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Sample records for room-temperature ferroelectric phase

  1. Room-temperature saturated ferroelectric polarization in BiFeO3 ceramics synthesized by rapid liquid phase sintering

    International Nuclear Information System (INIS)

    Wang, Y.P.; Zhou, L.; Zhang, M.F.; Chen, X.Y.; Liu, J.-M.; Liu, Z.G.

    2004-01-01

    Single-phased ferroelectromagnet BiFeO 3 ceramics with high resistivity were synthesized by a rapid liquid phase sintering technique. Saturated ferroelectric hysteresis loops were observed at room temperature in the ceramics sintered at 880 deg. C for 450 s. The spontaneous polarization, remnant polarization, and the coercive field are 8.9 μC/cm 2 , 4.0 μC/cm 2 , and 39 kV/cm, respectively, under an applied field of 100 kV/cm. It is proposed that the formation of Fe 2+ and an oxygen deficiency leading to the higher leakage can be greatly suppressed by the very high heating rate, short sintering period, and liquid phase sintering technique. The latter was also found effective in increasing the density of the ceramics. The sintering technique developed in this work is expected to be useful in synthesizing other ceramics from multivalent or volatile starting materials

  2. CuInP₂S₆ Room Temperature Layered Ferroelectric.

    Science.gov (United States)

    Belianinov, A; He, Q; Dziaugys, A; Maksymovych, P; Eliseev, E; Borisevich, A; Morozovska, A; Banys, J; Vysochanskii, Y; Kalinin, S V

    2015-06-10

    We explore ferroelectric properties of cleaved 2-D flakes of copper indium thiophosphate, CuInP2S6 (CITP), and probe size effects along with limits of ferroelectric phase stability, by ambient and ultra high vacuum scanning probe microscopy. CITP belongs to the only material family known to display ferroelectric polarization in a van der Waals, layered crystal at room temperature and above. Our measurements directly reveal stable, ferroelectric polarization as evidenced by domain structures, switchable polarization, and hysteresis loops. We found that at room temperature the domain structure of flakes thicker than 100 nm is similar to the cleaved bulk surfaces, whereas below 50 nm polarization disappears. We ascribe this behavior to a well-known instability of polarization due to depolarization field. Furthermore, polarization switching at high bias is also associated with ionic mobility, as evidenced both by macroscopic measurements and by formation of surface damage under the tip at a bias of 4 V-likely due to copper reduction. Mobile Cu ions may therefore also contribute to internal screening mechanisms. The existence of stable polarization in a van-der-Waals crystal naturally points toward new strategies for ultimate scaling of polar materials, quasi-2D, and single-layer materials with advanced and nonlinear dielectric properties that are presently not found in any members of the growing "graphene family".

  3. Concurrent transition of ferroelectric and magnetic ordering near room temperature.

    Science.gov (United States)

    Ko, Kyung-Tae; Jung, Min Hwa; He, Qing; Lee, Jin Hong; Woo, Chang Su; Chu, Kanghyun; Seidel, Jan; Jeon, Byung-Gu; Oh, Yoon Seok; Kim, Kee Hoon; Liang, Wen-I; Chen, Hsiang-Jung; Chu, Ying-Hao; Jeong, Yoon Hee; Ramesh, Ramamoorthy; Park, Jae-Hoon; Yang, Chan-Ho

    2011-11-29

    Strong spin-lattice coupling in condensed matter gives rise to intriguing physical phenomena such as colossal magnetoresistance and giant magnetoelectric effects. The phenomenological hallmark of such a strong spin-lattice coupling is the manifestation of a large anomaly in the crystal structure at the magnetic transition temperature. Here we report that the magnetic Néel temperature of the multiferroic compound BiFeO(3) is suppressed to around room temperature by heteroepitaxial misfit strain. Remarkably, the ferroelectric state undergoes a first-order transition to another ferroelectric state simultaneously with the magnetic transition temperature. Our findings provide a unique example of a concurrent magnetic and ferroelectric transition at the same temperature among proper ferroelectrics, taking a step toward room temperature magnetoelectric applications.

  4. Room temperature ferroelectricity in continuous croconic acid thin films

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Xuanyuan; Lu, Haidong; Yin, Yuewei; Ahmadi, Zahra; Costa, Paulo S. [Department of Physics and Astronomy, University of Nebraska, Lincoln, Nebraska 68588 (United States); Zhang, Xiaozhe [Department of Physics and Astronomy, University of Nebraska, Lincoln, Nebraska 68588 (United States); Department of Physics, Xi' an Jiaotong University, Xi' an 710049 (China); Wang, Xiao; Yu, Le; Cheng, Xuemei [Department of Physics, Bryn Mawr College, Bryn Mawr, Pennsylvania 19010 (United States); DiChiara, Anthony D. [Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Gruverman, Alexei, E-mail: alexei-gruverman@unl.edu, E-mail: a.enders@me.com, E-mail: xiaoshan.xu@unl.edu; Enders, Axel, E-mail: alexei-gruverman@unl.edu, E-mail: a.enders@me.com, E-mail: xiaoshan.xu@unl.edu; Xu, Xiaoshan, E-mail: alexei-gruverman@unl.edu, E-mail: a.enders@me.com, E-mail: xiaoshan.xu@unl.edu [Department of Physics and Astronomy, University of Nebraska, Lincoln, Nebraska 68588 (United States); Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588 (United States)

    2016-09-05

    Ferroelectricity at room temperature has been demonstrated in nanometer-thin quasi 2D croconic acid thin films, by the polarization hysteresis loop measurements in macroscopic capacitor geometry, along with observation and manipulation of the nanoscale domain structure by piezoresponse force microscopy. The fabrication of continuous thin films of the hydrogen-bonded croconic acid was achieved by the suppression of the thermal decomposition using low evaporation temperatures in high vacuum, combined with growth conditions far from thermal equilibrium. For nominal coverages ≥20 nm, quasi 2D and polycrystalline films, with an average grain size of 50–100 nm and 3.5 nm roughness, can be obtained. Spontaneous ferroelectric domain structures of the thin films have been observed and appear to correlate with the grain patterns. The application of this solvent-free growth protocol may be a key to the development of flexible organic ferroelectric thin films for electronic applications.

  5. Above-room-temperature ferroelectricity and antiferroelectricity in benzimidazoles

    Science.gov (United States)

    Horiuchi, Sachio; Kagawa, Fumitaka; Hatahara, Kensuke; Kobayashi, Kensuke; Kumai, Reiji; Murakami, Youichi; Tokura, Yoshinori

    2012-12-01

    The imidazole unit is chemically stable and ubiquitous in biological systems; its proton donor and acceptor moieties easily bind molecules into a dipolar chain. Here we demonstrate that chains of these amphoteric molecules can often be bistable in electric polarity and electrically switchable, even in the crystalline state, through proton tautomerization. Polarization-electric field (P-E) hysteresis experiments reveal a high electric polarization ranging from 5 to 10 μC cm-2 at room temperature. Of these molecules, 2-methylbenzimidazole allows ferroelectric switching in two dimensions due to its pseudo-tetragonal crystal symmetry. The ferroelectricity is also thermally robust up to 400 K, as is that of 5,6-dichloro-2-methylbenzimidazole (up to ~373 K). In contrast, three other benzimidazoles exhibit double P-E hysteresis curves characteristic of antiferroelectricity. The diversity of imidazole substituents is likely to stimulate a systematic exploration of various structure-property relationships and domain engineering in the quest for lead- and rare-metal-free ferroelectric devices.

  6. An EPR investigation of room temperature radiation damage and molecular motion in the ferroelectric phosphates

    International Nuclear Information System (INIS)

    Dalal, N.S.; Herak, J.N.; McDowell, C.A.

    1976-01-01

    Several types of paramagnetic centers have been detected in the room temperature irradiated KH 2 PO 4 , KD 2 PO 4 , KH 2 PO 4 -KH 2 AsO 4 , KD 2 PO 4 -KD 2 AsO 4 and in the newly discovered ferroelectric NaTh 2 (PO 4 ) 3 . Comparative studies of temperature dependence in the EPR spectra show that as in KH 2 PO 4 -type crystals, the ferroelectric phase transition in NaTh 2 (PO 4 ) 3 crystals also seems to be related to the motion of the PO 4 units. The results help to clarify some earlier observed anomalies on the effects of γ-irradiation on dielectric properties of KH 2 PO 4 and in particular, show that the extent of the damage can be controlled by changing the impurity content of the unirradiated samples. (Auth.)

  7. Origin of Ferrimagnetism and Ferroelectricity in Room-Temperature Multiferroic ɛ -Fe2O3

    Science.gov (United States)

    Xu, K.; Feng, J. S.; Liu, Z. P.; Xiang, H. J.

    2018-04-01

    Exploring and identifying room-temperature multiferroics is critical for developing better nonvolatile random-access memory devices. Recently, ɛ -Fe2O3 was found to be a promising room-temperature multiferroic with a large polarization and magnetization. However, the origin of the multiferroicity in ɛ -Fe2O3 is still puzzling. In this work, we perform density-functional-theory calculations to reveal that the spin frustration between tetrahedral-site Fe3 + spins gives rise to the unexpected ferrimagnetism. For the ferroelectricity, we identify a low-energy polarization switching path with an energy barrier of 85 meV /f .u . by performing a stochastic surface walking simulation. The switching of the ferroelectric polarization is achieved by swapping the tetrahedral Fe ion with the octahedral Fe ion, different from the usual case (e.g., in BaTiO3 and BiFeO3 ) where the coordination number remains unchanged after the switching. Our results not only confirm that ɛ -Fe2O3 is a promising room-temperature multiferroic but also provide guiding principles to design high-performance multiferroics.

  8. Room temperature p-type conductivity and coexistence of ferroelectric order in ferromagnetic Li doped ZnO nanoparticles

    KAUST Repository

    Awan, Saif Ullah; Hasanain, S. K.; Anjum, Dalaver H.; Awan, M. S.; Shah, Saqlain A.

    2014-01-01

    for long range order ferromagnetic coupling in Li doped samples. Room temperature ferroelectric hysteresis loops were observed in 8% and 10% Li doped samples. We demonstrated ferroelectric coercivity (remnant polarization) 2.5kV/cm (0.11 μC/cm2) and 2.8k

  9. Structure of the fully ferroelectric/fully ferroelastic orthohombic room-temperature phase of cobalt bromine boracite, Co3B7O13Br and nickel chlorine boracite, Ni3B7O13Cl

    International Nuclear Information System (INIS)

    Kubel, F.; Mao, S.Y.; Schmid, H.

    1992-01-01

    The X-ray crystal structures of optically controlled single-domain crystals of fully ferroelectric/fully ferroelastic cobalt bromine boracite, Co 3 B 7 O 13 Br (Co-Br) at 298 K [M r = 540.38, orthorhombic, Pca2 1 , a = 8.5614 (2), b = 8.5657 (2), c = 12.1196 (3) A, V = 888.78 (4) A 3 , Z = 4, D x = 4.04 Mg m -3 , λ(Mo Kα) = 0.7107 A, μ = 10.61 mm -1 , F(000) = 1020, R = 7.0, wR = 5.4%, 2824 reflections] and of nickel chlorine boracite, Ni 3 B 7 O 13 Cl (Ni-Cl) at 298 K [M r = 495.25, orthorhombic, Pca2 1 , a = 8.5105 (4), b = 8.4984 (4), c = 12.0324 (5) A, V = 870.25 (7) A 3 , Z = 4, D x = 3.78 Mg m -3 , λ(Mo Kα) = 0.7107 A, μ = 6.8 mm -1 , F(000) = 960, R = 3.5, wR = 3.1%, 2082 reflections] are reported. The metal surroundings of Co-Br and Ni-Cl were analyzed in detail and show two metal sites (Co2, Co3; Ni2, Ni3) with chemically similar environments and one metal site (Co1; Ni1) with a different environment. Six B atoms have a tetrahedral or slightly distorted tetrahedral coordination, whereas one B atom (B4) has triangular surroundings in both compounds. (orig.)

  10. Room Temperature Monoclinic Phase in BaTiO3 Single Crystals

    Science.gov (United States)

    Denev, Sava; Kumar, Amit; Barnes, Andrew; Vlahos, Eftihia; Shepard, Gabriella; Gopalan, Venkatraman

    2010-03-01

    BaTiO3 is a well studied ferroelectric material for the last half century. It is well known to show phase transitions to tetragonal, orthorhombic and rhombohedral phases upon cooling. Yet, some old and some recent studies have argued that all these phases co-exist with a second phase with monoclinic distortion. Using optical second harmonic generation (SHG) at room temperature we directly present evidence for such monoclininc phase co-existing with tetragonal phase at room temperature. We observe domains with the expected tetragonal symmetry exhibiting 90^o and 180^o domain walls. However, at points of higher stress at the tips of the interpenetrating tetragonal domains we observe a well pronounced metastable ``staircase pattern'' with a micron-scale fine structure. Polarization studies show that this phase can be explained only by monoclinic symmetry. This phase is very sensitive to external perturbations such as temperature and fields, hence stabilizing this phase at room temperature could lead to large properties' tunability.

  11. Observation of room temperature saturated ferroelectric polarization in Dy substituted BiFeO3 ceramics

    KAUST Repository

    Zhang, Shuxia

    2012-04-06

    High quality Bi1− x Dy x FeO3 (0 ≤ x ≤ 0.15) ceramics have been fabricated by sintering Dy-doped BiFeO3 (BFO) precursor powders at a low temperature of 780 °C. The magnetic properties of BFO were improved by the introduction of Dy on the Bi-site. More importantly, well saturated ferroelectric hysteresis loops and polarization switching currents have been observed at room temperature. A large remnant polarization (2P r) value of 62 μC/cm2 is achieved, which is the highest value reported so far for rare-earth-doped BFO ceramics. Moreover, mechanisms for improved multiferroic properties depending on chemical doping-caused structure evolutions have also been discussed.

  12. Observation of room temperature saturated ferroelectric polarization in Dy substituted BiFeO3 ceramics

    KAUST Repository

    Zhang, Shuxia; Wang, Lei; Chen, Yao; Wang, Dongliang; Yao, Yingbang; Ma, Yanwei

    2012-01-01

    High quality Bi1− x Dy x FeO3 (0 ≤ x ≤ 0.15) ceramics have been fabricated by sintering Dy-doped BiFeO3 (BFO) precursor powders at a low temperature of 780 °C. The magnetic properties of BFO were improved by the introduction of Dy on the Bi-site. More importantly, well saturated ferroelectric hysteresis loops and polarization switching currents have been observed at room temperature. A large remnant polarization (2P r) value of 62 μC/cm2 is achieved, which is the highest value reported so far for rare-earth-doped BFO ceramics. Moreover, mechanisms for improved multiferroic properties depending on chemical doping-caused structure evolutions have also been discussed.

  13. Multiferroicity in polar phase LiNbO{sub 3} at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Manikandan, M. [Department of Nuclear Physics, University of Madras, Guindy Campus, Chennai 600 025 (India); Saravana Kumar, K. [Department of Physics, SRM University, Ramapuram Campus, Chennai 600 089 (India); Aparnadevi, N.; Praveen Shanker, N. [Department of Nuclear Physics, University of Madras, Guindy Campus, Chennai 600 025 (India); Venkateswaran, C., E-mail: cvunom@hotmail.com [Department of Nuclear Physics, University of Madras, Guindy Campus, Chennai 600 025 (India)

    2015-10-01

    LiNbO{sub 3}, prepared by ball milling assisted ceramic method, exhibits weak ferromagnetism and ferroelectricity at room temperature. X-ray diffraction pattern reveals the rhombohedral phase of LiNbO{sub 3} with hexagonal unit cell symmetry. The weak ferromagnetic behavior, obtained using VSM, has been explained using Dzyaloshinskii–Moriya interaction caused by the ferroelectric distortion in its magnetic order. The P–E loop measurement shows lossy natured ferroelectric loop. Electrical and dielectric properties analyzed using impedance spectroscopy show two thermally activated conduction processes, derived from the Arrhenius plot. A gradual increase in the dielectric constant below 493 K and a rapid increase above 493 K reveals the contribution of polarization components and Lithium ion hopping. - Highlights: • LiNbO{sub 3} sample was prepared by ball milling assisted ceramic method. • Observed weak-ferromagnetism in ferroelectric LiNbO{sub 3} makes it suitable for spintronics applications. • The observed magnetism was explained using Dzyaloshinskii–Moriya interactions. • LiNbO{sub 3} sample exhibits lossy natured ferroelectric loop. • The dc conductivity study reveals two thermally activated conduction processes.

  14. Room temperature p-type conductivity and coexistence of ferroelectric order in ferromagnetic Li doped ZnO nanoparticles

    KAUST Repository

    Awan, Saif Ullah

    2014-10-28

    Memory and switching devices acquired new materials which exhibit ferroelectric and ferromagnetic order simultaneously. We reported multiferroic behavior in Zn1-yLiyO(0.00≤y≤0.10) nanoparticles. The analysis of transmission electron micrographs confirmed the hexagonal morphology and wurtzite crystalline structure. We investigated p-type conductivity in doped samples and measured hole carriers in range 2.4×1017/cc to 7.3×1017/cc for different Li contents. We found that hole carriers are responsible for long range order ferromagnetic coupling in Li doped samples. Room temperature ferroelectric hysteresis loops were observed in 8% and 10% Li doped samples. We demonstrated ferroelectric coercivity (remnant polarization) 2.5kV/cm (0.11 μC/cm2) and 2.8kV/cm (0.15 μC/cm2) for y=0.08 and y=0.10 samples. We propose that the mechanism of Li induced ferroelectricity in ZnO is due to indirect dipole interaction via hole carriers. We investigated that if the sample has hole carriers ≥5.3×1017/cc, they can mediate the ferroelectricity. Ferroelectric and ferromagnetic measurements showed that higher electric polarization and larger magnetic moment is attained when the hole concentration is larger and vice versa. Our results confirmed the hole dependent coexistence of ferromagnetic and ferroelectric behavior at room temperature, which provide potential applications for switchable and memory devices.

  15. A novel perovskite oxide chemically designed to show multiferroic phase boundary with room-temperature magnetoelectricity

    Science.gov (United States)

    Fernández-Posada, Carmen M.; Castro, Alicia; Kiat, Jean-Michel; Porcher, Florence; Peña, Octavio; Algueró, Miguel; Amorín, Harvey

    2016-09-01

    There is a growing activity in the search of novel single-phase multiferroics that could finally provide distinctive magnetoelectric responses at room temperature, for they would enable a range of potentially disruptive technologies, making use of the ability of controlling polarization with a magnetic field or magnetism with an electric one (for example, voltage-tunable spintronic devices, uncooled magnetic sensors and the long-searched magnetoelectric memory). A very promising novel material concept could be to make use of phase-change phenomena at structural instabilities of a multiferroic state. Indeed, large phase-change magnetoelectric response has been anticipated by a first-principles investigation of the perovskite BiFeO3-BiCoO3 solid solution, specifically at its morphotropic phase boundary between multiferroic polymorphs of rhombohedral and tetragonal symmetries. Here, we report a novel perovskite oxide that belongs to the BiFeO3-BiMnO3-PbTiO3 ternary system, chemically designed to present such multiferroic phase boundary with enhanced ferroelectricity and canted ferromagnetism, which shows distinctive room-temperature magnetoelectric responses.

  16. Coexistence of room temperature ferroelectricity and ferrimagnetism in multiferroic BiFeO3-Bi0.5Na0.5TiO3 solid solution

    International Nuclear Information System (INIS)

    Tian, Z.M.; Wang, C.H.; Yuan, S.L.; Wu, M.S.; Ma, Z.Z.; Duan, H.N.; Chen, L.

    2011-01-01

    Highlights: → In this study, the coexistence of ferroelectrics and ferrimagnetism have been observed at room temperature for the (1 - x)BiFeO 3 -xBi 0.5 Na 0.5 TiO 3 (x = 0.37) solid solutions. → X-ray diffraction and Raman spectroscopy measurements show a single-phase perovskite structure with no impurities identified. → A magnetic transition from paramagnetic (PM) to ferrimagnetic (Ferri) ordering is observed for the solution with Curie temperature T C ∼ 330 K. - Abstract: The structure, ferroelectric and magnetic properties of (1 - x)BiFeO 3 -xBi 0.5 Na 0.5 TiO 3 (x = 0.37) solid solution fabricated by a sol-gel method have been investigated. X-ray diffraction and Raman spectroscopy measurements show a single-phase perovskite structure with no impurities identified. Compared with pure BiFeO 3 , the coexistence of ferroelectricity and ferrimagnetism have been observed at room temperature for the solution with remnant polarization P r = 1.41 μC/cm 2 and remnant magnetization M r = 0.054 emu/g. Importantly, a magnetic transition from ferrimagnetic (FM) ordering to paramagnetic (PM) state is observed, with Curie temperature T C ∼ 330 K, being explained in terms of the suppression of cycloid spin configuration by the structural distortion.

  17. High Power Room Temperature Terahertz Local Oscillator, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to build a high-power, room temperature compact continuous wave terahertz local oscillator for driving heterodyne receivers in the 1-5 THz frequency...

  18. Room-Temperature Voltage Tunable Phonon Thermal Conductivity via Reconfigurable Interfaces in Ferroelectric Thin Films

    Energy Technology Data Exchange (ETDEWEB)

    Ihlefeld, Jon F. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Foley, Brian M. [Univ. of Virginia, Charlottesville, VA (United States). Dept. of Mechanical and Aerospace Engineering; Scrymgeour, David A. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Michael, Joseph R. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); McKenzie, Bonnie B. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Medlin, Douglas L. [Sandia National Laboratories, Livermore, CA; Wallace, Margeaux [Pennsylvania State Univ., University Park, PA (United States). Dept. of Materials Science and Engineering; Trolier-McKinstry, Susan [Pennsylvania State Univ., University Park, PA (United States). Dept. of Materials Science and Engineering; Hopkins, Patrick E. [Univ. of Virginia, Charlottesville, VA (United States). Dept. of Mechanical and Aerospace Engineering

    2015-02-19

    Dynamic control of thermal transport in solid-state systems is a transformative capability with the promise to propel technologies including phononic logic, thermal management, and energy harvesting. A solid-state solution to rapidly manipulate phonons has escaped the scientific community. Here, we demonstrate active and reversible tuning of thermal conductivity by manipulating the nanoscale ferroelastic domain structure of a Pb(Zr0.3Ti0.7)O3 film with applied electric fields. With subsecond response times, the room-temperature thermal conductivity was modulated by 11%.

  19. Room-temperature voltage tunable phonon thermal conductivity via reconfigurable interfaces in ferroelectric thin films.

    Science.gov (United States)

    Ihlefeld, Jon F; Foley, Brian M; Scrymgeour, David A; Michael, Joseph R; McKenzie, Bonnie B; Medlin, Douglas L; Wallace, Margeaux; Trolier-McKinstry, Susan; Hopkins, Patrick E

    2015-03-11

    Dynamic control of thermal transport in solid-state systems is a transformative capability with the promise to propel technologies including phononic logic, thermal management, and energy harvesting. A solid-state solution to rapidly manipulate phonons has escaped the scientific community. We demonstrate active and reversible tuning of thermal conductivity by manipulating the nanoscale ferroelastic domain structure of a Pb(Zr0.3Ti0.7)O3 film with applied electric fields. With subsecond response times, the room-temperature thermal conductivity was modulated by 11%.

  20. Structure determination at room temperature and phase transition ...

    Indian Academy of Sciences (India)

    Unknown

    Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560 012, India. MS received 9 May 2002 ... exhibit a ferroelectric–paraelectric phase transition at ele- ..... The pattern decomposition and peak extraction methods ...

  1. A phase transition close to room temperature in BiFeO{sub 3} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kreisel, J; Jadhav, P; Chaix-Pluchery, O [Laboratoire des Materiaux et du Genie Physique, Grenoble INP, CNRS, Minatec, 3, parvis Louis Neel, 38016 Grenoble (France); Varela, M [Departamento Fisica Aplicada i Optica, Universitat de Barcelona, Carrer MartI i Franques 1. 08028 Campus UAB, Bellaterra 08193 (Spain); Dix, N; Sanchez, F; Fontcuberta, J, E-mail: jens.kreisel@grenoble-inp.fr [Institut de Ciencia de Materials de Barcelona (ICMAB-CSIC), Campus UAB, Bellaterra 08193 (Spain)

    2011-08-31

    BiFeO{sub 3} (BFO) multiferroic oxide has a complex phase diagram that can be mapped by using appropriately substrate-induced strain in epitaxial films. By using Raman spectroscopy, we conclusively show that films of the so-called supertetragonal T-BFO phase, stabilized under compressive strain, display a reversible temperature-induced phase transition at about 100 deg. C, and thus close to room temperature. (fast track communication)

  2. Stress-induced phase transformation and room temperature aging in Ti-Nb-Fe alloys

    Energy Technology Data Exchange (ETDEWEB)

    Cai, S.; Schaffer, J.E. [Fort Wayne Metals Research Products Corp, 9609 Ardmore Ave., Fort Wayne, IN 46809 (United States); Ren, Y. [Advanced Photon Source, Argonne National Laboratory, 9700 S. Cass Ave., Argonne, IL 60439 (United States)

    2017-01-05

    Room temperature deformation behavior of Ti-17Nb-1Fe and Ti-17Nb-2Fe alloys was studied by synchrotron X-ray diffraction and tensile testing. It was found that, after proper heat treatment, both alloys were able to recover a deformation strain of above 3.5% due to the Stress-induced Martensite (SIM) phase transformation. Higher Fe content increased the beta phase stability and onset stress for SIM transformation. A strong {110}{sub β} texture was produced in Ti-17Nb-2Fe compared to the {210}{sub β} texture that was observed in Ti-17Nb-1Fe. Room temperature aging was observed in both alloys, where the formation of the omega phase increased the yield strength (also SIM onset stress), and decreased the ductility and strain recovery. Other metastable beta Ti alloys may show a similar aging response and this should draw the attention of materials design engineers.

  3. Structure of the fully ferroelectric/fully ferroelastic orthohombic room-temperature phase of cobalt bromine boracite, Co[sub 3]B[sub 7]O[sub 13]Br and nickel chlorine boracite, Ni[sub 3]B[sub 7]O[sub 13]Cl

    Energy Technology Data Exchange (ETDEWEB)

    Kubel, F; Mao, S Y; Schmid, H [Dept. de Chemie Minerale, Analytique et Applique, Geneva Univ. (Switzerland)

    1992-07-15

    The X-ray crystal structures of optically controlled single-domain crystals of fully ferroelectric/fully ferroelastic cobalt bromine boracite, Co[sub 3]B[sub 7]O[sub 13]Br (Co-Br) at 298 K [M[sub r] = 540.38, orthorhombic, Pca2[sub 1], a = 8.5614 (2), b = 8.5657 (2), c = 12.1196 (3) A, V = 888.78 (4) A[sup 3], Z = 4, D[sub x] = 4.04 Mg m[sup -3], [lambda](Mo K[alpha]) = 0.7107 A, [mu] = 10.61 mm[sup -1], F(000) = 1020, R = 7.0, wR = 5.4%, 2824 reflections] and of nickel chlorine boracite, Ni[sub 3]B[sub 7]O[sub 13]Cl (Ni-Cl) at 298 K [M[sub r] = 495.25, orthorhombic, Pca2[sub 1], a = 8.5105 (4), b = 8.4984 (4), c = 12.0324 (5) A, V = 870.25 (7) A[sup 3], Z = 4, D[sub x] = 3.78 Mg m[sup -3], [lambda](Mo K[alpha]) = 0.7107 A, [mu] = 6.8 mm[sup -1], F(000) = 960, R = 3.5, wR = 3.1%, 2082 reflections] are reported. The metal surroundings of Co-Br and Ni-Cl were analyzed in detail and show two metal sites (Co2, Co3; Ni2, Ni3) with chemically similar environments and one metal site (Co1; Ni1) with a different environment. Six B atoms have a tetrahedral or slightly distorted tetrahedral coordination, whereas one B atom (B4) has triangular surroundings in both compounds. (orig.).

  4. Photoluminescence at room temperature of liquid-phase crystallized silicon on glass

    Directory of Open Access Journals (Sweden)

    Michael Vetter

    2016-12-01

    Full Text Available The room temperature photoluminescence (PL spectrum due band-to-band recombination in an only 8 μm thick liquid-phase crystallized silicon on glass solar cell absorber is measured over 3 orders of magnitude with a thin 400 μm thick optical fiber directly coupled to the spectrometer. High PL signal is achieved by the possibility to capture the PL spectrum very near to the silicon surface. The spectra measured within microcrystals of the absorber present the same features as spectra of crystalline silicon wafers without showing defect luminescence indicating the high electronic material quality of the liquid-phase multi-crystalline layer after hydrogen plasma treatment.

  5. Analysis and Optimization of Thin Film Ferroelectric Phase Shifters

    Science.gov (United States)

    Romanofsky, Robert R.; VanKeuls, Fred W.; Warner, Joseph D.; Mueller, Carl H.; Alterovitz, Samuel A.; Miranda, Felix A.; Qureshi, A. Haq; Romanofsky, Robert R. (Technical Monitor)

    2000-01-01

    Microwave phase shifters have been fabricated from (YBa2Cu3O(7-delta) or Au)/SrTiO3 and Au/Ba(x)Sr(1-x)TiO3 films on LaAlO3 and MgO substrates. These coupled microstrip devices rival the performance of their semiconductor counter-parts parts at Ku- and K-band frequencies. Typical insertion loss for room temperature ferroelectric phase shifters at K-band is approximately equal 5 dB. An experimental and theoretical investigation of these novel devices explains the role of the ferroelectric film in overall device performance. A roadmap to the development of a 3 dB insertion loss phase shifter that would enable a new type of phased array antenna is discussed.

  6. Room-temperature solid phase ionic liquid (RTSPIL) coated Ω-transaminases: Development and application in organic solvents

    DEFF Research Database (Denmark)

    Grabner, B.; Nazario, M. A.; Gundersen, M. T.

    2018-01-01

    ω-Transaminases ATA-40, ATA-47 and ATA-82P were coated with room-temperature solid phase ionic liquids (RTSPILs) by means of three methods, melt coating, precipitation coating, and co‐lyophilization, and showed increased stability in all of the five tested organic solvents. Co‐lyophilization and ......ω-Transaminases ATA-40, ATA-47 and ATA-82P were coated with room-temperature solid phase ionic liquids (RTSPILs) by means of three methods, melt coating, precipitation coating, and co‐lyophilization, and showed increased stability in all of the five tested organic solvents. Co...

  7. Vapor Phase Synthesis of Organometal Halide Perovskite Nanowires for Tunable Room-Temperature Nanolasers.

    Science.gov (United States)

    Xing, Jun; Liu, Xin Feng; Zhang, Qing; Ha, Son Tung; Yuan, Yan Wen; Shen, Chao; Sum, Tze Chien; Xiong, Qihua

    2015-07-08

    Semiconductor nanowires have received considerable attention in the past decade driven by both unprecedented physics derived from the quantum size effect and strong isotropy and advanced applications as potential building blocks for nanoscale electronics and optoelectronic devices. Recently, organic-inorganic hybrid perovskites have been shown to exhibit high optical absorption coefficient, optimal direct band gap, and long electron/hole diffusion lengths, leading to high-performance photovoltaic devices. Herein, we present the vapor phase synthesis free-standing CH3NH3PbI3, CH3NH3PbBr3, and CH3NH3PbIxCl3(-x) perovskite nanowires with high crystallinity. These rectangular cross-sectional perovskite nanowires have good optical properties and long electron hole diffusion length, which ensure adequate gain and efficient optical feedback. Indeed, we have demonstrated optical-pumped room-temperature CH3NH3PbI3 nanowire lasers with near-infrared wavelength of 777 nm, low threshold of 11 μJ/cm(2), and a quality factor as high as 405. Our research advocates the promise of optoelectronic devices based on organic-inorganic perovskite nanowires.

  8. Room temperature ferromagnetism in liquid-phase pulsed laser ablation synthesized nanoparticles of nonmagnetic oxides

    International Nuclear Information System (INIS)

    Singh, S. C.; Gopal, R.; Kotnala, R. K.

    2015-01-01

    Intrinsic Room Temperature Ferromagnetism (RTF) has been observed in undoped/uncapped zinc oxide and titanium dioxide spherical nanoparticles (NPs) obtained by a purely green approach of liquid phase pulsed laser ablation of corresponding metal targets in pure water. Saturation magnetization values observed for zinc oxide (average size, 9 ± 1.2 nm) and titanium dioxide (average size, 4.4 ± 0.3 nm) NPs are 62.37 and 42.17 memu/g, respectively, which are several orders of magnitude larger than those of previous reports. In contrast to the previous works, no postprocessing treatments or surface modification is required to induce ferromagnetism in the case of present communication. The most important result, related to the field of intrinsic ferromagnetism in nonmagnetic materials, is the observation of size dependent ferromagnetism. Degree of ferromagnetism in titanium dioxide increases with the increase in particle size, while it is reverse for zinc oxide. Surface and volume defects play significant roles for the origin of RTF in zinc oxide and titanium dioxide NPs, respectively. Single ionized oxygen and neutral zinc vacancies in zinc oxide and oxygen and neutral/ionized titanium vacancies in titanium dioxide are considered as predominant defect centres responsible for observed ferromagnetism. It is expected that origin of ferromagnetism is a consequence of exchange interactions between localized electron spin moments resulting from point defects

  9. Room-temperature ferromagnetism in Fe-based perovskite solid solution in lead-free ferroelectric Bi0.5Na0.5TiO3 materials

    Science.gov (United States)

    Hung, Nguyen The; Bac, Luong Huu; Trung, Nguyen Ngoc; Hoang, Nguyen The; Van Vinh, Pham; Dung, Dang Duc

    2018-04-01

    The integration of ferromagnetism in lead-free ferroelectric materials is important to fabricate smart materials for electronic devices. In this work, (1 - x)Bi0.5Na0.5TiO3 + xMgFeO3-δ materials (x = 0-9 mol%) were prepared through sol-gel method. X-ray diffraction characterization indicated that MgFeO3-δ materials existed as a well solid solution in lead-free ferroelectric Bi0.5Na0.5TiO3 materials. The rhombohedral structure of Bi0.5Na0.5TiO3 materials was distorted due to the random distribution of Mg and Fe cations into the host lattice. The reduced optical band gap and the induced room-temperature ferromagnetism were due to the spin splitting of transition metal substitution at the B-site of perovskite Bi0.5Na0.5TiO3 and the modification by A-site co-substitution. This work elucidates the role of secondary phase as solid solution in Bi0.5Na0.5TiO3 material for development of lead-free multiferroelectric materials.

  10. Facile room-temperature solution-phase synthesis of a spherical covalent organic framework for high-resolution chromatographic separation.

    Science.gov (United States)

    Yang, Cheng-Xiong; Liu, Chang; Cao, Yi-Meng; Yan, Xiu-Ping

    2015-08-07

    A simple and facile room-temperature solution-phase synthesis was developed to fabricate a spherical covalent organic framework with large surface area, good solvent stability and high thermostability for high-resolution chromatographic separation of diverse important industrial analytes including alkanes, cyclohexane and benzene, α-pinene and β-pinene, and alcohols with high column efficiency and good precision.

  11. Possible mechanism for the room-temperature stabilization of the Ge(111) T > 300 deg.C phase by Ga

    DEFF Research Database (Denmark)

    Böhringer, M.; Molinás-Mata, P.; Zegenhagen, J.

    1995-01-01

    At low coverages, Ga on Ge(111) induces a hexagonal, domain wall modulated (2 x 2) adatom phase, stable at room temperature, that is characterized in low energy electron diffraction (LEED) by split 1/2-order reflections. This pattern closely resembles the one observed for a phase of clean Ge(111......) appearing at temperatures above 300 degrees C (T > 300 degrees C phase). We report scanning tunneling microscopy, LEED, as well. as surface x-ray diffraction measurements on the Ga-induced room-temperature (RT) phase and compare it with a model for the T > 300 OC phase of clean Ge(111). RT deposition of Ga...... yields a metastable c(2 x 8) structure which upon annealing transforms to the hexagonal (2 x 2) one. The transition occurs at considerably lower temperatures compared to clean Ge(111) and is irreversible due to pinning of adatom domains at Ga-induced defects, preventing the reordering of the adatoms...

  12. Growth of Ca, Zr co-doped BaTiO3 lead-free ferroelectric single crystal and its room-temperature piezoelectricity

    Directory of Open Access Journals (Sweden)

    Donglin Liu

    2017-09-01

    Full Text Available Lead-free Ca, Zr co-doped BaTiO3 (BCZT single crystal with a dimension up to 2mm×2mm×2mm was grown by a spontaneous nucleation technique using KF as the flux. The composition of the studied single crystal was defined to be Ba0.798Ca0.202Zr0.006Ti0.994O3, corresponding to a tetragonal phase at room temperature. The oriented single crystal exhibited a quasi-static piezoelectric constant of approximately 232 pC/N. The effective piezoelectric coefficient d33* of the single domain crystal obtained under a unipolar electric field of 35 kV/cm was 179 pm/V. Rayleigh analysis was used to identify the intrinsic and extrinsic contributions to the room-temperature piezoelectricity of BCZT single crystal. The extrinsic contribution was estimated up to 40% due to the irreversible domain wall movement. Furthermore a sixth-order polynomial of Landau expansion was employed to analyze the intrinsic contribution to piezoelectricity of BCZT single crystal. The large energy barriers inhibited polarization rotations, leading to the relatively low piezoelectricity.

  13. Self-assembly of gas-phase synthesized magnesium nanoparticles on room temperature substrates

    International Nuclear Information System (INIS)

    Venturi, F; Calizzi, M; Pasquini, L; Bals, S; Perkisas, T

    2015-01-01

    Magnesium nanoparticles (NPs) with initial size in the 10–50 nm range were synthesized by inert gas condensation under helium flow and deposited on room temperature substrates. The morphology and crystal structure of the NPs ensemble were investigated as a function of the deposition time by complementary electron microscopy techniques, including high resolution imaging and chemical mapping. With increasing amount of material, strong coarsening phenomena were observed at room temperature: small NPs disappeared while large faceted NPs developed, leading to a 5-fold increase of the average NPs size within a few minutes. The extent of coarsening and the final morphology depended also on the nature of the substrate. Furthermore, large single-crystal NPs were seen to arise from the self-organization of primary NPs units, providing a mechanism for crystal growth. The dynamics of the self-assembly process involves the basic steps of NPs sticking, diffusion on substrate, coordinated rotation and attachment/coalescence. Key features are the surface energy anisotropy, reflected by the faceted shape of the NPs, and the low melting point of the material. The observed phenomena have strong implications in relation to the synthesis and stability of nanostructures based on Mg or other elements with similar features. (paper)

  14. Ferroelectric Phase Diagram of PVDF:PMMA

    OpenAIRE

    Li, Mengyuan; Stingelin, Natalie; Michels, Jasper J.; Spijkman, Mark-Jan; Asadi, Kamal; Feldman, Kirill; Blom, Paul W. M.; de Leeuw, Dago M.

    2012-01-01

    We have investigated the ferroelectric phase diagram of poly(vinylidene fluoride) (PVDF) and poly(methyl methacrylate) (PMMA). The binary nonequilibrium temperature composition diagram was determined and melting of alpha- and beta-phase PVDF was identified. Ferroelectric beta-PVDF:PMMA blend films were made by melting, ice quenching, and subsequent annealing above the glass transition temperature of PMMA, close to the melting temperature of PVDF. Addition of PMMA suppresses the crystallizatio...

  15. Room temperature superconductors

    International Nuclear Information System (INIS)

    Sleight, A.W.

    1995-01-01

    If the Holy Grail of room temperature superconductivity could be achieved, the impact on could be enormous. However, a useful room temperature superconductor for most applications must possess a T c somewhat above room temperature and must be capable of sustaining superconductivity in the presence of magnetic fields while carrying a significant current load. The authors will return to the subject of just what characteristics one might seek for a compound to be a room temperature superconductor. 30 refs., 3 figs., 1 tab

  16. Finite Atwood Number Effects on Deceleration-Phase Instability in Room-Temperature Direct-Drive Implosions

    Science.gov (United States)

    Miller, S.; Knauer, J. P.; Radha, P. B.; Goncharov, V. N.

    2017-10-01

    Performance degradation in direct-drive inertial confinement fusion implosions can be caused by several effects, one of which is Rayleigh-Taylor (RT) instability growth during the deceleration phase. In room-temperature plastic target implosions, this deceleration-phase RT growth is enhanced by the density discontinuity and finite Atwood numbers at the fuel-pusher interface. For the first time, an experimental campaign at the Omega Laser Facility systematically varied the ratio of deuterium-to-tritium (D-to-T) within the DT gas fill to change the Atwood number. The goal of the experiment was to understand the effects of Atwood number variation on observables like apparent ion temperature, yield, and variations in areal density and bulk fluid motion, which lead to broadening of neutron spectra along different lines of sight. Simulations by the hydrodynamic codes LILAC and DRACO were used to study growth rates for different D-to-T ratios and identify observable quantities effected by Atwood number variation. Results from simulations and the experiment are presented. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

  17. Determination of butyltin species in natural waters using aqueous phase ethylation and off-line room temperature trapping

    International Nuclear Information System (INIS)

    Bowles, Karl C.; Apte, Simon C.; Hales, Leigh T.

    2003-01-01

    Monobutyltin (MBT), dibutyltin (DBT) and tributyltin (TBT) were determined in natural water samples by aqueous phase ethylation with sodium tetraethylborate (STEB), room temperature trapping of the resulting volatile derivatives on Tenax TA[reg], followed by gas chromatography-quartz furnace atomic absorption spectrometry (GC-QFAAS). Recoveries of butyltin spikes from natural water samples were 90-109% at concentrations of ∼100 ng Sn/l. The method precision at ∼100 ng Sn/l was ≤6% RSD for butyltins spiked into natural waters. The detection limits for 1 l water samples were <1 ng Sn/l for all butyltin species. Sample throughput of the method is high (greater than three samples per hour) due to the two-stage nature of the procedure, which allows derivatisation/trapping and GC-QFAAS quantitation to be performed separately. Off-line trapping is also advantageous as it extends the life of the GC column and quartz furnace to at least 12 months due to minimisation of carry-over of co-purged material

  18. Phase locking of a 3.4 THz third-order distributed feedback quantum cascade laser using a room-temperature superlattice harmonic mixer

    NARCIS (Netherlands)

    Hayton, D. J.; Khudchencko, A.; Pavelyev, D. G.; Hovenier, J. N.; Baryshev, A.; Gao, J. R.; Kao, T. Y.; Hu, Q.; Reno, J. L.; Vaks, V.

    2013-01-01

    We report on the phase locking of a 3.4 THz third-order distributed feedback quantum cascade laser (QCL) using a room temperature GaAs/AlAs superlattice diode as both a frequency multiplier and an internal harmonic mixer. A signal-to-noise level of 60 dB is observed in the intermediate frequency

  19. Phase locking of a 3.4 THz third-order distributed feedback quantum cascade laser using a room-temperature superlattice harmonic mixer

    NARCIS (Netherlands)

    Hayton, D.J.; Khudchenko, A.; Pavelyev, D.G.; Hovenier, J.N.; Baryshev, A.; Gao, J.R.; Kao, T.Y.; Hu, Q.; Reno, J.L.; Vaks, V.

    2013-01-01

    We report on the phase locking of a 3.4 THz third-order distributed feedback quantum cascade laser (QCL) using a room temperature GaAs/AlAs superlattice diode as both a frequency multiplier and an internal harmonic mixer. A signal-to-noise level of 60?dB is observed in the intermediate frequency

  20. Development and application of an empirical formula for the high temperature behavior of ferroelectric ceramics switched by electric field at room temperature

    Directory of Open Access Journals (Sweden)

    Dae Won Ji

    2017-05-01

    Full Text Available The strain changes during temperature rise of a poled lead titanate zirconate rectangular parallelepiped switched by electric field at room temperature are obtained by integrating thermal expansion coefficients that are measured using an invar-specimen. By estimating and analyzing pyroelectric and thermal expansion coefficients, first-order differential equations are constructed for polarization and strain changes during temperature increase. The solutions to the differential equations are found and used to calculate the high temperature behavior of the materials. It is shown that the predictions are well compared with measured responses. Finally, the developed formulae are applied to calculate strain butterfly loops from a polarization hysteresis loop at a high temperature.

  1. Metal ion induced room temperature phase transformation and stimulated infrared spectroscopy on TiO{sub 2}-based surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Gole, James L. [Schools of Physics and Mechanical Engineering, Georgia Institute of Technology, 837 State Street, Atlanta, GA 30332-0430 (United States)], E-mail: jim.gole@physics.gatech.edu; Prokes, S.M. [Code 6876, NRL, Washington, DC 20375 (United States)], E-mail: prokes@estd.nrl.navy.mil; White, Mark G. [Dave C. Swalm School of Chemical Engineering, James Worth Bagley College of Engineering, Box 959, MS 39762 (United States)], E-mail: white@che.msstate.edu

    2008-11-30

    Raman and infrared spectroscopy are used to demonstrate (1) the high spin metal ion induced room temperature transformation of anatase to rutile TiO{sub 2} and (2) the phenomena of stimulated IR spectroscopy induced by simultaneous nitrogen doping and high spin metal ion seeding of a TiO{sub 2} nanocolloid lattice.

  2. Metal ion induced room temperature phase transformation and stimulated infrared spectroscopy on TiO2-based surfaces

    International Nuclear Information System (INIS)

    Gole, James L.; Prokes, S.M.; White, Mark G.

    2008-01-01

    Raman and infrared spectroscopy are used to demonstrate (1) the high spin metal ion induced room temperature transformation of anatase to rutile TiO 2 and (2) the phenomena of stimulated IR spectroscopy induced by simultaneous nitrogen doping and high spin metal ion seeding of a TiO 2 nanocolloid lattice

  3. High temperature phases in PZT ferroelectric films

    Czech Academy of Sciences Publication Activity Database

    Deineka, Alexander; Suchaneck, G.; Jastrabík, Lubomír; Gerlach, G.

    2003-01-01

    Roč. 293, - (2003), s. 111-118 ISSN 0015-0193 R&D Projects: GA ČR GP202/02/D078; GA MŠk LN00A015 Institutional research plan: CEZ:AV0Z1010914 Keywords : ferroelectric film * phase transition * film profile Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.406, year: 2003

  4. Determination of Three-Dimensional Morphology and Inner Structure of Second-Phase Inclusions in Metals by Non-Aqueous Solution Electrolytic and Room Temperature Organic Methods

    OpenAIRE

    Jing Guo; Keming Fang; Hanjie Guo; Yiwa Luo; Shengchao Duan; Xiao Shi; Wensheng Yang

    2018-01-01

    The secondary-phase particles in metals, particularly those composed of non-metallic materials, are often detrimental to the mechanical properties of metals; thus, it is crucial to control inclusion formation and growth. One of the challenges is determining the three-dimensional morphology and inner structures of such inclusions. In this study, a non-aqueous solution electrolytic method and a room-temperature organic technique were developed based on the principle of electrochemistry to deter...

  5. Ferroelectric InMnO{sub 3}: Growth of single crystals, structure and high-temperature phase transitions

    Energy Technology Data Exchange (ETDEWEB)

    Bekheet, Maged F., E-mail: maged.bekheet@ceramics.tu-berlin.de [Fachbereich Material‐ und Geowissenschaften, Technische Universität Darmstadt, Alarich-Weiss-Straße 2, 64287 Darmstadt (Germany); Fachgebiet Keramische Werkstoffe / Chair of Advanced Ceramic Materials, Institut für Werkstoffwissenschaften und -technologien, Technische Universität Berlin, Hardenbergstraße 40, 10623 Berlin (Germany); Svoboda, Ingrid; Liu, Na [Fachbereich Material‐ und Geowissenschaften, Technische Universität Darmstadt, Alarich-Weiss-Straße 2, 64287 Darmstadt (Germany); Bayarjargal, Lkhamsuren [Institut für Geowissenschaften, Goethe-Universität, Altenhöferallee 1, d-60438 Frankfurt a.M. (Germany); Irran, Elisabeth [Institut für Chemie, Technische Universität Berlin, Straße des 17, Juni 135, 10623 Berlin (Germany); Dietz, Christian; Stark, Robert W.; Riedel, Ralf [Fachbereich Material‐ und Geowissenschaften, Technische Universität Darmstadt, Alarich-Weiss-Straße 2, 64287 Darmstadt (Germany); Gurlo, Aleksander [Fachgebiet Keramische Werkstoffe / Chair of Advanced Ceramic Materials, Institut für Werkstoffwissenschaften und -technologien, Technische Universität Berlin, Hardenbergstraße 40, 10623 Berlin (Germany)

    2016-09-15

    To understand the origin of the ferroelectricity in InMnO{sub 3}, single crystals with average size of 1 mm were grown in PbF{sub 2} flux at 950 °C. The results of single crystal X-ray diffraction, second harmonic generation and piezoresponse force microscopy studies of high-quality InMnO{sub 3} single crystals reveal that the room-temperature state in this material is ferroelectric with P6{sub 3}cm symmetry. The polar InMnO{sub 3} specimen undergoes a reversible phase transition from non-centrosymmetric P6{sub 3}cm structure to a centrosymmetric P6{sub 3}/mmc structure at 700 °C as confirmed by the in situ high-temperature Raman spectroscopic and synchrotron X-ray diffraction experiments. - Graphical abstract: Piezoresponse fore microscopy (PFM) studies of high quality InMnO{sub 3} single crystal revealed that the room-temperature state of this material is ferroelectric with a clear cloverleaf pattern corresponding to six antiphase ferroelectric domains with alternating polarization ±P{sub z}. Display Omitted - Highlights: • InMnO{sub 3} single crystals with average size of 1 mm were grown in PbF{sub 2} flux at 950 °C. • The room-temperature state of InMnO{sub 3} is ferroelectric with polar P6{sub 3}cm structure. • PolarInMnO{sub 3} reversibly transforms to a centrosymmetric P6{sub 3}/mmc structure above 700 °C.

  6. 500 keV Ar2+ ion irradiation induced anatase to brookite phase transformation and ferromagnetism at room temperature in TiO2 thin films

    Science.gov (United States)

    Bharati, B.; Mishra, N. C.; Kanjilal, D.; Rath, Chandana

    2018-01-01

    In our earlier report, where we have demonstrated ferromagnetic behavior at room temperature (RT) in TiO2 thin films deposited through electron beam evaporation technique followed by annealing either in Ar or O2 atmosphere [Mohanty et al., Journal of Magnetism and Magnetic Materials 355 (2014) 240-245], here we have studied the evolution of structure and magnetic properties after irradiating the TiO2 thin films with 500 keV Ar2+ ions. The pristine film while exhibits anatase phase, the films become amorphous after irradiating at fluence in the range 1 × 1014 to 1 × 1016 ions/cm2. Increasing the fluence up to 5 × 1016 ions/cm2, amorphous to crystalline phase transformation occurs and the structure becomes brookite. Although anatase to rutile phase transformation is usually reported in literatures, anatase to brookite phase transformation is an unusual feature which we have reported here for the first time. Such anatase to brookite phase transformation is accompanied with grain growth without showing any change in film thickness evidenced from Rutherford's Back Scattering (RBS) measurement. From scanning probe micrographs (SPM), roughness is found to be more in amorphous films than in the crystalline ones. Anatase to brookite phase transformation could be realized by considering the importance of intermediate amorphous phase. Because due to amorphous phase, heat deposited by energetic ions are localized as dissipation of heat is less and as a result, the localized region crystallizes in brookite phase followed by grain growth as observed in highest fluence. Further, we have demonstrated ferromagnetic behavior at RT in irradiated films similar to pristine one, irrespective of their phase and crystallinity. Origin for room temperature ferromagnetism (RTFM) is attributed to the presence of oxygen vacancies which is confirmed by carrying out XPS measurement.

  7. Room temperature ionic liquids enhanced the speciation of Cr(VI) and Cr(III) by hollow fiber liquid phase microextraction combined with flame atomic absorption spectrometry

    International Nuclear Information System (INIS)

    Zeng, Chujie; Lin, Yao; Zhou, Neng; Zheng, Jiaoting; Zhang, Wei

    2012-01-01

    Highlights: ► First reported enhancement effect of RTILs in HF-LPME for the speciation of chromium. ► The addition of RTILs led to 3.5 times improvement of the sensitivity of Cr(VI). ► The proposed method is a simplicity, sensitivity, low cost, green method. - Abstract: A new method for the speciation of Cr(VI) and Cr(III) based on enhancement effect of room temperature ionic liquids (RTILs) for hollow fiber liquid phase microextraction (HF-LPME) combined with flame atomic absorption spectrometry (FAAS) was developed. Room temperature ionic liquids (RTILs) and diethyldithiocarbamate (DDTC) were used enhancement reagents and chelating reagent, respectively. The addition of room temperature ionic liquids led to 3.5 times improvement in the determination of Cr(VI). In this method, Cr(VI) reacts with DDTC yielding a hydrophobic complex, which is subsequently extracted into the lumen of hollow fiber, whereas Cr(III) is remained in aqueous solutions. The extraction organic phase was injected into FAAS for the determination of Cr(VI). Total Cr concentration was determined after oxidizing Cr(III) to Cr(VI) in the presence of KMnO 4 and using the extraction procedure mentioned above. Cr(III) was calculated by subtracting of Cr(VI) from the total Cr. Under optimized conditions, a detection limit of 0.7 ng mL −1 and an enrichment factor of 175 were achieved. The relative standard deviation (RSD) was 4.9% for Cr(VI) (40 ng mL −1 , n = 5). The proposed method was successfully applied to the speciation of chromium in natural water samples with satisfactory results.

  8. Room temperature ionic liquids enhanced the speciation of Cr(VI) and Cr(III) by hollow fiber liquid phase microextraction combined with flame atomic absorption spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, Chujie, E-mail: cjzeng@126.com [Department of Chemistry and Material, Yulin Normal College, Yulin, Guangxi 537000 (China); Lin, Yao; Zhou, Neng; Zheng, Jiaoting; Zhang, Wei [Department of Chemistry and Material, Yulin Normal College, Yulin, Guangxi 537000 (China)

    2012-10-30

    Highlights: Black-Right-Pointing-Pointer First reported enhancement effect of RTILs in HF-LPME for the speciation of chromium. Black-Right-Pointing-Pointer The addition of RTILs led to 3.5 times improvement of the sensitivity of Cr(VI). Black-Right-Pointing-Pointer The proposed method is a simplicity, sensitivity, low cost, green method. - Abstract: A new method for the speciation of Cr(VI) and Cr(III) based on enhancement effect of room temperature ionic liquids (RTILs) for hollow fiber liquid phase microextraction (HF-LPME) combined with flame atomic absorption spectrometry (FAAS) was developed. Room temperature ionic liquids (RTILs) and diethyldithiocarbamate (DDTC) were used enhancement reagents and chelating reagent, respectively. The addition of room temperature ionic liquids led to 3.5 times improvement in the determination of Cr(VI). In this method, Cr(VI) reacts with DDTC yielding a hydrophobic complex, which is subsequently extracted into the lumen of hollow fiber, whereas Cr(III) is remained in aqueous solutions. The extraction organic phase was injected into FAAS for the determination of Cr(VI). Total Cr concentration was determined after oxidizing Cr(III) to Cr(VI) in the presence of KMnO{sub 4} and using the extraction procedure mentioned above. Cr(III) was calculated by subtracting of Cr(VI) from the total Cr. Under optimized conditions, a detection limit of 0.7 ng mL{sup -1} and an enrichment factor of 175 were achieved. The relative standard deviation (RSD) was 4.9% for Cr(VI) (40 ng mL{sup -1}, n = 5). The proposed method was successfully applied to the speciation of chromium in natural water samples with satisfactory results.

  9. Portevin-Le Chatelier effect in a Ni–Cr–Mo alloy containing ordered phase with Pt{sub 2}Mo-type structure at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, Liang, E-mail: yuanliang031@163.com [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072 (China); Hu, Rui, E-mail: rhu@nwpu.edu.cn [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072 (China); Li, Jinshan [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072 (China); Zhang, Xiaoqing; Yang, Yan’an [Xi’an Filter Metal Materials Co., Ltd., Xi’an 710072 (China)

    2016-01-05

    Serrated flow behavior or the Portevin-Le Chatelier (PLC) effect in a Ni–Cr–Mo alloy containing ordered phase was investigated at uniaxial tensile and nanoindentation tests at room temperature. Results demonstrate that the periodic arrangement of atoms for nano-sized ordered phase with Pt{sub 2}Mo-type structure obtained by ageing treatment at 600 °C, induces the appearance of an embedded serration (a small serration is embedded in two adjacent large serrations) in the alloy during uniaxial tensile tests at room temperature with strain rates of 10{sup −3} and 10{sup −4} s{sup −1}. The behavior characteristic of small serration is almost independent on strain rate, but that of large serration is significantly dependent on strain rate. Both the stress drop (Δσ) of the large serration and the interval (t{sub w}) between adjacent large serrations increase with decreasing strain rate from 10{sup −3} to 10{sup −4} s{sup −1}. Moreover, a single serration also appears in load-displacement curve of aged sample at loading rate of 10{sup −3} s{sup −1}. Both formation of order-disorder transformation-induced twins and twinning of ordered phase itself are responsible for the occurrence of the embedded serrations.

  10. Room-Temperature and Aqueous-Phase Synthesis of Plasmonic Molybdenum Oxide Nanoparticles for Visible-Light-Enhanced Hydrogen Generation.

    Science.gov (United States)

    Shi, Jiayuan; Kuwahara, Yasutaka; Wen, Meicheng; Navlani-García, Miriam; Mori, Kohsuke; An, Taicheng; Yamashita, Hiromi

    2016-09-06

    A straightforward aqueous synthesis of MoO3-x nanoparticles at room temperature was developed by using (NH4 )6 Mo7 O24 ⋅4 H2 O and MoCl5 as precursors in the absence of reductants, inert gas, and organic solvents. SEM and TEM images indicate the as-prepared products are nanoparticles with diameters of 90-180 nm. The diffuse reflectance UV-visible-near-IR spectra of the samples indicate localized surface plasmon resonance (LSPR) properties generated by the introduction of oxygen vacancies. Owing to its strong plasmonic absorption in the visible-light and near-infrared region, such nanostructures exhibit an enhancement of activity toward visible-light catalytic hydrogen generation. MoO3-x nanoparticles synthesized with a molar ratio of Mo(VI) /Mo(V) 1:1 show the highest yield of H2 evolution. The cycling catalytic performance has been investigated to indicate the structural and chemical stability of the as-prepared plasmonic MoO3-x nanoparticles, which reveals its potential application in visible-light catalytic hydrogen production. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Novel room temperature ferromagnetic semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, Amita [KTH Royal Inst. of Technology, Stockholm (Sweden)

    2004-06-01

    distribution of Mn substituting for Zn a 2+ state in the ZnO lattice. Ferromagnetic Resonance (FMR) technique is used to confirm the existence of ferromagnetic ordering at temperatures as high as 425K. The ab initio calculations were found to be consistent with the observation of ferromagnetism arising from fully polarized Mn 2+ state. The key to observed room temperature ferromagnetism in this system is the low temperature processing, which prevents formation of clusters, secondary phases and the host ZnO from becoming n-type. The electronic structure of the same Mn doped ZnO thin films studied using XAS, XES and RIXS, revealed a strong hybridization between Mn 3d and O 2p states, which is an important characteristic of a Dilute magnetic Semiconductor (DMS). It is shown that the various processing conditions like sintering temperature, dopant concentration and the properties of precursors used for making of DMS have a great influence on the final properties. Use of various experimental techniques to verify the physical properties, and to understand the mechanism involved to give rise to ferromagnetism is presented. Methods to improve the magnetic moment in Mn doped ZnO are also described. New promising DMS materials (such as Cu doped ZnO are explored). The demonstrated new capability to fabricate powder, pellets, and thin films of room temperature ferromagnetic semiconductors thus makes possible the realization of a wide range of complex elements for a variety of new multifunctional phenomena related to Spintronic devices as well as magneto-optic components.

  12. Formation of (111) orientation-controlled ferroelectric orthorhombic HfO{sub 2} thin films from solid phase via annealing

    Energy Technology Data Exchange (ETDEWEB)

    Mimura, Takanori; Katayama, Kiliha [Department of Innovative and Engineered Materials, Tokyo Institute of Technology, Yokohama 226-8502 (Japan); Shimizu, Takao [Materials Research Center for Element Strategy, Tokyo Institute of Technology, Yokohama 226-8503 (Japan); Uchida, Hiroshi [Department of Materials and Life Sciences, Sophia University, Tokyo 102-8554 (Japan); Kiguchi, Takanori; Akama, Akihiro; Konno, Toyohiko J. [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Sakata, Osami [Synchrotron X-ray Station at SPring-8 and Synchrotron X-ray Group, National Institute for Materials Science, Sayo, Hyogo 679-5148 (Japan); Funakubo, Hiroshi, E-mail: funakubo.h.aa@m.titech.ac.jp [Department of Innovative and Engineered Materials, Tokyo Institute of Technology, Yokohama 226-8502 (Japan); Materials Research Center for Element Strategy, Tokyo Institute of Technology, Yokohama 226-8503 (Japan); School of Materials and Chemical Technology, Tokyo Institute of Technology, Yokohama 226-8502 (Japan)

    2016-08-01

    0.07YO{sub 1.5}-0.93HfO{sub 2} (YHO7) films were prepared on various substrates by pulse laser deposition at room temperature and subsequent heat treatment to enable a solid phase reaction. (111)-oriented 10 wt. % Sn-doped In{sub 2}O{sub 3}(ITO)//(111) yttria-stabilized zirconia, (111)Pt/TiO{sub x}/SiO{sub 2}/(001)Si substrates, and (111)ITO/(111)Pt/TiO{sub x}/SiO{sub 2}/(001)Si substrates were employed for film growth. In this study, X-ray diffraction measurements including θ–2θ measurements, reciprocal space mappings, and pole figure measurements were used to study the films. The film on (111)ITO//(111)yttria-stabilized zirconia was an (111)-orientated epitaxial film with ferroelectric orthorhombic phase; the film on (111)ITO/(111)Pt/TiO{sub x}/SiO{sub 2}/(001)Si was an (111)-oriented uniaxial textured film with ferroelectric orthorhombic phase; and no preferred orientation was observed for the film on the (111)Pt/TiO{sub x}/SiO{sub 2}/(001)Si substrate, which does not contain ITO. Polarization–hysteresis measurements confirmed that the films on ITO covered substrates had saturated ferroelectric hysteresis loops. A remanent polarization (P{sub r}) of 9.6 and 10.8 μC/cm{sup 2} and coercive fields (E{sub c}) of 1.9 and 2.0 MV/cm were obtained for the (111)-oriented epitaxial and uniaxial textured YHO7 films, respectively. These results demonstrate that the (111)-oriented ITO bottom electrodes play a key role in controlling the orientation and ferroelectricity of the phase formation of the solid films deposited at room temperature.

  13. Single-phase {beta}-FeSi{sub 2} thin films prepared on Si wafer by femtosecond laser ablation and its photoluminescence at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Lu Peixiang [State Key Laboratory of Laser Technology and Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074 (China)]. E-mail: lupeixiang@mail.hust.edu.cn; Zhou Youhua [State Key Laboratory of Laser Technology and Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074 (China) and Physics and Information School, Jianghan University, Wuhan 430056 (China)]. E-mail: yhzhou@jhun.edu.cn; Zheng Qiguang [State Key Laboratory of Laser Technology and Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074 (China); Yang Guang [State Key Laboratory of Laser Technology and Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2006-02-06

    Single-phase {beta}-FeSi{sub 2} thin films were prepared on Si(100) and Si(111) wafers by using femtosecond laser deposition with a FeSi{sub 2} alloy target for the first time. X-ray diffraction (XRD), field scanning electron microscopy (FSEM), scanning probe microscopy (SPM), electron backscattered diffraction pattern (EBSD), and Fourier-transform Raman infrared spectroscopy (FTRIS) were used to characterize the structure, composition, and properties of the {beta}-FeSi{sub 2}/Si films. The orientation of {beta}-FeSi{sub 2} grains was found to depend on the orientation of the Si substrates, and photoluminescence at wavelength of 1.53 {mu}m was observed from the single-phase {beta}-FeSi{sub 2}/Si thin film at room temperature (20 {sup o}C)

  14. Ferroelectric properties of tungsten bronze morphotropic phase boundary systems

    International Nuclear Information System (INIS)

    Oliver, J.R.; Neurgaonkar, R.R.; Cross, L.E.; Pennsylvania State Univ., University Park, PA

    1989-01-01

    Tungsten bronze ferroelectrics which have a morphotropic phase boundary (MPB) can have a number or enhanced dielectric, piezoelectric, and electrooptic properties compared to more conventional ferroelectric materials. The structural and ferroelectric properties of several MPB bronze systems are presented, including data from sintered and hot-pressed ceramics, epitaxial thin films, and bulk single crystals. Included among these are three systems which had not been previously identified as morphotropic. The potential advantages and limitations of these MPB systems are discussed, along with considerations of the appropriate growth methods for their possible utilization in optical, piezoelectric, or pyroelectric device applications

  15. Emergent Low-Symmetry Phases and Large Property Enhancements in Ferroelectric KNbO 3 Bulk Crystals

    Energy Technology Data Exchange (ETDEWEB)

    Lummen, Tom T. A. [Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16802 USA; Leung, J. [Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16802 USA; Kumar, Amit [School of Mathematics and Physics, Queen' s University Belfast, University Road, Belfast BT71NN Northern Ireland UK; Wu, X. [Department of Physics, University of Texas at Austin, Austin TX 78712 USA; Ren, Y. [Department of Physics, University of Texas at Austin, Austin TX 78712 USA; VanLeeuwen, Brian K. [Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16802 USA; Haislmaier, Ryan C. [Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16802 USA; Holt, Martin [Center for Nanoscale Materials, Argonne National Laboratory, Argonne IL 60439 USA; Lai, Keji [Department of Physics, University of Texas at Austin, Austin TX 78712 USA; Kalinin, Sergei V. [Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge TN 37831 USA; Gopalan, Venkatraman [Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16802 USA

    2017-06-19

    The design of new or enhanced functionality in materials is traditionally viewed as requiring the discovery of new chemical compositions through synthesis. Large property enhancements may however also be hidden within already well-known materials, when their structural symmetry is deviated from equilibrium through a small local strain or field. Here, the discovery of enhanced material properties associated with a new metastable phase of monoclinic symmetry within bulk KNbO3 is reported. This phase is found to coexist with the nominal orthorhombic phase at room temperature, and is both induced by and stabilized with local strains generated by a network of ferroelectric domain walls. While the local microstructural shear strain involved is only approximate to 0.017%, the concurrent symmetry reduction results in an optical second harmonic generation response that is over 550% higher at room temperature. Moreover, the meandering walls of the low-symmetry domains also exhibit enhanced electrical conductivity on the order of 1 S m(-1). This discovery reveals a potential new route to local engineering of significant property enhancements and conductivity through symmetry lowering in ferroelectric crystals.

  16. Room temperature chemically oxidized La2CuO4+y: Phase separation induced by thermal treatment

    DEFF Research Database (Denmark)

    Rial,C.; Moran, E.; Alario-Franco, M.A.

    1997-01-01

    The structure of roam temperature chemically oxidized La2CuO4+y [y = 0.103(4)] has been refined from powder neutron diffraction data using the space group Bmab. The modifications induced in the CuO2 and the LaO planes by the insertion of oxygen are consistent with the high T-c measured for this m......The structure of roam temperature chemically oxidized La2CuO4+y [y = 0.103(4)] has been refined from powder neutron diffraction data using the space group Bmab. The modifications induced in the CuO2 and the LaO planes by the insertion of oxygen are consistent with the high T-c measured...... a short treatment at 433 K, La2CuO4.103(4) undergoes a phase separation into two phases: phase 1, with estimated y(1) = 0.086(4) and T-cl = 30 K, and phase 2, with estimated y(2) = 0.12(1) and T-c2 = 17 K. By increasing the annealing times, phase 2 transforms to phase I and finally disappears. Therefore...

  17. Heterogeneous Ferroelectric Solid Solutions Phases and Domain States

    CERN Document Server

    Topolov, Vitaly

    2012-01-01

    The book deals with perovskite-type ferroelectric solid solutions for modern materials science and applications, solving problems of complicated heterophase/domain structures near the morphotropic phase boundary and applications to various systems with morphotropic phases. In this book domain state–interface diagrams are presented for the interpretation of heterophase states in perovskite-type ferroelectric solid solutions. It allows to describe the stress relief in the presence of polydomain phases, the behavior of unit-cell parameters of coexisting phases and the effect of external electric fields. The novelty of the book consists in (i) the first systematization of data about heterophase states and their evolution in ferroelectric solid solutions (ii) the general interpretation of heterophase and domain structures at changing temperature, composition or electric field (iii) the complete analysis of interconnection domain structures, unit-cell parameters changes, heterophase structures and stress relief.

  18. Theoretical study of ferroelectric nanoparticles using phase reconstructed electron microscopy

    Science.gov (United States)

    Phatak, C.; Petford-Long, A. K.; Beleggia, M.; De Graef, M.

    2014-06-01

    Ferroelectric nanostructures are important for a variety of applications in electronic and electro-optical devices, including nonvolatile memories and thin-film capacitors. These applications involve stability and switching of polarization using external stimuli, such as electric fields. We present a theoretical model describing how the shape of a nanoparticle affects its polarization in the absence of screening charges, and quantify the electron-optical phase shift for detecting ferroelectric signals with phase-sensitive techniques in a transmission electron microscope. We provide an example phase shift computation for a uniformly polarized prolate ellipsoid with varying aspect ratio in the absence of screening charges.

  19. Determination of enrofloxacin by room-temperature phosphorimetry after solid phase extraction on an acrylic polymer sorbent

    Science.gov (United States)

    de Souza, Cabrini F.; Martins, Renata K. S.; da Silva, Andrea R.; da Cunha, Alessandra L. M. C.; Aucélio, Ricardo Q.

    A phosphorimetric method was developed to enable the determination of enrofloxacin using photochemical derivatization which was used to both improve detection limits and to minimize the uncertainty of measurements. Phosphorescence was induced on cellulose containing TlNO3. Absolute limit of detection at the ng range and linear analytical response over three orders of magnitude were achieved. A metrological study was made to obtain the combined uncertainty value and to identify that the precision was mainly affected by the changing of substrates when measuring the signal from each replicate. Pharmaceutical formulations containing enrofloxacin were successfully analyzed by the method and the results were similar to the ones achieved using a HPLC method. A solid phase extraction on an acrylic polymer was optimized to separate enrofloxacin from interferents such as diclofenac and other components from biological matrices, which allowed the successful use of the method in urine analysis.

  20. Temperature-dependent high energy-resolution EELS of ferroelectric and paraelectric BaTiO3 phases

    Science.gov (United States)

    Bugnet, Matthieu; Radtke, Guillaume; Woo, Steffi Y.; Zhu, Guo-zhen; Botton, Gianluigi A.

    2016-01-01

    Probing the ferroelectricity at the nanometer scale is of particular interest for a wide range of applications. In this Rapid Communication, the structural distortion of BaTiO3 (BTO) is studied in its ferroelectric (rhombohedral and tetragonal), and paraelectric phases from the O K near edge structures in electron energy loss spectroscopy. Modifications of the electronic structure are detected in the lowest energy fine structure (FS) of the O K edge in the ferroelectric phases, and are interpreted by core-hole valence-electron screening geometry. For the paraelectric phase, the lowest energy FS of the O K edge is comparable to the one obtained at room temperature, which is inconsistent with an expected cubic structure. The variations observed in the O K near edge structures, such as a broader and more asymmetric lowest energy FS at low temperature, suggest that the magnitude of the Ti+4 off-centering along increases in lower-temperature phases. These findings demonstrate the sensitivity of the O K near edge structures to the structural distortions of BTO polymorphs, and form a basis for further investigations on defective or strained BTO at the nanoscale.

  1. Room-temperature subnanosecond waveguide lasers in Nd:YVO4 Q-switched by phase-change VO2: A comparison with 2D materials.

    Science.gov (United States)

    Nie, Weijie; Li, Rang; Cheng, Chen; Chen, Yanxue; Lu, Qingming; Romero, Carolina; Vázquez de Aldana, Javier R; Hao, Xiaotao; Chen, Feng

    2017-04-06

    We report on room-temperature subnanosecond waveguide laser operation at 1064 nm in a Nd:YVO 4 crystal waveguide through Q-switching of phase-change nanomaterial vanadium dioxide (VO 2 ). The unique feature of VO 2 nanomaterial from the insulating to metallic phases offers low-saturation-intensity nonlinear absorptions of light for subnanosecond pulse generation. The low-loss waveguide is fabricated by using the femtosecond laser writing with depressed cladding geometry. Under optical pump at 808 nm, efficient pulsed laser has been achieved in the Nd:YVO 4 waveguide, reaching minimum pulse duration of 690 ps and maximum output average power of 66.7 mW. To compare the Q-switched laser performances by VO 2 saturable absorber with those based on two-dimensional materials, the 1064-nm laser pulses have been realized in the same waveguide platform with either graphene or transition metal dichalcogenide (in this work, WS 2 ) coated mirror. The results on 2D material Q-switched waveguide lasers have shown that the shortest pulses are with 22-ns duration, whilst the maximum output average powers reach ~161.9 mW. This work shows the obvious difference on the lasing properties based on phase-change material and 2D materials, and suggests potential applications of VO 2 as low-cost saturable absorber for subnanosecond laser generation.

  2. Atomically engineered ferroic layers yield a room-temperature magnetoelectric multiferroic

    Science.gov (United States)

    Mundy, Julia A.; Brooks, Charles M.; Holtz, Megan E.; Moyer, Jarrett A.; Das, Hena; Rébola, Alejandro F.; Heron, John T.; Clarkson, James D.; Disseler, Steven M.; Liu, Zhiqi; Farhan, Alan; Held, Rainer; Hovden, Robert; Padgett, Elliot; Mao, Qingyun; Paik, Hanjong; Misra, Rajiv; Kourkoutis, Lena F.; Arenholz, Elke; Scholl, Andreas; Borchers, Julie A.; Ratcliff, William D.; Ramesh, Ramamoorthy; Fennie, Craig J.; Schiffer, Peter; Muller, David A.; Schlom, Darrell G.

    2016-09-01

    Materials that exhibit simultaneous order in their electric and magnetic ground states hold promise for use in next-generation memory devices in which electric fields control magnetism. Such materials are exceedingly rare, however, owing to competing requirements for displacive ferroelectricity and magnetism. Despite the recent identification of several new multiferroic materials and magnetoelectric coupling mechanisms, known single-phase multiferroics remain limited by antiferromagnetic or weak ferromagnetic alignments, by a lack of coupling between the order parameters, or by having properties that emerge only well below room temperature, precluding device applications. Here we present a methodology for constructing single-phase multiferroic materials in which ferroelectricity and strong magnetic ordering are coupled near room temperature. Starting with hexagonal LuFeO3—the geometric ferroelectric with the greatest known planar rumpling—we introduce individual monolayers of FeO during growth to construct formula-unit-thick syntactic layers of ferrimagnetic LuFe2O4 (refs 17, 18) within the LuFeO3 matrix, that is, (LuFeO3)m/(LuFe2O4)1 superlattices. The severe rumpling imposed by the neighbouring LuFeO3 drives the ferrimagnetic LuFe2O4 into a simultaneously ferroelectric state, while also reducing the LuFe2O4 spin frustration. This increases the magnetic transition temperature substantially—from 240 kelvin for LuFe2O4 (ref. 18) to 281 kelvin for (LuFeO3)9/(LuFe2O4)1. Moreover, the ferroelectric order couples to the ferrimagnetism, enabling direct electric-field control of magnetism at 200 kelvin. Our results demonstrate a design methodology for creating higher-temperature magnetoelectric multiferroics by exploiting a combination of geometric frustration, lattice distortions and epitaxial engineering.

  3. Room-temperature heteroepitaxy of single-phase Al1−xInxN films with full composition range on isostructural wurtzite templates

    International Nuclear Information System (INIS)

    Hsiao, Ching-Lien; Palisaitis, Justinas; Junaid, Muhammad; Persson, Per O.Å.; Jensen, Jens; Zhao, Qing-Xiang; Hultman, Lars; Chen, Li-Chyong; Chen, Kuei-Hsien; Birch, Jens

    2012-01-01

    Al 1−x In x N heteroepitaxial layers covering the full composition range have been realized by magnetron sputter epitaxy on basal-plane AlN, GaN, and ZnO templates at room temperature (RT). Both Al 1−x In x N single layers and multilayers grown on these isostructural templates show single phase, single crystal wurtzite structure. Even at large lattice mismatch between the film and the template, for instance InN/AlN (∼ 13% mismatch), heteroepitaxy is achieved. However, RT-grown Al 1−x In x N films directly deposited on non-isostructural c-plane sapphire substrate exhibit a polycrystalline structure for all compositions, suggesting that substrate surface structure is important for guiding the initial nucleation. Degradation of Al 1−x In x N structural quality with increasing indium content is attributed to the formation of more point- and structural defects. The defects result in a prominent hydrostatic tensile stress component, in addition to the biaxial stress component introduced by lattice mismatch, in all RT-grown Al 1−x In x N films. These effects are reflected in the measured in-plane and out-of-plane strains. The effect of hydrostatic stress is negligible compared to the effects of lattice mismatch in high-temperature grown AlN layers thanks to their low amount of defects. We found that Vegard’s rule is applicable to determine x in the RT-grown Al 1−x In x N epilayers if the lattice constants of RT-sputtered AlN and InN films are used instead of those of the strain-free bulk materials. - Highlights: ► Magnetron sputter epitaxy of single-phase Al 1−x In x N(0001) at room temperature ► Growing Al 1−x In x N onto temperature sensitive substrates is desirable. ► Substrate surface structure plays a vital role at nucleation stage. ► Point and extended defects produce hydrostatic tensile stress. ► The applicability of Vegard's rule for these compounds is confirmed.

  4. Ferroelectric domains and phase evolution in (Fe:) KTa{sub 1−x}Nb{sub x}O{sub 3} crystals

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Hongyang; Cai, Kang; Fan, Ziran; Huang, Zhideng [Hubei Key Laboratory of Plasma Chemistry and Advanced Materials, Department of Materials Science and Engineering, Wuhan Institute of Technology, 693 Xiongchu Road, Wuhan 430073 (China); Ma, Zhibin, E-mail: mazb@wit.edu.cn [Hubei Key Laboratory of Plasma Chemistry and Advanced Materials, Department of Materials Science and Engineering, Wuhan Institute of Technology, 693 Xiongchu Road, Wuhan 430073 (China); Jia, Tingting; Kimura, Hideo [National Institute for Materials Science, Sengen 1-2-1, Tsukuba 305-0047 (Japan); Yang, Yuguo [New Materials Research Institute, Shandong Academy of Sciences, No. 19, Keyuan Road, Jinan 250014 (China); Matsumoto, Takao; Tohei, Tetsuya; Shibata, Naoya; Ikuhara, Yuichi [Institute of Engineering Innovation, School of Engineering, University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-8656 (Japan)

    2017-08-15

    Highlights: • Three phase transitions were observed: the R–O, O–T, T–C evolutions. • KTN ferroelectric domain switching is because of the nano-polar-regions. • The domain evolution showed KTN has triangle shape, but Fe: KTN has straight line. - Abstract: The domain structures and phase evolution in mixed ferroelectric (Fe): KTa{sub 1−x}Nb{sub x}O{sub 3} (KTN) crystals were investigated. Temperature dependent Raman spectra show that Curie temperatures of KTN and Fe: KTN are far below room temperature, but the ferroelectric domain switching was still visualized by scanning probe microscopy at room temperature. These observed domains origin from the nano-regions near the grain boundaries. In addition, the intrinsic domains (triangle for KTN and straight line/stripe for Fe: KTN) could only be observed at low temperature by transmission electron microscopy. Three phase transitions in Fe: KTN crystals were found by Raman spectroscopy and dielectric testing: 175 K for Rhombohedral-to-Orthorhombic (R–O), 210 K for Orthorhombic-to-Tetragonal (O–T) and 250 K for Tetragonal-to-Cubic (T–C), which is consistent with the domain behavior.

  5. Phase diagrams of ferroelectric nanocrystals strained by an elastic matrix

    Science.gov (United States)

    Nikitchenko, A. I.; Azovtsev, A. V.; Pertsev, N. A.

    2018-01-01

    Ferroelectric crystallites embedded into a dielectric matrix experience temperature-dependent elastic strains caused by differences in the thermal expansion of the crystallites and the matrix. Owing to the electrostriction, these lattice strains may affect polarization states of ferroelectric inclusions significantly, making them different from those of a stress-free bulk crystal. Here, using a nonlinear thermodynamic theory, we study the mechanical effect of elastic matrix on the phase states of embedded single-domain ferroelectric nanocrystals. Their equilibrium polarization states are determined by minimizing a special thermodynamic potential that describes the energetics of an ellipsoidal ferroelectric inclusion surrounded by a linear elastic medium. To demonstrate the stability ranges of such states for a given material combination, we construct a phase diagram, where the inclusion’s shape anisotropy and temperature are used as two parameters. The ‘shape-temperature’ phase diagrams are calculated numerically for PbTiO3 and BaTiO3 nanocrystals embedded into representative dielectric matrices generating tensile (silica glass) or compressive (potassium silicate glass) thermal stresses inside ferroelectric inclusions. The developed phase maps demonstrate that the joint effect of thermal stresses and matrix-induced elastic clamping of ferroelectric inclusions gives rise to several important features in the polarization behavior of PbTiO3 and BaTiO3 nanocrystals. In particular, the Curie temperature displays a nonmonotonic variation with the ellipsoid’s aspect ratio, being minimal for spherical inclusions. Furthermore, the diagrams show that the polarization orientation with respect to the ellipsoid’s symmetry axis is controlled by the shape anisotropy and the sign of thermal stresses. Under certain conditions, the mechanical inclusion-matrix interaction qualitatively alters the evolution of ferroelectric states on cooling, inducing a structural transition

  6. Determination of Three-Dimensional Morphology and Inner Structure of Second-Phase Inclusions in Metals by Non-Aqueous Solution Electrolytic and Room Temperature Organic Methods

    Directory of Open Access Journals (Sweden)

    Jing Guo

    2018-01-01

    Full Text Available The secondary-phase particles in metals, particularly those composed of non-metallic materials, are often detrimental to the mechanical properties of metals; thus, it is crucial to control inclusion formation and growth. One of the challenges is determining the three-dimensional morphology and inner structures of such inclusions. In this study, a non-aqueous solution electrolytic method and a room-temperature organic technique were developed based on the principle of electrochemistry to determine the three-dimensional morphologies and inner structures of non-metallic inclusions in Al-killed steel, Si-killed steel, and ductile cast iron. The inclusions were first extracted without any damage to the inclusions, and then the collected inclusions were wrapped and cut through Cu ion deposition. The results revealed that the inclusions in Al-killed steel had an irregular morphology, that those in the Si-killed steel were mainly spherical, and that almost all the spheroidal graphite in the ductile cast iron featured a uniform globular morphology. In addition, nucleation was not observed in the inner structures of the inclusions in the Al-killed steel, while some dendritic or rod-like MnS phase precipitates appeared on the silicate inclusion surfaces, and some silicate-rich phases were detected in their inner matrix. For spheroidal graphite, rare-earth oxides (one particle or more were observed as nuclei in the center of almost every graphite particle. The formation and evolution of inclusions in these types of metals can be better understood by means of the two developed methods.

  7. Organic non-volatile memories from ferroelectric phase separated blends

    Science.gov (United States)

    Asadi, Kamal; de Leeuw, Dago; de Boer, Bert; Blom, Paul

    2009-03-01

    Ferroelectric polarisation is an attractive physical property for non-volatile binary switching. The functionality of the targeted memory should be based on resistive switching. Conductivity and ferroelectricity however cannot be tuned independently. The challenge is to develop a storage medium in which the favourable properties of ferroelectrics such as bistability and non-volatility can be combined with the beneficial properties provided by semiconductors such as conductivity and rectification. In this contribution we present an integrated solution by blending semiconducting and ferroelectric polymers into phase separated networks. The polarisation field of the ferroelectric modulates the injection barrier at the semiconductor--metal contact. This combination allows for solution-processed non-volatile memory arrays with a simple cross-bar architecture that can be read-out non-destructively. Based on this general concept a non-volatile, reversible switchable Schottky diode with relatively fast programming time of shorter than 100 microseconds, long information retention time of longer than 10^ days, and high programming cycle endurance with non-destructive read-out is demonstrated.

  8. Hydrogenation of 4-nitrophenol to 4-aminophenol at room temperature: Boosting palladium nanocrystals efficiency by coupling with copper via liquid phase pulsed laser ablation

    International Nuclear Information System (INIS)

    Park, Hanbit; Reddy, D. Amaranatha; Kim, Yujin; Lee, Seunghee; Ma, Rory; Lim, Manho; Kim, Tae Kyu

    2017-01-01

    Highlights: • PdCu bimetallic nanospheres fabricated by laser ablation. • Physical characterizations of synthesized PdCu nanospheres. • Assessments of catalytic performance of PdCu nanospheres for the reduction of nitrophenol. • Significant improvement of the catalytic activity in PdCu bimetallic nanocrystals. - Abstract: Ultra-dispersed bimetallic nanomaterials have attracted much attention in the hydrogenation of highly toxic aromatic nitro compounds to aromatic amines owing to their high stability, superior activity, reusability, and unique optical and electronic properties, as compared to monometalic nanocrystals. However, the lack of facile and economically controllable strategies of producing highly pure ultra-dispersed bimetallic nanocatalysts limits their practical industrial applications. Considering the above obstacles, we present a simple and effective strategy for the formation of bimetallic (PdCu) nanocrystals by liquid phase pulsed laser ablation using a bulk Pd metal plate submerged in CuCl 2 solutions with different concentrations, in contrast to the complex and costly experimental methods used previously. The microstructural and optical properties of the synthesized nanocrystals indicate that the obtained bimetallic nanostructures are highly pure and monodispersed. Moreover, bimetallic PdCu nanostructures show a higher catalytic activity than monometallic Pd nanocrystals for the hydrogenation of 4-nitrophenol to 4-aminophenol at room temperature, also exhibiting high stability for up to four recycles. The mechanism of the enhanced catalytic activity and stability of bimetallic nanocrystals is discussed in detail. Finally, we believe that the presented design strategy and utilization of bimetallic nanocrystals for catalytic applications enables the development of novel bimetallic nanostructures by liquid phase pulsed laser ablation and their catalytic application for environmental remediation.

  9. Hydrogenation of 4-nitrophenol to 4-aminophenol at room temperature: Boosting palladium nanocrystals efficiency by coupling with copper via liquid phase pulsed laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Park, Hanbit; Reddy, D. Amaranatha; Kim, Yujin; Lee, Seunghee; Ma, Rory; Lim, Manho, E-mail: mhlim@pusan.ac.kr; Kim, Tae Kyu, E-mail: tkkim@pusan.ac.kr

    2017-04-15

    Highlights: • PdCu bimetallic nanospheres fabricated by laser ablation. • Physical characterizations of synthesized PdCu nanospheres. • Assessments of catalytic performance of PdCu nanospheres for the reduction of nitrophenol. • Significant improvement of the catalytic activity in PdCu bimetallic nanocrystals. - Abstract: Ultra-dispersed bimetallic nanomaterials have attracted much attention in the hydrogenation of highly toxic aromatic nitro compounds to aromatic amines owing to their high stability, superior activity, reusability, and unique optical and electronic properties, as compared to monometalic nanocrystals. However, the lack of facile and economically controllable strategies of producing highly pure ultra-dispersed bimetallic nanocatalysts limits their practical industrial applications. Considering the above obstacles, we present a simple and effective strategy for the formation of bimetallic (PdCu) nanocrystals by liquid phase pulsed laser ablation using a bulk Pd metal plate submerged in CuCl{sub 2} solutions with different concentrations, in contrast to the complex and costly experimental methods used previously. The microstructural and optical properties of the synthesized nanocrystals indicate that the obtained bimetallic nanostructures are highly pure and monodispersed. Moreover, bimetallic PdCu nanostructures show a higher catalytic activity than monometallic Pd nanocrystals for the hydrogenation of 4-nitrophenol to 4-aminophenol at room temperature, also exhibiting high stability for up to four recycles. The mechanism of the enhanced catalytic activity and stability of bimetallic nanocrystals is discussed in detail. Finally, we believe that the presented design strategy and utilization of bimetallic nanocrystals for catalytic applications enables the development of novel bimetallic nanostructures by liquid phase pulsed laser ablation and their catalytic application for environmental remediation.

  10. Modeling two-phase ferroelectric composites by sequential laminates

    International Nuclear Information System (INIS)

    Idiart, Martín I

    2014-01-01

    Theoretical estimates are given for the overall dissipative response of two-phase ferroelectric composites with complex particulate microstructures under arbitrary loading histories. The ferroelectric behavior of the constituent phases is described via a stored energy density and a dissipation potential in accordance with the theory of generalized standard materials. An implicit time-discretization scheme is used to generate a variational representation of the overall response in terms of a single incremental potential. Estimates are then generated by constructing sequentially laminated microgeometries of particulate type whose overall incremental potential can be computed exactly. Because they are realizable, by construction, these estimates are guaranteed to conform with any material constraints, to satisfy all pertinent bounds and to exhibit the required convexity properties with no duality gap. Predictions for representative composite and porous systems are reported and discussed in the light of existing experimental data. (paper)

  11. Room temperature ferromagnetic and photoluminescence ...

    Indian Academy of Sciences (India)

    32

    electrode, photo electronic devices, photo sensors, liquid crystal displays, electrochromic windows, solar panels and transparent coatings for solar-energy heat mirrors [11-13]. Here we report on magnetic properties of ITO nanoparticles at room temperature and at 100 K. 2. Experimental. The In1.9Sn0.1O3 powder samples ...

  12. Room Temperature Thin Film Ba(x)Sr(1-x)TiO3 Ku-Band Coupled MicrostripPhase Shifters: Effects of Film Thickness, Doping, Annealing and Substrate Choice

    Science.gov (United States)

    VanKeuls, F. W.; Mueller, C. H.; Miranda, F. A.; Romanofsky, R. R.; Canedy, C. L.; Aggarwal, S.; Venkatesan, T.; Ramesh, R.; Horwitz, S.; Chang, W.

    1999-01-01

    We report on measurements taken on over twenty Ku-band coupled microstrip phase shifters (CMPS) using thin ferroelectric films of Ba(x)Sr(1-x)TiO3. This CMPS design is a recent innovation designed to take advantage of the high tunability and tolerate the high dielectric constant of ferroelectric films at Ku- and K-band frequencies. These devices are envisioned as a component in low-cost steerable beam phased area antennas, Comparisons are made between devices with differing film thickness, annealed vs unannealed, Mn-doped vs. undoped, and also substrates of LaAlO3 and MgO. A comparison between the CMPS structure and a CPW phase shifter was also made oil the same ferroelectric film.

  13. Phase coexistence in ferroelectric solid solutions: Formation of monoclinic phase with enhanced piezoelectricity

    Directory of Open Access Journals (Sweden)

    Xiaoyan Lu

    2016-10-01

    Full Text Available Phase morphology and corresponding piezoelectricity in ferroelectric solid solutions were studied by using a phenomenological theory with the consideration of phase coexistence. Results have shown that phases with similar energy potentials can coexist, thus induce interfacial stresses which lead to the formation of adaptive monoclinic phases. A new tetragonal-like monoclinic to rhombohedral-like monoclinic phase transition was predicted in a shear stress state. Enhanced piezoelectricity can be achieved by manipulating the stress state close to a critical stress field. Phase coexistence is universal in ferroelectric solid solutions and may provide a way to optimize ultra-fine structures and proper stress states to achieve ultrahigh piezoelectricity.

  14. Characterization, phase change and conductivity crossover of new luminescent ferroelectric Mn (II) organic-inorganic hybrid

    Energy Technology Data Exchange (ETDEWEB)

    Mostafa, Mohga F., E-mail: Mohga40@yahoo.com; El Dean, Thana Sh., E-mail: th_sh2000@yahoo.com; Tammam, Ahmed K., E-mail: physicsoman@yahoo.com

    2016-09-01

    Synthesis and characterization of new luminescent ferroelectric [(CH{sub 3})(C{sub 6}H{sub 5}){sub 3}P]{sub 2}MnBr{sub 4} organic-inorganic hybrid (OIH) are reported. Powder x-ray diffraction showed the following phases: {sup P2/m} {sup (280 K)} Phase (IV) {sup P21} {sup (298 K)} Phase (III) {sup Pna21} {sup (350 K)} Phase (II) {sup Pnma} {sup (370 K)} Phase (I). Room temperature lattice parameters are a = 9.6233 (Å), b = 12.5653 (Å) c = 16.4503 (Å) and β = 105.6° (T = 298 K). UV-VIS and Ac magnetic susceptibility confirm tetrahedral symmetry of [MnBr{sub 4}]{sup 2−}. DSC and dielectric measurements showed four phase transitions at T{sub 4peak} = 279.1 ± 1 K (ΔS = 1.03 J/mol K), T{sub 3peak} = 300.1 ± 2 K (ΔS = 2.33 J/mol K), T{sub 2peakt} = 353.2 ± 3 K (ΔS = 2.68 J/mol K) and T{sub 1peak} = 379.1 ± 3 K (ΔS = 2.43 J/mol K). Calculated lattice potential energy values vary from 827 (kJ/mol) at 280 K to (797 kJ/mol) at 370 K. Ac conductivity measurements (220 < T(K) < 400) and (0.081 < f (kHz) < 30) are presented. It is ferroelectric with Curie temperature T{sub c} = 309 K. Hybrid is semiconductor in the temperature range 309 ± 14 K, where conductivity follows Jonscher’s universal dielectric response otherwise it is an insulator where crossover to super-linear power law prevails. Comparison to the corresponding chloride is discussed. - Graphical abstract: Plot of real part of permittivity [ln(ε′)] versus temperature (K). - Highlights: • Conductivity crossover from SlPL to UDR is confirmed. • Change from semiconductor to insulator. • Structural phase transformation.

  15. Room Temperature Ferromagnetic Mn:Ge(001

    Directory of Open Access Journals (Sweden)

    George Adrian Lungu

    2013-12-01

    Full Text Available We report the synthesis of a room temperature ferromagnetic Mn-Ge system obtained by simple deposition of manganese on Ge(001, heated at relatively high temperature (starting with 250 °C. The samples were characterized by low energy electron diffraction (LEED, scanning tunneling microscopy (STM, high resolution transmission electron microscopy (HRTEM, X-ray photoelectron spectroscopy (XPS, superconducting quantum interference device (SQUID, and magneto-optical Kerr effect (MOKE. Samples deposited at relatively elevated temperature (350 °C exhibited the formation of ~5–8 nm diameter Mn5Ge3 and Mn11Ge8 agglomerates by HRTEM, while XPS identified at least two Mn-containing phases: the agglomerates, together with a Ge-rich MnGe~2.5 phase, or manganese diluted into the Ge(001 crystal. LEED revealed the persistence of long range order after a relatively high amount of Mn (100 nm deposited on the single crystal substrate. STM probed the existence of dimer rows on the surface, slightly elongated as compared with Ge–Ge dimers on Ge(001. The films exhibited a clear ferromagnetism at room temperature, opening the possibility of forming a magnetic phase behind a nearly ideally terminated Ge surface, which could find applications in integration of magnetic functionalities on semiconductor bases. SQUID probed the co-existence of a superparamagnetic phase, with one phase which may be attributed to a diluted magnetic semiconductor. The hypothesis that the room temperature ferromagnetic phase might be the one with manganese diluted into the Ge crystal is formulated and discussed.

  16. Colossal Terahertz Magnetoresistance at Room Temperature in Epitaxial La0.7Sr0.3MnO3 Nanocomposites and Single-Phase Thin Films.

    Science.gov (United States)

    Lloyd-Hughes, J; Mosley, C D W; Jones, S P P; Lees, M R; Chen, A; Jia, Q X; Choi, E-M; MacManus-Driscoll, J L

    2017-04-12

    Colossal magnetoresistance (CMR) is demonstrated at terahertz (THz) frequencies by using terahertz time-domain magnetospectroscopy to examine vertically aligned nanocomposites (VANs) and planar thin films of La 0.7 Sr 0.3 MnO 3 . At the Curie temperature (room temperature), the THz conductivity of the VAN was dramatically enhanced by over 2 orders of magnitude under the application of a magnetic field with a non-Drude THz conductivity that increased with frequency. The direct current (dc) CMR of the VAN is controlled by extrinsic magnetotransport mechanisms such as spin-polarized tunneling between nanograins. In contrast, we find that THz CMR is dominated by intrinsic, intragrain transport: the mean free path was smaller than the nanocolumn size, and the planar thin-film exhibited similar THz CMR to the VAN. Surprisingly, the observed colossal THz magnetoresistance suggests that the magnetoresistance can be large for alternating current motion on nanometer length scales, even when the magnetoresistance is negligible on the macroscopic length scales probed by dc transport. This suggests that colossal magnetoresistance at THz frequencies may find use in nanoelectronics and in THz optical components controlled by magnetic fields. The VAN can be scaled in thickness while retaining a high structural quality and offers a larger THz CMR at room temperature than the planar film.

  17. Effect of extrapolation length on the phase transformation of epitaxial ferroelectric thin films

    International Nuclear Information System (INIS)

    Hu, Z.S.; Tang, M.H.; Wang, J.B.; Zheng, X.J.; Zhou, Y.C.

    2008-01-01

    Effects of extrapolation length on the phase transformation of epitaxial ferroelectric thin films on dissimilar cubic substrates have been studied on the basis of the mean-field Landau-Ginzburg-Devonshire (LGD) thermodynamic theory by taking an uneven distribution of the interior stress with thickness into account. It was found that the polarization of epitaxial ferroelectric thin films is strongly dependent on the extrapolation length of films. The physical origin of the extrapolation length during the phase transformation from paraelectric to ferroelectric was revealed in the case of ferroelectric thin films

  18. Room temperature cryogenic test interface

    International Nuclear Information System (INIS)

    Faris, S. M.; Davidson, A.; Moskowitz, P. A.; Sai-Halasz, G. A.

    1985-01-01

    This interface permits the testing of high speed semiconductor devices (room-temperature chips) by a Josephson junction sampling device (cryogenic chip) without intolerable loss of resolution. The interface comprises a quartz pass-through plug which includes a planar transmission line interconnecting a first chip station, where the cryogenic chip is mounted, and a second chip station, where the semiconductor chip to be tested is temporarily mounted. The pass-through plug has a cemented long half-cylindrical portion and short half-cylindrical portion. The long portion carries the planar transmission line, the ends of which form the first and second chip mounting stations. The short portion completes the cylinder with the long portion for part of its length, where a seal can be achieved, but does not extend over the chip mounting stations. Sealing is by epoxy cement. The pass-through plug is sealed in place in a flange mounted to the chamber wall. The first chip station, with the cryogenic chip attached, extends into the liquid helium reservoir. The second chip station is in the room temperature environment required for semiconductor operation. Proper semiconductor operating temperature is achieved by a heater wire and control thermocouple in the vicinity of each other and the second chip mounting station. Thermal isolation is maintained by vacuum and seals. Connections for power and control, for test result signals, for temperature control and heating, and for vacuum complete the test apparatus

  19. Light refraction in PbMgsub(1/3)Nbsub(2/3)Osub(3) ferroelectric with a diffuse phase transition

    International Nuclear Information System (INIS)

    Korshunov, O.Yu.; Markovin, P.A.; Pisarev, R.V.

    1983-01-01

    In PbMgsub(1/2)Nbsub(2/3)Osub(3) ferroelectric with a diffuse phase transition refractive indeX variations with temperature are studied for two wavelengths of 0.63 and 0.44 μm in the 140-600 K temperature range, and refractive index dispersion is measured at room temperature. A broad smooth peak of rate of light refraction temperation changes in the 300-310 K range that coincides with the previously observed by other authors on the temperatUre dependence of microwave dielectric permittivity. A refractive properties anomaly is also observed at 156 K that is related with another phase transition at this temperature. Mechanisms of refractive index thermal variations are analyzed and a ferroelectric contribution into light refraction that equals approximately 4x10 -2 at 140 K is found. The contribution remains up to 600 K due to polarization fluctuations. It is shown that within the frames of dispersion theory the effect of ferroelectric ordering on light refraction can be explained by changes of both frequency and effective oscillator force

  20. Electro-caloric effect in lead-free Sn doped BaTiO3 ceramics at room temperature and low applied fields

    International Nuclear Information System (INIS)

    Upadhyay, Sanjay Kumar; Reddy, V. Raghavendra; Bag, Pallab; Rawat, R.; Gupta, S. M.; Gupta, Ajay

    2014-01-01

    Structural, dielectric, ferroelectric (FE), 119 Sn Mössbauer, and specific heat measurements of polycrystalline BaTi 1–x Sn x O 3 (x = 0% to 15%) ceramics are reported. Phase purity and homogeneous phase formation with Sn doping is confirmed from x-ray diffraction and 119 Sn Mössbauer measurements. With Sn doping, the microstructure is found to change significantly. Better ferroelectric properties at room temperature, i.e., increased remnant polarization (38% more) and very low field switchability (225% less) are observed for x = 5% sample as compared to other samples and the results are explained in terms of grain size effects. With Sn doping, merging of all the phase transitions into a single one is observed for x ≥ 10% and for x = 5%, the tetragonal to orthorhombic transition temperature is found close to room temperature. As a consequence better electro-caloric effects are observed for x = 5% sample and therefore is expected to satisfy the requirements for non-toxic, low energy (field) and room temperature based applications.

  1. First principles study of CaTIO3 crystal in paraelectric and ferroelectric phases

    International Nuclear Information System (INIS)

    Hashemi, H.; Kompany, A.; Hosseini, M.

    2005-01-01

    Electronic properties of CaTiO 3 crystal in paraelectric and ferroelectric phases have been studied by first principles, using Hohenberg-kohn-sham density functional theory. In paraelectric phase the results show an indirect band gap of about at 2eV at Γ-R direction in the Brillouin zone and a strong hybridization between Ti-3d an O-2P orbital. In ferroelectric phase a direct band gap of about 1 eV is seen at ***Γ point. Up to our knowledge no data has been reported on the ferroelectric phase so far, therefore our results might be useful for the future works

  2. Tunable Injection Barrier in Organic Resistive Switches Based on Phase-Separated Ferroelectric-Semiconductor Blends

    NARCIS (Netherlands)

    Asadi, Kamal; de Boer, Tom G.; Blom, Paul W. M.; de Leeuw, Dago M.

    2009-01-01

    Organic non-volatile resistive bistable diodes based on phase-separated blends of ferroelectric and semiconducting polymers are fabricated. The polarization field of the ferroelectric modulates the injection barrier at the semiconductor-electrode contact and, hence, the resistance of the comprising

  3. Tunable injection barrier in organic resistive switches based on phase-separated ferroelectric-semiconductor blends

    NARCIS (Netherlands)

    Asadi, K.; Boer, T.G. de; Blom, P.W.M.; Leeuw, D.M. de

    2009-01-01

    Organic non-volatile resistive bistable diodes based on phase-separated blends of ferroelectric and semiconducting polymers are fabricated. The polarization field of the ferroelectric modulates the injection barrier at the semiconductor-electrode contact and, hence, the resistance of the comprising

  4. Materials for room temperature magnetic refrigeration

    Energy Technology Data Exchange (ETDEWEB)

    Rosendahl Hansen, B.

    2010-07-15

    Magnetic refrigeration is a cooling method, which holds the promise of being cleaner and more efficient than conventional vapor-compression cooling. Much research has been done during the last two decades on various magnetic materials for this purpose and today a number of materials are considered candidates as they fulfill many of the requirements for a magnetic refrigerant. However, no one material stands out and the field is still active with improving the known materials and in the search for a better one. Magnetic cooling is based on the magnetocaloric effect, which causes a magnetic material to change its temperature when a magnetic field is applied or removed. For room temperature cooling, one utilizes that the magnetocaloric effect peaks near magnetic phase transitions and so the materials of interest all have a critical temperature within the range of 250 - 310 K. A magnetic refrigerant should fulfill a number of criteria, among these a large magnetic entropy change, a large adiabatic temperature change, preferably little to no thermal or magnetic hysteresis and the material should have the stability required for long term use. As the temperature range required for room temperature cooling is some 40 - 50 K, the magnetic refrigerant should also be able to cover this temperature span either by exhibiting a very broad peak in magnetocaloric effect or by providing the opportunity for creating a materials series with varying transition temperatures. (Author)

  5. On the room temperature multiferroic BiFeO3: magnetic, dielectric and thermal properties

    Science.gov (United States)

    Lu, J.; Günther, A.; Schrettle, F.; Mayr, F.; Krohns, S.; Lunkenheimer, P.; Pimenov, A.; Travkin, V. D.; Mukhin, A. A.; Loidl, A.

    2010-06-01

    Magnetic dc susceptibility between 1.5 and 800 K, ac susceptibility and magnetization, thermodynamic properties, temperature dependence of radio and audio-wave dielectric constants and conductivity, contact-free dielectric constants at mm-wavelengths, as well as ferroelectric polarization are reported for single crystalline BiFeO3. A well developed anomaly in the magnetic susceptibility signals the onset of antiferromagnetic order close to 635 K. Beside this anomaly no further indications of phase or glass transitions are indicated in the magnetic dc and ac susceptibilities down to the lowest temperatures. The heat capacity has been measured from 2 K up to room temperature and significant contributions from magnon excitations have been detected. From the low-temperature heat capacity an anisotropy gap of the magnon modes of the order of 6 meV has been determined. The dielectric constants measured in standard two-point configuration are dominated by Maxwell-Wagner like effects for temperatures T > 300 K and frequencies below 1 MHz. At lower temperatures the temperature dependence of the dielectric constant and loss reveals no anomalies outside the experimental errors, indicating neither phase transitions nor strong spin phonon coupling. The temperature dependence of the dielectric constant was measured contact free at microwave frequencies. At room temperature the dielectric constant has an intrinsic value of 53. The loss is substantial and strongly frequency dependent indicating the predominance of hopping conductivity. Finally, in small thin samples we were able to measure the ferroelectric polarization between 10 and 200 K. The saturation polarization is of the order of 40 μC/cm2, comparable to reports in literature.

  6. Interrelationship between flexoelectricity and strain gradient elasticity in ferroelectric nanofilms: A phase field study

    Science.gov (United States)

    Jiang, Limei; Xu, Xiaofei; Zhou, Yichun

    2016-12-01

    With the development of the integrated circuit technology and decreasing of the device size, ferroelectric films used in nano ferroelectric devices become thinner and thinner. Along with the downscaling of the ferroelectric film, there is an increasing influence of two strain gradient related terms. One is the strain gradient elasticity and the other one is flexoelectricity. To investigate the interrelationship between flexoelectricity and strain gradient elasticity and their combined effect on the domain structure in ferroelectric nanofilms, a phase field model of flexoelectricity and strain gradient elasticity on the ferroelectric domain evolution is developed based on Mindlin's theory of strain-gradient elasticity. Weak form is derived and implemented in finite element formulations for numerically solving the model equations. The simulation results show that upper bounds for flexoelectric coefficients can be enhanced by increasing strain gradient elasticity coefficients. While a large flexoelectricity that exceeds the upper bound can induce a transition from a ferroelectric state to a modulated/incommensurate state, a large enough strain gradient elasticity may lead to a conversion from an incommensurate state to a ferroelectric state. Strain gradient elasticity and the flexoelectricity have entirely opposite effects on polarization. The observed interrelationship between the strain gradient elasticity and flexoelectricity is rationalized by an analytical solution of the proposed theoretical model. The model proposed in this paper could help us understand the mechanism of phenomena observed in ferroelectric nanofilms under complex electromechanical loads and provide some guides on the practical application of ferroelectric nanofilms.

  7. Magnetocaloric refrigeration near room temperature (invited)

    International Nuclear Information System (INIS)

    Brueck, E.; Tegus, O.; Thanh, D.T.C.; Buschow, K.H.J.

    2007-01-01

    Modern society relies on readily available refrigeration. The ideal cooling machine would be a compact, solid state, silent and energy-efficient heat pump that does not require maintenance. Magnetic refrigeration has three prominent advantages compared to compressor-based refrigeration. First, there are no harmful gases involved, second it may be built more compact as the working material is a solid and third magnetic refrigerators generate much less noise. Recently, a new class of magnetic refrigerant materials for room-temperature applications was discovered. These new materials have important advantages over existing magnetic coolants: They exhibit a large magnetocaloric effect (MCE) in conjunction with a magnetic phase transition of first order. This MCE is, larger than that of Gd metal, which is used in the demonstration refrigerators built to explore the potential of this evolving technology. In the present review, we compare the different materials considering both scientific aspects and industrial applicability

  8. Materials for Room Temperature Magnetic Refrigeration

    DEFF Research Database (Denmark)

    Hansen, Britt Rosendahl

    Magnetic refrigeration is a cooling method, which holds the promise of being cleaner and more efficient than conventional vapor-compression cooling. Much research has been done during the last two decades on various magnetic materials for this purpose and today a number of materials are considered...... candidates as they fulfill many of the requirements for a magnetic refrigerant. However, no one material stands out and the field is still active with improving the known materials and in the search for a better one. Magnetic cooling is based on the magnetocaloric effect, which causes a magnetic material...... to change its temperature when a magnetic field is applied or removed. For room temperature cooling, one utilizes that the magnetocaloric effect peaks near magnetic phase transitions and so the materials of interest all have a critical temperature within the range of 250 – 310 K. A magnetic refrigerant...

  9. Ionothermal synthesis of β-NH4AlF4 and the determination by single crystal X-ray diffraction of its room temperature and low temperature phases

    International Nuclear Information System (INIS)

    Parnham, Emily R.; Slawin, Alex M.Z.; Morris, Russell E.

    2007-01-01

    β-NH 4 AlF 4 has been synthesised ionothermally using 1-ethyl-3-methylimidazolium hexafluorophosphate as solvent and template provider. β-NH 4 AlF 4 crystals were produced which were suitable for single crystal X-ray diffraction analysis. A phase transition occurs between room temperature (298 K) and low temperature (93 K) data collections. At 298 K the space group=I4/mcm (no. 140), α=11.642(5), c=12.661(5) A, Z=2 (10NH 4 AlF 4 ), wR(F 2 )=0.1278, R(F)=0.0453. At 93 K the space group=P4 2 /ncm (no. 138), α=11.616(3), c=12.677(3) A, Z=2 (10NH 4 AlF 4 ), wR(F 2 )=0.1387, R(F)=0.0443. The single crystal X-ray diffraction study of β-NH 4 AlF 4 shows the presence of two different polymorphs at low and room temperature, indicative of a phase transition. The [AlF 4/2 F 2 ] - layers are undisturbed except for a small tilting of the AlF 6 octahedra in the c-axis direction. -Ionothermal synthesis, the use of an ionic liquid as the solvent in materials preparation, has been used to prepare β-NH 4 AlF 4 , and structural characterisation indicates that there are two versions of the structure, a low temperature primitive phase at 93 K and a high temperature body-centered phase at 298 K

  10. A thermally robust and thickness independent ferroelectric phase in laminated hafnium zirconium oxide

    Directory of Open Access Journals (Sweden)

    S. Riedel

    2016-09-01

    Full Text Available Ferroelectric properties in hafnium oxide based thin films have recovered the scaling potential for ferroelectric memories due to their ultra-thin-film- and CMOS-compatibility. However, the variety of physical phenomena connected to ferroelectricity allows a wider range of applications for these materials than ferroelectric memory. Especially mixed HfxZr1-xO2 thin films exhibit a broad compositional range of ferroelectric phase stability and provide the possibility to tailor material properties for multiple applications. Here it is shown that the limited thermal stability and thick-film capability of HfxZr1-xO2 can be overcome by a laminated approach using alumina interlayers.

  11. Room temperature multiferroic properties of (Fe{sub x}, Sr{sub 1−x})TiO{sub 3} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Kyoung-Tae; Kim, Cheolbok; Fang, Sheng-Po; Yoon, Yong-Kyu, E-mail: ykyoon@ece.ufl.edu [Department of Electrical and Computer Engineering, University of Florida, Gainesville, Florida 32611 (United States)

    2014-09-08

    This letter reports the structural, dielectric, ferroelectric, and magnetic properties of Fe substituted SrTiO{sub 3} thin films in room temperature. The structural data obtained from x-ray diffraction indicates that (Fe{sub x},Sr{sub 1−x})TiO{sub 3}, the so called FST, transforms from pseudocubic to tetragonal structures with increase of the Fe content in SrTiO{sub 3} thin films, featuring the ferroelectricity, while vibrating sample magnetometer measurements show magnetic hysteresis loops for the samples with low iron contents indicating their ferromagnetism. The characterized ferroelectricity and ferromagnetism confirms strong multiferroitism of the single phase FST thin films in room temperature. Also, an FST thin film metal-insulator-metal multiferroic capacitor has been fabricated and characterized in microwave frequencies between 10 MHz and 5 GHz. A capacitor based on Fe{sub 0.1}Sr{sub 0.9}TiO{sub 3} with a thickness of 260 nm shows a high electric tunability of 18.6% at 10 V and a maximum magnetodielectric value of 1.37% at 0.4 mT with a loss tangent of 0.021 at 1 GHz. This high tuning and low loss makes this material as a good candidate for frequency agile microwave devices such as tunable filters, phase shifters, and antennas.

  12. A comparative study of the Aurivillius phase ferroelectrics CaBi 4Ti 4O 15 and BaBi 4Ti 4O 15

    Science.gov (United States)

    Tellier, J.; Boullay, Ph.; Manier, M.; Mercurio, D.

    2004-06-01

    The room temperature structures of the four-layer Aurivillius phase ferroelectrics CaBi 4Ti 4O 15 and BaBi 4Ti 4O 15 are determined by means of single crystal X-ray diffraction. Regarding the CaBi 4Ti 4O 15 phase, in agreement with the tolerance factor, a significant deformation of the perovskite blocks is observed. The rotation system of the octahedra is typical from even layer Aurivillius phases and leads to the use of the space group A2 1am. For the BaBi 4Ti 4O 15 phase, only a weak variation with respect to the F2 mm space group can be suggested from single crystal X-ray diffraction. A significant presence of Ba atoms in the [ M2O 2] slabs is confirmed in agreement with the previous works but specific Ba 2+ and Bi 3+ sites have to be considered due to the large difference in bounding requirement of these cations. Possible origins for the ferroelectric relaxor behavior of the Ba-based compound are discussed in view of the presented structural analyses.

  13. Organic non-volatile memories from ferroelectric phase-separated blends

    Science.gov (United States)

    Asadi, Kamal; de Leeuw, Dago M.; de Boer, Bert; Blom, Paul W. M.

    2008-07-01

    New non-volatile memories are being investigated to keep up with the organic-electronics road map. Ferroelectric polarization is an attractive physical property as the mechanism for non-volatile switching, because the two polarizations can be used as two binary levels. However, in ferroelectric capacitors the read-out of the polarization charge is destructive. The functionality of the targeted memory should be based on resistive switching. In inorganic ferroelectrics conductivity and ferroelectricity cannot be tuned independently. The challenge is to develop a storage medium in which the favourable properties of ferroelectrics such as bistability and non-volatility can be combined with the beneficial properties provided by semiconductors such as conductivity and rectification. Here we present an integrated solution by blending semiconducting and ferroelectric polymers into phase-separated networks. The polarization field of the ferroelectric modulates the injection barrier at the semiconductor-metal contact. The combination of ferroelectric bistability with (semi)conductivity and rectification allows for solution-processed non-volatile memory arrays with a simple cross-bar architecture that can be read out non-destructively. The concept of an electrically tunable injection barrier as presented here is general and can be applied to other electronic devices such as light-emitting diodes with an integrated on/off switch.

  14. Magnetic-field-induced irreversible antiferromagnetic–ferromagnetic phase transition around room temperature in as-cast Sm–Co based SmCo{sub 7−x}Si{sub x} alloys

    Energy Technology Data Exchange (ETDEWEB)

    Feng, D.Y.; Zhao, L.Z.; Liu, Z.W., E-mail: zwliu@scut.edu.cn

    2016-04-15

    A magnetic-field-induced irreversible metamagnetic phase transition from antiferro- to ferromagnetism, which leads to an anomalous initial-magnetization curve lying outside the magnetic hysteresis loop, is reported in arc-melted SmCo{sub 7−x}Si{sub x} alloys. The transition temperatures are near room temperature, much higher than other compounds with similar initial curves. Detailed investigation shows that this phenomenon is dependent on temperature, magnetic field and Si content and shows some interesting characteristics. It is suggested that varying interactions between the Sm and Co layers in the crystal are responsible for the formation of a metastable AFM structure, which induces the anomalous phenomenon in as-cast alloys. The random occupation of 3g sites by Si and Co atoms also has an effect on this phenomenon.

  15. High Strength-High Ductility Combination Ultrafine-Grained Dual-Phase Steels Through Introduction of High Degree of Strain at Room Temperature Followed by Ultrarapid Heating During Continuous Annealing of a Nb-Microalloyed Steel

    Science.gov (United States)

    Deng, Yonggang; Di, Hongshuang; Hu, Meiyuan; Zhang, Jiecen; Misra, R. D. K.

    2017-07-01

    Ultrafine-grained dual-phase (UFG-DP) steel consisting of ferrite (1.2 μm) and martensite (1 μm) was uniquely processed via combination of hot rolling, cold rolling and continuous annealing of a low-carbon Nb-microalloyed steel. Room temperature tensile properties were evaluated and fracture mechanisms studied and compared to the coarse-grained (CG) counterpart. In contrast to the CG-DP steel, UFG-DP had 12.7% higher ultimate tensile strength and 10.7% greater uniform elongation. This is partly attributed to the increase in the initial strain-hardening rate, decrease in nanohardness ratio of martensite and ferrite. Moreover, a decreasing number of ferrite grains with {001} orientation increased the cleavage fracture stress and increased the crack initiation threshold stress with consequent improvement in ductility UFG-DP steel.

  16. On the room-temperature phase diagram of high pressure hydrogen: An ab initio molecular dynamics perspective and a diffusion Monte Carlo study

    International Nuclear Information System (INIS)

    Chen, Ji; Ren, Xinguo; Li, Xin-Zheng; Alfè, Dario; Wang, Enge

    2014-01-01

    The finite-temperature phase diagram of hydrogen in the region of phase IV and its neighborhood was studied using the ab initio molecular dynamics (MD) and the ab initio path-integral molecular dynamics (PIMD). The electronic structures were analyzed using the density-functional theory (DFT), the random-phase approximation, and the diffusion Monte Carlo (DMC) methods. Taking the state-of-the-art DMC results as benchmark, comparisons of the energy differences between structures generated from the MD and PIMD simulations, with molecular and dissociated hydrogens, respectively, in the weak molecular layers of phase IV, indicate that standard functionals in DFT tend to underestimate the dissociation barrier of the weak molecular layers in this mixed phase. Because of this underestimation, inclusion of the quantum nuclear effects (QNEs) in PIMD using electronic structures generated with these functionals leads to artificially dissociated hydrogen layers in phase IV and an error compensation between the neglect of QNEs and the deficiencies of these functionals in standard ab initio MD simulations exists. This analysis partly rationalizes why earlier ab initio MD simulations complement so well the experimental observations. The temperature and pressure dependencies for the stability of phase IV were also studied in the end and compared with earlier results

  17. Flexoelectricity: strain gradient effects in ferroelectrics

    Energy Technology Data Exchange (ETDEWEB)

    Ma Wenhui [Department of Physics, Shantou Unversity, Shantou, Guangdong 515063 (China)

    2007-12-15

    Mechanical strain gradient induced polarization effect or flexoelectricity in perovskite-type ferroelectric and relaxor ferroelectric ceramics was investigated. The flexoelectric coefficients measured at room temperature ranged from about 1 {mu} C m{sup -1} for lead zirconate titanate to 100 {mu} C m{sup -1} for barium strontium titanate. Flexoelectric effects were discovered to be sensitive to chemical makeup, phase symmetry, and domain structures. Based on phenomenological discussion and experimental data on flexoelectricity, the present study proposed that mechanical strain gradient field could influence polarization responses in a way analogous to electric field. Flexoelectric coefficients were found to be nonlinearly enhanced by dielectric permittivity and strain gradient. Interfacial mismatch in epitaxial thin films can give rise to high strain gradients, enabling flexoelectric effects to make a significant impact in properly engineered ferroelectric heterostructure systems.

  18. Room Temperature Optical Constants and Band Gap Evolution of Phase Pure M1-VO2 Thin Films Deposited at Different Oxygen Partial Pressures by Reactive Magnetron Sputtering

    Directory of Open Access Journals (Sweden)

    Meng Jiang

    2014-01-01

    Full Text Available Spectroscopic ellipsometry study was employed for phase pure VO2(M1 thin films grown at different oxygen partial pressures by reactive magnetron sputtering. The optical constants of the VO2(M1 thin films have been determined in a photon energy range between 0.73 and 5.05 eV. The near-infrared extinction coefficient and optical conductivity of VO2(M1 thin films rapidly increase with decreasing O2-Ar ratios. Moreover, two electronic transitions can be uniquely assigned. The energy gaps correlated with absorption edge (E1 at varied O2-Ar ratios are almost the same (~2.0 eV; consequently, the absorption edge is not significantly changed. However, the optical band gap corresponding to semiconductor-to-metal phase transition (E2 decreases from 0.53 to 0.18 eV with decreasing O2-Ar ratios.

  19. Room temperature creep in metals and alloys

    Energy Technology Data Exchange (ETDEWEB)

    Deibler, Lisa Anne [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Materials Characterization and Performance

    2014-09-01

    Time dependent deformation in the form of creep and stress relaxation is not often considered a factor when designing structural alloy parts for use at room temperature. However, creep and stress relaxation do occur at room temperature (0.09-0.21 Tm for alloys in this report) in structural alloys. This report will summarize the available literature on room temperature creep, present creep data collected on various structural alloys, and finally compare the acquired data to equations used in the literature to model creep behavior. Based on evidence from the literature and fitting of various equations, the mechanism which causes room temperature creep is found to include dislocation generation as well as exhaustion.

  20. IMPROVED SYNTHESIS OF ROOM TEMPERATURE IONIC LIQUIDS

    Science.gov (United States)

    Room temperature ionic liquids (RTILs), molten salts comprised of N-alkylimidazolium cations and various anions, have received significant attention due to their commercial potential in a variety of chemical applications especially as substitutes for conventional volatile organic...

  1. Room temperature multiferroic properties of Pb(Fe{sub 0.5}Nb{sub 0.5})O{sub 3}–Co{sub 0.65}Zn{sub 0.35}Fe{sub 2}O{sub 4} composites

    Energy Technology Data Exchange (ETDEWEB)

    Pradhan, Dhiren K., E-mail: dhirenkumarp@gmail.com, E-mail: rkatiyar@hpcf.upr.edu; Katiyar, Ram S., E-mail: dhirenkumarp@gmail.com, E-mail: rkatiyar@hpcf.upr.edu [Department of Physics and Institute of Functional Nanomaterials, University of Puerto Rico, San Juan, Puerto Rico 00936 (United States); Puli, Venkata S. [Department of Physics and Engineering Physics, Tulane University, New Orleans, Louisiana 70118 (United States); Narayan Tripathy, Satya; Pradhan, Dillip K. [Department of Physics, National Institute of Technology, Rourkela 769008 (India); Scott, J. F. [Department of Physics and Institute of Functional Nanomaterials, University of Puerto Rico, San Juan, Puerto Rico 00936 (United States); Department of Physics, Cavendish Laboratory, University of Cambridge, Cambridge (United Kingdom)

    2013-12-21

    We report the crystal structure, magnetic, ferroelectric, dielectric, and magneto-dielectric properties of [Pb(Fe{sub 0.5}Nb{sub 0.5})O{sub 3}]{sub (1−x)}[Co{sub 0.65}Zn{sub 0.35}Fe{sub 2}O{sub 4}]{sub 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 Co{sub 0.65}Zn{sub 0.35}Fe{sub 2}O{sub 4} (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/cm{sup 3}) and charge-curve energy density (∼0.84 to 0.11 J/cm{sup 3}) 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.

  2. Enhancing the activation of silicon carbide tracer particles for PEPT applications using gas-phase deposition of alumina at room temperature and atmospheric pressure

    Energy Technology Data Exchange (ETDEWEB)

    Valdesueiro, D. [Delft University of Technology, Department of Chemical Engineering, 2628 BL Delft (Netherlands); Garcia-Triñanes, P., E-mail: p.garcia@surrey.ac.uk [Department of Chemical and Process Engineering, Faculty of Engineering and Physical Sciences, University of Surrey, Guildford, Surrey GU2 7XH (United Kingdom); Meesters, G.M.H.; Kreutzer, M.T. [Delft University of Technology, Department of Chemical Engineering, 2628 BL Delft (Netherlands); Gargiuli, J.; Leadbeater, T.W.; Parker, D.J. [Positron Imaging Centre, School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom); Seville, J.P.K. [Department of Chemical and Process Engineering, Faculty of Engineering and Physical Sciences, University of Surrey, Guildford, Surrey GU2 7XH (United Kingdom); Ommen, J.R. van, E-mail: j.r.vanommen@tudelft.nl [Delft University of Technology, Department of Chemical Engineering, 2628 BL Delft (Netherlands)

    2016-01-21

    We have enhanced the radio-activation efficiency of SiC (silicon carbide) particles, which by nature have a poor affinity towards {sup 18}F ions, to be employed as tracers in studies using PEPT (Positron Emission Particle Tracking). The resulting SiC–Al{sub 2}O{sub 3} core–shell structure shows a good labelling efficiency, comparable to γ-Al{sub 2}O{sub 3} tracer particles, which are commonly used in PEPT. The coating of the SiC particles was carried at 27±3 °C and 1 bar in a fluidized bed reactor, using trimethylaluminium and water as precursors, by a gas phase technique similar to atomic layer deposition. The thickness of the alumina films, which ranged from 5 to 500 nm, was measured by elemental analysis and confirmed with FIB-TEM (focused ion beam – transmission electron microscope), obtaining consistent results from both techniques. By depositing such a thin film of alumina, properties that influence the hydrodynamic behaviour of the SiC particles, such as size, shape and density, are hardly altered, ensuring that the tracer particle shows the same flow behaviour as the other particles. The paper describes a general method to improve the activation efficiency of materials, which can be applied for the production of tracer particles for many other applications too. - Highlights: • We deposited Al{sub 2}O{sub 3} films on SiC particles at ambient conditions in a fluidized bed. • The affinity of {sup 18}F ions towards Al{sub 2}O{sub 3}–SiC particle was improved compared to SiC. • We used the Al{sub 2}O{sub 3}–SiC activated particle as tracer in a PEPT experiment. • Tracer particles have suitable activity for accurate tracking. • The Al{sub 2}O{sub 3} film is thin enough not to alter the particle size, shape and density.

  3. Room temperature large self-biased magnetoelectric effect in non-lead based piezoelectric and magnetostrictive (0−3) particulate composite system

    International Nuclear Information System (INIS)

    Kumari, Mukesh; Prakash, Chandra; Chatterjee, Ratnamala

    2017-01-01

    In this work, room temperature magnetoelectric properties of (0−3) particulate composites of non lead based piezoelectric BNTKNNLTS [0.97(Bi 0.5 Na 0.5 TiO 3 )–0.03(K 0.47 Na 0.47 Li 0.06 Nb 0.74 Sb 0.06 Ta 0.2 O 3 ) and magnetostrictive CZFMO (Co 0.6 Zn 0.4 Fe 1.7 Mn 0.3 O 4 ) are presented. Composite samples of (1-x)(BNTKNNLTS)-x(CZFMO) , with x=0.1 and 0.5, are synthesized by solid state reaction route. X-ray diffraction confirms the single phase formation of parent phases and the presence of two phases in the composites. Similar sintering conditions of the two individual components lead to optimal ferroelectric and ferromagnetic properties in the composites. A large self-biased magnetoelectric (ME) coupling ~74 mV/cm.Oe for the sample with x=0.1 (measured in longitudinally magnetized-transversely polarized configuration) is observed at room temperature. - Highlights: • Modified BNT-CFO based (0−3) particulate composites have been synthesized. • Similar sintering conditions of two components lead to optimal multiferroicity. • A large self-biased ME coupling ~74 mV/cm. Oe is obtained at room temperature.

  4. Phase transition properties of a cylindrical ferroelectric nanowire

    Indian Academy of Sciences (India)

    Based on the transverse Ising model (TIM) and using the mean-field theory, we inves- ... workers [11–13] to study the static and dynamic properties of ferroelectric superlattices. ... The mean-field expressions is usually used for a qualitative.

  5. Theoretical study of ferroelectric nanoparticles using phase reconstructed electron microscopy

    DEFF Research Database (Denmark)

    Phatak, C.; Petford-Long, A. K.; Beleggia, Marco

    2014-01-01

    Ferroelectric nanostructures are important for a variety of applications in electronic and electro-optical devices, including nonvolatile memories and thin-film capacitors. These applications involve stability and switching of polarization using external stimuli, such as electric fields. We prese...

  6. Elastic-modulus enhancement during room-temperature aging and its suppression in metastable Ti–Nb-Based alloys with low body-centered cubic phase stability

    International Nuclear Information System (INIS)

    Tane, M.; Hagihara, K.; Ueda, M.; Nakano, T.; Okuda, Y.

    2016-01-01

    Changes in the elastic properties during room-temperature aging (RT aging) of metastable Ti–Nb-based alloy single crystals with low body-centered cubic (bcc)-phase stability were investigated. The elastic stiffness components of Ti–Nb–Ta–Zr alloys with different Nb concentrations were measured by resonant ultrasound spectroscopy during RT aging; the results revealed that shear moduli c ′ and c 44 were increased by RT aging. In the alloy with the lowest Nb concentration, i.e., with the lowest bcc phase stability, shear moduli c ′ and c 44 were enhanced by the largest amount. The increase rates were ∼5% for 1.1 × 10 7  s (127 days), whereas the bulk modulus was hardly changed by aging. In Ti–Nb–Ta–Zr–O alloys with different oxygen concentrations, shear moduli c ′ and c 44 of the alloy with the lowest oxygen concentration increased most significantly. Moreover, the electrical resistivity of Ti–Nb–Ta–Zr and Ti–Nb–Ta–Zr–O alloys was increased by RT aging. Importantly, the enhancements of shear moduli and electrical resistivity were suppressed by increases in the bcc-phase stability (i.e., increase in the Nb concentration) and oxygen concentration; these factors are known to suppress ω (hexagonal) phase formation. However, transmission electron microscopy (TEM) observations revealed that only a diffuse ω structure—an ω-like lattice distortion—was formed after RT aging. On the basis of alloying element effects, TEM observations, and analysis of the changes in elastic properties by using a micromechanics model, it was deduced that the enhancements of shear moduli and electrical resistivity were possibly caused by the formation of a diffuse ω structure.

  7. Non-Resonant Magnetoelectric Energy Harvesting Utilizing Phase Transformation in Relaxor Ferroelectric Single Crystals

    Directory of Open Access Journals (Sweden)

    Peter Finkel

    2015-12-01

    Full Text Available Recent advances in phase transition transduction enabled the design of a non-resonant broadband mechanical energy harvester that is capable of delivering an energy density per cycle up to two orders of magnitude larger than resonant cantilever piezoelectric type generators. This was achieved in a [011] oriented and poled domain engineered relaxor ferroelectric single crystal, mechanically biased to a state just below the ferroelectric rhombohedral (FR-ferroelectric orthorhombic (FO phase transformation. Therefore, a small variation in an input parameter, e.g., electrical, mechanical, or thermal will generate a large output due to the significant polarization change associated with the transition. This idea was extended in the present work to design a non-resonant, multi-domain magnetoelectric composite hybrid harvester comprised of highly magnetostrictive alloy, [Fe81.4Ga18.6 (Galfenol or TbxDy1-xFe2 (Terfenol-D], and lead indium niobate–lead magnesium niobate–lead titanate (PIN-PMN-PT domain engineered relaxor ferroelectric single crystal. A small magnetic field applied to the coupled device causes the magnetostrictive element to expand, and the resulting stress forces the phase change in the relaxor ferroelectric single crystal. We have demonstrated high energy conversion in this magnetoelectric device by triggering the FR-FO transition in the single crystal by a small ac magnetic field in a broad frequency range that is important for multi-domain hybrid energy harvesting devices.

  8. Prospects and applications near ferroelectric quantum phase transitions: a key issues review

    Science.gov (United States)

    Chandra, P.; Lonzarich, G. G.; Rowley, S. E.; Scott, J. F.

    2017-11-01

    The emergence of complex and fascinating states of quantum matter in the neighborhood of zero temperature phase transitions suggests that such quantum phenomena should be studied in a variety of settings. Advanced technologies of the future may be fabricated from materials where the cooperative behavior of charge, spin and current can be manipulated at cryogenic temperatures. The progagating lattice dynamics of displacive ferroelectrics make them appealing for the study of quantum critical phenomena that is characterized by both space- and time-dependent quantities. In this key issues article we aim to provide a self-contained overview of ferroelectrics near quantum phase transitions. Unlike most magnetic cases, the ferroelectric quantum critical point can be tuned experimentally to reside at, above or below its upper critical dimension; this feature allows for detailed interplay between experiment and theory using both scaling and self-consistent field models. Empirically the sensitivity of the ferroelectric T c’s to external and to chemical pressure gives practical access to a broad range of temperature behavior over several hundreds of Kelvin. Additional degrees of freedom like charge and spin can be added and characterized systematically. Satellite memories, electrocaloric cooling and low-loss phased-array radar are among possible applications of low-temperature ferroelectrics. We end with open questions for future research that include textured polarization states and unusual forms of superconductivity that remain to be understood theoretically.

  9. Designing switchable near room-temperature multiferroics via the discovery of a novel magnetoelectric coupling

    Science.gov (United States)

    Feng, J. S.; Xu, Ke; Bellaiche, Laurent; Xiang, H. J.

    2018-05-01

    Magnetoelectric (ME) coupling is the key ingredient for realizing the cross-control of magnetism and ferroelectricity in multiferroics. However, multiferroics are not only rare, especially at room-temperature, in nature but also the overwhelming majority of known multiferroics do not exhibit highly-desired switching of the direction of magnetization when the polarization is reversed by an electric field. Here, we report group theory analysis and ab initio calculations demonstrating, and revealing the origin of, the existence of a novel form of ME coupling term in a specific class of materials that does allow such switching. This term naturally explains the previously observed electric field control of magnetism in the first known multiferroics, i.e., the Ni–X boracite family. It is also presently used to design a switchable near room-temperature multiferroic (namely, LaSrMnOsO6 perovskite) having rather large ferroelectric polarization and spontaneous magnetization, as well as strong ME coupling.

  10. Room temperature exchange bias in SmFeO_3 single crystal

    International Nuclear Information System (INIS)

    Wang, Xiaoxiong; Cheng, Xiangyi; Gao, Shang; Song, Junda; Ruan, Keqing; Li, Xiaoguang

    2016-01-01

    Exchange bias phenomenon is generally ascribed to the unidirectional magnetic shift along the field axes at interface of two magnetic materials. Room temperature exchange bias is found in SmFeO_3 single crystal. The behavior after different cooling procedure is regular, and the training behavior is attributed to the athermal training and its pinning origin is attributed to the antiferromagnetic clusters. Its being single phase and occurring at room temperature make it an appropriate candidate for application. - Graphical abstract: Room temperature exchange bias was found in oxide single crystal. Highlights: • Room temperature exchange bias has been discovered in single-crystalline SmFeO_3. • Its pinning origin is attributed to the antiferromagnetic clusters. • Its being single phase and occurring at room temperature make it an appropriate candidate for application.

  11. Giant Magnetoelectric Energy Conversion Utilizing Inter-Ferroelectric Phase Transformations in Ferroics

    Science.gov (United States)

    Finkel, Peter; Staruch, Margo

    Phase transition-based electromechanical transduction permits achieving a non-resonant broadband mechanical energy conversion see (Finkel et al Actuators, 5 [1] 2. (2015)) , the idea is based on generation high energy density per cycle , at least 100x of magnitude larger than linear piezoelectric type generators in stress biased [011]cut relaxor ferroelectric Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) single crystal can generate reversible strain >0.35% at remarkably low fields (0.1 MV/m) for tens of millions of cycles. Recently we demonstrated that large strain and polarization rotation can be generated for over 40 x 106cycles with little fatigue by realization of reversible ferroelectric-ferroelectric phase transition in [011] cut PIN-PMN-PT relaxor ferroelectric single crystal while sweeping through the transition with a low applied electric field <0.18 MV/m under mechanical stress. This methodology was extended in the present work to propose magnetoelectric (ME) composite hybrid system comprised of highly magnetostrictive alloymFe81.4Ga18.6 (Galfenol), and lead indium niobate-lead magnesium niobate-lead titanate (PIN-PMN-PT) domain engineered relaxor ferroelectric single crystal. A small time-varying magnetic field applied to this system causes the magnetostrictive element to expand, and the resulting stress forces the phase change in the relaxor ferroelectric single crystal. ME coupling coefficient was fond to achieve 80 V/cm Oe near the FR-FO phase transition that is at least 100X of magnitude higher than any currently reported values.

  12. Room temperature synthesis of biodiesel using sulfonated ...

    Science.gov (United States)

    Sulfonation of graphitic carbon nitride (g-CN) affords a polar and strongly acidic catalyst, Sg-CN, which displays unprecedented reactivity and selectivity in biodiesel synthesis and esterification reactions at room temperature. Prepared for submission to Royal Society of Chemistry (RSC) journal, Green Chemistry as a communication.

  13. Room-temperature antiferromagnetic memory resistor.

    Science.gov (United States)

    Marti, X; Fina, I; Frontera, C; Liu, Jian; Wadley, P; He, Q; Paull, R J; Clarkson, J D; Kudrnovský, J; Turek, I; Kuneš, J; Yi, D; Chu, J-H; Nelson, C T; You, L; Arenholz, E; Salahuddin, S; Fontcuberta, J; Jungwirth, T; Ramesh, R

    2014-04-01

    The bistability of ordered spin states in ferromagnets provides the basis for magnetic memory functionality. The latest generation of magnetic random access memories rely on an efficient approach in which magnetic fields are replaced by electrical means for writing and reading the information in ferromagnets. This concept may eventually reduce the sensitivity of ferromagnets to magnetic field perturbations to being a weakness for data retention and the ferromagnetic stray fields to an obstacle for high-density memory integration. Here we report a room-temperature bistable antiferromagnetic (AFM) memory that produces negligible stray fields and is insensitive to strong magnetic fields. We use a resistor made of a FeRh AFM, which orders ferromagnetically roughly 100 K above room temperature, and therefore allows us to set different collective directions for the Fe moments by applied magnetic field. On cooling to room temperature, AFM order sets in with the direction of the AFM moments predetermined by the field and moment direction in the high-temperature ferromagnetic state. For electrical reading, we use an AFM analogue of the anisotropic magnetoresistance. Our microscopic theory modelling confirms that this archetypical spintronic effect, discovered more than 150 years ago in ferromagnets, is also present in AFMs. Our work demonstrates the feasibility of fabricating room-temperature spintronic memories with AFMs, which in turn expands the base of available magnetic materials for devices with properties that cannot be achieved with ferromagnets.

  14. Characterization of Phase Transitions in PZT Ferroelectric films with spectral Ellipsometry

    Czech Academy of Sciences Publication Activity Database

    Deineka, Alexander; Suchaneck, G.; Jastrabík, Lubomír; Gerlach, G.

    11-12, - (2002), s. 377-380 ISSN 0447-6441 R&D Projects: GA MŠk LN00A015; GA ČR GA202/00/1425 Institutional research plan: CEZ:AV0Z1010921 Keywords : ferroelectric film * phase transition * film profile Subject RIV: BH - Optics, Masers, Lasers

  15. The origin of ultrahigh piezoelectricity in relaxor-ferroelectric solid solution crystals

    Energy Technology Data Exchange (ETDEWEB)

    Li, Fei; Zhang, Shujun; Yang, Tiannan; Xu, Zhuo; Zhang, Nan; Liu, Gang; Wang, Jianjun; Wang, Jianli; Cheng, Zhenxiang; Ye, Zuo-Guang; Luo, Jun; Shrout, Thomas R.; Chen, Long-Qing (Penn); (Xian Jiaotong); (CIW); (Simon); (TRS Techn); (Wollongong)

    2016-12-19

    The discovery of ultrahigh piezoelectricity in relaxor-ferroelectric solid solution single crystals is a breakthrough in ferroelectric materials. A key signature of relaxor-ferroelectric solid solutions is the existence of polar nanoregions, a nanoscale inhomogeneity, that coexist with normal ferroelectric domains. Despite two decades of extensive studies, the contribution of polar nanoregions to the underlying piezoelectric properties of relaxor ferroelectrics has yet to be established. Here we quantitatively characterize the contribution of polar nanoregions to the dielectric/piezoelectric responses of relaxor-ferroelectric crystals using a combination of cryogenic experiments and phase-field simulations. The contribution of polar nanoregions to the room-temperature dielectric and piezoelectric properties is in the range of 50–80%. A mesoscale mechanism is proposed to reveal the origin of the high piezoelectricity in relaxor ferroelectrics, where the polar nanoregions aligned in a ferroelectric matrix can facilitate polarization rotation. This mechanism emphasizes the critical role of local structure on the macroscopic properties of ferroelectric materials.

  16. The origin of ultrahigh piezoelectricity in relaxor-ferroelectric solid solution crystals.

    Science.gov (United States)

    Li, Fei; Zhang, Shujun; Yang, Tiannan; Xu, Zhuo; Zhang, Nan; Liu, Gang; Wang, Jianjun; Wang, Jianli; Cheng, Zhenxiang; Ye, Zuo-Guang; Luo, Jun; Shrout, Thomas R; Chen, Long-Qing

    2016-12-19

    The discovery of ultrahigh piezoelectricity in relaxor-ferroelectric solid solution single crystals is a breakthrough in ferroelectric materials. A key signature of relaxor-ferroelectric solid solutions is the existence of polar nanoregions, a nanoscale inhomogeneity, that coexist with normal ferroelectric domains. Despite two decades of extensive studies, the contribution of polar nanoregions to the underlying piezoelectric properties of relaxor ferroelectrics has yet to be established. Here we quantitatively characterize the contribution of polar nanoregions to the dielectric/piezoelectric responses of relaxor-ferroelectric crystals using a combination of cryogenic experiments and phase-field simulations. The contribution of polar nanoregions to the room-temperature dielectric and piezoelectric properties is in the range of 50-80%. A mesoscale mechanism is proposed to reveal the origin of the high piezoelectricity in relaxor ferroelectrics, where the polar nanoregions aligned in a ferroelectric matrix can facilitate polarization rotation. This mechanism emphasizes the critical role of local structure on the macroscopic properties of ferroelectric materials.

  17. Self-Assembled Layered Supercell Structure of Bi2AlMnO6 with Strong Room-Temperature Multiferroic Properties.

    Energy Technology Data Exchange (ETDEWEB)

    Li, Leigang; Boullay, Philippe; Lu, Ping; Perez, Olivier; Steciuk, Gwladys; Wang, Xuejing; Jian, Jie; Huang, Jijie; Gao, Xingyao; Zhang, Wenrui; Zhang, Xinghang; Wang, Haiyan

    2017-02-01

    Room-temperature (RT) multiferroics, possessing ferroelectricity and ferromagnetism simultaneously at RT, hold great promise in miniaturized devices including sensors, actuators, transducers, and multi-state memories. In this work, we report a novel 2D layered RT multiferroic system with self-assembled layered supercell structure consisting of two mismatch-layered sub-lattices of [Bi3O3+δ] and [MO2]1.84 (M=Al/Mn, simply named as BAMO), i.e., alternative layered stacking of two mutually incommensurate sublattices made of a three-layer-thick Bi-O slab and a one-layer-thick Al/Mn-O octahedra slab along the out-of-plane direction. Strong room-temperature multiferroic responses, e.g., ferromagnetic and ferroelectric properties, have been demonstrated and attributed to the highly anisotropic 2D nature of the non-ferromagnetic and ferromagnetic sublattices which are highly mismatched. The work demonstrates an alternative design approach for new 2D layered oxide materials that hold promises as single-phase multiferroics, 2D oxides with tunable bandgaps, and beyond.

  18. Shape-Controlled Synthesis of CuO Nanocrystals by a Room Temperature Solid-Phase Route%室温固相合成形貌可控的CuO纳米晶及其表征

    Institute of Scientific and Technical Information of China (English)

    王文忠; 王丽娟

    2012-01-01

    通过室温固相反应法成功制备出具有一维棒状和球型状的CuO纳米晶.研究结果表明,在反应过程中,表面活性剂对CuO纳米晶的形貌起着决定性的作用.当反应过程在表面活性剂聚乙二醇400液态环境中进行时,所制备的CuO为一维棒状纳米晶.纳米棒的直径为6~14 nm、长度为100~400 nm;当反应过程在表面活性剂聚氧乙烯9醚液态环境中进行时,则所制备的CuO为球形纳米粒子,纳米粒子的直径为4~11nm,平均直径为7 nm.用X射线粉末衍射和透射显微镜技术对所制备纳米晶的成分、晶相、形状和尺寸进行了表征分析.对不同形貌CuO纳米晶的形成机理作了深入的讨论,提出了CuO纳米棒的表面活性剂软模板诱导自组装生长机理.%A room temperature solid-phase route has been developed for the synthesis of CuO nanocrystals with rod- and spherical-like morphology by using surfaetant as shape controller. The results indicate that the surfactant plays a key role in controlling the shape of CuO nanocrystals. The monoclinic phase CuO rod-like nanocrystals with diameter of 6 ~ 14 nm and length of 100 - 400 nm were successfully synthesized when the surfactant polyethylene glycol 400 was used as shape controller. If the surfactant nonylphenyl ether(9)was used as shape controller, keeping the other ecperimental conditions constant, the monoclinic phase CuO spherical nanocrystals with diameter of 4 - 11 nm and an average diameter of 7 nm were fabricated. XRD and TEM techniques were used to study on composition, phase, morphology and size of the as-prepaped CuO nanocrystals. The growth mechanism of CuO nanocrystals has been discussed in detail. A surfactant soft template induced self- assemble growth mechanism was proposed for the formation of Cuo nanorods.

  19. Phase-Field Simulations of Topological Structures and Topological Phase Transitions in Ferroelectric Oxide Heterostructures

    Science.gov (United States)

    Zijian Hong

    Ferroelectrics are materials that exhibit spontaneous electric polarization which can be switched between energy-degenerated states by external stimuli (e.g., mechanical force and electric field) that exceeds a critical value. They have wide potential applications in memories, capacitors, piezoelectric and pyroelectric sensors, and nanomechanical systems. Topological structures and topological phase transitions have been introduced to the condensed matter physics in the past few decades and have attracted broad attentions in various disciplines due to the rich physical insights and broad potential applications. Ferromagnetic topological structures such as vortex and skyrmion are known to be stabilized by the antisymmetric chiral interaction (e.g., Dzyaloshinskii-Moriya interaction). Without such interaction, ferroelectric topological structures (i.e., vortex, flux-closure, skyrmions, and merons) have been studied only recently with other designing strategies, such as reducing the dimension of the ferroelectrics. The overarching goal of this dissertation is to investigate the topological structures in ferroelectric oxide perovskites as well as the topological phase transitions under external applied forces. Pb(Zr,Ti)O3 (PZT) with morphotropic phase boundary is widely explored for high piezoelectric and dielectric properties. The domain structure of PZT tetragonal/rhombohedral (T/R) bilayer is investigated. Strong interfacial coupling is shown, with large polarization rotation to a lower symmetry phase near the T/R interface. Interlayer domain growth can also be captured, with T-domains in the R layer and R-domains in the T layer. For thin PZT bilayer with 5nm of T-layer and 20 nm of R-layer, the a1/a 2 twin domain structure is formed in the top T layer, which could be fully switched to R domains under applied bias. While a unique flux-closure pattern is observed both theoretically and experimentally in the thick bilayer film with 50 nm of thickness for both T and R

  20. Room-temperature ductile inorganic semiconductor

    Science.gov (United States)

    Shi, Xun; Chen, Hongyi; Hao, Feng; Liu, Ruiheng; Wang, Tuo; Qiu, Pengfei; Burkhardt, Ulrich; Grin, Yuri; Chen, Lidong

    2018-05-01

    Ductility is common in metals and metal-based alloys, but is rarely observed in inorganic semiconductors and ceramic insulators. In particular, room-temperature ductile inorganic semiconductors were not known until now. Here, we report an inorganic α-Ag2S semiconductor that exhibits extraordinary metal-like ductility with high plastic deformation strains at room temperature. Analysis of the chemical bonding reveals systems of planes with relatively weak atomic interactions in the crystal structure. In combination with irregularly distributed silver-silver and sulfur-silver bonds due to the silver diffusion, they suppress the cleavage of the material, and thus result in unprecedented ductility. This work opens up the possibility of searching for ductile inorganic semiconductors/ceramics for flexible electronic devices.

  1. Coexistence of weak ferromagnetism and ferroelectricity in the high pressure LiNbO3-type phase of FeTiO3.

    Science.gov (United States)

    Varga, T; Kumar, A; Vlahos, E; Denev, S; Park, M; Hong, S; Sanehira, T; Wang, Y; Fennie, C J; Streiffer, S K; Ke, X; Schiffer, P; Gopalan, V; Mitchell, J F

    2009-07-24

    We report the magnetic and electrical characteristics of polycrystalline FeTiO_{3} synthesized at high pressure that is isostructural with acentric LiNbO_{3} (LBO). Piezoresponse force microscopy, optical second harmonic generation, and magnetometry demonstrate ferroelectricity at and below room temperature and weak ferromagnetism below approximately 120 K. These results validate symmetry-based criteria and first-principles calculations of the coexistence of ferroelectricity and weak ferromagnetism in a series of transition metal titanates crystallizing in the LBO structure.

  2. A Designed Room Temperature Multilayered Magnetic Semiconductor

    Science.gov (United States)

    Bouma, Dinah Simone; Charilaou, Michalis; Bordel, Catherine; Duchin, Ryan; Barriga, Alexander; Farmer, Adam; Hellman, Frances; Materials Science Division, Lawrence Berkeley National Lab Team

    2015-03-01

    A room temperature magnetic semiconductor has been designed and fabricated by using an epitaxial antiferromagnet (NiO) grown in the (111) orientation, which gives surface uncompensated magnetism for an odd number of planes, layered with the lightly doped semiconductor Al-doped ZnO (AZO). Magnetization and Hall effect measurements of multilayers of NiO and AZO are presented for varying thickness of each. The magnetic properties vary as a function of the number of Ni planes in each NiO layer; an odd number of Ni planes yields on each NiO layer an uncompensated moment which is RKKY-coupled to the moments on adjacent NiO layers via the carriers in the AZO. This RKKY coupling oscillates with the AZO layer thickness, and it disappears entirely in samples where the AZO is replaced with undoped ZnO. The anomalous Hall effect data indicate that the carriers in the AZO are spin-polarized according to the direction of the applied field at both low temperature and room temperature. NiO/AZO multilayers are therefore a promising candidate for spintronic applications demanding a room-temperature semiconductor.

  3. Variation of the energy gap of the SbSI crystals at ferroelectric phase transition

    International Nuclear Information System (INIS)

    Audzijonis, A.; Zaltauskas, R.; Zigas, L.; Vinokurova, I.V.; Farberovich, O.V.; Pauliukas, A.; Kvedaravicius, A.

    2006-01-01

    Variation of the forbidden gap of SbSI crystals in the phase transition region is analyzed on the pseudopotential method for antiferroelectric and ferroelectric phase. The band gap at several special points of the Brillouin zone and some characteristic parameters of the band are considered. During the phase transition, the most significant changes are observed with the valence band top at points Q, C, R, H, E and with the conduction band bottom at points H, T and E of the Brillouin zone. At the ferroelectric phase transition, the valence and conduction bands change due to displacement of Sb and S atoms with respect to I and with respect to each other as a result of order-disorder and displacement-type transition. The obtained band gap values agree quite well with the experiment. This is apparently due to application of neutral rather than ionic atomic functions and inclusion of sufficiently many plane waves in the basis set for calculation

  4. ENDOR-investigations in the environment of the ferroelectric phase transition temperature of γ-irradiated TSCC

    International Nuclear Information System (INIS)

    Welter, M.

    1983-01-01

    The structure of the CH 3 NHCH 2 COOH radical in the paraelectric phase and during the transition into the ferroelectric phase has been determined by means of ENDOR measurements. The carboxyl group of the radical is a sensitive probe for the study of crystal field changes. Structural differences of the radical between the paraelectric and the ferroelectric phase were attributed to structural changes within the nearest environment

  5. Large low field room temperature magneto-dielectric response from (Sr_0_._5Ba_0_._5)Nb_2O_6/Co(Cr_0_._4Fe_1_._6)O_4 bulk 3-0 composites

    International Nuclear Information System (INIS)

    Rathore, Satyapal Singh; Vitta, Satish

    2016-01-01

    Highlights: • The essential highlights of this work are;. • Bulk composite with varying amounts of relaxor and ferromagnetic phases has been synthesized by simple steps. • Processing yields an optimal structure with 30% ferromagnetic phase to couple the two ferroic orders. • Magneto dielectric constant shows large changes, 3.2%, at room temperature in moderate magnetic fields. • Large changes in dielectric constant are due to configurational arrangement of the two phases. - Abstract: Bulk magneto-dielectric composites with a 3-0 configuration comprised of ferroelectric-magnetostrictive phases have been synthesized using (Sr_0_._5Ba_0_._5)Nb_2O_6–Co(Cr_0_._4Fe_1_._6)O_4 as the two constituents, respectively. The ferroelectric phase made by a dual stage sintering process has a uniform grain size of 15 μm while the magnetostrictive phase has a grain size of 2–3 μm. Composites synthesized by conventional solid state processing using these two constituents exhibit large magneto-dielectric coupling at room temperature which increases with increasing magnetic field. The composite with 30% magnetostrictive phase distributed uniformly in the ferroelectric phase has the most desirable microstructure and exhibits a large coupling with 3.2% change in the dielectric constant at 1 kHz and 8 kOe magnetic field. This change in dielectric constant was found to be a maximum with respect to variation of the fraction of magnetostrictive phase, indicating that 30% is the optimal value to realize large coupling between the two phases. The decrease in magneto-dielectric constant upon application of an external magnetic field is possibly due to the inherent magnetoresistance of the magnetic component. The resistivity of the magnetic component decreases in an external magnetic field leading to the formation of 3D percolating conducting paths. This causes the coupling to decrease in composites with >30% magnetostrictive phase.

  6. Raman scattering study of the ferroelectric phase transition in BaT i2O5

    Science.gov (United States)

    Tsukada, Shinya; Fujii, Yasuhiro; Yoneda, Yasuhiro; Moriwake, Hiroki; Konishi, Ayako; Akishige, Yukikuni

    2018-02-01

    Uniaxial ferroelectric BaT i2O5 with a Curie temperature TC of 743 K was investigated to clarify its paraelectric-ferroelectric phase-transition behavior. The mechanism is discussed on the basis of the structure from short to long ranges determined by synchrotron x-ray diffraction and the lattice dynamics probed by Raman spectroscopy. BaT i2O5 is regarded as a homogeneous system, and the lattice dynamics can be interpreted by the selection rules and tensor properties of the homogeneous structure. Angle-resolved polarized Raman spectroscopy clearly shows that an A -mode-type overdamped phonon plays the key role in the phase transition. Using a combination of experimental results and first-principles calculations, we explain the phase transition as follows: In one of three Ti O6 octahedral units, Ti vibrates along the b axis opposite an oxygen octahedral unit with large damping in the paraelectric phase, whereas this vibration is frozen in the ferroelectric phase, leading to a change in the space group from nonpolar C 2 /m to polar C 2 .

  7. Characterization Of Graphene-Ferroelectric Superlattice Hybrid Devices

    Science.gov (United States)

    Yusuf, Mohammed; Du, Xu; Dawber, Matthew

    2013-03-01

    Ferroelectric materials possess a spontaneous electrical polarization, which can be controlled by an electric field. A good interface between ferroelectric surface and graphene sheets can introduce a new generation of multifunctional devices, in which the ferroelectric material can be used to control the properties of graphene. In our approach, problems encountered in previous efforts to combine ferroelectric/carbon systems are overcome by the use of artificially layered superlattice materials grown in the form of epitaxial thin films. In these materials the phase transition temperature and dielectric response of the material can be tailored, allowing us to avoid polarization screening by surface absorbates, whilst maintaining an atomically smooth surface and optimal charge doping properties. Using ferroelectric PbTiO3/SrTiO3 superlattices, we have shown ultra-low-voltage operation of graphene field effect devices within +/- 1 V at room temperature. The switching of the graphene field effect transistors is characterized by pronounced resistance hysteresis, suitable for ultra-fast non-volatile electronics. Low temperature characterization confirmed that the coercive field required for the ferroelectric domain switching increases significantly with decreasing temperatures. National Science Foundation (NSF) (grant number 1105202)

  8. Neutron and x-ray scattering studies of ferroelectric phase transitions

    International Nuclear Information System (INIS)

    Dolling, G.

    1982-08-01

    The subject of ferroelectric type phase transitions is introduced by means of examples of two main classes (a) displacive transitions, e.g. KNbO 3 , and (b) order-disorder transitions, e.g. NaNO 2 . The significance of crystal structure and crystal dynamics (i.e. the phonon dispersion relations) for ferroelectric behaviour is emphasized. The chief methods for structure determination are x-ray and neutron diffraction, while the most powerful of all techniques for studying phonon properties is that of coherent inelastic neutron scattering. The most useful type of neutron spectrometer for phase transition studies, the triple axis crystal spectrometer, is discussed in detail. The history of the soft mode theory of displacive phase transitions, and its application to the antiferroelectric and 'almost ferroelectric' transitions in SrTiO 3 , provides an introduction to more recent developments in this area, including over-damped soft modes, central peaks and critical scattering, incommensurate phase transitions (e.g. K 2 SeO 4 ), amplitudons, phasons and finally solitions. The treatment throughout is descriptive and introductory, designed for graduate students

  9. Role of oxygen disorder in the ferroelectric phase transitions for various materials

    International Nuclear Information System (INIS)

    Pasciak, Marek; Goossens, Darren J.; Welberry, Richard T.

    2009-01-01

    Full text: The nature of ferroelectric phase transitions in many materials have been questioned for many years. Whereas some methods provide definitive evidence of mode softening, other methods, such as local structure probes, indicate the existence of disorder in the paraelectric phase [1]. It is now widely accepted, that the ferroelectric phase transition usually has two components - soft-mode displacive and order-disorder. The latter leads inevitably to some form of pretransitional clusters in the paraelectric phase [2]. In relaxor ferroelectrics, in which disorder drives the transformation, such polar clusters can exist over a wide range of temperatures. Diffuse scattering is a powerful tool for studying such disorder and also for studying short-range order correlations in atomic displacements [3]. In this work we concentrate on the role of oxygens in various materials. By different means of molecular simulations we build models in which the oxygens constitute a framework for short range order correlations. This leads to a discussion of the differences between x-ray and neutron diffuse scattering patterns that may arise due to the disorder of oxygens.

  10. Room temperature deposition of magnetite thin films on organic substrate

    International Nuclear Information System (INIS)

    Arisi, E.; Bergenti, I.; Cavallini, M.; Murgia, M.; Riminucci, A.; Ruani, G.; Dediu, V.

    2007-01-01

    We report on the growth of magnetite films directly on thin layers of organic semiconductors by means of an electron beam ablation method. The deposition was performed at room temperature in a reactive plasma atmosphere. Thin films show ferromagnetic (FM) hysteresis loops and coercive fields of hundreds of Oersted. Micro Raman analysis indicates no presence of spurious phases. The morphology of the magnetite film is strongly influenced by the morphology of the underlayer of the organic semiconductor. These results open the way for the application of magnetite thin films in the field of organic spintronics

  11. Control of magnetic relaxation by electric-field-induced ferroelectric phase transition and inhomogeneous domain switching

    Energy Technology Data Exchange (ETDEWEB)

    Nan, Tianxiang; Emori, Satoru; Wang, Xinjun; Hu, Zhongqiang; Xie, Li; Gao, Yuan; Lin, Hwaider; Sun, Nian, E-mail: n.sun@neu.edu [Department of Electrical and Computer Engineering, Northeastern University, Boston, Massachusetts 02115 (United States); Peng, Bin; Liu, Ming, E-mail: mingliu@mail.xjtu.edu.cn [Electronic Materials Research Laboratory, Xi' an Jiaotong University, Xi' an 710049 (China); Jiao, Jie; Luo, Haosu [Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 201800 (China); Budil, David [Department of Chemistry, Northeastern University, Boston, Massachusetts 02115 (United States); Jones, John G.; Howe, Brandon M.; Brown, Gail J. [Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson AFB, Ohio 45433 (United States)

    2016-01-04

    Electric-field modulation of magnetism in strain-mediated multiferroic heterostructures is considered a promising scheme for enabling memory and magnetic microwave devices with ultralow power consumption. However, it is not well understood how electric-field-induced strain influences magnetic relaxation, an important physical process for device applications. Here, we investigate resonant magnetization dynamics in ferromagnet/ferroelectric multiferroic heterostructures, FeGaB/PMN-PT and NiFe/PMN-PT, in two distinct strain states provided by electric-field-induced ferroelectric phase transition. The strain not only modifies magnetic anisotropy but also magnetic relaxation. In FeGaB/PMN-PT, we observe a nearly two-fold change in intrinsic Gilbert damping by electric field, which is attributed to strain-induced tuning of spin-orbit coupling. By contrast, a small but measurable change in extrinsic linewidth broadening is attributed to inhomogeneous ferroelastic domain switching during the phase transition of the PMN-PT substrate.

  12. High-performance ferroelectric memory based on phase-separated films of polymer blends

    KAUST Repository

    Khan, Yasser; Bhansali, Unnat Sampatraj; Almadhoun, Mahmoud N.; Odeh, Ihab N.; Cha, Dong Kyu; Alshareef, Husam N.

    2013-01-01

    High-performance polymer memory is fabricated using blends of ferroelectric poly(vinylidene-fluoride-trifluoroethylene) (P(VDF-TrFE)) and highly insulating poly(p-phenylene oxide) (PPO). The blend films spontaneously phase separate into amorphous PPO nanospheres embedded in a semicrystalline P(VDF-TrFE) matrix. Using low molecular weight PPO with high miscibility in a common solvent, i.e., methyl ethyl ketone, blend films are spin cast with extremely low roughness (Rrms ≈ 4.92 nm) and achieve nanoscale phase seperation (PPO domain size < 200 nm). These blend devices display highly improved ferroelectric and dielectric performance with low dielectric losses (<0.2 up to 1 MHz), enhanced thermal stability (up to ≈353 K), excellent fatigue endurance (80% retention after 106 cycles at 1 KHz) and high dielectric breakdown fields (≈360 MV/m). © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. High-performance ferroelectric memory based on phase-separated films of polymer blends

    KAUST Repository

    Khan, Yasser

    2013-10-29

    High-performance polymer memory is fabricated using blends of ferroelectric poly(vinylidene-fluoride-trifluoroethylene) (P(VDF-TrFE)) and highly insulating poly(p-phenylene oxide) (PPO). The blend films spontaneously phase separate into amorphous PPO nanospheres embedded in a semicrystalline P(VDF-TrFE) matrix. Using low molecular weight PPO with high miscibility in a common solvent, i.e., methyl ethyl ketone, blend films are spin cast with extremely low roughness (Rrms ≈ 4.92 nm) and achieve nanoscale phase seperation (PPO domain size < 200 nm). These blend devices display highly improved ferroelectric and dielectric performance with low dielectric losses (<0.2 up to 1 MHz), enhanced thermal stability (up to ≈353 K), excellent fatigue endurance (80% retention after 106 cycles at 1 KHz) and high dielectric breakdown fields (≈360 MV/m). © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. A general analytical equation for phase diagrams of an N-layer ferroelectric thin film with two surface layers

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Z X; Teng, B H; Rong, Y H; Lu, X H; Yang, X [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China)], E-mail: phytbh@163.com

    2010-03-15

    Within the framework of effective-field theory with correlations, the phase diagrams of an N-layer ferroelectric thin film with two surface layers are studied by the differential operator technique based on the spin-1/2 transverse Ising model. A general analytical equation for the phase diagram of a ferroelectric thin film with arbitrary layer number as well as exchange interactions and transverse fields is derived, and then the effects of exchange interactions and transverse fields on phase diagrams are discussed for an arbitrary layer number N. Meanwhile, the crossover features, from the ferroelectric-dominant phase diagram (FPD) to the paraelectric-dominant phase diagram (PPD), for various parameters of an N-layer ferroelectric thin film with two surface layers are investigated. As a result, an N-independent common intersection point equation is obtained, and the three-dimensional curved surfaces for the crossover values are constructed. In comparison with the usual mean-field approximation, the differential operator technique with correlations reduces to some extent the ferroelectric features of a ferroelectric thin film.

  15. Theoretical study on phase coexistence in ferroelectric solid solutions near the tricritical point

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Xiaoyan, E-mail: luxy@hit.edu.cn, E-mail: dzk@psu.edu; Li, Hui [Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education, School of Civil Engineering, Harbin Institute of Technology, Harbin 150001 (China); Zheng, Limei [Condensed Matter Science and Technology Institute, Harbin Institute of Technology, Harbin 150001 (China); Cao, Wenwu [Condensed Matter Science and Technology Institute, Harbin Institute of Technology, Harbin 150001 (China); Department of Mathematics and Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States)

    2015-04-07

    Phase coexistence in ferroelectric solid solutions near the tricritical point has been theoretically analyzed by using the Landau-Devonshire theory. Results revealed that different phases having similar potential wells could coexist in a narrow composition range near the tricritical point in the classical Pb(Zr{sub 1−x}Ti{sub x})O{sub 3} system. The potential barrier between potential wells increases with the decrease of temperature. Coexisting phases or different domains of the same phase can produce adaptive strains to maintain atomic coherency at the interfaces or domain walls. Such compatibility strains have influence on the energy potential as well as the stability of relative phases, leading to the appearance of energetically unfavorable monoclinic phases. Those competing and coexisting phases also construct an easy phase transition path with small energy barrier in between, so that very small stimuli can produce large response in compositions near the morphotropic phase boundary, especially near the tricritical point.

  16. Theoretical study on phase coexistence in ferroelectric solid solutions near the tricritical point

    International Nuclear Information System (INIS)

    Lu, Xiaoyan; Li, Hui; Zheng, Limei; Cao, Wenwu

    2015-01-01

    Phase coexistence in ferroelectric solid solutions near the tricritical point has been theoretically analyzed by using the Landau-Devonshire theory. Results revealed that different phases having similar potential wells could coexist in a narrow composition range near the tricritical point in the classical Pb(Zr 1−x Ti x )O 3 system. The potential barrier between potential wells increases with the decrease of temperature. Coexisting phases or different domains of the same phase can produce adaptive strains to maintain atomic coherency at the interfaces or domain walls. Such compatibility strains have influence on the energy potential as well as the stability of relative phases, leading to the appearance of energetically unfavorable monoclinic phases. Those competing and coexisting phases also construct an easy phase transition path with small energy barrier in between, so that very small stimuli can produce large response in compositions near the morphotropic phase boundary, especially near the tricritical point

  17. Study of glass-nanocomposite and glass-ceramic containing ferroelectric phase

    Energy Technology Data Exchange (ETDEWEB)

    Abdel-Khalek, E.K., E-mail: Eid_khalaf0@yahoo.com [Department of Physics, Faculty of Science, Al Azhar University, Nasr City 11884, Cairo (Egypt); Mohamed, E.A. [Department of Physics, Faculty of Science (Girl' s Branch), Al Azhar University, Nasr City, Cairo (Egypt); Salem, Shaaban M.; Ebrahim, F.M.; Kashif, I. [Department of Physics, Faculty of Science, Al Azhar University, Nasr City 11884, Cairo (Egypt)

    2012-03-15

    Highlights: Black-Right-Pointing-Pointer Glass nanocomposites was synthesized. Black-Right-Pointing-Pointer Glass nanocomposites exhibit both optical transmission bands at 598 and 660 nm and broad dielectric anomalies. Black-Right-Pointing-Pointer The ferroelectricity in pure single-phase oxide glass has not yet been discovered. - Abstract: Transparent glass nanocomposite in the pseudo binary system (100 - x) Li{sub 2}B{sub 4}O{sub 7}-xBaTiO{sub 3} with x = 0 and 60 (in mol%) were prepared. Amorphous and glassy characteristics of the as-prepared samples were established via X-ray powder diffraction (XRD) and differential scanning calorimetry (DSC) respectively. The precipitated BaTiO{sub 3} nanocrystal phase embedded in the glass sample at x = 60 mol% was identified by transmission electron microscopic (TEM). The optical transmission bands at 598 and 660 nm were assigned to Ti{sup 3+} ions in tetragonal distorted octahedral sites. The precipitated Li{sub 2}B{sub 4}O{sub 7}, BaTi(BO{sub 3}){sub 2} and BaTiO{sub 3} nanocrystallites phases with heat-treatment at 923 K for 6 h (HT923) in glass-ceramic were identified by XRD, TEM and infrared absorption spectroscopy. The as-prepared at x = 60 mol% and the HT923 samples exhibit broad dielectric anomalies in the vicinity of the ferroelectric-to-paraelectric transition temperature. The results demonstrate that the method presented may be an effective way to fabricate ferroelectric host and development of multifunctional ferroelectrics.

  18. Ferroelectric phase transition in hydrogen-bonded 2-aminopyridine phosphate (NC sub 4 H sub 4 NH sub 2)centre dot H sub 3 PO sub 4

    CERN Document Server

    Czapla, Z; Waskowska, A

    2003-01-01

    A new crystal of 2-aminopyridine phosphate (NC sub 4 H sub 4 NH sub 2)centre dot H sub 3 PO sub 4 has been grown and its x-ray structure and physical properties were studied. At room temperature the crystals are monoclinic, space group C2/c. The flat 2-aminopyridine cations are hydrogen bonded to the anionic [PO sub 4 ] groups. The interesting feature of the crystal structure is the three-dimensional network of hydrogen bonds including, among others, two strong, symmetrical O centre dot centre dot centre dot H, H centre dot centre dot centre dot O interactions with disordered proton locations. Symmetrically related PO sub 4 anions linked through these protons form infinite (PO sub 4) subinfinity chains along the crystal a-axis. The anomalies in the temperature dependence of the electric permittivity showed that the crystal undergoes ferroelectric phase transition at T sub c = 103.5 K. The spontaneous polarization takes place along the crystal a-axis, being parallel to the chains of the hydrogen-bonded PO sub ...

  19. Room temperature isotherms for Mo and Ni

    International Nuclear Information System (INIS)

    Masse, J.L.

    1986-11-01

    Isotherms at room temperature for Mo and Ni are proposed. They are of three types: BIRCH, KEANE and BORN-MIE. The adjustable constants appearing in these isotherms have been determined from experimental quantities at zero pressure. An evaluation of the limit of (δB T /δP) T as P #-> # ∞, where B T is the isothermal bulk modulus, has been also used. These three isotherms obtained for Mo and Ni are compared with isotherms derived from shock-wave data according to the PRIETO's model. There is a good agreement between these and these derived from shock-wave data. The three isotherms proposed for Mo and Ni can be considered as valid until pressures of several B To , where B To is the bulk modulus B T at P = o [fr

  20. Magnetic heat pumping near room temperature

    Science.gov (United States)

    Brown, G. V.

    1976-01-01

    It is shown that magnetic heat pumping can be made practical at room temperature by using a ferromagnetic material with a Curie point at or near operating temperature and an appropriate regenerative thermodynamic cycle. Measurements are performed which show that gadolinium is a resonable working material and it is found that the application of a 7-T magnetic field to gadolinium at the Curie point (293 K) causes a heat release of 4 kJ/kg under isothermal conditions or a temperature rise of 14 K under adiabatic conditions. A regeneration technique can be used to lift the load of the lattice and electronic heat capacities off the magnetic system in order to span a reasonable temperature difference and to pump as much entropy per cycle as possible

  1. Above Room Temperature Lead Salt VECSELs

    Science.gov (United States)

    Rahim, M.; Khiar, A.; Felder, F.; Fill, M.; Chappuis, D.; Zogg, H.

    2010-01-01

    Mid-infrared vertical external cavity surface emitting lasers (VECSEL) were developed for the wavelength range 4 to 5 μm. The devices are based on lead salt materials grown by MBE on BaF2 or Si substrate. The VECSELs are optically pumped with a 1.55 μm wavelength laser. They are operating up to above room temperature. An output power 6 mWp was reached at a temperature of +27°C. The VECSELs are temperature tunable and lasing is observed from ˜4.8 μm at -60°C down to ˜4.2 μm at +40°C heat sink temperature.

  2. Fast ferroelectric phase shifters for energy recovery linacs

    Directory of Open Access Journals (Sweden)

    S. Yu Kazakov

    2010-11-01

    Full Text Available Fast phase shifters are described that use a novel barium strontium titanate ceramic that can rapidly change its dielectric constant as an external bias voltage is changed. These phase shifters promise to reduce by ∼10 times the power requirements for the rf source needed to drive an energy recovery linac (ERL. Such phase shifters will be coupled with superconducting radiofrequency cavities so as to tune them to compensate for phase instabilities, whether beam-driven or those caused by microphonics. The most promising design is presented, which was successfully cold tested and demonstrated a switching speed of ∼30  ns for 77 deg, corresponding to <0.5  ns per deg of rf phase. Other crucial issues (losses, phase shift values, etc. are discussed.

  3. Room temperature large self-biased magnetoelectric effect in non-lead based piezoelectric and magnetostrictive (0−3) particulate composite system

    Energy Technology Data Exchange (ETDEWEB)

    Kumari, Mukesh [Magnetics & Advanced Ceramics Laboratory, Indian Institute of Technology, Delhi-110016 India (India); Prakash, Chandra [Solid State Physics Laboratory Timarpur, Delhi-110054 India (India); Chatterjee, Ratnamala, E-mail: rmala@physics.iitd.ac.in [Magnetics & Advanced Ceramics Laboratory, Indian Institute of Technology, Delhi-110016 India (India)

    2017-05-01

    In this work, room temperature magnetoelectric properties of (0−3) particulate composites of non lead based piezoelectric BNTKNNLTS [0.97(Bi{sub 0.5}Na{sub 0.5}TiO{sub 3})–0.03(K{sub 0.47}Na{sub 0.47}Li{sub 0.06}Nb{sub 0.74}Sb{sub 0.06}Ta{sub 0.2}O{sub 3}) and magnetostrictive CZFMO (Co{sub 0.6}Zn{sub 0.4}Fe{sub 1.7}Mn{sub 0.3}O{sub 4}) are presented. Composite samples of (1-x)(BNTKNNLTS)-x(CZFMO){sub ,} with x=0.1 and 0.5, are synthesized by solid state reaction route. X-ray diffraction confirms the single phase formation of parent phases and the presence of two phases in the composites. Similar sintering conditions of the two individual components lead to optimal ferroelectric and ferromagnetic properties in the composites. A large self-biased magnetoelectric (ME) coupling ~74 mV/cm.Oe for the sample with x=0.1 (measured in longitudinally magnetized-transversely polarized configuration) is observed at room temperature. - Highlights: • Modified BNT-CFO based (0−3) particulate composites have been synthesized. • Similar sintering conditions of two components lead to optimal multiferroicity. • A large self-biased ME coupling ~74 mV/cm. Oe is obtained at room temperature.

  4. Surface topography and crystal and domain structures of films of ferroelectric copolymer of vinylidene difluoride and trifluoroethylene

    Energy Technology Data Exchange (ETDEWEB)

    Kochervinskii, V. V., E-mail: kochval@mail.ru [Karpov Institute of Physical Chemistry, Branch (Russian Federation); Kiselev, D. A.; Malinkovich, M. D. [National University of Science and Technology MISiS (Russian Federation); Korlyukov, A. A.; Lokshin, B. V. [Russian Academy of Sciences, Nesmeyanov Institute of Organoelement Compounds (Russian Federation); Volkov, V. V. [Russian Academy of Sciences, Shubnikov Institute of Crystallography, Federal Scientific Research Centre “Crystallography and Photonics” (Russian Federation); Kirakosyan, G. A. [Russian Academy of Sciences, Kurnakov Institute of General and Inorganic Chemistry (Russian Federation); Pavlov, A. S. [Karpov Institute of Physical Chemistry, Branch (Russian Federation)

    2017-03-15

    The crystallization of a copolymer from a solution at room temperature is found to lead to the formation of a metastable structure, characterized by the coexistence of ferroelectric and paraelectric phases. The fraction of the latter decreases after annealing above the Curie point. Atomic force microscopy (AFM) has revealed a difference in the surface topographies between the films contacting with air and the films contacting with a glass substrate. The microstructure of copolymer chains has been investigated by {sup 19}F NMR spectroscopy. The chain fragments with “defect” attached monomeric units are ejected to the surface. The character of the ferroelectric domains formed during crystallization and their size distribution are analyzed.

  5. Synthesis of manganese spinel nanoparticles at room temperature by coprecipitation

    Energy Technology Data Exchange (ETDEWEB)

    Giovannelli, F., E-mail: fabien.giovannelli@univ-tours.fr [GREMAN, UMR 7347 CNRS-CEA, Universite Francois Rabelais, 15 rue de la chocolaterie, 41000 BLOIS (France); Autret-Lambert, C.; Mathieu, C.; Chartier, T.; Delorme, F. [GREMAN, UMR 7347 CNRS-CEA, Universite Francois Rabelais, 15 rue de la chocolaterie, 41000 BLOIS (France); Seron, A [BRGM, 3 Avenue Claude Guillemin, BP 36009, 45060 ORLEANS Cedex 2 (France)

    2012-08-15

    This paper is focused on a new route to synthesize Mn{sub 3}O{sub 4} nanoparticles by alkalisation by sodium hydroxide on a manganeous solution at room temperature. The precipitates obtained at different pH values have been characterized by XRD and TEM. Since the first addition of sodium hydroxide, a white Mn(OH){sub 2} precipitate appears. At pH=7, {gamma}-MnOOH phase is predominant with needle like shaped particles. At pH=10, hausmanite nanoparticles, which exhibits well defined cubic shape in the range 50-120 nm are obtained. This new precipitation route is a fast and easy environmentally friendly process to obtain well crystallized hausmanite nanoparticles. - Graphical abstract: TEM image showing Mn{sub 3}O{sub 4} particles after a precipitation at pH=10. Highlights: Black-Right-Pointing-Pointer A new route to synthesize Mn{sub 3}O{sub 4} nanoparticles has been demonstrated. Black-Right-Pointing-Pointer Synthesis has been performed by precipitation at room temperature. Black-Right-Pointing-Pointer The size of the Mn{sub 3}O{sub 4} nanoparticles is between 50 and 120 nm.

  6. Magnetic refrigeration--towards room-temperature applications

    International Nuclear Information System (INIS)

    Brueck, E.; Tegus, O.; Li, X.W.; Boer, F.R. de; Buschow, K.H.J.

    2003-01-01

    Modern society relies very much on readily available cooling. Magnetic refrigeration based on the magneto-caloric effect (MCE) has become a promising competitive technology for the conventional gas-compression/expansion technique in use today. Recently, there have been two breakthroughs in magnetic-refrigeration research: one is that American scientists demonstrated the world's first room-temperature, permanent-magnet, magnetic refrigerator; the other one is that we discovered a new class of magnetic refrigerant materials for room-temperature applications. The new materials are manganese-iron-phosphorus-arsenic (MnFe(P,As)) compounds. This new material has important advantages over existing magnetic coolants: it exhibits a huge MCE, which is larger than that of Gd metal; and its operating temperature can be tuned from about 150 to about 335 K by adjusting the P/As ratio. Here we report on further improvement of the materials by increasing the Mn content. The large entropy change is attributed to a field-induced first-order phase transition enhancing the effect of the applied magnetic field. Addition of Mn reduces the thermal hysteresis, which is intrinsic to the first-order transition. This implies that already moderate applied magnetic fields of below 2 T may suffice

  7. Unveiling the Role of CNTs on the Phase Formation of 1D Ferroelectrics

    KAUST Repository

    Mahajan, Amit

    2015-05-21

    Carbon nanotubes (CNTs) have the potential to act as templates or bottom electrodes for three dimension (3D) capacitor arrays, which utilise one dimension (1D) ferroelectric nanostructures to increase memory size and density. However, growing a ferroelectric on the surface of CNTs is non-trivial. Here, we demonstrate that multi-walled (MW) CNTs decrease the time and temperature for formation of lead zirconium titanate Pb(Zr1-xTix)O3 (PZT) by ~100 ºC commensurate with a decrease in activation energy from 68±15 kJ/mol to 27±2 kJ/mol. As a consequence, monophasic PZT was obtained at 575 ºC for MWCNTs/PZT whereas for pure PZT traces of pyrochlore were still present at 650 ºC, where PZT phase formed due to homogeneous nucleation. The piezoelectric nature of MWCNT/PZT synthesised at 500 ºC for 1 h was proved. Although further work is required to prove the concept of 3D capacitor arrays, our result suggests that it is feasible to utilise MWCNTs as templates/electrodes for the formation of 1D PZT nano ferroelectrics.

  8. Dual strain mechanisms in a lead-free morphotropic phase boundary ferroelectric

    DEFF Research Database (Denmark)

    Walker, Julian; Simons, Hugh; Alikin, Denis O

    2016-01-01

    Electromechanical properties such as d33 and strain are significantly enhanced at morphotropic phase boundaries (MPBs) between two or more different crystal structures. Many actuators, sensors and MEMS devices are therefore systems with MPBs, usually between polar phases in lead (Pb)-based ferroe......Electromechanical properties such as d33 and strain are significantly enhanced at morphotropic phase boundaries (MPBs) between two or more different crystal structures. Many actuators, sensors and MEMS devices are therefore systems with MPBs, usually between polar phases in lead (Pb......)-based ferroelectric ceramics. In the search for Pb-free alternatives, systems with MPBs between polar and non-polar phases have recently been theorized as having great promise. While such an MPB was identified in rare-earth (RE) modified bismuth ferrite (BFO) thin films, synthesis challenges have prevented its...... realization in ceramics. Overcoming these, we demonstrate a comparable electromechanical response to Pb-based materials at the polar-to-non-polar MPB in Sm modified BFO. This arises from 'dual' strain mechanisms: ferroelectric/ferroelastic switching and a previously unreported electric-field induced...

  9. Electrorecovery of actinides at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Stoll, Michael E [Los Alamos National Laboratory; Oldham, Warren J [Los Alamos National Laboratory; Costa, David A [Los Alamos National Laboratory

    2008-01-01

    There are a large number of purification and processing operations involving actinide species that rely on high-temperature molten salts as the solvent medium. One such application is the electrorefining of impure actinide metals to provide high purity material for subsequent applications. There are some drawbacks to the electrodeposition of actinides in molten salts including relatively low yields, lack of accurate potential control, maintaining efficiency in a highly corrosive environment, and failed runs. With these issues in mind we have been investigating the electrodeposition of actinide metals, mainly uranium, from room temperature ionic liquids (RTILs) and relatively high-boiling organic solvents. The RTILs we have focused on are comprised of 1,3-dialkylimidazolium or quaternary ammonium cations and mainly the {sup -}N(SO{sub 2}CF{sub 3}){sub 2} anion [bis(trif1uoromethylsulfonyl)imide {equivalent_to} {sup -}NTf{sub 2}]. These materials represent a class of solvents that possess great potential for use in applications employing electrochemical procedures. In order to ascertain the feasibility of using RTILs for bulk electrodeposition of actinide metals our research team has been exploring the electron transfer behavior of simple coordination complexes of uranium dissolved in the RTIL solutions. More recently we have begun some fundamental electrochemical studies on the behavior of uranium and plutonium complexes in the organic solvents N-methylpyrrolidone (NMP) and dimethylsulfoxide (DMSO). Our most recent results concerning electrodeposition will be presented in this account. The electrochemical behavior of U(IV) and U(III) species in RTILs and the relatively low vapor pressure solvents NMP and DMSO is described. These studies have been ongoing in our laboratory to uncover conditions that will lead to the successful bulk electrodeposition of actinide metals at a working electrode surface at room temperature or slightly elevated temperatures. The RTILs we

  10. Why is the electrocaloric effect so small in ferroelectrics?

    Directory of Open Access Journals (Sweden)

    G. G. Guzmán-Verri

    2016-06-01

    Full Text Available Ferroelectrics are attractive candidate materials for environmentally friendly solid state refrigeration free of greenhouse gases. Their thermal response upon variations of external electric fields is largest in the vicinity of their phase transitions, which may occur near room temperature. The magnitude of the effect, however, is too small for useful cooling applications even when they are driven close to dielectric breakdown. Insight from microscopic theory is therefore needed to characterize materials and provide guiding principles to search for new ones with enhanced electrocaloric performance. Here, we derive from well-known microscopic models of ferroelectricity meaningful figures of merit for a wide class of ferroelectric materials. Such figures of merit provide insight into the relation between the strength of the effect and the characteristic interactions of ferroelectrics such as dipolar forces. We find that the long range nature of these interactions results in a small effect. A strategy is proposed to make it larger by shortening the correlation lengths of fluctuations of polarization. In addition, we bring into question other widely used but empirical figures of merit and facilitate understanding of the recently observed secondary broad peak in the electrocalorics of relaxor ferroelectrics.

  11. Titanium nitride room-temperature ferromagnetic nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Morozov, Iu.G., E-mail: morozov@ism.ac.ru [Institute of Structural Macrokinetics and Materials Science, Russian Academy of Sciences, 8 Academician Osipyan Street, Chernogolovka, Moscow Region, 142432 (Russian Federation); Belousova, O.V. [Institute of Structural Macrokinetics and Materials Science, Russian Academy of Sciences, 8 Academician Osipyan Street, Chernogolovka, Moscow Region, 142432 (Russian Federation); Belyakov, O.A. [Ogarev Mordovia State University, Saransk, 68 Bol' shevistskaya Street, 430005 (Russian Federation); Parkin, I.P., E-mail: i.p.parkin@ucl.ac.uk [Department of Chemistry, Materials Chemistry Research Centre, University College London, 20 Gordon Street, London, WC1H 0AJ (United Kingdom); Sathasivam, S. [Department of Chemistry, Materials Chemistry Research Centre, University College London, 20 Gordon Street, London, WC1H 0AJ (United Kingdom); Kuznetcov, M.V., E-mail: maxim1968@mail.ru [All-Russian Research Institute on Problems of Civil Defense and Emergencies of Emergency Control Ministry of Russia (EMERCOM), 7 Davidkovskaya Street, Moscow, 121352 (Russian Federation)

    2016-08-05

    Cubic and near-spherical TiN nanoparticles ranging in average size from 20 to 125 nm were prepared by levitation-jet aerosol synthesis through condensation of titanium vapor in an inert gas flow with gaseous nitrogen injection. The nanoparticles were characterized by using scanning electron microscopy (SEM), X-ray diffraction (XRD), BET measurements, UV–Vis, FT-IR, Raman spectroscopy, XPS, and vibrating-sample magnetometry. Room-temperature ferromagnetism with maximum magnetization up to 2.5 emu/g was recorded for the nanoparticles. The results indicate that the observed ferromagnetic ordering was related to the defect Ti–N structures on the surface of nanoparticles. This suggestion is in good correlation with the measured spectroscopical data. - Highlights: • Levitation-jet aerosol synthesis of TiN nanoparticles (NPs). • SEM, XRD, BET, UV–vis, FT-IR, Raman, XPS and magnetic characterization of the NPs. • Correlation between optical and XPS measurements data and maximum magnetization of the NPs.

  12. Ferroelectric, antiferroelectric and TGB phases in lactic acid derivatives

    Czech Academy of Sciences Publication Activity Database

    Novotná, Vladimíra; Kašpar, Miroslav; Hamplová, Věra; Podoliak, Natalia; Glogarová, Milada; Pociecha, D.

    2012-01-01

    Roč. 39, č. 4 (2012), s. 477-486 ISSN 0267-8292 R&D Projects: GA ČR(CZ) GAP204/11/0723 Institutional research plan: CEZ:AV0Z10100520 Keywords : liquid crystals * lactate derivatives * TGB phases Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.959, year: 2012 http://www.tandfonline.com/doi/abs/10.1080/02678292.2011.653411

  13. Tunable, Room Temperature THZ Emitters Based on Nonlinear Photonics

    Science.gov (United States)

    Sinha, Raju

    The Terahertz (1012 Hz) region of the electromagnetic spectrum covers the frequency range from roughly 300 GHz to 10 THz, which is in between the microwave and infrared regimes. The increasing interest in the development of ultra-compact, tunable room temperature Terahertz (THz) emitters with wide-range tunability has stimulated in-depth studies of different mechanisms of THz generation in the past decade due to its various potential applications such as biomedical diagnosis, security screening, chemical identification, life sciences and very high speed wireless communication. Despite the tremendous research and development efforts, all the available state-of-the-art THz emitters suffer from either being large, complex and costly, or operating at low temperatures, lacking tunability, having a very short spectral range and a low output power. Hence, the major objective of this research was to develop simple, inexpensive, compact, room temperature THz sources with wide-range tunability. We investigated THz radiation in a hybrid optical and THz micro-ring resonators system. For the first time, we were able to satisfy the DFG phase matching condition for the above-mentioned THz range in one single device geometry by employing a modal phase matching technique and using two separately designed resonators capable of oscillating at input optical waves and generated THz waves. In chapter 6, we proposed a novel plasmonic antenna geometry – the dimer rod-tapered antenna (DRTA), where we created a hot-spot in the nanogap between the dimer arms with a very large intensity enhancement of 4.1x105 at optical resonant wavelength. Then, we investigated DFG operation in the antenna geometry by incorporating a nonlinear nanodot in the hot-spot of the antenna and achieved continuously tunable enhanced THz radiation across 0.5-10 THz range. In chapter 8, we designed a multi-metallic resonators providing an ultrasharp toroidal response at THz frequency, then fabricated and

  14. Room temperature luminescence and ferromagnetism of AlN:Fe

    Energy Technology Data Exchange (ETDEWEB)

    Li, H., E-mail: lihui@mail.iee.ac.cn, E-mail: wjwang@aphy.iphy.ac.cn [The Key Laboratory of Solar Thermal Energy and Photovoltaic System, Institute of Electrical engineering, Chinese Academy of Sciences, Beijing 100190 (China); Cai, G. M. [School of Materials Science and Engineering, Central South University, Changsha, Hunan 410083 (China); Wang, W. J., E-mail: lihui@mail.iee.ac.cn, E-mail: wjwang@aphy.iphy.ac.cn [Research and Development Center for Functional Crystals, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)

    2016-06-15

    AlN:Fe polycrystalline powders were synthesized by a modified solid state reaction (MSSR) method. Powder X-ray diffraction and transmission electron microscopy results reveal the single phase nature of the doped samples. In the doped AlN samples, Fe is in Fe{sup 2+} state. Room temperature ferromagnetic behavior is observed in AlN:Fe samples. Two photoluminescence peaks located at about 592 nm (2.09 eV) and 598 nm (2.07 eV) are observed in AlN:Fe samples. Our results suggest that AlN:Fe is a potential material for applications in spintronics and high power laser devices.

  15. Room temperature ferromagnetism in a phthalocyanine based carbon material

    International Nuclear Information System (INIS)

    Honda, Z.; Sato, K.; Sakai, M.; Fukuda, T.; Kamata, N.; Hagiwara, M.; Kida, T.

    2014-01-01

    We report on a simple method to fabricate a magnetic carbon material that contains nitrogen-coordinated transition metals and has a large magnetic moment. Highly chlorinated iron phthalocyanine was used as building blocks and potassium as a coupling reagent to uniformly disperse nitrogen-coordinated iron atoms on the phthalocyanine based carbon material. The iron phthalocyanine based carbon material exhibits ferromagnetic properties at room temperature and the ferromagnetic phase transition occurs at T c  = 490 ± 10 K. Transmission electron microscopy observation, X-ray diffraction analysis, and the temperature dependence of magnetization suggest that the phthalocyanine molecules form three-dimensional random networks in the iron phthalocyanine based carbon material

  16. Room temperature luminescence and ferromagnetism of AlN:Fe

    Directory of Open Access Journals (Sweden)

    H. Li

    2016-06-01

    Full Text Available AlN:Fe polycrystalline powders were synthesized by a modified solid state reaction (MSSR method. Powder X-ray diffraction and transmission electron microscopy results reveal the single phase nature of the doped samples. In the doped AlN samples, Fe is in Fe2+ state. Room temperature ferromagnetic behavior is observed in AlN:Fe samples. Two photoluminescence peaks located at about 592 nm (2.09 eV and 598 nm (2.07 eV are observed in AlN:Fe samples. Our results suggest that AlN:Fe is a potential material for applications in spintronics and high power laser devices.

  17. Room temperature ferromagnetism in a phthalocyanine based carbon material

    Energy Technology Data Exchange (ETDEWEB)

    Honda, Z., E-mail: honda@fms.saitama-u.ac.jp; Sato, K.; Sakai, M.; Fukuda, T.; Kamata, N. [Graduate School of Science and Engineering, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama 338-8570 (Japan); Hagiwara, M.; Kida, T. [KYOKUGEN (Center for Quantum Science and Technology under Extreme Conditions), Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531 (Japan)

    2014-02-07

    We report on a simple method to fabricate a magnetic carbon material that contains nitrogen-coordinated transition metals and has a large magnetic moment. Highly chlorinated iron phthalocyanine was used as building blocks and potassium as a coupling reagent to uniformly disperse nitrogen-coordinated iron atoms on the phthalocyanine based carbon material. The iron phthalocyanine based carbon material exhibits ferromagnetic properties at room temperature and the ferromagnetic phase transition occurs at T{sub c} = 490 ± 10 K. Transmission electron microscopy observation, X-ray diffraction analysis, and the temperature dependence of magnetization suggest that the phthalocyanine molecules form three-dimensional random networks in the iron phthalocyanine based carbon material.

  18. Water in Room Temperature Ionic Liquids

    Science.gov (United States)

    Fayer, Michael

    2014-03-01

    Room temperature ionic liquids (or RTILs, salts with a melting point below 25 °C) have become a subject of intense study over the last several decades. Currently, RTIL application research includes synthesis, batteries, solar cells, crystallization, drug delivery, and optics. RTILs are often composed of an inorganic anion paired with an asymmetric organic cation which contains one or more pendant alkyl chains. The asymmetry of the cation frustrates crystallization, causing the salt's melting point to drop significantly. In general, RTILs are very hygroscopic, and therefore, it is of interest to examine the influence of water on RTIL structure and dynamics. In addition, in contrast to normal aqueous salt solutions, which crystallize at low water concentration, in an RTIL it is possible to examine isolated water molecules interacting with ions but not with other water molecules. Here, optical heterodyne-detected optical Kerr effect (OHD-OKE) measurements of orientational relaxation on a series of 1-alkyl-3-methylimidazolium tetrafluoroborate RTILs as a function of chain length and water concentration are presented. The addition of water to the longer alkyl chain RTILs causes the emergence of a long time bi-exponential orientational anisotropy decay. Such decays have not been seen previously in OHD-OKE experiments on any type of liquid and are analyzed here using a wobbling-in-a-cone model. The orientational relaxation is not hydrodynamic, with the slowest relaxation component becoming slower as the viscosity decreases for the longest chain, highest water content samples. The dynamics of isolated D2O molecules in 1-butyl-3-methylimidazolium hexafluorophosphate (BmImPF6) were examined using two dimensional infrared (2D IR) vibrational echo spectroscopy. Spectral diffusion and incoherent and coherent transfer of excitation between the symmetric and antisymmetric modes are examined. The coherent transfer experiments are used to address the nature of inhomogeneous

  19. Enhanced room temperature ferromagnetism in antiferromagnetic NiO nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Ravikumar, Patta; Kisan, Bhagaban; Perumal, A., E-mail: perumal@iitg.ernet.in [Department of Physics, Indian institute of Technology Guwahati, Guwahati 781 039 (India)

    2015-08-15

    We report systematic investigations of structural, vibrational, resonance and magnetic properties of nanoscale NiO powders prepared by ball milling process under different milling speeds for 30 hours of milling. Structural properties revealed that both pure NiO and as-milled NiO powders exhibit face centered cubic structure, but average crystallite size decreases to around 11 nm along with significant increase in strain with increasing milling speed. Vibrational properties show the enhancement in the intensity of one-phonon longitudinal optical (LO) band and disappearance of two-magnon band due to size reduction. In addition, two-phonon LO band exhibits red shift due to size-induced phonon confinement effect and surface relaxation. Pure NiO powder exhibit antiferromagnetic nature, which transforms into induced ferromagnetic after size reduction. The average magnetization at room temperature increases with decreasing the crystallite size and a maximum moment of 0.016 μ{sub B}/f.u. at 12 kOe applied field and coercivity of 170 Oe were obtained for 30 hours milled NiO powders at 600 rotation per minute milling speed. The change in the magnetic properties is also supported by the vibrational properties. Thermomagnetization measurements at high temperature reveal a well-defined magnetic phase transition at high temperature (T{sub C}) around 780 K due to induced ferromagnetic phase. Electron paramagnetic resonance (EPR) studies reveal a good agreement between the EPR results and magnetic properties. The observed results are described on the basis of crystallite size variation, defect density, large strain, oxidation/reduction of Ni and interaction between uncompensated surfaces and particle core with lattice expansion. The obtained results suggest that nanoscale NiO powders with high T{sub C} and moderate magnetic moment at room temperature with cubic structure would be useful to expedite for spintronic devices.

  20. Enhanced room temperature ferromagnetism in antiferromagnetic NiO nanoparticles

    Directory of Open Access Journals (Sweden)

    Patta Ravikumar

    2015-08-01

    Full Text Available We report systematic investigations of structural, vibrational, resonance and magnetic properties of nanoscale NiO powders prepared by ball milling process under different milling speeds for 30 hours of milling. Structural properties revealed that both pure NiO and as-milled NiO powders exhibit face centered cubic structure, but average crystallite size decreases to around 11 nm along with significant increase in strain with increasing milling speed. Vibrational properties show the enhancement in the intensity of one-phonon longitudinal optical (LO band and disappearance of two-magnon band due to size reduction. In addition, two-phonon LO band exhibits red shift due to size-induced phonon confinement effect and surface relaxation. Pure NiO powder exhibit antiferromagnetic nature, which transforms into induced ferromagnetic after size reduction. The average magnetization at room temperature increases with decreasing the crystallite size and a maximum moment of 0.016 μB/f.u. at 12 kOe applied field and coercivity of 170 Oe were obtained for 30 hours milled NiO powders at 600 rotation per minute milling speed. The change in the magnetic properties is also supported by the vibrational properties. Thermomagnetization measurements at high temperature reveal a well-defined magnetic phase transition at high temperature (TC around 780 K due to induced ferromagnetic phase. Electron paramagnetic resonance (EPR studies reveal a good agreement between the EPR results and magnetic properties. The observed results are described on the basis of crystallite size variation, defect density, large strain, oxidation/reduction of Ni and interaction between uncompensated surfaces and particle core with lattice expansion. The obtained results suggest that nanoscale NiO powders with high TC and moderate magnetic moment at room temperature with cubic structure would be useful to expedite for spintronic devices.

  1. Glass Transitions and Low-Frequency Dynamics of Room-Temperature Ionic Liquids

    International Nuclear Information System (INIS)

    Yamamuro, O.; Inamura, Y.; Hayashi, S.; Hamaguchi, H.

    2006-01-01

    We have measured the heat capacity and neutrion quasi- and inelastic scattering spectra of some salts of 1-butyl-3-methylimidazolium ion bmim+, which is a typical cation of room-temperature ionic liquids, and its derivatives. The heat capacity measurements revealed that the room-temperature ionic liquids have glass transitions as molecular liquids. The temperature dependence of configurational entropy demonstrated that the room-temperature ionic liquids are 'fragile liquids'. Both heat capacity and inelastic neutron scattering data revealed that the glassy phases exhibit large low-energy excitations usually called 'boson peak'. The quasielastic neutron scattering data showed that so-called 'fast process' appears around Tg as in molecular and polymer glasses. The temperature dependence of the self-diffusion coefficient derived from the neutron scattering data indicated that the orientation of bmim+ ions and/or butyl-groups of bmim+ ions is highly disordered and very flexible in an ionic liquid phase

  2. Neutron diffraction study of crystal structures of deuterated glycinium phosphite in paraelectric and ferroelectric phases

    International Nuclear Information System (INIS)

    Machida, Mitsuo; Uchida, Hiroyuki; Ishibashi, Toku; Taniguchi, Hiroki; Komukae, Masaru; Osaka, Toshio; Koyano, Nobumitsu

    2004-01-01

    Crystal structure of deuterated glycinium phosphite was studied in the paraelectric (P) phase at 348 K and in the ferroelectric (F) phase at 223 K by means of the single crystal neutron diffraction. Deuteration rate is estimated to be 0.939 by the least-squares refinement. In the P phase, quasi-one-dimensional hydrogen bond chains are built by mutually linking the DPO 3 2- anions through two different types of hydrogen bonds with the bond angles of 179.2 and 171.6deg. Two independent deuterons within the hydrogen bonds forming the chains are disordered over two sites separated by 0.545 and 0.539A. In the F phase, they order at a position nearly equal to one of two sites related by the disorder in the P phase. With the ordering of the deuterons, the P-O bonds with covalently bonded deuteron elongate, and those without covalently bonded deuteron reduce their lengths to some extend from the values determined in the P phase. Two oxygens involved in the hydrogen bond with the bond angle 179.2deg exhibits especially large displacements in the F phase. This suggests strongly an importance of this hydrogen bond in the polarization appearance and in the ferroelectric transition. Comparison with results of non-deuterated salt indicates that only the hydrogen bonds forming the chains show significant isotope shift. In particular, the hydrogen bond with the bond angle 179.2deg exhibits the most pronounced shift on the angle parameter defined by the angle between the line connecting two sites of disordered proton or deuteron and the line connecting two oxygens involved in the hydrogen bond. (author)

  3. Pressure-induced ferroelectric to antiferroelectric phase transformation in porous PZT95/5 ceramics

    International Nuclear Information System (INIS)

    Zeng, T.; Dong, X.L.; Chen, X.F.; Yao, C.H.; He, H.L.

    2007-01-01

    The hydrostatic pressure-induced ferroelectric to antiferroelectric (FE-AFE) phase transformation of PZT95/5 ceramics was investigated as a function of porosity, pore shape and pore size. FE-AFE phase transformations were more diffuse and occurred at lower hydrostatic pressures with increasing porosity. The porous PZT95/5 ceramics with spherical pores exhibited higher transformation pressures than those with irregular pores. Moreover, FE-AFE phase transformations of porous PZT95/5 ceramics with polydisperse irregular pores were more diffuse than those of porous PZT95/5 ceramics with monodisperse irregular pores. The relation between pore structure and hydrostatic pressure-induced FE-AFE transformation was established according to stress concentration theory. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  4. Modification of phase transitions in swift heavy ion irradiated and MMA-grafted ferroelectric fluoro-polymers

    International Nuclear Information System (INIS)

    Petersohn, E.; Betz, N.; Le Moel, A.

    1994-01-01

    Ferroelectric polyvinylidene fluoride (β) and copolymers of vinylidene fluoride trifluoroethylene (P(VDF/TrFE)) films were irradiated with swift heavy ions and post irradiation grafted with methyl methacrylate (MMA). We have studied the influence of irradiation parameters such as the ion fluence, the type of ion and the electronic stopping power, on the melting and crystallization temperatures and the ferroelectric-paraelectric phase transitions, by differential scanning calorimetry (DSC) and dielectric measurements. The relation between the shift in the transition temperatures and the ion fluence is described by a single term equation. Ion track grafting with MMA affects the ferroelectric-paraelectric phase transitions in P(VDF/TrFE) and leads to a strong amorphization of the polymer films. The grafting in β PVDF occurs mainly on the surface of the samples and no change in the transition temperatures is observed. (authors). 12 refs., 6 figs., 2 tabs

  5. A phase field approach for the fully coupled thermo-electro-mechanical dynamics of nanoscale ferroelectric actuators

    Science.gov (United States)

    Wang, Dan; Du, Haoyuan; Wang, Linxiang; Melnik, Roderick

    2018-05-01

    The fully coupled thermo-electro-mechanical properties of nanoscale ferroelectric actuators are investigated by a phase field model. Firstly, the thermal effect is incorporated into the commonly-used phase field model for ferroelectric materials in a thermodynamic consistent way and the governing equation for the temperature field is derived. Afterwards, the modified model is numerically implemented to study a selected prototype of the ferroelectric actuators, where strain associated with electric field-induced non-180° domain switching is employed. The temperature variation and energy flow in the actuation process are presented, which enhances our understanding of the working mechanism of the actuators. Furthermore, the influences of the input voltage frequency and the thermal boundary condition on the temperature variation are demonstrated and carefully discussed in the context of thermal management for real applications.

  6. Room temperature single-crystal diffuse scattering and ab initio lattice dynamics in CaTiSiO5.

    Science.gov (United States)

    Gutmann, M J; Refson, K; Zimmermann, M V; Swainson, I P; Dabkowski, A; Dabkowska, H

    2013-08-07

    Single-crystal diffuse scattering data have been collected at room temperature on synthetic titanite using both neutrons and high-energy x-rays. A simple ball-and-springs model reproduces the observed diffuse scattering well, confirming its origin to be primarily due to thermal motion of the atoms. Ab initio phonons are calculated using density-functional perturbation theory and are shown to reproduce the experimental diffuse scattering. The observed diffuse x-ray and neutron scattering patterns are consistent with a summation of mode frequencies and displacement eigenvectors associated with the entire phonon spectrum, rather than with a simple, short-range static displacement. A band gap is observed between 600 and 700 cm(-1) with only two modes crossing this region, both associated with antiferroelectric Ti-O motion along a. One of these modes (of Bu symmetry), displays a large LO-TO mode-splitting (562-701.4 cm(-1)) and has a dominant component coming from Ti-O bond-stretching and, thus, the mode-splitting is related to the polarizability of the Ti-O bonds along the chain direction. Similar mode-splitting is observed in piezo- and ferroelectric materials. The calculated phonon dispersion model may be of use to others in future to understand the phase transition at higher temperatures, as well as in the interpretation of measured phonon dispersion curves.

  7. Phase transformations im smart materials

    International Nuclear Information System (INIS)

    Newnham, R.E.

    1998-01-01

    One of the qualities that distinguishes living systems from inanimate matter is the ability to adapt to changes in the environment. Smart materials have the ability to perform both sensing and actuating functions and are, therefore, capable of imitating this rudimentary aspect of life. Four of the most widely used smart materials are piezoelectric Pb(Zr, Ti)O 3 , electrostrictive Pb(Mg, Nb)O 3 , magnetostrictive (Tb, Dy)Fe 2 and the shape-memory alloy NiTi. All four are ferroic with active domain walls and two phase transformations, which help to tune the properties of these actuator materials. Pb(Zr, Ti)O 3 is a ferroelectric ceramic which is cubic at high temperature and becomes ferroelectric on cooling through the Curie temperature. At room temperature, it is poised on a rhombohedral-tetragonal phase boundary which enhances the piezoelectric coefficients. Terfenol, (Tb, Dy)Fe 2 , is also cubic at high temperature and then becomes magnetic on cooling through its Curie temperature. At room temperature, it too is poised on a rhombohedral-tetragonal transition which enhances its magnetostriction coefficients. Pb(Mg, Nb)O 3 and nitinol (NiTi) are also cubic at high temperatures and on annealing transform to a partially ordered state. On further cooling, Pb(Mg, Nb)O 3 passes through a diffuse phase transformation at room temperature where it exhibits very large dielectric and electrostrictive coefficients. Just below room temperature, it transforms to a ferroelectric rhombohedral phase. The partially ordered shape-memory alloy NiTi undergoes an austenitic (cubic) to martensitic (mono-clinic) phase change just above room temperature. It is easily deformed in the martensitic state but recovers its original shape when reheated to austenite

  8. Room temperature magneto-electric coupling in La-Zn doped Ba{sub 1-x}La{sub x}Fe{sub 12-x}Zn{sub x}O{sub 19} (x = 0.0-0.4) hexaferrite

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Pawan; Gaur, Anurag [National Institute of Technology, Department of Physics, Kurukshetra (India)

    2017-12-15

    Barium hexaferrite powder samples with substitution of La{sup +3} at Ba{sup +2} and Zn{sup +2} at Fe{sup +3} site, according to the series formula Ba{sub 1-x}La{sub x}Fe{sub 12-x}Zn{sub x}O{sub 19} (x = 0.0, 0.1, 0.2, 0.3, 0.4) have been prepared by the co-precipitation method. These samples were characterized by X-ray diffractometer (XRD), scanning electron microscopy, Polarization versus electric field loop tracer and vibrating sample magnetometer techniques. XRD patterns and Rietveld refinement indicate the single-phase formation of the magneto-plumbite barium hexaferrite for all the samples. Significant changes in dielectric properties are obtained by the different doping concentration of La and Zn. Ferroelectric loop for all the samples shows the lossy ferroelectric behaviour. Large spontaneous polarization is observed for x = 0.2 sample at room temperature. With increasing La and Zn doping content, the value of saturation magnetization and retentivity increases, and reaches a maximum value of 40.0 emu/gm and 24.0 emu/gm, respectively, for x = 0.2 sample and then decreases. To confirm the magneto-electric coupling, the second-order magneto-electric coupling coefficient β is measured through the dynamic method with the maximum value of ∝ 1.69 x 10{sup -6} mV/cm.Oe{sup 2} for x = 0.2 sample at room temperature. The observations of room temperature magneto-electric coupling in these samples are useful for evolution of new multifunctional devices. (orig.)

  9. Exploiting fast detectors to enter a new dimension in room-temperature crystallography

    International Nuclear Information System (INIS)

    Owen, Robin L.; Paterson, Neil; Axford, Danny; Aishima, Jun; Schulze-Briese, Clemens; Ren, Jingshan; Fry, Elizabeth E.; Stuart, David I.; Evans, Gwyndaf

    2014-01-01

    A departure from a linear or an exponential decay in the diffracting power of macromolecular crystals is observed and accounted for through consideration of a multi-state sequential model. A departure from a linear or an exponential intensity decay in the diffracting power of protein crystals as a function of absorbed dose is reported. The observation of a lag phase raises the possibility of collecting significantly more data from crystals held at room temperature before an intolerable intensity decay is reached. A simple model accounting for the form of the intensity decay is reintroduced and is applied for the first time to high frame-rate room-temperature data collection

  10. All-polymer bistable resistive memory device based on nanoscale phase-separated PCBM-ferroelectric blends

    KAUST Repository

    Khan, Yasser; Bhansali, Unnat Sampatraj; Cha, Dong Kyu; Alshareef, Husam N.

    2012-01-01

    All polymer nonvolatile bistable memory devices are fabricated from blends of ferroelectric poly(vinylidenefluoride-trifluoroethylene (P(VDF-TrFE)) and n-type semiconducting [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). The nanoscale phase

  11. Enhanced field emission of ZnO nanoneedle arrays via solution etching at room temperature

    DEFF Research Database (Denmark)

    Ma, Huanming; Qin, Zhiwei; Wang, Zaide

    2017-01-01

    ZnO nanoneedle arrays (ZnO nns) were synthesized by a facile two-step solution-phase method based on the etching of pre-synthesized ZnO nanowire arrays (ZnO nws) with flat ends at room temperature. Field emission measurement results showed that the turn-on electronic fields of ZnO nns and nws wer...

  12. Two-dimensional ferroelectrics

    Energy Technology Data Exchange (ETDEWEB)

    Blinov, L M; Fridkin, Vladimir M; Palto, Sergei P [A.V. Shubnikov Institute of Crystallography, Russian Academy of Sciences, Moscow, Russian Federaion (Russian Federation); Bune, A V; Dowben, P A; Ducharme, Stephen [Department of Physics and Astronomy, Behlen Laboratory of Physics, Center for Materials Research and Analysis, University of Nebraska-Linkoln, Linkoln, NE (United States)

    2000-03-31

    The investigation of the finite-size effect in ferroelectric crystals and films has been limited by the experimental conditions. The smallest demonstrated ferroelectric crystals had a diameter of {approx}200 A and the thinnest ferroelectric films were {approx}200 A thick, macroscopic sizes on an atomic scale. Langmuir-Blodgett deposition of films one monolayer at a time has produced high quality ferroelectric films as thin as 10 A, made from polyvinylidene fluoride and its copolymers. These ultrathin films permitted the ultimate investigation of finite-size effects on the atomic thickness scale. Langmuir-Blodgett films also revealed the fundamental two-dimensional character of ferroelectricity in these materials by demonstrating that there is no so-called critical thickness; films as thin as two monolayers (1 nm) are ferroelectric, with a transition temperature near that of the bulk material. The films exhibit all the main properties of ferroelectricity with a first-order ferroelectric-paraelectric phase transition: polarization hysteresis (switching); the jump in spontaneous polarization at the phase transition temperature; thermal hysteresis in the polarization; the increase in the transition temperature with applied field; double hysteresis above the phase transition temperature; and the existence of the ferroelectric critical point. The films also exhibit a new phase transition associated with the two-dimensional layers. (reviews of topical problems)

  13. Lead palladium titanate: A room-temperature multiferroic

    Science.gov (United States)

    Gradauskaite, Elzbieta; Gardner, Jonathan; Smith, Rebecca M.; Morrison, Finlay D.; Lee, Stephen L.; Katiyar, Ram S.; Scott, James F.

    2017-09-01

    There have been a large number of papers on bismuth ferrite (BiFe O3 ) over the past few years, trying to exploit its room-temperature magnetoelectric multiferroic properties. Although these are attractive, BiFe O3 is not the ideal multiferroic due to weak magnetization and the difficulty in limiting leakage currents. Thus there is an ongoing search for alternatives, including such materials as gallium ferrite (GaFe O3 ). In the present work we report a comprehensive study of the perovskite PbT i1 -xP dxO3 with 0 phases present in the samples, with special attention paid to minor phases identified as PdO, PbPd O2 , and P d3Pb . The work is remarkable in two ways: Pd is difficult to substitute into A B O3 perovskite oxides (where it might be useful for catalysis), and Pd is magnetic under only unusual conditions (under strain or internal electric fields).

  14. Room Temperature Ultralow Threshold GaN Nanowire Polariton Laser

    KAUST Repository

    Das, Ayan; Heo, Junseok; Jankowski, Marc; Guo, Wei; Zhang, Lei; Deng, Hui; Bhattacharya, Pallab

    2011-01-01

    , and 2 orders of magnitude lower than any existing room-temperature polariton devices. Spectral, polarization, and coherence properties of the emission were measured to confirm polariton lasing. © 2011 American Physical Society.

  15. Submicrosecond electro-optic switching in the liquid-crystal smectic A phase: The soft-mode ferroelectric effect

    Science.gov (United States)

    Andersson, G.; Dahl, I.; Keller, P.; Kuczyński, W.; Lagerwall, S. T.; Skarp, K.; Stebler, B.

    1987-08-01

    A new liquid-crystal electro-optic modulating device similar to the surface-stabilized ferroelectric liquid-crystal device is described. It uses the same kind of ferroelectric chiral smectics and the same geometry as that device (thin sample in the ``bookshelf '' layer arrangement) but instead of using a tilted smectic phase like the C* phase, it utilizes the above-lying, nonferroelectric A phase, taking advantage of the electroclinic effect. The achievable optical intensity modulation that can be detected through the full range of the A phase is considerably lower than for the surface-stabilized device, but the response is much faster. Furthermore, the response is strictly linear with respect to the applied electric field. The device concept is thus appropriate for modulator rather than for display applications. We describe the underlying physics and present measurements of induced tilt angle, of light modulation depth, and of rise time.

  16. Electric-field-induced paraelectric to ferroelectric phase transformation in prototypical polycrystalline BaTiO3

    International Nuclear Information System (INIS)

    Wang, Zhiyang; Hinterstein, Manuel; Daniels, John E.; Webber, Kyle G.; Hudspeth, Jessica M.

    2014-01-01

    An electric-field-induced paraelectric cubic to ferroelectric tetragonal phase transformation has been directly observed in prototypical polycrystalline BaTiO 3 at temperatures above the Curie point (T C ) using in situ high-energy synchrotron X-ray diffraction. The transformation persisted to a maximum temperature of 4 °C above T C . The nature of the observed field-induced transformation and the resulting development of domain texture within the induced phase were dependent on the proximity to the transition temperature, corresponding well to previous macroscopic measurements. The transition electric field increased with increasing temperature above T C , while the magnitude of the resultant tetragonal domain texture at the maximum electric field (4 kV mm −1 ) decreased at higher temperatures. These results provide insights into the phase transformation behavior of a prototypical ferroelectric and have important implications for the development of future large-strain phase-change actuator materials.

  17. A qualitative test for intrinsic size effect on ferroelectric phase transitions

    OpenAIRE

    Wang, Jin; Tagantsev, Alexander K.; Setter, Nava

    2010-01-01

    The size effect in ferroelectrics is treated as a competition between the geometrical symmetry of the ferroelectric sample and its crystalline symmetry. The manifestation of this competition is shown to be polarization rotation, which is driven by temperature and/or size variations, thus providing a qualitative indication of intrinsic finite size effect on ferroelectrics. The concept is demonstrated in a simple case of PbTiO3 nanowires having their axis parallel to [111]C direction, where the...

  18. Neutron absorbing room temperature vulcanizable silicone rubber compositions

    International Nuclear Information System (INIS)

    Zoch, H.L.

    1979-01-01

    A neutron absorbing composition is described and consists of a one-component room temperature vulcanizable silicone rubber composition or a two-component room temperature vulcanizable silicone rubber composition in which the composition contains from 25 to 300 parts by weight based on the base silanol or vinyl containing diorganopolysiloxane polymer of a boron compound or boron powder as the neutron absorbing ingredient. An especially useful boron compound in this application is boron carbide. 20 claims

  19. Room-temperature synthesis of ultraviolet-emitting nanocrystalline GaN films using photochemical vapor deposition

    International Nuclear Information System (INIS)

    Yamazaki, Shunsuke; Yatsui, Takashi; Ohtsu, Motoichi; Kim, Taw-Won; Fujioka, Hiroshi

    2004-01-01

    We fabricated UV-emitting nanocrystalline gallium nitride (GaN) films at room temperature using photochemical vapor deposition (PCVD). For the samples synthesized at room temperature with V/III ratios exceeding 5.0x10 4 , strong photoluminescence peaks at 3.365 and 3.310 eV, which can be ascribed to transitions in a mixed phase of cubic and hexagonal GaN, were observed at 5 K. A UV emission spectrum with a full width at half-maximum of 100 meV was observed, even at room temperature. In addition, x-ray photoelectron spectroscopy measurement revealed that the film deposited by PCVD at room temperature was well nitridized

  20. On the polarization dynamics in the presence of flexoelectricity and morphotropic phase boundary in ferroelectrics

    Energy Technology Data Exchange (ETDEWEB)

    Pikin, S. A., E-mail: pikin@ns.crys.ras.ru [Russian Academy of Sciences, Shubnikov Institute of Crystallography, Federal Scientific Research Centre “Crystallography and Photonics” (Russian Federation)

    2017-03-15

    It is shown that anomalous piezoelectric properties of epitaxial nanostructures arise on the morphotropic phase boundary (MPB) due to the strong flexoelectric effect on dislocation walls. The MPB (typical of many materials) exhibits a coexistence of various phases and partition of these phases to minimum sizes. This minimum size l{sub c} (nanoscale) is found using the dislocation theory; it coincides with the distance between individual dislocations in dislocation walls, which is much larger than the Burgers vector b, regardless of the type of crystalline material. The flexoelectric coefficients f are estimated taking into account dimensional relations and experimental data on the rotations of ferroelectric nanodomains in multiferroics. These estimates coincide with classical values. The critical value l{sub c} ~ 10b specifies the measured dependence on the dielectric susceptibility χ{sub e}, f ~ χ{sub e}{sup 1/2}. The quantity χ{sub e} depends on the frequency of the ac electric field applied to a sample and on the dislocation density. The Ba{sub 0.6}Sr{sub 0.4}TiO{sub 3}/Ni{sub 0.8}Zn{sub 0.2}Fe{sub 2}O{sub 4} ceramic composite shows typical frequency dispersion of χ{sub e} in a wide frequency range. The frequency dependence of flexoelecric coefficients is shown to reproduce the frequency dependence of permittivity at high frequencies.

  1. Studies on room temperature electrochemical oxidation and its effect on the transport properties of TBCCO films

    International Nuclear Information System (INIS)

    Shirage, P M; Shivagan, D D; Pawar, S H

    2004-01-01

    A novel room temperature electrochemical process for the synthesis of single-phase Tl 2 Ba 2 Ca 2 Cu 3 O 10 (TBCCO/Tl-2223) superconducting films has been developed. Electrochemical parameters were optimized by studying linear sweep voltammetry (LSV), cyclic voltammetry (CV) and chronoamperometry (CA) for the deposition of Tl-Ba-Ca-Cu alloy at room temperature. The superconducting films of the TBCCO were obtained by two oxidation techniques. In the first technique, the electrodeposited Tl-Ba-Ca-Cu alloyed films were oxidized at various temperatures in flowing oxygen atmosphere. In the second technique, stoichiometric electrocrystallization to get Tl 2 Ba 2 Ca 2 Cu 3 O 10 (Tl-2223) was completed by electrochemically intercalating oxygen species into Tl-Ba-Ca-Cu alloy at room temperature for various lengths of time. The oxygen content in the samples was varied by varying the electrochemical oxidation period, and the changes in the crystal structure, superconducting transition temperature (T c ) and critical current density (J c ) were recorded. The high temperature furnace oxidation technique was replaced by the room temperature electrochemical oxidation technique. The dependence of superconducting parameters on oxygen content is correlated with structure-property relations

  2. X-ray and neutron single crystal diffraction on (NH4)3H(SO4)2. II. Refinement of crystal structure of phase II at room temperature

    International Nuclear Information System (INIS)

    Reehuis, M.; Wozniak, K.; Dominiak, P.; Smirnov, L.S.; Natkaniec, I.; Baranov, A.I.; Dolbinina, V.V.

    2006-01-01

    The (NH 4 ) 3 H(SO 4 ) 2 is of special interest due to the possible influence of ammonium ions on a series of phase transitions: I => II => III => IV => V => VII. Earlier, the X-ray single crystal diffraction study of phase II of (NH 4 ) 3 H(SO 4 ) 2 showed that the crystal structure of this compound has two crystallographically independent groups of ammonium ions NH 4 (1) and NH 4 (2), but orientational positions of these ammonium ions were not determined exactly. The refinement of NH 4 (1) and NH 4 (2) orientational positions in phase II is carried out with the help of the X-ray and neutron single crystal diffraction study. The analyses of differential Fourier maps of electron charge density and nuclear density point out the possibility of disordering of NH 4 (2) ammonium ions

  3. Microstructure research for ferroelectric origin in the strained Hf0.5Zr0.5O2 thin film via geometric phase analysis

    Science.gov (United States)

    Bi, Han; Sun, Qingqing; Zhao, Xuebing; You, Wenbin; Zhang, David Wei; Che, Renchao

    2018-04-01

    Recently, non-volatile semiconductor memory devices using a ferroelectric Hf0.5Zr0.5O2 film have been attracting extensive attention. However, at the nano-scale, the phase structure remains unclear in a thin Hf0.5Zr0.5O2 film, which stands in the way of the sustained development of ferroelectric memory nano-devices. Here, a series of electron microscopy evidences have illustrated that the interfacial strain played a key role in inducing the orthorhombic phase and the distorted tetragonal phase, which was the origin of the ferroelectricity in the Hf0.5Zr0.5O2 film. Our results provide insight into understanding the association between ferroelectric performances and microstructures of Hf0.5Zr0.5O2-based systems.

  4. Dynamics of nonlinear dielectric susceptibility of ferroelectrics near the morphotropic phase boundary

    International Nuclear Information System (INIS)

    Ibrahim, Abdel-Baset M A; Osman, Junaidah

    2013-01-01

    The dynamics of the nonlinear (NL) dielectric susceptibility of ferroelectrics (FE) near the morphotropic phase boundary (MPB) is theoretically investigated based on the Landau–Devonshire free energy approach and the concept of FE soft modes. To do so, the NL dielectric susceptibility elements of FE material in the tetragonal phase are expressed as functions of optical phonon modes. These are the E modes with normal characteristic frequency ω E 2 and the A modes with ω A 2 . On the one hand, the tetragonal E modes appear to exhibit a double soft-mode character, i.e. the mode softens either when the thermodynamic temperature T approaches the transition temperature T c or when the free energy parameter β 1 approaches β 2 . On the other hand, the A modes exhibit single soft-mode character when T approaches T c . Within this formulation, the dynamics of first-, second- and third-order NL susceptibility elements are investigated. The origin of the anomalous behavior of certain NL elements at the MPB appears to be a manifestation of FE mode-softening. This approach provides a simple yet powerful technique to understand the dynamics of the NL dielectric susceptibility elements of FE material near the MPB. (paper)

  5. Low-temperature structure and the ferroelectric phase transitions in the CdTi O3 perovskite

    Science.gov (United States)

    Kennedy, Brendan J.; Zhou, Qingdi; Zhao, Shipeng; Jia, Fanhao; Ren, Wei; Knight, Kevin S.

    2017-12-01

    The paraelectric-ferroelectric transition in CdTi O3 has been monitored using high-resolution neutron diffraction data. This necessitated preparing a sample enriched in 114Cd. A subtle, but significant, anisotropy in the thermal expansion of the lattice parameters for CdTi O3 associated with the transition to the polar structure was observed. First-principles calculations are presented to understand energies, phonon dispersion, and structures of possible phases with different symmetries.

  6. Growth and characterization of epitaxial thin films and multiferroic heterostructures of ferromagnetic and ferroelectric materials

    Science.gov (United States)

    Mukherjee, Devajyoti

    Multiferroic materials exhibit unique properties such as simultaneous existence of two or more of coupled ferroic order parameters (ferromagnetism, ferroelectricity, ferroelasticity or their anti-ferroic counterparts) in a single material. Recent years have seen a huge research interest in multiferroic materials for their potential application as high density non-volatile memory devices. However, the scarcity of these materials in single phase and the weak coupling of their ferroic components have directed the research towards multiferroic heterostructures. These systems operate by coupling the magnetic and electric properties of two materials, generally a ferromagnetic material and a ferroelectric material via strain. In this work, horizontal heterostructures of composite multiferroic materials were grown and characterized using pulsed laser ablation technique. Alternate magnetic and ferroelectric layers of cobalt ferrite and lead zirconium titanate, respectively, were fabricated and the coupling effect was studied by X-ray stress analysis. It was observed that the interfacial stress played an important role in the coupling effect between the phases. Doped zinc oxide (ZnO) heterostructures were also studied where the ferromagnetic phase was a layer of manganese doped ZnO and the ferroelectric phase was a layer of vanadium doped ZnO. For the first time, a clear evidence of possible room temperature magneto-elastic coupling was observed in these heterostructures. This work provides new insight into the stress mediated coupling mechanisms in composite multiferroics.

  7. Colloquium: High pressure and road to room temperature superconductivity

    Science.gov (United States)

    Gor'kov, Lev P.; Kresin, Vladimir Z.

    2018-01-01

    future use of tunneling spectroscopy. This feature leads to nonmonotonic and strongly asymmetric pressure dependence of Tc . Other hydrides, e.g., CaH6 and MgH6 , can be expected to display even higher values of Tc up to room temperature. The fundamental challenge lies in the creation of a structure capable of displaying high Tc at ambient pressure.

  8. Room Temperature Memory for Few Photon Polarization Qubits

    Science.gov (United States)

    Kupchak, Connor; Mittiga, Thomas; Jordan, Bertus; Nazami, Mehdi; Nolleke, Christian; Figueroa, Eden

    2014-05-01

    We have developed a room temperature quantum memory device based on Electromagnetically Induced Transparency capable of reliably storing and retrieving polarization qubits on the few photon level. Our system is realized in a vapor of 87Rb atoms utilizing a Λ-type energy level scheme. We create a dual-rail storage scheme mediated by an intense control field to allow storage and retrieval of any arbitrary polarization state. Upon retrieval, we employ a filtering system to sufficiently remove the strong pump field, and subject retrieved light states to polarization tomography. To date, our system has produced signal-to-noise ratios near unity with a memory fidelity of >80 % using coherent state qubits containing four photons on average. Our results thus demonstrate the feasibility of room temperature systems for the storage of single-photon-level photonic qubits. Such room temperature systems will be attractive for future long distance quantum communication schemes.

  9. Spin dynamics in bulk CdTe at room temperature

    International Nuclear Information System (INIS)

    Nahalkova, P.; Nemec, P.; Sprinzl, D.; Belas, E.; Horodysky, P.; Franc, J.; Hlidek, P.; Maly, P.

    2006-01-01

    In this paper, we report on the room temperature dynamics of spin-polarized carriers in undoped bulk CdTe. Platelets of CdTe with different concentration of preparation-induced dislocations were prepared by combining the mechanical polishing and chemical etching. Using the polarization-resolved pump-probe experiment in transmission geometry, we have observed a systematic decrease of both the signal polarization and the electron spin dephasing time (from 52 to 36 ps) with the increased concentration of defects. We have suggested that the Elliot-Yafet mechanism might be the dominant spin dephasing mechanism in platelets of CdTe at room temperature

  10. Microstructure stability of silver electrodeposits at room temperature

    International Nuclear Information System (INIS)

    Hansen, Karsten; Pantleon, Karen

    2008-01-01

    In situ quantitative X-ray diffraction analysis was used to investigate the kinetics of microstructure evolution at room temperature (self-annealing) in an electrodeposited silver layer. As a function of time at room temperature the as-deposited nanocrystalline microstructure evolved considerably: orientation-dependent grain growth and changes of the preferred grain orientation occurred. It is demonstrated for the first time that self-annealing occurs for electrodeposited silver layers and, hence, is not a unique feature of copper as often suggested

  11. Mechanical Behaviour of 304 Austenitic Stainless Steel Processed by Room Temperature Rolling

    Science.gov (United States)

    Singh, Rahul; Goel, Sunkulp; Verma, Raviraj; Jayaganthan, R.; Kumar, Abhishek

    2018-03-01

    To study the effect of room temperature rolling on mechanical properties of 304 Austenitic Stainless Steel, the as received 304 ASS was rolled at room temperature for different percentage of plastic deformation (i.e. 30, 50, 70 and 90 %). Microstructural study, tensile and hardness tests were performed in accordance with ASTM standards to study the effect of rolling. The ultimate tensile strength (UTS) and hardness of a rolled specimen have enhanced with rolling. The UTS has increased from 693 MPa (as received) to 1700 MPa (after 90% deformation). The improvement in UTS of processed samples is due to combined effect of grain refinement and stress induced martensitic phase transformation. The hardness values also increases from 206 VHN (as received) to 499 VHN (after 90% deformation). Magnetic measurements were also conducted to confirm the formation of martensitic phase.

  12. Phase transitions and domain structures in multiferroics

    Science.gov (United States)

    Vlahos, Eftihia

    2011-12-01

    Thin film ferroelectrics and multiferroics are two important classes of materials interesting both from a scientific and a technological prospective. The volatility of lead and bismuth as well as environmental issues regarding the toxicity of lead are two disadvantages of the most commonly used ferroelectric random access memory (FeRAM) materials such as Pb(Zr,Ti)O3 and SrBi2Ta2O9. Therefore lead-free thin film ferroelectrics are promising substitutes as long as (a) they can be grown on technologically important substrates such as silicon, and (b) their T c and Pr become comparable to that of well established ferroelectrics. On the other hand, the development of functional room temperature ferroelectric ferromagnetic multiferroics could lead to very interesting phenomena such as control of magnetism with electric fields and control of electrical polarization with magnetic fields. This thesis focuses on the understanding of material structure-property relations using nonlinear optical spectroscopy. Nonlinear spectroscopy is an excellent tool for probing the onset of ferroelectricity, and domain dynamics in strained ferroelectrics and multiferroics. Second harmonic generation was used to detect ferroelectricity and the antiferrodistortive phase transition in thin film SrTiO3. Incipient ferroelectric CaTiO3 has been shown to become ferroelectric when strained with a combination of SHG and dielectric measurements. The tensorial nature of the induced nonlinear polarization allows for probing of the BaTiO3 and SrTiO3 polarization contributions in nanoscale BaTiO3/SrTiO3 superlattices. In addition, nonlinear optics was used to demonstrate ferroelectricity in multiferroic EuTiO3. Finally, confocal SHG and Raman microscopy were utilized to visualize polar domains in incipient ferroelectric and ferroelastic CaTiO3.

  13. Investigation of Room Temperature Synthesis of Titanium Dioxide Nanoclusters Dispersed on Cubic MCM-48 Mesoporous Materials

    OpenAIRE

    Sridhar Budhi; Chia-Ming Wu; Dan Zhao; Ranjit T. Koodali

    2015-01-01

    Titania containing cubic MCM-48 mesoporous materials were synthesized successfully at room temperature by a modified Stöber method. The integrity of the cubic mesoporous phase was retained even at relatively high loadings of titania. The TiO2-MCM-48 materials were extensively characterized by a variety of physico-chemical techniques. The physico-chemical characterization indicate that Ti4+ ions can be substituted in framework tetrahedral positions. The relative amount of Ti4+ ions in tetrahe...

  14. Visualization of dielectric constant-electric field-temperature phase maps for imprinted relaxor ferroelectric thin films

    International Nuclear Information System (INIS)

    Frederick, J. C.; Kim, T. H.; Maeng, W.; Brewer, A. A.; Podkaminer, J. P.; Saenrang, W.; Vaithyanathan, V.; Schlom, D. G.; Li, F.; Chen, L.-Q.; Trolier-McKinstry, S.; Rzchowski, M. S.; Eom, C. B.

    2016-01-01

    The dielectric phase transition behavior of imprinted lead magnesium niobate–lead titanate relaxor ferroelectric thin films was mapped as a function of temperature and dc bias. To compensate for the presence of internal fields, an external electric bias was applied while measuring dielectric responses. The constructed three-dimensional dielectric maps provide insight into the dielectric behaviors of relaxor ferroelectric films as well as the temperature stability of the imprint. The transition temperature and diffuseness of the dielectric response correlate with crystallographic disorder resulting from strain and defects in the films grown on strontium titanate and silicon substrates; the latter was shown to induce a greater degree of disorder in the film as well as a dielectric response lower in magnitude and more diffuse in nature over the same temperature region. Strong and stable imprint was exhibited in both films and can be utilized to enhance the operational stability of piezoelectric devices through domain self-poling.

  15. Experimental study on the double barrier structure at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Sheng, H Y; Chua, S J [Centre for Optoelectronics, Dept. of Electrical Engineering, National Univ. of Singapore (Singapore)

    1994-06-15

    An experimental study of AlAs / GaAs / AlAs double barrier structure is carried out. The double barrier and quantum well structure are grown by MBE. The peak-to-valley ratio 2.6 : 1 with peak current density of 1.6 kA/cm/sup 2 at room temperature have been achieved. (authors)

  16. Gold catalysed synthesis of 3-alkoxyfurans at room temperature.

    Science.gov (United States)

    Pennell, Matthew N; Foster, Robert W; Turner, Peter G; Hailes, Helen C; Tame, Christopher J; Sheppard, Tom D

    2014-02-09

    Synthetically important 3-alkoxyfurans can be prepared efficiently via treatment of acetal-containing propargylic alcohols (obtained from the addition of 3,3-diethoxypropyne to aldehydes) with 2 mol% gold catalyst in an alcohol solvent at room temperature. The resulting furans show useful reactivity in a variety of subsequent transformations.

  17. Enhanced room temperature multiferroicity in Gd doped BFO

    CSIR Research Space (South Africa)

    Pradhan, SK

    2009-01-01

    Full Text Available deficient Gd doped multiferroic BFO system. At particular doping level of Gd, this bulk ceramics showed spectacular M~H behavior at room temperature which is likely to open a new avenue for the potential applications in information storing technology as well...

  18. Ferroelectrics principles, structure and applications

    CERN Document Server

    Merchant, Serena

    2014-01-01

    Ferroelectric physics is a theory on ferroelectric phase transition for explaining various related phenomena, which is different from dielectric physics. Ferroelectric materials are important functional materials for various applications such as NVRAMs, high energy density capacitors, actuators, MEMs, sonar sensors, microphones and scanning electron microscopes (SEM). This book investigates the dielectric, ferroelectric and energy storage properties of barium zirconate-titanate/barium calcium-titanate (BZT-BCT) based ceramic for high energy density capacitors. It also compares the energy storage capabilities of ceramic powders with polymer-ceramic nanocomposites; and discusses dielectric properties of ferroelectricity in composition distributions.

  19. Low-temperature synthesis and structural properties of ferroelectric K 3WO 3F 3 elpasolite

    Science.gov (United States)

    Atuchin, V. V.; Gavrilova, T. A.; Kesler, V. G.; Molokeev, M. S.; Aleksandrov, K. S.

    2010-06-01

    Low-temperature ferroelectric G2 polymorph of K 3WO 3F 3 has been prepared by chemical synthesis. Structural and chemical properties of the final product have been evaluated with X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Structure parameters of G2-K 3WO 3F 3 are refined by the Rietveld method from XRD data measured at room temperature (space group Cm, Z = 2, a = 8.7350(3) Å, b = 8.6808(5) Å, c = 6.1581(3) Å, β = 135.124(3) Å, V = 329.46(3) Å 3; RB = 2.47%). Partial ordering of oxygen and fluorine atoms has been found over anion positions. Mechanism of ferroelectric phase transition in A 2BMO 3F 3 oxyfluorides is discussed.

  20. Protocols for dry DNA storage and shipment at room temperature.

    Science.gov (United States)

    Ivanova, Natalia V; Kuzmina, Masha L

    2013-09-01

    The globalization of DNA barcoding will require core analytical facilities to develop cost-effective, efficient protocols for the shipment and archival storage of DNA extracts and PCR products. We evaluated three dry-state DNA stabilization systems: commercial Biomatrica(®) DNAstable(®) plates, home-made trehalose and polyvinyl alcohol (PVA) plates on 96-well panels of insect DNA stored at 56 °C and at room temperature. Controls included unprotected samples that were stored dry at room temperature and at 56 °C, and diluted samples held at 4 °C and at -20 °C. PCR and selective sequencing were performed over a 4-year interval to test the condition of DNA extracts. Biomatrica(®) provided better protection of DNA at 56 °C and at room temperature than trehalose and PVA, especially for diluted samples. PVA was the second best protectant after Biomatrica(®) at room temperature, whereas trehalose was the second best protectant at 56 °C. In spite of lower PCR success, the DNA stored at -20 °C yielded longer sequence reads and stronger signal, indicating that temperature is a crucial factor for DNA quality which has to be considered especially for long-term storage. Although it is premature to advocate a transition to DNA storage at room temperature, dry storage provides an additional layer of security for frozen samples, protecting them from degradation in the event of freezer failure. All three forms of DNA preservation enable shipment of dry DNA and PCR products between barcoding facilities. © 2013 The Authors. Molecular Ecology Resources published by John Wiley & Sons Ltd.

  1. Why is the electrocaloric effect so small in ferroelectrics?

    Science.gov (United States)

    Guzman-Verri, Gian G.; Littlewood, Peter B.

    2015-03-01

    Ferroelectrics are attractive candidate materials for environmentally friendly solid state refrigeration free of greenhouse gases. Their thermal response upon variations of external electric fields is largest in the vicinity of their phase transitions, which may occur near room temperature. The magnitude of the effect, however, is too small for useful cooling applications even when they are driven close to dielectric breakdown. Insight from microscopic theory is therefore needed to characterize materials and provide guiding principles to search for new ones with enhanced electrocaloric performance. Here, we present meaningful figures of merit derived from well-known microscopic models of ferroelectricity which provide insight into the relation between the strength of the effect and the characteristic interactions of ferroelectrics such as dipole forces. We find that the long range nature of these interactions results in a small effect. A strategy is proposed to make it larger by shortening the correlation lengths of fluctuations of polarization. Work at Argonne is supported by the U.S. Department of Energy, Office of Basic Energy Sciences under Contract No. DE-AC02-06CH11357.

  2. Influence of KF substitution on the ferroelectric phase transition of lead titanate single crystals studied by Brillouin light scattering

    Directory of Open Access Journals (Sweden)

    Seonhyeop Shin

    2015-06-01

    Full Text Available The elastic properties of KF-substituted perovskite lead titanate (PbTiO3 were investigated by dielectric measurements and Brillouin light scattering. The ferroelectric phase transition occurred at substantially lower temperature due to KF substitution, which was attributed to the modification of the covalency in Pb–O and Ti–O bonds. The longitudinal acoustic (LA mode of KF-substituted PbTiO3 showed a frequency softening in the paraelectric phase, which was accompanied by increasing acoustic damping. This indicated that polarization fluctuations responsible for the acoustic anomalies were enhanced by KF substitution.

  3. Room temperature ferromagnetism in nano-crystalline Co:ThO2 powders

    International Nuclear Information System (INIS)

    Bhide, M.K.; Kadam, R.M.; Godbole, S.V.; Tyagi, A.K.; Salunke, H.G.

    2012-01-01

    The major interest in dilute magnetic semiconductors (DMS's) had been directed towards the synthesis of room temperature ferromagnetic (RTF) materials for their potential applications in spintronic devices. Room temperature (RT) ferromagnetism was initially reported in Co doped TiO 2 , ZnO 2 and SnO 2 thin films and in the recent past in transition metal doped wide band gap materials. In the present paper we report the synthesis of Co doped ThO 2 nano powders by urea combustion method. The XRD characterization of 300℃ annealed samples confirmed formation of ThO 2 in the cubic phase and the average crystallite size obtained using Scherrer's formula was around 6 nm

  4. Metal nanoparticle film-based room temperature Coulomb transistor.

    Science.gov (United States)

    Willing, Svenja; Lehmann, Hauke; Volkmann, Mirjam; Klinke, Christian

    2017-07-01

    Single-electron transistors would represent an approach to developing less power-consuming microelectronic devices if room temperature operation and industry-compatible fabrication were possible. We present a concept based on stripes of small, self-assembled, colloidal, metal nanoparticles on a back-gate device architecture, which leads to well-defined and well-controllable transistor characteristics. This Coulomb transistor has three main advantages. By using the scalable Langmuir-Blodgett method, we combine high-quality chemically synthesized metal nanoparticles with standard lithography techniques. The resulting transistors show on/off ratios above 90%, reliable and sinusoidal Coulomb oscillations, and room temperature operation. Furthermore, this concept allows for versatile tuning of the device properties such as Coulomb energy gap and threshold voltage, as well as period, position, and strength of the oscillations.

  5. Metal nanoparticle film–based room temperature Coulomb transistor

    Science.gov (United States)

    Willing, Svenja; Lehmann, Hauke; Volkmann, Mirjam; Klinke, Christian

    2017-01-01

    Single-electron transistors would represent an approach to developing less power–consuming microelectronic devices if room temperature operation and industry-compatible fabrication were possible. We present a concept based on stripes of small, self-assembled, colloidal, metal nanoparticles on a back-gate device architecture, which leads to well-defined and well-controllable transistor characteristics. This Coulomb transistor has three main advantages. By using the scalable Langmuir-Blodgett method, we combine high-quality chemically synthesized metal nanoparticles with standard lithography techniques. The resulting transistors show on/off ratios above 90%, reliable and sinusoidal Coulomb oscillations, and room temperature operation. Furthermore, this concept allows for versatile tuning of the device properties such as Coulomb energy gap and threshold voltage, as well as period, position, and strength of the oscillations. PMID:28740864

  6. Room temperature excitation spectroscopy of single quantum dots

    Directory of Open Access Journals (Sweden)

    Christian Blum

    2011-08-01

    Full Text Available We report a single molecule detection scheme to investigate excitation spectra of single emitters at room temperature. We demonstrate the potential of single emitter photoluminescence excitation spectroscopy by recording excitation spectra of single CdSe nanocrystals over a wide spectral range of 100 nm. The spectra exhibit emission intermittency, characteristic of single emitters. We observe large variations in the spectra close to the band edge, which represent the individual heterogeneity of the observed quantum dots. We also find specific excitation wavelengths for which the single quantum dots analyzed show an increased propensity for a transition to a long-lived dark state. We expect that the additional capability of recording excitation spectra at room temperature from single emitters will enable insights into the photophysics of emitters that so far have remained inaccessible.

  7. Electrically Injected Twin Photon Emitting Lasers at Room Temperature

    Directory of Open Access Journals (Sweden)

    Claire Autebert

    2016-08-01

    Full Text Available On-chip generation, manipulation and detection of nonclassical states of light are some of the major issues for quantum information technologies. In this context, the maturity and versatility of semiconductor platforms are important assets towards the realization of ultra-compact devices. In this paper we present our work on the design and study of an electrically injected AlGaAs photon pair source working at room temperature. The device is characterized through its performances as a function of temperature and injected current. Finally we discuss the impact of the device’s properties on the generated quantum state. These results are very promising for the demonstration of electrically injected entangled photon sources at room temperature and let us envision the use of III-V semiconductors for a widespread diffusion of quantum communication technologies.

  8. Room temperature Sieving of Hydrogen Isotopes Using 2-D Materials

    Energy Technology Data Exchange (ETDEWEB)

    Hitchcock, D. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Colon-Mercado, H. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Krentz, T. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Serkiz, S. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Velten, J. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Xiao, S. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2017-09-28

    Hydrogen isotope separation is critical to the DOE’s mission in environmental remediation and nuclear nonproliferation. Isotope separation is also a critical technology for the NNSA, and the ability to perform the separations at room temperature with a relatively small amount of power and space would be a major advancement for their respective missions. Recent work has shown that 2-D materials such as graphene and hexagonal boron nitride can act as an isotopic sieve at room temperature; efficiently separating hydrogen isotopes in water with reported separation ratios of 10:1 for hydrogen: deuterium separation for a single pass. The work performed here suggests that this technique has merit, and furthermore, we are investigating optimization and scale up of the required 2-D material based membranes.

  9. Mechanical Resonators for Quantum Optomechanics Experiments at Room Temperature.

    Science.gov (United States)

    Norte, R A; Moura, J P; Gröblacher, S

    2016-04-08

    All quantum optomechanics experiments to date operate at cryogenic temperatures, imposing severe technical challenges and fundamental constraints. Here, we present a novel design of on-chip mechanical resonators which exhibit fundamental modes with frequencies f and mechanical quality factors Q_{m} sufficient to enter the optomechanical quantum regime at room temperature. We overcome previous limitations by designing ultrathin, high-stress silicon nitride (Si_{3}N_{4}) membranes, with tensile stress in the resonators' clamps close to the ultimate yield strength of the material. By patterning a photonic crystal on the SiN membranes, we observe reflectivities greater than 99%. These on-chip resonators have remarkably low mechanical dissipation, with Q_{m}∼10^{8}, while at the same time exhibiting large reflectivities. This makes them a unique platform for experiments towards the observation of massive quantum behavior at room temperature.

  10. Synthesis of cadmium chalcogenide nanotubes at room temperature

    KAUST Repository

    Pan, Jun

    2012-10-01

    Cadmium chalcogenide (CdE, E=S, Se, Te) polycrystalline nanotubes have been synthesized from precursor of CdS/cadmium thiolate complex at room temperature. The precursor was hydrothermally synthesized at 180 °C using thioglycolic acid (TGA) and cadmium acetate as starting materials. The transformation from the rod-like precursor of CdS/cadmium thiolate complex to CdS, CdSe and CdTe nanotubes were performed under constant stirring at room temperature in aqueous solution containing S 2-, Se 2- and Te 2-, respectively. The nanotube diameter can be controlled from 150 to 400 nm related to the dimension of templates. The XRD patterns show the cadmium chalcogenide nanotubes all corresponding to face-centered cubic structure. © 2012 Elsevier B.V. All rights reserved.

  11. Synthesis of cadmium chalcogenide nanotubes at room temperature

    KAUST Repository

    Pan, Jun; Qian, Yitai

    2012-01-01

    Cadmium chalcogenide (CdE, E=S, Se, Te) polycrystalline nanotubes have been synthesized from precursor of CdS/cadmium thiolate complex at room temperature. The precursor was hydrothermally synthesized at 180 °C using thioglycolic acid (TGA) and cadmium acetate as starting materials. The transformation from the rod-like precursor of CdS/cadmium thiolate complex to CdS, CdSe and CdTe nanotubes were performed under constant stirring at room temperature in aqueous solution containing S 2-, Se 2- and Te 2-, respectively. The nanotube diameter can be controlled from 150 to 400 nm related to the dimension of templates. The XRD patterns show the cadmium chalcogenide nanotubes all corresponding to face-centered cubic structure. © 2012 Elsevier B.V. All rights reserved.

  12. Room temperature electrodeposition of actinides from ionic solutions

    Science.gov (United States)

    Hatchett, David W.; Czerwinski, Kenneth R.; Droessler, Janelle; Kinyanjui, John

    2017-04-25

    Uranic and transuranic metals and metal oxides are first dissolved in ozone compositions. The resulting solution in ozone can be further dissolved in ionic liquids to form a second solution. The metals in the second solution are then electrochemically deposited from the second solutions as room temperature ionic liquid (RTIL), tri-methyl-n-butyl ammonium n-bis(trifluoromethansulfonylimide) [Me.sub.3N.sup.nBu][TFSI] providing an alternative non-aqueous system for the extraction and reclamation of actinides from reprocessed fuel materials. Deposition of U metal is achieved using TFSI complexes of U(III) and U(IV) containing the anion common to the RTIL. TFSI complexes of uranium were produced to ensure solubility of the species in the ionic liquid. The methods provide a first measure of the thermodynamic properties of U metal deposition using Uranium complexes with different oxidation states from RTIL solution at room temperature.

  13. Room-Temperature-Cured Copolymers for Lithium Battery Gel Electrolytes

    Science.gov (United States)

    Meador, Mary Ann B.; Tigelaar, Dean M.

    2009-01-01

    Polyimide-PEO copolymers (PEO signifies polyethylene oxide) that have branched rod-coil molecular structures and that can be cured into film form at room temperature have been invented for use as gel electrolytes for lithium-ion electric-power cells. These copolymers offer an alternative to previously patented branched rod-coil polyimides that have been considered for use as polymer electrolytes and that must be cured at a temperature of 200 C. In order to obtain sufficient conductivity for lithium ions in practical applications at and below room temperature, it is necessary to imbibe such a polymer with a suitable carbonate solvent or ionic liquid, but the high-temperature cure makes it impossible to incorporate and retain such a liquid within the polymer molecular framework. By eliminating the high-temperature cure, the present invention makes it possible to incorporate the required liquid.

  14. Xenon Recovery at Room Temperature using Metal-Organic Frameworks

    Energy Technology Data Exchange (ETDEWEB)

    Elsaidi, Sameh K. [Physical and Computational Science Directorate, Pacific Northwest National Laboratory, Richland WA 99352 USA; Chemistry Department, Faculty of Science, Alexandria University, P. O. Box 426 Ibrahimia Alexandria 21321 Egypt; Ongari, Daniele [Laboratory of Molecular Simulation, Institut des Sciences et Ingeénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne (EPFL), Rue de l' Industrie 17 1951 Sion Valais Switzerland; Xu, Wenqian [X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne IL 60439 USA; Mohamed, Mona H. [Chemistry Department, Faculty of Science, Alexandria University, P. O. Box 426 Ibrahimia Alexandria 21321 Egypt; Haranczyk, Maciej [IMDEA Materials Institute, c/Eric Kandel 2 28906 Getafe, Madrid Spain; Thallapally, Praveen K. [Physical and Computational Science Directorate, Pacific Northwest National Laboratory, Richland WA 99352 USA

    2017-07-24

    Xenon is known to be a very efficient anesthetic gas but its cost prohibits the wider use in medical industry and other potential applications. It has been shown that Xe recovery and recycle from anesthetic gas mixture can significantly reduce its cost as anesthetic. The current technology uses series of adsorbent columns followed by low temperature distillation to recover Xe, which is expensive to use in medical facilities. Herein, we propose much efficient and simpler system to recover and recycle Xe from simulant exhale anesthetic gas mixture at room temperature using metal organic frameworks. Among the MOFs tested, PCN-12 exhibits unprecedented performance with high Xe capacity, Xe/N2 and Xe/O2 selectivity at room temperature. The in-situ synchrotron measurements suggest the Xe is occupied in the small pockets of PCN-12 compared to unsaturated metal centers (UMCs). Computational modeling of adsorption further supports our experimental observation of Xe binding sites in PCN-12.

  15. Room temperature ferromagnetism of tin oxide nanocrystal based on synthesis methods

    Energy Technology Data Exchange (ETDEWEB)

    Sakthiraj, K.; Hema, M. [Department of Physics, Kamaraj College of Engineering and Technology, Virudhunagar 626001, Tamil Nadu (India); Balachandrakumar, K. [Department of Physics, Raja Doraisingam Government Arts College, Sivagangai 630561, Tamil Nadu (India)

    2016-04-15

    The experimental conditions used in the preparation of nanocrystalline oxide materials play an important role in the room temperature ferromagnetism of the product. In the present work, a comparison was made between sol–gel, microwave assisted sol–gel and hydrothermal methods for preparing tin oxide nanocrystal. X-ray diffraction analysis indicates the formation of tetragonal rutile phase structure for all the samples. The crystallite size was estimated from the HRTEM images and it is around 6–12 nm. Using optical absorbance measurement, the band gap energy value of the samples has been calculated. It reveals the existence of quantum confinement effect in all the prepared samples. Photoluminescence (PL) spectra confirms that the luminescence process originates from the structural defects such as oxygen vacancies present in the samples. Room temperature hysteresis loop was clearly observed in M–H curve of all the samples. But the sol–gel derived sample shows the higher values of saturation magnetization (M{sub s}) and remanence (M{sub r}) than other two samples. This study reveals that the sol–gel method is superior to the other two methods for producing room temperature ferromagnetism in tin oxide nanocrystal.

  16. FAST TRACK COMMUNICATION: Reproducible room temperature giant magnetocaloric effect in Fe-Rh

    Science.gov (United States)

    Manekar, Meghmalhar; Roy, S. B.

    2008-10-01

    We present the results of magnetocaloric effect (MCE) studies in polycrystalline Fe-Rh alloy over a temperature range of 250-345 K across the first order antiferromagnetic to ferromagnetic transition. By measuring the MCE under various thermomagnetic histories, contrary to the long held belief, we show here explicitly that the giant MCE in Fe-Rh near room temperature does not vanish after the first field cycle. In spite of the fact that the virgin magnetization curve is lost after the first field cycle near room temperature, reproducibility in the MCE under multiple field cycles can be achieved by properly choosing a combination of isothermal and adiabatic field variation cycles in the field-temperature phase space. This reproducible MCE leads to a large effective refrigerant capacity of 324.42 J kg-1, which is larger than that of the well-known magnetocaloric material Gd5Si2Ge2. This information could be important as Fe-Rh has the advantage of having a working temperature of around 300 K, which can be used for room temperature magnetic refrigeration.

  17. Chemical approach to neutral-ionic valence instability, quantum phase transition, and relaxor ferroelectricity in organic charge-transfer complexes

    International Nuclear Information System (INIS)

    Horiuchi, Sachio; Kumai, Reiji; Okimoto, Yoichi; Tokura, Yoshinori

    2006-01-01

    Neutral-ionic (NI) phase transition is a reversible switching of organic charge-transfer complexes between distinct valence states by external stimuli. This phase transformation in the low-dimensional system is demonstrated to provide a variety of novel dielectric, structural, and electronic properties. Importantly, ionization of the electron donor-acceptor pairs is usually accompanied by a ferroelectric or antiferroelectric order of the molecular lattice, leading to huge dielectric response near the transition point. Although these characteristics are potentially useful for future electronic and optical applications, the thermally accessible NI transition (TINIT) is still an extremely rare case. The TINIT compounds including some new materials are overviewed in order to provide convenient guides to their design and experimental identifications. The phase transition and dielectric properties can be closely controlled in various ways depending on chemical and physical modifications of the crystals. Among them, a quantum phase transition and relaxor ferroelectricity, both of which are currently attracting subjects from both scientific and practical perspectives, are highlighted as the first achievements in organic charge-transfer complexes

  18. Micelle-stabilized room-temperature phosphorescence with synchronous scanning

    International Nuclear Information System (INIS)

    Femia, R.A.; Love, L.J.C.

    1984-01-01

    The experimental requirements for synchronous wavelength scanning micelle-stabilized room temperature phosphorescence and the factors affecting peak resolution are presented and compared with those for synchronous wavelength scanning fluorescence. Identification of individual compounds in a four-component mixture is illustrated, and criteria to identify and minimize triplet state energy transfer are given. Considerable improvement in resolution of the synchronous peaks is obtained via second derivative spectra. 20 references, 7 figures, 2 tables

  19. Adaptive Beam Loading Compensation in Room Temperature Bunching Cavities

    Energy Technology Data Exchange (ETDEWEB)

    Edelen, J. P. [Fermilab; Chase, B. E. [Fermilab; Cullerton, E. [Fermilab; Varghese, P. [Fermilab

    2017-10-01

    In this paper we present the design, simulation, and proof of principle results of an optimization based adaptive feedforward algorithm for beam-loading compensation in a high impedance room temperature cavity. We begin with an overview of prior developments in beam loading compensation. Then we discuss different techniques for adaptive beam loading compensation and why the use of Newton?s Method is of interest for this application. This is followed by simulation and initial experimental results of this method.

  20. Room Temperature Ultralow Threshold GaN Nanowire Polariton Laser

    KAUST Repository

    Das, Ayan

    2011-08-01

    We report ultralow threshold polariton lasing from a single GaN nanowire strongly coupled to a large-area dielectric microcavity. The threshold carrier density is 3 orders of magnitude lower than that of photon lasing observed in the same device, and 2 orders of magnitude lower than any existing room-temperature polariton devices. Spectral, polarization, and coherence properties of the emission were measured to confirm polariton lasing. © 2011 American Physical Society.

  1. Room temperature ferromagnetism in Cu doped ZnO

    Science.gov (United States)

    Ali, Nasir; Singh, Budhi; Khan, Zaheer Ahmed; Ghosh, Subhasis

    2018-05-01

    We report the room temperature ferromagnetism in 2% Cu doped ZnO films grown by RF magnetron sputtering in different argon and oxygen partial pressure. X-ray photoelectron spectroscopy was used to ascertain the oxidation states of Cu in ZnO. The presence of defects within Cu-doped ZnO films can be revealed by electron paramagnetic resonance. It has been observed that saturated magnetic moment increase as we increase the zinc vacancies during deposition.

  2. A Room Temperature Low-Threshold Ultraviolet Plasmonic Nanolaser

    Science.gov (United States)

    2014-09-23

    samples were pasted to the cold finger of the cryostat with silver paste to ensure good thermal conduction. The time-resolve photoluminescence (TRPL...laser by total internal reflection. Nat. Mater. 10, 110–113 (2011). 13. Lu, Y. J. et al. Plasmonic nanolaser using epitaxially grown silver film. Science...1129 (1973). 30. Wang, Y. G. et al. Room temperature lasing with high group index in metal- coated GaN nanoring . Appl. Phys. Lett. 99, 251111 (2011

  3. Room temperature CO and H2 sensing with carbon nanoparticles

    International Nuclear Information System (INIS)

    Kim, Daegyu; Pikhitsa, Peter V; Yang, Hongjoo; Choi, Mansoo

    2011-01-01

    We report on a shell-shaped carbon nanoparticle (SCNP)-based gas sensor that reversibly detects reducing gas molecules such as CO and H 2 at room temperature both in air and inert atmosphere. Crystalline SCNPs were synthesized by laser-assisted reactions in pure acetylene gas flow, chemically treated to obtain well-dispersed SCNPs and then patterned on a substrate by the ion-induced focusing method. Our chemically functionalized SCNP-based gas sensor works for low concentrations of CO and H 2 at room temperature even without Pd or Pt catalysts commonly used for splitting H 2 molecules into reactive H atoms, while metal oxide gas sensors and bare carbon-nanotube-based gas sensors for sensing CO and H 2 molecules can operate only at elevated temperatures. A pristine SCNP-based gas sensor was also examined to prove the role of functional groups formed on the surface of functionalized SCNPs. A pristine SCNP gas sensor showed no response to reducing gases at room temperature but a significant response at elevated temperature, indicating a different sensing mechanism from a chemically functionalized SCNP sensor.

  4. Outrunning free radicals in room-temperature macromolecular crystallography

    Energy Technology Data Exchange (ETDEWEB)

    Owen, Robin L., E-mail: robin.owen@diamond.ac.uk; Axford, Danny [Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE (United Kingdom); Nettleship, Joanne E.; Owens, Raymond J. [Rutherford Appleton Laboratory, Didcot OX11 0FA (United Kingdom); The Henry Wellcome Building for Genomic Medicine, Roosevelt Drive, Oxford OX3 7BN (United Kingdom); Robinson, James I.; Morgan, Ann W. [University of Leeds, Leeds LS9 7FT (United Kingdom); Doré, Andrew S. [Heptares Therapeutics Ltd, BioPark, Welwyn Garden City AL7 3AX (United Kingdom); Lebon, Guillaume; Tate, Christopher G. [MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH (United Kingdom); Fry, Elizabeth E.; Ren, Jingshan [The Henry Wellcome Building for Genomic Medicine, Roosevelt Drive, Oxford OX3 7BN (United Kingdom); Stuart, David I. [Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE (United Kingdom); The Henry Wellcome Building for Genomic Medicine, Roosevelt Drive, Oxford OX3 7BN (United Kingdom); Evans, Gwyndaf [Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE (United Kingdom)

    2012-06-15

    A systematic increase in lifetime is observed in room-temperature protein and virus crystals through the use of reduced exposure times and a fast detector. A significant increase in the lifetime of room-temperature macromolecular crystals is reported through the use of a high-brilliance X-ray beam, reduced exposure times and a fast-readout detector. This is attributed to the ability to collect diffraction data before hydroxyl radicals can propagate through the crystal, fatally disrupting the lattice. Hydroxyl radicals are shown to be trapped in amorphous solutions at 100 K. The trend in crystal lifetime was observed in crystals of a soluble protein (immunoglobulin γ Fc receptor IIIa), a virus (bovine enterovirus serotype 2) and a membrane protein (human A{sub 2A} adenosine G-protein coupled receptor). The observation of a similar effect in all three systems provides clear evidence for a common optimal strategy for room-temperature data collection and will inform the design of future synchrotron beamlines and detectors for macromolecular crystallography.

  5. Outrunning free radicals in room-temperature macromolecular crystallography

    International Nuclear Information System (INIS)

    Owen, Robin L.; Axford, Danny; Nettleship, Joanne E.; Owens, Raymond J.; Robinson, James I.; Morgan, Ann W.; Doré, Andrew S.; Lebon, Guillaume; Tate, Christopher G.; Fry, Elizabeth E.; Ren, Jingshan; Stuart, David I.; Evans, Gwyndaf

    2012-01-01

    A systematic increase in lifetime is observed in room-temperature protein and virus crystals through the use of reduced exposure times and a fast detector. A significant increase in the lifetime of room-temperature macromolecular crystals is reported through the use of a high-brilliance X-ray beam, reduced exposure times and a fast-readout detector. This is attributed to the ability to collect diffraction data before hydroxyl radicals can propagate through the crystal, fatally disrupting the lattice. Hydroxyl radicals are shown to be trapped in amorphous solutions at 100 K. The trend in crystal lifetime was observed in crystals of a soluble protein (immunoglobulin γ Fc receptor IIIa), a virus (bovine enterovirus serotype 2) and a membrane protein (human A 2A adenosine G-protein coupled receptor). The observation of a similar effect in all three systems provides clear evidence for a common optimal strategy for room-temperature data collection and will inform the design of future synchrotron beamlines and detectors for macromolecular crystallography

  6. A room temperature light source based on silicon nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Lo Faro, M.J. [CNR-IPCF, Istituto per i Processi Chimico-Fisici, V. le F. Stagno D' Alcontres 37, 98158 Messina (Italy); MATIS CNR-IMM, Istituto per la Microelettronica e Microsistemi, Via Santa Sofia 64, 95123 Catania (Italy); Dipartimento di Fisica e Astronomia, Università di Catania, Via Santa Sofia 64, 95123 Catania (Italy); D' Andrea, C. [MATIS CNR-IMM, Istituto per la Microelettronica e Microsistemi, Via Santa Sofia 64, 95123 Catania (Italy); Messina, E.; Fazio, B. [CNR-IPCF, Istituto per i Processi Chimico-Fisici, V. le F. Stagno D' Alcontres 37, 98158 Messina (Italy); Musumeci, P. [Dipartimento di Fisica e Astronomia, Università di Catania, Via Santa Sofia 64, 95123 Catania (Italy); Franzò, G. [MATIS CNR-IMM, Istituto per la Microelettronica e Microsistemi, Via Santa Sofia 64, 95123 Catania (Italy); Gucciardi, P.G.; Vasi, C. [CNR-IPCF, Istituto per i Processi Chimico-Fisici, V. le F. Stagno D' Alcontres 37, 98158 Messina (Italy); Priolo, F. [MATIS CNR-IMM, Istituto per la Microelettronica e Microsistemi, Via Santa Sofia 64, 95123 Catania (Italy); Dipartimento di Fisica e Astronomia, Università di Catania, Via Santa Sofia 64, 95123 Catania (Italy); Scuola Superiore di Catania, Via Valdisavoia 9, 95123 Catania (Italy); Iacona, F. [MATIS CNR-IMM, Istituto per la Microelettronica e Microsistemi, Via Santa Sofia 64, 95123 Catania (Italy); Irrera, A., E-mail: irrera@me.cnr.it [CNR-IPCF, Istituto per i Processi Chimico-Fisici, V. le F. Stagno D' Alcontres 37, 98158 Messina (Italy)

    2016-08-31

    We synthesized ultrathin Si nanowires (NWs) by metal assisted chemical wet etching, using a very thin discontinuous Au layer as precursor for the process. A bright room temperature emission in the visible range due to electron–hole recombination in quantum confined Si NWs is reported. A single walled carbon nanotube (CNT) suspension was prepared and dispersed in Si NW samples. The hybrid Si NW/CNT system exhibits a double emission at room temperature, both in the visible (due to Si NWs) and the IR (due to CNTs) range, thus demonstrating the realization of a low-cost material with promising perspectives for applications in Si-based photonics. - Highlights: • Synthesis of ultrathin Si nanowires (NWs) by metal-assisted chemical etching • Synthesis of NW/carbon nanotube (CNT) hybrid systems • Structural characterization of Si NWs and Si NW/CNT • Room temperature photoluminescence (PL) properties of Si NWs and of Si NW/CNT • Tuning of the PL properties of the Si NW/CNT hybrid system.

  7. Continuous-wave room-temperature diamond maser

    Science.gov (United States)

    Breeze, Jonathan D.; Salvadori, Enrico; Sathian, Juna; Alford, Neil Mcn.; Kay, Christopher W. M.

    2018-03-01

    The maser—the microwave progenitor of the optical laser—has been confined to relative obscurity owing to its reliance on cryogenic refrigeration and high-vacuum systems. Despite this, it has found application in deep-space communications and radio astronomy owing to its unparalleled performance as a low-noise amplifier and oscillator. The recent demonstration of a room-temperature solid-state maser that utilizes polarized electron populations within the triplet states of photo-excited pentacene molecules in a p-terphenyl host paves the way for a new class of maser. However, p-terphenyl has poor thermal and mechanical properties, and the decay rates of the triplet sublevel of pentacene mean that only pulsed maser operation has been observed in this system. Alternative materials are therefore required to achieve continuous emission: inorganic materials that contain spin defects, such as diamond and silicon carbide, have been proposed. Here we report a continuous-wave room-temperature maser oscillator using optically pumped nitrogen–vacancy defect centres in diamond. This demonstration highlights the potential of room-temperature solid-state masers for use in a new generation of microwave devices that could find application in medicine, security, sensing and quantum technologies.

  8. Synthesis and characterization of CoPt nanoparticles prepared by room temperature chemical reduction with PAMAM dendrimer as template.

    Science.gov (United States)

    Wan, Haiying; Shi, Shifan; Bai, Litao; Shamsuzzoha, Mohammad; Harrell, J W; Street, Shane C

    2010-08-01

    We describe an approach to synthesize monodisperse CoPt nanoparticles with dendrimer as template by a simple chemical reduction method in aqueous solution using NaBH4 as reducing agent at room temperature. The as-made CoPt nanoparticles buried in the dendrimer matrix have the chemically disordered fcc structure and can be transformed to the fct phase after annealing at 700 degrees C. This is the first report of dendrimer-mediated room temperature synthesis of monodisperse magnetic nanoparticles in aqueous solution.

  9. Ab initio study on mechanical-bending-induced ferroelectric phase transition in ultrathin perovskite nanobelts

    International Nuclear Information System (INIS)

    Li, H.F.; Zhang, G.H.; Zheng, Yue; Wang, Biao; Chen, W.J.

    2014-01-01

    Based on first-principles calculations, we systematically investigated the structural, ferroelectric (FE), energetic and electronic properties of bended ultrathin PbTiO 3 and BaTiO 3 nanobelts in between flat sheet and nanotube configurations. It is found that both PbTiO 3 and BaTiO 3 ultrathin nanobelts can possess axial antiferrodistortive structural distortion (AFD distortion), and the magnitude of the AFD rotation angle is obviously determined by the bending curvature of the nanobelts. Meanwhile, spontaneous polarization can be retained in these single-unit-cell-thick nanobelts with contributions from the axial improper ferroelectricity and the radial flexoelectricity, which indicates that ultrathin perovskite nanobelts do not have a critical thickness. On the other hand, we found that the AFD distortion is stable and significant in PbTiO 3 nanobelts while it is metastable in BaTiO 3 nanobelts in comparison with the stable non-AFD structure without AFD distortion. This is due to the competition between AFD distortion and circumferential lattice extension in releasing the elastic energy in BaTiO 3 material. Moreover, we found that the electronic structure and bandgap of the nanobelts can be tuned by the bending curvature, indicating potential control of transport properties by mechanical bending. Our results gave more insight into the inherence of improper ferroelectricity in low-dimensional perovskite ferroelectrics

  10. The variation of PbTiO.sub.3./sub. bandgap at ferroelectric phase transition

    Czech Academy of Sciences Publication Activity Database

    Železný, Vladimír; Chvostová, Dagmar; Šimek, Daniel; Máca, František; Mašek, Jan; Setter, N.; Huang, Y.H.

    2016-01-01

    Roč. 28, č. 2 (2016), 1-8, č. článku 025501. ISSN 0953-8984 R&D Projects: GA ČR(CZ) GAP204/11/1011 Institutional support: RVO:68378271 Keywords : band gap * ellipsometry * ferroelectrics Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.649, year: 2016

  11. Processing and Low Voltage Switching of Organic Ferroelectric Phase-Separated Bistable Diodes

    NARCIS (Netherlands)

    Li, Mengyuan; Stingelin, Natalie; Michels, Jasper J.; Spijkman, Mark-Jan; Asadi, Kamal; Beerends, Rene; Biscarini, Fabio; Blom, Paul W. M.; de Leeuw, Dago M.

    2012-01-01

    The processing of solution-based binary blends of the ferroelectric random copolymer poly(vinylidene fluoride-trifluoroethylene) P(VDF-TrFE) and the semiconducting polymer poly(9,9-dioctylfluorenyl-2,7-diyl) (PFO) applied by spin-coating and wire-bar coating is investigated. By systematic variation

  12. Processing and low voltage switching of organic ferroelectric phase-separated bistable diodes

    NARCIS (Netherlands)

    Li, M.; Stingelin, N.; Michels, J.J.; Spijkman, M.-J.; Asadi, K.; Beerends, R.; Biscarini, F.; Blom, P.W.M.; Leeuw, D.M. de

    2012-01-01

    The processing of solution-based binary blends of the ferroelectric random copolymer poly(vinylidene fluoride-trifluoroethylene) P(VDF-TrFE) and the semiconducting polymer poly(9,9-dioctylfluorenyl-2,7-diyl) (PFO) applied by spin-coating and wire-bar coating is investigated. By systematic variation

  13. A frequency output ferroelectric phase PNZT capacitor-based temperature sensor

    KAUST Repository

    Khan, Naveed; Omran, Hesham; Yao, Yingbang; Salama, Khaled N.; Arsalan, Muhammad

    2016-01-01

    measured below the Curie temperature of the ferroelectric capacitor. The capacitance of the 20/80 (Zr/Ti) composition PNZT capacitor changes by 29% for a temperature change from 10°C to 100°C, which translates to 0.32%/°C temperature sensitivity

  14. Phase-field model simulation of ferroelectric/antiferroelectric materials microstructure evolution under multiphysics loading

    Science.gov (United States)

    Zhang, Jingyi

    Ferroelectric (FE) and closely related antiferroelectric (AFE) materials have unique electromechanical properties that promote various applications in the area of capacitors, sensors, generators (FE) and high density energy storage (AFE). These smart materials with extensive applications have drawn wide interest in the industrial and scientific world because of their reliability and tunable property. However, reliability issues changes its paradigms and requires guidance from detailed mechanism theory as the materials applications are pushed for better performance. A host of modeling work were dedicated to study the macro-structural behavior and microstructural evolution in FE and AFE material under various conditions. This thesis is focused on direct observation of domain evolution under multiphysics loading for both FE and AFE material. Landau-Devonshire time-dependent phase field models were built for both materials, and were simulated in finite element software Comsol. In FE model, dagger-shape 90 degree switched domain was observed at preexisting crack tip under pure mechanical loading. Polycrystal structure was tested under same condition, and blocking effect of the growth of dagger-shape switched domain from grain orientation difference and/or grain boundary was directly observed. AFE ceramic model was developed using two sublattice theory, this model was used to investigate the mechanism of energy efficiency increase with self-confined loading in experimental tests. Consistent results was found in simulation and careful investigation of calculation results gave confirmation that origin of energy density increase is from three aspects: self-confinement induced inner compression field as the cause of increase of critical field, fringe leak as the source of elevated saturation polarization and uneven defects distribution as the reason for critical field shifting and phase transition speed. Another important affecting aspect in polycrystalline materials is the

  15. Transmission electron microscope studies of phase transitions in single crystals and ceramics of ferroelectric Pb(Sc1/2Ta1/2)O3

    International Nuclear Information System (INIS)

    Baba-Kishi, K.Z.; Barber, D.J.

    1990-01-01

    An account is given of transmission electron microscope investigations of the phase transitions in single crystals and ceramics of the complex perovskite-structured ferroelectric 'relaxor' compound Pb(Sc 1/2 Ta 1/2 )O 3 . The crystal symmetries pertaining to both the non-polar paraelectric (PE) and polar ferroelectric (FE) states have been studied by the technique of convergent-beam electron diffraction. A new phase transition has been discovered in the temperature range for which the FE and PE states coexist. The new phase transition is interpreted as the creation of a modulated antiferroelectric state, and this is viewed as marking a departure from relaxor behaviour towards more 'normal' ferroelectric behaviour. (orig.)

  16. Perovskite oxides for visible-light-absorbing ferroelectric and photovoltaic materials.

    Science.gov (United States)

    Grinberg, Ilya; West, D Vincent; Torres, Maria; Gou, Gaoyang; Stein, David M; Wu, Liyan; Chen, Guannan; Gallo, Eric M; Akbashev, Andrew R; Davies, Peter K; Spanier, Jonathan E; Rappe, Andrew M

    2013-11-28

    Ferroelectrics have recently attracted attention as a candidate class of materials for use in photovoltaic devices, and for the coupling of light absorption with other functional properties. In these materials, the strong inversion symmetry breaking that is due to spontaneous electric polarization promotes the desirable separation of photo-excited carriers and allows voltages higher than the bandgap, which may enable efficiencies beyond the maximum possible in a conventional p-n junction solar cell. Ferroelectric oxides are also stable in a wide range of mechanical, chemical and thermal conditions and can be fabricated using low-cost methods such as sol-gel thin-film deposition and sputtering. Recent work has shown how a decrease in ferroelectric layer thickness and judicious engineering of domain structures and ferroelectric-electrode interfaces can greatly increase the current harvested from ferroelectric absorber materials, increasing the power conversion efficiency from about 10(-4) to about 0.5 per cent. Further improvements in photovoltaic efficiency have been inhibited by the wide bandgaps (2.7-4 electronvolts) of ferroelectric oxides, which allow the use of only 8-20 per cent of the solar spectrum. Here we describe a family of single-phase solid oxide solutions made from low-cost and non-toxic elements using conventional solid-state methods: [KNbO3]1 - x[BaNi1/2Nb1/2O3 - δ]x (KBNNO). These oxides exhibit both ferroelectricity and a wide variation of direct bandgaps in the range 1.1-3.8 electronvolts. In particular, the x = 0.1 composition is polar at room temperature, has a direct bandgap of 1.39 electronvolts and has a photocurrent density approximately 50 times larger than that of the classic ferroelectric (Pb,La)(Zr,Ti)O3 material. The ability of KBNNO to absorb three to six times more solar energy than the current ferroelectric materials suggests a route to viable ferroelectric semiconductor-based cells for solar energy conversion and

  17. Adaptive ferroelectric state at morphotropic phase boundary: Coexisting tetragonal and rhombohedral phases

    International Nuclear Information System (INIS)

    Zhang, Yang; Xue, Dezhen; Wu, Haijun; Ding, Xiangdong; Lookman, Turab; Ren, Xiaobing

    2014-01-01

    With a focus on local symmetry, the microstructural basis for high piezoelectric performance in PbMg 1/3 Nb 2/3 O 3 –xPbTiO 3 (PMN–PT) ceramics at the morphotropic phase boundary (MPB) composition was investigated by means of convergent-beam electron diffraction analysis and twin diffraction pattern analysis. The local structure was found to consist of coexisting (1 0 1)-type tetragonal nanotwins and (0 0 1)-type rhombohedral nanotwins. A phenomenological theory based on crystallography is proposed to show that such nanoscale coexistence can give rise to an average monoclinic structure through strain accommodation. The average monoclinic structures (Ma and Mc) vary with temperature and composition due to the dependence on temperature and composition of the lattice parameters. Based on in situ X-ray diffraction data, we demonstrate how the polarization rotates across the MPB region in PMN–PT ceramics with varying temperatures and compositions

  18. Nanoscale Ferroelectric Switchable Polarization and Leakage Current Behavior in (Ba0.50Sr0.50(Ti0.80Sn0.20O3 Thin Films Prepared Using Chemical Solution Deposition

    Directory of Open Access Journals (Sweden)

    Venkata Sreenivas Puli

    2015-01-01

    Full Text Available Nanoscale switchable ferroelectric (Ba0.50Sr0.50(Ti0.80Sn0.20O3-BSTS polycrystalline thin films with a perovskite structure were prepared on Pt/TiOx/SiO2/Si substrate by chemical solution deposition. X-ray diffraction (XRD spectra indicate that a cubic perovskite crystalline structure and Raman spectra revealed that a tetragonal perovskite crystalline structure is present in the thin films. Sr2+ and Sn4+ cosubstituted film exhibited the lowest leakage current density. Piezoresponse Force Microscopy (PFM technique has been employed to acquire out-of-plane (OPP piezoresponse images and local piezoelectric hysteresis loop in polycrystalline BSTS films. PFM phase and amplitude images reveal nanoscale ferroelectric switching behavior at room temperature. Square patterns with dark and bright contrasts were written by local poling and reversible nature of the piezoresponse behavior was established. Local piezoelectric butterfly amplitude and phase hysteresis loops display ferroelectric nature at nanoscale level. The significance of this paper is to present ferroelectric/piezoelectric nature in present BSTS films at nanoscale level and corroborating ferroelectric behavior by utilizing Raman spectroscopy. Thus, further optimizing physical and electrical properties, BSTS films might be useful for practical applications which include nonvolatile ferroelectric memories, data-storage media, piezoelectric actuators, and electric energy storage capacitors.

  19. Room temperature ferromagnetism in ZnO prepared by microemulsion

    Directory of Open Access Journals (Sweden)

    Qingyu Xu

    2011-09-01

    Full Text Available Clear room temperature ferromagnetism has been observed in ZnO powders prepared by microemulsion. The O vacancy (VO clusters mediated by the VO with one electron (F center contributed to the ferromagnetism, while the isolated F centers contributed to the low temperature paramagnetism. Annealing in H2 incorporated interstitial H (Hi in ZnO, and removed the isolated F centers, leading to the suppression of the paramagnetism. The ferromagnetism has been considered to originate from the VO clusters mediated by the Hi, leading to the enhancement of the coercivity. The ferromagnetism disappeared after annealing in air due to the reduction of Hi.

  20. Room-Temperature Dephasing in InAs Quantum Dots

    DEFF Research Database (Denmark)

    Borri, Paola; Langbein, Wolfgang; Mørk, Jesper

    2000-01-01

    The room temperature dephasing in InAs/InGaAs/GaAs self-assembled quantum dots, embedded in a waveguide for laser applications, is measured using two independent methods: spectral hole burning and four-wave mixing. Without the application of bias current for electrical carrier injection......, a dephasing time of ~260 fs, weakly dependent on the optical excitation density, is found and attributed to phonon interaction. The application of bias current, leading to population inversion in the dot ground state and optical gain, strongly decreases the dephasing time to less than 50 fs, likely due...

  1. Thermoluminescence in KBr:D electron irradiated at room temperature

    International Nuclear Information System (INIS)

    Paredes Campoy, J.C.; Lopez Carranza, E.

    1991-07-01

    The thermoluminescence of KBr:D samples electron irradiated at room temperature after thermal annealing at 673 K for 1 hour have been studied in the temperature range 360-730 K. The experimental TL-curve was discomposed by computer analysis in seven overlapping TL peaks, giving for them the order of the kinetics of thermal stimulation, the activation energy, the frequency factor, the relative values of the electronic concentration in traps at the initial heating temperature and the temperature at the maximum of the peak. (author). 18 refs, 1 fig., 3 tabs

  2. Ferroelectric and magnetic properties in high-pressure synthesized BiFeO3 compound

    International Nuclear Information System (INIS)

    Zhai, L.; Shi, Y.G.; Gao, J.L.; Tang, S.L.; Du, Y.W.

    2011-01-01

    Highlights: → A high-density polycrystalline BiFeO 3 compound was synthesized by high-pressure annealing method. → The sample showed weak ferromagnetic at room temperature, which could be attributed to the lattice distortion induced by the high-pressure annealing. → Irregular domains were observed on the surface of the sample by piezoresponse force microscopy, and a typical hysteresis loop was obtained. - Abstract: High-density polycrystalline BiFeO 3 compound was synthesized by high-pressure annealing. Measurements of crystal structure, magnetic, and ferroelectric properties were made on the sample. It was found that the sample was almost single phase with a distorted R3c structure. The results of the X-ray photoelectron spectra demonstrate that the oxidation state of Fe in the sample is Fe 3+ . The room-temperature field dependence of magnetization for BiFeO 3 exhibits a hysteretic behavior. The observed weak ferromagnetism could be ascribed to the lattice distortion induced by the high-pressure annealing. In addition, the local ferroelectric performance of the sample was studied by piezoresponse force microscopy.

  3. Effects of different oxyanions in solution on the precipitation of jarosite at room temperature.

    Science.gov (United States)

    Yeongkyoo, Kim

    2018-04-09

    The effects of five different oxyanions, AsO 4 , SeO 3 , SeO 4 , MoO 4 , and CrO 4 , on the precipitation of jarosite at room temperature were investigated by X-ray diffraction, scanning electron microscopy, and chemical analysis. Different amounts (2, 5, and 10 mol%) of oxyanions in the starting solution and different aging times (1 h-40 days) were used for the experiment. In the initial stage, only the amorphous phase appears for all samples. With increasing aging time, jarosite and jarosite with oxyanions start precipitating at room temperature with different precipitation rates and crystallinities. Jarosite with AsO 4 shows the lowest precipitation rate and lowest crystallinity. With increasing amounts of oxyanions, the crystallization rate decreases, especially for jarosite with AsO 4 . The jarosite samples with CrO 4 and SeO 4 show the fastest precipitation and highest crystallinities. For the jarosite samples with a low precipitation rate and low crystallinity, the amorphous phase contains high concentrations of oxyanions, probably because of the fast precipitation of the amorphous iron oxyanion phase; however, the phase with fast jarosite precipitation contains fewer oxyanions. The results show that coprecipitation of jarosite can play a more important role in controlling the behavior of CrO 4 than AsO 4 in acid mine drainage. Copyright © 2018 Elsevier B.V. All rights reserved.

  4. Room temperature deformation of in-situ grown quasicrystals embedded in Al-based cast alloy

    Directory of Open Access Journals (Sweden)

    Boštjan Markoli

    2013-12-01

    Full Text Available An Al-based cast alloy containing Mn, Be and Cu has been chosen to investigate the room temperature deformation behavior of QC particles embedded in Al-matrix. Using LOM, SEM (equipped with EDS, conventional TEM with SAED and controlled tensile and compression tests, the deformation response of AlMn2Be2Cu2 cast alloy at room temperature has been examined. Alloy consisted of Al-based matrix, primary particles and eutectic icosahedral quasicrystalline (QC i-phase and traces of Θ-Al2Cu and Al10Mn3. Tensile and compression specimens were used for evaluation of mechanical response and behavior of QC i-phase articles embedded in Al-cast alloy. It has been established that embedded QC i-phase particles undergo plastic deformation along with the Al-based matrix even under severe deformation and have the response resembling that of the metallic materials by formation of typical cup-and-cone feature prior to failure. So, we can conclude that QC i-phase has the ability to undergo plastic deformation along with the Al-matrix to greater extent contrary to e.g. intermetallics such as Θ-Al2Cu for instance.

  5. An investigation on phase transition behaviors in MgO-doped Pb{sub 0.99}(Zr{sub 0.95}Ti{sub 0.05}){sub 0.98}Nb{sub 0.02}O{sub 3} ferroelectric ceramics by Raman and dielectric measurements

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Junxia, E-mail: wjunxia2002@163.com [Key Laboratory of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials, Southwest University of Science and Technology, Mianyang 621010 (China); Wang, Genshui; Chen, Xuefeng [Key Laboratory of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Hu, Zhigao [Key Laboratory of Polar Materials and Devices, Ministry of Education, Department of Electronic Engineering, East China Normal University, Shanghai 200241 (China); Nie, Hengchang; Cao, Fei [Key Laboratory of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Dong, Xianlin, E-mail: xldong@mail.sic.ac.cn [Key Laboratory of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China)

    2015-03-15

    Highlights: • The phase transition behaviors were strongly dependent on MgO concentration. • The F{sub R(LT)}–F{sub R(HT)} phase transition temperature obviously shifted toward a lower temperature with increasing MgO addition. • The F{sub R(HT)}–cubic paraelectric (P{sub C}) phase transition changed to a higher temperature with increasing MgO addition. • The distortion of BO{sub 6} oxygen octahedron caused by B-site replacement of Mg{sup 2+} ions is proposed to explain the observed behaviors. • Superior room-temperature pyroelectric properties were obtained in 0.1 wt% MgO-modified PZTN 95/5 ceramics during F{sub R(LT)}–F{sub R(HT)} phase transition. - Abstract: The phase transition behaviors of Pb{sub 0.99}(Zr{sub 0.95}Ti{sub 0.05}){sub 0.98}Nb{sub 0.02}O{sub 3} ferroelectric ceramics doped with different MgO concentrations (0–0.2 wt%) were systematically investigated by Raman and dielectric measurements. Raman results showed that the phase transitions were strongly dependent on MgO concentration. It was found that the low temperature rhombohedral (F{sub R(LT)})–high temperature rhombohedral (F{sub R(HT)}) ferroelectric phase transition shifted toward a lower temperature with increasing MgO concentration up to 0.1 wt%, while the F{sub R(HT)}–cubic paraelectric (P{sub C}) phase transition changed to a higher temperature. The Raman results were in good agreement with phase transition determined by dielectric measurements. Moreover, it was indicated that the changes of Raman active modes were related to distortion of BO{sub 6} octahedra during the phase transitions. Then, the distortion of BO{sub 6} octahedron caused by B-site replacement of Mg{sup 2+} ions was proposed to explain the observed behaviors. In addition, the effects of MgO doping on the dielectric, ferroelectric and pyroelectric properties were also discussed.

  6. Microscopic Superconductivity and Room Temperature Electronics of High-Tc Cuprates

    International Nuclear Information System (INIS)

    Liu Fusui; Chen Wanfang

    2008-01-01

    This paper points out that the Landau criterion for macroscopic superfluidity of He II is only a criterion for microscopic superfluidity of 4 He, extends the Landau criterion to microscopic superconductivity in fermions (electron and hole) system and system with Cooper pairs without long-range phase coherence. This paper gives another three non-superconductive systems that are of microscopic superconductivity. This paper demonstrates that one application of microscopic superconductivity is to establish room temperature electronics of the high-T c cuprates

  7. Spectroscopic evidence for 5f bands at room temperature in uranium-based heavy fermions

    International Nuclear Information System (INIS)

    Arko, A.J.; Koelling, D.D.; Dunlap, B.D.; Capasso, C.; del Giudice, M.

    1988-01-01

    We present data on the alloy system UPd/sub 3-x/Pt/sub x/ and show that in the double hexagonal phase (x 2.4) as well, except that the low-binding energy feature is locked in at E/sub F/ and shows evidence of energy dispersion at room temperature/endash/consistent with well-defined bands. Conversely, we show that even in well-behaved narrow band systems (USn 3 there is evidence for satellite formation. 44 refs., 8 figs

  8. Synthesis of monoclinic potassium niobate nanowires that are stable at room temperature.

    Science.gov (United States)

    Kim, Seungwook; Lee, Ju-Hyuck; Lee, Jaeyeon; Kim, Sang-Woo; Kim, Myung Hwa; Park, Sungnam; Chung, Haegeun; Kim, Yong-Il; Kim, Woong

    2013-01-09

    We report the synthesis of KNbO(3) nanowires (NWs) with a monoclinic phase, a phase not observed in bulk KNbO(3) materials. The monoclinic NWs can be synthesized via a hydrothermal method using metallic Nb as a precursor. The NWs are metastable, and thermal treatment at ∼450 °C changed the monoclinic phase into the orthorhombic phase, which is the most stable phase of KNbO(3) at room temperature. Furthermore, we fabricated energy-harvesting nanogenerators by vertically aligning the NWs on SrTiO(3) substrates. The monoclinic NWs showed significantly better energy conversion characteristics than orthorhombic NWs. Moreover, the frequency-doubling efficiency of the monoclinic NWs was ∼3 times higher than that of orthorhombic NWs. This work may contribute to the synthesis of materials with new crystalline structures and hence improve the properties of the materials for various applications.

  9. Room temperature ferromagnetism in Mn-doped NiO nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Layek, Samar, E-mail: samarlayek@gmail.com; Verma, H.C.

    2016-01-01

    Mn-doped NiO nanoparticles of the series Ni{sub 1−x}Mn{sub x}O (x=0.00, 0.02, 0.04 and 0.06) are successfully synthesized using a low temperature hydrothermal method. Samples up to 6% Mn-doping are single phase in nature as observed from powder x-ray diffraction (XRD) studies. Rietveld refinement of the XRD data shows that all the single phase samples crystallize in the NaCl like fcc structure with space group Fm-3m. Unit cell volume decreases with increasing Mn-doping. Pure NiO nanoparticles show weak ferromagnetism, may be due to nanosize nature. Introduction of Mn within NiO lattice improves the magnetic properties significantly. Room temperature ferromagnetism is found in all the doped samples whereas the magnetization is highest for 2% Mn-doping and then decreases with further doping. The ZFC and FC branches in the temperature dependent magnetization separate well above 350 K indicating transition temperature well above room temperature for 2% Mn-doped NiO Nanoparticle. The ferromagnetic Curie temperature is found to be 653 K for the same sample as measured by temperature dependent magnetization study using vibrating sample magnetometer (VSM) in high vacuum. - Highlights: • Mn-doped NiO nanoparticles are prepared by a simple hydrothermal method. • Unit cell volume decreases with increasing doping concentration. • Mn-doping leads to room temperature ferromagnetism in NiO nanoparticles. • Magnetization is highest for 2% Mn-doping. • Above 2%, magnetization decreases with increasing doping.

  10. Room temperature ferromagnetism in Mn-doped NiO nanoparticles

    International Nuclear Information System (INIS)

    Layek, Samar; Verma, H.C.

    2016-01-01

    Mn-doped NiO nanoparticles of the series Ni_1_−_xMn_xO (x=0.00, 0.02, 0.04 and 0.06) are successfully synthesized using a low temperature hydrothermal method. Samples up to 6% Mn-doping are single phase in nature as observed from powder x-ray diffraction (XRD) studies. Rietveld refinement of the XRD data shows that all the single phase samples crystallize in the NaCl like fcc structure with space group Fm-3m. Unit cell volume decreases with increasing Mn-doping. Pure NiO nanoparticles show weak ferromagnetism, may be due to nanosize nature. Introduction of Mn within NiO lattice improves the magnetic properties significantly. Room temperature ferromagnetism is found in all the doped samples whereas the magnetization is highest for 2% Mn-doping and then decreases with further doping. The ZFC and FC branches in the temperature dependent magnetization separate well above 350 K indicating transition temperature well above room temperature for 2% Mn-doped NiO Nanoparticle. The ferromagnetic Curie temperature is found to be 653 K for the same sample as measured by temperature dependent magnetization study using vibrating sample magnetometer (VSM) in high vacuum. - Highlights: • Mn-doped NiO nanoparticles are prepared by a simple hydrothermal method. • Unit cell volume decreases with increasing doping concentration. • Mn-doping leads to room temperature ferromagnetism in NiO nanoparticles. • Magnetization is highest for 2% Mn-doping. • Above 2%, magnetization decreases with increasing doping.

  11. One-Dimensional Vanadium Dioxide Nanostructures for Room Temperature Hydrogen Sensors

    Directory of Open Access Journals (Sweden)

    Aline Simo

    2015-06-01

    Full Text Available In relation to hydrogen (H2 economy in general and gas sensing in particular, an extensive set of one dimensional (1-D nano-scaled oxide materials are being investigated as ideal candidates for potential gas sensing applications. This is correlated to their set of singular surface characteristics, shape anisotropy and readiness for integrated devices. Nanostructures of well- established gas sensing materials such as Tin Oxide (SnO2, Zinc Oxide (ZnO, Indium (III Oxide (In2O3, and Tungsten Trioxide (WO3 have shown higher sensitivity and gas selectivity, quicker response, faster time recovery, as well as an enhanced capability to detect gases at low concentrations. While the overall sensing characteristics of these so called 1-D nanomaterials are superior, they are efficient at high temperature; generally above 200 0C. This operational impediment results in device complexities in integration that limit their technological applications, specifically in their miniaturized arrangements. Unfortunately, for room temperature applications, there is a necessity to dope the above mentioned nano-scaled oxides with noble metals such as Platinum (Pt, Palladium (Pd, Gold (Au, Ruthenium (Ru. This comes at a cost. This communication reports, for the first time, on the room temperature enhanced H2 sensing properties of a specific phase of pure Vanadium Dioxide (VO2 phase A in their nanobelt form. The relatively observed large H2 room temperature sensing in this Mott type specific oxide seems to reach values as low as 14 ppm H2 which makes it an ideal gas sensing in H2 fuelled systems.

  12. Diffraction study of duty-cycle error in ferroelectric quasi-phase-matching gratings with Gaussian beam illumination

    Science.gov (United States)

    Dwivedi, Prashant Povel; Kumar, Challa Sesha Sai Pavan; Choi, Hee Joo; Cha, Myoungsik

    2016-02-01

    Random duty-cycle error (RDE) is inherent in the fabrication of ferroelectric quasi-phase-matching (QPM) gratings. Although a small RDE may not affect the nonlinearity of QPM devices, it enhances non-phase-matched parasitic harmonic generations, limiting the device performance in some applications. Recently, we demonstrated a simple method for measuring the RDE in QPM gratings by analyzing the far-field diffraction pattern obtained by uniform illumination (Dwivedi et al. in Opt Express 21:30221-30226, 2013). In the present study, we used a Gaussian beam illumination for the diffraction experiment to measure noise spectra that are less affected by the pedestals of the strong diffraction orders. Our results were compared with our calculations based on a random grating model, demonstrating improved resolution in the RDE estimation.

  13. Uniaxial ratcheting behavior of Zircaloy-4 tubes at room temperature

    International Nuclear Information System (INIS)

    Wen, Mingjian; Li, Hua; Yu, Dunji; Chen, Gang; Chen, Xu

    2013-01-01

    In this study, a series of uniaxial tensile, strain cycling and uniaxial ratcheting tests were conducted at room temperature on Zircaloy-4 (Zr-4) tubes used as nuclear fuel cladding in Pressurized Water Reactors (PWRs) for the purpose to investigate the uniaxial ratcheting behavior of Zr-4 and the factors which may influence it. The experimental results show that at room temperature this material features cyclic softening remarkably within the strain range of 1.6%, and former cycling under larger strain amplitude cannot retard cyclic softening of later cycling under lower strain amplitude. Uniaxial ratcheting strain accumulates in the direction of mean stress, and the ratcheting stain level is larger under tensile mean stress than that under compressive mean stress. Uniaxial ratcheting strain level increases with the increase of mean stress and stress amplitude, and decreases with the increase of loading rate. The sequence of loading rate appears to have no effects on the final ratcheting strain accumulation. Loading history has great influence on the uniaxial ratcheting behavior. Lower stress level after loading history with higher stress level leads to the shakedown of ratcheting. Higher loading rate after loading history with lower loading rate brings down the ratcheting strain rate. Uniaxial ratcheting behavior is sensitive to compressive pre-strain, and the decay rate of the ratcheting strain rate is slowed down by pre-compression

  14. Does nanocrystalline Cu deform by Coble creep near room temperature?

    International Nuclear Information System (INIS)

    Li, Y.J.; Blum, W.; Breutinger, F.

    2004-01-01

    The proposal that nanocrystalline Cu produced by electro deposition (ED) creeps at temperatures slightly above room temperature by diffusive flow via grain boundaries (Coble creep) has been checked by compression tests. It was found that the minimum creep rates obtained in tension are significantly larger than those in compression, probably due to interference of tensile fracture. Scanning electron microscopic investigation showed that the spacing between large-angle grain boundaries is about 10 μm rather than the reported value of 30 nm. Comparison with coarse grained and ultrafine grained Cu produced by equal channel angular pressing showed that the ED-Cu work hardens similarly to coarse grained Cu in contrast to ultrafine grained Cu which reaches its maximum deformation resistance within a small strain interval of 0.04 and has distinctly higher strain rate sensitivity of flow stress. The present results are consistent with the established knowledge that there is no softening by grain boundaries, e.g. due to Coble creep, near room temperature in Cu with grain sizes above 1 μm. The grain boundary effect observed in ultrafine grained Cu is interpreted in terms of modification of dislocation generation and dislocation annihilation by grain boundaries

  15. Chemical synthesis of Cu2Se nanoparticles at room temperature

    International Nuclear Information System (INIS)

    Rong, Fengxia; Bai, Yan; Chen, Tianfeng; Zheng, Wenjie

    2012-01-01

    Graphical abstract: The Cu 2 Se nanoparticles were synthesized by a simple and rapid method at room temperature. The TEM and SEM images show that the Cu 2 Se nanoparticles were spherical. Highlights: ► Cu 2 Se nanoparticles were synthesized by the reaction of nanoSe 0 sol with Cu + ions. ► The Cu 2 Se nanoparticles were spherical with cubic structure and well crystallized. ► Optical and electrochemical properties of Cu 2 Se nanoparticles were observed. ► The formation mechanism of Cu 2 Se nanoparticles was proposed. -- Abstract: A simple and rapid method has been developed to synthesize cuprous selenide (Cu 2 Se) nanoparticles by the reaction of selenium nanoparticles sol with copper sulfate solution containing ascorbic acid at room temperature. Cu 2 Se nanoparticles were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and energy dispersive X-ray analysis (EDX). The results indicated that Cu 2 Se nanoparticles were cubic crystal structure and spherical with the diameter about 75 nm. The ultraviolet–visible absorption spectrum (UV–vis) and cyclic voltammetry of Cu 2 Se nanoparticles were also investigated. The optical band gap energy of Cu 2 Se nanoparticles was 1.94 eV. On the basis of a series of experiments and characterizations, the formation mechanism of Cu 2 Se nanoparticles was discussed.

  16. Room-temperature atmospheric pressure plasma plume for biomedical applications

    International Nuclear Information System (INIS)

    Laroussi, M.; Lu, X.

    2005-01-01

    As low-temperature nonequilibrium plasmas come to play an increasing role in biomedical applications, reliable and user-friendly sources need to be developed. These plasma sources have to meet stringent requirements such as low temperature (at or near room temperature), no risk of arcing, operation at atmospheric pressure, preferably hand-held operation, low concentration of ozone generation, etc. In this letter, we present a device that meets exactly such requirements. This device is capable of generating a cold plasma plume several centimeters in length. It exhibits low power requirements as shown by its current-voltage characteristics. Using helium as a carrier gas, very little ozone is generated and the gas temperature, as measured by emission spectroscopy, remains at room temperature even after hours of operations. The plasma plume can be touched by bare hands and can be directed manually by a user to come in contact with delicate objects and materials including skin and dental gum without causing any heating or painful sensation

  17. Unconditional polarization qubit quantum memory at room temperature

    Science.gov (United States)

    Namazi, Mehdi; Kupchak, Connor; Jordaan, Bertus; Shahrokhshahi, Reihaneh; Figueroa, Eden

    2016-05-01

    The creation of global quantum key distribution and quantum communication networks requires multiple operational quantum memories. Achieving a considerable reduction in experimental and cost overhead in these implementations is thus a major challenge. Here we present a polarization qubit quantum memory fully-operational at 330K, an unheard frontier in the development of useful qubit quantum technology. This result is achieved through extensive study of how optical response of cold atomic medium is transformed by the motion of atoms at room temperature leading to an optimal characterization of room temperature quantum light-matter interfaces. Our quantum memory shows an average fidelity of 86.6 +/- 0.6% for optical pulses containing on average 1 photon per pulse, thereby defeating any classical strategy exploiting the non-unitary character of the memory efficiency. Our system significantly decreases the technological overhead required to achieve quantum memory operation and will serve as a building block for scalable and technologically simpler many-memory quantum machines. The work was supported by the US-Navy Office of Naval Research, Grant Number N00141410801 and the Simons Foundation, Grant Number SBF241180. B. J. acknowledges financial assistance of the National Research Foundation (NRF) of South Africa.

  18. Xenon Recovery at Room Temperature using Metal-Organic Frameworks

    Energy Technology Data Exchange (ETDEWEB)

    Elsaidi, Sameh K. [Physical and Computational Science Directorate, Pacific Northwest National Laboratory, Richland WA 99352 USA; Chemistry Department, Faculty of Science, Alexandria University, P. O. Box 426 Ibrahimia Alexandria 21321 Egypt; Ongari, Daniele [Laboratory of Molecular Simulation, Institut des Sciences et Ingeénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne (EPFL), Rue de l' Industrie 17 1951 Sion Valais Switzerland; Xu, Wenqian [X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne IL 60439 USA; Mohamed, Mona H. [Chemistry Department, Faculty of Science, Alexandria University, P. O. Box 426 Ibrahimia Alexandria 21321 Egypt; Haranczyk, Maciej [IMDEA Materials Institute, c/Eric Kandel 2 28906 Getafe, Madrid Spain; Thallapally, Praveen K. [Physical and Computational Science Directorate, Pacific Northwest National Laboratory, Richland WA 99352 USA

    2017-07-24

    Xenon is known to be a very efficient anesthetic gas but its cost prohibits the wider use in medical industry and other potential applications. It has been shown that Xe recovery and recycle from anesthetic gas mixture can significantly reduce its cost as anesthetic. The current technology uses series of adsorbent columns followed by low temperature distillation to recover Xe, which is expensive to use in medical facilities. Herein, we propose much efficient and simpler system to recover and recycle Xe from simulant exhale anesthetic gas mixture at room temperature using metal organic frameworks. Among the MOFs tested, PCN-12 exhibits unprecedented performance with high Xe capacity, Xe/O2, Xe/N2 and Xe/CO2 selectivity at room temperature. The in-situ synchrotron measurements suggest the Xe is occupied in the small pockets of PCN-12 compared to unsaturated metal centers (UMCs). Computational modeling of adsorption further supports our experimental observation of Xe binding sites in PCN-12.

  19. Room temperature ferromagnetism of nanocrystalline Nd1.90Ni0.10O3-δ

    Science.gov (United States)

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

    2018-05-01

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

  20. All-polymer bistable resistive memory device based on nanoscale phase-separated PCBM-ferroelectric blends

    KAUST Repository

    Khan, Yasser

    2012-11-21

    All polymer nonvolatile bistable memory devices are fabricated from blends of ferroelectric poly(vinylidenefluoride-trifluoroethylene (P(VDF-TrFE)) and n-type semiconducting [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). The nanoscale phase separated films consist of PCBM domains that extend from bottom to top electrode, surrounded by a ferroelectric P(VDF-TrFE) matrix. Highly conducting poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) polymer electrodes are used to engineer band offsets at the interfaces. The devices display resistive switching behavior due to modulation of this injection barrier. With careful optimization of the solvent and processing conditions, it is possible to spin cast very smooth blend films (Rrms ≈ 7.94 nm) and with good reproducibility. The devices exhibit high Ion/I off ratios (≈3 × 103), low read voltages (≈5 V), excellent dielectric response at high frequencies (Ïμr ≈ 8.3 at 1 MHz), and excellent retention characteristics up to 10 000 s. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Features of the low-frequency polarization response in the region of the ferroelectric phase transition in multiferroic TbMnO.sub.3./sub.

    Czech Academy of Sciences Publication Activity Database

    Trepakov, Vladimír; Kvyatkovskii, O.E.; Savinov, Maxim; Dejneka, Alexandr; Wang, X.; Cheong, S.W.

    2016-01-01

    Roč. 58, č. 10 (2016), s. 2021-2026 ISSN 1063-7834 Institutional support: RVO:68378271 Keywords : low-frequency * polarization response * ferroelectric, phase * transition * multiferroic * TbMnO 3 Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 0.860, year: 2016

  2. Ferroelectric properties and diffuse phase transition in (Pb,La)Zrsub(0.55)Tisub(0.45)O3 ceramics

    International Nuclear Information System (INIS)

    Wolters, M.

    1976-01-01

    A preparation technique for (Pb,La)Zrsub(0.55)Tisub(0.45)O 3 ceramics is described by which inhomogeneities are eliminated. Grain size effects are studied and ferroelectric-paraelectric phase-transitions are investigated by means of X-ray diffraction analysis and dielectric weak-field (permittivity) and high-field (dc bias and hysteresis) measurements

  3. Nanoscale organic ferroelectric resistive switches

    NARCIS (Netherlands)

    Khikhlovskyi, V.; Wang, R.; Breemen, A.J.J.M. van; Gelinck, G.H.; Janssen, R.A.J.; Kemerink, M.

    2014-01-01

    Organic ferroelectric resistive switches function by grace of nanoscale phase separation in a blend of a semiconducting and a ferroelectric polymer that is sandwiched between metallic electrodes. In this work, various scanning probe techniques are combined with numerical modeling to unravel their

  4. Mesoporous Structure Control of Silica in Room-Temperature Synthesis under Basic Conditions

    Directory of Open Access Journals (Sweden)

    Jeong Wook Seo

    2015-01-01

    Full Text Available Various types of mesoporous silica, such as continuous cubic-phase MCM-48, hexagonal-phase MCM-41, and layer-phase spherical silica particles, have been synthesized at room temperature using cetyltrimethylammonium bromide as a surfactant, ethanol as a cosurfactant, tetraethyl orthosilicate as a silica precursor, and ammonia as a condensation agent. Special care must be taken both in the filtering of the resultant solid products and in the drying process. In the drying process, further condensation of the silica after filtering was induced. As the surfactant and cosurfactant concentrations in the reaction mixture increased and the NH3 concentration decreased, under given conditions, continuous cubic MCM-48 and layered silica became the dominant phases. A cooperative synthesis mechanism, in which both the surfactant and silica were involved in the formation of mesoporous structures, provided a good explanation of the experimental results.

  5. Multiferroic tunnel junctions and ferroelectric control of magnetic state at interface (invited)

    KAUST Repository

    Yin, Y. W.

    2015-03-03

    As semiconductor devices reach ever smaller dimensions, the challenge of power dissipation and quantum effect place a serious limit on the future device scaling. Recently, a multiferroic tunnel junction (MFTJ) with a ferroelectric barrier sandwiched between two ferromagnetic electrodes has drawn enormous interest due to its potential applications not only in multi-level data storage but also in electric field controlled spintronics and nanoferronics. Here, we present our investigations on four-level resistance states, giant tunneling electroresistance (TER) due to interfacial magnetoelectric coupling, and ferroelectric control of spin polarized tunneling in MFTJs. Coexistence of large tunneling magnetoresistance and TER has been observed in manganite/(Ba, Sr)TiO3/manganite MFTJs at low temperatures and room temperature four-resistance state devices were also obtained. To enhance the TER for potential logic operation with a magnetic memory, La0.7Sr0.3MnO3/BaTiO3/La0.5Ca0.5MnO3 /La0.7Sr0.3MnO3 MFTJs were designed by utilizing a bilayer tunneling barrier in which BaTiO3 is ferroelectric and La0.5Ca0.5MnO3 is close to ferromagnetic metal to antiferromagnetic insulator phase transition. The phase transition occurs when the ferroelectric polarization is reversed, resulting in an increase of TER by two orders of magnitude. Tunneling magnetoresistance can also be controlled by the ferroelectric polarization reversal, indicating strong magnetoelectric coupling at the interface.

  6. Room temperature ferromagnetism in Mn-doped NiO nanoparticles

    Science.gov (United States)

    Layek, Samar; Verma, H. C.

    2016-01-01

    Mn-doped NiO nanoparticles of the series Ni1-xMnxO (x=0.00, 0.02, 0.04 and 0.06) are successfully synthesized using a low temperature hydrothermal method. Samples up to 6% Mn-doping are single phase in nature as observed from powder x-ray diffraction (XRD) studies. Rietveld refinement of the XRD data shows that all the single phase samples crystallize in the NaCl like fcc structure with space group Fm-3m. Unit cell volume decreases with increasing Mn-doping. Pure NiO nanoparticles show weak ferromagnetism, may be due to nanosize nature. Introduction of Mn within NiO lattice improves the magnetic properties significantly. Room temperature ferromagnetism is found in all the doped samples whereas the magnetization is highest for 2% Mn-doping and then decreases with further doping. The ZFC and FC branches in the temperature dependent magnetization separate well above 350 K indicating transition temperature well above room temperature for 2% Mn-doped NiO Nanoparticle. The ferromagnetic Curie temperature is found to be 653 K for the same sample as measured by temperature dependent magnetization study using vibrating sample magnetometer (VSM) in high vacuum.

  7. Room temperature ferromagnetism in Fe-doped CuO nanoparticles.

    Science.gov (United States)

    Layek, Samar; Verma, H C

    2013-03-01

    The pure and Fe-doped CuO nanoparticles of the series Cu(1-x)Fe(x)O (x = 0.00, 0.02, 0.04, 0.06 and 0.08) were successfully prepared by a simple low temperature sol-gel method using metal nitrates and citric acid. Rietveld refinement of the X-ray diffraction data showed that all the samples were single phase crystallized in monoclinic structure of space group C2/c with average crystallite size of about 25 nm and unit cell volume decreases with increasing iron doping concentration. TEM micrograph showed nearly spherical shaped agglomerated particles of 4% Fe-doped CuO with average diameter 26 nm. Pure CuO showed weak ferromagnetic behavior at room temperature with coercive field of 67 Oe. The ferromagnetic properties were greatly enhanced with Fe-doping in the CuO matrix. All the doped samples showed ferromagnetism at room temperature with a noticeable coercive field. Saturation magnetization increases with increasing Fe-doping, becomes highest for 4% doping then decreases for further doping which confirms that the ferromagnetism in these nanoparticles are intrinsic and are not resulting from any impurity phases. The ZFC and FC branches of the temperature dependent magnetization (measured in the range of 10-350 K by SQUID magnetometer) look like typical ferromagnetic nanoparticles and indicates that the ferromagnetic Curie temperature is above 350 K.

  8. Room temperature ferromagnetism in Eu-doped ZnO nanoparticulate powders prepared by combustion reaction method

    International Nuclear Information System (INIS)

    Franco, A.; Pessoni, H.V.S.; Soares, M.P.

    2014-01-01

    Nanoparticulate powders of Eu-doped ZnO with 1.0, 1.5, 2.0 and 3.0 at% Eu were synthesized by combustion reaction method using zinc nitrate, europium nitrate and urea as fuel without subsequent heat treatments. X-ray diffraction patterns (XRD) of all samples showed broad peaks consistent with the ZnO wurtzite structure. The absence of extra reflections in the diffraction patterns ensures the phase purity, except for x=0.03 that exhibits small reflection corresponding to Eu 2 O 3 phase. The average crystallite size determined from the most prominent (1 0 1) peak of the diffraction using Scherrer's equation was in good agreement with those determined by transmission electron microscopy (TEM); being ∼26 nm. The magnetic properties measurements were performed using a vibrating sample magnetometer (VSM) in magnetic fields up to 2.0 kOe at room temperature. The hysteresis loops, typical of magnetic behaviors, indicating that the presence of an ordered magnetic structure can exist in the Eu-doped ZnO wurtzite structure at room temperature. The room temperature ferromagnetism behavior increases with the Eu 3+ doping concentration. All samples exhibited the same Curie temperature (T C ) around ∼726 K, except for x=0.01; T C ∼643 K. High resolution transmission electron microscopy (HRTEM) images revealed defects/strain in the lattice and grain boundaries of Eu-doped ZnO nanoparticulate powders. The origin of room temperature ferromagnetism in Eu-doped ZnO nanoparticulate powders was discussed in terms of these defects, which increase with the Eu 3+ doping concentration. - Highlights: • Room-temperature ferromagnetism. • Structural and magnetic properties of nanoparticulate powders of Zn 1−x Eu x O. • Combustion reaction method

  9. Crystal structure, dielectric, ferroelectric and energy storage properties of La-doped BaTiO3 semiconducting ceramics

    Directory of Open Access Journals (Sweden)

    Venkata Sreenivas Puli

    2015-09-01

    Full Text Available Polycrystalline La-doped BaTiO3 (Ba(1-xLax\tTiO3 [x=0,0.0005,0.001,0.003] ceramics (denoted as BTO,BLT1,BLT2,BLT3 were synthesized by conventional solid-state reaction method and characterized by X-ray diffraction (XRD, scanning electron microscopy (SEM, and Raman spectroscopy. XRD and Raman spectra revealed single-phase tetragonal perovskite crystalline structure. Well-saturated polarization–electric field (P–E hysteresis loops were observed with the measurement frequency of 50 Hz at room temperature and confirmed ferroelectric nature of these ceramics and a high recoverable electrical energy storage density of 0.350 J/cm3 with energy efficiency (n∼9%, which is useful in energy storage capacitor applications. Dielectric studies revealed anomalies around 415–420 K and near the Curie temperature. The latter is attributed to the ferroelectric to paraelectric phase transition. Better dielectric performances were obtained for La-doped samples sintered at 1350°C for 4 h. Grain growth is inhibited with lanthanum (La incorporation into the BTO lattice. Room temperature semiconducting behavior with positive temperature coefficient of resistivity (PTCR behavior at TC is attributed to electron compensation mechanism.

  10. Electric-field-induced phase transitions in co-doped Pb(Zr1−xTixO3 at the morphotropic phase boundary

    Directory of Open Access Journals (Sweden)

    Daniel J Franzbach

    2014-02-01

    Full Text Available The strain- and polarization-electric field behavior was characterized at room temperature for Pb0.98Ba0.01(Zr1−xTix0.98Nb0.02O3, 0.40 ≤ x ≤ 0.60. The investigated compositions were located in the vicinity of the morphotropic phase boundary, giving insight into the influence of crystal structure on the hysteretic ferroelectric behavior. The remanent strain of particular compositions is shown to be larger than theoretically allowed by ferroelectric switching alone, indicating the presence of additional remanent strain mechanisms. A phenomenological free energy analysis was used to simulate the effect of an applied electric field on the initial equilibrium phase. It is shown that electric-field-induced phase transitions in polycrystalline ferroelectrics can account for the experimental observations. The experimental and simulation results are contrasted to neutron diffraction measurements performed on representative compositions in the virgin and remanent states.

  11. Stretchable microelectrode array using room-temperature liquid alloy interconnects

    International Nuclear Information System (INIS)

    Wei, P; Ziaie, B; Taylor, R; Chung, C; Higgs, G; Pruitt, B L; Ding, Z; Abilez, O J

    2011-01-01

    In this paper, we present a stretchable microelectrode array for studying cell behavior under mechanical strain. The electrode array consists of gold-plated nail-head pins (250 µm tip diameter) or tungsten micro-wires (25.4 µm in diameter) inserted into a polydimethylsiloxane (PDMS) platform (25.4 × 25.4 mm 2 ). Stretchable interconnects to the outside were provided by fusible indium-alloy-filled microchannels. The alloy is liquid at room temperature, thus providing the necessary stretchability and electrical conductivity. The electrode platform can withstand strains of up to 40% and repeated (100 times) strains of up to 35% did not cause any failure in the electrodes or the PDMS substrate. We confirmed biocompatibility of short-term culture, and using the gold pin device, we demonstrated electric field pacing of adult murine heart cells. Further, using the tungsten microelectrode device, we successfully measured depolarizations of differentiated murine heart cells from embryoid body clusters

  12. Room Temperature Anodization of Aluminum at Low Voltage

    International Nuclear Information System (INIS)

    Kamal, A.; Abdel-Karim, R.; El-Raghy, S.; EL-Sherif, R.M.; Wheed, A.

    2013-01-01

    Membranes with nanometer-scale features have many applications, such as in optics, electronics, catalysis, selective molecule separation, filtration and purification, bio sensing, and single-molecule detection. Anodization process was conducted using 15, 20, 30 and 35% by volume phosphoric acid. Results showed that Porous Anodized Aluminum (PAA) with ideal nano pore arrays can be fabricated at room temperature by one-step anodization on high purity aluminum foil at 5 V. Morphology of the PAA was characterized by scanning electron microscopy (SEM). The electrochemical behavior of anodized aluminum was studied in 0.1 M Na 2 SO 4 solutions using electrochemical impedance spectroscopy (EIS). The highest resistance of the porous layer (R p ) was detected for the samples anodized in 20% phosphoric acid

  13. Thermal power generation during heat cycle near room temperature

    Science.gov (United States)

    Shibata, Takayuki; Fukuzumi, Yuya; Kobayashi, Wataru; Moritomo, Yutaka

    2018-01-01

    We demonstrate that a sodium-ion secondary battery (SIB)-type thermocell consisting of two types of Prussian blue analogue (PBA) with different electrochemical thermoelectric coefficients (S EC ≡ ∂V/∂T V and T are the redox potential and temperature, respectively) produces electrical energy during heat cycles. The device produces an electrical energy of 2.3 meV/PBA per heat cycle between 295 K (= T L) and 323 K (= T H). The ideal thermal efficiency (η = 1.0%), which is evaluated using the heat capacity (C = 4.16 meV/K) of ideal Na2Co[Fe(CN)6], reaches 11% of the Carnot efficiency (ηth = 8.7%). Our SIB-type thermocell is a promising thermoelectric device that harvests waste heat near room temperature.

  14. Modification of embedded Cu nanoparticles: Ion irradiation at room temperature

    International Nuclear Information System (INIS)

    Johannessen, B.; Kluth, P.; Giulian, R.; Araujo, L.L.; Llewellyn, D.J.; Foran, G.J.; Cookson, D.J.; Ridgway, M.C.

    2007-01-01

    Cu nanoparticles (NPs) with an average diameter of ∼25 A were synthesized in SiO 2 by ion implantation and thermal annealing. Subsequently, the NPs were exposed to ion irradiation at room temperature simultaneously with a bulk Cu reference film. The ion species/energy was varied to achieve different values for the nuclear energy loss. The short-range atomic structure and average NP diameter were measured by means of extended X-ray absorption fine structure spectroscopy and small angle X-ray scattering, respectively. Transmission electron microscopy yielded complementary results. The short-range order of the Cu films remained unchanged consistent with the high regeneration rate of bulk elemental metals. For the NP samples it was found that increasing nuclear energy loss yielded gradual dissolution of NPs. Furthermore, an increased structural disorder was observed for the residual NPs

  15. Reversible temper brittleness on tensile tests at room temperature

    International Nuclear Information System (INIS)

    Quadros, N.F. de; Cabral, U.Q.

    1976-01-01

    Tensile tests were carried out on unnotched test pieces at room temperature and three strain rates: 2,5x10 -4 , 2,5x10 -3 and 1,0x10 -2 s -1 in a low alloy No-Cr-Mo steel to observe the variation in its mechanical properties with the occurrence of reversible temper brittleness. The brittle samples showed a sensitivity of 50 0 C in a 48 hour heat treatment at 500 0 C. The tests showed that at the strain rate of 2,5x10 -4 s -1 there are statistically significant differences between the elongations of the material in the brittle and the nonbrittle and regenerated states. A short review of reversible temper brittleness is given and a theory suggested for the mechanism [pt

  16. Room-temperature ferromagnetism in hydrogenated ZnO nanoparticles

    International Nuclear Information System (INIS)

    Xue, Xudong; Liu, Liangliang; Wang, Zhu; Wu, Yichu

    2014-01-01

    The effect of hydrogen doping on the magnetic properties of ZnO nanoparticles was investigated. Hydrogen was incorporated by annealing under 5% H 2 in Ar ambient at 700 °C. Room-temperature ferromagnetism was induced in hydrogenated ZnO nanoparticles, and the observed ferromagnetism could be switched between “on” and “off” states through hydrogen annealing and oxygen annealing process, respectively. It was found that Zn vacancy and OH bonding complex (V Zn  + OH) was crucial to the observed ferromagnetism by using the X-ray photoelectron spectroscopy and positron annihilation spectroscopy analysis. Based on first-principles calculations, V Zn  + OH was favorable to be presented due to the low formation energy. Meanwhile, this configuration could lead to a magnetic moment of 0.57 μ B . The Raman and photoluminescence measurements excluded the possibility of oxygen vacancy as the origin of the ferromagnetism

  17. Room-temperature ferromagnetism in hydrogenated ZnO nanoparticles

    Science.gov (United States)

    Xue, Xudong; Liu, Liangliang; Wang, Zhu; Wu, Yichu

    2014-01-01

    The effect of hydrogen doping on the magnetic properties of ZnO nanoparticles was investigated. Hydrogen was incorporated by annealing under 5% H2 in Ar ambient at 700 °C. Room-temperature ferromagnetism was induced in hydrogenated ZnO nanoparticles, and the observed ferromagnetism could be switched between "on" and "off" states through hydrogen annealing and oxygen annealing process, respectively. It was found that Zn vacancy and OH bonding complex (VZn + OH) was crucial to the observed ferromagnetism by using the X-ray photoelectron spectroscopy and positron annihilation spectroscopy analysis. Based on first-principles calculations, VZn + OH was favorable to be presented due to the low formation energy. Meanwhile, this configuration could lead to a magnetic moment of 0.57 μB. The Raman and photoluminescence measurements excluded the possibility of oxygen vacancy as the origin of the ferromagnetism.

  18. Energy-filtered cold electron transport at room temperature.

    Science.gov (United States)

    Bhadrachalam, Pradeep; Subramanian, Ramkumar; Ray, Vishva; Ma, Liang-Chieh; Wang, Weichao; Kim, Jiyoung; Cho, Kyeongjae; Koh, Seong Jin

    2014-09-10

    Fermi-Dirac electron thermal excitation is an intrinsic phenomenon that limits functionality of various electron systems. Efforts to manipulate electron thermal excitation have been successful when the entire system is cooled to cryogenic temperatures, typically distribution corresponds to an effective electron temperature of ~45 K, can be transported throughout device components without external cooling. This is accomplished using a discrete level of a quantum well, which filters out thermally excited electrons and permits only energy-suppressed electrons to participate in electron transport. The quantum well (~2 nm of Cr2O3) is formed between source (Cr) and tunnelling barrier (SiO2) in a double-barrier-tunnelling-junction structure having a quantum dot as the central island. Cold electron transport is detected from extremely narrow differential conductance peaks in electron tunnelling through CdSe quantum dots, with full widths at half maximum of only ~15 mV at room temperature.

  19. Thermal investigations of a room temperature magnetic refrigerator

    Energy Technology Data Exchange (ETDEWEB)

    Smaili, Arezki; Chiba, Younes [Ecole Nationale Polytechnique d' Alger (Algeria)], email: arezki.smaili@enp.edu.dz

    2011-07-01

    Magnetic refrigeration is a concept based on the magnetocaloric effect that some materials exhibit when the external magnetic field changes. The aim of this paper is to assess the performance of a numerical model in predicting parameters of an active magnetic regenerator refrigerator. Numerical simulations were conducted to perform a thermal analysis on an active magnetic regenerator refrigerator operating near room temperature with and without applied cooling load. Curves of temperature span, cooling capacity and thermal efficiency as functions of the operating conditions were drawn and are presented in this paper. Results showed that at fixed frequency Ql versus mf has an optimum and COP was increased with cycle frequency values. This study demonstrated that the proposed numerical model could be used to predict parameters of an active magnetic regenerator refrigerator as it provides consistent results.

  20. Electromagnon Resonance at Room Temperature with Gigantic Magnetochromism

    Science.gov (United States)

    Shishikura, H.; Tokunaga, Y.; Takahashi, Y.; Masuda, R.; Taguchi, Y.; Kaneko, Y.; Tokura, Y.

    2018-04-01

    The elementary excitation characteristic of magnetoelectric (ME) multiferroics is a magnon endowed with electric activity, which is referred to as an electromagnon. The electromagnon resonance mediated by the bilinear exchange coupling potentially exhibits strong terahertz light-matter interaction with optical properties different from the conventional magnon excitation. Here we report the robust electromagnon resonance on helimagnetic Y -type hexaferrites in a wide temperature range including room temperature. Furthermore, the efficient magnetic field controls of the electromagnon are demonstrated on the flexible spin structure of these compounds, leading to the generation or annihilation of the resonance as well as the large resonance energy shift. These terahertz characteristics of the electromagnon exemplify the versatile magneto-optical functionality driven by the ME coupling in multiferroics, paving a way for possible terahertz applications as well as terahertz control of a magnetic state of matter.

  1. Towards room temperature, direct, solvent free synthesis of tetraborohydrides

    International Nuclear Information System (INIS)

    Remhof, A; Yan, Y; Friedrichs, O; Kim, J W; Mauron, Ph; Borgschulte, A; Züttel, A; Wallacher, D; Buchsteiner, A; Hoser, A; Oh, K H; Cho, Y W

    2012-01-01

    Due to their high hydrogen content, tetraborohydrides are discussed as potential synthetic energy carriers. On the example of lithium borohydride LiBH 4 , we discuss current approaches of direct, solvent free synthesis based on gas solid reactions of the elements or binary hydrides and/or borides with gaseous H 2 or B 2 H 6 . The direct synthesis from the elements requires high temperature and high pressure (700°C, 150bar D 2 ). Using LiB or AlB 2 as boron source reduces the required temperature by more than 300 K. Reactive milling of LiD with B 2 H 6 leads to the formation of LiBD 4 already at room temperature. The reactive milling technique can also be applied to synthesize other borohydrides from their respective metal hydrides.

  2. Ratcheting tests on stainless steel 316 L at room temperature

    International Nuclear Information System (INIS)

    Cousseran, Pierre; Lebey, Jacques; Roche, Roland; Corbel, P.

    1980-06-01

    An experimental study on progressive distortion (tension-torsion) of simple structures (thin tubes) has been undertaken at the CEA. Results of tests performed on 316 L steel at room temperature are reported in this paper. There are chiefly: - plastic iso-deformation curves in the field of the 2 loadings applied to the specimen, i.e. the constant primary loading P (tension) and the secondary loading ΔQ (cyclic torsion at controled deformation); - indications on the evolution of torque and of torsion plastic deformation, during the cycling; - a convenient rule for evaluation of the progressive distortion is proposed. It is based on the use of an effective stress Psub(eff), which is determined from the tensile characteristics of the material, of when creep occurs, from creep curves [fr

  3. Room-temperature ferromagnetism in cerium dioxide powders

    Energy Technology Data Exchange (ETDEWEB)

    Rakhmatullin, R. M., E-mail: rrakhmat@kpfu.ru; Pavlov, V. V.; Semashko, V. V.; Korableva, S. L. [Kazan Federal University, Institute of Physics (Russian Federation)

    2015-08-15

    Room-temperature ferromagnetism is detected in a CeO{sub 2} powder with a grain size of about 35 nm and a low (<0.1 at %) manganese and iron content. The ferromagnetism in a CeO{sub 2} sample with a submicron crystallite size and the same manganese and iron impurity content is lower than in the nanocrystalline sample by an order of magnitude. Apart from ferromagnetism, both samples exhibit EPR spectra of localized paramagnetic centers, the concentration of which is lower than 0.01 at %. A comparative analysis of these results shows that the F-center exchange (FCE) mechanism cannot cause ferromagnetism. This conclusion agrees with the charge-transfer ferromagnetism model proposed recently.

  4. Field Effect Devices Sensitive to CO at Room Temperature

    Directory of Open Access Journals (Sweden)

    Ricardo ARAG?N

    2014-10-01

    Full Text Available [5,10,15-Tris(2,6-dichlorophenylcorrolate] cobalt(III was used to chemisorb CO selectively, on the gap-gate of MOS capacitors and the state of charge monitored by voltage shifts of the photocurrent induced by pulsed illumination under constant D. C. bias, proportionally to CO concentration in air. Negative chemically induced charges at room temperature induce positive responses above and negative shifts below the threshold voltage, conforming to acceptor behavior, and the dynamic range (125 ppm is limited by the silicon doping concentration. The linear proportionality between CO concentration and surface charge (6.46[ppm.m2.µC-1] corresponds to the low concentration limit of the Langmuir isotherm. Sluggish CO desorption can be compensated by photo stimulation at 395 nm.

  5. Stable room-temperature thallium bromide semiconductor radiation detectors

    Science.gov (United States)

    Datta, A.; Fiala, J.; Becla, P.; Motakef, Shariar

    2017-10-01

    Thallium bromide (TlBr) is a highly efficient ionic semiconductor with excellent radiation detection properties. However, at room temperature, TlBr devices polarize under an applied electric field. This phenomenon not only degrades the charge collection efficiency of the detectors but also promotes chemical reaction of the metal electrodes with bromine, resulting in an unstable electric field and premature failure of the device. This drawback has been crippling the TlBr semiconductor radiation detector technology over the past few decades. In this exhaustive study, this polarization phenomenon has been counteracted using innovative bias polarity switching schemes. Here the highly mobile Br- species, with an estimated electro-diffusion velocity of 10-8 cm/s, face opposing electro-migration forces during every polarity switch. This minimizes the device polarization and availability of Br- ions near the metal electrode. Our results indicate that it is possible to achieve longer device lifetimes spanning more than 17 000 h (five years of 8 × 7 operation) for planar and pixelated radiation detectors using this technique. On the other hand, at constant bias, 2500 h is the longest reported lifetime with most devices less than 1000 h. After testing several biasing switching schemes, it is concluded that the critical bias switching frequency at an applied bias of 1000 V/cm is about 17 μHz. Using this groundbreaking result, it will now be possible to deploy this highly efficient room temperature semiconductor material for field applications in homeland security, medical imaging, and physics research.

  6. Stable room-temperature thallium bromide semiconductor radiation detectors

    Directory of Open Access Journals (Sweden)

    A. Datta

    2017-10-01

    Full Text Available Thallium bromide (TlBr is a highly efficient ionic semiconductor with excellent radiation detection properties. However, at room temperature, TlBr devices polarize under an applied electric field. This phenomenon not only degrades the charge collection efficiency of the detectors but also promotes chemical reaction of the metal electrodes with bromine, resulting in an unstable electric field and premature failure of the device. This drawback has been crippling the TlBr semiconductor radiation detector technology over the past few decades. In this exhaustive study, this polarization phenomenon has been counteracted using innovative bias polarity switching schemes. Here the highly mobile Br− species, with an estimated electro-diffusion velocity of 10−8 cm/s, face opposing electro-migration forces during every polarity switch. This minimizes the device polarization and availability of Br− ions near the metal electrode. Our results indicate that it is possible to achieve longer device lifetimes spanning more than 17 000 h (five years of 8 × 7 operation for planar and pixelated radiation detectors using this technique. On the other hand, at constant bias, 2500 h is the longest reported lifetime with most devices less than 1000 h. After testing several biasing switching schemes, it is concluded that the critical bias switching frequency at an applied bias of 1000 V/cm is about 17 μHz. Using this groundbreaking result, it will now be possible to deploy this highly efficient room temperature semiconductor material for field applications in homeland security, medical imaging, and physics research.

  7. Synthesis and ferroelectric properties of rare earth compounds with tungsten bronze-type structure

    Energy Technology Data Exchange (ETDEWEB)

    Bouziane, M., E-mail: bouzianemeryem@yahoo.fr [Laboratoire de Chimie du Solide Appliquee, Faculte des Sciences, Avenue Ibn Batouta, BP 1014, Rabat (Morocco); Taibi, M. [Laboratoire de Physico-Chimie des Materiaux, LAF 502, Ecole Normale Superieure, BP 5118, Rabat (Morocco); Boukhari, A. [Laboratoire de Chimie du Solide Appliquee, Faculte des Sciences, Avenue Ibn Batouta, BP 1014, Rabat (Morocco)

    2011-10-03

    Highlights: {center_dot} Polycrystalline materials with the tungsten bronze-type structure have been synthesized and characterized. {center_dot} Effect of the incorporation of rare earth ions and paramagnetic cations (Fe{sup 3+}) into a matrix ferroelectrically active was studied. {center_dot} Ferroelectric transition is pronounced by a large thermal hysteresis during the heating and cooling cycles. {center_dot} Phase transitions around T{sub c} were confirmed by differential scanning calorimetry (DSC) measurements. - Abstract: Polycrystalline materials with a general formula Pb{sub 2}Na{sub 0.8}R{sub 0.2}Nb{sub 4.8}Fe{sub 0.2}O{sub 15} (R = Dy, Eu, Sm, Nd, La) have been synthesized, in air by a high temperature solid state reaction method. X-ray diffraction study, at room temperature, revealed that they crystallize in the tungsten bronze-type structure. Dielectric properties were performed, in the temperature range 25-500 deg. C, at three different frequencies 10, 100 and 1000 kHz. The ferroelectric transition is pronounced by a large thermal hysteresis during the heating and cooling cycles. The determined Curie temperature values T{sub c} were discussed as a function of rare earth size. Phase transitions around T{sub c} for the investigated compounds were confirmed by differential scanning calorimetry (DSC) measurements.

  8. Predicting the effective response of bulk polycrystalline ferroelectric ceramics via improved spectral phase field methods

    Science.gov (United States)

    Vidyasagar, A.; Tan, W. L.; Kochmann, D. M.

    2017-09-01

    Understanding the electromechanical response of bulk polycrystalline ferroelectric ceramics requires scale-bridging approaches. Recent advances in fast numerical methods to compute the homogenized mechanical response of materials with heterogeneous microstructure have enabled the solution of hitherto intractable systems. In particular, the use of a Fourier-based spectral method as opposed to the traditional finite element method has gained significant interest in the homogenization of periodic microstructures. Here, we solve the periodic, electro-mechanically-coupled boundary value problem at the mesoscale of polycrystalline ferroelectrics in order to extract the effective response of barium titanate (BaTiO3) and lead zirconate titanate (PZT) under applied electric fields. Results include the effective electric hysteresis and the associated butterfly curve of strain vs. electric field for mean stress-free electric loading. Computational predictions of the 3D polycrystalline response show convincing agreement with our experimental electric cycling and strain hysteresis data for PZT-5A. In addition to microstructure-dependent effective physics, we also show how finite-difference-based approximations in the spectral solution scheme significantly reduce instability and ringing phenomena associated with spectral techniques and lead to spatial convergence with h-refinement, which have been major challenges when modeling high-contrast systems such as polycrystals.

  9. Synthesis of Eu3+-doped calcium and strontium carbonate phosphors at room temperature

    International Nuclear Information System (INIS)

    Pan Yuexiao; Wu Mingmei; Su Qiang

    2003-01-01

    Red phosphors CaCO 3 :Eu 3+ and SrCO 3 :Eu 3+ have been prepared by co-precipitation with ammonium bicarbonate (NH 4 HCO 3 ) at room temperature. Pure calcite CaCO 3 can be obtained by prolonging the reaction time at 220 deg. C and it decomposes to cubic CaO at 1000 deg. C. Trivalent Eu 3+ acts as a luminescent probe to determine both the calcite and the mixed phase of calcite and vaterite phase of CaCO 3 host and to analyze its decomposition process. High temperature sintering improved both the crystallization and luminescence of SrCO 3 :Eu 3+ in aragonite phase

  10. Hole-transporting transistors and circuits based on the transparent inorganic semiconductor copper(I) thiocyanate (CuSCN) processed from solution at room temperature

    KAUST Repository

    Pattanasattayavong, Pichaya

    2012-12-27

    The wide bandgap and highly transparent inorganic compound copper(I) thiocyanate (CuSCN) is used for the first time to fabricate p-type thin-film transistors processed from solution at room temperature. By combining CuSCN with the high-k relaxor ferroelectric polymeric dielectric P(VDF-TrFE-CFE), we demonstrate low-voltage transistors with hole mobilities on the order of 0.1 cm2 V-1 s-1. By integrating two CuSCN transistors, unipolar logic NOT gates are also demonstrated. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Nonsymmorphic cubic Dirac point and crossed nodal rings across the ferroelectric phase transition in LiOsO3

    Science.gov (United States)

    Yu, Wing Chi; Zhou, Xiaoting; Chuang, Feng-Chuan; Yang, Shengyuan A.; Lin, Hsin; Bansil, Arun

    2018-05-01

    Crystalline symmetries can generate exotic band-crossing features, which can lead to unconventional fermionic excitations with interesting physical properties. We show how a cubic Dirac point—a fourfold-degenerate band-crossing point with cubic dispersion in a plane and a linear dispersion in the third direction—can be stabilized through the presence of a nonsymmorphic glide mirror symmetry in the space group of the crystal. Notably, the cubic Dirac point in our case appears on a threefold axis, even though it has been believed previously that such a point can only appear on a sixfold axis. We show that a cubic Dirac point involving a threefold axis can be realized close to the Fermi level in the nonferroelectric phase of LiOsO3. Upon lowering temperature, LiOsO3 has been shown experimentally to undergo a structural phase transition from the nonferroelectric phase to the ferroelectric phase with spontaneously broken inversion symmetry. Remarkably, we find that the broken symmetry transforms the cubic Dirac point into three mutually crossed nodal rings. There also exist several linear Dirac points in the low-energy band structure of LiOsO3, each of which is transformed into a single nodal ring across the phase transition.

  12. Ferroelectric and octahedral tilt twin disorder and the lead-free piezoelectric, sodium potassium niobate system

    International Nuclear Information System (INIS)

    Schiemer, Jason; Withers, Ray L.; Liu, Yun; Yi, Zhiguo

    2012-01-01

    Using electron diffraction, trends in the local structural behaviour of the K x Na 1−x NbO 3 (KNN x) ‘solid solution’ system are investigated and interpreted using an order/disorder based theoretical framework. At room temperature, electron diffraction shows a single plane of transverse polarised, diffuse intensity perpendicular to [0 1 0] p ⁎ (p for parent sub-structure) across the entire phase diagram, indicative of ferroelectric disorder along the [0 1 0] p direction co-existing with long range ferroelectric order along the orthogonal [1 0 0] p and [0 0 1] p directions. An additional characteristic pattern of diffuse scattering is also observed, involving rods of diffuse intensity running along the [1 0 0] p * and [0 0 1] p * directions of the perovskite sub-structure and indicative of octahedral tilt disorder about the [1 0 0] p and [0 0 1] p axes co-existing with long range ordered octahedral tilting around the [0 1 0] p direction. A possible crystal chemical explanation for the existence of this latter octahedral tilt disorder is explored through bond valence sum calculations. The possible influence of both types of disorder on the previously refined, room temperature space group/s and average crystal structure/s is examined. - Graphical abstract: [−3,0.−1]p zone axis EDP of K 0.46 Na 0.54 NbO 3 indexed according to both the relevant Pcm21 space groups (no subscripts) and the parent perovskite subcell (denoted by a subscript p). Highlights: ► Characterises ferroelectric and octahedral tilt disorder in the KNN solid solution. ► Discusses the possible driving forces for this disorder. ► Discusses the implications of this disorder for physical properties. ► Discusses the effects of this disorder on powder diffraction data.

  13. Fabrication and Microstructure of Hydroxyapatite Coatings on Zirconia by Room Temperature Spray Process.

    Science.gov (United States)

    Seo, Dong Seok; Chae, Hak Cheol; Lee, Jong Kook

    2015-08-01

    Hydroxyapatite coatings were fabricated on zirconia substrates by a room temperature spray process and were investigated with regards to their microstructure, composition and dissolution in water. An initial hydroxyapatite powder was prepared by heat treatment of bovine-bone derived powder at 1100 °C for 2 h, while dense zirconia substrates were fabricated by pressing 3Y-TZP powder and sintering it at 1350 °C for 2 h. Room temperature spray coating was performed using a slit nozzle in a low pressure-chamber with a controlled coating time. The phase composition of the resultant hydroxyapatite coatings was similar to that of the starting powder, however, the grain size of the hydroxyapatite particles was reduced to about 100 nm due to their formation by particle impaction and fracture. All areas of the coating had a similar morphology, consisting of reticulated structure with a high surface roughness. The hydroxyapatite coating layer exhibited biostability in a stimulated body fluid, with no severe dissolution being observed during in vitro experimentation.

  14. Room-temperature InP/InAsP Quantum Discs-in-Nanowire Infrared Photodetectors.

    Science.gov (United States)

    Karimi, Mohammad; Jain, Vishal; Heurlin, Magnus; Nowzari, Ali; Hussain, Laiq; Lindgren, David; Stehr, Jan Eric; Buyanova, Irina A; Gustafsson, Anders; Samuelson, Lars; Borgström, Magnus T; Pettersson, Håkan

    2017-06-14

    The possibility to engineer nanowire heterostructures with large bandgap variations is particularly interesting for technologically important broadband photodetector applications. Here we report on a combined study of design, fabrication, and optoelectronic properties of infrared photodetectors comprising four million n + -i-n + InP nanowires periodically ordered in arrays. The nanowires were grown by metal-organic vapor phase epitaxy on InP substrates, with either a single or 20 InAsP quantum discs embedded in the i-segment. By Zn compensation of the residual n-dopants in the i-segment, the room-temperature dark current is strongly suppressed to a level of pA/NW at 1 V bias. The low dark current is manifested in the spectrally resolved photocurrent measurements, which reveal strong photocurrent contributions from the InAsP quantum discs at room temperature with a threshold wavelength of about 2.0 μm and a bias-tunable responsivity reaching 7 A/W@1.38 μm at 2 V bias. Two different processing schemes were implemented to study the effects of radial self-gating in the nanowires induced by the nanowire/SiO x /ITO wrap-gate geometry. Summarized, our results show that properly designed axial InP/InAsP nanowire heterostructures are promising candidates for broadband photodetectors.

  15. Quantum Correlations of Light from a Room-Temperature Mechanical Oscillator

    Science.gov (United States)

    Sudhir, V.; Schilling, R.; Fedorov, S. A.; Schütz, H.; Wilson, D. J.; Kippenberg, T. J.

    2017-07-01

    When an optical field is reflected from a compliant mirror, its intensity and phase become quantum-correlated due to radiation pressure. These correlations form a valuable resource: the mirror may be viewed as an effective Kerr medium generating squeezed states of light, or the correlations may be used to erase backaction from an interferometric measurement of the mirror's position. To date, optomechanical quantum correlations have been observed in only a handful of cryogenic experiments, owing to the challenge of distilling them from thermomechanical noise. Accessing them at room temperature, however, would significantly extend their practical impact, with applications ranging from gravitational wave detection to chip-scale accelerometry. Here, we observe broadband quantum correlations developed in an optical field due to its interaction with a room-temperature nanomechanical oscillator, taking advantage of its high-cooperativity near-field coupling to an optical microcavity. The correlations manifest as a reduction in the fluctuations of a rotated quadrature of the field, in a frequency window spanning more than an octave below mechanical resonance. This is due to coherent cancellation of the two sources of quantum noise contaminating the measured quadrature—backaction and imprecision. Supplanting the backaction force with an off-resonant test force, we demonstrate the working principle behind a quantum-enhanced "variational" force measurement.

  16. Room temperature creep behavior of Ti–Nb–Ta–Zr–O alloy

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Wei-dong [State Key Laboratory of Powder Metallurgy, Central South University, Changsha, Hunan 410083 (China); Liu, Yong, E-mail: yonliu@csu.edu.cn [State Key Laboratory of Powder Metallurgy, Central South University, Changsha, Hunan 410083 (China); Wu, Hong; Lan, Xiao-dong [State Key Laboratory of Powder Metallurgy, Central South University, Changsha, Hunan 410083 (China); Qiu, Jingwen [College of Electrical and Mechanical Engineering, Hunan University of Science and Technology, Xiangtan, Hunan 411201 (China); Hu, Te [State Key Laboratory of Powder Metallurgy, Central South University, Changsha, Hunan 410083 (China); Tang, Hui-ping [State Key Laboratory of Porous Metal Materials, Northwestern Institute of Nonferrous Metal Research, Xi' an, Shaanxi 710012 (China)

    2016-08-15

    The room temperature creep behavior and deformation mechanisms of a Ti–Nb–Ta–Zr–O alloy, which is also called “gum metal”, were investigated with the nanoindentation creep and conventional creep tests. The microstructure was observed with electron backscattered diffraction analysis (EBSD) and transmission electron microscopy (TEM). The results show that the creep stress exponent of the alloy is sensitive to cold deformation history of the alloy. The alloy which was cold swaged by 85% shows high creep resistance and the stress exponent is approximately equal to 1. Microstructural observation shows that creep process of the alloy without cold deformation is controlled by dislocation mechanism. The stress-induced α' martensitic phase transformation also occurs. The EBSD results show that the grain orientation changes after the creep tests, and thus, the creep of the cold-worked alloy is dominated by the shear deformation of giant faults without direct assistance from dislocations. - Highlights: •Nanoindentation was used to investigate room temperature creep behavior of gum metal. •The creep stress exponent of gum metal is sensitive to the cold deformation history. •The creep stress exponent of cold worked gum metal is approximately equal to 1. •The creep of the cold-worked gum metal is governed by the shear deformation of giant faults.

  17. Observation of paramorphic phenomenon and non-tilted orthogonal smectic phases in hydrogen bonded ferroelectric liquid crystals for photonic applications

    Science.gov (United States)

    Subhasri, P.; Venugopal, D.; Jayaprakasam, R.; Chitravel, T.; Vijayakumar, V. N.

    2018-06-01

    A new class of hydrogen bonded ferroelectric liquid crystals (HBFLC) have been designed and synthesized by intermolecular hydrogen bonds between mesogenic 4-decyloxybenzoic acid (10OBA) and non-mesogenic (R)-(+)-Methylsuccinic acid (MSA) which have been confirmed through experimental and theoretical studies. Further, Mulliken population analysis clearly reveals that the existence of hydrogen bonds, strength and dynamic properties. Textural observation and its corresponding enthalpy values are analyzed by polarizing optical microscope (POM) and differential scanning calorimetry (DSC) respectively. Paramorphic changes in Sm C* phase due to the change of refractive index, which clearly reveal that the complex could be used for filtering action in photonic devices. The transition from lone pair to π* with large stabilization energy evidently exposes the chiral phases in the present HBFLC complex. Intermolecular interaction is analyzed by using natural bond orbital (NBO) studies. The highest energy in the HOMO-LUMO shows the stable phase in the HBFLC complex. Molecular structure of the HBFLC complex possesses the monoclinic which has been evinced through x-ray analysis. The randomly oriented bunch of homogeneous molecules in Sm A* phase of the HBFLC complex is reported.

  18. Influence of Starting Powders on Hydroxyapatite Coatings Fabricated by Room Temperature Spraying Method.

    Science.gov (United States)

    Seo, Dong Seok; Lee, Jong Kook; Hwang, Kyu Hong; Hahn, Byung Dong; Yoon, Seog Young

    2015-08-01

    Three types of raw materials were used for the fabrication of hydroxyapatite coatings by using the room temperature spraying method and their influence on the microstructure and in vitro characteristics were investigated. Starting hydroxyapatite powders for coatings on titanium substrate were prepared by a heat treatment at 1100 °C for 2 h of bovine bone, bone ash, and commercial hydroxyapatite powders. The phase compositions and Ca/P ratios of the three hydroxyapatite coatings were similar to those of the raw materials without decomposition or formation of a new phase. All hydroxyapatite coatings showed a honeycomb structure, but their surface microstructures revealed different features in regards to surface morphology and roughness, based on the staring materials. All coatings consisted of nano-sized grains and had dense microstructure. Inferred from in vitro experiments in pure water, all coatings have a good dissolution-resistance and biostability in water.

  19. Rapidly reversible redox transformation in nanophase manganese oxides at room temperature triggered by changes in hydration.

    Science.gov (United States)

    Birkner, Nancy; Navrotsky, Alexandra

    2014-04-29

    Chemisorption of water onto anhydrous nanophase manganese oxide surfaces promotes rapidly reversible redox phase changes as confirmed by calorimetry, X-ray diffraction, and titration for manganese average oxidation state. Surface reduction of bixbyite (Mn2O3) to hausmannite (Mn3O4) occurs in nanoparticles under conditions where no such reactions are seen or expected on grounds of bulk thermodynamics in coarse-grained materials. Additionally, transformation does not occur on nanosurfaces passivated by at least 2% coverage of what is likely an amorphous manganese oxide layer. The transformation is due to thermodynamic control arising from differences in surface energies of the two phases (Mn2O3 and Mn3O4) under wet and dry conditions. Such reversible and rapid transformation near room temperature may affect the behavior of manganese oxides in technological applications and in geologic and environmental settings.

  20. Method for stabilizing low-level mixed wastes at room temperature

    Science.gov (United States)

    Wagh, Arun S.; Singh, Dileep

    1997-01-01

    A method to stabilize solid and liquid waste at room temperature is provided comprising combining solid waste with a starter oxide to obtain a powder, contacting the powder with an acid solution to create a slurry, said acid solution containing the liquid waste, shaping the now-mixed slurry into a predetermined form, and allowing the now-formed slurry to set. The invention also provides for a method to encapsulate and stabilize waste containing cesium comprising combining the waste with Zr(OH).sub.4 to create a solid-phase mixture, mixing phosphoric acid with the solid-phase mixture to create a slurry, subjecting the slurry to pressure; and allowing the now pressurized slurry to set. Lastly, the invention provides for a method to stabilize liquid waste, comprising supplying a powder containing magnesium, sodium and phosphate in predetermined proportions, mixing said powder with the liquid waste, such as tritium, and allowing the resulting slurry to set.

  1. Nuclear Fuel Fretting Mechanisms in a Room Temperature Unlubricated Condition

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Young Ho; Kim, Hyung Kyu [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2008-10-15

    Recently, efforts for evaluating the fretting wear mechanism have been carried out by many researchers in various conditions. In an unlubricated condition, especially, effects of a wear debris and/or its layer on the fretting wear behavior were proposed that the formation of a well-developed glaze layer has a beneficial effect for decreasing a friction coefficient. Otherwise, a wear rate was accelerated by a third-body abrasion. At this time, it is well known that wear debris behaviors are affected by test variables such as a temperature, environment, material characteristics, etc. In a nuclear fuel fretting, however, its contact condition is quite different when compared with general fretting wear studies and could be summarized as the following; first, a fuel rod is supported by spacer grid springs and dimples that were elastically deformable. This results in a unique friction loop and a different fretting mechanism when a fuel rod is vibrated due to a flow-induced vibration (FIV). Next, it is possible that some region of the wear scar area with a specific spring shape condition could be hidden due to different wear debris behavior. So, some of the wear debris layers could be found on the worn surfaces in previous studies even though fretting wear tests were performed in a water lubricated condition. Finally, initial contact condition could be changed both an actual operating condition in power plants (i.e. high temperature and pressurized water (HTHP) under severe irradiation conditions) and the fretting wear tests for evaluating the wear resistant spring in lab conditions (i.e. from room temperature to HTHP without irradiation conditions) due to material degradations and the formation of the wear scar, respectively. In summary, the spring shape effect and the variation of the contact condition with increasing fretting cycle should be evaluated in order to improve the wear resistance of the spacer grid spring. So, in this study, fretting wear tests have been

  2. Structure of photosystem II and substrate binding at room temperature.

    Science.gov (United States)

    Young, Iris D; Ibrahim, Mohamed; Chatterjee, Ruchira; Gul, Sheraz; Fuller, Franklin; Koroidov, Sergey; Brewster, Aaron S; Tran, Rosalie; Alonso-Mori, Roberto; Kroll, Thomas; Michels-Clark, Tara; Laksmono, Hartawan; Sierra, Raymond G; Stan, Claudiu A; Hussein, Rana; Zhang, Miao; Douthit, Lacey; Kubin, Markus; de Lichtenberg, Casper; Long Vo, Pham; Nilsson, Håkan; Cheah, Mun Hon; Shevela, Dmitriy; Saracini, Claudio; Bean, Mackenzie A; Seuffert, Ina; Sokaras, Dimosthenis; Weng, Tsu-Chien; Pastor, Ernest; Weninger, Clemens; Fransson, Thomas; Lassalle, Louise; Bräuer, Philipp; Aller, Pierre; Docker, Peter T; Andi, Babak; Orville, Allen M; Glownia, James M; Nelson, Silke; Sikorski, Marcin; Zhu, Diling; Hunter, Mark S; Lane, Thomas J; Aquila, Andy; Koglin, Jason E; Robinson, Joseph; Liang, Mengning; Boutet, Sébastien; Lyubimov, Artem Y; Uervirojnangkoorn, Monarin; Moriarty, Nigel W; Liebschner, Dorothee; Afonine, Pavel V; Waterman, David G; Evans, Gwyndaf; Wernet, Philippe; Dobbek, Holger; Weis, William I; Brunger, Axel T; Zwart, Petrus H; Adams, Paul D; Zouni, Athina; Messinger, Johannes; Bergmann, Uwe; Sauter, Nicholas K; Kern, Jan; Yachandra, Vittal K; Yano, Junko

    2016-12-15

    Light-induced oxidation of water by photosystem II (PS II) in plants, algae and cyanobacteria has generated most of the dioxygen in the atmosphere. PS II, a membrane-bound multi-subunit pigment protein complex, couples the one-electron photochemistry at the reaction centre with the four-electron redox chemistry of water oxidation at the Mn 4 CaO 5 cluster in the oxygen-evolving complex (OEC). Under illumination, the OEC cycles through five intermediate S-states (S 0 to S 4 ), in which S 1 is the dark-stable state and S 3 is the last semi-stable state before O-O bond formation and O 2 evolution. A detailed understanding of the O-O bond formation mechanism remains a challenge, and will require elucidation of both the structures of the OEC in the different S-states and the binding of the two substrate waters to the catalytic site. Here we report the use of femtosecond pulses from an X-ray free electron laser (XFEL) to obtain damage-free, room temperature structures of dark-adapted (S 1 ), two-flash illuminated (2F; S 3 -enriched), and ammonia-bound two-flash illuminated (2F-NH 3 ; S 3 -enriched) PS II. Although the recent 1.95 Å resolution structure of PS II at cryogenic temperature using an XFEL provided a damage-free view of the S 1 state, measurements at room temperature are required to study the structural landscape of proteins under functional conditions, and also for in situ advancement of the S-states. To investigate the water-binding site(s), ammonia, a water analogue, has been used as a marker, as it binds to the Mn 4 CaO 5 cluster in the S 2 and S 3 states. Since the ammonia-bound OEC is active, the ammonia-binding Mn site is not a substrate water site. This approach, together with a comparison of the native dark and 2F states, is used to discriminate between proposed O-O bond formation mechanisms.

  3. All-Aluminum Thin Film Transistor Fabrication at Room Temperature

    Directory of Open Access Journals (Sweden)

    Rihui Yao

    2017-02-01

    Full Text Available Bottom-gate all-aluminum thin film transistors with multi conductor/insulator nanometer heterojunction were investigated in this article. Alumina (Al2O3 insulating layer was deposited on the surface of aluminum doping zinc oxide (AZO conductive layer, as one AZO/Al2O3 heterojunction unit. The measurements of transmittance electronic microscopy (TEM and X-ray reflectivity (XRR revealed the smooth interfaces between ~2.2-nm-thick Al2O3 layers and ~2.7-nm-thick AZO layers. The devices were entirely composited by aluminiferous materials, that is, their gate and source/drain electrodes were respectively fabricated by aluminum neodymium alloy (Al:Nd and pure Al, with Al2O3/AZO multilayered channel and AlOx:Nd gate dielectric layer. As a result, the all-aluminum TFT with two Al2O3/AZO heterojunction units exhibited a mobility of 2.47 cm2/V·s and an Ion/Ioff ratio of 106. All processes were carried out at room temperature, which created new possibilities for green displays industry by allowing for the devices fabricated on plastic-like substrates or papers, mainly using no toxic/rare materials.

  4. Room-temperature ballistic transport in III-nitride heterostructures.

    Science.gov (United States)

    Matioli, Elison; Palacios, Tomás

    2015-02-11

    Room-temperature (RT) ballistic transport of electrons is experimentally observed and theoretically investigated in III-nitrides. This has been largely investigated at low temperatures in low band gap III-V materials due to their high electron mobilities. However, their application to RT ballistic devices is limited by their low optical phonon energies, close to KT at 300 K. In addition, the short electron mean-free-path at RT requires nanoscale devices for which surface effects are a limitation in these materials. We explore the unique properties of wide band-gap III-nitride semiconductors to demonstrate RT ballistic devices. A theoretical model is proposed to corroborate experimentally their optical phonon energy of 92 meV, which is ∼4× larger than in other III-V semiconductors. This allows RT ballistic devices operating at larger voltages and currents. An additional model is described to determine experimentally a characteristic dimension for ballistic transport of 188 nm. Another remarkable property is their short carrier depletion at device sidewalls, down to 13 nm, which allows top-down nanofabrication of very narrow ballistic devices. These results open a wealth of new systems and basic transport studies possible at RT.

  5. “A Long March to Room Temperature Superconductivity”

    CERN Multimedia

    CERN. Geneva

    2015-01-01

    In the last 29 years, great progress has been made in all areas of high temperature superconductivity (HTS) research from raising the transition temperature Tc and discovering new HTS compounds to developing theoretical models of HTS and fabricating and testing HTS prototype devices. For example, the Tc has been increased to 164 K in cuprate HgBa2Ca2Cu3Ox under 30 GPa in 1993 at Houston, more than 200 HTS compounds have been found, numerous theoretical models have been developed, and many HTS prototype devices have been tested to display superior performance to that of their non-superconducting counterparts. The strong electron-phonon interaction required for the high Tc observed has been considered to be able to induce catastrophic structure collapse before high Tc can be realized, and a novel magnetism-based interaction in different forms has thus been proposed for high Tc. However, room temperature superconductivity is still elusive and a comprehensive microscopic theory of HTS remains to be achieved. The...

  6. Ratcheting fatigue behavior of Zircaloy-2 at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Rajpurohit, R.S., E-mail: rsrajpurohit.rs.met13@iitbhu.ac.in [Department of Metallurgical Engineering, Indian Institute of Technology, Banaras Hindu University, Varanasi, 221005 (India); Sudhakar Rao, G. [Nuclear Energy and Safety Department, Paul Scherrer Institute, Villigen, CH-5232 (Switzerland); Chattopadhyay, K.; Santhi Srinivas, N.C.; Singh, Vakil [Department of Metallurgical Engineering, Indian Institute of Technology, Banaras Hindu University, Varanasi, 221005 (India)

    2016-08-15

    Nuclear core components of zirconium alloys experience asymmetric stress or strain cycling during service which leads to plastic strain accumulation and drastic reduction in fatigue life as well as dimensional instability of the component. Variables like loading rate, mean stress, and stress amplitude affect the influence of asymmetric loading. In the present investigation asymmetric stress controlled fatigue tests were conducted with mean stress from 80 to 150 MPa, stress amplitude from 270 to 340 MPa and stress rate from 30 to 750 MPa/s to study the process of plastic strain accumulation and its effect on fatigue life of Zircaloy-2 at room temperature. It was observed that with increase in mean stress and stress amplitude accumulation of ratcheting strain was increased and fatigue life was reduced. However, increase in stress rate led to improvement in fatigue life due to less accumulation of ratcheting strain. - Highlights: • Ratcheting strain accumulation occurred due to asymmetric cyclic loading. • Accumulation of ratcheting strain increased with mean stress and stress amplitude. • Ratcheting strain accumulation decreased with increase in stress rate. • With increase in mean stress and stress amplitude there was reduction in fatigue life. • Fatigue life is improved with increase in stress rate.

  7. Proactive aquatic ecotoxicological assessment of room-temperature ionic liquids

    Science.gov (United States)

    Kulacki, K.J.; Chaloner, D.T.; Larson, J.H.; Costello, D.M.; Evans-White, M. A.; Docherty, K.M.; Bernot, R.J.; Brueseke, M.A.; Kulpa, C.F.; Lamberti, G.A.

    2011-01-01

    Aquatic environments are being contaminated with a myriad of anthropogenic chemicals, a problem likely to continue due to both unintentional and intentional releases. To protect valuable natural resources, novel chemicals should be shown to be environmentally safe prior to use and potential release into the environment. Such proactive assessment is currently being applied to room-temperature ionic liquids (ILs). Because most ILs are water-soluble, their effects are likely to manifest in aquatic ecosystems. Information on the impacts of ILs on numerous aquatic organisms, focused primarily on acute LC50 and EC50 endpoints, is now available, and trends in toxicity are emerging. Cation structure tends to influence IL toxicity more so than anion structure, and within a cation class, the length of alkyl chain substituents is positively correlated with toxicity. While the effects of ILs on several aquatic organisms have been studied, the challenge for aquatic toxicology is now to predict the effects of ILs in complex natural environments that often include diverse mixtures of organisms, abiotic conditions, and additional stressors. To make robust predictions about ILs will require coupling of ecologically realistic laboratory and field experiments with standard toxicity bioassays and models. Such assessments would likely discourage the development of especially toxic ILs while shifting focus to those that are more environmentally benign. Understanding the broader ecological effects of emerging chemicals, incorporating that information into predictive models, and conveying the conclusions to those who develop, regulate, and use those chemicals, should help avoid future environmental degradation. ?? 2011 Bentham Science Publishers Ltd.

  8. Room temperature triplet state spectroscopy of organic semiconductors.

    Science.gov (United States)

    Reineke, Sebastian; Baldo, Marc A

    2014-01-21

    Organic light-emitting devices and solar cells are devices that create, manipulate, and convert excited states in organic semiconductors. It is crucial to characterize these excited states, or excitons, to optimize device performance in applications like displays and solar energy harvesting. This is complicated if the excited state is a triplet because the electronic transition is 'dark' with a vanishing oscillator strength. As a consequence, triplet state spectroscopy must usually be performed at cryogenic temperatures to reduce competition from non-radiative rates. Here, we control non-radiative rates by engineering a solid-state host matrix containing the target molecule, allowing the observation of phosphorescence at room temperature and alleviating constraints of cryogenic experiments. We test these techniques on a wide range of materials with functionalities spanning multi-exciton generation (singlet exciton fission), organic light emitting device host materials, and thermally activated delayed fluorescence type emitters. Control of non-radiative modes in the matrix surrounding a target molecule may also have broader applications in light-emitting and photovoltaic devices.

  9. Room-temperature ferromagnetism in hydrogenated ZnO nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Xue, Xudong; Liu, Liangliang; Wang, Zhu; Wu, Yichu, E-mail: ycwu@whu.edu.cn [School of Physics and Technology, Hubei Nuclear Solid Physics Key Laboratory, Wuhan University, Wuhan 430072 (China)

    2014-01-21

    The effect of hydrogen doping on the magnetic properties of ZnO nanoparticles was investigated. Hydrogen was incorporated by annealing under 5% H{sub 2} in Ar ambient at 700 °C. Room-temperature ferromagnetism was induced in hydrogenated ZnO nanoparticles, and the observed ferromagnetism could be switched between “on” and “off” states through hydrogen annealing and oxygen annealing process, respectively. It was found that Zn vacancy and OH bonding complex (V{sub Zn} + OH) was crucial to the observed ferromagnetism by using the X-ray photoelectron spectroscopy and positron annihilation spectroscopy analysis. Based on first-principles calculations, V{sub Zn} + OH was favorable to be presented due to the low formation energy. Meanwhile, this configuration could lead to a magnetic moment of 0.57 μ{sub B}. The Raman and photoluminescence measurements excluded the possibility of oxygen vacancy as the origin of the ferromagnetism.

  10. Cyclic deformation of zircaloy-4 at room temperature

    International Nuclear Information System (INIS)

    Armas, A. F; Herenu, S; Bolmaro, R; Alvarez-Armas, I

    2003-01-01

    Annealed materials hardens under low cyclic fatigue tests.However, FCC metals tested with medium strain amplitudes show an initial cyclic softening.That behaviour is related with the strong interstitial atom-dislocation interactions.For HCP materials the information is scarce.Commercial purity Zirconium and Zircaloy-4 alloys show also a pronounced cyclic softening, similar to Titanium alloys.Recently the rotation texture induced softening model has been proposed according to which the crystals are placed in a more favourable deformation orientation by prismatic slip due to the cyclic strain.The purpose of the current paper is the presentation of decisive results to discuss the causes for cyclic softening of Zircaloy-4. Low cycle fatigue tests were performed on recrystallized Zircaloy-4 samples.The cyclic behaviour shows an exponential softening at room temperature independently of the deformation range.Only at high temperature a cyclic hardening is shown at low number of cycles.Friction stresses, related with dislocation movement itself, and back stresses, related with dislocation pile-ups can be calculated from the stress-strain loops.The cyclic softening is due to diminishing friction stress while the starting hardening behaviour is due to increasing back stresses.The rotation texture induced softening model is ruled out assuming instead a model based on dislocation unlocking from interstitial oxygen solute atoms

  11. A room-temperature liquid calorimeter prototype for the SSC

    International Nuclear Information System (INIS)

    Brandenburg, G.W.; Geer, S.H.; Oliver, J.; Sadowski, E.; Theriot, D.

    1990-01-01

    Calorimeters will be an extremely important part of SSC detectors as they have been in existing collider detectors. The main issues that need to be addressed are: (1) energy resolution of jets and electrons, (2) segmentation, (3) hermiticity, (4) response time, and (5) radiation resistance. An attractive possibility on all these counts is the use of room-temperature liquids together with uranium, as pioneered by UA1. The authors are planning a prototype calorimeter which consists of a sealed vessel containing both the radiator plates and the readout pads. This geometry has been appropriately named the swimming pool design. The general mechanical starting point is similar to the SLD liquid argon calorimeters. The points they wish to address are the following: (1) Simple and reliable modular construction techniques, (2) Satisfactory electrical connections with minimal geometric impact, (3) The necessity of isolating radiator plates and liquid to maintain purity, (4) What materials can be immersed without compromising the liquid purity. The design and construction of the swimming pool electromagnetic calorimeter prototype is being carried out at the Harvard High Energy Physics Laboratory. This is one of the first attempts to build a full-scale prototype of such a design

  12. Boron lattice location in room temperature ion implanted Si crystal

    International Nuclear Information System (INIS)

    Piro, A.M.; Romano, L.; Mirabella, S.; Grimaldi, M.G.

    2005-01-01

    The B lattice location in presence of a Si-self-interstitial (I Si ) supersaturation, controlled by energetic proton bombardment, has been studied by means of ion channelling and massive Monte Carlo simulations. B-doped layers of Si crystals with a B concentration of 1 x 10 2 B/cm 3 were grown by Molecular Beam Epitaxy. Point defect engineering techniques, with light energetic ion implants, have been applied to generate an I Si uniform injection in the electrically active layer. The displacement of B atoms out of substitutional lattice sites was induced by 650 keV proton irradiations at room temperature (R.T.) and the resultant defect configuration was investigated by ion channelling and Nuclear Reaction Analysis (NRA) techniques. Angular scans were measured both through and axes along the (1 0 0) plane using the 11 B(p,α) 8 Be nuclear reaction at 650 keV proton energy. Monte Carlo simulated angular scans were calculated considering a variety of theoretical defect configurations, supported by literature, and compared with experimental data. Our experimental scans can be fitted by a linear combination of small (0.3 A) and large B displacements (1.25 A) along the direction, compatible with the B-dumbbell oriented along as proposed by ab initio calculations

  13. Behavior of porous tungsten under shock compression at room temperature

    International Nuclear Information System (INIS)

    Dandekar, D.P.; Lamothe, R.M.

    1977-01-01

    This work reports the results of room-temperature shock-compression experiments on porous tungsten. The porous tungsten was fabricated by sintering 1-μm tungsten particles. The initial density of the material was 15290 kg/m 3 . Around 97% of the pores in the material were interconnected. The main features of the results are as follows: (1) porous tungsten behaves as a linear elastic material to 1.43 GPa; (2) the shock wave following the elastic precursor is unstable in the material in the stress range 1.43--2.7 GPa; (3) a stable two-wave structure is established at and above 6.4 GPa; (4) the response of porous tungsten is accurately described by the Mie-Grueneisen equation of state at stresses above 4.9 GPa, the stress at which the voids suffer a complete extinction in the material; (5) the deformations induced in the material due to shock compression are irreversible; (6) the recentered Hugoniot of porous tungsten becomes stiffer with the increasing magnitude of initial compressive stress

  14. Rf breakdown studies in room temperature electron linac structures

    International Nuclear Information System (INIS)

    Loew, G.A.; Wang, J.W.

    1988-05-01

    This paper is an overall review of studies carried out by the authors and some of their colleagues on RF breakdown, Field Emission and RF processing in room temperature electron linac structure. The motivation behind this work is twofold: in a fundamental way, to contribute to the understanding of the RF breakdown phenomenon, and as an application, to determine the maximum electric field gradient that can be obtained and used safely in future e/sup +-/ linear colliders. Indeed, the next generation of these machines will have to reach into the TeV (10 12 eV) energy range, and the accelerating gradient will be to be of the crucial parameters affecting their design, construction and cost. For a specified total energy, the gradient sets the accelerator length, and once the RF structure, frequency and pulse repetition rate are selected, it also determines the peak and average power consumption. These three quantities are at the heart of the ultimate realizability and cost of these accelerators. 24 refs., 19 figs., 4 tabs

  15. A computed room temperature line list for phosphine

    Science.gov (United States)

    Sousa-Silva, Clara; Yurchenko, Sergei N.; Tennyson, Jonathan

    2013-06-01

    An accurate and comprehensive room temperature rotation-vibration transition line list for phosphine (31PH3) is computed using a newly refined potential energy surface and a previously constructed ab initio electric dipole moment surface. Energy levels, Einstein A coefficients and transition intensities are computed using these surfaces and a variational approach to the nuclear motion problem as implemented in the program TROVE. A ro-vibrational spectrum is computed, covering the wavenumber range 0-8000 cm-1. The resulting line list, which is appropriate for temperatures up to 300 K, consists of a total of 137 million transitions between 5.6 million energy levels. Several of the band centres are shifted to better match experimental transition frequencies. The line list is compared to the most recent HITRAN database and other laboratorial sources. Transition wavelengths and intensities are generally found to be in good agreement with the existing experimental data, with particularly close agreement for the rotational spectrum. An analysis of the comparison between the theoretical data created and the existing experimental data is performed, and suggestions for future improvements and assignments to the HITRAN database are made.

  16. Branched carbon nanofiber network synthesis at room temperature using radio frequency supported microwave plasmas

    OpenAIRE

    Boskovic, BO; Stolojan, V; Zeze, DA; Forrest, RD; Silva, SRP; Haq, S

    2004-01-01

    Carbon nanofibers have been grown at room temperature using a combination of radio frequency and microwave assisted plasma-enhanced chemical vapor deposition. The nanofibers were grown, using Ni powder catalyst, onto substrates kept at room temperature by using a purposely designed water-cooled sample holder. Branched carbon nanofiber growth was obtained without using a template resulting in interconnected carbon nanofiber network formation on substrates held at room temperatur...

  17. Room temperature ferromagnetism and CH{sub 4} gas sensing of titanium oxynitride induced by milling and annealing

    Energy Technology Data Exchange (ETDEWEB)

    Bolokang, Amogelang S., E-mail: Sylvester.Bolokang@transnet.net [DST/CSIR National Centre for Nano-Structured Materials, Council for Scientific and Industrial Research, Pretoria, 0001 (South Africa); Transnet Engineering, Product Development, Private Bag X 528, Kilnerpark, 0127 (South Africa); Tshabalala, Zamaswazi P. [DST/CSIR National Centre for Nano-Structured Materials, Council for Scientific and Industrial Research, Pretoria, 0001 (South Africa); Malgas, Gerald F. [Department of Physics, University of the Western Cape, Private Bag X17, Bellville, 7535 (South Africa); Kortidis, Ioannis [DST/CSIR National Centre for Nano-Structured Materials, Council for Scientific and Industrial Research, Pretoria, 0001 (South Africa); West Virginia University, Department of Mechanical & Aerospace Engineering, Evansdale Campus, Morgantown, WV, 26506 (United States); Swart, Hendrik C. [Department of Physics, University of the Free State, P.O. Box 339, Bloemfontein, ZA9300 (South Africa); Motaung, David E., E-mail: dmotaung@csir.co.za [DST/CSIR National Centre for Nano-Structured Materials, Council for Scientific and Industrial Research, Pretoria, 0001 (South Africa)

    2017-06-01

    We report on the room temperature ferromagnetism and CH{sub 4} gas sensing of titanium oxynitride prepared by milling and annealing at 1100 °C in a nitrogen gas environment. Structural analyses revealed a metastable orthorhombic TiO{sub 2} phase after milling for 120 h. The 120 h milled TiO{sub 2} particles and subsequently annealed in nitrogen gas at 1100 °C showed the formation of titanium oxynitride (TiO{sub x}N{sub y}) with a tetragonal crystal structure. An FCC metastable TiO{sub x}N{sub y} phase was also observed with a lattice parameter a = 4.235 Å. The vibrating sample magnetometer and electron paramagnetic analyses showed that the milled and TiO{sub x}N{sub y} samples possess room temperature ferromagnetism. Gas sensing measurements were carried out toward CH{sub 4} and H{sub 2} gases. The TiO{sub x}N{sub y} nanostructures demonstrated higher sensing response and selectivity to CH{sub 4} gas at room temperature. The enhanced response of 1010 and sensitivity of 50.12 ppm{sup -1} at a concentration of 20 ppm CH{sub 4} are associated with higher surface area, pore diameter and surface defects such as oxygen vacancies and Ti{sup 3+}, as evidenced from the Brunauer–Emmet–Teller, photoluminescence, electron paramagnetic resonance and x-ray photoelectron analyses. - Highlights: • Ball milled of TiO{sub 2} structure revealed metastable orthorhombic phase. • Upon nitridation tetragonal and FCC TiO{sub x}N{sub y} crystal structures were induced. • The magnetic properties of TiO{sub 2} nanoparticles was transformed by milling. • TiO{sub x}N{sub y} sensing response for CH{sub 4} gas at room temperature was high.

  18. Ferroelectric devices

    CERN Document Server

    Uchino, Kenji

    2009-01-01

    Updating its bestselling predecessor, Ferroelectric Devices, Second Edition assesses the last decade of developments-and setbacks-in the commercialization of ferroelectricity. Field pioneer and esteemed author Uchino provides insight into why this relatively nascent and interdisciplinary process has failed so far without a systematic accumulation of fundamental knowledge regarding materials and device development.Filling the informational void, this collection of information reviews state-of-the-art research and development trends reflecting nano and optical technologies, environmental regulat

  19. Evolution of interphase and intergranular strain in zirconium-niobium alloys during deformation at room temperature

    Science.gov (United States)

    Cai, Song

    Zr-2.5Nb is currently used for pressure tubes in the CANDU (CANada Deuterium Uranium) reactor. A complete understanding of the deformation mechanism of Zr-2.5Nb is important if we are to accurately predict the in-reactor performance of pressure tubes and guarantee normal operation of the reactors. This thesis is a first step in gaining such an understanding; the deformation mechanism of ZrNb alloys at room temperature has been evaluated through studying the effect of texture and microstructure on deformation. In-situ neutron diffraction was used to monitor the evolution of the lattice strain of individual grain families along both the loading and Poisson's directions and to track the development of interphase and intergranular strains during deformation. The following experiments were carried out with data interpreted using elasto-plastic modeling techniques: (1) Compression tests of a 100%betaZr material at room temperature. (2) Tension and compression tests of hot rolled Zr-2.5Nb plate material. (3) Compression of annealed Zr-2.5Nb. (4) Cyclic loading of the hot rolled Zr-2.5Nb. (5) Compression tests of ZrNb alloys with different Nb and oxygen contents. The experimental results were interpreted using a combination of finite element (FE) and elasto-plastic self-consistent (EPSC) models. The phase properties and phase interactions well represented by the FE model, the EPSC model successfully captured the evolution of intergranular constraint during deformation and provided reasonable estimates of the critical resolved shear stress and hardening parameters of different slip systems under different conditions. The consistency of the material parameters obtained by the EPSC model allows the deformation mechanism at room temperature and the effect of textures and microstructures of ZrNb alloys to be understood. This work provides useful information towards manufacturing of Zr-2.5Nb components and helps in producing ideal microstructures and material properties for

  20. Very large phase shift of microwave signals in a 6 nm Hf x Zr1-x O2 ferroelectric at ±3 V

    Science.gov (United States)

    Dragoman, Mircea; Modreanu, Mircea; Povey, Ian M.; Iordanescu, Sergiu; Aldrigo, Martino; Romanitan, Cosmin; Vasilache, Dan; Dinescu, Adrian; Dragoman, Daniela

    2017-09-01

    In this letter, we report for the first time very large phase shifts of microwaves in the 1-10 GHz range, in a 1 mm long gold coplanar interdigitated structure deposited over a 6 nm Hf x Zr1-x O2 ferroelectric grown directly on a high resistivity silicon substrate. The phase shift is larger than 60° at 1 GHz and 13° at 10 GHz at maximum applied DC voltages of ±3 V, which can be supplied by a simple commercial battery. In this way, we demonstrate experimentally that the new ferroelectrics based on HfO2 could play an important role in the future development of wireless communication systems for very low power applications.

  1. Anisotropic thermal properties and ferroelectric phase transitions in layered CuInP2S6 and CuInP2Se6 crystals

    Science.gov (United States)

    Liubachko, V.; Shvalya, V.; Oleaga, A.; Salazar, A.; Kohutych, A.; Pogodin, A.; Vysochanskii, Yu. M.

    2017-12-01

    Thermal diffusivity and thermal conductivity have been studied for the layered crystals CuInP2S6, CuInP2Se6 from 30 K to 350 K, showing a relevant thermal anisotropy. Heat is much more efficiently transferred within the layers than perpendicular to them. The ferrielectric transition in CuInP2S6 is proven to be clearly first order while the ferroelectric one in CuInP2Se6 has a weak first order character. The behavior of the thermal conductivity as a function of temperature in the ferroelectric phases shows that heat conduction is phonon driven. Disorder in the paraelectric phases due to hopping motions of Cu ions significantly reduces the thermal conductivity to extremely low values.

  2. A frequency output ferroelectric phase PNZT capacitor-based temperature sensor

    KAUST Repository

    Khan, Naveed

    2016-09-05

    In this paper, a frequency output temperature sensor based on a 4% Niobium doped 20/80 Zr/Ti Lead Zirconate Titanate (PNZT) capacitor is proposed. The sensor capacitance vs temperature and capacitance vs voltage characteristics are experimentally measured below the Curie temperature of the ferroelectric capacitor. The capacitance of the 20/80 (Zr/Ti) composition PNZT capacitor changes by 29% for a temperature change from 10°C to 100°C, which translates to 0.32%/°C temperature sensitivity. The measured sensor characteristics show less than ∼0.7°C deviation from the ideal linear response. A Wien bridge oscillator based temperature sensor is demonstrated based on the PNZT capacitors. Mathematical analysis for the effect of the op-amp finite unity-gain frequency on the sensor circuit oscillation frequency is provided. The experimentally realized frequency output temperature sensor shows -17.6% relative frequency change for a temperature change from 10°C to 100°C. The proposed capacitive temperature sensor can be used in low-power smart sensor nodes without the need for extensive calibration. © 2015 IEEE.

  3. Growth of room temperature ferromagnetic Ge1-xMnx quantum dots on hydrogen passivated Si (100) surfaces

    Science.gov (United States)

    Gastaldo, Daniele; Conta, Gianluca; Coïsson, Marco; Amato, Giampiero; Tiberto, Paola; Allia, Paolo

    2018-05-01

    A method for the synthesis of room-temperature ferromagnetic dilute semiconductor Ge1-xMnx (5 % < x < 8 %) quantum dots by molecular beam epitaxy by selective growth on hydrogen terminated silicon (100) surface is presented. The functionalized substrates, as well as the nanostructures, were characterized in situ by reflection high-energy electron diffraction. The quantum dots density and equivalent radius were extracted from field emission scanning electron microscope pictures, obtained ex-situ. Magnetic characterizations were performed by superconducting quantum interference device vibrating sample magnetometry revealing that ferromagnetic order is maintained up to room temperature: two different ferromagnetic phases were identified by the analysis of the field cooled - zero field cooled measurements.

  4. CDZNTE ROOM-TEMPERATURE SEMICONDUCTOR GAMMA-RAY DETECTOR FOR NATIONAL-SECURITY APPLICATIONS.

    Energy Technology Data Exchange (ETDEWEB)

    CAMARDA,G.S.; BOLOTNIKOV, A.E.; CUI, Y.; HOSSAIN, A.; KOHMAN, K.T.; JAMES, R.B.

    2007-05-04

    One important mission of the Department of Energy's National Nuclear Security Administration is to develop reliable gamma-ray detectors to meet the widespread needs of users for effective techniques to detect and identify special nuclear- and radioactive-materials. Accordingly, the Nonproliferation and National Security Department at Brookhaven National Laboratory was tasked to evaluate existing technology and to develop improved room-temperature detectors based on semiconductors, such as CdZnTe (CZT). Our research covers two important areas: Improving the quality of CZT material, and exploring new CZT-based gamma-ray detectors. In this paper, we report on our recent findings from the material characterization and tests of actual CZT devices fabricated in our laboratory and from materials/detectors supplied by different commercial vendors. In particular, we emphasize the critical role of secondary phases in the current CZT material and issues in fabricating the CZT detectors, both of which affect their performance.

  5. Crack resistance behaviour of an intermetallic Ti-Al-Si-Nb alloy at room temperature

    International Nuclear Information System (INIS)

    Wittkowsky, B.U.; Pfuff, M.J.

    1996-01-01

    The room temperature crack growth behaviour of a Ti-Al-Si-Nb alloy consisting of the two intermetallic phases (Ti, Nb) 3 (Al, Si) and (Ti, Nb) 5 (Si, Al) 3 is investigated in the present paper. The material exhibits a heterogeneous disordered microstructure and fails in a brittle manner. Crack growth is associated with a pronounced crack resistance behaviour. For a sample of nominally identical specimens the R-curves scatter around a mean curve with a standard deviation which remains roughly constant as the crack grows. A natural extension of the bundle model introduced in a previous paper is used to simulate R-curves and their scatter is in reasonably good agreement with the experimental findings. (orig.)

  6. Above room-temperature ferromagnetism of Mn delta-doped GaN nanorods

    International Nuclear Information System (INIS)

    Lin, Y. T.; Wadekar, P. V.; Kao, H. S.; Chen, T. H.; Chen, Q. Y.; Tu, L. W.; Huang, H. C.; Ho, N. J.

    2014-01-01

    One-dimensional nitride based diluted magnetic semiconductors were grown by plasma-assisted molecular beam epitaxy. Delta-doping technique was adopted to dope GaN nanorods with Mn. The structural and magnetic properties were investigated. The GaMnN nanorods with a single crystalline structure and with Ga sites substituted by Mn atoms were verified by high-resolution x-ray diffraction and Raman scattering, respectively. Secondary phases were not observed by high-resolution x-ray diffraction and high-resolution transmission electron microscopy. In addition, the magnetic hysteresis curves show that the Mn delta-doped GaN nanorods are ferromagnetic above room temperature. The magnetization with magnetic field perpendicular to GaN c-axis saturates easier than the one with field parallel to GaN c-axis

  7. Room-temperature ferromagnetism in Co and Nb co-doped TiO2 nanoparticles

    International Nuclear Information System (INIS)

    Hachisu, M.; Mori, K.; Hyodo, K.; Morimoto, S.; Yamazaki, T.; Ichiyanagi, Y.

    2015-01-01

    Co- and Nb-doped TiO 2 nanoparticles encapsulated with amorphous SiO 2 were synthesized by our novel preparation method. An anatase TiO 2 single-phase structure was confirmed using X-ray diffraction. The particle size could be controlled to be about 5 nm. The composition of these nanoparticles was investigated by X-ray fluorescence analysis. X-ray absorption near-edge structure spectra showed that the Ti 4+ and Co 2+ states were dominant in our prepared samples. A reduction in the coordination number was also confirmed. The dependence of the electrical conductivity on the frequency was measured by an LCR meter, and the carrier concentration was determined. The magnetization curves for the nanoparticles indicated ferromagnetic behavior at room temperature. We concluded that the ferromagnetism originated in oxygen vacancies around the transition metal ions

  8. Room temperature ferromagnetism in Mg-doped ZnO nanoparticles

    International Nuclear Information System (INIS)

    Singh, Jaspal; Vashihth, A.; Gill, Pritampal Singh; Verma, N. K.

    2015-01-01

    Zn 1-x Mg x O (x = 0, 0,10) nanoparticles were successfully synthesized using sol-gel method. X-ray diffraction (XRD) confirms that the synthesized nanoparticles possess wurtzite phase having hexagonal structure. Morphological analysis was carried out using transmission electron microscopy (TEM) which depicts the spherical morphology of ZnO nanoparticles. Energy dispersive spectroscopy (EDS) showed the presence of Mg in ZnO nanoparticles. Electron spin resonance (ESR) signal was found to be decreasing with increasing of Mg-doping concentration. The room temperature ferromagnetism was observed in undoped and Mg-doped ZnO nanoparticles. The increase of Mg-doping concentration resulted in decrease of saturation magnetization value which could be attributed to decrease of oxygen vacancies present in host nanoparticles

  9. Pentacene on Ni(111): room-temperature molecular packing and temperature-activated conversion to graphene.

    Science.gov (United States)

    Dinca, L E; De Marchi, F; MacLeod, J M; Lipton-Duffin, J; Gatti, R; Ma, D; Perepichka, D F; Rosei, F

    2015-02-21

    We investigate, using scanning tunnelling microscopy, the adsorption of pentacene on Ni(111) at room temperature and the behaviour of these monolayer films with annealing up to 700 °C. We observe the conversion of pentacene into graphene, which begins from as low as 220 °C with the coalescence of pentacene molecules into large planar aggregates. Then, by annealing at 350 °C for 20 minutes, these aggregates expand into irregular domains of graphene tens of nanometers in size. On surfaces where graphene and nickel carbide coexist, pentacene shows preferential adsorption on the nickel carbide phase. The same pentacene to graphene transformation was also achieved on Cu(111), but at a higher activation temperature, producing large graphene domains that exhibit a range of moiré superlattice periodicities.

  10. Trivalent europium speciation in a room-temperature ionic liquid

    International Nuclear Information System (INIS)

    Mekki, S.

    2006-10-01

    Since the nuclear industry is playing an important role in the power production field, a relevant number of problems have been revealed. Indeed, high-level radioactive long-lived nuclear wastes present a real difficulty for nuclear wastes management. Minor actinides, which compose most of these wastes, will be radioactive for several thousands of years. For eventual disposal deep underground, their reprocessing needs to be optimized. The extraction processes used industrially to separate actinides and lanthanides from other metal species characterizing the spent nuclear fuel produce, nevertheless, enormous quantities of contaminated liquid wastes directly issued from the liquid/liquid extraction step. During the last decade, some room-temperature ionic liquid have been studied and integrated into industrial processes. The interest on this class of solvent came out from their 'green' properties (non volatile, non flammable, recyclable, etc...), but also from the variability of their physico-chemical properties (stability, hydrophobicity, viscosity) as a function of the RTIL chemical composition. Indeed, it has been shown that classical chemical industrial processes could be transferred into those media, even more improved, while a certain number of difficulties arising from using traditional solvent can be avoided. In this respect, it could be promising to investigate the ability to use room-temperature ionic liquid into the spent nuclear fuel reprocessing field. The aim of this thesis is to test the ability of the specific ionic liquid bumimTf 2 N to allow trivalent europium extraction. The choice of this metal is based on the chemical analogy with trivalent minor actinides Curium and Americium which are contributing the greatest part of the long-lived high-level radioactive wastes. Handling these elements needs to be very cautious for the safety and radioprotection aspect. Moreover, europium is a very sensitive luminescent probe to its environment even at the

  11. Effect of calcination temperature on formaldehyde oxidation performance of Pt/TiO2 nanofiber composite at room temperature

    Science.gov (United States)

    Xu, Feiyan; Le, Yao; Cheng, Bei; Jiang, Chuanjia

    2017-12-01

    Catalytic oxidation at room temperature over well-designed catalysts is an environmentally friendly method for the abatement of indoor formaldehyde (HCHO) pollution. Herein, nanocomposites of platinum (Pt) and titanium dioxide (TiO2) nanofibers with various phase compositions were prepared by calcining the electrospun TiO2 precursors at different temperatures and subsequently depositing Pt nanoparticles (NPs) on the TiO2 through a NaBH4-reduction process. The phase compositions and structures of Pt/TiO2 can be easily controlled by varying the calcination temperature. The Pt/TiO2 nanocomposites showed a phase-dependent activity towards the catalytic HCHO oxidation. Pt/TiO2 containing pure rutile phase showed enhanced activity with a turnover frequency (TOF) of 16.6 min-1 (for a calcination temperature of 800 °C) as compared to those containing the anatase phase or mixed phases. Density functional theory calculation shows that TiO2 nanofibers with pure rutile phase have stronger adsorption ability to Pt atoms than anatase phase, which favors the reduction of Pt over rutile phase TiO2, leading to higher contents of metallic Pt in the nanocomposite. In addition, the Pt/TiO2 with rutile phase possesses more abundant oxygen vacancies, which is conducive to the activation of adsorbed oxygen. Consequently, the Pt/rutile-TiO2 nanocomposite exhibited better catalytic activity towards HCHO oxidation at room temperature.

  12. Short- and long-range polar order contributions to the Ferroelectric phase of Ca.sup.2+./sup. doped SrTiO.sub.3./sub.

    Czech Academy of Sciences Publication Activity Database

    Markovin, P.A.; Trepakov, Vladimír; Guzhva, M.E.; Razdobarin, A.G.; Tagantsev, A. K.; Andreev, D. A.; Dejneka, Alexandr

    2016-01-01

    Roč. 3, č. 11 (2016), s. 1-12, č. článku 115705. ISSN 2053-1591 R&D Projects: GA ČR GA15-13778S Institutional support: RVO:68378271 Keywords : quantum paraelectrics * impurities and defects * low-temperature polar state * ferroelectric phase * long-range order * short-range Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.068, year: 2016

  13. Exchange of hydrogen isotopes in oxide ceramics at room temperature

    International Nuclear Information System (INIS)

    Suzuki, H.; Morita, K.; Soda, K.

    2001-01-01

    The decay curves of D and up-take curves of H on the exchange of D implanted into Li 2 TiO 3 for H in H 2 O vapor caused by exposure to normal-air at room temperature have been measured as a function of exposure time at different implantation concentrations by means of the elastic recoil detection technique. The re-emission curves of D retained and H up-taken in a specimen by isochronal annealing for 10 min have been also measured. It is found that the thermal re-emission of D and H takes place uniformly over the whole specimen due to local molecular recombination in the bulk and that the re-emission rates of H and D in the near-surface layers are slower than those in the deeper layers. It is also found that the decay of D caused by the D-H exchange takes place rapidly in the beginning and the retained amount of D attains at a constant level and the retained fraction of D are higher as the initial implantation concentrations of D are lower. The decay curves of D and the up-take curves of H have been analysed using the mass balance equations, in which the elementary processes are taken into account according to the exchange model of one way diffusion from the surface into the bulk. It is shown that the solution of the mass balance equations reproduces well the experimental data. The rate constants of the elementary processes determined are discussed. (orig.)

  14. Room-temperature macromolecular serial crystallography using synchrotron radiation

    Directory of Open Access Journals (Sweden)

    Francesco Stellato

    2014-07-01

    Full Text Available A new approach for collecting data from many hundreds of thousands of microcrystals using X-ray pulses from a free-electron laser has recently been developed. Referred to as serial crystallography, diffraction patterns are recorded at a constant rate as a suspension of protein crystals flows across the path of an X-ray beam. Events that by chance contain single-crystal diffraction patterns are retained, then indexed and merged to form a three-dimensional set of reflection intensities for structure determination. This approach relies upon several innovations: an intense X-ray beam; a fast detector system; a means to rapidly flow a suspension of crystals across the X-ray beam; and the computational infrastructure to process the large volume of data. Originally conceived for radiation-damage-free measurements with ultrafast X-ray pulses, the same methods can be employed with synchrotron radiation. As in powder diffraction, the averaging of thousands of observations per Bragg peak may improve the ratio of signal to noise of low-dose exposures. Here, it is shown that this paradigm can be implemented for room-temperature data collection using synchrotron radiation and exposure times of less than 3 ms. Using lysozyme microcrystals as a model system, over 40 000 single-crystal diffraction patterns were obtained and merged to produce a structural model that could be refined to 2.1 Å resolution. The resulting electron density is in excellent agreement with that obtained using standard X-ray data collection techniques. With further improvements the method is well suited for even shorter exposures at future and upgraded synchrotron radiation facilities that may deliver beams with 1000 times higher brightness than they currently produce.

  15. A Non-Volatile SRAM For Spaceborne Applications Using a Novel Ferroelectric Non-Linear Dielectric, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — A ferroelectric non-linear dielectric was recently discovered that, in their film form, possess a number of properties that make it an excellent choice for...

  16. The influence of room temperature on Mg isotope measurements by MC-ICP-MS.

    Science.gov (United States)

    Zhang, Xing-Chao; Zhang, An-Yu; Zhang, Zhao-Feng; Huang, Fang; Yu, Hui-Min

    2018-03-24

    We observed that the accuracy and precision of magnesium (Mg) isotope analyses could be affected if the room temperature oscillated during measurements. To achieve high quality Mg isotopic data, it is critical to evaluate how the unstable room temperature affects Mg isotope measurements by multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). We measured the Mg isotopes for the reference material DSM-3 using MC-ICP-MS under oscillating room temperatures in spring. For a comparison, we also measured the Mg isotopes under stable room temperatures, which was achieved by the installation of an improved temperature control system in the laboratory. The δ 26 Mg values measured under oscillating room temperatures have a larger deviation (δ 26 Mg from -0.09 to 0.08‰, with average δ 26 Mg = 0.00 ± 0.08 ‰) than those measured under a stable room temperature (δ 26 Mg from -0.03 to 0.03‰, with average δ 26 Mg = 0.00 ± 0.02 ‰) using the same MC-ICP-MS system. The room temperature variation can influence the stability of MC-ICP-MS. Therefore, it is critical to keep the room temperature stable to acquire high precise and accurate isotopic data when using MC-ICP-MS, especially when using the sample-standard bracketing (SSB) correction method. This article is protected by copyright. All rights reserved.

  17. Thermomechanical analysis of Natural Rubber behaviour stressed at room temperature.

    Directory of Open Access Journals (Sweden)

    Chrysochoos A.

    2010-06-01

    Full Text Available Owing to their high molecular mobility, stressed rubber chains can easily change their conformations and get orientated. This phenomena leads to so high reversible draw ratio that this behaviour is called rubber elasticity [1-3]. The analogy with ideal gases leads to an internal energy independent of elongation, the stress being attributed to a so-called configuration entropy. However, this analysis cannot take thermal expansion into account and moreover prohibits predicting standard thermo-elastic effect noticed at small elongations and the thermoelastic inversion effects [4]. This paper aims at : observing and quantifying dissipative and coupling effects associated with deformation energy, generated when Natural Rubber is stretched. re-examine the thermomechanical behaviour model of rubberlike materials, under the generalised standard material concept. From an experimental viewpoint, energy balance is created using infrared and quantitative imaging techniques. Digital Image Correlation (DIC provides in-the-plane displacement fields and, after derivation, strain and strain-rate fields. We have used those techniques to evidence the thermoelastic inversion effect as shown on Figure 1 where different weights have been fixed to warmed specimen and we monitored the sample deformation while it recovers room temperature. But we have also used those techniques to perform energy balance : analysis of the mechanical equilibrium allows estimates of the stress pattern and computation of deformation energy rates under a plane stress hypothesis [5]. Infrared Thermography (IRT gives the surface temperature of the sample. To estimate the distribution of heat sources, image processing with a local heat equation and a minimal set of approximation functions (image filtering was used. The time courses of deformation energy and heat associated with cyclic process are plotted in Figure 2. The time derivatives of both forms of energy are approximately similar. This

  18. Chemical Synthesis of Porous Barium Titanate Thin Film and Thermal Stabilization of Ferroelectric Phase by Porosity-Induced Strain.

    Science.gov (United States)

    Suzuki, Norihiro; Osada, Minoru; Billah, Motasim; Bando, Yoshio; Yamauchi, Yusuke; Hossain, Shahriar A

    2018-03-27

    Barium titanate (BaTiO3, hereafter BT) is an established ferroelectric material first discovered in the 1940s and still widely used because of its well-balanced ferroelectricity, piezoelectricity, and dielectric constant. In addition, BT does not contain any toxic elements. Therefore, it is considered to be an eco-friendly material, which has attracted considerable interest as a replacement for lead zirconate titanate (PZT). However, bulk BT loses its ferroelectricity at approximately 130 °C, thus, it cannot be used at high temperatures. Because of the growing demand for high-temperature ferroelectric materials, it is important to enhance the thermal stability of ferroelectricity in BT. In previous studies, strain originating from the lattice mismatch at hetero-interfaces has been used. However, the sample preparation in this approach requires complicated and expensive physical processes, which are undesirable for practical applications. In this study, we propose a chemical synthesis of a porous material as an alternative means of introducing strain. We synthesized a porous BT thin film using a surfactant-assisted sol-gel method, in which self-assembled amphipathic surfactant micelles were used as an organic template. Through a series of studies, we clarified that the introduction of pores had a similar effect on distorting the BT crystal lattice, to that of a hetero-interface, leading to the enhancement and stabilization of ferroelectricity. Owing to its simplicity and cost effectiveness, this fabrication process has considerable advantages over conventional methods.

  19. Accompanying growth and room-temperature ferromagnetism of η-Mn3N2 thin films by molecular beam epitaxy

    International Nuclear Information System (INIS)

    Yu, Fengmei; Liu, Yajing; Yang, Mei; Wu, Shuxiang; Zhou, Wenqi; Li, Shuwei

    2013-01-01

    η-phase manganese nitride films have been grown on LaAlO 3 (100) and LaSrAlO 4 (001) substrates by using plasma-assisted molecular beam epitaxy. On the basis of reflective high energy electron diffraction, X-ray diffraction, and X-ray photoemission spectroscopy, it is confirmed that two types of η-Mn 3 N 2 with different lattice constants coexist in the films due to the lattice mismatches between the Mn 3 N 2 films and the substrates. Magnetic properties of the films were characterized by a superconducting quantum interference device magnetometer at room temperature. The Mn 3 N 2 films on LaAlO 3 substrate were found to have room-temperature ferromagnetism. Two potential interaction mechanisms are proposed regarding the origin of the observed ferromagnetism. - Highlights: ► The films of two types of η-Mn 3 N 2 have been grown by molecular beam epitaxy. ► Mn 3 N 2 A and Mn 3 N 2 B coexisted in the films on LaAlO 3 and LaSrAlO 4 . ► The room-temperature ferromagnetism of the Mn 3 N 2 films on LaAlO 3 was obtained

  20. Activation of room temperature ferromagnetism in ZnO films by surface functionalization with thiol and amine

    International Nuclear Information System (INIS)

    Jayalakshmi, G.; Gopalakrishnan, N.; Balasubramanian, T.

    2013-01-01

    Highlights: ► Room temperature ferromagnetism (RTFM) is observed in surface functionalized ZnO films. ► Surface functionalization is a new approach to make ZnO as ferromagnetic. ► The RTFM is attributed to the interaction between the adsorbates and the surface of ZnO. ► The oxygen vacancies are passivated upon surface functionalization. - Abstract: In this paper, we report the activation of room temperature ferromagnetism in ZnO films by surface functionalization with thiol and amine. The pure and surface functionalized ZnO films have been examined by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) and vibrating sample magnetometer (VSM) measurements. XRD measurements show that all the films have single phase and (0 0 2) preferred orientation. The chemical bonding of ZnO with thiol and amine molecules has been confirmed by XPS measurements. The quenching of visible emission in PL spectra indicates that the surface defects are passivated by functionalization with thiol and amine. Surface functionalization of ZnO films with thiol and amine induces robust room temperature ferromagnetism in ZnO films as evidenced from VSM measurements. It is concluded that the observed ferromagnetic behavior in functionalized ZnO films is attributed to the different electronegativity of the atom in the thiol (or amine) and the surface of ZnO.

  1. In situ synthesis of manganese oxides on polyester fiber for formaldehyde decomposition at room temperature

    International Nuclear Information System (INIS)

    Wang, Jinlong; Yunus, Rizwangul; Li, Jinge; Li, Peilin; Zhang, Pengyi; Kim, Jeonghyun

    2015-01-01

    Graphical abstract: - Highlights: • The MnO x particles assembled with nanosheets were uniformly coated on PET fibers. • The growth process of MnO x layer on PET is clearly clarified. • MnO x /PET showed good activity for HCHO decomposition at room temperature. • MnO x /PET material is promising for indoor air purification due to its light, flexible and low air-resistant properties. - Abstract: Removal of low-level formaldehyde (HCHO) is of great interest for indoor air quality improvement. Supported materials especially those with low air pressure drop are of necessity for air purification. Manganese oxides (MnO x ) was in situ deposited on the surface of fibers of a non-woven fabric made of polyethylene terephthalate (PET). As-synthesized MnO x /PET were characterized by SEM, XRD, TEM, ATR-FTIR and XPS analysis. The growth of MnO x layer on PET is thought to start with partial hydrolysis of PET, followed by surface oxidation by KMnO 4 and then surface-deposition of MnO x particles from the bulk phase. The MnO x particles assembled with nanosheets were uniformly coated on the PET fibers. MnO x /PET showed good activity for HCHO decomposition at room temperature which followed the Mars–van Krevelen mechanism. The removal of HCHO was kept over 94% after 10 h continuous reaction under the conditions of inlet HCHO concentration ∼0.6 mg/m 3 , space velocity ∼17,000 h −1 and relative humidity∼50%. This research provides a facile method to deposit active MnO x onto polymers with low air resistance, and composite MnO x /PET material is promising for indoor air purification.

  2. In situ synthesis of manganese oxides on polyester fiber for formaldehyde decomposition at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jinlong [State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084 (China); Collaborative Innovation Center for Regional Environmental Quality (China); Yunus, Rizwangul [State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084 (China); Xinjiang Zhongtai Chemical Company, Xinjiang 831511 (China); Li, Jinge; Li, Peilin [State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084 (China); Zhang, Pengyi, E-mail: zpy@tsinghua.edu.cn [State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084 (China); Collaborative Innovation Center for Regional Environmental Quality (China); Kim, Jeonghyun [State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084 (China); Collaborative Innovation Center for Regional Environmental Quality (China)

    2015-12-01

    Graphical abstract: - Highlights: • The MnO{sub x} particles assembled with nanosheets were uniformly coated on PET fibers. • The growth process of MnO{sub x} layer on PET is clearly clarified. • MnO{sub x}/PET showed good activity for HCHO decomposition at room temperature. • MnO{sub x}/PET material is promising for indoor air purification due to its light, flexible and low air-resistant properties. - Abstract: Removal of low-level formaldehyde (HCHO) is of great interest for indoor air quality improvement. Supported materials especially those with low air pressure drop are of necessity for air purification. Manganese oxides (MnO{sub x}) was in situ deposited on the surface of fibers of a non-woven fabric made of polyethylene terephthalate (PET). As-synthesized MnO{sub x}/PET were characterized by SEM, XRD, TEM, ATR-FTIR and XPS analysis. The growth of MnO{sub x} layer on PET is thought to start with partial hydrolysis of PET, followed by surface oxidation by KMnO{sub 4} and then surface-deposition of MnO{sub x} particles from the bulk phase. The MnO{sub x} particles assembled with nanosheets were uniformly coated on the PET fibers. MnO{sub x}/PET showed good activity for HCHO decomposition at room temperature which followed the Mars–van Krevelen mechanism. The removal of HCHO was kept over 94% after 10 h continuous reaction under the conditions of inlet HCHO concentration ∼0.6 mg/m{sup 3}, space velocity ∼17,000 h{sup −1} and relative humidity∼50%. This research provides a facile method to deposit active MnO{sub x} onto polymers with low air resistance, and composite MnO{sub x}/PET material is promising for indoor air purification.

  3. Photophysics of α-furil at room temperature and 77 K: Spectroscopic and quantum chemical studies

    Energy Technology Data Exchange (ETDEWEB)

    Kundu, Pronab; Chattopadhyay, Nitin, E-mail: nitin.chattopadhyay@yahoo.com [Department of Chemistry, Jadavpur University, Kolkata 700 032 (India)

    2016-06-21

    Steady state and time resolved spectroscopic measurements have been exploited to assign the emissions from different conformations of α-furil (2, 2′-furil) in solution phase at room temperature as well as cryogen (liquid nitrogen, LN{sub 2}) frozen matrices of ethanol and methylcyclohexane. Room temperature studies reveal a single fluorescence from the trans-planar conformer of the fluorophore or two fluorescence bands coming from the trans-planar and the relaxed skew forms depending on excitation at the nπ{sup ∗} or the ππ{sup ∗} absorption band, respectively. Together with the fluorescence bands, the LN{sub 2} studies in both the solvents unambiguously ascertain two phosphorescence emissions with lifetimes 5 ± 0.3 ms (trans-planar triplet) and 81 ± 3 ms (relaxed skew triplet). Quantum chemical calculations have been performed using density functional theory at CAM-B3LYP/6-311++G{sup ∗∗} level to prop up the spectroscopic surveillance. The simulated potential energy curves (PECs) illustrate that α-furil is capable of giving two emissions from each of the S{sub 1} and the T{sub 1} states—one corresponding to the trans-planar and the other to the relaxed skew conformation. Contrary to the other 1,2-dicarbonyl molecular systems like benzil and α-naphthil, α-furil does not exhibit any fluorescence from its second excited singlet (S{sub 2}) state. This is ascribed to the proximity of the minimum of the PEC of the S{sub 2} state and the hill-top of the PEC of the S{sub 1} state.

  4. Enhanced magnetic and ferroelectric properties in scandium doped nano Bi2Fe4O9

    International Nuclear Information System (INIS)

    Dutta, Dimple P.; Sudakar, C.; Mocherla, Pavana S.V.; Mandal, Balaji P.; Jayakumar, Onnatu D.; Tyagi, Avesh K.

    2012-01-01

    In this study we report the synthesis of undoped and Sc 3+ doped Bi 2 Fe 4 O 9 nanoparticles using sonochemical technique. X-ray diffraction reveals that all samples are single phase with no impurities detected. EDS analysis was done to confirm the extent of Sc 3+ doping in the samples. The size and morphology of the nanoparticles have been analyzed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The Bi 2 Fe 4 O 9 nanoparticles show a weak ferromagnetic behavior at room temperature, which is quite different from the linear M–H relationship reported for bulk Bi 2 Fe 4 O 9 . A magnetization of 0.144 μB/f.u. is obtained at 300 K, which is mainly attributed to the uncompensated moments at the disordered particle surface resulting from the reduced coordination of the surface spins, arising due to lattice strain or oxygen deficiency. Addition of Sc 3+ dopant in varying concentrations in these Bi 2 Fe 4 O 9 nanoparticles, improves their magnetic as well as ferroelectric properties. The leakage current is considerably reduced and electric polarization increases significantly in case of Bi 2 Fe 4(1−x) Sc x O 9 (x = 0.1) nanoparticles. Thus it can be inferred that Sc 3+ doped Bi 2 Fe 4 O 9 nanoparticles shows promise as good multiferroic materials. -- Graphical abstract: Undoped and Sc 3+ doped Bi 2 Fe 4 O 9 nanoparticles have been synthesized using sonochemical technique. The bi-functionalities of Sc 3+ doped Bi 2 Fe 4 O 9 nanoparticles have been demonstrated. The Bi 2 Fe 4(1−x) Sc x O 9 (x = 0.1) nanoparticles showed enhanced magnetic and ferroelectric properties with considerably less lossy characteristics compared to the bulk Bi 2 Fe 4 O 9 . Highlights: ► Phase pure Bi 2 Fe 4 O 9 nanostructures synthesized using a facile sonochemical technique. ► Nanoparticles show a weak ferromagnetic order at room temperature. ► Sc 3+ doping in Bi 2 Fe 4 O 9 nanoparticles alters their magnetic and ferroelectric properties. ► A

  5. Evolution of interphase and intergranular stresses in Zr-2.5Nb during room temperature deformation

    International Nuclear Information System (INIS)

    Cai, S.; Daymond, M.R.; Holt, R.A.; Gharghouri, M.A.; Oliver, E.C.

    2009-01-01

    Both in situ tension and compression tests have been carried out on textured Zr-2.5Nb plate material at room temperature. Deformation along all the three principle plate directions has been studied and the evolution of interphase and intergranular strains along the loading and the principle Poisson's directions has been investigated by neutron diffraction. The evolution of interphase and intergranular strain was determined by the relative phase properties, crystal properties and texture distribution. The average phase behaviors are similar during tension and compression, where the β-phase in this material is stronger than the α-phase. The asymmetric yielding of the α-{0 0 0 2} grain family results in a relatively large intergranular strain in the loading direction during compression and different dependence of strength during tension and compression on texture. The combination of the thermal residual stress and the asymmetric CRSS in the axis gives the {0 0 0 2} grain family a higher strength in compression than in tension

  6. Origin of room temperature ferromagnetic moment in Rh-rich [Rh/Fe] multilayer thin films

    International Nuclear Information System (INIS)

    Kande, Dhishan; Laughlin, David; Zhu Jiangang

    2010-01-01

    B2 ordered FeRh thin films switch from antiferromagnetic (AFM) to ferromagnetic (FM) state on heating above 350 K and switch back on cooling, with a hysteresis. This property makes FeRh a very attractive choice as a write-assist layer material for low temperature heat assisted magnetic recording (HAMR) media. Studies have shown that as we decrease the thickness of the FeRh films, the B2 phase is no longer AFM even below 350 K and there is a thickness dependant FM stabilization of the B2 phase. It was also proved that slightly Rh-richer compositions (>50 at. % Rh) were more preferable to stabilize the AFM phase. The current study focuses on growing highly ordered FeRh films by alternate layer rf sputtering of thin layers of iron and rhodium onto a heated substrate. It has been shown that films with rhodium content beyond 55 at. % contain a disordered bcc FM phase which gives rise to residual moment at room temperature even for thicker films.

  7. Graphene-ferroelectric metadevices for nonvolatile memory and reconfigurable logic-gate operations

    Science.gov (United States)

    Kim, Woo Young; Kim, Hyeon-Don; Kim, Teun-Teun; Park, Hyun-Sung; Lee, Kanghee; Choi, Hyun Joo; Lee, Seung Hoon; Son, Jaehyeon; Park, Namkyoo; Min, Bumki

    2016-01-01

    Memory metamaterials are artificial media that sustain transformed electromagnetic properties without persistent external stimuli. Previous memory metamaterials were realized with phase-change materials, such as vanadium dioxide or chalcogenide glasses, which exhibit memory behaviour with respect to electrically/optically induced thermal stimuli. However, they require a thermally isolated environment for longer retention or strong optical pump for phase-change. Here we demonstrate electrically programmable nonvolatile memory metadevices realised by the hybridization of graphene, a ferroelectric and meta-atoms/meta-molecules, and extend the concept further to establish reconfigurable logic-gate metadevices. For a memory metadevice having a single electrical input, amplitude, phase and even the polarization multi-states were clearly distinguishable with a retention time of over 10 years at room temperature. Furthermore, logic-gate functionalities were demonstrated with reconfigurable logic-gate metadevices having two electrical inputs, with each connected to separate ferroelectric layers that act as the multi-level controller for the doping level of the sandwiched graphene layer.

  8. Voltage tunability of thermal conductivity in ferroelectric materials

    Science.gov (United States)

    Ihlefeld, Jon; Hopkins, Patrick Edward

    2016-02-09

    A method to control thermal energy transport uses mobile coherent interfaces in nanoscale ferroelectric films to scatter phonons. The thermal conductivity can be actively tuned, simply by applying an electrical potential across the ferroelectric material and thereby altering the density of these coherent boundaries to directly impact thermal transport at room temperature and above. The invention eliminates the necessity of using moving components or poor efficiency methods to control heat transfer, enabling a means of thermal energy control at the micro- and nano-scales.

  9. Phase segregation and dielectric, ferroelectric, and piezoelectric properties of MgO-doped NBT-BT lead-free ferroelecric ceramics

    Science.gov (United States)

    Liu, Gang; Wang, Ziyang; Zhang, Leiyang; Shi, Wenjing; Jing, Jiayi; Chen, Yi; Liu, Hongbo; Yan, Yan

    2018-03-01

    MgO doped NBT-BT ceramics were prepared by the conventional electroceramic processing. The effects of MgO on the phase, microstructures and electrical properties of NBT-BT ceramics were systematically investigated. When doping content is more than 1%, a second phase appeared, which has great effect on dielectric, ferroelectric, and piezoelectric properties, such as the T F-R peak weakened, moved to the higher temperature, and eventually disappeared. When the doping content is above 1.5%, the ceramic samples show a strong relaxation. The detailed analysis and discussion can be found within this study.

  10. Low-voltage operating flexible ferroelectric organic field-effect transistor nonvolatile memory with a vertical phase separation P(VDF-TrFE-CTFE)/PS dielectric

    Science.gov (United States)

    Xu, Meili; Xiang, Lanyi; Xu, Ting; Wang, Wei; Xie, Wenfa; Zhou, Dayu

    2017-10-01

    Future flexible electronic systems require memory devices combining low-power operation and mechanical bendability. However, high programming/erasing voltages, which are universally needed to switch the storage states in previously reported ferroelectric organic field-effect transistor (Fe-OFET) nonvolatile memories (NVMs), severely prevent their practical applications. In this work, we develop a route to achieve a low-voltage operating flexible Fe-OFET NVM. Utilizing vertical phase separation, an ultrathin self-organized poly(styrene) (PS) buffering layer covers the surface of the ferroelectric polymer layer by one-step spin-coating from their blending solution. The ferroelectric polymer with a low coercive field contributes to low-voltage operation in the Fe-OFET NVM. The polymer PS contributes to the improvement of mobility, attributing to screening the charge scattering and decreasing the surface roughness. As a result, a high performance flexible Fe-OFET NVM is achieved at the low P/E voltages of ±10 V, with a mobility larger than 0.2 cm2 V-1 s-1, a reliable P/E endurance over 150 cycles, stable data storage retention capability over 104 s, and excellent mechanical bending durability with a slight performance degradation after 1000 repetitive tensile bending cycles at a curvature radius of 5.5 mm.

  11. Determination of the physical properties of room temperature ionic liquids using a Love wave device.

    Science.gov (United States)

    Ouali, F Fouzia; Doy, Nicola; McHale, Glen; Hardacre, Christopher; Ge, Rile; Allen, Ray W K; MacInnes, Jordan M; Newton, Michael I

    2011-09-01

    In this work, we have shown that a 100 MHz Love wave device can be used to determine whether room temperature ionic liquids (RTILs) are Newtonian fluids and have developed a technique that allows the determination of the density-viscosity product, ρη, of a Newtonian RTIL. In addition, a test for a Newtonian response was established by relating the phase change to insertion loss change. Five concentrations of a water-miscible RTIL and seven pure RTILs were measured. The changes in phase and insertion loss were found to vary linearly with the square root of the density-viscosity product for values up to (ρη)(1/2) ~ 10 kg m(-2) s(-1/2). The square root of the density-viscosity product was deduced from the changes in either phase or insertion loss using glycerol as a calibration liquid. In both cases, the deduced values of ρη agree well with those measured using viscosity and density meters. Miniaturization of the device, beyond that achievable with the lower-frequency quartz crystal microbalance approach, to measure smaller volumes is possible. The ability to fabricate Love wave and other surface acoustic wave sensors using planar metallization technologies gives potential for future integration into lab-on-a-chip analytical systems for characterizing ionic liquids.

  12. Effect of thermal strain on the ferroelectric phase transition in polycrystalline Ba0.5Sr0.5TiO3 thin films studied by Raman spectroscopy

    International Nuclear Information System (INIS)

    Tenne, D.A.; Soukiassian, A.; Xi, X.X.; Taylor, T.R.; Hansen, P.J.; Speck, J.S.; York, R.A.

    2004-01-01

    We have applied Raman spectroscopy to study the influence of thermal strain on the vibrational properties of polycrystalline Ba 0.5 Sr 0.5 TiO 3 films. The films were grown by rf magnetron sputtering on Pt/SiO 2 surface using different host substrates: strontium titanate, sapphire, silicon, and vycor glass. These substrates provide a systematic change in the thermal strain while maintaining the same film microstructure. From the temperature dependence of the ferroelectric A 1 soft phonon intensity, the ferroelectric phase transition temperature, T C , was determined. We found that T C decreases with increasing tensile stress in the films. This dependence is different from the theoretical predictions for epitaxial ferroelectric films. The reduction of the ferroelectric transition temperature with increasing biaxial tensile strain is attributed to the suppression of in-plane polarization due to the small lateral grain size in the films

  13. Integration and High-Temperature Characterization of Ferroelectric Vanadium-Doped Bismuth Titanate Thin Films on Silicon Carbide

    Science.gov (United States)

    Ekström, Mattias; Khartsev, Sergiy; Östling, Mikael; Zetterling, Carl-Mikael

    2017-07-01

    4H-SiC electronics can operate at high temperature (HT), e.g., 300°C to 500°C, for extended times. Systems using sensors and amplifiers that operate at HT would benefit from microcontrollers which can also operate at HT. Microcontrollers require nonvolatile memory (NVM) for computer programs. In this work, we demonstrate the possibility of integrating ferroelectric vanadium-doped bismuth titanate (BiTV) thin films on 4H-SiC for HT memory applications, with BiTV ferroelectric capacitors providing memory functionality. Film deposition was achieved by laser ablation on Pt (111)/TiO2/4H-SiC substrates, with magnetron-sputtered Pt used as bottom electrode and thermally evaporated Au as upper contacts. Film characterization by x-ray diffraction analysis revealed predominately (117) orientation. P- E hysteresis loops measured at room temperature showed maximum 2 P r of 48 μC/cm2, large enough for wide read margins. P- E loops were measurable up to 450°C, with losses limiting measurements above 450°C. The phase-transition temperature was determined to be about 660°C from the discontinuity in dielectric permittivity, close to what is achieved for ceramics. These BiTV ferroelectric capacitors demonstrate potential for use in HT NVM applications for SiC digital electronics.

  14. Phase transition sequence in ferroelectric Aurivillius compounds investigated by single crystal X-ray diffraction

    Science.gov (United States)

    Boullay, P.; Tellier, J.; Mercurio, D.; Manier, M.; Zuñiga, F. J.; Perez-Mato, J. M.

    2012-09-01

    The investigation of the phase transition sequence in SrBi2Ta2O9 (SBT) and SrBi2Nb2O9 (SBN) is reported using single-crystal X-ray diffraction. By monitoring specific reflections as a function of temperature, sensitive either to the superstructure formation or to polar displacements, it was possible to check the existence or not of an intermediate phase. This latter was confirmed in SBT, but within experimental accuracy could not be detected in SBN.

  15. Study of the ferroelectric phase transition in germanium telluride using time-domain terahertz spectroscopy

    Czech Academy of Sciences Publication Activity Database

    Kadlec, Filip; Kadlec, Christelle; Kužel, Petr; Petzelt, Jan

    2011-01-01

    Roč. 84, č. 20 (2011), 205209/1-205209/8 ISSN 1098-0121 R&D Projects: GA ČR GC202/09/J045 Institutional research plan: CEZ:AV0Z10100520 Keywords : terahertz spectroscopy * phase transition * semiconductor Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.691, year: 2011

  16. Phase coexistence and electric-field control of toroidal order in oxide superlattices.

    Science.gov (United States)

    Damodaran, A R; Clarkson, J D; Hong, Z; Liu, H; Yadav, A K; Nelson, C T; Hsu, S-L; McCarter, M R; Park, K-D; Kravtsov, V; Farhan, A; Dong, Y; Cai, Z; Zhou, H; Aguado-Puente, P; García-Fernández, P; Íñiguez, J; Junquera, J; Scholl, A; Raschke, M B; Chen, L-Q; Fong, D D; Ramesh, R; Martin, L W

    2017-10-01

    Systems that exhibit phase competition, order parameter coexistence, and emergent order parameter topologies constitute a major part of modern condensed-matter physics. Here, by applying a range of characterization techniques, and simulations, we observe that in PbTiO 3 /SrTiO 3 superlattices all of these effects can be found. By exploring superlattice period-, temperature- and field-dependent evolution of these structures, we observe several new features. First, it is possible to engineer phase coexistence mediated by a first-order phase transition between an emergent, low-temperature vortex phase with electric toroidal order and a high-temperature ferroelectric a 1 /a 2 phase. At room temperature, the coexisting vortex and ferroelectric phases form a mesoscale, fibre-textured hierarchical superstructure. The vortex phase possesses an axial polarization, set by the net polarization of the surrounding ferroelectric domains, such that it possesses a multi-order-parameter state and belongs to a class of gyrotropic electrotoroidal compounds. Finally, application of electric fields to this mixed-phase system permits interconversion between the vortex and the ferroelectric phases concomitant with order-of-magnitude changes in piezoelectric and nonlinear optical responses. Our findings suggest new cross-coupled functionalities.

  17. Phase coexistence and electric-field control of toroidal order in oxide superlattices

    International Nuclear Information System (INIS)

    Damodaran, A. R.; Clarkson, J. D.; Hong, Z.

    2017-01-01

    Systems that exhibit phase competition, order parameter coexistence, and emergent order parameter topologies constitute a major part of modern condensed-matter physics. Here, by applying a range of characterization techniques, and simulations, we observe that in PbTiO 3 /SrTiO 3 superlattices all of these effects can be found. By exploring superlattice period-, temperature- and field-dependent evolution of these structures, we observe several new features. First, it is possible to engineer phase coexistence mediated by a first-order phase transition between an emergent, low-temperature vortex phase with electric toroidal order and a high-temperature ferroelectric a 1 /a 2 phase. At room temperature, the coexisting vortex and ferroelectric phases form a mesoscale, fibre-textured hierarchical superstructure. The vortex phase possesses an axial polarization, set by the net polarization of the surrounding ferroelectric domains, such that it possesses a multi-order-parameter state and belongs to a class of gyrotropic electrotoroidal compounds. Finally, application of electric fields to this mixed-phase system permits interconversion between the vortex and the ferroelectric phases concomitant with order-of-magnitude changes in piezoelectric and nonlinear optical responses. Here, our findings suggest new cross-coupled functionalities.

  18. Experimental evidence of enhanced ferroelectricity in Ca doped BiFeO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Costa, L.V.; Deus, R.C. [Universidade Estadual Paulista, UNESP, Faculdade de Engenharia de Guaratinguetá, Av. Dr. Ariberto Pereira da Cunha, 333, Bairro Portal das Colinas, CEP 12516-410 Guaratinguetá, SP (Brazil); Foschini, C.R.; Longo, E. [Universidade Estadual Paulista, UNESP, Faculdade de Engenharia de Bauru, Dept. de Eng. Mecânica, Av. Eng. Luiz Edmundo C. Coube 14-01, 17033-360 Bauru, SP (Brazil); Cilense, M. [Universidade Estadual Paulista, UNESP, Instituto de Química – Laboratório Interdisciplinar em Cerâmica (LIEC), Rua Professor Francisco Degni s/n, 14800-90 Araraquara, SP (Brazil); Simões, A.Z., E-mail: alezipo@yahoo.com [Universidade Estadual Paulista, UNESP, Faculdade de Engenharia de Guaratinguetá, Av. Dr. Ariberto Pereira da Cunha, 333, Bairro Portal das Colinas, CEP 12516-410 Guaratinguetá, SP (Brazil)

    2014-04-01

    Calcium (Ca)-doped bismuth ferrite (BiFeO{sub 3}) thin films prepared by using the polymeric precursor method (PPM) were characterized by X-ray diffraction (XRD), field emission gun scanning electron microscopy (FEG-SEM), transmission electron microscopy (TEM), polarization and piezoelectric measurements. Structural studies by XRD and TEM reveal the co-existence of distorted rhombohedral and tetragonal phases in the highest doped BiFeO{sub 3} where enhanced ferroelectric and piezoelectric properties are produced by internal strain. Resistive switching is observed in BFO and Ca-doped BFO which are affected by the barrier contact and work function of multiferroic materials and Pt electrodes. A high coercive field in the hysteresis loop is observed for the BiFeO{sub 3} film. Piezoelectric properties are improved in the highest Ca-doped sample due to changes in the crystal structure of BFO for a primitive cubic perovskite lattice with four-fold symmetry and a large tetragonal distortion within the crystal domain. This observation introduces magnetoelectronics at room temperature by combining electronic conduction with electric and magnetic degrees of freedom which are already present in the multiferroic BiFeO{sub 3}. - Highlights: • Ca doped BiFeO{sub 3} thin films were obtained by the polymeric precursor method. • Co-existence of distorted rhombohedral and tetragonal phases are evident. • Enhanced ferroelectric and piezoelectric properties are produced by the internal strain in the Ca doped BiFeO{sub 3} film.

  19. Electrical properties and Raman studies of phase transitions in ferroelectric [N(CH3)4]2CoCl2Br2

    Science.gov (United States)

    Ben Mohamed, C.; Karoui, K.; Bulou, A.; Ben Rhaiem, A.

    2018-03-01

    The present paper accounted for the synthesis, electric properties and vibrational spectroscopy of [N(CH3)4]2CoCl2Br2. The dielectric spectra were measured in the frequency range 10-1-105 Hz and temperature interval from 223 to 393 K. The dielectical properties confirm the ferroelectric-paraelectric phase transition at 290 K, which is reported by Abdallah Ben Rhaiem et al. (2013). The equivalent circuit based on the Z-View-software was proposed and the conduction mechanisms were determined. The obtained results have been discussed in terms of the correlated barrier hopping model (CBH) in phase I and non-overlapping small polaron tunneling model (NSPT) in phases II and III. Raman spectra as function temperature have been used to characterize the phase transitions and their nature, which indicates a change of the some peak near the transitions phase.

  20. Electric-Field Control of Magnetism in Co40Fe40B20/(1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 Multiferroic Heterostructures with Different Ferroelectric Phases.

    Science.gov (United States)

    Liu, Yan; Zhao, Yonggang; Li, Peisen; Zhang, Sen; Li, Dalai; Wu, Hao; Chen, Aitian; Xu, Yang; Han, X F; Li, Shiyan; Lin, Di; Luo, Haosu

    2016-02-17

    Electric-field control of magnetism in multiferroic heterostructures composed of Co40Fe40B20 (CoFeB) and (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-xPT) with different ferroelectric phases via changing composition and temperature is explored. It is demonstrated that the nonvolatile looplike bipolar-electric-field-controlled magnetization, previously found in the CoFeB/PMN-xPT heterostructures with PMN-xPT in the rhombohedral (R) phase around the morphotropic phase boundary (MPB), also occurs for PMN-xPTs with both R phase (far away from MPB) and monoclinic (M) phase, suggesting that the phenomenon is the common feature of CoFeB/PMN-xPT multiferroic heterostructures for PMN-xPT with different phases. The magnitude of the effect changes with increasing temperature and volatile bipolar-electric-field-controlled magnetization with a butterflylike behavior occurs when the ferroelectric phase changes to the tetragonal phase (T). Moreover, for the R-phase sample with x = 0.18, an abrupt and giant increase of magnetization is observed at a characteristic temperature in the temperature dependence of magnetization curve. These results are discussed in terms of coupling between magnetism and ferroelectric domains including macro- and microdomains for different ferroelectric phases. This work is helpful for understanding the phenomena of electric-field control of magnetism in FM/FE multiferroic heterostructures and is also important for applications.

  1. Effects of minor Si on microstructures and room temperature fracture toughness of niobium solid solution alloys

    Energy Technology Data Exchange (ETDEWEB)

    Kong, Bin, E-mail: kongbin@buaa.edu.cn; Jia, Lina, E-mail: jialina@buaa.edu.cn; Su, Linfen, E-mail: sulinfen@mse.buaa.edu.cn; Guan, Kai, E-mail: guankai@mse.buaa.edu.cn; Weng, Junfei, E-mail: wengjf@mse.buaa.edu.cn; Zhang, Hu, E-mail: zhanghu@buaa.edu.cn

    2015-07-15

    Controlling the elements content in the niobium solid solution (Nb{sub SS}) is significant for the better comprehensive performance of Nb-silicide-based alloys. In this paper, the effects of minor Si on the microstructures and room temperature fracture toughness of Nb–(0/0.5/1/2)Si–27.63Ti–12.92Cr–2.07Al–1.12Hf (at%, unless stated otherwise) solid solution alloys were investigated. The alloys were processed by vacuum arc-casting (AC), and then heat treated (HT) at 1425 °C for 10 h. In HT alloys, Nb{sub SS} grains are refined gradually with the increase of Si content. Meanwhile, the volume fraction of Cr{sub 2}Nb and silicides phases precipitates increases. The fracture toughness of HT alloys decreases at first but then increases in the range of 0 to 2% Si, because it is a combinatorial process of positive and negative effects caused by the addition of Si. The refinement of Nb{sub SS} grains displays positive effect on fracture toughness, while the increase of solid solubility of Si in Nb{sub SS} and brittle Cr{sub 2}Nb and Nb-silicides precipitate phases display negative effect.

  2. Controlling the selective formation of calcium sulfate polymorphs at room temperature.

    Science.gov (United States)

    Tritschler, Ulrich; Van Driessche, Alexander E S; Kempter, Andreas; Kellermeier, Matthias; Cölfen, Helmut

    2015-03-23

    Calcium sulfate is a naturally abundant and technologically important mineral with a broad scope of applications. However, controlling CaSO4 polymorphism and, with it, its final material properties still represents a major challenge, and to date there is no universal method for the selective production of the different hydrated and anhydrous forms under mild conditions. Herein we report the first successful synthesis of pure anhydrite from solution at room temperature. We precipitated calcium sulfate in alcoholic media at low water contents. Moreover, by adjusting the amount of water in the syntheses, we can switch between the distinct polymorphs and fine-tune the outcome of the reaction, yielding either any desired CaSO4 phase in pure state or binary mixtures with predefined compositions. This concept provides full control over phase selection in CaSO4 mineralization and may allow for the targeted fabrication of corresponding materials for use in various areas. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Room temperature resistive state switching with hysteresis in GdMnO3 thin film with low threshold voltage

    International Nuclear Information System (INIS)

    Nath, Rajib; Raychaudhuri, A. K.; Mukovskii, Ya. M.; Andreev, N.; Chichkov, Vladimir

    2014-01-01

    In this paper, we report a room temperature resistive state switching with hysteresis, in a thin film of GdMnO 3 grown on NdGaO 3 substrate. The switched states have a resistance ratio ≈10 3 . The switching is unipolar in nature, with a low set voltage <3 V, while the reset voltage <0.3 V. The switching occurs between a high resistance polaronic insulating state and a low resistance metallic state. The resistance state transition has been ascribed to an electronic mechanism that originates from co-existing phases (created by charge disproportionation) that can undergo a percolative transition enabled by the applied bias

  4. Scalable room-temperature conversion of copper(II) hydroxide into HKUST-1 (Cu3 (btc)2).

    Science.gov (United States)

    Majano, Gerardo; Pérez-Ramírez, Javier

    2013-02-20

    Copper(II) hydroxide is converted directly to HKUST-1 (Cu(3) (btc)(2) ) after only 5 min at room-temperature in aqueous ethanolic solution without the need of additional solvents. Scale up to the kilogram scale does not influence porous properties yielding pure-phase product with a remarkable total surface area exceeding 1700 m(2) g(-1) featuring aggregates of nanometer-sized crystals (<600 nm) and extremely high space-time yields. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Red photoluminescence of living systems at the room temperature: measurements and results

    International Nuclear Information System (INIS)

    Kudryashova, I S; Rud, V Yu; Shpunt, V Ch; Rud, Yu V; Glinushkin, A P

    2016-01-01

    Presents results of a study of the red luminescence of living plants at room temperature. The analysis of obtained results allows to conclude that the photoluminescence spectra for green leaves in all cases represent the two closely spaced bands. (paper)

  6. Stability of 2-Alkylcyclobutanones in irradiated retort pouch Gyudon topping during room temperature storage

    International Nuclear Information System (INIS)

    Kitagawa, Yoko; Okihashi, Masahiro; Takatori, Satoshi; Fukui, Naoki; Kajimura, Keiji; Obana, Hirotaka; Furuta, Masakazu

    2016-01-01

    2-Alkylcyclobutanones (ACBs), such as 2-dodecylcyclobutanone (DCB) and 2-tetradecylcylobutanone (TCB) are specific products in the irradiated liquid. Thus, DCB and TCB are suitable for indicators of the irradiation history of food. We previously reported DCB and TCB concentrations in irradiated retort pouch Gyudon topping (instant Gyudon mixes which were made from a beef, onion and soy sauce and could be preserved for a long term at room temperature) after storage for one year. Here, we have evaluated the stability of ACBs preserved in irradiated retort pouch Gyudon topping at room temperature for three years. Although interfering peaks were detected frequently after the storage at room temperature, it was possible for the detection of the irradiation history and there was no apparent decrease of ACBs concentrations in comparison with the one year storage after irradiation. These results concluded that DCB and TCB formed in retort pouch would be stable at room temperature for three years. (author)

  7. Hydrogen-induced room-temperature plasticity in TC4 and TC21 alloys

    DEFF Research Database (Denmark)

    Yuan, Baoguo; Jin, Yongyue; Hong, Chuanshi

    2017-01-01

    In order to reveal the effect of hydrogen on the room-temperature plasticity of the titanium alloys TC4 and TC21, compression tests have been carried out at room temperature. Results show that an appropriate amount of hydrogen can improve the room-temperature plasticity of both the TC4 and TC21...... alloys. The ultimate compression strain of the TC4 alloy containing a hydrogen concentration of 0.5 wt.% increases by 39% compared to the untreated material. For the TC21 alloy the ultimate compression strain is increased by 33% at a hydrogen concentration of 0.6 wt.%. The main reason for the improvement...... of hydrogen-induced room-temperature plasticity of the TC4 and TC21 alloys is discussed....

  8. Controlled laser biochemistry in room-temperature polar liquids by ultrashort laser pulses

    DEFF Research Database (Denmark)

    Gruzdev, Vitaly; Korkin, Dmitry; Mooney, Brian P.

    2018-01-01

    Traditional laser methods to control chemical modifications of biomolecules are not applicable under biologically relevant conditions. We report controlled modifications of peptides and insulin by femtosecond laser in water, methanol, and acetonitrile at room temperature...

  9. Branched carbon nanofiber network synthesis at room temperature using radio frequency supported microwave plasmas

    International Nuclear Information System (INIS)

    Boskovic, Bojan O.; Stolojan, Vlad; Zeze, Dagou A.; Forrest, Roy D.; Silva, S. Ravi P.; Haq, Sajad

    2004-01-01

    Carbon nanofibers have been grown at room temperature using a combination of radio frequency and microwave assisted plasma-enhanced chemical vapor deposition. The nanofibers were grown, using Ni powder catalyst, onto substrates kept at room temperature by using a purposely designed water-cooled sample holder. Branched carbon nanofiber growth was obtained without using a template resulting in interconnected carbon nanofiber network formation on substrates held at room temperature. This method would allow room-temperature direct synthesized nanofiber networks over relatively large areas, for a range of temperature sensitive substrates, such as organic materials, plastics, and other polymers of interest for nanoelectronic two-dimensional networks, nanoelectromechanical devices, nanoactuators, and composite materials

  10. Nickel-catalyzed synthesis of aryl trifluoromethyl sulfides at room temperature.

    Science.gov (United States)

    Zhang, Cheng-Pan; Vicic, David A

    2012-01-11

    Inexpensive nickel-bipyridine complexes were found to be active for the trifluoromethylthiolation of aryl iodides and aryl bromides at room temperature using the convenient [NMe(4)][SCF(3)] reagent. © 2011 American Chemical Society

  11. Room-Temperature Single-Photon Source for Secure Quantum Communication

    Data.gov (United States)

    National Aeronautics and Space Administration — We are asking for four years of support for PhD student Justin Winkler's work on a research project entitled "Room temperature single photon source for secure...

  12. Influence of sequential room-temperature compressive creep on flow stress of TA2

    Science.gov (United States)

    Mengyuan, Zhang; Boqin, Gu; Jiahui, Tao

    2018-03-01

    This paper studied the sequential room temperature compressive creep and its effects on compressive properties of TA2 with stress-control loading pattern by using cylindrical compressive test specimen. The significant time-dependent deformation under constant load was observed in the TA2 at room temperature, and the deformation was dependent on the loading process under the same loading stress rate. It was also found that the occurrence of room temperature compressive creep obviously enhanced the subsequent yielding strength and flow stress of TA2 due to the increase of network dislocation density. And the effects of room temperature creep on the strain rate-stress behavior could be explained by the local mobile dislocation density model.

  13. Monitoring and understanding the paraelectric-ferroelectric phase transition in the metal-organic framework [NH4 ][M(HCOO)3 ] by solid-state NMR spectroscopy.

    Science.gov (United States)

    Xu, Jun; Lucier, Bryan E G; Sinelnikov, Regina; Terskikh, Victor V; Staroverov, Viktor N; Huang, Yining

    2015-10-05

    The paraelectric-ferroelectric phase transition in two isostructural metal-organic frameworks (MOFs) [NH4 ][M(HCOO)3 ] (M=Mg, Zn) was investigated by in situ variable-temperature (25) Mg, (67) Zn, (14) N, and (13) C solid-state NMR (SSNMR) spectroscopy. With decreasing temperature, a disorder-order transition of NH4 (+) cations causes a change in dielectric properties. It is thought that [NH4 ][Mg(HCOO)3 ] exhibits a higher transition temperature than [NH4 ][Zn(HCOO)3 ] due to stronger hydrogen-bonding interactions between NH4 (+) ions and framework oxygen atoms. (25) Mg and (67) Zn NMR parameters are very sensitive to temperature-induced changes in structure, dynamics, and dielectric behavior; stark spectral differences across the paraelectric-ferroelectric phase transition are intimately related to subtle changes in the local environment of the metal center. Although (25) Mg and (67) Zn are challenging nuclei for SSNMR experiments, the highly spherically symmetric metal-atom environments in [NH4 ][M(HCOO)3 ] give rise to relatively narrow spectra that can be acquired in 30-60 min at a low magnetic field of 9.4 T. Complementary (14) N and (13) C SSNMR experiments were performed to probe the role of NH4 (+) -framework hydrogen bonding in the paraelectric-ferroelectric phase transition. This multinuclear SSNMR approach yields new physical insights into the [NH4 ][M(HCOO)3 ] system and shows great potential for molecular-level studies on electric phenomena in a wide variety of MOFs. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Ferroelectricity in undoped hafnium oxide

    International Nuclear Information System (INIS)

    Polakowski, Patrick; Müller, Johannes

    2015-01-01

    We report the observation of ferroelectric characteristics in undoped hafnium oxide thin films in a thickness range of 4–20 nm. The undoped films were fabricated using atomic layer deposition (ALD) and embedded into titanium nitride based metal-insulator-metal (MIM) capacitors for electrical evaluation. Structural as well as electrical evidence for the appearance of a ferroelectric phase in pure hafnium oxide was collected with respect to film thickness and thermal budget applied during titanium nitride electrode formation. Using grazing incidence X-Ray diffraction (GIXRD) analysis, we observed an enhanced suppression of the monoclinic phase fraction in favor of an orthorhombic, potentially, ferroelectric phase with decreasing thickness/grain size and for a titanium nitride electrode formation below crystallization temperature. The electrical presence of ferroelectricity was confirmed using polarization measurements. A remanent polarization P r of up to 10 μC cm −2 as well as a read/write endurance of 1.6 × 10 5 cycles was measured for the pure oxide. The experimental results reported here strongly support the intrinsic nature of the ferroelectric phase in hafnium oxide and expand its applicability beyond the doped systems

  15. Evolution from successive phase transitions to "morphotropic phase boundary" in BaTiO3-based ferroelectrics

    Science.gov (United States)

    Zhou, Chao; Ke, Xiaoqin; Yao, Yonggang; Yang, Sen; Ji, Yuanchao; Liu, Wenfeng; Yang, Yaodong; Zhang, Lixue; Hao, Yanshuang; Ren, Shuai; Zhang, Le; Ren, Xiaobing

    2018-04-01

    Obtaining superior physical properties for ferroic materials by manipulating the phase transitions is a key concern in solid state physics. Here, we investigated the dielectric permittivity, piezoelectric coefficient d33, storage modulus, and crystal symmetry of (1-x)Ba(Ti0.8Zr0.2)O3-x(Ba1-yCay)TiO3 (BZT-xBCyT) systems to demonstrate the gradual evolution process from successive phase transitions in BaTiO3 to the morphotropic phase boundary (MPB) regime in BZT-xBC0.3T. Furthermore, we analysed with a Landau-type theoretical model to show that the high field-sensitive response (dielectric permittivity) originates from a small polarization anisotropy and low energy barrier at the quadruple point. Together, the intermediate orthorhombic phase regime and the tetragonal-orthorhombic and orthorhombic-rhombohedral phase boundaries constitute the MPB. Our work not only reconciles the arguments regarding whether the structural state around the MPB corresponds to a single-phase regime or a multiple-phase-coexistence regime but also suggests an effective method to design high-performance functional ferroic materials by tailoring the successive phase transitions.

  16. Crystalline Microporous Organosilicates with Reversed Functionalities of Organic and Inorganic Components for Room-Temperature Gas Sensing.

    Science.gov (United States)

    Fabbri, Barbara; Bonoldi, Lucia; Guidi, Vincenzo; Cruciani, Giuseppe; Casotti, Davide; Malagù, Cesare; Bellussi, Giuseppe; Millini, Roberto; Montanari, Luciano; Carati, Angela; Rizzo, Caterina; Montanari, Erica; Zanardi, Stefano

    2017-07-26

    A deepened investigation on an innovative organic-inorganic hybrid material, referred to as ECS-14 (where ECS = Eni carbon silicates), revealed the possibility to use them as gas sensors. Indeed, among ECS phases, the crystalline state and the hexagonal microplateletlike morphology characteristic of ECS-14 seemed favorable properties to obtain continuous and uniform films. ECS-14 phase was used as functional material in screen-printable compositions and was thus deposited by drop coating for morphological, structural, thermal, and electrical characterizations. Possible operation at room temperature was investigated as technological progress, offering intrinsic safety in sensors working in harsh or industrial environments and avoiding high power consumption of most common sensors based on metal oxide semiconductors. Electrical characterization of the sensors based on ECS-14 versus concentrations of gaseous analytes gave significant results at room temperature in the presence of humidity, thereby demonstrating fundamental properties for a good quality sensor (speed, reversibility, and selectivity) that make them competitive with respect to systems currently in use. Remarkably, we observed functionality reversal of the organic and inorganic components; that is, in contrast to other hybrids, for ECS-14 the functional site has been ascribed to the inorganic phase while the organic component provided structural stability to the material. The sensing mechanism for humidity was also investigated.

  17. Microstructure and Room-Temperature Mechanical Properties of FeCrMoVTi x High-Entropy Alloys

    Science.gov (United States)

    Guo, Jun; Huang, Xuefei; Huang, Weigang

    2017-07-01

    FeCrMoVTi x ( x values represent the molar ratio, where x = 0, 0.5, 1.0, 1.5, and 2.0) high-entropy alloys were prepared by a vacuum arc melting method. The effects of Ti element on the microstructure and room-temperature mechanical properties of the as-cast FeCrMoVTi x alloys were investigated. The results show that the prepared alloys exhibited typical dendritic microstructure and the size of the microstructure became fine with increasing Ti content. The FeCrMoV alloy exhibited a single body-centered cubic structure (BCC1) and the alloys prepared with Ti element exhibited BCC1 + BCC2 mixed structure. The new BCC2 phase is considered as (Fe, Ti)-rich phase and was distributed in the dendrite region. With the increase of Ti content, the volume fraction of the BCC2 phase increased and its shape changed from a long strip to a network. For the FeCrMoV alloy, the fracture strength, plastic strain, and hardness reached as high as 2231 MPa, 28.2%, and 720 HV, respectively. The maximum hardness of 887 HV was obtained in the FeCrMoVTi alloy. However, the fracture strength, yield stress, and plastic strain of the alloys decreased continuously as Ti content increased. In the room-temperature compressive test, the alloys showed typical brittle fracture characteristics.

  18. Room Temperature Tunable Multiferroic Properties in Sol-Gel-Derived Nanocrystalline Sr(Ti1−xFexO3−δ Thin Films

    Directory of Open Access Journals (Sweden)

    Yi-Guang Wang

    2017-09-01

    Full Text Available Sr(Ti1−xFexO3−δ (0 ≤ x ≤ 0.2 thin films were grown on Si(100 substrates with LaNiO3 buffer-layer by a sol-gel process. Influence of Fe substitution concentration on the structural, ferroelectric, and magnetic properties, as well as the leakage current behaviors of the Sr(Ti1−xFexO3−δ thin films, were investigated by using the X-ray diffractometer (XRD, atomic force microscopy (AFM, the ferroelectric test system, and the vibrating sample magnetometer (VSM. After substituting a small amount of Ti ion with Fe, highly enhanced ferroelectric properties were obtained successfully in SrTi0.9Ti0.1O3−δ thin films, with a double remanent polarization (2Pr of 1.56, 1.95, and 9.14 μC·cm−2, respectively, for the samples were annealed in air, oxygen, and nitrogen atmospheres. The leakage current densities of the Fe-doped SrTiO3 thin films are about 10−6–10−5 A·cm−2 at an applied electric field of 100 kV·cm−1, and the conduction mechanism of the thin film capacitors with various Fe concentrations has been analyzed. The ferromagnetic properties of the Sr(Ti1−xFexO3−δ thin films have been investigated, which can be correlated to the mixed valence ions and the effects of the grain boundary. The present results revealed the multiferroic nature of the Sr(Ti1−xFexO3−δ thin films. The effect of the annealing environment on the room temperature magnetic and ferroelectric properties of Sr(Ti0.9Fe0.1O3−δ thin films were also discussed in detail.

  19. Room temperature synthesis of Ni-based alloy nanoparticles by radiolysis.

    Energy Technology Data Exchange (ETDEWEB)

    Nenoff, Tina Maria; Berry, Donald T.; Lu, Ping; Leung, Kevin; Provencio, Paula Polyak; Stumpf, Roland Rudolph; Huang, Jian Yu; Zhang, Zhenyuan

    2009-09-01

    Room temperature radiolysis, density functional theory, and various nanoscale characterization methods were used to synthesize and fully describe Ni-based alloy nanoparticles (NPs) that were synthesized at room temperature. These complementary methods provide a strong basis in understanding and describing metastable phase regimes of alloy NPs whose reaction formation is determined by kinetic rather than thermodynamic reaction processes. Four series of NPs, (Ag-Ni, Pd-Ni, Co-Ni, and W-Ni) were analyzed and characterized by a variety of methods, including UV-vis, TEM/HRTEM, HAADF-STEM and EFTEM mapping. In the first focus of research, AgNi and PdNi were studied. Different ratios of Ag{sub x}- Ni{sub 1-x} alloy NPs and Pd{sub 0.5}- Ni{sub 0.5} alloy NP were prepared using a high dose rate from gamma irradiation. Images from high-angle annular dark-field (HAADF) show that the Ag-Ni NPs are not core-shell structure but are homogeneous alloys in composition. Energy filtered transmission electron microscopy (EFTEM) maps show the homogeneity of the metals in each alloy NP. Of particular interest are the normally immiscible Ag-Ni NPs. All evidence confirmed that homogeneous Ag-Ni and Pd-Ni alloy NPs presented here were successfully synthesized by high dose rate radiolytic methodology. A mechanism is provided to explain the homogeneous formation of the alloy NPs. Furthermore, studies of Pd-Ni NPs by in situ TEM (with heated stage) shows the ability to sinter these NPs at temperatures below 800 C. In the second set of work, CoNi and WNi superalloy NPs were attempted at 50/50 concentration ratios using high dose rates from gamma irradiation. Preliminary results on synthesis and characterization have been completed and are presented. As with the earlier alloy NPs, no evidence of core-shell NP formation occurs. Microscopy results seem to indicate alloying occurred with the CoNi alloys. However, there appears to be incomplete reduction of the Na{sub 2}WO{sub 4} to form the W

  20. Formation of rutile fasciculate zone induced by sunlight irradiation at room temperature and its hemocompatibility

    International Nuclear Information System (INIS)

    Zhang, Xuan-Hui; Zheng, Xiang; Cheng, Yuan; Li, Guo-Hua; Chen, Xiao-Ping; Zheng, Jian-Hui

    2013-01-01

    The fasciculate zone of phase pure rutile was fabricated under sunlight irradiation at room temperature, using titanium tetrachloride as a sole precursor. The crystal phase, morphology and microstructure, and optical absorption behavior of the samples were characterized by X-ray Diffraction, High-Resolution Transmission Electron Microscope (HRTEM) and UV–vis Diffuse Reflectance Spectra (DRS), respectively. XRD results show that the crystal phase of the sample is composed of rutile only, and a lattice distortion displays in the crystallite of the sample. HRTEM results show that the morphology of rutile particle is fasciculate zone constituted of nanoparticles with a diameter of 4–7 nm, and these particles grow one by one and step by step. The pattern of the selected area electron diffraction of the sample is Kikuchi type, which can be attributed to the predominant orientation growth of rutile nanoparticles along [001] induced by sunlight irradiation. DRS results show that the absorption threshold of the sample is 415 nm, corresponding to the band gap energy of 2.99 eV, which is lower than the band gap energy of rutile, 3.03 eV. Blood compatibility measurement shows that the sample has no remarkable effect on hemolytic and coagulation activity. The percent hemolysis of red blood cells is less than 5% even treated with a big dosage of the fasciculate rutile and under UV irradiation, and there are no obvious changes of plasma recalcification time after the rutile treatment. Thus, the novel structure of rutile fasciculate has low potential toxicity for blood and is hemocompatibility safe. Highlights: • A novel approach to fabricate the fasciculate zone of phase pure rutile • The fasciculate grows from a particle to nanorod and to fasciculate, step by step. • A preferred orientation growth induced by sunlight irradiation in the fasciculate • The rutile fasciculate is low toxicity for blood and is hemocompatibility safe

  1. Abnormal room temperature ferromagnetism in CuO/ZnO nanocomposites via hydrothermal method

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Ping; Zhou, Wei; Li, Ying; Wang, Jianchun; Wu, Ping, E-mail: pingwu@tju.edu.cn

    2017-03-31

    Highlights: • CuO/ZnO nanocomposites have been synthesized by a one-step hydrothermal method. • The interaction between ZnO and CuO causes a modification of electronic structure. • The abnormal RTFM is discovered at the interface of CuO/ZnO. • The M{sub S} can be tuned by changing the phase ratios of the CuO and ZnO. • The indirect double-exchange model was employed to explain the origin of magnetism. - Abstract: CuO/ZnO nanocomposites have been successfully synthesized by a one-step hydrothermal method with different phase ratios. Field emission scanning electron microscopy and transmission electron microscopy results show that the obtained products of nanosheets are composed of small primary particles with an average size of about 20 nm. With the increasing proportion of CuO phase, nanosheets have significant collapse and the amount of small sheets increases obviously. The abnormal room temperature ferromagnetism was discovered at the interface between diamagnetic ZnO and antiferromagnetic CuO, which can be tuned by changing the phase ratios. Optical spectra indicate that the interaction between ZnO and CuO modifies the electronic structure of nanocomposites. XPS results verify the valence change of Cu ions and the presence of oxygen vacancies, which are ultimately responsible for the observed ferromagnetism. The indirect double-exchange model was employed to explain the origin of magnetism. Our study suggests that magnetically functional interfaces exhibit very appealing properties for novel devices.

  2. Evolution of ferroelectric SrBi2Nb2O9 phase embedded in tellurite glass

    Science.gov (United States)

    Mohamed, E. A.

    2017-12-01

    Glasses with the composition, [(100-x)TeO2- x(SrO-Bi2O3-Nb2O5)] with x = 20, 30 and 40 (in mol %) were prepared. The X-ray diffraction (XRD) pattern and differential thermal analysis (DTA) for the as-prepared samples confirmed the amorphous and glassy characteristics, respectively. The SrBi2Nb2O9 phase in tellurite glass for HT773 sample at x = 40 mol % is formed and confirmed by the Rietveld refinement. DTA curves for all glass samples exhibit two endothermic dips while the two broad exothermic peaks at lower x reduced to one at higher x. Infrared (IR) results revealed that the glassy matrix are composed of TeO3, TeO3+1, TeO4, BiO6 and NbO6 structural units. The changes in the density (ρ), molar volume (Vm), oxygen molar volume (V0) and oxygen packing fraction (OPD) have correlated with structural changes in the glass network. The optical studies show an absorption bands below the absorption edge in the glass samples.

  3. In situ synthesis of manganese oxides on polyester fiber for formaldehyde decomposition at room temperature

    Science.gov (United States)

    Wang, Jinlong; Yunus, Rizwangul; Li, Jinge; Li, Peilin; Zhang, Pengyi; Kim, Jeonghyun

    2015-12-01

    Removal of low-level formaldehyde (HCHO) is of great interest for indoor air quality improvement. Supported materials especially those with low air pressure drop are of necessity for air purification. Manganese oxides (MnOx) was in situ deposited on the surface of fibers of a non-woven fabric made of polyethylene terephthalate (PET). As-synthesized MnOx/PET were characterized by SEM, XRD, TEM, ATR-FTIR and XPS analysis. The growth of MnOx layer on PET is thought to start with partial hydrolysis of PET, followed by surface oxidation by KMnO4 and then surface-deposition of MnOx particles from the bulk phase. The MnOx particles assembled with nanosheets were uniformly coated on the PET fibers. MnOx/PET showed good activity for HCHO decomposition at room temperature which followed the Mars-van Krevelen mechanism. The removal of HCHO was kept over 94% after 10 h continuous reaction under the conditions of inlet HCHO concentration ∼0.6 mg/m3, space velocity ∼17,000 h-1 and relative humidity∼50%. This research provides a facile method to deposit active MnOx onto polymers with low air resistance, and composite MnOx/PET material is promising for indoor air purification.

  4. CuO nanostructures on copper foil by a simple wet chemical route at room temperature

    International Nuclear Information System (INIS)

    Jana, S.; Das, S.; Das, N.S.; Chattopadhyay, K.K.

    2010-01-01

    Uniform CuO nanostructures have been synthesized on copper foil substrates by oxidation of Cu in alkaline condition by a simple wet chemical route at room temperature. By controlling the alkaline condition (pH value) different CuO nanostructures like nanoneedles, self-assembled nanoflowers and staking of flake-like structures were achieved. The phase formation and the composition of the films were characterized by X-ray diffraction and energy dispersive analysis of X-ray studies. X-ray photoelectron spectroscopic studies indicated that the samples were composed of CuO. The morphologies of the films were investigated by scanning electron microscopy. A possible growth mechanism is also proposed here. Band gap energies of the nanostructures were determined from the optical reflectance spectra. The different CuO nanostructures showed good electron field emission properties with turn-on fields in the range 6-11.3 V μm -1 . The field emission current was significantly affected by the morphologies of the CuO films.

  5. Investigation of Pristine Graphite Oxide as Room-Temperature Chemiresistive Ammonia Gas Sensing Material

    Directory of Open Access Journals (Sweden)

    Alexander G. Bannov

    2017-02-01

    Full Text Available Graphite oxide has been investigated as a possible room-temperature chemiresistive sensor of ammonia in a gas phase. Graphite oxide was synthesized from high purity graphite using the modified Hummers method. The graphite oxide sample was investigated using scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, thermogravimetry and differential scanning calorimetry. Sensing properties were tested in a wide range of ammonia concentrations in air (10–1000 ppm and under different relative humidity levels (3%–65%. It was concluded that the graphite oxide–based sensor possessed a good response to NH3 in dry synthetic air (ΔR/R0 ranged from 2.5% to 7.4% for concentrations of 100–500 ppm and 3% relative humidity with negligible cross-sensitivity towards H2 and CH4. It was determined that the sensor recovery rate was improved with ammonia concentration growth. Increasing the ambient relative humidity led to an increase of the sensor response. The highest response of 22.2% for 100 ppm of ammonia was achieved at a 65% relative humidity level.

  6. Bipolar resistive switching in room temperature grown disordered vanadium oxide thin-film devices

    Science.gov (United States)

    Wong, Franklin J.; Sriram, Tirunelveli S.; Smith, Brian R.; Ramanathan, Shriram

    2013-09-01

    We demonstrate bipolar switching with high OFF/ON resistance ratios (>104) in Pt/vanadium oxide/Cu structures deposited entirely at room temperature. The SET (RESET) process occurs when negative (positive) bias is applied to the top Cu electrode. The vanadium oxide (VOx) films are amorphous and close to the vanadium pentoxide stoichiometry. We also investigated Cu/VOx/W structures, reversing the position of the Cu electrode, and found the same polarity dependence with respect to the top and bottom electrodes, which suggests that the bipolar nature is linked to the VOx layer itself. Bipolar switching can be observed at 100 °C, indicating that it not due to a temperature-induced metal-insulator transition of a vanadium dioxide second phase. We discuss how ionic drift can lead to the bipolar electrical behavior of our junctions, similar to those observed in devices based on several other defective oxides. Such low-temperature processed oxide switches could be of relevance to back-end or package integration processing schemes.

  7. Room temperature ionic liquids interacting with bio-molecules: an overview of experimental and computational studies

    Science.gov (United States)

    Benedetto, Antonio; Ballone, Pietro

    2016-03-01

    We briefly review experimental and computational studies of room temperature ionic liquids (RTILs) interacting with important classes of biomolecules, including phospholipids, peptides and proteins, nucleic acids and carbohydrates. Most of these studies have been driven by the interest for RTILs applications as solvents. Thus, available experimental data cover primarily thermodynamic properties such as the reciprocal solubility of RTILs and bio-molecules, as well as phase boundaries. Less extensive data are also available on transport properties such as diffusion and viscosity of homogeneous binary (RTILs/biomolecules) and ternary (RTIL/biomolecules/water) solutions. Most of the structural information at the atomistic level, of interest especially for biochemical, pharmaceutical and nanotechnology applications, has been made available by molecular dynamics simulations. Major exceptions to this statement are represented by the results from NMR and circular dichroism spectroscopy, by selected neutron and X-ray scattering data, and by recent neutron reflectometry measurements on lipid bilayers on surfaces, hydrated by water-RTIL solutions. A final section of our paper summarizes new developments in the field of RTILs based on amino acids, that combine in themselves the two main aspects of our discussion, i.e. ionic liquids and bio-molecules.

  8. Free standing CuO-MnO2 nanocomposite for room temperature ammonia sensing

    Science.gov (United States)

    Bhuvaneshwari, S.; Papachan, Seethal; Gopalakrishnan, N.

    2017-05-01

    CuO nanostructures and CuO-MnO2 nanocomposite were successfully synthesized using hydrothermal method without any aid of growth controlling agents. The synthesized CuO nanostructures have monoclinic structure. The XRD pattern of CuO-MnO2 observed with mixed phases of monoclinic CuO and birnessite-type MnO2 which confirms the formation of nanocomposite. SEM images revealed the turmeric-like morphology for CuO and intercalated sheets with flowers on the surface for CuO-MnO2. The length and breadth of turmeric-like structure is about 642.2 nm and 141.8 nm, respectively. The band gap of 1.72 eV for CuO nanostructure and 1.9 eV for CuO-MnO2 nanocomposite were observed from the absorption spectra. The free standing devices of CuO-MnO2 showed nearly a 3 fold increase sensing response to ammonia at room temperature when compared to the constituent CuO. The composite sensor showed response time of 120 s and recovered within 600 s. This enhanced response can be asserted to the peculiar morphology of the composite that provides more adsorption site for gas diffusion to take place.

  9. Revealing a room temperature ferromagnetism in cadmium oxide nanoparticles: An experimental and first-principles study

    KAUST Repository

    Bououdina, Mohamed

    2015-03-26

    We obtain a single cadmium oxide phase from powder synthesized by a thermal decomposition method of cadmium acetate dehydrate. The yielded powder is annealed in air, vacuum, and H2 gas in order to create point defects. Magnetization-field curves reveal the appearance of diamagnetic behavior with a ferromagnetic component for all the powders. Powder annealing under vacuum and H2 atmosphere leads to a saturation magnetization 1.15 memu g-1 and 1.2 memu g-1 respectively with an increase by 45% and 16% compared to the one annealed in air. We show that annealing in vacuum produces mainly oxygen vacancies while annealing in H2 gas creates mainly Cd vacancy leading to room temperature ferromagnetic (RTFM) component together with known diamagnetic properties. Ab initio calculations performed on the CdO nanoparticles show that the magnetism is governed by polarized hybrid states of the Cd d and O p orbitals together with the vacancy. © The Royal Society of Chemistry 2015.

  10. Room temperature zeolitization of boiler slag from a Bulgarian thermal power plant

    Directory of Open Access Journals (Sweden)

    Pascova Radost D.

    2017-01-01

    Full Text Available A simple and cost-effective method was applied for the synthesis of zeolite composites utilising wet bottom boiler slag from the Bulgarian coal-fired thermal power plant “Sviloza”, near the town of Svishtov. The method consisted of a prolonged alkali treatment at room temperature of this waste. Experimental techniques, such as scanning electron microscopy, energy-dispersive X-ray and X-ray diffraction analyses, are employed to characterize the initial slag and the final products with respect to their morphology, and elemental and mineral compositions. The composites synthesized in this way contained two Na-type zeolite phases: zeolite X (type FAU and zeolite Linde F (type EDI. The zeolited products and the starting slag were tested as adsorbents for a textile dye (Malachite Green from aqueous solutions. In comparison with the initial slag, the zeolite composite possessed substantially better adsorption properties: it almost completely adsorbs the dye in much shorter times. The results of this investigations revealed a new, easy and low cost route for recycling boiler slag into a material with good adsorption characteristics, which could find different applications, e.g., for purifying polluted waters, including those from the textile industry.

  11. Nanocrystalline CdSnO3 Based Room Temperature Methanol Sensor

    Directory of Open Access Journals (Sweden)

    Shanabhau BAGUL

    2017-04-01

    Full Text Available Synthesis of nanocrystalline CdSnO3 powder by ultrasonic atomizer assisted wet chemical method is reported in this paper. Synthesized CdSnO3 powder was characterized by X-Ray Diffraction (XRD, Field Emission Scanning Electron Microscopy (FESEM and Transmission Electron Microscopy (TEM to examine phase and microstructure. FESEM and TEM analysis reveals that the CdSnO3 powder prepared here is porous monodisperse nanocrystalline in nature, with average particle size of approximately 17 nm or smaller. The material is also characterized by UV-Visible and Photoluminescence (PL spectroscopy. Thick films of synthesized CdSnO3 powder fired at 850 0C are made by using screen printing method. The films surface is modified by using dipping method. CuCl2 (0.005 M dipped (for 2 min thick film shows high response (R= 477 to 100 ppm methanol at room temperature (35 0C. The sensor shows good selectivity and fast response recovery time to methanol. The excellent methanol sensing performance, particularly high response values is observed to be mainly due to porous CdSnO3 surface.

  12. Dielectric response and pyroelectric properties of lead-free ferroelectric Ba3(VO42

    Directory of Open Access Journals (Sweden)

    Biswajit Pati

    2015-03-01

    Full Text Available The current paper presents results of dielectric response, pyroelectric behavior and conductivity study of lead-free ferroelectric barium orthovanadate (Ba3(VO42 or Ba3V2O8 ceramic, for a wide range of temperature and frequency. An X-ray diffraction study suggests the formation of a single-phase compound in trigonal crystal system. The SEM micrograph of gold-coated pellet sample shows well-defined and homogeneous morphology. Detailed studies of dielectric parameters (εr and tan δ of the compound as a function of temperature and frequency reveal their independence over a wide range of temperature and frequency. The nature of Polarization versus electric field (P–E hysteresis loop of Ba3V2O8 at room temperature suggests its ferroelectric nature. The temperature dependence of pyroelectric coefficient and figure of merits of the sample support its dielectric response. The nature of variation of dc conductivity with temperature confirms the Arrhenius and negative temperature coefficient of resistance (NTCR behavior of the material.

  13. Towards room temperature solid state quantum devices at the edge of quantum chaos for long-living quantum states

    International Nuclear Information System (INIS)

    Prati, Enrico

    2015-01-01

    Long living coherent quantum states have been observed in biological systems up to room temperature. Light harvesting in chromophoresis realized by excitonic systems living at the edge of quantum chaos, where energy level distribution becomes semi-Poissonian. On the other hand, artificial materials suffer the loss of coherence of quantum states in quantum information processing, but semiconductor materials are known to exhibit quantum chaotic conditions, so the exploitation of similar conditions are to be considered. The advancements of nanofabrication, together with the control of implantation of individual atoms at nanometric precision, may open the experimental study of such special regime at the edge of the phase transitions for the electronic systems obtained by implanting impurity atoms in a silicon transistor. Here I review the recent advancements made in the field of theoretical description of the light harvesting in biological system in its connection with phase transitions at the few atoms scale and how it would be possible to achieve transition point to quantum chaotic regime. Such mechanism may thus preserve quantum coherent states at room temperature in solid state devices, to be exploited for quantum information processing as well as dissipation-free quantum electronics. (paper)

  14. Tunable Curie temperature around room temperature and magnetocaloric effect in ternary Ce–Fe–B amorphous ribbons

    International Nuclear Information System (INIS)

    Li, Zhu-bai; Zhang, Le-le; Zhang, Xue-feng; Li, Yong-feng; Zhao, Qian; Zhao, Tong-yun; Shen, Bao-gen

    2017-01-01

    Ce 13−x Fe 81+x B 6 ( x   =  0, 0.5, 1, 1.5, and 2) amorphous magnets were prepared by melt-spinning method. These magnets are magnetically soft at low temperature, and undergo a second-order phase transition from ferromagnetic to paramagnetic state near room temperature with a broad temperature span. The phase-transition temperature is tunable by the variation of the Ce/Fe atomic ratio, which is mainly due to the change of the coordination number of Fe atoms in these ternary Ce–Fe–B amorphous magnets. Though the entropy change is low, the refrigeration capacities are in the ranges of 116–150 J kg −1 and 319–420 J kg −1 , respectively, for the magnetic field changes of 0–2 T and 0–5 T, which is comparable with those of conventional magnetic materials for room-temperature refrigeration. Given the low cost of Fe and Ce, Ce–Fe–B amorphous magnets are attractive magnetic refrigerant candidates. (paper)

  15. Room temperature desorption of helium-3 from metal tritides

    International Nuclear Information System (INIS)

    Beavis, L.C.; Kass, W.J.

    1976-10-01

    It has long been known that helium-3 accumulates in metal tritides as tritium decays. Early in life nearly 100% of the helium-3 is retained in the lattice, but when a critical concentration is reached (material dependent), the lattice will no longer retain the helium-3 and it is emitted at about the generation rate. Measurements were recently made on a number of erbium tritides with varying concentrations in the ditritide phase. The expected early release characteristics are observed for all of the samples. However, ditritides with higher tritium concentrations reach the rapid release state at much lower helium-3 concentrations. For instance, the helium to metal concentration for rapid release in the unsaturated ditritide is about 0.22, whereas it is only one-tenth this value in the saturated ditritide. The additional tritium in the tritide appears to be the cause of this effect

  16. Combined intrinsic elastocaloric and electrocaloric properties of ferroelectrics

    Science.gov (United States)

    Khassaf, H.; Patel, T.; Alpay, S. P.

    2017-04-01

    In multiferroic materials, adiabatic temperature changes can be obtained by the combined application of electric, stress, and magnetic fields. These external stimuli provide additional channels of entropy variations resulting in a multi-caloric response. In ferroelectric (FE) materials, caloric responses can be obtained with the application of electric and mechanical fields. Here, we compute the intrinsic elastocaloric and stress-mediated electrocaloric behavior of prototypical FE materials using the Landau-Devonshire theory of phase transformations with appropriate electrical and electro-mechanical boundary conditions. We show that an elastocaloric adiabatic temperature variation of 12.7 °C can be obtained in PbTiO3 with the application of uniaxial tensile stress of 500 MPa near its Curie point. This is 59% higher than its pure intrinsic electrocaloric response for an electric field difference of 100 kV/cm. Moreover, external stresses allow the maximum electro-elastocaloric response to be tuned towards room temperature. Our calculations show that relaxor FEs should exhibit large adiabatic temperature variations in relatively broad temperature ranges. These findings indicate that caloric responses in ferroic materials can be deterministically controlled and enhanced by utilizing a variety of external stimuli.

  17. Impacts of exhalation flow on the microenvironment around the human body under different room temperatures

    Science.gov (United States)

    Jafari, Mohammad Javad; Gharari, Noradin; Azari, Mansour Rezazade; Ashrafi, Khosro

    2018-04-01

    Exhalation flow and room temperature can have a considerable effect on the microenvironment in the vicinity of human body. In this study, impacts of exhalation flow and room temperature on the microenvironment around a human body were investigated using a numerical simulation. For this purpose, a computational fluid dynamic program was applied to study thermal plume around a sitting human body at different room temperatures of a calm indoor room by considering the exhalation flow. The simulation was supported by some experimental measurements. Six different room temperatures (18 to 28 °C) with two nose exhalation modes (exhalation and non-exhalation) were investigated. Overhead and breathing zone velocities and temperatures were simulated in different scenarios. This study finds out that the exhalation through the nose has a significant impact on both quantitative and qualitative features of the human microenvironment in different room temperatures. At a given temperature, the exhalation through the nose can change the location and size of maximum velocity at the top of the head. In the breathing zone, the effect of exhalation through the nose on velocity and temperature distribution was pronounced for the point close to mouth. Also, the exhalation through the nose strongly influences the thermal boundary layer on the breathing zone while it only minimally influences the convective boundary layer on the breathing zone. Overall results demonstrate that it is important to take the exhalation flow into consideration in all areas, especially at a quiescent flow condition with low temperature.

  18. Possible room temperature superconductivity in conductors obtained by bringing alkanes into contact with a graphite surface

    Directory of Open Access Journals (Sweden)

    Yasushi Kawashima

    2013-05-01

    Full Text Available Electrical resistances of conductors obtained by bringing alkanes into contact with a graphite surface have been investigated at room temperatures. Ring current in a ring-shaped container into which n-octane-soaked thin graphite flakes were compressed did not decay for 50 days at room temperature. After two HOPG plates were immersed into n-heptane and n-octane at room temperature, changes in resistances of the two samples were measured by four terminal technique. The measurement showed that the resistances of these samples decrease to less than the smallest resistance that can be measured with a high resolution digital voltmeter (0.1μV. The observation of persistent currents in the ring-shaped container suggests that the HOPG plates immersed in n-heptane and n-octane really entered zero-resistance state at room temperature. These results suggest that room temperature superconductor may be obtained by bringing alkanes into contact with a graphite surface.

  19. Room temperature mushrooming of gallium wires and its growth mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, P.; Shen, L.W.; Ouyang, J.; Zhang, Y.M.; Wu, S.Q. [School of Materials Science and Engineering, Southeast University, Nanjing 211189, Jiangsu (China); Sun, Z.M., E-mail: sunzhengming@gmail.com [School of Materials Science and Engineering, Southeast University, Nanjing 211189, Jiangsu (China); National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8569 (Japan)

    2015-01-15

    Highlights: • Fast spontaneous growth of Ga wires (∼200 nm/s) from a composite system of Cr{sub 2}GaC–Ga is reported. • The fact that Ga wires’ growth phenomena on the composite share most features with metals whiskers with metal/alloy substrates suggests the same mechanism highly likely operating with both systems. • Compelling evidences indicate that the popular stress-based mechanism developed in metal/alloy systems does not hold water in the Cr{sub 2}GaC–Ga composite system. • A new catalysis mechanism is proposed, in which the cleavage planes of Cr{sub 2}GaC grains act as a catalyst for the Ga wires growth. • The new findings in this composite system would lead a new route to address this old problem, and it might see significance in the electronics industry. On the other hand, it is likely to be harnessed to engineer a promising and facile route to prepare various metal wires in large scale. - Abstract: Spontaneous growth of Ga wires at high rate (∼200 nm/s) from a composite system of Cr{sub 2}GaC (a MAX phase) and Ga is presented. A Ga wire growth mechanism based on a catalysis model, which involves fractured Cr{sub 2}GaC grains as the catalyst, is proposed. Regarding the morphologies and the incubation time of the Ga wires, this system shares most features with metal/alloy substrates, such as tin and zinc, where the whiskering phenomenon has been well established and has resisted interpretation for 60+ years. The same growth mechanism is thus considered to operate across different substrates, including the composite one in this study. However, the experimental findings in this composite system oppose the popular stress-based mechanism for the whisker growth with metal/alloy substrates, and provide new sights on this phenomenon. In addition, compelling evidences strongly indicate that fractured Cr{sub 2}GaC grains produced by ball milling initiated the growth of Ga wires, like a ‘catalyst’, and the pristine Cr{sub 2}GaC grains do not

  20. Room Temperature Hard Radiation Detectors Based on Solid State Compound Semiconductors: An Overview

    Science.gov (United States)

    Mirzaei, Ali; Huh, Jeung-Soo; Kim, Sang Sub; Kim, Hyoun Woo

    2018-05-01

    Si and Ge single crystals are the most common semiconductor radiation detectors. However, they need to work at cryogenic temperatures to decrease their noise levels. In contrast, compound semiconductors can be operated at room temperature due to their ability to grow compound materials with tunable densities, band gaps and atomic numbers. Highly efficient room temperature hard radiation detectors can be utilized in biomedical diagnostics, nuclear safety and homeland security applications. In this review, we discuss room temperature compound semiconductors. Since the field of radiation detection is broad and a discussion of all compound materials for radiation sensing is impossible, we discuss the most important materials for the detection of hard radiation with a focus on binary heavy metal semiconductors and ternary and quaternary chalcogenide compounds.

  1. Direct writing of room temperature and zero field skyrmion lattices by a scanning local magnetic field

    KAUST Repository

    Zhang, Senfu; Zhang, Junwei; Zhang, Qiang; Barton, Craig; Neu, Volker; Zhao, Yuelei; Hou, Zhipeng; Wen, Yan; Gong, Chen; Kazakova, Olga; Wang, Wenhong; Peng, Yong; Garanin, Dmitry A.; Chudnovsky, Eugene M.; Zhang, Xixiang

    2018-01-01

    Magnetic skyrmions are topologically protected nanoscale spin textures exhibiting fascinating physical behaviors. Recent observations of room temperature skyrmions in sputtered multilayer films are an important step towards their use in ultra-low power devices. Such practical applications prefer skyrmions to be stable at zero magnetic fields and room temperature. Here, we report the creation of skyrmion lattices in Pt/Co/Ta multilayers by a scanning local field using magnetic force microscopy tips. We also show that those newly created skyrmion lattices are stable at both room temperature and zero fields. Lorentz transmission electron microscopy measurements reveal that the skyrmions in our films are of Néel-type. To gain a deeper understanding of the mechanism behind the creation of a skyrmion lattice by the scanning of local fields, we perform micromagnetic simulations and find the experimental results to be in agreement with our simulation data. This study opens another avenue for the creation of skyrmion lattices in thin films.

  2. Direct writing of room temperature and zero field skyrmion lattices by a scanning local magnetic field

    Science.gov (United States)

    Zhang, Senfu; Zhang, Junwei; Zhang, Qiang; Barton, Craig; Neu, Volker; Zhao, Yuelei; Hou, Zhipeng; Wen, Yan; Gong, Chen; Kazakova, Olga; Wang, Wenhong; Peng, Yong; Garanin, Dmitry A.; Chudnovsky, Eugene M.; Zhang, Xixiang

    2018-03-01

    Magnetic skyrmions are topologically protected nanoscale spin textures exhibiting fascinating physical behaviors. Recent observations of room temperature skyrmions in sputtered multilayer films are an important step towards their use in ultra-low power devices. Such practical applications prefer skyrmions to be stable at zero magnetic fields and room temperature. Here, we report the creation of skyrmion lattices in Pt/Co/Ta multilayers by a scanning local field using magnetic force microscopy tips. We also show that those newly created skyrmion lattices are stable at both room temperature and zero fields. Lorentz transmission electron microscopy measurements reveal that the skyrmions in our films are of Néel-type. To gain a deeper understanding of the mechanism behind the creation of a skyrmion lattice by the scanning of local fields, we perform micromagnetic simulations and find the experimental results to be in agreement with our simulation data. This study opens another avenue for the creation of skyrmion lattices in thin films.

  3. Room Temperature Hard Radiation Detectors Based on Solid State Compound Semiconductors: An Overview

    Science.gov (United States)

    Mirzaei, Ali; Huh, Jeung-Soo; Kim, Sang Sub; Kim, Hyoun Woo

    2018-03-01

    Si and Ge single crystals are the most common semiconductor radiation detectors. However, they need to work at cryogenic temperatures to decrease their noise levels. In contrast, compound semiconductors can be operated at room temperature due to their ability to grow compound materials with tunable densities, band gaps and atomic numbers. Highly efficient room temperature hard radiation detectors can be utilized in biomedical diagnostics, nuclear safety and homeland security applications. In this review, we discuss room temperature compound semiconductors. Since the field of radiation detection is broad and a discussion of all compound materials for radiation sensing is impossible, we discuss the most important materials for the detection of hard radiation with a focus on binary heavy metal semiconductors and ternary and quaternary chalcogenide compounds.

  4. Room-temperature spin-polarized organic light-emitting diodes with a single ferromagnetic electrode

    Energy Technology Data Exchange (ETDEWEB)

    Ding, Baofu, E-mail: b.ding@ecu.edu.au; Alameh, Kamal, E-mail: k.alameh@ecu.edu.au [Electron Science Research Institute, Edith Cowan University, 270 Joondalup Drive, Joondalup WA 6027 Australia (Australia); Song, Qunliang [Institute for Clean Energy and Advanced Materials, Southwest University, Chongqing 400715 (China)

    2014-05-19

    In this paper, we demonstrate the concept of a room-temperature spin-polarized organic light-emitting diode (Spin-OLED) structure based on (i) the deposition of an ultra-thin p-type organic buffer layer on the surface of the ferromagnetic electrode of the Spin-OLED and (ii) the use of oxygen plasma treatment to modify the surface of that electrode. Experimental results demonstrate that the brightness of the developed Spin-OLED can be increased by 110% and that a magneto-electroluminescence of 12% can be attained for a 150 mT in-plane magnetic field, at room temperature. This is attributed to enhanced hole and room-temperature spin-polarized injection from the ferromagnetic electrode, respectively.

  5. Tunable room-temperature ferromagnet using an iron-oxide and graphene oxide nanocomposite

    KAUST Repository

    Lin, Aigu L.; Rodrigues, J. N B; Su, Chenliang; Milletari, M.; Loh, Kian Ping; Wu, Tao; Chen, Wei; Neto, A. H Castro; Adam, Shaffique; Wee, Andrew T S

    2015-01-01

    Magnetic materials have found wide application ranging from electronics and memories to medicine. Essential to these advances is the control of the magnetic order. To date, most room-temperature applications have a fixed magnetic moment whose orientation is manipulated for functionality. Here we demonstrate an iron-oxide and graphene oxide nanocomposite based device that acts as a tunable ferromagnet at room temperature. Not only can we tune its transition temperature in a wide range of temperatures around room temperature, but the magnetization can also be tuned from zero to 0.011 A m2/kg through an initialization process with two readily accessible knobs (magnetic field and electric current), after which the system retains its magnetic properties semi-permanently until the next initialization process. We construct a theoretical model to illustrate that this tunability originates from an indirect exchange interaction mediated by spin-imbalanced electrons inside the nanocomposite. © 2015 Scientific Reports.

  6. A Promising New Method to Estimate Drug-Polymer Solubility at Room Temperature

    DEFF Research Database (Denmark)

    Knopp, Matthias Manne; Gannon, Natasha; Porsch, Ilona

    2016-01-01

    The established methods to predict drug-polymer solubility at room temperature either rely on extrapolation over a long temperature range or are limited by the availability of a liquid analogue of the polymer. To overcome these issues, this work investigated a new methodology where the drug-polymer...... solubility is estimated from the solubility of the drug in a solution of the polymer at room temperature using the shake-flask method. Thus, the new polymer in solution method does not rely on temperature extrapolations and only requires the polymer and a solvent, in which the polymer is soluble, that does...... not affect the molecular structure of the drug and polymer relative to that in the solid state. Consequently, as this method has the potential to provide fast and precise estimates of drug-polymer solubility at room temperature, we encourage the scientific community to further investigate this principle both...

  7. Room-temperature ferromagnetism observed in C-/N-/O-implanted MgO single crystals

    Science.gov (United States)

    Li, Qiang; Ye, Bonian; Hao, Yingping; Liu, Jiandang; Zhang, Jie; Zhang, Lijuan; Kong, Wei; Weng, Huimin; Ye, Bangjiao

    2013-01-01

    MgO single crystals were implanted with 70 keV C/N/O ions at room temperature with respective doses of 2 × 1016 and 2 × 1017 ions/cm2. All samples with high-dose implantation showed room temperature hysteresis in magnetization loops. Magnetization and slow positron annihilation measurements confirmed that room temperature ferromagnetism in O-implanted samples was attributed to the presence of Mg vacancies. Furthermore, the introduction of C or N played more effective role in ferromagnetic performance than Mg vacancies. Moreover, the magnetic moment possibly occurred from the localized wave function of unpaired electrons and the exchange interaction formed a long-range magnetic order.

  8. Tunable room-temperature ferromagnet using an iron-oxide and graphene oxide nanocomposite

    KAUST Repository

    Lin, Aigu L.

    2015-06-23

    Magnetic materials have found wide application ranging from electronics and memories to medicine. Essential to these advances is the control of the magnetic order. To date, most room-temperature applications have a fixed magnetic moment whose orientation is manipulated for functionality. Here we demonstrate an iron-oxide and graphene oxide nanocomposite based device that acts as a tunable ferromagnet at room temperature. Not only can we tune its transition temperature in a wide range of temperatures around room temperature, but the magnetization can also be tuned from zero to 0.011 A m2/kg through an initialization process with two readily accessible knobs (magnetic field and electric current), after which the system retains its magnetic properties semi-permanently until the next initialization process. We construct a theoretical model to illustrate that this tunability originates from an indirect exchange interaction mediated by spin-imbalanced electrons inside the nanocomposite. © 2015 Scientific Reports.

  9. Direct writing of room temperature and zero field skyrmion lattices by a scanning local magnetic field

    KAUST Repository

    Zhang, Senfu

    2018-03-29

    Magnetic skyrmions are topologically protected nanoscale spin textures exhibiting fascinating physical behaviors. Recent observations of room temperature skyrmions in sputtered multilayer films are an important step towards their use in ultra-low power devices. Such practical applications prefer skyrmions to be stable at zero magnetic fields and room temperature. Here, we report the creation of skyrmion lattices in Pt/Co/Ta multilayers by a scanning local field using magnetic force microscopy tips. We also show that those newly created skyrmion lattices are stable at both room temperature and zero fields. Lorentz transmission electron microscopy measurements reveal that the skyrmions in our films are of Néel-type. To gain a deeper understanding of the mechanism behind the creation of a skyrmion lattice by the scanning of local fields, we perform micromagnetic simulations and find the experimental results to be in agreement with our simulation data. This study opens another avenue for the creation of skyrmion lattices in thin films.

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

    Directory of Open Access Journals (Sweden)

    Priyanka A. PATIL

    2017-05-01

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

  11. Room temperature magnetic and dielectric properties of cobalt doped CaCu3Ti4O12 ceramics

    Science.gov (United States)

    Mu, Chunhong; Song, Yuanqiang; Wang, Haibin; Wang, Xiaoning

    2015-05-01

    CaCu3Ti4-xCoxO12 (x = 0, 0.2, 0.4) ceramics were prepared by a conventional solid state reaction, and the effects of cobalt doping on the room temperature magnetic and dielectric properties were investigated. Both X-ray diffraction and energy dispersive X-ray spectroscopy confirmed the presence of Cu and Co rich phase at grain boundaries of Co-doped ceramics. Scanning electron microscopy micrographs of Co-doped samples showed a striking change from regular polyhedral particle type in pure CaCu3Ti4O12 (CCTO) to sheet-like grains with certain growth orientation. Undoped CaCu3Ti4O12 is well known for its colossal dielectric constant in a broad temperature and frequency range. The dielectric constant value was slightly changed by 5 at. % and 10 at. % Co doping, whereas the second relaxation process was clearly separated in low frequency region at room temperature. A multirelaxation mechanism was proposed to be the origin of the colossal dielectric constant. In addition, the permeability spectra measurements indicated Co-doped CCTO with good magnetic properties, showing the initial permeability (μ') as high as 5.5 and low magnetic loss (μ″ < 0.2) below 3 MHz. And the interesting ferromagnetic superexchange coupling in Co-doped CaCu3Ti4O12 was discussed.

  12. The growth of manganese layers on Si(1 0 0) at room temperature: A photoelectron spectroscopy study

    Energy Technology Data Exchange (ETDEWEB)

    Nolph, C.A. [University of Virgina, Department of Materials Science and Engineering, 395 McCormick Road, Charlottesville, VA 22904 (United States); Vescovo, E. [National Synchrotron Light Source, Brookhaven National Laboratory, Upton, NY 11973-5000 (United States); Reinke, P., E-mail: pr6e@virginia.edu [University of Virgina, Department of Materials Science and Engineering, 395 McCormick Road, Charlottesville, VA 22904 (United States)

    2009-06-15

    The combination of spin-and charge based electronics in future devices requires the magnetic doping of group IV semiconductors, and the formation of ferromagnetic contacts. The doping of Mn with Si is one of the material systems which is discussed in this context. The present study focuses on the growth of Mn on a Si(100)(2x1) surface, and the evolution of the surface was observed as a function of Mn coverage with synchrotron-based photoelectron spectroscopy. The reaction of Mn with the Si(100) surface at room temperature leads the formation of silicide at the boundary between the Si substrate and the Mn-overlayer, presumably with MnSi stoichiometry. The residual sub-oxide reacts with the Mn and therefore incorporates a few percent of Mn-O-Si at the interface. The analysis of the sub-oxide composition indicates that the Si{sup +1} component is the most reactive oxidation state. The overlayer is dominated by Mn, either as Mn-metal or as a Mn-rich silicide phase, and the metallic layer introduces a band bending in Si. As a consequence of our observations, including information from a recent STM study, the formation of ferromagnetic contacts which require ideally a flat and compositionally homogenous overlayer, cannot be achieved through room temperature deposition of Mn on the Si(100) (2x1) surface. The influence of residual oxides and surface defects on the growth process will be further investigated.

  13. Evidence of Room Temperature Ferromagnetism Due to Oxygen Vacancies in (In1- x Fe x )2O3 Thin Films

    Science.gov (United States)

    Chakraborty, Deepannita; Munuswamy, Kuppan; Shaik, Kaleemulla; Nasina, Madhusudhana Rao; Dugasani, Sreekantha Reddy; Inturu, Omkaram

    2018-03-01

    Iron substituted indium oxide (In1- x Fe x )2O3 thin films at x = 0.00, 0.03, 0.05 and 0.07 were coated onto Corning 7059 glass substrates using the electron beam evaporation technique followed by annealing at different temperatures. The prepared thin films were subjected to different characterization techniques to study their structural, optical and magnetic properties. The structural properties of the thin films were studied using x-ray diffractometry (XRD). From the XRD results it was found that the films were crystallized in cubic structure, and no change in crystal structure was observed with annealing temperature. No secondary phases related to iron were observed from the XRD profiles. The chemical composition and surface morphology of the films were examined by field emission scanning electron microscope (FE-SEM) attached with energy dispersive analysis of x-ray (EDAX). The valence state of the elements were studied by x-ray photoelectron spectroscopy (XPS) and found that the indium, iron and oxygen were in In+3, Fe+3 and O-2 states. From the data, the band gap of the (In1- x Fe x )2O3 thin films were calculated and it increased with increase of annealing temperature. The magnetic properties of the films were studied at room temperature by vibrating sample magnetometer (VSM). The films exhibited ferromagnetism at room temperature.

  14. Room temperature synthesis of Si-MCM-41 using polymeric version of ethyl silicate as a source of silica

    International Nuclear Information System (INIS)

    Gaydhankar, T.R.; Samuel, V.; Jha, R.K.; Kumar, R.; Joshi, P.N.

    2007-01-01

    Synthesis of mesoporous MCM-41 materials at room temperature using less expensive polymeric version of ethyl silicate (40 wt% SiO 2 ) as a source of silica was established. The influence of crucial synthesis parameters such as molar ratios of H 2 O/NH 4 OH, NH 4 OH/SiO 2 and CTMABr/SiO 2 in gel on the quality of the phase formed was investigated. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and low temperature N 2 adsorption-desorption isotherms have been employed to characterize the products. The magnitude of orderness, textural properties and thermal stability of the Si-MCM-41 samples prepared under identical judiciously pre-controlled synthesis conditions using ethyl silicate and conventional tetraethyl orthosilicate (TEOS) were assessed. Even though, ethyl silicate has proved to be suitable source for the preparation of MCM-41 at room temperature, there exists an optimum value of H 2 O/NH 4 OH for different NH 4 OH/SiO 2 molar ratios in the gel. Changes in the morphology were observed when NH 4 OH/SiO 2 , H 2 O/NH 4 OH molar ratios in the gels were changed

  15. Structure-Function Relationships of Ferroelectric Polymers.

    Science.gov (United States)

    Pavlopoulou, Eleni; Maiz, Jon; Spampinato, Nicoletta; Maglione, Mario; Hadziioannou, Georges

    Poly(vinylidene fluoride), PVDF, and its copolymers with trifluoroethylene, P(VDF-co-TrFE) have been long appreciated for their excellent ferroelectric properties. Although they have been mainly studied in the 80s and 90s, understanding their performance is still lacking. Yet the increasing use of P(VDF-co-TrFE) thin films in organic electronic devices during the last ten years revives the need for apprehending the function of these materials. In this work we investigate the structure of P(VDF-co-TrFE) films and correlate it to their ferroelectric properties. Our results show that ferroelectric performance is solely driven by the fraction of polymer that has been crystallized in the ferroelectric phases of PVDF. The relations between remnant polarization, coercive field and dipole switching rate of P(VDF-co-TrFE) with the ferroelectric crystallinity are demonstrated. The French Research Agency (ANR), the Aquitaine Region, Arkema and STMicroelectronics are kindly acknowledged for financial support.

  16. Ferroelectric Electron Emission Principles and Technology

    CERN Document Server

    Riege, H

    1997-01-01

    The spontaneous electrical polarization of ferroelectric materials can be changed either by reversal or by phase transition from a ferroelectric into a non-ferroelectric state or vice versa. If spontaneous polarization changes are induced with fast heat, mechanical pressure, laser or electric field pulses on a submicrosecond time scale, strong uncompensated surface charge densities and related polarization fields are generated, which may lead to the intense self-emission of electrons from the negatively charged free surface areas of the ferroelectric sample. Hence, electron guns can be built with extraction-field-free ferroelectric cathodes, which may be easily separated from the high-field regions of post-accelerating gap structures. The intensity, the energy, the temporal and spatial distribution, and the repetitition rate of the emitted electron beams can be controlled within wide limits via the excitation pulses and external focusing and accelerating electromagnetic fields. The technological advantages an...

  17. Anisotropic phonon coupling in the relaxor ferroelectric (Na1/2Bi1/2)TiO3 near its high-temperature phase transition

    Science.gov (United States)

    Cai, Ling; Toulouse, Jean; Luo, Haosu; Tian, Wei

    2014-08-01

    The lead free relaxor Na1/2Bi1/2TiO3 (NBT) undergoes a structural cubic-to-tetragonal transition near 800 K which is caused by the cooperative rotations of O6 octahedra. These rotations are also accompanied by the displacements of the cations and the formation of the polar nanodomains (PNDs) that are responsible for the characteristic dielectric dispersion of relaxor ferroelectrics. Because of their intrinsic properties, spontaneous polarization, and lack of inversion symmetry, these PNDs are also piezoelectric and can mediate an interaction between polarization and strain or couple the optic and acoustic phonons. Because PNDs introduce a local tetragonal symmetry, the phonon coupling they mediate is found to be anisotropic. In this paper we present inelastic neutron scattering results on coupled transverse acoustic (TA) and transverse optic (TO) phonons in the [110] and [001] directions and across the cubic-tetragonal phase transition at TC˜800 K. The phonon spectra are analyzed using a mode coupling model. In the [110] direction, as in other relaxors and some ferroelectric perovskites, a precipitous drop of the TO phonon into the TA branch or "waterfall" is observed at a certain qwf˜0.14 r.l.u. In the [001] direction, the highly overdamped line shape can be fitted with closely positioned bare mode energies which are largely overlapping along the dispersion curves. Two competing lattice coupling mechanism are proposed to explain these observations.

  18. Multiscale modeling for ferroelectric materials: identification of the phase-field model’s free energy for PZT from atomistic simulations

    International Nuclear Information System (INIS)

    Völker, Benjamin; Landis, Chad M; Kamlah, Marc

    2012-01-01

    Within a knowledge-based multiscale simulation approach for ferroelectric materials, the atomic level can be linked to the mesoscale by transferring results from first-principles calculations into a phase-field model. A recently presented routine (Völker et al 2011 Contin. Mech. Thermodyn. 23 435–51) for adjusting the Helmholtz free energy coefficients to intrinsic and extrinsic ferroelectric material properties obtained by DFT calculations and atomistic simulations was subject to certain limitations: caused by too small available degrees of freedom, an independent adjustment of the spontaneous strains and piezoelectric coefficients was not possible, and the elastic properties could only be considered in cubic instead of tetragonal symmetry. In this work we overcome such restrictions by expanding the formulation of the free energy function, i.e. by motivating and introducing new higher-order terms that have not appeared in the literature before. Subsequently we present an improved version of the adjustment procedure for the free energy coefficients that is solely based on input parameters from first-principles calculations performed by Marton and Elsässer, as documented in Völker et al (2011 Contin. Mech. Thermodyn. 23 435–51). Full sets of adjusted free energy coefficients for PbTiO 3 and tetragonal Pb(Zr,Ti)O 3 are presented, and the benefits of the newly introduced higher-order free energy terms are discussed. (paper)

  19. Upconversion luminescence, ferroelectrics and piezoelectrics of Er Doped SrBi{sub 4}Ti{sub 4}O{sub 15}

    Energy Technology Data Exchange (ETDEWEB)

    Peng Dengfeng [Functional Materials Research Laboratory, Tongji University, 1239 Siping Road, Shanghai 200092 (China); National Institute of Advanced Industrial Science and Technology, Kyushu, 807-1 Shuku, Tosu, Saga 841-0052 (Japan); Zou Hua; Wang Xusheng; Yao Xi [Functional Materials Research Laboratory, Tongji University, 1239 Siping Road, Shanghai 200092 (China); Xu Chaonan [National Institute of Advanced Industrial Science and Technology, Kyushu, 807-1 Shuku, Tosu, Saga 841-0052 (Japan); Lin Jian; Sun Tiantuo [School of Material Science and Engineering, Tongji University, 4800 Cao' an Highway, Shanghai 201804 (China)

    2012-12-15

    Er{sup 3+} doped SrBi{sub 4}Ti{sub 4}O{sub 15} (SBT) bismuth layered-structure ferroelectric ceramics were synthesized by the traditional solid-state method, and their upconversion photoluminescent (UC) properties were investigated as a function of Er{sup 3+} concentration and incident pump power. Green (555 nm) and red (670 nm) emission bands were obtained under 980 nm excitation at room temperature, which corresponded to the radiative transitions from {sup 4}S{sub 3/2}, and {sup 4}F{sub 9/2} to {sup 4}I{sub 15/2}, respectively. The emission color of the samples could be changed with moderating the doping concentrations. The dependence of UC intensity on pumping power indicated a two-photon emission process. Studies on dielectric properties indicated that the introduction of Er increased the ferroelectric-paraelectric phase transition temperature (Tc) of SBT, thus making this ceramic suitable for piezoelectric sensor applications at higher temperatures. Piezoelectric measurement showed that the doped SBT had a relative higher piezoelectric constant d{sub 33} compared with the non-doped ceramics. The thermal annealing behaviors of the doped sample revealed a stable piezoelectric property. The doped SBT showed bright UC emission while simultaneously having increased Tc and d{sub 33}. As a multifunctional material, Er doped SBT ferroelectric oxide showed great potential in application of sensor, future optical-electro integration and coupling devices.

  20. Surface Acoustic Waves in ferroelectrics

    Czech Academy of Sciences Publication Activity Database

    Tarasenko A., Nataliya; Jastrabík, Lubomír; Tarasenko, Alexander

    2004-01-01

    Roč. 298, - (2004), s. 325-333 ISSN 0015-0193 R&D Projects: GA AV ČR IBS1010203 Keywords : Rayleigh waves * ferroelectric films * phase transition Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.517, year: 2004

  1. Evolution of the microstructure in electrochemically deposited copper films at room temperature

    DEFF Research Database (Denmark)

    Pantleon, Karen; Somers, Marcel A. J.

    2007-01-01

    The room temperature evolution of the microstructure in copper electrodeposits (self-annealing) was investigated by means of X-ray diffraction analysis and simultaneous measurement of the electrical resistivity as a function of time with an unprecedented time resolution. Independent of the copper...... the crystallographic texture changes by a multiple twinning mechanism. The kinetics of self-annealing is strongly affected by the thickness of the deposit. Storage of the copper films at sub-zero temperatures effectively hinders self-annealing and does not affect the kinetics of self-annealing upon reheating to room...... temperature....

  2. Evolution of the microstructure in nanocrystalline copper electrodeposits during room temperature storage

    DEFF Research Database (Denmark)

    Pantleon, Karen; Somers, Marcel A. J.

    2007-01-01

    The microstructure evolution in copper electrodeposits at room temperature (self-annealing) was investigated by means of X-ray diffraction analysis and simultaneous measurement of the electrical resistivity as a function of time. In-situ studies were started immediately after electrodeposition......, crystallographic texture changes by multiple twinning and a decrease of the electrical resistivity occurred as a function of time at room temperature. The kinetics of self-annealing is strongly affected by the layer thickness: the thinner the layer the slower is the microstructure evolution and self-annealing...

  3. Defect types and room-temperature ferromagnetism in undoped rutile TiO2 single crystals

    Science.gov (United States)

    Li, Dong-Xiang; Qin, Xiu-Bo; Zheng, Li-Rong; Li, Yu-Xiao; Cao, Xing-Zhong; Li, Zhuo-Xin; Yang, Jing; Wang, Bao-Yi

    2013-03-01

    Room-temperature ferromagnetism has been experimentally observed in annealed rutile TiO2 single crystals when a magnetic field is applied parallel to the sample plane. By combining X-ray absorption near the edge structure spectrum and positron annihilation lifetime spectroscopy, Ti3+—VO defect complexes (or clusters) have been identified in annealed crystals at a high vacuum. We elucidate that the unpaired 3d electrons in Ti3+ ions provide the observed room-temperature ferromagnetism. In addition, excess oxygen ions in the TiO2 lattice could induce a number of Ti vacancies which obviously increase magnetic moments.

  4. CeBr3 as a room-temperature, high-resolution gamma-ray detector

    International Nuclear Information System (INIS)

    Guss, Paul; Reed, Michael; Yuan Ding; Reed, Alexis; Mukhopadhyay, Sanjoy

    2009-01-01

    Cerium bromide (CeBr 3 ) has become a material of interest in the race for high-resolution gamma-ray spectroscopy at room temperature. This investigation quantified the potential of CeBr 3 as a room-temperature, high-resolution gamma-ray detector. The performance of CeBr 3 crystals was compared to other scintillation crystals of similar dimensions and detection environments. Comparison of self-activity of CeBr 3 to cerium-doped lanthanum tribromide (LaBr 3 :Ce) was performed. Energy resolution and relative intrinsic efficiency were measured and are presented.

  5. Multiwalled carbon nanotubes sensor for organic liquid detection at room temperature

    Science.gov (United States)

    Chaudhary, Deepti; Khare, Neeraj; Vankar, V. D.

    2016-04-01

    We have explored the possibility of using multiwalled carbon nanotubes (MWCNTs) as room temperature chemical sensor for the detection of organic liquids such as ethanol, propanol, methanol and toluene. MWCNTs were synthesized by thermal chemical vapor deposition (TCVD) technique. The interdigitated electrodes were fabricated by conventional photolithography technique. The sensor was fabricated by drop depositing MWCNT suspension onto the interdigitated electrodes. The sensing properties of MWCNTs sensor was studied for organic liquids detection. The resistance of sensor was found to increase upon exposure to these liquids. Sensor shows good reversibility and fast response at room temperature. Charge transfer between the organic liquid and sensing element is the dominant sensing mechanism.

  6. Photoexcited Individual Nanowires: Key Elements in Room Temperature Detection of Oxidizing Gases

    International Nuclear Information System (INIS)

    Prades, J. D.; Jimenez-Diaz, R.; Manzanares, M.; Andreu, T.; Cirera, A.; Romano-Rodriguez, A.; Hernandez-Ramirez, F.; Morante, J. R.

    2009-01-01

    Illuminating metal oxide semiconductors with ultra-violet light is a feasible alternative to activate chemical reactions at their surface and thus, using them as gas sensors without the necessity of heating them. Here, the response at room temperature of individual single-crystalline SnO 2 nanowires towards NO 2 is studied in detail. The results reveal that similar responses to those obtained with thermally activated sensors can be achieved by choosing the optimal illumination conditions. This finding paves the way to the development of conductometric gas sensors operated at room temperature. The power consumption in these devices is in range with conventional micromachined sensors.

  7. Quantum confinement of zero-dimensional hybrid organic-inorganic polaritons at room temperature

    Science.gov (United States)

    Nguyen, H. S.; Han, Z.; Abdel-Baki, K.; Lafosse, X.; Amo, A.; Lauret, J.-S.; Deleporte, E.; Bouchoule, S.; Bloch, J.

    2014-02-01

    We report on the quantum confinement of zero-dimensional polaritons in perovskite-based microcavity at room temperature. Photoluminescence of discrete polaritonic states is observed for polaritons localized in symmetric sphere-like defects which are spontaneously nucleated on the top dielectric Bragg mirror. The linewidth of these confined states is found much sharper (almost one order of magnitude) than that of photonic modes in the perovskite planar microcavity. Our results show the possibility to study organic-inorganic cavity polaritons in confined microstructure and suggest a fabrication method to realize integrated polaritonic devices operating at room temperature.

  8. Quantum confinement of zero-dimensional hybrid organic-inorganic polaritons at room temperature

    International Nuclear Information System (INIS)

    Nguyen, H. S.; Lafosse, X.; Amo, A.; Bouchoule, S.; Bloch, J.; Han, Z.; Abdel-Baki, K.; Lauret, J.-S.; Deleporte, E.

    2014-01-01

    We report on the quantum confinement of zero-dimensional polaritons in perovskite-based microcavity at room temperature. Photoluminescence of discrete polaritonic states is observed for polaritons localized in symmetric sphere-like defects which are spontaneously nucleated on the top dielectric Bragg mirror. The linewidth of these confined states is found much sharper (almost one order of magnitude) than that of photonic modes in the perovskite planar microcavity. Our results show the possibility to study organic-inorganic cavity polaritons in confined microstructure and suggest a fabrication method to realize integrated polaritonic devices operating at room temperature

  9. Defect types and room-temperature ferromagnetism in undoped rutile TiO2 single crystals

    International Nuclear Information System (INIS)

    Li Dong-Xiang; Cao Xing-Zhong; Li Zhuo-Xin; Yang Jing; Wang Bao-Yi; Qin Xiu-Bo; Zheng Li-Rong; Li Yu-Xiao

    2013-01-01

    Room-temperature ferromagnetism has been experimentally observed in annealed rutile TiO 2 single crystals when a magnetic field is applied parallel to the sample plane. By combining X-ray absorption near the edge structure spectrum and positron annihilation lifetime spectroscopy, Ti 3+ —V O defect complexes (or clusters) have been identified in annealed crystals at a high vacuum. We elucidate that the unpaired 3d electrons in Ti 3+ ions provide the observed room-temperature ferromagnetism. In addition, excess oxygen ions in the TiO 2 lattice could induce a number of Ti vacancies which obviously increase magnetic moments

  10. Room-Temperature Synthesis of Transition Metal Clusters and Main Group Polycations from Ionic Liquids

    OpenAIRE

    Ahmed, Ejaz

    2011-01-01

    Main group polycations and transition metal clusters had traditionally been synthesized via high-temperature routes by performing reactions in melts or by CTR, at room-temperature or lower temperature by using so-called superacid solvents, and at room-temperature in benzene–GaX3 media. Considering the major problems associated with higher temperature routes (e.g. long annealing time, risk of product decomposition, and low yield) and taking into account the toxicity of benzene and liquid SO2 i...

  11. Spectroscopic investigation of an intrinsic room temperature ferromagnetism in Co doped ZnO nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    N, Srinatha [Department of Physics, JB Campus, Bangalore University, Bangalore 560056 (India); Angadi, Basavaraj, E-mail: brangadi@gmail.com [Department of Physics, JB Campus, Bangalore University, Bangalore 560056 (India); Nair, K.G.M. [UGC-DAE-CSR, Kalpakkam Node, Kalpakkam, Kokilamedu 603 102 (India); Deshpande, Nishad G.; Shao, Y.C.; Pong, Way-Faung [Department of Physics, Tamkang University, Tamsui, Taipei 251, Taiwan (China)

    2014-08-15

    Highlights: • For the first time L-Valine was used as a fuel to synthesize Co:ZnO nanoparticles by solution combustion method. • Single phase and ferromagnetic nature were confirmed through XRD, SQUID, NEXAFS and XMCD. • Through NEXAFS and XMCD, the effect of ‘Co’ substitution at O K-edge, Co L{sub 3,2} edge, Zn L{sub 3,2} edge have been investigated. • Spectral features of NEXAFS and XMCD confirms an intrinsic RTFM by substitution of ‘Co{sup 2+}’ at ‘Zn{sup 2+}’ site and rules out the presence of secondary phases. - Abstract: Pure and Co substituted ZnO nano crystalline particles were prepared by solution combustion technique using L-Valine as a fuel. As synthesized powder samples were characterized by X-ray diffractometer and SQUID magnetometer to confirm the formation of single phase wurtzite structure and to study the bulk magnetic response of the sample, respectively. Magnetic studies show that Co doped ZnO nanoparticles exhibit ferromagnetism (FM) at room temperature (RT). Furthermore, the electronic structure and element specific magnetic properties were investigated by near-edge X-ray absorption fine structure (NEXAFS) and X-ray magnetic circular dichroism (XMCD) measurements, respectively. The effect of Co substitution on the spectral features of Co–ZnO at O K-edge, Co L{sub 3,2} edge, Zn L{sub 3,2} edge have been investigated. The spectral features of NEXAFS at Co L{sub 3,2} edge is entirely different from the spectral features of metallic clusters and other impurity phases, which rules out the presence of impurity phases. The valence state of ‘Co’ ion is found to be in +2 state. The FM nature of the sample was confirmed through XMCD spectra, which is due to the incorporation of divalent ‘Co’ ions. Hence the presented results confirm the substitution of ‘Co’ ions at ‘Zn’ site in the host lattice, which is responsible for the RTFM.

  12. Fast, high-fidelity, all-optical and dynamically-controlled polarization gate using room-temperature atomic vapor

    Energy Technology Data Exchange (ETDEWEB)

    Li, Runbing [National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071 (China); Center for Cold Atom Physics, Chinese Academy of Sciences, Wuhan 430071 (China); Zhu, Chengjie [National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); School of Physics Science and Engineering, Tongji University, Shanghai 200092 (China); Deng, L.; Hagley, E. W. [National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States)

    2014-10-20

    We demonstrate a fast, all-optical polarization gate in a room-temperature atomic medium. Using a Polarization-Selective-Kerr-Phase-Shift (PSKPS) technique, we selectively write a π phase shift to one circularly-polarized component of a linearly-polarized input signal field. The output signal field maintains its original strength but acquires a 90° linear polarization rotation, demonstrating fast, high-fidelity, dynamically-controlled polarization gate operation. The intensity of the polarization-switching field used in this PKSPK-based polarization gate operation is only 2 mW/cm{sup 2}, which would be equivalent to 0.5 nW of light power (λ = 800 nm) confined in a typical commercial photonic hollow-core fiber. This development opens a realm of possibilities for potential future extremely low light level telecommunication and information processing systems.

  13. Room temperature metathetic synthesis and characterization of α-hopeite, Zn3(PO4)2.4H2O

    International Nuclear Information System (INIS)

    Parhi, Purnendu; Manivannan, V.; Kohli, Sandeep; McCurdy, Patrick

    2008-01-01

    The synthesis of crystalline zinc phosphates (α-hopeite phase) through the metathetic pathway has been investigated. The reaction has been carried out by room-temperature grinding. High lattice energy of the by-product NaCl has driven the reaction in the forward direction, and as a result, stable phosphate phases have been synthesized. Reaction of a different phosphorus source (like Na 3 PO 4 , Na 2 HPO 4 , NaH 2 PO 4 , and K 2 HPO 4 ) with ZnCl 2 has been attempted. The structural, vibrational, thermal, optical, and chemical properties of synthesized powders are determined by powder X-ray diffraction (XRD), scanning electron microscope (SEM), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and diffused reflectance spectra (DR) in the UV-vis range. The direct band gap of the title compound was determined to be 3.6 ± 0.2 eV

  14. X-ray diffraction and dielectric studies across morphotropic phase boundary in (1 - x) [Pb(Mg0.5W0.5)O3]-xPbTiO3 ceramics

    International Nuclear Information System (INIS)

    Singh, A.K.; Singh, Akhilesh Kumar

    2011-01-01

    Research highlights: → Structural studies reveal pseudocubic structure of PMW-xPT for the x ≤ 0.42, tetragonal for the x ≥ 0.72 and the coexistences of the two phases for intermediate compositions (0.46 ≤ x 0.68). → Temperature dependent dielectric constant for compositions in the two phase region shows two dielectric anomalies above room temperature and not just one as reported by earlier workers. → Rietveld structural analysis of PMW-xPT ceramics is presented for the first time to determine the fraction of the coexisting phases in MPB region. - Abstract: We present here the results of comprehensive X-ray diffraction and dielectric studies on several compositions of (1 - x)[Pb(Mg 0.5 W 0.5 )O 3 ]-xPbTiO 3 (PMW-xPT) solid solution across the morphotropic phase boundary. Rietveld analysis of the powder X-ray diffraction data reveals cubic (space group Fm3m) structure of PMW-xPT ceramics for the compositions with x ≤ 0.42, tetragonal (space group P4mm) structure for the compositions with x ≥ 0.72 and coexistence of the tetragonal and cubic phases for the intermediate compositions (0.46 ≤ x ≤ 0.68). Temperature dependence of the dielectric permittivity above room temperature exhibits diffuse nature of phase transitions for the compositions in the cubic and two phase region while the compositions with tetragonal structure at room temperature exhibit sharp ferroelectric to paraelectric phase transition. The PMW-xPT compositions with coexistence of tetragonal and cubic phases at room temperature exhibit two anomalies in the temperature dependence of the dielectric permittivity above room temperature. Using results of structural and dielectric studies a partial phase diagram of PMW-xPT ceramics is also presented.

  15. Room-Temperature Multiferroics and Thermal Conductivity of 0.85BiFe1-2xTixMgxO3-0.15CaTiO3 Epitaxial Thin Films (x = 0.1 and 0.2).

    Science.gov (United States)

    Zhang, Ji; Sun, Wei; Zhao, Jiangtao; Sun, Lei; Li, Lei; Yan, Xue-Jun; Wang, Ke; Gu, Zheng-Bin; Luo, Zhen-Lin; Chen, Yanbin; Yuan, Guo-Liang; Lu, Ming-Hui; Zhang, Shan-Tao

    2017-08-02

    Thin films of 0.85BiFe 1-2x Ti x Mg x O 3 -0.15CaTiO 3 (x = 0.1 and 0.2, abbreviated to C-1 and C-2, respectively) have been fabricated on (001) SrTiO 3 substrate with and without a conductive La 0.7 Sr 0.3 MnO 3 buffer layer. The X-ray θ-2θ and ϕ scans, atomic force microscopy, and cross-sectional transmission electron microscopy confirm the (001) epitaxial nature of the thin films with very high growth quality. Both the C-1 and C-2 thin films show well-shaped magnetization-magnetic field hysteresis at room temperature, with enhanced switchable magnetization values of 145.3 and 42.5 emu/cm 3 , respectively. The polarization-electric loops and piezoresponse force microscopy measurements confirm the room-temperature ferroelectric nature of both films. However, the C-1 films illustrate a relatively weak ferroelectric behavior and the poled states are easy to relax, whereas the C-2 films show a relatively better ferroelectric behavior with stable poled states. More interestingly, the room-temperature thermal conductivity of C-1 and C-2 films are measured to be 1.10 and 0.77 W/(m·K), respectively. These self-consistent multiferroic properties and thermal conductivities are discussed by considering the composition-dependent content and migration of Fe-induced electrons and/or charged point defects. This study not only provides multifunctional materials with excellent room-temperature magnetic, ferroelectric, and thermal conductivity properties but may also stimulate further work to develop BiFeO 3 -based materials with unusual multifunctional properties.

  16. The first demonstration of room temperature stimulated emission from metal halides -its evidence in CsPbBr3 films

    OpenAIRE

    中西, 貴之; 高橋, 一彰; 斎藤, 忠昭; 近藤, 新一

    2005-01-01

    Photoluminescence from CsPbBr3 films prepared by crystallization from the amorphous phase is measured under N2 laser excitation. Stimulated emission due to free exaction-free exaction inelastic collision occurs not only at cryogenic temperature but also elevated temperatures. The intensity of the stimulated emission more rapidly increases with pumping intensity at room temperature than at 77K. The temperature dependence of the stimulated emission measured under 1100kW cm-2 pumping shows th...

  17. An investigation into the room temperature mechanical properties of nanocrystalline austenitic stainless steels

    International Nuclear Information System (INIS)

    Eskandari, Mostafa; Zarei-Hanzaki, Abbas; Abedi, Hamid Reza

    2013-01-01

    Highlights: ► Strength of nanocrystalline specimens follows a trend of a remarkable rise along with a small drop in ductility in comparison to the coarse-grained one. ► Universal correlation of linear type (UTS = mτ max ) between shear punch test data and the tensile strength may be unreliable for the nanocrystalline materials. ► Actual relation between the maximum shear and ultimate tensile strength follows an empirical formula of UTS=0.013τ max 2 -25.62τ max +13049. -- Abstract: The present work has been conducted to evaluate the mechanical properties of nanostructured 316L and 301 austenitic stainless steels. The nanocrystalline structures were produced through martensite treatment which includes cold rolling followed by annealing treatment. The effect of equivalent rolling strain and annealing parameters on the room temperature mechanical behavior of the experimental alloys have been studied using the shear punch testing technique. The standard uniaxial tension tests were also carried out to adapt the related correlation factors. The microstructures and the volume fraction of phases were characterized by transmission electron microscopy and feritscopy methods, respectively. The results indicate that the strength of nanocrystalline specimens remarkably increases, but the ductility in comparison to the coarse-grained one slightly decreases. In addition the strength of nanocrystalline specimens has been increased by decreasing the annealing temperature and increasing the equivalent rolling strain. The analysis of the load–displacement data has also disclosed that the universal correlation of linear type (UTS = mτ max ) between shear punch test data and the tensile strength is somehow unreliable for the nanocrystalline materials. The results suggest that the actual relation between the maximum shear strength and ultimate tensile strength follows a second order equation of type UTS=aτ max 2 -bτ max +c.

  18. Extraction of lithium from salt lake brine using room temperature ionic liquid in tributyl phosphate

    International Nuclear Information System (INIS)

    Shi, Chenglong; Jia, Yongzhong; Zhang, Chao; Liu, Hong; Jing, Yan

    2015-01-01

    Highlights: • We proposed a new system for Li recovery from salt lake brine by extraction using an ionic liquid. • Cation exchange was proposed to be the mechanism of extraction followed in ionic liquid. • This ionic liquid system shown considerable extraction ability for lithium and the single extraction efficiency of lithium reached 87.28% under the optimal conditions. - Abstract: Lithium is known as the energy metal and it is a key raw material for preparing lithium isotopes which have important applications in nuclear energy source. In this work, a typical room temperature ionic liquid (RTILs), 1-butyl-3-methyl-imidazolium hexafluorophosphate ([C 4 mim][PF 6 ]), was used as an alternative solvent to study liquid/liquid extraction of lithium from salt lake brine. In this system, the ionic liquid, NaClO 4 and tributyl phosphate (TBP) were used as extraction medium, co-extraction reagent and extractant respectively. The effects of solution pH value, phase ratio, ClO 4 − amount and other factors on lithium extraction efficiency had been investigated. Optimal extraction conditions of this system include the ratio of TBP/IL at 4/1 (v/v), O/A at 2:1, n(ClO 4 − )/n(Li + ) at 2:1, the equilibration time of 10 min and unadjusted pH. Under the optimal conditions, the single extraction efficiency of lithium was 87.28% which was much higher than the conventional extraction system. Total extraction efficiency of 99.12% was obtained by triple-stage countercurrent extraction. Study on the mechanism revealed that the use of ionic liquid increased the extraction yield of lithium through cation exchange in this system. Preliminary results indicated that the use of [C 4 mim][PF 6 ] as an alternate solvent to replace traditional organic solvents (VOCs) in liquid/liquid extraction was very promising

  19. Dielectric response and room temperature ferromagnetism in Cr doped anatase TiO2 nanoparticles

    Science.gov (United States)

    Naseem, Swaleha; Khan, Wasi; Khan, Shakeel; Husain, Shahid; Ahmad, Abid

    2018-02-01

    In the present work, nanocrystalline samples of Ti1-xCrxO2 (x = 0, 0.02, 0.04, 0.06 and 0.08) were synthesized in anatase phase through simple and cost effective acid modified sol gel method. The influence of Cr doping on thermal, microstructural, electrical and magnetic properties was investigated in TiO2 host matrix. The surface morphology has revealed less agglomeration and considerable reduction in particle size in case of Cr doped TiO2 as compared to undoped TiO2 nanoparticles (NPs). Energy dispersive x-ray spectroscopy (EDS), Raman and X-ray photoelectron spectroscopy (XPS) established high purity, appropriate stoichiometry and oxidation states of the compositions. The dielectric properties of the nanoparticles were altered by the doping concentration, applied frequency as well as temperature variation. The variation in dielectric constant (ε‧), dielectric loss (δ) and ac conductivity as a function of frequency and temperature at different doping concentration of Cr were interpreted in the light of Maxwell Wagner theory, space charge polarization mechanism and drift mobility of charge carriers. Both undoped and Cr doped TiO2 samples exhibit room temperature ferromagnetism (RTFM) that remarkably influenced by means of the Cr content. The significant enhancement in the magnetization was observed at 4% Cr doping. However, decrease in magnetization for higher doping signify antiferromagnetic interactions between Cr ions or superexchange mechanism. These results reveal that the oxygen vacancies play a crucial role to initiate the RTFM. Therefore, the present investigation suggests the potential applications of Cr doped TiO2 nanoparticles for spintronics application.

  20. Structure and dynamics of POPC bilayers in water solutions of room temperature ionic liquids

    International Nuclear Information System (INIS)

    Benedetto, Antonio; Bingham, Richard J.; Ballone, Pietro

    2015-01-01

    Molecular dynamics simulations in the NPT ensemble have been carried out to investigate the effect of two room temperature ionic liquids (RTILs), on stacks of phospholipid bilayers in water. We consider RTIL compounds consisting of chloride ([bmim][Cl]) and hexafluorophosphate ([bmim][PF 6 ]) salts of the 1-buthyl-3-methylimidazolium ([bmim] + ) cation, while the phospholipid bilayer is made of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC). Our investigations focus on structural and dynamical properties of phospholipid and water molecules that could be probed by inelastic and quasi-elastic neutron scattering measurements. The results confirm the fast incorporation of [bmim] + into the lipid phase already observed in previous simulations, driven by the Coulomb attraction of the cation for the most electronegative oxygens in the POPC head group and by sizeable dispersion forces binding the neutral hydrocarbon tails of [bmim] + and of POPC. The [bmim] + absorption into the bilayer favours the penetration of water into POPC, causes a slight but systematic thinning of the bilayer, and further stabilises hydrogen bonds at the lipid/water interface that already in pure samples (no RTIL) display a lifetime much longer than in bulk water. On the other hand, the effect of RTILs on the diffusion constant of POPC (D POPC ) does not reveal a clearly identifiable trend, since D POPC increases upon addition of [bmim][Cl] and decreases in the [bmim][PF 6 ] case. Moreover, because of screening, the electrostatic signature of each bilayer is only moderately affected by the addition of RTIL ions in solution. The analysis of long wavelength fluctuations of the bilayers shows that RTIL sorption causes a general decrease of the lipid/water interfacial tension and bending rigidity, pointing to the destabilizing effect of RTILs on lipid bilayers

  1. Structure and dynamics of POPC bilayers in water solutions of room temperature ionic liquids

    Energy Technology Data Exchange (ETDEWEB)

    Benedetto, Antonio [School of Physics, University College Dublin, Dublin 4 (Ireland); Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, 5232 Villigen (Switzerland); Bingham, Richard J. [York Centre for Complex Systems Analysis, University of York, York YO10 5GE (United Kingdom); Ballone, Pietro [Center for Life Nano Science @Sapienza, Istituto Italiano di Tecnologia (IIT), 00185 Roma (Italy); Department of Physics, Università di Roma “La Sapienza,” 00185 Roma (Italy)

    2015-03-28

    Molecular dynamics simulations in the NPT ensemble have been carried out to investigate the effect of two room temperature ionic liquids (RTILs), on stacks of phospholipid bilayers in water. We consider RTIL compounds consisting of chloride ([bmim][Cl]) and hexafluorophosphate ([bmim][PF{sub 6}]) salts of the 1-buthyl-3-methylimidazolium ([bmim]{sup +}) cation, while the phospholipid bilayer is made of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC). Our investigations focus on structural and dynamical properties of phospholipid and water molecules that could be probed by inelastic and quasi-elastic neutron scattering measurements. The results confirm the fast incorporation of [bmim]{sup +} into the lipid phase already observed in previous simulations, driven by the Coulomb attraction of the cation for the most electronegative oxygens in the POPC head group and by sizeable dispersion forces binding the neutral hydrocarbon tails of [bmim]{sup +} and of POPC. The [bmim]{sup +} absorption into the bilayer favours the penetration of water into POPC, causes a slight but systematic thinning of the bilayer, and further stabilises hydrogen bonds at the lipid/water interface that already in pure samples (no RTIL) display a lifetime much longer than in bulk water. On the other hand, the effect of RTILs on the diffusion constant of POPC (D{sub POPC}) does not reveal a clearly identifiable trend, since D{sub POPC} increases upon addition of [bmim][Cl] and decreases in the [bmim][PF{sub 6}] case. Moreover, because of screening, the electrostatic signature of each bilayer is only moderately affected by the addition of RTIL ions in solution. The analysis of long wavelength fluctuations of the bilayers shows that RTIL sorption causes a general decrease of the lipid/water interfacial tension and bending rigidity, pointing to the destabilizing effect of RTILs on lipid bilayers.

  2. Thermogravimetric study on the hydration of reactive magnesia and silica mixture at room temperature

    International Nuclear Information System (INIS)

    Jin, Fei; Al-Tabbaa, Abir

    2013-01-01

    Highlights: • The characteristics of reactive MgO vary significantly in terms of their impurity content and reactivity depending on their sources and calcination conditions. • The synthesis of magnesium silicate hydrate (MSH) is affected by the characteristics of the precursors, i.e., MgO and silica. • The reaction process in the MgO–SiO 2 –H 2 O system can be followed by TGA, and is essential to develop MSH-based materials. - Abstract: The synthesis of magnesium silicate hydrate (MSH), which has wide applications in both construction and environmental fields, has been studied for decades. However, it is known that the characteristics of magnesia (MgO) vary significantly depending on their calcination conditions, which is expected to affect their performance in the MgO–SiO 2 –H 2 O system. This paper investigated the effect of different MgO and silica sources on the formation of magnesium silicate hydrate (MSH) at room temperature. The hydration process was studied by mixing commercial reactive MgO and silica powders with water and curing for 1, 7 and 28 days. The hydration products were analysed with the help of X-ray diffraction (XRD) and thermogravimatric analysis (TGA). The results showed the continuous consumption of MgO and the existence of MSH and brucite and other minor phases such as magnesite and calcite. It is found that the Mg and Si sources have significant effect on the hydration process of MgO–SiO 2 –H 2 O system. The reaction degree is controlled by the availability of dissolved Mg and Si in the solution. The former is determined by the reactivity of MgO and the latter is related to the reactivity of the silica as well as the pH of the system

  3. Room temperature magnetocaloric effect in Ni-Mn-In-Cr ferromagnetic shape memory alloy thin films

    Energy Technology Data Exchange (ETDEWEB)

    Akkera, Harish Sharma [Functionalnanomaterials Research Lab, Department of Physics, Indian Institute of Technology Roorkee, Uttarakhand-247667 (India); Singh, Inderdeep [Mechanical and Industrial Engineering Department, Indian Institute of Technology Roorkee, Uttarakhand-24667 (India); Kaur, Davinder, E-mail: dkaurfph@iitr.ernet.in [Functionalnanomaterials Research Lab, Department of Physics, Indian Institute of Technology Roorkee, Uttarakhand-247667 (India)

    2017-02-15

    The influence of Cr substitution for In on the martensitic phase transformation and magnetocaloric effect (MCE) has been investigated in Ni-Mn-Cr-In ferromagnetic shape memory alloy (FSMA) thin films fabricated by magnetron sputtering. Temperature dependent magnetization (M-T) measurements demonstrated that the martensitic transformation temperatures (T{sub M}) monotonously increase with the increase of Cr content due to change in valence electron concentration (e/a) and cell volume. From the study of isothermal magnetization curves (M-H), magnetocaloric effect around the martensitic transformation has been investigated in these FSMA thin films. The magnetic entropy change ∆S{sub M} of 7.0 mJ/cm{sup 3}-K was observed in Ni{sub 51.1}Mn{sub 34.9}In{sub 9.5}Cr{sub 4.5} film at 302 K in an applied field of 2 T. Further, the refrigerant capacity (RC) was also calculated for all the films in an applied field of 2 T. These findings indicate that the Cr doped Ni-Mn-In FSMA thin films are potential candidates for room temperature micro-length-scale magnetic refrigeration applications. - Highlights: • The Cr content leads to an increase in the martensitic transformation temperature. • The ∆S{sub M} =7 mJ/cm{sup 3}-K at 302 K was observed in the Ni{sub 51.1}Mn{sub 34.9}In{sub 9.5}Cr{sub 4.5}. • The RC =39.2 mJ/K at 2 T was obtained in Ni{sub 51.1}Mn{sub 34.9}In{sub 9.5}Cr{sub 4.5} film.

  4. Synthesis of zinc oxide microrods and nano-fibers with dominant exciton emission at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Ramos-Brito, F., E-mail: fro_brito@yahoo.com.m [Laboratorio de Materiales Optoelectronicos del Centro de Ciencias de Sinaloa, Ave. de las Americas 2771 Col. Villa Universidad 80010, Culiacan, Sinaloa (Mexico); Alejo-Armenta, C. [Laboratorio de Materiales Optoelectronicos del Centro de Ciencias de Sinaloa, Ave. de las Americas 2771 Col. Villa Universidad 80010, Culiacan, Sinaloa (Mexico); Garcia-Hipolito, M. [Departamento de Materiales Metalicos y Ceramicos, Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, AP 70-360, Coyoacan 04510, DF (Mexico); Camarillo, E.; Hernandez A, J. [Instituto de Fisica, Universidad Nacional Autonoma de Mexico, AP 20-364, Alvaro Obregon 01000, DF (Mexico); Falcony, C. [Departamento de Fisica, CINVESTAV-IPN, AP 14-740, 07000, DF (Mexico); Murrieta S, H. [Instituto de Fisica, Universidad Nacional Autonoma de Mexico, AP 20-364, Alvaro Obregon 01000, DF (Mexico)

    2011-05-15

    Employing a simple chemical synthesis method, hexagonal-shaped zinc oxide microrods and zinc oxide nano-fibers were deposited on pyrex-glass and aluminum substrates, respectively. Both kinds of deposits showed zincite crystalline phase with lattice parameters: a=3.2498 A and c=5.2066 A. Microrods showed very uniform wide and large sizes of around 1 and 10 {mu}m, respectively. Both deposits were homogeneous over all substrate surfaces. Microrods and nano-fibers resulted with good optical quality and with preferential crystalline growth in [1 0 1 0]and [0 0 0 1]directions. The principal optical characteristics for both microrods and nano-fibers were: a) room-temperature photo and cathodo-luminescent spectra with strong exciton emission centered around 390 nm and with FWHMs around 125 and 160 meV, respectively, b) poor photo and cathode-luminescent emissions in the visible region of the electromagnetic spectrum, c) energy band gap of 3.32 eV, d) good emission efficiency supported by the not-required high energy densities to obtain strong exciton emission and e) good ZnO stoichiometry endorsed by photoluminescent results. These characteristics make of these microrods and nano-fibers good for potential photonic applications. - Research highlights: {yields} Microrods and nano-fibers resulted with good optical quality and with preferential crystalline growth in [1 0 1 0]and [0 0 0 1]directions. {yields} Microrods and nano-fibers resulted with good emission efficiency supported by the not-required high energy densities to obtain strong exciton emission. {yields} The wet chemical method is appropriated for deposition of microrods and nano-fibers with the desired optical properties for its possible application in photonics.

  5. Synthesis of zinc oxide microrods and nano-fibers with dominant exciton emission at room temperature

    International Nuclear Information System (INIS)

    Ramos-Brito, F.; Alejo-Armenta, C.; Garcia-Hipolito, M.; Camarillo, E.; Hernandez A, J.; Falcony, C.; Murrieta S, H.

    2011-01-01

    Employing a simple chemical synthesis method, hexagonal-shaped zinc oxide microrods and zinc oxide nano-fibers were deposited on pyrex-glass and aluminum substrates, respectively. Both kinds of deposits showed zincite crystalline phase with lattice parameters: a=3.2498 A and c=5.2066 A. Microrods showed very uniform wide and large sizes of around 1 and 10 μm, respectively. Both deposits were homogeneous over all substrate surfaces. Microrods and nano-fibers resulted with good optical quality and with preferential crystalline growth in [1 0 1 0] and [0 0 0 1] directions. The principal optical characteristics for both microrods and nano-fibers were: a) room-temperature photo and cathodo-luminescent spectra with strong exciton emission centered around 390 nm and with FWHMs around 125 and 160 meV, respectively, b) poor photo and cathode-luminescent emissions in the visible region of the electromagnetic spectrum, c) energy band gap of 3.32 eV, d) good emission efficiency supported by the not-required high energy densities to obtain strong exciton emission and e) good ZnO stoichiometry endorsed by photoluminescent results. These characteristics make of these microrods and nano-fibers good for potential photonic applications. - Research highlights: → Microrods and nano-fibers resulted with good optical quality and with preferential crystalline growth in [1 0 1 0] and [0 0 0 1] directions. → Microrods and nano-fibers resulted with good emission efficiency supported by the not-required high energy densities to obtain strong exciton emission. → The wet chemical method is appropriated for deposition of microrods and nano-fibers with the desired optical properties for its possible application in photonics.

  6. Ferroelastic phase in SrBi.sub.2./sub.Ta.sub.2./sub.O.sub.9./sub. and study of the ferroelectric phase-transition dynamicy

    Czech Academy of Sciences Publication Activity Database

    Kamba, Stanislav; Pokorný, Jan; Porokhonskyy, Viktor; Petzelt, Jan; Moret, M. P.; Garg, A.; Barber, Z. H.; Zallen, R.

    2002-01-01

    Roč. 81, č. 6 (2002), s. 1056-1058 ISSN 0003-6951 R&D Projects: GA ČR GA202/01/0612; GA AV ČR IAA1010213 Institutional research plan: CEZ:AV0Z1010914 Keywords : ferroelectrics * ferroelastics * domains * soft mode Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 4.207, year: 2002

  7. Structural, dielectric and ferroelectric studies of (x) Mg{sub 0.25}Cu{sub 0.25}Zn{sub 0.5}Fe{sub 2}O{sub 4} + (1-x) BaTiO{sub 3} magnetoelectric nano-composites

    Energy Technology Data Exchange (ETDEWEB)

    Khader, S. Abdul, E-mail: khadersku@gmail.com; Sankarappa, T., E-mail: sankarappa@rediffmail.com [Department of Physics, Gulbarga University, Gulbarga-585106, Karnataka (India); Muneeswaran, M.; Giridharan, N. V. [Department of Physics, National Institute of Technology, Tiruchirapalli-620015 (India)

    2016-05-06

    The Particulate nano-composites of ferrite and ferroelectric phases having the general formula (x) Mg{sub 0.25}Cu{sub 0.25}Zn{sub 0.5}Fe{sub 2}O{sub 4} + (1-x) BaTiO{sub 3} (x=15%, 30% and 45%) were synthesized by sintering mixtures of highly ferroelectric BaTiO{sub 3} (BT) and highly magneto-strictive magnetic component Mg{sub 0.25}Cu{sub 0.25}Zn{sub 0.5}Fe{sub 2}O{sub 4}(MCZF). The presence of constituent phases of ferrite, ferroelectric and their composites were probed and confirmed by X-ray diffraction (XRD) studies. Surface morphology of the samples has been investigated using Field Emission Scanning Electron Microscope (FESEM). The variation of dielectric constant and dissipation factor as a function of frequency from 100 Hz to 1 MHz at room temperature were carried out using a Hioki LCR Hi-Tester. The dielectric constant and dielectric loss were found to decrease rapidly in the low frequency region and became almost constant in the high frequency region. The electrical conductivity deduced from the measured dielectric data has been thoroughly analyzed and found that the conduction mechanism in these composites is in conformity with small polaron hopping model. The ferroelectric properties of synthesized magneto-electric nano-composites were measured using P-E loop tracer.

  8. Stability of 2-Alkylcyclobutanones in irradiated retort pouch Gyudon topping during room temperature storage

    International Nuclear Information System (INIS)

    Kitagawa, Yoko; Okihashi, Masahiro; Takatori, Satoshi; Fukui, Naoki; Kajimura, Keiji; Obana, Hirotaka; Furuta, Masakazu

    2014-01-01

    2-Alkylcyclobutanones (ACBs), such as 2-dodecylcyclobutanone (DCB) and 2-tetradecylcylobutanone (TCB) are specific products from irradiated lipid. Thus, DCB and TCB are suitable for indicators of the irradiation history of food. The purpose of this study was to clarify the stability of ACBs in food, kept at room temperature for a long period. We evaluated DCB and TCB in irradiated retort pouch Gyudon topping (instant Gyudon mixes which were made from a beef, onion and soy sauce), which could be preserved for a long term at room temperature, after storage for one year. DCB and TCB were detected at doses of 0.6-4.5 kGy in irradiated retort pouch Gyudon topping. The peaks of DCB and TCB were separated from other peaks on the chromatogram with GC-MS. The concentration of DCB and TCB were periodically determined till 12 months later of irradiation. The dose-response curves of DCB and TCB were almost identical with those obtained from the samples after the 12 months storage at room temperature. These results concluded that DCB and TCB formed in retort pouch would stable at room temperature at least 12 months. (author)

  9. Transient optical studies of charge recombination dynamics in a polymer/fullerene composite at room temperature

    NARCIS (Netherlands)

    Montanari, Ivan; Nogueira, Ana F.; Nelson, Jenny; Durrant, James R.; Winder, Christoph; Loi, Maria Antonietta; Sariciftci, Niyazi Serdar; Brabec, Christoph

    2002-01-01

    The recombination kinetics of photogenerated charge carriers in a composite of poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1-4-phenylene vinylene], (MDMO–PPV) and the functionalised fullerene 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C61 are investigated at room temperature by transient absorption

  10. Structure determination of an integral membrane protein at room temperature from crystals in situ

    International Nuclear Information System (INIS)

    Axford, Danny; Foadi, James; Hu, Nien-Jen; Choudhury, Hassanul Ghani; Iwata, So; Beis, Konstantinos; Evans, Gwyndaf; Alguel, Yilmaz

    2015-01-01

    The X-ray structure determination of an integral membrane protein using synchrotron diffraction data measured in situ at room temperature is demonstrated. The structure determination of an integral membrane protein using synchrotron X-ray diffraction data collected at room temperature directly in vapour-diffusion crystallization plates (in situ) is demonstrated. Exposing the crystals in situ eliminates manual sample handling and, since it is performed at room temperature, removes the complication of cryoprotection and potential structural anomalies induced by sample cryocooling. Essential to the method is the ability to limit radiation damage by recording a small amount of data per sample from many samples and subsequently assembling the resulting data sets using specialized software. The validity of this procedure is established by the structure determination of Haemophilus influenza TehA at 2.3 Å resolution. The method presented offers an effective protocol for the fast and efficient determination of membrane-protein structures at room temperature using third-generation synchrotron beamlines

  11. Construction of hydrophobic wood surfaces by room temperature deposition of rutile (TiO2) nanostructures

    Science.gov (United States)

    Rongbo Zheng; Mandla A. Tshabalala; Qingyu Li; Hongyan Wang

    2015-01-01

    A convenient room temperature approach was developed for growing rutile TiO2 hierarchical structures on the wood surface by direct hydrolysis and crystallization of TiCl3 in saturated NaCl aqueous solution.The morphology and the crystal structure of TiO2 coated on the wood surface were characterized...

  12. Selective electrochemical extraction of REEs from NdFeB magnet waste at room temperature

    NARCIS (Netherlands)

    Venkatesan, P.; Vander Hoogerstraete, Tom; Hennebel, Tom; Binnemans, Koen; Sietsma, J.; Yang, Y.

    2018-01-01

    NdFeB magnet waste is one of the important secondary resources from which rare-earth elements (REEs) can be recovered. Herein we present an electrochemical route to selectively extract REEs from the magnet waste at room temperature. First, the magnet waste was partially leached with HCl. The

  13. Red-light-emitting laser diodes operating CW at room temperature

    Science.gov (United States)

    Kressel, H.; Hawrylo, F. Z.

    1976-01-01

    Heterojunction laser diodes of AlGaAs have been prepared with threshold current densities substantially below those previously achieved at room temperature in the 7200-8000-A spectral range. These devices operate continuously with simple oxide-isolated stripe contacts to 7400 A, which extends CW operation into the visible (red) portion of the spectrum.

  14. Red-light-emitting laser diodes operating cw at room temperature

    International Nuclear Information System (INIS)

    Kressel, H.; Hawrylo, F.Z.

    1976-01-01

    Heterojunction laser diodes of AlGaAs have been prepared with threshold current densities substantially below those previously achieved at room temperature in the 7200 to 8000-A spectral range. These devices operate cw with simple oxide-isolated stripe contacts to 7400 A, which extends cw operation for the first time into the visible (red) portion of the spectrum

  15. Room-temperature near-field reflection spectroscopy of single quantum wells

    DEFF Research Database (Denmark)

    Langbein, Wolfgang Werner; Hvam, Jørn Marcher; Madsen, Steen

    1997-01-01

    . This technique suppresses efficiently the otherwise dominating far-field background and reduces topographic artifacts. We demonstrate its performance on a thin, strained near-surface CdS/ZnS single quantum well at room temperature. The optical structure of these topographically flat samples is due to Cd...

  16. Electrochemical applications of room temperature ionic liquids in nuclear fuel cycle

    International Nuclear Information System (INIS)

    Venkatesan, K.A.; Srinivasan, T.G.; Vasudeva Rao, P.R.

    2008-01-01

    Applications of room temperature ionic liquids (RTILs) have invaded all branches of science. They are also receiving an upsurge, in recent years, for possible applications in various stages of nuclear fuel cycle. Ionic liquids are compounds composed entirely of ions existing in liquid state and RTILs are ionic liquids molten at temperatures lower than 373 K. RTILs are generally made up of an organic cation and an inorganic or an organic anion. Room temperature ionic liquids have several fascinating properties, which are unique to a particular combination of cation and anion. The properties such as insignificant vapor pressure, amazing ability to dissolve organic and inorganic compounds, wide electrochemical window are the specific advantages when dealing with application of RTILs for reprocessing of spent nuclear fuel. The ionic liquids are regarded as designer or tailor-made solvents as their properties can be tuned for desired application by appropriate cation-anion combinations. An excellent review by Wilkes describes about the historical perspectives of room temperature ionic liquids, pioneers in that area, events and the products delivered till 2001. Furthermore, several comprehensive reviews have been made on room temperature ionic liquids by various authors

  17. A review on the electrochemical applications of room temperature ionic liquids in nuclear fuel cycle

    International Nuclear Information System (INIS)

    Venkatesan, K.A.; Srinivasan, T.G.; Vasudeva Rao, P.R.

    2009-01-01

    A mini review on the electrochemical applications of room temperature ionic liquids (RTIL) in nuclear fuel cycle is presented. It is shown that how the fascinating properties of RTIL can be tuned to deliver desirable application in aqueous and non-aqueous reprocessing and in nuclear waste management. (author)

  18. Application of room temperature ionic liquids in advanced fuel cycles RIAR research concept program users

    International Nuclear Information System (INIS)

    Bychkov, Alexander V.; Kormilitsyn, Michael V.; Savochkin, Yuri P.; Osipenko, Alexander G.; Smolensky, Valeri V.; Shadrin, Alexander Yu.; Babain, Vladimir A.

    2005-01-01

    The paper reviews briefly the research program on application of Room Temperature Ionic Liquids (RTILs) in some processes of the nuclear fuel reprocessing, particularly in the uranium-aluminum fuel reprocessing and separation of TPEs and REEs from the PUREX process liquid waste, and approaches to implementation of this program. (author)

  19. Heat Capacity of Room-Temperature Ionic Liquids: A Critical Review

    Science.gov (United States)

    Paulechka, Yauheni U.

    2010-09-01

    Experimental data on heat capacity of room-temperature ionic liquids in the liquid state were compiled and critically evaluated. The compilation contains data for 102 aprotic ionic liquids from 63 literature references and covers the period of time from 1998 through the end of February 2010. Parameters of correlating equations for temperature dependence of the heat capacities were developed.

  20. Spin Squeezing and Entanglement with Room Temperature Atoms for Quantum Sensing and Communication

    DEFF Research Database (Denmark)

    Shen, Heng

    magnetometer at room temperature is reported. Furthermore, using spin-squeezing of atomic ensemble, the sensitivity of magnetometer is improved. Deterministic continuous variable teleportation between two distant atomic ensembles is demonstrated. The fidelity of teleportating dynamically changing sequence...... of spin states surpasses a classical benchmark, demonstrating the true quantum teleportation....

  1. Room temperature Compton profiles of conduction electrons in α-Ga ...

    Indian Academy of Sciences (India)

    Room temperature Compton profiles of momentum distribution of conduction electrons in -Ga metal are calculated in band model. For this purpose, the conduction electron wave functions are determined in a temperature-dependent non-local model potential. The profiles calculated along the crystallographic directions, ...

  2. Spin-on nanostructured silicon-silica film displaying room-temperature nanosecond lifetime photoluminescence

    Energy Technology Data Exchange (ETDEWEB)

    Cohen, Y.; Hatton, B.; Miguez, H.; Coombs, N.; Fournier-Bidoz, S.; Ozin, G.A. [Materials Chemistry Research Group, Department of Chemistry, Lash Miller Chemical Laboratories, University of Toronto, 80 St. George Street, Toronto, Ontario, M5S 3H6 (Canada); Grey, J.K.; Beaulac, R.; Reber, C. [Department of Chemistry, University of Montreal, Montreal, Quebec H3C 3J7 (Canada)

    2003-04-17

    A yellow transparent mesoporous silica film has been achieved by the incorporation of silicon nanoclusters into its channels. The resulting nanocomposite - fabricated using a combination of evaporation induced self- assembly and chemical vapor deposition - emits light brightly at visible wavelengths and has nanosecond radiative lifetimes at room temperature when excited by ultraviolet light (see Figure). (Abstract Copyright [2003], Wiley Periodicals, Inc.)

  3. Room temperature strong coupling effects from single ZnO nanowire microcavity

    KAUST Repository

    Das, Ayan; Heo, Junseok; Bayraktaroglu, Adrian; Guo, Wei; Ng, Tien Khee; Phillips, Jamie; Ooi, Boon S.; Bhattacharya, Pallab

    2012-01-01

    Strong coupling effects in a dielectric microcavity with a single ZnO nanowire embedded in it have been investigated at room temperature. A large Rabi splitting of ?100 meV is obtained from the polariton dispersion and a non

  4. Comparison of room temperature and cyrogenic sample processing in the analysis of chemical contaminants in foods

    Science.gov (United States)

    In this study, analytical results were compared when using different approaches to bulk food sample comminution, consisting of a vertical chopper (Blixer) at room temperature and at dry ice cryogenic conditions, followed by further subsample processing (20 g) using liquid nitrogen cryogenic conditio...

  5. Effect of irradiation on fresh-keeping of strawberry stored at room temperature

    International Nuclear Information System (INIS)

    Zhao Yongfu; Xie Zongchuan; Lu Zhaoxin

    1999-01-01

    The fresh keeping period of strawberry irradiated with 4.0 kGy dose and stored at room temperature was prolonged to 6 days. Further experiment showed that the irradiation treatment decreased the number of mold in strawberry by two orders of magnitude, inhibited the strawberry fruit respiration and water loss, therefore, improved the effect of strawberry fresh-keeping

  6. A method for electrochemical growth of homogeneous nanocrystalline ZnO thin films at room temperature

    Czech Academy of Sciences Publication Activity Database

    Pauporté, T.; Jirka, Ivan

    2009-01-01

    Roč. 54, č. 28 (2009), s. 7558-7564 ISSN 0013-4686 R&D Projects: GA AV ČR IAA400400909 Institutional research plan: CEZ:AV0Z40400503 Keywords : electrodeposition * ZnO * room temperature * photoluminiscence Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.325, year: 2009

  7. CdO necklace like nanobeads decorated with PbS nanoparticles: Room temperature LPG sensor

    Energy Technology Data Exchange (ETDEWEB)

    Sonawane, N.B. [Department of Physics, School of Physical Sciences, North Maharashtra University, Jalgaon, 425001 M.S. (India); K.A.M.P. & N.K.P. Science College, Pimpalner, Sakri, Dhule, M.S. (India); Baviskar, P.K. [Department of Physics, School of Physical Sciences, North Maharashtra University, Jalgaon, 425001 M.S. (India); Ahire, R.R. [S.G. Patil Science, Sakri, Dhule, M.S. (India); Sankapal, B.R., E-mail: brsankapal@gmail.com [Nano Materials and Device Laboratory, Department of Applied Physics, Visvesvaraya National Institute of Technology, South Ambazari Road, Nagpur, 440010 M.S. (India)

    2017-04-15

    Simple chemical route has been employed to grow interconnected nanobeads of CdO having necklace like structure through air annealing of cadmium hydroxide nanowires. This nanobeads of n-CdO with high surface area has been decorated with p-PbS nanoparticles resulting in the formation of nano-heterojunction which has been utilized effectively as room temperature liquefied petroleum gas (LPG) sensor. The room temperature gas response towards C{sub 2}H{sub 5}OH, Cl{sub 2}, NH{sub 3}, CO{sub 2} and LPG was investigated, among which LPG exhibits significant response. The maximum gas response of 51.10% is achieved with 94.54% stability upon exposure of 1176 ppm concentration of LPG at room temperature (27 °C). The resulting parameters like gas response, response and recovery time along with stability studies has been studied and results are discussed herein. - Highlights: • Conversion of Cd(OH){sub 2} nanowires to CdO nanonecklace by air annealing at 290 °C. • Decoration of PbS nanoparticles over CdO nanobeads by SILAR method. • Formation of n-CdO/p-PbS nano-heterojunction as room temperature LPG sensor. • Maximum gas response of 51.10% with 94.54% stability.

  8. Non-local electrical spin injection and detection in germanium at room temperature

    Science.gov (United States)

    Rortais, F.; Vergnaud, C.; Marty, A.; Vila, L.; Attané, J.-P.; Widiez, J.; Zucchetti, C.; Bottegoni, F.; Jaffrès, H.; George, J.-M.; Jamet, M.

    2017-10-01

    Non-local carrier injection/detection schemes lie at the very foundation of information manipulation in integrated systems. This paradigm consists in controlling with an external signal the channel where charge carriers flow between a "source" and a well separated "drain." The next generation electronics may operate on the spin of carriers in addition to their charge and germanium appears as the best hosting material to develop such a platform for its compatibility with mainstream silicon technology and the predicted long electron spin lifetime at room temperature. In this letter, we demonstrate injection of pure spin currents (i.e., with no associated transport of electric charges) in germanium, combined with non-local spin detection at 10 K and room temperature. For this purpose, we used a lateral spin valve with epitaxially grown magnetic tunnel junctions as spin injector and spin detector. The non-local magnetoresistance signal is clearly visible and reaches ≈15 mΩ at room temperature. The electron spin lifetime and diffusion length are 500 ps and 1 μm, respectively, the spin injection efficiency being as high as 27%. This result paves the way for the realization of full germanium spintronic devices at room temperature.

  9. Achieving Room Temperature Orange Lasing Using InGaP/InAlGaP Diode Laser

    KAUST Repository

    Al-Jabr, Ahmad

    2015-09-28

    We demonstrated the first orange laser diode at room temperature with a decent total output power of ∼46mW and lasing wavelength of 608nm, using a novel strain-induced quantum well intermixing in InGaP/InAlGaP red laser structure.

  10. Room-temperature base-free copper-catalyzed trifluoromethylation of organotrifluoroborates to trifluoromethylarenes

    KAUST Repository

    Huang, Yuanyuan; Fang, Xin; Lin, Xiaoxi; Li, Huaifeng; He, Weiming; Huang, Kuo-Wei; Yuan, Yaofeng; Weng, Zhiqiang

    2012-01-01

    An efficient room temperature copper-catalyzed trifluoromethylation of organotrifluoroborates under the base free condition using an electrophilic trifluoromethylating reagent is demonstrated. The corresponding trifluoromethylarenes were obtained in good to excellent yields and the reaction tolerates a wide range of functional groups. © 2012 Elsevier Ltd. All rights reserved.

  11. Structure determination of an integral membrane protein at room temperature from crystals in situ

    Energy Technology Data Exchange (ETDEWEB)

    Axford, Danny [Diamond Light Source, Harwell Science and Innovation Campus, Oxfordshire OX11 0DE (United Kingdom); Foadi, James [Diamond Light Source, Harwell Science and Innovation Campus, Oxfordshire OX11 0DE (United Kingdom); Imperial College London, London SW7 2AZ (United Kingdom); Hu, Nien-Jen; Choudhury, Hassanul Ghani [Diamond Light Source, Harwell Science and Innovation Campus, Oxfordshire OX11 0DE (United Kingdom); Imperial College London, London SW7 2AZ (United Kingdom); Rutherford Appleton Laboratory, Oxfordshire OX11 0FA (United Kingdom); Iwata, So [Diamond Light Source, Harwell Science and Innovation Campus, Oxfordshire OX11 0DE (United Kingdom); Diamond Light Source, Harwell Science and Innovation Campus, Oxfordshire OX11 0DE (United Kingdom); Imperial College London, London SW7 2AZ (United Kingdom); Rutherford Appleton Laboratory, Oxfordshire OX11 0FA (United Kingdom); Kyoto University, Kyoto 606-8501 (Japan); Beis, Konstantinos [Diamond Light Source, Harwell Science and Innovation Campus, Oxfordshire OX11 0DE (United Kingdom); Imperial College London, London SW7 2AZ (United Kingdom); Rutherford Appleton Laboratory, Oxfordshire OX11 0FA (United Kingdom); Evans, Gwyndaf, E-mail: gwyndaf.evans@diamond.ac.uk [Diamond Light Source, Harwell Science and Innovation Campus, Oxfordshire OX11 0DE (United Kingdom); Alguel, Yilmaz, E-mail: gwyndaf.evans@diamond.ac.uk [Diamond Light Source, Harwell Science and Innovation Campus, Oxfordshire OX11 0DE (United Kingdom); Imperial College London, London SW7 2AZ (United Kingdom); Rutherford Appleton Laboratory, Oxfordshire OX11 0FA (United Kingdom)

    2015-05-14

    The X-ray structure determination of an integral membrane protein using synchrotron diffraction data measured in situ at room temperature is demonstrated. The structure determination of an integral membrane protein using synchrotron X-ray diffraction data collected at room temperature directly in vapour-diffusion crystallization plates (in situ) is demonstrated. Exposing the crystals in situ eliminates manual sample handling and, since it is performed at room temperature, removes the complication of cryoprotection and potential structural anomalies induced by sample cryocooling. Essential to the method is the ability to limit radiation damage by recording a small amount of data per sample from many samples and subsequently assembling the resulting data sets using specialized software. The validity of this procedure is established by the structure determination of Haemophilus influenza TehA at 2.3 Å resolution. The method presented offers an effective protocol for the fast and efficient determination of membrane-protein structures at room temperature using third-generation synchrotron beamlines.

  12. Room-temperature base-free copper-catalyzed trifluoromethylation of organotrifluoroborates to trifluoromethylarenes

    KAUST Repository

    Huang, Yuanyuan

    2012-12-01

    An efficient room temperature copper-catalyzed trifluoromethylation of organotrifluoroborates under the base free condition using an electrophilic trifluoromethylating reagent is demonstrated. The corresponding trifluoromethylarenes were obtained in good to excellent yields and the reaction tolerates a wide range of functional groups. © 2012 Elsevier Ltd. All rights reserved.

  13. The physics and chemistry of room-temperature liquid-filled ionization chambers

    International Nuclear Information System (INIS)

    Holroyd, R.A.

    1985-01-01

    The properties of excess electrons in non-polar liquids, such as tetramethylsilane and 2,2,4,4-tetramethylpentane, which are suitable for room-temperature liquid-filled ionization chambers are reviewed. Such properties as mobility, ionization yield, conduction band energy, trapping, and the influence of the electric field are considered. (orig.)

  14. Room-temperature 1.2-J Fe{sup 2+}:ZnSe laser

    Energy Technology Data Exchange (ETDEWEB)

    Velikanov, S D; Zaretsky, N A; Zotov, E A; Maneshkin, A A; Yutkin, I M [Russian Federal Nuclear Center ' All-Russian Research Institute of Experimental Physics' , Sarov, Nizhnii Novgorod region (Russian Federation); Kazantsev, S Yu; Kononov, I G; Firsov, K N [A M Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Korostelin, Yu V; Frolov, M P [P N Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

    2016-01-31

    The characteristics of a laser based on a Fe{sup 2+}:ZnSe single crystal pumped by an electric-discharge HF laser at room temperature are studied. The HF laser beam diameter on the crystal surface was 17 mm. The achieved laser energy was 1.2 J with an efficiency of ∼ 25% with respect to the pump energy. (letters)

  15. Room temperature synthesis of protonated layered titanate sheets using peroxo titanium carbonate complex solution.

    Science.gov (United States)

    Sutradhar, Narottam; Sinhamahapatra, Apurba; Pahari, Sandip Kumar; Bajaj, Hari C; Panda, Asit Baran

    2011-07-21

    We report the synthesis of peroxo titanium carbonate complex solution as a novel water-soluble precursor for the direct synthesis of layered protonated titanate at room temperature. The synthesized titanates showed excellent removal capacity for Pb(2+) and methylene blue. Based on experimental observations, a probable mechanism for the formation of protonated layered dititanate sheets is also discussed.

  16. Room temperature vortex fluidic synthesis of monodispersed amorphous proto-vaterite.

    Science.gov (United States)

    Peng, Wenhong; Chen, Xianjue; Zhu, Shenmin; Guo, Cuiping; Raston, Colin L

    2014-10-11

    Monodispersed particles of amorphous calcium carbonate (ACC) 90 to 200 nm in diameter are accessible at room temperature in ethylene glycol and water using a vortex fluidic device (VFD). The ACC material is stable for at least two weeks under ambient conditions.

  17. Aqueous synthesis of porous platinum nanotubes at room temperature and their intrinsic peroxidase-like activity.

    Science.gov (United States)

    Cai, Kai; Lv, Zhicheng; Chen, Kun; Huang, Liang; Wang, Jing; Shao, Feng; Wang, Yanjun; Han, Heyou

    2013-07-11

    Platinum nanotubes (PtNTs) exhibiting high porosity were constructed by sacrificing the exterior of tellurium nanowires (TeNWs) and disintegrating the inner part spontaneously in aqueous solution at room temperature, in which the Kirkendall effect may play an important role. The present PtNTs exhibited intrinsic peroxidase-like activity in the presence of H2O2.

  18. Room temperature aerobic oxidation of amines by a nanocrystalline ruthenium oxide pyrochlore nafion composite catalyst.

    Science.gov (United States)

    Venkatesan, Shanmuganathan; Kumar, Annamalai Senthil; Lee, Jyh-Fu; Chan, Ting-Shan; Zen, Jyh-Myng

    2012-05-14

    The aerobic oxidation of primary amines to their respective nitriles has been carried out at room temperature using a highly reusable nanocrystalline ruthenium oxide pyrochlore Nafion composite catalyst (see figure). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. The synthesis of [2-13C]2-nitropropane at room temperature and at atmospheric pressure

    NARCIS (Netherlands)

    Jacquemijns M; Zomer G

    1990-01-01

    In this report the synthesis of [2-13C]2-nitropropane at room temperature is described. [2-13C]Acetone was converted into the oxime with hydroxy hydrochloridelamine and sodium carbonate. Treatment with hypobromic acid resulted in 2-13C]2-bromo-2-nitropropane. Hydrogenation with sodium borohydride

  20. Highly selective room temperature NO2 gas sensor based on rGO-ZnO composite

    Science.gov (United States)

    Jyoti, Kanaujiya, Neha; Varma, G. D.

    2018-05-01

    Blending metal oxide nanoparticles with graphene or its derivatives can greatly enhance gas sensing characteristics. In the present work, ZnO nanoparticles have been synthesized via reflux method. Thin films of reduced graphene oxide (rGO) and composite of rGO-ZnO have been fabricated by drop casting method for gas sensing application. The samples have been characterized by X-ray diffraction (XRD) and Field-emission scanning electron microscope (FESEM) for the structural and morphological studies respectively. Sensing measurements have been carried out for the composite film of rGO-ZnO for different concentrations of NO2 ranging from 4 to 100 ppm. Effect of increasing temperature on the sensing performance has also been studied and the rGO-ZnO composite sensor shows maximum percentage response at room temperature. The limit of detection (LOD) for rGO-ZnO composite sensor is 4ppm and it exhibits a high response of 48.4% for 40 ppm NO2 at room temperature. To check the selectivity of the composite sensor, sensor film has been exposed to 40 ppm different gases like CO, NH3, H2S and Cl2 at room temperature and the sensor respond negligibly to these gases. The present work suggests that rGO-ZnO composite material can be a better candidate for fabrication of highly selective room temperature NO2 gas sensor.

  1. Room temperature Compton profiles of conduction electrons in α-Ga ...

    Indian Academy of Sciences (India)

    B P PANDA and N C MOHAPATRA*. Department of Physics, Chikiti Mahavidyalaya, Chikiti 761 010, India. £Department of Physics, Berhampur University, Berhampur 760 007, India. Email: ncmphy123@hotmail.com. MS received 18 January 2003; accepted 21 June 2003. Abstract. Room temperature Compton profiles of ...

  2. GREEN SYNTHESIS OF SILVER AND PALLADIUM NANOPARTICLES AT ROOM TEMPERATURE USING COFFEE AND TEA EXTRACT

    Science.gov (United States)

    An extremely simple green approach that generates bulk quantities of nanocrystals of noble metals such as silver (Ag) and palladium (Pd) using coffee and tea extract at room temperature is described. The single-pot method uses no surfactant, capping agent, and/or template. The ob...

  3. Instantaneous radioiodination of rose bengal at room temperature and a cold-kit therefor. [DOE patent application

    Science.gov (United States)

    O'Brien, H. Jr.; Hupf, H.B.; Wanek, P.M.

    The disclosure relates to the radioiodination of rose bengal at room temperature and a cold-kit therefor. A purified rose bengal tablet is stirred into acidified ethanol at or near room temperature, until a suspension forms. Reductant-free /sup 125/I/sup -/ is added and the resulting mixture stands until the exchange label reaction occurs at room temperature. A solution of sterile isotonic phosphate buffer and sodium hydroxide is added and the final resulting mixture is sterilized by filtration.

  4. Ferroelectric ultrathin perovskite films

    Science.gov (United States)

    Rappe, Andrew M; Kolpak, Alexie Michelle

    2013-12-10

    Disclosed herein are perovskite ferroelectric thin-film. Also disclosed are methods of controlling the properties of ferroelectric thin films. These films can be used in a variety materials and devices, such as catalysts and storage media, respectively.

  5. Functional relationship of room temperature and setting time of alginate impression material

    Directory of Open Access Journals (Sweden)

    Dyah Irnawati

    2009-09-01

    Full Text Available Background: Indonesia is a tropical country with temperature variation. A lot of dental clinics do not use air conditioner. The room temperature influences water temperature for mixing alginate impression materials. Purpose: The aim of this study was to investigate the functional relationship of room temperature and initial setting time of alginate impression materials. Methods: The New Kromopan® alginate (normal and fast sets were used. The initial setting time were tested at 23 (control, 24, 25, 26, 27, 28, 29, 30 and 31 degrees Celcius room temperatures (n = 5. The initial setting time was tested based on ANSI/ADA Specification no. 18 (ISO 1563. The alginate powder was mixed with distilled water (23/50 ratio, put in the metal ring mould, and the initial setting time was measured by test rod. Data were statistically analyzed by linear regression (α = 0.05. result: The initial setting times were 149.60 ± 0.55 (control and 96.40 ± 0.89 (31° C seconds for normal set, and 122.00 ± 1.00 (control and 69.60 ± 0.55 (31° C seconds for fast set. The coefficient of determination of room temperature to initial setting time of alginate were R2 = 0.74 (normal set and R2 = 0.88 (fast set. The regression equation for normal set was Y = 257.6 – 5.5 X (p < 0.01 and fast set was Y = 237.7 – 5.6 X (p < 0.01. Conclusions: The room temperature gave high contribution and became a strength predictor for initial setting time of alginates. The share contribution to the setting time was 0.74% for normal set and 0.88% for fast set alginates.

  6. Performance evaluation of ZnO–CuO hetero junction solid state room temperature ethanol sensor

    International Nuclear Information System (INIS)

    Yu, Ming-Ru; Suyambrakasam, Gobalakrishnan; Wu, Ren-Jang; Chavali, Murthy

    2012-01-01

    Graphical abstract: Sensor response (resistance) curves of time were changed from 150 ppm to 250 ppm alcohol concentration of ZnO–CuO 1:1. The response and recovery times were measured to be 62 and 83 s, respectively. The sensing material ZnO–CuO is a high potential alcohol sensor which provides a simple, rapid and highly sensitive alcohol gas sensor operating at room temperature. Highlights: ► The main advantages of the ethanol sensor are as followings. ► Novel materials ZnO–CuO ethanol sensor. ► The optimized ZnO–CuO hetero contact system. ► A good sensor response and room working temperature (save energy). -- Abstract: A semiconductor ethanol sensor was developed using ZnO–CuO and its performance was evaluated at room temperature. Hetero-junction sensor was made of ZnO–CuO nanoparticles for sensing alcohol at room temperature. Nanoparticles were prepared by hydrothermal method and optimized with different weight ratios. Sensor characteristics were linear for the concentration range of 150–250 ppm. Composite materials of ZnO–CuO were characterized using X-ray diffraction (XRD), temperature-programmed reduction (TPR) and high-resolution transmission electron microscopy (HR-TEM). ZnO–CuO (1:1) material showed maximum sensor response (S = R air /R alcohol ) of 3.32 ± 0.1 toward 200 ppm of alcohol vapor at room temperature. The response and recovery times were measured to be 62 and 83 s, respectively. The linearity R 2 of the sensor response was 0.9026. The sensing materials ZnO–CuO (1:1) provide a simple, rapid and highly sensitive alcohol gas sensor operating at room temperature.

  7. Room-temperature nine-µm-wavelength photodetectors and GHz-frequency heterodyne receivers

    Science.gov (United States)

    Palaferri, Daniele; Todorov, Yanko; Bigioli, Azzurra; Mottaghizadeh, Alireza; Gacemi, Djamal; Calabrese, Allegra; Vasanelli, Angela; Li, Lianhe; Davies, A. Giles; Linfield, Edmund H.; Kapsalidis, Filippos; Beck, Mattias; Faist, Jérôme; Sirtori, Carlo

    2018-04-01

    Room-temperature operation is essential for any optoelectronics technology that aims to provide low-cost, compact systems for widespread applications. A recent technological advance in this direction is bolometric detection for thermal imaging, which has achieved relatively high sensitivity and video rates (about 60 hertz) at room temperature. However, owing to thermally induced dark current, room-temperature operation is still a great challenge for semiconductor photodetectors targeting the wavelength band between 8 and 12 micrometres, and all relevant applications, such as imaging, environmental remote sensing and laser-based free-space communication, have been realized at low temperatures. For these devices, high sensitivity and high speed have never been compatible with high-temperature operation. Here we show that a long-wavelength (nine micrometres) infrared quantum-well photodetector fabricated from a metamaterial made of sub-wavelength metallic resonators exhibits strongly enhanced performance with respect to the state of the art up to room temperature. This occurs because the photonic collection area of each resonator is much larger than its electrical area, thus substantially reducing the dark current of the device. Furthermore, we show that our photonic architecture overcomes intrinsic limitations of the material, such as the drop of the electronic drift velocity with temperature, which constrains conventional geometries at cryogenic operation. Finally, the reduced physical area of the device and its increased responsivity allow us to take advantage of the intrinsic high-frequency response of the quantum detector at room temperature. By mixing the frequencies of two quantum-cascade lasers on the detector, which acts as a heterodyne receiver, we have measured a high-frequency signal, above four gigahertz (GHz). Therefore, these wide-band uncooled detectors could benefit technologies such as high-speed (gigabits per second) multichannel coherent data

  8. Theoretical and experimental study of disordered Ba0.45Sr0.55 TiO3 photoluminescence at room temperature

    International Nuclear Information System (INIS)

    Souza, I.A.; Gurgel, M.F.C.; Santos, L.P.S.; Goes, M.S.; Cava, S.; Cilense, M.; Rosa, I.L.V.; Paiva-Santos, C.O.; Longo, E.

    2006-01-01

    Disordered and crystalline Ba 0.45 Sr 0.55 TiO 3 (BST) powder processed at low temperature was synthesized by the polymeric precursor method. The single-phase perovskite structure of the ceramics was identified by the Raman and X-ray diffraction techniques. Photoluminescence at room temperature was observed only in a disordered BST sample. Increasing the calcination time intensified the photoluminescence (PL), which reached its maximum value in the sample heat treated at 300 deg. C for 30 h. This emission may be correlated with the structural disorder. Periodic ab initio quantum-mechanical calculations using the CRYSTAL98 program can yield important information regarding the electronic and structural properties of crystalline and disordered solids. The experimental and theoretical results indicate the presence of intermediary energy levels in the band gap. This is ascribed to the break in symmetry, which is responsible for visible photoluminescence in the material's disordered state at room temperature

  9. Room temperature photoluminescence from In{sub x}Al{sub (1−x)}N films deposited by plasma-assisted molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Kong, W., E-mail: wei.kong@duke.edu; Jiao, W. Y.; Kim, T. H.; Brown, A. S. [Department of Electrical and Computer Engineering, Duke University, Durham, North Carolina 27708 (United States); Mohanta, A. [Oak Ridge Institute for Science and Education, Research Participation Program, U.S. Army Aviation and Missile Research, Development and Engineering Center (AMRDEC), Redstone Arsenal, Alabama 35898 (United States); Roberts, A. T. [Charles Bowden Research Lab, Army Aviation and Missile RD and E Center, Redstone Arsenal, Alabama 35898 (United States); Fournelle, J. [Department of Geoscience, University of Wisconsin, Madison, Wisconsin 53706 (United States); Losurdo, M. [Plasma Chemistry Research Center-CNR, via Orabona, 4-70126 Bari (Italy); Everitt, H. O. [Charles Bowden Research Lab, Army Aviation and Missile RD and E Center, Redstone Arsenal, Alabama 35898 (United States); Department of Physics, Duke University, Durham, North Carolina 27708 (United States)

    2014-09-29

    InAlN films deposited by plasma-assisted molecular beam epitaxy exhibited a lateral composition modulation characterized by 10–12 nm diameter, honeycomb-shaped, columnar domains with Al-rich cores and In-rich boundaries. To ascertain the effect of this microstructure on its optical properties, room temperature absorption and photoluminescence characteristics of In{sub x}Al{sub (1−x)}N were comparatively investigated for indium compositions ranging from x = 0.092 to 0.235, including x = 0.166 lattice matched to GaN. The Stokes shift of the emission was significantly greater than reported for films grown by metalorganic chemical vapor deposition, possibly due to the phase separation in these nanocolumnar domains. The room temperature photoluminescence also provided evidence of carrier transfer from the InAlN film to the GaN template.

  10. Observation of room temperature ferromagnetism in ZnTe:Cr films grown onto glass substrate by thermal evaporation method

    Energy Technology Data Exchange (ETDEWEB)

    Soundararajan, D; Mangalaraj, D; Nataraj, D [Thin Film Laboratory, Department of Physics, Bharathiar University, Coimbatore -641 046 (India); Dorosinskii, L [National Institute of Metrology (TUBITAK -UME), P.K. 54, 41470, Gebze -Kocaeli (Turkey); Santoyo-Salazar, J, E-mail: dorosins@ume.tubitak.gov.t [Universidad Nacional Autonoma de Mexico, Instituto de Investigaciones en Materiales, Mexico D.F. 04510 (Mexico)

    2009-03-01

    ZnTe and ZnTe:Cr films were prepared onto glass substrates using thermal evaporation method. Structural properties of the prepared samples were analyzed using X-ray diffractometer, and the presence of ZnCrTe phase was identified along with poor crystallinity. Composition analysis was done using XPS and the Cr content in the film was found to be 0.05 atomic percent. Transmittance spectra were recorded using UV-Vis spectrophotometer. The valence state of Cr in ZnTe:Cr film is determined to be +2 using electron spin resonance (ESR) spectroscopy. Magnetic moment data as a function of magnetic field were recorded using Superconducting Quantum Interference Device (SQUID) magnetometer at temperatures 5, 77 and 300 K. The results showed minority ferromagnetic behavior even at room temperature. Magnetic domains were observed using Magnetic Force Microscopy and the average value of domain size is 3.7 nm.

  11. Anti-M antibodies: Biphasic (reactive at room temperature and at 37°C: A case series

    Directory of Open Access Journals (Sweden)

    Siddhi P Shah

    2016-01-01

    Full Text Available Anti-M antibody, which is not reactive at 37°C, is not clinically significant. Reports of clinically significant anti-M antibodies causing hemolytic disease of the fetus and the newborn (HDFN and delayed hemolytic transfusion reaction (DHTR are available. We report 13 cases of anti-M antibodies reactive at room temperature (RT and at 37°C. These were found in patients of varied age groups (11 months to 85 years with varied clinical diagnosis. All the female patients were multigravida. In all cases, antibody screening was positive at RT as well as at the indirect antiglobulin test (IAT phase. Providing “M”-antigen negative transfusions is the best therapy in this situation. Provision of red blood cell (RBC antigen phenotyped donor registry shall ensure quick provision of antigen-negative blood for transfusion in emergency situations.

  12. Quality improvement of ZnO thin layers overgrown on Si(100 substrates at room temperature by nitridation pretreatment

    Directory of Open Access Journals (Sweden)

    Peng Wang

    2012-06-01

    Full Text Available To improve the quality of ZnO thin film overgrown on Si(100 substrate at RT (room temperature, the Si(100 surface was pretreated with different methods. The influence of interface on the overgrown ZnO layers was investigated by atomic force microscopy, photoluminescence and X-ray diffraction. We found that the nitridation pretreatment could significantly improve the quality of RT ZnO thin film through two-fold effects: one was to buffer the big lattice mismatch and ease the stress resulted from heterojunction growth; the other was to balance the interface charge, block the symmetric inheritance from the cubic Si (100 substrate and thus restrain the formation of zincblende phase.

  13. The effect of nanocrystallization and free volume on the room temperature plasticity of Zr-based bulk metallic glasses

    International Nuclear Information System (INIS)

    Mondal, K.; Ohkubo, T.; Toyama, T.; Nagai, Y.; Hasegawa, M.; Hono, K.

    2008-01-01

    To understand the mechanism of the room temperature plasticity of bulk metallic glasses (BMGs), microstructure observations, density measurements and positron annihilation studies were carried out for Zr-based BMGs cast at various temperatures and post-annealed under different conditions. We found that higher casting temperatures cause partial crystallization, which enhance the plasticity as long as the volume fraction of the crystalline phase is low. However, a similar nanocrystalline microstructure produced by post-annealing often leads to a large loss of plasticity, while certain conditions enhance the plasticity. Based on density measurements and positron annihilation lifetime spectroscopy, we conclude that the relative contribution of free volume and nanocrystallization is important for acquiring plasticity in metallic glasses

  14. Room-temperature synthesis of TiO 2 nanospheres and their solar driven photoelectrochemical hydrogen production

    KAUST Repository

    Avasare, Vidya

    2015-08-13

    Highly monodisperse and crystalline anatase phase TiO2 nanospheres have been synthesized at room temperature from organometallic precursor, titanocene dichloride and sodium azide. The photoelectrochemical (PEC) water splitting performance on the TiO2 nanospheres was studied under illumination of AM 1.5G. The optimized photocurrent density and photoconversion efficiency of TiO2 NSPs were observed ~0.95mAcm-2 at 1.23V and 0.69%, respectively. The transient photocurrent response measurements on the TiO2 NSPs during repeated ON/OFF visible light illumination cycles at 1.23V vs RHE show that both samples exhibited fast and reproducible photocurrent responses. The TiO2 NSPs show excellent catalytic stability, and significant dark current was not observed even at high potentials (2.0V vs RHE). © 2015 John Wiley & Sons, Ltd.

  15. A novel one-pot room-temperature synthesis route to produce very small photoluminescent silicon nanocrystals

    Science.gov (United States)

    Douglas-Gallardo, Oscar A.; Burgos-Paci, Maxi A.; Mendoza-Cruz, Rubén; Putnam, Karl G.; Josefina Arellano-Jiménez, M.; José-Yacamán, Miguel; Mariscal, Marcelo M.; Macagno, Vicente A.; Sánchez, Cristián G.; Pérez, Manuel A.

    2018-03-01

    A novel strategy to synthesize photoluminescent silicon nanocrystals (SiNCs) from a reaction between tetraethylorthosilicate (TEOS) and trimethyl-hexadecyl-ammonium borohydride (CTABH4) in organic solvent is presented. The formation reaction occurs spontaneously at room temperature in homogeneous phase. The produced silicon nanocrystals are characterized by using their photoluminescent properties and via HRTEM. In addition, theoretical calculations of the optical absorption spectrum of silicon quantum dots in vacuum with different sizes and surface moieties were performed in order to compare with the experimental findings. The new chemical reaction is simple and can be implemented to produce silicon nanocrystal with regular laboratory materials by performing easy and safe procedures. [Figure not available: see fulltext.

  16. High-accuracy determination for optical indicatrix rotation in ferroelectric DTGS

    OpenAIRE

    O.S.Kushnir; O.A.Bevz; O.G.Vlokh

    2000-01-01

    Optical indicatrix rotation in deuterated ferroelectric triglycine sulphate is studied with the high-accuracy null-polarimetric technique. The behaviour of the effect in ferroelectric phase is referred to quadratic spontaneous electrooptics.

  17. Controlling the properties of ferroelectric-nickelate interfaces

    Science.gov (United States)

    Marshall, Matthew S. J.; Malashevich, Andrei; Disa, Ankit; Han, Myung-Geun; Zhu, Yimei; Ismail-Beigi, Sohrab; Walker, Frederick; Ahn, Charles

    2015-03-01

    Ferroelectrics are a class of materials that exhibit a stable, reversible polarization making them useful for non-volatile electronic devices. In devices consisting of thin film ferroelectric PZT acting as a gate and a thin film of the conductive oxide LaNiO3 grown on LaAlO3(001) acting as a channel, we have realized a large change in room temperature channel resistance by switching the ferroelectric polarization. The effect of switching the polarization of the ferroelectric is to modify the electronic structure of the interface between the gate and channel, resulting in conduction in the otherwise insulating ferroelectric. Here, we discuss how changing the epitaxial strain and interface termination of LaNiO3 can result in larger changes in resistivity. The epitaxial strain is varied by growing the devices on LaAlO3 for tensile strain and SrTiO3 for compressive strain. An interface termination of either an atomic layer of NiO2 or LaO is achieved via atomic layering using oxygen plasma assisted molecular beam epitaxy (MBE).

  18. Magnetic enhancement of ferroelectric polarization in a self-grown ferroelectric-ferromagnetic composite

    Science.gov (United States)

    Kumar, Amit; Narayan, Bastola; Pachat, Rohit; Ranjan, Rajeev

    2018-02-01

    Ferroelectric-ferromagnetic multiferroic composites are of great interest both from the scientific and technological standpoints. The extent of coupling between polarization and magnetization in such two-phase systems depends on how efficiently the magnetostrictive and electrostrictive/piezoelectric strain gets transferred from one phase to the other. This challenge is most profound in the easy to make 0-3 ferroelectric-ferromagnetic particulate composites. Here we report a self-grown ferroelectric-ferromagnetic 0-3 particulate composite through controlled spontaneous precipitation of ferrimagnetic barium hexaferrite phase (BaF e12O19 ) amid ferroelectric grains in the multiferroic alloy system BiFe O3-BaTi O3 . We demonstrate that a composite specimen exhibiting merely ˜1% hexaferrite phase exhibits ˜34% increase in saturation polarization in a dc magnetic field of ˜10 kOe. Using modified Rayleigh analysis of the polarization field loop in the subcoercive field region we argue that the substantial enhancement in the ferroelectric switching is associated with the reduction in the barrier heights of the pinning centers of the ferroelectric-ferroelastic domain walls in the stress field generated by magnetostriction in the hexaferrite grains when the magnetic field is turned on. Our study proves that controlled precipitation of the magnetic phase is a good strategy for synthesis of 0-3 ferroelectric-ferromagnetic particulate multiferroic composite as it not only helps in ensuring a good electrical insulating character of the composite, enabling it to sustain high enough electric field for ferroelectric switching, but also the factors associated with the spontaneity of the precipitation process ensure efficient transfer of the magnetostrictive strain/stress to the surrounding ferroelectric matrix making domain wall motion easy.

  19. High-performance ferroelectric and magnetoresistive materials for next-generation thermal detector arrays

    Science.gov (United States)

    Todd, Michael A.; Donohue, Paul P.; Watton, Rex; Williams, Dennis J.; Anthony, Carl J.; Blamire, Mark G.

    2002-12-01

    This paper discusses the potential thermal imaging performance achievable from thermal detector arrays and concludes that the current generation of thin-film ferroelectric and resistance bolometer based detector arrays are limited by the detector materials used. It is proposed that the next generation of large uncooled focal plane arrays will need to look towards higher performance detector materials - particularly if they aim to approach the fundamental performance limits and compete with cooled photon detector arrays. Two examples of bolometer thin-film materials are described that achieve high performance from operating around phase transitions. The material Lead Scandium Tantalate (PST) has a paraelectric-to-ferroelectric phase transition around room temperature and is used with an applied field in the dielectric bolometer mode for thermal imaging. PST films grown by sputtering and liquid-source CVD have shown merit figures for thermal imaging a factor of 2 to 3 times higher than PZT-based pyroelectric thin films. The material Lanthanum Calcium Manganite (LCMO) has a paramagnetic to ferromagnetic phase transition around -20oC. This paper describes recent measurements of TCR and 1/f noise in pulsed laser-deposited LCMO films on Neodymium Gallate substrates. These results show that LCMO not only has high TCR's - up to 30%/K - but also low 1/f excess noise, with bolometer merit figures at least an order of magnitude higher than Vanadium Oxide, making it ideal for the next generation of microbolometer arrays. These high performance properties come at the expense of processing complexities and novel device designs will need to be introduced to realize the potential of these materials in the next generation of thermal detectors.

  20. Hybrid improper ferroelectricity in Ruddlesden-Popper Ca{sub 3}(Ti,Mn){sub 2}O{sub 7} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Liu, X. Q., E-mail: xqliu@zju.edu.cn, E-mail: xmchen59@zju.edu.cn; Wu, J. W.; Shi, X. X.; Zhao, H. J.; Zhou, H. Y.; Chen, X. M., E-mail: xqliu@zju.edu.cn, E-mail: xmchen59@zju.edu.cn [Laboratory of Dielectric Materials, School of Materials Science and Engineering, Zhejiang University, 38 Zheda Road, Hangzhou 310027 (China); Qiu, R. H.; Zhang, W. Q. [Department of Physics, Shanghai University, 99 Shangda Road, Shanghai 200444 (China)

    2015-05-18

    The hybrid improper ferroelectricity (HIF) has been proposed as a promising way to create multiferroic materials with strong magnetoelectric coupling by the first-principle calculation, and the experimental evidences of HIF in Ruddlesden-Poper Ca{sub 3}(Ti{sub 1−x}Mn{sub x}){sub 2}O{sub 7} (x = 0, 0.05, 0.1, and 0.15) ceramics have been shown in the present work. The room temperature ferroelectric hysteresis loops are observed in these ceramics, and a polar orthorhombic structure with two oxygen tilting modes has been confirmed by the X-ray powder diffraction. A first-order phase transition around 1100 K in Ca{sub 3}Ti{sub 2}O{sub 7} was evidenced, and the temperatures of phase transitions decrease linearly with increasing of the contents of Mn{sup 4+} ions. Based on the result of first-principle calculations, the polarization should be reversed by switching through the mediated Amam phase in Ca{sub 3}Ti{sub 2}O{sub 7} ceramics.