al2O3. Furthermore, lower copper accumulation was the main factor that mitigated copper toxicity with the addition of nano-Al2O3. The decreased copper uptake could be attributed to the adsorption of copper onto nanoparticles and the subsequent decrease of available copper in water. PMID:27294942

  5. Magnetic properties of solid solutions between BiCrO3 and BiGaO3 with perovskite structures.

    Science.gov (United States)

    Belik, Alexei A

    2015-04-01

    Magnetic properties of BiCr 1- x Ga x O 3 perovskite-type solid solutions are reported, and a magnetic phase diagram is established. As-synthesized BiCrO 3 and BiCr 0.9 Ga 0.1 O 3 crystallize in a monoclinic ( m ) C2/c structure. The Néel temperature ( T N ) decreases from 111 K in BiCrO 3 to 98 K in BiCr 0.9 Ga 0.1 O 3 , and spin-reorientation transition temperature increases from 72 K in BiCrO 3 to 83 K in BiCr 0.9 Ga 0.1 O 3 . o -BiCr 0.9 Ga 0.1 O 3 with a PbZrO 3 -type orthorhombic structure is obtained by heating m -BiCr 0.9 Ga 0.1 O 3 up to 573 K in air; it shows similar magnetic properties with those of m -BiCr 0.9 Ga 0.1 O 3 . T N of BiCr 0.8 Ga 0.2 O 3 is 81 K, and T N of BiCr 0.7 Ga 0.3 O 3 is 63 K. Samples with x = 0.4, 0.5, 0.6 and 0.7 crystallize in a polar R3c structure. Long-range antiferromagnetic order with weak ferromagnetism is observed below T N = 56 K in BiCr 0.6 Ga 0.4 O 3 , T N = 36 K in BiCr 0.5 Ga 0.5 O 3 and T N = 18 K in BiCr 0.4 Ga 0.6 O 3 . BiCr 0.3 Ga 0.7 O 3 shows a paramagnetic behaviour because the Cr concentration is below the percolation threshold of 31%.

  6. Electric field effects in graphene/LaAlO3/SrTiO3 heterostructures and nanostructures

    Directory of Open Access Journals (Sweden)

    Mengchen Huang

    2015-06-01

    Full Text Available We report the development and characterization of graphene/LaAlO3/SrTiO3 heterostructures. Complex-oxide heterostructures are created by pulsed laser deposition and are integrated with graphene using both mechanical exfoliation and transfer from chemical-vapor deposition on ultraflat copper substrates. Nanoscale control of the metal-insulator transition at the LaAlO3/SrTiO3 interface, achieved using conductive atomic force microscope lithography, is demonstrated to be possible through the graphene layer. LaAlO3/SrTiO3-based electric field effects using a graphene top gate are also demonstrated. The ability to create functional field-effect devices provides the potential of graphene-complex-oxide heterostructures for scientific and technological advancement.

  7. Ionic liquid-based hydrothermal synthesis of Lu2O3 and Lu2O3:Eu3+ microcrysals

    Science.gov (United States)

    Li, Yinyan; Xu, Shiqing

    2016-09-01

    Uniform and well-defined Lu2O3 and Lu2O3:Eu3+ microarchitectures have been successfully synthesized via a green and facile ionic liquid-based hydrothermal method followed by a subsequent calcination process. Novel 3D micro-rodbundles and 1D microrods of Lu2O3 and Lu2O3:Eu3+ were controllably obtained through this method. X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy and photoluminescence spectra were used to characterize the micromaterials. The proposed formation mechanisms have been investigated on the basis of a series of SEM studies of the products obtained at different hydrothermal durations. The results indicated that hydrothermal temperature and the ionic liquid-tetrabutylammonium hydroxide were two key factors for the formation as well as the morphology control of the Lu2O3 and Lu2O3:Eu3+ microarchitectures.

  8. High field-effect mobility at the (Sr,Ba)SnO3/BaSnO3 interface

    Science.gov (United States)

    Fujiwara, Kohei; Nishihara, Kazuki; Shiogai, Junichi; Tsukazaki, Atsushi

    2016-08-01

    A perovskite oxide, BaSnO3, has been classified as one of transparent conducting materials with high electron mobility, and its application for field-effect transistors has been the focus of recent research. Here we report transistor operation in BaSnO3-based heterostructures with atomically smooth surfaces, fabricated on SrTiO3 substrates by the (Sr,Ba)SnO3 buffer technique. Indeed, modulation of band profiles at the channel interfaces with the insertion of wide bandgap (Sr,Ba)SnO3 as a barrier layer results in a significant improvement of field-effect mobility, implying effective carrier doping at the regulated heterointerface. These results provide an important step towards realization of high-performance BaSnO3-based field-effect transistors.

  9. High field-effect mobility at the (Sr,BaSnO3/BaSnO3 interface

    Directory of Open Access Journals (Sweden)

    Kohei Fujiwara

    2016-08-01

    Full Text Available A perovskite oxide, BaSnO3, has been classified as one of transparent conducting materials with high electron mobility, and its application for field-effect transistors has been the focus of recent research. Here we report transistor operation in BaSnO3-based heterostructures with atomically smooth surfaces, fabricated on SrTiO3 substrates by the (Sr,BaSnO3 buffer technique. Indeed, modulation of band profiles at the channel interfaces with the insertion of wide bandgap (Sr,BaSnO3 as a barrier layer results in a significant improvement of field-effect mobility, implying effective carrier doping at the regulated heterointerface. These results provide an important step towards realization of high-performance BaSnO3-based field-effect transistors.

  10. Hydrothermal preparation of BaSnO3 and Au-BaSnO3 nanorods.

    Science.gov (United States)

    Athawale, A A; Bapat, M S; Desai, P A

    2008-08-01

    Barium stannate nanorods have been synthesized using chloride precursors, which were activated to form composite complexes and subjected to hydrothermal treatment in a teflon lined reactor. The reaction time was varied between 0.5 to 6.0 h. The reaction conditions included alkaline pH, pressure of 75 kg/cm2 and temperature below 200 degrees C. The sample powders were further calcined at 200, 400 and 600 degrees C for 4 h each. The phase formation was confirmed by IR and XRD. The cubic phase of BaSnO3 powder obtained at 600 degrees C was observed under electron microscope and revealed the formation of long rods of length 2-5 microm with a diameter of 50-60 nm. The use of TMAOH as a mineralizer resulted in the formation of shorter and finer nanofibres. The nanorods were sonicated in presence of auric chloride solution in alkaline medium and the formation of Au-BaSnO3 composite powder was confirmed by UV-visible spectroscopy and X-ray diffraction technique.

  11. Direct Observation of Room-Temperature Stable Magnetism in LaAlO3/SrTiO3 Heterostructures.

    Science.gov (United States)

    Yang, Ming; Ariando; Zhou, Jun; Asmara, Teguh Citra; Krüger, Peter; Yu, Xiao Jiang; Wang, Xiao; Sanchez-Hanke, Cecilia; Feng, Yuan Ping; Venkatesan, T; Rusydi, Andrivo

    2018-03-21

    Along with an unexpected conducting interface between nonmagnetic insulating perovskites LaAlO 3 and SrTiO 3 (LaAlO 3 /SrTiO 3 ), striking interfacial magnetisms have been observed in LaAlO 3 /SrTiO 3 heterostructures. Interestingly, the strength of the interfacial magnetic moment is found to be dependent on oxygen partial pressures during the growth process. This raises an important, fundamental question on the origin of these remarkable interfacial magnetic orderings. Here, we report a direct evidence of room-temperature stable magnetism in a LaAlO 3 /SrTiO 3 heterostructure prepared at high oxygen partial pressure by using element-specific soft X-ray magnetic circular dichroism at both Ti L 3,2 and O K edges. By combining X-ray absorption spectroscopy at both Ti L 3,2 and O K edges and first-principles calculations, we qualitatively ascribe that this strong magnetic ordering with dominant interfacial Ti 3+ character is due to the coexistence of LaAlO 3 surface oxygen vacancies and interfacial (Ti Al -Al Ti ) antisite defects. On the basis of this new understanding, we revisit the origin of the weak magnetism in LaAlO 3 /SrTiO 3 heterostructures prepared at low oxygen partial pressures. Our calculations show that LaAlO 3 surface oxygen vacancies are responsible for the weak magnetism at the interface. Our result provides direct evidence on the presence of room-temperature stable magnetism and a novel perspective to understand magnetic and electronic reconstructions at such strategic oxide interfaces.

  12. Study of the solid-solid surface adsorption of Eu2O3 on various Al2O3 supports

    International Nuclear Information System (INIS)

    Liu Rongchuan; Yu Zhi; Zhou Yuan; Yoshitake Yamazaki

    1997-12-01

    Solid-solid surface interactions of Eu 2 O 3 on various oxide substrates are investigated with X-ray and Moessbauer experiments. The results indicate that the interaction of Eu 2 O 3 on the complex support differs from that having simple support. An incorporation model is used to explain how Eu 2 O 3 disperses onto the surface of γ-alumina or η-alumina

  13. Growth mechanism of NaClO3 and NaBrO3 crystals from aqueous ...

    Indian Academy of Sciences (India)

    Unknown

    tamura (1978) developed a sophisticated apparatus for in situ observation and studied the growth of NaClO3 crys- tals. Tsukamoto and Sunagawa (1990) made a systematic study of the growth of KCl in the presence of Pb ions. Though we have reported studies on growth of NaClO3 and NaBrO3 crystals, they were largely ...

  14. Scanning probe manipulation of magnetism at the LaAlO3/SrTiO3 heterointerface.

    Science.gov (United States)

    Kalisky, Beena; Bert, Julie A; Bell, Christopher; Xie, Yanwu; Sato, Hiroki K; Hosoda, Masayuki; Hikita, Yasuyuki; Hwang, Harold Y; Moler, Kathryn A

    2012-08-08

    Manipulation of magnetism is a longstanding goal of research in exotic materials. In this work, we demonstrate that the small ferromagnetic patches in LaAlO(3)/SrTiO(3) heterostructures can be dramatically changed by in situ contact of a scanning probe. Our results provide a platform for manipulation of small magnets through either a strong magneto-elastic coupling or sensitivity to surface modification. The ability to locally control magnetism is particularly interesting due to the presence of superconductivity with strong spin-orbit coupling in LaAlO(3)/SrTiO(3).

  15. Tunable bilayer two-dimensional electron gas in LaAlO3/SrTiO3 superlattices

    International Nuclear Information System (INIS)

    Ma, H. J. Harsan; Annadi, A.; Zeng, S. W.; Ariando; Huang, Z.; Lü, W. M.; Wong, L. M.; Wang, S. J.; Venkatesan, T.

    2014-01-01

    We report magnetotransport properties of double heterointerfaces in LaAlO 3 /SrTiO 3 /LaAlO 3 /SrTiO 3 (001) (LAO/STO/LAO/STO). A strong nonlinearity in the Hall resistivity is found when the temperature is below 80 K. This effect is attributed to multichannel conduction of interfacial charges generated in double heterostructures of LAO/STO where two-dimensional electron gas (2DEG) is produced. The multichannel conduction is confirmed by back gating modulation of Hall effect. Our result suggests the possibility to achieve coupled bilayer 2DEG layers in LAO/STO superlattices.

  16. Nanostructured Fe2O3/Al2O3 Adsorbent for removal of As (V from water

    Directory of Open Access Journals (Sweden)

    Faranak Akhlaghian

    2017-04-01

    Full Text Available The presence of arsenate in drinking water causes adverse health effects including skin lesions, diabetes, cancer, damage to the nervous system, and cardiovascular diseases. Therefore, the removal of As (V from water is necessary. In this work, nanostructured adsorbent Fe2O3/Al2O3 was synthesized via the sol-gel method and applied to remove arsenate from polluted waters. First, the Fe2O3 load of the adsorbent was optimized. The Fe2O3/Al2O3 adsorbent was characterized by means of XRF, XRD, ASAP, and SEM techniques. The effects of the operating conditions of the batch process of As (V adsorption such as pH, adsorbent dose, contact time, and initial concentration of As (V solution were studied, and optimized. The thermodynamic study of the process showed that arsenate adsorption was endothermic. The kinetic model corresponded to the pseudo-second-order model. The Langmuir adsorption isotherm was better fitted to the experimental data. The Fe2O3/Al2O3 adsorbent was immobilized on leca granules and applied for As (V adsorption. The results showed that the immobilization of Fe2O3/Al2O3 on leca particles improved the As (V removal efficiency.

  17. 2DEGs at perovskite interfaces between KTaO3 or KNbO3 and stannates.

    Directory of Open Access Journals (Sweden)

    Xiaofeng Fan

    Full Text Available We report density functional studies of electron rich interfaces between KTaO3 or KNbO3 and CaSnO3 or ZnSnO3 and in particular the nature of the interfacial electron gasses that can be formed. We find that depending on the details these may occur on either the transition metal or stannate sides of the interface and in the later case can be shifted away from the interface by ferroelectricity. We also present calculations for bulk KNbO3, KTaO3, CaSnO3, BaSnO3 and ZnSnO3, showing the different transport and optical properties that may be expected on the two sides of such interfaces. The results suggest that these interfaces may display a wide range of behaviors depending on conditions, and in particular the interplay with ferroelectricity suggests that electrical control of these properties may be possible.

  18. Voltage-controlled ferromagnetism and magnetoresistance in LaCoO3/SrTiO3 heterostructures

    International Nuclear Information System (INIS)

    Hu, Chengqing; Park, Keun Woo; Yu, Edward T.; Posadas, Agham; Demkov, Alexander A.; Jordan-Sweet, Jean L.

    2013-01-01

    A LaCoO 3 /SrTiO 3 heterostructure grown on Si (001) is shown to provide electrically switchable ferromagnetism, a large, electrically tunable magnetoresistance, and a vehicle for achieving and probing electrical control over ferromagnetic behavior at submicron dimensions. Fabrication of devices in a field-effect transistor geometry enables application of a gate bias voltage that modulates strain in the heterostructure via the converse piezoelectric effect in SrTiO 3 , leading to an artificial inverse magnetoelectric effect arising from the dependence of ferromagnetism in the LaCoO 3 layer on strain. Below the Curie temperature of the LaCoO 3 layer, this effect leads to modulation of resistance in LaCoO 3 as large as 100%, and magnetoresistance as high as 80%, both of which arise from carrier scattering at ferromagnetic-nonmagnetic interfaces in LaCoO 3 . Finite-element numerical modeling of electric field distributions is used to explain the dependence of carrier transport behavior on gate contact geometry, and a Valet-Fert transport model enables determination of spin polarization in the LaCoO 3 layer. Piezoresponse force microscopy is used to confirm the existence of piezoelectric response in SrTiO 3 grown on Si (001). It is also shown that this structure offers the possibility of achieving exclusive-NOR logic functionality within a single device

  19. Nano -propylsulphonated -Fe 2 O 3: A novel magnetically ...

    Indian Academy of Sciences (India)

    Nano -propylsulphonated -Fe2O3 (NPS--Fe2O3) was applied as a new magnetically recyclable heterogeneous catalyst for the efficient one-pot synthesis of bis(pyrazolyl)methanes in water. The catalyst was easily isolated from the reaction mixture by a magnetic bar and reused at least five times without significant ...

  20. Facile combustion synthesis of novel CaZrO 3

    Indian Academy of Sciences (India)

    Abstract. A facile sol–gel combustion route was reported for the direct preparation of CaZrO3:Eu3+ and CaZrO3:Eu3+, Gd3+. The obtained deposits were characterized by XRD, TGA-DSC, SEM, EDS, PL measurements and microscope fluorescence. When the Gd3+ ions were introduced in this compound, the emissions of ...

  1. BiFeO3 Crystal Structure at Low Temperatures

    International Nuclear Information System (INIS)

    Palewicz, A.; Sosnowska, I.; Przenioslo, R.; Hewat, A.W.

    2010-01-01

    The crystal and magnetic structure of BiFeO 3 have been studied with the use of high resolution neutron diffraction between 5 K and 300 K. The atomic coordinates in BiFeO 3 are almost unchanged between 5 K and 300 K. (authors)

  2. TiO3 borosilicate glass–ceramics

    Indian Academy of Sciences (India)

    phase of the glass–ceramic sample with x ≤ 0·5 was found to have cubic structure similar to SrTiO3 ceramic. Scanning electron microscopy has been carried out to see the surface morphology of the crystallites dispersed in the glassy matrix. Keywords. (PbSr)TiO3 borosilicate glasses; infrared spectroscopy; DTA; XRD and ...

  3. NaIrO3-A pentavalent post-perovskite

    International Nuclear Information System (INIS)

    Bremholm, M.; Dutton, S.E.; Stephens, P.W.; Cava, R.J.

    2011-01-01

    Sodium iridium (V) oxide, NaIrO 3, was synthesized by a high pressure solid state method and recovered to ambient conditions. It is found to be isostructural with CaIrO 3 , the much-studied structural analog of the high-pressure post-perovskite phase of MgSiO 3 . Among the oxide post-perovskites, NaIrO 3 is the first example with a pentavalent cation. The structure consists of layers of corner- and edge-sharing IrO 6 octahedra separated by layers of NaO 8 bicapped trigonal prisms. NaIrO 3 shows no magnetic ordering and resistivity measurements show non-metallic behavior. The crystal structure, electrical and magnetic properties are discussed and compared to known post-perovskites and pentavalent perovskite metal oxides. -- Graphical abstract: Sodium iridium(V) oxide, NaIrO 3 , synthesized by a high pressure solid state method and recovered to ambient conditions is found to crystallize as the post-perovskite structure and is the first example of a pentavalent ABO 3 post-perovskite. Research highlights: → NaIrO 3 post-perovskite stabilized by pressure. → First example of a pentavalent oxide post-perovskite. → Non-metallic and non-magnetic behavior of NaIrO 3 .

  4. Ellipsometric studies of ErMnO3 single crystals

    DEFF Research Database (Denmark)

    Babonas, G.-J.; Grivel, Jean-Claude; Reza, A.

    2007-01-01

    Ellipsometric studies of ErMnO3 single crystals have been carried out in the spectral range of 1-5 eV by means of photometric ellipsometers. Experimental ellipsometric data were analysed in the uniaxial crystal model. For the first time, the components of dielectric function of ErMnO3 were...

  5. Neutronic analysis of Gd2O3 as burnable poison

    International Nuclear Information System (INIS)

    Lecot, C.A.

    1990-01-01

    For the reactors core design, the use of burnable poisons is one of the options for the control of in excess reactivity and the power form factor. As alternative procedures, the absorbing material may be included in pellets of an inert material or in fuel pellets. Besides, a cladding material and the locations of the fuel elements must be chosen for the first case. The CAREM reactor core design foresees the use of gadolinium oxide (Gd 2 O 3 ) as burnable poison. In this work, a comparative study was made, from the neutronic point of view, among the following alternatives for the poisons location: a) Gd 2 O 3 bars supports in alumina (Al 2 O 3 ), sheathed in steel; b) Gd 2 O 3 bars supports in alumina sheathed in Zry-4; c) Gd 2 O 3 in uranium dioxide (UO 2 ) fuel pellets. (Author) [es

  6. Influence of B2O3 content on sintering behaviour and dielectric properties of La2O3-B2O3-CaO/Al2O3 glass-ceramic composites for LTCC applications

    Science.gov (United States)

    Wang, F. L.; Zhang, Y. W.; Chen, X. Y.; Mao, H. J.; Zhang, W. J.

    2018-01-01

    La2O3-B2O3-CaO glasses with different B2O3 content were synthesized by melting method to produce glass/ceramic composites in this work. XRD and DSC results revealed that the diminution of B2O3 content was beneficial to increase the crystallization tendency of glass and improve the quality of crystalline phase, while decreasing the effect of glass during sintering process as sintering aids. The choice of glass/ceramic mass ratio was also influenced by the B2O3 content of glass. Dense samples sintered at 875 ºC showed good dielectric properties which meet the requirement of LTCC applications: moderate dielectric constant (7.8-9.4) and low dielectric loss (2.0×10-3).

  7. Highly flexible, conductive and transparent MoO3/Ag/MoO3 multilayer electrode for organic photovoltaic cells

    International Nuclear Information System (INIS)

    Abachi, T.; Cattin, L.; Louarn, G.; Lare, Y.; Bou, A.; Makha, M.; Torchio, P.

    2013-01-01

    MoO 3 /Ag/MoO 3 (MAM) multilayer structures were deposited by vacuum evaporation on polyethylene terephthalate (PET) substrate. We demonstrate that, as in the case of glass substrate, the sheet resistance of such structures depends significantly on the Ag film deposition rate. When it is deposited between 0.2 and 0.4 nm/s, an Ag thickness of 11 nm allows achieving sheet resistance of 13 Ω/sq and an averaged transmission of 74%. A study of the influence of the PET substrate on the optimum MoO 3 thicknesses was done. A good qualitative agreement between the theoretical calculations of the variation of the optical transmittance of the MoO 3 /Ag/MoO 3 structures is obtained. The optimum MAM structures MoO 3 (17.5 nm)/Ag (11 nm)/MoO 3 (35 nm) has a factor of merit F M = 4.21 10 −3 (Ω/sq) −1 . Proven by the scotch test the MAM structures exhibit a good adhesion to the PET substrates. The MAM structures were also submitted to bending tests. For outer bending, the samples exhibit no variation of their resistance value, while for inner bending there is a small increase of the resistance of the MAM structures. However this increasing is smaller than that exhibited by Indium Tin Oxide. When the PET/MAM structures are used as anode in organic photovoltaic cells, it is shown that the need to use thicker Ag films inside the multilayer and to cover the MAM with Au to obtain promising Current density vs Voltage characteristics is due to the heating of the PET substrate during the deposition process. - Highlights: • MoO 3 /Ag/MoO 3 structures deposited on polyethylene terephthalate substrate. • MoO 3 /Ag/MoO 3 structures deposited by vacuum evaporation. • The Ag deposition rate influences the properties of the structures. • The MoO 3 /Ag/MoO 3 optimum structure has a factor of merit F M = 4.21 10 −3 (Ω/sq) −1 . • The MoO 3 /Ag/MoO 3 structures exhibit a high flexibility

  8. Transformation of dissolved organic matter in concentrated leachate from nanofiltration during ozone-based oxidation processes (O3, O3/H2O2and O3/UV).

    Science.gov (United States)

    Wang, Hua-Wei; Li, Xiao-Yue; Hao, Zhi-Peng; Sun, Ying-Jie; Wang, Ya-Nan; Li, Wei-Hua; Tsang, Yiu Fai

    2017-04-15

    In this study, the transformation of dissolved organic matter (DOM) in nanofiltration concentrated leachate during three ozone-based oxidation processes (i.e., O 3 , O 3 /H 2 O 2 and O 3 /UV) was investigated. The transformation characteristics of DOM were evaluated by gel filtration chromatography (GFC), XAD-8 resin fractionation, excitation-emission matrix fluorescence spectroscopy (EEM) and Fourier transform infrared spectroscopy (FTIR). Compared with O 3 -alone process, the removal efficiencies of COD, TOC, and color were improved in O 3 -combined processes (i.e., O 3 /H 2 O 2 and O 3 /UV) approximately by 10-15%, 7-15%, and 15-20%, respectively. Humic acid (HA) was completely degraded and preferentially reacted with the oxidants during ozonation processes. HA was first converted into fulvic acid (FA), and then the majority of these intermediates were further converted to hydrophilic fraction (HyI). The GFC results indicated that the broader molecular weight distribution of DOM was observed, and high molecular weight DOM (i.e., 0.45 μm-100 kDa) was successfully converted to low molecular weight organics in the range of 1-10 kDa after ozonation reactions. The EEM spectra also showed that HA and FA were effectively converted into HyI after ozonation for 90 min. It is suggested that ozone-based oxidation processes could effectively change the DOM distribution and fluorescence features of concentrated leachate. Copyright © 2017 Elsevier Ltd. All rights reserved.

  9. Methylene blue removal from contaminated waters using O3, natural zeolite, and O3/zeolite.

    Science.gov (United States)

    Valdés, H; Tardón, R F; Zaror, C A

    2009-01-01

    This paper compares experimental results on methylene blue (MB) removal systems based on ozone oxidation, zeolite adsorption, and simultaneous adsorption-oxidation using ozone in the presence of natural zeolite. The effect of pH (2-8), and the presence of radical scavengers (sodium acetate) on process rates and removal efficiencies are assessed at laboratory scale. The experimental system consisted of a 1 L differential circular flow reactor and an ozone generator rated at 5 g O3/h. Results show that ozone oxidation combined with zeolite adsorption increases the overall MB oxidation rate with respect to ozonation process and zeolite adsorption. In presence of free radical scavenger, only a 25% of reduction on MB removal rate are observed in the simultaneous treatment, as compared with 70% when ozonation treatment is used, suggesting that MB oxidation reactions take mainly place on the zeolite surface.

  10. FoxO3a contributes to the reprogramming process and the differentiation of induced pluripotent stem cells.

    Science.gov (United States)

    Wang, Yongxiang; Tian, Changhai; Zheng, Jialin C

    2013-11-15

    Induced pluripotent stem (iPS) cells, which are morphologically and functionally similar with embryonic stem (ES) cells, have been successfully generated from somatic cells through defined reprogramming transcription factors. Forkhead class O3a (FoxO3a) has been recently reported to play an important role in the homeostasis and maintenance of certain types of stem cells; however, the role of FoxO3a in the reprogramming process and differentiation of iPS cells remains unclear. In this study, we investigate the function of FoxO3a during the reprogramming process and characterize the properties of iPS cells from FoxO3a-wild type and -null mouse embryonic fibroblasts (MEFs). Our results show that the FoxO3a-null iPS cells are similar to the wild-type iPS cells in the levels of ES cell markers, alkaline phosphatase activity, and formation of teratoma in vivo. The reprogramming process is delayed in the FoxO3a-null MEFs compared to the wild-type MEFs; whereas the overexpression of FoxO3a partially recovers the impaired reprogramming efficiency in the null group. More importantly, FoxO3a deficiency impairs the neuronal lineage differentiation potential of iPS cells in vitro. These results suggest that FoxO3a affects the reprogramming kinetics and the neuronal lineage differentiation potential of the resulting iPS cells. Therefore, this study demonstrates a novel function of FoxO3a in cell reprogramming, which will help the development of alternative strategies for generating iPS cells.

  11. Multiphase nanodomains in a strained BaTiO3 film on a GdScO3 substrate

    Science.gov (United States)

    Kobayashi, Shunsuke; Inoue, Kazutoshi; Kato, Takeharu; Ikuhara, Yuichi; Yamamoto, Takahisa

    2018-02-01

    Controlling the crystal structure of ferroelectric materials via epitaxial strain, which is a well-known technique in strain engineering, can lead to the formation of unique domain structures generating non-intrinsic phenomena such as electronic conductivity, photovoltages, and enhanced piezoelectric characteristics. Strained BaTiO3 films are promising ferroelectric materials as theoretical modeling predicts that different domain morphologies can introduce additional properties not observed in conventional BaTiO3 ceramics. To rationally design materials for practical application, a thorough understanding of the formation mechanisms and stabilities of different domain structures in strained BaTiO3 films is required. However, there have been very few experimental reports on this topic, and details about the domain structures in strained BaTiO3 films are currently lacking. In this paper, we report multiphase nanodomains in a strained BaTiO3 film deposited on an orthorhombic GdScO3 substrate. The phase-transition behavior of the strained BaTiO3 film reveals that it contains multiple phases at room temperature; the film first undergoes a phase-transition upon heating at around 550 K, and then a paraelectric phase forms at temperatures above 690 K. A picometer-scale analysis of the Ti ion displacements, using an advanced scanning transmission electron microscopy technique, is used to characterize the complex multiphase nanodomains, providing useful insights into the control of domain structures in BaTiO3 films by applying epitaxial strain.

  12. Densification and dielectric properties of SrO–Al2O3–B2O3 ceramic ...

    Indian Academy of Sciences (India)

    Abstract. The influence of SrO (0·0–5·0 wt%) on partial substitution of alpha alumina (corundum) in ceramic com- position (95 Al2O3–5B2O3) have been studied by co-precipitated process and their phase composition, microstruc- ture, microchemistry and microwave dielectric properties were studied. Phase composition ...

  13. Transport limits in defect-engineered LaAlO3/SrTiO3 bilayers

    NARCIS (Netherlands)

    Gunkel, F.; Wicklein, S.; Hoffmann-Eifert, S.; Meuffels, P.; Brinks, Peter; Huijben, Mark; Waser, R.; Dittmann, R.

    2014-01-01

    The electrical properties of the metallic interface in LaAlO3/SrTiO3 (LAO/STO) bilayers are investigated with focus on the role of cationic defects in thin film STO. Systematic growth-control of the STO thin film cation stoichiometry (defect-engineering) yields a relation between cationic defects in

  14. High oxygen ion conduction in sintered oxides of the Bi2O3---Ln2O3 system

    NARCIS (Netherlands)

    Verkerk, M.J.; Burggraaf, A.J.

    1981-01-01

    The conditions leading to optimum conductivity of the Bi2O3---Ln2O3 system were investigated. The highest conductivity was found for Ln = Er or Tm. Ordering in the oxygen lattice was investigated using neutron diffraction. Correlations were found between the neutron diffraction data and the

  15. Stability and electronic structure studies of LaAlO3/SrTiO3 (110) heterostructures

    International Nuclear Information System (INIS)

    Du Yan-Ling; Wang Chun-Lei; Li Ji-Chao; Xu Pan-Pan; Zhang Xin-Hua; Liu Jian; Su Wen-Bin; Mei Liang-Mo

    2014-01-01

    The first-principles calculations are employed to investigate the stability, magnetic, and electrical properties of the oxide heterostructure of LaAlO 3 /SrTiO 3 (110). By comparing their interface energies, it is obtained that the buckled interface is more stable than the abrupt interface. This result is consistent with experimental observation. At the interface of LaAlO 3 /SrTiO 3 (110) heterostructure, the Ti—O octahedron distortions cause the Ti t 2g orbitals to split into the two-fold degenerate d xz /d yz and nondegenerate d xy orbitals. The former has higher energy than the latter. The partly filled two-fold degenerate t 2g orbitals are the origin of two-dimensional electron gas, which is confined at the interface. Lattice mismatch between LaAlO 3 and SrTiO 3 leads to ferroelectric-like lattice distortions at the interface, and this is the origin of spin-splitting of Ti 3d electrons. Hence the magnetism appears at the interface of LaAlO 3 /SrTiO 3 (110). (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  16. Acoustic investigations on PbO–Al2O3–B2O3 glasses doped with ...

    Indian Academy of Sciences (India)

    Unknown

    increasing temperature of measurement. From these results (together with IR spectra of these glasses), an attempt is made to throw some light on the mechanical strength of these glasses. Keywords. PbO–Al2O3–B2O3 glasses; rare earth ions; elastic moduli. 1. Introduction. The study of elastic/acoustic and thermodynamic ...

  17. Preparation of MoO3/Al2O3 Catalysts with Sharp Eggshell Mo Distribution by Slurry Impregnation

    Czech Academy of Sciences Publication Activity Database

    Kaluža, Luděk; Zdražil, Miroslav

    2002-01-01

    Roč. 78, 1-4 (2002), s. 313-318 ISSN 1011-372X R&D Projects: GA ČR GA104/01/0544 Keywords : MoO3/Al2O3 catalyst * eggshell Mo catalyst * slurry impregnation Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 1.559, year: 2002

  18. Acoustic investigations on PbO–Al2O3–B2O3 glasses doped with ...

    Indian Academy of Sciences (India)

    Abstract. Elastic moduli (, ), Poisson's ratio (), microhardness () and some thermodynamical parameters such as Debye temperature (), diffusion constant (), latent heat of melting ( ) etc of PbO–Al2O3–B2O3 glasses doped with rare earth ions viz. Pr3+, Nd3+, Sm3+, Eu3+, Tb3+, Dy3+, Ho3+, Er3+ and Yb3+, ...

  19. Experimental and Theoretical Study of the Interactions between Fe2O3/Al2O3 and CO

    Directory of Open Access Journals (Sweden)

    Zhiyong Liang

    2017-04-01

    Full Text Available The behavior of Fe2O3/Al2O3 particles as oxygen carriers (OCs for CO chemical looping combustion (CLC under different reaction temperatures (700 °C, 800 °C, 900 °C, and 1000 °C were tested in a lab-scale fluidized bed and a thermogravimetric analysis (TGA unit. The results show that the oxygen carrier presents the highest reactivity at 800 °C, even after 30 cycles of redox reaction in a fluidized bed, while more obvious carbon deposition occurred for the case at 700 °C, and agglomeration for the case at 1000 °C. Moreover, the detailed behavior of the prepared Fe2O3/Al2O3 particle was detected in the TGA apparatus at different reaction temperatures. Furthermore, temperature-programming TGA experiments were performed to investigate the influence of different CO concentrations and CO/CO2 concentrations on the reaction between CO and OC during the chemical looping combustion processes. Based on these experimental behaviors of the prepared Fe2O3/Al2O3 during the CLC of CO, the detailed models and electronic properties of the pure and reduced Fe2O3/Al2O3 supported the slabs, CO adsorption, and oxidation, and the decomposition reactions on these surfaces were revealed using density functional theory (DFT calculations which went deep into the nature of the synergetic effect of the support of Al2O3 on the activity of Fe2O3 for the CLC of CO.

  20. Role of Tricoordinate Al Sites in CH3ReO3/Al2O3 Olefin Metathesis Catalysts.

    Science.gov (United States)

    Valla, Maxence; Wischert, Raphael; Comas-Vives, Aleix; Conley, Matthew P; Verel, René; Copéret, Christophe; Sautet, Philippe

    2016-06-01

    Re2O7 supported on γ-alumina is an alkene metathesis catalyst active at room temperature, compatible with functional groups, but the exact structures of the active sites are unknown. Using CH3ReO3/Al2O3 as a model for Re2O7/Al2O3, we show through a combination of reactivity studies, in situ solid-state NMR, and an extensive series of DFT calculations, that μ-methylene structures (Al-CH2-ReO3-Al) containing a Re═O bound to a tricoordinated Al (AlIII) and CH2 bound to a four-coordinated Al (AlIVb) are the precursors of the most active sites for olefin metathesis. The resting state of CH3ReO3/Al2O3 is a distribution of μ-methylene species formed by the activation of the C-H bond of CH3ReO3 on different surface Al-O sites. In situ reaction with ethylene results in the formation of Re metallacycle intermediates, which were studied in detail through a combination of solid-state NMR experiments, using labeled ethylene, and DFT calculations. In particular, we were able to distinguish between metallacycles in TBP (trigonal-bipyramidal) and SP (square-pyramidal) geometry, the latter being inactive and detrimental to catalytic activity. The SP sites are more likely to be formed on other Al sites (AlIVa/AlIVa). Experimentally, the activity of CH3ReO3/Al2O3 depends on the activation temperature of alumina; catalysts activated at or above 500 °C contain more active sites than those activated at 300 °C. We show that the dependence of catalytic activity on the Al2O3 activation temperature is related to the quantity of available AlIII-defect sites and adsorbed H2O.

  1. Elemental intermixing within an ultrathin SrRuO3 electrode layer in epitaxial heterostructure BaTiO3/SrRuO3/SrTiO3

    Directory of Open Access Journals (Sweden)

    H. B. Zhang

    2016-01-01

    Full Text Available Aberration corrected scanning transmission electron microscopy is used to directly observe atom columns in an epitaxial BaTiO3 thin film deposited on a 3.6 nm-thick SrRuO3 electrode layer above an SrTiO3 (001 substrate. Compositional gradients across the heterointerfaces were examined using electron energy-loss spectroscopy techniques. It was found that a small amount of Ba and Ti had diffused into the SrRuO3 layer, and that this layer contained a non-negligible concentration of oxygen vacancies. Such point defects are expected to degrade the electrode’s electronic conductivity drastically, resulting in a much longer screening length. This may explain the discrepancy between experimental measurements and theoretical estimates of the ferroelectric critical thickness of a BaTiO3 ferroelectric barrier sandwiched between metallic SrRuO3 electrodes, since theoretical calculations generally assume ideal (stoichiometric perovskite SrRuO3.

  2. Zn2(TeO3)Br2

    Science.gov (United States)

    Zhang, Dong; Johnsson, Mats

    2008-01-01

    Single crystals of dizinc tellurium dibromide trioxide, Zn2(TeO3)Br2, were synthesized via a transport reaction in sealed evacuated silica tubes. The compound has a layered crystal structure in which the building units are [ZnO4Br] distorted square pyramids, [ZnO2Br2] distorted tetra­hedra, and [TeO3 E] tetra­hedra (E being the 5s 2 lone pair of Te4+) joined through sharing of edges and corners to form layers of no net charge. Bromine atoms and tellurium lone pairs protrude from the surfaces of each layer towards adjacent layers. This new compound Zn2(TeO3)Br2 is isostructural with the synthetic compounds Zn2(TeO3)Cl2, CuZn(TeO3)2, Co2(TeO3)Br2 and the mineral sophiite, Zn2(SeO3)Cl2. PMID:21202162

  3. A comparative study of radiation damage in Al2O3, FeTiO3, and MgTiO3

    International Nuclear Information System (INIS)

    Mitchell, J.N.; Yu, Ning; Sickafus, K.E.; Nastasi, M.; Taylor, T.N.; McClellan, K.J.; Nord, G.L. Jr.

    1995-01-01

    Oriented single crystals of synthetic alpha-alumina (α-Al 2 O 3 ), geikielite (MgTiO 3 ) natural ilmenite (FeTiO 3 ) were irradiated with 200 keV argon ions under cryogenic conditions (100 K) to assess their damage response. Using Rutherford backscattering spectrometry combined with ion channeling techniques, it was found that ilmenite amorphized readily at doses below 5x10 14 , alumina amorphized at a dose of 1-2x 15 , and geikielite was amorphized at ∼2x10 15 Ar cm -2 . The radiation damage response of the ilmenite crystal may be complicated by the presence of hematite exsolution lamellae and the experimentally induced oxidation of iron. The relative radiation-resistance of geikielite holds promise for similar behavior in other Mg-Ti oxides

  4. Influence of Impurities on the Luminescence of Er3+ Doped BaTiO3 Nanophosphors

    Directory of Open Access Journals (Sweden)

    G. D. Webler

    2014-01-01

    Full Text Available The influence of the presence of barium carbonate (BaCO3 phase on the luminescence properties of barium titanate nanocrystals (BaTiO3 powders was investigated. Structural and optical characterizations of erbium (Er3+ doped BaTiO3 synthesized by the sol-emulsion-gel were performed. Using Fourier transform infrared spectroscopy and X-ray powder diffraction, we identified the presence of impurities related to BaCO3 and quantified its fraction. It was observed that the presence of BaCO3 phase, even at low levels, depletes significantly the infrared-to-visible upconverted luminescence efficiency of the produced nanopowders.

  5. Structural and magnetoresistance study of LaxMnyO3±z

    International Nuclear Information System (INIS)

    Jimenez, M.; Martinez, J.L.; Prieto, C.; de Andres, A.; Alonso, J.; Gonzalez-Calbet, J.; Fernandez-Diaz, M.T.

    1997-01-01

    We study the system La x MnO 3±z in order to produce proper self-doping (Mn 3+ /Mn 4+ ratio) by La vacancies only, in place of divalent substitution. The system is stable in the range 0.8 C spanning from 200 to 300 K depending on the doping level, with a saturation value ∼2.7μ B /Mn atom. La x MnO 3±z present a metallic-insulator transition, and a magneto-resistance effect close to 75% at 200 K under an applied magnetic field of 9 T, with RT (300 K) value close to 50%. (orig.)

  6. Controlled High Filler Loading of Functionalized Al2O3-Filled Epoxy Composites for LED Thermal Management

    Science.gov (United States)

    Permal, Anithambigai; Devarajan, Mutharasu; Hung, Huong Ling; Zahner, Thomas; Lacey, David; Ibrahim, Kamarulazizi

    2018-03-01

    Thermal management in light-emitting diode (LED) has been extensively researched recently. This study is intended to develop an effective thermally conductive epoxy composite as thermal interface material (TIM) for headlamp LEDs. Silane-functionalized aluminum oxide (Al2O3) powder of different average particle sizes (44 and 10 µm) was studied for its feasibility as filler at its maximum loading. A detailed comparison of three different methods of particle dispersions, hand-mix, speed-mix and calendaring process (3-roll mill), has been reported. The dispersion of Al2O3 particles, the thermal conductivity and thermal degradation characteristics of the composites were investigated and explained in detail. At 75 wt.% filler loading, 10 and 44 µm Al2O3 achieved composite thermal conductivities of 1.13 and 2.08 W/mK, respectively, which is approximately 528 and 1055% of enhancement with respect to neat epoxy. The package-level thermal performance of the LED employing the Al2O3-filled TIMs was carried out using thermal transient analysis. The experimental junction-to-ambient thermal resistances ( R thJ-A) achieved were 6.65, 7.24, and 8.63 K/W for Al2O3_44µm, Al2O3_10µm and neat epoxy, respectively. The results revealed that the Al2O3_44µm fillers-filled composite performed better in both material-level and package-level thermal characteristics.

  7. Controlled High Filler Loading of Functionalized Al2O3-Filled Epoxy Composites for LED Thermal Management

    Science.gov (United States)

    Permal, Anithambigai; Devarajan, Mutharasu; Hung, Huong Ling; Zahner, Thomas; Lacey, David; Ibrahim, Kamarulazizi

    2018-01-01

    Thermal management in light-emitting diode (LED) has been extensively researched recently. This study is intended to develop an effective thermally conductive epoxy composite as thermal interface material (TIM) for headlamp LEDs. Silane-functionalized aluminum oxide (Al2O3) powder of different average particle sizes (44 and 10 µm) was studied for its feasibility as filler at its maximum loading. A detailed comparison of three different methods of particle dispersions, hand-mix, speed-mix and calendaring process (3-roll mill), has been reported. The dispersion of Al2O3 particles, the thermal conductivity and thermal degradation characteristics of the composites were investigated and explained in detail. At 75 wt.% filler loading, 10 and 44 µm Al2O3 achieved composite thermal conductivities of 1.13 and 2.08 W/mK, respectively, which is approximately 528 and 1055% of enhancement with respect to neat epoxy. The package-level thermal performance of the LED employing the Al2O3-filled TIMs was carried out using thermal transient analysis. The experimental junction-to-ambient thermal resistances (R thJ-A) achieved were 6.65, 7.24, and 8.63 K/W for Al2O3_44µm, Al2O3_10µm and neat epoxy, respectively. The results revealed that the Al2O3_44µm fillers-filled composite performed better in both material-level and package-level thermal characteristics.

  8. Theoretical investigation of the structure of κ-Al2O3

    DEFF Research Database (Denmark)

    Yourdshahyan, Y.; Engberg, U.; Bengtsson, L.

    1997-01-01

    Using plane-wave pseudopotential calculations based on density-functional theory at the local-density-approximation level we investigate all the possible kappa-Al2O3 structures which are permitted by the known crystal symmetry. We find that structures with sixfold coordinated Al atoms...

  9. Modeling the Influence of Hemispheric Transport on Trends in O3 Distributions

    Science.gov (United States)

    We describe the development and application of the hemispheric version of the CMAQ to examine the influence of long-range pollutant transport on trends in surface level O3 distributions. The WRF-CMAQ model is expanded to hemispheric scales and multi-decadal model simulations were...

  10. Synthesis of CaTiO3 from calcium titanyl oxalate hexahydrate (CTO ...

    Indian Academy of Sciences (India)

    TECS

    Abstract. Calcium titanate, CaTiO3, an importantmicrowave dielectric material and one of major phases in syn- roc (synthetic rock), a titanate ceramic with potential application for fixation of high level nuclear waste was synthesized from calcium titanyl oxalate [CaTiO (C2O4)2⋅6H2O] (CTO) by employing microwave heating ...

  11. Properties of MoO3 thin film polymorphs

    International Nuclear Information System (INIS)

    McCarron, E.M.; Carcia, P.F.

    1987-01-01

    Thin film polymorphs of molybdenum trioxide have been synthesized by RF sputtering. Films deposited on thermally floating substrates are polycrystalline and exhibit preferred orientation. Depending upon the oxygen partial pressure maintained during sputtering, the films can be made to crystallize in either the thermodynamically stable orthorhombic α MoO 3 form (unique 2D-layered structure) or the metastable monoclinic β MoO 3 phase (3D ReO 3 -related structure). Metastable β films can be converted thermally to the α phase and the transformation appears topotactic. Films deposited on the cooled substrates are amorphous. A correlation between the particular phase formed and adatom mobility is noted

  12. Synthesis of nanometre-thick MoO3 sheets

    Science.gov (United States)

    Kalantar-Zadeh, Kourosh; Tang, Jianshi; Wang, Minsheng; Wang, Kang L.; Shailos, Alexandros; Galatsis, Kosmas; Kojima, Robert; Strong, Veronica; Lech, Andrew; Wlodarski, Wojtek; Kaner, Richard B.

    2010-03-01

    The formation of MoO3 sheets of nanoscale thickness is described. They are made from several fundamental sheets of orthorhombic α-MoO3, which can be processed in large quantities via a low cost synthesis route that combines thermal evaporation and mechanical exfoliation. These fundamental sheets consist of double-layers of linked distorted MoO6 octahedra. Atomic force microscopy (AFM) measurements show that the minimum resolvable thickness of these sheets is 1.4 nm which is equivalent to the thickness of two double-layers within one unit cell of the α-MoO3 crystal.

  13. Flame Spray Synthesis and Ammonia Sensing Properties of Pure α-MoO3 Nanosheets

    Directory of Open Access Journals (Sweden)

    Gagan Jodhani

    2016-01-01

    Full Text Available This paper highlights the flame spray synthesis of α-MoO3 using ammonium molybdate as precursor. The as-synthesized particles obtained were found to be ammonium molybdenum oxide and belonged to the triclinic crystal system. The particles crystallized to α-MoO3 upon thermal treatment at 500°C. Sensors were prepared by drop coating the powders onto alumina substrates coated with platinum electrodes and sensing tests were conducted evaluating the detection of ammonia concentrations down to ppb level concentration in air. The flame synthesized α-MoO3 based sensors show high sensitivity towards ammonia and may potentially be used in breath ammonia gas diagnostics.

  14. Electric-field gradients at Ta donor impurities in Cr2O3(Ta) semiconductor

    International Nuclear Information System (INIS)

    Darriba, G.N.; Errico, L.A.; Munoz, E.L; Richard, D.; Eversheim, P.D.; Renteria, M.

    2009-01-01

    We report perturbed-angular-correlation (PAC) experiments on 181 Hf(→ 181 Ta)-implanted corundum Cr 2 O 3 powder samples in order to determine the magnitude and symmetry of the electric-field gradient (EFG) tensor at Ta donor impurity sites of this semiconductor. These results are analyzed in the framework of ab initio full-potential augmented-plane wave plus local orbitals (FP-APW+lo) calculations. The results are also compared with EFG results coming from PAC experiments in isomorphous α-Al 2 O 3 and α-Fe 2 O 3 doped with 111 In→ 111 Cd and 181 Hf→ 181 Ta tracers. This combined analysis enables us to quantify the magnitude of the lattice relaxations induced by the presence of the impurity and to determine the charge state of the impurity donor level introduced by Ta in the band gap of the semiconductor.

  15. LiNbO3 :Pr3+ : A Multipiezo Material with Simultaneous Piezoelectricity and Sensitive Piezoluminescence.

    Science.gov (United States)

    Tu, Dong; Xu, Chao-Nan; Yoshida, Akihito; Fujihala, Masayoshi; Hirotsu, Jou; Zheng, Xu-Guang

    2017-06-01

    Red-emitting piezoluminescence (elasticoluminescence) is achieved by doping rare earth Pr 3+ into the well-known piezoelectric matrix, LiNbO 3 . By precisely tuning the Li/Nb ratio in nonstoichiometric Li x NbO 3 :Pr 3+ , a material that exhibits an unusually high piezoluminescence intensity, which far exceeds that of any well-known piezoelectric material, is produced. Li x NbO 3 :Pr 3+ shows excellent strain sensitivity at the lowest strain level, with no threshold for stress sensing. These multipiezo properties of sensitive piezoluminescence in a piezoelectric matrix are ideal for microstress sensing, damage diagnosis, electro-mechano-optical energy conversion, and multifunctional control in optoelectronics. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Temporal characterization and regional contribution to O3 and NOx at an urban and a suburban site in Nanjing, China.

    Science.gov (United States)

    Xie, Min; Zhu, Kuanguang; Wang, Tijian; Chen, Pulong; Han, Yong; Li, Shu; Zhuang, Bingliang; Shu, Lei

    2016-05-01

    To improve our understanding of the interplay among local and regional photochemical pollutants in the typical city of the Yangtze River Delta (YRD) region, the concurrent observation of O3 and NOx concentrations at an urban and a suburban site in Nanjing during 2008 is presented. In general, the annual mean O3 concentration is 2.35ppbv lower in the downtown than at suburban due to higher NOx pollution levels correlated with heavy traffic. At both sites, O3 shows a distinct seasonality with the spring maximum and the winter minimum, while the minimum concentration of NOx appears in summertime. Besides the chemical processes of O3 sensitivity in the daytime and the NOx titration at night, meteorological conditions also play an essential role in these monthly and diurnal variations. The ozone weekend effect that can be attributed to the weekly routine of human activities is observed in the urban atmosphere of Nanjing as well, with O3 concentrations 2.09ppbv higher and NOx concentrations 6.20ppbv lower on weekends than on weekdays. The chemical coupling of NO, NO2 and O3 is investigated to show that the OX-component (O3 and NO2) partitioning point occurs at about 35ppbv for NOx, with O3 being the dominant form at lower levels and NO2 dominating at higher levels. And it is also discovered that the level of OX is made up of two contributions, including the regional contribution affected by regional background O3 level and the local contribution correlated with the level of primary pollution. The diurnal peak of regional contribution appears 2-5h after the peak of local contribution, implying that OX in Nanjing might prominently affected by the pollutants from a short distance. The highest regional contribution and the second highest local contribution lead to the spring peak of O3 observed in Nanjing, whereas the highest local contribution and the moderate regional contribution make the O3 concentrations in summer higher than those in autumn and winter. Our results

  17. Impact of La2O3 interfacial layers on InGaAs metal-oxide-semiconductor interface properties in Al2O3/La2O3/InGaAs gate stacks deposited by atomic-layer-deposition

    Science.gov (United States)

    Chang, C.-Y.; Ichikawa, O.; Osada, T.; Hata, M.; Yamada, H.; Takenaka, M.; Takagi, S.

    2015-08-01

    We examine the electrical properties of atomic layer deposition (ALD) La2O3/InGaAs and Al2O3/La2O3/InGaAs metal-oxide-semiconductor (MOS) capacitors. It is found that the thick ALD La2O3/InGaAs interface provides low interface state density (Dit) with the minimum value of ˜3 × 1011 cm-2 eV-1, which is attributable to the excellent La2O3 passivation effect for InGaAs surfaces. It is observed, on the other hand, that there are a large amount of slow traps and border traps in La2O3. In order to simultaneously satisfy low Dit and small hysteresis, the effectiveness of Al2O3/La2O3/InGaAs gate stacks with ultrathin La2O3 interfacial layers is in addition evaluated. The reduction of the La2O3 thickness to 0.4 nm in Al2O3/La2O3/InGaAs gate stacks leads to the decrease in hysteresis. On the other hand, Dit of the Al2O3/La2O3/InGaAs interfaces becomes higher than that of the La2O3/InGaAs ones, attributable to the diffusion of Al2O3 through La2O3 into InGaAs and resulting modification of the La2O3/InGaAs interface structure. As a result of the effective passivation effect of La2O3 on InGaAs, however, the Al2O3/10 cycle (0.4 nm) La2O3/InGaAs gate stacks can realize still lower Dit with maintaining small hysteresis and low leakage current than the conventional Al2O3/InGaAs MOS interfaces.

  18. Preparation, structural, dielectric and magnetic properties of LaFeO3–PbTiO3 solid solutions

    International Nuclear Information System (INIS)

    Ivanov, S.A.; Tellgren, R.; Porcher, F.; Ericsson, T.; Mosunov, A.; Beran, P.; Korchagina, S.K.; Kumar, P. Anil; Mathieu, R.; Nordblad, P.

    2012-01-01

    Highlights: ► Solid-solutions of (1−x)LaFeO 3 –(x)PbTiO 3 were synthesized by solid-state reaction. ► XRPD and NPD evidence orthorhombic (x 0.8) crystal structures. ► LaFeO 3 -rich compositions order antiferromagnetically (x 3 -rich compositions exhibit ferroelectric order (x larger than 0.8). ► Magnetic and dielectric (relaxor) ordering coexist near room-temperature around x = 0.4. -- Abstract: Solid solutions of (1−x)LaFeO 3 –(x)PbTiO 3 (0 3+ cations in the B-site with propagation vector k = (0,0,0). Based on the obtained experimental data, a combined structural and magnetic phase diagram has been constructed. The factors governing the structural, dielectric and magnetic properties of (1−x)LaFeO 3 –(x)PbTiO 3 solid solutions are discussed, as well as their possible multiferroicity.

  19. Preparation and catalytic activities of LaFeO3 and Fe2O3 for HMX thermal decomposition.

    Science.gov (United States)

    Wei, Zhi-Xian; Xu, Yan-Qing; Liu, Hai-Yan; Hu, Chang-Wen

    2009-06-15

    Perovskite-type LaFeO(3) and alpha-Fe(2)O(3) with high specific surface areas were directly prepared with appropriate stearic acid-nitrates ratios by a novel stearic acid solution combustion method. The obtained powders were characterized by XRD, FT-IR and XPS techniques. The catalytic activities of perovskite-type LaFeO(3) and alpha-Fe(2)O(3) for the thermal decomposition of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) were investigated by TG and TG-EGA techniques. The experimental results show that the catalytic activity of perovskite-type LaFeO(3) was much higher than that of alpha-Fe(2)O(3) because of higher concentration of surface-adsorbed oxygen (O(ad)) and hydroxyl of LaFeO(3). The study points out a potential way to develop new and more active perovskite-type catalysts for the HMX thermal decomposition.

  20. Structural characterization of LaInO3/BaSnO3 interface via synchrotron scattering

    Science.gov (United States)

    Lau, Claudia; Kim, Youjung; Char, Kookrin; Ahn, Charles; Walker, Fred

    The alkaline earth stannate BaSnO3 has one of the highest measured room-temperature mobilities of the conducting perovskite oxides. FETs based on BaSnO3 display a large on/off ratio, Ion / Ioff = 107, and high field effect mobility, μ = 90 cm2/Vs. It has been suggested that in these polar devices, which use a LaInO3 dielectric, the polar discontinuity between the polar LaInO3 dielectric and the nonpolar Ba0.93La0.07SnO3 channel leads to an electronic reconstruction. LaInO3 remotely dopes Ba0.93La0.07SnO3 with electrons, creating the high observed mobility. Using synchrotron radiation, we measure crystal truncation rods (CTRs) of thin film LIO/BSO/STO grown by pulsed-laser deposition. Fitting these CTRs, we determine a layer-resolved atomic structure for the LIO/BSO interface. We observe octahedral rotations and polarization in the LIO layer for films as thin as 6 unit-cells, similar to the rotations observed in bulk LIO. We discuss how these rotations may be coupled to the polarization near the interface.

  1. Local structure in BaTi O3-BiSc O3 dipole glasses

    Science.gov (United States)

    Levin, I.; Krayzman, V.; Woicik, J. C.; Bridges, F.; Sterbinsky, G. E.; Usher, T.-M.; Jones, J. L.; Torrejon, D.

    2016-03-01

    Local structures in cubic perovskite-type (B a0.6B i0.4) (T i0.6S c0.4) O3 solid solutions that exhibit reentrant dipole glass behavior have been studied with variable-temperature x-ray/neutron total scattering, extended x-ray absorption fine structure, and electron diffraction methods. Simultaneous fitting of these data using a reverse Monte Carlo algorithm provided instantaneous atomic configurations, which have been used to extract local displacements of the constituent species. The smaller Bi and Ti atoms exhibit probability density distributions that consist of 14 and 8 split sites, respectively. In contrast, Ba and Sc feature single-site distributions. The multisite distributions arise from large and strongly anisotropic off-center displacements of Bi and Ti. The cation displacements are correlated over a short range, with a correlation length limited by chemical disorder. The magnitudes of these displacements and their anisotropy, which are largely determined by local chemistry, change relatively insignificantly on cooling from room temperature. The structure features a nonrandom distribution of local polarization with low-dimensional polar clusters that are several unit cells in size. In situ measurements of atomic pair-distribution function under applied electric field were used to study field-induced changes in the local structure; however, no significant effects besides lattice expansion in the direction of the field could be observed up to electric-field values of 4 kV m m-1 .

  2. Doping of Fe to In2O3

    International Nuclear Information System (INIS)

    Kohiki, Shigemi; Sasaki, Masakuni; Murakawa, Yusuke; Hori, Kyoko; Okada, Koichi; Shimooka, Hirokazu; Tajiri, Takayuki; Deguchi, Hiroyuki; Matsushima, Shigenori; Oku, Masaoki; Shishido, Toetsu; Arai, Masao; Mitome, Masanori; Bando, Yoshio

    2006-01-01

    Model cluster calculations by discrete variational-Xα method for the Fe 3+ ions at 8b and 24d sites of the In 2 O 3 crystal lattice demonstrated that the density of states of the Fe 3+ 3d electrons located around the center of the band gap, and the spin density of states for the Fe 3+ ions at 8b and 24d sites are asymmetric. For Fe-doped In 2 O 3 powders, we found a cusp at ∼ 30 K overlapping cluster glass behavior in dc susceptibility, though the cusp showed no frequency dependence in ac susceptibility. The cusp at ∼ 30 K for the Fe-doped In 2 O 3 powders can be attributed to superexchange interactions between Fe 3+ ions substituted for In 3+ ions of the In 2 O 3 crystal lattice

  3. Efficient regioselective O3-monodesilylation by hydrochloric acid in cyclodextrins.

    Science.gov (United States)

    Gu, Jiamin; Chen, Tong; Wang, Qifang; Chen, Tieyu; Ling, Chang-Chun

    2015-06-17

    An efficient O3-monodesilylation method has been developed for the derivatization of per-3-O-silylated cyclodextrin (CD) derivatives. Using hydrochloric acid as a reagent, the O3-monodesilylation was found to be regioselective, mild, practical and general as it can be applied to all α-, β- and γ-CDs. The advantage of the methodology is that the acid-catalyzed O3-desilylation can be carried out in a stepwise manner so that different types of functional groups can be introduced to a CD molecule at different stage of the O3-desilylations. This makes the current methodology flexible and versatile. This current methodology constitutes one of the few methodologies available for the regioselective modification of CDs at the secondary face. Copyright © 2015 Elsevier Ltd. All rights reserved.

  4. Anharmonic phonons and magnons in BiFeO3

    Energy Technology Data Exchange (ETDEWEB)

    Delaire, Olivier A [ORNL; Ma, Jie [ORNL; Stone, Matthew B [ORNL; Huq, Ashfia [ORNL; Gout, Delphine J [ORNL; Brown, Craig [National Institute of Standards and Technology (NIST); Wang, Kefeng [Nanjing National Laboratory of Microstructures, Nanjing University, Nanjing; Ren, Zhifeng [Boston College, Chestnut Hill

    2012-01-01

    The phonon density of states (DOS) and magnetic excitation spectrum of polycrystalline BiFeO3 were measured for temperatures 200 < T < 750K , using inelastic neutron scattering (INS). Our results indicate that the magnetic spectrum of BiFeO3 closely resembles that of similar Fe perovskites, such as LaFeO3, despite the cycloid modulation in BiFeO3. We do not find any evidence for a spin gap. A strong T-dependence of the phonon DOS was found, with a marked broadening of the whole spectrum, providing evidence of strong anharmonicity. This anharmonicity is corroborated by large amplitude motions of Bi and O ions observed with neutron diffraction. These results highlight the importance of spin-phonon coupling in this material.

  5. Surface cation nonstoichiometry in undoped BaTiO3

    International Nuclear Information System (INIS)

    Zhang, Z.; Nowotny, J.; Pigram, P.J.; Lamb, R.N.

    1998-01-01

    This paper considers the effect of high temperature treatment on the local chemistry of the surface region of undoped BaTiO 3 . Segregation-induced cation nonstoichiometry has been investigated using X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). Samples were thermally treated at 1000 deg C in a tube furnace under different oxygen activities, and then cooled to room temperature at different rates. For slowly cooled samples, Ti enrichment is found in the surface region of oxidised BaTiO 3 , while less Ti segregation occurs in reduced BaTiO3. Increasing the cooling rate reduces the degree of Ti segregation, but it does not change the general behaviour of segregation in either oxidised or reduced BaTiO 3

  6. Formation and surface characterization of nanostructured Al2O3 ...

    Indian Academy of Sciences (India)

    Administrator

    Page 1. Electronic Supplementary Material. Graphical abstract. Formation and surface characterization of nanostructured Al2O3–TiO2 coatings by Vairamuthu Raj and Mohamed Sirajudeen Mumjitha. (pp 1411–1418).

  7. Stomatal uptake of O3 in a Schima superba plantation in subtropical China derived from sap flow measurements.

    Science.gov (United States)

    Niu, Junfeng; Zhao, Ping; Sun, Zhenwei; Zhu, Liwei; Ni, Guangyan; Zeng, Xiaoping; Zhang, Zhenzhen; Zhao, Xiuhua; Zhao, Peiqiang; Gao, Jianguo; Hu, Yanting; Zeng, Xiaomin; Ouyang, Lei

    2016-03-01

    Canopy stomatal ozone (O3) flux (Fst,O3) in a plantation of Schima superba, an ecologically and economically important evergreen pioneer tree species in subtropical China, was quantified based on sap flow measurements during a 2-year period. Mean Fst,O3 and accumulated Fst,O3 (AFst0) were significantly higher in wet seasons from April to September (4.62 nmol m(-2) s(-1) and 35.37 mmol m(-2), respectively) than in dry seasons from October to March (3.90 nmol m(-2) s(-1) and 24.15 mmol m(-1), respectively), yet comparable between the 2 years of the experiment, being 4.23 nmol m(-2) s(-1) and 58.23 mmol m(-2) in April 2013-March 2014 and 4.29 nmol m(-2) s(-1) and 60.80 mmol m(-2) in April 2014-March 2015, respectively. At the diurnal scale, Fst,O3 generally peaked in the early to middle afternoon hours (13:00-15:00), while the maximum stomatal conductance (Gst,O3) typically occurred in the middle to late morning hours (09:00-11:00). Monthly integrated AFst0 reached the maximum in July, although accumulated O3 exposure (SUM0) was highest in October. Seasonally or yearly, the accumulated O3 doses, either exposure-based or flux-based, notably exceeded the currently adopted critical thresholds for the protection of forest trees. These results, on the one hand, demonstrated the decoupling between the stomatal uptake of O3 and its environmental exposure level; on the other hand, indicated the potential O3 risk for S. superba in the experimental site. Therefore, the present study endorses the use of sap flow measurements as a feasible tool for estimating Fst,O3, and the transition from the exposure-based toward flux-based metrics for assessing O3 risk for forest trees. Further studies are urgently needed to relate stomatal O3 uptake doses with tree growth reductions for an improved understanding of O3 effects on trees under natural conditions. Copyright © 2015 Elsevier B.V. All rights reserved.

  8. RAMAN/Cr3+ FLUORESCENCE MAPPING OF MELT-GROWN Al2O3/GdAlO3 EUTECTICS

    OpenAIRE

    Gouadec , Gwénael; Colomban , Philippe; Piquet , Nicolas; Trichet , Marie-France; Mazerolles , Léo

    2005-01-01

    International audience; The paper reports on the Raman/fluorescence study of melt-grown Al2O3/GdAlO3 eutectic composites. Raman bands from the Α-alumina and gadolinium perovskite phases identified by X-ray diffraction were systematically observed together in the domains optically visible, even when the latter were much larger than the Raman probe. This suggests a more complex interlocking pattern than appearing on SEM or optical microscopy images. The polarization of alumina and GdAlO3 Raman ...

  9. Visible-light-enhanced gating effect at the LaAlO3/SrTiO3 interface

    DEFF Research Database (Denmark)

    Lei, Y.; Li, Y.; Chen, Yunzhong

    2014-01-01

    Electrostatic gating field and light illumination are two widely used stimuli for semiconductor devices. Via capacitive effect, a gate field modifies the carrier density of the devices, while illumination generates extra carriers by exciting trapped electrons. Here we report an unusual illumination......-enhanced gating effect in a two-dimensional electron gas at the LaAlO3/SrTiO3 interface, which has been the focus of emergent phenomena exploration. We found that light illumination decreases, rather than increases, the carrier density of the gas when the interface is negatively gated through the SrTiO3 layer...

  10. Fe2O3/MWCNTs nanocomposite decorated glassy carbon electrode ...

    Indian Academy of Sciences (India)

    35

    preparation of Fe2O3/MWCNTs, 197.6mg K3[Fe(CN)6] was dissolved in 40 mL of distilled water with PH to 12, and then the .... difficult may be attributed to the shortage of proton [34-37]. So with the increase in ... Fe2O3/MWCNTs/GCE modified electrode showed excellent determination of nitrites in tap water. 4. Conclusion.

  11. Characterization and optical properties of Pr2O3-doped ...

    Indian Academy of Sciences (India)

    2017-06-09

    Jun 9, 2017 ... yMoO3–xPr2O3 (where x = 0.5 and 1.0 mol% and y = 0 and 5 mol%) were prepared by conventional melt-quenching technique. Thermal, optical and structural analyses are carried out using DSC, UV and FTIR spectra. The physical parame- ters, like glass transition (Tg), stability factor (T), optical energy ...

  12. 26 CFR 301.6501(o)-3 - Partnership items.

    Science.gov (United States)

    2010-04-01

    ... § 301.6501(o)-3 Partnership items. (a) Partnership item defined. For purposes of section 6501(o) (as it... 26 Internal Revenue 18 2010-04-01 2010-04-01 false Partnership items. 301.6501(o)-3 Section 301..., and § 301.6511(g)-1, the term “partnership item” means— (1) Any item required to be taken into account...

  13. Dry deposition of O3 and SO2 estimated from gradient measurements above a temperate mixed forest.

    Science.gov (United States)

    Wu, Zhiyong; Staebler, Ralf; Vet, Robert; Zhang, Leiming

    2016-03-01

    Vertical profiles of O3 and SO2 concentrations were monitored at the Borden Forest site in southern Ontario, Canada from May 2008 to April 2013. A modified gradient method (MGM) was applied to estimate O3 and SO2 dry deposition fluxes using concentration gradients between a level above and a level below the canopy top. The calculated five-year mean (median) dry deposition velocity (Vd) were 0.35 (0.27) and 0.59 (0.54) cm s(-1), respectively, for O3 and SO2. Vd(O3) exhibited large seasonal variations with the highest monthly mean of 0.68 cm s(-1) in August and the lowest of 0.09 cm s(-1) in February. In contrast, seasonal variations of Vd(SO2) were smaller with monthly means ranging from 0.48 (May) to 0.81 cm s(-1) (December). The different seasonal variations between O3 and SO2 were caused by the enhanced SO2 uptake by snow surfaces in winter. Diurnal variations showed a peak value of Vd in early morning in summer months for both O3 and SO2. Canopy wetness increased the non-stomatal uptake of O3 while decreasing the stomatal uptake. This also applied to SO2, but additional factors such as surface acidity also played an important role on the overall uptake. Crown Copyright © 2015. Published by Elsevier Ltd. All rights reserved.

  14. Ferromagnetism and antiferromagnetism coexistence in Sr1-xLaxRuO3 induced by La-doping

    Science.gov (United States)

    Xu, Sheng; Gu, Yanni; Wu, Xiaoshan

    2018-02-01

    Recently, a spin-glass state appeared experimentally along with suppression of ferromagnetism in polycrystalline La-doped Sr1-xLaxRuO3. Here, we investigated the structural, magnetic and electronic properties of Sr1-xLaxRuO3 (x = 0, 0.125, 0.25, 0.5, 1) based on generalized gradient approximation plus U (GGA + U) by first-principles calculations. The entire series of Sr1-xLaxRuO3 (x = 0, 0.125, 0.25, 0.5, 1) stabilize in the orthorhombic perovskite structure. The spin-polarized calculations give a ferromagnetic half-metal ground state at 0 ≤ x ≤ 0.25, coexistence of a ferromagnetic half-metal state and antiferromagnetic insulating state at x = 0.5 and an antiferromagnetic metal state at x = 1, in good agreement with experimental results. La substitution for Sr decreases Rusbnd Osbnd Ru bond angles, resulting in stronger GdFeO3 distortion. The stronger GdFeO3 distortion reduces density of states at the Fermi level, with broadening of Van-hove singularity near the Fermi level. Therefore, suppression of magnetism in Sr1-xLaxRuO3 becomes stronger with increasing x. La-doping weakens a Stoner mechanism for ferromagnetism in SrRuO3. These theoretical results interpret well experiments.

  15. Long-term O3–precursor relationships in Hong Kong: field observation and model simulation

    Directory of Open Access Journals (Sweden)

    Y. Wang

    2017-09-01

    Full Text Available Over the past 10 years (2005–2014, ground-level O3 in Hong Kong has consistently increased in all seasons except winter, despite the yearly reduction of its precursors, i.e. nitrogen oxides (NOx =  NO + NO2, total volatile organic compounds (TVOCs, and carbon monoxide (CO. To explain the contradictory phenomena, an observation-based box model (OBM coupled with CB05 mechanism was applied in order to understand the influence of both locally produced O3 and regional transport. The simulation of locally produced O3 showed an increasing trend in spring, a decreasing trend in autumn, and no changes in summer and winter. The O3 increase in spring was caused by the net effect of more rapid decrease in NO titration and unchanged TVOC reactivity despite decreased TVOC mixing ratios, while the decreased local O3 formation in autumn was mainly due to the reduction of aromatic VOC mixing ratios and the TVOC reactivity and much slower decrease in NO titration. However, the decreased in situ O3 formation in autumn was overridden by the regional contribution, resulting in elevated O3 observations. Furthermore, the OBM-derived relative incremental reactivity indicated that the O3 formation was VOC-limited in all seasons, and that the long-term O3 formation was more sensitive to VOCs and less to NOx and CO in the past 10 years. In addition, the OBM results found that the contributions of aromatics to O3 formation decreased in all seasons of these years, particularly in autumn, probably due to the effective control of solvent-related sources. In contrast, the contributions of alkenes increased, suggesting a continuing need to reduce traffic emissions. The findings provide updated information on photochemical pollution and its impact in Hong Kong.

  16. Silicon solar cells with Al2O3 antireflection coating

    Science.gov (United States)

    Dobrzański, Leszek A.; Szindler, Marek; Drygała, Aleksandra; Szindler, Magdalena M.

    2014-09-01

    The paper presents the possibility of using Al2O3 antireflection coatings deposited by atomic layer deposition ALD. The ALD method is based on alternate pulsing of the precursor gases and vapors onto the substrate surface and then chemisorption or surface reaction of the precursors. The reactor is purged with an inert gas between the precursor pulses. The Al2O3 thin film in structure of the finished solar cells can play the role of both antireflection and passivation layer which will simplify the process. For this research 50×50 mm monocrystalline silicon solar cells with one bus bar have been used. The metallic contacts were prepared by screen printing method and Al2O3 antireflection coating by ALD method. Results and their analysis allow to conclude that the Al2O3 antireflection coating deposited by ALD has a significant impact on the optoelectronic properties of the silicon solar cell. For about 80 nm of Al2O3 the best results were obtained in the wavelength range of 400 to 800 nm reducing the reflection to less than 1%. The difference in the solar cells efficiency between with and without antireflection coating was 5.28%. The LBIC scan measurements may indicate a positive influence of the thin film Al2O3 on the bulk passivation of the silicon.

  17. The phase diagram of KNO3-KClO3

    International Nuclear Information System (INIS)

    Zhang Xuejun; Tian Jun; Xu Kangcheng; Gao Yici

    2004-01-01

    The binary phase diagram of KNO 3 -KClO 3 is studied by means of differential scanning calorimetry (DSC) and high-temperature X-ray diffraction. The limited solid solutions, K(NO 3 ) 1-x (ClO 3 ) x (0 3 ) 1-x (ClO 3 ) x (0.90 3 -based solid solutions and KClO 3 -based solid solutions phase, respectively. For KNO 3 -based solid solutions, KNO 3 ferroelectric phase can be stable from 423 to 223 K as a result of substituting of NO 3 by ClO 3 -radicals. The temperatures for solidus and liquidus have been determined based on limited solid solutions. Two models, Henrian solution and regular solution theory for KNO 3 -based (α) phase and KClO 3 -based (β) phase, respectively, are employed to reproduce solidus and liquidus of the phase diagram. The results are in good agreement with the DSC data. The thermodynamic properties for α and β solid solutions have been derived from an optimization procedure using the experimental data. The calculated phase diagram and optimized thermodynamic parameters are thermodynamically self-consistent

  18. Up- and Downconversion Luminescence Properties of Nd3+ Ions Doped in Bi2O3–BaO–B2O3 Glass System

    Directory of Open Access Journals (Sweden)

    R. Ruamnikhom

    2014-01-01

    Full Text Available Physical, optical, and luminescence properties of Nd3+ ions in bismuth barium borate glass system were studied. The glasses prepared by a melt quenching method were doped at various Nd2O3 concentrations in compositions (40-xB2O3 : 40Bi2O3 : 20BaO : xNd2O3 (where x = 0.00, 0.50, 1.00, 1.50, 2.00, and 2.50 in mol%. Luminescence properties of the glasses were studied under two excitations of 585 and 750 nm for downconversion. From both excitations, the results show emission bands in NIR region corresponding to the transitions between 4F3/2 → 4I9/2 (900 nm, 4F3/2 → 4I11/2 (1,060 nm, and 4F3/2 → 4I13/2 (1,345 nm. The luminescence intensity obtained with 585 nm excitation was stronger than 750 nm, with the strongest NIR emission at 1,060 nm. The upconversion emission spectrum exhibits strong fluorescence bands in the UV region at 394 nm (λex=591 nm. The processes are associated with excited state absorption (ESA from 4F3/2 level to 4D3/2 level and it is the radiative decay from the 4D3/2 to ground levels (4D3/2 → 4I13/2 which are responsible for the emission at 394 nm.

  19. Investigations of the physical and chemical properties of solid solutions Pb/Mnsub(1/2), Nbsub(1/2)/O3 - PbTiO3 - PbZrO3

    International Nuclear Information System (INIS)

    Szadkowska, A.; Majewska-Pilchowska, K.

    1981-01-01

    The preparation of the PMTZ materials on the basis of solid solutions Pb/Mnsub(1/2)/O 3 - PbTiO 3 - PbZrO 3 has been described. The X-ray analysis of the examined materials has been made, and porosity and grain size have been determined. Dielectric constant and mechanical quality factor as a function of PbZrO 3 content have been determined. The obtained results indicate that solid solutions Pb/Mnsub(1/2), Nbsub(1/2)/O 3 - PbTiO 3 - PbZrO 3 are useful piezoelectric materials. (author)

  20. Temporal Variations of O3 and NO x in the Urban Background Atmosphere of Nanjing, East China.

    Science.gov (United States)

    An, Junlin; Shi, Yuanzhe; Wang, Junxiu; Zhu, Bin

    2016-08-01

    Rapid economic growth has given rise to a significant increase in ozone (O3)-precursor emissions in many regions of China. An improved understanding of O3 formation in response to different precursor emissions is imperative to address the highly nonlinear O3 problem and to provide a solid scientific basis for efficient O3 abatement in these regions. To this end, this study was performed in Nanjing using a set of observational data from June 1, 2013, to May 31, 2014. The results showed that O3 concentrations were positively correlated with wind speed and temperature and were significantly negatively correlated with relative humidity. The highest monthly daytime, nighttime, and daily average O3 concentrations were observed in summer with values of approximately 46, 18 and 30 ppb, respectively. The lowest O3 concentrations were observed in November through January with values as low as 17, 4, and 9 ppb for the daytime, nighttime, and daily concentrations, respectively. The highest daytime average NO and NO2 concentrations were observed in December, whereas the lowest concentrations were observed in July. A unimodal O3 peak was observed with the highest O3 levels in summer followed by spring and then autumn; the lowest levels observed in the winter. The O3 concentration reached maximum levels at 14:00 to 15:00 h (local standard time). It was found that the crossover occurred with approximately several hours difference with the earliest occurring in summer (06:00 h) followed by spring (08:00 h), autumn (09:00 h), and winter (10:30 h). Furthermore, the highest constant rate of O3 accumulation was observed in summer (5.6 ppb/h) followed by autumn (4.8 ppb/h), spring (4.5 ppb/h), and winter (2.7 ppb/h). The oxidant intercept ranged from 28.4 ppb in January to 58.6 ppb in June, although the slope also shows substantial variation from 0.18 in June to 0.67 in August. The weekend effect is stronger in spring and summer than in autumn and winter and is more intense

  1. Sensitization of Perovskite Strontium Stannate SrSnO3 towards Visible-Light Absorption by Doping

    Directory of Open Access Journals (Sweden)

    Hungru Chen

    2014-01-01

    Full Text Available Perovskite strontium stannate SrSnO3 is a promising photocatalyst. However, its band gap is too large for efficient solar energy conversion. In order to sensitize SrSnO3 toward visible-light activities, the effects of doping with various selected cations and anions are investigated by using hybrid density functional calculations. Results show that doping can result in dopant level to conduction band transitions which lie lower in energy compared to the original band gap transition. Therefore, it is expected that doping SrSnO3 can induce visible-light absorption.

  2. Combinatorial processing libraries for bulk BiFeO3-PbTiO3 piezoelectric ceramics

    International Nuclear Information System (INIS)

    Hu, W.; Tan, X.; Rajan, K.

    2010-01-01

    A high throughput approach for generating combinatorial libraries with varying processing conditions for bulk ceramics has been developed. This approach utilized the linear temperature gradient in a tube furnace to screen a whole temperature range for optimized preparation. With this approach, the processing of 0.98[0.6BiFeO 3 -0.4PbTiO 3 ]-0.02Pb(Mg 1/3 Nb 2/3 )O 3 ceramic powders and pellets for high-temperature piezoelectric applications was demonstrated to identify the best synthesis conditions for phase purity. The dielectric property measurement on the as-processed solid solution ceramics confirmed the high Curie temperature and the improved loss tangent with the Pb(Mg 1/3 Nb 2/3 )O 3 doping. (orig.)

  3. Effect of Al2O3 and TiO2 nanoparticles on aquatic organisms

    International Nuclear Information System (INIS)

    Gosteva, I; Morgalev, Yu; Morgaleva, T; Morgalev, S

    2015-01-01

    Environmental toxicity of aqueous disperse systems of nanoparticles of binary compounds of titanium dioxides (with particle size Δ 50 =5 nm, Δ 50 =50 nm, Δ 50 =90 nm), aluminum oxide alpha-forms (Δ 50 =7 nm and Δ 50 =70 nm) and macro forms (TiO 2 Δ 50 =350 nm, Al 2 O 3 A 50 =4000 nm) were studied using biological testing methods. The bioassay was performed using a set of test organisms representing the major trophic levels. We found the dependence of the toxic effect concentration degree of nTiO 2 and nAl 2 O 3 on the fluorescence of the bacterial biosensor 'Ekolyum', the chemotactic response of ciliates Paramecium caudatum, the growth of unicellular algae Chlorella vulgaris Beijer and mortality of entomostracans Daphnia magna Straus. We revealed the selective dependence of nTiO 2 and nAl 2 O 3 toxicity on the size, concentration and chemical nature of nanoparticles. The minimal concentration causing an organism's response on nTiO 2 and nAl 2 O 3 effect depends on the type of the test- organism and the test reaction under study. We specified L(E)C 50 and acute toxicity categories for all the studied nanoparticles. We determined that nTiO 2 (Δ 50 =5 nm) belong to the category «Acute toxicity 1», nTiO 2 (A 50 =90 nm) and nAl 2 O 3 (Δ 50 =70 nm) – to the category «Acute toxicity 2», nAl 2 O 3 (Δ 50 =7 nm) – to the category «Acute toxicity 3». No acute toxicity was registered for nTiO 2 (Δ 50 =50 nm) and macro form TiO 2 . (paper)

  4. Effect of AL2O3 and TiO2 nanoparticles on aquatic organisms

    Science.gov (United States)

    Gosteva, I.; Morgalev, Yu; Morgaleva, T.; Morgalev, S.

    2015-11-01

    Environmental toxicity of aqueous disperse systems of nanoparticles of binary compounds of titanium dioxides (with particle size Δ50=5 nm, Δ50=50 nm, Δ50=90 nm), aluminum oxide alpha-forms (Δ50=7 nm and Δ50=70 nm) and macro forms (TiO2 Δ50=350 nm, Al2O3 A50=4000 nm) were studied using biological testing methods. The bioassay was performed using a set of test organisms representing the major trophic levels. We found the dependence of the toxic effect concentration degree of nTiO2 and nAl2O3 on the fluorescence of the bacterial biosensor "Ekolyum", the chemotactic response of ciliates Paramecium caudatum, the growth of unicellular algae Chlorella vulgaris Beijer and mortality of entomostracans Daphnia magna Straus. We revealed the selective dependence of nTiO2 and nAl2O3 toxicity on the size, concentration and chemical nature of nanoparticles. The minimal concentration causing an organism's response on nTiO2 and nAl2O3 effect depends on the type of the test- organism and the test reaction under study. We specified L(E)C50 and acute toxicity categories for all the studied nanoparticles. We determined that nTiO2 (Δ50=5 nm) belong to the category «Acute toxicity 1», nTiO2 (A50=90 nm) and nAl2O3 (Δ50=70 nm) - to the category «Acute toxicity 2», nAl2O3 (Δ50=7 nm) - to the category «Acute toxicity 3». No acute toxicity was registered for nTiO2 (Δ50=50 nm) and macro form TiO2.

  5. Effect of the undoped BaSnO3 space layer on the high mobility LaInO3/Ba1-xLaxSnO3 polar interface

    Science.gov (United States)

    Shin, Juyeon; Park, Chulkwon; Kim, Young Mo; Kim, Youjung; Char, Kookrin

    We have recently reported on the sheet conductance enhancement at the interface between two band insulators: LaInO3 (LIO) and BaSnO3 (BSO). The advantages of the two-dimensional electron gas-like (2DEG) state at the LIO/Ba1-xLaxSnO3 (BLSO) polar interface are its stability, the controllability of the local carrier concentration, and the high electron mobility of BLSO. The origin of enhanced conductance at the interface is still under investigation, but the doping level of BSO is a critical parameter for the polar charge contribution. We have investigated a new structure using an undoped BSO space layer at the LIO/BLSO interface. On one hand, this new structure will improve the mobility of the LIO/BLSO structure by reducing La impurity scattering. On the other hand, through this new structure we can answer the issues related with La diffusion at the LIO/BLSO polar interface and trace the origin of the 2DEG-like charge. This new modified structure of the LIO/BSO polar interface looks promising for higher electron mobility devices.

  6. The Nature of Magnetoelectric Coupling in Pb(Zr,Ti)O3-Pb(Fe,Ta)O3

    OpenAIRE

    Evans, Donald M.; Alexe, Marin; Schilling, Alina; Kumar, Ashok; Sanchez, Dilsom; Ortega, Nora; Katiyar, Ram S.; Scott, James F.; Gregg, James Marty

    2015-01-01

    The coupling between magnetization and polarization in a room temperature multiferroic (Pb(Zr,Ti)O3–Pb(Fe,Ta)O3) is explored by monitoring changes in capacitance that occur when a magnetic field is applied in each of three orthogonal directions. Magnetocapacitance effects, consistent with P2M2 coupling, are strongest when fields are applied in the plane of the single crystal sheet investigated.

  7. Theoretical studies of structural and magnetic properties of cubic perovskites PrCoO 3 and NdCoO 3

    Science.gov (United States)

    Ali, Z.; Ahmad, Iftikhar; Amin, B.; Maqbool, M.; Murtaza, G.; Khan, I.; Akhtar, M. J.; Ghaffor, F.

    2011-10-01

    The structural and magnetic properties of cubic perovskites, PrCoO 3 and NdCoO 3, are studied using the full potential linearized augmented plane wave (FP-LAPW) method within the frame work of density functional theory (DFT). The structural parameters are also investigated by analytical techniques. The calculated structural parameters are consistent with the experimental results. The strong hybridization of the O-2p, Co-3d and Pr/Nd-4 f states around the Fermi level reveals that these compounds are metallic. It is also found that the origin of ferromagnetism in these compounds is double-exchange interaction between Co-3d states via O-2p states (Co-O-Co).

  8. Optimization and interpretation of O3 and O3/H2O2 oxidation processes to pretreat hydrocortisone pharmaceutical wastewater.

    Science.gov (United States)

    Li, Guiju; He, Jingjing; Wang, Dandan; Meng, Panpan; Zeng, Ming

    2015-01-01

    Chemical synthetic pharmaceutical wastewater must be pretreated before traditional biological treatment to improve the biodegradability of pollutants due to their high concentration and complex composition. This study investigated O3 and O3/H2O2 systems to pretreat hydrocortisone wastewater. The optimum treatment efficiency of the O3 system was achieved under pH value of 5.76, dosage of O3 of 217.5 mg/L, and reaction time of 90 min. The removal efficiency of chemical oxygen demand (COD) and total organic carbon (TOC) was 94% and 92%, respectively. The ratio of biochemical oxygen demand (BOD) and COD (B/C) increased from 0.066 to 0.310. Moreover, the optimum H2O2/O3 molar ratio was 0.3 with the optimum pH of 3, and reaction time was reduced to 15 min to reach COD removal efficiency of 67.3% in the O3/H2O2 oxidation system. Interestingly, isobutanol was assumed to be a good hydroxyl radical trapping agent due to the great decrease of Fenton reagent reaction rate constant. By comparing two different kinetic models, oxidation mechanism could be interpreted by the pseudo first-order kinetic model with the high correlation coefficient R2 above 0.9787. It can be concluded that ozonation system was controlled by both direct oxidation and free radical oxidation, and particularly the later one played a dominant role.

  9. Energy Storage Characteristics of BiFeO3/BaTiO3 Bi-Layers Integrated on Si

    Directory of Open Access Journals (Sweden)

    Menglin Liu

    2016-11-01

    Full Text Available BiFeO3/BaTiO3 bi-layer thick films (~1 μm were deposited on Pt/Ti/SiO2/(100 Si substrates with LaNiO3 buffer layers at 500 °C via a rf magnetron sputtering process. X-ray diffraction (XRD analysis revealed that both BiFeO3 and BaTiO3 layers have a (00l preferred orientation. The films showed a small remnant polarization (Pr ~ 7.8 μC/cm2 and a large saturated polarization (Ps ~ 65 μC/cm2, resulting in a slim polarization-electric field (P-E hysteresis loop with improved energy storage characteristics (Wc = 71 J/cm3, η = 61%. The successful “slim-down” of the P-E loop from that of the pure BiFeO3 film can be attributed to the competing effects of space charges and the interlayer charge coupling on charge transport of the bi-layer film. The accompanying electrical properties of the bi-layer films were measured and the results confirmed their good quality.

  10. Directed laser processing of compacted powder mixtures Al2O3-TiO2-Y2O3

    Directory of Open Access Journals (Sweden)

    Vlasova M.

    2013-01-01

    Full Text Available The phase formation, microstructure and surface texture of laser treated ternary powder mixtures of Al2O3-TiO2-Y2O3 had been studied. Rapid high temperature heating and subsequent rapid cooling due to the directed movement of the laser beam forms concave ceramic tracks. Phase composition and microstructure of the tracks depends on the Al2O3 content and the TiO2/Y2O3 ratio of the initial mixtures. The main phases observed are Y3Al5O12, Y2Ti2O7, Al2O3 and Al2TiO5. Due to the temperature gradient in the heating zone, complex layered structures are formed. The tracks consist of three main layers: a thin surface layer, a layer of crystallization products of eutectic alloys, and a lower sintered layer. The thickness of the crystallization layer and the shrinkage of the irradiation zone depend on the amount of Y3Al5O12 and Al2O3 crystallized from the melt.

  11. Pilot-scale treatment of atrazine production wastewater by UV/O3/ultrasound: Factor effects and system optimization.

    Science.gov (United States)

    Jing, Liang; Chen, Bing; Wen, Diya; Zheng, Jisi; Zhang, Baiyu

    2017-12-01

    This study shed light on removing atrazine from pesticide production wastewater using a pilot-scale UV/O 3 /ultrasound flow-through system. A significant quadratic polynomial prediction model with an adjusted R 2 of 0.90 was obtained from central composite design with response surface methodology. The optimal atrazine removal rate (97.68%) was obtained at the conditions of 75 W UV power, 10.75 g h -1 O 3 flow rate and 142.5 W ultrasound power. A Monte Carlo simulation aided artificial neural networks model was further developed to quantify the importance of O 3 flow rate (40%), UV power (30%) and ultrasound power (30%). Their individual and interaction effects were also discussed in terms of reaction kinetics. UV and ultrasound could both enhance the decomposition of O 3 and promote hydroxyl radical (OH·) formation. Nonetheless, the dose of O 3 was the dominant factor and must be optimized because excess O 3 can react with OH·, thereby reducing the rate of atrazine degradation. The presence of other organic compounds in the background matrix appreciably inhibited the degradation of atrazine, while the effects of Cl - , CO 3 2- and HCO 3 - were comparatively negligible. It was concluded that the optimization of system performance using response surface methodology and neural networks would be beneficial for scaling up the treatment by UV/O 3 /ultrasound at industrial level. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. [Effects of elevated O3 on leaf litter decomposition and nutrient release of Quercus mongolica in city].

    Science.gov (United States)

    Su, Li-li; Xu, Sheng; Fu, Wei; He, Xing-yuan; Chen, Wei; Zhao, Yi; Ping, Qin

    2016-02-01

    The leaf litters of 10-year-old Quercus mongolica were put in nylon bags and exposed to elevated 03 level (120 nmol . mol-1) with the control of 40 nmol . mol-1 in open top chambers (OTCs) for 150 days to test the effect of high O3 on the litter decomposition. The results showed that no significant difference was observed in residual mass between elevated O3 treatment and the control. Elevated 03 inhibited the release of C and K during the decomposition, the residual rate of K under elevated O3 treatment (23.9%) was significantly higher than that of the control (17.1%) after 150-day decomposition. Compared with the control, N mineralization and lignin degradation in elevated O3 treatment were inhibited during early period of decomposition (0-60 d), but were promoted in later period (90-150 d). The changes of lignin/N showed no significant difference between elevated O3 treatment and the control during the decomposition. Elevated O3 generally promoted the release of P in leaf litter of Q. mongolica during the decomposition. C/P ratio was higher under elevated 03 than that under control. Significant positive correlation was shown between residual dry mass of leaf litters and the residual rate of C, N, K, C/N ratio during decomposition. Elevated 03 might play an important role in the nutrient cycle of forest ecosystem in high-O3 pollution area.

  13. Origin of enhanced visible light driven water splitting by (Rh, Sb)-SrTiO3.

    Science.gov (United States)

    Modak, Brindaban; Ghosh, Swapan K

    2015-06-21

    A systematic calculation, using hybrid density functional theory, has been carried out to investigate the origin of the enhancement of photo-conversion efficiency of Rh-doped SrTiO3 with codoping of Sb. In the case of Rh-doped SrTiO3, partially unoccupied states are introduced above the valence band, thus lowering the hole oxidation at the valence band (VB) drastically, which explains the poor oxygen evolution activity of Rh-doped SrTiO3. We show that the partially occupied t2g subset of the Rh 4d orbital is completely filled in the presence of Sb due to the transfer of the extra electron to the Rh center. As a result, acceptor states are completely passivated in the case of (Rh, Sb)-codoped SrTiO3 and a continuous band structure with reduced band gap is formed, which is responsible for the observed enhanced photocatalytic activity of (Rh, Sb)-codoped SrTiO3. We have shown that the relative positions of the band edges of (Rh, Sb)-codoped SrTiO3 with respect to the water redox levels are in favor of the spontaneous release of both hydrogen and oxygen during water splitting, which is consistent with the experimental observation. We have also studied the effect of codoping in different proportions (1 : 2 and 2 : 1) of Rh and Sb. Although 1 : 2 (Rh, Sb)-codoping leads to the formation of a clean band structure with the reduction of the band gap by a larger extent, it shows lower photo-conversion efficiency due to its charge non-compensated nature. In addition, the presence of acceptor states above the VB limits the oxygen evolution efficiency of 2 : 1 (Rh, Sb)-codoped SrTiO3. Thus, the present approach successfully reproduces the experimental features of the Rh-monodoped as well as (Rh, Sb)-codoped SrTiO3 and also explains their origin.

  14. Use of Combined Observational- and Model-Derived Photochemical Indicators to Assess the O3-NOx-VOC System Sensitivity in Urban Areas

    Directory of Open Access Journals (Sweden)

    Edson R. Carrillo-Torres

    2017-01-01

    Full Text Available Tropospheric levels of O3 have historically exceeded the official annual Mexican standards within the Monterrey Metropolitan Area (MMA in NE Mexico. High-frequency and high-precision measurements of tropospheric O3, NOy, NO2, NO, CO, SO2, PM10 and PM2.5 were made at the Obispado monitoring site near the downtown MMA from September 2012 to August 2013. The seasonal cycles of O3 and NOy are driven by changes in meteorology and to a lesser extent by variations in primary emissions. The NOy levels were positively correlated with O3 precursors and inversely correlated with O3 and wind speed. Recorded data were used to assess the O3-Volatile Organic Compounds (VOC-NOx system’s sensitivity through an observational-based approach. The photochemical indicator O3/NOy was derived from measured data during the enhanced O3 production period (12:00–18:00 Central Daylight Time (CDT, GMT-0500. The O3/NOy ratios calculated for this time period showed that the O3 production within the MMA is VOC sensitive. A box model simulation of production rates of HNO3 (PHNO3 and total peroxides (Pperox carried out for O3 episodes in fall and spring confirmed the VOC sensitivity within the MMA environment. No significant differences were observed in O3/NOy from weekdays to weekends or for PHNO3/Pperox ratios, confirming the limiting role of VOCs in O3 production within the MMA. The ratified photochemical regime observed may allow the environmental authorities to revise and verify the current policies for air quality control within the MMA.

  15. Effects of Tropospheric O3 on Trembling Aspen and Interaction with CO2: Results From An O3-Gradient and a Face Experiment

    Science.gov (United States)

    D.F. Karnosky; B. Mankovska; K. Percy; R.E. Dickson; G.K. Podila; J. Sober; A. Noormets; G. Hendrey; Mark D. Coleman; M. Kubiske; K.S. Pregitzer; J.G. Isebrands

    1999-01-01

    Abstract. Over the years, a series of trembling aspen (Populus tremuloides Michx.) clones differing in O3 sensitivity have been identified from OTC studies. Three clones (216 and 271[(O3 tolerant] and 259 [O3 sensitive]) have been characterized for O3...

  16. Effects of Tropospheric O3 on Trembling Aspen and Interaction with CO2: Results from an O3-Gradient and a FACE Experiment

    Science.gov (United States)

    D. F. Karnosky; B. Mankovska; K. Percy; R. E. Dickson; G. K. Podila; J. Sober; A. Noormets; G. Hendrey; M. D. Coleman; M. Kubiske; K. S. Pregitzer; J. G. Isebrands

    1999-01-01

    Over the years, a series of trembling aspen (Populus tremuloides Michx.) clones differing in O3 sensitivity have been identified from OTC studies. Three clones (216 and 271[O3 tolerant] and 259 [O3 sensitive]) have been characterized for O3 sensitivity by growth and biomass...

  17. Mechanochemically synthesized Al2O3-TiC nanocomposite

    International Nuclear Information System (INIS)

    Mohammad Sharifi, E.; Karimzadeh, F.; Enayati, M.H.

    2010-01-01

    Al 2 O 3 -TiC nanocomposite was synthesized by ball milling of aluminum, titanium oxide and graphite powder mixtures. Effect of the milling time and heat treatment temperatures were investigated. The structural evolution of powder particles after different milling times was studied by X-ray diffractometry and scanning electron microscopy. The results showed that after 40 h of ball milling the Al/TiO 2 /C reacted with a self-propagating combustion mode producing Al 2 O 3 -TiC nanocomposite. In final stage of milling, alumina and titanium carbide crystallite sizes were less than 10 nm. After annealing at 900 o C for 1 h, Al 2 O 3 and TiC crystallite sizes remained constant, however increasing annealing temperature to 1200 o C increased Al 2 O 3 and TiC crystallite size to 65 and 30 nm, respectively. No phase change was observed after annealing of the synthesized Al 2 O 3 -TiC powder.

  18. Microwave absorption behavior in Cr2O3 nanopowders

    International Nuclear Information System (INIS)

    Montiel, H.; Alvarez, G.; Conde-Gallardo, A.; Zamorano, R.

    2015-01-01

    Highlights: • We have investigated the microwave power absorption in Cr 2 O 3 nanopowders. • EMR spectra show the contributions of the core and the surface of the nanoparticles. • MAMMAS detected an antiferro-paramagnetic transition due to core of the nanoparticles. • LFMA signal is associated with the ferromagnetic order on the surface of the nanoparticles. - Abstract: We have investigated the microwave power absorption at X-band (8.8–9.8 GHz) in Cr 2 O 3 nanopowders, for the 294–400 K temperature range. For all temperatures, two different kinds of microwave absorptions are observed: the electron magnetic resonance (EMR) at high magnetic field and the low-field microwave absorption (LFMA) around zero field. EMR spectrum can be separated in two contributions associated with two different resonant absorption modes, where this result is interpreted as the combination of two different magnetic phases; corresponding to the core (mode A) and the surface (mode B) of the Cr 2 O 3 nanoparticles. Also, we have detected the onset of the antiferro-paramagnetic transition in resonant mode A, which is characteristic of Cr 2 O 3 samples; being confirmed the magnetic transition by means of the magnetically modulated microwave absorption spectroscopy (MAMMAS). Additionally, the temperature behaviors of the resonant mode B and the LFMA signal are associated with a ferromagnetic state on the surface of the Cr 2 O 3 nanoparticles

  19. Untilting BiFeO3: The influence of substrate boundary conditions in ultra-thin BiFeO3 on SrTiO3

    Directory of Open Access Journals (Sweden)

    Yongsoo Yang

    2013-11-01

    Full Text Available We report on the role of oxygen octahedral tilting in the monoclinic-to-tetragonal phase transition in ultra-thin BiFeO3 films grown on (001 SrTiO3 substrates. Reciprocal space maps clearly show the disappearance of the integer-order Bragg peak splitting associated with the monoclinic phase when the film thickness decreases below 20 unit cells. This monoclinic-to-tetragonal transition is accompanied by the evolution of the half-order diffraction peaks, which reflects untilting of the oxygen octahedra around the [110] axis, proving that the octahedral tilting is closely correlated with the transition. This structural change is thickness-dependent, and different from a strain-induced transition in the conventional sense.

  20. Leakage current behavior in lead-free ferroelectric (K,Na)NbO3-LiTaO3-LiSbO3 thin films

    Science.gov (United States)

    Abazari, M.; Safari, A.

    2010-12-01

    Conduction mechanisms in epitaxial (001)-oriented pure and 1 mol % Mn-doped (K0.44,Na0.52,Li0.04)(Nb0.84,Ta0.1,Sb0.06)O3 (KNN-LT-LS) thin films on SrTiO3 substrate were investigated. Temperature dependence of leakage current density was measured as a function of applied electric field in the range of 200-380 K. It was shown that the different transport mechanisms dominate in pure and Mn-doped thin films. In pure (KNN-LT-LS) thin films, Poole-Frenkel emission was found to be responsible for the leakage, while Schottky emission was the dominant mechanism in Mn-doped thin films at higher electric fields. This is a remarkable yet clear indication of effect of 1 mol % Mn on the resistive behavior of such thin films.

  1. Second Phase (BaGeO3, BaSiO3) Nanocolumns in Yba2Cu3O7-x Films (Postprint)

    Science.gov (United States)

    2010-01-01

    chemical compatibility of BaSnO3 (BSO) and BaZrO3 (BZO) as observed in YBCO+BSO and YBCO+BZO is critical to process high Jc YBCO films. 15. SUBJECT TERMS...flux pinning, BaSnO3 , BaGeO3, BaSiO3, YBa2Cu3O7-x, coated conductors, pulsed laser deposition 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF...compatibility of BaSnO3 (BSO) and BaZrO3 (BZO) as observed in YBCO+BSO and YBCO+BZO is critical to process high Jc YBCO films KEYWORDS: Flux pinning

  2. Estudio del mecanismo de compensación de BaTiO3 dopado con La2O3

    Directory of Open Access Journals (Sweden)

    Castro, M. S.

    2004-06-01

    Full Text Available In this work, the incorporation of several concentrations of the La3+ ion into the BaTiO3 lattice was studied. It was verified that low La3+ concentrations inhibits the grain growth and produces a highly densified material. However, a delay in the sintering behavior in ceramics with high doping concentrations was observed. The La3+ donor incorporation in the BaTiO3 modified the defects structure, favored titanium vacancies formation, and stabilized a pseudocubic phase. This effect influences the dielectric properties and the cubic-tetragonal transition temperature.En este trabajo se estudió la incorporación del ión La3+ en la red de BaTiO3. Se comprobó que bajas concentraciones de La3+ inhiben el crecimiento de los granos de BaTiO3 significativamente, a la vez que originan un material altamente densificado. Sin embargo, se confirmó que existe un límite de concentración de La2O3 a partir del cual se observó un retardo en el sinterizado del BaTiO3. La incorporación de La3+ como donor en el BaTiO3 modificó su estructura de defectos, favoreció la formación de vacantes de titanio y lo estabilizó en una fase pseudocúbica. Este efecto también se refleja en las propiedades dieléctricas del material y en la temperatura de transición de fases cúbica-tetragonal.

  3. Electromechanical properties of Na0.5Bi0.5TiO3-SrTiO3-PbTiO3 solid solutions

    Science.gov (United States)

    Svirskas, Šarūnas; Dunce, Marija; Birks, Eriks; Sternberg, Andris; Banys, Jūras

    2018-03-01

    Thorough studies of electric field-induced strain are presented in 0.4Na1/2Bi1/2TiO3-(0.6-x)SrTiO3-xPbTiO3 (NBT-ST-PT) ternary solid solutions. The increase of concentration of lead x induces crossover from relaxor to ferroelectric. Strain in a relaxor state can be described by electrostrictive behavior. The electrostrictive coefficients correspond to other well-known relaxor ferroelectrics. The concentration region with a stable ferroelectric phase revealed that the polarization dependence of strain does not exhibit nonlinearity, although they are inherent to the electric field dependence of strain. In this case, electric field dependence of strain is described in terms of the Rayleigh law and the role of domain wall contribution is extracted. Finally, the character of strain at the electric field-induced phase transition between the nonpolar and the ferroelectric states is studied. The data shows that in the vicinity of the electric field induced phase transition the strain vs. electric field displays electrostrictive character.

  4. Interface Control of Ferroelectricity in an SrRuO3/BaTiO3/SrRuO3Capacitor and its Critical Thickness.

    Science.gov (United States)

    Shin, Yeong Jae; Kim, Yoonkoo; Kang, Sung-Jin; Nahm, Ho-Hyun; Murugavel, Pattukkannu; Kim, Jeong Rae; Cho, Myung Rae; Wang, Lingfei; Yang, Sang Mo; Yoon, Jong-Gul; Chung, Jin-Seok; Kim, Miyoung; Zhou, Hua; Chang, Seo Hyoung; Noh, Tae Won

    2017-05-01

    The atomic-scale synthesis of artificial oxide heterostructures offers new opportunities to create novel states that do not occur in nature. The main challenge related to synthesizing these structures is obtaining atomically sharp interfaces with designed termination sequences. In this study, it is demonstrated that the oxygen pressure (PO2) during growth plays an important role in controlling the interfacial terminations of SrRuO 3 /BaTiO 3 /SrRuO 3 (SRO/BTO/SRO) ferroelectric (FE) capacitors. The SRO/BTO/SRO heterostructures are grown by a pulsed laser deposition method. The top SRO/BTO interface, grown at high PO2 (around 150 mTorr), usually exhibits a mixture of RuO 2 -BaO and SrO-TiO 2 terminations. By reducing PO2, the authors obtain atomically sharp SRO/BTO top interfaces with uniform SrO-TiO 2 termination. Using capacitor devices with symmetric and uniform interfacial termination, it is demonstrated for the first time that the FE critical thickness can reach the theoretical limit of 3.5 unit cells. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Enhanced flux pinning by BaZrO3 and (Gd,y)2O3 nano-structures in metal organic chemical vapor deposited GdYBCO high temperature superconductor tapes

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Y [SuperPower Incorporated, Schenectady, New York; Selvamanickam, V. [SuperPower Incorporated, Schenectady, New York; Paranthaman, Mariappan Parans [ORNL; Cantoni, Claudia [ORNL; Aytug, Tolga [ORNL; Goyal, Amit [ORNL; Lee, Dominic F [ORNL; Specht, Eliot D [ORNL; Zuev, Yuri L [ORNL; Zhang, Yifei [ORNL

    2009-01-01

    We have formed BaZrO3 nano-columns and (Gd,Y)2O3 nano-precipitates in reel-to-reel MOCVD processed (Gd,Y)Ba2Cu3O7-x coated conductors and increased the critical currents (Ic) of the conductors in applied magnetic fields to remarkable levels. A (Gd,Y)Ba2Cu3O7-x tape of 1m length with 6.5% Zr-additions and 30% composition rich in both Gd and Y showed Ic values of 813 A/cm-width at (self-field, 77K) and above 186 A/cm-width at (1T, 77K). The strongly enhanced flux pinning over a wide range of magnetic field orientations can be attributed to the bidirectionally aligned defect structures of BaZrO3 and (Gd,Y)2O3 created by optimized MOCVD conditions.

  6. Resistive switching in polycrystalline YMnO3 thin films

    Directory of Open Access Journals (Sweden)

    A. Bogusz

    2014-10-01

    Full Text Available We report a unipolar, nonvolatile resistive switching in polycrystalline YMnO3 thin films grown by pulsed laser deposition and sandwiched between Au top and Ti/Pt bottom electrodes. The ratio of the resistance in the OFF and ON state is larger than 103. The observed phenomena can be attributed to the formation and rupture of conductive filaments within the multiferroic YMnO3 film. The generation of conductive paths under applied electric field is discussed in terms of the presence of grain boundaries and charged domain walls inherently formed in hexagonal YMnO3. Our findings suggest that engineering of the ferroelectric domains might be a promising route for designing and fabrication of novel resistive switching devices.

  7. Synthesis and characterization of FeTiO3 ceramics

    Directory of Open Access Journals (Sweden)

    Anil B. Gambhire

    2016-09-01

    Full Text Available Nanocrystalline FeTiO3 ceramic powders were prepared by the sol–gel process combined with a surfactant-assisted template method. The resulting powders were calcined at different temperatures ranging from 150 °C to 600 °C for 2 h in air. The results revealed that a pure hexagonal phase of FeTiO3 could be obtained at a low temperature, 600 °C. The phase evolution of FeTiO3 was investigated by X-ray diffraction patterns (XRD, Fourier-transform infrared spectroscopy (FT-IR, and X-ray photoelectron spectroscopy (XPS. Particle size and morphology were studied by transmission electron microscopy (TEM.

  8. Fe2O3 hollow sphere nanocomposites for supercapacitor applications

    Science.gov (United States)

    Zhao, Yu; Wen, Yang; Xu, Bing; Lu, Lu; Ren, Reiming

    2018-02-01

    Nanomaterials have attracted increasing interest in electrochemical energy storage and conversion. Hollow sphere Fe2O3 nanocomposites were successfully prepared through facile low temperature water-bath method with carbon sphere as hard template. The morphology and microstructure of samples were characterized by X-ray diffraction (XRD) and Scanning electron microscope (SEM), respectively. Through hydrolysis mechanism, using ferric chloride direct hydrolysis, iron hydroxide coated on the surface of carbon sphere, after high temperature calcination can form the hollow spherical iron oxide materials. Electrochemical performances of the hollow sphere Fe2O3 nanocomposites electrodes were investigated by cyclic voltammery (CV) and galvanostatic charge/discharge. The Pure hollow sphere Fe2O3 nanocomposites achieves a specific capacitance of 125 F g-1 at the current density of 85 mA g-1. The results indicate that the uniform dispersion of hollow ball structure can effectively reduce the particle reunion in the process of charging and discharging.

  9. Conductive Nature of Grain Boundaries in Nanocrystalline Stabilized Bi2O3Thin-Film Electrolyte.

    Science.gov (United States)

    Jeong, Seung Jin; Kwak, No Woo; Byeon, Pilgyu; Chung, Sung-Yoon; Jung, WooChul

    2018-02-21

    Stabilized Bi 2 O 3 has gained a considerable amount of attention as a solid electrolyte material for low-temperature solid oxide fuel cells due to its superior oxygen-ion conductivity at the temperature of relevance (≤500 °C). Despite many research efforts to measure the transport properties of stabilized Bi 2 O 3 , the effects of grain boundaries on the electrical conductivity have rarely been reported and their results are even controversial. Here, we attempt quantitatively to assess the grain boundary contribution out of the total ionic conductivity at elevated temperatures (350-500 °C) by fabricating epitaxial and nano-polycrystalline thin films of yttrium-stabilized Bi 2 O 3 . Surprisingly, both epitaxial and polycrystalline films show nearly identical levels of ionic conductivity, as measured by alternating current impedance spectroscopy and this is the case despite the fact that the polyfilm possesses nanosized columnar grains and thus an extremely high density of the grain boundaries. The highly conductive nature of grain boundaries in stabilized Bi 2 O 3 is discussed in terms of the clean and chemically uniform grain boundary without segregates, and the implications for device application are suggested.

  10. Intrinsic defects and spectral characteristics of SrZrO3 perovskite

    Science.gov (United States)

    Li, Zhenzhang; Duan, He; Jin, Yahong; Zhang, Shaoan; Lv, Yang; Xu, Qinfang; Hu, Yihua

    2018-04-01

    First-principles calculations and experiment analysis were performed to study the internal relation between seven types of intrinsic defects and the persistent luminescence in SrZrO3 host material. The calculation shows that rich zirconium defects have the low energy cost and thus are easy to form. Zr vacancies are too high energy to play any role in defect which is related luminescence phenomenon of SrZrO3 phosphor. However, oxygen vacancies stand out as a likely candidate, because it can yield two carrier reservoirs: a fully-occupied singlet electron's reservoir which lies above the valence band maximum, and an empty triply degenerate hole's reservoir which is just below the conduction band minimum. Sr vacancies are not directly relevant to the persistent luminescence due to its too shallow electron trap level. The characteristics of these defects are fully explained by the equilibrium properties of SrZrO3. An experimental study of the thermoluminescence glow for these defects is conducted and the calculation is consistent with the experimental results. A mechanism of the persistent luminescence for SrZrO3:Pr3+, Eu3+ is explained according to oxygen vacancies trap center. Findings of this study may serve as theoretical references for controlling intrinsic traps by more refined experiments.

  11. Rarity of upper-tropospheric low O3 mixing ratio events during MOZAIC flights

    Directory of Open Access Journals (Sweden)

    W. A. H. Asman

    2003-01-01

    Full Text Available Only a few previous observations of very low O3 mixing ratios in the upper troposphere are available. The aim of this study was to examine the rich MOZAIC data set for more. Flights with at least 25 4 s averaged mixing ratios less than 8 ppbv at pressures lower than 500 hPa measured using commercial aircraft within the MOZAIC project have been analysed. There are eleven flights that fulfil these conditions (excluding artefacts as discussed below, representing about 0.001% of all measurements during the analysed period August 1994-December 1997. The low O3 events occurred over Southeast Asia, Africa, Brazil and the sea area 200 km east of Florida (US and were all likely to be associated with transport of air masses from tropical sea areas. These low mixing ratio events occur in the upper troposphere during periods with generally low mixing ratios. They are not only found over sea, but also over land at pressure levels as low as 179 hPa. It could well be that some of the low O3 mixing ratio events measured during two or more flights belong to the same bigger low O3 mixing ratio area.

  12. Pulsed laser deposition of epitaxial Sr(RuxSn1-x)O3 thin film electrodes and KNbO3/Sr(RuxSn1-x)O3 bilayers

    International Nuclear Information System (INIS)

    Christen, H.M.; Boatner, L.A.; English, L.Q.; Geea, L.A.; Marrero, P.J.; Norton, D.P.

    1995-01-01

    Sr(Ru x Sn 1-x ) 3 is proposed as a new conducting oxide for use in epitaxial multilayer structures. The Sr(Ru o 48 Sn 0.52 )0 3 composition exhibits an excellent lattice match with (100)-oriented KTaO 3 , and films of this composition grown by pulsed laser deposition on KTaO 3 , SrTiO 3 , and LaAlO 3 substrates have been analyzed by X-ray diffraction, Rutherford backscattering/ion channeling, and resistivity measurements. Epitaxial KNbO 3 /Sr(Ru 0.48 Sn 0.52 )O 3 bilayers have been successfully grown

  13. Catalytic Methane Decomposition over Fe-Al2O3

    KAUST Repository

    Zhou, Lu

    2016-05-09

    The presence of a Fe-FeAl2O4 structure over an Fe-Al2O3 catalysts is demonstrated to be vital for the catalytic methane decomposition (CMD) activity. After H2 reduction at 750°C, Fe-Al2O3 prepared by means of a fusion method, containing 86.5wt% FeAl2O4 and 13.5wt% Fe0, showed a stable CMD activity at 750°C for as long as 10h. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Leaching of Al2O3 in simulated repository conditions

    International Nuclear Information System (INIS)

    Svensson, B.-M.; Dahl, L.

    1978-06-01

    Al 2 O 3 material has been leached at 90 deg C in: simulated ground water at pH 8.5, embedded in bentonite + silica sand saturated with the same water, and in simulated ground water at pH 6 and pH 10. Leaching periods varied from 30 days to 300 days. We observed slight weight increments in all cases from deposits on samples from the environment. These mask weight losses from Al 2 O 3 that may have occurred. (author)

  15. Review of SHARC 2. 0 O3 kinetics and spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Lang, V.I.

    1993-04-01

    A critical review of rate constants assigned to vibrational excitation and deexcitation processes for O3 in the Strategic High Altitude Atmospheric Radiance Code (SHARC 2.0) is presented. A complete list of O3 pure rotational and rovibrational band parameters, based on the 1991/92 version fo the HITRAN data base, is included. Modifications to specific energy transfer processes used in the SHARC 2.0 scheme have been recommended based on recent experimental literature data and on recent atmospheric observations.

  16. Focussed multiple scattering in compressed ReO3

    International Nuclear Information System (INIS)

    Alberding, N.; Crozier, E.D.; Ingalls, R.; Houser, B.

    1986-01-01

    ReO 3 is a Perovskite consisting of oxygen-bridged rhenium atoms. The bridging angle can be continuously varied by application of pressure above a phase transition at 5.1 kbar. EXAFS spectra of ReO 3 has been measured as a function of pressure up to 22 kbar. The data are related to the angle-dependent oxygen scattering amplitude, f 0 (β,k). These experimental results are useful in verifying theoretical calculations and for analyzing other systems in which the bridging angle is unknown

  17. Ultrathin BaTiO3 templates for multiferroic nanostructures

    OpenAIRE

    Chen, Xumin; Yang, Seolun; Kim, Ji-Hyun; Kim, Hyung-Do; Kim, Jae-Sung; Rojas, Geoffrey; Skomski, Ralph; Lu, Haidong; Bhattacharya, Anand; Santos, Tiffany; Guisinger, Nathan; Bode, Matthias; Gruverman, Alexei; Enders, Axel

    2011-01-01

    Structural, electronic and dielectric properties of high-quality ultrathin BaTiO3 films are investigated. The films, which are grown by ozone-assisted molecular beam epitaxy on Nb-doped SrTiO3 (001) substrates and having thicknesses as thin 8 unit cells (3.2 nm), are unreconstructed and atomically smooth with large crystalline terraces. A strain-driven transition to 3D island formation is observed for films of of 13 unit cells thickness (5.2 nm). The high structural quality of the surfaces, t...

  18. High Pressure Phase Transitions in Yttria, Y2O3

    International Nuclear Information System (INIS)

    Bose, Preyoshi P; Gupta, M K; Mittal, R; Chaplot, S L; Rols, S; Achary, S N; Tyagi, A K

    2012-01-01

    We have carried out neutron inelastic scattering measurement of the phonon density of states and lattice dynamic calculations for Y 2 O 3 using ab-initio density functional perturbation theory and interatomic potential model. The calculations are found to be in good agreement with experimental data, indicating that the potential model can be used for the calculation of phase diagram of Y 2 O 3 . The model is then used for free energy calculation to understand the stability of various phases as a function of pressure and temperature.

  19. Magneto-structural study of the multiferroic BiFeO3–SrTiO3

    International Nuclear Information System (INIS)

    Vura, Sandeep; Anil Kumar, P.S.; Senyshyn, Anatoliy; Ranjan, Rajeev

    2014-01-01

    The structural and magnetic study of the pseudo-binary multiferroic (1−x)BiFeO 3 −(x)SrTiO 3 has been investigated as a function of composition and temperature. In contrary to the previous studies, detailed examination revealed that the reported anomaly in the magnetization at x–0.30 does not occur at the composition induced rhombohedral–cubic phase boundary, but within the rhombohedral phase itself. The rhombohedral to cubic transition occurs at x>0.4. Evidence of magneto-elastic coupling near the Neel temperature and nucleation-growth mode of the rhombohedral–cubic transformation, with both the phases coexisting over a range of temperature was found. - Highlights: • The paper reports magneto-structural study of BiFeO 3 –SrTiO 3 multiferroic. • Evidence of magneto-elastic coupling near the Neel temperature is shown. • The magnetization anomaly at 30 mol% SrTiO 3 occurs within the rhombohedral phase

  20. Electric-field gradients at 181Ta impurity sites in Ho2O3 and Eu2O3 bixbyites

    International Nuclear Information System (INIS)

    Errico, Leonardo A.; Renteria, Mario; Bibiloni, Anibal G.; Freitag, Kristian

    2007-01-01

    The time-differential γ-γ perturbed-angular-correlation (PAC) technique with ion-implanted 181 Hf tracers has been applied to study the hyperfine interactions of 181 Ta impurities in the cubic bixbyite structure of Ho 2 O 3 and Eu 2 O 3 . The PAC experiments were performed in air in the temperature range 300-1373 K (in the case of Ho 2 O 3 ) and 77-1273 K (in the case of Eu 2 O 3 ). For both oxides, two electric-quadrupole interactions were found and attributed to the electric-field gradients (EFGs) acting on 181 Ta probes substitutionally located at the two free-of-defects nonequivalent cation sites of the bixbyite structure. In the case of Ho 2 O 3 , two additional interactions were found in the temperature range 300-573 K. These results, as well as previous characterizations of the EFG at 181 Ta sites in bixbyites, were compared to those obtained in experiments using 111 Cd as probe, and to point-charge model calculations. Very recent ab initio predictions for the EFG tensor at impurities sites in binary oxides are also discussed. All these results enable us to discuss the validity of the widely used ionic model to describe the EFG in these highly ionic compounds

  1. Field effect in perovskite heterostructures based on BaSnO3 and BaHfO3

    Science.gov (United States)

    Kim, Young Mo; Park, Chulkwon; Kim, Useong; Shin, Juyeon; Kim, Youjung; Char, Kookrin

    Perovskite La-doped BaSnO3 (BLSO) was reported to possess high electron mobility and excellent oxygen stability. We fabricated a field effect transistor on SrTiO3 substrate using BLSO as a channel layer and BaHfO3 (BHO) as a gate insulator. To reduce the threading dislocations and enhance the electrical properties of the channel, undoped BaSnO3 (BSO) buffer layer was grown on SrTiO3 substrates before the channel layer deposition. X-ray diffraction measurement confirms the epitaxial growth of BHO on BSO. We investigated optical and dielectric properties of the BHO gate insulator; the optical bandgap and the dielectric constant were measured to be 6.1 eV and 37.8, respectively. Using BHO as the gate insulator, we obtained the conductivity modulation in the channel by field effect. We will report on the electrical properties of the field effect transistor such as the output characteristics, the transfer characteristics, the Ion/Ioff ratio, the subthreshold swing and the field effect mobility.

  2. Structure and thermal expansion of Lu2O3 and Yb2O3 up to the melting points

    Science.gov (United States)

    Pavlik, Alfred; Ushakov, Sergey V.; Navrotsky, Alexandra; Benmore, Chris J.; Weber, Richard J. K.

    2017-11-01

    Knowledge of thermal expansion and high temperature phase transformations is essential for prediction and interpretation of materials behavior under the extreme conditions of high temperature and intense radiation encountered in nuclear reactors. Structure and thermal expansion of Lu2O3 and Yb2O3 were studied in oxygen and argon atmospheres up to their melting temperatures using synchrotron X-ray diffraction on laser heated levitated samples. Both oxides retained the cubic bixbyite C-type structure in oxygen and argon to melting. In contrast to fluorite-type structures, the increase in the unit cell parameter of Yb2O3 and Lu2O3 with temperature is linear within experimental error from room temperature to the melting point, with mean thermal expansion coefficients (8.5 ± 0.6) · 10-6 K-1 and (7.7 ± 0.6) · 10-6 K-1, respectively. There is no indication of a superionic (Bredig) transition in the C-type structure or of a previously suggested Yb2O3 phase transformation to hexagonal phase prior to melting.

  3. Spin-Orbit Interaction and Kondo Scattering at the PrAlO3/SrTiO3 Interface

    Science.gov (United States)

    Mozaffari, Shirin; Guchhait, Samaresh; Markert, John

    We have investigated the effect of oxygen content, in the PO2 range of 6 ×10-6 - 1 ×10-3 torr, on the spin-orbit (SO) interaction at PrAlO3/SrTiO3 interface. The most-conducting 2-D-like PrAlO3 interfaces were not as conducting as comparable LaAlO3 samples, indicating either a steric or mixed-valent effect. The least-conducting, most oxygenated PrAlO3 interface exhibits hole conductivity, a departure from the typical electron-doped behavior. For 10-5 and 10-4 torr samples, high-temperature metallic behavior is accompanied by an upturn in resistivity at low temperatures, consistent with Kondo scattering theory; analysis gives a Kondo temperature 17 K. The magnetoresistance (MR) for the low PO2-grown samples was modeled with a positive part due to weak anti-localization (WAL) from a strong SO interaction, and a negative part due to the Kondo effect. The variation of MR suggests a strong SO interaction for the 10-5 torr sample with HSO = 1.25 T in both field orientations. The WAL effect is smaller for higher PO2-grown samples, where the high-field MR is dominated by the Kondo effect.

  4. Epitaxial growth and thermodynamic stability of SrIrO3/SrTiO3 heterostructures

    Science.gov (United States)

    Groenendijk, D. J.; Manca, N.; Mattoni, G.; Kootstra, L.; Gariglio, S.; Huang, Y.; van Heumen, E.; Caviglia, A. D.

    2016-07-01

    Obtaining high-quality thin films of 5d transition metal oxides is essential to explore the exotic semimetallic and topological phases predicted to arise from the combination of strong electron correlations and spin-orbit coupling. Here, we show that the transport properties of SrIrO3 thin films, grown by pulsed laser deposition, can be optimized by considering the effect of laser-induced modification of the SrIrO3 target surface. We further demonstrate that bare SrIrO3 thin films are subject to degradation in air and are highly sensitive to lithographic processing. A crystalline SrTiO3 cap layer deposited in-situ is effective in preserving the film quality, allowing us to measure metallic transport behavior in films with thicknesses down to 4 unit cells. In addition, the SrTiO3 encapsulation enables the fabrication of devices such as Hall bars without altering the film properties, allowing precise (magneto)transport measurements on micro- and nanoscale devices.

  5. Charge driven metal-insulator transitions in LaMnO3|SrTiO3 (111) superlattices

    KAUST Repository

    Cossu, Fabrizio

    2017-08-01

    Interfaces of perovskite oxides, due to the strong interplay between the lattice, charge and spin degrees of freedom, can host various phase transitions, which is particularly interesting if these transitions can be tuned by external fields. Recently, ferromagnetism was found together with a seemingly insulating state in superlattices of manganites and titanates. We therefore study the (111) oriented $(\\\\text{LaMnO}_3)_{6-x}\\\\vert(\\\\text{SrTiO}_3)_{6+x}~(x = -0.5, 0, 0.5)$ superlattices by means of ab initio calculations, predicting a ferromagnetic ground state due to double exchange in all cases. We shed light on the ferromagnetic coupling in the LaMnO3 region and at the interfaces. The insulating states of specific superlattices can be understood on the basis of Jahn-Teller modes and electron/hole doping.

  6. Tunnel and electrostatic coupling in graphene-LaAlO3/SrTiO3 hybrid systems

    Directory of Open Access Journals (Sweden)

    I. Aliaj

    2016-06-01

    Full Text Available We report on the transport properties of hybrid devices obtained by depositing graphene on a LaAlO3/SrTiO3 oxide junction hosting a 4 nm-deep 2-dimensional electron system. At low graphene-oxide inter-layer bias, the two electron systems are electrically isolated, despite their small spatial separation. A very efficient reciprocal gating of the two neighboring 2-dimensional systems is shown. A pronounced rectifying behavior is observed for larger bias values and ascribed to the interplay between electrostatic field-effects and tunneling across the LaAlO3 barrier. The relevance of these results in the context of strongly coupled bilayer systems is discussed.

  7. Ferroelectricity driven magnetism at domain walls in LaAlO3/PbTiO3 superlattices

    Science.gov (United States)

    Zhou, P. X.; Dong, S.; Liu, H. M.; Ma, C. Y.; Yan, Z. B.; Zhong, C. G.; Liu, J. -M.

    2015-01-01

    Charge dipole moment and spin moment rarely coexist in single-phase bulk materials except in some multiferroics. Despite the progress in the past decade, for most multiferroics their magnetoelectric performance remains poor due to the intrinsic exclusion between charge dipole and spin moment. As an alternative approach, the oxide heterostructures may evade the intrinsic limits in bulk materials and provide more attractive potential to realize the magnetoelectric functions. Here we perform a first-principles study on LaAlO3/PbTiO3 superlattices. Although neither of the components is magnetic, magnetic moments emerge at the ferroelectric domain walls of PbTiO3 in these superlattices. Such a twist between ferroelectric domain and local magnetic moment, not only manifests an interesting type of multiferroicity, but also is possible useful to pursuit the electrical-control of magnetism in nanoscale heterostructures. PMID:26269322

  8. x-T phase diagram of La-substituted BiFeO3-PbTiO3

    Directory of Open Access Journals (Sweden)

    K. K. Mishra

    2011-09-01

    Full Text Available Single-phase polycrystalline powders of 0.5(Bi1-xLaxFeO3-0.5PbTiO3 solid-solution were synthesized for x ≤ 0.3 using solid-state reaction method. The mixed crystals exhibit a tetragonal structure at ambient and the c/a ratio decreases with x. In-situ X-ray diffraction measurements at elevated temperatures show a structural transition to a cubic phase. The transition temperatures have been obtained for different x and a x-T phase diagram has been proposed.

  9. Soil Microbial Responses to Elevated CO2 and O3 in a Nitrogen-Aggrading Agroecosystem

    Science.gov (United States)

    Cheng, Lei; Booker, Fitzgerald L.; Burkey, Kent O.; Tu, Cong; Shew, H. David; Rufty, Thomas W.; Fiscus, Edwin L.; Deforest, Jared L.; Hu, Shuijin

    2011-01-01

    Climate change factors such as elevated atmospheric carbon dioxide (CO2) and ozone (O3) can exert significant impacts on soil microbes and the ecosystem level processes they mediate. However, the underlying mechanisms by which soil microbes respond to these environmental changes remain poorly understood. The prevailing hypothesis, which states that CO2- or O3-induced changes in carbon (C) availability dominate microbial responses, is primarily based on results from nitrogen (N)-limiting forests and grasslands. It remains largely unexplored how soil microbes respond to elevated CO2 and O3 in N-rich or N-aggrading systems, which severely hinders our ability to predict the long-term soil C dynamics in agroecosystems. Using a long-term field study conducted in a no-till wheat-soybean rotation system with open-top chambers, we showed that elevated CO2 but not O3 had a potent influence on soil microbes. Elevated CO2 (1.5×ambient) significantly increased, while O3 (1.4×ambient) reduced, aboveground (and presumably belowground) plant residue C and N inputs to soil. However, only elevated CO2 significantly affected soil microbial biomass, activities (namely heterotrophic respiration) and community composition. The enhancement of microbial biomass and activities by elevated CO2 largely occurred in the third and fourth years of the experiment and coincided with increased soil N availability, likely due to CO2-stimulation of symbiotic N2 fixation in soybean. Fungal biomass and the fungi∶bacteria ratio decreased under both ambient and elevated CO2 by the third year and also coincided with increased soil N availability; but they were significantly higher under elevated than ambient CO2. These results suggest that more attention should be directed towards assessing the impact of N availability on microbial activities and decomposition in projections of soil organic C balance in N-rich systems under future CO2 scenarios. PMID:21731722

  10. Electro-optical properties of tetragonal KNbO3

    Indian Academy of Sciences (India)

    Solid State Physics Division, Bhabha Atomic Research Centre, Trombay,. Mumbai 400 085, India. E-mail: psastry@apsara.barc.ernet.in. MS received 12 November 2006; revised 6 March 2007; accepted 16 March 2007. Abstract. Linear electro-optical tensor coefficients and optical susceptibility of tetrag- onal KNbO3 are ...

  11. Synthesis of BiFeO3 by carbonate precipitation

    Indian Academy of Sciences (India)

    The precipitate yielded BiFeO3 at an optimal calcination temperature of ∼560◦C. Energy dispersive X-ray (EDX) analysis ... C (Michel et al 1969; Fischer et al 1980). ..... C and used to synthesize this material by conventional ceramic synthesis method. Detailed exam- ination of the precipitate revealed that it consists of bis-.

  12. Depolarization temperature and piezoelectric properties of TiO3 ...

    Indian Academy of Sciences (India)

    WINTEC

    Lead-free piezoelectric ceramics; depolarization temperature; perovskite structure; piezoelectric properties. 1. Introduction. Increasing interest concerning the environmental pro- blems of Pb(Zr, Ti)O3(PZT)-based ceramics has led to the demand of lead-free ferroelectric ceramics in electronic applications (Shieh et al 2007).

  13. Arabidopsis transcriptional responses differentiate between O3 and herbicides

    Science.gov (United States)

    Using published data based on Affymetrix ATH1 Gene-Chips we characterized the transcriptional response of Arabidopsis thaliana Columbia to O3 and a few other major environmental stresses including oxidative stress . A set of 101 markers could be extracted which provided a compo...

  14. Synthesis of BiFeO3 by carbonate precipitation

    Indian Academy of Sciences (India)

    Magnetoelectric multiferroic BiFeO3 (BFO) was synthesized by a simple carbonate precipitation technique of metal nitrate solutions. X-ray powder diffraction and thermo-gravimetric analysis (TGA) revealed that the precipitate consists of an intimate mixture of crystalline bismuth carbonate and an amorphous hydroxide of ...

  15. Structures and energetics of Ga2O3 polymorphs

    International Nuclear Information System (INIS)

    Yoshioka, S; Hayashi, H; Kuwabara, A; Oba, F; Matsunaga, K; Tanaka, I

    2007-01-01

    First-principles calculations are made for five Ga 2 O 3 polymorphs. The structure of ε-Ga 2 O 3 with the space group Pna 2 1 (No. 33, orthorhombic), which is sometimes called κ-Ga 2 O 3 in the literature, is consistent with experimental reports. The structure of γ-Ga 2 O 3 is optimized within 14 inequivalent configurations of defective spinel structures. Phonon dispersion curves of four polymorphs are obtained. The volume expansivity, bulk modulus, and specific heat at constant volume are computed as a function of temperature within the quasi-harmonic approximation. The Helmholtz free energies of the polymorphs are thus compared. The expansivity shows a relationship of β<ε<α<δ, while β<ε<δ<α for the bulk modulus. The formation free energies have the tendency β<ε<α<δ<γ at low temperatures. With the increase of temperature, the difference in free energy between the β-phase and the ε-phase becomes smaller. Eventually the ε phase becomes more stable at above 1600 K

  16. Fe2O3/MWCNTs nanocomposite decorated glassy carbon electrode ...

    Indian Academy of Sciences (India)

    35

    Keywords: Fe2O3; MWCNTs; electrochemical determination; nitrite. 1. Introduction. As is known to all that nitrite is universally found within the live process and environment and is generally used as a corrosion inhibitor or additive in some foods [1,2]. However, carcinogenic nitrosamines can be formed by nitrite interact with ...

  17. Vacancy induced magnetism in SrTiO3

    International Nuclear Information System (INIS)

    Zhang Yongjia; Hu Jifan; Cao Ensi; Sun Li; Qin Hongwei

    2012-01-01

    Vacancy-induced magnetism in perovskite SrTiO 3 is investigated by ab initio calculations and magnetic measurements. The calculations of the generalized gradient approximation (GGA), the local density approximation (LDA) and the local density approximation with on-site effect U (LDA+U) methods show that stoichiometric SrTiO 3 is nonmagnetic. The GGA calculated results indicate that Ti or O vacancy could induce magnetism rather than Sr vacancy. The LDA and LDA+U calculations show that the Ti vacancy could induce magnetism, while Sr and O vacancies couldn't. The experimental results confirm that SrTiO 3 nanocrystalline powders exhibit room-temperature ferromagnetism (FM) and the magnetic moment results from cation vacancies. - Highlights: ► The possible ferromagnetism (FM) in perovskite SrTiO 3 is investigated. ► The vacancy could induce the magnetism in perovskite materials. ► Theoretical and experimental results indicated that cation vacancy could induce the FM.

  18. Formation and surface characterization of nanostructured Al2O3 ...

    Indian Academy of Sciences (India)

    Administrator

    1411. Formation and surface characterization of nanostructured Al2O3–TiO2 coatings. VAIRAMUTHU RAJ* and MOHAMED SIRAJUDEEN MUMJITHA. Advanced Materials ... of the coatings (thickness, growth rate, coating ratio) showed a linear regime with current density and electro- ..... Electronic Supplementary Material.

  19. Fe2O3/MWCNTs nanocomposite decorated glassy carbon electrode ...

    Indian Academy of Sciences (India)

    2018-03-23

    Mar 23, 2018 ... result shows that the Fe2O3/MWCNTs-modified GCE can be used to detect nitrite concentration in a wide linear range of. 10–1000 μM with a detection limit of .... drous ethanol and sonicated in ultrapure water bath for 5 min before use. .... nitrites were not stable and could undergo the following conversion:.

  20. IR and Raman spectra of LaH(SeO3)2 and FeH(SeO3)2

    International Nuclear Information System (INIS)

    Ratheesh, R.; Suresh, G.; Nayar, V.U.; Morris, R.E.

    1995-01-01

    The infrared and Raman spectra of LaH(SeO 3 ) 2 and FeH(SeO 3 ) 2 crystals are recorded and analysed. Bands confirm the coexistence of HSeO 3 - and SeO 3 2- ions in both LaH(SeO 3 ) 2 and FeH(SeO 3 ) 2 crystals. The Se-OH stretching vibrations are observed to be at lower wavenumbers in LaH(SeO 3 ) 2 than that in the iron compound in agreement with the short O-O distance in the former. Observed bands indicate that the SeO 3 2- ions are more angularly distorted in FeH(SeO 3 ) 2 crystal. ABC bands, characteristic of strong hydrogen bonded systems are observed in the infrared spectra of both the crystals. (author). 15 refs., 2 figs., 1 tab

  1. Epitaxial growth and electric properties of γ-Al2O3(110) films on β-Ga2O3(010) substrates

    Science.gov (United States)

    Hattori, Mai; Oshima, Takayoshi; Wakabayashi, Ryo; Yoshimatsu, Kohei; Sasaki, Kohei; Masui, Takekazu; Kuramata, Akito; Yamakoshi, Shigenobu; Horiba, Koji; Kumigashira, Hiroshi; Ohtomo, Akira

    2016-12-01

    Epitaxial growth and electrical properties of γ-Al2O3 films on β-Ga2O3(010) substrates were investigated regarding the prospect of a gate oxide in a β-Ga2O3-based MOSFET. The γ-Al2O3 films grew along the [110] direction and inherited the oxygen sublattice from β-Ga2O3 resulting in the unique in-plane epitaxial relationship of γ-Al2O3 [\\bar{1}10] ∥ β-Ga2O3[001]. We found that the γ-Al2O3 layer had a band gap of 7.0 eV and a type-I band alignment with β-Ga2O3 with conduction- and valence-band offsets of 1.9 and 0.5 eV, respectively. A relatively high trap density (≅ 2 × 1012 cm-2 eV-1) was found from the voltage shift of photoassisted capacitance-voltage curves measured for a Au/γ-Al2O3/β-Ga2O3 MOS capacitor. These results indicate good structural and electric properties and some limitations hindering the better understanding of the role of the gate dielectrics (a γ-Al2O3 interface layer naturally crystallized from amorphous Al2O3) in the β-Ga2O3 MOSFET.

  2. Changes in nutrients and decay rate of Ginkgo biloba leaf litter exposed to elevated O3 concentration in urban area

    Directory of Open Access Journals (Sweden)

    Wei Fu

    2018-03-01

    Full Text Available Ground-level ozone (O3 pollution has been widely concerned in the world, particularly in the cities of Asia, including China. Elevated O3 concentrations have potentially influenced growth and nutrient cycling of trees in urban forest. The decomposition characteristics of urban tree litters under O3 exposure are still poorly known. Ginkgo biloba is commonly planted in the cities of northern China and is one of the main tree species in the urban forest of Shenyang, where concentrations of ground-level O3 are very high in summer. Here, we hypothesized that O3 exposure at high concentrations would alter the decomposition rate of urban tree litter. In open-top chambers (OTCs, 5-year-old G. biloba saplings were planted to investigate the impact of elevated O3 concentration (120 ppb on changes in nutrient contents and decomposition rate of leaf litters. The results showed that elevated O3 concentration significantly increased K content (6.31 ± 0.29 vs 17.93 ± 0.40, P < 0.01 in leaves of G. biloba, significantly decreased the contents of total phenols (2.82 ± 0.93 vs 1.60 ± 0.44, P < 0.05 and soluble sugars (86.51 ± 19.57 vs 53.76 ± 2.40, P < 0.05, but did not significantly alter the contents of C, N, P, lignin and condensed tannins, compared with that in ambient air. Furthermore, percent mass remaining in litterbags after 150 days under ambient air and elevated O3 concentration was 56.0% and 52.8%, respectively. No significant difference between treatments was observed in mass remaining at any sampling date during decomposition. The losses of the nutrients in leaf litters of G. biloba showed significant seasonal differences regardless of O3 treatment. However, we found that elevated O3 concentration slowed down the leaf litter decomposition only at the early decomposition stage, but slightly accelerated the litter decomposition at the late stage (after 120 days. This study provides our understanding of the ecological processes regulating

  3. Syntheses, crystal structures and characterizations of BaZn(SeO3)2 and BaZn(TeO3)Cl2

    International Nuclear Information System (INIS)

    Jiang Hailong; Feng Meiling; Mao Jianggao

    2006-01-01

    Two new barium zinc selenite and tellurite, namely, BaZn(SeO 3 ) 2 and BaZn(TeO 3 )Cl 2 , have been synthesized by the solid state reaction. The structure of BaZn(SeO 3 ) 2 features double chains of [Zn(SeO 3 ) 2 ] 2- anions composed of four- and eight-member rings which are alternatively along a-axis. The double chains of [Zn 2 (TeO 3 ) 2 Cl 3 ] 3- anions in BaZn(TeO 3 )Cl 2 are formed by Zn 3 Te 3 rings in which each tellurite group connects with three ZnO 3 Cl tetrahedra. BaZn(SeO 3 ) 2 and BaZn(TeO 3 )Cl 2 are wide bandgap semiconductors based on optical diffuse reflectance spectrum measurements. -- Graphical abstract: Two new barium zinc selenite and tellurite, namely, BaZn(SeO 3 ) 2 and BaZn(TeO 3 )Cl 2 , have been synthesized by solid state reaction. The structure of BaZn(SeO 3 ) 2 features 1D double chains of [Zn(SeO 3 ) 2 ] 2- anions composed of four- and eight-member rings which are alternatively along a-axis. The 1D double chains of [Zn 2 (TeO 3 ) 2 Cl 3 ] 3- anions in BaZn(TeO 3 )Cl 2 are formed by Zn 3 Te 3 rings in which each tellurite group connects with one ZnO 3 Cl and two ZnO 2 Cl 2 tetrahedra. BaZn(SeO 3 ) 2 and BaZn(TeO 3 )Cl 2 are wide bandgap semiconductors based on optical diffuse reflectance spectrum measurements

  4. Ferroelectric properties of NaNbO3-BaTiO3 thin films deposited on SrRuO3/(001)SrTiO3 substrate by pulsed laser deposition

    International Nuclear Information System (INIS)

    Yamazoe, Seiji; Oda, Shinya; Sakurai, Hiroyuki; Wada, Takahiro; Adachi, Hideaki

    2009-01-01

    (NaNbO 3 ) 1-x (BaTiO 3 ) x (NN-xBT) thin films with low BaTiO 3 (BT) concentrations x (x=0.05 and 0.10) were fabricated on SrRuO 3 /(001)SrTiO 3 (SRO)/(001)STO) substrate by pulsed laser deposition (PLD). X-ray diffraction pattern (XRD) and transmission electron diffraction pattern (TED) showed that NN-0.10BT thin film was epitaxially grown on SRO/(001)STO substrate with a crystallographic relationship of [001] NN-xBT parallel [001] STO . From reciprocal space maps, the lattice parameters of the out-of-plane direction of NN-xBT thin films became larger with an increase in BT concentration, although the lattice parameter of the in-plane was hardly changed by the BT concentration. The value of relative dielectric constant ε r of the NN-xBT thin films were increased with BT concentration. The ε r and the dielectric loss tanδ of NN-0.10BT were 1220 and 0.02 at 1 kHz, respectively. The P-E hysteresis loops of the NN-xBT thin films showed clear ferroelectricity. Although the value of remanent polarization P r decreased with the BT concentration, the behaviors of ε r , P r , and coercive electric field E c of the NN-xBT thin films against the BT concentration accorded with those of NN-xBT ceramics, in which NN-0.10BT ceramics exhibited the largest piezoelectric property. Therefore, the NN-0.10BT thin film is expected to show high piezoelectricity. (author)

  5. Spatially separated atomic layer deposition of Al2O3, a new option for high-throughput Si solar cell passivation

    NARCIS (Netherlands)

    Vermang, B.; Werner, F.; Stals, W; Lorenz, A.; Rothschild, A.; Racz, A.; John, J.; Poortmans, J.; Mertens, R.; Gortzen, R.M.W.; Poodt, P.W.G.; Tiba, V.; Roozeboom, F.; Schmidt, J.

    2011-01-01

    A next generation material for surface passivation of crystalline Si is Al2O3. It has been shown that both thermal and plasma-assisted (PA) atomic layer deposition (ALD) A l2O3 provide an adequate level of surface passivation for both p- and n-type Si substrates. However, conventional time-resolved

  6. Direct evidence of the existence of Mn3+ ions in MnTiO3

    Science.gov (United States)

    Maurya, R. K.; Sharma, Priyamedha; Patel, Ashutosh; Bindu, R.

    2017-08-01

    We investigate the room temperature electronic properties of MnTiO3 synthesised by different preparation conditions. For this purpose, we prepared MnTiO3 under two different cooling rates, one is naturally cooled while the other is quenched in liq.nitrogen. The samples were studied using optical absorbance, photoemission spectroscopy and band structure calculations. We observe significant changes in the structural parameters as a result of quenching. Interestingly, in the parent compound, our combined core level, valence band and optical absorbance studies give evidence of the Mn existence in both 2+ and 3+ states. The fraction of Mn3+ ions has been found to increase on quenching MnTiO3 suggests an increase in oxygen non-stoichiometry. The increase in the fraction of the Mn3+ ions has been manifested a) as slight enhancement in the intensity of the optical absorbance in the visible region. There occurs persistent photo-resistance when the incident light is terminated after shining; b) in the behaviour of the features (close to Fermi level) in the valence band spectra. Hence, the combined analysis of the core level, valence band and optical absorbance spectra suggests that the charge carriers are hole like which further leads to the increase in the electrical conductivity of the quenched sample. The present results provide a recipe to tune the optical absorption in the visible range for its applications in optical sensors, solar cell, etc.

  7. Self-diffusion of Er and Hf inpure and HfO2-doped polycrystalline Er2O3

    International Nuclear Information System (INIS)

    Scheidecker, R.W.

    1979-01-01

    Using a tracer technique, self-diffusion of Er and Hf was measured over the approximate temperature interval of 1600 to 1970 0 C in pure and HfO 2 -doped polycryatalline Er 2 O 3 . Up to about 10 m/o HfO 2 dopant level, the Er self-diffusion coefficients followed a relationship based on cation vacancies. Above 10 m/o HfO 2 , deviation from this relationship occurred, apparently due to clustering of cation vacancies and oxygen interstitials around the dopant hafnia ion. The activation energy for the self-diffusion of Er in pure Er 2 O 3 was 82.2 Kcal/mole and increased with the HfO 2 dopant level present. Self-diffusion of Hf was measured in pure Er 2 O 3 having two impurity levels, and a separation of the grain boundary. The volume diffusion of Hf showed both extrinsic and intrinsic behavior with the transition temperature increasing with the impurity level present in Er 2 O 3 . The activation energy for Hf volume diffusion in the intrinsic region was high, i.e. 235 -+ 9.5 Kcal/mole. The grain boundary diffusion was apparently extrinsic over the entire temperature interval Very low Hf self diffusion rates were found in both pure and HfO 2 doped Er 2 O 3 compositions. Despite a clustering effect, the HfO 2 dopant increased the Hf volume diffusion coefficients

  8. In vivo immunotoxicity evaluation of Gd2O3 nanoprobes prepared by laser ablation in liquid for MRI preclinical applications

    Science.gov (United States)

    Tian, Xiumei; Guan, Xiaoying; Luo, Ningqi; Yang, Fanwen; Chen, Dihu; Peng, Ye; Zhu, Jixiang; He, Fupo; Li, Li; Chen, Xiaoming

    2014-09-01

    Gd2O3 nanoprobes prepared by laser ablation in liquid can be used as magnetic resonance imaging contrast agent. However, their immunotoxicity in vivo remains unknown. In this article, the in vitro biocompatibility of the Gd2O3 nanoprobe was evaluated in terms of cell uptake, cell viability, and apoptosis. In vivo immunotoxicity was detected by monitoring the levels of the immunity mediator, cluster of differentiation (CD) markers in Balb/c mice. The results show that no in vitro cytotoxicity was observed, and no significant changes in the expression levels of CD206 and CD69 between the nanoprobe-injected group and the Gd-DTPA group in mice were observed. Importantly, the immunotoxicity data revealed significant differences in the expression levels of CD40, CD80, CD11b, and reactive oxygen species. In addition, transmission electron microscopy images showed that few Gd2O3 nanoprobes were localized in phagosomes by the endocytic pathway. In conclusion, the toxic effects of our Gd2O3 nanoprobe may be due to endocytosis during which the microstructure or ultrastructure of cells is slightly damaged and induces the generation of an oxidative stress reaction that further stimulates the innate immune response. Therefore, it is important to use a sensitive assay for the in vivo immunotoxicity measurements to evaluate the risk assessment of Gd2O3-based biomaterials at the molecular level.

  9. A Highly Selective Room Temperature NH3 Gas Sensor based on Nanocrystalline a-Fe2O3

    Directory of Open Access Journals (Sweden)

    Priyanka A. PATIL

    2017-05-01

    Full Text Available Nanocrystalline a-Fe2O3 powder was synthesized by simple, inexpensive sol-gel method. The obtained powder was calcined at 700 0C in air atmosphere for 2 hours. The structural and morphological properties of calcined powder were studied by X-ray diffraction (XRD and Field Emission Scanning Electron Microscopy (FESEM respectively. Thermal properties of dried gel were studied by Thermogravimetric Analysis/Differential Scanning Calorimetry (TGA/DSC. The XRD pattern of the powder confirmed the a-Fe2O3 (hematite phase of iron oxide with average crystalline size of 30.87 nm calculated from Scherrer equation. The FESEM images showed uniform wormlike morphology of a-Fe2O3 powder. TGA result indicated that a-Fe2O3 is thermodynamically stable. Room temperature NH3 sensing characteristics of a-Fe2O3 were studied for various concentration levels (250-2500 ppm of NH3 at various humid conditions. The sensor based on a-Fe2O3 exhibited good selectivity and excellent sensitivity (S=92 towards 1000 ppm of NH3 with quick response of 4 sec and fast recovery of 9 sec. Room temperature sensing mechanism is also discussed.

  10. Electronic and magnetic properties of SrTiO(3)/LaAlO(3) interfaces from first principles.

    Science.gov (United States)

    Chen, Hanghui; Kolpak, Alexie M; Ismail-Beigi, Sohrab

    2010-07-20

    A number of intriguing properties emerge upon the formation of the epitaxial interface between the insulating oxides LaAlO(3) and SrTiO(3). These properties, which include a quasi two-dimensional conducting electron gas, low temperature superconductivity, and magnetism, are not present in the bulk materials, generating a great deal of interest in the fundamental physics of their origins. While it is generally accepted that the novel behavior arises as a result of a combination of electronic and atomic reconstructions and growth-induced defects, the complex interplay between these effects remains unclear. In this report, we review the progress that has been made towards unraveling the complete picture of the SrTiO(3)/LaAlO(3) interface, focusing primarily on present ab initio theoretical work and its relation to the experimental data. In the process, we highlight some key unresolved issues and discuss how they might be addressed by future experimental and theoretical studies.

  11. Carrier density modulation by structural distortions at modified LaAlO3/SrTiO3 interfaces

    International Nuclear Information System (INIS)

    Schoofs, Frank; Vickers, Mary E; Egilmez, Mehmet; Fix, Thomas; Kleibeuker, Josée E; MacManus-Driscoll, Judith L; Blamire, Mark G; Carpenter, Michael A

    2013-01-01

    In order to study the fundamental conduction mechanism of LaAlO 3 /SrTiO 3 (LAO/STO) interfaces, heterostructures were modified with a single unit cell interface layer of either an isovalent titanate ATiO 3 (A = Ca, Sr, Sn, Ba) or a rare earth modified Sr 0.5 RE 0.5 TiO 3 (RE = La, Nd, Sm, Dy) between the LAO and the STO. A strong coupling between the lattice strain induced in the LAO layer by the interfacial layers and the sheet carrier density in the STO substrate is observed. The observed crystal distortion of the LAO is large and it is suggested that it couples into the sub-surface STO, causing oxygen octahedral rotation and deformation. We propose that the ‘structural reconstruction’ which occurs in the STO surface as a result of the stress in the LAO is the enabling trigger for two-dimensional conduction at the LAO/STO interface by locally changing the band structure and releasing trapped carriers. (paper)

  12. Electric Field Control of Interfacial Ferromagnetism in CaMnO3/CaRuO3 Heterostructures

    Science.gov (United States)

    Grutter, A. J.; Kirby, B. J.; Gray, M. T.; Flint, C. L.; Alaan, U. S.; Suzuki, Y.; Borchers, J. A.

    2015-07-01

    New mechanisms for achieving direct electric field control of ferromagnetism are highly desirable in the development of functional magnetic interfaces. To that end, we have probed the electric field dependence of the emergent ferromagnetic layer at CaRuO3/CaMnO3 interfaces in bilayers fabricated on SrTiO3. Using polarized neutron reflectometry, we are able to detect the ferromagnetic signal arising from a single atomic monolayer of CaMnO3, manifested as a spin asymmetry in the reflectivity. We find that the application of an electric field of 600 kV /m across the bilayer induces a significant increase in this spin asymmetry. Modeling of the reflectivity suggests that this increase corresponds to a transition from canted antiferromagnetism to full ferromagnetic alignment of the Mn4 + ions at the interface. This increase from 1 μB to 2.5 - 3.0 μB per Mn is indicative of a strong magnetoelectric coupling effect, and such direct electric field control of the magnetization at an interface has significant potential for spintronic applications.

  13. Microhardness studies on as-grown faces of NaClO3 and NaBrO3 ...

    Indian Academy of Sciences (India)

    Unknown

    Jr. College, Hanamkonda 506 001, India. MS received 1 April 2002; revised 6 September 2002 ... and finally hardness becoming load independent at higher loads, was also observed (Pandya and Shah 1981; Seal ... of 40 g whereas such a clear load independence region could not be reached in NaBrO3 crystals as the ...

  14. Anomalous Transport in Sketched Nanostructures at the LaAlO_{3}/SrTiO_{3} Interface

    Directory of Open Access Journals (Sweden)

    Guanglei Cheng

    2013-03-01

    Full Text Available The oxide heterostructure LaAlO_{3}/SrTiO_{3} supports a two-dimensional electron liquid with a variety of competing phases, including magnetism, superconductivity, and weak antilocalization because of Rashba spin-orbit coupling. Further confinement of this two-dimensional electron liquid to the quasi-one-dimensional regime can provide insight into the underlying physics of this system and reveal new behavior. Here, we describe magnetotransport experiments on narrow LaAlO_{3}/SrTiO_{3} structures created by a conductive atomic force microscope lithography technique. Four-terminal local-transport measurements on Hall bar structures about 10 nm wide yield longitudinal resistances that are comparable to the resistance quantum h/e^{2} and independent of the channel length. Large nonlocal resistances (as large as 10^{4}  Ω are observed in some but not all structures with separations between current and voltage that are large compared to the two-dimensional mean-free path. The nonlocal transport is strongly suppressed by the onset of superconductivity below about 200 mK. The origin of these anomalous transport signatures is not understood, but may arise from coherent transport defined by strong spin-orbit coupling and/or magnetic interactions.

  15. Acoustic investigations on PbO–Al2O3–B2O3 glasses doped with ...

    Indian Academy of Sciences (India)

    Unknown

    variation of fs, the adhesive used for cementing the glass sample with quartz transducer was a very thin layer of paste containing calcium carbonate and sodium silicate in .... have complex compositions and are an admixture of net- work formers and modifiers. B2O3 is a well known net- work former with BO3 structural units.

  16. Relaxation electron excitations in Al2O3, Y3Al5O12 and YAlO3

    International Nuclear Information System (INIS)

    Kuznetsov, A.I.; Namozov, B.R.; Myurk, V.V.

    1985-01-01

    Excitation spectra of short-wave Al 2 O 3 , YAlO 3 and Y 3 Al 5 O 12 crystal luminescence, cathodoluminescence (including time resolution) and lay-temperature thermoluminescence are investigated. Analysis of experimental data permits to distingnish among these objects pairs of bands of supposedly characteristic luminescences: 7.5 and 3.8 eV (Al 2 O 3 ), 5.9 and 4.2 eV (YAlO 3 ), and 4.9 and 4.2 eV (Y 3 Al 5 O 12 ), where recombination luminescence is characteristic for long-wave ones, at that time exciton-like luminescence - for short-wave ones. A hypothesis about strong difference between states of an autolocalized exciton and ''autolocalized hole + electron'' (responsible for short-wave and long-wave bands of characteristic luminescence) is expressed; the difference is based on their genetic origin from different regions of a valent zone (in particular, long-wave bands - from the subzone of heavy holes of a valent zone ceiling, originating from nonbinding 2p-orbitals of oxygen)

  17. Synthesis and structural characterization of (Bi2O3)1–x (Y2O3)x and ...

    Indian Academy of Sciences (India)

    Unknown

    tent of dopant concentration (x) for the Y2O3 doped system and obeys Vegard's rule. The unit cell parameters ... cal benefits provided suitable high performance material can be developed. Among the various types of .... Hagenmuller P 1978 Solid electrolytes (New York: Academic. Press). Harwig H A and Gerads A G 1978 ...

  18. Revealing the atomic and electronic structure of a SrTiO3/LaNiO3/SrTiO3 heterostructure interface

    International Nuclear Information System (INIS)

    Zhang, Zaoli; Soltan, S.; Schmid, H.; Habermeier, H.-U.; Keimer, B.; Kaiser, U.

    2014-01-01

    The atomic structures of SrTiO 3 (STO)/LaNiO 3 (LNO)/STO heterostructure interfaces were investigated by spherical aberration-corrected (C S ) (scanning) transmission electron microscopy. Atomic displacement and lattice distortion measurements and electron energy loss spectroscopy (EELS) were used to quantitatively analyze the distortion of the interfacial octahedra and the bond length at the interfaces. Combined with high-resolution transmission electron microscopy (HRTEM) and scanning transmission electron microscopy analyses, two distinct interfacial atomic terminating layers are unambiguously determined. Ensuing quantitative HRTEM measurements revealed that the Ni-O bond length in the interfacial octahedral is elongated at the bottom interface (–NiO 2 -SrO–). Atomic displacement shows structural relaxation effects when crossing the interfaces and lattice distortions across the interface is more pronounced in LNO than in STO. The Ti/O atomic ratio, La and Ti relative atomic ratio as derived by EELS quantification indicate non-stoichiometric composition at the interfaces. Distinct fine structures of Ti-L 2,3 edge and O-K edge at the bottom and top interfaces are observed. By comparison, we are able to estimate Ti valency at both interfaces. Combining the structural distortions and Ti valency, the polar discontinuity and charge transfer at the interfaces are discussed

  19. Synthesis and electrical properties of BaBiO3 and high resistivity BaTiO3–BaBiO3 ceramics

    Directory of Open Access Journals (Sweden)

    Nitish Kumar

    2016-12-01

    Full Text Available Ceramics of the composition BaBiO3 (BB were sintered in oxygen to obtain a single phase with monoclinic I2/m symmetry as suggested by high-resolution X-ray diffraction. X-ray photoelectron spectroscopy confirmed the presence of bismuth in two valence states — 3+ and 5+. Optical spectroscopy showed presence of a direct bandgap at ∼ 2.2eV and a possible indirect bandgap at ∼ 0.9eV. This combined with determination of the activation energy for conduction of 0.25eV, as obtained from ac impedance spectroscopy, suggested that a polaron-mediated conduction mechanism was prevalent in BB. The BB ceramics were crushed, mixed with BaTiO3 (BT, and sintered to obtain BT–BB solid solutions. All the ceramics had tetragonal symmetry and exhibited a normal ferroelectric-like dielectric response. Using ac impedance and optical spectroscopy, it was shown that resistivity values of BT–BB were orders of magnitude higher than BT or BB alone, indicating a change in the fundamental defect equilibrium conditions. A shift in the site occupancy of Bi to the A-site is proposed to be the mechanism for the increased electrical resistivity.

  20. Thermodynamic modeling of La2O3-SrO-Mn2O3-Cr2O3 for solid oxide fuel cell applications

    DEFF Research Database (Denmark)

    Povoden-Karadeniz, E.; Chen, Ming; Ivas, Toni

    2012-01-01

    The thermodynamic La–Sr–Mn–Cr–O oxide database is obtained as an extension of thermodynamic descriptions of oxide subsystems using the calculation of phase diagrams approach. Concepts of the thermodynamic modeling of solid oxide phases are discussed. Gibbs energy functions of SrCrO4, Sr2.67Cr2O8,...... thermodynamics of traditional lanthanum manganite cathode with Cr-impurities. It represents the fundament for extensions to higher orders, aiming on thermodynamic calculations in noble symmetric solid oxide fuel cells......The thermodynamic La–Sr–Mn–Cr–O oxide database is obtained as an extension of thermodynamic descriptions of oxide subsystems using the calculation of phase diagrams approach. Concepts of the thermodynamic modeling of solid oxide phases are discussed. Gibbs energy functions of SrCrO4, Sr2.67Cr2O8......, Sr2CrO4, and SrCr2O4 are presented, and thermodynamic model parameters of La–Sr–Mn–Chromite perovskite are given. Experimental solid solubilities and nonstoichiometries in La1xSrxCrO3d and LaMn1xCrxO3d are reproduced by the model. The presented oxide database can be used for applied computational...

  1. Universality of electron mobility in LaAlO3/SrTiO3 and bulk SrTiO3

    Science.gov (United States)

    Trier, Felix; Reich, K. V.; Christensen, Dennis Valbjørn; Zhang, Yu; Tuller, Harry L.; Chen, Yunzhong; Shklovskii, B. I.; Pryds, Nini

    2017-08-01

    Metallic LaAlO3/SrTiO3 (LAO/STO) interfaces attract enormous attention, but the relationship between the electron mobility and the sheet electron density, ns, is poorly understood. Here, we derive a simple expression for the three-dimensional electron density near the interface, n3 D , as a function of ns and find that the mobility for LAO/STO-based interfaces depends on n3 D in the same way as it does for bulk doped STO. It is known that undoped bulk STO is strongly compensated with N ≃5 ×1018 cm-3 background donors and acceptors. In intentionally doped bulk STO with a concentration of electrons n3 DN , the mobility collapses because scattering happens on n3 D intentionally introduced donors. For LAO/STO, the polar catastrophe which provides electrons is not supposed to provide an equal number of random donors and thus the mobility should be larger. The fact that the mobility is still the same implies that for the LAO/STO, the polar catastrophe model should be revisited.

  2. Lower tropospheric distributions of O3 and aerosol over Raoyang, a rural site in the North China Plain

    Science.gov (United States)

    Wang, Rui; Xu, Xiaobin; Jia, Shihui; Ma, Ruisheng; Ran, Liang; Deng, Zhaoze; Lin, Weili; Wang, Ying; Ma, Zhiqiang

    2017-03-01

    The North China Plain (NCP) has become one of the most polluted regions in China, with the rapidly increasing economic growth in the past decades. High concentrations of ambient O3 and aerosol have been observed at urban as well as rural sites in the NCP. Most of the in situ observations of air pollutants have been conducted near the ground so that current knowledge about the vertical distributions of tropospheric O3 and aerosol over the NCP region is still limited. In this study, vertical profiles of O3 and size-resolved aerosol concentrations below 2.5 km were measured in summer 2014 over a rural site in the NCP, using an unmanned aerial vehicle (UAV) equipped with miniature analyzers. In addition, vertical profiles of aerosol scattering property in the lower troposphere and vertical profiles of O3 below 1 km were also observed at the site using a lidar and tethered balloon, respectively. The depths of the mixed layer and residual layer were determined according to the vertical gradients of lidar particle extinction and aerosol number concentration. Average O3 and size-resolved aerosol number concentration in both the mixed and residual layer were obtained from the data observed in seven UAV flights. The results show that during most of the flights the O3 levels above the top of mixed layer were higher than those below. Such a positive gradient in the vertical distribution of O3 makes the residual layer an important source of O3 in the mixed layer, particularly during the morning when the top of mixed layer is rapidly elevated. In contrast to O3, aerosol number concentration was normally higher in the mixed layer than in the residual layer, particularly in the early morning. Aerosol particles were overwhelmingly distributed in the size range urban areas. Compared with the historic O3 vertical profiles over Beijing from the Measurement of Ozone and Water Vapor by Airbus In-Service Aircraft (MOZAIC), a strong increase in O3 can be found at all heights below 2.5 km

  3. Strain and electric field mediated manipulation of magnetism in La(1-x)SrxMnO3/BaTiO3 heterostructures

    International Nuclear Information System (INIS)

    Schmitz, Markus

    2016-01-01

    Heterostructures of ferromagnetic La 1-x Sr x MnO 3 (LSMO) and ferroelectric BaTiO 3 (BTO) were produced and investigated for their structural and magnetic properties. The combination of these ferroic properties can lead to an artificial multiferroic. Special emphasis was given to the manipulation of magnetic properties by applying electric fields. A magneto-electric coupling could be observed in the heterostructures under investigation. Epitaxial LSMO thin films were grown on BTO substrates using a state-of-the-art oxide molecular beam epitaxy (OMBE) and a high oxygen sputtering system (HOPSS). Stoichiometric La 1-x Sr x MnO 3 films with doping levels of x=0.5 and x=0.3 were produced. The film quality in terms of roughness and crystalline structure was confirmed by X-ray scattering methods. The presence of structural domains in the BaTiO 3 single crystal substrate, whose proportion could be altered due to the application of electric fields, was shown by X-ray diffraction. Tensile strain is induced into the epitaxial La 1-x Sr x MnO 3 films in the whole temperature range under investigation. The magnetization of LSMO alteres by the variation of strain induced into the film, generated by the different structural phases of single crystal BaTiO 3 substrates. The magnetization shows sharp steps at the structural phase transition temperatures of BTO. The evaluation of magnetic hysteresis loops reveals a change of the magnetic anisotropy of LSMO for each structural phase of BTO, but also within the orthorhombic phase. Special focus was given to the manipulation of magnetic properties by the application of electric fields. A newly established measurement option was used to determine the magnetic response to an applied electric field as a function of temperature and magnetic field. The electrically induced modification of the magnetization is profound near the structural phase transition temperatures. Electrical hysteresis loops give a detailed view on the influence of the

  4. Structural properties of Y2O3–Al2O3 liquids and glasses: An overview

    Energy Technology Data Exchange (ETDEWEB)

    Wilding, Martin C.; Wilson, Mark; McMillan, Paul F.; Benmore, Chris J.; Weber, J. K.R.; Deschamps, Thierry; Champagnon, Bernard

    2015-01-01

    Liquids in the system Y2O3- Al2O3 have been the subject of considerable study because of the reported occurrence of a first-order density and entropy-driven liquid-liquid phase transition (LLPT) in the supercooled liquid state. The observations have become controversial because of the presence of crystalline material that can be formed simultaneously and that can mask the nucleation and growth of the lower density liquid. The previous work is summarized here along with arguments for and against the different viewpoints. Also two studies have been undertaken to investigate the LLPT in this refractory system with emphasis on determining the structure of unequivocally amorphous materials. These include the in situ high energy X-ray diffraction (HEXRD) of supercooled Y2O3 - Al2O3 liquids and the low frequency vibrational dynamics of recovered glasses. Manybody molecular dynamics simulations are also used to interpret the results of both studies. The HEXRD measurements, combined with aerodynamic levitation and rapid data acquisition techniques, show that for the 20 mol% Y2O3 (i.e. AlY20) liquid there is a shift in the position of the first peak in the diffraction pattern over a narrow temperature range (2100-1800 K) prior to crystallization. Microbeam Raman spectroscopy measurements made on AlY20 glasses clearly show contrasting spectra in the low frequency part of the spectrum for low(LDA) and high-density (HDA) glassy regions. The molecular dynamics simulations identify contrasting coordination environments around oxygen anions for the high- (HDL) and low-density (LDL) liquids. (C) 2014 Elsevier B.V. All rights reserved.

  5. Quantifying the direct effects of SO2 and O3 on forest growth

    International Nuclear Information System (INIS)

    Mohren, G.M.J.; Jorritsma, I.T.M.; Vermetten, A.W.M.; Kropff, M.J.; Smeets, W.L.M.; Tiktak, A.

    1992-01-01

    The direct effects of sulphur dioxide (SO 2 ) and ozone (O 3 ) on the growth of two Douglas-fir stands are quantified from continuous measurements of the concentration of air pollution above the canopy combined with a quantitative description of the direct effects of gaseous uptake of pollutants on photosynthesis and respiration. Effects at the leaf level are scaled up to the stand level, using a deterministic model of forest growth that uses time steps of 1 day. This approach enables total uptake of gaseous air pollutants and their effects on canopy assimilation and growth to be quantified, taking ambient weather conditions and stand structure into account. By using a description of water balance in the model, the influence of limitations in oil moisture availability can also be incorporated, and the combined effects of air pollution and water shortage can be accounted for. Under Dutch conditions, with average daily concentrations of 10 μg m -1 for SO 2 and 50 μg m -3 for O 3 , the short-term effects on tree growth appear to be minor, except near local sources, and during episodes of high concentrations under stable weather conditions. The possible magnitude of long-term effects of exposure to O 3 is assessed using a hypothetical relationship between dose (exposure multiplied by duration) and foliage loss. From this it is concluded that long-term effects may be significant in stands with a low leaf area index

  6. Antiferromagnetic transitions in `tetragonal-like' BiFeO3

    Energy Technology Data Exchange (ETDEWEB)

    MacDougall, Gregory J [ORNL; Christen, Hans M [ORNL; Siemons, Wolter [ORNL; Biegalski, Michael D [ORNL; Zarestky, Jerel L [ORNL; Liang, Shuhua [ORNL; Dagotto, Elbio R [ORNL; Nagler, Stephen E [ORNL

    2012-01-01

    Recent studies have reported the existence of an epitaxially-stabilized tetragonal-like (`T-like') monoclinic phase in BiFeO3 thin-films with high levels of compressive strain. Though there is abundant evidence that structural and ferroelectric properties are di erent than in rhombohedral-like (`R-like') films with lower levels of strain, little information exists on magnetic properties. Here,we report a detailed neutron scattering study of a nearly phase-pure film of T-like BiFeO3. By tracking the temperature dependence and relative intensity of several superstructure peaks in the reciprocal lattice cell, we confirm antiferromagnetism with largely G-type character and T_N = 324 K. A minority magnetic phase with C-type character is also reported with T_N= 260 K. The co-existence of the two phases in T-like BiFeO3 and the difference in ordering temperatures between R-like and T-like systems is explained through simple Fe-O-Fe bond distance considerations.

  7. Effect of Al-doped YCrO3 on structural, electronic and magnetic properties

    Science.gov (United States)

    Durán, A.; Verdín, E.; Conde, A.; Escamilla, R.

    2018-05-01

    Structural, dielectric and magnetic properties were investigated in the YCr1-xAlxO3 with 0 cell volume of the orthorhombic structure without changes in the oxidation state of the Cr3+ ions. We discuss two mechanisms that could have a significant influence on the magnetic properties. The first is related to local deformation occurring for x structure. The local deformation is controlled by the inclination of the octahedrons and the octahedral distortion having a strong effect on the TN and the coercive field at low Al concentrations. On the other hand, the decreasing of the magnetization values (Mr and Hc) is ascribed to changes in the electronic structure, which is confirmed by a decreasing of the contribution of Cr 3d states at Fermi level due to increasing Al3+ content. Thus, we analyzed and discussed that both mechanisms influence the electronic properties of the YCr1-xAlxO3 solid solution.

  8. Intrinsic electronic defects and multiple-atom processes in the oxidic semiconductor Ga2O3

    Science.gov (United States)

    Schmeißer, Dieter; Henkel, Karsten

    2018-04-01

    We report on the electronic structure of gallium oxide (Ga2O3) single crystals as studied by resonant photoelectron spectroscopy (resPES). We identify intrinsic electronic defects that are formed by mixed-atomic valence states. We differentiate three coexisting defect states that differ in their electronic correlation energy and their spatial localization lengths. Their relative abundance is described by a fractional ionicity with covalent and ionic bonding contributions. For Ga2O3, our analyses of the resPES data enable us to derive two main aspects: first, experimental access is given to determine the ionicity based on the original concepts of Pauling and Phillips. Second, we report on multi-atomic energy loss processes in the Ga2p core level and X-ray absorption data. The two experimental findings can be explained consistently in the same context of mixed-atomic valence states and intrinsic electronic defects.

  9. Regional background O3 and NOx in the Houston–Galveston–Brazoria (TX region: a decadal-scale perspective

    Directory of Open Access Journals (Sweden)

    L. G. Suciu

    2017-06-01

    Full Text Available Ozone (O3 in the lower troposphere is harmful to people and plants, particularly during summer, when photochemistry is most active and higher temperatures favor local chemistry. Local precursor emissions, such as those of volatile organic compounds (VOCs and nitrogen oxides (NOx, together with their chemistry contribute to the O3 and NOx mixing ratios in the Houston–Galveston–Brazoria (HGB region. In addition to local emissions, chemistry and transport, larger-scale factors also contribute to local O3 and NOx. These additional contributions (often referred to as regional background are not well quantified within the HGB region, impeding more efficient controls on precursor emissions to achieve compliance with the National Ambient Air Quality Standards for O3. In this study, we estimate ground-level regional background O3 and NOx in the HGB region and quantify their decadal-scale trends.We use four different approaches based on principal component analysis (PCA to quantify background O3 and NOx. Three of these approaches consist of independent PCA on both O3 and NOx for both 1 and 8 h levels to compare our results with previous studies and to highlight the effect of both temporal and spatial scales. In the fourth approach, we co-varied O3, NOx and meteorology.Our results show that the estimation of regional background O3 has less inherent uncertainty when it was constrained by NOx and meteorology, yielding a statistically significant temporal trend of −0.68 ± 0.27 ppb yr−1. Likewise, the estimation of regional background NOx trend constrained by O3 and meteorology was −0.04 ± 0.02 ppb yr−1 (upper bound and −0.03 ± 0.01 ppb yr−1 (lower bound. Our best estimates of the 17-year average of season-scale background O3 and NOx were 46.72 ± 2.08 ppb and 6.80 ± 0.13 ppb (upper bound or 4.45 ± 0.08 ppb (lower bound, respectively. Average background O3 is consistent with previous studies and

  10. Valence band electronic structure of Ho-doped La0.67Ca0.33MnO3 using ultra-violet photoemission spectroscopy

    Science.gov (United States)

    Rout, S. K.; Mukharjee, R. N.; Mishra, D. K.; Roul, B. K.; Sekhar, B. R.; Dalai, M. K.

    2017-05-01

    In this manuscript we report the valence band electronic structure of Ho doped La0.67Ca0.33MnO3 using ultraviolet photoemission spectroscopy. We compared the density of states of La0.67Ca0.33MnO3, La0.67Ca0.3Ho0.03MnO3 and La0.64Ho0.03Ca0.33MnO3 near the Fermi level at various temperatures. Significant amount of changes have been observed at higher temperatures (220 K and 300 K) where the near Fermi level density of states increases with Ho doping into La0.67Ca0.33MnO3 indicating the enhancement of magnitude of change in metallicity (conductivity).

  11. Carbonization kinetics of La2O3-Mo cathode materials

    International Nuclear Information System (INIS)

    Jinshu, W.; Meiling, Z.; Tieyong, Z.; Jiuxing, Z.; Zuoren, N.

    2001-01-01

    The carbonization kinetics of La 2 O 3 -Mo cathode materials has been studied by thermal analysis method. Three-stage model of the carbonization has been presented in this paper. The carbonization rate is initially controlled by chemical reaction, then controlled by chemical reaction mixed with diffusion, finally controlled by diffusion. After the initial experimental data are processed according to this model, the correlation coefficients of the kinetic curves are satisfactory. The apparent activation energy of carbonization of La 2 O 3 -Mo cathode materials has been obtained. At the same time, we have deduced the empirical expressions of the amount of weight increased per unit area after carbonization, temperature and time in the temperature range 1393 K - 1493 K. (author)

  12. Thermoluminescent response of LaAlO3:Pr

    International Nuclear Information System (INIS)

    Morales H, A.; Zarate M, J.; Azorin N, J.; Rivera M, T.

    2015-10-01

    In this study, the thermoluminescence response of doped lanthanum aluminate (LaAlO 3 ) with praseodymium ion (Pr) obtained by the Pechini method and drying by the spraying technique Spry Dryer was studied. The obtained powders were analyzed structurally by the X-ray diffraction technique; the morphological characterization was by the scanning electron microscopy technique. The obtained powders at 800 degrees C presented crystallinity and showed a Rhombohedral crystal structure, this phase was observed by X-ray diffraction patterns. Thermoluminescence response of LaAlO 3 :Pr showed a brightness curve with a peak centered at 157 degrees C. The sensitivity of the doped samples was improved about 90 times in comparison with the undoped sample. Thermoluminescence response in function of the wavelength showed a maximum at 230 nm, reproducibility of thermoluminescence response was ±50%. Also the fading in thermoluminescence response was studied. (Author)

  13. Inelastic neutron scattering in tetragonal KNbO3

    International Nuclear Information System (INIS)

    Fontana, M.D.; Dolling, G.; Kugel, G.E.; Carabatos, C.

    1979-01-01

    Inelastic neutron scattering experiments in tetragonal KNbO 3 show a high anisotropy in some regions of the phonon dispersion relation and the existence of strong one-dimensional intercell correlations between atomic motions along the [100] and [010] directions, in agreement with x-ray diffuse-scattering measurements in the same phase. The transverse phonon modes propagating normally to these directions of strong correlations, that is, with polarization vectors parallel to them, are relatively soft, not only near the zone center but all the way to the zone boundary. Comparison of these results with the Raman, neutron, and x-ray data obtained in the other phases suggests a description of the ferroelectric phase transition mechanism in KNbO 3 in terms of soft modes and dynamic correlations in each phase. (author)

  14. Degradation of Y2O3:Eu phosphor powders

    International Nuclear Information System (INIS)

    Ntwaeaborwa, O.M.; Hillie, K.T.; Swart, H.C.

    2004-01-01

    Degradation of cathodoluminescent (CL) intensity and changes in the surface chemistry of Y 2 O 3 :Eu phosphor powders were investigated using CL spectroscopy and Auger electron spectroscopy (AES), respectively. Y 2 O 3 :Eu phosphor powders were exposed to an electron beam of energy 2 keV and a current density of 88.5 mA/cm 2 at room temperature for different oxygen pressures. The degradation of CL intensity is due to the formation of a non-luminescent ''dead layer'' on the specimen surface, resulting from non-radiative recombination of electron-hole pairs via surface states. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  15. alpha-Fe2O3 versus beta-Fe2O3: Controlling the Phase of the Transformation Product of epsilon-Fe2O3 in the Fe2O3/SiO2 System

    Czech Academy of Sciences Publication Activity Database

    Brázda, Petr; Kohout, J.; Bezdička, Petr; Kmjec, T.

    2014-01-01

    Roč. 14, č. 3 (2014), s. 1039-1046 ISSN 1528-7483 R&D Projects: GA ČR GAP204/10/0035 Institutional support: RVO:61388980 Keywords : CHEMICAL-VAPOR-DEPOSITION * OXIDE THIN-FILMS * X-RAY * GAMMA-FE2O3 NANOPARTICLES * THERMAL-DECOMPOSITION Subject RIV: CA - Inorganic Chemistry Impact factor: 4.891, year: 2014

  16. Spin waves in vanadium sesquioxide V2O3

    Science.gov (United States)

    Word, R. E.; Werner, S. A.; Yelon, W. B.; Honig, J. M.; Shivashankar, S.

    1981-04-01

    We have carried out inelastic neutron scattering measurements of the spin waves propagating along the [00l] trigonal axis and along the [hh0] axis in the antiferromagnetic phase of V2O3. We find an energy gap in the spin-wave spectrum at the zone center of 4.75 meV. We obtain exchange parameters and the anisotropy energy from these data using a nearest-neighbor and next-nearest-neighbor Heisenberg Hamiltonian model.

  17. Thermal stability of nanocrystalline ε-Fe2O3

    Czech Academy of Sciences Publication Activity Database

    Brázda, Petr; Večerníková, Eva; Pližingrová, Eva; Lančok, Adriana; Nižňanský, D.

    2014-01-01

    Roč. 117, č. 1 (2014), s. 85-91 ISSN 1388-6150 R&D Projects: GA ČR GAP204/10/0035 Institutional support: RVO:61388980 Keywords : ε-Fe2O3 * Differential thermal analysis * Evolved gas analysis * Infrared spectroscopy * Thermogravimetry * X-ray powder diffraction Subject RIV: CA - Inorganic Chemistry Impact factor: 2.042, year: 2014

  18. Controlling the conductivity of amorphous LaAlO3/SrTiO3 interfaces by in-situ application of an electric field during fabrication

    DEFF Research Database (Denmark)

    Trier, Felix; Amoruso, S.; Christensen, Dennis Valbjørn

    2013-01-01

    Amorphous-LaAlO3/SrTiO3 interfaces present metallic conductivity similar to those found in their all-crystalline counterparts. Here, the conductivity of amorphous-LaAlO3/SrTiO3 interfaces is modified by an external electric field applied in-situ with a biased truncated cone electrode (−10 V ≤ Vbias...

  19. Magnetoelectric effect in Cr2O3 thin films

    Science.gov (United States)

    He, Xi; Wang, Yi; Sahoo, Sarbeswar; Binek, Christian

    2008-03-01

    Magnetoelectric materials experienced a recent revival as promising components of novel spintronic devices [1, 2, 3]. Since the magnetoelectric (ME) effect is relativistically small in traditional antiferromagnetic compounds like Cr2O3 (max. αzz 4ps/m ) and also cross- coupling between ferroic order parameters is typically small in the modern multiferroics, it is a challenge to electrically induce sufficient magnetization required for the envisioned device applications. A straightforward approach is to increase the electric field at constant voltage by reducing the thickness of the ME material to thin films of a few nm. Since magnetism is known to be affected by geometrical confinement thickness dependence of the ME effect in thin film Cr2O3 is expected. We grow (111) textured Cr2O3 films with various thicknesses below 500 nm and study the ME effect for various ME annealing conditions as a function of temperature with the help of Kerr-magnetometry. [1] P. Borisov et al. Phys. Rev. Lett. 94, 117203 (2005). [2] Ch. Binek, B.Doudin, J. Phys. Condens. Matter 17, L39 (2005). [3] R. Ramesh and Nicola A. Spaldin 2007 Nature Materials 6 21.

  20. Plasmons at the LaAlO3/SrTiO3 interface and in the graphene-LaAlO3/SrTiO3 double layer

    Science.gov (United States)

    Faridi, A.; Asgari, Reza

    2017-04-01

    We study plasmon modes of the two-dimensional electron gas residing at the interface of band insulators LaAlO3 and SrTiO3 (LAO/STO) and the plasmon excitations of graphene-LAO/STO double layer as well. Considering the electron-electron interaction within random phase approximation, we calculate the plasmon dispersions of both systems numerically and in the long-wavelength limit analytical expressions for collective modes are found. One optical mode and two (three) acoustic modes are predicted for the LAO/STO (graphene-LAO/STO) system where only the uppermost acoustic mode of both systems can emerge above the electron-hole continuum depending on the characteristics of each system. In the case of LAO/STO interface, thanks to the spatial separation between t2 g orbitals, the upper acoustic mode might be undamped at the long-wavelength limit depending on the exact value of the dielectric constant of SrTiO3. Same as other double layer systems, the interlayer distance for the graphene-LAO/STO system plays a crucial role in damping the upper acoustic mode. Faster damping of all plasmon modes of the present double layer system in comparison with the ones with conventional two-dimensional electron gas instead of t2 g electron gas is also found due to heavier effective masses of the gas and also stronger interlayer Coulomb interaction.

  1. Nonlinear electrostrictive lattice response of EuTiO3

    Science.gov (United States)

    Pappas, P.; Calamiotou, M.; Köhler, J.; Bussmann-Holder, A.; Liarokapis, E.

    2017-07-01

    An epitaxial EuTiO3 (ETO) film grown on the SrTiO3 substrate was studied at room temperature with synchrotron XRD and in situ application of an electric field (nominally up to 7.8 kV/cm) in near grazing incidence geometry, in order to monitor the response of the lattice to the field. 2D diffraction images show that apparently misoriented coherently diffracting domains are present close to the surface whereas the film diffracts more as a single crystal towards the interface. Diffraction intensity profiles recorded from the near surface region of the EuTiO3 film showed systematic modifications upon the application of the electric field, indicating that at a critical electric field (nominally above 3.1 kV/cm), there is a clear change in the lattice response to the field, which was much stronger when the field was almost parallel to the diffraction vector. The data suggest that the ETO film, nominally paraelectric at room temperature, transforms under the application of a critical electric field to piezoelectric in agreement with a theoretical analysis based on a double-well potential. In order to exclude effects arising from the substrate, this has been investigated separately and shown not to be affected by the field.

  2. Mecanosíntese do composto BiFeO3 Mechanosynthesis of the BiFeO3 compound

    Directory of Open Access Journals (Sweden)

    V. F. Freitas

    2008-09-01

    Full Text Available Os compostos cerâmicos BiFeO3 puro e modificado (Bi0,95R0,05FeO3, com terras raras R = Gd ou Eu, foram sintetizados por moagem em altas energias. As amostras foram analisadas por difração de raios X, microscopia eletrônica de varredura e espectroscopia por energia dispersiva de raios X. A difração de raios X indicou que as amostras modificadas com Eu são monofásicas, enquanto que as amostras puras e modificadas com Gd apresentaram majoritariamente a fase BiFeO3, com uma pequena quantidade de outras fases. A espectroscopia por energia dispersiva de raios X revelou a presença dos átomos modificantes na amostra e o mapeamento destes átomos indicou uma distribuição homogênea deles em toda a amostra. A microscopia eletrônica de varredura mostrou uma significante diminuição no tamanho das partículas, estando estas com dimensões sub-micrométricas e com diâmetro médio em torno de 500 nm. Estudos de densificação dos corpos cerâmicos indicaram compostos altamente densos, com densidades relativas acima de 0,9 sendo que o composto modificado com Eu alcançou a densidade relativa ρ/ρ0 = 0,98.The, pure and rare earth modified (Bi0.95R0.05FeO3 / R = Gd or Eu BiFeO3 compounds were synthesized by high-energy ball milling. The samples were analyzed by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. The X-ray diffraction results indicated single phase Eu modified samples, while the pure and Gd modified ones presented the BiFeO3 as majority phase, and small amount of the spurious phase. The energy dispersive spectroscopy revealed the presence of the modifiers atoms in the sample and the mapping of these atoms indicated the homogeneous distribution of them in the whole samples. The scanning electron microscopy showed a decrease significant on the particle size, with medium diameter around 500 nm. Densification studies indicated high-dense ceramics body, with relative density above of 0.9, were Eu

  3. The electrode resistance of ZrO2---Y2O3(-Bi2O3) solid electrolytes with Pt electrodes

    NARCIS (Netherlands)

    Winnubst, Aloysius J.A.; Scharenborg, A.H.A.; Burggraaf, A.J.

    1984-01-01

    The electrode resistance (Re1) at low over-voltages has been determined for Bi2O3 free and Bi2O3 doped yttria-stabilized zirconia with sputtered platinum electrodes. The anode and cathode resistances are measured separately and are equal. Bi2O3 causes a decrease of the electrode resistance at small

  4. ??????????? ??????????????? ????? ??????-???????? ????????????? ?????????? ??????? ?aO?Al2O3?TiO2 ??? ???????? ?????? ?????

    OpenAIRE

    ???????, ????; ??????, ?????????

    2011-01-01

    ? ????? ?????? ?????????? ???????? ?????????????? ??????????? ????????????? ??? ??????-????????? ???????????????? ?????????? ??????? ?aO?Al2O3?TiO2, ?? ???????? ??????? ? ???????????? ??????? ??? ???????? ? ?????? ????????? ?????? ?????. ???????? ?????????? ???????? ??? ??????????? ?????????? ??????? ????????? ???????????? ?????????? ??? ??????????? 12000?, ?? ????????? ?????????????? ????????????? ???????, ????????? ???? ? ?????????? ????? ???????? ??????? ???????????. ????????, ?? ?? ...

  5. Line positions and intensities for the gamma 1 + gamma 2 and gamma 2 + gamma 3 bands of (16)O3

    Science.gov (United States)

    Devi, V. Malathy; Flaud, J.-M.; Canypeyret, C.; Rinsland, C. P.; Smith, M. A. H.

    1988-01-01

    Using 0.005 cm-resolution Fourier transform spectra of (16)O3, generated by electric discharge from a greater than 99.98 percent pure sample of (16)O3, an extensive analysis of the gamma 1 + gamma 2 and the gamma 2 + gamma 3 bands in the 5.7 micron region was performed. The rotational energy levels of the upper (110) and (011) vibrational states of (16)O3 were reproduced within their experimental uncertainties using a Hamiltonian which takes explicitly into account the Coriolis-type interaction occurring between the rotational energy levels of both states. Improved vibrational energies and rotational and coupling constants were also derived for the (110) and (011) states. Precise transition moment constants for these two bands were deduced from analysis of 220 measured line intensities. Finally, a complete list of line positions, intensities, and lower state energies for both bands has been generated.

  6. Time-Dependent Negative Capacitance Effects in Al2O3/BaTiO3 Bilayers.

    Science.gov (United States)

    Kim, Yu Jin; Yamada, Hiroyuki; Moon, Taehwan; Kwon, Young Jae; An, Cheol Hyun; Kim, Han Joon; Kim, Keum Do; Lee, Young Hwan; Hyun, Seung Dam; Park, Min Hyuk; Hwang, Cheol Seong

    2016-07-13

    The negative capacitance (NC) effects in ferroelectric materials have emerged as the possible solution to low-power transistor devices and high-charge-density capacitors. Although the steep switching characteristic (subthreshold swing capacitance (charge) boosting could be achieved without the hysteresis from the Al2O3/BaTiO3 bilayer capacitors through short-pulse charging. This work revealed that the hysteresis phenomenon in NC devices originated from the dielectric leakage of the dielectric layer. The suppression of charge injection via the dielectric leakage, which usually takes time, inhibits complete ferroelectric polarization switching during a short pulse time. It was demonstrated that a nonhysteretic NC effect can be achieved only within certain limited time and voltage ranges, but that these are sufficient for critical device applications.

  7. Favorable ultraviolet photoelectric effects in TbMnO3/Nb-SrTiO3 heterostructures

    KAUST Repository

    Jin, Kexin

    2014-12-01

    The rectifying properties and ultraviolet photoelectric effects in TbMnO3/Nb-doped SrTiO3 heterostructures have been investigated. The ideality factors and the diffusion voltages obtained from the current-voltage curves nonlinearly decrease with increasing the temperature. It is observed that the maximum photovoltaic values of the heterostructure irradiated by the 365 nm (2.6 mW/mm2) and 248 nm (0.71 mJ/mm2) lights are about 0.121 V and 0.119 V at T=300 K, respectively. The relations between the relaxation of photovoltages after the irradiation and the power intensity are revealed. These results suggest the potential applications in the development of ultraviolet detectors using oxides-based heterostructures.

  8. High mobility of the strongly confined hole gas in AgTaO3/SrTiO3

    KAUST Repository

    Nazir, Safdar

    2012-05-18

    A theoretical study of the two-dimensional hole gas at the (AgO)−/(TiO2)0 p-type interface in the AgTaO3/SrTiO3 (001) heterostructure is presented. The Ag 4d states strongly hybridize with the O 2p states and contribute to the hole gas. It is demonstrated that the holes are confined to an ultra thin layer (∼4.9Å) with a considerable carrier density of ∼1014cm−2. We estimate a hole mobility of 18.6 cm2 V−1 s−1, which is high enough to enable device applications.

  9. Photoinduced modulation and relaxation characteristics in LaAlO3/SrTiO3 heterointerface

    KAUST Repository

    Jin, K. X.

    2015-03-05

    We report the modulation and relaxation characteristics in the two-dimensional electron gas system at LaAlO3/SrTiO3 heterointerface induced by the ultraviolet light illumination (365 nm). The suppression of Kondo effect at the interface illuminated by the light originates from the light irradiation-induced decoherence effect of localized states. It is interesting to note that the persistent and transient photoinduced effects are simultaneously observed and the photoinduced maximum change values in resistance are 80.8% and 51.4% at T = 20 K, respectively. Moreover, the photoinduced relaxation processes after the irradiation are systematically analyzed using the double exponential model. These results provide the deeper understanding of the photoinduced effect and the experimental evidence of tunable Kondo effect in oxides-based two-dimensional electron gas systems.

  10. Synthesis of LaAlO3 by metal organic decomposition on SrTiO3 substrates

    Science.gov (United States)

    Ampuero, J. L.; Iliescu, I.; Boudard, M.; Jamaoui, A.; Rapenne, L.; Jimenez, C.; Roussel, H.

    2013-11-01

    LaAlO3 (LAO) films on SrTiO3 (STO) substrates have been produced by metal organic decomposition using La(C5H7O2)3 and Al(C5H7O2)3 as precursors dissolved in propionic acid. The process consists of growing thin layers through dip coating and subsequent annealing. After testing different cationic ratios of La and Al, it was determined that an optimal ratio leads to a single LAO phase film that grows epitaxially (cube on cube) on top of the STO. This was shown by X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses. These analyses, as well as additional X-ray reflectivity analysis, also revealed that the LAO's thickness obtained in one dip ranges from 8 nm to 16 nm. Taking advantage of the epitaxial conditions, several layers can be stacked by successive dip coatings and annealing to form an epitaxial structure.

  11. High charge carrier density at the NaTaO3/SrTiO3 hetero-interface

    KAUST Repository

    Nazir, Safdar

    2011-08-05

    The formation of a (quasi) two-dimensional electron gas between the band insulators NaTaO3 and SrTiO3 is studied by means of the full-potential linearized augmented plane-wave method of density functional theory. Optimization of the atomic positions points to only small changes in the chemical bonding at the interface. Both the p-type (NaO)−/(TiO2)0 and n-type (TaO2)+/(SrO)0 interfaces are found to be metallic with high charge carrier densities. The effects of O vacancies are discussed. Spin-polarized calculations point to the formation of isolated O 2pmagnetic moments, located in the metallic region of the p-type interface.

  12. The metallic interface between the two band insulators LaGaO3 and SrTiO3

    KAUST Repository

    Nazir, Safdar

    2011-06-28

    The formation of metallic interface states between the two band insulators LaGaO3 and SrTiO3 is studied by the full-potential linearized augmented plane-wave method based on density functional theory.Structural optimization of the atomic positions points to only small changes of the chemical bonding at the interface. The n-type (LaO/TiO2) and p-type (GaO2/SrO) interfaces turn out to be metallic. Reduction of the O content increases the conductivity of the n-type interface, while the p-type interface can be turned gradually from a hole doped into an electron doped state.

  13. First principles study of the magnetic properties and charge transfer of Ni-doped BiFeO3

    Science.gov (United States)

    Sun, Yuan; Sun, Zhenghao; Wei, Ren; Huang, Yuxin; Wang, Lili; Leng, Jing; Xiang, Peng; Lan, Min

    2018-03-01

    We present a first-principles study of electronic structures and magnetic properties in Ni-doped BiFeO3 using the density functional theory + U methods. The BiNixFe1-xO3 (x = 0.125, 0.25, 0.5) multiferroic ceramics represent ferromagnetic properties due to the ferrimagnetic order in Ni-O-Fe, and the magnetic moment rises with increase in Ni doping concentration agreeing well with experimental results. Ni atoms prefer to occupy the diagonal positions in the quasi-plane Ni-O-Fe eight-membered ring. Charge transfer from Bi 6s state to Ni 3d state through O 2p orbital lead to the 2+ oxidation state of Ni, indicating high Néel temperatures of BiNixFe1-xO3, and the electronic state of the system can be described as Bi4+xBi3+1-xNi2+xFe3+1-xO3. The spin polarization of Bi 6s state and O 2p state near the Fermi level contributes to the total magnetic moment. A spin-polarized acceptor level of about 0.4 eV constituted by Bi 6s state and O 2p state is found, which is responsible for the increase in leakage current of Ni-doped BiFeO3.

  14. Unique virulence properties of Yersinia enterocolitica O:3--an emerging zoonotic pathogen using pigs as preferred reservoir host.

    Science.gov (United States)

    Valentin-Weigand, Peter; Heesemann, Jürgen; Dersch, Petra

    2014-10-01

    Enteropathogenic Yersinia enterocolitica bioserotype 4/O:3 are the most frequent cause of human yersiniosis worldwide with symptoms ranging from mild diarrhea to severe complications of mesenteric lymphadenitis, liver abscesses and postinfectious extraintestinal sequelae. The main reservoir host of 4/O:3 strains are pigs, which represent a substantial disease-causing potential for humans, as they are usually asymptomatic carriers. Y. enterocolitica O:3 initiates infections by tight attachment to the intestinal mucosa. Colonization of the digestive tract is frequently followed by invasion of the intestinal layer primarily at the follicle-associated epithelium, allowing the bacteria to propagate in the lamina propria and disseminate into deeper tissues. Molecular characterization of Y. enterocolitica O:3 isolates led to the identification of (i) alternative virulence and fitness factors and (ii) small genetic variations which cause profound changes in their virulence gene expression pattern (e.g. constitutive expression of the primary invasion factor InvA). These changes provoke a major difference in the virulence properties, i.e. reduced colonization of intestinal tissues in mice, but improved long-term colonization in the pig intestine. Y. enterocolitica O:3 strains cause also a considerably lower level of proinflammatory cytokine IL-8 and higher levels of the anti-inflammatory cytokine IL-10 in porcine primary macrophages, as compared to murine macrophages, which could contribute to limiting inflammation, immunopathology and severity of the infection in pigs. Copyright © 2014 Elsevier GmbH. All rights reserved.

  15. Growth mechanism of NaClO3 and NaBrO3 crystals from aqueous ...

    Indian Academy of Sciences (India)

    Unknown

    of graticule attached to the eye-piece and photographs were taken at fixed intervals. 3. Results and discussion. 3.1 Growth of sodium chlorate and sodium bromate crystals. Figure 2 shows photographs of the complete recovery process of a seed crystal of NaClO3 of size 1⋅5 mm in length and 1 mm in breadth. As discussed ...

  16. Comparing Pt/SrTiO3 to Rh/SrTiO3 for hydrogen photocatalytic production from ethanol

    KAUST Repository

    Wahab, A. K.

    2013-08-13

    Photocatalytic hydrogen production from ethanol as an example of biofuel is studied over 0.5 wt% Rh/SrTiO3 and 0.5 wt% Pt/SrTiO3 perovskite materials. The rate of hydrogen production, rH2, over Pt/SrTiO3 is found to be far higher than that observed over Rh/SrTiO3 (4 × 10−6 mol of H2 g catal. −1 min−1 (1.1 × 10−6 mol of H2 m catal. −2 min−1) compared to 0.7 × 10−6 mol of H2 g catal. −1 min−1 (5.5 × 10−8 mol of H2 m catal. −2 min−1), respectively, under UV excitation with a flux equivalent to that from the sun light (ca. 1 mW cm−2). Analyses of the XPS Rh3d and XPS Pt4f indicate that Rh is mainly present in its ionic form (Rh3+) while Pt is mainly present in its metallic form (Pt0). A fraction of the non-metallic state of Rh in the catalyst persisted even after argon ion sputtering. The tendency of Rh to be oxidized compared to Pt might be the reason behind the lower activity of the former compared to the later. On the contrary, a larger amount of methane are formed on the Rh containing catalyst compared to that observed on the Pt containing catalyst due to the capacity of Rh to break the carbon–carbon bond of the organic compound.

  17. Conductivity Dynamics of the Metal to Insulator Transition in EuNiO3/LANiO3 Superlattices

    Science.gov (United States)

    2016-02-07

    Structural, magnetic and electronic properties of RNiO3 perovskites (R = rare earth),” Journal of Physics: Condensed Matter 9, 1679 (1997). [12...of freedom in TMOs determine macroscopic properties . In this STIR project an initial foray into non-equilibrium studies in nickelate superlattices...Superlattices," invited talk at 8th International Conference on Materials for Advanced Technologies, Symposium I, Optical Properties of Two-Dimensional

  18. High ozone (O3 affects the fitness associated with the microbial composition and abundance of Q biotype Bemisia tabaci

    Directory of Open Access Journals (Sweden)

    Yanyun Hong

    2016-10-01

    Full Text Available Abstract Ozone (O3 affects the fitness of an insect, such as its development, reproduction and protection against fungal pathogens, but the mechanism by which it does so remains unclear. Here, we compared the fitness (i.e., the growth and development time, reproduction and protection against Beauveria bassiana (B. bassiana of Q biotype whiteflies fumigated under hO3 (280 ± 20 ppb and control O3 (50 ± 10 ppb concentrations. Moreover, we determined that gene expression was related to development, reproduction and immunity to B. bassiana and examined the abundance and composition of bacteria and fungi inside of the body and on the surface of the Q biotype whitefly. We observed a significantly enhanced number of eggs that were laid by a female, shortened developmental time, prolonged adult lifespan, decreased weight of one eclosion, and reduced immunity to B. bassiana in whiteflies under hO3, but hO3 did not significantly affect the expression of genes related to development, reproduction and immunity. However, hO3 obviously changed the composition of the bacterial communities inside of the body and on the surface of the whiteflies, significantly reducing Rickettsia and enhancing Candidatus_Cardinium. Similarly, hO3 significantly enhanced Thysanophora penicillioides from the Trichocomaceae family and reduced Dothideomycetes (at the class level inside of the body. Furthermore, positive correlations were found between the abundance of Candidatus_Cardinium and the female whitefly ratio and the fecundity of a single female, and positive correlations were found between the abundance of Rickettsia and the weight of adult whiteflies just after eclosion and immunity to B. bassiana. We conclude that hO3 enhances whitefly development and reproduction but impairs immunity to B. bassiana, and our results also suggest that the changes to the microbial environments inside of the body and on the surface could be crucial factors that alter whitefly fitness under

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

    Science.gov (United States)

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

    2016-11-01

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

  20. Initial stages of ion beam-induced phase transformations in Gd2O3 and Lu2O3

    Science.gov (United States)

    Chen, Chien-Hung; Tracy, Cameron L.; Wang, Chenxu; Lang, Maik; Ewing, Rodney C.

    2018-02-01

    The atomic-scale evolution of lanthanide sesquioxides Gd2O3 and Lu2O3 irradiated with 1 MeV Kr ions at room temperature and 120 K, up to fluences of 1 × 1016 ions/cm2 (˜20 dpa), has been characterized by in situ transmission electron microscopy. At room temperature, both oxides exhibited high radiation tolerance. Irradiation did not cause any observable structural change in either material, likely due to the mobility of irradiation-induced point defects, causing efficient defect annihilation. For Gd2O3, having the larger cation ionic radius of the two materials, an irradiation-induced stacking fault structure appeared at low fluences in the low temperature irradiation. As compared with the cubic-to-monoclinic phase transformations known to result from higher energy (˜GeV) ion irradiation, Kr ions of lower energies (˜MeV) yield much lower rates of damage accumulation and thus less extensive structural modification. At a fluence of 2.5 × 1015 ions/cm2, only the initial stages of the cubic-to-monoclinic (C to B) phase transformation process, consisting of the formation and aggregation of defects, have been observed.

  1. Research Update: Conductivity and beyond at the LaAlO3/SrTiO3 interface

    Directory of Open Access Journals (Sweden)

    S. Gariglio

    2016-06-01

    Full Text Available In this review, we focus on the celebrated interface between two band insulators, LaAlO3 and SrTiO3, that was found to be conducting, superconducting, and to display a strong spin-orbit coupling. We discuss the formation of the 2-dimensional electron liquid at this interface, the particular electronic structure linked to the carrier confinement, the transport properties, and the signatures of magnetism. We then highlight distinctive characteristics of the superconducting regime, such as the electric field effect control of the carrier density, the unique tunability observed in this system, and the role of the electronic subband structure. Finally we compare the behavior of Tc versus 2D doping with the dome-like behavior of the 3D bulk superconductivity observed in doped SrTiO3. This comparison reveals surprising differences when the Tc behavior is analyzed in terms of the 3D carrier density for the interface and the bulk.

  2. Preparation of Eggshell MoO3/Al2O3 Catalysts by Solvent Assisted Spreading of MoO3 over Al2O3 Extrudates: Effect of MoO3 Particle Size and Temperature on Rate of Spreading

    Czech Academy of Sciences Publication Activity Database

    Zdražil, Miroslav; Kaluža, Luděk; Gulková, Daniela

    2005-01-01

    Roč. 1, 1-2 (2005), s. 1-10 R&D Projects: GA AV ČR(CZ) IAA4072306 Institutional research plan: CEZ:AV0Z40720504 Keywords : MoO3/Al2O3 catalyst * eggshell profiles * hydrodesulfurization Subject RIV: CF - Physical ; Theoretical Chemistry

  3. Strain-engineering stabilization of BaTi O3 -based polar metals

    Science.gov (United States)

    Ma, Chao; Jin, Kui-juan; Ge, Chen; Yang, Guo-zhen

    2018-03-01

    Polar metals, which possess ferroelectriclike polar structure and conductivity simultaneously, have attracted wide interest since the first solid example, LiOs O3 (below 140 K), was discovered. However, the lack of room-temperature polar metals hinders further research and applications. Thus abundant properties of polar metals are unexplored. Here, with first-principles calculations, we report that the polar metal phase can be stabilized in the strain-engineered BaTi O3 with electron doping. The mechanism relates to the competition between the shifting of the t2 g energy levels and the narrowing of their bandwidth. Surprisingly, it is predicted that the ferroelectric-to-paraelectric transition temperature can be increased by electron doping when the strain is large enough, which holds potential for room-temperature polar metals. Our results indicate that strain engineering is a promising way to achieve BaTi O3 -based polar metals, and they should have practical significance for obtaining easily accessible, ecofriendly, and potential room-temperature polar metals.

  4. First-principles investigation of Fe-doped MgSiO3-ilmenite

    International Nuclear Information System (INIS)

    Stashans, Arvids; Rivera, Krupskaya; Pinto, Henry P.

    2012-01-01

    First principles density functional theory and generalised gradient approximation (GGA) have been exploited to investigate Fe-doped ilmenite-type MgSiO 3 mineral. Strong electron correlation effects not included in a density-functional formalism are described by a Hubbard-type on-site Coulomb repulsion (the DFT+U approach). Microstructure of equilibrium geometries, electronic band structures as well as magnetic properties are computed and discussed in detail. Hartree-Fock methodology is used as an extra tool to study optical properties of the same system. For equilibrium state of the doped mineral we find zigzag-type atomic rearrangements around the Fe impurity. The inclusion of correlation effects leads to an improved description of the electronic properties. In particular, it is discovered that Fe incorporation produces local energy levels within the band-gap of the material. Using ΔSCF method optical absorption energies are found to be equal to 2.2 and 2.6 eV leading to light absorption at longer wavelengths compared to the undoped MgSiO 3 . Our results provide evidence on the occurrence of local magnetic moment in the region surrounding iron dopant. According to the outcomes, the Fe⇒Mg reaction can be described as substitutionally labile with Fe 2+ complex being found in the high-spin state at low pressure MgSiO 3 -ilmenite conditions.

  5. Fundamental limits on the electron mobility of β-Ga2O3

    Science.gov (United States)

    Kang, Youngho; Krishnaswamy, Karthik; Peelaers, Hartwin; Van de Walle, Chris G.

    2017-06-01

    We perform first-principles calculations to investigate the electronic and vibrational spectra and the electron mobility of β-Ga2O3. We calculate the electron-phonon scattering rate of the polar optical phonon modes using the Vogl model in conjunction with Fermi’s golden rule; this enables us to fully take the anisotropic phonon spectra of the monoclinic lattice of β-Ga2O3 into account. We also examine the scattering rate due to ionized impurities or defects using a Yukawa-potential-based model. We consider scattering due to donor impurities, as well as the possibility of compensation by acceptors such as Ga vacancies. We then calculate the room-temperature mobility of β-Ga2O3 using the Boltzmann transport equation within the relaxation time approximation, for carrier densities in the range from 1017 to 1020 cm-3. We find that the electron-phonon interaction dominates the mobility for carrier densities of up to 1019 cm-3. We also find that the intrinsic anisotropy in the mobility is small; experimental findings of large anisotropy must therefore be attributed to other factors. We attribute the experimentally observed reduction of the mobility with increasing carrier density to increasing levels of compensation, which significantly affect the mobility.

  6. Huge spin-driven polarizations at room temperature in bulk BiFeO3

    Science.gov (United States)

    Lee, Jun Hee; Fishman, Randy

    2015-03-01

    Although BiFeO3 is one of the most investigated multiferroics, its magnetoelectricity and spin-driven polarizations are barely understood on an atomistic level. By combining a first-principles approach with a spin-cycloid model, we report hidden but huge spin-driven polarizations at room temperature in bulk BiFeO3. One of the polarizations reaches ~ 0.03 C/m2, which is larger than any other spin-driven polarization in a bulk material by one order of magnitude. By comparing our results with intrinsic measurements such as neutron scattering, Raman spectroscopy, IR directional dichroism, and high magnetic-field measurements, we disentangle all the hidden spin-driven polarizations due to exchange-striction, spin-current, and single-ion-anisotropy. We find that the broken inversion symmetries of the R3c structure of BiFeO3 induce the strong response of the magnetic couplings to an electric field and are responsible for the associated huge spin-driven polarizations. This research is sponsored by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division and by the Scientific User Facilities Division, Office of Basic Energy Sciences, US Department of Energy.

  7. On the nature of change in Ni oxidation state in BaTiO3-SrTiO3 system

    OpenAIRE

    Lebedev, A. I.; Sluchinskaya, I. A.

    2016-01-01

    XAFS studies of Ni-doped Ba$_{1-x}$Sr$_x$TiO$_3$ solid solution reveal that the Ni oxidation state changes from 4 in SrTiO$_3$ to 2.5 in BaTiO$_3$ when varying $x$. This change is accompanied by a noticeable change in the interatomic Ni-O distances in the first shell. The first-principles calculations show that nickel creates an impurity band in the forbidden band gap of BaTiO$_3$ and SrTiO$_3$, which explains the appearance of intense absorption of Ni-doped samples in the visible region. The...

  8. Hydrothermal–galvanic couple synthesis of directionally oriented BaTiO3 thin films on TiN-coated substrates

    International Nuclear Information System (INIS)

    Yang, Chia-Jung; Tsai, Di-You; Chan, Pei-Hsuan; Wu, Chu-Tsun; Lu, Fu-Hsing

    2013-01-01

    BaTiO 3 films were synthesized on TiN-coated Si substrate below 100 °C by a hydrothermal–galvanic couple technique in barium contained alkaline solutions. X-ray diffraction and electron backscatter diffraction results show that the BaTiO 3 thin films were directionally oriented grown on the TiN/Si substrates, i.e., (111) BaTiO 3 over (111) TiN. The surface morphologies revealed that BaTiO 3 nucleated and grew over the TiN surface with a single layer. From kinetic analyses, the growth rates of BaTiO 3 films prepared by the hydrothermal–galvanic couple technique were faster than a hydrothermal method. The galvanic effects were confirmed by investigating the induced currents and energies. The galvanic currents were generated and controlled by both the dissolution of TiN and the formation of BaTiO 3 . The output electric energies increased rapidly with the reaction time and leveled off at the full coverage of BaTiO 3 . - Highlights: • Cubic BaTiO 3 films are synthesized by a hydrothermal–galvanic couple method (HT–GC). • Growth rates of BaTiO 3 films made by HT–GC are faster than a hydrothermal method. • BaTiO 3 films are directionally oriented grown on the TiN/Si substrates. • Galvanic currents are controlled by dissolution of TiN and formation of BaTiO 3

  9. Size dependent structural, vibrational and magnetic properties of BiFeO3 and core-shell structured BiFeO3@SiO2 nanoparticles

    International Nuclear Information System (INIS)

    Chauhan, Sunil; Kumar, Manoj; Chhoker, Sandeep; Katyal, S. C.

    2014-01-01

    Bulk BiFeO 3 , BiFeO 3 nanoparticles and core-shell structured BiFeO 3 @SiO 2 nanoparticles were synthesized by solid state reaction method, sol-gel and Stöber process (SiO 2 shell) respectively. Transmission electron microscopy image confirmed the core-shell structure of BiFeO 3 @SiO 2 nanoparticles with BiFeO3 core ∼50-90 nm and SiO 2 shell ∼16 nm. X-ray diffraction and FTIR spectroscopy results showed the presence of distorted rhombohedral structure with R3c space group in all three samples. The magnetic measurement indicated the existence of room-temperature weak ferromagnetism in core-shell BiFeO 3 @SiO 2 nanoparticles and BiFeO3 nanoparticles, whereas bulk BiFeO 3 showed antiferromagnteic nature. Electron Spin Resonance results confirmed the enhancement in magnetic properties of coreshell structured BiFeO 3 @SiO 2 nanoparticles in comparison with BiFeO 3 nanoparticles and bulk BiFeO 3

  10. Investigation on gamma and neutron radiation shielding parameters for BaO/SrO‒Bi2O3‒B2O3 glasses

    Science.gov (United States)

    Sayyed, M. I.; Lakshminarayana, G.; Dong, M. G.; Ersundu, M. Çelikbilek; Ersundu, A. E.; Kityk, I. V.

    2018-04-01

    In this work, mass attenuation coefficients (μ/ρ), effective atomic number (Zeff), electron density (Ne), mean free path (MFP), and half-value layer (HVL) of 20 BaO/SrO‒(x) Bi2O3‒(80‒x) B2O3 glasses (where x=10, 20, 30, 40, 50 and 60 mol%) were calculated using WinXCom program and MCNP5 code. The obtained (μ/ρ) results using both MCNP5 code and WinXCom program were in good agreement. It is found that the addition of Bi2O3 leads to increase the Zeff values in both BaO/SrO‒Bi2O3‒B2O3 glass systems. However, the Zeff values of the BaO‒Bi2O3‒B2O3 glass system are higher than those of the SrO‒Bi2O3‒B2O3 glasses. The fast neutrons effective removal cross sections (ΣR) for 20 SrO‒40 Bi2O3‒40 B2O3 glass is the highest among all studied glasses. The calculated half-value layer values were compared with different glass systems and it was found that the shielding properties of the selected glasses are comparable or even better than other glass systems such as phosphate glasses.

  11. Improvement of electron mobility in La:BaSnO3 thin films by insertion of an atomically flat insulating (Sr,Ba)SnO3 buffer layer

    Science.gov (United States)

    Shiogai, Junichi; Nishihara, Kazuki; Sato, Kazuhisa; Tsukazaki, Atsushi

    2016-06-01

    One perovskite oxide, ASnO3 (A = Sr, Ba), is a candidate for use as a transparent conductive oxide with high electron mobility in single crystalline form. However, the electron mobility of films grown on SrTiO3 substrates does not reach the bulk value, probably because of dislocation scattering that originates from the large lattice mismatch. This study investigates the effect of insertion of bilayer BaSnO3 / (Sr,Ba)SnO3 for buffering this large lattice mismatch between La:BaSnO3 and SrTiO3 substrate. The insertion of 200-nm-thick BaSnO3 on (Sr,Ba)SnO3 bilayer buffer structures reduces the number of dislocations and improves surface smoothness of the films after annealing as proved respectively by scanning transmission electron microscopy and atomic force microscopy. A systematic investigation of BaSnO3 buffer layer thickness dependence on Hall mobility of the electron transport in La:BaSnO3 shows that the highest obtained value of mobility is 78 cm2V-1s-1 because of its fewer dislocations. High electron mobility films based on perovskite BaSnO3 can provide a good platform for transparent-conducting-oxide electronic devices and for creation of fascinating perovskite heterostructures.

  12. Improvement of electron mobility in La:BaSnO3 thin films by insertion of an atomically flat insulating (Sr,BaSnO3 buffer layer

    Directory of Open Access Journals (Sweden)

    Junichi Shiogai

    2016-06-01

    Full Text Available One perovskite oxide, ASnO3 (A = Sr, Ba, is a candidate for use as a transparent conductive oxide with high electron mobility in single crystalline form. However, the electron mobility of films grown on SrTiO3 substrates does not reach the bulk value, probably because of dislocation scattering that originates from the large lattice mismatch. This study investigates the effect of insertion of bilayer BaSnO3 / (Sr,BaSnO3 for buffering this large lattice mismatch between La:BaSnO3 and SrTiO3 substrate. The insertion of 200-nm-thick BaSnO3 on (Sr,BaSnO3 bilayer buffer structures reduces the number of dislocations and improves surface smoothness of the films after annealing as proved respectively by scanning transmission electron microscopy and atomic force microscopy. A systematic investigation of BaSnO3 buffer layer thickness dependence on Hall mobility of the electron transport in La:BaSnO3 shows that the highest obtained value of mobility is 78 cm2V−1s−1 because of its fewer dislocations. High electron mobility films based on perovskite BaSnO3 can provide a good platform for transparent-conducting-oxide electronic devices and for creation of fascinating perovskite heterostructures.

  13. Phase and Microstructure Evolution and Toughening Mechanism of a Hierarchical Architectured Al2O3-Y2O3 Coating under High Temperature

    Science.gov (United States)

    Rong, Jian; Yang, Kai; Zhuang, Yin; Ni, Jinxing; Zhao, Huayu; Tao, Shunyan; Zhong, Xinghua; Ding, Chuanxian

    2018-02-01

    In recent years, numerous techniques have been developed to mimic nacre-like hierarchical architectures in order to improve the damage tolerance of materials. We present herein a simple strategy to fabricate such a hierarchical architectured Al2O3-Y2O3 composite coating via atmospheric plasma spraying. The evolution of the phase and microstructure of the Al2O3-Y2O3 composite coating were characterized under conditions of high-temperature exposure in air at 800-1350 °C. The hardness and porosity of several typical coatings were determined. In situ formation of dense hierarchical architectured Al2O3-YAG composite coating with improved hardness was achieved after heat treatment at 1350 °C. Compared with Al2O3 coating, elevated toughness was found for the hierarchical architectured Al2O3-YAG composite coating, which can be ascribed to the distribution of YAG phase that contributed to crack termination and deflection, and microbridging. After thermal aging treatment at 1350 °C, the hierarchical architectured Al2O3-YAG composite coating was quite stable after 100 h of thermal exposure. Furthermore, the Al2O3-Y2O3 composite coating exhibited superior sintering resistance compared with the Al2O3 coating.

  14. [Characterizing spatial patterns of NO(x), SO2 and O3 in Pearl River Delta by passive sampling].

    Science.gov (United States)

    Zhao, Yang; Shao, Min; Wang, Chen; Wang, Bo-Guang; Lu, Si-Hua; Zhong, Liu-Ju

    2011-02-01

    Concentrations of NO(x), SO2 and O3 were measured by passive sampling within 200km x 200km grid in Pearl River Delta (PRD). Sampling period was two weeks in November, 2009. Spatial distributions of NO(x), SO2 and O3 were obtained by Kriging interpolation method. The results were compared with emission inventories and modeling results. The transportations of O3 were evaluated by using backward trajectories of air parcels. During the sampling period, the mean concentrations of NO(x), SO2 and O3 were 75.9 microg/m3, 37.3 microg/m3 and 36.2 microg/m3, respectively. And the highest concentrations of NO(x), SO2 and O3 were 195.7 microg/m3, 95.9 microg/m3 and 81.8 microg/m3. Comparing with routine measurements from the regional monitoring network in PRD, the results by passive method were 18.6%, 33.5% and 37.5% lower for NO(x), SO2 and O3, respectively. The spatial patterns demonstrated that higher NO(x) concentrations often appeared in cities such as Guangzhou, Foshan and Shenzhen. SO2 concentrations were higher in west and lower in east. High SO2 concentrations are mainly from emission of power plants and industrial sources. Concentrations of O3 showed the highest levels in the south of PRD. Backward trajectory analysis for higher ozone areas indicated that 53% of the air masses were from the region with high concentration of NO(x). The horizontal transportation caused higher ozone in the south while lower in north in PRD.

  15. Ana o 3-specific IgE is a good predictor for clinically relevant cashew allergy in children.

    Science.gov (United States)

    Lange, L; Lasota, L; Finger, A; Vlajnic, D; Büsing, S; Meister, J; Broekaert, I; Pfannenstiel, C; Friedrichs, F; Price, M; Trendelenburg, V; Niggemann, B; Beyer, K

    2017-04-01

    Component-resolved diagnostics using specific IgE to 2 S albumins has shown to be a valuable new option in diagnostic procedure. Ana o 3 is a 2 S albumin from cashew. The aim of this study was to investigate the role of Ana o 3-specific serum IgE in the diagnosis of cashew allergy and to identify cut-off levels to replace oral food challenges. Moreover, the value of additional determination of total IgE has been investigated. In a multicentre study, we analysed specific IgE to cashew extract and Ana o 3 as well as total IgE in children with suspected cashew allergy using the ImmunoCAP-FEIA and a standardized diagnostic procedure including oral challenges where indicated. A total of 61 patients were included in the study. Forty-two were allergic to cashew, and 19 were tolerant. In receiver operating curves, Ana o 3 discriminates between allergic and tolerant children better than cashew-specific IgE with an area under the curve of 0.94 vs 0.78. The ratio of Ana o 3-specific IgE to total IgE did not further improve the diagnostic procedure. Probability curves for Ana o 3-specific IgE have been calculated, and a 95% probability could be estimated at 2.0 kU/l. Specific IgE to Ana o 3 is a valuable tool for the diagnosis of cashew allergy. Considering its positive predictive value, it might allow to make a considerable number of oral challenges superfluous. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  16. Ultrafast microwave hydrothermal synthesis and characterization of Bi1−xLaxFeO3 micronized particles

    International Nuclear Information System (INIS)

    Ponzoni, C.; Cannio, M.; Boccaccini, D.N.; Bahl, C.R.H.; Agersted, K.; Leonelli, C.

    2015-01-01

    In this work a microwave assisted hydrothermal method is applied to successfully synthesize lanthanum doped bismuth ferrites (BLFO, Bi 1−x La x FeO 3 where x = 0, 0.15, 0.30 and 0.45). The growth mechanism of the Bi 1−x La x FeO 3 crystallites is discussed in detail. The existence of the single-phase perovskite structure for all the doped samples is confirmed by the X-ray powder diffraction patterns. A peak shift, observed at lower angle with increasing La doping concentration, indicates that the BiFeO 3 lattice is doped. The results of TG/DTA show a shift in the transition temperature from 805 °C to 815 °C as function of the La-doping for all the doped powders. At higher levels of La doping, i.e. x = 0.30 and 0.45, significant weight losses occur above 860 °C suggesting a change in the physical and chemical properties. Finally, magnetic measurements are carried out at room temperature for pure BiFeO 3 and Bi 0.85 La 0.15 FeO 3 . The results indicate that the materials are both weakly ferromagnetic, with no significant hysteresis in the curves. - Graphical abstract: Display Omitted - Highlights: • MW hydrothermal method applied to synthesize Bi 1−x La x FeO 3 , x = 0, 0.15, 0.30, 0.45. • A single-phase perovskite structure for all the samples was confirmed by XRD. • A T c shift in La doped BiFeO 3 DTA was observed as function of the La-doping. • Magnetic measurements indicate that the materials are weakly ferromagnetic

  17. Production, characterization and application of Gd2O3 and Er2O3 nanoparticles as radiosensitizers in radiotherapy beams

    International Nuclear Information System (INIS)

    Corrêa, Eduardo de Lima

    2017-01-01

    In this study Gd 2 O 3 and Er 2 O 3 nanoparticles were produced for application as radiosensitizers in radiotherapy beams. They were synthesized at the Hyperfine Interactions Laboratory, IPEN, using thermal decomposition method and characterized by X-ray diffraction, to verify crystalline structure, transmission electron microscopy, to obtain information about shape, size and size distribution, neutron activation analysis, whereby it was possible to determine samples purity and gadolinium and erbium concentration. Magnetization and perturbed γ-γ angular correlation (PAC) measurements were performed in order to study particles magnetic behavior and quadrupole interactions, respectively. Characterization results showed a bixbyite structure, 5 nm diameter post-synthesis particles with narrow size distribution. Rare-earth mass determination in each sample was important to perform normalization in magnetic susceptibility measurements, making possible the view of a high magnetization under 30 K for post-synthesis samples, what was not observed in larger particles, together with an effective magnetic moment enhancement for nanoparticles, not seen in bulk samples, and a change in the antiferromagnetic ordering temperature for Er 2 O 3 . PAC spectroscopy results show possible surface effects. The absence of a well-defined frequency in 5 nm samples indicates the amount of 111 In( 111 Cd) at particle surface is bigger than in the core, resulting in a non-evident hyperfine interaction between the probe nuclei and the host. The X-ray diffraction and PAC spectroscopy joint was vital to understand the particles structural damage caused by 60 Co irradiation. About radiosensitizer measurements a dose enhancement factor (DEF) of up to 1,67 and 1,09 for Gd 2 O 3 nanoparticles under 60 Co and 6MV irradiation, respectively, were observed. Under same conditions DEF values of up to 1,37 and 1,06 were found for Er 2 O 3 samples. Results reached in this study provide not only important

  18. Experimental Study on the Behavior of TiN and Ti2O3 Inclusions in Contact with CaO‐Al2O3‐SiO2‐MgO Slags

    Directory of Open Access Journals (Sweden)

    S. K. Michelic

    2017-01-01

    Full Text Available TiN and Ti2O3 are the predominant inclusion types in Ti-alloyed ferritic chromium stainless steels. In order to ensure the required steel cleanness level, an effective removal of such inclusions in the slag during secondary metallurgy is essential. This inclusion removal predominantly takes place via dissolution of the inclusion in the slag. The dissolution behavior of TiN and Ti2O3 in CaO-SiO2-Al2O3-MgO slags as well as their agglomeration behavior in the liquid steel is investigated using High Temperature Laser Scanning Confocal Microscopy and Tammann Furnace experiments. Thermodynamic calculations are performed using FactSage 7.0. The behavior of TiN is observed to be completely different to that of oxides. Ti2O3 dissolves quickly in slags, and its dissolution behavior is comparable to that of other already well examined oxides. In contrast, TiN shows a very intense gas reaction which is attributed to the release of nitrogen during contact with slag. Slags with higher SiO2 content show a significantly higher ability for the dissolution of TiN as compared to Al2O3-rich slags. The gas reaction is found to also significantly influence the final steel cleanness. Despite the easy absorption of TiN in the slag, the formed nitrogen supports the formation of pinholes in the steel.

  19. Effect of Sr-doping of LaMnO3 spacer on modulation-doped two-dimensional electron gases at oxide interfaces

    DEFF Research Database (Denmark)

    Chen, Yunzhong; Gan, Yulin; Christensen, Dennis Valbjørn

    2017-01-01

    Modulation-doped oxide two-dimensional electron gas formed at the LaMnO3 (LMO) buffered disorderd-LaAlO3/SrTiO3 (d-LAO/LMO/STO) heterointerface provides new opportunities for electronics as well as quantum physics. Herein, we studied the dependence of Sr-doping of La1-xSrxMnO3 (LSMO, x = 0, 1/8, ...... of LSMO during the deposition of disordered LAO or that the energy levels of Mn 3d electrons at the interface of LSMO/STO are hardly varied even when changing the LSMO composition from LMO to SrMnO3....

  20. Biosphere-Atmosphere Exchange of NOx and O3 in Central Amazon

    Science.gov (United States)

    Wiedemann, K. T.; Swofsy, S. C.; Munger, J. W.; Saleska, S. R.; Rizzo, L. V.; Silva Campos, K.

    2017-12-01

    The primary source of atmospheric OH is the photolysis of O3 in the presence of water vapor. NOx gases are the main precursors of O3 and OH. In NOx-rich environments that have both high humidity and high solar radiation, OH concentrations are enhanced, making tropical forests dominant in global oxidation of long lived gases. The Amazon rain forest has a unique combination of vegetation with diverse characteristics, climate, and a dynamic land use, factors that altogether govern the emission and fate of trace gases, particle formation and atmospheric chemistry. Understanding the interactions among the mechanisms that govern local precursor emissions will lead to a better description of the local atmospheric chemistry and its global impacts. As part of the GoAmazon project, an array of complementary measurements was conducted in a research site in central Amazon, near Santarem (PA, Brazil), inside the Tapajos National Forest. The research site is surrounded by intact rain forest in a 6km radius, and a 45m canopy. The 67m tower was assembled in the site in 2001 for flux measurements (CO2 and H2O). In mid 2014 additional instrumentation were added, measuring NOx, O3, CH4, and SO2 fluxes and profiles. The low concentrations of SO2 (up to 0.1ppb during the peak of the dry season), and a small vertical gradient, suggest the predominance of biogenic sources. O3 show no significant seasonality between the daytime and nighttime vertical profiles, but occasional nighttime high concentrations for levels below canopy were observed. Hourly ozone fluxes suggest a production of O3 under canopy. NO soil emissions are indicated by concentrations in the ppb range for lower profile levels, decreasing to a few hundreds ppt above the canopy, and emission rates of NO from Amazonian soils may be higher than expected from earlier measurements. Daytime data indicate that not all of this NOx escapes to the atmosphere, however. Fluxes of NO average 133x109 molec cm-2 s-1, a factor of 4 higher

  1. Evaluation of the reliability of Si3N4-Al2O3 -CTR2O3 ceramics through Weibull analysis

    Directory of Open Access Journals (Sweden)

    Santos Claudinei dos

    2003-01-01

    Full Text Available The objective of this work has been to compare the reliability of two Si3N4 ceramics, with Y2O3/Al2O3 or CTR2O3/Al2O3 mixtures as additives, in regard to their 4-point bending strength and to confirm the potential of the rare earth oxide mixture, CTR2O3, produced at FAENQUIL, as an alternative, low cost sinter additive for pure Y2O3 in the sintering of Si3N4 ceramics. The oxide mixture CTR2O3 is a solid solution formed mainly by Y2O3, Er2O3, Yb2O3 and Dy2O3 with other minor constituents and is obtained at a cost of only 20% of pure Y2O3. Samples were sintered by a gas pressure sintering process at 1900 °C under a nitrogen pressure of 1.5 MPa and an isothermal holding time of 2 h. The obtained materials were characterized by their relative density, phase composition and bending strength. The Weibull analysis was used to describe the reliability of these materials. Both materials produced presented relative densities higher than 99.5%t.d., b-Si3N4 and Y3Al5O12 (YAG as cristalline phases and bending strengths higher than 650 MPa, thus demonstrating similar behaviors regarding their physical, chemical and mechanical characteristics. The statistical analysis of their strength also showed similar results for both materials, with Weibull moduli m of about 15 and characteristic stress values s o of about 700 MPa. These results confirmed the possibility of using the rare earth oxide mixture, CTR2O3, as sinter additive for high performance Si3N4 ceramics, without prejudice of the mechanical properties when compared to Si3N4 ceramics sintered with pure Y2O3.

  2. High-temperature mass spectrometric study of the vaporization processes and thermodynamic properties in the Gd2O3-Y2O3-HfO2system.

    Science.gov (United States)

    Kablov, Eugene N; Stolyarova, Valentina L; Lopatin, Sergey I; Vorozhtcov, Viktor A; Karachevtsev, Fedor N; Folomeikin, Yuriy I

    2017-07-15

    The refractory properties of the Gd 2 O 3 -Y 2 O 3 -HfO 2 system are considered promising for the production of many high-temperature materials, e.g., thermal barrier coatings and casting molds for gas turbine engine blades. At high temperatures, components of the Gd 2 O 3 -Y 2 O 3 -HfO 2 system may vaporize selectively and this may significantly change the physicochemical properties of the materials. Therefore, information on vaporization processes and thermodynamic properties of the Gd 2 O 3 -Y 2 O 3 -HfO 2 system is of great importance. The vaporization processes and thermodynamic properties of the Gd 2 O 3 -Y 2 O 3 -HfO 2 system were studied using high-temperature Knudsen effusion mass spectrometry with a MS-1301 mass spectrometer. Vaporization was carried out using a tungsten twin effusion cell containing the samples under study and pure Gd 2 O 3 as a reference substance. Electron ionization at an energy of 25 eV was employed in the present study. It was shown that at a temperature of 2500 K the vapor over the samples in the Gd 2 O 3 -Y 2 O 3 -HfO 2 system consisted of the GdO, YO and O vapor species. The Gd 2 O 3 and Y 2 O 3 activities in the samples in the Gd 2 O 3 -Y 2 O 3 -HfO 2 system as well as their vaporization rates were derived from the partial pressures of the vapor species. Using these data the HfO 2 activities, the Gibbs energy of mixing and the excess Gibbs energy in this system were calculated at 2500 K. The thermodynamic properties of the Gd 2 O 3 -Y 2 O 3 -HfO 2 system, i.e., the component activities in the samples and the excess Gibbs energy, obtained in the present study at 2500 K, exhibited negative deviations from ideal behavior. The concentration dependence of excess Gibbs energy of the Gd 2 O 3 -Y 2 O 3 -HfO 2 system was approximated with an empirical equation. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

  3. Impacts of ethylenediurea (EDU) soil drench and foliar spray in Salix sachalinensis protection against O3-induced injury.

    Science.gov (United States)

    Agathokleous, Evgenios; Paoletti, Elena; Saitanis, Costas J; Manning, William J; Sugai, Tetsuto; Koike, Takayoshi

    2016-12-15

    It is widely accepted that elevated levels of surface ozone (O 3 ) negatively affect plants. Ethylenediurea (EDU) is a synthetic substance which effectively protects plants against O 3 -caused phytotoxicity. Among other questions, the one still open is: which EDU application method is more appropriate for treating fast-growing tree species. The main aims of this study were: (i) to test if chronic exposure of Salix sachalinensis plants to 200-400mgEDUL -1 , the usually applied range for protection against O 3 phytotoxicity, is beneficial to plants; (ii) to evaluate the effects of chronic exposure to elevated O 3 on S. sachalinensis; (iii) to assess the efficacy of two methods (i.e. soil drench and foliar spray) of EDU application to plants; (iv) to investigate the appropriate concentration of EDU to protect against elevated O 3 -induced damage in S. sachalinensis; and (v) to compare the two methods of EDU application in terms of effectiveness and EDU consumption. Current-year cuttings grown in infertile soil free from organic matter were exposed either to low ambient O 3 (AOZ, 10-h≈28.3nmolmol -1 ) or to elevated O 3 (EOZ, 10-h≈65.8nmolmol -1 ) levels during daylight hours. Over the growing season, plants were treated every nine days with 200mL soil drench of 0, 200 or 400mgEDUL -1 or with foliar spray of 0, 200 or 400mgEDUL -1 (in two separate experiments). We found that EDU per se had no effects on plants exposed to AOZ. EOZ practically significantly injured S. sachalinensis plants, and the impact was indifferent between the experiments. EDU did not protect plants against EOZ impact when applied as soil drench but it did protect them when applied as 200-400mgL -1 foliar spray. We conclude that EDU may be more effective against O 3 phytotoxicity to fast-growing species when applied as a spray than when applied as a drench. Keymessage: Soil-drenched EDU was ineffective in protecting willow plants against O 3 -induced injury, whereas foliar-sprayed EDU was

  4. Unidirectional THz radiation propagation in BiFeO3

    Science.gov (United States)

    Room, Toomas

    The mutual coupling between magnetism and electricity present in many multiferroic materials permit the magnetic control of the electric polarization and the electric control of the magnetization. These static magnetoelectric (ME) effects are of enormous interest: The ability to write a magnetic state current-free by an electric voltage would provide a huge technological advantage. However, ME coupling changes the low energy electrodynamics of these materials in unprecedented way - optical ME effects give rise to unidirectional light propagation as recently observed in low-temperature multiferroics. The transparent direction can be switched with dc magnetic or electric field, thus opening up new possibilities to manipulate the propagation of electromagnetic waves in multiferroic materials. We studied the unidirectional transmission of THz radiation in BiFeO3 crystals, the unique multiferroic compound offering a real potential for room temperature applications. The electrodynamics of BiFeO3 at 1THz and below is dominated by the spin wave modes of cycloidal spin order. We found that the optical magnetoelectric effect generated by spin waves in BiFeO3 is robust enough to cause considerable nonreciprocal directional dichroism in the GHz-THz range even at room temperature. The supporting theory attributes the observed unidirectional transmission to the spin-current-driven dynamic ME effect. Our work demonstrates that the nonreciprocal directional dichroism spectra of low energy excitations and their theoretical analysis provide microscopic model of ME couplings in multiferroic materials. Recent THz spectroscopy studies of multiferroic materials are an important step toward the realization of optical diodes, devices which transmit light in one but not in the opposite direction.

  5. LiNbO3 surfaces from a microscopic perspective

    Science.gov (United States)

    Sanna, Simone; Gero Schmidt, Wolf

    2017-10-01

    A large number of oxides has been investigated in the last twenty years as possible new materials for various applications ranging from opto-electronics to heterogeneous catalysis. In this context, ferroelectric oxides are particularly promising. The electric polarization plays a crucial role at many oxide surfaces, and it largely determines their physical and chemical properties. Ferroelectrics offer in addition the possibility to control/switch the electric polarization and hence the surface chemistry, allowing for the realization of domain-engineered nanoscale devices such as molecular detectors or highly efficient catalysts. Lithium niobate (LiNbO3) is a ferroelectric with a high spontaneous polarization, whose surfaces have a huge and largely unexplored potential. Owing to recent advances in experimental techniques and sample preparation, peculiar and exclusive properties of LiNbO3 surfaces could be demonstrated. For example, water films freeze at different temperatures on differently polarized surfaces, and the chemical etching properties of surfaces with opposite polarization are strongly different. More important, the ferroelectric domain orientation affects temperature dependent surface stabilization mechanisms and molecular adsorption phenomena. Various ab initio theoretical investigations have been performed in order to understand the outcome of these experiments and the origin of the exotic behavior of the lithium niobate surfaces. Thanks to these studies, many aspects of their surface physics and chemistry could be clarified. Yet other puzzling features are still not understood. This review gives a résumé on the present knowledge of lithium niobate surfaces, with a particular view on their microscopic properties, explored in recent years by means of ab initio calculations. Relevant aspects and properties of the surfaces that need further investigation are briefly discussed. The review is concluded with an outlook of challenges and potential payoff

  6. Radiative forcing for changes in tropospheric O3

    International Nuclear Information System (INIS)

    Grossman, A.S.; Wuebbles, D.J.; Grant, K.E.

    1994-06-01

    We have evaluated the radiative forcing for assumed changes in tropospheric O 3 in the 500-1650 cm -1 wavenumber range. The radiative forcing calculations were performed as a function of latitude as well as for a globally and seasonally averaged model atmosphere, both in a clear sky approximation and in a model containing a representative cloud distribution. The scenarios involved radiative forcing calculations for O 3 at normal atmospheric abundance and at a tropospheric abundance depleted by 25 ppbv, at each altitude, for all northern hemisphere latitudes. Normal abundances of H 2 O, CO 2 , CH 4 , and N 2 O were included in the calculations. The IR radiative forcing was calculated using a correlated k-distribution radiative transfer model. The tropospheric radiative forcing values are compared to the IPCC formulae for ozone tropospheric forcing as well as other published values to determine the validity of the correlated k-distribution approach to the radiative forcing calculations. The results for the global average atmosphere show agreement with previous results to the order of 10 percent. We conclude that the O 3 forcing is linear in the background abundance and that the radiative forcing for ozone for the globally averaged atmosphere and the latitude averaged radiative forcing in the clear sky approximation are in agreement to within 10 percent. For the case of an atmosphere in which the tropospheric ozone has been depleted by 25 ppbv at all altitudes in the northern hemisphere, the mid latitude zone contributes ∼50 percent of the forcing, tropic zone contributes ∼37 percent of the forcing and the polar zone contributes ∼13 percent of the total forcing

  7. Strain-induced nanostructure of Pb(Mg1/3Nb2/3)O3-PbTiO3 on SrTiO3 epitaxial thin films with low PbTiO3 concentration

    Science.gov (United States)

    Kiguchi, Takanori; Fan, Cangyu; Shiraishi, Takahisa; Konno, Toyohiko J.

    2017-10-01

    The singularity of the structure in (1 - x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-xPT) (x = 0-50 mol %) epitaxial thin films of 100 nm thickness was investigated from the viewpoint of the localized residual strain in the nanoscale. The films were deposited on SrTiO3 (STO) (001) single-crystal substrates by chemical solution deposition (CSD) using metallo-organic decomposition (MOD) solutions. X-ray and electron diffraction patterns revealed that PMN-xPT thin films included a single phase of the perovskite-type structure with the cube-on-cube orientation relationship between PMN-xPT and STO: (001)Film ∥ (001)Sub, [100]Film ∥ [100]Sub. X-ray reciprocal space maps showed an in-plane tensile strain in all the compositional ranges considered. Unit cells in the films were strained from the rhombohedral (pseudocubic) (R) phase to a lower symmetry crystal system, the monoclinic (MB) phase. The morphotropic phase boundary (MPB) that split the R and tetragonal (T) phases was observed at x = 30-35 for bulk crystals of PMN-xPT, whereas the strain suppressed the transformation from the R phase to the T phase in the films up to x = 50. High-angle annular dark field-scanning transmission electron microscopy (HAADF-STEM) analysis and its related local strain analysis revealed that all of the films have a bilayer morphology. The nanoscale strained layer formed only above the film/substrate semi-coherent interface. The misfit dislocations generated the localized and periodic strain fields deformed the unit cells between the dislocation cores from the R to an another type of the monoclinic (MA) phase. Thus, the singular and localized residual strains in the PMN-xPT/STO (001) epitaxial thin films affect the phase stability around the MPB composition and result in the MPB shift phenomena.

  8. Structural and electrical properties of Barium Titanate (BaTiO3) and Neodymium doped BaTiO3 (Ba0.995Nd0.005TiO3)

    Science.gov (United States)

    Sulong, Tuan Amirah Tuan; Aina Maulat Osman, Rozana; Sobri Idris, Mohd; Azhar Zahid Jamal, Zul

    2017-11-01

    Barium titanate (BaTiO3) and Neodymium (Nd) doped BaTiO3 with composition Ba0.995Nd0.005TiO3 were prepared using conventional solid state reaction method to study the dielectric properties of materials. Pure phase samples were found at final heating temperature of 1400°C for overnight. X-ray diffraction analysis reveals the changes in the lattice parameter and unit cell volume of the pure perovskite tetragonal structure with space group (P4mm). Electrical analysis is carried out to investigate the dielectric properties, conductivity behaviour and dielectric loss of BaTiO3 and Ba0.995Nd0.005TiO3. Ba0.995Nd0.005TiO3 have a broaden dielectric peaks with high permittivity of 8000 and reasonably low loss tan δ which is about 0.004 (1 kHz).

  9. Dielectric investigations of BiFeO3 ceramics

    Directory of Open Access Journals (Sweden)

    Simonas Greičius

    2009-06-01

    Full Text Available In this paper we present the results from the investigation of the dielectric permittivity of BiFeO3 ceramics, prepared by mechanochemical synthesis method in a broad frequency and temperature range. The dielectric permittivity is mainly caused by high conductivity, which is suppressed in the frequencies above 1 MHz. The investigated ceramics showed conductivity activation energy E/k=11280±12 K, and σ0=54161±800 S. The plots of M* revealed conductivity mechanism with τ0=1.12·10^-13 s, and E/k=9245 K.

  10. Thermal properties of UO2 - Gd2O3 fuel

    International Nuclear Information System (INIS)

    Kim, G. S.; Yang, J. H.; Kang, K. W.; Kim, Y. M.; Song, G. W.

    2000-01-01

    The thermal properties (thermal conductivity, oxygen potential and thermal expansion) of UO 2 -Gd 2 O 3 fuels were measured by the laser-flash, TGA and dilatometry method. The thermal conductivity decreased with Gd content, but the oxygen potential and thermal expansion increased with Gd content. Substitution of Gd +3 ion in UO 2 structure increases the scattering site for thermal phonon propagation and thereby decreases the thermal conductivity. The oxygen potential of Gd-doped UO 2 increase mainly because the Gd +3 ions, which are inert to oxidation, make it difficult for oxygen interstitials to access just near them

  11. Heat capacity of SrThO3

    International Nuclear Information System (INIS)

    Kumar, Ginish; Raut, Sheetal; Agarwal, Renu; Mukerjee, S.K.

    2016-01-01

    Thorium is more abundant in nature than uranium, therefore, it is expected to play an important role in the third stage of Indian nuclear power generation program. An advanced heavy water reactor, with thorium oxide based fuels, is being developed in India, with an aim of utilizing thorium for power generation. Alkaline earth elements, Ba and Sr, with significant fission yield (6.3%), react with fuel and precipitate out as a separate phase. Thermodynamic properties of fuel-fission product compounds are needed to understand behaviour of fuel at high burn-ups, therefore, it was decided to investigate heat capacity of SrThO 3

  12. Phase stabilization in plasma sprayed BaTiO3

    Czech Academy of Sciences Publication Activity Database

    Ctibor, Pavel; Seiner, Hanuš; Sedláček, J.; Pala, Zdeněk; Vaněk, Přemysl

    2013-01-01

    Roč. 39, č. 5 (2013), s. 5039-5048 ISSN 0272-8842 R&D Projects: GA ČR(CZ) GA101/09/0702 Institutional support: RVO:61389021 ; RVO:61388998 ; RVO:68378271 Keywords : Spectroscopy * BaTiO3 * Plasma spraying * Spark plasma sintering Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass; BJ - Thermodynamics (UT-L); JH - Ceramics, Fire-Resistant Materials and Glass (FZU-D) Impact factor: 2.086, year: 2013 http://www.sciencedirect.com/science/article/pii/S0272884212013582

  13. Theory of Valence Transition in BiNiO$_3$

    OpenAIRE

    Naka, Makoto; Seo, Hitoshi; Motome, Yukitoshi

    2015-01-01

    Motivated by the colossal negative thermal expansion recently found in BiNiO$_3$, the valence transition accompanied by the charge transfer between the Bi and Ni sites is theoretically studied. We introduce an effective model for Bi-$6s$ and Ni-$3d$ orbitals with taking into account the valence skipping of Bi cations, and investigate the ground-state and finite-temperature phase diagrams within the mean-field approximation. We find that the valence transition is caused by commensurate locking...

  14. Pembuatan Katalis Asam (Ni/γ-Al2O3 dan Katalis Basa (Mg/γ-Al2O3 untuk Aplikasi Pembuatan Biodiesel dari Bahan Baku Minyak Jelantah

    Directory of Open Access Journals (Sweden)

    . Savitri

    2016-05-01

    Full Text Available Biodiesel is an alternative energy fuel a substitute for diesel oil produced from vegetable oil or animal fat which have the advantage easily used, they are biodegradable, not toxic and sulfur free. This research aims to do process of prosucing biodiesel using acid catalysts (Ni/γ-Al2O3 for a esterification process and base catalyst (Mg/γ-Al2O3 for transesterification  process with the variation of catalyst concentration Ni/γ-Al2O3 (0.5%; 0.75%; 1% and 2% and the time (60 minutes, 120 minutes, and 180 minutes. Research of methodology starting to the process impregnation Ni and Mg metal into a buffer γ-Al2O3, characterization a catalyst with XRD, FTIR, and the SAA, and the esterification process to lower levels of FFA and transesterification process for making it biodiesel. The characterization with X-RD does not appear a new peak, only just occurred a shift peak, and declines intensity of Ni/γ-Al2O3 and Mg/γ-Al2O3. The analysis result of the SAA, a decline in the surface area (the decline in active side of catalyst suspected the process impregnation not run perfect because Ni and Mg metal only distributed on the surface of buffer pore. The results of the FTIR analysis does not occur the addition of acidity and alkalinity. The steady of catalyst concentration from esterification process is 1% within 120 minutes produce levels of FFA 6.85%.  Keywords: Biodiesel, esterification, impregnation, used cooking oil, transesterificationDOI : http://dx.doi.org/10.15408/jkv.v2i1.3104

  15. Effect of Fe2O3/ZnO on two glass compositions for solidification on Swedish nuclear wastes

    International Nuclear Information System (INIS)

    Nogues, J.L.; Hench, L.L.

    1981-11-01

    Low melting alkaliborosilicate glasses have been considered for use in the immobilization of high level radioactive wastes for years. A recent study comparing the surface behavior of two nuclear waste glasses concluded that ''Addition of Fe 2 O 3 to a soda borosilicate nuclear waste glass significantly reduces damage by water attack because of a Fe-rich film that forms on the glass surface''. However, in the previous study there were significant differences in the concentration of SiO 2 , B 2 O 3 , CaO and simulated fission products in the glasses which made it impossible to ascribe the improved leach resistance solely to Fe 2 O 3 content. Thus, the objective of the present investigation is to compare the leaching and surface behavior of two nuclear waste glasses which differ only by the substitution of Fe 2 O 3 for some of the ZnO in the glass. By this comparison the authors hope to establish whether Fe 2 O 3 provides a unique contribution to improvements in the leach resistance of these complex glasses. Both glass compositions studied are compatible with the low melting temperature, 0 C, required for the French AVM Process. The quantity of simulated waste products is 9%, characteristic of the Swedish nuclear waste program. (Auth.)

  16. Study of crystal-field excitations and Raman active phonons in o-DyMnO3

    International Nuclear Information System (INIS)

    Jandl, S.; Mansouri, S.; Mukhin, A.A.; Yu Ivanov, V.; Balbashov, A.; Gospodino, M.M.; Nekvasil, V.; Orlita, M.

    2011-01-01

    In DyMnO 3 orthorhombic single crystals, the weak Raman active phonon softening below T=100 K is correlated with the study of infrared active Dy 3+ CF excitations as a function of temperature and under applied magnetic field. We detect five H 13/2 CF transitions that we predict with appropriate CF Hamiltonian and we confirm that the magnetic easy axis lies in the ab plane. While the CF energy level shifts below T=100 K reflect different displacements of the oxygen ions that contribute to the phonon softening, lifting of the ground state Kramers doublet degeneracy (∼30 cm -1 ) is observed below T N =39 K due to the anisotropic Mn 3+ -Dy 3+ interaction, which could be responsible for the stability of the bc-cycloid ferroelectric phase. - Research highlights: → Origin of Raman active phonon softening in the multiferroic o-DyMnO 3 . → A crystal-field study under magnetic field of Dy 3+ in o-DyMnO 3 . → Location of the magnetic easy axis in o-DyMnO 3 . → Lifting of Kramers doublet degeneracy in o-DyMnO 3 .

  17. [Responses of rice growth and development to elevated near-surface layer ozone (O3) concentration: a review].

    Science.gov (United States)

    Yang, Lian-xin; Wang, Yu-long; Shi, Guang-yao; Wang, Yun-xia; Zhu, Jian-guo

    2008-04-01

    Ozone (O3) is recognized as one of the most important air pollutants. At present, the worldwide average tropospheric O3 concentration has been increased from an estimated pre-industrial level of 38 nl L(-1) (25-45 nl L(-1), 8-h summer seasonal average) to approximately 50 nl L(-1) in 2000, and to 80 nl L(-1) by 2100 based on most pessimistic projections. Oryza sativa L. (rice) is the most important grain crop in the world, and thus, to correctly evaluate how the elevated near-surface layer O3 concentration will affect the growth and development of rice is of great significance. This paper reviewed the chamber (including closed and open top chamber)-based studies about the effects of atmospheric ozone enrichment on the rice visible injury symptoms, photosynthesis, water relationship, phenology, dry matter production and allocation, leaf membrane protective system, and grain yield and its components. Further research directions in this field were discussed.

  18. Crystal and magnetic structures of hexagonal YMnO3.

    Science.gov (United States)

    Howard, Christopher J; Campbell, Branton J; Stokes, Harold T; Carpenter, Michael A; Thomson, Richard I

    2013-12-01

    The available data on the structural and magnetic transitions in multiferroic hexagonal YMnO3 have been reviewed, first making use of the computer programs from the group theoretical ISOTROPY software suite to list possible crystal and magnetic structures, then taking into account the capability of neutron diffraction and other physical methods to distinguish them. This leads to a clear view of the transformation sequence, as follows. Hexagonal YMnO3 is paraelectric in P63/mmc at elevated temperatures, and undergoes a single structural transition on cooling through 1250 K to a ferrielectric phase in P63cm that is retained through room temperature. At a much lower temperature, 70 K, there is a magnetic transition from paramagnetic to a triangular antiferromagnetic arrangement, most likely with symmetry P63'cm'. Comment is made on the unusual coupling of ferroelectric and magnetic domains reported to occur in this material, as well as on the so-called `giant magneto-elastic' effect.

  19. local structure study of V2O3 powder

    Science.gov (United States)

    Chen, Hao; Dmouski, Wojtek; Egami, Takeshi

    2001-03-01

    Vanadium sesquioxide undergoes a phase transition at 155K 165K from an antiferromagnetic insulator to paramagnetic metal with the crystal structure changing from monoclinic(I2/a) to trigonal (R3C)) with a 1.4volume at elevated temperature. The metal-insulator transition in V2O3 is generally believed to be driven by the Mott-Hubbard (MH) mechanism. However, recent experiments show there is still controversy with the metal-insulator transition model. It should be emphasized that since the MH mechanism depends on the distance between the first few neighboring atoms and the corresponding overlap of their wave functions, the measurements of the local structure may help to determine whether this or some other mechanism holds. In this paper, v2O3 Powder is detected by X-ray and Neutron rays. The result shows that PDF patterns of monoclinic phase and trigonal phase are similar, which means the local structure of both phases do not change. The fact, that local structures of both phases are similar, cannot be explained by the pure orbital occupation of Mott-Hubbard type of transition. Other mechanism, including electronic and magnetic structure change may take an important role in the transition

  20. LCAO calculations of SrTiO3 nanotubes

    Science.gov (United States)

    Evarestov, Robert; Bandura, Andrei

    2011-06-01

    The large-scale first-principles simulation of the structure and stability of SrTiO3 nanotubes is performed for the first time using the periodic PBE0 LCAO method. The initial structures of the nanotubes have been obtained by the rolling up of the stoichiometric SrTiO3 slabs consisting of two or four alternating (001) SrO and TiO2 atomic planes. Nanotubes (NTs) with chiralities (n,0) and (n,n) have been studied. Two different NTs were constructed for each chirality: (I) with SrO outer shell, and (II) with TiO2 outer shell. Positions of all atoms have been optimized to obtain the most stable NT structure . In the majority of considered cases the inner or outer TiO2 shells of NT undergo a considerable reconstruction due to shrinkage or stretching of interatomic distances in the initial cubic perovskite structure. There were found two types of surface reconstruction: (1) breaking of Ti-O bonds with creating of Ti = O titanyl groups in outer surface; (2) inner surface folding due to Ti-O-Ti bending. Based on strain energy calculations the largest stability was found for (n,0) NTs with TiO2 outer shell.

  1. The new magnetic structure of LaMnO3

    International Nuclear Information System (INIS)

    Gontchar, L.E.; Nikiforov, A.E.

    1999-01-01

    Complete text of publication follows. The LaMnO 3 is known to be a parent compound for materials having colossal magnetoresistance. The magnetic and structural properties of LaMnO 3 are of the great interest now. In the present work, the new four-sublattices magnetic structure - (A x , F y , G z ) + (G x , C y , A z ) - is proposed. The Spin-Hamiltonian used in this model is based on calculated crystal structure and includes isotropic exchange interaction, the single-ion anisotropy and the antisymmetric exchange and Zeeman interactions. All of these components depend upon JT distortion. The spin-wave approximation is used and the dispersion dependencies of the spin waves are calculated. Our previous consideration of KCuF 3 shows that spin-wave method is not sensitive to small antisymmetric exchange interaction and inequivalency of the g tensors, but these small effects could not be neglected in calculations of magnetic structure. The dependence of antiferromagnetic resonance field upon angle is predicted. It could clarify the real magnetic structure. In spite of the sufficient energy gap in the Γ-point of magnetic Brillouin zone (ΔE = 2.7 meV) the measurements of this dependence could be carried out. (author)

  2. Evolution of the SrTiO3/MoO3 interface electronic structure: An in situ photoelectron spectroscopy study

    KAUST Repository

    Du, Yuanmin

    2015-05-12

    Modifying the surface energetics, particularly the work function, of advanced materials is of critical importance for a wide range of surface- and interface-based devices. In this work, using in situ photoelectron spectroscopy, we investigated the evolution of electronic structure at the SrTiO3 surface during the growth of ultrathin MoO3 layers. Thanks to the large work function difference between SrTiO3 and MoO3, the energy band alignment on the SrTiO3 surface is significantly modified. The charge transfer and dipole formation at the SrTiO3/MoO3 interface leads to a large modulation of work function and an apparent doping in SrTiO3. The measured evolution of electronic structure and upward band bending suggest that the growth of ultrathin MoO3 layers is a powerful tool to modulate the surface energetics of SrTiO3, and this surface-engineering approach could be generalized to other functional oxides.

  3. La interstitial defect-induced insulator-metal transition in the oxide heterostructures LaAl O3 /SrTi O3

    Science.gov (United States)

    Zhou, Jun; Yang, Ming; Feng, Yuan Ping; Rusydi, Andrivo

    2017-11-01

    Perovskite oxide interfaces have attracted tremendous research interest for their fundamental physics and promising all-oxide electronic applications. Here, based on first-principles calculations, we propose a surface La interstitial promoted interface insulator-metal transition in LaAl O3 /SrTi O3 (110). Compared with surface oxygen vacancies, which play a determining role on the insulator-metal transition of LaAl O3 /SrTi O3 (001) interfaces, we find that surface La interstitials can be more experimentally realistic and accessible for manipulation and more stable in an ambient atmospheric environment. Interestingly, these surface La interstitials also induce significant spin-splitting states with a Ti dy z/dx z character at a conducting LaAl O3 /SrTi O3 (110) interface. On the other hand, for insulating LaAl O3 /SrTi O3 (110) (properties of LaAl O3 /SrTi O3 (110) for different possibilities in electronic and magnetic applications.

  4. Magnetic two-dimensional electron gas at the manganite-buffered LaAlO3/SrTiO3 interface

    DEFF Research Database (Denmark)

    R. Zhang, H.; Zhang, Y.; Zhang, H.

    2017-01-01

    Fabrication of highly mobile spin-polarized two-dimensional electron gas (2DEG) is crucially important for both fundamental and applied research. Usually, spin polarization appears below 10 K for the 2DEG of LaAlO3/SrTiO3 interface, stemming from the magnetic ordering of Ti3+ ions with the mediat......Fabrication of highly mobile spin-polarized two-dimensional electron gas (2DEG) is crucially important for both fundamental and applied research. Usually, spin polarization appears below 10 K for the 2DEG of LaAlO3/SrTiO3 interface, stemming from the magnetic ordering of Ti3+ ions...... with the mediation of itinerant electrons. Herein, we report a magnetic 2DEG at a La7/8Sr1/8MnO3-buffered LaAlO3/SrTiO3 interface, which simultaneously shows electrically tunable anomalous Hall effect and high conductivity. The spin-polarized temperature for the 2DEG is promoted to 30 K while the mobility remains...... high. The magnetism likely results from a gradient manganese interdiffusion into SrTiO3. The present work demonstrates the great potential of manganite-buffered LaAlO3/SrTiO3 interfaces for spintronic applications....

  5. Two anionically derivatized scandium oxoselenates(IV): ScF[SeO3] and Sc2O2[SeO3

    Science.gov (United States)

    Greiner, Stefan; Chou, Sheng-Chun; Schleid, Thomas

    2017-02-01

    Scandium fluoride oxoselenate(IV) ScF[SeO3] and scandium oxide oxoselenate(IV) Sc2O2[SeO3] could be synthesized through solid-state reactions. ScF[SeO3] was obtained phase-pure, by reacting mixtures of Sc2O3, ScF3 and SeO2 (molar ratio: 1:1:3) together with CsBr as fluxing agent in corundum crucibles embedded into evacuated glassy silica ampoules after firing at 700 °C for seven days. Sc2O2[SeO3] first emerged as by-product during the attempts to synthesize ScCl[SeO3] following aforementioned synthesis route and could later be reproduced from appropriate Sc2O3/SeO3 mixtures. ScF[SeO3] crystallizes monoclinically in space group P21/m with a=406.43(2), b =661.09(4), c=632.35(4) pm, β=93.298(3)° and Z=2. Sc2O2[SeO3] also crystallizes in the monoclinic system, but in space group P21/n with a=786.02(6), b=527.98(4), c=1086.11(8) pm, β=108.672(3)° for Z=4. The crystal structures of both compounds are strongly influenced by the stereochemically active lone pairs of the ψ1-tetrahedral [SeO3]2- anions. They also show partial structures, where the derivatizing F- or O2- anions play an important role. For ScF[SeO3] chains of the composition 2+∞ 1[FS c 2 / 2 ] form from connected [FSc2]5+ dumbbells, while [OSc3]7+ pyramids and [OSc4]10+ tetrahedra units are condensed to layers according to 2+ ∞ 2[O2Sc2 ] in Sc2O2[SeO3].

  6. Imaging of domains in single crystals of BiFeO3-PbTiO3 using various microscopy techniques

    Science.gov (United States)

    Burnett, T. L.; Comyn, T. P.; Bell, A. J.; Condliffe, E.; Lloyd, G.

    2006-02-01

    Single crystals of BiFeO3-PbTiO3 have been grown from a PbO:Bi2O3 flux by cooling at a rate of 2°C/hour from the melt. Faceted crystals of various morphologies were produced and the size of the crystals ranged from less than 0.5mm to 5mm. Initial measurements were made using the scanning electron microscope (SEM) with energy dispersive X-ray analysis (EDX) semi-quantifying the composition of the crystals as well as electron probe microanalysis (EPMA). Powder X-ray diffraction (XRD) of the crushed and sieved crystals established that the structure was rhombohedral perovskite for the (BiFeO3)0.75-(PbTiO3)0.25 composition and tetragonal perovskite for the (BiFeO3)0.50-(PbTiO3)0.50 composition and mixed phase for the (BiFeO3)0.65-(PbTiO3)0.35 and (BiFeO3)0.70- (PbTiO3)0.30. X-ray pole figures verified that the (BiFeO3)0.75-(PbTiO3)0.25 crystal had grown with a single orientation, the [100] direction. Structures that are believed to be domains have been observed through optical and electron microscopy in backscattered mode. This interim report of on going investigations seeks to eventually confirm the domain structure in the crystals with electron back-scattered diffraction (EBSD).

  7. Frustration of Tilts and A-Site Driven Ferroelectricity in KNbO3-LiNbO3 Alloys

    Science.gov (United States)

    Bilc, D. I.; Singh, D. J.

    2006-04-01

    Density functional calculations for K0.5Li0.5NbO3 show strong A-site driven ferroelectricity, even though the average tolerance factor is significantly smaller than unity and there is no stereochemically active A-site ion. This is due to the frustration of tilt instabilities by A-site disorder. There are very large off centerings of the Li ions, which contribute strongly to the anisotropy between the tetragonal and rhombohedral ferroelectric states, yielding a tetragonal ground state even without strain coupling.

  8. Structure and magnetocaloric properties of La1-xKxMnO3 manganites

    International Nuclear Information System (INIS)

    Aliev, A.M.; Gamzatov, A.G.; Batdalov, A.B.; Mankevich, A.S.; Korsakov, I.E.

    2011-01-01

    A technology of obtaining the single-phase ceramic samples of La 1-x K x MnO 3 manganites and the dependence of their structural parameters on the content of potassium has been described. Magnetocaloric effect (MCE) in the obtained samples has been measured by two independent methods: classical direct methodic and a method of magnetic field modulation. The values of MCE obtained by both methods substantially differ. The explanation of the observed divergences is given. The correlation between the level of doping and MCE value has been defined. The value of T C determined by the MCE maximum conforms with the literature data obtained by other methods.

  9. The Study Into Potential Enhacement Of Metalworking Fluids Biodegradability By The Application Of O3/UV

    Directory of Open Access Journals (Sweden)

    Gerulová Kristína

    2015-06-01

    Full Text Available The increase in mineralization and biodegradability of MWFs by ozone/ultraviolet in comparison with ozone were investigated. Studied were two similar synthetic fluids pre-treated by the combination of the O3/UV advanced oxidative method. Expectations that the pre-treatment could enhance biodegradability of the metalworking fluid were not confirmed. The combined oxidation process at the defined conditions resulted in 1-35 % decrease of the achieved primary degradation level. Samples were prepared from real concentrates and diluted to approximately 350 mg/L of TOC.

  10. Mott Transition in GdMnO3: an Ab Initio Study

    Science.gov (United States)

    Ferreira, W. S.; Moreira, E.; Frazão, N. F.

    2018-04-01

    Orthorhombic GdMnO3 is studied using density functional theory considering the pseudo-potential plane-wave method within local-spin-density approximation, LSDA. The electronic band structure and density of states, for several hydrostatic pressures, are studied. The Mott transition was observed at 60 GPa. Calculated lattice parameters are close to the experimental measurements, and some indirect band gaps (S→Γ) were obtained within the LSDA level of calculation, between the occupied O-2 p and unoccupied Gd-4 f states. The variation of the gap reduces with increasing pressure, being well fitted to a quadratic function.

  11. From flexoelectricity to absolute deformation potentials: The case of SrTiO3

    Science.gov (United States)

    Stengel, Massimiliano

    2015-11-01

    Based on recent developments in the first-principles theory of flexoelectricity, I generalize the concept of absolute deformation potential to arbitrary nonpiezoelectric insulators and deformation fields. To demonstrate this formalism, I calculate the response of the band edges of SrTiO3 to both dynamic (sound waves) and static (bending) mechanical loads, respectively, at the bulk level and in a slab geometry. The results have important implications for the understanding of strain-gradient-related phenomena in crystalline insulators, formally unifying the description of band-structure and electrostatic effects.

  12. Species characteristics and intraspecific variation in growth and photosynthesis of Cryptomeria japonica under elevated O3 and CO2.

    Science.gov (United States)

    Hiraoka, Yuichiro; Iki, Taiichi; Nose, Mine; Tobita, Hiroyuki; Yazaki, Kenichi; Watanabe, Atsushi; Fujisawa, Yoshitake; Kitao, Mitsutoshi

    2017-06-01

    In order to predict the effects of future atmospheric conditions on forest productivity, it is necessary to clarify the physiological responses of major forest tree species to high concentrations of ozone (O3) and carbon dioxide (CO2). Furthermore, intraspecific variation of these responses should also be examined in order to predict productivity gains through tree improvements in the future. We investigated intraspecific variation in growth and photosynthesis of Cryptomeria japonica D. Don, a major silviculture species in Japan, in response to elevated concentrations of O3 (eO3) and CO2 (eCO2), separately and in combination. Cuttings of C. japonica were grown and exposed to two levels of O3 (ambient and twice-ambient levels) in combination with two levels of CO2 (ambient and 550 µmol mol-1 in the daytime) for two growing seasons in a free-air CO2 enrichment experiment. There was no obvious negative effect of eO3 on growth or photosynthetic traits of the C. japonica clones, but a positive effect was observed for annual height increments in the first growing season. Dry mass production and the photosynthetic rate increased under eCO2 conditions, while the maximum carboxylation rate decreased. Significant interaction effects of eO3 and eCO2 on growth and photosynthetic traits were not observed. Clonal effects on growth and photosynthetic traits were significant, but the interactions between clones and O3 and/or CO2 treatments were not. Spearman's rank correlation coefficients between growth traits under ambient conditions and for each treatment were significantly positive, implying that clonal ranking in growth abilities might not be affected by either eO3 or eCO2. The knowledge obtained from this study will be helpful for species selection in afforestation programs, to continue and to improve current programs involving this species, and to accurately predict the CO2 fixation capacity of Japanese forests. © The Author 2017. Published by Oxford University Press. All

  13. Trees in urban parks and forests reduce O3, but not NO2 concentrations in Baltimore, MD, USA

    Science.gov (United States)

    Yli-Pelkonen, Vesa; Scott, Anna A.; Viippola, Viljami; Setälä, Heikki

    2017-10-01

    Trees and other vegetation absorb and capture air pollutants, leading to the common perception that they, and trees in particular, can improve air quality in cities and provide an important ecosystem service for urban inhabitants. Yet, there has been a lack of empirical evidence showing this at the local scale with different plant configurations and climatic regions. We studied the impact of urban park and forest vegetation on the levels of nitrogen dioxide (NO2) and ground-level ozone (O3) while controlling for temperature during early summer (May) using passive samplers in Baltimore, USA. Concentrations of O3 were significantly lower in tree-covered habitats than in adjacent open habitats, but concentrations of NO2 did not differ significantly between tree-covered and open habitats. Higher temperatures resulted in higher pollutant concentrations and NO2 and O3 concentration were negatively correlated with each other. Our results suggest that the role of trees in reducing NO2 concentrations in urban parks and forests in the Mid-Atlantic USA is minor, but that the presence of tree-cover can result in lower O3 levels compared to similar open areas. Our results further suggest that actions aiming at local air pollution mitigation should consider local variability in vegetation, climate, micro-climate, and traffic conditions.

  14. Visible light-induced electronic structure modulation of Nb- and Ta-doped α-Fe2O3 nanorods for effective photoelectrochemical water splitting

    Science.gov (United States)

    Chang, Han-Wei; Fu, Yanming; Lee, Wan-Yi; Lu, Ying-Rui; Huang, Yu-Cheng; Chen, Jeng-Lung; Chen, Chi-Liang; Chou, Wu Ching; Chen, Jin-Ming; Lee, Jyh-Fu; Shen, Shaohua; Dong, Chung-Li

    2018-02-01

    The photoelectrochemical (PEC) water splitting activity of Nb and Ta-doped hematite (α-Fe2O3) nanorods was investigated with reference to electronic structures by in situ synchrotron x-ray absorption spectroscopy (XAS). Current density-potential measurements demonstrate that the PEC activity of α-Fe2O3 nanorods depends strongly on the species and concentrations of dopants. The doping of α-Fe2O3 nanorods with a low level of Nb or Ta can improve their electrical conductivity and thereby facilitate charge transport and reduced electron-hole recombination therein. The photoconversion effects of Nb and Ta-doped α-Fe2O3 by in situ XAS in the dark and under illumination revealed opposite evolutions of the spectral intensities of the Fe L-edge and Nb/Ta L-edge, indicating that charge transfer and a conduction pathway are involved in the photoconversion. Analytic in situ XAS results reveal that the α-Fe2O3 that is doped with a low level of Nb has a greater photoconversion efficiency than that doped with Ta because Nb sites are more active than Ta sites in α-Fe2O3. The correlation between PEC activity and the electronic structure of Nb/Ta-doped α-Fe2O3 is examined in detail using in situ XAS and helps to elucidate the mechanism of PEC water splitting in terms of the electronic structure.

  15. Charge transfer mechanism for the formation of metallic states at the KTaO3/SrTiO3 interface

    KAUST Repository

    Nazir, Safdar

    2011-03-29

    The electronic and optical properties of the KTaO3/SrTiO3 heterointerface are analyzed by the full-potential linearized augmented plane-wave approach of density functional theory. Optimization of the atomic positions points at subordinate changes in the crystal structure and chemical bonding near the interface, which is due to a minimal lattice mismatch. The creation of metallic interface states thus is not affected by structural relaxation but can be explained by charge transfer between transition metal and oxygen atoms. It is to be expected that a charge transfer is likewise important for related interfaces such as LaAlO3/SrTiO3. The KTaO3/SrTiO3 system is ideal for disentangling the complex behavior of metallic interface states, since almost no structural relaxation takes place.

  16. Enhanced self-repairing capability of sol-gel derived SrTiO3/nano Al2O3 composite films

    International Nuclear Information System (INIS)

    Yao, Manwen; Peng, Yong; Xiao, Ruihua; Li, Qiuxia; Yao, Xi

    2016-01-01

    SrTiO 3 /nano Al 2 O 3 inorganic nanocomposites were prepared by using a conventional sol-gel spin coating process. For comparison, SrTiO 3 films doped by equivalent amount of sol-Al 2 O 3 have also been investigated. Aluminum deposited by using vacuum evaporation was used as the top electrode. The nanocomposites exhibited a significantly enhanced dielectric strength of 506.9 MV/m, which was increased by 97.4% as compared with the SrTiO 3 films doped with sol-Al 2 O 3 . The leakage current maintained of the same order of microampere until the ultimate breakdown of the nanocomposites. The excellent electrical performances are ascribed to the anodic oxidation reaction in origin, which can repair the internal and/or surface defects of the films.

  17. Al2O3 dielectric layers on H-terminated diamond: Controlling surface conductivity

    Science.gov (United States)

    Yang, Yu; Koeck, Franz A.; Dutta, Maitreya; Wang, Xingye; Chowdhury, Srabanti; Nemanich, Robert J.

    2017-10-01

    This study investigates how the surface conductivity of H-terminated diamond can be preserved and stabilized by using a dielectric layer with an in situ post-deposition treatment. Thin layers of Al2O3 were grown by plasma enhanced atomic layer deposition (PEALD) on H-terminated undoped diamond (100) surfaces. The changes of the hole accumulation layer were monitored by correlating the binding energy of the diamond C 1s core level with electrical measurements. The initial PEALD of 1 nm Al2O3 resulted in an increase of the C 1s core level binding energy consistent with a reduction of the surface hole accumulation and a reduction of the surface conductivity. A hydrogen plasma step restored the C 1s binding energy to the value of the conductive surface, and the resistance of the diamond surface was found to be within the range for surface transfer doping. Further, the PEALD growth did not appear to degrade the surface conductive layer according to the position of the C 1s core level and electrical measurements. This work provides insight into the approaches to establish and control the two-dimensional hole-accumulation layer of the H-terminated diamond and improve the stability and performance of H-terminated diamond electronic devices.

  18. High refractive index gold nanoparticle doped Bi2O3-B2O3 glasses for THz frequencies

    Science.gov (United States)

    Singla, Shivani; Achanta, Venu Gopal; Mahendru, Nancy; Prabhu, Shriganesh S.; Falconieri, Mauro; Sharma, Gopi

    2017-10-01

    Direct incorporation of gold nanoparticles from suspensions in 30%Bi2O3:70%B2O3 glass was achieved. This method has advantage over traditional methods where a gold salt is added to the precursor mixture and gold nanoparticles are obtained with subsequent heat treatment, eventually inducing crystallization with associated scattering of light and hence resulting in reduced optical quality of material. X-ray diffraction and differential thermal analysis were carried out in order to confirm the amorphous nature of the material and thermal properties of the prepared glasses, respectively. The size of the gold nanoparticles in the prepared glass matrix was measured using scanning electron microscopy. Optical characterization of prepared glass samples in ultraviolet-visible and terahertz regions was performed using ellipsometry, UV-VIS spectrophotometry and THz-time-domain spectroscopy. Comparison was made between glasses with and without gold nanoparticles and the effect of gold nanoparticle concentration on their optical behaviour is studied. These glasses are found to have high refractive index in the THz region making them suitable for photonic applications.

  19. Spin and orbital Ti magnetism at LaMnO3/SrTiO3 interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Garcial-Barriocanal, J [Universidad Complutense, Spain; Cezar, J. C. [European Synchrotron Radiation Facility (ESRF); Bruno, F. Y. [Universidad Complutense, Spain; Thakur, P. [European Synchrotron Radiation Facility (ESRF); Brookes, N. B. [European Synchrotron Radiation Facility (ESRF); Utfeld, C. [University of Bristol, UK; Riviera-Calzada, A. [Universidad Complutense, Spain; Giblin, S. R. [ISIS Facility, Rutherford Appleton Laboratory; Taylor, J. W. [ISIS Facility, Rutherford Appleton Laboratory; Duffy, J. A. [University of Warwick, UK; Dugdale, S. B. [University of Bristol, UK; Nakamura, T. [Japan Synchrotron Radiation Research Institute, SPring-8; Kodama, K. [Japan Synchrotron Radiation Research Institute, SPring-8; Leon, C. [Universidad Complutense, Spain; Okamoto, Satoshi [ORNL; Santamaria, J. [Universidad Complutense, Spain

    2010-01-01

    In systems with strong electron-lattice coupling, such as manganites, orbital degeneracy is lifted, what causes a null expectation value of the orbital moment. Magnetic structure is thus determined by spin-spin superexchange. In titanates, however, with much smaller Jahn-Teller distortions, orbital degeneracy might allow non-zero values of the orbital magnetic moment. Accordingly, novel forms of ferromagnetic superexchange interaction unique to t2g electrons systems have been theoretically predicted, although their experimental observation has remained elusive. Here we report a new kind of Ti3+ ferromagnetism at LaMnO3/SrTiO3 epitaxial interfaces. It results from charge transfer to the empty conduction band of the titanate and has spin and orbital contributions evidencing the role played by orbital degeneracy. The possibility of tuning magnetic alignment (ferromagnetic or antiferromagnetic) of Ti and Mn moments by structural parameters is demonstrated. This result will provide important clues for the understanding of the effects of orbital degeneracy in superexchange coupling.

  20. Signatures of electronic nematicity in (111) LaAlO3/SrTiO3 interfaces

    Science.gov (United States)

    Davis, S.; Huang, Z.; Han, K.; Ariando, Venkatesan, T.; Chandrasekhar, V.

    2018-01-01

    The two-dimensional conducting gas (2DCG) that forms at the interface between LaAlO3 (LAO) and SrTiO3 (STO) has been widely studied due to the multitude of in situ tunable phenomena that exist at the interface. Recently it has been shown that nearly every property of the 2DEG that forms at the interface of (111) oriented LAO/STO is strongly anisotropic with respect to the in-plane crystal direction. This in-plane rotational symmetry breaking points to the existence of an electronic nematic phase at the interface that can be modified by an in situ electrostatic back-gate potential. Here we show that the onset temperature of the anisotropy in the longitudinal resistance is T ≈22 K , which does not match up with any known structural transition, and coincides with the onset of anisotropy in the Hall response of the system. Furthermore, below 22 K, charge transport is activated in nature with different activation energies along the two in-plane crystal directions. Such a response implies that the band edges along the two directions are different and provides further evidence of an electronic nematic state at the interface.

  1. Magnetoresistance in the superconducting state at the (111) LaAlO3/SrTiO3 interface

    Science.gov (United States)

    Davis, S.; Huang, Z.; Han, K.; Ariando, Venkatesan, T.; Chandrasekhar, V.

    2017-10-01

    Condensed-matter systems that simultaneously exhibit superconductivity and ferromagnetism are rare due the antagonistic relationship between conventional spin-singlet superconductivity and ferromagnetic order. In materials in which superconductivity and magnetic order are known to coexist (such as some heavy-fermion materials), the superconductivity is thought to be of an unconventional nature. Recently, the conducting gas that lives at the interface between the perovskite band insulators LaAlO3 (LAO) and SrTiO3 (STO) has also been shown to host both superconductivity and magnetism. Most previous research has focused on LAO/STO samples in which the interface is on the (001) crystal plane. Relatively little work has focused on the (111) crystal orientation, which has hexagonal symmetry at the interface, and has been predicted to have potentially interesting topological properties, including unconventional superconducting pairing states. Here we report measurements of the magnetoresistance of (111) LAO/STO heterostructures at temperatures at which they are also superconducting. As with the (001) structures, the magnetoresistance is hysteretic, indicating the coexistence of magnetism and superconductivity, but in addition, we find that this magnetoresistance is anisotropic. Such an anisotropic response is completely unexpected in the superconducting state and suggests that (111) LAO/STO heterostructures may support unconventional superconductivity.

  2. Photoconductivity of transparent perovskite oxide semiconductors BaSnO3 and SrTiO3 epitaxial thin films

    Science.gov (United States)

    Park, Jisung; Kim, Useong; Char, Kookrin; Institute of Applied Physics, Department of Physics; Astronomy, Seoul National University, Seoul Team

    We have measured the photoconductivity (PC) of epitaxial thin films of transparent semiconductor BaSnO3 (BSO) and SrTiO3 (STO) at room temperature. The epitaxial thin films of BSO and STO were grown by pulsed laser ablation technique on the MgO substrates to exclude any conductance from the substrate owing to its large bandgap (~7.8 eV). Despite the same crystalline structure and similar band gap sizes (~3.2 eV), the PC of BSO behaved very differently. The slowly varying component in the PC of BSO is much larger than that of STO; the PC of BSO increased slowly, reached higher magnitude after the same duration of illumination, and persisted longer than many hours after the light was turned off, whereas the PC of STO showed little persistent conductivity. The spectral responses of the PC of BSO and STO showed their highest peaks below 400 nm when measured by a UV monochromator system, suggesting that the electron-hole pair generation is the main mechanism of the PC for both materials. The higher mobility of BSO should be partially responsible for the higher PC. The large persistent PC of BSO seems related to the dislocations that trap electrons easily.

  3. Equilibrium phases in the multiferroic BiFeO3-PbTiO3 system – a revisit

    Directory of Open Access Journals (Sweden)

    Kothai V.

    2014-07-01

    Full Text Available The(1-x BiFeO3-(x PbTiO3 solid solution exhibiting a Morphotropic Phase Boundary (MPB has attracted considerable attention recently because of its unique features such as multiferroic, high Curie point (TC ~ 700°C and giant tetragonality (c/a -1 ~ 0.19. Different research groups have reported different composition range of MPB for this system. In this work we have conclusively proved that the wide composition range of MPB reported in the literature is due to kinetic arrest of the metastable rhombohedral phase and that if sufficient temperature and time is allowed the metastable phase disappears. The genuine MPB was found to be x=0.27 for which the tetragonal and the rhombohedral phases are in thermodynamic equilibrium. In-situ high temperature structural study of x=0.27 revealed the sluggish kinetics associated with the temperature induced structural transformation. Neutron powder diffraction study revealed that themagnetic ordering at room temperature occurs in the rhombohedral phase. The magnetic structure was found to be commensurate G-type antiferromagnetic with magnetic moments parallel to the c-direction (of the hexagonal cell. The present study suggests that the equilibrium properties in this solid solution series should be sought for x=0.27.

  4. Effective theory of exotic superconductivity in LaAlO3/SrTiO3 interfaces

    Science.gov (United States)

    Esmailzadeh, Haniyeh; Moghaddam, Ali G.

    2018-05-01

    Motivated by experimental and theoretical works about superconductivity at the oxide interfaces, we provide a simple model for possible unconventional pairings inside the exotic two-dimensional electron gas formed in heterostructures of SrTiO3 and LaAlO3. At the low energy limit, the electron gas at the interfaces is usually modeled with an effective three band model considering of 3d t2g orbitals which are slightly coupled by atomic spin-orbit couplings (SOC). Considering direct superconducting pairing in two higher delocalized bands and by exploiting a perturbative scheme based on canonical transformation, we derive the effective pairing amplitudes with possibly exotic nature inside the localized dxy band as well as various inter-band pairing components. In particular we show that equal-spin triplet pairings are possible between the band dxy and any of other dxz and dyz bands. In addition weaker effective pairings take place inside the localized band itself and between delocalized dxz and dyz bands with singlet and opposite-spin triplet characters. These unconventional effective pairings are indeed mediated by SOC-induced higher order virtual transitions between the bands and particularly into the localized band. Our model suggest that unconventional effective superconductivity is possible at oxide interfaces, simply, due to the special band structure and important role of atomic SOC and perhaps other magnetic effects present at these heterostructures.

  5. Photocatalytic Active Bismuth Fluoride/Oxyfluoride Surface Crystallized 2Bi2O3-B2O3 Glass-Ceramics

    Science.gov (United States)

    Sharma, Sumeet Kumar; Singh, V. P.; Chauhan, Vishal S.; Kushwaha, H. S.; Vaish, Rahul

    2018-03-01

    The present article deals with 2Bi2O3-B2O3 (BBO) glass whose photocatalytic activity has been enhanced by the method of wet etching using an aqueous solution of hydrofluoric acid (HF). X-ray diffraction of the samples reveals that etching with an aqueous solution of HF leads to the formation of BiF3 and BiO0.1F2.8 phases. Surface morphology obtained from scanning electron microscopy show granular and plate-like morphology on the etched glass samples. Rhodamine 6G (Rh 6G) has been used to investigate the photocatalytic activity of the as-quenched and etched glasses. Enhanced visible light-driven photocatalytic activity was observed in HF etched glass-ceramics compared to the as-quenched BBO glass. Contact angle of the as-quenched glass was 90.2°, which decreases up to 20.02° with an increase in concentration of HF in the etching solution. Enhanced photocatalytic activity and increase in the hydrophilic nature suggests the efficient treatment of water pollutants by using the prepared surface crystallized glass-ceramics.

  6. Performance characterization and kinetic modeling of ozonation using a new method: ROH,O3concept.

    Science.gov (United States)

    Kwon, Minhwan; Kye, Homin; Jung, Youmi; Yoon, Yeojoon; Kang, Joon-Wun

    2017-10-01

    Ozonation is an effective treatment for removing various organic pollutants from aquatic systems. The R ct concept, which is defined as the ratio of OH exposure to O 3 exposure, has been widely used to predict the removal efficiency of target compounds, but it has significant variations by water temperature and initial O 3 dose which are crucial parameters in drinking water plant. The R OH,O3 concept, which is defined as the OH exposure by O 3 consumption, was proposed as a kinetic parameter for characterization and kinetic modeling for ozonation. The R OH,O3 concept is independent of temperature and initial O 3 dose. A higher R OH,O3 value indicates a higher OH formation when the same amount of O 3 is consumed in different water samples; therefore, the OH yield from O 3 decomposition of the water samples can be compared using the R OH,O3 values. The R OH,O3 concept can also be used to characterize and model the initial ozone demand phase, and it is more convenient method compared to Rct concept. Using the R OH,O3 concept, the dynamic O 3 and OH kinetics and the removal efficiencies of iopromide and ibuprofen were well predicted (R 2  = 0.98) over a wide range of experimental conditions (n = 124). Copyright © 2017 Elsevier Ltd. All rights reserved.

  7. Photoelectrochemical Performance Observed in Mn-Doped BiFeO3 Heterostructured Thin Films

    Directory of Open Access Journals (Sweden)

    Hao-Min Xu

    2016-11-01

    Full Text Available Pure BiFeO3 and heterostructured BiFeO3/BiFe0.95Mn0.05O3 (5% Mn-doped BiFeO3 thin films have been prepared by a chemical deposition method. The band structures and photosensitive properties of these films have been investigated elaborately. Pure BiFeO3 films showed stable and strong response to photo illumination (open circuit potential kept −0.18 V, short circuit photocurrent density was −0.023 mA·cm−2. By Mn doping, the energy band positions shifted, resulting in a smaller band gap of BiFe0.95Mn0.05O3 layer and an internal field being built in the BiFeO3/BiFe0.95Mn0.05O3 interface. BiFeO3/BiFe0.95Mn0.05O3 and BiFe0.95Mn0.05O3 thin films demonstrated poor photo activity compared with pure BiFeO3 films, which can be explained by the fact that Mn doping brought in a large amount of defects in the BiFe0.95Mn0.05O3 layers, causing higher carrier combination and correspondingly suppressing the photo response, and this negative influence was more considerable than the positive effects provided by the band modulation.

  8. Structural, spectroscopic, and dielectric characterizations of Mn-doped 0.67BiFeO3-0.33BaTiO3 multiferroic ceramics

    KAUST Repository

    Hang, Qiming

    2013-09-07

    0.67BiFeO3-0.33BaTiO3 multiferroic ceramics doped with x mol% MnO2 (x = 2–10) were synthesized by solid-state reaction. The formation of a perovskite phase with rhombohedral symmetry was confirmed by X-ray diffraction (XRD). The average grain sizes were reduced from 0.80 μm to 0.50 μm as increasing the Mn-doped levels. Single crystalline nature of the grains was revealed by high-resolution transmission electron microscopy (HRTEM) images and electron diffraction patterns. Polar nano-sized ferroelectric domains with an average size of 9 nm randomly distributed in the ceramic samples were revealed by TEM images. Ferroelectric domain lamellae (71° ferroelectric domains) with an average width of 5 nm were also observed. Vibrational modes were examined by Raman spectra, where only four Raman peaks at 272 cm−1 (E-4 mode), 496 cm−1 (A 1-4 mode), 639 cm−1, and 1338 cm−1 were observed. The blue shifts in the E-4 and A 1-4 Raman mode frequencies were interpreted by a spring oscillator model. The dieletric constants of the present ceramics as a function of the Mn-doped levels exhibited a V-typed curve. They were in the range of 350–700 measured at 103 Hz, and the corresponding dielectric losses were in range of 0.43–0.96, approaching to 0.09 at 106 Hz.

  9. (1−x)[(K$_{0.5}$Na$_{0.5}$)NbO$_3$–LiSbO$_3

    Indian Academy of Sciences (India)

    Lead-free piezoelectric ceramics ( 1 − x ) [0.95(K 0.5 Na 0.5 )NbO 3 –0.05LiSbO 3 ]– x BiFe 0.8 Co 0.2 O 3 (KNN–LS– x BFC) were prepared by a conventional sintering technique. The effect of BFC content on the structure, piezoelectricand electrical properties of KNN–LS ceramics was investigated. The results reveal that ...

  10. Insights from in situ and environmental TEM on the oriented attachment of α-Fe2O3 nanoparticles during α-Fe2O3 nanorod formation

    DEFF Research Database (Denmark)

    Almeida, Trevor P.; Fay, Michael W.; Hansen, Thomas Willum

    2014-01-01

    ’ with the developing NR to adopt a perfect single crystal. Conversely, the heating of partially developed α-Fe2O3 NRs up to 250 °C, under vacuum, during iTEM, demonstrated the progressive coalescence of loosely packed α-Fe2O3 NPs and the coarsening of α-Fe2O3 NRs, without any direct evidence for an intermediate OA...

  11. Magneto-transport properties of La0.7Ca0.3MnO3/ SrTiO3/La0 ...

    Indian Academy of Sciences (India)

    Magneto-transport properties of La0.7Ca0.3MnO3/. SrTiO3/La0.7Ce0.3MnO3 tunnel junction. P RAYCHAUDHURI1,∗. , C MITRA2, K DORR2, K H MULLER2,. G KOBERNIK2 and R PINTO3. 1Department of Physics and Astronomy, University of Birmingham, B15 2TT, UK. 2Institut fur Festkorper und Wekstofforschung, ...

  12. Water-Assisted Spreading of MoO3 onto SiO2-Al2O3 Supports for Preparation of Sulfide CoMo Hydrodesulfurization Catalysts

    Czech Academy of Sciences Publication Activity Database

    Kaluža, Luděk; Gulková, Daniela; Vít, Zdeněk; Zdražil, Miroslav

    2013-01-01

    Roč. 112, OCT (2013), s. 272-276 ISSN 0016-2361 R&D Projects: GA ČR GAP106/11/0902 Institutional support: RVO:67985858 Keywords : MoO3/SiO2-Al2O3 * CoMo/SiO2-Al2O3 * water-assisted spreading Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.406, year: 2013

  13. Magneto-transport properties of La 0.7 Ca 0.3 MnO 3/SrTiO 3/La 0.7 ...

    Indian Academy of Sciences (India)

    transport properties of La0.7Ca0.3MnO3/SrTiO3/La0.7Ce0.3MnO3 tunnel junction. P Raychaudhuri C Mitra K Dorr K H Muller G Kobernik R Pinto. Thin file & devices Volume 58 Issue 5-6 May-June 2002 pp 1179-1182 ...

  14. CH3-ReO3 on gamma-Al2O3: understanding its structure, initiation,and reactivity in olefin metathesis

    Energy Technology Data Exchange (ETDEWEB)

    Salameh, Alain; Joubert, Jerome; Baudouin, Anne; Lukens, Wayne; Delbecq, Francoise; Sautet, Philippe; Basset, Jean Marie; Coperet,Christophe

    2007-01-20

    Me-ReO3 on gamma-alumina: understanding the structure, theinitiation and thereactivity of a highly active olefin metathesiscatalyst Heterolytic splitting of the C-H bond of the methyl group ofCH3ReO3 on AlsO reactive sites of alumina as a way to generate the activesite of CH3ReO3 supported on gamma-Al203.

  15. Synthesis, structural transformation, thermal stability, valence state, and magnetic and electronic properties of PbNiO3 with perovskite- and LiNbO3-type structures.

    Science.gov (United States)

    Inaguma, Yoshiyuki; Tanaka, Kie; Tsuchiya, Takeshi; Mori, Daisuke; Katsumata, Tetsuhiro; Ohba, Tomonori; Hiraki, Ko-ichi; Takahashi, Toshihiro; Saitoh, Hiroyuki

    2011-10-26

    We synthesized two high-pressure polymorphs PbNiO(3) with different structures, a perovskite-type and a LiNbO(3)-type structure, and investigated their formation behavior, detailed structure, structural transformation, thermal stability, valence state of cations, and magnetic and electronic properties. A perovskite-type PbNiO(3) synthesized at 800 °C under a pressure of 3 GPa crystallizes as an orthorhombic GdFeO(3)-type structure with a space group Pnma. The reaction under high pressure was monitored by an in situ energy dispersive X-ray diffraction experiment, which revealed that a perovskit-type phase was formed even at 400 °C under 3 GPa. The obtained perovskite-type phase irreversibly transforms to a LiNbO(3)-type phase with an acentric space group R3c by heat treatment at ambient pressure. The Rietveld structural refinement using synchrotron X-ray diffraction data and the XPS measurement for both the perovskite- and the LiNbO(3)-type phases reveal that both phases possess the valence state of Pb(4+)Ni(2+)O(3). Perovskite-type PbNiO(3) is the first example of the Pb(4+)M(2+)O(3) series, and the first example of the perovskite containing a tetravalent A-site cation without lone pair electrons. The magnetic susceptibility measurement shows that the perovskite- and LiNbO(3)-type PbNiO(3) undergo antiferromagnetic transition at 225 and 205 K, respectively. Both the perovskite- and LiNbO(3)-type phases exhibit semiconducting behavior.

  16. Crystal structure and magnetism in κ-Al2O3-type AlxFe2-xO3 films on SrTiO3(111)

    Science.gov (United States)

    Hamasaki, Yosuke; Shimizu, Takao; Yasui, Shintaro; Shiraishi, Takahisa; Akama, Akihiro; Kiguchi, Takanori; Taniyama, Tomoyasu; Itoh, Mitsuru

    2017-07-01

    We prepared κ-Al2O3-type structured AlxFe2-xO3 films in the range of x = 0 - 1.70 deposited on SrTiO3(111) substrates and investigated their crystal structures and magnetic properties. All films could be stabilized in the κ-Al2O3-type orthorhombic phase, and the lattice parameters were found to be monotonically decreased with an increase in the Al content. Néel temperature of AlxFe2-xO3 films was found to decrease with an increase in Al content, until the Al1.70Fe0.30O3 film showed paramagnetic behavior. On the other hand, saturation magnetization showed a maximum 0.79 μB/Fe at 10 K in the Al0.91Fe1.09O3 film, manifesting the preferential occupation of Al in the tetrahedral site. Cross sectional TEM observation has revealed the columnar growth of AlxFe2-xO3 films with an average width of ˜10 nm on the bottom layer that may have a similar cation arrangement with a bixbyite-type structure.

  17. Influence of Y2O3 Addition on Crystallization, Thermal, Mechanical, and Electrical Properties of BaO-Al2O3-B2O3-SiO2 Glass-Ceramic for Ceramic Ball Grid Array Package

    Science.gov (United States)

    Li, Bo; Li, Wei; Zheng, Jingguo

    2018-01-01

    Y2O3 addition has a significant influence on the crystallization, thermal, mechanical, and electrical properties of BaO -Al2O3 -B2O3 -SiO2 (BABS) glass-ceramics. Semi-quantitative calculation based on x-ray diffraction demonstrated that with increasing Y2O3 content, both the crystallinity and the phase content of cristobalite gradually decreased. It is effective for the additive Y2O3 to inhibit the formation of cristobalite phase with a large coefficient of thermal expansion value. The flexural strength and the Young's modulus, thus, are remarkably increased from 140 MPa to 200 MPa and 56.5 GPa to 63.7 GPa, respectively. Also, the sintering kinetics of BABS glass-ceramics with various Y2O3 were investigated using the isothermal sintering shrinkage curve at different sintering temperatures. The sintering activation energy Q sharply decreased from 99.8 kJ/mol to 81.5 kJ/mol when 0.2% Y2O3 was added, which indicated that a small amount of Y2O3 could effectively promote the sintering procedure of BABS glass-ceramics.

  18. Características elétricas do sistema varistor ZnO.Bi2O3.Co2O 3.MnO2 dopado com Ni2O3 Electrical characteristics of Ni2O3- doped ZnO. Bi2O3.Co2O3.MnO2 varistor systems

    Directory of Open Access Journals (Sweden)

    Ana Cristina F. M. Costa

    1998-08-01

    Full Text Available Este trabalho tem como objetivo analisar o efeito do óxido de níquel sobre as propriedades elétricas do sistema varistor ZnO.Bi2O3.Co2O3.MnO2 . Os sistemas foram sinterizados a 1100ºC, 1150 ºC, 1200 ºC e 1250 ºC, por 1 hora. A caracterização elétrica foi feita por meio de medidas de densidade de corrente em função do campo elétrico aplicado. A caracterização microestrutural foi obtida por meio de difração de raios X e microscopia eletrônica de varredura. As melhores propriedades elétricas foram obtidas para o sistema contendo 1,0% em mol de óxido de níquel, sinterizado a 1100 oC. A elevação da temperatura de sinterização causou uma redução nas propriedades elétricas, provavelmente devido a formação de uma microestrutura mais heterogênea.The effect of nickel oxide addition on the electrical properties of the ZnO. Bi2O3. Co2O3. MnO2 varistor system was investigated. This system was sintered at 1100 ºC, 1150 ºC, 1200 ºC and 1250 ºC for one hour and electrical measurements (current density as a function of the applied electrical field were carried out. The microstructural analyses were performed by scanning electron microscopy and X-ray diffraction. The best electrical properties were obtained for the system containing 1.0 mol% of nickel oxide, and sintered at 1100 ºC. A degradation in the electrical properties with increasing sintering temperature has been observed, probably due to an increase in the microstructural heterogeneity.

  19. A Tropical Lake Breeze System : The Effect on Surface NO, NO2, O3, and CO2 Mixing Ratios

    Science.gov (United States)

    Lima Moura, M. A.; Eça D'Almeida Rocha, C. H.; Trebs, I.; Andreae, M. O.; Meixner, F. X.

    2003-04-01

    During the Cooperative LBA Airborne Regional Experiment 2001 (CLAIRE2001, July 2001), we investigated diel variations of nitric oxide (NO), nitrogen dioxide (NO_2), ozone (O_3) and carbon dioxide (CO_2) mixing ratios at Balbina Limnological Station (01^o55'994''S, 59^o28'071''W, Amazonia,Brazil). We applied sensitive and species-specific chemiluminescence (NO, NO_2, O_3) and NDIR (CO_2) analysers to record ambient mixing ratios on 1 min intervals. Simultaneously, we extensively monitored (micro-)meteorological qauntities (air temperature, relative humidity, wind speed and -direction, thermal stratification, rainfall intensity, soil temperatures and moisture, as well as radiation fluxes (global, net, short wave, NO_2 photolysis, and photosynthetic active)). Balbina Limnological Station is located just a few hundred meters south of a 2.360 km^2 hydroelectric power dam (Usina Hidrelétrica de Balbina) and about 100m north from the edge of a primary rainforest. Marked differences in surface albedo and heat storage capacity generate a local wind system, the lake breeze, which advects air from the dam (09:00 to 15:00 local) and from the rainforest (18:00 to 06:00 local), respectively. Generally, we observed marked diel variations of NO, NO_2, O_3, and CO_2 (high/low levels during night/day) and O_3 (low/high levels during night/day). Especially in the tropics, this behaviour is usually related to (a) accumulation of soil emissions (NO, CO_2), chemical reactions (NO, from NO_2-O_3 reaction) and surface destruction (O_3) in a shallow and strong nocturnal boundary layer inversion, and (b) to soil emission (NO), photochemical reactions (NO-NO_2-O_3), dry deposition/plant uptake (NO_2, O_3, and CO_2) and strong turbulent vertical mixing in the daytime mixed layer. However, under the specific conditions of the lake breeze soil emission and dry deposition/ plant uptake can be neglected during daytime. Consequently, the investigation of daytime mixing ratios can be confined to

  20. Linear thermal expansion of SrTiO3

    International Nuclear Information System (INIS)

    Tsunekawa, S.; Watanabe, H.F.J.; Takei, H.

    1984-01-01

    The linear thermal expansion of SrTiO 3 in the temperature range 10 to 150 K is measured with a relative accuracy of 5 x 10 -7 by using a three-terminal capacitance dilatometer. The dilation ΔL/L of a single-domain crystal is converted to the ratio of the pseudo-cubic cell constants a(T)/a(T/sub a/) by the equation a(T)/a(T/sub a/) = [1 + (ΔL/L)/sub T/]/[1 + (ΔL/L)/sub T//sub a/], where L is the specimen length, T/sub a/ is the cubic-to-tetragonal transition temperature and T 6 octahedra around the [001] axis. The temperature at which the dilation shows a minimum, 37.5 K, is very close to the transition point T/sub c/ = (32 +- 5) K predicted by Cowley. (author)

  1. The unusual magnetism of nanoparticle LaCoO3

    International Nuclear Information System (INIS)

    Durand, A M; Belanger, D P; Hamil, T J; Ye, F; Chi, S; Fernandez-Baca, J A; Booth, C H; Abdollahian, Y; Bhat, M

    2015-01-01

    Bulk and nanoparticle powders of LaCoO 3 (LCO) were synthesized and their magnetic and structural properties were studied using SQUID magnetometry and neutron diffraction. The bulk and large nanoparticles exhibit weak ferromagnetism (FM) below T ≈ 85 K and a crossover from strong to weak antiferromagnetic (AFM) correlations near a transition expressed in the lattice parameters, T o ≈40 K. This crossover does not occur in the smallest nanoparticles; instead, the magnetic behavior is predominantly ferromagnetic. The amount of FM in the nanoparticles depends on the amount of Co 3 O 4 impurity phase, which induces tensile strain on the LCO lattice. A core-interface model is introduced, with the core region exhibiting the AFM crossover and with FM in the interface region near surfaces and impurity phases. (paper)

  2. Superparamagnetism in AFM Cr2O3 nanoparticles

    International Nuclear Information System (INIS)

    Tobia, D.; Winkler, E.L.; Zysler, R.D.; Granada, M.; Troiani, H.E.

    2010-01-01

    In this work we report the size effects on the magnetic properties of AFM Cr 2 O 3 nanoparticles. From transmission electron microscopy we determined that the system presents high crystallinity and narrow lognormal size distribution centred at = 7.8 nm with σ = 0.3. The magnetic properties of the nanoparticles were studied by magnetization and electron paramagnetic resonance (EPR) experiments. By EPR spectroscopy we established that the AFM order temperature, T N , shifted to ∼270 K when the size is reduced (T N (Bulk) ∼ 308 K). From the zero-field-cooling and the field-cooling magnetization curves we determined the blocking temperature T B = 28 K. Below T B the system presents exchange bias effect. We discuss the results by using recent models in terms of the internal magnetic structures of the nanoparticles.

  3. Coupled skyrmion sublattices in Cu2OSeO3

    Energy Technology Data Exchange (ETDEWEB)

    Langner, M.C.; Roy,, S.; Mishra, S. K.; Lee, J. C. T.; Shi,, X. W.; Hossain, M. A.; Chuang, Y.-D.; Seki, S.; Tokura, Y.; Kevan, S. D.; Schoenlein, R. W.

    2014-04-18

    We report the observation of a skyrmion lattice in the chiral multiferroic insulator Cu2OSeO3 using Cu L3-edge resonant soft x-ray diffraction. We observe the unexpected existence of two distinct skyrmion sub-lattices that arise from inequivalent Cu sites with chemically identical coordination numbers but different magnetically active orbitals . The skyrmion sublattices are rotated with respect to each other implying a long wavelength modulation of the lattice. The modulation vector is controlled with an applied magnetic field, associating this Moir'e-like phase with a continuous phase transition. Our findings will open a new class of science involving manipulation of quantum topological states.

  4. Correlation of High Magnetoelectric Coupling with Oxygen Vacancy Superstructure in Epitaxial Multiferroic BaTiO3-BiFeO3 Composite Thin Films

    OpenAIRE

    Lorenz, Michael; Wagner, Gerald; Lazenka, Vera; Schwinkendorf, Peter; Bonholzer, Michael; Van Bael, Margriet J.; Vantomme, Andr?; Temst, Kristiaan; Oeckler, Oliver; Grundmann, Marius

    2016-01-01

    Epitaxial multiferroic BaTiO3-BiFeO3 composite thin films exhibit a correlation between the magnetoelectric (ME) voltage coefficient αME and the oxygen partial pressure during growth. The ME coefficient αME reaches high values up to 43 V/(cm·Oe) at 300 K and at 0.25 mbar oxygen growth pressure. The temperature dependence of αME of the composite films is opposite that of recently-reported BaTiO3-BiFeO3 superlattices, indicating that strain-mediated ME coupling alone cannot explain its origin. ...

  5. Fabrication of Multiferroic Co-Substituted BiFeO3 Epitaxial Films on SrTiO3 (100 Substrates by Radio Frequency Magnetron Sputtering

    Directory of Open Access Journals (Sweden)

    Yasuo Ando

    2011-06-01

    Full Text Available The 10 at.% Co-substituted BiFeO3 films (of thickness 50 nm were successfully prepared by radio frequency (r.f. magnetron sputtering on SrTiO3 (100 substrates with epitaxial relationships of [001](001Co-BiFeO3//[001](001SrTiO3. In this study, a single phase Co-substituted BiFeO3 epitaxial film was fabricated by r.f. magnetron sputtering. Sputtering conditions such as Ar, O2 gas pressure, annealing temperature, annealing atmosphere, and sputtering power were systematically changed. It was observed that a low Ar gas pressure and low sputtering power is necessary to suppress the formation of the secondary phases of BiOx. The Co-substituted BiFeO3 films were crystalized with post-annealing at 600 °C in air. The process window for single phase films is narrower than that for pure BiFeO3 epitaxial films. By substituting Fe with Co in BiFeO3, the magnetization at room temperature increased to 20 emu/cm3. This result suggests that Co-substituted BiFeO3 films can be used in spin-filter devices.

  6. The MgO-Al2O3-SiO2 system - Free energy of pyrope and Al2O3-enstatite. [in earth mantle formation

    Science.gov (United States)

    Saxena, S. K.

    1981-01-01

    The model of fictive ideal components is used to determine Gibbs free energies of formation of pyrope and Al2O3-enstatite from the experimental data on coexisting garnet and orthopyroxene and orthopyroxene and spinel in the temperature range 1200-1600 K. It is noted that Al2O3 forms an ideal solution with MgSiO3. These thermochemical data are found to be consistent with the Al2O3 isopleths that could be drawn using most recent experimental data and with the reversed experimental data on the garnet-spinel field boundary.

  7. Antimicrobial effect of Al2O3, Ag and Al2O3/Ag thin films on Escherichia coli and Pseudomonas putida

    International Nuclear Information System (INIS)

    Angelov, O; Stoyanova, D; Ivanova, I; Todorova, S

    2016-01-01

    The influence of Al 2 O 3 , Ag and Al 2 O 3 /Ag thin films on bacterial growth of Gramnegative bacteria Pseudomonas putida and Escherichia coli is studied. The nanostructured thin films are deposited on glass substrates without intentional heating through r.f. magnetron sputtering in Ar atmosphere of Al 2 O 3 and Ag targets or through sequential sputtering of Al 2 O 3 and Ag targets, respectively. The individual Ag thin films (thickness 8 nm) have a weak bacteriostatic effect on Escherichia coli expressed as an extended adaptive phase of the bacteria up to 5 hours from the beginning of the experiment, but the final effect is only 10 times lower bacterial density than in the control. The individual Al 2 O 3 film (20 nm) has no antibacterial effect against two strains E. coli - industrial and pathogenic. The Al 2 O 3 /Ag bilayer films (Al 2 O 3 20 nm/Ag 8 nm) have strong bactericidal effect on Pseudomonas putida and demonstrate an effective time of disinfection for 2 hours. The individual films Al2O3 and Ag have not pronounced antibacterial effect on Pseudomonas putida . A synergistic effect of Al2O3/Ag bilayer films in formation of oxidative species on the surface in contact with the bacterial suspension could be a reason for their antimicrobial effect on E. coli and P. putida . (paper)

  8. Synthesis, Characterization, and NIR Reflectance of Highly Dispersed NiTiO3 and NiTiO3/TiO2 Composite Pigments

    OpenAIRE

    Yuping Tong; Jing Fu; Zheng Chen

    2016-01-01

    The highly dispersed nanostructured NiTiO3 pigments and NiTiO3/TiO2 composite pigments can be synthesized at relative low temperature. The activation energy of crystal growth of NiTiO3 during calcinations via salt-assistant combustion method is 9.35 kJ/mol. The UV-vis spectra results revealed that the absorbance decreased with the increasing of calcinations temperature due to small size effect of nanometer particles. The optical data of NiTiO3 nanocrystals were analyzed at the near-absorption...

  9. Spin reorientation in α-Fe2O3 nanoparticles induced by interparticle exchange interactions in alpha-Fe2O3/NiO nanocomposites

    DEFF Research Database (Denmark)

    Frandsen, Cathrine; Lefmann, Kim; Lebech, Bente

    2011-01-01

    We report that the spin structure of alpha-Fe2O3 nanoparticles rotates coherently out of the basal (001) plane at low temperatures when interacting with thin plate-shaped NiO nanoparticles. The observed spin reorientation (up to similar to 70 degrees) in alpha-Fe2O3 nanoparticles has, in appearan......, similarities to the Morin transition in bulk alpha-Fe2O3, but its origin is different-it is caused by exchange coupling between aggregated nanoparticles of alpha-Fe2O3 and NiO with different directions of easy axes of magnetization....

  10. Antimicrobial effect of Al2O3, Ag and Al2O3/Ag thin films on Escherichia coli and Pseudomonas putida

    Science.gov (United States)

    Angelov, O.; Stoyanova, D.; Ivanova, I.; Todorova, S.

    2016-10-01

    The influence of Al2O3, Ag and Al2O3/Ag thin films on bacterial growth of Gramnegative bacteria Pseudomonas putida and Escherichia coli is studied. The nanostructured thin films are deposited on glass substrates without intentional heating through r.f. magnetron sputtering in Ar atmosphere of Al2O3 and Ag targets or through sequential sputtering of Al2O3 and Ag targets, respectively. The individual Ag thin films (thickness 8 nm) have a weak bacteriostatic effect on Escherichia coli expressed as an extended adaptive phase of the bacteria up to 5 hours from the beginning of the experiment, but the final effect is only 10 times lower bacterial density than in the control. The individual Al2O3 film (20 nm) has no antibacterial effect against two strains E. coli - industrial and pathogenic. The Al2O3/Ag bilayer films (Al2O3 20 nm/Ag 8 nm) have strong bactericidal effect on Pseudomonas putida and demonstrate an effective time of disinfection for 2 hours. The individual films Al2O3 and Ag have not pronounced antibacterial effect on Pseudomonas putida. A synergistic effect of Al2O3/Ag bilayer films in formation of oxidative species on the surface in contact with the bacterial suspension could be a reason for their antimicrobial effect on E. coli and P. putida.

  11. Temperature-programmed reaction of CO2 reduction in the presence of hydrogen over Fe/Al2O3, Re/Al2O3 and Cr-Mn-O/Al2O3 catalysts

    International Nuclear Information System (INIS)

    Mirzabekova, S.R.; Mamedov, A.B.; Krylov, O.V.

    1996-01-01

    Regularities in CO 2 reduction have been studied using the systems Fe/Al 2 O 3 , Re/Al 2 O 3 and Cr-Mn-O/Al 2 O 3 under conditions of thermally programmed reaction by way of example. A sharp increase in the reduction rate in the course of CO 2 interaction with reduced Fe/Al 2 O 3 and Re/Al 2 O 3 , as well as with carbon fragments with addition in CO 2 flow of 1-2%H 2 , has been revealed. The assumption is made on intermediate formation of a formate in the process and on initiating effect of hydrogen on CO 2 reduction by the catalyst. Refs. 26, figs. 10

  12. Electrical and piezoelectric properties of BiFeO3 thin films grown on SrxCa1−xRuO3-buffered SrTiO3 substrates

    KAUST Repository

    Yao, Yingbang

    2012-06-01

    (001)-oriented BiFeO 3 (BFO) thin films were grown on Sr xCa 1-xRuO 3- (SCRO; x = 1, 0.67, 0.33, 0) buffered SrTiO 3 (001) substrates using pulsed laser deposition. The microstructural, electrical, ferroelectric, and piezoelectric properties of the thin films were considerably affected by the buffer layers. The interface between the BFO films and the SCRO-buffer layer was found to play a dominant role in determining the electrical and piezoelectric behaviors of the films. We found that films grown on SrRuO 3-buffer layers exhibited minimal electrical leakage while films grown on Sr 0.33Ca 0.67RuO 3-buffer layers had the largest piezoelectric response. The origin of this difference is discussed. © 2012 American Institute of Physics.

  13. Magnetocapacitance effect in ferromagnetic LiNbO3 nanoparticles

    International Nuclear Information System (INIS)

    Díaz-Moreno, Carlos; Lopez, Jorge; González-Hernández, Jesus; Escudero, Roberto; Heiras, Jesus L.; Yacamán, Miguel J.; Mendez-Nonell, Juan; Hurtado-Macias, Abel

    2016-01-01

    Magnetocapacitance and magnetization behavior as a function of reduction heat treatment at 650 °C and 900 °C in a 5%H 2 –Ar atmosphere on LiNbO 3 nanocrystalline are reported. There is a change of intrinsic dielectric constant (κ) from 822 to 860 produced by spin polarization using an external magnetic field. The Raman, X-ray photoelectron spectroscopy and electron paramagnetic resonance spectroscopy, indicate vibration mode changes localized at Nb–O bonds in the octahedron NbO 6 , shifts in the binding energy of the electronic structure of ions of niobium (3d) and the oxygen (1s). It is due to the oxygen vacancies caused by reduction heat treatment process. Moreover there is ions redistribution of Nb +3 , Nb +4 and Nb +5 at the surface of the nanoparticles. - Highlights: • Magnetocapacitance and magnetization behavior as a function of reduction heat treatment on LiNbO 3 nanocrystalline. • There is a change of intrinsic dielectric constant (¯) from 822 to 860 produced by spin polarization using an external magnetic field. • The Raman and X-ray photoelectron spectroscopy, indicate vibration mode changes localized at Nb–O bonds in the octahedron NbO6. • Magnetization curves measured at external field 9 T at 300 K for two different reduction heat treatment samples 650 °;C and 900 °;C in comparison without RHT. • Measurements are made at room temperature and at nine different frequencies ranging from 50 Hz to 1 MHz.

  14. RNA adducts with Na 2SeO 4 and Na 2SeO 3 - Stability and structural features

    Science.gov (United States)

    Nafisi, Shohreh; Manouchehri, Firouzeh; Montazeri, Maryam

    2011-12-01

    Selenium compounds are widely available in dietary supplements and have been extensively studied for their antioxidant and anticancer properties. Low blood Se levels were found to be associated with an increased incidence and mortality from various types of cancers. Although many in vivo and clinical trials have been conducted using these compounds, their biochemical and chemical mechanisms of efficacy are the focus of much current research. This study was designed to examine the interaction of Na 2SeO 4 and Na 2SeO 3 with RNA in aqueous solution at physiological conditions, using a constant RNA concentration (6.25 mM) and various sodium selenate and sodium selenite/polynucleotide (phosphate) ratios of 1/80, 1/40, 1/20, 1/10, 1/5, 1/2 and 1/1. Fourier transform infrared, UV-Visible spectroscopic methods were used to determine the drug binding modes, the binding constants, and the stability of Na 2SeO 4 and Na 2SeO 3-RNA complexes in aqueous solution. Spectroscopic evidence showed that Na 2SeO 4 and Na 2SeO 3 bind to the major and minor grooves of RNA ( via G, A and U bases) with some degree of the Se-phosphate (PO 2) interaction for both compounds with overall binding constants of K(Na 2SeO 4-RNA) = 8.34 × 10 3 and K(Na 2SeO 3-RNA) = 4.57 × 10 3 M -1. The order of selenium salts-biopolymer stability was Na 2SeO 4-RNA > Na 2SeO 3-RNA. RNA aggregations occurred at higher selenium concentrations. No biopolymer conformational changes were observed upon Na 2SeO 4 and Na 2SeO 3 interactions, while RNA remains in the A-family structure.

  15. Oxidation of the GaAs semiconductor at the Al2O3/GaAs junction.

    Science.gov (United States)

    Tuominen, Marjukka; Yasir, Muhammad; Lång, Jouko; Dahl, Johnny; Kuzmin, Mikhail; Mäkelä, Jaakko; Punkkinen, Marko; Laukkanen, Pekka; Kokko, Kalevi; Schulte, Karina; Punkkinen, Risto; Korpijärvi, Ville-Markus; Polojärvi, Ville; Guina, Mircea

    2015-03-14

    Atomic-scale understanding and processing of the oxidation of III-V compound-semiconductor surfaces are essential for developing materials for various devices (e.g., transistors, solar cells, and light emitting diodes). The oxidation-induced defect-rich phases at the interfaces of oxide/III-V junctions significantly affect the electrical performance of devices. In this study, a method to control the GaAs oxidation and interfacial defect density at the prototypical Al2O3/GaAs junction grown via atomic layer deposition (ALD) is demonstrated. Namely, pre-oxidation of GaAs(100) with an In-induced c(8 × 2) surface reconstruction, leading to a crystalline c(4 × 2)-O interface oxide before ALD of Al2O3, decreases band-gap defect density at the Al2O3/GaAs interface. Concomitantly, X-ray photoelectron spectroscopy (XPS) from these Al2O3/GaAs interfaces shows that the high oxidation state of Ga (Ga2O3 type) decreases, and the corresponding In2O3 type phase forms when employing the c(4 × 2)-O interface layer. Detailed synchrotron-radiation XPS of the counterpart c(4 × 2)-O oxide of InAs(100) has been utilized to elucidate the atomic structure of the useful c(4 × 2)-O interface layer and its oxidation process. The spectral analysis reveals that three different oxygen sites, five oxidation-induced group-III atomic sites with core-level shifts between -0.2 eV and +1.0 eV, and hardly any oxygen-induced changes at the As sites form during the oxidation. These results, discussed within the current atomic model of the c(4 × 2)-O interface, provide insight into the atomic structures of oxide/III-V interfaces and a way to control the semiconductor oxidation.

  16. Sol-gel-cum-hydrothermal synthesis of mesoporous Co-Fe@Al2O3 ...

    Indian Academy of Sciences (India)

    surface area, and narrow pore distribution are the key factors for an efficient adsorption of methylene blue on .... 3.1 XRD analysis. Figure 1 shows the XRD pattern of mesoporous Al2O3 and monometallic and bimetallic@Al2O3−MCM-41 samples. Mesoporous Al2O3 is .... Si−O−Si vibration bands of MCM-41 and Al2O3−.

  17. A new combustion route to γ-Fe2O3 synthesis

    Indian Academy of Sciences (India)

    Unknown

    any explosives, and also the reaction is completed in a single step yielding magnetic iron oxide i.e. γ-Fe2O3. The as synthesized γ-Fe2O3 is ... pigments, semiconductors, recording materials and memory devices. The high stability and ... heat treatment is given to a mixture of α-Fe2O3 and PEG, α-Fe2O3 disperses in the ...

  18. Strain Effect on Electronic Structure and Work Function in α-Fe2O3 Films

    Directory of Open Access Journals (Sweden)

    Li Chen

    2017-03-01

    Full Text Available We investigate the electronic structure and work function modulation of α-Fe2O3 films by strain based on the density functional method. We find that the band gap of clean α-Fe2O3 films is a function of the strain and is influenced significantly by the element termination on the surface. The px and py orbitals keep close to Fermi level and account for a pronounced narrowing band gap under compressive strain, while unoccupied dz2 orbitals from conduction band minimum draw nearer to Fermi level and are responsible for the pronounced narrowing band gap under tensile strain. The spin polarized surface state, arising from localized dangling-bond states, is insensitive to strain, while the bulk band, especially for pz orbital, arising from extended Bloch states, is very sensitive to strain, which plays an important role for work function decreasing (increasing under compressive (tensile strain in Fe termination films. In particular, the work function in O terminated films is insensitive to strain because pz orbitals are less sensitive to strain than that of Fe termination films. Our findings confirm that the strain is an effective means to manipulate electronic structures and corrosion potential.

  19. Microstructure and deuterium retention after ion irradiation of W–Lu2O3 composites

    International Nuclear Information System (INIS)

    Lin, Jin–Shan; Luo, Lai–Ma; Xu, Qiu; Zan, Xiang; Zhu, Xiao–Yong; Wu, Yu–Cheng

    2017-01-01

    W–3Lu 2 O 3 composites were prepared by mechanical milling and spark plasma sintering. The obtained composites were subjected to He + irradiation experiments. The irradiated samples were characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, and measurement of Vickers hardness. Thermal desorption spectroscopy analysis was performed to analyze the samples at different damage levels after Fe 2+ and D + irradiation. Results showed varied degrees of He + damage under different energies. Fuzz structures were observed on the surface of the material after irradiation. TEM results indicated that the existence of these fuzz structures was related to the formation of He bubbles. Amorphous, polycrystalline, and γ-W phases formed in areas where He bubbles existed. The measured Vickers hardness proved that radiation hardening occurred after irradiation. After Fe 2+ irradiation at different damage levels, the total retained deuterium amount of W–3Lu 2 O 3 and pure W differed, and the impact of Fe 2+ radiation for deuterium retention on pure tungsten was greater.

  20. Estudio de la región rica en Bi2O3 en el sistema binario ZnO-Bi2O3

    Directory of Open Access Journals (Sweden)

    Caballero, A. C.

    2004-08-01

    Full Text Available Ceramic materials based in the ZnO- Bi2O3 system have their principal application as varistors. The binary system ZnO-Bi2O3 is specially relevant to the formation of the microstructure responsable of the varistor behaviour. The study of the different equilibrium phases at high temperatures at the Bi2O3-rich region of the ZnO-Bi2O3 will allow a correct understanding of the microstructural development. Equilibrium phases have been analyzed by XRD, SEM and DTA. Different temperature treatments of samples formulated in the Bi2O3 rich region of the ZnO-Bi2O3 binary system have allowed to determine the phase 19Bi2O3•ZnO as the equilibrium one instead of the 24Bi2O3•ZnO phase.Los materiales cerámicos basados en el sistema binario ZnO-Bi2O3 tienen su principal aplicación en el campo de los varistores. El sistema binario ZnO-Bi2O3 resulta especialmente relevante para la formación de la microestructura funcional de varistores. La determinación de las diferentes fases en equilibrio a alta temperatura en la región rica en Bi2O3 en el sistema binario ZnO-Bi2O3 permitirá interpretar correctamente el desarrollo microestructural. El estudio de las fases en equilibrio se ha llevado a cabo mediante difracción de rayos X, microscopía electrónica de barrido (MEB y análisis térmico diferencial (ATD. Tratamientos a diferentes temperaturas, en la zona rica en Bi2O3 del sistema, han permitido determinar la presencia del compuesto 19Bi2O3•ZnO como fase estable en equilibrio, en lugar del compuesto 24Bi2O3•ZnO.

  1. A study on the damping capacity of BaTiO3-reinforced Al-matrix ...

    Indian Academy of Sciences (India)

    strength and high damping capacity. Ferroelectric and piezoelectric ceramics can exhibit con- siderable high vibration damping capacity due to the anelas- tic response of ferroelastic domains to an external applied stress. Some piezoelectric materials such as BaTiO3 PZT. (Pb(ZrTi)O3) and LiNbO3 have been focussed and ...

  2. Novel silver-doped NiTiO3: auto-combustion synthesis ...

    African Journals Online (AJOL)

    ... Ag-NiTiO3 film was directly deposited on top of the TiO2 prepared by electrophoresis deposition method. Furthermore, solar cell result indicates that an inexpensive solar cell could be developed by the synthesized Ag-NiTiO3 nanoparticles. Keywords: Ag-NiTiO3, sol-gel method, semiconductor, photovoltaic, doping ...

  3. A study on the damping capacity of BaTiO3-reinforced Al-matrix ...

    Indian Academy of Sciences (India)

    To study the damping capacity of BaTiO 3 /Al composites, Al composites reinforced with BaTiO 3 powder (average grain sizes: 100 and 1000 nm) were fabricated by the hot-pressing sintering method. The damping properties of pure Al and BaTiO 3 /Al composites were investigated and compared based on the dynamic ...

  4. 40 CFR 721.10010 - Barium manganese oxide (BaMnO3).

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Barium manganese oxide (BaMnO3). 721... Substances § 721.10010 Barium manganese oxide (BaMnO3). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as barium manganese oxide (BaMnO3) (PMN P-00...

  5. α-Ga2O3 grown by low temperature atomic layer deposition on sapphire

    Science.gov (United States)

    Roberts, J. W.; Jarman, J. C.; Johnstone, D. N.; Midgley, P. A.; Chalker, P. R.; Oliver, R. A.; Massabuau, F. C.-P.

    2018-04-01

    α-Ga2O3 is a metastable phase of Ga2O3 of interest for wide bandgap engineering since it is isostructural with α-In2O3 and α-Al2O3. α-Ga2O3 is generally synthesised under high pressure (several GPa) or relatively high temperature (∼500 °C). In this study, we report the growth of α-Ga2O3 by low temperature atomic layer deposition (ALD) on sapphire substrate. The film was grown at a rate of 0.48 Å/cycle, and predominantly consists of α-Ga2O3 in the form of (0001) -oriented columns originating from the interface with the substrate. Some inclusions were also present, typically at the tips of the α phase columns and most likely comprising ε-Ga2O3. The remainder of the Ga2O3 film - i.e. nearer the surface and between the α-Ga2O3 columns, was amorphous. The film was found to be highly resistive, as is expected for undoped material. This study demonstrates that α-Ga2O3 films can be grown by low temperature ALD and suggests the possibility of a new range of ultraviolet optoelectronic and power devices grown by ALD. The study also shows that scanning electron diffraction is a powerful technique to identify the different polymorphs of Ga2O3 present in multiphase samples.

  6. Evidence of non-Dzyaloshinskii–Moriya ferromagnetism in epitaxial BiFeO3 films

    NARCIS (Netherlands)

    Prokhorov, V.G.; Kaminsky, G.G.; Kim, J.M.; Eom, T.W.; Park, J.S.; Lee, Y.P.; Svetchnikov, V.L.; Levtchenko, G.G.; Nikolaenko, Y.M.; Khokhlov, V.A.

    2011-01-01

    X-ray diffraction analysis and high-resolution electron microscopy of BiFeO3 films prepared by dc magnetron sputtering on single-crystal LaAlO3 (001) substrates reveal that the films have a highly c-oriented orthorhombic crystalline structure. The magnetic properties of the BiFeO3 films are typical

  7. Domain walls and their conduction properties in ferroelectric BiFeO3 thin films

    NARCIS (Netherlands)

    Farokhipoor, Saeedeh

    2013-01-01

    Geleidingseigenschappen BiFeO3 onderzocht In haar proefschrift behandelt Saeedeh Farokhipoor geleidingseigenschappen van BiFeO3, een materiaal waarvan typisch isolerend gedrag verwacht mag worden. Het onderzoek naar BiFeO3 staat recent in de belangstelling. Het is namelijk één van de weinige

  8. Study on electrical properties of Ni-doped SrTiO3 ceramics using ...

    Indian Academy of Sciences (India)

    Unknown

    Ni doped SrTiO3; impedance spectroscopy; grain; grain boundary; acceptor. 1. Introduction. In commercial multilayer ceramic capacitors (MLCs), perovskite structure titanate are frequently used as high permittivity dielectrics. Alkaline earth titanates like BaTiO3,. SrTiO3 etc are widely used in microelectronic devices.

  9. Synthesis of MoO3 and its polyvinyl alcohol nanostructured film

    Indian Academy of Sciences (India)

    The solvent casting method is adopted for the synthesis of MoO3 dispersed polyvinyl alcohol nanostructured film (MoO3–PVA). These synthesized MoO3 and their composite samples are characterized for their structure, morphology, bonding and thermal behaviour by XRD, SEM, IR and DSC techniques, respectively.

  10. Mechanical properties and fracture behaviour of ZrO2-Y2O3 ceramics

    NARCIS (Netherlands)

    Winnubst, Aloysius J.A.; Keizer, Klaas; Burggraaf, A.J.

    1983-01-01

    Stabilized ZrO2-Y2O3 ceramics have been prepared with varying grain sizes and microstructures with the help of different preparation techniques. Bi2O3 has been added as a sinter aid to some of the samples. This results in a certain amount of a zirconia-rich second phase. For Bi2O3-free samples the

  11. (CaA)SiO3 [A = Ba or Sr] phosphors

    Indian Academy of Sciences (India)

    Unknown

    378 terized by photoluminescence (PL), X-ray diffraction. (XRD), differential thermal analysis (DTA) and scanning electron microscopy (SEM) techniques. 2. Experimental. Eu doped CaSiO3, (Ca, Ba) SiO3 and (Ca, Sr) SiO3 pow- ders were prepared by sol–gel technique. Analar grade powder CaCO3, tetra ethyl orthosilicate ...

  12. Synthesis of MoO 3 and its polyvinyl alcohol nanostructured film

    Indian Academy of Sciences (India)

    The solvent casting method is adopted for the synthesis of MoO3 dispersed polyvinyl alcohol nanostructured film (MoO3–PVA). These synthesized MoO3 and their composite samples are characterized for their structure, morphology, bonding and thermal behaviour by XRD, SEM, IR and DSC techniques, respectively.

  13. MLS/Aura Near-Real-Time L2 Ozone (O3) Mixing Ratio V003

    Data.gov (United States)

    National Aeronautics and Space Administration — ML2O3_NRT is the EOS Aura Microwave Limb Sounder (MLS) Near-Real-Time (NRT) product for ozone (O3). This product contains daily O3 profiles taken from the 240 GHz...

  14. Residual stresses in the Al2O3 matrix of Al2O3ZrO2

    International Nuclear Information System (INIS)

    Feng, G.; Tsakalakos, T.; Mayo, W.; Wilfinger, K.; Cannon, W.R.

    1989-01-01

    Residual stresses in the Al 2 O 3 matrix of ground and unground surfaces of zirconia toughened alumina were measured with x-ray techniques. No net residual stresses were found on as-fired surfaces, but residual stresses were found on ground surfaces, increasing with severity of grinding and were proportional to the percent ZrO 2 undergoing the tetragonal monoclinic transformation during grinding. Principal stresses and directions with respect to the grinding direction were obtained. Also Warren-Averbach measurements were made on as- fired surfaces to determine the nonuniform stresses surrounding the particles. These stresses were also found to depend on the monoclinic content which in turn was controlled by the size of the particles

  15. Atomic Center interactions in BaO; Al2O3; B2O3 glasses containing silver

    International Nuclear Information System (INIS)

    Pontuschka, W.M.; Piccini, A.

    1979-01-01

    The EPR study of borate glasses, with 30% of BaO and 5% mole of silver, X-irradiated at 77 0 K, showed Ag 0 and Ag ++ centers. In addition were detected the boron electron center (BEC) and the boron hole center. The silver centers and BEC were studied in detail and the spin Hamiltonian parameters are given. The different Al 2 O 3 concentrations exerted only little influence on the tabulated constants. The Ag + 2 center was not observed, indicating that the collisions between Ag atoms are not very frequent in these glasses, even during the process of thermal bleaching. The hfs of the boron electron center suffered severe variation as one compared the spectra of base glasses and those containing silver. This is an evidence of the action of silver as a glass modifier like the alkali atoms [pt

  16. Suppressing the Photocatalytic Activity of TiO2 Nanoparticles by Extremely Thin Al2O3 Films Grown by Gas-Phase Deposition at Ambient Conditions

    Directory of Open Access Journals (Sweden)

    Jing Guo

    2018-01-01

    Full Text Available This work investigated the suppression of photocatalytic activity of titanium dioxide (TiO2 pigment powders by extremely thin aluminum oxide (Al2O3 films deposited via an atomic-layer-deposition-type process using trimethylaluminum (TMA and H2O as precursors. The deposition was performed on multiple grams of TiO2 powder at room temperature and atmospheric pressure in a fluidized bed reactor, resulting in the growth of uniform and conformal Al2O3 films with thickness control at sub-nanometer level. The as-deposited Al2O3 films exhibited excellent photocatalytic suppression ability. Accordingly, an Al2O3 layer with a thickness of 1 nm could efficiently suppress the photocatalytic activities of rutile, anatase, and P25 TiO2 nanoparticles without affecting their bulk optical properties. In addition, the influence of high-temperature annealing on the properties of the Al2O3 layers was investigated, revealing the possibility of achieving porous Al2O3 layers. Our approach demonstrated a fast, efficient, and simple route to coating Al2O3 films on TiO2 pigment powders at the multigram scale, and showed great potential for large-scale production development.

  17. Improving Visible Light-Absorptivity and Photoelectric Conversion Efficiency of a TiO2 Nanotube Anode Film by Sensitization with Bi2O3 Nanoparticles

    Directory of Open Access Journals (Sweden)

    Menglei Chang

    2017-05-01

    Full Text Available This study presents a novel visible light-active TiO2 nanotube anode film by sensitization with Bi2O3 nanoparticles. The uniform incorporation of Bi2O3 contributes to largely enhancing the solar light absorption and photoelectric conversion efficiency of TiO2 nanotubes. Due to the energy level difference between Bi2O3 and TiO2, the built-in electric field is suggested to be formed in the Bi2O3 sensitized TiO2 hybrid, which effectively separates the photo-generated electron-hole pairs and hence improves the photocatalytic activity. It is also found that the photoelectric conversion efficiency of Bi2O3 sensitized TiO2 nanotubes is not in direct proportion with the content of the sensitizer, Bi2O3, which should be carefully controlled to realize excellent photoelectrical properties. With a narrower energy band gap relative to TiO2, the sensitizer Bi2O3 can efficiently harvest the solar energy to generate electrons and holes, while TiO2 collects and transports the charge carriers. The new-type visible light-sensitive photocatalyst presented in this paper will shed light on sensitizing many other wide-band-gap semiconductors for improving solar photocatalysis, and on understanding the visible light-driven photocatalysis through narrow-band-gap semiconductor coupling.

  18. Structural and functional properties of La1-xBaxMnO3 thin films on SrTiO3

    International Nuclear Information System (INIS)

    Belenchuk, A.; Kantser, V.; Shapoval, O.; Zasavitsky, E.; Moshnyaga, V.

    2011-01-01

    Full text: Colossal magneto resistive manganites such as La 1-x Ba x MnO3 (LBMO) show a reach diversity of a attractive physical properties and the epitaxy of manganites has figured conspicuously in the search for new generations of electronic materials for information processing, data storage, and sensing. All applications require manganite films with a smooth morphology and perfect functional properties such as a large magnetization and a small residual resistivity. We investigated the structural and functional properties of the epitaxial LBMO thin films grown on the near perfect matched SrTiO 3 substrates by metalorganic aerosol deposition technique. AFM surface analysis shows a very smooth films surface indicating the layer-by-layer growth mode. The occurrence of a distinct Laue thickness fringes in X-ray diffraction spectra indicates a high quality single-crystalline growth of an uniformly strained LBMO films. But the small-angle x-ray scattering reveals the presence of a few unit cells intermediate layer with a modified electronic density. Transport measurements determine a high metal-insulator transition temperature (T MI >340 K) confirming near optimal Ba doping of LBMO with the residual resistivity of 350 μΩcm at 50 K. According to the inductive coupled plasma emission spectroscopy analysis the LBMO has level of Ba doping x=0.32. However, SQUID magnetization measurements reveal the coexistence of a high Curie temperature (T C =335 K) and a low coercitive field (27-30 Oe) with a reduced saturation magnetization (∼3 μ B /Mn) and broadened para-ferromagnetic transition. The presence of magnetic phase inhomogeneity can be further revealed from the form of low-temperature magnetization loops. We discuss the results within the concept of a 'hidden' magnetic layer situated close to the film-substrate interface and the presence of magnetic phase separation phenomenon in the main part of the LBMO film. (authors)

  19. Strong near-infrared luminescence in BaSnO3.

    Science.gov (United States)

    Mizoguchi, Hiroshi; Woodward, Patrick M; Park, Cheol-Hee; Keszler, Douglas A

    2004-08-11

    Powdered samples of the perovskite BaSnO(3) exhibit strong near-infrared (NIR) luminescence at room temperature, following band-gap excitation at 380 nm (3.26 eV). The emission spectrum is characterized by a broad band centered at 905 nm (1.4 eV), tailing on the high-energy side to approximately 760 nm. The Stokes shift is 1.9 eV, and measured lifetimes in the range 7-18 ms depend on preparative conditions. These extraordinary long values indicate that the luminescence involves a defect state(s). At low temperatures, both a sharp peak and a broad band appear in the visible portion of the luminescence spectrum at approximately 595 nm. Upon cooling, the intensity of the NIR emission decreases, while the integrated intensities of the visible emission features increase to approximately 40% of the NIR intensity at 77 K. Room-temperature photoluminescence (PL) is observed across the Ba(1-x)Sr(x)SnO(3) series. As the strontium content increases, the excitation maximum and band gap shift further into the UV, while the intensity of the NIR emission peak decreases and shifts further into the infrared. This combination leads to an unexpectedly large increase in the Stokes shift. The unusual NIR PL in BaSnO(3) may originate from recombination of a photogenerated valence-band hole and an occupied donor level, probably associated with a Sn(2+) ion situated roughly 1.4 eV above the valence-band edge.

  20. Effects of the Cr2O3 Content on the Viscosity of CaO-SiO2-10 Pct Al2O3-Cr2O3 Quaternary Slag

    Science.gov (United States)

    Wu, Tuo; Zhang, Yanling; Yuan, Fang; An, Zhuoqing

    2018-04-01

    The present study experimentally investigates the effect of Cr2O3 on the viscosity of molten slags. The viscosities of CaO-SiO2-10 pct Al2O3-Cr2O3 quaternary slags with two different binary basicities (R, basic slag with R = 1.2 and acidic slag with R = 0.8) were measured by the rotating cylindrical method from 1813 K to 1953 K (1540 °C to 1680 °C). The results showed that the viscosity of both types of slag decreased as the Cr2O3 content increased, but the viscosity of acidic slags exhibited a greater decrease. The slags showed good Newtonian behavior at such high temperatures. Cr2O3 could act as a network modifier to simplify the Si-O-Si tetrahedral structure, as verified by the Raman spectral analysis, which was consistent with the decreasing trend of viscosity. The activation energy of viscous flow decreased slightly with increasing Cr2O3, but increasing the basicity seemed to be more effective in decreasing the viscosity than adding Cr2O3.

  1. Dielectric and piezoelectric properties of BiFeO3 modified Bi0.5Na0.5TiO3-Bi0.5K0.5TiO3 lead-free piezoelectric ceramics

    International Nuclear Information System (INIS)

    Zhou Changrong; Liu Xinyu; Li Weizhou

    2008-01-01

    The (0.82 - x)Bi 0.5 Na 0.5 TiO 3 -0.18Bi 0.5 K 0.5 TiO 3 -xBiFeO 3 (x = 0-0.07) lead-free piezoelectric ceramics were fabricated by a conventional solid-state reaction method and the effect of BiFeO 3 addition on microstructure and electrical properties of the ceramics was investigated. The specimens with x ≤ 0.05 maintained a rhombohedral-tetragonal phase coexistence and changed into a rhombohedral phase when x > 0.05 in crystal structure. The addition of BiFeO 3 caused a promoted grain growth. All the specimens reveal a low-frequency dielectric dispersion in the frequency range of 40-1 MHz. The piezoelectric constant d 33 and the electromechanical coupling factor k p show an obvious improvement by the addition of small amount of BiFeO 3 , which shows optimum values of d 33 = 170 pC/N and k p = 0.366 at x = 0.03. Contrary to the enhancement of piezoelectric properties, Q m decreases with increasing BiFeO 3 content. The mechanisms of intrinsic and extrinsic contributions to the dielectric and piezoelectric responses have been proposed. Intrinsic contributions are from the relative ion/cation shift that preserves the ferroelectric crystal structure. The remaining extrinsic contributions are from the domain-wall motion and point defects

  2. Investigation of radiation shielding properties for MeO-PbCl2-TeO2 (MeO = Bi2O3, MoO3, Sb2O3, WO3, ZnO) glasses

    Science.gov (United States)

    Sayyed, M. I.; Çelikbilek Ersundu, M.; Ersundu, A. E.; Lakshminarayana, G.; Kostka, P.

    2018-03-01

    In this work, glasses in the MeO-PbCl2-TeO2 (MeO = Bi2O3, MoO3, Sb2O3, WO3, ZnO) system, which show a great potential for optoelectronic applications, were used to evaluate their resistance under high energy ionizing radiations. The basic shielding quantities for determining the penetration of radiation in glass, such as mass attenuation coefficient (μ/ρ), half value layer (HVL), mean free path (MFP) and exposure buildup factor (EBF) values were investigated within the energy range 0.015 MeV ‒ 15 MeV using XCOM program and variation of shielding parameters were compared with different glass systems and ordinary concrete. From the derived results, it was determined that MeO-PbCl2-TeO2 (MeO = Bi2O3, MoO3, Sb2O3, WO3, ZnO) glasses show great potentiality to be used under high energy radiations. Among the studied glass compositions, Bi2O3 and WO3 containing glasses were found to possess superior gamma-ray shielding effectiveness.

  3. Development and characterization of nickel catalysts supported in CeO2-ZrO2-Al2O3, CeO2-La2O3-Al2O3 e ZrO2-La2O3-Al2O3 matrixes evaluated for methane reforming reactions

    International Nuclear Information System (INIS)

    Abreu, Amanda Jordão de

    2012-01-01

    Nowadays, the methane reforming is large interest industrial for the take advantage of these gas in production the hydrogen and synthesis gas (syngas). Among in the reactions of methane stand of the reactions steam reforming and carbon dioxide reforming of methane. The main catalysts uses in the methane reforming is Ni/Al 2 O 3 . However, the supported-nickel catalyst is susceptible to the deactivation or the destruction by coke deposition. The carbon dissolves in the nickel crystallite and its diffuses through the nickel, leading for formation of the carbon whiskers, which results in fragmentation of the catalyst. Modification of such catalysts, like incorporation of suitable promoters, is desirable to achieve reduction of the methane hydrogenolysis and/or promotion of the carbon gasification. Catalysts 5%Ni/Al 2 O 3 supported on solid solutions formed by ZrO 2 -CeO 2 , La 2 O 3 and CeO 2 -ZrO 2 -La 2 O 3 were prepared, characterized and evaluated in reactions steam and carbon dioxide reforming and partial oxidation of methane with objective the value effect loading solution solid in support. The supports were prepared by co-precipitation method and catalysts were prepared by impregnation method and calcined at 500 deg C. The supports and catalysts were characterized by Nitrogen Adsorption, method -rays diffraction (XRD), X-rays dispersive spectroscopy (XDS), spectroscopy in the region of the ultraviolet and the visible (UV-vis NIR) to and temperature programmed reduction (TPR), Raman Spectroscopy, X-ray absorption spectroscopy and Thermogravimetric Analysis. After all the catalytic reactions check which the addition of solid solution is beneficial for Ni/Al 2 O 3 catalysts and the best catalysts are Ni/CeO 2 -La 2 O 3 -Al 2 O 3 . (author)

  4. Winter- and summertime continental influences on tropospheric O3 and CO observed by TES over the western North Atlantic Ocean

    Directory of Open Access Journals (Sweden)

    R. Talbot

    2010-04-01

    Full Text Available The distributions of tropospheric ozone (O3 and carbon monoxide (CO, and the synoptic factors regulating these distributions over the western North Atlantic Ocean during winter and summer were investigated using profile retrievals from the Tropospheric Emission Spectrometer (TES for 2004–2006. Seasonal composites of TES retrievals, reprocessed to remove the influence of the a priori on geographical and seasonal structure, exhibited strong seasonal differences. At the 681 hPa level during winter months of December, January and February (DJF the composite O3 mixing ratios were uniformly low (~45 ppbv, but continental export was evident in a channel of enhanced CO (100–110 ppbv flowing eastward from the US coast. In summer months June, July, and August (JJA O3 mixing ratios were variable (45–65 ppbv and generally higher due to increased photochemical production. The summer distribution also featured a channel of enhanced CO (95–105 ppbv flowing northeastward around an anticyclone and exiting the continent over the Canadian Maritimes around 50° N. Offshore O3-CO slopes were generally 0.15–0.20 mol mol−1 in JJA, indicative of photochemical O3 production. Composites for 4 predominant synoptic patterns or map types in DJF suggested that export to the lower free troposphere (681 hPa level was enhanced by the warm conveyor belt airstream of mid-latitude cyclones while stratospheric intrusions increased TES O3 levels at 316 hPa. A major finding in the DJF data was that offshore 681 hPa CO mixing ratios behind cold fronts could be enhanced up to >150 ppbv likely by lofting from the surface via shallow convection resulting from rapid destabilization of cold air flowing over much warmer ocean waters. In JJA composites for 3 map types showed that the general export pattern of the seasonal composites was associated with a synoptic pattern featuring the Bermuda High. However, weak cyclones and frontal troughs could enhance offshore 681 hPa CO

  5. The structure of H2TiO3-a short discussion on "Lithium recovery from salt lake brine by H2TiO3".

    Science.gov (United States)

    Yu, Cheng-Long; Wang, Fei; Cao, Shu-Yao; Gao, Dan-Peng; Hui, Huai-Bing; Guo, Ying-Yan; Wang, Dao-Yi

    2015-09-21

    A short discussion on the structure of H2TiO3 presented in the article entitled Lithium recovery from salt lake brine by H2TiO3 (R. Chitrakar, Y. Makita, K. Ooi and A. Sonoda, Dalton Trans., 2014, 43, 8933) is presented. In our opinion, it is not correct to identify the phase of H2TiO3 as monoclinic. The XRD pattern of H2TiO3 differs substantially from that of Li2TiO3. XRD pattern simulation shows that the peak (1[combining macron]33) and the peak (2[combining macron]06) cannot be fully collapsed or substantially decrease in intensity by substitution of Li(+) with H(+) if H2TiO3 shares a similar space group and lattice parameters with Li2TiO3. A direct verification of a similar structure by N. V. Tarakina and co-workers may aid the confirmation of the structure. The layered double hydroxide type with the 3R1 sequence of oxygen layers is more reasonable for H2TiO3 and can be described as a stacking of charge-neutral metal oxyhydroxide slabs [(OH)2OTi2O(OH)2].

  6. Effect of relative humidity on O3 and NO2 oxidation of SO2 on α-Al2O3 particles

    Science.gov (United States)

    Liu, Wenjun; He, Xiang; Pang, Shufeng; Zhang, Yunhong

    2017-10-01

    Heterogeneous reactions of SO2/O3 and SO2/NO2 with α-Al2O3 particles at different RHs were investigated using a gas-flow system combined with microscopic Fourier transform infrared (micro-FTIR) spectrometer. The results show that the trace gas O3 or NO2 leads to rapid conversion of SO2 to sulfate on the surface of α-Al2O3 particles in initial stage and then conversion rate decreases in the following stages. The rate of sulfate formation and uptake coefficient (γ) for SO2 in the two systems as a function of relative humidity (RH) are determined for the first time, which are all strongly enhanced more than seven-fold as the RH increase from 15% to 95% in initial stage for SO2/O3 and SO2/NO2. Moreover, the γ in the system of SO2/O3 on α-Al2O3 particles is more than 3-fold than that of SO2/NO2 for the similar RH condition. Our results may be broadly applicable to understand the effects of RH and trace gases (e.g., O3, NO2) for the converting SO2 into sulfate on the mineral dust, which supply basic data for atmospheric chemistry modeling studies.

  7. Degradation of the interfacial conductivity in LaAlO3/SrTiO3 heterostructures during storage at controlled environments

    DEFF Research Database (Denmark)

    Trier, Felix; Christensen, Dennis; Chen, Yunzhong

    2013-01-01

    The remarkable discovery of a two-dimensional electron gas confined at the interface of the two oxide band-insulators SrTiO3 (STO) and LaAlO3 (LAO) has spurred a great interest in the heterostructure leading to the discovery of a plethora of other exciting properties. Recently, the formation...

  8. Influence of strain on the electronic structure of the TbMnO3/SrTiO3 epitaxial interface

    NARCIS (Netherlands)

    Venkatesan, S.; Doumlblinger, M.; Daumont, C.; Kooi, B.; Noheda, Beatriz; De Hosson, J. T. M.; Scheu, C.; Döblinger, M.

    2011-01-01

    Understanding the magnetotransport properties of epitaxial strained thin films requires knowledge of the chemistry at the interface. We report on the change in Mn electronic structure at the epitaxially strained TbMnO3/SrTiO3 interface. Scanning transmission electron microscopy shows an abrupt

  9. Operando Raman spectroscopy study on the deactivation of Pt/Al2O3 and Pt–Sn/Al2O3 propane dehydrogenation catalysts

    NARCIS (Netherlands)

    Sattler, J.J.H.B.|info:eu-repo/dai/nl/328235601; Beale, A.M.|info:eu-repo/dai/nl/325802068; Weckhuysen, B.M.|info:eu-repo/dai/nl/285484397

    2013-01-01

    The deactivation of 0.5 wt% Pt/Al2O3 and 0.5 wt% Pt–1.5 wt% Sn/Al2O3 catalysts has been studied by operando Raman spectroscopy during the dehydrogenation of propane and subsequent regeneration in air for 10 successive dehydrogenation–regeneration cycles. Furthermore, the reaction feed was altered by

  10. Caractérisation et approche structurale de verres du systeme La 2O 3-MgO-B 2O 3

    Science.gov (United States)

    Lafjij, M.; El Jouhari, N.; Benarafa, L.; Lautie, A.; Le Flem, G.

    2003-05-01

    In this paper, a vitreous domain of the ternary system: xLa 2O 3- yMgO- zB 2O 3 characterised by X-ray diffraction is shown. Structural approach using vibrational spectroscopy and optical probe is realized for some of these glasses and compared to crystalline LaMgB 5O 10.

  11. Simulation of thermal stress in Er2O3 and Al2O3 tritium penetration barriers by finite-element analysis

    Science.gov (United States)

    Ze, LIU; Guogang, YU; Anping, HE; Ling, WANG

    2017-09-01

    The physical vapor deposition method is an effective way to deposit Al2O3 and Er2O3 on 316L stainless steel substrates acting as tritium permeation barriers in a fusion reactor. The distribution of residual thermal stress is calculated both in Al2O3 and Er2O3 coating systems with planar and rough substrates using finite element analysis. The parameters influencing the thermal stress in the sputter process are analyzed, such as coating and substrate properties, temperature and Young’s modulus. This work shows that the thermal stress in Al2O3 and Er2O3 coating systems exhibit a linear relationship with substrate thickness, temperature and Young’s modulus. However, this relationship is inversed with coating thickness. In addition, the rough substrate surface can increase the thermal stress in the process of coating deposition. The adhesive strength between the coating and the substrate is evaluated by the shear stress. Due to the higher compressive shear stress, the Al2O3 coating has a better adhesive strength with a 316L stainless steel substrate than the Er2O3 coating. Furthermore, the analysis shows that it is a useful way to improve adhesive strength with increasing interface roughness.

  12. Theoretical and experimental analysis of structural phase transitions for ScF[SeO3] and YF[SeO3

    International Nuclear Information System (INIS)

    Chou, Sheng-Chun; Greiner, Stefan; Schleid, Thomas; Magdysyuk, Oxana V.; Dinnebier, Robert E.

    2014-01-01

    Phase-pure ScF[SeO 3 ] and YF[SeO 3 ] were synthesized via solid-state reactions of the corresponding rare-earth metal sesquioxides and trifluorides with selenium dioxide in excess of fluxing cesium bromide at 700 C for 7 d. To avoid the formation of oxosilicates, these reactions took place in corundum crucibles embedded inside of evacuated fused silica ampoules. Upon cooling down below 13 C, a pseudo-second-order phase transition (P2 1 /m → P anti 1 or P1) for ScF[SeO 3 ] occurs, which is similar to the high-temperature phase transition of LuF[SeO 3 ]. By heating YF[SeO 3 ] above 319 C, it undergoes a first-order phase transition (P2 1 /c → P2 1 /m) without passing the intermediate P anti 1 modification in contrast to LuF[SeO 3 ]. Both the high-temperature phase transition of YF[SeO 3 ] and the low-temperature phase transition of ScF[SeO 3 ] were characterized by in-situ X-ray powder diffraction, X-ray single-crystal diffraction, thermal analysis DSC, and distortion-mode analysis. For both cases the driving forces for the symmetry-breaking phase transitions from the high- to the low-temperature phases are discussed. (Copyright copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  13. Effect of Fe2O3 and Binder on the Electrochemical Properties of Fe2O3/AB (Acetylene Black) Composite Electrodes

    Science.gov (United States)

    Anh, Trinh Tuan; Thuan, Vu Manh; Thang, Doan Ha; Hang, Bui Thi

    2017-06-01

    In an effort to find the best anode material for Fe/air batteries, a Fe2O3/AB (Acetylene Black) composite was prepared by dry-type ball milling using Fe2O3 nanoparticles and AB as the active and additive materials, respectively. The effects of various binders and Fe2O3 content on the electrochemical properties of Fe2O3/AB electrodes in alkaline solution were investigated. It was found that the content of Fe2O3 strongly affected the electrochemical behavior of Fe2O3/AB electrodes; with Fe2O3 nanopowder content reaching 70 wt.% for the electrode and showing improvement of the cyclability. When the electrode binder polytetrafluoroethylene (PTFE) was used, clear redox peaks were observed via cyclic voltammetry (CV), while polyvinylidene fluoride-containing electrodes provided CV curves with unobservable redox peaks. Increasing either binder content in the electrode showed a negative effect in terms of the cyclability of the Fe2O3/AB electrode.

  14. Electron spin resonance study of a-Cr2 O3 and Cr2 O3·nH 2 O quasi-spherical nanoparticles

    CSIR Research Space (South Africa)

    Khamlich, S

    2011-12-01

    Full Text Available The quasi-spherical nanoparticles of hydrated Cr2 O3 · nH 2 O, and crystalline -Cr2 O3, have been synthesized by reduction of the first row (3d) transition metal complex of K2Cr2 O7. The temperaturedependence of electron spin resonance (ESR) spectrum...

  15. Synthesis, Characterization, and NIR Reflectance of Highly Dispersed NiTiO3 and NiTiO3/TiO2 Composite Pigments

    Directory of Open Access Journals (Sweden)

    Yuping Tong

    2016-01-01

    Full Text Available The highly dispersed nanostructured NiTiO3 pigments and NiTiO3/TiO2 composite pigments can be synthesized at relative low temperature. The activation energy of crystal growth of NiTiO3 during calcinations via salt-assistant combustion method is 9.35 kJ/mol. The UV-vis spectra results revealed that the absorbance decreased with the increasing of calcinations temperature due to small size effect of nanometer particles. The optical data of NiTiO3 nanocrystals were analyzed at the near-absorption edge. SEM showed that the obtained NiTiO3 nanocrystals and NiTiO3/TiO2 nanocomposite were composed of highly dispersed spherical-like and spherical particles with uniform size distribution, respectively. The chromatic properties and diffuse reflectance of samples were investigated. The obtained NiTiO3/TiO2 composite samples have higher NIR reflectance than NiTiO3 pigments.

  16. Influence of charge compensation mechanisms on the sheet electron density at conducting LaAlO3/SrTiO3-interfaces

    NARCIS (Netherlands)

    Gunkel, F.; Brinks, Peter; Hoffmann-Eifert, S.; Dittmann, R.; Huijben, Mark; Kleibeuker, J.E.; Koster, Gertjan; Rijnders, Augustinus J.H.M.

    2012-01-01

    The equilibrium conductance of LaAlO3/SrTiO3 (LAO/STO)-heterointerfaces was investigated at high temperatures (950¿K-1100¿K) as a function of ambient oxygen partial pressure (pO2). Metallic LAO/STO-interfaces were obtained for LAO grown on STO single crystals as well as on STO-buffered

  17. Hard x-ray photoemission and density functional theory study of the internal electric field in SrTiO3/LaAlO3 oxide heterostructures

    NARCIS (Netherlands)

    Slooten, E.; Zhong, Zhicheng; Molegraaf, Hajo; Eerkes, P.D.; de Jong, S.; Massee, F.; van Heumen, E.; Kruize, Michelle; Wenderich, Sander; Kleibeuker, J.E.; Gorgoi, M.; Hilgenkamp, Johannes W.M.; Brinkman, Alexander; Huijben, Mark; Rijnders, Augustinus J.H.M.; Blank, David H.A.; Koster, Gertjan; Kelly, Paul J.; Golden, M.S.

    2013-01-01

    A combined experimental and theoretical investigation of the electronic structure of the archetypal oxide heterointerface system LaAlO3 on SrTiO3 is presented. High-resolution, hard x-ray photoemission is used to uncover the occupation of Ti 3d states and the relative energetic alignment—and hence

  18. In-plane reversal of the magnetic anisotropy in (110)-oriented LaCoO3/La0.67Sr0.33MnO3 heterostructures

    Science.gov (United States)

    Zhang, Jing; Yan, Xi; Han, Furong; Zhang, Jine; Liu, Dan; Shen, Baogen; Sun, Jirong

    2018-05-01

    The interface engineering of the complex oxides with strongly coupled degrees of freedom opens a wide space for the exploration of novel effects. La0.67Sr0.33MnO3 is one of the most typical complex oxides used for atomic level material engineering. Herein we reported an in-plane reversal of the magnetic anisotropy in (110)-oriented LaCoO3/La0.67Sr0.33MnO3 (LCO/LSMO) bilayers grown on (110)-oriented LaAlO3 substrates. Fixing the LSMO layer thickness to 8 nm and varying the LCO layer from 0 to 8 nm, totally six bilayers were fabricated. Without the LCO layer, the LSMO film exhibits an easy axis along the [1-10] direction. However, when the thickness of the LCO layer exceeds 1 nm, a signature of spin-reorientation appears; the easy axis turns from the [1-10] to the [001] direction below 225 K. This tendency is continuously enhanced by increasing the LCO. We reveal that lattice strains are different along these two directions. The magnetic anisotropy is not only controlled by lattice strain but also by structural distortion at interface. This work shows the great potential of the interface engineering with differently structured oxides for the exploration of novel functional materials.

  19. Electrical and structural characterizations of crystallized Al2O3/GaN interfaces formed by in situ metalorganic chemical vapor deposition

    International Nuclear Information System (INIS)

    Liu, X.; Yeluri, R.; Kim, J.; Keller, S.; Mishra, U. K.; Jackson, C. M.; Arehart, A. R.; Ringel, S. A.; Wu, F.; Mazumder, B.; Speck, J. S.

    2016-01-01

    Al 2 O 3 films were grown in situ by metalorganic chemical vapor deposition at 900 °C on GaN of both Ga- and N-face polarities. High-resolution transmission electron microscopy revealed that the Al 2 O 3 films were crystalline and primarily γ-phase. The Al 2 O 3 /Ga-GaN and Al 2 O 3 /N-GaN interfaces were both atomically sharp, and the latter further exhibited a biatomic step feature. The corresponding current-voltage (J-V) characteristics were measured on a metal-Al 2 O 3 -semiconductor capacitor (MOSCAP) structure. The leakage current was very high when the Al 2 O 3 thickness was comparable with the size of the crystalline defects, but was suppressed to the order of 1 × 10 −8 A/cm 2 with larger Al 2 O 3 thicknesses. The interface states densities (D it ) were measured on the same MOSCAPs by using combined ultraviolet (UV)-assisted capacitance-voltage (C-V), constant capacitance deep level transient spectroscopy (CC-DLTS), and constant capacitance deep level optical spectroscopy (CC-DLOS) techniques. The average D it measured by CC-DLTS and CC-DLOS were 6.6 × 10 12 and 8.8 × 10 12 cm −2 eV −1 for Al 2 O 3 /Ga-GaN and 8.6 × 10 12 and 8.6 × 10 12  cm −2 eV −1 for Al 2 O 3 /N-GaN, respectively. The possible origins of the positive (negative) polarization compensation charges in Al 2 O 3 /Ga-GaN (Al 2 O 3 /N-GaN), including the filling of interface states and the existence of structure defects and impurities in the Al 2 O 3 layer, were discussed in accordance with the experimental results and relevant studies in the literature

  20. Superior Properties of Energetically Stable La2/3Sr1/3MnO3/Tetragonal BiFeO3 Multiferroic Superlattices

    KAUST Repository

    Feng, Nan

    2015-04-30

    The superlattice of energetically stable La2/3Sr1/3MnO3 and tetragonal BiFeO3 is investigated by means of density functional theory. The superlattice as a whole exhibits a half-metallic character, as is desired for spintronic devices. The interfacial electronic states and exchange coupling are analyzed in details. We demonstrate that the interfacial O atoms play a key role in controlling the coupling. The higher ferroelectricity of tetragonal BiFeO3 and stronger response to the magnetic moment in La2/3Sr1/3MnO3/BiFeO3 superlattice show a strongly enhanced electric control of the magnetism as compared to the rhombohedral one. Therefore, it is particularly practical interest in the magnetoelectric controlled spintronic devices.