Science.gov

Sample records for 0-5 cm depth

  1. Wide-Pulse Evaluation of 0.5 CM2 Silicon Carbide SGTO

    DTIC Science & Technology

    2009-06-01

    the surface of the chip. Figure 3. SGTO packaged at ARL using power package, AuSn die attach, 5-mil wire bonds, and silicone -based potting. Figure 5...WIDE-PULSE EVALUATION OF 0.5 CM2 SILICON CARBIDE SGTO Heather O’Brien, Aderinto Ogunniyi, Charles J. Scozzie U.S. Army Research Laboratory, 2800...3026 E. Cornwallis Rd Research Triangle Park, NC 27709 USA Victor Temple Silicon Power Corp., 958 Main St., Suite A Clifton Park, NY 12065 USA

  2. Incidence of H I 21-cm absorption in strong Fe II systems at 0.5 < z < 1.5

    NASA Astrophysics Data System (ADS)

    Dutta, R.; Srianand, R.; Gupta, N.; Joshi, R.; Petitjean, P.; Noterdaeme, P.; Ge, J.; Krogager, J.-K.

    2017-03-01

    We present the results from our search for H I 21-cm absorption in a sample of 16 strong Fe II systems [Wr(Mg II λ2796) ≥ 1.0 Å and Wr(Fe II λ2600) or W_{Fe II} ≥ 1 Å] at 0.5 < z < 1.5 using the Giant Metrewave Radio Telescope and the Green Bank Telescope. We report six new H I 21-cm absorption detections from our sample, which have increased the known number of detections in strong Mg II systems at this redshift range by ∼50 per cent. Combining our measurements with those in the literature, we find that the detection rate of H I 21-cm absorption increases with W_{Fe II}, being four times higher in systems with W_{Fe II} ≥ 1 Å compared to systems with W_{Fe II} < 1 Å. The N(H I) associated with the H I 21-cm absorbers would be ≥2 × 1020 cm-2, assuming a spin temperature of ∼500 K (based on H I 21-cm absorption measurements of damped Lyman α systems at this redshift range) and unit covering factor. We find that H I 21-cm absorption arises on an average in systems with stronger metal absorption. We also find that quasars with H I 21-cm absorption detected towards them have systematically higher E(B - V) values than those which do not. Further, by comparing the velocity widths of H I 21-cm absorption lines detected in absorption- and galaxy-selected samples, we find that they show an increasing trend (significant at 3.8σ) with redshift at z < 3.5, which could imply that the absorption originates from more massive galaxy haloes at high z. Increasing the number of H I 21-cm absorption detections at these redshifts is important to confirm various trends noted here with higher statistical significance.

  3. Polynomial coefficients for calculating O2 Schumann-Runge cross sections at 0.5/cm resolution

    NASA Technical Reports Server (NTRS)

    Minschwaner, K.; Anderson, G. P.; Hall, L. A.; Yoshino, K.

    1992-01-01

    O2 cross sections from 49,000 to 57,000/cm have been fitted with temperature dependent polynomial expressions, providing an accurate and efficient means of determining Schumann-Runge band cross sections for temperatures between 130 and 500 K. The least squares fits were carried out on a 0.5/cm spectral grid, using cross sections obtained from a Schumann-Runge line-by-line model that incorporates the most recent spectroscopic data. The O2 cross sections do not include the underlying Herzberg continuum, but they do contain contributions from the temperature dependent Schumann-Runge continuum. The cross sections are suitable for use in UV transmission calculations at high spectral resolution. They should also prove useful for updating existing parameterizations of ultraviolet transmission and O2 photolysis.

  4. Experimental characterization and system simulations of depth of interaction PET detectors using 0.5 mm and 0.7 mm LSO arrays.

    PubMed

    James, Sara St; Yang, Yongfeng; Wu, Yibao; Farrell, Richard; Dokhale, Purushottam; Shah, Kanai S; Cherry, Simon R

    2009-07-21

    Small animal PET scanners may be improved by increasing the sensitivity, improving the spatial resolution and improving the uniformity of the spatial resolution across the field of view. This may be achieved by using PET detectors based on crystal elements that are thin in the axial and transaxial directions and long in the radial direction, and by employing depth of interaction (DOI) encoding to minimize the parallax error. With DOI detectors, the diameter of the ring of the PET scanner may also be decreased. This minimizes the number of detectors required to achieve the same solid angle coverage as a scanner with a larger ring diameter and minimizes errors due to non-collinearity of the annihilation photons. In this study, we characterize prototype PET detectors that are finely pixelated with individual LSO crystal element sizes of 0.5 mm x 0.5 mm x 20 mm and 0.7 mm x 0.7 mm x 20 mm, read out at both ends by position sensitive avalanche photodiodes (PSAPDs). Both a specular reflector and a diffuse reflector were evaluated. The detectors were characterized based on the ability to clearly resolve the individual crystal elements, the DOI resolution and the energy resolution. Our results indicate that a scanner based on any of the four detector designs would offer improved spatial resolution and more uniform spatial resolution compared to present day small animal PET scanners. The greatest improvements to spatial resolution will be achieved when the detectors employing the 0.5 mm x 0.5 mm x 20 mm crystals are used. Monte Carlo simulations were performed to demonstrate that 2 mm DOI resolution is adequate to ensure uniform spatial resolution for a small animal PET scanner geometry using these detectors. The sensitivity of such a scanner was also simulated using Monte Carlo simulations and was shown to be greater than 10% for a four ring scanner with an inner diameter of 6 cm, employing 20 detectors per scanner ring.

  5. Experimental characterization and system simulations of depth of interaction PET detectors using 0.5 mm and 0.7 mm LSO arrays

    NASA Astrophysics Data System (ADS)

    James, Sara St; Yang, Yongfeng; Wu, Yibao; Farrell, Richard; Dokhale, Purushottam; Shah, Kanai S.; Cherry, Simon R.

    2009-07-01

    Small animal PET scanners may be improved by increasing the sensitivity, improving the spatial resolution and improving the uniformity of the spatial resolution across the field of view. This may be achieved by using PET detectors based on crystal elements that are thin in the axial and transaxial directions and long in the radial direction, and by employing depth of interaction (DOI) encoding to minimize the parallax error. With DOI detectors, the diameter of the ring of the PET scanner may also be decreased. This minimizes the number of detectors required to achieve the same solid angle coverage as a scanner with a larger ring diameter and minimizes errors due to non-collinearity of the annihilation photons. In this study, we characterize prototype PET detectors that are finely pixelated with individual LSO crystal element sizes of 0.5 mm × 0.5 mm × 20 mm and 0.7 mm × 0.7 mm × 20 mm, read out at both ends by position sensitive avalanche photodiodes (PSAPDs). Both a specular reflector and a diffuse reflector were evaluated. The detectors were characterized based on the ability to clearly resolve the individual crystal elements, the DOI resolution and the energy resolution. Our results indicate that a scanner based on any of the four detector designs would offer improved spatial resolution and more uniform spatial resolution compared to present day small animal PET scanners. The greatest improvements to spatial resolution will be achieved when the detectors employing the 0.5 mm × 0.5 mm × 20 mm crystals are used. Monte Carlo simulations were performed to demonstrate that 2 mm DOI resolution is adequate to ensure uniform spatial resolution for a small animal PET scanner geometry using these detectors. The sensitivity of such a scanner was also simulated using Monte Carlo simulations and was shown to be greater than 10% for a four ring scanner with an inner diameter of 6 cm, employing 20 detectors per scanner ring.

  6. Muon and neutrino results from KGF experiment at a depth of 7000 hg/square cm

    NASA Technical Reports Server (NTRS)

    Krishnaswamy, M. R.; Menon, M. G. K.; Mondal, N. K.; Narasimham, V. S.; Streekantan, B. V.; Hayashi, Y.; Ito, N.; Kawakami, S.; Miyake, S.

    1985-01-01

    The KGF nucleon decay experiment at a depth of 7000 hg/sq cm has provided valuable data on muons and neutrinos. The detector comprised of 34 crossed layers of proportional counters (cross section 10 x 10 sq cm; lengths 4m and 6m) sandwiched between 1.2 cm thick iron plates can record tracks of charged particles to an accuracy of 1 deg from tracks that traverse the whole of the detector. A special two-fold coincidence system enables the detector to record charged particles that enter at very large zenith angles. In a live time of 3.6 years about 2600 events have been recorded. These events include atmospheric muons, neutrino induced muons from rock, stopping muons, showers and events which have their production vertex inside the detectors. The results on atmospheric muons and neutrino events are presented.

  7. A case study demonstration of the soil temperature extrema recovery rates after precipitation cooling at 10-cm soil depth

    NASA Technical Reports Server (NTRS)

    Welker, Jean Edward

    1991-01-01

    Since the invention of maximum and minimum thermometers in the 18th century, diurnal temperature extrema have been taken for air worldwide. At some stations, these extrema temperatures were collected at various soil depths also, and the behavior of these temperatures at a 10-cm depth at the Tifton Experimental Station in Georgia is presented. After a precipitation cooling event, the diurnal temperature maxima drop to a minimum value and then start a recovery to higher values (similar to thermal inertia). This recovery represents a measure of response to heating as a function of soil moisture and soil property. Eight different curves were fitted to a wide variety of data sets for different stations and years, and both power and exponential curves were fitted to a wide variety of data sets for different stations and years. Both power and exponential curve fits were consistently found to be statistically accurate least-square fit representations of the raw data recovery values. The predictive procedures used here were multivariate regression analyses, which are applicable to soils at a variety of depths besides the 10-cm depth presented.

  8. PRECISE MEASUREMENT OF THE REIONIZATION OPTICAL DEPTH FROM THE GLOBAL 21 cm SIGNAL ACCOUNTING FOR COSMIC HEATING

    SciTech Connect

    Fialkov, Anastasia; Loeb, Abraham E-mail: aloeb@cfa.harvard.edu

    2016-04-10

    As a result of our limited data on reionization, the total optical depth for electron scattering, τ, limits precision measurements of cosmological parameters from the Cosmic Microwave Background (CMB). It was recently shown that the predicted 21 cm signal of neutral hydrogen contains enough information to reconstruct τ with sub-percent accuracy, assuming that the neutral gas was much hotter than the CMB throughout the entire epoch of reionization (EoR). Here we relax this assumption and use the global 21 cm signal alone to extract τ for realistic X-ray heating scenarios. We test our model-independent approach using mock data for a wide range of ionization and heating histories and show that an accurate measurement of the reionization optical depth at a sub-percent level is possible in most of the considered scenarios even when heating is not saturated during the EoR, assuming that the foregrounds are mitigated. However, we find that in cases where heating sources had hard X-ray spectra and their luminosity was close to or lower than what is predicted based on low-redshift observations, the global 21 cm signal alone is not a good tracer of the reionization history.

  9. Precise Measurement of the Reionization Optical Depth from the Global 21 cm Signal Accounting for Cosmic Heating

    NASA Astrophysics Data System (ADS)

    Fialkov, Anastasia; Loeb, Abraham

    2016-04-01

    As a result of our limited data on reionization, the total optical depth for electron scattering, τ, limits precision measurements of cosmological parameters from the Cosmic Microwave Background (CMB). It was recently shown that the predicted 21 cm signal of neutral hydrogen contains enough information to reconstruct τ with sub-percent accuracy, assuming that the neutral gas was much hotter than the CMB throughout the entire epoch of reionization (EoR). Here we relax this assumption and use the global 21 cm signal alone to extract τ for realistic X-ray heating scenarios. We test our model-independent approach using mock data for a wide range of ionization and heating histories and show that an accurate measurement of the reionization optical depth at a sub-percent level is possible in most of the considered scenarios even when heating is not saturated during the EoR, assuming that the foregrounds are mitigated. However, we find that in cases where heating sources had hard X-ray spectra and their luminosity was close to or lower than what is predicted based on low-redshift observations, the global 21 cm signal alone is not a good tracer of the reionization history.

  10. Estimation of CO2 diffusion coefficient at 0-10 cm depth in undisturbed and tilled soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Diffusion coefficients (D) of CO2 at 0 – 10 cm layers in undisturbed and tilled soil conditions were estimated using Penman, Millington-Quirk, Ridgwell et al. (1999), Troeh et al., and Moldrup et al. models. Soil bulk density and volumetric soil water content ('v) at 0 – 10 cm were measured on April...

  11. Depth.

    PubMed

    Koenderink, Jan J; van Doorn, Andrea J; Wagemans, Johan

    2011-01-01

    Depth is the feeling of remoteness, or separateness, that accompanies awareness in human modalities like vision and audition. In specific cases depths can be graded on an ordinal scale, or even measured quantitatively on an interval scale. In the case of pictorial vision this is complicated by the fact that human observers often appear to apply mental transformations that involve depths in distinct visual directions. This implies that a comparison of empirically determined depths between observers involves pictorial space as an integral entity, whereas comparing pictorial depths as such is meaningless. We describe the formal structure of pictorial space purely in the phenomenological domain, without taking recourse to the theories of optics which properly apply to physical space-a distinct ontological domain. We introduce a number of general ways to design and implement methods of geodesy in pictorial space, and discuss some basic problems associated with such measurements. We deal mainly with conceptual issues.

  12. Assessing the effectiveness of RegCM4 regional climate model in simulating the aerosol optical depth patterns over the region of Eastern Mediterranean

    NASA Astrophysics Data System (ADS)

    Georgoulias, Aristeidis K.; Tsikerdekis, Athanasios; Ntogras, Christos; Zanis, Prodromos

    2014-05-01

    In this work, the ability of the regional climate model RegCM4 to simulate the aerosol optical depth (AOD) patterns over the region of Eastern Mediterranean is assessed. Three separate runs were implemented within the framework of the QUADIEEMS project for the time period 2000-2010 at a horizontal resolution of 50km covering the region of Europe. ERA-interim data were used as lateral boundary conditions while the model was driven by emissions from CMIP5. In the first case, the total of the aerosol types that RegCM4 accounts for were included (sulfate, black carbon, sea salt, dust), while in the other two cases only anthropogenic and dust particles were taken into account, respectively. The total AOD patterns were compared against level-2 satellite observations from MODIS TERRA and AQUA and ground-based measurements from 12 AERONET sites located in the region. In addition, the RegCM4 anthropogenic and dust AOD patterns were compared against the anthropogenic and dust component of MODIS AOD which was calculated using a combination of various satellite, model and reanalysis products. Our results indicate a significant underestimation of the anthropogenic AOD, while, on the contrary, the dust AOD fields are simulated in a more efficient way. The QUADIEEMS project is co-financed by the European Social Fund (ESF) and national resources under the operational programme Education and Lifelong Learning (EdLL) within the framework of the Action "Supporting Postdoctoral Researchers".

  13. 43 CFR 2720.0-5 - Definitions.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 43 Public Lands: Interior 2 2014-10-01 2014-10-01 false Definitions. 2720.0-5 Section 2720.0-5..., DEPARTMENT OF THE INTERIOR LAND RESOURCE MANAGEMENT (2000) CONVEYANCE OF FEDERALLY-OWNED MINERAL INTERESTS Conveyance of Federally-Owned Mineral Interests § 2720.0-5 Definitions. As used in this subpart, the term:...

  14. 28 CFR 0.5 - Attorney General.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 28 Judicial Administration 1 2010-07-01 2010-07-01 false Attorney General. 0.5 Section 0.5... Attorney General § 0.5 Attorney General. The Attorney General shall: (a) Supervise and direct the administration and operation of the Department of Justice, including the offices of U.S. Attorneys and...

  15. Impact of mechanical stress on ferroelectricity in (Hf0.5Zr0.5)O2 thin films

    NASA Astrophysics Data System (ADS)

    Shiraishi, Takahisa; Katayama, Kiliha; Yokouchi, Tatsuhiko; Shimizu, Takao; Oikawa, Takahiro; Sakata, Osami; Uchida, Hiroshi; Imai, Yasuhiko; Kiguchi, Takanori; Konno, Toyohiko J.; Funakubo, Hiroshi

    2016-06-01

    To investigate the impact of mechanical stress on their ferroelectric properties, polycrystalline (Hf0.5Zr0.5)O2 thin films were deposited on (111)Pt-coated SiO2, Si, and CaF2 substrates with thermal expansion coefficients of 0.47, 4.5, and 22 × 10-6/ °C, respectively. In-plane X-ray diffraction measurements revealed that the (Hf0.5Zr0.5)O2 thin films deposited on SiO2 and Si substrates were under in-plane tensile strain and that their volume fraction of monoclinic phase decreased as this strain increased. In contrast, films deposited on CaF2 substrates were under in-plane compressive strain, and their volume fraction of monoclinic phase was the largest among the three kinds of substrates. The maximum remanent polarization of 9.3 μC/cm2 was observed for Pt/(Hf0.5Zr0.5)O2/Pt/TiO2/SiO2, while ferroelectricity was barely observable for Pt/(Hf0.5Zr0.5)O2/Pt/TiO2/SiO2/CaF2. This result suggests that the in-plane tensile strain effectively enhanced the ferroelectricity of the (Hf0.5Zr0.5)O2 thin films.

  16. 43 CFR 3180.0-5 - Definitions.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... Act of August 7, 1947 (30 U.S.C. 351, et seq.); or the Act of November 16, 1981 (Pub. L. 97-98, 95... 43 Public Lands: Interior 2 2014-10-01 2014-10-01 false Definitions. 3180.0-5 Section 3180.0-5... Onshore Oil and Gas Unit Agreements: General § 3180.0-5 Definitions. The following terms, as used in...

  17. 43 CFR 2361.0-5 - Definitions.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... resources which include crude oil, gases of all kinds (natural gas, hydrogen, carbon dioxide, helium, and... 43 Public Lands: Interior 2 2014-10-01 2014-10-01 false Definitions. 2361.0-5 Section 2361.0-5..., DEPARTMENT OF THE INTERIOR LAND RESOURCE MANAGEMENT (2000) NATIONAL PETROLEUM RESERVE IN ALASKA...

  18. 43 CFR 9212.0-5 - Definitions.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 43 Public Lands: Interior 2 2014-10-01 2014-10-01 false Definitions. 9212.0-5 Section 9212.0-5 Public Lands: Interior Regulations Relating to Public Lands (Continued) BUREAU OF LAND MANAGEMENT, DEPARTMENT OF THE INTERIOR TECHNICAL SERVICES (9000) FIRE MANAGEMENT Wildfire Prevention §...

  19. 43 CFR 9212.0-5 - Definitions.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 43 Public Lands: Interior 2 2012-10-01 2012-10-01 false Definitions. 9212.0-5 Section 9212.0-5 Public Lands: Interior Regulations Relating to Public Lands (Continued) BUREAU OF LAND MANAGEMENT, DEPARTMENT OF THE INTERIOR TECHNICAL SERVICES (9000) FIRE MANAGEMENT Wildfire Prevention §...

  20. 43 CFR 9212.0-5 - Definitions.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 43 Public Lands: Interior 2 2013-10-01 2013-10-01 false Definitions. 9212.0-5 Section 9212.0-5 Public Lands: Interior Regulations Relating to Public Lands (Continued) BUREAU OF LAND MANAGEMENT, DEPARTMENT OF THE INTERIOR TECHNICAL SERVICES (9000) FIRE MANAGEMENT Wildfire Prevention §...

  1. 43 CFR 9212.0-5 - Definitions.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 43 Public Lands: Interior 2 2011-10-01 2011-10-01 false Definitions. 9212.0-5 Section 9212.0-5 Public Lands: Interior Regulations Relating to Public Lands (Continued) BUREAU OF LAND MANAGEMENT, DEPARTMENT OF THE INTERIOR TECHNICAL SERVICES (9000) FIRE MANAGEMENT Wildfire Prevention §...

  2. 43 CFR 3142.0-5 - Definitions.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 43 Public Lands: Interior 2 2014-10-01 2014-10-01 false Definitions. 3142.0-5 Section 3142.0-5 Public Lands: Interior Regulations Relating to Public Lands (Continued) BUREAU OF LAND MANAGEMENT, DEPARTMENT OF THE INTERIOR MINERALS MANAGEMENT (3000) LEASING IN SPECIAL TAR SAND AREAS Paying...

  3. 43 CFR 3142.0-5 - Definitions.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 43 Public Lands: Interior 2 2013-10-01 2013-10-01 false Definitions. 3142.0-5 Section 3142.0-5 Public Lands: Interior Regulations Relating to Public Lands (Continued) BUREAU OF LAND MANAGEMENT, DEPARTMENT OF THE INTERIOR MINERALS MANAGEMENT (3000) LEASING IN SPECIAL TAR SAND AREAS Paying...

  4. 43 CFR 3142.0-5 - Definitions.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 43 Public Lands: Interior 2 2012-10-01 2012-10-01 false Definitions. 3142.0-5 Section 3142.0-5 Public Lands: Interior Regulations Relating to Public Lands (Continued) BUREAU OF LAND MANAGEMENT, DEPARTMENT OF THE INTERIOR MINERALS MANAGEMENT (3000) LEASING IN SPECIAL TAR SAND AREAS Paying...

  5. 43 CFR 3142.0-5 - Definitions.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 43 Public Lands: Interior 2 2011-10-01 2011-10-01 false Definitions. 3142.0-5 Section 3142.0-5 Public Lands: Interior Regulations Relating to Public Lands (Continued) BUREAU OF LAND MANAGEMENT, DEPARTMENT OF THE INTERIOR MINERALS MANAGEMENT (3000) LEASING IN SPECIAL TAR SAND AREAS Paying...

  6. 43 CFR 1601.0-5 - Definitions.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 43 Public Lands: Interior 2 2014-10-01 2014-10-01 false Definitions. 1601.0-5 Section 1601.0-5 Public Lands: Interior Regulations Relating to Public Lands (Continued) BUREAU OF LAND MANAGEMENT, DEPARTMENT OF THE INTERIOR GENERAL MANAGEMENT (1000) PLANNING, PROGRAMMING, BUDGETING Planning §...

  7. 43 CFR 1601.0-5 - Definitions.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 43 Public Lands: Interior 2 2012-10-01 2012-10-01 false Definitions. 1601.0-5 Section 1601.0-5 Public Lands: Interior Regulations Relating to Public Lands (Continued) BUREAU OF LAND MANAGEMENT, DEPARTMENT OF THE INTERIOR GENERAL MANAGEMENT (1000) PLANNING, PROGRAMMING, BUDGETING Planning §...

  8. 43 CFR 1601.0-5 - Definitions.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 43 Public Lands: Interior 2 2011-10-01 2011-10-01 false Definitions. 1601.0-5 Section 1601.0-5 Public Lands: Interior Regulations Relating to Public Lands (Continued) BUREAU OF LAND MANAGEMENT, DEPARTMENT OF THE INTERIOR GENERAL MANAGEMENT (1000) PLANNING, PROGRAMMING, BUDGETING Planning §...

  9. 43 CFR 1601.0-5 - Definitions.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 43 Public Lands: Interior 2 2013-10-01 2013-10-01 false Definitions. 1601.0-5 Section 1601.0-5 Public Lands: Interior Regulations Relating to Public Lands (Continued) BUREAU OF LAND MANAGEMENT, DEPARTMENT OF THE INTERIOR GENERAL MANAGEMENT (1000) PLANNING, PROGRAMMING, BUDGETING Planning §...

  10. Enhanced electrostricitive properties and thermal endurance of textured (Bi0.5Na0.5)TiO3-BaTiO3-(K0.5Na0.5)NbO3 ceramics

    NASA Astrophysics Data System (ADS)

    Hao, Jigong; Ye, Chenggen; Shen, Bo; Zhai, Jiwei

    2013-08-01

    Textured 0.92(Bi0.5Na0.5)TiO3-0.06BaTiO3-0.02(K0.5Na0.5)NbO3 (BNT-BT-KNN) ceramics have been produced by tape casting with pure-phase (Bi0.5Na0.5)TiO3 templates. Through the approach of texture construction, enhanced electrostrictive response was obtained with an electrostrictive coefficient Q33 (˜0.024 m4/C2 at 60 kV/cm) and good thermostability comparable with that of traditional Pb-based electrostrictors. Even at an electric-field as low as 35 kV/cm or at a temperature as high as 180 °C, samples still possess a large electrostrictive response with Q33 > 0.022 m4/C2, suggesting it is very promising for practical applications as a lead-free electrostrictive material owning to its wide usage range. Moreover, reducing the applied electric-filed or increasing temperature can both induce the predominant to pure electrostriction transition due to the little contributions of electrostriction strain from ferroelectric domain switching. Our work may provide a new recipe for designing high-performance BNT-based lead-free electrostrictive materials by means of texture construction.

  11. 43 CFR 2094.0-5 - Definitions.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ..., DEPARTMENT OF THE INTERIOR LAND RESOURCE MANAGEMENT (2000) SPECIAL LAWS AND RULES Special Resource Values; Shore Space § 2094.0-5 Definitions. The term navigable waters is defined in section 2 of the Act of...

  12. 43 CFR 2094.0-5 - Definitions.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ..., DEPARTMENT OF THE INTERIOR LAND RESOURCE MANAGEMENT (2000) SPECIAL LAWS AND RULES Special Resource Values; Shore Space § 2094.0-5 Definitions. The term navigable waters is defined in section 2 of the Act of...

  13. 43 CFR 2094.0-5 - Definitions.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ..., DEPARTMENT OF THE INTERIOR LAND RESOURCE MANAGEMENT (2000) SPECIAL LAWS AND RULES Special Resource Values; Shore Space § 2094.0-5 Definitions. The term navigable waters is defined in section 2 of the Act of...

  14. 43 CFR 2094.0-5 - Definitions.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ..., DEPARTMENT OF THE INTERIOR LAND RESOURCE MANAGEMENT (2000) SPECIAL LAWS AND RULES Special Resource Values; Shore Space § 2094.0-5 Definitions. The term navigable waters is defined in section 2 of the Act of...

  15. 43 CFR 2520.0-5 - Definitions.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ..., DEPARTMENT OF THE INTERIOR LAND RESOURCE MANAGEMENT (2000) DESERT-LAND ENTRIES Desert-Land Entries: General § 2520.0-5 Definitions. (a) As used in the desert-land laws and the regulations of this subpart:...

  16. 43 CFR 2520.0-5 - Definitions.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ..., DEPARTMENT OF THE INTERIOR LAND RESOURCE MANAGEMENT (2000) DESERT-LAND ENTRIES Desert-Land Entries: General § 2520.0-5 Definitions. (a) As used in the desert-land laws and the regulations of this subpart:...

  17. 43 CFR 2520.0-5 - Definitions.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ..., DEPARTMENT OF THE INTERIOR LAND RESOURCE MANAGEMENT (2000) DESERT-LAND ENTRIES Desert-Land Entries: General § 2520.0-5 Definitions. (a) As used in the desert-land laws and the regulations of this subpart:...

  18. 43 CFR 2520.0-5 - Definitions.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ..., DEPARTMENT OF THE INTERIOR LAND RESOURCE MANAGEMENT (2000) DESERT-LAND ENTRIES Desert-Land Entries: General § 2520.0-5 Definitions. (a) As used in the desert-land laws and the regulations of this subpart:...

  19. 43 CFR 1815.0-5 - Definitions.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ....0-5 Definitions. Major disaster means any hurricane, tornado, storm, flood, high water, winddriven... catastrophe occurs or threatens to occur certifies the need for Federal disaster assistance and...

  20. 43 CFR 1815.0-5 - Definitions.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ....0-5 Definitions. Major disaster means any hurricane, tornado, storm, flood, high water, winddriven... catastrophe occurs or threatens to occur certifies the need for Federal disaster assistance and...

  1. 43 CFR 1815.0-5 - Definitions.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ....0-5 Definitions. Major disaster means any hurricane, tornado, storm, flood, high water, winddriven... catastrophe occurs or threatens to occur certifies the need for Federal disaster assistance and...

  2. Solid-State Synthesis and Thermoelectric Properties of Mg2Si0.5Ge0.5Sb m

    NASA Astrophysics Data System (ADS)

    You, Sin-Wook; Shin, Dong-Kil; Ur, Soon-Chul; Kim, Il-Ho

    2015-06-01

    Mg2Si0.5Ge0.5Sb m ( m = 0, 0.005, 0.01, 0.02, and 0.03) solid solutions were synthesized by a solid-state reaction and consolidated by hot pressing. All specimens showed n-type conduction, and carrier concentrations were increased from 4.0 × 1017 cm-3 to 3.2 × 1021 cm-3 by Sb doping. The electrical conductivity remarkably increased with increasing Sb doping content, but the absolute value of the Seebeck coefficient was reduced as the Sb doping content increased, which was attributed to the increased carrier concentration. The lowest thermal conductivity was 2.3 W/mK for Mg2Si0.5Ge0.5Sb0.02 at 723 K, and the maximum ZT value of 0.56 was obtained for Mg2Si0.5Ge0.5Sb0.02 at 823 K.

  3. Proton conduction and chemical stability of (La{sub 0.5}Sr{sub 0.5})(Mg{sub 0.5+y}Nb{sub 0.5-y})O{sub 3-{delta}}

    SciTech Connect

    Kawasaki, Yuya; Okada, Sachio; Ito, Naoki; Matsumoto, Hiroshige Ishihara, Tatsumi

    2009-02-04

    Electrical conduction properties of complex perovskite-type oxides in the (La{sub 0.5}Sr{sub 0.5})(Mg{sub 0.5+y}Nb{sub 0.5-y})O{sub 3-{delta}} (y = 0.02-0.06) series at intermediate-high temperatures were investigated; introduction of protons by hydration of oxide-ion vacancies was expected by increasing the Mg/Nb ratio from unity. The conductivity depended on y and a maximum conductivity was obtained at y = 0.04: {sigma} = 4.9 x 10{sup -6} S cm{sup -1} at 400 deg. C in wet H{sub 2} atmospheres. From electromotive force measurements of hydrogen and water vapor concentration cells, electrical conduction in wet H{sub 2} atmospheres can be attributed to ionic conduction, and proton conduction is dominant below 700 deg. C. Unlike other perovskite-type proton conductors, (La{sub 0.5}Sr{sub 0.5})(Mg{sub 0.54}Nb{sub 0.46})O{sub 3-{delta}} was stable in CO{sub 2} atmospheres even in the low-intermediate temperature region due to dilution of reactive strontium by lanthanum.

  4. 43 CFR 3802.0-5 - Definitions.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... Public Lands: Interior Regulations Relating to Public Lands (Continued) BUREAU OF LAND MANAGEMENT, DEPARTMENT OF THE INTERIOR MINERALS MANAGEMENT (3000) MINING CLAIMS UNDER THE GENERAL MINING LAWS Exploration and Mining, Wilderness Review Program § 3802.0-5 Definitions. As used in this subpart, the term:...

  5. 43 CFR 3141.0-5 - Definitions.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ..., DEPARTMENT OF THE INTERIOR MINERALS MANAGEMENT (3000) LEASING IN SPECIAL TAR SAND AREAS Leasing in Special Tar Sand Areas § 3141.0-5 Definitions. As used in this subpart, the term: (a) Combined hydrocarbon lease means a lease issued in a Special Tar Sand Area for the removal of any gas and...

  6. 43 CFR 3141.0-5 - Definitions.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ..., DEPARTMENT OF THE INTERIOR MINERALS MANAGEMENT (3000) LEASING IN SPECIAL TAR SAND AREAS Leasing in Special Tar Sand Areas § 3141.0-5 Definitions. As used in this subpart, the term: (a) Combined hydrocarbon lease means a lease issued in a Special Tar Sand Area for the removal of any gas and...

  7. 43 CFR 3141.0-5 - Definitions.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ..., DEPARTMENT OF THE INTERIOR MINERALS MANAGEMENT (3000) LEASING IN SPECIAL TAR SAND AREAS Leasing in Special Tar Sand Areas § 3141.0-5 Definitions. As used in this subpart, the term: (a) Combined hydrocarbon lease means a lease issued in a Special Tar Sand Area for the removal of any gas and...

  8. 43 CFR 3141.0-5 - Definitions.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ..., DEPARTMENT OF THE INTERIOR MINERALS MANAGEMENT (3000) LEASING IN SPECIAL TAR SAND AREAS Leasing in Special Tar Sand Areas § 3141.0-5 Definitions. As used in this subpart, the term: (a) Combined hydrocarbon lease means a lease issued in a Special Tar Sand Area for the removal of any gas and...

  9. 43 CFR 8224.0-5 - Definitions.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ..., DEPARTMENT OF THE INTERIOR RECREATION PROGRAMS PROCEDURES Fossil Forest Research Natural Area § 8224.0-5... Land Management designated to perform the duties described in this subpart: (b) Fossil means the..., bitumen, lignite, asphaltum and tar sands, even though they are of biologic origin: (c) Fossil Forest...

  10. 43 CFR 8224.0-5 - Definitions.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ..., DEPARTMENT OF THE INTERIOR RECREATION PROGRAMS PROCEDURES Fossil Forest Research Natural Area § 8224.0-5... Land Management designated to perform the duties described in this subpart: (b) Fossil means the..., bitumen, lignite, asphaltum and tar sands, even though they are of biologic origin: (c) Fossil Forest...

  11. 43 CFR 8224.0-5 - Definitions.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ..., DEPARTMENT OF THE INTERIOR RECREATION PROGRAMS PROCEDURES Fossil Forest Research Natural Area § 8224.0-5... Land Management designated to perform the duties described in this subpart: (b) Fossil means the..., bitumen, lignite, asphaltum and tar sands, even though they are of biologic origin: (c) Fossil Forest...

  12. 43 CFR 8224.0-5 - Definitions.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ..., DEPARTMENT OF THE INTERIOR RECREATION PROGRAMS PROCEDURES Fossil Forest Research Natural Area § 8224.0-5... Land Management designated to perform the duties described in this subpart: (b) Fossil means the..., bitumen, lignite, asphaltum and tar sands, even though they are of biologic origin: (c) Fossil Forest...

  13. 43 CFR 1815.0-5 - Definitions.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ....0-5 Definitions. Major disaster means any hurricane, tornado, storm, flood, high water, winddriven water, tidal wave, earthquake, drought, fire, or other catastrophe in any part of the United States... assurance of the expenditure of a reasonable amount of the funds of such State, its local governments,...

  14. 43 CFR 3150.0-5 - Definitions.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... placing explosive charges, where permissible, for seismic exploration. (b) Casual use means activities..., DEPARTMENT OF THE INTERIOR MINERALS MANAGEMENT (3000) ONSHORE OIL AND GAS GEOPHYSICAL EXPLORATION Onshore Oil and Gas Geophysical Exploration; General § 3150.0-5 Definitions. As used in this part, the term:...

  15. 43 CFR 3400.0-5 - Definitions.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... in excess of the rentals and royalties that accrues to the United States because of coal resource... lands, resources or improvements, for example, activities which do not involve use of heavy equipment or...) Maximum economic recovery has the meaning set forth in § 3480.0-5(a)(24) of this title. (y)...

  16. Radiation hardness of Ga0.5In0.5 P/GaAs tandem solar cells

    NASA Technical Reports Server (NTRS)

    Kurtz, Sarah R.; Olson, J. M.; Bertness, K. A.; Friedman, D. J.; Kibbler, A.; Cavicchi, B. T.; Krut, D. D.

    1991-01-01

    The radiation hardness of a two-junction monolithic Ga sub 0.5 In sub 0.5 P/GaAs cell with tunnel junction interconnect was investigated. Related single junction cells were also studied to identify the origins of the radiation losses. The optimal design of the cell is discussed. The air mass efficiency of an optimized tandem cell after irradiation with 10(exp 15) cm (-2) 1 MeV electrons is estimated to be 20 percent using currently available technology.

  17. Lattice Dynamics of (Mg0.5Fe0.5)O at High-Pressures

    NASA Astrophysics Data System (ADS)

    Solomatova, N. V.; Jackson, J. M.; Sturhahn, W.; Wicks, J. K.; Steinhardt, W. M.; Chen, B.

    2012-12-01

    Earth's lower mantle, composed primarily of silicate perovskites and (Mg,Fe)O "ferropericlase", occupies ~60% of Earth's volume. Knowledge of the sound velocities and density of lower mantle minerals are essential for interpreting seismic complexity in the deep Earth. Although it is suggested that (Mg,Fe)O represents a major volume fraction of Earth's interior, the iron concentration of (Mg,Fe)O is not very well constrained at all depths of the lower mantle. Near the base of the lower mantle, an enhanced iron content may be found due to melting events in Earth's history and/or reactions with the iron-dominant liquid outer core. However, few measurements sensitive to the vibrational thermodynamics of ferropericlase exist at pressures above 100 GPa. We have determined the elastic, vibrational, and magnetic properties of (Mg0.5Fe0.5)O ("Fp50") from nuclear resonant inelastic x-ray scattering (NRIXS), synchrotron Mössbauer spectroscopy (SMS), and x-ray diffraction (XRD) measurements in diamond-anvil cells up to ~120 GPa at 300 K. This intermediate composition will help assess how varying concentrations of iron affect the lattice dynamics and magnetic states of (Mg,Fe)O as a function of pressure. All experiments were performed using a panoramic diamond-anvil cell at beamline 3ID-B of the Advanced Photon Source at Argonne National Laboratory. The synthetic powdered 57Fe-enriched Fp50 sample was loaded into a beryllium gasket with a boron epoxy insert to maintain sample thickness at high-pressures and reduce axial gradients. The pressures were determined from in-situ volume measurements at 3ID-B combined with an equation of state for (Mg,Fe)O with a similar composition. Several geophysical-relevant parameters of Fp50 at high-pressure will be discussed. In this contribution, we will present derived partial phonon density of states, Debye sound velocities, and compressional and shear sound velocities for Fp50. Our results on Fp50, including the spin state of Fe, will be

  18. Ultrathin Hf0.5Zr0.5O2 Ferroelectric Films on Si.

    PubMed

    Chernikova, Anna; Kozodaev, Maksim; Markeev, Andrei; Negrov, Dmitrii; Spiridonov, Maksim; Zarubin, Sergei; Bak, Ohheum; Buragohain, Pratyush; Lu, Haidong; Suvorova, Elena; Gruverman, Alexei; Zenkevich, Andrei

    2016-03-23

    Because of their immense scalability and manufacturability potential, the HfO2-based ferroelectric films attract significant attention as strong candidates for application in ferroelectric memories and related electronic devices. Here, we report the ferroelectric behavior of ultrathin Hf0.5Zr0.5O2 films, with the thickness of just 2.5 nm, which makes them suitable for use in ferroelectric tunnel junctions, thereby further expanding the area of their practical application. Transmission electron microscopy and electron diffraction analysis of the films grown on highly doped Si substrates confirms formation of the fully crystalline non-centrosymmetric orthorhombic phase responsible for ferroelectricity in Hf0.5Zr0.5O2. Piezoresponse force microscopy and pulsed switching testing performed on the deposited top TiN electrodes provide further evidence of the ferroelectric behavior of the Hf0.5Zr0.5O2 films. The electronic band lineup at the top TiN/Hf0.5Zr0.5O2 interface and band bending at the adjacent n(+)-Si bottom layer attributed to the polarization charges in Hf0.5Zr0.5O2 have been determined using in situ X-ray photoelectron spectroscopy analysis. The obtained results represent a significant step toward the experimental implementation of Si-based ferroelectric tunnel junctions.

  19. Thickness dependence of superconductivity in FeSe0.5Te0.5 nanodevices

    NASA Astrophysics Data System (ADS)

    Yue, Chunlei; Hu, Jin; Liu, Xue; Mao, Zhiqiang; Wei, Jiang

    2014-03-01

    We investigated the thickness dependence of superconductivity on thin film single-crystal FeSe0.5Te0.5 nanodevices. We designed two independent approaches of exfoliation and ion milling to reduce the crystal thickness. On both methods, we discovered that once the thickness of crystal is reduced below 20nm, the superconductivity disappears. When the thickness is approaching to the critical thickness of 20nm, the normal state becomes more insulating, and transition temperature (14K) shifts toward lower temperature. In addition, ion milling method reveals that there is always about 6nm of non- stoichiometric FeSexTe1-x developed on the surface of FeSe0.5Te0.5 single crystal in ambient environment.

  20. Nanostructural and electrical properties of LA0.5SR0.5CoO3

    NASA Astrophysics Data System (ADS)

    Bahari, A.; Ramzannezhad, A.; Shajari, D.; Najafi, H.

    2017-02-01

    A group of ABO3 perovskite-type oxides is currently under intensive studies for their potential as chemical sensing, ferroelectric memories, gas separation and computer devices. This group includes LaxSr1‑xCoO3 (LSCO). In the present work, we have synthesized LSCO samples by using the sol-gel method and studied their nano structural and electrical properties with using the scanning electron microscopy (SEM), energy dispersive X-ray (EDX), Current density-voltage (J-V) and Fourier transform infrared spectroscopy (FTIR) techniques. We synthesized nanoparticles with diameters between 50 and 100 nm by calcination of the pulverized gel powders, and then studied its structure. The band gap characteristics of the La0.5Sr0.5CoO3 structure were also analyzed. The obtained results show that La0.5Sr0.5CoO3 with favorable carrier mobility ( ˜ 1.7 × 10‑2 cm2v‑2s‑1) and dielectric constant (16) exhibits a variety of interesting physical properties which include ferroelectric, dielectric, pyroelectric and piezoelectric behavior.

  1. An In0.5Ga0.5N nanowire photoanode for harvesting deep visible light photons

    NASA Astrophysics Data System (ADS)

    Fan, S.; Woo, S. Y.; Vanka, S.; Botton, G. A.; Mi, Z.

    2016-07-01

    III-nitride semiconductors hold tremendous promise for realizing high efficiency photoelectrodes. However, previously reported InGaN photoelectrodes generally exhibit very low photocurrent densities, due to the presence of extensive defects, dislocations, and indium phase separation. Here, we show that In0.5Ga0.5N nanowires with nearly homogeneous indium distribution can be achieved by plasma-assisted molecular beam epitaxy. Under AM1.5G one sun illumination, the InGaN nanowire photoanode exhibits a photocurrent density of 7.3 mA/cm2 at 1.2 V (vs. NHE) in 1M HBr. The incident-photon-to-current efficiency is above 10% at 650 nm, which is significantly higher than previously reported values of metal oxide photoelectrodes.

  2. Metamagnetic Transitions in La_{0.5}Pr_{0.5}Mn_2Si_2

    NASA Astrophysics Data System (ADS)

    Duman, Eyüp; Acet, Mehmet; Krenke, Thorsten; Ouladdiaf, Bachir; Suard, Emmanual

    2017-03-01

    La_{0.5}Pr_{0.5}Mn_2Si_2 undergoes an antiferromagnetic-ferromagnetic transition at about 250 K (-23°C). This transition can also be induced by an external magnetic field leading to a metamagnetic transition. This can lead to a large change in the magnetic entropy, which is useful for magnetic cooling and studying the magnetocaloric effect. We investigated the details of the spin configuration as the magnetic ordering progresses from AF to FM by neutron diffraction techniques under magnetic fields up to 5 T and using spectral refining methods.

  3. Superhard W0.5Ta0.5B nanowires prepared at ambient pressure

    NASA Astrophysics Data System (ADS)

    Yeung, Michael T.; Akopov, Georgiy; Lin, Cheng-Wei; King, Daniel J.; Li, Rebecca L.; Sobell, Zachary C.; Mohammadi, Reza; Kaner, Richard B.

    2016-11-01

    The primary focus of superhard materials development has relied on chemical tuning of the crystal structure. While these intrinsic effects are invaluable, there is a strong possibility that hardness can be dramatically enhanced using extrinsic effects. Here, we demonstrate that the superhard metal W0.5Ta0.5B can be prepared as nanowires through flux growth. The aspect ratios of the nanowires are controlled by the concentration of boride in molten aluminum, and the nanowires grow along the boron-boron chains, confirmed via electron diffraction. This morphology inherently results from the crystal habit of borides and can inspire the development of other nanostructured materials.

  4. Depth dependence of electron backscatter: An energy spectral and dosimetry study using Monte Carlo simulation

    SciTech Connect

    Chow, James C. L.; Owrangi, Amir M.

    2009-02-15

    This study investigated the depth dependence of electron backscatter from a layer of lead (Pb) for clinical electron beams. The change in the electron backscatter with variation in the water depth above the Pb was determined. Electron energy spectra and relative depth doses as a function of depth in water over the Pb layer were calculated using a Monte Carlo simulation and studied. Phase-space files for 4 and 9 MeV electron beams (10x10 cm{sup 2} applicator and cutout) based on the Varian 21 EX linear accelerator were generated using the EGSnrc-based BEAMNRC code. 3 mm of Pb, at depths of 0.5 and 1 cm in water, was irradiated with electrons. The source-to-surface distance is equal to 100 cm. Electron energy spectra and relative depth doses with and without the presence of the Pb layer at different depths in water were determined using the BEAMNRC code. For the 4 MeV electron energy spectra at a depth of 0.5 cm in water, electron backscatter was found to originate at the Pb-water interface and extend to 0.5 cm above the Pb insert. However, at a depth of 1 cm in water, electron backscatter almost disappeared at 0.5 and 1 cm above th ePb insert. This is due to the increased attenuation of the incident 4 MeV electron beam in a thicker layer of water as well as increased attenuation of the electron backscatter above the Pb. This resulted in a 23% decrease in relative dose at a measurement point of 0.5 cm depth, when the depth of the Pb insert was changed from 1 to 0.5 cm. For the electron energy spectra of the 9 MeV beams with a 0.5 cm depth of water, only a small amount of electron backscatter was observed. However, more electron backscatter was found when the water depth was increased to 1 cm. This is because the electron beam energy was decreased more due to the increase in attenuation from the increased depth of water compared to 0.5 cm. Since the electron energy spectrum and relative depth dose above the Pb layer vary with depth of water on top of the Pb, the

  5. High current superconductivity in FeSe0.5Te0.5-coated conductors at 30 tesla.

    PubMed

    Si, Weidong; Han, Su Jung; Shi, Xiaoya; Ehrlich, Steven N; Jaroszynski, J; Goyal, Amit; Li, Qiang

    2013-01-01

    Although high-temperature superconductor cuprates have been discovered for more than 25 years, superconductors for high-field application are still based on low-temperature superconductors, such as Nb(3)Sn. The high anisotropies, brittle textures and high manufacturing costs limit the applicability of the cuprates. Here we demonstrate that the iron superconductors, without most of the drawbacks of the cuprates, have a superior high-field performance over low-temperature superconductors at 4.2 K. With a CeO(2) buffer, critical current densities >10(6)  A cm(-2) were observed in iron-chalcogenide FeSe(0.5)Te(0.5) films grown on single-crystalline and coated conductor substrates. These films are capable of carrying critical current densities exceeding 10(5) A cm(-2) under 30 tesla magnetic fields, which are much higher than those of low-temperature superconductors. High critical current densities, low magnetic field anisotropies and relatively strong grain coupling make iron-chalcogenide-coated conductors particularly attractive for high-field applications at liquid helium temperatures.

  6. Ellipsometric study of Si(0.5)Ge(0.5)/Si strained-layer superlattices

    NASA Technical Reports Server (NTRS)

    Sieg, R. M.; Alterovitz, S. A.; Croke, E. T.; Harrell, M. J.

    1993-01-01

    An ellipsometric study of two Si(0.5)Ge(0.5)/Si strained-layer super lattices grown by MBE at low temperature (500 C) is presented, and results are compared with x ray diffraction (XRD) estimates. Excellent agreement is obtained between target values, XRD, and ellipsometry when one of two available Si(x)Ge(1-x) databases is used. It is shown that ellipsometry can be used to nondestructively determine the number of superlattice periods, layer thicknesses, Si(x)Ge(1-x) composition, and oxide thickness without resorting to additional sources of information. It was also noted that we do not observe any strain effect on the E(sub 1) critical point.

  7. Ellipsometric study of Si(0.5)Ge(0.5)/Si strained-layer superlattices

    NASA Technical Reports Server (NTRS)

    Sieg, R. M.; Alterovitz, S. A.; Croke, E. T.; Harrell, M. J.

    1993-01-01

    We present an ellipsometric study of two Si(0.5)Ge(0.5)/Si strained-layer superlattices grown by MBE at low temperature (500 C), and compare our results with X-ray diffraction (XRD) estimates. Excellent agreement is obtained between target values, XRD, and ellipsometry when one of two available Si(x)Ge(1-x) databases is used. We show that ellipsometry can be used to nondestructively determine the number of superlattice periods, layer thicknesses, Si(x)Ge(1-x) composition, and oxide thickness without resorting to additional sources of information. We also note that we do not observe any strain effect on the E1 critical point.

  8. Phase transitions in Fe0.5Co0.5 (110) thin films

    NASA Astrophysics Data System (ADS)

    Ramírez-Dámaso, G.; Castillo-Alvarado, F. L.; Rojas-Hernández, E.

    2016-12-01

    In this paper, we present calculations for two second-order phase transitions in (110) Fe0.5Co0.5 thin films with 11, 15, and 19 monoatomic layers. The lattice and magnetic transitions are based on thermodynamic equilibrium considerations of the magnetic alloy. The procedure proposed by Valenta and Sukiennicki was applied to calculate the composition x(i), the lattice order parameter t(i), and the magnetic order parameter σ(i) as a function of temperature T. We confirmed that both phase transitions, lattice and magnetic, are of the second order, in accordance with experimental results in the literature. The obtained behavior of these parameters indicates their inhomogeneity due to the boundary conditions on the surfaces of the thin film.

  9. Efficacy and safety of 0.5% levobupivacaine versus 0.5% bupivacaine for peribulbar anesthesia

    PubMed Central

    Pacella, Elena; Pacella, Fernanda; Troisi, Fabiana; Dell’Edera, Domenico; Tuchetti, Paolo; Lenzi, Tommaso; Collini, Saul

    2013-01-01

    Background This randomized double-blind study examined the use of a new anesthetic agent, levobupivacaine 0.5%, which is the S(−)-enantiomer of a racemic mixture of bupivacaine, for peribulbar anesthesia and compared it with racemic bupivacaine 0.5% alone or in combination with hyaluronidase 10 IU/mL. Methods A total of 160 patients undergoing ophthalmic surgery were randomized into four groups (n = 40 each) to receive inferotemporal peribulbar injection of levobupivacaine 0.5% (group L), racemic bupivacaine 0.5% (group B), levobupivacaine + hyaluronidase 10 IU/mL (group LH), or racemic bupivacaine + hyaluronidase 10 IU/mL (group BH) by two anesthetists and two ophthalmologists in a ratio of 25% each. Ocular akinesia and orbicularis oculi function were evaluated using a three-point scale; a value < 5 points was considered as requiring surgery, and movements were re-evaluated the day following surgery to confirm regression of the block. Results The time to onset (12 ± 2.6 minutes versus 13 ± 2.8 minutes) and duration of anesthesia (185 ± 33.2 minutes versus 188 ± 35.7 minutes) were similar between groups L and B. Complete akinesia (score 0) was obtained more frequently when hyaluronidase was used in addition to the anesthetic, with occurrences of 72.5% versus 57.5% in group LH versus L, respectively, and 67.5% versus 45% in group BH versus B. Moderate hypotension (<30% of baseline) was observed in four patients (10%) in group L, two (5.0%) in group B, one (2.5%) in group LH, and three (7.5%) in group BH. The time to onset was significantly different between groups L and BH, B and BH, and LH and BH, and the duration of anesthesia differed significantly between groups B and LH, B and BH, and L and LH. The akinesia score differed significantly between groups L and LH and between groups B and LH (P = 0.043 and P = 0.018, respectively), and the number of patients with a score of 0 differed significantly between groups B and LH and between groups B and BH (P = 0

  10. Structural, electronic and optical properties of the Zn0.5V0.5S in three phases

    NASA Astrophysics Data System (ADS)

    Yin, Zhu-Hua; Zhang, Jian-Min

    2016-10-01

    The structural, electronic and optical properties of the Zn0.5V0.5SZB, Zn0.5V0.5SW and Zn0.5V0.5SRS are studied by the spin-polarized first-principles calculation. The Zn0.5V0.5SZB and Zn0.5V0.5SRS are metals in tetragonal structures, while the Zn0.5V0.5SW in trigonal structure is half-metal with 100% spin polarization. The Zn0.5V0.5SRS has the biggest static dielectric constant 𝜀1(0) and static refractive index n(0), which may be ascribed to the highest crystal symmetry. The maximum absorption peaks of the Zn0.5V0.5SZB, Zn0.5V0.5SW and Zn0.5V0.5SRS are located about 44 eV in the ultraviolet region, indicating these materials have good prospect for optoelectronic materials in the ultraviolet range.

  11. Isosbestic Point and Magnetoresistance Components in Ho_{0.5} Lu_{0.5} B_{12}

    NASA Astrophysics Data System (ADS)

    Khoroshilov, A. L.; Azarevich, A. N.; Bogach, A. V.; Glushkov, V. V.; Demishev, S. V.; Krasnorussky, V. N.; Voronov, V. V.; Shitsevalova, N. Yu; Filippov, V. B.; Gabani, S.; Flachbart, K.; Sluchanko, N. E.

    2016-12-01

    We present the results of precise magnetoresistance (MR) measurements of an antiferromagnetic cage-glass solid solution Ho_{0.5}Lu_{0.5}B_{12} in magnetic fields up to 80 kOe and at temperatures between 1.9 and 100 K. The analysis of results allows to separate the positive and negative contributions to MR. The dominant MR-term was found to be the high field positive contribution Δ ρ /ρ _{(m+)} =μ _D^2 H^2 which is caused by the drift mobility μ _D of charge carriers. It was also shown that the negative MR observed at temperatures T ≤ 10 K may be described by the well-known relation between MR and local magnetization Δ ρ /ρ _{(-)} =M_{loc}^2 obtained by Yosida in the framework of s-d exchange model. We discuss as well the scattering of charge carriers on antiferromagnetic nanosize domains of Ho^{3+} ions with effective magnetic moments 3.5-5.5 μ _B as the mechanism responsible for the appearance of the negative MR component.

  12. Neutron structural characterization and transport properties of oxidized and reduced La0.5Sr0.5M0.5Ti0.5O3 (M = Mn, Fe) perovskites: Possible electrode materials in solid-oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Martínez-Coronado, R.; Alonso, J. A.; Aguadero, A.; Perez-Coll, D.; Fernández-Díaz, M. T.

    2013-03-01

    Oxygen-stoichiometric La0.5Sr0.5M0.5Ti0.5O3 (M = Mn, Fe) perovskites and the corresponding reduced specimens, of La0.5Sr0.5M0.5Ti0.5O3-δ composition, have been prepared and characterized by x-ray diffraction and neutron powder diffraction (NPD), in complement with thermal analysis, electrical conductivity, and thermal expansion measurements. NPD data show that these perovskites are all orthorhombic, space group Pbnm (No. 62). The total reduction of M3+ to M2+ in the reduced phases is accompanied with the occurrence of oxygen vacancies, which was confirmed by thermogravimetric analysis (TGA). Above room-temperature, these phases undergo two structural phase transitions studied in situ from NPD data; the former to a tetragonal (I4/mcm) structure, and the second one to a cubic (Pm-3m) phase. All the oxides display a semiconductor-like behavior with a maximum conductivity value of 15 S.cm-1 for the oxidized La0.5Sr0.5Mn0.5Ti0.5O3 phase at 850 °C. The measured thermal expansion coefficients perfectly match with the values usually displayed by solid-oxide fuel cell (SOFC) electrolytes. The obtained results present these perovskites as alternative electrodes for SOFCs.

  13. Structural characteristics of thermally evaporated Cu0.5Ag0.5InSe2 thin films

    NASA Astrophysics Data System (ADS)

    Gullu, H. H.; Parlak, M.

    2016-05-01

    In this work, Cu0.5Ag0.5InSe2 (CAIS) thin film samples were prepared by thermal evaporation of Cu, Ag, InSe and Se evaporants sequentially on glass substrates. Following the deposition, annealing processes were applied at different temperatures. The as-grown and annealed CAIS samples were nearly stoichiometric in the detection limit of the compositional measurement. The x-ray diffraction (XRD) measurements revealed that they were in polycrystalline structure with a preferred orientation along the (112) direction. Moreoever, the crystallinity of the films improved with increasing annealing temperature. According to the results of Raman measurements, the highest Raman intensity was found in the A1 mode which is directly proportional to the crystallinity of the samples. The surface properties of the thin films were analyzed by means of scanning electron microscopy (SEM) and atomic force microscopy (AFM). These results showed that there was a Se agglomeration on the deposited film surfaces and with annealing processes segregation effects were observed on the surface of the annealed samples. X-ray photoelectron spectroscopy (XPS) measurements were carried out to get information about surface and near-surface properties of the films. The results from the surface and depth surface analyses of the films were found to be in agreement with the energy dispersive spectroscopy (EDS) analysis.

  14. (Y0.5In0.5)Ba(Co,Zn)4O7 cathodes with superior high-temperature phase stability for solid oxide fuel cells

    SciTech Connect

    Young Nam, Kim; Kim, Jung-Hyun; Paranthaman, Mariappan Parans; Manthiram, Arumugam; Huq, Ashfia

    2012-01-01

    (Y0.5In0.5)BaCo4-xZnxO7 (1.0 x 2.0) oxides crystallizing in a trigonal P31c structure have been synthesized and explored as cathode materials for solid oxide fuel cells (SOFC). At a given Zn content, the (Y0.5In0.5)BaCo4-xZnxO7 sample with 50 % Y and 50 % In exhibits much improved phase stability at intermediate temperatures (600 - 800 oC) compared to the samples with 100 % Y or In. However, the substitution of Zn for Co in (Y0.5In0.5)Ba(Co4-xZnx)O7 (1.0 x 2.0) decreases the amount of oxygen loss on heating, total electrical conductivity, and cathode performance in SOFC while providing good long-term phase stability at high temperatures. Among the various chemical compositions investigated in the (Y0.5In0.5)Ba(Co4-xZnx)O7 system, the (Y0.5In0.5)BaCo3ZnO7 sample offers a combination of good electrochemical performance and low thermal expansion coefficient (TEC) while maintaining superior phase stability at 600 800 oC for 100 h. Fuel cell performances of the (Y0.5In0.5)Ba(Co3Zn)O7 + Ce0.8Gd0.2O1.9 (GDC) (50 : 50 wt. %) composite cathodes collected with anode-supported single cell reveal a maximum power density value of 521 mW cm-2 at 700 oC.

  15. BaZr0.5Ti0.5O3 : Lead-free relaxor ferroelectric or dipolar glass

    NASA Astrophysics Data System (ADS)

    Filipič, C.; Kutnjak, Z.; Pirc, R.; Canu, G.; Petzelt, J.

    2016-06-01

    Glassy freezing dynamics was investigated in BaZr0.5Ti0.5O3 (BZT50) ceramic samples by means of dielectric spectroscopy in the frequency range 0.001 Hz-1 MHz at temperatures 10 cm it has been found that a ferroelectric state cannot be induced, in contrast to the case of typical relaxors. This suggests that—at least for the above field amplitudes—BZT50 effectively behaves as a dipolar glass, which can be characterized by a negative value of the static third order nonlinear permittivity. The relaxation spectrum has been analyzed by means of the frequency-temperature plot, which shows that the longest relaxation time obeys the Vogel-Fulcher relation τ =τ0exp [E0/(T -T0) ] with the freezing temperature of 48.1 K, whereas the corresponding value for the shortest relaxation time is ˜0 K, implying an Arrhenius type behavior. By applying a standard expression for the static linear permittivity of dipolar glasses and/or relaxors the value of the Edwards-Anderson order parameter q (T ) has been evaluated. It is further shown that q (T ) can be described by the spherical random bond-random field model of relaxors.

  16. Anharmonicity of Zone-Center Optical Phonons: Raman Scattering Spectra of GaSe0.5S0.5 Layered Crystal

    NASA Astrophysics Data System (ADS)

    Gasanly, N. M.; Aydinli, A.; Aydinli, A.; Kocabaş, C.; Özkan, H.

    The temperature dependencies (10-300 K) of the eight Raman-active mode frequencies and linewidths in GaSe0.5S0.5 layered crystal have been measured in the frequency range from 10 to 320 cm-1. We observed softening and broadening of the optical phonon lines with increasing temperature. Comparison of the experimental data with the theories of the shift and broadening of the interlayer and intralayer phonon lines showed that the temperature dependencies can be explained by the contributions from thermal expansion, lattice anharmonicity and crystal disorder. The purely anharmonic contribution (phonon-phonon coupling) is found to be due to three-phonon processes. It was established that the effect of crystal disorder on the broadening of phonon lines is greater for GaSe0.5S0.5 than for binary compounds GaSe and GaS.

  17. Enhanced second-harmonic generation in Pr0.5Ca0.5MnO3/La0.5Sr0.5MnO3 superlattices

    NASA Astrophysics Data System (ADS)

    Lee, J. S.; Nakamura, M.; Kawasaki, M.; Tokura, Y.

    2013-12-01

    We investigated second harmonic generation for manganite superlattices composed of Pr0.5Ca0.5MnO3 and La0.5Sr0.5MnO3. While the second harmonic intensity shows a strong variation as a function of the constituent layer thickness, it is dramatically enhanced when each layer has a same thickness of about 1.4 nm and endows its own ground state nature, i.e., a charge-orbital ordered antiferromagnetic insulator for Pr0.5Ca0.5MnO3 and a ferromagnetic metal for La0.5Sr0.5MnO3. From the detailed symmetry analysis, we discuss a possible role of the coexisting phases and their boundaries in the enhancement of the polar character in this manganese oxide superlattice.

  18. Synthesis and electrochemical assessment of Ce{sub 0.5}Yb{sub 0.5}O{sub 1.75} ceramics and derived composite electrolytes

    SciTech Connect

    Martins, Natércia C.T.; Rajesh, Surendran; Marques, Fernando M.B.

    2015-10-15

    Highlights: • Ce{sub 0.5}Yb{sub 0.5}O{sub 1.75} prepared for the first time through solid state reaction. • High energy milling needed to assist the ceramic route. • Ce{sub 0.5}Yb{sub 0.5}O{sub 1.75} is oxide-ion conductor in air and n-type conductor at low pO{sub 2}. • Ce{sub 0.5}Yb{sub 0.5}O{sub 1.75} decomposes slightly when exposed to alkaline carbonates. • Composites based on Ce{sub 0.5}Yb{sub 0.5}O{sub 1.75} show standard electrical performance. - Abstract: Ce{sub 0.5}Yb{sub 0.5}O{sub 1.75} was prepared for the first time through high temperature (1600 °C for 5 h) solid state reaction, after high energy milling to enhance the mechano-chemical interaction of precursor oxides (CeO{sub 2} and Yb{sub 2}O{sub 3}). Single phase formation was confirmed by powder X-ray diffraction. Impedance spectroscopy data obtained under wide temperature (300–800 °C) and oxygen partial pressure (0.21 to about 10{sup −25} atm) ranges indicates that this material exhibits predominant oxide-ion conductivity under oxidizing conditions while n-type electronic conductivity prevails at low oxygen partial pressure. The mixed oxide shows modest ionic conductivity (1.1 × 10{sup −3} S cm{sup −1} at 800 °C) with activation energy of 1.3 eV in the 600–800 °C temperature range. When combined with molten carbonates (Li{sub 2}CO{sub 3} + Na{sub 2}CO{sub 3}, 1:1 molar ratio) to produce composite electrolytes, Ce{sub 0.5}Yb{sub 0.5}O{sub 1.75} slightly decomposed. However, the composite electrical performance is still acceptable and closely matches the conductivity of similar materials (>0.1 S cm{sup −1} immediately above 500 °C)

  19. Eu3+-doped (Y0.5La0.5)2O3: new nanophosphor with the bixbyite cubic structure

    NASA Astrophysics Data System (ADS)

    Đorđević, Vesna; Nikolić, Marko G.; Bartova, Barbora; Krsmanović, Radenka M.; Antić, Željka; Dramićanin, Miroslav D.

    2013-01-01

    New red sesquioxide phosphor, Eu3+-doped (Y0.5La0.5)2O3, was synthesized in the form of nanocrystalline powder with excellent structural ordering in cubic bixbyite-type, and with nanoparticle sizes ranging between 10 and 20 nm. Photoluminescence measurements show strong, Eu3+ characteristic, red emission ( x = 0.66 and y = 0.34 CIE color coordinates) with an average 5D0 emission lifetime of about 1.3 ms. Maximum splitting of the 7F1 manifold of the Eu3+ ion emission behaves in a way directly proportional to the crystal field strength parameter, and experimental results show perfect agreement with theoretical values for pure cubic sesquioxides. This could be used as an indicator of complete dissolution of Y2O3 and La2O3, showing that (Y0.5La0.5)2O3:Eu3+ behaves as a new bixbyite structure oxide, M2O3, where M acts as an ion having average ionic radius of constituting Y3+ and La3+. Emission properties of this new phosphor were documented with detailed assignments of Eu3+ energy levels at 10 K and at room temperature. Second order crystal field parameters were found to be B 20 = -66 cm-1 and B 22 = -665 cm-1 at 10 K and B 20 = -78 cm-1 and B 22 = -602 cm-1 at room temperature, while for the crystal field strength the value of 1495 cm-1 was calculated at 10 K and 1355 cm-1 at room temperature.

  20. Investigation of phase formation of (Zn, Mg)0.5Co0.5Fe2O4 nanoferrites

    NASA Astrophysics Data System (ADS)

    Msomi, J. Z.; Dlamini, W. B.; Moyo, T.; Ezekiel, P.

    2015-01-01

    Zn0.5Co0.5Fe2O4 and Mg0.5Co0.5Fe2O4 nanoparticles have been prepared through high energy ball milling of single phase mixtures of ZnFe2O4 and CoFe2O4 or MgFe2O4 and CoFe2O4 nanosized oxides. The Mössbauer spectra of the milled products ZnFe2O4/CoFe2O4 and MgFe2O4/CoFe2O4 reveal the presence of Zn0.5Co0.5Fe2O4 and Mg0.5Co0.5Fe2O4, respectively. In an alternative route, Zn0.5Co0.5Fe2O4 and Mg0.5Co0.5Fe2O4 compounds were prepared directly from metal chloride solutions through glycol-thermal reaction. The coercive fields of the Zn0.5Co0.5Fe2O4 and Mg0.5Co0.5Fe2O4 oxides produced by glycol-thermal reaction were found to be about 100 Oe and 161 Oe, respectively. Larger coercive fields of about 184 Oe and 255 Oe have been observed for the milled ZnFe2O4/CoFe2O4 and MgFe2O4/CoFe2O4 oxides.

  1. Ni-doped La0.5Sr0.5TiO3 nanofibers: Fabrication and intrinsic ferromagnetism

    NASA Astrophysics Data System (ADS)

    Ponhan, Wichaid; Amornkitbamrung, Vittaya; Maensiri, Santi

    2016-06-01

    We report room-temperature ferromagnetism in ˜104-133 nm nanofibers of La0.5Sr0.5Ti1- x Ni x O3 (0.02 ≤ x ≤ 0.05). As-spun nanofibers of La0.5Sr0.5Ti1- x Ni x O3 are fabricated by an electrospinning technique. Nanofibers of the as spun and calcined La0.5Sr0.5Ti1- x Ni x O3 samples are characterized using X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM), X-ray photoelectron microscopy (XPS), X-ray absorption near edge structure (XANES) determination, and vibrating sample magnetometry (VSM). The results of XRD analysis and TEM together with selected electron diffraction (SEAD) analysis indicate that La0.5Sr0.5Ti1- x Ni x O3 nanofibers have a cubic perovskite structure with no secondary phase. The as-spun samples are paramagnetic, whereas the La0.5Sr0.5Ti1- x Ni x O3 samples are ferromagnetic having specific magnetizations of 0.098-0.484 emu/g at 10 kOe. The XPS spectra show that there are some oxygen vacancies in the nanofibers, which its may play an important role in inducing room-temperature ferromagnetism in La0.5Sr0.5Ti1- x Ni x O3 nanofibers. XANES spectra show that most of the Ni ions in La0.5Sr0.5Ti1- x Ni x O3 nanofibers are in the Ni2+ state mixed with some Ni metal. The finding of room temperature ferromagnetism in this nanofibrous structure of the La0.5Sr0.5Ti1- x Ni x O3 system is of interest in research on diluted magnetic oxides.

  2. Near-infrared emitting CdTe0.5Se0.5/Cd0.5Zn0.5S quantum dots: synthesis and bright luminescence

    PubMed Central

    2012-01-01

    We present how CdTe0.5Se0.5 cores can be coated with Cd0.5Zn0.5S shells at relatively low temperature (around 200°C) via facile synthesis using organic ammine ligands. The cores were firstly fabricated via a less toxic procedure using CdO, trioctylphosphine (TOP), Se, Te, and trioctylamine. The cores with small sizes (3.2-3.5 nm) revealed green and yellow photoluminescence (PL) and spherical morphologies. Hydrophobic core/shell CdTe0.5Se0.5/Cd0.5Zn0.5S quantum dots (QDs) with tunable PL between green and near-infrared (a maximum PL peak wavelength of 735 nm) were then created through a facile shell coating procedure using trioctylphosphine selenium with cadmium and zinc acetate. The QDs exhibited high PL efficiencies up to 50% because of the formation of a protective Cd0.5Zn0.5S shell on the CdTe0.5Se0.5 core, even though the PL efficiency of the cores is low (≤1%). Namely, the slow growth process of the shell plays an important role for getting high PL efficiencies. The properties of the QDs are largely determined by the properties of CdTe0.5Se0.5 cores and shells preparation conditions such as reaction temperature and time. The core/shell QDs exhibited a small size diameter. For example, the average diameter of the QDs with a PL peak wavelength of 735 nm is 6.1 nm. Small size and tunable bright PL makes the QDs utilizable as bioprobes because the size of QD-based bioprobes is considered as the major limitation for their broad applications in biological imaging. PMID:23130948

  3. Magnetic ordering in the rutile molecular magnets MII[N(CN)2]2 (M=Ni, Co, Fe, Mn, Ni0.5Co0.5, and Ni0.5Fe0.5)

    NASA Astrophysics Data System (ADS)

    Lappas, Alexandros; Wills, Andrew S.; Green, Mark A.; Prassides, Kosmas; Kurmoo, Mohamedally

    2003-04-01

    Rietveld refinement of powder neutron diffraction data, combined with group theory considerations, is used to determine the magnetic structures of the binary metal dicyanamide, MII[N(CN)2]2 where M=Ni, Co, Fe, Mn, Ni0.5Co0.5, and Ni0.5Fe0.5. Compounds with M=Mn or Fe show a canted antiferromagnetic arrangement of spin oriented in the ab crystallographic plane, with antiparallel components of the two sublattices along the a axis and parallel along the b axis. Symmetry considerations forbid an additional moment, whether compensated or not, to be present along the c axis. The compounds with fewer unpaired electrons (Co and Ni) are ferromagnets, with all moments oriented along the c axis. The mixed composition of Ni0.5Co0.5 displays the same collinear ferromagnetic structure as its parent compounds. However, the composition with M=Ni0.5Fe0.5, whose parent compounds show different magnetic behavior, does not exhibit long-range magnetic ordering down to 1.7 K. Magnetostriction was observed for the ferromagnets for which we investigated the variable temperature powder neutron diffraction. The cobalt-rich compounds show more pronounced effects, consistent with their increasing magnetocrystalline anisotropy.

  4. 16 CFR 0.5 - Laws authorizing monetary claims.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 16 Commercial Practices 1 2012-01-01 2012-01-01 false Laws authorizing monetary claims. 0.5... ORGANIZATION § 0.5 Laws authorizing monetary claims. The Commission is authorized to entertain monetary claims..., unless the adjudicative officer finds that the party has committed a willful violation of law...

  5. 16 CFR 0.5 - Laws authorizing monetary claims.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 16 Commercial Practices 1 2011-01-01 2011-01-01 false Laws authorizing monetary claims. 0.5... ORGANIZATION § 0.5 Laws authorizing monetary claims. The Commission is authorized to entertain monetary claims..., unless the adjudicative officer finds that the party has committed a willful violation of law...

  6. Thermochromic effect at room temperature of Sm0.5Ca0.5MnO3 thin films

    NASA Astrophysics Data System (ADS)

    Boileau, A.; Capon, F.; Barrat, S.; Laffez, P.; Pierson, J. F.

    2012-06-01

    Sm0.5Ca0.5MnO3 thermochromic thin films were synthesized using dc reactive magnetron co-sputtering and subsequent annealing in air. The film structure was studied by x-ray diffraction analysis. To validate the thermochromic potentiality of Sm0.5Ca0.5MnO3, electrical resistivity and infrared transmittance spectra were recorded for temperatures ranging from 77 K to 420 K. The temperature dependence of the optical band gap was estimated in the near infrared range. Upon heating, the optical transmission decreases in the infrared domain showing a thermochromic effect over a wide wavelength range at room temperature.

  7. Superconductivity in a new layered bismuth oxyselenide: LaO(0.5)F(0.5)BiSe₂.

    PubMed

    Krzton-Maziopa, A; Guguchia, Z; Pomjakushina, E; Pomjakushin, V; Khasanov, R; Luetkens, H; Biswas, P K; Amato, A; Keller, H; Conder, K

    2014-05-28

    We report superconductivity at T(c) ≈ 2.6 K in a new layered bismuth oxyselenide LaO(0.5)F(0.5)BiSe2 with the ZrCuSiAs-type structure composed of alternating superconducting BiSe2 and blocking LaO layers. The superconducting properties of LaO(0.5)F(0.5)BiSe2 were investigated by means of dc magnetization, resistivity and muon-spin rotation experiments, revealing the appearance of bulk superconductivity with a rather large superconducting volume fraction of ≈ 70% at 1.8 K.

  8. Preparation and Thermoelectric Properties of the Skutterudite-Related Phase Ru(0.5)Pd(0.5)Sb3

    NASA Technical Reports Server (NTRS)

    Caillat, T.; Kulleck, J.; Borshchevsky, A.; Fleurial, J.-P.

    1996-01-01

    A new skutterudite phase Ru(0.5)Pd(0.5)Sb3 was prepared. This new phase adds to a large number of already known materials with the skutterudite structure which have shown good potential for thermoelectric applications. Single phase, polycrystalline samples were prepared and characterized by x-ray analysis, electron probe microanalysis, density, sound velocity, thermal-expansion coefficient, and differential thermal analysis measurements. Ru(0.5)Pd(0.5)Sb3 has a cubic lattice, space group Im3 (T(sup 5, sub h)), with a = 9.298 A and decomposes at about 920 K. The Seebeck coefficient, the electrical resistivity, the Hall effect, and the thermal conductivity were measured on hot-pressed samples over a wide range of temperatures. Preliminary results show that Ru(0.5)Pd(0.5)Sb3 behaves as a heavily doped semiconductor with an estimated band gap of about 0.6 eV. The lattice thermal conductivity of Ru(0.5)Pd(0.5)Sb3 is substantially lower than that of the binary isostructural compounds CoSb3 and IrSb3. The unusually low thermal conductivity might be explained by additional hole and charge transfer phonon scattering in this material. The potential of this material for thermoelectric applications is discussed.

  9. Fully gapped superconductivity in In-doped topological crystalline insulator Pb0.5Sn0.5Te

    DOE PAGES

    Du, Guan; Gu, G. D.; Du, Zengyi; ...

    2015-07-27

    In this study, superconductors derived from topological insulators and topological crystalline insulators by chemical doping have long been considered to be candidates as topological superconductors. Pb0.5Sn0.5Te is a topological crystalline insulator with mirror symmetry protected surface states on (001)-, (011)-, and (111)-oriented surfaces. The superconductor (Pb0.5Sn0.5)0.7In0.3Te is produced by In doping in Pb0.5Sn0.5Te, and is thought to be a topological superconductor. Here we report scanning tunneling spectroscopy measurements of the superconducting state as well as the superconducting energy gap in (Pb0.5Sn0.5)0.7In0.3Te on a (001)-oriented surface. The spectrum can be well fitted by an anisotropic s-wave gap function of Δ =more » 0.72 + 0.18cos4θ meV using Dynes model. The results show that the superconductor seems to be a fully gapped one without any in-gap states, in contradiction with the expectation of a topological superconductor.« less

  10. Cu-induced localization in the Fe-based superconductor FeTe0.5Se0.5

    NASA Astrophysics Data System (ADS)

    Wen, Jinsheng; Xu, Zhijun; Zhang, Cheng; Matsuda, Masa; Sobolev, Oleg; Park, Jitae; Bourret, Edith; Lee, Dunghai; Li, Qiang; Gu, Genda; Xu, Guangyong; Tranquada, John; Birgeneau, Robert

    2013-03-01

    We report neutron scattering and resistivity results on the Cu-substitution effects in FeTe0.5Se0.5 with a Tc of ~15 K. With a 2 % Cu substitution, the Tc is reduced to 8 K, and for Fe0.9Cu0.1Te0.5Se0.5, it is not superconducting. In Fe0.9Cu0.1Te0.5Se0.5, the low-energy magnetic excitations around the in-plane wave vector (0.5, 0.5) is greatly enhanced. Upon heating, the magnetic scattering is weakened, which is different from the temperature dependences of the Cu-free and 2 % Cu-doped sample. The spectral weight reduction upon warming decreases with increasing energy in the 10 % Cu-doped sample. We take these as evidences that Cu drives the system towards localization, which is confirmed by our resistivity data. These observations probably explain why superconductivity is absent in the Cu-doped BaFe2As2 system and demonstrate the inadequacy of the rigid-band shift model on the substitution effects of the 3 d transition metals. The work is supported by the U.S. Department of Energy.

  11. Fully gapped superconductivity in In-doped topological crystalline insulator Pb0.5Sn0.5Te

    NASA Astrophysics Data System (ADS)

    Du, Guan; Du, Zengyi; Fang, Delong; Yang, Huan; Zhong, R. D.; Schneeloch, J.; Gu, G. D.; Wen, Hai-Hu

    2015-07-01

    Superconductors derived from topological insulators and topological crystalline insulators by chemical doping have long been considered to be candidates as topological superconductors. Pb0.5Sn0.5Te is a topological crystalline insulator with mirror symmetry protected surface states on (001)-, (011)-, and (111)-oriented surfaces. The superconductor (Pb0.5Sn0.5 )0.7In0.3Te is produced by In doping in Pb0.5Sn0.5Te , and is thought to be a topological superconductor. Here we report scanning tunneling spectroscopy measurements of the superconducting state as well as the superconducting energy gap in (Pb0.5Sn0.5 )0.7In0.3Te on a (001)-oriented surface. The spectrum can be well fitted by an anisotropic s -wave gap function of Δ (θ )=0.72 +0.18 cos4 θ meV using Dynes model. The results show that the superconductor seems to be a fully gapped one without any in-gap states, in contradiction with the expectation of a topological superconductor.

  12. Surface magnetic disorder in nanostructured Ni 0.5Zn 0.5Fe 2O 4 particles

    NASA Astrophysics Data System (ADS)

    Nedkov, I.; Vandenberghe, R. E.; Zaleski, A.

    2010-09-01

    Nanostructured ferroxide particles with initial formula Ni 0.5Zn 0.5Fe 2O 4 are investigated. The aim was to explore the monodomain and the superparamagnetic states of the ferrospinel and the impact of the surface magnetic disorder on the magnetization processes. Mössbauer spectroscopy (MöS) demonstrated that the ion distribution follows the general formula (Zn 0.5Fe 0.5) A[Ni 0.5Fe 1.5] BO 4, where A is the tetrahedral and B, the octahedral sublattice. MöS in an external magnetic field (5 T) at 4.2 K shows non-collinearity of the sublattices' magnetic moments and deviations in the hyperfine magnetic field that could be related to a canting effect. Magnetic measurements were applied to characterize the temperature behavior of the magnetic properties and the a.c. complex magnetic susceptibility.

  13. Acceptor diffusion and segregation in (AlxGa1-x)0.5In0.5P heterostructures

    NASA Astrophysics Data System (ADS)

    Grillot, P. N.; Stockman, S. A.; Huang, J. W.; Bracht, H.; Chang, Y. L.

    2002-04-01

    Acceptor segregation is investigated as a function of compositional difference, Δx, between adjacent layers in (AlxGa1-x)0.5In0.5P heterostructures. Magnesium, Zn, Be, and Mn acceptor species are all shown to segregate out of the high band gap Al-rich (AlxGa1-x)0.5In0.5P layers and into the low band gap Al-poor (AlxGa1-x)0.5In0.5P layers during high temperature epitaxial growth of such heterostructures. The observed acceptor segregation appears to be independent of growth method or dopant incorporation method (metalorganic chemical vapor deposition, gas source molecular-beam epitaxy, or ion implantation), and increases with increasing compositional difference between adjacent (AlxGa1-x)0.5In0.5P layers. A theoretical model is developed to describe acceptor segregation based on charge separation and the resulting electric field across the heterointerface, and the resulting acceptor segregation is shown to vary as (mh AL*/mh CL*)3/2 exp(ΔEV/kT) where mh AL* and mh CL* are the hole effective masses in the active layer and confining layer, and ΔEV is the valence band offset. Comparison between experimentally measured and theoretically predicted acceptor segregation ratios gives excellent agreement for (AlxGa1-x)0.5In0.5P heterostructures over the range of compositional differences from Δx=0.12 to Δx=0.93.

  14. Structure and dielectric dispersion in cubic-like 0.5K0.5Na0.5NbO3-0.5Na1/2Bi1/2TiO3 ceramic

    NASA Astrophysics Data System (ADS)

    Liu, Laijun; Knapp, Michael; Schmitt, Ljubomira Ana; Ehrenberg, Helmut; Fang, Liang; Fuess, Hartmut; Hoelzel, Markus; Hinterstein, Manuel

    2016-05-01

    The nature of the cubic-like state in the lead-free piezoelectric ceramics 0.5K0.5Na0.5NbO3-0.5Na1/2Bi1/2TiO3 (KNN-50BNT) has been examined in detail by synchrotron x-ray diffraction (SD), selected-area electron diffraction (SAED), neutron diffraction (ND), and temperature-dependent dielectric characterization. The SD pattern of KNN-50BNT presents a pure perovskite structure with pseudocubic symmetry. However, superlattice reflections were observed by SAED and completely indexed by tetragonal symmetry with P4bm space group in ND pattern. The relaxor behavior of KNN-50BNT is compared with Pb-based and Ba-based relaxors and discussed in the framework of the Vogel-Fulcher law and the new glass model. The KNN-50BNT ceramic exhibits the strongest dielectric dispersion among them.

  15. Giant strain in lead-free piezoceramics Bi0.5Na0.5TiO3-BaTiO3-K0.5Na0.5NbO3 system

    NASA Astrophysics Data System (ADS)

    Zhang, Shan-Tao; Kounga, Alain Brice; Aulbach, Emil; Ehrenberg, Helmut; Rödel, Jürgen

    2007-09-01

    Piezoelectric actuators convert electrical into mechanical energy and are implemented for many large-scale applications such as piezoinjectors and ink jet printers. The performance of these devices is governed by the electric-field-induced strain. Here, the authors describe the development of a class of lead-free (0.94-x)Bi0.5Na0.5TiO3-0.06BaTiO3-xK0.5Na0.5NbO3 ceramics. These can deliver a giant strain (0.45%) under both unipolar and bipolar field loadings, which is even higher than the strain obtained with established ferroelectric Pb(Zr ,Ti)O3 ceramics and is comparable to strains obtained in Pb-based antiferroelectrics.

  16. Studies on the structural, electrical and magnetic properties of LaCrO{sub 3}, LaCr{sub 0.5}Cu{sub 0.5}O{sub 3} and LaCr{sub 0.5}Fe{sub 0.5}O{sub 3} by sol–gel method

    SciTech Connect

    Nithya, V.D.; Jacob Immanuel, R.; Senthilkumar, S.T.; Sanjeeviraja, C.; Perelshtein, I.; Zitoun, D.; Kalai Selvan, R.

    2012-08-15

    Highlights: ► LaCr{sub 0.5}M{sub 0.5}O{sub 3} (M = Cr{sup 3+}, Cu{sup 2+} and Fe{sup 3+}) was synthesized by simple sol–gel technique with subsequent heat treatment. ► The compound formation temperature was optimized through XRD analysis. ► The effects of Cu{sup 2+} and Fe{sup 3+} on the electrical properties of LaCrO{sub 3} were studied using impedance spectroscopy. ► The temperature dependence of electrical conductivity was discussed for LaCr{sub 0.5}Cu{sub 0.5}O{sub 3}. ► The magnetization was found to be enhanced in the LaCr{sub 0.5}Fe{sub 0.5}O{sub 3}. -- Abstract: The structural, electrical and magnetic properties of LaCr{sub 0.5}M{sub 0.5}O{sub 3} (M = Cr{sup 3+}, Cu{sup 2+} and Fe{sup 3+}) synthesized by a sol–gel technique were studied. The X-ray diffraction pattern shows the structure to be orthorhombic and the size of the particles is around 100 nm as seen from the TEM images. The effects of Cu{sup 2+} and Fe{sup 3+} on the electrical properties of LaCrO{sub 3} were studied using impedance spectroscopy at room temperature (RT). The properties of LaCr{sub 0.5}Cu{sub 0.5}O{sub 3} were studied over a wide range of temperature from RT to 533 K. A maximum conductivity of 1.7 × 10{sup −3} S cm{sup −1} was observed for LaCr{sub 0.5}Cu{sub 0.5}O{sub 3} at a measured temperature of 533 K. The impedance spectra indicate a negative temperature coefficient of resistance (NTCR) and also imply the conduction is through bulk of the material. The magnetic studies performed using a SQUID magnetometer interpret the antiferromagnetically ordered LaCrO{sub 3} to behave ferromagnetically on the addition of Cu{sup 2+} and Fe{sup 3+}, and the magnetization was found to be enhanced in the LaCr{sub 0.5}Fe{sub 0.5}O{sub 3}.

  17. Observation of selective surface element substitution in FeTe0.5Se0.5 superconductor thin film exposed to ambient air by synchrotron radiation spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhang, Nian; Liu, Chen; Zhao, Jia-Li; Lei, Tao; Wang, Jia-Ou; Qian, Hai-Jie; Wu, Rui; Yan, Lei; Guo, Hai-Zhong; Ibrahim, Kurash

    2016-09-01

    A systematic investigation of oxidation on a superconductive FeTe0.5Se0.5 thin film, which was grown on Nb-doped SrTiO3 (001) by pulsed laser deposition, has been carried out. The sample was exposed to ambient air for one month for oxidation. Macroscopically, the exposed specimen lost its superconductivity due to oxidation. The specimen was subjected to in situ synchrotron radiation photoelectron spectroscopy (PES) and x-ray absorption spectroscopy (XAS) measurements following cycles of annealing and argon ion etching treatments to unravel what happened in the electronic structure and composition after exposure to air. By the spectroscopic measurements, we found that the as-grown FeTe0.5Se0.5 superconductive thin film experienced an element selective substitution reaction. The oxidation preferentially proceeds through pumping out the Te and forming Fe-O bonds by O substitution of Te. In addition, our results certify that in situ vacuum annealing and low-energy argon ion etching methods combined with spectroscopy are suitable for depth element and valence analysis of layered structure superconductor materials. Project supported by the Chinese Academy of Sciences (Grant No. 1G2009312311750101) and the National Natural Science Foundation of China (Grant Nos. 11375228, 11204303, and U1332105).

  18. Superconductivity induced by In substitution into the topological crystalline insulator Pb0.5Sn0.5Te

    NASA Astrophysics Data System (ADS)

    Zhong, R. D.; Schneeloch, J. A.; Liu, T. S.; Camino, F. E.; Tranquada, J. M.; Gu, G. D.

    2014-07-01

    Indium substitution turns the topological crystalline insulator (TCI) Pb0.5Sn0.5Te into a possible topological superconductor. To investigate the effect of the indium concentration on the crystal structure and superconducting properties of (Pb0.5Sn0.5)1-xInxTe, we have grown high-quality single crystals using a modified floating-zone method and have performed systematic studies for indium content in the range 0≤x≤0.35. We find that the single crystals retain the rocksalt structure up to the solubility limit of indium (x ˜0.30). Experimental dependencies of the superconducting transition temperature (Tc) and the upper critical magnetic field (Hc2) on the indium content x have been measured. The maximum Tc is determined to be 4.7 K at x =0.30, with μ0Hc2(T =0)≈5 T.

  19. Superconductivity in (NH3) yN axFeS e0.5T e0.5

    NASA Astrophysics Data System (ADS)

    Zheng, Lu; Sakai, Yusuke; Miao, Xiao; Nishiyama, Saki; Terao, Takahiro; Eguchi, Ritsuko; Goto, Hidenori; Kubozono, Yoshihiro

    2016-11-01

    Na-intercalated FeS e0.5T e0.5 was prepared using the liquid N H3 technique, and a superconducting phase exhibiting a superconducting transition temperature (Tc) as high as 27 K was discovered. This can be called the high-Tc phase since a 21 K superconducting phase was previously obtained in (NH3) yN axFeS e0.5T e0.5 . The chemical composition of the high-Tc phase was determined to be (NH3)0.61 (4 )N a0.63 (5 )F e0.85S e0.55 (3 )T e0.44 (2 ) . The x-ray diffraction patterns of both phases show that a larger lattice constant c (i.e., FeS e0.5T e0.5 plane spacing) produces a higher Tc. This behavior is the same as that of metal-doped FeSe, suggesting that improved Fermi-surface nesting produces the higher Tc. The high-Tc phase converted to the low-Tc phase within several days, indicating that it is a metastable phase. The temperature dependence of resistance for both phases was recorded at different magnetic fields, and the critical fields were determined for both phases. Finally, the Tc versus c phase diagram was prepared for the metal-doped FeS e0.5T e0.5 , which is similar to that of metal-doped FeSe, although the Tc is lower.

  20. Special Quasirandom Structures to Study the (K0.5Na0.5)NbO3 Random Alloy

    DTIC Science & Technology

    2014-07-31

    After drying for 20 h, the powders were calcined at 950 ◦C for 5 h. The composition and phase purity of the specimen were verified using a Siemens Model...taken for the calcined (K0.5Na0.5)NbO3 powder. The pattern indicates a single perovskite phase and is indexed based on the primitive cubic cell. 024105

  1. Solid state synthesis and characterization of bulk FeTe0.5Se0.5 superconductors

    NASA Astrophysics Data System (ADS)

    Onar, K.; Yakinci, M. E.

    2016-01-01

    FeTe0.5Se0.5 polycrystalline superconductor samples were synthesized by solid- state reaction method at different heating temperatures. The morphological and structural characterization of FeTe0 5Se0.5 samples were carried out by X-rays Diffraction, Scanning Electron Microscope and Energy Dispersive X-ray Spectroscopy. The electrical, magnetic and thermal transport properties were investigated up to 8 T by using physical property measurement system. The results reveal that the sensitivity of electrical and magnetic properties strongly depends on the heat treatment cycles. The upper critical field, Hc2(0), was determined with the magnetic field parallel to the sample surface. It gives a maximum value of 36.3 T. The lower critical field, Hc1(T), was obtained as 210, 140 and 70 Oe at 5, 8 and 12 K, respectively. The coherence length, ξ, at the zero field, was calculated to be 1.94 nm and suggested a transparent intergrain boundaries peculiarity. The μ0Hc2(0)/kBTc rate shows higher value (3.36 T/K) than the Pauli limit (1.84 T/K) which suggests unconventional nature of superconductivity for the polycrystalline FeTe0.5Se0.5 superconducting samples.

  2. Electrical Characteristics and Preparation of (Ba0.5Sr0.5)TiO3 Films by Spray Pyrolysis and Rapid Thermal Annealing

    NASA Astrophysics Data System (ADS)

    Koo, Horng-Show; Chen, Mi; Ku, Hong-Kou; Kawai, Tomoji

    2007-04-01

    Functional films of (Ba0.5Sr0.5)TiO3 on Pt (1000 Å)/Ti (100 Å)/SiO2 (2000 Å)/Si substrates are prepared by spray pyrolysis and subsequently rapid thermal annealing. Barium nitrate, strontium nitrate and titanium isopropoxide are used as starting materials with ethylene glycol as solvent. For (Ba0.5Sr0.5)TiO3 functional thin film, thermal characteristics of the precursor powder scratched from as-sprayed films show a remarkable peak around 300-400 °C and 57.7% weight loss up to 1000 °C. The as-sprayed precursor film with coffee-like color and amorphous-like phase is transformed into the resultant film with white, crystalline perovskite phase and characteristic peaks (110) and (100). The resultant films show correspondent increases of dielectric constant, leakage current and dissipation factor with increasing annealing temperatures. The dielectric constant is 264 and tangent loss is 0.21 in the resultant films annealed at 750 °C for 5 min while leakage current density is 1.5× 10-6 A/cm2 in the film annealed at 550 °C for 5 min.

  3. Synthesis and Properties of [Bi0.5(Na1-xAgx)0.5]1-yBayTiO3 Piezoelectric Ceramics

    NASA Astrophysics Data System (ADS)

    Wu, Lang; Xiao, Ding-Quan; Lin, Dun-Min; Zhu, Jian-Guo; Yu, Ping

    2005-12-01

    A new group of ABO3-type lead-free piezoelectric ceramics, [Bi0.5(Na1-xAgx)0.5]1-yBayTiO3, was developed, and the corresponding invention patent was submitted. The ceramics were synthesized by the conventional ceramic sintering technique using electronic grade raw materials, and the preparation techniques are very stable and convenient. The crystalline phase, microstructure and electric properties of the ceramics were also investigated. All the ceramics have high densities of about 5.70-5.84 g/cm3, which are more than 95% of the theoretical values. This system provides high piezoelectric performances: d33=168 pC/N, kp=0.31 when x=0.06, y=0.06. Moreover, the samples doped with a moderate amount of Mn could increase the mechanical quality factor Qm and reduce the dielectric loss \\mathop{tg}δ simultaneously. The temperature dependence of piezoelectric properties measured show that at up to 180°C, d33 can still remain 126 pC/N for [Bi0.5(Na0.96Ag0.04)0.5]0.90Ba0.10TiO3 ceramics, which has a d33 of 137 pC/N at room temperature.

  4. Anomalous reduction of the switching voltage of Bi-doped Ge{sub 0.5}Se{sub 0.5} ovonic threshold switching devices

    SciTech Connect

    Seo, Juhee; Ahn, Hyung-Woo; Shin, Sang-yeol; Cheong, Byung-ki; Lee, Suyoun

    2014-04-14

    Switching devices based on Ovonic Threshold Switching (OTS) have been considered as a solution to overcoming limitations of Si-based electronic devices, but the reduction of switching voltage is a major challenge. Here, we investigated the effect of Bi-doping in Ge{sub 0.5}Se{sub 0.5} thin films on their thermal, optical, electrical properties, as well as on the characteristics of OTS devices. As Bi increased, it was found that both of the optical energy gap (E{sub g}{sup opt}) and the depth of trap states decreased resulting in a drastic reduction of the threshold voltage (V{sub th}) by over 50%. In addition, E{sub g}{sup opt} was found to be about three times of the conduction activation energy for each composition. These results are explained in terms of the Mott delocalization effect by doping Bi.

  5. Structural transformations in high-capacity Li2Cu0.5Ni0.5O2 cathodes

    DOE PAGES

    Ruther, Rose E.; Pandian, Amaresh Samuthira; Yan, Pengfei; ...

    2017-03-09

    Cathode materials that can cycle >1 Li+ per transition metal are of substantial interest for increasing the overall energy density of lithium-ion batteries. Li2Cu0.5Ni0.5O2 has a very high theoretical capacity of ~500 mAh/g assuming both Li+ ions are cycled reversibly. The Cu2+/3+ and Ni2+/3+/4+ redox couples are also at high voltage, which could further boost the energy density of this system. Despite such promise, Li2Cu0.5Ni0.5O2 undergoes irreversible phase changes during charge (delithiation) that result in large first-cycle irreversible loss and poor long-term cycling stability. Oxygen evolves before the Cu2+/3+ or Ni3+/4+ transitions are accessed. In this contribution, X-ray diffraction, transmissionmore » electron microscopy (TEM), and transmission X-ray microscopy combined with X-ray absorption near edge structure (TXM–XANES) are used to follow the chemical and structural changes that occur in Li2Cu0.5Ni0.5O2 during electrochemical cycling. Li2Cu0.5Ni0.5O2 is a solid solution of orthorhombic Li2CuO2 and Li2NiO2, but the structural changes more closely mimic the changes that the Li2NiO2 endmember undergoes. Li2Cu0.5Ni0.5O2 loses long-range order during charge, but TEM analysis provides clear evidence of particle exfoliation and the transformation from orthorhombic to a partially layered structure. Linear combination fitting and principal component analysis of TXM–XANES are used to map the different phases that emerge during cycling ex situ and in situ. Lastly, significant changes in the XANES at the Cu and Ni K-edges correlate with the onset of oxygen evolution.« less

  6. In0.5Ga0.5As self-assembled quantum dots on GaP/Si

    NASA Astrophysics Data System (ADS)

    Song, Yuncheng

    This thesis focuses on demonstrating monolithic integration of III-V optoelectronic devices with Si by means of GaP on Si templates. Though high-quality epitaxial GaP on Si has been developed, GaP itself is not useful for most photonic applications due to its indirect bandgap. Historically, deep level impurities have allowed the realization of GaP light emitting diodes (LEDs), but these devices had low efficiency and the gain was insufficient for laser action. The lattice matched dilute nitride material Ga(NAsP) is an option for direct bandgap material on GaP, but N-related point defects make the material challenging to grow. InxGa1--xAs self-assembled quantum dots (SAQDs) grown on GaP offer another path to integration of direct-bandgap III-V material onto Si. The use of InxGa 1--xAs allows access to a wide range of bulk bandgaps (1.42-0.36 eV for x=0-1) and the potential for great flexibility in emission wavelength from visible to near-infrared. While chip-to-chip optical communication remains a goal, a range of sensing applications could also benefit from the direction integration of Si electronics with light sources. Sample growth was carried out by solid-source molecular beam epitaxy (MBE) using conditions similar to those used for the well-known case of InAs/GaAs SAQDs. SAQD formation was through Stranski--Krastanov (S-K) growth mode, as evidenced by reflection high-energy electron diffraction (RHEED) and transmission electron microscopy (TEM). Cross-sectional transmission microscopy (XTEM) with several two-beam conditions confirmed that both the SAQDs and the GaP cap layer were free of dislocations. Intense photoluminescence was visible from the quantum dots at both 80 K and room temperature to the unaided eye in ambient lighting. The photoluminescence results also showed that emission energy can be controlled by varying the In0.5Ga0.5As deposition thickness. The commercial availability of high-quality GaP/Si templates enabled research on In0.5Ga0.5As

  7. Doubling the critical current density in superconducting FeSe0.5Te0.5 thin films by low temperature oxygen annealing

    DOE PAGES

    Zhang, Cheng; Si, Weidong; Li, Qiang

    2016-11-14

    Iron chalcogenide superconducting thin films and coated conductors are attractive for potential high field applications at liquid helium temperature for their high critical current densities Jc, low anisotropies, and relatively strong grain couplings. Embedding flux pinning defects is a general approach to increase the in-field performance of superconductors. However, many effective pinning defects can adversely affect the zero field or self-field Jc, particularly in cuprate high temperature superconductors. Here, we report the doubling of the self-field Jc in FeSe0.5Te0.5 films by low temperature oxygen annealing, reaching ~3 MA/cm2. In-field performance is also dramatically enhanced. In conclusion, our results demonstrate thatmore » low temperature oxygen annealing is a simple and cost-efficient post-treatment technique which can greatly help to accelerate the potential high field applications of the iron-based superconductors.« less

  8. Synthesis and characterization of Sm0.5Ba0.5MnO3-δ as anode materials for solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Abdalla, A. M.; Radenahmad, N.; Abu Bakar, M. S.; . I. Petra, Pg M.; Azad, A. K.

    2016-03-01

    The material performance is a crucial issue in the current fuel cell technology, and for this reason we present this new series of Samarium family which can be used as electrode giving a high performance in a particular application. Sm0.5Ba0.5MnO3-δ was prepared by solid state reaction method and characterized by using X-ray diffraction (XRD), and thermogravimetric analysis (TGA). Rietveld analysis of XRD data shows that the material has an Orthorhombic crystal structure with cell parameter a = 3.883(1) Å b = 3.8742(5) Å c = 7. 762(4) Å, in the Pmmm space group. TGA analyses shows that the materials is going to decrease by 0.32%. The density of the materials was calculated from structural refinement and found to be 8.372 gm/cm3.

  9. Large electrocaloric effect in lead-free K0.5Na0.5NbO3-SrTiO3 ceramics

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

    The electrocaloric effect (ECE), i.e., the adiabatic temperature change ΔTEC, of the lead-free relaxor ferroelectric 0.85K0.5Na0.5NbO3-0.15SrTiO3 (KNN-STO) ceramics is investigated. The ECE data obtained by a direct method show the existence of a large ECE near the temperature of the dielectric permittivity maximum. Due to the high break-down electric field, a large ΔTEC exceeding 1.2 K at 300 K and 1.9 K at 340 K was observed at 159 kV/cm in a broad temperature range of 80 K. Such a high ECE response near the room temperature is comparable to that found in lead-based ceramic materials, thus making KNN-STO a strong candidate to replace lead-based materials in future electrocaloric applications.

  10. Synthesis and characterization of (Bi{sub 0.5}Ba{sub 0.5}) (Fe{sub 0.5}Ti{sub 0.5}) O{sub 3} ceramic

    SciTech Connect

    Parida, B.N.; Das, Piyush R.; Padhee, R.; Suara, D.; Mishra, A.; Rout, J.; Choudhary, R.N.P.

    2015-01-15

    Graphical abstract: Temperature variation of (a) dielectric constant (b) dielectric loss of the sample. - Highlights: • The high values of dielectric permittivity and low value of tangent loss. • It used for microwave applications. • The impedance and dielectric relaxation in the material is non exponential and non Debye-type. • Its ac conductivity obeys Jonscher universal power law. - Abstract: The polycrystalline sample of (Bi{sub 0.5}Ba{sub 0.5}) (Fe{sub 0.5}Ti{sub 0.5}) O{sub 3} (BF–BT) was prepared by a standard mixed oxide method. Analysis of room temperature XRD pattern and Raman/FTIR spectra of the compound does not exhibit any change in its crystal structure of BaTiO{sub 3} on addition of BiFeO{sub 3} in equal ratio. The surface morphology of the gold-plated sintered pellet sample recorded by SEM (scanning electron microscope) exhibits a uniform distribution of grains with less porosity. Detailed studies of nature and quantity of variation of dielectric constant, tangent loss, and polarization with temperature and frequency indicate the existence of ferroelectric phase transition at high-temperature. There is a low-temperature anti-ferromagnetic phase transition below 375 °C in the material. Detailed studies of electrical properties (impedance, modulus, etc.) of the material confirmed a strong correlation between micro-structure and properties.

  11. Pure and strong red photoluminescence from Na0.5Gd0.5TiO3: Eu ferroelectric thin films under ultraviolet light excitation

    NASA Astrophysics Data System (ADS)

    Gao, Feng; Sun, Lina; Tan, Jun; Li, Xinsheng; Liu, Dongyun; Liang, Duoqiang

    2017-02-01

    A series of novel photoluminescent ferroelectric thin films Na0.5Gd0.5TiO3: xEu (NGT: Eu) with various Eu3+ doping concentrations were prepared at various heat-treated temperature, which have single pseudo-cubic perovskite structure at proper heat-treated temperature from 700 °C to 800 °C according to X-ray diffraction results. There existed narrow and intensive emission bands located at red light region ascribed to 5D0 → 7F2 and 5D0 → 7F1 transitions of Eu3+ by 283 nm excitation. The strong energy absorption of NGT host and efficient energy transfer to Eu3+ should be primarily responsible for the emissions. Gd3+ acts as sensitizer which has an important role on the energy transfer from the host NGT to Eu3+. The luminescence from NGT: 0.25Eu thin films is the strongest for all the NGT: Eu films, and its color coordinate is (0.65, 0.32) close to ideal red light. The quenching concentration in NGT: Eu films reaches as high as 25%. The lifetime of emissive energy level Eu3+: 5D0 in NGT: 0.1Eu and NGT: 0.5Eu thin films is 1.024 ms and 0.931 ms, respectively. Finally, the ferroelectric property of NGT: 0.25Eu thin films was tested and the remanent polarization (2Pr) is 7.10 μC/cm2 lower than that of Na0.5Bi0.5TiO3.

  12. Excess Conductivity Analysis of (Cu0.5Tl0.5)-1223 Substituted by Pr and La

    NASA Astrophysics Data System (ADS)

    Abou-Aly, A. I.; Awad, R.; Kamal, M.; Anas, M.

    2011-05-01

    Series of superconducting samples of type Cu0.5Tl0,5 Ba2Ca2- y R y Cu3O10- δ , where R=Pr and La with 0≤ y≤0.20, were prepared in a sealed quartz tube via a single-step solid-state reaction technique. The prepared samples were characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM), and electron dispersive X-ray (EDX). XRD studies indicated that the tetragonal structure of (Cu0.5Tl0.5)-1223 phase does not change by Pr or La-substitutions whereas the lattice parameters a and c do. The elemental compositions analysis, determined from EDX, indicated that both Pr and La were successfully introduced into the microstructure of (Cu0.5Tl0.5)-1223 phase. The electrical resistivity ρ( T) was measured as a function of temperature using conventional dc four-probe technique. The fluctuation conductivity Δ σ, above the superconducting transition temperature T c, was analyzed as a function of temperature using Aslamazov and Larkin model. It exhibits four different fluctuation regions namely critical (cr), three-dimensional (3D), two-dimensional (2D), and short-wave (sw). The zero-temperature coherence length, effective layer thickness of the two-dimensional system and inter-layer coupling strength were estimated as a function of the substitution-content y. Furthermore, the thermodynamics critical field, lower critical magnetic field, upper critical magnetic field, critical current density and Fermi energy were calculated from the Ginzburg number. The data indicated that both Pr and La-substitutions have quite similar behaviors.

  13. Temperature- and magnetic-field-induced magnetization reversal in perovskite YFe0.5Cr0.5O3

    NASA Astrophysics Data System (ADS)

    Mao, Jinhua; Sui, Yu; Zhang, Xingquan; Su, Yantao; Wang, Xianjie; Liu, Zhiguo; Wang, Yi; Zhu, Ruibin; Wang, Yang; Liu, Wanfa; Tang, Jinke

    2011-05-01

    Perovskite YFe0.5Cr0.5O3 exhibits magnetization reversal at low applied fields due to the competition between the single ion magnetic anisotropy and the antisymmetric Dzyaloshinsky-Moriya interaction. Below a compensation temperature (Tcomp), a tunable bipolar switching of magnetization is demonstrated by changing the magnitude of the field while keeping it in the same direction. The present compound also displays both normal and inverse magnetocaloric effects above and below 260 K, respectively. These phenomena coexisting in a single magnetic system can be tuned in a predictable manner and have potential applications in electromagnetic devices.

  14. Photogalvanic effects for interband transition in p-Si0.5Ge0.5/Si multiple quantum wells

    NASA Astrophysics Data System (ADS)

    Wei, C. M.; Cho, K. S.; Chen, Y. F.; Peng, Y. H.; Chiu, C. W.; Kuan, C. H.

    2007-12-01

    Circular photogalvanic effect (CPGE) and linear photogalvanic effect for interband transition have been observed simultaneously in Si0.5Ge0.5/Si multiple quantum wells. The signature of the CPGE is evidenced by the change of its sign upon reversing the radiation helicity. It is found that the observed CPGE photocurrent is an order of magnitude greater than that obtained for intersubband transition. The dependences of the CPGE on the angle of incidence and the excitation intensities can be well interpreted based on its characteristics. The large signal of spin generation observed here at room temperature should be very useful for the realization of practical application of spintronics.

  15. A new Bi{sub 0.5}Na{sub 0.5}TiO{sub 3} based lead-free piezoelectric system with calculated end-member Bi(Zn{sub 0.5}Hf{sub 0.5})O{sub 3}

    SciTech Connect

    Liu, Feng; Wahyudi, Olivia; Li, Yongxiang

    2014-03-21

    The phase structure, dielectric and piezoelectric properties of a new lead-free piezoelectric system (1 − x)Bi{sub 0.5}Na{sub 0.5}TiO{sub 3}–xBi(Zn{sub 0.5}Hf{sub 0.5})O{sub 3} [(1 − x)BNT–xBZH, x = 0, 0.01, 0.02, 0.03, and 0.04] were investigated. The structure of Bi(Zn{sub 0.5}Hf{sub 0.5})O{sub 3} was calculated using first-principles method and (1 − x)BNT–xBZH ceramics were fabricated by conventional solid-state process. At room temperature, a morphotropic phase boundary (MPB) from rhombohedral to pseudocubic is identified near x = 0.02 by the analysis of X-ray diffraction patterns. The ceramics with MPB near room temperature exhibit excellent electrical properties: the Curie temperature, maximum polarization, remnant polarization, and coercive field are 340 °C, 56.3 μC/cm{sup 2}, 43.5 μC/cm{sup 2}, and 5.4 kV/mm, respectively, while the maximum positive bipolar strain and piezoelectric coefficient are 0.09% and 92 pC/N, respectively. In addition, a linear relationship between the MPB phase boundary composition and the calculated tetragonality of non-BNT end-member was demonstrated. Thus, this study not only shows a new BNT-based lead-free piezoelectric system but also suggest a new way to predict the composition at MPB a priori when designing new lead-free piezoelectric system.

  16. Li(V0.5Ti0.5)S2 as a 1 V lithium intercalation electrode

    NASA Astrophysics Data System (ADS)

    Clark, Steve J.; Wang, Da; Armstrong, A. Robert; Bruce, Peter G.

    2016-03-01

    Graphite, the dominant anode in rechargeable lithium batteries, operates at ~0.1 V versus Li+/Li and can result in lithium plating on the graphite surface, raising safety concerns. Titanates, for example, Li4Ti5O12, intercalate lithium at~1.6 V versus Li+/Li, avoiding problematic lithium plating at the expense of reduced cell voltage. There is interest in 1 V anodes, as this voltage is sufficiently high to avoid lithium plating while not significantly reducing cell potential. The sulfides, LiVS2 and LiTiS2, have been investigated as possible 1 V intercalation electrodes but suffer from capacity fading, large 1st cycle irreversible capacity or polarization. Here we report that the 50/50 solid solution, Li1+x(V0.5Ti0.5)S2, delivers a reversible capacity to store charge of 220 mAhg-1 (at 0.9 V), 99% of theoretical, at a rate of C/2, retaining 205 mAhg-1 at C-rate (92% of theoretical). Rate capability is excellent with 200 mAhg-1 at 3C. C-rate is discharge in 1 h. Polarization is low, 100 mV at C/2. To the best of our knowledge, the properties/performances of Li(V0.5Ti0.5)S2 exceed all previous 1 V electrodes.

  17. Investigation of the origin of glassiness in La0.5Sr0.5CoO3

    NASA Astrophysics Data System (ADS)

    Manna, Kaustuv; Elizabeth, Suja; Anil Kumar, P. S.

    2013-05-01

    A comprehensive magnetic study has been carried out on the two sets of La0.5Sr0.5CoO3 samples with a view to understand the origin of low temperature glassiness in the ferromagnetic state. The samples prepared by the conventional solid-state synthesis method show a low temperature shoulder in both dc magnetization as well as in the ac susceptibility measurements, which exhibit characteristics of glassiness such as the frequency dependence and memory effect. These observations suggest the existence of a distinct low temperature cluster-glass like phase within dominant ferromagnetic phase. But, once the same sample is properly homogenized by repeated grinding and annealing process, the low temperature glassy phase disappears, and it shows a pure ferromagnetic behavior. Our comparative study clearly reveals that the reentrant spin-glass like nature is not intrinsic to La0.5Sr0.5CoO3 system, in fact this is an outcome of the compositional inhomogeneity.

  18. Spin-reorientation and weak ferromagnetism in antiferromagnetic TbMn0.5Fe0.5O3

    NASA Astrophysics Data System (ADS)

    Nhalil, Hariharan; Nair, Harikrishnan S.; Sanathkumar, R.; Strydom, André M.; Elizabeth, Suja

    2015-05-01

    Orthorhombic single crystals of TbMn0.5Fe0.5O3 are found to exhibit spin-reorientation, magnetization reversal, and weak ferromagnetism. Strong anisotropy effects are evident in the temperature dependent magnetization measurements along the three crystallographic axes a, b, and c. A broad magnetic transition is visible at TN Fe / Mn = 286 K due to paramagnetic to AxGyCz ordering. A sharp transition is observed at TS R Fe / Mn = 28 K , which is pronounced along c axis in the form of a sharp jump in magnetization where the spins reorient to GxAyFz configuration. The negative magnetization observed below TS R Fe / Mn along c axis is explained in terms of domain wall pinning. A component of weak ferromagnetism is observed in field-scans along c-axis but below 28 K. Field-induced steps-like transitions are observed in hysteresis measurement along b axis below 28 K. It is noted that no sign of Tb-order is discernible down to 2 K. TbMn0.5Fe0.5O3 could be highlighted as a potential candidate to evaluate its magneto-dielectric effects across the magnetic transitions.

  19. Dielectric Properties in the Microwave Range of K0.5Na0.5NbO3 Ceramics

    NASA Astrophysics Data System (ADS)

    Gao, Lu; Zhou, Wancheng; Luo, Fa; Zhu, Dongmei

    2017-01-01

    Dielectric properties of a potassium sodium niobate (KNN) system in the microwave range up to GHz have rarely been studied. Since K0.5Na0.5NbO3 is the most common and typical type of KNN materials, non-doped K0.5Na0.5 NbO3 ceramics were synthesized at different temperatures (1080°C, 1090°C, 1100°C, and 1110°C) by a traditional solid reaction method for further characterization and analysis. The ceramics were in perovskite phase with orthorhombic symmetry. A small quantity of second phase was found in the 1110°C sintered specimen, which resulted from the volatilization of alkali oxides as the temperature increased. The complex permittivity was measured for the first time in the microwave range (8.2-12.4 GHz) and in the temperature range from 100°C to 220°C, and the effects of annealing on the dielectric properties were studied. The results indicate that the complex permittivity of KNN ceramics over the microwave range increases mainly due to high bulk density and the additional dielectric contributions of oxygen vacancies at high temperature.

  20. Critical behavior and spontaneous magnetization estimation in La0.5Sr0.5MnO3 compound

    NASA Astrophysics Data System (ADS)

    Hazzez, M.; Ihzaz, N.; Boudard, M.; Oumezzine, M.

    2015-07-01

    We report the critical behavior in La0.5Sr0.5MnO3 perovskite oxide manganite using methods including modified Arrott plot, Kouvel-Fisher plot, and critical isotherm analysis. By means of the above techniques around the ferromagnetic-paramagnetic (FM-PM) transition, the magnetic data analyzed shows the sample attending the second-order magnetic phase transition with the critical parameters β = 0.553±0.020 with TC=352.02±0.63 K (from the spontaneous magnetization MS(T) below TC) and γ =1.169±0.058 with TC=352.49±0.85 K (from the inverse initial susceptibility χ 0 - 1 (T) above TC). The exponent δ =3,216 independently obtained from the critical magnetization isotherm satisfies the Widom scaling relation δ = 1 + β / γ . Moreover, the critical exponents are in the theoretically expected values for mean-field interaction model rather than the other universal theory and also follow the single scaling equation of M (H , ε)ε-β =f± (H /ε β + γ) . Furthermore, to estimate the spontaneous magnetization of La0.5Sr0.5MnO3 perovskite, we used the magnetic entropy change (-ΔSM), obtained from isothermal magnetization. The results of this approach are compared to results obtained from classical analysis using Arrott curves.

  1. Fabrication by Annealing at Approximately 1030°C and Electrical Characterization of Lead-Free (1 - x)Bi0.5K0.5TiO3-xBa(Fe0.5Nb0.5)0.05Ti0.95O3 Piezoelectric Ceramics

    NASA Astrophysics Data System (ADS)

    Truong-Tho, N.; Nghi-Nhan, N. T.

    2017-03-01

    Sintered (1 - x)Bi0.5K0.5TiO3-xBa(Fe0.5Nb0.5)0.05Ti0.95O3 [(1 - x)BKT-xBFNT] piezoelectric ceramics have been fabricated by conventional annealing at 1000°C to 1050°C. X-ray diffraction (XRD) analysis revealed that the 0.9BKT-0.1BFNT ceramic sintered at 1030°C showed high transition temperature of T C = 514°C due to presence of Bi4Ti3O12 in solid solution. Although the P-E ferroelectric loop was not yet saturated, the remanent polarization and coercive electric field of the 0.9BKT-0.1BFNT showed good values of P r = 18.5 μC/cm2 and E c = 4.3 kV/cm, respectively. The piezoelectric parameters of the ceramic included planar-mode electromechanical coupling factor of k p = 0.17 and mechanical quality factor of Q m = 145, larger than the values of 0.17 and 57, respectively, obtained for BKT ceramic.

  2. The preparation of high-J c Gd0.5Y0.5Ba2Cu3O7-δ thin films by the MOCVD process

    NASA Astrophysics Data System (ADS)

    Zhao, R. P.; Zhang, F.; Liu, Q.; Xia, Y. D.; Lu, Y. M.; Cai, C. B.; Tao, B. W.; Li, Y. R.

    2016-06-01

    A home-designed metal organic chemical vapor deposition (MOCVD) system has been employed to prepare high critical current density (J c) Gd0.5Y0.5Ba2Cu3O7-δ (GdYBCO) thin films on LaMnO3/epitaxial MgO/ion beam assisted deposition (IBAD)-MgO/solution deposition planarization (SDP)-Y2O3-buffered Hastelloy tapes; the thin films were directly heated by the Joule effect after applying an heating current (I h ) through the Hastelloy tapes. The effect of the mole ratio of the metal organic sources has been systematically investigated. X-ray diffraction (XRD) and scanning electron microscope (SEM) analyses indicated that the GdYBCO films crystallized better and became denser with the increasing of the Cu/Ba ratio from 1.0 to 1.1, yielding a J c at 77 K and 0 T of 200 nm GdYBCO film increasing from 2.5 MA cm-2 to 7 MA cm-2. In addition, SEM and energy dispersive spectrometer (EDS) characterizations revealed that more and more outgrowths appeared and the density of the film was reduced with an increase in the Cu/Ba ratio from 1.1 to 1.2. When the I h was 26.8 A and the mole ratio of Gd(tmhd)3, Y(tmhd)3, Ba(tmhd)2 and Cu(tmhd)2 in the precursor was 0.55:0.55:2:2.2, the critical current (I c) of the deposited 200 nm-thick GdYBCO film reached a 140 A cm-1 width (77 K, 0 T), corresponding to the J c 7 MA cm-2 (77 K, 0 T).

  3. Structural state of relaxor ferroelectrics PbSc0.5Ta0.5O3 and PbSc0.5Nb0.5O3 at high pressures up to 30 GPa

    NASA Astrophysics Data System (ADS)

    Maier, B. J.; Waeselmann, N.; Mihailova, B.; Angel, R. J.; Ederer, C.; Paulmann, C.; Gospodinov, M.; Friedrich, A.; Bismayer, U.

    2011-11-01

    The pressure-induced structural changes in perovskite-type (ABO3) Pb-based relaxor ferroelectrics are studied on the basis of in situ single-crystal synchrotron x-ray diffraction and Raman scattering experiments on PbSc0.5Ta0.5O3 and PbSc0.5Nb0.5O3 conducted under hydrostatic conditions up to 30 GPa. Complementary density functional theory calculations have been performed to compare the stability of various atomic configurations for both compounds at high pressures. By combining the experimental and theoretical results, the following sequence of structural transformations is proposed. At a characteristic pressure p1 the mesoscopic polar order is violated and a local antipolar order of Pb atoms as well as quasidynamical long-range order of antiphase octahedral tilts is developed. These structural changes facilitate the occurrence of a continuous phase transition at pc1>p1 from cubic to a nonpolar rhombohedral structure comprising antiphase octahedral tilts of equal magnitude (a-a-a-). At a characteristic pressure p2>pc1 the octahedral tilts around the cubic [100], [010], and [001] directions become different from each other on the mesoscopic scale. The latter precedes a second phase transition at pc2, which involves long-range order of Pb antipolar displacements along cubic [uv0] directions and a compatible mixed tilt system (a+b-b-) or long-range ordered antiphase tilts with unequal magnitudes (a0b-b-) without Pb displacement ordering. The phase-transition pattern at pc2 depends on the fine-scale degree of chemical B-site order in the structure.

  4. Magnetic properties and magnetocaloric effect in Ni0.5Mn0.5-xSb x alloys

    NASA Astrophysics Data System (ADS)

    Duc, N. H.; Thanh, T. D.; Yen, N. H.; Thanh, P. T.; Dan, N. H.; Phan, T. L.

    2012-02-01

    Ni0.5Mn0.5- x Sb x ( x = 0.1, 0.2, 0.3, and 0.4) ingots fabricated by arc-melting high-pure metals have been studied to determine their structure and magnetic properties and to identify the magnetocaloric effect. X-ray diffraction analyses reveal that the sample with x = 0.2 is close to a single phase in a cubic structure while the others have the secondary phases. This influences strongly the magnetic properties of Ni0.5Mn0.5- x Sb x . With increasing Sb content, the Curie temperature ( T C ) increases from ˜210 (for x = 0.1) to 435 K (for x = 0.4). Among the studied alloys, two samples, x = 0.2 and 0.3, have the greatest saturation magnetization values, which were recorded at 300 K. Under an applied field of 12.0 kOe, the maximum magnetic entropy changes are about 1.0 and 0.5 J.kg-1·K-1 for x = 0.2 and 0.3, respectively. Detailed analyses related to isothermal M-H curves in the vicinity of T C by using the modified Arrott method reveal that these samples undergo a second-order phase transition with critical exponents of β = 0.40 ± 0.01 and γ = 1.27 ± 0.08 for x = 0.2 and of β = 0.69 ± 0.09 and γ = 0.85 ± 0.10 for x = 0.3. The differences in the critical parameters are likely related to the presence of Ni-related secondary phases.

  5. Suppressed 3D conductivity in Mn doped Cu0.5Tl0.5Ba2Ca2-yMnyCu3O10-δ superconductors

    NASA Astrophysics Data System (ADS)

    Qurat-ul-Ain, Khan, Nawazish A.

    2013-04-01

    We have synthesised Mn-doped Cu0.5Tl0.5Ba2(Ca2-yMny)Cu3O10-δ superconducting samples and studied their Fluctuation Induced Conductivity (FIC) analysis. The Tc(R = 0) and magnitude of diamagnetism are suppressed with increased Mn-doping in the final compound. FIC analyses have shown a suppression of 3D Lawrence and Doniach (LD) regime and a significant enhancement of 2D LD regime of Mn-doping of y = 0.35. In the sample with Mn-doping of y = 0.5, the 3D LD regime vanishes altogether and only 2D LD regime is observed, showing the confinement of superconductivity in the two dimensional planes. The coherence length along the c-axis and the Fermi velocity of the carriers are suppressed with increased Mn doping. Using the Ginzburg-Landau (GL) number [NG] and GL equations, the thermodynamic critical magnetic field Bc(0), the lower critical field Bc1(0), the upper critical field Bc2(0), the critical current density Jc(0), and penetration depth λp.d are determined. The values of critical fields Bc(0) and Bc1(0) increases, despite suppression in the Tc(R = 0) with increased Mn-doping. The values of Jc(0), the penetration depth Λp.d, and inter-layer coupling are suppressed with enhanced Mn-doping. These observations suggested that Mn ions act as sub-nano-scale pinning centers between the CuO2 planes and their presence at the Ca-sites promote the de-coupling of CuO2 planes.

  6. High-performance FeSe0.5Te0.5 thin films fabricated on less-well-textured flexible coated conductor templates

    NASA Astrophysics Data System (ADS)

    Xu, Zhongtang; Yuan, Pusheng; Ma, Yanwei; Cai, Chuanbing

    2017-03-01

    We report on the transport properties of FeSe0.5Te0.5 (FST) thin films fabricated on less-well-textured flexible coated conductor templates with LaMnO3 (LMO) as buffer layers using pulsed laser deposition. The LMO buffer layers exhibit large in-plane misalignment of ˜7.72°, which is unfavorable for cuprate-coated conductors due to the high grain boundaries. The FST thin films show a superconducting transition temperature of 16.8 K, higher than that of bulk materials due to the compressive strain between LMO and FST. Atomic force microscopy observations reveal that island-like features appear at the surfaces of both LMO and FST, confirming the island growth mode. A self-field transport critical-current density of up to 0.43 MA cm-2 at 4.2 K has been observed in FST thin films, which is much higher than that in powder-in-tube processed FST tapes. The films are capable of carrying current densities of over 105 A cm-2 in the whole applied magnetic field up to 9 T, showing great potential for high-field applications. The results indicate that, for FST, highly textured metal tapes are not needed to produce coated conductors with high performance, which is of great advantage over cuprate-coated conductors.

  7. Magnetic anisotropy and interlayer coupling in Fe{sub 0.5}Co{sub 0.5}(100) films on GaAs(100)

    SciTech Connect

    Pechan, Michael J.; Compton, Robert L.; Bennett, Douglas; Chen, L. C.; Palmstrom, C. J.; Allen, S. James

    2001-06-01

    Epitaxial Fe{sub 0.5}Co{sub 0.5}(100) films have been grown via MBE on GaAs (100) at reduced temperatures in order to minimize interfacial reactions. In-plane magnetization measurements reveal an overall twofold anisotropy superimposed with a fourfold component. Ferromagnetic resonance (FMR) measurements as a function of in-plane angle confirmed the mixed anisotropy state and provided energy densities of {minus}2.4{times}10{sup 5}erg/cm{sup 3} and {minus}2.2{times}10{sup 5}erg/cm{sup 3} for the twofold and fourfold terms, respectively. Two FeCo/InAs/FeCo trilayer samples were prepared to examine interlayer coupling effects. The samples differed in growth temperature (95{degree}C and 150{degree}C) of the InAs layer. FMR shows evidence for interlayer coupling in the 95{degree}C, but not the 150{degree}C sample. {copyright} 2001 American Institute of Physics.

  8. High performance FeSe0.5Te0.5 thin films grown at low temperature by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Yuan, Pusheng; Xu, Zhongtang; Zhang, Haitao; Wang, Dongliang; Ma, Yanwei; Zhang, Ming; Li, Jianqi

    2015-06-01

    We report on fully epitaxial FeSe0.5Te0.5 (FST) thin films of high quality grown on CaF2 (00l) substrate at a low temperature of 300 °C by pulsed laser deposition. The transport Jc of thin films is up to 1.36 MA cm-2 in self-field and 0.97 MA cm-2 in 9 T at 4.2 K, indicating very weak field dependence. A near isotropy of Jc (γ = JcH//ab/JcH//c) as low as 1.09 at 9 T is achieved in the FST thin films. Moreover, there is no clear amorphous interfacial layer between the film and the substrate, probably due to low temperature and low laser repetition rate, while the thickness of the reaction layer is approximate 5 nm in many other works. The transmission electron microscopy evidence shows that some lattices with lateral size <5 nm × 20 nm seem to be disturbed. These location defects are thought to be responsible for the nearly isotropic behavior of the superconductivity.

  9. MOCVD-derived multilayer Gd0.5Y0.5Ba2Cu3O7-δ films based on a novel heating method

    NASA Astrophysics Data System (ADS)

    Zhao, Ruipeng; Zhang, Fei; Liu, Qing; Xia, Yudong; Lu, Yuming; Cai, Chuanbing; Xiong, Jie; Tao, Bowan; Li, Yanrong

    2017-02-01

    Multilayer Gd0.5Y0.5Ba2Cu3O7-δ (GdYBCO) films have been deposited by the metal organic chemical vapor deposition process on LaMnO3/epitaxial MgO/ion beam assisted deposition (IBAD)-MgO/solution deposition planarization-Y2O3-buffered Hastelloy tapes. The buffered tapes were heated by the Joule effect after applying a heating current (I h) through the Hastelloy metal substrates. For this kind of current heating method, the heating energy is transmitted from the Hastelloy metal substrate to the oxide buffer layers, thereby the surface temperature of the tape will decline with an increase in the thickness of the deposited GdYBCO film if the heating current is unchanged. Therefore, the multilayer GdYBCO film structure where I h was adjusted for each layer was adopted to make sure that the surface temperature was always high enough to deposit purely c-axis oriented GdYBCO films. With this method, four-layer 1000 nm thick GdYBCO films were successfully prepared and the critical current (I c) reached 328 A cm-1 width (77 K, 0 T), corresponding to the critical current density (J c) of 3.28 MA cm-2 (77 K, 0 T).

  10. Effect of nanostructured carbon coatings on the electrochemical performance of Li1.4Ni0.5Mn0.5O2+ x-based cathode materials

    PubMed Central

    Kurilenko, Konstantin A; Brylev, Oleg A; Petukhov, Dmitry I; Garshev, Alexey V

    2016-01-01

    Nanocomposites of Li1.4Ni0.5Mn0.5O2+ x and amorphous carbon were obtained by the pyrolysis of linear and cross-linked poly(vinyl alcohol) (PVA) in presence of Li1.4Ni0.5Mn0.5O2+ x. In the case of linear PVA, the formation of nanostructured carbon coatings on Li1.4Ni0.5Mn0.5O2+ x particles is observed, while for cross-linked PVA islands of mesoporous carbon are located on the boundaries of Li1.4Ni0.5Mn0.5O2+ x particles. The presence of the carbon framework leads to a decrease of the polarization upon cycling and of the charge transfer resistance and to an increase in the apparent Li+ diffusion coefficient from 10−16 cm2·s−1 (pure Li1.4Ni0.5Mn0.5O2+ x) to 10−13 cm2·s−1. The nanosized carbon coatings also reduce the deep electrochemical degradation of Li1.4Ni0.5Mn0.5O2+ x during electrochemical cycling. The nanocomposite obtained by the pyrolysis of linear PVA demonstrates higher values of the apparent lithium diffusion coefficient, a higher specific capacity and lower values of charge transfer resistance, which can be related to the more uniform carbon coatings and to the significant content of sp2-hybridized carbon detected by XPS and by Raman spectroscopy. PMID:28144544

  11. Zr and Sn substituted (Na0.5Bi0.5)TiO3 -based solid solutions

    NASA Astrophysics Data System (ADS)

    Ishchuk, V. M.; Gusakova, L. G.; Kisel, N. G.; Kuzenko, D. V.; Spiridonov, N. A.; Sobolev, V. L.

    2016-02-01

    The paper attempts to investigate the phase formation of a Zr- and Sn-substituted [(Na0.5Bi0.5)0.80Ba0.20](Ti1-yBy)O3 system during its solid state synthesis. The synthesis was found to be a multi-step process associated with the formation of a number of intermediate phases which however depended on the compositions and sintering temperatures. Single phase solid solutions were obtained when the sintering temperature was increased to 1000 °C-1100 °C. Increase in the concentration of substituting ions, on the one hand, tends to linearly increase the crystal cell size whereas the tolerance factor, on the other hand, gets reduced bolstering the stability of anti-ferroelectric phase as compared to that of ferroelectric phase’.

  12. Pressure-induced superconductivity in Ba0.5Sr0.5Fe2As2.

    PubMed

    Tsoi, Georgiy M; Malone, Walter; Uhoya, Walter; Mitchell, Jonathan E; Vohra, Yogesh K; Wenger, Lowell E; Sefat, Athena S; Weir, S T

    2012-12-12

    High-pressure electrical resistance measurements have been performed on single crystal Ba(0.5)Sr(0.5)Fe(2)As(2) platelets to pressures of 16 GPa and temperatures down to 10 K using designer diamond anvils under quasi-hydrostatic conditions with an insulating steatite pressure medium. The resistance measurements show evidence of pressure-induced superconductivity with an onset transition temperature at ∼31 K and zero resistance at ∼22 K for a pressure of 3.3 GPa. The transition temperature decreases gradually with increasing pressure before completely disappearing for pressures above 12 GPa. The present results provide experimental evidence that a solid solution of two 122-type materials, i.e., Ba(1-x)Sr(x)Fe(2)As(2) (0 < x < 1), can also exhibit superconductivity under high pressure.

  13. Ferroelectricity and ferroelectric resistive switching in sputtered Hf0.5Zr0.5O2 thin films

    NASA Astrophysics Data System (ADS)

    Fan, Zhen; Xiao, Juanxiu; Wang, Jingxian; Zhang, Lei; Deng, Jinyu; Liu, Ziyan; Dong, Zhili; Wang, John; Chen, Jingsheng

    2016-06-01

    Ferroelectric properties and ferroelectric resistive switching (FE-RS) of sputtered Hf0.5Zr0.5O2 (HZO) thin films were investigated. The HZO films with the orthorhombic phase were obtained without capping or post-deposition annealing. Ferroelectricity was demonstrated by polarization-voltage (P-V) hysteresis loops measured in a positive-up negative-down manner and piezoresponse force microscopy. However, defects such as oxygen vacancies caused the films to become leaky. The observed ferroelectricity and semiconducting characteristics led to the FE-RS effect. The FE-RS effect may be explained by a polarization modulated trap-assisted tunneling model. Our study not only provides a facile route to develop ferroelectric HfO2-based thin films but also explores their potential applications in FE-RS memories.

  14. Exchange bias in a mixed metal oxide based magnetocaloric compound YFe0.5Cr0.5O3

    NASA Astrophysics Data System (ADS)

    Sharma, Mohit K.; Singh, Karan; Mukherjee, K.

    2016-09-01

    We report a detailed investigation of magnetization, magnetocaloric effect and exchange bias studies on a mixed metal oxide YFe0.5Cr0.5O3 belonging to perovskite family. Our results reveal that the compound is in canted magnetic state (CMS) where ferromagnetic correlations are present in an antiferromagnetic state. Magnetic entropy change of this compound follows a power law (∆SM∼Hm) dependence of magnetic field. In this compound, inverse magnetocaloric effect (IMCE) is observed below 260 K while conventional magnetocaloric effect (CMCE) above it. The exponent 'm' is found to be independent of temperature and field only in the IMCE region. Investigation of temperature and magnetic field dependence studies of exchange bias, reveal a competition between effective Zeeman energy of the ferromagnetic regions and anisotropic exchange energy at the interface between ferromagnetic and antiferromagnetic regions. Variation of exchange bias due to temperature and field cycling is also investigated.

  15. Sinterability studies on K 0.5Na 0.5NbO 3 using laser as energy source

    NASA Astrophysics Data System (ADS)

    Tian, Xiaoyong; Dittmar, Anne; Melcher, Jörg; Heinrich, Jürgen G.

    2010-08-01

    The sinterability of K 0.5Na 0.5NbO 3 (KNN) ceramics by a laser beam has been investigated in the present research. A 100 W CO 2 laser with a beam diameter of 0.6 mm has been used to sinter the KNN specimens prepared on a uniaxial pressing machine. The relations between laser power and thickness of densified layer, crystallographic structures and phase compositions have been studied. A comparison has been made between laser and furnace sintered KNN samples according to the SEM, XRD and XRF results. The possibility of KNN used for the layer-wise laser direct sintering 3D components has been confirmed in this paper.

  16. Synthesis and crystal structure of Bi6(Bi0.5Cu0.5)V2O15+y

    NASA Astrophysics Data System (ADS)

    Gupta, Akanksha; Uma, S.

    2015-10-01

    The structure of the oxide with composition Bi6(Bi0.5Cu0.5)V2O15+y has been solved based on single crystal X-ray diffraction and is found to be monoclinic (S. G. I2), a=11.276(1) Å, b=5.4513(2) Å, c=11.055(3) Å, β=96.70°(1). The crystal was twinned by 180° rotoinversion about [ 1 bar 0 1] in the direct lattice as found in the the phosphates, Bi6TiP2O16 and Bi6+xM1-xP2O15+y (M=Mn, Fe and Ni), wherein chains of edge sharing (OBi4) tetrahedral units are connected by layers of VO4 tetrahedra and (Bi/Cu)O6-x (x=oxygen vacancies) octahedra.

  17. A magnetic atomic laminate from thin film synthesis: (Mo0.5Mn0.5)2GaC

    NASA Astrophysics Data System (ADS)

    Meshkian, R.; Ingason, A. S.; Arnalds, U. B.; Magnus, F.; Lu, J.; Rosen, J.

    2015-07-01

    We present synthesis and characterization of a new magnetic atomic laminate: (Mo0.5Mn0.5)2GaC. High quality crystalline films were synthesized on MgO(111) substrates at a temperature of ˜530 °C. The films display a magnetic response, evaluated by vibrating sample magnetometry, in a temperature range 3-300 K and in a field up to 5 T. The response ranges from ferromagnetic to paramagnetic with change in temperature, with an acquired 5T-moment and remanent moment at 3 K of 0.66 and 0.35 μB per metal atom (Mo and Mn), respectively. The remanent moment and the coercive field (0.06 T) exceed all values reported to date for the family of magnetic laminates based on so called MAX phases.

  18. The mixed glass former effect in 0.5(Sodium Sulfide) + 0.5[x(Germanium Sulfide) + (1-x)PS5/2] glasses

    NASA Astrophysics Data System (ADS)

    Bischoff, Christian Michael

    The rapidly growing global energy demand, especially for energy from renewable sources, requires development of longer-lasting, safer, and smaller batteries. Ion-conducting glasses are of particular interest as candidates for solid electrolyte materials in next-generation batteries. Commercial solid-state electrolytes require an ionic conductivity of at least 10-3 S/cm. In order to meet this design constraint, development of new ion-conducting glasses is required. An increase or decrease in the ionic conductivity of glasses can be achieved by mixing two glass former cations at constant fraction of the mobile cation, known as the mixed glass former effect (MGFE). This enhancement or depression of the ionic conductivity is non-linear and non-additive, and its cause is currently unknown. The 0.5Na2S + 0.5[xGeS 2 + (1-x)PS5/2] glasses exhibit a negative MGFE in Na + ion conductivity. If the cause of this depression in the Na + ion conductivity is better understood, it may enable the design of mixed glass former systems that will exhibit enhancement of the ionic conductivity. We hypothesis that changes in short range order structures occur when the thio-phosphate and thio-germanate glass networks are mixed, causing the negative MGFE. Our comprehensive study of the glass structure and physical properties of the 0.5Na2S + 0.5[xGeS2 + (1-x)PS5/2] glasses shows that structural changes in the ternary glasses strongly correlate with the decrease in the ionic conductivity.

  19. ED cuts LWBS from 5% to 0.5%.

    PubMed

    2010-04-01

    The leaders at King's Daughters Medical Center in Ashland, KY, firmly believe that solving ED throughput problems must be the responsibility of the entire hospital. They must be on the right track. A recent initiative has slashed the rate of patients who left without being seen from 5% to 0.5%. When beds are available in the ED, presenting patients are moved there immediately and then triaged by the bed nurse. Throughput assessments are conducted hourly so that problems can be addressed immediately. When the ED is in danger of becoming overwhelmed, all department leaders are paged and direct their units to take appropriate action.

  20. Investigation of multiferroicity, spin-phonon coupling, and unusual magnetic ordering close to room temperature in LuMn0.5Fe0.5O3

    NASA Astrophysics Data System (ADS)

    Sarkar, Tanushree; Manna, Kaustuv; Elizabeth, Suja; Anil Kumar, P. S.

    2017-02-01

    We report the detailed experimental characteristics of LuMn0.5Fe0.5O3 synthesized by the wet chemical method and proclaim it as a new member of the multiferroic family. The compound stabilizes in P63cm crystal symmetry. It exhibits a spin re-orientation transition at TSR and an antiferromagnetic transition at TN. In addition, our magnetization vs. temperature data reveals an extra broad maximum close to room temperature; unseen in earlier studies. By invoking the compatible nature of the magnetic exchange path in P63cm symmetry, we have argued that the origin lies in the intraplane short-range spin ordering. Heat capacity is measured and analysed to elucidate the magnetic entropy. Though long-range antiferromagnetic ordering vanishes at TN ˜ 103 K, we find the experimental magnetic entropy calculated till 200 K is less by a significant amount from the value of theoretical spin randomization magnetic entropy; further supporting the existence of spin ordering beyond TN and even above 200 K. While the specific heat data and phonon modes of Raman spectra show a signature of spin-phonon coupling at TSR and TN both, dielectric anomaly indicating a magnetoelectric effect is seen only at TN. Piezoresponse force microscopy and ferroelectric hysteresis loop measurement confirm the room-temperature weak ferroelectricity with a saturation polarization value 0.007 μC/cm2 and low coercive field. Furthermore high-temperature dielectric characteristics reveal the ferroelectric transition at around 900 K and exhibit Maxwell-Wagner type relaxation. The present work serves as a bridge between h-RMnO3 and rare earth ferrite RFeO3. It assumes significance in the light of recent research developments in hexagonal RFeO3 (mainly h-LuFeO3) in the context of room-temperature multiferroicity and magnetoelectricity.

  1. Mössbauer study of Cu0.5Fe0.5Cr2S4

    NASA Astrophysics Data System (ADS)

    Ok, Hang Nam; Baek, Kyung Seon; Lee, Heung Soo; Kim, Chul Sung

    1990-01-01

    Cu0.5Fe0.05Cr2S4 has been studied by Mössbauer spectroscopy and x-ray diffraction. The crystal structure is found to be a cubic spinel with the lattice parameter a0=9.922 Å. The temperature dependence of both the magnetic hyperfine field and magnetization is explained by the Néel theory of ferrimagnetism using three exchange integrals: JFe-Cr/kB=-13.7 K, JFe-Fe/kB=-8.3 K, and JCr-Cr/kB=8.7 K.

  2. Luminous Red Galaxies at Z=0.4-0.5

    NASA Technical Reports Server (NTRS)

    Heap, Sally; Lindler, Don

    2009-01-01

    We report on a study of approx.20,000 luminous red galaxies (LRG's) at z=0.4-0.5 observed by the Sloan Digital Sky Survey. In order to differentiate among them, we measured restframe magnitudes, u (3000-3500 A), b (4200-4800 A), and y (5700-6300 A) from the spectra themselves. The galaxies show a significant range in restframe colors and absolute magnitudes. We binned the spectra according to the restframe u-b color and y-band absolute magnitude in order to increase the S/N. We used 3 approaches to estimate the ages and metal content of these binned spectra: via their spectral energy distributions, from spectral-line indices, and by full spectral fitting. The three methods usually produce discordant results

  3. Upper critical field and AC-Susceptibility studies on FeTe0.5Se0.5 superconductor

    NASA Astrophysics Data System (ADS)

    Zargar, Rayees A.; Pal, Anand; Hafiz, A. K.; Awana, V. P. S.

    2015-06-01

    In this study we present synthesis and characterization of FeTe0.5Se0.5 sample that has been prepared by solid state reaction route by encapsulation of stoichiometric high purity (5N) ingredients in an evacuated quartz tube at 750 °C. The resultant compound is crystallized in single phase tetragonal structure with space group P4/nmm, having lattice parameters a = 3.792(1) Å and c = 6.0081(3) Å. The studied compound is superconducting at below 13K in both magnetic and transport measurements. Further superconductivity is barely affected by external applied magnetic field, giving rise to upper critical field of above 180 Tesla at 0 K. The sample is studied extensively for AC susceptibility measurements in superconducting state. The AC drive field and frequency are varied from 1-13 Oe and 33-9999 Hz respectively. It is concluded that though the grain boundaries of this superconductor are mainly metallic the minor (undetectable in XRD) foreign phases and the role of porosity cannot be ruled out completely. This is because both frequency and amplitude affects slightly the superconductivity coupling temperature of the grains.

  4. Improved magnetic properties of microwave processed Mn0.5Zn0.5Fe2O4 particles

    NASA Astrophysics Data System (ADS)

    Suneetha, T.; Kashyap, Subhash C.; Gupta, Hem C.

    2013-02-01

    Mn0.5Zn0.5Fe2O4 nanoparticles, first prepared by citrate precursor route, have been processed by two different methods to obtain polycrystalline samples. In one case the pressed pellets are processed in microwave H-field at 500 °C for different duration: 1, 3 and 5 min, and in another case the pellets are conventionally sintered at 500 °C for 180 min. The powder x-ray diffraction patterns confirmed the single cubic phase in the all samples. The scanning electron micrographs revealed the grain growth during microwave processing, with the particle size increasing to 1μm for the sample heated at 500 °C for 5 min, whereas the sintered samples had a particle size of ˜20 nm. A maximum saturation magnetization of 56 emu/g at room temperature was estimated by vibration sample magnetometer for this sample; where as conventional sintered sample has 24 emu/g. With microwave processing we can obtain microcrystalline samples with improved magnetization in a short span of 5 min.

  5. Study of Co0.5Zn0.5Fe2O4 nanoparticles for magnetic hyperthermia

    NASA Astrophysics Data System (ADS)

    Kamzin, A. S.; Nikam, D. S.; Pawar, S. H.

    2017-01-01

    The structural characteristics, magnetic properties, and processes of magnetic heating in an alternating magnetic field of magnetic nanoparticles (MNPs) Co0.5Zn0.5Fe2O4 (cobalt-zinc ferrite, CZF) are studied to explore the possibilities of their application in medicine, namely, for magnetic hyperthermia treatment (the heating of particles with external alternating magnetic field). CZF magnetic nanoparticles were obtained by coprecipitation using sodium hydroxide (NaOH) as a precipitating agent. Based on the data obtained by transmission electron microscopy in the transmission geometry, it is found that CZF magnetic nanoparticles have an almost spherical shape with an average particle size of 13 nm. X-ray diffraction and Mössbauer studies showed that CZF magnetic nanoparticles are single-phase, and their structure corresponds to a cubic spinel structure. The saturation magnetization M s of CZF nanoparticles is measured at room temperature using a vibrating sample magnetometer. The possibility of heating CZF magnetic nanoparticles with an external alternating magnetic field was studied using an induction heating system. The specific absorption rate is determined by applying an external alternating magnetic field in the range of 167.5 to 335.2 Oe at a fixed frequency of 265 kHz. It is found that the maximum amount of heat (114.98 W/g) is produced at a concentration of 5 mg/L under a field of 335.2 Oe.

  6. Exchange bias induced at a Co2FeAl0.5Si0.5/Cr interface

    NASA Astrophysics Data System (ADS)

    Yu, C. N. T.; Vick, A. J.; Inami, N.; Ono, K.; Frost, W.; Hirohata, A.

    2017-03-01

    In order to engineer the strength of an exchange bias in a cubic Heusler alloy layer, crystalline strain has been induced at a ferromagnet/antiferromagnet interface by their lattice mismatch in addition to the conventional interfacial exchange coupling between them. Such interfaces have been formed in (Co2FeAl0.5Si0.5(CFAS)/Cr)3 structures grown by ultrahigh vacuum molecular beam epitaxy. The magnetic and structural properties have been characterised to investigate the exchange interactions at the CFAS/Cr interfaces. Due to the interfacial lattice mismatch of 1.4%, the maximum offset of 18 Oe in a magnetisation curve has been measured for the case of a CFAS (2 nm)/Cr (0.9 nm) interface at 193 K. The half-metallic property of CFAS has been observed to remain unchanged, which agrees with the theoretical prediction by Culbert et al (2008 J. Appl. Phys. 103 07D707). Such a strain-induced exchange bias may provide insight of the interfacial interactions and may offer a wide flexibility in spintronic device design.

  7. Magnetic structure of the kagome mixed compound (Co0.5Ni0.5)3V2O8

    NASA Astrophysics Data System (ADS)

    Qureshi, N.; Fuess, H.; Ehrenberg, H.; Ouladdiaf, B.; Rodríguez-Carvajal, J.; Hansen, T. C.; Wolf, Th; Meingast, C.; Zhang, Q.; Knafo, W.; Löhneysen, H. v.

    2008-06-01

    We report the magnetic structure of (Co0.5Ni0.5)3V2O8 (CNVO) deduced by single crystal neutron diffraction. This compound exhibits features which differ from that of its parent compounds, which are absolutely collinear along the a axis for Co3V2O8 (CVO) or exhibit magnetic moments predominantly in the a-b plane with small components along c in the case of Ni3V2O8 (NVO). The averaged magnetic moments of the statistically distributed Ni2+ and Co2+ ions in CNVO are oriented in the a-c plane and form loops of quasiferromagnetically coupled spins. These loops are connected along the a axis and separated along the c axis by cross-tie spins forming a quasiferromagnetic wave with the upper part of the respective neighbouring loops. The magnetic moments are sinusoidally modulated by the propagation vector k = (0.49,0,0) with an average amplitude of 1.59(1) μB for a magnetic ion on a cross-tie site and 1.60(1) μB for the spine site. In addition to neutron diffraction, specific heat and magnetization data, which confirm that the only magnetic phase transition above 1.8 K is the onset of antiferromagnetic order at TN = 7.4(1) K, are presented.

  8. Compositional inhomogeneityand segregation in (K0.5Na0.5)NbO3 ceramics

    DOE PAGES

    Chen, Kepi; Tang, Jing; Chen, Yan

    2016-03-11

    The effects of the calcination temperature of (K0.5Na0.5)NbO3 (KNN) powder on the sintering and piezoelectric properties of KNN ceramics have been investigated in this report. KNN powders are synthesized via the solid-state approach. Scanning electron microscopy and X-ray diffraction characterizations indicate that the incomplete reaction at 700 °C and 750 °C calcination results in the compositional inhomogeneity of the K-rich and Na-rich phases while the orthorhombic single phase is obtained after calcination at 900 °C. During the sintering, the presence of the liquid K-rich phase due to the lower melting point has a significant impact on the densification, the abnormalmore » grain growth and the deteriorated piezoelectric properties. From the standpoint of piezoelectric properties, the optimal calcination temperature obtained for KNN ceramics calcined at this temperature is determined to be 800 °C, with piezoelectric constant d33=128.3 pC/N, planar electromechanical coupling coefficient kp=32.2%, mechanical quality factor Qm=88, and dielectric loss tan δ=2.1%.« less

  9. PSYCHOLOGY OF BOYS AT RISK: INDICATORS FROM 0-5.

    PubMed

    Golding, Paul; Fitzgerald, Hiram E

    2017-01-01

    In utero and during the first 5 years of life, boys face unique risks as a result of neurobiological and environmental factors. This introductory article to the Special Issue describes the background of this gender-specific inquiry and outlines some of those risks, drawing attention to the areas that will be covered in depth in the following contributions. We also describe the basis of this inquiry as the link between early life and the subsequent difficulties that adolescent boys and many young men face, and pay particular attention to the circumstances of young men of color and to the growing knowledge about the contributions of fathers to boys' development.

  10. Anomalous alternating current magnetoresistance in La0.5Ca0.5Mn1-xNixO3 (x = 0.04)

    NASA Astrophysics Data System (ADS)

    Barik, S. K.; Mahendiran, R.

    2011-04-01

    We report the magnetic field and temperature dependences of ac electrical transport in La0.5Ca0.5 Mn0.96Ni0.04O3 as a function of frequency. The ac magnetoresistance shows an anomalous behavior as a function of field: it is negative and exhibits a bell shaped curve about the origin (H = 0 T) at f = 0.1 MHz, but it transforms into a valley at the origin (accompanied by a positive peak on either side of the origin) for f ≥ 3 MHz at T = 125 K. With increasing frequency, the depth of the valley increases and the position of the peak shifts toward higher field. However, the magnetoreactance is negative and exhibits only a single peak at the origin for all temperatures and frequencies. At T = 125 K and f = 5 MHz, a magnetoresistance of +80% and a magnetoreactance of -90% were found for H = 2 T. These results are very different from those for La0.7Sr0.3MnO3, and we discuss the possible origins of the observed anomalous ac magnetotransport in this compound.

  11. Aberration-corrected STEM-EELS studies of epitaxial La0.5Sr0.5CoO3 thin films

    NASA Astrophysics Data System (ADS)

    Varela, Maria; Gazquez, Jaume; Biskup, Neven; Pennycook, Stephen; Torija, Maria; Sharma, Manish; Bose, Shameek; Leighton, Chris

    2012-02-01

    Cobaltite thin films provide a unique opportunity to study magneto-electronic phase separation, which can be strong in this reduced dimensionality environment. Here we present an investigation of epitaxial La0.5Sr0.5CoO3 thin films on SrTiO3 and LaAlO3 substrates by scanning transmission electron microscopy and electron energy loss spectroscopy. The different degrees of strain and also different orientations of the substrates (such as (001) vs. (110)) induce major changes of the crystal structure and the depth profile of the chemical composition, observed both in the La/Sr and O sub-lattices. These effects can lead to lower effective doping level at the interface, favoring interfacial magneto-electronic phase separation. Research Council Starting Investigator Award (JS, NB) and the U.S. Dept. of Energy, Office of Basic Energy Sciences, Materials Sciences and Engineering Div. (MV, SJP). Work at UMN supported by NSF and DOE (scattering).

  12. Layed Perovskite PRBA0.5SR0.5CO205 as High Performance Cathode for Solid Oxide Fuels Using Photon Conducting Electrolyte

    SciTech Connect

    Brinkman, K.

    2010-05-05

    The layered perovskite PrBa{sub 0.5}Sr{sub 0.5}Co{sub 2}O{sub 5+{delta}} (PBSC) was investigated as a cathode material for a solid oxide fuel cell using a proton-conducting electrolyte based on BaCe{sub 0.7}Y{sub 0.2}Zr{sub 0.1}O{sub 3-{delta}} (BCYZ). The sintering conditions for the PBSC-BCYZ composite cathode were optimized resulting in the lowest area-specific resistance and apparent activation energy obtained with the cathode sintered at 1200 C for 2h. The maximum power densities of the PBSC-BCYZ/BZCY/NiO-BCYZ cell were 0.179, 0.274, 0.395, and 0.522 Wcm{sup -2} at 550, 600, 650, and 700 C, respectively with a 15{micro}m thick electrolyte. A relatively low cell interfacial polarization resistance of 0.132 {Omega}cm{sup 2} at 700 C indicated that the PBSC-BCYZ could be a good cathode candidate for intermediate temperature SOFCs with proton-conducting electrolyte.

  13. Conduction mechanism in Eu0.5Sr0.5Mn0.9Cr0.1O3 perovskite

    NASA Astrophysics Data System (ADS)

    Modi, Anchit; Bhat, Masroor Ahmad; Pandey, Devendra K.; Gaur, N. K.

    2016-05-01

    A systematic study of polycrystalline sample with composition Eu0.5Sr0.5Mn0.9Cr0.1O3 has been undertaken and synthesized by conventional solid state reaction techniques. The room temperature XRD study reveals the single phase formation of the reported compound with orthorhombic structure having Pbnm space group. The temperature dependent resistivity study indicates the highly resistive nature of the compound especially in the low temperature region exhibits a semiconductor behavior and favored the variable range hopping conduction model. The obtained experimental data in the temperature range of our study can be described by the equation ρ(T) = ρ0exp[(T*/T)1/4]. The fitting results are used for the calculation of the temperature scale T* ˜ 9.05×106 K and finally the density of state at Fermi level N(EF) is calculated to be ˜ 61.63 × 1018 eV-1 cm-3.

  14. Structural and magnetic properties of epitaxial Heusler alloy Fe{sub 2}Cr{sub 0.5}Co{sub 0.5}Si

    SciTech Connect

    Wang, Yu-Pu; Han, Gu-Chang; Qiu, Jinjun; Yap, Qi-Jia; Lu, Hui; Teo, Kie-Leong

    2014-05-07

    This paper reports the study of structural and magnetic properties of Heusler alloy Fe{sub 2}Cr{sub 0.5}Co{sub 0.5}Si (FCCS) thin film and its tunnel magnetoresistance (TMR) effect. The smooth quaternary Heusler alloy FCCS film with surface roughness of rms value of 0.25 nm measured by atomic force microscopy and partial L2{sub 1} phase was obtained by magnetron sputtering at room temperature followed by in-situ annealing at 400 °C. The saturation magnetization and coercivity of FCCS are 410 emu/cm{sup 3} and 20 Oe, respectively. The magnetic tunnel junctions (MTJs) using FCCS as free layer were studied in detail as a function of post-annealing temperature. A TMR ratio of 15.6% has been achieved with 300 °C post-annealing. This is about twice the highest TMR ratio obtained in MTJs using Fe{sub 2}CrSi. The enhancement of TMR ratio can be attributed to the successful tuning of the Fermi level of Fe{sub 2}CrSi close to the center of the minority band gap by Co-doping.

  15. Accelerated materials design of Na0.5Bi0.5TiO3 oxygen ionic conductors based on first principles calculations.

    PubMed

    He, Xingfeng; Mo, Yifei

    2015-07-21

    We perform a first principles computational study of designing the Na0.5Bi0.5TiO3 (NBT) perovskite material to increase its oxygen ionic conductivity. In agreement with the previous experiments, our computation results confirm fast oxygen ionic diffusion and good stability of the NBT material. The oxygen diffusion mechanisms in this new material were systematically investigated, and the effects of local atomistic configurations and dopants on oxygen diffusion were revealed. Novel doping strategies focusing on the Na/Bi sublattice were predicted and demonstrated by the first principles calculations. In particular, the K doped NBT compound achieved good phase stability and an order of magnitude increase in oxygen ionic conductivity of up to 0.1 S cm(-1) at 900 K compared to the previous Mg doped compositions. This study demonstrated the advantages of first principles calculations in understanding the fundamental structure-property relationship and in accelerating the materials design of the ionic conductor materials.

  16. Room temperature operation of epitaxially grown Si/Si0.5Ge0.5/Si resonant interband tunneling diodes

    NASA Astrophysics Data System (ADS)

    Rommel, Sean L.; Dillon, Thomas E.; Dashiell, M. W.; Feng, H.; Kolodzey, J.; Berger, Paul R.; Thompson, Phillip E.; Hobart, Karl D.; Lake, Roger; Seabaugh, Alan C.; Klimeck, Gerhard; Blanks, Daniel K.

    1998-10-01

    Resonant interband tunneling diodes on silicon substrates are demonstrated using a Si/Si0.5Ge0.5/Si heterostructure grown by low temperature molecular beam epitaxy which utilized both a central intrinsic spacer and δ-doped injectors. A low substrate temperature of 370 °C was used during growth to ensure a high level of dopant incorporation. A B δ-doping spike lowered the barrier for holes to populate the quantum well at the valence band discontinuity, and an Sb δ-doping reduces the doping requirement of the n-type bulk Si by producing a deep n+ well. Samples studied from the as-grown wafers showed no evidence of negative differential resistance (NDR). The effect of postgrowth rapid thermal annealing temperature was studied on tunnel diode properties. Samples which underwent heat treatment at 700 and 800 °C for 1 min, in contrast, exhibited NDR behavior. The peak-to-valley current ratio (PVCR) and peak current density of the tunnel diodes were found to depend strongly on δ-doping placement and on the annealing conditions. PVCRs ranging up to 1.54 were measured at a peak current density of 3.2 kA/cm2.

  17. Compositional variations in In(0.5)Ga(0.5)N nanorods grown by molecular beam epitaxy.

    PubMed

    Cherns, D; Webster, R F; Novikov, S V; Foxon, C T; Fischer, A M; Ponce, F A; Haigh, S J

    2014-05-30

    The composition of InxGa1 - xN nanorods grown by molecular beam epitaxy with nominal x = 0.5 has been mapped by electron microscopy using Z-contrast imaging and x-ray microanalysis. This shows a coherent and highly strained core-shell structure with a near-atomically sharp boundary between a Ga-rich shell (x ∼ 0.3) and an In-rich core (x ∼ 0.7), which itself has In- and Ga-rich platelets alternating along the growth axis. It is proposed that the shell and core regions are lateral and vertical growth sectors, with the core structure determined by spinodal decomposition.

  18. Magnetic properties and specific heat of new spin glass Mn0.5Fe0.5PS3

    NASA Astrophysics Data System (ADS)

    Takano, Yoshiki; Arai, Atsuko; Takahashi, Yumiko; Takase, Kouichi; Sekizawa, Kazuko

    2003-05-01

    We have found spin glass phenomena in a layered Mn0.5Fe0.5PS3 compound and investigated its magnetic properties and specific heat. The temperature dependence of the zero field cooled (ZFC) magnetization along the easy axis, M∥ under dc applied field Ha below 1 kOe shows a cusp at Tg=32.6 K. The FC and ZFC curves measured at Ha below 1 kOe separate at almost the same temperature as Tg. For Ha larger than 1 kOe, the temperature at which FC and ZFC curves separate deviates from Tg and shifts toward lower temperature and the peak becomes broader. Magnetic hysteresis is still observed above 70 kOe at 2 K. The remarkable feature of this spin glass phase is that the spin freezing is not suppressed up to a rather high magnetic field compared with similar spin glass (Mn,Fe)TiO3. The cusp temperature of χ'(ω) does not show magnetic field amplitude dependence from 1 to 10 Oe and increases with an increase in frequency, obeying the Vogel-Fulcher rule. The temperature dependence of χ″(ω) shows two extra peaks at Tm1 and Tm2 below Tg. The time dependence of thermoremanent magnetization MTRM below Tg shows power law dependence. The value of the molar specific heat is about an order of magnitude larger than that of MnPS3 and FePS3 at 2 K. The T-linear term characteristic of spin glass is observed below about 10 K. The temperature dependence of the magnetic specific heat shows no anomaly at Tg, Tm1=9 and Tm2=16 K, and shows two peaks at Tc1=13 and Tc2=67 K.

  19. Grain size engineering for ferroelectric Hf{sub 0.5}Zr{sub 0.5}O{sub 2} films by an insertion of Al{sub 2}O{sub 3} interlayer

    SciTech Connect

    Kim, Han Joon; Park, Min Hyuk; Kim, Yu Jin; Lee, Young Hwan; Jeon, Woojin; Gwon, Taehong; Moon, Taehwan; Kim, Keum Do; Hwang, Cheol Seong

    2014-11-10

    The degradation of ferroelectric (FE) properties of atomic layer deposited Hf{sub 0.5}Zr{sub 0.5}O{sub 2} films with increasing thickness was mitigated by inserting 1 nm-thick Al{sub 2}O{sub 3} interlayer at middle position of the thickness of the FE film. The large P{sub r} of 10 μC/cm{sup 2}, which is 11 times larger than that of single layer Hf{sub 0.5}Zr{sub 0.5}O{sub 2} film with equivalent thickness, was achieved from the films as thick as 40 nm. The Al{sub 2}O{sub 3} interlayer could interrupt the continual growth of Hf{sub 0.5}Zr{sub 0.5}O{sub 2} films, and the resulting decrease of grain size prevented the formation of non-ferroelectric monoclinic phase. The Al{sub 2}O{sub 3} interlayer also largely decreased the leakage current of the Hf{sub 0.5}Zr{sub 0.5}O{sub 2} films.

  20. Solution processed Ni-doped TiO2 p-type channel in field effect transistor assembly with <10 nm thin Ba0.5Sr0.5TiO3 dielectric layer

    NASA Astrophysics Data System (ADS)

    Das, Soumen; Kim, Jin-Hwan; Park, Yong-Kyu; Hahn, Yoon-Bong

    2011-05-01

    Solution processed field effect transistor structures were fabricated by inserting a Ba0.5Sr0.5TiO3 layer to form Ag/ZnO/Ba0.5Sr0.5TiO3/Ni2+:TiO2/n-Si assembly. Such assembly registered an on-to-off current ratio as large as 103 with very low off-state current ˜10-12 A. The low leakage current is attributed to the appreciably higher values of valence/conduction band off-set of Ba0.5Sr0.5TiO3/semiconductor heterojunction. The device response was studied as a function of temperature in the range of 25-175 °C. The hole diffusion coefficient and mobility of p-TiO2 was calculated ˜10-3 cm2/s and ˜0.13-0.15 cm-2 V-1 s-1, respectively.

  1. Ubiquitous CM and DM

    NASA Technical Reports Server (NTRS)

    Crowley, Sandra L.

    2000-01-01

    Ubiquitous is a real word. I thank a former Total Quality Coach for my first exposure some years ago to its existence. My version of Webster's dictionary defines ubiquitous as "present, or seeming to be present, everywhere at the same time; omnipresent." While I believe that God is omnipresent, I have come to discover that CM and DM are present everywhere. Oh, yes; I define CM as Configuration Management and DM as either Data or Document Management. Ten years ago, I had my first introduction to the CM world. I had an opportunity to do CM for the Space Station effort at the NASA Lewis Research Center. I learned that CM was a discipline that had four areas of focus: identification, control, status accounting, and verification. I was certified as a CMIl graduate and was indoctrinated about clear, concise, and valid. Off I went into a world of entirely new experiences. I was exposed to change requests and change boards first hand. I also learned about implementation of changes, and then of technical and CM requirements.

  2. Formation of solar cells based on Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} (BST) ferroelectric thick film

    SciTech Connect

    Irzaman, Syafutra, H. Arif, A. Alatas, H.; Hilaluddin, M. N.; Kurniawan, A.; Iskandar, J.; Dahrul, M.; Ismangil, A.; Yosman, D.; Aminullah; Prasetyo, L. B.; Yusuf, A.; Kadri, T. M.

    2014-02-24

    Growth of Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} (BST) 1 M thick films are conducted with variation of annealing hold time of 8 hours, 15 hours, 22 hours, and 29 hours at a constant temperature of 850 °C on p-type Si (100) substrate using sol-gel method then followed by spin coating process at 3000 rpm for 30 seconds. The BST thick film electrical conductivity is obtained to be 10{sup −5} to 10{sup −4} S/cm indicate that the BST thick film is classified as semiconductor material. The semiconductor energy band gap value of BST thick film based on annealing hold time of 8 hours, 15 hours, 22 hours, and 29 hours are 2.58 eV, 3.15 eV, 3.2 eV and 2.62 eV, respectively. The I-V photovoltaic characterization shows that the BST thick film is potentially solar cell device, and in accordance to annealing hold time of 8 hours, 15 hours, 22 hours and 29 hours have respective solar cell energy conversion efficiencies of 0.343%, 0.399%, 0.469% and 0.374%, respectively. Optical spectroscopy shows that BST thick film solar cells with annealing hold time of 8 hours, 15 hours, and 22 hours absorb effectively light energy at wavelength of ≥ 700 nm. BST film samples with annealing hold time of 29 hours absorb effectively light energy at wavelength of ≤ 700 nm. The BST thick film refraction index is between 1.1 to 1.8 at light wavelength between ±370 to 870 nm.

  3. Electrostatic versus Electrochemical Doping and Control of Ferromagnetism in Ion-Gel-Gated Ultrathin La0.5Sr0.5CoO3-δ.

    PubMed

    Walter, Jeff; Wang, Helin; Luo, Bing; Frisbie, C Daniel; Leighton, Chris

    2016-08-23

    Recently, electrolyte gating techniques employing ionic liquids/gels in electric double layer transistors have proven remarkably effective in tuning charge carrier density in a variety of materials. The ability to control surface carrier densities at levels above 10(14) cm(-2) has led to widespread use in the study of superconductivity, insulator-metal transitions, etc. In many cases, controversy remains over the doping mechanism, however (i.e., electrostatic vs electrochemical (e.g., redox-based)), and the technique has been less applied to magnetic materials. Here, we discuss ion gel gating of nanoscale 8-unit-cell-thick hole-doped La0.5Sr0.5CoO3-δ (LSCO) films, probing in detail the critical bias windows and doping mechanisms. The LSCO films, which are under compressive stress on LaAlO3(001) substrates, are metallic and ferromagnetic (Curie temperature, TC ∼ 170 K), with strong anomalous Hall effect and perpendicular magnetic anisotropy. Transport measurements reveal that negative gate biases lead to reversible hole accumulation (i.e., predominantly electrostatic operation) up to some threshold, whereas positive bias immediately induces irreversibility. Experiments in inert/O2 atmospheres directly implicate oxygen vacancies in this irreversibility, supported by atomic force microscopy and X-ray photoelectron spectroscopy. The results are thus of general importance, suggesting that hole- and electron-doped oxides may respond very differently to electrolyte gating. Reversible voltage control of electronic/magnetic properties is then demonstrated under hole accumulation, including resistivity, magnetoresistance, and TC. The sizable anomalous Hall coefficient and perpendicular anisotropy in LSCO provide a particularly powerful probe of magnetism, enabling direct extraction of the voltage-dependent order parameter and TC shift. The latter amounts to ∼7%, with potential for much stronger modulation at lower Sr doping.

  4. Microstructure and microchemistry of flash sintered K0.5Na0.5NbO3

    DOE PAGES

    Corapcioglu, Gulcan; Gulgun, Mehmet Ali; Kisslinger, Kim; ...

    2016-04-30

    In this paper, flash sintering experiments were performed, for the first time, on sodium potassium niobate (KNN) ceramics. A theoretical density of 94% was achieved in 30 s under 250 V/cm electric-field at 990°C. These conditions are ~100°C lower and faster than the conventional sintering conditions. Grains tended to grow after 30 s. flash sintering duration under constant electric-field. Detailed microstructural and chemical investigations of the sample showed that there was inhomogenous Na, K distribution and it resembles a core–shell structure where K is more in the shell and Na is more in the core region. The inhomogenous distribution ofmore » Na and K was correlated with the doubling of the unit cell within the grain along 002 direction. Compositional equilibrium is achieved after a heat treatment at 1000°C for 4 h. Finally, the compositional variations appeared to have been linked to grain boundary melting during flash and consequent recrystallization as the sample cooled.« less

  5. X-ray photoelectron spectroscopic study of direct reforming catalysts Ln0.5Sr0.5Ti0.5Mn0.5O3±d (Ln = La, Nd, and Sm) for high temperature-operating solid oxide fuel cell

    NASA Astrophysics Data System (ADS)

    Kim, Keunsoo; Jeong, Jihoon; Azad, Abul K.; Jin, Sang Beom; Kim, Jung Hyun

    2016-03-01

    Chemical states of lanthanide doped perovskite for direct reforming anode catalysts, Ln0.5Sr0.5Ti0.5Mn0.5O3±d (Ln = La, Nd, and Sm) have been studied by X-ray Photoelectron Spectroscopy (XPS) in order to determine the effects of various lanthanide substitution in complex perovskites for high temperature-operating solid oxide fuel cells (HT-SOFC). The charge state of lanthanide ions remained at 3+ and the binding energies of the lanthanide ions in Ln0.5Sr0.5Ti0.5Mn0.5O3±d were located in a relatively lower range compared to those of conventional lanthanide oxides. Mn and Ti were regarded as charge compensation components in Ln0.5Sr0.5Ti0.5Mn0.5O3±d; Mn was more influential than Ti. In the cases of substituting Nd and Sm into Ln0.5Sr0.5Ti0.5Mn0.5O3±d, some portion of Ti showed metallic behavior; the specific Mn satellite peak indicating an electro-catalytic effect had occurred. Three types of oxygen species comprised of lattice oxygen, carbonate species, and adsorbed oxygen species were observed in Ln0.5Sr0.5Ti0.5Mn0.5O3±d from the O 1s spectra; a high portion of lattice oxygen was observed in both Nd0.5Sr0.5Ti0.5Mn0.5O3±d (NSTM) and Sm0.5Sr0.5Ti0.5Mn0.5O3±d (SSTM). In various respects, NSTM and SSTM will be desirable reforming catalysts and anode candidates for high temperature solid oxide fuel cell.

  6. Electron attachment to Fe(CO)n (n = 0-5).

    PubMed

    Shuman, Nicholas S; Miller, Thomas M; Friedman, Jeffrey F; Viggiano, Albert A

    2013-02-14

    The rate constants of thermal electron attachment at 300 and 400 K to Fe(CO)(n) (n = 0-5) have been measured using a flowing afterglow Langmuir probe apparatus. The stable species Fe(CO)(5) was studied using the traditional method of monitoring electron depletion as a function of reaction time, and the remaining short-lived species were studied using the variable electron and neutral density attachment mass spectrometry (VENDAMS) technique. Attachment to Fe(CO)(5) is purely dissociative and about 20% efficient with a rate constant of (7.9 ± 1.4) × 10(-8) cm(3) s(-1) at 300 K and (8.8 ± 2) × 10(-8) cm(3) s(-1) at 400 K. The attachment rate constants decrease significantly as each CO ligand is removed, with Fe(CO)(n) (n = 4 to 1) attaching with efficiencies on the order of 10%, 1%, 0.1%, and 0.01% respectively. Under the conditions here, attachment to Fe(CO)(4) and Fe(CO)(3) are likely entirely dissociative, whereas attachment to Fe(CO)(2) and Fe(CO) are almost entirely associative. A statistical kinetic modeling approach is used to explain the strong dependence of the attachment rate constant on the number of ligands present in the neutral species through a combination of increasing autodetachment rates and decreasing exothermicities to dissociative attachment. The VENDAMS data also define the 300 K mutual neutralization rate constant of Fe(CO)(4)(-) + Ar(+) to be (5.0 ± 0.8) × 10(-8) cm(3) s(-1) with an upper limit to branching fraction of 0.5 to yield Fe(CO)(4), indicating that significant fragmentation to smaller Fe(CO)(n) occurs.

  7. Structure and photoluminescence properties of Ce0.5Zr0.5O2:Eu3+ nanoparticles synthesized by hydrothermal method

    NASA Astrophysics Data System (ADS)

    Ozawa, Masakuni; Yoshimura, Yusuke; Kobayashi, Katsutoshi

    2017-01-01

    Eu3+-doped Ce0.5Zr0.5O2 nanocrystals were prepared by a hydrothermal method. The structural and optical properties of the samples were characterized by X-ray diffraction, Raman scattering and photoluminescence spectra. No luminescence was observed for Ce0.5Zr0.5O2, while Ce0.5Zr0.5O2:Eu3+ nanoparticles as-prepared and calcined at 400 °C showed emission due to Eu3+. The emission spectrum of the Eu3+ site shows that the total intensity decreases with increasing concentration of Eu3+ from 1 to 10% in Ce0.5Zr0.5O2. The broad band in the excitation spectrum of calcined Ce0.5Zr0.5O2:Eu3+ originates from the charge transfer (CT) transition. The local distortion and the asymmetry factor around the Eu3+ centers were discussed with the Raman and photoluminescence spectra. The present study provides both knowledge expected to lead to novel nanocrystal phosphor materials and a useful measure for analyzing the catalytic properties of nanocrystalline Ce0.5Zr0.5O2.

  8. Effect of crystal structure and cationic order on phonon modes across ferroelectric phase transformation in Pb(Fe{sub 0.5-x}Sc{sub x}Nb{sub 0.5})O{sub 3} bulk ceramics

    SciTech Connect

    Mallesham, B.; Ranjith, R.; Viswanath, B.

    2016-01-15

    Pb(Fe{sub 0.5-x}Sc{sub x}Nb{sub 0.5})O{sub 3} [(PFSN) (0 ≤ x ≤ 0.5)] multiferroic relaxors were synthesized and the temperature dependence of phonon modes across ferroelectric to paraelectric transition was studied. With varying Sc content from x = 0 to 0.25 the structure remains monoclinic and with further addition (x = 0.3 - 0.5) the structure transforms into rhombohedral symmetry. Structural refinement studies showed that the change in crystal structure from monoclinic to rhombohedral symmetry involves a volume increment of 34-36%. Associated changes in the tolerance factor (1.024 ≤ t ≤ 0.976) and bond angles were observed. Structure assisted B′-B″ cation ordering was confirmed through the superlattice reflections in selected area electron diffraction (SAED) pattern of Pb(Sc{sub 0.5}Nb{sub 0.5})O{sub 3} (x = 0.5). Cation ordering is also evident from the evolution of Pb-O phonon mode in Raman spectra of compositions with rhombohedral symmetry (x ≥ 0.3). The high temperature Raman scattering studies show that the B-localized mode [F{sub 1u}, ∼250 cm{sup −1}] and BO{sub 6} octahedral rotational mode [F{sub 1g}, ∼200 cm{sup −1}], both originating from polar nano regions (PNRs) behave like coupled phonon modes in rhombohedral symmetry. However, in monoclinic symmetry they behave independently across the transition. Softening of B localized mode across the transition followed by the hardening for all compositions confirms the diffusive nature of the ferroelectric transformation. The presence of correlation between the B localized and BO{sub 6} rotational modes introduces a weak relaxor feature for systems with rhombohedral symmetry in PFSN ceramics, which was confirmed from the macroscopic dielectric studies.

  9. One-dimensional SrFe12O19/Ni(0.5)Zn(0.5)Fe2O4 composite ferrite nanofibers and enhancement magnetic property.

    PubMed

    Song, Fuzhan; Shen, Xiangqian; Liu, Mingquan; Xiang, Jun

    2011-08-01

    SrFe12O19/Ni(0.5)Zn(0.5)Fe2O4 composite ferrite nanofibers of diameters about 100 nm with mass ratio 1:1 have been prepared by the electrospinning and calcination process. The SrFe12O19/Ni(0.5)Zn(0.5)Fe2O4 composite ferrites are formed after calcined at 700 degrees C for 2 hours. The composite ferrite nanofibers are fabricated from nanosized Ni(0.5)Zn(0.5)Fe2O4 and SrFe12O19 ferrite grains with a uniform phase distribution. The ferrite grain size increases from about 11 to 36 nm for Ni(0.5)Zn(0.5)Fe12O4 and 24 to 56 nm for SrFe12O19 with the calcination temperature increasing from 700 to 1100 degrees C. With the ferrite grain size increasing, the coercivity (Hc) and remanence (Mr) for the SrFe12O19/Ni(0.5)Zn(0.5)Fe2O4 composite ferrite nanofibers initially increase, reaching a maximum value of 118.4 kA/m and 31.5 Am2/kg at the grain size about 40 nm (SrFe12O19) and 24 nm (Ni(0.5)Zn(0.5)Fe2O4) respectively, and then show a reduction tendency with a further increase of the ferrite grain size. The specific saturation magnetization (Msh) of 63.2 Am2/kg for the SrFe12O19/Ni(0.5)Zn(0.5)Fe2O4 composite ferrite nanofibers obtained at 900 degrees C for 2 hours locates between that for the single SrFe12O19 ferrite (48.5 Am2/kg) and the single Ni(0.5)Zn(0.5)Fe2O4 ferrite (69.3 Am2/kg). In particular, the Mr value 31.5 Am2/kg for the SrFe12O19/Ni(0.5)Zn(0.5)Fe2O4 composite ferrite nanofibers is much higher than that for the individual SrFe12O19 (25.9 Am2/kg) and Ni(0.5)Zn(0.5)Fe2O4 ferrite (11.2 Am2/kg). These enhanced magnetic properties for the composite ferrite nanofibers can be attributed to the exchange-coupling interaction in the composite.

  10. Superconductivity phase diagram of Se-substituted CeO0.5F0.5Bi(S1-xSex)2

    NASA Astrophysics Data System (ADS)

    Mizuguchi, Yoshikazu; Hiroi, Takafumi; Miura, Osuke

    2016-02-01

    We investigated the effects of Se substitution on the lattice constants and superconducting properties of CeO0.5F0.5Bi(S1-xSex)2. With increasing Se concentration, the a lattice constant increased, while the c lattice constant did not show any significant increase between x = 0.1 and x = 0.5. Bulk superconductivity was observed in samples with x = 0.2-0.4, and the superconducting transition temperature was the highest at x = 0.3. The obtained superconductivity phase diagram was compared to those of LaO0.5F0.5Bi(S1-xSex)2 and NdO0.5F0.5Bi(S1-xSex)2.

  11. A study of room-temperature LixMn1.5Ni0.5O4 solid solutions

    PubMed Central

    Saravanan, Kuppan; Jarry, Angelique; Kostecki, Robert; Chen, Guoying

    2015-01-01

    Understanding the kinetic implication of solid-solution vs. biphasic reaction pathways is critical for the development of advanced intercalation electrode materials. Yet this has been a long-standing challenge in materials science due to the elusive metastable nature of solid solution phases. The present study reports the synthesis, isolation, and characterization of room-temperature LixMn1.5Ni0.5O4 solid solutions. In situ XRD studies performed on pristine and chemically-delithiated, micron-sized single crystals reveal the thermal behavior of LixMn1.5Ni0.5O4 (0 ≤ x ≤ 1) cathode material consisting of three cubic phases: LiMn1.5Ni0.5O4 (Phase I), Li0.5Mn1.5Ni0.5O4 (Phase II) and Mn1.5Ni0.5O4 (Phase III). A phase diagram capturing the structural changes as functions of both temperature and Li content was established. The work not only demonstrates the possibility of synthesizing alternative electrode materials that are metastable in nature, but also enables in-depth evaluation on the physical, electrochemical and kinetic properties of transient intermediate phases and their role in battery electrode performance. PMID:25619504

  12. A study of room-temperature LixMn1.5Ni0.5O4 solid solutions

    NASA Astrophysics Data System (ADS)

    Saravanan, Kuppan; Jarry, Angelique; Kostecki, Robert; Chen, Guoying

    2015-01-01

    Understanding the kinetic implication of solid-solution vs. biphasic reaction pathways is critical for the development of advanced intercalation electrode materials. Yet this has been a long-standing challenge in materials science due to the elusive metastable nature of solid solution phases. The present study reports the synthesis, isolation, and characterization of room-temperature LixMn1.5Ni0.5O4 solid solutions. In situ XRD studies performed on pristine and chemically-delithiated, micron-sized single crystals reveal the thermal behavior of LixMn1.5Ni0.5O4 (0 <= x <= 1) cathode material consisting of three cubic phases: LiMn1.5Ni0.5O4 (Phase I), Li0.5Mn1.5Ni0.5O4 (Phase II) and Mn1.5Ni0.5O4 (Phase III). A phase diagram capturing the structural changes as functions of both temperature and Li content was established. The work not only demonstrates the possibility of synthesizing alternative electrode materials that are metastable in nature, but also enables in-depth evaluation on the physical, electrochemical and kinetic properties of transient intermediate phases and their role in battery electrode performance.

  13. A study of room-temperature LixMn1.5Ni0.5O4 solid solutions

    DOE PAGES

    Saravanan, Kuppan; Jarry, Angelique; Kostecki, Robert; ...

    2015-01-26

    Understanding the kinetic implication of solid-solution vs. biphasic reaction pathways is critical for the development of advanced intercalation electrode materials. Yet this has been a long-standing challenge in materials science due to the elusive metastable nature of solid solution phases. The present study reports the synthesis, isolation, and characterization of room-temperature LixMn1.5Ni0.5O4 solid solutions. In situ XRD studies performed on pristine and chemically-delithiated, micron-sized single crystals reveal the thermal behavior of LixMn1.5Ni0.5O4 (0 ≤ x ≤ 1) cathode material consisting of three cubic phases: LiMn1.5Ni0.5O4 (Phase I), Li0.5Mn1.5Ni0.5O4 (Phase II) and Mn1.5Ni0.5O4 (Phase III). A phase diagram capturing the structuralmore » changes as functions of both temperature and Li content was established. In conclusion, the work not only demonstrates the possibility of synthesizing alternative electrode materials that are metastable in nature, but also enables in-depth evaluation on the physical, electrochemical and kinetic properties of transient intermediate phases and their role in battery electrode performance.« less

  14. Lead-free piezoelectric ceramics based on (0.97 - x)K0.48Na0.52NbO3-0.03Bi0.5(Na0.7K0.2Li0.1)0.5ZrO3-xB0.5Na0.5TiO3 ternary system

    NASA Astrophysics Data System (ADS)

    Cheng, Xiaojing; Wu, Jiagang; Wang, Xiaopeng; Zhang, Binyu; Zhu, Jianguo; Xiao, Dingquan; Wang, Xiangjian; Lou, Xiaojie; Liang, Wenfeng

    2013-09-01

    In this work, the ternary system of potassium-sodium niobate has been designed to enhance the piezoelectric properties without sacrificing the Curie temperature greatly, and (0.97 - x)K0.48Na0.52NbO3-0.03Bi0.5(Na0.7K0.2Li0.1)0.5ZrO3-xB0.5Na0.5TiO3 ceramics have been prepared by the conventional solid-state method. The effect of B0.5Na0.5TiO3 content on the microstructure and electrical properties of the ceramics is studied. The phase diagram shows a phase boundary of the rhombohedral-tetragonal (R-T) phase coexistence in the composition range of 0.5% < x < 1.5%, and then an enhanced dielectric, ferroelectric, and piezoelectric behavior is obtained at such a phase boundary zone. The ceramic with x = 0.01 has an optimum electrical behavior of d33 ˜ 285 pC/N, kp ˜ 0.40, ɛr ˜ 1235, tan δ ˜ 0.031, Pr ˜ 14.9 μC/cm2, and Ec ˜ 15.2 kV/cm, together with a high Curie temperature of ˜347 °C. The large d33 in such a ternary system is due to a composition-induced R-T phase transition and a higher ɛrPr, and the thermal stability performance is strongly dependent on the phase structure. As a result, the design of the ternary system is an effective way to enhance the piezoelectric properties of potassium-sodium niobate materials.

  15. Measurements of Output Factors For Small Photon Fields Up to 10 cm x 10 cm

    NASA Astrophysics Data System (ADS)

    Bacala, Angelina

    Field output factors (OF) for photon beams from a 6 MV medical accelerator were measured using five different detectors in a scanning water phantom. The measurements were taken for square field sizes of integral widths ranging from 1 cm to 10 cm for two reference source-to-surface distances (SSD) and depths in water. For the diode detectors, square field widths as small as 2.5 mm were also studied. The photon beams were collimated by using either the jaws or the multileaf collimators. Measured OFs are found to depend upon the field size, SSD, depth and also upon the type of beam collimation, size and type of detector used. For field sizes larger than 3 cm x 3 cm, the OF measurements agree to within 1% or less. The largest variation in OF occurs for jawsshaped field of size 1 cm x 1cm, where a difference of more than 18% is observed.

  16. NuSTAR observations of heavily obscured quasars at z ∼ 0.5

    SciTech Connect

    Lansbury, G. B.; Alexander, D. M.; Moro, A. Del; Gandhi, P.; Aird, J.; Assef, R. J.; Stern, D.; Ballantyne, D. R.; Baloković, M.; Grefenstette, B. W.; Harrison, F. A.; Bauer, F. E.; Boggs, S. E.; Brandt, W. N.; Christensen, F. E.; Craig, W. W.; Elvis, M.; Hailey, C. J.; Hickox, R. C.; Koss, M.; and others

    2014-04-10

    We present NuSTAR hard X-ray observations of three Type 2 quasars at z ≈ 0.4-0.5, optically selected from the Sloan Digital Sky Survey. Although the quasars show evidence for being heavily obscured, Compton-thick systems on the basis of the 2-10 keV to [O III] luminosity ratio and multiwavelength diagnostics, their X-ray absorbing column densities (N {sub H}) are poorly known. In this analysis, (1) we study X-ray emission at >10 keV, where X-rays from the central black hole are relatively unabsorbed, in order to better constrain N {sub H}. (2) We further characterize the physical properties of the sources through broad-band near-UV to mid-IR spectral energy distribution analyses. One of the quasars is detected with NuSTAR at >8 keV with a no-source probability of <0.1%, and its X-ray band ratio suggests near Compton-thick absorption with N {sub H} ≳ 5 × 10{sup 23} cm{sup –2}. The other two quasars are undetected, and have low X-ray to mid-IR luminosity ratios in both the low-energy (2-10 keV) and high-energy (10-40 keV) X-ray regimes that are consistent with extreme, Compton-thick absorption (N {sub H} ≳ 10{sup 24} cm{sup –2}). We find that for quasars at z ∼ 0.5, NuSTAR provides a significant improvement compared to lower energy (<10 keV) Chandra and XMM-Newton observations alone, as higher column densities can now be directly constrained.

  17. Toxicity and horizontal transfer of 0.5% fipronil dust against Formosan subterranean termites.

    PubMed

    Gautam, Bal K; Henderson, Gregg; Davis, Robert W

    2012-10-01

    The toxicity and horizontal transfer of a new formulation of fipronil, 0.5% fipronil dust, was tested against Coptotermes formosanus Shiraki in the laboratory. The formulation was applied in three different ways: 1) Directly applied to termites (donors) and mixed with untreated termites (recipients) at three ratios, viz., 50 donors: 50 recipients, 20 donors: 80 recipients and 10 donors: 90 recipients. 2) Applied onto the surface of 3 mm thick sand or soil substrate in a petri dish and then topped with another 3 mm thick sand or soil layer whereupon termites were released. 3) Applied to the inner surface of a tube (either 5 cm or 15 cm long) that connected two foraging dishes, one containing dry sand and the other moist sand plus a wood block and termites were released into the dry sand dish. All donors and >93% of the recipients were dead by 42 h after treatment in the direct treatment experiment. Significant mortalities of both donors and recipients were observed at 5 h after treatment at all donor: recipient ratios. During this period, the mortality of the recipients (but not donors) at 10:90 was significantly lower than those at the other two ratios. All termites were dead at 65 h after exposure (HAE) on the sand treatment and at 190 HAE on soil treatment. More than 96% mortality was observed at 40 HAE on the sand treatment as compared with only 6% mortality onsoil treatment during the same time period. In the tube treatment experiment, > 97% mortality was observed at 90 h after release for both tube lengths as compared with < 3% mortality in controls. About half of the termites were dead by 15 h after release regardless of the tube length. Our results showed that 0.5% fipronil dust is nonrepellent and readily transferred from treated to nontreated termites.

  18. NuSTAR Observations of Heavily Obscured Quasars at z Is Approximately 0.5

    NASA Technical Reports Server (NTRS)

    Lansbury, G. B.; Alexander, D. M.; Del Moro, A.; Gandhi, P.; Assef, R. J.; Stern, D.; Aird, J.; Ballantyne, D. R.; Balokovic, M.; Bauer, F. E.; Boggs, S. E.; Brandt, W. N.; Christensen, F. E.; Craig, W. W.; Elvis, M.; Grefenstette, B. W.; Hailey, C. J.; Harrison, F. A.; Hickox, R. C.; Koss, M.; LaMassa, S. M.; Luo, B.; Mullaney, J. R.; Teng, S. H.; Urry, C. M.; Zhang, W. W.

    2014-01-01

    We present NuSTAR hard X-ray observations of three Type 2 quasars at z approx. = 0.4-0.5, optically selected from the Sloan Digital Sky Survey. Although the quasars show evidence for being heavily obscured, Compton-thick systems on the basis of the 2-10 keV to [O(sub III)] luminosity ratio and multiwavelength diagnostics, their X-ray absorbing column densities (N(sub H)) are poorly known. In this analysis, (1) we study X-ray emission at greater than 10 keV, where X-rays from the central black hole are relatively unabsorbed, in order to better constrain N(sub H). (2) We further characterize the physical properties of the sources through broad-band near-UV to mid-IR spectral energy distribution analyses. One of the quasars is detected with NuSTAR at greater than 8 keV with a no-source probability of less than 0.1%, and its X-ray band ratio suggests near Compton-thick absorption with N(sub H) is approximately greater than 5 × 10(exp 23) cm(exp -2). The other two quasars are undetected, and have low X-ray to mid-IR luminosity ratios in both the low-energy (2-10 keV) and high-energy (10-40 keV) X-ray regimes that are consistent with extreme, Compton-thick absorption (N(sub H) is approximately greater than 10(exp 24) cm(exp -2)). We find that for quasars at z is approximately 0.5, NuSTAR provides a significant improvement compared to lower energy (less than 10 keV) Chandra and XMM-Newton observations alone, as higher column densities can now be directly constrained.

  19. Atomic disorder of Li0.5Ni0.5O thin films caused by Li doping: estimation from X-ray Debye–Waller factors

    PubMed Central

    Yang, Anli; Sakata, Osami; Yamauchi, Ryosuke; Kumara, L. S. R.; Song, Chulho; Katsuya, Yoshio; Matsuda, Akifumi; Yoshimoto, Mamoru

    2015-01-01

    Cubic type room-temperature (RT) epitaxial Li0.5Ni0.5O and NiO thin films with [111] orientation grown on ultra-smooth sapphire (0001) substrates were examined using synchrotron-based thin-film X-ray diffraction. The 11 and 22 rocking curves including six respective equivalent reflections of the Li0.5Ni0.5O and NiO thin films were recorded. The RT B 1 factor, which appears in the Debye–Waller factor, of a cubic Li0.5Ni0.5O thin film was estimated to be 1.8 (4) Å2 from its 11 and 22 reflections, even though the Debye model was originally derived on the basis of one cubic element. The corresponding Debye temperature is 281 (39) K. Furthermore, the B 2 factor in the pseudo-Debye–Waller factor is proposed. This parameter, which is evaluated using one reflection, was also determined for the Li0.5Ni0.5O thin film by treating Li0.5Ni0.5O and NiO as ideal NaCl crystal structures. A structural parameter for the atomic disorder is introduced and evaluated. This parameter includes the combined effects of thermal vibration, interstitial atoms and defects caused by Li doping using the two Debye–Waller factors. PMID:26664345

  20. Artificial layered perovskite oxides A(B{sub 0.5}B′{sub 0.5})O{sub 3} as potential solar energy conversion materials

    SciTech Connect

    Chen, Hungru; Umezawa, Naoto

    2015-02-07

    Perovskite oxides with a d{sup 0} electronic configuration are promising photocatalysts and exhibit high electron mobilities. However, their band gaps are too large for efficient solar energy conversion. On the other hand, transition metal cations with partially filled d{sup n} electronic configurations give rise to visible light absorption. In this study, by using hybrid density functional theory calculations, it is demonstrated that the virtues of the two categories of materials can be combined in perovskite oxide A(B{sub 0.5}B′{sub 0.5})O{sub 3} with a layered B-site ordering along the [001] direction. The electronic structures of the four selected perovskite oxide compounds, La(Ti{sub 0.5}Ni{sub 0.5})O{sub 3}, La(Ti{sub 0.5}Zn{sub 0.5})O{sub 3}, Sr(Nb{sub 0.5}Cr{sub 0.5})O{sub 3}, and Sr(Nb{sub 0.5}Fe{sub 0.5})O{sub 3} are calculated and discussed.

  1. Synthesis and superconductivity in spark plasma sintered pristine and graphene-doped FeSe0.5Te0.5

    NASA Astrophysics Data System (ADS)

    Puneet, Pooja; Podila, Ramakrishna; He, Jian; Rao, Apparao; Howard, Austin; Cornell, Nicholas; Zakhidov, Anvar A.; Department of Physics; Astronomy, Clemson Nanomaterials Center, Clemson University Team; Nanotech Institute, University of Texas at Dallas Team

    2015-03-01

    Replace this text with your abstract body. Here, we present a new ball-milling and spark plasma sintering based technique for the facile synthesis FeSe0.5Te0.5 superconductors (SC) without the need for pre-alloying. This method is advantageous since it is quick and flexible for incorporating other dopants such as graphene for vortex pinning. We observed that FeSe0.5Te0.5 exhibits a coexistence of ferromagnetic (FM) and SC signature plausibly arising from a FM core-SC shell structure. More importantly, the Hc2 values observed from resistivity data are higher than 7 T indicating that SPS process synthesized FeSe0.5Te0.5 samples could lead to nextgeneration superconducting wires and cables.

  2. Origin of Room Temperature Ferromagnetism in Cr-Doped Lead-Free Ferroelectric Bi0.5Na0.5TiO3 Materials

    NASA Astrophysics Data System (ADS)

    Thanh, L. T. H.; Doan, N. B.; Dung, N. Q.; Cuong, L. V.; Bac, L. H.; Duc, N. A.; Bao, P. Q.; Dung, D. D.

    2017-01-01

    The development of multiferroic materials based on lead-free ferroelectric material provides an opportunity to fabricate next-generation electronic devices. In this work, Cr-doped lead-free ferroelectric Bi0.5Na0.5TiO3 materials were synthesized by using the sol-gel method. The optical band gap was reduced from 3.12 eV to 2.12 eV for undoped and 9 mol.% Cr-doped Bi0.5Na0.5TiO3 with the substitution of Cr at the Ti-site. Cr-doped Bi0.5Na0.5TiO3 materials exhibited weak ferromagnetism at room temperature. Saturation magnetization was approximately 0.08 μ B/Cr at 5 K. Our work will facilitate the further understanding of the role of transition metal ferromagnetism in lead-free ferroelectric materials at room temperature.

  3. Observation of direct and indirect magnetoelectricity in lead free ferroelectric (Na0.5Bi0.5TiO3)-magnetostrictive (CoFe2O4) particulate composite

    NASA Astrophysics Data System (ADS)

    Srinivas, A.; Krishnaiah, R. V.; Karthik, T.; Suresh, P.; Asthana, Saket; Kamat, S. V.

    2012-08-01

    A particulate composite consisting of 65 mol. % Na0.5Bi0.5TiO3 and 35 mol. % CoFe2O4 was synthesized, and it's structure, microstructure, ferroelectric, magnetostrictive, magnetic, and direct/indirect magnetoelectric properties were studied. The composite showed different magnetization behaviour under electrically poled and un-poled conditions. The percentage change in magnetization as a result of poling is approximately -15% at 500 Oe magnetic field. Magnetostriction measurements displayed a value of λ11 = -57 × 10-6 and piezomagnetic coefficient δλ11/δH = 0.022 × 10-6 kOe-1 at 2.2 kOe for the composite. The maximum magnetoelectric output varied from 1350 mV/cm to 2000 mV/cm with change in the electrical poling conditions.

  4. Maxwell-Wagner relaxation and magnetodielectric properties of Bi0.5La0.5MnO3 ceramics

    NASA Astrophysics Data System (ADS)

    Turik, A. V.; Pavlenko, A. V.; Reznichenko, L. A.

    2016-08-01

    The complex permittivity ɛ = ɛ'- iɛ″ of manganite bismuth-lanthanum Bi0.5La0.5MnO3 ceramics has been measured at temperature T = 78 K in the frequency range f = 200-105 Hz and in the magnetic induction range B = 0-5 T. Dielectric relaxation and the pronounced magnetodielectric effect have been detected. The explanation based on the superposition of Maxwell-Wagner relaxation and the magnetoresistance effect has been proposed.

  5. Influence of Co-substitution on the structural and magnetic properties of nanocrystalline Ba0.5Sr0.5Fe12O19

    NASA Astrophysics Data System (ADS)

    Ezhil Vizhi, R.; Harikrishnan, V.; Saravanan, P.; Rajan Babu, D.

    2016-10-01

    One-step citrate gel combustion method followed by annealing (800 °C/2 h) was employed to synthesize cobalt substituted barium strontium hexaferrite with a chemical composition of Ba0.5Sr0.5Fe12-xCoxO19 (x=0, 0.5, 0.7, and 0.9). A combination of thermo-gravimetric analysis and differential scanning calorimetry was employed to understand the thermo-chemical behavior of Ba0.5Sr0.5Fe12O19. X-ray diffraction (XRD) was used to evaluate the hexagonal phase evolution for the barium strontium ferrite nanopowders and a formation of secondary phase: α-Fe2O3 is evident for the Ba0.5Sr0.5Fe12O19. Raman spectroscopy confirmed the presence of different sublattices of Fe3+ present in the hexaferrite structure. Fourier transform infrared spectroscopy demonstrated the usual stretching vibrations of tetrahedral and octahedral M-O bands. The morphology and chemical composition of the samples were analyzed by transmission electron microscopy and field emission scanning electron microscopy attached with energy dispersive X-ray analysis, respectively. Selected area electron diffraction studies showed the nanocrystalline nature of the samples. The magnetic parameters such as saturation magnetization MS, coercivity, HC and remanent magnetization, MR were estimated from the hysteresis loops. Maximum value of MS (70.5 emu/g) was obtained for the Ba0.5Sr0.5Fe11.5Co0.5O19 nanoparticles. A possible growth mechanism on the crystallization of Ba0.5Sr0.5Fe12O19 hexagonal platelets during the citrate gel combustion synthesis is highlighted.

  6. Effect of Tb and Al substitution within the rare earth and cobalt sublattices on magnetothermal properties of Dy0.5Ho0.5Co2

    NASA Astrophysics Data System (ADS)

    Chzhan, V. B.; Tereshina, E. A.; Mikhailova, A. B.; Politova, G. A.; Tereshina, I. S.; Kozlov, V. I.; Ćwik, J.; Nenkov, K.; Alekseeva, O. A.; Filimonov, A. V.

    2017-06-01

    The effect of Tb and Al substitution within the rare earth and cobalt sublattices on structural and magnetothermal properties of Dy0.5Ho0.5Co2 has been studied. Multicomponent Laves phase alloys Tbx(Dy0.5Ho0.5)1-xCo2-yAly (x = 0, 0.3, 0.4, 0.5; y = 0, 0.25) synthesized using high-purity metals have been studied using X-ray diffraction analysis, heat capacity and magnetocaloric measurements. Dy0.5Ho0.5Co2 has a first order phase transition at the Curie temperature TC ≈ 110 K. Both Tb and Al substitution leads to increase of the TC. The increasing Tb content leads to the decreases slightly the MCE and all the transitions near the Curie temperature are of the first order. As for the Al-containing compounds, MCE measurements show that the phase transition type changes from the first to the second-order. The advantage of Tbx(Dy0.5Ho0.5)1-xCo1.75Al0.25 as compared with Al-free alloys is 'table-like' behavior of MCE.

  7. Soft ferromagnetism and semiconductor to metal transition in Li0.5Mn0.5Fe2O4 ferrite

    NASA Astrophysics Data System (ADS)

    Vijayasri, G.; Bhowmik, R. N.

    2013-02-01

    Polycrystalline Li0.5Mn0.5Fe2O4 ferrite was synthesized by solid state route. The samples were characterized by XRD, EDX, dc magnetization and ac conductivity measurements. The samples are soft ferromagnet with spontaneous magnetization (MS) ˜ 61-64 emu/g and coercivity (HC) ˜ 22-30 Oe. Frequency activated ac conductivity measurement at different temperature suggested polaron hopping mechanism in the samples. Remarkably, there is a semiconductor to metallic transition in the temperature range 803 K-873 K depending on sintering temperature of Li0.5Mn0.5Fe2O4 ferrite.

  8. Crystal structure and carbon vacancy hardening of (W0.5Al0.5)C1-x prepared by a solid-state reaction.

    PubMed

    Yan, Junmin; Ma, Xianfeng; Zhao, Wei; Tang, Huaguo; Zhu, Changjun; Cai, Shuguang

    2005-10-14

    Novel solid solutions of aluminum in tungsten carbide (WC) with or without carbon vacancies, which can be expressed by the chemical formula (W(0.5)Al(0.5))C(1-x) (x=0.0-0.5), have been synthesized by the solid-state reaction of W(0.5)Al(0.5) alloy and the proper amount of carbon at around 1673 K in vacuum. The reaction time decreases from 73 to 50 h on increasing the carbon vacancy concentration from 0 to 50 %. The formation of the intended products is certified, by X-ray diffraction, environmental scanning electron microscopy-energy-dispersive X-ray analysis, and inductively coupled plasma-atomic emission spectroscopy, even though the carbon vacancy concentration reaches the astonishing value of 50 %. The as-prepared (W(0.5)Al(0.5))C(1-x) samples have been identified as the hexagonal WC-type structure belonging to the space group P6m2 (Z=1). Moreover, the crystallographic results reveal that the substituting aluminum atoms in the WC are located in the 1a site (the W atom position of the WC structure) and the cell parameters decrease slightly with increasing vacancy concentration. The hardness of the (W(0.5)Al(0.5))C(1-x) system increases up to a maximum 2659 kg mm(-2) at a carbon vacancy concentration of about 35 %, and the density of (W(0.5)Al(0.5))C(1-x) is far lower than that of WC.

  9. Reduction properties of phases in the system La 0.5Sr 0.5MO 3 ( M=Fe, Co)

    NASA Astrophysics Data System (ADS)

    Berry, Frank J.; Marco, José F.; Ren, Xiaolin

    2005-04-01

    Phases formed by the reduction of compounds of the type La 0.5Sr 0.5MO 3 ( M=Fe, Co) have been characterized by means of temperature programmed reduction, X-ray powder diffraction, 57Fe Mössbauer spectroscopy and Fe K-, Co K-, Sr K-, and La L III-edge X-ray absorption spectroscopy. The results show that treatment of the material of composition La 0.5Sr 0.5FeO 3 (which contains 50% Fe 4+ and 50% Fe 3+) at 650 °C in a flowing 90% hydrogen/10% nitrogen atmosphere results in the formation of an oxygen-deficient perovskite-related phase containing only trivalent iron. Further heating in the gaseous reducing environment at 1150 °C results in the formation of the Fe 3+-containing phase SrLaFeO 4, which has a K 2NiF 4-type structure, and metallic iron. The material of composition La 0.5Sr 0.5CoO 3 is more susceptible to reduction than the compound La 0.5Sr 0.5FeO 3 since, after heating at 520 °C in the hydrogen/nitrogen mixture, all the Co 4+ and Co 3+ are reduced to metallic cobalt with the concomitant formation of strontium- and lanthanum-oxides.

  10. Topotactic reduction and reoxidation of hexagonal RCu{sub 0.5}Ti{sub 0.5}O{sub 3} (R = Y, Eu-Lu) Phases

    SciTech Connect

    Jiang, Peng; Berthelot, Romain; Li, Jun; Sleight, A.W.; Subramanian, M.A.

    2013-06-01

    Highlights: ► Topotactic reduction of hexagonal RCu{sub 0.5}Ti{sub 0.5}O{sub 3} phases is performed. ► TGA and magnetism indicate a formula of RCu{sub 0.5}Ti{sub 0.5}O{sub 2.78} for the reduced phase. ► Topotactic reoxidation occurs on heating these phases to 400 °C in air. - Abstract: Hexagonal AMO{sub 2} and AMO{sub 3} phases have the same basic structure, and intermediate compositions for this structure have been prepared by topotactic oxidation of AMO{sub 2} phases such as RCuO{sub 2}, where R is a trivalent rare earth cation. We now find that such intermediate phases can also be prepared by topotactic reduction of hexagonal RCu{sub 0.5}Ti{sub 0.5}O{sub 3} (R = Y, Tb-Lu) phases. Our TGA and magnetic susceptibility studies indicate a formula of RCu{sub 0.5}Ti{sub 0.5}O{sub 2.78} for these reduced phases. Topotactic reoxidation occurs on heating these phases to 400 °C in air.

  11. Effect of rare-earth (Er and Gd) substitution on the magnetic and multiferroic properties of DyFe0.5Cr0.5O3

    NASA Astrophysics Data System (ADS)

    Sharma, Mohit K.; Basu, Tathamay; Mukherjee, K.; Sampathkumaran, E. V.

    2016-10-01

    We report the results of our investigations on the influence of partial substitution of Er and Gd for Dy on the magnetic and magnetoelectric properties of DyFe0.5Cr0.5O3, which is known to be a multiferroic system. Magnetic susceptibility and heat capacity data, apart from confirming the occurrence of magnetic transitions at ~121 and 13 K in DyFe0.5Cr0.5O3, bring out that the lower transition temperature only is suppressed by rare-earth substitution. Multiferroic behavior is found to persist in Dy0.4Ln0.6Fe0.5Cr0.5O3 (Ln  =  Er and Gd). There is an evidence for magnetoelectric coupling in all these materials with qualitative differences in its behavior as the temperature is changed across these two transitions. Remnant electric polarization is observed for all the compounds. The most notable observation is that electric polarization is seen to get enhanced as a result of rare-earth substitution with respect to that in DyFe0.5Cr0.5O3. Interestingly, a similar trend is seen in the magnetocaloric effect, consistent with the existence of magnetoelectric coupling. The results thus provide evidence for the tuning of magnetoelectric coupling by rare-earth substitution in this family of oxides.

  12. First principles study of Ca in BaTiO3 and Bi0.5Na0.5TiO3

    NASA Astrophysics Data System (ADS)

    Fongkaew, Ittipon; T-Thienprasert, Jiraroj; Limpijumnong, Sukit

    2015-11-01

    BaTiO3-Bi0.5Na0.5TiO3 is one of the promising candidates as a high-temperature relaxor with a high Curie temperature and several preferred dielectric characteristics. It has been found experimentally for a long time that adding calcium to BaTiO3-Bi0.5Na0.5TiO3 improves its temperature characteristic of the capacitance [J. Electron. Mater. 39, 2471]. In this study, Calcium (Ca) defects in perovskite BaTiO3 and Bi0.5Na0.5TiO3 have been studied based on first-principles calculations. In both BaTiO3 and Bi0.5Na0.5TiO3, our calculations showed that Ca atom energetically prefers to substitute for the cations, that is Ba, Bi, Na and Ti, depending on the growth conditions. In most cases, Ca predominantly substitutes on the A-site without providing additional electrical carriers (serve as either neutral defects or self-compensating defects). The growth conditions where Ca can be forced to substitute for B-site (with limited amount) and the conditions where Ca can be forced to serve as an acceptor are identified. Details of the local structures, formation energies and electronic properties of these Ca defects are reported.

  13. Fully gapped superconductivity in In-doped topological crystalline insulator Pb0.5Sn0.5Te

    SciTech Connect

    Du, Guan; Gu, G. D.; Du, Zengyi; Fang, Delong; Yang, Huan; Zhong, R. D.; Schneeloch, J.; Wen, Hai -Hu

    2015-07-27

    In this study, superconductors derived from topological insulators and topological crystalline insulators by chemical doping have long been considered to be candidates as topological superconductors. Pb0.5Sn0.5Te is a topological crystalline insulator with mirror symmetry protected surface states on (001)-, (011)-, and (111)-oriented surfaces. The superconductor (Pb0.5Sn0.5)0.7In0.3Te is produced by In doping in Pb0.5Sn0.5Te, and is thought to be a topological superconductor. Here we report scanning tunneling spectroscopy measurements of the superconducting state as well as the superconducting energy gap in (Pb0.5Sn0.5)0.7In0.3Te on a (001)-oriented surface. The spectrum can be well fitted by an anisotropic s-wave gap function of Δ = 0.72 + 0.18cos4θ meV using Dynes model. The results show that the superconductor seems to be a fully gapped one without any in-gap states, in contradiction with the expectation of a topological superconductor.

  14. Frequency dependent dielectric properties of Cu0.5Tl0.5Ba2Ca2(Cu3-yMy)O10-δ superconductor

    NASA Astrophysics Data System (ADS)

    Mumtaz, M.; Khan, Nawazish A.; Khan, Sajid

    2012-01-01

    The frequency dependent dielectric properties such as dielectric constants (ɛ/r, ɛ//r), absolute dielectric loss |tanδ|, and ac-conductivity (σac) of Cu0.5Tl0.5Ba2Ca2(Cu3-yMy)O10-δ (M = Si, Ge, Sn, y = 0, 1) superconductor have been investigated by means of capacitance (C) and conductance (G) measurements with the test frequency (f) in the range of 10 KHz to 10 MHz at various temperatures from superconducting state to normal conducting state. The negative capacitance has been observed in all Cu0.5Tl0.5Ba2Ca2(Cu3-yMy)O10-δ samples. The large values of negative dielectric constant (ɛ/r) at lower frequencies and temperatures are linked with reduced thermal vibrations of the atoms due to which polarizability has been enhanced. The decreased value of dielectric constant observed in the Ge-doped samples may possibly be linked with its greater electronegativity (EN) and less polarization. The electronegativity of Si and Sn has approximately the same values as that of Cu, so almost all the dielectric properties do not vary significantly in Si-doped Cu0.5Tl0.5Ba2 Ca2(Cu2Si1)O10-δ and Sn-doped Cu0.5Tl0.5Ba2Ca2(Cu2Sn1)O10-δ samples. These experimental investigations on dielectric properties of Cu0.5Tl0.5Ba2Ca2(Cu3-yMy)O10-δ superconductor have shown lower dielectric loss and higher ac-conductivity at all frequencies and temperatures as compared to that of other high Tc superconductor families. The decreased dielectric loss in Cu0.5Tl0.5Ba2Ca2(Cu3-yMy)O10-δ samples suggests that the polarization is most likely arising from the charge carriers between Cu0.5Tl0.5Ba2O4-δ charge reservoir layer and conducting CuO2/MO2 planes; since the charge reservoir layer has localized charge carriers at Ba+2, Tl+3, and Cu+2 sites, whereas CuO2/MO2 planes contain mobile charge carriers, which are displaced from their equilibrium position by external applied ac-field.

  15. Metamorphic Al0.5Ga0.5N:Si on AlN/sapphire for the growth of UVB LEDs

    NASA Astrophysics Data System (ADS)

    Enslin, Johannes; Mehnke, Frank; Mogilatenko, Anna; Bellmann, Konrad; Guttmann, Martin; Kuhn, Christian; Rass, Jens; Lobo-Ploch, Neysha; Wernicke, Tim; Weyers, Markus; Kneissl, Michael

    2017-04-01

    In this paper we investigate the growth of metamorphic Al0.5Ga0.5 N :Si on c-plane AlN/sapphire. The structural properties of the AlGaN:Si pseudo substrates and the electro-optical characteristics of subsequently grown UVB LEDs are being examined. We demonstrate, that superlattices allow the controlled strain relaxation of Al0.5Ga0.5 N by rearrangement of threading dislocations, thus preventing the formation of cracks. This study investigates AlN/GaN superlattices with a nominal GaN layer thickness between 1.0 nm and 2.5 nm at a fixed AlN layer thickness of 2.5 nm. The number of superlattice-periods was also varied between 20 and 120. It was found that beyond a GaN layer thickness of 1.5 nm three-dimensional structures are formed. Additionally, these three-dimensional structures reduce the local defect density of the subsequently grown Al0.5Ga0.5 N layer. Although the Al0.5Ga0.5 N layer appears to be almost fully relaxed, the relaxation state of this pseudo substrate, was found to be dependent on the GaN layer thickness in the superlattice. After optimizing the superlattice structure we were able to grow crack free 4 μm thick Si-doped Al0.5Ga0.5 N layers and on top UVB LEDs with a fully strained active region emitting at 310 nm with output powers of more than 18 mW at 500 mA.

  16. Li2Ni(0.5)Mn(0.5)SnO4/C: A Novel Hybrid Composite Electrode for High Rate Applications.

    PubMed

    Vellaisamy, Mani; Nallathamby, Kalaiselvi

    2015-09-08

    A novel Li2Ni(0.5)Mn(0.5)SnO4/C composite electrode, existing as a hybrid consisting of monoclinic Li2SnO3 and layered LiNi(0.5)Mn(0.5)O2, has been identified and validated for high capacity and high rate lithium battery applications. Of the components, LiNi(0.5)Mn(0.5)O2 upon discharge forms the corresponding dilithium oxide, viz., Li2Ni(0.5)Mn(0.5)O2, and facilitates the progressive electrochemical performance of the composite electrode. Similarly, Li2SnO3 upon discharge forms Li2O and SnO2, wherein the unacceptable volume expansion related issues of SnO2 are addressed by the buffering activity of Li2O phase. A combination of alloying/dealloying, conversion, and redox mechanism is responsible for the excellent electrochemical behavior of Li2Ni(0.5)Mn(0.5)SnO4/C electrode. With this newer formulation of dilithium stannate composite, a superior capacity of >3000 mAh g(-1) at 100 mA g(-1) current density has been demonstrated. The study opens up a newer gateway for the entry of Li2SnO3·LiM1M2O2 hybrid formulations for exploitation up to 1 A g(-1) rate, thus ensuring the sustainable development of potential electrode materials for high rate applications.

  17. Temperature Evolution of Physical Properties of BaTi0.9(Nb0.5Yb0.5)0.1O3 Lead-Free Ceramic

    NASA Astrophysics Data System (ADS)

    Abdelkafi, Z.; Abdelmoula, N.; Khemakhem, H.

    2016-11-01

    BaTi0.9(Nb0.5Yb0.5)0.1O3 lead-free ceramic was prepared by a solid-state reaction method. The structure of BaTi0.9(Nb0.5Yb0.5)0.1O3 has been characterized by means of x-ray diffraction, showing the coexistence of cubic (31.1%) and tetragonal (68.9%) phases at room temperature. Dielectric spectroscopy shows that BaTi0.9(Nb0.5Yb0.5)0.1O3 composition sintered at 1380°C exhibits a relaxor behavior with a weak diffuse phase transition obeying a Lorentz-type quadratic relationship. The ferroelectric-paraelectric phase transition T C decreased from 420 K for BaTiO3 to 284 K for BaTi0.9(Nb0.5Yb0.5)0.1O3. The dielectric loss of this ceramic was <0.09 over a wide temperature range (<400 K). The temperature behavior of the main piezoelectric parameters, such as the piezoelectric coefficient d 31 and the electromechanical coupling factor k p, was investigated. d 31 sets a maximum about 32.5 pC/N at temperature of 220 K. Nevertheless, k p undergoes more or less important changes between 120 K and 200 K. Over 200 K, k p degrades very rapidly due to the depoling effect deduced from the hysterisis measurements. Dielectric and structural properties of BaTi0.9(Nb0.5Yb0.5)0.1O3 were confirmed by Raman spectroscopy.

  18. Structural and Mössbauer spectroscopy characterization of bulk and nanostructured TiFe0.5 Ni0.5/graphite compounds and their hydrides

    NASA Astrophysics Data System (ADS)

    Martínez, M. A. R.; André-Filho, J.; Félix, L. L.; Coaquira, J. A. H.; Garg, V. K.; Oliveira, A. C.; Mestnik-Filho, J.

    2015-06-01

    The structural and hyperfine properties of bulk TiFe0.5Ni0.5 intermetallic and ball-milled TiFe0.5Ni0.5/graphite compounds and their hydrides have been studied. The bulk and nanostructured TiFe0.5Ni0.5 compounds crystallize in the cubic crystal structure of CsCl (B2). After hydrogenation, the formation of hydrogen-poor phase (∝-phase) and hydride phase ( β-phase) have been determined for the bulk compound. However, the formation of the ∝-phase and the hydrogen-richest phase ( γ-phase) and other secondary phases have been determined for the ball-milled TiFe0.5Ni0.5/graphite sample. It has been determined that the ball-milled TiFe0.5Ni0.5/graphite sample presents a large amount of the γ-phase which indicates that the presence of graphite nearby nanostructured intermetallic grains enhances the absorption of hydrogen. Mossbauer results are consistent with the structural results. Meanwhile, no significant changes in the isomer shift (IS) value has been determined for the α-phase with respect to the intermetallic compound, a strong increase in the IS value has been determined for the β- and γ-phases with respect to the ∝-phase. That increase indicates a decrease of the s-electron density at the Fe nuclei due to the charge transfer from the metal to the nearby hydrogen atoms.

  19. CONDENSED MATTER: STRUCTURE, THERMAL AND MECHANICAL PROPERTIES: Fabrication and magnetic properties of Ni0.5Zn0.5Fe2O4 nanofibres by electrospinning

    NASA Astrophysics Data System (ADS)

    Xiang, Jun; Shen, Xiang-Qian; Song, Fu-Zhan; Liu, Ming-Quan

    2009-11-01

    NiZn ferrite/polyvinylpyrrolidone composite fibres were prepared by sol-gel assisted electrospinning. Ni0.5Zn0.5Fe2O4 nanofibres with a pure cubic spinel structure were obtained subsequently by calcination of the composite fibres at high temperatures. This paper investigates the thermal decomposition process, structures and morphologies of the electrospun composite fibres and the calcined Ni0.5Zn0.5Fe2O4 nanofibres at different temperatures by thermo-gravimetric and differential thermal analysis, x-ray diffraction, Fourier transform infrared spectroscopy and field emission scanning electron microscopy. The magnetic behaviour of the resultant nanofibres was studied by a vibrating sample magnetometer. It is found that the grain sizes of the nanofibres increase significantly and the nanofibre morphology gradually transforms from a porous structure to a necklace-like nanostructure with the increase of calcination temperature. The Ni0.5Zn0.5Fe2O4 nanofibres obtained at 1000 °C for 2 h are characterized by a necklace-like morphology and diameters of 100-200 nm. The saturation magnetization of the random Ni0.5Zn0.5Fe2O4 nanofibres increases from 46.5 to 90.2 emu/g when the calcination temperature increases from 450 to 1000 °C. The coercivity reaches a maximum value of 11.0 kA/m at a calcination temperature of 600 °C. Due to the shape anisotropy, the aligned Ni0.5Zn0.5Fe2O4 nanofibres exhibit an obvious magnetic anisotropy and the ease magnetizing direction is parallel to the nanofibre axis.

  20. Structural, thermal and electrical conductivity characteristics of Ln{sub 0.5}Sr{sub 0.5}Ti{sub 0.5}Mn{sub 0.5}O{sub 3±d} (Ln: La, Nd and Sm) complex perovskites as anode materials for solid oxide fuel cell

    SciTech Connect

    Jeong, Jihoon; Azad, Abul K.; Schlegl, Harald; Kim, Byungjun; Baek, Seung-Wook; Kim, Keunsoo; Kang, Hyunil; Kim, Jung Hyun

    2015-03-15

    The Ti and Mn replaced complex perovskites, Ln{sub 0.5}Sr{sub 0.5}Ti{sub 0.5}Mn{sub 0.5}O{sub 3±d} (Ln: La, Nd and Sm), were reported as potential anode materials for high temperature-operating solid oxide fuel cells (HT-SOFCs). For the present research study, synthesis, crystallographic, thermal and electrical conductivity properties of Ln{sub 0.5}Sr{sub 0.5}Ti{sub 0.5}Mn{sub 0.5}O{sub 3±d} complex perovskites were investigated using X-ray diffraction (XRD), Rietveld method, thermogravimetric analysis (TGA) and electrical conductivity to apply these oxide materials for the HT-SOFC anode materials. XRD results showed that Ln{sub 0.5}Sr{sub 0.5}Ti{sub 0.5}Mn{sub 0.5}O{sub 3±d} oxide systems synthesized as single phases did not react with 8 mol% yttria stabilized zirconia (8YSZ) and 10 mol% Gd-doped cerium oxide (CGO91) up to 1500 °C and did not decompose under dry 3.9% hydrogen at 850 °C. The crystal structures of La{sub 0.5}Sr{sub 0.5}Ti{sub 0.5}Mn{sub 0.5}O{sub 3±d} (LSTM), Nd{sub 0.5}Sr{sub 0.5}Ti{sub 0.5}Mn{sub 0.5}O{sub 3±d} (NSTM) and Sm{sub 0.5}Sr{sub 0.5}Ti{sub 0.5}Mn{sub 0.5}O{sub 3±d} (SSTM) showed orthorhombic symmetry with the space group Pbnm and SSTM showed a more distorted structure. Thermogravimetric analysis (TGA) proved weight gains in these three sample occurred under oxidizing conditions and weight loss under reducing conditions. Electrical conductivity values of NSTM were higher than those of LSTM and SSTM under oxidizing and reducing conditions. - Graphical abstract: The B-site cations (Ti/Mn) are surrounded by regular octahedra of oxygen in Nd{sub 0.5}Sr{sub 0.5}Ti{sub 0.5}Mn{sub 0.5}O{sub 3±d}(NSTM). These octahedra are linked together in a corner sharing three dimensional framework, while Nd/Sr ion occupies 12-coordinated A-site between these octahedra. The Ti/Mn–O{sub 6} octahedra are elongated along the c-axis. The crystal structure distortion was due to the smaller ionic radius of the A-site cations, which force the (Ti

  1. Characterization of Cu3P phase in Sn3.0Ag0.5Cu0.5P/Cu solder joints

    NASA Astrophysics Data System (ADS)

    Chen, Jian-xun; Zhao, Xing-ke; Zou, Xu-chen; Huang, Ji-hua; Hu, Hai-chun; Luo, Hai-lian

    2014-01-01

    This article reports the effects of phosphorus addition on the melting behavior, microstructure, and mechanical properties of Sn3.0Ag0.5Cu solder. The melting behavior of the solder alloys was determined by differential scanning calorimetry. The interfacial microstructure and phase composition of solder/Cu joints were studied by scanning electron microscopy and energy dispersive spectrometry. Thermodynamics of Cu-P phase formation at the interface between Sn3.0Ag0.5Cu0.5P solder and the Cu substrate was characterized. The results indicate that P addition into Sn3.0Ag0.5Cu solder can change the microstructure and cause the appearance of rod-like Cu3P phase which is distributed randomly in the solder bulk. The Sn3.0Ag0.5Cu0.5P joint shows a mixture of ductile and brittle fracture after shear testing. Meanwhile, the solidus temperature of Sn3.0Ag0.5Cu solder is slightly enhanced with P addition.

  2. Thermal Stability and Humidity Resistance of ScTaO4 Modified (K0.5Na0.5)NbO3 Ceramics

    NASA Astrophysics Data System (ADS)

    Zheng, Li-Mei; Wang, Jin-Feng; Wang, Chun-Ming; Wu, Qing-Zao; Zang, Guo-Zhong

    2009-12-01

    Lead-free (Na0.5K0.5)NbO3-xmol% ScTaO4 (x = 0-1.5) ceramics are prepared using the conventional solid-state reaction method and their properties are investigated in detail. The results indicate that the piezoelectric properties and density are improved by the introduction of ScTaO4. Due to the high orthorhombic-tetragonal phase transition temperature TO-T (around 200° C), stable piezoelectric properties against temperature are obtained. In a wide temperature range of 15-160° C, kp of the (Na0.5K0.5)NbO3-0.5 mol% ScTaO4 ceramic remains almost unchanged and d31 increases slightly from 59 pC/N to 71 pC/N. The deliquescent problem is effectively solved by the addition of ScTaO4. The piezoelectric properties of ScTaO4 modified (Na0.5K0.5)NbO3 ceramics show no obvious reduction and dielectric loss increases slightly after 120 h of immersion. From the analysis, it is suggested that the density is an important factor that improves the humidity resistance of the specimens.

  3. Effect of Zn2+ Substitution on the Structure and Magnetic Properties of Co0.5Cu0.5Fe2O4 Synthesized by Solvothermal Method

    NASA Astrophysics Data System (ADS)

    Huang, Xusheng; Zhou, Yuan; Wu, Wenwei; Xu, Jiawei; Liu, Shangqian; Liu, Dongsheng; Wu, Juan

    2016-06-01

    A series of Zn2+ doped Co-Cu ferrites with the formula Co0.5Cu0.5- x Zn x Fe2O4 (0.0 ≤ x ≤ 0.3) have been successfully synthesized using the solvothermal method. X-ray diffraction and scanning electron microscopy results indicate that a high-crystallized cubic Co0.5Cu0.5- x Zn x Fe2O4 with rod-like structure is obtained when the precursor is calcined at 800°C in air for 3 h. The lattice parameters increase with the increase of Zn2+ additional amount, attributed to the larger ionic radius of the substituted ion Zn2+ than Cu2+ ionic radius. Zn2+ substitution can improve the magnetic properties of Co0.5Cu0.5- x Zn x Fe2O4. Co0.5Cu0.4Zn0.1Fe2O4 obtained at 800°C has the highest specific saturation magnetization (73.7 ± 0.9 emu/g) and magnetic moment (3.13 ± 0.04 B.M.).

  4. Temperature dependent structures and properties of Bi0.5Na0.5TiO3-based lead free piezoelectric composite.

    PubMed

    Zhang, Ji; Sun, Lei; Geng, Xiao-Yu; Zhang, Bin-Bin; Yuan, Guo-Liang; Zhang, Shan-Tao

    2016-07-05

    The thermal depolarization around 100 °C of the Bi0.5Na0.5TiO3-based piezoelectric solid solutions leads to the disappearance of macroscopic ferroelectric/piezoelectric properties and remains a long-standing obstacle for their actual applications. In this communication, we report lead-free piezoelectric composites of 0.94Bi0.5Na0.5TiO3-0.06BaTiO3:0.5ZnO (BNT-6BT:0.5ZnO, where 0.5 is the mole ratio of ZnO to BNT-6BT) with deferred thermal depolarization, which is experimentally confirmed by systematic temperature dependent dielectric, ferroelectric, piezoelectric measurements. Especially, based on temperature dependent X-ray diffraction measurements on unpoled and poled samples, thermal depolarization is confirmed to have no relationship with the structural phase transition, the possible mechanism for the deferred thermal depolarization is correlated with the ZnO-induced local electric field which can suppress the depolarization field. We believe our results may be helpful for understanding the origin of thermal depolarization in BNT-based piezoelectric materials, and thus provide an effective way to overcoming this obstacle.

  5. Synergetic effect of Zn substitution on the electron and phonon transport in Mg2Si0.5Sn0.5-based thermoelectric materials.

    PubMed

    Gao, Hongli; Zhu, Tiejun; Zhao, Xinbing; Deng, Yuan

    2014-10-07

    Mg2Si1-xSnx alloys are a prospective material for thermoelectric generators at moderate temperatures. The thermoelectric properties of Mg2Si0.5Sn0.5-based thermoelectric materials with only Zn substitution or Zn/Sb co-doping were investigated. Isoelectronic Zn substitution did not affect the carrier concentration, but improved the carrier mobility. Zn atoms incorporated into a Sb-doped Mg2Si0.5Sn0.5 matrix simultaneously boosted the power factor and suppressed the lattice thermal conductivity, leading to an enhancement of the thermoelectric figure of merit ZT of the resulting bulk materials. The interplay between the electron and phonon transport of Mg2Si0.5Sn0.49Sb0.01 substituted with Zn at Mg sites results in an enhancement of the ZT by 25% at ∼730 K, from ZT≈ 0.8 in Mg2Si0.5Sn0.49Sb0.01 to ZT≈ 1.0 in Mg1.98Zn0.02Si0.5Sn0.49Sb0.01. Solid solutions in the Mg2Si-Mg2Sn system appear to be more promising for thermoelectric applications.

  6. Robust NdBa0.5Sr0.5Co1.5Fe0.5O5+δ cathode material and its degradation prevention operating logic for intermediate temperature-solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Lee, Tae-Hee; Park, Ka-Young; Kim, Nam-In; Song, Sun-Ju; Hong, Ki-Ha; Ahn, Docheon; Azad, Abul K.; Hwang, Junyeon; Bhattacharjee, Satadeep; Lee, Seung-Cheol; Lim, Hyung-Tae; Park, Jun-Young

    2016-11-01

    We report solutions (durable material and degradation prevention method) to minimize the performance degradation of cell components occurring in the solid oxide fuel cell (SOFC) operation. Reliability testing is carried out with the Nisbnd Nd0.1Ce0.9O2-δ (NDC) anode-supported intermediate temperature-SOFCs. For the cathode materials, single perovskite structured Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) and double perovskite structured NdBa0.5Sr0.5Co1.5Fe0.5O5+δ (NBSCF) are prepared and evaluated under harsh SOFC operating conditions. The double perovskite NBSCF cathode shows excellent stability in harsh SOFC environments of high humidity and low flow rate of air. Furthermore, we propose the concurrent fuel and air starvation mode, in which the cell potential is temporarily reduced due to the formation of both fuel-starvation (in the anode) and air-depletion (in the cathode) concurrently under a constant load. This is carried out in order to minimize the performance decay of the stable NBSCF-cell through the periodic and extra reduction of aH2 O (and aO2) in the anode. The operating-induced degradation of SOFCs, which are ordinarily assumed to be unrecoverable, can be completely circumvented by the proposed periodical operation logic to prevent performance degradation (concurrent fuel-starvation and air-depletion mode).

  7. La{sub 0.5}Sr{sub 0.5}TiO{sub 3} nanopowders prepared by the hydrothermal method

    SciTech Connect

    Putjuso, Thanin; Maensiri, Santi; Hunpratub, Sitchai; Swatsitang, Ekaphan

    2012-09-15

    Graphical abstract: LRTEM image of the single-phase La{sub 0.5}Sr{sub 0.5}TiO{sub 3} particles. It is seen from the figure that the product has a plate-like morphology with average particles sizes in the range of 100–300 nm. In addition, the SAED data taken from an individual particle (lower inset) shows the presence of sharp diffraction rings, which are indicative of polycrystalline La{sub 0.5}Sr{sub 0.5}TiO{sub 3} formation. The high-resolution TEM image (upper inset) shows for further confirmation of a crystalline structure of La{sub 0.5}Sr{sub 0.5}TiO{sub 3} powder. This image shows a clearly resolved crystalline domain with uniform interplanar spacing of 0.276 nm. Highlights: ► La{sub 0.5}Sr{sub 0.5}TiO{sub 3} nanopowder is prepared in 2 M KOH solution by hydrothermal method. ► The solution is heat treated at 220 °C for 24 h in air. ► LRTEM reveals a plate-like morphology of particle with average size of 100–300 nm. ► HRTEM image shows a crystalline domain with interplanar spacing of 0.276 nm. -- Abstract: La{sub 0.5}Sr{sub 0.5}TiO{sub 3} nanopowders were prepared by the hydrothermal method. The influence of processing parameters, including KOH concentration, reaction temperature and reaction time on the obtained products were studied. The structure and morphology of the obtained products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The XRD results show that pure phase La{sub 0.5}Sr{sub 0.5}TiO{sub 3} nanopowders can be successfully synthesized with 2 M KOH concentration at a low temperature of 220 °C for 24 h. In addition, the product has a plate-like shape with particle sizes in the range of 25–100 nm as estimated by TEM.

  8. 125Te Synchrotron-Radiation-Based Mössbauer Spectroscopy of Fe1.1Te and FeTe0.5Se0.5

    NASA Astrophysics Data System (ADS)

    Kurokuzu, Masayuki; Kitao, Shinji; Kobayashi, Yasuhiro; Saito, Makina; Masuda, Ryo; Mitsui, Takaya; Yoda, Yoshitaka; Seto, Makoto

    2014-04-01

    The 125Te Mössbauer spectra of Fe1.1Te and FeTe0.5Se0.5 were measured using synchrotron-radiation-based Mössbauer spectroscopy. The hyperfine field of Te in the antiferromagnetic phase of Fe1.1Te was evaluated to be 4(1) T at 20 K, and this hyperfine field is considered to be due to the transferred hyperfine field from Fe magnetic moments. The evaluated hyperfine field was comparatively large, suggesting the strong correlation with the magnetic moment of Fe that forms a double-stripe type magnetic structure. For the superconductor FeTe0.5Se0.5, no marked change in its Mössbauer parameters was observed below or above the superconducting transition temperature, indicating that the change in the electronic state of Te was small.

  9. Investigation of Coulomb scattering on sSi/Si0.5Ge0.5/sSOI quantum-well p-MOSFETs

    NASA Astrophysics Data System (ADS)

    Jiao, Wen; Qiang, Liu; Chang, Liu; Yize, Wang; Bo, Zhang; Zhongying, Xue; Zengfeng, Di; Wenjie, Yu; Qingtai, Zhao

    2016-09-01

    sSi/Si0.5Ge0.5/sSOI quantum-well (QW) p-MOSFETs with HfO2/TiN gate stack were fabricated and characterized. According to the low temperature experimental results, carrier mobility of the strained Si0.5Ge0.5 QW p-MOSFET was mainly governed by phonon scattering from 300 to 150 K and Coulomb scattering below 150 K, respectively. Coulomb scattering was intensified by the accumulated inversion charges in the Si cap layer of this Si/SiGe heterostructure, which led to a degradation of carrier mobility in the SiGe channel, especially at low temperature. Project supported by the National Natural Science Foundation of China (Nos. 61306126, 61306127, 61106015) and the CAS International Collaboration and Innovation Program on High Mobility Materials Engineering.

  10. Electric field-induced tuning of magnetism in PbFe{sub 0.5}Nb{sub 0.5}O{sub 3} at room temperature

    SciTech Connect

    Rayaprol, S. E-mail: brangadi@gmail.com; Mukherjee, S.; Kaushik, S. D.; Matteppanavar, S.; Angadi, B. E-mail: brangadi@gmail.com

    2015-08-07

    We study the influence of electrical poling, carried out at room temperature, on the structure and magnetism of Pb(Fe{sub 0.5}Nb{sub 0.5})O{sub 3} by analyzing the differences observed in structural and magnetic properties before and after the electrical poling. The changes observed in magnetization of Pb(Fe{sub 0.5}Nb{sub 0.5})O{sub 3} before and after electrical poling exhibit considerably strong converse magnetoelectric effect at room temperature. In addition, the strengthening of Fe/Nb-O bond due to electrical poling is discussed on the basis of Raman spectral studies and analysis of neutron diffraction patterns. The potential tunability of magnetization with electrical poling can be an ideal tool for realization of application potential of this multiferroic material.

  11. Phase competition and effect of chemical ordering in ferroelectric relaxor PbSc0.5Nb0.5O3 from first principles

    NASA Astrophysics Data System (ADS)

    Paściak, M.; Welberry, T. R.; Hlinka, J.

    2016-08-01

    We present results of first principles calculations for ferroelectric relaxor PbSc0.5Nb0.5O3. An ordered supercell with Sc and Nb atoms alternating in all directions (NaCl-like superstructure) has a ferroelectric ground state with R3 spacegroup. It is characterized by a tilt system a-a-a- as well as different sizes of adjacent oxygen octahedra. Analysis of phonon instabilities in cubic ? reveals similarity with an antiferroelectric PbZrO3. This is further confirmed by the fact that possibly antiferroelectric P21/b structure of PbSc0.5Nb0.5O3 (symmetry lowered from Pbam due to Sc/Nb superstructure) is energetically very close to the ground state. The ferroelectric order is shown to be less sensitive to deviations in the B-site distribution than the antiferroelectric one.

  12. Effects of capping on GaN quantum dots deposited on Al{sub 0.5}Ga{sub 0.5}N by molecular beam epitaxy

    SciTech Connect

    Korytov, M.; Benaissa, M.; Huault, T.; Neisius, T.

    2009-04-06

    The impact of the capping process on the structural and morphological properties of GaN quantum dots (QDs) grown on fully relaxed Al{sub 0.5}Ga{sub 0.5}N templates was studied by transmission electron microscopy. A morphological transition between the surface QDs, which have a pyramidal shape, and the buried ones, which have a truncated pyramid shape, is evidenced. This shape evolution is accompanied by a volume change: buried QDs are bigger than surface ones. Furthermore a phase separation into Al{sub 0.5}Ga{sub 0.5}N barriers was observed in the close vicinity of buried QDs. As a result, the buried QDs were found to be connected with the nearest neighbors by thin Ga-rich zones, whereas Al-rich zones are situated above the QDs.

  13. Low-temperature synthesis and growth of superparamagnetic Zn 0.5Ni 0.5Fe 2O 4 nanosized particles

    NASA Astrophysics Data System (ADS)

    Li, Xia; Wang, Guisu

    2009-05-01

    Mono-disperse spinel Ni 0.5Zn 0.5Fe 2O 4 nanosized particles have been synthesized via a hydrothermal method at low temperature. X-ray diffraction (XRD), transmission electron microscope (TEM) and high-resolution transmission electron microscope (HRTEM) analysis indicated that the synthesized nanocrystals were of pure cubic spinel structure with the size about 6-20 nm. The activation energy of grain growth is 35.06 kJ/mol experimented by the Arrhenius equation. A primary experimental model was put forward to shed light on the growth mechanism of crystallined spinel Ni-Zn ferrite nanosized particles under hydrothermal conditions. The magnetic measurements shows that the prepared Ni 0.5Zn 0.5Fe 2O 4 nanoparticle possess good superparamagnetic behavior.

  14. Neutron Scattering Study of Magnetic Excitation Spectrum on Fe1-x(Ni/Cu)xTe0.5Se0.5

    NASA Astrophysics Data System (ADS)

    Xu, Zhijun; Wen, Jinsheng; Xu, Guangyong; Gu, Genda; Tranquada, John

    2012-02-01

    We have performed a series of neutron scattering and magnetization measurements on Fe1-x(Ni/Cu)xTe0.5Se0.5 with different Ni/Cu compositions to study the interplay between magnetism and superconductivity. Substituting 2% and 4% of Ni for Fe reduces Tc from 15 K to 12 K and 8 K, while 10% of Cu results in lost of superconductivity. Spin resonance with lower energy are found in all superconducting samples. The overall shape of the low energy magnetic dispersion changes from two incommensurate vertical columns at T>>Tc to a distinctly different U-shaped dispersion at low temperature in superconducting samples. This spectral reconstruction is apparent for temperature up to 3Tc. On the other hand, no static order around (0.5,0,0.5) was found in any of these samples.

  15. Strikingly dissimilar effect of Mn and Zn dopants imposed on local structural distortion of Ba0.5K0.5Fe2As2 superconductor.

    PubMed

    Cheng, Jie; Dong, Peng; Chu, Wangsheng; Xu, Wei; Wen, Haihu; Marcelli, Augusto; Wu, Ziyu

    2013-05-01

    To clarify the contrasting impurity effects of Mn and Zn dopants on the critical temperature of optimally doped Ba0.5K0.5Fe2As2 superconductors, extended X-ray absorption fine-structure spectroscopy was implemented at the Fe and As K-edge. In Mn-doped compounds a gradual deviation of the symmetric FeAs4 tetrahedron and weakening of the Fe-As bond was observed. Conversely, in Zn-doped compounds the perfect FeAs4 tetrahedron is maintained and the Fe-As bond is rigid. The local structural details are consistent with the development of superconductivity in these two systems, suggesting a significant role played by the topology of the FeAs4 tetrahedron and rigidness of the Fe-As bond in Mn/Zn-doped Ba0.5K0.5Fe2As2 superconductors.

  16. Thermochromic effect at room temperature of Sm{sub 0.5}Ca{sub 0.5}MnO{sub 3} thin films

    SciTech Connect

    Boileau, A.; Capon, F.; Barrat, S.; Pierson, J. F.; Laffez, P.

    2012-06-01

    Sm{sub 0.5}Ca{sub 0.5}MnO{sub 3} thermochromic thin films were synthesized using dc reactive magnetron co-sputtering and subsequent annealing in air. The film structure was studied by x-ray diffraction analysis. To validate the thermochromic potentiality of Sm{sub 0.5}Ca{sub 0.5}MnO{sub 3}, electrical resistivity and infrared transmittance spectra were recorded for temperatures ranging from 77 K to 420 K. The temperature dependence of the optical band gap was estimated in the near infrared range. Upon heating, the optical transmission decreases in the infrared domain showing a thermochromic effect over a wide wavelength range at room temperature.

  17. Global and local structural variations near the antiferroelectric regime in Na{sub 0.5}Bi{sub 0.5}TiO{sub 3}

    SciTech Connect

    Thangavelu, Karthik; Rayaprol, S.; Siruguri, V.; Sastry, P. U.; Asthana, Saket

    2015-06-24

    Rietveld refinement of neutron and x-ray diffraction data of Na{sub 0.5}Bi{sub 0.5}TiO{sub 3} shows R3c phase stabilization at room temperature. The intermediate antiferroelectric region between 180°C to 280°C exhibits phase coexistence i.e R3c + Pnma, along with decrease in octahedral tilt angle and increase in unit cell volume. The local structural changes observed from Raman scattering in the A-O, Ti-O and TiO{sub 6} phonon modes favor the global structural variation. A possible antiparallel cation displacement due to Pnma phase formation leads to the origin of antiferroelectric ordering in Na{sub 0.5}Bi{sub 0.5}TiO{sub 3}.

  18. Dielectric characterization of multiferroic magnetoelectric double-perovskite Y(Ni0.5Mn0.5)O3 thin films

    NASA Astrophysics Data System (ADS)

    Coy, L. E.; Fina, I.; Ventura, J.; Yate, L.; Langenberg, E.; Polo, M. C.; Ferrater, C.; Varela, M.

    2016-10-01

    We report on the functional properties of the Y(Ni0.5Mn0.5)O3 epitaxial thin films, growth by pulsed laser deposition, observing the clear features of their ferroelectric and ferromagnetic nature at cryogenic temperature. The characterization of temperature-dependent complex impedance spectroscopy has shown a dielectric anomaly around the ferromagnetic Curie temperature (≈100 K) indicative of coupling between magnetic and electric orders.

  19. Fully ALD-grown TiN/Hf0.5Zr0.5O2/TiN stacks: Ferroelectric and structural properties

    NASA Astrophysics Data System (ADS)

    Zarubin, Sergei; Suvorova, Elena; Spiridonov, Maksim; Negrov, Dmitrii; Chernikova, Anna; Markeev, Andrey; Zenkevich, Andrei

    2016-11-01

    Since the discovery of ferroelectricity (FE) in HfO2-based thin films, they are gaining increasing attention as a viable alternative to conventional FE in the next generation of non-volatile memory devices. In order to further increase the density of elements in the integrated circuits, it is essential to adopt a three-dimensional design. Since atomic layer deposition (ALD) processes are extremely conformal, ALD is the favored approach in the production of 3D ferroelectric random access memory. Here, we report the fabrication of fully ALD-grown capacitors comprising a 10-nm-thick FE Hf0.5Zr0.5O2 layer sandwiched between TiN electrodes, which are subjected to a detailed investigation of the structural and functional properties. The robust FE properties of Hf0.5Zr0.5O2 films in capacitors are established by several alternative techniques. We demonstrate a good scalability of TiN/Hf0.5Zr0.5O2/TiN FE capacitors down to 100-nm size and the polarization retention in the test "one transistor-one capacitor" (1T-1C) cells after 1010 writing cycles. The presence of a non-centrosymmetric orthorhombic phase responsible for FE properties in the alloyed polycrystalline Hf0.5Zr0.5O2 films is established by transmission electron microscopy. Given the ability of the ALD technique to grow highly conformal films and multilayered structures, the obtained results indicate the route for the design of FE non-volatile memory devices in 3D integrated circuits.

  20. Ultrasonic Study on Charge Ordering in Nd0:5Ca0:5Mn1-xAlxO3 (x=0,0.03)

    NASA Astrophysics Data System (ADS)

    Liu, Yi; Kong, Hui; Su, Jin-rui; Zh, Chang-fei

    2006-12-01

    The ultrasonic, magnetic and transport properties of Nd0:5Ca0:5Mn1-xAlxO3 (x=0,0.03) were studied from 15 to 300 K. The temperature dependencies of resistivity and magnetization show that Nd0:5Ca0:5MnO3 undergoes a charge ordering transition at TCO ~ 257 K. An obvious softening of the longitudinal sound velocity above TCO and a dramatic stiffening below TCO accompanied by an attenuation peak were observed. These features imply a strong electron-phonon interaction via the Jahn-Teller effect in the sample. Another broad attenuation peak was observed at around Tp ~ 80 K. This anomaly is attributed to the phase separation between the antiferromagnetic (AFM) and paramagnetic (PM) phases and gives a direct evidence for spin-phonon coupling in the compound. For the x=0.03 sample, both the minimum of sound velocity and attenuation peaks shift to a lower temperature. The results indicate that the charge ordering and CE-type AFM state in Nd0:5Ca0:5MnO3 are both partially suppressed by replacing Mn with Al.

  1. Co-doping of (Bi(0.5)Na(0.5))TiO(3): secondary phase formation and lattice site preference of Co.

    PubMed

    Schmitt, V; Staab, T E M

    2012-11-14

    Bismuth sodium titanate (Bi(0.5)Na(0.5))TiO(3) (BNT) is considered to be one of the most promising lead-free alternatives to piezoelectric lead zirconate titanate (PZT). However, the effect of dopants on the material has so far received little attention from an atomic point of view. In this study we investigated the effects of cobalt-doping on the formation of additional phases and determined the preferred lattice site of cobalt in BNT. The latter was achieved by comparing the measured x-ray absorption near-edge structure (XANES) spectra to numerically calculated spectra of cobalt on various lattice sites in BNT. (Bi(0.5)Na(0.5))TiO(3) + x mol% Co (x = 0.0, 0.5, 1.0, 2.6) was synthesized via solid state reaction. As revealed by SEM backscattering images, a secondary phase formed in all doped specimens. Using both XRD and SEM-EDX, it was identified as Co(2)TiO(4) for dopant levels >0.5 mol%. In addition, a certain amount of cobalt was incorporated into BNT, as shown by electron probe microanalysis. This amount increased with increasing dopant levels, suggesting that an equilibrium forms together with the secondary phase. The XANES experiments revealed that cobalt occupies the octahedral B-site in the BNT perovskite lattice, substituting Ti and promoting the formation of oxygen vacancies in the material.

  2. Enhancement of magnetic ordering temperature and magnetodielectric coupling by hole doping in a multiferroic DyFe0.5Cr0.5O3

    NASA Astrophysics Data System (ADS)

    Sharma, Mohit K.; Basu, Tathamay; Mukherjee, K.; Sampathkumaran, E. V.

    2017-03-01

    We report the results of our investigation of magnetic, thermodynamic and dielectric properties of Ca substituted half-doped orthochromite, Dy0.6Ca0.4Fe0.5Cr0.5O3. Magnetic susceptibility and heat capacity data bring out that this compound undergoes two antiferromagnetic transitions, one at ~132 and the other at ~22 K. These values are higher than those of DyFe0.5Cr0.5O3. This finding highlights that non-magnetic hole doping in form of Ca+2 in the place of magnetic Dy+3 tends to enhance magnetic transition temperatures in this half-doped orthochromite. We attribute it to possible change in the valence state of Cr/Fe-ion ions due to hole doping. Dielectric anomalies are also seen near the magnetic ordering temperatures indicating magnetodielectric coupling, which is confirmed by magnetic field dependent dielectric studies. The most notable observation is that magnetodielectric coupling strength gets significantly enhanced as compared to DyFe0.5Cr0.5O3. The results reveal that it is possible to tune magnetodielectric coupling by hole doping in this system.

  3. Grain boundary defect compensation in Ti-doped BaFe0.5Nb0.5O3 ceramics

    NASA Astrophysics Data System (ADS)

    Sun, Xiaojun; Deng, Jianming; Liu, Saisai; Yan, Tianxiang; Peng, Biaolin; Jia, Wenhao; Mei, Zaoming; Su, Hongbo; Fang, Liang; Liu, Laijun

    2016-09-01

    Giant dielectric ceramics Ba(Nb0.5Fe0.5- x Ti x )O3 (BNFT) have been fabricated by a conventional solid-state reaction. According to X-ray diffraction analysis, the crystal structure of these ceramics can be described by the cubic centrosymmetric with Pm- 3m space group. The real part ( ɛ') of dielectric permittivity and dielectric loss (tan δ) of the BNFT ceramics was measured in a frequency range from 40 Hz to 100 MHz at room temperature. The ( ɛ') of all these samples displays a high value (~6500) and a small frequency-dependence from 1 kHz to 1 MHz. We have established a link between conductivity activation energy and defect compensation at grain boundaries. The Ti4+-doped Ba(Nb0.5Fe0.5)O3 as a donor makes a great influence on the grain boundary behavior, which restricts the migration of oxygen vacancy and depresses dielectric loss factor for Ba(Nb0.5Fe0.5)O3 ceramics.

  4. Valence states and metamagnetic phase transition in partially B -site-disordered perovskite EuMn0.5Co0.5O3

    NASA Astrophysics Data System (ADS)

    Vasiliev, A. N.; Volkova, O. S.; Lobanovskii, L. S.; Troyanchuk, I. O.; Hu, Z.; Tjeng, L. H.; Khomskii, D. I.; Lin, H.-J.; Chen, C. T.; Tristan, N.; Kretzschmar, F.; Klingeler, R.; Büchner, B.

    2008-03-01

    The valence states of transition metals were studied by measuring the x-ray absorption spectra at both MnL2,3 and CoL2,3 edges of partially B -site-disordered perovskite EuMn0.5Co0.5O3 . By comparison with analogous spectra in various Co- and Mn-based compounds, the divalent state of the Co ions and the tetravalent state of the Mn ions were established analogous to Mn4+/Co2+ charge ordering found by Dass and Goodenough [Phys. Rev. B 67, 014401 (2003)] in LaMn0.5Co0.5O3 . The specific heat and magnetic susceptibility data indicate the formation of the magnetically ordered state at TC˜120K . The first-order metamagnetic transitions seen in EuMn0.5Co0.5O3 at T

  5. Preparation of nanocrystalline-coated carbon nanotube/Ni0.5Zn0.5Fe2O4 composite with excellent electromagnetic property as microwave absorber

    NASA Astrophysics Data System (ADS)

    Zhou, Xiao-Bing; Shen, Lu; Li, Lei; Huang, Tong-Ming; Hu, Chun-Feng; Pan, Wei-Ming; Jin, Xi-Hai; Sun, Jing; Gao, Lian; Huang, Qing

    2013-04-01

    A combined precipitation-hydrothermal method was used to fabricate carbon nanotube/Ni0.5Zn0.5Fe2O4 ferrite composite powders. The phase, microstructure and electromagnetic properties of CNT/Ni0.5Zn0.5Fe2O4 composites were investigated. After surface modification, The zeta potential value of CNTs could maintain at about -50 mV when pH is higher than 8, which affords a suitable surface environment for in situ coating of Ni0.5Zn0.5Fe2O4 nanocrystallines. With increasing CNTs content, the saturation magnetization of the composites is gradually reduced, while the complex magnetic permeability changes little. The complex dielectric constant of the composites is significantly increased when the concentration of CNTs approaches the percolation threshold value of 2 wt%. When CNTs content is 5 wt%, the reflection ratios are less than -10 dB within the frequency range 2-9 GHz, and the reflection ratios reach a minimum -32.5 dB at a frequency of about 3.9 GHz.

  6. Phase transition and electrical properties of (K0.5Na0.5)(Nb1-xTax)O3 lead-free piezoelectric ceramics

    NASA Astrophysics Data System (ADS)

    Lin, Dunmin; Kwok, K. W.; Chan, H. L. W.

    2008-04-01

    (K0.5Na0.5)(Nb1-xTax)O3 lead-free piezoelectric ceramics have been prepared by an ordinary sintering technique. The results of X-ray diffraction reveal that Ta5+ diffuses into the K0.5Na0.5NbO3 lattices to form a solid solution with an orthorhombic perovskite structure. Because of the high melting temperature of KTaO3, the (K0.5Na0.5)(Nb1-xTax)O3 ceramics can be sintered at higher temperatures. The partial substitution of Ta5+ for the B-site ion Nb5+ decreases both paraelectric/cubic ferroelectric/tetragonal and ferroelectric/tetragonal ferroelectric/orthorhombic phase transition temperatures, TC and TO-T. It also induces a relaxor phase transition and weakens the ferroelectricity of the ceramics. The ceramics become ‘softened’, leading to improvements in d33, kp, kt and ɛr and a decease in Ec, Qm and Np. The ceramics with x=0.075 0.15 become optimum, having d33=127 151 pC/N, kp=0.43 0.44, kt=0.43 0.44, ɛr=541 712, tanδ=1.75 2.48% and TC=378 329 °C.

  7. Realisation of magnetically and atomically abrupt half-metal/semiconductor interface: Co2FeSi0.5Al0.5/Ge(111).

    PubMed

    Nedelkoski, Zlatko; Kuerbanjiang, Balati; Glover, Stephanie E; Sanchez, Ana M; Kepaptsoglou, Demie; Ghasemi, Arsham; Burrows, Christopher W; Yamada, Shinya; Hamaya, Kohei; Ramasse, Quentin M; Hasnip, Philip J; Hase, Thomas; Bell, Gavin R; Hirohata, Atsufumi; Lazarov, Vlado K

    2016-11-21

    Halfmetal-semiconductor interfaces are crucial for hybrid spintronic devices. Atomically sharp interfaces with high spin polarisation are required for efficient spin injection. In this work we show that thin film of half-metallic full Heusler alloy Co2FeSi0.5Al0.5 with uniform thickness and B2 ordering can form structurally abrupt interface with Ge(111). Atomic resolution energy dispersive X-ray spectroscopy reveals that there is a small outdiffusion of Ge into specific atomic planes of the Co2FeSi0.5Al0.5 film, limited to a very narrow 1 nm interface region. First-principles calculations show that this selective outdiffusion along the Fe-Si/Al atomic planes does not change the magnetic moment of the film up to the very interface. Polarized neutron reflectivity, x-ray reflectivity and aberration-corrected electron microscopy confirm that this interface is both magnetically and structurally abrupt. Finally, using first-principles calculations we show that this experimentally realised interface structure, terminated by Co-Ge bonds, preserves the high spin polarization at the Co2FeSi0.5Al0.5/Ge interface, hence can be used as a model to study spin injection from half-metals into semiconductors.

  8. Synthesis, structure and electrochemical properties of LiNaCo0.5Fe0.5PO4F fluoride-phosphate

    NASA Astrophysics Data System (ADS)

    Fedotov, Stanislav S.; Kuzovchikov, Sergey M.; Khasanova, Nellie R.; Drozhzhin, Oleg A.; Filimonov, Dmitriy S.; Karakulina, Olesia M.; Hadermann, Joke; Abakumov, Artem M.; Antipov, Evgeny V.

    2016-10-01

    LiNaCo0.5Fe0.5PO4F fluoride-phosphate was synthesized via conventional solid-state and novel freeze-drying routes. The crystal structure was refined based on neutron powder diffraction (NPD) data and validated by electron diffraction (ED) and high-resolution transmission electron microscopy (HRTEM). The alkali ions are ordered in LiNaCo0.5Fe0.5PO4F and the transition metals jointly occupy the same crystallographic sites. The oxidation state and oxygen coordination environment of the Fe atoms were verified by 57Fe Mössbauer spectroscopy. Electrochemical tests of the LiNaCo0.5Fe0.5PO4F cathode material demonstrated a reversible activity of the Fe3+/Fe2+ redox couple at the electrode potential near 3.4 V and minor activity of the Co3+/Co2+ redox couple over 5 V vs Li/Li+. The material exhibited the discharge capacity of more than 82% (theo.) regarding Fe3+/Fe2+ in the 2.4÷4.6 V vs Li/Li+ potential range.

  9. Ordered structure and thermal expansion in tungsten bronze Pb₂K(0.5)Li(0.5)Nb₅O₁₅.

    PubMed

    Lin, Kun; Rong, Yangchun; Wu, Hui; Huang, Qingzhen; You, Li; Ren, Yang; Fan, Longlong; Chen, Jun; Xing, Xianran

    2014-09-02

    The crystal structure and thermal expansion behaviors of a new tetragonal tungsten bronze (TTB) ferroelectric, Pb2K(0.5)Li(0.5)Nb5O15, were systematically investigated by selected-area electron diffraction (SAED), neutron powder diffraction, synchrotron X-ray diffraction (XRD), and high-temperature XRD. SAED and Rietveld refinement reveal that Pb2K(0.5)Li(0.5)Nb5O15 displays a commensurate superstructure of simple orthorhombic TTB structure at room temperature. The structure can be described with space group Bb2₁m. The transition to a paraelectric phase (P4/mbm) occurs at 500 °C. Compared with Pb2KNb5O15 (PKN), the substitution of 0.5K(+) with small 0.5Li(+) into PKN causes the tilting of NbO6 octahedra away from the c axis with Δθ ≈ 10° and raises the Curie temperature by 40 °C, and the negative thermal expansion coefficient along the polar b axis increases more than 50% in the temperature range 25-500 °C. We present that, by introduction of Li(+), the enhanced spontaneous polarization is responsible for the enhanced negative thermal expansion along the b axis, which may be caused by more Pb(2+) in the pentagonal caves.

  10. Spin state and magnetic ordering of half-doped Nd0.5Sr0.5CoO3 cobaltite

    NASA Astrophysics Data System (ADS)

    Reis, M. S.; Rocco, D. L.; Caraballo Vivas, R. J.; Pimentel, B.; Checca, N. R.; Torrão, R.; Paixão, L.; dos Santos, A. M.

    2017-01-01

    Cobaltites show intriguing magnetic and transport properties, when compared with manganites for instance, as they exhibit an additional degree of freedom: the spin state of the Co ions. For Nd0.5Sr0.5CoO3 this spin configuration is not well-established, as well as the magnetic ordering below the Curie temperature. Thus, in the present effort, magnetization measurements and a mean-field theoretical model were developed in order to understand in detail these aspects of the half-doped Nd0.5Sr0.5CoO3 cobaltite. These results show that the Co and Nd magnetic sub-lattices couple antiferromagnetically below Curie temperature Tc=215 K down to very low temperature. These findings clarify the presence of the plateau observed at 80 K on M(T) curve, which is erroneously attributed, in the literature, to the onset of an antiferromagnetic ordering. Magnetization data also clearly shows that Co3+ and Co4+ are in an intermediate spin state. In addition, experimental and theoretical magnetic entropy changes were determined and a comparative analysis among these two leads to ratify the results above claimed. Finally, from all those results, a magnetic phase diagram for Nd0.5Sr0.5CoO3. could be drawn.

  11. Bulk Superconductivity Induced by In-Plane Chemical Pressure Effect in Eu0.5La0.5FBiS2-xSex

    NASA Astrophysics Data System (ADS)

    Jinno, Gen; Jha, Rajveer; Yamada, Akira; Higashinaka, Ryuji; Matsuda, Tatsuma D.; Aoki, Yuji; Nagao, Masanori; Miura, Osuke; Mizuguchi, Yoshikazu

    2016-12-01

    We have investigated the Se substitution effect on the superconductivity of optimally doped BiS2-based superconductor Eu0.5La0.5FBiS2. Eu0.5La0.5FBiS2-xSex samples with x = 0-1 were synthesized. With increasing x, in-plane chemical pressure is enhanced. For x ≥ 0.6, superconducting transitions with a large shielding volume fraction are observed in magnetic susceptibility measurements, and the highest Tc is 3.8 K for x = 0.8. From low-temperature electrical resistivity measurements, a zero-resistivity state is observed for all the samples, and the highest Tc is observed for x = 0.8. With increasing Se concentration, the characteristic electrical resistivity changes from semiconducting-like to metallic, suggesting that the emergence of bulk superconductivity is linked with the enhanced metallicity. A superconductivity phase diagram of the Eu0.5La0.5FBiS2-xSex superconductor is established.

  12. Realisation of magnetically and atomically abrupt half-metal/semiconductor interface: Co2FeSi0.5Al0.5/Ge(111)

    NASA Astrophysics Data System (ADS)

    Nedelkoski, Zlatko; Kuerbanjiang, Balati; Glover, Stephanie E.; Sanchez, Ana M.; Kepaptsoglou, Demie; Ghasemi, Arsham; Burrows, Christopher W.; Yamada, Shinya; Hamaya, Kohei; Ramasse, Quentin M.; Hasnip, Philip J.; Hase, Thomas; Bell, Gavin R.; Hirohata, Atsufumi; Lazarov, Vlado K.

    2016-11-01

    Halfmetal-semiconductor interfaces are crucial for hybrid spintronic devices. Atomically sharp interfaces with high spin polarisation are required for efficient spin injection. In this work we show that thin film of half-metallic full Heusler alloy Co2FeSi0.5Al0.5 with uniform thickness and B2 ordering can form structurally abrupt interface with Ge(111). Atomic resolution energy dispersive X-ray spectroscopy reveals that there is a small outdiffusion of Ge into specific atomic planes of the Co2FeSi0.5Al0.5 film, limited to a very narrow 1 nm interface region. First-principles calculations show that this selective outdiffusion along the Fe-Si/Al atomic planes does not change the magnetic moment of the film up to the very interface. Polarized neutron reflectivity, x-ray reflectivity and aberration-corrected electron microscopy confirm that this interface is both magnetically and structurally abrupt. Finally, using first-principles calculations we show that this experimentally realised interface structure, terminated by Co-Ge bonds, preserves the high spin polarization at the Co2FeSi0.5Al0.5/Ge interface, hence can be used as a model to study spin injection from half-metals into semiconductors.

  13. Realisation of magnetically and atomically abrupt half-metal/semiconductor interface: Co2FeSi0.5Al0.5/Ge(111)

    PubMed Central

    Nedelkoski, Zlatko; Kuerbanjiang, Balati; Glover, Stephanie E.; Sanchez, Ana M.; Kepaptsoglou, Demie; Ghasemi, Arsham; Burrows, Christopher W.; Yamada, Shinya; Hamaya, Kohei; Ramasse, Quentin M.; Hasnip, Philip J.; Hase, Thomas; Bell, Gavin R.; Hirohata, Atsufumi; Lazarov, Vlado K.

    2016-01-01

    Halfmetal-semiconductor interfaces are crucial for hybrid spintronic devices. Atomically sharp interfaces with high spin polarisation are required for efficient spin injection. In this work we show that thin film of half-metallic full Heusler alloy Co2FeSi0.5Al0.5 with uniform thickness and B2 ordering can form structurally abrupt interface with Ge(111). Atomic resolution energy dispersive X-ray spectroscopy reveals that there is a small outdiffusion of Ge into specific atomic planes of the Co2FeSi0.5Al0.5 film, limited to a very narrow 1 nm interface region. First-principles calculations show that this selective outdiffusion along the Fe-Si/Al atomic planes does not change the magnetic moment of the film up to the very interface. Polarized neutron reflectivity, x-ray reflectivity and aberration-corrected electron microscopy confirm that this interface is both magnetically and structurally abrupt. Finally, using first-principles calculations we show that this experimentally realised interface structure, terminated by Co-Ge bonds, preserves the high spin polarization at the Co2FeSi0.5Al0.5/Ge interface, hence can be used as a model to study spin injection from half-metals into semiconductors. PMID:27869132

  14. Enhancement of magnetic ordering and magnetodielectric coupling by hole doping in a multiferroic DyFe0.5Cr0.5O3.

    PubMed

    Sharma, Mohit; Basu, Tathamay; Mukherjee, Kaustav; Sampathkumaran, E

    2016-12-19

    We report the results of our investigations of magnetic, thermodynamic and dielectric properties of Ca substituted half-doped orthochromite, Dy0.6Ca0.4Fe0.5Cr0.5O3. Magnetic susceptibility and heat capacity data bring out that this compound undergoes two magnetic transitions, one at ~ 132 and the other at ~22 K. These values are higher than that those of DyFe0.5Cr0.5O3. This finding highlights that non-magnetic hole doping of Ca+2 in the place of magnetic Dy+3 tends to enhance magnetic transition temperatures in this half-doped orthochromite. We attribute it to possible change in the valence state of Cr/Fe-ion ions due to hole doping. Dielectric anomalies are also seen near the magnetic ordering temperatures indicating magnetodielectric coupling, which is confirmed by magnetic field dependent dielectric studies. The most notable observation is that magnetodielectric coupling strength gets significantly enhanced as compared to DyFe0.5Cr0.5O3. The results reveal that it is possible to tune magnetoelectric coupling by hole doping in this system.

  15. 30 CFR 57.22233 - Actions at 0.5 percent methane (I-C mines).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Actions at 0.5 percent methane (I-C mines). 57... MINES Safety Standards for Methane in Metal and Nonmetal Mines Ventilation § 57.22233 Actions at 0.5 percent methane (I-C mines). If methane reaches 0.5 percent in the mine atmosphere, ventilation...

  16. 77 FR 53892 - Determination That ALOXI (Palonosetron Hydrochloride) Capsules, 0.5 Milligram (Base), Were Not...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-09-04

    ...) Capsules, 0.5 Milligram (Base), Were Not Withdrawn From Sale for Reasons of Safety or Effectiveness AGENCY... determined that ALOXI (palonosetron hydrochloride (HCl)) Capsules, 0.5 milligram (mg) (base), were not... abbreviated new drug applications (ANDAs) for palonosetron HCl capsules, 0.5 mg (base), if all other legal...

  17. 30 CFR 57.22233 - Actions at 0.5 percent methane (I-C mines).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Actions at 0.5 percent methane (I-C mines). 57... MINES Safety Standards for Methane in Metal and Nonmetal Mines Ventilation § 57.22233 Actions at 0.5 percent methane (I-C mines). If methane reaches 0.5 percent in the mine atmosphere, ventilation...

  18. Upper Critical Field, Critical Current Density and Activation Energy of the New La1-xSmxO0.5F0.5BiS2 (x = 0.2, 0.8) Superconductors

    NASA Astrophysics Data System (ADS)

    Kalai Selvan, Ganesan; Singh Thakur, Gohil; Manikandan, Krishnan; Uwatoko, Yoshia; Haque, Zeba; Gupta, Laxmi Chand; Ganguli, Ashok Kumar; Arumugam, Sonachalam

    2015-12-01

    Critical current density (Jc), thermal activation energy (U0), and upper critical field (Hc2) of La1-xSmxO0.5F0.5BiS2 (x = 0.2, 0.8) superconductors are investigated from magnetic field dependent ρ(T) studies. The estimated upper critical field (Hc2) has low values of 1.04 T for x = 0.2 and 1.41 T for x = 0.8. These values are lower than Sm free LaO0.5F0.5BiS2 superconductor (1.9 T). The critical current density (Jc) is estimated to be 1.35 × 105 and 5.07 × 105 A/cm2 (2 K) for x = 0.2 and 0.8 respectively, using the Bean's model. The thermal activation energy (U0/kB) is 61 K for x = 0.2 and 140 K for x = 0.8 as calculated from Arrhenius plots at low magnetic field (1 T) and indicates a strong flux pinning potential which might be co-existing with applied magnetic field.

  19. The energy-down-shift effect of Cd(0.5)Zn(0.5)S-ZnS core-shell quantum dots on power-conversion-efficiency enhancement in silicon solar cells.

    PubMed

    Baek, Seung-Wook; Shim, Jae-Hyoung; Park, Jea-Gun

    2014-09-14

    We found that Cd0.5Zn0.5S-ZnS core (4.2 nm in diameter)-shell (1.2 nm in thickness) quantum dots (QDs) demonstrated a typical energy-down-shift (2.76-4.96 → 2.81 eV), which absorb ultra-violet (UV) light (250-450 nm in wavelength) and emit blue visible light (∼442 nm in wavelength). They showed the quantum yield of ∼80% and their coating on the SiNX film textured p-type silicon solar-cells enhanced the external-quantum-efficiency (EQE) of ∼30% at 300-450 nm in wavelength, thereby enhancing the short-circuit-current-density (JSC) of ∼2.23 mA cm(-2) and the power-conversion-efficiency (PCE) of ∼1.08% (relatively ∼6.04% increase compared with the reference without QDs for p-type silicon solar-cells). In particular, the PCE peaked at a specific coating thickness of the Cd0.5Zn0.5S-ZnS core-shell QD layer; i.e., the 1.08% PCE enhancement at the 8.8 nm thick QD layer.

  20. Ergodic Relaxor State with High Energy Storage Performance Induced by Doping Sr0.85Bi0.1TiO3 in Bi0.5Na0.5TiO3 Ceramics

    NASA Astrophysics Data System (ADS)

    Li, Qing-Ning; Zhou, Chong-Rong; Xu, Ji-Wen; Yang, Ling; Zhang, Xin; Zeng, Wei-Dong; Yuan, Chang-Lai; Chen, Guo-Hua; Rao, Guang-Hui

    2016-10-01

    The large maximum polarization P max and low remnant polarization P r in relaxor ferroelectrics are key features for the energy storage density ( W) and energy-storage efficiency ( η) in materials selection. In this study, the ergodic relaxor (ER) state with high energy storage performance associated with low P r and large P max, induced by Sr0.85Bi0.1TiO3(SBT) addition in (1 - x)Bi0.5Na0.5TiO3- xSr0.85Bi0.1TiO3 (BNT-SBT x with x = 0.25-0.45, Bi0.5Na0.5TiO3 abbreviated as BNT) ceramics has been observed. In particular, significantly increased energy storage density ( W = 1.5 J/cm3) and energy-storage efficiency ( η = 73%) are obtained for BNT-SBT ergodic relaxor ceramics. These results suggest a new means of designing lead-free energy-storage materials.

  1. Optimization Study of the Ames 0.5 Two-Stage Light Gas Gun

    NASA Technical Reports Server (NTRS)

    Bogdanoff, D. W.

    1996-01-01

    There is a need for more faithful simulation of space debris impacts on various space vehicles. Space debris impact velocities can range up to 14 km/sec and conventional two-stage light gas guns with moderately heavy saboted projectiles are limited to launch velocities of 7-8 km/sec. Any increases obtained in the launch velocities will result in more faithful simulations of debris impacts. It would also be valuable to reduce the maximum gun and projectile base pressures and the gun barrel erosion rate. In this paper, the results of a computational fluid dynamics (CFD) study designed to optimize the performance of the NASA Ames 0.5' gun by systematically varying seven gun operating parameters are reported. Particularly beneficial effects were predicted to occur if (1) the piston mass was decreased together with the powder mass and the hydrogen fill pressure and (2) the pump tube length was decreased. The optimum set of changes in gun operating conditions were predicted to produce an increase in muzzle velocity of 0.7-1.0 km/sec, simultaneously with a substantial decrease in gun erosion. Preliminary experimental data have validated the code predictions. Velocities of up to 8.2 km/sec with a 0.475 cm diameter saboted aluminum sphere have been obtained, along with large reductions in gun erosion rates.

  2. Treatment of trichostasis spinulosa with 0.5-millisecond pulsed 755-nm alexandrite laser.

    PubMed

    Badawi, Ashraf; Kashmar, Mouhamad

    2011-11-01

    Trichostasis spinulosa (TS) is a follicular disorder in which multiple hairs in a keratinous sheath project above the skin surface. Current treatments provide temporary relief and side effects are common. We report the successful treatment of TS in 20 patients using a short-pulsed 755-nm alexandrite laser. The 20 patients (skin types II-V) presented with TS lesions on the tip of their nose. All patients received a single treatment (one to three passes) with the laser with cold air cooling but without anaesthesia or analgesia. Treatment parameters were as follows: pulse duration 0.5 ms, fluence 15-17 J/cm(2), and spot size 5 mm. The entire procedure required less than 5 min to perform. The patients were followed up for 3 months for any adverse effects or recurrence. In all patients the lesions disappeared immediately after treatment with minimal or no pain. Erythema was minimal and lasted 5-20 min in all patients. Patients were very satisfied. The treated areas were still clear 4 to 5 weeks later, and a second treatment was not considered necessary. There were adverse effects other than the erythema and there was no recurrence within the follow-up period of 3 months. A single treatment with a short-pulsed 755-nm alexandrite laser appears to be a rapid, minimally painful, and effective treatment for TS in patients of skin types II to V.

  3. Sub-cm Particles in Saturn's Rings from VIMS, UVIS, and RSS occultations

    NASA Astrophysics Data System (ADS)

    Jerousek, Richard Gregory; Colwell, Josh E.; Hedman, Matthew M.; Marouf, Essam A.; Esposito, Larry W.; Nicholson, Philip D.; French, Richard G.

    2016-10-01

    Particles sizes in Saturn's rings roughly follow a truncated power law. One way to determine the governing parameters of the size distribution is through the analysis of differential optical depths (Zebker et al. 1983). Non-axisymmetric self-gravity wakes complicate this approach when optical depth measurements at different wavelengths are not made at same viewing geometry. Using occultations spanning a wide range of viewing angles and from multiple instruments onboard Cassini (the Ultraviolet Imaging Spectrograph (UVIS), the Visual and Infrared Mapping Spectrometer (VIMS), and the Radio Science Subsystem (RSS)), we forward-model the properties of the self-gravity wakes in Saturn's A and B rings while simultaneously constraining the parameters of the cm - sub-cm particle size distribution. In the absence of wakes, and in regions where particles smaller than ~ 8.86 mm are present, VIMS stellar occultations measure larger optical depths than UVIS stellar occultations due to the diffraction of 2.9 μm light out of the small (0.25 × 0.5 mrad) VIMS field of view compared with UVIS which measures shorter wavelength (0.15 μm) light over a much larger (6.4 × 6.0 mrad) field of view. This excess optical depth combined with RSS X-band (λ = 3.6 cm) optical depths provides a way to probe both the power law slope and the minimum particle size. In the A and B rings where self-gravity wakes are prevalent, we use the wake model of Colwell et al. (2006, 2007) with an additional free parameter representing the excess optical depth which would be measured through the gaps between opaque wakes, by VIMS compared to UVIS. In the B ring and inner A ring we find and absence of sub-cm particles and power law slopes of q ~ 2.8. In the trans-Encke region, where there are a multitude of satellite driven resonances, we find an increasing abundance of sub-cm particles as the outer edge of the A ring is approached. In the C Ring and the Cassini Division, where self-gravity wakes are absent

  4. Growth and orientation dependence of electrical properties of 0.92Na0.5Bi0.5TiO3-0.08 K0.5Bi0.5TiO3 lead-free piezoelectric single crystal

    NASA Astrophysics Data System (ADS)

    Sun, Renbing; Zhao, Xiangyong; Zhang, Qinhui; Fang, Bijun; Zhang, Haiwu; Li, Xiaobing; Lin, Di; Wang, Sheng; Luo, Haosu

    2011-06-01

    A 0.92Na0.5Bi0.5TiO3-0.08 K0.5Bi0.5TiO3 (0.92NBT-0.08KBT) lead-free piezoelectric single crystal with dimensions of Φ 35 × 10 mm was successfully grown by the top-seeded solution growth method. The effective segregation coefficient for K was calculated to be 0.27. An x-ray powder diffraction measurement showed that the as-grown crystal possesses a rhombohedral perovskite structure at room temperature. The room-temperature dielectric constants for poled <001>, <110>, and <111> oriented crystal samples are found to be 683, 567, and 435 at 1 kHz, respectively. The (Tm, ɛm) values for <001>, <110>, and <111> oriented crystals are (316 °C, 4318), (317 °C, 4160), and (318 °C, 4348) at 1 kHz, which indicate that the dielectric parameters of the as-grown crystals show weaker anisotropy. The curves, ɛ(T), for the three crystallographic orientations show two anomalies at about 170 and 320 °C, respectively, relating to the ferroelectric-antiferroelectric phase and the antiferroelectric-paraelectric phase. There is a thermal hysteresis, ΔT ≈ 35 °C for the ferroelectric-antiferroelectric phase transformation between heating and cooling. The antiferroelectric phase, the thermal hysteresis, and the dielectric relaxor behavior around 170 °C can be attributed to the formation of an intermediate orthorhombic modulated phase at 170-320 °C. For the <001>, <110>, and <111> crystal samples, the room-temperature piezoelectric constants, d33, reach 175, 130, and 70 pC/N, respectively. The remanent polarization for the <001>, <110>, and <111> crystal samples are 8.1, 10.8, and 13.5 μC/cm2, respectively, and the ratio is 1:1.33:1.67, close to 1:√2 :√3 . The diffusive factors, α, are found to be 1.94, 1.91, and 1.50 for the <001>, <110>, and <111> oriented crystal samples, which indicate that the antiferroelectric-paraelectric phase transition of the as-grown 0.92NBT-0.08KBT crystal is a strong diffuse one. The electromechanical coupling coefficients for the <001>, <110

  5. Highly efficient and robust cathode materials for low-temperature solid oxide fuel cells: PrBa0.5Sr0.5Co(2-x)Fe(x)O(5+δ).

    PubMed

    Choi, Sihyuk; Yoo, Seonyoung; Kim, Jiyoun; Park, Seonhye; Jun, Areum; Sengodan, Sivaprakash; Kim, Junyoung; Shin, Jeeyoung; Jeong, Hu Young; Choi, YongMan; Kim, Guntae; Liu, Meilin

    2013-01-01

    Solid oxide fuel cells (SOFC) are the cleanest, most efficient, and cost-effective option for direct conversion to electricity of a wide variety of fuels. While significant progress has been made in anode materials with enhanced tolerance to coking and contaminant poisoning, cathodic polarization still contributes considerably to energy loss, more so at lower operating temperatures. Here we report a synergistic effect of co-doping in a cation-ordered double-perovskite material, PrBa0.5Sr0.5Co(2-x)Fe(x)O(5+δ), which has created pore channels that dramatically enhance oxygen ion diffusion and surface oxygen exchange while maintaining excellent compatibility and stability under operating conditions. Test cells based on these cathode materials demonstrate peak power densities ~2.2 W cm(-2) at 600°C, representing an important step toward commercially viable SOFC technologies.

  6. Angular-dependent vortex pinning mechanism and magneto-optical characterizations of FeSe0.5Te0.5 thin films grown on CaF2 substrates

    NASA Astrophysics Data System (ADS)

    Yuan, Pusheng; Xu, Zhongtang; Ma, Yanwei; Sun, Yue; Tamegai, Tsuyoshi

    2016-03-01

    Magneto-optical (MO) characterizations and the angular-dependent critical current density (J c(Θ)) of epitaxial FeSe0.5Te0.5 (FST) thin films grown on CaF2 single-crystalline substrates were performed. The MO images show typical rooftop patterns in the remanent state from which a large, homogeneous, and almost isotropic self-field J c over 2 × 106 A cm-2 at 8 K was obtained. The vortex pinning mechanism is investigated measuring the magnetic field and angular-dependent critical current density J c. The FST films exhibit small anisotropy of J c in the whole applied magnetic field range below 15 K. The Dew-Hughes model and angular scaling analyses prove that pointlike normal cores, which are distributed randomly in the FST film, dominate the pinning in the FST films on CaF2 substrates.

  7. Band gap modification and ferroelectric properties of Bi{sub 0.5}(Na,K){sub 0.5}TiO{sub 3}-based by Li substitution

    SciTech Connect

    Quan, Ngo Duc; Hung, Vu Ngoc; Quyet, Nguyen Van; Chung, Hoang Vu; Dung, Dang Duc

    2014-01-15

    We report on the reduction of band gap in Bi{sub 0.5}(Na{sub 0.82-x}Li{sub x}K{sub 0.18}){sub 0.5}(Ti{sub 0.95}Sn{sub 0.05})O{sub 3} from 2.99 eV to 2.84 eV due to the substitutions of Li{sup +} ions to Na{sup +} sites. In addition, the lithium substitution samples exhibit an increasing of the maximal polarizations from 21.8 to 25.7 μC/cm{sup 2}. The polarization enhancement of ferroelectric and reduction of the band gaps are strongly related to the Li substitution concentration as evaluated via the electronegative between A-site and oxygen and tolerance factor. The results are promising for photovoltaic and photocatalytic applications.

  8. Radio perspectives on the Monoceros SNR G205.5+0.5

    NASA Astrophysics Data System (ADS)

    Xiao, L.; Zhu, M.

    2012-09-01

    Context. The Monoceros supernova remnant (SNR G205.5+0.5) is a large shell-type SNR located in the Rosette molecular complex and thought to be interacting with the Rosette Nebula. Aims: We aim to re-examine the radio spectral index and its spatial variation over the Monoceros SNR as well as study its properties of evolution within the complex interstellar medium. Methods: We extracted radio continuum data for the Monoceros complex region from the Effelsberg 21 cm and 11 cm surveys and the Urumqi 6 cm polarization survey. We used the new Arecibo GALFA-HI survey data with much higher resolution and sensitivity than that previously available to identify the HI shell related with the SNR. Multi-wavelengths data are included to investigate the properties of the SNR. Results: The spectral index α (Sν ∝ να) averaged over the SNR is -0.41 ± 0.16. The TT-plots and the distribution of α over the SNR show spatial variations that steepen toward the inner western filamentary shell. Polarized emission is prominent on the western filamentary shell region. The RM there is estimated to be about 30 ± 77n rad m-2, where the n = 1 solution is preferred, and the magnetic field has a strength of about 9.5 μG. From the HI channel maps, further evidence is provided for an interaction between the Monoceros SNR and the Rosette Nebula. We identify partial neutral hydrogen shell structures in the northwestern region at velocities of +15 km s-1 circumscribing the continuum emission. The HI shell has swept up a mass of about 4000 M⊙ for a distance of 1.6 kpc. The western HI shell, well associated with the dust emission, is found to lie outside of the radio shell. We suggest that the Monoceros SNR is evolving within a cavity blown out by the progenitor and has triggered part of the star formation in the Rosette Nebula. Conclusions: The Monoceros SNR is interacting with the ambient interstellar medium with ultra-high energy emission detected. Its interaction with the Rosette Nebula is

  9. Structural and Magnetic Properties Evolution of Li-Substituted Co0.5Ni0.5Fe2O4 Ferrite

    NASA Astrophysics Data System (ADS)

    Wu, Xuehang; Chen, Wen; Wu, Wenwei; Li, Hongjiao; Lin, Cuiwu

    2017-01-01

    Four types of Co-Ni based ferrites materials with the general formula Li x Co0.5Ni0.5- x Fe2O4 (0.0 ≤ x≤0.3) were successfully synthesized by thermal decomposition of oxalates in air. The effect of substitution of diamagnetic Li+ ions for partial Ni2+ ions in a spinel lattice on the crystalline structure and the magnetic properties of Co-Ni ferrites was studied. X-ray diffraction examination confirms that a high-crystallized Li x Co0.5Ni0.5- x Fe2O4 with cubic spinel structure is obtained when the precursor is calcined at 900°C in air for 3 h. The substitution of Li+ ions for partial Ni2+ ions does not change the spinel crystalline structure of MFe2O4, but crystallinity of Li x Co0.5Ni0.5- x Fe2O4 can be improved. The incorporation of Li+ ions in place of Ni2+ ions in Co-Ni ferrites decreases the average crystallite size and results in higher specific saturation magnetization as compared to un-substituted Co-Ni ferrites. In this study, Li0.1Co0.5Ni0.4Fe2O4, obtained at 900°C, exhibits the highest specific saturation magnetization of 88 emu/g ± 2 emu/g and magnetic moment (3.60 μ B ± 0.05 μ B).

  10. Investigation of structural and temperature dependent electromagnetic properties of Co0.5Zn0.5CrxFe2-xO4

    NASA Astrophysics Data System (ADS)

    Khan, M. H. R.; Hossain, A. K. M. Akther

    2015-10-01

    Mixed ferrites with nominal chemical compositions Co0.5Zn0.5CrxFe2-xO4 ranging from x=0 to 0.5 in the steps of 0.1 have been prepared by the standard solid state reaction method. XRD patterns confirm single phase and formation of cubic spinel structure. The lattice constant (a0), average grain size (D) and bulk density (ρB) are decreased with increasing Cr content. The ρB decreases with Cr content due to lighter atomic weight. On the other hand, both D and ρB of each composition increase with increasing sintering temperature (Ts). All samples show reentrant spin glass transition at low temperature in zero field cooled magnetization. The saturation magnetization (Ms) and Néel temperature (TN) decrease with Cr substitution due to weakening the super-exchange interaction. The coercivity (Hc) increases with increasing Cr content for various Co0.5Zn0.5CrxFe2-xO4. It may be attributed to the effect of decreasing D. Frequency dependent initial permeability (μ‧i) decreases with increasing Cr content. The Ms and ρB play an important role in changing μ‧i. On the other hand, the μ‧i for each composition increases with increasing Ts. The highest relative quality factor (Q) is observed for various Co0.5Zn0.5CrxFe2-xO4 sintered at 1573 K. The DC electrical resistivity (ρDC) of these samples increases with increasing Cr content due to decreasing Fe3+ ions at B-site.

  11. Ferroelectric dielectric properties of Ba{sub 0.5}Sr{sub 0.5}(Ti{sub 0.80}Sn{sub 0.20})O{sub 3} thin films grown by the soft chemical method

    SciTech Connect

    Souza, I.A.; Cavalcante, L.S.; Cilense, M.

    2006-10-15

    Polycrystalline Ba{sub 0.5}Sr{sub 0.5}(Ti{sub 0.80}Sn{sub 0.20})O{sub 3} (BST:Sn) thin films with a perovskite structure were prepared by the soft chemical method on a platinum-coated silicon substrate from spin-coating technique. The resulting thin films showed a dense structure with uniforain size distribution. The dielectric constant of the films estimated from C-V curve is around 1134 and can be ascribed to a reduction in the oxygen vacancy concentration. The ferroelectric nature of the film indicated by butterfly-shaped C-V curves and confirmed by the hysteresis curve, showed remnant polarization of 14{mu}C/cm{sup 2} and coercive field of 74kV/cm at frequency of 1MHz. At the same frequency, the leakage current density at 1.0V is equal to 1.5x10{sup -7}A/cm{sup 2}. This work clearly reveals the highly promising potential of BST:Sn for application in memory devices.

  12. Co-electrolysis of steam and CO2 in a solid oxide electrolysis cell with La0.75Sr0.25Cr0.5Mn0.5O3-δ -Cu ceramic composite electrode

    NASA Astrophysics Data System (ADS)

    Xing, Ruimin; Wang, Yarong; Zhu, Yongqiang; Liu, Shanhu; Jin, Chao

    2015-01-01

    Cu impregnation has been performed to improve electronic conductivity of La0.75Sr0.25Cr0.5Mn0.5O3-δ (LSCM) material in reducing atmosphere, and solid oxide electrolysis cells (SOECs) with the configuration of LSCF|LSGM|LSCM-Cu are prepared and evaluated for high temperature steam and carbon dioxide co-electrolysis. Electrochemical impedance spectra (EIS) and voltage-current curves are carried out to characterize the cell performances. Compared with LSCF|LSGM|LSCM cell without Cu impregnation for steam electrolysis under the same conditions, EIS results show that LSCF|LSGM|LSCM-Cu cell not only displays lower ohmic resistance and better electrochemical performances, but also their resistance increases with the percentage of the fed CO2 under open circuit voltage, in which the polarization resistance dominates. With the applied electrolysis voltage of 1.65 V and the operating temperature of 750 °C, the maximum consumed current density increases from 1.31 A cm-2 without CO2 to 1.82 A cm-2 with 37.5% CO2. Although there is an increase of 2.0% in the applied electrolysis voltage, the cell has exhibited an excellent durability test for more than 50 h with the electrolysis current density of 0.33 A cm-2 and the gas mixture of 50% AH-25% H2-25% CO2 at 750 °C.

  13. Investigation of Sm 0.5Sr 0.5CoO 3- δ/Co 3O 4 composite cathode for intermediate-temperature solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Zhang, Haizhou; Liu, Huanying; Cong, You; Yang, Weishen

    The electrochemical properties of an Sm 0.5Sr 0.5CoO 3- δ/Co 3O 4 (SSC/Co 3O 4) composite cathode were investigated as a function of the cathode-firing temperature, SSC/Co 3O 4 composition, oxygen partial pressure and CO 2 treatment. The results showed that the composite cathodes had an optimal microstructure at a firing temperature of about 1100 °C, while the optimum Co 3O 4 content in the composite cathode was about 40 wt.%. A single cell with this optimized C 40-1100 cathode exhibited a very low polarization resistance of 0.058 Ω cm 2, and yielded a maximum power density of 1092 mW cm -2 with humidified hydrogen fuel and air oxidant at 600 °C. The maximum power density reached 1452 mW cm -2 when pure oxygen was used as the oxidant for a cell with a C 30-1100 cathode operating at 600 °C due to the enhanced open-circuit voltage and accelerated oxygen surface-exchange rate. X-ray diffraction and thermogravimetric analyses, as well as the electrochemical properties of a CO 2-treated cathode, also implied promising applications of such highly efficient SSC/Co 3O 4 composite cathodes in single-chamber fuel cells with direct hydrocarbon fuels operating at temperatures below 500 °C.

  14. A 0.5 cm(3) four-channel 1.1 mW wireless biosignal interface with 20 m range.

    PubMed

    Morrison, Tim; Nagaraju, Manohar; Winslow, Brent; Bernard, Amy; Otis, Brian P

    2014-02-01

    This paper presents a self-contained, single-chip biosignal monitoring system with wireless programmability and telemetry interface suitable for mainstream healthcare applications. The system consists of low-noise front end amplifiers, ADC, MICS/ISM transmitter and infrared programming capability to configure the state of the chip. An on-chip packetizer ensures easy pairing with standard off-the-shelf receivers. The chip is realized in the IBM 130 nm CMOS process with an area of 2×2 mm(2). The entire system consumes 1.07 mW from a 1.2 V supply. It weighs 0.6 g including a zinc-air battery. The system has been extensively tested in in vivo biological experiments and requires minimal human interaction or calibration.

  15. Enhanced performance of solid oxide fuel cells with Ni/CeO 2 modified La 0.75Sr 0.25Cr 0.5Mn 0.5O 3- δ anodes

    NASA Astrophysics Data System (ADS)

    Zhu, Xingbao; Lü, Zhe; Wei, Bo; Chen, Kongfa; Liu, Mingliang; Huang, Xiqiang; Su, Wenhui

    The optimization of electrodes for solid oxide fuel cells (SOFCs) has been achieved via a wet impregnation method. Pure La 0.75Sr 0.25Cr 0.5Mn 0.5O 3- δ (LSCrM) anodes are modified using Ni(NO 3) 2 and/or Ce(NO 3) 3/(Sm,Ce)(NO 3) x solution. Several yttria-stabilized zirconia (YSZ) electrolyte-supported fuel cells are tested to clarify the contribution of Ni and/or CeO 2 to the cell performance. For the cell using pure-LSCrM anodes, the maximum power density (P max) at 850 °C is 198 mW cm -2 when dry H 2 and air are used as the fuel and oxidant, respectively. When H 2 is changed to CH 4, the value of P max is 32 mW cm -2. After 8.9 wt.% Ni and 5.8 wt.% CeO 2 are introduced into the LSCrM anode, the cell exhibits increased values of P max 432, 681, 948 and 1135 mW cm -2 at 700, 750, 800 and 850 °C, respectively, with dry H 2 as fuel and air as oxidant. When O 2 at 50 mL min -1 is used as the oxidant, the value of P max increases to 1450 mW cm -2 at 850 °C. When dry CH 4 is used as fuel and air as oxidant, the values of P max reach 95, 197, 421 and 645 mW cm -2 at 750, 800, 850 and 900 °C, respectively. The introduction of Ni greatly improves the performance of the LSCrM anode but does not cause any carbon deposit.

  16. The hot corrosion of Co-25Cr-10Ni-5Ta-3Al-0.5Y alloy /S-57/

    NASA Technical Reports Server (NTRS)

    Santoro, G. J.

    1978-01-01

    A cobalt-base alloy, Co-25Cr-10Ni-5Ta-3Al-0.5Y (S-57), was subjected to hot corrosion in Mach 0.3 burner-rig combustion gases at maximum alloy temperatures of 900 and 1000 C. Various salt concentrations were injected into the burner: 0.5, 2,5, and 10 parts per million synthetic sea salt and 4 parts per million sodium sulfate (Na2SO4). The extent of corrosion was determined by measuring the maximum depth of corrosion in the alloy, and the corrosion process was studied by metallography, X-ray diffraction, scanning electron microscopy, and electron microprobe analysis. While S-57 was found to possess only moderate oxidation resistance at these temperatures, this alloy resisted significant hot corrosion attack under all but the most severe test conditions. The process of hot corrosion attack under the most severe conditions of this study was primarily sulfidation.

  17. Unusual high-spin Fe5 +-Ni3 + state and strong ferromagnetism in the mixed perovskite SrFe0.5Ni0.5O3

    NASA Astrophysics Data System (ADS)

    Fan, Fengren; Li, Zhengwei; Zhao, Zhen; Yang, Ke; Wu, Hua

    2016-12-01

    The charge-spin-orbital state plays a vital role in correlated oxides with mixed transition-metal elements, and it is often a matter of debate. Here, we address this issue for the newly synthesized unusual high-valence perovskite SrFe1 -xNixO3 , using an analysis of crystal-field level diagrams, density functional calculations, and Monte Carlo simulations. We have identified the formal high-spin Fe5 +(t2g 3, S =3 /2 ) and high-spin Ni3 +(t2g 5eg2 , S =3 /2 ) state for SrFe0.5Ni0.5O3 , rather than the previously suggested high-spin Fe4 +(t2g 3eg1, S =2 ) and low-spin Ni4 + (t2g 6, S =0 ) state. Moreover, our model and the present results well explain the observed small lattice variation of SrFe1 -xNixO3 (0 ≤x ≤0.5 ) and the above room temperature ferromagnetic order in SrFe0.5Ni0.5O3 regardless of a Fe-Ni atomic order or disorder.

  18. Dielectric relaxation and magnetodielectric response in DyMn{sub 0.5}Cr{sub 0.5}O{sub 3}

    SciTech Connect

    Yuan, B.; Yang, J. Zuo, X. Z.; Zhu, X. B.; Dai, J. M.; Song, W. H.; Kan, X. C.; Zu, L.; Sun, Y. P.

    2015-09-28

    We investigate the structural, magnetic, and magnetodielectric properties of DyMn{sub 0.5}Cr{sub 0.5}O{sub 3}. The sample can be indexed with an orthorhombic phase with B site disordered space group Pbnm. The valence state of both Mn and Cr ions are suggested to be +3 based on the results of x-ray photoelectron spectroscopy. Two thermally excited dielectric relaxation at temperatures T{sub N2} < T< 300 K and large magnetodielectric effect (MDC = 20%–30%) due to the disordered arrangement of Mn{sup 3+}/Cr{sup 3+} ions associated with electron hopping between them are observed. The absence of any noticeable magnetoresistance effect (MR < 0.5%) demonstrates that the observed magnetodielectric effect is an intrinsic behavior. These results suggest that DyMn{sub 0.5}Cr{sub 0.5}O{sub 3} is a magnetodielectric compound, whose dielectric properties are dependence of the applied magnetic field, which exhibits such effects near room temperature and holds great promise for future device applications.

  19. Structural, electrochemical and magnetic characterization of the layered-type PrBa{sub 0.5}Sr{sub 0.5}Co{sub 2}O{sub 5+δ} perovskite

    SciTech Connect

    Azad, Abul K.; Kim, Jung H.; Irvine, John T.S.

    2014-05-01

    Structural, electrical and magnetic properties of the layered cobaltite PrBa{sub 0.5}Sr{sub 0.5}Co{sub 2}O{sub 5+δ} have been investigated by means of neutron diffraction, electron diffraction, thermogravimetric analysis and SQUID magnetometry. Rietveld analysis of neutron diffraction data shows the ordered distribution of oxygen vacancies in [PrO{sub δ}] planes which doubles the lattice parameters from the simple perovskite cell parameter as a≈2a{sub p} and c≈2a{sub p} (a{sub p} is the cell parameter of the simple Perovskite) yielding tetragonal symmetry in the P4/mmm space group. On heating, above 573 K in air, structural rearrangement takes place and the structure can be defined as a≈a{sub p} and c≈2a{sub p} in the same space group. Oxygen occupancies have been determined as a function of temperature from neutron diffraction results. Initially (≥373 K), oxygen occupancy was increased and then decreased with increasing temperature. It was found that at 973 K the total oxygen loss is calculated about 0.265 oxygen/formula unit. Oxygen vacancy ordering was observed below 573 K, and the oxygen occupancy decreases as cell volume increases with increasing temperature. Area specific resistance (ASR) measurements show a resistance of 0.153 Ωcm{sup 2} and 0.286 Ωcm{sup 2} at 973 K and 923 K, respectively. On cooling, paramagnetic to ferromagnetic and an incomplete ferromagnetic to antiferromagnetic transition takes place. Different behaviours in field cooled and zero-field-cooled measurements leads to a coexistence of ferromagnetic and antiferromagnetic order. - Graphical abstract: Structural phase changes in PrBa{sub 0.5}Sr{sub 0.5}Co{sub 2}O{sub 5+δ} at elevated temperatures determined by neutron powder diffraction. Depending on oxygen occupancy it form different phases at different temperatures. This pictures show the schematic 3D diagram of PrBa{sub 0.5}Sr{sub 0.5}Co{sub 2}O{sub 5+δ} at 295 K (a), 373 K (b) and 573 K (c). Co atoms are inside the

  20. Barrier height of Pt-InxGa1-xN (0<=x<=0.5) nanowire Schottky diodes

    NASA Astrophysics Data System (ADS)

    Guo, Wei; Banerjee, Animesh; Zhang, Meng; Bhattacharya, Pallab

    2011-05-01

    The barrier height of Schottky diodes made on InxGa1-xN nanowires have been determined from capacitance-voltage measurements. The nanowires were grown undoped on n-type (001) silicon substrates by plasma-assisted molecular beam epitaxy. The length, diameter and density of the nanowires are ˜1 μm, 20 nm, and 1×1011 cm-2. The Schottky contact was made on the top surface of the nanowires with Pt after planarizing with parylene. The measured barrier height ΦB varies from 1.4 eV (GaN) to 0.44 eV (In0.5Ga0.5N) and agrees well with the ideal barrier heights in the Schottky limit.

  1. Improvement in synthesis of (K0.5Na0.5)NbO3 powders by Ge4+ acceptor doping

    NASA Astrophysics Data System (ADS)

    Zhao, Yajing; Chen, Yan; Chen, Kepi

    2016-11-01

    In this paper, the effects of doping with GeO2 on the synthesis temperature, phase structure and morphology of (K0.5Na0.5)NbO3 (KNN) ceramic powders were studied using XRD and SEM. The results show that KNN powders with good crystallinity and compositional homogeneity can be obtained after calcination at up to 900°C for 2 h. Introducing 0.5 mol.% GeO2 into the starting mixture improved the synthesis of the KNN powders and allowed the calcination temperature to be decreased to 800°C, which can be ascribed to the formation of the liquid phase during the synthesis.

  2. Optical Properties of Ferroelectric Epitaxial K0.5Na0.5NbO3 Films in Visible to Ultraviolet Range

    PubMed Central

    Pacherova, O.; Kocourek, T.; Jelinek, M.; Dejneka, A.; Tyunina, M.

    2016-01-01

    The complex index of refraction in the spectral range of 0.74 to 4.5 eV is studied by variable-angle spectroscopic ellipsometry in ferroelectric K0.5Na0.5NbO3 films. The 20-nm-thick cube-on-cube-type epitaxial films are grown on SrTiO3(001) and DyScO3(011) single-crystal substrates. The films are transparent and exhibit a significant difference between refractive indices Δn = 0.5 at photon energies below 3 eV. The energies of optical transitions are in the range of 3.15–4.30 eV and differ by 0.2–0.3 eV in these films. The observed behavior is discussed in terms of lattice strain and strain-induced ferroelectric polarization in epitaxial perovskite oxide films. PMID:27074042

  3. A Randomized Controlled Study of 0.5% Bupivacaine, 0.5% Ropivacaine and 0.75% Ropivacaine for Supraclavicular Brachial Plexus Block

    PubMed Central

    Kumar, Prabhat; Trissur, Ramachandran R.; George, Sagiev Koshy

    2016-01-01

    Introduction For any surgery in the upper extremity that does not involve the shoulder, a supraclavicular block is preferred, as it is a safe procedure associated with rapid onset and reliable anaesthesia. Although ropivacaine has been extensively studied for epidural anaesthesia, very few reports exist on its use in supraclavicular brachial plexus block. Aim This study was conducted to investigate and compare the effectiveness of supraclavicular brachial plexus anaesthesia with two different concentrations of ropivacaine (0.5% and 0.75%) and to compare them with the standard 0.5% bupivacaine. Materials and Methods Ninety patients of age 18 to 60 years belonging to American Society of Anaesthesiologists (ASA) status 1 or 2, admitted to Pondicherry Institute of Medical Sciences were chosen for the study and were divided into three groups. Group A received 30 ml of 0.5% bupivacaine, group B received 30 ml of 0.5% ropivacaine and group C received 30 ml of 0.75% ropivacaine into the supraclavicular region, by a nerve-stimulator technique. Onset time of each of the drug was recorded both for the sensory and motor block. Duration of sensory and motor block was recorded along with peri-operative haemodynamic monitoring. Results The onset of complete sensory and motor block observed with both ropivacaine groups and bupivacaine was similar (16.85±6.67 min in group A, 17.79±5.03 min in group B and 18.48±6.14 in group C, p>0.05); onset of motor block (21.45±4.45 min in group A, 22.23±4.05 min in group B and 22.33±5.17 in group C, p < 0.05). The duration of sensory block with 0.5% bupivacaine was 11.58 hours, with 0.5% ropivacaine was 9.02 hours with 0.75% ropivacaine was 8.87 hours (p<0.001). The duration of motor block with 0.5% bupivacaine was 12.94 hours, with 0.5% ropivacaine was 8.29 hours with 0.75% ropivacaine was 7.89 hours (p<0.001). Multiple comparison test with Bonferroni correction showed there was statistically significant difference in mean duration of

  4. Thermoelectric and Magnetic Properties of Sn1- x O2:Mn0.5 x Co0.5 x Nanoparticles Produced by the Microwave Technique

    NASA Astrophysics Data System (ADS)

    Salah, Numan; Habib, Sami; Azam, Ameer

    2017-02-01

    Nanoparticles (NPs) of Sn1- x O2:Mn0.5 x Co0.5 x with x = 0.02, 0.04, 0.06, 0.08 and 0.1 were synthesized by the microwave-assisted route and characterized for their thermoelectric and magnetic properties. As a result of Mn and Co co-doping, a considerable increase in the values of energy band gap and lattice constant c of Sn1- x O2:Mn0.5 x Co0.5 x NPs was observed. The x-ray photoelectron spectroscopy spectra revealed that Mn and Co ions were incorporated in their 4+ and 2+ states, respectively. The resistivity and calculated activation energy of these NPs were found to decrease by increasing the Mn and Co contents. A negative Seebeck coefficient was observed, whose value was found to be significantly increased by increasing the value of x. The magnetic measurement results revealed that all the microwave-synthesized Sn1- x O2:Mn0.5 x Co0.5 x NPs including the pure SnO2 have distinctly wide hysteresis loops. This indicates that samples have room-temperature ferromagnetism. The optimum value for x to have maximum saturation magnetism was observed to be 0.04. Diamagnetic contributions from the core of these NPs were noticed at higher magnetic fields. The observed magnetism was attributed to the presence of defects at the NPs' interfacing sites, grain boundaries, atom vacancies and an optimum level of Mn and Co co-dopants. The observed wide hysteresis loops in these NPs might be useful for producing nanoscale magnets and magnetic memory devices. Moreover, the observed thermoelectric properties, i.e. Seebeck coefficient and power factor in these NPs, might be useful for the development of thermoelectric devices.

  5. Coexistence of interacting ferromagnetic clusters and small antiferromagnetic clusters in La0.5Ba0.5CoO3

    NASA Astrophysics Data System (ADS)

    Kumar, Devendra; Banerjee, A.

    2013-05-01

    We report detailed dc magnetization and linear and nonlinear ac susceptibility measurements on the hole doped disordered cobaltite La0.5Ba0.5CoO3. Our results show that the magnetically ordered state of the system consists of coexisting non-ferromagnetic phases along with percolating ferromagnetic clusters. The percolating ferromagnetic clusters possibly start a magnetic ordering at the Curie temperature of 201.5(5) K. The non-ferromagnetic phases mainly consist of antiferromagnetic clusters with size smaller than the ferromagnetic clusters. Below the Curie temperature the system exhibits an irreversibility in the field cooled and zero field cooled magnetization and a frequency dependence in the peak of ac susceptibility. These dynamical features indicate the possible coexistence of spin-glass phase along with ferromagnetic clusters similar to La1-xSrxCoO3 (x ≥ 0.18), but the absence of field divergence in the third harmonic of ac susceptibility and zero field cooled memory clearly rule out any such possibility. We argue that the spin-glass phase in La1-xSrxCoO3 (x ≥ 0.18) is associated with the presence of incommensurate antiferromagnetic ordering in non-ferromagnetic phases, which is absent in La0.5Ba0.5CoO3. Our analysis shows that the observed dynamical features in La0.5Ba0.5CoO3 may be due to progressive thermal blocking of ferromagnetic clusters, which is further confirmed by Wohlfarth’s model of superparamagnetism. The frequency dependence of the peak of ac susceptibility obeys the Vogel-Fulcher law with τ0 ≈ 10-9 s. This together with the existence of an AT-line in H-T space indicates the presence of significant inter-cluster interaction among these ferromagnetic clusters.

  6. Photoluminescence and electrical properties of Eu-doped (Na0.5Bi0.5)TiO3 ferroelectric single crystals

    NASA Astrophysics Data System (ADS)

    Zhang, Haiwu; Zhao, Xiangyong; Deng, Hao; Chen, Chao; Lin, Di; Li, Xiaobing; Yan, Jun; Luo, Haosu

    2014-02-01

    Eu3+-doped Na0.5Bi0.5TiO3 (Eu:NBT) single crystals were grown by a top-seeded solution growth method. Photoluminescence emission and excitation spectra of Eu:NBT were investigated. The two transitions in 7F0 → 5D0 excitation spectra reveal that Eu3+ ions were incorporated into two adjacent crystallographic sites in NBT, i.e., Bi3+ and Na+ sites. The former has a symmetrical surrounding, while the later has a disordered environment, which was confirmed by decay curve measurements. The dielectric dispersion behavior was depressed and the piezoelectric and ferroelectric properties were improved after Eu doping.

  7. Contribution of oxygen vacancies to the ferroelectric behavior of Hf0.5Zr0.5O2 thin films

    NASA Astrophysics Data System (ADS)

    Shimizu, Takao; Yokouchi, Tatsuhiko; Oikawa, Takahiro; Shiraishi, Takahisa; Kiguchi, Takanori; Akama, Akihiro; Konno, Toyohiko J.; Gruverman, Alexei; Funakubo, Hiroshi

    2015-03-01

    The ferroelectric properties of the (Hf0.5Zr0.5)O2 films on Pt/Ti/SiO2/Si substrate are investigated. It is found that the films crystallized by annealing in O2 and N2 atmospheres have similar crystal structures as well as remanent polarization and coercive fields. Weak temperature and frequency dependences of the ferroelectric properties indicate that the hysteretic behavior in HfO2-based films originates not from the mobile defects but rather from the lattice ionic displacement, as is the case of the typical ferroelectric materials.

  8. Optical properties of Ag nanoparticles embedded Ba0.5Sr0.5TiO3 films prepared by alternating pulsed laser deposition.

    PubMed

    Kim, Ji-Suk; Lee, Kyeong-Seok; Kim, Sang Sub

    2006-11-01

    Nanocomposite thin films consisting of nanometer-sized Ag particles embedded in amorphous Ba0.5Sr0.5TiO3 matrix were prepared on fused silica substrates by an alternating pulsed laser deposition method. Their optical nonlinearities have been studied using the Z-scan method. The surface plasmon resonance (SPR) peak shifts to red and increases with the increasing the volume fraction of Ag in the nanocomposite films. The magnitude of the third-order nonlinear susceptibility of the nanocomposite with an Ag volume fraction of 3.3% was calculated to be approximately 2 x 10(-8) esu at the SPR wavelength.

  9. Effect of grain size on charge and spin correlations in Bi0.5Ca0.5MnO3 manganite nanoparticles

    NASA Astrophysics Data System (ADS)

    Ade, Ramesh; Singh, Rajender

    2016-11-01

    In this work we report the electron spin resonance (ESR) and magnetization (M) studies to understand the effect of grain size (GS) on the charge ordering and spin correlations in Bi0.5Ca0.5MnO3 manganite synthesized by sol-gel method. The suppression of charge ordering (CO), long-range antiferromagnetic (AFM) state, shifting of ferromagnetic (FM)-cluster glass (CG) transition towards higher temperatures and evolution of different magnetic correlations with decrease in GS are discussed in view of the changes in surface to volume ratio of nano-grains.

  10. Synthesis of manganite perovskite Ca{sub 0.5}Sr{sub 0.5}MnO{sub 3} nanoparticles in w/o-microemulsion

    SciTech Connect

    Lopez-Trosell, Alejandra . E-mail: Lopez.Alejandra@chem.tu-berlin.de; Schomaecker, Reinhard . E-mail: schomaecker@tu-berlin.de

    2006-02-02

    In this paper, w/o-microemulsions were employed to produce nanoparticles of the perovskite Ca{sub 0.5}Sr{sub 0.5}MnO{sub 3}, which have a size of approximately 20-50 nm. The procedure was carried out using sodium hydroxide or ammonia as co-precipitation agent. The precursor was transformed to perovskite by calcinations at 580 deg. C. Nanosized particles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and N{sub 2} adsorption (BET)

  11. Characterization of (Ba(0.5)Sr(0.5)) TiO3 Thin Films for Ku-Band Phase Shifters

    NASA Technical Reports Server (NTRS)

    Mueller, Carl H.; VanKeuls, Fredrick W.; Romanofsky, Robert R.; Miranda, Felix A.; Warner, Joseph D.; Canedy, Chadwick L.; Ramesh, Rammamoorthy

    1999-01-01

    The microstructural properties of (Ba(0.5)Sr(0.5)TiO3) (BSTO) thin films (300, 700, and 1400 nm thick) deposited on LaAlO3 (LAO) substrates were characterized using high-resolution x-ray diffractometry. Film crystallinity was the parameter that most directly influenced tunability, and we observed that a) the crystalline quality was highest in the thinnest film and progressively degraded with increasing film thickness; and b) strain at the film/substrate interface was completely relieved via dislocation formation. Paraelectric films such as BSTO offer an attractive means of incorporating low-cost phase shifter circuitry into beam-steerable reflectarray antennas.

  12. Effects of cation disorder and size on metamagnetism in A-site substituted Pr0.5Ca0.5MnO3 system

    NASA Astrophysics Data System (ADS)

    Mavani, K. R.; Paulose, P. L.

    2005-04-01

    The effects of A-site cation disorder and size on metamagnetism of ABO3 type charge and orbital ordered Pr0.5Ca0.5MnO3 system have been studied by substituting Ba+2 for Ca+2 or La+3 for Pr+3. Substitution of 5% Ba+2 or 5% La+3 drastically reduces the critical magnetic field (Hc) for metamagnetism and induces successive steplike metamagnetic transitions at low temperatures. Interestingly, with further increase in substitution, Hc rises. We find that there is a sharp decrease in electrical resistivity corresponding to the metamagnetic transitions, which is indicative of strongly correlated magnetic and electronic transitions in these manganites.

  13. Direct band-gap measurement on epitaxial Co{sub 2}FeAl{sub 0.5}Si{sub 0.5} Heusler-alloy films

    SciTech Connect

    Alhuwaymel, Tariq F.; Carpenter, Robert; Yu, Chris Nga Tung; Kuerbanjiang, Balati; Lazarov, Vlado K.; Abdullah, Ranjdar M.; El-Gomati, Mohamed; Hirohata, Atsufumi

    2015-05-07

    In this study, a newly developed band-gap measurement technique has been used to characterise epitaxial Co{sub 2}FeAl{sub 0.5}Si{sub 0.5} (CFAS) films. The CFAS films were deposited on MgO(001) substrate by ultra high vacuum molecular beam epitaxy. The band-gap for the as deposited films was found to be ∼110 meV when measured at room temperature. This simple technique provides a macroscopic analysis of the half-metallic properties of a thin film. This allows for simple optimisation of growth and annealing conditions.

  14. Effect of La-substitution on structural, dielectric and electrical properties of (Bi0.5Pb0.5) (Fe0.5Zr0.25Ti0.25)O3

    NASA Astrophysics Data System (ADS)

    Panda, Niranjan; Pattanayak, Samita; Choudhary, R. N. P.; Kumar, Ashok

    2016-09-01

    As lead zirconium titanate and bismuth ferrite (BFO), members of perovskite family, have high dielectric constant and ferroelectric/ferromagnetic phase transition temperature, they are used for many potential applications including random access memory, sensors. The present work describes the modifications in the ferroelectric behaviour of PZT doped BFO due to substitution of few molar percent of La on Fe-site. A thorough comparative investigation of the frequency and temperature response of dielectric permittivity, dielectric loss, electric modulus, complex impedance and ferroelectric properties of Bi0.5Pb0.5 [Fe(0.5- x) La x (Zr0.25Ti0.25)] O3, where x = 0.0, 0.1, 0.2, 0.3 (hence forth called as BFPZLTO) compounds were studied in a wide frequency range 10 kHz to 1 MHz at temperature range 25-400 °C using ac impedance spectroscopy and electric modulus analysis. The structural analysis of compound revealed the tetragonal phase with space group P4 mm at room temperature. Cole-Cole plots are used for interpretation of relaxation mechanism in the materials. The materials especially the compound with x = 0.3 found more suitable to be used in transducers, RAMs, flip-flop memories, etc., for electronics applications.

  15. Electrical Characterization Induced by Structural Modulation in (Ca0.28Ba0.72)2.5-0.5 x (Na0.5K0.5) x Nb5O15 Ceramics

    NASA Astrophysics Data System (ADS)

    Yang, Bian; Wei, Lingling; Wang, Zhongming; Kang, Shoucheng; Chao, Xiaolian; Yang, Zupei

    2016-01-01

    (Ca0.28Ba0.72)2.5-0.5 x (Na0.5K0.5) x Nb5O15 ceramics (CBNKN, 0.0 ≤ x ≤ 0.4) with `unfilled' tungsten bronze structure were prepared by the conventional solid-state reaction method. Effects of alkalis-introducing concentration in A-sites on the microstructure, dielectric and ferroelectric properties were investigated in detail. Pure tungsten bronze structure could be obtained in all compositions according to the x-ray diffraction patterns. Raman spectroscopy results showed that co-introducing Na+ and K+ in A sites to decrease the structural vacancy could enhance the dielectric and ferroelectric properties, which was attributed to the stronger interaction inside NbO6 octahedron and large distortion degree of NbO6 polar unit. Traditional temperature dependence of dielectric characteristics and well-saturated ferroelectric hysteresis loops were observed for all CBNKN ceramics. The better comprehensive dielectric and ferroelectric properties were obtained at x = 0.2 due to the bigger distortion degree of NbO6 polar unit and the highest densification. Whereas higher alkalis-introducing concentration would deteriorate the physical and electrical properties due to the poor sintering behavior. In addition, the frequency dependence of ɛ around transition temperature ( T c) and the temperature dependence of ferroelectric properties were discussed to further clarify the relationship between composition and performance.

  16. Scandium induced structural transformation and B′:B″ cationic ordering in Pb(Fe{sub 0.5}Nb{sub 0.5})O{sub 3} multiferroic ceramics

    SciTech Connect

    Mallesham, B.; Ranjith, R.; Manivelraja, M.

    2014-07-21

    The current study explores non-magnetic Sc{sup 3+} induced structural transformation, evolution of local B-site cation ordering and associated effect on ferroelectric phase transition temperature T{sub max} (temperature corresponding to dielectric maxima) on increasing the atom percent of Sc substitution in [Pb(Fe{sub 0.5}Nb{sub 0.5})O{sub 3} (PFN)] ceramics. In this regard, the phase pure Pb[(Fe{sub 0.5−x}Sc{sub x})Nb{sub 0.5}]O{sub 3} ceramics with x varying from 0 to 0.5 were synthesized through solid state reaction route. The detailed structural analysis through Rietveld refinement confirms the room temperature transformation from a monoclinic Cm to rhombohedral R3m structure at x = 0.3 mol. % of Sc. Absorption spectra studies show that there is a considerable increment in the bandgap at higher scandium content. Most interestingly, the T{sub max} exhibited an increment for lower scandium contents (x = 0.1 to 0.25) followed by a drop in T{sub max} (x = 0.3 to 0.5). Such anomalous behavior in T{sub max} is expected to arise due to the onset of B′, B″ local cation ordering beyond Sc content x = 0.25. The B-site cation ordering at and beyond x = 0.3 was also confirmed by the evolution of cation order induced Pb-O coupled vibrational mode in Raman scattering studies. In addition, the Mössbauer spectra of PFN (x = 0) and Pb(Fe{sub 0.4}Sc{sub 0.1}Nb{sub 0.5})O{sub 3} (x = 0.1) are reported to verify the spin state and oxidation state of iron. The lattice distortion due to the radius ratio difference between a Sc{sup 3+} cation and Fe{sup 3+} cation in low spin state is responsible for the structural transformation, which in turn facilitates a B′:B″ cation ordering.

  17. High thermal stability of piezoelectric properties in (Na0.5Bi0.5TiO3)x-(BaTiO3)y-(Na0.5K0.5NbO3)1-x-y ceramics

    NASA Astrophysics Data System (ADS)

    Gupta, Shashaank; Priya, Shashank

    2013-01-01

    We report the piezoelectric and ferroelectric properties of (Na0.5Bi0.5TiO3)x-(BaTiO3)y-(Na0.5K0.5NbO3)1-x-y ceramics for Na0.5K0.5NbO3 rich end of composition (x, y ≤ 0.04 mol. %). These compositions were found to exhibit significantly improved thermal stability of piezoresponse. Variation of dielectric constant as a function of temperature revealed that orthorhombic-tetragonal (To-t) and tetragonal-cubic (Tc) transition temperatures for these compositions were in the vicinity of 0 °C and 330 °C, respectively. Dynamic scaling and temperature dependent X-ray diffraction analysis were conducted. Results are discussed in terms of intrinsic and extrinsic contributions to the piezoelectric response explaining the temperature dependent behavior.

  18. Synthesis, Structure, and Electrochemical Performance of High Capacity Li2Cu0.5Ni0.5O2 Cathodes

    DOE PAGES

    Ruther, Rose E; Zhou, Hui; Dhital, Chetan; ...

    2015-09-08

    Orthorhombic Li2NiO2, Li2CuO2, and solid solutions thereof have been studied as potential cathode materials for lithium-ion batteries due to their high theoretical capacity and relatively low cost. While neither endmember shows good cycling stability, the intermediate composition, Li2Cu0.5Ni0.5O2, yields reasonably high reversible capacities. A new synthetic approach and detailed characterization of this phase and the parent Li2CuO2 are presented. The cycle life of Li2Cu0.5Ni0.5O2 is shown to depend critically on the voltage window. The formation of Cu1+ at low voltage and oxygen evolution at high voltage limit the electrochemical reversibility. In situ X-ray absorption spectroscopy (XAS), in situ Raman spectroscopy,more » and gas evolution measurements are used to follow the chemical and structural changes that occur as a function of cell voltage.« less

  19. Enhancement of transition temperature in Fe{sub x}Se{sub 0.5}Te{sub 0.5} film via iron vacancies

    SciTech Connect

    Zhuang, J. C.; Yeoh, W. K. E-mail: zxshi@seu.edu.cn; Cui, X. Y.; Ringer, S. P.; Kim, J. H.; Shi, D. Q.; Wang, X. L.; Dou, S. X.; Shi, Z. X. E-mail: zxshi@seu.edu.cn

    2014-06-30

    The effects of iron deficiency in Fe{sub x}Se{sub 0.5}Te{sub 0.5} thin films (0.8 ≤ x ≤ 1) on superconductivity and electronic properties have been studied. A significant enhancement of the superconducting transition temperature (T{sub C}) up to 21 K was observed in the most Fe deficient film (x = 0.8). Based on the observed and simulated structural variation results, there is a high possibility that Fe vacancies can be formed in the Fe{sub x}Se{sub 0.5}Te{sub 0.5} films. The enhancement of T{sub C} shows a strong relationship with the lattice strain effect induced by Fe vacancies. Importantly, the presence of Fe vacancies alters the charge carrier population by introducing electron charge carriers, with the Fe deficient film showing more metallic behavior than the defect-free film. Our study provides a means to enhance the superconductivity and tune the charge carriers via Fe vacancy, with no reliance on chemical doping.

  20. Multiferroicity and magnetoelectric coupling enhanced large magnetocaloric effect in DyFe{sub 0.5}Cr{sub 0.5}O{sub 3}

    SciTech Connect

    Yin, L. H.; Yang, J.; Dai, J. M.; Song, W. H.; Zhang, R. R.; Sun, Y. P.

    2014-01-20

    DyFe{sub 0.5}Cr{sub 0.5}O{sub 3} has been synthesized using a sol-gel method. It exhibits ferroelectricity at the antiferromagnetic ordering temperature T{sub N1}∼261 K. Large magnetocaloric effect (MCE) (11.3 J/kg K at 4.5 T) enhanced by magnetoelectric coupling due to magnetic field and temperature induced magnetic transition was observed. Temperature-dependent Raman study shows an anomalous behavior near T{sub N1} in the phonon modes related to the vibration of Dy atoms and stretching of CrO{sub 6}/FeO{sub 6} octahedra, suggesting the ferroelectricity in DyFe{sub 0.5}Cr{sub 0.5}O{sub 3} is associated with the spin-phonon coupling with respect to both Dy and Cr/Fe ions. These results suggest routes to obtain high-temperature multiferroicity and large MCE for practical applications.

  1. Poling-Written Ferroelectricity in Bulk Multiferroic Double-Perovskite BiFe0.5Mn0.5O3.

    PubMed

    Delmonte, Davide; Mezzadri, Francesco; Gilioli, Edmondo; Solzi, Massimo; Calestani, Gianluca; Bolzoni, Fulvio; Cabassi, Riccardo

    2016-06-20

    We present a comprehensive study of the electrical properties of bulk polycrystalline BiFe0.5Mn0.5O3, a double perovskite synthesized in high-pressure and high-temperature conditions. BiFe0.5Mn0.5O3 shows an antiferromagnetic character with TN = 288 K overlapped with an intrinsic antiferroelectricity due to the Bi(3+) stereochemical effect. Beyond this, the observation of a semiconductor-insulator transition at TP ≈ 140 K allows one to define three distinct temperature ranges with completely different electrical properties. For T > TN, electric transport follows an ordinary thermally activated Arrhenius behavior; the system behaves as a paramagnetic semiconductor. At intermediate temperatures (TP < T < TN), electric transport is best described by Mott's variable range hopping model with lowered dimensionality D = 1, stabilized by the magnetic ordering process and driven by the inhomogeneity of the sample on the B site of the perovskite. Finally, for T < TP, the material becomes a dielectric insulator, showing very unusual poling-induced soft ferroelectricity with high saturation polarization, similar to the parent compound BiFeO3. Under external electric poling, the system irreversibly evolves from antiferroelectric to polar arrangement.

  2. Epitaxial Ferroelectric Ba(0.5)Sr(0.5)TiO3 Thin Films for Room-Temperature High-Frequency Tunable Element Applications

    NASA Technical Reports Server (NTRS)

    Chen, C. L.; Feng, H. H.; Zhang, Z.; Brazdeikis, A.; Miranda, F. A.; VanKeuls, F. W.; Romanofsky, R. R.; Huang, Z. J.; Liou, Y.; Chu, W. K.; Chu, C. W.

    1999-01-01

    Perovskite Ba(0.5)SR(0.5)TiO3 thin films have been synthesized on (001) LaAl03 substrates by pulsed laser ablation. Extensive X-ray diffraction, rocking curve, and pole-figure studies suggest that the films are c-axis oriented and exhibit good in-plane relationship of <100>(sub BSTO)//<100>(sub LAO). Rutherford Backscattering Spectrometry studies indicate that the epitaxial films have excellent crystalline quality with an ion beam minimum yield chi(sub min) Of only 2.6 %. The dielectric property measurements by the interdigital technique at 1 MHz show room temperature values of the relative dielectric constant, epsilon(sub r), and loss tangent, tan(sub delta), of 1430 and 0.007 with no bias, and 960 and 0.001 with 35 V bias, respectively. The obtained data suggest that the as-grown Ba(0.5)SR(0.5)TiO3 films can be used for development of room-temperature high-frequency tunable elements.

  3. Oxygen-Vacancy-Induced Antiferromagnetism to Ferromagnetism Transformation in Eu0.5Ba0.5TiO3−δ Multiferroic Thin Films

    PubMed Central

    Li, Weiwei; Zhao, Run; Wang, Le; Tang, Rujun; Zhu, Yuanyuan; Lee, Joo Hwan; Cao, Haixia; Cai, Tianyi; Guo, Haizhong; Wang, Can; Ling, Langsheng; Pi, Li; Jin, Kuijuan; Zhang, Yuheng; Wang, Haiyan; Wang, Yongqiang; Ju, Sheng; Yang, Hao

    2013-01-01

    Oxygen vacancies (VO) effects on magnetic ordering in Eu0.5Ba0.5TiO3−δ (EBTO3−δ) thin films have been investigated using a combination of experimental measurements and first-principles density-functional calculations. Two kinds of EBTO3−δ thin films with different oxygen deficiency have been fabricated. A nuclear resonance backscattering spectrometry technique has been used to quantitatively measure contents of the VO. Eu0.5Ba0.5TiO3 ceramics have been known to exhibit ferroelectric (FE) and G-type antiferromagnetic (AFM) properties. While, a ferromagnetic (FM) behavior with a Curie temperature of 1.85 K has been found in the EBTO3−δ thin films. Spin-polarized Ti3+ ions, which originated from the VO, has been proven to mediate a FM coupling between the local Eu 4f spins and were believed to be responsible for the great change of the magnetic ordering. Considering the easy formation of VO, our work opens up a new avenue for achieving co-existence of FM and FE orders in oxide materials. PMID:24018399

  4. A study on the wake-up effect of ferroelectric Hf0.5Zr0.5O2 films by pulse-switching measurement

    NASA Astrophysics Data System (ADS)

    Kim, Han Joon; Park, Min Hyuk; Kim, Yu Jin; Lee, Young Hwan; Moon, Taehwan; Kim, Keum Do; Hyun, Seung Dam; Hwang, Cheol Seong

    2016-01-01

    The appearance of ferroelectric (FE) and anti-ferroelectric (AFE) properties in HfO2-based thin films is highly intriguing in terms of both the scientific context and practical application in various electronic and energy-related devices. Interestingly, these materials showed a ``wake-up effect'', which refers to the increase in remanent polarization with increasing electric field cycling number before the occurrence of the fatigue effect. In this work, the wake-up effect from Hf0.5Zr0.5O2 was carefully examined by the pulse-switching experiment. In the pristine state, the Hf0.5Zr0.5O2 film mostly showed FE-like behavior with a small contribution from AFE-like distortion, which could be ascribed to the involvement of the AFE phase. The field cycling of only 100 cycles almost completely transformed the AFE phase into the FE phase by depinning the pinned domains. The influence of field cycling on the interfacial layer was also examined through the pulse-switching experiments.

  5. Theoretical study of magnetic properties and x-ray magnetic circular dichroism of the ordered Fe{sub 0.5}Pd{sub 0.5} alloy

    SciTech Connect

    Galanakis, I.; Ostanin, S.; Alouani, M.; Dreysse, H.; Wills, J. M.

    2000-01-01

    A detailed theoretical study of magnetic and structural properties of Fe{sub 0.5}Pd{sub 0.5} ordered face-centered tetragonal (fct) alloy, using both the local spin density approximation (LSDA) and the generalized gradient approximation (GGA), is presented. The total energy surface as a function of the lattice parameters a and c shows a long valley where stable structures may exist. Our calculation using the GGA predicts a magnetic phase transition from perpendicular to parallel magnetization as a function of the lattice parameter, whereas LSDA favors always the [001] magnetization axis for all values of the lattice parameters. The spin and orbital magnetic moments and x-ray magnetic circular dichroism spectra are calculated for the easy [001] and the hard [100] magnetization axis and for three sets of experimental lattice parameters, and are compared to the available experimental results on these films. A supercell calculation for a 4 monolayer Fe{sub 0.5}Pd{sub 0.5} thin film produced similar results. While the spin magnetic moments are in fair agreement with experiment, the orbital magnetic moments are considerably underestimated. To improve the agreement with experiment we included an atomic orbital polarization term; however, the computed orbital moments scarcely changed. (c) 2000 The American Physical Society.

  6. Piezoelectric properties of Li- and Ta-modified (K0.5Na0.5)NbO3 ceramics

    NASA Astrophysics Data System (ADS)

    Hollenstein, Evelyn; Davis, Matthew; Damjanovic, Dragan; Setter, Nava

    2005-10-01

    Lead-free, potassium sodium niobate piezoelectric ceramics substituted with lithium (K0.5-x/2,Na0.5-x/2,Lix)NbO3 or lithium and tantalum (K0.5-x/2,Na0.5-x/2,Lix)(Nb1-y,Tay)O3 have been synthesized by traditional solid state sintering. The compositions chosen are among those recently reported to show high piezoelectric properties [Y. Saito, H. Takao, T. Tani, T. Nonoyama, K. Takatori, T. Homma, T. Nagaya, and M. Nakamura, Nature (London) 42, 84 (2004); Y. Guo, K. Kakimoto, and H. Ohsato, Appl. Phys. Lett. 85, 4121 (2004); Mater. Lett. 59, 241 (2005)]. We show that high densities and piezoelectric properties can be obtained for all compositions by pressureless sintering in air, without cold isostatic pressing, and without any sintering aid or special powder treatment. Resonance and converse piezoelectric (strain-field) measurements show a thickness coupling coefficient kt of 53% and converse piezoelectric coefficient d33 around 200pm/V for the Li-substituted ceramics, and a kt of 52% and d33 over 300pm/V for the Li- and Ta-modified samples. The unipolar strain-field hysteresis is small and comparable to that measured under similar conditions in hard Pb(Zr ,Ti)O3. A peak of piezoelectric properties can be noted close to the morphotropic phase boundary. These ceramics look very promising as possible, practicable, lead-free replacements for lead zirconate titanate.

  7. Structure and magnetic properties of the perovskite YCo{sub 0.5}Fe{sub 0.5}O{sub 3}

    SciTech Connect

    Wei, Yingfen; Gui, Hong; Zhao, Zhenjie; Xie, Wenhui; Li, Junrui; Li, Xiaohong; Liu, Yong; Xin, Shengwei

    2014-12-15

    Y Co{sub 0.5}Fe{sub 0.5}O{sub 3}, in a structure of perovskite, has been successfully prepared with citrate precursors at 950-1100 °C in air by the sol-gel method. The X-ray diffraction patterns show that the samples are orthorhombic within the space group Pnma, where the Co and Fe ions are disordered at the 4b crystallographic sites. The crystal structure refinement undertaken by the Rietveld method has shown that the distortion of Co(Fe)O{sub 6} octahedra are large, where the ratio of Co/Fe-O bonding length along a axis to that in the bc plane is about 1.07. Such a large crystal lattice distortion implies a strong lattice-magnetism coupling, which may be utilized in the magnetoelectric devices. Magnetic measurement indicates that the Y Co{sub 0.5}Fe{sub 0.5}O{sub 3} is antiferromagnetic but showing weak ferromagnetism. We find that Fe{sup 3+} ions are in high-spin states, while Co{sup 3+} ions are in low-spin states which do not contribute to the magnetism. Both Fe{sup 3+} and Co{sup 3+} ions are not Jahn-Teller activated although the lattice distortion is large.

  8. Pressure-induced phase transition in La1–xSmxO0.5F0.5BiS2

    DOE PAGES

    Fang, Y.; Yazici, D.; White, B. D.; ...

    2015-09-15

    Electrical resistivity measurements on La1–xSmxO0.5F0.5BiS2 (x = 0.1, 0.3, 0.6, 0.8) have been performed under applied pressures up to 2.6 GPa from 2 K to room temperature. The superconducting transition temperature Tc of each sample significantly increases at a Sm-concentration dependent pressure Pt, indicating a pressure-induced phase transition from a low-Tc to a high-Tc phase. At ambient pressure, Tc increases dramatically from 2.8 K at x = 0.1 to 5.4 K at x = 0.8; however, the Tc values at P > Pt decrease slightly with x and Pt shifts to higher pressures with Sm substitution. In the normal state,more » semiconducting-like behavior is suppressed and metallic conduction is induced with increasing pressure in all of the samples. Furthermore, these results suggest that the pressure dependence of Tc for the BiS2-based superconductors is related to the lattice parameters at ambient pressure and enable us to estimate the evolution of Tc for SmO0.5F0.5BiS2 under pressure.« less

  9. Synthesis of nanosized (Li0.5xFe0.5xZn1-x)Fe2O4 particles and magnetic properties

    NASA Astrophysics Data System (ADS)

    Gee, S. H.; Hong, Y. K.; Park, M. H.; Erickson, D. W.; Lamb, P. J.; Sur, J. C.

    2002-05-01

    In an attempt to synthesize nanosized (Li0.5xFe0.5xZn1-x)Fe2O4 (0⩽x⩽1) particles with high magnetic saturation and low coercivity, the energetic ball milling technique was employed. LiCO3, α-Fe2O3, and ZnO powders were used as starting materials. The ball milled, partially crystallized lithium zinc ferrite starts to crystallize at about 600 °C. This is much lower than the temperature of 1000 °C, which is used in conventional methods. Particle size of lithium zinc ferrite was in the range of 20 to 50 nm. Regardless of the annealing temperature, the saturation magnetization increases with increasing x and reaches the maximum (about 80 emu/g) at x=0.7 [(Li0.35Fe0.35Zn0.3)Fe2O4], followed by a decrease to 60 emu/g for x=1 [(Li0.5Fe0.5)Fe2O4]. On the other hand, the coercivity of x=0.7 composition decreases with increasing annealing temperatures. Saturation magnetization and low coercivity for x=0.7 annealed at various temperatures are discussed in terms of site occupation.

  10. The proton conducting electrolyte BaTi0.5In0.5O2.75: determination of the deuteron site and its local environment.

    PubMed

    Norberg, Stefan T; Rahman, Seikh M H; Hull, Stephen; Knee, Christopher S; Eriksson, Sten G

    2013-11-13

    Deuterated BaTi0.5In0.5O2.75 has been studied with neutron total (Bragg plus diffuse) scattering data, using both the Rietveld refinement method and the reverse Monte Carlo (RMC) modelling technique, to investigate the preferred proton site and its local structural environment. The Rietveld analysis shows an excellent fit between experimental data and a long-range cubic description of the BaTi0.5In0.5O2.53(OD)0.44 perovskite structure containing a statistical distribution of Ti and In ions at the centre of regular (Ti/In)O6 octahedra. However, an RMC analysis of the data reveals substantial local structural features that reflect limitations of the Rietveld method for studies of this type. The Ti-O and In-O pair distribution functions given by the RMC analysis are markedly different from each other, with average Ti-O and In-O bond distances of 2.035 Å and 2.159 Å, respectively. The InO6 octahedra are regular in shape whereas the TiO6 octahedra are distorted. The average O-D bond distance is roughly 0.96 Å, and the preferred deuteron sites have a second nearest oxygen distance of 2.13 Å, which confirms localized tilting of the deuteron and indicates a substantial degree of hydrogen bonding. The impact of octahedral distortion and hydrogen bonding on the proton conduction mechanism is discussed.

  11. Location of trivalent lanthanide dopant energy levels in (Lu{sub 0.5}Gd{sub 0.5}){sub 2}O{sub 3}

    SciTech Connect

    Retot, H.; Viana, B.; Bessiere, A.; Galtayries, A.

    2011-06-15

    The location of Ln{sup 3+} dopant energy levels relative to bands in (Lu{sub 0.5}Gd{sub 0.5}){sub 2}O{sub 3} was studied. A several-steps analysis of XPS measurements on heavy lanthanides sesquioxides Ln{sub 2}O{sub 3} (Ln = Gd, Tb, Dy, Er, Tm, Yb, Lu) and on Sc{sub 2}O{sub 3} and Y{sub 2}O{sub 3} reference materials were used to locate Ln{sup 3+} dopant ground state relative to the top of the valence band in (Lu{sub 0.5}Gd{sub 0.5}){sub 2}O{sub 3} within an error bar of {+-}0.4 eV. The agreement between XPS data and model was found improved relative to previous studies. When compared to XPS analysis, prediction based on optical absorption shows a slight underestimation attributed to the lack of precision in Ce{sup 4+} charge transfer band measurement.

  12. A study on the wake-up effect of ferroelectric Hf0.5Zr0.5O2 films by pulse-switching measurement.

    PubMed

    Kim, Han Joon; Park, Min Hyuk; Kim, Yu Jin; Lee, Young Hwan; Moon, Taehwan; Kim, Keum Do; Hyun, Seung Dam; Hwang, Cheol Seong

    2016-01-21

    The appearance of ferroelectric (FE) and anti-ferroelectric (AFE) properties in HfO2-based thin films is highly intriguing in terms of both the scientific context and practical application in various electronic and energy-related devices. Interestingly, these materials showed a "wake-up effect", which refers to the increase in remanent polarization with increasing electric field cycling number before the occurrence of the fatigue effect. In this work, the wake-up effect from Hf0.5Zr0.5O2 was carefully examined by the pulse-switching experiment. In the pristine state, the Hf0.5Zr0.5O2 film mostly showed FE-like behavior with a small contribution from AFE-like distortion, which could be ascribed to the involvement of the AFE phase. The field cycling of only 100 cycles almost completely transformed the AFE phase into the FE phase by depinning the pinned domains. The influence of field cycling on the interfacial layer was also examined through the pulse-switching experiments.

  13. Enhanced photocatalytic activity over Cd0.5Zn0.5S with stacking fault structure combined with Cu2+ modified carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Gong, Beini; Lu, Yonghong; Wu, Pingxiao; Huang, Zhujian; Zhu, Yajie; Dang, Zhi; Zhu, Nengwu; Lu, Guining; Huang, Junyi

    2016-03-01

    For enhanced photocatalytic performance of visible light responsive CdZnS, a series of Cd0.5Zn0.5S solid solutions were fabricated by different methods. It was found that the semiconductor obtained through the precipitation-hydrothermal method (CZS-PH) exhibited the highest photocatalytic hydrogen production rate of 2154 μmol h-1 g-1. The enhanced photocatalytic hydrogen production of CZS-PH was probably due to stacking fault formation as well as narrow bandgap, a large surface area and a small crystallite size. Based on this, carbon nanotubes modified with Cu2+ (CNTs (Cu)) were used as a cocatalyst for CZS-PH. The addition of CNTs (Cu) enhanced notably the absorption of the composites for visible light. The highest photocatalytic hydrogen production rate of the Cd0.5Zn0.5S-CNTs (Cu) composite was 2995 μmol h-1 g-1 with 1.0 wt.% of CNTs (Cu). The improvement of the photocatalytic activity by loading of CNTs (Cu) was not due to alteration of bandgap energy or surface area, and was probably attributed to suppression of the electron-hole recombination by the CNTs, with Cu2+ anchored in the interface optimizing the photogenerated electron transfer pathway between the semiconductor and CNTs. We report here the successful combination of homojunction and heterojunction in CdZnS semiconductor, which resulted in promotion of charge separation and enhanced photocatalytic activity.

  14. Evolution of Eu valence and superconductivity in layered Eu0.5La0.5FBiS2 -xSex system

    NASA Astrophysics Data System (ADS)

    Mizuguchi, Y.; Paris, E.; Wakita, T.; Jinno, G.; Puri, A.; Terashima, K.; Joseph, B.; Miura, O.; Yokoya, T.; Saini, N. L.

    2017-02-01

    We have studied the effect of Se substitution on Eu valence in a layered Eu0.5La0.5FBiS2 -xSex superconductor using a combined analysis of x-ray absorption near-edge structure (XANES) and x-ray photoelectron spectroscopy (XPS) measurements. Eu L3-edge XANES spectra reveal that Eu is in the mixed valence state with coexisting Eu2 + and Eu3 +. The average Eu valence decreases sharply from ˜2.3 for x =0.0 to ˜2.1 for x =0.4 . Consistently, Eu 3 d XPS shows a clear decrease in the average valence by Se substitution. Bi 4 f XPS indicates that effective charge carriers in the BiCh2 (Ch = S, Se) layers are slightly increased by Se substitution. On the basis of the present results it has been discussed that the metallic character induced by Se substitution in Eu0.5La0.5FBiS2 -xSex is likely to be due to increased in-plane orbital overlap driven by reduced in-plane disorder that affects the carrier mobility.

  15. Estimation of Joule heating and its role in nonlinear electrical response of Tb0.5Sr0.5MnO3 single crystal

    NASA Astrophysics Data System (ADS)

    Nhalil, Hariharan; Elizabeth, Suja

    2016-12-01

    Highly non-linear I-V characteristics and apparent colossal electro-resistance were observed in non-charge ordered manganite Tb0.5Sr0.5MnO3 single crystal in low temperature transport measurements. Significant changes were noticed in top surface temperature of the sample as compared to its base while passing current at low temperature. By analyzing these variations, we realize that the change in surface temperature (ΔTsur) is too small to have caused by the strong negative differential resistance. A more accurate estimation of change in the sample temperature was made by back-calculating the sample temperature from the temperature variation of resistance (R-T) data (ΔTcal), which was found to be higher than ΔTsur. This result indicates that there are large thermal gradients across the sample. The experimentally derived ΔTcal is validated with the help of a simple theoretical model and estimation of Joule heating. Pulse measurements realize substantial reduction in Joule heating. With decrease in sample thickness, Joule heating effect is found to be reduced. Our studies reveal that Joule heating plays a major role in the nonlinear electrical response of Tb0.5Sr0.5MnO3. By careful management of the duty cycle and pulse current I-V measurements, Joule heating can be mitigated to a large extent.

  16. Superparamagnetic behavior of heat treated Mg0.5Zn0.5Fe2O4 ferrite nanoparticles studied by Mössbauer spectroscopy

    NASA Astrophysics Data System (ADS)

    Srinivas, Ch.; Singh, S. B.; Tirupanyam, B. V.; Meena, S. S.; Yusuf, S. M.; Prasad, S. A. V.; Krishna, K. S. Rama; Sastry, D. L.

    2016-05-01

    Nanoparticles of Mg0.5Zn0.5Fe2O4 ferrite have been synthesized by co-precipitation method. XRD and Mössbauer spectroscopic results of Mg0.5Zn0.5Fe2O4 annealed at 200 °C, 500 °C and 800 °C are reported. It was observed that the crystallite size increases and the lattice parameter decreases with increase in annealing temperature. The observed decrease in lattice strain supports the increase in crystallite size. The Mössbauer spectra of the samples annealed at 200 °C and 500 °C exhibits superparamagnetic doublets whereas the Mössbauer spectrum of the sample annealed at 800 °C exhibits paramagnetic doublet along with weak sextet of hyperfine interaction. The values of isomer shift resemble the presence of high spin iron ions. The studied ferrite nanoparticles are suitable for biomedical applications. The results are incorporated employing core-shell model and cation redistribution.

  17. Chemically stable perovskites as cathode materials for solid oxide fuel cells: La-doped Ba0.5Sr0.5Co0.8Fe0.2O(3-δ).

    PubMed

    Kim, Junyoung; Choi, Sihyuk; Jun, Areum; Jeong, Hu Young; Shin, Jeeyoung; Kim, Guntae

    2014-06-01

    Ba0.5Sr0.5Co0.8Fe0.2O(3-δ) (BSCF) has won tremendous attention as a cathode material for intermediate-temperature solid-oxide fuel cells (IT-SOFC) on the basis of its fast oxygen-ion transport properties. Nevertheless, wide application of BSCF is impeded by its phase instabilities at intermediate temperature. Here we report on a chemically stable SOFC cathode material, La0.5Ba0.25Sr0.25Co0.8Fe0.2O(3-δ) (LBSCF), prepared by strategic approaches using the Goldschmidt tolerance factor. The tolerance factors of LBSCF and BSCF indicate that the structure of the former has a smaller deformation of cubic symmetry than that of the latter. The electrical property and electrochemical performance of LBSCF are improved compared with those of BSCF. LBSCF also shows excellent chemical stability under air, a CO2-containg atmosphere, and low oxygen partial pressure while BSCF decomposed under the same conditions. Together with this excellent stability, LBSCF shows a power density of 0.81 W cm(-2) after 100 h, whereas 25 % degradation for BSCF is observed after 100 h.

  18. Magnetoelectric coupling study in multiferroic Pb(Fe{sub 0.5}Nb{sub 0.5})O{sub 3} ceramics through small and large electric signal standard measurements

    SciTech Connect

    Raymond, Oscar; Siqueiros, Jesus M.; Font, Reynaldo; Portelles, Jorge

    2011-05-01

    Multifunctional multiferroic materials such as the single phase compound Pb(Fe{sub 0.5}Nb{sub 0.5})O{sub 3} (PFN), where ferroelectric and antiferromagnetic order coexist, are very promising and have great interest from the academic and technological points of view. In this work, coupling of the ferroelectric and magnetic moments is reported. For this study, a combination of the small signal response using the impedance spectroscopy technique and the electromechanical resonance method with the large signal response through standard ferroelectric hysteresis measurement, has been used with and without an applied magnetic field. The measurements to determine the electrical properties of the ceramic were performed as functions of the bias and poling electric fields. A simultaneous analysis of the complex dielectric constant {epsilon}-tilde, impedance Z-tilde, electric modulus M-tilde, admittance Y-tilde, and the electromechanical parameters and coupling factors is presented. The results are correlated with a previous study of structural, morphological, small signal dielectric frequency-temperature response, and the ferroelectric hysteretic, magnetic and magnetodielectric behaviors. The observed shifts of the resonance and antiresonance frequency values can be associated with change of the ferroelectric domain size favored by the readjustment of the oxygen octahedron when the magnetic field is applied. From P-E hysteresis loops obtained without and with an external applied magnetic field, a dc magnetoelectric coupling effect with maximum value of 4 kV/cm T (400 mV/cm Oe) was obtained.

  19. Room temperature multiferroic properties of Pb(Fe0.5Nb0.5)O3-Co0.65Zn0.35Fe2O4 composites

    NASA Astrophysics Data System (ADS)

    Pradhan, Dhiren K.; Puli, Venkata S.; Narayan Tripathy, Satya; Pradhan, Dillip K.; Scott, J. F.; Katiyar, Ram S.

    2013-12-01

    We report the crystal structure, magnetic, ferroelectric, dielectric, and magneto-dielectric properties of [Pb(Fe0.5Nb0.5)O3](1-x)[Co0.65Zn0.35Fe2O4]x: (x = 0.1, 0.2, 0.3, and 0.4) composites. Rietveld refinement results of X-ray diffraction patterns confirm the formation of these composites for all x values. All the composites show well-saturated ferroelectric and ferromagnetic hysteresis (multiferroic-composite behavior) at room temperature. With increase in Co0.65Zn0.35Fe2O4 (CZFO) content an increase in saturation magnetization, and decrease in saturation polarization, remanent polarization, and dielectric constant are observed. The ferroelectric phase transition temperature increases with increase in CZFO content. All of the compositions undergo second-order ferroelectric phase transitions, which can be explained by Landau-Devonshire theory. The recoverable energy density (˜0.20 to 0.04 J/cm3) and charge-curve energy density (˜0.84 to 0.11 J/cm3) decrease with increase in the CZFO content. The room-temperature magneto-dielectric measurements provide direct evidence of magneto-electric coupling via strain at room temperature.

  20. A robust high performance cobalt-free oxygen electrode La0.5Sr0.5Fe0.8Cu0.15Nb0.05O3-δ for reversible solid oxide electrochemical cell

    NASA Astrophysics Data System (ADS)

    Zhou, Ning; Yin, Yi-Mei; Li, Jingcheng; Xu, Lei; Ma, Zi-Feng

    2017-02-01

    A novel cobalt-free perovskite oxide La0.5Sr0.5Fe0.8Cu0.15Nb0.05O3-δ (LSFCN) has been synthesized and evaluated as oxygen electrode for reversible solid oxide electrochemical cells (RSOCs). The performance and stability of the LSFCN based RSOCs have been characterized in fuel cell and electrolysis modes, and the reversibility of the cells has been proven. In FC mode, the cell exhibits the maximum power density of 1.10 Wcm-2 at 800 °C, and a stable output under 0.7 V at 700 °C during 108 h. The performance and stability of the cell in electrolysis mode are also remarkable. An electrolysis current of 0.85 A cm-2 is achieved at 750 °C with an applied voltage of 1.3 V, and no degradation as well as delamination are observed for the cell after 50 h electrolysis under voltage of 1.60 V (∼1.27 A cm-2) at 800 °C. The high performance of the LSFCN at both cathodic and anodic conditions may be attributed to the inherent high electrochemical activity of copper-iron based perovskites; and the incorporation of Nb5+ cations into perovskite lattice is responsible for the stability of LSFCN, which leads to the more stable crystal structure, lower thermal expansion coefficient and the reduced Sr segregation at surface.

  1. Structure and properties of Bi(Zn0.5Ti0.5)O3- Pb(Zr(1-x)Ti(x))O3 ferroelectric single crystals grown by a top-seeded solution growth technique.

    PubMed

    Wang, Bixia; Wu, Xiaoqing; Ren, Wei; Ye, Zuo-Guang

    2015-06-01

    Bi(Zn0.5Ti0.5)O3 (BZT)-modified Pb(Zr(1-x)Ti(x))O3 (PZT) single crystals have been grown using a top-seeded solution growth technique and characterized by various methods. The crystal structure is found to be rhombohedral by means of X-ray powder diffraction. The composition and homogeneity of the as-grown single crystals are studied by laser ablation inductively coupled plasma mass spectrometry and X-ray photoelectron spectroscopy. The domain structure of a (001)(cub) platelet is investigated by polarized light microscopy (PLM), which confirms the rhombohedral symmetry. The paraelectric-to-ferroelectric phase transition temperature T(C) is found to be 313°C with the absence of rhombohedral-tetragonal phase transition. The ferroelectric properties of the ternary crystals are enhanced by the BZT substitution with a remanent polarization of 28 μC/cm(2) and a coercive field E(C) of 22.1 kV/cm.

  2. 47 CFR 0.5 - General description of Commission organization and operations.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... and operations. 0.5 Section 0.5 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL COMMISSION... Engineering and Technology. (3) Office of General Counsel. (4) Office of Strategic Planning and Policy.... (8) Office of Communications Business Opportunities. (9) Office of Administrative Law Judges....

  3. Effect of current induced charge-order melting of Pr0.5Ca0.5MnO3 in partially masked superconducting Pr0.5Ca0.5MnO3/YBa2Cu3O7 bilayer

    NASA Astrophysics Data System (ADS)

    Kumar Baisnab, Dipak; Janawadkar, M. P.; Vaidhyanathan, L. S.; Bharathi, A.

    2013-12-01

    In order to investigate the effect of current induced charge-order melted ferromagnetic Pr0.5Ca0.5MnO3 on superconducting YBa2Cu3O7, current and magnetic field dependent resistance measurements have been carried out in Pr0.5Ca0.5MnO3/YBa2Cu3O7 thin film heterostructure in which a part of the YBa2Cu3O7 thin film is covered by Pr0.5Ca0.5MnO3. The measurements show that superconducting transition temperature of the uncovered YBa2Cu3O7 is suppressed to lower temperatures with a progressive increase in current. Results show the possibility of controlling the superconducting properties of the uncovered part of the YBa2Cu3O7 thin film by influencing the part covered by Pr0.5Ca0.5MnO3.

  4. Experimental determination of compressional-wave seismic velocity of talc at high temperature at 0.5 GPa

    NASA Astrophysics Data System (ADS)

    Bailey, Edward

    2000-10-01

    Compressional wave velocity, VP, in talc has been measured as a function of temperature at 0.5 GPa by a time of flight ultrasonic method in an internally heated gas pressure vessel. At this pressure, VP decreases from 5.27 +/- 0.23 km s-1 at 25°C to 4.35 +/- 0.15 km s-1 at 800°C. VP in a hydrated peridotite has also been measured, at 0.5 GPa, 600°C, but with no useable results. Combining the results for talc with a previously published bulk modulus K and deltaK/deltaP, gives a Poissons ratio, nu, of 0.268 and a shear modulus, G, of 22.6 GPa under atmospheric conditions. Assuming nu is independent of temperature gives a deltaKs/deltaT value of -19.3 +/- 0.64 MPa K-1 at 0.5 GPa. These experimental data, in combination with published data, have been used to calculate the Voigt, Reuss, and Hashin-Shtrikman-Walpole bounds, and the Voigt-Reuss-Hill average of the elastic moduli of a peridotite, hydrated with talc, just above a cold subducting lithosphere, and seismic velocities derived from those. A talc-beating assemblage containing only 0.9 weight% H2O has elastic wave velocities (calculated from the Voigt-Reuss-FEII average) slower than the anhydrous rock by an average of 7.6% for VP , and 9.7% for shear waves Vs at 700°C, between 0.5 and 4 GPa. These results are examined in connection with seismic observations of converted elastic wave phase behavior near the surface of cold subducting slabs in the northern Pacific. Although a layer of peridotite, just above the subducting slab, hydrated by talc could explain these observations at depths shallower than 155 km, the silica content of peridotite is not high enough to stabilize talc at these depths. The hypothesis that the low velocity layer is caused by a metastable subducting oceanic crust better explains the observations. Talc is likely, however to be an important hydrous phase at depths between 30 and 60 km, i.e. from the top of the mantle down to the pressure stability limit of talc. In some regions of

  5. A Temperature-Insensitive Ba3.75Nd9.5Ti17.5(Cr0.5Nb0.5)0.5O54 Microwave Dielectric Ceramic by Bi3+ Substitution

    NASA Astrophysics Data System (ADS)

    Chen, Hetuo; Tang, Bin; Guo, Xia; Wei, Meng; Si, Feng; Yuan, Ying; Zhang, Shuren

    2017-02-01

    In this study, effects of Bi3+ substitution upon microwave dielectric properties of the (Cr0.5Nb0.5)4+ replaced Ba3.75Nd9.5Ti18O54 (0 ≤ x ≤ 0.2) ceramic have been reported. The x-ray diffraction (XRD) result shows a single phase for all compositions with peak position fluctuation. Within the whole x range, while the quality factor ( Q) is degraded, the dielectric constant ( ɛ r) can be improved by as high as 32% and the temperature coefficient of resonant frequency ( τ f) is tailored from around +40 ppm/°C to the vicinity of zero. Considering practical requirements, we can obtain a series of temperature-insensitive ceramics ( τ f ˜ 0 ppm/°C) with relative permittivity about 95 and Qf (defined as Q times the resonant frequency f) higher than 6000 GHz. They have the potential of being utilized in wireless microwave communication applications.

  6. High P-T Raman study of transitions in relaxor multiferroic Pb(Fe0.5Nb0.5)O3

    DOE PAGES

    Wilfong, Brandon; Ahart, Muhtar; Gramsch, Stephen A.; ...

    2015-09-02

    The vibrational and structural properties of Pb(Fe0.5Nb0.5)O3 have been investigated using Raman spectroscopy up to 40 GPa at 300 K and from 300 to 415 K at selected pressures. The measurements reveal three phase transitions at 5.5, 8.7 and 24 GPa at room temperature. The temperature dependences of the spectra indicated transitions at 1.5 GPa, at 335 and 365 K. The results support the appearance of an intermediate tetragonal P4mm phase between ferroelectric R3m and paraelectric Pm-3m phases. Furthermore, a P-T phase diagram is proposed that allows further insight into the magnetoelectric coupling present in this material.

  7. Efficient Removal of Uranium from Aqueous Solution by Reduced Graphene Oxide-Zn0.5Ni0.5Fe2O4 Ferrite-Polyaniline Nanocomposite

    NASA Astrophysics Data System (ADS)

    Tran, Dat Quang; Pham, Hung Thanh; Do, Hung Quoc

    2017-03-01

    Reduced graphene oxide-Zn0.5Ni0.5Fe2O4 ferrite-polyaniline nanocomposite (RGO-ZNF-PANI) was synthesized by a three-step method. The prepared samples were characterized by x-ray diffraction, Raman spectroscopy, scanning electron microscopy and vibrating sample magnetometer. In particular, we found that this material is capable of effectively removing uranium from an aquatic environment. This is confirmed by our experimental results using the method of inductively coupled plasma mass spectrometry. Adsorptive behaviour of uranium from an aqueous solution on the RGO-ZNF-PANI nanocomposite was examined as a function of pH, contact time, and equilibrium. Uranium concentration was carried out by batch techniques. The adsorption isotherm agrees well with the Langmuir model, having a maximum sorption capacity of 1885 mg/g, at pH 5 and 25°C.

  8. Series resistance effects in La0.5Ca0.5MnO3/SrTiO3:Nb(0 0 1) heterojunctions

    NASA Astrophysics Data System (ADS)

    Wang, J. F.; Cao, D.; Zhou, Y.; Wang, X. Y.; Jiao, Z. W.; Gao, J.

    2015-09-01

    The effects of series resistance in heterojunctions composed of La0.5Ca0.5MnO3 (LCMO) and Nb:SrTiO3 with 0.05 wt.% and 0.7 wt.% of Nb doping (0.05NbSTO and 0.7NbSTO) have been investigated in detail using current-voltage curves with and without light illumination. Two linear plots, namely, dV/dlnJ versus J and H(J)[≡V-(nk B T/q)ln(J/A**T 2)] versus J, have been used to extract the series resistance. These two plots give very close values. The extracted series resistance exhibits a monotonous increase with decreasing temperatures, which could explain the observed anomalous temperature dependence of short circuit current in LCMO/0.7NbSTO.

  9. The energy gap of the compound FeSe0.5Te0.5 determined by specific heat and Point Contact Spectroscopy

    NASA Astrophysics Data System (ADS)

    Escudero, Roberto; López-Romero, Rodolfo E.

    2015-10-01

    The superconductor FeSe0.5Te0.5 was studied with Point Contact spectroscopy and specific heat in polycrystalline samples. The transition temperature determined by magnetic measurement was TC=14.5 K. The size of the energy gap measured by junctions is Δ = 1.9 meV, whereas the gap determined by the specific heat measurements was Δ = 2.3 meV. The gap evolution with temperature follows BCS, the ratio 2Δ/KBTC has values between 2.88 ≤ 2 Δ /KBTC ≤ 3.04. The compound was grown by solid state synthesis in quartz ampoules under vacuum at 950 °C. Crystal structure was characterized by X-ray diffraction. The superconducting properties were characterized by magnetization, resistivity and specific heat. This superconductor shows an isotropic energy gap as observed with the fitting of the specific heat at low temperature.

  10. Reduced Graphene Oxide-Cu0.5Ni0.5Fe2O4-Polyaniline Nanocomposite: Preparation, Characterization and Microwave Absorption Properties

    NASA Astrophysics Data System (ADS)

    Dat, Tran Quang; Ha, Nguyen Tran; Hung, Do Quoc

    2017-02-01

    Reduced graphene oxide-Cu0.5Ni0.5Fe2O4-polyaniline nanocomposite (RGO-CNF-PANI) was synthesized by a three-step method. The morphology, structure and magnetic properties of composite samples were characterized by scanning electron microscopy, x-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy (RAMAN) and vibrating sample magnetometer. It was found that reduced graphene oxide was exfoliated and decorated homogeneously with ferrite nanoparticles having diameters between 11 nm and 21 nm. The polyaniline was coated by an in situ chemical oxidation polymerization. The measurement of magnetic properties found the remanence (Mr) and coercive field (Hc) were near zero, indicating that the obtained material was superparamagnetic. The microwave measurements found that the nanocomposite exhibited a good absorption property with the optimum matching thickness of 3 mm in the frequency of 8-12 GHz. The value of the maximum RL was -40.7 dB at 9.8 GHz.

  11. Simultaneous laser excitation of backward volume and perpendicular standing spin waves in full-Heusler Co2FeAl0.5Si0.5 films

    PubMed Central

    Chen, Zhifeng; Yan, Yong; Li, Shufa; Xu, Xiaoguang; Jiang, Yong; Lai, Tianshu

    2017-01-01

    Spin-wave dynamics in full-Heusler Co2FeAl0.5Si0.5 films are studied using all-optical pump-probe magneto-optical polar Kerr spectroscopy. Backward volume magnetostatic spin-wave (BVMSW) mode is observed in films with thickness ranging from 20 to 100 nm besides perpendicular standing spin-wave (PSSW) mode, and found to be excited more efficiently than the PSSW mode. The field dependence of the effective Gilbert damping parameter appears especial extrinsic origin. The relationship between the lifetime and the group velocity of BVMSW mode is revealed. The frequency of BVMSW mode does not obviously depend on the film thickness, but the lifetime and the effective damping appear to do so. The simultaneous excitation of BVMSW and PSSW in Heusler alloy films as well as the characterization of their dynamic behaviors may be of interest for magnonic and spintronic applications. PMID:28195160

  12. Vacancy related defects in La{sub 0.5}Sr{sub 0.5}CoO{sub 3-{delta}} thin films

    SciTech Connect

    Keeble, D.J.; Krishnan, A.; Nielsen, B.

    1996-12-31

    Laser ablated La{sub 0.5}Sr{sub 0.5}CoO{sub 3-{delta}} thin films have been studied by Doppler-broadening-detected positron annihilation using a variable-energy positron beam. The oxygen partial pressure during cooling from the growth temperature was altered through the range 760 torr to 10{sup -5} torr to change the oxygen non-stoichiometry of the films. The measured Doppler broadened lineshape parameter S was found to increase with increasing oxygen nonstoichiometry. For films cooled with an oxygen partial pressure of {le} 10{sup -4} Torr positron trapping to monovacancy type defects is inferred. For the film cooled in 10{sup -5} torr oxygen the magnitude of the increase in S, with respect to that measured from the film cooled in 760 Torr oxygen, showed positron trapping to vacancy cluster defects was occurring.

  13. Effect of Natural Aging and Cold Working on Microstructures and Mechanical Properties of Al-4.6Cu-0.5Mg-0.5Ag alloy

    NASA Astrophysics Data System (ADS)

    Chen, Yu-Te; Lee, Sheng-Long; Bor, Hui-Yun; Lin, Jing-Chie

    2013-06-01

    This research investigates the effects of natural aging and cold working prior to artificial aging on microstructures and mechanical properties of Al-4.6Cu-0.5Mg-0.5Ag alloy. Mechanical properties relative to microstructure variations were elucidated by the observations of the optical microscope (OM), differential scanning calorimeter (DSC), electrical conductivity meter (pct IACS), and transmission electron microscopy (TEM). The results showed that natural aging treatment has little noticeable benefit on the quantity of precipitation strengthening phases and mechanical properties, but it increases the precipitation strengthening rate at the initial stage of artificial aging. Cold working brings more lattice defects which suppress Al-Cu (GP zone) and Mg-Ag clustering, and therefore the precipitation of Ω phase decreases. Furthermore, more dislocations are formed, leading to precipitate the more heterogeneous nucleation of θ' phase. The above-mentioned precipitation phenomena and strain hardening effect are more obvious with higher degrees of cold working.

  14. 4-ps passively mode-locked Nd:Gd0.5Y0.5VO4 laser with a semiconductor saturable-absorber mirror.

    PubMed

    He, Jing-Liang; Fan, Ya-Xian; Du, Juan; Wang, Yong-Gang; Liu, Sheng; Wang, Hui-Tian; Zhang, Lian-Han; Hang, Yin

    2004-12-01

    We have demonstrated a passively mode-locked diode end-pumped all-solid-state laser, which is composed of a Nd:Gd0.5Y0.5VO4 crystal and a folded cavity with a semiconductor saturable-absorber mirror grown by metal-organic chemical-vapor deposition. Stable cw mode locking with a 3.8-ps pulse duration at a repetition rate of 112 MHz was obtained. At 13.6 W of the incident pump power, a clean mode-locked fundamental-mode average output power of 3.9 W was achieved with an overall optical-to-optical efficiency of 29.0%, and the slope efficiency was 38.1%.

  15. A novel counter electrode material of La0.5Sr0.5CoO3 for dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Zhong, Yongfeng; Qin, Tianze; Yang, Bo; Zuo, Xueqin; Li, Guang; Wu, Mingzai; Ma, Yongqing; Jin, Shaowei; Zhu, Kerong

    2016-11-01

    In this work, La0.5Sr0.5CoO3 (LSCO) perovskite oxide with perfect crystallinity was successfully synthesized via a sol-gel method and then used as counter electrodes (CEs) for dye-sensitized solar cells (DSSCs). The DSSCs with LSCO CEs exhibited excellent electrocatalytic activity for the triiodide reduction and yielded a power conversion efficiency of 7.17%, which is greater than that of the Pt electrode (7.06%). Compared with the hydrothermal method and solvothermal method, sol-gel method is more suitable for large scale preparation. This work should open up a new class of CE materials for low-cost and high-efficiency DSSCs.

  16. The microstructures and superconducting properties of FeSe0.5Te0.5 bulks with original milled powders

    NASA Astrophysics Data System (ADS)

    Li, Xiaoting; Gao, Zhiming; Liu, Yongchang; Ma, Zongqing; Yu, Liming; Li, Huijun; Yang, Hanzhang

    2013-10-01

    A combination of mechanical alloying (MA) and solid-state reaction was applied to synthesize bulk FeSe0.5Te0.5 superconductor. The influence of milling time on microstructures and superconducting properties were investigated in detail. The results showed that both the grain size and the amount of β-FeSe in the final sintered samples decreased as the milling time increased. In addition, lattice parameters a and c of β-FeSe also decreased with the milling time increasing, implying the introduction of a positive chemical pressure, which was not favorable for superconductivity of Fe chalcogenides. According to the measured results of resistivity, only the 20 h-milled sintered sample exhibited superconductivity, with Tconset and Tc0 of values 14 K and 10 K, respectively. As the milling time increased, the superconductivity was depressed or even damaged completely.

  17. Unraveling the magnetic properties of BiFe{sub 0.5}Cr{sub 0.5}O{sub 3} thin films

    SciTech Connect

    Vinai, G.; Petrov, A. Yu.; Panaccione, G.; Torelli, P.; Khare, A.; Rana, D. S.; Di Gennaro, E.; Scotti di Uccio, U.; Miletto Granozio, F.; Gobaut, B.; Moroni, R.; Rossi, G.

    2015-11-01

    We investigate the structural, chemical, and magnetic properties on BiFe{sub 0.5}Cr{sub 0.5}O{sub 3} (BFCO) thin films grown on (001) (110) and (111) oriented SrTiO{sub 3} (STO) substrates by x-ray magnetic circular dichroism and x-ray diffraction. We show how highly pure BFCO films, differently from the theoretically expected ferrimagnetic behavior, present a very weak dichroic signal at Cr and Fe edges, with both moments aligned with the external field. Chemically sensitive hysteresis loops show no hysteretic behavior and no saturation up to 6.8 T. The linear responses are induced by the tilting of the Cr and Fe moments along the applied magnetic field.

  18. Anisotropic magnetoresistance of epitaxial Pr{sub 0.5}Sr{sub 0.5}MnO{sub 3} film

    SciTech Connect

    Chen, X. G.; Yang, Y. B.; Wang, C. S.; Liu, S. Q.; Zhang, Y.; Han, J. Z.; Yang, Y. C.; Yang, J. B.

    2014-01-28

    The magnetic field and temperature dependent anisotropic magnetoresistance (AMR) of the epitaxial grown Pr{sub 0.5}Sr{sub 0.5}MnO{sub 3} thin films was investigated. It was found that the magnetoresistance exhibited the characteristics of magnetic polaron hopping. A two-fold symmetric AMR occurred in the ferromagnetic region (∼220 K < T < ∼150 K), while a four-fold symmetric AMR appeared under a high magnetic field in the antiferromagnetic orbital ordered region (T < ∼150 K). The angular dependence of the resistance showed a hysteresis effect under magnetic field at low temperature. It is believed that these phenomena are attributed to the spin canting effect, which originates from the melting of orbital ordering under the external magnetic field in the antiferromagnetic region.

  19. Magnetoresistance reversal in antiperovskite compound Mn{sub 3}Cu{sub 0.5}Zn{sub 0.5}N

    SciTech Connect

    Zhang, X. H.; Yin, Y.; Yuan, Q.; Han, J. C.; Zhang, Z. H.; Jian, J. K.; Zhao, J. G. E-mail: songbo@hit.edu.cn; Song, B. E-mail: songbo@hit.edu.cn

    2014-03-28

    We report detailed investigations of the structure, magnetic properties, electronic transport, and specific heat in Mn-based antiperovskite compounds Mn{sub 3}Cu{sub 0.5}Zn{sub 0.5}N. Most strikingly, there are several fascinating features: (i) The magnetoresistance at 30 kOe (40 kOe) exceeds ∼1% (∼2%) over a temperature span of ∼70 K (∼25 K) from 5 to 140 K; (ii) magnetoresistance fluctuates at temperatures of 100–200 K, including an obvious sign reversal from negative to positive at ∼140 K. Analysis of the specific heat reveals that the magnetoresistance reversal may originate from the reconstruction of the Fermi surface accompanying an antiferromagnetic-ferromagnetic transition.

  20. Neither Goodenough ionic model nor Zener polaron model for Bi 0.5Ca 0.5Mn 1- xNi xO 3- δ system

    NASA Astrophysics Data System (ADS)

    Toulemonde, O.; Skovsen, I.; Mesguich, F.; Gaudin, E.

    2008-04-01

    The magnetic susceptibilities of three Bi 0.5Ca 0.5MnO 3- δ compounds synthesised by three different methods were characterised and analysed. Large magnetic Mn x clusters ( x ≥ 4) were considered to explain the high value of the Curie-Weiss constant. Unlike previous studies on similar systems, Goodenough ionic model or Zener polaron model is not suitable. In all cases, cluster behaviour is observed at low field and at low temperature. The influence of the oxygen stoichiometry and the homogeneity of the cation distribution depending on the method of the synthesis used is discussed. Finally, the effects of nickel doping on the magnetic properties were studied and the cluster behaviour was confirmed. The distribution in size of the clusters depends on the amount of nickel and it induces a glassy magnetic behaviour.

  1. Pressure-Induced Antiferromagnetic Fluctuations in the Pnictide Superconductor FeSe0.5Te0.5: 125Te NMR Study

    NASA Astrophysics Data System (ADS)

    Shimizu, Yasuhiro; Yamada, Takato; Takami, Tsuyoshi; Niitaka, Seiji; Takagi, Hidenori; Itoh, Masayuki

    2009-12-01

    To investigate the relationship between superconductivity and low-energy spin fluctuations in the iron-based superconductor FeSe0.5Te0.5, we have conducted 125Te NMR measurements at ambient pressure and 2 GPa. As the superconducting transition temperature Tc is increased by applying pressure, the nuclear spin-lattice relaxation rate divided by temperature, 1/T1T, shows the development of antiferromagnetic fluctuations upon lowering temperature toward Tc. This supports the scenario that spin fluctuations promote superconducting pairing. The depressed Knight shift 125K and the absence of a coherence peak in 1/T1 below Tc are consistent with spin-singlet superconducting pairing with an anisotropic order parameter. In the normal metallic state, the comparison between the uniform and dynamic spin susceptibilities suggests the existence of a Fermi level located near the singularity of the band structure.

  2. Identical superconducting gap on different Fermi surfaces of Ca(Al0.5Si0.5)2 with the AlB2 structure

    NASA Astrophysics Data System (ADS)

    Tsuda, S.; Yokoya, T.; Shin, S.; Imai, M.; Hase, I.

    2004-03-01

    Angle-resolved photoemission spectroscopy of Ca(Al0.5Si0.5)2 (CaAlSi), which is a superconductor (transition temperature is 7.7 K) with the AlB2 structure, revealed that superconducting gaps on two Fermi surfaces (FSs) with three-dimensional character around Γ(A) and M(L) in the Brillouin zone provide essentially the same superconducting gap value (˜1.2 meV±0.2 meV). This is in contrast to the case of MgB2, in which different FSs exhibit different gap values. The reduced gap value 2Δ(0)/kBTc of ˜4.2±0.2 classifies CaAlSi as a moderately strong-coupling superconductor.

  3. Milling time and BPR dependence on permeability and losses of Ni 0.5Zn 0.5Fe 2O 4 synthesized via mechanical alloying process

    NASA Astrophysics Data System (ADS)

    Ismail, Ismayadi; Hashim, Mansor; Amin Matori, Khamirul; Alias, Rosidah; Hassan, Jumiah

    2011-06-01

    Ni 0.5Zn 0.5Fe 2O 4 has been synthesized using mechanical alloying method with two variables (milling time and ball-to-powder weight ratio (BPR)) were varied in order to study its effect on the magnetic properties of the material. The effects of these two variables were studied using XRD, SEM, TEM and later by impedance analyzer with the frequency range from 1 MHz to 1.8 GHz. The results obtained however show that there are no significant trends to relate the milling time and BPR with the permeability and losses of the material studied. After being sintered at 1150 °C, all the effects of alloying process seem to diminish.

  4. Effect of Oxygen-deficiencies on Resistance Switching in Amorphous YFe0.5Cr0.5O3−d films

    PubMed Central

    Wang, Xianjie; Hu, Chang; Song, Yongli; Zhao, Xiaofeng; Zhang, Lingli; Lv, Zhe; Wang, Yang; Liu, Zhiguo; Wang, Yi; Zhang, Yu; Sui, Yu; Song, Bo

    2016-01-01

    Herein, we demonstrate the contribution of the oxygen-deficiencies on the bipolar resistance switching (RS) properties of amorphous-YFe0.5Cr0.5O3−d (a-YFCO) films. The a-YFCO films were prepared under various oxygen pressures to tune the concentration of oxygen-deficiencies in the films. The XPS data verify that the oxygen-deficiencies increase with decreasing oxygen pressure. The RS property becomes more pronounced with more oxygen-deficiencies in a-YFCO films. Based on the Ohmic conduction measurements in the low resistance state, we confirm that the RS mechanism is related to the migration of oxygen-deficiencies. The enhanced RS and long retention in a-YFCO suggest a great potential for applications in nonvolatile memory devices. PMID:27452114

  5. Electronic structure of random Al sub 0. 5 Ga sub 0. 5 As alloys: Test of the special-quasirandom-structures'' description

    SciTech Connect

    Hass, K.C.; Davis, L.C. ); Zunger, A. )

    1990-08-15

    The spectral properties of an {ital sp}{sup 3}{ital s*} tight-binding Hamiltonian for a random, unrelaxed Al{sub 0.5}Ga{sub 0.5}As alloy are calculated using three different techniques: the coherent-potential approximation, the recursion method (as applied to a {gt}2000 atom supercell), and the recently introduced special-quasirandom-structures'' (SQS) approach. Over a broad range of scattering strengths, the dominant spectral features predicted by the first two techniques are well reproduced by calculations for an SQS with 16 atoms/unit-cell ( SQS-8''). This suggests that the SQS approach might also be useful in cases where the other methods are difficult to apply, e.g., in first-principles calculations for structurally relaxed alloys.

  6. A magnetic atomic laminate from thin film synthesis: (Mo{sub 0.5}Mn{sub 0.5}){sub 2}GaC

    SciTech Connect

    Meshkian, R. Ingason, A. S.; Lu, J.; Rosen, J.; Arnalds, U. B.; Magnus, F.

    2015-07-01

    We present synthesis and characterization of a new magnetic atomic laminate: (Mo{sub 0.5}Mn{sub 0.5}){sub 2}GaC. High quality crystalline films were synthesized on MgO(111) substrates at a temperature of ∼530 °C. The films display a magnetic response, evaluated by vibrating sample magnetometry, in a temperature range 3-300 K and in a field up to 5 T. The response ranges from ferromagnetic to paramagnetic with change in temperature, with an acquired 5T-moment and remanent moment at 3 K of 0.66 and 0.35 μ{sub B} per metal atom (Mo and Mn), respectively. The remanent moment and the coercive field (0.06 T) exceed all values reported to date for the family of magnetic laminates based on so called MAX phases.

  7. Charge density wave excitations in stripe-type charge ordered Pr0.5Sr0.5MnO3 manganite

    NASA Astrophysics Data System (ADS)

    Rana, Rakesh; Rana, D. S.; Mavani, K. R.; Kawayama, I.; Murakami, H.; Tonouchi, M.

    2012-12-01

    We show that a charge-density wave mode submerged in large conductivity of the stripe-type charge-ordered (CO) crystal of Pr0.5Sr0.5MnO3 (PSMO) can be extracted by exciting selective crystallographic planes using polarized terahertz field. Low energy (1-7 meV) dynamics have been explored in the (100), (110), and (111) epitaxial films of PSMO manganite. Of (110) and (111) films representing bulk-like CO, the former exhibits a peak in the conductivity-energy spectrum with attributes of charge-density wave mode along a specific in-plane axis. On the contrary, the CO (111) and the phase-separated (100) films lack this low energy mode but exhibit a Drude-like spectral behavior in the metallic regime. These studies reveal a variety in isothermal charge dynamics originating from the anisotropic nature of the stripe charge-order.

  8. Evolution of photoinduced effects in phase-separated Sm0.5Sr0.5Mn1−yCryO3 thin films

    PubMed Central

    Chai, Xiaojie; Xing, Hui; Jin, Kexin

    2016-01-01

    Systematic study on electrical transport properties has been performed in Sm0.5Sr0.5Mn1−yCryO3 thin films illuminated by the light. An evolution of persistent and transient photoinduced effects induced by the impurity doping and temperature has been observed, which is closely related to the number of ferromagnetic clusters. The maximum persistent photoinduced effect is observed at y = 0.08 and the corresponding value is about 61.7% at the power density of 13.7 mW/mm2. The underlying mechanism can be understood by the coexistence and competition of the multiphases in phase-separated manganites induced by Cr-doping. These results would pave the way for practical applications in innovative photoelectric devices of all-oxides. PMID:27001006

  9. Correlation between electrical and magnetic properties of polycrystalline La0.5Ca0.5Mn0.98Bi0.02O3

    NASA Astrophysics Data System (ADS)

    Krichene, A.; Bourouina, M.; Venkateshwarlu, D.; Solanki, P. S.; Rayaprol, S.; Ganesan, V.; Boujelben, W.; Kuberkar, D. G.

    2016-06-01

    We have reported in this work the study of correlation between electrical transport and magnetic properties of La0.5Ca0.5Mn0.98Bi0.02O3 polycrystalline sample prepared by solid state method. Structural analysis reveals that presently studied compound crystallizes in the orthorhombic structure with Pnma space group. Temperature dependence of magnetization indicates that our studied compound undergoes a paramagnetic-ferromagnetic transition at Curie temperature TC=237 K. Magnetotransport analysis was successfully carried out using percolation model in the temperature range 40-300 K for magnetic field values up to 14 T. Strong correlation between electrical and magnetic properties was observed along with the absence of charge ordering inside the structure of our sample.

  10. Inter particle interaction in Ni0.5Zn0.5Fe2O4 prepared by self combustion method

    NASA Astrophysics Data System (ADS)

    Sudheesh, V. D.; Vinesh, A.; Lakshmi, N.; Venugopalan, K.

    2012-06-01

    Ni0.5Zn0.5Fe2O4 has been prepared by self combustion method and studied using X-ray diffraction, Mössbauer spectroscopy and DC magnetization techniques. X-ray diffractogram shows highly crystalline nano sized sample with no impurity phases. The room temperature Mössbauer and magnetization measurements show the co-existence of superparamagnetic and ferrimagnetic particles in the sample. The presence of inter particle interaction is confirmed from the δM(H) curve at 20K. The dependence of magnetic moment below blocking temperature in the field cooling curve indicates that the inter particle interaction is weak in the as prepared sample.

  11. Demonstration of half-metallicity in fermi-level-tuned Heusler alloy Co2FeAl0.5Si0.5 at room temperature.

    PubMed

    Shan, R; Sukegawa, H; Wang, W H; Kodzuka, M; Furubayashi, T; Ohkubo, T; Mitani, S; Inomata, K; Hono, K

    2009-06-19

    Fermi level tuning has been successfully demonstrated in Co-based full-Heusler alloy Co(2)FeAl(0.5)Si(0.5) (CFAS). The half-metallic band gap of CFAS was proved by the behavior of differential conductance of CFAS/(MgAl(2))O(x)/CoFe magnetic tunneling junctions with an unexplored crystalline (MgAl(2))O(x) barrier. CFAS exhibits the highest effective spin polarization (P_{eff}) at 300 K and the weakest temperature dependence of P_{eff} among all known half metals. Further study shows that P_{eff} of CFAS decays with increasing temperature (T) following T;{3/2} law perfectly, which indicates that the depolarization of CFAS is determined by spin wave excitation only.

  12. Half-metallicity at the Heusler alloy Co(2)Cr(0.5)Fe(0.5)Al(001) surface and its interface with GaAs(001).

    PubMed

    Zarei, Sareh; Javad Hashemifar, S; Akbarzadeh, Hadi; Hafari, Zohre

    2009-02-04

    Electronic and magnetic properties of the Heusler alloy Co(2)Cr(0.5)Fe(0.5)Al(001) surfaces and its interfaces with GaAs(001) are studied within the framework of density functional theory by using the plane-wave pseudopotential approach. The phase diagram obtained by ab initio atomistic thermodynamics shows that the CrAl surface is the most stable (001) termination of this Heusler alloy. We discuss that, at the ideal surfaces and interfaces with GaAs, half-metallicity of the alloy is lost, although the CrAl surface keeps high spin polarization. The energy band profile of the stable interface is investigated and a negative p Schottky barrier of -0.78 eV is obtained for this system.

  13. Enhanced low-energy magnetic excitations via suppression of the itinerancy in Fe0.98-zCuzTe0.5Se0.5

    NASA Astrophysics Data System (ADS)

    Wen, Jinsheng; Li, Shichao; Xu, Zhijun; Zhang, Cheng; Matsuda, M.; Sobolev, O.; Park, J. T.; Christianson, A. D.; Bourret-Courchesne, E.; Li, Qiang; Gu, Genda; Lee, Dung-Hai; Tranquada, J. M.; Xu, Guangyong; Birgeneau, R. J.

    2013-10-01

    We have performed resistivity and inelastic neutron scattering measurements on three samples of Fe0.98-zCuzTe0.5Se0.5 with z=0, 0.02, and 0.1. It is found that with increasing Cu doping the sample's resistivity deviates progressively from that of a metal. However, in contrast to expectations that replacing Fe with Cu would suppress the magnetic correlations, the low-energy (≤12 meV) magnetic scattering is enhanced in strength, with greater spectral weight and longer dynamical spin-spin correlation lengths. Such enhancements can be a consequence of either enlarged local moments or a slowing down of the spin fluctuations. In either case, the localization of the conduction states induced by the Cu doping should play a critical role. Our results are not applicable to models that treat 3d transition metal dopants simply as effective electron donors.

  14. Magnetic properties and spin reorientation of perovskite SmFe0.5Mn0.5O3 single crystal

    NASA Astrophysics Data System (ADS)

    Kang, Jian; Cui, Xiaopeng; Fang, Yifei; Zhang, Jincang

    2016-12-01

    The crystal structure and magnetic properties of the rare-earth perovskite SmFe0.5Mn0.5O3 single crystal were studied. The single crystal was successfully synthesized by optical-floating-zone method. M-T and M-H curves were measured to study the magnetic state in the single crystal. Strong magnetic anisotropy was observed in temperature dependent magnetization measurements along three crystallographic axes a, b and c. The first magnetic phase transition at TN=286 K is paramagnetic to antiferromagnetic transition. The M-T curve then undergoes a second intriguing transition from 254 K to 244 K and this transition is spin orientation from Γ4 (Gx, Ay, Fz) to Γ1 (Ax, Gy, Cz) due to anisotropic Mn3+ ions and complex interaction in our sample. Magnetic transition of rare earth oxides was tuned by Mn3+ doping, which has potential for future application.

  15. Simultaneous laser excitation of backward volume and perpendicular standing spin waves in full-Heusler Co2FeAl0.5Si0.5 films

    NASA Astrophysics Data System (ADS)

    Chen, Zhifeng; Yan, Yong; Li, Shufa; Xu, Xiaoguang; Jiang, Yong; Lai, Tianshu

    2017-02-01

    Spin-wave dynamics in full-Heusler Co2FeAl0.5Si0.5 films are studied using all-optical pump-probe magneto-optical polar Kerr spectroscopy. Backward volume magnetostatic spin-wave (BVMSW) mode is observed in films with thickness ranging from 20 to 100 nm besides perpendicular standing spin-wave (PSSW) mode, and found to be excited more efficiently than the PSSW mode. The field dependence of the effective Gilbert damping parameter appears especial extrinsic origin. The relationship between the lifetime and the group velocity of BVMSW mode is revealed. The frequency of BVMSW mode does not obviously depend on the film thickness, but the lifetime and the effective damping appear to do so. The simultaneous excitation of BVMSW and PSSW in Heusler alloy films as well as the characterization of their dynamic behaviors may be of interest for magnonic and spintronic applications.

  16. Spin reorientation transition in Sm{sub 0.5}Tb{sub 0.5}FeO{sub 3} orthoferrite single crystal

    SciTech Connect

    Zhao, Xiangyang; Wang, Bo; Zhang, Kailin; Liu, Xiumei; Xu, Kai; Cao, Shixun; Ma, Guohong E-mail: ghma@staff.shu.edu.cn; Wu, Anhua E-mail: ghma@staff.shu.edu.cn; Su, Liangbi

    2016-01-15

    Single crystal of Sm{sub 0.5}Tb{sub 0.5}FeO{sub 3} was grown by an optical floating zone method. The spin reorientation transition behavior (Γ{sub 2} → Γ{sub 24} → Γ{sub 4}) is observed in the temperature range from 150 to 250 K. The dynamics of spin reorientation transition is studied by terahertz time-domain spectroscopy (THz-TDS). FM mode was only discovered when temperature is below 55 K. And the FM mode resonant frequency increases from 0.216 THz to 0.268 THz with temperature deceasing from 55 K to 39 K. The AFM mode resonant frequency is fixed at 0.542 THz except in the very low temperature range. Our results demonstrate that THz-TDS is an effective means to study the dynamical iron ions SRT in RFeO{sub 3}.

  17. Manipulation of magnetism in perpendicularly magnetized Heusler alloy Co2FeAl0.5Si0.5 by electric-field at room temperature

    NASA Astrophysics Data System (ADS)

    Wang, H. L.; Wu, Y.; Yu, H. J.; Jiang, Y.; Zhao, J. H.

    2016-09-01

    The electrical manipulation of magnetic properties in perpendicularly magnetized Co2FeAl0.5Si0.5 ultra-thin films has been investigated. An electric-field is applied by utilizing either a solid-state dielectric HfO2 film or an ionic gel film as the gate insulator in the form of a field effect parallel capacitor. Obvious changes of the coercive field and Curie temperature (˜24 K) by gating voltage are observed for a 0.8 nm thick film, while a clear change of the magnetic anisotropy is obtained for the 1.1 nm thick one. The experimental results have been attributed to both the electric-field-induced modulation of carrier density near the interface and the oxidation-reduction effect inside the magnetic films.

  18. Role of the local structure in superconductivity of LaO0.5F0.5BiS2‑x Se x system

    NASA Astrophysics Data System (ADS)

    Paris, E.; Mizuguchi, Y.; Hacisalihoglu, M. Y.; Hiroi, T.; Joseph, B.; Aquilanti, G.; Miura, O.; Mizokawa, T.; Saini, N. L.

    2017-04-01

    We have studied the local structure of LaO0.5F0.5BiS2‑x Se x by Bi L1-edge extended x-ray absorption fine structure (EXAFS). We find a significant effect of Se substitution on the local atomic correlations with a gradual elongation of average in-plane Bi-S bondlength. The associated mean square relative displacement, measuring average local distortions in the BiS2 plane, hardly shows any change for small Se substitution, but decreases significantly for x≥slant 0.6 . The Se substitution appears to suppress the local distortions within the BiS2 plane that may optimize in-plane orbital hybridization and hence the superconductivity. The results suggest that the local structure of the BiS2-layer is one of the key ingredients to control the physical properties of the BiS2-based dichalcogenides.

  19. Giant elastocaloric effect in ferroelectric Ba0.5Sr0.5TiO3 alloys from first-principles

    NASA Astrophysics Data System (ADS)

    Lisenkov, S.; Ponomareva, I.

    2012-09-01

    As the need for efficient energy converting devices has been rapidly increasing, the materials that exhibit large or even giant caloric responses have emerged as promising candidates for solid-state refrigeration, which is an energy-efficient and environmentally friendly alternative to the conventional refrigeration technology. However, despite recent ground breaking discoveries of giant caloric responses in some materials, they appear to remain one of nature's rarities. Here we predict the existence of giant elastocaloric effect in ferroelectric Ba0.5Sr0.5TiO3 alloys, which adds one more member to this exclusive collection. Moreover, this computational finding reveals the multicaloric nature of such alloys, which could lead to new paradigms for cooling devices.

  20. Ultra-sharp metamagnetic transitions in the half-doped manganite compound Eu0.5Sr0.5MnO3

    NASA Astrophysics Data System (ADS)

    Rana, D. S.; Nirmala, R.; Malik, S. K.

    2005-05-01

    Magnetization, electrical-resistance and specific-heat measurements have been performed on the ABO3-type half-doped Eu0.5Sr0.5MnO3 manganite compound. These studies reveal successive sharp step-like metamagnetic transitions at low temperatures. The steps are sharp at T <= 3 K but smeared above 3 K, signifying the transformation from a homogenous to an inhomogenous phase-separated state at 3 K. Earlier such successive sharp steps have been observed mostly in Pr-based manganites (in which Pr is magnetic). The observation of the similar steps in the present Eu-based system (in which Eu is non-magnetic), along with the irreversibility in the magnetization isotherms, suggests that rare-earth magnetism has no role in the occurrence of this fascinating property.

  1. Good Quality Factor in GdMnO3-Doped (K0.5Na0.5)NbO3 Piezoelectric Ceramics

    NASA Astrophysics Data System (ADS)

    Bucur, Raul Alin; Badea, Iuliana; Bucur, Alexandra Ioana; Novaconi, Stefan

    2016-06-01

    (1 - x)(K0.5Na0.5)NbO3 - xGdMnO3 (KNN- xGM) ferroelectric ceramics (0 ≤ x ≤ 5 mol.%) were obtained through a solid state technique. For all the studied compositions, orthorhombic perovskite crystalline structures were obtained at room temperature. GdMnO3 suppresses the grain growth and gives rather homogenous microstructures as the concentration increases. The doped ceramics exhibita good dielectric response, a "hard" ferroelectric behavior and good piezoelectric properties. An improved mechanical quality factor of 1180 and a high Curie temperature T C = 400°C, coupled with k p = 0.426, makes the composition x = 1 mol.% GdMnO3 suitable for lead-free piezoelectric materials for high-power and high-temperature applications.

  2. Microwave dielectric and optical properties of amorphous and crystalline Ba0.5Sr0.5TiO3 thin films

    NASA Astrophysics Data System (ADS)

    Goud, J. Pundareekam; Joseph, Andrews; Ramakanth, S.; Naidu, Kuna Lakshun; Raju, K. C. James

    2016-05-01

    The thin films of composition Ba0.5Sr0.5TiO3 (BST5) were deposited by Pulsed Laser Deposition technique on amorphous fused silica substrates at room temperature (RT) and at 700°C. The film deposited at RT is amorphous while the other crystallized in cubic structure. The refractive index (n) and optical band gap (Eg) extracted from transmission spectra in the 190 -2500 nm range. Microwave dielectric properties were investigated using the Split Post Dielectric Resonators (SPDR) technique at spot frequencies of 10GHz and 20GHz. The experimental results show that thin films deposited at high temperature (700°C) shows very high dielectric constant for both 10GHz and 20 GHz. These high dielectric constant films can be used in a wide range of applications such as capacitors, non-volatile high speed random access memories, and electro-optic devices.

  3. Observation of indium ion migration-induced resistive switching in Al/Mg0.5Ca0.5TiO3/ITO

    NASA Astrophysics Data System (ADS)

    Lin, Zong-Han; Wang, Yeong-Her

    2016-08-01

    Understanding switching mechanisms is very important for resistive random access memory (RRAM) applications. This letter reports an investigation of Al/Mg0.5Ca0.5TiO3 (MCTO)/ITO RRAM, which exhibits bipolar resistive switching behavior. The filaments that connect Al electrodes with indium tin oxide electrodes across the MCTO layer at a low-resistance state are identified. The filaments composed of In2O3 crystals are observed through energy-dispersive X-ray spectroscopy, high-resolution transmission electron microscopy, nanobeam diffraction, and comparisons of Joint Committee on Powder Diffraction Standards (JCPDS) cards. Finally, a switching mechanism resulting from an electrical field induced by In3+ ion migration is proposed. In3+ ion migration forms/ruptures the conductive filaments and sets/resets the RRAM device.

  4. Unexpected ferromagnetic ordering enhancement with crystallite size growth observed in La{sub 0.5}Ca{sub 0.5}MnO₃ nanoparticles

    SciTech Connect

    Iniama, G.; Ita, B. I.; Presa, P. de la Hernando, A.; Alonso, J. M.; Multigner, M.; Cortés-Gil, R.; Ruiz-González, M. L.; Gonzalez-Calbet, J. M.

    2014-09-21

    In this paper, the physical properties of half-doped manganite La{sub 0.5}Ca{sub 0.5}MnO₃ with crystallite sizes ranging from 15 to 40 nm are investigated. As expected, ferromagnetic order strengthens at expense of antiferromagnetic one as crystallite size is reduced to 15 nm. However, contrary to previously reported works, an enhancement of saturation magnetization is observed as crystallite size increases from 15 to 22 nm. This unexpected behavior is accompanied by an unusual cell volume variation that seems to induce ferromagnetic-like behavior at expense of antiferromagnetic one. Besides, field cooled hysteresis loops show exchange bias field and coercivity enhancement for increasing cooling fields, which suggest a kind of core-shell structure with AFM-FM coupling for crystallite sizes as small as 15 nm. It is expected that inner core orders antiferromagnetically, whereas uncompensated surface spins behave as spin glass with ferromagnetic-like ordering.

  5. Organic matter evolution throughout a 100-cm ombrotrophic profile from an Italian floating mire

    NASA Astrophysics Data System (ADS)

    Zaccone, Claudio; D'Orazio, Valeria; Lobianco, Daniela; Miano, Teodoro M.

    2015-04-01

    .1%). Main atomic ratios seem to confirm what found during the visual inspection of the core, i.e., Sphagnum material so well preserved that it is hard to classify it as 'peat'. In fact, the F14C age dating suggests that the first 95 cm of Sphagnum material accumulate in less than 55 yrs, thus resulting in an average growing rate of ca. 1.7-1.8 cm yr-1. At the same time, C/N, H/C and O/C ratios show their lowest values between 20 and 55 cm of depth, corresponding to the section with highest bulk density (0.025-0.059 g cm-3). This seems to suggest a slightly more decomposed material. Consequently, the depth of 55-60 cm could represent the emerged (i.e., less anaerobic) section of this floating mire. Finally, the first 100 cm of the core show a great potential to be used as archive of environmental changes, especially considering their high resolution (1 cm = 0.5 yr ca.), although the short time-space covered could be a limiting factor. The Authors thank the Municipality of Posta Fibreno (FR), Managing Authority of the Regional Natural Reserve of Lake Posta Fibreno, for allowing peat cores sampling. C.Z. is indebted to the Staff of the Regional Natural Reserve for the help during samplings and for their continuous feedbacks.

  6. Colossal thermoelectric power in charge ordered lanthanum calcium manganites (La0.5Ca0.5MnO3)

    NASA Astrophysics Data System (ADS)

    Joy, Lija K.; Shanmukharao Samatham, S.; Thomas, Senoy; Ganesan, V.; Al-Harthi, Salim; Liebig, A.; Albrecht, M.; Anantharaman, M. R.

    2014-12-01

    Lanthanum calcium manganites (La0.5Ca0.5MnO3) with a composition close to charge ordering, synthesized by high energy ball milling, was found to exhibit colossal thermoelectric power. Thermoelectric power (TEP) data was systematically analyzed by dividing the entire temperature range (5 K-300 K) into three different regimes to explore different scattering mechanisms involved. Mandal's model has been applied to explain TEP data in the region below the Curie temperature (TC). It has been found that the variation of thermoelectric power with temperature is pronounced when the system enters the charge ordered region at T < 200 K. For temperatures lower than 120 K, due to the co-existence of charge ordered state with a spin-glass state, the variation of thermoelectric power is maximum and exhibited a peak value of -80 mV/K at 58 K. This has been explained by incorporating Kondo properties of the spin-glass along with magnon scattering. FC-ZFC magnetization measurements indicate the existence of a glassy state in the region corresponding to a maximum value of thermoelectric power. Phonon drag contribution instead of spin-glass contribution is taken into account to explain TEP in the region 120 K < T < TC. Mott's polaronic contribution of charge carriers are considered to interpret TEP in the high temperature region (T > TC). The optimal Mn4+-Mn3+ concentration in charge ordered La0.5Ca0.5MnO3 was examined by X-ray Photoelectron Spectroscopy analysis which confirms the charge ordered nature of this compound.

  7. Coercivity enhancement driven by interfacial magnetic phase separation in SrTiO3(001)/Nd0.5Sr0.5CoO3

    SciTech Connect

    Sharma, M; Gazquez Alabart, Jaume; Varela del Arco, Maria; Schmitt, J.; Leighton, chris

    2011-01-01

    Thin-film perovskite cobaltites have been found to exhibit coercivity values enhanced by almost 2 orders of magnitude in comparison to bulk. In this paper, we have investigated this unexplained coercivity enhancement in detail, focusing on epitaxial SrTiO{sub 3}(001)/Nd{sub 0.5}Sr{sub 0.5}CoO{sub 3} [SrTiO{sub 3} = STO] films, which display coercivity values up to 40 kOe at low temperatures. Thickness-dependent (10-800 {angstrom}) magnetometry and magnetotransport studies demonstrate that nanoscopic magnetic phase separation occurs in the interface region of Nd{sub 0.5}Sr{sub 0.5}CoO{sub 3} [consistent with recent work on SrTiO{sub 3}(001)/La{sub 1-x}Sr{sub x}CoO{sub 3}], which is responsible for the degradation in magnetic and electronic properties in the very-thin-film limit. The coercivity is shown to be intimately related to the existence of this (70-{angstrom}-thick) interfacial phase-separated layer, leading us to advance an explanation for the coercivity enhancement in terms of the pinning of domain walls by interfacial nanoscopic ferromagnetic clusters and a crossover to single domain clusters at very low thickness. Simple estimates of the magnetocrystalline anisotropy (from the maximum coercivity), cluster dimensions (from the superparamagnetic blocking temperature), multidomain to single domain crossover point, and domain-wall width, provide quantitative support for this picture.

  8. Topology and temperature dependence of the diffuse X-ray scattering in Na0.5Bi0.5TiO3 ferroelectric single crystals.

    PubMed

    Gorfman, Semën; Keeble, Dean S; Bombardi, Alessandro; Thomas, Pam A

    2015-10-01

    The results of high-resolution measurements of the diffuse X-ray scattering produced by a perovskite-based Na0.5Bi0.5TiO3 ferroelectric single crystal between 40 and 620 K are reported. The study was designed as an attempt to resolve numerous controversies regarding the average structure of Na0.5Bi0.5TiO3, such as the mechanism of the phase transitions between the tetragonal, P4bm, and rhombohedral | monoclinic, R3c | Cc, space groups and the correlation between structural changes and macroscopic physical properties. The starting point was to search for any transformations of structural disorder in the temperature range of thermal depoling (420-480 K), where the average structure is known to remain unchanged. The intensity distribution around the {032} pseudocubic reflection was collected using a PILATUS 100K detector at the I16 beamline of the Diamond Light Source (UK). The data revealed previously unknown features of the diffuse scattering, including a system of dual asymmetric L-shaped diffuse scattering streaks. The topology, temperature dependence, and relationship between Bragg and diffuse intensities suggest the presence of complex microstructure in the low-temperature R3c | Cc phase. This microstructure may be formed by the persistence of the higher-temperature P4bm phase, built into a lower-temperature R3c | Cc matrix, accompanied by the related long-range strain fields. Finally, it is shown that a correlation between the temperature dependence of the X-ray scattering features and the temperature regime of thermal depoling is present.

  9. Griffiths phase and colossal magnetoresistance in Nd0.5Sr0.5MnO3 oxygen-deficient thin films

    NASA Astrophysics Data System (ADS)

    Solin, N. I.; Korolyov, A. V.; Medvedev, Yu. V.; Nikolaenko, Yu. M.; Khokhlov, V. A.; Prokhorov, A. Yu.; Levchenko, G. G.

    2013-05-01

    This work is devoted to study the influence of the Griffiths phase in colossal magnetoresistance manganites. Griffiths-phase-like behavior of the paramagnetic susceptibility χ0 is observed in Nd0.5Sr0.5MnO3 oxygen-deficient thin films fabricated by magnetron sputtering deposition. In Nd0.5Sr0.5MnO3-δ films with oxygen deficiency for ТG≈260-280 K>T>TC=138 K (ТG and ТС—Griffiths and Curie temperatures, respectively), paramagnetic matrix consists of a magnetic phase with short-range order (˜1-1.5 nm) (which is responsible for the colossal magnetoresistance (CMR) above ТС), and is embedded in this matrix region with long-range ferromagnetic order (≫10 nm), responsible for the Griffiths phase-like behavior of the paramagnetic susceptibility. Electrical resistivity is caused by carrier tunneling between the localized states and obeys the Efros-Shklovskii law. Magnetic resistivity is caused by change of the localized state sizes under the magnetic field. The temperature and magnetic field dependencies of size of the phase inhomogeneity inclusions, found from measurements of magneto-transport properties, can be satisfactorily described by the model of thermodynamic phase separation into metallic droplets of small radius in a paramagnetic matrix. Intrinsic nanoscale inhomogeneities caused by thermodynamic phase separation, rather than the Griffiths phase, determine the electrical resistivity and colossal magnetoresistance of the films. In half-doped manganites, the nature of long-range ordered magnetic phases may be related, besides the chemical heterogeneity, to proximity to a ferromagnetic-antiferromagnetic boundary at the phase diagram as well. The results are in good agreement with the model of existence of an analog of Griffiths phase temperature in half-doped manganites.

  10. Effect of particle size distribution on the structure, hyperfine, and magnetic properties of Ni0.5Zn0.5Fe2O4 nanopowders

    NASA Astrophysics Data System (ADS)

    Bhattacharjee, Kaustav; Pati, Satya P.; Das, G. C.; Das, D.; Chattopadhyay, K. K.

    2014-12-01

    Ni0.5Zn0.5Fe2O4 nano powders were synthesized by an auto combustion method and then heat treated at different temperatures in air for a fixed time. As a consequence, a distribution in particle size and strain was incorporated within the specimens, as estimated from the Rietveld refinement analysis of the powder x-ray diffraction data. The changes in the microstructure and crystal structure parameters were carefully extracted through the refinement analysis. Thermal annealing causes increment in the dispersion and mean of the size distribution. Reallocation of cations in the lattice sites occur as a consequence of the heat treatment which was manifested in their altered unit cell length (a), r.m.s. strain (⟨ɛ2⟩1/2), oxygen positional parameter (u), metal-oxygen bond lengths ( RO A and RO B ), and the band positions (ν1and ν2) in the vibrational spectroscopy. We also investigate the hyperfine and magnetic properties of the samples using different instrumental techniques (with different operating time scales) like Mössbauer spectroscopy, electron paramagnetic resonance spectroscopy, and superconducting quantum interference device magnetometry. Results show that the effect of particle size distribution was manifested in their hyperfine field distribution profile, paramagnetic resonance spectra, and magnetic anisotropy energy distribution profile. Co-existence of superparamagnetic and ferrimagnetic phase was recorded at room temperature in the samples when annealed at lower temperature. However, with increase in annealing temperature, the nature of the size distribution changes and ferrimagnetic ordering predominates for the larger size nanoparticles. Thus, the effect of particle size distribution on the structural, hyperfine, and magnetic properties of various Ni0.5Zn0.5Fe2O4 nanoparticles was investigated herein which hitherto has not been discussed in the literature.

  11. Spin-reorientation and weak ferromagnetism in antiferromagnetic TbMn{sub 0.5}Fe{sub 0.5}O{sub 3}

    SciTech Connect

    Nhalil, Hariharan E-mail: hariharan.nhalil@gmail.com; Sanathkumar, R.; Elizabeth, Suja; Nair, Harikrishnan S.; Strydom, André M.

    2015-05-07

    Orthorhombic single crystals of TbMn{sub 0.5}Fe{sub 0.5}O{sub 3} are found to exhibit spin-reorientation, magnetization reversal, and weak ferromagnetism. Strong anisotropy effects are evident in the temperature dependent magnetization measurements along the three crystallographic axes a, b, and c. A broad magnetic transition is visible at T{sub N}{sup Fe/Mn}=286 K due to paramagnetic to A{sub x}G{sub y}C{sub z} ordering. A sharp transition is observed at T{sub SR}{sup Fe/Mn}=28 K, which is pronounced along c axis in the form of a sharp jump in magnetization where the spins reorient to G{sub x}A{sub y}F{sub z} configuration. The negative magnetization observed below T{sub SR}{sup Fe/Mn} along c axis is explained in terms of domain wall pinning. A component of weak ferromagnetism is observed in field-scans along c-axis but below 28 K. Field-induced steps-like transitions are observed in hysteresis measurement along b axis below 28 K. It is noted that no sign of Tb-order is discernible down to 2 K. TbMn{sub 0.5}Fe{sub 0.5}O{sub 3} could be highlighted as a potential candidate to evaluate its magneto-dielectric effects across the magnetic transitions.

  12. Li(V0.5Ti0.5)S2 as a 1 V lithium intercalation electrode

    PubMed Central

    Clark, Steve J.; Wang, Da; Armstrong, A. Robert; Bruce, Peter G.

    2016-01-01

    Graphite, the dominant anode in rechargeable lithium batteries, operates at ∼0.1 V versus Li+/Li and can result in lithium plating on the graphite surface, raising safety concerns. Titanates, for example, Li4Ti5O12, intercalate lithium at∼1.6 V versus Li+/Li, avoiding problematic lithium plating at the expense of reduced cell voltage. There is interest in 1 V anodes, as this voltage is sufficiently high to avoid lithium plating while not significantly reducing cell potential. The sulfides, LiVS2 and LiTiS2, have been investigated as possible 1 V intercalation electrodes but suffer from capacity fading, large 1st cycle irreversible capacity or polarization. Here we report that the 50/50 solid solution, Li1+x(V0.5Ti0.5)S2, delivers a reversible capacity to store charge of 220 mAhg−1 (at 0.9 V), 99% of theoretical, at a rate of C/2, retaining 205 mAhg−1 at C-rate (92% of theoretical). Rate capability is excellent with 200 mAhg−1 at 3C. C-rate is discharge in 1 h. Polarization is low, 100 mV at C/2. To the best of our knowledge, the properties/performances of Li(V0.5Ti0.5)S2 exceed all previous 1 V electrodes. PMID:26996753

  13. Colossal thermoelectric power in charge ordered lanthanum calcium manganites (La{sub 0.5}Ca{sub 0.5}MnO{sub 3})

    SciTech Connect

    Joy, Lija K.; Anantharaman, M. R.; Shanmukharao Samatham, S.; Ganesan, V.; Thomas, Senoy; Al-Harthi, Salim; Liebig, A.; Albrecht, M.

    2014-12-07

    Lanthanum calcium manganites (La{sub 0.5}Ca{sub 0.5}MnO{sub 3}) with a composition close to charge ordering, synthesized by high energy ball milling, was found to exhibit colossal thermoelectric power. Thermoelectric power (TEP) data was systematically analyzed by dividing the entire temperature range (5 K–300 K) into three different regimes to explore different scattering mechanisms involved. Mandal's model has been applied to explain TEP data in the region below the Curie temperature (T{sub C}). It has been found that the variation of thermoelectric power with temperature is pronounced when the system enters the charge ordered region at T < 200 K. For temperatures lower than 120 K, due to the co-existence of charge ordered state with a spin-glass state, the variation of thermoelectric power is maximum and exhibited a peak value of −80 mV/K at 58 K. This has been explained by incorporating Kondo properties of the spin-glass along with magnon scattering. FC-ZFC magnetization measurements indicate the existence of a glassy state in the region corresponding to a maximum value of thermoelectric power. Phonon drag contribution instead of spin-glass contribution is taken into account to explain TEP in the region 120 K < T < T{sub C}. Mott's polaronic contribution of charge carriers are considered to interpret TEP in the high temperature region (T > T{sub C}). The optimal Mn{sup 4+}-Mn{sup 3+} concentration in charge ordered La{sub 0.5}Ca{sub 0.5}MnO{sub 3} was examined by X-ray Photoelectron Spectroscopy analysis which confirms the charge ordered nature of this compound.

  14. Analysis of conductivity and dielectric spectra of Mn0.5Zn0.5Fe2O4 with coupled Cole-Cole type anomalous relaxations

    NASA Astrophysics Data System (ADS)

    Kumar, N. S. K.; Shahid, T. S.; Govindaraj, G.

    2016-05-01

    Most of the crystalline materials seldom show a well-defined dielectric loss peak due to domination of dc conductivity contribution, but effects of loss peaks are seen at high frequencies. Ac electrical data of nano-crystalline Mn0.5Zn0.5Fe2O4 synthesised by chemical co-precipitation method show such behaviour. Properly combined and formulated conduction and dielectric relaxation functions are required for such materials. Cole-Cole type relaxation function in the combined conduction and dielectric process is formulated for complex resistivity ρ*(ω), complex permittivity ε*(ω), complex conductivity σ*(ω) and complex electric modulus M*(ω). Conduction and dielectric relaxation are linked to Jonscher's idea of 'pinned dipole' and 'free dipole' to understand the relaxation dynamics. The physical parameters of 'pinned dipole' and 'free dipole' formalism are unique for all representations like ρ*(ω), ε*(ω), σ*(ω) and M*(ω). 'Pinned dipole' relaxation time τc related to conduction process and 'free dipole' relaxation time τd related to dielectric process show Arrhenius behaviour with the same activation energy. Correlation of dc conductivity σc with τc and τd indicates the coupled dynamics of 'pinned dipole' and 'free dipole'. Time-temperature scaling of conduction and dielectric relaxation reveals that the mechanism of coupled dynamics of 'pinned dipole' and 'free dipole' is temperature independent. Hopping of charge carriers with dynamics of disordered cation distribution of host matrix generates a coupled conduction and dielectric relaxation in Mn0.5Zn0.5Fe2O4.

  15. A study on the extent of exchange coupling between (Ba0.5Sr0.5Fe12O19)1-x(CoFe2O4)x magnetic nanocomposites synthesized by solgel combustion method

    NASA Astrophysics Data System (ADS)

    Harikrishnan, V.; Ezhil Vizhi, R.

    2016-11-01

    One step citrate gel combustion method followed by high temperature annealing was employed for preparing (Ba0.5Sr0.5Fe12O19)1-x(CoFe2O4)x (x=0.1, 0.2, and 0.3) composite ferrite powders. The powders were subjected to annealing at 800 °C in order to decisively study the phase evolution of the combined hard and soft ferrites. Thermogravitry (TGA)/differential scanning calorimetry (DSC) analysis exhibited three stages of decomposition in the precursor gels combined with an exothermic peak at 210 °C. X-ray diffraction (XRD) analysis confirmed that the diffraction peaks were perfectly indexed to the hexagonal magnetoplumbite structure of Ba0.5Sr0.5Fe12O19 and the cubic spinel structure of CoFe2O4. Fourier transform infrared spectroscopy (FT-IR) analysis for the samples showed a Co-O stretching vibration accompanied with Co-O-Co or Fe-O-Fe bands at 1220 cm-1. The morphology of the samples were examined by field emission scanning electron microscope (FE-SEM) and transmission electron microscope (TEM). The crystallinity of a selected sample was evaluated by using the high resolution transmission electron microscope (HR-TEM) and selected area electron diffraction (SAED) pattern. It confirmed the presence of planes comprising the hard and soft phases in the synthesized nanocomposites. The magnetic parameters like saturation magnetization MS, remanent magnetization MR, squareness ratio SR, coercivity HC and magnetic moment μB were evaluated using hysteresis by employing vibrating sample magnetometer (VSM). Maximum HC of 4.7 kOe and MS of 60.4 emu/g were obtained for (Ba0.5Sr0.5Fe12O19)0.9(CoFe2O4)0.1. Switching field distribution curves were analysed by using the demagnetization curve. The exchange coupling between the hard and soft phases were analysed by the dM/dH plots and it indicated the exchange coupling first increased with the increase in the concentration of spinels and then decreased. The possible comparison of exchange coupling between the hard and soft phases

  16. Monoclinic Sr(1-x)Na(x)SiO(3-0.5x): new superior oxide ion electrolytes.

    PubMed

    Singh, Preetam; Goodenough, John B

    2013-07-10

    Oxide ion electrolytes determine the temperature of operation of solid oxide fuel cells, oxygen separation membranes, and oxygen sensors. There is a strong incentive to lower their operating temperatures, in a solid oxide fuel cell, for example, from Top > 800 °C to Top ≈ 500 °C. The use of low-cost Na(+) rather than K(+) as the dopant in monoclinic SrSiO3 (C12/C1) is shown to provide a larger solid solution range (0 < x ≤ 0.45) in Sr1-xNaxSiO3-0.5x and to achieve an oxide ion conductivity σo ≥ 10(-2) S·cm(-1) by 525 °C as a result of lowering the temperature of a smooth transition to full disorder of the mobile oxide ions. The Sr1-xNaxSiO3-0.5x electrolytes are much less hygroscopic than Sr1-xKxSiO3-0.5x and are stable with a nickel composite anode in 5% H2/Ar as well as with cathodes such as La1-xSrxMnO3-δ and Sr0.7Y0.3CoO3-δ in air, which makes them candidate electrolytes for intermediate-temperature solid oxide fuel cells or for other applications of oxide ion electrolytes.

  17. Donor-doping and reduced leakage current in Nb-doped Na0.5Bi0.5TiO3

    NASA Astrophysics Data System (ADS)

    Li, Ming; Li, Linhao; Zang, Jiadong; Sinclair, Derek C.

    2015-03-01

    Low levels of so-called "donor-doping" in titanate-based perovskite oxides such as La for Ba, Sr, and Nb for Ti in (Ba, Sr)TiO3 can significantly reduce the resistivity of these typical (d0) dielectric materials and expand application areas to positive temperature coefficient resistors, thermoelectrics, conductive wafers as thin film substrates, and solid oxide fuel cell anode materials. Here, we show low levels of Nb-doping (≤1 at. %) on the Ti-site in the well-known lead-free piezoelectric perovskite oxide Na0.5Bi0.5TiO3 (NBT) produces completely different behaviours whereby much higher resistivity is obtained, therefore indicating a different donor-doping (substitution) mechanism. There is a switch in conduction mechanism from oxygen-ions in undoped NBT with an activation energy (Ea) of <0.9 eV to electronic (band gap) conduction in 0.5-1 at. % Nb-doped NBT with Ea ˜ 1.5-1.8 eV. This demonstrates the necessity of further systematic doping studies to elucidate the defect chemistry of NBT which is clearly different to that of (Ba,Sr)TiO3. This defect chemistry needs to be understood if NBT-based materials are going to be manufactured on a large scale for commercial applications. This study also illustrates different donor-doping mechanisms to exist within the family of d0 titanate-based perovskites.

  18. The cross-plane thermoelectric properties of p-Ge/Si{sub 0.5}Ge{sub 0.5} superlattices

    SciTech Connect

    Ferre Llin, L.; Samarelli, A.; Weaver, J. M. R.; Dobson, P. S.; Paul, D. J.; Cecchi, S.; Chrastina, D.; Isella, G.; Etzelstorfer, T.; Stangl, J.; Müller Gubler, E.

    2013-09-30

    The electrical conductivity, Seebeck coefficients, and thermal conductivities of a range of p-type Ge/Si{sub 0.5}Ge{sub 0.5} superlattices designed for thermoelectric generation and grown by low energy plasma enhanced chemical vapor deposition have been measured using a range of microfabricated test structures. For samples with barriers around 0.5 nm in thickness, the measured Seebeck coefficients were comparable to bulk p-SiGe at similar doping levels suggesting the holes see the material as a random bulk alloy rather than a superlattice. The Seebeck coefficients for Ge quantum wells of 2.85 ± 0.85 nm increased up to 533 ± 25 μV/K as the doping was reduced. The thermal conductivities are between 4.5 to 6.0 Wm{sup −1}K{sup −1} which are lower than comparably doped bulk Si{sub 0.3}Ge{sub 0.7} but higher than undoped Si/Ge superlattices. The highest measured figure of merit ZT was 0.080 ± 0.011 obtained for the widest quantum well studied. Analysis suggests that interface roughness is presently limiting the performance and a reduction in the strain between the quantum wells and barriers has the potential to improve the thermoelectric performance.

  19. Field-induced magnetic phase transition in Pr3+ doped Sm0.5Sr0.5MnO3 manganites

    NASA Astrophysics Data System (ADS)

    Giri, S. K.; Nath, T. K.

    2013-05-01

    Magnetic properties of Pr3+ doped Sm0.5Sr0.5MnO3 manganite with the variation of particle size down to 30 nm have been investigated in detail. We have critically examined the magnetic field (H) dependence of the order of the ferromagnetic (FM) to paramagnetic (PM) phase transition in this Sm0.35Pr0.15Sr0.5MnO3 manganite. It has been shown that all the particle sizes (bulk to nano) exhibit first order FM → PM phase transition under low magnetic field accompanied by magnetization with thermal hysteresis in the field cooled cooling and warming cycle. However, the samples exhibit a second order magnetic phase transition above a critical field HCR. Again with decreasing the particle size, the ferromagnetic transition temperature, the thermal hysteresis width in the magnetizations, and the critical field HCR significantly decrease, which indicate that the ferromagnetism is weakened and the first-order magnetic phase transition is softened. We have also used the Banerjee criteria to distinguish the first-order magnetic phase transition from the second-order one. A detailed analysis of the magnetization measurements of this manganite reveal the disorder-induced softening of the first order phase transition in this phase separated manganite.

  20. PrBa0.5Sr0.5Co2O5+δ layered perovskite cathode for intermediate temperature solid oxide fuel cells

    SciTech Connect

    Ding, Hanping; Xue, Xingjian

    2010-02-06

    Layered perovskite oxides have ordered A-cations localizing oxygen vacancies, and may potentially improve oxygen ion diffusivity and surface exchange coefficient. The A-site-ordered layered perovskite PrBa0.5Sr0.5Co2O5+δ (PBSC) was evaluated as new cathode material for intermediate temperature solid oxide fuel cells (IT-SOFCs). The material was characterized using electrochemical impedance spectroscopy in a symmetrical cell system (PBSC/Ce0.9Sm0.1O1.9 (SDC)/PBSC), exhibiting excellent performance in the intermediate temperature range of 500–700 °C. An area-specific-resistance (ASR) of 0.23 Ω cm2 was achieved at 650 °C for cathode polarization. The low activation energy (Ea) 124 kJ mol-1 is comparable to that of La0.8Sr0.2CoO3-δ. A laboratory-scaled SDC-based tri-layer cell of Ni-SDC/SDC/PBSC was tested in intermediate temperature conditions of 550 to 700 °C. A maximum power density of 1045 mW cm-2 was achieved at 700 °C. The interfacial polarization resistance is as low as 0.285, 0.145, 0.09 and 0.05 Ω cm2 at 550, 600, 650 and 700 °C, respectively. Layered perovskite PBSC shows promising performance as cathode material for IT-SOFCs.

  1. Large dielectric tuning and microwave phase shift at low electric field in epitaxial Ba0.5Sr0.5TiO3 on SrTiO3

    NASA Astrophysics Data System (ADS)

    Leach, J. H.; Liu, H.; Avrutin, V.; Xiao, B.; Özgür, Ü.; Morkoç, H.; Das, J.; Song, Y. Y.; Patton, C. E.

    2010-04-01

    Dielectric properties of annealed and as-grown ferroelectric Ba0.5Sr0.5TiO3 (BST) grown by pulsed laser deposition on sputtered BST seed layers on strontium titanate (STO) substrates were investigated at microwave frequencies in the realm of tunability of its dielectric constant as well as phase shifters based on this material. The as-grown layers were nearly fully relaxed with measured lattice parameters nearly identical to those of bulk BST. The tuning of the relative dielectric constant (˜1750 at zero bias at 10 GHz) of the annealed BST was found to be as high as 59% and 56% at 10 and 19 GHz, respectively. The analysis of the loss in the BST results in a measured tan δ of 0.02 for the annealed as well as the unannealed films at a frequency of 18 GHz. Phase shifters also exhibited high tuning with differential phase shift figures of merit of 35 and 55°/dB at a field of 60 kV/cm at 10 and 19 GHz, respectively. Serendipitously, most of the tuning occurs at low fields, and thus we propose a new figure of merit, taking into account the amplitude of applied electric field in order to achieve the phase shift. In this new realm we achieved the values of this overall figure of merit of 1.2 and 1.8° cm/dB kV at 10 and 19 GHz, respectively, using an applied electric field of only 10 kV/cm.

  2. Nanocrystalline Zn1-x Co0.5xNi0.5x Fe2O4 ferrites: Fabrication via co-precipitation route with enhanced magnetic and electrical properties

    NASA Astrophysics Data System (ADS)

    Hassan, Amna; Azhar Khan, Muhammad; Shahid, Muhammad; Asghar, M.; Shakir, Imran; Naseem, Shahzad; Riaz, Saira; Farooq Warsi, Muhammad

    2015-11-01

    Co and Ni substituted znic ferrite nanoparticles (Zn1-xCo0.5xNi0.5xFe2O4) (0.00≤x≥0.75) were synthesized by co-precipitation method. X-ray diffraction and Fourier transform infrared spectroscopy confirmed the single phase spinel structure. The lattice constant decreased with the increased Co and Ni contents. The bulk density was found less as compared to the X-ray density and this difference was explained in terms of porosity. The crystallite size was calculated by Scherrer's formula and found in the range 20-50 nm. Two prominent stretching bands were observed in FTIR spectra around 400-600 cm-1. These two bands confirmed the spinel structure of the prepared nanoparticles. The saturation magnetization was found to increase upto x=0.60 from 1.31 emu/g to 81.2 emu/g then it decreased for x=0.75 to the value of 75.1 emu/g. The coercivity and retentivity were found in the range 35.36-226.125 Oe and 0.0135-19.8 emu/g, respectively. Dielectric parameters were decreased with the increased Ni-Co contents. About nine fold increase in the DC-electrical resistivity was obtained for the Zn0.25Co0.375Ni0.375Fe2O4 (2.8979×1010 Ω cm) as compared to the ZnFe2O4 (0.2974×1010 Ω cm) nanoparticles.

  3. A CO2-tolerant La2NiO4+δ-coated PrBa0.5Sr0.5Co1.5Fe0.5O5+δ cathode for intermediate temperature solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Li, Jin; Zhang, Qian; Qiu, Peng; Jia, Lichao; Chi, Bo; Pu, Jian; Li, Jian

    2017-02-01

    La2NiO4+δ (LN)-coated PrBa0.5Sr0.5Co1.5Fe0.5O5+δ (PBSCF) composite cathode, designated as PBSCF-LN, for the intermediate temperature solid oxide fuel cells (IT-SOFCs) is prepared by solution infiltration, and investigated comparatively with single phase PBSCF cathode in the half and full cells using Ag and/or Pt paste as the current collector. Compared with Pt, Ag current collector results in a decrease of cathode polarization resistance (RP) by an order of magnitude, which suggests that Ag is electrocatalytically active and not suitable for the use of studying the cathode performance of IT-SOFCs. The RP value of PBSCF-LN cathode is significantly lower than that of PBSCF cathode, no matter whether Pt or Ag current collector is used for the measurement. High power densities ranging from 0.24 to 0.94 W cm-2 at temperatures between 600 and 750 °C are achieved using a full cell with PBSCF-LN cathode. Upon exposure to a CO2-rich atmosphere, carbonate particles are formed on the surface of PBSCF cathode, causing irreversible degradation of electrochemical performance. In contrast, the surface of PBSCF-LN cathode remains clean, and its performance degradation due to CO2 adsorption is recoverable.

  4. SU-E-T-499: Comparison of Measured Tissue Phantom Ratios (TPR) Against Calculated From Percent Depth Doses (PDD) with and Without Peak Scatter Factor (PSF) in 6MV Open Beam

    SciTech Connect

    Narayanasamy, G; Cruz, W; Gutierrez, Alonso; Mavroidis, Panayiotis; Papanikolaou, N; Stathakis, S; Breton, C

    2014-06-01

    Purpose: To examine the accuracy of measured tissue phantom ratios (TPR) values with TPR calculated from percentage depth dose (PDD) with and without peak scatter fraction (PSF) correction. Methods: For 6MV open beam, TPR and PDD values were measured using PTW Semiflex (31010) ionization field and reference chambers (0.125cc volume) in a PTW MP3-M water tank. PDD curves were measured at SSD of 100cm for 7 square fields from 3cm to 30cm. The TPR values were measured up to 22cm depth for the same fields by continuous water draining method with ionization chamber static at 100cm from source. A comparison study was performed between the (a) measured TPR, (b) TPR calculated from PDD without PSF, (c) TPR calculated from PDD with PSF and (d) clinical TPR from RadCalc (ver 6.2, Sun Nuclear Corp). Results: There is a field size, depth dependence on TPR values. For 10cmx10cm, the differences in surface dose (DDs), dose at 10cm depth (DD10) <0.5%; differences in dmax (Ddmax) <2mm for the 4 methods. The corresponding values for 30cmx30cm are DDs, DD10 <0.2% and Ddmax<3mm. Even though for 3cmx3cm field, DDs and DD10 <1% and Ddmax<1mm, the calculated TPR values with and without PSF correction differed by 2% at >20cm depth. In all field sizes at depths>28cm, (d) clinical TPR values are larger than that from (b) and (c) by >3%. Conclusion: Measured TPR in method (a) differ from calculated TPR in methods (b) and (c) to within 1% for depths < 28cm in all 7 fields in open 6MV beam. The dmax values are within 3mm of each other. The largest deviation of >3% was observed in clinical TPR values in method (d) for all fields at depths < 28cm.

  5. Effects of Mg substitution on the structural and magnetic properties of Co0.5Ni0.5-x Mg x Fe2O4 nanoparticle ferrites

    NASA Astrophysics Data System (ADS)

    R, M. Rosnan; Z, Othaman; R, Hussin; Ali, A. Ati; Alireza, Samavati; Shadab, Dabagh; Samad, Zare

    2016-04-01

    In this study, nanocrystalline Co-Ni-Mg ferrite powders with composition Co0.5Ni0.5-x Mg x Fe2O4 are successfully synthesized by the co-precipitation method. A systematic investigation on the structural, morphological and magnetic properties of un-doped and Mg-doped Co-Ni ferrite nanoparticles is carried out. The prepared samples are characterized using x-ray diffraction (XRD) analysis, Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), and vibrating sample magnetometry (VSM). The XRD analyses of the synthesized samples confirm the formation of single-phase cubic spinel structures with crystallite sizes in a range of ˜ 32 nm to ˜ 36 nm. The lattice constant increases with increasing Mg content. FESEM images show that the synthesized samples are homogeneous with a uniformly distributed grain. The results of IR spectroscopy analysis indicate the formation of functional groups of spinel ferrite in the co-precipitation process. By increasing Mg2+ substitution, room temperature magnetic measurement shows that maximum magnetization and coercivity increase from ˜ 57.35 emu/g to ˜ 61.49 emu/g and ˜ 603.26 Oe to ˜ 684.11 Oe (1 Oe = 79.5775 A·m-1), respectively. The higher values of magnetization M s and M r suggest that the optimum composition is Co0.5Ni0.4Mg0.1Fe2O4 that can be applied to high-density recording media and microwave devices. Project supported by the Ibnu Sina Institute for Scientific and Industrial Research, Physics Department of Universiti Teknologi Malaysia and the Ministry of Education Malaysia (Grant Nos. Q.J130000.2526.04H65).

  6. X-ray emission and photoelectron spectra of Pr{sub 0.5}Sr{sub 0.5}MnO{sub 3}

    SciTech Connect

    Kurmaev, E.Z.; Korotin, M.A.; Galakhov, V.R.; Finkelstein, L.D.; Zabolotzky, E.I.; Efremova, N.N.; Lobachevskaya, N.I.; Stadler, S.; Ederer, D.L.; Callcott, T.A.; Zhou, L.; Moewes, A.; Bartkowski, S.; Neumann, M.; Matsuno, J.; Mizokawa, T.; Fujimori, A.; Mitchell, J.

    1999-05-01

    The results of measurements of x-ray photoelectron (XPS), x-ray emission (XES), and x-ray absorption spectra and local spin-density approximation band structure (LSDA) calculations of Pr{sub 0.5}Sr{sub 0.5}MnO{sub 3} are presented. The excitation energy dependence of Mn L{sub 2,3} and O K{alpha} x-ray emission spectra of Pr{sub 0.5}Sr{sub 0.5}MnO{sub 3} is measured using tunable synchrotron radiation. The XES measurements yielded no photon energy dependence for the O K{alpha} spectra, but the Mn L{sub 2,3} spectra yielded inelastic scattering losses of 2 and 6 eV, corresponding to features in the structure of the occupied part of the valence band. Comparing XPS and XES measurements with LSDA band-structure calculations, one concludes that the electronic structure of the compound consists mainly of Mn 3d and O 2p states. States of 3d character localized at the Mn site predominate near the top of the valence band (VB). Some differences in the Mn 3d distribution in this part of the XPS valence band and Mn L{sub 3} XES with {ital d} symmetry due to spin-selection rules that govern the Mn L{sub 3} XES. In addition, the Mn 3d states distribution is hybridized with the O 2p part of the VB. Mn L{sub 3} XES spectra were determined relative to the Fermi energy by assuming normal x-ray emission begins from the lowest level of the p{sup 5}d{sup n+1}L intermediate state (which is the Mn 2p ionizatation threshold). From the local spin-density approximation, the orbital character of the Mn 3d electrons can be assigned e{sub g} symmetry at the top of the valence band T{sub 2g} in the central part of the VB, and equal contributions of e{sub g} and t{sub 2g} states at the bottom of the valence band. {copyright} {ital 1999} {ital The American Physical Society}

  7. Optimization of the depth resolution for deuterium depth profiling up to large depths

    NASA Astrophysics Data System (ADS)

    Wielunska, B.; Mayer, M.; Schwarz-Selinger, T.

    2016-11-01

    The depth resolution of deuterium depth profiling by the nuclear reaction D(3He,p)α is studied theoretically and experimentally. General kinematic considerations are presented which show that the depth resolution for deuterium depth profiling using the nuclear reaction D(3He,p)α is best at reaction angles of 0° and 180° at all incident energies below 9 MeV and for all depths and materials. In order to confirm this theoretical prediction the depth resolution was determined experimentally with a conventional detector at 135° and an annular detector at 175.9°. Deuterium containing thin films buried under different metal cover layers of aluminum, molybdenum and tungsten with thicknesses in the range of 0.5-11 μm served as samples. For all materials and depths an improvement of the depth resolution with the detector at 175.9° is achieved. For tungsten as cover layer a better depth resolution up to a factor of 18 was determined. Good agreement between the experimental results and the simulations for the depth resolution is demonstrated.

  8. Giant strain with ultra-low hysteresis and high temperature stability in grain oriented lead-free K0.5Bi0.5TiO3-BaTiO3-Na0.5Bi0.5TiO3 piezoelectric materials

    PubMed Central

    Maurya, Deepam; Zhou, Yuan; Wang, Yaojin; Yan, Yongke; Li, Jiefang; Viehland, Dwight; Priya, Shashank

    2015-01-01

    We synthesized grain-oriented lead-free piezoelectric materials in (K0.5Bi0.5TiO3-BaTiO3-xNa0.5Bi0.5TiO3 (KBT-BT-NBT) system with high degree of texturing along the [001]c (c-cubic) crystallographic orientation. We demonstrate giant field induced strain (~0.48%) with an ultra-low hysteresis along with enhanced piezoelectric response (d33 ~ 190pC/N) and high temperature stability (~160°C). Transmission electron microscopy (TEM) and piezoresponse force microscopy (PFM) results demonstrate smaller size highly ordered domain structure in grain-oriented specimen relative to the conventional polycrystalline ceramics. The grain oriented specimens exhibited a high degree of non-180° domain switching, in comparison to the randomly axed ones. These results indicate the effective solution to the lead-free piezoelectric materials. PMID:25716551

  9. [Cutaneous Melanoma (CM): Current Diagnosis and Treatment].

    PubMed

    Gallegos Hernández, José Francisco; Nieweg, Omgo E

    2014-12-01

    Cutaneous melanoma (CM) is the third most common cancer of the skin, but it is the neoplasia with the greatest impact on mortality. Its etiology is multifactorial and it has been reported that its prevalence has increased in the last two decades. In Mexico, CM ranks seventh in frequency among all malignancies and 80% of cases are in locally advanced stages. The prognosis depends on the stage. The prognostic factors with greatest impact in survival are nodal status, tumor thickness or Breslow depth, ulceration, and in thin melanomas (< 1 mm thickness, without ulceration and Clarck level III), the mitotic index. The diagnostic approach is of great importance to achieve adequate treatment. Adherence to global guidelines of treatment allows us to obtain the best rates of locoregional control, which is the first target to be achieved in patients with CM. The goal of this manuscript is to provide a synthesis of the most important aspects in the diagnosis and treatment of CM, based on current evidence obtained in the literature.

  10. Crystal and magnetic study of the disordered perovskites Ca(Mn{sub 0.5}Sb{sub 0.5})O{sub 3} and Ca(Fe{sub 0.5}Sb{sub 0.5})O{sub 3}

    SciTech Connect

    Retuerto, M.; Martinez-Lope, M.J.; Garcia-Hernandez, M.; Munoz, A.; Fernandez-Diaz, M.T.; Alonso, J.A.

    2010-10-15

    We have investigated the double perovskites Ca{sub 2}MSbO{sub 6} (M = Mn, Fe) that have been prepared by solid-state reaction (M = Fe) and wet chemistry procedures (M = Mn). The crystal and magnetic structures have been studied from X-ray (XRD) and neutron powder diffraction (NPD) data. Rietveld refinements show that the crystal structures are orthorhombic (space group Pbnm) with complete disorder of M and Sb cations, so the formula should be rewritten as Ca(M{sub 0.5}Sb{sub 0.5})O{sub 3}. Due to this disorder no evidences of Jahn-Teller distortion can be observed in the MnO{sub 6} octahedra of Ca(Mn{sub 0.5}Sb{sub 0.5})O{sub 3}, in contrast with the ordered double perovskite Sr{sub 2}MnSbO{sub 6}. Ca(Fe{sub 0.5}Sb{sub 0.5})O{sub 3} behaves as an antiferromagnet with an ordered magnetic moment for Fe{sup 3+} of 1.53(4){mu}{sub B} and a propagation vector k = 0, as investigated by low-temperature NPD. The antiferromagnetic ordering is a result of the high degree of Fe/Sb anti-site disorder of the sample, which originates the spontaneous formation of Fe-rich islands, characterized by the presence of strong Fe-O-Fe antiferromagnetic couplings with enough long-range coherence to produce a magnetic contribution perceptible by NPD. By contrast, the magnetic structure of Ca(Mn{sub 0.5}Sb{sub 0.5})O{sub 3} cannot be observed by low-temperature NPD because the magnitude of the ordered magnetic moments is below the detection threshold for neutrons.

  11. Neutral pH Gel Electrolytes for V2O5·0.5H2O-Based Energy Storage Devices.

    PubMed

    Qian, Aniu; Zhuo, Kai; Karthick Kannan, Padmanathan; Chung, Chan-Hwa

    2016-12-21

    Gel electrolytes are considered to be promising candidates for the use in supercapacitors. It is worthy to systematically evaluate the internal electrochemical mechanisms with a variety of cations (poly(vinyl alcohol) (PVA)-based Li(+), Na(+), and K(+)) toward redox-type electrode. Herein, we describe a quasi-solid-state PVA-KCl gel electrolyte for V2O5·0.5H2O-based redox-type capacitors, effectively avoiding electrochemical oxidation and structural breakdown of layered V2O5·0.5H2O during 10 000 charge-discharge cycles (98% capacitance retention at 400 mV s(-1)). With the gel electrolyte, symmetric V2O5·0.5H2O-reduced graphene oxide (V2O5·0.5H2O-rGO) devices exhibited a volumetric capacitance of 136 mF cm(-3), which was much higher than that of 68 mF cm(-3) for PVA-NaCl and 45 mF cm(-3) for PVA-LiCl. Additionally, hybrid full cells of activated carbon cloth//V2O5·0.5H2O-rGO delivered an energy density of 102 μWh cm(-3) and a power density of 73.38 mW cm(-3) over a wide potential window of 2 V. The present study provides direct experimental evidence for the contribution of PVA-KCl gel electrolytes toward quick redox reactions for redox-type capacitors, which is also helpful for the development of neutral pH gel electrolytes for energy storage devices.

  12. Synthesis and thermoelectric properties of the novel A-site deficient Zn{sub 0.5}Rh{sub 2}O{sub 4} compound

    SciTech Connect

    Nakamura, Yuta; Kakemoto, Hirofumi; Nishiyama, Shin; Irie, Hiroshi

    2012-08-15

    A novel thermoelectric material, A-site-deficient spinel Zn{sub 0.5}Rh{sub 2}O{sub 4}, was prepared by subtracting Li ions from Li{sub 0.5}Zn{sub 0.5}Rh{sub 2}O{sub 4} immersed in a K{sub 2}S{sub 2}O{sub 8} aqueous solution. The electric conductivity ({sigma}) increased 6-fold after extracting Li ({sigma}=8.8 S/cm (Li{sub 0.5}Zn{sub 0.5}Rh{sub 2}O{sub 4}), 50 S/cm (Zn{sub 0.5}Rh{sub 2}O{sub 4}) at 600 Degree-Sign C), whereas the Seebeck coefficient (S) only slightly increased (S=203 {mu}V/K (Li{sub 0.5}Zn{sub 0.5}Rh{sub 2}O{sub 4}), 216 {mu}V/K (Zn{sub 0.5}Rh{sub 2}O{sub 4}) at 600 Degree-Sign C). In Zn{sub 0.5}Rh{sub 2}O{sub 4}, a mixed-valence configuration of Rh{sup 3+} and Rh{sup 4+} at a ratio of 1 to 1 and a half-deficient A-site were realized, resulting in high {sigma} and even slightly increased S, which were likely attributed to the rather high power factor of 2.3 Multiplication-Sign 10{sup -4} W/m K{sup 2} at 600 Degree-Sign C. Our findings demonstrate that controlling the Rh{sup 4+}/Rh{sup 3+} ratio is a promising method for enhancing the thermoelectric properties. - Graphical abstract: Temperature dependence of power factor (PF) of Li{sub 0.5}Zn{sub 0.5}Rh{sub 2}O{sub 4}, Li{sub 0.25}Zn{sub 0.5}Rh{sub 2}O{sub 4}, and Zn{sub 0.5}Rh{sub 2}O{sub 4} thin films. Highlights: Black-Right-Pointing-Pointer A-site-deficient Zn{sub 0.5}Rh{sub 2}O{sub 4} was prepared by subtracting Li from Li{sub 0.5}Zn{sub 0.5}Rh{sub 2}O{sub 4}. Black-Right-Pointing-Pointer A mixed-valence configuration with a Rh{sup 4+}/Rh{sup 3+} ratio of 1 was likely realized. Black-Right-Pointing-Pointer Such a configuration lead to an enhanced {sigma} of 50S/cm and S of 216 {mu}V/K at 600 Degree-Sign C. Black-Right-Pointing-Pointer Controlling the Rh{sup 4+}/Rh{sup 3+} ratio is a candidate for enhancing the thermoelectricity.

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  14. Tuning the metal-insulator transition temperature of Sm0.5Nd0.5NiO3 thin films via strain

    NASA Astrophysics Data System (ADS)

    Gardner, H. Jeffrey; Singh, Vijay; Zhang, Le; Hong, Xia

    2014-03-01

    We have investigated the effect of substrate induced strain and film thickness on the metal-insulator transition of the correlated oxide Sm0.5Nd0.5NiO3 (SNNO). We have fabricated epitaxial 3 - 40 nm thick SNNO films on (001) LaAlO3 (LAO), (001) SrTiO3 (STO), and (110) NdGaO3 (NGO) via off-axis RF magnetron sputtering. The SNNO films are atomically smooth with (001) orientation as determined by atomic force microscopy and x-ray diffraction. SNNO films grown on LAO, subject to compressive strain, exhibit a sharp metal-insulator transition at lower temperatures. Conversely, films grown on STO and NGO, subject to tensile strain, exhibit a smeared albeit above room temperature metal-insulator transition. For all substrates, we have observed that the metal-insulator transition temperature (TMI) increases monotonically with decreasing film thickness until the electrically dead layer is reached (below 4 nm). We discuss the effect of strain and oxygen deficiencies on the TMI of SNNO thin films.

  15. Dielectric and magnetic studies of BaTi0.5Fe0.5O3 ceramic materials, synthesized by solid state sintering

    NASA Astrophysics Data System (ADS)

    Samuvel, K.; Ramachandran, K.

    2015-02-01

    A comparative study of the surface morphology, dielectric and magnetic properties of the BaTi0.5Fe0.5O3 (BTFO) ceramics materials. This has been carried out by synthesizing the samples in different routes. BTFO samples have shown single phased 12R type hexagonal structure with R 3m ‾ , P4mm space group. Interfacial effects on the dielectric properties of the samples have been understood by Cole-Cole plots in complex impedance and modulus formalism. It has been identified that huge dielectric constant (103-106) at lower frequencies is largely contributed by the heterogeneous electronic microstructure at the interfaces of grains. Modulus formalism has identified the effects of both grain and grain boundary microstructure on the dielectric properties, particularly in chemical routed samples. The order of grain boundary resistivity suggests the semiconductor/insulator class of the material. The grain boundary resistivity of the mechanical alloyed samples is remarkably lower than the solid state and chemical routed samples. Few samples have of the samples have exhibited signature of ferromagnetism at the room temperature.

  16. Methane oxidation at redox stable fuel cell electrode La0.75Sr0.25Cr0.5Mn0.5O(3-delta).

    PubMed

    Tao, Shanwen; Irvine, John T S; Plint, Steven M

    2006-11-02

    Because of its widespread availability, natural gas is the most important fuel for early application of stationary fuel cells, and furthermore, methane containing biogases are one of the most promising renewable energy alternatives; thus, it is very important to be able to efficiently utilize methane in fuel cells. Typically, external steam reforming is applied to allow methane utilization in high temperature fuel cells; however, direct oxidation will provide a much better solution. Recently, we reported good electrochemical performance for an oxide anode La0.75Sr0.25Cr0.5Mn0.5O3 (LSCM) in low moisture (3% H2O) H2 and CH4 fuels without significant coking in CH4. Here, we investigate the catalytic activity of this oxide with respect to its ability to utilize methane. This oxide is found to exhibit fairly low reforming activity for both H2O and CO2 reforming but is active for methane oxidation. LSCM is found to be a full oxidation catalyst rather than a partial oxidation catalyst as CO2 production dominates CO production even in CH4-rich CH4/O2 mixtures. X-ray adsorption spectroscopy was utilized to confirm that Mn was the redox active species, clearly demonstrating that this material has the oxidation catalytic behavior that might be expected from a Mn perovskite and that the Cr ion is only present to ensure stability under fuel atmospheres.

  17. Sintering effect on structural, magnetic and optical properties of Ni0.5Zn0.5Fe2O4 ferrite nano particles

    NASA Astrophysics Data System (ADS)

    Kannan, Y. B.; Saravanan, R.; Srinivasan, N.; Ismail, I.

    2017-02-01

    Ni0.5Zn0.5Fe2O4 nano ferrite particles have been prepared by mechanical alloying via high energy ball milling and sintered at different temperatures from 700 °C to 1000 °C. Spinel structure is confirmed from the analysis of XRD data. Rietveld refinement method is employed to refine the XRD powder data and the structural parameters are calculated from the refinement. Small amount of hematite phase is found in all samples. The SEM, EDAX and XRF analysis reveals respectively the morphology, stoichiometric composition and purity of the powder samples. Using Maximum Entropy Method (MEM) the values of the bond strength between various sites interactions in ferrites are evaluated and compared with theoretical predictions of strengthening/weakening of various sites interactions from the values of interionic distances and interionic bond angles. Ferromagnetic nature of the samples is confirmed from the vibrating sample magnetometer study. The obtained low saturation magnetization values are attributed to presence of second phase. The optical band gap energy of the samples was determined by using UV-VIS techniques.

  18. Band offsets and electronic structures of interface between In{sub 0.5}Ga{sub 0.5}As and InP

    SciTech Connect

    Cai, Genwang; Wang, Changhong; Wang, Weichao; Liang, Erjun

    2016-02-07

    III–V semiconductor interfacing with high-κ gate oxide is crucial for the high mobility metal-oxide-semiconductor field transistor device. With density functional theory calculations, we explored the band offsets and electronic structures of the In{sub 0.5}Ga{sub 0.5}As/InP interfaces with various interfacial bondings. Among six different bonding interfaces, we found that P-In(Ga) bonding interface showed the highest stability. Local density of states calculations was adopted to calculate the band offsets. Except for the metallic interface, we noticed that neither valence band offset nor conduction band offset depended on the interfacial bondings. For the most stable P-In(Ga) interface, we did not observe any gap states. Furthermore, we explored the P-In(Ga) interfaces with interfacial P-As exchange defects, which slightly modified the interface stability and the band offsets but did not produce any gap states. These findings provide solid evidence that InP could serve as a promising interfacial passivation layer between III–V material and high-κ oxide in the application of high mobility devices.

  19. Unravelling the complex nanostructure of La0.5-xLi0.5-xSr2xTiO3 Li ionic conductors.

    PubMed

    García-González, Ester; Urones-Garrote, Esteban; Várez, Alejandro; Sanz, Jesús

    2016-04-28

    The origin of the intricate nanostructure of La0.5-xLi0.5-xSr2xTiO3 (0.0625 ≤ x ≤ 0.25) perovskite-type Li ion conductors has been investigated. Reciprocal space electron diffraction analysis and aberration-corrected STEM by combining annular bright field (ABF) and high angle annular dark field (HAADF) imaging methods have been used to elucidate the complex local atomic arrangements which cannot be adequately described by average crystal structure models. Two different local crystal structures endotaxially-related at the nanoscale without compositional phase separation associated, constituting the crystals. Self-organization of the two different ordered regions arises as a consequence of the competition between two distortive forces in the crystal lattice: octahedral tilting and second-order Jahn-Teller distortion of TiO6 octahedra. Changes in the distribution of A species suggest different Li ion conduction pathways for the two structures and this scenario has difficult long-range Li mobility. The detailed study performed may be helpful in understanding the local structural changes affecting Li and their relation to the conductivity in LLTO-derived ionic conductors.

  20. Structural; magnetic and catalytic properties of nanocrystalline Cu0.5Zn0.5Fe2O4 synthesized by microwave combustion and ball milling methods

    NASA Astrophysics Data System (ADS)

    Mahmoud, M. H.; Hassan, Azza M.; Said, Abd El-Aziz A.; Hamdeh, H. H.

    2016-06-01

    Effects of high energy ball-milling on nanosized Cu0.5Zn0.5Fe2O4 powders were studied at 30 and 330 min of milling. The powders were initially synthesized from its stoichiometric metal nitrates and urea mixtures, using a microwave assisted combustion method. Ball-milling induced electromechanical reaction was examined by XRD, TEM, Mössbauer spectroscopy, magnetization, and catalytic performance by exploring potential changes in size, phases and chemical structure. Before Milling, the as-prepared powders were comprised of small grains of poor spinel crystallinity and very small crystallite size, and a minor α-Fe2O3 phase. Progressive milling significantly reduced the grain size, increased chemical disorder, and reduced the hematite phase. These changes are also manifested in the magnetization measurements. The Catalytic activity performance was carried out using dehydrogenation of isopropyl alcohol. The observed activity was correlated to the presence of Cu2+ and Fe3+ catalysts at octahedral sites before and after milling.

  1. Compound biomimetic structures for efficiency enhancement of Ga(0.5)In(0.5)P/GaAs/Ge triple-junction solar cells.

    PubMed

    Hung, Mu-Min; Han, Hau-Vei; Hong, Chung-Yu; Hong, Kuo-Hsuan; Yang, Tung-Ting; Yu, Peichen; Wu, Yu-Rue; Yeh, Hong-Yih; Huang, Hong-Cheng

    2014-03-10

    Biomimetic nanostructures have shown to enhance the optical absorption of Ga(0.5)In(0.5)P/GaAs/Ge triple junction solar cells due to excellent antireflective (AR) properties that, however, are highly dependent on their geometric dimensions. In practice, it is challenging to control fabrication conditions which produce nanostructures in ideal periodic arrangements and with tapered side-wall profiles, leading to sacrificed AR properties and solar cell performance. In this work, we introduce compound biomimetic nanostructures created by depositing a layer of silicon dioxide (SiO(2)) on top of titanium dioxide (TiO(2)) nanostructures for triple junction solar cells. The device exhibits photogenerated current and power conversion efficiency that are enhanced by ~8.9% and ~6.4%, respectively, after deposition due to their improved antireflection characteristics. We further investigate and verify the optical properties of compound structures via a rigorous coupled wave analysis model. The additional SiO(2) layer not only improves the geometric profile, but also serves as a double-layer dielectric coating. It is concluded that the compound biomimetic nanostructures exhibit superior AR properties that are relatively insensitive to fabrication constraints. Therefore, the compound approach can be widely adopted for versatile optoelectronic devices and applications.

  2. Dielectric relaxation and anhydrous proton conduction in [C2H5NH3][Na0.5Fe0.5(HCOO)3] metal-organic frameworks.

    PubMed

    Sieradzki, A; Pawlus, S; Tripathy, S N; Gągor, A; Ptak, M; Paluch, M; Mączka, M

    2017-03-14

    Metal-organic frameworks (MOFs), in which metal clusters are coupled by organic moieties, exhibit inherent porosity and crystallinity. Although these systems have been examined for vast potential applications, the elementary proton conduction in anhydrous MOFs still remains elusive. One of the approaches to deal with this problem is the utilization of protic organic molecules, to be accommodated in the porous framework. In this work we report the temperature-dependent crystal structure and proton conduction in [C2H5NH3][Na0.5Fe0.5(HCOO)3] metal-organic frameworks using X-ray diffraction and broadband dielectric spectroscopic techniques. The detailed analysis of the crystal structure reveals disorder of the terminal ethylene groups in the polar phase (space group Pn). The structural phase transition from Pn to P21/n at T ≈ 363 K involves the distortion of the metal formate framework and ordering of EtA(+) cations due to the reduction of the cell volume. The dielectric data have been presented in the dynamic window of permittivity formalism to understand the ferroelectric phase transition. The relaxation times have been estimated from the Kramers-Kronig transformation of the dielectric permittivity. A Grotthuss type mechanism of the proton conduction is possible at low temperatures with the activation energy of 0.23 eV. This type of experimental observation is expected to provide new prospective on the fundamental aspect of elementary proton transfer in anhydrous MOFs.

  3. Signatures of correlation between magnetic and electrical properties of Tb0.5Sr0.5MnO3 single crystals

    NASA Astrophysics Data System (ADS)

    Nhalil, Hariharan; Elizabeth, Suja

    2016-12-01

    Here, we report the dielectric, impedance and transport studies of non-charge-ordered magnetic glass, Tb0.5Sr0.5MnO3 single crystals. The temperature- and frequency-dependent real (ε') and imaginary (ε'' or tanδ) parts of the dielectric constant display large frequency dispersion. The colossal dielectric constant observed (≈ 3000) above 100 K is considered extrinsic. The activation energy of thermally activated relaxation is calculated using the Arrhenius law. Interestingly, two relaxation regions, each with different activation energies (E a ) are clearly evident, one occurring above and the other below the glassy magnetic transition temperature (Tg = 44 \\text{K}) . E a relates to the electron hopping between Mn3+ and Mn4+ ions and the origin of dielectric dispersion. E a in the glassy region is lower than that in paramagnetic region due to a lower energy spent in hopping between frozen spins. Bulk capacitance and resistivity derived from impedance measurements reveal anomalies around T g . Electrical transport data between 60 and 300 K shows insulating behavior and the calculated E a is in good agreement with the value obtained from dielectric measurements. Although, these results cannot be interpreted in terms of magneto-electric coupling, the correlation observed between magnetic and electronic states of the system is significant.

  4. Effect of Ru-substitution on electrical and magnetocaloric properties of Nd0.5Ca0.5MnO3

    NASA Astrophysics Data System (ADS)

    Krishnamoorthi, C.; Barik, S. K.; Mahendiran, R.

    2011-01-01

    It is shown that the charge-orbital ordered antiferromagnetic insulating state of the parent compound (y=0) in Nd0.5Ca0.5Mn1-yRuyO3 (y=0, 0.03, 0.05, & 0.10) series is destabilized and a ferromagnetic metallic state is induced by Ru substitution as small as 3%. The ferromagnetic transition temperature (TC) increases with Ru content from 215 K (y=0.03) to 255 K (y=0.10). The magnetic entropy change (ΔSm) of y=0 changes sign from negative to positive as the temperature is lowered below the charge ordering temperature. However, ΔSm is negative and exhibits a peak close to TC in Ru-doped samples. The peak values of ΔSm are -0.33, -3.8, -3.6, and -3.5 J kg-1 K-1 for y=0, 0.03, 0.05, & 0.10 respectively, for a field change of ΔH=5 T. The relative cooling power (RCP) decreases with increasing Ru content from 268 J/kg for x=0.03 to 234 J/kg for x=0.10 for ΔH=5 T whereas the y=0 sample shows 17 J/kg. The large RCP and ΔSm found in Ru-substituted samples will be interesting for magnetic refrigeration below room temperature.

  5. Mechanism of γ-irradiation induced phase transformations in nanocrystalline Mn0.5Zn0.5Fe2O4 ceramics

    NASA Astrophysics Data System (ADS)

    Jagadeesha Angadi, V.; Anupama, A. V.; Choudhary, Harish K.; Kumar, R.; Somashekarappa, H. M.; Mallappa, M.; Rudraswamy, B.; Sahoo, B.

    2017-02-01

    The structural, infrared absorption and magnetic property transformations in nanocrystalline Mn0.5Zn0.5Fe2O4 samples irradiated with different doses (0, 15, 25 and 50 kGy) of γ-irradiation were investigated in this work and a mechanism of phase transformation/decomposition is provided based on the metastable nature of the Mn-atoms in the spinel lattice. The nano-powder sample was prepared by solution combustion route and the pellets of the sample were exposed to γ-radiation. Up to a dose of 25 kGy of γ-radiation, the sample retained the single phase cubic spinel (Fd-3m) structure, but the disorder in the sample increased. On irradiating the sample with 50 kGy γ-radiation, the spinel phase decomposed into new stable phases such as α-Fe2O3 and ZnFe2O4 phases along with amorphous MnO phase, leading to a change in the surface morphology of the sample. Along with the structural transformations the magnetic properties deteriorated due to breakage of the ferrimagnetic order with higher doses of γ-irradiation. Our results are important for the understanding of the stability, durability and performance of the Mn-Zn ferrite based devices used in space applications.

  6. Synthesis and dielectric properties of Na0.5Bi0.5Cu3Ti4O12 ceramic by molten salt method

    NASA Astrophysics Data System (ADS)

    Su, Yanli; Wang, Ying

    2016-03-01

    Na0.5Bi0.5Cu3Ti4O12 (NBCTO) powder was prepared by molten salt method at 700, 750, 800, and 850 °C in NaCl-KCl flux salts, respectively. X-ray diffraction data revealed that the main NBCTO phase of powder was synthesized at a low temperature of 700 °C for 2 h in NaCl-KCl flux, which was reduced by about 250 °C compared with the conventional solid-state reaction method. The evolution of the microstructure was observed by scanning electron microscopy, and the dielectric properties of NBCTO ceramics affected by sintering temperature and sintering time were studied in detail in this paper. The complex impedance plots were also employed to analyze the dielectric properties of NBCTO ceramics. The average grain size of the sintered ceramic increased with the increase in sintering temperature, which lead to the increased dielectric constant of the NBCTO ceramic, whereas the sintering time has affected the dielectric constant slightly. A high dielectric constant of more than 104 and a low loss tangent (tan δ) of 0.06 (at 10 kHz) were obtained for the NBCTO ceramic sintered at 1040 °C for 12 h.

  7. Room temperature ferrimagnetism and ferroelectricity in strained, thin films of BiFe 0.5 Mn 0.5 O 3

    SciTech Connect

    Choi, Eun -Mi; Fix, Thomas; Kursumovic, Ahmed; Kinane, Christy J.; Arena, Darío; Sahonta, Suman -Lata; Bi, Zhenxing; Xiong, Jie; Yan, Li; Lee, Jun -Sik; Wang, Haiyan; Langridge, Sean; Kim, Young -Min; Borisevich, Albina Y.; MacLaren, Ian; Ramasse, Quentin M.; Blamire, Mark G.; Jia, Quanxi; MacManus-Driscoll, Judith L.

    2014-10-14

    Highly strained films of BiFe0.5Mn0.5O₃ (BFMO) grown at very low rates by pulsed laser deposition were demonstrated to exhibit both ferrimagnetism and ferroelectricity at room temperature and above. Magnetisation measurements demonstrated ferrimagnetism (TC ~ 600K), with a room temperature saturation moment (MS) of up to 90 emu/cc (~ 0.58 μB/f.u) on high quality (001) SrTiO₃. X-ray magnetic circular dichroism showed that the ferrimagnetism arose from antiferromagnetically coupled Fe³⁺ and Mn³⁺. While scanning transmission electron microscope studies showed there was no long range ordering of Fe and Mn, the magnetic properties were found to be strongly dependent on the strain state in the films. The magnetism is explained to arise from one of three possible mechanisms with Bi polarization playing a key role. A signature of room temperature ferroelectricity in the films was measured by piezoresponse force microscopy and was confirmed using angular dark field scanning transmission electron microscopy. The demonstration of strain induced, high temperature multiferroism is a promising development for future spintronic and memory applications at room temperature and above.

  8. Room temperature ferrimagnetism and ferroelectricity in strained, thin films of BiFe 0.5 Mn 0.5 O 3

    DOE PAGES

    Choi, Eun -Mi; Fix, Thomas; Kursumovic, Ahmed; ...

    2014-10-14

    Highly strained films of BiFe0.5Mn0.5O₃ (BFMO) grown at very low rates by pulsed laser deposition were demonstrated to exhibit both ferrimagnetism and ferroelectricity at room temperature and above. Magnetisation measurements demonstrated ferrimagnetism (TC ~ 600K), with a room temperature saturation moment (MS) of up to 90 emu/cc (~ 0.58 μB/f.u) on high quality (001) SrTiO₃. X-ray magnetic circular dichroism showed that the ferrimagnetism arose from antiferromagnetically coupled Fe³⁺ and Mn³⁺. While scanning transmission electron microscope studies showed there was no long range ordering of Fe and Mn, the magnetic properties were found to be strongly dependent on the strain statemore » in the films. The magnetism is explained to arise from one of three possible mechanisms with Bi polarization playing a key role. A signature of room temperature ferroelectricity in the films was measured by piezoresponse force microscopy and was confirmed using angular dark field scanning transmission electron microscopy. The demonstration of strain induced, high temperature multiferroism is a promising development for future spintronic and memory applications at room temperature and above.« less

  9. Spin reorientation, magnetization reversal, and negative thermal expansion observed in R F e0.5C r0.5O3 perovskites (R =Lu ,Yb ,Tm )

    NASA Astrophysics Data System (ADS)

    Pomiro, Fernando; Sánchez, Rodolfo D.; Cuello, Gabriel; Maignan, Antoine; Martin, Christine; Carbonio, Raúl E.

    2016-10-01

    Three members of the perovskite family R F e0.5C r0.5O3 (R =Lu ,Yb , and Tm) have been synthesized and characterized. A systematic study of the crystal and magnetic structures was performed by neutron powder diffraction combined with magnetization measurements. All these compounds crystallize in a Pbnm orthorhombic unit cell and they are already antiferromagnetic at room temperature. The study of the magnetic structure vs temperature showed the occurrence of a progressive spin reorientation from Γ4TM to Γ2TM for the transition metal sublattice, and in the Tm-based sample, a long-range magnetic order of the T m3 + sublattice was found (Γ8R) . These results are in excellent agreement with the magnetic susceptibility measurements. No spin reorientation is observed in the Lu-based sample for which a magnetization reversal at a compensation temperature Tcomp= 225 K was detected. A clear magnetostrictive effect was observed in the samples with R =Yb and Tm associated with a negative thermal expansion and was assigned to a magnetoelastic effect produced by repulsion between the magnetic moments of neighboring transition metal ions.

  10. Room Temperature Ferrimagnetism and Ferroelectricity in Strained, Thin Films of BiFe0.5Mn0.5O3.

    PubMed

    Choi, Eun-Mi; Fix, Thomas; Kursumovic, Ahmed; Kinane, Christy J; Arena, Darío; Sahonta, Suman-Lata; Bi, Zhenxing; Xiong, Jie; Yan, Li; Lee, Jun-Sik; Wang, Haiyan; Langridge, Sean; Kim, Young-Min; Borisevich, Albina Y; MacLaren, Ian; Ramasse, Quentin M; Blamire, Mark G; Jia, Quanxi; MacManus-Driscoll, Judith L

    2014-12-01

    Highly strained films of BiFe0.5Mn0.5O3 (BFMO) grown at very low rates by pulsed laser deposition were demonstrated to exhibit both ferrimagnetism and ferroelectricity at room temperature and above. Magnetisation measurements demonstrated ferrimagnetism (TC ∼ 600K), with a room temperature saturation moment (MS ) of up to 90 emu/cc (∼ 0.58 μB /f.u) on high quality (001) SrTiO3. X-ray magnetic circular dichroism showed that the ferrimagnetism arose from antiferromagnetically coupled Fe(3+) and Mn(3+). While scanning transmission electron microscope studies showed there was no long range ordering of Fe and Mn, the magnetic properties were found to be strongly dependent on the strain state in the films. The magnetism is explained to arise from one of three possible mechanisms with Bi polarization playing a key role. A signature of room temperature ferroelectricity in the films was measured by piezoresponse force microscopy and was confirmed using angular dark field scanning transmission electron microscopy. The demonstration of strain induced, high temperature multiferroism is a promising development for future spintronic and memory applications at room temperature and above.

  11. Correlating structural, magnetic, and luminescence properties with the cation distribution of Co0.5Zn0.5+xFe2-xO4 nanoferrite

    NASA Astrophysics Data System (ADS)

    Wahba, Adel Maher; Mohamed, Mohamed Bakr; Imam, N. G.

    2016-06-01

    Structural, magnetic, and luminescence properties have been investigated for Co0.5Zn0.5+xFe2-xO4 nanoferrite (0.0≤x≤0.4, with a step increment of 0.1) prepared by citrate autocombustion method. X-ray diffraction (XRD) patterns and Fourier-transform infrared (FTIR) spectra proved the formation of a pure cubic spinel phase for all AP samples. Although the ionic radius of Zn2+ is larger than that of either Fe3+ or Co2+, Rietveld analysis showed that the lattice parameter mostly decreases with increasing Zn substitution. The crystallite size of AP samples decreases gradually with increasing Zn substitution from 16 to 10 nm, which is confirmed with high-resolution (HRTEM) micrographs. Magnetic parameters such as saturation magnetization, coercivity, and remanent field obtained from vibrating sample magnetometry (VSM) revealed a strong dependence on the cation distribution being proposed according to the experimental data of XRD, FTIR, and VSM. The cation distribution indicated that introduced nonstoichiometry is compensated by oxidizing Co2+ into Co3+, which explains the trend of the lattice parameter with increasing x. The distribution of Fe3+ ions between octahedral and tetrahedral sites was further confirmed by photoluminescence (PL) emission spectra.

  12. Downscaling at submicrometer scale of the gap width of interdigitated Ba0.5Sr0.5TiO3 capacitors.

    PubMed

    Khalfallaoui, Abderrazek; Burgnies, Ludovic; Blary, Karine; Velu, Gabriel; Lippens, Didier; Carru, Jean-Claude

    2015-02-01

    The goal of this work was to study the influence of shrinking the gap width between the fingers of interdigitated tunable capacitors (IDCs). Voltage control of the capacitance was achieved with a 500-nm-thick Ba0.5Sr0.5TiO3 film which is in paraelectric state at room temperature. Eight devices with finger spacing ranging from 3 μm down to 0.25 μm were fabricated by the sol-gel deposition technique, electron beam patterning, and gold evaporation. The equivalent capacitance, quality factor, and tunability of the devices were measured subsequently by vector network analysis from 40 MHz to 40 GHz and for a dc bias voltage varying from -30 V to +30 V. This experimental study mainly shows that a decrease of the gap below 1 μm 1) introduces a frequency dependence of the capacitance caused by resonance effects with the finger inductance; 2) degrades the quality factor above 20 GHz, and 3) optimizes the tunability of the devices by enhancing the local electric field values. As a consequence, some trade-offs are pointed out related to the goal of ultra-thin ferroelectric film which can be voltage controlled by means of finger-shaped electrodes with deep submicrometer spacing.

  13. Direct evidence of non-Zhang-Rice Cu3+ centers in La2Li0.5Cu0.5O4

    NASA Astrophysics Data System (ADS)

    Moskvin, A. S.; Gippius, A. A.; Tkachev, A. V.; Mahajan, A. V.; Chakrabarty, T.; Presniakov, I. A.; Sobolev, A. V.; Demazeau, G.

    2012-12-01

    A well-isolated Zhang-Rice (ZR) singlet as a ground state of the Cu3+ center in hole-doped cuprates is a leading paradigm in modern theories of high-temperature superconductivity. However, a dramatic temperature evolution of the 6,7Li NMR signal in La2Li0.5Cu0.5O4, a system with a regular lattice of well-isolated Cu3+ centers, reveals significant magnetic fluctuations and suggests a quasidegeneracy to be a generic property of their ground state at variance with the simple ZR model. We argue for a competition of the ZR state with nearby states formed by a “doped” hole occupying purely oxygen nonbonding a2g(π) and eu(π) orbitals rather than a conventional b1g(dx2-y2) Cu 3d-O 2p hybrid. The temperature variation of the 6,7Li NMR line shape and spin-lattice relaxation rate point to a gradual slowing down of some magnetic order parameter's fluctuations without distinct signatures of a phase transition down to T=2 K. This behavior agrees with a stripelike ferrodistortive fluctuating Ammm order in a two-dimensional structure of the (CuLi)O2 planes accompanied by unconventional oxygen orbital antiferromagnetic fluctuations.

  14. Soft magnetic property and enhanced microwave absorption of nanoparticles of Co0.5Zn0.5Fe2O4 incorporated in MWCNT

    NASA Astrophysics Data System (ADS)

    Mallick, A.; Mahapatra, A. S.; Mitra, A.; Chakrabarti, P. K.

    2016-10-01

    Nanoparticles of Co0.5Zn0.5Fe2O4 (CZFO) are prepared by coprecipitation method where CoCl2·H2O, ZnCl2·6H2O and FeCl3 are used as precursor materials. To enhance the microwave absorption, nanoparticles of CZFO are incorporated in the matrix of multiwall carbon nanotubes (MWCNT). X-ray diffractogram (XRD) and its analysis confirmed the formation of the desired crystallographic phase of the sample. The average crystallite size is evaluated by using the Debye-Scherrer formula. Micrographs observed in high resolution transmission electron microscope confirm the successful incorporation of CZFO in the matrix of MWCNT. Results obtained from the high resolution lattice fringe and selected area electron diffraction patterns are in good agreement with the findings extracted from the XRD analysis. Analysis of Raman spectra confirms the presence of CZFO and MWCNT in the nanocomposite sample. Magnetic properties recorded in SQUID magnetometer confirm the presence of mixed state of superparamagnetic and ferrimagnetic nanoparticles. Reflection losses in X (8-12 GHz) and Ku (12-18 GHz) bands of microwave region are significantly high (~-38.2 dB at 16.9 GHz). High magnetization (~36.5 emu/g at 300 K), low coercive field (~30.1 Oe at 300 K) and high reflection loss of CZFO-MWCNT would be suitable for application in microwave devices.

  15. Effects of Ge4+ acceptor dopant on sintering and electrical properties of (K0.5Na0.5)NbO3 lead-free piezoceramics

    NASA Astrophysics Data System (ADS)

    Chen, Kepi; Jiao, Yanlin

    2017-03-01

    Lead-free (K0.5Na0.5)(Nb1- x Ge x )O3 (KNN- xGe, where x = 0-0.01) piezoelectric ceramics were prepared by conventional ceramic processing. The effects of Ge4+ cation doping on the phase compositions, microstructure and electrical properties of KNN ceramics were studied. SEM images show that Ge4+ cation doping improved the sintering and promoted the grain growth of the KNN ceramics. Dielectric and ferroelectric measurements proved that Ge4+ cations substituted Nb5+ ions as acceptors, and the Curie temperature ( T C) shows an almost linear decrease with increasing the Ge4+ content. Combining this result with microstructure observations and electrical measurements, it is concluded that the optimal sintering temperature for KNN- xGe ceramics was 1020°C. Ge4+ doping less than 0.4 mol.%can improve the compositional homogeneity and piezoelectric properties of KNN ceramics. The KNN- xGe ceramics with x = 0.2% exhibited the best piezoelectric properties: piezoelectric constant d 33 = 120 pC/N, planar electromechanical coupling coefficient k p = 34.7%, mechanical quality factor Q m = 130, and tan δ = 3.6%.

  16. Room Temperature Ferrimagnetism and Ferroelectricity in Strained, Thin Films of BiFe0.5Mn0.5O3

    PubMed Central

    Choi, Eun-Mi; Fix, Thomas; Kursumovic, Ahmed; Kinane, Christy J; Arena, Darío; Sahonta, Suman-Lata; Bi, Zhenxing; Xiong, Jie; Yan, Li; Lee, Jun-Sik; Wang, Haiyan; Langridge, Sean; Kim, Young-Min; Borisevich, Albina Y; MacLaren, Ian; Ramasse, Quentin M; Blamire, Mark G; Jia, Quanxi; MacManus-Driscoll, Judith L

    2014-01-01

    Highly strained films of BiFe0.5Mn0.5O3 (BFMO) grown at very low rates by pulsed laser deposition were demonstrated to exhibit both ferrimagnetism and ferroelectricity at room temperature and above. Magnetisation measurements demonstrated ferrimagnetism (TC ∼ 600K), with a room temperature saturation moment (MS) of up to 90 emu/cc (∼ 0.58 μB/f.u) on high quality (001) SrTiO3. X-ray magnetic circular dichroism showed that the ferrimagnetism arose from antiferromagnetically coupled Fe3+ and Mn3+. While scanning transmission electron microscope studies showed there was no long range ordering of Fe and Mn, the magnetic properties were found to be strongly dependent on the strain state in the films. The magnetism is explained to arise from one of three possible mechanisms with Bi polarization playing a key role. A signature of room temperature ferroelectricity in the films was measured by piezoresponse force microscopy and was confirmed using angular dark field scanning transmission electron microscopy. The demonstration of strain induced, high temperature multiferroism is a promising development for future spintronic and memory applications at room temperature and above. PMID:26213531

  17. Study of AC magnetic heating characteristics of Co0.5Zn0.5Fe2O4 nanoparticles for magnetic hyperthermia therapy

    NASA Astrophysics Data System (ADS)

    Nikam, D. S.; Jadhav, S. V.; Khot, V. M.; Phadatare, M. R.; Pawar, S. H.

    2014-01-01

    Structural, magnetic properties and an alternating current (AC) magnetic heating characteristics of Co0.5Zn0.5Fe2O4 nanoparticles (CZF NPs) have been investigated with respect to the possible application for magnetic hyperthermia treatments. The Specific Absorption Rate (SAR) was measured in alternating magnetic fields of 167.5-335.2 Oe at fixed frequency of 265 kHz. CZF NPs were fabricated by the chemical co-precipitation method using sodium hydroxide (NaOH) as the precipitating agent. The morphology of the particles was analysed by Transmission Electron microscopy (TEM). The TEM reveals that the grains are nearly spherical in shape with average particles size of 19 nm. X-ray diffraction pattern indicated the sole existence of cubic spinel phase of CZF NPs. The magnetization (Ms) of CZF NPs was measured at room temperature (300 K) using a Vibrating Sample Magnetometer (VSM). The magnetic heating ability of NPs was studied with an induction heating system. A highest SAR value of 114.98 W/g for 5 mg/mL sample concentration (265 kHz, 335.2 Oe) was determined.

  18. Dielectric and AC-conductivity studies of Dy2O3 doped (K0.5Na0.5)NbO3 ceramics

    NASA Astrophysics Data System (ADS)

    Peddigari, Mahesh; Thota, Subhash; Pamu, Dobbidi

    2014-08-01

    (K0.5Na0.5)NbO3 + x wt.% Dy2O3 (x = 0-1.5) ferroelectric ceramics were prepared by conventional solid state reaction method. XRD patterns revealed that orthorhombic symmetry has transformed into psuedocubic symmetry with increasing the substitution of Dy3+ in the Na+ site. Temperature and frequency dependences of relative dielectric permittivity maximum conforms the transformation from normal ferroelectric to relaxor ferroelectric behaviour. Frequency dependence of the relative dielectric permittivity maximum temperature observed for the samples with x ≥ 1.0 and satisfied the Vogel-Fulcher law. The diffuseness exponent γ (1.27-1.95) estimated from the high temperature slopes of the diffused dielectric permittivity data reveals that the degree of relaxor behavior increases with increasing the amount of Dy2O3. The temperature dependence of AC-conductivity σAC (T) analysis in the range 310 K < T < 470 K reveals the existence of variable range hopping of charge carriers with average hopping length RH and hopping energy EH are in the range 8.5-27 Å and 48-153 meV, respectively. Voltage dependent dielectric constant measurements confirm the ferroelectric nature of KNN+ x wt% Dy2O3 ceramics.

  19. Parallel charge sheets of electron liquid and gas in La0.5Sr0.5TiO3/SrTiO3 heterostructures

    PubMed Central

    Renshaw Wang, X.; Sun, L.; Huang, Z.; Lü, W. M.; Motapothula, M.; Annadi, A.; Liu, Z. Q.; Zeng, S. W.; Venkatesan, T.; Ariando

    2015-01-01

    We show here a new phenomenon in La0.5Sr0.5TiO3/SrTiO3 (LSTO/STO) heterostructures; that is a coexistence of three-dimensional electron liquid (3DEL) and 2D electron gas (2DEG), separated by an intervening insulating LSTO layer. The two types of carriers were revealed through multi-channel analysis of the evolution of nonlinear Hall effect as a function of film thickness, temperature and back gate voltage. We demonstrate that the 3D electron originates from La doping in LSTO film and the 2D electron at the surface of STO is due to the polar field in the intervening insulating layer. As the film thickness is reduced below a critical thickness of 6 unit cells (uc), an abrupt metal-to-insulator transition (MIT) occurs without an intermediate semiconducting state. The properties of the LSTO layer grown on different substrates suggest that the insulating phase of the intervening layer is a result of interface strain induced by the lattice mismatch between the film and substrate. Further, by fitting the magnetoresistance (MR) curves, the 6 unit cell thick LSTO is shown to exhibit spin-orbital coupling. These observations point to new functionalities, in addition to magnetism and superconductivity in STO-based systems, which could be exploited in a multifunctional context. PMID:26669575

  20. Coherent A1g Phonon in thin Film Superconductor FeSe0.5Te0.5: π/2 Phase Difference over Superconducting Phase Transition

    NASA Astrophysics Data System (ADS)

    Zhao, Jimin; Wu, Yanling; Hu, Minhui; Tian, Yichao; Cao, Lixin; Wang, Rui

    2014-03-01

    Coherent A1 g phonon mode in a thin film superconductor FeSe0.5Te0.5 was generated and detected using ultrafast laser pulses. At below and above the transition temperature Tc, the coherent lattice oscillation we observed exhibited a π/2 phase difference, manifesting a ``displacive limit ~ impulsive limit'' transition upon crossing a phase transition within the same sample. We ascribe this π/2 phase difference to the different lifetimes (τc) of excited charge density components that couples to the fully symmetric A1 g phonon mode, i.e. the different strength of electron-phonon couplings. In the superconducting and paramagnetic metallic states the lifetimes of such carrier excitations are largely different. Our investigation reveals possible correlation of superconducting electrons with zone-center optical phonons. Our 170nm thin film sample contains tension stress, which leads to enhanced Tc and thus facilitated our measurements. Financially supported by the National Basic Research Program of China (2012CB821402), the NSFC (11274372, 10974246) and the External Cooperation Program of Chinese Academy of Sciences (GJHZ1403).

  1. Preferential polarization and its reversal in polycrystalline BiFeO3/La0.5Sr0.5CoO3 heterostructures

    NASA Astrophysics Data System (ADS)

    Roy Choudhury, Palash; Parui, Jayanta; Chiniwar, Santosh; Krupanidhi, S. B.

    2015-04-01

    Polycrystalline BiFeO3 thin films were grown on La0.5Sr0.5CoO3 buffered Pt (200)/TiO2/SiO2/Si substrates under different oxygen partial pressures (10, 25, 50 and 100 mTorr) by pulsed laser ablation. Piezoresponse Force Microscopy and Piezo-Force Spectroscopy have shown that all the films are ferroelectric in nature with locally switchable domains. It has also revealed a preferential downward domain orientation in as-grown films grown under lower oxygen partial pressure (10 and 25 mTorr) with a reversal of preferential domain orientation as the oxygen partial pressure is increased to 100 mTorr during laser ablation. Such phenomena are atypical of multi-grained polycrystalline ferroelectric films and have been discussed on the basis of defect formation with changing growth conditions. For the 50 mTorr grown film, asymmetric domain stability and retention during write-read studies has been observed which is attributed to grain-size-related defect concentration, affecting pinning centres that inhibit domain wall motion.

  2. Strain-induced structural, band-structure and piezoelectric evolutions in Al0.5Ga0.5N alloy

    NASA Astrophysics Data System (ADS)

    Duan, Yifeng; Lv, Dong; Liu, Kun; Wu, Hongbo; Qin, Lixia; Shi, Liwei; Tang, Gang

    2015-01-01

    Structural phase transition, band structure, and piezoelectric response of Al0.5Ga0.5N alloy under uniaxial and biaxial strains are systematically investigated using first-principle calculations. The main findings are summarized as follows: (I) Although the wurtzite structure transforms to an intermediate graphite-like structure for both uniaxial and biaxial strains, the second-order phase transition is found for uniaxial strain and the first-order transition for biaxial strain. The transition is driven by the mechanical and dynamical instabilities for uniaxial strain, and by the mechanical instability for biaxial strain. (II) The wurtzite phase always remains the direct band structure, whereas the band gap of graphite-like phase is always indirect. The band gaps of wurtzite and graphite-like phases are greatly reduced by internal strains. (III) The drastic enhancements in piezoelectric response are observed near phase transition, which is attributed to the flat and shallow local energy minima associated with two different phases. Our calculated results are compared with the available experimental and other theoretical data, and good agreements are obtained.

  3. Spin dynamics, short range order and spin freezing in Y0.5Ca0.5BaCo4O7

    SciTech Connect

    Stewart, John Ross; Ehlers, Georg; Fouquet, Peter; Mutka, Hannu; Payen, Christophe; Lortz, Rolf

    2011-01-01

    Y0.5Ca0.5BaCo4O7 was recently introduced as a possible candidate for capturing some of the predicted classical spin kagome ground-state features. Stimulated by this conjecture, we have taken up a more complete study of the spin correlations in this compound with neutron scattering methods on a powder sample characterized with high-resolution neutron diffraction and the temperature dependence of magnetic susceptibility and specific heat. We have found that the frustrated near-neighbor magnetic correlations involve not only the kagome planes but concern the full Co sublattice, as evidenced by the analysis of the wave-vector dependence of the short-range order. We conclude from our results that the magnetic moments are located on the Co sublattice as a whole and that correlations extend beyond the two-dimensional kagome planes. We identify intriguing dynamical properties, observing high-frequency fluctuations with a Lorentzian linewidth G?20 meV at ambient temperature. On cooling a low-frequency ({approx}1 meV) dynamical component develops alongside the high-frequency fluctuations, which eventually becomes static at temperatures below T {approx} 50 K. The high-frequency response with an overall linewidth of {approx}10 meV prevails at T?2 K, coincident with a fully elastic short-range-ordered contribution.

  4. Characterization of Au/PbTi0.5Fe0.5O3/Si structure for possible multiferroic based non-volatile memory applications

    NASA Astrophysics Data System (ADS)

    Nawaz, S.; Roy, S.; Tulapurkar, A. A.; Palkar, V. R.

    2017-03-01

    Magnetoelectric multiferroic PbTi0.5Fe0.5O3 films are deposited on a ⟨100⟩ conducting p-Si substrate without any buffer layer by using pulsed laser deposition and characterized for possible non-volatile memory applications. Their crystalline structure and surface morphology were characterized by using x-ray diffraction and AFM techniques. HRTEM was employed to determine the film-substrate interface. The electronic structure of the film was investigated by XPS, and no signature of metal was found for all the elements. The chemical shift of the Ti 2p XPS peak is attributed to the replacement of Ti with Fe in the PbTiO3 matrix. Piezoelectric force microscopy (PFM) results indicate the 180° phase shift of ferroelectric polarization. The upward self-polarization phenomenon is also observed in the PFM study. Magnetic and magneto-electric coupling measurements were carried out to confirm the magnetic nature and electro-magnetic coupling characteristics. C-V measurements exhibit clock-wise hysteresis loops with a maximum memory window of 1.2 V and a sweep voltage of ±7 V. This study could influence the fabrication of silicon compatible multiple memory device structures.

  5. Effects of Ge4+ acceptor dopant on sintering and electrical properties of (K0.5Na0.5)NbO3 lead-free piezoceramics

    NASA Astrophysics Data System (ADS)

    Chen, Kepi; Jiao, Yanlin

    2017-01-01

    Lead-free (K0.5Na0.5)(Nb1-x Ge x )O3 (KNN-xGe, where x = 0-0.01) piezoelectric ceramics were prepared by conventional ceramic processing. The effects of Ge4+ cation doping on the phase compositions, microstructure and electrical properties of KNN ceramics were studied. SEM images show that Ge4+ cation doping improved the sintering and promoted the grain growth of the KNN ceramics. Dielectric and ferroelectric measurements proved that Ge4+ cations substituted Nb5+ ions as acceptors, and the Curie temperature (T C) shows an almost linear decrease with increasing the Ge4+ content. Combining this result with microstructure observations and electrical measurements, it is concluded that the optimal sintering temperature for KNN-xGe ceramics was 1020°C. Ge4+ doping less than 0.4 mol.%can improve the compositional homogeneity and piezoelectric properties of KNN ceramics. The KNN-xGe ceramics with x = 0.2% exhibited the best piezoelectric properties: piezoelectric constant d 33 = 120 pC/N, planar electromechanical coupling coefficient k p = 34.7%, mechanical quality factor Q m = 130, and tanδ = 3.6%.

  6. Pulse and quasi-static remagnetization peculiarities and relaxation properties of Nd0.5Sr0.5MnO3 single crystal

    NASA Astrophysics Data System (ADS)

    Dovgii, V. T.; Linnik, A. I.; Kamenev, V. I.; Tarenkov, V. Yu.; Sidorov, S. L.; Todris, B. M.; Mikhailov, V. I.; Davideiko, N. V.; Linnik, T. A.; Popov, Ju. F.; Balbashov, A. M.

    2016-06-01

    Hysteresis features of magnetization and resistance of Nd0.5Sr0.5MnO3 single crystal in quasi-static (up to 9 T) and pulse (up to 14 T) magnetic fields are studied. The relaxation processes of magnetization and resistance after the action of a magnetic field of 9 T are also studied. It is shown that relaxation curves are approximated by two exponents with different time constants. These two constants relate to relaxation of the metastable ferromagnetic phase towards two different crystal structures (Imma and p21/m). Mechanism of phase transitions: antiferromagnetic insulator↔ferromagnetic metal (AFM/I↔FM/M) and existence of a high-conductive state of a sample after removal of magnetizing field in the temperature range below 150 K is proposed. The mechanism is connected with structural transition induced by magnetic field (due to magnetostriction) and slow relaxation of the FM-phase (larger volume) to the equilibrium AFM-phase (smaller volume) after field removal. It is shown that during pulse magnetization at the temperature 18 K time required for the AFM/I→FM/M phase transition is by six-seven orders of magnitude less than for realization of the FM/M→AFM/I phase transition.

  7. Specific features of pulse and quasi-static remagnetization and relaxation properties of Nd0.5Sr0.5MnO3 single crystals

    NASA Astrophysics Data System (ADS)

    Dovgii, V. T.; Linnik, A. I.; Kamenev, V. I.; Tarenkov, V. Yu.; Sidorov, S. L.; Todris, B. M.; Mikhailov, V. I.; Davydeiko, N. V.; Linnik, T. A.; Popov, Yu. F.; Balbashov, A. M.

    2015-12-01

    The hysteresis features in the behavior of the magnetization and resistance of Nd0.5Sr0.5MnO3 single crystals in quasi-static (up to 9 T) and pulsed (up to 14 T) magnetic fields have been studied. Relaxation processes of magnetization and resistance after the action of a magnetic field of 9 T have also been investigated. It has been shown that relaxation curves are approximated by two exponents with different time constants, which are related to relaxation of the metastable ferromagnetic phase towards two different antiferromagnetic crystal structures ( I mma and p21/ m). Mechanism of the phase transitions antiferromagnetic insulator ↔ ferromagnetic metal (AFM/I ↔ FM/M) and existence of a high-conductive state of a sample after removal of magnetizing field in the temperature range below 150 K is proposed. The mechanism is determined by the structural transition, which is induced by a magnetic field (due to magnetostriction), and by a slow relaxation of the FM-phase (larger volume) to the stable AFM-phase (smaller volume) after field removal. It has been shown that, during pulse magnetization at the temperature 18 K, the time required for the AFM/I → FM/M phase transition is six-seven orders of magnitude shorter than that for the FM/M → AFM/I phase transition.

  8. Probing the existing magnetic phases in Pr0.5Ca0.5MnO3 (PCMO) nanowires and nanoparticles: magnetization and magneto-transport investigations

    NASA Astrophysics Data System (ADS)

    Rao, S. S.; Bhat, S. V.

    2010-03-01

    We show from conventional magnetization measurements that the charge order (CO) is completely suppressed in 10 nm Pr0.5Ca0.5MnO3(PCMO 10) nanoparticles. Novel magnetization measurements, designed by a special high field measurement protocol, show that the dominant ground state magnetic phase is ferromagnetic-metallic (FM-M), which is an equilibrium phase, which coexists with the residual charge ordered anti-ferromagnetic phase (CO AFM) (an arrested phase) and exhibits the characteristic features of a 'magnetic glassy state' at low temperatures. It is observed that there is a drastic reduction in the field required to induce the AFM to FM transition (~5-6 T) compared to their bulk counterpart (~27 T) this phase transition is of first order in nature, broad, irreversible and the coexisting phases are tunable with the cooling field. Temperature-dependent magneto-transport data indicate the occurrence of a size-induced insulator-metal transition (TM - I) and anomalous resistive hysteresis (R-H) loops, pointing out the presence of a mixture of the FM-M phase and AFM-I phase.

  9. Enhanced dielectric constant and relaxor behavior realized by dual stage sintering of Sr0.5Ba0.5Nb2O6

    NASA Astrophysics Data System (ADS)

    Rathore, Satyapal S.; Vitta, Satish

    2014-04-01

    The relaxor ferroelectric compound, Sr0.5Ba0.5Nb2O6 (SBN50) was synthesized by solid state reaction followed by sintering under two different conditions: single and dual stage sintering. The impact of sintering process on structural and dielectric properties has been studied in detail using X-ray diffraction, scanning electron microscopy and broadband dielectric spectroscopy. The crystal structure determined by performing Rietveld refinement of X-ray diffractogram was found to be identical in both cases. SBN50 crystallizes in the ferroelectric tetragonal tungsten bronze, P4bm structure. It was observed that uniform grain growth can be controlled by dual stage sintering and relatively narrow distribution of grains can be achieved with an average grain size of ˜15 μm. The dielectric studies show that SBN50 exhibits a relaxor ferroelectric behavior with the transformation taking place at ˜ 380 K due to formation of polar nano regions. Although both single and dual stage sintered SBN50 exhibits relaxor behaviour, the maximum dielectric constant of dual stage sintered SBN50 is found to be 1550 compare to 1440 for single stage sintering.

  10. Relaxation dynamics and thermodynamic properties of glassy Tb0.5Sr0.5MnO3 single crystal

    NASA Astrophysics Data System (ADS)

    Nhalil, Hariharan; Elizabeth, Suja

    2017-03-01

    Single crystals of Tb0.5Sr0.5MnO3 were grown in an optical float zone furnace and their magnetic and thermodynamic properties were studied. Temperature dependent DC magnetization measurements at different fields show strong irreversibility below the magnetic anomaly at 44 K. The upward deviation from ideal CW behavior well above the transition temperature and its field independent nature are signatures of non-Griffiths phase. The origin non-Griffiths phase owe to competition between the antiferromagnetic and ferromagnetic Mn3+-Mn4+ interactions mediated through intervening oxygen. Further, 44 K transition is confirmed as a magnetic glassy transition. The estimated dynamical spin flip time (τ0=2.11(3)×10-14 s) and zν(9.3(2)) values fall into the range of typical spin-glass systems. Detailed memory and temperature cycling relaxation measurements were performed and support the Hierarchical relaxation model. Low-temperature specific heat data displays a linear term, identifying the glassy magnetic phase contribution.

  11. Cellulose-precursor synthesis of nanocrystalline Co{sub 0.5}Cu{sub 0.5}Fe{sub 2}O{sub 4} spinel ferrites

    SciTech Connect

    Ounnunkad, Kontad; Phanichphant, Sukon

    2012-02-15

    Highlights: Black-Right-Pointing-Pointer Synthesis of spinel copper cobalt nanoferrite particles from a cellulose precursor for the first time. Control of nanosize and properties of nanoferrites can take place by varying the calcining temperature. The simple, low cost, easy cellulose process is a choice of nanoparticle processing technology. -- Abstract: Nanocrystalline Cu{sub 0.5}Co{sub 0.5}Fe{sub 2}O{sub 4} powders were prepared via a metal-cellulose precursor synthetic route. Cellulose was used as a fuel and a dispersing agent. The resulting precursors were calcined in the temperature range of 450-600 Degree-Sign C. The phase development of the samples was determined by using Fourier transform infrared (FT-IR) spectroscopy and powder X-ray diffraction (XRD). The field-dependent magnetizations of the nanopowders were measured by vibrating sample magnetometer (VSM). All XRD patterns are of a spinel ferrite with cubic symmetry. Microstructure of the ferrites showed irregular shapes and uniform particles with agglomeration. From XRD data, the crystallite sizes are in range of 16-42 nm. Saturation magnetization and coercivity increased with increasing calcining temperature due to enhancement of crystallinity and reduction of oxygen vacancies.

  12. Dielectric and magnetic studies of BaTi0.5Fe0.5O3 ceramic materials, synthesized by solid state sintering.

    PubMed

    Samuvel, K; Ramachandran, K

    2015-02-05

    A comparative study of the surface morphology, dielectric and magnetic properties of the BaTi0.5Fe0.5O3 (BTFO) ceramics materials. This has been carried out by synthesizing the samples in different routes. BTFO samples have shown single phased 12R type hexagonal structure with R3m, P4mm space group. Interfacial effects on the dielectric properties of the samples have been understood by Cole-Cole plots in complex impedance and modulus formalism. It has been identified that huge dielectric constant (10(3)-10(6)) at lower frequencies is largely contributed by the heterogeneous electronic microstructure at the interfaces of grains. Modulus formalism has identified the effects of both grain and grain boundary microstructure on the dielectric properties, particularly in chemical routed samples. The order of grain boundary resistivity suggests the semiconductor/insulator class of the material. The grain boundary resistivity of the mechanical alloyed samples is remarkably lower than the solid state and chemical routed samples. Few samples have of the samples have exhibited signature of ferromagnetism at the room temperature.

  13. Magnetization dynamics in rare earth Gd3+ doped Mn(0.5)Zn(0.5)Fe2O4 magnetic fluid: electron spin resonance study.

    PubMed

    Parekh, Kinnari; Upadhyay, R V

    2012-12-01

    The electron spin resonance (ESR) technique has been applied to study the spin dynamics in broad temperature range for rare earth doped Mn(0.5)Zn(0.5)Fe(1.9)Gd(0.1)O(4) (MZG5) magnetic fluid. Zero field cooled (ZFC) ESR spectra of MZG5 fluid exhibit an isotropic shift in the resonance field below 40 K, while the field cooled (FC) ESR spectra show a deviation from sin(2)θ behavior and an angle dependent hysteresis, this unambiguously points to the dominating unidirectional freezing of surface spins below 40 K. Above 60 K, the resonance field exhibits sin(2)θ behavior, indicating the uniaxial anisotropy contribution of core spin. This indicates that surface spin freezing temperature is around 40 K. The presence of surface spin freezing and the coupling between core and surface spins are further supported by cycle dependent FC ESR spectra measured at 20 K, which show the systematic increase in resonance field (H(res)) and intensity. The double peak behavior of blocking temperature distribution retrieved from ZFC-FC magnetization measurement is an additional corroboration of the existence of surface spin glass like layer.

  14. Chemical durability and leaching mechanism of Ce0.5Eu0.5PO4 ceramics: Effects of temperature and pH values

    NASA Astrophysics Data System (ADS)

    Zhao, Xiaofeng; Teng, Yuancheng; Wu, Lang; Huang, Yi; Ma, Jiyan; Wang, Guolong

    2015-11-01

    Ce0.5Eu0.5PO4 ceramics with high relative density were prepared by hot-press (HPS) and pressureless (PLS) sintering. The effects of temperature and pH values on the chemical durability of the ceramics were investigated. The results show that an increase of acidity significantly accelerated the corrosion of the samples. In alkaline leachates, further release elements were prevented by the newborn surface precipitation. The leach rate (Rn) of HPS sample was similar to that of PLS specimen in deionized water, but higher Rn for PLS sample was found in pH = 11 solution. Moreover, apparent activation energy of the dissolution of Eu (40 ± 4 kJ mol-1) is much higher than that of Ce (20 ± 1 kJ mol-1), leading to the higher normalized elemental leach rate of Eu. Both the Eu and Ce elements have low leach rates (10-12-10-9 m d-1) after 42 days in all the leachates studied in this work.

  15. Magnetic and natural optical activity of f- f transitions in multiferroic Nd0.5Gd0.5Fe3(BO3)4

    NASA Astrophysics Data System (ADS)

    Malakhovskii, A. V.; Sukhachev, A. L.; Leont'ev, A. A.; Temerov, V. L.

    2016-05-01

    Spectra of absorption, magnetic circular dichroism, and natural circular dichroism of the f-f transitions 4 I 9/2 → 4 F 3/2, 2 H 9/2 + 4 F 5/2, 4 S 3/2 + 4 F 7/2, 2 G 7/2 + 4 G 5/2, 2 K 13/2 + 4 G 7/2, and 4 G 9/2 in the Nd3+ ions in the Nd0.5Gd0.5Fe3(BO3)4 crystal have been measured as a function of the temperature in the interval of 90-300 K. Temperature dependences of the magneto-optical activity (MOA) and natural optical activity (NOA) of the transitions have been obtained. It has been found that, in contrast to allowed transitions, the temperature dependence of the MOA of the f-f transitions does not obey the Curie-Weiss law and the NOA depends on temperature. The NOA of some transitions changes the sign with variation in temperature. These phenomena have been explained by the presence of three contributions to the allowance of the f-f transitions, which lead to three contributions of different signs to the MOA and NOA. The range of the MOA of the f-f transitions in the Nd3+ ion has been predicted theoretically and confirmed experimentally.

  16. Compositional inhomogeneityand segregation in (K0.5Na0.5)NbO3 ceramics

    SciTech Connect

    Chen, Kepi; Tang, Jing; Chen, Yan

    2016-03-11

    The effects of the calcination temperature of (K0.5Na0.5)NbO3 (KNN) powder on the sintering and piezoelectric properties of KNN ceramics have been investigated in this report. KNN powders are synthesized via the solid-state approach. Scanning electron microscopy and X-ray diffraction characterizations indicate that the incomplete reaction at 700 °C and 750 °C calcination results in the compositional inhomogeneity of the K-rich and Na-rich phases while the orthorhombic single phase is obtained after calcination at 900 °C. During the sintering, the presence of the liquid K-rich phase due to the lower melting point has a significant impact on the densification, the abnormal grain growth and the deteriorated piezoelectric properties. From the standpoint of piezoelectric properties, the optimal calcination temperature obtained for KNN ceramics calcined at this temperature is determined to be 800 °C, with piezoelectric constant d33=128.3 pC/N, planar electromechanical coupling coefficient kp=32.2%, mechanical quality factor Qm=88, and dielectric loss tan δ=2.1%.

  17. Tuning of Cr3+ ions doping on the magnetic and magnetocaloric properties of La0.5Sr0.5Mn1-xCrxO3

    NASA Astrophysics Data System (ADS)

    Shang, C.; Xia, Z. C.; Wei, M.; Jin, Z.; Chen, B. R.; Shi, L. R.; Xiao, G. L.; Huang, S.

    2016-12-01

    The effects of Cr3+ ions doping on the magnetic and magnetocaloric properties of manganites La0.5Sr0.5Mn1-xCrxO3 (x=0.05, 0.1, 0.15, and 0.2) have been investigated. The magnetization measurements show that a ferromagnetic cluster behavior is induced by Cr3+ dopants and the paramagnetic to ferromagnetic transition temperature TC decreases from 319 to 251 K with increasing Cr3+ content from 0.05 to 0.2. The positive slope of the Arrott plots near TC indicates a second order phase transition. The magnetic entropy change (-ΔSM) is estimated from the isothermal magnetization measurements, and the maximum of the magnetic entropy change (-ΔSmaxM) near TC shows a power law dependence of magnetic field: -ΔSmaxM = m(μ0 H) n with n being close to the predicted value 2/3. The experimental results suggest that the magnetic entropy change and TC can be tuned by changing the Cr3+ ions doping level, which offers an effective method for finding an optimal doping level for magnetic refrigeration near room temperature.

  18. Tuning of magnetoelectric coupling in (1-y)Bi0.8Dy0.2FeO3-yNi0.5Zn0.5Fe2O4 multiferroic composites

    NASA Astrophysics Data System (ADS)

    Mazumdar, S. C.; Khan, M. N. I.; Islam, Md. Fakhrul; Hossain, A. K. M. Akther

    2016-03-01

    Magnetoelectric composites (1-y)Bi0.8Dy0.2FeO3 (BDFO)-yNi0.5Zn0.5Fe2O4 (NZFO) with y=0.0, 0.1, 0.2, 0.3, 0.4, 0.5 and 1.0 are synthesized by conventional solid state reaction route. The X-ray diffraction analysis confirms the coexistence of orthorhombic perovskite BDFO and spinel NZFO phases with no third phase. Microstructural and surface morphology are studied by Field Emission Scanning Electron Microscopy. Quantitative elemental analysis of the samples is carried out by Energy Dispersive X-ray Spectroscopy. The real part of the initial permeability increases and relative quality peak broadens with the ferrite content in the composites. Dielectric constant, loss tangent, relative quality factor and ac conductivity are measured as a function of frequency at room temperature. The dielectric constant shows usual dielectric dispersion at lower frequencies due to Maxwell-Wagner type interfacial polarization. The complex impedance spectroscopy is used to distinguish between the grain and grain boundary contribution to the total resistance. The modulus study reveals the ease of polaron hopping and negligibly small contribution of electrode effect. The magnetic hysteresis has been studied to know the response of NZFO phase to the applied magnetic field in the composite. The saturation and remanent magnetization are found to increase with increase in NZFO in the composite. The magnetoelectric voltage coefficient, αME is measured as a function of applied dc magnetic field. The tuning of ferrite percentage and dc magnetic field results in highest αME (~66 mV/cm Oe) for the composite with 40% NZFO at 4.7 kOe which is attributed to the enhanced mechanical coupling between the two phases. The incorporation of BDFO and NZFO enhances the multiferroic properties in the present composite which are quite promising from application point of view.

  19. Magnetic and optical properties of MgAl2O4-(Ni0.5Zn0.5)Fe2O4 thin films prepared by pulsed laser deposition.

    PubMed

    Misu, Takeshi; Sakamoto, Naonori; Shinozaki, Kazuo; Adachi, Nobuyasu; Suzuki, Hisao; Wakiya, Naoki

    2011-06-01

    Thin films composed of MgAl2O4 and (Ni0.5Zn0.5)Fe2O4 ([MA(100-x)-NZFx] films) were grown on fused SiO2 substrates by pulsed laser deposition. X-ray diffraction measurements revealed that the films were polycrystalline, and that their lattice constant varied linearly with composition, indicating the formation of a solid solution. The film with x=60 was paramagnetic and those with x ≥ 70 were ferromagnetic. The films had a transparency above 75% in the visible range, but the transparency decreased with the x value. The optical band gaps were 2.95, 2.55, 2.30 and 1.89 eV for x=20, 40, 60, 80 and 100, respectively. The Faraday rotation angle increased with x in the visible range, and the film with x=70 exhibited a value of 2000 degrees cm(-1) at 570 nm, which is comparable to the rotation angle of Y3Fe5O12. Owing to their high transparency, which extends into the visible range, the [MA(100-x)-NZFx] films can be used in novel magneto-optical devices.

  20. Doubling the critical current density in superconducting FeSe0.5Te0.5 thin films by low temperature oxygen annealing

    SciTech Connect

    Zhang, Cheng; Si, Weidong; Li, Qiang

    2016-11-14

    Iron chalcogenide superconducting thin films and coated conductors are attractive for potential high field applications at liquid helium temperature for their high critical current densities Jc, low anisotropies, and relatively strong grain couplings. Embedding flux pinning defects is a general approach to increase the in-field performance of superconductors. However, many effective pinning defects can adversely affect the zero field or self-field Jc, particularly in cuprate high temperature superconductors. Here, we report the doubling of the self-field Jc in FeSe0.5Te0.5 films by low temperature oxygen annealing, reaching ~3 MA/cm2. In-field performance is also dramatically enhanced. In conclusion, our results demonstrate that low temperature oxygen annealing is a simple and cost-efficient post-treatment technique which can greatly help to accelerate the potential high field applications of the iron-based superconductors.

  1. EFFECTS OF PRECURSOR SOLUTION MODIFICATION ON THE CRYSTALLINITY AND ELECTRICAL PROPERTIES OF Na0.5Bi0.5TiO3-BiFeO3 BASED THIN FILM

    NASA Astrophysics Data System (ADS)

    Sui, Huiting; Yang, Changhong; Wang, Gaoyun; Feng, Chao

    2014-07-01

    For chemical solution decomposition process, the precursor solution is a basic factor affecting the quality of the deposited-film. In this paper, we choose (l00)-oriented 0.7[(Bi0.95Ce0.05)0.5Na0.5(Ti0.99Fe0.01)O3]-0.3BiFe0.97Mn0.03O3(0.7NBTCeFe-0.3BFOMn) thin films prepared by various precursor solutions for investigation. The roles of precursor solution modification on crystallinity, ferroelectric and dielectric properties are characterized. With the addition of polyethylene glycol into the solution, phase-pure perovskite structure can be obtained. Furthermore, when the volume ratio for the solvents (ethylene glycol to acetic acid) is modified as 2:1, enhanced ferroelectricity can be achieved with a remanent polarization (Pr) of 27.5 μC/cm2, which coincides well with the capacitance-voltage curve with relatively sharp feature. Also, the 0.7NBTCeFe-0.3BFOMn film exhibits a dielectric constant (ɛr) of 576 and dielectric loss (tan δ) of 0.123 at 100 kHz.

  2. Effect of the symmetric cell preparation temperature on the activity of Ba0.5Sr0.5Fe0.8Cu0.2O3-δ as cathode for intermediate temperature Solid Oxide Fuel Cells

    NASA Astrophysics Data System (ADS)

    Vázquez, Santiago; Basbus, Juan; Soldati, Analía L.; Napolitano, Federico; Serquis, Adriana; Suescun, Leopoldo

    2015-01-01

    In this work we studied the electrochemical performance of Ba0.5Sr0.5Fe0.8Cu0.2O3-δ (BSFCu) as cathode for Intermediate Temperature Solid Oxide Fuel Cells (IT-SOFC) with Ce0.9Gd0.1O1.95 (CGO) electrolyte and the effect of the symmetric cell preparation temperature on the oxygen reduction reaction (ORR) activity. Symmetrical cells with the configuration BSFCu/CGO/BSFCu were prepared at 900 °C, 950 °C and 1000 °C to perform the electrochemical characterization in the 500-700 °C temperature range. The resultant area specific resistance (ASR) of the cells with different preparation temperatures followed the tendency: ASR900°C < ASR950°C < ASR1000°C. The symmetric cell constructed at 900 °C showed ASR values of 0.18, 0.078 and 0.035 Ω cm2 at 600, 650 and 700 °C respectively, which demonstrated superior electrochemical activities than previous reports. Additional, X-ray diffraction (XRD), scanning and transmission electron microscopies (SEM and TEM) techniques were used to characterize the microstructure of the original and fired BSFCu materials and correlate it with the cell preparation temperature.

  3. Electrical behaviors of c-axis textured 0.975Bi0.5Na0.5TiO3-0.025BiCoO3 thin films grown by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Guo, Feifei; Yang, Bin; Zhang, Shantao; Liu, Danqing; Wu, Fengmin; Wang, Dali; Cao, Wenwu

    2013-10-01

    The thin films of 0.975Bi0.5Na0.5TiO3-0.025BiCoO3 (BNT-BC) have been successfully deposited on (1 1 1) Pt/Ti/SiO2/Si (1 0 0) substrates by pulse laser deposition and their ferroelectric, dielectric, local piezoelectric properties and temperature dependent leakage current behaviors have been investigated systematically. X-ray diffraction indicates the films are single phased and c-axis oriented. The thin films exhibit ferroelectric polarization-electric field (P-E) hysteresis loop with a remnant polarization (Pr) of 10.0 μC/cm2 and an excellent fatigue resistance property up to 5 × 109 switching cycles. The dielectric constant and dielectric loss are 500 and 0.22 at 1 kHz, respectively. The tunability of the dielectric constant is about 12% at 20 kV/mm. The piezo-phase response hysteresis loop and piezo-amplitude response butterfly curve are observed by switching spectroscopy mode of piezoelectric force microscope (SS-PFM) and the piezoelectric coefficient d33 is about 19-63 pm/V, which is comparable to other reports. The dominant leakage current conduction mechanisms are ohmic conduction at low electric field and Schottky emission at high electric field, respectively. Our results may be helpful for further work on BNT-based thin films with improved electric properties.

  4. Core-shell structure and dielectric properties of (K0.5Na0.5)NbO3-SrZrO3 for high-temperature capacitors

    NASA Astrophysics Data System (ADS)

    Aman, Sanshiro; Kubo, Keiko; Akiba, Hiroki; Iwanaga, Daisuke

    2016-10-01

    The microstructure and dielectric properties of (K0.5Na0.5)NbO3-SrZrO3 were investigated. The dielectric constant is high and stable in a wide temperature range. The rate of change in dielectric constant is within ±10% in the temperature range from -55 to 200 °C. This effect is thought to be due to the core-shell structure composed of a K-rich shell and a Na-rich core, which have different Curie temperatures. This core-shell structure can be controlled on the basis of sintering temperature. The width of the K-rich shell of a sample sintered at 1250 °C is larger than that of a sample sintered at 1180 °C. In addition, the insulation resistance of this material is high at high temperatures. The specific resistance of this material is 109 Ω cm at 200 °C. This material can be used for high-temperature multilayer ceramic capacitors, which have stable capacitance and high reliability at high temperatures.

  5. Visible Light-Induced Photocatalytic and Antibacterial Activity of Li-Doped Bi0.5Na0.45K0.5TiO3-BaTiO3 Ferroelectric Ceramics

    NASA Astrophysics Data System (ADS)

    Kushwaha, H. S.; Halder, Aditi; Jain, D.; Vaish, Rahul

    2015-11-01

    The visible light-active ferroelectric photocatalyst Bi0.5Na0.45Li0.05K0.5TiO3-BaTiO3 (BNKLBT) was synthesized by a solid-state method and its photocatalytic, photoelectrochemical, and antibacterial properties were investigated. In a chronoamperometric study the current density under visible light was 30 μA/cm2, which is three times more than that observed under dark conditions. The compound's visible light photocatalytic activity was investigated for degradation of an organic dye (methyl orange) and an estrogenic pollutant (estriol).The kinetic rate constants calculated for photocatalytic degradation of methyl orange and estriol were 0.007 and 0.056 min-1, respectively. High photocatalytic and photoelectrochemical activity was a result of effective separation of photo-generated charge carriers, because of the ferroelectric nature of the catalyst. The effect of different charge-trapping agents on photocatalytic degradation was studied to investigate the effect of active species and the degradation pathway. Antimicrobial activity was investigated for Escherichia coli and Aspergillus flavus. The anti-bacterial action of BNKLBT was compared with that of the commercial antibiotic kanamycin (k30).

  6. Lead-free 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 nanowires for energy harvesting.

    PubMed

    Zhou, Zhi; Bowland, Christopher C; Malakooti, Mohammad H; Tang, Haixiong; Sodano, Henry A

    2016-03-07

    Lead-free piezoelectric nanowires (NWs) show strong potential in sensing and energy harvesting applications due to their flexibility and ability to convert mechanical energy to electric energy. Currently, most lead-free piezoelectric NWs are produced through low yield synthesis methods and result in low electromechanical coupling, which limit their efficiency as energy harvesters. In order to alleviate these issues, a scalable method is developed to synthesize perovskite type 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 (BZT-BCT) NWs with high piezoelectric coupling coefficient. The piezoelectric coupling coefficient of the BZT-BCT NWs is measured by a refined piezoresponse force microscopy (PFM) testing method and shows the highest reported coupling coefficient for lead-free piezoelectric nanowires of 90 ± 5 pm V(-1). Flexible nanocomposites utilizing dispersed BZT-BCT NWs are fabricated to demonstrate an energy harvesting application with an open circuit voltage of up to 6.25 V and a power density of up to 2.25 μW cm(-3). The high electromechanical coupling coefficient and high power density demonstrated with these lead-free NWs produced via a scalable synthesis method shows the potential for high performance NW-based devices.

  7. Lead-free 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 nanowires for energy harvesting

    NASA Astrophysics Data System (ADS)

    Zhou, Zhi; Bowland, Christopher C.; Malakooti, Mohammad H.; Tang, Haixiong; Sodano, Henry A.

    2016-02-01

    Lead-free piezoelectric nanowires (NWs) show strong potential in sensing and energy harvesting applications due to their flexibility and ability to convert mechanical energy to electric energy. Currently, most lead-free piezoelectric NWs are produced through low yield synthesis methods and result in low electromechanical coupling, which limit their efficiency as energy harvesters. In order to alleviate these issues, a scalable method is developed to synthesize perovskite type 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 (BZT-BCT) NWs with high piezoelectric coupling coefficient. The piezoelectric coupling coefficient of the BZT-BCT NWs is measured by a refined piezoresponse force microscopy (PFM) testing method and shows the highest reported coupling coefficient for lead-free piezoelectric nanowires of 90 +/- 5 pm V-1. Flexible nanocomposites utilizing dispersed BZT-BCT NWs are fabricated to demonstrate an energy harvesting application with an open circuit voltage of up to 6.25 V and a power density of up to 2.25 μW cm-3. The high electromechanical coupling coefficient and high power density demonstrated with these lead-free NWs produced via a scalable synthesis method shows the potential for high performance NW-based devices.

  8. Hierarchical Mesoporous/Macroporous Perovskite La0.5Sr0.5CoO3-x Nanotubes: A Bifunctional Catalyst with Enhanced Activity and Cycle Stability for Rechargeable Lithium Oxygen Batteries.

    PubMed

    Liu, Guoxue; Chen, Hongbin; Xia, Lu; Wang, Suqing; Ding, Liang-Xin; Li, Dongdong; Xiao, Kang; Dai, Sheng; Wang, Haihui

    2015-10-14

    Perovskites show excellent specific catalytic activity toward both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in alkaline solutions; however, small surface areas of the perovskites synthesized by traditional sol-gel methods lead to low utilization of catalytic sites, which gives rise to poor Li-O2 batteries performance and restricts their application. Herein, a hierarchical mesporous/macroporous perovskite La0.5Sr0.5CoO3-x (HPN-LSC) nanotube is developed to promote its application in Li-O2 batteries. The HPN-LSC nanotubes were synthesized via electrospinning technique followed by postannealing. The as-prepared HPN-LSC catalyst exhibits outstanding intrinsic ORR and OER catalytic activity. The HPN-LSC/KB electrode displays excellent performance toward both discharge and charge processes for Li-O2 batteries, which enhances the reversibility, the round-trip efficiency, and the capacity of resultant batteries. The synergy of high catalytic activity and hierarchical mesoporous/macroporous nanotubular structure results in the Li-O2 batteries with good rate capability and excellent cycle stability of sustaining 50 cycles at a current density of 0.1 mA cm(-2) with an upper-limit capacity of 500 mAh g(-1). The results will benefit for the future development of high-performance Li-O2 batteries using hierarchical mesoporous/macroporous nanostructured perovskite-type catalysts.

  9. Electrostatic doping limits and control of magnetism in electrolyte gated LaAlO3(001)/La0.5Sr0.5CoO3-δ thin films

    NASA Astrophysics Data System (ADS)

    Walter, Jeff; Wang, Helin; Leighton, Chris

    Recently developed ionic liquid/gel gating techniques have proven remarkably expedient in the study of charge density effects in a variety of conductors, ranging from organics to complex oxides. Here we present electrolyte gate control of magnetism in ultrathin (8 u.c.) La0.5Sr0.5CoO3-δ (LSCO) films, using ion gels in electric double layer transistors. The LSCO films are initially metallic and ferromagnetic (Tc ~ 170 K), with anomalous Hall conductivity up to 40 S/cm, and strong perpendicular magnetic anisotropy. Based on extensive temperature and gate voltage dependences we first determined the limits for electrostatic vs. electrochemical operation, concluding that negative bias enables reversible hole accumulation, whereas positive bias irreversibly induces oxygen vacancies. Following this we demonstrated clear voltage-control of resistivity, magnetoresistance, andTc. Utilizing the anomalous Hall conductivity as an exceptional probe of the magnetic order parameter in the gated surface region, a 12 K shift in Tc is obtained. This compares favorably to the state-of-the-art and exhibits potential for much larger modulation in films of lower Sr content. Work supported by NSF MRSEC.

  10. Magnetic and optical properties of MgAl2O4-(Ni0.5Zn0.5)Fe2O4 thin films prepared by pulsed laser deposition

    PubMed Central

    Misu, Takeshi; Sakamoto, Naonori; Shinozaki, Kazuo; Adachi, Nobuyasu; Suzuki, Hisao; Wakiya, Naoki

    2011-01-01

    Thin films composed of MgAl2O4 and (Ni0.5Zn0.5)Fe2O4 ([MA(100-x)-NZFx] films) were grown on fused SiO2 substrates by pulsed laser deposition. X-ray diffraction measurements revealed that the films were polycrystalline, and that their lattice constant varied linearly with composition, indicating the formation of a solid solution. The film with x=60 was paramagnetic and those with x ≥ 70 were ferromagnetic. The films had a transparency above 75% in the visible range, but the transparency decreased with the x value. The optical band gaps were 2.95, 2.55, 2.30 and 1.89 eV for x=20, 40, 60, 80 and 100, respectively. The Faraday rotation angle increased with x in the visible range, and the film with x=70 exhibited a value of 2000 degrees cm-1 at 570 nm, which is comparable to the rotation angle of Y3Fe5O12. Owing to their high transparency, which extends into the visible range, the [MA(100-x)-NZFx] films can be used in novel magneto-optical devices. PMID:27877399

  11. Constraining the redshifted 21-cm signal with the unresolved soft X-ray background

    NASA Astrophysics Data System (ADS)

    Fialkov, Anastasia; Cohen, Aviad; Barkana, Rennan; Silk, Joseph

    2017-01-01

    We use the observed unresolved cosmic X-ray background (CXRB) in the 0.5-2 keV band and existing upper limits on the 21-cm power spectrum to constrain the high-redshift population of X-ray sources, focusing on their effect on the thermal history of the Universe and the cosmic 21-cm signal. Because the properties of these sources are poorly constrained, we consider hot gas, X-ray binaries and mini-quasars (i.e. sources with soft or hard X-ray spectra) as possible candidates. We find that (1) the soft-band CXRB sets an upper limit on the X-ray efficiency of sources that existed before the end of reionization, which is one-to-two orders of magnitude higher than typically assumed efficiencies, (2) hard sources are more effective in generating the CXRB than the soft ones, (3) the commonly assumed limit of saturated heating is not valid during the first half of reionization in the case of hard sources, with any allowed value of X-ray efficiency, (4) the maximal allowed X-ray efficiency sets a lower limit on the depth of the absorption trough in the global 21-cm signal and an upper limit on the height of the emission peak, while in the 21-cm power spectrum it sets a minimum amplitude and frequency for the high-redshift peaks, and (5) the existing upper limit on the 21-cm power spectrum sets a lower limit on the X-ray efficiency for each model. When combined with the 21-cm global signal, the CXRB will be useful for breaking degeneracies and helping constrain the nature of high-redshift heating sources.

  12. Investigation on structural, Mössbauer and ferroelectric properties of (1-x)PbFe0.5Nb0.5O3-(x)BiFeO3 solid solution

    NASA Astrophysics Data System (ADS)

    Dadami, Sunanda T.; Matteppanavar, Shidaling; Shivaraja, I.; Rayaprol, Sudhindra; Angadi, Basavaraj; Sahoo, Balaram

    2016-11-01

    In this study, (1-x)PbFe0.5Nb0.5O3(PFN)-(x)BiFeO3(BFO) multiferroic solid solutions with x=0.0, 0.1, 0.2, 0.3 and 0.4 were synthesized through single step solid state reaction method and characterized thoroughly through X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Fourier Transform Infra-Red (FTIR), Raman, Mössbauer spectroscopy and ferroelectric studies. The room temperature (RT) XRD studies confirmed the formation of single phase with negligible amount of secondary phases (x=0.2 and 0.4). The zoomed XRD patterns of (1-x)PFN-(x)BFO solid solutions showed the clear structural phase transition from monoclinic (Cm) to rhombohedral (R3c) at x=0.4. The Raman spectra of the (1-x)PFN-(x)BFO solid solutions showed the composition dependent phase transition from monoclinic (Cm) to rhombohedral (R3c). With increasing x in PFN, the modes related monoclinic symmetry changes to those of rhombohedral symmetry. The RT Mössbauer spectroscopy results evidenced the existence of composition dependent phase transition from paramagnetic to weak antiferromagnetic ordering and weak antiferromagnetic to antiferromagnetic ordering. The Mössbauer spectroscopy showed paramagnetic behavior with a doublet for x=0.0, 0.1 and 0.2 are shows the weak antiferromagnetic with paramagnetic ordering. For x=0.3 and 0.4 shows the sextet pattern and it is a clear evidence of antiferromagnetism. The ferroelectric (P-E) loops at RT indicate the presence of small polarization, as the x concentration increases in PFN, the remnant polarization and coercive field were decreased, which may due to the increase in the conductivity and leaky behavior of the samples.

  13. Influence of structural evolution on energy storage properties in Bi0.5Na0.5TiO3-SrTiO3-NaNbO3 lead-free ferroelectric ceramics

    NASA Astrophysics Data System (ADS)

    Li, Feng; Zhai, Jiwei; Shen, Bo; Liu, Xing; Yang, Ke; Zhang, Yang; Li, Peng; Liu, Baihui; Zeng, Huarong

    2017-02-01

    Lead-free (1-x)(0.8Bi0.5Na0.5TiO3-0.2SrTiO3)-xNaNbO3 (x = 0-0.1, abbreviated as BNT-ST-xNN) ceramics were fabricated by a conventional sintering route with pure perovskite phase via XRD analysis. Raman spectrum was exploited in order to give an insight into the variation of local structural evolution. All compositions exhibited an obvious evolution of dielectric relaxation behaviors. Dielectric and ferroelectric properties clarified that a crossover from nonergodic to ergodic relaxor properties was obtained with the addition of NN content. A relatively large energy storage density was obtained WRec ˜ 0.74 J/cm3 at 7 kV/mm for x = 0.05 at room temperature. Particularly, the energy storage properties exhibited temperature (25-160 °C) and frequency stability (0.1-20 Hz) with WRec around 0.6 J/cm3 at 6 kV/mm for x = 0.05 within the ergodic region. Pulsed discharging current waveforms were measured under different electric fields to detect the energy storage density and discharging speed behavior. An illustration of the charge-discharge process for the nonergodic and ergodic relaxor was depicted in order to disclose the difference of energy storage properties in BNT-ST-xNN system, and it is believed that this concept can be a guideline for fixing a position when designing a new energy-storage system for BNT-based relaxor ferroelectric ceramics.

  14. Performance and sulfur poisoning of Ni/CeO2 impregnated La0.75Sr0.25Cr0.5Mn0.5O3-δ anode in solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Li, Yiqian; Zhang, Yaohui; Zhu, Xingbao; Wang, Zhihong; Lü, Zhe; Huang, Xiqiang; Zhou, Yongjun; Zhu, Lin; Jiang, Wei

    2015-07-01

    In this study, comparison experiments are conducted based on yttria-stabilized zirconia (YSZ) electrolyte supported single solid oxide fuel cells (SOFCs) with pure La0.75Sr0.25Cr0.5Mn0.5O3-δ (LSCrM) or Ni/CeO2 impregnated LSCrM anodes. The single cells are tested in dry H2 and H2/H2S (50 ppm) mixture, respectively. Compared with the pure LSCrM anode, the cell with Ni/CeO2 impregnated LSCrM presents a significant performance improvement when the pure H2 is fueled to the anode, and shows a good stability during a constant-current discharge testing (398 mA cm-2). When the fuel is switched to H2/H2S mixture, the cell with Ni/CeO2 impregnated LSCrM anode still shows a remarkable constant-current discharge (120 mA cm-2) performance compared with pure LSCrM anode. The Ni/CeO2 impregnation can improve the electrochemical performance of the LSCrM anode without any sacrifice of sulfur tolerance ability. The Ni/CeO2 impregnated LSCrM might be a potential anode material for solid oxide fuel cell operating in sulfur-containing fuels. The XRD and XPS results demonstrate that the anode poisoning product is composed of adsorbed sulfur, metal sulfides and sulfate radical. The mass spectrum result confirms that the poisoning mechanism involves the reaction of sulfur with anode rather than the direct reaction between H2S gas and anode.

  15. Preparation Process and Dielectric Properties of Ba(0.5)Sr(0.5)TiO3-P(VDF-CTFE) Nanocomposites

    NASA Technical Reports Server (NTRS)

    Zhang, Lin; Wu, Peixuang; Li, Yongtang; Cheng, Z. -Y.; Brewer, Jeffrey C.

    2014-01-01

    Ceramic-polymer 0-3 nanocomposites, in which nanosized Ba(0.5)Sr(0.5)TiO3 (BST) powders were used as ceramic filler and P(VDF-CTFE) 88/12 mol% [poly(vinylidene fluoridechlorotrifluoroethylene)] copolymer was used as matrix, were studied over a concentration range from 0 to 50 vol.% of BST powders. It is found that the solution cast composites are porous and a hot-press process can eliminate the porosity, which results in a dense composite film. Two different configurations used in the hot-press process are studied. Although there is no clear difference in the uniformity and microstructure of the composites prepared using these two configurations, the composite prepared using one configuration exhibit a higher dielectric constant with a lower loss. For the composite with 40 vol. BST, a dielectric constant of 70 with a loss of 0.07 at 1 kHz is obtained at room temperature. The composites exhibit a lower dielectric loss than the polymer matrix at high frequency. However, at low frequency, the composites exhibit a higher loss than the polymer matrix due to a low frequency relaxation process that appears in the composites. It is believed that this relaxation process is related to the interfacial layer formed between BST particle and the polymer matrix. The temperature dependence of the dielectric property of the composites was studied. It is found that the dielectric constant of these composites is almost independent of the temperature over a temperature range from 20 to 120 C. Key words: A. Polymer-matrix composites (PMCs); B. Electrical Properties; E. Casting; E. Heat treatment; Dielectric properties.

  16. Spin-state transition of iron in (Ba0.5Sr0.5)(Fe0.8Zn0.2)O perovskite

    NASA Astrophysics Data System (ADS)

    Feldhoff, Armin; Martynczuk, Julia; Arnold, Mirko; Myndyk, Maxym; Bergmann, Ingo; Šepelák, Vladimir; Gruner, Wolfgang; Vogt, Ulrich; Hähnel, Angelika; Woltersdorf, Jörg

    2009-11-01

    The redox behavior of iron during heating of a high-performance perovskite for ceramic oxygen separation membranes was studied by combined electron energy-loss (EELS, esp. ELNES) and Mössbauer spectroscopical in situ methods. At room temperature, the iron in (Ba0.5Sr0.5)(Fe0.8Zn0.2)O (BSFZ) is in a mixed valence state of 75% Fe in the high-spin state and 25% Fe predominantly in the low-spin state. When heated to 900C, a slight reduction of iron is observed that increases the quantity of Fe species. However, the dominant occurrence is a gradual transition in the spin-state of trivalent iron from a mixed low-spin/high-spin to a pure high-spin configuration. In addition, a remarkable amount of hybridization is found in the Fe-O bonds that are highly polar rather than purely ionic. The coupled valence/spin-state transition correlates with anomalies in thermogravimetry and thermal expansion behavior observed by X-ray diffraction and dilatometry, respectively. Since the effective cationic radii depend not only on the valence but also on the spin-state, both have to be considered when estimating under which conditions a cubic perovskite will tolerate specific cations. It is concluded that an excellent phase stability of perovskite-based membrane materials demands a tailoring, which enables pure high-spin states under operational conditions, even if mixed valence states are present. The low spin-state transition temperature of BSFZ provides that all iron species are in a pure high-spin configuration already above ca. 500C making this ceramic highly attractive for intermediate temperature applications ( 500-800C).

  17. Brillouin light scattering investigation of the thickness dependence of Dzyaloshinskii-Moriya interaction in C o0.5F e0.5 ultrathin films

    NASA Astrophysics Data System (ADS)

    Belmeguenai, M.; Gabor, M. S.; Roussigné, Y.; Stashkevich, A.; Chérif, S. M.; Zighem, F.; Tiusan, C.

    2016-05-01

    C o0.5F e0.5 (CoFe) ultrathin films of various thicknesses (0.8 nm ≤tCoFe≤1.6 nm ) have been grown by sputtering on (001) MgO single crystal or Si/SiO2 substrates, using Pt as capping or buffer layers, respectively. The x-ray diffraction revealed an in-plane epitaxial (isotropic) growth of Pt on MgO (Si). Their magnetic properties have been studied by vibrating sample magnetometry and Brillouin light scattering (BLS) in the Damon-Eshbach geometry. Vibrating sample magnetometry characterizations show that films grown on MgO are in-plane magnetized, while films deposited on Si are perpendicularly magnetized for CoFe thickness below 1.4 nm. The BLS measurements reveal a pronounced nonreciprocal spin waves propagation, which increases with decreasing CoFe thickness. This nonreciprocity was attributed to an interfacial Dzyaloshinskii-Moriya interaction (DMI) induced by Pt interface with CoFe. Moreover, the DMI sign has been found to depend on the stacks order: it is positive (negative) for CoFe/Pt (Pt/CoFe). The effective thickness dependence of the DMI effective constant shows two regimes due to the degradation of the interfaces as the CoFe thickness decreases. We thus show that the magnetic dead layer should be taken into account to precisely determine the surface DMI constant Ds. Therefore, for the thickest samples, the surface DMI constants are nearly opposite: -1.27 and 1.32 pJ m-1 for Pt/CoFe and its reversed system, respectively.

  18. Magnetic and magnetocaloric properties of the first-order phase transition in Sm0.5+ x Sr0.5- x MnO3 compounds

    NASA Astrophysics Data System (ADS)

    Thanh, Tran Dang; Linh, Dinh Chi; Manh, Tien Van; Nan, Wen-Zhe; Yu, Seong-Cho; Piao, Hong-Guang; Pan, Liqing

    2016-08-01

    In this work, we present a detailed study on the magnetic and the magnetocaloric properties of Sm0.5+ x Sr0.5- x MnO3 compounds with x = 0 - 0.1, which were prepared by using a solid-state reaction method. The x-dependent magnetic, as well as magnetocaloric, properties, including the magnetic phase transition, have been studied. The increase in Sm/Sr ratio plays an important role in controlling the Curie temperature ( T C ). We point out that all the samples undergo a first-order phase transition and exhibit a giant magnetocaloric effect. The magnetic entropy change (Δ S m ) of samples was calculated based on isothermal M( H, T) data. The maximum value of Δ S m (denoted as |Δ S max|) at around T C is found to be 2.6 - 8.9 J·kg -1·K -1 for Δ H = 30 kOe and depends on the value of x. We have also used the universal master curve method for the temperature dependences of Δ S m curves measured at different Δ H values, Δ S m ( T,Δ H), to distinguish the magnetic order in the samples. Interestingly, none of the Δ S m ( T,Δ H) curves for the samples follow the universal master curve, Δ S m ( T,Δ H)/Δ S max versus θ = ( T -T C )/( T r - T C ). As a consequence, a breakdown in the universal behavior of Δ S m ( T,Δ H)/Δ S max versus θ curve is another feature confirming a first-order phase-transition nature.

  19. Strain heterogeneity and magnetoelastic behaviour of nanocrystalline half-doped La, Ca manganite, La0.5Ca0.5MnO3.

    PubMed

    Pagliari, L; Dapiaggi, M; Maglia, F; Sarkar, T; Raychaudhuri, A K; Chatterji, T; Carpenter, M A

    2014-10-29

    Elastic and anelastic properties of La0.5Ca0.5MnO3 determined by resonant ultrasound spectroscopy in the frequency range ∼100-1200 kHz have been used to evaluate the role of grain size in determining the competition between ferromagnetism and Jahn-Teller/charge order of manganites which show colossal magneto resistance. At crystallite sizes of ∼75 and ∼135 nm the dominant feature is softening of the shear modulus as the charge order transition point, Tco (∼225 K), is approached from above and below, matching the form of softening seen previously in samples with 'bulk' properties. This is consistent with a bilinear dominant strain/order parameter coupling, which occurs between the tetragonal shear strain and the Jahn-Teller (Γ3(+)) order parameter. At crystallite sizes of ∼34 and ∼42 nm the charge ordered phase is suppressed but there is still softening of the shear modulus, with a minimum near Tco. This indicates that some degree of pseudoproper ferroelastic behaviour is retained. The primary cause of the suppresion of the charge ordered structure in nanocrystalline samples is therefore considered to be due to suppression of macroscopic strain, even though MnO6 octahedra must develop some Jahn-Teller distortions on a local length scale. This mechanism for stabilizing ferromagnetism differs from imposition of either an external magnetic field or a homogeneous external strain field (from a substrate), and is likely to lead both to local strain heterogeneity within the nanocrystallites and to different tilting of octahedra within the orthorhombic structure. An additional first order transition occurs near 40 K in all samples and appears to involve some very small strain contrast between two ferromagnetic structures.

  20. Improved electrochemical properties of LiFe0.5Mn0.5PO4/C composite materials via a surface coating process

    NASA Astrophysics Data System (ADS)

    Yang, Chun-Chen; Hung, Yen-Wei; Lue, Shingjiang Jessie

    2016-09-01

    In this work, a LiFe0.5Mn0.5PO4/C (LFMP/C) material was prepared by a simple solid-state ball-mill method by using LiH2PO4, γ-MnO2, and hollow α-Fe2O3 nano-sized materials. Both γ-MnO2 and hollow α-Fe2O3 were synthesized by a hydrothermal process. LFMP/C composites coated with different amounts (1-3wt%) of Li4Ti5O12 (LTO) were synthesized by a sol-gel method. Their typical properties are studied using X-ray diffraction, micro-Raman spectroscopy, scanning electron microscopy/energy-dispersive X-ray spectroscopy, transmission electron microscopy, the AC impedance method, and the galvanostatic charge-discharge method. The results revealed that a 1 wt%-LTO-coated LFMP/C composite shows the highest performance among all LFMP/C composite samples. The long-term cycling performance of the LFMP/C composite improves considerably when the LTO ionic conductor is applied on it. Moreover, the 1 wt%-LTO-coated LFMP/C composite, which has the lowest fading rate, maintains high cycling stability at 1 C (141 mAh g-1) and 10 C (133 mAh g-1) at 55 °C after 100 cycles; by contrast, a bare LFMP/C sample, which demonstrates the highest fading rate, exhibits an unfavorable life cycle, and its discharge capacity decreases rapidly. The ionic conductor coating thus improves the high-temperature performance of LFMP/C composites. A LFMP/C-KS6/SiO2 full cell is assembled and tested.

  1. Conduction phenomenon of Al3+ modified lead free (Na0.5Bi0.5)0.92Ba0.08TiO3 electroceramics

    NASA Astrophysics Data System (ADS)

    Borkar, Hitesh; Kumar, Ashok

    2016-05-01

    Choice of proper dopants at A or B-site of ABO3 perovskite structure can modify the morphotropic phase boundary (MPB), and hence functional properties of polar systems. The chemical nature of donor or acceptor will significantly influence the fundamental properties. Lead-free ferroelectrics have vast potential to replace the lead-based ceramics. The (Na0.5Bi0.5)1-xBaxTiO3 (NBT-BT) (at x=0.08) near MPB with small substitution of trivalent cations (Al3+) has been synthesized by solid state reaction route. The aim to choose the trivalent cations (Al3+) was its relatively smaller radii than that of Bi3+ cations to develop the antipolar phases in the ferroelectric ceramic. Structural, morphological and elemental compositional analyses were studied by X-ray diffraction (XRD), Secondary electron microscope (SEM) and Energy-dispersive X-ray spectroscopy (EDAX), respectively. Ferroelectric studies were carried out on various compositions of (Na0.46Bi0.46-xAlxBa0.08)TiO3 (NBAT-BT) (x=0, 0.05, 0.07, 0.10) electroceramics. It was observed that with increase in concentration of Al the ferroelectricity state changes from soft to hard. Temperature dependent dielectric spectroscopy shows broad dielectric dispersion. The Al doping diminishes the relaxor behavior of NBT-BT ceramics. Impedance spectroscopy shows that electrical resistivity and relaxation frequency decreases with increase in Al-concentration. Modulus spectra indicate that Al significantly change the bulk capacitance of NBT-BT.

  2. The 0.5 micrometer-2.2 micrometer Scattered Light Spectrum of the Disk Around TW Hya

    NASA Technical Reports Server (NTRS)

    Debes, John H.; Jang-Condell, Hannah; Weinberger, Alycia J.; Roberg, Aki; Schneider, Glenn

    2012-01-01

    We present a 0.5-2.2micron scattered light spectrum of the circumstellar disk around TW Hya from a combination of spatially resolved HST STIS spectroscopy and NICMOS coronagraphic images of the disk. \\Ve investigate the morphology at the disk at distances> 40 AU over this wide range of wavelengths. We measure the surface brightness, azimuthal symmetry, and spectral character of the disk as a function of radius. We find that the scattering efficiency of the dust is largely neutral to blue over the observed wavelengths. We find a good fit to the data over a wide range of distances from the star if we use a model disk with a partial gap of 30% depth at 80 AU and with steep disk truncation exterior to 100 AU. If the gap is caused by a planetary companion in the process of accreting disk gas, it must be less than 20 Solar mass.

  3. Thermoelectric properties of Cu-dispersed bi0.5sb1.5te3.

    PubMed

    Kim, Il-Ho; Choi, Soon-Mok; Seo, Won-Seon; Cheong, Dong-Ik

    2012-01-05

    A novel and simple approach was used to disperse Cu nanoparticles uniformly in the Bi0.5Sb1.5Te3 matrix, and the thermoelectric properties were evaluated for the Cu-dispersed Bi0.5Sb1.5Te3. Polycrystalline Bi0.5Sb1.5Te3 powder prepared by encapsulated melting and grinding was dry-mixed with Cu(OAc)2 powder. After Cu(OAc)2 decomposition, the Cu-dispersed Bi0.5Sb1.5Te3 was hot-pressed. Cu nanoparticles were well-dispersed in the Bi0.5Sb1.5Te3 matrix and acted as effective phonon scattering centers. The electrical conductivity increased systematically with increasing level of Cu nanoparticle dispersion. All specimens had a positive Seebeck coefficient, which confirmed that the electrical charge was transported mainly by holes. The thermoelectric figure of merit was enhanced remarkably over a wide temperature range of 323-523 K.PACS: 72.15.Jf: 72.20.Pa.

  4. Thermoelectric properties of Cu-dispersed bi0.5sb1.5te3

    NASA Astrophysics Data System (ADS)

    Kim, Il-Ho; Choi, Soon-Mok; Seo, Won-Seon; Cheong, Dong-Ik

    2012-01-01

    A novel and simple approach was used to disperse Cu nanoparticles uniformly in the Bi0.5Sb1.5Te3 matrix, and the thermoelectric properties were evaluated for the Cu-dispersed Bi0.5Sb1.5Te3. Polycrystalline Bi0.5Sb1.5Te3 powder prepared by encapsulated melting and grinding was dry-mixed with Cu(OAc)2 powder. After Cu(OAc)2 decomposition, the Cu-dispersed Bi0.5Sb1.5Te3 was hot-pressed. Cu nanoparticles were well-dispersed in the Bi0.5Sb1.5Te3 matrix and acted as effective phonon scattering centers. The electrical conductivity increased systematically with increasing level of Cu nanoparticle dispersion. All specimens had a positive Seebeck coefficient, which confirmed that the electrical charge was transported mainly by holes. The thermoelectric figure of merit was enhanced remarkably over a wide temperature range of 323-523 K. PACS: 72.15.Jf: 72.20.Pa

  5. The efficacy of topical ivermectin versus malation 0.5% lotion for the treatment of scabies.

    PubMed

    Goldust, Mohamad; Rezaee, Elham

    2013-05-06

    Objective: There are different medications for the treatment of scabies but the treatment of choice is still controversial. This study aimed at comparing the efficacy of topical ivermectin versus malation 0.5% lotion for the treatment of scabies. Methods: In total, 340 patients with scabies were enrolled, and randomized into two groups: the first group received 1% ivermectin applied topically to the affected skin and the second group received topical malation 0.5% lotion and were told to apply this twice with 1 week interval. Treatment was evaluated at intervals of 2 and 4 weeks, and if there was treatment failure at the 2-week follow-up, treatment was repeated. Results: Two application of topical ivermectin provided a cure rate of 67.6% at the 2-week follow-up, which increased to 85.2% at the 4-week follow-up after repeating the treatment. Treatment with two applications of malation 0.5% lotion was effective in 44.1% of patients at the 2-week follow-up, which increased to 67.6% at the 4-week follow-up after this treatment was repeated. Conclusion:Two application of ivermectin was as effective as single applications of malation 0.5% lotion at the 2-week follow-up. After repeating the treatment, ivermectin was superior to malation 0.5% lotion at the 4-week follow up.

  6. The electrochemical behaviors of Mg-8Li-3Al-0.5Zn and Mg-8Li-3Al-1.0Zn in sodium chloride solution

    NASA Astrophysics Data System (ADS)

    Lv, Yanzhuo; Liu, Min; Xu, Yan; Cao, Dianxue; Feng, Jing

    2013-03-01

    The electrochemical oxidation behaviors of Mg-8Li-3Al-0.5Zn and Mg-8Li-3Al-1.0Zn electrodes in 0.7 mol L-1 NaCl solution are investigated by methods of potentiodynamic polarization, potentiostatic oxidation, electrochemical impedance spectroscopy and scanning electron microscopy. The phase composition of Mg-8Li-3Al-0.5Zn and Mg-8Li-3Al-1.0Zn alloys is analyzed conducted by X-ray diffraction. The performances of Mg-8Li-3Al-0.5Zn and Mg-8Li-3Al-1.0Zn as the anode of Mg-H2O2 semi fuel cells are determined. The effect of Zn content on the corrosion resistant of these Mg-Li-based alloys is studied. It is found that the Mg-8Li-3Al-0.5Zn electrode has higher discharge activity and less corrosion resistance than that of Mg-8Li-3Al-1.0Zn electrode in 0.7 mol L-1 NaCl solution. The Mg-H2O2 semi fuel cell with Mg-8Li-3Al-0.5Zn anode presents a maximum power density of 100 mW cm-2 at room temperature, which is higher than that of Mg-8Li-3Al-1.0Zn anode (80 mW cm-2). The performance of semi fuel cell with the Mg-8Li-3Al-0.5Zn electrode is better than that with Mg-8Li-3Al-1.0Zn electrode, especially at higher current density (>30 mA cm-2).

  7. Thermal shock behavior of W-0.5 wt% Y2O3 alloy prepared via a novel chemical method

    NASA Astrophysics Data System (ADS)

    Zhao, Mei-Ling; Luo, Lai-Ma; Lin, Jing-Shan; Zan, Xiang; Zhu, Xiao-Yong; Luo, Guang-Nan; Wu, Yu-Cheng

    2016-10-01

    A wet-chemical method combined with spark plasma sintering was used to prepare W-0.5 wt% Y2O3 alloy. The W-0.5 wt% Y2O3 precursor was reduced at 800 °C for 4 h under different hydrogen flow rates of 300, 400, 500, 600, and 700 ml/min. The reduced powder was analyzed by X-ray diffraction (XRD), laser particle size analyzer (LPSA), and scanning electron microscopy (SEM). An optimized process for reducing precursor was discussed. After sintering, the specimens were exposed to different laser beam irradiation energies (90, 120, 150, and 180 W) to simulate loads as expected for edge localized modes (ELMs). Top surface and cross-sectional morphology were observed by SEM, and the changes in hardness were evaluated. The changes in microstructural properties (i.e., Y2O3-particle distribution, crack propagation direction, depth of thermal shock effect, and grain size of the recrystallization region) after thermal shock were investigated.

  8. Serpentine Nanotubes in CM Chondrites

    NASA Technical Reports Server (NTRS)

    Zega, Thomas J.; Garvie, Laurence A. J.; Dodony, Istvan; Buseck, Peter R.

    2004-01-01

    The CM chondrites are primitive meteorites that formed during the early solar system. Although they retain much of their original physical character, their matrices and fine-grained rims (FGRs) sustained aqueous alteration early in their histories [1- 3]. Serpentine-group minerals are abundant products of such alteration, and information regarding their structures, compositions, and spatial relationships is important for determining the reactions that produced them and the conditions under which they formed. Our recent work on FGRs and matrices of the CM chondrites has revealed new information on the structures and compositions of serpentine-group minerals [4,5] and has provided insights into the evolution of these primitive meteorites. Here we report on serpentine nanotubes from the Mighei and Murchison CM chondrites [6].

  9. Clustering of galaxies around the GRB 021004 sight-line at z ~ 0.5

    NASA Astrophysics Data System (ADS)

    Sokolov, Ilya V.; Castro-Tirado, A. J.; Verkhodanov, O. V.; Zhelenkova, O. P.; Baryshev, Yu. V.

    2016-06-01

    In this report we test for reliability any signatures of field galaxies clustering in the GRB 021004 line of sight. The first signature is the BTA and Hubble GRB 021004 field photometric redshift distribution with a peak at z ~ 0.5 estimated from multicolor photometry. The second signature is the MgII 2796,2803 absorption doublet at z ~ 0.5 in the GRB 021004 afterglow spectrum. The third signature is some inhomogeneity in Plank + GRB 021004 fields. And the fourth signature may be the galaxy clustering with an effective redshift of z = 0.5 from the Baryon Oscillation Spectroscopic Survey (BOSS), which is a part of the Sloan Digital Sky Survey III (SDSS-III).

  10. The modified equipartition calculation for supernova remnants with the spectral index α = 0.5

    NASA Astrophysics Data System (ADS)

    Urošević, Dejan; Pavlović, Marko Z.; Arbutina, Bojan; Dobardžić, Aleksandra

    2015-03-01

    Recently, the modified equipartition calculation for supernova remnants (SNRs) has been derived by Arbutina et al. (2012). Their formulae can be used for SNRs with the spectral indices between 0.5 < α < 1. Here, by using approximately the same analytical method, we derive the equipartition formulae useful for SNRs with spectral index α=0.5. These formulae represent next step upgrade of Arbutina et al. (2012) derivation, because among 30 Galactic SNRs with available observational parameters for the equipartition calculation, 16 have spectral index α = 0.5. For these 16 Galactic SNRs we calculated the magnetic field strengths which are approximately 40 per cent higher than those calculated by using Pacholczyk (1970) equipartition and similar to those calculated by using Beck & Krause (2005) calculation.

  11. A 'rule of 0.5' for the metabolite-likeness of approved pharmaceutical drugs.

    PubMed

    O Hagan, Steve; Swainston, Neil; Handl, Julia; Kell, Douglas B

    We exploit the recent availability of a community reconstruction of the human metabolic network ('Recon2') to study how close in structural terms are marketed drugs to the nearest known metabolite(s) that Recon2 contains. While other encodings using different kinds of chemical fingerprints give greater differences, we find using the 166 Public MDL Molecular Access (MACCS) keys that 90 % of marketed drugs have a Tanimoto similarity of more than 0.5 to the (structurally) 'nearest' human metabolite. This suggests a 'rule of 0.5' mnemonic for assessing the metabolite-like properties that characterise successful, marketed drugs. Multiobjective clustering leads to a similar conclusion, while artificial (synthetic) structures are seen to be less human-metabolite-like. This 'rule of 0.5' may have considerable predictive value in chemical biology and drug discovery, and may represent a powerful filter for decision making processes.

  12. Single crystal growth, crystal structure characterization and magnetic properties of UCo0.5Sb2

    SciTech Connect

    Bukowski, Z. . E-mail: bukowski@int.pan.wroc.pl; Tran, V.H.; Stepien-Damm, J.; Troc, R.

    2004-11-01

    Single crystals of uranium intermetallic compound UCo0.5Sb2 were grown by means of the antimony-flux technique. The characterization of the samples has been carried out utilizing single crystal X-ray diffraction and magnetization measurements. UCo0.5Sb2 is found to crystallize in the tetragonal HfCuSi2-type structure, space group P4/nmm with Z=2 formula units per cell, and the lattice parameters a=0.4300(1) and c=0.8958(2)nm. The refinement of the occupancy parameters and the energy dispersive X-ray analysis have indicated a distinct deficiency on the cobalt sites. The results of magnetization measurements showed that UCo0.5Sb2 orders ferromagnetically below 65K with a huge magnetocrystalline anisotropy with the c direction being the easy magnetization axis.

  13. Polarization switching characteristics of 0.5BaTi{sub 0.8}Zr{sub 0.2}O{sub 3}-0.5Ba{sub 0.7}Ca{sub 0.3}TiO{sub 3} lead free ferroelectric thin films by pulsed laser deposition

    SciTech Connect

    Kolekar, Y. D.; Bhaumik, A.; Ghosh, K.; Shaikh, P. A.; Ramana, C. V.

    2014-04-21

    We report on the ferroelectricity for morphotropic-phase-boundary lead (Pb) free 0.5BaTi{sub 0.8}Zr{sub 0.2}O{sub 3}-0.5Ba{sub 0.7}Ca{sub 0.3}TiO{sub 3} (0.5BZT-0.5BCT) thin films. Thin films were grown on Pt/Ti/SiO{sub 2}/Si substrate using pulsed laser deposition. Raman spectroscopic data combined with the X-ray diffraction analyses confirm body centered tetragonal crystallographic structure 0.5BZT-0.5 BCT thin films on Pt/Ti/SiO{sub 2}/Si. Polarization studies demonstrate that these 0.5BZT-0.5BCT films exhibit a large remnant and saturation polarization of 37 μC/cm{sup 2} and 40 μC/cm{sup 2}, respectively, with a coercive field of 140 kV/cm. A correlation between polarization dynamics, structural distortion, and phonon vibration is established. The splitting of X-ray diffraction peak of the thin film in the 2θ range of 44.5° to 46.5° represents high degree of tetragonality. The tetragonality factor calculated by Rietveld analysis was found to be 0.006 and can be a major cause for the increased remnant polarization value. It is established from Raman spectra that the non-centrosymmetricity due to the displacement of Ti/Zr ions from its octahedral position is related to the peak position as well as the broadening of the A{sub 1} (LO) optical phonon mode. This increase of broadness in the thin film causes an increase in the dipole moment of the unit cell and, hence, the net increase in polarization values.

  14. Early fluid resuscitation with hyperoncotic hydroxyethyl starch 200/0.5 (10%) in severe burn injury

    PubMed Central

    2010-01-01

    Introduction Despite large experience in the management of severe burn injury, there are still controversies regarding the best type of fluid resuscitation, especially during the first 24 hours after the trauma. Therefore, our study addressed the question whether hyperoncotic hydroxyethyl starch (HES) 200/0.5 (10%) administered in combination with crystalloids within the first 24 hours after injury is as effective as 'crystalloids only' in severe burn injury patients. Methods 30 consecutive patients were enrolled to this prospective interventional open label study and assigned either to a traditional 'crystalloids only' or to a 'HES 200/0.5 (10%)' volume resuscitation protocol. Total amount of fluid administration, complications such as pulmonary failure, abdominal compartment syndrome, sepsis, renal failure and overall mortality were assessed. Cox proportional hazard regression analysis was performed for binary outcomes and adjustment for potential confounders was done in the multivariate regression models. For continuous outcome parameters multiple linear regression analysis was used. Results Group differences between patients receiving crystalloids only or HES 200/0.5 (10%) were not statistically significant. However, a large effect towards increased overall mortality (adjusted hazard ratio 7.12; P = 0.16) in the HES 200/0.5 (10%) group as compared to the crystalloids only group (43.8% versus 14.3%) was present. Similarly, the incidence of renal failure was 25.0% in the HES 200/0.5 (10%) group versus 7.1% in the crystalloid only group (adjusted hazard ratio 6.16; P = 0.42). Conclusions This small study indicates that the application of hyperoncotic HES 200/0.5 (10%) within the first 24 hours after severe burn injury may be associated with fatal outcome and should therefore be used with caution. Trial registration NCT01120730. PMID:20584291

  15. The APSU 0.5m Telescope: Helping to Transform Undergraduate Education

    NASA Astrophysics Data System (ADS)

    Buckner, Spencer L.; Allyn Smith, J.; Juelfs, Elizabeth; Gaither, Bryan; Wilson, Tyler; Roberts, Fred

    2016-01-01

    We present details of the newly rebuilt APSU 0.5m telescope and discuss its role in the Physics & Astronomy curriculum at Austin Peay State University. This telescope enables advanced astronomical course work, student projects, a small research capability, and a large public outreach effort for the APSU Physics & Astronomy Department.We discuss the basic capabilities of the telescope, the current instrument suite including potential growth options for the 0.5m, our plans for student led and faculty research efforts, and early EPO work. Initial results from the commissioning data are presented to illustrate the research and imaging capabilities of the system.

  16. Strain induced modulation of the correlated transport in epitaxial Sm0.5Nd0.5NiO3 thin films.

    PubMed

    Zhang, L; Gardner, H J; Chen, X G; Singh, V R; Hong, X

    2015-04-10

    We report a study of the effect of epitaxial strain on the correlated transport properties of 2-40 nm Sm0.5Nd0.5NiO3 (SNNO) films grown on different substrates. The metal-insulator transition (MIT) temperature T(MI) of the SNNO films increases with increasing tensile strain. While films on (0 0 1) LaAlO3 and (1 1 0) NdGaO3 substrates exhibit a sharp MIT and thermal hysteresis in the cooling-heating cycle, signaling a first-order transition, films on (0 0 1) SrTiO3 show a broad, second-order MIT. Hall effect measurements reveal hole-type charge carriers and thermally activated temperature dependence of the carrier density below T(MI). The corresponding activation energy is ∼80 meV for films on LaAlO3 and NdGaO3, and is suppressed to 25 meV for films on SrTiO3. The carrier mobility in the metallic state and variable range hopping (VRH) transport at a low temperature point significantly enhanced electron localization in SNNO on STO, which we believe is not simply driven by extrinsic effects such as oxygen vacancies, but rather is an intrinsic characteristic for films subject to tensile strain due to the elongated Ni-O bond and hence enhanced dynamic Jahn-Teller distortion. In ultrathin films above the electrical dead layer thickness (2-3 nm), we observe a more than 100 K increase of T(MI) for films on LaAlO3, which has been correlated with a crossover from 3D to 2D transport as revealed from VRH. We attribute the distinct transport characteristics to strain induced modulation of various energy scales associated with the Ni-O-Ni bond angle and Ni-O bond length, which collectively determine the delocalization bandwidth of the system.

  17. Investigation of scanning tunneling spectra on iron-based superconductor FeSe0.5Te0.5(in Chinese)

    DOE PAGES

    Du, Z. -Y.; Fang, D. -L.; Wang, Z. -Y.; ...

    2015-05-05

    FeSe0.5Te0.5 single crystals with superconducting critical temperature of 13.5 K are investigated by scanning tunneling microscopy/spectroscopy (STM/STS) measureflents in detail. STM image on the top surface shows an atomically resolved square lattice consisted by white and dark spots with a constant of about 3.73± 0.03 Å which is consistent with the lattice constant 3.78 Å. The Se and Te atoms with a height difference of about 0.35 Å are successfully identified since the sizes of the two kinds of atoms are different. The tunneling spectra show very large zero-bias conductance value and asymmetric coherent peaks in the superconducting state. Accordingmore » to the positions of coherence peaks, we determine the superconducting gap 2Δ = 5.5 meV, and the reduced gap 2Δ/kBTc = 4.9 is larger than the value predicted by the weak-coupling BCS theory. The zero-bias conductance at 1.7 K only have a decrease of about 40% compared with the normal state conductance, which may originate from some scattering and broadening mechanism in the material. This broadening effect will also make the superconducting gap determined by the distance between the coherence peaks larger than the exact gap value. The asymmetric structure of the tunneling spectra near the superconducting gap is induced by the hump on the background. This hump appears at temperature more than twice the superconducting critical temperature. This kind of hump has also been observed in other iron pnictides and needs further investigation. A possible bosonic mode outside the coherence peak with a mode energy Ω of about 5.5 meV is observed in some tunneling spectra, and the ratio between the mode energy and superconducting transition temperature Ω/kBTc ≈ 4.7 is roughly consistent with the universal ratio 4.3 in iron-based superconductors. The high-energy background of the spectra beyond the superconducting gaps shows a V-shape feature. The slopes of the differential conductance spectra at high energy are

  18. The effects of Na on high pressure phases of CuIn(0.5)Ga(0.5)Se(2) from ab initio calculation.

    PubMed

    Pluengphon, P; Bovornratanaraks, T; Vannarat, S; Pinsook, U

    2012-03-07

    The effects of Na atoms on high pressure structural phase transitions of CuIn(0.5)Ga(0.5)Se(2) (CIGS) were studied by an ab initio method using density functional theory. At ambient pressure, CIGS is known to have chalcopyrite (I42d) structure. The high pressure phase transitions of CIGS were proposed to be the same as the order in the CuInSe(2) phase transitions which are I42d → Fm3m → Cmcm structures. By using the mixture atoms method, the Na concentration in CIGS was studied at 0.1, 1.0 and 6.25%. The positive mixing enthalpy of Na at In/Ga sites (Na(InGa)) is higher than that of Na at Cu sites (Na(Cu)). It confirmed previous studies that Na preferably substitutes on the Cu sites more than the (In, Ga) sites. From the energy-volume curves, we found that the effect of the Na substitutes is to reduce the hardness of CIGS under high pressure. The most significant effects occur at 6.25% Na. We also found that the electronic density of states of CIGS near the valence band maximum is increased noticeably in the chalcopyrite phase. The band gap is close in the cubic and orthorhombic phases. Also, the Na(Cu)-Se bond length in the chalcopyrite phase is significantly reduced at 6.25% Na, compared with the pure Cu-Se bond length. Consequently, the energy band gap in this phase is wider than in pure CIGS, and the gap increased at the rate of 31 meV GPa(-1) under pressure. The Na has a small effect on the transition pressure. The path of transformation from the cubic to orthorhombic phase was derived. The Cu-Se plane in the cubic phase displaced relatively parallel to the (In, Ga)-Se plane by 18% in order to transform to the Cmcm phase. The enthalpy barrier is 0.020 eV/atom, which is equivalent to a thermal energy of 248 K. We predicted that Fm3m and Cmcm can coexist in some pressure range.

  19. Investigation of scanning tunneling spectra on iron-based superconductor FeSe0.5Te0.5

    SciTech Connect

    Du, Z. -Y.; Fang, D. -L.; Wang, Z. -Y.; Du, G.; Yang, X.; Yang, H.; Gu, G.; -H, Wen H.

    2015-05-05

    FeSe0.5Te0.5 single crystals with superconducting critical temperature of 13.5 K are investigated by scanning tunneling microscopy/spectroscopy (STM/STS) measureflents in detail. STM image on the top surface shows an atomically resolved square lattice consisted by white and dark spots with a constant of about 3.73± 0.03 Å which is consistent with the lattice constant 3.78 Å. The Se and Te atoms with a height difference of about 0.35 Å are successfully identified since the sizes of the two kinds of atoms are different. The tunneling spectra show very large zero-bias conductance value and asymmetric coherent peaks in the superconducting state. According to the positions of coherence peaks, we determine the superconducting gap 2Δ = 5.5 meV, and the reduced gap 2Δ/kBTc = 4.9 is larger than the value predicted by the weak-coupling BCS theory. The zero-bias conductance at 1.7 K only have a decrease of about 40% compared with the normal state conductance, which may originate from some scattering and broadening mechanism in the material. This broadening effect will also make the superconducting gap determined by the distance between the coherence peaks larger than the exact gap value. The asymmetric structure of the tunneling spectra near the superconducting gap is induced by the hump on the background. This hump appears at temperature more than twice the superconducting critical temperature. This kind of hump has also been observed in other iron pnictides and needs further investigation. A possible bosonic mode outside the coherence peak with a mode energy Ω of about 5.5 meV is observed in some tunneling spectra, and the ratio between the mode energy and superconducting transition temperature Ω/kBTc ≈ 4.7 is roughly consistent with the universal ratio 4.3 in iron-based superconductors. The high-energy background of the spectra beyond the superconducting gaps shows a V-shape feature. The slopes of the differential conductance spectra at high

  20. Elastic and magnetoelastic relaxation behaviour of multiferroic (ferromagnetic + ferroelectric + ferroelastic) Pb(Fe0.5Nb0.5)O3 perovskite

    NASA Astrophysics Data System (ADS)

    Carpenter, M. A.; Schiemer, J. A.; Lascu, I.; Harrison, R. J.; Kumar, A.; Katiyar, R. S.; Ortega, N.; Sanchez, D. A.; Salazar Mejia, C.; Schnelle, W.; Echizen, M.; Shinohara, H.; Heap, A. J. F.; Nagaratnam, R.; Dutton, S. E.; Scott, J. F.

    2015-07-01

    Resonant Ultrasound Spectroscopy has been used to characterize elastic and anelastic anomalies in a polycrystalline sample of multiferroic Pb(Fe0.5Nb0.5)O3 (PFN). Elastic softening begins at ~550 K, which is close to the Burns temperature marking the development of dynamical polar nanoregions. A small increase in acoustic loss at ~425 K coincides with the value of T* reported for polar nanoregions starting to acquire a static or quasi-static component. Softening of the shear modulus by ~30-35% through ~395-320 K, together with a peak in acoustic loss, is due to classical strain/order parameter coupling through the cubic → tetragonal → monoclinic transition sequence of ferroelectric/ferroelastic transitions. A plateau of high acoustic loss below ~320 K is due to the mobility under stress of a ferroelastic microstructure but, instead of the typical effects of freezing of twin wall motion at some low temperature, there is a steady decrease in loss and increase in elastic stiffness below ~85 K. This is attributed to freezing of a succession of strain-coupled defects with a range of relaxation times and is consistent with a report in the literature that PFN develops a tweed microstructure over a wide temperature interval. No overt anomaly was observed near the expected Néel point, ~145 K, consistent with weak/absent spin/lattice coupling but heat capacity measurements showed that the antiferromagnetic transition is actually smeared out or suppressed. Instead, the sample is weakly ferromagnetic up to ~560 K, though it has not been possible to exclude definitively the possibility that this could be due to some magnetic impurity. Overall, evidence from the RUS data is of a permeating influence of static and dynamic strain relaxation effects which are attributed to local strain heterogeneity on a mesoscopic length scale. These, in turn, must have a role in determining the magnetic properties and multiferroic character of PFN.

  1. Raman, dielectric and variable range hopping nature of Gd2O3-doped K0.5N0.5NbO3 piezoelectric ceramics

    NASA Astrophysics Data System (ADS)

    Peddigari, Mahesh; Dobbidi, Pamu

    2015-10-01

    (K0.5Na0.5)NbO3 (KNN) + x wt% Gd2O3 (x = 0 -1.5) ceramics have been prepared by conventional solid state reaction method. The effect of Gd2O3 on the structural, microstructural and dielectric properties of KNN ceramics were studied systematically. The effect of Gd2O3 on phase transformation from orthorhombic to psuedocubic structure is explained interms of changes in the internal vibration modes of NbO6 octahedra. The Raman intensity of the stretching mode v1 enhanced and shifted toward higher wavenumber with Gd2O3 concentration, which is attributed to the increase in polarizability and change in the O-Nb-O bond angles. Microstructural analysis revealed that the grain size of the KNN ceramics decreases from 2.26 ± 1.07 μm to 0.35 ± 0.13 μm and becomes homogenous with an increase in Gd2O3 concentration. The frequency dependent dielectric spectra are analyzed by using Havriliak-Negami function. The fitted symmetry parameter and relaxation time (τ) are found to be 0.914 and 8.78 × 10-10 ± 5.5 × 10-11 s, respectively for the sample doped with x = 1.0. The addition of Gd2O3 to the KNN shifted the polymorphic phase transition orthorhombic to tetragonal transition temperature (TO-T) from 199oC to 85oC with enhanced dielectric permittivity (ɛ' = 1139 at 1 MHz). The sample with x = 1.0, shown a high dielectric permittivity (ɛ' = 879) and low dielectric loss (<5%) in the broad temperature range (-140oC - 150oC) with the Curie temperature 307 oC can have the potential for high temperature piezoelectric and tunable RF circuit applications. The temperature dependent AC-conductivity follows the variable range hopping conduction mechanism by obtaining the slope -0.25 from the ln[ln(ρac)] versus ln(T) graph in the temperature range of 133 K-308 K. The effect of Gd2O3 on the Mott's parameters such as density of states (N(EF)), hopping length (RH), and hopping energy (WH) have been discussed.

  2. 344 cm x 86 cm low mass vacuum window

    SciTech Connect

    Reimers, R.M.; Porter, J.; Meneghetti, J.; Wilde, S.; Miller, R.

    1983-08-01

    The LBL Heavy Ion Spectrometer System (HISS) superconducting magnet contains a 1 m x 3.45 m x 2 m vacuum tank in its gap. A full aperture thin window was needed to minimize background as the products of nuclear collisions move from upstream targets to downstream detectors. Six windows were built and tested in the development process. The final window's unsupported area is 3m/sup 2/ with a 25 cm inward deflection. The design consists of a .11 mm Nylon/aluminum/polypropylene laminate as a gas seal and .55 mm woven aramid fiber for strength. Total mass is 80 milligrams per cm/sup 2/. Development depended heavily on past experience and testing. Safety considerations are discussed.

  3. Effect of Ti Doping on Structural and Electrical Properties of Ba(Fe{sub 0.5}Nb{sub .0.5})O{sub 3} Ceramic

    SciTech Connect

    Kumar, Sudhir; Behera, Banarji; Choudhary, R. N. P.

    2008-10-23

    Polycrystalline samples of Ba(Fe{sub 1-x}Ti{sub 2x}Nb{sub 1-x}){sub 0.5}O{sub 3}(BFTN) with x = 0, 0.1, 0.2 have been synthesized using a high-temperature solid-state reaction technique. The X-ray diffraction of the sample (x = 0) at room temperature shows a monoclinic phase. When the doped contents of Ti are over 10 mole% the structure changes from monoclinic to tetragonal. Scanning electron micrographs of the compounds show that grains are uniformly and densely distributed over the entire surface of the sample. The complex impedance plots show that there is only bulk (grain) contribution in the compounds in the said temperature range, and is of non-Debye type of relaxation. Bulk resistance of the material has been observed to be concentration dependent. Conductivity analysis indicates that ac/dc conductivity of the materials increases with increase in temperature. It shows a typical negative temperature coefficient of resistance (NTCR) behaviour like a semiconductor. The conductivity has been found to decrease on Ti doping.

  4. The effect of temperature on the structure and magnetic properties of Co0.5Ni0.5Fe2O4 spinel nanoferrite

    NASA Astrophysics Data System (ADS)

    Abdallah, Hafiz M. I.; Moyo, Thomas; Ngema, Nokwanda

    2015-11-01

    Nanocrystalline Co0.5Ni05Fe2O4 ferrite with average crystallite size of 7.6 nm and lattice constant of 0.8372 nm was synthesized via a glycol-thermal process. The structure parameters and morphology of the as-synthesized sample and annealed samples were characterized by XRD, EDX, FTIR, HRSEM and HRTEM. The hyperfine interactions, iron distribution on the tetrahedral and octahedral sites for the as-synthesized sample and samples annealed at 500 °C were deduced by Mössbauer spectroscopy measurements at 300 K. The magnetization measurements for the as-synthesized and annealed samples (300-900 °C) were obtained by a vibrating sample magnetometer on a cryogen free measurement system at different isothermal temperatures (4-300 K) in external applied magnetic fields of ±5 T. The temperature dependence of the magnetic properties such as coercive field, saturation magnetization, remanent magnetization and squareness of hysteresis loops were investigated. The sample transformed from single-domain to multi-domain configuration at particle size of about 31 nm. At 300 K, the sample annealed at 700 °C exhibits a maximum coercivity. The as-prepared sample shows a substantial increase in coercivity from 0.182 kOe at 300 K to 6.018 kOe at 4 K.

  5. Effect of lateral electric field on the transition energies of neutral and charged excitons in In0.5Ga0.5As /GaAs quantum dots

    NASA Astrophysics Data System (ADS)

    Saito, Toshio; Nakaoka, Toshihiro; Arakawa, Yasuhiko

    2015-03-01

    We have calculated the transition energies of neutral and charged excitons in In0.5Ga 0.5As /GaAs quantum dots (QDs) under a lateral electric field up to 40 kV/cm. First, the single-particle electron and hole states under the lateral field are calculated using the 8-band k .p theory. The linear and quadratic piezoelectricity is included. Next, the transition energies are calculated from the electron-hole, electron-electron, and hole-hole Coulomb energies. For a QD with 15-nm base length under a lateral electric field along the [100 ] direction, the transition energy of the positively charged exciton exhibits a blueshift with increasing field up to 28 kV/cm, followed by a redshift under higher field. In contrast, those of the neutral and negatively charged excitons exhibit only redshifts accompanied by a crossing of the two exciton levels. The calculated result for the positively charged exciton reproduces the unconventional "M"-shaped exciton energy shift observed in our experiment by Nakaoka et al. [Appl. Phys. Lett. 99, 181109 (2011), 10.1063/1.3658639]. The origin of the blueshift calculated for the positively charged exciton is the enhanced hole density in the QD base corner due to the modification of the piezoelectric potential by the lateral electric field, which causes an increase in the hole-hole Coulomb energy. We found that the amount of the blueshift increases with the QD size. In order to understand the effect of the lateral field direction, we calculate the transition energies under a lateral electric field of 20 kV/cm along the [1 1 ¯0 ],[100 ] , and [110 ] directions. For the positively charged exciton, the transition energy exhibits a redshift for the [1 1 ¯0 ] direction, and blueshifts of different amounts for the [100 ] and [110 ] directions, indicating that the effects of the lateral field are not equivalent for the [1 1 ¯0 ] and [110 ] directions. It is demonstrated that the direction dependence of the transition energy reflects the symmetry

  6. The Reuse-Oriented Software Evolution (ROSE) Process Model Ver 0.5. (Draft)

    DTIC Science & Technology

    1993-07-31

    This document is closely associated with two earlier STARS documents entitled STARS Reuse Concepts Volume I- Conceptual Framework for Reuse Processes...CFRP), Version 2. 0 and STARS Conceptual Framework for Reuse Processes (CFRP): Application, Version 0.5 . These two documents define a conceptual

  7. Structure, Stability, and Reorganization of 0.5 L0 Topography in Block Copolymer Thin Films.

    PubMed

    Maher, Michael J; Self, Jeffrey L; Stasiak, Pawel; Blachut, Gregory; Ellison, Christopher J; Matsen, Mark W; Bates, Christopher M; Willson, C Grant

    2016-11-22

    The structure, stability, and reorganization of lamella-forming block copolymer thin film surface topography ("islands" and "holes") were studied under boundary conditions driving the formation of 0.5 L0 thick structures at short thermal annealing times. Self-consistent field theory predicts that the presence of one perfectly neutral surface renders 0.5 L0 topography thermodynamically stable relative to 1 L0 thick features, in agreement with previous experimental observations. The calculated through-film structures match cross-sectional scanning electron micrographs, collectively demonstrating the pinning of edge dislocations at the neutral surface. Remarkably, near-neutral surface compositions exhibit 0.5 L0 topography metastability upon extended thermal treatment, slowly transitioning to 1 L0 islands or holes as evidenced by optical and atomic force microscopy. Surface restructuring is rationalized by invoking commensurability effects imposed by slightly preferential surfaces. The results described herein clarify the impact of interfacial interactions on block copolymer self-assembly and solidify an understanding of 0.5 L0 topography, which is frequently used to determine neutral surface compositions of considerable importance to contemporary technological applications.

  8. Pupillometry study of brimonidine tartrate 0.2% and apraclonidine 0.5%.

    PubMed

    Besada, Eulogio; Reed, Kimberly; Najman, Perla; Shechtman, Diana; Hardigan, Patrick

    2011-12-01

    This study investigated possible effects of brimonidine tartrate 0.2% and apraclonidine 0.5% on pupil diameter. Ten subjects between 20 and 40 years of age participated. A Colvard pupillometer (Oasis Medical) was used to measure pupil diameter. Baseline and serial measurements were obtained at 3 luminance levels (>6.4, <0.82-0.4, and <0.2-0.02 cd/m(2)) during a 4-hour interval following instillation of 1 drop of brimonidine tartrate 0.2% or apraclonidine 0.5% in one eye versus a placebo in the contralateral eye. The measurements for each drug were obtained on different days. A nested random effects model controlling for subject's age, race, and sex was used for statistical analysis. A maximum reduction in pupil diameter was observed at 90 minutes from instillation (1.40 mm at >6.4 cd/m(2), 1.69 mm at <0.82-0.4 cd/m(2), and 1.55 mm at <0.2-0.02 cd/m(2)) for brimonidine tartrate 0.2%. At all time intervals and illumination levels, miosis (P < .01) occurred. Apraclonidine 0.5% did not produce a significant effect on pupil diameter. Brimonidine tartrate 0.2% produced a moderate miotic effect. No effect was observed for apraclonidine 0.5%. A predominant agonistic effect on α-2 receptors of the iris dilator may explain this behavior.

  9. An analysis of lead-free (Bi{sub 0.5}Na{sub 0.5}){sub 0.915}-(Bi{sub 0.5}K{sub 0.5}){sub 0.05}Ba{sub 0.02}Sr{sub 0.015}TiO{sub 3} ceramic for efficient refrigeration and thermal energy harvesting

    SciTech Connect

    Vats, Gaurav; Vaish, Rahul; Bowen, Chris R.

    2014-01-07

    This article demonstrates the colossal energy harvesting capability of a lead-free (Bi{sub 0.5}Na{sub 0.5}){sub 0.915}-(Bi{sub 0.5}K{sub 0.5}){sub 0.05}Ba{sub 0.02}Sr{sub 0.015}TiO{sub 3} ceramic using the Olsen cycle. The maximum harvestable energy density estimated for this system is found to be 1523 J/L (1523 kJ/m{sup 3}) where the results are presented for extreme ambient conditions of 20–160 °C and electric fields of 0.1–4 MV/m. This estimated energy density is 1.7 times higher than the maximum reported to date for the lanthanum-doped lead zirconate titanate (thin film) system. Moreover, this study introduces a generalized and effective solid state refrigeration cycle in contrast to the ferroelectric Ericson refrigeration cycle. The cycle is based on a temperature induced polarization change on application of an unipolar electric field to ferroelectric ceramics.

  10. Introducing a New Classification of Early Childhood Disorders: DC:0-5

    ERIC Educational Resources Information Center

    Zeanah, Charles H.; Carter, Alice S.; Cohen, Julie; Egger, Helen; Gleason, Mary Margaret; Keren, Miri; Lieberman, Alicia; Mulrooney, Kathleen; Oser, Cindy

    2017-01-01

    This article introduces the revised and updated "DC:0-5™: Diagnostic Classification of Mental Health and Developmental Disorders of Infancy and Early Childhood." The authors describe the past and current efforts to create a developmentally based classification system for very young children. DC:0-3, published in 1994 by ZERO TO THREE,…

  11. Efficacy of liposome-encapsulated 0.5% ropivacaine in maxillary dental anaesthesia.

    PubMed

    Franz-Montan, M; de Paula, E; Groppo, F C; Ranali, J; Volpato, M C

    2012-07-01

    The aim of this study was to evaluate the effectiveness of liposome-encapsulated ropivacaine (0.5%) in dental anaesthesia. This randomised, double-blind, crossover, four-period treatment study included 40 volunteers who were given 1.8 ml of the following local anaesthetics into the buccal sulcus at the right level of the upper canine: 0.5% ropivacaine; 0.5% ropivacaine with 1:200,000 adrenaline; liposome-encapsulated 0.5% ropivacaine; and 2% lignocaine with 1:100,000 adrenaline. Onset of pulpal anaesthesia; the success of anaesthesia; and the duration of labial, gingival, and pulpal anaesthesia involving the upper right canine and first premolar were evaluated. At the end of each injection, volunteers rated the pain on injection on a visual analogue scale (VAS). Both ropivacaine and adrenaline, and lignocaine with adrenaline, were more successful anaesthetic agents than liposome-encapsulated ropivacaine or plain ropivacaine (p<0.05). There were no significant differences among the anaesthetic preparations in the onset of pulpal anaesthesia. Ropivacaine and adrenaline and lignocaine and adrenaline gave a significantly longer duration of pulpal anaesthesia. VAS showed no significant differences among the groups tested. The results showed that encapsulation of liposome did not improve the anaesthetic efficacy of ropivacaine.

  12. Large strain response based on relaxor-antiferroelectric coherence in Bi0.5Na0.5TiO3-SrTiO3-(K0.5Na0.5)NbO3 solid solutions

    NASA Astrophysics Data System (ADS)

    Liu, Laijun; Shi, Danping; Knapp, Michael; Ehrenberg, Helmut; Fang, Liang; Chen, Jun

    2014-11-01

    The effect of (K0.5Na0.5)NbO3 (KNN) addition on the ferroelectric and dielectric behavior of 90Bi0.5Na0.5TiO3-10SrTiO3 (BNT-ST) lead-free piezoceramics was investigated. Polarization and strain hysteresis loops indicate that a relaxor-antiferroelectric coherence will be produced with the addition of KNN as a replacement for ST up to 5% and the destabilization of the phase coherence is accompanied by an enhancement of the bipolar strain with the increase of temperature, which is ˜0.37% (corresponding to a large signal d33* of ˜530 pm/V at 90 °C) at 5 mol. % KNN content. This strain was analyzed as derived from an electrostrictive effect at lower electric fields and a field-induced antiferroelectric-ferroelectric phase transition at higher electric fields. The large polar strain response would be of great interest for environmental friendly high-temperature actuators.

  13. Extinction and optical depth of contrails

    NASA Astrophysics Data System (ADS)

    Voigt, C.; Schumann, U.; Jessberger, P.; Jurkat, T.; Petzold, A.; Gayet, J.-F.; Krämer, M.; Thornberry, T.; Fahey, D. W.

    2011-06-01

    One factor limiting the understanding of the climate impact from contrails and aircraft induced cloud modifications is the accurate determination of their optical depth. To this end, 14 contrails were sampled for 2756 s with instruments onboard the research aircraft Falcon during the CONCERT (CONtrail and Cirrus ExpeRimenT) campaign in November 2008. The young (<10 min old) contrails were produced by 9 commercial aircraft with weights of 47 to 508 t, among them the largest operating passenger aircraft, the Airbus A380. The contrails were observed at temperatures between 214 and 224 K and altitudes between 8.8 and 11.1 km. The measured mean in-contrail relative humidity with respect to ice was 89 ± 12%. Six contrails were observed in cloud free air, the others were embedded in thin cirrus clouds. The observed contrails exhibited a mean ice water content of 2 mg m-3 and had a mean number concentration of 117 cm-3 and effective radius of 2.9 μm assuming asphericle particles with an aspect ratio of 0.5. Probability density functions of the extinction, with a mean (median) of 1.2 (0.7) km-1, and of the optical depth τ, with a mean (median) of 0.27 (0.13), are derived from the in situ measurements and are likely representative for young contrails from the present-day commercial aircraft fleet at observation conditions. Radiative transfer estimates using the in-situ measured contrail optical depth lead to a year-2005 estimate of line-shaped contrail radiative forcing of 15.9 mWm-2 with an uncertainty range of 11.1-47.7 mWm-2.

  14. Source Parameters and High Frequency Characteristics of Local Events (0.5 ≤ M L ≤ 2.9) Around Bilaspur Region of the Himachal Himalaya

    NASA Astrophysics Data System (ADS)

    Vandana; Kumar, Ashwani; Gupta, S. C.; Mishra, O. P.; Kumar, Arjun; Sandeep

    2017-02-01

    Source parameters of 41 local events (0.5 ≤ M L ≤ 2.9) occurred around Bilaspur region of the Himachal Lesser Himalaya from May 2013 to March 2014 have been estimated adopting Brune model. The estimated source parameters include seismic moments (M o), source radii (r), and stress drops (Δσ), and found to vary from 4.9 × 1019 to 7 × 1021 dyne-cm, about 187-518 m and less than 1 bar to 51 bars, respectively. The decay of high frequency acceleration spectra at frequencies above f max has been modelled using two functions: a high-cut filter and κ factor. Stress drops of 11 events, with M 0 between 1 × 1021 and 7 × 1021 dyne-cm, vary from 11 bars to 51 bars with an average of 22 bars. From the variation of the maximum stress drop with focal depth it appears that the strength of the upper crust decreases below 20 km. A scaling law M 0 = 2 × 1022 f {c/-3.03} between M 0, and corner frequency (f c), has been developed for the region. This law almost agrees with that for the Kameng region of the Arunachal Lesser Himalaya. f c is found to be source dependent whereas f max is source independent and seems to indicate that the size of the cohesive zone is not sensitive to the earthquake size. At four sites f max is found to vary from 14 to 23, 11 to 19, 9 to 23 and 4 to 11 Hz, respectively. The κ is found to vary from 0.01 to 0.035 s with an average of 0.02 s. This range of variation is a large compared to the κ variation between 0.023 and 0.07 s for the Garhwal and Kumaon Himalaya. For various regions of the world, the κ varies over a broad range from 0.003 to 0.08 s, and for the Bilaspur region the κ estimates are found to be consistent with other regions of the world.

  15. GWPs and GTPs for forest bioenergy and products with global coverage at 0.5° x 0.5° spatial resolution

    NASA Astrophysics Data System (ADS)

    Cherubini, Francesco; Huijbrets, Mark; Kindermann, Georg; Bright, Ryan; Van Zelm, Rosalie; Van Der Velde, Marijn; Strømman, Anders

    2014-05-01

    The effects on climate of various greenhouse gas (GHG) emissions can be aggregated in common units through a variety of emission metrics. The Global Warming Potential (GWP), introduced by the IPCC in 1990, is based on the integrated radiative forcing of a pulse emission divided by an equivalent integration for the reference gas, usually CO2, at an arbitrary time horizon (TH). The Global Temperature change Potential (GTP) is the ratio between the temperature response to a GHG emission pulse at a certain point in time and the temperature response for a reference gas. Other metrics like the integrated GTP (iGTP), TEMP, and metrics embedding economic considerations or a dynamic, target-specific TH are used in the literature. Recent studies developed impulse response functions and emission metrics for CO2 emissions from biomass combustion or oxidation for applications in bioenergy and harvested wood products (HWP) analyses. As the resulting metrics depend on the resource turnover time and hence on site specific characteristics like the type of biomass species, local climate, site productivity and other factors, these metrics are today available only for a limited number of cases and selected locations. In this work, we provide spatially-explicit GWPs and GTPs for bioenergy and HWP sourced from renewable forests with a global coverage of forest areas at a resolution of 0.5 degrees x 0.5 degrees. The Global Forest Model (G4M) developed at IIASA is used to provide the mean annual increments (MAI), rotation periods and above ground carbon of the forests of the globe. G4M uses a dynamic Net Primary Production (NPP) model to simulate how growth rates are affected by changes in temperature, precipitation, radiation, and CO2 concentrations. NPP post harvest dynamics are then modeled using tree-specific functions combined with the grid-specific MAI. Heterotrophic respiration (Rh) is exogenously modeled with the YASSO model. NPP and Rh are then combined in a Net Ecosystem

  16. THERMAL AND ELECTRICAL PROPERTIES OF Ba0.5Sr0.5CoxFe1-x-yNiyO3-δ (x = 0.4, 0 ≤ y ≤ 0.25) AS CATHODE MATERIAL FOR IT-SOFCs

    NASA Astrophysics Data System (ADS)

    Burnwal, Suman Kumar; Kistaiah, P.

    2015-03-01

    Ba0.5Sr0.5CoxFe1-x-yNiyO3-δ (BSCFNi; x = 0.4, 0 ≤ y ≤ 0.25) were studied in relation to their potential use as intermediate temperature solid oxide fuel cell (IT-SOFC) cathode. An emphasis is made on the effect of Ni-doping on crystal structure, thermal expansion coefficient (TEC) and dc electrical conductivity. A cubic perovskite structure was observed in the X-ray diffraction (XRD) measurement. The TEC of BSCFNi obtained for 0 ≤ y ≤ 0.25, varies in the range of (12.38-18.81) × 10-6 K-1, measured in the temperature range of 30°C to 800°C. The electrical conductivity which is a major defect of Ba0.5Sr0.5CoxFe1-xO3-δ (BSCF) was improved by Ni-doping. The compound with y = 0.20 and 0.25 demonstrated a conductivity of σ = 62.59 S-cm-1 and 72.64 S-cm-1 at 400°C and 77.01 S-cm-1 and 89.68 S-cm-1 at 500°C.

  17. Superconducting triple-spoke cavity for beta = 0.5 ions.

    SciTech Connect

    Shepard, K. W.; Kelly, M. P.; Fuerst, J. D.; Kedzie, M.; Conway, Z. A.; Physics

    2005-01-01

    This paper reports the development status of a 345 MHz, three-spoke-loaded, TEM-class superconducting cavity with a transit-time factor peaked at = v/c = 0.63. The cavity has a 4 cm diameter beam aperture, a transverse diameter of 45.8 cm, and an interior length of 85 cm. The cavity is the second of two three-spoke loaded cavities being developed for the RIA driver linac and other high-intensity ion linac applications. Construction of a prototype niobium cavity has been completed and the cavity has been chemically processed. Results of initial cold tests are discussed.

  18. Decoupling of the CuO2 plane and superconductivity in Cu0.5Tl0.5Ba2(Ca2-ySry)Cu3O10-δ(y = 0-0.4) samples

    NASA Astrophysics Data System (ADS)

    Khan, Nawazish A.; Usman Muzaffar, M.

    2016-05-01

    Cu0.5Tl0.5Ba2(Ca2-ySry)Cu3O10-δ(y = 0-0.4) samples have been synthesized at normal pressure at 860∘C. The main objectives of these experiments to study the role of inter-plane decoupling in suppressing the superconductivity of high temperature superconductors (HTSC). These samples have shown orthorhombic crystal structure and the c-axis length increases with increased Sr-doping. All the samples have shown metallic variations of resistivity (ρ) from room temperature down to the onset of superconductivity. The magnitude of the superconductivity is suppressed and the apical oxygen modes are hardened with Sr-doping. These studies have shown that Sr-doping promotes decoupling of conducting CuO2 planes which suppress the superconducting properties of final compound. The excess conductivity analyses have shown increases in the width of two-dimensional (2D) Lawrence-Doniach (LD) regime with Sr-doping. The coherence length along the c-axis ξc(0), the inter-layer coupling J, the phase relaxation time of the carriers τφ and the Fermi velocity vF of superconductor carriers is suppressed. The underlying reason for the suppression of superconductor properties is the decrease in the density of carriers in the superconductor planes. However, the values of Bc0(T), Bc1(T) and Jc(0) have been found to increase with the increased Sr-doping, which is suggested to be originating from the enhancement in the flux pinning character which is induced by Sr-doping. The values of magnetic field penetration depth λp.d and the Ginzburg-Landau (GL) parameter κ decrease with Sr-doping and it is also suggested to be originating from the increase of flux pinning character of the samples with Sr-doping.

  19. Magnetism of hexagonal Mn{sub 1.5}X{sub 0.5}Sn (X = Cr, Mn, Fe, Co) nanomaterials

    SciTech Connect

    Fuglsby, R.; Kharel, P.; Zhang, W.; Sellmyer, D. J.; Valloppilly, S.; Huh, Y.

    2015-05-07

    Mn{sub 1.5}X{sub 0.5}Sn (X = Cr, Mn, Fe, Co) nanomaterials in the hexagonal Ni{sub 2}In-type crystal structure have been prepared using arc-melting and melt spinning. All the rapidly quenched Mn{sub 1.5}X{sub 0.5}Sn alloys show moderate saturation magnetizations with the highest value of 458 emu/cm{sup 3} for Mn{sub 1.5}Fe{sub 0.5}Sn, but their Curie temperatures are less than 300 K. All samples except the Cr containing one show spin-glass-like behavior at low temperature. The magnetic anisotropy constants calculated from the high-field magnetization curves at 100 K are on the order of 1 Merg/cm{sup 3}. The vacuum annealing of the ribbons at 550 °C significantly improved their magnetic properties with the Curie temperature increasing from 206 K to 273 K for Mn{sub 1.5}Fe{sub 0.5}Sn.

  20. Part I: Electronic and ionic transport properties of the ordered and disordered LiNi0.5Mn1.5O4 spinel cathode

    NASA Astrophysics Data System (ADS)

    Amin, Ruhul; Belharouk, Ilias

    2017-04-01

    Here, we report on the electronic and ionic conductivity and diffusivity of the ordered (P4332) and disordered (Fd 3 bar m) LiNi0.5Mn1.5O4 spinel material, which have been determined by using ion and electron blocking cell configurations as a function of lithium concentration and temperature. The disordered phase exhibits about fifteen-time higher electronic conductivity than the ordered phase at room temperature in the lithiated state. Upon delithiation, the electronic conductivity of the ordered LiNi0.5Mn1.5O4 phase increases and reaches the same levels observed for the disordered phase. The ionic conductivity and diffusivity of LiNi0.5Mn1.5O4, in the ordered and disordered forms, are in the range of ∼1 × 10-9 S/cm and ∼5 × 10-9 cm2/s, respectively. Both phases exhibit similar activation energies for the ionic conductivity and diffusivity, i.e. 0.70 ± 0.2eV and 0.74 ± 0.2eV, respectively. It can be concluded from the obtained results that the electrochemical performance of LiNi0.5Mn1.5O4, whether ordered or disordered, is limited by lithium transport, but is fast enough to allow charge/discharge of micron-scale particles at practical C-rates.

  1. Comparison of superconducting properties between FeSe0.5Te0.5/CeO2/SrTiO3 and FeSe0.5Te0.5/SrTiO3 thin films

    NASA Astrophysics Data System (ADS)

    Chen, S. H.; Han, Y. Y.; Liu, J. Z.; Wang, T.; Tian, M. L.; Wen, H. H.; Xing, Z. W.

    2016-09-01

    The electrical resistance behaviors under angle-dependent magnetic fields up to 16 T are investigated in superconducting FeSe0.5Te0.5 (FST) thin films grown on SrTiO3 (STO) substrates without or with a CeO2 buffer layer. It is found that the FST/CeO2/STO films have an enhanced superconducting transition temperature Tc and slightly increased superconducting anisotropy in comparison with the FST/STO films. The enhancement of Tc in the presence of the CeO2 buffer is closely related to the changes in both the out-of-plane lattice constant and Se-Fe-Se (Te-Fe-Te) bond angle.

  2. A 3He gas heat switch for the 0.5-2 K temperature range

    NASA Astrophysics Data System (ADS)

    Smith, Eric N.; Parpia, Jeevak M.; Beamish, John R.

    2000-07-01

    We have constructed a prototype heat switch for use in a cyclic demagnetization apparatus. The desired operating range of the switch is from 0.5 to 1.8 K. The measured conductivity of the switch is 50 μW/ K at 1.5 K when ‘off ’ and 8 mW/K at 0.5 K when ‘on’. The switching is carried out by 3He gas which is admitted and extracted from the device by a miniature charcoal adsorption pump which is controlled by electrical heat and a weak thermal link to a pumped 4He bath. In this paper we discuss details of construction and the performance as a function of temperature, and consider the switching time between on and off states.

  3. Electric field induced monoclinic phase stability in Ca doped Na0.5Bi0.5TiO3: Case of 0.93Na0.5Bi0.5 TiO3 - 0.07CaTiO3 ferroelectric ceramics

    NASA Astrophysics Data System (ADS)

    Roukos, Roy; Geoffroy, Nicolas; Chaumont, Denis

    2017-01-01

    The ferroelectric perovskite complex 0.93Na0.5Bi0.5TiO3 - 0.07CaTiO3 (NBT -0.07CT) ceramics were studied by a simple X-ray diffraction upon application of an increasing electric field. It is shown that the field induced rhombohedral (R3c) to monoclinic (Cc) phase transition at room temperature. This induced phase is stable after removal the electric field. Our results has been interpreted by intrinsic polarization rotation theory, in comparison with Pb-base system such as PMT-PT, PZN-PT, …near the morphotropic phase boundary (MPB) region. Apparently, the NBT - 0.07CT pretends to have a ferroelectric and structural instability around room temperature.

  4. Acoustic properties of bovine cancellous bone from 0.5 to 1.5 MHz

    NASA Astrophysics Data System (ADS)

    Lee, Kang Il; Roh, Heui-Seol; Yoon, S. W.

    2002-05-01

    Most previous studies using ultrasound for the diagnosis of osteoporosis have employed ultrasound in the frequency range from 0.2 to 1 MHz. Acoustic properties of 14 defatted bovine cancellous bone specimens were investigated in vitro. Speed of sound (SOS) and broadband ultrasonic attenuation (BUA) were measured using two matched pairs of transducers with the center frequencies of 1 and 2.25 MHz, respectively, in order to cover a broad frequency range from 0.5 to 1.5 MHz. In this frequency range, SOS and BUA show significant linear positive correlations with apparent bone density. These results suggest that the frequency range from 0.5 to 1.5 MHz may also be useful in the diagnosis of osteoporosis. [Work supported by BK21 Program, KRF (KRF-2000-015-DP0718), and KOSEF (KOSEF-2000-0238-100) in Korea.] a)For (Biomedical Ultrasound/Bioresponse to Vibration) Best Student Paper Award.

  5. Low temperature magnetic properties of Cr0.25Co0.25Zn0.5Fe2O4 nano particles

    NASA Astrophysics Data System (ADS)

    Bhargava, Hina; Lakshmi, N.; Sharma, Ram Kripal; Venugopalan, K.

    2008-04-01

    Low temperature Mössbauer and AC susceptibility have been used to study relaxation phenomena in nano-sized particles of Cr0.25Co0.25Zn0.5Fe2O4. From these studies, the energy density constant for this system has been estimated to be 4 x 106 erg/cm3. Cation distribution has also been determined and the observed results are correlated to calculated relaxation times.

  6. ICL light in a z~0.5 cluster: the MUSE perspective

    NASA Astrophysics Data System (ADS)

    Pompei, E.; Adami, C.; XXL Team

    2017-03-01

    Intracluster light is contributed by both stars and gas and it is an important tracer of the interaction history of galaxies within a cluster. We present here the results obtained from MUSE observations of an intermediate redshift (z~ 0.5) cluster taken from the XXL survey and we conclude that the most plausible process responsible for the observed amount of ICL is ram pressure stripping.

  7. Structural And Electrical Properties oF (La{sub 0.5-x}Pr{sub x}Ba{sub 0.5})(Mn{sub 0.5}Ti{sub 0.5})O{sub 3} Perovskite

    SciTech Connect

    Alias, Nor Hayati; Shaari, Abdul Halim; Wan Yusoff, Wan Mohd Daud; Mahmood, Che Seman

    2010-01-05

    A single phase monoclinic new perovskite based titano-manganite (La{sub 0.5-x}Pr{sub x}Ba{sub 0.5})(Mn{sub 0.5}Ti{sub 0.5})O{sub 3} has been successfully prepared by ceramic solid-state technique at sintering temperature of 1300 deg. C. The concentration of Pr (Praseodymium), x, in molar proportion in A site has been varied as x = 0, 0.02 and 0.2. Analysis has been carried out to determine the electrical properties of the synthesized material at frequency ranging from 5 Hz to 1 MHz; and at temperature range between 25 deg. C to 200 deg. C. It is found that Pr addition promoted liquid phase sintering diffusion, porosity and agglomeration formation at 1300 deg. C. Dual relaxation is observed in unsubstituted Pr sample x = 0 and high Pr substituted sample x = 0.2. This phenomenon was a combinational contribution from a quasi dc (QDC) or low frequency dispersion (LFD), two cole-cole relaxational responses and a resistor. While low concentrated Pr substituted sampled x = 0.02 shows a combinational contribution from a quasi dc (QDC) or low frequency dispersion (LFD), single cole-cole relaxational response and a resistor at room temperature. Pr substitution at x = 0(max 12000) and x = 0.2(max 16000) showed high dielectric values compared to low substituted sample x = 0.02. Variation of dielectric loss tangent (tan delta) are observed for all samples at temperature ranged studied.

  8. Defect energetics of concentrated solid-solution alloys from ab initio calculations: Ni0.5Co0.5, Ni0.5Fe0.5, Ni0.8Fe0.2 and Ni0.8Cr0.2.

    PubMed

    Zhao, Shijun; Stocks, G Malcolm; Zhang, Yanwen

    2016-09-14

    It has been shown that concentrated solid solution alloys possess unusual electronic, magnetic, transport, mechanical and radiation-resistant properties that are directly related to underlying chemical complexity. Because every atom experiences a different local atomic environment, the formation and migration energies of vacancies and interstitials in these alloys exhibit a distribution, rather than a single value as in a pure metal or dilute alloy. Using ab initio calculations based on density functional theory and special quasirandom structures, we have characterized the distribution of defect formation energy and migration barrier in four Ni-based solid-solution alloys: Ni0.5Co0.5, Ni0.5Fe0.5, Ni0.8Fe0.2, and Ni0.8Cr0.2. As defect formation energies in finite-size models depend sensitively on the elemental chemical potential, we have developed a computationally efficient method for determining it which takes into account the global composition and the local short-range order. In addition we have compared the results of our ab initio calculations to those obtained from available embedded atom method (EAM) potentials. Our results indicate that the defect formation and migration energies are closely related to the specific atoms in the structure, which further determines the elemental diffusion properties. Different EAM potentials yield different features of defect energetics in concentrated alloys, pointing to the need for additional potential development efforts in order to allow spatial and temporal scale-up of defect and simulations, beyond those accessible to ab initio methods.

  9. Defect energetics of concentrated solid-solution alloys from ab initio calculations: Ni0.5Co0.5, Ni0.5Fe0.5, Ni0.8Fe0.2 and Ni0.8Cr0.2

    DOE PAGES

    Zhao, Shijun; Stocks, George Malcolm; Zhang, Yanwen

    2016-08-03

    It has been shown that concentrated solid solution alloys possess unusual electronic, magnetic, transport, mechanical and radiation-resistant properties that are directly related to underlying chemical complexity. Because every atom experiences a different local atomic environment, the formation and migration energies of vacancies and interstitials in these alloys exhibit a distribution, rather than a single value as in a pure metal or dilute alloy. In this study, using ab initio calculations based on density functional theory and special quasirandom structure, we have characterized the distribution of defect formation energy and migration barrier in four Ni-based solid-solution alloys: Ni0.5Co0.5, Ni0.5Fe0.5, Ni0.8Fe0.2 andmore » Ni0.8Cr0.2. As defect formation energies in finite-size models depend sensitively on the elemental chemical potential, we have developed a computationally efficient method for determining it which takes into account the global composition and the local short-range order. In addition we have compared the results of our ab initio calculations to those obtained from available embedded atom method (EAM) potentials. Our results indicate that the defect formation and migration energies are closely related to the specific atomic size in the structure, which further determines the elemental diffusion properties. In conclusion, different EAM potentials yield different features of defect energetics in concentrated alloys, pointing to the need for additional potential development efforts in order to allow spatial and temporal scale-up of defect and simulations, beyond those accessible to ab initio methods.« less

  10. Lead-free piezoceramics with giant strain in the system Bi0.5Na0.5TiO3-BaTiO3-K0.5Na0.5NbO3. II. Temperature dependent properties

    NASA Astrophysics Data System (ADS)

    Zhang, Shan-Tao; Kounga, Alain Brice; Aulbach, Emil; Jo, Wook; Granzow, Torsten; Ehrenberg, Helmut; Rödel, Jürgen

    2008-02-01

    The temperature dependence of the dielectric and ferroelectric properties of lead-free piezoceramics of the composition (1-x-y)Bi0.5Na0.5TiO3-xBaTiO3-yK0.5Na0.5NbO3 (0.05⩽x⩽0.07, 0.01⩽y⩽0.03) was investigated. Measurements of the polarization and strain hystereses indicate a transition to predominantly antiferroelectric order when heating from room temperature to 150°C, while for 150

  11. Static and dynamic magnetic properties of monodispersed Mn0.5Zn0.5Fe2O4 nanomagnetic particles

    NASA Astrophysics Data System (ADS)

    Parekh, Kinnari; Upadhyay, R. V.

    2010-03-01

    Static and dynamic magnetic properties of oleic acid/oleyamine coated Mn-Zn ferrite nanoparticles of diameter 82 Å are reported. The zero-field-cooled peak temperature decreases with increasing magnetic field and obeys the well known de Almeida-Thouless line. The zero-field-cooled magnetization data are simulated by assuming noninteracting magnetic particles with uniaxial anisotropy and lognormal particle size distribution. The relevant parameters give the values of particle diameter (D) 80 Å, standard deviation 0.3 in ln(D), and the anisotropy constant K to be 5.8×105 erg/cm3. The observed higher value of standard deviation is due to the interparticle interaction. The complex magnetic susceptibility was measured as a function of temperature for frequencies ranging from 67 to 1800 Hz. The temperature at which the maximum in the ac-susceptibility curve is observed is well accounted by the Vogel-Fulcher law for both χ' and χ″. The peak is also observed in a plot of χ″/χ' versus temperature, which may mean the existence of magnetic aftereffect, and furthermore, it has an Arrhenius as well as Vogel-Fulcher law type dependence. An observed nonthermal activation type relaxation mechanism at 12 K is attributed to possible quantum tunneling effect in Mn-Zn ferrite nanoparticles.

  12. Microstructure and microchemistry of flash sintered K0.5Na0.5NbO3

    SciTech Connect

    Corapcioglu, Gulcan; Gulgun, Mehmet Ali; Kisslinger, Kim; Sturm, Saso; Jha, Shikhar K.; Raj, Rishi

    2016-04-30

    In this paper, flash sintering experiments were performed, for the first time, on sodium potassium niobate (KNN) ceramics. A theoretical density of 94% was achieved in 30 s under 250 V/cm electric-field at 990°C. These conditions are ~100°C lower and faster than the conventional sintering conditions. Grains tended to grow after 30 s. flash sintering duration under constant electric-field. Detailed microstructural and chemical investigations of the sample showed that there was inhomogenous Na, K distribution and it resembles a core–shell structure where K is more in the shell and Na is more in the core region. The inhomogenous distribution of Na and K was correlated with the doubling of the unit cell within the grain along 002 direction. Compositional equilibrium is achieved after a heat treatment at 1000°C for 4 h. Finally, the compositional variations appeared to have been linked to grain boundary melting during flash and consequent recrystallization as the sample cooled.

  13. Albedo Properties of Small (0.5 to 20 km) Main Belt Asteroids

    NASA Astrophysics Data System (ADS)

    Ryan, Erin L.; Woodward, C. E.

    2010-01-01

    Serendipitous observations of main belt asteroids by the Spitzer Space Telescope have enabled determination of main belt asteroid albedos and diameters for targets as small as 0.5 km (eg., Ryan et al. 2009, AJ, 137, 5134). We have used multi-epoch data at 5.8, 8.0 and 24 microns from the MIPSGAL and Taurus Legacy Surveys to obtain diameters and albedos for a sample of approximately 2000 main belt asteroids. Using STM and NEATM, we have obtained diameters ranging from 0.5 to 30 km and albedos ranging from 0.02 to 0.5. Results of this program reveal an albedo distribution that is more diverse in range than the albedo distribution seen in the IRAS and MSX surveys. This diversity may reflect effects of space weathering reddening which is selectively reddening larger asteroids. This reddening effect may reinforce the findings from accretion models that indicate that asteroids in the early solar system were 100 km and larger (Morbidelli et al., 2009, Icarus, in press), by suggesting that the larger asteroids are indeed the oldest members of the main belt. We will present results on the albedo distribution as a function of semi-major axis and new analysis of the mean albedo of dynamical families within the main belt. Support for this work provided in part by a National Science Foundation grant AST-0706980 to the University of Minnesota.

  14. Adaptive Circuits for the 0.5-V Nanoscale CMOS Era

    NASA Astrophysics Data System (ADS)

    Itoh, Kiyoo; Yamaoka, Masanao; Oshima, Takashi

    The minimum operating voltage, Vmin, of nanoscale CMOS LSIs is investigated to breach the 1-V wall that we are facing in the 65-nm device generation, and open the door to the below 0.5-V era. A new method using speed variation is proposed to evaluate Vmin. It shows that Vmin is very sensitive to the lowest necessary threshold voltage, Vt0, of MOSFETs and to threshold-voltage variations, ΔVt, which become more significant with device scaling. There is thus a need for low-Vt0 circuits and ΔVt-immune MOSFETs to reduce Vmin. For memory-rich LSIs, the SRAM block is particularly problematic because it has the highest Vmin. Various techniques are thus proposed to reduce the Vmin: using RAM repair, shortening the data line, up-sizing, and using more relaxed MOSFET scaling. To effectively reduce Vmin of other circuit blocks, dual-Vt0 and dual-VDD circuits using gate-source reverse biasing, temporary activation, and series connection of another small low-Vt0 MOSFET are proposed. They are dynamic logic circuits enabling the power-delay product of the conventional static CMOS inverter to be reduced to 0.09 at a 0.2-V supply, and a DRAM dynamic sense amplifier and power switches operable at below 0.5V. In addition, a fully-depleted structure (FD-SOI) and fin-type structure (FinFET) for Vt-immune MOSFETs are discussed in terms of their low-voltage potential and challenges. As a result, the height up-scalable FinFETs turns out to be quite effective to reduce Vmin to less than 0.5V, if combined with the low-Vt0 circuits. For mixed-signal LSIs, investigation of low-voltage potential of analog circuits, especially for comparators and operational amplifiers, reveals that simple inverter op-amps, in which the low gain and nonlinearity are compensated for by digitally assisted analog designs, are crucial to 0.5-V operations. Finally, it is emphasized that the development of relevant devices and fabrication processes is the key to the achievement of 0.5-V nanoscale LSIs.

  15. Synthesis and characterization of FeSe{sub 1−x}Te{sub x} (x=0, 0.5, 1) superconductors

    SciTech Connect

    Zargar, Rayees A. Hafiz, A. K.; Awana, V. P. S.

    2015-08-28

    In this study, FeTe{sub 1-x}Se{sub x} (x=0,0.5,1) samples were prepared by conventional solid state reaction method and investigated by powder XRD, SEM, Raman and resistivity measurement techniques to reveal the effect of tellurium (Te) substitution in FeSe matrix. Rietveld analysis was performed on room temperature recorded, X-ray diffraction (XRD) patterns of pure FeSe, FeTe and FeSe{sub 0.5}Te{sub 0.5} which shows that all the compounds are crystallized in a tetragonal structure. SEM images show the dense surface morphology. Raman spectra recorded in the range from 100 to 700 cm{sup −1} at ambient temperature has been interpreted by P4/nmm space group of the lattice. The variation in intensity and shift in peak positions of some phonon modes has been discussed on the basis of variation in crystalline field effect by substituting Te in FeSe lattice. The resistivity versus temperature curves reveals that FeSe becomes superconductor at 7 K and FeSe{sub 0.5}Te{sub 0.5} shows superconductivity below 14 K while FeTe is non-superconducting compound.

  16. Detailed modelling of the 21-cm forest

    NASA Astrophysics Data System (ADS)

    Semelin, B.

    2016-01-01

    The 21-cm forest is a promising probe of the Epoch of Reionization. The local state of the intergalactic medium (IGM) is encoded in the spectrum of a background source (radio-loud quasars or gamma-ray burst afterglow) by absorption at the local 21-cm wavelength, resulting in a continuous and fluctuating absorption level. Small-scale structures (filaments and minihaloes) in the IGM are responsible for the strongest absorption features. The absorption can also be modulated on large scales by inhomogeneous heating and Wouthuysen-Field coupling. We present the results from a simulation that attempts to preserve the cosmological environment while resolving some of the small-scale structures (a few kpc resolution in a 50 h-1 Mpc box). The simulation couples the dynamics and the ionizing radiative transfer and includes X-ray and Lyman lines radiative transfer for a detailed physical modelling. As a result we find that soft X-ray self-shielding, Ly α self-shielding and shock heating all have an impact on the predicted values of the 21-cm optical depth of moderately overdense structures like filaments. A correct treatment of the peculiar velocities is also critical. Modelling these processes seems necessary for accurate predictions and can be done only at high enough resolution. As a result, based on our fiducial model, we estimate that LOFAR should be able to detect a few (strong) absorptions features in a frequency range of a few tens of MHz for a 20 mJy source located at z = 10, while the SKA would extract a large fraction of the absorption information for the same source.

  17. Stereo depth distortions in teleoperation

    NASA Technical Reports Server (NTRS)

    Diner, Daniel B.; Vonsydow, Marika

    1988-01-01

    In teleoperation, a typical application of stereo vision is to view a work space located short distances (1 to 3m) in front of the cameras. The work presented here treats converged camera placement and studies the effects of intercamera distance, camera-to-object viewing distance, and focal length of the camera lenses on both stereo depth resolution and stereo depth distortion. While viewing the fronto-parallel plane 1.4 m in front of the cameras, depth errors are measured on the order of 2cm. A geometric analysis was made of the distortion of the fronto-parallel plane of divergence for stereo TV viewing. The results of the analysis were then verified experimentally. The objective was to determine the optimal camera configuration which gave high stereo depth resolution while minimizing stereo depth distortion. It is found that for converged cameras at a fixed camera-to-object viewing distance, larger intercamera distances allow higher depth resolutions, but cause greater depth distortions. Thus with larger intercamera distances, operators will make greater depth errors (because of the greater distortions), but will be more certain that they are not errors (because of the higher resolution).

  18. Thermal Behaviour of Sm0.5 R 0.5FeO3 ( R = Pr, Nd) Probed by High-Resolution X-ray Synchrotron Powder Diffraction

    NASA Astrophysics Data System (ADS)

    Pavlovska, Olena; Vasylechko, Leonid; Buryy, Oleh

    2016-02-01

    Mixed ferrites Sm0.5Pr0.5FeO3 and Sm0.5Nd0.5FeO3 with orthorhombic perovskite structure isotypic with GdFeO3 were synthesized by solid-state reaction technique in air at 1473 K. Structural parameters obtained at room temperature prove a formation of continuous solid solutions in the SmFeO3-PrFeO3 and SmFeO3-NdFeO3 pseudo-binary systems. Sm0.5Pr0.5FeO3 and Sm0.5Nd0.5FeO3 show strongly anisotropic nonlinear thermal expansion: thermal expansion in the b direction is twice lower than in the a and c directions. The average linear thermal expansion coefficients of Sm0.5Pr0.5FeO3 and Sm0.5Nd0.5FeO3 in the temperature range of 298-1173 K are in the limits of (9.0-11.1) × 10-6 K-1, which is close to the values reported for the parent RFeO3 compounds. Subtle anomalies in the lattice expansion of Sm0.5Pr0.5FeO3 and Sm0.5Nd0.5FeO3 detected at 650-750 K reflect magnetoelastic coupling at the magnetic ordering temperature T N.

  19. The most massive galaxies in clusters are already fully grown at z ∼ 0.5

    NASA Astrophysics Data System (ADS)

    Oldham, L. J.; Houghton, R. C. W.; Davies, Roger L.

    2017-02-01

    By constructing scaling relations for galaxies in the massive cluster MACSJ0717.5 at z = 0.545 and comparing with those of Coma, we model the luminosity evolution of the stellar populations and the structural evolution of the galaxies. We calculate magnitudes, surface brightnesses and effective radii using Hubble Space Telescope (HST)/ACS images and velocity dispersions using Gemini/GMOS spectra, and present a catalogue of our measurements for 17 galaxies. We also generate photometric catalogues for ∼3000 galaxies from the HST imaging. With these, we construct the colour-magnitude relation, the Fundamental Plane, the mass-to-light versus mass relation, the mass-size relation and the mass-velocity dispersion relation for both clusters. We present a new, coherent way of modelling these scaling relations simultaneously using a simple physical model in order to infer the evolution in luminosity, size and velocity dispersion as a function of redshift, and show that the data can be fully accounted for with this model. We find that (a) the evolution in size and velocity dispersion undergone by these galaxies between z ∼ 0.5 and z ∼ 0 is mild, with Re(z) ∼ (1 + z)-0.40 ± 0.32 and σ(z) ∼ (1 + z)0.09 ± 0.27, and (b) the stellar populations are old, ∼10 Gyr, with a ∼3 Gyr dispersion in age, and are consistent with evolving purely passively since z ∼ 0.5 with Δ log M/L_B = -0.55_{-0.07}^{+0.15} z. The implication is that these galaxies formed their stars early and subsequently grew dissipationlessly so as to have their mass already in place by z ∼ 0.5, and suggests a dominant role for dry mergers, which may have accelerated the growth in these high-density cluster environments.

  20. The Herschel ATLAS: Evolution of the 250 Micrometer Luminosity Function Out to z = 0.5

    NASA Technical Reports Server (NTRS)

    Dye, S.; Dunne, L.; Eales, S.; Smith, D. J. B.; Amblard, A.; Auld, R.; Baes, M.; Baldry, I. K.; Bamford, S.; Blain, A. W.; Bonfield, D. G.; Bremer, M.; Burgarella, D.; Buttiglione, S.; Cameron, E.; Cava, A.; Clements, D. L.; Cooray, A.; Croom, S.; Dariush, A.; de Zotti, G.; Driver, S.; Dunlop, J. S.; Frayer, D.; Leeuw, L.

    2010-01-01

    We have determined the luminosity function of 250 micrometer-selected galaxies detected in the approximately equal to 14 deg(sup 2) science demonstration region of the Herschel-ATLAS project out to a redshift of z = 0.5. Our findings very clearly show that the luminosity function evolves steadily out to this redshift. By selecting a sub-group of sources within a fixed luminosity interval where incompleteness effects are minimal, we have measured a smooth increase in the comoving 250 micrometer luminosity density out to z = 0.2 where it is 3.6(sup +1.4) (sub -0.9) times higher than the local value.