WorldWideScience

Sample records for colossal dielectric response

  1. Defect driven tailoring of colossal dielectricity of Reduced Graphene Oxide

    Energy Technology Data Exchange (ETDEWEB)

    Sarkar, S.; Mondal, A. [Department of Physics, Jadavpur University, Kolkata 700 032 (India); Dey, K. [Department of Solid State Physics, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032 (India); Ray, R., E-mail: juphyruma@gmail.com [Department of Physics, Jadavpur University, Kolkata 700 032 (India)

    2016-02-15

    Highlights: • Reduced graphene oxides (RGO) are prepared by two chemical routes. • Defects in RGO are characterized by Raman, FTIR and XPS studies. • Defects tailor colossal dielectricity in RGO. - Abstract: Reduced graphene oxide (RGO) is prepared in two different chemical routes where reduction of graphene oxide is performed by hydrazine hydrate and through high pressure in hydrothermal reactor. Samples are characterized by X-ray powdered diffraction (XRD), thermo gravimetric analysis (TGA), field emission scanning electron microscopy (FESEM) and tunneling electron microscopy (TEM). Types of defects are probed by Raman, FTIR spectroscopy and X-ray photoelectron spectroscopy (XPS). UV–vis absorption reveals different optical band gaps of the two RGOs. Conductivity mechanism is studied through I–V measurements displaying different characteristic features which are addressed due to the presence of defects appeared in different synthesis. Significantly high value (∼10{sup 4}) of dielectric permittivity at 10 MHz is attractive for technological application which could be tuned by the defects present in RGO.

  2. Rb2Ti2O5 : Superionic conductor with colossal dielectric constant

    Science.gov (United States)

    Federicci, Rémi; Holé, Stéphane; Popa, Aurelian Florin; Brohan, Luc; Baptiste, Benoît.; Mercone, Silvana; Leridon, Brigitte

    2017-08-01

    Electrical conductivity and high dielectric constant are in principle self-excluding, which makes the terms insulator and dielectric usually synonymous. This is certainly true when the electrical carriers are electrons, but not necessarily in a material where ions are extremely mobile, electronic conduction is negligible, and the charge transfer at the interface is immaterial. Here we demonstrate in a perovskite-derived structure containing five-coordinated Ti atoms, a colossal dielectric constant (up to 109) together with very high ionic conduction 10-3Scm-1 at room temperature. Coupled investigations of I -V and dielectric constant behavior allow us to demonstrate that, due to ion migration and accumulation, this material behaves like a giant dipole, exhibiting colossal electrical polarization (of the order of 0.1Ccm-2 ). Therefore it may be considered as a "ferro-ionet" and is extremely promising in terms of applications.

  3. Colossal Dielectric Behavior of Ga+Nb Co-Doped Rutile TiO2.

    Science.gov (United States)

    Dong, Wen; Hu, Wanbiao; Berlie, Adam; Lau, Kenny; Chen, Hua; Withers, Ray L; Liu, Yun

    2015-11-18

    Stimulated by the excellent colossal permittivity (CP) behavior achieved in In+Nb co-doped rutile TiO2, in this work we investigate the CP behavior of Ga and Nb co-doped rutile TiO2, i.e., (Ga(0.5)Nb(0.5))(x)Ti(1-x)O2, where Ga(3+) is from the same group as In(3+) but with a much smaller ionic radius. Colossal permittivity of up to 10(4)-10(5) with an acceptably low dielectric loss (tan δ = 0.05-0.1) over broad frequency/temperature ranges is obtained at x = 0.5% after systematic synthesis optimizations. Systematic structural, defect, and dielectric characterizations suggest that multiple polarization mechanisms exist in this system: defect dipoles at low temperature (∼10-40 K), polaronlike electron hopping/transport at higher temperatures, and a surface barrier layer capacitor effect. Together these mechanisms contribute to the overall dielectric properties, especially apparent observed CP. We believe that this work provides comprehensive guidance for the design of new CP materials.

  4. Colossal dielectric constant and Maxwell-Wagner relaxation in $Pb(Fe_{1/2}Nb_{1/2})O_{3-x}PbTiO_3$ single crystals

    OpenAIRE

    Liu, K.; Zhang, X. Y.

    2008-01-01

    Recently, materials exhibiting colossal dielectric constant ($CDC$) have attracted significant attention because of their high dielectric constant and potential applications in electronic devices, such as high dielectric capacitors, capacitor sensors, random access memories and so on.

  5. Tuning of colossal dielectric constant in gold-polypyrrole composite nanotubes using in-situ x-ray diffraction techniques

    Directory of Open Access Journals (Sweden)

    Abhisakh Sarma

    2014-09-01

    Full Text Available In-situ x-ray diffraction technique has been used to study the growth process of gold incorporated polypyrrole nanotubes that exhibit colossal dielectric constant due to existence of quasi-one-dimensional charge density wave state. These composite nanotubes were formed within nanopores of a polycarbonate membrane by flowing pyrrole monomer from one side and mixture of ferric chloride and chloroauric acid from other side in a sample cell that allows collection of x-ray data during the reaction. The size of the gold nanoparticle embedded in the walls of the nanotubes was found to be dependent on chloroauric acid concentration for nanowires having diameter more than 100 nm. For lower diameter nanotubes the nanoparticle size become independent of chloroauric acid concentration and depends on the diameter of nanotubes only. The result of this study also shows that for 50 nm gold-polypyrrole composite nanotubes obtained with 5.3 mM chloroauric acid gives colossal dielectric constant of about 107. This value remain almost constant over a frequency range from 1Hz to 106 Hz even at 80 K temperature.

  6. Tuning of colossal dielectric constant in gold-polypyrrole composite nanotubes using in-situ x-ray diffraction techniques

    Energy Technology Data Exchange (ETDEWEB)

    Sarma, Abhisakh; Sanyal, Milan K., E-mail: milank.sanyal@saha.ac.in [Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700 064 (India)

    2014-09-15

    In-situ x-ray diffraction technique has been used to study the growth process of gold incorporated polypyrrole nanotubes that exhibit colossal dielectric constant due to existence of quasi-one-dimensional charge density wave state. These composite nanotubes were formed within nanopores of a polycarbonate membrane by flowing pyrrole monomer from one side and mixture of ferric chloride and chloroauric acid from other side in a sample cell that allows collection of x-ray data during the reaction. The size of the gold nanoparticle embedded in the walls of the nanotubes was found to be dependent on chloroauric acid concentration for nanowires having diameter more than 100 nm. For lower diameter nanotubes the nanoparticle size become independent of chloroauric acid concentration and depends on the diameter of nanotubes only. The result of this study also shows that for 50 nm gold-polypyrrole composite nanotubes obtained with 5.3 mM chloroauric acid gives colossal dielectric constant of about 10{sup 7}. This value remain almost constant over a frequency range from 1Hz to 10{sup 6} Hz even at 80 K temperature.

  7. Origin of colossal dielectric permittivity of rutile Ti₀.₉In₀.₀₅Nb₀.₀₅O₂: single crystal and polycrystalline.

    Science.gov (United States)

    Song, Yongli; Wang, Xianjie; Sui, Yu; Liu, Ziyi; Zhang, Yu; Zhan, Hongsheng; Song, Bingqian; Liu, Zhiguo; Lv, Zhe; Tao, Lei; Tang, Jinke

    2016-02-12

    In this paper, we investigated the dielectric properties of (In + Nb) co-doped rutile TiO2 single crystal and polycrystalline ceramics. Both of them showed colossal, up to 10(4), dielectric permittivity at room temperature. The single crystal sample showed one dielectric relaxation process with a large dielectric loss. The voltage-dependence of dielectric permittivity and the impedance spectrum suggest that the high dielectric permittivity of single crystal originated from the surface barrier layer capacitor (SBLC). The impedance spectroscopy at different temperature confirmed that the (In + Nb) co-doped rutile TiO2 polycrystalline ceramic had semiconductor grains and insulating grain boundaries, and that the activation energies were calculated to be 0.052 eV and 0.35 eV for grain and grain boundary, respectively. The dielectric behavior and impedance spectrum of the polycrystalline ceramic sample indicated that the internal barrier layer capacitor (IBLC) mode made a major contribution to the high ceramic dielectric permittivity, instead of the electron-pinned defect-dipoles.

  8. Colossal magnetoresistance

    International Nuclear Information System (INIS)

    Fontcuberta, J.

    1999-01-01

    In 1986 Alex Mueller and Georg Bednorz of IBM Zurich discovered high-temperature superconductivity in copper-based oxides. This finding, which was rewarded with the Nobel Prize for Physics in the following year, triggered intense research into the properties of the transition metal oxides. Since then scientists have questioned the very nature of the metallic state in these materials. A few years after the initial discovery, in 1993, more excitement greeted reports that certain manganese oxides showed a huge change in electrical resistivity when a magnetic field was applied. This effect is generally known as magnetoresistance, but the resistivity change observed in these oxides was so large that it could not be compared with any other forms of magnetoresistance. The effect observed in these materials the manganese perovskites was therefore dubbed ''colossal'' magnetoresistance to distinguish it from the giant magnetoresistance observed in magnetic multilayers. In this article the author explains why magnetoresistance is an expanding field of physics research. (UK)

  9. Coloss project

    International Nuclear Information System (INIS)

    2005-01-01

    The COLOSS project was a shared-cost action, co-ordinated by IRSN within the Euratom Research Framework Programme 1998-2002. Started in February 2000, the project lasted three years. The work-programme performed by 19 partners was shaped around complementary activities aimed at improving severe accident codes. Unresolved risk-relevant issues regarding H2 production, melt generation and the source term were studied, through a large number of experiments such as a) dissolution of fresh and high burn-up UO 2 and MOX by molten Zircaloy, b) simultaneous dissolution of UO 2 and ZrO 2 by molten Zircaloy, c) oxidation of U-O-Zr mixtures by steam, d) degradation-oxidation of B 4 C control rods. Significant results have been produced from separate-effects, semi-global and large-scale tests on COLOSS topics. Break-through were achieved on some issues. Nevertheless, more data are needed for consolidation of the modelling on burn-up effects on UO 2 and MOX dissolution and on oxidation of U-O-Zr and B 4 C-metal mixtures. There was experimental evidence that the oxidation of these mixtures can contribute significantly to the large H2 production observed during the reflooding of degraded cores under severe accident conditions. Based on the experimental results obtained on the COLOSS topics, corresponding models were developed and were successfully implemented in several severe accident codes. Upgraded codes were then used for plant calculations to evaluate the consequences of new models on key severe accident sequences occurring in different plants designs involving B 4 C control rods (EPR, BWR, VVER- 1000) as well as in the TMI-2 accident. The large series of plant calculations involved sensitivity studies and code benchmarks. Main severe accident codes in use in the EU for safety studies were used such as ICARE/CATHARE, SCDAP/RELAP5, ASTEC, MELCOR and MAAP4. This activity enabled: a) the assessment of codes to calculate core degradation, b) the identification of main

  10. Coloss project; Le projet Coloss

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2005-07-01

    The COLOSS project was a shared-cost action, co-ordinated by IRSN within the Euratom Research Framework Programme 1998-2002. Started in February 2000, the project lasted three years. The work-programme performed by 19 partners was shaped around complementary activities aimed at improving severe accident codes. Unresolved risk-relevant issues regarding H2 production, melt generation and the source term were studied, through a large number of experiments such as a) dissolution of fresh and high burn-up UO{sub 2} and MOX by molten Zircaloy, b) simultaneous dissolution of UO{sub 2} and ZrO{sub 2} by molten Zircaloy, c) oxidation of U-O-Zr mixtures by steam, d) degradation-oxidation of B{sub 4}C control rods. Significant results have been produced from separate-effects, semi-global and large-scale tests on COLOSS topics. Break-through were achieved on some issues. Nevertheless, more data are needed for consolidation of the modelling on burn-up effects on UO{sub 2} and MOX dissolution and on oxidation of U-O-Zr and B{sub 4}C-metal mixtures. There was experimental evidence that the oxidation of these mixtures can contribute significantly to the large H2 production observed during the reflooding of degraded cores under severe accident conditions. Based on the experimental results obtained on the COLOSS topics, corresponding models were developed and were successfully implemented in several severe accident codes. Upgraded codes were then used for plant calculations to evaluate the consequences of new models on key severe accident sequences occurring in different plants designs involving B{sub 4}C control rods (EPR, BWR, VVER- 1000) as well as in the TMI-2 accident. The large series of plant calculations involved sensitivity studies and code benchmarks. Main severe accident codes in use in the EU for safety studies were used such as ICARE/CATHARE, SCDAP/RELAP5, ASTEC, MELCOR and MAAP4. This activity enabled: a) the assessment of codes to calculate core degradation, b) the

  11. Terahertz-frequency dielectric response of liquids

    DEFF Research Database (Denmark)

    Jepsen, Peter Uhd; Møller, Uffe; Cooke, David

    The dielectric response of liquids spans many decades in frequency. The dielectric response of a polar liquid is typically determined by relaxational dynamics of the dipolar moments of the liquid. In contrast, the dielectric response of a nonpolar liquid is determined by much weaker collision......-induced dipole moments. In the polar liquid water the fastest relaxational dynamics is found at terahertz frequencies, just below the first intermolecular vibrational and librational modes. In this presentation we will discuss optical terahertz spectroscopic techniques for measurement of the full dielectric...... function of liquids at terahertz frequencies. We will review the current understanding of the high-frequency dielectric spectrum of water, and discuss the relation between the dielectric spectrum and the thermodynamic properties of certain aqueous solutions....

  12. Colossal magnetodielectric effect caused by magnetoelectric effect ...

    Indian Academy of Sciences (India)

    The colossal magnetodielectric effect is reported in Pb(Zr,Ti)O3/Terfenol-D laminate composite under low magnetic field. When the composite is placed in an external a.c. magnetic field, magnetoelectric effect is produced, as a result, the dielectric properties of the Pb(Zr,Ti)O3 is changed, i.e. magnetodielectric effect. Both the ...

  13. Colossal magnetoresistance manganites

    Indian Academy of Sciences (India)

    Keywords. Manganites; colossal magnetoresistance; strongly correlated electron systems; metal-insulator transitions and other electronic transitions; Jahn-Teller polarons and electron-phonon interaction.

  14. Actuation response of polyacrylate dielectric elastomers

    DEFF Research Database (Denmark)

    Kofod, G.; Kornbluh, R.; Pelrine, R.

    2001-01-01

    Polyacrylate dielectric elastomers have yielded extremely large strain and elastic energy density suggesting that they are useful for many actuator applications. A thorough understanding of the physics underlying the mechanism of the observed response to an electric field can help develop improved......, though there are discrepancies. Further analysis suggests that these arise mostly from imperfect manufacture of the actuators, though there is a small contribution from an explicitly electrostrictive behavior of the acrylic adhesive. Measurements of the dielectric constant of stretched polymer reveal...... that the dielectric constant drops, when the polymer is strained, indicating the existence of a small electrostrictive effect. Finally, measurements of the electric breakdown field were made. These also show a dependence upon the strain. In the unstrained state the breakdown field is 20 WV/m, which grows to 218MV...

  15. Dielectric response in guiding center plasma

    International Nuclear Information System (INIS)

    Krommes, J.A.; Similon, P.

    1979-12-01

    The dielectric function for guiding center plasma is derived from the direct-interaction approximation. For the special case of thermal equilibrium, the reslt agrees with, although is more detailed than, an earlier calculation of Taylor. An explicit formula for the collision operator Σ' is given. The calculation illustrates several important features of renormalized turbulence theory: cancellation between the so-called diffusion and polarization parts of Σ', and the role of the renormalization in providing the proper description of adiabatic response

  16. Dielectric response of planar relativistic quantum plasmas

    International Nuclear Information System (INIS)

    Bardos, D.C.; Frankel, N.E.

    1991-01-01

    The dielectric response of planar relativistic charged particle-antiparticle plasmas is investigated, treating Fermi and Bose plasmas. The conductivity tensor in each case is derived in the self-consistent Random Phase Approximation. The tensors are then evaluated at zero temperature for the case of no external fields, leading to explicit dispersion relations for the electrodynamic modes of the plasma. The longitudinal and transverse modes are in general coupled for plasma layers. This coupling vanishes, however, in the zero field case, allowing 'effective' longitudinal and transverse dielectric functions to be defined in terms of components of the conductivity tensor. Solutions to the longitudinal mode equations (i.e. plasmon modes) are exhibited, while purely transverse modes are found not to exist. In the case of the Bose plasma the screening of a test charge is investigated in detail. 41 refs., 1 fig

  17. Direct view at colossal permittivity in donor-acceptor (Nb, In) co-doped rutile TiO2

    International Nuclear Information System (INIS)

    Mandal, Suman; Pal, Somnath; Hazarika, Abhijit; Kundu, Asish K.; Menon, Krishnakumar S. R.; Rioult, Maxime; Belkhou, Rachid

    2016-01-01

    Topical observations of colossal permittivity (CP) with low dielectric loss in donor-acceptor cations co-doped rutile TiO 2 have opened up several possibilities in microelectronics and energy-storage devices. Yet, the precise origin of the CP behavior, knowledge of which is essential to empower the device integration suitably, is highly disputed in the literature. From spectromicroscopic approach besides dielectric measurements, we explore that microscopic electronic inhomogeneities along with the nano-scale phase boundaries and the low temperature polaronic relaxation are mostly responsible for such a dielectric behavior, rather than electron-pinned defect-dipoles/grain-boundary effects as usually proposed. Donor-acceptor co-doping results in a controlled carrier-hopping inevitably influencing the dielectric loss while invariably upholding the CP value.

  18. Direct view at colossal permittivity in donor-acceptor (Nb, In) co-doped rutile TiO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Mandal, Suman, E-mail: suman.mandal@sscu.iisc.ernet.in; Pal, Somnath; Hazarika, Abhijit [Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru 560012 (India); Kundu, Asish K.; Menon, Krishnakumar S. R. [Surface Physics and Material Science Division, Saha Institute of Nuclear Physics, Kolkata 700064 (India); Rioult, Maxime; Belkhou, Rachid [Synchrotron SOLEIL, L' Orme des Merisiers Saint-Aubin, 91192 Gif-sur-Yvette (France)

    2016-08-29

    Topical observations of colossal permittivity (CP) with low dielectric loss in donor-acceptor cations co-doped rutile TiO{sub 2} have opened up several possibilities in microelectronics and energy-storage devices. Yet, the precise origin of the CP behavior, knowledge of which is essential to empower the device integration suitably, is highly disputed in the literature. From spectromicroscopic approach besides dielectric measurements, we explore that microscopic electronic inhomogeneities along with the nano-scale phase boundaries and the low temperature polaronic relaxation are mostly responsible for such a dielectric behavior, rather than electron-pinned defect-dipoles/grain-boundary effects as usually proposed. Donor-acceptor co-doping results in a controlled carrier-hopping inevitably influencing the dielectric loss while invariably upholding the CP value.

  19. Computation of Dielectric Response in Molecular Solids for High Capacitance Organic Dielectrics.

    Science.gov (United States)

    Heitzer, Henry M; Marks, Tobin J; Ratner, Mark A

    2016-09-20

    The dielectric response of a material is central to numerous processes spanning the fields of chemistry, materials science, biology, and physics. Despite this broad importance across these disciplines, describing the dielectric environment of a molecular system at the level of first-principles theory and computation remains a great challenge and is of importance to understand the behavior of existing systems as well as to guide the design and synthetic realization of new ones. Furthermore, with recent advances in molecular electronics, nanotechnology, and molecular biology, it has become necessary to predict the dielectric properties of molecular systems that are often difficult or impossible to measure experimentally. In these scenarios, it is would be highly desirable to be able to determine dielectric response through efficient, accurate, and chemically informative calculations. A good example of where theoretical modeling of dielectric response would be valuable is in the development of high-capacitance organic gate dielectrics for unconventional electronics such as those that could be fabricated by high-throughput printing techniques. Gate dielectrics are fundamental components of all transistor-based logic circuitry, and the combination high dielectric constant and nanoscopic thickness (i.e., high capacitance) is essential to achieving high switching speeds and low power consumption. Molecule-based dielectrics offer the promise of cheap, flexible, and mass producible electronics when used in conjunction with unconventional organic or inorganic semiconducting materials to fabricate organic field effect transistors (OFETs). The molecular dielectrics developed to date typically have limited dielectric response, which results in low capacitances, translating into poor performance of the resulting OFETs. Furthermore, the development of better performing dielectric materials has been hindered by the current highly empirical and labor-intensive pace of synthetic

  20. Nonlinear dielectric response in ferroelectric thin films

    Directory of Open Access Journals (Sweden)

    Lente, M. H.

    2004-08-01

    Full Text Available Electrical permittivity dependence on electric external bias field was investigated in PZT thin films. The results revealed the existence of two mechanisms contributing to the electrical permittivity. The first one was related to the domain reorientation, which was responsible for a strong no linear dielectric behavior, acting only during the poling process. The second mechanism was associated with the domain wall vibrations, which presented a reasonable linear electrical behavior with the applied bias field, contributing always to the permittivity independently of the poling state of the sample. The results also indicated that the gradual reduction of the permittivity with the increase of the bias field strength may be related to the gradual bending of the domain walls. It is believed that the domain wall bending induces a hardening and/or a thinning of the walls, thus reducing the electrical permittivity. A reinterpretation of the model proposed in the literature to explain the dielectric characteristics of ferroelectric materials at high electric field regime is proposed.

    Se ha estudiado la dependencia de la permitividad eléctrica con un campo bias externo en láminas delgadas de PZT. Los resultados revelaron la existencia de dos mecanismos que contribuyen a la permitividad eléctrica. El primero está relacionado con la reorientación de dominios, actúa sólo durante el proceso de polarización y es responsable de un comportamiento dieléctrico fuertemente no lineal. El segundo mecanismo se asocia a las vibraciones de las paredes de dominio, presentando un comportamiento eléctrico razonablemente lineal con el campo bias aplicado, contribuyendo siempre a la permitividad independientemente del estado de polarización de la muestra. Los resultados indicaron también que la reducción gradual de la permitividad con el aumento de la fuerza del campo bias podría estar relacionada con el “bending” gradual de las paredes de dominio

  1. Defects in codoped NiO with gigantic dielectric response

    Science.gov (United States)

    Wu, Ping; Ligatchev, Valeri; Yu, Zhi Gen; Zheng, Jianwei; Sullivan, Michael B.; Zeng, Yingzhi

    2009-06-01

    We combine first-principles, statistical, and phenomenological methods to investigate the electronic and dielectric properties of NiO and clarify the nature of the gigantic dielectric response in codoped NiO. Unlike previous models which are dependent on grain-boundary effects, our model based on small polaron hopping in homogeneous material predicts the dielectric permittivity (104-5) for heavily Li- and MD -codoped NiO (MD=Ti,Al,Si) . Furthermore, we reproduce the experimental trends in dielectric properties as a function of the dopants nature and their concentrations, as well as the reported activation energies for the relaxation in Li- and Ti-codoped NiO (0.308 eV or 0.153 eV depending on the Fermi-level position). In this study, we demonstrate that small polaron hopping on dopant levels is the dominant mechanism for the gigantic dielectric response in these codoped NiO.

  2. Features of dielectric response in PMN-PT ferroelectric ceramics

    International Nuclear Information System (INIS)

    Guerra, J D S; Araujo, E B; Guarany, C A; Reis, R N; Lima, E C

    2008-01-01

    In this paper, electrical and structural properties were reported for pyrochlore free (1 - x)[Pb(Mg 1/3 Nb 2/3 )O 3 ] - xPbTiO 3 (PMN-PT) (with 35 mol% PbTiO 3 ) ceramics obtained from fine powders. Dielectric studies were focused on the investigation of the complex dielectric permittivity (ε' - iε'') as a function of frequency and temperature. The effects of the dc applied electric field on dielectric response were also investigated. Results revealed a field dependence dielectric anomaly in the dielectric permittivity curves (ε(T)) in the low dc electric field region, which in turn prevails in the whole analysed frequency interval. To the best of our knowledge, these properties for the PMN-PT ceramic system have not been reported before as in this work. The results were analysed within the framework of the current models found in the literature.

  3. Electrical response of relaxing dielectrics compressed by arbitrary stress pulses

    International Nuclear Information System (INIS)

    Lysne, P.C.

    1983-01-01

    The theoretical problem of the electric response of biased dielectrics and piezoelectrics subjected to planar stress pulse loading is considered. The materials are taken to exhibit dielectric relaxation in the sense that changes in the polarization induced by electric fields do not occur instantaneously with changes in the fields. While this paper considers arbitrary stress pulse loading of the specimen, examples that are amenable to projectile impact techniques are considered in detail. They are shock reverberation, thin pulse, and ramp loading experiments. It is anticipated that these experiments will play a role in investigations of dielectric relaxation caused by shock induced damage in insulators

  4. Electromechanical response of silicone dielectric elastomers

    Science.gov (United States)

    Cârlescu, V.; Prisăcaru, G.; Olaru, D.

    2016-08-01

    This paper presents an experimental technique to investigate the electromechanical properties of silicone dielectric elastomers actuated with high DC electric fields. A non-contact measurement technique is used to capture and monitor the thickness strain (contraction) of a circular film placed between two metallic disks electrodes. Two active fillers such as silica (10, 15 and 30 wt%) and barium titanate (5 and 15 wt%) were incorporated in order to increase the actuation performance. Thickness strain was measured at HV stimuli up to 4.5 kV and showed a quadratic dependence against applied electric field indicating that the induced strain is triggered by the Maxwell effect and/or electrostriction phenomenon as reported in literature. The actuation process evidences a rapid contraction upon HV activation and a slowly relaxation when the electrodes are short-circuit due to visco-elastic nature of elastomers. A maximum of 1.22 % thickness strain was obtained at low actuating field intensity (1.5 V/pm) comparable with those reported in literature for similar dielectric elastomer materials.

  5. Transformation Algorithm of Dielectric Response in Time-Frequency Domain

    Directory of Open Access Journals (Sweden)

    Ji Liu

    2014-01-01

    Full Text Available A transformation algorithm of dielectric response from time domain to frequency domain is presented. In order to shorten measuring time of low or ultralow frequency dielectric response characteristics, the transformation algorithm is used in this paper to transform the time domain relaxation current to frequency domain current for calculating the low frequency dielectric dissipation factor. In addition, it is shown from comparing the calculation results with actual test data that there is a coincidence for both results over a wide range of low frequencies. Meanwhile, the time domain test data of depolarization currents in dry and moist pressboards are converted into frequency domain results on the basis of the transformation. The frequency domain curves of complex capacitance and dielectric dissipation factor at the low frequency range are obtained. Test results of polarization and depolarization current (PDC in pressboards are also given at the different voltage and polarization time. It is demonstrated from the experimental results that polarization and depolarization current are affected significantly by moisture contents of the test pressboards, and the transformation algorithm is effective in ultralow frequency of 10−3 Hz. Data analysis and interpretation of the test results conclude that analysis of time-frequency domain dielectric response can be used for assessing insulation system in power transformer.

  6. Nonlinear Dielectric Response of Water Treed XLPE Cable Insulation

    Energy Technology Data Exchange (ETDEWEB)

    Hvidsten, Sverre

    1999-07-01

    Condition assessment of XLPE power cables is becoming increasingly important for the utilities, due to a large number of old cables in service with high probability of failure caused by water tree degradation. The commercial available techniques are generally based upon measurements of the dielectric response, either by time (polarisation/depolarisation current or return voltage) or frequency domain measurements. Recently it has been found that a high number of water trees in XLPE insulated cables causes the dielectric response to increase more than linearly with increasing test voltage. This nonlinear feature of water tree degraded XLPE insulation has been suggested to be of a great importance, both for diagnostic purposes, and for fundamental understanding of the water tree phenomenon itself. The main purpose of this thesis have been to study the nonlinear feature of the dielectric response measured on watertreed XLPE insulation. This has been performed by dielectric response measurements in both time and frequency domain, numerical calculations of losses of simplified water tree models, and fmally water content and water permeation measurements on single water trees. The dielectric response measurements were performed on service aged cable samples and laboratory aged Rogowski type objects. The main reason for performing laboratory ageing was to facilitate diagnostic testing as a function of ageing time of samples containing mainly vented water trees. A new method, based upon inserting NaC1 particles at the interface between the upper semiconductive screen and the insulation, was found to successfully enhance initiation and growth of vented water trees. AC breakdown strength testing show that it is the vented water trees that reduce the breakdown level of both the laboratory aged test objects and service aged cable samples. Vented water treeing was found to cause the dielectric response to become nonlinear at a relatively low voltage level. However, the measured

  7. Dielectric response and ac conductivity analysis of hafnium oxide nanopowder

    International Nuclear Information System (INIS)

    Karahaliou, P K; Xanthopoulos, N; Krontiras, C A; Georga, S N

    2012-01-01

    The dielectric response of hafnium oxide nanopowder was studied in the frequency range of 10 -2 -10 6 MHz and in the temperature range of 20-180 °C. Broadband dielectric spectroscopy was applied and the experimental results were analyzed and discussed using the electric modulus (M*) and alternating current (ac) conductivity formalisms. The analyses of the dc conductivity and electric modulus data revealed the presence of mechanisms which are thermally activated, both with almost the same activation energy of 1.01 eV. A fitting procedure involving the superposition of the thermally activated dc conductivity, the universal dielectric responce and the near constant loss terms has been used to describe the frequency evolution of the real part of the specific electrical conductivity. The conductivity master curve was obtained, suggesting that the time-temperature superposition principle applies for the studied system, thus implying that the conductivity mechanisms are temperature independent.

  8. Colossal magnetoresistance in manganites and related prototype devices

    International Nuclear Information System (INIS)

    Liu Yu-Kuai; Yin Yue-Wei; Li Xiao-Guang

    2013-01-01

    We review colossal magnetoresistance in single phase manganites, as related to the field sensitive spin-charge interactions and phase separation; the rectifying property and negative/positive magnetoresistance in manganite/Nb:SrTiO 3 p—n junctions in relation to the special interface electronic structure; magnetoelectric coupling in manganite/ferroelectric structures that takes advantage of strain, carrier density, and magnetic field sensitivity; tunneling magnetoresistance in tunnel junctions with dielectric, ferroelectric, and organic semiconductor spacers using the fully spin polarized nature of manganites; and the effect of particle size on magnetic properties in manganite nanoparticles. (topical review - magnetism, magnetic materials, and interdisciplinary research)

  9. Dielectric response of periodic systems from quantum Monte Carlo calculations.

    Science.gov (United States)

    Umari, P; Willamson, A J; Galli, Giulia; Marzari, Nicola

    2005-11-11

    We present a novel approach that allows us to calculate the dielectric response of periodic systems in the quantum Monte Carlo formalism. We employ a many-body generalization for the electric-enthalpy functional, where the coupling with the field is expressed via the Berry-phase formulation for the macroscopic polarization. A self-consistent local Hamiltonian then determines the ground-state wave function, allowing for accurate diffusion quantum Monte Carlo calculations where the polarization's fixed point is estimated from the average on an iterative sequence, sampled via forward walking. This approach has been validated for the case of an isolated hydrogen atom and then applied to a periodic system, to calculate the dielectric susceptibility of molecular-hydrogen chains. The results found are in excellent agreement with the best estimates obtained from the extrapolation of quantum-chemistry calculations.

  10. Reduced dielectric response in spatially varying electric fields

    DEFF Research Database (Denmark)

    Hansen, Jesper Schmidt

    2015-01-01

    relations between the flux and the gradient of the polarization. Comparison between the theory and molecular dynamics simulations confirms this effect. The effect is significant for small length scale electric field variations and the inclusion of the flux is thus important in nanoscale modeling......In this paper, the dynamical equation for polarization is derived. From this the dielectric response to a spatially varying electric field is analyzed showing a reduced response due to flux of polarization in the material. This flux is modeled as a diffusive process through linear constitutive...

  11. Identification of structural relaxation in the dielectric response of water

    DEFF Research Database (Denmark)

    Hansen, Jesper Schmidt; Kisliuk, Alexander; Solokov, Alexei P.

    2016-01-01

    One century ago pioneering dielectric results obtained for water and n-alcohols triggered the advent of molecular rotation diffusion theory considered by Debye to describe the primary dielectric absorption in these liquids. Comparing dielectric, viscoelastic, and light scattering results, we...... unambiguously demonstrate that the structural relaxation appears only as a high-frequency shoulder in the dielectric spectra of water. In contrast, the main dielectric peak is related to a supramolecular structure, analogous to the Debye-like peak observed in monoalcohols....

  12. Positron annihilation response and broadband dielectric spectroscopy: salol.

    Science.gov (United States)

    Bartoš, J; Iskrová, M; Köhler, M; Wehn, R; Sauša, O; Lunkenheimer, P; Krištiak, J; Loidl, A

    2011-09-01

    A phenomenological analysis of the ortho-positronium (o-Ps) annihilation from positron annihilation lifetime spectroscopy (PALS) and the dynamics from broadband dielectric spectroscopy (BDS) are reported on a small molecular glass former of intermediate H-bonding and fragility: salol. The dielectric spectra extend over a very broad frequency range of about 2 × 10(-2)-3.5 × 10(11) Hz, providing information on the α-relaxation, the secondary relaxation giving rise to the excess wing, and the shallow high-frequency minimum in the micro- to milli-meter wave range. A number of empirical correlations between the o-Ps lifetime, τ(3)(T), and the various spectral and relaxation features have been observed. Thus, the phenomenological evaluation of the τ(3)(T) dependence of the PALS response of the amorphous sample reveals three characteristic PALS temperatures: T(g)(PALS), T(b1)(L) = 1.15T(g)(PALS) and T(b2)(L) = 1.25T(g)(PALS), which are discussed in relation to similar findings for some typical small molecular vdW- and H-bonded glass formers. A slighter change of the slope at T(b1)(L) appears to be related to the transition from excess wing to the primary α-process-dominated behavior, with the secondary process dominating in the deeply supercooled liquid state below T(b1)(L). The high-temperature plateau effect in the τ (3)(T) plot occurs at T(b2)(L) and agrees with the characteristic Stickel temperature, T(B)(ST), marking a qualitative change of the primary α process, but it does not follow the relation T(b2)(L) application of the two-order parameter (TOP) model to the structural relaxation as represented by the primary α relaxation times from BDS leads to the characteristic TOP temperature, T(m)(c), close to T(b1) from PALS. Within this model the phenomenological interpretation is offered based on changes in the probability of occurrence of solid-like and liquid-like domains to explain the dynamic as well as PALS responses. In summary, all the empirical

  13. Shear and dielectric responses of propylene carbonate, tripropylene glycol, and a mixture of two secondary amides

    DEFF Research Database (Denmark)

    Gainaru, Catalin; Hecksher, Tina; Olsen, Niels Boye

    2012-01-01

    Propylene carbonate and a mixture of two secondary amides, N-ethylformamide and Nethylacetamide, are investigated by means of broadband dielectric and mechanical shear spectroscopy. The similarities between the rheological and the dielectric responses of these liquids and of the previously invest...... in the secondary amides. In addition, the predictions of the shoving model are confirmed for the investigated liquids...

  14. Colossal magnetodielectric effect and spin flop in magnetoelectric Co4Nb2O9 crystal

    International Nuclear Information System (INIS)

    Yin, L. H.; Yang, J.; Dai, J. M.; Song, W. H.; Zhu, X. B.; Zou, Y. M.; Sun, Y. P.

    2016-01-01

    We have investigated the detailed magnetic, magnetoelectric (ME), magnetodielectric (MD) and thermal expansion properties in Co 4 Nb 2 O 9 crystal. A magnetic-field-induced spin flop was observed below antiferromagnetic (AFM) transition temperature T N . Dielectric constant at applied magnetic field nearly diverges around the AFM transition, giving rise to a colossal MD effect as high as ∼138% around T N . Theoretical analysis of the ME and MD data revealed a major contribution of critical spin fluctuation to the colossal MD effect in Co 4 Nb 2 O 9 . These results suggest that linear ME materials with large ME coupling might be potentially used to realize large MD effect for future application.

  15. UV response on dielectric properties of nano nematic liquid crystal

    Directory of Open Access Journals (Sweden)

    Kamal Kumar Pandey

    2018-03-01

    Full Text Available In this work, we investigate the effect of UV light irradiation on the dielectric parameters of nematic liquid crystal (5CB and ZnO nanoparticles dispersed liquid crystal. With addition of nanoparticles in nematic LC are promising new materials for a variety of application in energy harvesting, displays and photonics including the liquid crystal laser. To realize many applications, however we optimize the properties of liquid crystal and understand how the UV light irradiation interact the nanoparticles and LC molecules in dispersed/doped LC. The dielectric permittivity and loss factor have discussed the pure nematic LC and dispersed/doped system after, during and before UV light exposure. The dielectric relaxation spectroscopy was carried out in the frequency range 100 Hz–10 MHz in the nematic mesophase range. Keywords: Dielectric permittivity, Relaxation frequency, Nematic liquid crystal, UV light irradiation

  16. Hydrostatic pressure effects on the dielectric response of potassium cyanide

    International Nuclear Information System (INIS)

    Ortiz Lopez, J.

    1992-01-01

    The complex dielectric constant of crystalline KCN was measured under hydrostatic pressures up to 6.1 kbar in the temperature and frequency ranges of 50-300 K and 10-10 5 Hz, respectively. It is found that the pressure derivative of the real part of the dielectric constant at all measured temperatures is negative. From these results we obtain estimates for the pressure and volume derivatives of polarizabilities. The anomaly in the real part of the dielectric constant at the elastic order-disorder transition shifts to higher temperatures with increasing pressure at a rate of 2.05 K/kbar. By carefully avoiding thermal cycling through this transition we find no evidence of the monoclinic phase reported to exist in the P-T phase diagram of KCN at relatively low pressures. Dielectric loss measurements show thermally-activated CN - reorientation rates in the elastically ordered phase with pressure-independent reorientational barriers and decreasing attempt frequencies for increasing pressures. Additional pressure effects on dielectric loss allow to obtain the pressure derivative of the antiferroelectric transition temperature as 1.97 K/kbar. (Author)

  17. Dielectric response of fully and partially depleted ferroelectric thin films and inversion of the thickness effect

    International Nuclear Information System (INIS)

    Misirlioglu, I B; Yildiz, M

    2013-01-01

    We study the effect of full and partial depletion on the dielectric response characteristics of ferroelectric thin films with impurities via a computational approach. Using a thermodynamic approach along with the fundamental equations for semiconductors, we show that films with partial depletion display unique features and an enhanced dielectric response compared with those fully depleted. We find that the capacitance peak at switching can be significantly suppressed in the case of high impurity densities (>10 25 m −3 ) with relatively low ionization energy, of the order of 0.5 eV. For conserved number of species in films, electromigration of ionized impurities at room temperature is negligible and has nearly no effect on the dielectric response. In films with high impurity density, the dielectric response at zero bias is enhanced with respect to charge-free films or those with relatively low impurity density ( 24 m −3 ). We demonstrate that partially depleted films should be expected to exhibit peculiar capacitance–voltage characteristics at low and high bias and that the thickness effect probed in experiments in ferroelectric thin films could be entirely inverted in thin films with depletion charges where a higher dielectric response can be measured in thicker films. Therefore, depletion charge densities in ferroelectric thin films should be estimated before size-effect-related studies. Finally, we noted that these findings are in good qualitative agreement with dielectric measurements carried out on PbZr x Ti 1−x O 3 . (paper)

  18. Colossal Magnetoresistance Manganites and Related Prototype Devices

    OpenAIRE

    Liu, Yukuai; Yin, Yuewei; Li, Xiaoguang

    2013-01-01

    We review colossal magnetoresistance in single phase manganites, as related to the field sensitive spin charge interactions and phase separation; the rectifying property and negative/positive magnetoresistance in manganite/Nb:SrTiO3 pn junctions in relation to the special interface electronic structure; magnetoelectric coupling in manganite/ferroelectric structures that takes advantage of strain, carrier density, and magnetic field sensitivity; tunneling magnetoresistance in tunnel junctions ...

  19. Total-dielectric-function approach to electron and phonon response in solids

    International Nuclear Information System (INIS)

    Penn, D.R.; Lewis, S.P.; Cohen, M.L.

    1995-01-01

    The interaction between two test charges, the response of a solid to an external field, and the normal modes of the solid can be determined from a total dielectric function that includes both electronic and lattice polarizabilities as well as local-field effects. In this paper we examine the relationship between superconductivity and the stability of a solid and derive sum rules for the electronic part of the dielectric function. It is also shown that there are negative eigenvalues of the total static dielectric function, implying the possibility of an attractive interaction between test charges. An attractive interaction is required for superconductivity

  20. Dielectric Response of Corn Leaves to Water Stress

    NARCIS (Netherlands)

    van Emmerik, T.H.M.; Steele-Dunne, S.C.; Judge, J; van de Giesen, N.C.

    2016-01-01

    Radar backscatter from vegetated surface is sensitive to direct backscatter from the canopy, and two-way attenuation of the signal as it travels through the canopy. Both mechanisms are affected by the dielectric properties of {the individual elements of the canopy, which are primarily a function of

  1. Dielectric response of capacitor structures based on PZT annealed at different temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Kamenshchikov, Mikhail V., E-mail: Mikhailkamenshchikov@yandex.ru [Tver State University, 170002, Tver (Russian Federation); Solnyshkin, Alexander V. [Tver State University, 170002, Tver (Russian Federation); Pronin, Igor P. [Ioffe Institute, 194021, St. Petersburg (Russian Federation)

    2016-12-09

    Highlights: • Correlation of the microstructure of PZT films and dielectric response was found. • Difference of dielectric responses under low and high bias is caused by domains. • Internal fields is discussed on the basis of the space charges. • Dependences of PZT films characteristics on synthesis temperature are extremal. - Abstract: Dielectric response of thin-film capacitor structures of Pt/PZT/Pt deposited by the RF magnetron sputtering method and annealed at temperatures of 540–570 °C was investigated. It was found that dielectric properties of these structures depend on the synthesis temperature. Stability of a polarized state is considered on the basis of the analysis of hysteresis loops and capacitance–voltage (C–V) characteristics. The contribution of the domain mechanism in the dielectric response of the capacitor structure comprising a ferroelectric is discussed. Extreme dependences of electrophysical characteristics of PZT films on their synthesis temperature were observed. Correlation of dielectric properties with microstructure of these films is found out.

  2. Dielectric response of KCN crystals at ultra-low frequencies

    OpenAIRE

    Ziemath, Ervino C.; Aegerter, Michel A.; Slaets, J.

    1987-01-01

    We describe an ultra low frequency equipment employing programmable digital technique. The system is used to measure the dielectric parameters et, en and tg d or pure KCN crystals as a function of temperature in the frequency range 10-2 Hz to 40 Hz. The relaxation time of the Cn dipoles presents a classical temperature activated reorientation behaviour characterized by an Arrhenius law t=to exp (U/kT) with t0=7,26 x 10-15 s and U = 0,147 eV.

  3. Thermal analysis and temperature dependent dielectric responses of Co doped anatase TiO2 nanoparticles

    International Nuclear Information System (INIS)

    Alamgir; Khan, Wasi; Ahammed, Nashiruddin; Naqvi, A. H.; Ahmad, Shabbir

    2015-01-01

    Nanoparticles (NPs) of pure and 5 mol % cobalt doped TiO 2 synthesized through acid modified sol-gel method were characterized to understand their thermal, structural, morphological, and temperature dependent dielectric properties. Thermogravimetric analysis (TGA) has been used for thermal studies and indicates the weight loss in two steps due to the removal of residual organics. X-ray diffraction study was employed to confirm the formation of single anatase phase with tetragonal symmetry for both pure and 5 mol % Co doped TiO 2 NPs. The average crystallite size of both samples was calculated from the Scherrer’s formula and was found in the range from 9-11 nm. TEM micrographs of these NPs reflect their shape and distribution. The dielectric constant (ε′), dielectric loss (tanδ) and ac conductivity (σ ac ) were also studied as a function of temperature at different frequencies. Electrical responses of the synthesized NPs have been analyzed carefully in the framework of relevant models. It is also noticed that the dielectric constant (ε′) of the samples found to decrease with increasing frequency but increases with increasing temperature up to a particular value and then sharply decreases. Temperature variation of dielectric constant exhibits step like escalation and shows relaxation behavior. Study of dielectric properties shows dominant dependence on the grain size as well as Co ion incorporation in TiO 2

  4. Dielectric response of molecules in empirical tight-binding theory

    Science.gov (United States)

    Boykin, Timothy B.; Vogl, P.

    2002-01-01

    In this paper we generalize our previous approach to electromagnetic interactions within empirical tight-binding theory to encompass molecular solids and isolated molecules. In order to guarantee physically meaningful results, we rederive the expressions for relevant observables using commutation relations appropriate to the finite tight-binding Hilbert space. In carrying out this generalization, we examine in detail the consequences of various prescriptions for the position and momentum operators in tight binding. We show that attempting to fit parameters of the momentum matrix directly generally results in a momentum operator which is incompatible with the underlying tight-binding model, while adding extra position parameters results in numerous difficulties, including the loss of gauge invariance. We have applied our scheme, which we term the Peierls-coupling tight-binding method, to the optical dielectric function of the molecular solid PPP, showing that this approach successfully predicts its known optical properties even in the limit of isolated molecules.

  5. Dielectric response of biconcave erythrocyte membranes to D- and L-Glucose

    International Nuclear Information System (INIS)

    Livshits, L; Caduff, A; Talary, M S; Feldman, Y

    2007-01-01

    In this paper, we report on the influence of D- and L-glucose on the dielectric properties of native shaped (biconcave) human erythrocytes using time domain dielectric spectroscopy. The dielectric spectra of biconcave cells were analysed using a modified form of the model originally reported for spheroid particle suspensions (Asami and Yonezawa 1995 Biochim. Biophys. Acta. 1245 317-24) The observed increase in the specific membrane capacitance of the biconcave erythrocytes was correlated with an increase in the concentration of D-glucose. In contrast, no associated correlation was found to changes in the membrane capacitance with increasing concentrations of L-glucose. A similar analysis of the dielectric response of osmotically swollen erythrocytes to changes in D-glucose concentration revealed a significantly different calculated specific cell membrane capacitance at elevated (>12 mM) D-glucose concentrations. The paper outlines and discusses the possible biochemical mechanisms that could be responsible for the measured dielectric properties of the erythrocyte membrane capacitances

  6. Insight into the dielectric response of transformer oil-based nanofluids

    Directory of Open Access Journals (Sweden)

    Ming Dong

    2017-02-01

    Full Text Available The oil-based nanofluids with greater dielectric strength have attracted much attention as a crucial insulating materials in high-voltage oil-immersed power equipment. In fact, the different microstructures of the transformer oil-based nanofluids (TNFs would result in different dielectric properties. In this work, the broadband dielectric spectroscopy measurement was used to establish the linkage between the electric double layer (EDL and dielectric response properties of TNFs which was performed at 298K temperature and with frequency range from 10-2Hz∼106Hz. The modified Havriliak-Negami (HN model function was used to analyze the measured results. The results demonstrate that both the real and imaginary parts of dielectric spectra of two kinds of oil are composed of the conductivity and polarization process. Compared with pure oil, two polarization process could be observed for the TNFs, explained by the EDL structure reasonably. The introduction of the EDL structure provides an idea to account for the insulating strength improvement of TNFs for the first time.

  7. Dielectric response and transport properties of alkylammonium formate ionic liquids

    Science.gov (United States)

    Nazet, Andreas; Buchner, Richard

    2018-05-01

    Dielectric relaxation spectra of three members of the alkylammonium formate family of protic ionic liquids (PILs), namely, ethylammonium formate (EAF), n-butylammonium formate (BuAF), and n-pentylammonium formate (PeAF), as well as the pseudo-PIL triethylamine + formic acid (molar ratio 1:2; TEAF) have been studied over a wide frequency (50 MHz to 89 GHz) and temperature range (5-65 °C), complemented by measurements of their density, viscosity, and conductivity. It turned out that the dominating relaxation of EAF, BuAF, and PeAF arises from both cation and anion reorientations which are synchronized in their dynamics due to hydrogen bonding. Amplitudes and relaxation times of this mode reflect the—compared to nitrate—different nature of H bonding between the formate anion and ethylammonium cation, as well as increasing segregation of the PIL structure into polar and non-polar domains. The TEAF data suggest that its dominating relaxation is due to the rotation of the complex triethylamineṡ(formic acid)2 in which no significant proton transfer to an ion pair occurred. Weak dissociation of this complex into ions was postulated to account for the high conductivity of TEAF.

  8. Core loss during a severe accident (COLOSS)

    International Nuclear Information System (INIS)

    Adroguer, B.; Bertrand, F.; Chatelard, P.; Cocuaud, N.; Van Dorsselaere, J.P.; Bellenfant, L.; Knocke, D.; Bottomley, D.; Vrtilkova, V.; Belovsky, L.; Mueller, K.; Hering, W.; Homann, C.; Krauss, W.; Miassoedov, A.; Schanz, G.; Steinbrueck, M.; Stuckert, J.; Hozer, Z.; Bandini, G.; Birchley, J.; Berlepsch, T. von; Kleinhietpass, I.; Buck, M.; Benitez, J.A.F.; Virtanen, E.; Marguet, S.; Azarian, G.; Caillaux, A.; Plank, H.; Boldyrev, A.; Veshchunov, M.; Kobzar, V.; Zvonarev, Y.; Goryachev, A.

    2005-01-01

    The COLOSS project was a 3-year shared-cost action, which started in February 2000. The work-programme performed by 19 partners was shaped around complementary activities aimed at improving severe accident codes. Unresolved risk-relevant issues regarding H 2 production, melt generation and the source term were studied through a large number of experiments such as (a) dissolution of fresh and high burn-up UO 2 and MOX by molten Zircaloy (b) simultaneous dissolution of UO 2 and ZrO 2 (c) oxidation of U-O-Zr mixtures (d) degradation-oxidation of B 4 C control rods. Corresponding models were developed and implemented in severe accident computer codes. Upgraded codes were then used to apply results in plant calculations and evaluate their consequences on key severe accident sequences in different plants involving B 4 C control rods and in the TMI-2 accident. Significant results have been produced from separate-effects, semi-global and large-scale tests on COLOSS topics enabling the development and validation of models and the improvement of some severe accident codes. Breakthroughs were achieved on some issues for which more data are needed for consolidation of the modelling in particular on burn-up effects on UO 2 and MOX dissolution and oxidation of U-O-Zr and B 4 C-metal mixtures. There was experimental evidence that the oxidation of these mixtures can contribute significantly to the large H 2 production observed during the reflooding of degraded cores under severe accident conditions. The plant calculation activity enabled (a) the assessment of codes to calculate core degradation with the identification of main uncertainties and needs for short-term developments and (b) the identification of safety implications of new results. Main results and recommendations for future R and D activities are summarized in this paper

  9. Controlled dissolution of colossal quantities of nitrogen in stainless steel

    DEFF Research Database (Denmark)

    Christiansen, Thomas; Somers, Marcel A. J.

    2006-01-01

    The solubility of nitrogen in austenitic stainless steel was investigated thermogravimetrically by equilibrating thin foils of AISI 304 and AISI 316 in ammonia/hydrogen gas mixtures. Controlled dissolution of colossal amounts of nitrogen under metastable equilibrium conditions was realized...

  10. Ab-initio study of the dielectric response of high-permittivity perovskites for energy storage

    International Nuclear Information System (INIS)

    Do-Amaral-De-Andrade-Sophia, Gustavo

    2014-01-01

    Many of materials based on transition metals have a wide range of applications, such as the storage of energy, due to their peculiar properties (high-dielectric constants, ferro-electricity,...). The knowledge of their bulk properties is essential in designing targeted devices with high performance. For instance, ABO 3 perovskites are peculiarly interesting for their atomic structural flexibility, allowing high number of atoms substitution and giving them specific chemical and electrical properties compared to the pure compounds. In this context, first principles calculations can be useful to understand the structural and electronic properties of these materials. The pressure-induced giant dielectric anomaly of ABO 3 perovskites has been investigated at the ab initio level. Its mechanism has been analyzed in terms of thermodynamic phase stability, structural and phonon contributions and Born effective charges. It is shown that the IR-active soft phonon is responsible for the anomaly. This mode always involves a displacement and a deformation of the oxygen octahedra, while the roles of A and B ions vary among the materials and between high- and low-pressure phase transitions. A sharp increase in the phonon amplitude near the phase transition gives rise to the dielectric anomaly. The use of hybrid functionals is required for agreement with experimental data. The calculations show that the dielectric anomaly in the pressure-induced phase transitions of these perovskites is a property of the bulk material. (author)

  11. Interpreting the nonlinear dielectric response of glass-formers in terms of the coupling model

    International Nuclear Information System (INIS)

    Ngai, K. L.

    2015-01-01

    Nonlinear dielectric measurements at high electric fields of glass-forming glycerol and propylene carbonate initially were carried out to elucidate the dynamic heterogeneous nature of the structural α-relaxation. Recently, the measurements were extended to sufficiently high frequencies to investigate the nonlinear dielectric response of faster processes including the so-called excess wing (EW), appearing as a second power law at high frequencies in the loss spectra of many glass formers without a resolved secondary relaxation. While a strong increase of dielectric constant and loss is found in the nonlinear dielectric response of the α-relaxation, there is a lack of significant change in the EW. A surprise to the experimentalists finding it, this difference in the nonlinear dielectric properties between the EW and the α-relaxation is explained in the framework of the coupling model by identifying the EW investigated with the nearly constant loss (NCL) of caged molecules, originating from the anharmonicity of the intermolecular potential. The NCL is terminated at longer times (lower frequencies) by the onset of the primitive relaxation, which is followed sequentially by relaxation processes involving increasing number of molecules until the terminal Kohlrausch α-relaxation is reached. These intermediate faster relaxations, combined to form the so-called Johari-Goldstein (JG) β-relaxation, are spatially and dynamically heterogeneous, and hence exhibit nonlinear dielectric effects, as found in glycerol and propylene carbonate, where the JG β-relaxation is not resolved and in D-sorbitol where it is resolved. Like the linear susceptibility, χ 1 (f), the frequency dispersion of the third-order dielectric susceptibility, χ 3 (f), was found to depend primarily on the α-relaxation time, and independent of temperature T and pressure P. I show this property of the frequency dispersions of χ 1 (f) and χ 3 (f) is the characteristic of the many-body relaxation

  12. Effects of sintering on microstructure and dielectric response in ...

    Indian Academy of Sciences (India)

    Single phase nanocrystalline YCrO3 has been prepared by combustion. ... (1,−1) setting of 1 1 1 reflections from silicon single crystals with specimen between .... tion, hopping, jumping, diffusion etc, which is mainly responsible for the loss in.

  13. Dielectric response of a relativistic degenerate electron plasma in a strong magnetic field

    International Nuclear Information System (INIS)

    Delsante, A.E.; Frankel, N.E.

    1979-01-01

    The longitudinal dielectric response of a relativistic ultradegenerate electron plasma in a strong magnetic field is obtained via a relativistic generalization of the Hartree self-consistent field method. Dispersion relations and damping conditions for plasma oscillations both parallel and perpendicular to the magnetic field are obtained. Detailed results for the zero-field case, and applications to white dwarf stars and pulsars are given

  14. Dielectric response, functionality and energy storage in epoxy nanocomposites: Barium titanate vs exfoliated graphite nanoplatelets

    International Nuclear Information System (INIS)

    Patsidis, A.C.; Kalaitzidou, K.; Psarras, G.C.

    2012-01-01

    Barium titanate/epoxy and exfoliated graphite nanoplatelets/epoxy nanocomposites were prepared and studied varying the filler content. Morphological characteristics were examined via scanning electron microscopy, while structural changes occurring in barium titanate as a function of temperature were investigated by means of X-ray diffraction. Broadband dielectric spectroscopy was employed for determining the dielectric response of the prepared systems. Based on the conducted analysis it was found that three relaxation processes are present in the spectra of the examined materials. From the slower to the faster one, these are interfacial polarization, glass to rubber transition of the polymer matrix, and rearrangement of polar side groups of the polymer chain. Systems' functionality and energy storing efficiency were assessed in terms of dielectric reinforcing function. Finally, the energy density of all systems was evaluated. Composite systems with embedded graphite nanoplatelets exhibit higher energy storing efficiency, while thermally induced structural changes in ferroelectric particles provide functional behavior to barium titanate composites. -- Graphical abstract: Systems' functionality, electrical relaxations and energy storing efficiency were assessed in terms of dielectric permittivity, electric modulus and dielectric reinforcing function (G). Further, the energy density (U) of all systems was evaluated. Composite systems with embedded graphite nanoplatelets exhibit higher energy storing efficiency, while thermally induced structural changes in ferroelectric particles provide functional behavior to barium titanate composites. Highlights: ► Relaxation phenomena were found to be present in all studied systems. ► Two processes emanate from the polymer matrix (α-mode and β-mode). ► Systems' electrical heterogeneity gives rise to interfacial polarization. ► BaTiO 3 /epoxy composites exhibit functional behavior due to structural changes. ► x

  15. Effect of organo-clay on the dielectric relaxation response of silicone rubber

    International Nuclear Information System (INIS)

    Gharavi, N; Razzaghi-Kashani, M; Golshan-Ebrahimi, N

    2010-01-01

    Dielectric elastomers are light weight, low-cost, highly deformable and fast response smart materials capable of converting electrical energy into mechanical work or vice versa. Silicone rubber is a well-known dielectric elastomer which is used as actuator, and in order to enhance the efficiency of this smart material, compounding of silicone rubber with various fillers can be carried out. The effect of organically modified montmorillonite (OMMT) nano-clay on improvement of dielectric properties, actuation stress and its relaxation response was considered in this study. OMMT was dispersed in room temperature vulcanized (RTV) silicone rubber, and a composite film was cast. Using an in-house actuation set-up, it was shown that the actuation stress for a given electric field intensity is higher for composites than that for pristine silicone rubber. Also, the time-dependent actuation response of the samples was evaluated, and it was shown that the characteristic relaxation time of the actuation stress for composites is less than for the pristine rubber as a result of OMMT addition

  16. Pulsed EM Field Response of a Thin, High-Contrast, Finely Layered Structure With Dielectric and Conductive Properties

    NARCIS (Netherlands)

    De Hoop, A.T.; Jiang, L.

    2009-01-01

    The response of a thin, high-contrast, finely layered structure with dielectric and conductive properties to an incident, pulsed, electromagnetic field is investigated theoretically. The fine layering causes the standard spatial discretization techniques to solve Maxwell's equations numerically to

  17. Giant dielectric response in (Sr, Sb) codoped CaCu3Ti4O12 ceramics: A novel approach

    Science.gov (United States)

    Pradhan, M. K.; Rao, T. Lakshmana; Karna, Lipsarani; Dash, S.

    2018-04-01

    The CaCu3Ti4O12 (CCTO) remains as the best material for practical applications due to its high dielectric constant. To improve further the dielectric properties of CCTO to several orders in magnitude, a novel approach is adopted by codoping of Sr, Sb ions. The ceramic samples were fabricated by the conventional solid state route. The structure, morphology and detail dielectric properties were investigated systematically. All the samples crystalizes in a cubic symmetry with Im-3 space group. Sr substituted in Ca site can effectively suppress the grain growth, achieving a fine grained ceramic structure; however the grain size decreased slightly as Sb concentration increased further; whereas the dielectric permittivity of the ceramics increased drastically. The giant dielectric response was considered to be closely related with a reduction in the potential barrier height at grain boundaries (GBs) supported by the reduction in the activation energy for the conduction process.

  18. Optical response of nanostructured metal/dielectric composites and multilayers

    Science.gov (United States)

    Smith, Geoffrey B.; Maaroof, Abbas I.; Allan, Rodney S.; Schelm, Stefan; Anstis, Geoffrey R.; Cortie, Michael B.

    2004-08-01

    The homogeneous optical response in conducting nanostructured layers, and in insulating layers containing dense arrays of self assembled conducting nanoparticles separated by organic linkers, is examined experimentally through their effective complex indices (n*, k*). Classical effective medium models, modified to account for the 3-phase nanostructure, are shown to explain (n*, k*) in dense particulate systems but not inhomogeneous layers with macroscopic conductance for which a different approach to homogenisation is discussed. (n*, k*) data on thin granular metal films, thin mesoporous gold, and on thin metal layers containing ordered arrays of voids, is linked to properties of the surface plasmon states which span the nanostructured film. Coupling between evanescent waves at either surface counterbalanced by electron scattering losses must be considered. Virtual bound states for resonant photons result, with the associated transit delay leading to a large rise in n* in many nanostructures. Overcoating n-Ag with alumina is shown to alter (n*, k*) through its impact on the SP coupling. In contrast to classical optical homogenisation, effective indices depend on film thickness. Supporting high resolution SEM images are presented.

  19. Moisture effect on the dielectric response and space charge behaviour of mineral oil impregnated paper insulation

    International Nuclear Information System (INIS)

    Hao Jian; Liao Ruijin; Chen, George

    2011-01-01

    Dielectric response and space charge behaviour of oil-paper insulation sample with different moisture contents were investigated using the frequency dielectric spectroscopy (FDS) and the pulsed electroacoustic (PEA) technique, respectively. The influence of moisture on the dielectric response and space charge behaviour of oil impregnated paper insulation was analysed. Results show that the moisture has great effect on the FDS and space charge behaviour of oil impregnated paper insulation. In the frequency range of 10 -2 ∼10 6 Hz, the conductivity and the capacitance of oil impregnated paper increases with its moisture content. The space charge distribution of oil-paper sample with lower and higher moisture contents is very different from each other. The higher the moisture concentration of the oil impregnated paper, the easier the negative charge penetration into the insulation paper. There is a significant amount of positive charge accumulated at the paper-paper interface near to the cathode for oilpaper sample with lower moisture content. However, the positive charge appears in the middle layer paper for oil-paper sample with higher moisture content. Due to the high conductivity, the charge trapped in the oil-paper sample with higher moisture content disappears much faster than that in the oil-paper sample with lower moisture content after removing the voltage.

  20. LDPE/HDPE/Clay Nanocomposites: Effects of Compatibilizer on the Structure and Dielectric Response

    Directory of Open Access Journals (Sweden)

    B. Zazoum

    2013-01-01

    Full Text Available PE/clay nanocomposites were prepared by mixing a commercially available premixed polyethylene/O-MMT masterbatch into a polyethylene blend matrix containing 80 wt% low-density polyethylene and 20 wt% high-density polyethylene with and without anhydride modified polyethylene (PE-MA as the compatibilizer using a corotating twin-screw extruder. In this study, the effect of nanoclay and compatibilizer on the structure and dielectric response of PE/clay nanocomposites has been investigated. The microstructure of PE/clay nanocomposites was characterized using wide-angle X-ray diffraction (WAXD and a scanning electron microscope (SEM. Thermal properties were examined using differential scanning calorimetry (DSC. The dielectric response of neat PE was compared with that of PE/clay nanocomposite with and without the compatibilizer. The XRD and SEM results showed that the PE/O-MMT nanocomposite with the PE-MA compatibilizer was better dispersed. In the nanocomposite materials, two relaxation modes are detected in the dielectric losses. The first relaxation is due to a Maxwell-Wagner-Sillars interfacial polarization, and the second relaxation can be related to dipolar polarization. A relationship between the degree of dispersion and the relaxation rate fmax of Maxwell-Wagner-Sillars was found and discussed.

  1. LDPE/HDPE/Clay Nano composites: Effects of Compatibilizer on the Structure and Dielectric Response

    International Nuclear Information System (INIS)

    David, Z.E.; Ngo, A.D.

    2013-01-01

    PE/clay nano composites were prepared by mixing a commercially available premixed polyethylene/O-MMT master batch into a polyethylene blend matrix containing 80 wt% low-density polyethylene and 20 wt% high-density polyethylene with and without anhydride modified polyethylene (PE-MA) as the compatibilizer using a corotating twin-screw extruder. In this study, the effect of nano clay and compatibilizer on the structure and dielectric response of PE/clay nano composites has been investigated. The microstructure of PE/clay nano composites was characterized using wide-angle X-ray diffraction (WAXD) and a scanning electron microscope (SEM). Thermal properties were examined using differential scanning calorimetry (DSC). The dielectric response of neat PE was compared with that of PE/clay nano composite with and without the compatibilizer. The XRD and SEM results showed that the PE/O-MMT nano composite with the PE-MA compatibilizer was better dispersed. In the nano composite materials, two relaxation modes are detected in the dielectric losses. The first relaxation is due to a Maxwell-Wagner-Sillars interfacial polarization, and the second relaxation can be related to dipolar polarization. A relationship between the degree of dispersion and the relaxation rate f m ax of Maxwell-Wagner-Sillars was found and discussed.

  2. Effect of lanthanum substitution on dielectric relaxation, impedance response, conducting and magnetic properties of strontium hexaferrite

    Energy Technology Data Exchange (ETDEWEB)

    Want, Basharat, E-mail: bawant@kashmiruniversity.ac.in; Bhat, Bilal Hamid; Ahmad, Bhat Zahoor

    2015-04-05

    Highlights: • The substitution of La affects the dielectric and magnetic properties of strontium hexaferrite. • The electric behaviour of the compound follows the Koop’s phenomenological theory. • The impedance study shows the role of grain boundaries to the electric properties of the compound. • The substitution of La to strontium hexaferrite reduces the resistive nature of grain boundaries. - Abstract: Lanthanum strontium hexaferrite Sr{sub 1−x}La{sub x}Fe{sub 12}O{sub 19} (x = 0, 0.08, 0.13 , 0.18) has been successfully synthesized by using citrate-precursor method and characterized by different techniques. The X-ray diffraction results revealed that the sample is crystalline in nature and is of single phase with the space group P63/mmc. The dielectric, conducting and impedance related studies have been carried out as a function of frequency and concentration of lanthanum in the frequency ranges of 20 Hz–3 MHz. Impedance studies were performed in the frequency domain to distinguish between bulk and grain boundary contributions of the material to the overall dielectric response. The electric response of the material was also modeled by an equivalent circuit and different circuit parameters were calculated. Magnetic characterization of the material was also performed and the effect of lanthanum concentration was studied. The hysteresis loop obtained from the magnetometer showed that with the increase of lanthanum concentration, the saturation magnetisation decreases while as coercivity increases.

  3. 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.

  4. Tunable optical response at the plasmon-polariton frequency in dielectric-graphene-metamaterial systems

    Science.gov (United States)

    Calvo-Velasco, D. M.; Porras-Montenegro, N.

    2018-04-01

    By using the scattering matrix formalism, it is studied the optical properties of one dimensional photonic crystals made of multiple layers of dielectric and uniaxial anisotropic single negative electric metamaterial with Drude type responses, with inclusions of graphene in between the dielectric-dielectric interfaces (DGMPC). The transmission spectra for transverse electric (TE) and magnetic (TM) polarization are presented as a function of the incidence angle, the graphene chemical potential, and the metamaterial plasma frequencies. It is found for the TM polarization the tunability of the DGMPC optical response with the graphene chemical potential, which can be observed by means of transmission or reflexion bands around the metamaterial plasmon-polariton frequency, with bandwidths depending on both the incidence angle and the metamaterial plasma frequency. Also, the transmission band is observed when losses in the metamaterial slabs are considered for finite systems. The conditions for the appearance of these bands are shown analytically. We consider this work contributes to open new possibilities to the design of photonic devices with DGMPCs.

  5. Moisture effect on the dielectric response and space charge behaviour of mineral oil impregnated paper insulation

    Energy Technology Data Exchange (ETDEWEB)

    Hao Jian; Liao Ruijin [State Key Laboratory of Power Transmission Equipment and System Security and New Technology, Chongqing University (China); Chen, George, E-mail: jh210v@ecs.soton.ac.uk [School of Electronics and Computer Science, University of Southampton (United Kingdom)

    2011-08-12

    Dielectric response and space charge behaviour of oil-paper insulation sample with different moisture contents were investigated using the frequency dielectric spectroscopy (FDS) and the pulsed electroacoustic (PEA) technique, respectively. The influence of moisture on the dielectric response and space charge behaviour of oil impregnated paper insulation was analysed. Results show that the moisture has great effect on the FDS and space charge behaviour of oil impregnated paper insulation. In the frequency range of 10{sup -2}{approx}10{sup 6}Hz, the conductivity and the capacitance of oil impregnated paper increases with its moisture content. The space charge distribution of oil-paper sample with lower and higher moisture contents is very different from each other. The higher the moisture concentration of the oil impregnated paper, the easier the negative charge penetration into the insulation paper. There is a significant amount of positive charge accumulated at the paper-paper interface near to the cathode for oilpaper sample with lower moisture content. However, the positive charge appears in the middle layer paper for oil-paper sample with higher moisture content. Due to the high conductivity, the charge trapped in the oil-paper sample with higher moisture content disappears much faster than that in the oil-paper sample with lower moisture content after removing the voltage.

  6. Hopping model for the non-Debye dielectric response in ionic crystals

    International Nuclear Information System (INIS)

    Wang, J.C.; Bates, J.B.

    1988-10-01

    A model based on ion hopping in potential double-wells is proposed to explain the non-Debye dielectric response in solids. Relying on some assumptions, an attempt is made to remove the ''average'' nature of previous diffusion theories. This results in a distribution of activation energies, G(E), which decays exponentially on both sides of some given value E/sub o/. It is shown that the existence of a dielectric loss peak is a result of the decay of G(E) for E > E 0 the constant-phase-angle behavior above the loss peak is associated with the decay of G(E) for E 0 , and G(E) can produce all the main features of the empirical Havriliak-Negami function. An interesting property of this G(E) is that it broadens with increasing temperature, consistent with many experimental observations. 18 refs., 3 figs

  7. Surface structures and dielectric response of ultrafine BaTiO3 particles

    International Nuclear Information System (INIS)

    Jiang, B.; Peng, J.L.; Bursill, L.A.

    1998-01-01

    Characteristic differences are observed for the dielectric response and microstructures of BaTiO 3 nanoscale fine powders prepared using sol gel (SG) and steric acid gel (SAG) methods. The former exhibit a critical size below which there is no paraelectric/ferroelectric phase transition whereas BaTiO 3 prepared via the SAG route remained cubic for all conditions. Atomic resolution images of both varieties showed a high density of interesting surface steps and facets. Computer simulated images of surface structure models showed that the outer (100) surface was typically a BaO layer and that at corners and ledges the steps are typically finished with Ba+2 ions; i.e. the surfaces and steps are Ba-rich. Otherwise the surfaces were typically clean and free of amorphous layers. The relationship between the observed surfaces structures and theoretical models for size effects on the dielectric properties is discussed. (authors)

  8. Colossal magnetodielectric effect caused by magnetoelectric effect ...

    Indian Academy of Sciences (India)

    -D laminate composite under low magnetic field. When the composite is placed in an external a.c. magnetic field, magnetoelectric effect is produced, as a result, the dielectric properties of the Pb(Zr,Ti)O3 is changed, i.e. magnetodielectric effect ...

  9. Ac-conductivity and dielectric response of new zinc-phosphate glass/metal composites

    Energy Technology Data Exchange (ETDEWEB)

    Maaroufi, A., E-mail: maaroufi@fsr.ac.ma [University of Mohammed V, Laboratory of Composite Materials, Polymers and Environment, Department of Chemistry, Faculty of Sciences, P.B. 1014, Rabat-Agdal (Morocco); Oabi, O. [University of Mohammed V, Laboratory of Composite Materials, Polymers and Environment, Department of Chemistry, Faculty of Sciences, P.B. 1014, Rabat-Agdal (Morocco); Lucas, B. [XLIM UMR 7252 – Université de Limoges/CNRS, 123 avenue Albert Thomas, 87060 Limoges Cedex (France)

    2016-07-01

    The ac-conductivity and dielectric response of new composites based on zinc-phosphate glass with composition 45 mol%ZnO–55 mol%P{sub 2}O{sub 5}, filled with metallic powder of nickel (ZP/Ni) were investigated by impedance spectroscopy in the frequency range from 100 Hz to 1 MHz at room temperature. A high percolating jump of seven times has been observed in the conductivity behavior from low volume fraction of filler to the higher fractions, indicating an insulator – semiconductor phase transition. The measured conductivity at higher filler volume fraction is about 10{sup −1} S/cm and is frequency independent, while, the obtained conductivity for low filler volume fraction is around 10{sup −8} S/cm and is frequency dependent. Moreover, the elaborated composites are characterized by high dielectric constants in the range of 10{sup 5} for conductive composites at low frequencies (100 Hz). In addition, the distribution of the relaxation processes was also evaluated. The Debye, Cole-Cole, Davidson–Cole and Havriliak–Negami models in electric modulus formalism were used to model the observed relaxation phenomena in ZP/Ni composites. The observed relaxation phenomena are fairly simulated by Davidson–Cole model, and an account of the interpretation of results is given. - Highlights: • Composites of ZnO-P{sub 2}O{sub 5}/metal were investigated by impedance spectroscopy. • Original ac-conductivity behavior was discovered in ZnO-P{sub 2}O{sub 5}/metal composites. • High dielectric constant is measured in ZnO-P{sub 2}O{sub 5}/metal composites. • Dielectric constant as filler function is well interpreted with percolation theory. • Observed relaxation processes are well described using electric modulus formalism.

  10. Optically-Induced Magnetic Response in All-Dielectric Nanodisk Composite Structures

    Science.gov (United States)

    Chong, Katie Eve

    Optical technologies developed throughout history have been exploiting the electric response in matters in order to control light. However, little has been explored for the magnetic response in matter at optical frequencies due to the lack of magnetic materials in this spectral region. Recently, specially engineered materials, namely metamaterials, have been developed to exploit the magnetic responses in matter for light manipulation. In particular, researchers have made use of the optically-induced magnetic responses (OIMRs) generated in metallic nanostructures to achieve optical effects not seen in nature. Such magnetic responses serve as a second channel to control light, providing an alternative and an addition to the electric responses and leading to novel observations and innovative ideas for light manipulation. This creates many opportunities for the development of the next generation nano-optics and nanophotonic devices. Dielectric nanostructures have recently been discovered to also support OIMR, which is useful for applications requiring low loss and simpler fabrication procedures, such as wavefront control and robust nanoscale sensing. In this thesis, I present the study of OIMR in several all-dielectric systems based on silicon nanodisks, namely single, clusters and regular arrays of nanodisks. The study of these systems provides knowledge for and insight into harnessing the OIMRs in dielectric nanostructures for future applications. Chapter 1 provides a comprehensive introduction to OIMR by presenting a historic overview of the topic and the basic concepts involved for high-index dielectric particles. This is followed by a description of the pioneer works on OIMR in dielectric spherical nanoparticles, including the Mie theory and its recent experimental verification. The similarities and differences between the properties of plasmonic and dielectric nanostructures in the context of metamaterials are also described and explained. Finally, the motivation

  11. High-frequency dielectric response of polyaniline pellets as nanocomposites of metallic emeraldine salt and dielectric base

    Czech Academy of Sciences Publication Activity Database

    Nuzhnyy, Dmitry; Petzelt, Jan; Rychetský, Ivan; Trchová, Miroslava; Stejskal, Jaroslav

    2015-01-01

    Roč. 209, Nov (2015), s. 561-569 ISSN 0379-6779 R&D Projects: GA ČR GAP204/12/0232; GA ČR(CZ) GAP205/12/0911 Institutional support: RVO:68378271 ; RVO:61389013 Keywords : polyaniline * infrared and THz spectroscopy * optical conductivity * dielectric permittivity * vibrational mode * effective medium approach Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.299, year: 2015

  12. Effects of confinement on the dielectric response of water extends up to mesoscale dimensions

    DEFF Research Database (Denmark)

    De Luca, Sergio; Kannam, Sridhar Kumar; Todd, B.D.

    2016-01-01

    of confined water under the influence of external electric fields along with the dipolar fluctuations at equilibrium. The confinement induces a strong anisotropic effect which is evident up to 100 nm channel width, and may extend to macroscopic dimensions. The root-mean-square fluctuations of the total...... dimensions. Consistent with dipole moment fluctuations, the effect of confinement on the dielectric response also persists up to channel widths considerably beyond 100 nm. When an electric field is applied in the perpendicular direction, the orientational relaxation is 3 orders of magnitude faster than...

  13. Interpreting the nonlinear dielectric response of glass-formers in terms of the coupling model

    Energy Technology Data Exchange (ETDEWEB)

    Ngai, K. L. [CNR-IPCF, Largo Bruno Pontecorvo 3, I-56127 Pisa, Italy and Dipartimento di Fisica, Università di Pisa, Largo B. Pontecorvo 3, I-56127 Pisa (Italy)

    2015-03-21

    Nonlinear dielectric measurements at high electric fields of glass-forming glycerol and propylene carbonate initially were carried out to elucidate the dynamic heterogeneous nature of the structural α-relaxation. Recently, the measurements were extended to sufficiently high frequencies to investigate the nonlinear dielectric response of faster processes including the so-called excess wing (EW), appearing as a second power law at high frequencies in the loss spectra of many glass formers without a resolved secondary relaxation. While a strong increase of dielectric constant and loss is found in the nonlinear dielectric response of the α-relaxation, there is a lack of significant change in the EW. A surprise to the experimentalists finding it, this difference in the nonlinear dielectric properties between the EW and the α-relaxation is explained in the framework of the coupling model by identifying the EW investigated with the nearly constant loss (NCL) of caged molecules, originating from the anharmonicity of the intermolecular potential. The NCL is terminated at longer times (lower frequencies) by the onset of the primitive relaxation, which is followed sequentially by relaxation processes involving increasing number of molecules until the terminal Kohlrausch α-relaxation is reached. These intermediate faster relaxations, combined to form the so-called Johari-Goldstein (JG) β-relaxation, are spatially and dynamically heterogeneous, and hence exhibit nonlinear dielectric effects, as found in glycerol and propylene carbonate, where the JG β-relaxation is not resolved and in D-sorbitol where it is resolved. Like the linear susceptibility, χ{sub 1}(f), the frequency dispersion of the third-order dielectric susceptibility, χ{sub 3}(f), was found to depend primarily on the α-relaxation time, and independent of temperature T and pressure P. I show this property of the frequency dispersions of χ{sub 1}(f) and χ{sub 3}(f) is the characteristic of the many

  14. Ion association at discretely-charged dielectric interfaces: Giant charge inversion [Dielectric response controlled ion association at physically heterogeneous surfaces: Giant charge reversal

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Zhi -Yong [Chongqing Univ. of Technology, Chongqing (China); Univ. of California, Riverside, CA (United States); Wu, Jianzhong [Univ. of California, Riverside, CA (United States)

    2017-07-11

    Giant charge reversal has been identified for the first time by Monte Carlo simulation for a discretely charged surface in contact with a trivalent electrolyte solution. It takes place regardless of the surface charge density under study and the monovalent salt. In stark contrast to earlier predictions based on the 2-dimensional Wigner crystal model to describe strong correlation of counterions at the macroion surface, we find that giant charge reversal reflects an intricate interplay of ionic volume effects, electrostatic correlations, surface charge heterogeneity, and the dielectric response of the confined fluids. While the novel phenomenon is yet to be confirmed with experiment, the simulation results appear in excellent agreement with a wide range of existing observations in the subregime of charge inversion. Lastly, our findings may have far-reaching implications to understanding complex electrochemical phenomena entailing ionic fluids under dielectric confinements.

  15. Mixed-phase description of colossal magnetoresistive manganites

    Czech Academy of Sciences Publication Activity Database

    Weiáe, A.; Loos, Jan; Fehske, H.

    2003-01-01

    Roč. 68, č. 2 (2003), s. 024402-1 - 021102-6 ISSN 0163-1829 Grant - others:DFG(DE) 436 TSE 113/33/0-2 Institutional research plan: CEZ:AV0Z1010914 Keywords : polarons * metal-insulator transitions * colossal magnetoresistance Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.962, year: 2003

  16. Colossal Magnetoresistance in La-Y-Ca-Mn-O Films

    NARCIS (Netherlands)

    Chen, L.H.; Tiefel, T.H.; Jin, S.; Palstra, T.T.M.; Ramesh, R.; Kwon, C.

    1996-01-01

    Magnetoresistance behavior of La0.60Y0.07CaMnOx, thin films epitaxially grown on LaAlO3 has been investigated. The films exhibit colossal magnetoresistance with the MR ratio in excess of 10^8% at ~60K, H = 7T, which is the highest ever reported for thin film manganites. The partial substitution of

  17. Electronic structure, dielectric response, and surface charge distribution of RGD (1FUV) peptide.

    Science.gov (United States)

    Adhikari, Puja; Wen, Amy M; French, Roger H; Parsegian, V Adrian; Steinmetz, Nicole F; Podgornik, Rudolf; Ching, Wai-Yim

    2014-07-08

    Long and short range molecular interactions govern molecular recognition and self-assembly of biological macromolecules. Microscopic parameters in the theories of these molecular interactions are either phenomenological or need to be calculated within a microscopic theory. We report a unified methodology for the ab initio quantum mechanical (QM) calculation that yields all the microscopic parameters, namely the partial charges as well as the frequency-dependent dielectric response function, that can then be taken as input for macroscopic theories of electrostatic, polar, and van der Waals-London dispersion intermolecular forces. We apply this methodology to obtain the electronic structure of the cyclic tripeptide RGD-4C (1FUV). This ab initio unified methodology yields the relevant parameters entering the long range interactions of biological macromolecules, providing accurate data for the partial charge distribution and the frequency-dependent dielectric response function of this peptide. These microscopic parameters determine the range and strength of the intricate intermolecular interactions between potential docking sites of the RGD-4C ligand and its integrin receptor.

  18. Thermal analysis and temperature dependent dielectric responses of Co doped anatase TiO{sub 2} nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Alamgir [Department of Physics, Aligarh Muslim University, Aligarh-202002 (India); Centre of Excellence in Materials Science (Nanomaterials), Department of Applied Physics, Z.H. College of Engineering and Technology, Aligarh Muslim University, Aligarh-202002 (India); Khan, Wasi; Ahammed, Nashiruddin; Naqvi, A. H. [Centre of Excellence in Materials Science (Nanomaterials), Department of Applied Physics, Z.H. College of Engineering and Technology, Aligarh Muslim University, Aligarh-202002 (India); Ahmad, Shabbir [Department of Physics, Aligarh Muslim University, Aligarh-202002 (India)

    2015-05-15

    Nanoparticles (NPs) of pure and 5 mol % cobalt doped TiO{sub 2} synthesized through acid modified sol-gel method were characterized to understand their thermal, structural, morphological, and temperature dependent dielectric properties. Thermogravimetric analysis (TGA) has been used for thermal studies and indicates the weight loss in two steps due to the removal of residual organics. X-ray diffraction study was employed to confirm the formation of single anatase phase with tetragonal symmetry for both pure and 5 mol % Co doped TiO{sub 2} NPs. The average crystallite size of both samples was calculated from the Scherrer’s formula and was found in the range from 9-11 nm. TEM micrographs of these NPs reflect their shape and distribution. The dielectric constant (ε′), dielectric loss (tanδ) and ac conductivity (σ{sub ac}) were also studied as a function of temperature at different frequencies. Electrical responses of the synthesized NPs have been analyzed carefully in the framework of relevant models. It is also noticed that the dielectric constant (ε′) of the samples found to decrease with increasing frequency but increases with increasing temperature up to a particular value and then sharply decreases. Temperature variation of dielectric constant exhibits step like escalation and shows relaxation behavior. Study of dielectric properties shows dominant dependence on the grain size as well as Co ion incorporation in TiO{sub 2}.

  19. Mixed-space formalism for the dielectric response in periodic systems

    International Nuclear Information System (INIS)

    Blase, X.; Rubio, A.; Louie, S.G.; Cohen, M.L.

    1995-01-01

    We present a useful formalism for the calculation of the polarizability and dielectric response of periodic systems. Our approach is to introduce intermediate ''mixed-space'' functions with the full translational periodicity of the lattice. This is a considerable advantage over existing real-space methods since the decay length of a response function [such as ε(r,r'|ω)] can be significantly larger than the Wigner-Seitz cell radius. Further, we show that, in supercell calculations, these mixed-space functions decay as fast as the corresponding real-space quantities within one supercell, so that the present scheme can be combined with usual real-space cutoff techniques. The advantage of the present method compared to a standard reciprocal space approach is exemplified for the case of bulk silicon and for the case of a Si surface in a slab geometry

  20. Phenomenological theory of the dielectric response of lead magnesium niobate and lead scandium tantalate

    International Nuclear Information System (INIS)

    Qian, H.; Bursill, L.A.

    1997-01-01

    The influence of the random field effects originating from charges chemical defects and non-domain textures of the formation and dynamics of polar clusters is analyzed. The spatial distribution of the local fields is not totally random but contains some correlations in direction and strength. Polar clusters are classified to be dynamic or frozen according to their dynamic characteristics in the random fields. The relaxation formula of a dipolar moment in an anisotropic double-well potential is deduced. Two percolation models are introduced, one to account for frustration effects associated with multiple orientations of polar clusters, which results in a broad diffuse dielectric response and the second to account for the case whereby there may be a phase transition to a ferroelectric state. The dielectric permittivity and dissipation factor of the typical relaxors lead magnesium niobate and lead scandium tantalate are predicted as a function of both temperature and frequency, which results are in good agreement with the experimental measurements. 30 refs., 9 figs

  1. Stable dielectric response of low-loss aromatic polythiourea thin films on Pt/SiO2 substrate

    Directory of Open Access Journals (Sweden)

    A. Eršte

    2016-03-01

    Full Text Available We have investigated dielectric properties of aromatic polythiourea (ArPTU, a polar polymer containing high dipolar moments with very low defect levels thin films that were developed on Pt/SiO2 substrate. The detected response is compared to the response of commercially available polymers, such as high density polyethylene (HDPE and polypropylene (PP, which are at present used in foil capacitors. Stable values of the dielectric constant ε′≈5 (being twice higher than in HDPE and PP over broad temperature and frequency ranges and dielectric losses as low as in commercial systems suggest ArPTU as a promising candidate for future use in a variety of applications.

  2. Lattice strain accompanying the colossal magnetoresistance effect in EuB6.

    Science.gov (United States)

    Manna, Rudra Sekhar; Das, Pintu; de Souza, Mariano; Schnelle, Frank; Lang, Michael; Müller, Jens; von Molnár, Stephan; Fisk, Zachary

    2014-08-08

    The coupling of magnetic and electronic degrees of freedom to the crystal lattice in the ferromagnetic semimetal EuB(6), which exhibits a complex ferromagnetic order and a colossal magnetoresistance effect, is studied by high-resolution thermal expansion and magnetostriction experiments. EuB(6) may be viewed as a model system, where pure magnetism-tuned transport and the response of the crystal lattice can be studied in a comparatively simple environment, i.e., not influenced by strong crystal-electric field effects and Jahn-Teller distortions. We find a very large lattice response, quantified by (i) the magnetic Grüneisen parameter, (ii) the spontaneous strain when entering the ferromagnetic region, and (iii) the magnetostriction in the paramagnetic temperature regime. Our analysis reveals that a significant part of the lattice effects originates in the magnetically driven delocalization of charge carriers, consistent with the scenario of percolating magnetic polarons. A strong effect of the formation and dynamics of local magnetic clusters on the lattice parameters is suggested to be a general feature of colossal magnetoresistance materials.

  3. Influence of Conductive and Semi-Conductive Nanoparticles on the Dielectric Response of Natural Ester-Based Nanofluid Insulation

    Directory of Open Access Journals (Sweden)

    M. Z. H. Makmud

    2018-02-01

    Full Text Available Nowadays, studies of alternative liquid insulation in high voltage apparatus have become increasingly important due to higher concerns regarding safety, sustainable resources and environmentally friendly issues. To fulfil this demand, natural ester has been extensively studied and it can become a potential product to replace mineral oil in power transformers. In addition, the incorporation of nanoparticles has been remarkable in producing improved characteristics of insulating oil. Although much extensive research has been carried out, there is no general agreement on the influence on the dielectric response of base oil due to the addition of different amounts and conductivity types of nanoparticle concentrations. Therefore, in this work, a natural ester-based nanofluid was prepared by a two-step method using iron oxide (Fe2O3 and titanium dioxide (TiO2 as the conductive and semi-conductive nanoparticles, respectively. The concentration amount of each nanoparticle types was varied at 0.01, 0.1 and 1.0 g/L. The nanofluid samples were characterised by visual inspection, morphology and the dynamic light scattering (DLS method before the dielectric response measurement was carried out for frequency-dependent spectroscopy (FDS, current-voltage (I-V, and dielectric breakdown (BD strength. The results show that the dielectric spectra and I-V curves of nanofluid-based iron oxide increases with the increase of iron oxide nanoparticle loading, while for titanium dioxide, it exhibits a decreasing response. The dielectric BD strength is enhanced for both types of nanoparticles at 0.01 g/L concentration. However, the increasing amount of nanoparticles at 0.1 and 1.0 g/L led to a contrary dielectric BD response. Thus, the results indicate that the augmentation of conductive nanoparticles in the suspension can lead to overlapping mechanisms. Consequently, this reduces the BD strength compared to pristine materials during electron injection in high electric

  4. The effect of nonlocal dielectric response on the surface-enhanced Raman and fluorescence spectra of molecular systems

    Science.gov (United States)

    Wei, Yong; Pei, Huan; Li, Li; Zhu, Yanying

    2018-06-01

    We present a theoretical study on the influence of the nonlocal dielectric response on surface-enhanced resonant Raman scattering (SERRS) and fluorescence (SEF) spectra of a model molecule confined in the center of a Ag nanoparticle (NP) dimer. In the simulations, the nonlocal dielectric response caused by the electron–hole pair generation in Ag NPs was computed with the d-parameter theory, and the scattering spectra of a model molecule representing the commonly used fluorescent dye rhodamine 6G (R6G) were obtained by density-matrix calculations. The influence of the separation between Ag NP dimers on the damping rate and scattering spectra with and without the nonlocal response were systematically analyzed. The results show that the nonlocal dielectric response is very sensitive to the gap distance of the NP dimers, and it undergoes much faster decay with the increase of the separation than the radiative and energy transfer rates. The Raman and fluorescence peaks as simulated with the nonlocal dielectric response are relative weaker than that without the nonlocal effect for smaller NP separations because the extra decay rates of the nonlocal effect could reduce both the population of the excited state and the interband coherence between the ground and excited states. Our result also indicates that the nonlocal effect is more prominent on the SEF process than the SERRS process.

  5. A variational constitutive framework for the nonlinear viscoelastic response of a dielectric elastomer

    KAUST Repository

    Khan, Kamran

    2012-11-10

    We formulate a variational constitutive framework that accounts for nonlinear viscous behavior of electrically sensitive polymers, specifically Dielectric Elastomers (DEs), under large deformation. DEs are highly viscoelastic and their actuation response is greatly affected in dynamic applications. We used the generalized Maxwell model to represent the viscoelastic response of DE allowing the material to relax with multiple mechanisms. The constitutive updates at each load increment are obtained by minimizing an objective function formulated using the free energy and electrostatic energy of the elastomer, in addition to the viscous dissipation potential of the dashpots in each Maxwell branch. The model is then used to predict the electromechanical instability (EMI) of DE. The electro-elastic response of the DE is verified with available analytical solutions in the literature and then the material parameters are calibrated using experimental data. The model is integrated with finite element software to perform a variety of simulations on different types of electrically driven actuators under various electromechanical loadings. The electromechanical response of the DE and the critical conditions at which EMI occurs were found to be greatly affected by the viscoelasticity. Our model predicts that under a dead load EMI can be avoided if the DE operates at a high voltage rate. Subjected to constant, ramp and cyclic voltage, our model qualitatively predicts responses similar to the ones obtained from the analytical solutions and experimental data available in the literature. © 2012 Springer-Verlag Berlin Heidelberg.

  6. Dielectric response of particle-antiparticle plasmas in a magnetic field

    International Nuclear Information System (INIS)

    Frankel, N.E.; Hines, K.C.; Kowalenko, V.

    1982-01-01

    We have considered the longitudinal dielectric response of an ultra-degenerate relativistic plasma composed of electrons and positrons. We have used the relativistic Hartree self-consistent field method to investigate the dispersion relations and damping parameters of such a plasma in the presence of a magnetic field. These properties must be studied in the various regimes appropriate for a relativistic plasma as detailed by Tsytovich and Jancovici. Although it is hoped that this work will yield new insight into certain astrophysical phenomena (such as pulsars), it is interesting to note that laboratory electron-positron plasmas may be a thing of the immediate future as a result of suggested new experiments using an intense relativistic electron beam. (author)

  7. The polarization response function and the dielectric permittivity of a plasma

    International Nuclear Information System (INIS)

    Gnavi, G.; Gratton, F.

    1984-01-01

    We give a simple direct derivation of the polarization response function h for linear electrostatic excitations of a plasma (without magnetic field) considering the effect of a percussion on the electrons. The physical meaning of the procedure is discussed, thus bringing into light basic facts of the plasma dielectric behavior. The result h = ω 2 /sub p/ fo(x/t) (where f/sub o/ is the electron distribution function in velocity space and ω /sub p/ the plasma frequency) is obtained without passing through the Vlasov-Poisson equations as in the standard theory. We show that the equivalence between the present method and the classic Landau analysis rests on properties of the Fourier transform applied on velocity space

  8. A continuous-time random-walk approach to the Cole-Davidson dielectric response of dipolar liquids

    DEFF Research Database (Denmark)

    Szabat, B.; Langner, K. M.; Klösgen-Buchkremer, Beate Maria

    2004-01-01

    We show how the Cole-Davidson relaxation response, characteristic of alcoholic systems, can be derived within the framework of the continuous-time random walk (CTRW). Using the random-variable formalism, we indicate that the high-frequency power law of dielectric spectra is determined by the heavy...

  9. A continuous-time random-walk approach to the Cole-Davidson dielectric response of dipolar liquids

    DEFF Research Database (Denmark)

    Szabat, Bozena; Langner, Karol M.; Klösgen, Beate Maria

    2005-01-01

    We show how the Cole-Davidson relaxation response, characteristic of alcoholic systems, can be derived within the framework of the continuous-time random walk 4CTRW). Using the random-variable formalism, we indicate that the high-frequency power law of dielectric spectra is determined by the heav...

  10. Temperature hysteretic effect and its influence on colossal ...

    Indian Academy of Sciences (India)

    Record values of colossal magnetoresistance (CMR) have been achieved. The CMR value reaches nearly 99% in the temperature ranges of 90 K to 140 K and 90 K to 170 K for 20 kOe and 40 kOe magnetic fields in the cooling mode, respectively. The observed unusual behavior is attributed to the co-existence of La-rich ...

  11. Magnetic response from a composite of metal-dielectric particles in the visible range: T-matrix simulation

    Directory of Open Access Journals (Sweden)

    O. Zhuromskyy

    2011-09-01

    Full Text Available The optical response of a particle composed of a dielectric core surrounded by a densely packed shell of small metal spheres is simulated with the superposition Tmatrix method for realistic material parameters. In order to compute the electric and magnetic particle polarizabilities a single expansion T-matrix is derived from a particle centered T-matrix. Finally the permeability of a medium comprising such particles is found to deviate considerable from unity resulting in a noticeable optical response.

  12. The dielectric calibration of capacitance probes for soil hydrology using an oscillation frequency response model

    Directory of Open Access Journals (Sweden)

    D. A. Robinson

    1998-01-01

    Full Text Available Capacitance probes are a fast, safe and relatively inexpensive means of measuring the relative permittivity of soils, which can then be used to estimate soil water content. Initial experiments with capacitance probes used empirical calibrations between the frequency response of the instrument and soil water content. This has the disadvantage that the calibrations are instrument-dependent. A twofold calibration strategy is described in this paper; the instrument frequency is turned into relative permittivity (dielectric constant which can then be calibrated against soil water content. This approach offers the advantages of making the second calibration, from soil permittivity to soil water content. instrument-independent and allows comparison with other dielectric methods, such as time domain reflectometry. A physically based model, used to calibrate capacitance probes in terms of relative permittivity (εr is presented. The model, which was developed from circuit analysis, predicts, successfully, the frequency response of the instrument in liquids with different relative permittivities, using only measurements in air and water. lt was used successfully to calibrate 10 prototype surface capacitance insertion probes (SCIPS and a depth capacitance probe. The findings demonstrate that the geometric properties of the instrument electrodes were an important parameter in the model, the value of which could be fixed through measurement. The relationship between apparent soil permittivity and volumetric water content has been the subject of much research in the last 30 years. Two lines of investigation have developed, time domain reflectometry (TDR and capacitance. Both methods claim to measure relative permittivity and should therefore be comparable. This paper demonstrates that the IH capacitance probe overestimates relative permittivity as the ionic conductivity of the medium increases. Electrically conducting ionic solutions were used to test the

  13. Low Frequency Dispersion Mechanism of Dielectric Response for Oil-paper Insulation Diagnosis

    Institute of Scientific and Technical Information of China (English)

    ZHOU Lijun; LI Xianlang; WU Guangning

    2013-01-01

    Both the real part and imaginary part of complex permittivity approximately have a log-linear frequency dependency at low frequencies,especially at ultra-low frequencies under conditions of different moisture concentrations and temperatures,which is recognized as the low frequency dispersion (LFD).In order to explain this dispersion,a new mechanism of dielectric response of LFD of oil-paper insulation is proposed.A simplified one-dimensional mathematical model of concentration polarization carrier caused by slow migration is developed and solved,which indicates that ion mobility is closely related to the size of gap and the adsorption capacity of cellulose molecular chains to ions.A stochastic statistical model of the carrier mobility induced LFD is also developed.Moreover,actual tests under 50 ℃and 2% moisture content were put forward,as well as simulations with according current waveforms.The simulation results agreed well with the experimental data in that concentration polarization of carriers caused by slow migration is the probable cause of low frequency dispersion ofdielectric response for oil-paper insulation diagnosis.

  14. Theory of tailorable optical response of two-dimensional arrays of plasmonic nanoparticles at dielectric interfaces.

    Science.gov (United States)

    Sikdar, Debabrata; Kornyshev, Alexei A

    2016-09-22

    Two-dimensional arrays of plasmonic nanoparticles at interfaces are promising candidates for novel optical metamaterials. Such systems materialise from 'top-down' patterning or 'bottom-up' self-assembly of nanoparticles at liquid/liquid or liquid/solid interfaces. Here, we present a comprehensive analysis of an extended effective quasi-static four-layer-stack model for the description of plasmon-resonance-enhanced optical responses of such systems. We investigate in detail the effects of the size of nanoparticles, average interparticle separation, dielectric constants of the media constituting the interface, and the nanoparticle position relative to the interface. Interesting interplays of these different factors are explored first for normally incident light. For off-normal incidence, the strong effects of the polarisation of light are found at large incident angles, which allows to dynamically tune the reflectance spectra. All the predictions of the theory are tested against full-wave simulations, proving this simplistic model to be adequate within the quasi-static limit. The model takes seconds to calculate the system's optical response and makes it easy to unravel the effect of each system parameter. This helps rapid rationalization of experimental data and understanding of the optical signals from these novel 'metamaterials', optimised for light reflection or harvesting.

  15. Electromechanical response and failure modes of a dielectric elastomer tube actuator with boundary constraints

    International Nuclear Information System (INIS)

    Zhou, Jianyou; Jiang, Liying; Khayat, Roger E

    2014-01-01

    As a widely used configuration for dielectric elastomer (DE) actuators, DE tube actuators (or cylindrical actuators) are also found to be susceptible to electromechanical instability (EMI), which may lead to a premature electrical breakdown (EB), and inhibit the potential actuation of DE actuators. This work investigates the electromechanical response of a DE tube actuator with and without boundary constraints to demonstrate an alternative to avoid EMI while achieving large actuation. Our simulation results based on the Gent strain energy model show that the EMI of a DE tube actuator can be eliminated, and larger actuation deformation can be achieved by applying boundary constraints. As a result of these constraints, consideration is also given to the possible mechanical buckling failure that may occur. Mechanisms of possible failure modes of constrained and unconstrained DE tube actuators, such as electromechanical instability, electrical breakdown and mechanical buckling, are elucidated. This paper should provide better theoretical guidance on how to improve the actuation performance of DE actuators, thus leading to the optimal design of DE-based devices. (paper)

  16. Linear and Non-Linear Dielectric Response of Periodic Systems from Quantum Monte Carlo

    Science.gov (United States)

    Umari, Paolo

    2006-03-01

    We present a novel approach that allows to calculate the dielectric response of periodic systems in the quantum Monte Carlo formalism. We employ a many-body generalization for the electric enthalpy functional, where the coupling with the field is expressed via the Berry-phase formulation for the macroscopic polarization. A self-consistent local Hamiltonian then determines the ground-state wavefunction, allowing for accurate diffusion quantum Monte Carlo calculations where the polarization's fixed point is estimated from the average on an iterative sequence. The polarization is sampled through forward-walking. This approach has been validated for the case of the polarizability of an isolated hydrogen atom, and then applied to a periodic system. We then calculate the linear susceptibility and second-order hyper-susceptibility of molecular-hydrogen chains whith different bond-length alternations, and assess the quality of nodal surfaces derived from density-functional theory or from Hartree-Fock. The results found are in excellent agreement with the best estimates obtained from the extrapolation of quantum-chemistry calculations.P. Umari, A.J. Williamson, G. Galli, and N. MarzariPhys. Rev. Lett. 95, 207602 (2005).

  17. Investigation of transport properties of colossal magnetoresistive materials

    International Nuclear Information System (INIS)

    Kaurav, Netram

    2006-01-01

    The transport properties, i.e. resistivity, heat capacity, thermal conductivity and optical conductivity have been theoretically analysed for colossal magnetoresistive materials within the framework of double exchange mechanism. Following an effective interaction potential, we deduce acoustic (optical) phonon modes, coupling strength for electron-phonon and phonon-impurities, the phonon (magnon) scattering rate and constants characterise the scattering of charge and heat carriers with various disorders in the crystal. The theoretical models have been developed to account the anomalies observed in the transport phenomenon. It is noticed that electron-electron, electron-phonon and electron-magnon interactions are essential in discussing the transport behaviour of doped magnetites. (author)

  18. Dielectric Response at THz Frequencies of Fe Water Complexes and Their Interaction with O3 Calculated by Density Functional Theory

    Science.gov (United States)

    2012-10-24

    geometric arrangement of the atoms in a chemical system , at the maximal peak of the energy surface separating reactants from products . In the...Sonnenberg, M. Hada, M. Ehara, K. Toyota , R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda , O. Kitao, H. Nakai, T. Vreven, J. A. Montgomery... using DFT. The calculation of ground state resonance structure is for the construction of parameterized dielectric response functions for excitation

  19. Identification of defect distribution at ferroelectric domain walls from evolution of nonlinear dielectric response during the aging process

    Czech Academy of Sciences Publication Activity Database

    Mokrý, Pavel; Sluka, T.

    2016-01-01

    Roč. 93, č. 6 (2016), č. článku 064114. ISSN 2469-9950 R&D Projects: GA ČR(CZ) GA14-32228S Institutional support: RVO:61389021 Keywords : Nonlinear dielectric response * ferroelectric domain walls * aging process * phase field simulations Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.836, year: 2016 http://journals.aps.org/prb/abstract/10.1103/PhysRevB.93.064114

  20. Spin crossover-induced colossal positive and negative thermal expansion in a nanoporous coordination framework material.

    Science.gov (United States)

    Mullaney, Benjamin R; Goux-Capes, Laurence; Price, David J; Chastanet, Guillaume; Létard, Jean-François; Kepert, Cameron J

    2017-10-20

    External control over the mechanical function of materials is paramount in the development of nanoscale machines. Yet, exploiting changes in atomic behaviour to produce controlled scalable motion is a formidable challenge. Here, we present an ultra-flexible coordination framework material in which a cooperative electronic transition induces an extreme abrupt change in the crystal lattice conformation. This arises due to a change in the preferred coordination character of Fe(II) sites at different spin states, generating scissor-type flexing of the crystal lattice. Diluting the framework with transition-inactive Ni(II) sites disrupts long-range communication of spin state through the lattice, producing a more gradual transition and continuous lattice movement, thus generating colossal positive and negative linear thermal expansion behaviour, with coefficients of thermal expansion an order of magnitude greater than previously reported. This study has wider implications in the development of advanced responsive structures, demonstrating electronic control over mechanical motion.

  1. Dielectric response and electric conductivity of ceramics obtained from BiFeO{sub 3} synthesized by microwave hydrothermal method

    Energy Technology Data Exchange (ETDEWEB)

    Chybczyńska, K.; Markiewicz, E., E-mail: ewamar@ifmpan.poznan.pl; Błaszyk, M.; Hilczer, B.; Andrzejewski, B.

    2016-06-25

    BiFeO{sub 3} powder which formed ball-like structures resembling flowers was obtained by microwave hydrothermal synthesis. The flowers were of a dozen or so μm in diameter and the thickness of the crystallites forming petals could be controlled. The material was characterized by X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy. Dielectric response of ceramics obtained from the powder contained three extrinsic contributions, which could be correlated with the differences in temperature variation of the ac conductivity. The dielectric relaxation between 150 K and 300 K was related to reorientations of Fe{sup 3+}–Fe{sup 2+} dipoles and characterized by an activation energy of 0.4 eV, which was independent of the petal thickness. The dielectric and electric response in the range 300 K ÷ 450 K usually ascribed to the grain boundary and interfacial polarization effect was diffused and could not be characterized. Above 450 K the activation energy of dc conductivity was 1.73 eV and 1.52 eV for ceramics consisting of crystallites of mean thickness of 160 nm and 260 nm, respectively. The energies, which are considerably higher than those reported earlier for BFO nanoceramics, were discussed considering the interactions between oxygen vacancies and size scaled ferroelectric domain walls, which in BiFeO{sub 3} are associated with electrostatic potential steps. - Highlights: • BiFeO{sub 3} with controllable thickness of crystallites was synthesized hydrothermally. • The powder and ceramics obtained were characterized by XRD, SEM and XPS methods. • Dielectric response of the ceramics is correlated with the ac conductivity. • Size-scaled ferroelectric domains and oxygen vacancies interact above 450 K.

  2. Low frequency complex dielectric (conductivity) response of dilute clay suspensions: Modeling and experiments.

    Science.gov (United States)

    Hou, Chang-Yu; Feng, Ling; Seleznev, Nikita; Freed, Denise E

    2018-04-11

    In this work, we establish an effective medium model to describe the low-frequency complex dielectric (conductivity) dispersion of dilute clay suspensions. We use previously obtained low-frequency polarization coefficients for a charged oblate spheroidal particle immersed in an electrolyte as the building block for the Maxwell Garnett mixing formula to model the dilute clay suspension. The complex conductivity phase dispersion exhibits a near-resonance peak when the clay grains have a narrow size distribution. The peak frequency is associated with the size distribution as well as the shape of clay grains and is often referred to as the characteristic frequency. In contrast, if the size of the clay grains has a broad distribution, the phase peak is broadened and can disappear into the background of the canonical phase response of the brine. To benchmark our model, the low-frequency dispersion of the complex conductivity of dilute clay suspensions is measured using a four-point impedance measurement, which can be reliably calibrated in the frequency range between 0.1 Hz and 10 kHz. By using a minimal number of fitting parameters when reliable information is available as input for the model and carefully examining the issue of potential over-fitting, we found that our model can be used to fit the measured dispersion of the complex conductivity with reasonable parameters. The good match between the modeled and experimental complex conductivity dispersion allows us to argue that our simplified model captures the essential physics for describing the low-frequency dispersion of the complex conductivity of dilute clay suspensions. Copyright © 2018 Elsevier Inc. All rights reserved.

  3. Characterization of dielectric materials

    Energy Technology Data Exchange (ETDEWEB)

    King, Danny J.; Babinec, Susan; Hagans, Patrick L.; Maxey, Lonnie C.; Payzant, Edward A.; Daniel, Claus; Sabau, Adrian S.; Dinwiddie, Ralph B.; Armstrong, Beth L.; Howe, Jane Y.; Wood, III, David L.; Nembhard, Nicole S.

    2017-06-27

    A system and a method for characterizing a dielectric material are provided. The system and method generally include applying an excitation signal to electrodes on opposing sides of the dielectric material to evaluate a property of the dielectric material. The method can further include measuring the capacitive impedance across the dielectric material, and determining a variation in the capacitive impedance with respect to either or both of a time domain and a frequency domain. The measured property can include pore size and surface imperfections. The method can still further include modifying a processing parameter as the dielectric material is formed in response to the detected variations in the capacitive impedance, which can correspond to a non-uniformity in the dielectric material.

  4. Improved dielectric properties and grain boundary response in neodymium-doped Y_2_/_3Cu_3Ti_4O_1_2 ceramics

    International Nuclear Information System (INIS)

    Liang, Pengfei; Yang, Zupei; Chao, Xiaolian

    2016-01-01

    Rare earth element neodymium was adopted to refine grain and in turn increase the volume of grain boundary of Y_2_/_3Cu_3Ti_4O_1_2 ceramics, which could strongly increase the resistance of grain boundary. Proper amount of Nd substitution in Y_2_/_3_−_xNd_xCu_3Ti_4O_1_2 ceramics could significantly depress the low-frequency dielectric loss. When the doping level is 0.06 and 0.09, the samples exhibited a relatively low dielectric loss (below 0.050 between 0.3 and 50 kHz) and high dielectric constant above 11000 over a wide frequency range from 40 Hz to 100 kHz. Based on the ε′-T plots, dielectric relaxation intensity was substantially weakened by Nd doping so that the temperature stability of dielectric constant was improved obviously. The correlations between low-frequency dielectric loss and the resistance of grain boundary were revealed. After Nd doping, the activation energies for the conduction behavior in grain boundaries were significantly enhanced, and the activation energies for the dielectric relaxation process in grain boundaries were slightly influenced. - Highlights: • Significant decrease in dielectric loss of Y_2_/_3_−_xNd_xCu_3Ti_4O_1_2 ceramics was realized. • The enhanced grain boundary density is responsible for the lowered dielectric loss. • Nd doping could improve the temperature stability of dielectric constant. • Oxygen vacancies contribute to conduction and relaxation process of grain boundaries.

  5. Anisotropic dielectric response of lead zirconate crystals in the terahertz and infrared range at low temperature

    Czech Academy of Sciences Publication Activity Database

    Ostapchuk, Tetyana; Kadlec, Christelle; Kužel, Petr; Kroupa, Jan; Železný, Vladimír; Hlinka, Jiří; Petzelt, Jan; Dec, J.

    2014-01-01

    Roč. 87, 10-11 (2014), s. 1129-1137 ISSN 0141-1594 R&D Projects: GA ČR GA13-15110S Institutional support: RVO:68378271 Keywords : antiferroelectrics * infrared and terahertz spectroscopy * lead zirconate * phonons * complex dielectric permittivity Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.954, year: 2014

  6. Dielectric response and percolation behavior of Ni–P(VDF–TrFE nanocomposites

    Directory of Open Access Journals (Sweden)

    Lin Zhang

    2017-06-01

    Full Text Available Conductor–dielectric 0–3 nanocomposites using spherical nickel nanoparticles as filler and poly(vinylidene fluoride–trifluoroethylene 70/30mol.% as matrix are prepared using a newly developed process that combines a solution cast and a hot-pressing method with a unique configuration and creates a uniform microstructure in the composites. The uniform microstructure results in a high percolation threshold φc (>55 vol.%. The dielectric properties of the nanocomposites at different frequencies over a temperature range from −70∘C to 135∘C are studied. The results indicate that the composites exhibit a lower electrical conductivity than the polymer matrix. It is found that the nanocomposites can exhibit an ultra-high dielectric constant, more than 1500 with a loss of about 1.0 at 1kHz, when the Ni content (53 vol.% is close to percolation threshold. For the nanocomposites with 50 vol.% Ni particles, a dielectric constant more than 600 with a loss less than 0.2 is achieved. It is concluded that the loss including high loss is dominated by polarization process rather than the electrical conductivity. It is also found that the appearance of Ni particles has a strong influence on the crystallization process in the polymer matrix so that the polymer is converted from a typical ferroelectric to a relaxor ferroelectric. It is also demonstrated that the widely used relationship between the dielectric constant and the composition of the composites may not be valid.

  7. Studies of colossal magnetoresistive oxides with radioactive isotopes

    CERN Document Server

    CERN. Geneva. ISOLDE and Neutron Time-of-Flight Experiments Committee; Amaral, V S; Araújo, J P; Butz, T; Correia, J G; Dubourdieu, C; Habermeier, H U; Lourenço, A A; Marques, J G; Da Silva, M F A; Senateur, J P; Soares, J C; Sousa, J B; Suryan, R; Tokura, Y; Tavares, P B; Tomioka, Y; Tröger, W; Vantomme, A; Vieira, J M; Wahl, U; Weiss, F P; INTC

    2000-01-01

    We propose to study Colossal Magnetoresistive (CMR) oxides with several nuclear techniques, which use radioactive elements at ISOLDE. Our aim is to provide local and element selective information on some of the doping mechanisms that rule electronic interactions and magnetoresistance, in a complementary way to the use of conventional characterisation techniques. Three main topics are proposed: \\\\ \\\\ a) Studies of local [charge and] structural modifications in antiferromagnetic LaMnO$_{3+ \\delta}$ and La$_{1-x}$R$_{x}$MnO$_{3}$ with R=Ca and Cd, doped ferromagnetic systems with competing interactions: - research on the lattice site and electronic characterisation of the doping element. \\\\ \\\\ b) Studies of self doped La$_{x}$R$_{1-x}$MnO$_{3+\\delta}$ systems, with oxygen and cation non-stoichiometry: -learning the role of defects in the optimisation of magnetoresistive properties. \\\\ \\\\ c) Probing the disorder and quenched random field effects in the vicinity of the charge or orbital Ordered/Ferromagnetic phase...

  8. Correlated evolution of colossal thermoelectric effect and Kondo insulating behavior

    Directory of Open Access Journals (Sweden)

    M. K. Fuccillo

    2013-12-01

    Full Text Available We report the magnetic and transport properties of the Ru1−xFexSb2 solid solution, showing how the colossal thermoelectric performance of FeSb2 evolves due to changes in the amount of 3d vs. 4d electron character. The physical property trends shed light on the physical picture underlying one of the best low-T thermoelectric power factors known to date. Some of the compositions warrant further study as possible n- and p-type thermoelements for Peltier cooling well below 300 K. Our findings enable us to suggest possible new Kondo insulating systems that might behave similarly to FeSb2 as advanced thermoelectrics.

  9. Colossal Tooling Design: 3D Simulation for Ergonomic Analysis

    Science.gov (United States)

    Hunter, Steve L.; Dischinger, Charles; Thomas, Robert E.; Babai, Majid

    2003-01-01

    The application of high-level 3D simulation software to the design phase of colossal mandrel tooling for composite aerospace fuel tanks was accomplished to discover and resolve safety and human engineering problems. The analyses were conducted to determine safety, ergonomic and human engineering aspects of the disassembly process of the fuel tank composite shell mandrel. Three-dimensional graphics high-level software, incorporating various ergonomic analysis algorithms, was utilized to determine if the process was within safety and health boundaries for the workers carrying out these tasks. In addition, the graphical software was extremely helpful in the identification of material handling equipment and devices for the mandrel tooling assembly/disassembly process.

  10. Studies of Colossal Magnetoresistive Oxides with Radioactive Isotopes

    CERN Multimedia

    2002-01-01

    We propose to study Colossal Magnetoresistive (CMR) oxides with several nuclear techniques, which use radioactive elements at ISOLDE. Our aim is to provide local and element selective information on some of the doping mechanisms that rule electronic interactions and magneto- resistance, in a complementary way to the use of conventional characterisation techniques. Three main topics are proposed: \\\\ \\\\ a) Studies of local [charge and] structural modifications in antiferromagnetic LaMnO$_{3+\\delta}$ and La$_{1-x}$R$_{x}$MnO$_{3}$ with R=Ca and Cd, doped ferromagnetic systems with competing interactions: - research on the lattice site and electronic characterisation of the doping element. \\\\ \\\\ b) Studies of self doped La$_{x}$R$_{1-x}$MnO$_{3+\\delta}$ systems, with oxygen and cation non- stoichiometry: - learning the role of defects in the optimisation of magnetoresestive properties. \\\\ \\\\ c) Probing the disorder and quenched random field effects in the vicinity of the charge or orbital Ordered/Ferromagnetic p...

  11. Moessbauer Study of Materials Displaying Colossal Magnetic Resistivity

    International Nuclear Information System (INIS)

    Klencsar, Z.; Vertes, A.; Nemeth, Z.; Kuzmann, E.; Homonnay, Z.; Kotsis, I.; Nagy, M.; Simopoulos, A.; Devlin, E.; Kallias, G.

    2003-01-01

    In the last decade the discovery of colossal magnetoresistance in Mn based perovskites brought various perovskite and spinel materials, displaying the effect of magnetoresistance, into the center of scientific interest. The physical and chemical effects, underlying the phenomenon of negative magnetoresistance in these compounds, are not yet fully understood. In this article we investigate the local electronic and magnetic state of iron in three different type of perovskite and spinel compounds: the double perovskite Sr 2 Fe 1+x Mo 1-x O 6 with an excess of iron (x≅0.12), the perovskite La 0.8 Sr 0.2 Fe 0.3 Co 0.7 O 3-z , and the chalcogenide spinel FeCr 2 S 4 .

  12. Thermoluminescence and dielectric response of LiKSO{sub 4}:Gd to {gamma}-radiation

    Energy Technology Data Exchange (ETDEWEB)

    El-Kolaly, M.A.; Kassem, M.E.; Higazy, A.A.; Ismail, L.Z.; Al-Houty, L.I. [Qatar Univ., Doha (Qatar). Dept. of Physics

    1994-10-01

    The effect of {gamma}-radiation dose up to about 324 kGy on the thermoluminescence and dielectric properties of LiKSO{sub 4}:Gd was studied. All glow curves exhibited a single peak around 373 K. The activation energy of this peak was estimated to be about 0.82 eV. The variation of the TL intensity with {gamma}-dose is characterized by a maximum at 6.75 kGy. The dielectric dispersion was studied as a function of irradiation dose. In the low frequency range straight line behaviour was obtained for low dose (up to 12.3 kGy) while for higher {gamma}-dose, semicircles are obtained. The bulk conductivity was found to increase with dose up to 6.75 kGy. (author).

  13. Low-temperature microwave and THz dielectric response in novel microwave ceramics

    Czech Academy of Sciences Publication Activity Database

    Kamba, Stanislav; Noujni, Dmitri; Pashkin, Alexej; Petzelt, Jan; Pullar, R. C.; Axelsson, A.-K.; McN Alford, N.

    2006-01-01

    Roč. 26, - (2006), s. 1845-1851 ISSN 0955-2219 R&D Projects: GA ČR(CZ) GA202/04/0993; GA AV ČR(CZ) IAA1010213; GA MŠk(CZ) OC 525.20 Institutional research plan: CEZ:AV0Z10100520 Keywords : dielectric properties * spectroscopy * perovskites * microwave ceramics Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.576, year: 2006

  14. Time-dependent non-equilibrium dielectric response in QM/continuum approaches

    Energy Technology Data Exchange (ETDEWEB)

    Ding, Feizhi; Lingerfelt, David B.; Li, Xiaosong, E-mail: benedetta.mennucci@unipi.it, E-mail: li@chem.washington.edu [Department of Chemistry, University of Washington, Seattle, Washington 98195 (United States); Mennucci, Benedetta, E-mail: benedetta.mennucci@unipi.it, E-mail: li@chem.washington.edu [Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via Risorgimento 35, 56126 Pisa (Italy)

    2015-01-21

    The Polarizable Continuum Models (PCMs) are some of the most inexpensive yet successful methods for including the effects of solvation in quantum-mechanical calculations of molecular systems. However, when applied to the electronic excitation process, these methods are restricted to dichotomously assuming either that the solvent has completely equilibrated with the excited solute charge density (infinite-time limit), or that it retains the configuration that was in equilibrium with the solute prior to excitation (zero-time limit). This renders the traditional PCMs inappropriate for resolving time-dependent solvent effects on non-equilibrium solute electron dynamics like those implicated in the instants following photoexcitation of a solvated molecular species. To extend the existing methods to this non-equilibrium regime, we herein derive and apply a new formalism for a general time-dependent continuum embedding method designed to be propagated alongside the solute’s electronic degrees of freedom in the time domain. Given the frequency-dependent dielectric constant of the solvent, an equation of motion for the dielectric polarization is derived within the PCM framework and numerically integrated simultaneously with the time-dependent Hartree fock/density functional theory equations. Results for small molecular systems show the anticipated dipole quenching and electronic state dephasing/relaxation resulting from out-of-phase charge fluctuations in the dielectric and embedded quantum system.

  15. 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.

  16. Lattice dynamics and central-mode phenomena in the dielectric response of ferroelectrics and related materials

    Czech Academy of Sciences Publication Activity Database

    Buixaderas, Elena; Kamba, Stanislav; Petzelt, Jan

    2004-01-01

    Roč. 308, - (2004), s. 131-192 ISSN 0015-0193 R&D Projects: GA ČR GA202/01/0612; GA AV ČR IAA1010213; GA MŠk OC 525.20 Institutional research plan: CEZ:AV0Z1010914 Keywords : phonons in crystal lattice * commensurate-incommensurate transitions * dielectric properties of solids and liquids * ferroelectricity and antiferroelectricity * niobates * tantantalates * PZT ceramics Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.517, year: 2004

  17. Evaluation of area strain response of dielectric elastomer actuator using image processing technique

    Science.gov (United States)

    Sahu, Raj K.; Sudarshan, Koyya; Patra, Karali; Bhaumik, Shovan

    2014-03-01

    Dielectric elastomer actuator (DEA) is a kind of soft actuators that can produce significantly large electric-field induced actuation strain and may be a basic unit of artificial muscles and robotic elements. Understanding strain development on a pre-stretched sample at different regimes of electrical field is essential for potential applications. In this paper, we report about ongoing work on determination of area strain using digital camera and image processing technique. The setup, developed in house consists of low cost digital camera, data acquisition and image processing algorithm. Samples have been prepared by biaxially stretched acrylic tape and supported between two cardboard frames. Carbon-grease has been pasted on the both sides of the sample, which will be compliant with electric field induced large deformation. Images have been grabbed before and after the application of high voltage. From incremental image area, strain has been calculated as a function of applied voltage on a pre-stretched dielectric elastomer (DE) sample. Area strain has been plotted with the applied voltage for different pre-stretched samples. Our study shows that the area strain exhibits nonlinear relationship with applied voltage. For same voltage higher area strain has been generated on a sample having higher pre-stretched value. Also our characterization matches well with previously published results which have been done with costly video extensometer. The study may be helpful for the designers to fabricate the biaxial pre-stretched planar actuator from similar kind of materials.

  18. Excellent microwave response derived from the construction of dielectric-loss 1D nanostructure

    Science.gov (United States)

    Dai, Sisi; Quan, Bin; Liang, Xiaohui; Lv, Jing; Yang, Zhihong; Ji, Guangbin; Du, Youwei

    2018-05-01

    Increasing efforts have recently been devoted to the artificial design and function of nanostructures for their application prospects in catalysis, drug delivery, energy storage, and microwave absorption. With the advantages of natural abundance, low cost, and environment friendliness, a one-dimensional (1D) MnO2 nanowire (MW) is the representative dielectric-loss absorber for its special morphology and crystalline structure. However, its low reflection loss (RL) value due to its thin thickness limits its wide development and application in the microwave absorption field. In this work, artificially designed MnO2@AIR@C (MCs), namely, 1D hollow carbon nanotubes filled with nano-MnO2, were designed and synthesized. It is found that the RL value of the MC is almost lower than -10 dB. Furthermore, the RL value was able to achieve -18.9 dB with an effective bandwidth (-10 dB) of 5.84 GHz at 2.25 mm. Simultaneously, the dielectric and interfacial polarization became stronger while the impedance matching was much better than in the single MWs. Hence, the rational design and fabrication of micro-architecture are essential and MC has great potential to be an outstanding microwave absorber.

  19. Dielectric response and electric modulus of Y{sub 2}CrCoO{sub 6} perovskite

    Energy Technology Data Exchange (ETDEWEB)

    Pecovska-Gjorgjevich, M., E-mail: mpecovska@gmail.com; Popeski-Dimovski, R. [Department of Physics, Faculty of Natural Sciences and Mathematics, “Ss. Cyril and Methodius” University, Arhimedova 3, 1000 Skopje, R. Macedonia (Macedonia, The Former Yugoslav Republic of); Dimitrovska-Lazova, S. [Department of Chemistry, Faculty of Natural Sciences and Mathematics, “Ss. Cyril and Methodius” University, Arhimedova 5, 1000 Skopje, R. Macedonia (Macedonia, The Former Yugoslav Republic of); Aleksovska, S. [Department of Chemistry, Faculty of Natural Sciences and Mathematics, “Ss. Cyril and Methodius” University, Arhimedova 5, 1000 Skopje, R. Macedonia (Macedonia, The Former Yugoslav Republic of); Research Center for Environment and Materials, Macedonian Academy of Sciences and Arts, Bul. “Krste Misirkov” 2, P.O. Box 428, 1000 Skopje, Republic of Macedonia (Macedonia, The Former Yugoslav Republic of)

    2016-03-25

    Y{sub 2}CrCoO{sub 6} perovskite prepared by solution combustion method and sintered at 1073 K has been characterized by dielectric spectroscopy and electric modulus formalism. Temperature and frequency dependent measurements of permitivitty reveal that observed relaxation might be related to the hopping conductivity, i.e. universal dielectric response. The presence of electrode polarization is dominant at low frequencies. The electric modulus dependencies enable us to distinguish and separate the relaxation processes connected to the conduction processes in the material. The presences of both grain and grain boundary effects are established, each dominant in different frequency and temperature range. The conductivity through grain boundaries obeys metalic behavior, while conductivity through grains shows semiconductor behavior. The electrical behavior of this material depends on the differences in (Cr-O) and (Co-O) bond lenghts, Co{sup 3+} being in the low-spin state, resulting in shorter Co-O and thus stronger π bonding e.g. more efficient overlapping of the Co{sup 3+} d-orbitals with oxygen p{sub π} orbitals.

  20. Colossal magnetocaloric effect in magneto-auxetic systems

    Science.gov (United States)

    Dudek, M. R.; Wojciechowski, K. W.; Grima, J. N.; Caruana-Gauci, R.; Dudek, K. K.

    2015-08-01

    We show that a mechanically driven magnetocaloric effect (MCE) in magneto-auxetic systems (MASs) in the vicinity of room temperature is possible and the effect can be colossal. Even at zero external magnetic field, the magnetic entropy change in this reversible process can be a few times larger in magnitude than in the case of the giant MCE discovered by Pecharsky and Gschneidner in Gd5(Si2Ge2). MAS represent a novel class of metamaterials having magnetic insertions embedded within a non-magnetic matrix which exhibits a negative Poisson’s ratio. The auxetic behaviour of the non-magnetic matrix may either enhance the magnetic ordering process or it may result in a transition to the disordered phase. In the MAS under consideration, a spin 1/2 system is chosen for the magnetic component and the well-known Onsager solution for the two-dimensional square lattice Ising model at zero external magnetic field is used to show that the isothermal change in magnetic entropy accompanying the auxetic behaviour can take a large value at room temperature. The practical importance of our findings is that MCE materials used in present engineering applications may be further enhanced by changing their geometry such that they exhibit auxetic behaviour.

  1. Colossal magnetocaloric effect in magneto-auxetic systems

    International Nuclear Information System (INIS)

    Dudek, M R; Dudek, K K; Wojciechowski, K W; Grima, J N; Caruana-Gauci, R

    2015-01-01

    We show that a mechanically driven magnetocaloric effect (MCE) in magneto-auxetic systems (MASs) in the vicinity of room temperature is possible and the effect can be colossal. Even at zero external magnetic field, the magnetic entropy change in this reversible process can be a few times larger in magnitude than in the case of the giant MCE discovered by Pecharsky and Gschneidner in Gd 5 (Si 2 Ge 2 ). MAS represent a novel class of metamaterials having magnetic insertions embedded within a non-magnetic matrix which exhibits a negative Poisson’s ratio. The auxetic behaviour of the non-magnetic matrix may either enhance the magnetic ordering process or it may result in a transition to the disordered phase. In the MAS under consideration, a spin 1/2 system is chosen for the magnetic component and the well-known Onsager solution for the two-dimensional square lattice Ising model at zero external magnetic field is used to show that the isothermal change in magnetic entropy accompanying the auxetic behaviour can take a large value at room temperature. The practical importance of our findings is that MCE materials used in present engineering applications may be further enhanced by changing their geometry such that they exhibit auxetic behaviour. (paper)

  2. Voltage-Controllable Colossal Magnetocrystalline Anisotropy in Single Layer Dichalcogenides

    Science.gov (United States)

    Sui, Xuelei; Hu, Tao; Wang, Jianfeng; Gu, Bing-Lin; Duan, Wenhui; Miao, Mao-Sheng

    Materials with large magnetocrystalline anisotropy and strong electric field effects are in great need for new types of memory devices that are based on electric field control of spin orientations. Instead of using modified transition metal films, we propose that some monolayer transition metal dichalcogenides are ideal candidate materials for this purpose. Using density functional calculations, we illustrate that they exhibit not only exceedingly large magnetocrystalline anisotropy (MCA) but also colossal voltage modulation under external field. Especially, spins in some materials like CrSe2 and FeSe2, which is strongly preferred to in-plane orientation, can be totally switched to out-of-plane direction. The effect is attributed to the large band character alteration of transition metal d-states around the Fermi level by electric field. We further demonstrate that strain can also greatly change MCA, and can help to improve the modulation efficiency while combining with electric field. Acknowledge the support of the Ministry of Science and Technology of China (Grant No.2016YFA0301001), and the National Natural Science Foundation of China (Grants No. 11674188 and 11334006), NSF-funded XSEDE resources (TG-DMR130005) especially on Stampede.

  3. Microscopic properties of nanopore water from its time-dependent dielectric response

    International Nuclear Information System (INIS)

    Koefinger, Juergen; Dellago, Christoph

    2010-01-01

    We present a simple kinetic model for the orientational dynamics of a chain of hydrogen-bonded molecules due to the diffusion of orientational defects. We derive an event-driven algorithm which allows us to do kinetic simulations for chains from nanoscopic to macroscopic lengths, spanning huge orders of magnitude in time. Our simulations and analytical calculations show that nanopore water exhibits Debye behavior arising from the diffusive dynamics of orientational defects. For the limits of short and long chains we derive analytical expressions for the relaxation times which allow to extract the diffusion constant, the effective interaction, and the excitation energy of these defects from dielectric spectroscopy experiments. We also discuss the possibility to use such experiments to detect if the two possible kinds of orientational defects differ in excitation energy and diffusion constant.

  4. Propagation of electromagnetic waves in stratified media with nonlinearity in both dielectric and magnetic responses.

    Science.gov (United States)

    Kim, Kihong; Phung, D K; Rotermund, F; Lim, H

    2008-01-21

    We develop a generalized version of the invariant imbedding method, which allows us to solve the electromagnetic wave equations in arbitrarily inhomogeneous stratified media where both the dielectric permittivity and magnetic permeability depend on the strengths of the electric and magnetic fields, in a numerically accurate and efficient manner. We apply our method to a uniform nonlinear slab and find that in the presence of strong external radiation, an initially uniform medium of positive refractive index can spontaneously change into a highly inhomogeneous medium where regions of positive or negative refractive index as well as metallic regions appear. We also study the wave transmission properties of periodic nonlinear media and the influence of nonlinearity on the mode conversion phenomena in inhomogeneous plasmas. We argue that our theory is very useful in the study of the optical properties of a variety of nonlinear media including nonlinear negative index media fabricated using wires and split-ring resonators.

  5. Dielectric Response and Born Dynamic Charge of BN Nanotubes from Ab Initio Finite Electric Field Calculations

    Science.gov (United States)

    Guo, Guang-Yu; Ishibashi, Shoji; Tamura, Tomoyuki; Terakura, Kiyoyuki

    2007-03-01

    Since the discovery of carbon nanotubes (CNTs) in 1991 by Iijima, carbon and other nanotubes have attracted considerable interest worldwide because of their unusual properties and also great potentials for technological applications. Though CNTs continue to attract great interest, other nanotubes such as BN nanotubes (BN-NTs) may offer different opportunities that CNTs cannot provide. In this contribution, we present the results of our recent systematic ab initio calculations of the static dielectric constant, electric polarizability, Born dynamical charge, electrostriction coefficient and piezoelectric constant of BN-NTs using the latest crystalline finite electric field theory [1]. [1] I. Souza, J. Iniguez, and D. Vanderbilt, Phys. Rev. Lett. 89, 117602 (2002); P. Umari and A. Pasquarello, Phys. Rev. Lett. 89, 157602 (2002).

  6. Probing the dielectric response of the interfacial buffer layer in epitaxial graphene via optical spectroscopy

    Science.gov (United States)

    Hill, Heather M.; Rigosi, Albert F.; Chowdhury, Sugata; Yang, Yanfei; Nguyen, Nhan V.; Tavazza, Francesca; Elmquist, Randolph E.; Newell, David B.; Hight Walker, Angela R.

    2017-11-01

    Monolayer epitaxial graphene (EG) is a suitable candidate for a variety of electronic applications. One advantage of EG growth on the Si face of SiC is that it develops as a single crystal, as does the layer below, referred to as the interfacial buffer layer (IBL), whose properties include an electronic band gap. Although much research has been conducted to learn about the electrical properties of the IBL, not nearly as much work has been reported on the optical properties of the IBL. In this work, we combine measurements from Mueller matrix ellipsometry, differential reflectance contrast, atomic force microscopy, and Raman spectroscopy, as well as calculations from Kramers-Kronig analyses and density-functional theory, to determine the dielectric function of the IBL within the energy range of 1 eV to 8.5 eV.

  7. A semi-analytical method to evaluate the dielectric response of a tokamak plasma accounting for drift orbit effects

    Science.gov (United States)

    Van Eester, Dirk

    2005-03-01

    A semi-analytical method is proposed to evaluate the dielectric response of a plasma to electromagnetic waves in the ion cyclotron domain of frequencies in a D-shaped but axisymmetric toroidal geometry. The actual drift orbit of the particles is accounted for. The method hinges on subdividing the orbit into elementary segments in which the integrations can be performed analytically or by tabulation, and it relies on the local book-keeping of the relation between the toroidal angular momentum and the poloidal flux function. Depending on which variables are chosen, the method allows computation of elementary building blocks for either the wave or the Fokker-Planck equation, but the accent is mainly on the latter. Two types of tangent resonance are distinguished.

  8. Control-focused, nonlinear and time-varying modelling of dielectric elastomer actuators with frequency response analysis

    International Nuclear Information System (INIS)

    Jacobs, William R; Dodd, Tony J; Anderson, Sean R; Wilson, Emma D; Porrill, John; Assaf, Tareq; Rossiter, Jonathan

    2015-01-01

    Current models of dielectric elastomer actuators (DEAs) are mostly constrained to first principal descriptions that are not well suited to the application of control design due to their computational complexity. In this work we describe an integrated framework for the identification of control focused, data driven and time-varying DEA models that allow advanced analysis of nonlinear system dynamics in the frequency-domain. Experimentally generated input–output data (voltage-displacement) was used to identify control-focused, nonlinear and time-varying dynamic models of a set of film-type DEAs. The model description used was the nonlinear autoregressive with exogenous input structure. Frequency response analysis of the DEA dynamics was performed using generalized frequency response functions, providing insight and a comparison into the time-varying dynamics across a set of DEA actuators. The results demonstrated that models identified within the presented framework provide a compact and accurate description of the system dynamics. The frequency response analysis revealed variation in the time-varying dynamic behaviour of DEAs fabricated to the same specifications. These results suggest that the modelling and analysis framework presented here is a potentially useful tool for future work in guiding DEA actuator design and fabrication for application domains such as soft robotics. (paper)

  9. Grain boundary and size effect on the dielectric, infrared and Raman response of SrTiO.sub.3./sub. nanograin ceramics

    Czech Academy of Sciences Publication Activity Database

    Petzelt, Jan; Ostapchuk, Tetyana; Gregora, Ivan; Noujni, Dmitri; Rychetský, Ivan; Maca, K.; Shen, Z.

    2008-01-01

    Roč. 363, č. 1 (2008), s. 227-244 ISSN 0015-0193 R&D Projects: GA AV ČR KJB100100704; GA MŠk OC 101; GA ČR GP202/06/P219 Institutional research plan: CEZ:AV0Z10100520 Keywords : strontium titanate nanoceramics * core-shell composite * dead layer * effective dielectric and infrared response * Raman response Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.562, year: 2008

  10. Toward a unified description of nonlinearity and frequency dispersion of piezoelectric and dielectric responses in Pb(Zr,Ti)O3

    International Nuclear Information System (INIS)

    Damjanovic, D.; Bharadwaja, S.S.N.; Setter, N.

    2005-01-01

    A phenomenological approach is proposed describing both nonlinearity and frequency dispersion in dielectric and piezoelectric properties of lead zirconate titanate, Pb(Zr,Ti)O 3 (PZT), thin films and ceramics. The approach couples the frequency dependent response in form of the power law, 1/ω β , with the rate-independent nonlinear response described by the Rayleigh law. The main experimental trends are well described by the model

  11. Dielectric nanoresonators for light manipulation

    Science.gov (United States)

    Yang, Zhong-Jian; Jiang, Ruibin; Zhuo, Xiaolu; Xie, Ya-Ming; Wang, Jianfang; Lin, Hai-Qing

    2017-07-01

    Nanostructures made of dielectric materials with high or moderate refractive indexes can support strong electric and magnetic resonances in the optical region. They can therefore function as nanoresonators. In addition to plasmonic metal nanostructures that have been widely investigated, dielectric nanoresonators provide a new type of building blocks for realizing powerful and versatile nanoscale light manipulation. In contrast to plasmonic metal nanostructures, nanoresonators made of appropriate dielectric materials are low-cost, earth-abundant and have very small or even negligible light energy losses. As a result, they will find potential applications in a number of photonic devices, especially those that require low energy losses. In this review, we describe the recent progress on the experimental and theoretical studies of dielectric nanoresonators. We start from the basic theory of the electromagnetic responses of dielectric nanoresonators and their fabrication methods. The optical properties of individual dielectric nanoresonators are then elaborated, followed by the coupling behaviors between dielectric nanoresonators, between dielectric nanoresonators and substrates, and between dielectric nanoresonators and plasmonic metal nanostructures. The applications of dielectric nanoresonators are further described. Finally, the challenges and opportunities in this field are discussed.

  12. A variational constitutive framework for the nonlinear viscoelastic response of a dielectric elastomer

    KAUST Repository

    Khan, Kamran; Wafai, Husam; El Sayed, Tamer S.

    2012-01-01

    to perform a variety of simulations on different types of electrically driven actuators under various electromechanical loadings. The electromechanical response of the DE and the critical conditions at which EMI occurs were found to be greatly affected

  13. Colossal magnetoresistance in layered manganite Nd2−2xSr1+ ...

    Indian Academy of Sciences (India)

    starting compounds, have been obtained. Except for x=0.4, which is found to be an antiferromagnetic insulator, all other x values yielded metal–insulator transition and ferromagnetic ordering. Keywords. Colossal magnetoresistance; layered manganites; Nd2−2x Sr1+2x Mn2O7. PACS Nos 75.30.Vn; 71.30.+h. 1. Introduction.

  14. Towards an ab initio evaluation of the wave - vector- and frequency-dependent dielectric response function for crystalline water

    Energy Technology Data Exchange (ETDEWEB)

    Zaider, M [Columbia Univ., New York, NY (USA). Radiological Research Labs.; Fry, J L; Orr, D E [Texas Univ., Arlington, TX (USA)

    1990-01-01

    We describe an ab initio calculation of the properties of energy loss by electrons in crystalline water using its dielectric response function, {epsilon}(q,{omega}), where q and {omega} are, respectively, the wave vector and frequency. The calculation was performed on a model system (cubic ice) in order to take advantage of its ordered structure (i.e. Block's theorem), but also because of evidence that liquid water in biological systems ('structured' water) contains residues with tetrahedral structure (i.e. ice) over time scales of at least 10{sup -11} s. The main features of the calculation are (a) {epsilon}(q,{omega}) is evaluated in the random phase approximation (we used the expression given by Ehrenreich and Cohen), (b) the crystal potential is expressed as a sum of water-molecule self-consistent potentials, and (c) wave functions are expanded using tight binding functions (ultimately employing a Gaussian base set). A total of seven states (bands), five occupied and two conduction, are considered. We report the band structure and the density of states of the crystal, as well as values of {epsilon}(q,{omega}) at selected values of q and {omega}. Results are compared with energy loss measurements and with absorption spectra (XPS, UPS, and VUV data). The possibility of using an empirical combination of molecular potentials as a phenomenological Hamiltonian is also examined. (author).

  15. Visible-Light Modulation on Lattice Dielectric Responses of a Piezo-Phototronic Soft Material.

    Science.gov (United States)

    Huang, E-Wen; Hsu, Yu-Hsiang; Chuang, Wei-Tsung; Ko, Wen-Ching; Chang, Chung-Kai; Lee, Chih-Kung; Chang, Wen-Chi; Liao, Tzu-Kang; Thong, Hao Cheng

    2015-12-16

    In situ synchrotron X-ray diffraction is used to investigate a three-way piezo-phototronic soft material. This new system is composed of a semi-crystalline poly(vinylidene fluoride-co-trifluoroethylene) piezoelectric polymer and titanium oxide nanoparticles. Under light illumination, photon-induced piezoelectric responses are nearly two times higher at both the lattice-structure and the macroscopic level than under conditions without light illumination. A mechanistic model is proposed. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Pyroelectric response mechanism of barium strontium titanate ceramics in dielectric bolometer mode: The underlying essence of the enhancing effect of direct current bias field

    International Nuclear Information System (INIS)

    Mao, Chaoliang; Cao, Sheng; Yan, Shiguang; Yao, Chunhua; Cao, Fei; Wang, Genshui; Dong, Xianlin; Hu, Xu; Yang, Chunli

    2013-01-01

    Pyroelectric response mechanism of Ba 0.70 Sr 0.30 TiO 3 ceramics under dielectric bolometer (DB) mode was investigated by dielectric and pyroelectric properties measurement. The variations of total, intrinsic, and induced pyroelectric coefficients (p tot , p int , p ind ) with temperatures and bias fields were analyzed. p int plays the dominant role to p tot through most of the temperature range and p ind will be slightly higher than p int above T 0 . The essence of the enhancing effect of DC bias field on pyroelectric coefficient can be attributed to the high value of p int . This mechanism is useful for the pyroelectric materials (DB mode) applications.

  17. Quantum theory of longitudinal dielectric response properties of a two-dimensional plasma in a magnetic field

    International Nuclear Information System (INIS)

    Horing, N.J.M.; Yildiz, M.M.

    1976-01-01

    An analysis of dynamic and nonlocal longitudinal dielectric response properties of a two-dimensional Landau-quantized plasma is carried out, using a thermodynamic Green's function formulation of the RPA with a two-dimensional thermal Green's function for electron propagation in a magnetic field developed in closed form. The longitudinal-electrostatic plasmon dispersion relation is discussed in the low wave-number regime with nonlocal corrections, and Bernstein mode structure is studied for arbitrary wavenumber. All regimes of magnetic field strength and statistics are investigated. The class of integrals treated here should have broad applicability in other two-dimensional and finite slab plasma studies.The two-dimensional static shielding law in a magnetic field is analyzed for low wavenumber, and for large distances we find V (r) approx. = Q/k 2 2 r 3 . The inverse screening length k 0 =2πe 2 partial rho/ partialxi (rho= density, xi= chemical potential) is evaluated in all regimes of magnetic field strength and all statistical regimes. k 0 exhibits violent DHVA oscillatory behavior in the degenerate zero-temperature case at higher field strengths, and the shielding is complete when xi =r'hω/subc/ but there is no shielding when xi does not = r'hω/subc/. A careful analysis confirms that there is no shielding at large distances in the degenerate quantum strong field limit h3π/subc/>xi. Since shielding does persist in the nondegenerate quantum strong field limit hω/subc/>KT, there should be a pronounced change in physical properties that depend on shielding if the system is driven through a high field statistical transition. Finally, we find that the zero field two-dimensional Friedel--Kohn ''wiggle'' static shielding phenomenon is destroyed by the dispersal of the zero field continuum of electron states into the discrete set of Landau-quantized orbitals due to the imposition of the magnetic field

  18. Colossal negative thermal expansion in BiNiO3 induced by intermetallic charge transfer.

    Science.gov (United States)

    Azuma, Masaki; Chen, Wei-tin; Seki, Hayato; Czapski, Michal; Olga, Smirnova; Oka, Kengo; Mizumaki, Masaichiro; Watanuki, Tetsu; Ishimatsu, Naoki; Kawamura, Naomi; Ishiwata, Shintaro; Tucker, Matthew G; Shimakawa, Yuichi; Attfield, J Paul

    2011-06-14

    The unusual property of negative thermal expansion is of fundamental interest and may be used to fabricate composites with zero or other controlled thermal expansion values. Here we report that colossal negative thermal expansion (defined as linear expansion linear expansion coefficient for Bi(0.95)La(0.05)NiO(3) is -137×10(-6) K(-1) and a value of -82×10(-6) K(-1) is observed between 320 and 380 K from a dilatometric measurement on a ceramic pellet. Colossal negative thermal expansion materials operating at ambient conditions may also be accessible through metal-insulator transitions driven by other phenomena such as ferroelectric orders.

  19. Joining Chemical Pressure and Epitaxial Strain to Yield Y-doped BiFeO3 Thin Films with High Dielectric Response

    Science.gov (United States)

    Scarisoreanu, N. D.; Craciun, F.; Birjega, R.; Ion, V.; Teodorescu, V. S.; Ghica, C.; Negrea, R.; Dinescu, M.

    2016-05-01

    BiFeO3 is one of the most promising multiferroic materials but undergoes two major drawbacks: low dielectric susceptibility and high dielectric loss. Here we report high in-plane dielectric permittivity (ε’ ∼2500) and low dielectric loss (tan δ priced target.

  20. Two cases of colossal heamtometra in old women with a difficult preoperative diagnostic technique

    International Nuclear Information System (INIS)

    Aono, Kaname; Fukumoto, Satoru

    1980-01-01

    With the progress in diagnostic imaging techniques, the preoperative diagnostic technique for lesion in the pelvic cavity has become comparatively easy and its clinical usefulness is in high estimation. However, in case of an atypical lesion, it is not always easy to recognize the original organ by traditional imaging pattern. In the present report two cases of colossal hematometra in old women which presented a cystic lesion pattern are dealt with and discussed from a point of medical imagings for diagnosis. (author)

  1. Magnon Broadening Effect by Magnon-Phonon Interaction in Colossal Magnetoresistance Manganites

    OpenAIRE

    Furukawa, Nobuo

    1999-01-01

    In order to study the magnetic excitation behaviors in colossal magnetoresistance manganites, a magnon-phonon interacting system is investigated. Sudden broadening of magnon linewidth is obtained when a magnon branch crosses over an optical phonon branch. Onset of the broadening is approximately determined by the magnon density of states. Anomalous magnon damping at the brillouine zone boundary observed in low Curie temperature manganites is explained.

  2. Complex dielectric modulus and relaxation response at low microwave frequency region of dielectric ceramic Ba6-3xNd8+2xTi18O54

    Directory of Open Access Journals (Sweden)

    Chian Heng Lee

    2014-10-01

    Full Text Available The desirable characteristics of Ba6-3xNd8+2xTi18O54 include high dielectric constant, low loss tangent, and high quality factor developed a new field for electronic applications. The microwave dielectric properties of Ba6-3xNd8+2xTi18O54, with x = 0.15 ceramics at different sintering temperatures (600–1300°C were investigated. The phenomenon of polarization produced by the applied electric field was studied. The dielectric properties with respect to frequency from 1 MHz to 1.5 GHz were measured using Impedance Analyzer, and the results were compared and analyzed. The highest dielectric permittivity and lowest loss factor were defined among the samples. The complex dielectric modulus was evaluated from the measured parameters of dielectric measurement in the same frequency range, and used to differentiate the contribution of grain and grain boundary.

  3. Grain boundary effects on dielectric, infrared and Raman response of SrTiO.sub.3./sub. nanograin ceramics

    Czech Academy of Sciences Publication Activity Database

    Petzelt, Jan; Ostapchuk, Tetyana; Gregora, Ivan; Savinov, Maxim; Chvostová, Dagmar; Liu, J.; Shen, Z.

    2006-01-01

    Roč. 26, - (2006), s. 2855-2859 ISSN 0955-2219 R&D Projects: GA ČR(CZ) GA202/04/0993; GA MŠk(CZ) OC 525.20 Institutional research plan: CEZ:AV0Z10100520 Keywords : SrTiO 3 * grain boundaries * spectroscopy * dielectric properties * ferroelectric properties Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.576, year: 2006

  4. Glassy dielectric response in Tb2NiMnO6 double perovskite with similarities to a Griffiths phase

    Science.gov (United States)

    Nhalil, Hariharan; Nair, Harikrishnan S.; Bhat, H. L.; Elizabeth, Suja

    2013-12-01

    Results of frequency-dependent and temperature-dependent dielectric measurements performed on the double-perovskite Tb2NiMnO6 are presented. The real (\\epsilon_1 (f,T)) and imaginary (\\epsilon_2 (f,T)) parts of dielectric permittivity show three plateaus suggesting dielectric relaxation originating from the bulk, grain boundaries and the sample-electrode interfaces, respectively. The \\epsilon_1 (f,T) and \\epsilon_2 (f,T) are successfully simulated by a RC circuit model. The complex plane of impedance, Z'\\text{-}Z'' , is simulated using a series network with a resistor R and a constant phase element. Through the analysis of \\epsilon (f,T) using the modified Debye model, two different relaxation time regimes separated by a characteristic temperature, T^* , are identified. The temperature variation of R and C corresponding to the bulk and the parameter α from modified Debye fit lend support to this hypothesis. Interestingly, the T^* compares with the Griffiths temperature for this compound observed in magnetic measurements. Though these results cannot be interpreted as magnetoelectric coupling, the relationship between lattice and magnetism is markedly clear. We assume that the observed features have their origin in the polar nanoregions which originate from the inherent cationic defect structure of double perovskites.

  5. Quantitative evaluation of the piezoelectric response of unpoled ferroelectric ceramics from elastic and dielectric measurements: Tetragonal BaTiO3

    Science.gov (United States)

    Cordero, F.

    2018-03-01

    A method is proposed for evaluating the potential piezoelectric response, that a ferroelectric material would exhibit after full poling, from elastic and dielectric measurements of the unpoled ceramic material. The method is based on the observation that the softening in a ferroelectric phase with respect to the paraelectric phase is of piezoelectric origin, and is tested on BaTiO3. The angular averages of the piezoelectric softening in unpoled ceramics are calculated for ferroelectric phases of different symmetries. The expression of the orientational average with the piezoelectric and dielectric constants of single crystal tetragonal BaTiO3 from the literature reproduces well the softening of the Young's modulus of unpoled ceramic BaTiO3, after a correction for the porosity. The agreement is good in the temperature region sufficiently far from the Curie temperature and from the transition to the orthorhombic phase, where the effect of fluctuations should be negligible, but deviations are found outside this region, and possible reasons for this are discussed. This validates the determination of the piezoelectric response by means of purely elastic measurements on unpoled samples. The method is indirect and, for quantitative assessments, requires the knowledge of the dielectric tensor. On the other hand, it does not require poling of the sample, and therefore is insensitive to inaccuracies from incomplete poling, and can even be used with materials that cannot be poled, for example, due to excessive electrical conductivity. While the proposed example of the Young's modulus of a ceramic provides an orientational average of all the single crystal piezoelectric constants, a Resonant Ultrasound Spectroscopy measurement of a single unpoled ceramic sample through the ferroelectric transition can in principle measure all the piezoelectric constants, together with the elastic ones.

  6. 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.

  7. Origin of Colossal Ionic Conductivity in Oxide Multilayers: Interface Induced Sublattice Disorder

    International Nuclear Information System (INIS)

    Pennycook, Timothy J.; Pantelides, Sokrates T.; Beck, Matthew J.; Varga, Kalman; Varela, Maria; Pennycook, Stephen J.

    2010-01-01

    Oxide ionic conductors typically operate at high temperatures, which limits their usefulness. Colossal room-temperature ionic conductivity was recently discovered in multilayers of yttria-stabilized zirconia (YSZ) and SrTiO 3 . Here we report density-functional calculations that trace the origin of the effect to a combination of lattice-mismatch strain and O-sublattice incompatibility. Strain alone in bulk YSZ enhances O mobility at high temperatures by inducing extreme O disorder. In multilayer structures, O-sublattice incompatibility causes the same extreme disorder at room temperature.

  8. Electronic band structure study of colossal magnetoresistance in Tl 2Mn 2O 7

    Science.gov (United States)

    Seo, D.-K.; Whangbo, M.-H.; Subramanian, M. A.

    1997-02-01

    The electronic structure of Tl 2Mn 2O 7 was examined by performing tight binding band calculations. The overlap between the Mn t 2g- and Tl 6 s-block bands results in a partial filling of the Tl 6 s-block bands. The associated Fermi surface consists of 12 cigar-shape electron pockets with each electron pocket about {1}/{1000} of the first Brillouin zone in size. The Tl 6 s-block bands have orbital contributions from the Mn atoms, and the carrier density is very low. These are important for the occurrence of a colossal magnetoresistance in Tl 2Mn 2O 7.

  9. Molecular beam epitaxy of single crystal colossal magnetoresistive material

    International Nuclear Information System (INIS)

    Eckstein, J.N.; Bozovic, I.; Rzchowski, M.; O'Donnell, J.; Hinaus, B.; Onellion, M.

    1996-01-01

    The authors have grown films of (LaSr)MnO 3 (LSMO) and (LaCa)MnO 3 (LCMO) using atomic layer-by-layer molecular beam epitaxy (ALL-MBE). Depending on growth conditions, substrate lattice constant and the exact cation stoichiometry, the films are either pseudomorphic or strain relaxed. The pseudomorphic films show atomically flat surfaces, with a unit cell terrace structure that is a replica of that observed on the slightly vicinal substrates, while the strain relaxed films show bumpy surfaces correlated with a dislocation network. All films show tetragonal structure and exhibit anisotropic magnetoresistance, with a low field response, (1/R)(dR/dH) as large as 5 T -1

  10. Dielectric and biochemical response of a PLA-PGA-HAp-Chitosan-Collagen coated on Ti6Al4V

    International Nuclear Information System (INIS)

    Montanez Superlano, Nerly Deyanira; Pena Ballesteros, Dario Yesid; Estupinan Duran, Hugo Armando

    2016-01-01

    The interaction of a polymeric biomaterial with a culture medium and osteoblast cells, electrodeposited on Ti6Al4V was evaluated. The compound is integrated of polylactic acid-polyglycolic acid-hydroxyapatite, modified with collagen and chitosan. The relative permittivity data embodied in a dielectric impedance spectrum identified the alpha and beta dispersions related to the ion exchange and the polarization of the cell membrane was calculated. Adhesion and cell proliferation was analyzed by epifluorescence microscopy, where it was observed on the third day of the cell culture process represented by mitosis core condensation and separation of the chromosomes. The surface morphology by SEM (Scanning Electron Microscope) and AFM (Atomic Force Microscope) biomaterial was observed and cellular activity was assessed by measuring alkaline phosphatase. Finally the best surface for adhesion and cell growth was found by statistical analysis, which corresponded to the coating with the highest concentration of chitosan and collagen

  11. The combined effect of side-coupled gain cavity and lossy cavity on the plasmonic response of metal-dielectric-metal surface plasmon polariton waveguide

    International Nuclear Information System (INIS)

    Zhu, Qiong-gan; Wang, Zhi-guo; Tan, Wei

    2014-01-01

    The combined effect of side-coupled gain cavity and lossy cavity on the plasmonic response of metal-dielectric-metal (MDM) surface plasmon polariton (SPP) waveguide is investigated theoretically using Green's function method. Our result suggests that the gain and loss parameters influence the amplitude and phase of the fields localized in the two cavities. For the case of balanced gain and loss, the fields of the two cavities are always of equi-amplitude but out of phase. A plasmon induced transparency (PIT)-like transmission peak can be achieved by the destructive interference of two fields with anti-phase. For the case of unbalanced gain and loss, some unexpected responses of structure are generated. When the gain is more than the loss, the system response is dissipative at around the resonant frequency of the two cavities, where the sum of reflectance and transmittance becomes less than one. This is because the lossy cavity, with a stronger localized field, makes the main contribution to the system response. When the gain is less than the loss, the reverse is true. It is found that the metal loss dissipates the system energy but facilitates the gain cavity to make a dominant effect on the system response. This mechanism may have a potential application for optical amplification and for a plasmonic waveguide switch. (paper)

  12. Achievement of High-Response Organic Field-Effect Transistor NO2 Sensor by Using the Synergistic Effect of ZnO/PMMA Hybrid Dielectric and CuPc/Pentacene Heterojunction

    Directory of Open Access Journals (Sweden)

    Shijiao Han

    2016-10-01

    Full Text Available High-response organic field-effect transistor (OFET-based NO2 sensors were fabricated using the synergistic effect the synergistic effect of zinc oxide/poly(methyl methacrylate (ZnO/PMMA hybrid dielectric and CuPc/Pentacene heterojunction. Compared with the OFET sensors without synergistic effect, the fabricated OFET sensors showed a remarkable shift of saturation current, field-effect mobility and threshold voltage when exposed to various concentrations of NO2 analyte. Moreover, after being stored in atmosphere for 30 days, the variation of saturation current increased more than 10 folds at 0.5 ppm NO2. By analyzing the electrical characteristics, and the morphologies of organic semiconductor films of the OFET-based sensors, the performance enhancement was ascribed to the synergistic effect of the dielectric and organic semiconductor. The ZnO nanoparticles on PMMA dielectric surface decreased the grain size of pentacene formed on hybrid dielectric, facilitating the diffusion of CuPc molecules into the grain boundary of pentacene and the approach towards the conducting channel of OFET. Hence, NO2 molecules could interact with CuPc and ZnO nanoparticles at the interface of dielectric and organic semiconductor. Our results provided a promising strategy for the design of high performance OFET-based NO2 sensors in future electronic nose and environment monitoring.

  13. Achievement of High-Response Organic Field-Effect Transistor NO₂ Sensor by Using the Synergistic Effect of ZnO/PMMA Hybrid Dielectric and CuPc/Pentacene Heterojunction.

    Science.gov (United States)

    Han, Shijiao; Cheng, Jiang; Fan, Huidong; Yu, Junsheng; Li, Lu

    2016-10-21

    High-response organic field-effect transistor (OFET)-based NO₂ sensors were fabricated using the synergistic effect the synergistic effect of zinc oxide/poly(methyl methacrylate) (ZnO/PMMA) hybrid dielectric and CuPc/Pentacene heterojunction. Compared with the OFET sensors without synergistic effect, the fabricated OFET sensors showed a remarkable shift of saturation current, field-effect mobility and threshold voltage when exposed to various concentrations of NO₂ analyte. Moreover, after being stored in atmosphere for 30 days, the variation of saturation current increased more than 10 folds at 0.5 ppm NO₂. By analyzing the electrical characteristics, and the morphologies of organic semiconductor films of the OFET-based sensors, the performance enhancement was ascribed to the synergistic effect of the dielectric and organic semiconductor. The ZnO nanoparticles on PMMA dielectric surface decreased the grain size of pentacene formed on hybrid dielectric, facilitating the diffusion of CuPc molecules into the grain boundary of pentacene and the approach towards the conducting channel of OFET. Hence, NO₂ molecules could interact with CuPc and ZnO nanoparticles at the interface of dielectric and organic semiconductor. Our results provided a promising strategy for the design of high performance OFET-based NO₂ sensors in future electronic nose and environment monitoring.

  14. Achievement of High-Response Organic Field-Effect Transistor NO2 Sensor by Using the Synergistic Effect of ZnO/PMMA Hybrid Dielectric and CuPc/Pentacene Heterojunction

    Science.gov (United States)

    Han, Shijiao; Cheng, Jiang; Fan, Huidong; Yu, Junsheng; Li, Lu

    2016-01-01

    High-response organic field-effect transistor (OFET)-based NO2 sensors were fabricated using the synergistic effect the synergistic effect of zinc oxide/poly(methyl methacrylate) (ZnO/PMMA) hybrid dielectric and CuPc/Pentacene heterojunction. Compared with the OFET sensors without synergistic effect, the fabricated OFET sensors showed a remarkable shift of saturation current, field-effect mobility and threshold voltage when exposed to various concentrations of NO2 analyte. Moreover, after being stored in atmosphere for 30 days, the variation of saturation current increased more than 10 folds at 0.5 ppm NO2. By analyzing the electrical characteristics, and the morphologies of organic semiconductor films of the OFET-based sensors, the performance enhancement was ascribed to the synergistic effect of the dielectric and organic semiconductor. The ZnO nanoparticles on PMMA dielectric surface decreased the grain size of pentacene formed on hybrid dielectric, facilitating the diffusion of CuPc molecules into the grain boundary of pentacene and the approach towards the conducting channel of OFET. Hence, NO2 molecules could interact with CuPc and ZnO nanoparticles at the interface of dielectric and organic semiconductor. Our results provided a promising strategy for the design of high performance OFET-based NO2 sensors in future electronic nose and environment monitoring. PMID:27775653

  15. Experimental Characterization of Dielectric Properties in Fluid Saturated Artificial Shales

    OpenAIRE

    Beloborodov, Roman; Pervukhina, Marina; Han, Tongcheng; Josh, Matthew

    2017-01-01

    High dielectric contrast between water and hydrocarbons provides a useful method for distinguishing between producible layers of reservoir rocks and surrounding media. Dielectric response at high frequencies is related to the moisture content of rocks. Correlations between the dielectric permittivity and specific surface area can be used for the estimation of elastic and geomechanical properties of rocks. Knowledge of dielectric loss-factor and relaxation frequency in shales is critical for t...

  16. Transient, polarity-dependent dielectric response in a twisted nematic liquid crystal under very low frequency excitation.

    Science.gov (United States)

    Krishnamurthy, K S

    2015-09-01

    The electric Freedericksz transition is a second-order quadratic effect, which, in a planarly aligned nematic liquid crystal layer, manifests above a threshold field as a homogeneous symmetric distortion with maximum director-tilt in the midplane. We find that, upon excitation by a low frequency (wave field, the instability becomes spatially and temporally varying. This is demonstrated using calamitic liquid crystals, initially in the 90°-twisted planar configuration. The distortion occurs close to the negative electrode following each polarity switch and, for low-voltage amplitudes, decays completely in time. We use the elastically favorable geometry of Brochard-Leger walls to establish the location of maximum distortion. Thus, at successive polarity changes, the direction of extension of both annular and open walls switches between the alignment directions at the two substrates. For high voltages, this direction is largely along the midplane director, while remaining marginally oscillatory. These results are broadly understood by taking into account the time-varying and inhomogeneous field conditions that prevail soon after the polarity reverses. Polarity dependence of the instability is traced to the formation of intrinsic double layers that lead to an asymmetry in field distribution in the presence of an external bias. Momentary field elevation near the negative electrode following a voltage sign reversal leads to locally enhanced dielectric and gradient flexoelectric torques, which accounts for the surface-like phenomenon observed at low voltages. These spatiotemporal effects, also found earlier for other instabilities, are generic in nature.

  17. Super dielectric capacitor using scaffold dielectric

    OpenAIRE

    Phillips, Jonathan

    2018-01-01

    Patent A capacitor having first and second electrodes and a scaffold dielectric. The scaffold dielectric comprises an insulating material with a plurality of longitudinal channels extending across the dielectric and filled with a liquid comprising cations and anions. The plurality of longitudinal channels are substantially parallel and the liquid within the longitudinal channels generally has an ionic strength of at least 0.1. Capacitance results from the migrations of...

  18. Dielectric polarization in random media

    International Nuclear Information System (INIS)

    Ramshaw, J.D.

    1984-01-01

    The theory of dielectric polarization in random media is systematically formulated in terms of response kernels. The primary response kernel K(12) governs the mean dielectric response at the point r 1 to the external electric field at the point r 2 in an infinite system. The inverse of K(12) is denoted by L(12);. it is simpler and more fundamental than K(12) itself. Rigorous expressions are obtained for the effective dielectric constant epsilon( in terms of L(12) and K(12). The latter expression involves the Onsger-Kirkwood function (epsilon(-epsilon 0 (2epsilon(+epsilon 0 )/epsilon 0 epsilon( (where epsilon 0 is an arbitrary reference value), and appears to be new to the random medium context. A wide variety of series representations for epsilon( are generated by means of general perturbation expansions for K(12) and L(12). A discussion is given of certain pitfalls in the theory, most of which are related to the fact that the response kernels are long ranged. It is shown how the dielectric behavior of nonpolar molecular fluids may be treated as a special case of the general theory. The present results for epsilon( apply equally well to other effective phenomenological coefficients of the same generic type, such as thermal and electrical conductivity, magnetic susceptibility, and diffusion coefficients

  19. Pressure effect on magnetic and magnetotransport properties of intermetallic and colossal magnetoresistance oxide compounds

    International Nuclear Information System (INIS)

    Arnold, Z; Ibarra, M R; Algarabel, P A; Marquina, C; Teresa, Jose MarIa de; Morellon, L; Blasco, J; Magen, C; Prokhnenko, O; Kamarad, J; Ritter, C

    2005-01-01

    The joint power of neutron diffraction and pressure techniques allows us to characterize under unique conditions the nature and different role of basic interactions in solids. We have covered a broad phenomenology in archetypical compounds: intermetallics and magnetic oxides. We have selected compounds in which the effect of moderate pressure is able to modify the electronic structure and bond angles that in turn are in the bases of magnetic and structural transitions. Complex magnetic and structural phase diagrams are reported for compounds with magnetic (Tb 1-X Y X Mn 2 ) and structural (RE 5 Si 4-X Ge X ) instabilities. Pressure-induced change of the magnetic structure in (R 2 Fe 17 ) intermetallics and the effect on the colossal magnetoresistance manganites are described

  20. Half-metallic perovskite superlattices with colossal thermoelectric figure of merit

    KAUST Repository

    Upadhyay Kahaly, M.; Ozdogan, K.; Schwingenschlö gl, Udo

    2013-01-01

    Nowadays heavy experimental efforts are focussed on doped oxide thermoelectrics to increase the thermopower and thermoelectric performance. We propose a high thermoelectric figure of merit for half-metallic SrTi1−xCoxO3 (x = 0, 0.125, 0.25, 0.375, and 0.5) in a superlattice with SrTiO3, which is stable at high temperatures and in an oxygen environment. The maximal value of Z hardly depends on the doping, while the temperature at which the maximum occurs increases with the Co concentration. The easy tunability from being an insulator to a half-metal under substitutional doping combined with the colossal figure of merit opens up great potential in the emerging field of spin-caloritronics.

  1. Half-metallic perovskite superlattices with colossal thermoelectric figure of merit

    KAUST Repository

    Upadhyay Kahaly, M.

    2013-05-09

    Nowadays heavy experimental efforts are focussed on doped oxide thermoelectrics to increase the thermopower and thermoelectric performance. We propose a high thermoelectric figure of merit for half-metallic SrTi1−xCoxO3 (x = 0, 0.125, 0.25, 0.375, and 0.5) in a superlattice with SrTiO3, which is stable at high temperatures and in an oxygen environment. The maximal value of Z hardly depends on the doping, while the temperature at which the maximum occurs increases with the Co concentration. The easy tunability from being an insulator to a half-metal under substitutional doping combined with the colossal figure of merit opens up great potential in the emerging field of spin-caloritronics.

  2. Materials Fundamentals of Gate Dielectrics

    CERN Document Server

    Demkov, Alexander A

    2006-01-01

    This book presents materials fundamentals of novel gate dielectrics that are being introduced into semiconductor manufacturing to ensure the continuous scalling of the CMOS devices. This is a very fast evolving field of research so we choose to focus on the basic understanding of the structure, thermodunamics, and electronic properties of these materials that determine their performance in device applications. Most of these materials are transition metal oxides. Ironically, the d-orbitals responsible for the high dielectric constant cause sever integration difficulties thus intrinsically limiting high-k dielectrics. Though new in the electronics industry many of these materials are wel known in the field of ceramics, and we describe this unique connection. The complexity of the structure-property relations in TM oxides makes the use of the state of the art first-principles calculations necessary. Several chapters give a detailed description of the modern theory of polarization, and heterojunction band discont...

  3. Inertial polarization of dielectrics

    OpenAIRE

    Zavodovsky, A. G.

    2011-01-01

    It was proved that accelerated motion of a linear dielectric causes its polarization. Accelerated translational motion of a dielectric's plate leads to the positive charge of the surface facing the direction of motion. Metal plates of a capacitor were used to register polarized charges on a dielectric's surface. Potential difference between the capacitor plates is proportional to acceleration, when acceleration is constant potential difference grows with the increase of a dielectric's area, o...

  4. Optimal Super Dielectric Material

    Science.gov (United States)

    2015-09-01

    plate capacitor will reduce the net field to an unprecedented extent. This family of materials can form materials with dielectric values orders of... Capacitor -Increase Area (A)............8 b. Multi-layer Ceramic Capacitor -Decrease Thickness (d) .......10 c. Super Dielectric Material-Increase...circuit modeling, from [44], and B) SDM capacitor charge and discharge ...................................................22 Figure 15. Dielectric

  5. Dielectrics in electric fields

    CERN Document Server

    Raju, Gorur G

    2003-01-01

    Discover nontraditional applications of dielectric studies in this exceptionally crafted field reference or text for seniors and graduate students in power engineering tracks. This text contains more than 800 display equations and discusses polarization phenomena in dielectrics, the complex dielectric constant in an alternating electric field, dielectric relaxation and interfacial polarization, the measurement of absorption and desorption currents in time domains, and high field conduction phenomena. Dielectrics in Electric Fields is an interdisciplinary reference and text for professionals and students in electrical and electronics, chemical, biochemical, and environmental engineering; physical, surface, and colloid chemistry; materials science; and chemical physics.

  6. Lattices of dielectric resonators

    CERN Document Server

    Trubin, Alexander

    2016-01-01

    This book provides the analytical theory of complex systems composed of a large number of high-Q dielectric resonators. Spherical and cylindrical dielectric resonators with inferior and also whispering gallery oscillations allocated in various lattices are considered. A new approach to S-matrix parameter calculations based on perturbation theory of Maxwell equations, developed for a number of high-Q dielectric bodies, is introduced. All physical relationships are obtained in analytical form and are suitable for further computations. Essential attention is given to a new unified formalism of the description of scattering processes. The general scattering task for coupled eigen oscillations of the whole system of dielectric resonators is described. The equations for the  expansion coefficients are explained in an applicable way. The temporal Green functions for the dielectric resonator are presented. The scattering process of short pulses in dielectric filter structures, dielectric antennas  and lattices of d...

  7. A dielectric approach to high temperature superconductivity

    International Nuclear Information System (INIS)

    Mahanty, J.; Das, M.P.

    1989-01-01

    The dielectric response of an electron-ion system to the presence of a pair of charges is investigated. From the nature of the dielectric function, it is shown that a strong attractive pair formation is possible depending on the dispersion of the ion branches. The latter brings a reduction to the sound velocity which is used as a criterion for the superconductivity. By solving the BCS equation with the above dielectric function, we obtain a reasonable value of T/sub c/. 17 refs., 1 fig

  8. Lattice dynamics and dielectric response of undoped, soft and hard PbZr.sub.0.42./sub.Ti.sub.0.58./sub.O.sub.3./sub..

    Czech Academy of Sciences Publication Activity Database

    Buixaderas, Elena; Nuzhnyy, Dmitry; Vaněk, Přemysl; Gregora, Ivan; Petzelt, Jan; Porokhonskyy, V.; Jin, L.; Damjanović, D.

    2010-01-01

    Roč. 83, 10-11 (2010), s. 917-930 ISSN 0141-1594 R&D Projects: GA AV ČR KAN301370701; GA ČR GAP204/10/0616 Institutional research plan: CEZ:AV0Z10100520 Keywords : infrared and Raman spectroscopy * THz spectroscopy * phonons * dielectric response * soft and hard PZT ceramics Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.006, year: 2010

  9. A probabilistic mechanism hidden behind the universal power law for dielectric relaxation. 2 - Discussion of the response function

    International Nuclear Information System (INIS)

    Weron, K.

    1991-08-01

    This paper is a continuation of our previous work, where the new probabilistic model based directly on the reaction picture of relaxation was introduced and a general relaxation equation was derived. Here we show the universal character of distributions of damping rates and waiting times used in this model. Moreover, we discuss in detail a physical significance of the response function derived as a solution of the general relaxation equation. (author). 23 refs, 4 figs

  10. Dielectric Actuation of Polymers

    Science.gov (United States)

    Niu, Xiaofan

    Dielectric polymers are widely used in a plurality of applications, such as electrical insulation, dielectric capacitors, and electromechanical actuators. Dielectric polymers with large strain deformations under an electric field are named dielectric elastomers (DE), because of their relative low modulus, high elongation at break, and outstanding resilience. Dielectric elastomer actuators (DEA) are superior to traditional transducers as a muscle-like technology: large strains, high energy densities, high coupling efficiency, quiet operation, and light weight. One focus of this dissertation is on the design of DE materials with high performance and easy processing. UV radiation curing of reactive species is studied as a generic synthesis methodology to provide a platform for material scientists to customize their own DE materials. Oligomers/monomers, crosslinkers, and other additives are mixed and cured at appropriate ratios to control the stress-strain response, suppress electromechanical instability of the resulting polymers, and provide stable actuation strains larger than 100% and energy densities higher than 1 J/g. The processing is largely simplified in the new material system by removal of the prestretching step. Multilayer stack actuators with 11% linear strain are demonstrated in a procedure fully compatible with industrial production. A multifunctional DE derivative material, bistable electroactive polymer (BSEP), is invented enabling repeatable rigid-to-rigid deformation without bulky external structures. Bistable actuation allows the polymer actuator to have two distinct states that can support external load without device failure. Plasticizers are used to lower the glass transition temperature to 45 °C. Interpenetrating polymer network structure is established inside the BSEP to suppress electromechanical instability, providing a breakdown field of 194 MV/m and a stable bistable strain as large as 228% with a 97% strain fixity. The application of BSEP

  11. Influence of Zn doping on structural, optical and dielectric properties of LaFeO3

    Science.gov (United States)

    Manzoor, Samiya; Husain, Shahid

    2018-05-01

    The effect of Zn doping on structural, optical and dielectric properties of nano-crystalline LaFe1‑xZnxO3 (0.0 ≤ x ≤ 0.3) samples have been investigated. These samples are synthesized using conventional solid state reaction route. X-ray diffraction patterns with Rietveld analysis confirm the single phase nature of samples. Further, the sample formation has been confirmed by FTIR spectroscopy. All the samples are formed in orthorhombic crystal symmetry with Pbnm space group. The average crystallite sizes, calculated from the Scherer’s formula, lie in the range below 50 nm. Rietveld refinement technique is used to determine lattice parameters, bond lengths and unit cell volume. Williamson-Hall analysis has been performed to calculate the crystallite size and lattice strain. Crystallite sizes are found to be of nanometer range while the strain is of the order of 10‑3. Zn doping leads to the expansion of volume due to the tensile strain. Optical bandgap has been determined from Kubelka-Munk function using Tauc’s relation. Zinc doping in LaFeO3 leads to decrease in optical bandgap. Dielectric constant as a function of frequency is measured in the frequency range of 75 kHz–5 MHz. The dielectric behavior has been investigated by analyzing ‘universal dielectric response’ (UDR) model. The dielectric constant (ε‧) shows colossal value with Zn doping in the whole frequency range. However, the imaginary part (ε″) shows relaxational behavior which may be attributed to the strong correlation that exists between conduction mechanism and dielectric behavior in ferrites. Cole-Cole analysis has been done that confirms the dielectric material does not follow the ideal Debye theory but shows distribution of relaxation times. The a.c conductivity increases with frequency and with Zn doping due to the increased polaron hopping.

  12. Colossal positive magnetoresistance in surface-passivated oxygen-deficient strontium titanite

    KAUST Repository

    David, Adrian

    2015-05-15

    Modulation of resistance by an external magnetic field, i.e. magnetoresistance effect, has been a long-lived theme of research due to both fundamental science and device applications. Here we report colossal positive magnetoresistance (CPMR) (>30,000% at a temperature of 2 K and a magnetic field of 9 T) discovered in degenerate semiconducting strontium titanite (SrTiO3) single crystals capped with ultrathin SrTiO3/LaAlO3 bilayers. The low-pressure high-temperature homoepitaxial growth of several unit cells of SrTiO3 introduces oxygen vacancies and high-mobility carriers in the bulk SrTiO3, and the three-unit-cell LaAlO3 capping layer passivates the surface and improves carrier mobility by suppressing surface-defect-related scattering. The coexistence of multiple types of carriers and inhomogeneous transport lead to the emergence of CPMR. This unit-cell-level surface engineering approach is promising to be generalized to others oxides, and to realize devices with high-mobility carriers and interesting magnetoelectronic properties.

  13. NMR of Colossal Magnetoresistive Manganites and Expanded Lattice Intermetallics at High Pressure

    International Nuclear Information System (INIS)

    Kapusta, Cz.; Riedi, P. C.

    2001-01-01

    A survey is given of NMR studies of colossal magnetoresistive manganese perovskites (RE,Ca,Sr,Ba)MnO 3 (RE = rare earth) and the interstitially modified permanent magnet materials, RE 2 Fe 17 A x (A = N, C, H) at ambient pressure and at applied pressures of up to 10 kbar. The different pressure behavior of the Mn hyperfine field found in the metallic and in the insulating manganite compounds is discussed and related to the micro- and macroscopic properties of these magnetically inhomogeneous materials. In the RE 2 Fe 17 A x compounds a different pressure behavior of the hyperfine field at the RE sites with different number and type of interstitial atom neighbors is discussed in terms of local compressibility. The influence of the interstitial modification and the applied pressure on the RE hyperfine field and quadrupole splitting is analyzed and the impact of the 'chemical pressure' and covalent effects on these quantities is compared. A comparison of the behavior of the magnetic state of the 4f electron shell with pressure and with interstitial modification is made and the relation to the magnetocrystalline anisotropy is discussed

  14. Inductive dielectric analyzer

    International Nuclear Information System (INIS)

    Agranovich, Daniel; Popov, Ivan; Ben Ishai, Paul; Feldman, Yuri; Polygalov, Eugene

    2017-01-01

    One of the approaches to bypass the problem of electrode polarization in dielectric measurements is the free electrode method. The advantage of this technique is that, the probing electric field in the material is not supplied by contact electrodes, but rather by electromagnetic induction. We have designed an inductive dielectric analyzer based on a sensor comprising two concentric toroidal coils. In this work, we present an analytic derivation of the relationship between the impedance measured by the sensor and the complex dielectric permittivity of the sample. The obtained relationship was successfully employed to measure the dielectric permittivity and conductivity of various alcohols and aqueous salt solutions. (paper)

  15. Method of making dielectric capacitors with increased dielectric breakdown strength

    Science.gov (United States)

    Ma, Beihai; Balachandran, Uthamalingam; Liu, Shanshan

    2017-05-09

    The invention is directed to a process for making a dielectric ceramic film capacitor and the ceramic dielectric laminated capacitor formed therefrom, the dielectric ceramic film capacitors having increased dielectric breakdown strength. The invention increases breakdown strength by embedding a conductive oxide layer between electrode layers within the dielectric layer of the capacitors. The conductive oxide layer redistributes and dissipates charge, thus mitigating charge concentration and micro fractures formed within the dielectric by electric fields.

  16. Stretched exponential relaxation and ac universality in disordered dielectrics

    DEFF Research Database (Denmark)

    Milovanov, Alexander V.; Rypdal, Kristoffer; Juul Rasmussen, Jens

    2007-01-01

    This paper is concerned with the connection between the properties of dielectric relaxation and alternating-current (ac) conduction in disordered dielectrics. The discussion is divided between the classical linear-response theory and a self-consistent dynamical modeling. The key issues are stretc......This paper is concerned with the connection between the properties of dielectric relaxation and alternating-current (ac) conduction in disordered dielectrics. The discussion is divided between the classical linear-response theory and a self-consistent dynamical modeling. The key issues...

  17. Experimental Characterization of Dielectric Properties in Fluid Saturated Artificial Shales

    Directory of Open Access Journals (Sweden)

    Roman Beloborodov

    2017-01-01

    Full Text Available High dielectric contrast between water and hydrocarbons provides a useful method for distinguishing between producible layers of reservoir rocks and surrounding media. Dielectric response at high frequencies is related to the moisture content of rocks. Correlations between the dielectric permittivity and specific surface area can be used for the estimation of elastic and geomechanical properties of rocks. Knowledge of dielectric loss-factor and relaxation frequency in shales is critical for the design of techniques for effective hydrocarbon extraction and production from unconventional reservoirs. Although applicability of dielectric measurements is intriguing, the data interpretation is very challenging due to many factors influencing the dielectric response. For instance, dielectric permittivity is determined by mineralogical composition of solid fraction, volumetric content and composition of saturating fluid, rock microstructure and geometrical features of its solid components and pore space, temperature, and pressure. In this experimental study, we investigate the frequency dependent dielectric properties of artificial shale rocks prepared from silt-clay mixtures via mechanical compaction. Samples are prepared with various clay contents and pore fluids of different salinity and cation compositions. Measurements of dielectric properties are conducted in two orientations to investigate the dielectric anisotropy as the samples acquire strongly oriented microstructures during the compaction process.

  18. Infrared and THz spectroscopy of nanostructured dielectrics

    Directory of Open Access Journals (Sweden)

    Jan Petzelt

    2009-09-01

    Full Text Available Results achieved using the infrared/THz spectroscopy of various inhomogeneous dielectrics in the Department of Dielectrics, Institute of Physics, Prague, during the last decade are briefly reviewed. The discussion concerns high-permittivity ceramics with inevitable low-permittivity dead layers along the grain boundaries, relaxor ferroelectrics with highly anisotropic polar nano-regions, classical matrix-type composites, core-shell composites, filled nanoporous glasses, polycrystalline and epitaxial thin films, heterostructures and superlattices on dielectric substrates. The analysis using models based on the effective medium approach is discussed. The importance of depolarizing field and of the percolation of components on the effective ac dielectric response and the excitations contributing to it are emphasized.

  19. Contemporary dielectric materials

    CERN Document Server

    Saravanan, R

    2016-01-01

    This book deals with experimental results of the physical characterization of several important, dielectric materials of great current interest. The experimental tools used for the analysis of these materials include X-ray diffraction, dielectric measurements, magnetic measurements using a vibrating sample magnetometer, optical measurements using a UV-Visible spectrometer etc.

  20. Dielectric Modulated FET (DMFET)

    Indian Academy of Sciences (India)

    First page Back Continue Last page Graphics. Working Principle: Change in Dielectric constant due to immobilization of biomolecules in the nanogap cavity leads to change in effective gate capacitance and thus gate bias for FET. Working Principle: Change in Dielectric constant due to immobilization of biomolecules in the ...

  1. Thermal dielectric function

    International Nuclear Information System (INIS)

    Moneta, M.

    1999-01-01

    Thermal dielectric functions ε(k,ω) for homogeneous electron gas were determined and discussed. The ground state of the gas is described by the Fermi-Dirac momentum distribution. The low and high temperature limits of ε(k,ω) were related to the Lindhard dielectric function and to ε(k, omega) derived for Boltzmann and for classical momentum distributions, respectively. (author)

  2. Light in complex dielectrics

    NARCIS (Netherlands)

    Schuurmans, F.J.P.

    1999-01-01

    In this thesis the properties of light in complex dielectrics are described, with the two general topics of "modification of spontaneous emission" and "Anderson localization of light". The first part focuses on the spontaneous emission rate of an excited atom in a dielectric host with variable

  3. Spectroscopy and Biosensing with Optically Resonant Dielectric Nanostructures

    OpenAIRE

    Krasnok, Alex; Caldarola, Martin; Bonod, Nicolas; Alú, Andrea

    2017-01-01

    Resonant dielectric nanoparticles (RDNs) made of materials with large positive dielectric permittivity, such as Si, GaP, GaAs, have become a powerful platform for modern light science, enabling various fascinating applications in nanophotonics and quantum optics. In addition to light localization at the nanoscale, dielectric nanostructures provide electric and magnetic resonant responses throughout the visible and infrared spectrum, low dissipative losses and optical heating, low doping effec...

  4. Influence of voltage on magnetization of ferromagnetic semiconductors with colossal magnetoresistance

    Energy Technology Data Exchange (ETDEWEB)

    Povzner, A.A., E-mail: a.a.povzner@urfu.ru; Volkov, A.G., E-mail: agvolkov@yandex.ru

    2017-06-15

    Graphical abstract: We investigate nonequilibrium states of strongly correlated electron subsystem of lanthanum manganite, resulting in an external electric field. It is shown that the Joule heat leads to localization of electrons. As result, electric resistance, magnetization and other characteristics of the electronic system are depending on the applied voltage. This leads to the formation of the bistable state of the electronic system in the vicinity of the Curie point in an external electric field. This manifests itself in non-linear current-voltage characteristics of these substances, and should lead to oscillations of the magnetization and current. - Abstract: The nonequilibrium processes of “self-heating” arising during the flow of electric current are studied for ferromagnetic semiconductors with colossal magnetoresistance near the Curie temperature. These processes lead to the emergence of “hot” paramagnons and the destruction of ferromagnetic order. The solution to the heat balance equation takes into account the temperature dependence of the electrical conductivity caused by Anderson localization of electrons due to their scattering on magnetic inhomogeneities. Description of delocalized electrons subsystem takes into account the spin-flip processes leading to the double exchange. At that, the value of the Anderson percolation threshold and the double exchange depends on the amplitude of spin fluctuations. It was found that N-shaped current-voltage characteristics and hysteresis dependencies of magnetization on the voltage arise in a steady state due to the emergence of “hot” (by internal sample temperature) semiconductor paramagnetic phase. It is shown that the occurrence of self-oscillations of current and magnetization there may be.

  5. Influence of voltage on magnetization of ferromagnetic semiconductors with colossal magnetoresistance

    International Nuclear Information System (INIS)

    Povzner, A.A.; Volkov, A.G.

    2017-01-01

    Graphical abstract: We investigate nonequilibrium states of strongly correlated electron subsystem of lanthanum manganite, resulting in an external electric field. It is shown that the Joule heat leads to localization of electrons. As result, electric resistance, magnetization and other characteristics of the electronic system are depending on the applied voltage. This leads to the formation of the bistable state of the electronic system in the vicinity of the Curie point in an external electric field. This manifests itself in non-linear current-voltage characteristics of these substances, and should lead to oscillations of the magnetization and current. - Abstract: The nonequilibrium processes of “self-heating” arising during the flow of electric current are studied for ferromagnetic semiconductors with colossal magnetoresistance near the Curie temperature. These processes lead to the emergence of “hot” paramagnons and the destruction of ferromagnetic order. The solution to the heat balance equation takes into account the temperature dependence of the electrical conductivity caused by Anderson localization of electrons due to their scattering on magnetic inhomogeneities. Description of delocalized electrons subsystem takes into account the spin-flip processes leading to the double exchange. At that, the value of the Anderson percolation threshold and the double exchange depends on the amplitude of spin fluctuations. It was found that N-shaped current-voltage characteristics and hysteresis dependencies of magnetization on the voltage arise in a steady state due to the emergence of “hot” (by internal sample temperature) semiconductor paramagnetic phase. It is shown that the occurrence of self-oscillations of current and magnetization there may be.

  6. Development of novel nonvolatile memory devices using the colossal magnetoresistive oxide praseodymium-calcium-manganese trioxide

    Science.gov (United States)

    Papagianni, Christina

    Pr0.7Ca0.3MnO3 (PCMO) manganese oxide belongs in the family of materials known as transition metal oxides. These compounds have received increased attention due to their perplexing properties such as Colossal Magnetoresistance effect, Charge-Ordered phase, existence of phase-separated states etc. In addition, it was recently discovered that short electrical pulses in amplitude and duration are sufficient to induce reversible and non-volatile resistance changes in manganese perovskite oxide thin films at room temperature, known as the EPIR effect. The existence of the EPIR effect in PCMO thin films at room temperature opens a viable way for the realization of fast, high-density, low power non-volatile memory devices in the near future. The purpose of this study is to investigate, optimize and understand the properties of Pr0.7Ca0.3MnO 3 (PCMO) thin film devices and to identify how these properties affect the EPIR effect. PCMO thin films were deposited on various substrates, such as metals, and conducting and insulating oxides, by pulsed laser and radio frequency sputtering methods. Our objective was to understand and compare the induced resistive states. We attempted to identify the induced resistance changes by considering two resistive models to be equivalent to our devices. Impedance spectroscopy was also utilized in a wide temperature range that was extended down to 70K. Fitted results of the temperature dependence of the resistance states were also included in this study. In the same temperature range, we probed the resistance changes in PCMO thin films and we examined whether the phase transitions affect the EPIR effect. In addition, we included a comparison of devices with electrodes consisting of different size and different materials. We demonstrated a direct relation between the EPIR effect and the phase diagram of bulk PCMO samples. A model that could account for the observed EPIR effect is presented.

  7. Phase transition and enhanced magneto-dielectric response in BiFeO{sub 3}-DyMnO{sub 3} multiferroics

    Energy Technology Data Exchange (ETDEWEB)

    Tripathy, Satya N., E-mail: satyanarayantripathy@gmail.com; Pradhan, Dillip K., E-mail: dillip.pradhan79@gmail.com [Department of Physics and Astronomy, National Institute of Technology, Rourkela 769008 (India); Pradhan, Dhiren K.; Palai, Ratnakar; Katiyar, Ram S. [Department of Physics and Institute for Functional Nanomaterials, University of Puerto Rico, San Juan, Puerto Rico 00936 (United States); Mishra, Karuna K. [Condensed Matter Physics Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India); Sen, Shrabanee [Sensor and Actuator Division, Central Glass and Ceramics Research Institute, Kolkata 700032 (India); Paulch, Marian [Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007 Katowice (Poland); Scott, James F. [Department of Physics, Cavendish Laboratory, University of Cambridge, Cambridge CB3 OHE (United Kingdom)

    2015-04-14

    We report systematic studies on crystal structure and magneto-dielectric properties of (1 − x) BiFeO{sub 3}-x DyMnO{sub 3} (0.0 ≤ x ≤ 0.2) nanoceramics synthesized by auto-combustion method. Rietveld refinement of X-ray diffraction data indicates a structural transition from R3c to R3c + Pn2{sub 1}a at x = 0.1. Field emission scanning electron micrographs display a decrease in grain size with increase in x. The presence of dielectric anomalies around antiferromagnetic transition temperature implies the magnetoelectric coupling. Dielectric measurements showed decrease in magnetic ordering temperature with increasing x in agreement with differential scanning calorimetry results. A significant increase in magnetization has been found with increasing DyMnO{sub 3} substitution. Magneto-impedance spectroscopy reveals a significant change (∼18%) in dielectric permittivity at H = 2 T for x = 0.2.

  8. Colossal elastoresistance, electroresistance and magnetoresistance in Pr0.5Sr0.5MnO3 thin films

    International Nuclear Information System (INIS)

    Chen, Liping; Guo, Xuexiang; Gao, J.

    2016-01-01

    Pr 0.5 Sr 0.5 MnO 3 thin films on substrates of (001)-oriented LaAlO 3 were epitaxially grown by pulsed laser deposition. It was found that a substrate-induced strain of ~1.3% brings a great resistivity change of ~98% at 25 K. We studied the dependence of resistivity on the applied electric current and magnetic field. In the greatly strained films of 60 nm thickness the electroresistance ER=[ρ(I 1 μA )−ρ(I 1000 μA )]/ρ(I 1 μA ) reaches ~70% at T=25 K, much higher than ER~7% in the strain-relaxed films of 400 nm thickness, implying the strain effect on ER. Also the magnetoresistance of the film falls with strain-relaxation. Therefore the electric properties of the film could be efficiently modified by strain, electric current and magnetic field. All of them may be explained by the effect on the percolative phase separation and competition in the half-doped manganite material. The manganite films located at phase boundary are expected to be an ideal compound for providing practical colossal effects of elastoresistance, electroresistance and magnetoresistance due to the multiphase coexistence. - Highlights: • The electric current-induced electroresistance (ER) and magnetoresistance (MR)studies on PLD grown Pr 0.5 Sr 0.5 MnO 3 /(001) LaAlO 3 films were found to be greatly sensitive to the film thickness arising from the strain. • It is shown that, 60 nm film exhibit compressive in-plane strain which leads to phase separation and hence colossal MR and ER. • Our results suggest that the manganites located at phase boundary may be an ideal compound for providing practical colossal effects of elastoresistance, electroresistance and magnetoresistance.

  9. Magnetic, electronic, dielectric and optical properties of Pr(Ca:Sr)MnO 3

    Science.gov (United States)

    Sichelschmidt, J.; Paraskevopoulos, M.; Brando, M.; Wehn, R.; Ivannikov, D.; Mayr, F.; Pucher, K.; Hemberger, J.; Pimenov, A.; Krug von Nidda, H.-A.; Lunkenheimer, P.; Ivanov, V. Yu.; Mukhin, A. A.; Balbashov, A. M.; Loidl, A.

    2001-03-01

    The charge-ordered perovskite Pr0.65Ca0.28Sr0.07MnO3 was investigated by means of magnetic susceptibility, specific heat, dielectric and optical spectroscopy and electron-spin resonance techniques. Under moderate magnetic fields, the charge order melts yielding colossal magnetoresistance effects with changes of the resistivity over eleven orders of magnitude. The optical conductivity is studied from audio frequencies far into the visible spectral regime. Below the phonon modes hopping conductivity is detected. Beyond the phonon modes the optical conductivity is explained by polaronic excitations out of a bound state. ESR techniques yield detailed informations on the (H,T ) phase diagram and reveal a broadening of the linewidth which can be modeled in terms of activated polaron hopping.

  10. Improved Dielectric Films For Capacitors

    Science.gov (United States)

    Yen, Shiao-Ping S.; Lewis, Carol R.; Cygan, Peter J.; Jow, T. Richard

    1994-01-01

    Dielectric films made from blends of some commercially available high-dielectric-constant cyanoresins with each other and with cellulose triacetate (CTA) have both high dielectric constants and high breakdown strengths. Dielectric constants as high as 16.2. Films used to produce high-energy-density capacitors.

  11. Dielectric constant of ionic solutions: a field-theory approach.

    Science.gov (United States)

    Levy, Amir; Andelman, David; Orland, Henri

    2012-06-01

    We study the variation of the dielectric response of a dielectric liquid (e.g. water) when a salt is added to the solution. Employing field-theoretical methods, we expand the Gibbs free energy to first order in a loop expansion and calculate self-consistently the dielectric constant. We predict analytically the dielectric decrement which depends on the ionic strength in a complex way. Furthermore, a qualitative description of the hydration shell is found and is characterized by a single length scale. Our prediction fits rather well a large range of concentrations for different salts using only one fit parameter related to the size of ions and dipoles.

  12. Dielectric spectroscopy of Ag-starch nanocomposite films

    Science.gov (United States)

    Meena; Sharma, Annu

    2018-04-01

    In the present work Ag-starch nanocomposite films were fabricated via chemical reduction route. The formation of Ag nanoparticles was confirmed using transmission electron microscopy (TEM). Further the effect of varying concentration of Ag nanoparticles on the dielectric properties of starch has been studied. The frequency response of dielectric constant (ε‧), dielectric loss (ε″) and dissipation factor tan(δ) has been studied in the frequency range of 100 Hz to 1 MHz. Dielectric data was further analysed using Cole-Cole plots. The dielectric constant of starch was found to be 4.4 which decreased to 2.35 in Ag-starch nanocomposite film containing 0.50 wt% of Ag nanoparticles. Such nanocomposites with low dielectric constant have potential applications in microelectronic technologies.

  13. Dielectric materials for electrical engineering

    CERN Document Server

    Martinez-Vega, Juan

    2013-01-01

    Part 1 is particularly concerned with physical properties, electrical ageing and modeling with topics such as the physics of charged dielectric materials, conduction mechanisms, dielectric relaxation, space charge, electric ageing and life end models and dielectric experimental characterization. Part 2 concerns some applications specific to dielectric materials: insulating oils for transformers, electrorheological fluids, electrolytic capacitors, ionic membranes, photovoltaic conversion, dielectric thermal control coatings for geostationary satellites, plastics recycling and piezoelectric poly

  14. Cast dielectric composite linear accelerator

    Science.gov (United States)

    Sanders, David M [Livermore, CA; Sampayan, Stephen [Manteca, CA; Slenes, Kirk [Albuquerque, NM; Stoller, H M [Albuquerque, NM

    2009-11-10

    A linear accelerator having cast dielectric composite layers integrally formed with conductor electrodes in a solventless fabrication process, with the cast dielectric composite preferably having a nanoparticle filler in an organic polymer such as a thermosetting resin. By incorporating this cast dielectric composite the dielectric constant of critical insulating layers of the transmission lines of the accelerator are increased while simultaneously maintaining high dielectric strengths for the accelerator.

  15. Optics of dielectric microstructures

    DEFF Research Database (Denmark)

    Søndergaard, Thomas

    2002-01-01

    From the work carried out within the ph.d. project two topics have been selected for this thesis, namely emission of radiation by sources in dielectric microstructures, and planar photonic crystal waveguides. The work done within the first topic, emission of radiation by sources in dielectric...... microstructures, will be presented in the part I of this thesis consisting of the chapters 2-5. An introductions is given in chapter 2. In part I three methods are presented for calculating spontaneous and classical emission from sources in dielectric microstructures. The first method presented in chapter 3...... is based on the Fermi Golden Rule, and spontaneous emission from emitters in a passive dielectric microstructure is calculated by summing over the emission into each electromagnetic mode of the radiation field. This method is applied to investigate spontaneous emission in a two-dimensional photonic crystal...

  16. Broadband dielectric response of Ba(Zr,Ti)O.sub.3./sub. ceramics: From incipient via relaxor and diffuse up to classical ferroelectric behavior

    Czech Academy of Sciences Publication Activity Database

    Nuzhnyy, Dmitry; Petzelt, Jan; Savinov, Maxim; Ostapchuk, Tetyana; Bovtun, Viktor; Kempa, Martin; Hlinka, Jiří; Buscaglia, V.; Buscaglia, M. T.; Nanni, P.

    2012-01-01

    Roč. 86, č. 1 (2012), "014106-1"-"014106-9" ISSN 1098-0121 R&D Projects: GA ČR GAP204/12/0232 Institutional research plan: CEZ:AV0Z10100520 Keywords : dielectric spectroscopy * soft mode * central mode * diffuse ferroelectric transition * relaxor ferroelectric transition Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.767, year: 2012

  17. Colossal X-Ray-Induced Persistent Photoconductivity in Current-Perpendicular-to-Plane Ferroelectric/Semiconductor Junctions

    KAUST Repository

    Hu, Weijin

    2017-12-07

    Persistent photoconductivity (PPC) is an intriguing physical phenomenon, where electric conduction is retained after the termination of electromagnetic radiation, which makes it appealing for applications in a wide range of optoelectronic devices. So far, PPC has been observed in bulk materials and thin-film structures, where the current flows in the plane, limiting the magnitude of the effect. Here using epitaxial Nb:SrTiO3/Sm0.1Bi0.9FeO3/Pt junctions with a current-perpendicular-to-plane geometry, a colossal X-ray-induced PPC (XPPC) is achieved with a magnitude of six orders. This PPC persists for days with negligible decay. Furthermore, the pristine insulating state could be fully recovered by thermal annealing for a few minutes. Based on the electric transport and microstructure analysis, this colossal XPPC effect is attributed to the X-ray-induced formation and ionization of oxygen vacancies, which drives nonvolatile modification of atomic configurations and results in the reduction of interfacial Schottky barriers. This mechanism differs from the conventional mechanism of photon-enhanced carrier density/mobility in the current-in-plane structures. With their persistent nature, such ferroelectric/semiconductor heterojunctions open a new route toward X-ray sensing and imaging applications.

  18. Nonlinear electroelastic deformations of dielectric elastomer composites: II - Non-Gaussian elastic dielectrics

    Science.gov (United States)

    Lefèvre, Victor; Lopez-Pamies, Oscar

    2017-02-01

    This paper presents an analytical framework to construct approximate homogenization solutions for the macroscopic elastic dielectric response - under finite deformations and finite electric fields - of dielectric elastomer composites with two-phase isotropic particulate microstructures. The central idea consists in employing the homogenization solution derived in Part I of this work for ideal elastic dielectric composites within the context of a nonlinear comparison medium method - this is derived as an extension of the comparison medium method of Lopez-Pamies et al. (2013) in nonlinear elastostatics to the coupled realm of nonlinear electroelastostatics - to generate in turn a corresponding solution for composite materials with non-ideal elastic dielectric constituents. Complementary to this analytical framework, a hybrid finite-element formulation to construct homogenization solutions numerically (in three dimensions) is also presented. The proposed analytical framework is utilized to work out a general approximate homogenization solution for non-Gaussian dielectric elastomers filled with nonlinear elastic dielectric particles that may exhibit polarization saturation. The solution applies to arbitrary (non-percolative) isotropic distributions of filler particles. By construction, it is exact in the limit of small deformations and moderate electric fields. For finite deformations and finite electric fields, its accuracy is demonstrated by means of direct comparisons with finite-element solutions. Aimed at gaining physical insight into the extreme enhancement in electrostriction properties displayed by emerging dielectric elastomer composites, various cases wherein the filler particles are of poly- and mono-disperse sizes and exhibit different types of elastic dielectric behavior are discussed in detail. Contrary to an initial conjecture in the literature, it is found (inter alia) that the isotropic addition of a small volume fraction of stiff (semi

  19. PREFACE: Dielectrics 2009: Measurement Analysis and Applications

    Science.gov (United States)

    Vaughan, Alun; Williams, Graham

    2009-07-01

    2001 the Annual Meetings focused on numerous topics, including relaxation and conduction processes in liquids, solids, liquid crystals, synthetic polymers and biopolymers, piezoelectric materials, electrets and ferroelectrets, interfacial phenomena, high field conduction and breakdown phenomena in solids, liquids and gases and, importantly, the remarkable developments in dielectric instrumentation during this period. These activities reflected the need, and willingness, to move dielectrics researches with the times. As examples of the variety and diversity of these meetings we may refer briefly to the 1981, 1989 and 1996 Meetings. The 1981 Oxford Meeting on High Field Phenomena in Dielectrics included strong themes on fundamental and practical effects of high E-fields on the dielectric and conduction behaviour of liquids and solids, electrical treeing and dielectric breakdown, non-linear dielectric effects, electrets, thin-film devices and electro-rheology. The late 1980's had seen large initiatives in the UK and globally in the general area of Molecular Electronics so, in timely fashion, this was the subject of the 1989 Meeting in Bangor. The 1996 Smart Dielectrics Meeting at Canterbury reported subsequent advances in designer materials having electro-responsive and electro-optical properties. The programme concerned electro- and photo-active materials, mainly organic, in the form of polar dielectrics, polyelectrolytes, organic semi- and photo-conductors, photo-refractive polymer films, organic ferroelectric films, liquid crystalline polymer films, piezo- and pyro-electric polymer films, electroluminescent polymers, electro-rheological fluids and non-linear optical polymer films as described by leading international scientists. The physico-chemical functions of the materials were demonstrated and interpreted in terms of fundamental molecular properties. An Archive, containing full details of all the Meetings of the DDG and the Dielectrics Society, has been placed on

  20. Large anisotropy in colossal magnetoresistance of charge orbital ordered epitaxial Sm0.5Ca0.5MnO3 films

    DEFF Research Database (Denmark)

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

    2009-01-01

    We investigated the structure and magnetotransport properties of Sm0.5Ca0.5MnO3 (SCMO) films epitaxially grown on (011)-oriented SrTiO3 substrates, which exhibited clear charge/orbital ordering transition. A significant anisotropy of ~1000 in the colossal magnetoresistance (CMR) effect was observ...

  1. Mrs. Miniver's Girls: Plucky Girls in "Hidden Figures," "The Zookeeper's Wife," "Their Finest," and "Colossal"

    Science.gov (United States)

    Beck, Bernard

    2017-01-01

    Four recent movies, "Hidden Figures," "The Zookeeper's Wife," "Their Finest," and "Colossal" exemplify a new cultural version of the movie heroine. This version combines feminism with commitment to solving an overwhelming problem. These heroines, thus, display the character virtues of Wonder Woman and Mrs.…

  2. Dielectric and infrared response of Ba.sub.0.77./sub.Ca.sub.0.23./sub.TiO.sub.3./sub..

    Czech Academy of Sciences Publication Activity Database

    Savinov, Maxim; Trepakov, Vladimír; Kamba, Stanislav; Kapphan, S. E.; Petzelt, Jan; Pankrath, R.; Kislova, I. L.; Kutshenko, A. B.; Jastrabík, Lubomír

    2003-01-01

    Roč. 295, - (2003), s. 31-38 ISSN 0015-0193 R&D Projects: GA MŠk LN00A015; GA AV ČR IAA1010213; GA ČR GA202/01/0612 Grant - others:NATO(XX) PST.CLG.977348; NATO(XX) LGPST.CLG.977561 Institutional research plan: CEZ:AV0Z1010914 Keywords : dielectric permittivity * infrared spectroscopy * Ba 1-x Ca x TiO 3 Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.406, year: 2003

  3. Thermal response of Ru electrodes in contact with SiO2 and Hf-based high-k gate dielectrics

    International Nuclear Information System (INIS)

    Wen, H.-C.; Lysaght, P.; Alshareef, H.N.; Huffman, C.; Harris, H.R.; Choi, K.; Senzaki, Y.; Luan, H.; Majhi, P.; Lee, B.H.; Campin, M. J.; Foran, B.; Lian, G.D.; Kwong, D.-L.

    2005-01-01

    A systematic experimental evaluation of the thermal stability of Ru metal gate electrodes in direct contact with SiO 2 and Hf-based dielectric layers was performed and correlated with electrical device measurements. The distinctly different interfacial reactions in the Ru/SiO 2 , Ru/HfO 2 , and Ru/HfSiO x film systems were observed through cross-sectional high-resolution transmission electron microscopy, high angle annular dark field scanning transmission electron microscopy with electron-energy-loss spectra, and energy dispersive x-ray spectra analysis. Ru interacted with SiO 2 , but remained stable on HfO 2 at 1000 deg. C. The onset of Ru/SiO 2 interfacial interactions is identified via silicon substrate pitting possibly from Ru diffusion into the dielectric in samples exposed to a 900 deg. C/10-s anneal. The dependence of capacitor device degradation with decreasing SiO 2 thickness suggests Ru diffuses through SiO 2 , followed by an abrupt, rapid, nonuniform interaction of ruthenium silicide as Ru contacts the Si substrate. Local interdiffusion detected on Ru/HfSiO x samples may be due to phase separation of HfSiO x into HfO 2 grains within a SiO 2 matrix, suggesting that SiO 2 provides a diffusion pathway for Ru. Detailed evidence consistent with a dual reaction mechanism for the Ru/SiO 2 system at 1000 deg. C is presented

  4. Super Dielectric Materials.

    Science.gov (United States)

    Fromille, Samuel; Phillips, Jonathan

    2014-12-22

    Evidence is provided here that a class of materials with dielectric constants greater than 10⁵ at low frequency (dielectric materials (SDM), can be generated readily from common, inexpensive materials. Specifically it is demonstrated that high surface area alumina powders, loaded to the incipient wetness point with a solution of boric acid dissolved in water, have dielectric constants, near 0 Hz, greater than 4 × 10⁸ in all cases, a remarkable increase over the best dielectric constants previously measured for energy storage capabilities, ca. 1 × 10⁴. It is postulated that any porous, electrically insulating material (e.g., high surface area powders of silica, titania, etc. ), filled with a liquid containing a high concentration of ionic species will potentially be an SDM. Capacitors created with the first generated SDM dielectrics (alumina with boric acid solution), herein called New Paradigm Super (NPS) capacitors display typical electrostatic capacitive behavior, such as increasing capacitance with decreasing thickness, and can be cycled, but are limited to a maximum effective operating voltage of about 0.8 V. A simple theory is presented: Water containing relatively high concentrations of dissolved ions saturates all, or virtually all, the pores (average diameter 500 Å) of the alumina. In an applied field the positive ionic species migrate to the cathode end, and the negative ions to the anode end of each drop. This creates giant dipoles with high charge, hence leading to high dielectric constant behavior. At about 0.8 V, water begins to break down, creating enough ionic species to "short" the individual water droplets. Potentially NPS capacitor stacks can surpass "supercapacitors" in volumetric energy density.

  5. Super Dielectric Materials

    Directory of Open Access Journals (Sweden)

    Samuel Fromille

    2014-12-01

    Full Text Available Evidence is provided here that a class of materials with dielectric constants greater than 105 at low frequency (<10−2 Hz, herein called super dielectric materials (SDM, can be generated readily from common, inexpensive materials. Specifically it is demonstrated that high surface area alumina powders, loaded to the incipient wetness point with a solution of boric acid dissolved in water, have dielectric constants, near 0 Hz, greater than 4 × 108 in all cases, a remarkable increase over the best dielectric constants previously measured for energy storage capabilities, ca. 1 × 104. It is postulated that any porous, electrically insulating material (e.g., high surface area powders of silica, titania, etc., filled with a liquid containing a high concentration of ionic species will potentially be an SDM. Capacitors created with the first generated SDM dielectrics (alumina with boric acid solution, herein called New Paradigm Super (NPS capacitors display typical electrostatic capacitive behavior, such as increasing capacitance with decreasing thickness, and can be cycled, but are limited to a maximum effective operating voltage of about 0.8 V. A simple theory is presented: Water containing relatively high concentrations of dissolved ions saturates all, or virtually all, the pores (average diameter 500 Å of the alumina. In an applied field the positive ionic species migrate to the cathode end, and the negative ions to the anode end of each drop. This creates giant dipoles with high charge, hence leading to high dielectric constant behavior. At about 0.8 V, water begins to break down, creating enough ionic species to “short” the individual water droplets. Potentially NPS capacitor stacks can surpass “supercapacitors” in volumetric energy density.

  6. Thermally switchable dielectrics

    Science.gov (United States)

    Dirk, Shawn M.; Johnson, Ross S.

    2013-04-30

    Precursor polymers to conjugated polymers, such as poly(phenylene vinylene), poly(poly(thiophene vinylene), poly(aniline vinylene), and poly(pyrrole vinylene), can be used as thermally switchable capacitor dielectrics that fail at a specific temperature due to the non-conjugated precursor polymer irreversibly switching from an insulator to the conjugated polymer, which serves as a bleed resistor. The precursor polymer is a good dielectric until it reaches a specific temperature determined by the stability of the leaving groups. Conjugation of the polymer backbone at high temperature effectively disables the capacitor, providing a `built-in` safety mechanism for electronic devices.

  7. On dielectric breakdown statistics

    International Nuclear Information System (INIS)

    Tuncer, Enis; James, D Randy; Sauers, Isidor; Ellis, Alvin R; Pace, Marshall O

    2006-01-01

    In this paper, we investigate the dielectric breakdown data of some insulating materials and focus on the applicability of the two- and three-parameter Weibull distributions. A new distribution function is also proposed. In order to assess the model distribution's trustworthiness, we employ the Monte Carlo technique and, randomly selecting data-subsets from the whole dielectric breakdown data, determine whether the selected probability functions accurately describe the breakdown data. The utility and strength of the proposed expression are illustrated distinctly by the numerical procedure. The proposed expression is shown to be a valuable alternative to the Weibull ones

  8. Colossal enhancement in thermoelectric effect in a laterally coupled double-quantum-dot chain by the Coulomb interactions

    International Nuclear Information System (INIS)

    Xiong, Lun; Yi, Lin

    2014-01-01

    Thermoelectric effects, including Seebeck coefficient (S), thermal conductance (κ), and figure of merit (ZT), in a laterally coupled double-quantum-dot (DQD) chain with two external nonmagnetic contacts are investigated theoretically by the nonequilibrium Green's function formalism. In this system, the DQD chain between two contacts forms a main channel for thermal electrons transporting, and each QD in the main chain couples laterally to a dangling one. The numerical calculations show that the Coulomb interactions not only lead to the splitting of the asymmetrical double-peak structure of the Seebeck coefficient, but also make the thermal spectrum show a strong violation of the Wiedemann–Franz law, leading to a colossal enhancement in ZT. These results indicate that the coupled DQD chain has potential applications in the thermoelectric devices with high thermal efficiency.

  9. Surface characterization of colossal magnetoresistive manganites La1-xSr xMnO3 using photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Mannella, N.; Rosenhahn, A.; Nambu, A.; Sell, B.C.; Mun, B.S.; Yang, S.-H.; Marchesini, S.; Watanabe, M.; Ibrahim, K.; Ritchey, S.B.; Tomioka, Y.; Fadley, C.S.

    2006-01-01

    We have studied the temperature and time dependence of Surface chemical composition and atomic structure of in situ fractured colossal magnetoresistive perovskites La 1-x Sr x MnO (x = 0.3, 0.4) using core-level photoelectron spectroscopy and diffraction, simultaneous with observing marked changes in both core and valence electronic structure on going above the Curie temperature [N. Mannella et al., Phys. Rev. Lett. 92 (2004) 166401]. Stoichiometric analyses via core-level intensity ratios show that the near-surface composition is very nearly the same as that of the nominal (bulk) stoichiometry and further show that, during duration of our experiments, the degree of surface stoichiometry alteration or contamination has been minimal. The effects of photoelectron diffraction on such analyses are also explored. We comment on the degree to which near-surface composition or atomic-structure alterations might influence spectroscopic investigations of these manganites, or other strongly correlated materials

  10. Millimeter wave and terahertz dielectric properties of biological materials

    Science.gov (United States)

    Khan, Usman Ansar

    Broadband dielectric properties of materials can be employed to identify, detect, and characterize materials through their unique spectral signatures. In this study, millimeter wave, submillimeter wave, and terahertz dielectric properties of biological substances inclusive of liquids, solids, and powders were obtained using Dispersive Fourier Transform Spectroscopy (DFTS). Two broadband polarizing interferometers were constructed to test materials from 60 GHz to 1.2 THz. This is an extremely difficult portion of the frequency spectrum to obtain a material's dielectric properties since neither optical nor microwave-based techniques provide accurate data. The dielectric characteristics of liquids such as cyclohexane, chlorobenzene, benzene, ethanol, methanol, 1,4 dioxane, and 10% formalin were obtained using the liquid interferometer. Subsequently the solid interferometer was utilized to determine the dielectric properties of human breast tissues, which are fixed and preserved in 10% formalin. This joint collaboration with the Tufts New England Medical Center demonstrated a significant difference between the dielectric response of tumorous and non-tumorous breast tissues across the spectrum. Powders such as anthrax, flour, talc, corn starch, dry milk, and baking soda have been involved in a number of security threats and false alarms around the globe in the last decade. To be able to differentiate hoax attacks and serious security threats, the dielectric properties of common household powders were also examined using the solid interferometer to identify the powders' unique resonance peaks. A new sample preparation kit was designed to test the powder specimens. It was anticipated that millimeter wave and terahertz dielectric characterization will enable one to clearly distinguish one powder from the other; however most of the powders had relatively close dielectric responses and only Talc had a resonance signature recorded at 1.135 THz. Furthermore, due to

  11. Ionic Structure at Dielectric Interfaces

    Science.gov (United States)

    Jing, Yufei

    The behavior of ions in liquids confined between macromolecules determines the outcome of many nanoscale assembly processes in synthetic and biological materials such as colloidal dispersions, emulsions, hydrogels, DNA, cell membranes, and proteins. Theoretically, the macromolecule-liquid boundary is often modeled as a dielectric interface and an important quantity of interest is the ionic structure in a liquid confined between two such interfaces. The knowledge gleaned from the study of ionic structure in such models can be useful in several industrial applications, such as biosensors, lithium-ion batteries double-layer supercapacitors for energy storage and seawater desalination. Electrostatics plays a critical role in the development of such functional materials. Many of the functions of these materials, result from charge and composition heterogeneities. There are great challenges in solving electrostatics problems in heterogeneous media with arbitrary shapes because electrostatic interactions remains unknown but depend on the particular density of charge distributions. Charged molecules in heterogeneous media affect the media's dielectric response and hence the interaction between the charges is unknown since it depends on the media and on the geometrical properties of the interfaces. To determine the properties of heterogeneous systems including crucial effects neglected in classical mean field models such as the hard core of the ions, the dielectric mismatch and interfaces with arbitrary shapes. The effect of hard core interactions accounts properly for short range interactions and the effect of local dielectric heterogeneities in the presence of ions and/or charged molecules for long-range interactions are both analyzed via an energy variational principle that enables to update charges and the medium's response in the same simulation time step. In particular, we compute the ionic structure in a model system of electrolyte confined by two planar dielectric

  12. Magnetically tunable dielectric, impedance and magnetoelectric response in MnFe{sub 2}O{sub 4}/(Pb{sub 1−x}Sr{sub x})TiO{sub 3} composites thin films

    Energy Technology Data Exchange (ETDEWEB)

    Bala, Kanchan, E-mail: bala.kanchan1987@gmail.com [Department of Physics, Himachal Pradesh University, Shimla 171005 (India); Kotnala, R.K. [CSIR, National Physical Laboratory, Dr. K.S. Krishnan Road, New Delhi 110012 (India); Negi, N.S., E-mail: nsn_phy_hpu@yahoo.com [Department of Physics, Himachal Pradesh University, Shimla 171005 (India)

    2017-02-15

    We have synthesized piezomagnetic–piezoelectric composites thin films MnFe{sub 2}O{sub 4}/(Pb{sub 1−x}Sr{sub x})TiO{sub 3}, where x=0.1, 0.2, and 0.3, using the metalorganic deposition (MOD) reaction method. The structural and microstructural analysis using the X-ray diffraction (XRD), AFM, and SEM reveals the presence of homogenous growth of both pervoskite and spinel phases in the composite films. Our results show that all the composites films exhibit good multiferroic as well as considerable magnetoelectric coupling. The impedance (Z′ and Z″) and electrical modulus (M′ and M″) Nyquist plots show distinct electrical responses with the magnetic field. Our analyses suggest that this electrical response arises due to the coexistence of the high resistive phase and the comparatively conductive phase in the MFO/PST composite films. The maximum magnetoelectric coefficient (α) is found to be 4.29 V Oe{sup −1} cm{sup −1} and 2.82 V Oe{sup −1} cm{sup −1} for compositions x=0.1 and 0.2. These values are substantially larger than those reported for bilayer composites thin films in literature and make them interesting for room temperature device applications. - Highlights: • Influence of Sr doping on multiferroic and magnetoelectric properties composites thin films of MnFe{sub 2}O{sub 4} and (Pb, Sr)TiO{sub 3}. • Dielectric constant and dielectric loss with application of magnetic field. • Magnetically tunable AC electrical properties. • Magnetoelectric coupling in MnFe{sub 2}O{sub 4}/(Pb, Sr)TiO{sub 3} composite films by passive method.

  13. Dielectric response of the relaxor ferroelectric Pb(Mg1/3Nb2/3)O3 in the nonergodic state after a DC electric field is turned off

    International Nuclear Information System (INIS)

    Kolpakova, N. N.; Czarnecki, P.

    2006-01-01

    The Pb(Mg 1/3 Nb 2/3 )O 3 (PMN) relaxor system is used as an example to analyze the temperature dependences of the low-frequency dielectric permitivity (ε'(T)) measured during zero-field heating (ZFH) from T = 10 K to T = 300 K after using different field cooling (FC) conditions. No changes in the temperature dependences of the permittivity have been detected during the transition from a nonergodic relaxor state (NERS) into an ergodic relaxor state (ERS) (at T f ∼ 216 K). However, the difference Δε'(T) between the curves corresponding to different field cooling conditions in the same electric field has different shapes and different values below and above T → (T f + 9 K) - (for E dc = 1.52 kV/cm). The reduced permittivities ε' r (T, f) recorded under different cooling conditions are shown to change their behavior when passing through T = T f + 9 K. In NERS, these curves diverge: the stronger the field (0 ≤ E dc ≤ 3 kV/cm), the larger the divergence. In ERS, however, the ε' r (T, f) curves coincide under different cooling conditions irrespective of the field. The character of the changes in Δε'(T) and ε' r (T, f) during the NERS-ERS transition is frequency-independent. The difference in the behavior of the dielectric response during ZFH after cooling in different (ZFC, FC) modes (even in a weak field), for both transition through T f and cooling down to T = 10 K, indicates different NERSs forming under these conditions. The contribution to ε'(T) from slowly relaxing regions (ω ∼ 0.1 mHz), whose polarization is reoriented after the field is turned off, is responsible for the fact that, during the NERS-ERS transition, the ε' r (T, f) curves coincide at a temperature that is higher than T = T f

  14. Toward superlensing with metal-dielectric composites and multilayers

    DEFF Research Database (Denmark)

    Nielsen, Rasmus Bundgaard; Thoreson, M.D.; Chen, W.

    2010-01-01

    We report on the fabrication of two types of adjustable, near-field superlens designs: metal–dielectric composites and metal–dielectric multilayer films. We fabricated a variety of films with different materials, thicknesses and compositions. These samples were characterized physically...... and optically to determine their film composition, quality, and optical responses. Our results on metal–dielectric composites indicate that although the real part of the effective permittivity generally follows effective medium theory predictions, the imaginary part does not and substantially higher losses...

  15. Dielectric loss of strontium titanate thin films

    Science.gov (United States)

    Dalberth, Mark Joseph

    1999-12-01

    Interest in strontium titanate (STO) thin films for microwave device applications continues to grow, fueled by the telecommunications industry's interest in phase shifters and tunable filters. The optimization of these devices depends upon increasing the phase or frequency tuning and decreasing the losses in the films. Currently, the dielectric response of thin film STO is poorly understood through lack of data and a theory to describe it. We have studied the growth of STO using pulsed laser deposition and single crystal substrates like lanthanum aluminate and neodymium gallate. We have researched ways to use ring resonators to accurately measure the dielectric response as a function of temperature, electric field, and frequency from low radio frequencies to a few gigahertz. Our films grown on lanthanum aluminate show marked frequency dispersion in the real part of the dielectric constant and hints of thermally activated loss behavior. We also found that films grown with conditions that optimized the dielectric constant showed increased losses. In an attempt to simplify the system, we developed a technique called epitaxial lift off, which has allowed us to study films removed from their growth substrates. These free standing films have low losses and show obvious thermally activated behavior. The "amount of tuning," as measured by a figure of merit, KE, is greater in these films than in the films still attached to their growth substrates. We have developed a theory that describes the real and imaginary parts of the dielectric constant. The theory models the real part using a mean field description of the ionic motion in the crystal and includes the loss by incorporating the motion of charged defects in the films.

  16. Center for dielectric studies

    Science.gov (United States)

    Cross, L. E.; Newnham, R. E.; Biggers, J. V.

    1984-05-01

    This report focuses upon the parts of the Center program which have drawn most extensively upon Navy funds. In the basic study of polarization processes in high K dielectrics, major progress has been made in understanding the mechanisms in relaxor ferroelectric in the perovskite structure families. A new effort is also being mounted to obtain more precise evaluation of the internal stress effects in fine grained barium titanate. Related to reliability, studies of the effects of induced macro-defects are described, and preparation for the evaluation of space charge by internal potential distribution measurements discussed. To develop new processing methods for very thin dielectric layers, a new type of single barrier layer multilayer is discussed, and work on the thermal evaporation of oriented crystalline antimony sulphur iodide describe.

  17. Dielectric properties of polyethylene

    International Nuclear Information System (INIS)

    Darwish, S.; Riad, A.S.; El-Shabasy, M.

    2005-01-01

    The temperature dependence of dielectric properties in polyethylene was measured in the frequency range from 10 to 105 Hz. The frequency dependence of the complex impedance in the complex plane could be fitted by semicircles. The system could be represented by an equivalent circuit of a bulk resistance in series with parallel surface resistance-capacitance combination. The relaxation time, has been evaluated from experimental results. Results reveal that the temperature dependence, is a thermally activated process

  18. Dielectric Wakefield Researches

    International Nuclear Information System (INIS)

    Kiselev, V.A.; Linnik, A.F.; Onishchenko, N.I.; Uskov, V.V.; Marshall, T.C.

    2006-01-01

    Excitation of wakefield in cylindrical dielectric waveguide/resonator by a sequence of relativistic electron bunches was investigated using an electron linac 'Almaz-2' (4.5 MeV, 6·10 3 bunches of duration 60 ps and charge 0.32 nC each). Energy spectrum of electrons, radial topography and longitudinal distribution of wakefield, and total energy of excited wakefield were measured by means of magnetic analyzer, high frequency probe, and a sensitive calorimeter

  19. Dielectric lattice gauge theory

    International Nuclear Information System (INIS)

    Mack, G.

    1983-06-01

    Dielectric lattice gauge theory models are introduced. They involve variables PHI(b)epsilong that are attached to the links b = (x+esub(μ),x) of the lattice and take their values in the linear space g which consists of real linear combinations of matrices in the gauge group G. The polar decomposition PHI(b)=U(b)osub(μ)(x) specifies an ordinary lattice gauge field U(b) and a kind of dielectric field epsilonsub(ij)proportionalosub(i)osub(j)sup(*)deltasub(ij). A gauge invariant positive semidefinite kinetic term for the PHI-field is found, and it is shown how to incorporate Wilson fermions in a way which preserves Osterwalder Schrader positivity. Theories with G = SU(2) and without matter fields are studied in some detail. It is proved that confinement holds, in the sense that Wilson loop expectation values show an area law decay, if the Euclidean action has certain qualitative features which imply that PHI = 0 (i.e. dielectric field identical 0) is the unique maximum of the action. (orig.)

  20. Dielectric lattice gauge theory

    International Nuclear Information System (INIS)

    Mack, G.

    1984-01-01

    Dielectric lattice gauge theory models are introduced. They involve variables PHI(b)element ofG that are attached to the links b = (x+esub(μ), x) of the lattice and take their values in the linear space G which consists of real linear combinations of matrices in the gauge group G. The polar decomposition PHI(b)=U(b)sigmasub(μ)(x) specifies an ordinary lattice gauge field U(b) and a kind of dielectric field epsilonsub(ij)proportional sigmasub(i)sigmasub(j)sup(*)deltasub(ij). A gauge invariant positive semidefinite kinetic term for the PHI-field is found, and it is shown how to incorporate Wilson fermions in a way which preserves Osterwalder-Schrader positivity. Theories with G = SU(2) and without matter fields are studied in some detail. It is proved that confinement holds, in the sense that Wilson-loop expectation values show an area law decay, if the euclidean action has certain qualitative features which imply that PHI=0 (i.e. dielectric field identical 0) is the unique maximum of the action. (orig.)

  1. Dielectric Behavior of Low Microwave Loss Unit Cell for All Dielectric Metamaterial

    Directory of Open Access Journals (Sweden)

    Tianhuan Luo

    2015-01-01

    Full Text Available With a deep study of the metamaterial, its unit cells have been widely extended from metals to dielectrics. The dielectric based unit cells attract much attention because of the advantage of easy preparation, tunability, and higher frequency response, and so forth. Using the conventional solid state method, we prepared a kind of incipient ferroelectrics (calcium titanate, CaTiO3 with higher microwave permittivity and lower loss, which can be successfully used to construct metamaterials. The temperature and frequency dependence of dielectric constant are also measured under different sintering temperatures. The dielectric spectra showed a slight permittivity decrease with the increase of temperature and exhibited a loss of 0.0005, combined with a higher microwave dielectric constant of ~167 and quality factor Q of 2049. Therefore, CaTiO3 is a kind of versatile and potential metamaterial unit cell. The permittivity of CaTiO3 at higher microwave frequency was also examined in the rectangular waveguide and we got the permittivity of 165, creating a new method to test permittivity at higher microwave frequency.

  2. 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.

  3. Dielectric properties of lunar surface

    Science.gov (United States)

    Yushkova, O. V.; Kibardina, I. N.

    2017-03-01

    Measurements of the dielectric characteristics of lunar soil samples are analyzed in the context of dielectric theory. It has been shown that the real component of the dielectric permittivity and the loss tangent of rocks greatly depend on the frequency of the interacting electromagnetic field and the soil temperature. It follows from the analysis that one should take into account diurnal variations in the lunar surface temperature when interpreting the radar-sounding results, especially for the gigahertz radio range.

  4. Phonons and colossal thermal expansion behavior of Ag3Co(CN)6 and Ag3Fe(CN)6.

    Science.gov (United States)

    Mittal, R; Zbiri, M; Schober, H; Achary, S N; Tyagi, A K; Chaplot, S L

    2012-12-19

    Recently colossal volume thermal expansion has been observed in the framework compounds Ag(3)Co(CN)(6) and Ag(3)Fe(CN)(6). We have measured phonon spectra using neutron time-of-flight spectroscopy as a function of temperature and pressure. Ab initio calculations were carried out for the sake of analysis and interpretation. Bonding is found to be very similar in the two compounds. At ambient pressure, modes in the intermediate frequency part of the vibrational spectra in the Co compound are shifted slightly to higher energies as compared to the Fe compound. The temperature dependence of the phonon spectra gives evidence for a large explicit anharmonic contribution to the total anharmonicity for low-energy modes below 5 meV. We have found that modes are mainly affected by the change in size of the unit cell, which in turn changes the bond lengths and vibrational frequencies. Thermal expansion has been calculated via the volume dependence of phonon spectra. Our analysis indicates that Ag phonon modes within the energy range 2-5 meV are strongly anharmonic and major contributors to thermal expansion in both systems. The application of pressure hardens the low-energy part of the phonon spectra involving Ag vibrations and confirms the highly anharmonic nature of these modes.

  5. Fermi surfaces, spin-mixing parameter, and colossal anisotropy of spin relaxation in transition metals from ab initio theory

    Science.gov (United States)

    Zimmermann, Bernd; Mavropoulos, Phivos; Long, Nguyen H.; Gerhorst, Christian-Roman; Blügel, Stefan; Mokrousov, Yuriy

    2016-04-01

    The Fermi surfaces and Elliott-Yafet spin-mixing parameter (EYP) of several elemental metals are studied by ab initio calculations. We focus first on the anisotropy of the EYP as a function of the direction of the spin-quantization axis [B. Zimmermann et al., Phys. Rev. Lett. 109, 236603 (2012), 10.1103/PhysRevLett.109.236603]. We analyze in detail the origin of the gigantic anisotropy in 5 d hcp metals as compared to 5 d cubic metals by band structure calculations and discuss the stability of our results against an applied magnetic field. We further present calculations of light (4 d and 3 d ) hcp crystals, where we find a huge increase of the EYP anisotropy, reaching colossal values as large as 6000 % in hcp Ti. We attribute these findings to the reduced strength of spin-orbit coupling, which promotes the anisotropic spin-flip hot loops at the Fermi surface. In order to conduct these investigations, we developed an adapted tetrahedron-based method for the precise calculation of Fermi surfaces of complicated shape and accurate Fermi-surface integrals within the full-potential relativistic Korringa-Kohn-Rostoker Green function method.

  6. Colossal elastoresistance, electroresistance and magnetoresistance in Pr0.5Sr0.5MnO3 thin films

    Science.gov (United States)

    Chen, Liping; Guo, Xuexiang; Gao, J.

    2016-05-01

    Pr0.5Sr0.5MnO3 thin films on substrates of (001)-oriented LaAlO3 were epitaxially grown by pulsed laser deposition. It was found that a substrate-induced strain of 1.3% brings a great resistivity change of 98% at 25 K. We studied the dependence of resistivity on the applied electric current and magnetic field. In the greatly strained films of 60 nm thickness the electroresistance ER=[ρ(I1 μA)-ρ(I1000 μA)]/ρ(I1 μA) reaches 70% at T=25 K, much higher than ER 7% in the strain-relaxed films of 400 nm thickness, implying the strain effect on ER. Also the magnetoresistance of the film falls with strain-relaxation. Therefore the electric properties of the film could be efficiently modified by strain, electric current and magnetic field. All of them may be explained by the effect on the percolative phase separation and competition in the half-doped manganite material. The manganite films located at phase boundary are expected to be an ideal compound for providing practical colossal effects of elastoresistance, electroresistance and magnetoresistance due to the multiphase coexistence.

  7. Boron nitride as two dimensional dielectric: Reliability and dielectric breakdown

    Energy Technology Data Exchange (ETDEWEB)

    Ji, Yanfeng; Pan, Chengbin; Hui, Fei; Shi, Yuanyuan; Lanza, Mario, E-mail: mlanza@suda.edu.cn [Institute of Functional Nano and Soft Materials, Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, 199 Ren-Ai Road, Suzhou 215123 (China); Zhang, Meiyun; Long, Shibing [Key Laboratory of Microelectronics Devices & Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029 (China); Lian, Xiaojuan; Miao, Feng [National Laboratory of Solid State Microstructures, School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China); Larcher, Luca [DISMI, Università di Modena e Reggio Emilia, 42122 Reggio Emilia (Italy); Wu, Ernest [IBM Research Division, Essex Junction, Vermont 05452 (United States)

    2016-01-04

    Boron Nitride (BN) is a two dimensional insulator with excellent chemical, thermal, mechanical, and optical properties, which make it especially attractive for logic device applications. Nevertheless, its insulating properties and reliability as a dielectric material have never been analyzed in-depth. Here, we present the first thorough characterization of BN as dielectric film using nanoscale and device level experiments complementing with theoretical study. Our results reveal that BN is extremely stable against voltage stress, and it does not show the reliability problems related to conventional dielectrics like HfO{sub 2}, such as charge trapping and detrapping, stress induced leakage current, and untimely dielectric breakdown. Moreover, we observe a unique layer-by-layer dielectric breakdown, both at the nanoscale and device level. These findings may be of interest for many materials scientists and could open a new pathway towards two dimensional logic device applications.

  8. Dielectric Properties Of Nanoferrites

    International Nuclear Information System (INIS)

    Jankov, Stevan B.; Cvejic, Zeljka N.; Rakic, Srdjan; Srdic, Vladimir

    2007-01-01

    Dielectric properties: permittivity, loss factor, tan delta and ionic conductivity of nanostructured ferrites have been measured. Samples used were nickel, zinc and yttrium doped ferrites mixed in various ratios. The synthesis has been performed using precipitation method and obtained powders were pressed in pellets under varying pressure. X-ray diffractography approach for the refinement of structure and microstructural analysis has been performed. All parameters have been measured in 1 Hz to 100 kHz frequency range and 30 deg. C to 80 deg. C temperature range. Significant improvements in permittivity, loss factor and ionic conductivity comparing to bulk samples have been observed

  9. Dielectric materials and electrostatics

    CERN Document Server

    Gallot-Lavalle, Olivier

    2013-01-01

    An introduction to the physics of electrical insulation, this book presents the physical foundations of this discipline and the resulting applications. It is structured in two parts. The first part presents a mathematical and intuitive approach to dielectrics; various concepts, including polarization, induction, forces and losses are discussed. The second part provides readers with the keys to understanding the physics of solid, liquid and gas insulation. It comprises a phenomenological description of discharges in gas and its resulting applications. Finally, the main electrical properties

  10. The Dielectric Behavior of Cyano-Substituted Poly imides

    International Nuclear Information System (INIS)

    Elshazly, E.S.; Abdelrahman, A.A.M.; Elmasry, M.A.A.

    2013-01-01

    A number of amorphous poly imides containing polar functional groups, cyano group, have been synthesized and investigated for potential use as high temperature piezoelectric sensors. The piezoelectric constants are related to the polarization. The remanent polarization and hence piezoelectric response of a material is determined by dielectric relaxation strength which is the difference in dielectric constant at the glass transition temperature vicinity. The intent of this work is to clarify the mechanism and key components required for developing piezoelectricity in amorphous polymers and further to apply this understanding in designing a unique high temperature piezoelectric polyimide. In this paper, experimental investigations of dielectric constant of piezoelectric cyano -substituted poly imides have been tested as a function of temperature to measure the dielectric relaxation strength in the glass transition temperature region.

  11. Functional silicone copolymers and elastomers with high dielectric permittivity

    DEFF Research Database (Denmark)

    Madsen, Frederikke Bahrt; Daugaard, Anders Egede; Hvilsted, Søren

    Dielectric elastomers (DEs) are a new and promising transducer technology and are often referred to as ‘artificial muscles’, due to their ability to undergo large deformations when stimulated by electric fields. DEs consist of a soft and thin elastomeric film sandwiched between compliant electrodes......, thereby forming a capacitor [1]. Silicone elastomers are one of the most used materials for DEs due to their high efficiency, fast response times and low viscous losses. The major disadvantage of silicone elastomers is that they possess relatively low dielectric permittivity, which means that a high...... electrical field is necessary to operate the DE. The necessary electrical field can be lowered by creating silicone elastomers with higher dielectric permittivity, i.e. with a higher energy density.The aim of this work is to create new and improved silicone elastomers with high dielectric permittivity...

  12. Discharge ignition near a dielectric

    NARCIS (Netherlands)

    Sobota, A.; Veldhuizen, van E.M.; Stoffels, W.W.

    2008-01-01

    Electrical breakdown in noble gas near a dielectric is an important issue in lighting industry. In order to investigate the influence of the dielectric on the ignition process, we perform measurements in argon, with pressure varying from 0.1 to 1 bar, using a pin–pin electrode geometry. Here, we

  13. Generalized dielectric permittivity tensor

    International Nuclear Information System (INIS)

    Borzdov, G.N.; Barkovskii, L.M.; Fedorov, F.I.

    1986-01-01

    The authors deal with the question of what is to be done with the formalism of the electrodynamics of dispersive media based on the introduction of dielectric-permittivity tensors for purely harmonic fields when Voigt waves and waves of more general form exist. An attempt is made to broaden and generalize the formalism to take into account dispersion of waves of the given type. In dispersive media, the polarization, magnetization, and conduction current-density vectors of point and time are determined by the values of the electromagnetic field vectors in the vicinity of this point (spatial dispersion) in the preceding instants of time (time dispersion). The dielectric-permittivity tensor and other tensors of electrodynamic parameters of the medium are introduced in terms of a set of evolution operators and not the set of harmonic function. It is noted that a magnetic-permeability tensor and an elastic-modulus tensor may be introduced for an acoustic field in dispersive anisotropic media with coupling equations of general form

  14. Influence of Conductivity and Dielectric Constant of Water–Dioxane Mixtures on the Electrical Response of SiNW-Based FETs

    NARCIS (Netherlands)

    Mescher, M.; Brinkman, A.G.M.; Bosma, D.; Klootwijk, J.H.; Sudhölter, E.J.R.; De Smet, L.C.P.M.

    2014-01-01

    In this study, we report on the electrical response of top-down, p-type silicon nanowire field-effect transistors exposed to water and mixtures of water and dioxane. First, the capacitive coupling of the back gate and the liquid gate via an Ag/AgCl electrode were compared in water. It was found that

  15. Plasmonic and Dielectric Metasurfaces: Design, Fabrication and Applications

    Directory of Open Access Journals (Sweden)

    Jian Wang

    2016-09-01

    Full Text Available Two-dimensional metasurfaces are widely focused on for their ability for flexible light manipulation (phase, amplitude, polarization over sub-wavelength propagation distances. Most of the metasurfaces can be divided into two categories by the material type of unit structure, i.e., plasmonic metasurfaces and dielectric metasurfaces. For plasmonic metasurfaces, they are made on the basis of metallic meta-atoms whose optical responses are driven by the plasmon resonances supported by metallic particles. For dielectric metasurfaces, the unit structure is constructed with high refractive index dielectric resonators, such as silicon, germanium or tellurium, which can support electric and magnetic dipole responses based on Mie resonances. The responses of plasmonic and dielectric metasurfaces are all relevant to the characteristics of unit structure, such as dimensions and materials. One can manipulate the electromagnetic field of light wave scattered by the metasurfaces through designing the dimension parameters of each unit structure in the metasurfaces. In this review article, we give a brief overview of our recent progress in plasmonic and dielectric metasurface-assisted nanophotonic devices and their design, fabrication and applications, including the metasurface-based broadband and the selective generation of orbital angular momentum (OAM carrying vector beams, N-fold OAM multicasting using a V-shaped antenna array, a metasurface on conventional optical fiber facet for linearly-polarized mode (LP11 generation, graphene split-ring metasurface-assisted terahertz coherent perfect absorption, OAM beam generation using a nanophotonic dielectric metasurface array, as well as Bessel beam generation and OAM multicasting using a dielectric metasurface array. It is believed that metasurface-based nanophotonic devices are one of the devices with the most potential applied in various fields, such as beam steering, spatial light modulator, nanoscale

  16. Colossal elastoresistance, electroresistance and magnetoresistance in Pr{sub 0.5}Sr{sub 0.5}MnO{sub 3} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Liping, E-mail: chenliping0003@163.com [Department of Physics, Zhejiang Normal University, Jinhua 321004 (China); Department of Physics, Hong Kong University, Hong Kong (China); Guo, Xuexiang [Department of Physics, Zhejiang Normal University, Jinhua 321004 (China); Gao, J. [Department of Physics, Hong Kong University, Hong Kong (China)

    2016-05-01

    Pr{sub 0.5}Sr{sub 0.5}MnO{sub 3} thin films on substrates of (001)-oriented LaAlO{sub 3} were epitaxially grown by pulsed laser deposition. It was found that a substrate-induced strain of ~1.3% brings a great resistivity change of ~98% at 25 K. We studied the dependence of resistivity on the applied electric current and magnetic field. In the greatly strained films of 60 nm thickness the electroresistance ER=[ρ(I{sub 1} {sub μA})−ρ(I{sub 1000} {sub μA})]/ρ(I{sub 1} {sub μA}) reaches ~70% at T=25 K, much higher than ER~7% in the strain-relaxed films of 400 nm thickness, implying the strain effect on ER. Also the magnetoresistance of the film falls with strain-relaxation. Therefore the electric properties of the film could be efficiently modified by strain, electric current and magnetic field. All of them may be explained by the effect on the percolative phase separation and competition in the half-doped manganite material. The manganite films located at phase boundary are expected to be an ideal compound for providing practical colossal effects of elastoresistance, electroresistance and magnetoresistance due to the multiphase coexistence. - Highlights: • The electric current-induced electroresistance (ER) and magnetoresistance (MR)studies on PLD grown Pr{sub 0.5}Sr{sub 0.5}MnO{sub 3}/(001) LaAlO{sub 3} films were found to be greatly sensitive to the film thickness arising from the strain. • It is shown that, 60 nm film exhibit compressive in-plane strain which leads to phase separation and hence colossal MR and ER. • Our results suggest that the manganites located at phase boundary may be an ideal compound for providing practical colossal effects of elastoresistance, electroresistance and magnetoresistance.

  17. Laser amplification in excited dielectrics

    DEFF Research Database (Denmark)

    Winkler, Thomas; Haahr-Lillevang, Lasse; Sarpe, Cristian

    2018-01-01

    Wide-bandgap dielectrics such as glasses or water are transparent at visible and infrared wavelengths. This changes when they are exposed to ultrashort and highly intense laser pulses. Different interaction mechanisms lead to the appearance of various transient nonlinear optical phenomena. Using...... these, the optical properties of dielectrics can be controlled from the transparent to the metal-like state. Here we expand this range by a yet unexplored mechanism in excited dielectrics: amplification. In a two-colour pump-probe experiment, we show that a 400nm femtosecond laser pulse is coherently...

  18. Intrinsic colossal magnetoresistance effect in thin-film Pr0.5Sr0.5MnO3 through dimensionality switching.

    Science.gov (United States)

    Uozu, Y; Wakabayashi, Y; Ogimoto, Y; Takubo, N; Tamaru, H; Nagaosa, N; Miyano, K

    2006-07-21

    A homogeneous colossal magnetoresistance (CMR) effect at low temperatures has been found in a thin-film perovskite manganite Pr0.5Sr0.5MnO3. The transition is driven not by the spin alignment as in usual CMR in bulk samples but by the localization-delocalization transition switched by the change in the effective dimensionality. Two-dimensional (x2-y2)-orbital ordering enhanced by the substrate strain is essential for the stabilization of the insulating localized state, which is on the verge of the first-order transition to the three-dimensional metallic ferromangetic state.

  19. The 'emergent scaling' phenomenon and the dielectric properties of random resistor-capacitor networks

    CERN Document Server

    Bouamrane, R

    2003-01-01

    An efficient algorithm, based on the Frank-Lobb reduction scheme, for calculating the equivalent dielectric properties of very large random resistor-capacitor (R-C) networks has been developed. It has been used to investigate the network size and composition dependence of dielectric properties and their statistical variability. The dielectric properties of 256 samples of random networks containing: 512, 2048, 8192 and 32 768 components distributed randomly in the ratios 60% R-40% C, 50% R-50% C and 40% R-60% C have been computed. It has been found that these properties exhibit the anomalous power law dependences on frequency known as the 'universal dielectric response' (UDR). Attention is drawn to the contrast between frequency ranges across which percolation determines dielectric response, where considerable variability is found amongst the samples, and those across which power laws define response where very little variability is found between samples. It is concluded that the power law UDRs are emergent pr...

  20. Magnetorefractive effect in manganites with a colossal magnetoresistance in the visible spectral region

    Energy Technology Data Exchange (ETDEWEB)

    Sukhorukov, Yu. P., E-mail: suhorukov@imp.uran.ru; Telegin, A. V. [Russian Academy of Sciences, Institute of Metal Physics, Ural Branch (Russian Federation); Granovsky, A. B., E-mail: granov@magn.ru; Gan' shina, E. A. [Moscow State University, Faculty of Physics (Russian Federation); Zhukov, A.; Gonzalez, J. [Universidad del Pais Vasco (UPV)/Euskal Herriko Unibertsitatea (EHU), Departamento de Fisica de Materiales, Facultad de Quimica (Spain); Herranz, G. [Institut de Ciencia de Materials de Barcelona (ICMAB)-CSIC (Spain); Caicedo, J. M. [Universidad del Pais Vasco (UPV)/Euskal Herriko Unibertsitatea (EHU), Departamento de Fisica de Materiales, Facultad de Quimica (Spain); Yurasov, A. N. [Moscow State Institute of Radio-Engineering, Electronics, and Automation (Technical University) (Russian Federation); Bessonov, V. D. [Russian Academy of Sciences, Institute of Metal Physics, Ural Branch (Russian Federation); Kaul' , A. R.; Gorbenko, O. Yu.; Korsakov, I. E. [Moscow State University, Faculty of Physics (Russian Federation)

    2012-01-15

    The magnetotransmission, magnetoreflection, and magnetoresistance of the La{sub 0.7}Ca{sub 0.3}MnO{sub 3} and La{sub 0.9}Ag{sub 0.1}MnO{sub 3} epitaxial films have been investigated. It has been found that the films exhibit a significant magnetorefractive effect in the case of reflection and transmission of light in the fundamental absorption region both in the vicinity of the Curie temperature and at low temperatures. It has been shown that the magnetorefractive effect in the infrared spectral region of the manganites is determined by a high-frequency response to magnetoresistance, whereas the magnetorefractive effect in the visible spectral region of these materials is associated with a change in the electronic structure in response to a magnetic field, which, in turn, leads to a change in the electron density of states, the probability of interband optical transitions, and the shift of light absorption bands. The obtained values of the magnetotransmittance and magnetoreflectance in the visible spectral region are less than those observed in the infrared region of the spectrum, but they are several times greater than the linear magneto-optical effects. As a result, the magnetorefractive effect, which is a nongyrotropic phenomenon, makes it possible to avoid the use of light analyzers and polarizers in optical circuits.

  1. Magnetorefractive effect in manganites with a colossal magnetoresistance in the visible spectral region

    International Nuclear Information System (INIS)

    Sukhorukov, Yu. P.; Telegin, A. V.; Granovsky, A. B.; Gan’shina, E. A.; Zhukov, A.; Gonzalez, J.; Herranz, G.; Caicedo, J. M.; Yurasov, A. N.; Bessonov, V. D.; Kaul’, A. R.; Gorbenko, O. Yu.; Korsakov, I. E.

    2012-01-01

    The magnetotransmission, magnetoreflection, and magnetoresistance of the La 0.7 Ca 0.3 MnO 3 and La 0.9 Ag 0.1 MnO 3 epitaxial films have been investigated. It has been found that the films exhibit a significant magnetorefractive effect in the case of reflection and transmission of light in the fundamental absorption region both in the vicinity of the Curie temperature and at low temperatures. It has been shown that the magnetorefractive effect in the infrared spectral region of the manganites is determined by a high-frequency response to magnetoresistance, whereas the magnetorefractive effect in the visible spectral region of these materials is associated with a change in the electronic structure in response to a magnetic field, which, in turn, leads to a change in the electron density of states, the probability of interband optical transitions, and the shift of light absorption bands. The obtained values of the magnetotransmittance and magnetoreflectance in the visible spectral region are less than those observed in the infrared region of the spectrum, but they are several times greater than the linear magneto-optical effects. As a result, the magnetorefractive effect, which is a nongyrotropic phenomenon, makes it possible to avoid the use of light analyzers and polarizers in optical circuits.

  2. Dielectric inspection of erythrocyte morphology

    International Nuclear Information System (INIS)

    Hayashi, Yoshihito; Oshige, Ikuya; Katsumoto, Yoichi; Omori, Shinji; Yasuda, Akio; Asami, Koji

    2008-01-01

    We performed a systematic study of the sensitivity of dielectric spectroscopy to erythrocyte morphology. Namely, rabbit erythrocytes of four different shapes were prepared by precisely controlling the pH of the suspending medium, and their complex permittivities over the frequency range from 0.1 to 110 MHz were measured and analyzed. Their quantitative analysis shows that the characteristic frequency and the broadening parameter of the dielectric relaxation of interfacial polarization are highly specific to the erythrocyte shape, while they are insensitive to the cell volume fraction. Therefore, these two dielectric parameters can be used to differentiate erythrocytes of different shapes, if dielectric spectroscopy is applied to flow-cytometric inspection of single blood cells. In addition, we revealed the applicability and limitations of the analytical theory of interfacial polarization to explain the experimental permittivities of non-spherical erythrocytes

  3. Dielectric inspection of erythrocyte morphology

    Energy Technology Data Exchange (ETDEWEB)

    Hayashi, Yoshihito; Oshige, Ikuya; Katsumoto, Yoichi; Omori, Shinji; Yasuda, Akio [Life Science Laboratory, Materials Laboratories, Sony Corporation, Sony Bioinformatics Center, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo 113-8510 (Japan); Asami, Koji [Laboratory of Molecular Aggregation Analysis, Division of Multidisciplinary Chemistry, Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011 (Japan)], E-mail: Yoshihito.Hayashi@jp.sony.com

    2008-05-21

    We performed a systematic study of the sensitivity of dielectric spectroscopy to erythrocyte morphology. Namely, rabbit erythrocytes of four different shapes were prepared by precisely controlling the pH of the suspending medium, and their complex permittivities over the frequency range from 0.1 to 110 MHz were measured and analyzed. Their quantitative analysis shows that the characteristic frequency and the broadening parameter of the dielectric relaxation of interfacial polarization are highly specific to the erythrocyte shape, while they are insensitive to the cell volume fraction. Therefore, these two dielectric parameters can be used to differentiate erythrocytes of different shapes, if dielectric spectroscopy is applied to flow-cytometric inspection of single blood cells. In addition, we revealed the applicability and limitations of the analytical theory of interfacial polarization to explain the experimental permittivities of non-spherical erythrocytes.

  4. Silicone-based Dielectric Elastomers

    DEFF Research Database (Denmark)

    Skov, Anne Ladegaard

    Efficient conversion of energy from one form to another (transduction) is an important topic in our daily day, and it is a necessity in moving away from the fossil based society. Dielectric elastomers hold great promise as soft transducers, since they are compliant and light-weight amongst many...... energy efficient solutions are highly sought. These properties allow for interesting products ranging very broadly, e.g. from eye implants over artificial skins over soft robotics to huge wave energy harvesting plants. All these products utilize the inherent softness and compliance of the dielectric...... elastomer transducers. The subject of this thesis is improvement of properties of silicone-based dielectric elastomers with special focus on design guides towards electrically, mechanically, and electromechanically reliable elastomers. Strategies for improving dielectric elastomer performance are widely...

  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. Interconnect Between a Waveguide and a Dielectric Waveguide Comprising an Impedance Matched Dielectric Lens

    Science.gov (United States)

    Decrossas, Emmanuel (Inventor); Chattopadhyay, Goutam (Inventor); Chahat, Nacer (Inventor); Tang, Adrian J. (Inventor)

    2016-01-01

    A lens for interconnecting a metallic waveguide with a dielectric waveguide is provided. The lens may be coupled a metallic waveguide and a dielectric waveguide, and minimize a signal loss between the metallic waveguide and the dielectric waveguide.

  7. A comparative study of nano-SiO2 and nano-TiO2 fillers on proton conductivity and dielectric response of a silicotungstic acid-H3PO4-poly(vinyl alcohol) polymer electrolyte.

    Science.gov (United States)

    Gao, Han; Lian, Keryn

    2014-01-08

    The effects of nano-SiO2 and nano-TiO2 fillers on a thin film silicotungstic acid (SiWA)-H3PO4-poly(vinyl alcohol) (PVA) proton conducting polymer electrolyte were studied and compared with respect to their proton conductivity, environmental stability, and dielectric properties, across a temperature range from 243 to 323 K. Three major effects of these fillers have been identified: (a) barrier effect; (b) intrinsic dielectric constant effect; and (c) water retention effect. Dielectric analyses were used to differentiate these effects on polymer electrolyte-enabled capacitors. Capacitor performance was correlated to electrolyte properties through dielectric constant and dielectric loss spectra. Using a single-ion approach, proton density and proton mobility of each polymer electrolyte were derived as a function of temperature. The results allow us to deconvolute the different contributions to proton conductivity in SiWA-H3PO4-PVA-based electrolytes, especially in terms of the effects of fillers on the dynamic equilibrium of free protons and protonated water in the electrolytes.

  8. 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.

  9. Stable isotopes, beaks and predators: a new tool to study the trophic ecology of cephalopods, including giant and colossal squids.

    Science.gov (United States)

    Cherel, Yves; Hobson, Keith A

    2005-08-07

    Cephalopods play a key role in the marine environment but knowledge of their feeding habits is limited by lack of data. Here, we have developed a new tool to investigate their feeding ecology by combining the use of their predators as biological samplers together with measurements of the stable isotopic signature of their beaks. Cephalopod beaks are chitinous hard structures that resist digestion and the stable isotope ratios of carbon (delta13C) and nitrogen (delta15N) are indicators of the foraging areas and trophic levels of consumers, respectively. First, a comparison of delta13C and delta15N values of different tissues from the same individuals showed that beaks were slightly enriched in 13C but highly impoverished in 15N compared with lipid-free muscle tissues. Second, beaks from the same species showed a progressive increase in their delta15N values with increasing size, which is in agreement with a dietary shift from lower to higher trophic levels during cephalopod growth. In the same way, there was an increase in the delta15N signature of various parts of the same lower beaks in the order rostrum, lateral walls and wings, which reflects the progressive growth and chitinization of the beaks in parallel with dietary changes. Third, we investigated the trophic structure of a cephalopod community for the first time. Values of delta15N indicate that cephalopods living in slope waters of the subantarctic Kerguelen Islands (n=18 species) encompass almost three distinct trophic levels, with a continuum of two levels between crustacean- and fish-eaters and a distinct higher trophic level occupied by the colossal squid Mesonychoteuthis hamiltoni. delta13C values demonstrated that cephalopods grow in three different marine ecosystems, with 16 species living and developing in Kerguelen waters and two species migrating from either Antarctica (Slosarczykovia circumantarctica) or the subtropics (the giant squid Architeuthis dux). The stable isotopic signature of beaks

  10. Measurement of subcutaneous fibrosis after postmastectomy radiotherapy by dielectric properties of breast skin

    International Nuclear Information System (INIS)

    Lahtinen, T.; Tirkkonen, A.; Tenhunen, M.; Nuutinen, J.; Nuortio, L.; Auvinen, P.

    1995-01-01

    Dielectric properties of a biological material determine the interaction of high frequency electromagnetic (EM) fields and material. Since radiation induces changes in the structure and composition of the tissue, measurement of the altered dielectric properties could yield useful data on the radiation reactions. Dielectric constant of irradiated breast skin of 36 patients was measured 64 to 99 months after postmastectomy radiotherapy with three dose-fractionation schedules. A single dose-fractionation schedule consisted of a photon and electron or a photon and 150 kV x-ray beam. An EM frequency of 300 MHz was guided into the skin via a specially constructed coaxial probe. The attenuation and the phase shift of the reflected wave was measured by the network analyzer. From these data the dielectric constant of the skin could be calculated. Although there was a general tendency that the dielectric constant in the treated side was higher than in the untreated side, the increase was statistically significant only with one photon and electron beam. A significant negative correlation was found between the dielectric constant and the occurrence of clinically assessed mild fibrosis or when all degrees of fibrosis were combined. The study demonstrates that the dielectric measurements are useful in the assessment of the response of radiotherapy dose-fractionation schedules for the development and follow-up of subcutaneous fibrosis. Due to the large variation of the dielectric constants between patients in various dose-fractionation schedules, the dielectric measurements are not capable of differentiating different degrees of fibrosis

  11. Time domain PD-detection vs. dielectric spectroscopy

    DEFF Research Database (Denmark)

    Holbøll, Joachim T.; Edin, Hans; Gäfvert, Uno

    1997-01-01

    A theoretically developed relationship between partial discharges and the response from a system for dielectric spectroscopy was experimentally confirmed. The losses caused by the discharges were highest at test voltages with low frequencies. At 0.1 Hz, tanδ tip-up at discharge inception was very...

  12. Dielectric constant of graphene-on-polarized substrate: A tight ...

    Indian Academy of Sciences (India)

    Sivabrata Sahu

    Corresponding author. E-mail: gcr@iopb.res.in. Published online 24 June 2017. Abstract. We report here a microscopic tight-binding theoretical study of the dynamic dielectric response of graphene-on-polarizable substrate with impurity. The Hamiltonian consists of first, second and third nearest- neighbour electron hopping ...

  13. Dielectric constant of graphene-on-polarized substrate: A tight ...

    Indian Academy of Sciences (India)

    2017-06-24

    Jun 24, 2017 ... We report here a microscopic tight-binding theoretical study of the dynamic dielectric response of graphene-on-polarizable substrate with impurity. The Hamiltonian consists of first, second and third nearest neighbour electron hopping interactions besides doping and substrate-induced effects on graphene.

  14. Electrical actuation of dielectric droplets

    International Nuclear Information System (INIS)

    Kumari, N; Bahadur, V; Garimella, S V

    2008-01-01

    Electrical actuation of liquid droplets at the microscale offers promising applications in the fields of microfluidics and lab-on-a-chip devices. Much prior research has targeted the electrical actuation of electrically conducting liquid droplets; however, the actuation of dielectric droplets has remained relatively unexplored, despite the advantages associated with the use of a dielectric droplet. This paper presents modeling and experimental results on the electrical actuation of dielectric droplets between two flat plates. A first-order analytical model, based on the energy-minimization principle, is developed to estimate the electrical actuation force on a dielectric droplet as it moves between two flat plates. Two versions of this analytical model are benchmarked for their suitability and accuracy against a detailed numerical model. The actuation force prediction is then combined with available semi-analytical expressions for predicting the forces opposing droplet motion to develop a model that predicts transient droplet motion under electrical actuation. Electrical actuation of dielectric droplets is experimentally demonstrated by moving transformer oil droplets between two flat plates under the influence of an actuation voltage. Droplet velocities and their dependence on the plate spacing and the applied voltage are experimentally measured and showed reasonable agreement with predictions from the models developed

  15. Control of the colossal magnetoresistance by strain effect in Nd.sub.0.5./sub.Ca.sub.0.5./sub.MnO.sub.3./sub. thin films

    Czech Academy of Sciences Publication Activity Database

    Buzin, R. E.; Prellier, W.; Simon, Ch.; Mercone, S.; Mercey, B.; Raveau, B.; Šebek, Josef; Hejtmánek, Jiří

    2001-01-01

    Roč. 79, č. 5 (2001), s. 647-649 ISSN 0003-6951 Institutional research plan: CEZ:AV0Z1010914 Keywords : manganite thin films * colossal magnetoresistance Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.849, year: 2001

  16. Dielectric dispersion in pure and doped lithium rubidium sulphate

    Science.gov (United States)

    Kassem, M. E.; El-Muraikhi, M.; Al-Houty, L.; Mohamed, A. A.

    The frequency (102 - 105 Hz) dependence of the dielectric properties of lithium rubidium sulphate (LRS) are reported in the vicinity of the transition temperature Tc = 477 K. The a.c. conductivity σ(ω) shows a strong temperature dependence and weak frequency response. The dielectric constant in this region shows a strong frequency dispersion. A Cole-Cole diagram was used to determine the distribution parameter and the molecular relaxation time. The effect of doping with Dy+3, Sm+3 and V+3, was also studied. It was found that doping gives rise to localized states which produce a disorder in the structure of LiRbSO4.

  17. Quantitative nanometer-scale mapping of dielectric tunability

    Energy Technology Data Exchange (ETDEWEB)

    Tselev, Alexander [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Klein, Andreas [Technische Univ. Darmstadt (Germany); Gassmann, Juergen [Technische Univ. Darmstadt (Germany); Jesse, Stephen [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Li, Qian [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Kalinin, Sergei V. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Wisinger, Nina Balke [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2015-08-21

    Two scanning probe microscopy techniques—near-field scanning microwave microscopy (SMM) and piezoresponse force microscopy (PFM)—are used to characterize and image tunability in a thin (Ba,Sr)TiO3 film with nanometer scale spatial resolution. While sMIM allows direct probing of tunability by measurement of the change in the dielectric constant, in PFM, tunability can be extracted via electrostrictive response. The near-field microwave imaging and PFM provide similar information about dielectric tunability with PFM capable to deliver quantitative information on tunability with a higher spatial resolution close to 15 nm. This is the first time that information about the dielectric tunability is available on such length scales.

  18. Laser amplification in excited dielectrics

    Science.gov (United States)

    Winkler, Thomas; Haahr-Lillevang, Lasse; Sarpe, Cristian; Zielinski, Bastian; Götte, Nadine; Senftleben, Arne; Balling, Peter; Baumert, Thomas

    2018-01-01

    Wide-bandgap dielectrics such as glasses or water are transparent at visible and infrared wavelengths. This changes when they are exposed to ultrashort and highly intense laser pulses. Different interaction mechanisms lead to the appearance of various transient nonlinear optical phenomena. Using these, the optical properties of dielectrics can be controlled from the transparent to the metal-like state. Here we expand this range by a yet unexplored mechanism in excited dielectrics: amplification. In a two-colour pump-probe experiment, we show that a 400 nm femtosecond laser pulse is coherently amplified inside an excited sapphire sample on a scale of a few micrometres. Simulations strongly support the proposed two-photon stimulated emission process, which is temporally and spatially controllable. Consequently, we expect applications in all fields that demand strongly localized amplification.

  19. Dielectric function of semiconductor superlattice

    International Nuclear Information System (INIS)

    Qin Guoyi.

    1990-08-01

    We present a calculation of the dielectric function for semiconductor GaAs/Ga 1-x Al x As superlattice taking account of the extension of the electron envelope function and the difference of both the dielectric constant and width between GaAs and Ga 1-x Al x As layers. In the appropriate limits, our results exactly reduce to the well-known results of the quasi two-dimensional electron gas obtained by Lee and Spector and of the period array of two-dimensional electron layers obtained by Das Sarma and Quinn. By means of the dielectric function of the superlattice, the dispersion relation of the collective excitation and the screening property of semiconductor superlattice are discussed and compared with the results of the quasi two-dimensional system and with the results of the periodic array of the two-dimensional electron layers. (author). 4 refs, 3 figs

  20. Dielectric Properties of PE/Clay Nanocomposites

    Directory of Open Access Journals (Sweden)

    E. David

    2013-01-01

    Full Text Available Polyethylene/nanoclay specimens containing from 0 to 5% nanoclays were prepared from a commercially available premixed PE/nanoclay masterbatch containing 50% wt of nanoclay. The masterbatch was diluted to the desired concentration by adding PE along with various amounts of compatibilizer in order to achieve the best possible dispersion of the nanoclay platelets. The dielectric response of the compounded samples was investigated using a combination of time and frequency-domain spectroscopy in order to cover a wide frequency window. Both techniques were in good agreement when the time-domain data was transformed into frequency-domain data. Despite their low concentration, the addition of the dispersed nanoclays led to a significant alteration of the material dielectric response in the form of the appearance of various interfacial relaxation processes and an increase of charge carrier transport within the insulation material. Moreover, an onset of nonlinear charge transport process was observed at moderate fields for specimens containing a relatively low level of nanoclays. The high-field breakdown strength was shown to have been improved by the incorporation of the nanoparticles, particularly when the exfoliation was enhanced by the use of a maleic anhydride grafted polyethylene compatibilizer.

  1. Pressure-induced anomalous phase transitions and colossal enhancement of piezoelectricity in PbTiO3.

    Science.gov (United States)

    Wu, Zhigang; Cohen, Ronald E

    2005-07-15

    We find an unexpected tetragonal-to-monoclinic-to-rhombohedral-to-cubic phase transition sequence induced by pressure, and a morphotropic phase boundary in a pure compound using first-principles calculations. Huge dielectric and piezoelectric coupling constants occur in the transition regions, comparable to those observed in the new complex single-crystal solid-solution piezoelectrics such as Pb(Mg(1/3)Nb(2/3))O3-PbTiO3, which are expected to revolutionize electromechanical applications. Our results show that morphotropic phase boundaries and giant piezoelectric effects do not require intrinsic disorder, and open the possibility of studying this effect in simple systems.

  2. Effect of paramagnetic manganese ions doping on frequency and high temperature dependence dielectric response of layered Na1.9Li0.1Ti3O7 ceramics

    International Nuclear Information System (INIS)

    Pal, Dharmendra; Pandey, J.L.

    2010-01-01

    The manganese doped layered ceramic samples (Na 1.9 Li 0.1 )Ti 3 O 7 : XMn (0.01 ≤ X ≤ 0.1) have been prepared using high temperature solid state reaction. The room temperature electron paramagnetic resonance (EPR) investigations exhibit that at lower percentage of doping the substitution of manganese ions occur as Mn 3+ at Ti 4+ sites, whereas for higher percentage of doping Mn 2+ ions occupy the two different interlayer sodium/lithium sites. In both cases, the charge compensation mechanism should operate to maintain the overall charge neutrality of the lattice. The manganese doped derivatives of layered Na 1.9 Li 0. 1Ti 3 O 7 (SLT) ceramics have been investigated through frequency dependence dielectric spectroscopy in this work. The results indicate that the dielectric losses in these ceramics are the collective contribution of electric conduction, dipole orientation and space charge polarization. Smeared peaks in temperature dependence of permittivity plots suggest diffuse nature of high temperature ferroelectric phase transition. The light manganese doping in SLT enhances the dielectric constant. However, manganese doping decreases dielectric loss due to inhibition of domain wall motion, enhances electron-hopping conduction, and impedes the interlayer ionic conduction as well. Manganese doping also gives rise to contraction of interlayer space. (author)

  3. Temperature dependence of microwave and THz dielectric response in Srn.sub.+1./sub.TinO.sub.3./sub.n.sub.+1./sub. (n=1-4)

    Czech Academy of Sciences Publication Activity Database

    Noujni, Dmitri; Kamba, Stanislav; Pashkin, Alexej; Bovtun, Viktor; Petzelt, Jan; Axlesson, A. K.; McN Alford, N.; Wise, P. L.; Reaney, I. M.

    2004-01-01

    Roč. 62, - (2004), s. 199-203 ISSN 1058-4587 R&D Projects: GA AV ČR KSK1010104 Keywords : Ruddlesden. Popper * MW dielectric properties * infrared and THz spectroscopy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.427, year: 2004

  4. Capacitive Cells for Dielectric Constant Measurement

    Science.gov (United States)

    Aguilar, Horacio Munguía; Maldonado, Rigoberto Franco

    2015-01-01

    A simple capacitive cell for dielectric constant measurement in liquids is presented. As an illustrative application, the cell is used for measuring the degradation of overheated edible oil through the evaluation of their dielectric constant.

  5. Dielectric behaviour of strontium tartrate single crystals

    Indian Academy of Sciences (India)

    Unknown

    dielectric loss (tan δ) as functions of frequency and temperature. Ion core type ... Since the data on dielectric properties of strontium tartrate trihydrate (STT) do not ... through 'AE' make 15-amp dimmerstat, the rate of heating was maintained ...

  6. The Dielectric Constant of Lubrication Oils

    National Research Council Canada - National Science Library

    Carey, A

    1998-01-01

    The values of the dielectric constant of simple molecules is discussed first, along with the relationship between the dielectric constant and other physical properties such as boiling point, melting...

  7. Colossal creations of gravity

    DEFF Research Database (Denmark)

    Skielboe, Andreas

    Gravity governs the evolution of the universe on the largest scales, and powers some of the most extreme objects at the centers of galaxies. Determining the masses and kinematics of galaxy clusters provides essential constraints on the large-scale structure of the universe, and act as direct probes...

  8. Silicone elastomers with high dielectric permittivity and high dielectric breakdown strength based on tunable functionalized copolymers

    DEFF Research Database (Denmark)

    Madsen, Frederikke Bahrt; Yu, Liyun; Daugaard, Anders Egede

    2015-01-01

    system, with respect to functionalization, is achieved. It is investigated how the different functionalization variables affect essential DE properties, including dielectric permittivity, dielectric loss, elastic modulus and dielectric breakdown strength, and the optimal degree of chemical......%) was obtained without compromising other vital DE properties such as elastic modulus, gel fraction, dielectric and viscous loss and electrical breakdown strength....

  9. Dielectric response in high Tc superconductors

    International Nuclear Information System (INIS)

    Lopez-Aguilar, F.; Costa-Quintana, J.; Febrero, F.; Aurell, M.T.; Sanchez, A.; Munoz, J.S.; Balle, S.

    1989-01-01

    The random phase approximation integral equation is solved for obtaining the dynamically screened interaction between d electrons (W d (ω)), p electrons (W p (ω)) and p/d electrons (W pd (ω)). Some characteristic divergences of this last interaction correspond to the plasmon frequencies which one can relate with the effective masses of the p and d electrons close to E F by means of the relation ω p1 /ω p2 = (m 2 /m 1 ) 1/2 . Another feature of this W pd (ω) interaction is the attractive character for low frequencies. The lowest frequency for which ε pd = O decreases when the localization of states close to E F arising from the x 2 - y 2 symmetry increases

  10. Dielectric response in high Tc superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Lopez-Aguilar, F.; Costa-Quintana, J.; Febrero, F.; Aurell, M.T.; Sanchez, A.; Munoz, J.S. (Dept. de Fisica, Grupo de Electromagnetismo, Univ. Autonoma de Barcelona (Spain)); Balle, S. (Dept. de Fisica, Univ. de les Illes Balears, Palma de Mallorca (Spain))

    1989-12-01

    The random phase approximation integral equation is solved for obtaining the dynamically screened interaction between d electrons (W{sub d}({omega})), p electrons (W{sub p}({omega})) and p/d electrons (W{sub pd}({omega})). Some characteristic divergences of this last interaction correspond to the plasmon frequencies which one can relate with the effective masses of the p and d electrons close to E{sub F} by means of the relation {omega}{sub p1}/{omega}{sub p2} = (m{sub 2}/m{sub 1}){sup 1/2}. Another feature of this W{sub pd}({omega}) interaction is the attractive character for low frequencies. The lowest frequency for which {epsilon}{sub pd} = 0 decreases when the localization of states close to E{sub F} arising from the x{sup 2}-y{sup 2} symmetry increases. (orig.).

  11. Geometric phase from dielectric matrix

    International Nuclear Information System (INIS)

    Banerjee, D.

    2005-10-01

    The dielectric property of the anisotropic optical medium is found by considering the polarized photon as two component spinor of spherical harmonics. The Geometric Phase of a polarized photon has been evaluated in two ways: the phase two-form of the dielectric matrix through a twist and the Pancharatnam phase (GP) by changing the angular momentum of the incident polarized photon over a closed triangular path on the extended Poincare sphere. The helicity in connection with the spin angular momentum of the chiral photon plays the key role in developing these phase holonomies. (author)

  12. Charge accumulation in lossy dielectrics: a review

    DEFF Research Database (Denmark)

    Rasmussen, Jørgen Knøster; McAllister, Iain Wilson; Crichton, George C

    1999-01-01

    At present, the phenomenon of charge accumulation in solid dielectrics is under intense experimental study. Using a field theoretical approach, we review the basis for charge accumulation in lossy dielectrics. Thereafter, this macroscopic approach is applied to planar geometries such that the mat......At present, the phenomenon of charge accumulation in solid dielectrics is under intense experimental study. Using a field theoretical approach, we review the basis for charge accumulation in lossy dielectrics. Thereafter, this macroscopic approach is applied to planar geometries...

  13. Sol–gel deposited ceria thin films as gate dielectric for CMOS ...

    Indian Academy of Sciences (India)

    Sol–gel deposited ceria thin films as gate dielectric for CMOS technology. ANIL G KHAIRNAR ... The semiconductor roadmap following Moore's law is responsible for ..... The financial support from University Grants Commi- ssion (UGC), New ...

  14. Role of Ge incorporation in the physical and dielectric properties of ...

    Indian Academy of Sciences (India)

    It is inferred that on adding Ge, the physical properties ..... over a considerable distance, and the contribution to dielectric response can therefore be ... 1 and 103 Hz. The sum of these four types of polarization represents the total polarization.

  15. Thermal, FT–IR and dielectric studies of gel grown sodium oxalate ...

    Indian Academy of Sciences (India)

    WINTEC

    Institute of Diploma Studies, Nirma University of Science and Technology, Ahmedabad 384 481, India. MS received 29 ... dielectric response at various frequencies of applied field. ... 1987). Many oxalates exist in nature, for example, copper.

  16. Temperature Effects of Dielectric Properties of ER Fluids

    Science.gov (United States)

    Qiu, Z. Y.; Hu, L.; Liu, M. W.; Bao, H. X.; Jiang, Y. G.; Zhou, L. W.; Tang, Y.; Gao, Z.; Sun, M.; Korobko, E. V.

    Under the consideration of the role that energy transfer and dissipation play in ER effect, an improved theory frame for ER effects, polarization-dissipation-structure-rheology, is suggested. The theory frame is substantiated by the basic physical laws and certain critical experimental facts. The dielectric response of a diatomite ER fluid to temperature is measured in the temperature range of 140 K to 400 K. By comparison of the DC conductivity with the AC effective conductivity of the sample, we found that the AC dielectric loss consists of two parts. One part comes from the DC conductivity, the other from the response of the bound charges in scope of particle to AC field. It is suggested that the response of bound charges is very important to ER effects. Besides, the effect of temperature on shear stress is measured, and interpreted based on the dielectric measurements. The source of two loss peaks in the curve of the dielectric loss versus temperature is not clear.

  17. Cellulose Triacetate Dielectric Films For Capacitors

    Science.gov (United States)

    Yen, Shiao-Ping S.; Jow, T. Richard

    1994-01-01

    Cellulose triacetate investigated for use as dielectric material in high-energy-density capacitors for pulsed-electrical-power systems. Films of cellulose triacetate metalized on one or both sides for use as substrates for electrodes and/or as dielectrics between electrodes in capacitors. Used without metalization as simple dielectric films. Advantages include high breakdown strength and self-healing capability.

  18. Theory of Dielectric Elastomers

    Science.gov (United States)

    2010-10-25

    feature of life is to receive and process information from the environment, and then move. The movements are responsible for diverse functions, far...beyond the function of going from place to place. For example, an octopus can change its color at an astonishing speed, for camouflage and signaling...in engineering are indeed apt in mimicking the salient feature of life: movements in response to stimuli. An electric field can cause an elastomer

  19. Temperature dependence of colossal electro-resistance of Pr0.7Ca0.3MnO3 thin films

    International Nuclear Information System (INIS)

    Odagawa, A.; Kanno, T.; Adachi, H.; Sato, H.; Inoue, I.H.; Akoh, H.; Kawasaki, M.; Tokura, Y.

    2005-01-01

    The electronic conduction through a Pr 0.7 Ca 0.3 MnO 3 thin film is investigated by measurements using dc and pulsed bias. Pr 0.7 Ca 0.3 MnO 3 films sandwiched by electrodes exhibit two stable resistance states by means of applying voltage pulses. Both of the states show semiconducting behavior. The ratio of the two resistance states induces a colossal electro-resistance (CER) effect greater than 1000%. The CER behavior is seen in the temperature range of 300 K down to 150 K. The observed conduction characteristics exhibit the space-charge-limited-current effect, and the switching behavior can be ascribed to a carrier trapping/detrapping of the trap sites in the perovskite manganite

  20. Suppression of structural and magnetotransport transitions in compressed Pr0.5Sr0.5MnO3 thin films resulting in colossal magnetoresistance effect

    International Nuclear Information System (INIS)

    Mercey, B.; Hervieu, M.; Prellier, W.; Wolfman, J.; Simon, C.; Raveau, B.

    2001-01-01

    Thin films of Pr 0.5 Sr 0.5 MnO 3 have been deposited on [100]-LaAlO 3 using laser ablation. In contrast to the bulk compounds, such films do not exhibit any structural and magnetotransport transitions versus temperature; more particularly the A-type antiferromagnetic phase with the Fmmm structure which exists in the bulk below T N =135K is suppressed, and the film is an insulator in the absence of a magnetic field. However a colossal magnetoresistance effect is observed, with resistance ratios much larger than in the bulk. These differences with respect to the bulk, are explained by the presence of substrate-induced strains. [copyright] 2001 American Institute of Physics

  1. Large anisotropy in colossal magnetoresistance of charge orbital ordered epitaxial Sm(0.5)Ca(0.5)MnO(3) films.

    Science.gov (United States)

    Chen, Y Z; Sun, J R; Zhao, J L; Wang, J; Shen, B G; Pryds, N

    2009-11-04

    We investigated the structure and magnetotransport properties of Sm(0.5)Ca(0.5)MnO(3) (SCMO) films epitaxially grown on (011)-oriented SrTiO(3) substrates, which exhibited clear charge/orbital ordering transition. A significant anisotropy of ∼1000 in the colossal magnetoresistance (CMR) effect was observed in the films with a thickness between 50 and 80 nm, which was distinctly different from the basically isotropic CMR effect in bulk SCMO. The large anisotropy in the CMR can be ascribed to the intrinsic asymmetric strain in the film, which plays an important role in tuning the spin-orbit coupling in manganite films. The origin of the peculiar CMR effect is discussed.

  2. A New Concept for Non-Volatile Memory: The Electric-Pulse Induced Resistive Change Effect in Colossal Magnetoresistive Thin Films

    Science.gov (United States)

    Liu, S. Q.; Wu, N. J.; Ignatiev, A.

    2001-01-01

    A novel electric pulse-induced resistive change (EPIR) effect has been found in thin film colossal magnetoresistive (CMR) materials, and has shown promise for the development of resistive, nonvolatile memory. The EPIR effect is induced by the application of low voltage (resistance of the thin film sample depending on pulse polarity. The sample resistance change has been shown to be over two orders of magnitude, and is nonvolatile after pulsing. The sample resistance can also be changed through multiple levels - as many as 50 have been shown. Such a device can provide a way for the development of a new kind of nonvolatile multiple-valued memory with high density, fast write/read speed, low power-consumption, and potential high radiation-hardness.

  3. Dielectric waveguide amplifiers and lasers

    NARCIS (Netherlands)

    Pollnau, Markus

    The performance of semiconductor amplifiers and lasers has made them the preferred choice for optical gain on a micro-chip. In the past few years, we have demonstrated that also rare-earth-ion-doped dielectric waveguides show remarkable performance, ranging from a small-signal gain per unit length

  4. Dielectric properties of fly ash

    Indian Academy of Sciences (India)

    Unknown

    India's annual coal production is used in about 72 power- generating plants and ... performance of this material as cracking catalyst was investigated with ... Chemically, the FA was silica to an extent of 55–70%, followed by ... Cu, Pb, Cd, Ag, Mn, Fe, Ti, Na, Mo, S, P, Zn and Cl in different ... two-probe method. The dielectric ...

  5. Improved di-electric composition

    Energy Technology Data Exchange (ETDEWEB)

    Sharp, R C

    1915-03-29

    An improved di-electric composition is disclosed composed of pitch or bitumen which is melted, and to which is added, while molten, a quantity of finely ground or pulverized spent shale, the whole being mixed or stirred to make a homogeneous composition, substantially as described.

  6. Investigation of the dielectric properties of shale

    International Nuclear Information System (INIS)

    Martemyanov, Sergey M.

    2011-01-01

    The article is dedicated to investigation of the dielectric properties of oil shale. Investigations for samples prepared from shale mined at the deposit in Jilin Province in China were done. The temperature and frequency dependences of rock characteristics needed to calculate the processes of their thermal processing are investigated. Frequency dependences for the relative dielectric constant and dissipation factor of rock in the frequency range from 0,1 Hz to 1 MHz are investigated. The temperature dependences for rock resistance, dielectric capacitance and dissipation factor in the temperature range from 20 to 600°C are studied. Key words: shale, dielectric properties, relative dielectric constant, dissipation factor, temperature dependence, frequency dependence

  7. Nonlinear dielectric spectroscopy of propylene carbonate derivatives

    Science.gov (United States)

    Casalini, R.; Roland, C. M.

    2018-04-01

    Nonlinear dielectric measurements were carried out on two strongly polar liquids, 4-vinyl-1,3-dioxolan-2-one (VPC) and 4-ethyl-1,3-dioxolan-2-one (EPC), having chemical structures differing from propylene carbonate (PC) only by the presence of a pendant group. Despite their polarity, the compounds are all non-associated, "simple" liquids. From the linear component of the dielectric response, the α relaxation peak breadth was found to be invariant at a fixed value of the relaxation time, τα. From spectra from the nonlinear component, the number of dynamically correlated molecules was determined; it was also constant at fixed τα. Thus, two manifestations of dynamic heterogeneity depend only on the time constant for structural reorientation. More broadly, the cooperativity of molecular motions for non-associated glass-forming materials is connected to (i.e., reciprocally governs) the time scale. The equation of state for the two liquids was also obtained from density measurements made over a broad range of pressures and temperatures. Using these data, it was determined that the relaxation times of both liquids conform to density scaling. The effect of density, relative to thermal effects, on the α relaxation increases going from PC < VPC < EPC.

  8. Broadband dielectric response and grain-size effect in K.sub.0.5./sub.Na.sub.0.5./sub.NbO.sub.3./sub. ceramics

    Czech Academy of Sciences Publication Activity Database

    Buixaderas, Elena; Bovtun, Viktor; Kempa, Martin; Savinov, Maxim; Nuzhnyy, Dmitry; Kadlec, Filip; Vaněk, Přemysl; Petzelt, Jan; Eriksson, M.; Shen, Z.

    2010-01-01

    Roč. 107, č. 1 (2010), 014111/1-014111/10 ISSN 0021-8979 R&D Projects: GA AV ČR KJB100100704; GA AV ČR IAA100100701; GA MŠk OC 101; GA ČR(CZ) GA202/06/0403 Institutional research plan: CEZ:AV0Z10100520 Keywords : dielectric spectroscopy * time domain THz spectroscopy * piezoelectrics Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.064, year: 2010

  9. Two-phase mixed media dielectric with macro dielectric beads for enhancing resistivity and breakdown strength

    Science.gov (United States)

    Falabella, Steven; Meyer, Glenn A; Tang, Vincent; Guethlein, Gary

    2014-06-10

    A two-phase mixed media insulator having a dielectric fluid filling the interstices between macro-sized dielectric beads packed into a confined volume, so that the packed dielectric beads inhibit electro-hydrodynamically driven current flows of the dielectric liquid and thereby increase the resistivity and breakdown strength of the two-phase insulator over the dielectric liquid alone. In addition, an electrical apparatus incorporates the two-phase mixed media insulator to insulate between electrical components of different electrical potentials. And a method of electrically insulating between electrical components of different electrical potentials fills a confined volume between the electrical components with the two-phase dielectric composite, so that the macro dielectric beads are packed in the confined volume and interstices formed between the macro dielectric beads are filled with the dielectric liquid.

  10. Dielectric properties investigation of Cu2O/ZnO heterojunction thin films by electrodeposition

    International Nuclear Information System (INIS)

    Li, Qiang; Xu, Mengmeng; Fan, Huiqing; Wang, Hairong; Peng, Biaolin; Long, Changbai; Zhai, Yuchun

    2013-01-01

    Highlights: ► Bottom-up self-assembly Cu 2 O/ZnO heterojunction was fabricated by electrochemical deposition on indium tin oxide (ITO) flexible substrate (polyethylene terephthalate-PET). ► The dielectric response of Cu 2 O/ZnO heterojunction thin films had been investigated. ► The universal dielectric response was used to investigate the hopping behavior in Cu 2 O/ZnO heterojunction. -- Abstract: Structures and morphologies of the Cu 2 O/ZnO heterojunction electrodeposited on indium tin oxide (ITO) flexible substrate (polyethylene terephthalate-PET) were investigated by X-ray diffraction (XRD), scanning electronic microscopy (SEM), high resolution transmission electron microscopy (HRTEM), respectively. The dielectric response of bottom-up self-assembly Cu 2 O/ZnO heterojunction was investigated. The low frequency dielectric dispersion (LFDD) was observed. The universal dielectric response (UDR) was used to investigate the frequency dependence of dielectric response for Cu 2 O/ZnO heterojunction, which was attributed to the long range and the short range hopping charge carriers at the low frequency and the high frequency region, respectively

  11. Dielectric and complex impedance studies of BaTi0·85W0·15O3+δ ...

    Indian Academy of Sciences (India)

    Keywords. Ferroelectrics; grain boundaries; dielectric response; X-ray diffraction. 1. Introduction. Since the discovery of BaTiO3, these materials have been extensively studied owing to their interesting dielectric, ferroelectric, piezoelectric and pyroelectric properties. (Goodman and Buchanan 1986; Hench and West 1990;.

  12. Dielectric coatings on metal substrates

    International Nuclear Information System (INIS)

    Glaros, S.S.; Baker, P.; Milam, D.

    1976-01-01

    Large aperture, beryllium substrate-based mirrors have been used to focus high intensity pulsed laser beams. Finished surfaces have high reflectivity, low wavefront distortion, and high laser damage thresholds. This paper describes the development of a series of metallic coatings, surface finishing techniques, and dielectric overcoatings to meet specified performance requirements. Beryllium substrates were coated with copper, diamond-machined to within 5 micro-inches to final contour, nickel plated, and abrasively figured to final contour. Bond strengths for several bonding processes are presented. Dielectric overcoatings were deposited on finished multimetallic substrates to increase both reflectivity and the damage thresholds. Coatings were deposited using both high and low temperature processes which induce varying stresses in the finished coating substrate system. Data are presented to show the evolution of wavefront distortion, reflectivity, and damage thresholds throughout the many steps involved in fabrication

  13. Origin of giant dielectric permittivity and weak ferromagnetic behavior in (1−xLaFeO3−xBaTiO3 (0.0 ≤ x ≤ 0.25 solid solutions

    Directory of Open Access Journals (Sweden)

    T. Sreenivasu

    2016-12-01

    Full Text Available The solid solutions of (1−x LaFeO3–xBaTiO3 (0.0≤x≤0.25 have been synthesized successfully by the conventional solid-state reaction method. Room temperature (RT X-ray diffraction studies reveal the stabilization of orthorhombic phase with Pbnm space group. Complete solubility in the perovskite series was demonstrated up to x=0.25. The dielectric permittivity shows colossal dielectric constant (CDC at RT. The doping of BaTiO3 in LaFeO3 exhibit pronounced CDC up to a composition x=0.15, further it starts to decrease. The frequency-dependent dielectric loss exhibits polaronic conduction, which can attribute to presence of multiple valence of iron. The relaxation frequency and polaronic conduction mechanism was shifted towards RT as function of x. Moreover, large magnetic moment with weak ferromagnetic behavior is observed in doped LaFeO3 solid solution, which might be the destruction of spin cycloid structure due to insertion of Ti in Fe–O–Fe network of LaFeO3.

  14. Asymmetric Dielectric Elastomer Composite Material

    Science.gov (United States)

    Stewart, Brian K. (Inventor)

    2014-01-01

    Embodiments of the invention provide a dielectric elastomer composite material comprising a plurality of elastomer-coated electrodes arranged in an assembly. Embodiments of the invention provide improved force output over prior DEs by producing thinner spacing between electrode surfaces. This is accomplished by coating electrodes directly with uncured elastomer in liquid form and then assembling a finished component (which may be termed an actuator) from coated electrode components.

  15. Coherent multimoded dielectric wakefield accelerators

    International Nuclear Information System (INIS)

    Power, J.

    1998-01-01

    There has recently been a study of the potential uses of multimode dielectric structures for wakefield acceleration [1]. This technique is based on adjusting the wakefield modes of the structure to constructively interfere at certain delays with respect to the drive bunch, thus providing an accelerating gradient enhancement over single mode devices. In this report we examine and attempt to clarify the issues raised by this work in the light of the present state of the art in wakefield acceleration

  16. Haptic interfaces using dielectric electroactive polymers

    Science.gov (United States)

    Ozsecen, Muzaffer Y.; Sivak, Mark; Mavroidis, Constantinos

    2010-04-01

    Quality, amplitude and frequency of the interaction forces between a human and an actuator are essential traits for haptic applications. A variety of Electro-Active Polymer (EAP) based actuators can provide these characteristics simultaneously with quiet operation, low weight, high power density and fast response. This paper demonstrates a rolled Dielectric Elastomer Actuator (DEA) being used as a telepresence device in a heart beat measurement application. In the this testing, heart signals were acquired from a remote location using a wireless heart rate sensor, sent through a network and DEA was used to haptically reproduce the heart beats at the medical expert's location. A series of preliminary human subject tests were conducted that demonstrated that a) DE based haptic feeling can be used in heart beat measurement tests and b) through subjective testing the stiffness and actuator properties of the EAP can be tuned for a variety of applications.

  17. Tunable electromechanical actuation in silicone dielectric film

    International Nuclear Information System (INIS)

    Lamberti, Andrea; Di Donato, Marco; Giorgis, Fabrizio; Chiappone, Annalisa; Canavese, Giancarlo

    2014-01-01

    Dielectric elastomer actuator films were fabricated on transparent conductive electrode using bi-component poly(dimethyl)siloxane (PDMS). PDMS is a well-known material in microfluidics and soft lithography for biomedical applications, being easy to process, low cost, biocompatible and transparent. Moreover its mechanical properties can be easily tuned by varying the mixing ratio between the oligomer base and the crosslinking agent. In this work we investigate the chemical composition and the electromechanical properties of PDMS thin film verifying for the first time the tuneable actuation response by simply modifying the amount of the curing agent. We demonstrate that, for a 20:1 ratio of base:crosslinker mixture, a striking 150% enhancement of Maxwell strain occurs at 1 Hz actuating frequency. (paper)

  18. Energy storage in ceramic dielectrics

    International Nuclear Information System (INIS)

    Love, G.R.

    1990-01-01

    Historically, multilayer ceramic capacitors (MLC's) have not been considered for energy storage applications for two primary reasons. First, physically large ceramic capacitors were very expensive and, second, total energy density obtainable was not nearly so high as in electrolytic capacitor types. More recently, the fabrication technology for MLC's has improved significantly, permitting both significantly higher energy density and significantly lower costs. Simultaneously, in many applications, total energy storage has become smaller, and the secondary requirements of very low effective series resistance and effective series inductance (which, together, determine how efficiently the energy may be stored and recovered) have become more important. It is therefore desirable to reexamine energy storage in ceramics for contemporary commercial and near-commercial dielectrics. Stored energy is proportional to voltage squared only in the case of paraelectric insulators, because only they have capacitance that is independent of bias voltage. High dielectric constant materials, however, are ferroics (that is ferroelectric and/or antiferroelectric) and display significant variation of effective dielectric constant with bias voltage

  19. Dielectric-filled radiofrequency linacs

    Energy Technology Data Exchange (ETDEWEB)

    Faehl, R J; Keinigs, R K; Pogue, E W [Los Alamos National Lab., NM (United States)

    1997-12-31

    High current, high brightness electron beam accelerators promise to open up dramatic new applications. Linear induction accelerators are currently viewed as the appropriate technology for these applications. A concept by Humphries and Hwang may permit radiofrequency accelerators to fulfill the same functions with greater simplicity and enhanced flexibility. This concept involves the replacement of vacuum rf cavities with dielectric filled ones. Simple analysis indicates that the resonant frequencies are reduced by a factor of ({epsilon}{sub 0}/{epsilon}){sup 1/2} while the stored energy is increased by {epsilon}/{epsilon}{sub 0}. For a high dielectric constant like water, this factor can approach 80. A series of numerical calculations of simple pill-box cavities was performed. Eigenfunctions and resonant frequencies for a full system configuration, including dielectric material, vacuum beamline, and a ceramic window separating the two have been computed. These calculations are compared with the results of a small experimental cavity which have been constructed and operated. Low power tests show excellent agreement. (author). 4 figs., 8 refs.

  20. Colossal anisotropic resistivity and oriented magnetic domains in strained La{sub 0.325}Pr{sub 0.3}Ca{sub 0.375}MnO{sub 3} films

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Tao; Yang, Shengwei; Liu, Yukuai; Zhao, Wenbo; Feng, Lei; Li, Xiaoguang, E-mail: lixg@ustc.edu.cn [Hefei National Laboratory for Physical Sciences at Microscale, Department of Physics, University of Science and Technology of China, Hefei 230026 (China); Zhou, Haibiao; Lu, Qingyou [Hefei National Laboratory for Physical Sciences at Microscale, Department of Physics, University of Science and Technology of China, Hefei 230026 (China); High Magnetic Field Laboratory, Chinese Academy of Sciences and University of Science and Technology of China, Hefei 230031 (China); Hou, Yubin [High Magnetic Field Laboratory, Chinese Academy of Sciences and University of Science and Technology of China, Hefei 230031 (China)

    2014-05-19

    Magnetic and resistive anisotropies have been studied for the La{sub 0.325}Pr{sub 0.3}Ca{sub 0.375}MnO{sub 3} films with different thicknesses grown on low symmetric (011)-oriented (LaAlO{sub 3}){sub 0.3}(SrAl{sub 0.5}Ta{sub 0.5}O{sub 3}){sub 0.7} substrates. In the magnetic and electronic phase separation region, a colossal anisotropic resistivity (AR) of ∼10{sup 5}% and an anomalous large anisotropic magnetoresistance can be observed for 30 nm film. However, for 120 nm film, the maximum AR decreases significantly (∼2 × 10{sup 3}%) due to strain relaxation. The colossal AR is strongly associated with the oriented formation of magnetic domains, and the features of the strain effects are believed to be useful for the design of artificial materials and devices.

  1. Thermal strain-induced dielectric anisotropy in Ba0.7Sr0.3TiO3 thin films grown on silicon-based substrates

    International Nuclear Information System (INIS)

    Zhu, X. H.; Defaye, E.; Aied, M.; Guigues, B.; Dubarry, C.

    2009-01-01

    Dielectric properties of Ba 0.7 Sr 0.3 TiO 3 (BST) thin films, which were prepared on silicon-based substrates by ion beam sputtering and postdeposition annealing method, were systematically investigated in different electrode configurations of metal-insulator-metal and coplanar interdigital capacitors. It was found that a large dielectric anisotropy exists in the films with better in-plane dielectric properties (higher dielectric permittivity and tunability) than those along the out-of-plane direction. The observed anisotropic dielectric responses are explained qualitatively in terms of a thermal strain effect that is related to dissimilar film strains along the in-plane and out-of-plane directions. Another reason for the dielectric anisotropy is due to different influences of the interfacial low-dielectric layer between the BST film and the substrate (metal electrode).

  2. Thermal strain-induced dielectric anisotropy in Ba0.7Sr0.3TiO3 thin films grown on silicon-based substrates

    Science.gov (United States)

    Zhu, X. H.; Guigues, B.; Defaÿ, E.; Dubarry, C.; Aïd, M.

    2009-07-01

    Dielectric properties of Ba0.7Sr0.3TiO3 (BST) thin films, which were prepared on silicon-based substrates by ion beam sputtering and postdeposition annealing method, were systematically investigated in different electrode configurations of metal-insulator-metal and coplanar interdigital capacitors. It was found that a large dielectric anisotropy exists in the films with better in-plane dielectric properties (higher dielectric permittivity and tunability) than those along the out-of-plane direction. The observed anisotropic dielectric responses are explained qualitatively in terms of a thermal strain effect that is related to dissimilar film strains along the in-plane and out-of-plane directions. Another reason for the dielectric anisotropy is due to different influences of the interfacial low-dielectric layer between the BST film and the substrate (metal electrode).

  3. Non-linear dielectric monitoring of biological suspensions

    International Nuclear Information System (INIS)

    Treo, E F; Felice, C J

    2007-01-01

    Non-linear dielectric spectroscopy as a tool for in situ monitoring of enzyme assumes a non-linear behavior of the sample when a sinusoidal voltage is applied to it. Even many attempts have been made to improve the original experiments, all of them had limited success. In this paper we present upgrades made to a non-linear dielectric spectrometer developed and the results obtained when using different cells. We emphasized on the electrode surface, characterizing the grinding and polishing procedure. We found that the biological medium does not behave as expected, and the non-linear response is generated in the electrode-electrolyte interface. The electrochemistry of this interface can bias unpredictably the measured non-linear response

  4. Frequency and Temperature Dependent Dielectric Properties of Free-standing Strontium Titanate Thin Films.

    Science.gov (United States)

    Dalberth, Mark J.; Stauber, Renaud E.; Anderson, Britt; Price, John C.; Rogers, Charles T.

    1998-03-01

    We will report on the frequency and temperature dependence of the complex dielectric function of free-standing strontium titanate (STO) films. STO is an incipient ferroelectric with electric-field tunable dielectric properties of utility in microwave electronics. The films are grown epitaxially via pulsed laser deposition on a variety of substrates, including lanthanum aluminate (LAO), neodymium gallate (NGO), and STO. An initial film of yttrium barium cuprate (YBCO) is grown on the substrate, followed by deposition of the STO layer. Following deposition, the sacrificial YBCO layer is chemically etched away in dilute nitric acid, leaving the substrate and a released, free-standing STO film. Coplanar capacitor structures fabricated on the released films allow us to measure the dielectric response. We observe a peak dielectric function in excess of 5000 at 35K, change in dielectric constant of over a factor of 8 for 10Volt/micron electric fields, and temperature dependence above 50K that is very similar to bulk material. The dielectric loss shows two peaks, each with a thermally activated behavior, apparently arising from two types of polar defects. We will discuss the correlation between dielectric properties, growth conditions, and strain in the free-standing STO films.

  5. Electromechanical performance analysis of inflated dielectric elastomer membrane for micro pump applications

    Science.gov (United States)

    Saini, Abhishek; Ahmad, Dilshad; Patra, Karali

    2016-04-01

    Dielectric elastomers have received a great deal of attention recently as potential materials for many new types of sensors, actuators and future energy generators. When subjected to high electric field, dielectric elastomer membrane sandwiched between compliant electrodes undergoes large deformation with a fast response speed. Moreover, dielectric elastomers have high specific energy density, toughness, flexibility and shape processability. Therefore, dielectric elastomer membranes have gained importance to be applied as micro pumps for microfluidics and biomedical applications. This work intends to extend the electromechanical performance analysis of inflated dielectric elastomer membranes to be applied as micro pumps. Mechanical burst test and cyclic tests were performed to investigate the mechanical breakdown and hysteresis loss of the dielectric membrane, respectively. Varying high electric field was applied on the inflated membrane under different static pressure to determine the electromechanical behavior and nonplanar actuation of the membrane. These tests were repeated for membranes with different pre-stretch values. Results show that pre-stretching improves the electromechanical performance of the inflated membrane. The present work will help to select suitable parameters for designing micro pumps using dielectric elastomer membrane. However this material lacks durability in operation.This issue also needs to be investigated further for realizing practical micro pumps.

  6. Development of a dielectric ceramic based on diatomite-titania part two: dielectric properties characterization

    Directory of Open Access Journals (Sweden)

    Medeiros Jamilson Pinto

    1998-01-01

    Full Text Available Dielectric properties of sintered diatomite-titania ceramics are presented. Specific capacitance, dissipation factor, quality factor and dielectric constant were determined as a function of sintering temperature, titania content and frequency; the temperature coefficient of capacitance was measured as a function of frequency. Besides leakage current, the dependence of the insulation resistance and the dielectric strength on the applied dc voltage were studied. The results show that diatomite-titania compositions can be used as an alternative dielectric.

  7. Frequency and temperature dependent dielectric properties of TiO2-V2O5 nanocomposites

    Science.gov (United States)

    Ray, Apurba; Roy, Atanu; De, Sayan; Chatterjee, Souvik; Das, Sachindranath

    2018-03-01

    In this manuscript, we have reported the crystal structure, dielectric response, and transport phenomenon of TiO2-V2O5 nanocomposites. The nanocomposites were synthesized using a sol-gel technique having different molar ratios of Ti:V (10:10, 10:15, and 10:20). The phase composition and the morphology have been studied using X-ray diffraction and field emission scanning electron microscope, respectively. The impedance spectroscopy studies of the three samples over a wide range of temperature (50 K-300 K) have been extensively described using the internal barrier layer capacitor model. It is based on the contribution of domain and domain boundary, relaxations of the materials, which are the main crucial factors for the enhancement of the dielectric response. The frequency dependent ac conductivity of the ceramics strongly obeys the well-known Jonscher's power law, and it has been clearly explained using the theory of jump relaxation model. The temperature dependent bulk conductivity is fairly recognized to the variable-range hopping of localized polarons. The co-existence of mixed valence state of Ti ions (Ti3+ and Ti4+) in the sample significantly contributes to the change of dielectric property. The overall study of dielectric response explains that the dielectric constant and the dielectric loss are strongly dependent on temperature and frequency and decrease with an increase of frequency as well as temperature.

  8. Electrical breakdown phenomena of dielectric elastomers

    DEFF Research Database (Denmark)

    Mateiu, Ramona Valentina; Yu, Liyun; Skov, Anne Ladegaard

    2017-01-01

    Silicone elastomers have been heavily investigated as candidates for dielectric elastomers and are as such almost ideal candidates with their inherent softness and compliance but they suffer from low dielectric permittivity. This shortcoming has been sought optimized by many means during recent...... years. However, optimization with respect to the dielectric permittivity solely may lead to other problematic phenomena such as premature electrical breakdown. In this work, we investigate the electrical breakdown phenomena of various types of permittivity-enhanced silicone elastomers. Two types...... of silicone elastomers are investigated and different types of breakdown are discussed. Furthermore the use of voltage stabilizers in silicone-based dielectric elastomers is investigated and discussed....

  9. Silicone elastomers with high dielectric permittivity and high dielectric breakdown strength based on dipolar copolymers

    DEFF Research Database (Denmark)

    Madsen, Frederikke Bahrt; Yu, Liyun; Daugaard, Anders Egede

    2014-01-01

    Dielectric elastomers (DES) are a promising new transducer technology, but high driving voltages limit their current commercial potential. One method used to lower driving voltage is to increase dielectric permittivity of the elastomer. A novel silicone elastomer system with high dielectric...

  10. Ferroelectric dielectrics integrated on silicon

    CERN Document Server

    Defay, Emmanuel

    2013-01-01

    This book describes up-to-date technology applied to high-K materials for More Than Moore applications, i.e. microsystems applied to microelectronics core technologies.After detailing the basic thermodynamic theory applied to high-K dielectrics thin films including extrinsic effects, this book emphasizes the specificity of thin films. Deposition and patterning technologies are then presented. A whole chapter is dedicated to the major role played in the field by X-Ray Diffraction characterization, and other characterization techniques are also described such as Radio frequency characterizat

  11. Broadband cloaking using composite dielectrics

    Directory of Open Access Journals (Sweden)

    Ruey-Bing Hwang

    2011-03-01

    Full Text Available In this paper, we present a novel cloaking structure that is able to make a metallic block invisible in a metallic waveguide. Such a cloak is made up of a stack of commonly used dielectric slabs. We carry out the numerical simulation and observe the detour of the vector Poynting power through the cloak. Moreover, the experiment is conducted for measuring the scattering characteristics including the reflection and transmission coefficients. The great improvement in the transmission coefficient in a broad bandwidth after cloaking is demonstrated. Significantly, the theory of mode conversion is developed for explaining the cloaking phenomenon.

  12. An analytical longitudinal dielectric function of primitive electrolyte solutions and its application in predicting thermodynamic properties

    International Nuclear Information System (INIS)

    Xiao, Tiejun

    2015-01-01

    In this paper, the longitudinal dielectric function ϵ_l(k) of primitive electrolyte solutions is discussed. Starting from a modified mean spherical approximation, an analytical dielectric function in terms of two parameters is established. These two parameters can be related to the first two decay parameters k_1_,_2 of the dielectric response modes of the bulk system, and can be determined using constraints of k_1_,_2 from statistical theories. Furthermore, a combination of this dielectric function and the molecular Debye-Hückel theory[J. Chem. Phys. 135(2011)104104] leads to a self-consistent mean filed description of electrolyte solutions. Our theory reveals a relationship between the microscopic structure parameters of electrolyte solutions and the macroscopic thermodynamic properties, which is applied to concentrated electrolyte solutions.

  13. Tuning the dielectric properties of thiourea analog crystals for efficient nonlinear optical applications

    International Nuclear Information System (INIS)

    Sabari Girisun, T.C.; Dhanuskodi, S.

    2010-01-01

    Materials with low dielectric constant have attracted a great deal of interest in the field of nonlinear applications and microelectronic industry. Metal complexes of thiourea with group II transition metals (Zn, Cd) as central atom and period III elements (S, Cl) were synthesized by chemical reaction method and single crystals were grown from aqueous solution by slow evaporation method. By parallel plate capacitor technique, the dielectric response, dissipation factor, ac conductivity and impedance of virgin and metal complexes have been studied in the frequency (100 Hz to 5 MHz) and temperature (303-423 K) ranges. Metal complexes of thiourea with cadmium substitute have a low dielectric constant less than 10. Also the presence of chlorine in the metal complex induces noncentro symmetric structure. Hence the role of group II transition metals and period III elements in tuning the dielectric properties for efficient nonlinear applications has been studied.

  14. High thermal conductivity lossy dielectric using a multi layer configuration

    Science.gov (United States)

    Tiegs, Terry N.; Kiggans, Jr., James O.

    2003-01-01

    Systems and methods are described for loss dielectrics. A loss dielectric includes at least one high dielectric loss layer and at least one high thermal conductivity-electrically insulating layer adjacent the at least one high dielectric loss layer. A method of manufacturing a loss dielectric includes providing at least one high dielectric loss layer and providing at least one high thermal conductivity-electrically insulating layer adjacent the at least one high dielectric loss layer. The systems and methods provide advantages because the loss dielectrics are less costly and more environmentally friendly than the available alternatives.

  15. Thermally stimulated discharge current (TSDC) and dielectric ...

    Indian Academy of Sciences (India)

    Unknown

    2001-10-09

    Oct 9, 2001 ... Measurements of TSDC and dielectric constant, ε′, have been ... Keywords. Semiconducting glass; TSDC; trap energy; dielectric constant. 1. ... determination of mean depth of the internal charge, activation ... thermal charging, viz. (i) internal ... the basis of d.c. conductivity and short range Na+ ion motion.

  16. Dielectric spectroscopy of watermelons for quality sensing

    Science.gov (United States)

    Nelson, Stuart O.; Guo, Wen-chuan; Trabelsi, Samir; Kays, Stanley J.

    2007-07-01

    Dielectric properties of four small-sized watermelon cultivars, grown and harvested to provide a range of maturities, were measured with an open-ended coaxial-line probe and an impedance analyser over the frequency range from 10 MHz to 1.8 GHz. Probe measurements were made on the external surface of the melons and also on tissue samples from the edible internal tissue. Moisture content and soluble solids content (SSC) were measured for internal tissue samples, and SSC (sweetness) was used as the quality factor for correlation with the dielectric properties. Individual dielectric constant and loss factor correlations with SSC were low, but a high correlation was obtained between the SSC and permittivity from a complex-plane plot of dielectric constant and loss factor, each divided by SSC. However, SSC prediction from the dielectric properties by this relationship was not as high as expected (coefficient of determination about 0.4). Permittivity data (dielectric constant and loss factor) for the melons are presented graphically to show their relationships with frequency for the four melon cultivars and for external surface and internal tissue measurements. A dielectric relaxation for the external surface measurements, which may be attributable to a combination of bound water, Maxwell-Wagner, molecular cluster or ion-related effects, is also illustrated. Coefficients of determination for complex-plane plots, moisture content and SSC relationship, and penetration depth are also shown graphically. Further studies are needed for determining the practicality of sensing melon quality from their dielectric properties.

  17. Dielectric material options for integrated capacitors

    NARCIS (Netherlands)

    Ruhl, G.; Lehnert, W.; Lukosius, M.; Wenger, C.; Baristiran Kaynak, C.; Blomberg, T.; Haukka, S.; Baumann, P.K.; Besling, W.F.A.; Roest, A.L.; Riou, B.; Lhostis, S.; Halimaou, A.; Roozeboom, F.; Langereis, E.; Kessels, W.M.M.; Zauner, A.; Rushworth, S.A.

    2014-01-01

    Future MIM capacitor generations will require significantly increased specific capacitances by utilization of high-k dielectric materials. In order to achieve high capacitance per chip area, these dielectrics have to be deposited in three-dimensional capacitor structures by ALD or AVD (atomic vapor

  18. Analysis of electron interactions in dielectric gases

    International Nuclear Information System (INIS)

    Olivet, Aurelio; Duque, Daniel; Vega, Lourdes F.

    2007-01-01

    We present and discuss results concerning electron interactions processes of dielectric gases and their relationship with the macroscopic behavior of these gases, in particular, with their dielectric strength. Such analysis is based on calculating energies of reactions for molecular ionization, dissociative ionization, parent negative ion formation, and dissociative electron attachment processes. We hypothesize that the estimation of the required energy for a reduced number of processes that take place in electrically stressed gases could be related to the gas' capability to manage the electron flow during an electrical discharge. All calculations were done with semiempirical quantum chemistry methods, including an initial optimization of molecular geometry and heat of formation of the dielectric gases and all of species that appear during electron interaction reactions. The performance of semiempirical methods Austin model 1 and Parametric model 3 (PM3) was compared for several compounds, PM3 being superior in most cases. Calculations performed for a sample of nine dielectric gases show that electron attachment and detachment processes occur in different energy bands that do not overlap for any value of the dielectric strength. We have also analyzed the relationship between dielectric strength and two physical properties: electron affinity and ionization energy. Calculations performed for 43 dielectric gases show no clear correlation between them, although certain guidelines for the qualitative estimation of dielectric strength can still be assessed

  19. Aging of Dielectric Properties below Tg

    DEFF Research Database (Denmark)

    Olsen, Niels Boye; Dyre, Jeppe; Christensen, Tage Emil

    The dielectric loss at 1Hz in TPP is studied during a temperature step from one equilibrium state to another. In the applied cryostate the temperature can be equilibrated on a timescale of 1 second. The aging time dependence of the dielectric loss is studied below Tg applying temperature steps...

  20. Microscopic resolution broadband dielectric spectroscopy

    International Nuclear Information System (INIS)

    Mukherjee, S; Watson, P; Prance, R J

    2011-01-01

    Results are presented for a non-contact measurement system capable of micron level spatial resolution. It utilises the novel electric potential sensor (EPS) technology, invented at Sussex, to image the electric field above a simple composite dielectric material. EP sensors may be regarded as analogous to a magnetometer and require no adjustments or offsets during either setup or use. The sample consists of a standard glass/epoxy FR4 circuit board, with linear defects machined into the surface by a PCB milling machine. The sample is excited with an a.c. signal over a range of frequencies from 10 kHz to 10 MHz, from the reverse side, by placing it on a conducting sheet connected to the source. The single sensor is raster scanned over the surface at a constant working distance, consistent with the spatial resolution, in order to build up an image of the electric field, with respect to the reference potential. The results demonstrate that both the surface defects and the internal dielectric variations within the composite may be imaged in this way, with good contrast being observed between the glass mat and the epoxy resin.

  1. Microscopic resolution broadband dielectric spectroscopy

    Science.gov (United States)

    Mukherjee, S.; Watson, P.; Prance, R. J.

    2011-08-01

    Results are presented for a non-contact measurement system capable of micron level spatial resolution. It utilises the novel electric potential sensor (EPS) technology, invented at Sussex, to image the electric field above a simple composite dielectric material. EP sensors may be regarded as analogous to a magnetometer and require no adjustments or offsets during either setup or use. The sample consists of a standard glass/epoxy FR4 circuit board, with linear defects machined into the surface by a PCB milling machine. The sample is excited with an a.c. signal over a range of frequencies from 10 kHz to 10 MHz, from the reverse side, by placing it on a conducting sheet connected to the source. The single sensor is raster scanned over the surface at a constant working distance, consistent with the spatial resolution, in order to build up an image of the electric field, with respect to the reference potential. The results demonstrate that both the surface defects and the internal dielectric variations within the composite may be imaged in this way, with good contrast being observed between the glass mat and the epoxy resin.

  2. Bistable scattering in graphene-coated dielectric nanowires.

    Science.gov (United States)

    Li, Rujiang; Wang, Huaping; Zheng, Bin; Dehdashti, Shahram; Li, Erping; Chen, Hongsheng

    2017-06-22

    In nonlinear plasmonics, the switching threshold of optical bistability is limited by the weak nonlinear responses from the conventional Kerr dielectric media. Considering the giant nonlinear susceptibility of graphene, here we develop a nonlinear scattering model under the mean field approximation and study the bistable scattering in graphene-coated dielectric nanowires based on the semi-analytical solutions. We find that the switching intensities of bistable scattering can be smaller than 1 MW cm -2 at the working frequency. To further decrease the switching intensities, we show that the most important factor that restricts the bistable scattering is the relaxation time of graphene. Our work not only reveals some general characteristics of graphene-based bistable scattering, but also provides a guidance to further applications of optical bistability in the high speed all-optical signal processing.

  3. Numerical investigation of dielectric barrier discharges

    Science.gov (United States)

    Li, Jing

    1997-12-01

    A dielectric barrier discharge (DBD) is a transient discharge occurring between two electrodes in coaxial or planar arrangements separated by one or two layers of dielectric material. The charge accumulated on the dielectric barrier generates a field in a direction opposite to the applied field. The discharge is quenched before an arc is formed. It is one of the few non-thermal discharges that operates at atmospheric pressure and has the potential for use in pollution control. In this work, a numerical model of the dielectric barrier discharge is developed, along with the numerical approach. Adaptive grids based on the charge distribution is used. A self-consistent method is used to solve for the electric field and charge densities. The Successive Overrelaxation (SOR) method in a non-uniform grid spacing is used to solve the Poisson's equation in the cylindrically-symmetric coordinate. The Flux Corrected Transport (FCT) method is modified to solve the continuity equations in the non-uniform grid spacing. Parametric studies of dielectric barrier discharges are conducted. General characteristics of dielectric barrier discharges in both anode-directed and cathode-directed streamer are studied. Effects of the dielectric capacitance, the applied field, the resistance in external circuit and the type of gases (O2, air, N2) are investigated. We conclude that the SOR method in an adaptive grid spacing for the solution of the Poisson's equation in the cylindrically-symmetric coordinate is convergent and effective. The dielectric capacitance has little effect on the g-factor of radical production, but it determines the strength of the dielectric barrier discharge. The applied field and the type of gases used have a significant role on the current peak, current pulse duration and radical generation efficiency, discharge strength, and microstreamer radius, whereas the external series resistance has very little effect on the streamer properties. The results are helpful in

  4. Cluster synthesis of monodisperse rutile-TiO2 nanoparticles and dielectric TiO2-vinylidene fluoride oligomer nanocomposites

    International Nuclear Information System (INIS)

    Balasubramanian, Balamurugan; Kraemer, Kristin L; Valloppilly, Shah R; Ducharme, Stephen; Sellmyer, David J

    2011-01-01

    The embedding of oxide nanoparticles in polymer matrices produces a greatly enhanced dielectric response by combining the high dielectric strength and low loss of suitable host polymers with the high electric polarizability of nanoparticles. The fabrication of oxide-polymer nanocomposites with well-controlled distributions of nanoparticles is, however, challenging due to the thermodynamic and kinetic barriers between the polymer matrix and nanoparticle fillers. In the present study, monodisperse TiO 2 nanoparticles having an average particle size of 14.4 nm and predominant rutile phase were produced using a cluster-deposition technique without high-temperature thermal annealing and subsequently coated with uniform vinylidene fluoride oligomer (VDFO) molecules using a thermal evaporation source, prior to deposition as TiO 2 -VDFO nanocomposite films on suitable substrates. The molecular coatings on TiO 2 nanoparticles serve two purposes, namely to prevent the TiO 2 nanoparticles from contacting each other and to couple the nanoparticle polarization to the matrix. Parallel-plate capacitors made of TiO 2 -VDFO nanocomposite film as the dielectric exhibit minimum dielectric dispersion and low dielectric loss. Dielectric measurements also show an enhanced effective dielectric constant in TiO 2 -VDFO nanocomposites as compared to that of pure VDFO. This study demonstrates for the first time a unique electroactive particle coating in the form of a ferroelectric VDFO that has high-temperature stability as compared to conventionally used polymers for fabricating dielectric oxide-polymer nanocomposites.

  5. Disclosed dielectric and electromechanical properties of hydrogenated nitrile–butadiene dielectric elastomer

    International Nuclear Information System (INIS)

    Yang, Dan; Tian, Ming; Dong, Yingchao; Liu, Haoliang; Yu, Yingchun; Zhang, Liqun

    2012-01-01

    This paper presents a comprehensive study of the effects of acrylonitrile content, crosslink density and plasticization on the dielectric and electromechanical performances of hydrogenated nitrile–butadiene dielectric elastomer. It was found that by increasing the acrylonitrile content of hydrogenated nitrile–butadiene dielectric elastomer, the dielectric constant will be improved accompanied with a sharp decrease of electrical breakdown strength leading to a small actuated strain. At a fixed electric field, a high crosslink density increased the elastic modulus of dielectric elastomer, but it also enhanced the electrical breakdown strength leading to a high actuated strain. Adding a plasticizer into the dielectric elastomer decreased the dielectric constant and electrical breakdown strength slightly, but reduced the elastic modulus sharply, which was beneficial for obtaining a large strain at low electric field from the dielectric elastomer. The largest actuated strain of 22% at an electric field of 30 kV mm −1 without any prestrain was obtained. Moreover, the hydrogenated nitrile–butadiene dielectric actuator showed good history dependence. This proposed material has great potential to be an excellent dielectric elastomer. (paper)

  6. The color dielectric model of QCD

    International Nuclear Information System (INIS)

    Pirner, H.-J.; Massachusetts Inst. of Tech., Cambridge, MA; Massachusetts Inst. of Tech., Cambridge, MA

    1992-01-01

    This paper demonstrates the emergence of valence gluons and their bound states, the glueballs from perturbative quantum chromodynamics (QCD). We discuss the phenomenological constraints and theoretical method needed to generate effective glueballs actions. We show how color dielectric confinement works naively and in the lattice model of color dielectrics. This lattice model is derived for SU(2) color by a blockspinning Monte Carlo renormalization group procedure. We interpret the resulting long-distance as a strongly interacting lattice string theory where the valence link gluon fields randomize in the color dielectric background which mimics the integrated out high-frequency gluon modes in the vacuum. The fluctuations of the color dielectric fields are related to color neutral glueballs modes. We give the extension of this color dielectric SU(2) theory for general SU(N) with quarks and address the problems associated with combining confinement and chiral symmetry breaking. Finally we prove the efficiency of the effective theory in applications to the heavy quark system, the the baryon, to the nucleon-nucleon interaction, to baryon models and the gluon plasma transition. In all those cases the behavior of the higher energy gluons can be monitored via the color dielectric fields. An increase in the energy density from ''deconfining'' the higher frequency modes inside the flux tube or in thermally excited matter shows up as an increase in the value of the color dielectric field and its associated energy density. (Author)

  7. Virtual gap dielectric wall accelerator

    Science.gov (United States)

    Caporaso, George James; Chen, Yu-Jiuan; Nelson, Scott; Sullivan, Jim; Hawkins, Steven A

    2013-11-05

    A virtual, moving accelerating gap is formed along an insulating tube in a dielectric wall accelerator (DWA) by locally controlling the conductivity of the tube. Localized voltage concentration is thus achieved by sequential activation of a variable resistive tube or stalk down the axis of an inductive voltage adder, producing a "virtual" traveling wave along the tube. The tube conductivity can be controlled at a desired location, which can be moved at a desired rate, by light illumination, or by photoconductive switches, or by other means. As a result, an impressed voltage along the tube appears predominantly over a local region, the virtual gap. By making the length of the tube large in comparison to the virtual gap length, the effective gain of the accelerator can be made very large.

  8. Standards for dielectric elastomer transducers

    International Nuclear Information System (INIS)

    Carpi, Federico; Frediani, Gabriele; Anderson, Iain; Bauer, Siegfried; Gallone, Giuseppe; Gei, Massimiliano; Graaf, Christian; Jean-Mistral, Claire; Kaal, William; Kofod, Guggi; Kollosche, Matthias; Kornbluh, Roy; Pelrine, Ron; Lassen, Benny; Rechenbach, Björn; Matysek, Marc; Michel, Silvain; Nowak, Stephan; O’Brien, Benjamin; Pei, Qibing

    2015-01-01

    Dielectric elastomer transducers consist of thin electrically insulating elastomeric membranes coated on both sides with compliant electrodes. They are a promising electromechanically active polymer technology that may be used for actuators, strain sensors, and electrical generators that harvest mechanical energy. The rapid development of this field calls for the first standards, collecting guidelines on how to assess and compare the performance of materials and devices. This paper addresses this need, presenting standardized methods for material characterisation, device testing and performance measurement. These proposed standards are intended to have a general scope and a broad applicability to different material types and device configurations. Nevertheless, they also intentionally exclude some aspects where knowledge and/or consensus in the literature were deemed to be insufficient. This is a sign of a young and vital field, whose research development is expected to benefit from this effort towards standardisation. (paper)

  9. Standards for dielectric elastomer transducers

    Science.gov (United States)

    Carpi, Federico; Anderson, Iain; Bauer, Siegfried; Frediani, Gabriele; Gallone, Giuseppe; Gei, Massimiliano; Graaf, Christian; Jean-Mistral, Claire; Kaal, William; Kofod, Guggi; Kollosche, Matthias; Kornbluh, Roy; Lassen, Benny; Matysek, Marc; Michel, Silvain; Nowak, Stephan; O'Brien, Benjamin; Pei, Qibing; Pelrine, Ron; Rechenbach, Björn; Rosset, Samuel; Shea, Herbert

    2015-10-01

    Dielectric elastomer transducers consist of thin electrically insulating elastomeric membranes coated on both sides with compliant electrodes. They are a promising electromechanically active polymer technology that may be used for actuators, strain sensors, and electrical generators that harvest mechanical energy. The rapid development of this field calls for the first standards, collecting guidelines on how to assess and compare the performance of materials and devices. This paper addresses this need, presenting standardized methods for material characterisation, device testing and performance measurement. These proposed standards are intended to have a general scope and a broad applicability to different material types and device configurations. Nevertheless, they also intentionally exclude some aspects where knowledge and/or consensus in the literature were deemed to be insufficient. This is a sign of a young and vital field, whose research development is expected to benefit from this effort towards standardisation.

  10. Role of dielectric effects in the red-green switching of porous silicon luminescence

    International Nuclear Information System (INIS)

    Chazalviel, J.N.; Ozanam, F.; Dubin, V.M.

    1994-01-01

    Trapping of a carrier at an ionized impurity in porous silicon may be significantly hindered when the material is embedded in a high-dielectric-constant medium such as an aqueous electrolyte. This effect is estimated for a geometry of cylindrical silicon wires, and by modeling the two media with wavevector-independent dielectric constants. The self-image potential of the electron is taken into account, and the frequency dependence of the outer dielectric constant is treated in a simple manner. The results demonstrate that the impurity states are not accessible in the presence of the electrolyte, just due to the dielectric relaxation of the embedding medium. This result may apply to different kinds of localized electronic states, including those responsible for the red luminescence in dry porous silicon. This provides a plausible explanation for the red to green switching of the luminescence when the porous silicon is wet and suggests that using embedding media of intermediate dielectric constants should allow one to observe a progressive transition between red and green luminescence. Observation of porous silicon luminescence in solvents of various dielectric constants provides a preliminary test of this prediction. (orig.)

  11. Radiation pressure on a dielectric surface

    International Nuclear Information System (INIS)

    Hirose, A.

    2010-01-01

    The radiation pressure on an insulating dielectric medium should be calculable from the force acting on the polarization vector P. The well-known force proposed by Gordon (Phys. Rev. A, 8, 14 (1973) disappears in the case of a steady-state plane wave. A new form of force explicitly involving the polarization vector is proposed and applied to determine the partition of the incident momentum among the reflected and transmitted wave, and the dielectric medium. The momentum of electromagnetic wave in a dielectric medium thus found is consistent with the classical relationship, wave momentum flux density = wave intensity/wave velocity. (author)

  12. Modeling the dielectric logging tool at high frequency

    International Nuclear Information System (INIS)

    Chew, W.C.

    1987-01-01

    The high frequency dielectric logging tool has been used widely in electromagnetic well logging, because by measuring the dielectric constant at high frequencies (1 GHz), the water saturation of rocks could be known without measuring the water salinity in the rocks. As such, it could be used to delineate fresh water bearing zones, as the dielectric constant of fresh water is much higher than that of oil while they may have the same resistivity. The authors present a computer model, though electromagnetic field analysis, the response of such a measurement tool in a well logging environment. As the measurement is performed at high frequency, usually with small separation between the transmitter and receivers, some small geological features could be measured by such a tool. They use the computer model to study the behavior of such a tool across geological bed boundaries, and also across thin geological beds. Such a study could be very useful in understanding the limitation on the resolution of the tool. Furthermore, they could study the standoff effect and the depth of investigation of such a tool. This could delineate the range of usefulness of the measurement

  13. Photoinduced Giant Dielectric Constant in Lead Halide Perovskite Solar Cells.

    Science.gov (United States)

    Juarez-Perez, Emilio J; Sanchez, Rafael S; Badia, Laura; Garcia-Belmonte, Germá; Kang, Yong Soo; Mora-Sero, Ivan; Bisquert, Juan

    2014-07-03

    Organic-inorganic lead trihalide perovskites have emerged as an outstanding photovoltaic material that demonstrated a high 17.9% conversion efficiency of sunlight to electricity in a short time. We have found a giant dielectric constant (GDC) phenomenon in these materials consisting on a low frequency dielectric constant in the dark of the order of ε0 = 1000. We also found an unprecedented behavior in which ε0 further increases under illumination or by charge injection at applied bias. We observe that ε0 increases nearly linearly with the illumination intensity up to an additional factor 1000 under 1 sun. Measurement of a variety of samples of different morphologies, compositions, and different types of contacts shows that the GDC is an intrinsic property of MAPbX3 (MA = CH3NH3(+)). We hypothesize that the large dielectric response is induced by structural fluctuations. Photoinduced carriers modify the local unit cell equilibrium and change the polarizability, assisted by the freedom of rotation of MA. The study opens a way for the understanding of a key aspect of the photovoltaic operation of high efficiency perovskite solar cells.

  14. A simple method for reducing inevitable dielectric loss in high-permittivity dielectric elastomers

    DEFF Research Database (Denmark)

    Madsen, Frederikke Bahrt; Yu, Liyun; Mazurek, Piotr Stanislaw

    2016-01-01

    elastomer matrix, with high dielectric permittivity and a low Young's modulus, aligned with no loss of mechanical stability, was prepared through the use of commercially available chloropropyl-functional silicone oil mixed into a tough commercial liquid silicone rubber silicone elastomer. The addition...... also decreased the dielectric losses of an elastomer containing dielectric permittivity-enhancing TiO2 fillers. Commercially available chloropropyl-functional silicone oil thus constitutes a facile method for improved silicone DEs, with very low dielectric losses.......Commercial viability of dielectric elastomers (DEs) is currently limited by a few obstacles, including high driving voltages (in the kV range). Driving voltage can be lowered by either decreasing the Young's modulus or increasing the dielectric permittivity of silicone elastomers, or a combination...

  15. Colossal magnetoresistance in amino-functionalized graphene quantum dots at room temperature: manifestation of weak anti-localization and doorway to spintronics

    Science.gov (United States)

    Roy, Rajarshi; Thapa, Ranjit; Kumar, Gundam Sandeep; Mazumder, Nilesh; Sen, Dipayan; Sinthika, S.; Das, Nirmalya S.; Chattopadhyay, Kalyan K.

    2016-04-01

    In this work, we have demonstrated the signatures of localized surface distortions and disorders in functionalized graphene quantum dots (fGQD) and consequences in magneto-transport under weak field regime (~1 Tesla) at room temperature. Observed positive colossal magnetoresistance (MR) and its suppression is primarily explained by weak anti-localization phenomenon where competitive valley (inter and intra) dependent scattering takes place at room temperature under low magnetic field; analogous to low mobility disordered graphene samples. Furthermore, using ab-initio analysis we show that sub-lattice sensitive spin-polarized ground state exists in the GQD as a result of pz orbital asymmetry in GQD carbon atoms with amino functional groups. This spin polarized ground state is believed to help the weak anti-localization dependent magneto transport by generating more disorder and strain in a GQD lattice under applied magnetic field and lays the premise for future graphene quantum dot based spintronic applications.In this work, we have demonstrated the signatures of localized surface distortions and disorders in functionalized graphene quantum dots (fGQD) and consequences in magneto-transport under weak field regime (~1 Tesla) at room temperature. Observed positive colossal magnetoresistance (MR) and its suppression is primarily explained by weak anti-localization phenomenon where competitive valley (inter and intra) dependent scattering takes place at room temperature under low magnetic field; analogous to low mobility disordered graphene samples. Furthermore, using ab-initio analysis we show that sub-lattice sensitive spin-polarized ground state exists in the GQD as a result of pz orbital asymmetry in GQD carbon atoms with amino functional groups. This spin polarized ground state is believed to help the weak anti-localization dependent magneto transport by generating more disorder and strain in a GQD lattice under applied magnetic field and lays the premise for

  16. Epoxy matrix with triaromatic mesogenic unit in dielectric spectroscopy observation

    Science.gov (United States)

    Włodarska, Magdalena; Mossety-Leszczak, Beata; Bąk, Grzegorz W.; Kisiel, Maciej; Dłużniewski, Maciej; Okrasa, Lidia

    2018-04-01

    This paper describes the dielectric response of a selected liquid crystal epoxy monomer (plain and in curing systems) in a wide range of frequency and temperature. The dielectric spectroscopy, thanks to its sensitivity, is a very good tool for studying phase transitions, reaction progress, or material properties. This sensitivity is important in the case of liquid crystal epoxy resins, where properties of the final network depend on the choice of monomers, curing agents, curing conditions and post-curing treatment, or applying an external electric or magnetic field during the reaction. In most of the obtained cured products, the collected dielectric data show two relaxation processes. The α-process is related to a structural reorientation; it can usually be linked with the glass transition and the mechanical properties of the material. The β-process can be identified as a molecular motion process, probably associated with the carboxyl groups in the mesogen. A transient Maxwell-Wagner relaxation observed in one of the compositions after the initial curing is removed by post-curing treatment at elevated temperatures. Post-curing is therefore necessary for obtaining uniformly cured products in those cases. In the investigated systems, the choice of a curing agent can change the glass transition temperature by at least 70 °C. The obtained results are in a good agreement with an earlier study employing other techniques. Finally, we assess the influence of the direction of mesogen alignment on the dielectric properties of one selected system, where a global order was induced by applying an external magnetic field in the course of curing.

  17. Colossal change in thermopower with temperature-driven p-n-type conduction switching in La x Sr2-x TiFeO6 double perovskites

    Science.gov (United States)

    Roy, Pinku; Maiti, Tanmoy

    2018-02-01

    Double perovskite materials have been studied in detail by many researchers, as their magnetic and electronic properties can be controlled by the substitution of alkaline earth metals or lanthanides in the A site and transition metals in the B site. Here we report the temperature-driven, p-n-type conduction switching assisted, large change in thermopower in La3+-doped Sr2TiFeO6-based double perovskites. Stoichiometric compositions of La x Sr2-x TiFeO6 (LSTF) with 0  ⩽  x  ⩽  0.25 were synthesized by the solid-state reaction method. Rietveld refinement of room-temperature XRD data confirmed a single-phase solid solution with cubic crystal structure and Pm\\bar{3}m space group. From temperature-dependent electrical conductivity and Seebeck coefficient (S) studies it is evident that all the compositions underwent an intermediate semiconductor-to-metal transition before the semiconductor phase reappeared at higher temperature. In the process of semiconductor-metal-semiconductor transition, LSTF compositions demonstrated temperature-driven p-n-type conduction switching behavior. The electronic restructuring which occurs due to the intermediate metallic phase between semiconductor phases leads to the colossal change in S for LSTF oxides. The maximum drop in thermopower (ΔS ~ 2516 µV K-1) was observed for LSTF with x  =  0.1 composition. Owing to their enormous change in thermopower of the order of millivolts per kelvin, integrated with p-n-type resistance switching, these double perovskites can be used for various high-temperature multifunctional device applications such as diodes, sensors, switches, thermistors, thyristors, thermal runaway monitors etc. Furthermore, the conduction mechanisms of these oxides were explained by the small polaron hopping model.

  18. Temperature dependent evolution of the electronic and local atomic structure in the cubic colossal magnetoresistive manganite La1-xSrxMnO3

    International Nuclear Information System (INIS)

    Arenholz, Elke; Mannella, N.; Booth, C.H.; Rosenhahn, A.; Sell, B.C.; Nambu, A.; Marchesini, S.; Mun, B. S.; Yang, S.-H.; Watanabe, M.; Ibrahim, K.; Arenholz, E.; Young, A.; Guo, J.; Tomioka, Y.; Fadley, C.S.

    2007-01-01

    We have studied the temperature-dependent evolution of the electronic and local atomic structure in the cubic colossal magnetoresistive manganite La 1-x Sr x MnO 3 (x= 0.3-0.4) with core and valence level photoemission (PE), x-ray absorption spectroscopy (XAS), x-ray emission spectroscopy (XES), resonant inelastic x-ray scattering (RIXS), extended x-ray absorption fine structure (EXAFS) spectroscopy and magnetometry. As the temperature is varied across the Curie temperature T c , our PE experiments reveal a dramatic change of the electronic structure involving an increase in the Mn spin moment from ∼ 3 (micro)B to ∼ 4 (micro)B, and a modification of the local chemical environment of the other constituent atoms indicative of electron localization on the Mn atom. These effects are reversible and exhibit a slow-timescale ∼200 K-wide hysteresis centered at T c . Based upon the probing depths accessed in our PE measurements, these effects seem to survive for at least 35-50 (angstrom) inward from the surface, while other consistent signatures for this modification of the electronic structure are revealed by more bulk sensitive spectroscopies like XAS and XES/RIXS. We interpret these effects as spectroscopic fingerprints for polaron formation, consistent with the presence of local Jahn-Teller distortions of the MnO 6 octahedra around the Mn atom, as revealed by the EXAFS data. Magnetic susceptibility measurements in addition show typical signatures of ferro-magnetic clusters formation well above the Curie temperature

  19. Effects of dopant ion and Mn valence state in the La1-xAxMnO3 (A=Sr,Ba) colossal magnetoresistance films

    International Nuclear Information System (INIS)

    Choi, Sun Gyu; Wang, Seok-Joo; Park, Hyung-Ho; Hong, MunPyo; Kwon, Kwang-Ho

    2010-01-01

    The structural and electrical properties of Mn-based colossal magnetoresistance (CMR) thin films with controlled tolerance factor and Mn ion valance ratio were studied using crystal structure and chemical bonding character analyses. La 0.7 Sr 0.3 MnO 3 , La 0.7 Ba 0.3 MnO 3 , and La 0.82 Ba 0.18 MnO 3 thin films with different contents of divalent cations and Mn 3+ /Mn 4+ ratios were deposited on amorphous SiO 2 /Si substrate by rf magnetron sputtering at a substrate temperature of 350 deg. C. The films showed the same crystalline structure as the pseudocubic structure. The change in the sheet resistance of films was analyzed according to strain state of the unit cell, chemical bonding character of Mn-O, and Mn 3+ /Mn 4+ ratio controlling the Mn 3+ -O 2- -Mn 4+ conducting path. Mn L-edge x-ray absorption spectra revealed that the Mn 3+ /Mn 4+ ratio changed according to different compositions of Sr or Ba and the Mn 2p core level x-ray photoelectron spectra showed that the Mn 2p binding energy was affected by the covalence of the Mn-O bond and Mn 3+ /Mn 4+ ratio. In addition, O K-edge x-ray absorption spectra showed covalently mixed Mn 3d and O 2p states and matched well with the resistivity changes of CMR films. Temperature coefficient of resistance values were obtained at approximately -2.16%/K to -2.46%/K of the CMR films and were correct for infrared sensor applications.

  20. Twinning microstructure and charge ordering in the colossal magnetoresistive manganite Nd1/2Sr1/2MnO3

    International Nuclear Information System (INIS)

    Luo, Z.P.; Miller, D.J.; Mitchell, J.F.

    2000-01-01

    Charge ordering (C.O.) in the colossal magnetoresistive (CMR) manganites gives rise to an insulating, high-resistance state. This charge ordered state can be melted into a low-resistance metallic-like state by the application of magnetic field. Thus, the potential to attain high values of magnetoresistance with the application of small magnetic fields may be aided by a better understanding of the charge-ordering phenomenon. This study focused on microstructural characterization in Nd 1/2 Sr 1/2 MnO 3 . In Nd 1/2 Sr 1/2 MnO 3 , the nominal valence of Mn is 3.5+. On cooling, charge can localize and lead to a charge ordering between Mn 3+ and Mn 4+. The ordering of charge results in a superlattice structure and a reduction in symmetry. Thin foil specimens were prepared from bulk samples by conventional thinning and ion milling (at LiqN 2 temperature) methods. The room temperature TEM observation of Nd 1/2 Sr 1/2 MnO 3 reveals that it contains a highly twinned microstructure, together with a small number of stacking faults (SFS). A figure shows the same area of the specimen at different zone axes obtained by tilting around two perpendicular directions as indicated. Three grains A, B and C are labeled for each of the zone axes. The room temperature EDPs from the matrix and twins shows an approximate 90degree rotation suggesting a 90degree twin orientation. These results are further confirmed by C.O. at low temperatures. The twinning planes can be determined by tilting with large angles

  1. Colossal thermoelectric power in charge ordered lanthanum calcium manganites (La{sub 0.5}Ca{sub 0.5}MnO{sub 3})

    Energy Technology Data Exchange (ETDEWEB)

    Joy, Lija K.; Anantharaman, M. R., E-mail: mraiyer@yahoo.com [Department of Physics, Cochin University of Science and Technology, Cochin 682022 (India); Shanmukharao Samatham, S.; Ganesan, V. [Low temperature division, UGC-DAE Consortium for Scientific Research, Indore (India); Thomas, Senoy [Material Science and Technology Division, National Institute for Interdisciplinary Science and Technology, Thiruvananthapuram–695019 (India); Al-Harthi, Salim [Department of Physics, Sultan Qaboos University, Muscat PC 123, Sultanate of Oman (Oman); Liebig, A.; Albrecht, M. [Institute of Physics, University of Augsburg, Augsburg 86135 (Germany)

    2014-12-07

    Lanthanum calcium manganites (La{sub 0.5}Ca{sub 0.5}MnO{sub 3}) with a composition close to charge ordering, synthesized by high energy ball milling, was found to exhibit colossal thermoelectric power. Thermoelectric power (TEP) data was systematically analyzed by dividing the entire temperature range (5 K–300 K) into three different regimes to explore different scattering mechanisms involved. Mandal's model has been applied to explain TEP data in the region below the Curie temperature (T{sub C}). It has been found that the variation of thermoelectric power with temperature is pronounced when the system enters the charge ordered region at T < 200 K. For temperatures lower than 120 K, due to the co-existence of charge ordered state with a spin-glass state, the variation of thermoelectric power is maximum and exhibited a peak value of −80 mV/K at 58 K. This has been explained by incorporating Kondo properties of the spin-glass along with magnon scattering. FC-ZFC magnetization measurements indicate the existence of a glassy state in the region corresponding to a maximum value of thermoelectric power. Phonon drag contribution instead of spin-glass contribution is taken into account to explain TEP in the region 120 K < T < T{sub C}. Mott's polaronic contribution of charge carriers are considered to interpret TEP in the high temperature region (T > T{sub C}). The optimal Mn{sup 4+}-Mn{sup 3+} concentration in charge ordered La{sub 0.5}Ca{sub 0.5}MnO{sub 3} was examined by X-ray Photoelectron Spectroscopy analysis which confirms the charge ordered nature of this compound.

  2. Effect of combined external uniaxial stress and dc bias on the dielectric property of BaTiO3-based dielectrics in multilayer ceramic capacitor: thermodynamics and experiments

    International Nuclear Information System (INIS)

    Yang Gang; Yue Zhenxing; Sun Tieyu; Gou Huanlin; Li Longtu

    2008-01-01

    The dielectric properties of (Nb, Y)-doped BaTiO 3 in a multilayer ceramic capacitor (MLCC) under combined external uniaxial compressive stress and dc bias field were investigated at room temperature by using a modified Ginsburg-Landau-Devonshire thermodynamic theory and the dielectric measurement. It is found that although dc bias decreases the dielectric properties dominantly, the influence of the external uniaixial compressive stress should not be neglected. When applied along a direction perpendicular to the internal electrode layer in the MLCC, the external uniaixal compressive stress will strengthen the negative effect of dc bias. In contrast, the external uniaxial compressive stress along a direction parallel to the internal electrode layer in the MLCC will increase the dielectric permittivity under dc bias field, i.e. improve the ε-V response of the MLCC. Furthermore, although there is a difference between the calculated permittivity and the measured permittivity, the effects of the combined external uniaxial compressive stress and dc bias field on the dielectric permittivity described through two approaches are in good agreement

  3. Stress measurements of planar dielectric elastomer actuators

    International Nuclear Information System (INIS)

    Osmani, Bekim; Aeby, Elise A.; Müller, Bert

    2016-01-01

    Dielectric elastomer actuator (DEA) micro- and nano-structures are referred to artificial muscles because of their specific continuous power and adequate time response. The bending measurement of an asymmetric, planar DEA is described. The asymmetric cantilevers consist of 1 or 5 μm-thin DEAs deposited on polyethylene naphthalate (PEN) substrates 16, 25, 38, or 50 μm thick. The application of a voltage to the DEA electrodes generates an electrostatic pressure in the sandwiched silicone elastomer layer, which causes the underlying PEN substrate to bend. Optical beam deflection enables the detection of the bending angle vs. applied voltage. Bending radii as large as 850 m were reproducibly detected. DEA tests with electric fields of up to 80 V/μm showed limitations in electrode’s conductivity and structure failures. The actuation measurement is essential for the quantitative characterization of nanometer-thin, low-voltage, single- and multi-layer DEAs, as foreseen for artificial sphincters to efficiently treat severe urinary and fecal incontinence.

  4. A soft compressive sensor using dielectric elastomers

    International Nuclear Information System (INIS)

    Zhang, Hongying; Wang, Michael Yu; Li, Jisen; Zhu, Jian

    2016-01-01

    This paper proposes a methodology to design, analyze and fabricate a soft compressive sensor, made of dielectric elastomers that are able to recover from large strain. Each module of the compressive sensor is modeled as a capacitor, comprising a DE membrane sandwiched between two compliant electrodes. When the sensor modules aligned in an array were subject to a compressive load, the induced deformation on the corresponding module resulted in capacitance increase. By detecting the capacitance signal, not only the position but also the magnitude of the compressive load were obtained. We built an analytical model to simulate the mechanical–electrical responses of two common soft sensor structures, namely with and without an embedded air chamber. The simulation results showed that the air embedded prototype improved the sensitivity of the sensor significantly, which was consistent with the experimental results, where the sensitivity is enhanced from 0.05 N −1 to 0.91 N −1 . Furthermore, the effect of the air chamber dimension on the sensitivity is also discussed theoretically and experimentally. It concluded that the detection range increased with the air chamber height over length ratio. (paper)

  5. Stress measurements of planar dielectric elastomer actuators

    Energy Technology Data Exchange (ETDEWEB)

    Osmani, Bekim; Aeby, Elise A.; Müller, Bert [Biomaterials Science Center, University of Basel, Gewerbestrasse 14, 4123 Allschwil (Switzerland)

    2016-05-15

    Dielectric elastomer actuator (DEA) micro- and nano-structures are referred to artificial muscles because of their specific continuous power and adequate time response. The bending measurement of an asymmetric, planar DEA is described. The asymmetric cantilevers consist of 1 or 5 μm-thin DEAs deposited on polyethylene naphthalate (PEN) substrates 16, 25, 38, or 50 μm thick. The application of a voltage to the DEA electrodes generates an electrostatic pressure in the sandwiched silicone elastomer layer, which causes the underlying PEN substrate to bend. Optical beam deflection enables the detection of the bending angle vs. applied voltage. Bending radii as large as 850 m were reproducibly detected. DEA tests with electric fields of up to 80 V/μm showed limitations in electrode’s conductivity and structure failures. The actuation measurement is essential for the quantitative characterization of nanometer-thin, low-voltage, single- and multi-layer DEAs, as foreseen for artificial sphincters to efficiently treat severe urinary and fecal incontinence.

  6. Dielectric properties of nanosilica filled epoxy nanocomposites

    Indian Academy of Sciences (India)

    M G Veena

    Polymer nanocomposites are the 21st century engineering materials with wide range of ... the electronic industry for dielectric materials in electrical insulation ..... be ascribed to the interface barriers and chain entangle- ments towards the ...

  7. The Electrical Breakdown of Thin Dielectric Elastomers

    DEFF Research Database (Denmark)

    Zakaria, Shamsul Bin; Morshuis, Peter H. F.; Yahia, Benslimane Mohamed

    2014-01-01

    Dielectric elastomers are being developed for use in actuators, sensors and generators to be used in various applications, such as artificial eye lids, pressure sensors and human motion energy generators. In order to obtain maximum efficiency, the devices are operated at high electrical fields....... This increases the likelihood for electrical breakdown significantly. Hence, for many applications the performance of the dielectric elastomers is limited by this risk of failure, which is triggered by several factors. Amongst others thermal effects may strongly influence the electrical breakdown strength....... In this study, we model the electrothermal breakdown in thin PDMS based dielectric elastomers in order to evaluate the thermal mechanisms behind the electrical failures. The objective is to predict the operation range of PDMS based dielectric elastomers with respect to the temperature at given electric field...

  8. imide, crystal structure, thermal and dielectric studies

    Indian Academy of Sciences (India)

    methyl imidazolium methylidene bis(trifluoromethanesulfonyl)imide, crystal structure, thermal and dielectric studies. BOUMEDIENE HADDAD1,2,3,∗, TAQIYEDDINE MOUMENE2, DIDIER VILLEMIN1,. JEAN-FRANÇOIS LOHIER1 and EL-HABIB ...

  9. Multiscale dipole relaxation in dielectric materials

    DEFF Research Database (Denmark)

    Hansen, Jesper Schmidt

    2016-01-01

    Dipole relaxation from thermally induced perturbations is investigated on different length scales for dielectric materials. From the continuum dynamical equations for the polarisation, expressions for the transverse and longitudinal dipole autocorrelation functions are derived in the limit where ...

  10. Photoconductivity and dielectric studies of potassium pentaborate

    Indian Academy of Sciences (India)

    Single crystal of potassium pentaborate (KB5) has been grown by solution growth ... equipped with the Gunn Oscillator guided with rectangular wave-guide. ... its dielectric behaviour with the change of frequency has also been investigated.

  11. Organic dielectrics in high voltage cables

    Energy Technology Data Exchange (ETDEWEB)

    Vermeer, J

    1962-03-01

    It appears that the limit has been reached in the applicability of oil-impregnated paper as the dielectric for ehv cables, as with rising voltages the prevention of conductor losses becomes increasingly difficult, while the dielectric losses of the insulation, increasing as the square of the voltage, contribute to a greater extent to the temperature rise of the conductor. The power transmitting capacity of ehv cables reaches a maximum at 500 to 600 kV for these reasons. Apart from artificial cooling, a substantial improvement can be obtained only with the use of insulating materials with much lower dielectric losses; these can moreover be applied with a smaller wall thickness, but this means higher field strengths. Synthetic polymer materials meet these requirements but can be used successfully only in the form of lapped film tapes impregnated with suitable liquids. The electrical properties of these heterogeneous dielectrics, in particular, their impulse breakdown strengths are studied in detail.

  12. A model for the scattering of high-frequency electromagnetic fields from dielectrics exhibiting thermally-activated electrical losses

    Science.gov (United States)

    Hann, Raiford E.

    1991-01-01

    An equivalent circuit model (ECM) approach is used to predict the scattering behavior of temperature-activated, electrically lossy dielectric layers. The total electrical response of the dielectric (relaxation + conductive) is given by the ECM and used in combination with transmission line theory to compute reflectance spectra for a Dallenbach layer configuration. The effects of thermally-activated relaxation processes on the scattering properties is discussed. Also, the effect of relaxation and conduction activation energy on the electrical properties of the dielectric is described.

  13. Confinement in the color dielectric model

    International Nuclear Information System (INIS)

    Pirner, H.J.

    1990-01-01

    The paper consists of several parts. In Section 2, I give an introduction to the main physics of lattice gauge theory. Section 3 gives an outline of the colour dielectric model and first numerical results on the effective action after one block-spinning step. Section 4 reviews some new work on the generalization of the colour dielectric model to SU3 colour . (orig./HSI)

  14. In-beam dielectric properties of alumina

    International Nuclear Information System (INIS)

    Molla, J.; Ibarra, A.; Hodgson, E.R.

    1995-01-01

    The dielectric properties (permittivity and loss tangent) of a 99.7% purity alumina grade have been measured over a wide frequency range (1 kHz-15 GHz) before and after 2 MeV electron irradiation at different temperatures. The dielectric properties at 15 GHz were measured during irradiation. Both prompt and fluence effects are observed together with permanent changes which continue to evolve following irradiation. The behaviour is complex, consistent with both radiation induced electronic effects and aggregation processes. ((orig.))

  15. Dielectric spectroscopy as a sensor of membrane headgroup mobility and hydration

    DEFF Research Database (Denmark)

    Klösgen, B; Reichle, C; Kohlsmann, S

    1996-01-01

    Dielectric spectroscopy is based on the response of the permanent dipoles to a driving electric field. The phospholipid membrane systems of dimyristoylphosphatidylcholine and dioleoylphosphatidylcholine can be prepared as samples of multilamellar liposomes with a well known amount of interlamellar...... water. For optimal resolution in dielectric spectroscopy one has to design the experimental set-up so that the direction of the permanent headgroup dipole moment is mostly parallel to the field vector of the external radio frequency (rf) electric field in this layered system. A newly developed coaxial...... probe technique makes it possible to sweep the measuring frequency between 1 and 1000 MHz in the temperature range 286-323 K. The response yields both the dispersion (epsilon') and the absorption part (epsilon") of the complex dielectric permittivity, which are attributed to the rotational diffusions...

  16. Dielectric properties of PMMA/Soot nanocomposites.

    Science.gov (United States)

    Clayton, Lanetra M; Cinke, Martin; Meyyappan, M; Harmon, Julie P

    2007-07-01

    Dielectric analysis (DEA) of relaxation behavior in poly(methyl methacrylate) (PMMA) soot nanocomposites is described herein. The soot, an inexpensive material, consists of carbon nanotubes, amorphous and graphitic carbon and metal particles. Results are compared to earlier studies on PMMA/multi-walled nanotube (MWNT) composites and PMMA/single-walled nanotube (SWNT) composites. The beta relaxation process appeared to be unaffected by the presence of the soot, as was noted earlier in nanotube composites. The gamma relaxation region in PMMA, normally dielectrically inactive, was "awakened" in the PMMA/soot composite. This occurrence is consistent with previously published data on nanotube composites. The dielectric permittivity, s', increased with soot content. The sample with 1% soot exhibited a permittivity (at 100 Hz and 25 degrees C) of 7.3 as compared to 5.1 for neat PMMA. Soot increased the dielectric strength, deltaE, of the composites. The 1% soot sample exhibited a dielectric strength of 6.38, while the neat PMMA had a value of 2.95 at 40 degrees C. The symmetric broadening term (alpha) was slightly higher for the 1% composite at temperatures near the secondary relaxation and near the primary relaxation, but all samples deviated from symmetrical semi-circular behavior (alpha = 1). The impact of the soot filler is seen more clearly in dielectric properties than in mechanical properties studies conducted earlier.

  17. Dielectric loss against piezoelectric power harvesting

    Science.gov (United States)

    Liang, Junrui; Shu-Hung Chung, Henry; Liao, Wei-Hsin

    2014-09-01

    Piezoelectricity is one of the most popular electromechanical transduction mechanisms for constructing kinetic energy harvesting systems. When a standard energy harvesting (SEH) interface circuit, i.e., bridge rectifier plus filter capacitor, is utilized for collecting piezoelectric power, the previous literature showed that the power conversion can be well predicted without much consideration for the effect of dielectric loss. Yet, as the conversion power gets higher by adopting power-boosting interface circuits, such as synchronized switch harvesting on inductor (SSHI), the neglect of dielectric loss might give rise to deviation in harvested power estimation. Given the continuous progress on power-boosting interface circuits, the role of dielectric loss in practical piezoelectric energy harvesting (PEH) systems should receive attention with better evaluation. Based on the integrated equivalent impedance network model, this fast track communication provides a comprehensive study on the susceptibility of harvested power in PEH systems under different conditions. It shows that, dielectric loss always counteracts piezoelectric power harvesting by causing charge leakage across piezoelectric capacitance. In particular, taking corresponding ideal lossless cases as references, the counteractive effect might be aggravated under one of the five conditions: larger dielectric loss tangent, lower vibration frequency, further away from resonance, weaker electromechanical coupling, or using power-boosting interface circuit. These relationships are valuable for the study of PEH systems, as they not only help explain the role of dielectric loss in piezoelectric power harvesting, but also add complementary insights for material, structure, excitation, and circuit considerations towards holistic evaluation and design for practical PEH systems.

  18. Dielectric silicone elastomers with mixed ceramic nanoparticles

    International Nuclear Information System (INIS)

    Stiubianu, George; Bele, Adrian; Cazacu, Maria; Racles, Carmen; Vlad, Stelian; Ignat, Mircea

    2015-01-01

    Highlights: • Composite ceramics nanoparticles (MCN) with zirconium dioxide and lead zirconate. • Dielectric elastomer films wDith PDMS matrix and MCN as dielectric filler. • Hydrophobic character—water resistant and good flexibility specific to siloxanes. • Increased value of dielectric constant with the content of MCN in dielectric films. • Increased energy output from uniaxial deformation of the dielectric elastomer films. - Abstract: A ceramic material consisting in a zirconium dioxide-lead zirconate mixture has been obtained by precipitation method, its composition being proved by wide angle X-ray powder diffraction and energy-dispersive X-ray spectroscopy. The average diameter of the ceramic particles ranged between 50 and 100 nm, as revealed by transmission electron microscopy images. These were surface treated and used as filler for a high molecular mass polydimethylsiloxane-α,ω-diol (Mn = 450,000) prepared in laboratory, the resulted composites being further processed as films and crosslinked. A condensation procedure, unusual for polydimethylsiloxane having such high molecular mass, with a trifunctional silane was approached for the crosslinking. The effect of filler content on electrical and mechanical properties of the resulted materials was studied and it was found that the dielectric permittivity of nanocomposites increased in line with the concentration of ceramic nanoparticles

  19. Dielectric silicone elastomers with mixed ceramic nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Stiubianu, George, E-mail: george.stiubianu@icmpp.ro [“Petru Poni” Institute of Macromolecular Chemistry, Aleea Gr. Ghica Voda 41A, Iasi 700487 (Romania); Bele, Adrian; Cazacu, Maria; Racles, Carmen; Vlad, Stelian [“Petru Poni” Institute of Macromolecular Chemistry, Aleea Gr. Ghica Voda 41A, Iasi 700487 (Romania); Ignat, Mircea [National R& D Institute for Electrical Engineering ICPE-CA Bucharest, Splaiul Unirii 313, District 3, Bucharest 030138 (Romania)

    2015-11-15

    Highlights: • Composite ceramics nanoparticles (MCN) with zirconium dioxide and lead zirconate. • Dielectric elastomer films wDith PDMS matrix and MCN as dielectric filler. • Hydrophobic character—water resistant and good flexibility specific to siloxanes. • Increased value of dielectric constant with the content of MCN in dielectric films. • Increased energy output from uniaxial deformation of the dielectric elastomer films. - Abstract: A ceramic material consisting in a zirconium dioxide-lead zirconate mixture has been obtained by precipitation method, its composition being proved by wide angle X-ray powder diffraction and energy-dispersive X-ray spectroscopy. The average diameter of the ceramic particles ranged between 50 and 100 nm, as revealed by transmission electron microscopy images. These were surface treated and used as filler for a high molecular mass polydimethylsiloxane-α,ω-diol (Mn = 450,000) prepared in laboratory, the resulted composites being further processed as films and crosslinked. A condensation procedure, unusual for polydimethylsiloxane having such high molecular mass, with a trifunctional silane was approached for the crosslinking. The effect of filler content on electrical and mechanical properties of the resulted materials was studied and it was found that the dielectric permittivity of nanocomposites increased in line with the concentration of ceramic nanoparticles.

  20. Strain tunable ferroelectric and dielectric properties of BaZrO3

    International Nuclear Information System (INIS)

    Zhang, Yajun; Liu, Man; Shimada, Takahiro; Kitamura, Takayuki; Wang, Jie

    2014-01-01

    The crucial role of epitaxial (in-plane) strain on the structural, electronic, energetic, ferroelectric, and dielectric properties of BaZrO 3 (BZO) is investigated using density-functional theory calculations. We demonstrate that the BZO crystal subjected to a critical compressive (or tensile) strain exhibits non-trivial spontaneous polarization that is higher than that of well-known ferroelectrics BaTiO 3 , while the BZO crystal is essentially paraelectric in the absence of strain. The electronic structure and Born-effective-charge analyses elucidate that the strain-induced paraelectric-to-ferroelectric transition is driven by the orbital hybridization of d-p electrons between zirconium and oxygen. Through the strain-induced paraelectric-to-ferroelectric phase transition, the dielectric response of BZO is significantly enhanced by the in-plane strain. The tensile strain increases the in-plane dielectric constant by a factor of seven with respect to that without the strain, while the compression tends to enhance the out-of-plane dielectric response. Therefore, strain engineering makes BZO an important electromechanical material due to the diversity in ferroelectric and dielectric properties.

  1. Prehistory effect on dielectric properties of NaNbO3-Gd1/3NbO3

    International Nuclear Information System (INIS)

    Burkhanov, A.I.; Bondarenko, P.V.; Shil'nikov, A.V.; Raevskaya, S.I.; Raevskij, I.P.

    2006-01-01

    One studied the low- and the infralow-frequency dielectric response of 0.9NaNbO 3 -0.1Gd 1/3 NbO 3 (NNG10) composition ceramics and single crystal at the material different prehistory. One revealed the differences in the nature of dielectric aging in NaNbO 3 antiferroelectric base material with a diffused phase transition in contrast to manifestation of similar phenomena in ferroelectrics-relaxors [ru

  2. A many-particle quantum-kinetic formalism for describing properties of light emitters in frozen dielectrics

    Directory of Open Access Journals (Sweden)

    Gladush M.G.

    2017-01-01

    Full Text Available A many particle quantum-kinetic formalism is suggested to derive the Maxwell-Bloch-type equations which describe the interaction of quantum emitters with light in a frozen dielectric. It is shown that the quantum-kinetic formalism can meet the concept of local variations of dielectric properties and their influence on the emitter. The definitions of the local response and the effective refractive index in macroscopically homogeneous media are discussed.

  3. Enhanced performance in capacitive force sensors using carbon nanotube/polydimethylsiloxane nanocomposites with high dielectric properties

    Science.gov (United States)

    Jang, Hyeyoung; Yoon, Hyungsuk; Ko, Youngpyo; Choi, Jaeyoo; Lee, Sang-Soo; Jeon, Insu; Kim, Jong-Ho; Kim, Heesuk

    2016-03-01

    Force sensors have attracted tremendous attention owing to their applications in various fields such as touch screens, robots, smart scales, and wearable devices. The force sensors reported so far have been mainly focused on high sensitivity based on delicate microstructured materials, resulting in low reproducibility and high fabrication cost that are limitations for wide applications. As an alternative, we demonstrate a novel capacitive-type force sensor with enhanced performance owing to the increased dielectric properties of elastomers and simple sensor structure. We rationally design dielectric elastomers based on alkylamine modified-multi-walled carbon nanotube (MWCNT)/polydimethylsiloxane (PDMS) composites, which have a higher dielectric constant than pure PDMS. The alkylamine-MWCNTs show excellent dispersion in a PDMS matrix, thus leading to enhanced and reliable dielectric properties of the composites. A force sensor array fabricated with alkylamine-MWCNT/PDMS composites presents an enhanced response due to the higher dielectric constant of the composites than that of pure PDMS. This study is the first to report enhanced performance of capacitive force sensors by modulating the dielectric properties of elastomers. We believe that the disclosed strategy to improve the sensor performance by increasing the dielectric properties of elastomers has great potential in the development of capacitive force sensor arrays that respond to various input forces.Force sensors have attracted tremendous attention owing to their applications in various fields such as touch screens, robots, smart scales, and wearable devices. The force sensors reported so far have been mainly focused on high sensitivity based on delicate microstructured materials, resulting in low reproducibility and high fabrication cost that are limitations for wide applications. As an alternative, we demonstrate a novel capacitive-type force sensor with enhanced performance owing to the increased

  4. Atomistic determination of flexoelectric properties of crystalline dielectrics

    Science.gov (United States)

    Maranganti, R.; Sharma, P.

    2009-08-01

    Upon application of a uniform strain, internal sublattice shifts within the unit cell of a noncentrosymmetric dielectric crystal result in the appearance of a net dipole moment: a phenomenon well known as piezoelectricity. A macroscopic strain gradient on the other hand can induce polarization in dielectrics of any crystal structure, even those which possess a centrosymmetric lattice. This phenomenon, called flexoelectricity, has both bulk and surface contributions: the strength of the bulk contribution can be characterized by means of a material property tensor called the bulk flexoelectric tensor. Several recent studies suggest that strain-gradient induced polarization may be responsible for a variety of interesting and anomalous electromechanical phenomena in materials including electromechanical coupling effects in nonuniformly strained nanostructures, “dead layer” effects in nanocapacitor systems, and “giant” piezoelectricity in perovskite nanostructures among others. In this work, adopting a lattice dynamics based microscopic approach we provide estimates of the flexoelectric tensor for certain cubic crystalline ionic salts, perovskite dielectrics, III-V and II-VI semiconductors. We compare our estimates with experimental/theoretical values wherever available and also revisit the validity of an existing empirical scaling relationship for the magnitude of flexoelectric coefficients in terms of material parameters. It is interesting to note that two independent groups report values of flexoelectric properties for perovskite dielectrics that are orders of magnitude apart: Cross and co-workers from Penn State have carried out experimental studies on a variety of materials including barium titanate while Catalan and co-workers from Cambridge used theoretical ab initio techniques as well as experimental techniques to study paraelectric strontium titanate as well as ferroelectric barium titanate and lead titanate. We find that, in the case of perovskite

  5. Dielectric dispersion and thermodynamic behavior of stearic acid binary mixtures with alcohol as co-solvent using time domain reflectometry

    Directory of Open Access Journals (Sweden)

    M. Maria Sylvester

    2017-08-01

    Full Text Available Dielectric permittivity and relaxation dynamics of binary and ternary mixture of stearic acid on various concentration and their thermodynamic effects are studied. The static dielectric constant (ε0, dielectric permittivity (ε′ and dielectric loss (ε′′ are found by bilinear calibration. The relaxation time (τ, dielectric strength (Δε and the excess permittivity (εE are found. The thermodynamic parameters such as enthalpy (ΔH, entropy (ΔS and Gibb’s free energy (ΔG are evolved. The significant changes in dielectric parameters are due to the intramolecular and intermolecular interactions in response to the applied frequency. The permittivity spectra of stearic acid–alcohol in the frequency range of 10MHz to 30GHz have been measured using picoseconds Time Domain Reflectometry (TDR. The dielectric parameters (ε0, ε′, ε′′ are found by bilinear calibration method. Influence of temperature in intermolecular interaction and the relaxation process are also studied. The FT-IR spectral analysis reveals that the conformation of functional groups and formation for hydrogen bonding are present in both binary and ternary mixtures of stearic acid.

  6. Radiation Characteristics Enhancement of Dielectric Resonator Antenna Using Solid/Discrete Dielectric Lenses

    Directory of Open Access Journals (Sweden)

    H. A. E. Malhat

    2015-02-01

    Full Text Available The radiation characteristics of the dielectric resonator antennas (DRA is enhanced using different types of solid and discrete dielectric lenses. One of these approaches is by loading the DRA with planar superstrate, spherical lens, or by discrete lens (transmitarray. The dimensions and dielectric constant of each lens are optimized to maximize the gain of the DRA. A comparison between the radiations characteristics of the DRA loaded with different lenses are introduced. The design of the dielectric transmitarray depends on optimizing the heights of the dielectric material of the unit cell. The optimized transmitarray achieves 7 dBi extra gain over the single DRA with preserving the circular polarization. The proposed antenna is suitable for various applications that need high gain and focused antenna beam.

  7. Dielectric properties, optimum formulation and microwave baking conditions of chickpea cakes.

    Science.gov (United States)

    Alifakı, Yaşar Özlem; Şakıyan, Özge

    2017-03-01

    The aim of this study was to correlate dielectric properties with quality parameters, and to optimize cake formulation and baking conditions by response surface methodology. Weight loss, color, specific volume, hardness and porosity were evaluated. The samples with different DATEM (0.4, 0.8 and 1.2%) and chickpea flour concentrations (30, 40 and 50%) were baked in microwave oven at different power (300, 350, 400 W) and baking times (2.50, 3.0, 3.50 min). It was found that microwave power showed significant effect on color, while baking time showed effect on weight loss, porosity, hardness, specific volume and dielectric properties. Emulsifier level affected porosity, specific volume and dielectric constant. Chickpea flour level affected porosity, color, hardness and dielectric properties of cakes. The optimum microwave power, baking time, DATEM level and chickpea flour level were found as 400 W, 2.84 min, 1.2% and 30%, respectively. The comparison between conventionally baked and the microwave baked cakes at optimum points showed that color difference, weight loss, specific volume and porosity values of microwave baked cakes were less than those of conventionally baked cakes, on the other hand, hardness values were higher. Moreover, a negative correlation between dielectric constant and porosity, and weight loss values were detected for microwave baked samples. A negative correlation between dielectric loss factor and porosity was observed. These correlations indicated that quality characteristics of a microwave baked cake sample can be assessed from dielectric properties. These correlations provides understanding on the behavior of food material during microwave processing.

  8. Dielectric effect on electric fields in the vicinity of the metal–vacuum–dielectric junction

    International Nuclear Information System (INIS)

    Chung, M.S.; Mayer, A.; Miskovsky, N.M.; Weiss, B.L.; Cutler, P.H.

    2013-01-01

    The dielectric effect was theoretically investigated in order to describe the electric field in the vicinity of a junction of a metal, dielectric, and vacuum. The assumption of two-dimensional symmetry of the junction leads to a simple analytic form and to a systematic numerical calculation for the field. The electric field obtained for the triple junction was found to be enhanced or reduced according to a certain criterion determined by the contact angles and dielectric constant. Further numerical calculations of the dielectric effect show that an electric field can experience a larger enhancement or reduction for a quadruple junction than that achieved for the triple junction. It was also found that even though it changes slowly in comparison with the shape effect, the dielectric effect was noticeably large over the entire range of the shape change. - Highlights: ► This work explains how a very strong electric field can be produced due to the dielectric in the vicinity of metal–dielectric contact. ► This work deals with configurations which enhance electric fields using the dielectric effect. The configuration is a type of junction at which metal, vacuum and dielectric meet. ► This work suggests the criterion to determine whether field enhancement occurs or not in the triple junction of metal, vacuum and dielectric. ► This work suggests that a quadruple junction is more effective in enhancing the electric field than a triple junction. The quadruple junction is formed by an additional vacuum portion to the triple junction. ► This work suggests that a triple junction can be a breakthrough candidate for a cold electron source

  9. Dielectric properties of binary solutions a data handbook

    CERN Document Server

    Akhadov, Y Y

    1980-01-01

    Dielectric Properties of Binary Solutions focuses on the investigation of the dielectric properties of solutions, as well as the molecular interactions and mechanisms of molecular processes that occur in liquids. The book first discusses the fundamental formulas describing the dielectric properties of liquids and dielectric data for binary systems of non-aqueous solutions. Topics include permittivity and dielectric dispersion parameters of non-aqueous solutions of organic and inorganic compounds. The text also tackles dielectric data for binary systems of aqueous solutions, including permittiv

  10. Dielectric relaxation studies in 5CB nematic liquid crystal at 9 GHz ...

    Indian Academy of Sciences (India)

    Resonance width, shift in resonance frequency, relaxation time and activation energy of 5CB nematic liquid crystal are measured using microwave cavity technique under the influence of an external magnetic field at 9 GHz and at different temperatures. The dielectric response in liquid crystal at different temperatures and ...

  11. Prospects for poor-man's cloaking with low-contrast all-dielectric optical elements

    DEFF Research Database (Denmark)

    Mortensen, Asger; Sigmund, Ole; Breinbjerg, Olav

    2009-01-01

    We discuss the prospects for low-contrast all-dielectric cloaking and offer a simple picture illustrating the basic obstacle for perfect cloaking without materials with an effective double-negative response. However, the same simple picture also gives directions for less perfect designs allowing ......-lens arrays perform in the opposite limit with L l...

  12. Accelerating Dielectrics Design Using Thinking Machines

    Science.gov (United States)

    Ramprasad, R.

    2013-03-01

    High energy density capacitors are required for several pulsed power and energy storage applications, including food preservation, nuclear test simulations, electric propulsion of ships and hybrid electric vehicles. The maximum electrostatic energy that can be stored in a capacitor dielectric is proportional to its dielectric constant and the square of its breakdown field. The current standard material for capacitive energy storage is polypropylene which has a large breakdown field but low dielectric constant. We are involved in a search for new classes of polymers superior to polypropylene using first principles computations combined with statistical and machine learning methods. Essential to this search are schemes to efficiently compute the dielectric constant of polymers and the intrinsic dielectric breakdown field, as well as methods to determine the stable structures of new classes of polymers and strategies to efficiently navigate through the polymer chemical space offered by the periodic table. These methodologies have been combined with statistical learning paradigms in order to make property predictions rapidly, and promising classes of polymeric systems for energy storage applications have been identified. This work is being supported by the Office of Naval Research.

  13. Evaluation of high temperature capacitor dielectrics

    Science.gov (United States)

    Hammoud, Ahmad N.; Myers, Ira T.

    1992-01-01

    Experiments were carried out to evaluate four candidate materials for high temperature capacitor dielectric applications. The materials investigated were polybenzimidazole polymer and three aramid papers: Voltex 450, Nomex 410, and Nomex M 418, an aramid paper containing 50 percent mica. The samples were heat treated for six hours at 60 C and the direct current and 60 Hz alternating current breakdown voltages of both dry and impregnated samples were obtained in a temperature range of 20 to 250 C. The samples were also characterized in terms of their dielectric constant, dielectric loss, and conductivity over this temperature range with an electrical stress of 60 Hz, 50 V/mil present. Additional measurements are underway to determine the volume resistivity, thermal shrinkage, and weight loss of the materials. Preliminary data indicate that the heat treatment of the films slightly improves the dielectric properties with no influence on their breakdown behavior. Impregnation of the samples leads to significant increases in both alternating and direct current breakdown strength. The results are discussed and conclusions made concerning their suitability as high temperature capacitor dielectrics.

  14. Dielectric Spectroscopic Detection of Early Failures in 3-D Integrated Circuits.

    Science.gov (United States)

    Obeng, Yaw; Okoro, C A; Ahn, Jung-Joon; You, Lin; Kopanski, Joseph J

    The commercial introduction of three dimensional integrated circuits (3D-ICs) has been hindered by reliability challenges, such as stress related failures, resistivity changes, and unexplained early failures. In this paper, we discuss a new RF-based metrology, based on dielectric spectroscopy, for detecting and characterizing electrically active defects in fully integrated 3D devices. These defects are traceable to the chemistry of the insolation dielectrics used in the through silicon via (TSV) construction. We show that these defects may be responsible for some of the unexplained early reliability failures observed in TSV enabled 3D devices.

  15. Structural, magnetic and dielectric investigations in antimony doped nano-phased nickel-zinc ferrites

    Energy Technology Data Exchange (ETDEWEB)

    Lakshmi, Ch.S. [Department of Physics, Regency Institute of Technology, Adivipolam Yanam 533464, Pondicherry (India); Sridhar, Ch.S.L.N. [Department of Physics, Vignana Bharathi Institute of Technology, Aushapur(v) Ghatkesar (M), Hyderabad 501301, Telangana (India); Govindraj, G. [Department of Physics, School of Physical, Chemical and Applied Sciences, Pondicherry University, R.V.Nagar, Kalapet, Pondicherry 605014 (India); Bangarraju, S. [Department of Physics, Andhra University, Visakhapatnam 530003, Andhrapradesh (India); Potukuchi, D.M., E-mail: potukuchidm@yahoo.com [Department of Physics, University College of Engineering, Jawaharlal Nehru Technological University:Kakinada, Kakinada 533003 (India)

    2015-02-15

    Nanocrystalline Ni–Zn–Sb ferrites synthesized by hydrothermal method are reported. Influence of Sb{sup 5+} ions on structural, magnetic and dielectric properties of ferrites is studied. Phase identification, lattice parameter and crystallite size studies are carried out using by X-ray diffraction (XRD). Addition of dopant resulted for decrease in lattice parameter. Crystallite size gets reduced from 62 nm to 38 nm with doping of Antimony. Crystallite size and porosity exhibit similar trends with doping. Morphological study is carried out by Field Emission Scanning Electron Microscopy (FESEM). Strong FTIR absorption bands at 400–600 cm{sup −1} confirm the formation of ferrite structure. Increase of porosity is attributed to the grain size. Doping with Antimony results for decrease in saturation magnetization and increase in coercivity. An initial increase of saturation magnetization for x=0.1 is attributed to the unusually high density. Reversed trend of coercivity with crystallite size are observed. Higher value of dielectric constant ε′(ω) is attributed to the formation of excess of Fe{sup 2+} ions caused by aliovalent doping of Sb{sup 5+} ions. Variation of dielectric constant infers hopping type of conductivity mechanism. The dielectric loss factor tanδ attains lower values of ∼10{sup −2}. High ac resistivity ρ(ω) of 10{sup 8} Ω cm is witnessed for antimony doped ferrites. Higher saturation magnetization and enhanced dielectric response directs for a possible utility as microwave oscillators and switches.

  16. Molecular dynamics simulations of the dielectric properties of fructose aqueous solutions

    International Nuclear Information System (INIS)

    Sonoda, Milton T; Dolores Elola, M; Skaf, Munir S

    2016-01-01

    The static dielectric permittivity and dielectric relaxation properties of fructose aqueous solutions of different concentrations ranging from 1.0 to 4.0 mol l −1 are investigated by means of molecular dynamics simulations. The contributions from intra- and interspecies molecular correlations were computed individually for both the static and frequency-dependent dielectric properties, and the results were compared with the available experimental data. Simulation results in the time- and frequency-domains were analyzed and indicate that the presence of fructose has little effect on the position of the fast, high-frequency (>500 cm −1 ) components of the dielectric response spectrum. The low-frequency (<0.1 cm −1 ) components, however, are markedly influenced by sugar concentration. Our analysis indicates that fructose–fructose and fructose–water interactions strongly affect the rotational-diffusion regime of molecular motions in the solutions. Increasing fructose concentration not only enhances sugar–sugar and sugar-water low frequency contributions to the dielectric loss spectrum but also slows down the reorientational dynamics of water molecules. These results are consistent with previous computer simulations carried out for other disaccharide aqueous solutions. (paper)

  17. Thickness-Dependent Dielectric Constant of Few-Layer In 2 Se 3 Nanoflakes

    KAUST Repository

    Wu, Di

    2015-11-17

    © 2015 American Chemical Society. The dielectric constant or relative permittivity (εr) of a dielectric material, which describes how the net electric field in the medium is reduced with respect to the external field, is a parameter of critical importance for charging and screening in electronic devices. Such a fundamental material property is intimately related to not only the polarizability of individual atoms but also the specific atomic arrangement in the crystal lattice. In this Letter, we present both experimental and theoretical investigations on the dielectric constant of few-layer In2Se3 nanoflakes grown on mica substrates by van der Waals epitaxy. A nondestructive microwave impedance microscope is employed to simultaneously quantify the number of layers and local electrical properties. The measured εr increases monotonically as a function of the thickness and saturates to the bulk value at around 6-8 quintuple layers. The same trend of layer-dependent dielectric constant is also revealed by first-principles calculations. Our results of the dielectric response, being ubiquitously applicable to layered 2D semiconductors, are expected to be significant for this vibrant research field.

  18. Depolarization current relaxation process of insulating dielectrics after corona poling under different charging conditions

    Directory of Open Access Journals (Sweden)

    J. W. Zhang

    2017-10-01

    Full Text Available As an insulating dielectric, polyimide is favorable for the application of optoelectronics, electrical insulation system in electric power industry, insulating, and packaging materials in space aircraft, due to its excellent thermal, mechanical and electrical insulating stability. The charge storage profile of such insulating dielectric is utmost important to its application, when it is exposed to electron irradiation, high voltage corona discharge or other treatments. These treatments could induce changes in physical and chemical properties of treated samples. To investigate the charge storage mechanism of the insulating dielectrics after high-voltage corona discharge, the relaxation processes responsible for corona charged polyimide films under different poling conditions were analyzed by the Thermally Stimulated Discharge Currents method (TSDC. In the results of thermal relaxation process, the appearance of various peaks in TSDC spectra provided a deep insight into the molecular status in the dielectric material and reflected stored space charge relaxation process in the insulating polymers after corona discharge treatments. Furthermore, the different space charge distribution status under various poling temperature and different discharge voltage level were also investigated, which could partly reflect the influence of the ambiance condition on the functional dielectrics after corona poling.

  19. Depolarization current relaxation process of insulating dielectrics after corona poling under different charging conditions

    Science.gov (United States)

    Zhang, J. W.; Zhou, T. C.; Wang, J. X.; Yang, X. F.; Zhu, F.; Tian, L. M.; Liu, R. T.

    2017-10-01

    As an insulating dielectric, polyimide is favorable for the application of optoelectronics, electrical insulation system in electric power industry, insulating, and packaging materials in space aircraft, due to its excellent thermal, mechanical and electrical insulating stability. The charge storage profile of such insulating dielectric is utmost important to its application, when it is exposed to electron irradiation, high voltage corona discharge or other treatments. These treatments could induce changes in physical and chemical properties of treated samples. To investigate the charge storage mechanism of the insulating dielectrics after high-voltage corona discharge, the relaxation processes responsible for corona charged polyimide films under different poling conditions were analyzed by the Thermally Stimulated Discharge Currents method (TSDC). In the results of thermal relaxation process, the appearance of various peaks in TSDC spectra provided a deep insight into the molecular status in the dielectric material and reflected stored space charge relaxation process in the insulating polymers after corona discharge treatments. Furthermore, the different space charge distribution status under various poling temperature and different discharge voltage level were also investigated, which could partly reflect the influence of the ambiance condition on the functional dielectrics after corona poling.

  20. Dielectric properties of Ga{sub 2}O{sub 3}-doped barium iron niobate ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Sanjoom, Kachaporn [Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai, 50200 (Thailand); Thailand Center of Excellence in Physics, Commission on Higher Education, 328 Sri Ayutthaya Road, Bangkok, 10400 (Thailand); Pengpat, Kamonpan; Eitssayeam, Sukum; Tunkasiri, Tawee [Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai, 50200 (Thailand); Materials Science Research Center, Faculty of Science, Chiang Mai University, Chiang Mai, 50200 (Thailand); Rujijanagul, Gobwute [Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai, 50200 (Thailand); Materials Science Research Center, Faculty of Science, Chiang Mai University, Chiang Mai, 50200 (Thailand); Thailand Center of Excellence in Physics, Commission on Higher Education, 328 Sri Ayutthaya Road, Bangkok, 10400 (Thailand)

    2014-08-15

    Ga-doped BaFe{sub 0.5}Nb{sub 0.5}O{sub 3} (Ba(Fe{sub 1-x}Ga{sub x}){sub 0.5}Nb{sub 0.5}O{sub 3}) ceramics were fabricated and their properties were investigated. All ceramics showed perovskite structure with cubic symmetry and the solubility of Ga in BFN ceramics had a limit at x = 0.2. Examination of the dielectric spectra indicated that all ceramic samples presented high dielectric constants that were frequency dependent. The x = 0.2 ceramic showed a very high dielectric constant (ε{sub r} > 240 000 at 1 kHz) while the x = 0.4 sample exhibited high thermal stability of dielectric constant with low loss tangent from room temperature (RT) to 100 C with ε{sub r} > 28 000 (at 1 kHz) when compared to other samples. By using a complex impedance analysis technique, bulk grain, grain boundary, and electrode response were found to affect the dielectric behavior that could be related to the Maxwell-Wagner polarization mechanism. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  1. Dielectric properties of Ga2O3-doped barium iron niobate ceramics

    International Nuclear Information System (INIS)

    Sanjoom, Kachaporn; Pengpat, Kamonpan; Eitssayeam, Sukum; Tunkasiri, Tawee; Rujijanagul, Gobwute

    2014-01-01

    Ga-doped BaFe 0.5 Nb 0.5 O 3 (Ba(Fe 1-x Ga x ) 0.5 Nb 0.5 O 3 ) ceramics were fabricated and their properties were investigated. All ceramics showed perovskite structure with cubic symmetry and the solubility of Ga in BFN ceramics had a limit at x = 0.2. Examination of the dielectric spectra indicated that all ceramic samples presented high dielectric constants that were frequency dependent. The x = 0.2 ceramic showed a very high dielectric constant (ε r > 240 000 at 1 kHz) while the x = 0.4 sample exhibited high thermal stability of dielectric constant with low loss tangent from room temperature (RT) to 100 C with ε r > 28 000 (at 1 kHz) when compared to other samples. By using a complex impedance analysis technique, bulk grain, grain boundary, and electrode response were found to affect the dielectric behavior that could be related to the Maxwell-Wagner polarization mechanism. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  2. Vertical dielectric screening of few-layer van der Waals semiconductors.

    Science.gov (United States)

    Koo, Jahyun; Gao, Shiyuan; Lee, Hoonkyung; Yang, Li

    2017-10-05

    Vertical dielectric screening is a fundamental parameter of few-layer van der Waals two-dimensional (2D) semiconductors. However, unlike the widely-accepted wisdom claiming that the vertical dielectric screening is sensitive to the thickness, our first-principles calculation based on the linear response theory (within the weak field limit) reveals that this screening is independent of the thickness and, in fact, it is the same as the corresponding bulk value. This conclusion is verified in a wide range of 2D paraelectric semiconductors, covering narrow-gap ones and wide-gap ones with different crystal symmetries, providing an efficient and reliable way to calculate and predict static dielectric screening of reduced-dimensional materials. Employing this conclusion, we satisfactorily explain the tunable band gap in gated 2D semiconductors. We further propose to engineer the vertical dielectric screening by changing the interlayer distance via vertical pressure or hybrid structures. Our predicted vertical dielectric screening can substantially simplify the understanding of a wide range of measurements and it is crucial for designing 2D functional devices.

  3. Advanced dielectric continuum model of preferential solvation

    Science.gov (United States)

    Basilevsky, Mikhail; Odinokov, Alexey; Nikitina, Ekaterina; Grigoriev, Fedor; Petrov, Nikolai; Alfimov, Mikhail

    2009-01-01

    A continuum model for solvation effects in binary solvent mixtures is formulated in terms of the density functional theory. The presence of two variables, namely, the dimensionless solvent composition y and the dimensionless total solvent density z, is an essential feature of binary systems. Their coupling, hidden in the structure of the local dielectric permittivity function, is postulated at the phenomenological level. Local equilibrium conditions are derived by a variation in the free energy functional expressed in terms of the composition and density variables. They appear as a pair of coupled equations defining y and z as spatial distributions. We consider the simplest spherically symmetric case of the Born-type ion immersed in the benzene/dimethylsulfoxide (DMSO) solvent mixture. The profiles of y(R ) and z(R ) along the radius R, which measures the distance from the ion center, are found in molecular dynamics (MD) simulations. It is shown that for a given solute ion z(R ) does not depend significantly on the composition variable y. A simplified solution is then obtained by inserting z(R ), found in the MD simulation for the pure DMSO, in the single equation which defines y(R ). In this way composition dependences of the main solvation effects are investigated. The local density augmentation appears as a peak of z(R ) at the ion boundary. It is responsible for the fine solvation effects missing when the ordinary solvation theories, in which z =1, are applied. These phenomena, studied for negative ions, reproduce consistently the simulation results. For positive ions the simulation shows that z ≫1 (z =5-6 at the maximum of the z peak), which means that an extremely dense solvation shell is formed. In such a situation the continuum description fails to be valid within a consistent parametrization.

  4. Ion transport study in polymer-nanocomposite films by dielectric spectroscopy and conductivity scaling

    Science.gov (United States)

    Tripathi, Namrata; Thakur, Awalendra K.; Shukla, Archana; Marx, David T.

    2015-07-01

    The dielectric and conductivity response of polymer nanocomposite electrolytes (films of PMMA4LiClO4 dispersed with nano-CeO2 powder) have been investigated. The dielectric behavior was analyzed via the dielectric permittivity (ε‧) and dissipation factor (tan δ) of the samples. The analysis has shown the presence of space charge polarization at lower frequencies. The real part of ac conductivity spectra of materials obeys the Jonscher power law. Parameters such as dc conductivity, hopping rate, activation energies and the concentration of charge carriers were determined from conductivity data using the Almond West formalism. It is observed that the higher ionic conductivity at higher temperature is due to increased thermally-activated hopping rates accompanied by a significant increase in carrier concentration. The contribution of carrier concentration to the total conductivity is also confirmed from activation energy of migration conduction and from Summerfield scaling. The ac conductivity results are also well correlated with TEM results.

  5. Plasmon transmutation: inducing new modes in nanoclusters by adding dielectric nanoparticles.

    Science.gov (United States)

    Wen, Fangfang; Ye, Jian; Liu, Na; Van Dorpe, Pol; Nordlander, Peter; Halas, Naomi J

    2012-09-12

    Planar clusters of coupled plasmonic nanoparticles support nanoscale electromagnetic "hot spots" and coherent effects, such as Fano resonances, with unique near and far field signatures, currently of prime interest for sensing applications. Here we show that plasmonic cluster properties can be substantially modified by the addition of individual, discrete dielectric nanoparticles at specific locations on the cluster, introducing new plasmon modes, or transmuting existing plasmon modes to new ones, in the resulting metallodielectric nanocomplex. Depositing a single carbon nanoparticle in the junction between a pair of adjacent nanodisks induces a metal-dielectric-metal quadrupolar plasmon mode. In a ten-membered cluster, placement of several carbon nanoparticles in junctions between multiple adjacent nanoparticles introduces a collective magnetic plasmon mode into the Fano dip, giving rise to an additional subradiant mode in the metallodielectric nanocluster response. These examples illustrate that adding dielectric nanoparticles to metallic nanoclusters expands the number and types of plasmon modes supported by these new mixed-media nanoscale assemblies.

  6. Dielectric and electro-optical parameters of two ferroelectric liquid crystals: a comparative study

    International Nuclear Information System (INIS)

    Kumar Misra, Abhishek; Kumar Srivastava, Abhishek; Shukla, J P; Manohar, Rajiv

    2008-01-01

    Dielectric relaxation and an electro-optical study of two ferroelectric liquid crystals having different spontaneous polarizations (Felix 16/100 and Felix 17/000) showing SmC* and SmA phases have been performed in the temperature range 30-80 compfn C. The experimental data have been used to determine different relaxation parameters, viz. distribution parameter, relaxation frequency, dielectric strength and rotational viscosity. The Goldstone mode of dielectric permittivity has been well observed for both the samples under investigation. The activation energy of both the samples has also been determined by the best theoretical fitting of the Arrhenius plot. We have also evaluated the optical response time and anchoring energy coefficients from electro-optical measurement techniques for these samples.

  7. Dielectric spectra of proteins in conducting media

    International Nuclear Information System (INIS)

    Ruderman, G.; Xammar Oro, J.R. de

    1990-10-01

    Dielectric measurements of serum albumin and myoglobin in solutions of varying conductivities were performed. The results presented confirm that also for protein solutions, the Maxwell predictions of a threshold frequency in conducting materials holds. The threshold frequency of a serum albumin solution was experimentally determined. Attention should be recalled that, if the dielectric spectra of proteins solutions want to be measured, three distinct frequency regions are to be observed: a low frequency region, where the sample behaves like a conductor; an intermediate region centered around the threshold frequency, where the free charges partially screen the fixed ones; and a high frequency region where the sample behaves like a good dielectric. (author). 8 refs, 5 figs

  8. Bimodal condensation silicone elastomers as dielectric elastomers

    DEFF Research Database (Denmark)

    Yu, Liyun; Madsen, Frederikke Bahrt; Skov, Anne Ladegaard

    Lately, dielectric elastomers (DEs) which consist of an elastomer sandwiched between electrodes on both sides, have gained interest as materials for actuators, generators, and sensors. An ideal elastomer for DE uses is characterized by high extensibility, flexibility and good mechanical fatigue...... elastomers were prepared by mixing different mass ratios (9:1, 8:2, 7:3, 6:4, 5:5, 4:6) between long polydimethylsiloxane (PDMS) chains and short PDMS chains. The resulting elastomers were investigated with respect to their rheology, dielectric properties, tensile strength, electrical breakdown, as well.......Moreover, a series of elastomers with the same mass ratio (7:3) between long and short PDMS chains were made at different humidity (90%, 70%, 50%, 30%, 10%) at 23oC. The dielectric and mechincal properties of the resulting elastomers were shown to depend strongly on the atmospheric humidity level.In addition...

  9. Electron-beam-induced conduction in dielectrics

    Energy Technology Data Exchange (ETDEWEB)

    Acris, F C; Davies, P M; Lewis, T J [University Coll. of North Wales, Bangor (UK). School of Electronic Engineering Science

    1976-03-14

    A model for the enhanced conduction induced in dielectric films under electron bombardment while electrically stressed is discussed. It is assumed that the beam produces a virtual electrode at the end of its range in the dielectric and, as a consequence, the induced conduction is shown to depend on the properties of that part of the dielectric beyond the range of the beam. This model has also been discussed recently by Nunes de Oliviera and Gross. In the present treatment, it is shown how the model permits investigation of beam scattering and carrier generation and recombination processes. Experiments on electron-bombardment-induced conduction of thin (72 to 360 nm) films of anodic tantalum oxide are reported and it is shown that the theoretical model provides a very satisfactory explanation of all features of the results including the apparent threshold energy for enhanced conduction.

  10. On equilibrium charge distribution above dielectric surface

    Directory of Open Access Journals (Sweden)

    Yu.V. Slyusarenko

    2009-01-01

    Full Text Available The problem of the equilibrium state of the charged many-particle system above dielectric surface is formulated. We consider the case of the presence of the external attractive pressing field and the case of its absence. The equilibrium distributions of charges and the electric field, which is generated by these charges in the system in the case of ideally plane dielectric surface, are obtained. The solution of electrostatic equations of the system under consideration in case of small spatial heterogeneities caused by the dielectric surface, is also obtained. These spatial inhomogeneities can be caused both by the inhomogeneities of the surface and by the inhomogeneous charge distribution upon it. In particular, the case of the "wavy" spatially periodic surface is considered taking into account the possible presence of the surface charges.

  11. Studies on metal-dielectric plasmonic structures.

    Energy Technology Data Exchange (ETDEWEB)

    Chettiar, Uday K. (Purdue University, West Lafayette, IN); Liu, Zhengtong (Purdue University, West Lafayette, IN); Thoreson, Mark D. (Purdue University, West Lafayette, IN); Shalaev, Vladimir M. (Purdue University, West Lafayette, IN); Drachev, Vladimir P. (Purdue University, West Lafayette, IN); Pack, Michael Vern; Kildishev, Alexander V. (Purdue University, West Lafayette, IN); Nyga, Piotr (Purdue University, West Lafayette, IN)

    2010-01-01

    The interaction of light with nanostructured metal leads to a number of fascinating phenomena, including plasmon oscillations that can be harnessed for a variety of cutting-edge applications. Plasmon oscillation modes are the collective oscillation of free electrons in metals under incident light. Previously, surface plasmon modes have been used for communication, sensing, nonlinear optics and novel physics studies. In this report, we describe the scientific research completed on metal-dielectric plasmonic films accomplished during a multi-year Purdue Excellence in Science and Engineering Graduate Fellowship sponsored by Sandia National Laboratories. A variety of plasmonic structures, from random 2D metal-dielectric films to 3D composite metal-dielectric films, have been studied in this research for applications such as surface-enhanced Raman sensing, tunable superlenses with resolutions beyond the diffraction limit, enhanced molecular absorption, infrared obscurants, and other real-world applications.

  12. Dielectric function of two-phase colloid-polymer nanocomposite.

    Science.gov (United States)

    Mitzscherling, S; Cui, Q; Koopman, W; Bargheer, M

    2015-11-28

    The plasmon resonance of metal nanoparticles determines their optical response in the visible spectral range. Many details such as the electronic properties of gold near the particle surface and the local environment of the particles influence the spectra. We show how the cheap but highly precise fabrication of composite nanolayers by spin-assisted layer-by-layer deposition of polyelectrolytes can be used to investigate the spectral response of gold nanospheres (GNS) and gold nanorods (GNR) in a self-consistent way, using the established Maxwell-Garnett effective medium (MGEM) theory beyond the limit of homogeneous media. We show that the dielectric function of gold nanoparticles differs from the bulk value and experimentally characterize the shape and the surrounding of the particles thoroughly by SEM, AFM and ellipsometry. Averaging the dielectric functions of the layered surrounding by an appropriate weighting with the electric field intensity yields excellent agreement for the spectra of several nanoparticles and nanorods with various cover-layer thicknesses.

  13. Method for fabrication of crack-free ceramic dielectric films

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Beihai; Narayanan, Manoj; Balachandran, Uthamalingam; Chao, Sheng; Liu, Shanshan

    2017-12-05

    The invention provides a process for forming crack-free dielectric films on a substrate. The process comprises the application of a dielectric precursor layer of a thickness from about 0.3 .mu.m to about 1.0 .mu.m to a substrate. The deposition is followed by low temperature heat pretreatment, prepyrolysis, pyrolysis and crystallization step for each layer. The deposition, heat pretreatment, prepyrolysis, pyrolysis and crystallization are repeated until the dielectric film forms an overall thickness of from about 1.5 .mu.m to about 20.0 .mu.m and providing a final crystallization treatment to form a thick dielectric film. The process provides a thick crack-free dielectric film on a substrate, the dielectric forming a dense thick crack-free dielectric having an overall dielectric thickness of from about 1.5 .mu.m to about 20.0 .mu.m.

  14. New calibration algorithms for dielectric-based microwave moisture sensors

    Science.gov (United States)

    New calibration algorithms for determining moisture content in granular and particulate materials from measurement of the dielectric properties at a single microwave frequency are proposed. The algorithms are based on identifying empirically correlations between the dielectric properties and the par...

  15. Method for fabrication of crack-free ceramic dielectric films

    Science.gov (United States)

    Ma, Beihai; Balachandran, Uthamalingam; Chao, Sheng; Liu, Shanshan; Narayanan, Manoj

    2014-02-11

    The invention provides a process for forming crack-free dielectric films on a substrate. The process comprise the application of a dielectric precursor layer of a thickness from about 0.3 .mu.m to about 1.0 .mu.m to a substrate. The deposition is followed by low temperature heat pretreatment, prepyrolysis, pyrolysis and crystallization step for each layer. The deposition, heat pretreatment, prepyrolysis, pyrolysis and crystallization are repeated until the dielectric film forms an overall thickness of from about 1.5 .mu.m to about 20.0 .mu.m and providing a final crystallization treatment to form a thick dielectric film. Also provided was a thick crack-free dielectric film on a substrate, the dielectric forming a dense thick crack-free dielectric having an overall dielectric thickness of from about 1.5 .mu.m to about 20.0 .mu.m.

  16. Growth, characterization and dielectric property studies of gel grown ...

    Indian Academy of Sciences (India)

    Administrator

    chemical reaction method. Plate-like single ... Barium succinate; gel growth; single crystals; dielectric constant; dielectric loss. 1. .... The chemical reaction involved in the birth of a new .... due to the displacement of electrons and ions, respec-.

  17. Effect of deformation and dielectric filling on electromagnetic ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    great significance in the development of microwave communication networks and ... media. Rectangular dielectric waveguide structures are analysed by Bierwirth ..... Schweig E, Bridges W B 1984 Computer analysis of dielectric waveguide: A ...

  18. Dielectric loss against piezoelectric power harvesting

    International Nuclear Information System (INIS)

    Liang, Junrui; Shu-Hung Chung, Henry; Liao, Wei-Hsin

    2014-01-01

    Piezoelectricity is one of the most popular electromechanical transduction mechanisms for constructing kinetic energy harvesting systems. When a standard energy harvesting (SEH) interface circuit, i.e., bridge rectifier plus filter capacitor, is utilized for collecting piezoelectric power, the previous literature showed that the power conversion can be well predicted without much consideration for the effect of dielectric loss. Yet, as the conversion power gets higher by adopting power-boosting interface circuits, such as synchronized switch harvesting on inductor (SSHI), the neglect of dielectric loss might give rise to deviation in harvested power estimation. Given the continuous progress on power-boosting interface circuits, the role of dielectric loss in practical piezoelectric energy harvesting (PEH) systems should receive attention with better evaluation. Based on the integrated equivalent impedance network model, this fast track communication provides a comprehensive study on the susceptibility of harvested power in PEH systems under different conditions. It shows that, dielectric loss always counteracts piezoelectric power harvesting by causing charge leakage across piezoelectric capacitance. In particular, taking corresponding ideal lossless cases as references, the counteractive effect might be aggravated under one of the five conditions: larger dielectric loss tangent, lower vibration frequency, further away from resonance, weaker electromechanical coupling, or using power-boosting interface circuit. These relationships are valuable for the study of PEH systems, as they not only help explain the role of dielectric loss in piezoelectric power harvesting, but also add complementary insights for material, structure, excitation, and circuit considerations towards holistic evaluation and design for practical PEH systems. (fast track communications)

  19. Dielectric optical antenna thermal emitters and metamaterials

    Science.gov (United States)

    Schuller, Jonathan Aaron

    Optical antennas are critical components in nanophotonics research due to their unparalleled ability to concentrate electromagnetic energy into nanoscale volumes. Researchers typically construct such antennas from wavelength-size metallic structures. However, recent research has begun to exploit the scattering resonances of high-permittivity particles to realize all-dielectric optical antennas, emitters, and metamaterials. In this thesis, we experimentally and theoretically characterize the resonant modes of subwavelength rod-shaped dielectric particles and demonstrate their use in negative index metamaterials and novel infrared light emitters. At mid-infrared frequencies, Silicon Carbide (SiC) is an ideal system for studying the behavior of dielectric optical antennas. At frequencies below the TO phonon resonance, SiC behaves like a dielectric with very large refractive index. Using infrared spectroscopy and analytical Mie calculations we show that individual rod-shaped SiC particles exhibit a multitude of resonant modes. Detailed investigations of these SiC optical antennas reveal a wealth of new physics and applications. We discuss the distinct electromagnetic field profile for each mode, and demonstrate that two of the dielectric-type Mie resonances can be combined in a particle array to form a negative index metamaterial. We further show that these particles can serve as "broadcasting" antennas. Using a custom-built thermal emission microscope we collect emissivity spectra from single SiC particles at elevated temperatures, highlighting their use as subwavelength resonant light emitters. Finally, we derive and verify a variety of general analytical results applicable to all cylindrical dielectric antennas.

  20. Dielectric Optical Antenna Emitters and Metamaterials

    Science.gov (United States)

    Schuller, Jon

    2009-03-01

    Optical antennas are critical components in nanophotonics research due to their unparalleled ability to concentrate electromagnetic energy into nanoscale volumes. Researchers typically construct such antennas from wavelength-size metallic structures. However, recent research has begun to exploit the scattering resonances of high-permittivity particles to realize all-dielectric optical antennas, emitters, and metamaterials. In this talk, we experimentally and theoretically characterize the resonant modes of subwavelength rod-shaped dielectric particles and demonstrate their use in negative index metamaterials and novel infrared light emitters. At mid-infrared frequencies, Silicon Carbide (SiC) is an ideal system for studying the behavior of dielectric optical antennas. At frequencies below the TO phonon resonance, SiC behaves like a dielectric with very large refractive index. Using infrared spectroscopy and analytical Mie calculations we show that individual rod-shaped SiC particles exhibit a multitude of resonant modes. Detailed investigations of these SiC optical antennas reveal a wealth of new physics and applications. We discuss the distinct electromagnetic field profile for each mode, and demonstrate that two of the dielectric-type Mie resonances can be combined in a particle array to form a negative index metamaterial [1]. We further show that these particles can serve as ``broadcasting'' antennas. Using a custom-built thermal emission microscope we collect emissivity spectra from single SiC particles at elevated temperatures, highlighting their use as subwavelength resonant light emitters. Finally, we derive and verify a variety of general analytical results applicable to all cylindrical dielectric antennas and discuss extensions of the demonstrated concepts to different materials systems and frequency regimes. [1] J.A. Schuller, et al., Phys. Rev. Lett. 99, 107401 (2007)

  1. Scaling parallels in the non-Debye dielectric relaxation of ionic glasses and dipolar supercooled liquids

    International Nuclear Information System (INIS)

    Sidebottom, D.L.; Green, P.F.; Brow, R.K.

    1997-01-01

    We compare the dielectric response of ionic glasses and dipolar liquids near the glass transition. Our work is divided into two parts. In the first section we examine ionic glasses and the two prominent approaches to analyzing the dielectric response. The conductivity of ion-conducting glasses displays a power law dispersion σ(ω)∝ω n , where n∼0.67, but frequently the dielectric response is analyzed using the electrical modulus M * (ω)=1/var-epsilon * (ω), where var-epsilon * (ω)=var-epsilon(ω)-iσ(ω)/ω is the complex permittivity. We reexamine two specific examples where the shape of M * (ω) changes in response to changes in (a) temperature and (b) ion concentration, to suggest fundamental changes in ion dynamics are occurring. We show, however, that these changes in the shape of M * (ω) occur in the absence of changes in the scaling properties of σ(ω), for which n remains constant. In the second part, we examine the dielectric relaxation found in dipolar liquids, for which var-epsilon * (ω) likewise exhibits changes in shape on approach to the glass transition. Guided by similarities of M * (ω) in ionic glasses and var-epsilon * (ω) in dipolar liquids, we demonstrate that a recent scaling approach proposed by Dixon and co-workers for var-epsilon * (ω) of dipolar relaxation also appears valid for M * (ω) in the ionic case. While this suggests that the Dixon scaling approach is more universal than previously recognized, we demonstrate how the dielectric response can be scaled in a linear manner using an alternative data representation. copyright 1997 The American Physical Society

  2. Electromagnetic properties of metal-dielectric media and their applications

    Science.gov (United States)

    Animilli, Shravan Rakesh

    The main objective of this dissertation is to investigate nano-structured random composite materials, which exhibit anomalous phenomena, such as the extraordinary enhancements of linear and non-linear optical processes due to excitation of collective electronic states, surface plasmons (SP). The main goal is to develop a time and memory efficient novel numerical method to study the properties of these random media in three dimensions (3D) by utilization of multi core processing and packages such as MPI for parallel execution. The developed numerical studies are then utilized to provide a comprehensive characterization and optimization of a surface plasmon enhanced solar cell (SPESC) and to serve as a test bed for enhanced bio and chemical sensing. In this context, this thesis work develops an efficient and exact numerical algorithm here referred to as Block Elimination Method (BE) which provides the unique capability of modeling extremely large scale composite materials (with up to 1 million strongly interacting metal or dielectric particles). This capability is crucial in order to study the electromagnetic response of large scale inhomogeneous (fractal) films and bulk composites at critical concentrations (percolation). The developed numerical method is used to accurately estimate parameters that describe the composite materials, including the effective conductivity and correlation length scaling exponents, as well as density of states and localization length exponents at the band center. This works reveals, for a first time, a unique de-localization mechanism that plays an important role in the excitation of charge-density waves, i.e. surface plasmons (SP), in metal-dielectric composites. It also shows that in 3D metal-dielectric percolation systems the local fields distribution function for frequencies close to the single particle plasmon resonance is log-normal which is a signature of a metal-dielectric phase transition manifested in the optical response of the

  3. Nanocomposite dielectrics-properties and implications

    Energy Technology Data Exchange (ETDEWEB)

    Nelson, J K; Hu, Y [Department of Electrical, Computer and Systems Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180 (United States)

    2005-01-21

    The incorporation of nanoparticles into thermosetting resins is seen to impart desirable dielectric properties when compared with conventional (micron-sized particulates) composites. Although the improvements are accompanied by the mitigation of internal charge in the materials, the nature of the interfacial region is shown to be pivotal in determining the dielectric behaviour. In particular, it is shown that the conditions and enhanced area of the interface changes the bonding that may give rise to an interaction zone, which affects the interfacial polarization through the formation of local conductivity.

  4. Dielectric barrier discharge image processing by Photoshop

    Science.gov (United States)

    Dong, Lifang; Li, Xuechen; Yin, Zengqian; Zhang, Qingli

    2001-09-01

    In this paper, the filamentary pattern of dielectric barrier discharge has been processed by using Photoshop, the coordinates of each filament can also be obtained. By using Photoshop two different ways have been used to analyze the spatial order of the pattern formation in dielectric barrier discharge. The results show that the distance of the neighbor filaments at U equals 14 kV and d equals 0.9 mm is about 1.8 mm. In the scope of the experimental error, the results from the two different methods are similar.

  5. FDTD Method for Piecewise Homogeneous Dielectric Media

    Directory of Open Access Journals (Sweden)

    Zh. O. Dombrovskaya

    2016-01-01

    Full Text Available In this paper, we consider a numerical solution of Maxwell’s curl equations for piecewise uniform dielectric medium by the example of a one-dimensional problem. For obtaining the second order accuracy, the electric field grid node is placed into the permittivity discontinuity point of the medium. If the dielectric permittivity is large, the problem becomes singularly perturbed and a contrast structure appears. We propose a piecewise quasi-uniform mesh which resolves all characteristic solution parts of the problem (regular part, boundary layer and transition zone placed between them in detail. The features of the mesh are discussed. 

  6. Gold nanoparticles extraction from dielectric scattering background

    Science.gov (United States)

    Hong, Xin; Wang, Jingxin

    2014-11-01

    The unique advantages such as brightness, non-photobleaching, good bio-compatibility make gold nanoparticles desirable labels and play important roles in biotech and related research and applications. Distinguishing gold nanoparticles from other dielectric scattering particles is of more importance, especially in bio-tracing and imaging. The enhancement image results from the localized surface plasmon resonance associated with gold nanopartilces makes themselves distinguishable from other dielectric particles, based on which, we propose a dual-wavelength detection method by employing a high sensitive cross-polarization microscopy.

  7. Optical dielectric function of intrinsic amorphous silicon

    International Nuclear Information System (INIS)

    Ching, W.Y.; Lin, C.C.

    1978-01-01

    The imaginary part of the optical dielectric function epsilon 2 (ω) has been calculated using a continuous-random-tetrahedral network as the structural model for the atomic positions. Here the electronic energies and wave functions are determined by first-principles calculations with the method of linear combinations of atomic orbitals (LCAO), and the momentum matrix elements are evaluated directly from the LCAO wave functions. The calculated dielectric function is in good overall agreement with experiment. At energies within 1 eV above the threshold, the epsilon 2 curve shows some structures that are due to interband transitions between the localized states near the band gap

  8. Mass of polaritons in different dielectric media

    International Nuclear Information System (INIS)

    Dzedolik, I V; Lapayeva, S N

    2011-01-01

    Some models of electromagnetic field interactions with linear and nonlinear dielectric media based on the approach of polarization and electromagnetic wave propagation in media are considered. It is shown that quasi-particles generated in the dielectric medium, called polaritons, have mass whose quantity depends on the efficiency of the electromagnetic field and interaction with the medium. The mass and velocity of polaritons can be controlled by the external electric field. The value of the mass of polaritons was measured in a transparent crystal

  9. Theory of the dielectric wakefield accelerator

    International Nuclear Information System (INIS)

    Mtingwa, S.K.

    1990-10-01

    The general theory for all angular modes m of the dielectric wakefield accelerator is reformulated. The expressions for the accelerating electric fields and transverse wake forces are written in terms of matrices, the zeros of one of which determine the excitation frequencies of the dielectric structure. In this scheme it is possible to obtain a maximum accelerating gradient of 2.0 megavolts per meter per nanoCoulomb of driver beam charge, for a driver beam of 0.7 millimeters rms bunch length. 29 refs., 5 figs

  10. Elaboration and dielectric characterization of a doped ferroelectric ...

    African Journals Online (AJOL)

    ... 1150,1180 and 1200 °C successively to optimize the sintering temperature optimal where the density of the sample is maximum (near theoretical density) and therefore the product has better physical quality. The study of dielectric properties of all samples showed a high permittivity dielectric εr = 18018, low dielectric loss: ...

  11. RF cavity using liquid dielectric for tuning and cooling

    Science.gov (United States)

    Popovic, Milorad [Warrenville, IL; Johnson, Rolland P [Newport News, VA

    2012-04-17

    A system for accelerating particles includes an RF cavity that contains a ferrite core and a liquid dielectric. Characteristics of the ferrite core and the liquid dielectric, among other factors, determine the resonant frequency of the RF cavity. The liquid dielectric is circulated to cool the ferrite core during the operation of the system.

  12. Temperature dependence of the dielectric properties of rubber wood

    Science.gov (United States)

    Mohammed Firoz Kabir; Wan M. Daud; Kaida B. Khalid; Haji A.A. Sidek

    2001-01-01

    The effect of temperature on the dielectric properties of rubber wood was investigated in three anisotropic directions—longitudinal, radial, and tangential, and at different measurement frequencies. Low frequency measurements were conducted with a dielectric spectrometer, and high frequencies used microwave applied with open-ended coaxial probe sensors. Dielectric...

  13. Analyzing the effect of gate dielectric on the leakage currents

    Directory of Open Access Journals (Sweden)

    Sakshi

    2016-01-01

    Full Text Available An analytical threshold voltage model for MOSFETs has been developed using different gate dielectric oxides by using MATLAB software. This paper explains the dependency of threshold voltage on the dielectric material. The variation in the subthreshold currents with the change in the threshold voltage sue to the change of dielectric material has also been studied.

  14. Note: On the dielectric constant of nanoconfined water

    OpenAIRE

    Zhang, Chao

    2018-01-01

    Investigations of dielectric properties of water in nanoconfinement are highly relevant for various applications. Here, using a simple capacitor model, we show that the low dielectric constant of nanoconfined water found in molecular dynamics simulations can be largely explained by the so-called dielectric dead-layer effect known for ferroelectric nanocapacitors.

  15. Electrode/Dielectric Strip For High-Energy-Density Capacitor

    Science.gov (United States)

    Yen, Shiao-Ping S.

    1994-01-01

    Improved unitary electrode/dielectric strip serves as winding in high-energy-density capacitor in pulsed power supply. Offers combination of qualities essential for high energy density: high permittivity of dielectric layers, thinness, and high resistance to breakdown of dielectric at high electric fields. Capacitors with strip material not impregnated with liquid.

  16. Norbornylene-based polymer systems for dielectric applications

    Science.gov (United States)

    Dirk, Shawn M [Albuquerque, NM; Wheeler, David R [Albuquerque, NM

    2012-07-17

    A capacitor having at least one electrode pair being separated by a dielectric component, with the dielectric component being made of a polymer such as a norbornylene-containing polymer with a dielectric constant greater than 3 and a dissipation factor less than 0.1 where the capacitor has an operating temperature greater than 100.degree. C. and less than 170.degree. C.

  17. Dielectric measurements on PWB materials at microwave frequencies

    Indian Academy of Sciences (India)

    Unknown

    the angular frequency and c0 the velocity of light, c the thickness of the ... Dielectric parameters, absorption index and refractive index for pure PSF and pure PMMA at 8⋅92 GHz frequency and at 35°C temperature. Dielectric. Dielectric. Loss. Relaxation. Conductivity Absorption. Refractive. Thickness, constant loss tangent.

  18. The colossal task of Ouranos

    International Nuclear Information System (INIS)

    Grondin, N.

    2003-01-01

    Ouranos is a new consortium on climatology and adaptation to climate change consisting of researchers from Hydro-Quebec, the Quebec government and the Meteorological Service of Canada who are analyzing the long-range trends and regional impacts of climate change. One general trend that has been pointed out by the Intergovernmental Panel on Climate Change (IPCC) is that the average global temperature rose faster in the past century (+0.6 degrees C) than in the preceding thousand years. It is expected to rise 1.6 to 6 degrees C by the end of the twenty-first century. The rise in temperature has already resulted in a global loss of snow cover, glacial melt at the North Pole, increased precipitation worldwide, and rising sea levels. The IPCC cautions that the world's climate system could break down within a few decades if emissions of carbon dioxide and other greenhouse gases continue at the current rate. The signs of climate change that have already been observed in Quebec include a high number of stationary weather patterns that are expressed in long cold snaps in winter and severe summer droughts. Decision makers are faced with the challenge of how to manage water resources and predict the impact of changes in precipitation on forest fire frequency and insect infestation. In addition, they must determine if adjustments should be made to the design of treatment plant intakes, the height of harbour wharves, and dike dimensions. In order to help plan the future, Ouranos has invested $2.5 million into a supercomputer that will be drawing the North American weather map for the period 2040-2065 to evaluate various scenarios through a reliable meteorological model. 4 figs

  19. Dielectric and photo-dielectric properties of TlGaSeS crystals

    Indian Academy of Sciences (India)

    Administrator

    cDepartment of Physics, Middle East Technical University, 06800 Ankara, Turkey. MS received ... The crystals are observed to exhibit a dark high frequency effective dielectric constant value of ~ 10\\65 x ... communication systems. Keywords.

  20. Ceramic-polymer nanocomposites with increased dielectric permittivity and low dielectric loss

    International Nuclear Information System (INIS)

    Bhardwaj, Sumit; Paul, Joginder; Raina, K. K.; Thakur, N. S.; Kumar, Ravi

    2014-01-01

    The use of lead free materials in device fabrication is very essential from environmental point of view. We have synthesized the lead free ferroelectric polymer nanocomposite films with increased dielectric properties. Lead free bismuth titanate has been used as active ceramic nanofillers having crystallite size 24nm and PVDF as the polymer matrix. Ferroelectric β-phase of the polymer composite films was confirmed by X-ray diffraction pattern. Mapping data confirms the homogeneous dispersion of ceramic particles into the polymer matrix. Frequency dependent dielectric constant increases up to 43.4 at 100Hz, whereas dielectric loss decreases with 7 wt% bismuth titanate loading. This high dielectric constant lead free ferroelectric polymer films can be used for energy density applications

  1. Third order dielectric susceptibility in a model quantum paraelectric

    International Nuclear Information System (INIS)

    Martonak, R.; Tosatti, E.

    1996-02-01

    In the context of perovskite quantum paraelectrics, we study the effects of a quadrupolar interaction J q , in addition to the standard dipolar one J d . We concentrate here on the nonlinear dielectric response χ (3) P , as the main response function sensitive to quadrupolar (in our case antiquadrupolar) interactions. We employ a 3D quantum four-state lattice model and mean-field theory. The results show that inclusion of quadrupolar coupling of moderate strength (J q ∼ 1/4J d ) is clearly accompanied by a double change of sign of χ (3) P from negative to positive, near the quantum temperature T Q where the quantum paraelectric behaviour sets in. We fit our χ (3) to recent experimental data for SrTiO 3 , where the sign change is identified close to T Q ∼ 37 K. (author). 40 refs, 2 figs

  2. Structural, dielectric and electrical properties of ...

    Indian Academy of Sciences (India)

    Administrator

    Detailed studies of dielectric properties of the compound as a function of temperature at ... Microscope (Jeol, JSM-840), operated at 20 kV. The sin- tered pellet was .... grain boundaries, and provides the true picture of the electrical properties of ...

  3. Quantum optics of dispersive dielectric media

    International Nuclear Information System (INIS)

    Lenac, Z.

    2003-01-01

    We quantize the electromagnetic field in a polar medium starting with the fundamental equations of motion. In our model the medium is described by a Lorenz-type dielectric function ε(r,ω) appropriate, e.g., for ionic crystals, metals, and inert dielectrics. There are no restrictions on the spatial behavior of the dielectric function, i.e., there can be many different polar media with arbitrary shapes. We assume no losses in our system so the dielectric function for the whole space is assumed as real. The quantization procedure is based on an expansion of the total field (transverse and longitudinal) in terms of the coupled (polariton) eigenmodes, and this approach incorporates all previous results derived for similar but restricted systems (e.g., without spatial or frequency dependence of coupled modes). Within the same model, we also quantize the Hamiltonian of a nonretarded electromagnetic field in polar media. Particular attention is paid to the derivation of the orthogonality and closure relations, which are used in a discussion of the fundamental (equal-time) commutation relations between the conjugate field operators

  4. Partial discharges and bulk dielectric field enhancement

    DEFF Research Database (Denmark)

    McAllister, Iain Wilson; Johansson, Torben

    2000-01-01

    A consequence of partial discharge activity within a gaseous void is the production of a field enhancement in the solid dielectric in the proximity of the void. This situation arises due to the charge created by the partial discharges accumulating at the void wall. The influence of the spatial...

  5. 7th International Symposium on Gaseous Dielectrics

    CERN Document Server

    James, David

    1994-01-01

    The Seventh International Symposium on Gaseous Dielectrics was held in Knoxville, Tennessee, U. S. A. , on April 24-28, 1994. The symposium continued the interdisciplinary character and comprehensive approach of the preceding six symposia. Gaseous DielecIries VII is a detailed record of the symposium proceedings. It covers recent advances and developments in a wide range of basic, applied and industrial areas of gaseous dielectrics. It is hoped that Gaseous DielecIries VII will aid future research and development in, and encourage wider industrial use of, gaseous dielectrics. The Organizing Committee of the Seventh International Symposium on Gaseous Dielectrics consisted of G. Addis (U. S. A. ), L. G. Christophorou (U. S. A. ), F. Y. Chu (Canada), A. H. Cookson (U. S. A. ), O. Farish (U. K. ), I. Gallimberti (Italy) , A. Garscadden (U. S. A. ), D. R. James (U. S. A. ), E. Marode (France), T. Nitta (Japan), W. Pfeiffer (Germany), Y. Qiu (China), I. Sauers (U. S. A. ), R. J. Van Brunt (U. S. A. ), and W. Zaengl...

  6. Pentaquarks in chiral color dielectric model

    Indian Academy of Sciences (India)

    Recent experiments indicate that a narrow baryonic state having strangeness +1 and mass of about 1540 MeV may be existing. Such a state was predicted in chiral model by Diakonov et al. In this work I compute the mass and width of this state in chiral color dielectric model. I show that the computed width is about 30 MeV.

  7. Spontaneous emission from active dielectric microstructures

    DEFF Research Database (Denmark)

    Søndergaard, Thomas; Tromborg, Bjarne

    2001-01-01

    and engineered due to the dependence of the emission rate on the location and polarisation of the emitters in the structure. This paper addresses the methods of quantum electrodynamics of dielectric media which enable calculation of the local rate of spontaneous emission in active microstructures....

  8. Dielectric barrier discharges applied for optical spectrometry

    Czech Academy of Sciences Publication Activity Database

    Brandt, S.; Schütz, A.; Klute, F. D.; Kratzer, Jan; Franzke, J.

    2016-01-01

    Roč. 123, SEP (2016), s. 6-32 ISSN 0584-8547 R&D Projects: GA ČR GA14-23532S Institutional support: RVO:68081715 Keywords : dielectric barrier discharge * analytical spectroscopy * applications Subject RIV: CB - Analytical Chemistry , Separation Impact factor: 3.241, year: 2016

  9. Test plan for prototype dielectric permittivity sensor

    International Nuclear Information System (INIS)

    Pfeifer, M.C.

    1993-07-01

    The digface characterization project funded by the Buried Waste Integrated Demonstration (BWID) is designed to test a new method of monitoring hazardous conditions during the remediation at waste sites. Often on a large scale, the exact cause of each anomaly is difficult to determine and ambiguities remain in the characterization of a site. The digface characterization concept is designed to alleviate some of this uncertainty by creating systems that monitor small volumes of soil and detect anomalous areas during remediation before they are encountered. The goal of the digface characterization demonstration is to detect changes in the physical properties from one volume to another and relate these changes in physical properties to changes in the level of contamination. Dielectric permittivity mapping is a method that might prove useful in digface characterization. In this project, the role of a dielectric permittivity monitoring device is under investigation. This project addresses two issues: what are the optimal means of mapping dielectric permittivity contrasts and what types of targets can be detected using dielectric permittivity mapping

  10. Thermal aspects of resistors embedded in dielectrics

    International Nuclear Information System (INIS)

    Caprari, R.S.

    1995-10-01

    This note presents a formula for estimating the temperature of a distributed resistor or resistor chain that is immersed in a dielectric medium, which in turn is surrounded by a heat reservoir. An example computation from an actual instrument in included. 6 refs

  11. Characterization of a surface dielectric barrier discharge

    NARCIS (Netherlands)

    Pemen, A.J.M.; Beckers, F.J.C.M.; Heesch, van E.J.M.

    2009-01-01

    A surface dielectric barrier discharge (SDBD) reactor provides a homogeneous plasma over a large surface area. This allows surface treatments of foils, textiles or fibers. Here we present results of a study to characterize the AC and pulsed performance of SDBD with regard to ozone production,

  12. Dielectric image line groove antennas for millimeterwaves

    Science.gov (United States)

    Solbach, K.; Wolff, I.

    Grooves in the ground plane of dielectric image lines are proposed as a new radiating structure. A figure is included showing the proposed groove structure as a discontinuity in a dielectric image line. A wave incident on the dielectric image line is partly reflected by the discontinuity, partly transmitted across the groove, and partly radiated into space above the line. In a travelling-wave antenna, a number of grooves are arranged below a dielectric guide, with spacings around one guide wavelength to produce a beam in the upper half space. A prescribed aperture distribution can be effected by tapering the series radiation resistance of the grooves. This can be done by adjusting the depths of the grooves with a constant width or by varying the widths of the grooves with a constant depth. Attention is also given to circular grooves. Here, the widths of the holes are chosen so that they can be considered as waveguides operating far below the cut-off frequency of the fundamental circular waveguide mode.

  13. Dielectric barrier discharges applied for optical spectrometry

    Czech Academy of Sciences Publication Activity Database

    Brandt, S.; Schütz, A.; Klute, F. D.; Kratzer, Jan; Franzke, J.

    2016-01-01

    Roč. 123, SEP (2016), s. 6-32 ISSN 0584-8547 R&D Projects: GA ČR GA14-23532S Institutional support: RVO:68081715 Keywords : dielectric barrier discharge * analytical spectroscopy * applications Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 3.241, year: 2016

  14. Vegetable oil based liquid nanocomposite dielectric

    Directory of Open Access Journals (Sweden)

    Leon Chetty

    2013-01-01

    Full Text Available Physically smaller dielectric materials would improve the optimisation of space for power systems. Development of nanotechnology provides an effective way to improve the performances of insulating oils used in power system applications. In this research study, we focused on the development of nanomodified vegetable oils to be used in power transformers. Higher conduction currents were observed in virgin linseed oil than in virgin castor oil. However, for both virgin linseed and virgin castor oil, the DC conduction current increased approximately linearly with the applied DC voltage. In nanomodified linseed oil, the characteristic curve showed two distinct regions: a linear region (at lower applied voltage and a saturation region (at slightly higher voltage. Conversely, in nanomodified castor oil, the characteristic curve showed three distinct regions: a linear region (at lower applied voltage, a saturation region (at intermediate applied voltage and an exponential growth region (at higher applied voltage. The nanomodified linseed oil exhibited a better dielectric performance than the nanomodified castor oil. Overall, the addition of nanodielectrics to vegetable oils decreased the dielectric performance of the vegetable oils. The results of this study contribute to the understanding of the pre-breakdown phenomenon in liquid nanocomposite dielectrics.

  15. Testing quantised inertia on emdrives with dielectrics

    Science.gov (United States)

    McCulloch, M. E.

    2017-05-01

    Truncated-cone-shaped cavities with microwaves resonating within them (emdrives) move slightly towards their narrow ends, in contradiction to standard physics. This effect has been predicted by a model called quantised inertia (MiHsC) which assumes that the inertia of the microwaves is caused by Unruh radiation, more of which is allowed at the wide end. Therefore, photons going towards the wide end gain inertia, and to conserve momentum the cavity must move towards its narrow end, as observed. A previous analysis with quantised inertia predicted a controversial photon acceleration, which is shown here to be unnecessary. The previous analysis also mispredicted the thrust in those emdrives with dielectrics. It is shown here that having a dielectric at one end of the cavity is equivalent to widening the cavity at that end, and when dielectrics are considered, then quantised inertia predicts these results as well as the others, except for Shawyer's first test where the thrust is predicted to be the right size but in the wrong direction. As a further test, quantised inertia predicts that an emdrive's thrust can be enhanced by using a dielectric at the wide end.

  16. Microwave dielectric properties of nanostructured nickel ferrite

    Indian Academy of Sciences (India)

    Wintec

    Abstract. Nickel ferrite is one of the important ferrites used in microwave devices. In the present work, we have synthesized nanoparticles of nickel ferrite using chemical precipitation technique. The crystal structure and grain size of the particles are studied using XRD. The microwave dielectric properties of nanostructured.

  17. Effects of Radiation on Capacitor Dielectrics

    Science.gov (United States)

    Bouquet, F. L.; Somoano, R. B.; Frickland, P. O.

    1987-01-01

    Data gathered on key design parameters. Report discusses study of electrical and mechanical properties of irradiated polymer dielectric materials. Data compiled for use by designers of high-energy-density capacitors that operate in presence of ionizing radiation. Study focused on polycarbonates, polyetheretherketones, polymethylpentenes, polyimides (including polyetherimide), polyolefins, polysulfones (including polyethersulfone and polyphenylsulfone), and polyvinylidene fluorides.

  18. Polyvinylidene fluoride film as a capacitor dielectric

    Science.gov (United States)

    Dematos, H. V.

    1981-01-01

    Thin strips of polyvinylidene fluoride film (PVDF) with vacuum deposited electrodes were made into capacitors by conventional winding and fabrication techniques. These devices were used to identify and evaluate the performance characteristics offered by the PVDF in metallized film capacitors. Variations in capacitor parameters with temperature and frequence were evaluated and compared with other dielectric films. Their impact on capacitor applications is discussed.

  19. Improvement in the microwave dielectric properties of ...

    Indian Academy of Sciences (India)

    Administrator

    ... linearly with x. Relative permittivity (εr) increased from 47⋅2 to 54⋅5, unloaded ... and are used in the manufacture of DRs for mobile phone handsets and base ... Microwave dielectric properties were measured using a. R3767CH Agilent ...

  20. Conductivity, dielectric behaviour and magnetoelectric effect in ...

    Indian Academy of Sciences (India)

    intensity of the magnetic field. The maximum value of ME coefficient was observed for 75% ferroelectric phase composite. Keywords. Conductivity; dielectric behaviour; magnetoelectric effect; CuFe2O4; BaTiO3. 1. Introduction. Magnetoelectric composites consist of two phases viz. piezoelectric and piezomagnetic. The ME ...

  1. DIELECTRIC WAKE FIELD RESONATOR ACCELERATOR MODULE

    Energy Technology Data Exchange (ETDEWEB)

    Hirshfield, Jay L.

    2013-11-06

    Results are presented from experiments, and numerical analysis of wake fields set up by electron bunches passing through a cylindrical or rectangular dielectric-lined structure. These bunches excite many TM-modes, with Ez components of the wake fields sharply localized on the axis of the structure periodically behind the bunches. The experiment with the cylindrical structure, carried out at ATF Brookhaven National Laboratory, used up to three 50 MeV bunches spaced by one wake field period (21 cm) to study the superposition of wake fields by measuring the energy loss of each bunch after it passed through the 53-cm long dielectric element. The millimeter-wave spectrum of radiation excited by the passage of bunches is also studied. Numerical analysis was aimed not only to simulate the behavior of our device, but in general to predict dielectric wake field accelerator performance. It is shown that one needs to match the radius of the cylindrical dielectric channel with the bunch longitudinal rms-length to achieve optimal performance.

  2. Impedance Spectroscopy of Dielectrics and Electronic Conductors

    DEFF Research Database (Denmark)

    Bonanos, Nikolaos; Pissis, Polycarpos; Macdonald, J. Ross

    2013-01-01

    Impedance spectroscopy is used for the characterization of materials, such as electroceramics, solid and liquid electrochemical cells, dielectrics and also fully integrated devices, such as fuel cells. It consists of measuring the electrical impedance - or a closely related property, such as admi......Impedance spectroscopy is used for the characterization of materials, such as electroceramics, solid and liquid electrochemical cells, dielectrics and also fully integrated devices, such as fuel cells. It consists of measuring the electrical impedance - or a closely related property......, such as admittance or dielectric constant - as a function of frequency and comparing the results with expectations based on physical, chemical, and microstructural models. This article reviews the principles and practical aspects of the technique, the representations of the results, the analysis of data......, and procedures for the correction of measurement errors. The applications of impedance spectroscopy are illustrated with examples from electroceramics and polymer-based dielectric systems. The way in which the technique is applied to the two classes of materials is compared with reference to the different models...

  3. Femtosecond laser excitation of dielectric materials

    DEFF Research Database (Denmark)

    Wædegaard, Kristian Juncher; Balling, Peter; Frislev, Martin Thomas

    2012-01-01

    We report an approach to modeling the interaction between ultrashort laser pulses and dielectric materials. The model includes the excitation of carriers by the laser through strongfield excitation, collisional excitation, and absorption in the plasma consisting of conduction-band electrons formed...

  4. Surface waves on metal-dielectric metamaterials

    DEFF Research Database (Denmark)

    Takayama, Osamu; Shkondin, Evgeniy; Panah, Mohammad Esmail Aryaee

    2016-01-01

    In this paper we analyze surface electromagnetic waves supported at an interface between an isotropic medium and an effective anisotropic material that can be realized by alternating conductive and dielectric layers with deep subwavelength thicknesses. This configuration can host various types...

  5. Characterization of Dielectric Electroactive Polymer transducers

    DEFF Research Database (Denmark)

    Nielsen, Dennis; Møller, Martin B.; Sarban, Rahimullah

    2014-01-01

    This paper analysis the small-signal model of the Dielectric Electro Active Polymer (DEAP) transducer. The DEAP transducer have been proposed as an alternative to the electrodynamic transducer in sound reproduction systems. In order to understand how the DEAP transducer works, and provide...

  6. Vectorial analysis of dielectric photonic crystal VCSEL

    DEFF Research Database (Denmark)

    Chung, Il-Sug; Mørk, Jesper

    2009-01-01

    A new vertical-cavity surface-emitting laser structure employing a dielectric photonic crystal mirror has been suggested and been numerically investigated. The new structure has a smaller threshold gain, a moderate strength of single-transverse-mode operation, a high quality of emission beam free...

  7. Large scale processing of dielectric electroactive polymers

    DEFF Research Database (Denmark)

    Vudayagiri, Sindhu

    Efficient processing techniques are vital to the success of any manufacturing industry. The processing techniques determine the quality of the products and thus to a large extent the performance and reliability of the products that are manufactured. The dielectric electroactive polymer (DEAP...

  8. Characterization of dielectric charging in RF MEMS

    NARCIS (Netherlands)

    Herfst, R.W.; Huizing, H.G.A.; Steeneken, P.G.; Schmitz, Jurriaan

    2005-01-01

    Capacitive RF MEMS switches show great promise for use in wireless communication devices such as mobile phones, but the successful application of these switches is hindered by the reliability of the devices: charge injection in the dielectric layer (SiN) can cause irreversible stiction of the moving

  9. Electrical breakdown phenomena of dielectric elastomers

    DEFF Research Database (Denmark)

    Yu, Liyun; Mateiu, Ramona Valentina; Skov, Anne Ladegaard

    2017-01-01

    years. However, optimization with respect to the dielectric permittivity solely may lead to other problematic phenomena such as premature electrical breakdown. In this work, we focus on the chloro propyl functionalized silicone elastomers prepared in Madsen et al[2] and we investigate the electrical...

  10. Analytical solutions of nonlocal Poisson dielectric models with multiple point charges inside a dielectric sphere

    Science.gov (United States)

    Xie, Dexuan; Volkmer, Hans W.; Ying, Jinyong

    2016-04-01

    The nonlocal dielectric approach has led to new models and solvers for predicting electrostatics of proteins (or other biomolecules), but how to validate and compare them remains a challenge. To promote such a study, in this paper, two typical nonlocal dielectric models are revisited. Their analytical solutions are then found in the expressions of simple series for a dielectric sphere containing any number of point charges. As a special case, the analytical solution of the corresponding Poisson dielectric model is also derived in simple series, which significantly improves the well known Kirkwood's double series expansion. Furthermore, a convolution of one nonlocal dielectric solution with a commonly used nonlocal kernel function is obtained, along with the reaction parts of these local and nonlocal solutions. To turn these new series solutions into a valuable research tool, they are programed as a free fortran software package, which can input point charge data directly from a protein data bank file. Consequently, different validation tests can be quickly done on different proteins. Finally, a test example for a protein with 488 atomic charges is reported to demonstrate the differences between the local and nonlocal models as well as the importance of using the reaction parts to develop local and nonlocal dielectric solvers.

  11. Trends of microwave dielectric materials for antenna application

    International Nuclear Information System (INIS)

    Sulong, T. A. T.; Osman, R. A. M.; Idris, M. S.

    2016-01-01

    Rapid development of a modern microwave communication system requires a high quality microwave dielectric ceramic material to be used as mobile and satellite communication. High permittivity of dielectric ceramics leads to fabrication of compact device for electronic components. Dielectric ceramics which used for microwave applications required three important parameters such as high or appropriate permittivity (ε_r), high quality factor (Q _f ≥ 5000 GH z) and good temperature coefficient of resonant frequency (τ_f). This paper review of various dielectric ceramic materials used as microwave dielectric materials and related parameters for antenna applications.

  12. Preparation and Characterization of Pure Organic Dielectric Composites for Capacitors

    Directory of Open Access Journals (Sweden)

    Mao Xin

    2018-01-01

    Full Text Available This work reports the excellent dielectric composites were prepared from polyimide (PI and poly(vinylidene fluoride (PVDF via solution blending and thermal imidization or chemical imidization. The dielectric and thermal properties of the composites were studied. Results indicated that the dielectric properties of the composites synthesized by these two methods were enhanced through the introduction of PVDF, and the composites exhibited excellent thermal stability. Compared to the thermal imidization, the composites prepared by chemical imidization exhibited superior dielectric properties. This study demonstrated that the PI/PVDF composites were potential dielectric materials in the field of electronics.

  13. Trends of microwave dielectric materials for antenna application

    Energy Technology Data Exchange (ETDEWEB)

    Sulong, T. A. T., E-mail: tuanamirahtuansulong@gmail.com; Osman, R. A. M., E-mail: rozana@unimap.edu.my [School of Microelectronic Engineering, Universiti Malaysia Perlis, Pauh Putra Campus, 02600 Arau, Perlis (Malaysia); Idris, M. S., E-mail: sobri@unimap.edu.my [Sustainable Engineering Research Cluster, School of Material Engineering, Universiti Malaysia Perlis, Blok B, Taman Pertiwi Indah, Seriab, 01000 Kangar, Perlis (Malaysia)

    2016-07-19

    Rapid development of a modern microwave communication system requires a high quality microwave dielectric ceramic material to be used as mobile and satellite communication. High permittivity of dielectric ceramics leads to fabrication of compact device for electronic components. Dielectric ceramics which used for microwave applications required three important parameters such as high or appropriate permittivity (ε{sub r}), high quality factor (Q {sub f} ≥ 5000 GH z) and good temperature coefficient of resonant frequency (τ{sub f}). This paper review of various dielectric ceramic materials used as microwave dielectric materials and related parameters for antenna applications.

  14. The effect of organo-clay on the dielectric properties of silicone rubber

    International Nuclear Information System (INIS)

    Razzaghi-Kashani, M; Gharavi, N; Javadi, S

    2008-01-01

    Dielectric elastomers are highly deformable and fast response smart materials capable of actuation under electric fields. Among commercially available dielectric elastomers, silicone rubber can be compounded with different fillers in order to modify its electrical and mechanical properties. To study the effect of organically modified montmorillonite (OMMT) on the dielectric properties of silicone rubber, OMMT was added to this rubber at two levels, 2% and 5%, using two methods, low-shear and high-shear mixing. Composites were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The XRD patterns showed different crystallite structures for silicate platelets in the rubber matrix as a result of the two different mixing methods. In low-shear mixing, the ordered crystallite structure of the clay remains almost unchanged, whereas in high-shear mixing it loses its ordered structure, leading to the disappearance of the diffraction peaks. SEM and AFM micrographs depicted better dispersion and more uniform distribution of the organo-clay under high-shear mixing compared to those obtained by low-shear mixing. The tensile properties also confirmed the different degree of dispersion of the nano-clay resulting from the two different methods of mixing. The dielectric properties of the composites were measured under AC electric fields, and the results were compared with reference silicone rubbers with no OMMT. It was shown that the order of organo-clay layers in the less dispersed structure of the clay imparts an additional ionic polarization and higher dielectric permittivity compared to the case where the clay layers are more dispersed and lost their order. The storage and loss dielectric constants of base silicone rubber increase when it is compounded with OMMT

  15. A novel variable stiffness mechanism for dielectric elastomer actuators

    Science.gov (United States)

    Li, Wen-Bo; Zhang, Wen-Ming; Zou, Hong-Xiang; Peng, Zhi-Ke; Meng, Guang

    2017-08-01

    In this paper, a novel variable stiffness mechanism is proposed for the design of a variable stiffness dielectric elastomer actuator (VSDEA) which combines a flexible strip with a DEA in a dielectric elastomer minimum energy structure. The DEA induces an analog tuning of the transverse curvature of the strip, thus conveniently providing a voltage-controllable flexural rigidity. The VSDEA tends to be a fully flexible and compact structure with the advantages of simplicity and fast response. Both experimental and theoretical investigations are carried out to reveal the variable stiffness performances of the VSDEA. The effect of the clamped location on the bending stiffness of the VSDEA is analyzed, and then effects of the lengths, the loading points and the applied voltages on the bending stiffness are experimentally investigated. An analytical model is developed to verify the availability of this variable stiffness mechanism, and the theoretical results demonstrate that the bending stiffness of the VSDEA decreases as the applied voltage increases, which agree well with the experimental data. Moreover, the experimental results show that the maximum change of the relative stiffness can reach about 88.80%. It can be useful for the design and optimization of active variable stiffness structures and DEAs for soft robots, vibration control, and morphing applications.

  16. Hidden symmetries in N-layer dielectric stacks

    Science.gov (United States)

    Liu, Haihao; Shoufie Ukhtary, M.; Saito, Riichiro

    2017-11-01

    The optical properties of a multilayer system with arbitrary N layers of dielectric media are investigated. Each layer is one of two dielectric media, with a thickness one-quarter the wavelength of light in that medium, corresponding to a central frequency f 0. Using the transfer matrix method, the transmittance T is calculated for all possible 2 N sequences for small N. Unexpectedly, it is found that instead of 2 N different values of T at f 0 (T 0), there are only (N/2+1) discrete values of T 0, for even N, and (N + 1) for odd N. We explain this high degeneracy in T 0 values by finding symmetry operations on the sequences that do not change T 0. Analytical formulae were derived for the T 0 values and their degeneracies as functions of N and an integer parameter for each sequence we call ‘charge’. Additionally, the bandwidth at f 0 and filter response of the transmission spectra are investigated, revealing asymptotic behavior at large N.

  17. Theory of radiation pressure on magneto–dielectric materials

    International Nuclear Information System (INIS)

    Barnett, Stephen M; Loudon, Rodney

    2015-01-01

    We present a classical linear response theory for a magneto–dielectric material and determine the polariton dispersion relations. The electromagnetic field fluctuation spectra are obtained and polariton sum rules for their optical parameters are presented. The electromagnetic field for systems with multiple polariton branches is quantized in three dimensions and field operators are converted to 1–dimensional forms appropriate for parallel light beams. We show that the field–operator commutation relations agree with previous calculations that ignored polariton effects. The Abraham (kinetic) and Minkowski (canonical) momentum operators are introduced and their corresponding single–photon momenta are identified. The commutation relations of these and of their angular analogues support the identification, in particular, of the Minkowski momentum with the canonical momentum of the light. We exploit the Heaviside–Larmor symmetry of Maxwell’s equations to obtain, very directly, the Einsetin–Laub force density for action on a magneto–dielectric. The surface and bulk contributions to the radiation pressure are calculated for the passage of an optical pulse into a semi–infinite sample. (paper)

  18. Directional Emission from Dielectric Leaky-Wave Nanoantennas

    Science.gov (United States)

    Peter, Manuel; Hildebrandt, Andre; Schlickriede, Christian; Gharib, Kimia; Zentgraf, Thomas; Förstner, Jens; Linden, Stefan

    2017-07-01

    An important source of innovation in nanophotonics is the idea to scale down known radio wave technologies to the optical regime. One thoroughly investigated example of this approach are metallic nanoantennas which employ plasmonic resonances to couple localized emitters to selected far-field modes. While metals can be treated as perfect conductors in the microwave regime, their response becomes Drude-like at optical frequencies. Thus, plasmonic nanoantennas are inherently lossy. Moreover, their resonant nature requires precise control of the antenna geometry. A promising way to circumvent these problems is the use of broadband nanoantennas made from low-loss dielectric materials. Here, we report on highly directional emission from active dielectric leaky-wave nanoantennas made of Hafnium dioxide. Colloidal semiconductor quantum dots deposited in the nanoantenna feed gap serve as a local light source. The emission patterns of active nanoantennas with different sizes are measured by Fourier imaging. We find for all antenna sizes a highly directional emission, underlining the broadband operation of our design.

  19. Tribo-electric charging of dielectric solids of identical composition

    Science.gov (United States)

    Angus, John C.; Greber, Isaac

    2018-05-01

    Despite its long history and importance in many areas of science and technology, there is no agreement on the mechanisms responsible for tribo-electric charging, including especially the tribo-charging of chemically identical dielectric solids. Modeling of the excitation, diffusional transport, and de-excitation of electrons from hot spots shows that a difference in local surface roughness of otherwise identical solid dielectric objects leads to different transient excited electron concentrations during tribo-processes. The model predicts that excited electron concentrations are lower and concentration gradients higher in solids with rougher rather than smoother surfaces. Consequently, during contact, the flux of charge carriers (electrons or holes) from hot spots will be greater into the rougher solid than into the smoother solid. These predictions are in agreement with current and historical observations of tribo-electric charge transfer between solids of the same composition. This effect can take place in parallel with other processes and may also play a role in the charging of solids of different composition.

  20. Dielectric properties of alumina/zirconia composites at millimeter wavelengths

    International Nuclear Information System (INIS)

    Molla, J.; Heidinger, R.; Ibarra, A.; Link, G.

    1994-01-01

    Alumina-zirconia composites with ZrO 2 contents up to 20% and negligible porosity were investigated at millimeter (mm) wavelengths to determine the changes appearing in the dielectric properties of pure alumina ceramics when unstabilized or partially stabilized ZrO 2 is added to improve the mechanical strength. It is demonstrated that it essential to distinguish between the contributions of the monoclinic and the tetragonal phase of zirconia (m-ZrO 2 , t-ZrO 2 ). Permittivity is raised with increasing content of either phases; the effective permittivity can be assessed by the rule of mixtures (Maxwell-Garnett formulation of the generalized Clasussius-Mossotti relation) using permittivity values of 10 for Al 2 O 3 , 14-21 for m-ZrO 2 and 40-45 for t-ZrO 2 . The permittivity data show only a small variation in the investigated range of 9-145 GHz. For the dielectric loss, there is evidence of a predominant contribution of m-ZrO 2 ; in addition, the marked increase in loss with frequency becomes sharper. The t-ZrO 2 , which is responsible for strengthening, does not show any significant influence on losses. It is therefore concluded, that ZrO 2 strengthening of alumina is feasible without affecting mm-wave losses at room temperature as long as the presence of m-ZrO 2 is avoided

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

    International Nuclear Information System (INIS)

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

    2014-01-01

    Relaxation like dielectric anomaly is observed in Y 3+ and Mn 2+ doped barium strontium titanate ceramics when the temperature is over 450 K. Apart from the conventional dielectric relaxation analysis method with Debye or modified Debye equations, which is hard to give exact temperature dependence of the relaxation process, dielectric response in the form of complex impedance, assisted with Cole-Cole impedance model corrected equivalent circuits, is adopted to solve this problem and chase the polarization mechanism in this paper. Through this method, an excellent description to temperature dependence of the dielectric relaxation anomaly and its dominated factors are achieved. Further analysis reveals that the exponential decay of the Cole distribution parameter n with temperature is confirmed to be induced by the microscopic lattice distortion due to ions doping and the interaction between the defects. At last, a clear sight to polarization mechanism containing both the intrinsic dipolar polarization and extrinsic distributed oxygen vacancies hopping response under different temperature is obtained.

  2. Significantly Elevated Dielectric and Energy Storage Traits in Boron Nitride Filled Polymer Nano-composites with Topological Structure

    Science.gov (United States)

    Feng, Yefeng; Zhang, Jianxiong; Hu, Jianbing; Li, Shichun; Peng, Cheng

    2018-03-01

    Interface induced polarization has a prominent influence on dielectric properties of 0-3 type polymer based composites containing Si-based semi-conductors. The disadvantages of composites were higher dielectric loss, lower breakdown strength and energy storage density, although higher permittivity was achieved. In this work, dielectric, conductive, breakdown and energy storage properties of four nano-composites have been researched. Based on the cooperation of fluoropolymer/alpha-SiC layer and fluoropolymer/hexagonal-BN layer, it was confirmed constructing the heterogeneous layer-by-layer composite structure rather than homogeneous mono-layer structure could significantly reduce dielectric loss, promote breakdown strength and increase energy storage density. The former worked for a larger dielectric response and the latter layer acted as a robust barrier of charge carrier transfer. The best nano-composite could possess a permittivity of 43@100 Hz ( 3.3 times of polymer), loss of 0.07@100 Hz ( 37% of polymer), discharged energy density of 2.23 J/cm3@249 kV/cm ( 10 times of polymer) and discharged energy efficiency of 54%@249 kV/cm ( 5 times of polymer). This work might enlighten a facile route to achieve the promising high energy storage composite dielectrics by constructing the layer-by-layer topological structure.

  3. Dielectric spectroscopy platform to measure MCF10A epithelial cell aggregation as a model for spheroidal cell cluster analysis.

    Science.gov (United States)

    Heileman, K L; Tabrizian, M

    2017-05-02

    3-Dimensional cell cultures are more representative of the native environment than traditional cell cultures on flat substrates. As a result, 3-dimensional cell cultures have emerged as a very valuable model environment to study tumorigenesis, organogenesis and tissue regeneration. Many of these models encompass the formation of cell aggregates, which mimic the architecture of tumor and organ tissue. Dielectric impedance spectroscopy is a non-invasive, label free and real time technique, overcoming the drawbacks of established techniques to monitor cell aggregates. Here we introduce a platform to monitor cell aggregation in a 3-dimensional extracellular matrix using dielectric spectroscopy. The MCF10A breast epithelial cell line serves as a model for cell aggregation. The platform maintains sterile conditions during the multi-day assay while allowing continuous dielectric spectroscopy measurements. The platform geometry optimizes dielectric measurements by concentrating cells within the electrode sensing region. The cells show a characteristic dielectric response to aggregation which corroborates with finite element analysis computer simulations. By fitting the experimental dielectric spectra to the Cole-Cole equation, we demonstrated that the dispersion intensity Δε and the characteristic frequency f c are related to cell aggregate growth. In addition, microscopy can be performed directly on the platform providing information about cell position, density and morphology. This platform could yield many applications for studying the electrophysiological activity of cell aggregates.

  4. Optimization of silver-dielectric-silver nanoshell for sensing applications

    International Nuclear Information System (INIS)

    Shirzaditabar, Farzad; Saliminasab, Maryam

    2013-01-01

    In this paper, resonance light scattering (RLS) properties of a silver-dielectric-silver nanoshell, based on quasi-static approach and plasmon hybridization theory, are investigated. Scattering spectrum of silver-dielectric-silver nanoshell has two intense and clearly separated RLS peaks and provides a potential for biosensing based on surface plasmon resonance and surface-enhanced Raman scattering. The two RLS peaks in silver-dielectric-silver nanoshell are optimized by tuning the geometrical dimensions. In addition, the optimal geometry is discussed to obtain the high sensitivity of silver-dielectric-silver nanoshell. As the silver core radius increases, the sensitivity of silver-dielectric-silver nanoshell decreases whereas increasing the middle dielectric thickness increases the sensitivity of silver-dielectric-silver nanoshell

  5. Inverse scattering of a layered and dispersionless dielectric half-space - 1. reflection data from plane waves at normal incidence

    International Nuclear Information System (INIS)

    Coen, S.

    1981-01-01

    The theory given by Moses and deRidder is modified so that the derivative of the solution of the Gelfand-Levitan integral equation is not required. Based on this modification, a numerical procedure is developed which approximately constructs the dielectric profile of the layered half-space from the impulse response. Moreover, an inverse scattering theory is developed for a Goupillaud-type dielectric medium, and a fast numerical procedure based on the Berryman and Greene algorithm is presented. The performance of the numerical algorithms is examined by applying them to pecise and imprecise artificial impulse response data. 11 refs

  6. Reversible dielectric property degradation in moisture-contaminated fiber-reinforced laminates

    Science.gov (United States)

    Rodriguez, Luis A.; García, Carla; Fittipaldi, Mauro; Grace, Landon R.

    2016-03-01

    The potential for recovery of dielectric properties of three water-contaminated fiber-reinforced laminates is investigated using a split-post dielectric resonant technique at X-band (10 GHz). The three material systems investigated are bismaleimide (BMI) reinforced with an eight-harness satin weave quartz fabric, an epoxy resin reinforced with an eight- harness satin weave glass fabric (style 7781), and the same epoxy reinforced with a four-harness woven glass fabric (style 4180). A direct correlation between moisture content, dielectric constant, and loss tangent was observed during moisture absorption by immersion in distilled water at 25 °C for five equivalent samples of each material system. This trend is observed through at least 0.72% water content by weight for all three systems. The absorption of water into the BMI, 7781 epoxy, and 4180 epoxy laminates resulted in a 4.66%, 3.35%, and 4.01% increase in dielectric constant for a 0.679%, 0.608%, and 0.719% increase in water content by weight, respectively. Likewise, a significant increase was noticed in loss tangent for each material. The same water content is responsible for a 228%, 71.4%, and 64.1% increase in loss tangent, respectively. Subsequent to full desorption through drying at elevated temperature, the dielectric constant and loss tangent of each laminate exhibited minimal change from the dry, pre-absorption state. The dielectric constant and loss tangent change after the absorption and desorption cycle, relative to the initial state, was 0.144 % and 2.63% in the BMI, 0.084% and 1.71% in the style 7781 epoxy, and 0.003% and 4.51% in the style 4180 epoxy at near-zero moisture content. The similarity of dielectric constant and loss tangent in samples prior to absorption and after desorption suggests that any chemical or morphological changes induced by the presence of water have not caused irreversible changes in the dielectric properties of the laminates.

  7. Dielectric Elastomers for Fluidic and Biomedical Applications

    Science.gov (United States)

    McCoul, David James

    Dielectric elastomers have demonstrated tremendous potential as high-strain electromechanical transducers for a myriad of novel applications across all engineering disciplines. Because their soft, viscoelastic mechanical properties are similar to those of living tissues, dielectric elastomers have garnered a strong foothold in a plethora of biomedical and biomimetic applications. Dielectric elastomers consist of a sheet of stretched rubber, or elastomer, coated on both sides with compliant electrode materials; application of a voltage generates an electrostatic pressure that deforms the elastomer. They can function as soft generators, sensors, or actuators, and this last function is the focus of this dissertation. Many design configurations are possible, such as stacks, minimum energy structures, interpenetrating polymer networks, shape memory dielectric elastomers, and others; dielectric elastomers are already being applied to many fields of biomedicine. The first part of the original research presented in this dissertation details a PDMS microfluidic system paired with a dielectric elastomer stack actuator of anisotropically prestrained VHB(TM) 4910 (3M(TM)) and single-walled carbon nanotubes. These electroactive microfluidic devices demonstrated active increases in microchannel width when 3 and 4 kV were applied. Fluorescence microscopy also indicated an accompanying increase in channel depth with actuation. The cross-sectional area strains at 3 and 4 kV were approximately 2.9% and 7.4%, respectively. The device was then interfaced with a syringe pump, and the pressure was measured upstream. Linear pressure-flow plots were developed, which showed decreasing fluidic resistance with actuation, from 0.192 psi/(microL/min) at 0 kV, to 0.160 and 0.157 psi/(microL/min) at 3 and 4 kV, respectively. This corresponds to an ~18% drop in fluidic resistance at 4 kV. Active de-clogging was tested in situ with the device by introducing ~50 microm diameter PDMS microbeads and

  8. Dielectric Properties of Flocculated Water-in-Oil Emulsions

    Energy Technology Data Exchange (ETDEWEB)

    Skodvin, T.

    1995-12-31

    When an offshore oil field is near completion, water occupies a large fraction of the available pore volume. Thus, in collecting the oil and gas reserves, one has to deal with a high co-production of either formation- or injected water. This doctoral thesis focuses on the effect of water-in-oil emulsions on the dielectric properties, in particular the effect of flocculation. Various dielectric models are applied to obtain methods for qualitative and quantitative characterization of the flocculated state. Permittivity and measurement of dielectric properties are discussed as a basis for the interpretation of the dielectric properties of the emulsions. Various flocculation models are presented. It is concluded that the dielectric properties of water-in-oil emulsions are strongly influenced by continuously ongoing processes in the system. Because of flocculation and sedimentation the traditional dielectric mixture models cannot satisfactorily predict the dielectric behaviour. The experimentally obtained permittivities for the emulsions can be reproduced by including flocculation in the models and treating the floc aggregates as spheroids or subsystems with dielectric properties given by the degree of flocculation. The models discussed have difficulties reproducing the complete frequency behaviour found experimentally. This is probably because the dielectric relaxation may be influenced by processes not included in the models, such as the effects of dipolar or multipolar interactions between the droplets. For further research it is recommended that rheological and dielectric measurements be combined. 227 refs., 61 figs., 16 tabs.

  9. Dielectric Properties of Flocculated Water-in-Oil Emulsions

    Energy Technology Data Exchange (ETDEWEB)

    Skodvin, T

    1996-12-31

    When an offshore oil field is near completion, water occupies a large fraction of the available pore volume. Thus, in collecting the oil and gas reserves, one has to deal with a high co-production of either formation- or injected water. This doctoral thesis focuses on the effect of water-in-oil emulsions on the dielectric properties, in particular the effect of flocculation. Various dielectric models are applied to obtain methods for qualitative and quantitative characterization of the flocculated state. Permittivity and measurement of dielectric properties are discussed as a basis for the interpretation of the dielectric properties of the emulsions. Various flocculation models are presented. It is concluded that the dielectric properties of water-in-oil emulsions are strongly influenced by continuously ongoing processes in the system. Because of flocculation and sedimentation the traditional dielectric mixture models cannot satisfactorily predict the dielectric behaviour. The experimentally obtained permittivities for the emulsions can be reproduced by including flocculation in the models and treating the floc aggregates as spheroids or subsystems with dielectric properties given by the degree of flocculation. The models discussed have difficulties reproducing the complete frequency behaviour found experimentally. This is probably because the dielectric relaxation may be influenced by processes not included in the models, such as the effects of dipolar or multipolar interactions between the droplets. For further research it is recommended that rheological and dielectric measurements be combined. 227 refs., 61 figs., 16 tabs.

  10. Information authentication using an optical dielectric metasurface

    International Nuclear Information System (INIS)

    Wang, Xiaogang; Mei, Shengtao

    2017-01-01

    Metasurfaces that consist of a monolayer of photonic artificial atoms are emerging as attractive materials for optical wavefront-shaping and polarization-control devices. By integrating nanophotonics with a phase-encoding technique, we demonstrate theoretically an information authentication method using dielectric metasurfaces that can be verified without information disclosure at visible wavelengths. The required secured diffraction pattern can be simply achieved by a metasurface hologram with a small number of pixels, which means increased efficiency and lower costs of production. Although the decrypted image is noisy, it can be authenticated by recognition algorithms where the primary image is used as a reference. The results show that the dielectric metasurface approach, providing great flexibility in the design of the wavefront of light and compatible with the CMOS technology, can be potentially applied in optical information security. (letter)

  11. Broadband dielectric spectroscopy of oxidized porous silicon

    International Nuclear Information System (INIS)

    Axelrod, Ekaterina; Urbach, Benayahu; Sa'ar, Amir; Feldman, Yuri

    2006-01-01

    Dielectric measurements accompanied by infrared absorption and photoluminescence (PL) spectroscopy were used to investigate the electrical and optical properties of oxidized porous silicon (PS). As opposed to non-oxidized PS, only high temperature relaxation processes could be resolved for oxidized PS. Two relaxation processes have been observed. The first process is related to dc-conductivity that dominates at high temperatures and low frequencies. After subtraction of dc-conductivity we could analyse a second high-temperature relaxation process that is related to interface polarization induced by charge carriers trapped at the host matrix-pore interfaces. We found that, while the main effect of the oxidation on the PL appears to be a size reduction in the silicon nanocrystals that gives rise to a blue shift of the PL spectrum, its main contribution to the dielectric properties turns out to be blocking of transport channels in the host tissue and activation of hopping conductivity between silicon nanocrystals

  12. Colour dielectric model of the proton

    International Nuclear Information System (INIS)

    Jen, P.K.; Pradhan, T.

    1984-01-01

    A model of the proton with its constituent quarks bound in a colour polarizable medium with dielectric constant varying as (a/r - b 2 ) from a fixed centre, is presented. The Dirac equation modified by the colour polarization is solved and the analytic expression for the wavefunction of the quarks obtained shows that quarks with higher energy lie closer to the fixed centre. The energy spectrum is equispaced without any continuum. A semiclassical approximation scheme yields closed orbits for quarks which have smaller size for higher energies and no orbits with size bigger than a certain maximum, thereby rendering the quarks permanently confined. The wavefunctions of the three quarks constituting the proton are used to calculate physical parameters of the proton such as its mass, charge radius and weak coupling constant which with suitable choice of the constants a and b appearing in the dielectric constant agree fairly well with experimental results. (author)

  13. Dielectric Constant Measurements of Solid 4He

    Science.gov (United States)

    Yin, L.; Xia, J. S.; Huan, C.; Sullivan, N. S.; Chan, M. H. W.

    2011-03-01

    Careful measurements of the dielectric properties of solid 4He have been carried out down to 35 mK, considerably lower than the temperature range of previous studies. The sample was prepared from high purity gas with 3He concentrations of the order of 200 ppb and were formed by the blocked capillary method. The molar volume of the sample was 20.30 cm3. The dielectric constant of the samples was found to be independent of temperature down to 120 mK before showing a continuous increase with decreasing temperature and saturating below 50 mK. The total increase in ɛ is 2 parts in 10-5. The temperature dependence of ɛ mimics the increase in the resonant frequency found in the torsional oscillator studies and also the increase found in the shear modulus measurements.

  14. Broadband dielectric spectroscopy of oxidized porous silicon

    Energy Technology Data Exchange (ETDEWEB)

    Axelrod, Ekaterina [Department of Applied Physics, Hebrew University of Jerusalem, Jerusalem, 91904 (Israel); Urbach, Benayahu [Racah Institute of Physics and the Center for Nanoscience and Nanotechnology, Hebrew University of Jerusalem, Jerusalem, 91904 (Israel); Sa' ar, Amir [Racah Institute of Physics and the Center for Nanoscience and Nanotechnology, Hebrew University of Jerusalem, Jerusalem, 91904 (Israel); Feldman, Yuri [Department of Applied Physics, Hebrew University of Jerusalem, Jerusalem, 91904 (Israel)

    2006-04-07

    Dielectric measurements accompanied by infrared absorption and photoluminescence (PL) spectroscopy were used to investigate the electrical and optical properties of oxidized porous silicon (PS). As opposed to non-oxidized PS, only high temperature relaxation processes could be resolved for oxidized PS. Two relaxation processes have been observed. The first process is related to dc-conductivity that dominates at high temperatures and low frequencies. After subtraction of dc-conductivity we could analyse a second high-temperature relaxation process that is related to interface polarization induced by charge carriers trapped at the host matrix-pore interfaces. We found that, while the main effect of the oxidation on the PL appears to be a size reduction in the silicon nanocrystals that gives rise to a blue shift of the PL spectrum, its main contribution to the dielectric properties turns out to be blocking of transport channels in the host tissue and activation of hopping conductivity between silicon nanocrystals.

  15. Enhanced dielectric-wall linear accelerator

    Science.gov (United States)

    Sampayan, Stephen E.; Caporaso, George J.; Kirbie, Hugh C.

    1998-01-01

    A dielectric-wall linear accelerator is enhanced by a high-voltage, fast e-time switch that includes a pair of electrodes between which are laminated alternating layers of isolated conductors and insulators. A high voltage is placed between the electrodes sufficient to stress the voltage breakdown of the insulator on command. A light trigger, such as a laser, is focused along at least one line along the edge surface of the laminated alternating layers of isolated conductors and insulators extending between the electrodes. The laser is energized to initiate a surface breakdown by a fluence of photons, thus causing the electrical switch to close very promptly. Such insulators and lasers are incorporated in a dielectric wall linear accelerator with Blumlein modules, and phasing is controlled by adjusting the length of fiber optic cables that carry the laser light to the insulator surface.

  16. Response

    Science.gov (United States)

    Higgins, Chris

    2012-01-01

    This article presents the author's response to the reviews of his book, "The Good Life of Teaching: An Ethics of Professional Practice." He begins by highlighting some of the main concerns of his book. He then offers a brief response, doing his best to address the main criticisms of his argument and noting where the four reviewers (Charlene…

  17. Oblique surface waves at an interface between a metal-dielectric superlattice and an isotropic dielectric

    International Nuclear Information System (INIS)

    Vuković, Slobodan M; Miret, Juan J; Zapata-Rodriguez, Carlos J; Jakšić, Zoran

    2012-01-01

    We investigate the existence and dispersion characteristics of surface waves that propagate at an interface between a metal-dielectric superlattice and an isotropic dielectric. Within the long-wavelength limit, when the effective-medium (EM) approximation is valid, the superlattice behaves like a uniaxial plasmonic crystal with the main optical axes perpendicular to the metal-dielectric interfaces. We demonstrate that if such a semi-infinite plasmonic crystal is cut normally to the layer interfaces and brought into contact with a semi-infinite dielectric, a new type of surface mode can appear. Such modes can propagate obliquely to the optical axes if favorable conditions regarding the thickness of the layers and the dielectric permittivities of the constituent materials are met. We show that losses within the metallic layers can be substantially reduced by making the layers sufficiently thin. At the same time, a dramatic enlargement of the range of angles for oblique propagation of the new surface modes is observed. This can lead, however, to field non-locality and consequently to failure of the EM approximation.

  18. Dielectric properties of proton irradiated PES

    International Nuclear Information System (INIS)

    Shah, Nilam; Singh, N.L.; Singh, K.P.

    2005-01-01

    Polyethersulfone films were irradiated with 3 MeV proton beam at fluences ranging from 10 13 to 10 15 ions/cm 2 . AC electrical properties of irradiated samples were studied in the frequency range 100 Hz to 1MHz by LCR meter. There is an exponential increase in conductivity with frequency but the effect of irradiation is not significant. The dielectric loss/constant are observed to change with fluence. (author)

  19. Modeling of Dielectric Heating within Lyophilization Process

    Directory of Open Access Journals (Sweden)

    Jan Kyncl

    2014-01-01

    Full Text Available A process of lyophilization of paper books is modeled. The process of drying is controlled by a dielectric heating system. From the physical viewpoint, the task represents a 2D coupled problem described by two partial differential equations for the electric and temperature fields. The material parameters are supposed to be temperature-dependent functions. The continuous mathematical model is solved numerically. The methodology is illustrated with some examples whose results are discussed.

  20. Cellulose triacetate, thin film dielectric capacitor

    Science.gov (United States)

    Yen, Shiao-Ping S. (Inventor); Jow, T. Richard (Inventor)

    1995-01-01

    Very thin films of cellulose triacetate are cast from a solution containing a small amount of high boiling temperature, non-solvent which evaporates last and lifts the film from the casting surface. Stretched, oriented, crystallized films have high electrical breakdown properties. Metallized films less than about 2 microns in thickness form self-healing electrodes for high energy density, pulsed power capacitors. Thicker films can be utilized as a dielectric for a capacitor.

  1. Measurement of dielectric and magnetic properties of soil

    International Nuclear Information System (INIS)

    Patitz, W.E.; Brock, B.C.; Powell, E.G.

    1995-11-01

    The possibility of subsurface imaging using SAR technology has generated a considerable amount of interest in recent years. One requirement for the successful development of a subsurface imagin system is an understanding of how the soil affects the signal. In response to a need for an electromagnetic characterization of the soil properties, the Radar/Antenna department has developed a measurement system which determines the soils complex electric permittivity and magnetic permeability at UHF frequencies. The one way loss in dB is also calculated using the measured values. There are many reports of measurements of the electric properties of soil in the literature. However, most of these are primarily concerned with measuring only a real dielectric constant. Because some soils have ferromagnetic constituents it is desirable to measure both the electric and magnetic properties of the soil

  2. Coupling Phenomenon in Diode with Dielectric Gridded Cathode

    International Nuclear Information System (INIS)

    Lahav, A.; Berezovsky, V.; Schachter, L.

    1999-01-01

    We investigated the current characteristic in a vacuum diode with a Gridded cathode. The grid is located on a top of a Ferro - Electric disk with a uniform cathode on its back side. We found experimental evidence that the current in such a system exceeds Child - Langmuir limit, in agreement with results reported in [1]. Explanations to this phenomenon were given in term of the non-linear characteristic of the ferro - electric ceramic or by plasma-assisted emission and gap closure. Recently [2] it has been shown theoretically that electrostatic coupling between the dielectric disk and the vacuum gap is directly responsible to the excess of current. We shall report experimental results that may support this possibility

  3. Structural, photoconductivity, and dielectric studies of polythiophene-tin oxide nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Murugavel, S., E-mail: starin85@gmail.com; Malathi, M., E-mail: mmalathi@vit.ac.in

    2016-09-15

    Highlights: • Synthesis of polythiophene-tin oxide nanocomposites confirmed by FTIR and EDAX. • SEM shows SnO{sub 2} nanoparticles embedded within polythiophene matrix. • Stability and isoelectric point suggest nanoparticle–matrix interaction. • High dielectric constant due to high Maxwell–Wagner interfacial polarization. - Abstract: Polythiophene-tinoxide (PT-SnO{sub 2}) nanocomposites were prepared by in situ chemical oxidative polymerization, in the presence of various concentrations of SnO{sub 2} nanoparticles. Samples were characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy and Zeta potential measurements. Morphologies and elemental compositions were investigated by transmission electron microscopy, field-emission scanning electron microscopy and energy-dispersive X-ray spectroscopy. The photoconductivity of the nanocomposites was studied by field-dependent dark and photo conductivity measurements. Their dielectric properties were investigated using dielectric spectroscopy, in the frequency range of 1kHz–1 MHz. The results indicated that the SnO{sub 2} nanoparticles in the PT-SnO{sub 2} nanocomposite were responsible for its enhanced dielectric performance.

  4. Analysis of transmittance properties in 1D hybrid dielectric photonic crystal containing superconducting thin films

    Science.gov (United States)

    Soltani, Osswa; Zaghdoudi, Jihene; Kanzari, Mounir

    2018-06-01

    By means of two fluid model and transfer matrix method (TMM), we investigate theoretically the transmittance properties of a defective hybrid dielectric-dielectric photonic crystal that contains a superconducting material as a defect layer. The considered hybrid photonic structure is: H(LH) 7(HLSLH) P H(LH) 7 , where H is the high refractive index dielectric, L is the low refractive index dielectric, S is the superconducting material and P is the repetitive number. The results show that the variation of the number and the positions of the transmissions modes depend strongly on the repetitive number P, the temperature T and the thickness of the layer S. An improvement of the spectral response is obtained with the exponential gradation of layer thicknesses dj =d0 + βejα , where d0 is the initial thickness of the layer j, α and β are two particular constants for each material. In addition, the effect of the incident angle for both transverse electric (TE) and transverse magnetic (TM) polarizations on the transmittance spectrum is discussed. As a result, we propose a tunable narrow stop-band polychromatic filter that covers the visible wavelength.

  5. Effect of nanocomposite gate-dielectric properties on pentacene microstructure and field-effect transistor characteristics.

    Science.gov (United States)

    Lee, Wen-Hsi; Wang, Chun-Chieh

    2010-02-01

    In this study, the effect of surface energy and roughness of the nanocomposite gate dielectric on pentacene morphology and electrical properties of pentacene OTFT are reported. Nanoparticles TiO2 were added in the polyimide matrix to form a nanocomposite which has a significantly different surface characteristic from polyimide, leading to a discrepancy in the structural properties of pentacene growth. A growth mode of pentacene deposited on the nanocomposite is proposed to explain successfully the effect of surface properties of nanocomposite gate dielectric such as surface energy and roughness on the pentacene morphology and electrical properties of OTFT. To obtain the lower surface energy and smoother surface of nanocomposite gate dielectric that is responsible for the desired crystalline, microstructure of pentacene and electrical properties of device, a bottom contact OTFT-pentacene deposited on the double-layer nanocomposite gate dielectric consisting of top smoothing layer of the neat polyimide and bottom layer of (PI+ nano-TiO2 particles) nanocomposite has been successfully demonstrated to exhibit very promising performance including high current on to off ratio of about 6 x 10(5), threshold voltage of -10 V and moderately high filed mobility of 0.15 cm2V(-1)s(-1).

  6. Porogen residues detection in optical properties of low-k dielectrics cured by ultraviolet radiation

    Energy Technology Data Exchange (ETDEWEB)

    Marsik, Premysl, E-mail: marsik@physics.muni.c [UFKL, Masaryk University, Kotlarska 2, 61137 Brno (Czech Republic); IMEC, Kapeldreef 75, 3001 Leuven (Belgium); Verdonck, Patrick [IMEC, Kapeldreef 75, 3001 Leuven (Belgium); De Roest, David [ASM Belgium, Kapeldreef 75, 3001 Leuven (Belgium); Baklanov, Mikhail R. [IMEC, Kapeldreef 75, 3001 Leuven (Belgium)

    2010-05-31

    The optical properties of low dielectric constant (low-k) films have been determined by variable angle spectroscopic ellipsometry in the range from 2 eV to 9 eV to characterize the process of porogen removal during the UV-cure. The studied carbon doped oxide (SiCOH) porous dielectric films have been prepared by plasma enhanced chemical vapor deposition. The films have been deposited as a composition of a matrix precursor and an organic porogen. After deposition, the films have been cured by thermal annealing and UV irradiation ({lambda} = 172 nm) to remove the porogen and create a porosity of 33%, reaching a dielectric constant of 2.3. The process of porogen decomposition and removal has been studied on series of low-k samples, UV-cured for various times. Additional samples have been prepared by the deposition and curing of the porogen film, without SiCOH matrix, and the matrix material itself, without porogen. The analysis of the optical response of the porous dielectric as a mixture of matrix material, porogen and voids, together with Fourier transform infrared analysis, allows the sensitive detection of the volume of the porogen and indicates the existence of decomposed porogen residues inside the pores, even for long curing time. The variation of the deposition and curing conditions can control the amount of the porogen residues and the final porosity.

  7. Cordierite Glass-Ceramics for Dielectric Materials

    International Nuclear Information System (INIS)

    Siti Mazatul Azwa Saiyed Mohd Nurddin; Selamat, Malek; Ismail, Abdullah

    2007-01-01

    The objective of this project is to examine the potential of using Malaysian silica sand deposit as SiO2 raw material in producing cordierite glass-ceramics (2MgO-2Al2O3-5SiO2) for dielectric materials. Upgraded silica sands from Terengganu and ex-mining land in Perak were used in the test-works. The glass batch of the present work has a composition of 45.00% SiO2, 24.00% Al2O3, 15.00% MgO and 8.50% TiO2 as nucleation agent. From the differential thermal analysis results, the crystallization temperature was found to start around 900 deg. C. The glass samples were heat-treated at 900 deg. C and 1000 deg. C. The X-ray diffraction analysis (XRD) results showed glass-ceramics from Terengganu samples containing mainly cordierite and minor β-quartz crystals. However, glass-ceramics from ex-mining land samples contained mainly α-quartz and minor cordierite crystals. Glass-ceramics with different crystal phases exhibit different mechanical, dielectric and thermal properties. Based on the test works, both silica sand deposits, can be potentially used to produce dielectric material component

  8. Macroscopic polarization in crystalline dielectrics: the geometric phase approach

    International Nuclear Information System (INIS)

    Resta, R.

    1994-01-01

    The macroscopic electric polarization of a crystal is often defined as the dipole of a unit cell. In fact, such a dipole moment is ill defined, and the above definition is incorrect. Looking more closely, the quantity generally measured is differential polarization, defined with respect to a ''reference state'' of the same material. Such differential polarizations include either derivatives of the polarization (dielectric permittivity, Born effective charges, piezoelectricity, pyroelectricity) or finite differences (ferroelectricity). On the theoretical side, the differential concept is basic as well. Owing to continuity, a polarization difference is equivalent to a macroscopic current, which is directly accessible to the theory as a bulk property. Polarization is a quantum phenomenon and cannot be treated with a classical model, particularly whenever delocalized valence electrons are present in the dielectric. In a quantum picture, the current is basically a property of the phase of the wave functions, as opposed to the charge, which is a property of their modulus. An elegant and complete theory has recently been developed by King-Smith and Vanderbilt, in which the polarization difference between any two crystal states--in a null electric field--takes the form of a geometric quantum phase. This gives a comprehensive account of this theory, which is relevant for dealing with transverse-optic phonons, piezoelectricity, and ferroelectricity. Its relation to the established concepts of linear-response theory is also discussed. Within the geometric phase approach, the relevant polarization difference occurs as the circuit integral of a Berry connection (or ''vector potential''), while the corresponding curvature (or ''magnetic field'') provides the macroscopic linear response

  9. The study of dielectric properties of the endohedral fullerenes

    Science.gov (United States)

    Bhusal, Shusil

    Dielectric response of the metal nitride fullerenes is studied using the density functional theory at the all-electron level using generalized gradient approximation. The dielectric response is studied by computing the static dipole polarizabilities using the finite field method, i.e. by numerically differentiating the dipole moments with respect to electric field. The endohedral fullerenes studied in this work are Sc3N C68(6140), Sc3N C68(6146), Sc3N C70(7854), Sc3N C70(7960), Sc3N C76(17490), Sc3N C78(22010), Sc3N C80(31923), Sc3N C80(31924), Sc3N C82(39663), Sc3N C90(43), Sc3N C90(44), Sc3N C92(85), Sc3N C94(121), Sc3N C96(186), Sc3N C98(166). Using the Voronoi and Hirschfield approaches as implemented in our NRLMOL code, we determine the atomic contributions to the total polarizability. The site-specific contributions to the polarizability of endohedral fullerenes allowed us to determine the polarizability of two subsystems: the fullerene shell and the encapsulated Sc3N unit. Our results showed that the contributions to the total polarizability from the encapsulated Sc3N units are vanishingly small. Thus, the total polarizability of the endohedral fullerene is almost entirely due to the outer fullerene shell. These fullerenes are excellent molecular models of a Faraday cage.

  10. Theoretical investigation of resonance frequencies in long wavelength electromagnetic wave scattering process from plasma prolate and oblate spheroids placed in a dielectric layer

    Science.gov (United States)

    Ahmadizadeh, Y.; Jazi, B.; Abdoli-Arani, A.

    2014-01-01

    Response of a prolate spheroid plasma and/or an oblate spheroid plasma in presence of long wavelength electromagnetic wave has been studied. The resonance frequencies of these objects are obtained and it is found that they reduce to the resonance frequency of spherical cold plasma. Moreover, the resonant frequencies of prolate spheroid plasma and oblate spheroid plasma covered by a dielectric are investigated as well. Furthermore, their dependency on dielectric permittivity and geometry dimensions is simulated.

  11. Dielectric properties of agricultural materials and their applications

    CERN Document Server

    Nelson, Stuart

    2015-01-01

    Dielectric Properties of Agricultural Materials and Their Applications provides an understanding of the fundamental principles governing dielectric properties of materials, describes methods for measuring such properties, and discusses many applications explored for solving industry problems. The information in this reference stimulates new research for solving problems associated with production, handling, and processing of agricultural and food products. Anyone seeking a better understanding of dielectric properties of materials and application of radio-frequency and microwave electromagnetic energy for solution of problems in agriculture and related fields will find this an essential resource. Presents applications of dielectric properties for sensing moisture in grain and seed and the use of such properties in radio-frequency and microwave dielectric heating of agricultural materials Offers information for finding correlations between dielectric properties and quality attributes such as sweetness in melon...

  12. Properties of dielectric barrier discharges in different arrangements

    International Nuclear Information System (INIS)

    Pietsch, G.J.

    2001-01-01

    Dielectric barrier discharges (DBDs) occur in arrangements where at least one dielectric is positioned in a gas space in between conducting electrodes. When breakdown field strength is reached in such a device, charge carriers are created in the gas region, accelerated, multiplied and finally collected on the surface(s) of the dielectric(s). The charge accumulation on the dielectric creates a counter field to that resulting from the power supply and as all of these processes are rather fast, the discharge quenches rapidly. The dielectric has two tasks, it limits the transferred charge and by this the energy conversion and distributes the discharge over the electrode area. That is why DBDs are non-thermal discharges which exist even at atmospheric pressure

  13. Fabrication of Nonvolatile Memory Effects in High-k Dielectric Thin Films Using Electron Irradiation

    International Nuclear Information System (INIS)

    Park, Chanrock; Cho, Daehee; Kim, Jeongeun; Hwang, Jinha

    2010-01-01

    Electron Irradiation can be applied towards nano-floating gate memories which are recognized as one of the next-generation nonvolatile memory semiconductors. NFGMs can overcome the preexisting limitations encountered in Dynamic Random Access Memories and Flash memories with the excellent advantages, i. e. high-density information storage, high response speed, high compactness, etc. The traditional nano-floating gate memories are fabricated through multi-layered nano structures of the dissimilar materials where the charge-trapping portions are sandwiched into the high-k dielectrics. However, this work reports the unique nonvolatile responses in single-layered high-k dielectric thin films if irradiated with highly accelerated electron beams. The implications of the electron irradiation will be discussed towards high-performance nano-floating gate memories

  14. Perfect coupling of light to a periodic dielectric/metal/dielectric structure

    Science.gov (United States)

    Wang, Zhengling; Li, Shiqiang; Chang, R. P. H.; Ketterson, John B.

    2014-07-01

    Using the finite difference time domain method, it is demonstrated that perfect coupling can be achieved between normally incident light and a periodic dielectric/metal/dielectric structure. The structure serves as a diffraction grating that excites modes related to the long range surface plasmon and short range surface plasmon modes that propagate on continuous metallic films. By optimizing the structural dimensions, perfect coupling is achieved between the incident light and these modes. A high Q of 697 and an accompanying ultrasharp linewidth of 0.8 nm are predicted for a 10 nm silver film for optimal conditions.

  15. The dielectric properties of biological tissues: III. Parametric models for the dielectric spectrum of tissues

    International Nuclear Information System (INIS)

    Gabriel, S.; Lau, R.W.; Gabriel, C.

    1996-01-01

    A parametric model was developed to describe the variation of dielectric properties of tissues as a function of frequency. The experimental spectrum from 10 Hz to 100 GHz was modelled with four dispersion regions. The development of the model was based on recently acquired data, complemented by data surveyed from the literature. The purpose is to enable the prediction of dielectric data that are in line with those contained in the vast body of literature on the subject. The analysis was carried out on a Microsoft Excel spreadsheet. Parameters are given for 17 tissue types. (author)

  16. Dielectric behaviour of erbium substituted Mn–Zn ferrites

    Indian Academy of Sciences (India)

    Unknown

    Abstract. Dielectric properties such as dielectric constant (ε′) and dielectric loss tangent (tan δ) of mixed. Mn–Zn–Er ferrites having the compositional formula Mn0⋅58Zn0⋅37Fe2⋅05–xErxO4 (where x = 0⋅2, 0⋅4, 0⋅6, 0⋅8 and. 1⋅0) were measured at room temperature in the frequency range 1–13 MHz using a HP ...

  17. Dielectric relaxation in AgI doped silver selenomolybdate glasses

    Science.gov (United States)

    Palui, A.; Shaw, A.; Ghosh, A.

    2016-05-01

    We report the study of dielectric properties of some silver ion conducting silver selenomolybdate mixed network former glasses in a wide frequency and temperature range. The experimental data have been analyzed in the framework of complex dielectric permittivity. The dielectric permittivity data have been well interpreted using the Cole-Cole function. The temperature dependence of relaxation time obtained from real part of dielectric permittivity data shows an Arrhenius behavior. The activation energy shows a decreasing trend with the increase of doping content. Values of stretched exponential parameter are observed to be independent of temperature and composition.

  18. Improved dielectric functions in metallic films obtained via template stripping

    Science.gov (United States)

    Hyuk Park, Jong; Nagpal, Prashant; Oh, Sang-Hyun; Norris, David J.

    2012-02-01

    We compare the dielectric functions of silver interfaces obtained via thermal evaporation with those obtained with template stripping. Ellipsometry measurements show that the smoother template-stripped surfaces exhibit effective dielectric functions with a more negative real component and a smaller imaginary component, implying higher conductivity and less energy loss, respectively. These results agree with the relation between dielectric function and surface roughness derived from combining the effective-medium model and the Drude-Lorentz model. The improvement in the effective dielectric properties shows that metallic films prepared via template stripping can be favorable for applications in electronics, nanophotonics, and plasmonics.

  19. Dielectric behaviors of lead zirconate titanate ceramics with coplanar electrodes

    International Nuclear Information System (INIS)

    Wang, Y.; Cheng, Y.L.; Zhang, Y.W.; Chan, H.L.W.; Choy, C.L.

    2003-01-01

    This paper reports on the dielectric behaviors of lead zirconate titanate (PZT) capacitors with coplanar electrodes. Usually a ferroelectric device has a metal-ferroelectric-metal configuration (parallel plate capacitor); when both the electrodes are on one side of a ceramic to form a coplanar capacitor, different dielectric behaviors will be anticipated because of the change in the distribution of the test field inside the dielectrics. This paper describes how the capacitance and dielectric loss of PZT-based coplanar capacitors change with electrode distance, area and test frequency

  20. Suppression of electromechanical instability in fiber-reinforced dielectric elastomers

    Directory of Open Access Journals (Sweden)

    Rui Xiao

    2016-03-01

    Full Text Available The electromechanical instability of dielectric elastomers has been a major challenge for the application of this class of active materials. In this work, we demonstrate that dielectric elastomers filled with soft fiber can suppress the electromechanical instability and achieve large deformation. Specifically, we developed a constitutive model to describe the dielectric and mechanical behaviors of fiber-reinforced elastomers. The model was applied to study the influence of stiffness, nonlinearity properties and the distribution of fiber on the instability of dielectric membrane under an electric field. The results show that there exists an optimal fiber distribution condition to achieve the maximum deformation before failure.