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Sample records for static dielectric properties

  1. Static dielectric properties of dense ionic fluids

    E-print Network

    Grigory Zarubin; Markus Bier

    2015-05-13

    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. Measurement of dielectric properties of pumpable food materials under static and continuous flow conditions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Continuous flow microwave sterilization is an emerging technology which has the potential to replace the conventional heating processes for viscous and pumpable food products. Dielectric properties of pumpable food products were measured by a new approach (under continuous flow conditions) at a temp...

  3. Theoretical investigation of dielectric properties of rare earth stillwellite compounds

    NASA Astrophysics Data System (ADS)

    Shaltaf, R.; Khalifeh, J.

    2015-07-01

    Ab initio density functional calculations are performed to investigate the dielectric properties of LnBSiO5 (Ln = Ce, Pr, Nd) with the stillwellite structure. The calculated structural parameters are found to agree well with existing experimental results. The three compounds possess insulating electronic structure with nearly isotropic high frequency dielectric permittivity tensors. On the other hand, the static dielectric permittivity tensors are found to be less isotropic. The anisotropy of static dielectric tensors are found to increase as the atomic number of the lanthanide increases.

  4. Dielectric Properties of Piezoelectric Polyimides

    NASA Technical Reports Server (NTRS)

    Ounaies, Z.; Young, J. A.; Simpson, J. O.; Farmer, B. L.

    1997-01-01

    Molecular modeling and dielectric measurements are being used to identify mechanisms governing piezoelectric behavior in polyimides such as dipole orientation during poling, as well as degree of piezoelectricity achievable. Molecular modeling on polyimides containing pendant, polar nitrile (CN) groups has been completed to determine their remanent polarization. Experimental investigation of their dielectric properties evaluated as a function of temperature and frequency has substantiated numerical predictions. With this information in hand, we are then able to suggest changes in the molecular structures, which will then improve upon the piezoelectric response.

  5. CORRELATING HONEYDEW MELON QUALITY WITH DIELECTRIC PROPERTIES

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Honeydew melons were grown and harvested with a range of maturities for measurement of tissue permittivities (dielectric constant and loss factor) to study possible correlations between the dielectric properties and soluble solids (sweetness) for nondestructive sensing of maturity. Permittivities of...

  6. Dielectric properties of gel collected from shark electrosensors

    NASA Astrophysics Data System (ADS)

    Hughes, Mary E.; Brown, Brandon R.; Hutchison, John C.; Murray, Royce W.

    2003-03-01

    To investigate the physical mechanism of the electric sense, we present an initial characterization of the dielectric properties of the glycoprotein gel that fills the electrosensitive organs of marine elasmobranches (sharks, skates, and rays). To ascertain the properties of the gel, low-frequency impedance spectroscopy is used. The impedance data collected from a dialyzed sample show large values of static permittivity and a loss peak corresponding to a long relaxation time (about 1 ms). Impedance measurements of the native (nondialyzed) gel reliable to 0.1 Hz will be presented and compared to the dialyzed gel. Ramifications of the gel's dielectric properties for the electric sense will be explored.

  7. Dielectric Properties of Ice and Liquid Water from First-Principles Calculations

    NASA Astrophysics Data System (ADS)

    Lu, Deyu; Gygi, François; Galli, Giulia

    2008-04-01

    We present a first-principles study of the static dielectric properties of ice and liquid water. The eigenmodes of the dielectric matrix ? are analyzed in terms of maximally localized dielectric functions similar, in their definition, to maximally localized Wannier orbitals obtained from Bloch eigenstates of the electronic Hamiltonian. We show that the lowest eigenmodes of ?-1 are localized in real space and can be separated into groups related to the screening of lone pairs, intra-, and intermolecular bonds, respectively. The local properties of the dielectric matrix can be conveniently exploited to build approximate dielectric matrices for efficient, yet accurate calculations of quasiparticle energies.

  8. Microwave Dielectric Properties of Cereal Grains

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dielectric properties of five cereal grains (wheat, corn, barley, oats, and grain sorghum) were 19 measured at 23 oC over broad microwave frequency range (5 GHz to 15 GHz) with a free-space-transmission 20 technique. Results of dielectric properties measurement are tabulated for each material for mo...

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

    SciTech Connect

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

    2015-05-15

    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.

  10. 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.

  11. Tailoring dielectric properties of ferroelectric-dielectric multilayers

    SciTech Connect

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

    2014-01-13

    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 Ba{sub 0.6}Sr{sub 0.4}TiO{sub 3}-, BaTiO{sub 3}-, and PbZr{sub 0.2}Ti{sub 0.8}O{sub 3} (PZT)-SrTiO{sub 3} (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.

  12. How does static stretching decrease the dielectric constant of VHB 4910 elastomer?

    NASA Astrophysics Data System (ADS)

    Vu-Cong, T.; Nguyen-Thi, N.; Jean-Mistral, C.; Sylvestre, A.

    2014-03-01

    Subject to a voltage, dielectric elastomers deform by the effect of Maxwell stress which is depended directly on the dielectric constant of the material. The combination of large strain, soft elastic response and good dielectric properties has established VHB 4910 elastomer as the most used material for dielectric elastomer actuators. However, the effect of stretch on the dielectric constant for this elastomer is much debated topic while controversy results are demonstrated in the literature. The dielectric constant of this material is studied and demonstrated that it decreases slightly or hugely among the stretch but any pertinent response and any physic explications are validated by the scientific community. In this paper, we presented a detail study about dielectric behavior of VHB 4910 elastomer versus a broadband of stretch and temperature. We found that the dielectric constant of this material depends strongly on the stretch following a polynomial law. Among all the explanations of stretch dependence of the dielectric constant of VHB 4910 in the literature: the crystallization, the change of glass transition temperature, the decrease of dipole orientation, the electrostriction effect under stress; and based on our experimental result, we conclude that the decrease of dipole orientation seems the main reason to the drop of dielectric constant of VHB 4910 elastomer versus the stretch. We proposed also an accurate model describing the dielectric constant of this material for a large range of stretch and temperature.

  13. Dielectric Properties of Water Under Extreme Conditions

    NASA Astrophysics Data System (ADS)

    Pan, Ding

    2014-03-01

    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 has greatly limited 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. We also computed the electronic dielectric constant of water as a function of pressure and we found that, contrary to expectations based on widely used simple models, both the refractive index and the electronic band gap of water increase under pressure. The work is supported by DOE-CMCSN under Grant DE-SC0005180 and by the Sloan Foundation through the Deep Carbon Observatory.

  14. 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

  15. Tunable Dielectric Properties of Ferrite-Dielectric Based Metamaterial

    PubMed Central

    Bi, K.; Huang, K.; Zeng, L. Y.; Zhou, M. H.; Wang, Q. M.; Wang, Y. G.; Lei, M.

    2015-01-01

    A ferrite-dielectric metamaterial composed of dielectric and ferrite cuboids has been investigated by experiments and simulations. By interacting with the electromagnetic wave, the Mie resonance can take place in the dielectric cuboids and the ferromagnetic precession will appear in the ferrite cuboids. The magnetic field distributions show the electric Mie resonance of the dielectric cuboids can be influenced by the ferromagnetic precession of ferrite cuboids when a certain magnetic field is applied. The effective permittivity of the metamaterial can be tuned by modifying the applied magnetic field. A good agreement between experimental and simulated results is demonstrated, which confirms that these metamaterials can be used for tunable microwave devices. PMID:25993433

  16. Variational and rigidity properties of static potentials

    E-print Network

    Galloway, Gregory J

    2014-01-01

    In this paper we study some global properties of static potentials on asymptotically flat $3$-manifolds $(M,g)$ in the nonvacuum setting. Heuristically, a static potential $f$ represents the (signed) length along $M$ of an irrotational timelike Killing vector field, which can degenerate on surfaces corresponding to the zero set of $f$. Assuming a suitable version of the null energy condition, we prove that a noncompact component of the zero set must be area minimizing. From this we obtain some rigidity results for static potentials that have noncompact zero set components, or equivalently, that are unbounded. Roughly speaking, these results show, at the pure initial data level, that `boost-type' Killing vector fields can exist only under special circumstances.

  17. 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.

  18. 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)...

  19. 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.

  20. Coherence properties of discrete static kinks

    E-print Network

    H. Landa

    2010-02-01

    A chain of interacting particles subject also to a nonlinear on-site potential admits stable soliton-like configurations : static kinks. The linear normal-modes around such a kink contain a discrete set of localized, gap-separated modes. Quantization of the Hamiltonian in these modes results in an interacting system of phonons. We investigate numerically the coherence properties of such localized modes at low temperatures using a non-Markovian master equation. We show that low decoherence rates can be achieved in these nonlinear configurations for a surprisingly long time. If realized in the ion trap, kink internal modes may be advantageously used for Quantum Information Processing.

  1. Dielectric properties of agricultural materials and their application

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This book is prepared as a comprehensive source of information on dielectric properties of agricultural materials for scientific researchers and engineers involved in practical application of radio-frequency and microwave energy for potential problem solutions. Dielectric properties of materials det...

  2. 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 ...

  3. High temperature dielectric properties of YMnO3 ceramics

    NASA Astrophysics Data System (ADS)

    Tomczyk, Monika; Maria Vilarinho, Paula; Moreira, Agostinho; Almeida, Abílio

    2011-09-01

    The temperature dependence of the dielectric properties and ac conduction of YMnO3 ceramics annealed under different atmospheres is investigated from 25 to 700 °C. The origin of the dielectric anomalies is clarified. Two dielectric peaks in the permittivity accompanied by a single anomaly in the dielectric losses characterize the dielectric response. Simultaneously, three different regions can be distinguished in the temperature dependence of ac conductivity. Oxygen vacancies with an activation energy for the conduction of 1.13 eV are suggested to be responsible for the dielectric anomaly observed at < 400 °C. For temperatures > 400 °C, the dielectric data are influenced by conductivity and no ferroelectric anomaly is obvious.

  4. Microwave axial dielectric properties of carbon fiber

    NASA Astrophysics Data System (ADS)

    Hong, Wen; Xiao, Peng; Luo, Heng; Li, Zhuan

    2015-10-01

    Randomly distributed carbon fibers (CFs) reinforced epoxy resin composites are prepared by the pouring method, the dielectric properties of CF composites with different fiber content and length have been performed in the frequency range from 8.2 to 12.4?GHz. The complex permittivity of the composite increases with the fiber length, which is attributed to the decrease of depolarization field, and increases with the volume fraction, which is attributed to the increase of polarization. A formula, based on the theory of Reynolds-Hugh, is proposed to calculate the effective permittivity of CF composites, and validated by the experiments. The proposed formula is further applied to derive the axial permittivity of CF and analyze the effect of fiber length on the axial permittivity.

  5. Microwave axial dielectric properties of carbon fiber.

    PubMed

    Hong, Wen; Xiao, Peng; Luo, Heng; Li, Zhuan

    2015-01-01

    Randomly distributed carbon fibers (CFs) reinforced epoxy resin composites are prepared by the pouring method, the dielectric properties of CF composites with different fiber content and length have been performed in the frequency range from 8.2 to 12.4?GHz. The complex permittivity of the composite increases with the fiber length, which is attributed to the decrease of depolarization field, and increases with the volume fraction, which is attributed to the increase of polarization. A formula, based on the theory of Reynolds-Hugh, is proposed to calculate the effective permittivity of CF composites, and validated by the experiments. The proposed formula is further applied to derive the axial permittivity of CF and analyze the effect of fiber length on the axial permittivity. PMID:26477579

  6. Microwave axial dielectric properties of carbon fiber

    PubMed Central

    Hong, Wen; Xiao, Peng; Luo, Heng; Li, Zhuan

    2015-01-01

    Randomly distributed carbon fibers (CFs) reinforced epoxy resin composites are prepared by the pouring method, the dielectric properties of CF composites with different fiber content and length have been performed in the frequency range from 8.2 to 12.4?GHz. The complex permittivity of the composite increases with the fiber length, which is attributed to the decrease of depolarization field, and increases with the volume fraction, which is attributed to the increase of polarization. A formula, based on the theory of Reynolds-Hugh, is proposed to calculate the effective permittivity of CF composites, and validated by the experiments. The proposed formula is further applied to derive the axial permittivity of CF and analyze the effect of fiber length on the axial permittivity. PMID:26477579

  7. Microwave Dielectric Properties Models for Grain and Seed

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Based on microwave dielectric properties of wheat, corn, barley, oats, grain sorghum, soybeans, canola, shelled peanuts and pod peanuts measured over ranges of frequency and moisture content, models are developed for predicting the dielectric constant and loss factor of these commodities. Nearly lin...

  8. Frequency and temperature dependence of dielectric properties of chicken meat

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dielectric properties of chicken breast meat were measured with an open-ended coaxial-line probe between 200 MHz and 20 GHz at temperatures ranging from -20 degree C to +25 degree C. At a given temperature, the frequency dependence of the dielectric constant reveals two relaxations while those of th...

  9. Automated Monitoring Of Dielectric Properties Of Tree Trunks

    NASA Technical Reports Server (NTRS)

    Mcdonald, Kyle C.; Chun, William

    1996-01-01

    Semiautomated instrumentation system called "dielectric monitoring system" (DMS) developed for measuring microwave permittivities of selected components of plants, in particular, of active xylems in tree trunks. System set up with coaxial probes inserted in tree trunks to measure dielectric properties. Can be left to operate unattended to gather data on permittivities as function of time.

  10. Models for the Microwave Dielectric Properties of Grain and Seed

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Based on microwave dielectric properties of wheat, corn, barley, oats, grain sorghum, soybeans, canola, shelled peanuts and pod peanuts measured over ranges of frequency and moisture content, models are developed for predicting the dielectric constant and loss factor of these commodities. Nearly li...

  11. 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.

  12. Dielectric properties of FeCl3 doped PVA films

    NASA Astrophysics Data System (ADS)

    Mahavar, H. K.; Rawat, A.; Singh, P. J.

    2013-06-01

    Polyvinyl alcohol (PVA) and FeCl3 doped films with different concentrations were prepared using solution grown technique, in order to investigate the effect of FeCl3 doping (up to 10%) on dielectric properties of PVA host at microwave frequency and at room temperature. Measurements of the dielectric parameters such as dielectric permittivity, dielectric loss, loss tangent, a. c. conductivity and relaxation time were carried out. The changes in the dielectric parameters have been observed with doping concentration of FeCl3 in PVA matrix. We have used dielectric data at microwave frequencies as a tool to evaluate optical constants, like extinction coefficient `k' and refractive index `n' of the films.

  13. Dielectric properties of human placenta, umbilical cord and amniotic fluid

    NASA Astrophysics Data System (ADS)

    Peyman, A.; Gabriel, C.; Benedickter, H. R.; Fröhlich, J.

    2011-04-01

    The dielectric properties of freshly delivered human placenta, umbilical cord and amniotic fluid have been acquired at 37 °C and in the frequency range of 200 MHz-10 GHz. The experimental data were fitted to a Cole-Cole expression. The results show that dielectric properties of the umbilical cord are significantly higher than placenta due to the presence of high water content Wharton's jelly. The results also demonstrate large differences in the dielectric properties of amniotic and cerebrospinal fluids. The data presented can be used in numerical simulations of the exposure of pregnant women to electromagnetic fields.

  14. First-principles calculations of the dielectric and vibrational properties of ferroelectric and paraelectric BaAl2O4

    NASA Astrophysics Data System (ADS)

    Xie, Congwei; Zeng, Qingfeng; Dong, Dong; Gao, Shuang; Cai, Yongqing; Oganov, Artem R.

    2014-05-01

    First-principles calculations have been conducted to study the structural, dielectric, and vibrational properties of ferroelectric and paraelectric BaAl2O4. High-frequency and static dielectric constants, and phonon frequencies at the Brillouin zone center are reported. Both BaAl2O4 polymorphs are promising infrared-transparent materials due to their low electronic dielectric constants. The ferroelectric and paraelectric BaAl2O4 have much smaller permittivity compared to the classical ferroelectric materials. From an atomic nanostructure standpoint, the abnormally low permittivity of BaAl2O4 polymorphs is mainly related to low coordination numbers of Ba (9) and Al (4).

  15. Structural and Dielectric Properties of Subnanometric Laminates of Binary Oxides.

    PubMed

    Kahouli, Abdelkader; Lebedev, Oleg; Ben Elbahri, Marwa; Mercey, Bernard; Prellier, Wilfrid; Riedel, Stefan; Czernohorsky, Malte; Lallemand, Florent; Bunel, Catherine; Lüders, Ulrike

    2015-11-25

    Capacitors with a dielectric material consisting of amorphous laminates of Al2O3 and TiO2 with subnanometer individual layer thicknesses can show strongly enhanced capacitance densities compared to the bulk or laminates with nanometer layer thickness. In this study, the structural and dielectric properties of such subnanometer laminates grown on silicon by state-of-the-art atomic layer deposition are investigated with varying electrode materials. The laminates show a dielectric constant reaching 95 combined with a dielectric loss (tan ?) of about 0.2. The differences of the observed dielectric properties in capacitors with varying electrodes indicate that chemical effects at the interface with the TiN electrode play a major role, while the influence of the local roughness of the individual layers is rather limited. PMID:26523935

  16. Dielectric and magnetic properties of some gadolinium silica nanoceramics

    SciTech Connect

    Coroiu, I. Pascuta, P. Bosca, M. Culea, E.

    2013-11-13

    Some nanostructure gadolinium silica glass-ceramics were obtained undergoing a sol gel method and a heat-treatment at 1000°C about two hours. The magnetic and dielectric properties of these samples were studied. The magnetic properties were evidenced performing susceptibility measurements in the 80-300K temperature range. A Curie-Weiss behavior has acquired. The values estimated for paramagnetic Curie temperature being small and positive suggest the presence of weak ferromagnetic interactions between Gd{sup 3+} ions. The dielectric properties were evaluated from dielectric permittivity (?{sub r}) and dielectric loss (tan?) measurements at the frequency 1 kHz, 10 kHz and 100 kHz, in the 25-225°C temperature range and dielectric dispersion at room temperature for 79.5 kHz - 1GHz frequency area. The dielectric properties suggest that the main polarization mechanism corresponds to interfacial polarization, characteristic for polycrystalline-structured dielectrics. The polycrystalline structure of the samples is due to the polymorphous transformations of the nanostructure silica crystallites in the presence of gadolinium oxide. They were highlighted by SEM micrographs.

  17. A Database for the Static Dielectric Constant of Water and Steam

    NASA Astrophysics Data System (ADS)

    Fernández, Diego P.; Mulev, Y.; Goodwin, A. R. H.; Levelt Sengers, J. M. H.

    1995-01-01

    All reliable sources of data for the static dielectric constant or relative permittivity of water and steam, many of them unpublished or inaccessible, have been collected, evaluated, corrected when required, and converted to the ITS-90 temperature scale. The data extend over a temperature range from 238 to 873 K and over a pressure range from 0.1 MPa up to 1189 MPa. The evaluative part of this work includes a review of the different types of measurement techniques, and the corrections for frequency dependence due to the impedance of circuit components, and to electrode polarization. It also includes a detailed assessment of the uncertainty of each particular data source, as compared to other sources in the same range of pressure and temperature. Both the raw and the corrected data have been tabulated, and are also available on diskette. A comprehensive list of references to the literature is included.

  18. 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

  19. Millimeter wave analysis of the dielectric properties of oil shales

    E-print Network

    John A. Scales; Michael Batzle

    2006-06-06

    Natural sedimentation processes give rise to fine layers in shales. If these layers alternate between organic-rich and organic-poor sediments, then the contrast in dielectric properties gives rise to an effective birefringence as the presence of hydrocarbons suppresses the dielectric constant of the host rock. We have measured these effects with a quasioptical millimeter wave setup that is rapid and noncontacting. We find that the strength of this birefringence and the overall dielectric permittivity provide two useful diagnostic of the organic content of oil shales.

  20. Recent progress on dielectric properties of protic ionic liquids

    NASA Astrophysics Data System (ADS)

    Wojnarowska, Zaneta; Paluch, Marian

    2015-02-01

    Protic ionic liquids (PILs) are key materials for a wide range of emerging technologies. In particular, these systems have long been envisioned as promising candidates for fuel cells. Therefore, in recent years special attention has been devoted to thorough studies of these compounds. Amongst others, dielectric properties of PILs at ambient and elevated pressure have become the subject of intense research. The reason for this lies in the role of broadband dielectric spectroscopy in recognizing the conductivity mechanism in protic ionic systems. In this paper, we summarize the dielectric results of various PILs reflecting recent advances in this field.

  1. Recent progress on dielectric properties of protic ionic liquids.

    PubMed

    Wojnarowska, Zaneta; Paluch, Marian

    2015-02-25

    Protic ionic liquids (PILs) are key materials for a wide range of emerging technologies. In particular, these systems have long been envisioned as promising candidates for fuel cells. Therefore, in recent years special attention has been devoted to thorough studies of these compounds. Amongst others, dielectric properties of PILs at ambient and elevated pressure have become the subject of intense research. The reason for this lies in the role of broadband dielectric spectroscopy in recognizing the conductivity mechanism in protic ionic systems. In this paper, we summarize the dielectric results of various PILs reflecting recent advances in this field. PMID:25634823

  2. Electrical properties and dielectric spectroscopy of Ar{sup +} implanted polycarbonate

    SciTech Connect

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

    2015-05-15

    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{sup +} ions in the fluence ranging from 1×10{sup 14} to 1×10{sup 16} ions cm{sup ?2}. The beam current used was ?0.40?µA cm{sup ?2}. The electrical conduction behaviour of virgin and Ar{sup +} 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 (?{sub s}), optical dielectric constant (?{sub ?}), spreading factor (?), average relaxation time (?{sub 0}) and molecular relaxation time (?). The dielectric behaviour has been found to be significantly affected due to Ar{sup +} implantation. The possible correlation between this behaviour and the changes induced by the implantation has been discussed.

  3. 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

  4. 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

  5. Dielectric properties of biomass and biochar mixtures for bioenergy applications

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Biomass is an abundant and renewable energy resource, which may be converted into energy-dense products through thermochemical processes such as pyrolysis and gasification. Since microwave heating depends on the dielectric properties of the biomass material, these properties were measured at freque...

  6. 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.

  7. Diurnal changes in the dielectric properties and water status of eastern hemlock and red spruce from Howland, ME

    NASA Technical Reports Server (NTRS)

    Salas, W. A.; Ranson, K. J.; Rock, B. N.; Moss, D. M.

    1991-01-01

    The diurnal characteristics of microwave dielectric properties and water potential of two conifer species were investigated in July and September, 1990. P-band and C-band radial dielectric profiles of hemlock and red spruce, as well as hemlock diurnal water potential and dielectric profiles, are presented. The resulting radial dielectric profiles matched the regions of the functional sapwood (water transport component of the active xylem) in both species such that the sapwood was characterized by a higher dielectric than the bark and heartwood tissues. This is probably due to characteristic differences in the water content of each tissue. As the hemlocks progressed through their diurnal water potential pattern, the dielectric profile remained static until mid-afternoon. As the tension in the water column relaxed (2 to 3 bars) the dielectric constant decreased by 30 to 40 percent. There are several possible explanations for this phenomenon, and these may relate to the dependency of the dielectric measurements on temperature, salinity, and volumetric water content.

  8. First principles studies of interface dielectric properties of polymer/metal-oxide nanocomposites

    NASA Astrophysics Data System (ADS)

    Yu, Liping

    This thesis is devoted to studying interface dielectric properties of polymer nanocomposites from first principles. We aim to understand at atomic scale the role of interface effects and the dielectric finite size effects of nanoparticles in determining the effective dielectric properties of polymer nanocomposites. To study surface effects from first principles, we first investigate the two common methods, namely dipole correction and Coulomb cutoff, used to eliminate the artificial effects introduced by using the supercell approximation. We implement Coulomb cutoff technique in a plane-wave-based density functional theory code and compare it with dipole correction for the same system under the same conditions. By comparison, both methods are shown to be equivalent and able to remove the artificial effects of periodic images very accurately. We also find that a combination of these two methods offers an easy way to distinguish the localized bound states of interest from highly delocalized unoccupied states while using a relatively small supercell, and to ascertain the convergence of the results with respect to supercell size. To understand the dielectric properties at the atomic scale, we develop a new nanoscale averaging model to connect the macroscopic quantities to the corresponding microscopic ones. This model allows us to compute the spatially resolved local dielectric permittivity, including the critically important ionic contributions, for interfaces and other complex structures. In this model, a simple way of evaluating real-space decay length of the nonlocal dielectric functions is also proposed. By using the dipole correction and our averaging model in supercells, we calculate the optical and static local dielectric permittivity profiles for polymer (polypropylene)/metal-oxide (PbTiO3 and alumina) nanocomposites. Our ab-initio results show that metal-oxide/polymer interface effects are very localized and are mostly confined to the metal-oxide surface side, and that nanoscale metal-oxide slabs can on average retain the macroscopic value of bulk dielectric permittivity. These findings suggest that classical mixing laws associated with macroscopic composites can be applied to model the overall dielectric constant of a real polymer/metal-oxide nanocomposite system.

  9. 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

  10. Optical properties of semiconductors and dielectrics

    NASA Astrophysics Data System (ADS)

    Mushinskii, V. P.

    The volume contains theoretical and experimental papers on nonequilibrium processes in semiconductors and dielectrics. Topics discussed include analysis of exciton and biexciton states in anisotropic multilayer structures, the Cotton-Mouton effect at local centers in ion crystals, and consideration of the polariton effect in the theory of small impurity centers. Papers are also presented on photoconductivity and photoluminescence effects in some binary semiconductors and on optical data recording using a multilayer structure containing bismuth germanate.

  11. 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.)

  12. Dielectric properties of inorganic fillers filled epoxy thin film

    NASA Astrophysics Data System (ADS)

    Norshamira, A.; Mariatti, M.

    2015-07-01

    The demand on the small size and high performance electronics has driven changes in the electronic packaging requirements from discrete capacitor to embedded capacitor. Embedded capacitor can improve electrical performance compared with discrete capacitor. This study aimed to achieve high dielectric of epoxy thin film composite that were targeted for application as embedded capacitor. In this study, inorganic fillers such as Calcium Copper Titanate (CCTO), Iron(III) Oxide (Fe2O3) and Titanium Dioxide (TiO2) were loaded in epoxy system at 5 and 20vol%. Morphology and dielectric properties were investigated to identify the effect of fillers loading and types of fillers on the properties of epoxy thin film composite. Based on the study, CCTO with 20vol% loading was found to have good dielectric properties compared to other type of fillers.

  13. 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.

  14. Impedance and dielectric properties of mercury cuprate at nonsuperconducting state

    NASA Astrophysics Data System (ADS)

    Özdemir, Z. Güven; Çataltepe, Ö. Aslan; Onba?l?, Ü.

    2015-10-01

    In this paper, impedance and dielectric properties of nonsuperconducting state of the mercury-based cuprate have been investigated by impedance measurements within the frequency interval of 10 Hz-10 MHz for the first time. The dielectric loss factor (tg?) and ac conductivity (?ac) parameters have also been calculated for non-superconducting state. According to impedance spectroscopy analysis, the equivalent circuit of the mercury cuprate system manifests itself as a semicircle in the Nyquist plot that corresponds to parallel connected resistance-capacitance circuit. The oscillation frequency of the circuit has been determined as approximately 45 kHz which coincides with the low frequency radio waves. Moreover, it has been revealed that the mercury-based cuprate investigated has high dielectric constants and hence it may be utilized in microelectronic industry such as capacitors, memory devices etc., at room temperature. In addition, negative capacitance (NC) effect has been observed for the mercury cuprate regardless of the operating temperatures at nonsuperconducting state. Referring to dispersions in dielectric properties, the main contribution to dielectric response of the system has been suggested as dipolar and interfacial polarization mechanisms.

  15. Dielectric and pyroelectric properties of barium strontium titanate films on orthorhombic substrates with ,,110.../ /,,100... epitaxy

    E-print Network

    Alpay, S. Pamir

    Dielectric and pyroelectric properties of barium strontium titanate films on orthorhombic of anisotropic misfit strains on the spontaneous polarization, dielectric properties, and pyroelectric response phases that cannot be observed in single-crystal perovskite ferroelectrics can be stabilized due

  16. Virtual crystal approximation revisited: Application to dielectric and piezoelectric properties of perovskites

    E-print Network

    Vanderbilt, David

    to predict the anomalous dielectric and piezoelectric properties of perovskite solid solutions. A secondARTICLES Virtual crystal approximation revisited: Application to dielectric and piezoelectric properties of perovskites L. Bellaiche Physics Department, University of Arkansas, Fayetteville, Arkansas

  17. Investigation on dielectric properties of atomic layer deposited Al{sub 2}O{sub 3} dielectric films

    SciTech Connect

    Y?ld?z, Dilber Esra; Y?ld?r?m, Mert; Gökçen, Muharrem

    2014-05-15

    Al/Al{sub 2}O{sub 3}/p-Si Schottky barrier diodes (SBDs) were fabricated using atomic layer deposition technique in order to investigate dielectric properties of SBDs. For this purpose, admittance measurements were conducted at room temperature between ?1?V and 3?V in the frequency range of 10 kHz and 1?MHz. In addition to the investigation of Al{sub 2}O{sub 3} morphology using atomic force microscope, dielectric parameters; such as dielectric constant (??), dielectric loss (??), dielectric loss tangent (tan??), and real and imaginary parts of dielectric modulus (M? and M?, respectively), were calculated and effect of frequency on these parameters of Al/Al{sub 2}O{sub 3}/p-Si SBDs was discussed. Variations in these parameters at low frequencies were associated with the effect of interface states in low frequency region. Besides dielectric parameters, ac electrical conductivity of these SBDs was also investigated.

  18. 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...

  19. MICROWAVE DIELECTRIC PROPERTIES OF CEREAL GRAIN AND SEED

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dielectric properties of wheat, corn and soybeans were measured with a free-space-transmission technique at room temperature between 2.0 and 18.0 GHz over wide ranges of bulk density and moisture content of practical interest. For better accuracy and optimum use of the vector network analyzer (VNA) ...

  20. Ferroelectric and dielectric properties of strontium bismuth niobate vanadates

    E-print Network

    Cao, Guozhong

    Ferroelectric and dielectric properties of strontium bismuth niobate vanadates Yun Wu and Guozhong 19 November 1999; accepted 20 April 2000) Strontium bismuth niobate vanadates, SrBi2(VxNb1-x)2O9 qualitatively different nondestructive read op- erations.3 Recently, bismuth oxide layered perovskite materials

  1. Dielectric Properties of Honeydew Melons and Correlation with Quality

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dielectric properties of three honeydew melon cultivars, grown and harvested to provide a range of maturities, were measured with an open-ended coaxial-line probe and impedance analyzer over the frequency range from 10 MHz to 1.8 GHz. Probe measurements were made on the external surface of the melo...

  2. Dielectric Properties of Watermelons and Correlation with Soluble Solids Content

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dielectric properties of four small-sized watermelon cultivars, grown and harvested to provide a range of maturities, were measured with an open-ended coaxial-line probe and impedance analyzer over the frequency range from 10 MHz to 1.8 GHz. Probe measurements were made on the external surface of t...

  3. MEASURING SOIL HYDROLOGIC PROPERTIES USING DIELECTRIC SENSORS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Knowledge of soil hydrologic properties is essential to many aspects of environmental research. Soil hydrologic properties determined from laboratory analyses often are non-representative of field conditions. In this work, we compare soil hydrologic properties determined in the field with values obt...

  4. Electrical, optical and dielectric properties of HCl doped polyaniline nanorods

    NASA Astrophysics Data System (ADS)

    Chutia, P.; Kumar, A.

    2014-03-01

    In this report we have investigated the optical, electrical and dielectric properties of HCl doped polyaniline nanorods synthesized by the interfacial polymerization technique. High resolution transmission electron microscope (HRTEM) micrographs confirm the formation of nanorods. X-ray diffraction pattern shows the semicrystalline nature of polyaniline nanorods with a diameter distribution in the range of 10-22 nm. The chemical and electronic structures of the polyaniline nanorods are investigated by micro-Raman and UV-vis spectroscopy. Dielectric relaxation spectroscopy has been applied to study the dielectric permittivity, modulus formalism and ac conductivity as a function of frequency and temperature. The ac conductivity follows a power law with frequency. The variation of frequency exponent with temperature suggests that the correlated barrier hopping is the dominant charge transport mechanism. The existence of both polaron and bipolaron in the transport mechanism has been confirmed from the binding energy calculations.

  5. Electrical conductivity and dielectric property of fly ash geopolymer pastes

    NASA Astrophysics Data System (ADS)

    Hanjitsuwan, Sakonwan; Chindaprasirt, Prinya; Pimraksa, Kedsarin

    2011-02-01

    The electrical conductivity and dielectric property of fly ash geopolymer pastes in a frequency range of 100 Hz-10 MHz were studied. The effects of the liquid alkali solution to ash ratios (L/A) were analyzed. The mineralogical compositions and microstructures of fly ash geopolymer materials were also investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The 10 mol sodium hydroxide solution and sodium silicate solution at a sodium silicate-to-sodium hydroxide ratio of 1.0 were used in making geopolymer pastes. The pastes were cured at 40°C. It is found that the electrical conductivity and dielectric constant are dependent on the frequency range and L/A ratios. The conductivity increases but the dielectric constant decreases with increasing frequency.

  6. Technique for Performing Dielectric Property Measurements at Microwave Frequencies

    NASA Technical Reports Server (NTRS)

    Barmatz, Martin B.; Jackson, Henry W.

    2010-01-01

    A paper discusses the need to perform accurate dielectric property measurements on larger sized samples, particularly liquids at microwave frequencies. These types of measurements cannot be obtained using conventional cavity perturbation methods, particularly for liquids or powdered or granulated solids that require a surrounding container. To solve this problem, a model has been developed for the resonant frequency and quality factor of a cylindrical microwave cavity containing concentric cylindrical samples. This model can then be inverted to obtain the real and imaginary dielectric constants of the material of interest. This approach is based on using exact solutions to Maxwell s equations for the resonant properties of a cylindrical microwave cavity and also using the effective electrical conductivity of the cavity walls that is estimated from the measured empty cavity quality factor. This new approach calculates the complex resonant frequency and associated electromagnetic fields for a cylindrical microwave cavity with lossy walls that is loaded with concentric, axially aligned, lossy dielectric cylindrical samples. In this approach, the calculated complex resonant frequency, consisting of real and imaginary parts, is related to the experimentally measured quantities. Because this approach uses Maxwell's equations to determine the perturbed electromagnetic fields in the cavity with the material(s) inserted, one can calculate the expected wall losses using the fields for the loaded cavity rather than just depending on the value of the fields obtained from the empty cavity quality factor. These additional calculations provide a more accurate determination of the complex dielectric constant of the material being studied. The improved approach will be particularly important when working with larger samples or samples with larger dielectric constants that will further perturb the cavity electromagnetic fields. Also, this approach enables the ability to have a larger sample of interest, such as a liquid or powdered or granulated solid, inside a cylindrical container.

  7. Modelling of the static and dynamic mechanical properties of human

    E-print Network

    Haslwanter, Thomas

    Modelling of the static and dynamic mechanical properties of human otoliths DISSERTATION zur and dynamic prop- erties of the otoliths. The otoliths are a part of the vestibular system, located of the otoliths can be distinguished with respect to their function in the sensory apparatus, the otolith membrane

  8. Mass properties measurement system: Dynamics and statics measurements

    NASA Technical Reports Server (NTRS)

    Doty, Keith L.

    1993-01-01

    This report presents and interprets experimental data obtained from the Mass Properties Measurement System (MPMS). Statics measurements yield the center-of-gravity of an unknown mass and dynamics measurements yield its inertia matrix. Observations of the MPMS performance has lead us to specific design criteria and an understanding of MPMS limitations.

  9. 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.

  10. Toward Automated Benchmarking of Atomistic Force Fields: Neat Liquid Densities and Static Dielectric Constants from the ThermoML Data Archive.

    PubMed

    Beauchamp, Kyle A; Behr, Julie M; Rustenburg, Ariën S; Bayly, Christopher I; Kroenlein, Kenneth; Chodera, John D

    2015-10-01

    Atomistic molecular simulations are a powerful way to make quantitative predictions, but the accuracy of these predictions depends entirely on the quality of the force field employed. Although experimental measurements of fundamental physical properties offer a straightforward approach for evaluating force field quality, the bulk of this information has been tied up in formats that are not machine-readable. Compiling benchmark data sets of physical properties from non-machine-readable sources requires substantial human effort and is prone to the accumulation of human errors, hindering the development of reproducible benchmarks of force-field accuracy. Here, we examine the feasibility of benchmarking atomistic force fields against the NIST ThermoML data archive of physicochemical measurements, which aggregates thousands of experimental measurements in a portable, machine-readable, self-annotating IUPAC-standard format. As a proof of concept, we present a detailed benchmark of the generalized Amber small-molecule force field (GAFF) using the AM1-BCC charge model against experimental measurements (specifically, bulk liquid densities and static dielectric constants at ambient pressure) automatically extracted from the archive and discuss the extent of data available for use in larger scale (or continuously performed) benchmarks. The results of even this limited initial benchmark highlight a general problem with fixed-charge force fields in the representation low-dielectric environments, such as those seen in binding cavities or biological membranes. PMID:26339862

  11. Analysis of Dielectric and Thermal Properties of Polyamide Enamel Filled with Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Selvaraj, D. Edison; Sugumaran, C. Pugazhendhi; Ganesan, Lieutenant J.; Ramathilagam, J.

    2013-06-01

    In recent days, there was a significant development in the area of nanoparticles and nanoscale fillers on dielectric, thermal and mechanical properties of polymeric materials. The dielectric and thermal properties of standard polyamide and nanoscale-filled samples were detailed and analyzed. Carbon nanotubes were used as nanofillers. Carbon nanotubes were synthesized by chemical vapor deposition (CVD). The basic properties such as dielectric loss tangent (tan ?), dielectric constant (?), dielectric strength, partial discharge inception voltage, surface resistivity, quality factor, phase angle, dielectric conductivity, dielectric power loss and thermal withstand strength of the polyamide enamel filled with carbon nanotubes were analyzed and compared with the properties of the standard enamel. The experimental results show that carbon nanotubes mixed with polyamide enamel had better thermal properties when compared to that of standard enamel.

  12. Structural and dielectric properties of yttrium substituted nickel ferrites

    SciTech Connect

    Ognjanovic, Stevan M.; Tokic, Ivan; Cvejic, Zeljka; Rakic, Srdjan; Srdic, Vladimir V.

    2014-01-01

    Graphical abstract: - Highlights: • Dense NiFe{sub 2?x}Y{sub x}O{sub 4} ceramics (with 0 ? x ? 0.3) were prepared. • Pure spinels were obtained for x ? 0.07 while for x ? 0.15 samples had secondary phases. • With addition of yttrium, ac conductivity slightly increased. • We suggest several effects that can explain the observed changes in ac conduction. • With addition of yttrium, dielectric constant increased while the tg ? decreased. - Abstract: The influence of Y{sup 3+} ions on structural and dielectric properties of nickel ferrites (NiFe{sub 2?x}Y{sub x}O{sub 4}, where 0 ? x ? 0.3) has been studied. The as-synthesized samples, prepared by the co-precipitation method, were analyzed by XRD and FTIR which suggested that Y{sup 3+} ions were incorporated into the crystal lattice for all the samples. However, the XRD analysis of the sintered samples showed that secondary phases appear in the samples with x > 0.07. The samples have densities greater than 90% TD and the SEM images showed that the grain size decreases with the addition of yttrium. Dielectric properties measured from 150 to 25 °C in the frequency range of 100 Hz–1 MHz showed that the addition of yttrium slightly increases the ac conductivity and decreases the tg ? therefore making the materials better suited for the use in microwave devices.

  13. 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.

  14. Protein dielectrophoresis and the link to dielectric properties

    PubMed Central

    Camacho-Alanis, Fernanda; Ros, Alexandra

    2015-01-01

    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

  15. Dielectric properties of 'diamondlike' carbon prepared by RF plasma deposition

    NASA Technical Reports Server (NTRS)

    Lamb, J. D.; Woollam, J. A.

    1985-01-01

    Metal-carbon-metal structures were fabricated using either gold or aluminum evaporated electrodes and RF plasma (methane) deposited 'diamondlike' carbon films. Alternating-current conductance and capacitance versus voltage and frequency (10 Hz to 13 MHz) data were taken to determine the dielectric properties of these films. Conductance versus frequency data fit a generalized power law, consistent with both dc and hopping conduction components. The capacitance versus frequency data are well matched to the conductance versus frequency data, as predicted by a Kramers-Kronig analysis. The dielectric loss tangent is nearly constant at 0.5 to 1.0 percent over the frequency range from 1 to 100 kHz. The dc resistivity is above 10 to the 13th ohm cm, and the dc breakdown strength is above 8 x 10 to the 6th V/cm is properly prepared samples.

  16. First-principles study of structural, electronic, vibrational, dielectric and elastic properties of tetragonal Ba?YTaO?

    SciTech Connect

    Ganeshraj, C.; Santhosh, P. N.

    2014-10-14

    We report first-principles study of structural, electronic, vibrational, dielectric, and elastic properties of Ba?YTaO?, a pinning material in high temperature superconductors (HTS), by using density functional theory. By using different exchange-correlation potentials, the accuracy of the calculated lattice constants of Ba?YTaO? has been achieved with GGA-RPBE, since many important physical quantities crucially depend on change in volume. We have calculated the electronic band structure dispersion, total and partial density of states to study the band gap origin and found that Ba?YTaO? is an insulator with a direct band gap of 3.50 eV. From Mulliken population and charge density studies, we conclude that Ba?YTaO? have a mixed ionic-covalent character. Moreover, the vibrational properties, born effective charges, and the dielectric permittivity tensor have been calculated using linear response method. Vibrational spectrum determined through our calculations agrees well with the observed Raman spectrum, and allows assignment of symmetry labels to modes. We perform a detailed analysis of the contribution of the various infrared-active modes to the static dielectric constant to explain its anisotropy, while electronic dielectric tensor of Ba?YTaO? is nearly isotropic, and found that static dielectric constant is in good agreement with experimental value. The six independent elastic constants were calculated and found that tetragonal Ba?YTaO? is mechanically stable. Other elastic properties, including bulk modulus, shear modulus, Young's modulus, Poisson's ratio, and elastic anisotropy ratios are also investigated and found that Poisson's ratio and Young's modulus of Ba?YTaO? are similar to that of other pinning materials in HTS.

  17. Improving the dielectric properties of an electrowetting-on-dielectric microfluidic device with a low-pressure chemical vapor deposited Si3N4 dielectric layer.

    PubMed

    Shen, Hsien-Hua; Chung, Lung-Yuan; Yao, Da-Jeng

    2015-03-01

    Dielectric breakdown is a common problem in a digital microfluidic system, which limits its application in chemical or biomedical applications. We propose a new fabrication of an electrowetting-on-dielectric (EWOD) device using Si3N4 deposited by low-pressure chemical vapor deposition (LPCVD) as a dielectric layer. This material exhibits a greater relative permittivity, purity, uniformity, and biocompatibility than polymeric films. These properties also increase the breakdown voltage of a dielectric layer and increase the stability of an EWOD system when applied in biomedical research. Medium droplets with mouse embryos were manipulated in this manner. The electrical properties of the Si3N4 dielectric layer-breakdown voltage, refractive index, relative permittivity, and variation of contact angle with input voltage-were investigated and compared with a traditional Si3N4 dielectric layer deposited as a plasma-enhanced chemical vapor deposition to confirm the potential of LPCVD Si3N4 applied as the dielectric layer of an EWOD digital microfluidic system. PMID:25825614

  18. Ferroelectric and dielectric properties of ferrite-ferroelectric ceramic composites

    SciTech Connect

    Elena Ciomaga, Cristina; Maria Neagu, Alexandra; Valentin Pop, Mihai; Mitoseriu, Liliana; Airimioaei, Mirela; Tascu, Sorin; Schileo, Giorgio; Galassi, Carmen

    2013-02-21

    Particulate composites of ferrite and ferroelectric phases with xNiFe{sub 2}O{sub 4} (NF) and (1 - x)Pb{sub 0.988}(Zr{sub 0.52}Ti{sub 0.48}){sub 0.976}Nb{sub 0.024}O{sub 3} (where x = 2, 10, 20, 30, 50, 70, and 100 wt. %) were prepared in situ by sol-gel method. The presence of a diphase composition was confirmed by X-ray diffraction while the microstructure of the composites was studied by scanning electron microscopy revealing a good mixing of the two phases and a good densification of the bulk ceramics. The dielectric permittivity shows usual dielectric dispersion behavior with increasing frequency due to Maxwell-Wagner interfacial polarization. AC conductivity measurements made in frequency range 1 Hz-1 MHz suggest that the conduction process is due to mixed polaron hopping. The effect of NF phase concentration on the P-E and M-H hysteresis behavior and dielectric properties of the composites was investigated. At low NF concentration a sharp ferro-paraelectric transition peak can be observed at around 360 Degree-Sign C while for higher NF concentrations a trend to a diffuse phase transition occurs. All the composite samples exhibit typical ferromagnetic hysteresis loops, indicating the presence of ordered magnetic structure.

  19. Connexions between density and dielectric properties of water

    NASA Astrophysics Data System (ADS)

    Pedroza, Luana; Elton, Daniel; Fernandez-Serra, Marivi

    2013-03-01

    As it is well known, water has a high dielectric constant, which is connected both to the molecular dipole moment and to the intermolecular bonding through hydrogen bonds. Although some classical force fields can reproduce this dielectric constant, they do not take into account the environment-dependent perturbations of the individual dipoles and their relation to the local structure and network of the liquid. In this work, we investigate in detail the distribution of molecular dipoles for different densities of liquid water, obtained with ab initio molecular dynamics simulations and compare them to those obtained using a classical, polarizable, empirical force field. We calculate the dipole moment for different choices of exchange-correlation functionals, including van der Waals correction. In addition, we analyze the correlation between the dipolar coupling and the vibrational spectrum of water. In this way, we can get a better understanding on how local electronic effects play a role in the determination of global properties of water, such as its dielectric constant and density This work is supported by DOE Grant No. DE-SC0003871.

  20. Dielectric properties of silver-gelatin granular suspensions

    NASA Astrophysics Data System (ADS)

    Davis, V. A.; Schwartz, L.

    1986-05-01

    Recently, some authors have employed a lattice-gas version of the coherent-potential approximation (LG-CPA) to describe the optical properties of composites formed by the suspension of Ag grains in a gelatin host. We show here that a direct approach to structural disorder, based on Roth's effective-medium approximation (EMA), yields results that are, at least, of comparable accuracy to those of the LG-CPA. The dependence of the EMA dielectric function on the input parameters that characterize metal-insulator suspensions is examined and found to be physically reasonable.

  1. Measurement of dielectric and magnetic properties of soil

    SciTech Connect

    Patitz, W.E.; Brock, B.C.; Powell, E.G.

    1995-11-01

    The possibility of subsurface imaging using SAR technology has generated a considerable amount of interest in recent years. One requirement for the successful development of a subsurface imagin system is an understanding of how the soil affects the signal. In response to a need for an electromagnetic characterization of the soil properties, the Radar/Antenna department has developed a measurement system which determines the soils complex electric permittivity and magnetic permeability at UHF frequencies. The one way loss in dB is also calculated using the measured values. There are many reports of measurements of the electric properties of soil in the literature. However, most of these are primarily concerned with measuring only a real dielectric constant. Because some soils have ferromagnetic constituents it is desirable to measure both the electric and magnetic properties of the soil.

  2. 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...

  3. Thermal properties of dielectric solids below 4 K. I - Polycarbonate

    NASA Technical Reports Server (NTRS)

    Cieloszyk, G. S.; Cruz, M. T.; Salinger, G. L.

    1973-01-01

    Polymers and other dielectric materials are frequently used for many purposes in the construction of cryogenic apparatus. Yet very few values of the thermal properties of these materials below 4 K have been reported. It is, however, known that one can not use the Debye theory to extrapolate to lower temperatures the measurements of the specific heat capacity above 1 K. The thermal conductivity also follows no theoretically predictable temperature dependence. As a by-product of our studies of the thermal properties of amorphous and partly crystalline materials below 4 K, we wish to report values for the thermal conductivity, specific heat capacity, and velocity of sound below 4 K in materials useful for the construction of cryogenic apparatus. In this article we will describe our measurement techniques and report values for polycarbonate (Lexan). In subsequent notes we will give values for other materials of interest.

  4. Disclosed dielectric and electromechanical properties of hydrogenated nitrile-butadiene dielectric elastomer

    NASA Astrophysics Data System (ADS)

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

    2012-03-01

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

  5. 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.

  6. The unified Skyrmion profiles and Static Properties of Nucleons

    E-print Network

    Duo-Jie Jia; Xiao-Wei Wang

    2010-09-20

    An unified approximated solution for symmetric Skyrmions was proposed for the SU(2) Skyrme model for baryon numbers up to 8,which take the hybrid form of a kink-like solution and that given by the instanton method. The Skyrmion profiles are examined by computing lowest soliton energy as well as the static properties of nucleons within the framework of collective quantization, with a good agreement with the exact numeric results. The comparisons with the previous computations as well as the experimental data are also given.

  7. Consequence of cobalt on structural, optical and dielectric properties in ZnO nanostructures

    NASA Astrophysics Data System (ADS)

    Zia, Amir; Ahmed, S.; Shah, N. A.; Anis-ur-Rehman, M.; Khan, E. U.; Basit, M.

    2015-09-01

    The critical role of cobalt dopant in ZnO nanostructures with different cobalt concentrations has been explored on the basis of structural, optical and dielectric mechanisms. X-ray diffraction (XRD) analysis shows that the Co+2 ions replace Zn+2 ions in the ZnO matrix, producing lattice strain. Diffused Reflectance Spectroscopy (DRS) shows a red shift in optical energy band gap with increase in cobalt content, along with the presence of transitions in high spin states due to tetrahedrally coordinated cobalt ions. The dielectric characterization explains the disparity in dynamic dielectric parameters like capacitance, dielectric constant, tangent loss, AC conductivity and impedance as a function of frequency. Capacitance and both static and dynamic dielectric constants found to be decreasing with cobalt addition. The anomaly in these pronounced parameters can address the key problems of the material at higher frequencies device operation.

  8. 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...

  9. Processing Effects for Integrated PZT: Residual Stress, Thickness, and Dielectric Properties

    E-print Network

    Sottos, Nancy R.

    Processing Effects for Integrated PZT: Residual Stress, Thickness, and Dielectric Properties Ryan J-Champaign, Urbana, Illinois 61801 Processing effects on the dielectric properties of sol­gel-derived PbZrO3­PbTiO3 composition (Pb (Zr0.53Ti0.47)O3), phase content (perovskite), grain size (B110 nm), crystallographic

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

    SciTech Connect

    Zhu, X. H.; Defaye, E.; Suhm, A.; Fribourg-Blanc, E.; Aied, M.; Zhu, J. L.; Xiao, D. Q.; Zhu, J. G.

    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.

  11. Large dielectric permittivity and possible correlation between magnetic and dielectric properties in bulk BaFeO{sub 3??}

    SciTech Connect

    Sagdeo, Archna; Gautam, Kamini; Singh, M. N.; Sinha, A. K.; Ghosh, Haranath; Ganguli, Tapas; Chakrabarti, Aparna; Sagdeo, P. R.; Gupta, S. M.; Nigam, A. K.; Rawat, Rajeev

    2014-07-28

    We report structural, magnetic, and dielectric properties of oxygen deficient hexagonal BaFeO{sub 3??}. A large dielectric permittivity comparable to that of other semiconducting oxides is observed in BaFeO{sub 3??}. Magnetization measurements indicate magnetic inhomogeneity and the system shows a paramagnetic to antiferromagnetic transition at ?160?K. Remarkably, the temperature, at which paramagnetic to antiferromagnetic transition occurs, around this temperature, a huge drop in the dissipation factor takes place and resistivity shoots up; this indicates the possible correlation among magnetic and dielectric properties. First principle simulations reveal that some of these behaviors may be explained in terms of many body electron correlation effect in the presence of oxygen vacancy present in BaFeO{sub 3??} indicating its importance in both fundamental science as well as in applications.

  12. 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.

  13. Characterization of concrete properties from dielectric properties using ground penetrating radar

    SciTech Connect

    Lai, W.L.; Kou, S.C.; Tsang, W.F.; Poon, C.S.

    2009-08-15

    This paper presents the experimental results of a study of the relationships between light-weight (LWAC) and normal aggregate concrete (NAC) properties, as well as radar wave properties that are derived by using ground penetrating radar (GPR). The former (LWAC) refers to compressive strength, apparent porosity and saturated density, while the latter (NAC) refers to real part of dielectric permittivity ({epsilon}' or real permittivity) and wave energy level (E). Throughout the test period of the newly cast concrete cured for 90 days, the above mentioned material properties gradually changed which can be attributed to the effects of cement hydration, different types of aggregates and initial water to binder ratios. A number of plots describing various properties of concrete such as dielectric, strength and porosity perspectives were established. From these plots, we compare the characteristics of how much and how fast free water was turned to absorbed water in LWAC and NAC. The underlying mechanisms and a mechanistic model are then developed.

  14. Magnetic and dielectric properties of 3Y-TZP/strontium doped barium ferrite composite

    NASA Astrophysics Data System (ADS)

    Zhang, Chao; Wang, Shan-Shan; Guo, Rui-Song; Cai, Guang-Lan; Guo, Wei-Na; Wu, Chen

    2015-02-01

    Magnetic and dielectric properties of 3Y-TZP/20 wt.% Ba1-xSrxFe12O19 (x = 0, 0.25, 0.5, 0.75) composites prepared by solid state reaction method are investigated. The magnetic properties are improved in the composites with the strontium doped barium ferrite. When x = 0.25, the saturation magnetization of the ferrite reaches the maximum. This is due to the migration of Fe3+ induced by the Sr2+ doping. The dielectric properties are also improved in the composite with the strontium doped barium ferrite. When x = 0.5, the dielectric constant and dielectric loss possess the maximum. This is caused by the lattice distortion resulting from the Sr2+ doping. The dielectric properties are analyzed by the universal relaxation law.

  15. Dielectric Properties of Vesta's Surface as Constrained by Dawn VIR Observations

    E-print Network

    Palmer, Elizabeth M; Capria, Maria Teresa; Tosi, Federico

    2015-01-01

    Earth and orbital based radar observations of asteroids provide a unique opportunity to characterize surface roughness and the dielectric properties of their surfaces, as well as potentially explore some of their shallow subsurface physical properties. If the dielectric and topographic properties of asteroid's surfaces are defined, we can constrain their textural characteristics as well as potential subsurface volatile enrichment using the observed radar backscatter. To achieve this objective, we establish the first dielectric model of asteroid Vesta for the case of a dry, volatile-poor regolith -- employing an analogy to the dielectric properties of lunar regolith, and adjusted for the surface densities and temperatures deduced from Dawn's Visible and InfraRed mapping spectrometer (VIR). Our model suggests that the dielectric constant at the surface of Vesta is relatively constant, ranging from 2.0 to 2.1 from the night- to day-side of Vesta, while the loss tangent shows slight variation as a function of diu...

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

    SciTech Connect

    Zuo, X. Z.; Yang, J. Yuan, B.; Tang, X. W.; Zhang, K. J.; Zhu, X. B.; Song, W. H.; Dai, J. M.; Song, D. P.; Sun, Y. P.

    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.

  18. Local Electronic And Dielectric Properties at Nanosized Interfaces

    SciTech Connect

    Bonnell, Dawn A.

    2015-02-23

    Final Report to the Department of Energy for period 6/1/2000 to 11/30/2014 for Grant # DE-FG02-00ER45813-A000 to the University of Pennsylvania Local Electronic And Dielectric Properties at Nanosized Interfaces PI: Dawn Bonnell The behavior of grain boundaries and interfaces has been a focus of fundamental research for decades because variations of structure and composition at interfaces dictate mechanical, electrical, optical and dielectric properties in solids. Similarly, the consequence of atomic and electronic structures of surfaces to chemical and physical interactions are critical due to their implications to catalysis and device fabrication. Increasing fundamental understanding of surfaces and interfaces has materially advanced technologies that directly bear on energy considerations. Currently, exciting developments in materials processing are enabling creative new electrical, optical and chemical device configurations. Controlled synthesis of nanoparticles, semiconducting nanowires and nanorods, optical quantum dots, etc. along with a range of strategies for assembling and patterning nanostructures portend the viability of new devices that have the potential to significantly impact the energy landscape. As devices become smaller the impact of interfaces and surfaces grows geometrically. As with other nanoscale phenomena, small interfaces do not exhibit the same properties as do large interfaces. The size dependence of interface properties had not been explored and understanding at the most fundamental level is necessary to the advancement of nanostructured devices. An equally important factor in the behavior of interfaces in devices is the ability to examine the interfaces under realistic conditions. For example, interfaces and boundaries dictate the behavior of oxide fuel cells which operate at extremely high temperatures in dynamic high pressure chemical environments. These conditions preclude the characterization of local properties during fuel cell operation. The objective of this research was to determine the size and interface atomic structure dependence of the electronic properties of metal/oxide interfaces using model materials systems of noble metals on SrTiO3 surfaces; and to develop experimental techniques to probe spatially localized properties under extreme conditions. The outcomes of this research summarized in more detail below include; Discovery of the presence of multiple size dependent transport mechanisms at nanoscale interfaces and determination of the critical size parameter associated with a transition from one to another; Determination of the effect of interface atomic structure and electronic structure at nanoscale interfaces on electronic transport across the interfaces, in particular the role of states associated with under coordinated cations enabling resonant tunneling and/or band bending; Discovery and characterization of size dependent resistive switching at nanoscale interfaces; These advances required the development of a process to produce nanosized contacts with controlled interface orientation over sizes (diameters) ranging from 20-500nm and the determination of the mechanical and electrical parameters for robust and accurate measurement of frequency dependent properties of nanoscale interfaces; Invention of a chamber that enables in situ scanning probe microscopy and spectroscopy at high temperature and reactive gas environments; and First measurement of interface properties in an operating solid oxide fuel cell, quantifying the local electrical potentials and energies associated with two reaction mechanisms.

  19. 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.

  20. Excellent dielectric properties of polymer composites based on core-shell structured carbon/silica nanohybrid

    NASA Astrophysics Data System (ADS)

    Lei, Tuo; Xue, Qingzhong; Chu, Liangyong; Han, Zhide; Sun, Jin; Xia, Fujun; Zhang, Zhongyang; Guo, Qikai

    2013-07-01

    Polymer based composites with high dielectric constant and low dielectric loss were fabricated by dispersing core-shell structured carbon/silica nanohybrid (CS) into a poly (vinylidene fluoride) (PVDF) matrix. Due to the high conductive carbon core, nonconductive silica shell and the good dispersion of the CS fillers in PVDF, the CS/PVDF composites exhibited better dielectric properties than most nano-carbon materials/polymer composites. These experimental results can be understood by the percolation theory and microcapacitor model. Our strategy provides a pathway to achieve nano-carbon materials/polymer composites with good dielectric performances.

  1. Some simple explicit results for the elastic dielectric properties and stability of layered composites

    E-print Network

    Lopez-Pamies, Oscar

    dielectric composites with anisotropic microstructures, ranging from the choice of invariants to describeSome simple explicit results for the elastic dielectric properties and stability of layered composites Stephen A. Spinelli, Oscar Lopez-Pamies Department of Civil and Environmental Engineering

  2. A broad spectrum analysis of the dielectric properties of poly(2-hydroxyethyl methacrylate)

    E-print Network

    Harmon, Julie P.

    A broad spectrum analysis of the dielectric properties of poly(2-hydroxyethyl methacrylate) K response of the sub-Tg g transition of PHEMA has been widely studied before but little to no DEA data above 50 8C is present in the literature. In this study the dielectric spectrum is presented up

  3. TEMPERATURE-DEPENDENT BEHAVIOR OF MICROWAVE DIELECTRIC PROPERTIES OF BOUND WATER IN GRAIN AND SEED

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dielectric behavior of bound water in grain and seed was investigated through measurement of the dielectric properties at microwave frequencies over a wide temperature range between –70 degrees Celsius and +21 degrees Celsius. Samples of wheat and soybeans were cooled to –70 degrees Celsius and the...

  4. Intrinsic dielectric properties and charge transport in oligomers of organic semiconductor copper phthalocyanine

    E-print Network

    Bobnar, Vid

    Intrinsic dielectric properties and charge transport in oligomers of organic semiconductor copper in the experimentally detected dielectric response of organic semi- conductor copper phthalocyanine. While a giant these compounds are among the most interesting organic semiconductors, mainly due to their high chemical stability

  5. The dielectric properties of the diamond-like films grown by ion-plasma method

    NASA Astrophysics Data System (ADS)

    Brozdnichenko, A. N.; Dolgintsev, D. M.; Castro, R. A.

    2014-12-01

    Diamond-like films was deposited by ion-plasma method in impulse mode. The dielectric properties of the diamond-like films in the frequency of 10-1 - 106 Hz at room temperature were studied. The dispersion of the dielectric parameters indicates the existence of non-Debye relaxation mechanism correlates with structural changes. The charge transfer is temperature activated hopping process.

  6. Dielectric Properties of Uncooked Chicken Breast Muscles from 10 to 1800 MHz

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The dielectric properties, consisting of the dielectric constant and loss factor, were measured (by using an open-ended coaxial-line probe) for uncooked chicken breast muscle Pectoralis major and Pectoralis minor, deboned at 2 and 24 h postmortem, over the frequency range from 10 to 1800 MHz at tem...

  7. Dielectric properties of almond shells in the development of radio frequency and microwave pasteurization

    Technology Transfer Automated Retrieval System (TEKTRAN)

    To develop pasteurization treatments based on radio frequency (RF) or microwave energy, dielectric properties of almond shells were determined using an open-ended coaxial-probe with an impedance analyzer over a frequency range of 10 to 1800 MHz. Both the dielectric constant and loss factor of almond...

  8. Dielectric properties modelling of cellular structures with PDMS for micro-sensor applications

    NASA Astrophysics Data System (ADS)

    Kachroudi, Achraf; Basrour, Skandar; Rufer, Libor; Sylvestre, Alain; Jomni, Fathi

    2015-12-01

    Electro-active polymers are emerging in the fields of actuators and micro-sensors because their good dielectric and mechanical properties makes them suitable for such applications. In this work, we focus on micro-structured (cellular) polymer materials (referred as piezoelectrets or ferroelectrets) that need prior charging to attain piezoelectric behaviour. The development of such applications requires an in-depth knowledge of the intrinsic dielectric properties of such structures and models to enable the accurate prediction of a given micro-structured material’s dielectric properties. Various polymers including polypropylene, polytetrafluoroethylene, fluoroethylenepropylene, cyclo-olefines and poly(ethylene terephthalate) in a cellular form have been studied by researchers over the last fifteen years. However, there is still a lack of information on the intrinsic dielectric properties of the most recently used dielectric polymer (polydimethylsiloxane, PDMS) over wide frequency and temperature ranges. In this work, we shall propose an exhaustive equivalent electrical circuit model and explain how it can be used to predict the micro-structured PDMS complex permittivity versus frequency and temperature. The results obtained from the model were found to be in good agreement with experimental data for various micro-structured PDMS materials. Typically, for micro-sensor applications, the dielectric constant and dielectric losses are key factors which need to be minimized. We have developed a configuration which enables both to be strongly reduced with a reduction of 16% in the dielectric constant of a micro-structured PDMS compared with the bulk material. In addition, the phenomena responsible for dielectric losses variations with frequency and temperature are discussed and correlated with the theoretical model. Our model is thus proved to be a powerful tool for the control of the dielectric properties of micro-structured PDMS material for micro-sensor applications.

  9. Synthesis, characterization and dielectric properties of SnO2 thin films.

    PubMed

    Y?ld?r?m, M Ali; Y?ld?r?m, Sümeyra Tuna; Sakar, Emine Fedakar; Ate?, Aytunç

    2014-12-10

    SnO2 thin films have been grown on glass substrates using Successive Ionic Layer Adsorption and Reaction (SILAR) method at room temperature and ambient pressure. The annealing temperature effect on the structural, morphological, optical and electrical properties of SnO2 thin films has been investigated. The X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) studies have showed that all the films have exhibited polycrystalline nature with tetragonal structure and have been covered well on glass substrates. The crystalline and surface properties of the films have improved with increasing annealing temperature. The band gap values have been changed from 3.73 to 3.66eV depending on the annealing temperature. The refractive index (n), optical static and high frequency dielectric constants (?o, ??) values have been calculated as a function of the annealing temperature. The resistivity values of the films have changed between 10(-1) - 10(-3)?cm with annealing temperature and light at room temperature. PMID:24929316

  10. Synthesis, characterization and dielectric properties of SnO2 thin films

    NASA Astrophysics Data System (ADS)

    Y?ld?r?m, M. Ali; Y?ld?r?m, Sümeyra Tuna; Sakar, Emine Fedakar; Ate?, Aytunç

    2014-12-01

    SnO2 thin films have been grown on glass substrates using Successive Ionic Layer Adsorption and Reaction (SILAR) method at room temperature and ambient pressure. The annealing temperature effect on the structural, morphological, optical and electrical properties of SnO2 thin films has been investigated. The X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) studies have showed that all the films have exhibited polycrystalline nature with tetragonal structure and have been covered well on glass substrates. The crystalline and surface properties of the films have improved with increasing annealing temperature. The band gap values have been changed from 3.73 to 3.66 eV depending on the annealing temperature. The refractive index (n), optical static and high frequency dielectric constants (?o, ??) values have been calculated as a function of the annealing temperature. The resistivity values of the films have changed between 10-1 - 10-3 ? cm with annealing temperature and light at room temperature.

  11. 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.

  12. The influence of charged-induced variations in the local permittivity on the static and dynamic properties of polyelectrolyte solutions

    E-print Network

    Florian Fahrenberger; Owen A. Hickey; Jens Smiatek; Christian Holm

    2015-08-27

    There is a large body of literature investigating the static and dynamic properties of polyelectrolytes due both to their widespread application in industrial processes and their ubiquitous presence in biology. Because of their highly charged nature, polyelectrolytes tend to alter the local dielectric permittivity of the solution within a few nanometers of their backbone. This effect has, however, been almost entirely ignored in both simulations and theoretical work. In this article we apply our recently developed electrostatic solver based on Maxwell's equations to examine the effects of the permittivity reduction in the vicinity of the polyelectrolyte. We first verify our new approach by calculating and comparing ion distributions around a linear fixed polyelectrolyte and find both quantitative and qualitative changes in the ion distribution. Further simulations with an applied electric field show that the reduction in the local dielectric constant increases the mobility of the chains by approximately ten percent. More importantly, variations in the local dielectric constant lead to qualitatively different behavior of the conductivity.

  13. Structural, conductivity and dielectric properties of Li2SO4

    NASA Astrophysics Data System (ADS)

    Rama Rao, Samudrala; Bheema Lingam, Chittari; Rajesh, Desapogu; Pandu Vijayalakshmi, Raguru; Shamanna Sunandana, Channappayya

    2014-06-01

    Li2SO4 have been synthesized from lithium sulphate monohydrate by melting at 880 °C and slow cooling. The XRD results indicates that the melt cooled Li2SO4 is crystallized to monoclinic structure. The AC conductivity (?ac) and dielectric relaxation (tan ?) have been measured within the temperature range 170-250 °C and frequency range 100 Hz-120 kHz, respectively. The DC conductivities are conveniently extracted from ?ac (typical values ˜2 × 10-7 and ˜2 × 10-6 S/cm at 200 and 250 °C, respectively) and are fitted to linear Arrhenius plot. The slope of this linear plot leads to an activation energy of 1.10 eV. It is found that the conduction in Li2SO4 is mainly through Li+. Further, we carried out first principles calculations and obtained the structural and bonding properties of Li2SO4. From band structure, Li2SO4 is found to be a wide band gap insulator with a band gap of 6.1 eV. The partial density of states reveals the finite states of Li+ near to Fermi level, which limits its use of full capacity. This indicates a kinetic barrier for Li ions and electrons ambipolar diffusion.

  14. Dielectric Properties of Hydrothermal Nickel-Zinc Ferrites

    NASA Astrophysics Data System (ADS)

    Dias, Anderson; della Santina Mohallem, Nelcy; Luiz Moreira, Roberto

    1996-07-01

    NiZn ferrites were hydrothermally prepared and sintered at different experimental conditions, leading to materials of composition Ni{0.34}Zn{0.60}Fe{2.06}O{4}. An investigation of the dielectric properties over a wide frequency range showed the semiconductor character of the ferrites and the presence of a masked relaxation, revealed after a mathematical treatment. The relaxation was modeled using a Cole-Cole model and the parameters correlated with the microstructural evolution of the ferrites during the sintering. The contributions of hopping electrons and space charges to the total conductivity have been discussed. La méthode hydrothermale a été utilisée pour préparer des poudres de NiZn. Ces matériaux ont été synthétisés sous différentes conditions expérimentales. Après frittage, la composition est Ni{0,34}Zn{0,60}Fe{2,06}O{4}. L'investigation des propriétés diélectriques, sur une large intervalle de fréquence, a démontré le caractère semiconducteur des ferrites et l'existence d'une relaxation masquée, mise en évidence après un traitement mathématique. Cette relaxation a été traitée par un modèle de type Cole-Cole et les paramètres corrélés à l'évolution microstructurale des ferrites, pendant le processus de frittage. Les contributions à la conductivités complexe dues aux électrons (“hopping”) et aux charges d'espace ont été discutées.

  15. MICROWAVE DIELECTRIC PROPERTIES OF GRAIN IN NONEQUILIBRIUM STATE: EFFECT OF MOISTURE AND TEMPERATURE

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dielectric-based sensors for nondestructive and instantaneous determination of moisture content and bulk density in cereal grains are calibrated to predict these physical properties from measurement of the relative complex permittivity. At microwave frequencies, a temperature correction is needed, ...

  16. Experimental Characterization of Dielectric Properties of Clay Materials Under Martian-Like Conditions

    NASA Astrophysics Data System (ADS)

    Colantuono, L.; Baliva, A.; Lauro, S.; Mattei, E.; Marinangeli, L.; Pettinelli, E.; Seu, R.

    2014-07-01

    We analyzed the dielectric properties of natural clays at different frequencies and temperature and water content with a network TDR technique. This study can provide an important support to the interpretation of martian radar data.

  17. 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 ...

  18. 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

  19. Technique for Performing Dielectric Property Measurements at Microwave Frequencies

    NASA Technical Reports Server (NTRS)

    Barmatz, Martin B. (Inventor); Jackson, Henry W. (Inventor)

    2014-01-01

    A method, system, apparatus, and computer readable medium has been provided with the ability to obtain a complex permittivity dielectric or a complex permeability micron of a sample in a cavity. One or more complex-valued resonance frequencies f(sub m) of the cavity, wherein each f(sub m) is a measurement, are obtained. Maxwell's equations are solved exactly for dielectric, and/or micron, using the f(sub m) as known quantities, thereby obtaining the dielectric and/or micron of the sample.

  20. An overview of laminate materials with enhanced dielectric properties

    NASA Astrophysics Data System (ADS)

    Mumby, Stephen J.

    1989-03-01

    This report focuses on laminate materials (resins and reinforcements) having potential applications in the manufacture of multi-layer printed wiring boards (PWBs) that are required to efficiently transmit high-speed digital pulses. It is intended to be a primer and a reference for selection of candidate materials for such high-performance PWBs. Included are dielectric and physical properties, and where available chemical composition and/or structure, commercial availability, compatibility with typical PWB processing schemes and approximate relative cost. Recommendations are made as to the most viable candidate materials for this type of PWB application, based on a comparison of electrical and physical properties together with processing and cost considerations. The cyanate ester resin system appears promising. Such a resin may be reinforced with regular E-glass, or the more newly available S-glass, to produce a laminate useful for intermediate performance applications. For more demanding applications the E-glass will have to be replaced by a material of much lower relative permittivity. The expanded-PTFE reinforced laminates from W. L. Gore appear to be a good choice for these applications. The processing of the Gore materials can be expected to deviate from that used with FR-4 type materials, but is likely to be less problematic than laminates comprised of a fluorinated resin. Processing is a key obstacle to the implementation of any of the new materials herein. If implementation is to be successful, programs must be established to develop and optimize processing procedures. Cost will remain an important issue. However, the higher cost of the new materials may be justified in high-end products by the performance they deliver.

  1. Temporal Effects in Dielectric Properties of Some Antiferroelectric Complex Perovskites

    NASA Astrophysics Data System (ADS)

    Chan, Wai-Hung; Xu, Zheng Kui; Zhai, Jiwei; Chen, Haydn; Colla, Eugene V.

    2003-08-01

    Two complex perovskite antiferroelectric (AFE) systems were studied; they are Pb0.97La0.02(Zr0.6Sn0.3Ti0.1)O3 (PLZST) in ceramic form and Pb0.99Nb0.02(Zr0.82Sn0.12Ti0.04)0.98O3 (PNZST) in thin film form. Dielectric and transmission electron microscopy (TEM) studies of the PLZST ceramics confirmed the AFE nature of the specimen, but at low temperature the electrical field application could induce a temporary ferroelectric (FE) phase with characteristic life-time dependent on temperature This life-time reaches a value of ˜ 0.1s at 248K. Further decrease of temperature leads to a much faster than Arrhenius growth of the recovery time, which eventually exceeds the reasonable laboratory time scale below 210K. We believe that the strongly temperature-dependent kinetics arises from a cooperative freezing of the incommensurate AFE order in the presence of quenched composition disorder. The PNZST films' polarization properties are highly dependent on the film thickness and at the lowest studied limit (˜170 nm) the field application in the surface normal direction can induce the FE phase with the time of recovery back to the AFE state being a magnitude of several hours. In this case the filed-induced FE ordering is very asymmetric with respect to the field direction, is thickness dependent and the FE phase can be induced if the time of field application is on scale of a second. The application of the field for a much shorter time (e.g. 1ms) does not significantly affect the AFE properties of the film. We suggest that the substrate/film interface could be responsible for this phenomenon.

  2. Dielectric properties of Ni-coated BaTiO/sub 3-/PMMA composite.

    PubMed

    Park, Jung Min; Lee, Hee Young; Kim, Jeong-Joo; Park, Eun Tae; Chung, Yul-Kyo

    2008-05-01

    Dielectric properties of Ni-coated BaTiO(3)-PMMA (polymethyl methacrylate) composite were studied from an embedded capacitor application viewpoint. Volume loading of up to 50% was attempted, and the results were compared with uncoated BaTiO(3)-PMMA composite. Ni-coating on BaTiO(3) powder was found to greatly improve the dielectric properties of the composite, especially the dielectric constant value. K values of about 100 with temperature-stable X7E characteristics were realized. PMID:18519208

  3. Dielectric refractive index dependence of the focusing properties of a dielectric-cylinder-type decagonal photonic quasicrystal flat lens and its photon localization

    NASA Astrophysics Data System (ADS)

    Liu, Jianjun; Liu, Exian; Fan, Zhigang; Zhang, Xiong

    2015-11-01

    The focusing properties of a dielectric-cylinder-type decagonal photonic quasicrystal flat lens observed at different dielectric refractive indexes are numerically analyzed, showing that, within certain index ranges, the lens can generate images with a resolution below the diffraction limit for a point source. The lens exhibits a double focusing effect within a range of refractive indexes and induces ring photon localization near a certain dielectric refractive index for the point source with the TM mode.

  4. Preparation of barium titanate nanoparticle sphere arrays and their dielectric properties.

    PubMed

    Wada, Satoshi; Yazawa, Aki; Hoshina, Takuya; Kameshima, Yoshikazu; Kakemoto, Hirofumi; Tsurumi, Takaaki; Kuroiwa, Yoshihiro

    2008-09-01

    Barium titanate (BaTiO(3)) nanoparticles from 27 to 192 nm were prepared by the 2-step thermal decomposition method from barium titanyl oxalate nanoparticles. These particles were dispersed well into 1-propanol, and dense BaTiO(3); nanoparticle sphere arrays without stress-field were prepared by the meniscus method. Temperature dependence of dielectric properties was successfully measured using these dense nanoparticle sphere arrays, and size effect on dielectric properties was discussed. PMID:18986885

  5. DIELECTRIC PROPERTIES OF MATERIALS AND RELATED AGRICULTURAL APPLICATIONS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Potential Agricultural applications for RF and microwave energy include selective dielectric heating of insects in grain, treatment of seed to improve germination, and conditioning of products to improve nutritional value and shelf life. Measurement applications include permittivity-density relatio...

  6. Microstructure Study For Optimization Of Dielectric Property Of Electrical Porcelain

    SciTech Connect

    Tak, S. K.; Shekhawat, M. S.; Mangal, R.

    2010-06-29

    Five sample mixtures of kaolin, ball clay, feldspar and Quartz were formulated and porcelain samples fabricated. Crystalline phases and mullite morphology were studied using XRD and SEM respectively. A composition of 30% kaolin, 15% ball clay, 30% feldspar and 25% quartz yielded a body with high dielectric strength of 19 kV/mm compare to an ISO graded product having dielectric strength 14.6 KV/mm after firing at 1225 deg. C.

  7. Microstructure Study For Optimization Of Dielectric Property Of Electrical Porcelain

    NASA Astrophysics Data System (ADS)

    Tak, S. K.; Shekhawat, M. S.; Mangal, R.

    2010-06-01

    Five sample mixtures of kaolin, ball clay, feldspar and Quartz were formulated and porcelain samples fabricated. Crystalline phases and mullite morphology were studied using XRD and SEM respectively. A composition of 30% kaolin, 15% ball clay, 30% feldspar and 25% quartz yielded a body with high dielectric strength of 19kV/mm compare to an ISO graded product having dielectric strength 14.6 KV/mm after firing at 1225°C.

  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. Improved gas sensing and dielectric properties of Fe doped hydroxyapatite thick films: Effect of molar concentrations

    SciTech Connect

    Mene, Ravindra U.; Mahabole, Megha P.; Mohite, K.C.; Khairnar, Rajendra S.

    2014-02-01

    Highlights: • We report improved gas sensing and dielectric characteristics of Fe ion exchanged HAp films. • Fe doped HAp film shows maximum gas response at relatively lower temperature. • Response and gas uptake capacity of sensors is improved for appropriate amount of Fe ions in HAp matrix. • Fe-HAp films exhibit remarkable improvement in dielectric properties compared to pure HAp. • Fe doped HAp films show significant improvement in gas sensing as well as in dielectric properties. - Abstract: In the present work Fe doped hydroxyapatite (Fe-HAp) thick films has been successfully utilized to improve the gas sensing as well as its dielectric properties. Initially, HAp nano powder is synthesized by chemical precipitation process and later on Fe ions are doped in HAp by ion exchange process. Structural and morphological modifications are observed by means of X-ray diffraction and scanning electron microscopy analysis. The sensing parameters such as operating temperature, response/recovery time and gas uptake capacity are experimentally determined. The Fe-HAp (0.05 M) film shows improved CO and CO{sub 2} gas sensing capacity at lower operating temperature compared to pure HAp. Moreover, variation of dielectric constant and dielectric loss for pure and Fe-HAp thick films are studied as a function of frequency in the range of 10 Hz–1 MHz. The study reveals that Fe doped HAp thick films improve the sensing and dielectric characteristics as compared to pure HAp.

  10. Dielectric Properties of Live Yeast Cells Expressed with the Motor Protein Prestin

    NASA Astrophysics Data System (ADS)

    Miller, John; Pereira, Fred

    2005-03-01

    We report on the linear and nonlinear dielectric properties of budding yeast (S. cerevisiae) cells, one strain of which has been genetically modified to express prestin. This motor protein plays a crucial role in the large electromotility exhibited by the outer hair cells (OHCs) of mammalian inner ears. Live cell suspensions exhibit enormous dielectric responses, which can be used to probe metabolic activity, membrane potential, and other properties. We observe a broad peak, centered around 20 kHz, in the normalized difference in dielectric responses between the two strains, and also observe substantial differences in nonlinear harmonic responses. Our data appears to correlate with measurements showing piezoelectric resonances in OHCs. These results suggest that dielectric probes can be used to study the electrical properties of prestin and other proteins, either expressed in live cells or (from our other recent studies on tubulin) as pure protein suspensions.

  11. Electromechanical and relaxation dielectric properties of RbHSO4 crystal

    NASA Astrophysics Data System (ADS)

    Zachek, I. R.; Shchur, Ya.; Levitskii, R. R.

    2015-12-01

    The temperature dependence of static and dynamic dielectric permittivity, piezoelectric stresses, elastic constants and heat capacity of ferroelectric RbHSO4 are described based on the four-sublattice pseudo-spin model within the mean field approximation. The pseudo-spins are ascribed to SO4(1f) (f = 1, …, 4) groups which have the dynamic dipole moment in paraelectric phase and manifest a static distortion in ferroelectric phase. We established a set of adjustable model parameters which made it possible to interpret various experimental data.

  12. Structural Behavior of Alcohol-1,4-Dioxane Mixtures through Dielectric Properties Using TDR

    NASA Astrophysics Data System (ADS)

    Kumbharkhane, Ashok C.; Shinde, M. N.; Mehrotra, Suresh C.; Oshiki, Noriaki; Shinyashiki, Naoki; Yagihara, Shin; Sudo, Seiichi

    2009-08-01

    The values of complex permittivity for alcohol-1,4-dioxane (DX) mixtures with various concentrations have been determined in the frequency range 10 MHz to 20 GHz using the time domain reflectometry (TDR) method. Numbers of hydrogen bonds between alcohol-alcohol and alcohol-dioxane pairs are estimated from the values of the static dielectric constant by using the Luzar model. The model provides a satisfactory explanation of the experimental results related to the static dielectric constant. The binding energies for alcohol-alcohol (pair 11) and alcohol-DX (pair 12) are estimated to be -13.98 and -16.25 kJ/mol, respectively. The results have also been compared with previous results of the ethyleneglycol-DX system.

  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. 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.

  15. Analysis of the dielectric properties of trunk wood in dominant conifer species from New England and Siberia

    NASA Technical Reports Server (NTRS)

    Ranson, K. J.; Rock, B. N.; Salas, W. A.; Smith, K.; Williams, D. L.

    1992-01-01

    Data were collected for dominant conifer species. Dielectric properties of trunk wood were measured using a C-band dielectric probe. For certain specimens, electrical resistance was also measured using a shigometer. The water status of the trees studies was determined either by use of a Scholander pressure chamber on branch samples collected simultaneously with dielectric measurements or by fresh-weight/dry-weight assessment of wood core samples extracted and analyzed with the dielectric probe and shigometer. Diurnal delectric properties and xylem water column tension are inversely correlated such that real and imaginary dielectric values drop as tension increases. The dielectric properties were positively correlated with wood core moisture content while electrical resistance was poorly correlated with wood core moisture content in one species studied. Results support the view that dielectric properties are strongly correlated with moisture status in trunk wood, and possibly ion concentrations associated with decay processes in damaged specimens.

  16. Diurnal effect of water stress on the dielectric properties of corn

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    Microwave emission and backscatter of vegetated surfaces are influenced by the vegetation dielectric constant, a function of vegetation water content. In turn, the vegetation water content varies depending on the availability of moisture in the root zone. Understanding the variation in vegetation dielectric properties in response to root zone water availability could improve soil moisture retrievals using microwaves above vegetated areas. Here we present a unique dataset of leaf dielectric properties collected during a two month field campaign in Citra (Florida, USA). In-vivo dielectric property measurements were conducted on three corn leaves at various heights. Destructive sampling was used to determine vegetation water content. Water stress was quantified by calculating the evaporation deficit of the corn field and by monitoring the soil water tension. We will present results illustrating the influence of the observed increase in water stress on the vegetation water content and leaf dielectric properties. Simulations using the water-cloud model demonstrate the impact of the changes in vegetation water content on radar backscatter at different frequencies and polarizations. The dielectric measurements revealed the complex diurnal response of vegetation to water stress and highlight the potential for vegetation and soil water status monitoring using microwave remote sensing.

  17. 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.

  18. Dielectric properties of multiatomic alcohols: 1,4-butanediol

    NASA Astrophysics Data System (ADS)

    Zhuravlev, V. I.

    2015-12-01

    The dielectric spectra of 1,4-butanediol in the temperature range of 298-423 K are analyzed using the theoretical approaches of Debye, Davidson-Cole, and Forsman, based on the Dissado-Hill theory. It is shown that the dielectric spectra of 1,4-butanediol are described by the Davidson-Cole equation, and the ?DC parameter has a pronounced strong temperature dependence. In the Debye theory, the spectrum of the dielectric relaxation of 1,4-butanediol is presented as the sum of two region of dispersions. Conclusions are reached as to the possible mechanisms of dispersion responsible for the obtained regions. The relaxation times of 1,4-butanediol calculated using different equations describing the nonlinear behavior of the relaxation time are compared. The dipole moments of clusters are obtained for the first time and a preliminary analysis is performed using the Dissado-Hill cluster model.

  19. Electric and dielectric properties of nanostructured stoichiometric and excess-iron Ni-Zn ferrites

    NASA Astrophysics Data System (ADS)

    Sutka, A.; Mezinskis, G.; Lusis, A.

    2013-02-01

    In this paper, we report a study of the effect of excess iron on structural, microstructural, electric and dielectric properties of the nanostructured Ni-Zn ferrites Ni1-xZnxFe2+zO4-? of different compositions with x = 0, 0.3, 0.5, 0.7, 1 and z = 0, 0.1. The structural and microstructural properties are estimated from x-ray diffraction and atomic force microscopy (AFM) data. The average grain size, evaluated from AFM topographical analysis, is found to be below 70 nm. The samples exhibit low values of dielectric constant and dielectric loss and a high resistivity. Contrary to earlier conclusions regarding microstructured Ni-Zn ferrites, in nanostructured Ni-Zn ferrites sintered at relatively low temperature and duration, the excess of iron in the composition increases the electrical resistivity and reduces the dielectric constant and loss tangent.

  20. Dielectric properties of rat embryo and foetus as a function of gestation

    NASA Astrophysics Data System (ADS)

    Peyman, A.; Gabriel, C.

    2012-04-01

    The dielectric properties of rat embryos/foetuses have been acquired at several stages of gestation at 37 °C and in the frequency range of 40 MHz-20 GHz. Measurements were carried out on homogenized tissues, as trial experiments did not show any systematic difference between the dielectric data of intact and homogenized tissues at microwave frequencies. The results showed that dielectric properties of the foetus are generally higher than adult muscle and brain. The measured data also showed some decline for both permittivity and conductivity as the foetus grew from 18 to 20 days old; however, these changes were not statistically significant. Data were also collected for placenta and amniotic fluid which were in good agreement with those recently obtained from human tissues. Finally, tabulated numerical dielectric data for rat foetal tissues are presented for a wide range of medical and telecommunication frequencies.

  1. First-principles investigation of band offsets and dielectric properties of Silicon-Silicon Nitride interfaces

    NASA Astrophysics Data System (ADS)

    Pham, Tuan Anh; Li, Tianshu; Gygi, Francois; Galli, Giulia

    2011-03-01

    Silicon Nitride (Si3N4) is a possible candidate material to replace or be alloyed with SiO2 to form high-K dielectric films on Si substrates, so as to help prevent leakage currents in modern CMOS transistors. Building on our previous work on dielectric properties of crystalline and amorphous Si3N4 slabs, we present an analysis of the band offsets and dielectric properties of crystalline-Si/amorphous Si3N4 interfaces based on first principles calculations. We discuss shortcomings of the conventional bulk-plus line up approach in band offset calculations for systems with an amorphous component, and we present the results of band offsets obtained from calculations of local density of states. Finally, we describe the role of bonding configurations in determining band edges and dielectric constants at the interface. We acknowledge financial support from Intel Corporation.

  2. Grain size effect on magnetic and dielectric properties of hexagonal YbMnO3 nanoparticles

    NASA Astrophysics Data System (ADS)

    Han, Tai-Chun; Hsu, Hsin-Kai; Chu, Yih-Tsyr; Hu, Yu-Min

    2015-05-01

    We have synthesized a series of YbMnO3 nanoparticles with different grain sizes (25-450 nm) and study the effect of grain size on their structural, magnetic, and dielectric properties. The YbMnO3 nanoparticles crystallized in hexagonal perovskite-type structure. It shows that magnetic and dielectric properties are strongly dependent on the grain size. The magnetic characterization indicates that with increasing grain size, the antiferromagnetic (AFM) transition temperature increases from 70 to 86 K. A corresponding shift in the peak-positions of dielectric anomaly and AFM transition temperature is observed, indicating a strong correlation between the magnetic ordering and the electric polarization. As evidenced by the variation in the ab-plane lattice parameters and Mn-O bond lengths, the AFM interactions and dielectric anomalies of YbMnO3 can be effectively modulated by varying grain size.

  3. Dielectric property measurement of zirconia fibers at high temperatures

    SciTech Connect

    Vogt, G.J.; Tinga, W.R.; Plovnick, R.H.

    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.

  4. 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.

  5. Fluorinated polymides for interlayer dielectric applications: Tailoring of properties via copolymerization

    SciTech Connect

    Auman, B.C.; McKerrow, A.J.; Ho, P.S.

    1996-10-01

    Over the past several years DuPont has been exploring new, rod-like fluorinated polyimides for interlayer dielectric (ILD) applications. It has been shown that copolymerization is a versatile method for tailoring properties of these rigid polyimides. Initial product offerings from DuPont showed an excellent balance of properties for ILD applications. These materials, however, due to their highly rod-like structure and very low in-plane coefficient of thermal expansion (CTE), actually yielded negative thermal stresses on silicon at the 1 {mu}m thicknesses typical of interlayer dielectrics. More flexible materials with higher CTE typically yield positive stress values which can be undesirably quite high. The dielectric constant of these highly rod-like fluorinated polyimides was also somewhat anisotropic, again due to the rod-like nature and resulting high in-plane orientation of these polyimides. Since a thermal stress on silicon near zero and a more isotropic dielectric constant are likely the most desirable states for an ILD, the highly rod-like polyimide was further optimized by incorporation of a more flexible fluorinated comonomer, 6FDA, at various levels to increase CTE and balance dielectric constant. The various properties of this series of fluorinated polyimides were investigated. The results have shown that it is indeed possible to obtain near zero stress on silicon while attaining more isotropic dielectric constant via structure optimization.

  6. Perturbative no-hair property of form fields for higher dimensional static black holes

    SciTech Connect

    Shiromizu, Tetsuya; Ohashi, Seiju; Tanabe, Kentaro

    2011-04-15

    In this paper we examine the static perturbation of p-form field strengths around higher dimensional Schwarzschild spacetimes. As a result, we can see that the static perturbations do not exist when p{>=}3. This result supports the no-hair properties of p-form fields. However, this does not exclude the presence of the black objects having nonspherical topology.

  7. Photonic properties of two-dimensional photonic crystals based on monolayer of dielectric microspheres

    NASA Astrophysics Data System (ADS)

    Ayenew, Getachew T.; Chakaroun, Mahmoud; Fabre, Nathalie; Solard, Jean; Fischer, Alexis; Chen, Chii-Chang; Boudrioua, Azzedine; Chan, Chia-Hua

    2012-04-01

    The optical properties of two-dimensional (2D) photonic crystal (PhC) slabs based on self-assembled monolayer of dielectric microspheres are studied. The in-plane transmission spectra of 2D array of dielectric spheres with triangular lattice are investigated using the finite-difference-time-domain (FDTD) method. The structures studied are monolayer of dielectric spheres infiltrated with air ('opals') and air spheres infiltrated with dielectric material ('inverse opals'), with glass substrate sustaining the monolayer of spheres. The transmission spectra are calculated for different values of refractive index contrasts between the spheres and the infiltrated material and for different values of filling fractions (compactness of the spheres). As the refractive index is varied, compact spheres are assumed; and as the filling fraction is varied, the refractive index of the dielectric spheres or the dielectric matrix is fixed to be 2.5. For compact opal structure on glass substrate, a narrow photonic band gap (PBG) is observed in the transmission spectra for dielectric spheres with refractive index higher than around 1.9. When the refractive index is fixed at 2.5, the PBG is observed for more compact spherical arrangement and disappears for more separated spheres. While for inverse opal structure on glass substrate, using non-compact spheres enlarges the width of PBG which is not observed for compact spherical arrangement. The application of the study is to realize organic PhC microcavity laser.

  8. 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.

  9. Improving the Dielectric Properties of Ethylene-Glycol Alkanethiol Self-Assembled Monolayers

    PubMed Central

    2014-01-01

    Self-assembled monolayers (SAMs) can be formed at the interface between solids and fluids, and are often used to modify the surface properties of the solid. One of the most widely employed SAM systems is exploiting thiol-gold chemistry, which, together with alkane-chain-based molecules, provides a reliable way of SAM formation to modify the surface properties of electrodes. Oligo ethylene-glycol (OEG) terminated alkanethiol monolayers have shown excellent antifouling properties and have been used extensively for the coating of biosensor electrodes to minimize nonspecific binding. Here, we report the investigation of the dielectric properties of COOH-capped OEG monolayers and demonstrate a strategy to improve the dielectric properties significantly by mixing the OEG SAM with small concentrations of 11-mercaptoundecanol (MUD). The monolayer properties and composition were characterized by means of impedance spectroscopy, water contact angle, ellipsometry and X-ray photoelectron spectroscopy. An equivalent circuit model is proposed to interpret the EIS data and to determine the conductivity of the monolayer. We find that for increasing MUD concentrations up to about 5% the resistivity of the SAM steadily increases, which together with a considerable decrease of the phase of the impedance, demonstrates significantly improved dielectric properties of the monolayer. Such monolayers will find widespread use in applications which depend critically on good dielectric properties such as capacitive biosensor. PMID:24447311

  10. ON THE INFLUENCE OF MOISTURE ON DIELECTRIC PROPERTIES OF POLYETHERETHERKETONE (PEEK) CARBON-FIBER COMPOSITES

    EPA Science Inventory

    An analysis of local and global mechanisms of heat generation and distribution in carbon-fiber-based composites subjected to an alternating magnetic field has shown that heating is dependent upon the dielectric properties of the polymer matrix. These properties were investigated ...

  11. Millimeter-Wave Dielectric Properties of Single Crystal Ferroelectric and Dielectric Materials

    SciTech Connect

    McCloy, John S.; Korolev, Konstantin A.; Li, Zijing; Afsar, Mohammed N.; Sundaram, S. K.

    2011-01-03

    Transmittance measurements on various single crystal ferroelectric materials over a broad millimeter-wave frequency range have been performed. Frequency dependence of the complex dielectric permittivity has been determined in the millimeter wave region for the first time. The measurements have been employed using a free-space quasi-optical millimeter-wave spectrometer equipped with a set of high power backward wave oscillators (BWOs) as sources of coherent radiation, tunable in the range from 30 - 120 GHz. The uncertainties and possible sources of instrumentation and measurement errors related to the free-space millimeter-wave technique are discussed. This work has demonstrated that precise MMW permittivities can be obtained even on small thin crystals using the BWO quasi-optical approach.

  12. Dielectric properties of glassy disaccharides for electromagnetic interference shielding application

    NASA Astrophysics Data System (ADS)

    Wlodarczyk, P.; Hawelek, L.; Paluch, M.; Wlodarczyk, A.; Wojnarowska, Z.; Kolano-Burian, A.

    2015-11-01

    Three amorphous disaccharides (sucrose, trehalose, and lactulose) and their mixtures were studied in order to evaluate their ability to absorb a high frequency (>1 MHz) electromagnetic wave. The materials were characterized by a dielectric loss tangent. It was found out that the highest tan(?) value is observed in pure amorphous sucrose (tan(?) = 0.17 at f = 1 MHz at T = 293 K). Moreover, the best Tg/tan(?) ratio is observed in binary mixtures of sucrose and trehalose. A high glass transition temperature is advantageous as it increases operational temperatures of the material. The high tangent delta in microwave frequencies of sugars is connected with the mobility of sugar groups (possibly -CH2OH). The energy of the electromagnetic wave is converted into rotational movements of side groups and in consequence it is dissipated in the form of heat. It was proven that the polar low molecular glasses such as sugars may form dielectric components of composite microwave absorbers.

  13. 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

  14. Dielectric properties of wheat flour mixed with oat meal

    NASA Astrophysics Data System (ADS)

    ?uczycka, D.; Czubaszek, A.; Fujarczuk, M.; Pruski, K.

    2013-03-01

    Possibilities of using electric methods for determining admixtures of oat meal to wheat flour, type 650 are presented. In wheat flour, oat meal and mixtures containing 10, 20 and 30% of the oat meal, moisture, protein, starch and ash content, sedimentation value, yield and softening of wet gluten were determined. In samples containing 0, 5, 10, 15, 20, 25, 30 and 100% of oat meal, the dielectric loss factor and conductivity were determined using an impedance analyzer for electromagnetic field frequency ranging from 0.1-20 kHz. It was found that the dielectric loss factor varied for tested material. The best distinguishing between tested mixtures was obtained at the measuring electromagnetic field frequency of 20 kHz. The loss factor was significantly correlated with the yield of wet gluten and the sedimentation value, parameters indicating the amount and quality of gluten proteins in flour.

  15. 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.

  16. Functional group dependent dielectric properties of sulfated hydrocolloids extracted from green macroalgal biomass.

    PubMed

    Tsubaki, Shuntaro; Hiraoka, Masanori; Hadano, Shingo; Nishimura, Hiroshi; Kashimura, Keiichiro; Mitani, Tomohiko

    2014-07-17

    Dielectric properties of aqueous solutions of sulfated hydrocolloids (ulvan and rhamnan sulfate) extracted from green macroalgal biomass were studied in a frequency range of 100 MHz-10 GHz. Counterion exchange of native hydrocolloids (mixture of Na(+), Mg(2+) and Ca(2+)) to H(+)-form showed significant increase in loss factor due to ionic conduction. On the other hand, desulfations decreased their loss factors. The results suggested that ionic conduction of H(+) has significant contribution to loss factors. Additionally, H(+)-form hydrocolloids showed significant improvement in hydration, which might also affect the dielectric property of the solution by reducing the amount of free water. The viscosity, however, did not show apparent relevance with the dielectric property. PMID:24702935

  17. Microwave Dielectric Properties of (Ca1-xSrx)SiO3 Ring Silicate Solid Solutions

    NASA Astrophysics Data System (ADS)

    Kagomiya, Isao; Suzuki, Itaru; Ohsato, Hitoshi

    2009-09-01

    The microwave dielectric properties of ?-CaSiO3 and SrSiO3 synthesized by a solid-state reaction were ?r = 6.82, Qf = 42,200 GHz, ?f = -18.9 ppm/°C and ?r = 6.78, Qf = 13,100 GHz, ?f = -65.9 ppm/°C, respectively. (Ca1-xSrx)SiO3 solid-solution series were also synthesized by a solid-state reaction and their microwave dielectric properties were examined. Two structural-type solid solutions were formed in wide range of x = 0 to 0.4 and 0.6 to 1.0. Good microwave dielectric properties with ?r = 6.62, Qf = 66,700 GHz, and ?f = -40 ppm/°C were obtained with x = 0.8 of the (Ca1-xSrx)SiO3 series.

  18. Dielectric properties of wood from 2 to 3 GHz.

    PubMed

    Olmi, R; Bini, M; Ignesti, A; Riminesi, C

    2000-01-01

    Many applications of microwave energy to wooden materials have been developed in the last few decades, both for treatment and for diagnostic purposes. All these applications require a reliable estimation of the permittivity of the wood species of interest, which is the physical parameter of crucial importance in the absorption of electromagnetic energy. This paper presents results obtained in the dielectric characterization of five wood species in the frequency range from 2 to 3 GHz, including the ISM frequency of 2.45 GHz. Permittivity was measured by an open-ended coaxial-line probe of new design on wood samples conditioned at several moisture levels. The influence of the natural variability of wood characteristics on the measured permittivity was also investigated by a suitable experimental setup consisting of a poplar table including both sapwood and heartwood regions. Finally, a theoretical discussion on the meaning of a scalar measurement on anisotropic dielectrics is conducted in terms of an isotropic-equivalent permittivity, which is related to the permittivity tensor of the dielectric material. PMID:11098438

  19. Dielectric Properties of Titan's Surface using the Cassini RADAR Radiometer

    NASA Astrophysics Data System (ADS)

    Janssen, Michael A.; Paganelli, F.; Lorenz, R. D.; Cassini RADAR Team

    2006-09-01

    The Cassini Radar instrument includes a passive microwave radiometer that operates at 13.78 GHz ( 2.2 cm wavelength). The radiometer has been used to image the calibrated thermal emission from a significant portion of Titan's surface, at resolutions ranging from 5 - 500 km and at a variety of emission angles and polarizations. Interpretation in terms of surface dielectric models yields the following conclusions: 1) Globally, the effective dielectric constant of the surface is 2 or less, inconsistent with a solid ice surface, 2) Retrieved dielectric constants approaching unity over large regions in Xanadu and elsewhere indicate the presence of extensive and extreme surface roughness on wavelength scales, and 3) The generally low measured brightness temperatures relative to the physical temperature of the surface ( 80 K as opposed to 94 K) indicate that subsurface (volume) scattering is present at some level almost everywhere. Implications for the surface of Titan will be discussed. This work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

  20. 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

  1. Measurement of dielectric properties and determination of microwave emissivity of polluted waters

    NASA Technical Reports Server (NTRS)

    Blume, H.-J. C.

    1980-01-01

    The dielectric properties of polluted waters are measured with a reflection-type resonant cavity at 1.43 GHz. Very small water samples in quartz tubes of known volume are placed in the center of the maximum electric field. Measurement of the resonance-frequency variation and a change of the cavity's quality factor are used to determine the dielectric properties. The microwave emissivity of the polluted water is then calculated via the Fresnel equation and applied to data reductions of microwave radiometer measurements.

  2. Tailoring Dielectric Properties and Energy Density of Ferroelectric Polymer Nanocomposites by High-k Nanowires.

    PubMed

    Wang, Guanyao; Huang, Xingyi; Jiang, Pingkai

    2015-08-19

    High dielectric constant (k) polymer nanocomposites have shown great potential in dielectric and energy storage applications in the past few decades. The introduction of high-k nanomaterials into ferroelectric polymers has proven to be a promising strategy for the fabrication of high-k nanocomposites. One-dimensional large-aspect-ratio nanowires exhibit superiority in enhancing k values and energy density of polymer nanocomposites in comparison to their spherical counterparts. However, the impact of their intrinsic properties on the dielectric properties of polymer nanocomposites has been seldom investigated. Herein, four kinds of nanowires (Na2Ti3O7, TiO2, BaTiO3, and SrTiO3) with different inherent characteristics are elaborately selected to fabricate high-k ferroelectric polymer nanocomposites. Dopamine functionalization facilitates the excellent dispersion of these nanowires in the ferroelectric polymer matrix because of the strong polymer/nanowire interfacial adhesion. A thorough comparative study on the dielectric properties and energy storage capability of the nanowires-based nanocomposites has been presented. The results reveal that, among the four types of nanowires, BaTiO3 NWs show the best potential in improving the energy storage capability of the proposed nanocomposites, resulting from the most signficant increase of k while retaining the rather low dielectric loss and leakage current. PMID:26225887

  3. Numerical study of colloidal suspensions of soft spherical particles using the network method. 2. AC electrokinetic and dielectric properties.

    PubMed

    López-García, J J; Grosse, C; Horno, J

    2003-09-15

    The network simulation method is used to solve numerically the equation system that determines the dynamic electrophoretic mobility and the dielectric response of dilute suspensions of soft particles. This system was extensively studied theoretically by Ohshima (H. Ohshima, J. Colloid Interface Sci. 233 (2001) 142-152), who obtained analytical expressions for the static and dynamic electrophoretic mobility. However, the validity of his analytical result is restricted to relatively thick membranes with high drag coefficient and to relatively high electrolyte concentrations. As for the dielectric properties, there are only a few works dealing with particles without a core (ion exchange resins) and, to our knowledge, no numerical studies. Our theoretical model is basically similar to Ohshima's, except that we take into account the mechanical force acting on the surface of the core, which he neglects. The inclusion of this term is crucial when the general problem including arbitrary values of the parameters is analyzed. However, it has little bearing when the membrane is thick and the drag coefficient is high, so that our results for the electrophoretic mobility generally confirm Ohshima's equation when all the required conditions are met. PMID:12962668

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

    NASA Astrophysics Data System (ADS)

    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.

  5. Dielectric properties of Asteroid Vesta's surface as constrained by Dawn VIR observations

    NASA Astrophysics Data System (ADS)

    Palmer, Elizabeth M.; Heggy, Essam; Capria, Maria T.; Tosi, Federico

    2015-12-01

    Earth and orbital-based radar observations of asteroids provide a unique opportunity to characterize surface roughness and the dielectric properties of their surfaces, as well as potentially explore some of their shallow subsurface physical properties. If the dielectric and topographic properties of asteroid's surfaces are defined, one can constrain their surface textural characteristics as well as potential subsurface volatile enrichment using the observed radar backscatter. To achieve this objective, we establish the first dielectric model of asteroid Vesta for the case of a dry, volatile-poor regolith-employing an analogy to the dielectric properties of lunar soil, and adjusted for the surface densities and temperatures deduced from Dawn's Visible and InfraRed mapping spectrometer (VIR). Our model suggests that the real part of the dielectric constant at the surface of Vesta is relatively constant, ranging from 2.3 to 2.5 from the night- to day-side of Vesta, while the loss tangent shows slight variation as a function of diurnal temperature, ranging from 6 × 10-3 to 8 × 10-3. We estimate the surface porosity to be ?55% in the upper meter of the regolith, as derived from VIR observations. This is ?12% higher than previous estimation of porosity derived from previous Earth-based X- and S-band radar observation. We suggest that the radar backscattering properties of asteroid Vesta will be mainly driven by the changes in surface roughness rather than potential dielectric variations in the upper regolith in the X- and S-band.

  6. Disorder driven structural and dielectric properties of silicon substituted strontium titanate

    NASA Astrophysics Data System (ADS)

    Dugu, Sita; Pavunny, Shojan P.; Sharma, Yogesh; Scott, James F.; Katiyar, Ram S.

    2015-07-01

    A systematic study on structural, microstructural, optical, dielectric, and electrical properties of phase-pure silicon-modified SrTiO3 polycrystalline electroceramics synthesized using high energy solid state reaction techniques is presented. The asymmetry and splitting in the x-ray diffractometer spectra and the observation of first order transverse optical TO2 and longitudinal optical LO4 modes in Raman spectra (nominally forbidden) revealed the distortion in the cubic lattice as a result of breaking of inversion symmetry due to doping. A bandgap Eg of 3.27 eV was determined for the sample by diffuse reflectance spectroscopy. A high dielectric constant of ˜400 and very low dielectric loss of ˜0.03 were obtained at 100 kHz near ambient conditions. The temperature dependence of the dielectric data displayed features of high temperature relaxor ferroelectric behavior as evidence of existence of polar nano-regions. The ac conductivity as a function of frequency showed features typical of universal dynamic response and obeyed a power law ? a c = ? d c + A ? n . The temperature dependent dc conductivity followed an Arrhenius relation with activation energy of 123 meV in the 200-500 K temperature range. The linear dielectric response of Pt/SrSi0.03Ti0.97O3/Pt dielectric capacitors was well characterized. The measured leakage current was exceptionally low, 13 nA/cm2 at 8.7 kV/cm, revealing an interface blocked bulk conduction mechanism.

  7. Impact of apoptosis on the on-line measured dielectric properties of CHO cells.

    PubMed

    Zalai, Dénes; Tobak, Teodóra; Putics, Ákos

    2015-12-01

    Apoptosis is a common type of cell death in biopharmaceutical cell culture processes which causes decrease in viable cell density and product yield. The progression of apoptosis has been reported to influence the dielectric properties of mammalian cells; however, the on-line detection of these effects has been rarely described. This study provides a comprehensive analysis of the on-line detectability of dielectric changes upon apoptosis induction in an industrial fed-batch process of CHO cells expressing a recombinant monoclonal antibody. Using capacitance signals, measured at 25 frequencies, the impact of apoptosis on the dielectric spectra was investigated in eight bioreactor cultivations in which various process conditions were combined with two different apoptosis induction strategies (camptothecin treatment and glucose starvation). To differentiate the apoptosis-related information from the cell concentration-associated variance in the multivariate capacitance datasets, principal component analysis (PCA) was used. A second principal component, explaining an explicit proportion (>20 %) of the variance, was identified to be related to dielectric changes induced by apoptosis. Furthermore, the analysis of caspase-3 and -7 activation and DNA fragmentation showed that the detected dielectric change occurred in the early phase of apoptosis. The presented results verify that apoptosis has a considerable impact on the dielectric features of CHO cells and it can be monitored on-line with the introduced tool-set combining capacitance measurement with multivariate data analysis. PMID:26440966

  8. Four-dimensional dielectric property image obtained from electron spectroscopic imaging series.

    PubMed

    Lo, S C; Kai, J J; Chen, F R; Chang, L; Chen, L C; Chiang, C C; Ding, P; Chin, B; Zhang, H; Chen, F

    2001-01-01

    We have demonstrated a new quantitative method to characterize two-dimensional distributions of energy-dependent dielectric function of materials from low loss electron spectroscopic image (ESI) series. Two problems associated with extracted image-spectrum from the low-loss image series, under-sampling and loss of energy resolution, were overcome by using fast Fourier transformation (FFT) interpolation and maximum entropy deconvolution method. In this study, Black Diamond/Si3N4/SiO2/Si-substrate dielectric layer designed for copper metallization was used as the sample. We show that the reconstructed (FFT interpolated and maximum entropy deconvoluted) image-spectrum obtained from ESI series images can be quantified with the same accuracy as conventional electron energy-loss spectroscopy spectra. Since the analysis of the dielectric function is sensitive to the local thickness of the specimen using Kramers-Kronig analysis, we also developed a new method to quantitatively determine the dielectric constant for low-k materials. We have determined the thickness of the Black Diamond using the extrapolated thickness method from the materials of known dielectric constants. Using Kramers-Kronig formula, the dielectric function map can be deduced from two-dimensional reconstructed single scattering spectra with providing the information of thickness. We proposed a four-dimensional data presentation for revealing the uniformity of the energy dependent property. The accuracy of our methods depends on the thickness determination and on the quality of the reconstructed spectra from the image series. PMID:11918416

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

    SciTech Connect

    Miccio, Luis A. Colmenero, Juan; Kummali, Mohammed M.; Alegría, Ángel; Schwartz, Gustavo A.

    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.

  10. Dielectric properties of glasses at ultra low temperatures

    SciTech Connect

    Nishiyama, H.; Akimoto, H.; Okuda, Y.; Ishimoto, H.

    1992-11-01

    A temperature dependence in the dielectric constant of vitreous silica has been measured down to a few hundred microkelvin at frequencies between 110Hz and 10kHz. Homosil glass shows a logarithmic increase below 10 mK down to the lowest temperature of 0.61 mK. On the other hand, Suprasil glass exhibits a saturation behavior following a logarithmic increase above 3 mK. These phenomena are discussed on the basis of the two level system. 6 refs., 2 figs.

  11. Rapid and Nondestructive Determination of Moisture Content in Peanut Kernels from Microwave Measurement of Dielectric Properties of Pods

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A method for moisture determination in peanut kernels from measurement of the dielectric properties of peanut pods at microwave frequencies is presented. The dielectric properties of peanut kernels and pods were measured in free space with a vector network analyzer and a pair of focused beam horn-l...

  12. Dielectric Properties of Mafic Dust-Ice Mixtures: Case Study of the Martian Polar Layered Deposits

    NASA Astrophysics Data System (ADS)

    Heggy, E.; Clifford, S. M.

    2005-12-01

    The dielectric properties of the dust-ice mixtures (also referred as dirty ice) are key parameters in understanding the suitability of the layered deposits in the Martian poles for radar deep subsurface sounding and hence the investigation of the poles' stratigraphy and the potential presence of subglacier melting at the base of the structure. In a first step toward experimentally investigating the frequency, compositional and temperature dependence of this parameter, we measured the dielectric properties of several models of mafic dust and used the mixture formulas to investigate the effect of contamination in ice for different concentrations and temperatures in the frequency range 1 MHz-1 GHz. In light of this analysis, we suggest some outlines on the geoelectrical constraints in terms of losses and dielectric contrast for mapping the layering and the subglacier melt in the polar deposits.

  13. Tailoring Dielectric and Actuated Properties of Elastomer Composites by Bioinspired Poly(dopamine) Encapsulated Graphene Oxide.

    PubMed

    Ning, Nanying; Ma, Qin; Liu, Suting; Tian, Ming; Zhang, Liqun; Nishi, Toshio

    2015-05-27

    In this study, we obtained dielectric elastomer composites with controllable dielectric and actuated properties by using a biomimetic method. We used dopamine (DA) to simultaneously coat the graphene oxide (GO) and partially reduce GO by self-polymerization of DA on GO. The poly(dopamine) (PDA) coated GO (GO-PDA) was assembled around rubber latex particles by hydrogen bonding interaction between carboxyl groups of carboxylated nitrile rubber (XNBR) and imino groups or phenolic hydroxyl groups of GO-PDA during latex compounding, forming a segregated GO-PDA network at a low percolation threshold. The results showed that the introduction of PDA on GO prevented the restack of GO in the matrix. The dielectric and actuated properties of the composites depend on the thickness of PDA shell. The dielectric loss and the elastic modulus decrease, and the breakdown strength increases with increasing the thickness of PDA shell. The maximum actuated strain increases from 1.7% for GO/XNBR composite to 4.4% for GO-PDA/XNBR composites with the PDA thickness of about 5.4 nm. The actuated strain at a low electric field (2 kV/mm) obviously increases from 0.2% for pure XNBR to 2.3% for GO-PDA/XNBR composite with the PDA thickness of 1.1 nm, much higher than that of other DEs reported in previous studies. Thus, we successfully obtained dielectric composites with low dielectric loss and improved breakdown strength and actuated strain at a low electric field, facilitating the wide application of dielectric elastomers. PMID:25938262

  14. Temperature-dependent property measurements on multi-electroded thin-layer dielectrics

    SciTech Connect

    Tani, T.; Xu, Z.; Moses, P.; Payne, D.A. )

    1994-06-01

    A measurement system was designed and assembled for the automatic collection of electrical data for thin-layer dielectrics as a function of temperature. The dielectrics were deposited on platinized silicon by sol-gel processing, and the dielectric thickness was 0.2--0.4 [mu]m. Many ([gt]25) surface electrodes were formed by sputtering gold through a shadow mark, with a typical electrode size of 210[times]210 [mu]m[sup 2]. The measurement equipment was computer controlled, with three-axis digital stepping motors that could scan multi-electroded capacitors and collect statistically meaningful data. The temperature-dependent properties were measured between [minus]100 and 300 [degree]C as a function of frequency (100 Hz to 1 MHz) and applied field strength (0--50 MV/m). Data are reported for sol-gel-derived BaTiO[sub 3], PbZrO[sub 3], and (Pb,La)(Zr,Ti)O[sub 3] (i.e., PLZT) thin-layer capacitors. Capacitance values were typically 500--1000 pF, and the dielectric constant could be determined within a standard deviation of [plus minus]1.3%. Nanocrystalline BaTiO[sub 3] was found to have a dielectric constant of 210 at room temperature with no ferroelectric properties or dielectric anomalies between [minus]80 and 200 [degree]C. Antiferroelectric PbZrO[sub 3] had characteristic field-forced phase transformation behavior to the ferroelectric state with increasing bias. The field-induced polarization was approximately 300 mC/m[sup 2] and the coercive field was 22--28 MV/m. PLZT 8/65/35 had a dielectric constant of 556[plus minus]7 at 25 [degree]C, 100 KHz, and 50 mV.

  15. The effect of organo-clay on the dielectric properties of silicone rubber

    NASA Astrophysics Data System (ADS)

    Razzaghi-Kashani, M.; Gharavi, N.; Javadi, S.

    2008-12-01

    Dielectric elastomers are highly deformable and fast response smart materials capable of actuation under electric fields. Among commercially available dielectric elastomers, silicone rubber can be compounded with different fillers in order to modify its electrical and mechanical properties. To study the effect of organically modified montmorillonite (OMMT) on the dielectric properties of silicone rubber, OMMT was added to this rubber at two levels, 2% and 5%, using two methods, low-shear and high-shear mixing. Composites were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The XRD patterns showed different crystallite structures for silicate platelets in the rubber matrix as a result of the two different mixing methods. In low-shear mixing, the ordered crystallite structure of the clay remains almost unchanged, whereas in high-shear mixing it loses its ordered structure, leading to the disappearance of the diffraction peaks. SEM and AFM micrographs depicted better dispersion and more uniform distribution of the organo-clay under high-shear mixing compared to those obtained by low-shear mixing. The tensile properties also confirmed the different degree of dispersion of the nano-clay resulting from the two different methods of mixing. The dielectric properties of the composites were measured under AC electric fields, and the results were compared with reference silicone rubbers with no OMMT. It was shown that the order of organo-clay layers in the less dispersed structure of the clay imparts an additional ionic polarization and higher dielectric permittivity compared to the case where the clay layers are more dispersed and lost their order. The storage and loss dielectric constants of base silicone rubber increase when it is compounded with OMMT.

  16. Enhanced dielectric properties of doped barium titanate ceramics

    NASA Astrophysics Data System (ADS)

    Kumar Patel, Piyush; Rani, Jyoti; Adhlakha, Nidhi; Singh, Hemant; Yadav, K. L.

    2013-04-01

    Polycrystalline Ba1-xLax[Ti0.5(Fe0.5Nb0.5)0.5]1-x/4O3 [BT-LFN] ceramics with x=0, 0.02, 0.04 and 0.06 were prepared by the solid-state reaction method. The ceramics were subsequently examined at room temperature by X-ray diffraction to identify the phase. The structures of La doped samples were found to be mixed phases of tetragonal and rhombohedral structure. The variations of dielectric constant with temperature are very broad over a wide temperature range. We found the dielectric constant ˜3200 at room temperature and ˜10,000 at 350 °C for 6 mol% La-doped compositions at 1 kHz frequency. The hysteresis loop was observed having remnant polarization of 7.5 ?C/cm2 at room temperature for 6 mol% La-doped sample. Complex impedance analysis was used to estimate its electrical conductivity as well as its corresponding activation energies.

  17. Laboratory measurements of static and dynamic elastic properties in carbonate

    NASA Astrophysics Data System (ADS)

    Bakhorji, Aiman M.

    The fact that many of the giant hydrocarbon reservoirs, such as the Ghawar field in Saudi Arabia and the Grosmont formation in Alberta, are formed from carbonates make these rocks and the corresponding reservoirs important research topics. Compressional and shear wave velocities (at 1 MHz) and the quasi-static strains of thirty seven carbonate rock samples were measured as functions of saturating fluid and confining pressure. Furthermore, P- and S-wave velocities of the saturated samples were measured at constant differential pressure of 15 MPa. The quasi-static strains of the samples under jacketed and unjacketed conditions were also simultaneously acquired. The lithology, mineralogy, porosity and pore type and size distribution of each sample were obtained using a combination of thinsection and scanning electron microscopy, helium porosimetry and mercury intrusion porosimetry. Due to the lack of closing microcracks and compliant pores in low porosity samples, the travel times show slight changes with the confining pressure. Whereas the high porosity samples show remarkable reduction of travel time with the increase of confining pressure in both P- and S-wave. The samples show high sensitivity to the applied differential pressure specially the high porosity samples. We found that the sample physically deformed at pressure above 25 MPa. An evidence of inelastic deformation were observed in few samples even at 25 MPa differential pressure. The samples show no changes in travel time with increasing confining pressure under constant differential pressure, and this behavior is taken to be representative of full saturation of the sample and hence used as a measure of quality control. The comparisons of Biot, Gassmann, squirt-Biot and squirt-Gassmann model predictions with the measured water saturated velocities show that the squirt mechanism is not active on all the studied samples. Biot mechanism is likely to be the principle dispersion mechanism in these samples. For S-wave velocities, Gassmann's model consistently over-predict the saturated at low pressure and closely fit the measured velocities at high pressure, whereas, Biot model over-predicts the saturated velocities in most of the studied samples. The strains measured from the vertical and horizontal strain gages are differing by around 27%. The strains over the horizontal axis are higher than the vertical axis suggesting that the majority of the compliant pores and crack-like pores are oriented almost in direction parallel to the length of the sample. The static bulk modulus is always lower than dynamic one for all measured samples. There is no correlation between porosity and static-dynamic ratio. The measured grain bulk modulus obtained from the unjacketed test is reasonably close to the bulk modulus of the constituent mineral phases.

  18. Dielectric property of MoS(2) crystal in terahertz and visible regions.

    PubMed

    Yan, Xianding; Zhu, Lipeng; Zhou, Yixuan; E, Yiwen; Wang, Li; Xu, Xinlong

    2015-08-01

    Two-dimensional materials such as MoS2 have attracted much attention in recent years due to their fascinating optoelectronic properties. The dielectric response of MoS2 crystal in both the terahertz (THz) and visible regions is studied in this work. Time-domain THz spectroscopy is employed for the THz property investigation. The real and imaginary parts of the complex dielectric constant of MoS2 crystal are found to follow a Drude model, which is due to the intrinsic carrier absorption. In the visible region, ellipsometry is used to investigate the dielectric response. The general trend of the complex dielectric constant is found to be described with a Lorentz model, while two remarkable dielectric response peaks are observed to be located at 1.85 and 2.03 eV, which has been attributed to the splitting arising from the combined effect of interlayer coupling and spin-orbit coupling. This work can be the research foundation for future optoelectronic applications with MoS2. PMID:26368087

  19. Strain tunable ferroelectric and dielectric properties of BaZrO{sub 3}

    SciTech Connect

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

    2014-06-14

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

  20. Dielectric Properties of the Lamellar Niobates and Titanoniobates AM2Nb3O10 and ATiNbO5 (A ) H, K, M )

    E-print Network

    Dielectric Properties of the Lamellar Niobates and Titanoniobates AM2Nb3O10 and ATiNbO5 (A ) H, K the frequency-dependent dielectric properties of some representative lamellar niobates and titanoniobates

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

    E-print Network

    Saiz, Leonor

    components of the dipole density as well as the individual and total dipole moment autocorrelation functions liquids, see Ref. 1 . Among these liquids, water has focused the interest of most of the computer simulation stud- ies. In the case of alcohols, only the dielectric properties of liquid methanol2

  2. Radio Frequency (RF) dielectric properties of honeydew melon and watermelon juice and correlations with sugar content

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dielectric properties of juice of three honeydew melon cultivars and four watermelon cultivars of different maturities were measured with an open-ended coaxial-line probe and impedance analyzer over the frequency range from 10 MHz to 1.8 GHz. Soluble solids content (SSC) of fruit juice and moisture ...

  3. Frequency, temperature, density and moisture dependence of dielectric properties of unshelled and shelled peanuts

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dielectric properties of unshelled and shelled peanuts were measured with a free-space-transmission technique between 2 and 18 GHz over wide ranges of bulk density, moisture content, and temperature. For better accuracy a pair of horn/lens antennas providing a focused beam was used; the sample was p...

  4. Investigation of the Dielectric Properties of Layered PVDF/CNF Nanocomposite Materials

    E-print Network

    Collins, Gary S.

    . Films were allowed to dry in a 70 °C oven for at least 20 minutes. The films were then stacked in layersInvestigation of the Dielectric Properties of Layered PVDF/CNF Nanocomposite Materials Gavin nanocomposite are increasingly becoming attractive to scientists due to their ease of fabrication and good

  5. 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...

  6. FREE-SPACE MEASUREMENT OF DIELECTRIC PROPERTIES OF CEREAL GRAIN AND OILSEED AT MICROWAVE FREQUENCIES

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Principles of dielectric properties measurement by microwave free-space transmission measurements are presented, and the important sources of errors in such measurements are discussed. A system, including a vector network analyzer, horn/lens antennas, holder for grain and oilseed samples, and a rad...

  7. 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...

  8. 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

  9. Microwave dielectric properties of graded barium strontium titanate films M. W. Cole,1,a

    E-print Network

    Alpay, S. Pamir

    Microwave dielectric properties of graded barium strontium titanate films M. W. Cole,1,a C. V strontium titanate BaxSr1-xTiO3 or BST multilayers 5 mol % MgO doped and undoped were prepared via metallo, delay lines, filters, and phase shifters for steerable antennas.1­3 Barium strontium titanate BaxSr1-x

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

    E-print Network

    Suo, Zhigang

    The effect of stress on the dielectric properties of barium strontium titanate thin films T. M Barium strontium titanate thin films are being developed as capacitors in dynamic random access memories to their large permittivities, barium strontium titan- ate BST bulk ceramics have long been used to make high

  11. 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

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

    SciTech Connect

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

    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.

  13. Dielectric properties of composites based on nanocrystalline cellulose with triglycine sulfate

    NASA Astrophysics Data System (ADS)

    Nguen, Kh. T.; Milovidova, S. D.; Sidorkin, A. S.; Rogazinskaya, O. V.

    2015-03-01

    The dielectric properties and frequency dispersion of the dielectric characteristics of nanocrystalline cellulose-triglycine sulfate composites have been studied in the low- and infralow-frequency ranges (from 10-3 to 103 Hz) in a weak electric field. It has been shown that the phase transition in these composites is diffuse and displaced to the higher temperatures range as compared to the transition in bulk triglycine sulfate. In the composites under study, a significant dispersion of the permittivity, presumably caused by a positive Maxwell-Wagner relaxation, is observed.

  14. Dielectric properties of doping-free NaMn{sub 7}O{sub 12}: Origin of the observed colossal dielectric constant

    SciTech Connect

    Cabassi, R.; Bolzoni, F.; Gauzzi, A.; Gilioli, E.; Prodi, A.; Licci, F.

    2006-07-15

    The semiconducting NaMn{sub 7}O{sub 12} is a doping-free compound with several coexistent properties such as orbital ordering, charge ordering, and magnetic orderings of different types. We investigated its dielectric response by means of frequency impedance measurements in the range from 20 Hz to 1 MHz. Standard measurements on metallized samples exhibit an apparent colossal dielectric constant (CDC) with an {epsilon}{sub R} value of several thousands at low frequencies, but a careful equivalent circuit analysis allows one to ascribe the observed CDC to the effect of a depletion layer on the metal-semiconductor junctions. We bypass this effect by means of a nonstandard technique employing mica linings: the resulting dielectric behavior exhibits the presence of the charge ordering transition at T{sub CO}=176 K and shows a net bulk dielectric constant value {epsilon}{sub R}{approx_equal}68 at room temperature.

  15. Extraordinary refraction and self-collimation properties of multilayer metallic-dielectric stratified structures

    NASA Astrophysics Data System (ADS)

    Zhang, Liwei; Chen, Liang; Zhang, Zhengren; Wang, Wusong; Zhao, Yuhuan; Song, Kechao; Kang, Chaoyang

    2015-01-01

    The extraordinary refraction with negative or zero refraction angle of the layered metamaterial consisting of alternating dielectric and plasmonic layers is theoretically studied. It is shown that the electromagnetic properties can be tuned by the filling factor, the permittivity of the dielectric layer and the plasma frequency of the metallic layer. At different frequency, the layered structures possess different refraction properties with positive, zero or negative refraction angle. By choosing appropriate parameters, positive-to-zero-to-negative-to positive refraction at the desired frequency can be realized. At the frequency with flat equal frequency contour, self-collimation and slow light properties are also found. Such properties can be used in the performance of negative refraction, subwavelength imaging and information propagation.

  16. Study to determine dielectric properties of sandstone, shale, coal, and slate

    NASA Technical Reports Server (NTRS)

    Bassett, H. L.; Sheppard, A. P.

    1976-01-01

    Triplicate dielectric constant and loss tangent measurements on samples of sandstone, shale, coal, and slate were performed. Each of the three necessary configurations of the coal material was sampled to obtain measurements, with each sample machined parallel to the coal layering orientation. The coal samples were machined perpendicular to the coal layering and measured. They were conditioned at 100% humidity and at room temperature and remeasured; then conditioned in an elevated environment, and remeasured for dielectric properties. The coal data appear to remain relatively constant over the microwave frequency region. At the Ghz frequencies, the relative dielectric constant of coal is slightly higher for the E-field parallel to the layers than for the perpendicular case.

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

    SciTech Connect

    Ramesh, G.; Subramanian, V.; Sivasubramanian, V.

    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.

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

    SciTech Connect

    Mohanty, N. K. Behera, A. K. Satpathy, S. K. Behera, B. Nayak, P.

    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.

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

    SciTech Connect

    Biegalski, Michael D; Jang, J H; Bark, C; Eom, Professor Chang-Beom

    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.

  20. Dielectric, thermal and mechanical properties of zirconium silicate reinforced high density polyethylene composites for antenna applications.

    PubMed

    Varghese, Jobin; Nair, Dinesh Raghavan; Mohanan, Pezholil; Sebastian, Mailadil Thomas

    2015-06-14

    A low cost and low dielectric loss zirconium silicate (ZrSiO4) reinforced HDPE (high-density polyethylene) composite has been developed for antenna applications. The 0-3 type composite is prepared by dispersing ZrSiO4 fillers for various volume fractions (0.1 to 0.5) in the HDPE matrix by the melt mixing process. The composite shows good microwave dielectric properties with a relative permittivity of 5.6 and a dielectric loss of 0.003 at 5 GHz at the maximum filler loading of 0.5 volume fraction. The composite exhibits low water absorption, excellent thermal and mechanical properties. It shows a water absorption of 0.03 wt%, a coefficient of thermal expansion of 70 ppm per °C and a room temperature thermal conductivity of 2.4 W mK(-1). The composite shows a tensile strength of 22 MPa and a microhardness of 13.9 kg mm(-2) for the filler loading of 0.5 volume fraction. The HDPE-ZrSiO4 composites show good dielectric, thermal and mechanical properties suitable for microwave soft substrate applications. A microstrip patch antenna is designed and fabricated using the HDPE-0.5 volume fraction ZrSiO4 substrate and the antenna parameters are investigated. PMID:25981704

  1. Effect of high-pressure on calorimetric, rheological and dielectric properties of selected starch dispersions.

    PubMed

    Ahmed, Jasim; Singh, Ajaypal; Ramaswamy, H S; Pandey, Pramod K; Raghavan, G S V

    2014-03-15

    Effects of high-pressure (HP) treatment on the rheological, thermal and dielectric properties of the four selected starch dispersions (two modified starches, one native and one resistant) were evaluated. Differential scanning calorimetry (DSC) and oscillatory rheometry were employed to assess the extent of starch gelatinization and the developed gel rigidity (G') of starch gels after HP treatment. It was observed that starch dispersions gelatinized completely at 500 MPa with a 30-min holding time. The HP-treated starch samples exhibited predominantly solid-like (G'>G") behavior except for the resistant starch. Pressure-induced gel rigidity differed significantly among starch samples. The G' of starch gels increased with the pressure (400-600 MPa) in the studied frequency range (0.1-10 Hz) except for the native starch where a marginal decrease was recorded at similar condition. The holding time (15-30 min) and concentration (20-25% w/w) significantly attributed towards gel rigidity of starch samples. Measurement of dielectric properties of HP-treated samples over the frequency range 450-4450 MHz indicated differences in the dielectric constant (?'), loss factor (?") and penetration depth among starch gels. Pressure did not show any effect on dielectric property of the resistant starch sample. Power penetration depth decreased significantly with frequency and with the pressure. PMID:24528695

  2. Performance improvements of the hydrophobic and the dielectric properties of parylene C

    NASA Astrophysics Data System (ADS)

    Kahouli, A.; Sylvestre, A.; Laithier, J.-F.

    2013-10-01

    The increase in the hydrophobicity at the same time as the reduction in the dielectric properties of an insulating material are the main factors necessary to improve the signal response of the electrowetting-on-dielectric and the organic field effect transistor electronic devices. Oxygen (O2) and fluorine (CF4) plasma treatments on 3.7 ?m thicknesses-parylene C were carried out to understand the surface hydrophobicity character and their effect on the dielectric properties of the material. Fast hydrophobic recovery was observable during the first day after the O2 treatment due to the reorientation of the polar polymer end chains to the bulk of parylene C. CF4 plasma treatments reveal a noticeably increase of the hydrophobicity as the treatment time increases. Energy dispersive X-ray and Fourier transform infrared analyses have confirmed an increase in the number of fluorine containing CFx bonds where 1 ? x ? 3 after fluorine plasma treatments and after aging. The PPX C film treated with CF4 plasma at 500 W for 30 min indicated the best hydrophobic character and the best dielectric properties due to the highest loading fluorine content in our experimental conditions.

  3. Dielectric and complex impedance properties of tetravalent hafnium (HF 4+) integrated cobalt ferrite

    NASA Astrophysics Data System (ADS)

    Sanchez, Luis

    The work presented in this thesis was carried out to understand the effects of tetravalent hafnium (Hf4+) ion on the crystal structure and phase, surface morphology, electrical, dielectric and complex impedance properties of cobalt ferrite (CoFe2O4; CFO). Hafnium incorporated cobalt ferrite, CoFe2-xHfxO4, with x = 0.00, 0.05, 0.075, 0.10, 0.15 and 0.20 were prepared by the standard solid state ceramic synthesis method. X-ray diffraction (XRD) and scanning electron microscopy (SEM) characterizations were performed to determine the structural properties. Most important aspect of this study is to explore the dielectric and complex impedance properties as a function of variable temperature (T=300-1000 K) and frequency (f=20 Hz -1 MHz). Room temperature and the temperature dependence of dielectric constant, loss factor, complex impedance, and the ac resistivity measurements enabled us to understand the effect of temperature and frequency on the electrical and dielectric properties on CoFe2-xHfxO4 and, thus, to derive structure-property relation. X-ray diffraction (XRD) patterns for Hf-incorporated CFO confirm the formation of majority of CFO spinel [with space group Fd3m (227)] phase, in addition to the small amount of HfO2 monoclinic [space group, P1 21/c (14)] phase leading to formation of CFO-Hf composites. The lattice constant values derived from XRD for CFO-Hf were found to increase from 8.374 A (x = 0.000) to 8.391 A (x = 0.200). The lattice expansion is significant at the very first step of Hf-incorporation and then slows down with progressive Hf-incorporation. SEM imaging analysis indicates that Hf resides at the grain boundaries for CFO-Hf. The dielectric constant (epsilon') of CFO-Hf is T-independent at T<450 K, at which point increasing trend prevails. A grain bulk-boundary based two-layer model, where semiconducting-grains separated by insulating-grain boundaries, satisfactorily accounts for epsilon- T (>450 K) variation. Correspondingly, electrical responses in impedance formalism are attributed to the grain and grain-boundary effects, respectively, which also accounts for the observed two dielectric-relaxations. The results demonstrate that the dielectric phenomena in CFO-Hf can be tailored by tuning Hf-concentration.

  4. Dielectric and piezoelectric properties of BiFeO3 from molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Graf, M.; Sepliarsky, M.; Machado, R.; Stachiotti, M. G.

    2015-09-01

    A first-principles based atomistic scheme is used to investigate the dielectric and piezoelectric properties of BiFeO3. The atomistic model fitted from first-principles calculations reproduces very well the structural and polar properties of the material at finite temperature, predicting a direct transition from a low-temperature R3c ferroelectric phase to a Pbnm orthorhombic phase in agreement with experiments. We use this theoretical approach to calculate intrinsic single crystal properties, which are difficult to obtain from experiments due to decomposition and leakage problems. The whole set of dielectric and piezoelectric coefficients for BiFeO3 is computed as a function of temperature, together with the orientation dependence of the longitudinal coefficient d33*.

  5. 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.

  6. High dielectric, dynamic mechanical and thermal properties of polyimide composite film filled with carbon-coated silver nanowires

    NASA Astrophysics Data System (ADS)

    Wang, Lisi; Piao, Xiaoyu; Zou, Heng; Wang, Ya; Li, Hengfeng

    2015-01-01

    High dielectric permittivity materials are much desirable in the electric industry. Filling polymer matrix with conductive powders to form percolative composites is one of the most promising methods to achieve high dielectric permittivity. However, they do not always provide high mechanical properties and thermal stability, which seriously limit their applications. In this study, we present the preparation of functional core-shell structured silver nanowires/polyimide (AgNWs/PI) hybrid film with high dielectric permittivity and low loss dielectric. The core-shell structure of AgNWs was characterized by transmission electric microscopy. The dynamical mechanical analysis showed that AgNWs/PI hybrid films had relative high dynamic mechanical properties with storage modules over 1 Gpa. Moreover, the hybrid films exhibited excellent thermal stability with 5 % weight-loss temperature above 500 °C. The dielectric properties of the carbon-coated AgNWs hybrid films were remarkably improved. The maximum dielectric permittivity of hybrid films is 126 at 102 Hz, which was 39 times higher than that of pure PI matrix, while the dielectric loss of that is still remained at a low value. This study showed a new method to improve the dielectric, dynamic mechanical and thermal properties of films.

  7. Dielectric, ferroelectric and piezoelectric properties of La-modified PCT ceramics

    NASA Astrophysics Data System (ADS)

    Singh, Sarabjit; Thakur, O. P.; Prakash, Chandra; Raina, K. K.

    2005-12-01

    Polycrystalline samples of lanthanum-modified PCT ceramics with composition Pb 0.76-3x/2La xCa 0.24Mn 0.02Ti 0.98O 3 (PLCT); x=0-0.08 (in steps of 0.02) were prepared by using conventional dry ceramic technique. Samples were sintered at 1150 °C. X-ray analysis confirmed the formation of single-phase compound with tetragonal crystal structure. Dielectric properties were studied in detail as a function of frequency and temperature. From temperature variation of dielectric constant, Curie temperature ( Tc) was determined. Discussion on hysteresis behaviour for all the samples at room temperature is presented. Dielectric constant at room temperature shows an increasing trend and Curie temperature shows decreasing trend with the increase in lanthanum in PCT ceramics. Curie temperature determined from thermal expansion behaviour of sintered samples was found to be in good agreement with that determined from dielectric studies. Piezoelectric properties show a significant improvement with lanthanum substitution.

  8. Structural and dielectric properties of Cr-doped Ni-Zn nanoferrites

    NASA Astrophysics Data System (ADS)

    Nasir, S.; Anis-ur-Rehman, M.; Malik, Muhammad Ali

    2011-02-01

    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 Debye-Scherrer formula was 29-34 nm. Scanning electron microscope images showed that the particle size of the samples lies in the nanometer regime. The dielectric constant (?r), dielectric loss tangent (tan ?) and ac electrical conductivity (?ac) of nanocrystalline Cr-Ni-Zn ferrites were investigated as a function of frequency and Cr concentration. The dependence of ?r, tan ? and ?ac on the frequency of alternating applied electric field is in accordance with the Maxwell-Wagner model. The effect of Cr doping on the dielectric and electric properties was explained on the basis of cations distribution in the crystal structure.

  9. 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.

  10. Measuring Static and Dynamic Properties of Frozen Silty Soils

    SciTech Connect

    Furnish, M.D.

    1998-09-30

    A mechanical characterization of frozen silty soils has been conducted to support computer modeling of penetrators. The soils were obtained from the Eilson AFB (Alaska) vicinity. Quasi-static testing with a multiaxial system in a cold room and intermediate strain rate testing with a split Hopkinson pressure bar were conducted. Maximum stresses achieved were slightly above 1 GPa, apparently limiting the observed behavior primarily to elastic compression and pore crushing phenomena. Lower temperatures seem to increase the strength of the material markedly, although not by a simple factor. Lower temperatures and higher strain rates increase the apparent Young's and bulk moduli as well (an increase of {approximately} a factor of two is observed for strain rate increasing from 0.001 s{sup {minus}1} to 800 s{sup {minus}1}). The strength also depends strongly on strain rate. Increasing the strain rate from 0.001 {sup {minus}1} to 0.07 {sup {minus}1} increases the strength by a factor of five to ten (to values of order 1 GPa). However,only a small increase in strength is seen as strain rate is increased to {approximately} 10{sup 2}--10{sup 3} s{sup {minus}1}. The reliability of the strength measurements at strain rates< 1 s{sup {minus}1} is decreased due to details of the experimental geometry, although general trends are observable. A recipe is provided for a simulant soil based on bentonite, sand, clay-rich soil and water to fit the {approximately} 6% air-filled porosity, density and water content of the Alaska soils, based on benchtop mixing and jacketed compression testing of candidate mixes.

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

    SciTech Connect

    Shirzaditabar, Farzad; Saliminasab, Maryam

    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.

  12. 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

  13. 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.

  14. Effect of hafnium-incorporation on the microstructure and dielectric properties of cobalt ferrite ceramics

    NASA Astrophysics Data System (ADS)

    Wells, Stephen Josiah

    The effect of hafnium ion (Hf4+) incorporation in cobalt ferrite (CFO) was studied. Samples of Hf substituted CFO ceramic (CoFe 2-xHfxO4), were synthesized in the laboratory with hafnium concentrations ranging from x=0.000 to x=0.200. X-ray diffraction scans show that the Hafnium CFO crystalizes in the inverse spinel phase. Inclusion of hafnium causes lattice expansion, increasing the lattice parameter from 8.374 A for pure CoFe2O4 to 8.391 A for the highest concentration of hafnium tested (x=0.020). The dielectric properties of CFO are greatly enhanced by inclusion of hafnium. The enhancement is due to the distortion on the lattice from the larger Hf-ions substituting the smaller Fe-ions. Frequency variation of the dielectric properties is well modeled by the modified Debye function, which takes into account multiple ions contributing to relaxation.

  15. 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.

  16. Dielectric Properties and Applications of CVD Diamonds in the Millimeter and Terahertz Ranges

    NASA Astrophysics Data System (ADS)

    Garin, B. M.; Parshin, V. V.; Polyakov, V. I.; Rukovishnikov, A. I.; Serov, E. A.; Mocheneva, O. S.; Jia, Ch. Ch.; Tang, W. Z.; Lu, F. X.

    The results of investigation of the dielectric properties in the millimeter and terahertz ranges of diamond samples prepared by using the direct current arc plasma jet (APJ) and the microwave plasma chemical vapour deposition (MPCVD) techniques are presented. Various methods for the measurements of the dielectric properties using high-Q open resonators and cylindrical cavity resonators are discussed while the activation energy of the conductivity and point defect parameters (such as concentration and activation energy of the defect induced levels) in both kinds of diamonds are studied via Conductivity and Charge-based Deep Level Transient Spectroscopy (Q-DLTS) measurements (for the first time in APJ diamond) and compared. The absorption mechanisms in these diamonds grown by different methods are discussed.

  17. Structural, electronic, vibrational and dielectric properties of selected high-shape K semiconductor oxides

    NASA Astrophysics Data System (ADS)

    Scolfaro, L. M. R.; Leite Alves, H. W.; Borges, P. D.; Garcia, J. C.; da Silva, E. F., Jr.

    2014-10-01

    The semiconductor oxides SnO2, HfO2, ZrO2, TiO2 and SrTiO3 are interesting materials for applications as high-K dielectric gate materials in silicon-based devices and spintronics, among others. Here we review our theoretical work about the structural, electronic and vibrational properties of these oxides in their most stable structural phases, including dielectric properties as derived from the electronic structure taking into account the lattice contribution. Finally, we address the recent role played by the presence of transition metal atoms in semiconductor oxides, considering in particular SnO2 as an example in forming diluted magnetic alloys.

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

    SciTech Connect

    P, Sharmila P; Tharayil, Nisha J.

    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.

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

    NASA Astrophysics Data System (ADS)

    P, Sharmila P.; Tharayil, Nisha J.

    2014-10-01

    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.

  20. MICROWAVE DIELECTRIC METHODS FOR SENSING PHYSICAL PROPERTIES OF GRANULAR MATERIALS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Knowledge of the physical properties of granular materials is important in many industries including food and agriculture, pharmaceutical, chemical, and mining. They are often used in quality control as well as process monitoring and control. Therefore, they need to be determined reliably and in rea...

  1. Microwave dielectric materials with complex perovskite structure have been synthesized and their microwave, optical, structural, and electrical properties have been characterized. Among these,

    E-print Network

    Microwave dielectric materials with complex perovskite structure have been synthesized and their microwave, optical, structural, and electrical properties have been characterized. Among these, the microwave dielectric loss tangent has been focused on and its mechanism has been studied. We demonstrate

  2. 3-D Static Elastic Constants and Strength Properties of a Glass/Epoxy Unidirectional Laminate

    E-print Network

    . LAMINATE ELASTIC CONSTANTS1 VF = 56.8 ­ 58.2% Tensile Modulus EL (GPa) 44.6 Tensile Modulus ET (GPa) 173-D Static Elastic Constants and Strength Properties of a Glass/Epoxy Unidirectional Laminate 1366 epoxy resin. Results are given for elastic constants, strengths, and best- fits to stress

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

    E-print Network

    Reynolds, Albert C.

    as the tools of inverse and probability theory for data integration. #12;Contents ABSTRACTReport Title: Mapping of Reservoir Properties and Facies Through Integration of Static and Dynamic for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed

  4. Dielectric properties of vanadium doped barium titanate synthesized via high-energy ball milling

    NASA Astrophysics Data System (ADS)

    Dulian, Piotr; B?k, Wojciech; Wieczorek-Ciurowa, Krystyna; Kajtoch, Czes?aw

    2014-06-01

    The study shows the advisability of using a mechanochemical synthesis method, based on a high-energy planetary ball milling, to a modification of barium titanate by a vanadium doping. This method improves useful properties of BaTi0:95V0:05O3 as a capacitor material. It has a high value of electric permittivity ?' in the wide range of temperature and low dielectric losses ?? as well as a low electrical conductivity.

  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

    -1 PRELIMINARY NON-DESTRUCTIVE ASSESSMENT OF MOISTURE CONTENT, HYDRATION AND DIELECTRIC PROPERTIES OF PORTLAND CEMENT CONCRETE A Thesis by IVAN AVELAR LEZAMA Submitted to the Office of Graduate Studies of Texas A&M University... OF PORTLAND CEMENT CONCRETE A Thesis by IVAN AVELAR LEZAMA Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Approved by: Chair...

  6. Can diurnal variation in radar backscatter in vegetated areas be explained by changes in dielectric properties?

    NASA Astrophysics Data System (ADS)

    Steele-Dunne, S. C.; Friesen, J.; Van De Giesen, N.

    2012-12-01

    Two recent studies have identified a systematic difference in backscatter between the morning and evening passes of the Wind Scatterometer on the ERS 1/2 satellite in vegetated areas. In some areas, e.g. the West African savanna, these differences appear to correspond to the onset of vegetation water stress. The goal of this study is to test the hypothesis that changes in the dielectric properties of the canopy constituents due to changes in water status could explain the difference. Results will be presented from a numerical study in which the Michigan Microwave Canopy Scattering (MIMICS) model was used to examine the impact of leaf, branch, trunk and soil dielectric properties on C-band and L-band backscatter. For C-band vertically copolarized backscatter, the greatest sensitivity is to leaf moisture (and, hence, dielectric constant), but trunk moisture is significant at low values of leaf moisture content. This suggests that the difference observed in the ERS wind scatterometer observations may be due to changes in leaf moisture content (and hence dielectric constant). We also examined the impact on co- and cross-polarized L-band backscatter to explore the implications for NASA's upcoming SMAP mission. The cross-polarized backscatter was mainly sensitive to leaf properties, while the co-polarized backscatter was mainly sensitive to changes in trunk properties. These results suggest that the difference between morning and evening SMAP radar observations might contain useful information on the canopy water status, an indicator of the availability of water in the root zone.

  7. Effect of microstructures on the microwave dielectric properties of ZrTiO4 thin films

    E-print Network

    Park, Byungwoo

    Effect of microstructures on the microwave dielectric properties of ZrTiO4 thin films Yongjo Kim, which was made by sintering a mixture of TiO2 and ZrO2 powders with a 0.5/0.5 mole fraction at 1650 °C the substrate to the target, a flow-rate ratio of argon 99.999% to oxygen 99.995% of 4 to 1, an incident rf

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

    NASA Astrophysics Data System (ADS)

    Suherman, Phe Man; Smith, Geoff

    2003-02-01

    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 dielectric loss peak at higher frequency (called the varepsilon3 dispersion). The low frequency response conformed to a fractional power low of frequency, while the higher frequency response conformed to a Davidson-Cole model. The strength of both processes reached a maximum at a certain temperature within the experimental temperature range. This temperature is referred to as the percolation threshold (PT) and is thought to be associated with the percolation of protons between hydrogen-bonded water molecules. The relaxation times of the varepsilon3 dispersion conformed to Arrhenius behaviour at temperatures below the PT, from which an activation energy (DeltaH) could be calculated. This activation energy is thought to be a measure of the concentration of available charged sites through which proton transport is facilitated. The structural fractal dimension in the hydrated protein system was also calculated, and enabled the approximation of the pathway for charge percolation in the protein matrix.

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

    SciTech Connect

    Sokhansanj, Shahabaddine; Shrestha, Bijay; Wood, H.C.

    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.

  10. 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.

  11. Effect of magnesium substitution on dielectric and magnetic properties of Ni-Zn ferrite

    NASA Astrophysics Data System (ADS)

    Singh, Navneet; Agarwal, Ashish; Sanghi, Sujata; Singh, Paramjeet

    2011-02-01

    The dielectric and magnetic properties of Mg incorporated Ni-Zn spinel ferrites have been investigated. Ni 0.5- xZn 0.5Mg xFe 2O 4 ferrites have been prepared by sol-gel auto-combustion technique. The as prepared ferrites were annealed at 673, 873 and 1073 K. The X-ray diffraction studies reveal the spinel structure of annealed ferrites. The TEM results are in agreement with XRD results. FTIR study has also been carried out to get insight into the structure of these ferrites. The dielectric measurements show that the dielectric constant ( ??), dielectric loss (tan ?) and conductivity ( ?ac) increase on incorporation of Mg in the Ni-Zn ferrite. ??, tan ? and ?ac also show dependence on temperature, frequency of external applied electric field and microstructure of the samples. The magnetic moment measurements reveal that the saturation magnetization ( Ms) increases and coercivity ( Hc) decreases with the increase in concentration of Mg 2+ ions. Ms and Hc also show dependence on the annealing temperature.

  12. Effects of Nitrogen Doping on X-band Dielectric Properties of Carbon Nanotube/Polymer Nanocomposites.

    PubMed

    Arjmand, Mohammad; Sundararaj, Uttandaraman

    2015-08-19

    Nitrogen-doped and undoped carbon nanotubes (CNTs) were synthesized by selective passing of source and carrier gases (ethane, ammonia, hydrogen, and argon) over an alumina-supported iron catalyst in a quartz tubular reactor at 650 °C. Synthesized CNTs were mixed with polyvinylidene fluoride with an Alberta polymer asymmetric minimixer (APAM) mixer at 240 °C and 235 rpm, and the resulting nanocomposites were compression molded. Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and thermogravimetric analysis (TGA) techniques revealed that introducing nitrogen into the crystalline structure of CNTs resulted in higher crystalline defects. Dielectric measurements showed that nitrogen doping significantly increased dielectric permittivity for a known dielectric loss. This was ascribed to the role of the crystalline defects and nitrogen atoms, which acted as polarizing centers, blocked the nomadic charges, polarized them, and prevented them from moving along CNTs. The obtained results introduce nitrogen doping as a regulative tool to control the dielectric properties of CNT/polymer nanocomposites. PMID:26218098

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

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

    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.

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

    SciTech Connect

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

    2015-05-22

    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.

  15. Correlation of electrical conductivity, dielectric properties, microwave absorption, and matrix properties of composites filled with graphene nanoplatelets and carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Khurram, A. A.; Rakha, Sobia A.; Zhou, Peiheng; Shafi, M.; Munir, Arshad

    2015-07-01

    The DC electrical conductivity, percolation threshold, and dielectric properties of Graphene Nanoplatelets (GNPs) filled epoxy composites are studied and correlated with microwave absorption. The properties of GNPs filled composites are also compared with multiwalled carbon nanotubes (MWCNTs) composites, and GNPs are observed to have superior conductivity than MWCNTs. In all batches, the nanofillers have 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, and 3.5 wt. %. All composites irrespective of the type of nanofiller and viscosity of the matrix have shown electrical percolation threshold at 3.0 wt. %. The dielectric properties, i.e., complex permittivity, tan loss, and AC conductivity, are studied in 100 Hz-5.5 MHz. The DC and AC electrical conductivities (at and below the percolation) measured in 100 Hz-5.5 MHz are correlated to the GNPs and MWCNTs epoxy composites in the microwave frequency range (11-17 GHz). The maximum return loss of -12 dB and -6 dB was determined for MWCNTs and GNPs, respectively. The effects of nanofiller shape and the viscosity of the matrix on the dispersion and interparticle spacing of the conductive fillers within the polymer matrix have been discussed based on the results of conductivity, dielectric, and absorption properties.

  16. Dielectric properties of halloysite and halloysite-formamide intercalate

    SciTech Connect

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

    2014-01-14

    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.

  17. Optical, dielectric and electrical properties of PVA doped with Sn nanoparticles

    NASA Astrophysics Data System (ADS)

    Amin, G. A. M.; Abd-El Salam, M. H.

    2014-04-01

    Films of pure and doped polyvinyl alcohol (PVA) with different concentrations of Sn nanoparticles (??100 nm) were prepared using casting technique. The effect of Sn addition on micro-structural, optical, electrical and dielectric properties of PVA was investigated. Microstructure of Sn/PVA nanocomposite films was characterized by scanning electron microscopy (SEM). Dielectric properties and ac conductivity measurements were carried out at room temperature over a wide range of frequencies ranging from 50 Hz to 5 MHz. AC conductivity was found to increase with frequency. Besides, addition of Sn nanoparticles to PVA leads to a change in conductivities of the films. Coulomb blockade effect was found to dominate at certain concentrations of Sn which may be used to explain the obtained results. The dielectric properties of the Sn/PVA films were also investigated and results were discussed in correlation with the relevant models. The frequency dependence of the imaginary part of complex electric modulus for the Sn/PVA composites shows a loss peak attributed to interfacial polarization at a certain frequency. Optical energy gap of Sn/PVA films was determined and found to decrease for Sn concentrations up to 20% due to the interaction between the Sn nanoparticles and the host polymeric network leading to the creation of new molecular dipoles. For higher Sn concentrations, the optical energy gap starts to increase which may be resulting from structural changes leading to passivation of localized states near the band edges and hence widening of the energy gap.

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

    PubMed

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

    2013-04-23

    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

  19. 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

  20. Single-mode plasmonic waveguiding properties of metal nanowires with dielectric substrates.

    PubMed

    Wang, Yipei; Ma, Yaoguang; Guo, Xin; Tong, Limin

    2012-08-13

    Single-mode plasmonic waveguiding properties of metal nanowires with dielectric substrates are investigated using a finite-element method. Au and Ag are selected as plasmonic materials for nanowire waveguides with diameters down to 5-nm-level. Typical dielectric materials with relatively low to high refractive indices, including magnesium fluoride (MgF2), silica (SiO2), indium tin oxide (ITO) and titanium dioxide (TiO2), are used as supporting substrates. Basic waveguiding properties, including propagation constants, power distributions, effective mode areas, propagation distances and losses are obtained at the typical plasmonic resonance wavelength of 660 nm. Compared to that of a freestanding nanowire, the mode area of a substrate-supported nanowire could be much smaller while maintaining an acceptable propagation length. For example, the mode area and propagation length of a 100-nm-diameter Ag nanowire with a MgF2 substrate are about 0.004 ?m2 and 3.4 ?m, respectively. The dependences of waveguiding properties on geometric and material parameters of the nanowire-substrate system are also provided. Our results may provide valuable references for waveguiding dielectric-supported metal nanowires for practical applications. PMID:23038541

  1. 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

    2015-10-01

    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.

  2. Structure and dielectric properties of composite material based on surface-modified BaTiO3 nanoparticles in polystyrene

    NASA Astrophysics Data System (ADS)

    Emelianov, Nikita

    2015-01-01

    This article reports on studies of the structure and dielectric properties of composites materials based on BaTiO3 nanoparticles in the polymer matrix. It is shown that nanoparticles of barium titanate obtained by peroxide method, have surface enriched hydroxyl (-OH) groups, which allow the formation of strong chemical bonds with the molecules of surfactant. This surface modification prevents agglomeration of nanoparticles, which leads to heterogeneity of mechanical and dielectric properties of the composites. It is shown that the effective dielectric constant for the studied composite material agrees well with the modified Kerner equation for the volume content of nanoparticles within the range from 5 to 35%.

  3. Static and dynamic elastic properties of rocks from the Canadian Shield

    SciTech Connect

    King, M.S.

    1983-01-01

    As part of a number of research studies in the Canadian Shield associated with the stability of underground mine openings, seismic reflection surveys, and the proposed use of a tunnel-boring machine (TBM) for developing mine headings, a long-term laboratory rock mechanics program has been conducted to determine the static and dynamic elastic properties of samples of igneous and metamorphic rocks from the Canadian Shield. This paper reports the results of 174 measurements of static elastic modulus and 152 measurements of uniaxial compressive strength for these rocks as a function of dynamic elastic modulus. 20 references, 5 figures.

  4. Dynamic and Static Shell Properties of White and Brown Shell Eggs Exposed to Modified-pressure Microcrack Detection Technology

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dynamic and static shell properties of eggs provide important insight to egg quality. Understanding how processing and handling procedures affect both dynamic and static shell properties can enhance the safety and quality of egg reaching consumers. A study was conducted to determine if dynamic she...

  5. A large-scale study of the ultrawideband microwave dielectric properties of normal breast tissue obtained from reduction surgeries

    NASA Astrophysics Data System (ADS)

    Lazebnik, Mariya; McCartney, Leah; Popovic, Dijana; Watkins, Cynthia B.; Lindstrom, Mary J.; Harter, Josephine; Sewall, Sarah; Magliocco, Anthony; Booske, John H.; Okoniewski, Michal; Hagness, Susan C.

    2007-05-01

    The efficacy of emerging microwave breast cancer detection and treatment techniques will depend, in part, on the dielectric properties of normal breast tissue. However, knowledge of these properties at microwave frequencies has been limited due to gaps and discrepancies in previously reported small-scale studies. To address these issues, we experimentally characterized the wideband microwave-frequency dielectric properties of a large number of normal breast tissue samples obtained from breast reduction surgeries at the University of Wisconsin and University of Calgary hospitals. The dielectric spectroscopy measurements were conducted from 0.5 to 20 GHz using a precision open-ended coaxial probe. The tissue composition within the probe's sensing region was quantified in terms of percentages of adipose, fibroconnective and glandular tissues. We fit a one-pole Cole-Cole model to the complex permittivity data set obtained for each sample and determined median Cole-Cole parameters for three groups of normal breast tissues, categorized by adipose tissue content (0-30%, 31-84% and 85-100%). Our analysis of the dielectric properties data for 354 tissue samples reveals that there is a large variation in the dielectric properties of normal breast tissue due to substantial tissue heterogeneity. We observed no statistically significant difference between the within-patient and between-patient variability in the dielectric properties.

  6. Dielectric properties of wet sediments versus temperature at 10-6,000 MHz

    NASA Astrophysics Data System (ADS)

    Friddell, J. E.; Arcone, S. A.; Bartek, M. A.

    2004-05-01

    Knowledge of the dielectric properties of sediments is important to studies of subsurface radiowave propagation, especially as it applies to ground-penetrating radar (GPR) operating in the 50-1,000 MHz bandwidth. In areas contaminated by nuclear waste and in desert environments, water within the soils can be unusually warm, with temperatures ranging up to 50° C. For the GPR bandwidth, past results suggest that relaxation effects may cause significant dispersion and loss of the radar signal within the subsurface. To this end, we have employed a network analyzer-based system with a modified HP805 coaxial-type sample holder to investigate sand and silt at water contents ranging from 0% to 30% and temperatures ranging from 0° C to 50° C. The correct operation of this system has been verified with methanol, ethanol, and isopropyl alcohol which are dispersive in the GPR frequency range. Preliminary results suggest that dry sand and silt, which have relatively constant dielectric response across our frequency range of interest, experience no enhanced dispersion at elevated temperatures. With increasing water content, however, we find increasing dispersion at higher temperatures: for nearly saturated sand and silt, the real part of the complex dielectric permittivity decreases by up to 25% at frequencies above 100 MHz while it decreases less, or even slightly increases, below this frequency. Other than the low frequency peak in e'' due to conductivity effects, there are no additional imaginary dielectric loss peaks at elevated temperatures or water contents for sand and silt-sized materials. Further investigations are planned for clay soils to control for grain size in quantifying temperature-dependent dielectric dispersion effects.

  7. Changes in the dielectric properties of medaka fish embryos during development, studied by electrorotation

    SciTech Connect

    Shirakashi, Ryo; Mischke, Miriam; Fischer, Peter; Memmel, Simon; Krohne, Georg; Fuhr, Guenter R.; Zimmermann, Heiko; Sukhorukov, Vladimir L.

    2012-11-09

    Highlights: Black-Right-Pointing-Pointer Electrorotation offers a non-invasive tool for dielectric analysis of fish embryos. Black-Right-Pointing-Pointer The three-shell dielectric model matches the rotation spectra of medaka eggs. Black-Right-Pointing-Pointer The capacitance value suggests a double-membrane structure of yolk envelope. -- Abstract: 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.

  8. Effect of biphase on dielectric properties of Bi-doped lead strontium titanate thin films

    SciTech Connect

    Li, X.T.; Du, P.Y.; Zhao, Y.L.; Tu, Y.; Dai, J.L.; Weng, W.J.; Han, G.R.; Song, C.L.

    2010-11-15

    Pb{sub 0.4}Sr{sub 0.6}TiO{sub 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 0.2dielectric capacitance and dielectric loss. Display Omitted

  9. Dielectric properties of cereals at frequencies useful for processes with microwave heating.

    PubMed

    Torrealba-Meléndez, Richard; Sosa-Morales, María Elena; Olvera-Cervantes, José Luis; Corona-Chávez, Alonso

    2015-12-01

    Dielectric properties of barley, corn (white and yellow), sorghum, and wheat at microwave frequencies for heating purpose were analyzed. Properties were determined at 915, 2450 and 5800 MHz with the free space transmission method in the cereals at 20, 30, 40, 50 and 60 °C. ?´ and ?"of all the cereals decreased with increasing frequency. ?´ slightly increased with temperature, while ? "remained practically constant for all the cereals in the temperature range from 20 to 60 °C. Penetration depth decreased with increasing frequency for all the samples, and increased with increasing temperature at 915 MHz, except for barley. These results are useful for further microwave heating applications for the studies on cereals. PMID:26604422

  10. 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.

  11. Dielectric, electric and thermal properties of carboxylic functionalized multiwalled carbon nanotubes impregnated polydimethylsiloxane nanocomposite

    NASA Astrophysics Data System (ADS)

    Sagar, Sadia; Iqbal, Nadeem; Maqsood, Asghari

    2013-06-01

    The dielectric, electric and thermal properties of carboxylic functionalized multiwalled carbon nanotubes (F-MWCNT) incorporated into the polydimethylsiloxane (PDMS) were evaluated to determine their potential in the field of electronic materials. Carboxylic functionalization of the pristine multi walled carbon tubes (Ps-MWCNT) was confirmed through Fourier transform infrared spectroscopy, X-ray diffraction patterns for both Ps-MWCNTs and F-MWCNTs elaborated that crystalline behavior did not change with carboxylic moieties. Thermogravimetric and differential thermal analyses were performed to elucidate the thermal stability with increasing weight % addition of F-MWCNTs in the polymer matrix. Crystallization/glass transition / melting temperatures were evaluated using differential scanning calorimeter and it was observed that glass transition and crystallization temperatures were diminished while temperatures of first and second melting transitions were progressed with increasing F-MWCNT concentration in the PDMS matrix. Scanning electron microscopy and energy dispersive x-ray spectroscopy were carried out to confirm the morphology, functionalization, and uniform dispersion of F-MWCNTs in the polymer matrix. Electrical resistivity at temperature range (100-300°C), dielectric loss (tan?) and dielectric parameters (epsilon/ epsilon//) were measured in the frequency range (1MHz-3GHz). The measured data simulate that the aforementioned properties were influenced by increasing filler contents in the polymer matrix because of the high polarization of conductive F-MWCNTs at the reinforcement/polymer interface.

  12. Investigation of structural, optical, electrical and dielectric properties of catalytic sprayed hausmannite thin film

    SciTech Connect

    Larbi, T.; Ouni, B.; Boukhachem, A.; Boubaker, K. Amlouk, M.

    2014-12-15

    Hausmannite Mn{sub 3}O{sub 4} thin film have been synthesized using spray pyrolysis method. These films are characterized using X-ray diffraction (XRD), atomic force microscope AFM, UV–vis–NIR spectroscopy and impedance spectroscopy. XRD study confirms the tetragonal structure of the as-deposited films with lattice parameters, a = 5.1822 Å and c = 9.4563 Å and a grain size of about 56 nm. UV–vis–NIR spectroscopy was further used to estimate optical constants such as extinction coefficient, refractive index, band gap and Urbach energy. Moreover, impedance spectroscopy analysis was employed to estimate electrical and dielectrical properties of the sprayed thin films. The activation energy values deduced from DC conductivity and relaxation frequency were almost the same, revealing that the transport phenomena is thermally activated by hopping between localized states. The AC conductivity is found to be proportional to ?{sup s}. The temperature dependence of the AC conductivity and the frequency exponent, s was reasonably well interpreted in terms of the correlated barrier-hopping CBH model. The dielectric properties were sensitive to temperature and frequency. The study of the electrical modulus indicated that the charge carrier was localized. Experimental results concerning optical constants as Urbach energy, dielectric constant, electric modulus and AC and DC conductivity were discussed in terms of the hopping model as suggested by Elliott.

  13. Structure-dielectric properties relationships in copper-substituted magnesium ferrites

    SciTech Connect

    Druc, A.C.; Borhan, A.I.; Nedelcu, G.G.; Leontie, L.; Iordan, A.R.; Palamaru, M.N.

    2013-11-15

    Graphical abstract: - Highlights: • Synthesis of copper substituted magnesium ferrites materials is reported. • A shift from cubic to tetragonal structure starting with x = 0.84 was observed. • The dielectric properties are influenced by Cu-substitution. - Abstract: Nanocrystalline powders of copper-substituted magnesium ferrites with general formula Mg{sub 1?x}Cu{sub x}Fe{sub 2}O{sub 4} (x = 0.00, 0.17, 0.34, 0.50, 0.67, 0.84, 1.00) were prepared for the first time by sol–gel auto-combustion method, using glycine as fuel agent. Solid phase chemical reactions and the occurrence of spinel structure were monitored by using infrared spectroscopy. X-ray diffraction analysis confirmed the spinel single-phase formation. A shift from cubic structure to tetragonal structure starting with x = 0.84 was also observed. Microstructure of the samples was analyzed by scanning electron microscopy and particle size was estimated from the micrographs. Analysis of dielectric properties revealed very low values of dielectric loss at frequencies over 10 MHz.

  14. 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.

  15. Ferroelectric and dielectric properties of nanocrystalline BiFeO3 multiferroic ceramics synthesized by solution combustion method (SCM)

    NASA Astrophysics Data System (ADS)

    Chaudhari, Yogesh A.; Mahajan, Chandrashekhar M.; Abuassaj, Ebrahim M.; Jagtap, Prashant P.; Patil, Pramod B.; Bendre, Subhash T.

    2013-04-01

    Nanocrystalline multiferroic BiFeO3 ceramics was prepared by a novel solution combustion method (SCM). The X-ray diffraction (XRD) studies on structural properties of the synthesized ceramics reveal that the BiFeO3 ceramics has rhombhohedral perovskite structure with an average crystallite size of 15 nm. The ferroelectric P-E hysteresis loop measurement at room temperature shows unsaturated behavior with a partial reversal of polarization. Investigations on temperature dependence of dielectric constant in BiFeO3 demonstrate a clear dielectric anomaly at approximately around 380 °C, which corresponds to antiferromagnetic to paramagnetic phase transition (TN) and also evidences a possible coupling among the electric and magnetic dipoles of BiFeO3. A room temperature variation of dielectric constant " ?" and dielectric loss "tan ?" as a function of frequency in the range of 100 Hz — 1 MHz, confirms that both dielectric constant and loss are strong functions of frequency.

  16. Dielectric properties of lava flows west of Ascraeus Mons, Mars

    USGS Publications Warehouse

    Carter, L.M.; Campbell, B.A.; Holt, J.W.; Phillips, R.J.; Putzig, N.E.; Mattei, S.; Seu, R.; Okubo, C.H.; Egan, A.F.

    2009-01-01

    The SHARAD instrument on the Mars Reconnaissance Orbiter detects subsurface interfaces beneath lava flow fields northwest of Ascraeus Mons. The interfaces occur in two locations; a northern flow that originates south of Alba Patera, and a southern flow that originates at the rift zone between Ascraeus and Pavonis Montes. The northern flow has permittivity values, estimated from the time delay of echoes from the basal interface, between 6.2 and 17.3, with an average of 12.2. The southern flow has permittivity values of 7.0 to 14.0, with an average of 9.8. The average permittivity values for the northern and southern flows imply densities of 3.7 and 3.4 g cm-3, respectively. Loss tangent values for both flows range from 0.01 to 0.03. The measured bulk permittivity and loss tangent values are consistent with those of terrestrial and lunar basalts, and represent the first measurement of these properties for dense rock on Mars. Copyright 2009 by the American Geophysical Union.

  17. Dielectric and Thermal Properties of Polyimide-Poly(ethylene oxide) Nanofoamed Films

    NASA Astrophysics Data System (ADS)

    Zhang, Yi-He; Yu, Li; Zhao, Li-Hang; Tong, Wang-Shu; Huang, Hai-Tao; Ke, Shan-Ming; Chan, H. L. W.

    2012-08-01

    Polyimide nanofoamed films have been prepared by incorporating poly(ethylene oxide) (PEO) into poly(amide acid) (PAA) precursors with subsequent imidization of PAA precursors at high temperature. The porous structure, thermal decomposition temperature, and dielectric property of nanofoamed films were investigated by scanning electron microscopy, thermogravimetric analysis, and impedance spectroscopy. Nanopores with sizes around 40 nm to 200 nm were formed in nanofoamed films by pyrolysis of PEO during the imidization progress. The decomposition temperature of nanofoamed films decreased slightly with increasing volume fraction of nanopores and maintained the high decomposition temperature of 499.7 °C when the volume fraction of nanopores was 10.9 %. The dielectric constant of nanofoamed films decreased from 3.4 for pure PI to 2.4 at 103 Hz through the introduction of nanopores with volume fraction of 10.9 %.

  18. Tweaking Electrical and Dielectric Properties of Nickel Oxide Nanocrystals by Varying the Surfactant.

    PubMed

    Maheswari, A Uma; Mohan, Sreedevi R; Sivakumar, M; Kumar, S Saravana

    2015-12-01

    The influence of cationic cetyltrimethylammonium bromide (CTAB) and neutral polymeric polyvinylpyrrolidone (PVP) surfactants on electrical and dielectric properties of NiO nanocrystals is investigated. It is demonstrated that, compressive strain of nanocrystals is higher with PVP than that of CTAB. Consequently surfactant type has significant influence on intrinsic defects of nanocrystals. This is attributed to the difference in stabilization of metallic ions against agglomeration that leads to variation in rate of hydrolysis. Particularly, in the case of PVP assisted synthesis, higher stabilization leads to slow nucleation rate with lower defect density. As a result the hopping time of charge carriers decreases which in turn enhances the conductivity of nanocrystals as evidenced from the shifting of dielectric loss peak to higher frequency. PMID:26682362

  19. Nondestructive analysis of dielectric properties: application to ion beam irradiated tissue response microfibre.

    PubMed

    Mallick, Biswajit

    2014-01-01

    The aim of this work was to investigate the effect of 2.4 MeV proton irradiation on the dielectric property of polyethylene terephthalate (PET) microfibre nondestructively. The dielectric constant ?d of single-microfibre has been measured as-such applying laser diffraction technique. Applying this methodology ?d is found out to be slightly increases with proton fluence except at the fluence 1013 p/cm2 where material shows maximum crosslinking. The variations of the biological interaction with ?d of PET material are correlated. Proton beam modified PET microfibre is therefore accepted to have further potential applications in radiation processing tissue response microfibre, fabrication of medical devices etc. PMID:24642970

  20. Electrical, Magnetic and Dielectric Properties of Zn1-xCdxO System

    NASA Astrophysics Data System (ADS)

    Kamruzzaman, M.; Khan, M. K. R.; Rahman, M. M.; Karal, M. A. S.; Shahjahan, M.; Ahsan, M. Rafiqul

    The ternary system Zn1-xCdxO (x = 0.00, 0.01, 0.05, 0.10 and 0.15) samples have been synthesized by the solid solution route. The synthesized samples were characterized by their electrical, magnetic and dielectric properties. The resistivity of the samples decreases with increase of Cd concentration and temperature, respectively. The activation energy at 339 K varies from 0.426 to 0.146 eV. The ternary system possesses a negative mass susceptibility having pair of electrons confirmed by the magnetic mass susceptibility measurement. The dielectric constant of the samples increases with increase of Cd and decreases with frequency initially and then remains constant.

  1. Frequency dependent dielectric properties in Schottky diodes based on rubrene organic semiconductor

    NASA Astrophysics Data System (ADS)

    Bar??, Behzad

    2013-12-01

    Al/rubrene/p-Si Schottky diode has been fabricated by forming a rubrene layer on p type Si by using the spin coating method. The frequency and voltage dependent dielectric constant (??), dielectric loss (??), tangent loss (tan?), electrical modulus (M? and M?), and ac electrical conductivity (?) properties of Al/rubrene/p-Si Schottky diodes have been investigated in the frequency range of 1 kHz-1 MHz at room temperature. It is found that the values of the ??, ?? and tan? decrease with increasing frequency while an increase is observed in ? and the real component (M?) of the electrical modulus. The values of ??, ??, and tan? were found as 5.01, 2.55, and 0.51 for 1 kHz and 2.46, 0.069, and 0.028 for 1 MHz at zero bias, respectively. Furthermore, the imaginary component (M?) of the electric modulus showed a peak that shifts to a higher voltage with decreasing frequency.

  2. 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.

  3. Measurements along the growth direction of PMN-PT crystals: dielectric, piezoelectric, and elastic properties.

    PubMed

    Tian, Jian; Han, Pengdi; Payne, David A

    2007-09-01

    Property measurements are reported for Pb(Mg1/3Nb2/3)03-PbTiO3 (PMN-PT) single crystals grown along (001) by a seeded-melt method. Chemical segregation occurs during crystal growth, leading to property changes along the growth direction. Variations in dielectric, piezoelectric, and elastic properties were evaluated for specimens selected from the crystals. Room-temperature data are correlated with Tc and composition that ranged from 27 to 32% PT, i.e., in the vicinity of the morphotropic phase boundary (MPB). While there was little change in the high electromechanical coupling factor k33 (0.87-0.92), both the piezoelectric charge coefficient d33 (1100-1800 pC/N) and the free dielectric constant K3 (4400-7000) were found to vary significantly with position. Increases in d33 and KT33 were relatively offsetting in that the ratio yielded a relatively stable piezoelectric voltage coefficient g33 (27-31 x 10(-3) Vm/N). Values are also reported for the elastic compliance (3.3-6.3 x 10(-11) m2/N) determined from resonance measurements. Enhancements in d33 and K(T)33 were associated with lattice softening (increasing sE33) as the composition approached the MPB. Details are reported for the piezoelectric, dielectric, and elastic properties as a function of growth direction, Tc, and composition. The results are useful for an understanding of properties in PMN-PT crystals and for the design of piezoelectric devices. PMID:17941396

  4. 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

    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.

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

    E-print Network

    Patton, Carl

    ; published online 20 October 2006 A series of sintered composite materials was fabricated from ParascanTM barium strontium titanate BSTO and Trans-Tech nickel zinc ferrite powders. The ferrite loading was varied strontium titanate BSTO . X-ray diffraction XRD data indicate that the processing produced a titanium oxide

  6. Influence of O2 on the dielectric properties of CO2 at the elevated temperatures

    NASA Astrophysics Data System (ADS)

    Rong, Mingzhe; Sun, Hao; Yang, Fei; Wu, Yi; Chen, Zhexin; Wang, Xiaohua; Wu, Mingliang

    2014-11-01

    SF6 gas is widely used in the high voltage circuit breakers but considering its high global warming potential other substitutes are being sought. Among them CO2 was investigated and even has been used in some practical products. However, at room temperature, the dielectric properties of CO2 are relatively lower than SF6 and air. The goal of this work is to investigate a CO2-based gas to improve the performance of the pure CO2. In this paper, the dielectric properties of hot CO2/O2 mixtures related to the dielectric recovery phase of the circuit breaker were investigated in the temperature range from 300 K to 4000 K and in the pressure range from 0.01 MPa to 1.0 MPa. The species compositions of hot CO2/O2 were obtained based on Gibbs free energy minimization under the assumptions of local thermodynamic equilibrium and local chemical equilibrium. The reduced critical electric field strength of CO2/O2 was determined by balancing electron generation and loss. These were calculated using the electron energy distribution function by solving the Boltzmann transport equation. The validity of the calculation method and the cross sections data was confirmed by comparing the measurements and calculations of the electron swarm data in previous work. The results indicate that in pure CO2 the critical electric field strength is higher only in higher temperature range. By adding the O2 into the CO2, the critical electric field strength at lower temperature is effectively enhanced. CO2/O2 mixtures have a much better dielectric strength than both the pure CO2 and air and thus have the potential to improve the CO2-based gas circuit breakers. Similar conclusions can also be found in others' work, which further confirm the validity of these results.

  7. 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 ferroelectrics, such as SrTiO3 and KTaO3, ex- hibit increasing dielectric permittivity e0 with decreasing

  8. Effect of Sintering Temperature on Dielectric Properties of Iron Deficient Nickel-Ferrite

    SciTech Connect

    Rani, Renu; Singh, Sangeeta; Juneja, J. K.; Prakash, Chandra; Raina, K. K.

    2011-11-22

    Nickel Ferrite among all the magneto ceramic materials have been studied very much due to its large number of applications. But there is a large scope of modification of its properties. Thus people still working on it for improvisation of its properties via compositional and structural modifications. Present paper reporting the preparation and characterization of iron deficient Nickel ferrite for different sintering temperature. Ferrite samples having the general formula NiFe1.98O{sub 4} were prepared using the standard ceramic method. The phase formation was confirmed by X-ray diffraction technique. The effect of sintering temperature on the electrical properties and resistivity was studied. The data shows that dielectric properties are highly dependent on the sintering temperature.

  9. 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.

  10. 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.

  11. Dielectric and Electrical Properties of BiFeO3-PbZrO3 Composites

    NASA Astrophysics Data System (ADS)

    Satpathy, S. K.; Mohanty, N. K.; Behera, A. K.; Sen, S.; Behera, Banarji; Nayak, P.

    2015-11-01

    The dielectric and electrical properties of composites prepared by addition of two different amounts of PbZrO3 (PZO) to BiFeO3 (BFO) are discussed. The composites (1 - x)(BiFeO3)- x(PbZrO3) ( x = 0.5, 0.7; i.e., 0.5BF-0.5PZ and 0.3BF-0.7PZ) were synthesized by solid-state reaction. X-ray diffraction analysis confirmed formation of composites with a rhombohedral structure at room temperature. Scanning electron microscopy revealed homogeneously distributed grains. Dielectric constants and dielectric loss increased with decreasing PZO content whereas the transition temperature shifted to higher temperature with decreasing PZO content. Hysteresis loops confirmed the ferroelectric nature of the materials. The Nyquist plot was indicative of the contribution of the bulk effect and a small contribution from the grain boundary effect. Temperature-dependent relaxation occurred for both materials. Non-Debye type electrical impedance was confirmed by asymmetric peak broadening and a spread of relaxation times. Activation energies were calculated from plots of ac conductivity as a function of temperature by linear fitting. Dc and ac conductivity increased with increasing temperature. Activation energies calculated from the complex impedance plot and from the fitted Jonscher power law were very similar, implying conduction by a similar type of charge carrier in both composites.

  12. Dielectric properties of silicone rubber-titanium dioxide composites prepared by dielectrophoretic assembly of filler particles

    NASA Astrophysics Data System (ADS)

    Razzaghi Kashani, M.; Javadi, S.; Gharavi, N.

    2010-03-01

    Formation of a controlled morphology of fillers in polymeric composites may be difficult to achieve by conventional methods such as mechanical shear or chemical methods. A tunable structure of filler and anisotropic properties in composites can be obtained by exploiting dielectrophoretic assembly of fillers in a polymer composite by using electric fields. In this study, different concentrations of titanium dioxide (TiO2) particles in silicone rubber matrix were assembled in a chain-like structure by using an alternating electric field. The silicone rubber matrix was vulcanized to transform the liquid to solid and maintain the filler structure in the desired direction. Generation of the chain structure of the filler was verified by scanning electron microscopy (SEM) and equilibrium swelling. It was shown that dielectric permittivity of the oriented composite is higher whereas its dielectric loss is lower in the orientation (thickness) direction than those for composites with random distribution of filler. A critical concentration of filler was distinguished as the percolation point at which the change in dielectric behavior is amplified.

  13. A Study of the Dielectric Properties of Dry and Saturated Green River Oil Shale

    SciTech Connect

    Sweeney, J; Roberts, J; Harben, P

    2007-02-07

    We measured dielectric permittivity of dry and fluid-saturated Green River oil shale samples over a frequency range of 1 MHz to 1.8 GHz. Dry sample measurements were carried out between room temperature and 146 C, saturated sample measurements were carried out at room temperature. Samples obtained from the Green River formation of Wyoming and from the Anvil Points Mine in Colorado were cored both parallel and perpendicular to layering. The samples, which all had organic richness in the range of 10-45 gal/ton, showed small variations between samples and a relatively small level of anisotropy of the dielectric properties when dry. The real and imaginary part of the relative dielectric permittivity of dry rock was nearly constant over the frequency range observed, with low values for the imaginary part (loss factor). Saturation with de-ionized water and brine greatly increased the values of the real and imaginary parts of the relative permittivity, especially at the lower frequencies. Temperature effects were relatively small, with initial increases in permittivity to about 60 C, followed by slight decreases in permittivity that diminished as temperature increased. Implications of these observations for the in situ electromagnetic, or radio frequency (RF) heating of oil shale to produce oil and gas are discussed.

  14. Anomalous dielectric and thermal properties of Ba-doped PbZrO3 ceramics.

    PubMed

    Pirc, R; Roži?, B; Koruza, J; Cordoyiannis, G; Mali?, B; Kutnjak, Z

    2015-11-18

    The dielectric and thermal properties of an antiferroelectric (AFE) material characterised by an intermediate ferroelectric (FE) phase between the AFE and paraelectric phase in zero field are studied by means of a generalised Landau-Kittel model of AFEs. A temperature-dependent coupling of the two sublattices is introduced in accordance with the Rae-Dove (RD) model of re-entrant phase transitions. The sublattice polarisation components are calculated as functions of temperature and the applied electric field by minimising numerically the free energy. The calculated dielectric susceptibility shows anomalies at the boundaries of the intermediate FE phase, characteristic for first-order phase transitions. It is shown that this behaviour is in qualitative agreement with the measured dielectric constant in Ba-doped PbZrO3 ceramics. The model also predicts a negative adiabatic electrocaloric temperature change [Formula: see text] in a broad temperature range in the AFE phase, in qualitative agreement with experiments. The dipolar heat capacity is also predicted to be negative in the intermediate phase in zero field, in analogy with the results of the RD model. PMID:26490797

  15. Anomalous dielectric and thermal properties of Ba-doped PbZrO3 ceramics

    NASA Astrophysics Data System (ADS)

    Pirc, R.; Roži?, B.; Koruza, J.; Cordoyiannis, G.; Mali?, B.; Kutnjak, Z.

    2015-11-01

    The dielectric and thermal properties of an antiferroelectric (AFE) material characterised by an intermediate ferroelectric (FE) phase between the AFE and paraelectric phase in zero field are studied by means of a generalised Landau–Kittel model of AFEs. A temperature-dependent coupling of the two sublattices is introduced in accordance with the Rae–Dove (RD) model of re-entrant phase transitions. The sublattice polarisation components are calculated as functions of temperature and the applied electric field by minimising numerically the free energy. The calculated dielectric susceptibility shows anomalies at the boundaries of the intermediate FE phase, characteristic for first-order phase transitions. It is shown that this behaviour is in qualitative agreement with the measured dielectric constant in Ba-doped PbZrO3 ceramics. The model also predicts a negative adiabatic electrocaloric temperature change ? T in a broad temperature range in the AFE phase, in qualitative agreement with experiments. The dipolar heat capacity is also predicted to be negative in the intermediate phase in zero field, in analogy with the results of the RD model.

  16. 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.

  17. Vanadium oxide nanotubes VOx-NTs: Hydrothermal synthesis, characterization, electrical study and dielectric properties

    SciTech Connect

    Nefzi, H.; Sediri, F.

    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.

  18. Investigation of structural, dielectric and ferroelectric properties of Gd-doped lead magnesium niobate ceramics

    NASA Astrophysics Data System (ADS)

    Pandey, Adityanarayan H.; Srivastava, Arvind K.; Sinha, Anil K.; Gupta, Surya M.

    2015-09-01

    The structural, microstructural, local ordering of B-site cations, dielectric and ferroelectric properties have been investigated for Pb1-xGdx(Mg1/3Nb2/3)1-x/4O3 0 ? x ? 0.1. Charge imbalance due to Gd3+ ion substitution at Pb2+ is compensated by creating B-site vacancies. The Gd-ion doping at Pb sites in PMN results in the formation of a secondary GdNbO4 phase, which is explained by considering the ionic radii of the Gd ion and its solubility limit at Pb-ion sites. A reaction mechanism for the formation of GdNbO4 has been proposed. Selected area electron diffraction along the <110> axis reveals enhancement in size of the non-stoichiometric chemical ordered regions leading to a decrease in the size of polar nano regions and their correlations, which manifests in a decrease of Tm, a more diffused ?max peak and enhancement of the dielectric relaxation strength calculated from fitting of the frequency and temperature dependence of the dielectric behavior. Linear dependence between polarization and electric field also signifies reduction in the correlation between the PNRs resulting in the decrease of the value of Pmax (at ˜ 30 kV cm-1).

  19. 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.

  20. Dielectric properties and electrical conduction of high-k LaGdO3 ceramics

    NASA Astrophysics Data System (ADS)

    Pavunny, S. P.; Thomas, R.; Kumar, A.; Murari, N. M.; Katiyar, R. S.

    2012-05-01

    The temperature and frequency dependent dielectric properties and leakage conduction mechanism in LaGdO3 (LGO) ceramics have been studied, and this material has been identified as a potential high-k candidate for the future complementary metal-oxide-semiconductor (CMOS) and dynamic random access memory (DRAM) technology nodes. The dielectric constant and the loss tangent at 100 kHz were ˜21.5 and ˜0.003, respectively, at ambient conditions without any significant temperature and voltage dependence. The ac conductivity shows the typical features of universal dynamic response (UDR) and obey the double power law ?ac=?dc+A?n1+B?n2 with three types of temperature dependent conduction processes involved; (i) a dc plateau (< 3 kHz) due to long range translational hopping, (ii) a mid frequency region due to the short range hopping (3-100 kHz), and (iii) a high frequency region due to localized or reorientational hopping (100-1000 kHz). The temperature dependent dc conductivity follows the Arrhenius relation with activation energies of 0.05 eV in the 200-400 K range and 0.92 eV in the 400-600 K range. The leakage current behavior reveals bulk limited Poole-Frenkel (PF) conduction mechanism and the estimated optical dielectric constant (??) is 3.6.

  1. Magnetic, dielectric, and microwave absorbing properties of iron particles dispersed in rubber matrix in gigahertz frequencies

    NASA Astrophysics Data System (ADS)

    Kim, Sung-Soo; Kim, Sun-Tae; Yoon, Yeo-Choon; Lee, Kyung-Sub

    2005-05-01

    This study investigates high-frequency magnetic, dielectric, and microwave absorbing properties of iron particles dispersed in rubber matrix for the aim of thin microwave absorbers in gigahertz frequencies. High value of magnetic permeability and dielectric constant can be obtained in the composites containing thin flake iron particles which were prepared by mechanical forging of spherical iron powders using an attrition mill. The results are attributed to the reduction of eddy current loss (increase of permeability) and enhancement of space-charge polarization (increase of permittivity). However, if the initial particle size is too small (approaching to skin depth), milling effect for the increase of permeability is not observed and a low dielectric constant is predicted. If the particle size is too large, the permeability value is too small due to strong eddy current loss. With the iron particles controlled in size and shape (flakes) as the absorbent fillers, the thickness can be reduced as low as 1mm with respect to -5dB reflection loss in 1-2GHz.

  2. Dielectric properties of iron-containing bismuth titanate solid solutions with a layered perovskite structure

    NASA Astrophysics Data System (ADS)

    Shashkov, M. S.; Malyshkina, O. V.; Piir, I. V.; Koroleva, M. S.

    2015-03-01

    The complex oxides based on bismuth titanate with substituting iron atoms Bi4Ti2.98Fe0.02O11.99, Bi4Ti2.5Fe0.5O11.75, and Bi4Ti2Fe1O11.5 have been studied using dielectric spectroscopy in the frequency range from 30 to 106 Hz at a temperature of 296 K. The frequency dependences of permittivity ?', dielectric loss ??, and complex part of conductivity ?' have been studied, and the dependences ??(?') have been constructed. The microstructure images of the studied ceramic materials have been obtained using atomic force microscopy. It has been shown that, as Fe3+ ions are introduced as substituting atoms, there is a critical concentration x (0.5 < x < 1) above which the dielectric properties substantially change with variations in the number of perovskite-like layers, and the correlation is observed between the concentration of substituting Fe atoms and the grain size on the surface of the samples.

  3. Dielectric, ferroelectric and magnetic properties of Mn-doped LuFeO3 ceramics

    NASA Astrophysics Data System (ADS)

    Qin, Ying; Qiang Liu, Xiao; Ming Chen, Xiang

    2013-01-01

    LuFe1-xMnxO3 (x = 0, 0.05) ceramics with the orthorhombic distorted perovskite structure in space group Pbnm were synthesized using a solid-state reaction process. The dielectric, ferroelectric, and magnetic properties were investigated systematically. With Mn-substitution, the low temperature dielectric relaxation was suppressed and only one dielectric anomaly around 360-530 K was observed. Obvious ferroelectric hysteresis loops were detected at room temperature in LuFe0.95Mn0.05O3, the smaller polarization compared with LuFeO3 suggested the important role of the electron hopping between Fe2+ and Fe3+ ions in ferroelectricity. The results of thermal analysis indicated that the Néel temperature decreased with Mn-substitution, which could be ascribed to the weaker Fe3+-Mn3+ and Mn3+-Mn3+ exchange interactions compared with Fe3+-Fe3+ interaction. Due to the strong anisotropy of Mn3+ ions, a spin reorientation transition could be induced in LuFe0.95Mn0.05O3. Moreover, weak ferromagnetic characteristic was also detected at room temperature in LuFe0.95Mn0.05O3 ceramics.

  4. 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.

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

    E-print Network

    Duojie Jia; Xiao-wei Wang; Feng Liu

    2009-12-28

    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.

  6. Radiolysis of liquids with high static dielectric constant: An estimate of the total ionization yield, electron thermalization distance, and contribution of heterogeneous reactions

    SciTech Connect

    Ferradini, C.; Jay-Gerin, J.

    1988-12-01

    In a previous study, we found an exponential dependence of the free-ion yield (G/sub fi/) on the static dielectric constant (epsilon/sub s/) for a number of irradiated liquids with epsilon/sub s/>10. On the basis of this study, we develop here a simple model by which we quantitatively estimate the total ionization yield (G/sub tot/), the most probable electron thermalization distance (b), and the yield of solvated electrons that are removed by diffusion-controlled reactions during spur expansion (G/sub dif/). Using solvated electron yields available in the literature, we get G/sub tot/approx. =6.6 mol/100 eV (value nearly independent of the nature of the liquid) and bapprox. =29 A at 298 K. b is found not to depend appreciably on epsilon/sub s/ which indicates that the Coulomb attractive force between the ion and secondary electron is practically inefficient before electron thermalization occurs. The evaluation of G/sub dif/ teaches us that spur reactions have a profound influence in the fate of ion pairs formed during radiolysis of liquids of high epsilon/sub s/ values.

  7. Geometrical-optics code for computing the optical properties of large dielectric spheres.

    PubMed

    Zhou, Xiaobing; Li, Shusun; Stamnes, Knut

    2003-07-20

    Absorption of electromagnetic radiation by absorptive dielectric spheres such as snow grains in the near-infrared part of the solar spectrum cannot be neglected when radiative properties of snow are computed. Thus a new, to our knowledge, geometrical-optics code is developed to compute scattering and absorption cross sections of large dielectric particles of arbitrary complex refractive index. The number of internal reflections and transmissions are truncated on the basis of the ratio of the irradiance incident at the nth interface to the irradiance incident at the first interface for a specific optical ray. Thus the truncation number is a function of the angle of incidence. Phase functions for both near- and far-field absorption and scattering of electromagnetic radiation are calculated directly at any desired scattering angle by using a hybrid algorithm based on the bisection and Newton-Raphson methods. With these methods a large sphere's absorption and scattering properties of light can be calculated for any wavelength from the ultraviolet to the microwave regions. Assuming that large snow meltclusters (1-cm order), observed ubiquitously in the snow cover during summer, can be characterized as spheres, one may compute absorption and scattering efficiencies and the scattering phase function on the basis of this geometrical-optics method. A geometrical-optics method for sphere (GOMsphere) code is developed and tested against Wiscombe's Mie scattering code (MIE0) and a Monte Carlo code for a range of size parameters. GOMsphere can be combined with MIE0 to calculate the single-scattering properties of dielectric spheres of any size. PMID:12921277

  8. Structural and optical characterization of Cr{sub 2}O{sub 3} nanostructures: Evaluation of its dielectric properties

    SciTech Connect

    Abdullah, M. M.; Rajab, Fahd M.; Department of Chemical Engineering, College of Engineering, Najran University, P.O. Box 1988, Najran, 11001 ; Al-Abbas, Saleh M.

    2014-02-15

    The structural, optical and dielectric properties of as-grown Cr{sub 2}O{sub 3} nanostructures are demonstrated in this paper. Powder X-ray diffractometry analysis confirmed the rhombohedral structure of the material with lattice parameter, a = b = 4.953 Å; c = 13.578 Å, and average crystallize size (62.40 ± 21.3) nm. FE-SEM image illustrated the mixture of different shapes (disk, particle and rod) of as-grown nanostructures whereas; EDS spectrum confirmed the elemental purity of the material. FTIR spectroscopy, revealed the characteristic peaks of Cr–O bond stretching vibrations. Energy band gap (3.2 eV) of the nanostructures has been determined using the results of UV-VIS-NIR spectrophotometer. The dielectric properties of the material were checked in the wide frequency region (100Hz-30 MHz). In the low frequency region, the matrix of the dielectric behaves like source as well as sink of electrical energy within the relaxation time. Low value of dielectric loss exhibits that the materials posses good optical quality with lesser defects. The ac conductivity of the material in the high frequency region was found according to frequency power law. The physical-mechanism and the theoretical-interpretation of dielectric-properties of Cr{sub 2}O{sub 3} nanostructures attest the potential candidature of the material as an efficient dielectric medium.

  9. 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.

  10. Investigation of the dielectric properties of composites based on silicon dioxide with carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Goshev, A. A.; Eseev, M. K.; Kapustin, S. N.; Malkov, A. V.; Osokin, C. S.

    2015-11-01

    The aim of this work is an experimental study of the dielectric properties of nanocomposites with a matrix of silica reinforced with multi-walled CNTs at different concentrations and to determine the role of the CNT in the scattering and absorption of electromagnetic radiation in the range of extra-long and medium radio waves (25 Hz-1 MHz). The study found that in addition to the standard behavior of the electrical characteristics of nanocomposites with increasing concentration there was an optimum concentration of carbon nanotubes at which conductivity and absorption of electromagnetic radiation in the material greatly increased. This can be used to enhance the functionality of nanocomposites.

  11. 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.

  12. Process induced electroactive ?-polymorph in PVDF: effect on dielectric and ferroelectric properties.

    PubMed

    Sharma, Maya; Madras, Giridhar; Bose, Suryasarathi

    2014-07-28

    The effects of various processing conditions, like annealing, poling, mechanical rolling and their combinations, on the dielectric and ferroelectric properties of PVDF [poly(vinylidene fluoride)] were systematically studied in this work. Further, the effect of processing sequence on the structure and properties was investigated. While all the processing conditions adopted here resulted in phase transformation of the ?- to electroactive ?-polymorph in PVDF, the fraction of ?-phase developed was observed to be strongly contingent on the adopted process. The transformation of ? to electroactive ?-polymorph was determined by X-ray diffraction and FTIR. The neat PVDF showed only ?-phase, whereas mechanically rolled samples exhibited the highest ca. 85% ?-phase in PVDF. Both the permittivity and the loss tangent decreased in the samples which had undergone different processing conditions. The polarization-electric field (P-E) loops for all the samples were evaluated. Interestingly, the energy density, estimated from the electrical displacement-electric field (D-E) loops, was observed to be highest for the poled samples which were initially rolled. The results indicate that various processing conditions can influence the dielectric and the ferroelectric properties differently. PMID:24922560

  13. 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.

  14. 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.

  15. Enhancement of ferromagnetic and dielectric properties of lanthanum doped bismuth ferrite nanostructures

    SciTech Connect

    Chaudhuri, A.; Mandal, K.

    2012-04-15

    Highlights: Black-Right-Pointing-Pointer Rod shaped lanthanum doped bismuth ferrite was obtained. Black-Right-Pointing-Pointer The diameter of the particles were found to be decreasing on doping with lanthanum. Black-Right-Pointing-Pointer Both ferromagnetic and dielectric properties enhanced. Black-Right-Pointing-Pointer A transition due to spin canting is observed near 550 Degree-Sign C. Black-Right-Pointing-Pointer Electron spin resonance study shows the breakage of spin cycloid due to doping. -- Abstract: Cylindrical-shaped multiferroic Bi{sub 1-x}La{sub x}FeO{sub 3} (x = 0.0, 0.05, 0.1 and 0.15) were synthesized successfully by hydrothermal method. All samples were found to be rhombohedrally distorted perovskite structure. Diameter of the cylindrical particles reduces from {approx}450 nm for x = 0.0 to {approx}100 nm for x = 0.1 prepared under the same conditions. The Neel temperature as well as the dielectric constant was also found to increase with the increase in lanthanum content. Lanthanum doping also enhanced the magnetic properties. Magnetization measurements above room temperature show a significant increase in magnetization at around 400 Degree-Sign C. Enhanced magnetic properties due to lanthanum doping are caused by the breakage of spin cycloid as observed by electron spin resonance study.

  16. Cooperative Investigation of Relationship Between Static and Fatigue Properties of Wrought N-155 Alloy at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    1956-01-01

    Report presents the correlation of extensive data obtained relating properties of wrought n-155 alloy under static, combined static and dynamic, and complete reversed dynamic stress conditions. Time period for fracture ranged from 50 to 500 hours at room temperature, 1,000 degrees, 1,200 degrees, and 1,500 degrees F.

  17. Nonlinear Dielectric Properties of Yeast Cells Cultured in Different Environmental Conditions

    NASA Astrophysics Data System (ADS)

    Kawanishi, Gomon; Fukuda, Naoki; Muraji, Masafumi

    The harmonics of the electric current through yeast suspensions, the nonlinear dielectric properties of yeast cells, have particular patterns according to the biological activity of the cells and the measurement of these patterns is a technique for determining the activity of living cells. The concentration of glucose and oxygen in yeast culture medium influences the manifestation of fermentation or respiration of yeast cells. Measurements were made with yeast cells (Saccharomyces cerevisiae) cultured aerobically and anaerobically in sufficient glucose concentration, aerobic fermentation and anaerobic fermentation, and aerobically in limited glucose concentration, respiration. The results showed that the harmonics were barely apparent for yeast cells in aerobic fermentation and respiratory; however, cells in the anaerobic fermentation displayed substantial third and fifth harmonics. We can say that environmental condition affects the yeast cells' nonlinear properties, from another viewpoint, the measurements of the nonlinear properties are available to determine the activity of yeast cells adjusted to the conditions of their cultivation.

  18. 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

  19. MAPPING OF RESERVOIR PROPERTIES AND FACIES THROUGH INTEGRATION OF STATIC AND DYNAMIC DATA

    SciTech Connect

    Albert C. Reynolds; Dean S. Oliver; Yannong Dong; Ning Liu; Guohua Gao; Fengjun Zhang; Ruijian Li

    2004-12-01

    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. The volume of data that can potentially provide information on reservoir architecture and fluid distributions has increased enormously in the past decade. The techniques developed in this research will make it easier to use 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. In this project, we have developed computationally efficient automatic history matching techniques for generating geologically plausible reservoir models which honor both static and dynamic data. Specifically, we have developed methods for adjusting porosity and permeability fields to match both production and time-lapse seismic data and have also developed a procedure to adjust the locations of boundaries between facies to match production data. In all cases, the history matched rock property fields are consistent with a prior model based on static data and geologic information. Our work also indicates that it is possible to adjust relative permeability curves when history matching production data.

  20. Dielectric properties of CaNdAlO sub 4 at microwave frequencies

    SciTech Connect

    Konopka, J.; Wolff, I. ); Lewandowski, S.J. )

    1992-07-01

    Dielectric properties of CaNdAlO{sub 4} monocrystals, a prospective substrate material for the deposition of high-{ital T}{sub {ital c}} superconductors, were measured with high accuracy at microwave frequencies from 8 to 40 GHz in the temperature range from 10 to 300 K by measuring the resonant frequencies of a completely filled resonant cavity. The material was found to be highly anisotropic. At 300 K it exhibits the dielectric constant along {ital c} axis {epsilon}{sup {prime}}{sub {ital c}} = 17.68, while the dielectric constant in the {ital a}-{ital b} plane is {epsilon}{prime}=19.62, and loss tangent tan {delta}{sub {ital c}} {congruent} tan {delta} {congruent} 5.1{times} 10{sup {minus}4}. Both {epsilon}{sup {prime}}{sub {ital c}} and {epsilon}{prime} depend strongly on temperature and their thermal coefficients have opposite signs, apparently a unique property of CaNdAlO{sub 4}. Below 160 K microwave losses caused by electric field perpendicular to the optical {ital c} axis increase with decreasing temperature, exhibiting a maximum near 65 K followed by a minimum at 30 K. It is suggested that neodymium ions in CaNdAlO{sub 4} at lower temperatures become magnetically ordered, causing an increase of magnetic permeability {mu}{sup {prime}}{sub {ital c}} {gt} 1 and a significant increase of magnetic losses at microwave frequencies. A crystallographic phase transition below 60 K cannot also be excluded.

  1. High thermal robustness of molecularly thin perovskite nanosheets and implications for superior dielectric properties.

    PubMed

    Li, Bao-Wen; Osada, Minoru; Ebina, Yasuo; Akatsuka, Kosho; Fukuda, Katsutoshi; Sasaki, Takayoshi

    2014-06-24

    A systematic study has been conducted to examine the thermal stability of layer-by-layer assembled films of perovskite-type nanosheets, (Ca2Nb3O10(-))n (n = 1-10), which exhibit superior dielectric and insulating properties. In-plane and out-of-plane X-ray diffraction data as well as observations by atomic force microscopy and transmission electron microscopy indicated the high thermal robustness of the nanosheet films. In a monolayer film with an extremely small thickness of ?2 nm, the nanosheet was stable up to 800 °C, the temperature above which segregation into CaNb2O6 and Ca2Nb2O7 began. The critical temperature moderately decreased as the film thickness, or the number of nanosheet layers, increased, and reached 700 °C for seven- and 10-layer films, which is comparable to the phase transformation temperature for a bulk phase of the protonic layered oxide of HCa2Nb3O10·1.5H2O as a precursor of the nanosheet. This thermal stabilization of perovskite-type nanosheets should be associated with restricted nucleation and crystal growth peculiar to such ultrathin 2D bound systems. The stable high-k dielectric response (?r = 210) and highly insulating nature (J < 10(-7) A cm(-2)) remained substantially unchanged even after the nanosheet film was annealed up to 600 °C. This study demonstrates the high thermal stability of 2D perovskite-type niobate nanosheets in terms of structure and dielectric properties, which suggests promising potential for future high-k devices operable over a wide temperature range. PMID:24797417

  2. Optical properties of ultrafine line and space polymeric nanogratings coated with metal and metal-dielectric-metal thin films.

    PubMed

    Leong, Eunice Sok Ping; Wu, Siji; Zhang, Nan; Loh, Wei Wei; Khoo, Eng Huat; Si, Guang Yuan; Dai, Hai Tao; Liu, Yan Jun

    2014-02-01

    Noble metal and metal-dielectric-metal ultrathin films were deposited on the surfaces of ultrafine polymeric nanogratings, which were fabricated using nanoimprint lithography. Experimental results showed dramatic differences of the surface morphologies for single metal and triple metal-dielectric-metal films deposited on flat and corrugated polymeric surfaces. The effect of the surface morphology on the optical properties was hence investigated and analyzed under linearly polarized light. The surface plasmon resonances of single metal and triple metal-dielectric-metal films deposited on polymeric nanograting surfaces were also characterized based on the Kretschmann prism-coupling method. The single metal and triple metal-dielectric-metal films deposited on polymeric nanograting surfaces are important for the study of photon-plasmon interactions (i.e. couplings and conversions) at the interfaces between a nanograting and metal films. PMID:24406796

  3. Grain and grain boundary effects on the frequency and temperature dependent dielectric properties of cobalt ferrite-hafnium composites

    NASA Astrophysics Data System (ADS)

    Kolekar, Y. D.; Sanchez, L.; Rubio, E. J.; Ramana, C. V.

    2014-04-01

    We report on the frequency (f=20 Hz-1 MHz) and temperature (T=300-973 K) dependent dielectric properties of hafnium (Hf) incorporated cobalt ferrite (CoF2-xHfxO4 (CFO-Hf); x=0.00-0.20). The dielectric constant (?') of CFO-Hf is T-independent at T<450 K, at which point increasing trend prevails. A grain bulk-boundary based two-layer model, where semiconducting-grains separated by insulating-grain boundaries, satisfactorily accounts for ?-T (>450 K) variation. Correspondingly, electrical responses in impedance formalism are attributed to the grain and grain-boundary effects which also accounts for the observed two dielectric-relaxations. The results demonstrate that the dielectric phenomena in CFO-Hf can be tailored by tuning Hf-concentration.

  4. Effect of cation disorder on structural, magnetic and dielectric properties of La2MnCoO6 double perovskite.

    PubMed

    Barón-González, A J; Frontera, C; García-Muñoz, J L; Rivas-Murias, B; Blasco, J

    2011-12-14

    The origin of dielectric anomalies and magnetodielectric response of La(2)MnCoO(6) has been investigated by means of ultra-high resolution synchrotron x-ray powder diffraction, neutron powder diffraction, resistivity, magnetization and dielectric measurements. The study has been performed on two different bulk samples presenting different degrees of Mn/Co order: 95 and 74%. Beside the well-known influence on magnetic properties, our results show that the main effect of disorder lies on the electrical resistivity. Bond distances clearly show Mn(4+)/Co(2+) valence states in the well-ordered sample, while for the disordered one this picture still holds. AC resistivity data show dielectric anomalies and a small magnetodielectric effect, but impedance complex plane analyses prove that these phenomena appear at the frequency-temperature region where extrinsic effects dominate the dielectric response. PMID:22107735

  5. Influence of frequency, grade, moisture and temperature on Green River oil shale dielectric properties and electromagnetic heating processes

    SciTech Connect

    Hakala, J. Alexandra; Stanchina, William; Soong, Yee; Hedges, Sheila

    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. Dielectric properties of anodic films on sputter-deposited Ti-Si porous columnar films

    NASA Astrophysics Data System (ADS)

    Tanvir, M. Tauseef; Fujii, T.; Aoki, Y.; Fushimi, K.; Habazaki, H.

    2011-07-01

    For electrolytic capacitor application of the single-phase Ti alloys containing supersaturated silicon, which form anodic oxide films with superior dielectric properties, porous Ti-7 at% Si columnar films, as well as Ti columnar films, have been prepared by oblique angle magnetron sputtering on to aluminum substrate with a concave cell structure to enhance the surface area and hence capacitance. The deposited films of both Ti and Ti-7 at% Si have isolated columnar morphology with each column revealing nanogranular texture. The distances between columns are ˜500 nm, corresponding to the cell size of the textured substrate and the gaps between columns are 100-200 nm. When the porous Ti-7 at% Si film is anodized at a constant current density in ammonium pentaborate electrolyte, the growth of a uniform amorphous oxide film continues to ˜35 V, while it is limited to less than 6 V on the porous Ti film. The maximum voltage of the growth of uniform amorphous oxide films on the Ti-7 at% Si films is similar for both the flat and porous columnar films, suggesting little influence of surface roughness on the amorphous-to-crystalline transition of growing anodic oxide under the high electric field. Due to the suppression of crystallization to sufficiently high voltages, the anodic oxide films formed on the porous Ti-7 at% Si film shows markedly improved dielectric properties, in comparison with those on the porous Ti film.

  7. Structural and Interfacial Effects on the Dielectric Properties of PVDF and its Composites for Energy Storage

    NASA Astrophysics Data System (ADS)

    Jones, Jennifer; Mayo, Anthony; Zhu, Lei; Tolk, Norman; Mu, Richard

    2014-03-01

    High energy density capacitors based on dielectric polymers are a focus of increasing research effort motivated by the possibility to realize compact and flexible energy storage devices. Multilayered ferroelectric polyvinylidene fluoride (PVDF) systems are fabricated using enabling technology in co-extrusion for increased energy storage efficiency. These micro- and nano-layered polymeric systems result in much improved device performance and a three-time enhancement of capacitive electrical energy density has been demonstrated. PVDF thin film nanocomposites with ZnO nanofillers have also been fabricated and evaluated for further enhancement of energy density storage. To understand the physics of why these multilayered and nanocomposite systems perform better than single layer PVDF we are developing characterization techniques using confocal second harmonic generation (SHG), electric field induced second harmonic (EFISH) and Raman laser spectroscopy. Our results have shown that the combination of Raman and SHG is a very sensitive, non-destructive and versatile technique that can be used to study the ferroelectric and structural properties of these systems. The addition of the EFISH technique allows the interrogation of structural and dielectric properties within individual layers and at the interfaces.

  8. 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

  9. 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.

  10. Influence of semiconductor and metal nanoparticles on the dielectric properties of ionic matrix cadmium octanoate

    NASA Astrophysics Data System (ADS)

    Zhulai, Dmytro; Fedorenko, Denys; Kovalchuk, Alexander; Bugaychuk, Svetlana; Klimusheva, Gertruda Vasylivna; Mirnaya, Tetyana Alfredivna

    2015-02-01

    Dielectric properties of ionic composites consisted of cadmium octanoate matrix and semiconductor or metal nanoparticles have been investigated. The nanoparticles of different nature (semiconductor CdS, metal Au, and metal core-semiconductor shell Au-CdS) were chemically synthesized in the smectic A phase of (Cd+2(C7H15COO)-2, CdC8) that was used as a nanoreactor. These nanocomposites are very stable and well ordered; the size and shape of the nanoparticles (NPs) are well controlled during the synthesis. The main aim of the research was to examine the influence of nanoparticles on the dielectric properties of ionic matrix, which has smectic A ordered structure. Electrical characteristics were investigated at different temperatures, which correspond to different phases of the material. The conductivity of nanocomposites has an activation nature. The electrical conductivity anisotropy confirms the structural anisotropy of the nanocomposites. The conductivity of the nanocomposite along the cation-anion layers is higher by 2 orders of magnitude than that across the cation-anion layers. Basing on the experimental data, we proposed the simple model of the charge carriage process.

  11. Trapping-charging ability and electrical properties study of amorphous insulator by dielectric spectroscopy

    SciTech Connect

    Mekni, Omar Arifa, Hakim; Askri, Besma; Yangui, Béchir; Raouadi, Khaled; Damamme, Gilles

    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.

  12. Dielectric and pVT properties of metals in the critical region

    NASA Astrophysics Data System (ADS)

    Hensel, F.; Jüngst, S.; Knuth, B.; Uchtmann, H.; Yao, M.

    1986-05-01

    We report measurements of the shape of the liquid-vapour coexistence curve and of the temperature dependence of the dielectric constant ?1 in the immediate vicinity of the critical point of metals. The coexistence curves of cesium and rubidium are found to be noticeably different from those of simple nonconducting fluids in their extreme vapour-liquid asymmetry which causes the law of rectilinear diameter to break down over a large temperature range. The temperature dependence of ?1 of fluid mercury along isochores close to the critical isochore has a cusp-like anomaly near the critical temperature. The functional form of the diameters and the anomalous increase in ?1 provide compelling evidence that the strong thermodynamic-state-dependence of the electronic properties in metals, which is normally negligible for nonconducting fluids, leads to large amplitudes of the critical point singularities for both properties.

  13. 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.

  14. Determination of the voltage-dependent dielectric properties of piezoelectric materials with a high-voltage/high-power electromechanical impedance analyzer

    NASA Astrophysics Data System (ADS)

    Montes, R.; Castanien, Kevin E.; Liang, Chen; Bergh, Mathieu V.

    1996-02-01

    The dielectric properties of piezoelectric materials are important in many applications of piezoelectric materials, such as active structural control, underwater sonar, dielectric insulator, etc. The experimental measurement of dielectric properties of materials is usually done using commercial electrical impedance analyzer, LCR meter, or network analyzer, such as an HP 4194 impedance analyzer. The excitation voltage of these commercial analyzers is generally very low, e.g., 1.5 volts rms or under. However, the dielectric properties of piezoelectric materials (both dielectric constant and dielectric loss factor) can be very sensitive to the level of applied electric voltage (field). Since virtually all the applications of piezoelectric materials are under high field, it is important to develop measurement techniques to determine the voltage dependent dielectric material properties. This paper introduces a high- voltage/high-power electromechanical impedance analyzer developed based on a commercial electrical power analyzer/phase angle multimeter. The developed analyzer is then used to determine the dielectric constant and dielectric loss factor of G1195 PZT. The measurement results, dielectric constant and loss factor as a function of applied electric field, frequency, and ambient temperatures, are presented in the paper.

  15. Changes in the dielectric properties of ex vivo bovine liver during microwave thermal ablation at 2.45 GHz

    NASA Astrophysics Data System (ADS)

    Lopresto, Vanni; Pinto, Rosanna; Lovisolo, Giorgio A.; Cavagnaro, Marta

    2012-04-01

    In microwave thermal ablation (MTA) therapy, the dielectric properties of the target tissue play an important role in determining the radiation properties of the microwave ablation antenna. In this work, the ex vivo dielectric properties of bovine liver were experimentally characterized as a function of the temperature during MTA at the frequency of 2.45 GHz. The obtained data were compared with measurements performed at the end of the MTA treatment, and considering the heating achieved with a temperature-controlled water bath. Finally, measured data were used to perform a numerical study evaluating the effects of changes in tissue's dielectric properties during the MTA treatment on the radiation properties of a microwave interstitial ablation antenna, as well as on the obtained thermal lesion. Results evidenced a significant decrease of both relative permittivity (about 38%) and electric conductivity (about 33%) in the tissue during treatment as the temperature increased to over 60 °C, with a dramatic drop when the temperature approached 100 °C. Moreover, the numerical study evidenced that changes in tissue's dielectric properties during the MTA treatment affect the distribution of the power absorbed by the tissue (specific absorption rate—SAR, W kg-1) surrounding the microwave interstitial ablation antenna, leading to a peak SAR up to 20% lower, as well as to a thermal lesion up to 8% longer. This work may represent a preliminary step towards the future development of a procedure for MTA treatment planning.

  16. Changes in the dielectric properties of ex vivo bovine liver during microwave thermal ablation at 2.45 GHz.

    PubMed

    Lopresto, Vanni; Pinto, Rosanna; Lovisolo, Giorgio A; Cavagnaro, Marta

    2012-04-21

    In microwave thermal ablation (MTA) therapy, the dielectric properties of the target tissue play an important role in determining the radiation properties of the microwave ablation antenna. In this work, the ex vivo dielectric properties of bovine liver were experimentally characterized as a function of the temperature during MTA at the frequency of 2.45 GHz. The obtained data were compared with measurements performed at the end of the MTA treatment, and considering the heating achieved with a temperature-controlled water bath. Finally, measured data were used to perform a numerical study evaluating the effects of changes in tissue's dielectric properties during the MTA treatment on the radiation properties of a microwave interstitial ablation antenna, as well as on the obtained thermal lesion. Results evidenced a significant decrease of both relative permittivity (about 38%) and electric conductivity (about 33%) in the tissue during treatment as the temperature increased to over 60 °C, with a dramatic drop when the temperature approached 100 °C. Moreover, the numerical study evidenced that changes in tissue's dielectric properties during the MTA treatment affect the distribution of the power absorbed by the tissue (specific absorption rate-SAR, W kg(-1)) surrounding the microwave interstitial ablation antenna, leading to a peak SAR up to 20% lower, as well as to a thermal lesion up to 8% longer. This work may represent a preliminary step towards the future development of a procedure for MTA treatment planning. PMID:22460062

  17. Structural, electrical and dielectric properties of spinel nickel ferrite prepared by soft mechanochemical synthesis

    SciTech Connect

    Lazarevi?, Zorica Ž.; Jovaleki?, ?edomir; Sekuli?, Dalibor L.; Milutinovi?, Aleksandra; Baloš, Sebastian; Slankamenac, Miloš; Rom?evi?, Nebojša Ž.

    2013-10-15

    Graphical abstract: - Highlights: • Sintered NiFe{sub 2}O{sub 4} was prepared by a soft mechanochemical route from mixture powders. • XRD and Raman measurements indicate that the prepared samples have spinel structure. • The activation energy ?E are 0.653 and 0.452 eV for NiFe{sub 2}O{sub 4} samples. • Ferrite from Ni(OH){sub 2}/Fe{sub 2}O{sub 3} has lower DC conductivity than from Ni(OH){sub 2}/Fe(OH){sub 3} powders. • The values of dielectric constant of samples NiFe{sub 2}O{sub 4} are 70 and 200, respectively. - Abstract: Nickel ferrite, NiFe{sub 2}O{sub 4} was prepared by a soft mechanochemical route from a mixture of (1) Ni(OH){sub 2} and ?-Fe{sub 2}O{sub 3} and (2) Ni(OH){sub 2} and Fe(OH){sub 3} powders in a planetary ball mill for 25 h. The powder samples were sintered at 1100 °C for 2 h and were characterized by X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM). Impedance spectroscopy techniques were used to study the effect of grain and grain boundary on the electrical properties of the prepared samples. A difference in dielectric constant (?) and dielectric loss tangent (tan ?) of NiFe{sub 2}O{sub 4} samples obtained by the same methods but starting from different initial components was observed.

  18. 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.

  19. 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.

  20. Structural, dielectric and magnetic properties of Gd substituted manganese ferrite nanoparticles

    NASA Astrophysics Data System (ADS)

    Murugesan, C.; Sathyamoorthy, B.; Chandrasekaran, G.

    2015-08-01

    Gd3+ ion-substituted manganese ferrite nanoparticles with the chemical formula MnGdxFe2-xO4 (x = 0.0, 0.05, and 0.1) were synthesized by sol-gel auto combustion method. Thermal stability of the as-prepared sample was analyzed using thermo gravimetric and differential thermal analysis (TG-DTA) and the result reveals that the prepared sample is thermally stable above 300 °C. Structural and morphology studies were performed using powder x-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Indexed PXRD patterns confirm the formation of pure cubic spinel structure. The average crystallite sizes calculated using Sherrer’s formula decreased from 47 nm to 32 nm and lattice constant was enhanced from 8.407 Å to 8.432 Å. The FTIR spectrum of manganese ferrite shows a high frequency vibrational band at 564 cm-1 assigned to tetrahedral site and a low frequency vibrational band at 450 cm-1 assigned to octahedral site which are shifted to 556 cm-1 and 439 cm-1 for Gd3+ substitution and confirm the incorporation of Gd3+ into manganese ferrite. SEM analysis shows the presence of agglomerated spherical shaped particles at the surface. Room temperature dielectric and magnetic properties were studied using broadband dielectric spectroscopy (BDS) and vibrating sample magnetometry (VSM). Frequency dependent dielectric constant, ac conductivity and tan delta were found to increase with Gd3+ ion substitution. The measured values of saturation magnetization decrease from 46.6 emu g-1 to 41 emu g-1 with increase in Gd3+ concentration and coercivity decreases from 179.5 Oe to 143 Oe.

  1. Dielectric breakdown properties of hot SF6 gas contaminated by copper at temperatures of 300-3500?K

    NASA Astrophysics Data System (ADS)

    Wang, Xiaohua; Zhong, Linlin; Rong, Mingzhe; Yang, Aijun; Liu, Dingxin; Wu, Yi; Miao, Song

    2015-04-01

    The dielectric breakdown properties of hot SF6 gas during the dielectric recovery phase play an important role in understanding gas breakdown occurring in high-voltage circuit breakers. This paper is devoted to the theoretical investigation of dielectric breakdown properties of hot SF6 gas contaminated by copper at temperatures of 300-3500?K and pressures of 0.01-1.6?MPa. The equilibrium compositions of SF6-Cu mixtures are obtained with the consideration of condensed species. The unknown ionization cross sections for CuS, CuF and CuF2 are calculated using a Deutsch-Märk (DM) formalism based on quantum chemistry. The two-term Boltzmann equation is adopted to numerically calculate the electron energy distribution function, collision ionization coefficient and electron attachment coefficient. Then the reduced critical electric field strength is determined when the effective ionization coefficient equals to zero. The influences of the Cu proportion and gas pressure on the dielectric breakdown properties are investigated. It is shown that the existence of copper compounds increases the concentration of high-energy electrons significantly, even for the case with a very low percentage (e.g. 1% Cu). With the increase of copper content, the value of (E/N)cr is reduced remarkably at temperatures below 3000?K, but enhanced slightly above 3000?K. It is also found that the increase of pressure can improve the dielectric breakdown performance of hot SF6-Cu mixtures.

  2. 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.

  3. 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

    2015-10-01

    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.

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

    E-print Network

    York, Robert A.

    at cryogenic temperatures. This makes it an ideal candi- date for tunable microwave devices with high of thermal strain on the dielectric constants of Ba,Sr TiO3 thin films and saw a reduction in dielectric

  5. Dielectric properties of Jovian satellite ice analogs for subsurface radar exploration: A review

    NASA Astrophysics Data System (ADS)

    Pettinelli, Elena; Cosciotti, Barbara; Di Paolo, Federico; Lauro, Sebastian Emanuel; Mattei, Elisabetta; Orosei, Roberto; Vannaroni, Giuliano

    2015-09-01

    The first European mission dedicated to the exploration of Jupiter and its icy moons (JUpiter ICy moons Explorer—JUICE) will be launched in 2022 and will reach its final destination in 2030. The main goals of this mission are to understand the internal structure of the icy crusts of three Galilean satellites (Europa, Ganymede, and Callisto) and, ultimately, to detect Europa's subsurface ocean, which is believed to be the closest to the surface among those hypothesized to exist on these moons. JUICE will be equipped with the 9 MHz subsurface-penetrating radar RIME (Radar for Icy Moon Exploration), which is designed to image the ice down to a depth of 9 km. Moreover, a parallel mission to Europa, which will host onboard REASON (Radar for Europa Assessment and Sounding: Ocean to Near-surface) equipped with 9MHz and 60MHz antennas, has been recently approved by NASA. The success of these experiments strongly relies on the accurate prediction of the radar performance and on the optimal processing and interpretation of radar echoes that, in turn, depend on the dielectric properties of the materials composing the icy satellite crusts. In the present review we report a complete range of potential ice types that may occur on these icy satellites to understand how they may affect the results of the proposed missions. First, we discuss the experimental results on pure and doped water ice in the framework of the Jaccard theory, highlighting the critical aspects in terms of a lack of standard laboratory procedures and inconsistency in data interpretation. We then describe the dielectric behavior of extraterrestrial ice analogs like hydrates and icy mixtures, carbon dioxide ice and ammonia ice. Building on this review, we have selected the most suitable data to compute dielectric attenuation, velocity, vertical resolution, and reflection coefficients for such icy moon environments, with the final goal being to estimate the potential capabilities of the radar missions as a function of the frequency and temperature ranges of interest for the subsurface sounders. We present the different subsurface scenarios and associated radar signal attenuation models that have been proposed so far to simulate the structure of the crust of Europa and discuss the physical and geological nature of various dielectric targets potentially detectable with RIME. Finally, we briefly highlight several unresolved issues that should be addressed, in near future, to improve our capability to produce realistic electromagnetic models of icy moon crusts. The present review is of interest for the geophysical exploration of all solar system bodies, including the Earth, where ice can be present at the surface or at relatively shallow depths.

  6. Low temperature dielectric properties of YMn0.95Ru0.05O3

    NASA Astrophysics Data System (ADS)

    Thakur, Rajesh K.; Thakur, Rasna; Okram, G. S.; Kaurav, N.; Gaur, N. K.

    2013-02-01

    The single phase hexagonal YMn0.95Ru0.05O3 compound has been synthesized via solid state reaction method at sintering temperature 1280°C with space group P63cm (25-1079). The detailed dielectric properties were evaluated over broad temperature and frequency ranges. An obvious dielectric relaxation was observed near the antiferromagnetic (AFM) transition temperature. The temperature dependence of the ac resistivity at low frequency infers the semiconducting behavior and favored the variable range hopping conduction model. The obtained experimental data in the temperature range of our study can be described by the equation ?(T) = ?0exp[(T*/T)1/4]. The fitting results are used for the calculation of the temperature scale T* ˜ 0.8 × 104 K and finally the density of state at Fermi level N(EF). The activation energy Ea ˜ 0.0314 eV is calculated from the plot, peak temperature of the loss tangent near the magnetic transition region versus frequency using Arrhenius law.

  7. Dielectric property of NiTiO3 doped substituted ortho-chloropolyaniline composites

    NASA Astrophysics Data System (ADS)

    Lakshmi, Mohana; Roy, Aashish S.; Khasim, Syed; Faisal, Muhammad; Sajjan, K. C.; Revanasiddappa, M.

    2013-11-01

    Ortho-chloropolyaniline (OCP)-NiTiO3 composites have been synthesized via in-situ polymerization of ortho-chloroaniline with various weight percentages of NiTiO3. Fourier Transform Infrared spectroscopic studies of Ortho-chloropolyaniline and its composites indicated the formation of composites as a result of Vander Waal's interaction between OCP and NiTiO3 particles. Surface morphology of OCP and OCP-NiTiO3 composites were studied using Scanning Electron Microscope (SEM). The SEM micrographs indicated a modified morphology after the composite formation. Dielectric properties and electric modulus of OCP and OCP-NiTiO3 composites have been investigated in the frequency range of 50 Hz - 5 MHz. It has been noticed that electrical resistance decreases with increase in weight percentage of NiTiO3 particles in polymer matrix as well as with applied frequency. The display of semicircular arcs in Cole-Cole plots indicates the formation of series resistor and capacitor in network causing a decrease in the relaxation time and as a result conductivity enhances in these composites. The facile and cost effective synthesis process and excellent dielectric and conductivity response of these materials makes them promising materials for practical applications.

  8. Effects of Ultraviolet Photon Irradiation on the Dielectric Properties of Polyimide

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Akira; Ohki, Yoshimichi

    Ultraviolet photons were irradiated to the surface of all-aromatic polyimide films using a KrF excimer laser or a KrCl excimer lamp, and electrical properties such as permittivity, dielectric loss factor, conductivity, and space charge distribution were measured. In the case of the intense laser irradiation, the photo-induced change is drastic. The irradiated side of the sample is carbonized and becomes conductive. The apparent thickness of the remaining insulating region estimated by the space charge distribution measurements agrees with that observed by an optical microscope. The permittivity of the remaining apparently insulating region decreases as the irradiation proceeds, which is due to a decrease in the number of carbonyl groups. The dielectric loss factor and conductivity in this region increase since the leakage current increases even in this apparently insulating region. The activation energy of conduction also increases. In the case of the weak lamp irradiation, the permittivity decreases and the conductivity increases, although clear surface change is hardly observable. It is indicated from space charge distribution measurements that carrier traps are formed by the irradiation.

  9. Dielectric property of NiTiO{sub 3} doped substituted ortho-chloropolyaniline composites

    SciTech Connect

    Lakshmi, Mohana; Faisal, Muhammad; Roy, Aashish S.; Khasim, Syed; Department of Physics, University of Tabuk-71491 ; Sajjan, K. C.; Revanasiddappa, M.

    2013-11-15

    Ortho-chloropolyaniline (OCP)-NiTiO{sub 3} composites have been synthesized via in-situ polymerization of ortho-chloroaniline with various weight percentages of NiTiO{sub 3.} Fourier Transform Infrared spectroscopic studies of Ortho-chloropolyaniline and its composites indicated the formation of composites as a result of Vander Waal's interaction between OCP and NiTiO{sub 3} particles. Surface morphology of OCP and OCP-NiTiO{sub 3} composites were studied using Scanning Electron Microscope (SEM). The SEM micrographs indicated a modified morphology after the composite formation. Dielectric properties and electric modulus of OCP and OCP-NiTiO{sub 3} composites have been investigated in the frequency range of 50 Hz – 5 MHz. It has been noticed that electrical resistance decreases with increase in weight percentage of NiTiO{sub 3} particles in polymer matrix as well as with applied frequency. The display of semicircular arcs in Cole-Cole plots indicates the formation of series resistor and capacitor in network causing a decrease in the relaxation time and as a result conductivity enhances in these composites. The facile and cost effective synthesis process and excellent dielectric and conductivity response of these materials makes them promising materials for practical applications.

  10. Polyethylene nanocomposite dielectrics: Implications of nanofiller orientation on high field properties and energy storage

    NASA Astrophysics Data System (ADS)

    Tomer, V.; Polizos, G.; Randall, C. A.; Manias, E.

    2011-04-01

    Nanocomposite formation, through the incorporation of high aspect ratio nanoparticles, has been proven to enhance the dielectric properties of thermoplastic polymers, when the mitigation of internal charges and the nature of the interfacial regions are properly adjusted. Here, we explore polyethylene/montmorillonite nanocomposites, and we specifically investigate how to impart desirable dielectric behavior through controlled nanoscale texturing, i.e., through control of the spatial arrangement of the high aspect ratio nanofiller platelets. In particular, it is shown that filler alignment can be used to improve the high electric-field breakdown strength and the recoverable energy density. The origins of the improved high field performance were traced to improved charge-trapping by a synergy of nanofillers and polar maleic anhydride (MAH) groups—introduced via polyethylene-MAH copolymers—as templated by the inorganic nanofillers. Further, it is conclusively demonstrated that the alignment of the two-dimensional nanoparticles has a measurable positive effect on the breakdown strength of the materials and, consequently, on the maximum recoverable energy density.

  11. Structural, magnetic and dielectric properties of polyaniline/MnCoFe2O4 nanocomposites

    NASA Astrophysics Data System (ADS)

    Chitra, Palanisamy; Muthusamy, Athianna; Jayaprakash, Rajan

    2015-12-01

    Ferromagnetic PANI containing MnCoFe2O4 nanocomposites were synthesized by in-situ chemical polymerization of aniline incorporated MnCoFe2O4 nanoparticles (20%, 10% w/w of fine powders) with and without ultrasonic treatment. The MnCoFe2O4 nanoparticles were synthesized by auto combustion method. The PANI/MnCoFe2O4 nanocomposites were characterized with Fourier transform infrared (FTIR), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The average particle size of the resulting PANI/MnCoFe2O4 nanocomposites was confirmed from the TEM and XRD analysis. The structure and morphology of the composites were confirmed by FT-IR spectroscopy, XRD and SEM. In addition, the electrical and magnetic properties of the nanocomposites were investigated. The PANI/MnCoFe2O4 nanocomposites under applied magnetic field exhibited the hysteresis loops of ferromagnetic nature at room temperature. The variation of Dielectric constant, Dielectric loss, and AC conductivity of PANI/MnCoFe2O4 nanocomposites at room temperature as a function of frequency in the range 50 Hz-5 MHz has been studied. Effect of ultrasonication on the PANI/MnCoFe2O4 nanocomposites was also investigated.

  12. Synthesis and controlling the optical and dielectric properties of CMC/PVA blend via ?-rays irradiation

    NASA Astrophysics Data System (ADS)

    El Sayed, A. M.

    2014-02-01

    Carboxymethyl cellulose (CMC)/Polyvinyl alcohol (PVA) blend films were prepared by solution casting method. Then, these films were irradiated with ?-rays from a Co-60 source at doses over the range 0-70 kGy to investigate the modifications induced in the optical and dielectric properties. The dielectric constant (??) was measured in the temperature range 303-408 K and in the frequency range 10 kHz-1 MHz. The indirect optical band gap was found to increase within the dose range 0-10 kGy, and to decrease at the higher doses. The refractive index values, however, showed a reversed behavior. The highest transmittance percentage was obtained at 10 kGy dose. According to the frequency and temperature dependence of ??, ?- relaxation peaks were observed in all samples and assigned to the micro-Brownian motion of the blend chains. The values of ?? showed a decrease in the dose range 0-10 kGy and an increase in the dose range 10-70 kGy. The ac conductivity ?ac (T) showed an Arrhenius type behavior separated into two distinct regions. The results of the present system are compared with those of similar materials.

  13. Dielectric Property of Silicate-Doped CaBi4Ti4O15 Thin Films

    NASA Astrophysics Data System (ADS)

    Ogawa, Shota; Kondoh, Yohta; Kimura, Junichi; Funakubo, Hiroshi; Uchida, Hiroshi

    2012-09-01

    Thin films of silicate-doped CaBi4Ti4O15 were fabricated to enhance the insulating property of one-axis-oriented CaBi4Ti4O15 films under an applied electric field. The crystalline phase of CaBi4Ti4O15, a type of bismuth layer-structured dielectric (BLSD) compound, was successfully grown on (100)LaNiO3/(111)Pt/TiO2/(100)Si with the preferential orientation of the (001) plane by the addition of bismuth silicate with a nominal composition of Bi12SiO20 up to 1.00%. The crystallographic orientation of the (001)BLSD plane normal to the substrate surface was degraded by excessive bismuth silicate addition above 1.50%. The breakdown electric field was increased by bismuth silicate addition up to 2.00% without the degraded relative dielectric permittivity (?r) of approximately 230. The bismuth silicate could precipitate between the grain boundaries in the CaBi4Ti4O15 films without an interface reaction or a solid solution that enhances the insulating behavior of the BLSD films.

  14. 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.

  15. Effects of fluorine incorporation on the properties of Ge p -MOS capacitors with HfTiON dielectric

    NASA Astrophysics Data System (ADS)

    Li, C. X.; Leung, C. H.; Lai, P. T.; Xu, J. P.

    2010-07-01

    In this work, Ge p-MOS capacitors with HfTiON gate dielectric were fabricated by sputtering method. Pre-deposition fluorine plasma treatment and post-deposition fluorine plasma annealing were used to improve the electrical and reliability properties of Ge p-MOS capacitors. Experimental results showed that both methods could improve the interface quality with lower interface-state density, less frequency dispersion, and also enhance the reliability properties with smaller increases of oxide charge and gate leakage after high-field stressing. Compared with pre-deposition fluorine-plasma treatment, post-deposition fluorine plasma annealing achieved higher quality of high- k/Ge interface such as lower interface-state density, higher dielectric constant and lower stress-induced gate leakage current. By XPS and AFM analyses, the improvements should be due to the passivation effects of fluorine on oxygen vacancies, dangling bonds and the dielectric surface.

  16. Synthesis, characterization, UV and dielectric properties of hexagonal disklike ZnO particles embedded in polyimides

    SciTech Connect

    Vural, Sema; Koeytepe, Sueleyman; Seckin, Turgay; Adiguezel, Ibrahim

    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.

  17. In-situ monitoring of sea ice dielectric properties and implications for the tracking of seasonal evolution of microstructure

    NASA Astrophysics Data System (ADS)

    O'Sadnick, Megan

    The microstructure of sea ice evolves throughout the seasonal cycle, from ice formation in the fall through melt in the summer. Observations of this seasonal evolution and its effect on the interaction between sea ice and the surrounding environment face fundamental challenges, however. Any removal of ice cores to obtain data on ice properties results in the loss of brine and alterations of microstructure. The remoteness of field sites also limits observations. Methods to monitor sea ice microstructure continuously and non-destructively are therefore being explored. This thesis examines the potential for the electric properties of sea ice, highly sensitive to the brine distribution within the ice, to serve as a proxy for microstructure and hence other ice transport properties. Throughout the Spring of 2013 and 2014, measurements of low frequency complex dielectric permittivity in the range of 10 Hz to 95 kHz were made in landfast ice off the coast of Barrow, Alaska. Temperature and salinity measurements and ice samples were collected for ice microstructure characterization. Results reveal a significant correlation between measurements of complex dielectric permittivity, brine volume fraction, and microstructural characteristics including pore volume and connectivity. The influence of temperature and salinity variations and further explanation of the relationships between ice properties, microstructural characteristics, and dielectric behavior are explored through multivariate analysis of the combined data set. The findings are discussed in terms of future research directions and promising approaches for in-situ ice property monitoring based on dielectric measurements.

  18. Study of Some Dielectric Properties of Suspensions of Magnesium Particles in Mineral Oil

    NASA Technical Reports Server (NTRS)

    Altshuller, Aubrey P

    1954-01-01

    The variation of dielectric constant has been measured as a function of the concentration of magnesium particles; the shape, size, and degree of oxidation of the particles; the temperature; and the frequency of oscillation. The variation of dielectric constant and settling rate was investigated as a function of time. Also investigated were the effects of particle concentration, shape and time on dielectric losses.

  19. Material properties and thermal stability of hafnium and lanthanum based high-k gate dielectrics for MOSFET digital logic

    NASA Astrophysics Data System (ADS)

    Sivasubramani, Prasanna

    Hf and La based dielectrics have evolved into promising high- k gate dielectric candidates for the replacement of SiO2 and SiON in scaled complementary metal oxide semiconductor field effect transistor (C-MOSFET) devices due to favorable material properties. Strained Si xGe1-x(100) epilayers on Si(100) have attracted considerable interest due to hole mobility enhancement, as well as their compatibility with existing Si-based C-MOSFET technology that makes manufacturing very-large scale integrated circuits feasible. The introduction of these new material systems into the current CMOS process flow poses significant integration challenges. For example, the thermal stability of a high-k dielectric film in direct contact with the underlying Si substrate is essential because outdiffusion of metal impurity atoms into the channel region during processing can cause carrier mobility degradation and affect the electrical performance of the integrated circuit. Also, the inherent thermodynamic instability of SixGe1-xO2 offers a formidable challenge for the successful fabrication of high-k oxides on strained SixGe1-x(100). In this dissertation, the results of thermal stability studies of Hf and La based silicate and aluminate dielectrics in direct contact with Si(100) and SixGe1-x(100) is presented. The effect of nitrogen and germanium incorporation on the thermal stability is discussed. Dielectrics deposited by Sputter Deposition, Molecular Beam Deposition and Atomic Layer Deposition techniques are evaluated. X-ray Photoelectron Spectroscopy (XPS), X-ray Diffraction (XRD), High Resolution Transmission Electron Microscopy (HR-TEM), Backside Secondary Ion Mass Spectrometry (Backside SIMS), Atomic Force Microscopy (AFM) and Electrical Measurements are utilized to characterize the dielectric stacks. For Si(100), the thermal stability after a 1000°C, 10s source/drain activation anneal is evaluated. Due to strain relaxation of the SixGe1-x(100) substrates at temperatures >800°C, the stability of the dielectric - SixGe 1-x(100) stacks were evaluated at lower temperatures. In this dissertation, the suppression of crystallization and metal outdiffusion into Si(100) after the 1000°C, 10s anneal for sputter deposited LaAlON and HfAlON dielectrics is reported. The stability of the Hf-silicate dielectrics on Si xGe1-x(100) with N and Ge incorporation appears to be correlated to the stability of Ge bonding configuration at the dielectric - substrate interface. The prospects of novel dielectrics like La-scandate (LaScO 3) and Hf-germanate (HfGeO) are discussed.

  20. Retrieving the electronic properties of silicon nanocrystals embedded in a dielectric matrix by low-loss EELS.

    PubMed

    Eljarrat, Alberto; López-Conesa, Lluís; López-Vidrier, Julian; Hernández, Sergi; Garrido, Blas; Magén, César; Peiró, Francesca; Estradé, Sònia

    2014-12-21

    In this work we apply low-loss electron energy loss spectroscopy (EELS) to probe the structural and electronic properties of single silicon nanocrystals (NCs) embedded in three different dielectric matrices (SiO2, SiC and Si(3)N(4)). A monochromated and aberration corrected transmission electron microscope has been operated at 80 kV to avoid sample damage and to reduce the impact of radiative losses. We present a novel approach to disentangle the electronic features corresponding to pure Si-NCs from the surrounding dielectric material contribution through an appropriate computational treatment of hyperspectral datasets. First, the different material phases have been identified by measuring the plasmon energy. Due to the overlapping of Si-NCs and dielectric matrix information, the variable shape and position of mixed plasmonic features increases the difficulty of non-linear fitting methods to identify and separate the components in the EELS signal. We have managed to solve this problem for silicon oxide and nitride systems by applying multivariate analysis methods that can factorize the hyperspectral datacubes in selected regions. By doing so, the EELS spectra are re-expressed as a function of abundance of Si-NC-like and dielectric-like factors. EELS contributions from the embedded nanoparticles as well as their dielectric surroundings are thus studied in a new light, and compared with the dielectric material and crystalline silicon from the substrate. Electronic properties such as band gaps and plasmon shifts can be obtained by a straightforward examination. Finally, we have calculated the complex dielectric functions and the related electron effective mass and density of valence electrons. PMID:25363292

  1. The influence of fracture density and burial depth on the static and dynamic elastic properties of crystalline rocks

    NASA Astrophysics Data System (ADS)

    Blake, O. O.; Faulkner, D. R.; Tatham, D.

    2013-12-01

    Fracture in rock is a major factor that affects the rock's elastic properties. Elastic properties can be measured statically where stress and strain data are recorded during slow loading of a specimen, or dynamically, where the elasticity can be calculated from P- and S- wave velocity. During crustal deformation, rocks deform nearly statically, hence the relationship between the static and dynamic elastic properties must be known so that the dynamic elastic properties can be converted to static elastic properties to allow geomechanical and geodynamic modelling. In this study, the dynamic and static elastic properties were measured for dry crystalline rocks (Westerly granite) that were thermally treated to 250, 450, 650 and 850°C. Increasing the temperature produces an increased fracture density that is isotropically distributed. Experiments were carried out under confining pressure up to crack-closure pressure, 130MPa (~8km burial depth under hydrostatic pore pressure conditions). Increased fracture density within the rock results in a reduction in Young modulus and an increase in the Poisson's ratio, in both the static and dynamic case which is very significant above 573°C. The reduction and increase are retarded with increasing confining pressure. At crack-closure pressure the fracture density, in terms of effective medium models, is zero even though the rock still contains cracks. The crack-closure pressure is independent of fracture damage incurred in the rock. We compared the static and dynamic measurements and found a linear relationship between the static and dynamic Young's modulus with very high correlation and a gradient of one which is independent of confining pressure and the amount of fracturing incurred in the samples from thermal treatment. We also found that the static and dynamic Poisson's ratio are in agreement for values less than 0.34. Above this value, the static Poisson's ratio is much higher than the dynamic Poisson's ratio. Voigt-Reuss-Hill averaging technique, which inherently assumes zero crack density, was used to calculate the elastic properties so that a comparison could be made with what we assumed are zero crack density at 130MPa. The results from the Voigt-Reuss-Hill averaging technique are similar to the dynamic elastic properties at crack-closure pressure. Hence the dynamic elastic properties at this pressure could be incorporated into an effective medium model to predict the crack densities at pressure below the crack closure pressure. Changes in crack density are interpreted as creation or opening of cracks. We found that the crack density increased from ~0.2 to 1.8 at 10MPa confining pressure. The increase in the crack density is also retarded with increasing confining pressure.

  2. Dielectric properties of pyrochlore (Bi1.5Zn0.5)(Nb0.5M1.5)O7 (M =Ti, Sn, Zr, and Ce) dielectrics

    NASA Astrophysics Data System (ADS)

    Du, Huiling; Yao, Xi; Wang, Hong

    2006-05-01

    Pyrochlore type systems with generic formula (Bi1.5Zn0.5)(Nb0.5M1.5)O7 (M =Ti, Sn, Zr, and Ce) have been synthesized to investigate the influence of M on the dielectric properties. It was found that the incorporation of Sn or Ce resulted in a reasonably reduced dielectric constant. The incorporation of Zr and Ce has led to an appreciable increase in dc conductivity in high temperature. The dc conductivity diminishes as the size of M grows. Dielectric constants, temperature coefficient, and dc conductivity of series ceramics were studied and the relationships among composition, crystal structure, and properties were discussed.

  3. Effects of magnetic field treatment on dielectric properties of CCTO@Ni/PVDF composite with low concentration of ceramic fillers

    NASA Astrophysics Data System (ADS)

    Chi, Q. G.; Gao, L.; Wang, X.; Chen, Y.; Dong, J. F.; Cui, Y.; Lei, Q. Q.

    2015-11-01

    Using melt mixing, we produced a ceramic/polymer composite with a matrix of polyvinylidene fluoride (PVDF) and a filler of 5 vol.% Ni-deposited CaCu3Ti4O12 core-shell ceramic particles (CCTO@Ni), and studied its prominent dielectric characteristics for the first. Its phase composition and morphology were analyzed by X-ray diffraction and scanning electron microscopy, respectively. After treating the composite films with various durations of a magnetic field treatment, we compared their dielectric properties. We found that the CCTO@Ni ceramic had a typical urchin-like core-shell structure, and that different durations of the magnetic field treatment produced different distributions of ceramic particles in the PVDF matrix. The dielectric permittivity of the untreated CCTO@Ni/PVDF composite was 20% higher than that of neat PVDF, and it had a low loss tangent. However, only the composite treated for 30 min in the magnetic field had an ultra-high dielectric permittivity of 1.41 × 104 at 10 Hz, three orders of magnitude higher than the untreated composite, which declined dramatically with increasing frequency, accompanied by an insulating-conducting phase transition and an increase in loss tangent. Our results demonstrate that changes in the dielectric properties of PVDF composites with magnetic field treatment are closely related to the percolation effect and interfacial polarization.

  4. Gigantic enhancement in the dielectric properties of polymer-based composites using core/shell MWCNT/amorphous carbon nanohybrids

    NASA Astrophysics Data System (ADS)

    Guo, Qikai; Xue, Qingzhong; Sun, Jin; Dong, Mingdong; Xia, Fujun; Zhang, Zhongyang

    2015-02-01

    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.

  5. Heat treatment effects on structural and dielectric properties of Mn substituted CuFe2O4 and ZnFe2O4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Ranjith Kumar, E.; Arunkumar, T.; Prakash, T.

    2015-09-01

    Manganese substituted copper and zinc ferrite nanoparticles were synthesized by an auto-combustion technique using metal nitrates and urea. The nanoparticles were characterized by XRD, SEM, EDX, and TEM techniques. The effect of annealing temperature on structural and dielectric properties of Mn substituted spinel ferrite nanoparticles was analyzed. The presenting elements in the prepared samples are recorded by EDX. TEM analysis clearly showed the particles are in the nanometer range. The dielectric loss and dielectric constant have been measured in the frequency range of 100 kHz-5 MHz. The variation in structural and dielectric properties of the prepared and annealed samples are discussed.

  6. 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.

  7. Evolving density and static mechanical properties in plutonium from self-irradiation

    NASA Astrophysics Data System (ADS)

    Chung, B. W.; Thompson, S. R.; Lema, K. E.; Hiromoto, D. S.; Ebbinghaus, B. B.

    2009-03-01

    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 wt% of highly specific activity isotope 238Pu into the 239Pu metal to accelerate the aging process. This paper presents updated results of self-irradiation effects on 238Pu-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 ˜0.002% per year, without void swelling. Quasi-static tensile measurements show that the aging process increases the strength of plutonium alloys.

  8. 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.

  9. Dielectric properties of human diabetic blood: Thermodynamic characterization and new prospective for alternative diagnostic techniques

    NASA Astrophysics Data System (ADS)

    Farsaci, F.; Ficarra, S.; Russo, A.; Galtieri, A.; Tellone, E.

    2015-07-01

    In this paper, we will show the possibility of studying physical properties and irreversible phenomena that occur in blood by applying the dielectric Kluitenberg's nonequilibrium thermodynamic theory. Namely, we shall use some recent extensions of this theory that allow to infer its main characteristic parameters from experimental measures. Applying these results to the study of normal and diabetic blood we show, by comparing them, that it is possible to determine the difference, in some details, of the amount of particular phenomena occurring inside them and give a biological meaning to these phenomena. Moreover, observing a correspondence between a particular value of the frequency for which state coefficients are equal and glucose levels we introduce an alternative diagnostic method to measure the values of the glucose in the blood by determining only this frequency value. The thermodynamic description will be completed by determining the trend of the entropy production.

  10. 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.

  11. Optical properties of random metal-dielectric nanocomposite films: nanoparticle size effects

    NASA Astrophysics Data System (ADS)

    Moradi, Afshin

    2015-09-01

    The optical properties of a semicontinuous metal film that contains randomly distributed dielectric nanoparticles are analyzed by taking into account both filling ratios and nanoparticle size effects. A new generalization of the standard Maxwell-Garnett formula for the present system is derived, by means of the linearized hydrodynamic theory in conjunction with the Poisson equation and the appropriate boundary conditions. The dispersion curves of surface modes of the system are presented and found to be strongly dependent on the volume fraction of particles as well as the particles size. The attenuated total reflection spectra due to surface modes for the case of p-polarization are plotted and the effect of varying filling factor for fixed nanoparticles size is studied, as well as the effect of varying nanoinclusions size for a fixed volume fraction of particles.

  12. High-Temperature Dielectric Properties of Aluminum Nitride Ceramic for Wireless Passive Sensing Applications

    PubMed Central

    Liu, Jun; Yuan, Yukun; Ren, Zhong; Tan, Qiulin; Xiong, Jijun

    2015-01-01

    The accurate characterization of the temperature-dependent permittivity of aluminum nitride (AlN) ceramic is quite critical to the application of wireless passive sensors for harsh environments. Since the change of the temperature-dependent permittivity will vary the ceramic-based capacitance, which can be converted into the change of the resonant frequency, an LC resonator, based on AlN ceramic, is prepared by the thick film technology. The dielectric properties of AlN ceramic are measured by the wireless coupling method, and discussed within the temperature range of 12 °C (room temperature) to 600 °C. The results show that the extracted relative permittivity of ceramic at room temperature is 2.3% higher than the nominal value of 9, and increases from 9.21 to 10.79, and the quality factor Q is decreased from 29.77 at room temperature to 3.61 at 600 °C within the temperature range. PMID:26370999

  13. 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

  14. Development of Anatomically Realistic Numerical Breast Phantoms with Accurate Dielectric Properties for Modeling Microwave Interactions with the Human Breast

    PubMed Central

    Zastrow, Earl; Davis, Shakti K.; Lazebnik, Mariya; Kelcz, Frederick; Van Veen, Barry D.; Hagness, Susan C.

    2008-01-01

    Computational electromagnetics models of microwave interactions with the human breast serve as an invaluable tool for exploring the feasibility of new technologies and improving design concepts related to microwave breast cancer detection and treatment. In this paper we report the development of a collection of anatomically realistic 3D numerical breast phantoms of varying shape, size, and radiographic density which can be readily used in FDTD computational electromagnetics models. The phantoms are derived from T1-weighted magnetic resonance images (MRIs) of prone patients. Each MRI is transformed into a uniform grid of dielectric properties using several steps. First, the structure of each phantom is identified by applying image processing techniques to the MRI. Next, the voxel intensities of the MRI are converted to frequency-dependent and tissue-dependent dielectric properties of normal breast tissues via a piecewise-linear map. The dielectric properties of normal breast tissue are taken from the recently completed large-scale experimental study of normal breast tissue dielectric properties conducted by the Universities of Wisconsin and Calgary. The comprehensive collection of numerical phantoms is made available to the scientific community through an online repository. PMID:19126460

  15. Mesomorphic and dielectric properties of esters useful for formulation of nematic mixtures for dual frequency addressing system

    E-print Network

    Wu, Shin-Tson

    . Either compounds do not have the appropriate TN-I value to be major components of nematic mixturesMesomorphic and dielectric properties of esters useful for formulation of nematic mixtures for dual,4-difluorophenyl 4'-alkyl-2,3- difluoro-biphenyl-4-carboxylates. The compounds exhibit the nematic mesophase

  16. Optical, Dielectric and Ferroelectric Properties of LaCrO3 Single Crystals

    NASA Astrophysics Data System (ADS)

    Matam, Mahesh Kumar; Ye, Zuo Guang

    2001-03-01

    Perovskite LaCrO3 crystallizes in an orthorhombic structure, which is used in various applications as an electrode material due to its p-type semicondutivity. LaCrO3 shows an antiferromagnetic behavior up to a Neel temperature TN = 258 K, and supposedly also exhibit ferroelectricity. However, the dielectric and ferroelectric properties have not been characterized thoroughly. This situation is mainly due to the difficulties encountered both in the ceramics sintering and the crystal growth of LaCrO3 due to its highly refractory character, which has also limited certain applications. In this work, single crystals of LaCrO3 have been successfully grown using a complex flux of Bi_2O3 and B_2O3 by slow cooling. Crystals thus obtained are transparent, green and of 0.75 x 0.5 x 0.1 mm size. Dielectric measurements carried out at various frequencies show an anomaly, pointing to a phase transition around TC = 350 ^oC. A large increase in dissipation factor (tan?) is observed just above the phase transition, which is attributed to an increase in conductivity. A partially saturated hysteresis loop is displayed, indicating the presence of ferroelectric behavior. Studies by Polarized Light Microscopy reveal the ferroelastic domain structures. Temperature dependence of domain structures and birefrengence shows the phase transition at TC around 350 ^oC accompanied by a significant change in domain structure, which is consistent with measurements. With its multi-ferroic properties confirmed, LaCrO3 could become a potentially magnetoelectric material.

  17. Effect of magnetic spins flipping process on the dielectric properties of ?-Fe1.6Ga0.4O3 system

    NASA Astrophysics Data System (ADS)

    Lone, Abdul Gaffar; Bhowmik, R. N.

    2015-04-01

    The ?-Fe1.6Ga0.4O3 (Ga doped ?-Fe2O3) sample has been stabilized in rhombohedral structure. The sample is a canted ferromagnet at 300 K and above. The spins structure starts flipping from in-plane direction to out of plane direction of the rhombohedral structure to exhibit an antiferromagnetic order below a typical temperature ˜ 215 K, known as Morin transition. The magnetic and dielectric properties of ?-Fe1.6Ga0.4O3 system have been discussed in the temperature range 123 K to 350 K to examine the effect of magnetic spins flipping process on dielectric properties. The dielectric constant has shown an anomalous peak at ˜ 310 K, followed by a rapidly decrease of dielectric constant with temperature and becomes weakly temperature dependent below Morin transition. The temperature dependent dielectric constant is accompanied with the changes in electrical conductivity, dielectric loss and phase shift of the current with respect to applied ac voltage across the material. The magnetization and dielectric constant showed a linear relation over a wide range of temperature across the Morin transition. The dielectric constant at room temperature decreases under magnetic field, which indicates magneto-dielectric effect in the system. The signature of magneto-dielectric effect reveals a coupling between spins degrees of freedom (magnetic order) and charge degrees of freedom (electric polarization) in corundum structured non-traditional ferroelectric systems.

  18. 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.

  19. Influence of Al2O3 nano-filler on dielectric properties and conductivity of two different PVA-PEO blend systems

    NASA Astrophysics Data System (ADS)

    Joge, Prajakta; Kanchan, D. K.; Dave, Gargi

    2015-06-01

    System-1: PVA-PEO-PEG-AgNO3 and System-2: PVA-PEO-EC-LiCF3SO3, are two blend systems prepared for different concentrations of Al2O3 nano-filler ranging from 2 to 10 wt%. The effect of Al2O3 nano filler on the conductivity (?dc) and dielectric properties such as dielectric constant (?') and dielectric loss (?") of the systems is thoroughly investigated using impedance spectroscopic analysis technique.

  20. Structural, optical and dielectric property of Co doped Bi{sub 2}Fe{sub 4}O{sub 9}

    SciTech Connect

    Swain, Smita Mohapatra, S. R. Sahoo, B. Singh, A. K.

    2014-04-24

    Multiferroic Bi{sub 2}Fe{sub 4}O{sub 9} and Co doped Bi{sub 2}Fe{sub 4}O{sub 9} are prepared by solid state route reaction method using bismuth oxide(Bi{sub 2}O{sub 3}), iron oxide(Fe{sub 2}O{sub 3}) and cobalt oxide (Co{sub 3}O{sub 4}). Their structural optical and dielectric properties are studied and compared. X-ray diffraction (XRD) results confirm that there is no change in crystal structure due to Co doping. From dielectric constant measurement we conclude that dielectric constant increases due to Co doping. UV-Visible plot shows due to Co doping bang gap energy increases.

  1. Composites of hybrids BaTiO3/carbon nanotubes/polyvinylidene fluoride with high dielectric properties

    NASA Astrophysics Data System (ADS)

    Fan, Benhui; Bai, Jinbo

    2015-11-01

    High dielectric composites were prepared based on polyvinylidene fluoride (PVDF) and hybrids BaTiO3-carbon nanotubes (H-BT-CNTs) with a special structure. The hybrids that BT was a core and CNTs grew outside were fabricated by chemical vapor deposition. Due to the special structure, composite’s dielectric permittivity reached 1777 at 100 Hz and 80 at 1 MHz, while loss tangent maintained as 6 at 100 Hz and 0.56 at 1 MHz, respectively. Moreover, dielectric permittivity and ac conductivity of composite were further enhanced after annealing process at moderate temperature. These improved properties were originated from the reformation of conductive network and BT-CNTs structure inside PVDF matrix.

  2. Dielectric and Nonohmic Properties of CaCu3Ti4O12/SrTiO3 Ceramics

    NASA Astrophysics Data System (ADS)

    Xue, Renzhong; Liu, Dewei; Chen, Zhenping; Dai, Haiyang; Chen, Jing; Zhao, Gaoyang

    2015-04-01

    In this work, (1 - x)CaCu3Ti4O12- xSrTiO3 [(1 - x)CCTO/ xST, x = 0% to 2%] ceramic samples were prepared by the solid-state reaction method. The dielectric and electrical properties of CaCu3Ti4O12 (CCTO) and CaCu3Ti4O12/SrTiO3 (CCTO/ST) ceramics were investigated. The results show that a small amount of Sr2+ can enter the lattice of CCTO. The mean grain size of the ceramic samples increased greatly for x = 0.5% and then decreased for x = 0.75% to 2%. ST addition and Sr2+ preferential occupancy in CCTO grains should be responsible for the change of the microstructure. Interestingly, the dielectric constant ( ?) of the 0.5% ST-added sample increased significantly while the dielectric loss (tan ?) remained low. With further increase of the ST content, the ? and tan ? values of the CCTO ceramics decreased monotonically while the nonlinear current-voltage properties were significantly enhanced. The change in the potential barrier height is thought to be the main cause for the opposite behaviors in the dielectric properties and nonohmic characteristics.

  3. 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.

  4. Effects of pyrolysis conditions on dielectric properties of PLZT films derived from a polyvinylpyrrolidone-modified sol-gel process

    SciTech Connect

    Chao, Sheng; Ma, Beihai; Liu, Shanshan; Narayanan, Manoj; Balachandran, Uthamalingam

    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. 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.

  6. Mechanical property changes in porous low-k dielectric thin films during processing

    SciTech Connect

    Stan, G. Gates, R. S.; Kavuri, P.; Torres, J.; Michalak, D.; Ege, C.; Bielefeld, J.; King, S. W.

    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.

  7. Dielectric function and optical properties of quaternary AlInGaN alloys

    SciTech Connect

    Sakalauskas, E.; Gobsch, G.; Reuters, B.; Khoshroo, L. Rahimzadeh; Kalisch, H.; Vescan, A.; Heuken, M.; Roeppischer, M.; Cobet, C.; Goldhahn, R.

    2011-07-01

    The optical properties of quaternary Al{sub x}In{sub y}Ga{sub 1-x-y}N alloy films with 0.16dielectric 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 kxp 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.

  8. Structural, dielectric and optical properties of lithium borate-bismuth tungstate glass-ceramics

    SciTech Connect

    Murugan, G.S.; Varma, K.B.R.

    1999-12-01

    Glasses in the system (1 {minus} x)Li{sub 2}B{sub 4}O{sub 7}-xBi{sub 2}WO{sub 6} (0.1 {le} x {le} 0.35) were prepared by spat quenching technique. Powder X-ray diffraction (XRD) and differential thermal analysis (DTA) were employed to characterize the as-quenched glasses. High-resolution transmission electron microscopy (HR-TEM) revealed the presence of fine, nearly spherical crystallites of Bi{sub 2}WO{sub 6} varying from 1.5 to 20 nm in size, depending on x in the as-quenched glasses. The glasses (corresponding to x = 0.3) heat-treated at 723 K for 6 h gave rise to a clear crystalline phase of Bi{sub 2}WO{sub 6} embedded in the Li{sub 2}B{sub 4}O{sub 7} glass matrix, as observed by X-ray studies. The dielectric constants of the as-quenched glasses as well as the glass-ceramics decreased with increase in frequency (40Hz--100 kHz) at 300 K, and the value obtained for the glass-ceramic (x = 0.2) is in agreement with the values predicted using Maxwell's model and the logarithmic mixture rule. The dielectric constants for both the as-quenched glass and the glass-ceramic increased with increase in temperature (300--873 K) and exhibited anomalies close to the onset of the crystallization temperature of the host glass matrix. The optical transmission properties of these glass-ceramics were found to be compositional dependant.

  9. Spiral configuration of electrodes and dielectric material for sensing an environmental property

    NASA Technical Reports Server (NTRS)

    Laue, Eric G. (Inventor); Stephens, James B. (Inventor)

    1989-01-01

    A reliable moisture-indicating capactive sensor is provided with wire electrodes at least one of which includes a coating of moisture-absorbing dielectric material by spirally twisting the wire electrodes about each other, thereby establishing a pair of electrodes in contact with opposite surfaces of a layer of dielectric material, and assuring consistent contact of each electrode with the dielectric material despite changes in environmental conditions.

  10. A large-scale study of the ultrawideband microwave dielectric properties of normal, benign and malignant breast tissues obtained from cancer surgeries

    NASA Astrophysics Data System (ADS)

    Lazebnik, Mariya; Popovic, Dijana; McCartney, Leah; Watkins, Cynthia B.; Lindstrom, Mary J.; Harter, Josephine; Sewall, Sarah; Ogilvie, Travis; Magliocco, Anthony; Breslin, Tara M.; Temple, Walley; Mew, Daphne; Booske, John H.; Okoniewski, Michal; Hagness, Susan C.

    2007-10-01

    The development of microwave breast cancer detection and treatment techniques has been driven by reports of substantial contrast in the dielectric properties of malignant and normal breast tissues. However, definitive knowledge of the dielectric properties of normal and diseased breast tissues at microwave frequencies has been limited by gaps and discrepancies across previously published studies. To address these issues, we conducted a large-scale study to experimentally determine the ultrawideband microwave dielectric properties of a variety of normal, malignant and benign breast tissues, measured from 0.5 to 20 GHz using a precision open-ended coaxial probe. Previously, we reported the dielectric properties of normal breast tissue samples obtained from reduction surgeries. Here, we report the dielectric properties of normal (adipose, glandular and fibroconnective), malignant (invasive and non-invasive ductal and lobular carcinomas) and benign (fibroadenomas and cysts) breast tissue samples obtained from cancer surgeries. We fit a one-pole Cole-Cole model to the complex permittivity data set of each characterized sample. Our analyses show that the contrast in the microwave-frequency dielectric properties between malignant and normal adipose-dominated tissues in the breast is considerable, as large as 10:1, while the contrast in the microwave-frequency dielectric properties between malignant and normal glandular/fibroconnective tissues in the breast is no more than about 10%.

  11. Static and Field-Oriented Properties of Bowl-Shaped Polynuclear Aromatic Hydrocarbon Fragments.

    PubMed

    Zoppi, Laura; Ferretti, Andrea; Baldridge, Kim K

    2013-11-12

    First principles techniques are used to investigate the structure, linear polarizability, and field-oriented property trends of the series of bowl shaped polynuclear aromatic hydrocarbon fragments, C20H10, C30H10, C40H10, and C50H10. Such structures represent a sequence of minimalistic, capped bucky tube units based on the corannulene molecule, with interesting technological promise imparted by their curvature. Specific issues associated with how the intrinsic dipole and static linear polarizability influences the orientation of these structures in the presence of an external electric field are addressed and shown to correlate well with a simple analytical model. At moderate electric fields, the induced dipoles become comparable and even larger than the intrinsic dipoles due to the large in-plane polarizabilities in these systems. This generates a nontrivial and field dependent orientation of the molecule that can be exploited, for example, to induce switching behavior within molecular nanojunctions. PMID:26583398

  12. Elastic, piezoelectric, and dielectric properties of 0.58Pb,,Mg13Nb23...O3-0.42PbTiO3 single crystal

    E-print Network

    Cao, Wenwu

    temperature the PMN-42%PT single crystal has tetragonal symmetry. The measured piezoelectric constant d33 the morpho- tropic phase boundary MPB , possess large piezoelectric (d33 2500 pC/N), dielectric ( r 5000 into prominence due to their ultra-high dielectric and piezoelec- tric properties1­4 in contrast

  13. The changing dielectric properties of CHO cells can be used to determine early apoptotic events in a bioprocess.

    PubMed

    Braasch, Katrin; Nikolic-Jaric, Marija; Cabel, Tim; Salimi, Elham; Bridges, Greg E; Thomson, Doug J; Butler, Michael

    2013-11-01

    To ensure maximum productivity of recombinant proteins it is desirable to prolong cell viability during a mammalian cell bioprocess, and therefore important to carefully monitor cell density and viability. In this study, five different and independent methods of monitoring were applied to Chinese hamster ovary (CHO) cells grown in a batch culture in a controlled bioreactor to determine cell density and/or cell viability. They included: a particle counter, trypan blue exclusion (Cedex), an in situ bulk capacitance probe, an off-line fluorescent flow cytometer, and a prototype dielectrophoretic (DEP) cytometer. These various techniques gave similar values during the exponential growth phase. However, beyond the exponential growth phase the viability measurements diverged. Fluorescent flow cytometry with a range of fluorescent markers was used to investigate this divergence and to establish the progress of cell apoptosis: the cell density estimates by the intermediate stage apoptosis assay agreed with those obtained by the bulk capacitance probe and the early stage apoptosis assay viability measurements correlated well with the DEP cytometer. The trypan blue assay showed higher estimates of viable cell density and viability compared to the capacitance probe or the DEP cytometer. The DEP cytometer measures the dielectric properties of individual cells and identified at least two populations of cells, each with a distinct polarizability. As verified by comparison with the Nexin assay, one population was associated with viable (non-apoptotic) cells and the other with apoptotic cells. From the end of the exponential through the stationary and decline stages there was a gradual shift of cell count from the viable into the apoptotic population. However, the two populations maintained their individual dielectric properties throughout this shift. This leads to the conclusion that changes in bulk dielectric properties of cultures might be better modeled as shifts in cells between different dielectric sub-populations, rather than assuming a homogeneous dielectric population. This shows that bulk dielectric probes are sensitive to the early apoptotic changes in cells. DEP cytometry offers a novel and unique technology for analyzing and characterizing mammalian cells based on their dielectric properties, and suggests a potential application of the device as a low-cost, label-free, electronic monitor of physiological changes in cells. PMID:23818314

  14. Dielectric and Electrical Properties of the Double Perovskite PbBaBiNbO6

    NASA Astrophysics Data System (ADS)

    Panda, Niranjan; Parida, B. N.; Padhee, R.; Choudhary, R. N. P.

    2015-11-01

    The double perovskite PbBaBiNbO6 was synthesized by high-temperature solid-state reaction. Room-temperature x-ray data, energy-dispersive x-ray spectroscopy, and scanning electron microscopy of the sample confirmed formation of a single-phase compound and uniform distribution of grains of high density. Detailed studies of the dependence of the dielectric properties of the material on temperature and frequency confirmed its ferroelectric nature. The electrical transport properties of the material were indicative of non-exponential conductivity relaxation. We suggest this B-site Bi5+-doped ferroelectric perovskite material is a suitable candidate for the bulk photovoltaic effect and related solar applications. The low-lying 6s empty states of the electronegative Bi atom produce empty bands in the energy gap of the parent materials, effectively reducing the activation energy by ˜1 eV, depending on the composition of the ferroelectric end member and the concentration of Bi5+ in the solid solution.

  15. Structural, morphological, dielectrical and magnetic properties of Mn substituted cobalt ferrite

    NASA Astrophysics Data System (ADS)

    Yadav, S. P.; Shinde, S. S.; Kadam, A. A.; Rajpure, K. Y.

    2013-09-01

    The Co1-xMnxFe2O4 (0 <= x <= 0.5) ferrite system is synthesized by using an auto combustion technique using metal nitrates. The influence of Mn substitution on the structural, electrical, impedance and magnetic properties of cobalt ferrite is reported. X-ray diffraction patterns of the prepared samples confirm that the Bragg's peak belongs to a spinel cubic crystal structure. The lattice constant of cobalt ferrite increases with the increase in Mn content. The microstructural study is carried out by using the SEM technique and the average grain size continues to increase with increasing manganese content. AC conductivity analysis suggests that the conduction is due to small polaron hopping. DC electrical resistivity decreases with increasing temperature for a Co1-xMnxFe2O4 system showing semiconducting behavior. The activation energy is found to be higher in the paramagnetic region than the ferromagnetic region. Curie temperature decreases with Mn substitution in the host ferrite system. Dielectric dispersion having Maxwell—Wagner-type interfacial polarization has been observed for cobalt ferrite samples. Magnetic properties have been studied by measuring M—H plots. The saturation and remanent magnetization increases with Mn substitution.

  16. Orbital free ab initio molecular dynamics simulation study of some static and dynamic properties of liquid noble metals

    E-print Network

    G. M. Bhuiyan; L. E. González; D. J. González

    2012-10-08

    Several static and dynamic properties of liquid Cu, Ag and Au at thermodynamic states near their respective melting points, have been evaluated by means of the orbital free ab-initio molecular dynamics simulation method. The calculated static structure shows good agreement with the available X-ray and neutron diffraction data. As for the dynamic properties, the calculated dynamic structure factors point to the existence of collective density excitations along with a positive dispersion for l-Cu and l-Ag. Several transport coefficients have been obtained which show a reasonable agreement with the available experimental data.

  17. 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.

  18. Correlation of Heating Rates, Crystal Structures, and Microwave Dielectric Properties of Li2ZnTi3O8 Ceramics

    NASA Astrophysics Data System (ADS)

    Lu, Xuepeng; Zheng, Yong; Huang, Qi; Xiong, Weihao

    2015-11-01

    The correlation of heating rates, crystal structures, and microwave dielectric properties of Li2ZnTi3O8 ceramics was thoroughly investigated. Ionic polarizability, atomic packing fractions, bond strengths, and octahedral distortion of Li2ZnTi3O8 ceramics were calculated on the basis of structure refinement data. The "black core" phenomenon resulting from reduction of Ti4+ ions was observed for Li2ZnTi3O8 ceramic sintered at 1°/min; reduction of Ti4+ ions could be limited by heating more rapidly. For heating rates from 1 to 7°/min, the dielectric constants ( ? r) of Li2ZnTi3O8 ceramics were mainly determined by ionic polarizability. The temperature coefficient of the resonant frequency ( ? f ) of Li2ZnTi3O8 ceramics was determined by bond strengths. Li2ZnTi3O8 ceramic sintered at 1°/min had the lowest quality factor ( Q × f); this was related to the high dielectric loss as a result of oxygen vacancies formed by reduction of Ti4+ ions. Q × f values of Li2ZnTi3O8 ceramics also decreased with increasing heating rate from 3 to 7°/min, owing to reduced packing fractions and average grain sizes. Li2ZnTi3O8 ceramic sintered at 3°/min had the optimum microwave dielectric properties of ? r = 26.6, Q × f = 83,563 GHz, and ? f = -12.4 ppm/°C.

  19. The effects of carbon nano tubes on electric and dielectric properties of CNTs doped KBr (CNTs/KBr) compound

    NASA Astrophysics Data System (ADS)

    Dadras, Sedigheh; Farahani, Maryam Vasheghani

    2015-11-01

    Carbon nano tubes (CNTs) are synthesized by chemical vapor deposition method. We used X-ray diffraction and scanning electron microscopy, for characterization of the samples. After mixing different weight percentages (0-5 wt%) of the CNTs with potassium bromide insulator powder, we pressed it into pellets forming the CNTs/KBr compound samples. We investigated the DC electrical conductivity and dielectric properties of the compounds and applied the percolation theory to demonstrate the electrical property transition from insulator to conductor. We found that the DC conductivity of the samples increases with increasing CNTs in the compound and the electric percolation threshold is around 0.7 wt% CNTs and the critical exponent is 1.7. We investigated the capacity and dielectric function of the samples in different frequencies (10 Hz to 200 kHz) at room temperature, and studied the behavior of the real and imaginary parts of the dielectric function versus applied frequencies and CNTs percentages in the compound. We found that sample with 1.5 wt% CNT has higher dielectric constant.

  20. Multi-susceptibile single-phased ceramics with both considerable magnetic and dielectric properties by selectively doping.

    PubMed

    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 Fe(3+), such as Ti(4+), Nb(5+) and Zr(4+), into BaFe12O19. In terms of charge balance, Fe(3+)/Fe(2+) pair dipoles are produced through the substitution of Fe(3+) by high-valenced ions. The electron hopping between Fe(3+) and Fe(2+) 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

  1. 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

  2. Electronic, thermoelectric, and magneto-dielectric properties of Ca1-xNaxCr2O4

    NASA Astrophysics Data System (ADS)

    Kolodiazhnyi, Taras; Sakurai, Hiroya

    2013-06-01

    We report on electronic, thermoelectric, and magneto-dielectric properties of Ca1-xNaxCr2O4 series with a calcium ferrite-type structure prepared by high-pressure-high-temperature synthesis. Dielectric spectroscopy down to 2 K confirms that both CaCr2O4 and NaCr2O4 end members have an insulating ground state notwithstanding the fact that the latter compound has a mixed valence Cr3+/Cr4+ structure. A crossover from positive to negative charge carriers occurs in NaCr2O4 at T?230 K. Partial substitution of Ca for Na brings about a change from n to p type carriers at ca. x =0.75. A strong suppression of thermal conductivity below TN=21 K was found in CaCr2O4 indicating a scattering of acoustic phonons from a long wave-length cycloidal magnetic excitations. A pronounced dielectric anomaly at Néel temperature adds CaCr2O4 to the multiferroic family of compounds. Lattice contribution to dielectric properties of NaCr2O4 at TN=125 K is screened by high electric conductivity. An onset of the magnetocapacitance above 3 T correlates with the spin-flop transition in NaCr2O4 at a critical field of 3.5 T. A strong non-saturated magnetocapacitance in this compound cannot be entirely attributed to the colossal magnetoresistance.

  3. Measurement of elastic properties and static strength. Final report, 1 July 1983-1 October 1984

    SciTech Connect

    Johnson, T.L.

    1984-10-01

    Prediction of seismic coupling for nuclear monitoring requires theoretical models capable of calculating ground motions. The models must have a sound physical basis and be able to represent dynamic material behavior near the source. This portion of the study of stress-wave propagation in low-porosity rock is aimed at determining quasi-static properties of rock necessary to use in numerical models predicting wave propagation. Further, the failure process of low-porosity rock under simulated shock loading is being studied to establish the failure mechanisms. Initial effort supported by the contract was devoted mainly to obtaining and preparing samples of Westerly granite for experiments. Preliminary experiments to characterize the properties of Westerly granite were performed on small samples obtained from the Bonner Monument Co. Material properties measured agreed well with previous determinations. Deformation of Westerly Granite was measured under standard triaxial loading conditions and under a loading path mimiking shock-wave passage. Unlike high-porosity rocks, the different loading paths did not substantially affect the strength of the low-porosity granite. The failure envelope determined in standard triaxial tests agreed well with that measured under simulated shock loading.

  4. Dielectric and phase behavior of dipolar spheroids.

    PubMed

    Johnson, Lewis E; Benight, Stephanie J; Barnes, Robin; Robinson, Bruce H

    2015-04-23

    The Stockmayer fluid, composed of dipolar spheres, has a well-known isotropic-ferroelectric phase transition at high dipole densities. However, there has been little investigation of the ferroelectric transition in nearly spherical fluids at dipole densities corresponding to those found in many polar solvents and in guest-host organic electro-optic materials. In this work, we examine the transition to ordered phases of low-aspect-ratio spheroids under both unperturbed and poled conditions, characterizing both the static dielectric response and thermodynamic properties of spheroidal systems. Spontaneous ferroelectric ordering was confined to a small region of aspect ratios about unity, indicating that subtle changes in sterics can have substantial influence on the behavior of coarse-grained liquid models. Our results demonstrate the importance of molecular shape in obtaining even qualitatively correct dielectric responses and provide an explanation for the success of the Onsager model as a phenomenological representation for the dielectric behavior of polar organic liquids. PMID:25821921

  5. Microwave dielectric properties of ground and whole-muscle chicken meat and correlations with quality attributes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dielectric spectra of whole-muscle and ground chicken meat samples were obtained with an open-ended coaxial-line probe between 0.5 GHz and 50 GHz at 23 oC. The spectra show a dielectric behavior consistent with that expected for materials with high water content with differences between the whole-mu...

  6. Preparation and dielectric properties of oxide added NaCl KCl polycrystals

    NASA Astrophysics Data System (ADS)

    Priya, M.; Mahadevan, C. K.

    2008-01-01

    Pure and ZnO and CdO added (separately) polycrystals of NaCl, KCl and (NaCl) 0.5(KCl) 0.5 were prepared by the melt method. Density, atomic absorption spectroscopic and X-ray diffraction measurements indicate that the ZnO and CdO have entered into the lattices of alkali halide crystals. The dielectric measurements indicate that the dielectric parameters increase with the increase in temperature. Also, the dielectric constant and dielectric loss factor values decreased whereas the electrical conductivities increased with the increase in frequency of the AC applied. Significant changes have been observed with the dielectric parameters caused by ZnO and CdO additions. Also, the depth profile study was carried out on CdO added crystals which indicates that the dopant addition creates different layers along the crystal with increase of dopant content from top to bottom.

  7. New dielectric elastomers with improved properties for energy harvesting and actuation

    NASA Astrophysics Data System (ADS)

    Stiubianu, George; Bele, Adrian; Tugui, Codrin; Musteata, Valentina

    2015-02-01

    New materials with large value for dielectric constant were obtained by using siloxane and chemically modified lignin. The modified lignin does not act as a stiffening filler material for the siloxane but acts as bulk filler, preserving the softness and low value of Young's modulus specific for silicones. The measured values for dielectric constant compare positively with the ones for previously tested dielectric elastomers based on siloxane rubber or acrylic rubber loaded with ceramic nanoparticles. The new materials use the well-known silicone chemistry and lignin which is available worldwide in large amounts as a by-product of pulp and paper industry, making its manufacturing affordable. The prepared dielectric elastomers were tested for possible applications for wave, wind and kinetic body motion energy harvesting. Siloxane, lignin, dielectric

  8. 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.

  9. 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: rbjotania@gmail.com

    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)

  10. 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.

  11. The structural, dielectric, elastic, and piezoelectric properties of KNbO3 from first-principles methods

    NASA Astrophysics Data System (ADS)

    Wan, L. F.; Nishimatsu, T.; Beckman, S. P.

    2012-05-01

    The elastic and dielectric properties of the four experimentally known phases of KNbO3 (KNO) are investigated by first-principles methods. The atomic structure is reported along with the Born effective charge tensor to reveal the relation between Nb-O bonds hybridization and ferroelectric structural distortion. The dielectric, elastic, and piezoelectric properties of each phase are presented and compared to results in the literature. The computed structures are found to match experiment to an accuracy of approximately 2%. Although there have been very few experimental studies of single crystal KNO, it is found that the elastic parameters computed for orthorhombic KNO agree with the measured values to better than 25%, which is within the anticipated exchange-correlation error; however, the computed piezoelectric coefficient differ from the experimental values by as much as 50%, which suggests that the disagreement may not be solely due to the theoretical approximations.

  12. Dielectric and piezoelectric properties of S001< fiber-textured 0.675Pb,,Mg13Nb23...O3 0.325PbTiO3 ceramics

    E-print Network

    Messing, Gary L.

    Dielectric and piezoelectric properties of S001 to the application of the domain engineering concept for perovskite ferroelectrics which have a rhombohedral a high degree of grain orien- tation texture possess directionally dependent dielectric, pyroelectric

  13. Dielectric properties of micropatterns consisting of barium titanate single-crystalline nanocubes

    NASA Astrophysics Data System (ADS)

    Mimura, Ken-ichi; Kato, Kazumi

    2015-10-01

    Micropatterns of barium titanate nanocube (BT NC) assemblies were fabricated by dip-coating self-assembly using a micropatterned mold made of Si or polyimide (PI). The microstructure of the BT NC assembly in the micropatterned mold made of PI showed the closest packing structure. This result indicated that the polymer wall in the micropatterns is swollen by the organic solvent used in the dip-coating self-assembly process. As a result, this swelling might work effectively for the self-assembly of the NCs with high ordering assisted by capillary force. Moreover, it is clarified that the line-and-space-molds with a taper angle and a large width were more useful for the self-assembly of BT NCs in microtrenches selectively. The micropatterned mold made of PI could be removed by immersing in N-methyl-2-pyrrolidone at 65 °C. The ordered structure was not destroyed during the removal process. Micropatterned BT NC capacitor structures were obtained by this method after sintering at 850 °C. The interfaces of BT NCs were conjugated face-to-face, as shown by the obtained high-resolution transmission electron microscopy (HR-TEM) cross-sectional profiles. This process has a great potential for fabricating patterned assemblies directly on substrates. The dielectric properties of BT NC micropatterned assemblies in micropatterned molds made of Si were also characterized and compared with those of BT NC assemblies on Pt/Si substrates without micropatterning.

  14. Temporal change in the electromechanical properties of dielectric elastomer minimum energy structures

    SciTech Connect

    Buchberger, G. Hauser, B.; Jakoby, B.; Hilber, W.; Schoeftner, J.; Bauer, S.

    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.

  15. Particles Embedded in Poly(Arylene Ether Nitrile) Matrix with Enhanced Dielectric Properties

    NASA Astrophysics Data System (ADS)

    Pu, Zejun; Tong, Lifen; Long, Ya; Yang, Wei; Huang, Xu; Liu, Xiaobo

    2014-07-01

    Polymer-based composite films were prepared by employing core/shell-structured tetranitrophthalocyanine copper/titanium dioxide (TNCuPc-TiO2) hybrid particles as fillers and poly(arylene ether nitrile)s (PEN) as polymer matrix. Core/shell-structured TNCuPc-TiO2 hybrid particles were successfully synthesized through a facile solvothermal synthesis route. Compared with raw TiO2, the dispersibility and interfacial compatibility between TNCuPc-TiO2 hybrid particles and PEN matrix were observably improved because the TNCuPc decorated on the TiO2 can interact with nitrile groups in PEN. Consequently, core/shell-structured TNCuPc-TiO2 had a more significant enhancement effect on the properties of PEN. Although the mechanical strength was reduced to 41 MPa, all of the composite films exhibited excellent thermal stability. Their initial decomposition temperatures were up to 510°C, and the glass-transition temperatures were over 191°C. More importantly, the permittivity of the composite film was as high as 19.8 at 100 Hz when the weight fraction of TNCuPc-TiO2 hybrid particle loading reached 40.0 wt.%. Compared with the permittivity of PEN/TiO2 composite films with 40.0 wt.% raw TiO2 particle loading, the dielectric constant was increased by 161%.

  16. Optical properties and dielectric relaxation of polyvinylidene fluoride thin films doped with gadolinium chloride

    NASA Astrophysics Data System (ADS)

    El-Sayed, Somyia

    2014-12-01

    In this study, the properties of pure and GdCl3-doped polyvinylidene fluoride (PVDF) films were investigated. X-ray diffraction revealed that the PVDF was composed of mixed ? and ? phases. Adding GdCl3 to PVDF decreased the crystallinity of the polymer matrix. At room temperature, in the ultraviolet-visible range both the absorbance (a) and extinction coefficient (k) of PVDF decreased with GdCl3 content, demonstrating that the optical response of the doped films improved because of increasing optical energy gap (Eg). We also measured the dielectric loss (??), electric modulus (M?), and ac conductivity (?ac) at 300-450 K and 0.1-3000 kHz. The pure and doped PVDF exhibited different relaxation processes. The activation energy (Ea) of the ?c relaxation decreased with increasing GdCl3 content, following an Arrhenius relationship. The behavior of the ac conductivity revealed that the conduction mechanism for studied films followed correlated barrier hopping model. The hopping distance (R) was calculated at different temperatures for all investigated samples.

  17. Influence of steric interactions on the dielectric and electrokinetic properties in colloidal suspensions.

    PubMed

    López-García, José Juan; Horno, José; Grosse, Constantino

    2015-11-15

    One of the main assumptions of the standard electrokinetic model is that ions behave as point like entities. In this work we remove this assumption and analyze the main consequences of finite ionic size on the dielectric and electrokinetic properties of colloidal suspensions. We represent the steric interactions by means of the Bikerman and the Carnahan-Starling equations and solve numerically the standard linearized electrokinetic equations in the stationary and the frequency domains, for surface charge density and electrolyte solution concentration values typically encountered in colloidal suspensions. In all cases the steric interactions improve upon the predictions of the standard model since the surface potential, the electrophoretic mobility, and the conductivity and permittivity increments increase. However, the corrections introduced by the Bikerman equation are generally small: less than 10% as compared to the standard model. On the contrary, the Carnahan-Starling equation leads to corrections to the surface potential versus surface charge and the electrophoretic mobility values that easily surpass 10% and can attain values as high as 50%. Corrections to the conductivity and permittivity increments are smaller but still non negligible. PMID:26233558

  18. Investigation of optical properties of multilayer dielectric structures using prism-coupling technique

    NASA Astrophysics Data System (ADS)

    Sokolov, V. I.; Glebov, V. N.; Malyutin, A. M.; Molchanova, S. I.; Khaydukov, E. V.; Panchenko, V. Ya

    2015-09-01

    A method based on resonant excitation of waveguide modes with a prism coupler is proposed for measuring the thickness and refractive index of thin-film layers in multilayer dielectric structures. The peculiarities of reflection of TE- and TM-polarised light beams from a structure comprising eleven alternating layers of zinc sulfide (ZnS) and magnesium barium fluoride (MgBaF4), whose thicknesses are much less than the wavelength of light, are investigated. Using the mathematical model developed, we have calculated the coefficients of reflection of collimated TE and TM light beams from a multilayer structure and determined the optical constants and thicknesses of the structure layers. The refractive indices of the layers, obtained for TE and TM polarisation of incident light, are in good agreement. The thicknesses of ZnS and MgBaF4 layers, found for different polarisations, coincide with an accuracy of +/-1%. Thus, we have demonstrated for the first time that the prism-coupling technique allows one to determine the optical properties of thin-film structures when the number of layers in the structure exceeds ten layers.

  19. Iron doped hexagonal ErMnO3: structural, magnetic, and dielectric properties.

    PubMed

    Liu, P; Cheng, Z X; Wang, X L; Du, Y; Yu, Z W; Dou, S X; Zhao, H Y; Ozawa, K; Kimura, H

    2012-02-01

    The single phase ErFe(x)Mn1-xO3 (0 < or = x < or = 0.15) compounds were synthesized by the solid-state reaction method. The doping effects on the crystal structural, magnetic, thermal, and dielectric properties were systematically investigated. The XRD patterns show all samples crystallize in the hexagonal structure with P6(3)cm space group. The lattice parameters a and c first decrease with doping, which is followed by a subsequent increase at higher doping levels. Although both the Fe3+ and Mn3+ ions remain stable in high spin trivalent states in all samples, the magnetization is weakened with increasing Fe contents. The heat capacity data shows the antiferromagnetic transition slightly shifts from 77 K for ErMnO3 to 80 K for ErFe015Mn0.85O3, which can not be observed in the magnetic susceptibility data. The real part of complex impedance of these samples rises as the doping level increases, indicating the enhancement of insulativity of doped samples. PMID:22629929

  20. Structural, dielectric and magnetic properties of cobalt ferrite prepared using auto combustion and ceramic route

    NASA Astrophysics Data System (ADS)

    Murugesan, C.; Perumal, M.; Chandrasekaran, G.

    2014-09-01

    Cobalt ferrite is synthesized by using low temperature auto combustion and high temperature ceramic methods. The prepared samples have values of lattice constant equal to 8.40 Å and 8.38 Å for auto combustion and ceramic methods respectively. The FTIR spectrum of samples of the auto combustion method shows a high frequency vibrational band at 580 cm-1 assigned to tetrahedral site and a low frequency vibrational band at 409 cm-1 assigned to octahedral site which are shifted to 590 cm-1 and 412 cm-1 for the ceramic method sample. SEM micrographs of samples show a substantial difference in surface morphology and size of the grains between the two methods. The frequency dependent dielectric constant and ac conductivity of the samples measured from 1 Hz to 2 MHz at room temperature are reported. The room temperature magnetic hysteresis parameters of the samples are measured using VSM. The measured values of saturation magnetization, coercivity and remanent magnetization are 42 emu/g, 1553 Oe, 18.5 emu/g for the auto combustion method, 66.7 emu/g, 379.6 Oe, and 17.3 emu/g for the ceramic method, respectively. The difference in preparation methods and size of the grains causes interesting changes in electrical and magnetic properties.

  1. Dielectric properties of Bi2PbNb2O9 ceramics prepared by different techniques

    NASA Astrophysics Data System (ADS)

    Gritzner, G.; Pissenberger, A.

    2007-06-01

    Different techniques for the synthesis of Bi2PbNb2O9, namely the mixed oxide technique, molten salt synthesis, hydrothermal synthesis, co-precipitation and the tartaric acid gel method were investigated and the results on the dielectric properties are reported. The heat-treatment of the precursor powders was the same for all precursor powders. Sintering at 1040 °C under ambient pressure resulted in polycrystalline specimens, while hot-forging at 1040 °C with a pressure of 20 MPa produced c-axis aligned samples. Phase composition and crystallite orientation of the sintered bodies were analyzed by X-ray diffraction. Single-phase material was obtained in all cases. Hot-forging not only yielded c-axis orientation, but also increased the relative densities above 99.4%. The relative permittivity decreased for c-axis oriented material compared to polycrystalline ceramics. Values for the relative permittivity for the hot-forged specimens at 100 °C at 100 kHz varied between 165 and 250, depending on the fabrication method. The Curie temperature for the c-axis aligned samples was 568 °C, independent of the nature of the precursor powders.

  2. Dielectric properties and effect of electrical aging on space charge accumulation in polyimide/TiO2 nanocomposite films

    NASA Astrophysics Data System (ADS)

    Zha, Jun-Wei; Dang, Zhi-Min; Song, Hong-Tao; Yin, Yi; Chen, George

    2010-11-01

    In situ polymerized polyimide/TiO2 (PI/TiO2) nanocomposite films with good electrical aging resistance are studied. Space charge distribution in the PI/TiO2 nanocomposite films are measured using the pulsed electroacoustic method. Dielectric properties of the films are measured in the frequency range of 102 Hz-106 Hz by an impedance analyzer (Agilent 4294A) at room temperature. These nanocomposite films are also characterized by Fourier transform infrared spectroscopy and scanning electron microscopy (SEM). It is demonstrated that the nano-TiO2 particles strongly affect dielectric breakdown, lifetime and space charge distribution, and increase the voltage endurance of the nanocomposite films significantly. SEM analyses show that the nanocomposite films are destroyed after corona aging. The relation of space charge distribution with the concentration of the nano-TiO2 particles and the aging time is explored. Results show that an increase in dielectric permittivity of the nanocomposite films is observed with increasing filler concentration. However, the accumulation of space charge decreases with increasing nano-TiO2 particles concentration for the same corona aging time, and depends on the dielectric permittivity of the nanocomposite films.

  3. 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

  4. Correlation between structural, magnetic, and dielectric properties of manganese substituted cobalt ferrite

    SciTech Connect

    Ramana, C. V. Kolekar, Y. D.; Kamala Bharathi, K.; Sinha, B.; Ghosh, K.

    2013-11-14

    Manganese (Mn) substituted cobalt ferrites (CoFe{sub 2?x}Mn{sub x}O{sub 4}, referred to CFMO) were synthesized and their structural, magnetic, and dielectric properties were evaluated. X-ray diffraction measurements coupled with Rietveld refinement indicate that the CFMO materials crystallize in the inverse cubic spinel phase. Temperature (T?=?300?K and 10?K) dependent magnetization (M(H)) measurements indicate the long range ferromagnetic ordering in CoFe{sub 2?x}Mn{sub x}O{sub 4} (x?=?0.00–0.15) ferrites. The cubic anisotropy constant (K{sub 1}(T)) and saturation magnetization (M{sub s}(T)) were derived by using the “law of approach” to saturation that describes the field dependence of M(H) for magnetic fields much higher than the coercive field (H{sub c}). Saturation magnetization (M{sub s}), obtained from the model, decreases with increasing temperature. For CoFe{sub 2}O{sub 4}, M{sub s} decreases from 3.63??{sub B} per formula unit (f.u.) to 3.47??{sub B}/f.u. with increasing temperature from 10 to 300?K. CFMO (0.00–0.15) exhibit the similar trend while the magnitude of M{sub s} is dependent on Mn-concentration. M{sub s}-T functional relationship obeys the Bloch's law. The lattice parameter and magnetic moment calculated for CFMO reveals that Mn ions occupying the Fe and Co position at the octahedral site in the inverse cubic spinel phase. The structure and magnetism in CFMO are further corroborated by bond length and bond angle calculations. The dielectric constant dispersion of CFMO in the frequency range of 20?Hz–1?MHz fits to the modified Debye's function with more than one ion contributing to the relaxation. The relaxation time and spread factor derived from modeling the experimental data are ?10{sup ?4}?s and ?0.35(±0.05), respectively.

  5. The characterization of dielectric properties of platinum-Nafion-poly(3,4-ethylenedioxythiophene) system

    NASA Astrophysics Data System (ADS)

    Kim, Hyo-Seok

    The generation of electrical energy by piezoelectric polymer when mechanically stressed has motivated the investigation of poly(vinylidenefluoride-trifluoro ethylene) (PVDF-TrFE) devices as implantable physiological power supplies. The fragility, specific weight, and rigidity of traditional piezoelectric ceramics used have limited their applicability, although the concept of using piezoelectric elements as mechanically actuated electric power generators for implanted organs has been exploited to some extent. In contrast, piezoelectric polymers are flexible, light, resistant to mechanical fatigue, and efficient as voltage generators. Thus, they can be considered as a source for generating, through mechanical deformation, the electric power needed to fuel implanted artificial organs or to trigger assisting devices such as cardiac pacemakers. This study demonstrates the feasibility of power generation devices that create current from mechanical deformation. One type of power generating device is PVDF-TrFE copolymer and, when built on the pacemaker's lead, can use the motion of the heart as its power source. The other type of device is a Pt-Nafion-PEDOT (PNP) composite device which is fabricated using Perfluorosulfonate ionomeric polymer (Nafion) and conductive polymer, Poly(3,4-ethylenedioxythiophene), by electrochemical synthesis. The device will enable passive location-specific stimulation, thus mimicking the contraction signal of the normal heart. It can generate its own power and may therefore make the battery-lifetime longer. In other applications of these materials is an ultrasound transducer and receiver. Ultrasound transducer/receivers using PNP composite and PVDF as a reference transducer/receiver were studied in order to detect and locate the depth of material (alloy metal, polymer gel) by a pulse-echo method. In a time of flight (TOF) measurement, a transmitter emits short packets of ultrasound waves toward the surface of object in tissue, where they are reflected and then detected by a receiver. The time interval or frequency change between emission and detection is measured as an indicator for the distance. The purpose of this project is to conduct fundamental study into the material properties with an emphasis on polarization-related phenomena. This project specifically focuses on the power generating properties of the hybrid PNP composite device and its application. This device is a new system being applied for the first time because of its potential for generating power. The specific aspects of the devices being studied in the project encompass both macroscopic and microscopic properties of hybrid PNP composite. The microscopic properties include electrical property as measured by impedance spectroscopy and dielectric response characteristics to examine the power generating mechanism of induced polarization for PNP composite device. The produced current and power efficiency by mechanical deformation operation are compared.

  6. 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.

  7. 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, ...

  8. 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.

  9. HfO2 dielectric thickness dependence of electrical properties in graphene field effect transistors with double conductance minima

    NASA Astrophysics Data System (ADS)

    Zhang, Cheng; Xie, Dan; Xu, Jian-Long; Li, Xin-Ming; Sun, Yi-Lin; Dai, Rui-Xuan; Li, Xian; Zhu, Hong-Wei

    2015-10-01

    We investigate the electrical properties in back-gated graphene field effect transistors (GFETs) with SiO2 dielectric and different thickness of high-k HfO2 dielectric. The results show that transform characteristic (Ids-Vgs) curves of GFETs are uniquely W-shaped with two charge neutrality point (left and right) in both SiO2 and HfO2 dielectric (SiO2-GFETs and HfO2-GFETs). The gate voltage reduces drastically in HfO2-GFETs compared with that in SiO2-GFETs, and it becomes much smaller with the decline of HfO2 thickness. The left charge neutrality point in Id-Vg curves of all HfO2-GFETs is negative, compared to the positive ones in SiO2-GFETs, which means that there exists n-doping in graphene with HfO2 as bottom dielectric. We speculate that this n-doping comes from the HfO2 layer, which brings fixed charged impurities in close proximity to graphene. The carrier mobility is also researched, demonstrating a decreasing trend of hole mobility in HfO2-GFETs contrast to that in SiO2-GFETs. In a series of HfO2-GFETs with different HfO2 dielectric thickness, the hole mobility shows a tendency of rise when the thickness decreases to 7 nm. The possible reason might be due to the introduced impurities into HfO2 film from atomic layer deposition process, the concentration of which varies from the thickness of HfO2 layer.

  10. Vectran Fiber Time-Dependent Behavior and Additional Static Loading Properties

    NASA Technical Reports Server (NTRS)

    Fette, Russell B.; Sovinski, Marjorie F.

    2004-01-01

    Vectran HS appears from literature and testing to date to be an ideal upgrade from Kevlar braided cords for many long-term, static-loading applications such as tie-downs on solar arrays. Vectran is a liquid crystalline polymer and exhibits excellent tensile properties. The material has been touted as a zero creep product. Testing discussed in this report does not support this statement, though the creep is on the order of four times slower than with similar Kevlar 49 products. Previous work with Kevlar and new analysis of Vectran testing has led to a simple predictive model for Vectran at ambient conditions. The mean coefficient of thermal expansion (negative in this case) is similar to Kevlar 49, but is not linear. A positive transition in the curve occurs near 100 C. Out-gassing tests show that the material performs well within parameters for most space flight applications. Vectran also offers increased abrasion resistance, minimal moisture regain, and similar UV degradation. The effects of material construction appear to have a dramatic effect in stress relaxation for braided Vectran. To achieve the improved relaxation rate, upgrades must also examine alternate construction or preconditioning methods. This report recommends Vectran HS as a greatly improved replacement material for applications where time-dependent relaxation is a major factor.

  11. Static and Dynamic Properties of Magnetic Antivortices in Asteroid-Shaped Permalloy Nanomagnets

    NASA Astrophysics Data System (ADS)

    Habiboglu, Ali Taha; Karakas, Vedat; Mete, Mustafa; Coskuner, Ahmet; Kalyoncu, Yemliha Bilal; Gokce, Aisha; Ozatay, Ozhan; Giordano, Anna; Carpentieri, Mario; Finocchio, Giovanni; Celegato, Federica; Tiberto, Paola

    2015-03-01

    Patterned nanomagnets display unconventional spin configurations like vortex, anti-vortex, bubble, which have unique static and dynamic properties. Such micro-magnetic structures are potentially applicable to ultrafast memory, rf oscillators and detectors. Studies on magnetic thin films containing vortex structures exhibit interesting behavior under external field and/or current bias like polarity switching, core displacement and core gyration with high frequencies inside the nanomagnet. In this study, we report on our investigation of stable anti-vortex formation conditions and the subsequent magnetic field/dc current driven excitations in 2x2 ?m2 Permalloy based asteroid geometry devices which exhibit an anti-vortex pair nucleation at the center. The Magnetic Force Microscopy images show that the antivortex pair can be rotated around the center by an external magnetic field. We obtain a high frequency (GHz) signal measured via anisotropic magneto-resistance effect (AMR) under constant dc current-bias which triggers antivortex pair gyration around the center of the device through spin transfer torque. We study the dynamic response of the structure as a function of current and field to assess utilization of the device as a practical on-chip microwave oscillator.

  12. 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.

  13. A Novel Conversion Process for Waste Slag: The Preparation of Aluminosilicate Glass with Evaluation of the Dielectric Properties from Blast Furnace Slag

    NASA Astrophysics Data System (ADS)

    Li, Sheng; Huang, Sanxi; Liu, Hongting; Wu, Fengnian; Chang, Ziyuan; Yue, Yunlong

    2015-09-01

    In this paper, aluminosilicate glass was prepared from blast furnace slag and quartz sand. Fourier transform infrared, differential scanning calorimetry and density measurements were carried out to investigate the effects of SiO2 on the aluminosilicate glass network rigidity. The results indicate that glass structure would be enhanced if more SiO2 was introduced into the glass system. Meanwhile, both the glass transition temperature (T g) and the glass crystallization temperature (T c) increase slightly; the increase in density of the glass being further evidence of the enhancement in glass network rigidity. Dielectric measurements show that the dielectric constant and dielectric loss decrease with more SiO2. The properties of the prepared aluminosilicate glasses are comparable to those of E glass, indicating that blast furnace slags are suitable for producing aluminosilicate glass with low dielectric constant and dielectric loss.

  14. A Novel Conversion Process for Waste Slag: The Preparation of Aluminosilicate Glass with Evaluation of the Dielectric Properties from Blast Furnace Slag

    NASA Astrophysics Data System (ADS)

    Li, Sheng; Huang, Sanxi; Liu, Hongting; Wu, Fengnian; Chang, Ziyuan; Yue, Yunlong

    2015-11-01

    In this paper, aluminosilicate glass was prepared from blast furnace slag and quartz sand. Fourier transform infrared, differential scanning calorimetry and density measurements were carried out to investigate the effects of SiO2 on the aluminosilicate glass network rigidity. The results indicate that glass structure would be enhanced if more SiO2 was introduced into the glass system. Meanwhile, both the glass transition temperature ( T g) and the glass crystallization temperature ( T c) increase slightly; the increase in density of the glass being further evidence of the enhancement in glass network rigidity. Dielectric measurements show that the dielectric constant and dielectric loss decrease with more SiO2. The properties of the prepared aluminosilicate glasses are comparable to those of E glass, indicating that blast furnace slags are suitable for producing aluminosilicate glass with low dielectric constant and dielectric loss.

  15. Electrical and chemical properties of XeCl*(308 nm) exciplex lamp created by a dielectric barrier discharge

    SciTech Connect

    Baadj, S.; Harrache, Z. Belasri, A.

    2013-12-15

    The aim of this work is to highlight, through numerical modeling, the chemical and the electrical characteristics of xenon chloride mixture in XeCl* (308 nm) excimer lamp created by a dielectric barrier discharge. A temporal model, based on the Xe/Cl{sub 2} mixture chemistry, the circuit and the Boltzmann equations, is constructed. The effects of operating voltage, Cl{sub 2} percentage in the Xe/Cl{sub 2} gas mixture, dielectric capacitance, as well as gas pressure on the 308-nm photon generation, under typical experimental operating conditions, have been investigated and discussed. The importance of charged and excited species, including the major electronic and ionic processes, is also demonstrated. The present calculations show clearly that the model predicts the optimal operating conditions and describes the electrical and chemical properties of the XeCl* exciplex lamp.

  16. High energy-resolution electron energy-loss spectroscopy study of the dielectric properties of multi-shell nanoparticles.

    PubMed

    Nakahigashi, Naoyuki; Sato, Yohei; Terauchi, Masami; Uehara, Masato

    2014-11-01

    Nanoparticles, which have multi-shell structure, are expected to be stable and high efficient for the light-emitting devices. The efficiency of luminescence is considered to be affected by the multi-shell structure. In order to understand the mechanism of high efficiency luminescence, it is necessary to evaluate the multi-shell structure and dielectric properties from each particle. High energy-resolution electron energy-loss spectroscopy (HR-EELS) based on TEM is a powerful tool for this purpose. By comparing between the experimental and the simulated results, it is possible to evaluate the effect of the size and physical property of each shell material on the dielectric properties of multi-shell nanoparticles. In this study, simulations of EELS spectra of multi-shell nanoparticle (core: CdSe, inner shell: CdS, outer shell: ZnS) and mono-shell nanoparticle (core: CdSe, shell: CdS) were conducted by the dielectric continuum theory[1].Figure 1 shows calculated EELS spectra of multi and mono shell nanoparticles. The spectra are calculated from dielectric functions of single CdSe, CdS and ZnS crystals, which were experimentally derived from HR-EELS spectra by using Kramers-Kronig analysis. The radius of 6.9 nm for the nanoparticle in the simulation corresponds to the average size of actual synthesized nanoparticles. Energy positions of arrows in the inset correspond to band gap energies of CdSe, CdS and ZnS[2]. In the spectrum of multi-shell nanoparticle, the intensity corresponding to interband transition near band gap of CdSe is suppressed comparing with that of the mono shell nanoparticle. This result indicates that ZnS outer shell affects the intensity profile of EELS spectrum near band gap. This effect should be sensitive for the thickness of the shells. Thus, there is a possibility that the effect of size and thickness of each core and shell on dielectric properties of multi-shell nanoparticles could be evaluated by using HR-EELS technique.jmicro;63/suppl_1/i18/DFU039F1F1DFU039F1Fig. 1.Calculated EELS spectra. PMID:25359810

  17. Dielectric and piezoelectric properties of the KNN ceramic compound doped with Li, La and Ta

    NASA Astrophysics Data System (ADS)

    Fuentes, J.; Portelles, J.; Durruthy-Rodríguez, M. D.; H'Mok, H.; Raymond, O.; Heiras, J.; Cruz, M. P.; Siqueiros, J. M.

    2015-02-01

    With the purpose of improving the dielectric and piezoelectric properties of (K0.5Na0.5)NbO3 (KNN), a multiple doping strategy was tested in this research. Piezoceramics with composition [(K0.5Na0.5)0.94Li0.06]0.97La0.01(Nb0.9Ta0.1)O3 were prepared by the traditional ceramic method. The calcined powders were sintered in their own atmosphere at 1,100 °C for 1.0, 1.5 and 2.5 h. X-ray diffraction analysis showed that the Li+, La3+ and Ta5+ cations diffuse into the KNN structure to form a perovskite-structured solid solution. For 1 h sintering time, a dominant orthorhombic phase is obtained, whereas for the longer times, the dominant phase was tetragonal. The presence of a tetragonal tungsten-bronze minority second phase is confirmed. Scanning electron micrographs show rectangular-shaped grains with a mean size of 1.1 ± 0.2 ?m. The existence of pores and traces of a liquid phase favoring grain growth and homogeneity is also observed. Experimental results show an enhancement of the permittivity associated with the enlargement of the c parameter of the cell that increases with sintering time. Li+ incorporation into the structure is made evident by its transition temperature at 400 °C different from those of KNNLaTi (81-110 °C) and KNNLaTa (340 °C). An analysis of the phase transition of the samples indicates a normal rather than a diffuse transition. The electromechanical parameters k p, Q m, ? p, s 11, d 31 and g 31 are determined and compared to those of commercial PZT ceramics.

  18. Properties of reactively radio frequency-magnetron sputtered (Zr,Sn)TiO4 dielectric films

    NASA Astrophysics Data System (ADS)

    Huang, Cheng-Liang; Hsu, Cheng-Hsing

    2004-07-01

    Zirconium tin titanium oxide doped 1 wt % ZnO thin films on n-type Si substrate were deposited by rf magnetron sputtering at a fixed rf power of 350 W with various argon-oxygen (Ar/O2) mixture and different substrate temperatures. Electrical properties and microstructures of ZnO-doped (Zr0.8Sn0.2)TiO4 thin films prepared by rf magnetron sputtering on n-type Si(100) substrates at different Ar/O2 ratios and substrate temperatures have been investigated. The surface structural and morphological characteristics analyzed by x-ray diffraction, scanning electron microscopy, and atomic force microscope were sensitive to the deposition conditions, such as Ar/O2 ratio (100/0-80/20) and substrate temperature (350 °C-450 °C). The selected-area diffraction pattern showed that the deposited films exhibited a polycrystalline microstructure. All films exhibited ZST (111) orientation perpendicular to the substrate surface and the grain size as well as the deposition rate of the films increased with the increase of both the Ar partial pressure and the substrate temperature. At a Ar/O2 ratio of 100/0, rf power level of 350 W and substrate temperature of 450 °C, the Zr0.8Sn0.2TiO4 films with 6.44 ?m thickness possess a dielectric constant of 42 (at 10 MHz), a dissipation factor of 0.065 (at 10 MHz), and a leakage current density of 2×10-7 A/cm2 at an electrical field of 1 kV/cm.

  19. The correlation of in vivo and ex vivo tissue dielectric properties to validate electromagnetic breast imaging: initial clinical experience

    PubMed Central

    Halter, Ryan J; Zhou, Tian; Meaney, Paul M; Hartov, Alex; Barth, Richard J; Rosenkranz, Kari M; Wells, Wendy A; Kogel, Christine A; Borsic, Andrea; Rizzo, Elizabeth J; Paulsen, Keith D

    2009-01-01

    Electromagnetic (EM) breast imaging provides low-cost, safe and potentially a more specific modality for cancer detection than conventional imaging systems. A primary difficulty in validating these EM imaging modalities is that the true dielectric property values of the particular breast being imaged are not readily available on an individual subject basis. Here, we describe our initial experience in seeking to correlate tomographic EM imaging studies with discrete point spectroscopy measurements of the dielectric properties of breast tissue. The protocol we have developed involves measurement of in vivo tissue properties during partial and full mastectomy procedures in the operating room (OR) followed by ex vivo tissue property recordings in the same locations in the excised tissue specimens in the pathology laboratory immediately after resection. We have successfully applied all of the elements of this validation protocol in a series of six women with cancer diagnoses. Conductivity and permittivity gauged from ex vivo samples over the frequency range 100 Hz–8.5 GHz are found to be similar to those reported in the literature. A decrease in both conductivity and permittivity is observed when these properties are gauged from ex vivo samples instead of in vivo. We present these results in addition to a case study demonstrating how discrete point spectroscopy measurements of the tissue can be correlated and used to validate EM imaging studies. PMID:19491436

  20. Dielectric properties and relaxation behavior of the indium doped cadmium zinc telluride single crystal

    NASA Astrophysics Data System (ADS)

    Li, Qiang; Fan, Huiqing; Jie, Wanqi; Peng, Biaolin; Long, Changbai

    2012-04-01

    Low frequency dielectric dispersion behavior of the indium doped cadmium zinc telluride single crystal has been investigated. The temperature dependent of dielectric loss shows a broadening peak at high temperatures, which is attributed to thermally activated relaxation process. The large dielectric permittivity can be attributed to the influence of the dc conductivity and the predominance of the dc conduction in low frequency region overshadows the true behavior of the imaginary part of dielectric permittivity. The contribution of dc conduction and ac conduction has also been studied. A polaron theory indicates that the dielectric relaxation of the indium doped cadmium zinc telluride crystal at high temperature is associated with the hopping localized cadmium vacancies and telluride antisites defects. The hopping energy increases from 1.204 eV at 499 K to 1.267 eV at 534 K monotonically, which is close to the thermal activation energy 1.541 eV and dc conductivity activation energy 1.239 eV.

  1. Room temperature dielectric and magnetic properties of Gd and Ti co-doped BiFeO{sub 3} ceramics

    SciTech Connect

    Basith, M. A. E-mail: arima@yz.yamagata-u.ac.jp; Kurni, O.; Alam, M. S.; Sinha, B. L.; Ahmmad, Bashir E-mail: arima@yz.yamagata-u.ac.jp

    2014-01-14

    Room temperature dielectric and magnetic properties of BiFeO{sub 3} samples, co-doped with magnetic Gd and non-magnetic Ti in place of Bi and Fe, respectively, were reported. The nominal compositions of Bi{sub 0.9}Gd{sub 0.1}Fe{sub 1–x}Ti{sub x}O{sub 3} (x = 0.00-0.25) ceramics were synthesized by conventional solid state reaction technique. X-ray diffraction patterns revealed that the substitution of Fe by Ti induces a phase transition from rhombohedral to orthorhombic at x > 0.20. Morphological studies demonstrated that the average grain size was reduced from ?1.5??m to ?200?nm with the increase in Ti content. Due to Ti substitution, the dielectric constant was stable over a wide range of high frequencies (30 kHz to 20 MHz) by suppressing the dispersion at low frequencies. The dielectric properties of the compounds are associated with their improved morphologies and reduced leakage current densities probably due to the lower concentration of oxygen vacancies in the compositions. Magnetic properties of Bi{sub 0.9}Gd{sub 0.1}Fe{sub 1–x}Ti{sub x}O{sub 3} (x?=?0.00-0.25) ceramics measured at room temperature were enhanced with Ti substitution up to 20% compared to that of pure BiFeO{sub 3} and Ti undoped Bi{sub 0.9}Gd{sub 0.1}FeO{sub 3} samples. The enhanced magnetic properties might be attributed to the substitution induced suppression of spiral spin structure of BiFeO{sub 3}. An asymmetric shifts both in the field and magnetization axes of magnetization versus magnetic field curves was observed. This indicates the presence of exchange bias effect in these compounds notably at room temperature.

  2. Relation between the microscopic dielectric properties of Si wires and the experimental permittivity of porous Si.

    NASA Astrophysics Data System (ADS)

    Lugo, J. E.; Rubo, Yuri G.; Tagüeña-Martínez, J.; del Río, J. A.

    1998-03-01

    We present experimental data on the absorption and refraction coefficients of porous Si samples. The effective experimental transverse dielectric function, derived from these data, is analyzed in the framework of the theory of permittivity of binary composite systems ( B.R.Djordjevi?, J.Hetherington, M.F.Thorpe, Phys.Rev.B 53), 14862 (1996); M.Robles, J.Tagüeña-Martínez, J.A.del Río, Thin Solid Films 293, 320 (1996).. This approach allows the consideration of the dielectric response for an arbitrary concentration of circular inclusions, which are circular columns for the porous Si case. As a result, we obtain the microscopic dielectric function of the Si wires, which constitute the porous Si film. The microscopic response is characterized by the presence of sharp features at lower energies than the crystalline silicon one. We develop a simple phenomenological description of these features and analyze their behavior as a function of porosity.

  3. Effect of gamma irradiation on dielectric properties of manganese zinc nanoferrites

    SciTech Connect

    Angadi, V. Jagadeesha Rudraswamy, B.; Melagiriyappa, E.; Somashekarappa, H. M.; Nagabhushana, H.

    2014-04-24

    Naocrystalline ferrites Mn{sub 1?x}Zn{sub x}Fe{sub 2}O{sub 4} (x = 0.00, 0.25, 0.50, 0.75 and 1.00) were prepared by combustion method. The samples were characterized by XRD technique. The dielectric measurements were carried out in the frequency range 40 Hz to 100 MHz at room temperature. All the measurements were performed before and after gamma {sup 60}Co irradiation. The X-ray diffraction patterns revealed the formation of nanocrystalline and single-phase spinel structure. The lattice parameter decrease with zinc ion concentration and increased after the irradiation due to ferric ions of smaller radius converted to ferrous ions of larger radius. The dielectric behavior is attributed to the Maxwell-Wagner type interfacial polarization. The dielctric contant, dielectric loss and AC conductivity enhanced after the irradiation.

  4. Dielectric properties of SrTiO3-DyScO3 solid solutions

    NASA Astrophysics Data System (ADS)

    Smirnova, E. P.; Sotnikov, A. V.; Zaitseva, N. V.; Schmidt, H.; Weihnacht, M.

    2015-11-01

    The permittivity spectra of solid solutions (1- x)SrTiO3- xDyScO3 ( x = 0, 0.01, 0.03) and ceramic samples of strontium titanate doped with Sc3+ ions have been studied in the frequency range from 10 Hz to 1MHz. It has been found that the permittivity exhibits maxima at cryogenic temperatures, and the dielectric relaxation processes are observed in the temperature ranges of 60-100 and 170-300 K. The characteristic parameters of these processes have been determined. It has been shown that a linear dependence of the polarization on an applied electric field, which is characteristic of conventional dielectrics, is observed in the studied compositions in the temperature range of the dielectric anomalies.

  5. Impact of thermal stress on the piezoelectric and dielectric properties of PbTiO{sub 3} thick films on various substrates

    SciTech Connect

    Bai, Gang; Liu, Zhiguo; Yan, Xiaobing; Zhang, Changchun

    2014-08-07

    The impact of thermal stress on the polarization, as well as dielectric and piezoelectric properties of (001) oriented PbTiO{sub 3} (PTO) thick films deposited on various substrates was investigated based on Landau-Devonshire thermodynamic model. The results showed that dielectric and piezoelectric properties of PTO films depend strongly on the thermal stress in PTO films decided by the deposition temperature T{sub G} and the thermal expansion coefficients' difference between PTO films and substrates. For IC-compatible substrates such as Si, c-sapphire, and a-sapphire that induce tensile in-plane thermal stresses, the dielectric and piezoelectric responses and tunabilities of PTO films were enhanced. Whereas for PTO films on MgO, compressive thermal in-plane stresses can degraded the dielectric and piezoelectric responses and tunabilities of the films.

  6. Properties of Coarse-Grained Polymer Models: Statics, Dynamics, and Crystallinity

    NASA Astrophysics Data System (ADS)

    Grest, Gary; Salerno, K. Michael; Agrawal, Anupriya; Perahia, Dvora

    2015-03-01

    To capture large length and time scales, coarse-grained (CG) models that combine multiple atoms into one bead have been developed to model polymer melts. In the process microscopic detail is discarded in exchange for computational efficiency. However it is not well-understood how the scale of coarse-graining affects the polymer structure and dynamics. We compare results of atomistic simulations with CG models in which each CG bead represents three, four, or six methylene groups for C96H194, C480H962,andC960H1922. The CG potential is developed at 500K by iterative Boltzmann inversion. While static properties such as end-to-end distance and radius of gyration are captured by all CG models, the entanglement length deviates from experimental results with increased CG scale. The mean squared displacement of CG models is used to determine scale factors between the atomistic and CG models. During cooling to low temperature, the three and four-carbon models form a semi-crystalline structure while the six-carbon model and a four-carbon model based on the MARTINI force field remain amorphous at all temperatures. These findings show that the level of coarse-graining and CG interactions can strongly affect model temperature transferability. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's NNSA under Contract DE-AC04-94AL85000.

  7. Structural and dielectric properties of the lutetium (Lu) and yttrium (Y) doped nickel ferrite

    SciTech Connect

    Ugendar, Kodam Markandeyulu, G.

    2014-04-24

    The structural and dielectric characteristics of NiFe{sub 1.925}R{sub 0.075}O{sub 4} (R=Lu,Y) were investigated. The material crystallize in the cubic inverse spinel phase with a very small amount of RFeO{sub 3} (R=Lu,Y) as the additional phase. Frequency variation of the dielectric constant shows the dispersion that can be modeled with a modified Debye's function, which considers the possibility of more than one ion, contributing to the relaxation. Impedance spectroscopic analysis indicates the different relaxation mechanisms, bulk grain and grain-boundary contributions to the electrical conductivity and capacitance of these materials.

  8. Effect of Electric Field on Dielectric and Acoustic Properties of Triglycine Sulphate Crystal

    NASA Astrophysics Data System (ADS)

    Upadhyay, Trilok Chandra; Nautiyal, Ashish

    2011-11-01

    An extended two sublattice pseudospin lattice coupled mode model by adding third and fourth order phonon an harmonic interaction terms as well as external electric field term is considered for (CH2NH2COOH)3 H2SO4 crystal. With the help of double-time temperature dependent green's function method expression for shift width, soft mode frequency, dielectric constant loss tangent and Acoustic attenuation are derived. By fitting model values in the theoretical expressions. Temperature and electric field dependence of soft mode frequency, dielectric constant and loss tangent are calculated. The theoretical result compare well with experimental results of Bye et al [ferroelectrics, 4(1972)253].

  9. Theoretical study of ferroelectrics and dielectrics properties of novel pyroelectricc material triglycine sulphate crystal

    NASA Astrophysics Data System (ADS)

    Upadhyay, Trilok Chandra; Sharma, Sandeep

    2011-11-01

    An extended two sublattice pseudospin lattice coupled mode model of Chaudhuri et al [Phys.Rev.338 (1988) 689] by adding third and fourth-order phonon anharmonic interactions terms is considered for triglycine sulphate (CH2NH2COOH)3H2SO4 crystal and its isomorphs. With the help of double-time temperature dependent Green's function method, expressions for shift,width, soft mode frequency, dielectric constant and loss tangent are derived. By fitting model values in the theoritical expressions, temperature dependence of soft mode frequency, dielectric constant and loss tangent are calculated. The theoretical results compare well with experimental results of Aravazhi et al [Ferroelectrics200 (1997) 279.

  10. Dielectric and magnetic properties of low-temperature fired NiCuZn-BaTiO 3 composites

    NASA Astrophysics Data System (ADS)

    Su, Hua; Zhang, Huaiwu; Tang, Xiaoli; Jing, Yulan; Zhong, Zhiyong

    2009-09-01

    The composition effects on the dielectric and magnetic properties of NiCuZn-BaTiO 3 composites fired at low temperature were investigated. The coexistence of perovskite BaTiO 3 and spinel ferrite phases in the composites were observed; no significant chemical reactions occurred between BaTiO 3 and NiCuZn ceramics during sintering. The nanosized BaTiO 3 powders favored a decrease in grain size. The saturation magnetization, remanent magnetization and real permeability continuously decreased with increasing BaTiO 3 content. And the real permittivity continuously increased with the BaTiO 3 content. The Q-factor (quality factor) exhibited relatively high values with 20-30 wt% BaTiO 3. All composite materials exhibited a low dielectric loss below 100 MHz. Synthetically considerations, the composites with 20-30 wt% BaTiO 3 could obtain relatively high real permeability and real permittivity values, and the magnetic and dielectric losses were relatively low, so they were the best candidates to produce LC-integrated chip elements.

  11. Dielectric Properties of Percolative Pr1-xCaxMnO3/Polyvinylidene fluoride nanocomposites under various processing conditions

    NASA Astrophysics Data System (ADS)

    Chandrasekhar, K. Devi; Das, A. K.; Venimadhv, A.

    2010-10-01

    Single phase Pr1-xCaxMnO3(x = 0.4 and 0.5) (PCMO) nanoparticles were prepared by sol-gel method and these powders were dispersed in the polyvinylidene fluoride (PVDF) matrix in two different methods to make PCMO/PVDF nanocomposites. In method-A, PCMO (x = 0.4) nanopowder was mixed with PVDF in methanol and the pellets were annealed at higher temperature. In method-B, PCMO nanoparticles (x = 0.5) were dispersed in PVDF using N, N-dimethylformamide (DMF) followed by tape casting and hot moulding. Dielectric behaviour of Pr1-xCaxMnO3/polyvinylidene fluoride nanocomposites was investigated by varying the filler volume fraction. The percolation thresholds of the composites were found to be ˜0.1 in both the methods. A large effective dielectric permittivity was observed for composites prepared through method-A. The percolation behaviour has been understood using percolation theory and the enhanced dielectric properties have been explained by using boundary layer capacitance effect.

  12. Correlations between the structure and dielectric properties of Pb,,Sc23W13...O3 Pb,,TiZr...O3 relaxors

    E-print Network

    Rappe, Andrew M.

    Correlations between the structure and dielectric properties of Pb,,Sc2Õ3W1Õ3...O3 ­Pb,,TiÕZr...O3 dielectric responses. Even though PT has a much higher Curie temperature (490 °C) than PZ (230 °C), addition functional theory DFT calculations. For x 0.25 the B cations form a 1:1 ordered doubled perovskite structure

  13. Improved Dielectric Properties of Heterostructured Ba2.5Sr0.5TiO3 Thin Film Composites for Microwave Dielectric Devices

    NASA Technical Reports Server (NTRS)

    Jain, M.; Majumder, S. B.; Katiyar, R. S.; Bhalla, A. S.; Agrawal, D. C.; Kulkarni, V. N.; VanKeuls, F. W.; Miranda, F. A.; Romanofsky, R. R.; Mueller, C. H.; Fernandez, F.

    2002-01-01

    In the present work we have deposited MgO and Ba(sub 0.5)Sr(sub 0.5)TiO(sub 3)(BST50) thin layers in different sequences to make MgO:BST50 hetero-structured thin films. These films were characterized by X-ray diffraction and Rutherford backscattering technique and found to be highly (100) textured. The figure of merit {(C(sub0)-C(sub v)/(C(sub0-tandelta)} of the hetero-structured films was found to be higher as compared to pure BST50 films measured at 1 MHz frequency with electric field of 25.3 kV/cm. These films were used to make eight element coupled micro-strip phase shifter and characterized in a frequency range of 13-15 GHz. The high frequency figure of merit (kappa factor, defined as the ratio of degree of phase shift per dB loss) measured at around 14 GHz with electric field of 333 kV/cm has been markedly improved (around 64.28 deg/dB for hetero-structured film as compared to 24.65 deg /dB for pure film). Improvement in dielectric properties in a wide frequency range in the MgO:BST are believed to be due to the higher densification of the hetero-structured films.

  14. Effect of nanoclay reinforcement on the X-band dielectric properties of epoxy resins for use in radome applications

    NASA Astrophysics Data System (ADS)

    Garcia, Carla; Fittipaldi, Mauro; Grace, Landon R.

    2015-05-01

    The suitability of nanoclay reinforcement for improvement of structural and electrical properties of thermosetting epoxy systems at 10 GHz is investigated via a resonant technique. The potential of nanoclay reinforcement to improve mechanical properties and mitigate moisture diffusion in polymer materials has been well-documented in recent years. Further, evidence has shown that the presence of moisture in polymer systems has a profoundly deleterious effect on relative permittivity and loss tangent of the material. This is particularly important for construction or coating of radar protecting structures (radome), in which low relative permittivity and loss tangent are critical to radar transparency. Therefore, the addition of nanoclay reinforcement to polymer composites used in radome applications may prove a viable method for dielectric and structural performance improvement and moisture absorption minimization. The relative permittivity and loss tangent of two epoxy resin systems are evaluated as a function of organoclay weight percentage using a split-post dielectric resonator operating at an X-band frequency. Nanoclay content up to 5% by weight is investigated for both systems. The addition of nanoclay did not have a significant effect on the relative permittivity of the material, contributing only up to a 1% decrease (improvement) compared to the neat epoxy. The material loss tangent, however, exhibited a consistent downward trend, with a nearly 13% decrease recorded for the nanoclay content of 5% by weight in the most extreme case. Based on these results, the addition of nanoclay to polymer composite materials used in radome applications has no detrimental effect on the dielectric properties of the material, and as such may prove to be a viable option for improving radome performance and longevity.

  15. Complex dielectric properties of organic-rich mudrocks as functions of maturity

    E-print Network

    Rezwanur Rahman; John A. Scales; Manika Prasad

    2015-07-27

    Complex dielectric variations can address neatly the maturity of organic-rich mudrocks. We, therefore, apply an open hemispherical cavity resonator to measure complex dielectric permitivitties of five thin sections of oil (bakken) shales (with different maturity) of $\\sim$ 30 $\\mu$m thickness on glass-substrates around 2.15 mm thick in 100 - 165 GHz. The real part of complex dielectric permittivity ($\\epsilon_{re}$) are constant but show significant differences in magnitude based on maturity: (1) lowest, $\\sim$ 1.9, for immature or early maturation stage, (2) higher than the immature one, $\\sim$ 3.0 (also bundled up together), for three oil-matured stages, and (3) highest, $\\sim$ 4.9, for late or overmatured stage. The conductivity ($\\sigma_{re}$) from imaginary part of the complex dielectric constant ($\\epsilon_{im}$) emphasizes two important features of conductivity of oil shales: (1) frequency dispersion, and (2) maturity-dependence. We obtain increases of $\\sigma_{re}$ with maturity and frequency.

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

    E-print Network

    Sottos, Nancy R.

    orientation were measured by a laser Doppler heterodyne interferometer. The weak-field dielectric constants Ferroelectric ceramics have been employed extensively in a variety of sensors and actuators including strain gauges, pressure transducers, and accelerometers. Bulk ferroelectric ceramic sensors have certain

  17. Multisection transmission line scatter function theory for measurements of soil dielectric properties

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Vector network analyzers measure both reflection (S11) and transmission (S21) functions, but S21 has not been used to estimate soil dielectric permittivity independently. The objectives of this study were to: (1) derive the mathematical model for S21 of a multisection transmission line, and (2) tes...

  18. The dielectric properties of soil-water mixtures at microwave frequencies

    NASA Technical Reports Server (NTRS)

    Wang, J. R.

    1979-01-01

    Recent measurements on the dielectric constants of soil-water mixtures show the existence of two frequency regions in which the dielectric behavior of these mixtures was quite different. At the frequencies of 1.4 GHz to 5 GHz, there were strong evidences that the variations of the dielectric (epsilon) with water content (W) depended on soil type. While the real part of epsilon for sandy soils rose rapidly with the increase in W, epsilon for the high-clay content soils rose only slowly with W. As a consequence, epsilon was generally higher for the sandy soils than for the high-clay content soils at a given W. On the other hand, most of the measurements at frequencies 1 GHz indicated the increase of epsilon with W independent of soil types. At a given W, epsilon' (sandy soil) approximately equals epsilon (high-clay content soil) within the precision of the measurements. These observational features can be satisfactorily interpreted in terms of a simple dielectric relaxation model, with an appropriate choice of the mean relaxation frequency f(m) and the range of the activation energy (beta). It was found that smaller f(m) and larger beta were required for the high-clay content soils than the sandy soils in order to be consistent with the measured data.

  19. Effect of gamma irradiation on opto-structural, dielectric, and thermoluminescence properties of natural phlogopite mica

    SciTech Connect

    Kaur, Sukhnandan; Singh, Surinder; Singh, Lakhwant; Lochab, S. P.

    2013-09-07

    Gamma ray induced modifications in natural phlogopite mica have been studied in the dose range of 1–2000 kGy. These modifications were monitored using different techniques viz: ultraviolet-visible spectroscopy, Fourier Transform Infrared spectroscopy, dielectric measurements, X-ray diffraction, and thermoluminescence dosimeter. The analysis of the results reveals that the dose of 100 kGy produces significant change in the natural phlogopite mica as compared to pristine and other exposed samples. Ultraviolet-visible analysis provides the value of optical indirect, direct band gap, and Urbach energy. Cody model was used to calculate structural disorder from Urbach energy. Different dielectric parameters such as dielectric constant, dielectric loss, ac conductivity, and real and imaginary parts of electric modulus were calculated for pristine and irradiated samples at room temperature. Williamson Hall analysis was employed to calculate crystallite size and micro-strain of pristine and irradiated sheets. No appreciable changes in characteristic bands were observed after irradiation, indicating that natural phlogopite mica is chemically stable. The natural phlogopite mica may be recommended as a thermoluminescent dosimeter for gamma dose within 1 kGy–300 kGy.

  20. Dielectric properties of fully hydrated nucleotides in the terahertz frequency range

    NASA Astrophysics Data System (ADS)

    Glancy, P.; Beyermann, W. P.

    2010-06-01

    We use terahertz time domain spectroscopy (THz-TDS) to determine the complex frequency-dependent dielectric response of all four nucleotides at different dilute concentrations. In addition, the suspension model's ability to extract the dielectric response of just the nucleotide with the hydration shell ?b excluding the dielectric information relating to the bulk will be verified. The suspension model enables us to make the determination that the nucleotides have influences on the water molecules out to the fourth hydration shell. We use a two Debye relaxation fit model for water, all concentrations and all ?b values. We observed how the nucleotides affect the relaxation parameters in relation to that of pure bulk water. With this information, we notice a transition between purines and pyrimidines, where one is a hydrogen-bond network structure building type material with a low concentration increment and the other is a structure breaking type material with a low concentration decrement. Due to conductivity measurements, we determine that kinetic depolarization is a negligible affect compared to that of dielectric saturation, which we find to dominate where a decrement is found.

  1. Growth, mechanical, thermal and dielectric properties of pure and doped KHP single crystal

    NASA Astrophysics Data System (ADS)

    M, Lakshmipriya.; Babu, D. Rajan; Vizhi, R. Ezhil

    2015-06-01

    L-Arginine doped potassium hydrogen phthalate and L-Histidine doped potassium hydrogen phthalate single crystals were grown by slow evaporation method at room temperature. The grown crystal crystallizes in orthorhombic system which is confirmed by single crystal XRD analysis. The grown crystals are subjected to thermal, mechanical and dielectric analysis.

  2. Effect of Neodymium on Optical Bandgap and Microwave Dielectric Properties of Barium Zirconate Ceramic

    NASA Astrophysics Data System (ADS)

    Parida, Sabyasachi; Satapathy, A.; Sinha, E.; Bisen, Anurag; Rout, S. K.

    2015-03-01

    The ceramics with general formula Ba(1- x) Nd(2 x/3)ZrO3 ( x = 0.0,0.02, 0.04, 0.06, 0.08, and 0.1) were prepared by solid-state reaction. The phase formation of the powders was analyzed by means of X-ray diffraction (XRD), Fourier transform-Raman (FT-Raman), and Fourier transform infrared (FTIR) spectroscopy. XRD patterns revealed that all powders show a perovskite-type cubic structure with space group Pm-3 m. FT-Raman and FTIR spectra suggested the formation of higher degree of symmetry in the crystal. The optical bandgap was found to be decreasing while Urbach energy was found to be increasing with an increase of Nd3+ content. The surface morphology of sintered pellets was studied by scanning electron microscope. Microwave dielectric constant and quality factor were investigated by the TE01 ? mode dielectric resonator method. The microwave dielectric constant and temperature coefficient of resonant frequency decreases with increase in of Nd3+ content. The irregular nature of quality factor ( Q × f) was observed due to the extrinsic losses in materials. The dielectric resonator antenna (DRA) characteristics were investigated experimentally and numerically using a monopole antenna through an infinite ground plane and Ansoft's high-frequency structure simulator software, respectively. The resonant frequency and bandwidth of DRAs were also investigated for the ceramics.

  3. Nonlinear dielectric properties of planar structures based on ferroelectric betaine phosphite films

    NASA Astrophysics Data System (ADS)

    Balashova, E. V.; Krichevtsov, B. B.; Svinarev, F. B.; Yurko, E. I.

    2014-02-01

    Ferroelectric films of partly deuterated betaine phosphite are grown on NdGaO3(001) substrates with an interdigitated system of electrodes on their surfaces by evaporation at room temperature. These films have a high capacitance in the ferroelectric phase transition range. The dielectric nonlinearity of the grown structures is studied in small-signal and strong-signal response modes and in the intermediate region between these two modes by measuring the capacitance in a dc bias field, dielectric hysteresis loops, and the Fourier spectra of an output signal in the Sawyer-Tower circuit. In the phase transition range, the capacitance control ratio at a bias voltage U bias = 40 V is K ? 7. The dielectric nonlinearity of the structures in the paraelectric phase is described by the Landau theory of second-order phase transitions. The additional contribution to the nonlinearity in the ferroelectric phase is related to the motion of domain walls and manifests itself when the input signal amplitude is higher than U st ˜ 0.7-1.0 V. The relaxation times of domain walls are determined from an analysis of the frequency dependences of the dielectric hysteresis.

  4. Dielectric properties and Raman spectra of ZnO from a first principles finite-differences/finite-fields approach.

    PubMed

    Calzolari, Arrigo; Nardelli, Marco Buongiorno

    2013-01-01

    Using first principles calculations based on density functional theory and a coupled finite-fields/finite-differences approach, we study the dielectric properties, phonon dispersions and Raman spectra of ZnO, a material whose internal polarization fields require special treatment to correctly reproduce the ground state electronic structure and the coupling with external fields. Our results are in excellent agreement with existing experimental measurements and provide an essential reference for the characterization of crystallinity, composition, piezo- and thermo-electricity of the plethora of ZnO-derived nanostructured materials used in optoelectronics and sensor devices. PMID:24141391

  5. High-temperature dielectric properties of incipient ferroelectric Gd0.5Na0.5TiO3

    NASA Astrophysics Data System (ADS)

    Wang, Chunchang; Wang, Jing; Sun, Xiaohong; Li, Qiuju; Zhang, Jian; Zheng, Jun; Cheng, Chao

    2014-10-01

    Gd0.5Na0.5TiO3 ceramic samples were prepared by the solid-state reaction method. Incipient ferroelectricity was confirmed in the sample. Dielectric properties were investigated at temperatures from room temperature to 1073 K and the frequency range of 20 Hz-10 MHz. By means of electric modulus and impedance analysis, the sample was found to show two thermally activated relaxations with the high-frequency (low-temperature) one being the relaxation caused by hopping motion of oxygen vacancies and the low-frequency (high-temperature) one being the interfacial relaxation.

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

    NASA Astrophysics Data System (ADS)

    Cole, M. W.; Ngo, E.; Hubbard, C.; Hirsch, S. G.; Ivill, M.; Sarney, W. L.; Zhang, J.; Alpay, S. P.

    2013-10-01

    In order to enhance the permittivity and tunability of the dielectric component, a thin film dielectric composite consisting of a radio frequency sputtered SrTiO3 (STO) buffer layer and metalorganic solution deposited Mg-doped BaxSr1-xTiO3 (Mg-BST) thin film overgrowth was developed using affordable industry standard processes and materials. The effect of the STO buffer layer thickness on the dielectric response of the heterostructure was investigated. Our results demonstrate that the composite film heterostructure, evaluated in the metal-insulator-metal configuration Pt/STO/Mg-BST/Pt on sapphire substrate, with the thinner (9-17 nm) STO buffer layers possessed enhanced permittivity (?r ˜ 491) with respect to the thicker 41 nm buffer layer (?r ˜ 360) and that of a control Mg-BST film without a STO buffer layer (?r ˜ 380). Additionally, the composite film with the thinner buffer layers were shown to have low losses (tan ? ˜ 0.02), low leakage characteristics (J = 7.0 × 10-9 A/cm2), high breakdown voltage (VBR > 10 V), a large grain microstructure (˜125 nm), and smooth pin-hole free surfaces. The enhanced permittivity of the composite dielectric film resulted from three major factors: (i) the template-effect of the thin STO buffer layer on the thicker Mg-BST over-layer film to achieve a large grain microstructure, (ii) the low viscosity of the metallo-organic solution deposition (MOSD) solution, which ensured heterogeneous nucleation of the Mg-BST overgrowth film on the surface of the STO buffer layer, and (iii) minimization of the low permittivity grain boundary phase (TiO2-x phase). The dielectric response of the BST can be explained using a thermodynamic model taking into account interlayer electrostatic and electromechanical interactions. Additionally, Mg doping of the BST enabled low loss and low leakage characteristics of the heterostructure. The large permittivity, low loss, low leakage characteristics, and defect free surfaces of the composite dielectric heterostructure promote tunable device miniaturization and hold the potential to enable enhanced electromagnetic coupling in ferromagnetic/high permittivity dielectric heterostructures, which in turn would facilitate the realization of integrated charge mediated voltage controlled magnetic radio frequency/microwave communication devices.

  7. Dielectric and phonon properties of the multiferroic ferrimagnet Cu{sub 2}OSeO{sub 3}

    SciTech Connect

    Apostolova, I. N.

    2014-02-14

    We propose a microscopic model in order to study the multiferroic properties of Cu{sub 2}OSeO{sub 3} taking into account the ferrimagnetic interaction, frustration, linear magnetoelectric (ME) coupling, and anharmonic spin-phonon interaction. We have shown that the dielectric constant and the phonon energy and damping have a kink near the magnetic phase transition T{sub C}?=?58?K which disappears with increasing of an external magnetic field. This behavior is an evidence for a strong ME coupling and in qualitative agreement with the experimental data.

  8. Effect of H + ion implantation on structural, morphological, optical and dielectric properties of L-arginine monohydrochloride monohydrate single crystals

    NASA Astrophysics Data System (ADS)

    Sangeetha, K.; Babu, R. Ramesh; Kumar, P.; Bhagvannarayana, G.; Ramamurthi, K.

    2011-06-01

    L-arginine monohydrochloride monohydrate (LAHCl) single crystals have been implanted with 100 keV H + ions at different ion fluence ranging from 10 12 to 10 15 ions/cm 2. Implanted LAHCl single crystals have been investigated for property changes. Crystal surface and crystalline perfection of the pristine and implanted crystals were analyzed by atomic force microscope and high-resolution X-ray diffraction studies, respectively. Optical absorption bands induced by colour centers, refractive index and birefringence, mechanical stability and dielectric constant of implanted crystals were studied at different ion fluence and compared with that of pristine LAHCl single crystal.

  9. CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Electrical, dielectric and surface wetting properties of multi-walled carbon nanotubes/nylon-6 nanocomposites

    NASA Astrophysics Data System (ADS)

    Long, Yun-Ze; Li, Meng-Meng; Sui, Wan-Mei; Kong, Qing-Shan; Zhang, Lei

    2009-03-01

    This paper reports that the multi-walled carbon nanotubes (MWCNT)/nylon-6 (PA6) nanocomposites with different MWCNT loadings have been prepared by a simple melt-compounding method. The electrical, dielectric, and surface wetting properties of the CNT/PA6 composites have been studied. The temperature dependence of the conductivity of the CNT/PA6 composite with 10.0 wt% CNT loading (?RT ~ 10-4 S/cm) are measured, and afterwards a charge-energy-limited tunnelling model (ln ?(T) ~ T-1/2) is found. With increasing CNT weight percentage from 0.0 to 10.0 wt%, the dielectric constant of the CNT/PA6 composites enhances and the dielectric loss tangent increases two orders of magnitude. In addition, water contact angles of the CNT/PA6 composites increase and the composites with CNT loading larger than 2.0 wt% even become hydrophobic. The obtained results indicate that the electrical and surface properties of the composites have been significantly enhanced by the embedded carbon nanotubes.

  10. Modelling changes in the dielectric and scattering properties of young snow-covered sea ice at GHz frequencies

    NASA Technical Reports Server (NTRS)

    Drinkwater, Mark R.; Crocker, G. B.

    1988-01-01

    Observations of the physical properties of the snow cover and underlying young fast ice in Resolute Passage, Canada, were made during the winter of 1982. Detailed measurements of snow density and ice and snow temperatures, salinities, and brine volumes were made over a period of 46 d, beginning when the ice was 0.4 m thick and about 9 d old. The recorded values are used in a theoretical mixture model to predict the dielectric properties of the snow cover over the microwave frequency range. The results of this analysis are then used to investigate the effects of the snow properties on the radar backscatter signatures of young sea ice. The results show that backscatter is a function of the incidence angle and can change significantly over short periods of time during the early evolutionary phase of ice and snow-cover development. This has important consequences for the identification of young ice forms from SAR or SLAR images.

  11. Static and fatigue tensile properties of cross-ply laminates containing vascules for self-healing applications

    NASA Astrophysics Data System (ADS)

    Luterbacher, R.; Trask, R. S.; Bond, I. P.

    2016-01-01

    The effect of including hollow channels (vascules) within cross-ply laminates on static tensile properties and fatigue performance is investigated. No change in mechanical properties or damage formation is observed when a single vascule is included in the 0/90 interface, representing 0.5% of the cross sectional area within the specimen. During tensile loading, matrix cracks develop in the 90° layers leading to a reduction of stiffness and strength (defined as the loss of linearity) and a healing agent is injected through the vascules in order to heal them and mitigate the caused degradation. Two different healing agents, a commercial low viscosity epoxy resin (RT151, Resintech) and a toughened epoxy blend (bespoke, in-house formulation) have been used to successfully recover stiffness under static loading conditions. The RT151 system recovered 75% of the initial failure strength, whereas the toughened epoxy blend achieved a recovery of 67%. Under fatigue conditions, post healing, a rapid decay of stiffness was observed as the healed damage re-opened within the first 2500 cycles. This was caused by the high fatigue loading intensity, which was near the static failure strength of the healing resin. However, the potential for ameliorating (via self-healing or autonomous repair) more diffuse transverse matrix damage via a vascular network has been shown.

  12. Assessment of interatomic potentials for atomistic analysis of static and dynamic properties of screw dislocations in W

    NASA Astrophysics Data System (ADS)

    Cereceda, D.; Stukowski, A.; Gilbert, M. R.; Queyreau, S.; Ventelon, Lisa; Marinica, M.-C.; Perlado, J. M.; Marian, J.

    2013-02-01

    Screw dislocations in bcc metals display non-planar cores at zero temperature which result in high lattice friction and thermally-activated strain rate behavior. In bcc W, electronic structure molecular statics calculations reveal a compact, non-degenerate core with an associated Peierls stress between 1.7 and 2.8 GPa. However, a full picture of the dynamic behavior of dislocations can only be gained by using more efficient atomistic simulations based on semiempirical interatomic potentials. In this paper we assess the suitability of five different potentials in terms of static properties relevant to screw dislocations in pure W. Moreover, we perform molecular dynamics simulations of stress-assisted glide using all five potentials to study the dynamic behavior of screw dislocations under shear stress. Dislocations are seen to display thermally-activated motion in most of the applied stress range, with a gradual transition to a viscous damping regime at high stresses. We find that one potential predicts a core transformation from compact to dissociated at finite temperature that affects the energetics of kink-pair production and impacts the mechanism of motion. We conclude that a modified embedded-atom potential achieves the best compromise in terms of static and dynamic screw dislocation properties, although at an expense of about ten-fold compared to central potentials.

  13. A Study of the Dielectric Properties of Al2O3-TiO2 Composite in the Microwave and RF Regions

    NASA Astrophysics Data System (ADS)

    Campos, R. V. B.; Bezerra, C. L.; Oliveira, L. N. L.; Gouveia, D. X.; Silva, M. A. S.; Sombra, A. S. B.

    2015-11-01

    We have studied the effect of addition of titania, as a sintering agent, to alumina on the dielectric characteristics of the ceramic composites obtained. The dielectric properties of the titania-alumina composites were studied by use of impedance spectroscopy and the Hakki-Coleman method in the radio-frequency and microwave regions, respectively. The temperature coefficient of the resonant frequency ( ? f ) was also studied. Dielectric permittivity ( ?') was increased and the dielectric loss (tan ?) was improved by addition of titania, as a result of better sintering; addition of 10 wt.% titania resulted in ?' = 12.68 and tan ? = 8.23 × 10-4 in the microwave region. Increasing the concentration of TiO2 led to inversion of the ? f signal; values were positive when the concentration of TiO2 was >7.5 wt.%. The ceramic composites were evaluated as antennas; for all samples the return loss ( S 11) was <-10 dB and the gain was approximately 3 dBi. Addition of 7.5 wt.% titania to the Al2O3 improved antenna performance. In conclusion, addition of the TiO2 to alumina improves its dielectric properties, resulting in the possibility of use of such composites as dielectric resonator antennas (DRA).

  14. Studies on frequency and gate voltage effects on the dielectric properties of Au/n-Si (110) structure with PVA-nickel acetate composite film interfacial layer

    NASA Astrophysics Data System (ADS)

    Tunç, T.; Gökçen, M.; Uslu, ?.

    2012-11-01

    The admittance technique was used in order to investigate the frequency dependence of dielectric constant ( ?'), dielectric loss ( ??), dielectric loss tangent (tan ?), the ac electrical conductivity ( ? ac), and the electric modulus of PVA (Ni-doped) structure. Experimental results revealed that the values of ?' , ??, (tan ?), ? ac and the electric modulus show fairly large frequency and gate bias dispersion due to the interface charges and polarization. The ? ac is found to increase with both increasing frequency and voltage. It can be concluded that the interface charges and interfacial polarization have strong influence on the dielectric properties of metal-polymer-semiconductor (MIS) structures especially at low frequencies and in depletion and accumulation regions. The results of this study indicate that the ?' values of Au/PVA/n-Si with Nickel-doped PVA interfacial layer are quite higher compared to those with pure and other dopant/mixture's of PVA.

  15. EFFECT OF MgO ON STRUCTURE AND DIELECTRIC PROPERTIES OF CaO-Al2O3-B2O3-SiO2 GLASSES

    NASA Astrophysics Data System (ADS)

    Du, Zhao; Zhang, Xuehong; Yue, Yunlong; Wu, Haitao

    2012-12-01

    The effect of MgO on structure and dielectric properties of aluminoborosilicate glasses was investigated. FTIR data indicated that glass network was mainly built by tetrahedral [SiO4], [BO4], [AlO4] and trigonal [BO3]. A small amount of AlO5 or AlO6 units also existed. The glass system was characterized with lower dielectric constant (4.17 4.6) and dielectric loss (12.3 × 10-4 14.77 × 10-4) at 1 MHz. With the increase of MgO content, the quantity of AlO5 or AlO6 units decreased. The variation of density showed a decreasing tendency. The dielectric constant and loss were all found to decrease.

  16. Low-temperature sintering of silica-boric acid-doped willemite and microwave dielectric properties

    NASA Astrophysics Data System (ADS)

    Ando, Minato; Ohsato, Hitoshi; Igimi, Daisuke; Higashida, Yutaka; Kan, Akinori; Suzuki, Sadahiko; Yasufuku, Yoshitoyo; Kagomiya, Isao

    2015-10-01

    Millimeter-wave wireless communications in a high-level information society have been expanding in terms of high-density data transfer and radar for pre-crash safety systems. For these communications, millimeter-wave dielectrics have been expected for the development of substrates with high quality factor (Qf), low dielectric constant (?r), and near-zero temperature coefficient of resonance frequency (TCf). We have been studying several silicates such as forsterite, willemite, diopside, wollastonite, and cordierite/indialite glass ceramics. In this study, the synthesis of willemite and low-temperature-sintered willemite for low temperature co-fired ceramics (LTCC) is examined. The raw materials used for preparing slurries in doctor blade tape casting are also analyzed.

  17. Structural and dielectric properties of Nd/Ca co-doped bi-ferrite multiferroics

    SciTech Connect

    Kumar, Ashwini E-mail: ashu.dhanda@gmail.com; Sharma, Poorva E-mail: ashu.dhanda@gmail.com; Varshney, Dinesh E-mail: ashu.dhanda@gmail.com

    2014-04-24

    Single-phase polycrystalline samples of Bi{sub 0.8}Nd{sub 0.2?x}Ca{sub x}FeO{sub 3} (x = 0.0, 0.1) were synthesized by chemical coprecipitation method. X-ray diffraction patterns accompanied by Rietveld-refined crystal structure parameters reveal the phase transition of Bi{sub 0.8}Nd{sub 0.1}Ca{sub 0.1}FeO{sub 3} with rhombohedral R3c symmetry to triclinic structure of Bi{sub 0.8}Nd{sub 0.2}FeO{sub 3} sample. Frequency dependence of dielectric constant (?') and dielectric loss (tan?), infers enhancement of both ?' (tan?) in narrow band gap of Nd/Ca co-doped BFO as compare to wide band pristine BFO.

  18. Density functional theory approach for calculation of dielectric properties of warm dense matter

    NASA Astrophysics Data System (ADS)

    Saitov, Ilnur

    2015-06-01

    The reflectivity of shocked xenon was measured in the experiments of Mintsev and Zaporoghets for wavelength 1064 nm. But there is no adequate theoretical explanation of these reflectivity results in the framework of the standard methods of nonideal plasma theory. The assumption of significant width to the shock front gives a good agreement with the experimental data. However, there are no evidences of this effect in the experiment. Reflectivity of shocked compressed xenon plasma is calculated in the framework of the density functional theory approach as in. Dependencies on the frequency of incident radiation and on the plasma density are analyzed. The Fresnel formula for the reflectivity is used. The longitudinal expression in the long wavelength limit is applied for the calculation of the imaginary part of the dielectric function. The real part of the dielectric function is calculated by means of the Kramers-Kronig transformation. The approach for the calculation of plasma frequency is developed.

  19. Effect of dysprosium doping on structural, dielectric and ferroelectric properties of PLZT (65/35) ceramics

    NASA Astrophysics Data System (ADS)

    Kaur, Manpreet; Sharma, Nandini; Uniyal, Poonam

    2013-06-01

    Dy modified polycrystalline PLZT (65/35) i.e. Pb0.92-xLa0.08Dyx(Zr0.65Ti0.35)1-x/4O3 materials were synthesized by solid state reaction technique. X-ray pattern of compounds confirmed the formation of single rhombohedral phase. Detailed dielectric studies of the compounds as a function of temperature shows that broadening of permittivity peak and transition temperature depends on Dy3+ ions concentration. Analysis of Diffuseness (?) of the broadened dielectric peaks of materials gave its value between 1 & 2, indicating the different degree of substitutional disorder in the system. The transition temperature (Tc) was found to shift towards lower temperature by 40°C with Dy concentration. The P-E loop measurement at room temperature confirms the ferroelectric behavior.

  20. Measurement of Dielectric Properties and Microwave-Assisted Homogeneous Acid-Catalyzed Transesterification in a Monomode Reactor.

    PubMed

    Dall'Oglio, Evandro L; de Sousa, Paulo T; Campos, Deibnasser C; de Vasconcelos, Leonardo Gomes; da Silva, Alan Cândido; Ribeiro, Fabilene; Rodrigues, Vaniomar; Kuhnen, Carlos Alberto

    2015-08-27

    Microwave heating technology is dependent on the dielectric properties of the materials being processed. The dielectric properties of H2SO4, H3PO4, ClSO3H, and H3CSO3H were investigated in this study using a vector network analyzer in an open-ended coaxial probe method at various temperatures. Phosphoric and sulfuric acids presented higher loss tangents in the frequency range 0.3-13 GHz, reflecting greater mobility of the ions and counterions. The acids were employed as catalysts in microwave-assisted homogeneous transesterification reactions for the production of methylic and ethylic biodiesel. The effects of catalyst concentration, alcohol to oil molar ratio, and irradiation time on biodiesel conversions were investigated. The results showed a significant reduction in the reaction time for microwave-assisted transesterification reactions as compared to times for conventional heating. Also, despite its higher loss tangent, it was observed that H3PO4 leads to lower conversion to biodiesel, which can be explained by its lower carbonyl protonation capacity. PMID:26244612

  1. Crystallization kinetics and dielectric properties in sol-gel derived (Pb,La)(Zr,Sn,Ti)O3 ceramics

    NASA Astrophysics Data System (ADS)

    Zhai, Jiwei; Chen, Haydn

    2003-07-01

    Sol-gel derived (Pb,La)(Zr,Sn,Ti)O3 powders and sintered ceramics were prepared; their crystallization kinetics and dielectric properties were studied as a function of temperature. X-ray powder diffraction showed that the pyrochlore phase formed initially from an amorphous gel during low-temperature heat treatment around 200-300 °C. Further heat treatment to 600 °C resulted in the development of the perovskite phase with no significant growth of pyrochlore crystallites. At intermediate temperatures the sol-gel derived powders yielded a mixture of pyrochlore and perovskite phases. The crystallization kinetics of the perovskite phase was analyzed following the Avrami approach, which indicated that the process is diffusion limited. Those fine powders were utilized to prepare compact ceramics after sintering at various temperatures; their dielectric properties were analyzed. The electric field induced transformation from the antiferroelectric to the ferroelectric phase was clearly observed through the polarization reversal experiments. This material holds great promise for high energy density capacitors and microelectromechanical devices.

  2. Effects of the dielectric environment on the electron transport properties of single-layer MoS2

    NASA Astrophysics Data System (ADS)

    Bertolazzi, Simone; Allain, Adrien; Lembke, Dominik; Kis, Andras

    2014-03-01

    Two-dimensional materials, such as graphene, boron nitride and transition metal dichalcogenides, offer a wide range of electronic, optical and mechanical properties that can be advantageous for several applications in nanotechnology. Among these materials, single-layer molybdenum disulfide (MoS2) shows great potential for scaling field-effect transistor devices, due to an optimal electrostatic control of the 2D semiconducting sheet, large energy bandgap and minimal leakage currents. However, to fully exploit the potential of this atomically thin semiconductor, additional experimental efforts need to be undertaken to boost the device performance and access the theoretical intrinsic electron mobilities. To pursue this objective, it is mandatory to reduce the density of charged impurities, both in the semiconducting sheet and in its surrounding environment, and to limit carrier scattering induced by polar optical phonons in the dielectric surface. Here we present the results of our recent experimental investigation of the electron transport properties of single-layer MoS2 mechanically exfoliated/transferred onto different substrates, with varying surface chemistry, surface roughness and dielectric permittivity. We will show temperature-dependent four-terminal measurements of the electrical conductivity of single-layer MoS2 in contact with various insulating materials, including 2D sheets of hexagonal boron nitride, organic polymers and metal oxides.

  3. The influence of high dielectric constant aluminum oxide sputter deposition on the structure and properties of multilayer epitaxial graphene.

    PubMed

    Maneshian, Mohammad H; Kuo, Fang-Ling; Mahdak, Kristopher; Hwang, Junyeon; Banerjee, Rajarshi; Shepherd, Nigel D

    2011-05-20

    High dielectric constant aluminum oxide (Al(2)O(3)) is frequently used as the gate oxide in high electron mobility transistors and the impact of its deposition by radio frequency (RF) magnetron sputtering on the structural and electrical properties of multilayer epitaxial graphene (MLG) grown by graphitization of silicon carbide (SiC) is reported. Micro-Raman spectroscopy and temperature dependent Hall mobility measurements reveal that the processing induced changes to the structural and electrical properties of the MLG can be minimal when the oxide deposition conditions are optimal. High-resolution transmission electron microscopy (HRTEM) analysis confirms that the Al(2)O(3)/MLG interface is relatively sharp and that our thickness approximation of the MLG using angle resolved x-ray photoelectron spectroscopy (ARXPS) is accurate. An interface trap density of 5.1 × 10(10) eV(-1) cm(-2) was determined using capacitance-voltage techniques. The totality of our results indicates that ARXPS can be used as a nondestructive tool to measure the thickness of MLG, and that RF sputtered Al(2)O(3) can be used as a high dielectric (high-k) constant gate oxide in multilayer graphene based transistor applications. PMID:21444954

  4. The influence of high dielectric constant aluminum oxide sputter deposition on the structure and properties of multilayer epitaxial graphene

    NASA Astrophysics Data System (ADS)

    Maneshian, Mohammad H.; Kuo, Fang-Ling; Mahdak, Kristopher; Hwang, Junyeon; Banerjee, Rajarshi; Shepherd, Nigel D.

    2011-05-01

    High dielectric constant aluminum oxide (Al2O3) is frequently used as the gate oxide in high electron mobility transistors and the impact of its deposition by radio frequency (RF) magnetron sputtering on the structural and electrical properties of multilayer epitaxial graphene (MLG) grown by graphitization of silicon carbide (SiC) is reported. Micro-Raman spectroscopy and temperature dependent Hall mobility measurements reveal that the processing induced changes to the structural and electrical properties of the MLG can be minimal when the oxide deposition conditions are optimal. High-resolution transmission electron microscopy (HRTEM) analysis confirms that the Al2O3/MLG interface is relatively sharp and that our thickness approximation of the MLG using angle resolved x-ray photoelectron spectroscopy (ARXPS) is accurate. An interface trap density of 5.1 × 1010 eV - 1 cm - 2 was determined using capacitance-voltage techniques. The totality of our results indicates that ARXPS can be used as a nondestructive tool to measure the thickness of MLG, and that RF sputtered Al2O3 can be used as a high dielectric (high-k) constant gate oxide in multilayer graphene based transistor applications.

  5. Structural, optical and dielectric properties of Ce3+, Pr3+, Nd3+ doped LaF3 hexagonal nanoparticles

    NASA Astrophysics Data System (ADS)

    Gaurkhede, S. G.; Khandpekar, M. M.

    2015-06-01

    Well dispersed, elongated and hexagonal LaF3: Ce3+, Pr3+, Nd3+ nanocrystals have been synthesized by microwave assisted technique. X-ray diffraction (XRD) studies indicates the formation of nanocrystals with unit cell parameters a = b = 7.144 A0, c = 7.281 A0, (c/a = 1.019) and unit cell volume of 321.86 (A0)3 of average crystallite size 21 nm have been traced by from XRD analysis and it is close agreement with transmission electron microscope (TEM) analysis. Ultra-violet (UV) absorption spectrum shows an edge at 250 nm indicating presence of wide transparency window region between 200 nm-800 nm. Fundamental groups have been observed in the Fourier transformation infrared (FTIR) and FT-Raman spectra. The blue luminescent properties of the nanoparticles were investigated by excitation and emission spectra. Room temperature Electrical and dielectric properties were studied for the synthesized nanocrystals the values of conductivity & resistivity is found to be in the order of 10-6 Scm-1 and resistivity 105 ? cm. Low dielectric constant value was observed in the LaF3: Ce3+, Pr3+, and Nd3+ nanocrystals at high frequency indicating its suitability for electro optics applications.

  6. Geometric properties of static Einstein-Maxwell dilaton horizons with a Liouville potential

    NASA Astrophysics Data System (ADS)

    Abdolrahimi, Shohreh; Shoom, Andrey A.

    2011-05-01

    We study nondegenerate and degenerate (extremal) Killing horizons of arbitrary geometry and topology within the Einstein-Maxwell-dilaton model with a Liouville potential (the EMdL model) in d-dimensional (d?4) static space-times. Using Israel’s description of a static space-time, we construct the EMdL equations and the space-time curvature invariants: the Ricci scalar, the square of the Ricci tensor, and the Kretschmann scalar. Assuming that space-time metric functions and the model fields are real analytic functions in the vicinity of a space-time horizon, we study the behavior of the space-time metric and the fields near the horizon and derive relations between the space-time curvature invariants calculated on the horizon and geometric invariants of the horizon surface. The derived relations generalize similar relations known for horizons of static four- and five-dimensional vacuum and four-dimensional electrovacuum space-times. Our analysis shows that all the extremal horizon surfaces are Einstein spaces. We present the necessary conditions for the existence of static extremal horizons within the EMdL model.

  7. Surface passivation and interface properties of bulk GaAs and epitaxial-GaAs/Ge using atomic layer deposited TiAlO alloy dielectric.

    PubMed

    Dalapati, G K; Chia, C K; Tan, C C; Tan, H R; Chiam, S Y; Dong, J R; Das, A; Chattopadhyay, S; Mahata, C; Maiti, C K; Chi, D Z

    2013-02-01

    High quality surface passivation on bulk-GaAs substrates and epitaxial-GaAs/Ge (epi-GaAs) layers were achieved by using atomic layer deposited (ALD) titanium aluminum oxide (TiAlO) alloy dielectric. The TiAlO alloy dielectric suppresses the formation of defective native oxide on GaAs layers. X-ray photoelectron spectroscopy (XPS) analysis shows interfacial arsenic oxide (As(x)O(y)) and elemental arsenic (As) were completely removed from the GaAs surface. Energy dispersive X-ray diffraction (EDX) analysis and secondary ion mass spectroscopy (SIMS) analysis showed that TiAlO dielectric is an effective barrier layer for reducing the out-diffusion of elemental atoms, enhancing the electrical properties of bulk-GaAs based metal-oxide-semiconductor (MOS) devices. Moreover, ALD TiAlO alloy dielectric on epi-GaAs with AlGaAs buffer layer realized smooth interface between epi-GaAs layers and TiAlO dielectric, yielding a high quality surface passivation on epi-GaAs layers, much sought-after for high-speed transistor applications on a silicon platform. Presence of a thin AlGaAs buffer layer between epi-GaAs and Ge substrates improved interface quality and gate dielectric quality through the reduction of interfacial layer formation (Ga(x)O(y)) and suppression of elemental out-diffusion (Ga and As). The AlGaAs buffer layer and TiAlO dielectric play a key role to suppress the roughening, interfacial layer formation, and impurity diffusion into the dielectric, which in turn largely enhances the electrical property of the epi-GaAs MOS devices. PMID:23331503

  8. Structural and dielectric properties of Ba{sub 2}LaSbO{sub 6} ceramics

    SciTech Connect

    Kumari, Premlata; Dutta, Alo; Sinha, T. P.

    2014-04-24

    The ceramic Ba{sub 2}LaSbO{sub 6} (BLS) is synthesized by the solid state reaction technique. The Rietveld refinement of X-ray diffraction pattern at room temperature shows Monoclinic P2{sub 1}/n space group symmetry with lattice parameter a = 6.0720 (0) Å, b = 6.1058 (3) Å, c = 8.6016 (6) Å and ? =89.7091 ° (8). Dielectric study of sample has been performed in the temperature range from 30 °C to 300 °C in the frequency range 50 Hz to 1.1 MHz. Dielectric relaxation peaks are observed in the imaginary part of complex permittivity of the spectra. The frequency dependence of real and imaginary parts of dielectric permittivity is analyzed using Cole-Cole model. The temperature dependent relaxation time is found to obey the Arrhenius law having activation energy 0.48 eV which indicates that the conduction mechanism in the materials may be due to polaron hopping based on electron carriers. The complex plane plots of BLS shows the presence of both grain and grain boundary effects. Conductivity spectra follow the power law.

  9. Electrical and dielectric properties of lithium manganate nanomaterials doped with rare-earth elements

    NASA Astrophysics Data System (ADS)

    Iqbal, Muhammad Javed; Ahmad, Zahoor

    2008-05-01

    Substituted LiRxMn2 - xO4 (R = La3+, Ce3+, Pr3+ and x = 0.00 - 0.20) nanoparticles are prepared by the sol-gel method and the consequent changes in their lattice structure, dielectric and electrical parameters are determined by XRD, ED-XRF, SEM, LCR meter bridge and dc electrical resistivity measurements. Diffraction data show that the samples are single-phase spinel materials with crystallites sizes between 21 and 38 nm. The lattice parameter, cell volume and X-ray density are found to be affected by doping the Li-manganate with the rare-earth elements. The ED-XRF analysis confirms the stoichiometric composition of the synthesized samples and SEM reveals their morphology. Calculated values of the dielectric constant (?) and the dielectric loss (tan ?) decrease with the frequency of the applied field. This is attributed to Maxwell-Wagner polarization. Replacement of manganese by the rare-earth elements results in an improvement in the structural stability of the material, which is considered to be useful for enhancement of the cycleability of the compounds when used in lithium rechargeable batteries, and increases significantly the values of ? and tan ? (except for Ce). Lithium manganate nanomaterials with high ? and low tan ? may be attractive for application in memory storage devices.

  10. Structural, magnetic and dielectric properties of Sr and V doped BiFeO3 multiferroics

    NASA Astrophysics Data System (ADS)

    Dahiya, Reetu; Agarwal, Ashish; Sanghi, Sujata; Hooda, Ashima; Godara, Priyanka

    2015-07-01

    Bi0.85Sr0.15FeO3 (BSFO), Bi0.85Sr0.15Fe0.97V0.03O3 (BSFVO1) and Bi0.85Sr0.15Fe0.95V0.05O3 (BSFVO2) ceramics were synthesized by solid state reaction method. X-ray diffraction studies and Rietveld refinement results indicate that all the samples crystallized in rhombohedrally distorted perovskite structure. The remnant magnetization and coercive field of BSFVO2 were greatly enhanced in comparison with BSFO. The enhancement of remnant magnetization was attributed to collapse of the spiral spin structure caused by change in bond length and bond angles of BSFO on V substitution. The enhanced value of coercive field might be attributed to decreased grain size with V substitution. BSFO sample shows dispersion in dielectric constant (?) and dielectric loss (tan ?) values in lower frequency region. With V doping this dispersion is reduced resulting in frequency independent region. Dielectric anomaly peak due to charge defects in BSFO sample is also suppressed significantly on V substitution. BSFVO2 sample shows almost temperature stable behavior in ? and tan ? in the studied temperature range. Temperature dependence of index 's' of power law suggests that overlapping large polaron tunneling model is applicable for describing the conduction mechanism in BSFO sample while small polaron tunneling model is appropriate for BSFVO1 and BSFVO2 samples in the studied temperature range.

  11. Dielectric properties of low temperature nano engineered yttrium copper titanate ceramic

    NASA Astrophysics Data System (ADS)

    Sharma, Sunita; Singh, M. M.; Mandal, K. D.; Singh, Narsingh B.

    2015-05-01

    The complex perovskite ACu3Ti4O12 (A = Ca, Bi2/3, Y2/3) which possess high dielectric constant could be promising candidates to replace relaxors as dielectrics in DRAM, MLCCs and other memory devices. Their smaller capacitive components lead to miniaturization of electronic devices with efficient performance. Yttrium Copper Titanate (Y2/3Cu3Ti4O12) nano-ceramic is structurally analogous to CaCu3Ti4O12. XRD of Y2/3Cu3Ti4O12 shows the presence of all normal peaks of CaCu3Ti4O12. SEM micrograph exhibits the presence of bimodal grains of size ranging from 1-2 ?m. Bright field TEM image clearly displays nano-crystalline particle which is supported by presence of a few clear rings in the corresponding selected area electron diffraction pattern. It exhibits high dielectric constant (?'= 8434) at room temperature and 100 Hz frequency with characteristic relaxation peaks.

  12. Influence of O{sub 2} on the dielectric properties of CO{sub 2} at the elevated temperatures

    SciTech Connect

    Rong, Mingzhe; Sun, Hao; Yang, Fei Wu, Yi Chen, Zhexin; Wang, Xiaohua; Wu, Mingliang

    2014-11-15

    SF{sub 6} gas is widely used in the high voltage circuit breakers but considering its high global warming potential other substitutes are being sought. Among them CO{sub 2} was investigated and even has been used in some practical products. However, at room temperature, the dielectric properties of CO{sub 2} are relatively lower than SF{sub 6} and air. The goal of this work is to investigate a CO{sub 2}-based gas to improve the performance of the pure CO{sub 2}. In this paper, the dielectric properties of hot CO{sub 2}/O{sub 2} mixtures related to the dielectric recovery phase of the circuit breaker were investigated in the temperature range from 300?K to 4000?K and in the pressure range from 0.01?MPa to 1.0?MPa. The species compositions of hot CO{sub 2}/O{sub 2} were obtained based on Gibbs free energy minimization under the assumptions of local thermodynamic equilibrium and local chemical equilibrium. The reduced critical electric field strength of CO{sub 2}/O{sub 2} was determined by balancing electron generation and loss. These were calculated using the electron energy distribution function by solving the Boltzmann transport equation. The validity of the calculation method and the cross sections data was confirmed by comparing the measurements and calculations of the electron swarm data in previous work. The results indicate that in pure CO{sub 2} the critical electric field strength is higher only in higher temperature range. By adding the O{sub 2} into the CO{sub 2}, the critical electric field strength at lower temperature is effectively enhanced. CO{sub 2}/O{sub 2} mixtures have a much better dielectric strength than both the pure CO{sub 2} and air and thus have the potential to improve the CO{sub 2}-based gas circuit breakers. Similar conclusions can also be found in others’ work, which further confirm the validity of these results.

  13. Effect of A-site La3+ modified on dielectric and energy storage properties in lead zironate stannate titanate ceramics

    NASA Astrophysics Data System (ADS)

    Zhuo, Fangping; Li, Qiang; Li, Yuanyuan; Gao, Jinghan; Yan, Qingfeng; Zhang, Yiling; Chu, Xiangcheng; Cao, Wenwu

    2014-12-01

    (Pb1-1.5xLax)(Zr0.66Sn0.23Ti0.11)O3 (PLZST) ceramics with different lanthanum (La3+) content (x = 0-6%) were prepared by conventional solid state reaction process, and exhibited excellent electrical properties with high switching field from AFE to FE phase and electric breakdown strength. The maximum dielectric constant (?m) and its corresponding temperature (Tm) decreased with La3+ doping and a phase transition from rhombohedral ferroelectric (FE) to tetragonal antiferroelectric (AFE) state was found at 2% La3+ doping. At room temperature, a maximum energy density of 1.47 J cm-3 was obtained for x = 4%. In addition, electric-field-dependent energy storage properties of PLZST (x = 4%) ceramics have been investigated, which could be ascribed to the AFE-FE phase transition associated with the increase of strain.

  14. Dielectric properties and field-induced phase switching of lead zirconate titanate stannate antiferroelectric thick films on silicon substrates

    NASA Astrophysics Data System (ADS)

    Xu, Baomin; Ye, Yaohong; Cross, L. Eric

    2000-03-01

    Thick (˜5 ?m) films of antiferroelectric compositions in the lead zirconate titanate stannate family of solid state solutions have been fabricated by sol-gel methods on platinum-buffered silicon substrates. Dielectric properties, electric field induced ferroelectric polarization, and associated elastic strain and the temperature dependence of the dielectric response have been explored as a function of composition. Films with high tin content are shown to undergo a diffuse antiferroelectric-paraelectric phase transition with temperature, probably because of compositional inhomogeneity associated with the high tin content. This type of film also demonstrates a diffuse field-induced antiferroelectric-ferroelectric phase switching under high electric field with the appearance of "slim loop" double hysteresis, which can be attributed to the compositional heterogeneity and the high level of tensile stress in the film because of the thermal mismatch between the film and substrate. On the other hand, the film with high zirconium and low tin content demonstrates a typical antiferroelectric-paraelectric phase change with a sharp peak in dielectric constant on increasing temperature and a typical antiferroelectric-ferroelectric phase switching under high electric field with the appearance of "square loop" double hysteresis. Corresponding to the characteristic of polarization-field hysteresis the film with high tin content possesses a gradual increase of phase switching elastic strain with applied field, reaching a maximum strain level ˜0.38% and suitable for analogue actuation. The film with high zirconium content possesses a sharp jump of phase switching strain with applied field and reaches a maximum strain level ˜0.48%, attractive for high strain digital applications.

  15. Cobalt ferrite sphere-coated buckhorn-like barium titanate: Fabrication, characterization, its dielectric resonance, and microwave attenuation properties

    NASA Astrophysics Data System (ADS)

    Ji, Renlong; Cao, Chuanbao

    2014-10-01

    Barium titanate (BTO) with different morphology is prepared through hydrothermal method using titania spheres as precursor, then calcined at different temperatures and ultimately coated with cobalt ferrite (BTO/CFO). The dielectric dispersion of the composite containing BTO (75 wt. % ratio in paraffin wax) shows evidence of resonance behaviour in the microwave spectrum, rather than the usually observed relaxation mode. The imaginary part of permittivity (??) displays a strong peak in the 10-13 GHz frequency region, especially for buckhorn-like BTO (hydrothermally synthesized at 110 °C and calcined at 1100 °C). The dielectric response anomaly of BTO in special morphology is due to the emission of plane acoustic waves caused by electrostrictive and converse piezoelectric effects. An accepted model is adopted to simulate the resonance frequency. The minimum reflection loss of cauliflower-like BTO (hydrothermally synthesized at 110 °C, then calcined at 600 °C for 2 h, 75 wt. % ratio) in paraffin wax reaches -30.831 dB at 10.56 GHz with a matching thickness of 2 mm, lower than all the reported values. When the sintering temperature is changed to 1100 °C (buckhorn-like BTO), the minimum reflection loss value is -24.37 dB at 12.56 GHz under the thickness of 3 mm. After combination with CFO, the value reaches -42.677 dB when the thickness is 5.6 mm. The ginger-like BTO (hydrothermally synthesized at 200 °C and calcined at different temperatures) is inferior in microwave reflection reduction. The electromagnetic interference shielding effectiveness of buckhorn-like BTO composite is calculated to be -12.7 dB (94.6% shielding) at resonance frequency (2 mm, 11.52 GHz). This work clearly shows the potential to tune the dielectric property of ferroelectrics through control of morphology, facilitating new comprehension of the ferroelectrics in microwave regime.

  16. Effect of Al3+ Doping on Magnetic and Dielectric Properties of Ni-Zn Ferrites by One-Step Synthesis"

    NASA Astrophysics Data System (ADS)

    Ge, H. L.; Peng, Z. J.; Wang, C. B.; Fu, Z. Q.

    Al3+-doped Ni-Zn ferrites with composition of Ni0.5Zn0.5(Fe1-xAlx)2 O4 (where x = 0, 0.012, 0.023, 0.035 and 0.045) were prepared by a method named "one-step synthesis." The magnetic and dielectric properties of the as-prepared Ni-Zn ferrites were investigated. X-ray diffraction data indicated that all the ferrite samples had a single-phase spinel structure. The addition of Al3+ resulted in a reduction of the grain size, lattice constant, density, shrinkage and saturation magnetization of the as-prepared samples. The Curie temperatures, however, raised first and reduced later with increasing contents of Al3+ in the samples, but still kept high values. Both the real and imaginary parts of permeability of ferrites decreased with increasing amount of Al3+ doped before they reached peak value. As the applied frequency increased to higher than about 10 MHz, the real part of permeability of non-doped ferrite had already become lower than those of ferrites doped with Al3+. Moreover, the doping of Al3+ made their utility of magnetic permeability move to much higher frequency. The observed decreases in dielectric constants and dielectric loss tangent could be attributed to the decreased electron conductivity by substituting Fe3+ with Al3+ in the samples. The as-prepared high-performance soft magnetic materials prepared using such a simple and low-cost method will be much promising in high-frequency applications and industrialization.

  17. Effect of Pr 3+ doping on magnetic and dielectric properties of Ni-Zn ferrites by "one-step synthesis"

    NASA Astrophysics Data System (ADS)

    Peng, Zhijian; Fu, Xiuli; Ge, Huilin; Fu, Zhiqiang; Wang, Chengbiao; Qi, Longhao; Miao, Hezhuo

    2011-10-01

    Pr 3+-doped Ni-Zn ferrites with a nominal composition of Ni 0.5Zn 0.5Pr xFe 2- xO 4 (where x=0-0.08) were prepared by a one-step synthesis. The magnetic and dielectric properties of the as-prepared Ni-Zn ferrites were investigated. X-ray diffraction data indicated that, after doping, all samples consisted of the main spinel phase in combination of a small amount of a foreign PrFeO 3 phase. The lattice constants of the ferrites initially increased after Pr 3+ doping, but then became smaller with additional Pr 3+ doping. The addition of Pr 3+ resulted in a reduction of grain size and an increase of density and densification of the as-prepared samples. Magnetic measurement revealed that the saturation magnetization of the as-prepared ferrites, Ms, decreased, while the coercivity, Hc, increased with increasing substitution level, x, and the Curie temperature, Tc, kept a rather high value, fluctuating between 308 and 320 °C. Both the real and imaginary parts of permeability of the ferrites decreased slightly after Pr 3+ doping. However, the natural resonance frequency shifted towards higher frequency from 13.07 to 36.17 MHz after the addition of Pr 3+, driving the magnetic permeability to much higher frequency, reaching the highest value (36.17 MHz) when x=0.04. Introduction of Pr 3+ ions into the Ni-Zn ferrite reduced the values of the dielectric loss tangent, especially in the frequency range of 1-400 MHz. However, the magnitude of dielectric loss of the samples doped with different amounts of Pr 3+ raised little.

  18. Synthesis and properties of a novel UV-cured fluorinated siloxane graft copolymer for improved surface, dielectric and tribological properties of epoxy acrylate coating

    NASA Astrophysics Data System (ADS)

    Yan, Zhenlong; Liu, Weiqu; Gao, Nan; Wang, Honglei; Su, Kui

    2013-11-01

    A novel functional fluorinated siloxane graft copolymer bearing with vinyl end-groups was synthesized from dihydroxypropyl-terminated poly(dimethylsiloxane) (PDMS), dicarboxyl terminated poly(2,2,3,4,4,4-hexafluorobutyl acrylate) oligomer (CTHFA), 2,4-toluene diissocyanate (TDI) and 2-hydroxyethyl methacrylate (HEMA). The chemical structure was characterized by FT-IR and GPC. The effect of concentration of the vinyl-capped fluorosilicone graft copolymer (Vi-PFSi) on the surface, thermal properties, dielectric and tribological properties of UV-cured films was investigated. Contact angles and surface energies showed that the high hydrophobic and oleophobic surfaces were obtained by incorporation of Vi-PFSi at very low amount (0.5 wt%). X-ray photoelectron spectroscopy (XPS) evidenced that the fluorinated and siloxane moiety selectively migrated to the outermost surface of UV-cured film, thus reduced its surface energy from 45.42 to 15.40 mN/m2 without affecting its bulk properties. The morphology of fracture surface of modified film exhibited rough fracture surface only at the outermost surface, revealing fluorinated and siloxane groups migrated toward air-side surface. The dielectric constants decreased from 5.32 (1 MHz) for bisphenol-A epoxy methacrylate (EMA) to 2.82 (1 MHz) for modified film when the Vi-PFSi copolymer concentration increased from 0 to 0.8 wt%. Tribological results from abrasion tester suggested that the Vi-PFSi could obviously reduce the abrasion weight loss of modified films.

  19. Hydrothermal synthesis of doped lanthanum zirconate nanomaterials and the effect of V–Ge substitution on their structural, electrical and dielectric properties

    SciTech Connect

    Farid, Muhammad Asim; Asghar, Muhammad Adnan; Ashiq, Muhammad Naeem Ehsan, Muhammad Fahad; Athar, Muhammad

    2014-11-15

    Graphical abstract: Variation of dielectric constant with frequency for all the synthesized materials. - Highlights: • Hydrothermal method has been successfully employed to synthesize the zirconates. • XRD confirmed the formation of required phase. • Increased electrical resistivity makes these materials useful for microwave devices. • Dielectric parameters of zirconates decrease with increasing frequency. • Dielectric constant decreases with increasing substituents concentration. - Abstract: A hydrothermal method was successfully employed for the synthesis of a series of vanadium and germanium co-doped pyrochlore lanthanum zirconates with composition La{sub 2?x}V{sub x}Zr{sub 2?y}Ge{sub y}O{sub 7} (where x, y = 0.0, 0.25, 0.50, 0.75 and 1.0). The XRD and FTIR analyses confirmed the formation of single phase except vanadium and germanium substituted samples and the crystallite sizes are in the range of 7–31 nm for V{sup 3+}–Ge{sup 4+} substituted samples. The theoretical compositions are confirmed by the ED-XRF studies. The room temperature electrical resistivity increase with the substituents concentration which suggests that the synthesized materials can be used for microwave devices as such devices required highly resistive materials. Dielectric properties were measured in the frequency range of 6 kHz to 1 MHz. The dielectric parameters decrease with increase in frequency. The DC resistivity data is in good agreement with the dielectric data.

  20. Dielectric breakdown properties of hot SF{sub 6}/He mixtures predicted from basic data

    SciTech Connect

    Wang, Weizong; State Key Laboratory of Electrical Insulation and Power Equipment, Xi'an Jiaotong University, Xi'an Shaanxi 710049 ; Tu, Xin; Mei, Danhua; Rong, Mingzhe

    2013-11-15

    Sulfur hexafluoride (SF{sub 6}) gas has a quite high global warming potential and hence it is required that applying any substitute for SF{sub 6} gas. Much interest in the use of a mixture of helium and SF{sub 6} as arc quenching medium was investigated indicating a higher recovery performance of arc interruption than that of pure SF{sub 6}. It is known that the electrical breakdown in a circuit breaker after arc interruption occurs in a hot gas environment, with a complicated species composition because of the occurrence of dissociation and other reactions. The likelihood of breakdown relies on the electron interactions with all these species. The critical reduced electric field strength (the field at which breakdown can occur, relative to the number density) of hot SF{sub 6}/He mixtures related to the dielectric recovery phase of a high voltage circuit breaker is calculated in the temperature range from 300 K to 3500 K. The critically reduced electric field strength of these mixtures was obtained by balancing electron generation and loss mechanisms. These were evaluated using the electron energy distribution function derived from the Boltzmann transport equation under the two-term approximation. Good agreement was found between calculations for pure hot SF{sub 6} and pure hot He and experimental results and previous calculations. The addition of He to SF{sub 6} was found to decrease the critical reduced electric field strength in the whole temperature range due to a lack of electron impact attachment process for helium regardless its high ionization potential. This indicates that not the behaviour of dielectric strength but possibly the higher energy dissipation capability caused mainly by light mass and high specific heat as well as thermal conductivity of atomic helium contributes most to a higher dielectric recovery performance of arc interruption for SF{sub 6}/He mixtures.

  1. Magnetic behavior and dielectric properties of aluminum substituted M-type barium hexaferrite

    NASA Astrophysics Data System (ADS)

    El-Sayed, S. M.; Meaz, T. M.; Amer, M. A.; El Shersaby, H. A.

    2013-10-01

    Various parameters in the structural features of the aluminum substituted barium hexagonal ferrite particles BaAlxFe12-xO19 with 0?x?3.5 which were prepared by the solid state reaction method have been studied. The infrared transmission spectrum was measured in the wave number region 5000-200 cm-1 at room temperature. The results were interpreted in terms of the vibrations of the isolated molecular units in such a way to preserve the tetrahedral and octahedral clusters of metal oxides in the barium aluminum hexagonal ferrites. The infrared features are assigned to Fe-O and Ba-O bonds in M-type hexagonal ferrite (BaFe12O19) molecules. Also, the results explain the structural model, based on the effect of aluminum substitution “Al-O bond”. On the other hand, the magnetic behavior of the samples was studied using the vibrating sample magnetometer technique. The saturation magnetization (Ms) and magneton number (nB) decrease with increasing Al3+ substitution from 61.2 to 28.9 emu/g and from 12.2 to 5.3 ?B respectively. Also, all samples were characterized using X-ray diffraction and the values of grain size, microstrain and dislocation density of all samples were calculated. The dielectric parameters and ac conductivity measurements were performed within a temperature range 293-493 K. The ac conductivity showed a linear relation with the frequency power law with an exponent s?0.69-0.14 for BaFe12O19. It decreases with increasing temperature, indicating that the heterogeneous structures increase. While the dielectric constant (??) and the dielectric loss (??) decrease with increasing Al substitution.

  2. Dielectric breakdown properties of hot SF6/He mixtures predicted from basic data

    NASA Astrophysics Data System (ADS)

    Wang, Weizong; Tu, Xin; Mei, Danhua; Rong, Mingzhe

    2013-11-01

    Sulfur hexafluoride (SF6) gas has a quite high global warming potential and hence it is required that applying any substitute for SF6 gas. Much interest in the use of a mixture of helium and SF6 as arc quenching medium was investigated indicating a higher recovery performance of arc interruption than that of pure SF6. It is known that the electrical breakdown in a circuit breaker after arc interruption occurs in a hot gas environment, with a complicated species composition because of the occurrence of dissociation and other reactions. The likelihood of breakdown relies on the electron interactions with all these species. The critical reduced electric field strength (the field at which breakdown can occur, relative to the number density) of hot SF6/He mixtures related to the dielectric recovery phase of a high voltage circuit breaker is calculated in the temperature range from 300 K to 3500 K. The critically reduced electric field strength of these mixtures was obtained by balancing electron generation and loss mechanisms. These were evaluated using the electron energy distribution function derived from the Boltzmann transport equation under the two-term approximation. Good agreement was found between calculations for pure hot SF6 and pure hot He and experimental results and previous calculations. The addition of He to SF6 was found to decrease the critical reduced electric field strength in the whole temperature range due to a lack of electron impact attachment process for helium regardless its high ionization potential. This indicates that not the behaviour of dielectric strength but possibly the higher energy dissipation capability caused mainly by light mass and high specific heat as well as thermal conductivity of atomic helium contributes most to a higher dielectric recovery performance of arc interruption for SF6/He mixtures.

  3. Investigation of basic physical properties and dielectric behavior of a-Se-Sn-Ge-Sb system

    NASA Astrophysics Data System (ADS)

    Chaudhary, Shobhna; Modgil, Vivek; Nidhi, Anant Vidya; Kumar, Prashant; Rangra, V. S.

    2015-05-01

    The material is investigated for various physical parameters which gives us the formation about glass rigidity and glass forming ability. The cohesive energy has been interpreted using Chemical Bond Approach and glass transition temperature (Tg) has been calculated by using Tichy-Ticha approach. The decrease in glass transition temperature and weakening of structure of the material has been observed due to decrease in mean bond energy. The effect of Sb addition on the dielectric behavior of a bulk glassy material has also been studied at room temperature in the frequency range 20Hz to 1MHz.

  4. Dielectric and microwave attenuation properties of graphene nanoplatelet–epoxy composites

    SciTech Connect

    Wang, Zhou; Luo, Jia; Zhao, Guang–Lin

    2014-01-15

    Graphene nanoplatelet (GNP)–epoxy composites were fabricated for the investigation of the dielectric permittivity and microwave absorption in a frequency range from 8 to 20 GHz. The intrinsically conductive GNP particles and polarized interfacial centers in the composites contribute to the microwave absorption. A minimum reflection loss of ?14.5 dB at 18.9 GHz is observed for the GNP–epoxy composites with 15 wt. % GNP loading, which is mainly attributed to electric conductivity and the charge multipoles at the polarized interfaces in the GNP–epoxy composites.

  5. Exploring Vesta's Surface Roughness and Dielectric Properties Using VIR Spectrometer and Bistatic Radar Observations by the Dawn Mission

    NASA Astrophysics Data System (ADS)

    Palmer, E. M.; Heggy, E.; Capria, M. T.; Tosi, F.; Kofman, W. W.; Russell, C. T.

    2014-12-01

    Multiple lines of evidence from NASA's Dawn mission suggest transient volatile presence at the surface of asteroid Vesta. Radar remote sensing is a useful technique for the investigation of volatile content at the surface and shallow subsurface, but requires the use of accurate dielectric and topographic models in order to deconvolve the effect of surface roughness from the total observed radar backscatter. Toward this end, we construct a dielectric model for the dry, volatile-poor case of Vesta's surface to represent average surface conditions, and to assess the expected average range of dielectric properties due to known variations in mineralogy, temperature, and density as inferred from Dawn VIR data. We employ dielectric studies of lunar samples to serve as a suitable analog to the Vestan regolith, and in the case of 10-wavelength penetration depth of X-band frequency radar observations, our model yields ?' from 2.5 to 2.6 from the night to dayside of Vesta, and tan ? from 0.011 to 0.014. Our estimation of ?' corresponds to specular surface reflectivity of ~0.05. In addition to modeling, we have also conducted an opportunistic bistatic radar (BSR) experiment at Vesta using the communications antennas aboard Dawn and on Earth. In this configuration, Dawn transmits a continuous radar signal toward the Earth while orbiting Vesta. As the Dawn spacecraft passes behind Vesta (entering an occultation), the line of sight between Dawn and Earth intersects Vesta's surface, resulting in a reflection of radar waves from the surface and shallow subsurface, which are then received on Earth for analysis. The geometry of the Dawn BSR experiment results in high incidence angles on Vesta's surface, and leads to a differential Doppler shift of only a few 10s of Hz between the direct signal and the surface echo. As a consequence, this introduces ambiguity in the measurement of bandwidth and peak power of each surface echo. We report our interpretations of each surface echo in the context of relative surface roughness and relative surface reflectivity, and present suggestions for conducting future BSR experiments at small bodies.

  6. Zn-Al layered double hydroxide prepared at different molar ratios: Preparation, characterization, optical and dielectric properties

    SciTech Connect

    Ahmed, Abdullah Ahmed Ali; Talib, Zainal Abidin; Zobir bin Hussein, Mohd; Zakaria, Azmi

    2012-07-15

    The co-precipitation method was used to prepare Zn-Al-NO{sub 3}-LDH at different Zn{sup 2+}/Al{sup 3+} molar ratios (2, 3, 4, 5 and 6) and pH value of 7.5. The structure, textural, composition and morphological properties were investigated using powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR) and scanning electron microscope (SEM), respectively. The crystallinity of LDH samples were found to improve as molar ratio decreased which is attributed to the distortion of the hydroxide layers networks of the LDH crystal by the larger difference in ionic radii of Zn{sup 2+} and Al{sup 3+}. The optical band gap energy of LDH samples were evaluated using absorbance data from UV-Vis-NIR Diffuse reflectance spectroscopy. Band gaps were affected by the variation of the Zn{sup 2+}/Al{sup 3+} molar ratio is due to the formation of the low crystalline phases (ZnO and ZnAl{sub 2}O{sub 4}). The water molecules and anionic NO{sub 3}{sup -} in the LDH interlayer were responsible for the generation of the dielectric response. This response can be described by an anomalous low frequency dispersion using the second type of Universal Power Law. The dominance of ZnO dipoles and charge carriers (NO{sub 3}{sup -} ions) in the dielectric relaxation increases with the increasing molar ratio. - Graphical abstract: (a) Schematic diagram of Zn-Al- NO{sub 3}-LDH shows the LDH structure, (b) Kubelka-Munk transformed reflectance spectra and c. The dielectric constant versus frequency of Zn-Al- NO{sub 3}-LDH samples. Highlights: Black-Right-Pointing-Pointer Zn-Al-NO{sub 3}-LDH was prepared at different Zn{sup 2+}/Al{sup 3+} molar ratios (2, 3, 4, 5 and 6). Black-Right-Pointing-Pointer The crystallinity of LDH phase decreased with increase of Zn{sup 2+}/Al{sup 3+} molar ratio. Black-Right-Pointing-Pointer The optical band gaps of LDH samples have been measured. Black-Right-Pointing-Pointer Dielectric response of LDH can be described by anomalous low frequency dispersion.

  7. Defect chemistry and dielectric properties of Yb{sup 3+}:CaTiO{sub 3} perovskite

    SciTech Connect

    Bassoli, M.; Buscaglia, M. T.; Bottino, C.; Buscaglia, V.; Molinari, M.; Maglia, F.; Parravicini, G.; Dapiaggi, M.

    2008-01-01

    The defect chemistry of Yb{sup 3+}:CaTiO{sub 3} solid solutions has been investigated both theoretically and experimentally. Three different incorporation mechanisms with similar solution energy were predicted for Yb{sup 3+} by atomistic simulation: (i) Ca site substitution with Ca vacancy compensation; (ii) Ti site substitution with O vacancy compensation; (iii) simultaneous substitution at both Ca and Ti sites with self-compensation. X-ray diffraction and scanning electron microscopy results strongly support the possibility to realize the above defect chemistries in CaTiO{sub 3} by changing the Ca/Ti ratio to force Yb{sup 3+} on the Ca site (Ca/Ti<1), on Ti site (Ca/Ti>1), or on both sites (Ca/Ti=1) according to the calculations. The temperature dependence of the relative dielectric constant (10{sup 2}-10{sup 5} Hz) of ceramics corresponding to predominant Yb substitution either at the Ca site or the Ti site is qualitatively similar to that of undoped CaTiO{sub 3}. The Curie-Weiss temperature is shifted to more negative values in comparison to CaTiO{sub 3}, suggesting that the compositions Ca{sub 1-3/2x}Yb{sub x}TiO{sub 3} and CaYb{sub x}Ti{sub 1-x}O{sub 3} are further driven away from the ferroelectric instability. In contrast, the dielectric properties (10{sup 2}-10{sup 5} Hz) of ceramics corresponding to Ca{sub 1-x/2}Yb{sub x}Ti{sub 1-x/2}O{sub 3} are radically different. The relative dielectric constant is increased of about one order of magnitude (2200 at 30 K), is almost independent of temperature, with a maximum variation of 20% in range of 20-300 K, and shows frequency dispersion above 150 K. The loss tangent at 20-300 K is <5% for frequencies {>=}1 kHz. The possible mechanism for the observed dielectric behavior is discussed.

  8. Preparation of titanium metal/barium titanate composites with boundary layer structure by hydrothermal method and their dielectric properties

    NASA Astrophysics Data System (ADS)

    Ueno, Shintaro; Sakamoto, Yasunao; Kakiuchi, Hiroyuki; Nakashima, Kouichi; Wada, Satoshi

    2015-10-01

    To develop metal/insulator composite capacitors with a high effective dielectric constant, we focus on the microstructure of boundary layer (BL) capacitors. Titanium metal/barium titanate (Ti/BT) composites consisting of Ti metal grains and BT boundary nanolayers were successfully prepared from pressed Ti-BT core-shell particle compacts by a hydrothermal method below 230 °C. In this hydrothermal method, BT polycrystalline shell layers connected to each other by crystal growth via a dissolution and reprecipitation mechanism in barium hydroxide [Ba(OH)2] aqueous solutions. The thickness of BT boundary layers may increase with an increase in the Ba(OH)2 concentration and determine electrical properties. These Ti/BT composites prepared in 250 and 500 mmol/dm3 Ba(OH)2 solutions exhibit effective dielectric constants of over 5000 and 3000, and loss tangents below 0.075 and 0.060 in the frequency range of 100 Hz-100 kHz at room temperature, respectively.

  9. Effect of octa(aminophenyl) polyhedral oligomeric silsesquioxane functionalized graphene oxide on the mechanical and dielectric properties of polyimide composites.

    PubMed

    Liao, Wei-Hao; Yang, Shin-Yi; Hsiao, Sheng-Tsung; Wang, Yu-Sheng; Li, Shin-Ming; Ma, Chen-Chi M; Tien, Hsi-Wen; Zeng, Shi-Jun

    2014-09-24

    An effective method is proposed to prepare octa(aminophenyl) silsesquioxane (OAPS) functionalized graphene oxide (GO) reinforced polyimide (PI) composites with a low dielectric constant and ultrastrong mechanical properties. The amine-functionalized surface of OAPS-GO is a versatile starting platform for in situ polymerization, which promotes the uniform dispersion of OAPS-GO in the PI matrix. Compared with GO/PI composites, the strong interfacial interaction between OAPS-GO and the PI matrix through covalent bonds facilitates a load transfer from the PI matrix to the OAPS-GO. The OAPS-GO/PI composite film with 3.0 wt % OAPS-GO exhibited an 11.2-fold increase in tensile strength, and a 10.4-fold enhancement in tensile modulus compared with neat PI. The dielectric constant (D(k)) decreased with the increasing content of 2D porous OAPS-GO, and a D(k) value of 1.9 was achieved. PMID:25153775

  10. Structural and Electrical Properties of Zr x Y1-x O y Nanocomposites for Gate Dielectric Applications

    NASA Astrophysics Data System (ADS)

    Ebrahimzadeh, Masoud; Bahari, Ali

    2015-11-01

    The possibility of ultrathin Zr x Y1-x O y films was investigated as a good gate dielectric structure for metal-oxide-semiconductor field-effect transistors (MOSFETs). Zr-doped Y2O3 nanocrystallites were synthesized by the sol-gel method. The nanocrystallite size was determined using the Scherrer equation and x-ray powder method from the main peak of the sample phase observed in x-ray diffraction patterns. Moreover, qualitative elemental analysis was performed by energy-dispersive x-ray spectroscopy. The nanocrystallite properties were characterized by scanning electron microscopy. The nanocrystallite morphology was determined by atomic force microscopy, showing that the grain size of the nanoparticles observed at the surface depends on the type of metal dopant and the annealing temperature. The capacitance-voltage and current density-voltage characteristics of the Zr x Y1-x O y /Si structures were analyzed. The results indicate that the Zr0.1Y0.9O y nanocomposite can be used as a good gate dielectric for next-generation MOSFET devices. The conduction mechanism in electrical fields below 0.25 MV/cm and the temperature range of 333 K < T < 423 K was found to be ohmic emission. A thermal excitation model is proposed to explain the ohmic current conduction mechanism.

  11. Structure, dielectric, and magnetic properties of Sr{sub 2}TiMnO{sub 6} ceramics

    SciTech Connect

    Meher, K. R. S. Preethi; Varma, K. B. R.; Savinov, M.; Kamba, S.; Goian, V.

    2010-11-15

    Sr{sub 2}TiMnO{sub 6}, a double perovskite associated with high degree of B-site cation disorder was investigated in detail for its structural, magnetic, and dielectric properties. Though x-ray powder diffraction analysis confirms its cubic structure, first order Raman scattering and infrared reflectivity spectra indicate a breaking of the local cubic symmetry. The magnetization study reveals an anomaly at 14 K owing to a ferrimagnetic/canted antiferromagneticlike ordering arising from local Mn-O-Mn clusters. Saturated M-H hysteresis loops obtained at 5 K also reflect the weak ferromagnetic exchange interactions present in the system and an approximate estimation of Mn{sup 3+}/Mn{sup 4+} was done using the magnetization data for the samples sintered at different temperatures. The conductivity and dielectric behavior of this system has been investigated in a broad temperature range of 10 to 300 K. Intrinsic permittivity was obtained only below 100 K whereas giant permittivity due to conductivity and Maxwell-Wagner polarization was observed at higher temperatures. X-ray photoemission studies further confirmed the presence of mixed oxidation states of Mn and the valence band spectra analysis was carried out in detail.

  12. Phase transition and dielectric properties of La-doped Pb(Zr,Sn,Ti)O3 antiferroelectric ceramics under hydrostatic pressure and temperature

    NASA Astrophysics Data System (ADS)

    Xu, Zhuo; Feng, Yujen; Zheng, Shuguang; Jin, An; Wang, Fanglin; Yao, Xi

    2002-09-01

    Phase transition and dielectric properties of La-doped Pb(Zr,Sn,Ti)O3 antiferroelectric ceramics under hydrostatic pressure and temperature have been studied, and effects of temperature on the pressure-induced phase transition and the dielectric property dependence on the applied hydrostatic pressure have been investigated. It has been found from experimental results that the ferroelectric-antiferroelectric phase transition pressure is decreased with increasing temperature, and that when applying hydrostatic pressure the ferroelectric-antiferroelectric phase transition temperature is decreased and antiferroelectric-paraelectric phase transition temperature is increased. All these observed phenomena are very useful and informative for deep understanding of the behaviors of temperature and pressure-induced dielectric frequency dispersion and diffuse phase transition.

  13. Magnetic, dielectric and magnetodielectric properties of PVDF-La0.7Sr0.3MnO3 polymer nanocomposite film

    NASA Astrophysics Data System (ADS)

    Thirmal, Ch.; Nayek, Chiranjib; Murugavel, P.; Subramanian, V.

    2013-11-01

    We have investigated the structure, magnetic and dielectric properties of PVDF-La0.7Sr0.3MnO3 polymer nanocomposite thick film fabricated by dip coating technique along with the magnetodielectric effect. The structure and dielectric properties show the enhanced ? phase in the composite compared to the PVDF film. The coupling between the ferroelectric and magnetic phases in the composite is revealed in the form of dielectric anomaly at the ferromagnetic Curie temperature. We observed 1.9% magnetodielectric effect at 300 K with the possibility of enhanced effect near the transition temperature. In addition, the analysis of the electric modulus indicates that the composite exhibits interfacial related relaxation and it follows Arrhenius Law. Our study suggests that the ac conductivity of the PVDF-La0.7Sr0.3MnO3 composite could be explained by correlated barrier hopping mechanism.

  14. Superior dielectric properties for template assisted grown (100) oriented Gd{sub 2}O{sub 3} thin films on Si(100)

    SciTech Connect

    Roy Chaudhuri, Ayan Osten, H. J.; Fissel, A.

    2014-01-06

    We report about the single crystalline growth and dielectric properties of Gd{sub 2}O{sub 3}(100) thin films on Si(100) surface. Using a two step molecular beam epitaxy growth process, we demonstrate that controlled engineering of the oxide/Si interface is a key step to achieve the atypical (100) oriented growth of Gd{sub 2}O{sub 3}. Unusually, high dielectric constant values (?23–27) were extracted from capacitance voltage measurements. Such effect can be understood in terms of a two dimensional charge layer at the Gd{sub 2}O{sub 3}/Si interface (W. Sitaputra and R. Tsu, Appl. Phys. Lett. 101, 222903 (2012)) which can influence the dielectric properties of the oxide layer by forming an additional negative quantum capacitance.

  15. Magnetic, dielectric and magnetodielectric properties of PVDF-La{sub 0.7}Sr{sub 0.3}MnO{sub 3} polymer nanocomposite film

    SciTech Connect

    Thirmal, Ch.; Nayek, Chiranjib; Murugavel, P. Subramanian, V.

    2013-11-15

    We have investigated the structure, magnetic and dielectric properties of PVDF-La{sub 0.7}Sr{sub 0.3}MnO{sub 3} polymer nanocomposite thick film fabricated by dip coating technique along with the magnetodielectric effect. The structure and dielectric properties show the enhanced ? phase in the composite compared to the PVDF film. The coupling between the ferroelectric and magnetic phases in the composite is revealed in the form of dielectric anomaly at the ferromagnetic Curie temperature. We observed 1.9% magnetodielectric effect at 300 K with the possibility of enhanced effect near the transition temperature. In addition, the analysis of the electric modulus indicates that the composite exhibits interfacial related relaxation and it follows Arrhenius Law. Our study suggests that the ac conductivity of the PVDF-La{sub 0.7}Sr{sub 0.3}MnO{sub 3} composite could be explained by correlated barrier hopping mechanism.

  16. Evaluation of Dielectric-Barrier-Discharge Actuator Substrate Materials

    NASA Technical Reports Server (NTRS)

    Wilkinson, Stephen P.; Siochi, Emilie J.; Sauti, Godfrey; Xu, Tian-Bing; Meador, Mary Ann; Guo, Haiquan

    2014-01-01

    A key, enabling element of a dielectric barrier discharge (DBD) actuator is the dielectric substrate material. While various investigators have studied the performance of different homogeneous materials, most often in the context of related DBD experiments, fundamental studies focused solely on the dielectric materials have received less attention. The purpose of this study was to conduct an experimental assessment of the body-force-generating performance of a wide range of dielectric materials in search of opportunities to improve DBD actuator performance. Materials studied included commonly available plastics and glasses as well as a custom-fabricated polyimide aerogel. Diagnostics included static induced thrust, electrical circuit parameters for 2D surface discharges and 1D volume discharges, and dielectric material properties. Lumped-parameter circuit simulations for the 1D case were conducted showing good correspondence to experimental data provided that stray capacitances are included. The effect of atmospheric humidity on DBD performance was studied showing a large influence on thrust. The main conclusion is that for homogeneous, dielectric materials at forcing voltages less than that required for streamer formation, the material chemical composition appears to have no effect on body force generation when actuator impedance is properly accounted for.

  17. Dielectric properties and microstructure of sintered BaTiO3 fabricated by using mixed 150-nm and 80-nm powders with various additives

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    Recently, the use of small-sized BaTiO3 particles for ultra-thin MLCC research has increased as a method for minimizing the dielectric layer's thickness in thick film process. However, when particles smaller than 100 nm are used, the reduced particle size leads to a reduced dielectric constant. The use of nanoparticles, therefore, requires an increase in the amount of additive used due to the increase in the specific surface area, thus increasing the production cost. In this study, a novel method of coating 150-nm and 80-nm BaTiO3 powders with additives and mixing them together was employed, taking advantage of the effect obtained through the use of BaTiO3 particles smaller than 100 nm, to conveniently obtain the desired dielectric constant and thermal characteristics. Also, the microstructure and the dielectric properties were evaluated. The additives Dy, Mn, Mg, Si, and Cr were coated on a 150-nm powder, and the additives Dy, Mn, Mg, and Si were coated on 80-nm powder, followed by mixing at a ratio of 1:1. As a result, the microstructure revealed grain formation according to the liquid-phase additive Si; additionally, densification was well realized. However, non-reducibility was not obtained, and the material became a semiconductor. When the amount of added Mn in the 150-nm powder was increased to 0.2 and 0.3 mol%, insignificant changes in the microstructure were observed, and the bulk density after mixing was found to have increased drastically in comparison to that before mixing. Also, non-reducibility was obtained for certain conditions. The dielectric property was found to be consistent with the densification and the grain size. The mixed composition #1-0.3 had a dielectric constant over 2000, and the result somewhat satisfied the dielectric constant temperature dependency for X6S.

  18. Dielectric and Optical Properties of CdS-Polymer Nanocomposites Prepared by the Successive Ionic Layer Adsorption and Reaction (SILAR) Method

    NASA Astrophysics Data System (ADS)

    Azizian-Kalandaragh, Yashar; Aydemir, Umut; Altindal, ?emsettin

    2014-04-01

    The successive ionic layer adsorption and reaction (SILAR) method has been used to grow epitaxial CdS-polymer nanostructures as thin films with different surface morphology and particle size. The main purpose of the study was to investigate the dielectric properties and a.c. electrical conductivity ( ? a.c.), by a.c. impedance spectroscopy between 1 kHz and 1 MHz, at room temperature, of CdS-polymer nanocomposites produced by use of 2, 6, and 10 cycles of SILAR. The surface morphology and optical absorption of the samples were characterized by scanning electron microscopy (SEM) and UV-visible spectroscopy, respectively. Determination of the energy gaps of CdS-polymer nanocomposites prepared by use of different numbers of cycles of SILAR reveals that the band gap decreases with increasing number of cycles (J. Cryst. Growth 305, 175-180, 2007). This behavior is because of the growth of nanoparticles in the matrix materials, and can be explained by changes in the amount of confinement as a consequence of particle size variation. SEM images also confirm that different numbers of cycles lead to different morphology. Frequency-dependent dielectric properties and a.c. electrical conductivity of the samples prepared by use of different numbers of cycles of SILAR were investigated, and comparative studies on some electrophysical properties of the samples are reported. Experimental results show that values of the dielectric constant ( ?'), dielectric loss ( ??), dielectric loss tangent (tan ?), the real ( M') and imaginary ( M?) parts of electric modulus, and ? a.c. are highly dependent on the frequency and the number of cycles. It can be concluded that changing the frequency and the number of cycles substantially alters both the dielectric properties and a.c. electrical conductivity of the samples.

  19. Free-Space Time-Domain Method for Measuring Thin Film Dielectric Properties

    DOEpatents

    Li, Ming; Zhang, Xi-Cheng; Cho, Gyu Cheon

    2000-05-02

    A non-contact method for determining the index of refraction or dielectric constant of a thin film on a substrate at a desired frequency in the GHz to THz range having a corresponding wavelength larger than the thickness of the thin film (which may be only a few microns). The method comprises impinging the desired-frequency beam in free space upon the thin film on the substrate and measuring the measured phase change and the measured field reflectance from the reflected beam for a plurality of incident angles over a range of angles that includes the Brewster's angle for the thin film. The index of refraction for the thin film is determined by applying Fresnel equations to iteratively calculate a calculated phase change and a calculated field reflectance at each of the plurality of incident angles, and selecting the index of refraction that provides the best mathematical curve fit with both the dataset of measured phase changes and the dataset of measured field reflectances for each incident angle. The dielectric constant for the thin film can be calculated as the index of refraction squared.

  20. Optical properties of metal-dielectric based epsilon near zero metamaterials

    NASA Astrophysics Data System (ADS)

    Subramania, Ganapathi; Fischer, Arthur; Luk, Ting

    2014-03-01

    Epsilon(?) near zero(ENZ) materials are metamaterials where the effective dielectric constant(?) is close to zero for a range of wavelengths resulting in zero effective displacement field (D = ?E) and displacement current. ENZ structures are of great interest in many application areas such as optical nanocircuits, supercoupling, cloaking, emission enhancement etc. Effective ENZ behavior has been demonstrated using cut-off frequency region in a metallic waveguide where the modal index vanishes. Here we demonstrate the fabrication of ENZ metamaterials operating at visible wavelengths (? ~ 640nm) using an effective medium approach based on a metal-dielectric composites(App. Phys. Let.,101,241107(2012)) that can act as ``bulk'' ENZ material. The structure consists of a multilayer stack composite of alternating nanoscale thickness layers of Ag and TiO2. Optical spectroscopy shows transmission and absorption response is consistent with ENZ behavior and matches well with simulations. We will discuss the criteria necessary in the design and practical implementation of the composite that better approximates a homogenous effective medium including techniques to minimize the effect of optical losses to boost transmission. The potential for hosting gain media in the gratings to address losses and emission control will be discussed. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. DOE's National Nuclear Security Administration under contract DE-AC04-94AL85000.