Sample records for static dielectric properties

  1. Static dielectric properties of dense ionic fluids

    NASA Astrophysics Data System (ADS)

    Zarubin, Grigory; Bier, Markus

    2015-05-01

    The static dielectric properties of dense ionic fluids, e.g., room temperature ionic liquids (RTILs) and inorganic fused salts, are investigated on different length scales by means of grandcanonical Monte Carlo simulations. A generally applicable scheme is developed which allows one to approximately decompose the electric susceptibility of dense ionic fluids into the orientation and the distortion polarization contribution. It is shown that at long range, the well-known plasma-like perfect screening behavior occurs, which corresponds to a diverging distortion susceptibility, whereas at short range, orientation polarization dominates, which coincides with that of a dipolar fluid of attached cation-anion pairs. This observation suggests that the recently debated interpretation of RTILs as dilute electrolyte solutions might not be simply a yes-no-question but it might depend on the considered length scale.

  2. Static and high frequency magnetic and dielectric properties of ferrite-ferroelectric composite materials

    E-print Network

    Patton, Carl

    TM barium strontium titanate BSTO and Trans-Tech nickel zinc ferrite powders. The ferrite loading was variedStatic and high frequency magnetic and dielectric properties of ferrite-ferroelectric composite from zero BSTO only to 100 wt % ferrite only . X-ray diffraction data show the presence of a third

  3. Ion size effects on the dynamic and static dielectric properties of aqueous alkali solutions

    E-print Network

    Sridhar, Srinivas

    -Zhen Wei, Ping Chiang, and S. Sridhar Department of Physics, Northeastern University, Boston, Massachusetts 02115 (Received28 August 1991;accepted18November 1991) Dielectric spectroscopystudiesof aqueousionic

  4. Dielectric Properties Of Nanoferrites

    Microsoft Academic Search

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

    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

  5. Physical and dielectric properties of pharmaceutical powders

    Microsoft Academic Search

    C. M McLoughlin; W. A. M McMinn; T. R. A Magee

    2003-01-01

    The limited availability of published physical and dielectric property data for pharmaceutical powders hinders the design of processing systems, particularly dryers. In this study, the physical properties (solubility and boiling point) and dielectric properties, in terms of temperature rise, dielectric constant, and dielectric loss factor, of selected pharmaceutical powders were measured. The pharmaceutical actives, paracetamol and aspirin, and selected common

  6. Dielectric properties of insect tissues.

    PubMed

    Ondrácek, J; Brunnhofer, V

    1984-06-01

    In order to explain some effects of microwave irradiation on insects it is necessary to consider a mathematical model. The knowledge of dielectric properties of a typical insect tissue is crucial for such a model. A method based on shift of resonant frequency and of quality factor measurement in a resonator both before and after the insertion of samples was used. The method (measurements at a frequency of 2375 MHz) has been described in detail. A large number of measurements were performed on different kinds of typical insect tissues (cuticle, fat body, muscles, reproductive organs and eggs) for their dielectric properties. The values obtained compare well to those reported in the literature for some mammals. Differences seemed to depend on different water-to-fat content ratios. However, no simple dependence on the water content was found. Values obtained from insect tissue material have been discussed in detail. PMID:6479581

  7. Electronic, mechanical and dielectric properties of silicane under tensile strain

    NASA Astrophysics Data System (ADS)

    Jamdagni, Pooja; Kumar, Ashok; Sharma, Munish; Thakur, Anil; Ahluwalia, P. K.

    2015-05-01

    The electronic, mechanical and dielectric properties of fully hydrogenated silicene i.e. silicane in stable configuration are studied by means of density functional theory based calculations. The band gap of silicane monolayer can be flexibly reduced to zero when subjected to bi-axial tensile strain, leading to semi-conducting to metallic transition, whereas the static dielectric constant for in-plane polarization increases monotonically with increasing strain. Also the EEL function show the red shift in resonance peak with tensile strain. Our results offer useful insight for the application of silicane monolayer in nano-optical and electronics devices.

  8. Tailoring dielectric properties of ferroelectric-dielectric multilayers

    NASA Astrophysics Data System (ADS)

    Kesim, M. T.; Cole, M. W.; Zhang, J.; Misirlioglu, I. B.; Alpay, S. P.

    2014-01-01

    We develop a nonlinear thermodynamic model for multilayer ferroelectric heterostructures that takes into account electrostatic and electromechanical interactions between layers. We concentrate on the effect of relative layer fractions and in-plane thermal stresses on dielectric properties of Ba0.6Sr0.4TiO3-, BaTiO3-, and PbZr0.2Ti0.8O3 (PZT)-SrTiO3 (STO) multilayers on Si and c-sapphire. We show that dielectric properties of such multilayers can be significantly enhanced by tailoring the growth/processing temperature and the STO layer fraction. Our computations show that large tunabilities (˜90% at 400 kV/cm) are possible in carefully designed barium strontium titanate-STO and PZT-STO even on Si for which there exist substantially large in-plane strains.

  9. An ab-initio Computational Method to Determine Dielectric Properties of Biological Materials

    PubMed Central

    Abeyrathne, Chathurika D.; Halgamuge, Malka N.; Farrell, Peter M.; Skafidas, Efstratios

    2013-01-01

    Frequency dependent dielectric properties are important for understanding the structure and dynamics of biological materials. These properties can be used to study underlying biological processes such as changes in the concentration of biological materials, and the formation of chemical species. Computer simulations can be used to determine dielectric properties and atomic details inaccessible via experimental methods. In this paper, a unified theory utilizing molecular dynamics and density functional theory is presented that is able to determine the frequency dependent dielectric properties of biological materials in an aqueous solution from their molecular structure alone. The proposed method, which uses reaction field approximations, does not require a prior knowledge of the static dielectric constant of the material. The dielectric properties obtained from our method agree well with experimental values presented in the literature. PMID:23652459

  10. Dielectric Properties of Heavy Ice Ih (D2O Ice)

    Microsoft Academic Search

    Shuji Kawada

    1979-01-01

    Dielectric anisotropy of heavy ice Ih is examined in a wide temperature range by measuring the complex dielectric constants parallel and normal to the c axis, and it is compared with that of ordinary ice Ih (H2O ice). The increased anisotropy in the static dielectric constants including only the shift of the extrapolated Curie-Weiss temperature to 55 K was observed.

  11. Electrical properties and dielectric spectroscopy of Ar+ implanted polycarbonate

    NASA Astrophysics Data System (ADS)

    Chawla, Mahak; Shekhawat, Nidhi; Aggarwal, Sanjeev; Sharma, Annu; Nair, K. G. M.

    2015-05-01

    The aim of the present paper is to study the effect of argon ion implantation on electrical and dielectric properties of polycarbonate. Specimens were implanted with 130 keV Ar+ ions in the fluence ranging from 1×1014 to 1×1016 ions cm-2. The beam current used was ˜0.40 µA cm-2. The electrical conduction behaviour of virgin and Ar+ implanted polycarbonate specimens have been studied through current-voltage (I-V characteristic) measurements. It has been observed that after implantation conductivity increases with increasing ion fluence. The dielectric spectroscopy of these specimens has been done in the frequency range of 100 kHz-100 MHz. Relaxation processes were studied by Cole-Cole plot of complex permittivity (real part of complex permittivity, ?' vs. imaginary part of complex permittivity, ??). The Cole-Cole plots have also been used to determine static dielectric constant (?s), optical dielectric constant (??), spreading factor (?), average relaxation time (?0) and molecular relaxation time (?). The dielectric behaviour has been found to be significantly affected due to Ar+ implantation. The possible correlation between this behaviour and the changes induced by the implantation has been discussed.

  12. Dielectric nanocomposites with insulating properties

    Microsoft Academic Search

    Toshikatsu Tanaka

    2005-01-01

    Polymer nanocomposites possess promising high performances as engineering materials, if they are prepared and fabricated properly. Some work has been recently done on such polymer nanocomposites as dielectrics and electrical insulation. This was reviewed in 2004 based on the literatures published up to 2003. New significant findings have been added since then. Furthermore, a multi-core model with the far-distance effect,

  13. Static and dynamic properties of Fibonacci multilayers

    NASA Astrophysics Data System (ADS)

    Machado, L. D.; Bezerra, C. G.; Correa, M. A.; Chesman, C.; Pearson, J. E.; Hoffmann, A.

    2013-05-01

    We theoretically investigate static and dynamic properties of quasiperiodic magnetic multilayers. We considered identical ferromagnetic layers separated by non-magnetic spacers with two different thicknesses chosen based on the Fibonacci sequence. Using parameters for Fe/Cr, the minimum energy was determined and the equilibrium magnetization directions found were used to calculate magnetoresistance curves. Regarding dynamic behavior, ferromagnetic resonance (FMR) curves were calculated using an approximation known from the literature. Our numerical results illustrate the effects of quasiperiodicity on the static and dynamic properties of these structures.

  14. Spacecraft dielectric material properties and spacecraft charging

    SciTech Connect

    Frederickson, A.R.; Cotts, D.B.; Wall, J.A.; Bouquet, F.L.

    1986-01-01

    With an eye towards applications in the space radiation environment and in nuclear instrumentation, the contributors to this volume provide a multi-disciplinary review of theory and experimentation with conductivity in dielectrics, especially insulators, to establish guidelines for design of materials which do not electrically discharge or breakdown. The authors' analysis of polymer literature suggests several candidates for the purpose of proposing anti-static polymers for use in the space radiation environment. Experimental data is systematically referenced and suggestions for improving such data are made. The book also contains an extensive reference list.

  15. Dielectric properties of agricultural products-measurements and applications

    Microsoft Academic Search

    S. O. Nelson

    1991-01-01

    The nature of the variation of dielectric properties with frequency, temperature, and product density is discussed. Techniques for measurement of dielectric properties are briefly reviewed, and graphical data on the dielectric properties of grain and soybeans as functions of moisture content, frequency, temperature, and bulk of density are presented. Applications in the electrical measurement of the moisture content and in

  16. Microwave dielectric properties of plant materials

    NASA Technical Reports Server (NTRS)

    Ulaby, F. T.; Jedlicka, R. P.

    1984-01-01

    Three waveguide transmission systems covering the 1-2, 3.5-6.5, and 7.5-8.5 GHZ bands were used to measure the dielectric properties of vegetation material as a function of moisture content and microwave frequency. The materials measured included, primarily, the leaves and stalks of corn and wheat. Dielectric measurements also were made of the liquid included in the vegetation material after it was extracted from the vegetation by mechanical means. The extracted liquids were found to have an equivalent NaCl salinity of about 10 per mil, which can have a significant effect on the dielectric loss at frequencies below 5 GHz. The results of attempts to model the dielectric constant of the vegetatioon-water mixture in terms of the dielectric constants and volume fractions of its constituent parts (i.e., bulk vegetation, air, bound water, and free water) are discussed. Additionally, measurements of the temporal variations in the total attenuation at 10.2 GHz are presented for a corn canopy and a soybean canopy.

  17. Static magnetic properties of Maghemite nanoparticles

    NASA Astrophysics Data System (ADS)

    Zulfiqar; Rahman, Muneeb Ur; Usman, M.; Hasanain, Syed Khurshid; Zia-ur-Rahman; Ullah, Amir; Kim, Ill Won

    2014-12-01

    We report the static magnetic properties of Maghemite (?-Fe2O3) nanoparticles with an average crystallite size of 14 ± 1.8 nm synthesized via a co-precipitation method. The zero-field-cooled (ZFC) and the field-cooled (FC) magnetization measurements were performed using a physical properties measurements system (PPMS) at temperatures from 5 K to 300 K. The ZFC/FC measurements showed a typical superparamagnetic behavior with a narrow size distribution.

  18. A Study of Dielectric Properties of Proteinuria between 0.2 GHz and 50 GHz

    PubMed Central

    Mun, Peck Shen; Ting, Hua Nong; Ong, Teng Aik; Wong, Chew Ming; Ng, Kwan Hong; Chong, Yip Boon

    2015-01-01

    This paper investigates the dielectric properties of urine in normal subjects and subjects with chronic kidney disease (CKD) at microwave frequency of between 0.2 GHz and 50 GHz. The measurements were conducted using an open-ended coaxial probe at room temperature (25°C), at 30°C and at human body temperature (37°C). There were statistically significant differences in the dielectric properties of the CKD subjects compared to those of the normal subjects. Statistically significant differences in dielectric properties were observed across the temperatures for normal subjects and CKD subjects. Pearson correlation test showed the significant correlation between proteinuria and dielectric properties. The experimental data closely matched the single-pole Debye model. The relaxation dispersion and relaxation time increased with the proteinuria level, while decreasing with the temperature. As for static conductivity, it increased with proteinuria level and temperature. PMID:26066351

  19. Dielectric surface properties of Venus

    NASA Technical Reports Server (NTRS)

    Pettengill, G. H.; Wilt, R. J.; Ford, P. G.

    1992-01-01

    It has been known for over a decade that certain high-altitude regions on Venus exhibit bizarre radar-scattering and radiothermal-emission behavior. For example, observed values for normal-incidence power reflection coefficients in these areas can exceed 0.5; enhanced back scatter in some mountainous areas in the Magellan SAR images creates a bright surface with the appearance of snow; and reduced thermal emission in the anomalous areas makes the surface there appear hundreds of degrees cooler than the corresponding physical surface temperatures. The inferred radio emissivity in several of these regions falls to 0.3 for horizontal linear polarization at viewing angles in the range 20 deg - 40 deg. Several explanations have been offered for these linked phenomena. One involves single-surface reflection from a sharp discontinuity separating two media that have extremely disparate values of electromagnetic propagation. The mismatch may occur in either or both the real (associated with propagation velocity) or imaginary (associated with absorption) components of the relevant indices of refraction, and the discontinuity must take place over a distance appreciably shorter than a wavelength. An example of such an interaction of Earth would occur at the surface of a body of water. At radio wavelengths, water has an index of refraction of 9 (dielectric permittivity of about 80), and an associated loss factor that varies strongly with the amount of dissolved salts, but is generally significant. Its single-surface radar reflectivity at normal incidence is about 0.65, and the corresponding emissivity (viewed at the same angle) is therefore 0.35. Both these values are similar to the extremes found on Venus, but in the absence of liquid water, the process on Venus requires a different explanation. Two of the present authors (Pettengill and Ford) have suggested that scattering from a single surface possessing a very high effective dielectric permittivity could explain many of the unusual characteristics displayed by the Venus surface. A second explantion relates to the volume scattering that results from successive interactions with one or more interfaces interior to the planetary surface. If the near-surface material has a moderately low index of refraction (to ensure that a substantial fraction of the radiation incident from outside is not reflected, but rather penetrates into the surface), and a very low internal propagation loss, successive internal reflections can eventually redirect much of the energy back through the surface toward the viewer. The necessary conditions for this process to be effective are a low internal propagation loss coupled with efficient internal reflection. At sufficiently low temperatures, fractured water ice displays both the necessary low loss and near-total internal reflection. The possibility that this mechanism might be acting on Venus has recently been put forward.

  20. Dielectric Properties of Agricultural Products and Some Applications

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Abstract: The use of dielectric properties of agricultural products for sensing moisture in grain and seed and their application in radio-frequency and microwave dielectric heating is discussed briefly. Values for the dielectric properties of a number of products, including grain and seed, fruits ...

  1. DIELECTRIC PROPERTIES OF VARIOUS NANOCOMPOSITE MATERIALS

    SciTech Connect

    Tuncer, E. [Oak Ridge National Laboratory (ORNL); Polizos, G. [Oak Ridge National Laboratory (ORNL); James, D. R. [Oak Ridge National Laboratory (ORNL); Sauers, I. [Oak Ridge National Laboratory (ORNL); Ellis, A. R. [Oak Ridge National Laboratory (ORNL); More, K. L. [Oak Ridge National Laboratory (ORNL)

    2010-01-01

    Composite materials based on polymers are used in various engineering applications due to their ability to be tailored for a specific application. As a result a composite could be selected or designed for a high performance part such as field grading applications in high voltage technology. Presently, there exists no commercially available material for electric field control. For this reason in this study we characterize a polymeric system composed of a thermoplast polymer filled with nanometer size ceramic particles. Since it is hard to tailor or to predict properties of composites theoretically, an Edisonian approach is employed. Composites with different filler weight concentrations are prepared and their dielectric performance are characterized. Impedance spectroscopy technique at a constant frequency is used to determine the dielectric properties of the composites at low temperatures. Measurement results and potential applications of the composite systems are presented.

  2. Spacecraft dielectric material properties and spacecraft charging

    NASA Technical Reports Server (NTRS)

    Frederickson, A. R.; Wall, J. A.; Cotts, D. B.; Bouquet, F. L.

    1986-01-01

    The physics of spacecraft charging is reviewed, and criteria for selecting and testing semiinsulating polymers (SIPs) to avoid charging are discussed and illustrated. Chapters are devoted to the required properties of dielectric materials, the charging process, discharge-pulse phenomena, design for minimum pulse size, design to prevent pulses, conduction in polymers, evaluation of SIPs that might prevent spacecraft charging, and the general response of dielectrics to space radiation. SIPs characterized include polyimides, fluorocarbons, thermoplastic polyesters, poly(alkanes), vinyl polymers and acrylates, polymers containing phthalocyanine, polyacene quinones, coordination polymers containing metal ions, conjugated-backbone polymers, and 'metallic' conducting polymers. Tables summarizing the results of SIP radiation tests (such as those performed for the NASA Galileo Project) are included.

  3. Dielectric, magnetic, and phonon properties of nickel hydroxide

    NASA Astrophysics Data System (ADS)

    Hermet, P.; Gourrier, L.; Bantignies, J.-L.; Ravot, D.; Michel, T.; Deabate, S.; Boulet, P.; Henn, F.

    2011-12-01

    We carried out a complete study (magnetic, electronic, dielectric, dynamic, and elastic properties) of the nickel hydroxide [Ni(OH)2] from first-principles calculations based on density functional theory. No theoretical investigations of these physical properties have been previously reported in literature. Our work supports that Ni(OH)2 is an A-type antiferromagnetic material. In addition, it is negative uniaxial and semiconducting with a direct band gap at the ? point around 3 eV. By contrast to its electronic dielectric tensor, its static tensor is strongly anisotropic in the plane orthogonal to its optical axis. This anisotropy is mainly governed by a highly polar phonon centered around 510 cm-1 and assigned as a rotational Eu mode. Both Raman and infrared spectra have been computed to clarify the longstanding debate on the assignment of the Ni(OH)2 phonon modes reported in literature. All these theoretical results are fruitfully compared to the experimental ones obtained on large Ni(OH)2 “pseudosingle” crystals when available.

  4. Temperature and Moisture Dependent Dielectric Properties of Legume Flours Associated with Dielectric Heating

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dielectric property data are important in developing thermal treatments using radio frequency (RF) and microwave (MW) energy and essential to estimate the heating uniformity in electromagnetic fields. Dielectric properties of flour samples from four legumes (chickpea, green pea, lentil, and soybean)...

  5. Spacecraft dielectric surface charging property determination

    NASA Technical Reports Server (NTRS)

    Williamson, W. S.

    1987-01-01

    The charging properties of 127 micron thick polyimide, (a commonly used spacecraft dielectric material) was measured under conditions of irradiation by a low-current-density electron beam with energy between 2 and 14 keV. The observed charging characteristics were consistent with predictions of the NASCAP computer model. The use of low electron current density results in a nonlinearity in the sample-potential versus beam-energy characteristic which is attributed to conduction leakage through the sample. Microdischarges were present at relatively low beam energies.

  6. Dielectric and dielectrophoretic properties of DNA.

    PubMed

    Hölzel, R

    2009-06-01

    The physical properties of DNA are quite important for molecular genetics as well as for its nanotechnological applications. Studying the interactions of alternating current (AC) electric fields with deoxyribonucleic acid (DNA) allows one to draw conclusions about these properties. These interactions are usually investigated in two different ways. In dielectric spectroscopy, a DNA solution is placed in a homogeneous AC field and electronic parameters are measured over several frequency decades in the Hz to GHz range. These electronic data are then interpreted on the basis of physico-chemical models as a result of certain phenomena on the molecular level. In dielectrophoretic studies, a DNA solution is exposed to an inhomogeneous AC field and the spatial response of few or single molecules is monitored by optical or scanning force microscopy. This response can involve translation, elongation and orientation of the molecular strings. In this review, a survey is given of the literature dealing with the dielectric and dielectrophoretic properties of DNA as well as with applications of DNA dielectrophoresis. PMID:19485551

  7. Determination of dielectric property profile in cement-based materials using microwave reflection and transmission properties

    Microsoft Academic Search

    B. Akuthota; R. Zoughi; K. E. Kurtis

    2004-01-01

    Microwave characterization methods are effective means for evaluating dielectric properties of materials and correlating them to their important physical, chemical and mechanical properties. For characterization purposes most materials are considered homogeneous and the measurement of their dielectric properties is fairly straightforward. However, certain materials may be considered inhomogeneous in such a way that their dielectric properties vary in a preferred

  8. Dielectric properties of polypropylene containing nano-particles

    Microsoft Academic Search

    S. S. Bamji; M. Abou-Dakka; A. T. Bulinski; L. Utracki; K. Cole

    2005-01-01

    A thermoplastic such as polypropylene reinforced with small quantities (<5% by weight) of nano-sized particles could show reduced flammability as well as improved dielectric properties. This paper describes short-term dielectric properties of polypropylene containing 0%, 2%, and 4% by weight of dispersed organosilicates. AC and DC breakdown strength, tan?, electroluminescence emission, and space charge distribution due to AC poling of

  9. Temperature and moisture dependent dielectric properties of legume flours associated with dielectric heating

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dielectric properties of flour samples from four legumes (chickpea, green pea, lentil, and soybean) at four different moisture contents were measured using an open-ended coaxial probe and impedance analyzer at frequencies of 10 to 1800 MHz and temperatures of 20 to 90°C. The dielectric constant and ...

  10. Dielectric Properties of Onion-Like Carbon Composites

    NASA Astrophysics Data System (ADS)

    Macutkevic, J.; Grigalaitis, R.; Banys, J.; Hens, S.; Borjanovic, V.; Shenderova, O.; Kuznetsov, V.; Moseenkov, S.

    2013-05-01

    Dielectric properties of onion-like carbon and polyurethane composite prepared using different procedures were investigated in the frequency range up to 1 MHz. We show that broadband dielectric spectroscopy is powerful tool to determine technological fingerprints in the studied materials. It is demonstrated that cured samples annealed at temperature close to the melting point (450 K) exhibit substantially higher dielectric permittivity and electrical conductivity in comparison with untreated samples.

  11. High-? gate dielectrics: Current status and materials properties considerations

    Microsoft Academic Search

    G. D. Wilk; R. M. Wallace; J. M. Anthony

    2001-01-01

    Many materials systems are currently under consideration as potential replacements for SiO2 as the gate dielectric material for sub-0.1 ?m complementary metal–oxide–semiconductor (CMOS) technology. A systematic consideration of the required properties of gate dielectrics indicates that the key guidelines for selecting an alternative gate dielectric are (a) permittivity, band gap, and band alignment to silicon, (b) thermodynamic stability, (c) film

  12. Microwave scattering properties of dielectric cylinders with defects

    NASA Astrophysics Data System (ADS)

    Zoughi, Reza; Qaddoumi, Nasser

    The Zoughi and Moore (1989) study of the scattering properties of a dielectric rectangular disk with a center rib, and the interaction between two thin and finite dielectric cylinders, are presently adapted to study the effects of various defects in dielectric cylinders. Among the parameters that may indicate the presence of a defect are the scattering cross-section level, scattering pattern as a function of incidence angle, and frequency; frequency is especially important, in that it allows defect characterization.

  13. The dielectric properties of polymer-water systems 

    E-print Network

    Lewis, Joe Bill

    1976-01-01

    of water-containing poly- mers are helpful in arriving at a better understanding. For collagen and elastin, containing various amounts of water, the dielectric properties had been measured before, The curves for c" and e', the dielectric loss factor... of hydrogen-bonded water molecules. Another mechanism might interfere with this interpretation, however. Both collagen and elastin contain ionizable groups. The effects of ionic mobilities in a heterogeneous medium can lead to large dielectric effects...

  14. Dielectric properties of capacitor materials in the optical frequency range

    Microsoft Academic Search

    Michael Biegalski; Ryan Thayer; Juan Nino; Susan Trolier-McKinstry

    2002-01-01

    The optical properties and band gaps of capacitor materials are important for a number of reasons, including assessing the viability of candidate materials for gate dielectrics in semiconductors, identifying the electronic components of the polarizability, and monitoring degradation processes. This paper reports the high frequency dielectric function of several capacitor materials in the near UV to near IR range as

  15. Dielectric material properties investigated through space charge measurements

    Microsoft Academic Search

    Gian Carlo Montanari

    2004-01-01

    This paper investigates means of exploitation of space charge measurement results in order to achieve information about chemical, physical and microstructural properties of dielectric materials. The derivation of quantities as mean volume density of space charge, threshold for DC space charge accumulation, apparent-trap controlled mobility is discussed and various applications to dielectric materials are shown. In particular, the differences of

  16. Millimeter wave and terahertz dielectric properties of biological materials

    NASA Astrophysics Data System (ADS)

    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 polarization and birefringence effects, it was determined that one can not utilize the dielectric properties of powder-containing packages to differentiate hoax attacks and serious security threats.

  17. Characterisation of the dielectric properties of the propellants MON & MMH

    NASA Astrophysics Data System (ADS)

    Delil, A. A. M.

    1998-01-01

    Future (commercial) satellites will require accurate propellant gauging systems, in order to meet the end-of-life reorbiting requirement and the need for replacement planning. A capacitive Gauging Sensor Unit is currently being developed for the Meteosat Second Generation spacecraft. Its measurement principle is based on the difference of the dielectric properties of the propellant liquid and vapour. To optimise the sensor accuracy, the dielectric properties of propellants need to be accurately known as a function of the temperature (and pressure). Therefore the dielectric properties of MON (Mixed Oxides of Nitrides) and MMH (Mono Methyl Hydrazine) were to be measured. The test setup and the test results are described in detail.

  18. Tuning the dielectric properties of organic semiconductors via salt doping.

    PubMed

    Liu, Xien; Jeong, Kwang S; Williams, Bryan P; Vakhshouri, Kiarash; Guo, Changhe; Han, Kuo; Gomez, Enrique D; Wang, Qing; Asbury, John B

    2013-12-12

    Enhancing the dielectric permittivity of organic semiconductors may open new opportunities to control charge generation and recombination dynamics in organic solar cells. The potential to tune the dielectric permittivity of organic semiconductors by doping them with redox inactive salts was explored using a combination of organic synthesis, electrical characterization, and time-resolved infrared spectroscopy. The addition of the salt, LiTFSI (lithium bis(trifluoro-methyl-sulfonyl)imide), to a conjugated polymer specifically designed to incorporate ions into its bulk phase increased the density of holes and enhanced the static dielectric permittivity of the polymer blend by more than an order of magnitude. The frequency and phase dependence of the real dielectric function demonstrates that the increase in dielectric permittivity resulted from dipolar motion of bound ion pairs or clusters of ions. Interestingly, the increases in the hole density and dielectric permittivity were associated with enhancement of the hole mobility by 2 orders of magnitude relative to the undoped polymer. The charge recombination lifetime also increased by an order of magnitude in the blend with a fullerene electron acceptor when ions were added to the polymer. The findings indicate that ion doping enables organic semiconductors with large increases in low frequency dielectric permittivity and that these changes result in improved charge transport and suppressed charge recombination on the microsecond time scale. PMID:24073822

  19. Ultralow Dielectric Property of Electrospun Polylactide-Polyglycolide Nanofibrous Membranes

    NASA Astrophysics Data System (ADS)

    Liu, Shih-Jung; Chiou, Lung-Yi; Liao, Jun-Yi

    2011-10-01

    Polylactide-polyglycolide (PLGA) has been one of the most important biodegradable and biocompatible materials. In this study, nanofibrous membranes of PLGA were fabricated using an electro fiber spinning setup that consisted of a syringe and needle (the internal diameter is 0.42 mm), a ground electrode, an aluminum sheet, and a high voltage supply. The dielectric properties of the electrospun membranes were characterized. The experimental results suggested that the electrospun membranes exhibited ultralow dielectric behavior. The influences of the nanofibers diameter and the density of the membranes on the dielectric properties were also instigated. It was found that the dielectric constants decreased with the fiber diameter and increased with the density of the nanofibrous membranes. By employing the electrospinning process, one will be able to fabricate polymeric membranes with ultralow dielectric performance.

  20. Pyroelectric and dielectric properties of ferroelectric films with interposed dielectric buffer layers

    NASA Astrophysics Data System (ADS)

    Espinal, Y.; Kesim, M. T.; Misirlioglu, I. B.; Trolier-McKinstry, S.; Mantese, J. V.; Alpay, S. P.

    2014-12-01

    The dielectric and pyroelectric properties of c-domain ferroelectric films with linear dielectric buffer layers were investigated theoretically. Computations were carried out for multilayers consisting of PbZr0.2Ti0.8O3 with Al2O3, SiO2, Si3N4, HfO2, and TiO2 buffers on metalized Si. It is shown that the dielectric and pyroelectric properties of such multilayers can be increased by the presence of the buffer compared to ferroelectric monolayers. Calculations for PbZr0.2Ti0.8O3 films with 1% Al2O3 interposed between electrodes on Si show that the dielectric and pyroelectric coefficients are 310 and 0.070 ?C cm-2 °C-1, respectively. Both values are higher than the intrinsic response of PbZr0.2Ti0.8O3 monolayer on Si.

  1. Electronic properties of defects in polycrystalline dielectric materials

    Microsoft Academic Search

    K. P. McKenna; A. L. Shluger

    2009-01-01

    Grain boundaries have been implicated in current leakage and dielectric breakdown of CMOS devices. We calculate the electronic properties of oxygen vacancy defects near grain boundaries in the dielectric insulators MgO and HfO2 using first principles methods. In both materials we find that oxygen vacancies favourably segregate to grain boundaries, in various charge states. Their electronic properties are different from

  2. Vitrification media: toxicity, permeability, and dielectric properties.

    PubMed

    Wusteman, Monica C; Pegg, David E; Robinson, Martin P; Wang, Li-Hong; Fitch, Paul

    2002-02-01

    The aim of this study was to select a cryoprotectant for use in attempts to preserve tissues and organs by vitrification. The first step was to select a cell line with which to compare the toxicity of a range of commonly used cryoprotectants. An immortal vascular endothelial cell (ECV304) was exposed to vitrifying concentrations of four cryoprotectants: dimethyl sulfoxide (Me(2)SO; 45% w/w); 2,3 butanediol (BD; 32%); 1,2-propanediol (PD; 45%); and ethanediol (ED; 45%). Three times of exposure (1, 3, and 9 min) and two temperatures (22 and 2-4 degrees C) were studied. After removal of the cryoprotectant, the ability of the cells to adhere and divide in culture over a 2-day period was measured and expressed as a Cell Survival Index (CSI). There was no measurable loss of cells after exposure to the four cryoprotectants but 3-min exposure to BD, PD, or Me(2)SO at room temperature completely destroyed the ability of the cells to adhere and divide in culture. In contrast, exposure to all four cryoprotectants at 2-4 degrees C for up to 9 min permitted the retention of significant cell function, the CSIs, as a proportion of control, being 76.3+/-7.0% for BD, 63.6+/-7.1% for PD, 37.0+/-4.1 for Me(2)SO, and 33.2+/-3.0 for ED. The permeability properties of the cells for these four cryoprotectants was also measured at each temperature. Permeability to water was high, L(p) approximately equal 10(-7) cm/s/atm at 2-4 degrees C with all the cryoprotectants, but there were substantial differences in solute permeability: BD and PD were the most permeable at 2-4 degrees C (P(s)=4.1 and 3.0 x 10(-6) cm/s, respectively). Equilibration of intracellular cryoprotectant concentration was rapid, due in part to high water permeability; the cells were approximately 80% of their physiological volume after 10 min. Treatment at 2-4 degrees C with BD was the least damaging, but PD was not significantly worse. Exposure to vitrifying concentrations of ED and Me(2)SO, even at 2-4 degrees C, was severely damaging. Segments of rabbit carotid artery were treated with vitrifying concentrations of each of the two most favorable cryoprotectants, BD and PD, for 9 min. It was shown that each cryoprotectant reduced smooth muscle maximum contractility to a similar extent and abolished the acetylcholine response. However, vital staining revealed that exposure to BD also caused substantial damage to the endothelial lining, whereas the endothelium was completely intact after PD exposure, raising the possibility that the effect of PD on NO release may be reversible. In later stages of this project it is planned to use dielectric heating to rewarm the tissues and thereby avoid devitrification. The effects of each cryoprotectant on this mode of heating was therefore studied. Gelatin spheres containing vitrifiable concentrations of each cryoprotectant were rewarmed from -60 degrees C in a radiofrequency applicator. Because the uniformity of heating is related to the dielectric properties of the material, these properties were also measured. PD was the most suitable. These physical measurements, combined with the measurements of toxicity and permeability, indicate that PD is the most favorable cryoprotectant of those tested for use in subsequent stages of this study. PMID:12061845

  3. Conducting dielectric polymer properties at Terahertz wavelength

    Microsoft Academic Search

    E. Nguema; J. D. Delagnes; A. Elfatimy; P Mounaix

    The dielectric function of polyaniline (Pani) doped by couple drug\\/solvent sulphonic camphoracid\\/dichloroacetic CSA\\/DCAA is studied in the terahertz range. Numerous films of this polymer with different doping level are measured by Terahertz Time-Domain Spectroscopy (THz-TDS). The Fourier transmission spectrum, the permittivity and conductivity are then precisely obtained between 0.1 and 4 THz. The behavior of the dielectric function does not

  4. Optical Transmission Properties of Dielectric Aperture Arrays

    NASA Astrophysics Data System (ADS)

    Yang, Tao

    Optical detection devices such as optical biosensors and optical spectrometers are widely used in many applications for the functions of measurements, inspections and analysis. Due to the large dimension of prisms and gratings, the traditional optical devices normally occupy a large space with complicated components. Since cheaper and smaller optical devices are always in demand, miniaturization has been kept going for years. Thanks to recent fabrication advances, nanophotonic devices such as semiconductor laser chips have been growing in number and diversity. However, the optical biosensor chips and the optical spectrometer chips are seldom reported in the literature. For the reason of improving system integration, the study of ultra-compact, low-cost, high-performance and easy-alignment optical biosensors and optical spectrometers are imperative. This thesis is an endeavor in these two subjects and will present our research work on studying the optical transmission properties of dielectric aperture arrays and developing new optical biosensors and optical spectrometers. The first half of the thesis demonstrates that the optical phase shift associated with the surface plasmon (SP) assisted extraordinary optical transmission (EOT) in nano-hole arrays fabricated in a metal film has a strong dependence on the material refractive index value in close proximity to the holes. A novel refractive index sensor based on detecting the EOT phase shift is proposed by building a model. This device readily provides a 2-D biosensor array platform for non-labeled real-time detection of a variety of organic and biological molecules in a sensor chip format, which leads to a high packing density, minimal analyte volumes, and a large number of parallel channels while facilitating high resolution imaging and supporting a large space-bandwidth product (SBP). Simulation (FDTD Solutions, Lumerical Solutions Inc) results indicate an achievable sensitivity limit of 4.37x10-9 refractive index units (RIU) and a dynamic range as large as 0.17 RIU. Subsequently, optical transmission properties through a self-mixing interferometer array are studied and a novel high-resolution cost-effective optical spectrometer is proposed. The miniature interferometer-based spectrometer is made of polymethyl methacrylate (PMMA) with a CCD as the detector. The detected intensity of each CCD pixels contains the spectral information. Since each frequency component in the incoming beam corresponds to a unique phase difference of the two beam portions of each optical interferometer, the total intensity received by each CCD pixel, which is resulted from the addition of the interference signals from all the frequency components in the beam, should also be unique. Therefore, the spectrum calculation is a problem to solve an ill-posed linear system by using Tikhonov regularization method. Simulation results show that the resolution can reach picometer level. Apart from the choice of path difference between the interfering beams, the spectral resolution also depends on the signal-to-noise ratio and analogue-digital conversion resolution (dynamic range) of the CCD chip. In addition, the theory of uniform waveguide scattering is explored to expand the possibility of using such mini-interferometers for performing free-space spectral analysis of waveguide devices. At the same time, the method of least squares is used to correct the pixel non-uniformity of the CCD so as to improve the performance of the spectrometer. The sensor chip and spectrometer chip introduced here are based on the interference of light transmitted through dielectric aperture arrays. Their compact feature renders these devices ideal for miniaturization and integration as the systems in microfluidics architectures and lab-on-chip designs.

  5. Preliminary non-destructive assessment of moisture content, hydration and dielectric properties of Portland cement concrete 

    E-print Network

    Avelar Lezama, Ivan

    2007-04-25

    volumetric water content to high dielectric readings. In this study, compressive strength tests combined with dielectric and mass measurements are used to investigate how dielectric properties change with hydration. The results of this study suggest...

  6. Dielectric properties of KDP filled porous alumina nanocomposite thin films.

    PubMed

    Boni, O; Berger, S

    2001-12-01

    A new concept of a composite dielectric thin film fabrication is presented. The fabrication process consists of two stages. The first stage is anodizing a thin aluminum film to produce a porous alumina film that contains an array of nanometer sized parallel pores. The second stage is filling the pores with a saturated KDP (KH2PO4) liquid solution due to capillary forces. After drying KDP nanocrystals are formed inside the pores. This process results in a formation of a composite dielectric thin film composed of the alumina pores walls as one dielectric material and the KDP nanocrystals inside the pores as another dielectric material. The dielectric permittivity of this composite film is higher than that of the porous alumina film at all applied frequencies. The dielectric enhancement is more pronounced at low frequencies due to an interface polarization mechanism. This fabrication process enables controlling the size, composition, and microstructure of the composite dielectric film constituents and thus changing its dielectric properties over a wide range of values. PMID:12914085

  7. Dielectric properties and microstructures for various MLCCs coated with additives

    NASA Astrophysics Data System (ADS)

    Oh, Min Wook; Yeo, Dong Hun; Shin, Hyo Soon; Jeong, Dae Yong

    2013-12-01

    As electronic devices become smaller and have higher capacity, dielectric thin films are being used in the development of multilayer ceramic capacitors (MLCCs). Smaller BaTiO3 dielectric particles should be used to obtain the thickness of low dielectric layers. Further, MLCC properties are achieved through the uniform addition of various additives, but the existing method of adding nano additives has limitations. As such, this study evaluated the dielectric properties of BaTiO3 pellets after using the liquid coating method to add additives such as Dy, Mg, Mn, Cr, and Si to 150 nm BaTiO3 dielectric powder. Mn, Cr, and Si ions were each fixed at 0.1, 0.1, and 0.65 mol-%. Sintering was performed in a reducing atmosphere, and the microstructure and the dielectric properties were evaluated while varying Dy from 0.5 to 1.0 mol-% and Mg from 1.0 to 2.0 mol-%. Grain growth was observed for higher amounts of Dy, but were suppressed for higher amounts of Mg. With regards to changes in particle size, both the permittivity and the temperature coefficient of capacitance (TCC) increased with increasing particle size. The permittivity was highest for Si=0.65, Mn=0.1, Cr=0.1 Dy=0.75, and Mg=2.0 mol-%. These levels also satisfied the TCC properties of X7R. In the microstructure, the core-shell was the most developed.

  8. Dielectric plug-loaded two-port transmission line measurement technique for dielectric property characterization of granular and liquid materials

    Microsoft Academic Search

    Karl J. Bois; Larry F. Handjojo; Aaron D. Benally; Khalid Mubarak; Reza Zoughi

    1999-01-01

    There are numerous dielectric property characterization techniques available in the microwave regime each with its own uniqueness, advantages and disadvantages. The two-port completely-filled waveguide (transmission line) technique is a robust measurement approach which is well suited for solid dielectric materials. In this case, the dielectric material can be relatively easily machined to fit inside the waveguide and the subsequent measurement

  9. Low temperature dielectric properties of magnetoplumbite family of materials.

    SciTech Connect

    Venkateshwaran, B.; Yao, M.; Guo, R.; Bhalla, A.; Balachandran, U.; Energy Technology; Pennsylvania State Univ.

    1999-01-01

    The magnetoplumbite family of materials exhibit properties that make them suitable to be used as substrates materials for microwave application. Four members of the family studied in this work are LaMgAl{sub 11}O{sub 19}, NdGaMgAl{sub 10}O{sub 19}, CaGa{sub 6}Al{sub 6}O{sub 19} and CaGa{sub 12}O{sub 19}. Dielectric studies have been carried out over a temperature range of 4-300 K and a wide frequency range. All four exhibit a low dielectric constant with good temperature stability, low dielectric loss and favorable frequency dependence characteristics.

  10. Effects of dielectric material properties on graphene transistor performance

    NASA Astrophysics Data System (ADS)

    Jang, Sung Kyu; Jeon, Jaeho; Jeon, Su Min; Song, Young Jae; Lee, Sungjoo

    2015-07-01

    Graphene has attracted attention due to its excellent electrical properties; however, the electrical performance of graphene devices, including device hysteresis, mobility, and conductivity, tends to be limited by the supporting dielectric layer properties. In this work, the impact of a dielectric material on a graphene transistor was investigated by fabricating graphene field effect transistors integrated with four different dielectric substrates (SiO2, Al2O3, Si3N4 and hexagonal boron nitride) and by comparing the transistor performances. Results revealed that the carrier transport characteristics of the graphene transistors, including the hysteresis, Dirac point shift, and mobility, were highly correlated with the hydrophobicity-induced charge trapping and surface optical phonon energies of the dielectric materials.

  11. Interfacial effects on dielectric properties of polymer-particle nanocomposites

    NASA Astrophysics Data System (ADS)

    Siddabattuni, Sasidhar Veeranjaneyulu

    Dielectric materials that are capable of efficiently storing large amounts of electrical energy are desirable for many electronic and power devices. Since the electrical energy density in a dielectric material is limited to epsilonVb2/2, where is the dielectric permittivity of the material and Vb is the breakdown strength, increased permittivity and breakdown strength are required for large energy storage density. Interfacial effects can influence the dielectric properties, especially dielectric breakdown resistance in polymer-particle nanocomposites. Several functional organophosphates were used to modify the surface of titania and barium titanate nanofiller particles in order to achieve covalent interface when interacted with polymer and to study the influence the electronic nature of filler surfaces on dielectric properties, in particular the breakdown resistance. Surface modified powders were analyzed by thermogravimetric analysis (TGA) and by X-ray photoelectron spectroscopy (XPS). The dielectric composite films obtained by incorporating surface modified powders in epoxy thermosetting polymer were analyzed by differential scanning calorimetry (DSC), scanning electron microscopy (SEM), impedance spectroscopy, and dielectric breakdown strength measurements. At 30 vol-% filler concentration, a calculated energy density of ˜8 J/cm3 was observed for titania based composites and ˜8.3 J/cm3 for barium titanate based composites involving electron scavenging interface with minimal dielectric losses compared to pure polymer. Covalent interface composites yielded energy density of ˜7.5 J/cm3 for barium titanate based composites at 30 vol.-%. The data indicate that improved dispersion, breakdown strengths and energy densities resulted when electron-poor functional groups were located at the particle surfaces even compared to covalent interface.

  12. Dielectric and other properties of polyimide aerogels containing fluorinated blocks.

    PubMed

    Meador, Mary Ann B; McMillon, Emily; Sandberg, Anna; Barrios, Elizabeth; Wilmoth, Nathan G; Mueller, Carl H; Miranda, Félix A

    2014-05-14

    The dielectric and other properties of a series of low-density polyimide block copolymer aerogels have been characterized. Two different anhydride-capped polyimide oligomers were synthesized: one from 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and 4,4'-oxidianiline (ODA) and the other from biphenyl-3,3',4,4'-tetracarboxylic dianhydride and ODA. The oligomers were combined with 1,3,5-triaminophenoxybenzene to form a block copolymer networked structure that gelled in under 1 h. The polyimide gels were supercritically dried to give aerogels with relative dielectric constants as low as 1.08. Increasing the amount of 6FDA blocks by up to 50% of the total dianhydride decreased the density of the aerogels, presumably by increasing the free volume and also by decreasing the amount of shrinkage seen upon processing, resulting in a concomitant decrease in the dielectric properties. In this study, we have also altered the density independent of fluorine substitution by changing the polymer concentration in the gelation reactions and showed that the change in dielectric due to density is the same with and without fluorine substitution. The aerogels with the lowest dielectric properties and lowest densities still had compressive moduli of 4-8 MPa (40 times higher than silica aerogels at the same density), making them suitable as low dielectric substrates for lightweight antennas for aeronautic and space applications. PMID:24483208

  13. Expanded modeling of temperature-dependent dielectric properties for microwave thermal ablation.

    PubMed

    Ji, Zhen; Brace, Christopher L

    2011-08-21

    Microwaves are a promising source for thermal tumor ablation due to their ability to rapidly heat dispersive biological tissues, often to temperatures in excess of 100 °C. At these high temperatures, tissue dielectric properties change rapidly and, thus, so do the characteristics of energy delivery. Precise knowledge of how tissue dielectric properties change during microwave heating promises to facilitate more accurate simulation of device performance and helps optimize device geometry and energy delivery parameters. In this study, we measured the dielectric properties of liver tissue during high-temperature microwave heating. The resulting data were compiled into either a sigmoidal function of temperature or an integration of the time-temperature curve for both relative permittivity and effective conductivity. Coupled electromagnetic-thermal simulations of heating produced by a single monopole antenna using the new models were then compared to simulations with existing linear and static models, and experimental temperatures in liver tissue. The new sigmoidal temperature-dependent model more accurately predicted experimental temperatures when compared to temperature-time integrated or existing models. The mean percent differences between simulated and experimental temperatures over all times were 4.2% for sigmoidal, 10.1% for temperature-time integration, 27.0% for linear and 32.8% for static models at the antenna input power of 50 W. Correcting for tissue contraction improved agreement for powers up to 75 W. The sigmoidal model also predicted substantial changes in heating pattern due to dehydration. We can conclude from these studies that a sigmoidal model of tissue dielectric properties improves prediction of experimental results. More work is needed to refine and generalize this model. PMID:21791728

  14. Expanded modeling of temperature-dependent dielectric properties for microwave thermal ablation

    PubMed Central

    Ji, Zhen; Brace, Christopher L

    2011-01-01

    Microwaves are a promising source for thermal tumor ablation due to their ability to rapidly heat dispersive biological tissues, often to temperatures in excess of 100 °C. At these high temperatures, tissue dielectric properties change rapidly and, thus, so do the characteristics of energy delivery. Precise knowledge of how tissue dielectric properties change during microwave heating promises to facilitate more accurate simulation of device performance and helps optimize device geometry and energy delivery parameters. In this study, we measured the dielectric properties of liver tissue during high-temperature microwave heating. The resulting data were compiled into either a sigmoidal function of temperature or an integration of the time–temperature curve for both relative permittivity and effective conductivity. Coupled electromagnetic–thermal simulations of heating produced by a single monopole antenna using the new models were then compared to simulations with existing linear and static models, and experimental temperatures in liver tissue. The new sigmoidal temperature-dependent model more accurately predicted experimental temperatures when compared to temperature–time integrated or existing models. The mean percent differences between simulated and experimental temperatures over all times were 4.2% for sigmoidal, 10.1% for temperature–time integration, 27.0% for linear and 32.8% for static models at the antenna input power of 50 W. Correcting for tissue contraction improved agreement for powers up to 75 W. The sigmoidal model also predicted substantial changes in heating pattern due to dehydration. We can conclude from these studies that a sigmoidal model of tissue dielectric properties improves prediction of experimental results. More work is needed to refine and generalize this model. PMID:21791728

  15. Spacecraft dielectric material properties and spacecraft charging

    Microsoft Academic Search

    A. R. Frederickson; D. B. Cotts; J. A. Wall; F. L. Bouquet

    1986-01-01

    With an eye towards applications in the space radiation environment and in nuclear instrumentation, the contributors to this volume provide a multi-disciplinary review of theory and experimentation with conductivity in dielectrics, especially insulators, to establish guidelines for design of materials which do not electrically discharge or breakdown. The authors' analysis of polymer literature suggests several candidates for the purpose of

  16. Effective elastic, piezoelectric and dielectric properties of braided fabric composites

    Microsoft Academic Search

    X. Ruan; A. Safari; T.-W. Chou

    1999-01-01

    Composites based upon 3D textile preforms have found broad structural application. This paper presents an analytical methodology for functional composites using piezoceramic fibers in a 3D braided preform. The effective elastic, piezoelectric and dielectric properties of 2-step braided composites with a polymeric matrix have been investigated. In the analytical approach, the effective properties of the braider and axial yarns of

  17. Preparation, microstructure and properties of polyethylene aluminum nanocomposite dielectrics

    Microsoft Academic Search

    Xingyi Huang; Pingkai Jiang; Chonung Kim; Qingquan Ke; Genlin Wang

    2008-01-01

    Linear low density polyethylene (PE) aluminum (Al) nanocomposites were prepared and their morphology and properties were investigated. The particular attention was given to the structure\\/property relationship of the nanocomposites and an equivalent electric circuit model was proposed to interpret the dependences of the dielectric behaviors of the PE\\/Al nanocomposites on the nanoparticle concentration and the measuring frequency. The increase of

  18. Study mechanical, swelling and dielectric properties of prehydrolysed banana fiber – Waste polyurethane foam composites

    Microsoft Academic Search

    Magda G. El-Meligy; Samar H. Mohamed; Ragab M. Mahani

    2010-01-01

    Untreated and treated banana fiber by maleic anhydride together with waste polyurethane foam were used to produce composites. Treated banana fiber reduces swelling and improve strength and dielectric properties.Also, addition of aluminum silicate exhibited enhancements in its dielectric properties at constant concentration lower than 10%. While, abrupt increase can be seen in the dielectric constant (??) and dielectric loss (???)

  19. Dielectric properties of grain-grainboundary binary system

    NASA Astrophysics Data System (ADS)

    Cheng, Peng-Fei; Li, Sheng-Tao; Wang, Hui

    2014-09-01

    Dielectric properties of grain-grainboundary binary system are analyzed theoretically and compared with unary system and classical Maxwell-Wagner (MW) polarization in binary system. It is found that MW polarization appears at higher frequency compared with intrinsic polarization for grain-grainboundary binary system, which is abnormal compared with classical dielectric theory. This dielectric anomaly is premised on the existence of electronic relaxation at grainboundary. The origin of giant dielectric constant of CaCu3Ti4O12 (CCTO) ceramics is also investigated on the basis of the theoretical results. It is proposed that low frequency relaxation originates from electronic relaxation of oxygen vacancy at depletion layer, while high frequency relaxation comes from MW polarization. The results of this paper offer a quantitative identification of MW polarization from intrinsic polarization at grainboundary and a judgment of the mechanism and location of a certain polarization in grain-grainboundary binary system.

  20. Dielectric properties of soils as a function of moisture content

    NASA Technical Reports Server (NTRS)

    Cihlar, J.; Ulaby, F. T.

    1974-01-01

    Soil dielectric constant measurements are reviewed and the dependence of the dielectric constant on various soil parameters is determined. Moisture content is given special attention because of its practical significance in remote sensing and because it represents the single most influential parameter as far as soil dielectric properties are concerned. Relative complex dielectric constant curves are derived as a function of volumetric soil water content at three frequencies (1.3 GHz, 4.0 GHz, and 10.0 GHz) for each of three soil textures (sand, loam, and clay). These curves, presented in both tabular and graphical form, were chosen as representative of the reported experimental data. Calculations based on these curves showed that the power reflection coefficient and emissivity, unlike skin depth, vary only slightly as a function of frequency and soil texture.

  1. Dielectric properties of microporous glass in the microwave region

    SciTech Connect

    Yamamoto, J.K.; Bhalla, A.S.; Newnham, R.E.; Cross, L.E. (Pennsylvania State Univ., University Park, PA (United States). Materials Research Lab.); Lanagan, M.T. (Argonne National Lab., IL (United States))

    1989-06-01

    This paper reports on the dielectric properties of a high-silica microporous glass determined at 5.5 and 11.4 GHz. Two measurement methods were used to measure these properties, the resonate cavity and resonate post (Hakki-Coleman) techniques. The accuracy of the two measurement techniques was evaluated and the limiting conditions of measurement were determined. The glass, consisting of pore sizes on the order of tens of angstroms, was subjected to thermal treatments in an oxidizing atmosphere at temperatures from 300 {degrees} to 1100 {degrees} C. Heat treatment of the glass at 800 {degrees} C produced a minimum dielectric constant of 2.8 and loss of 0.001. The acid treatment had little effect on the dielectric properties.

  2. Methods for prediction of soil dielectric properties: a review

    NASA Astrophysics Data System (ADS)

    van Dam, Remke L.; Borchers, Brian; Hendrickx, Jan M. H.

    2005-06-01

    Electromagnetic sensors such as ground penetrating radar and electromagnetic induction sensors are among the most widely used methods for the detection of buried land mines and unexploded ordnance. However, the performance of these sensors depends on the dielectric properties of the soil, which in turn are related to soil properties such as texture, bulk density, and water content. To predict the performance of electromagnetic sensors it is common to estimate the soil dielectric properties using models. However, the wide variety of available models, each with its own characteristics, makes it difficult to select the appropriate one for each occasion. In this paper we present an overview of the available methods, ranging from phenomenological Cole-Cole and Debye models to volume-based dielectric mixing models, and (semi-) empirical pedotransfer functions.

  3. Microwave measurement and modeling of the dielectric properties of vegetation

    NASA Astrophysics Data System (ADS)

    Shrestha, Bijay Lal

    Some of the important applications of microwaves in the industrial, scientific and medical sectors include processing and treatment of various materials, and determining their physical properties. The dielectric properties of the materials of interest are paramount irrespective of the applications, hence, a wide range of materials covering food products, building materials, ores and fuels, and biological materials have been investigated for their dielectric properties. However, very few studies have been conducted towards the measurement of dielectric properties of green vegetations, including commercially important plant crops such as alfalfa. Because of its high nutritional value, there is a huge demand for this plant and its processed products in national and international markets, and an investigation into the possibility of applying microwaves to improve both the net yield and quality of the crop can be beneficial. Therefore, a dielectric measurement system based upon the probe reflection technique has been set up to measure dielectric properties of green plants over a frequency range from 300 MHz to 18 GHz, moisture contents from 12%, wet basis to 79%, wet basis, and temperatures from -15°C to 30°C. Dielectric properties of chopped alfalfa were measured with this system over frequency range of 300 MHz to 18 GHz, moisture content from 11.5%, wet basis, to 73%, wet basis, and density over the range from 139 kg m-3 to 716 kg m-3 at 23°C. The system accuracy was found to be +/-6% and +/-10% in measuring the dielectric constant and loss factor respectively. Empirical, semi empirical and theoretical models that require only moisture content and operating frequency were determined to represent the dielectric properties of both leaves and stems of alfalfa at 22°C. The empirical models fitted the measured dielectric data extremely well. The root mean square error (RMSE) and the coefficient of determination (r2) for dielectric constant and loss factor of leaves were 0.89 and 0.99, and 0.52 and 0.99 respectively. The RMSE and r2 values for dielectric constant and loss factor of stems were 0.89 and 0.99, and 0.77 and 0.99 respectively. Among semi empirical or theoretical models, Power law model showed better performance (RMSE = 1.78, r2 = 0.96) in modeling dielectric constant of leaves, and Debye-ColeCole model was more appropriate (RMSE = 1.23, r2 = 0.95) for the loss factor. For stems, the Debye-ColeCole models (developed on an assumption that they do not shrink as they dry) were found to be the best models to calculate the dielectric constant with RMSE 0.53 and r2 = 0.99, and dielectric loss factor with RMSE = 065 and r2 = 0.95. (Abstract shortened by UMI.)

  4. Dielectric properties of hypothermic rat artery.

    PubMed

    Marzec, E; Sosnowski, P; Olszewski, J; Krauss, H; Pi?tek, J; Samborski, W; Micker, M; Zawadzi?ski, J

    2013-01-01

    The temperature and frequency dependencies of the dielectric parameters for the rat artery are used to analyse effects of hypothermia on this tissue. Measurements were performed over the frequency range 500 Hz to 100 kHz and at temperatures from 19 to 60°C. The artery samples contained about 12% water by mass at room temperature at a relative humidity of 70%. The frequency dependencies of the loss tangent for the control, mild hypothermic and moderate hypothermic artery exhibit two peaks at 2 kHz and 35 kHz in the ?-dispersion region. The results were discussed in terms of the distribution of relaxation frequencies and the activation energy for the conduction and polarization mechanisms particularly in the elastin-water and collagen-water systems. The knowledge about dielectric behavior of the hypothermic rat artery in vitro is important due to clinical application of local and systemic hypothermia. PMID:22789782

  5. Dielectric and Piezoelectric Properties of Barium Titanate

    Microsoft Academic Search

    Shepard Roberts

    1947-01-01

    The dielectric constant and loss of barium titanate and barium-strontium titanate have been measured at biasing field strengths from 0 to 5 megavolts per meter, at temperatures from -50°C to +135°C and at frequencies from 0.1 to 25 megacycles. The measurements versus temperature indicate the expected agreement with the Curie-Weiss law at temperatures above the Curie point. Measurements versus field

  6. Thermal and compositional properties of cocoa butter during static crystallization

    Microsoft Academic Search

    Paul S. Dimick; Douglas M. Manning

    1987-01-01

    Studies were conducted using differential scanning calorimetry (DSC) and high performance liquid chromatography (HPLC) to\\u000a determine the thermal properties and glyceride composition of cocoa butter crystals formed under static conditions. In addition\\u000a to these studies, visual characterization of the crystallites was obtained with polarized light microscopy (PLM). Crystals\\u000a were formed under controlled static or motionless conditions at formation temperatures of

  7. Pyroelectric and dielectric properties of calcium barium niobate single crystals

    NASA Astrophysics Data System (ADS)

    Malyshkina, O. V.; Lisitsin, V. S.; Dec, J.; ?ukasiewicz, T.

    2014-09-01

    The effect of the calcium concentration on the pyroelectric and dielectric properties of Ca x Ba1 - x Nb2O6 (CBN) crystals has been studied over a wide temperature range. It has been shown that the calcium concentration only influences the Curie point of crystals of this class. It insignificantly changes the absolute values of the permittivity, the coercive field, and the remanent polarization and does not influence their temperature dependences and the shape of the dielectric hysteresis loop. The possibility of the existence of relaxor properties in CBN crystals has been discussed.

  8. Improvement in photoconductor film properties by changing dielectric layer structures

    NASA Astrophysics Data System (ADS)

    Kim, S.; Oh, K.; Lee, Y.; Jung, J.; Cho, G.; Jang, G.; Cha, B.; Park, J.; Nam, S.

    2011-01-01

    In recent times, digital X-ray detectors have been actively applied to the medical field; for example, digital radiography offers the potential of improved image quality and provides opportunities for advances in medical image management, computer-aided diagnosis and teleradiology. In this study, two candidate materials (HgI2 and PbI2) have been employed to study the influence of the dielectric structure on the performance of fabricated X-ray photoconducting films. Parylene C with high permittivity was deposited as a dielectric layer using a parylene deposition system (PDS 2060). The structural and morphological properties of the samples were evaluated field emission scanning electron microscopy and X-ray diffraction. Further, to investigate improvements in the electrical characteristics, a dark current in the dark room and sensitivity to X-ray exposure in the energy range of general radiography diagnosis were measured across the range of the operating voltage. The electric signals varied with the dielectric layer structure of the X-ray films. The PbI2 film with a bottom dielectric layer showed optimized electric properties. On the other hand, in the case of HgI2, the film with a top dielectric layer showed superior electric characteristics. Further, although the sensitivity of the film decreased, the total electrical efficiency of the film improved as a result of the decrease in dark current. When a dielectric layer is deposited on a photoconductor, the properties of the photoconductor, such as hole-electron mobility, should be considered to improve the image quality in digital medical imaging application. In this study, we have thus demonstrated that the use of dielectric layer structures improves the performance of photoconductors.

  9. Tuning the dielectric properties of metallic-nanoparticle/elastomer composites by strain.

    PubMed

    Gaiser, Patrick; Binz, Jonas; Gompf, Bruno; Berrier, Audrey; Dressel, Martin

    2015-03-14

    Tunable metal/dielectric composites are promising candidates for a large number of potential applications in electronics, sensor technologies and optical devices. Here we systematically investigate the dielectric properties of Ag-nanoparticles embedded in the highly flexible elastomer poly-dimethylsiloxane (PDMS). As tuning parameter we use uniaxial and biaxial strain applied to the composite. We demonstrate that both static variations of the filling factor and applied strain lead to the same behavior, i.e., the filling factor of the composite can be tuned by application of strain. In this way the effective static permittivity ?eff of the composite can be varied over a very large range. Once the Poisson's ratio of the composite is known, the strain dependent dielectric constant can be accurately described by effective medium theory without any additional free fit parameter up to metal filling factors close to the percolation threshold. It is demonstrated that, starting above the percolation threshold in the metallic phase, applying strain provides the possibility to cross the percolation threshold into the insulating region. The change of regime from conductive phase down to insulating follows the description given by percolation theory and can be actively controlled. PMID:25687891

  10. Tuning the dielectric properties of metallic-nanoparticle/elastomer composites by strain

    NASA Astrophysics Data System (ADS)

    Gaiser, Patrick; Binz, Jonas; Gompf, Bruno; Berrier, Audrey; Dressel, Martin

    2015-02-01

    Tunable metal/dielectric composites are promising candidates for a large number of potential applications in electronics, sensor technologies and optical devices. Here we systematically investigate the dielectric properties of Ag-nanoparticles embedded in the highly flexible elastomer poly-dimethylsiloxane (PDMS). As tuning parameter we use uniaxial and biaxial strain applied to the composite. We demonstrate that both static variations of the filling factor and applied strain lead to the same behavior, i.e., the filling factor of the composite can be tuned by application of strain. In this way the effective static permittivity ?eff of the composite can be varied over a very large range. Once the Poisson's ratio of the composite is known, the strain dependent dielectric constant can be accurately described by effective medium theory without any additional free fit parameter up to metal filling factors close to the percolation threshold. It is demonstrated that, starting above the percolation threshold in the metallic phase, applying strain provides the possibility to cross the percolation threshold into the insulating region. The change of regime from conductive phase down to insulating follows the description given by percolation theory and can be actively controlled.

  11. Method to characterize dielectric properties of powdery substances

    NASA Astrophysics Data System (ADS)

    Tuhkala, M.; Juuti, J.; Jantunen, H.

    2013-07-01

    An open ended coaxial cavity method for dielectric characterization of powdery substance operating at 4.5 GHz in TEM mode is presented. Classical mixing rules and electromagnetic modeling were utilized with measured effective permittivities and Q factors to determine the relative permittivity and dielectric loss tangent of different powders with ?r up to 30. The modeling enabled determination of the correction factor for the simplified equation for the relative permittivity of an open ended coaxial resonator and mixing rules having the best correlation with experiments. SiO2, Al2O3, LTCC CT 2000, ZrO2, and La2O3 powders were used in the experiments. Based on the measured properties and Bruggeman symmetric and Looyenga mixing rules, the determined dielectric characteristics of the powders exhibited good correlation with values in the literature. The presented characterization method enabled the determination of dielectric properties of powdery substances within the presented range, and therefore could be applied to various research fields and applications where dielectric properties of powders need to be known and controlled.

  12. Microwave Technologies-- Determination of Magnetic and Dielectric Materials Microwave Properties

    E-print Network

    Obol, Mahmut

    2009-01-01

    In this study, four different techniques are presented. 1 Rectangular waveguide measurement technique for normal microwave materials microwave properties such as permeability and permittivity. This technique removed guess parameter and dispersive effect issues of the old waveguide measurement techniques. It projects a new route for determination of any microwave materials magnetic and dielectric properties without using any guesses. 2 Coaxial probe measurement technique for the liquid and biological tissues dielectric permittivity. This coaxial probe technique has an advantage which is to attain the highest reflected signal from the coaxial probe tip, so that it is a fast and very sensitive technique to differentiate lossy materials dielectric permittivity. This technique could be useful non destructive detections for tumors in hospital and non destructive detections for chemical liquids as well. 3 A microstripline measurement technique for oxides microwave measurement at low frequency spectra where the waveg...

  13. Dielectric and Pyroelectric Properties of Epitaxial Multilayer Ferroelectrics with Dielectric Buffer Layers

    NASA Astrophysics Data System (ADS)

    Sun, Fu-Chang; Alpay, S. Pamir

    2015-03-01

    A nonlinear thermodynamic model is employed to compute the dielectric and pyroelectric properties of heteroepitaxial BaTiO3-SrTiO3 multilayers on SrTiO3, LaAlO3, MgO and Si substrates. The methodology takes into account electromechanical and electrostatic coupling and the strain relaxation due to the formation of misfit dislocations. Using different combinations of layer thickness, we show that the dielectric and pyroelectric properties can be enhanced using misfit strain and degree of strain relaxation as design parameters. This methodology can be used to optimize properties of ferroelectric multilayers in functional electronic devices for charge storage, IR sensing, and on-chip heating cooling.

  14. Dielectric and pyroelectric properties in the Pb(Mg1\\/3Nb2\\/3)O3-PbTiO3 system

    Microsoft Academic Search

    S. W. Choi; R. T. R. Shrout; S. J. Jang; A. S. Bhalla

    1989-01-01

    Dielectric and pyroelectric properties of relaxor ferroelectric in the (1-x) Pb(Mg1\\/3Nb2\\/3)O3-xPbTiO3 solid solution series have been investigated. The dielectric constant (K) and loss of poled and unpoled ceramic samples were determined. The pyroelectric coefficient and the spontaneous polarization were measured by the static Byer-Roundy method as a function of temperature and for various compositions in the binary system PMN-PT.An important

  15. Monitoring Coaxial-Probe Contact Force for Dielectric Properties Measurement

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A means is described for measuring and monitoring the contact force applied to a material sample with an open-ended coaxial-line probe for purposes of measuring the dielectric properties of semisolid material samples such as fruit, vegetable and animal tissues. The equipment consists of a stainless...

  16. Electrical Conduction and Dielectric Properties of Biodegradable Plastics

    Microsoft Academic Search

    Katsuyoshi Shinyama; Shigetaka Fujita

    2005-01-01

    We examined the electrical conduction and dielectric properties as well as thermal analysis of polylactic acid (PLA) that is biodegradable plastics. From the results of thermal analyses, it was found that the glass transition temperature (Tg) of PLA was about 60°C and the melting point (Tm) was about 166°C. For the temperature dependence of current density (J), J of PLA

  17. The dielectric properties of biological tissues: I. Literature survey

    Microsoft Academic Search

    C. Gabriel; S. Gabriel; E. Corthout

    1996-01-01

    The dielectric properties of tissues have been extracted from the literature of the past five decades and presented in a graphical format. The purpose is to assess the current state of knowledge, expose the gaps there are and provide a basis for the evaluation and analysis of corresponding data from an on-going measurement programme.

  18. Dielectric properties of ionic conductors : Yttria stabilized zirconia and forsterite

    E-print Network

    Paris-Sud XI, Université de

    Dielectric properties of ionic conductors : Yttria stabilized zirconia and forsterite Abstract. -- Two ionic conductors : yttria stabilized zirconia and nonstoichiometric forsterite were studied zirconia (0.85 Zr02 - 0.15 Y2 03 ) and non-stoichiometric forsterite (0.99 Mg2SiO4-0.01 Si02) have been

  19. Dielectric properties of biodegradable polylactic acid and starch ester

    Microsoft Academic Search

    N. Hirail; Y. Maeno; H. Tamura; D. Kaneko; T. Tanaka; Y. Ohki; Y. Tajitsu; M. Kohtoh; S. Okabe

    2004-01-01

    In order to examine the applicability of biodegradable polymers to the fields of electrical insulation, several dielectric properties of two typical biodegradable polymers, polylactic acid (PLA) and starch ester (SE), are examined. A fairly larger amount of space charge is accumulated in both polymers in comparison to low-density polyethylene (LDPE). This seems partly due to the presence of hydroxyl and

  20. Effects of Composite Particles Prepared by Mechanical Process on Dielectric Properties of Epoxy Hybrid Films

    Microsoft Academic Search

    Hui Joon Park; Seung Min Hong; Sang-Soo Lee; Junkyung Kim; Min Park

    2008-01-01

    A new type of composite filler mechanically treated with multi-walled carbon nanotubes (MWNTs) and (BT) particles was prepared to produce higher dielectric properties in the composite. The hybrid film fabricated by incorporating these composite fillers in an epoxy matrix had a high dielectric constant and similar dielectric loss as compared to the composite which contained neat BT particles. The dielectric

  1. Dielectric and pyroelectric properties of cadmium niobate ceramics

    SciTech Connect

    Swartz, S.L. (Battelle Columbus Div., Columbus, OH (US)); Randall, C.A.; Bhalla, A.S. (Materials Research Lab., Pennsylvania State Univ., University Park, PA (US))

    1989-04-01

    The low-temperature dielectric and pyroelectric properties of pyrochlore Cd{sub 2}Nb{sub 2}O{sub 7} ceramics have been investigated over the temperature range from 10 to 300 K. Dielectric data confirmed that two ferroelectric transitions occurred in the Cd{sub 2}Nb{sub 2}O{sub 7} ceramics at temperatures near 80 and 192 K. The higher-temperature ferroelectric transition is complex, with evidence for three separate transitions occurring within a narrow temperature range.

  2. Dielectric properties of lead-magnesium niobate ceramics

    SciTech Connect

    Swartz, S.L.; Shrout

    1984-05-01

    Dielectric properties are reported for lead magnesium niobate (PbMg /sub 1/3/ Nb /sub 2/3/ O/sub 3/) ceramics which were prepared as single phase (i.e., without pyrochlore) with an improved technique. Dielectric constants of 18,000 for pure PMN and 31,000 for PMN with 10% PbTiO/sub 3/ were achieved; these values are 50% larger than those reported in the literature. The dielectric constant of PMN ceramics was found to increase with both sintering temperature and excess MgO, and subsequent analysis of the microstructures confirmed that this was due to an increase in grain size. This grain-size dependence is explained as a consequence of low-permittivity grain boundaries.

  3. The dielectric properties of porous zinc oxide ceramics

    SciTech Connect

    Calame, J.P.; Carmel, Y.; Gershon, D.; Birman, A. [Univ. of Maryland, College Park, MD (United States). Inst. for Plasma Research; Martin, L.P.; Dadon, D.; Rosen, M. [Johns Hopkins Univ., Baltimore, MD (United States). Dept. of Materials Science

    1996-12-31

    Measurements of the complex dielectric constant of microwave sintered, porous ZnO at 2.45 GHz are presented. The dielectric properties as a function of porosity do not obey the standard Maxwell-Garnet dielectric mixing law with the ceramic material as the major phase, but instead behave as if the ceramic grains always remain in relatively poor electrical contact even at very high densities. Electromagnetic simulations, carried out for a variety of microstructure geometries, are performed to explore this observation. A model which treats the ceramic as an array of grains and pores, with the grains separated from each other by non- or slightly-percolating, fractal-geometry surfaces, provides a good description of the experimental results.

  4. Role of dielectric properties in terahertz field transmission

    NASA Astrophysics Data System (ADS)

    Seo, Minah; Lee, Joong Wook; Kim, Hwi

    2015-06-01

    We compare the field transmission characteristics of a freestanding perforated metal film (as a conducsssstor) and a polymethylmethacrylate-graphite composite film (as an absorber) in the terahertz frequency range. The role of dielectric properties of the materials and the contribution of surface waves toward enhanced transmission with periodic and random hole arrays are discussed. Periodic subwavelength hole arrays in metal films do support enhanced terahertz field transmission whereas random arrays do not. In contrast, neither periodic nor random arrays of subwavelength holes punctured in dielectric absorbers support such transmission. Notably, even a dielectric absorber with large holes, which is sufficiently larger than subwavelength holes, can result in features in transmission due to the shape resonance, but the effect is very small.

  5. Optical and dielectrical properties of azo quinoline thin films

    NASA Astrophysics Data System (ADS)

    El-Ghamaz, N. A.; El-Menyawy, E. M.; Diab, M. A.; El-Bindary, A. A.; El-Sonbati, A. Z.; Nozha, S. G.

    2014-04-01

    In this study, the optical and dielectrical properties of a novel series of quinoline azodyes (5-(4?-derivatives phenyl azo)-8-hydroxy-7-quinolinecarboxaldehyde) (AQL1-AQL5) were investigated and the obtained results were analyzed. The X-ray diffraction (XRD) patterns of AQLn show that the materials in the powder form are a mixture of amorphous and crystalline structure, while the thermally deposited thin films are completely amorphous. The optical constants such as the refractive index, n, the absorption index, k and the absorption coefficient, ?, were determined using spectrophotometric measurements of transmittance (T) and reflectance (R) in the wavelength range 200-2500 nm. According to the single oscillator model (SOM), some related parameters such as oscillation energy (Eo), the dispersion energy (Ed), the optical dielectric constant (??), the lattice dielectric constant (?L) and the ratio of free carrier concentration to its effective mass (N/m*) are estimated. The emission spectra of azo quinoline ligands (AQLn) exhibit dual fluorescence peaks in the region 512-580 nm. This finding reveals the formation of two stoichiometric hydrogen-bonding in the ground and excited state. The dielectrical properties and alternating current conductivity (?AC) are investigated in temperature range 298-483 K and frequency range 0.1-100 KHz.

  6. Quasi-static electric properties of insulating polymers at a high voltage for electro-bonded laminates

    NASA Astrophysics Data System (ADS)

    Di Lillo, L.; Carnelli, D. A.; Bergamini, A.; Busato, S.; Ermanni, P.

    2011-05-01

    This paper reports on a high voltage measurement set-up for determining the relative permittivity and the volume resistivity of dielectric polymers. These properties were evaluated on thin films at electric fields up to 80 V µm-1 and in the quasi-static regime at frequencies lower than 1 Hz. It is found that the high field properties of FEP, PFA, polyimide and Mylar are comparable to the respective low field values, while for ferroelectric PVDF poling behavior becomes evident at high fields. High field properties of dielectric polymers are of particular importance in the design of devices relying on electrostatic attraction, such as electro-bonded laminates applied in tunable bending stiffness structures.

  7. Ultrashort electric pulse induced changes in cellular dielectric properties.

    PubMed

    Garner, Allen L; Chen, George; Chen, Nianyong; Sridhara, Viswanadham; Kolb, Juergen F; Swanson, R James; Beebe, Stephen J; Joshi, Ravindra P; Schoenbach, Karl H

    2007-10-12

    The interaction of nanosecond duration pulsed electric fields (nsPEFs) with biological cells, and the models describing this behavior, depend critically on the electrical properties of the cells being pulsed. Here, we used time domain dielectric spectroscopy to measure the dielectric properties of Jurkat cells, a malignant human T-cell line, before and after exposure to five 10ns, 150kV/cm electrical pulses. The cytoplasm and nucleoplasm conductivities decreased dramatically following pulsing, corresponding to previously observed rises in cell suspension conductivity. This suggests that electropermeabilization occurred, resulting in ion transport from the cell's interior to the exterior. A delayed decrease in cell membrane conductivity after the nsPEFs possibly suggests long-term ion channel damage or use dependence due to repeated membrane charging and discharging. This data could be used in models describing the phenomena at work. PMID:17706595

  8. Optimization of dielectric properties of lead-magnesium niobate ceramics

    SciTech Connect

    Lejeune, M.; Boilot, J.P.

    1986-04-01

    Dielectric properties of PbMg/sub 1/3//Nb/sub 2/3//O/sup 3/-type ceramics can be improved both by using a preferred sintering cycle, which prevents the formation of a pyrochlore layer at the surface of the pellets, and by adding the correct amount of excess PbO, which results in dense ceramics with a nearly pure perovskite phase at a low sintering temperature (900/sup 0/C).

  9. Microwave dielectric properties of lanthanum aluminate ceramics and single crystal

    Microsoft Academic Search

    T. Shimada; Ken-ich Kakimoto; Hitoshi Ohsato

    2005-01-01

    Single crystal and ceramics of LaAlO3 were prepared by a Czochralski method and conventional solid phase reaction, respectively, using high purity reagents. Far infrared reflectivity spectra for single crystals and ceramics of LaAlO3 were measured and eigenfrequencies and damping constants of transverse and longitudinal optical modes were evaluated in order to discuss variations in the dielectric properties. The observed reflectivity

  10. Dielectric, ferroelectric, magnetic, and magnetoelectric properties of multiferroic laminated composites

    Microsoft Academic Search

    N. Cai; J. Zhai; C.-W. Nan; Y. Lin; Z. Shi

    2003-01-01

    Multiferroic laminated composites consisting of lead-zirconate titanate (PZT)\\/polyvinylidene-fluoride (PVDF) particulate composite layers and Tb-Dy-Fe alloy (Terfenol-D)\\/PVDF particulate composite layers, prepared by a simple hot-molding technique, were reported. In the laminated composites, the polymer PVDF is inert and used just as a binder. The measured dielectric, ferroelectric, magnetic, and magnetoelectric properties demonstrate strong dependence on volume fraction f of the PVDF

  11. Microstructures and dielectric properties of ferroelectric glass-ceramics

    Microsoft Academic Search

    Michael J. Reece; Clive A. Worrell; Graham J. Hill; Roger Morrell

    1996-01-01

    The microstructures of ferroelectric glass-ceramics derived from (Pb,Sr,Ba)NbâOâ solid solutions have been investigated systematically using electron microscopy (TEM, SEM) and X-ray diffraction (XRD). These data, together with the measured dielectric properties of the materials have been correlated with both the sintering\\/devitrification conditions and compositional changes to the base glass. The low incidence of ferroelectric domains suggests that an increase in

  12. Strongly correlated Fermions in optical lattices: static and dynamic properties

    NASA Astrophysics Data System (ADS)

    Schneider, Ulrich; Hackermüller, Lucia; Best, Thorsten; Will, Sebastian; Braun, Simon; Bloch, Immanuel

    2009-03-01

    Fermionic atoms in optical lattices can serve as a model system for condensed matter physics: They implement the Hubbard model with high experimental control of the relevant parameters. We study static and dynamic properties of ultracold fermions in different regimes, varying from a metal to a band insulator in the non-interacting system and including complex metals and the Fermionic Mott Insulator for strongly repulsive systems. In the experiment, spin mixtures of fermionic ^40K are loaded into a combination of a blue detuned three dimensional optical lattice and a red detuned dipole trap. This combination of optical potentials allows an independent control of lattice depth and harmonic confinement, thus enabling us to explore different regimes. In addition to the static properties we present measurements of the dynamic response of the system to changes of the external parameters.

  13. Structure-property relationships in polymers for dielectric capacitors

    NASA Astrophysics Data System (ADS)

    Gupta, Sahil

    Effective energy storage is a key challenge of the 21st century that has fueled research in the area of energy storage devices. In this dissertation, structure-property relationships have been evaluated for polymers that might be suitable for storing energy in high-energy density, high-temperature capacitors. Firstly, hydroxyl-modified polypropylenes (PPOH) were synthesized by copolymerization of the propylene and undecenyloxytrimethylsilane monomers. The presence of H-bonding in PPOH copolymers increased their glass-transition temperature. Steric hindrance by the comonomer reduced the PP crystal growth rate and crystal size, resulting in a melting point depression. The comonomer was restricted outside the crystalline domains leaving the alpha-monoclinic crystal structure of PP unaffected, but increasing the fold-surface free energy. Crystallization was slower for PPOH copolymers than PP, but exhibited a skewed bell curve as a function of hydroxyl concentration. H-bonding persisted even at melt temperatures up to 250°C resulting in a higher elasticity and viscosity for PPOH copolymers. Secondly, sulfonated poly(ether ether ketone) (HSPEEK) was synthesized by sulfonating PEEK with sulfuric acid, and further neutralized with Zn to obtain ZnSPEEK. The thermal and dielectric properties of SPEEK were compared with PEEK. The glass-transition increased and melting point were high enough to enable the use of polymer at 180°C. The incorporation of sulfonic groups in PEEK increased the dielectric constant. HSPEEK had a higher dielectric constant than ZnSPEEK due to higher dipolar mobility, but the dielectric loss was also higher for HSPEEK due to electrode polarization and DC conduction. These results were consistent with our observations from sulfonated polystyrene (HSPS), which was used as a >model&lang' polymer. Lastly, commercial poly(4-methyl-1-pentene) (P4MP) was characterized to check its viability as a high-temperature polymer dielectric. Thermal stability up to 200°C, high melting point (> 225°C) and melting onset at 160 - 190°C indicated that P4MP could be used at 180 - 200°C. Thin free-standing films (~10 mum) with controlled crystal structure and surface morphology were prepared using blade coating and their drying dynamics were measured using a custom-designed solvent-casting platform. These films were further stretched uniaxially or biaxially, and their effect on the dielectric properties of P4MP was studied.

  14. Improved instrumentation for monitoring the diurnal and seasonal cycles in the dielectric properties of forest canopies

    NASA Technical Reports Server (NTRS)

    Guerra, Abel G.; Mcdonald, Kyle C.; Way, Jobea

    1992-01-01

    The design and implementation of a dielectric measurement system that facilitates the automated and continuous in situ monitoring of the dielectric properties of several canopy constituents is presented. This system utilizes the same coaxial line reflection coefficient measurement technique as the portable dielectric probe (PDP) while incorporating several features that facilitate the automated monitoring of canopy dielectric properties. The new system is capable of continuously monitoring the dielectric properties of the canopy constituents in a near-simultaneous fashion. The implementation of a data logger as a user interface has increased the number of measurements that the instrument is able to store in memory while significantly improving system reliability.

  15. Dielectric characteristics of static shield for coil end of gas-insulated transformer

    Microsoft Academic Search

    T. Inoue; A. Inui; T. Teranishi; N. Murase; I. Ohshima; K. Toda

    1991-01-01

    The authors discuss the impulse breakdown characteristics of insulation models simulating static shields for coil ends of SF6 gas-insulated transformers. If a filler made of elastomer material is fitted closely on the covered electrode to eliminate gas gaps between the filler and the covered electrode, the impulse breakdown voltage of the static shield is higher than with gas gaps. If

  16. Protein dielectrophoresis and the link to dielectric properties.

    PubMed

    Camacho-Alanis, Fernanda; Ros, Alexandra

    2015-02-01

    There is a growing interest in protein dielectrophoresis (DEP) for biotechnological and pharmaceutical applications. However, the DEP behavior of proteins is still not well understood which is important for successful protein manipulation. In this paper, we elucidate the information gained in dielectric spectroscopy (DS) and electrochemical impedance spectroscopy (EIS) and how these techniques may be of importance for future protein DEP manipulation. EIS and DS can be used to determine the dielectric properties of proteins predicting their DEP behavior. Basic principles of EIS and DS are discussed and related to protein DEP through examples from previous studies. Challenges of performing DS measurements as well as potential designs to incorporate EIS and DS measurements in DEP experiments are also discussed. PMID:25697193

  17. Effect of dielectric properties of moist salinized soils on backscattering coefficients extracted from RADARSAT image

    Microsoft Academic Search

    Yun Shao; Qingrong Hu; Huadong Guo; Yuan Lu; Qing Dong; Chunming Han

    2003-01-01

    This paper presents the experimental results regarding changes in the dielectric properties of artificially moistened and salinized soils and on soil samples taken from a salt lake. The complex dielectric constants of soil samples were measured using a microwave network analyzer. We evaluated the real and imaginary parts of dielectric constants of artificially moistened and salinized soil samples prepared in

  18. Multimodal Solution for a Waveguide Radiating Into Multilayered Structures - Dielectric Property and Thickness Evaluation

    Microsoft Academic Search

    Mohammad Tayeb Ahmad Ghasr; Devin Simms; Reza Zoughi

    2009-01-01

    Open-ended rectangular waveguides are widely used for microwave and millimeter-wave nondestructive testing (NDT) applications, such as detecting disbond and delamination in multilayered composite structures, thickness evaluation of dielectric sheets and coatings on metal substrates, etc. When inspecting a complex multilayered composite structure that is made of generally lossy dielectric layers with arbitrary thicknesses and backing, the dielectric properties of a

  19. Improvement in electric and dielectric properties of nanoferrite synthesized via reverse micelle technique

    Microsoft Academic Search

    Sangeeta Thakur; S. C. Katyal; M. Singh

    2007-01-01

    Nano nickel zinc ferrite (Ni0.58Zn0.42Fe2O4) with fascinating dielectric properties which reveal a direction for application was synthesized by reverse micelle technique. Dielectric constant and dielectric losses are controlled up to a measurement temperature of around 473 K at higher frequency range of 9-19 MHz. The dielectric loss of the sample investigated at room temperature is only 0.003 at 19 MHz.

  20. Dielectric characteristics of static shield for coil-end of gas-insulated transformer

    Microsoft Academic Search

    A. Inui; T. Inoue; T. Teranishi; H. Murase; I. Ohshima; K. Toda

    1992-01-01

    The impulse breakdown characteristics of insulation models simulating static shields for coil ends of SF6 gas-insulated transformers are studied. The static shield is composed of a double-covered electrode and a filler between the coverings. If a filler made of elastomer material is fitted closely on the covered electrode to eliminate gas gaps between the filler and the covered electrode, the

  1. Semi-Automatic System for Testing Dielectric Properties of Low-Voltage Busbar

    Microsoft Academic Search

    Yang Xuemei; She Jiangfeng

    2010-01-01

    One semi-automatic system is developed for testing the dielectric properties and grounding resistance of low-voltage busbar, one type of large-capacity electric power transmission equipment. The dielectric properties mainly include the insulation resistance and leakage current of busbar under occasional high voltage. The withstanding voltage and insulation resistance tester is used for testing its dielectric properties, and the earth continuity tester

  2. Dielectric properties of cobalt ferrite nanoparticles in ultrathin nanocomposite films.

    PubMed

    Alcantara, Gustavo B; Paterno, Leonardo G; Fonseca, Fernando J; Pereira-da-Silva, Marcelo A; Morais, Paulo C; Soler, Maria A G

    2013-12-01

    Multilayered nanocomposite films (thickness 50-90 nm) of cobalt ferrite nanoparticles (np-CoFe2O4, 18 nm) were deposited on top of interdigitated microelectrodes by the layer-by-layer technique in order to study their dielectric properties. For that purpose, two different types of nanocomposite films were prepared by assembling np-CoFe2O4 either with poly(3,4-ethylenedioxy thiophene):poly(styrene sulfonic acid) or with polyaniline and sulfonated lignin. Despite the different film architectures, the morphology of both was dominated by densely-packed layers of nanoparticles surrounded by polyelectrolytes. The dominant effect of np-CoFe2O4 was also observed after impedance spectroscopy measurements, which revealed that dielectric behavior of the nanocomposites was largely influenced by the charge transport across nanoparticle-polyelectrolyte interfaces. For example, nanocomposites containing np-CoFe2O4 exhibited a single low-frequency relaxation process, with time constants exceeding 15 ms. At 1 kHz, the dielectric constant and the dissipation factor (tan ?) of these nanocomposites were 15 and 0.15, respectively. These values are substantially inferior to those reported for pressed pellets made exclusively of similar nanoparticles. Impedance data were further fitted with equivalent circuit models from which individual contributions of particle's bulk and interfaces to the charge transport within the nanocomposites could be evaluated. The present study evidences that such nanocomposites display a dielectric behavior dissimilar from that exhibited by their individual counterparts much likely due to enlarged nanoparticle-polyelectrolyte interfaces. PMID:24145704

  3. Structural, electrical and dielectric properties of yttrium substituted nickel ferrites

    Microsoft Academic Search

    M. Ishaque; M. U. Islam; M. Azhar Khan; I. Z. Rahman; A. Genson; S. Hampshire

    2010-01-01

    The influence of Y3+ substitution on the structural, electrical and dielectric properties of Ni–Y ferrites was studied in the ferrite series NiY2xFe2?2xO4 where x=0–0.12 in steps of 0.02. This series was prepared by conventional double sintering ceramic method. XRD analysis reveals single phase samples up to x=0.06. At x?0.08, a secondary phase of iron yttrium oxide (YFeO3) appears along with

  4. Tunable dielectric properties of lead barium zirconate niobate films

    NASA Astrophysics Data System (ADS)

    Kuo, Ya-Ling; Wu, Jenn-Ming

    2006-09-01

    The effect of substitution of niobium for zirconium on tunable behavior of lead barium zirconate (PBZ) films was investigated. Lead barium zirconate niobate films were grown on Pt /Ti/SiO2/Si substrates using chemical solution deposition method. The substitution of Nb for Zr enhances tunable properties of PBZ films. The dielectric tunabilities are excellent, all higher than 45% with a maximum=60%. The substitution of Nb for Zr raises values of figure of merit (FOM) of films. The maximum FOM takes place at 5mol% Nb with a value of 90, which is about three times that of the corresponding PBZ film.

  5. Synthesis and Dielectric Properties of Nanocrystalline BASRTIO3

    NASA Astrophysics Data System (ADS)

    Golmohammad, M.; Nemati, A.; Faghihi Sani, M. A.

    Ba0.7Sr0.3TiO3 was prepared via simple sol-gel method by using titanium tetrabutoxide, barium and strontium carbonates, citric acid and ethylene glycol as starting materials. Simultaneous Thermal Analysis (STA) was used to examine thermal behavior of xerogel. The crystallite size of BST was about 21nm calculated by X-Ray diffraction (XRD) and confirmed by transition electron microscopy (TEM). Using these nanocrystalline powders, BST pellets were prepared and sintered in various temperatures. The grain size effect on electrical properties was studied and found that as the grain size decreased, the dielectric constant decreased too.

  6. Measurement of the dielectric properties of sawdust between 0.5 and 15 GHz

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Rapid, nondestructive, and subsurface sensing of material properties such as water content can be achieved through dielectric measurements. The interaction between the electromagnetic waves and the material is defined by the dielectric properties, which can be used to determine the physical properti...

  7. Dielectric and Thermal Properties of Rice Cake Formulations Containing Different Gums Types

    Microsoft Academic Search

    Elif Turabi; Marc Regier; Gulum Sumnu; Serpil Sahin; Matthias Rother

    2010-01-01

    In this study, dielectric properties of rice cake formulations containing different gum types (xanthan, guar, locust bean, HPMC, and kappa-carrageenan) were determined at temperatures between 25 and 90°C at 2450 MHz. Moreover, thermal properties of these formulations were determined by using differential scanning calorimeter (DSC). Dielectric properties of cake batters were found to be dependent on cake formulation. Xanthan and

  8. Direct measurement of the dielectric polarization properties of DNA.

    PubMed

    Cuervo, Ana; Dans, Pablo D; Carrascosa, José L; Orozco, Modesto; Gomila, Gabriel; Fumagalli, Laura

    2014-09-01

    The electric polarizability of DNA, represented by the dielectric constant, is a key intrinsic property that modulates DNA interaction with effector proteins. Surprisingly, it has so far remained unknown owing to the lack of experimental tools able to access it. Here, we experimentally resolved it by detecting the ultraweak polarization forces of DNA inside single T7 bacteriophages particles using electrostatic force microscopy. In contrast to the common assumption of low-polarizable behavior like proteins (?r ? 2-4), we found that the DNA dielectric constant is ? 8, considerably higher than the value of ? 3 found for capsid proteins. State-of-the-art molecular dynamic simulations confirm the experimental findings, which result in sensibly decreased DNA interaction free energy than normally predicted by Poisson-Boltzmann methods. Our findings reveal a property at the basis of DNA structure and functions that is needed for realistic theoretical descriptions, and illustrate the synergetic power of scanning probe microscopy and theoretical computation techniques. PMID:25136104

  9. Doping effect on the dielectric property in bismuth titanate

    NASA Astrophysics Data System (ADS)

    Yao, Y. Y.; Song, C. H.; Bao, P.; Su, D.; Lu, X. M.; Zhu, J. S.; Wang, Y. N.

    2004-03-01

    The dielectric property complemented by the mechanical measurement (internal friction) in the doped Bi4Ti3O12 [Bi4-xLaxTi3O12 (x=0.5,0.75,1) and Bi4-y/3Ti3-yNbyO12 (y=0.015,0.03,0.06)] was systematically investigated from room temperature to 350 °C. In the plot of dielectric loss versus temperature for Bi4Ti3O12 (BiT), a relaxation peak was confirmed to be associated with the motion of the oxygen vacancy. It is found that the La doping at site A is in favor of improvement of the fatigue property, in contrast, the Nb doping at site B can mainly enhance the remanent polarization. Appropriate La doping at site A of perovskite-type unit in BiT enhances the chemical stability of oxygen vacancy by improving the height of the potential barrier for hopping and enhances the mobility of domain by the changing of domain structures. While the Nb doping at site B could induce the distortion of oxygen octahedral and reduce the oxygen vacancy concentration by a compensating effect so that it results in an enhancement of remanent polarization.

  10. Percolative properties in ferroelectric-dielectric composite ceramics

    SciTech Connect

    Zhang Qiwei; Zhai Jiwei; Yao Xi [Functional Materials Research Laboratory, Tongji University, Siping Road 1239, Shanghai 200092 (China); Kong Lingbing [Temasek Laboratories, National University of Singapore, 5A Engineering Drive 1, Singapore 117411 (Singapore)

    2010-11-01

    Percolative properties in dielectric (DE) tunability were observed in three ferroelectric (FE)-DE composite ceramics as follows: xBa{sub 0.5}Sr{sub 0.5}TiO{sub 3}-MgO, xBa{sub 0.4}Sr{sub 0.6}TiO{sub 3}-Mg{sub 2}TiO{sub 4}, and xBa{sub 0.5}Sr{sub 0.5}TiO{sub 3}-Mg{sub 3}B{sub 2}O{sub 6}. Dielectric constants of the composites increased monotonously with increasing volume fractions of FE component. Comparatively, their DE tunabilities exhibited a weak dependence on FE concentrations over a wide range. However, their tunabilities started to decrease substantially below a critical concentration of FE. The critical concentrations were 40 vol % for Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3}-MgO, 38 vol % for Ba{sub 0.4}Sr{sub 0.6}TiO{sub 3}-Mg{sub 2}TiO{sub 4}, and 33 vol % for Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3}-Mg{sub 3}B{sub 2}O{sub 6}. These results could be used as a guide to tailor the properties of FE-DE composites for tunable device applications.

  11. Microstructure and dielectric properties of biocarbon nanofiber composites

    NASA Astrophysics Data System (ADS)

    Dai, Bo; Ren, Yong; Wang, Gaihua; Ma, Yongjun; Zhu, Pei; Li, Shirong

    2013-06-01

    A kind of web-like carbon with interconnected nanoribbons was fabricated using bacterial cellulose pyrolyzed at various temperatures, and the microwave dielectric properties were investigated. Bacterial cellulose was converted into carbonized bacterial cellulose (CBC) with a novel three-dimensional web built of entangled and interconnected cellulose ribbons when the carbonization temperature was below 1,200°C; the web-like structure was destroyed at a temperature of 1,400°C. Composites of CBC impregnated with paraffin wax exhibited high complex permittivity over a frequency range of 2 to 18 GHz, depending on the carbonization temperature. Both real and imaginary parts were the highest for CBC pyrolyzed at 1,200°C. The complex permittivity also strongly depended on CBC loadings. For 7.5 wt.% loading, the real and imaginary permittivities were about 12 and 4.3, respectively, and the minimum reflection loss was -39 dB at 10.9 GHz. For 30 wt.% loading, the real and imaginary permittivities were about 45 and 80, respectively, and the shielding efficiency was more than 24 dB in the measured frequency range and could be up to 39 dB at 18 GHz. The electromagnetic properties were assumed to correlate with both the dielectric relaxation and the novel web-like structure.

  12. Structural, dielectric and magnetic properties of Ni substituted zinc ferrite

    NASA Astrophysics Data System (ADS)

    Kumbhar, S. S.; Mahadik, M. A.; Mohite, V. S.; Rajpure, K. Y.; Kim, J. H.; Moholkar, A. V.; Bhosale, C. H.

    2014-08-01

    NixZn1-xFe2O4 ferrite has been synthesized by the ceramic method using Ni CO3, ZnO, Fe2O3 precursors. The influence of Ni content on the structural, morphological, electrical and magnetic properties of NixZn1-xFe2O4 ferrites is studied. The X-ray diffraction (XRD) analysis reveals that the samples are polycrystalline with spinel cubic structure. The SEM images of NixZn1-xFe2O4 ferrite show that the grain size decreases with an increase in the Ni content. The tetrahedral and octahedral vibrations in the samples are studied by IR spectra. Frequency dependence of dielectric constant shows dielectric dispersion due to the Maxwell-Wagner type of interfacial polarization. Conduction mechanism due to polarons has been analyzed by measuring the AC conductivity. Impedance spectroscopy is used to study the electrical behavior. Magnetic properties of NixZn1-xFe2O4 are studied by using hysteresis loop measurement. The maximum value of saturation magnetization of 132.8 emu/g obtained for the composition, x=0.8, is attributed to magnetic moment of Fe3+ ions.

  13. Dielectric Properties of Fruits and Insect Pests as related to Radio Frequency and Microwave Treatments

    Microsoft Academic Search

    S. Wang; J. Tang; J. A. Johnson; E. Mitcham; J. D. Hansen; G. Hallman; S. R. Drake; Y. Wang

    2003-01-01

    Information on dielectric properties of commodities and insect pests is needed in developing thermal treatments for postharvest insect control based on radio frequency (RF) and microwave energy. Dielectric properties of six commodities along with four associated insect pests were measured between 1 and 1800MHz using an open-ended coaxial-line probe technique and at temperatures between 20 and 60°C. The dielectric loss

  14. Characterization of dielectric properties for PZN-PMNPT ferroelectric thin films at microwave frequencies

    Microsoft Academic Search

    H. M. Wong; B. Luo; L. C. Ong; K. Yao; Y. X. Guo

    2006-01-01

    Dielectric properties of pseudo-epitaxial perovskite ferroelectric PZN-PMN-PT thin films deposited on lanthanum aluminate (LAO) substrates were characterized for microwave application. Dielectric constant, voltage tunability, and loss tangent of the thin films were determined via coplanar waveguides (CPWs) and interdigital capacitors (IDCs) structures. Scattering parameters were extracted through measurements for both structures and the dielectric properties were obtained by the conformal

  15. The thermal and dielectric properties of high performance cyanate ester resins\\/microcapsules composites

    Microsoft Academic Search

    Li Yuan; Guozheng Liang; Aijuan Gu

    2011-01-01

    Novel high performance bisphenol A dicyanate ester (BADCy) resins\\/poly(urea-formaldehyde) microcapsules filled with epoxy resins (MCEs) composites have been prepared. The effects of different contents of MCEs on the thermal and dielectric properties of cured BADCy were investigated using dynamic mechanical analyzer (DMA), thermalgravimetric analyzer (TGA) and broadband dielectric analyzer. The dielectric properties of BADCy\\/MCEs treated in hot water and hot

  16. Effect of pressure on dielectric properties of polyvinylidene fluoride (PVDF) polymer

    NASA Astrophysics Data System (ADS)

    Razi, P. Muhammed; Rasi, U. P. Mohammed; Gangineni, R. B.

    2015-06-01

    Influence of pressure on the dielectric properties of Poly (vinylidene fluoride) (PVDF) has been investigated. The pressure is varied by applying a 5 Ton and 10 Ton pressure during pellet preparation. The broad band dielectric spectroscopy is utilized for understanding the dielectric constant disparity with respect to frequency and temperature. XRD and Raman spectroscopy are utilized to comprehend the structural characteristics of PVDF with respect to pressure. A relaxor type ferroelectric behavior is observed from the complex dielectric constant versus temperature measured at different frequencies. Further, the deviations in the dielectric constant versus temperatures are discussed with respect to the structural evolutions of the PVDF.

  17. Crystalline properties dependence of dielectric and energy storage properties of poly(vinylidene fluoride-chlorotrifluoroethylene)

    NASA Astrophysics Data System (ADS)

    Xia, Weimin; Xu, Zhuo; Wen, Fei; Li, Wenjing; Zhang, Zhicheng

    2010-11-01

    Thermal quenching at various temperatures has been employed to fabricate poly(vinylidene fluoride-co-chlorotrifluoroethylene) films with varied crystalline properties in an attempt to significantly improve their dielectric and energy storage properties. It has been shown that the film quenched at lower temperature possesses lower crystallinity and crystal grain size. The dielectric constant and dielectric loss of corresponding films are improved at low frequency and reduced at high frequency due to the response of dipoles in amorphous phase. The breakdown strength and polarization of the film quenched at lower temperature are larger than that quenched at higher temperature. Therefore, the low quenching temperature favors the high energy density both under the consistent electric field and the breakdown electric field.

  18. Multimodal Solution for a Rectangular Waveguide Radiating into a Multilayered Dielectric Structure and its Application for Dielectric Property and Thickness Evaluation

    Microsoft Academic Search

    M. T. Ghasr; R. Zoughi

    2008-01-01

    Open-ended rectangular waveguides are widely used for microwave and millimeter wave nondestructive testing applications. Applications have included detecting disbonds and delaminations in multilayered composite structures, thickness evaluation of dielectric sheets and coatings on metal substrates, etc. When inspecting a complex multilayered composite structure, made of generally lossy dielectric layers with arbitrary thicknesses and backing, the dielectric properties of a particular

  19. Measurement of Dielectric Properties of Ultrafine BaTiO3 Using an Organic-Inorganic Composite Method

    NASA Astrophysics Data System (ADS)

    Bao, Jie; Wang, Weiwang; Li, Shengtao; Liu, Johan

    2015-07-01

    Ultrafine BaTiO3, unlike traditional ferroelectric materials, demonstrates some interesting dielectric properties, such as a gradual transition from paraelectric to ferroelectric phase, which is similar to dielectric relaxation ferroelectrics. Although several methods have been recently proposed to measure the dielectric properties of ultrafine BaTiO3, the problem still remains unsolved. This paper proposes a new method to estimate the dielectric properties of ultrafine BaTiO3 by measuring and analyzing the dielectric properties of BaTiO3-epoxy composites. The Novocontrol dielectric measuring system was employed to measure the dielectric response of the composites. The dielectric behavior and relaxation characteristics of the BaTiO3 filler were estimated by modeling and calculating the dielectric constant based on different mixture theories. Results reveal that the effect of surface states yields dielectric relaxation in ultrafine BaTiO3.

  20. Dielectric properties of foods: Reported data in the 21st Century and their potential applications

    Microsoft Academic Search

    M. E. Sosa-Morales; L. Valerio-Junco; A. López-Malo; H. S. García

    2010-01-01

    Dielectric properties (DP) are the main parameters that provide information about how materials interact with electromagnetic energy during dielectric heating. These properties have gained great importance and applications for foods that are subjected to novel microwave (MW) or radio frequency (RF) heating treatments. The knowledge of the DP of a determined foodstuff is fundamental in order to understand and model

  1. Dielectric properties of canine acute and chronic myocardial infarction at a cell relaxation spectrum. II. Theory

    Microsoft Academic Search

    Serguei Y. Semenov; Robert H. Svenson; Galina Simonova; Alexander E. Bulyshev; A. E. Souvorov; Yu. E. Sizov; A. G. Nazarov; V. Y. Borisov; A. V. Pavlovsky; G. P. Tatsis; M. Taran; A. N. Starostin

    1997-01-01

    A new model of bulk myocardium dielectric properties as a composition of membrane covered cells modelled as infinite cylinders has been developed. This model utilizes the complex values of dielectric properties of the intracellular, extracellular media and the cellular membrane. The model was used to analyze the myocardial resistivity above and below the cell membrane relaxation spectrum in normal myocardium

  2. 10- to 1800-MHz dielectric properties of fresh apples during storage

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The dielectric properties of fresh apples of three cultivars were measured at 24 degrees C over 10 weeks in storage at 4 degrees C to determine whether these properties might be used to determine quality factors such as soluble solids content (SSC), firmness, moisture content and pH. The dielectric...

  3. Improving the dielectric and piezoelectric properties of screen-printed Low temperature PZT/polymer composite

    E-print Network

    in energy harvesting, sensing and actuating applications. Piezoelectric materials can be used in energyImproving the dielectric and piezoelectric properties of screen-printed Low temperature PZT. This paper reports an improvement in dielectric and piezoelectric properties of screen-printed PZT

  4. Electro-optic and dielectric properties of Hafnium-doped congruent lithiumniobate crystals

    E-print Network

    Boyer, Edmond

    1 Electro-optic and dielectric properties of Hafnium-doped congruent lithium­niobate crystals report the optical and dielectric properties in hafnium (Hf)-doped lithium niobate (LN) crystals. We affected by the introduction of hafnium ions and therefore Hf-doped LN has the advantage of low

  5. Heterogeneous Anthropomorphic Phantoms with Realistic Dielectric Properties for Microwave Breast Imaging Experiments

    PubMed Central

    Mashal, Alireza; Gao, Fuqiang; Hagness, Susan C.

    2011-01-01

    We present a technique for fabricating realistic breast phantoms for microwave imaging experiments. Using oil-in-gelatin dispersions that mimic breast tissue dielectric properties at microwave frequencies, we constructed four heterogeneous phantoms spanning the full range of volumetric breast densities. We performed CT scans and dielectric properties measurements to characterize each phantom. PMID:21866208

  6. TEMPERATURE-DEPENDENT DIELECTRIC PROPERTIES OF SELECTED SUBTROPICAL AND TROPICAL FRUITS AND ASSOCIATED INSECT PESTS

    Microsoft Academic Search

    S. Wang; M. Monzon; Y. Gazit; J. Tang; E. J. Mitcham; J. W. Armstrong

    Knowledge of the dielectric properties of commodities and insect pests is important in developing thermal treatments for postharvest insect control based on radio frequency (RF) and microwave energy. The dielectric properties of six subtropical and tropical fruits along with four associated insect pests were measured between 1 and 1800 MHz using an open-ended coaxial-line probe technique and at temperatures between

  7. Mechanical and Dielectric Breakdown Properties of Biodegradable Plastics

    NASA Astrophysics Data System (ADS)

    Shinyama, Katsuyoshi; Fujita, Shigetaka

    The mechanical and dielectric breakdown properties of polylactic acid (PLA), which is a biodegradable plastic, were examined, and a physicochemical analysis was performed. At room temperature, the tensile strength of PLA was about 100 MPa, almost the same as for PP, but at 100°C, even the value for LDPE decreased. The Young's modulus of PLA at room temperature was about 3.6 GPa, about 1.7 times the value for PP, and about 11 times the value for LDPE. The Young's modulus of PLA decreased slowly with a rise in temperature, and at high temperatures, 60°C and above, it decreased rapidly. The dielectric breakdown strength (EB) of PLA at room temperature was about 6.2 MV/cm, about 1.4 times the value for LDPE. The EB of PLA increased with an increase in temperature, and was about 6.9 MV/cm at 60°C (?EB/?T?0). In this region, it is thought that a secondary effect due to space charge occurred, as well as an electron avalanche breakdown. However, the EB of PLA decreased at temperatures higher than 60°C in the high temperature region (?EB/?T<0). In this domain, it is thought that thermal breakdown occurred, and that electromechanical breakdown also occurred in the high temperature domain of 80°C and above.

  8. Unraveling dielectric and electrical properties of ultralow-loss lead magnesium niobate titanate pyrochlore dielectric thin films for capacitive applications

    SciTech Connect

    Zhu, X. H. [Department of Materials Science, Sichuan University, Chengdu 610064 (China); CEA, LETI, MINATEC, 17 Rue des Martyrs, F38054 Grenoble (France); Defaye, E.; Suhm, A.; Fribourg-Blanc, E.; Aied, M. [CEA, LETI, MINATEC, 17 Rue des Martyrs, F38054 Grenoble (France); Zhu, J. L.; Xiao, D. Q.; Zhu, J. G. [Department of Materials Science, Sichuan University, Chengdu 610064 (China)

    2010-05-15

    PbO-MgO-Nb{sub 2}O{sub 5}-TiO{sub 2} (PMNT) pyrochlore thin films were prepared on Pt-coated silicon substrates by radio-frequency magnetron sputtering and postdeposition annealing method. Very interestingly, these pyrochlore-structured PMNT thin films exhibited ultralow dielectric losses, with a typical loss tangent as low as 0.001, and relatively high dielectric constants, typically {epsilon}{sub r{approx}}170. It was found that the relative permittivity slightly but continuously increased upon cooling without any signature of a structural phase transition, displaying a quantum paraelectriclike behavior; meanwhile, the PMNT pyrochlore thin films did not show any noticeable dielectric dispersion in the real part of permittivity over a wide temperature range (77-400 K). Their dielectric responses could, however, be efficiently tuned by applying a dc electric field. A maximum applied bias field of 1 MV/cm resulted in a {approx}20% tunability of the dielectric permittivity, giving rise to a fairly large coefficient of the dielectric nonlinearity, {approx}2.5x10{sup 9} J C{sup -4} m{sup -5}. Moreover, the PMNT pyrochlore films exhibited superior electrical insulation properties with a relatively high breakdown field (E{sub breakdown{approx}}1.5 MV/cm) and a very low leakage current density of about 8.2x10{sup -7} A/cm{sup 2} obtained at an electric field intensity as high as 500 kV/cm.

  9. Static properties and moisture content properties of polyester fabrics modified by plasma treatment and chemical finishing

    NASA Astrophysics Data System (ADS)

    Kan, C. W.; Yuen, C. W. M.

    2008-01-01

    Low temperature plasma treatment has been conducted in textile industry and has some success in the dyeing and finishing processes. In this paper, an attempt was made to apply low temperature plasma treatment to improve the anti-static property of polyester fabric. The polyester fabrics were treated under different conditions using low temperature plasma. An Orthogonal Array Testing Strategy was employed to determine the optimum treatment condition. After low temperature plasma treatment, the polyester fabrics were evaluated with different characterisation methods. Under the observation of scanning electron microscope, the surface structure of low temperature plasma-treated polyester fabric was seriously altered. This provided more capacity for polyester to capture moisture and hence increase the dissipation of static charges. The relationship between moisture content and half-life decay time for static charges was studied and the results showed that the increment of moisture content would result in shortening the time for the dissipation of static charges. Moreover, there was a great improvement in the anti-static property of the low temperature plasma-treated polyester fabric after comparing with that of the polyester fabric treated with commercial anti-static finishing agent.

  10. Structural, vibrational, and dielectric properties of Ruddlesden-Popper Ba2ZrO4 from first principles

    NASA Astrophysics Data System (ADS)

    Louis, Lydie; Nakhmanson, Serge M.

    2015-04-01

    Using first-principles computational techniques, we have investigated the structural, vibrational, and dielectric properties of a Ruddlesden-Popper-type layered oxide Ba2ZrO4 subjected to a wide range of biaxial strains emulating epitaxial thin-film environment. Under compressive strains, this compound experiences an incommensurate distortion characterized by planar displacements of individual perovskite slabs away from their high symmetry positions. On the other hand, under increasing epitaxial tension, the original centrosymmetric structure becomes unstable—first, with respect to antiferrodistortive oxygen cage rotations and then also with respect to in-plane polar distortions. Both the incommensurate-to-commensurate and the nonpolar-to-polar phase transformations are accompanied by anomalies of the static dielectric response, however, only in the latter case a divergence of the in-plane dielectric constant is observed. Remarkably, even after the transition into the ferroelectric state (with polarization of up to 0.12 C/m 2 at 3.5% tension) dielectric permittivity of Ba2ZrO4 remains unusually high, which is explained by an emergence of a Goldstone-like excitation in the system manifested through an in-plane libration of the polarization vector. Since Ba2ZrO4 displays a yet poorly understood tendency to absorb small molecules, such as water and CO2, acquiring better insights into the physical underpinnings of its behavior can produce more efficient functional materials for applications in advanced technologies for carbon sequestration.

  11. Microwave Dielectric Properties of Soil and Vegetation and Their Estimation From Spaceborne Radar

    NASA Technical Reports Server (NTRS)

    Dobson, M. Craig; McDonald, Kyle C.

    1996-01-01

    This paper is largely tutorial in nature and provides an overview of the microwave dielectric properties of certain natural terrestrial media (soils and vegetation) and recent results in estimating these properties remotely from airborne and orbital synthetic aperture radar (SAR).

  12. Property Specification and Static Verification of UML Models Igor Siveroni, Andrea Zisman and George Spanoudakis

    E-print Network

    Weyde, Tillman

    Property Specification and Static Verification of UML Models Igor Siveroni, Andrea Zisman,a.zisman,gespan}@soi.city.ac.uk Abstract We present a Static Verification Tool (SVT), a system that performs static verification on UML models composed of UML class and state machine diagrams. Additionally, the SVT allows the user to add

  13. Electrical Conduction and Dielectric Properties of Biodegradable Plastics

    NASA Astrophysics Data System (ADS)

    Shinyama, Katsuyoshi; Fujita, Shigetaka

    We examined the electrical conduction and dielectric properties as well as thermal analysis of polylactic acid (PLA) that is biodegradable plastics. From the results of thermal analyses, it was found that the glass transition temperature (Tg) of PLA was about 60°C and the melting point (Tm) was about 166°C. For the temperature dependence of current density (J), J of PLA became smaller than LDPE, PP and Polyester in the temperature from room temperature to 90°C. However, when sample became 90°C or the higher, J of PLA became larger than other plastics. On the other hand, as a result of measuring J of the same sample again, it became small. For the relative permittivity (?r') indicated intermediate values between that of polyester and those of LDPE and PP.

  14. Structural and dielectric properties of energetically deposited hafnium oxide films

    NASA Astrophysics Data System (ADS)

    Murdoch, B. J.; McCulloch, D. G.; Partridge, J. G.

    2014-12-01

    Amorphous hafnium oxide films, energetically deposited at room temperature from a filtered cathodic vacuum arc (FCVA) onto Si substrates, exhibit low current leakage (11 ?A cm?2 in an electric field of 100 kV cm?1), a dielectric constant (k) of 17 and a refractive index exceeding 2.1 over the visible spectrum. Cross-sectional transmission electron microscopy, energy-dispersive x-ray spectroscopy and electron energy loss spectroscopy revealed an amorphous microstructure and higher film density when compared with HfO2 deposited by reactive direct-current magnetron sputtering. The superior properties and higher density of the FCVA HfO2 are attributed to the elevated energy of the depositing flux.

  15. Report Title: Mapping of Reservoir Properties and Facies Through Integration of Static and Dynamic Data

    E-print Network

    Reynolds, Albert C.

    Report Title: Mapping of Reservoir Properties and Facies Through Integration of Static and Dynamic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 HISTORY MATCHING OF FACIES DISTRIBUTIONS 69 Background

  16. Characterization of dielectric properties of nanocellulose from wood and algae for electrical insulator applications.

    PubMed

    Le Bras, David; Strømme, Maria; Mihranyan, Albert

    2015-05-01

    Cellulose is one of the oldest electrically insulating materials used in oil-filled high-power transformers and cables. However, reports on the dielectric properties of nanocellulose for electrical insulator applications are scarce. The aim of this study was to characterize the dielectric properties of two nanocellulose types from wood, viz., nanofibrillated cellulose (NFC), and algae, viz., Cladophora cellulose, for electrical insulator applications. The cellulose materials were characterized with X-ray diffraction, nitrogen gas and moisture sorption isotherms, helium pycnometry, mechanical testing, and dielectric spectroscopy at various relative humidities. The algae nanocellulose sample was more crystalline and had a lower moisture sorption capacity at low and moderate relative humidities, compared to NFC. On the other hand, it was much more porous, which resulted in lower strength and higher dielectric loss than for NFC. It is concluded that the solid-state properties of nanocellulose may have a substantial impact on the dielectric properties of electrical insulator applications. PMID:25885570

  17. Dielectric and electro-optical properties of a photosensitive liquid crystal

    Microsoft Academic Search

    Y. Boussoualem; M. Ismaili; J. M. Buisine; C. Binet; G. Joly; H. T. Nguyen

    2009-01-01

    The temperature dependencies of the dielectric and electro-optical properties of a pure photo-ferroelectric liquid crystal have been investigated, in the chiral smectic C (SmC*) phase, with and without ultraviolet (UV) illumination. The SmC* dielectric Goldstone mode characteristics, the spontaneous polarization, the tilt angle and the rotational viscosity are affected by UV irradiation. Under increasing UV light intensities the dielectric strength

  18. A percolation cluster model of the temperature dependent dielectric properties of hydrated proteins

    Microsoft Academic Search

    Phe Man Suherman; Geoff Smith

    2003-01-01

    This study investigates the temperature dependence of the low frequency dielectric properties (0.1 Hz-1 MHz) of hydrated globular proteins (namely, ovalbumin, lysozyme and pepsin). The study aims to reveal the mechanisms of water-protein interaction from the dielectric response of these model proteins. Two principle dielectric responses were observed for each hydrated protein, namely, an anomalous low frequency dispersion and a

  19. Dielectric Properties of Lead Monoxide Filled Unsaturated Polyester Based Polymer Composites

    NASA Astrophysics Data System (ADS)

    Harish, V.; Kumar, H. G. Harish; Nagaiah, N.

    2011-07-01

    Lead monoxide filled isophthalate resin particulate polymer composites were prepared with different filler concentrations and investigated for physical, thermal, mechanical and gamma radiation shielding characteristics. This paper discusses about the dielectric properties of the composites. The present study showed that the dielectric constant (?'), dielectric loss (??) and ac conductivity (?ac) of isopthalate based unsaturated polyester resin increases with the increase in wt% PbO filler in polymer matrix.

  20. Magnetic, dielectric, and magneto-dielectric properties of rare-earth-substituted Aurivillius phase Bi?Fe?.?Co?.?Ti?O??

    SciTech Connect

    Zuo, X. Z.; Yang, J., E-mail: jyang@issp.ac.cn; Yuan, B.; Tang, X. W.; Zhang, K. J.; Zhu, X. B.; Song, W. H.; Dai, J. M., E-mail: jmdai@issp.ac.cn [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); Song, D. P. [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); University of Science and Technology of China, Hefei 230026 (China); Sun, Y. P. [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); University of Science and Technology of China, Hefei 230026 (China); High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei 230031 (China)

    2014-10-21

    We investigate the magnetic, dielectric, and magnetodielectric properties of rare-earth-substituted Aurivillius phase Bi?Fe?.?Co?.?Ti?O??. The room-temperature ferromagnetic behavior is observed in all samples, and the rare-earth-substituted samples exhibit an enhanced magnetization. The weak ferromagnetism can be ascribed to the spin canting of the antiferromagnetic coupling of the Fe-based and Co-based sublattices via Dzyaloshinsky-Moriya interaction. The dielectric loss of all samples exhibits two dielectric relaxation peaks corresponding to two different relaxation mechanisms. One relaxation process with E{sub a}=0.5 eV is related to the hoping process of oxygen vacancies and the other one with E{sub a}=1.6 eV can be ascribed to the intrinsic conduction. The Gd-doped sample exhibits a remarkable magnetodielectric effect (9.4%) at RT implying this Aurivillius phase may be the potential candidate for magnetodielectric applications.

  1. A novel method for determination of dielectric properties of materials using a combined embedded modulated scattering and near-field microwave techniques-Part II: dielectric property recalculation

    Microsoft Academic Search

    Dana Hughes; Reza Zoughi

    2005-01-01

    The use of combined embedded modulated scattering technique and near-field microwave nondestructive testing tech- niques is investigated as a novel method for evaluating the dielectric properties of a material. The forward formulation for determining the reflection coefficient at the aperture of a waveguide radiating into a dielectric half-space in which a PIN diode-loaded dipole (i.e., modulated scattering technique probe) is

  2. Testing techniques for determining static mechanical properties of Pneumatic tires

    NASA Technical Reports Server (NTRS)

    Dodge, R. N.; Larson, R. B.; Clark, S. K.; Nybakken, G. H.

    1974-01-01

    Fore-aft, lateral, and vertical spring rates of model and full-scale pneumatic tires were evaluated by testing techniques generally employed by industry and various testing groups. The purpose of this experimental program was to investigate what effects the different testing techniques have on the measured values of these important static tire mechanical properties. The testing techniques included both incremental and continuous loadings applied at various rates over half, full, and repeated cycles. Of the three properties evaluated, the fore-aft stiffness was demonstrated to be the most affected by the different testing techniques used to obtain it. Appreciable differences in the fore-aft spring rates occurred using both the increment- and continuous-loading techniques; however, the most significant effect was attributed to variations in the size of the fore-aft force loop. The dependence of lateral stiffness values on testing techniques followed the same trends as that for fore-aft stiffness, except to a lesser degree. Vertical stiffness values were found to be nearly independent of testing procedures if the nonlinear portion of the vertical force-deflection curves is avoided.

  3. Electroactive fluorinate-based polymers: Ferroelectric and dielectric properties

    NASA Astrophysics Data System (ADS)

    Yu, Zhi; Ang, Chen

    2004-12-01

    The dielectric, ferroelectric, and electroactive strain behavior of poly(vinylidene fluoride-trifluoroethylene) copolymers and poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) terpolymers is studied in a wide temperature and frequency range. The dielectric response from two dielectric polarization processes, modes A(A') and B, and the dielectric-background contribution can be identified for these polymers by using the Cole-Cole plot method. Therefore physically reasonable parameters are obtained by fitting the relaxation time to the Vogel-Fulcher relation. On the other hand, the dielectric relaxation step and high strain decrease simultaneously with decreasing temperature; this indicates that the dielectric relaxation process and high strain behavior are strongly correlated. The electron-irradiation effect in copolymers and the monomer effect in terpolymers are discussed.

  4. An In-Situ Measurement Technique for Through-Plane Thermal Properties of Thin Dielectric Films

    Microsoft Academic Search

    Thomas C. Hodge; Sue Ann Bidstrup; Paul A. Kohl; J. B. Lee; M. G. Allen

    1994-01-01

    In MCM-D applications, interlayer dielectrics separate and insulate metal conductors to form a threedimensional interconnection structure. Due to the three-dimensional nature of these structures, the electrical and mechanical properties of the dielectric materials must be known in all directions for proper device design. The most commonly used polymer in microelectronics, polyimide, exists in formulations which have been shown to have

  5. ANISOTROPY IN THERMAL, ELECTRICAL AND MECHANICAL PROPERTIES OF SPIN-COATED POLYMER DIELECTRICS

    E-print Network

    . Similarly, direct measurement of in-plane dielectric properties of in-situ, thin polymer films is difficult frequencies. This work proposes two in-situ measurement techniques capable of measuring through- plane CTE of insulating thin films. The first technique is based on in-situ dielectric measurements utilizing two

  6. TEMPERATURE-DEPENDENT BEHAVIOR OF DIELECTRIC PROPERTIES OF BOUND WATAER IN GRAIN AT MICROWAVE FREQUENCIES.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dielectric behavior of bound water in grain was investigated through measurement of the dielectric properties of hard red winter wheat at microwave frequencies over a wide temperature range between –80 degrees C and +10 degrees C. Measurements were performed in free space between 2 and 18 GHz on tw...

  7. Effect of "Natural" Water and "Added" Water on Dielectric Properties of Shelled Corn at Microwave Frequencies

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dielectric properties of samples of shelled corn of “natural” water content and those prepared by adding water were measured in free space at microwave frequencies and room temperature of 23 oC. Results of measurements of attenuation, phase shift and dielectric constant and loss factor at 6 GHz show...

  8. The effect of geometry and surface morphology on the optical properties of metal-dielectric systems

    Microsoft Academic Search

    Keisuke Hasegawa

    2008-01-01

    We analyze the effect of geometry and surface morphology on the optical properties of metal-dielectric systems. Using both analytical and numerical modeling, we study how surface curvature affects the propagation of surface plasmon polaritons (SPPs) along a metal-dielectric interface. We provide an intuitive explanation for how the curvature causes the phase front to distort, causing the SPPs to radiate their

  9. Effect of cenosphere on dielectric properties of low density polyethylene

    NASA Astrophysics Data System (ADS)

    Sharma, Janu; Chand, Navin; Bapat, M. N.

    2012-01-01

    Dielectric characterization of cenosphere filled low density polyethylene composites is reported in this paper. Cenosphere filled low density polyethylene (LDPE) composites with inhomogeneous dispersions of cenosphere were prepared and dielectric measurements have been performed on these composites in the temperature range 34-110 °C in the frequency range 1-10 kHz. The dielectric constants of the composites with filler concentrations 0%, 10%, 15% and 20 vol.% were measured. Effect of temperature and frequency variations on dielectric constant (??), dissipation factor (tan ?) and a.c. conductivity (?a.c.) was also determined. The frequency dependent dielectric and conductivity behaviour of flyash cenosphere filled low density polyethylene (LDPE) polymer composites have been studied. Appearance of peak in the dielectric loss curves for all the concentrations confirms the presence of relaxing dipoles in the cenosphere/LDPE composites. The effect of filler distribution on the dielectric constant is examined and the observed differences are attributed to the differences in two kinds of interfaces present: one formed between the touching cenosphere particles and the other formed between LDPE and cenosphere. With the increase of cenosphere content dielectric constant decreased gradually. Maxwell-Garnett approximation fairly fits for the dielectric data obtained experimentally for these composites.

  10. Fire safety properties of some transformer dielectric liquids

    SciTech Connect

    Lipowitz, J.

    1982-01-01

    This paper reviews the fire hazard properties of some transformer fluids of reduced flammability. Fluids examined include a silicone (polydimethylsiloxane), a high molecular weight aliphatic hydrocarbon and a polyalphaolefin. Fire hazard properties determined include ease of ignition, flame spread, fire growth and rate of heat release (large scale pool burns), rate of smoke evolution, fire-gas and smoke toxicity, and extinguishment behaviour. Large, static pool burns performed to simulate a 'worst case' scenario for a catastrophic transformer failure. The effect of ignition method and pool diameter on fire hazard properties is presented. Results clearly show the beneficial effect of silica ash formation on the surface of a burning silicone transformer fluid. The white, reflective ash layer effectively shields the fluid beneath from energy feedback by the flame. This effect leads to a substantially lower fire hazard for the silicone than is found for the hydrocarbon fluids, which do not form protective ash or char layers. The silicones demonstrate a lower degree of hazard than the hydrocarbons in all of the fire properties examined.

  11. Dielectric and electroactive strain properties of poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) terpolymers

    NASA Astrophysics Data System (ADS)

    Yu, Zhi; Ang, Chen; Cross, L. E.; Petchsuk, A.; Chung, T. C.

    2004-03-01

    The dielectric and electroactive strain properties of the poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) terpolymers with two different concentrations of chlorotrifluoroethylene (CTFE) have been studied down to cryogenic temperatures. The increase in the CTFE concentration shifts slightly the temperature where the dielectric constant maximum occurs to a lower temperature. High electroactive strain (˜1%) is obtained at room temperature for both compositions; however, the strain level decreases quickly with decreasing temperature. The dielectric relaxation process occurs for both compositions in the temperature range of 220 to 350 K, below which the dielectric constant decreases quickly to an "intrinsic" value (˜2.5). The similar variation tendency of the strain and the dielectric constant as a function of temperature indicates a close correlation between the dielectric behavior and strain activity.

  12. Small-signal ac response of dielectric materials containing static space-charge fields: Application to ionic conductors and MIS structures

    Microsoft Academic Search

    John A. Moriarty

    1981-01-01

    An efficient and quantitatively accurate scheme for obtaining the small-signal ac response of dielectric materials containing static space-charge fields near their boundaries is developed in the context of a general linear-response formalism. The technique improves and greatly extends the earlier method of Hoyen etal. used to treat space-charge-limited transport in the ionic conductor AgCl. The general formalism is here implemented

  13. Dielectric properties of Ge2Sb2Te5 phase-change films

    NASA Astrophysics Data System (ADS)

    Prokhorov, E.; Gervacio-Arciniega, J. J.; Luna-Bárcenas, G.; Kovalenko, Y.; Espinoza-Beltrán, F. J.; Trápaga, G.

    2013-03-01

    The static (?s) and high-frequency (??) dielectric constants of amorphous and NaCl-type crystalline Ge2Sb2Te5 were measured and the relaxation effects in films were studied using impedance spectroscopy. On the basis of a simple method that allows obtaining the dielectric constant in the low resistivity planar structure, static and high frequency dielectric constants and their temperature dependencies were calculated in both phases. A surprising value of ?s ? 750 in crystalline films was obtained, but the effective dielectric constant, ?eff, estimated from the Maxwell-Wagner effective medium model, is significantly lower (?eff ? 34.9). Such a high value of ?s obtained by electrical impedance measurements has been explained by Maxwell-Wagner relaxation, the separation of charges at the interface between grains and grain boundaries. Additionally, three relaxation processes (alpha, beta, and Ohmic relaxation) were observed in the amorphous phase and four relaxations (dipolar relaxation of grains, Ohmic relaxation of grains, dipolar relaxation of grain boundaries, and Maxwell-Wagner relaxation) were observed in the crystalline phase. From these results, a new rule for the selection of materials for optical phase-change data storage is proposed: polycrystalline films must have a high volume fraction of grain boundaries. This requirement increases the effective dielectric constant and the reflectance contrast between amorphous and crystalline phases.

  14. Measuring the dielectric properties of soil-organic mixtures using coaxial impedance dielectric reflectometry

    NASA Astrophysics Data System (ADS)

    Francisca, Franco M.; Montoro, Marcos A.

    2012-05-01

    Contamination of soils with non-aqueous phase liquids (NAPLs) is frequently produced by accidental spills and storage tanks or pipes leakage. The main goals dealing with soil and groundwater contamination include determining the extension of the affected zone, monitoring the contaminant plume and quantifying the pollution degree. The objective of this work is to evaluate the potential of dielectric permittivity measurements to detect the presence of NAPLs in sands. Tested samples were fine, medium, coarse and silty sand with different volumetric contents of water and paraffin oil. The dielectric permittivity was measured by means of a Coaxial Impedance Dielectric Reflectometry method in specimens with either known fluid content or at different stages during immiscible displacement tests. A simplified method was developed to quantify the amount of oil from dielectric permittivity measurements and effective mixture media models. Obtained results showed that groundwater contamination with NAPL and the monitoring of immiscible fluid displacement in saturated porous media can be clearly identified from dielectric measurements. Finally, very accurate results can be obtained when computing the contamination degree with the proposed method in comparison with the real volumetric content of NAPL (r2 > 90%).

  15. Dielectric and electromechanical properties of barium and zirconium co-doped sodium bismuth titanate

    E-print Network

    Sheets, Sossity A. (Sossity Amber), 1973-

    2000-01-01

    Compositional exploration was conducted within the alkaline bismuth titanate system by doping on the A- and B- sites with Ba?² and Zr??, respectively. Results on the phase, dielectric and electromechanical properties of ...

  16. Enhanced dielectric properties from barium strontium titanate films with strontium titanate buffer layers

    E-print Network

    Alpay, S. Pamir

    Enhanced dielectric properties from barium strontium titanate films with strontium titanate buffer in their PE state. One of the leading material candidates for tunable materials is barium strontium titanate

  17. Effects of thickness on the piezoelectric and dielectric properties of lead zirconate titanate thin films

    E-print Network

    Sottos, Nancy R.

    Effects of thickness on the piezoelectric and dielectric properties of lead zirconate titanate thin Lead zirconate titanate PZT thin films with a Zr/Ti ratio of 52/48 were deposited on platinized silicon

  18. Dielectric Properties of Two-Phase Mixture Ceramics Composed of Rutile and Its Compounds

    Microsoft Academic Search

    Kiyoshi Haga; Tsuyoshi Ishii; Jin-ichi Mashiyama; Takuro Ikeda

    1992-01-01

    Dielectric properties of two-phase mixture systems including rutile (TiO2) have been investigated. One of its binary compounds---MnTiO3, ZnTiO3, PbTiO3 and Al2TiO5-was chosen as the second component. Dielectric constants \\\\varepsilonr and their temperature coefficients tau\\\\varepsilon were first examined at 1 MHz. Dielectric properties in the microwave frequency region were measured in the TE011 mode of a cylindrical specimen. The temperature coefficient

  19. Addendum: Improvement in photoconductor film properties by changing dielectric layer structures Addendum: Improvement in photoconductor film properties by changing dielectric layer structures

    NASA Astrophysics Data System (ADS)

    Kim, S.; Oh, K.; Lee, Y.; Jung, J.; Cho, G.; Jang, G.; Cha, B.; Park, J.; Nam, S.

    2011-02-01

    In recent times, digital X-ray detectors have been actively applied to the medical field; for example, digital radiography offers the potential of improved image quality and provides opportunities for advances in medical image management, computer-aided diagnosis and teleradiology. In this study, two candidate materials (HgI2 and PbI2) have been employed to study the influence of the dielectric structure on the performance of fabricated X-ray photoconducting films. Parylene C with high permittivity was deposited as a dielectric layer using a parylene deposition system (PDS 2060). The structural and morphological properties of the samples were evaluated field emission scanning electron microscopy and X-ray diffraction. Further, to investigate improvements in the electrical characteristics, a dark current in the dark room and sensitivity to X-ray exposure in the energy range of general radiography diagnosis were measured across the range of the operating voltage. The electric signals varied with the dielectric layer structure of the X-ray films. The PbI2 film with a bottom dielectric layer showed optimized electric properties. On the other hand, in the case of HgI2, the film with a top dielectric layer showed superior electric characteristics. Further, although the sensitivity of the film decreased, the total electrical efficiency of the film improved as a result of the decrease in dark current. When a dielectric layer is deposited on a photoconductor, the properties of the photoconductor, such as hole-electron mobility, should be considered to improve the image quality in digital medical imaging application. In this study, we have thus demonstrated that the use of dielectric layer structures improves the performance of photoconductors

  20. Effect of powder purity and second phases on the dielectric properties of lead magnesium niobate ceramics

    SciTech Connect

    Chen, J.; Gorton, A.; Chan, H.M.; Harmer, M.P.

    1986-12-01

    The dielectric properties of lead magnesium niobate ceramics have been studied as a function of powder purity and microstructure. Starting powder purity was shown to have a pronounced effect on the resultant dielectric properties. Values of K/sub max/ as high as 20 000 were obtained using starting powders of exceptionally high purity (99.999%), despite the formation of a pyrochlore phase. The pyro-chlore phase formed as large isolated grains in the microstructure.

  1. Dielectric properties of residual water in amorphous lyophilized mixtures of sugar and drug

    Microsoft Academic Search

    R. El Moznine; G. Smith; E. Polygalov; P. M. Suherman; J. Broadhead

    2003-01-01

    Dielectric relaxation spectroscopy was used to investigate the properties of residual water in lyophilized formulations of a proprietary tri-phosphate drug containing a sugar (trehalose, lactose or sucrose) or dextran. The dielectric properties of each formulation were determined in the frequency range (0.1 Hz-0.1 MHz) and temperature range (30°C-Tg). The temperature dependence of the relaxation times for all samples showed Arrhenuis

  2. Investigation of Scattering Property for An Anisotropic Dielectric Circular Cylinder

    E-print Network

    Li, Y-L

    2010-01-01

    Utilizing the scales theory of electromagnetic theory, the anisotropic dielectric material is reconstructed into an isotropic medium. The analytic expressions of scattering field and the scattering breadth for an anisotropic material cylinder are first presented. Their validities are checked theoretically. The influences induced by the dielectric constant tensor etc. on the scattering breadth are simulated. The results show that the scatterings both in the forward direction and vertical direction to the incident direction are strong. The dielectric constant in the polarizing direction has a biggish effect on scattering field. The mechanism of results is presented

  3. Dielectric properties measurement of substrate and support materials

    NASA Astrophysics Data System (ADS)

    Wu, Te-Kao

    1990-08-01

    In this paper a fast and straightforward waveguide measurement technique is described for the determination of the dielectric constant and loss tangent of many commercially available materials. These dielectric materials include Cuflon, Teflon, Arlon's polyimides, Lockheed's ceramic foams, and Rogers Duroid materials. The effective dielectric constant and loss tangent of Hexsel's honeycomb material is also measured by this method and is compared to the predicted data obtained using the volume averaging theory. The accuracy and other features of this measurement technique are also discussed.

  4. Dielectric properties measurement of substrate and support materials

    NASA Technical Reports Server (NTRS)

    Wu, Te-Kao

    1990-01-01

    In this paper a fast and straightforward waveguide measurement technique is described for the determination of the dielectric constant and loss tangent of many commercially available materials. These dielectric materials include Cuflon, Teflon, Arlon's polyimides, Lockheed's ceramic foams, and Rogers Duroid materials. The effective dielectric constant and loss tangent of Hexsel's honeycomb material is also measured by this method and is compared to the predicted data obtained using the volume averaging theory. The accuracy and other features of this measurement technique are also discussed.

  5. Correlation between the dielectric properties and biological activities of human ex vivo hepatic tissue.

    PubMed

    Wang, Hang; He, Yong; Yan, Qingguo; You, Fusheng; Fu, Feng; Dong, Xiuzhen; Shi, Xuetao; Yang, Min

    2015-03-21

    Dielectric properties are vital biophysical features of biological tissues, and biological activity is an index to ascertain the active state of tissues. This study investigated the potential correlation between the dielectric properties and biological activities of human hepatic tissue with prolonged ex vivo time through correlation and regression analyses. The dielectric properties of 26 cases of normal human hepatic tissue at 10?Hz to 100?MHz were measured from 15?min after isolation to 24?h at 37?°C with 90% humidity. Cell morphologies, including nucleus area (NA) and alteration rate of intercellular area (ICAR), were analyzed as indicators of biological activities. Conductivity, complex resistivity, and NA exhibited opposing changes 1?h after isolation. Relative permittivity and ex vivo time were not closely correlated (p > 0.05). The dielectric properties measured at low frequencies (i.e. <1?MHz) were more sensitive than those measured at high frequencies in reflecting the biological activity of ex vivo tissue. Highly significant correlations were found between conductivity, resistivity and the ex vivo time (p < 0.05) as well as conductivity and the cell morphology (p < 0.05). The findings indicated that establishing the correlation between the dielectric properties and biological activities of human hepatic tissue is of great significance for promoting the role of dielectric properties in biological science, particularly in human biology. PMID:25761728

  6. Static and dynamic properties of critical fluctuations in lipid bilayers

    NASA Astrophysics Data System (ADS)

    Honerkamp-Smith, Aurelia Rose

    A current popular view in cell biology is that sub-micron, dynamic heterogeneity in lipid and protein composition arises within the plasma membranes of resting cells. Local changes in membrane composition may affect protein activity, which is sensitive to the lipid environment. We have observed dynamic heterogeneity in lipid membranes in the form of composition fluctuations near a miscibility critical point. In this thesis we quantitatively describe the dynamic and static properties of these fluctuations. We evaluate the temperature dependence of line tension between liquid domains and of fluctuation correlation lengths in lipid membranes in order to extract a critical exponent, nu. We obtain nu = 1.2 +/- 0.2, consistent with the Ising model prediction nu = 1. From probability distributions of pixel intensities in fluorescence images of membranes, we also extract an independent critical exponent of beta = 0.124 +/- 0.03, which is consistent with the Ising prediction of beta = 1/8. We have systematically measured the effective dynamic critical exponent z eff in a lipid membrane while cooling the system toward a critical point. We observe that zeff slightly increases from a value of roughly 2.6 as xi ? 0, to zeff = 3.0 +/- 0.15 at xi = 13 sm. Our measurements are consistent with the prediction that zeff ? 3.00 as T ? Tc for a 2-D system with conserved order parameter in contact with a bulk 3-D liquid. To our knowledge, no other systematic measurement of zeff with increasing xi exists for a 2-D system with conserved order parameter. We also report the solubility limit of several biologically relevant sterols in electroformed giant unilamellar vesicle membranes containing phosphatidylcholine (PC) lipids in ratios of 1:1:X DPPC:DOPC:sterol. We find solubility limits of cholesterol, lanosterol, ergosterol, stigmasterol, and beta-sitosterol using nuclear magnetic resonance.

  7. Intercellular adhesion: Modification by dielectric properties of the medium

    Microsoft Academic Search

    Gareth E. Jones

    1974-01-01

    Summary The low radio frequency dielectric constant of aqueous solutions of glycine, diglycine,d-sorbitol, Dextran and Ficoll were determined. These values were used to predict the dielectric constant of Hanks-199 tissue culture medium to which various concentrations of these compounds had been added. Single cell dispersions of two chick embryonic tissues, 7-day neural retina and 5-day limb bub, were prepared in

  8. Infrared Dielectric Properties of Low-stress Silicon Nitride

    NASA Technical Reports Server (NTRS)

    Cataldo, Giuseppe; Beall, James A.; Cho, Hsiao-Mei; McAndrew, Brendan; Niemack, Michael D.; Wollack, Edward J.

    2012-01-01

    Silicon nitride thin films play an important role in the realization of sensors, filters, and high-performance circuits. Estimates of the dielectric function in the far- and mid-IR regime are derived from the observed transmittance spectra for a commonly employed low-stress silicon nitride formulation. The experimental, modeling, and numerical methods used to extract the dielectric parameters with an accuracy of approximately 4% are presented.

  9. Dielectric properties of zinc oxide\\/low density polyethylene nanocomposites

    Microsoft Academic Search

    J. I. Hong; P. Winberg; L. S. Schadler; R. W. Siegel

    2005-01-01

    ZnO\\/low density polyethylene (LDPE) nanocomposites with either homogeneous or controlled inhomogeneous dispersions of ZnO nanoparticles were prepared. The dielectric constants of the composites with filler concentrations up to 40 vol.% were measured and compared with the dielectric constants of conventional submicron size ZnO filled LDPE composite. The filler particles were coated with silane coupling agents and mixed with LDPE to

  10. Effects of acidic functional groups on dielectric properties of sodium alginates and carrageenans in water.

    PubMed

    Tsubaki, Shuntaro; Hiraoka, Masanori; Hadano, Shingo; Okamura, Kei; Ueda, Tadaharu; Nishimura, Hiroshi; Kashimura, Keiichiro; Mitani, Tomohiko

    2015-01-22

    This study investigated the dielectric properties of sodium alginates and carrageenans in water at frequencies between 100 MHz and 20 GHz in regard to water-hydrocolloid interactions via acidic functional groups. Both sodium alginates and carrageenans showed conduction loss at lower frequencies and dielectric loss at higher frequencies. Reduction and desulfation of sodium alginates and carrageenans, which decreased the numbers of acidic functional groups, decreased their conduction loss. In addition, H(+)-form carrageenans showed the highest ionic conduction. Correlational analysis of dielectric properties and related physical parameters showed that the loss tangent (tan?) of the hydrocolloid solution was determined by the conductivity of the aqueous solution. Especially at pH below 2, strong H(+) conduction was associated with high tan? probably due to the Grotthuss mechanism. The molecular dynamics of free water and H(+), viscosity conditions were also suggested to be associated with dielectric property of water-hydrocolloid system. PMID:25439871

  11. The Dielectric Properties of Conducting Polypyrrole in the Far-Infrared

    NASA Astrophysics Data System (ADS)

    Phillips, Gregory C.

    The dielectric properties of conducting Polypyrole films were studied by performing reflection and transmission measurements using a Michelson interferometer in the Far Infrared. The experimental methods applied in sample preparation and data collection are described in detail. The complex index of refraction and optical conductivities were determined through the Fresnel equations. The conducting polymer films were characterized by the magnitude and dispersive nature of these dielectric quantities at different levels of doping. It is shown that the dielectric and electrical properties of conducting polypyrrole are readily tailorable. An attempt is made to fit the dielectric constants of the conducting polymer to Drude simple metal theory and the classical Debye model of polarizability. Electrical and thermal transport properties are compared to metals and systems with structural disorder such as amorphous semiconductors.

  12. Shear-induced particle rotation and its effect on electrorheological and dielectric properties in cellulose suspension

    NASA Astrophysics Data System (ADS)

    Misono, Y.; Negita, K.

    2004-12-01

    Electrorheological (ER) and dielectric properties under high electric fields were measured simultaneously on hydroxypropylcellulose suspension. When measuring these properties as a function of frequency of the electric field, we found a positive peak in each spectrum of the ER effect and the first-order dielectric permittivity while a negative one in the spectrum of the third-order dielectric permittivity with these peak frequencies nearly equal to (shearrate)/4? . Referring to the well-known results for the particle rotation in the sheared suspension, it is suggested that the observed peaks are due to shear-induced particle rotation and the rotation occurs even under high electric field. On the basis of these results, effects of the particle rotation on the ER and the dielectric properties are discussed.

  13. Electronic, dielectric and mechanical properties of MoS2/SiC hybrid bilayer: A first principle study

    NASA Astrophysics Data System (ADS)

    Sharma, Munish; Jamdagni, Pooja; Kumar, Ashok; Ahluwalia, P. K.

    2015-07-01

    The electronic, mechanical and dielectric properties of lateral MoS2/SiC heterobilayer are investigated using first principles calculations. Among various stacking conformations, the energetically favorable stackings namely AA2 and AB?1 have been considered in the present study. The band gap of the heterobilayer shows reduction as compared to constituent monolayers which also remains stacking dependent. The electronic band-gap is further tunable by applying mechanical strain and perpendicular electric field that rendered heterostructures from semiconductor to metal at critical value of applied strain/field. The stacking of heterobilayer strongly influence its mechanical properties e.g. ultimate tensile strength of considered two favorable stacking differ by more than 50%; the ultimate tensile strain of 17% and 21% respectively has been calculated for two different stackings. The static dielectric constant also shows tunability on heterostructuring the constituent monolayers as well as applying strain and field. These tunable properties of MoS2/SiC may be useful for the device applications at nanoscale.

  14. Radar properties of comets: Parametric dielectric modeling of Comet 67P/Churyumov-Gerasimenko

    NASA Astrophysics Data System (ADS)

    Heggy, Essam; Palmer, Elizabeth M.; Kofman, Wlodek; Clifford, Stephen M.; Righter, Kevin; Hérique, Alain

    2012-11-01

    In 2014, the European Space Agency’s Rosetta mission is scheduled to rendezvous with Comet 67P/Churyumov-Gerasimenko (Comet 67P). Rosetta’s CONSERT experiment aims to explore the cometary nucleus’ geophysical properties using radar tomography. The expected scientific return and inversion algorithms are mainly dependent on our understanding of the dielectric properties of the comet nucleus and how they vary with the spatial distribution of geophysical parameters. Using observations of Comets 9P/Tempel 1 and 81P/Wild 2 in combination with dielectric laboratory measurements of temperature, porosity, and dust-to-ice mass ratio dependencies for cometary analog material, we have constructed two hypothetical three-dimensional parametric dielectric models of Comet 67P’s nucleus to assess different dielectric scenarios of the inner structure. Our models suggest that dust-to-ice mass ratios and porosity variations generate the most significant measurable dielectric contrast inside the comet nucleus, making it possible to explore the structural and compositional hypotheses of cometary nuclei. Surface dielectric variations, resulting from temperature changes induced by solar illumination of the comet’s faces, have also been modeled and suggest that the real part of the dielectric constant varies from 1.9 to 3.0, hence changing the surface radar reflectivity. For CONSERT, this variation could be significant at low incidence angles, when the signal propagates through a length of dust mantle comparable to the wavelength. The overall modeled dielectric permittivity spatial and temporal variations are therefore consistent with the expected deep penetration of CONSERT’s transmitted wave through the nucleus. It is also clear that changes in the physical properties of the nucleus induce sufficient variation in the dielectric properties of cometary material to allow their inversion from radar tomography.

  15. Composition dependence of dielectric properties in Se100-xCux glassy alloys

    NASA Astrophysics Data System (ADS)

    Sharma, J.; Shrotriya, D.; Kumar, S.

    2015-06-01

    In this paper we report the composition dependent of dielectric properties in Se100-xCux (x = 0, 2, 4 and 6) glassy alloys. The temperature and frequency dependence of the dielectric constants and the dielectric losses in the above glassy systems in the frequency range (1k Hz-5 M Hz) and temperature range (300 K-350 K) have been measured. It has been found that dielectric constant and the dielectric loss both are highly dependent on frequency and temperature and also found to increase with increasing concentration of Cu in pure amorphous Se. The role of Cu, as an impurity in the pure a-Se glassy alloy, is also discussed in terms of electronegativity difference between the elements used in making the aforesaid glassy system. Apart from this, the results have been also correlated in terms of a dipolar model which considers the hopping of charge carriers over a potential barrier between charged defect states.

  16. Dielectric properties and microstructural characterization of cubic pyrochlored bismuth magnesium niobates

    NASA Astrophysics Data System (ADS)

    Zhang, Yuan; Zhang, Zhihao; Zhu, Xinhua; Liu, Zhiguo; Li, Yangyang; Al-Kassab, Talaat

    2014-05-01

    Cubic bismuth pyrochlores in the -MgO- system have been investigated as promising dielectric materials due to their high dielectric constant and low dielectric loss. Here, we report on the dielectric properties and microstructures of cubic pyrochlored (BMN) ceramic samples synthesized via solid-state reactions. The dielectric constant (measured at 1 MHz) was measured to be at room temperature, and the dielectric loss was as low as 0.001. X-ray diffraction patterns demonstrated that the BMN samples had a cubic pyrochlored structure, which was also confirmed by selected area electron diffraction (SAED) patterns. Raman spectrum revealed more than six vibrational models predicted for the ideal pyrochlore structure, indicating additional atomic displacements of the A and sites from the ideal atomic positions in the BMN samples. Structural modulations of the pyrochlore structure along the [110] and [ 121] directions were observed in SAED patterns and high-resolution transmission electron microscopy (HR-TEM) images. In addition, HR-TEM images also revealed that the grain boundaries (GBs) in the BMN samples were much clean, and no segregation or impure phase was observed forming at GBs. The high dielectric constants in the BMN samples were ascribed to the long-range ordered pyrochlore structures since the electric dipoles formed at the superstructural direction could be enhanced. The low dielectric loss was attributed to the existence of noncontaminated GBs in the BMN ceramics.

  17. Wave properties of surface polaritons in the dielectric-high-temperature superconductor-dielectric structure

    NASA Astrophysics Data System (ADS)

    Abramov, A. S.; Zolotovskii, I. O.; Sannikov, D. G.; Sementsov, D. I.

    2015-04-01

    The specific features of the surface polariton propagation in the dielectric-high-temperature superconductor-dielectric symmetric structure have been investigated in the temperature region T < T c /2, where the structure can be considered as non-absorbing. It has been shown that the dispersion curves contain two polariton branches, i.e., high-frequency and low-frequency ones, which correspond to symmetric and antisymmetric distributions of transverse components of the wave field. For the high-frequency branch, there is a propagation constant range where the group velocity and energy flux directions are opposite to the phase velocity direction. In this range, a significant deceleration of polariton waves is also observed.

  18. Dielectric properties of (Ba,Sr)TiO{sub 3} films by RF sputtering

    SciTech Connect

    Mikami, N.; Horikawa, T.; Makita, T.; Sato, K.; Kuroiwa, T.; Honda, T.; Watarai, H. [Mitsubishi Electric Corp. Semiconductor Research Lab., Tsukaguchi (Japan)

    1994-12-31

    The dielectric properties of (Ba,Sr)TiO{sub 3}(BST) thin films prepared by RF sputtering method, were investigated. Polycrystalline film structure and grain size were estimated by transmission electron microscopy (TEM) and Xray diffraction. The dielectric constant of BST films depends on their grain size rather than thickness of the film. A broad maximum in the temperature dependence of the dielectric constant of the films was observed, and Curie temperature was not clear. No hysteresis was observed in a D-E curve of the film at 77K.

  19. Dielectric properties of heterostructured BZT thin films prepared by sol–gel technique

    Microsoft Academic Search

    L. N. Gao; J. W. Zhai; X. Yao; Z. K. Xu

    2008-01-01

    In this work, we used the low loss and non-hygroscopic MgTiO3 (MT) for the fabrication of the Ba(Zr0.20Ti0.80)O3:MgTiO3 (BZT:MT) heterostructured thin films by sol–gel processing. The dielectric properties of heterostructured thin films were characterized by measuring the dielectric constant and dielectric loss as a function of temperature, applied electric field and frequency. As a result, both MT and BZT remained

  20. Optical and dielectric properties of L-methionine L-methioninium hydrogen maleate single crystal

    NASA Astrophysics Data System (ADS)

    Vasudevan, P.; Sankar, S.; Gokulraj, S.

    2013-02-01

    An organic nonlinear optical single crystal L-methionine L-methioninium hydrogen maleate has been grown by solution growth technique. It is confirmed from XRD data that the crystal belongs to monoclinic system with non-centrosymmetric space group P21. Photoluminescence study was carried out for the grown crystal and maximum emission occurs at 395 nm. Dielectric measurements were made for the frequency range from 100 Hz to 5 MHz. The lower value of dielectric constant and dielectric loss at higher frequencies reveal that the material possesses enhanced optical quality with lesser defects. Nonlinear optical property was confirmed by Kurtz and Perry technique.

  1. Dielectric and electret properties of nanoemulsion spin-on polytetrafluoroethylene films

    NASA Astrophysics Data System (ADS)

    Schwödiauer, Reinhard; Neugschwandtner, Gerhard S.; Bauer-Gogonea, Simona; Bauer, Siegfried; Rosenmayer, Tom

    2000-05-01

    Nanoemulsion polytetrafluoroethylene (nano-PTFE) is a promising low-dielectric-constant polymer, which can be prepared in thin-film form by spin-on techniques. Similarities and differences of the nano-PTFE material to the well-known class of PTFE polymers with respect to morphology and dielectric and electret characteristics are discussed. Nano-PTFE shows excellent dielectric properties up to 300 °C, and a charge stability that compares favorably with other members of the PTFE class. Nano-PTFE enlarges the family of PTFE materials and may become interesting for applications in microelectronics and miniaturized electret devices.

  2. Dielectric Properties of Two-Phase Mixture Ceramics Composed of Rutile and Its Compounds

    NASA Astrophysics Data System (ADS)

    Haga, Kiyoshi; Ishii, Tsuyoshi; Mashiyama, Jin-ichi; Ikeda, Takuro

    1992-09-01

    Dielectric properties of two-phase mixture systems including rutile (TiO2) have been investigated. One of its binary compounds—MnTiO3, ZnTiO3, PbTiO3 and Al2TiO5-was chosen as the second component. Dielectric constants \\varepsilonr and their temperature coefficients ?\\varepsilon were first examined at 1 MHz. Dielectric properties in the microwave frequency region were measured in the TE011 mode of a cylindrical specimen. The temperature coefficient of resonant frequency, ?f, of MnTiO3 was negative, and a zero coefficient was found at an intermediate composition x{=}0.13 in the (1-x) MnTiO3-xTiO2 system. In the PbTiO3-TiO2 system, zero ?\\varepsilon composition was confirmed at low frequencies, but composition modification trials aiming to make microwave dielectric measurements possible were unsuccessful throughout the entire system.

  3. Cross-linking effect on dielectric properties of polypropylene thin films and applications in electric energy storage

    Microsoft Academic Search

    Xuepei Yuan; T. C. Mike Chung

    2011-01-01

    A family of cross-linked polypropylene (x-PP) thin film dielectrics is systematically studied to understand the cross-linking effect on the dielectric properties. Evidently, the butylstyrene (BSt) cross-linkers increase both the dielectric constant (epsilo) and breakdown strength (E), without increasing energy loss. An x-PP dielectric, with 3.65 mol % BSt cross-linkers, exhibits a V~3, which is independent of a wide range of

  4. Dielectric Properties of Carbon Black-Epoxy Resin Composites Studied with Impedance Spectroscopy

    Microsoft Academic Search

    M. E. Achour; A. Mdarhri; F. Carmona; F. Lahjomri; A. Oueriagli

    2008-01-01

    Dielectric properties of carbon black–epoxy resin composites were studied in the frequency range between 100 Hz and 15 MHz and over a temperature range 23–98°C. The results show that the composites exhibit, below the critical concentration, a dielectric relaxation phenomenon due to dipolar groups of epoxy resin and to interfacial polarization. This relaxation phenomenon was modeled by the Cole–Cole model.

  5. Crystal Growth, Dielectric and Polarization Reversal Properties of Bi4Ti3O12 Single Crystal

    Microsoft Academic Search

    Yoichiro Masuda; Hiroshi Masumoto; Akira Baba; Takashi Goto; Toshio Hirai

    1992-01-01

    A Bi2O3-TiO2 phase diagram was determined using differential thermal analysis (DTA) apparatus. Bi4Ti3O12 (BIT) micalike single crystals grown by a flux method were clear and slightly grayish in color. Ferroelectric and dielectric properties of BIT crystals were observed from measurements of electric displacement vs electric field hysteresis loops and the dielectric constant. Also, the polarization switching characteristics of BIT crystals

  6. On Artificial Magneto-Dielectric Loading for Improving the Impedance Bandwidth Properties of Microstrip Antennas

    Microsoft Academic Search

    Pekka Ikonen; Stanislav Maslovski; Constantin Simovski; Sergei Tretyakov

    In the present paper we discuss the effect of artificial magneto-dielectric substrates on the impedance bandwidth properties of microstrip antennas. The results found in the literature for antenna miniaturization using magnetic or magneto-dielectric substrates are revised, and discussion is addressed to the practically realizable artificial magnetic media operating in the microwave regime. Using a transmission-line model we, first, reproduce the

  7. Asymmetric surface dielectric barrier discharge in air at atmospheric pressure: electrical properties and induced airflow characteristics

    Microsoft Academic Search

    Jérôme Pons; Eric Moreau; Gérard Touchard

    2005-01-01

    The electrical properties of an asymmetric surface dielectric barrier discharge in atmospheric air have been investigated experimentally. The discharge is used for airflow production close to the dielectric surface, and the time-averaged flow velocity spatial profiles have been measured. Velocities of up to 3.5 m s-1 at heights of 1-2 mm are reached when filamentary discharges with current peaks up

  8. Dielectric properties of Fe(OH) 3 thin films formed at solution-gas interface

    Microsoft Academic Search

    P S Nikam; K A Pathan

    1994-01-01

    Dielectric properties of solution-gas interface-formed Fe(OH)3 thin-film capacitors (Al\\/Fe(OH)3\\/Al) of various thicknesses have been studied in the frequency range 10–106 Hz at various temperatures (300–443 K). Dielectric constant, ?, increases with increasing film thickness (d) and temperature (T) and decreases with increase of frequency (f). The loss factor (tan ?), showing pronounced minimum with frequency, increases with rise of temperature,

  9. Dielectric and conductivity properties of composite polyaniline/polyurethane network

    NASA Astrophysics Data System (ADS)

    Liang, C.; Gest, J.; Leroy, G.; Carru, J.-C.

    2013-09-01

    In this work, we present the dielectric characterization of polyaniline/polyurethane composite. The samples consisting of 0.5%, 1%, and 5% of polyaniline were deposited on glass fiber, and the measurements were performed in a frequency range of 20 Hz to 20 GHz. The results showed a dielectric relaxation strongly dependent on the concentration of polyaniline. This phenomenon is explained by a theoretical model. In this model, we assume that the alternative conductivity of the polymer network systems is due to conducting clusters whose lengths followed a Gaussian distribution. Depending on their size and the frequency of the excitation signal, the clusters showed a resistive or capacitive effect.

  10. Dielectric property measurement of zirconia fibers at high temperatures

    SciTech Connect

    Vogt, G.J. [Los Alamos National Lab., NM (United States); Tinga, W.R. [Univ. of Alberta, Edmonton (Canada). Dept. of Electrical Engineering; Plovnick, R.H. [3M Ceramic Technology Center, St. Paul, MN (United States)

    1995-05-01

    Using a self-heating, electronically tunable microwave dielectrometer, the complex dielectric constant of zirconia-based filaments was measured at 915 MHz from 350{degrees} to 1100{degrees}C. This fibrous material cools rapidly to near room temperature within several seconds due to a large surface area to volume ratio. Such rapid sample cooling necessitates the use of a self-heating technique to measure the complex dielectric constant at temperatures up to 1100{degrees}C. Sample temperature was measured with optical fiber thermometry. The effect of sample temperature measurement on data accuracy is discussed.

  11. Temperature effects on soil dielectric properties measured at 50 MHz

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In recent years a number of soil water monitoring instruments have been developed and made commercially available. These instruments determine soil water content from a sensor signal from which soil dielectric permittivity is resolved, which is a complex number and composed of real and imaginary com...

  12. Dielectric properties of PET below its glass transition temperature

    Microsoft Academic Search

    Tatiana Pop; D. Iordache; A. Jonas

    1997-01-01

    Dielectric relaxation measurements on poly(ethylene terephthalate) (PET) samples of different microstructures (semicrystalline, amorphous, amorphous oriented), between 80 and 300 K for frequencies ranging from 102 to 105 Hz have been performed. The data pertaining to the ? relaxation of PET could be fitted to the Cole-Cole (CC) phenomenological equations, from which the relaxation strength, the average activation energies, and the

  13. Measuring Spectral Dielectric Properties Using Gated Time Domain Transmission Measurements

    Microsoft Academic Search

    R. Chawn Harlow; Eleanor J. Burke; Ty P. A. Ferre ´; John C. Bennett; W. James Shuttleworth

    2003-01-01

    at the canopy scale. Other common closed wave guide methods would require the construction of large, expen- A method to measure the frequency-dependent dielectric per- sive coaxial lines or wave guides. The objective of this mittivity of simple materials based on a time domain transmission technique is described. A vector network analyzer (VNA) was con- study is to examine the

  14. The Dielectric Properties of Water and Heavy Water

    Microsoft Academic Search

    C. H. Collie; J. B. Hasted; D. M. Ritson

    1948-01-01

    Measurements by a number of different methods of the dielectric constant and loss angle of water and heavy water at three widely separated wavelengths in the region of anomalous dispersion, ?=10 cm., 3 cm., 1.25 cm., are described. Results show that the Debye equations are exactly obeyed, there being a single time of relaxation varying with the temperature; the ratios

  15. Effect of La3+ Substitution on Electric, Dielectric and Magnetic Properties of Cobalt Nano-Ferrite

    NASA Astrophysics Data System (ADS)

    Kumar, Pawan; Singh, M.

    2011-07-01

    Ultrafine particles of CoLaxFe2-xO4 (x = 0, 0.20) were prepared by using co-precipitation method. X-ray diffraction studies show that the samples have cubic spinel structure and average crystallite size of x = 0 and x = 0.2 are 49.84 nm and 27.73 nm respectively. Dielectric and magnetic properties have been studied by impedance analyzer and magnetic properties of the ferrite system were studied using VSM respectively. La3+ ions modulate significantly the electric, dielectric and magnetic properties of cobalt spinel ferrites.

  16. Plant Water Stress Detection Using Radar: The Influence Of Water Stress On Leaf Dielectric Properties

    NASA Astrophysics Data System (ADS)

    van Emmerik, Tim; Steele-Dunne, Susan; Judge, Jasmeet; van de Giesen, Nick

    2015-04-01

    Recent research on an agricultural maize canopy has demonstrated that leaf water content can change considerably during the day and in response to water stress. Model simulations suggest that these changes have a significant impact on radar backscatter, particularly in times of water stress. Radar is already used for several vegetation and soil monitoring applications, and might be used for water stress detection in agricultural canopies. Radar observations of the land surface are sensitive because it results in two-way attenuation of the reflected signal from the soil surface, and vegetation contributes to total backscatter from the canopy itself. An important driver that determines the impact of vegetation on backscatter is the dielectric constant of the leaves, which is primarily a function of their moisture content. Understanding the effects of water stress on the dynamics of leaf dielectric properties might shed light on how radar can be used to detect vegetation water stress. Previous studies have investigated the dielectric properties of vegetation. However, this has mainly been done using destructive sampling or in-vivo measurements of tree trunks. Unfortunately, few in-vivo measurements of leaf dielectric properties exist. This study presents datasets of in-vivo dielectric measurements of maize leaves, taken during two field experiments. One experiment was done using was done during a period of water stress, the other during a period without. Field measurements revealed a different vertical profile in dielectric properties for the period with and without water stress. During a period of increased water stress, the diurnal dynamics of leaves at different heights responded differently to a decrease in bulk moisture content. This study provides insight in the effect of water stress on leaf dielectric properties and water content, and highlights the potential use of radar for water stress detection in agricultural canopies.

  17. The dielectric properties of granular media saturated with DNAPL//water mixtures

    E-print Network

    Ajo-Franklin, Jonathan

    . Broadband dielectric measurements were performed using a time domain reflectometry (TDR) system coupled: Groundwater quality; 5109 Physical Properties of Rocks: Magnetic and electrical properties; 5194 Physical fully saturated with water and then subjected to an axial TCE injection until breakthrough was observed

  18. Dielectric properties of liquid ethanol. A computer simulation study Leonor Saiz

    E-print Network

    Saiz, Leonor

    dedicated to investigate the mole- cular origin of the different analyzed properties. © 2000 American is fundamental for a deep understanding of polar liquids. Computer simulations provide a suitable tool to analyze simulation stud- ies. In the case of alcohols, only the dielectric properties of liquid methanol2

  19. Dielectric properties of crystalline and amorphous transition metal oxides and silicates

    NASA Astrophysics Data System (ADS)

    Rignanese, Gian-Marco

    2004-03-01

    Until recently, silicon dioxide has been the dielectric of choice in integrated MOS devices. By 2004, the thickness of this insulating layer is expected to decrease to 1.0 nm to 1.5 nm (about five silicon atoms deep) precluding its effective use due to severe leakage problems. An alternative high-permittivity (high-k) gate dielectric is required. In this framework, transition metal oxides and silicates have attracted considerable attention as possible substitutes. Their dielectric properties constitute an issue of great practical relevance. In particular, it is highly desirable to develop a better understanding of how the permittivity is related to the underlying microstructure. This is the aim of the present work. Using first-principles calculations, we investigate the dielectric properties of group IVB transition metal (Ti, Zr, and Hf) oxides and silicates. We first study various crystalline phases for the oxides (cubic, tetragonal, and rutile) and the silicates (zircon). Then, the amorphous silicates are considered. We introduce a scheme which relates the dielectric constants to the local bonding of silicon and metal atoms. This scheme is based on the definition of parameters characteristic of the basic structural units formed by silicon and metal atoms and their nearest neighbors, and allows us to avoid heavy large-scale calculations, which are beyond current computational capabilities. Applied to amorphous Zr silicates, our scheme provides a good description of the measured dielectric constants, and highlights the role of sixfold coordinated metal atoms.

  20. Dielectric Properties of CaCu3Ti4-xMnxO12 Ceramics

    NASA Astrophysics Data System (ADS)

    Makcharoen, W.; Tontrakoon, J.; Thavornyutikarn, P.; Tunkasiri, T.

    2009-07-01

    This paper reports the dielectric properties of the Mn doped CaCu3Ti4O12 (CCTO) ceramics synthesized by the conventional solid-state reaction method. By partial Mn for Ti substitution, the dielectric loss was suppressed significantly while the dielectric constant (?r) still remained high. The compound CaCu3Ti3.76Mn0.24O12 exhibits a high ?r (>1200) and a low dielectric loss (<0.06 at room temperature). Furthermore, the ?r value of this material is reasonably independent of temperature. SEM micrographs show no impurity in the Mn doped CCTO ceramics, which exhibit dense microstructures without abnormal grains. This CaCu3Ti4-xMnxO12 system appears to be a promising candidate for capacitor applications.

  1. Comparison effects and dielectric properties of different dose methylene-blue-doped hydrogels.

    PubMed

    Yalç?n, O; Co?kun, R; Okutan, M; Öztürk, M

    2013-08-01

    The dielectric properties of methylene blue (MB)-doped hydrogels were investigated by impedance spectroscopy. The real part (?') and the imaginary part (?") of the complex dielectric constant and the energy loss tangent/dissipation factor (tan ?) were measured in the frequency range of 10 Hz to 100 MHz at room temperature for pH 5.5 value. Frequency variations of the resistance, the reactance, and the impedance of the samples have also been investigated. The dielectric permittivity of the MB-doped hydrogels is sensitive to ionic conduction and electrode polarization in low frequency. Furthermore, the dielectric behavior in high-frequency parts was attributed to the Brownian motion of the hydrogen bonds. The ionic conduction for MB-doped samples was prevented for Cole-Cole plots, while the Cole-Cole plots for pure sample show equivalent electrical circuit. The alternative current (ac) conductivity increases with the increasing MB concentration and the frequency. PMID:23799863

  2. Effects of Cobalt substitution on the dielectric properties of Li Zn ferrites

    NASA Astrophysics Data System (ADS)

    Soibam, Ibetombi; Phanjoubam, Sumitra; Sharma, H. B.; Sarma, H. N. K.; Laishram, Radhapiyari; Prakash, Chandra

    2008-12-01

    The dielectric properties of Li 0.4-0.5 xZn 0.2Co xFe 2.4-0.5 xO 4 ferrites with x varying from 0.0 to 0.1 in steps of 0.02 synthesized by the citrate precursor method have been investigated as a function of composition and temperature. Room temperature dielectric constant studied at 1 kHz showed a decrease with addition of Co 2+ ions. The variation of dielectric constant with temperature was studied at different frequencies, and an increase was observed as the temperature rises. For certain composition, at particular frequency resonance maxima could be observed in the dielectric constant versus temperature curve. The possible mechanisms responsible for the above behaviour are explained.

  3. Microwave dielectric properties of inorganic fullerene-like tungsten disulfide nanoparticles

    NASA Astrophysics Data System (ADS)

    Chang, Hong; Dimitrakis, Georgios; Xu, Fang; Yi, Chenbo; Kingman, Samuel; Zhu, Yanqiu

    2013-01-01

    The dielectric response of inorganic fullerene-like (IF) tungsten disulfide (WS2) nanoparticles prepared by a sulfidization reaction of WO3 nanoparticles has been investigated, against commercial platelet 2H-WS2 particles, using a cavity perturbation technique at microwave frequencies at temperatures ranging from 20 to 750 °C. The IF-WS2 nanoparticles showed both temperature and frequency dependent dielectric properties. The different dielectric behaviour between the IF-WS2 and 2H-WS2 can be attributed to the different conductivity and structure peculiar to the materials. The microstructure and thermal stability of the IF-WS2 and 2H-WS2 were thoroughly examined, to correlate with the resulting dielectric responses.

  4. Measurement of dielectric properties of subcutaneous fat with open-ended coaxial sensors

    NASA Astrophysics Data System (ADS)

    Alanen, Esko; Lahtinen, Tapani; Nuutinen, Jouni

    1998-03-01

    A three-layer model of stratum corneum, epidermis/dermis and subcutaneous fat has been developed for the capacitance of an open-ended coaxial line in contact with human skin. Applying the model, the electrical properties of subcutaneous fat can be calculated from skin dielectric measurements with three probes of different sizes. The three-layer model is based on a variational formula for the capacitance of the coaxial probe. An accurate approximation for the dielectric constant of the multilayer cutaneous structure is presented for the inverse problem of solving the dielectric constants of various layers. The method was tested at 300 MHz with breast cancer patients who often have radiotherapy-induced late alterations in the structure of subcutaneous fat due to the development of subcutaneous fibrosis. Measurements from 206 sites yielded a good agreement between the dielectric constant of subcutaneous fat and the clinical score for subcutaneous fibrosis.

  5. Internal and Interfacial Dielectric Properties of Cytochrome c from Molecular Dynamics in Aqueous Solution

    NASA Astrophysics Data System (ADS)

    Simonson, Thomas; Perahia, David

    1995-02-01

    The dielectric properties of proteins are central to their stability and activity. We use the Frohlich-Kirkwood theory of dielectrics to analyze two 1-ns molecular dynamics simulations of ferro- and ferricytochrome c in spherical droplets of 1400 water molecules. Protein and solvent are idealized as a series of concentric, spherical, dielectric media. Analysis results depend strongly on the treatment of the charged protein side chains at the protein/solvent interface. If charged side chains are viewed as part of the protein medium, then the protein dipole fluctuations are dominated by large, mutually uncorrelated, anisotropic, motions of the charged side chains. It is then incorrect to view the protein region as a single, homogeneous dielectric material. If one does take this view, estimates of the protein "dielectric constant" vary from 16 to 37, depending on the exact choice of model parameters. In contrast, if the charged portions of the charged side chains are viewed as part of the solvent medium, then theory and simulation are consistent: the protein dipole fluctuations excluding charged side chains are roughly those of a homogeneous, isotropic dielectric medium, with a dielectric constant of 4.7 ± 1.0 (ferro) or 3.4 ± 1.0 (ferri), in agreement with powder experiments. Statistical uncertainty and sensitivity to model parameters are small. Analysis of the radial dependence of the dipole fluctuations suggests that the inner half of the protein has a somewhat lower dielectric constant of 1.5-2, consistent with its biological function in electron transfer. These results suggest that Poisson-Boltzmann models could treat the protein bulk as a low-dielectric medium and the charged surface groups as part of the solvent region.

  6. Determination of Microwave Dielectric Properties of Materials Using a Unique Application of Embedded Modulated Scatterer Technique

    NASA Astrophysics Data System (ADS)

    Freiburger, G.; Zoughi, R.

    2006-03-01

    The embedded modulated scatterer technique has been investigated in the past as a means of determining the dielectric properties of a material of interest using an open-ended rectangular waveguide and an embedded PIN diode-loaded dipole probe. This technique has been further explored in a unique application utilizing the complex ratio of dynamic reflection coefficients for the two states of the modulated dipole probe. By utilizing this ratio, the calculation of dielectric properties becomes independent of measurement parameters such as distance, orientation, and location of the dipole probe relative to the waveguide radiator. This paper explores this unique application of the embedded modulated scatterer technique and presents both theoretical and experimental results for evaluating complex dielectric properties of materials.

  7. Diabetes mellitus effect on rat corneal dielectric properties.

    PubMed

    Olszewski, J; Marzec, E; Florek, E; Kulza, M

    2012-03-01

    In the course of the study, we carried out a dielectric examination to determine the effect of diabetes mellitus on the rat corneal function. Measurements were performed over the frequency range of 500 Hz-100 kHz in air and at the temperatures from 25 to 150°C. The frequency dependencies of the loss tangent for the healthy and the diabetic cornea exhibit two peaks at 2 kHz and 16 kHz in the ?-dispersion region. The amplitude of these both peaks is smaller for the diabetic cornea than that for the healthy one. The temperature dependencies of the loss tangent for the healthy and the diabetic cornea reveal ?-relaxation in the range of 30-70°C and 50-90°C, respectively. The present study exhibits that the dielectric spectroscopy is useful in detection of the effect of diabetes mellitus on the corneal molecular behavior. PMID:22136803

  8. Pyroelectric and dielectric properties of lead indium niobate ceramics

    Microsoft Academic Search

    S. S. Park; W. K. Choo

    1991-01-01

    Perovskite lead indium niobate free of pyrochlore phase has been synthesized by a novel calcination process. The process is described, and the dielectric constant and pyroelectric coefficient of the ceramic body have been determined as a function of temperature. X-ray diffraction investigation shows no obvious indium\\/niobium atom ordering at the B-site on isothermal annealing. This lack of extended ordering is

  9. Organic photodetectors based on phthalocyanine and fullerenes: dielectric properties.

    PubMed

    Sahu, Satyajit; Pal, Amlan J

    2009-01-01

    Fabrication and characterization of organic photodetectors based on copper phthalocyanine and fullerenes are presented. We study current-voltage and impedance characteristics of the devices under dark and varied illumination conditions. The current-voltage characteristics in the reverse bias show little or no dark current and large photocurrent. The results show that photocurrent in the devices is associated with a decrease in bulk resistance and an increase in dielectric constant of the active material. PMID:19441333

  10. Dielectric, thermal and mechanical properties of ADP doped PVA composites

    NASA Astrophysics Data System (ADS)

    Naik, Jagadish; Bhajantri, R. F.; Ravindrachary, V.; Rathod, Sunil G.; Sheela, T.; Naik, Ishwar

    2015-06-01

    Polymer composites of poly(vinyl alcohol) (PVA), doped with different concentrations of ammonium dihydrogen phosphate (ADP) has been prepared by solution casting. The formation of complexation between ADP and PVA was confirmed with the help of Fourier transforms infrared (FTIR) spectroscopy. Thermogravimetric analysis (TGA) shows thermal stability of the prepared composites. Impedance analyzer study revealed the increase in dielectric constant and loss with increase the ADP concentration and the strain rate of the prepared composites decreases with ADP concentration.

  11. Dielectric properties of native and decoated spores of Bacillus megaterium.

    PubMed Central

    Carstensen, E L; Marquis, R E; Child, S Z; Bender, G R

    1979-01-01

    A general model for use in interpreting dielectric data obtained with bacterial endospores is developed and applied to past results for Bacillus cereus spores and new results for Bacillus megaterium spores. The latter were also subjected to a decoating treatment to yield dormant cells with damaged outer membranes that could be germinated with lysozyme. For both spore types, core ions appeared to be completely immobilized, and decoating of B. megaterium spores did not affect this extreme state of electrostasis in the core. The cortex of B. megaterium appeared to contain a high level of mobile ions, in the cortex of B. cereus. The outer membrane-coat complex of B. megaterium acted dielectrically as an insulating layer around the cortex, so that native dormant spores showed a Maxwell-Wagner dispersion over the frequency range from about 1 to 20 MHz. The decoating treatment resulted in a shift in the dispersion to frequencies below the range of observation. Increases in cell conductivity in response to increases in environmental ionic strength indicated that the coats. of B. megaterium could be penetrated by environmental ions and that they had an inherent fixed charge concentration of about 10 to 20 milliequivalents per liter. In contrast, the dispersion for B. cereus spores was very sensitive to changes in environmental ion concentration, and it appeared that some 40% of the spore volume could be penetrated by environmental ions and that these ions traversed a dielectrically effective layer, either the exosporium or the outer membrane. It appears that dormancy is associated with extreme electrostasis of core ions but not necessarily of ions in enveloping structures and that the coat-outer membrane complex is dielectrically effective but not required for maintenance of extreme electrostasis in the core. PMID:118161

  12. Temperature dependency and dielectric properties of EPDM with void

    Microsoft Academic Search

    Dong-Shick Kim; Moo-Seong Kang; Jae-Hyung Oh; Chang-Hun Lee; Dae-Hee Park; Yong-Joo Kim

    1997-01-01

    The dielectric characteristics of EPDM were characterized and the temperature dependency was also evaluated at the constant electric field. While the value of tan ? was 3.55×10-3(%) and increased with increasing temperature in EPDM without voids, the value of tan ? was lowered to 2.24×10-3(%) and the temperature influence on tan ? was not shown to be great in the

  13. Microwave Dielectric and Magnetic Properties of Co-Zn Ferrites

    NASA Astrophysics Data System (ADS)

    Lamani, A. R.; Jayanna, H. S.; Naveen, C. S.; Rajeeva, M. P.; Prasanna, G. D.

    2015-02-01

    The dielectric permittivity, loss tangent, in the frequency range 1MHz to 1.8 GHz and hysteresis loop parameters at room temperature were studied on a series of Zn substituted cobalt ferrites with general formula Co1-xZnx Fe2O4 where (x=0.0, 0.2, 0.4, 0.6, 1.0.). The experimental results indicate that the Zn substitution affects all these parameters. The observed dispersion in dielectric permittivity with frequency is in accordance with Maxwell-Wagner model. The high temperature sintering is used to synthesize these materials via solid state reaction route and these samples were characterized by X-ray diffractometer (XRD), vibrating sample magnetometer (VSM). The saturation magnetizations (MS) Hc and Mr of the Particles were measured at room temperature. Here for the smaller dopent concentration Ms increases with increasing in the Zn content this can explained on the basis of increased number of magnetic ions in the spinel lattice, at some point Ms decrease because of the difference between the magnetic moment of Fe2+ and Zn2+, the magnetic moment of the A sub lattice will increases and the moment of the B sub lattice will decrease. The variation of crystalline shape ellipsoid is correlated with variation of dielectric constant.

  14. Dual-cycle dielectrophoretic collection rates for probing the dielectric properties of nanoparticles

    PubMed Central

    Bakewell, David J; Holmes, David

    2013-01-01

    A new DEP spectroscopy method and supporting theoretical model is developed to systematically quantify the dielectric properties of nanoparticles using continuously pulsed DEP collection rates. Initial DEP collection rates, that are dependent on the nanoparticle dielectric properties, are an attractive alternative to the crossover frequency method for determining dielectric properties. The new method introduces dual-cycle amplitude modulated and frequency-switched DEP (dual-cycle DEP) where the first collection rate with a fixed frequency acts as a control, and the second collection rate frequency is switched to a chosen value, such that, it can effectively probe the dielectric properties of the nanoparticles. The application of the control means that measurement variation between DEP collection experiments is reduced so that the frequency-switched probe collection is more effective. A mathematical model of the dual-cycle method is developed that simulates the temporal dynamics of the dual-cycle DEP nanoparticle collection system. A new statistical method is also developed that enables systematic bivariate fitting of the multifrequency DEP collection rates to the Clausius–Mossotti function, and is instrumental for determining dielectric properties. A Monte-Carlo simulation validates that collection rates improve estimation of the dielectric properties, compared with the crossover method, by exploiting a larger number of independent samples. Experiments using 200 nm diameter latex nanospheres suspended in 0.2 mS/m KCl buffer yield a nanoparticle conductivity of 26 mS/m that lies within 8% of the expected value. The results show that the dual-frequency method has considerable promise particularly for automated DEP investigations and associated technologies. PMID:23172363

  15. Effect of random surface inhomogeneities on spectral properties of dielectric-disk microresonators: theory and modeling at millimeter wave range.

    PubMed

    Ganapolskii, E M; Eremenko, Z E; Tarasov, Yu V

    2009-04-01

    The influence of random axially homogeneous surface roughness on spectral properties of dielectric resonators of circular disk form is studied both theoretically and experimentally. To solve the equations governing the dynamics of electromagnetic fields, the method of eigenmode separation is applied previously developed with reference to inhomogeneous systems subject to arbitrary external static potential. We prove theoretically that it is the gradient mechanism of wave-surface scattering that is highly responsible for nondissipative loss in the resonator. The influence of side-boundary inhomogeneities on the resonator spectrum is shown to be described in terms of effective renormalization of mode wave numbers jointly with azimuth indices in the characteristic equation. To study experimentally the effect of inhomogeneities on the resonator spectrum, the method of modeling in the millimeter wave range is applied. As a model object, we use a dielectric disk resonator (DDR) fitted with external inhomogeneities randomly arranged at its side boundary. Experimental results show good agreement with theoretical predictions as regards the predominance of the gradient scattering mechanism. It is shown theoretically and confirmed in the experiment that TM oscillations in the DDR are less affected by surface inhomogeneities than TE oscillations with the same azimuth indices. The DDR model chosen for our study as well as characteristic equations obtained thereupon enable one to calculate both the eigenfrequencies and the Q factors of resonance spectral lines to fairly good accuracy. The results of calculations agree well with obtained experimental data. PMID:19518202

  16. A quick accurate method for measuring the microwave dielectric properties of small tissue samples.

    PubMed

    Land, D V; Campbell, A M

    1992-01-01

    A resonant cavity perturbation technique has been developed which provides a quick, simple and accurate method of measuring the microwave dielectric properties of small, easily prepared samples of tissues, tissue-simulating materials and biological fluids. The method gives dielectric properties averaged over the sample volume. The measurement accuracy with the apparatus used is +/- 2.2% for relative permittivity and +/- 3.5% for the loss factor for most tissue and biological material samples. With appropriate basic microwave equipment the method can be applied over the 1.5-6 GHz range of frequencies of interest for active and radiometric tissue microwave imaging. PMID:1741423

  17. Dielectric, magnetic, and magnetoelectric properties of La and Ti codoped BiFeO3

    NASA Astrophysics Data System (ADS)

    Cui, Y. F.; Zhao, Y. G.; Luo, L. B.; Yang, J. J.; Chang, H.; Zhu, M. H.; Xie, D.; Ren, T. L.

    2010-11-01

    The authors report on the dielectric, magnetic, and magnetoelectric (ME) properties of La and Ti codoped BiFeO3 (LBFTO). Codoping changes the structure of BiFeO3 from rhombohedral to tetragonal and the ferromagnetic properties of LBFTO are remarkably improved. More interestingly, the dielectric constant of LBFTO shows a linear increase with magnetic field and the slope decreases linearly with increasing temperature. The electric polarization of LBFTO also increases upon applying a magnetic field. The ME coupling coefficients of different orders were obtained by analyzing these data. The results were discussed by considering the doping induced destruction of the cycloidal structure in LBFTO.

  18. Dielectric Properties of BaTiO3-Based Ceramics under High Electric Field

    NASA Astrophysics Data System (ADS)

    Tsurumi, Takaaki; Adachi, Hiroshige; Kakemoto, Hirofumi; Wada, Satoshi; Mizuno, Youichi; Chazono, Hirokazu; Kishi, Hiroshi

    2002-11-01

    The dielectric properties under a high electric field (ac-field) of BaTiO3-based ceramics with core grains, shell grains and core-shell grains were compared with those of multilayer ceramic capacitors (MLCCs) with these three kinds of grains. The MLCCs with the X7R specification had a core-shell structure, and the relative dielectric permittivity (\\varepsilonr) of the dielectric layers in the MLCCs increased with increasing ac-field. Similar behavior was observed in the MLCCs consisting of only cores, indicating that the core predominantly determined the dielectric properties of MLCCs under high ac-fields. The dielectric properties of MLCCs and ceramic plates consisting of only shell grains showed that the shell was the relaxor ferroelectrics. A slight change in the shell composition yielded a large shift of the peak temperature of \\varepsilonr. The shell improved the temperature stability of \\varepsilonr at low temperatures under low ac-fields. In a ceramic plate with relatively large BaTiO3 grains (approximately 3 ?m), the maximum \\varepsilonr was observed at a moderate ac-field, which was explained from the electric displacement vs electric field hysteresis curves of ferroelectric BaTiO3. The MLCCs and ceramics plates with fine BaTiO3 grains (0.4 to 0.5 ?m) showed similar dielectric behavior to the MLCC with the core-shell structure. The size effect of BaTiO3 played an important role in determining the temperature stability of \\varepsilonr. For future MLCCs with very thin dielectric layers, a microstructure with fine BaTiO3 grains and grain boundary layers of the shell was proposed.

  19. Electronic Structure, Electrical and Dielectric Properties of BaSnO3 below 300 K

    NASA Astrophysics Data System (ADS)

    Singh, Prabhakar; Brandenburg, Benjamin J.; Sebastian, C. Peter; Singh, Prakash; Singh, Sindhu; Kumar, Devendra; Parkash, Om

    2008-05-01

    The electronic structure, electrical and dielectric properties of barium stannate, a semiconducting perovskite oxide prepared by solid state ceramic route were studied by employing X-ray photoelectron spectroscopy (XPS), Mössbauer and impedance spectroscopic techniques in the temperature range 77-300 K. X-ray diffraction (XRD) pattern of BaSnO3 confirms the cubic structure. Scanning electron microscopy (SEM) images show high porosity in the sample and the average grain size was found to be about 1.85 µm which corroborates with the particle size obtained through XRD line broadening analysis. Mössbauer spectra, at 298 and 78 K reveal that tin exists mainly in tetravalent, Sn4+ state. XPS study also shows the same results but it indicates the existence of a trace amount of Sn2+. Electrical conductivity and dielectric constant of this system have been measured in the temperature range 298 to 148 K and in the frequency range 10-2 to 106 Hz. Frequency and temperature dependent electrical conductivity/dielectric properties have been used to separate the contributions of grains and grain boundaries to the total observed conductivity and dielectric constant. Orientational polarisation and space charge polarisation contributes to the observed dielectric properties of the system.

  20. Dielectric spectroscopy at the nanoscale by atomic force microscopy: A simple model linking materials properties and experimental response

    SciTech Connect

    Miccio, Luis A., E-mail: luisalejandro-miccio@ehu.es; Colmenero, Juan [Centro de Física de Materiales (CSIC-UPV/EHU), P. M. de Lardizabal 5, 20018 San Sebastián (Spain); Donostia International Physics Center, P. M. de Lardizabal 4, 20018 San Sebastián (Spain); Departamento de Física de Materiales (UPV/EHU), 20080 San Sebastián (Spain); Kummali, Mohammed M.; Alegría, Ángel [Centro de Física de Materiales (CSIC-UPV/EHU), P. M. de Lardizabal 5, 20018 San Sebastián (Spain); Departamento de Física de Materiales (UPV/EHU), 20080 San Sebastián (Spain); Schwartz, Gustavo A. [Centro de Física de Materiales (CSIC-UPV/EHU), P. M. de Lardizabal 5, 20018 San Sebastián (Spain); Donostia International Physics Center, P. M. de Lardizabal 4, 20018 San Sebastián (Spain)

    2014-05-14

    The use of an atomic force microscope for studying molecular dynamics through dielectric spectroscopy with spatial resolution in the nanometer scale is a recently developed approach. However, difficulties in the quantitative connection of the obtained data and the material dielectric properties, namely, frequency dependent dielectric permittivity, have limited its application. In this work, we develop a simple electrical model based on physically meaningful parameters to connect the atomic force microscopy (AFM) based dielectric spectroscopy experimental results with the material dielectric properties. We have tested the accuracy of the model and analyzed the relevance of the forces arising from the electrical interaction with the AFM probe cantilever. In this way, by using this model, it is now possible to obtain quantitative information of the local dielectric material properties in a broad frequency range. Furthermore, it is also possible to determine the experimental setup providing the best sensitivity in the detected signal.

  1. THz Dielectric Properties of Molecular Clusters of PETN and TNT Calculated by Density Functional Theory

    NASA Astrophysics Data System (ADS)

    Huang, L.; Shabaev, A.; Lambrakos, S. G.; Massa, L.

    2012-08-01

    The need for better detection of explosive devices has imposed a necessity for determining the dielectric response properties of energetic materials with respect to electromagnetic wave excitation. Among the range of different frequencies for electromagnetic excitation, the THz frequency range is of particular interest because of its nondestructive nature. The present study is based on significant progress in density functional theory (DFT), and associated software technology, which is sufficiently mature for the determination of dielectric response functions, and actually provides complementary information to that obtained from experiment. This point is further demonstrated in this study by calculations of ground state resonance structure associated with molecular clusters of the high explosives PETN and TNT using DFT, which is for the construction of parameterized dielectric response functions for excitation by electromagnetic waves at frequencies within the THz range. These dielectric functions provide for different types of analyses concerning the dielectric response of explosives. In particular, these dielectric response functions provide quantitative initial estimates of spectral response features for subsequent adjustment with respect to additional information such as laboratory measurements and other types of theory-based calculations. With respect to qualitative analysis, these spectra provide for the molecular level interpretation of response structure. The DFT software GAUSSIAN was used for the calculations of ground state resonance structure presented here.

  2. Dielectric properties of I-III-VI2-type chalcopyrite semiconductors D. Xue, K. Betzler,* and H. Hesse

    E-print Network

    Osnabrück, Universität

    Dielectric properties of I-III-VI2-type chalcopyrite semiconductors D. Xue, K. Betzler,* and H Dielectric properties of I-III-VI2-type ternary chalcopyrite semiconductors, including linear and second. INTRODUCTION For more than 20 years, chalcopyrite semiconductors with the formula I-III-VI2 where I, III

  3. Nano-structured vanadium: processing and mechanical properties under quasi-static and dynamic compression

    E-print Network

    Wei, Qiuming

    Nano-structured vanadium: processing and mechanical properties under quasi-static and dynamic form 16 September 2003; accepted 9 October 2003 Abstract We have processed fully dense, nano that the grain size of the consolidated V is around 100 nm. Mechanical properties of the nano-structured V were

  4. Pultruded fibre-reinforced furfuryl alcohol resin composites: 2. Static, dynamic mechanical and thermal properties

    Microsoft Academic Search

    C. C. M Ma; M. S Yn; J. L Han; C. J Chang; H. D Wu

    1995-01-01

    A novel process has been developed to manufacture pultruded fibre-reinforced furfuryl alcohol (FA) resin composites. In this paper, the effects of fibre reinforcement type and content on the static, dynamic mechanical and thermal properties of the FA resin pultruded composites are investigated. The mechanical properties increase with increasing volume content of the glass or carbon fibres, with the glass fibre-reinforced

  5. Dielectric properties and temperature profile of fly ash-based geopolymer mortar

    Microsoft Academic Search

    Saysunee Jumrat; Burachat Chatveera; Phadungsak Rattanadecho

    2011-01-01

    In this paper, the fresh properties, dielectric properties and temperature profile of fly ash-based geopolymer mortars are investigated to observe the effect of mixture proportions and time after mixing. Sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) were used as the activators. The results of fresh properties revealed that the added water could improve the workability of geopolymer mortar. It is

  6. TOPICAL REVIEW: Dielectric properties of crystalline and amorphous transition metal oxides and silicates as potential high-? candidates: the contribution of density-functional theory

    NASA Astrophysics Data System (ADS)

    Rignanese, G.-M.

    2005-02-01

    A review is given of various first-principles studies of the dielectric properties of crystalline and amorphous transition metal oxides and silicates, which have drawn considerable attention as potential high-? materials. After a brief summary of the principal equations of density-functional theory related to the dielectric properties of solids, the results obtained for group IVb M = (Hf,Zr,Ti) and IIIb M = (Y,La,Lu) transition metals crystalline oxides and/or silicates are discussed. For the group IVb transition metals, four crystalline phases (cubic, tetragonal, monoclinic and rutile) of dioxide MO2 with M = (Hf,Zr,Ti) have been considered in the literature. The results of density-functional theory calculations of the dielectric properties of three crystalline transition metal silicates (hafnon HfSiO4, zircon ZrSiO4 and a hypothetical TiSiO4 structure) are also presented. For the group IIIb transition metals, two crystalline phases (cubic and hexagonal) of sesquioxides M2O3 with M = Lu have been investigated within density-functional theory. Finally, the first-principles results that have been obtained for the amorphous silicates are discussed. A presentation is given of a scheme recently introduced which relates the dielectric constants to the local bonding of Si and metal atoms. It is based on the definition of parameters characteristic of the basic structural units centred on Si and metals atoms and including their nearest O neighbours. Applied to amorphous Zr silicates, it provides a good description of the measured dielectric constants, both of the optical and the static ones.

  7. Magnetic, dielectric and sensing properties of manganese substituted copper ferrite nanoparticles

    NASA Astrophysics Data System (ADS)

    Kumar, E. Ranjith; Jayaprakash, R.; Devi, G. Sarala; Reddy, P. Siva Prasada

    2014-04-01

    Manganese substituted copper ferrite nanoparticles were synthesized by an auto-combustion technique using metal nitrates and urea for gas sensor application. The products were characterized by XRD, SEM, EDX, TEM and VSM techniques. The effect of annealing temperature on the particle size, magnetic and dielectric properties of Mn-Cu ferrite nanoparticles was analyzed. The size of the particles are in the range of ~9-45 nm. The effect of annealing on the magnetic properties is discussed with the help of variation in saturation magnetization (Ms) and coercivity (Hc) by vibrating sample magnetometer (VSM). The dielectric loss and dielectric constant have been measured in the frequency range of 100 kHz-5 MHz. Furthermore, Conductance response of Mn-Cu ferrite nanomaterial was measured by exposing the material to reducing gas like liquefied petroleum gas (LPG).

  8. Thermal Properties of Ultrathin Hafnium Oxide Gate Dielectric Films

    Microsoft Academic Search

    Matthew A. Panzer; Michael Shandalov; Jeremy A. Rowlette; Yasuhiro Oshima; Yi Wei Chen; Paul C. McIntyre; Kenneth E. Goodson

    2009-01-01

    Thin-film HfO2 is a promising gate dielectric material that will influence thermal conduction in modern transistors. This letter reports the temperature dependence of the intrinsic thermal conductivity and interface resistances of 56-200-Aring-thick HfO2 films. A picosecond pump-probe thermoreflectance technique yields room-temperature intrinsic thermal conductivity values between 0.49 and 0.95 W\\/(mmiddotK). The intrinsic thermal conductivity and interface resistance depend strongly on

  9. Strain tunable ferroelectric and dielectric properties of BaZrO3

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

    The crucial role of epitaxial (in-plane) strain on the structural, electronic, energetic, ferroelectric, and dielectric properties of BaZrO3 (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 BaTiO3, 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.

  10. Structural, spectral and dielectric properties of piezoelectric-piezomagnetic composites

    NASA Astrophysics Data System (ADS)

    Hemeda, O. M.; Tawfik, A.; Amer, M. A.; Kamal, B. M.; El Refaay, D. E.

    2012-10-01

    Composite materials of spinel ferrite (SF) NiZnFe2O4 (NZF) and barium titanate (BT) BaTiO3 were prepared by double sintering ceramic technique. X-ray diffraction patterns for the composite system (1-x) NZF+x BT, showed the presence of mainly of 2 phases, hence confirming the successful preparation of the composite. Some structural and microstructural parameters like porosity, X-ray density, particle size and lattice constant were deduced from the analysis of X-ray data for both phases. Scan electron microscope (SEM) analysis shows nearly a homogeneous microstructure with good dispersion of BT grains as well as the presence of some pores. There was also an enlargement of BT grains with increasing its content. Infra red (IR) spectra of the composite system indicate that BT content affects the intermolecular character of the SF phase. A rise in the dielectric constant occurred at high temperature which was attributed to the effect of space change resulting from the increase of the change carriers in the paramagnetic region. The dielectric loss (tan ?) decreased by increasing BT content.

  11. The influence of LF glow discharge treatment on the dielectric properties of PET film

    Microsoft Academic Search

    Alexander Drachev; Vladimir Pak; Alla Gilman; Alexander Kuznetsov

    2002-01-01

    The influence of low frequency glow discharge treatment on the dielectric properties of. PET film (loss angle and permittivity) was studied over a wide range of frequencies and temperatures. It was shown that the treatment of PET film does not influence the loss angle in the interval of frequencies 100 Hz-3 MHz and at temperatures from 20°C to 200°C: The

  12. Coaxial-probe contact-force monitoring for dielectric properties measurements

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A means is described for measuring and monitoring the contact force applied to a material sample with an open-ended coaxial-line probe for purposes of measuring the dielectric properties of semisolid material samples such as fruit, vegetable and animal tissues. The equipment consists of a stainless...

  13. Dielectric Properties of Apollo 11 Lunar Samples and Their Comparison with Earth Materials

    Microsoft Academic Search

    D. H. Chung; W. B. Westphal; Gene Simmons

    1970-01-01

    neering. The data can be used in planning future exploration of the moon. Study of the samples can also extend our knowledge of the physical properties of materials formed in extraterrestrial environments. In this paper, we report values of the dielectric constants and losses, and the conductivities that have been measured on Apollo 11 lunar samples 10020, 10057, and 10046,

  14. Influence of Water content of RF and Microwave Dielectric Properties of Foods

    Technology Transfer Automated Retrieval System (TEKTRAN)

    ABSTRACT The importance of dielectric properties of food materials is discussed with respect to their influence on the heating of materials by radio-frequency and microwave energy and their use for rapid, nondestructive sensing of quality characteristics of such materials. Data are presented graph...

  15. Effects of acid, salt and soaking time on the dielectric properties of acidified vegetables

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In order to design a continuous microwave process for pasteurization of acidified vegetables, equilibration phenomena in acid and salt solutions must be examined with regards to changes in dielectric properties. The objective of this study was to examine the effects of acid and salt concentration o...

  16. Dielectric properties of agricultural products – fundamental principles, influencing factors, and measurement techniques

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In this chapter, definitions of dielectric properties, or permittivity, of materials and a brief discussion of the fundamental principles governing their behavior with respect to influencing factors are presented. The basic physics of the influence of frequency of the electric fields and temperatur...

  17. Roles of wave impedance and refractive index in photonic crystals with magnetic and dielectric properties

    Microsoft Academic Search

    Chul-Sik Kee; Jae-Eun Kim; Hae Yong Park; H. Lim

    1999-01-01

    We investigated the roles of wave impedance and refractive index in photonic crystals by means of analytical expressions for edges frequencies of a photonic bandgap (PBG) in a one-dimensional photonic crystal with magnetic and dielectric properties. The analytical expressions were derived when the optical thicknesses of layers are the same. The wave impedance governs the formation of PBG's and the

  18. Zirconium tin titanate (ZST) for miniaturized high impedance surfaces: Microwave dielectric properties and applications

    Microsoft Academic Search

    S. Genovesi; F. Costa; B. Cioni; V. Miceli; G. Gallone; G. Levita; A. Lazzeri; G. Annino; A. Monorchio; G. Moruzzi

    2009-01-01

    A new approach for obtaining metasurfaces realized by employing Frequency Selective Surfaces (FSSs) with small periodicity printed on a new class of high dielectric constant materials is presented. The synergic use of ad-hoc engineered materials and innovative electromagnetic design provides an improvement of the overall device in terms of size reduction and radiative properties.

  19. Influence of stoichiometry on the dielectric properties of sputtered strontium titanate thin films

    E-print Network

    York, Robert A.

    application as the charge storage material in high density dynamic random access memories DRAMs .1 SrTiO3Influence of stoichiometry on the dielectric properties of sputtered strontium titanate thin films T. R. Taylor and P. J. Hansen Department of Materials, College of Engineering, University

  20. Contribution of space charges to the polarization of ferroelectric superlattices and its effect on dielectric properties

    E-print Network

    Alpay, S. Pamir

    on dielectric properties M. B. Okatan,1 I. B. Misirlioglu,2 and S. P. Alpay1,3,* 1 Materials Science are calculated as a function of the planar space-charge density and the volume fraction of the PTO layer. Similar is strongly dependent on the density of trapped charges at the interlayer interfaces. For charge-free 001 PTO

  1. The effect of stress on the dielectric properties of barium strontium titanate thin films

    E-print Network

    Suo, Zhigang

    charge-density capacitors. Thin films of BST are now being developed to replace silica­nitride laminatesThe effect of stress on the dielectric properties of barium strontium titanate thin films T. M) and M. Huang Mechanical and Aerospace Engineering Department and Materials Institute, Princeton

  2. EFFECT OF SALINITY ON THE DIELECTRIC PROPERTIES OF GEOLOGICAL MATERIALS : IMPLICATION FOR SOIL

    E-print Network

    Paris-Sud XI, Université de

    EFFECT OF SALINITY ON THE DIELECTRIC PROPERTIES OF GEOLOGICAL MATERIALS : IMPLICATION FOR SOIL of saline deposits for the detection and mapping of moisture in arid regions on both Earth and Mars. We then present a simulation and experimental study in order to assess the effect of salinity on the permittivity

  3. On the physico-chemical and dielectric properties of glutaraldehyde crosslinked galactomannan–collagen films

    Microsoft Academic Search

    S. D Figueiró; Júlio C Góes; R. A Moreira; A. S. B Sombra

    2004-01-01

    The effects of galactomannan, a plant polysaccharide widely distributed in nature, on the physicochemical properties of collagen films, were studied using infrared spectroscopy, dielectric spectroscopy, thermal analysis (DSC), swelling and scanning electron microscopy, with possible applications in biomedical, cosmetic and food industry. Infrared bands typical for collagen molecules (amide I, II and III) and galactomannan structure, present in the spectrum

  4. Influence of gold nanorods size on electro-optical and dielectric properties of ferroelectric liquid crystals

    Microsoft Academic Search

    Fedor V. Podgornov; Anna V. Ryzhkova; Wolfgang Haase

    2010-01-01

    The influence of the gold nanorods (GNRs) diameter on the electro-optic and dielectric properties of the ferroelectric liquid crystals (FLCs) was investigated. It was shown that dispersing of GNRs in FLCs could lead to an increase of the internal electric field inside the liquid crystalline layer. This effect results in a significant decrease of the switching time and the rotational

  5. Pulsed electric field induced changes in dielectric properties of biological cells

    Microsoft Academic Search

    Jie Zhuang; W. Hunter Baldwin; Karl H. Schoenbach; Juergen F. Kolb

    2010-01-01

    Different electrical characteristics of cells not only determine their initial electrical responses to pulsed electric field exposure, but also allow devising exposure conditions for pulsed electric field treatments that can preferentially target specific cells, such as cancer cells. We have investigated the dielectric properties of Jurkat cells, a malignant human T-cell line, before and after application of microsecond and nanosecond

  6. Dielectric properties of MgO-doped compositionally graded multilayer barium strontium titanate films

    E-print Network

    Alpay, S. Pamir

    Dielectric properties of MgO-doped compositionally graded multilayer barium strontium titanate shifters and filters operat- ing in the microwave regime.1­4 Ferroelectrics FEs such as barium strontium in monolithic BST films especially with low strontium content, although the addition of MgO causes a reduction

  7. Study made of dielectric properties of promising materials for cryogenic capacitors

    NASA Technical Reports Server (NTRS)

    Mathes, K. N.; Minnich, S. H.

    1967-01-01

    Experimental investigations were conducted to determine dielectric properties of promising materials for cryogenic capacitors to be used in energy storage and pulse applications. The three classes of materials investigated were inorganic bonded ferroelectric materials, anodic coatings on metal foils, and polar low temperature liquids.

  8. Studies on Epdm\\/Nr Blends. I. Dielectric and Mechanical Properties

    Microsoft Academic Search

    A. M. Ghoneim; M. N. Ismail

    1999-01-01

    Ethylene-propylene-diene terpolymer rubberlnatural rubber blends (EPDM\\/NR) in different proportions (100 : 0, 75 : 25, 50 : 50, 25 : 75, and 0 : 100) reinforced with 20 phr semireinforcing furnace carbon black have been studied. The permittivity ?' and dielectric loss ?? for these samples were determined in the frequency range 10–10 Hz. Also, their physico-mechanical properties were investigated.The

  9. The dielectric properties of glass-fibre-reinforced epoxy resin during polymerisation

    Microsoft Academic Search

    K Nixdorf; G Busse

    2001-01-01

    The change in dielectric properties of thermosets between 10 Hz and 1 MHz allows us to monitor the cure of these materials. During the first heating phase at 80°C the resin conductivity (which is correlated with the Newtonian viscosity by a power law) decreases by several decades. In the subsequent heating phase at 140°C, the glass transition process is observed

  10. The Dielectric Properties of Conducting Polypyrrole in the Far-Infrared

    Microsoft Academic Search

    Gregory C. Phillips

    1990-01-01

    The dielectric properties of conducting Polypyrole films were studied by performing reflection and transmission measurements using a Michelson interferometer in the Far Infrared. The experimental methods applied in sample preparation and data collection are described in detail. The complex index of refraction and optical conductivities were determined through the Fresnel equations. The conducting polymer films were characterized by the magnitude

  11. Generation of Extended Surface Barrier Discharge on Dielectric Surface Electrical Properties

    Microsoft Academic Search

    K. Takashima; N. Zouzou; E. Moreau; A. Mizuno; G. Touchard

    Dielectric barrier discharge (DBD) with a grounded electrode (sliding electrode) on the same surface as the high voltage electrode (three electrode DBD) was experimentally studied to generate homogeneous surface discharge. Application of AC high voltage generated stable and homogeneous surface plasma between high voltage and grounded electrode without arcing. Electrical properties of the three electrode DBD was experimentally studied. With

  12. Dielectric properties of blood: an investigation of temperature dependence.

    PubMed

    Jaspard, F; Nadi, M

    2002-08-01

    We have investigated the temperature dependence of the electrical parameters (permittivity and conductivity) of blood. The measuring system, composed of an impedancemeter (HP 4291 A), an open-ended coaxial line and a temperature controlling set, was designed for dielectric measurement in the frequency range of 1 MHz to 1 GHz. Measurements were performed on ex vivo blood of humans and animals (cow and sheep). The results obtained show the weak sensibility and a change of sign of the temperature coefficient of the relative permittivity (about 0.3% degrees C(-1) at 1 MHz and -0.3% degrees C(-1) at 1 GHz). The conductivity presents a more significant variation (of the order of 1% degrees C(-1) over the whole operating frequency range. PMID:12214762

  13. Acoustic and dielectric properties of propionic acid + amine mixtures

    NASA Astrophysics Data System (ADS)

    Orzechowski, K.; Gli?ski, J.; Kaatze, U.

    2005-10-01

    Acoustical attenuation measurements between 100?kHz and 2?GHz, complex (dielectric) permittivity measurements between 1 MHz and 40 GHz, as well as various auxiliary measurements (density, viscosity, heat of mixing, optical refractive index) of propionic acid mixtures with amines are reported. The data reveal a complex coupled reaction scheme, involving a variety of hydrogen bonded structures, of proton transfer complexes, and of completely dissociated species. The combined consideration of the data indicates the complexation of an acid molecule with another one or with a propionic acid-amine complex to be likely reflected by a high frequency relaxation term in the acoustical spectra of the mixtures. The additionally existing low frequency acoustical relaxation term is assigned to the formation of a complex from a molecule of base and an acid dimer.

  14. Influence of gold nanorods size on electro-optical and dielectric properties of ferroelectric liquid crystals

    NASA Astrophysics Data System (ADS)

    Podgornov, Fedor V.; Ryzhkova, Anna V.; Haase, Wolfgang

    2010-11-01

    The influence of the gold nanorods (GNRs) diameter on the electro-optic and dielectric properties of the ferroelectric liquid crystals (FLCs) was investigated. It was shown that dispersing of GNRs in FLCs could lead to an increase of the internal electric field inside the liquid crystalline layer. This effect results in a significant decrease of the switching time and the rotational viscosity of the FLC/GNRs nanodispersions independently on the GNRs diameter. Oppositely, the relaxation frequency and the dielectric strength of the Goldstone mode strongly depend on the GNRs diameter, which can be explained by the charge transfer between the GNRs and FLC molecules.

  15. Influence of gold nanorods size on electro-optical and dielectric properties of ferroelectric liquid crystals

    SciTech Connect

    Podgornov, Fedor V.; Ryzhkova, Anna V. [Eduard-Zintl-Institute for Inorganic and Physical Chemistry, Darmstadt University of Technology, Petersenstr. 20, Darmstadt D-64287 (Germany); Department of Physics, Electrical Engineering Technologies Laboratory, South Ural State University, Lenin Ave. 76, Chelyabinsk 454080 (Russian Federation); Haase, Wolfgang [Eduard-Zintl-Institute for Inorganic and Physical Chemistry, Darmstadt University of Technology, Petersenstr. 20, Darmstadt D-64287 (Germany)

    2010-11-22

    The influence of the gold nanorods (GNRs) diameter on the electro-optic and dielectric properties of the ferroelectric liquid crystals (FLCs) was investigated. It was shown that dispersing of GNRs in FLCs could lead to an increase of the internal electric field inside the liquid crystalline layer. This effect results in a significant decrease of the switching time and the rotational viscosity of the FLC/GNRs nanodispersions independently on the GNRs diameter. Oppositely, the relaxation frequency and the dielectric strength of the Goldstone mode strongly depend on the GNRs diameter, which can be explained by the charge transfer between the GNRs and FLC molecules.

  16. Effect of Vanadium Substitution on the Dielectric Properties of Glass Ceramic Bi2212 Superconductor

    Microsoft Academic Search

    ?. Çavdar; H. Koralay; ?. Alt?ndal

    2011-01-01

    Glass ceramic superconductors were prepared by the melt-quenching method. The frequency and temperature dependence of dielectric\\u000a constant (??), dielectric loss (??) and loss tangent (tan??) of these superconductors were investigated in the frequency range of 10 kHz–10 MHz and temperature range of 80–300 K using\\u000a the capacitance–voltage (C–V) and conductance-voltage (G\\/w-V) measurements. Effect of vanadium on bulk properties, dc electrical\\u000a resistivity (?) and

  17. Fabrication and Properties of Novel Polyetheretherketone/Barium Titanate Composites with Low Dielectric Loss

    NASA Astrophysics Data System (ADS)

    Goyal, R. K.; Madav, V. V.; Pakankar, P. R.; Butee, S. P.

    2011-11-01

    Dielectric, thermal, and microhardness properties of high-performance barium titanate (BaTiO3)-filled polyetheretherketone (PEEK) composites were studied. BaTiO3 was varied from 0 vol.% to 67 vol.% in the PEEK matrix. The dielectric constant of the composites measured at 1 MHz increased approximately 14-fold. There was no dispersion in the dielectric constant with frequency between 10 kHz and 15 MHz. The Lichtenecker equation and modified Lichtenecker equation agreed well with the experimental data. The dissipation factor of the composites varied from 0.0056 to 0.0096. Scanning electron microscopy showed uniform dispersion of BaTiO3 in the matrix. The microhardness of the composites increased by more than 2.5-fold compared with pure PEEK. The coefficient of thermal expansion measured below and above the glass-transition temperature was reduced by up to 56%. These results make these composites promising candidate high-temperature organic substrates.

  18. Structural and dielectric properties of sputtered SrxZr(1-x)Oy

    NASA Astrophysics Data System (ADS)

    Grube, Matthias; Martin, Dominik; Weber, Walter M.; Mikolajick, Thomas; Riechert, Henning

    2013-06-01

    Over the past years, high-k dielectrics have been incorporated into modern semiconductor devices. One example is ZrO2, which has been introduced in memory applications. This paper elucidates some difficulties with pure ZrO2 like unintended crystallization during the growth of the dielectric and the evolution of the monoclinic phase, which reduces the k-value. The admixture of Sr is shown as a solution to circumvent those issues. A detailed structural analysis for a varying stoichiometry ranging from pure ZrO2 to the perovskite SrZrO3 is given. The detected crystal structures are correlated to our observations of the dielectric properties obtained by an electrical characterization.

  19. Dielectric properties of lead indium niobate ceramics synthesized by conventional solid state reaction method

    SciTech Connect

    Ramesh, G. [Department of Physics, Indian Institute of Technology Madras, Chennai-600 036 (India)] [Department of Physics, Indian Institute of Technology Madras, Chennai-600 036 (India); Subramanian, V., E-mail: manianvs@iitm.ac.in [Department of Physics, Indian Institute of Technology Madras, Chennai-600 036 (India); Sivasubramanian, V. [Condensed Matter Physics Division, Indira Gandhi Center for Atomic Research, Kalpakkam -603 102 (India)] [Condensed Matter Physics Division, Indira Gandhi Center for Atomic Research, Kalpakkam -603 102 (India)

    2010-12-15

    Pyrochlore free lead indium niobate ceramics are successfully prepared using wolframite precursor by conventional solid state reaction method in air atmosphere, by adding an excess amount of MgO in PbO-InNbO{sub 4} mixture. The dielectric properties of lead indium niobate ceramic studied as a function of both temperature and frequency indicate relaxor ferroelectric behavior with maximum dielectric constant of 4310 at 40 {sup {omicron}}C for 1 kHz. Lowering of transition temperature and enhancement of dielectric constant at room temperature, compared to earlier reports, may be due to the diffusion of magnesium ion into the lead indium niobate. The saturation polarization P{sub s}, measured at room temperature, is found to be 22.5 {mu}C/cm{sup 2} for 40 kV/cm.

  20. Structural and dielectric properties of Gd doped bismuth ferrite-lead titanate

    SciTech Connect

    Mohanty, N. K., E-mail: Banarjibehera@gmail.com; Behera, A. K., E-mail: Banarjibehera@gmail.com; Satpathy, S. K., E-mail: Banarjibehera@gmail.com; Behera, B., E-mail: Banarjibehera@gmail.com; Nayak, P., E-mail: Banarjibehera@gmail.com [School of Physics, Sambalpur University, Jyoti Vihar, Burla-768019, Odisha (India)

    2014-04-24

    0.5BiGd{sub x}Fe{sub 1?x}O{sub 3}?0.5PbTiO{sub 3} with x=0.05, 0.10, 0.15, 0.20 composite was prepared by mixed oxide method. Structural characterization was performed by X-ray diffraction and studied that the materials show tetragonal structure at room temperature for all concentration of Gd. Studies of dielectric properties (?{sub r} and tan?) of the above compound at different frequencies in a wide range of temperature (25°-500°C) with an impedance analyser revealed that the dielectric constant increases with increase in Gd concentration as well temperature and the compound do not have any dielectric anomaly in the studied frequency and temperature range.

  1. On Artificial Magneto-Dielectric Loading for Improving the Impedance Bandwidth Properties of Microstrip Antennas

    E-print Network

    Ikonen, P; Simovski, C; Tretyakov, S A; Ikonen, Pekka; Maslovski, Stanislav; Simovski, Constantin; Tretyakov, Sergei

    2005-01-01

    In the present paper we discuss the effect of artificial magneto-dielectric substrates on the impedance bandwidth properties of microstrip antennas. The results found in the literature for antenna miniaturization using magnetic or magneto-dielectric substrates are revised, and discussion is addressed to the practically realizable artificial magnetic media operating in the microwave regime. Using a transmission-line model we, first, reproduce the known results for antenna miniaturization with non-dispersive material fillings. Next, a realistic dispersive behavior of a practically realizable artificial substrate is embedded into the model, and we show that frequency dispersion of the substrate plays a very important role in the impedance bandwidth characteristics of the loaded antenna. The impedance bandwidths of reduced size patch antennas loaded with dispersive magneto-dielectric substrates and high-permittivity substrates are compared. It is shown that unlike substrates with dispersion-free permeability, pra...

  2. Microwave Dielectric Properties of Ceramic and Nanocomposite Titanates of Transition Metal

    NASA Astrophysics Data System (ADS)

    Rinkevich, Anatoly B.; Kuznetsov, Evgeny A.; Perov, Dmitry V.; Ryabkov, Yury I.; Samoylovich, Mikhail I.; Klescheva, Svetlana M.

    2014-10-01

    Ceramic and nanocomosite samples of the titanates of transition metals have been synthesized and their microwave dielectric properties have been investigated. Frequency and magnetic field dependences of the transmission and reflection coefficients in centimeter and millimeter wavebands were measured. It is established for most of studied ceramic titanates that transmission coefficient increases and reflection coefficient decreases when frequency increases. An absorption maximum has been found for ceramic sample made of Co0.9Fe0.1TiO3. The real and imaginary parts of complex dielectric permittivity were determined from measurements of transmission and reflection coefficients. On the whole, real part of dielectric permittivity of nanocomposite titanates based on an opal matrix is less than for ceramic titanates.

  3. Temperature Dependence of Dielectric and Ferroelectric Properties of BiFeO3 Thin Films

    SciTech Connect

    Biegalski, Michael D [ORNL; Jang, J H [Univeristy of Wisconsson; Bark, C [University of Wisconsin, Madison; Eom, Professor Chang-Beom [University of Wisconsin, Madison

    2009-01-01

    Multiferroic materials, with their potential for novel devices and sensors, have spurred an immense amount of research. The most concentrated effort has been on BiFeO3 thin films due to their high N el temperature and high ferroelectric transition temperature. Most studies on BiFeO3 films suffer from electrical leakage, requiring the measurement of dielectric or ferroelectric properties to be conducted at low temperatures. In this work we show that room-temperature leakage is not intrinsic to BiFeO3. Results are shown for highly insulating films, including the temperature dependence (10K to 300K) of the dielectric properties, ferroelectric P-E loops, and leakage current. This data shows very little temperature change in the dielectric constant with a TCC of 0.38 K-1, and dielectric losses below 0.005. The remanent polarization similarly showed no temperature dependence within the error of the measurement with a Pr of 67 1 C/cm2. The leakage current remains below 3x10-4(A/cm2) at 100 kV/cm. This work proves that BiFeO3 does not intrinsically have high leakage, and validates the extrapolation of the properties of BiFeO3 films measured at low temperatures to room temperatures.

  4. FDTD simulations and analysis of thin sample dielectric properties measurements using coaxial probes

    SciTech Connect

    Bringhurst, S.; Iskander, M.F.; White, M.J. [Univ. of Utah, Salt Lake City, UT (United States). Electrical Engineering Dept.

    1996-12-31

    A metallized ceramic probe has been designed for high temperature broadband dielectric properties measurements. The probe was fabricated out of an alumina tube and rod as the outer and inner conductors respectively. The alumina was metallized with a 3 mil layer of moly-manganese and then covered with a 0.5 mil protective layer of nickel plating. The probe has been used to make complex dielectric properties measurements over the complete frequency band from 500 MHz to 3 GHz, and for temperatures as high as 1,000 C. A 3D Finite-Difference Time-Domain (FDTD) code was used to help investigate the feasibility of this probe to measure the complex permittivity of thin samples. It is shown that by backing the material under test with a standard material of known dielectric constant, the complex permittivity of thin samples can be measured accurately using the developed FDTD algorithm. This FDTD procedure for making thin sample dielectric properties measurements will be described.

  5. Dielectrophoretic capture voltage spectrum for measurement of dielectric properties and separation of cancer cells

    PubMed Central

    Wu, Liqun; Lanry Yung, Lin-Yue; Lim, Kian-Meng

    2012-01-01

    In this paper, a new dielectrophoresis (DEP) method based on capture voltage spectrum is proposed for measuring dielectric properties of biological cells. The capture voltage spectrum can be obtained from the balance of dielectrophoretic force and Stokes drag force acting on the cell in a microfluidic device with fluid flow and strip electrodes. The method was demonstrated with the measurement of dielectric properties of human colon cancer cells (HT-29 cells). From the capture voltage spectrum, the real part of Clausius–Mossotti factor of HT-29 cells for different frequencies of applied electric field was obtained. The dielectric properties of cell interior and plasma membrane were then estimated by using single-shell dielectric model. The cell interior permittivity and conductivity were found to be insensitive to changes in the conductivity of the medium in which the cells are suspended, but the measured permittivity and conductivity of cell membrane were found to increase with the increase of medium conductivity. In addition, the measurement of capture voltage spectrum was found to be useful in providing the optimum operating conditions for separating HT-29 cells from other cells (such as red blood cells) using dielectrophoresis. PMID:22662097

  6. Broadband dielectric/electric properties of epoxy thin films filled with multiwalled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Macutkevic, Jan; Kuzhir, Polina P.; Paddubskaya, Alesia G.; Banys, Juras; Maksimenko, Sergey A.; Stefanutti, Eleonora; Micciulla, Federico; Bellucci, Stefano

    2013-01-01

    Many attempts have been made to fully explore flexibility, resistance to corrosion, and processing advantage of epoxy resin filled with carbon nanotubes (CNTs) as conductive filler, although sometimes with a certain degradation of polymers' intrinsic properties. It is important to move the percolation threshold into the region of smaller CNTs' concentration. The results of a broadband dielectric investigation of multiwalled CNT (MWCNT)/epoxy resin composites in wide temperature range from room temperature to 450 K were analyzed for percolation. Far below the percolation threshold (0.25 wt. % MWCNT) the dielectric properties of the composite are mostly determined by alpha relaxation in pure polymer matrix and the freezing temperature decreases due to the extra free volume at the polymer-filler interface. Close to the percolation threshold, the composite shows the negative temperature coefficient effect in the temperature region, where the pure polymer matrix becomes conductive. The activation energy of DC conductivity increases with the MWCNT concentration far below the percolation threshold and decreases close to it (1.5 wt. % MWCNT). The dielectric analysis of the MWCNT/epoxy resin reveals a significant influence of the polymer matrix on the temperature dependence of composite dielectric properties.

  7. Static and transport properties of alkyltrimethylammonium cation-based room-temperature ionic liquids.

    PubMed

    Seki, Shiro; Tsuzuki, Seiji; Hayamizu, Kikuko; Serizawa, Nobuyuki; Ono, Shimpei; Takei, Katsuhito; Doi, Hiroyuki; Umebayashi, Yasuhiro

    2014-05-01

    We have measured physicochemical properties of five alkyltrimethylammonium cation-based room-temperature ionic liquids and compared them with those obtained from computational methods. We have found that static properties (density and refractive index) and transport properties (ionic conductivity, self-diffusion coefficient, and viscosity) of these ionic liquids show close relations with the length of the alkyl chain. In particular, static properties obtained by experimental methods exhibit a trend complementary to that by computational methods (refractive index ? [polarizability/molar volume]). Moreover, the self-diffusion coefficient obtained by molecular dynamics (MD) simulation was consistent with the data obtained by the pulsed-gradient spin-echo nuclear magnetic resonance technique, which suggests that computational methods can be supplemental tools to predict physicochemical properties of room-temperature ionic liquids. PMID:24702446

  8. Dielectric properties of biological tissues in which cells are connected by communicating junctions

    NASA Astrophysics Data System (ADS)

    Asami, Koji

    2007-06-01

    The frequency dependence of the complex permittivity of biological tissues has been simulated using a simple model that is a cubic array of spherical cells in a parallel plate capacitor. The cells are connected by two types of communicating junctions: one is a membrane-lined channel for plasmodesmata in plant tissues, and the other is a conducting patch of adjoining plasma membranes for gap junctions in animal tissues. Both junctions provided similar effects on the dielectric properties of the tissue model. The model without junction showed a dielectric relaxation (called ?-dispersion) that was expected from an interfacial polarization theory for a concentrated suspension of spherical cells. The dielectric relaxation was the same as that of the model in which neighbouring cells were connected by junctions perpendicular to the applied electric field. When neighbouring cells were connected by junctions parallel to the applied electric field or in all directions, a dielectric relaxation appeared at a lower frequency side in addition to the ?-dispersion, corresponding to the so called ?-dispersion. When junctions were randomly introduced at varied probabilities Pj, the low-frequency (LF) relaxation curve became broader, especially at Pj of 0.2-0.5, and its intensity was proportional to Pj up to 0.7. The intensity and the characteristic frequency of the LF relaxation both decreased with decreasing junction conductance. The simulations indicate that communicating junctions are important for understanding the LF dielectric relaxation in tissues.

  9. Small-signal ac response of dielectric materials containing static space-charge fields: Application to ionic conductors and MIS structures

    NASA Astrophysics Data System (ADS)

    Moriarty, John A.

    1981-05-01

    An efficient and quantitatively accurate scheme for obtaining the small-signal ac response of dielectric materials containing static space-charge fields near their boundaries is developed in the context of a general linear-response formalism. The technique improves and greatly extends the earlier method of Hoyen et al. used to treat space-charge-limited transport in the ionic conductor AgCl. The general formalism is here implemented in detail for the case of one fully mobile, nonrecombining carrier in a uniformly doped material subject to arbitrary electrode boundary conditions. Illustrative applications to metal-insulator-semiconductor (MIS) structures and ionic conductors are considered. Extension of the method to more complex situations, involving minority-carrier transport, nonuniform doping, and/or generation and recombination phenomena, appears readily feasible.

  10. The growth, dielectric and lattice dynamical properties of strontium titanate and barium strontium titanate thin films

    NASA Astrophysics Data System (ADS)

    Clark, Anna Maria

    Ferroelectric materials have become increasingly important in microelectronic applications, such as dynamic random access memory, ferroelectric random access memory, and tunable microwave devices. This requires the growth of high quality ferroelectric thin films, as well as fundamental understanding of their structural and dielectric properties, which often differ from those in respective bulk materials. The present thesis focuses on the investigation of the perovskite type ferroelectrics strontium titanate, SrTiO3 (STO) and barium strontium titanate, BaxSr1- xTiO3 (BST). Pulsed laser deposition is considered as one of the most advantageous methods for the growth of thin ferroelectric films, and was used to produce STO films of high quality for this thesis. Influence of several deposition conditions, such as type of substrate, deposition temperature and chemical treatments of the substrate were investigated to determine their effects on the structural and electrical properties of STO films and to optimize deposition process and improve film quality. The surface morphology of films was studied by atomic force microscopy. X-ray diffraction was used to study their crystalline structure. It is shown in this thesis that the substrate has a pronounced effect on the crystalline quality and surface morphology of the film. Temperature and electric field dependencies of dielectric constant and loss tangent in STO films were studied by low frequency electric measurements. Improvements of the measured dielectric properties are correlated to the film deposition parameters. Raman spectroscopy was used to characterize the film structure and study the lattice dynamics of the thin films. Raman spectra show the STO films grown on STO single crystal substrates have a structural phase transition near the phase transition temperature in bulk STO. The soft TO1 phonon, related to the ferroelectric state, was observed in the STO thin films. Raman results of the soft-mode study show a strong correlation between the measured soft-mode and the dielectric properties, demonstrating the Lyddane-Sachs-Teller relation is obeyed in STO thin films. The TO1 phonon in thin films is observed at a higher frequencies than in bulk STO, which is consistent with the reduction of the measured dielectric constant in thin films compared to bulk. Growth and characterization techniques developed for STO thin films were extended to BST. The soft-mode is observed in Raman spectra of BST thin films of Ba compositions x = 0.05, 0.2 and 0.5 deposited on STO substrates. Dielectric properties were correlated to the Raman spectroscopy data. According to results of Raman spectroscopy and dielectric measurements, the ferroelectric phase transition occurs over a broad range of temperatures in thin films, which is different from bulk behaviour.

  11. Rayleigh analysis of dielectric properties in textured K0.5Na0.5NbO3 ceramics

    NASA Astrophysics Data System (ADS)

    Haugen, Astri Bjørnetun; Morozov, Maxim I.; Jones, Jacob L.; Einarsrud, Mari-Ann

    2014-12-01

    Grain texturing is a known method of exploiting the intrinsic dielectric and piezoelectric anisotropy in ferroelectric ceramics. However, the role of crystallographic texture on anisotropic extrinsic contributions including domain wall motion is not yet understood. Here, we investigate the dielectric and piezoelectric properties and small signal dielectric nonlinearities in K0.5Na0.5NbO3 ceramics in different directions of textured specimens and compare to ceramics without crystallographic texture. We demonstrate that directions in which pseudo-cubic <100> poles have greatest orientation density exhibit both an enhanced longitudinal piezoelectric response and lower dielectric nonlinearity.

  12. Depolarization field effect on dielectric and piezoelectric properties of particulate ferroelectric ceramic-polymer composites

    NASA Astrophysics Data System (ADS)

    Ma, Fengde D.; Wang, Yu U.

    2015-03-01

    The effects of depolarization field on the dielectric and piezoelectric properties of ferroelectric ceramic particle-filled polymer-matrix composites are investigated at the underlying domain level. Phase field modeling and simulation reveals that the macroscopic properties of the composites are dominated by depolarization field effect, which depends on the arrangement and alignment rather than the size or internal grain structure of the ferroelectric particulates. It is found that 0-3 particulate composites with random dispersion of ferroelectric particles behave essentially like linear dielectric rather than ferroelectric materials, and domain-level analysis reveals the physical mechanism for lack of domain switching or hysteresis as attributed to strong depolarization effect. Thus, without effective reduction or elimination of the depolarization field, the composites cannot benefit from the functional fillers regardless of their superior properties. In order to exhibit the desired ferroelectric behaviors, it necessitates continuous ferroelectric phase connectivity in the composites.

  13. Dielectric properties of glassy Se80Te20 and Se80Te10M10 Cd, In and Sb) (*)

    E-print Network

    Boyer, Edmond

    169 Dielectric properties of glassy Se80Te20 and Se80Te10M10 (M = Cd, In and Sb) (*) R. Arora and A dipolaire qui considère le saut des porteurs de charge à travers la barrière de potentiel entre niveaux de défauts chargés. Abstract. 2014 The temperature and frequency dependence of dielectric constant and loss

  14. Effects of "Natural" Water and "Added" Water on Microwave Dielectric Properties of Shelled Corn at Microwave Frequencies

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dielectric properties of samples of shelled corn of “natural” water content and those prepared by adding water were measured in free space at microwave frequencies and 23 oC. Results of measurements of attenuation, phase shift and dielectric constant and loss factor at 6 GHz show no difference betw...

  15. A study of the static properties of a massspring network with a spiderweb topology

    E-print Network

    Montréal, Université de

    A study of the static properties of a mass­spring network with a spider­web topology Arash Habibi (droplet deformations [1]) in which this analytical work was used. 1 The spider­web spring­mass network 1.1 A level/slice structure A spider­web spring­mass model is composed of NM + 1 masses. These masses

  16. Optimization of silver-dielectric-silver nanoshell for sensing applications

    SciTech Connect

    Shirzaditabar, Farzad; Saliminasab, Maryam [Department of Physics, Razi University, Kermanshah 67144-15111 (Iran, Islamic Republic of)] [Department of Physics, Razi University, Kermanshah 67144-15111 (Iran, Islamic Republic of)

    2013-08-15

    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.

  17. Optimization of silver-dielectric-silver nanoshell for sensing applications

    NASA Astrophysics Data System (ADS)

    Shirzaditabar, Farzad; Saliminasab, Maryam

    2013-08-01

    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.

  18. Thermal, mechanical and dielectric properties of poly(vinyl alcohol)/graphene oxide composites

    NASA Astrophysics Data System (ADS)

    Rathod, Sunil G.; Bhajantri, R. F.; Ravindrachary, V.; Pujari, P. K.; Sheela, T.; Naik, Jagadish

    2014-04-01

    In this work the composite films of poly(vinyl alcohol) (PVA) doped with functionalized Graphene Oxide (GO) were prepared by solution casting method. The films were characterized using FT-IR, DSC, XRD, mechanical properties and dielectric studies at room temperature. FTIR spectra shows the formation of hydrogen bonds between hydroxyl groups of PVA and the hydroxy groups of GO. The DSC thermograms shows the addition of GO to PVA greatly improves the thermal stability of the composites. XRD patterns shows that the GO exfoliated and uniformly dispersed in PVA matrix. Mechanical properties are significantly improved in PVA/GO composites. The tensile strength increased from 8.2 to 13.7 MPa and the Young's modulus increased from 7.5 to 24.8 MPa for 5 wt% GO doped sample. Dielectric spectroscopy showed a highest dielectric constant for the 5 wt% GO doped PVA films. This work provides a potential design strategy on PVA/GO composite, which would lead to higher-performance, flexible dielectric materials, high charge-storage devices.

  19. A first-principles study of the dielectric properties of TiO? polymorphs.

    PubMed

    Thilagam, A; Simpson, D J; Gerson, A R

    2011-01-19

    We present an analysis of the dielectric properties of the three polymorphs of TiO? (rutile, anatase and brookite phases), using ab initio time-dependent density functional perturbation theory based on the Vignale-Kohn functional. We implement this functional, which incorporates many-body effects, using the periodic program BAND. The improved result for the density of states spectra for brookite is suggestive of increased titanium ion Jahn-Teller effects for this phase. The imaginary and real components of the frequency-dependent dielectric functions show notable dielectric anisotropies, with implications for excitonic interactions, for all three common phases of TiO?. Comparison of the electron energy-loss spectrum for undoped and doped rutile and anatase reveals the critical role of collective charge excitations in photocatalytic mechanisms. The correlation between plasmon peaks present at lower energies and decreased photocatalytic activity due to substitutional aluminum doping in combination with oxygen vacancies in rutile and anatase is highlighted. Moreover, there is clear correlation between dielectric properties and the microstructure of the TiO? polymorphs as suggested via the framework of the Born effective charge and Hirshfeld charge distribution schemes. PMID:21406847

  20. Microwave Dielectric Properties of CaO-Li2O-Ln2O3-TiO2 Ceramics

    Microsoft Academic Search

    Kenichi Ezaki; Yoko Baba; Hisakazu Takahashi; Kenichi Shibata; Shoichi Nakano

    1993-01-01

    We have investigated the microwave dielectric properties of the Li2O-Ln2O3-TiO2 system and the CaO-Li2O-Ln2O3-TiO2 system (Ln: Lanthanide), both of which have a perovskite structure. The relationship between the kind of lanthanide element and dielectric properties at microwave frequencies was confirmed. It was also found that the ionic radius of lanthanide ions has a strong influence on the dielectric properties. Excellent

  1. Effects of confinement on static and dynamical properties of water.

    PubMed

    Rovere, M; Gallo, P

    2003-09-01

    Molecular-dynamics results on water confined in a silica pore are reviewed and discussed in connection with experiments performed on water in Vycor and with studies of water in contact with proteins. The properties of confined water are studied as a function of both temperature and hydration level. The interaction of water in the film close to the substrate with the silica atoms induces a strong distortion of the hydrogen bond network. At high hydration levels a double dynamical regime is observed. At low hydration an anomalous diffusion is found upon supercooling with a transition from a Brownian to a non-Brownian regime on approaching the substrate in agreement with results found in studies of water in contact with globular proteins. PMID:15007683

  2. The use of dielectric properties and other physical analyses for assessing protein denaturation in beef biceps femoris muscle during cooking from 5 to 85 °C

    Microsoft Academic Search

    N. P. Brunton; J. G. Lyng; L. Zhang; J. C. Jacquier

    2006-01-01

    Dielectric properties of beef biceps femoris muscle were recorded during heating (5–85°C) to assess their linkage to phase changes monitored by differential scanning calorimetry (DSC) and rheology. DSC indicated endotherms between 56 and 81°C corresponding to denaturation of actin, collagen and myosin. Matching changes in dielectric properties (dielectric constant (??) and loss factor (??)) were noted at radio and\\/or microwave

  3. Measuring the dielectric properties of herpes simplex virus type 1 virions with dielectrophoresis.

    PubMed

    Hughes, Michael P; Morgan, Hywel; Rixon, Frazer J

    2002-05-10

    An investigation has been performed into the biophysical properties of the enveloped mammalian virus, herpes simplex virus type 1 (HSV-1). The dielectrophoretic behaviour of the virus particles was measured as a function of applied frequency (over the range 100 kHz-20 MHz) and conductivity of the suspending medium (over the range 1-100 mS m(-1)). The dielectric properties of the virus were determined from the dielectrophoretic data using the smeared-out shell model. The data suggest that the intact particle has a surface conductance of 0.3 nS, an internal and membrane permittivity of 75varepsilon(o) and 7.5varepsilon(o), respectively, an internal conductivity of approximately 0.1 S m(-1) and a zeta potential of 70 mV. The dielectric properties were measured for intact, fresh virus particles and also for particles following exposure to various modifying agents, such as treatment with enzymes, ionophores and ageing. It is shown that the observed changes in the dielectrophoretic spectrum, and the variations in the dielectric properties of the virus concur with the expected physiological effects of these agents. PMID:12031284

  4. Study of normal and malignant white blood cells by time domain dielectric spectroscopy

    Microsoft Academic Search

    I. Ermolina; Y. Polevaya; Y. Feldman; B.-Z. Ginzburg; M. Schlesinger

    2001-01-01

    The aim of this paper is to present a comprehensive theoretical and experimental study by means of time domain dielectric spectrometer (TDDS) of static and dynamic dielectric properties of normal and malignant blood cells. The successful use of the TDDS method as a tool of human cell study required a special protocol and algorithms for all stages of cell preparation,

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

    NASA Astrophysics Data System (ADS)

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

    2008-02-01

    The dielectric properties of (Nb, Y)-doped BaTiO3 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 ?-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.

  6. Ferroelectric Bi3.3La0.7Ti3O12-poly (vinylidene-fluoride) composites with enhanced dielectric properties

    NASA Astrophysics Data System (ADS)

    Bhardwaj, Sumit; Paul, Joginder; Chand, Subhash; Raina, K. K.; Kumar, Ravi

    2015-05-01

    Ferroelectric ceramic polymer composites of Poly (vinylidene-fluoride) and Bi3.3La0.7Ti3O12 (BLT) were prepared by simple solution casting method. The structural, dielectric and morphological properties were studied systemically. The dielectric results showed that the composites have high dielectric constant with very low dielectric loss. At room temperature, a 10 wt% loaded BLT/PVDF composite film showed a dielectric constant of 109.48, which is six times greater in comparison to pure PVDF. Morphological studies reveal the formation of spherulattic structure of PVDF. These lead free composites with enhanced dielectric properties may prove tremendous potential for energy storage devices.

  7. On the Dielectric Properties of the Martian-like Surface Sediments

    NASA Technical Reports Server (NTRS)

    Heggy, E.; Clifford, S. M.; Morris, R. V.; Paillou, P.; Ruffie, G.

    2004-01-01

    We have undertaken laboratory electromagnetic characterization of the total set of minerals identified by TES on the Martian surface in order to investigate experimentally the dielectric properties of the sediments covering it in the frequency range from 1 to 30 MHz. Volcanic Rocks with a well defined mineralogy and petrology from potential terrestrial analogues sites have also been included in the study. Our primary objective is to evaluate the range of electrical and magnetic losses that may be encountered by the various Radar sounding and imaging experiments dedicated to map the Martian subsurface searching for underground water. The electromagnetic properties of these Mars-like materials will be presented as a function of various geophysical parameters, such as porosity, bulk density and temperature. The secondary objective, is to locate regions were surface dielectric conditions are suitable for subsurface sounding.

  8. Synthesis and dielectric properties of zinc oxide nanoparticles using a biotemplate

    SciTech Connect

    P, Sharmila P, E-mail: sharmilavishram@gmail.com [Sree Narayana College, Kollam, Kerala, India and T.K Madhva Memorial College, Nangiarkulungara, Alapuzha, Kerala (India); Tharayil, Nisha J., E-mail: nishajohntharayil@gmail.com [Sree Narayana College for Women Kollam, Kerala (India)

    2014-10-15

    Zinc Oxide nanoparticles are synthesized using DNA as capping agent. Zinc oxide nanoparticles are synthesized using DNA as a capping agent. Structural and morphological characterizations are done using SEM, FTIR and XRD. The particle size and lattice parameters are calculated from the diffraction data. The optical properties are studied using UV-Vis absorption spectroscopy and bandgap variation with temperature is determined. The dielectric property of nanoparticles is studied by varying temperature and frequency. The dielectric constant and dispersion parameters are found out. Method of Cole-Cole analysis is used to study the high temperature dispersion of relaxation time. The variation of both AC and DC conductivity are studied and activation energy calculated.

  9. Structural, dielectric and AC conductivity properties of Co2+ doped mixed alkali zinc borate glasses

    NASA Astrophysics Data System (ADS)

    Madhu, B. J.; Banu, Syed Asma; Harshitha, G. A.; Shilpa, T. M.; Shruthi, B.

    2013-02-01

    The Co2+ doped 19.9ZnO+5Li2CO3+25Na2CO3+50B2O3 (ZLNB) mixed alkali zinc borate glasses have been prepared by a conventional melt quenching method. The structural (XRD & FT-IR), dielectric and a.c. conductivity (?ac) properties have been investigated. Amorphous nature of these glasses has been confirmed from their XRD pattern. The dielectric properties and electrical conductivity (?ac) of these glasses have been studied from 100Hz to 5MHz at the room temperature. Based on the observed trends in the a.c. conductivities, the present glass samples are found to exhibit a non-Debye behavior.

  10. Room temperature optical and dielectric properties of Sr and Ni doped lanthanum ferrite nanoparticles

    NASA Astrophysics Data System (ADS)

    Naseem, Swaleha; Khan, Wasi; Singh, B. R.; Naqvi, A. H.

    2015-06-01

    Strontium and nickel doped lanthanum ferrite (LaFeO3) nanoparticles (NPs) were prepared reverse micelle (RM) and calcinated at 700°C. Microstructural studies were carried by XRD and SEM/EDS techniques. The results of structural characterization show the formation of all samples in single phase without any impurity. Optical properties were studied by UV- visible spectroscopy and band gap energy was estimated 3.89 eV. Room temperature dielectric constant (?') decreases abruptly at lower frequencies owing to the charge transport relaxation time. The observed behavior of the dielectric properties can be attributed on the basis of Koop's theory based on Maxwell-Wagner's two layer model in studied nanoparticles.

  11. Properties of dielectric coatings produced by ion assisted deposition

    Microsoft Academic Search

    Pei-Fu Gu; Yen Ming Chen; Xue-Qun Hu; Jin-Fa Tang

    1989-01-01

    Some metal oxides, fluorides, and ZnS films deposited by ion assisted deposition are investigated as a function of ion energy, ion variety, and ion source type. Both optical and mechanical properties, such as optical stability, absorption and scattering losses, laser damage threshold, and durability, are examined for samples deposited with the assistance of four kinds of ion source and various

  12. Dielectric properties of zinc titanate thin films prepared by Rf magnetron sputtering

    Microsoft Academic Search

    Jin Suk Jung; Young Ho Kim; Sang Keun Gil; Dong Heon Kang

    2009-01-01

    Zinc titanate thin films of ~500 nm in thickness were synthesized by an RF magnetron sputtering using a sintered ceramic target.\\u000a After annealing in temperature ranges of 300–800 °C, their phase transition and dielectric properties were investigated as\\u000a a function of annealing temperature. Crystalline ZnTiO3 phase was first detected at the annealing temperature of 500 °C within XRD detection limit though the sputtered

  13. Sintering and microwave dielectric properties of LTCC-zinc titanate multilayers

    Microsoft Academic Search

    Q. L. Zhang; H. Yang; J. L. Zou; H. P. Wang

    2005-01-01

    The effects of ZnO–B2O3–SiO2 (ZBS) on the sintering behavior and microwave dielectric properties of ZnO–TiO2 system were investigated as a function of ZBS content and sintering temperature. Densities of the specimens were enhanced with an increase of ZBS up to 2 wt.% and then decreased. X-ray diffractometry analyses results indicated that the phase stability region of the hexagonal ZnTiO3 extended

  14. Dielectric properties and far infrared reflectivity of lanthanum aluminate–strontium titanate ceramics

    Microsoft Academic Search

    T. Shimada; K. Kura; S. Ohtsuki

    2006-01-01

    LaAlO3–SrTiO3 [(1?x) LAO–xSTO] ceramics were prepared by a conventional solid-phase reaction method using high-purity reagents. Far infrared reflectivity spectra for (1?x) LAO–xSTO ceramics were measured and eigenfrequencies and damping constants of the transverse and longitudinal optical modes were estimated in order to analyze the dielectric properties and lattice vibration parameters. The observed reflectivity spectra were fitted by 4 or 6

  15. Influence of core-shell structured grain on dielectric properties of cerium-modified barium titanate

    Microsoft Academic Search

    Yung Park; Se Ahn Song

    1995-01-01

    The dielectric properties and chemical inhomogenity of BaTiO3 ceramics sintered with additions of CeO2:1.5TiO2 were investigated using TEM XRD and EDS. Grains had three regions: grain shell severely doped with cerium, grain core BaTiO3 of greater purity, and a concentration gradient region where Curie temperatures were distributed. With decreasing temperatures, the volume fraction of ferroelectric domains in the concentration gradient

  16. Effect of organic gate dielectric material properties on interfacial charging and discharging of pentacene MIM device

    Microsoft Academic Search

    Kateryna Bazaka; Mohan V. Jacob; Dai Taguchi; Takaaki Manaka; Mitsumasa Iwamoto

    2011-01-01

    The effect of material properties of an environmentally friendly, optically transparent dielectric material, polyterpenol, on the carrier transients within the pentacene-based double-layer MTM device was investigated. Polyterpenol films were RF plasma polymerised under varied process conditions, with resultant films differing in surface chemistry and morphology. Independent of type of polyterpenol, time-resolved EFISHG study of IZO\\/polyterpenol\\/pentacene\\/Au structures showed similar transient behaviour

  17. Adhesive and Mechanical Properties of NanoParticle Filled Thermoplastic Polyimide Dielectric Films for Microelectronics Packaging

    Microsoft Academic Search

    M. B. Saeed; M. S. Zhan

    2006-01-01

    In this study the mechanical and adhesive properties of aluminum nitride (AlN) nano powder filled polyimide composite films (AlN-PI) are investigated to determine their usefulness as dielectric materials in microelectronic packaging. AlN nano powder was mixed in low wt% during synthesis at poly(amic acid) (PAA) stage. AlN-PI films were characterized using DMTA and tensile testing to determine viscoelastic behavior and

  18. Ab initio study of the dielectric properties of silicon and gallium arsenide using polarized Wannier functions

    Microsoft Academic Search

    Pablo Fernández; Andrea dal Corso; Alfonso Baldereschi

    1998-01-01

    We present a first-principles calculation of the electronic properties of crystalline silicon and gallium arsenide in a uniform electric field. Polarized Wannier-like functions which are confined in a finite region are obtained by minimizing a total-energy functional which depends explicitly on the macroscopic polarization of the solid. The polarization charge density and the electronic dielectric constant are computed via finite

  19. Piezoelectric, pyroelectric and dielectric properties of La and Sm-doped PZT ceramics

    Microsoft Academic Search

    C. Pramila; T. C. Goel; P. K. C. Pillai

    1993-01-01

    Pair-doped lead zirconate titanate (PZT) samples were prepared by introducing lanthanum (La) and samarium (Sm) into the PZT lattice. Three compositions of pair-doped PZT were prepared by a conventional method. The dielectric, piezoelectric and pyroelectric properties of these samples were studied and compared with that of PLZT(8\\/65\\/35) samples prepared under the same conditions. The piezoelectric and pyroelectric figures of merit

  20. Dielectric and orientational properties of nematogenic 4- n -octyl(4?-cyanophenyl)benzoate

    Microsoft Academic Search

    D. Bauman; J. Jadzyn; E. Wolarz; A. Modlinska; R. Dabrowski

    2010-01-01

    Experimental studies of the dielectric properties in the nematic and isotropic phases of 4-cyanophenyl-4?-n-octylbenzoate\\u000a (8CPB) have been performed in the frequency range from 50 kHz to 100 MHz. The relaxation process related to the rotation around\\u000a the short molecular axis has been analysed. The results obtained have revealed that in the vicinity of the I-N phase transition,\\u000a the molecular subdiffusional

  1. Fast-sintering of hydrothermally synthesized BaTiO3 powders and their dielectric properties

    Microsoft Academic Search

    W. ZHU; C. C. WANG; S. A. AKBAR; R. ASIAIE

    1997-01-01

    Hydrothermally synthesized barium titanate (BaTiO3) powders with a submicrometre particle size have been fast-sintered with a heating rate of ? 200 C min-1 at various temperatures (1250–1350 C) for short times (5 and 15 min). The microstructures and dielectric properties of the\\u000a sintered samples are studied and compared with those sintered conventionally. The sample fast-sintered at 1250 C for 5

  2. Dielectric, electromechanical, optical, and mechanical properties of lanthanum-modified lead titanate ceramics

    Microsoft Academic Search

    T. Yamamoto; HIDEJI IGARASHI; KIYOSHI OKAZAKI

    1983-01-01

    Dielectric, electromechanical, optical, and mechanical properties of hot-pressed lanthanum-modified PbTiOâ ceramics were measured as a function of crystal tetragonality, c\\/a, in a range of tetragonal-to-cubic phases. The results obtained in this study are summarized as follows: The c\\/a changes linearly as a function of lanthanum content. Similarly, Curie point changed linearly and remanent polarization, coercive field, and coupling factors decreased

  3. Electronic Structure, Electrical and Dielectric Properties of BaSnO3 below 300 K

    Microsoft Academic Search

    Prabhakar Singh; Benjamin J. Brandenburg; C. Peter Sebastian; Prakash Singh; Sindhu Singh; Devendra Kumar; Om Parkash

    2008-01-01

    The electronic structure, electrical and dielectric properties of barium stannate, a semiconducting perovskite oxide prepared by solid state ceramic route were studied by employing X-ray photoelectron spectroscopy (XPS), Mössbauer and impedance spectroscopic techniques in the temperature range 77-300 K. X-ray diffraction (XRD) pattern of BaSnO3 confirms the cubic structure. Scanning electron microscopy (SEM) images show high porosity in the sample

  4. Manifestation of magnetic quantum fluctuations in the dielectric properties of a multiferroic

    NASA Astrophysics Data System (ADS)

    Kim, Jae Wook; Khim, Seunghyun; Chun, Sae Hwan; Jo, Y.; Balicas, L.; Yi, H. T.; Cheong, S.-W.; Harrison, N.; Batista, C. D.; Hoon Han, Jung; Hoon Kim, Kee

    2014-07-01

    Insulating magnets can display novel signatures of quantum fluctuations as similar to the case of metallic magnets. However, their weak spin-lattice coupling has made such observations challenging. Here we find that antiferromagnetic (AF) quantum fluctuations manifest in the dielectric properties of multiferroic Ba2CoGe2O7, where a ferroelectric polarization develops concomitant to an AF ordering. Upon application of a magnetic field (H), dielectric constant shows a characteristic power-law dependence near absolute zero temperature and close to the critical field Hc=37.1?T due to enhanced AF quantum fluctuations. When H>Hc, the dielectric constant shows the temperature-dependent anomalies that reflect a crossover from a field-tuned quantum critical to a gapped spin-polarized state. We uncover theoretically that a linear relation between AF susceptibility and dielectric constant stems from the generic magnetoelectric coupling and directly explains the experimental findings, opening a new pathway for studying quantum criticality in condensed matter.

  5. Microwave Dielectric Properties of Alfalfa Leaves From 0.3 to 18 GHz

    SciTech Connect

    Sokhansanj, Shahabaddine [ORNL; Shrestha, Bijay [University of Saskatchewan; Wood, H.C. [University of Saskatchewan

    2011-01-01

    Dielectric properties (i.e., permittivity) are essential in designing, simulating, and modeling microwave applications. The permittivity of stacked leaves of alfalfa (Medicago sativa) were measured with a network analyzer and a coaxial probe, and the effect of moisture content (MC: 12% 73% wet basis), frequency (300 MHz to 18 GHz), bound water (Cole Cole dispersion equation), temperature ( 15 C and 30 C), leaf-orientation, and pressure (0 11 kPa) were investigated. The measured permittivity increased with MC. A critical moisture level (CML) of 23% was reported, below which the permittivity decreased with increasing frequency at 22 C. Above CML and up to 5 GHz, the dielectric constants followed the Cole Cole dispersion, and the dielectric loss factors consisted of ionic and bound water losses. Above 5 GHz, the behavior of the dielectric constant was similar to that of free water, and the polar losses became dominant. Above 0 C, the measured permittivity followed a trend similar to that of free saline water and was characterized by the Debye equation. Below 0 C, it was dominated by nonfreezing bound and unfrozen supercooled moistures. The relaxation parameters and the optimum pressure (9 kPa) for the leaf measurements were determined. The effects of variations among the samples, and their orientations had negligible effects on the measured permittivity.

  6. Electrical and dielectric properties of foam injection-molded polypropylene/multiwalled carbon nanotube composites

    NASA Astrophysics Data System (ADS)

    Ameli, A.; Nofar, M.; Saniei, M.; Hossieny, N.; Park, C. B.; Pötschke, P.

    2015-05-01

    A combination of high dielectric permittivity (?') and low dielectric loss (tan ?) is required for charge storage applications. In percolative systems such as conductive polymer composites, however, obtaining high ?' and low tan ? is very challenging due to the sharp insulation-conduction transition near the threshold region. Due to the particular arrangement of conductive fillers induced by both foaming and injection molding processes, they may address this issue. Therefore, this work evaluates the application of foam injection molding process in fabricating polymer nanocomposites for energy storage. Polypropylene-multiwalled carbon nanotubes (PP-MWCNT) composites were prepared by melt mixing and foamed in an injection molding process. Electrical conductivity (?), ?' and tan ? were then characterized. Also, scanning and transmission electron microscopy (SEM and TEM) was used to investigate the carbon nanotube's arrangement as well as cellular morphology. The results showed that foam injection-molded composites exhibited highly superior dielectric properties to those of solid counterparts. For instance, foamed samples had ?'=68.3 and tan ? =0.05 (at 1.25 vol.% MWCNT), as opposed to ?'=17.8 and tan ?=0.04 in solid samples (at 2.56 vol.% MWCNT). The results of this work reveal that high performance dielectric nanocomposites can be developed using foam injection molding technologies for charge storage applications.

  7. Controlling of dielectrical properties of hydroxyapatite by ethylenediamine tetraacetic acid (EDTA) for bone healing applications.

    PubMed

    Kaygili, Omer; Ates, Tankut; Keser, Serhat; Al-Ghamdi, Ahmed A; Yakuphanoglu, Fahrettin

    2014-08-14

    The hydroxyapatite (HAp) samples in the presence of various amounts of ethylenediamine tetraacetic acid (EDTA) were prepared by sol-gel method. The effects of EDTA on the crystallinity, phase structure, chemical, micro-structural and dielectric properties of HAp samples were investigated. With the addition of EDTA, the average crystallite size of the HAp samples is gradually decreased from 30 to 22 nm and the crystallinity is in the range of 65-71%. The values of the lattice parameters (a and c) and volume of the unit cell are decreased by stages with the addition of EDTA. The dielectric parameters such as relative permittivity, dielectric loss and relaxation time are affected by the adding of EDTA. The alternating current conductivity of the as-synthesized hydroxyapatites increases with the increasing frequency and obeys the universal power law behavior. The HAp samples exhibit a non-Debye relaxation mechanism. The obtained results that the dielectrical parameters of the HAp sample can be controlled by EDTA. PMID:24747847

  8. Plasmonic band structures and optical properties of subwavelength metal/dielectric/metal Bragg waveguides.

    PubMed

    Li, Chao; Zhou, Yun-Song; Wang, Huai-Yu

    2012-03-26

    In this paper, we applied the band structure theory to investigate the plasmonic band (PB) structures and optical properties of subwavelength metal/dielectric/metal Bragg waveguides in the near infrared range with either dielectric or geometric modulation. The Bloch wave vector, density of states, slowdown factor, propagation length and transmittance are calculated and analyzed. Both the modulations are in favor of manipulating surface-plasmon-polariton (SPP) waves. For the dielectric modulation, the PB structure is mainly formed by SPP modes and possesses a "regular pattern" in which the bands and gaps have a relatively even distribution. For the geometric modulation, due to the strong transverse scattering, the contributions of higher modes have to be considered and the gap widths have a significant increase compared to the dielectric modulation. A larger slowdown factor may emerge at the band edge; especially for the geometric modulation, the group velocity can be reduced to 1/100 of light, and negative group velocity is observed as well. While inside the bands, the slowdown factor is smaller and the bands are flat. The contribution of each eigenmode to the PB structure is analyzed. PMID:22453451

  9. Dielectric properties of water under extreme conditions and transport of carbonates in the deep Earth

    PubMed Central

    Pan, Ding; Spanu, Leonardo; Harrison, Brandon; Sverjensky, Dimitri A.; Galli, Giulia

    2013-01-01

    Water is a major component of fluids in the Earth’s mantle, where its properties are substantially different from those at ambient conditions. At the pressures and temperatures of the mantle, experiments on aqueous fluids are challenging, and several fundamental properties of water are poorly known; e.g., its dielectric constant has not been measured. This lack of knowledge of water dielectric properties greatly limits our ability to model water–rock interactions and, in general, our understanding of aqueous fluids below the Earth’s crust. Using ab initio molecular dynamics, we computed the dielectric constant of water under the conditions of the Earth’s upper mantle, and we predicted the solubility products of carbonate minerals. We found that MgCO3 (magnesite)—insoluble in water under ambient conditions—becomes at least slightly soluble at the bottom of the upper mantle, suggesting that water may transport significant quantities of oxidized carbon. Our results suggest that aqueous carbonates could leave the subducting lithosphere during dehydration reactions and could be injected into the overlying lithosphere. The Earth’s deep carbon could possibly be recycled through aqueous transport on a large scale through subduction zones. PMID:23513225

  10. Magnetic and Dielectric Property Studies in Fe- and NiFe-Based Polymer Nanocomposites

    NASA Astrophysics Data System (ADS)

    Sharma, Himani; Jain, Shubham; Raj, Pulugurtha Markondeya; Murali, K. P.; Tummala, Rao

    2015-06-01

    Metal-polymer composites were investigated for their microwave properties in the frequency range of 30-1000 MHz to assess their application as inductor cores and electromagnetic isolation shield structures. NiFe and Fe nanoparticles were dispersed in epoxy as nanocomposites, in different volume fractions. The permittivity, permeability, and loss tangents of the composites were measured with an impedance analyzer and correlated with the magnetic properties of the particle such as saturation magnetization and field anisotropy. Fe-epoxy showed lower magnetic permeability but improved frequency stability, compared to the NiFe-epoxy composites of the same volume loading. This is attributed to the differences in nanoparticle's structure such as effective metal core size and particle-porosity distribution in the polymer matrix. The dielectric properties of the nanocomposites were also characterized from 30 MHz to 1000 MHz. The instabilities in the dielectric constant and loss tangent were related to the interfacial polarization relaxation of the particles and the dielectric relaxation of the surface oxides.

  11. Dielectric properties of halloysite and halloysite-formamide intercalate

    NASA Astrophysics Data System (ADS)

    Adamczyk, M.; Rok, M.; Wolny, A.; Orzechowski, K.

    2014-01-01

    Due to a high increase in electromagnetic pollution, the protection from non-ionizing electromagnetic radiation (EMR) represents an important problem of contemporary environmental science. We are searching for natural materials with the potential for EMR screening. We have discovered that hydro-halloysite has interesting properties as an EMR absorber. Unfortunately, it is a very unstable material. Drying it for even a short period of time leads to the loss of desired properties. In the paper, we have demonstrated that the intercalation of halloysite (the process of introducing guest molecules into the mineral structure) makes it possible to recover the ability to absorb an electromagnetic wave and obtain a promising material for electromagnetic field shielding applications.

  12. Structural, dielectric, and optical properties of yttrium calcium borate glasses

    Microsoft Academic Search

    Cristiane N. Santos; Domingos de Sousa Meneses; Patrick Echegut; Daniel R. Neuville; Antonio C. Hernandes; Alain Ibanez

    2009-01-01

    Structural and optical properties of stable glasses in the Y2O3-CaO-B2O3 system, containing the same Y\\/Ca ratio as the YCa4O(BO3)3 (YCOB) crystal, were determined from Raman and reflectance infrared spectroscopy. Changes in optical functions with composition are associated with an increase in the number of non-bridging oxygen and to calcium\\/yttrium oxides content. Refractive indexes values (from 1.597 to 1.627 at lambda=2

  13. Structural, dielectric, and optical properties of yttrium calcium borate glasses

    Microsoft Academic Search

    Cristiane N. Santos; Domingos De Sousa Meneses; Patrick Echegut; Daniel R. Neuville; Antonio C. Hernandes; Alain Ibanez

    2009-01-01

    Structural and optical properties of stable glasses in the Y2O3–CaO–B2O3 system, containing the same Y\\/Ca ratio as the YCa4O(BO3)3 (YCOB) crystal, were determined from Raman and reflectance infrared spectroscopy. Changes in optical functions with composition are associated with an increase in the number of non-bridging oxygen and to calcium\\/yttrium oxides content. Refractive indexes values (from 1.597 to 1.627 at ?=2

  14. Effects of adding HfO2 on the microstructure and dielectric properties of giant dielectric constant ceramic CaCu3Ti4O12

    NASA Astrophysics Data System (ADS)

    Yuan, W. X.; Hark, S. K.

    2010-03-01

    CaCu3Ti4O12 (CCTO), an unusual perovskite-like ceramic, is known for its extraordinarily high (˜10^4) and relatively frequency independent dielectric constant. It has drawn a lot of attention recently because of its potential applications in microelectronics and microwave devices. In this investigation, HfO2 powder was added to a pre-reacted CCTO powder, which was synthesized by a conventional solid-state reaction, at different concentrations from 1 to 70 wt% and the mixture was sintered into disc-shaped ceramic samples. The effects of adding HfO2 on the microstructure and dielectric properties of CCTO ceramics were investigated. In general, we found that the dielectric constant tends to increase with HfO2 addition up to 8 wt% and then decrease with further addition. Moreover, the dielectric loss was also influenced by the addition of HfO2, and a low loss tangent of ˜0.035 was obtained. The ac conductivity, impedance, complex dielectric permittivity and electric modulus graphs were used to analyze the data. These observations were explained on the basis of the internal-barrier-layer capacitor model with Maxwell-Wagner relaxations.

  15. Complex dielectric properties of anhydrous polycrystalline glucose in the terahertz region

    NASA Astrophysics Data System (ADS)

    Sun, P.; Liu, W.; Zou, Y.; Jia, Qiong Z.; Li, Jia Y.

    2015-03-01

    We utilized terahertz time-domain spectroscopy (THz-TDS) to investigate the complex dielectric properties of solid polycrystalline material of anhydrous glucose (D-(+)-glucose with purity >99.9%). THz transmission spectra of samples were measured from 0.2 to 2.2 THz. The samples were prepared into tablets with thicknesses of 0.362, 0.447, 0.504, 0.522 and 0.626 mm, respectively. The imaginary part of the complex dielectric function of polycrystalline glucose showed that there were multiple characteristic absorption peaks at 1.232, 1.445, 1.522, 1.608, 1.811 and 1.987 THz, respectively. Moreover, for a given characteristic absorption peak, the real part of the complex dielectric function showed anomalous dispersion within the full width half maximum (FWHM) of the absorption peak. Both finite difference time-domain (FDTD) numerical simulations and experimental results showed that the complex dielectric function of anhydrous polycrystalline glucose fits well with the Lorentz dielectric mode. The plasma oscillation frequency was below the frequency of the light waves suggesting that the light waves passed through the polycrystalline glucose tablets. Calculations based on density functional theory (DFT) showed that the characteristic absorption peaks of polycrystalline glucose originated mainly from collective intermolecular vibrations such as hydrogen bonds and crystal phonon modes. The THz radiation can excite the vibrational or rotational energy levels of the biological macromolecules. This leads to changes in their spatial configuration or interactions. This study showed that THz-TDS has potential applications in biological and pharmaceutical research and food industry.

  16. Static and dynamic property experiments of giant magnetostrictive material-fiber Bragg grating magnetic field sensors

    NASA Astrophysics Data System (ADS)

    Ding, Guoping; Liu, Jiayi; Gao, Bin; Zhang, Biyun

    2015-02-01

    Nowadays, there are many kinds of magnetic field sensors such as Hall sensor, Gauss meter and so on. But few of them can be used in the small air gaps which size is about millimeter. A thin-slice Giant Magnetostrictive Material-fiber Bragg grating (GMM-FBG) magnetic field sensor was proposed with the size of 14mm×7mm×1.5mm. The FBG was bonded along the GMM slice length orientation, perpendicular to the major magnetostriction orientation, to measure the GMM's strain caused by external magnetic field. Experiment systems were established to test the GMM-FBG sensor's static and dynamic properties. The results show that the sensor's static property is consistent with the theoretical prediction, and the dynamic response is feasible in low frequencies from 1Hz to 20Hz.

  17. A neutral theory with environmental stochasticity explains static and dynamic properties of ecological communities.

    PubMed

    Kalyuzhny, Michael; Kadmon, Ronen; Shnerb, Nadav M

    2015-06-01

    Understanding the forces shaping ecological communities is crucial to basic science and conservation. Neutral theory has made considerable progress in explaining static properties of communities, like species abundance distributions (SADs), with a simple and generic model, but was criticised for making unrealistic predictions of fundamental dynamic patterns and for being sensitive to interspecific differences in fitness. Here, we show that a generalised neutral theory incorporating environmental stochasticity may resolve these limitations. We apply the theory to real data (the tropical forest of Barro Colorado Island) and demonstrate that it much better explains the properties of short-term population fluctuations and the decay of compositional similarity with time, while retaining the ability to explain SADs. Furthermore, the predictions are considerably more robust to interspecific fitness differences. Our results suggest that this integration of niches and stochasticity may serve as a minimalistic framework explaining fundamental static and dynamic characteristics of ecological communities. PMID:25903067

  18. Dielectric Properties of BaTiO3Modified BiFeO3 Ceramics

    Microsoft Academic Search

    Sujittra Chandarak; Athipong Ngamjarurojana; Suthum Srilomsak; Pitak Laoratanakul; Saroj Rujirawat; Rattikorn Yimnirun

    2010-01-01

    Multiferroic BiFeO3 has attracted extensive interest due to its potential in several applications. However, pure-phase BiFeO3 is very difficult to obtain. Hence, mixing BiFeO3 with other ferroelectrics, such as BaTiO3, is another approach to obtain materials with possible multiferroic properties. In this study, the BiFeO3 was modified with addition of BaTiO3 via a simple solid state reaction method. Dielectric properties

  19. Structural, dielectric, and optical properties of yttrium calcium borate glasses

    NASA Astrophysics Data System (ADS)

    Santos, Cristiane N.; De Sousa Meneses, Domingos; Echegut, Patrick; Neuville, Daniel R.; Hernandes, Antonio C.; Ibanez, Alain

    2009-04-01

    Structural and optical properties of stable glasses in the Y2O3-CaO-B2O3 system, containing the same Y/Ca ratio as the YCa4O(BO3)3 (YCOB) crystal, were determined from Raman and reflectance infrared spectroscopy. Changes in optical functions with composition are associated with an increase in the number of non-bridging oxygen and to calcium/yttrium oxides content. Refractive indexes values (from 1.597 to 1.627 at ? =2 ?m) are in good agreement with those of the YCOB crystal, an indication that these glasses are potential candidates for optical applications due to their ease of shaping as large bulk samples or fibers.

  20. Transport and dielectric properties of water and the influence of coarse-graining: comparing BMW, SPC/E, and TIP3P models.

    PubMed

    Braun, Daniel; Boresch, Stefan; Steinhauser, Othmar

    2014-02-14

    Long-term molecular dynamics simulations are used to compare the single particle dipole reorientation time, the diffusion constant, the viscosity, and the frequency-dependent dielectric constant of the coarse-grained big multipole water (BMW) model to two common atomistic three-point water models, SPC/E and TIP3P. In particular, the agreement between the calculated viscosity of BMW and the experimental viscosity of water is satisfactory. We also discuss contradictory values for the static dielectric properties reported in the literature. Employing molecular hydrodynamics, we show that the viscosity can be computed from single particle dynamics, circumventing the slow convergence of the standard approaches. Furthermore, our data indicate that the Kivelson relation connecting single particle and collective reorientation time holds true for all systems investigated. Since simulations with coarse-grained force fields often employ extremely large time steps, we also investigate the influence of time step on dynamical properties. We observe a systematic acceleration of system dynamics when increasing the time step. Carefully monitoring energy/temperature conservation is found to be a sufficient criterion for the reliable calculation of dynamical properties. By contrast, recommended criteria based on the ratio of fluctuations of total vs. kinetic energy are not sensitive enough. PMID:24527900

  1. Transport and dielectric properties of water and the influence of coarse-graining: Comparing BMW, SPC/E, and TIP3P models

    SciTech Connect

    Braun, Daniel; Boresch, Stefan; Steinhauser, Othmar [Department of Computational Biological Chemistry, University of Vienna, Währingerstrasse 17, A-1090 Vienna (Austria)] [Department of Computational Biological Chemistry, University of Vienna, Währingerstrasse 17, A-1090 Vienna (Austria)

    2014-02-14

    Long-term molecular dynamics simulations are used to compare the single particle dipole reorientation time, the diffusion constant, the viscosity, and the frequency-dependent dielectric constant of the coarse-grained big multipole water (BMW) model to two common atomistic three-point water models, SPC/E and TIP3P. In particular, the agreement between the calculated viscosity of BMW and the experimental viscosity of water is satisfactory. We also discuss contradictory values for the static dielectric properties reported in the literature. Employing molecular hydrodynamics, we show that the viscosity can be computed from single particle dynamics, circumventing the slow convergence of the standard approaches. Furthermore, our data indicate that the Kivelson relation connecting single particle and collective reorientation time holds true for all systems investigated. Since simulations with coarse-grained force fields often employ extremely large time steps, we also investigate the influence of time step on dynamical properties. We observe a systematic acceleration of system dynamics when increasing the time step. Carefully monitoring energy/temperature conservation is found to be a sufficient criterion for the reliable calculation of dynamical properties. By contrast, recommended criteria based on the ratio of fluctuations of total vs. kinetic energy are not sensitive enough.

  2. Correlations of structural, magnetic, and dielectric properties of undoped and doped CaCu3Ti4O12

    NASA Astrophysics Data System (ADS)

    Krohns, S.; Lu, J.; Lunkenheimer, P.; Brizé, V.; Autret-Lambert, C.; Gervais, M.; Gervais, F.; Bourée, F.; Porcher, É. F.; Loidl, A.

    2009-11-01

    The present work reports synthesis, as well as a detailed and careful characterization of structural, magnetic, and dielectric properties of differently tempered undoped and doped CaCu3Ti4O12 (CCTO) ceramics. For this purpose, neutron and X-ray powder diffraction, SQUID measurements, and dielectric spectroscopy have been performed. Mn-, Fe-, and Ni-doped CCTO ceramics were investigated in great detail to document the influence of low-level doping with 3d metals on the antiferromagnetic structure and dielectric properties. In the light of possible magnetoelectric coupling in these doped ceramics, the dielectric measurements were also carried out in external magnetic fields up to 7 T. At low temperatures the dielectric constant shows a minor but significant dependence on the applied magnetic field. Undoped CCTO is well-known for its colossal dielectric constant in a broad frequency and temperature range. With the present extended characterization of doped as well as undoped CCTO, we want to address the question why doping with only 1% Mn or 0.5% Fe decreases the room-temperature dielectric constant of CCTO by a factor of ~100 with a concomitant reduction of the conductivity, whereas 0.5% Ni doping changes the dielectric properties only slightly. In addition, diffraction experiments and magnetic investigations were undertaken to check for possible correlations of the magnitude of the colossal dielectric constants with structural details or with magnetic properties like the magnetic ordering, the Curie-Weiss temperatures, or the paramagnetic moment. It is revealed, that while the magnetic ordering temperature and the effective moment of all investigated CCTO ceramics are rather similar, there is a dramatic influence of doping and tempering time on the Curie-Weiss constant.

  3. Microstructures and dielectric properties of CaCu3Ti4O12 ceramics via combustion method

    NASA Astrophysics Data System (ADS)

    Yuan, W. X.; Li, Z. J.

    2012-01-01

    CaCu3Ti4O12 (CCTO) powder was synthesized by the combustion method. The effect of sintering temperature was studied on dielectric properties of the prepared ceramic samples. They have the dielectric constant of ~31 000 and 80 000 for the grain size of 0.3 and 30-100 ?m. It is unusual for CCTO with a grain size of 0.3 ?m to have a dielectric constant of ~31 000. Their giant dielectric constant could be explained by a two-step internal-barrier-layer-capacitor model, associated with grain boundaries and domain boundaries. The existence of domain boundaries helped to explain the contradiction of the dielectric mechanisms between polycrystalline and single-crystal CCTO.

  4. Analytical Solution for the SU(2) Hedgehog Skyrmion and Static Properties of Nucleons

    E-print Network

    Jia, Duojie; Liu, Feng

    2009-01-01

    An analytical solution for symmetric Skyrmion was proposed for the SU(2) Skyrme model, which take the form of the hybrid form of a kink-like solution and that given by the instanton method. The static properties of nucleons was then computed within the framework of collective quantization of the Skyrme model, with a good agreement with that given by the exact numeric solution. The comparisons with the previous results as well as the experimental values are also given.

  5. Static and dynamical properties of II–VI and III–V group binary solids

    Microsoft Academic Search

    D S Yadav; D V Singh

    2012-01-01

    In this paper, we extend to II–VI and III–V group binary solids of zinc blende (ZB) structure with conduction d-electrons the calculation of static and dynamical properties such as bulk modulus (B) and cohesive energy or total energy (Ecoh) using the plasma oscillation theory of solids formalism already employed for ternary chalcopyrite semiconductors. The present method is not limited to

  6. Quasi-static and high strain rate properties of a cross-ply metal matrix composite

    Microsoft Academic Search

    I. W. Hall; A. Tasdemirci; J. Derrick

    2009-01-01

    A series of compression tests has been carried out at quasi-static and high strain rates on cylindrical samples of an alumina fiber\\/Al-6061 metal matrix composite. The composite plates were prepared with fibers in the 0°, 0\\/90° and ±45° orientations. It was found that the mechanical properties were strongly dependent upon the imposed strain rate, with fracture stress increases of >50%

  7. Computer simulation and experiments on the quasi-static mechanics and transport properties of granular materials

    Microsoft Academic Search

    Xue-Jin Zhuang; J. D. Goddard

    1993-01-01

    This report presents the results of a new quasi-static algorithm developed to compute the mechanical and scalar transport properties of three dimensional sphere assemblages. The algorithm incorporates several new techniques, including a shuffling algorithm for generation of initial random granular packings, an improved microcell-adjacency method to accelerate particle-contact search, and a relaxation method to overcome a singularity in the quasilinear

  8. Relative influence upon microwave emissivity of fine-scale stratigraphy, internal scattering, and dielectric properties

    USGS Publications Warehouse

    England, A.W.

    1976-01-01

    The microwave emissivity of relatively low-loss media such as snow, ice, frozen ground, and lunar soil is strongly influenced by fine-scale layering and by internal scattering. Radiometric data, however, are commonly interpreted using a model of emission from a homogeneous, dielectric halfspace whose emissivity derives exclusively from dielectric properties. Conclusions based upon these simple interpretations can be erroneous. Examples are presented showing that the emission from fresh or hardpacked snow over either frozen or moist soil is governed dominantly by the size distribution of ice grains in the snowpack. Similarly, the thickness of seasonally frozen soil and the concentration of rock clasts in lunar soil noticeably affect, respectively, the emissivities of northern latitude soils in winter and of the lunar regolith. Petrophysical data accumulated in support of the geophysical interpretation of microwave data must include measurements of not only dielectric properties, but also of geometric factors such as finescale layering and size distributions of grains, inclusions, and voids. ?? 1976 Birkha??user Verlag.

  9. Theoretical study of the structural, vibrational and dielectric properties of PbSnTe alloys

    NASA Astrophysics Data System (ADS)

    Leite Alves, Horacio W.; Neto, Antonio R. R.; Petersen, John E.; Borges, Pablo D.; Scolfaro, Luisa M. R.

    2015-03-01

    Thermoelectric devices have promise in dealing with the challenges of the growing demand for alternative clean energy and Te-based materials well-known candidates for them. Recently, we have shown that the high values for the dielectric constant, together with anharmonic LA-TO coupling, reduces the lattice thermal conductivity and enhances the electronic conductivity in PbTe. Also, it was shown that by alloying this material with Se, the electronic conductivity of the alloys is also enhanced. But, it is not clear if the same occurs when alloying with Sn. We show, in this work, our ab initio results for the structural, vibrational and dielectric properties of Pb1-xSnxTe alloys. The calculations were carried out by using the Density Functional Theory, and the alloys were described by the Virtual Crystal Approximation. Our results show that their structural properties do not obey the Vegard rule. However, we have detected that the anharmonic LA-TO coupling still exists and the obtained values for the dielectric constant show higher values than that obtained for PbTe.

  10. Measurement of dielectric properties in ceramics under ionizing and displacive irradiation conditions

    NASA Astrophysics Data System (ADS)

    Stoller, R. E.; Goulding, R. H.; Zinkle, S. J.

    1992-09-01

    Several experiments have been completed in which the dielectric properties of ceramic materials were measured during ionizing and displacive irradiation. The experimental matrix included single crystal sapphire, commercial-grade polycrystalline alumina, magnesium aluminate spinel, silicon nitride, and aluminum nitride. These materials are candidates for use in a number of fusion reactor components. The measurements were made at 100 MHz using a capacitively loaded resonant cavity. Essentially no affect: of ionizing radiation alone was observed for damage rates up to about 5×10 5 Gy/h. However, pulsed fission reactor irradiation led to dramatic increases in the loss tangent. The fractional contributions of the ionizing and displacive fields to the total change observed during the neutron irradiations could not be unambiguously determined. The results of these experiments indicate that the use of postirradiation measurements leads to an underestimate of the radiation-induced dielectric degradation that occurs in the radiation field.

  11. Deposition and dielectric property of ion-beam assisted bismuth titanate film

    SciTech Connect

    Azimi, M.; Ghosh, P.K. [Syracuse Univ., NY (United States)

    1994-12-31

    Thin films of bismuth titanate (Bi{sub 4}Ti{sub 3}O{sub 12}) have been prepared on different substrates by ion-beam sputtering technique. These films were deposited using a Bi(bismuth)-rich Bi{sub 4}Ti{sub 3}O{sub 12} ceramic target. Films were deposited with substrate temperatures ranging from 320{degrees}C to 550{degrees}C. We observed that the dielectric behavior of the deposited films strongly depends on the deposition parameters (such as the substrate temperature, sputter gas mixture, etc.). Results, also, indicate that films deposited at substrate temperature of about 450{degrees}C have dielectric property comparable to that of single crystal bismuth titanate.

  12. Laboratory studies of electrical properties of insulating materials. [thermal insulation of spacecraft dielectrics

    NASA Technical Reports Server (NTRS)

    Nanevicz, J. E.; Adamo, R. C.; Grier, N.

    1978-01-01

    The characteristics of satellites are influenced by the electrical properties of the dielectric exterior. It was found in simulated space environment tests that the electrical conductivities of dielectrics are affected as the result of interactions with various components of the environment. The degree to which the conductivity was affected varied with material. In some instances the changes found to occur could be used to advantage, particularly if they could be enhanced. For example, the increased electrical conductivity of Kapton resulting from solar illumination could be used to advantage to eliminate the charge storage leading to electrical breakdown during magnetic substorms. Similarly the relative immunity of FEP Teflon to change from response to the space environment makes it a logical choice as a solar cell cover in a high-voltage solar array.

  13. Structural and optical properties of different dielectric thin films for planar waveguiding applications

    NASA Astrophysics Data System (ADS)

    Pearce, S. J.; Charlton, M. D. B.; Parker, G. J.; Wilkinson, J. S.

    2011-03-01

    Thin films of two different dielectric materials (Yttrium Oxide and Tantalum Pentoxide) were deposited by reactive sputtering and reactive evaporation to determine their suitability as a host for a rare earth doped planar waveguide upconversion laser. The optical properties, structure and crystalline phase of the films were found to be dependent on the deposition method and process parameters. X-ray diffraction (XRD) analysis on several of the 'as-deposited' thin films revealed that the films vary from amorphous to highly crystalline depending on material and process parameters. SEM imaging of the Yttrium Oxide layers revealed a regular column structure confirming their crystalline nature and SEM imaging of the Tantalum Pentoxide layers revealed a smooth amorphous layer confirming their XRD diffractrograms. The dielectric thin film layers which allowed guiding in both the visible and infra-red regions of the spectrum had a more amorphous structure.

  14. Thickness-dependent dielectric and tunable properties of barium stannate titanate thin films

    NASA Astrophysics Data System (ADS)

    Song, Sannian; Zhai, Jiwei; Gao, Lina; Yao, Xi; Lu, Shengbo; Xu, Zhengkui

    2009-07-01

    Barium stannate titanate Ba(Sn0.15Ti0.85)O3 (BTS) thin films with different thicknesses were grown by sol-gel process on single crystal LaAlO3 (LAO) and Pt/Ti/SiO2/Si substrates, respectively. Coplanar capacitance and parallel plate capacitance structure configurations were formed by preparing interdigital electrodes and parallel plate electrodes on BTS thin films. Both of the films exhibited an enhanced dielectric constant and tunability as the film thickness increases but these two cases are actually based on different mechanisms. The thickness dependent dielectric properties of the films deposited on Pt/Ti/SiO2/Si substrates were mainly attributed to the "dead layer" effect while those of the films grown on LAO substrates were due to strain and grain size of the films.

  15. Phase structure and dielectric properties of Bi[sub 2]O[sub 3]-ZnO-Nb[sub 2]O[sub 5]-based dielectric ceramics

    SciTech Connect

    Donhang Liu; Yi Liu; Huang, S.Q.; Xi Yao (Xi'an Jiaotong Univ. (China). Dept. of Electronic Engineering)

    1993-08-01

    Phase structures and dielectric properties of the compounds with formulas Bi[sub x]Zn[sub 2/3]Nb[sub 4/3]O[sub 4+3x/2] (group M), Bi[sub x]Zn[sub 8/3[minus]x]-Nb[sub 4/3]O[sub 6+x/2] (group V), and Bi[sub x]Zn[sub 2[minus]x/3]Nb[sub 2[minus]x/3]O[sub 7] (group W) have been investigated. Initial results indicate that a cubic pyrochlore structure is the predominant phase of these compounds. Most of the measured ceramic specimens exhibit dielectric properties suitable as temperature-stable and temperature-compensating dielectrics in the capacitor industry. The values of the dielectric constant K are 80-160, while those of the temperature coefficient are [minus]500 to +160 ppm/[degree]C. The composition limits of the single pyrochlore phase are determined mainly by Bi[sub 2]O[sub 3] additives.

  16. Effects of annealing conditions on the dielectric properties of solution-processed Al2O3 layers for indium-zinc-tin-oxide thin-film transistors.

    PubMed

    Kim, Yong-Hoon; Kim, Kwang-Ho; Park, Sung Kyu

    2013-11-01

    In this paper, the effects of annealing conditions on the dielectric properties of solution-processed aluminum oxide (Al2O3) layers for indium-zinc-tin-oxide (IZTO) thin-film transistors (TFTs) have been investigated. The dielectric properties of Al2O3 layers such as leakage current density and dielectric strength were largely affected by their annealing conditions. In particular, oxygen partial pressure in rapid thermal annealing, and the temperature profile of hot plate annealing had profound effects on the dielectric properties. From a refractive index analysis, the enhanced dielectric properties of Al2O3 gate dielectrics can be attributed to higher film density depending on the annealing conditions. With the low-temperature-annealed Al2O3 gate dielectric at 350 degrees C, solution-processed IZTO TFTs with a field-effect mobility of approximately 2.2 cm2/Vs were successfully fabricated. PMID:24245333

  17. Investigation of optical and interfacial properties of Ag/Ta2O5 metal dielectric multilayer structure

    NASA Astrophysics Data System (ADS)

    Sarkar, P.; Jena, S.; Tokas, R. B.; Rao, K. D.; Misal, J. S.; Prathap, C.; Thakur, S.; Sahoo, N. K.

    2015-06-01

    One-dimensional periodic metal-dielectric multilayer thin film structures consisting of Ag and Ta2O5 alternating layers are deposited on glass substrate using RF magnetron sputtering technique. The spectral property of the multilayers has been investigated using spectrophotometry technique. The optical parameters such as refractive index, extinction coefficient, band gap etc., along with film thickness as well as the interfacial layer properties which influence these properties have been probed with spectroscopic ellipsometry technique. Atomic force microscopy has been employed to characterize morphological properties of this metal-dielectric multilayer.

  18. Research Update: Polyimide/CaCu3Ti4O12 nanofiber functional hybrid films with improved dielectric properties

    NASA Astrophysics Data System (ADS)

    Yang, Yang; Wang, Ziyu; Ding, Yi; Lu, Zhihong; Sun, Haoliang; Li, Ya; Wei, Jianhong; Xiong, Rui; Shi, Jing; Liu, Zhengyou; Lei, Qingquan

    2013-11-01

    This work reports the excellent dielectric properties of polyimide (PI) embedded with CaCu3Ti4O12 (CCTO) nanofibers. The dielectric behaviors were investigated over a frequency of 100 Hz-1 MHz. It is shown that embedding CCTO nanofibers with high aspect ratio (67) is an effective means to enhance the dielectric permittivity and reduce the percolation threshold. The dielectric permittivity of PI/CCTO nanofiber composites is 85 with 1.5 vol.% loading of filler, also the dielectric loss is only 0.015 at 100 Hz. Monte Carlo simulation was used to investigate the percolation threshold of CCTO nanofibers reinforced polyimide matrix by using excluded volume theory and soft, hard-core models. The results are in good agreement with the percolation theory and the hard-core model can well explain the percolation phenomena in PI/CCTO nanofiber composites. The dielectric properties of the composites will meet the practical requirements for the application in high dielectric constant capacitors and high energy density materials.

  19. Static dielectric constants and molecular dipole distributions of liquid water and ice-Ih investigated by the PAW-PBE exchange-correlation functional

    NASA Astrophysics Data System (ADS)

    Rusnak, Andrew J.; Pinnick, Eric R.; Calderon, Camilo E.; Wang, Feng

    2012-07-01

    The static dielectric constants, ?s, of ice-Ih and liquid water were calculated using density functional theory with the Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional and the projector-augmented-wave (PAW) approach. Proton disordered ice configurations and uncorrelated liquid configurations were sampled with the electrostatic switching method using force fields specially designed to facilitate the ab initio free energy perturbation calculations. Our results indicate that PAW-PBE underestimates the ?s of both ice-Ih and liquid water but predicts the ratio of ice and water ?s in good agreement with experimental measurements. PAW-PBE gives average water dipole moments of 2.50 D in ice-Ih and 2.48 D in the liquid. Our results show that the fixed-charge water models developed by adaptive force matching can reproduce the PAW-PBE dipole moments with an error of approximately 5%. The ice and liquid models created in this work have polarizabilities of 1.32 Å3 and 1.30 Å3, respectively, along the HOH bisector direction.

  20. Static dielectric constants and molecular dipole distributions of liquid water and ice-Ih investigated by the PAW-PBE exchange-correlation functional.

    PubMed

    Rusnak, Andrew J; Pinnick, Eric R; Calderon, Camilo E; Wang, Feng

    2012-07-21

    The static dielectric constants, ?(s), of ice-Ih and liquid water were calculated using density functional theory with the Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional and the projector-augmented-wave (PAW) approach. Proton disordered ice configurations and uncorrelated liquid configurations were sampled with the electrostatic switching method using force fields specially designed to facilitate the ab initio free energy perturbation calculations. Our results indicate that PAW-PBE underestimates the ?(s) of both ice-Ih and liquid water but predicts the ratio of ice and water ?(s) in good agreement with experimental measurements. PAW-PBE gives average water dipole moments of 2.50 D in ice-Ih and 2.48 D in the liquid. Our results show that the fixed-charge water models developed by adaptive force matching can reproduce the PAW-PBE dipole moments with an error of approximately 5%. The ice and liquid models created in this work have polarizabilities of 1.32 Å(3) and 1.30 Å(3), respectively, along the HOH bisector direction. PMID:22830714

  1. Measurement of the dielectric properties of high-purity sapphire at 1.865 GHZ from 2-10 Kelvin

    SciTech Connect

    N. Pogue, P. McIntyre, Akhdiyor Sattarov, Charles Reece

    2012-06-01

    A dielectric test cavity was designed and tested to measure the microwave dielectric properties of ultrapure sapphire at cryogenic temperatures. Measurements were performed by placing a large cylindrical crystal of sapphire in a Nb superconducting cavity operating in the TE01 mode at 1.865 GHz. The dielectric constant, heat capacity, and loss tangent were all calculated using experimental data and RF modeling software. The motivation for these measurements was to determine if such a sapphire could be used as a dielectric lens to focus the magnetic field onto a sample wafer in a high field wafer test cavity. The measured properties have been used to finalize the design of the wafer test cavity.

  2. Influence of nanogold additives on phase formation, microstructure and dielectric properties of perovskite BaTiO3 ceramics

    NASA Astrophysics Data System (ADS)

    Nonkumwong, Jeeranan; Ananta, Supon; Srisombat, Laongnuan

    2015-06-01

    The formation of perovskite phase, microstructure and dielectric properties of nanogold-modified barium titanate (BaTiO3) ceramics was examined as a function of gold nanoparticle contents by employing a combination of X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray, Archimedes principle and dielectric measurement techniques. These ceramics were fabricated from a simple mixed-oxide method. The amount of gold nanoparticles was found to be one of the key factors controlling densification, grain growth and dielectric response in BaTiO3 ceramics. It was found that under suitable amount of nanogold addition (4 mol%), highly dense perovskite BaTiO3 ceramics with homogeneous microstructures of refined grains (~0.5-3.1 ?m) and excellence dielectric properties can be produced.

  3. Electrical properties of atomic layer deposited high-k dielectrics on Indium Nitride

    NASA Astrophysics Data System (ADS)

    Jia, Ye

    Indium nitride is a promising channel material for high frequency transistors because of its low effective electron mass (m* = 0.04m0) and high electron velocities. However, realizing practical InN devices has a number of challenges. One of the challenges is the presence of large surface electron accumulation layer. It is caused by InN surface Fermi level pinning above conduction band that results in downward bending of the bands at the surface. It has been reported that chemical surface treatment could un-pin the surface, reducing the electron accumulation density. In this work, hydrochloric acid, ammonium sulfide and trimethylaluminium (TMA) are used for the passivation of InN wafers before dielectric deposition. Metal-oxide-semiconductor capacitor (MOSCAP) structures are fabricated to study the effectiveness of the passivation methods. The current-voltage and capacitance-voltage characteristics are measured on MOSCAPs with atomic layer deposited high-k dielectrics. Current-voltage curves indicate that high-k dielectric layer shows excellent insulating properties with low leakage currents. Measured capacitance-voltage curves demonstrate surface electron accumulation even with passivation. Simulations of device structure are carried out to understand the capacitance-voltage behavior.

  4. The correlation between dielectric properties and microstructure of femoral bone in rats with different bone qualities.

    PubMed

    Tao, Feng; Fu, Feng; You, Fusheng; Ji, Zhenyu; Wen, Jun; Shi, Xuetao; Dong, Xiuzhen; Yang, Min

    2014-06-01

    Bone dielectric properties (DP) have been extensively studied. However, little literature has reported DP of bone from identical anatomical site under different status and its correlation with microstructure. Therefore, interrelationship between DP and microstructure of rat femurs with varying bone qualities (normal, osteoporotic and partially osteoporotic) was investigated. Diabetic osteoporosis was induced by streptozotocin (STZ) injection. 8 normal rats as control group together with 16 diabetic rats equally assigned to diabetes mellitus (DM) and DM treated by pulsed electromagnetic fields (PEMF) (DM + PEMF) group were used. DM + PEMF group was daily exposed to PEMF of 15 Hz, 1 mT for 8 weeks. After sacrifice, the femurs were harvested for microCT analysis and dielectric measurements (from 10 Hz to 1 MHz). It was found that DP (conductivity and permittivity) altered after PEMF stimulation improved femoral microstructures (p < 0.01). Significant correlations were found between microstructure indices (MI) and conductivity in the full frequency range (|r| ? 0.64, n = 24) as well as permittivity in middle and low frequencies (|r| ? 0.52, n = 24, from 1 Hz to 1 kHz). The findings demonstrated the good correlation between DP and MI of femoral bone in rats, which makes it possible to distinguish bone under different status and predict MI variation through dielectric measurements. PMID:24710797

  5. High temperature dielectric properties of Apical, Kapton, Peek, Teflon AF, and Upilex polymers

    NASA Technical Reports Server (NTRS)

    Hammoud, A. N.; Baumann, E. D.; Overton, E.; Myers, I. T.; Suthar, J. L.; Khachen, W.; Laghari, J. R.

    1992-01-01

    Reliable lightweight systems capable of providing electrical power at the magawatt level are a requirement for future manned space exploration missions. This can be achieved by the development of high temperature insulating materials which are not only capable of surviving the hostile space environment but can contribute to reducing the mass and weight of the heat rejection system. In this work, Apical, Upilex, Kapton, Teflon AF, and Peek polymers are characterized for AC and DC dielectric breakdown in air and in silicone oil at temperatures up to 250 C. The materials are also tested in terms of their dielectric constant and dissipation factor at high temperatures with an electrical stress of 60 Hz, 200 V/mil present. The effects of thermal aging on the properties of the films are determined after 15 hours of exposure to 200 and 250 C, each. The results obtained are discussed and conclusions are made concerning the suitability of these dielectrics for use in capacitors and cable insulations in high temperature environments.

  6. Anomalies in electrical and dielectric properties of nanocrystalline Ni-Co spinel ferrite

    SciTech Connect

    Mathe, V.L. [Novel Materials Research Laboratory, Department of Physics, University of Pune, Ganeshkhind, Pune 411 007, MS (India)], E-mail: vlmathe@physics.unipune.ernet.in; Kamble, R.B. [Novel Materials Research Laboratory, Department of Physics, University of Pune, Ganeshkhind, Pune 411 007, MS (India)

    2008-08-04

    Nanocrystalline Ni-substituted cobalt ferrite sample is prepared by chemical co-precipitation method. X-ray diffraction and scanning electron microscopy techniques are used to obtain structural and morphological characterizations. Nanocrystalline nature is clearly seen in SEM picture. Variation of electrical resistivity as a function of temperature in the range 300-900 K is investigated. ln {rho} versus 1/T plot shows four break resulting into five regions in 300-900 K temperature range of measurements. The magnetic transition temperature of the sample is determined from resistivity behavior with temperature. The activation energy in different regions is calculated and discussed. Variation of dielectric constant ({epsilon}') with increasing temperature show more than one peak; one at around 773 K and other around 833 K, which is unusual behavior of ferrites. The observed peaks in {epsilon}' variation with temperature show frequency dependence. Electrical and dielectric properties of Ni{sub 0.4}Co{sub 0.6}Fe{sub 2}O{sub 4} sample show unusual behavior in the temperature range 723-833 K. To our knowledge, nobody has discussed anomalous behavior in the temperature range 723-833 K for Ni{sub 0.4}Co{sub 0.6}Fe{sub 2}O{sub 4}. The possible mechanism responsible for the unusual electrical and dielectric behavior of the sample is discussed.

  7. Influence of isolated and clustered defects on electronic and dielectric properties of wüstite

    NASA Astrophysics Data System (ADS)

    Wdowik, Urszula D.; Piekarz, Przemys?aw; Jochym, Pawe? T.; Parlinski, Krzysztof; Ole?, Andrzej M.

    2015-05-01

    The influence of intrinsic Fe defects in FeO (either single cation vacancies or prototypical 4:1 vacancy clusters) on electronic and dielectric properties is studied within density-functional theory. The importance of local Coulomb interactions at Fe atoms is highlighted and shown to be responsible for the observed insulating Mott gap in FeO, which is reduced by the presence of defects. We investigate nonstoichiometric configurations of Fe1 -xO with x ranging from 3% to 9%, and we find the aliovalent Fe cations in both the regular and interstitial lattice sites of the considered configurations. Furthermore, we show that the trivalent Fe ions, induced by both isolated and clustered Fe vacancies, introduce the empty band states inside the insulating gap, which decreases monotonically with increasing cation vacancy concentration. The Fe1 -xO systems with high defect content become metallic for small values of the Coulomb interaction U , yielding an increase in the dielectric functions and optical reflectivity at low energies, in agreement with the experimental data. Due to the crystal defects, the infrared-active transverse optic phonons split and distribute over a wide range of frequencies, clarifying the origin of the exceptionally large spectral linewidths of the dielectric loss functions observed for wüstite in recent experiments.

  8. Electrical and dielectric properties of silver iodide doped selenium molybdate glassy conductors

    NASA Astrophysics Data System (ADS)

    Palui, A.; Deb, B.; Ghosh, A.

    2013-08-01

    Electrical conductivity and dielectric properties of silver iodide doped silver ion mixed-former conducting glasses have been studied in this paper. The frequency dependence of conductivity has been analyzed following the random free-energy barrier model. The charge carrier relaxation time and the activation energy for relaxation have been determined for the present glasses. The applicability of Barton-Nakajima-Namikawa relation has been tested for the present glasses using the results obtained from random free-energy barrier model. The scaling of the conductivity spectra has been performed to understand the effect of temperature as well as composition on the relaxation dynamics. The dielectric data have been analyzed employing the Cole-Cole function, and parameters such as dielectric strength and Cole-Cole exponent have been obtained. The electrode polarization phenomenon for the present glass samples has been studied depending on temperature as well as composition. The different characteristic transitions concerning electrode polarization related to the charge transport at the interface have been obtained and are correlated to the bulk behavior. An estimation of the dc conductivity has been obtained using the result obtained from electrode polarization study and is observed to be very close to the experimental values.

  9. Vanadium oxide nanotubes VOx-NTs: Hydrothermal synthesis, characterization, electrical study and dielectric properties

    SciTech Connect

    Nefzi, H. [Laboratoire de Chimie de la Matière Condensée IPEIT, Université de Tunis, 2 rue Jawaher Lel Nehru 1008, B.P. 229 Montfleury, Tunis (Tunisia); Sediri, F., E-mail: sediri68@gmail.com [Laboratoire de Chimie de la Matière Condensée IPEIT, Université de Tunis, 2 rue Jawaher Lel Nehru 1008, B.P. 229 Montfleury, Tunis (Tunisia); Faculté des Sciences de Tunis, Université de Tunis El Manar, 2092 El Manar, Tunis (Tunisia)

    2013-05-01

    Vanadium oxide nanotubes (VOx-NTs) have been synthesized via one-step hydrothermal treatment. The compounds were analyzed through X-ray powder diffraction; scanning electron microscope, UV–Visible spectroscopy, X-ray photoelectron spectroscopy (XPS) and complex impedance spectroscopy. The electrical and dielectric properties dependence on temperature (302–523 K) and on frequency (5 Hz to 13 MHz) of VOx-NTs have been reported. The complex impedance plots exhibits the presence of grain and grain boundaries. Dielectric data were analyzed using complex permittivity and complex electrical modulus for the sample at various temperatures. The presence of non-Debye type of relaxation has been confirmed by the complex modulus analysis. AC conductivity exhibits two conduction mechanisms: at high temperature, a translational motion with a sudden hopping and at low temperature, a localized hopping with a small hopping or reorientational motion. DC conductivity indicated, negative temperature coefficient of resistance (NTCR) type behavior. - Graphical abstract: The imaginary part of dielectric constant decreases with the increase in frequency at all temperatures and the values of ?´´ exhibit considerable frequency dispersion in the lower frequency range . Highlights: •Vanadium oxide nanotubes (VOx-NTs) were synthesized. •Non-debye type of relaxation has been confirmed. •AC conductivity exhibits two conduction mechanisms. •DC conductivity indicated negative temperature coefficient of resistance type behavior.

  10. Dielectric and Pyroelectric Properties of La- and Pr-Modified Tungsten-Bronze Ferroelectrics

    NASA Astrophysics Data System (ADS)

    Parida, B. N.; Das, Piyush R.; Padhee, R.; Choudhary, R. N. P.

    2013-08-01

    The polycrystalline materials Li2Pb2R2W2Ti4Nb4O30 (R = La, Pr) of the tungsten-bronze structural family have been synthesized using a high- temperature mixed-oxide method. Room-temperature x-ray diffraction (XRD) analysis confirms the formation of single-phase compounds. Room-temperature scanning electron micrography of the pellet samples shows a uniform distribution of well-defined different sizes of grains on the surface of the samples, confirming the formation of single-phase compounds. Study of the frequency and temperature dependence of the dielectric constant and loss tangent suggests the existence of dielectric dispersion in the materials. The ferroelectric phase transition in the samples has been studied based on the variation of fitting parameters (calculated from a theoretical model) with temperature. Studies of pyroelectric properties [figure of merit (FOM) and coefficient] show that the materials have reasonably high FOM useful for pyroelectric detectors. The variation of alternating-current (AC) and direct-current (DC) conductivity with inverse absolute temperature (obtained from dielectric data) follows a typical Arrhenius relation. The low leakage current and negative temperature coefficient of resistance behavior of the samples have been verified from J- E plots.

  11. Effect of biphase on dielectric properties of Bi-doped lead strontium titanate thin films

    NASA Astrophysics Data System (ADS)

    Li, X. T.; Du, P. Y.; Zhao, Y. L.; Tu, Y.; Dai, J. L.; Weng, W. J.; Han, G. R.; Song, C. L.

    2010-11-01

    Pb 0.4Sr 0.6TiO 3 (PST) thin films doped with various concentration of Bi were prepared by a sol-gel method. The phase status, surface morphology and dielectric properties of these thin films were measured by X-ray diffraction (XRD), scanning electron microscopy (SEM) and impedance analyzer, respectively. Results showed that the thin films with the maximum dielectric constant and minimum dielectric loss were obtained for x=0.15. For x<0.15, only pure PST perovskite phase were in the thin films. For 0.2< x<0.4, the PST/Bi 2Ti 2O 7 biphase were obtained. The thin films with pure Bi 2Ti 2O 7 pyrochlore phase were obtained for x=0.67. The biphase thin films had high tunability and high figure of merit (FOM). The FOM of PST/Bi 2Ti 2O 7 biphase thin film was about 6 times higher than that thin films formed with pure perovskite phase or pure pyrochlore phase.

  12. Dielectric loss, conductivity relaxation process and magnetic properties of Mg substituted Ni-Cu ferrites

    NASA Astrophysics Data System (ADS)

    Singh, Navneet; Agarwal, Ashish; Sanghi, Sujata; Khasa, Satish

    2012-08-01

    The dielectric properties, dc and ac electrical resistivities of Mg substituted Ni-Cu ferrites with general formula Ni0.5Cu0.5-xMgxFe2O4 (0.0?x?0.5) have been investigated as a function of frequency, temperature and composition. ac resistivity of all the samples decreases with increase in the frequency exhibiting normal ferrimagnetic behavior. The frequency dependence of dielectric loss tangent showed a maximum in between 10 Hz and 1 kHz in all the ferrites. The conductivity relaxation of the charge carriers was examined using the electrical modulus formulism, and the results indicate the presence of the non-Debye type of relaxation in the prepared ferrites. Similar values of activation energies for dc conduction and for conductivity relaxation reveal that the mechanism of electrical conduction and dielectric polarization is the same in these ferrites. A single 'master curve' for normalized plots of all the modulus isotherms observed for a given composition indicates that the distribution of relaxation time is temperature independent. The saturation magnetization and coercivity as calculated from the hysteresis loop measurement show striking dependence on composition.

  13. Dielectric Properties of Polypropylene-Based Nanocomposites with Ionic Liquid-Functionalized Multiwalled Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Xu, Pei; Gui, Haoguan; Hu, Yadong; Bahader, Ali; Ding, Yunsheng

    2014-07-01

    Nanocomposites were prepared from polypropylene (PP) and untreated multiwalled carbon nanotubes (MWCNTs) or MWCNTs surface-functionalized with ionic liquids (MIL), as fillers, and their dielectric properties were compared. The physical (cation-?/?-?) interaction between the ionic liquids and the MWCNTs was apparent from Raman spectroscopy and from thermogravimetric analysis. Morphology characterization revealed that ionic liquids improve the dispersibility of MWCNTs in the PP matrix. It is suggested that the substantial increase in the dielectric permittivity of the nanocomposites compared with that of the PP originates from a remarkable Maxwell-Wagner-Sillars (MWS) effect at percolation threshold where mobile charge carriers are blocked at internal interfaces between the MIL and the PP matrix. The high polarity of ionic liquids may reinforce the MWS effect, and the nonconducting organic groups of the ionic liquids promote the low loss tangent and low conductivity of the MIL/PP nanocomposites. Compared with MWCNTs/PP nanocomposites, lower loss tangent and higher dielectric permittivity were observed for MIL/PP nanocomposites, making the material more attractive for application in electronics.

  14. Dielectric properties of alginate beads and bound water relaxation studied by electrorotation.

    PubMed

    Esch, M; Sukhorukov, V L; Kürschner, M; Zimmermann, U

    1999-09-01

    The electrical and dielectric properties of Ba2+ and Ca2+ cross-linked alginate hydrogel beads were studied by means of single-particle electrorotation. The use of microstructured electrodes allowed the measurements to be performed over a wide range of medium conductivity from about 5 mS/m to 1 S/m. Within a conductivity range, the beads exhibited measurable electrorotation response at frequencies above 0.2 MHz with two well-resolved co- and antifield peaks. With increasing medium conductivity, both peaks shifted toward higher frequency and their magnitudes decreased greatly. The results were analyzed using various dielectric models that consider the beads as homogeneous spheres with conductive loss and allow the complex rotational behavior of beads to be explained in terms of conductivity and permittivity of the hydrogel. The rotation spectra could be fitted very accurately by assuming (a) a linear relationship between the internal hydrogel conductivity and the medium conductivity, and (b) a broad internal dispersion of the hydrogel centered between 20 and 40 MHz. We attribute this dispersion to the relaxation of water bound to the polysaccharide matrix of the beads. The dielectric characterization of alginate hydrogels is of enormous interest for biotechnology and medicine, where alginate beads are widely used for immobilization of cells and enzymes, for drug delivery, and as microcarriers for cell cultivation. PMID:10397786

  15. Changes in the dielectric properties of medaka fish embryos during development, studied by electrorotation.

    PubMed

    Shirakashi, Ryo; Mischke, Miriam; Fischer, Peter; Memmel, Simon; Krohne, Georg; Fuhr, Günter R; Zimmermann, Heiko; Sukhorukov, Vladimir L

    2012-11-01

    The Japanese medaka fish, Oryzias latipes, has become a powerful vertebrate model organism in developmental biology and genetics. The present study explores the dielectric properties of medaka embryos during pre-hatching development by means of the electrorotation (ROT) technique. Due to their layered structure, medaka eggs exhibited up to three ROT peaks in the kHz-MHz frequency range. During development from blastula to early somite stage, ROT spectra varied only slightly. But as the embryo progressed to the late-somite stage, the ROT peaks underwent significant changes in frequency and amplitude. Using morphological data obtained by light and electron microscopy, we analyzed the ROT spectra with a three-shell dielectric model that accounted for the major embryonic compartments. The analysis yielded a very high value for the ionic conductivity of the egg shell (chorion), which was confirmed by independent osmotic experiments. A relatively low capacitance of the yolk envelope was consistent with its double-membrane structure revealed by transmission electron microscopy. Yolk-free dead eggs exhibited only one co-field ROT peak, shifted markedly to lower frequencies with respect to the corresponding peak of live embryos. The dielectric data may be useful for monitoring the development and changes in fish embryos' viability/conditions in basic research and industrial aquaculture. PMID:23063978

  16. Investigation into the electromechanical properties of dielectric elastomers subjected to pre-stressing.

    PubMed

    Jiang, Liang; Betts, Anthony; Kennedy, David; Jerrams, Stephen

    2015-04-01

    Dielectric elastomers (DEs) are being exploited for biological applications such as artificial blood pumps, biomimetic grippers and biomimetic robots. Generally, polyacrylate and silicone rubber (SR) are the most widely used materials for fabricating DEs in terms of mixing with other polymers or compounding them with highly dielectric particles. Furthermore, pre-stretch offers an effective approach to increasing actuated strain and dielectric strength and eliminating 'pull-in' instability. In the work described here, a comparison in electromechanical properties was made between SR/10% barium titanate (BaTiO3) and commercial VHB 4910. Trends in these dielectric parameters are shown graphically for variation in pre-stretch ratio (?pre). It was found that permittivity of SR/10% BaTiO3 was independent of frequency, whereas permittivity was frequency-independent due to the polarization of polymer chains. The maximum deformation and the coupling efficiency for SR/10% BaTiO3 can be achieved at a pre-stretch ratio between 1.6 and 1.9. For VHB 4910, they can be obtained in the pre-stretch ratio range from 2.6 to 3.0. A maximum energy density of 0.05MJ/m(3) was achieved by SR/10% BaTiO3 (?pre=1.6) and VHB 4910 (?pre=3.4). The findings provide an insight into critical pre-stretch ratios required for a range of applications of DEs based on silicone and the commercially available polyacrylate VHB 4910. PMID:25687005

  17. Structural and dielectric properties of Cr-doped Ni-Zn nanoferrites

    Microsoft Academic Search

    S. Nasir; M. Anis-ur-Rehman; Muhammad Ali Malik

    2011-01-01

    Cr-doped Ni-Zn ferrite nanoparticles having the general formula Ni0.5Zn0.5CrxFe2-xO4 (x=0.1, 0.3, 0.5) were prepared by the simplified sol-gel method. The structural and dielectric properties of the samples sintered at 750±5 °C were studied. X-ray diffraction (XRD) patterns confirm the single-phase spinel structure of the prepared samples. The crystallite size calculated from the most intense peak (3 1 1) using the

  18. Dielectric properties of Li3VO4 single crystals grown by the Czochralski method

    NASA Astrophysics Data System (ADS)

    Kim, Dong Jin; Jun, Byeong Eog; Kim, Chung-Sik; Kim, Hyung Kook; Kim, Jung Nam; Hwang, Yoon-Hwae

    2003-02-01

    We studied dielectric properties of Li3VO4 single crystals grown by the Czochralski method along the a axis at temperatures ranging from room temperature to 800 °C and frequencies ranging from 100 Hz to 15 MHz. We analyzed the impedance data by introducing an equivalent circuit which consists of two parallel combinations of capacitors and resistors in series. The conductivity and the relaxation time of Li3VO4 are found to show the Arrhenius behavior with two different activation energies which crossed over at temperatures around 400 °C. The observed crossover seems to originate from a dissociation of the Li-O bond at high temperatures.

  19. Electronic and dielectric properties of vacancy clusters as quantum dot in silicane

    NASA Astrophysics Data System (ADS)

    Mohan, Brij; Sharma, Munish; Kumar, Ashok; Ahluwalia, P. K.

    2015-06-01

    First principal study of electronic and dielectric properties of a silicane nanostructure containing cluster of vacancies as quantum dot (QD) has been investigated within density functional theory (DFT). Electronic band structure and corresponding density of states show the decrease in band gap with increasing size of quantum dot. A band gap of 0.38 eV has been achieved for silicane containing 3QD. Electron energy loss spectra (EEL) function shows additional plasmonic features for QD containing silicane in visible region, which may have potential applications in optoelectronic devices.

  20. Dielectric properties of Al2O3 coatings deposited via atmospheric plasma spraying and dry-ice blasting correlated with microstructural characteristics

    NASA Astrophysics Data System (ADS)

    Dong, Shujuan; Song, Bo; Liao, Hanlin; Coddet, Christian

    2015-01-01

    In this work, atmospheric plasma spraying combined with dry-ice blasting have been used to prepare alumina (Al2O3) coatings designed for insulating applications. The microstructural characteristics and dielectric properties of Al2O3 coatings were presented. The electrical insulating properties, i.e., dielectric strength and breakdown voltage, were investigated by dielectric breakdown test using direct current and alternating current. Relationships between dielectric properties and coating characteristics were discussed. The results showed that dry-ice blasting used during atmospheric plasma spray process allowed the production of coatings with better dielectric properties than those prepared without dry-ice blasting. The dielectric properties were correlated with the microstructural characteristics, not with phase composition.

  1. Effect of SHI on dielectric and magnetic properties of metal oxide/PMMA nanocomposites

    NASA Astrophysics Data System (ADS)

    Gavade, Chaitali; Singh, N. L.; Avasthi, D. K.; Banerjee, Alok

    2010-10-01

    Magnetic nanoparticles embedded in polymer matrices have excellent potential for electromagnetic device applications like electromagnetic interference suppression, etc. The NiO nanoparticles were synthesized by simple method. These nanoparticles were dispersed in PMMA matrix and films were prepared by casting method with varying concentrations of nickel oxide nanoparticles. These films were irradiated with 50 MeV Li +3 ions at a fluence of 5 × 10 12 ions/cm 2. AC electrical properties of pristine and irradiated samples were studied in wide frequency range. Dependence of dielectric properties on frequency, ion beam fluence and filler concentration was studied. The results reveal the enhancement in dielectric properties after doping nanoparticles and also upon irradiation, which is also corroborated with field-cooled-zero-field-cooled (FC-ZFC) susceptibility measurement in which magnetization is increased upon irradiation. The Fourier transform infrared (FTIR) spectroscopy analysis revealed the change in the intensity of functional groups after irradiation. Average surface roughness observed to change with filler concentration and also with the irradiation fluence as obtained from AFM analysis.

  2. Measurement of insulating and dielectric properties of acrylic elastomer membranes at high electric fields

    NASA Astrophysics Data System (ADS)

    Di Lillo, L.; Schmidt, A.; Carnelli, D. A.; Ermanni, P.; Kovacs, G.; Mazza, E.; Bergamini, A.

    2012-01-01

    This work reports on the investigation of VHB 4910 acrylic elastomer insulating and dielectric properties. This material is widely exploited for the realization of actuators with large deformations, dielectric elastomer actuators (DEA), and belongs to the group of so-called electroactive polymers (EAP). Extensive investigations concerning its mechanical properties are available in literature while its electric behavior at working conditions has not received the same level of attention. In this work, the relative permittivity and the volume resistivity have been measured on VHB 4910 membranes under different fixed stretch conditions (?1, ?2 = 3, 3.6, 4, 5) using circular gold electrodes sputtered onto both sides of the specimens. The measured values of relative permittivity are in fairly good agreement with the results previously published by other groups. The volume resistivity, at field values close to the operational ones, has shown a field-dependent behavior revealing dissipative properties that should be considered in real applications. Further, measurements on circular actuators verify these findings. Consequences for modeling of VHB 4910 are drawn and new material model parameters proposed to account for the value of relative permittivity at high electric fields.

  3. Dielectric and electromechanical properties of rare earth calcium oxyborate piezoelectric crystals at high temperatures.

    PubMed

    Yu, Fapeng; Zhang, Shujun; Zhao, Xian; Yuan, Duorong; Qin, Lifeng; Wang, Qing-Ming; Shrout, Thomas R

    2011-04-01

    The electrical resistivity, dielectric, and electromechanical properties of ReCa(4)O(BO(3))(3) (ReCOB; Re = Er, Y, Gd, Sm, Nd, Pr, and La) piezoelectric crystals were investigated as a function of temperature up to 1000 °C. Of the studied crystals, ErCOB and YCOB were found to possess extremely high resistivity (p): p > 3 × 10(7) ?.cm at 1000 °C. The property variation in ReCOB crystals is discussed with respect to their disordered structure. The highest electromechanical coupling factor ?(26) and piezoelectric coefficient d(26) at 1000°C, were achieved in PrCOB crystals, with values being on the order of 24.7% and 13.1 pC/N, respectively. The high thermal stability of the electromechanical properties, with variation less than 25%, together with the low dielectric loss (<46%) and high mechanical quality factor (>1500) at elevated temperatures of 1000 °C, make ErCOB, YCOB, and GdCOB crystals promising for ultrahigh temperature electromechanical applications. PMID:21507766

  4. High Temperature Microwave Dielectric Properties of JSC-1AC Lunar Simulant

    NASA Technical Reports Server (NTRS)

    Allan, Shawn M.; Merritt, Brandon J.; Griffin, Brittany F.; Hintze, Paul E.; Shulman, Holly S.

    2011-01-01

    Microwave heating has many potential lunar applications including sintering regolith for lunar surface stabilization and heating regolith for various oxygen production reactors. The microwave properties of lunar simulants must be understood so this technology can be applied to lunar operations. Dielectric properties at microwave frequencies for a common lunar simulant, JSC-1AC, were measured up to 1100 C, which is approximately the melting point. The experimentally determined dielectric properties included real and imaginary permittivity (epsilon', epsilon"), loss tangent (tan delta), and half-power depth, the di stance at which a material absorbs 50% of incident microwave energy. Measurements at 2.45 GHz revealed tan delta of JSC-1A increases from 0.02 at 25 C to 0.31 at 110 C. The corresponding half-power depth decreases from a peak of 286 mm at 110 C, to 13 mm at 1100 C. These data indicate that JSC-1AC becomes more absorbing, and thus a better microwave heater as temperature increases. A half-power depth maximum at 100-200 C presents a barrier to direct microwave heating at low temperatures. Microwave heating experiments confirm the sluggish heating effect of weak absorption below 200 C, and increasingly strong absorption above 200 C, leading to rapid heating and melting of JSC-1AC.

  5. Microwave sintering of nanopowder ZnNb2O6: Densification, microstructure and microwave dielectric properties

    NASA Astrophysics Data System (ADS)

    Bafrooei, H. Barzegar; Nassaj, E. Taheri; Hu, C. F.; Huang, Q.; Ebadzadeh, T.

    2014-12-01

    High density ZnNb2O6 ceramics were successfully fabricated by microwave sintering of ZnO-Nb2O5 and ZnNb2O6 nanopowders. Phase formation, microstructure and microwave electrical properties of the microwave sintered (MS) and microwave reaction sintered (MRS) specimens were examined using X-ray diffraction, field emission scanning electron microscopy and microwave dielectric properties measurement. Specimens were sintered in a temperature range from 950 to 1075 °C for 30 min at an interval of 25 °C using a microwave furnace operated at 2.45 GHz frequency, 3 kW power. XRD pattern revealed the formation of pure columbite phase of ZnNb2O6. The SEM micrographs show grain growth and reduction in porosity of specimens with the increase in sintering temperature. Good combination of microwave dielectric properties (?r~23.6, Qf~64,300 GHz and ?f~-66 ppm/°C and ?r~24, Qf~75,800 GHz and ?f~-64 ppm/°C) was obtained for MS- and MRS-prepared samples at 1000 °C and 1050 °C for 30 min, respectively.

  6. Measurements of the thermal, dielectric, piezoelectric, pyroelectric and elastic properties of porous PZT samples

    NASA Astrophysics Data System (ADS)

    Lang, Sidney B.; Ringgaard, Erling

    2012-06-01

    The introduction of porosity into ferroelectric ceramics has been of great interest in recent years. In particular, studies of porous lead-zirconate-titanate ceramic (PZT) have been made. In the research reported, samples of Ferroperm Pz27 with porosities of 20, 25 and 30% were studied. Very complete measurements were made of all of the physical properties relevant for ferroelectric applications including thermal conductivity and diffusivity, heat capacity, dielectric, pyroelectric, piezoelectric and elastic properties. Scanning electron micrographs indicated a change from 3-0 to 3-3 connectivity with increasing porosity. Although most of the physical properties are degraded by the presence of porosity, both piezoelectric and pyroelectric figures-of-merit are improved because of the markedly reduced relative permittivity. Porous ferroelectric ceramics are very promising materials for a number of applications.

  7. Dielectric and Magnetic Properties of Bi1-x SmxFeO3 (0<=x<=1)

    NASA Astrophysics Data System (ADS)

    Melgarejo, Ricardo; Puli, Venkata; Panwar, Neeraj; Thomas, Reji; Katiyar, Ram

    2010-03-01

    Multiferroic materials like BiFeO3 (BFO) have recently gained worldwide attention due to their applications in nonvolatile memories, spintronics, sensors, and micro mechanical systems (MEMS). BiFeO3 is a naturally occurring multiferroics, however, the large leakage current has hampered its practical applications. To circumvent this problem generally, substitution is carried out at Bi and Fe sites. We have doped samarium (Sm) at Bi-site in BFO. Thin films were grown on Pt/Ti/SiO2 /Si substrates by spin coating method. XRD patterns showed well-grown perovskite structure with polycrystalline nature. Dielectric properties, leakage current, and magnetic properties were systematically studied. A correlation between these properties will be presented.

  8. Structural, optical, dielectric and magnetic properties of Mn1-xCoxO2 nanowires

    NASA Astrophysics Data System (ADS)

    Stella, C.; Soundararajan, N.; Ramachandran, K.

    2014-07-01

    Undoped and Co-doped ?-MnO2 nanowires were prepared by hydrothermal method at 140 °C. XRD revealed the tetragonal structure of ?-MnO2 and Co doping did not affect the structure of ?-MnO2. The morphology is found to be one dimensional nanowire, which is confirmed by SEM. The optical properties were studied by PL and FTIR. The PL emission spectra showed strong UV emission peak at 392 nm along with some weak emissions. The characteristic vibrational modes were analyzed by FTIR. The dielectric properties of undoped and doped samples were studied in the frequency range of 50 Hz to 1 MHz at different temperatures. Enhanced relative permittivity was observed for Co-doped MnO2 nanowire. The magnetic properties were analyzed by VSM, where ferromagnetic behavior along with antiferromagnetic component at room temperature was observed.

  9. Towards Automated Benchmarking of Atomistic Forcefields: Neat Liquid Densities and Static Dielectric Constants from the ThermoML Data Archive

    E-print Network

    Beauchamp, Kyle A; Rustenburg, Ariën S; Bayly, Christopher I; Kroenlein, Kenneth; Chodera, John D

    2015-01-01

    Atomistic molecular simulations are a powerful way to make quantitative predictions, but the accuracy of these predictions depends entirely on the quality of the forcefield employed. While experimental measurements of fundamental physical properties offer a straightforward approach for evaluating forcefield quality, the bulk of this information has been tied up in formats that are not machine-readable. Compiling benchmark datasets of physical properties from non-machine-readable sources require substantial human effort and is prone to accumulation of human errors, hindering the development of reproducible benchmarks of forcefield accuracy. Here, we examine the feasibility of benchmarking atomistic forcefields against the NIST ThermoML data archive of physicochemical measurements, which aggregates thousands of experimental measurements in a portable, machine-readable, self-annotating format. As a proof of concept, we present a detailed benchmark of the generalized Amber small molecule forcefield (GAFF) using t...

  10. Dielectric and geometric properties of plasmonics in metal\\/dielectric nanowires composites used in surface-enhanced Raman spectroscopy

    Microsoft Academic Search

    O. J. Glembocki; R. W. Rendell; S. M. Prokes; D. A. Alexson; M. A. Mastro; S. C. Badescu; A. Fu

    2007-01-01

    Finite elements calculations have been performed of the surface enhanced Raman (SERS) activity of Ag coated dielectric nanowires. It is shown that the SERS fields and the angle of the peak field from intersecting nanowires can be changed through the angle of the nanowires. In addition, it is shown that the strength of the SERS enhancement and its spatial profile

  11. Dielectric and geometric properties of plasmonics in metal\\/dielectric nanowires composites used in surface-enhanced Raman spectroscopy

    Microsoft Academic Search

    O. J. Glembocki; R. W. Rendell; D. A. Alexson; M. A. Mastro; S. C. Badescu; A. Fu

    Finite elements calculations have been performed of the surface enhanced Raman (SERS) activity of Ag coated dielectric nanowires. It is shown that the SERS fields and the angle of the peak field from intersecting nanowires can be changed through the angle of the nanowires. In addition, it is shown that the strength of the SERS enhancement and its spatial profile

  12. Dielectric and ferroelectric properties of c-axis oriented strontium bismuth tantalate thin films applied transverse electric fields

    E-print Network

    Tonouchi, Masayoshi

    Dielectric and ferroelectric properties of c-axis oriented strontium bismuth tantalate thin films and ferroelectric properties of c-axis oriented epitaxial strontium bismuth tantalate SBT thin films were American Institute of Physics. DOI: 10.1063/1.2205351 I. INTRODUCTION Strontium bismuth tantalate SBT has

  13. Control of the Casimir force by the modification of dielectric properties with light

    E-print Network

    F. Chen; G. L. Klimchitskaya; V. M. Mostepanenko; U. Mohideen

    2007-07-30

    The experimental demonstration of the modification of the Casimir force between a gold coated sphere and a single-crystal Si membrane by light pulses is performed. The specially designed and fabricated Si membrane was irradiated with 514 nm laser pulses of 5 ms width in high vacuum leading to a change of the charge-carrier density. The difference in the Casimir force in the presence and in the absence of laser radiation was measured by means of an atomic force microscope as a function of separation at different powers of the absorbed light. The total experimental error of the measured force differences at a separation of 100 nm varies from 10 to 20% in different measurements. The experimental results are compared with theoretical computations using the Lifshitz theory at both zero and laboratory temperatures. The total theoretical error determined mostly by the uncertainty in the concentration of charge carriers when the light is incident is found to be about 14% at separations less than 140 nm. The experimental data are consistent with the Lifshitz theory at laboratory temperature, if the static dielectric permittivity of high-resistivity Si in the absence of light is assumed to be finite. If the dc conductivity of high-resistivity Si in the absence of light is included into the model of dielectric response, the Lifshitz theory at nonzero temperature is shown to be experimentally inconsistent at 95% confidence. The demonstrated phenomenon of the modification of the Casimir force through a change of the charge-carrier density is topical for applications of the Lifshitz theory to real materials in fields ranging from nanotechnology and condensed matter physics to the theory of fundamental interactions.

  14. Static properties of 2D spin-ice as a sixteen-vertex model

    NASA Astrophysics Data System (ADS)

    Foini, Laura; Levis, Demian; Tarzia, Marco; Cugliandolo, Leticia F.

    2013-02-01

    We present a thorough study of the static properties of 2D models of spin-ice type on the square lattice or, in other words, the sixteen-vertex model. We use extensive Monte Carlo simulations to determine the phase diagram and critical properties of the finite-dimensional system. We put forward a suitable mean-field approximation, by defining the model on carefully chosen trees. We employ the cavity (Bethe-Peierls) method to derive self-consistent equations, the fixed points of which yield the equilibrium properties of the model on the tree-like graph. We compare mean-field and finite-dimensional results. We discuss our findings in the context of experiments in artificial two-dimensional spin-ice.

  15. Dynamical- and static-disorder effects on charge transport property of organic semiconductors

    NASA Astrophysics Data System (ADS)

    Ishii, Hiroyuki; Kobayashi, Nobuhiko; Hirose, Kenji

    2014-03-01

    In comparison with inorganic materials, electron transfer energy of typical organic semiconductors is small in the range of 10 - 100meV, which is comparable to the magnitude of dynamical disorder of transfer energy originating from the thermal fluctuations of molecular motions. Furthermore, the static disorder inevitably exists in realistic organic devices and disturbs the transport of charge carrier. To clarify the influence of the dynamical and static disorders on the mobility, we employ a realistic static-disorder potential, which is deduced from the data obtained by electron-spin-resonance spectroscopy. We evaluate the carrier mobilities of pentacene and rubrene semiconductors under the realistic situation, using our time-dependent wave-packet diffusion method. In this methodology, we carry out the quantum-mechanical time-evolution calculations of wave packets and the classical molecular dynamics simulations simultaneously. We clarify the relation between the charge transport property and these disorders. We will talk about these results in my presentation. This work was supported by JST, PRESTO, and a Grant-in-Aid for Scientific Research from the JSPS.

  16. Gauge-Invariant Calculation of Static and Dynamical Magnetic Properties from the Current Density

    NASA Astrophysics Data System (ADS)

    Raimbault, Nathaniel; de Boeij, Paul L.; Romaniello, Pina; Berger, J. A.

    2015-02-01

    In this work we solve two problems related to the calculation of static and dynamical magnetic properties with ab initio theories. First, we show that the dependence of the dynamical magnetic dipole moment on the reference point of the multipole expansion and on the gauge origin of the vector potential have a clear physical significance. They are due to a dynamical electric dipole moment and an electric field, respectively. Both are fully determined by the experimental setup and do not pose any fundamental problem, contrary to what is commonly assumed. Second, in the static case, any dependence on the gauge origin is an artifact of the computational method. We show that the artificial dependence on the gauge origin can be removed in an elegant way by the introduction of a sum rule that puts the diamagnetic and paramagnetic contributions on equal footing. Our approach can be applied to calculate any magnetic observable that can be derived from the current density, and can be used in combination with any ab initio theory from which it can be obtained. To illustrate our method we apply it here to time-dependent current-density-functional theory for the calculation of static and dynamical magnetizabilities of molecules.

  17. MAPPING OF RESERVOIR PROPERTIES AND FACIES THROUGH INTEGRATION OF STATIC AND DYNAMIC DATA

    SciTech Connect

    Albert C. Reynolds; Dean S. Oliver; Fengjun Zhang; Yannong Dong; Jan Arild Skjervheim; Ning Liu

    2003-01-01

    Knowledge of the distribution of permeability and porosity in a reservoir is necessary for the prediction of future oil production, estimation of the location of bypassed oil, and optimization of reservoir management. But while the volume of data that can potentially provide information on reservoir architecture and fluid distributions has increased enormously in the past decade, it is not yet possible to make use of all the available data in an integrated fashion. While it is relatively easy to generate plausible reservoir models that honor static data such as core, log, and seismic data, it is far more difficult to generate plausible reservoir models that honor dynamic data such as transient pressures, saturations, and flow rates. As a result, the uncertainty in reservoir properties is higher than it could be and reservoir management can not be optimized. The goal of this project is to develop computationally efficient automatic history matching techniques for generating geologically plausible reservoir models which honor both static and dynamic data. Solution of this problem is necessary for the quantification of uncertainty in future reservoir performance predictions and for the optimization of reservoir management. Facies (defined here as regions of relatively uniform petrophysical properties) are common features of all reservoirs. Because the flow properties of the various facies can vary greatly, knowledge of the location of facies boundaries is of utmost importance for the prediction of reservoir performance and for the optimization of reservoir management. When the boundaries between facies are fairly well known, but flow properties are poorly known, the average properties for all facies can be determined using traditional techniques. Traditional history matching honors dynamic data by adjusting petrophysical properties in large areas, but in the process of adjusting the reservoir model ignores the static data and often results in implausible reservoir models. In general, boundary locations, average permeability and porosity, relative permeability curves, and local flow properties may all need to be adjusted to achieve a plausible reservoir model that honors all data. In this project, we will characterize the distribution of geologic facies as an indicator random field, making use of the tools of geostatistics as well as the tools of inverse and probability theory for data integration.

  18. Static and Dynamic Properties of Trapped Fermionic Tonks-Girardeau Gases

    E-print Network

    M. D. Girardeau; E. M. Wright

    2005-01-11

    We investigate some exact static and dynamic properties of one-dimensional fermionic Tonks-Girardeau gases in tight de Broglie waveguides with attractive p-wave interactions induced by a Feshbach resonance. A closed form solution for the one-body density matrix for harmonic trapping is analyzed in terms of its natural orbitals, with the surprising result that for odd, but not for even, numbers of fermions the maximally occupied natural orbital coincides with the ground harmonic oscillator orbital and has the maximally allowed fermionic occupancy of unity. The exact dynamics of the trapped gas following turnoff of the p-wave interactions are explored.

  19. Effects of A-Site Occupancy of Bismuth Ions on the Dielectric Tunable Properties of Pyrochlore Bismuth Zinc Niobate Films

    NASA Astrophysics Data System (ADS)

    Nakajima, Mitsumasa; Yamada, Tomoaki; Okaura, Shingo; Funakubo, Hiroshi

    2012-09-01

    The A-site composition dependence of cubic pyrochlore Bi-Zn-Nb-O (BZN) thin films of dielectric tunable properties was investigated. (111)-textured BZN films with a wide range of Bi/Nb ratios (0.62-1.26) were fabricated by metal organic chemical vapor deposition. Raman spectral analysis revealed that by changing the Bi/Nb ratio in BZN films, the Bi concentration of the A-site mainly varied. Dielectric constant and dielectric tunability were found to increase with increasing Bi ion occupancy of the A site. These experimental findings suggest that the Bi occupancy of A site is an important factor for designing Bi based pyrochlore dielectric tunable materials.

  20. Dielectric properties of water and water/ethylene glycol mixtures for use in pulsed power system design

    SciTech Connect

    Zahn, M.; Ohki, Y.; Fenneman, D.B.; Gripshover, R.J.; Gehman, V.H. Jr.

    1986-09-01

    One class of modern pulse power generators use deionized water as an energy storage, switching and transmission dielectric. Water is chosen for its high dielectric constant and relatively high resistivity, which allows reasonably sized and efficient low-impedance high-voltage pulse lines where pulse durations are less than 100 ..mu..s. Water/ethylene glycol mixtures are being researched, so that rotating machinery, rather than the usual Marx generator, can be used as the primary energy store. The high resistivity and high dielectric constant of these mixtures at low temperature permit low-loss operation on millisecond time scales. Simple design criteria linking load parameters and charging circuit characteristics to the liquid dielectic are developed which show that the dielectric constant, breakdown strength, and relaxation time are the primary properties of interest to the pulse power engineer.

  1. Structural and dielectric properties of poly(vinylidene fluoride)-based terpolymer/copolymer blends developed on aluminum foil

    NASA Astrophysics Data System (ADS)

    Eršte, A.; Chen, X.-Z.; Cheng, Z.-X.; Shen, Q.-D.; Bobnar, V.

    2012-09-01

    We report structural, caloric, and dielectric properties in the blends of relaxor poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) terpolymer with small amount of poly(vinylidene fluoride-chlorotrifluoroethylene) copolymer, developed on aluminum surface. X-ray diffraction and differential scanning calorimetry results indicate that the copolymer additive disturbs the crystallizing process of the terpolymer. Consequently, relatively high values of the dielectric constant of ?80, detected in terpolymer films around room temperature, decrease to ?60 in blends. We show that addition of the copolymer does not influence the relaxor dielectric dynamics of the terpolymer and we explain the detected dielectric response by calculations that take into account the fact that in these heterogeneous systems two similar dynamic processes superimpose in the same temperature range, i.e., relaxor dynamics in the crystalline regions and a glassy transition in the amorphous matrix.

  2. Cross-linking effect on dielectric properties of polypropylene thin films and applications in electric energy storage

    NASA Astrophysics Data System (ADS)

    Yuan, Xuepei; Chung, T. C. Mike

    2011-02-01

    A family of cross-linked polypropylene (x-PP) thin film dielectrics is systematically studied to understand the cross-linking effect on the dielectric properties. Evidently, the butylstyrene (BSt) cross-linkers increase both the dielectric constant (?) and breakdown strength (E), without increasing energy loss. An x-PP dielectric, with 3.65 mol % BSt cross-linkers, exhibits a ? ˜3, which is independent of a wide range of temperatures and frequencies, slim D-E hysteresis loops, high breakdown strength (E=650 MV/m), narrow breakdown distribution, and reliable energy storage capacity >5 J/cm3 (double that of state-of-the-art biaxially oriented polypropylene capacitors), without showing any increase in energy loss.

  3. Dipolar Correlations and the Dielectric Permittivity of Water

    NASA Astrophysics Data System (ADS)

    Sharma, Manu; Resta, Raffaele; Car, Roberto

    2007-06-01

    The static dielectric properties of liquid and solid water are investigated within linear response theory in the context of ab initio molecular dynamics. Using maximally localized Wannier functions to treat the macroscopic polarization we formulate a first-principles, parameter-free, generalization of Kirkwood’s phenomenological theory. Our calculated static permittivity is in good agreement with experiment. Two effects of the hydrogen bonds, i.e., a significant increase of the average local moment and a local alignment of the molecular dipoles, contribute in almost equal measure to the unusually large dielectric constant of water.

  4. Investigation of low field dielectric properties of anisotropic porous Pb(Zr,Ti)O3 ceramics: Experiment and modeling

    NASA Astrophysics Data System (ADS)

    Olariu, C. S.; Padurariu, L.; Stanculescu, R.; Baldisserri, C.; Galassi, C.; Mitoseriu, L.

    2013-12-01

    Anisotropic porous Pb(Zr,Ti)O3 ceramics with various porosity degrees have been studied in order to determine the role of the pore shape and orientation on the low-field dielectric properties. Ceramic samples with formula Pb(Zr0.52Ti0.48)0.976Nb0.024O3 with different porosity degrees (dense, 10%, 20%, 40% vol.) have been prepared by solid state reaction. Taking into consideration the shape and orientation of the pore inclusions, the dielectric properties of porous ceramics have been described by using adapted mixing rules models. Rigorous bounds, derived on the basis on Variational Principle, were used to frame dielectric properties of porous composites. The finite element method (FEM) was additionally used to simulate the dielectric response of the porous composites under various applied fields. Among the few effective medium approximation models adapted for anisotropic oriented inclusions, the best results were obtained in case of needle-like shape inclusions (which do not correspond to the real shape of microstructure inclusions). The general case of Wiener bounds limited well the dielectric properties of anisotropic porous composites in case of parallel orientation. Among the theoretical approaches, FEM technique allowed to simulate the distribution of potential and electric field inside composites and provided a very good agreement between the computed permittivity values and experimental ones.

  5. Influence of frequency, grade, moisture and temperature on Green River oil shale dielectric properties and electromagnetic heating processes

    SciTech Connect

    Hakala, J. Alexandra [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States); Stanchina, William [Univ. of Pittsburgh, PA (United States); National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States); Soong, Yee [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States); Hedges, Sheila [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States)

    2011-01-01

    Development of in situ electromagnetic (EM) retorting technologies and design of specific EM well logging tools requires an understanding of various process parameters (applied frequency, mineral phases present, water content, organic content and temperature) on oil shale dielectric properties. In this literature review on oil shale dielectric properties, we found that at low temperatures (<200° C) and constant oil shale grade, both the relative dielectric constant (?') and imaginary permittivity (?'') decrease with increased frequency and remain constant at higher frequencies. At low temperature and constant frequency, ?' decreases or remains constant with oil shale grade, while ?'' increases or shows no trend with oil shale grade. At higher temperatures (>200º C) and constant frequency, epsilon' generally increases with temperature regardless of grade while ?'' fluctuates. At these temperatures, maximum values for both ?' and ?'' differ based upon oil shale grade. Formation fluids, mineral-bound water, and oil shale varve geometry also affect measured dielectric properties. This review presents and synthesizes prior work on the influence of applied frequency, oil shale grade, water, and temperature on the dielectric properties of oil shales that can aid in the future development of frequency- and temperature-specific in situ retorting technologies and oil shale grade assay tools.

  6. Effect of Processing Conditions on Dielectric Properties of CaCu3Ti4O12 Ceramics

    NASA Astrophysics Data System (ADS)

    Kashyap, Raman; Thakur, O. P.; Mehra, N. C.; Tandon, R. P.

    Samples of CaCu3Ti4O12 (CCTO) ceramics were prepared by solid state reaction method. X-ray diffraction analysis confirmed single phase formation for the powder calcined at 1173 K. Sintering was done at different temperatures viz. 1348 K, 1373 K and 1398 K with a fixed heating rate of 3 K/min. Detailed study of dielectric properties was carried out for the CCTO samples sintered at 1373 K for different duration of holding times (2 h and 10 h). It is found that dielectric properties are sensitive to both sintering time and temperature. With increasing sintering time from 2 h to 10 h dielectric constant increases from ?2.1 × 104 to ?2.5 × 104 measured at 1 kHz at room temperature. Impedance spectroscopy has been used for separating out of grain and grain boundary contributions to the overall electrical properties.

  7. Trapping-charging ability and electrical properties study of amorphous insulator by dielectric spectroscopy

    SciTech Connect

    Mekni, Omar, E-mail: omarmekni-lmop@yahoo.fr; Arifa, Hakim; Askri, Besma; Yangui, Béchir [Laboratory of Materials, Organization and Properties LR99ES17, University of Tunis El Manar, Campus Universities El Manar, 2092 Tunis (Tunisia); Raouadi, Khaled, E-mail: khaled-raouadi@yahoo.fr [Laboratory of Materials, Organization and Properties LR99ES17, University of Tunis El Manar, Campus Universities El Manar, 2092 Tunis (Tunisia); Faculty of Sciences of Bizerte, University of Carthage, 7021 Jarzouna (Tunisia); Damamme, Gilles [CEA/Gramat, BP 80200, 46500 Gramat (France)

    2014-09-14

    Usually, the trapping phenomenon in insulating materials is studied by injecting charges using a Scanning Electron Microscope. In this work, we use the dielectric spectroscopy technique for showing a correlation between the dielectric properties and the trapping-charging ability of insulating materials. The evolution of the complex permittivity (real and imaginary parts) as a function of frequency and temperature reveals different types of relaxation according to the trapping ability of the material. We found that the space charge relaxation at low frequencies affects the real part of the complex permittivity ?{sup ´} and the dissipation factor Tan(?). We prove that the evolution of the imaginary part of the complex permittivity against temperature ?{sup ??}=f(T) reflects the phenomenon of charge trapping and detrapping as well as trapped charge evolution Q{sub p}(T). We also use the electric modulus formalism to better identify the space charge relaxation. The investigation of trapping or conductive nature of insulating materials was mainly made by studying the activation energy and conductivity. The conduction and trapping parameters are determined using the Correlated Barrier Hopping (CBH) model in order to confirm the relation between electrical properties and charge trapping ability.

  8. Magnetic Field Effect on the dielectric properties of the Single Molecule Magnet V15

    NASA Astrophysics Data System (ADS)

    Vasic, Relja; Kaur, Narpinder; Brooks, James; Dalal, Naresh

    2005-11-01

    Single-molecule hysteresis and quantum tunneling of magnetization (QTM) have made single molecule magnets(SMMs) among the most widely studied compounds in the past decade. Best known SMMs are Mn12-acetate and Fe8Br8. Recently a polyoxovanadate compound K6[V15As6O42(H2O)].8H2O, henceforth V15, has been shown to exhibit some of the properties of SMMs despite an S=1/2 ground state, and no evident potential energy barrier to the reorientation of the magnetic moment. In this study we have investigated magnetic field effects on the dielectric properties of V15 using ac impedance technique. In preliminary experiments over the frequency range of 1-100kHz and temperature range of 10-300K, V15 is found to exhibit three independent relaxation mechanisms. On the application of magnetic field, the dielectric relaxation peaks shift towards higher temperatures. The presentation will discuss details of sample preparation, measurement techniques and theoretical interpretation of this newly observed effect.

  9. Three-Dimensional Microwave Breast Imaging: Dispersive Dielectric Properties Estimation using Patient-Specific Basis Functions

    PubMed Central

    Winters, David W.; Shea, Jacob D.; Kosmas, Panagiotis; Van Veen, Barry D.; Hagness, Susan C.

    2009-01-01

    Breast imaging via microwave tomography involves estimating the distribution of dielectric properties within the patient's breast on a discrete mesh. The number of unknowns in the discrete mesh can be very large for three-dimensional imaging, and this results in computational challenges. We propose a new approach where the discrete mesh is replaced with a relatively small number of smooth basis functions. The dimension of the tomography problem is reduced by estimating the coefficients of the basis functions instead of the dielectric properties at each element in the discrete mesh. The basis functions are constructed using knowledge of the location of the breast surface. The number of functions used in the basis can be varied to balance resolution and computational complexity. The reduced dimension of the inverse problem enables application of a computationally efficient, multiple-frequency inverse scattering algorithm in 3-D. The efficacy of the proposed approach is verified using two 3-D anatomically realistic numerical breast phantoms. It is shown for the case of single-frequency microwave tomography that the imaging accuracy is comparable to that obtained when the original discrete mesh is used, despite the reduction of the dimension of the inverse problem. Results are also shown for a multiple-frequency algorithm where it is computationally challenging to use the original discrete mesh. PMID:19211350

  10. Electrical resistivity and dielectric properties of helical microorganism cells coated with silver by electroless plating

    NASA Astrophysics Data System (ADS)

    Cai, Jun; Lan, Mingming; Zhang, Deyuan; Zhang, Wenqiang

    2012-09-01

    In this paper, microorganism cells (Spirulina platens) were used as forming templates for the fabrication of the helical functional particles by electroless silver plating process. The morphologies and ingredients of the coated Spirulina cells were analyzed with scanning electron microscopy and energy dispersive spectrometer. The crystal structures were characterized by employing the X-ray diffraction. The electrical resistivity and dielectric properties of samples containing different volume faction of sliver-coated Spirulina cells were measured and investigated by four-probe meter and vector network analyzer. The results showed that the Spirulina cells were successfully coated with a uniform silver coating and their initial helical shapes were perfectly kept. The electrical resistivity and dielectric properties of the samples had a strong dependence on the volume content of sliver-coated Spirulina cells and the samples could achieve a low percolation value owing to high aspect ratio and preferable helical shape of Spirulina cells. Furthermore, the conductive mechanism was analyzed with the classic percolation theory, and the values of ? and t were obtained.

  11. Extraction of Water from Polar Lunar Permafrost with Microwaves - Dielectric Property Measurements

    NASA Technical Reports Server (NTRS)

    Ethridge, Edwin C.; Kaukler, William

    2009-01-01

    Remote sensing indicates the presence of hydrogen rich regions associated with the lunar poles. The logical hypothesis is that there is cryogenically trapped water ice located in craters at the lunar poles. Some of the craters have been in permanent darkness for a billion years. The presence of water at the poles as well as other scientific advantages of a polar base, have influenced NASA plans for the lunar outpost. The lunar outpost has water and oxygen requirements on the order of 1 ton per year scaling up to as much as 10 tons per year. Microwave heating of the frozen permafrost has unique advantages for water extraction. Proof of principle experiments have successfully demonstrated that microwaves will couple to the cryogenic soil in a vacuum and the sublimed water vapor can be successfully captured on a cold trap. The dielectric properties of lunar soil will determine the hardware requirements for extraction processes. Microwave frequency dielectric property measurements of lunar soil simulant have been measured.

  12. Structural and mechanical properties of 7075 alloy strips fabricated by roll-casting in a static magnetic field

    NASA Astrophysics Data System (ADS)

    Su, Xin; Xu, Guang-ming; Jiang, Jiu-wen

    2014-07-01

    The influences of a 0.2 T static magnetic field on the microstructure of 7075 aluminum alloys sheets produced with a twin-roll continuous caster at 675°C were investigated in this paper. Under a uniform magnetic field, the primary dendrites were refined and tended to be equiaxed. The microstructure consisted of an intermediate case between dendritic and equiaxed grains. Moreover, the use of an external static field in the twin-roll casting process can reduce heat discharge, resulting in a decrease in undercooling, and may also account for the abatement of segregation bands. In addition, the static magnetic field effectively improved the solute mixing capacity, and the added atoms more easily diffused from precipitates to the ?-Al matrix, which resulted in an increase in the mechanical properties of the rolled sheets. Specimens prepared both in the presence of a static magnetic field and in the absence of a static magnetic field exhibited brittle-fracture characteristics.

  13. Improved electrical properties of metal-oxide-semiconductor capacitor with HfTiON gate dielectric by using HfSiON interlayer

    Microsoft Academic Search

    J. P. Xu; F. Ji; C. X. Li; P. T. Lai; J. G. Guan; Y. R. Liu

    2007-01-01

    Metal-oxide-semiconductor (MOS) capacitor with HfTiON\\/HfSiON stack structure as high-k gate dielectric is fabricated, and its electrical properties are compared with those of a similar device with HfTiON only as gate dielectric. Experimental results show that the device with HfTiON\\/HfSiON gate dielectric exhibits better interface properties, lower gate leakage current, and enhanced high-field reliability. All these improvements should be attributed to

  14. Effect of medium dielectric constant on the physical properties of single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Gao, J.; Gomulya, W.; Loi, M. A.

    2013-02-01

    The photophysical properties of semiconducting single walled carbon nanotubes (SWNTs) in different environments are analyzed by steady-state and time-resolved photoluminescence (PL) spectroscopy. The PL emission of SWNTs shows a red shift with the increase of the dielectric constant of the environments. The solvatochromic shift depends on the structural properties of the nanotubes and reaches almost 100 milli-electron volts in the case of (7, 5) tubes. These experimental results allow deriving a relationship between the PL shift and the structure of SWNTs. Moreover, the dynamics of 'bright' excitons in semiconducting SWNTs and the effect of the medium on the decay of the excitons are discussed by using time-resolved spectroscopy.

  15. Static friction properties between human palmar skin and five grabrail materials.

    PubMed

    O'Meara, D M; Smith, R M

    2001-09-15

    The purpose of this study was to investigate the static friction properties between human palmar skin and five grabrail materials (chrome, stainless steel, power-coated steel, textured aluminium and knurled steel) for dry, wet and soapy hands. Thirty subjects (15 female, 15 male) participated in this study, their ages ranging from 19 to 45 years with a mean age of 28 years. The normal force, friction force, and coefficient of static friction were determined by measuring three-dimensional forces while slipping the palm of the hand over the surface of a grabrail. A repeated measures ANOVA indicated that gender, age, hand size and trial effect had no significant influence (p>0.05) on these results. The coefficient of friction (p<0.001) and friction force (p<0.001) were significantly lower when the hand was soapy than when it was dry or wet. The normal force applied when the hand was soapy was significantly greater (p<0.001) than when it was dry or wet. No significant difference was found between dry and wet hands. The two textured materials displayed superior friction properties when the hand was soapy, while the smooth materials performed best when the hand was dry. PMID:11693248

  16. The dependence of lead-salt nanocrystal properties on morphology and dielectric environment

    NASA Astrophysics Data System (ADS)

    Bartnik, Adam Christopher

    The IV-VI semiconductors, and specifically the lead-salts (PbS, PbSe, and PbTe), are a natural choice for nanocrystal science. In nanocrystals, because of their narrow band gap, small effective masses, and large dielectric constants, they offer a unique combination of both strong confinement and strong dielectric contrast with their environment. Studying how these two effects modify optical and electrical properties of nanocrystals will be the topic of this dissertation. We begin with a summary of the synthesis of high-quality PbS and PbSe nanocrystals. Special care is taken to explain the chemical procedures in detail to an audience not expected to have significant prior chemistry knowledge. The synthesized nanocrystals have bright and tunable emission that spans the edge of the visible to the near-IR spectrum (700--1800 nm), and they are capped with organic ligands making them easily adaptable to different substrates or hosts. This combination of high optical quality and flexible device engineering make them extremely desirable for application. Moving beyond single-material nanocrystals, we next explore nanocrystal heterostructures, specifically materials with a spherical core of one semiconductor and a shell of another. Core-shell structures are commonly used in nanocrystals as a method to separate the core material, where the electrons and holes are expected to stay, from interfering effects at the surface. This typically results in improvements in stability and fluorescence quantum efficiency. To that end, we develop a model to explain how confinement plays out across abrupt changes in material, focusing on the optical and electrical properties of recently synthesized PbSe/PbS core-shell quantum dots. We show that for typical sizes of these nanocrystals, a novel type of nanocrystal heterostructure is created, where electrons and holes extend uniformly across the abrupt material boundary, and the shell does not act as a protecting layer. For very large sizes not yet achievable, we expect that the electron and hole will separate in different layers, with potentially measurable effects. Comparisons are made to optical and electrical measurements on these structures, showing good agreement. Next, we explore how shape can impact nanocrystal properties, on top of their intrinsic size or material dependence. By looking at cylindrically shaped nanocrystals, called "nanorods," with aspect ratios ? 10, we explore how having a slightly extended dimension can impact nanocrystal properties. A model is developed to explain their electronic structure, with surprising results. Foremost is that along the extended dimension, electrons and holes are strongly electrically bound, not with each other directly, but with their image charges in the outer host dielectric material. Nevertheless, the energy spectra of the excitons remains nearly host-independent, with the effects of this strong binding instead seen in a redistribution of transition oscillator strength. To test the model, we develop a novel synthesis of high quality PbSe nanorods, and find good agreement with measured absorption spectra. Finally, we present a study on the transfer of charge into and out of a nanocrystal. By modeling the charge transfer process within a modified Marcus Theory, we isolate the relevant parameters that can be used to control the rate of transfer. Primary among these are the values of the quantum dot energy levels, and the electrostatic charging energy of the acceptor. We vary the former by changing the quantum dot size, and the latter by varying the host dielectric constant. To test the model, we chemically bind a small molecular acceptor molecule to the surface of PbS nanocrystals and use transient fluorescence to measure the rate of charge transfer. Both the dependence of the rate on quantum dot size and host dielectric constant show good agreement with the model.

  17. Room temperature structure vibrational and dielectric properties of Ho modified YMnO3

    NASA Astrophysics Data System (ADS)

    Varshney, Dinesh; Sharma, Poorva; Kumar, Ashwini

    2015-07-01

    The structural, vibrational, and dielectric properties of bulk Ho-doped Y1?xHoxMnO3 (x = 0, 0.03, 0.05) solids prepared by standard solid-state reaction route were investigated. X-ray diffraction (XRD) patterns confirmed the hexagonal P63cm structure of Y1?xHoxMnO3 (x = 0.0, 0.03, 0.05) ceramics. Rietveld refinements of XRD data revealed that the doping ions led to unit cell contraction in three directions due to nearly equal ionic radii of Ho3+ ion (0.901 Å) substituted at the Y-site ion. The grain size of Ho-doped solids varied from 5 to 10 ?m. For pristine h-YMnO3, the experimentally observed Raman scattering lines at around 151, 305, 460, and 682 cm?1 are of A1 symmetry, those at 410 cm?1 are of E1 symmetry, and the lines at 139 and 219 cm?1 are of E2 symmetry. Another interesting observation is the existence of an A1 line at 682 cm?1 and an E1 line at about 410 cm?1 which are much stronger than the remaining lines of A1 and E1 symmetries, respectively. The high value of dielectric constant and dielectric loss tangent at low frequency is explained by space charge polarization and the saturation in the high-frequency region is due to the electric dipoles not being in pace with the frequency of the applied electric field.

  18. Measurements of the dielectric properties of simulated comet material as part of the KOSI 10 experiment

    NASA Technical Reports Server (NTRS)

    Ulamec, S.; Svedhem, H.; Kochan, H.

    1993-01-01

    The dielectric constant epsilon of the snow-mineral used for the comet simulation in the German KOSI 10 experiment was measured in the radio frequency range from 2 to 4 GHz. The traditional microwave bridge method was used, but instead of using a waveguide that contains the sample material small lambda/4 antennas were used as sensors. A change in the dielectric properties indicates a change in density and/or composition, respectively. The method is presented as an analytical tool for measuring such density or composition changes during alteration snow-dust materials. The KOSI (determined from the German: Kometen Simulation) experiments, performed in the Space simulator of the DLR/Institut for Raumsimulation, during the last years revealed many processes that presumably take place on comets. So far, modifications of the internal structure could be identified only during the post-experiment inspection via hardness tests. It was the aim of the KOSI 10 and KOSI 10a experiments to emphasize on a synoptic detection of events like particle emission or crust formation. The composition of the KOSI 10 sample material was an ice-mineral mixture with about 10 percent mineral (olivine) content. An excellent method to investigate the change of the density of the probe material during its exposure to the artificial sun in situ is to do it via the measurement of the dielectric constant. The traditional method to determine epsilon, by using a microwave-bridge to measure the transmission and the reflection factor of the sample material for electromagnetic waves in the radio frequency range, was modified, since the commonly used practice to fill the sample material into a waveguide was not compatible with the need for in situ measurements during the simulation experiment.

  19. Evolving Density and Static Mechanical Properties in Plutonium from Self-Irradiation

    SciTech Connect

    Chung, B W; Thompson, S R; Lema, K E; Hiromoto, D S; Ebbinghaus, B B

    2008-07-31

    Plutonium, because of its self-irradiation by alpha decay, ages by means of lattice damage and helium in-growth. These integrated aging effects result in microstructural and physical property changes. Because these effects would normally require decades to measure, studies are underway to assess the effects of extended aging on the physical properties of plutonium alloys by incorporating roughly 7.5 weight % of highly specific activity isotope {sup 238}Pu into the {sup 239}Pu metal to accelerate the aging process. This paper presents updated results of self-irradiation effects on {sup 238}Pu-enriched alloys measured by immersion density, dilatometry, and tensile tests. After nearly 90 equivalent years of aging, both the immersion density and dilatometry show that the enriched alloys continue to decreased in density by {approx}0.002% per year, without void swelling. Quasi-static tensile measurements show that the aging process increases the strength of plutonium alloys.

  20. Electroactive Phase Induced Bi4Ti3O12-Poly(Vinylidene Difluoride) Composites with Improved Dielectric Properties

    NASA Astrophysics Data System (ADS)

    Bhardwaj, Sumit; Paul, Joginder; Chand, Subhash; Raina, K. K.; Kumar, Ravi

    2015-06-01

    Lead-free ceramic-polymer composite films containing Bi4Ti3O12 (BIT) nanocrystals as the active phase and poly(vinylidene difluoride) as the passive matrix were synthesized by spin coating. The films' structural, morphological, and dielectric properties were systemically investigated by varying the weight fraction of BIT. Formation of electroactive ? and ? phases were strongly affected by the presence of BIT nanocrystals. Analysis was performed by Fourier-transform infrared and Raman spectroscopy. Morphological studies confirmed the homogeneous dispersion of BIT particles within the polymer matrix. The composite films had dielectric constants as high as 52.8 and low dielectric loss of 0.1 at 100 Hz when the BIT content was 10 wt.%. We suggest that the enhanced electroactive phase content of the polymer matrix and interfacial polarization may contribute to the improved dielectric performance of these composite films. Dielectric modulus analysis was performed to enable understanding of the dielectric relaxation process. Non-Debye-type relaxation behavior was observed for the composite films at high temperature.

  1. Effects of Cr/Zn Substitutions on Dielectric Properties of CaCu3Ti4O12 (CCTO) Ceramics

    NASA Astrophysics Data System (ADS)

    Rajmi, R.; Yahya, A. K.; Deni, M. S. M.

    2010-07-01

    Effects of Zn and Cr substitutions on dielectric properties of CaCu3-xZnxTi4-yCryO12 ceramics are reported. Dielectric measurements at room temperature for un-substituted CaCu3-xZnxTi4-yCryO12 (x = 0, y = 0) between 102-106 Hz showed dielectric constant of 2.7×104 at 102 Hz. Substitution of Zn for Cu in CaCu3-xZnxTi4-yCryO12 (y = 0, x = 0.10, 0.50)caused dielectric constant to drop with increasing x. Cr substitution at Ti-site in CaCu3-xZnxTi4-yCryO12 (x = 0, x = 0,) also caused decrease in dielectric constant. However, at x = 0.50, the dielectric constant at low frequency was enhanced compared to the un-substituted sample. Our results indicate that Cu and Ti sites play an important role in the formation of Internal Barrier Layer Capacitance (IBLC) in CCTO.

  2. Multimode solution for the reflection properties of an open-ended rectangular waveguide radiating into a dielectric half-space: the forward and inverse problems

    Microsoft Academic Search

    Karl J. Bois; Aaron D. Benally; Reza Zoughi

    1999-01-01

    Open-ended rectangular waveguides are extensively used in nondestructive dielectric material evaluation. The dielectric properties of an infinite-half space of a material are calculated from the measured reflection properties referenced to the waveguide aperture. This calculation relies on a theoretical and numerical derivation of the reflection coefficient likewise referenced to the waveguide aperture. Most of these derivations assume the dominant mode

  3. Solution-deposited GdCeO{sub x} thin films: Microstructure, band structure, and dielectric property

    SciTech Connect

    Lee, Myung Soo [School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)] [School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Park, Sang Han; Cho, Mann-Ho [Institute of Physics and Applied Physics, Yonsei University, Seoul 120-749 (Korea, Republic of)] [Institute of Physics and Applied Physics, Yonsei University, Seoul 120-749 (Korea, Republic of); Kim, Hyoungsub, E-mail: hsubkim@skku.edu [School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)] [School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)

    2012-06-15

    Highlights: ? Microstructural and electrical properties of sol–gel-deposited GdCeO{sub x} thin films with different mixing ratios. ? Ce incorporation enhanced crystallization and refractive index, reduced hysteresis, and increased dielectric constant. ? Bandgap gradually decreased with increasing Ce, which was primarily affected by VBO reduction. -- Abstract: The microstructural and electrical properties of solution-deposited GdCeO{sub x} dielectric thin films with different mixing ratios were studied. The Ce incorporation enhanced the degree of crystallization and the refractive index of the Gd{sub 2}O{sub 3} film, reduced the hysteresis and increased the dielectric constant. According to reflective electron energy loss spectroscopy and X-ray photoelectron spectroscopy analyses, the bandgap of the GdCeO{sub x} film gradually decreased with increasing Ce/(Gd + Ce) atomic ratio, which was primarily affected by the reduction of the valence band offset.

  4. Theoretical and experimental study of the structural, dynamical and dielectric properties of perovskite BaSnO3

    NASA Astrophysics Data System (ADS)

    Bévillon, Émile; Chesnaud, Anthony; Wang, Yanzhong; Dezanneau, Guilhem; Geneste, Grégory

    2008-04-01

    The structural, dynamical and dielectric properties of the cubic phase of perovskite barium stannate BaSnO3, a potential candidate as protonic conductor for solid oxide fuel cells, have been investigated by the means of first-principles density functional calculations, and the structural and electrical properties have been explored at low temperature. From density functional perturbative calculations, the phonon modes, the Born effective charges and the dielectric tensor are derived and analyzed, at zero pressure. The phonon band-structure of the cubic phase does not exhibit unstable modes, in good agreement with x-ray diffraction, which shows that BaSnO3 remains perfectly cubic down to 10 K. The dielectric response in BaSnO3 as measured and calculated is lower than in titanate and zirconate perovskites.

  5. CdSe nanocrystals ingrained dielectric nanocomposites: synthesis and photoluminescence properties

    NASA Astrophysics Data System (ADS)

    Dey, Chirantan; Goswami, Madhumita; Karmakar, Basudeb

    2015-01-01

    Cadmium selenide (CdSe) nanocrystals ingrained dielectric nanocomposites in a B2O3–SiO2–Al2O3–Na2O–K2O borosilicate glass system were synthesized by a single step in situ melt quenching technique. The sizes of the nanocrystals as well as the band gap of the nanocomposites were controlled by both concentration of CdSe and post thermal treatment duration. The nanocomposites were characterized by different instrumental techniques including detailed photoluminescence studies. The sizes of the CdSe nanocrystals were found to alter in the range 4–16 nm as estimated from the effective mass approximation model and optical absorption spectroscopy. However, the TEM analysis revealed the generation of two different size ranges, 3–4 and 23–45 nm, of the particles within the dielectric matrix. Selected area diffraction (SAED) and x-ray diffraction (XRD) patterns authenticate the formation of hexagonal nanostructures of CdSe. These nanocomposites were found to be capable of exhibiting strong visible red luminescence around 715 nm on excitation at 446 nm. This has originated from the electron–hole recombination of CdSe nanocrystal and defects or traps related transitions. The properties of these nanocomposites advocate their significant applications as semiconductor based luminescent materials.

  6. Dielectric and Electrical Properties of BiFeO3-LiTaO3 Systems

    NASA Astrophysics Data System (ADS)

    Mohanty, Suchismita; Choudhary, R. N. P.

    2015-07-01

    Materials of general formula (Bi1- x Li x )(Fe1- x Ta x )O3 ( x = 0.0, 0.5) were prepared from polycrystalline BiFeO3 and LiTaO3 by solid-state reaction. Analysis of the basic structural properties of the materials by room-temperature x-ray diffraction revealed the formation of single-phase tetragonal crystals for (Bi0.5Li0.5)(Fe0.5Ta0.5)O3. Scanning electron micrographs confirmed the polycrystalline nature of the materials. The microstructure of the materials comprised uniformly distributed grains of unequal size. Studies of the temperature-frequency dependence of dielectric did not reveal any dielectric anomaly or phase transition in the temperature range studied. The presence of hysteresis loops at room temperature confirmed the known ferroelectricity of BiFeO3 and (Bi0.5Li0.5)(Fe0.5Ta0.5)O3. Complex impedance spectroscopic analysis revealed the materials had negative temperature coefficient of resistance (NTCR)-type behavior. The electrical conductivity and relaxation characteristics of the materials suggested the presence of a thermally activated process, and their values suggested the materials had similar types of conductivity and relaxation species. The frequency dependence of the ac conductivity obeyed Jonscher's universal power law.

  7. Synthesis, characterization, UV and dielectric properties of hexagonal disklike ZnO particles embedded in polyimides

    SciTech Connect

    Vural, Sema; Koeytepe, Sueleyman [Inonu University, Chemistry Department, 44280 Malatya (Turkey)] [Inonu University, Chemistry Department, 44280 Malatya (Turkey); Seckin, Turgay, E-mail: tseckin@inonu.edu.tr [Inonu University, Chemistry Department, 44280 Malatya (Turkey)] [Inonu University, Chemistry Department, 44280 Malatya (Turkey); Adiguezel, Ibrahim [Inonu University, Physics Department, 44280 Malatya (Turkey)] [Inonu University, Physics Department, 44280 Malatya (Turkey)

    2011-10-15

    Graphical abstract: The hexagonal disklike ZnO particles with a diameter of 300-500 nm were synthesized from zinc acetate and NaOH in water with citric acid. ZnO/polyimide composite films with different ZnO contents was prepared. The prepared zinc oxide-polyimide composites were characterized for their structure, morphology and thermal behavior. Composites with ZnO particle contents from 1 to 5 wt% show good transparency in the visible region and luminescent properties. Highlights: {yields} A series of novel ZnO/polyimide composite films with different ZnO contents was prepared. {yields} The ZnO was homogeneously dispersed in the PI matrix. {yields} The composites showed the low dielectric constant of 50 at 10{sup 6} Hz. {yields} Homogenous dispersion and the amount of ZnO particles contributed to the dielectric properties of composites. -- Abstract: A series of novel ZnO/polyimide composite films with different ZnO contents was prepared through incorporation hexagonal disklike ZnO particles into poly(amic acid) of the pre polymer of the polyimide. The hexagonal disklike ZnO particles with a diameter of 300-500 nm were synthesized from zinc acetate and NaOH in water with citric acid. The prepared zinc oxide-polyimide composites were characterized for their structure, morphology, and thermal behavior employing Fourier transform infrared spectroscopy, scanning electron micrograph, X-ray diffraction and thermal analysis techniques. Thermal analyses show that the ZnO particles were successfully incorporated into the polymer matrix and these ZnO/polymer composites have a good thermal stability. Scanning electron microscopy studies indicate the ZnO particles were uniformly dispersed in the polymer and they remained at the original size (300-500 nm) before immobilization. All composite films with ZnO particle contents from 1 to 5 wt% show good transparency in the visible region and luminescent properties.

  8. The dielectric properties of soil-water mixtures at microwave frequencies

    Microsoft Academic Search

    J. R. Wang

    1980-01-01

    Recent measurements of the dielectric constants of soil-water mixtures have shown the existence of two frequency regions in which the dielectric behavior of these mixtures was quite different. At the frequencies of 1.4-5 GHz there was strong evidence that the variation of the dielectric constantwith water content W depended on soil type. While the real part of , ', for

  9. Material with high dielectric constant, low dielectric loss, and good mechanical and thermal properties produced using multi-wall carbon nanotubes wrapped with poly(ether sulphone) in a poly(ether ether ketone) matrix

    NASA Astrophysics Data System (ADS)

    Zhang, Shuling; Wang, Hongsong; Wang, Guibin; Jiang, Zhenhua

    2012-07-01

    A material with high dielectric constant, low dielectric loss, and good mechanical and thermal properties was produced using multi-wall carbon nanotubes (MWCNTs) wrapped with poly(ether sulphone) (PES) dispersed in a poly(ether ether ketone) (PEEK) matrix. The material was fabricated using melt-blending, and MWCNT/PEEK composites show different degrees of improvement in the measured dielectric, mechanical, and thermal properties as compared to pure PEEK. This is attributed to the high conductivity of MWCNTs, the effect of wrapping MWCNTs with PES, the good dispersion of the wrapped MWCNTs in PEEK, and the strong interfacial adhesion between the wrapped MWCNTs and the PEEK.

  10. Correlations between the Dielectric Properties and Exterior Morphology of Cells Revealed by Dielectrophoretic Field-Flow Fractionation

    PubMed Central

    Gascoyne, Peter R. C.; Shim, Sangjo; Noshari, Jamileh; Becker, Frederick F.; Stemke-Hale, Katherine

    2013-01-01

    Although dielectrophoresis (DEP) has great potential for addressing clinical cell isolation problems based on cell dielectric differences, a biological basis for predicting the DEP behavior of cells has been lacking. Here, the dielectric properties of the NCI-60 panel of tumor cell types have been measured by dielectrophoretic (DEP) field-flow fractionation, correlated with the exterior morphologies of the cells during growth, and compared with the dielectric and morphological characteristics of the subpopulations of peripheral blood. In agreement with earlier findings, cell total capacitance varied with both cell size and plasma membrane folding and the dielectric properties of the NCI-60 cell types in suspension reflected the plasma membrane area and volume of the cells at their growth sites. Therefore, the behavior of cells in DEP-based manipulations is largely determined by their exterior morphological characteristics prior to release into suspension. As a consequence, DEP is able to discriminate between cells of similar size having different morphological origins, offering a significant advantage over size-based filtering for isolating circulating tumor cells, for example. The findings provide a framework for anticipating cell dielectric behavior on the basis of structure-function relationships and suggest that DEP should be widely applicable as a surface marker-independent method for sorting cells. PMID:23172680

  11. Gigantic enhancement in the dielectric properties of polymer-based composites using core/shell MWCNT/amorphous carbon nanohybrids.

    PubMed

    Guo, Qikai; Xue, Qingzhong; Sun, Jin; Dong, Mingdong; Xia, Fujun; Zhang, Zhongyang

    2015-02-28

    Novel core/shell structured multi-walled carbon nanotube/amorphous carbon (MWCNT@AC) nanohybrids were successfully prepared using a simple and novel method. Subsequently, the MWCNT@AC nanohybrids were used as fillers to enhance the dielectric properties of poly(vinylidene fluoride) (PVDF) based composites. It is found that the dielectric constant of the MWCNT@AC/PVDF composites can reach 5910 (the dielectric loss is ?2), which is considerably better than that of MWCNT/PVDF composites. The uniform amorphous carbon shell provides an insulative layer between adjacent MWCNTs in the polymer matrix, which not only prevents the direct contact of MWCNTs but also improves the dispersibility of the MWCNTs. Therefore, a surprising number of microcapacitors could be formed in the composites before the formation of a conductive network, leading to a gigantic enhancement in the dielectric properties. Our strategy provides a new approach to fabricate excellent dielectric materials for energy storage capacitors. In addition, the design concept used in this work can be extended to other carbon materials. PMID:25640081

  12. Microwave dielectric properties of carbon black filled polymers under uniaxial tension

    NASA Astrophysics Data System (ADS)

    Mdarhri, A.; Brosseau, C.; Carmona, F.

    2007-04-01

    Broadband microwave spectroscopy is commonly employed in the determination of the wave transport properties in mesostructured polymers with embedded carbon black particles. However, very little is known on how uniaxial stress affects the effective permittivity of these percolative materials. In this work we carry out a comprehensive study of the complex permittivity spectra of carbon black filled ethylene butylacrylate copolymer which is submitted to a tensile stress up to 45% over the 0.1-3 GHz frequency range and at room temperature. Permittivity measurements indicated large decreases in the real and imaginary parts of the effective permittivity of the axially elongated samples. This set of experiments illustrates that these microwave permittivity data scale as a power law in frequency, where the exponent is strongly sensitive to stress. In addition, we show that our effective permittivity measurements under stress can be explained in terms of the Gaussian molecular network model in the limit of low stress. The observed variation of the effective permittivity is consistent with that reported for related materials, i.e., carbon black filled cross-linked rubber. Our analysis points out to the importance of local properties, i.e., properties associated with specific subsystems (e.g., aggregates of carbon black particles) in understanding the effective dielectric properties of these "macroscopic homogeneous" materials. Improved reliability through real-time monitoring of strain and material parameters (permittivity and permeability) simultaneously will result in significant benefits to the community in many areas, such as aerospace, power, and automotive industries.

  13. Microwave spectroscopy: a potential technique to analyse bitumen dielectric and physical properties

    NASA Astrophysics Data System (ADS)

    Ateeq, Muhammad; Wylie, Steve; Al-Shamma'a, Ahmed; Al-Nageim, Hassan

    2012-08-01

    Bitumen is a complex mixture of high molecular weight organic compounds, predominantly hydrocarbons, with carbon numbers greater than C24. It has high carbon to hydrogen ratios, and also contains small amount of metals such as nickel, iron and vanadium. The application of bitumen in the pavement industry is mainly as a binding agent for road construction/surfacing. Hence, this paper discusses the use of microwave spectroscopy (MS) as a potential technique to analyse bitumen's dielectric properties to indicate change in some of its physical properties after its interaction with both treated and untreated coarse rubber in the field of pavement engineering. A comparison of the existing techniques for the quantitative and qualitative analysis of bitumen is given. The drawbacks of the existing techniques are also discussed and the paper addresses how the MS technique can overcome these drawbacks. The MS technique is investigated by analysing different bitumen samples including pure bitumen and samples taken from rubber-bitumen blends. Each of the blends used rubber with different surface properties which have different effects on the properties of the resulting bitumen. The paper highlights the novelty and advantages for the MS technique in reducing analysis time, solvent usage and potential take-up by the industry.

  14. NEAR-FIELD IMAGING OF THE MICROWAVE DIELECTRIC PROPERTIES OF SINGLE-CRYSTAL PbTiO3

    E-print Network

    Reeves, Mark E.

    NEAR-FIELD IMAGING OF THE MICROWAVE DIELECTRIC PROPERTIES OF SINGLE-CRYSTAL PbTiO3 AND THIN-FILM Sr, DC, 20375 ABSTRACT A PbTiO3 crystal and Sr1;xBaxTiO3 lms have been studied by near- eld scanning With the rapid progress in communication technology and growing demand for high permittivity materials

  15. Dielectric properties of porcine brain tissue in the transition from life to death at frequencies from 800 to 1900 MHz.

    PubMed

    Schmid, Gernot; Neubauer, Georg; Illievich, Udo M; Alesch, François

    2003-09-01

    Ten experiments on pigs were performed to investigate possible postmortem changes of the dielectric properties of brain gray matter in the frequency range of 800-1900 MHz. After keeping the animals in stable anaesthesia for at least 45 min, they were euthanatised by an intravenous injection of hypertonic potassium chloride (KCl), causing cardiac arrest within 3 min. Measurements of the dielectric properties were performed repeatedly from at least 45 min prior to death to 18 h after euthanasia. The anaesthesia regimen was chosen to minimize influence on brain tissue characteristics such as brain water content, intracranial blood volume, and cerebral blood flow. The data showed a decline of mean gray matter equivalent conductivity of about 15% at 900 MHz and about 11% at 1800 MHz within the first hour after death. The decline in permittivity was less pronounced (about 3-4%) and almost frequency independent. The results indicate that in vitro measurements of dielectric properties of brain tissue underestimate equivalent conductivity as well as permittivity of living tissue. These changes may affect the generally accepted data of dielectric properties of brain tissue widely used in RF dosimetry. PMID:12929160

  16. Effect of weakly and strongly ionizing radiation on the optical, infrared, and dielectric properties of porous sol-gel glasses

    Microsoft Academic Search

    Ronald G. Pirich; Michael C. Stauber; Jerry Decarlo

    1994-01-01

    The effects of ionizing radiation on fiber optical materials and components can be quite dramatic and can adversely affect their transmission and loss in the optical and infrared. The effects of both weakly (gammas) and strongly (low energy protons) ionizing radiation exposure on the optical, infrared and dielectric properties of fully dense silica (quartz) and porous, alkoxide based sol-gel silica

  17. Dielectric and carrier transport properties of vanadium dioxide thin films across the phase transition utilizing gated capacitor devices

    E-print Network

    Yang, Zheng

    Dielectric and carrier transport properties of vanadium dioxide thin films across the phase; published 1 November 2010 Vanadium dioxide VO2 is a strongly correlated oxide that undergoes a sharp metal.22.Ch I. INTRODUCTION Vanadium dioxide VO2 is a material of great interest in condensed-matter physics

  18. Dielectric and piezoelectric properties of sodium lithium niobate Na1-xLixNbO3 lead free ferroelectric ceramics

    E-print Network

    Cao, Wenwu

    Dielectric and piezoelectric properties of sodium lithium niobate Na1-xLixNbO3 lead free # Springer Science + Business Media, LLC 2007 Abstract High density sodium lithium niobate lead free ce-to-paraelectric phase transition (tetragonal) takes place at about 354 °C (Curie temperature). Lithium Niobate LiNbO3

  19. Role of fiber\\/matrix interphases on dielectric, friction, and mechanical properties of glass fiber-reinforced epoxy composites

    Microsoft Academic Search

    B. Kechaou; M. Salvia; K. Benzarti; C. Turki; Z. Fakhfakh; D. Tréheux

    2012-01-01

    This study compares the mechanical, tribological, and dielectric properties of glass fiber-reinforced epoxy (GFRE), presenting various fiber\\/matrix adhesions. Three GFRE composites were studied. The only difference between them is in the initial preparation of fibers which is intentionally simplified compared to the complex sizings used in industry. Thus, fibers treated with aminosilane or silicone coupling agents were compared with fibers

  20. Interactions of light with rough dielectric surfaces - Spectral reflectance and polarimetric properties

    NASA Technical Reports Server (NTRS)

    Yon, S. A.; Pieters, C. M.

    1988-01-01

    The nature of the interactions of visible and NIR radiation with the surfaces of rock and mineral samples was investigated by measuring the reflectance and the polarization properties of scattered and reflected light for slab samples of obsidian and fine-grained basalt, prepared to controlled surface roughness. It is shown that the degree to which radiation can penetrate a surface and then scatter back out, an essential criterion for mineralogic determinations based on reflectance spectra, depends not only upon the composition of the material, but also on its physical condition such as sample grain size and surface roughness. Comparison of the experimentally measured reflectance and polarization from smooth and rough slab materials with the predicted models indicates that single Fresnel reflections are responsible for the largest part of the reflected intensity resulting from interactions with the surfaces of dielectric materials; multiple Fresnel reflections are much less important for such surfaces.

  1. Grain size effect on the nonlinear dielectric properties of barium titanate ceramics

    SciTech Connect

    Curecheriu, Lavinia; Mitoseriu, Liliana [Department of Physics, Alexandru Ioan Cuza University, Bv. Carol I No. 11, Iasi 700506 (Romania); Buscaglia, Maria Teresa; Buscaglia, Vincenzo [Institute of Energetics and Interphases (IENI)-CNR, Via De Marini No. 6, I-16149 Genoa (Italy); Zhao, Zhe [Department of Materials and Environmental Chemistry, University of Stockholm, SE-10691 Stockholm (Sweden)

    2010-12-13

    The nonlinear dielectric properties of dense BaTiO{sub 3} ceramics with grain size of 1 {mu}m-90 nm were investigated. In the finest ceramics, the permittivity reduces below 1000 and a remarkable nonhysteretic linear dc-tunability [{epsilon}(E)] is obtained at high field, above 40 kV/cm. The observed behavior was explained by considering the nanostructured ceramic as a composite formed by ferroelectric grains, whose nonlinearity is reducing, and by low-permittivity nonferroelectric grain boundaries, whose volume fraction increases when decreasing the grain size. Reducing the grain size in ferroelectric dense materials is an alternative route to accomplish the application requirements: nonhysteretic tunability and permittivity below 1000.

  2. Effect of organic gate dielectric material properties on interfacial charging and discharging of pentacene MIM device

    NASA Astrophysics Data System (ADS)

    Bazaka, Kateryna; Jacob, Mohan V.; Taguchi, Dai; Manaka, Takaaki; Iwamoto, Mitsumasa

    The effect of material properties of an environmentally friendly, optically transparent dielectric material, polyterpenol, on the carrier transients within the pentacene-based double-layer MTM device was investigated. Polyterpenol films were RF plasma polymerised under varied process conditions, with resultant films differing in surface chemistry and morphology. Independent of type of polyterpenol, time-resolved EFISHG study of IZO/polyterpenol/pentacene/Au structures showed similar transient behaviour with carriers injected into pentacene from Au electrode only, confirming polyterpenol to be a suitable blocking layer for visualisation of single-species carrier transportation during charging and discharging under different bias conditions. Polyterpenol fabricated under higher input power show better promise due to higher chemical and thermal stability, improved uniformity, and absence of defects.

  3. Growth and dielectric properties of ZnO nanoparticles deposited by using electrophoretic deposition

    NASA Astrophysics Data System (ADS)

    Chung, Yoonsung; Park, Hyejin; Kim, Dong-Joo; Cho, Sung Baek; Yoon, Young Soo

    2015-05-01

    The deposition behavior of ZnO nanoparticles on metal plates and conductive fabrics was investigated using electrophoretic deposition (EPD). The deposition kinetics on both metal plates and fabrics were examined using the Hamaker equation. Fabric substrates give more deposited weight than flat substrates due to their rougher shape and higher surface area. The morphologies and the structures of the deposited ZnO layers showed uniform deposition without any preferred orientation on both substrates. The dielectric properties of the ZnO layers formed by using EPD showed values that were reduced, but comparable to those of bulk ZnO. This result suggests that EPD is a convenient method to deposit functional oxides on flexible substrates.

  4. Invited paper: Dielectric properties of CaCu3Ti4O12 polycrystalline ceramics

    NASA Astrophysics Data System (ADS)

    Lee, Sung Yun; Hong, Youn Woo; Yoo, Sang Im

    2011-12-01

    We investigated the relationship between the microstructures and dielectric properties of various CaCu3Ti4O12 (CCTO) polycrystalline ceramics sintered in air. An abrupt increase in the dielectric constant ( ? r) from ˜3,000 to ˜170,000 at 1 kHz occurred with increasing the sintering temperature from 980 to 1000°C for 12 h, respectively, which was accompanied by a very large increase in the average grain size from 5 to 300 µm, respectively, due to an abnormal grain growth. With further increasing the sintering temperature, the ? r value at 1 kHz was slightly decreased to ˜150,000 at 1020°C with no variation in the average grain size, significantly decreased to ˜77,000 at 1040°C with a large decrease in the average grain size (˜150 µm), and then maintained the values of ˜76,000 and ˜69,000 at 1060 and 1080°C, respectively, without noticeable variation in the average grain size. While no abnormal grain growth occurred in the CCTO samples sintered at 980°C for the holding time to 24 h and thus their ? r values showed relatively lower ? r values (< ˜4,000 at 1 kHz), the abnormal grain growth occurred in the samples after a certain holding time at a given sintering temperature of higher than 1000°C and thus their ? r values abruptly increased. Analyses by the complex impedance ( Z*) and modulus ( M*) spectroscopy revealed that the ? r values of the CCTO samples were dominantly affected by the electrical properties of grain boundary so that high ? r values over 10,000 at 1 kHz were attributable to the high capacitance ( C) of grain boundary, which is in good agreement with grain boundary internal barrier layer capacitor (IBLC) model.

  5. Flux Trapping Properties of Bulk HIGH-TC Superconductors in Static Field-Cooling Magnetization

    NASA Astrophysics Data System (ADS)

    Deng, Z.; Tsuzuki, K.; Miki, M.; Felder, B.; Hara, S.; Izumi, M.

    2013-06-01

    The trapping process and saturation effect of trapped magnetic flux of bulk high-temperature superconductors by static field-cooling magnetization (FCM) are reported in the paper. With a cryogenic Bell Hall sensor attached on the center of the bulk surface, the synchronous magnetic signals were recorded during the whole magnetization process. It enables us to know the flux trapping behavior since the removal of the excitation field, as well as the subsequent flux relaxation phenomenon and the flux dissipation in the quench process of the bulk sample. With the help of flux mapping techniques, the relationship between the trapped flux and the applied field was further investigated; the saturation effect of trapped flux was discussed by comparing the peak trapped field and total magnetic flux of the bulk sample. These studies are useful to understand the basic flux trapping properties of bulk superconductors.

  6. Local Viscoelastic Properties of Live Cells Investigated Using Dynamic and Quasi-Static Atomic Force Microscopy Methods

    PubMed Central

    Cartagena, Alexander; Raman, Arvind

    2014-01-01

    The measurement of viscoelasticity of cells in physiological environments with high spatio-temporal resolution is a key goal in cell mechanobiology. Traditionally only the elastic properties have been measured from quasi-static force-distance curves using the atomic force microscope (AFM). Recently, dynamic AFM-based methods have been proposed to map the local in vitro viscoelastic properties of living cells with nanoscale resolution. However, the differences in viscoelastic properties estimated from such dynamic and traditional quasi-static techniques are poorly understood. In this work we quantitatively reconstruct the local force and dissipation gradients (viscoelasticity) on live fibroblast cells in buffer solutions using Lorentz force excited cantilevers and present a careful comparison between mechanical properties (local stiffness and damping) extracted using dynamic and quasi-static force spectroscopy methods. The results highlight the dependence of measured viscoelastic properties on both the frequency at which the chosen technique operates as well as the interactions with subcellular components beyond certain indentation depth, both of which are responsible for differences between the viscoelasticity property maps acquired using the dynamic AFM method against the quasi-static measurements. PMID:24606928

  7. Dielectric properties of Pr2O3 high-k films grown by metalorganic chemical vapor deposition on silicon

    Microsoft Academic Search

    Raffaella Lo Nigro; Vito Raineri; Corrado Bongiorno; Roberta Toro; Graziella Malandrino; Ignazio L. Fragalà

    2003-01-01

    Praseodymium oxide (Pr2O3) thin films have been deposited on Si(100) substrates by metalorganic chemical vapor deposition using praseodymium tris-2,2,6,6-tetramethyl-3,5-heptandionate as source material. Film structural, morphological, and compositional characterizations have been carried out. Dielectric properties have been studied as well by capacitance-voltage and current-voltage measurements on metal-oxide-semiconductor capacitors of several areas. The Pr2O3 films have shown a dielectric constant ?=23-25 and

  8. Low-temperature sintering and microwave dielectric properties of ZnTiO 3 -based LTCC materials

    Microsoft Academic Search

    Zhenxing Yue; Jing Yan; Fei Zhao; Zhilun Gui; Longtu Li

    2008-01-01

    The low-temperature sintered microwave dielectric ceramics with composition of ZnTiO3-0.25TiO2 were prepared by adding a small amount of low-melting compounds CuO-V2O5-Bi2O3 (CVB). The phase relationship and dielectric properties as a function of sintering temperature and the additional amount\\u000a were studied. It is demonstrated that the addition of low-melting CVB can suppress the formation of Zn2TiO4 at low temperature, but decrease

  9. Dielectric Properties of BaTiO3 Films Prepared by RF-Plasma Chemical Vapor Deposition

    Microsoft Academic Search

    Keigo Suzuki; Kazunori Kijima

    2005-01-01

    The size dependence of the dielectric properties of BaTiO3 nano-grains was investigated using films prepared by RF-plasma chemical vapor deposition. BaTiO3 nanoparticles were directly deposited on Pt\\/Al2O3\\/SiO2\\/Si substrates; then they were annealed at temperatures between 600 and 900°C in order to control the grain size. The dielectric constants of BaTiO3 nano-grains smaller than 30 nm were measured to be 200-300,

  10. Improved dielectric properties of lead zirconate titanate thin films deposited on metal foils with LaNiO3 buffer layers

    Microsoft Academic Search

    Q. Zou; H. E. Ruda; B. G. Yacobi

    2001-01-01

    Improved dielectric properties of lead zirconate titanate (PZT) films deposited on a variety of foils using buffer layers are reported. Foils include titanium, stainless steel, and nickel with LaNiO3(LNO) buffer layers which were prepared by sol-gel processing. High dielectric constant (330 for stainless steel, 420 for titanium, and 450 for nickel foils), low dielectric loss (<2.2% for titanium and 8%

  11. Interaction of static charges in graphene

    NASA Astrophysics Data System (ADS)

    Braguta, V. V.; Valgushev, S. N.; Nikolaev, A. A.; Polikarpov, M. I.; Ulybyshev, M. V.

    2015-05-01

    The study of the interaction potential between static charges within Monte-Carlo simulation of graphene is carried out. The numerical simulations are performed in the effective lattice field theory with noncompact 3 + 1-dimensional Abelian lattice gauge fields and 2 + 1-dimensional staggered lattice fermions. At low temperature the interaction can be described by the Coulomb potential reduced by some dielectric permittivity ?R. The dependence of ?R on the dielectric permittivity of substrate is determined. In addition, the renormalization of the quasiparticle charge is studied. At large temperatures the interaction potential can be described by the two-dimensional Debye screening. The dependence of Debye screening mass on the dielectric permittivity of substrate allows to determine the position of the insulator-semimetal phase transition. It is shown that graphene reveals in the semimetal phase the properties of the two-dimensional plasma of fermions excitations.

  12. Laboratory measurements of dielectric properties of compact and granular materials, in relation with Rosetta mission.

    NASA Astrophysics Data System (ADS)

    Brouet, Y.; Levasseur-Regourd, A. C.; Encrenaz, P.; Gheudin, M.; Ciarletti, V.; Gulkis, S.; Jambon, A.; Ruffié, G.; Prigent, C.

    2012-04-01

    The European Rosetta spacecraft (s/c), launched in 2004, will be the first s/c to orbit a comet and place a lander module on its surface. In 2014, the s/c will rendezvous with the comet 67P/Churyumov-Gerasimenko and place the lander on its surface thereby allowing in situ and remote sensing of the comet nucleus. Two radio experiments, one passive (MIRO [1]) and one active (CONSERT [2]), are aboard the Rosetta s/c. MIRO, composed of two radiometers, with center band frequencies at 190 GHz and at 563 GHz to determine the brightness temperatures of the target surfaces and sub-surfaces, has already observed asteroids (2867) Steins [3] and (21) Lutetia [4]. CONSERT will investigate the deep interior of the nucleus using 90 MHz radio-waves transmitted from the orbiter through the nucleus and returned to the orbiter from the lander. To support interpretations of MIRO and CONSERT observations, a program of dielectric properties measurements is under development on a large range of frequencies encompassing those of the above-mentioned experiments. Several instruments for dielectric constant determination are available at IMS laboratory (Bordeaux, France): impedance analyzer, coaxial sensor, resonant cavities (measuring respectively at 100 MHz, 0.5-6 GHz, 1.2-13.4 GHz). Millimeter benches are available at both IMS and LERMA laboratories (measuring respectively at 30-110 GHz and 70-230 GHz). Taking into account the possible presence of regolith layers on the surface of asteroids or nuclei and the very low density of cometary nuclei [5], the dependence of the dielectric constant on the structure and porosity of given granular materials needs also to be investigated (while the thermal and hygrometric conditions are carefully monitored). We have already reported measurements obtained on various meteorites, possibly representative of some asteroid surfaces [6, 7]. We will also report systematic measurements obtained on a large sample of pyroclastic deposits from Etna, providing different sizes distributions (i.e. surface to volume ratios), and possibly porosities. Dielectric constant determination at 190 GHz typically suggests that the real part of dielectric constant slowly increases with grain size: 2.86 ± 0.06, 2.96 ± 0.02 and 3.13 ± 0.05 for sizes respectively lower than 50 µm, between 50 and 160 µm and between 160 and 355 µm. Additional series of measurements on compact and granular samples of meteoritic analogues, such as carbonaceous chondrites are also to take place. [1] Gulkis et al. , Space Sci. Rev., 128, 561-597, 2007. [2] Kofman et al. , Space Sci. Rev., 128, 413-432, 2007. [3] Gulkis et al. , Space. Sci. Rev., 58, 1077-1087, 2010. [4] Gulkis et al. , Space. Sci. Rev., doi: 10.1016/j.pss.2011.12.004, 2011. [5] Levasseur-Regourd et al. , Planet. Space Sci., 57, 221-228, 2009. [6] McFadden et al., 40th LPSC, 2887, 2009. [7] Brouet el al. , EPSC-DPS Joint Meeting, p. 1083, 2011.

  13. Property and Lighting Manipulations for Static Volume Stylization Using a Painting Metaphor.

    PubMed

    Klehm, Oliver; Ihrke, Ivo; Seidel, Hans-Peter; Eisemann, Elmar

    2014-03-12

    Although volumetric phenomena are important for realistic rendering and can even be a crucial component in the image, the artistic control of the volume's appearance is challenging. Appropriate tools to edit volume properties are missing, which can make it necessary to use simulation results directly. Alternatively, high-level modifications that are rarely intuitive, e.g., the tweaking of noise function parameters, can be utilized. Our work introduces a solution to stylize single-scattering volumetric effects in static volumes. Hereby, an artistic and intuitive control of emission, scattering and extinction becomes possible, while ensuring a smooth and coherent appearance when changing the viewpoint. Our method is based on tomographic reconstruction, which we link to the volumetric rendering equation. It analyzes a number of target views provided by the artist and adapts the volume properties to match the appearance for the given perspectives. Additionally, we describe how we can optimize for the environmental lighting to match a desired scene appearance, while keeping volume properties constant. Finally, both techniques can be combined. We demonstrate several use cases of our approach and illustrate its effectiveness. PMID:24636982

  14. Static and dynamical properties of heavy water at ambient conditions from first-principles molecular dynamics

    E-print Network

    P. H-L. Sit; Nicola Marzari

    2005-04-08

    The static and dynamical properties of heavy water have been studied at ambient conditions with extensive Car-Parrinello molecular-dynamics simulations in the canonical ensemble, with temperatures ranging between 325 K and 400 K. Density-functional theory, paired with a modern exchange-correlation functional (PBE), provides an excellent agreement for the structural properties and binding energy of the water monomer and dimer. On the other hand, the structural and dynamical properties of the bulk liquid show a clear enhancement of the local structure compared to experimental results; a distinctive transition to liquid-like diffusion occurs in the simulations only at the elevated temperature of 400 K. Extensive runs of up to 50 picoseconds are needed to obtain well-converged thermal averages; the use of ultrasoft or norm-conserving pseudopotentials and the larger plane-wave sets associated with the latter choice had, as expected, only negligible effects on the final result. Finite-size effects in the liquid state are found to be mostly negligible for systems as small as 32 molecules per unit cell.

  15. Refinement of the theory for extracting cell dielectric properties from dielectrophoresis and electrorotation experiments.

    PubMed

    Lei, U; Sun, Pei-Hou; Pethig, Ronald

    2011-12-01

    A modified theory is proposed for extracting cell dielectric properties from the peak frequency measurement of electrorotation (ER) and the crossover frequency measurement of dielectrophoresis (DEP). Current theory in the literature is based on the low frequency (DC) approximations for the equivalent cell permittivity and conductivity, which are valid when the measurements are performed in a medium with conductivity less than 1 mS/m. The present theory extracts the cell properties through optimizing an expression for the medium conductivity in terms of the peak ER, or DEP crossover, frequency according to its definition using full expressions of equivalent cell permittivity and conductivity. Various levels of approximation of the theory are proposed and discussed through a scaling analysis. The present theory can extract both membrane and interior properties from the low and the high peak ER, or DEP crossover, frequencies for any medium conductivity provided the peak ER, or DEP crossover, frequency exists. It can be reduced to the linear theory for the low peak ER and DEP crossover frequencies in the literature when the medium conductivity is less than 10 mS/m. However, we can determine the membrane capacitance and conductance via the slope and intercept, respectively, of the straight line fitting of the ER peak and DEP frequency against medium conductivity data according to the linear theory only when the intercept dominates the experimental uncertainty, which occurs when the medium conductivity is less than 1 mS/m in practice. PMID:22662061

  16. Refinement of the theory for extracting cell dielectric properties from dielectrophoresis and electrorotation experiments

    PubMed Central

    Lei, U.; Sun, Pei-Hou; Pethig, Ronald

    2011-01-01

    A modified theory is proposed for extracting cell dielectric properties from the peak frequency measurement of electrorotation (ER) and the crossover frequency measurement of dielectrophoresis (DEP). Current theory in the literature is based on the low frequency (DC) approximations for the equivalent cell permittivity and conductivity, which are valid when the measurements are performed in a medium with conductivity less than 1 mS/m. The present theory extracts the cell properties through optimizing an expression for the medium conductivity in terms of the peak ER, or DEP crossover, frequency according to its definition using full expressions of equivalent cell permittivity and conductivity. Various levels of approximation of the theory are proposed and discussed through a scaling analysis. The present theory can extract both membrane and interior properties from the low and the high peak ER, or DEP crossover, frequencies for any medium conductivity provided the peak ER, or DEP crossover, frequency exists. It can be reduced to the linear theory for the low peak ER and DEP crossover frequencies in the literature when the medium conductivity is less than 10 mS/m. However, we can determine the membrane capacitance and conductance via the slope and intercept, respectively, of the straight line fitting of the ER peak and DEP frequency against medium conductivity data according to the linear theory only when the intercept dominates the experimental uncertainty, which occurs when the medium conductivity is less than 1 mS/m in practice. PMID:22662061

  17. Theoretical and experimental study of the structural, dynamical and dielectric properties of perovskite BaSnO3

    Microsoft Academic Search

    Émile Bévillon; Anthony Chesnaud; Yanzhong Wang; Guilhem Dezanneau; Grégory Geneste

    2008-01-01

    The structural, dynamical and dielectric properties of the cubic phase of perovskite barium stannate BaSnO3, a potential candidate as protonic conductor for solid oxide fuel cells, have been investigated by the means of first-principles density functional calculations, and the structural and electrical properties have been explored at low temperature. From density functional perturbative calculations, the phonon modes, the Born effective

  18. Electromagnetic properties of periodic and quasi-periodic one-dimensional, metallo-dielectric photonic band gap structures

    Microsoft Academic Search

    C. Sibilia; M. Scalora; M. Centini; M. Bertolotti; M. J. Bloemer; C. M. Bowden

    1999-01-01

    We discuss some of the electromagnetic properties of one-dimensional, metallo-dielectric photonic band gap structures. In our considerations, we include discussions of the transmissive and reflective properties of multilayer stacks, and the density of electromagnetic field modes for the structure. In particular, we highlight and contrast the role of quasi-periodic structures with respect to periodic structures, in the form of Cantor

  19. Improving the dielectric and piezoelectric properties of screen-printed Low temperature PZT/polymer composite using cold isostatic pressing

    NASA Astrophysics Data System (ADS)

    Almusallam, A.; Yang, K.; Cao, Z.; Zhu, D.; Tudor, J.; Beeby, S. P.

    2014-11-01

    This paper reports an improvement in dielectric and piezoelectric properties of screen-printed PZT/polymer films for flexible electronics applications using Cold Isostatic Pressing (CIP). The investigation involved half and fully cured PZT/polymer composite pastes with weight ratio of 12:1 to investigate the effect of the CIP process on the piezoelectric and dielectric properties. It was observed that the highest dielectric and piezoelectric properties are achieved at pressures of 5 and 10 MPa for half and fully cured films respectively. The relative dielectric constants were 300 and 245 measured at 1 kHz for the half and fully cured samples. Using unoptimised poling conditions, the initial d33 values were 30 and 35 pC/N for the half and fully cured films, respectively. The fully cured sample was then poled using optimized conditions and demonstrated a d33 of approximately 44 pC/N which is an increase of 7% compared with non-CIP processed materials.

  20. Effects of Processing Routes on Structures and Dielectric Properties of Lead Iron Niobate-Lead Magnesium Niobate Binary System

    NASA Astrophysics Data System (ADS)

    Yu, Youhua; Feng, Chude; Li, Chengen; Yang, Yi; Yan, Haixue

    2001-04-01

    The binary system of lead magnesium niobate [Pb(Mg1/3Nb2/3)O3, PMN] and lead iron niobate [Pb(Fe1/2Nb1/2)O3, PFN] has been chosen to investigate the influence of different preparation routes on the microstructures and properties by means of X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), energy dispersion spectrometer (EDS) and dielectric measurements. It is found that for the binary system (1-x)PFN-xPMN, the change in Curie temperature is approximately linear with respect to PMN content in the range of x=0 to 0.5. With the increase in x, the Curie points shift to lower temperatures. Both calcining and sintering conditions have a non-negligible influence on the microstructure and the dielectric properties. The dielectric and other properties of samples prepared by single-step and two-step precalcination routes are compared and the possible mechanisms are discussed. Samples mixed-sintered at an appropriate temperature exhibit a different dielectric behavior, which is also discussed in detail in this paper.

  1. Effects of the poling process on dielectric, piezoelectric, and ferroelectric properties of lead zirconate titanate

    NASA Astrophysics Data System (ADS)

    Prewitt, Anderson D.

    Smart materials are widely used in many of today's relevant technologies such as nano and micro electromechanical systems (NEMS and MEMS), sensors, actuators, nonvolatile memory, and solid state devices. Many of these systems rely heavily on the electromechanical properties of certain smart materials, such as piezoelectricity and ferroelectricity. By definition, piezoelectricity is a mechanical stress in a material that produces an electric displacement (known as the direct piezoelectric effect) or electrical charge in a material which produces a mechanical strain (known as the converse piezoelectric effect). Ferroelectricity is a sub-class of piezoelectricity in which the polarization occurs spontaneously and the dipoles can be reoriented. Domain walls are the nanoscale regions separating two finite distinctively polarized areas in a ferroelectric. The reorientation of polarization in a material is called the poling process and many factors can influence the effectiveness of this process. A more fundamental understanding of how electrical and mechanical loading changes the domain structure of these materials could lead to enhanced properties such as increased energy transduction and decreased nonlinear behavior. This research demonstrates the influence of mechanical pressure and electrical field during and after the poling process on domain walls. The effects of strong mechanical forces on large-scale domain switching and weak cyclic forces on small-scale domain wall motion are investigated to show how they affect the macroscopic behavior of these materials. Commercial lead zirconate titanate ceramics were studied under various poling conditions and the effect of domain wall motion on the piezoelectric, dielectric, and ferroelectric properties was investigated. Polarization and strain measurements from samples poled at specific conditions and converse piezoelectric coefficient and dielectric permittivity data was extracted and interpreted in the context of Rayleigh Law. Direct d33 was also measured. Mechanical loading measurements on the samples were conducted in situ during neutron diffraction experiments to determine how the domain structure behaved for the various poling conditions. The behavior of unpoled and poled samples under load was investigated. The goal of this research is to develop a better understanding of the ferroelectric poling process and its influence on domain wall behavior in order to better engineer material and device properties. Experimental results have shown that significant changes occur in the electromechanical behavior of the material depending on the poling conditions. These results provide insight on how to better design materials and devices with enhanced performance, improved capacity, and less degradation as a result of mechanical stress and electrical fields. Possible microstructural origins for this behavior are discussed.

  2. Dielectric and transport properties of magnetic insulators irradiated with GeV heavy ions

    NASA Astrophysics Data System (ADS)

    Costantini, J. M.; Salvetat, J. P.; Brisard, F.

    1997-11-01

    The dielectric and ac/dc transport properties of single crystals of yttrium iron garnet (Y3Fe5O12 and Y3Fe5O12:Si), and barium hexaferrite (BaFe12O19 and BaFe12O1 9:Co,Ti) were investigated after irradiations with Xe and Pb ions in the GeV range. In the virgin n-type samples (Y3Fe5O12:Si and BaFe12O19:Co,Ti), the strong dielectric relaxation below 100 kHz is found to correspond to a space-charge polarization at the blocking metal/insulator contacts yielding a nonohmic dc conductivity. The relaxation frequency decreases with increasing amorphization yield in relation to the decrease of the insulators bulk dc conductivity which becomes ohmic in the amorphous phases. The ac conductivity data of both crystalline and amorphous Y3Fe5O12:Si above 100 kHz and for 100 K180 K. The dc conductivity data of crystalline Y3Fe5O12:Si for 80 K125 K, in agreement with the activation energy around 0.28 eV of the space-charge dielectric relaxation frequency for T>180 K. All amorphous phases data are consistent with the picture of hopping conduction between gap states in a disordered medium with (i) an ?s dependence for the ac conductivity above a critical frequency proportional to the dc conductivity, (ii) and an exp(-T-1/4) law for the dc conductivity.

  3. The effect of in-service aerospace contaminants on X-band dielectric properties of a bismaleimide/quartz composite

    NASA Astrophysics Data System (ADS)

    Rodriguez, Luis A.; García, Carla; Grace, Landon R.

    2015-05-01

    The impact of three common aerospace in-service liquid contaminants on the X-band dielectric properties of a polymer composite radar protecting structure (radome) is investigated and quantified. The dielectric properties of the composite laminate are critical to radar transparency, and thus performance, of the radome structure. Further, polymer composites are highly susceptible to absorption of liquids. As such, the effect of common aerospace contaminants on the dielectric properties of composite laminates is crucial. Measurement of relative permittivity and loss tangent via a split-post dielectric resonant technique at 10 GHz is used to determine the effect of water, deicing fluid, and propylene glycol absorption in a three-ply quartz-reinforced bismaleimide laminate. Additionally, fluid uptake kinetics are investigated as a function of liquid type. An approximately linear relationship between fluid content and relative permittivity is observed for all three contaminant types. A 1% increase in contaminant content by weight results in a 7.8%, 4.5%, and 2.5% increase in relative permittivity of the material due to water, deicing fluid, and propylene glycol, respectively. A more significant impact is seen in material loss tangent, where a 1% increase in contaminant content by weight is responsible for a 378.5%, 593.0%, and 441.5% increase in loss tangent due to the aforementioned fluids, respectively. A fluid uptake weight content of 1.31%, 3.41%, and 4.28% is achieved for water, deicing fluid, and propylene glycol respectively, at approximately 1300 hours exposure. Based on the reported observations, the dielectric property degradation of composite laminates due to these commonly used fluids is of significant concern for in-service aircraft radar systems routinely exposed to these contaminants.

  4. Effects of pyrolysis conditions on dielectric properties of PLZT films derived from a polyvinylpyrrolidone-modified sol-gel process

    SciTech Connect

    Chao, Sheng, E-mail: Sheng.Chao@kennametal.com [Energy Systems Division, Argonne National Laboratory, Argonne, IL 60439 (United States)] [Energy Systems Division, Argonne National Laboratory, Argonne, IL 60439 (United States); Ma, Beihai; Liu, Shanshan; Narayanan, Manoj; Balachandran, Uthamalingam [Energy Systems Division, Argonne National Laboratory, Argonne, IL 60439 (United States)] [Energy Systems Division, Argonne National Laboratory, Argonne, IL 60439 (United States)

    2012-03-15

    Graphical abstract: SEM images showing the surface morphology of PLZT films derived from solutions with various PVP content and treated with either RTA (rapid thermal annealing) or SPT (step-wise preheat treatment) process. Highlights: Black-Right-Pointing-Pointer High-quality PLZT films were fabricated by using a polyvinylpyrrolidone-modified sol-gel method. Black-Right-Pointing-Pointer Improved film density and integrity was achieved by employing a novel step-wise preheat treatment (SPT) process. Black-Right-Pointing-Pointer Enhanced dielectric properties were correlated to the improved microstructures as a result of the SPT process. -- Abstract: Pb{sub 0.92}La{sub 0.08}Zr{sub 0.52}Ti{sub 0.48}O{sub 3} (PLZT) films were deposited on platinized silicon substrates (Pt/Si) using a polyvinylpyrrolidone (PVP) modified sol-gel method. Pyrolysis of the green films was conducted via two methods: rapid thermal annealing (RTA) and a step-wise preheat treatment (SPT). Microstructure analysis and dielectric property characterization were performed on samples treated by these two methods. Results showed that the SPT-pyrolyzed films exhibited much better dielectric properties when compared with the RTA-pyrolyzed films. The differences in dielectric properties were correlated to microstructural features caused by the different pyrolysis conditions. High-quality PLZT films with high dielectric constant ( Almost-Equal-To 860 at zero bias) and high breakdown strength ( Almost-Equal-To 2.1 MV/cm) were fabricated under controlled pyrolysis conditions. This work demonstrated the potential application of this material for power electronics in electric drive vehicles.

  5. Dielectric function and optical properties of quaternary AlInGaN alloys

    NASA Astrophysics Data System (ADS)

    Sakalauskas, E.; Reuters, B.; Khoshroo, L. Rahimzadeh; Kalisch, H.; Heuken, M.; Vescan, A.; Röppischer, M.; Cobet, C.; Gobsch, G.; Goldhahn, R.

    2011-07-01

    The optical properties of quaternary Alx Iny Ga1-x -yN alloy films with 0.16< x<0.64 and 0.02< y <0.13 are presented. The (0001)-oriented AlInGaN layers were grown by metal-organic vapor phase epitaxy on thick GaN/sapphire templates. High-resolution x-ray diffraction measurements revealed the pseudomorphic growth of the AlInGaN films on the GaN buffer. Rutherford backscattering and wavelength-dispersive x-ray spectroscopy analysis were used in order to determine the composition of the alloys. The ordinary dielectric function (DF) of the AlInGaN samples was determined in the range of 1-10 eV by spectroscopic ellipsometry (SE) at room temperature (synchrotron radiation: BESSY II). The sharp onset of the imaginary part of the DF defines the direct absorption edge of the alloys. At higher photon energies, pronounced peaks are observed in the DF indicating a promising optical quality of the material. These features are correlated to the critical points of the band structure (van Hove singularities). An analytical model, which permits us to accurately describe the dielectric function (or optical constants) in the range of 1-10 eV, is also presented. The band-gap and high-energy interband transition values are obtained by fitting the experimental DF with the analytical model. The strain influence on the bandgap is evaluated by using the k ×p formalism. Furthermore, an empirical expression is proposed which allows us to calculate the AlInGaN band-gap and high-energy inter-band transitions in the whole compositional range (x, y). The band-gap values obtained from the empirical expression are in good agreement with both the calculated ab initio and the experimental values determined by SE.

  6. Dielectric properties and frequency response of self-assembled monolayers of alkanethiols.

    PubMed

    Wang, Bing; Luo, Jianglong; Wang, Xiaoping; Wang, Haiqian; Hou, J G

    2004-06-01

    This paper presents dielectric properties of alkanethiol self-assembled monolayers (SAMs) under an ac electric field. Using a Hg-SAM/SAM-Hg junction, we measured the ac impedance of alkanethiol SAMs using a sinusoidal perturbation of 30 mV (peak-to-peak) with frequency ranging from 1 Hz to 1 MHz at zero bias. Semicircles at higher frequencies and at middle frequencies along with Warburg lines at lower frequencies were observed in complex plane impedance plots, that is, Nyquist plots. The frequency response of SAMs was analyzed by modeling the junction using an equivalent circuit and fitting the Nyquist plots. The semicircles at higher frequencies are attributed to the effect of the SAM/SAM interfaces, and the ones at middle frequencies are attributed to the effect of alkanethiol SAMs. The comparison in the plots of the imaginary part of the impedance Z against frequency for the bare Hg electrodes (in pure ethanal) and the SAM-covered Hg electrodes (in alkanethiol solution) supports the analysis. The Warburg lines are attributed to a certain ionic impurity. The dielectric loss spectra are further analyzed. Chain-length-dependent peaks, which correspond to different relaxation mechanisms, at higher frequencies and middle frequencies were observed in the spectra of the dissipation factor (tan delta vs frequency). The peaks move to small frequency with the increase of chain length of alkanethiols. Using a correlation of peak position with the chain length, we then derived active energies of 39-99 meV for alkanethiol SAMs of C7-C18 under an ac electric field. PMID:15984261

  7. Mechanical property changes in porous low-k dielectric thin films during processing

    SciTech Connect

    Stan, G., E-mail: gheorghe.stan@nist.gov; Gates, R. S. [Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); Kavuri, P. [Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); Torres, J.; Michalak, D.; Ege, C.; Bielefeld, J.; King, S. W. [Logic Technology Development, Intel Corporation, Hillsboro, Oregon 97124 (United States)

    2014-10-13

    The design of future generations of Cu-low-k dielectric interconnects with reduced electronic crosstalk often requires engineering materials with an optimal trade off between their dielectric constant and elastic modulus. This is because the benefits associated with the reduction of the dielectric constant by increasing the porosity of materials, for example, can adversely affect their mechanical integrity during processing. By using load-dependent contact-resonance atomic force microscopy, the changes in the elastic modulus of low-k dielectric materials due to processing were accurately measured. These changes were linked to alterations sustained by the structure of low-k dielectric films during processing. A two-phase model was used for quantitative assessments of the elastic modulus changes undergone by the organosilicate skeleton of the structure of porous and pore-filled dielectrics.

  8. Mechanical property changes in porous low-k dielectric thin films during processing

    NASA Astrophysics Data System (ADS)

    Stan, G.; Gates, R. S.; Kavuri, P.; Torres, J.; Michalak, D.; Ege, C.; Bielefeld, J.; King, S. W.

    2014-10-01

    The design of future generations of Cu-low-k dielectric interconnects with reduced electronic crosstalk often requires engineering materials with an optimal trade off between their dielectric constant and elastic modulus. This is because the benefits associated with the reduction of the dielectric constant by increasing the porosity of materials, for example, can adversely affect their mechanical integrity during processing. By using load-dependent contact-resonance atomic force microscopy, the changes in the elastic modulus of low-k dielectric materials due to processing were accurately measured. These changes were linked to alterations sustained by the structure of low-k dielectric films during processing. A two-phase model was used for quantitative assessments of the elastic modulus changes undergone by the organosilicate skeleton of the structure of porous and pore-filled dielectrics.

  9. Dynamic and quasi-static mechanical properties of iron-nickel alloy honeycomb

    NASA Astrophysics Data System (ADS)

    Clark, Justin L.

    Several metal honeycombs, termed Linear Cellular Alloys (LCAs), were fabricated via a paste extrusion process and thermal treatment. Two Fe-Ni based alloy compositions were evaluated. Maraging steel and Super Invar were chosen for their compatibility with the process and the wide range of properties they afforded. Cell wall material was characterized and compared to wrought alloy specifications. The bulk alloy was found to compare well with the more conventionally produced wrought product when porosity was taken into account. The presence of extrusion defects and raw material impurities were shown to degrade properties with respect to wrought alloys. The performance of LCAs was investigated for several alloys and cell morphologies. The results showed that out-of-plane properties exceeded model predictions and in-plane properties fell short due to missing cell walls and similar defects. Strength was shown to outperform several existing cellular metals by as much as an order of magnitude in some instances. Energy absorption of these materials was shown to exceed 150 J/cc at strains of 50% for high strength alloys. Finally, the suitability of LCAs as an energetic capsule was investigated. The investigation found that the LCAs added significant static strength and as much as three to five times improvement in the dynamic strength of the system. More importantly, it was shown that the pressures achieved with the LCA capsule were significantly higher than the energetic material could achieve alone. High pressures, approaching 3 GPa, coupled with the fragmentation of the capsule during impact increased the likelihood of initiation and propagation of the energetic reaction. This multi-functional aspect of the LCA makes it a suitable capsule material.

  10. W-Band Transmission MeasurementS and X-Band Dielectric Properties Measurements for a Radome Material Sample

    NASA Technical Reports Server (NTRS)

    Cravey, Robin L.; Tiemsin, Pacita I.

    1997-01-01

    This paper describes measurements which were performed on a sample of radome material in the Electromagnetic Properties Measurements Laboratory (EPML). The purpose of the measurements described in this paper was to determine the one-way transmission loss through the flat panel of radome material for a frequency range of 84 to 94 GHz, for varying incidence angles. The panel, which was manufactured by Norton Performance Plastics Corporation, was provided to the EPML by TRW. The size of the panel is 40 in x 36 in x 0.422 in and consists of a foam material with one side coated with a smooth white coating (this side will be referred to as the front side). The dielectric properties of the foam material from the inside of the panel were also determined at X-band (8.2-12.4 GHz). The W-band free space measurements are presented first, followed by the X-band dielectric properties measurements.

  11. Tuned dielectric, pyroelectric and piezoelectric properties of ferroelectric P(VDF-TrFE) thin films by using mechanical loads

    NASA Astrophysics Data System (ADS)

    Bai, G.; Li, R.; Liu, Z. G.; Xia, Y. D.; Yin, J.

    2012-02-01

    Using the phenomenological Landau thermodynamic theory, we have investigated the effect of external mechanical loads on the phase transition and physical properties of poly(vinylidene fluoride-trifluorethylene) [P(VDF-TrFE)] thin films. Quantitative calculation shows that the phase transition temperature, polarization, dielectric, pyroelectric, and piezoelectric properties are highly sensitive to external mechanical loads. External compressive stress increases the phase transition temperature and the out-of-plane polarization and decreases the out-of-plane dielectric constant below Tc, pyroelectric coefficient, and piezoelectric coefficient (absolute value) and vice versa. Compared with pervoskite-type ferroelectrics, the calculated results are opposite due to the different intrinsic parameters between pervoskite and polymer ferroelectrics, especially, electrostrictive constants. The ability to tailor the properties in ferroelectric P(VDF-TrFE) thin films with the mechanical load can offer a tremendously promising future for applications in multifunctional devices, such as agile mechanical sensors and transducers.

  12. Lattice dynamics and broad-band dielectric properties of the KTaO3 ceramics Sebastjan Glinsek,1,2,a)

    E-print Network

    Ku?el, Petr

    on the dielectric response in KTaO3 unlike in other ferroelectric or incipient ferroelectric perovskite ceramics. VCLattice dynamics and broad-band dielectric properties of the KTaO3 ceramics Sebastjan Glinsek,1,2,a) High-density KTaO3 ceramics were synthesized and studied by means of microwave, terahertz, infrared

  13. Dielectric properties of CaCu3Ti4O12-silicone resin composites

    NASA Astrophysics Data System (ADS)

    Babu, Sanjesh; Singh, Kirti; Govindan, Anil

    2012-06-01

    CaCu3Ti4O12 (CCTO)-silicone resin composites with various CCTO volume fractions were prepared. Relatively high dielectric constant ( ?=119) and low loss (tan ?=0.35) of the composites with CCTO volume fraction of 0.9 were observed. Two theoretical models were employed to predict the dielectric constant of these composites; the dielectric constant obtained via the Maxwell-Garnett model was in close agreement with the experimental data. The dielectric constant of CCTO-silicone resin composites showed a weak frequency dependence at the measuring frequency range and the loss tangent apparently decreases with increase in frequency.

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

    PubMed Central

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

    2015-01-01

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

  15. Effect of top metallization on the dielectric and ferroelectric properties of sol-gel derived PZT thin films

    SciTech Connect

    Teowee, G.; Baertlein, C.D. [Donnelly Corp., Tucson, AZ (United States); Kneer, E.A.; Boulton, J.M.; Uhlmann, D.R. [Arizona Materials Labs., Tucson, AZ (United States)

    1994-12-31

    Pt-PZT-Metal capacitors were prepared utilizing various top metallizations and PZT films which were previously fired to 700C to convert them into single-phase perovskite films. The dielectric (e.g. dielectric constants and leakage characteristics) and FE (e.g. remanent polarization and coercive field) properties were highly dependent in the choice of metals used. The highest dielectric constants were obtained for capacitors having noble or transition metals; the lowest leakage currents were obtained using Au or Pt top electrodes; and the highest polarizations (both remanent and spontaneous) were measured for capacitors having noble metals or Bi. There was not a consistent dependence of these properties (especially leakage currents) on the work function of the metal used. The electronegativity or affinity for oxygen of the electrode plays a more important role in affecting the junction characteristics. For several reactive top metals such as In, Zn, Cu and Al, the formation of interfacial oxide layers at the Pt-metal junctions leads to high values of coercive field ({approx}50kV/cm) compared to when noble metals or Zn are used ({approx}20-25kV/cm). The overall best dielectric and FE behaviors are derived from capacitors having noble metals, especially Pt, as the top and bottom electrodes.

  16. Selective substitution and tetragonality by Co-doping of dysprosium and thulium on dielectric properties of barium titanate ceramics

    NASA Astrophysics Data System (ADS)

    Kim, Jungdae; Kim, Dowan; Kim, Jinseong; Kim, Yong-Nam; Hui, K. N.; Lee, Heesoo

    2011-06-01

    Barium titanate (BaTiO3) ceramics co-doped with rare-earth elements were investigated in terms of selective substitution and tetragonality. The dielectrics were designed by addition of various Dy2O3 and Tm2O3 contents, for a total of 1 mol. % concentration, and analyzed in a temperature range from -55°C to 150°C. The dielectric constant of the 0.7 mol. % Dy2O3 and the 0.3 mol. % Tm2O3 co-doped BaTiO3 was 2250, which was about 27% higher than those of specimens doped with 1 mol. % Tm2O3 and 1 mol. % Dy2O3 at room temperature. The tendency of dielectric properties was verified through the changes of lattice parameters and binding energy. The substitution of Dy3+ led to a decrease of tetragonality and grain growth; however, amphoteric substitution caused by the co-doping of Dy2O3 and Tm2O3 compensated for those adverse effects. It can be concluded that the improvement of dielectric properties originated from the increase of the site substitution rate of Dy3+ and Tm3+ ions according to the ionic size the in rare-earth doped BaTiO3 system.

  17. Electric-field dependence of dielectric properties of sol-gel derived Ba(Zr0.2Ti0.8)O3 ceramics

    NASA Astrophysics Data System (ADS)

    Tang, X. G.; Liu, Q. X.; Wang, J.; Chan, H. L. W.

    2009-09-01

    The effect of a dc bias field on the diffuse phase transition and nonlinear dielectric properties of sol-gel derived Ba(Zr0.2Ti0.8)O3 (BZT) ceramics are investigated. Diffuse phase transitions were observed in BZT ceramics and the Curie-Weiss exponent (CWE) was ?˜2.0. The dielectric constant versus temperature characteristics and the ? in the modified Curie-Weiss law, ? -1= ? {/m -1}[1+( T- T m ) ? /C1](1? ??2), as a function of the dc bias field was obtained for BZT ceramics. The results indicated that ? is a function of dc bias field, and the ? value decreased from 2.04 to 1.73 with dc bias field increasing from 0 to 20 kV/cm. The dielectric constant decreases with increasing dc bias field, indicating a field-induced phase transition. The dc bias field has a strong effect on the position of the dielectric peak and affects the magnitude of the dielectric properties over a rather wide temperature range. The peak temperature of the dielectric loss does not coincide with the dielectric peak and an obvious minimum value for the dielectric loss at the temperature of the dielectric peaks is observed. At room temperature, 300 K, the high tunability ( K=80%), the low loss tangent (?0.01) and the large FOM (74), clearly imply that these ceramics are promising materials for tunable capacitor-device applications.

  18. Effects of Zr and Ti doping on the dielectric response of CeO: A comparative first-principles study

    NASA Astrophysics Data System (ADS)

    Dutta, Gargi; Saha, Srijan Kumar; Waghmare, Umesh V.

    2010-11-01

    Zr doping in ceria (CeO 2) results in enhanced static dielectric response compared to pure ceria. On the other hand, Ti doping in ceria keeps its dielectric constant unchanged. We use first-principles density functional theory calculations based on pseudopotentials and a plane wave basis to determine electronic properties and dielectric response of Zr/Ti-doped and oxygen-vacancy-introduced ceria. Softening of phonon modes is responsible for the enhancement in dielectric response of Zr-doped ceria compared to that of pure ceria. The ceria-zirconia mixed oxides should have potential use as high- k materials in the semiconductor industry.

  19. Dielectric Properties of Diala D, MIDEL 7131 and THESO Insulating Liquids

    Microsoft Academic Search

    I. V. Timoshkin; R. A. Fouracre; M. J. Given; S. J. MacGregor; P. Mason; R. Clephan

    2008-01-01

    Insulating oils can be used as dielectric materials in a wide range of high voltage applications. Most notable amongst these liquids are naphthenic mineral oils, which are used in elements of pulsed power systems, such as switches and capacitors. Dielectric liquids are also used as energy storage media in pulsed power systems. In this application the use of liquids with

  20. Dielectric Properties of Bi4Ti3O12 below the Curie Temperature

    Microsoft Academic Search

    Shaw Ehara; Kunitaka Muramatsu; Masaji Shimazu; Junzo Tanaka; Masashi Tsukioka; Yasumichi Mori; Takeshi Hattori; Hiroshi Tamura

    1981-01-01

    The dielectric permittivity, optical transmission spectrum and temperature dependence of resistance were investigated in single crystals of Bi4Ti3O12 and BaBi4Ti4O15. It is found that the dielectric anomalies previously reported below the Curie temperature are due electron space charges of inhomogeneous distribution in the material and near the non-ohmic electrodes.

  1. Dielectric Properties of Oil-Impregnated all Polypropylene Film, Power Capacitor Insulation System

    Microsoft Academic Search

    S. Yasufuku; T. Umemura; Y. Yasuda

    1978-01-01

    We have investigated the synthetic oil-impregnated power capacitor insulation system of all polypropylene film dielectrics which is currently used in company products. The results of dielectric measurements in low electric fields can be interpreted by chemical interaction of the polypropylene film with the aromatic synthetic fluid. These investigations' have proved to be quite helpful in the manufacture of power capacitors

  2. Zirconia doped barium titanate induced electroactive ? polymorph in PVDF-HFP: high energy density and dielectric properties

    NASA Astrophysics Data System (ADS)

    Sharma, Maya; Ranganatha, S.; Kalyani, Ajay Kumar; Ranjan, Rajeev; Madras, Giridhar; Bose, Suryasarathi

    2014-12-01

    Zirconium-doped barium titanate (BZT-08, Ba(Ti0.92 Zr0.08)O3) particles were synthesized and PVDF-HFP-based composites were prepared by melt mixing to design materials with tunable dielectric and ferroelectric properties. Composites of PVDF-HFP and barium titanate (BT) particles were also prepared to realize the exceptional properties associated with the BZT-08-like stabilization of two ferroelectric phases, i.e. tetragonal and orthorhombic at room temperature. To facilitate the uniform dispersion and interfacial adhesion with the matrix, the particles were modified with (3-aminopropyl) triethoxysilane. The dependence of the dielectric and ferroelectric properties of the as-prepared composites were systematically investigated in this study with respect to a wide range of frequencies. The composites with BZT-08 exhibited the significantly high dielectric permittivity of ca. 26 (at 100 Hz) and a high energy density (2.7 J cm?3 measured on 100 ?m thick film) at room temperature with respect to the control PVDF-HFP and PVDF-HFP/BT composites. Interestingly, the BZT-08 particles facilitated the electroactive ? polymorph in the PVDF-HFP and enhanced polarization in the composites, leading to improved ferroelectric properties in the composites.

  3. Reflectivity (visible and near IR), Moessbauer, static magnetic, and X ray diffraction properties of aluminum-substituted hematites

    NASA Technical Reports Server (NTRS)

    Morris, Richard V.; Schulze, Darrell G.; Lauer, Howard V., Jr.; Agresti, David G.; Shelfer, Tad D.

    1992-01-01

    The effect of substituting iron by aluminum in polymorphs of Fe2O3 and FeOOH on their reflectivity characteristics was investigated by comparing data on visible and NIR reflectivities and on static magnetic, XRD, and Moessbauer properties for a family of aluminum-substituted hematites alpha-(Fe,Al)2O3, with compositions where the values of the Al/(Al+Fe) ratio were up to 0.61. Samples were prepared by oxidation of magnetite, dehydroxylation of goethite, and direct precipitation. The analytical methods used for obtaining diffuse reflectivity spectra (350-2200 nm), Moessbauer spectra, and static magnetic data are those described by Morris et al. (1989).

  4. Low-?' dielectric properties of UV-treated bi-axially oriented polypropylene films

    NASA Astrophysics Data System (ADS)

    Dervos, C. T.; Tarantili, P. A.; Athanassopoulou, M. D.

    2009-07-01

    A 40 µm multilayer bi-axially oriented polypropylene (BOPP) film, was fabricated by the tenter process and its dielectric response was investigated after applying combined action of UV, humidity and heat. Dissipation factor (tan ?) and relative dielectric constant measurements were performed via the capacitance method for frequencies 20Hz-1 GHz. These results show that the relative dielectric constant (?') reduces towards ultra low values (1.8) with an increasing number of applied UV-condensation cycles without any subsequent increase in the dielectric loss. Having no added physical porosity and absence of fluorine atoms, the irradiated BOPP structures offer significant advantages over poly(tetrafluoroethylene) PTFE due to reduced polarization effects, lower dielectric constant values and chemical stability to the adjacent copper or aluminium conductors. Possible application fields are dry type high-voltage capacitors and insulation within electronic components.

  5. Heat treatment effects on dielectric properties of SRFe{sub 12}O{sub 19} hexaferrite prepared by an SHS route

    SciTech Connect

    Panchal, Nital R.; Jotania, Rajshree B., E-mail: natal_panchal@yahoo.co.in, E-mail: rbjotania@gmail.com [Department of Physics, University School of Sciences, Gujarat University, Ahmedabad (India)

    2011-07-01

    The M-type Strontium Hexaferrite SRFe{sub 12}O{sub 19} particles were prepared by a Self propagating High temperature Synthesis (SHS) route. Precursors were heated under two different conditions: microwave heating for 30 minutes and sintered at 950 deg C for 4 hrs. The dielectric properties: dielectric constant ({epsilon}{sup '}), dielectric loss (tan {delta} ) and ac conductivity ({sigma}{sub ac}) were measured at room temperature in the frequency range from 100 Hz to 2 MHz. The samples present a non-linear behavior for the dielectric constant at 1 kHz, 100 kHz and 2 MHz. The dielectric properties of prepared Strontium Hexaferrite samples were discussed in view of applications as a material for microwave devices, permanent magnets and high density magnetic recording media. (author)

  6. CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: The magnetic and dielectric properties of multiferroic Sr-substituted Zn2-Y hexagonal ferrites

    Microsoft Academic Search

    Fang Xu; Yang Bai; Fen Ai; Li-Jie Qiao

    2008-01-01

    The magnetic and dielectric properties of Sr-substituted Zn2-Y hexagonal ferrites (Ba2-xSrxZn2Fe12O22, 1.0 <= x <= 1.5) are studied in this paper. Sr substitution will lead to the variation of cation occupation, which influences both the magnetic and electric properties. As Sr content x rises from 1.0 to 1.5, magnetic hysteresis loop gets wider gradually and the permeability drops rapidly due

  7. Dielectric properties of lead lanthanum zirconate titanate thin films with and without ZrO2 insertion layers

    NASA Astrophysics Data System (ADS)

    Liu, Shanshan; Ma, Beihai; Narayanan, Manoj; Tong, Sheng; Koritala, Rachel E.; Hu, Zhongqiang; Balachandran, Uthamalingam

    2013-05-01

    The dielectric properties of lead lanthanum zirconate titanate (PLZT) thin films on platinized silicon (Pt/Si) with and without ZrO2 insertion layers were investigated in the temperature range from 20 °C to 300 °C. Permittivity, dielectric loss tangent, and tunability were reduced for the samples with ZrO2 insertion layers compared to those without the layers. Additionally, the permittivity was less dependent on frequency over the broad temperature range studied (20-300 °C). The leakage current behavior of the PLZT films with and without ZrO2 insertion layers was also investigated, and on the basis of those results, a probable conduction mechanism has been suggested. The improved electrical properties in the PLZT with ZrO2 layers are attributed to the ZrO2 layer blocking the mobile ionic defects and reducing free charge carriers to transport.

  8. Effect of Fe doping on electronic structure, chemical bonds and dielectric properties of o-Mn7C3

    NASA Astrophysics Data System (ADS)

    Li, Wei; Chen, Jin; Hao, Jiujiu; Guo, Lina; Han, Peide; Chen, Zhiliang

    2015-06-01

    The first-principles calculations were conducted to investigate the effect of Fe doping in different positions on the electronic structure, chemical bonds and dielectric properties of o-Mn7C3. In contrast with pure o-Mn7C3, the reduced density of states at the Fermi level and the increased peak separation between both sides of the Fermi level are observed in Fe-doped o-Mn7C3, suggesting that Fe doping enhances the covalency of Csbnd Mn bonds and yet weakens the metallicity of o-Mn7C3. Moreover, Fe doping causes a red shift of the dielectric properties. In microwave field, the interband transition of 3d electrons is apt to take place.

  9. Static properties and multiaxial strength criterion for design of composite automotive structures

    SciTech Connect

    Ruggles, M.B.; Yahr, G.T.; Battiste, R.L.

    1998-11-01

    The Durability of Lightweight Composite Structures Project was established at Oak Ridge National Laboratory (ORNL) by the US Department of Energy to provide the experimentally-based, durability-driven design guidelines necessary to assure long-term structural integrity of automotive composite components. The initial focus of the ORNL Durability Project was on one representative reference material -- an isocyanurate (polyurethane) reinforced with continuous strand, swirl-mat E-glass. The present paper describes tensile, compressive, flexure, and shear testing and results for the reference composite. Behavioral trends and proportional limit are established for both tension and compression. Damage development due to tensile loading, strain rate effects, and effects of temperature are discussed. Furthermore, effects on static properties of various fluids, including water at room and elevated temperatures, salt water, antifreeze, windshield washer fluid, used motor oil, battery acid, gasoline, and brake fluid, were investigated. Effects of prior loading were evaluated as well. Finally, the effect of multiaxial loading on strength was determined, and the maximum shear strength criterion was identified for design.

  10. Surface roughness, scratch resistance and tribological properties of hydrogenated amorphous carbon coatings prepared by low-pressure dielectric barrier discharge

    Microsoft Academic Search

    D. P. Liu; G. Benstetter; Y. H. Liu; J. L. Zhang; C. S. Ren; T. C. Ma

    2003-01-01

    In this study, we explored the surface roughness, scratch resistance and tribological properties of hydrogenated amorphous carbon (a-C:H) coatings deposited on silicon substrates from low-pressure dielectric barrier discharge (DBD) plasmas of CH4 by using an atomic force microscope (AFM), AFM-based scratch testing technique and lateral force microscope. The AFM and scratch measurements show that the surface roughness and scratch resistance

  11. Electrical Properties of Single Crystalline CeO2 High-k Gate Dielectrics Directly Grown on Si (111)

    Microsoft Academic Search

    Yukie Nishikawa; Noburu Fukushima; Naoki Yasuda; Kohei Nakayama; Sumio Ikegawa

    2002-01-01

    We have grown epitaxial single crystalline CeO2 directly on Si (111) by molecular beam epitaxy. Metal-insulator-semiconductor (MIS) capacitors were fabricated to evaluate electrical properties of CeO2 films. By eliminating an interfacial layer, equivalent oxide thickness (EOT) as small as 0.38 nm was obtained for a CeO2 physical thickness of 5 nm. The dielectric constant (\\\\varepsilon) was calculated to be \\\\varepsilon˜

  12. Dielectric properties of barium strontium titanate (BST)\\/yttrium aluminate (YAlO 3 ) thick films under DC bias field

    Microsoft Academic Search

    B. Su; T. W. Button; T. Price; D. Iddles; D. Cannell

    2008-01-01

    The DC bias dependence of the dielectric properties of BST thick films on YAlO3 substrates has been investigated for possible tunable microwave device applications. Rare earth aluminate (e.g. YAlO3) substrates were used to overcome the interfacial interactions between BST thick films and alumina substrates during high\\u000a temperature sintering. The results show that the BST films exhibit good chemical compatibility with

  13. Structural, dielectric, and ferroelectric properties of PbTiO 3 thin films by a simple sol–gel technique

    Microsoft Academic Search

    Dinghua Bao; Xi Yao; Naoki Wakiya; Kazuo Shinozaki; Nobuyasu Mizutani

    2002-01-01

    PbTiO3 (PT) thin films were prepared on various substrates by a simple sol–gel technique. The surface morphology and crystal structure, dielectric, and ferroelectric properties of the thin films were investigated. The orientation of PT thin films on Pt\\/Ti\\/Si substrates can gradually change with the annealing temperature from a-axis preferential orientation to c-axis preferential orientation. The PT films on Pt\\/Ti\\/SiO2\\/Si substrates

  14. Infrared dielectric properties and optical magnetoconductivity of CaRuO3\\/CaMnO3 superlattices

    Microsoft Academic Search

    A. V. Boris; P. Yordanov; P. Popovich; B. Keimer; J. W. Freeland; J. Chakhalian; H. N. Lee

    2008-01-01

    Spectroscopic ellipsometry and magneto-reflectivity in the far-infared spectral range is used to study the electronic properties of [(CaRuO3)N|(CaMnO3)10]6 superlattices (SLs). The nonlinear regression procedure is employed to extract the dynamical conductivity and dielectric permittivity of bare SLs within the effective medium approximation with a mixture of the ruthenate and manganite layers. We find that the infrared conductivity of the SLs

  15. Dielectric properties and spatial distribution of polarization in polyethylene aged under ac voltage in a humid atmosphere

    Microsoft Academic Search

    M. Wubbenhorst; J. Hornsby; M. Stachen; D. K. Das-Gupta; A. Bulinski; S. Bamji

    1998-01-01

    This paper reports the results of an investigation of the dielectric properties, growth of water tree density and spatial distribution of polarization in samples of non-stabilized LDPE. Samples were initially sand-blasted to accelerate initiation of water trees, and subsequently aged in salt solution for approximately three weeks under two regimes of temperature (room temperature and 65°C). Aging both with and

  16. Dielectric properties of glucose solutions in the millimetre-wave range and control of glucose content in blood

    NASA Astrophysics Data System (ADS)

    Meriakri, V. V.; Chigrai, E. E.; Kim, D.; Nikitin, I. P.; Pangonis, L. I.; Parkhomenko, M. P.; Won, J. H.

    2007-04-01

    The measurement of the dielectric properties of sugar solutions, as well as blood imitators and blood, in the millimetre-wave range allows one to obtain valuable information on the possibility of real-time control of glucose concentration in blood. These measurements are also of interest for other applications, for example in the wine industry and for the determination of water content in oil, oil products and other liquids.

  17. Controlled synthesis of core-shell iron-silica nanoparticles and their magneto-dielectric properties in polymer composites

    Microsoft Academic Search

    T. I. Yang; R. N. C. Brown; L. C. Kempel; P. Kofinas

    2011-01-01

    Low loss core-shell iron-silica nanocomposites with improved magneto-dielectric properties at radio frequencies (1 MHz-1 GHz) were successfully fabricated. A new simple method was developed to synthesize metallic iron (Fe) nanoparticles with uniform size distribution in an aqueous environment at room temperature. Citric acid and oleic acid served as surface-capping agents to control the particle size of the synthesized Fe nanoparticles.

  18. Dielectric changes in membrane properties and cell interiors of human mesothelial cells in vitro after crocidolite asbestos exposure.

    PubMed

    Dopp, E; Jonas, L; Nebe, B; Budde, A; Knippel, E

    2000-02-01

    Asbestos induces cytogenetic and genotoxic effects in cultured cell lines in vitro. For further investigations of the fiber-induced cellular changes, electrorotation (ROT) measurements can be used to determine early changes of surface properties and dielectric cellular changes. In the present study, human mesothelial cells (HMC) were exposed to nontoxic concentrations of crocidolite asbestos (1 microg/cm(2)) for 12, 24, 30, 50, and 72 hr, and were investigated for changes in dielectric properties, morphologic and biochemical changes using ROT measurements, electron microscopy, and flow cytometry, respectively. The results of ROT measurements revealed slightly increased internal conductivity and decreased membrane conductance of HMC during the first 12 hr of exposure to crocidolite. This may be due to functional changes of ion channels of the cellular membrane. However, after exposures of >= 30 hr, reduced internal conductivity and increased membrane conductance of HMC occurred. These effects may be caused by permeabilization of the cell membrane and the leakage of ions into the surrounding medium. The membrane capacitance of HMC is always decreased during exposure of cells to crocidolite fibers. This decreased membrane capacitance may result from the observed reduction in the number of microvilli and from the shrinkage of cells as observed by electron microscopy and flow cytometry. Changes in composition of the plasma membrane were also observed after the labeling of phosphatidylserines (PS) on the cell surface. These observed changes can be related to apoptotic events. Whereas during the first 50 hr of exposure only a small number of HMC with increased exposure of PS on the cell surface was detected by flow cytometry, the dielectric properties of HMC showed marked changes during this time. Our results show that surface property changes of the cellular membrane of HMC as well as interior dielectric changes occur after the exposure of cells to crocidolite fibers. The observed changes are discussed in terms of complex combined cellular effects after amphibole asbestos exposure. PMID:10656856

  19. Investigating surface properties of OHNS die steel after electrical discharge machining with manganese powder mixed in the dielectric

    Microsoft Academic Search

    Sanjeev Kumar; Rupinder Singh

    2010-01-01

    Although electrical discharge machining is essentially a material removal process, efforts have been made in the recent past\\u000a to use it as a surface treatment method. An additive powder in the dielectric medium affects the sparking action and helps\\u000a in improving the surface properties. It may melt at the high temperature of the plasma channel and alloy with the machined

  20. Physical, dielectric, and C band microwave scattering properties of first-year sea ice during advanced melt

    Microsoft Academic Search

    Randall K. Scharien; Torsten Geldsetzer; David G. Barber; John J. Yackel; A. Langlois

    2010-01-01

    This paper investigates the influence of solar heating and intermittent cloud cover on the physical and dielectric properties of naturally snow-free, warm (>?2°), first-year sea ice (FYI) in the southeastern margin of the Beaufort Sea during advanced melt. A simple three-layer physical model describing the surface is introduced and copolarized C band microwave signatures are simulated using a multilayer scattering

  1. Polyamide 12/ fullerene C60 composites: Investigation on their mechanical and dielectric properties

    NASA Astrophysics Data System (ADS)

    Zuev, Vjacheslav V.

    2014-05-01

    The effect of fullerene C60 on mechanical properties of polymer nanocomposites based on PA12 was investigated. The nanocomposites were prepared by in situ polymerization. The Young's modulus and tensile strength of the polymer nanocomposites are improved by about 20% with loading of 0.02-0.08 wt.% the fullerene C60. Dielectric spectroscopy was used to investigate the influence of nanoparticles on the relaxation processes in polymer matrix. The segmental relaxation processes become faster with the fullerene C60 addition, an effect associated with a decrease of the glass transition temperature. In contrast, the secondary or ? relaxation process of PA12/ fullerene C60 nanocomposites was observed to slow down with addition of fullerene C60. These observations indicate that fullerene C60 as filler has an effect opposite to antiplasticizing that slow down the secondary relaxation (stiffening the material) in the glass state, while at the same time reducing the alpha relaxation time associated with cooperative segmental motions. It behaviour can be connected with inclusion complex formation between PA12 and fullerene C60.

  2. Investigation of opto-dielectric properties of Ti-doped Ga2O3 thin films

    NASA Astrophysics Data System (ADS)

    Dakhel, A. A.

    2013-06-01

    Several Ti-incorporated Ga-oxide (Ga2O3) thin films with different amounts of Ti contents have been prepared by vacuum evaporation method on glass and silicon substrates. The Ti incorporation level was measured with energy dispersion X-ray spectroscopy (EDX) method. The crystalline structure of the prepared films was determined with X-ray diffraction method. Experimental data indicate that Ti4+ ions doped in host Ga2O3 form solid solutions (SS) even with so large Ti% content ˜10.4% wt. All the prepared solid solutions have the known orthorhombic (?-phase) phase of Ga2O3. The doping controls the optical and electrical properties of the host Ga2O3. It was found that the bandgap of the prepared undoped Ga oxide is 5.23 eV, which was decreased monotonically with increasing of Ti doping level so that it is possible to engineer the bandgap. Furthermore, the electrical measurements show that with Ti doping, it is possible to turn the high-k Ga oxide into low-k dielectric material. The optical sensitivity of the capacitance, dissipation factor, and ac-conductance of the Ga2O3:Ti films grown on Si was studied as a function of Ti-doping level. It was observed that the prepared Ga2O3:Ti film with 6-10% doping level has the highest photosensitivity among the other samples.

  3. Structural, magnetic, dielectric and optical properties of nickel ferrite nanoparticles synthesized by co-precipitation method

    NASA Astrophysics Data System (ADS)

    Joshi, Seema; Kumar, Manoj; Chhoker, Sandeep; Srivastava, Geetika; Jewariya, Mukesh; Singh, V. N.

    2014-11-01

    Nickel ferrite nanoparticles were synthesized by wet chemical co-precipitation method and the corresponding temperature dependent structural, magnetic and optical properties of these nanoparticles have been investigated. X-ray diffraction patterns show the single phase cubic spinal crystal structure belonging to the space group Fd3m. The average crystallite size varies in the range 8-20 nm with varying sintering temperature. Raman spectroscopy exhibits a doublet-like peak behaviour which indicates the presence of mixed spinel structure. The saturation magnetization, coercivity and remanence increase with increasing sintering temperature from 250 to 550 °C. The non-saturation and low values of magnetization at high fields indicate the strong surface effects to magnetization in NiFe2O4 nanoparticles. The g-value calculated from electron spin resonance spectrum indicates the transfer of divalent metallic ion from octahedral to tetrahedral site (i.e. mixed spinel structure). The dielectric permittivity, loss tangent and ac conductivity measurements show strong temperature dependence at all frequencies. The observed ac conductivity response suggests that the conduction in ferrite nanoparticles is due to feeble polaron hopping between Fe3+/Fe2+ ions. Room temperature UV-vis diffuse spectra indicate that NiFe2O4 is an indirect band gap material with band gap ranges from 1.27 to 1.47 eV with varying sintering temperature. The photoluminescence study clearly indicates that the Ni2+ ions occupy both octahedral and tetrahedral sites confirming mixed spinel structure.

  4. Structural and electric-dielectric properties of some bismuth -phosphate glasses

    NASA Astrophysics Data System (ADS)

    Shapaan, M.; El-Badry, S. A.; Mostafa, A. G.; Hassaan, M. Y.; Hazzaa, M. H.

    2012-03-01

    In the present study, glasses with composition XBi2O3 (60-X)P2O5 20Fe3O4 20Li2O (0?X?15) mol% have been prepared by the conventional melt quenching technique. The IR studies show the presence of FeO4, FeO6, BiO6, PO3, P?O and PO4 structural groups. The hyperfine structure of these glasses is investigated using Mössbauer spectroscopy. ME spectroscopy indicated the presence of two different oxidation states of iron (Fe2+ and Fe3+). The ferrous ions Fe2+ occupied tetrahedral coordination states, while the ferric ions Fe3+ occupied both tetrahedral and octahedral coordination states. The effect of partial replacement of P2O5 by Bi2O3 on the electric-dielectric properties is studied in more details. It is found that, unmonotonic variation in the ?dc, (?D/2), ?ac(?), ?1(?), and ?2(?), as a function of Bi2O3 contents. Also it is found that, the power law exponent, s, is temperature dependent and the CBH model is the most applicable conduction mechanism in all glass samples. Pseudo Cole-Cole diagram of the investigated glassy samples exhibit similar behavior where all plots show a single semicircle indicating a single relaxation process.

  5. Temporal change in the electromechanical properties of dielectric elastomer minimum energy structures

    SciTech Connect

    Buchberger, G., E-mail: erda.buchberger@jku.at; Hauser, B.; Jakoby, B.; Hilber, W. [Institute for Microelectronics and Microsensors, Johannes Kepler University Linz, 4040 Linz (Austria); Schoeftner, J. [Institute of Technical Mechanics, Johannes Kepler University Linz, 4040 Linz (Austria); Bauer, S. [Department of Soft Matter Physics, Johannes Kepler University Linz, 4040 Linz (Austria)

    2014-06-07

    Dielectric elastomer minimum energy structures (DEMES) are soft electronic transducers and energy harvesters with potential for consumer goods. The temporal change in their electromechanical properties is of major importance for engineering tasks. Therefore, we study acrylic DEMES by impedance spectroscopy and by optical methods for a total time period of approx. 4.5 months. We apply either compliant electrodes from carbon black particles only or fluid electrodes from a mixture of carbon black particles and silicone oil. From the measurement data, the equivalent series capacitances and resistances as well as the bending angles of the transducers are obtained. We find that the equivalent series capacitances change in average between ?12?%/1000?h and ?4.0?%/1000?h, while the bending angles decrease linearly with slopes ranging from ?15?%/1000?h to ?7?%/1000?h. Transducers with high initial bending angles and electrodes from carbon black particles show the smallest changes of the electromechanical characteristics. The capacitances decrease faster for DEMES with fluid electrodes. Some DEMES of this type reveal huge and unpredictable fluctuations of the resistances over time due to the ageing of the contacts. Design guidelines for DEMES follow directly from the observed transient changes of their electromechanical performance.

  6. Temporal change in the electromechanical properties of dielectric elastomer minimum energy structures

    NASA Astrophysics Data System (ADS)

    Buchberger, G.; Hauser, B.; Schoeftner, J.; Bauer, S.; Jakoby, B.; Hilber, W.

    2014-06-01

    Dielectric elastomer minimum energy structures (DEMES) are soft electronic transducers and energy harvesters with potential for consumer goods. The temporal change in their electromechanical properties is of major importance for engineering tasks. Therefore, we study acrylic DEMES by impedance spectroscopy and by optical methods for a total time period of approx. 4.5 months. We apply either compliant electrodes from carbon black particles only or fluid electrodes from a mixture of carbon black particles and silicone oil. From the measurement data, the equivalent series capacitances and resistances as well as the bending angles of the transducers are obtained. We find that the equivalent series capacitances change in average between -12 %/1000 h and -4.0 %/1000 h, while the bending angles decrease linearly with slopes ranging from -15 %/1000 h to -7 %/1000 h. Transducers with high initial bending angles and electrodes from carbon black particles show the smallest changes of the electromechanical characteristics. The capacitances decrease faster for DEMES with fluid electrodes. Some DEMES of this type reveal huge and unpredictable fluctuations of the resistances over time due to the ageing of the contacts. Design guidelines for DEMES follow directly from the observed transient changes of their electromechanical performance.

  7. Impedance spectroscopy of dielectric properties of perovskite ceramics Bi(Mg1/2Ti1/2)O3

    NASA Astrophysics Data System (ADS)

    Olekhnovich, N. M.; Salak, A. N.; Pushkarev, A. V.; Radyush, Yu. V.; Vyshatko, N. P.; Khalyavin, D. D.; Ferreira, V. M.

    2009-03-01

    The dielectric properties of metastable high-pressure perovskite ceramics Bi(Mg1/2Ti1/2)O3 were studied by impedance spectroscopy at frequencies of 25 Hz-1 MHz at various temperatures. It is established that, at temperatures higher than ˜450 K, the dc conductivity makes a significant contribution to the dielectric response of these ceramics. The charge-carrier activation energy ? E dc is found from the temperature dependence of the dc conductivity ?dc. As the temperature increases, the quantity ? E dc changes in a jump from 0.12 to 1.00 eV at T ˜ 450 K. With inclusion of the contribution from ?dc, the real and imaginary parts ( M {ac/'} and M {ac/?}) of the complex electrical modulus related only to the dielectric polarization are found. From analyzing the M {ac/?} - M {ac/'} diagrams, the contributions to the dielectric polarization from ceramic grains and their boundaries are estimated. The obtained data are interpreted in terms of the chemical composition of the ceramic compound Bi(Mg1/2Ti1/2)O3 and the existence of crystal-lattice defects formed during the synthesis under pressure. Based on an analysis of the temperature dependences of the permittivity of ceramic grains and antiparallel displacements of the Bi3+ cations, it is assumed that the dipole ordering in this perovskite compound is antiferroelectric in character.

  8. Dielectric properties of sol-gel derived barium-strontium-titanate (Ba(0.4)Sr(0.6)TiO(3)) thin films.

    PubMed

    Lahiry, S; Gupta, V; Sreenivas, K; Mansingh, A

    2000-01-01

    The structural and dielectric properties of sol-gel derived barium-strontium-titanate (Ba(0.4)Sr(0.6)TiO(3 )) thin films have been investigated. The as-fired films are found to be amorphous, and films crystallize to a cubic phase after a post deposition annealing at 700 degrees C for one hour in air. The variation of dielectric constant with temperature and field was investigated as a function of film thickness. These films display a nonlinear dielectric response that can be described in terms of a power series expansion of the free energy in polarization as in Landau-Ginzburg-Devonshire approach. The measured room temperature dielectric constant (epsilon') of the film was about 320. The dielectric constant did not show any significant frequency dependence up to 100 kHz. The temperature dependence of dielectric constant exhibited a diffused ferroelectric to paraelectric phase transition at -60 degrees C. The room temperature dielectric constant and magnitude of the dielectric peak at the Curie point was dependent on the thickness of the film. The obtained dielectric data on sol-gel barium strontium titanate thin films on platinized substrates were analyzed in the light of a barrier layer model. PMID:18238618

  9. Mechanical and dielectric properties of self-assembled, periodic nanoporous silica and organosilica materials

    NASA Astrophysics Data System (ADS)

    Hatton, Benjamin D.

    2005-11-01

    In recent years self-assembled, organic supramolecular or colloidal arrays have been used as templates for the design of a wide range of novel nanostructured porous materials, using sol-gel chemistry. Herein, mesoporous silica and organosilica films, and colloidal crystal (opal) films, have been synthesized, and various mechanical and dielectric properties investigated. A series of spin-coated mesoporous silica films were synthesized using a surfactant template, using evaporation-induced self-assembly (EISA). The porosity was controlled by the surfactant/silica molar ratio, thermally-induced collapse at 300--900°C, and deposition within the channels. The Young's modulus (E) and hardness (H) were measured using nanoindentation, and the results have been compared with conventional models for porous materials. A series of molecular mechanics atomic models of mesoporous silica were used to simulate the elastic and plastic deformation as a function of pore diameter. Highly-ordered, periodic mesoporous organosilica (PMO) thin films were synthesized from bridged silsesquioxane precursors of the type (EtO) 3SiRSi(OEt)3 (where R is an organic group), and a novel three-ring [(EtO)2Si( CH2)]3 precursor. Detailed structural characterization has been performed using PXRD, SAXS, SEM, and TEM. PMO films may have important applications as low dielectric constant (k) materials in microelectronics. Capacitance measurements showed that k decreased with organic content to ˜1.8. A novel 'self-hydrophobization' behaviour has been demonstrated, using a bridge-terminal transformation of the organic groups at 400--550°C, to lower k and make the films highly resistant to moisture adsorption. A series of novel dendrimer and 'semi-dendrimer' PMO thin films have been synthesized using cationic and block copolymer templates, to further increase the organic content. As a result, the number of organic bridges attached to each Si is increased as a series, from 0 to 4. Finally, chemical vapour deposition (CVD) was used to sinter silica opal films to systematically control the optical Bragg diffraction and the structural connectivity. SiCl4 and Si(OMe)4 vapour were used to deposit silica layers to grow necks between silica spheres. Nanoindentation was used to measure E and H as a function of the silica deposition.

  10. Dielectric properties of crystalline and amorphous transition metal oxides and silicates as potential high-? candidates: the contribution of density-functional theory

    Microsoft Academic Search

    G-M Rignanese

    2005-01-01

    A review is given of various first-principles studies of the dielectric properties of crystalline and amorphous transition metal oxides and silicates, which have drawn considerable attention as potential high-? materials. After a brief summary of the principal equations of density-functional theory related to the dielectric properties of solids, the results obtained for group IVb M = (Hf,Zr,Ti) and IIIb M

  11. Dielectric and ferroelectric properties of ceramics in the Pb(ZnââNbââ)Oâ-BaTiOâ-PbTiOâ system

    Microsoft Academic Search

    A. Halliyal; U. Kumar; R. E. Newnham; L. E. Cross

    1987-01-01

    The use of Pb(ZnââNbââ)Oâ ceramics is restricted by the formation of a pyrochlore phase detrimental to both dielectric and piezoelectric properties. Recently, it has been shown that a 6 mol% addition of BaTiOâ to PZN suppresses the formation of pyrochlore phase. Phase relations and dielectric properties of ceramics in the PZN-BT-PT system are reported in this paper.

  12. Microstructure, frequency and temperature-dependent dielectric properties of cobalt-substituted lithium ferrites

    Microsoft Academic Search

    S. C Watawe; B. D Sarwade; S. S Bellad; B. D Sutar; B. K Chougule

    2000-01-01

    Ferrites with the general formula Li0.5?x\\/2CoxFe2.5?x\\/2O4 (where x=0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7) were prepared by the standard ceramic method. AC resistivity (?AC), dielectric constant (??) and dielectric loss tangent (tan?) were measured as a function of frequency and temperature. The compositional variations of ?DC and ?? with x show inverse trends with each other. The dielectric constant increases

  13. Investigations on spectral and dielectric properties of semi-organic single crystal - morpholinium nitrate

    NASA Astrophysics Data System (ADS)

    Arul, H.; Babu, D. Rajan; Vizhi, R. Ezhil

    2015-06-01

    Semi organic nonlinear optical crystal Morpholinium nitrate (MN) was synthesized and subsequently grown from the solution by slow evaporation method. The sample has been subjected to powder X-ray diffraction to identify the crystalline nature and the prominent peaks were indexed. The crystal belongs to the monoclinic system with a space group P21/C. Carbon NMR analysis confirms the presence of carbon in the structure of the title compound. Dielectric studies have been carried out on the grown crystal as a function of frequencies at different temperatures. Dielectric constant, dielectric loss and AC conductivity were also calculated.

  14. Cryogenic Dielectric Property Measurements Applied to Constraining the Composition of Titan's Seas: Implications for the hydrocarbon cycle

    NASA Astrophysics Data System (ADS)

    Mitchell, K. L.; Barmatz, M.; Jamieson, C. S.; Lorenz, R. D.; Lunine, J. I.

    2014-12-01

    To model quantitatively the response of Titan's lakes and seas to Cassini's RADAR instrument, and thus determine surface reflectivity, attenuation and penetration depth, it is necessary to constrain the dielectric properties of their liquids at ~14 GHz. Pre-Cassini estimates of methane loss tangents ranged from ~1.6 to 1.7 (real component) and ~10-5 to 10-3(imaginary components). We present a new technique for measuring dielectric properties, used to measure the complex dielectric constant of relevant materials. A cylindrical cavity containing a cylindrical quartz tube, filled with pure methane or ethane situated along the cavity axis, was excited in TM0n0 modes, where the n= 2 mode had a resonant frequency of ~14 GHz at 90K. Calibration required measurement of cavity resonant frequency and quality factor for the empty cavity, the inserted empty tube, and the tube filled with a hydrocarbon liquid. These quantities were determined by fitting the measured amplitude versus frequency curve with a Lorentzian line shape. Several sets of measurements have been performed, giving complex dielectric constants (?' + ?" i) of 1.72 + 0.000049i for methane (tan ? = 2.8 x 10-5) and 2.00 + 0.000246i for ethane (tan ? = 1.23 x 10-4). Assuming that the dielectric properties of Ligeia Mare, as calculated by Mastrogiuseppe et al., are dominated by a nitrogen-saturated, binary methane-ethane mixture that obeys simple mixture modeling, our results are most consistent with pure methane-nitrogen. We can accommodate up to 13 vol% ethane, based on statistical uncertainties, or 19 vol% ethane, based on more conservative analytical uncertainties (incorporating uncertainties in measured quality factors, Lorentzian line shape fits, cavity radius, and quartz tube dimensions and calculated dielectric constant). All alternative compositions exhibit greater loss tangents, and so it is difficult to avoid the conclusion that methane is the dominant constituent of Ligeia Mare. We infer that ethane is either lost from or concentrated within Titan's hydrocarbon cycle.

  15. Development of multifunctional software for evaluating the photonic properties of new dielectric composite geometries

    E-print Network

    Cogswell, Daniel A. (Daniel Aaron)

    2006-01-01

    Software was developed for solving Maxwell's equations using the finite-difference time-domain method, and was used to study 2D and 3D dielectric composites. The software was written from the ground up to be fast, extensible, ...

  16. Intrinsic dielectric properties of magnetodielectric La2CoMnO6

    NASA Astrophysics Data System (ADS)

    Silva, R. X.; Moreira, R. L.; Almeida, R. M.; Paniago, R.; Paschoal, C. W. A.

    2015-06-01

    Manganite with a double perovskite structure is an attractive material because of its interesting magnetoelectric and dielectric responses. In particular, colossal dielectric constant (CDC) behavior has been observed in La2CoMnO6 (LCMO) at radio frequencies and at room temperature. In this paper, we used infrared-reflectivity spectroscopy to study a LCMO ceramic obtained through a modified Pechini's method to determine the phonon contribution to the intrinsic dielectric response of the system and to investigate the CDC origin. The analysis of the main polar modes and of the obtained phonon parameters indicate that the CDC effect of LCMO is of pure extrinsic origin. In addition, we estimated the dielectric constant and the quality factor of the material in the microwave region to be ?'s ˜ 16 and Qu × f ˜ 124 THz, which verifies that LCMO is appropriate for application in microwave devices and circuitry.

  17. Fabrication techniques and material properties of dielectric MgO thin films—A status review

    Microsoft Academic Search

    A. Moses Ezhil Raj; M. Jayachandran; C. Sanjeeviraja

    2010-01-01

    During the past few decades, considerable research effort has been directed towards the development of fundamental peculiarities of wide-gap (Eg>5eV) inorganic dielectric thin films. Wide-gap dielectrics are used for various technical and technological applications as laser materials, electronic components, radiation resistant materials, spectral transformers for luminescent lamps, detectors and dosimeters of several kind of radiations, various sensors and catalytic agents.

  18. Effect of temperature on dielectric properties of ice in the range 5-39 GHz

    Microsoft Academic Search

    Takeshi Matsuoka; Shuji Fujita; Shinji Mae

    1996-01-01

    The relative complex dielectric permittivity, &egr;*=&egr;??i&egr;?, of ice has been measured in the frequency range 5–39 GHz and in the temperature range 190–265 K. The cavity resonator method at 5 and 10 GHz and the open resonator method at 33 and 39 GHz were used to determine the low dielectric loss of ice. The real part of permittivity &egr;? was

  19. Dielectric properties of yeast cells: Effect of some ionic detergents on the plasma membranes

    Microsoft Academic Search

    Koji Asami; Tetsuya Hanai; Naokazu Koizumi

    1977-01-01

    Summary Dielectric measurements were made on suspensions of yeast cells treated with two homologous series of sodium alkyl (C8, C10, C12, C14) sulfonates and alkyl (C8, C10, C12, C14, C16, C18) benzyl dimethyl ammonium chlorides over a frequency range of 10 kHz to 100 MHz. Dielectric dispersions observed for the suspensions of intact yeast cells are found to be reduced

  20. Structural and dielectric properties of heterostructured BST thin films by sol–gel technique

    Microsoft Academic Search

    M. Jain; S. B. Majumder; R. S. Katiyar; A. S. Bhalla

    2004-01-01

    Ba1?xSrxTiO3(0.4?x?0.8) is attractive for microwave device applications due to its non-linear dielectric response in d.c. bias fields. The maximum tunability {(C0?Cv)\\/C0} with low dielectric losses is normally observed in the paraelectric phase close to the ferroelectric transition temperature. For the microwave transmission, the insertion loss in the device has to be minimized. In an effort to bring down the insertion